WO2012020816A1 - リチウム二次電池負極用黒鉛材料およびその製造方法、およびそれを用いたリチウム二次電池 - Google Patents
リチウム二次電池負極用黒鉛材料およびその製造方法、およびそれを用いたリチウム二次電池 Download PDFInfo
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- WO2012020816A1 WO2012020816A1 PCT/JP2011/068325 JP2011068325W WO2012020816A1 WO 2012020816 A1 WO2012020816 A1 WO 2012020816A1 JP 2011068325 W JP2011068325 W JP 2011068325W WO 2012020816 A1 WO2012020816 A1 WO 2012020816A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
- C01B32/205—Preparation
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0583—Construction or manufacture of accumulators with folded construction elements except wound ones, i.e. folded positive or negative electrodes or separators, e.g. with "Z"-shaped electrodes or separators
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- the present invention relates to a graphite material used as a negative electrode of a lithium secondary battery and a method for producing the same. Specifically, the present invention relates to a method for producing a graphite material used for a negative electrode of a highly durable lithium ion secondary battery in which capacity deterioration is suppressed, and a lithium ion secondary battery including a negative electrode using the same.
- Lithium ion secondary batteries are lighter and have higher input / output characteristics compared to conventional secondary batteries such as nickel cadmium batteries, nickel metal hydride batteries, and lead batteries. Expected as a power source.
- this type of battery is configured by a positive electrode containing lithium capable of reversible intercalation of lithium and a negative electrode made of a carbon material facing each other with a non-aqueous electrolyte interposed therebetween. Therefore, this type of battery is assembled in a discharged state and cannot be discharged unless it is charged.
- the charge / discharge reaction will be described by taking as an example a case where a lithium cobaltate (LiCoO 2 ) is used as the positive electrode, a carbon material as the negative electrode, and a non-aqueous electrolyte containing a lithium salt as the electrolyte.
- a lithium cobaltate LiCoO 2
- a carbon material as the negative electrode
- a non-aqueous electrolyte containing a lithium salt as the electrolyte.
- Carbon materials used as negative electrode materials for lithium ion secondary batteries are generally roughly classified into graphite and amorphous materials.
- the graphite-based carbon material has an advantage that the energy density per unit volume is higher than that of the amorphous carbon material. Accordingly, graphite-based carbon materials are generally used as negative electrode materials in lithium ion secondary batteries for mobile phones and notebook computers that are compact but require a large charge / discharge capacity.
- Graphite has a structure in which hexagonal network planes of carbon atoms are regularly stacked, and lithium ion insertion / extraction reaction proceeds at the edge of the crystallite during charge / discharge.
- this type of battery has been actively studied as a power storage device for automobiles, industrial use, and power supply infrastructure in recent years. Higher reliability is required than when it is used for personal computers.
- the reliability is a characteristic relating to the lifetime, and can be restated as a storage characteristic. Even when the charge / discharge cycle is repeated, when it is stored in a state where it is charged to a predetermined voltage, or when it is continuously charged at a constant voltage (when floating charge is performed), the charge / discharge capacity and internal It refers to the characteristic that resistance is difficult to change (it is difficult to deteriorate).
- the life characteristics of lithium ion secondary batteries that have been used in conventional mobile phones and notebook computers are largely dependent on the anode material.
- the reason is that, in principle, it is impossible to make the charge / discharge efficiency of the positive electrode reaction (formula 1) and the negative electrode reaction (formula 2) exactly the same, and the charge / discharge efficiency is lower in the negative electrode.
- the charge / discharge efficiency is the ratio of the electric capacity that can be discharged to the electric capacity consumed for charging.
- the positive electrode potential in the end-of-discharge state shifts in a more noble direction than the original potential before charge / discharge, while the negative electrode potential also has a more noble direction than the original potential before charge / discharge. Will be transferred to. This is because all of the lithium released during the charging process of the positive electrode is not occluded (does not return) during discharging, so the potential that has shifted in the noble direction during the charging process shifts in the naive direction during the discharging process.
- the discharge of the lithium ion secondary battery is completed when the battery voltage (that is, the difference between the positive electrode potential and the negative electrode potential) reaches a predetermined value (discharge end voltage). This is because if the potential becomes noble, the negative electrode potential shifts in the noble direction accordingly.
- this type of battery can be obtained within a predetermined voltage range (within a discharge end voltage and a charge end voltage range) by changing the operating region of the positive / negative electrode capacity when the charge / discharge cycle is repeated.
- a capacity degradation reaction mechanism has been reported in academic societies and the like (Non-Patent Documents 1 and 2).
- the positive and negative potentials once changed in the operating region are irreversible, cannot be restored in principle, and lack of capacity recovery means also exacerbates this problem.
- the reaction mechanism of capacity deterioration that occurs when the above-described charge / discharge cycle is repeated is basically the same as each reaction mechanism of capacity deterioration when the battery is stored in the charged state or capacity deterioration when the battery is floating charged. The same is true.
- the difference in the self-discharge rate between the positive and negative electrodes in the charged state is similar to the difference in the charge and discharge efficiency between the positive and negative electrodes described above. This is due to the higher rate of side reactions and competitive reactions that occur.
- the leakage current on the negative electrode side becomes larger than the leakage current on the positive electrode side, so that the negative electrode potential shifts to a direction in which the leakage current decreases, that is, a noble direction. Shifts in the direction of increasing, that is, the noble direction. Even when floating charging is performed in this manner, the operating areas of the positive and negative electrode capacities change irreversibly, resulting in a problem that the battery capacity deteriorates.
- a raw material carbon composition obtained by coking a heavy oil composition by a delayed coking process is generally known. This delayed coking process is very suitable for mass production of high-quality carbon materials, and various types of coke products are mass-produced by this process.
- a graphite material obtained by graphitization so that the crystallite size Lc (112) of the (112) diffraction line measured by the X-ray wide angle diffraction method is 4 nm or more is also used as negative electrode graphite of the lithium ion secondary battery. It is generally used as a material (for example, Patent Document 1).
- Non-Patent Document 4 it has been reported that when natural scaly graphite is used as a negative electrode material of a battery and a compression shear stress is applied thereto, the crystal structure of the graphite particle surface can be disturbed (for example, Non-Patent Document 4). And it has been reported that the disorder of the crystal structure on the surface of the graphite particles can improve the initial charge / discharge efficiency of the negative electrode (paragraph [0024] of Patent Document 2).
- a lithium ion battery manufactured using a graphite negative electrode having a highly developed crystal structure can provide a high electric capacity.
- the electrolyte is co-inserted from the edge of the crystallite into the graphite layer composed of hexagonal planes with high parallelism and decomposed.
- the charge / discharge efficiency of the negative electrode is lowered, which causes capacity deterioration.
- solvent co-insertion is more likely to occur as graphite crystals develop.
- Patent Document 1 it is described that a highly developed crystal structure on the particle surface can be disturbed by pulverizing and classifying the raw coal composition and then performing a mechanochemical treatment. It is described that the disturbance of the crystal structure introduced in this way remains as a low crystallinity region even after graphitization which is the final step, so that it is possible to improve the initial charge / discharge efficiency of the negative electrode.
- Patent Document 2 Specification Paragraph [0024]
- the disorder of the crystal structure introduced by mechanochemical treatment is a so-called isotropic state in which unstructured carbon crystallites are randomly oriented, and it is considered that many edge portions are exposed on the particle surface. .
- a large number of dangling bonds, that is, many localized electron states that exist without a partner of the valence bond are not saturated at the edge portion of the crystallite.
- the present inventors have provided a graphite material having a structure in which a region having a low crystallinity is introduced in a highly developed crystal structure and having a small crystallite edge exposure on the particle surface.
- the present invention is for suppressing the decrease in the capacity maintenance rate of the lithium ion secondary battery as described above, and its purpose is to repeat the charge / discharge cycle, the life in the charged state, and the floating charge.
- a crystallite edge has a large number of dangling bonds, that is, many states of localized electrons that are not saturated with valence electron bonds and exist without a bonding partner.
- the present inventors have found that these localized electrons are present on the surface of the negative electrode carbon material in the charging process, that is, at the interface where the electrolyte and the carbon material are in contact. It is presumed that the charging / discharging efficiency of the negative electrode is reduced by the catalytic action and the side reaction / competitive reaction caused by the reductive decomposition of the electrolyte.
- the first embodiment according to the present invention is obtained by graphitizing a pulverized and classified raw coal composition with a graphite precursor provided with compressive stress and shear stress, and is measured by an X-ray wide angle diffraction method (112).
- Lithium ion secondary battery negative electrode that has been treated has a ratio of hydrogen atom H to carbon atom C, an H / C atomic ratio of 0.30 to 0.50, and a microstrength of 7 to 17% by mass
- a graphite material is provided.
- the second form according to the present invention includes a step of pulverizing and classifying a raw coal composition obtained by coking treatment of a heavy oil composition by a delayed coking process, and compression into the pulverized and classified raw coal composition.
- a step of applying a stress and a shear stress to obtain a graphite precursor; and heating and graphitizing the graphite precursor and measuring by a X-ray wide angle diffraction method (112) Crystalline size Lc (112) ) Is a method for producing a graphite material for a negative electrode of a lithium ion secondary battery comprising at least a step of obtaining a graphite material having a thickness of 4 nm or more, wherein the pulverized and classified raw carbon composition includes hydrogen atoms H and carbon atoms.
- the third embodiment according to the present invention provides a lithium ion secondary battery using the graphite material obtained by this production method as a negative electrode material.
- a fourth form according to the present invention includes a step of pulverizing and classifying a raw coal composition obtained by coking a heavy oil composition by a delayed coking process, and heating the pulverized and classified raw coal composition To obtain a graphite particle having a crystallite size Lc (112) of 4 nm or more as measured by an X-ray wide angle diffraction method (112).
- a method for producing a graphite material for a negative electrode of a lithium ion secondary battery comprising at least a step and a step of applying a compression shear stress to the graphite particles to obtain a graphite material, wherein the raw carbon composition to be pulverized and classified comprises Production of a graphite material for a negative electrode of a lithium ion secondary battery having a hydrogen atom H to carbon atom C ratio, an H / C atom ratio of 0.30 to 0.50, and a microstrength of 7 to 17% by mass To provide a method.
- the fifth embodiment according to the present invention provides a lithium ion secondary battery using the graphite material obtained by this production method as a negative electrode material.
- the sixth form according to the present invention is obtained by coking a heavy oil composition by a delayed coking process, and H / C, which is an atomic ratio of hydrogen atom H to carbon atom C, is 0.30 to 0.00. And a raw coal composition having a micro strength of 7% by mass to 17% by mass and an average particle size of 0.1 to 10% by mass with respect to the raw material coal composition of 0.1 ⁇ m to 3.
- a seventh aspect according to the present invention is a lithium ion secondary battery including, as a negative electrode material, a graphite material produced by the production method of the sixth aspect.
- the eighth form according to the present invention is obtained by coking a heavy oil composition by a delayed coking process, and H / C, which is an atomic ratio of hydrogen atom H to carbon atom C, is 0.30 to 0.00. 50, and a mixture of a raw coal composition having a micro strength of 7% by mass to 17% by mass and 0.5% by mass to 10% by mass of acetylene black with respect to the raw coal composition Applying stress, obtaining a composite powder in which the acetylene black is embedded in the surface of the raw carbon composition, heating the composite powder to obtain carbide, and heating the carbide to produce graphite.
- a graphite material having a crystallite size of Lc (112) of 4 to 30 nm as a crystallite size of (112) diffraction line measured by an X-ray wide angle diffraction method is a lithium ion secondary battery including, as a negative electrode material, a graphite material manufactured by the manufacturing method according to the eighth aspect.
- the graphite material of the present invention can suppress the capacity deterioration of a lithium secondary battery and can provide a negative electrode material for a lithium secondary battery having high reliability. And the graphite material obtained by the manufacturing method of this invention can suppress the fall of the capacity
- the present inventors have H / C, which is an atomic ratio between hydrogen atom H and carbon atom C, obtained by coking the heavy oil composition by a delayed coking process, and is 0.30 to 0.50,
- the raw coal composition having a micro strength of 7% by mass to 17% by mass is pulverized and classified to obtain particles of the raw coal composition, and then the raw coal composition and the average particle size of 0.1 ⁇ m to 3.0 ⁇ m.
- the calcined coke is mixed with the raw coal composition at a ratio of 0.5 mass% to 10 mass%, and a compressive shear stress is applied to the particle surface of the raw coal composition.
- the composite powder was carbonized and graphitized to obtain a graphite material for a negative electrode of a lithium ion secondary battery.
- a graphite material having a structure in which a region with low crystallinity is partially introduced into a highly developed crystal structure and having few edge portions exposed on the particle surface. is there. Therefore, when the graphite material obtained by the production method of the present invention is used as a negative electrode material for a lithium ion secondary battery, it is possible to obtain a lithium ion secondary battery having excellent life characteristics, in which decomposition of the electrolyte is suppressed. It is.
- the inventors of the present invention have an H / C ratio of 0.30 to 0.50, which is an atomic ratio between hydrogen atoms H and carbon atoms C, obtained by coking the heavy oil composition by a delayed coking process.
- the raw coal composition having a micro strength of 7% by mass to 17% by mass is pulverized and classified to obtain particles of the raw coal composition, 0% of the raw coal composition and the raw coal composition
- the composite powder is obtained by mixing 5 mass% to 10 mass% of acetylene black and applying compressive shear stress to obtain a composite powder in which acetylene black is embedded on the surface of the raw carbon composition.
- the body was carbonized and graphitized to obtain a graphite material for a negative electrode of a lithium ion secondary battery.
- the production method of the present invention it is possible to obtain a graphite material having a structure in which a region with low crystallinity is partially introduced into a highly developed crystal structure and having few edge portions exposed on the particle surface. is there. Therefore, when the graphite material obtained by the production method of the present invention is used as a negative electrode material for a lithium ion secondary battery, it is possible to obtain a lithium ion secondary battery having excellent life characteristics, in which decomposition of the electrolyte is suppressed. It is.
- the crystallite size Lc (112) of the (112) diffraction line measured by the X-ray wide angle diffraction method is 4 nm or more.
- the reason why the thickness is 4 nm or more is that the graphite material with such highly developed crystals can secure a reversible capacity of 340 mAh / g or more. This is because the negative electrode material used for this type of battery is used. This is exactly the same as the reason why materials with highly developed crystals are preferably used.
- the raw carbon composition used for forming the graphite material of the present invention has a ratio of hydrogen atoms H to carbon atoms C, an H / C atomic ratio of 0.30 to 0.50, and a micro strength of 7 to 17. % By mass.
- a raw material carbon composition having such physical properties as a raw material a graphite material having a very small crystallite edge in the graphitized particle surface layer (the crystal surface in the graphitized particle surface layer has little crystal disorder) is obtained. be able to.
- the disorder of the crystal structure of the particle surface layer described in Patent Document 2 can improve the initial charge and discharge efficiency of the negative electrode, but there is a problem of capacity deterioration, and the reliability of the battery thereafter This is because there is a drawback that it cannot be improved.
- H / C of the raw coal composition is a ratio of the value obtained by dividing the total hydrogen content (TH (mass%)) by the atomic weight of hydrogen and the value obtained by dividing the total carbon content (TC (mass%)) by the atomic weight of carbon. It is.
- the total hydrogen is measured by completely burning the sample in an oxygen stream at 750 ° C. and determining the amount of water generated from the combustion gas by the coulometric titration method (Karl Fischer method).
- Karl Fischer method an electrolyte containing iodide ions, sulfur dioxide, base (RN) and alcohol as main components is placed in the titration cell in advance, and the sample is placed in the titration cell. Moisture reacts as shown in the following formula (4).
- a sample is measured, for example after cooling in a dry atmosphere after a caulking process.
- the iodine necessary for this reaction can be obtained by electrochemically reacting iodide ions (two-electron reaction) as shown in the following formula (5).
- the constant 96478 is the Faraday constant, and 18.5513 is the molecular weight of water.
- the amount of water can be determined. Furthermore, it converts into the amount of hydrogen from the obtained moisture content, and remove
- the total carbon was measured by burning the sample in an oxygen stream at 1150 ° C., converted into carbon dioxide (partially carbon monoxide), transported to an excess oxygen stream, and CO 2 + CO infrared detector, TC (mass%) is calculated.
- Micro strength is as follows: 2 g of 20-30 mesh sample and 12 steel balls of 5/16 inch (7.9 mm) in diameter are placed in a steel cylinder (inner diameter 25.4 mm, length 304.8 mm), and the vertical surface is a tube. After rotating at a right angle of 800 rpm at 25 rpm (that is, rotating the axis horizontally so that the top and bottom are switched from the upright position, rotating as if the propeller is rotating), sifting with 48 mesh, It is the value which showed the mass on a sieve in percent.
- the raw coal composition having an H / C atomic ratio of 0.30 to 0.50 is pulverized and classified so as to have a predetermined particle size, and a compressive stress and a shear stress are applied, the raw coal composition is constituted.
- An appropriately sized hexagonal mesh plane is particularly preferred because it is oriented so that no crystallite edges appear on the particle surface.
- the hexagonal mesh plane is easily oriented perpendicular to the stress application direction, it is possible to realize a state in which the particle surface is covered with the hexagonal mesh plane, and the crystallite edge located in the vertical direction of the hexagonal mesh plane is Since it becomes difficult to exist on the particle surface, the crystallite edge existing on the surface of the particle after graphitization is extremely small, and it becomes possible to extremely reduce unstructured carbon which causes a decrease in battery reliability.
- the anisotropy refers to a property that the region of the hexagonal mesh plane and the region of the crystallite edge are easily separated on the particle surface. In such a case, there is a region where crystallite edges are gathered on the particle surface, so even if compressive stress and shear stress are subsequently applied to the particle, the orientation of the hexagonal mesh plane on the particle surface is promoted. I can't let you.
- graphitized in such a particle state the crystallite edge is easily exposed on the surface, which is not preferable because it causes a decrease in the reliability of the battery.
- the H / C of the raw coal composition is limited to 0.30 to 0.50.
- the raw carbon composition having physical properties within this range is pulverized and classified so as to have a predetermined particle size, and by applying compressive stress and shear stress, the particle surface after graphitization has very few crystallite edges. The state can be realized.
- the micro strength of the raw coal composition is 7 to 17% by mass. This micro strength is an index indicating the bond strength between adjacent crystallites.
- unstructured carbon having a structure other than a benzene ring serving as a structural unit of a hexagonal network plane exists between adjacent crystallites, and has a function of bonding the adjacent crystallites. This unstructured carbon remains even after the raw coal composition is carbonized and / or graphitized, and plays a similar role.
- the micro strength of the raw coal composition is less than 7% by mass, it means that the bond strength between adjacent crystallites is extremely weak.
- a raw coal composition is pulverized and classified so as to have a predetermined particle size, and given compressive stress and shear stress, as described above, an appropriately sized hexagonal mesh plane constituting the raw coal composition, Since orientation is performed so that crystallite edges do not appear on the particle surface, a preferable structure is realized as a state of the raw coal composition.
- the bond between crystallites is weak, so the structure of the particle surface of the raw coal composition cannot be maintained, and the particle shape after graphitization becomes highly anisotropic.
- the edge is easily exposed on the particle surface, which is not preferable. This is because the bond between crystallites in the state of the raw coal composition is weaker than the stress accompanying the development of crystallites by graphitization.
- Unstructured carbon refers to carbon that is not incorporated into the carbon hexagonal network plane, and its characteristics are that the carbon hexagon gradually increases with increasing processing temperature while interfering with the growth and selective orientation of adjacent carbon crystallites. It is a carbon atom that is incorporated into the mesh plane. Even if such a raw carbon composition is pulverized and classified so as to have a predetermined particle size and a compressive stress and a shear stress are applied, the hexagonal mesh plane is not easily oriented on the particle surface, which is not preferable.
- the micro strength of the raw coal composition is limited to 7 to 17% by mass.
- the raw material carbon composition having physical properties within this range is pulverized and classified, and a compressive stress and a shear stress are applied, a state in which an appropriately sized hexagonal mesh plane is oriented on the particle surface is carbonized and / or It can be maintained after graphitization.
- a graphite material having extremely small crystallite edges on the particle surface after graphitization the crystal surface on the particle surface after graphitization is less disturbed by crystals.
- such a carbon material is used for the negative electrode of a lithium ion secondary battery, it becomes possible to ensure extremely high reliability.
- the raw coal composition having an H / C atomic ratio of 0.30 to 0.50 and a micro strength of 7 to 17% by mass is pulverized and classified so as to have a predetermined particle size, and compressive stress and shearing are obtained.
- crystallites of an appropriate size are oriented so that a hexagonal network plane is located on the particle surface, and the surface structure can be maintained even if carbonized and / or graphitized thereafter.
- the present invention can provide a desired graphite material after mixing desulfurized and desulfurized oil as a preferred embodiment of the raw material oil composition to obtain a raw material charcoal composition having a predetermined H / C atomic ratio and micro strength.
- the raw coal composition used in the present invention can be obtained by coking a heavy oil composition by a delayed coking process.
- Components of heavy oil composition include bottom oil of fluid catalytic cracking equipment (fluid catalytic cracking residual oil, FCC DO), aromatics extracted from fluid catalytic cracking residual oil, and advanced hydrodesulfurization treatment for heavy oil Hydrodesulfurized oil, vacuum residue (VR), desulfurized desulfurized oil, coal liquefied oil, coal solvent extract oil, atmospheric residual oil, shell oil, tar sand bitumen, naphtha tar pitch, ethylene bottom oil Coal tar pitch and heavy oil obtained by hydrorefining these.
- FCC DO fluid catalytic cracking residual oil
- VR vacuum residue
- desulfurized desulfurized oil coal liquefied oil
- coal solvent extract oil atmospheric residual oil, shell oil, tar sand bitumen, naphtha tar pitch, ethylene bottom oil Coal tar pitch and heavy oil obtained by hydrorefining these.
- the physical property of the raw coal composition obtained after coking treatment by a delayed coking process has an H / C atomic ratio of 0.30 to What is necessary is just to adjust a compounding ratio suitably according to the property of the raw material oil to be used so that it may become 0.50 and micro strength may be 7-17 mass%.
- the properties of the raw material oil vary depending on the type of crude oil and the processing conditions until the raw material oil is obtained from the crude oil.
- the bottom oil of the fluid catalytic cracking unit is a bottom of the fluidized bed type fluid catalytic cracking unit that uses a vacuum gas oil as a raw material oil and selectively performs a cracking reaction using a catalyst to obtain a high octane FCC gasoline.
- Oil used as the raw material oil is preferably a desulfurized vacuum gas oil obtained by directly desulfurizing atmospheric distillation residue oil (preferably a sulfur content of 500 mass ppm or less, a density of 0.8 / cm 3 or more at 15 ° C. ).
- the aromatic content extracted from the fluid catalytic cracking residual oil is the aromatic content when selectively extracted using dimethylformamide or the like and separated into an aromatic content and a saturated content.
- Hydrodesulfurized oil obtained by subjecting heavy oil to advanced hydrodesulfurization treatment is, for example, sulfur content obtained by hydrodesulfurization treatment of heavy oil having a sulfur content of 1% by mass or more at a hydrogen partial pressure of 10 MPa or more. It is a heavy oil with 0% by mass or less, nitrogen content of 0.5% by mass or less, and aromatic carbon fraction (fa) of 0.1 or more.
- the hydrodesulfurized oil is preferably a hydrodesulfurized oil obtained by hydrodesulfurizing an atmospheric distillation residue in the presence of a catalyst so that the hydrocracking rate is 25% or less.
- the vacuum residue (VR) is obtained by subjecting crude oil to an atmospheric distillation apparatus to obtain gas, light oil, and atmospheric residue, and then removing the atmospheric residue from the heating furnace at a reduced pressure of 10 to 30 Torr, for example.
- This is a bottom oil of a vacuum distillation apparatus obtained by changing the temperature in the range of 320 to 360 ° C.
- Desulfurized desulfurized oil is obtained by, for example, treating oil such as vacuum distillation residue oil with a solvent desulfurization apparatus using propane, butane, pentane, or a mixture thereof as a solvent, and removing the asphaltenes.
- desulfurized oil is preferably desulfurized using an indirect desulfurization apparatus (Isomax) or the like to a sulfur content of 0.05 to 0.40 mass%.
- Atmospheric residual oil is obtained by subjecting crude oil to an atmospheric distillation apparatus, for example, heating under normal pressure, and depending on the boiling point of the contained fraction, gas / LPG, gasoline fraction, kerosene fraction, light oil fraction, ordinary oil fraction, One of the fractions obtained when divided into pressure residue oil, the fraction with the highest boiling point.
- the heating temperature varies depending on the production area of the crude oil and is not limited as long as it can be fractionated into these fractions. For example, the crude oil is heated to 320 ° C.
- Examples of particularly preferred heavy oil compositions include (1) aromatic fraction (aromatic index) fa of 0.3 to 0.65, and (2) normal paraffin content of 5 to 20% by mass. And (3) a heavy oil composition satisfying the three conditions of containing desulfurized dewaxed oil in the range of 7 to 15% by mass.
- a heavy oil component that produces a good bulk mesophase and (2) when the bulk mesophase is polycondensed and carbonized and solidified, the size of the hexagonal mesh plane laminate constituting the mesophase is It is particularly preferable to use a raw oil composition containing a heavy oil component capable of generating a gas having a function of limiting to a small size, and (3) a component that binds the cut hexagonal mesh plane laminates together.
- a heavy oil component that produces a good bulk mesophase is a component that gives an aromatic index fa of 0.3 to 0.65
- a heavy oil component that can generate gas contains normal paraffin It is a component corresponding to 5 to 20% by mass of the ratio
- a desulfurized dewaxed oil containing a component for bonding hexagonal net plane laminates in the range of 7 to 15% by mass is preferably used as a raw material of the raw coal composition of the present invention.
- the hexagonal mesh plane formed by the heavy oil component that produces a good bulk mesophase is relatively small.
- desulfurization and desulfurization oils combine adjacent hexagonal mesh plane laminates appropriately. It is because it makes it.
- the aromatic carbon fraction (aromatic index) (fa) can be determined by the Knight method.
- the carbon distribution is divided into three components (A 1 , A 2 , A 3 ) as an aromatic carbon spectrum by the 13 C-NMR method.
- a 1 is the number of carbon atoms inside the aromatic ring, half of the substituted aromatic carbon and half of the unsubstituted aromatic carbon (corresponding to a peak of about 40-60 ppm of 13 C-NMR), and A 2 is substituted
- the remaining half of the aromatic carbon corresponding to about 60-80 ppm peak of 13 C-NMR
- a 3 is the number of aliphatic carbon (corresponding to about 130-190 ppm peak of 13 C-NMR)
- the 13 C-NMR method is the best method for quantitatively determining fa, which is the most basic amount of chemical structural parameters of pitches, as described in the literature ("Pitch Characterization II. Chemical Structure” Yokono, Sanada, (Carbon, 1981 (No. 105), p73-81).
- the content of normal paraffin in the raw oil composition means a value measured by a gas chromatograph equipped with a capillary column. Specifically, after testing with a normal paraffin standard substance, the sample of the non-aromatic component separated by the elution chromatography method is passed through a capillary column and measured. The content based on the total mass of the feedstock composition can be calculated from this measured value.
- the aromatic index fa of the heavy oil composition When the aromatic index fa of the heavy oil composition is less than 0.3, the yield of coke from the heavy oil composition becomes extremely low, and a good bulk mesophase cannot be formed. Even if graphitized, it is difficult to develop a crystal structure. If it exceeds 0.65, a large number of mesophases are generated abruptly in the matrix in the production process of raw coke, and abrupt coalescence of mesophases is mainly repeated rather than single growth of mesophases. For this reason, the rate of coalescence of the mesophases is faster than the rate of gas generation due to the normal paraffin-containing component, which makes it impossible to limit the hexagonal mesh plane of the bulk mesophase to a small size.
- the aromatic index fa of the heavy oil composition is particularly preferably in the range of 0.3 to 0.65.
- fa can be calculated from the density D and the viscosity V of the heavy oil composition.
- the density D is 0.91 to 1.02 g / cm 3 and the viscosity V is 10 to 220 mm 2 / sec.
- Particularly preferred are heavy oil compositions having a fa of 0.3 to 0.65.
- the normal paraffin component appropriately contained in the heavy oil composition plays an important role in limiting the size of the bulk mesophase to a small size by generating gas during the coking process. .
- This gas generation also has a function of uniaxially orienting adjacent mesophases limited to a small size and selectively orienting the entire system.
- the content of the normal paraffin-containing component is less than 5% by mass, the mesophase grows more than necessary and a huge carbon hexagonal plane is formed, which is not preferable.
- gas generation from normal paraffin becomes excessive, and it tends to work in a direction that disturbs the orientation of the bulk mesophase.
- the normal paraffin content is particularly preferably in the range of 5 to 20% by mass.
- the desulfurized dewaxed oil plays a role of appropriately bonding adjacent hexagonal net plane laminates, but the content in the heavy oil composition is in the range of 7 to 15% by mass. It is particularly preferred. When it is less than 7% by mass, or when it exceeds 15% by mass, the micro strength of the heavy oil composition obtained after coking is less than 7% by mass or may exceed 17% by mass, which is not preferable. .
- the heavy oil composition include a heavy oil composition containing two or more kinds selected from the group consisting of hydrodesulfurized oil, fluid catalytic cracking residual oil, and desulfurized dewaxed oil.
- the hydrodesulfurized oil and the fluid catalytic cracking residual oil are contained in a mass ratio of preferably 1: 3 to 1: 5, and further desulfurized dewaxed oil is contained in an amount of 7 to 15% by mass (a composition containing desulfurized dewaxed oil).
- Heavy oil composition containing 100% by mass in total).
- the heavy oil composition having such characteristics is coked to form the raw coal composition of the present invention.
- a delayed coking method is preferable. More specifically, a method is preferred in which raw coke is obtained by heat-treating the raw oil composition with a delayed coker under conditions where the coking pressure is controlled.
- preferable operating conditions of the delayed coker are a pressure of 0.1 to 0.8 MPa and a temperature of 400 to 600 ° C. The reason why a preferable range is set for the operating pressure of the coker is that the release rate of the gas generated from the component containing normal paraffin to the outside of the system can be limited by the pressure.
- the residence time of the generated gas in the system is an important control for determining the size of the hexagonal mesh plane. It becomes a parameter.
- the reason why a preferable range is set for the operating temperature of the coker is that the temperature is necessary for growing the mesophase from the heavy oil adjusted to obtain the effect of the present invention.
- the raw coal composition thus obtained is pulverized and classified so as to have a predetermined particle size.
- the average particle size is preferably pulverized to 30 ⁇ m or less, more preferably 5 to 30 ⁇ m. This is because the particle size is generally and preferably used as a negative electrode carbon material for lithium ion secondary batteries.
- the average particle size is based on measurement by a laser diffraction particle size distribution analyzer.
- the graphite material of the present invention is obtained by heating (carbonizing and / or graphitizing) the graphite precursor obtained by applying compressive stress and shear stress to the pulverized and classified raw carbon composition. It is done. At this time, in addition to compressive stress and shear stress, collision, friction, shear stress and the like are also generated. The mechanical energy given by these stresses is larger than the energy obtained by general agitation. By applying these energy to the particle surface, the mechanochemical phenomenon such as the spheroidization of particles and the compounding of particles The effect called is expressed.
- a device capable of simultaneously applying stress such as shearing, compression, collision, etc., which is limited to the structure and principle of the device. It is not something.
- a ball-type kneader such as a rotary ball mill, a wheel-type kneader such as an edge runner, a hybridization system (manufactured by Nara Machinery Co., Ltd.), Mechano-Fusion (manufactured by Hosokawa Micron), Nobilta (manufactured by Hosokawa Micron), COMPOSI (Japan) Coke industry).
- the manufacturing conditions in the process of applying compressive stress and shear stress vary depending on the apparatus to be used. For example, as shown in FIG. 4, the gap between the rotating blade blade 31 (rotation direction R1) 31 and the housing 32 is reduced.
- the peripheral speed of the blade is 5 to 100 m / s
- the gap between the two is 2 to 20 mm
- the processing time is 5 to 120 minutes. be able to.
- the peripheral speed is particularly preferably 20 to 80 m / s. When the peripheral speed is 20 m / s or less, the spheroidizing effect is weak, and when it exceeds 80 m / s, there is a problem in scaling up to a large machine.
- the peripheral speed difference between the blade and the housing may be 5 to 100 m / s, preferably 20 to 80 m / s.
- a graphite precursor having a higher sphericity can be obtained by performing the control at a treatment temperature of preferably 60 to 250 ° C. In particular, it is desirable to operate at a control temperature of 120 to 200 ° C. during processing.
- a uniform stress is easily applied to the particle surface, and a moderately sized hexagonal mesh plane is perpendicular to the applied stress on the particle surface.
- Selectively oriented in the direction since the raw material carbon composition in this application can realize this selective orientation, it becomes difficult to expose the crystallite edge on the particle surface after graphitization, and it becomes possible to improve the reliability as a negative electrode. .
- the surface treatment that applies compressive stress and shear stress to the particles of the raw coal composition is a process in which the corners of the particles are sharpened, but the sharpened portion instantly adheres to the particles and rounds the particles. It is better to carry out with almost no change. Therefore, it is not pulverization that generates fine powder and reduces the particle size.
- the raw coal composition has adhesiveness because it contains a volatile component, but this adhesiveness preferably works because it facilitates that the shaved portion adheres to the particles instantaneously.
- the graphite precursor obtained by applying compressive stress and shear stress to the raw carbon composition has a crystallite size Lc (112) of (112) diffraction line measured by X-ray wide angle diffraction method of 4 nm or more.
- the method of graphitization treatment is not particularly limited.
- the carbonization (preliminary) is performed in an inert gas atmosphere such as nitrogen, argon or helium with a maximum temperature of 900-1500 ° C. and a maximum temperature holding time of 0-10 hours. And then a heat treatment in a similar inert gas atmosphere at a maximum temperature of 2500 to 3200 ° C. and a maximum temperature holding time of 0 to 100 hours. After graphitization, it can be used as a negative electrode of a lithium ion secondary battery.
- the method for producing a negative electrode for a lithium secondary battery is not particularly limited.
- a graphite material to which the invention according to the present application is applied a binder (binder), a conductive assistant as required, and a mixture containing an organic solvent.
- a method in which (negative electrode mixture) is pressure-molded to a predetermined size is exemplified.
- a graphite material to which the invention according to the present application is applied, a binder (binder), a conductive auxiliary agent and the like are kneaded and slurried in an organic solvent, and the slurry is used as a current collector such as a copper foil.
- a method of rolling a coated and dried product (negative electrode mixture) and cutting it into a predetermined size can also be mentioned.
- binder examples include polyvinylidene fluoride, polytetrafluoroethylene, and SBR (styrene-butadiene rubber).
- the content of the binder in the negative electrode mixture may be appropriately set as necessary in terms of battery design from about 1 to 30 parts by mass with respect to 100 parts by mass of the carbon material.
- the conductive assistant examples include carbon black, graphite, acetylene black, conductive indium-tin oxide, or conductive polymers such as polyaniline, polythiophene, and polyphenylene vinylene.
- the amount of the conductive aid used is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the carbon material.
- the organic solvent examples include dimethylformamide, N-methylpyrrolidone, isopropanol, toluene and the like.
- the carbon material, the binder, and, if necessary, the conductive aid and the organic solvent known devices such as a screw type kneader, a ribbon mixer, a universal mixer, a planetary mixer and the like can be used.
- the mixture is formed by roll pressing or press pressing, and the pressure at this time is preferably about 100 to 300 MPa.
- the material of the current collector can be used without any limitation as long as it does not form an alloy with lithium.
- copper, nickel, titanium, stainless steel, etc. can be mentioned.
- the shape of the current collector can be used without any particular limitation, but as an example, a belt-like shape in the form of foil, perforated foil, mesh, or the like can be given.
- a porous material such as porous metal (foamed metal) or carbon paper can also be used.
- the method of applying the slurry to the current collector is not particularly limited, for example, metal mask printing method, electrostatic coating method, dip coating method, spray coating method, roll coating method, doctor blade method, gravure coating method, Known methods such as a screen printing method and a die coater method can be used. After coating, it is common to perform a rolling process using a flat plate press, a calender roll, or the like as necessary. Further, the integration of the negative electrode material slurry formed into a sheet shape, a pellet shape, and the like with the current collector can be performed by a known method such as a roll, a press, or a combination thereof.
- the lithium secondary battery using the graphite material for the negative electrode of the lithium ion secondary battery according to the present embodiment is disposed, for example, so that the negative electrode and the positive electrode manufactured as described above face each other with a separator interposed therebetween. It can be obtained by injecting a liquid.
- the active material used for the positive electrode is not particularly limited. For example, a metal compound, metal oxide, metal sulfide, or conductive polymer material that can be doped or intercalated with lithium ions may be used.
- lithium cobaltate LiCoO 2
- lithium nickelate LiNiO 2
- lithium manganate LiMn 2 O 4
- lithium vanadium compound V 2 O 5, V 6 O 13, VO 2, MnO 2, TiO 2, MoV 2 O 8, TiS 2, V 2 S 5, VS 2, MoS 2, MoS 3, Cr 3 O 8, Cr 2 O 5, olivine-type LiMPO 4 (M: Co, Ni , Mn, Fe), polyacetylene, polyaniline, polypyrrole Polythiophene, mention may be made of conductive polymers such as polyacene, porous carbon or the like and mixtures thereof.
- the separator for example, a nonwoven fabric, a cloth, a microporous film, or a combination thereof, which is mainly composed of polyolefin such as polyethylene or polypropylene, can be used.
- a separator when it is set as the structure where the positive electrode and negative electrode of the lithium ion secondary battery to produce are not in direct contact, it is not necessary to use a separator.
- an electrolytic solution and an electrolyte used for the lithium secondary battery known organic electrolytic solutions, inorganic solid electrolytes, and polymer solid electrolytes can be used.
- an organic electrolyte is preferable from the viewpoint of electrical conductivity.
- organic electrolyte examples include dibutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, ethylene glycol phenyl ether, and other ethers, N-methylformamide, N, N-dimethylformamide, N Amides such as ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, sulfur-containing compounds such as dimethylsulfoxide and sulfolane, methyl ethyl ketone, Dialkyl ketones such as methyl isobutyl ketone, cyclic ethers such as tetrahydrofuran and 2-methoxytetrahydrofuran, ethylene carbonate Cyclic carbonates such as butylene carbonate, propylene carbonate and vinyl
- lithium salts can be used as the solute of these solvents.
- Commonly known lithium salts include LiClO 4 , LiBF 4 , LiPF 6 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCl, LiCF 3 SO 3 , LiCF 3 CO 2 , LiN (CF 3 SO 2 ) 2, LiN (C 2 F 5 SO 2 ) 2 and the like.
- polymer solid electrolyte examples include a polyethylene oxide derivative and a polymer containing the derivative, a polypropylene oxide derivative and a polymer containing the derivative, a phosphate ester polymer, a polycarbonate derivative and a polymer containing the derivative. There are no restrictions on the selection of members other than those described above necessary for the battery configuration.
- the structure of the lithium ion secondary battery is not particularly limited, a wound electrode group in which a positive electrode and a negative electrode formed in a strip shape are wound in a spiral shape through a separator is inserted into a battery case and sealed.
- a structure in which a laminated electrode plate group in which a positive electrode and a negative electrode formed in a flat plate shape are sequentially laminated via a separator is enclosed in an exterior body.
- the lithium secondary battery is used as, for example, a paper-type battery, a button-type battery, a coin-type battery, a stacked battery, a cylindrical battery, a rectangular battery, or the like.
- the raw carbon composition used for forming the graphite material of the present invention has a ratio of hydrogen atoms H to carbon atoms C, an H / C atomic ratio of 0.30 to 0.50, and a micro strength of 7 to 17. % By mass.
- the graphite particles obtained by carbonizing and graphitizing the powder of the raw coal composition obtained by pulverizing and classifying the raw coal composition having such physical properties have an appropriate void volume inside, What has moderate bond strength between crystallites can be obtained.
- a void here is a gap formed between adjacent crystallites in a graphite particle, and these gaps are uniformly dispersed inside the particle.
- H / C of the raw coal composition is a value obtained by dividing the total hydrogen content (TH (mass%)) by the atomic weight of hydrogen and a value obtained by dividing the total carbon content (TC (mass%)) by the atomic weight of carbon. It is a ratio.
- the total hydrogen is measured by completely burning the sample in an oxygen stream at 750 ° C. and determining the amount of water generated from the combustion gas by the coulometric titration method (Karl Fischer method).
- Karl Fischer method an electrolyte containing iodide ions, sulfur dioxide, base (RN) and alcohol as main components is placed in the titration cell in advance, and the sample is placed in the titration cell. Moisture reacts as shown in the following formula (4).
- a sample is measured, for example after cooling in a dry atmosphere after a caulking process.
- the iodine necessary for this reaction can be obtained by electrochemically reacting iodide ions (two-electron reaction) as shown in the following formula (5).
- the constant 96478 is the Faraday constant, and 18.5513 is the molecular weight of water.
- the amount of water can be determined. Furthermore, it converts into the amount of hydrogen from the obtained moisture content, and remove
- the total carbon was measured by burning the sample in an oxygen stream at 1150 ° C., converted into carbon dioxide (partially carbon monoxide), transported to an excess oxygen stream, and CO 2 + CO infrared detector, TC (mass%) is calculated.
- the H / C atomic ratio of the raw coal composition mainly affects the size of the void volume in the graphite particles obtained by graphitizing the raw coal composition.
- the H / C atomic ratio of the raw coal composition is less than 0.30, the spread of the hexagonal mesh plane constituting the raw coal composition is large, so the raw coal composition having such physical properties is pulverized and classified.
- the void volume is small. Since the void volume is too small, the mechanical energy due to the compressive shear stress cannot be absorbed sufficiently by the voids present in the vicinity of the particle surface, so the energy imparted to the graphite particles acts directly on the hexagonal mesh plane constituting the crystallite. . Therefore, the carbon-carbon bond on the hexagonal network surface of the graphite particle surface is cut, and it is considered that dangling bonds exposed on the particle surface also increase.
- the H / C atomic ratio in the raw coal composition exceeds 0.50, the amount of carbon atoms in the raw coal composition is small and the hexagonal mesh plane is small.
- the graphite particles obtained by carbonizing and graphitizing the powder of the raw material carbon composition obtained by pulverization and classification have a large void volume. Since the void volume is too large, mechanical energy due to compressive shear stress tends to concentrate on the void, and the bonds between crystallites present in the void are broken, so that the edge surface with dangling bonds is exposed on the cut surface. I think that.
- the H / C of the raw coal composition is limited to 0.30 to 0.50.
- a raw material coal composition having physical properties within this range is pulverized and classified to a predetermined particle size to obtain a raw material carbon composition powder, which is then carbonized and graphitized to give compressive shear stress to the graphite particles.
- Micro strength is as follows: 2 g of 20-30 mesh sample and 12 steel balls of 5/16 inch (7.9 mm) in diameter are placed in a steel cylinder (inner diameter 25.4 mm, length 304.8 mm), and the vertical surface is a tube. After rotating at a right angle of 800 rpm at 25 rpm (that is, rotating the axis horizontally so that the top and bottom are switched from the upright position, rotating as if the propeller is rotating), sifting with 48 mesh, It is the value which showed the mass on a sieve in percent.
- the micro strength of the raw coal composition is 7 to 17% by mass. This micro strength is an index indicating the strength of the bond between adjacent crystallites. Here, it is the unstructured carbon present in the voids in the graphite particles that bears the function of intercrystallite bonding. These unstructured carbons remain after the raw coal composition is carbonized and graphitized, and play a similar role.
- the micro strength of the raw coal composition is limited to 7 to 17% by mass.
- a raw carbon composition having physical properties within this range is pulverized and classified, and compression shear stress is applied to the graphite particles that have undergone the carbonization / graphitization process, the relative position between adjacent crystallites on the particle surface changes. It is possible to obtain a graphite material in which disorder of the crystal structure is introduced and the edge surface exposed to the particle surface is extremely small.
- the raw coal composition used in the present invention can be obtained by coking a heavy oil composition by a delayed coking process.
- Components of heavy oil composition include bottom oil of fluid catalytic cracking equipment (fluid catalytic cracking residual oil, FCC DO), aromatics extracted from fluid catalytic cracking residual oil, and advanced hydrodesulfurization treatment for heavy oil Hydrodesulfurized oil, vacuum residue (VR), desulfurized desulfurized oil, coal liquefied oil, coal solvent extract oil, atmospheric residual oil, shell oil, tar sand bitumen, naphtha tar pitch, ethylene bottom oil Coal tar pitch and heavy oil obtained by hydrorefining these.
- FCC DO fluid catalytic cracking residual oil
- VR vacuum residue
- desulfurized desulfurized oil coal liquefied oil
- coal solvent extract oil atmospheric residual oil, shell oil, tar sand bitumen, naphtha tar pitch, ethylene bottom oil Coal tar pitch and heavy oil obtained by hydrorefining these.
- the physical property of the raw coal composition obtained after coking treatment by a delayed coking process has an H / C atomic ratio of 0.30 to What is necessary is just to adjust a compounding ratio suitably according to the property of the raw material oil to be used so that it may become 0.50 and micro strength may be 7-17 mass%.
- the properties of the raw material oil vary depending on the type of crude oil and the processing conditions until the raw material oil is obtained from the crude oil.
- the bottom oil of the fluid catalytic cracking unit is a bottom of the fluidized bed type fluid catalytic cracking unit that uses a vacuum gas oil as a raw material oil and selectively performs a cracking reaction using a catalyst to obtain a high octane FCC gasoline.
- Oil used as the raw material oil is preferably a desulfurized vacuum gas oil obtained by directly desulfurizing atmospheric distillation residue oil (preferably a sulfur content of 500 mass ppm or less, a density of 0.8 / cm 3 or more at 15 ° C. ).
- the aromatic content extracted from the fluid catalytic cracking residual oil is the aromatic content when selectively extracted using dimethylformamide or the like and separated into an aromatic content and a saturated content.
- Hydrodesulfurized oil obtained by subjecting heavy oil to advanced hydrodesulfurization treatment is, for example, sulfur content obtained by hydrodesulfurization treatment of heavy oil having a sulfur content of 1% by mass or more at a hydrogen partial pressure of 10 MPa or more. It is a heavy oil with 0% by mass or less, nitrogen content of 0.5% by mass or less, and aromatic carbon fraction (fa) of 0.1 or more.
- the hydrodesulfurized oil is preferably a hydrodesulfurized oil obtained by hydrodesulfurizing an atmospheric distillation residue in the presence of a catalyst so that the hydrocracking rate is 25% or less.
- the vacuum residue (VR) is obtained by subjecting crude oil to an atmospheric distillation apparatus to obtain gas, light oil, and atmospheric residue, and then removing the atmospheric residue from the heating furnace at a reduced pressure of 10 to 30 Torr, for example.
- This is a bottom oil of a vacuum distillation apparatus obtained by changing the temperature in the range of 320 to 360 ° C.
- Desulfurized desulfurized oil is obtained by, for example, treating oil such as vacuum distillation residue oil with a solvent desulfurization apparatus using propane, butane, pentane, or a mixture thereof as a solvent, and removing the asphaltenes.
- desulfurized oil is preferably desulfurized using an indirect desulfurization apparatus (Isomax) or the like to a sulfur content of 0.05 to 0.40 mass%.
- Atmospheric residual oil is obtained by subjecting crude oil to an atmospheric distillation apparatus, for example, heating under normal pressure, and depending on the boiling point of the contained fraction, gas / LPG, gasoline fraction, kerosene fraction, light oil fraction, ordinary oil fraction, One of the fractions obtained when divided into pressure residue oil, the fraction with the highest boiling point.
- the heating temperature varies depending on the production area of the crude oil and is not limited as long as it can be fractionated into these fractions. For example, the crude oil is heated to 320 ° C.
- Examples of particularly preferred heavy oil compositions include (1) aromatic fraction (aromatic index) fa of 0.3 to 0.65, and (2) normal paraffin content of 5 to 20% by mass. And (3) a heavy oil composition satisfying the three conditions of containing desulfurized dewaxed oil in the range of 7 to 15% by mass.
- the hydrodesulfurized oil and the fluid catalytic cracking residual oil are contained in a mass ratio of preferably 1: 3 to 1: 5, and further desulfurized dewaxed oil is contained in an amount of 7 to 15% by mass (a composition containing desulfurized dewaxed oil).
- Heavy oil composition containing 100% by mass in total).
- a heavy oil component that produces a good bulk mesophase is a component that gives an aromatic index fa of 0.3 to 0.65
- a heavy oil component that can generate gas contains normal paraffin It is a component corresponding to 5 to 20% by mass of the ratio
- a desulfurized dewaxed oil containing a component for bonding hexagonal net plane laminates in the range of 7 to 15% by mass is a component that gives an aromatic index fa of 0.3 to 0.65
- a heavy oil component that can generate gas contains normal paraffin It is a component corresponding to 5 to 20% by mass of the ratio
- a desulfurized dewaxed oil containing a component for bonding hexagonal net plane laminates in the range of 7 to 15% by mass.
- the aromatic carbon fraction (aromatic index) (fa) can be determined by the Knight method.
- the carbon distribution is divided into three components (A 1 , A 2 , A 3 ) as an aromatic carbon spectrum by the 13 C-NMR method.
- a 1 is the number of carbon atoms inside the aromatic ring, half of the substituted aromatic carbon and half of the unsubstituted aromatic carbon (corresponding to a peak of about 40-60 ppm of 13 C-NMR), and A 2 is substituted
- the remaining half of the aromatic carbon corresponding to about 60-80 ppm peak of 13 C-NMR
- a 3 is the number of aliphatic carbon (corresponding to about 130-190 ppm peak of 13 C-NMR)
- the 13 C-NMR method is the best method for quantitatively determining fa, which is the most basic amount of chemical structural parameters of pitches, as described in the literature ("Pitch Characterization II. Chemical Structure” Yokono, Sanada, (Carbon, 1981 (No. 105), p73-81).
- the content of normal paraffin in the heavy oil composition means a value measured by a gas chromatograph equipped with a capillary column. Specifically, after testing with a normal paraffin standard substance, the sample of the non-aromatic component separated by the elution chromatography method is passed through a capillary column and measured. The content rate based on the total mass of the heavy oil composition can be calculated from this measured value.
- the aromatic index fa of the heavy oil composition is less than 0.3, the yield of coke from the heavy oil composition becomes extremely low, and a good bulk mesophase cannot be formed. It is not preferable because the crystal structure hardly develops even if it is made to be. On the other hand, if it exceeds 0.65, a large number of mesophases are suddenly generated in the matrix in the production process of raw coke, and abrupt coalescence of mesophases is mainly repeated rather than single growth of mesophases. For this reason, the rate of coalescence between the mesophases is faster than the rate of gas generation due to the normal paraffin-containing component, which makes it impossible to limit the hexagonal mesh plane of the bulk mesophase to a small size.
- the aromatic index fa of the heavy oil composition is particularly preferably in the range of 0.3 to 0.65.
- fa can be calculated from the density D and the viscosity V of the heavy oil composition.
- the density D is 0.91 to 1.02 g / cm 3 and the viscosity V is 10 to 220 mm 2 / sec.
- Particularly preferred are heavy oil compositions having a fa of 0.3 to 0.65.
- the normal paraffin component appropriately contained in the heavy oil composition plays an important role in limiting the size of the bulk mesophase to a small size by generating gas during the coking process. .
- This gas generation also has a function of uniaxially orienting adjacent mesophases limited to a small size and selectively orienting the entire system.
- the content of the normal paraffin-containing component is less than 5% by mass, the mesophase grows more than necessary and a huge carbon hexagonal plane is formed, which is not preferable.
- gas generation from normal paraffin becomes excessive and tends to work in a direction that disturbs the orientation of the bulk mesophase.
- the normal paraffin content is particularly preferably in the range of 5 to 20% by mass.
- the desulfurized dewaxed oil plays a role of appropriately bonding adjacent hexagonal net plane laminates, but the content in the heavy oil composition is in the range of 7 to 15% by mass. It is particularly preferred. When it is less than 7% by mass, or when it exceeds 15% by mass, the micro strength of the heavy oil composition obtained after coking is less than 7% by mass or may exceed 17% by mass, which is not preferable. .
- the heavy oil composition having such characteristics is coked to form the raw coal composition of the present invention.
- a delayed coking method is preferable. More specifically, a method of obtaining raw coke by heat-treating a heavy oil composition with a delayed coker under conditions where the coking pressure is controlled is preferable.
- preferable operating conditions of the delayed coker are a pressure of 0.1 to 0.8 MPa and a temperature of 400 to 600 ° C. The reason why a preferable range is set for the operating pressure of the coker is that the release rate of the gas generated from the component containing normal paraffin to the outside of the system can be limited by the pressure.
- the residence time of the generated gas in the system is an important control for determining the size of the hexagonal mesh plane. It becomes a parameter.
- the reason why a preferable range is set for the operating temperature of the coker is that the temperature is necessary for growing the mesophase from the heavy oil adjusted to obtain the effect of the present invention.
- the raw coal composition thus obtained is pulverized and classified so as to have a predetermined particle size.
- the average particle size of the powder of the obtained raw coal composition is preferably 30 ⁇ m or less.
- the average particle size is based on measurement by a laser diffraction particle size distribution meter.
- the reason why the average particle size of the raw material carbon composition powder is 30 ⁇ m or less is that the particle size is generally and preferably used as the negative electrode carbon material of the lithium ion secondary battery. Further, the preferable average particle diameter is 5 to 30 ⁇ m.
- the raw carbon composition powder thus pulverized and classified is carbonized and crystallized so that the crystallite size Lc (112) of the diffraction line (112) measured by the X-ray wide angle diffraction method is 4 nm or more.
- Graphitizes The method of carbonization and graphitization treatment is not particularly limited, but usually carbonization is performed in an inert gas atmosphere such as nitrogen, argon or helium at a maximum temperature of 900 to 1500 ° C. and a maximum time of retention of 0 to 10 hours. (Pre-baking) and then a heat treatment under the same inert gas atmosphere at a maximum temperature of 2500-3200 ° C. and a maximum temperature holding time of 0-100 hours. After the carbonization, the heat treatment may be performed once for cooling and again for graphitization.
- an inert gas atmosphere such as nitrogen, argon or helium
- the reason why the crystallite size Lc (112) of the (112) diffraction line measured by the X-ray wide angle diffraction method is set to 4 nm or more as a physical property of the graphite particles to which the compressive shear stress is given is that This is because the highly developed crystallinity is maintained even in the graphite material produced using the graphite particles with high crystal growth as described above, and it is possible to secure a reversible capacity of 340 mAh / g or more. This is exactly the same as the reason why a highly crystallized material is preferably used as the negative electrode material used in the battery.
- the graphite material of the present invention is obtained by applying a compressive shear stress to the graphite particles obtained by carbonization and graphitization.
- a compressive shear stress in addition to compressive shear stress, collision, friction, shear stress and the like are also generated.
- the mechanical energy given by these stresses is larger than the energy obtained by general agitation, and when these energies are given to the particle surface, the mechanochemical phenomena such as the spheroidization of particles and the compounding of particles The effect called is expressed.
- it is sufficient to use a device capable of simultaneously applying stress such as shear, compression, collision, etc., which is limited to the structure and principle of the device. is not.
- a ball-type kneader such as a rotary ball mill
- a wheel-type kneader such as an edge runner
- a hybridization system manufactured by Nara Machinery Co., Ltd.
- Mechano-Fusion manufactured by Hosokawa Micron
- Nobilta manufactured by Hosokawa Micron
- COMPOSI Joint-I Coke industry
- the manufacturing conditions in the step of applying the compressive shear stress vary depending on the apparatus to be used.
- the blade 31 of the blade and the housing 32 are relatively rotated, preferably in opposite directions (rotational direction). It is possible to use a mechano-fusion device 30 having a structure in which the powder P is compacted and compressive stress is applied to the powder P through the gap 33 between them.
- the blade rotation speed is 600 to 4000 rpm and the processing time is 5 to 90 minutes.
- the rotational speed is less than 600 rpm, or when the treatment time is less than 5 minutes, sufficient compression shear stress cannot be applied to the graphite particles.
- the treatment is longer than 90 minutes, excessive compression shear stress is applied to the graphite particles, and the particle shape is remarkably deformed.
- the processing time is 5 to 90 minutes at a peripheral speed of 25 to 60 m / s.
- the peripheral speed is less than 25 m / s or when the treatment time is less than 5 minutes, sufficient compressive shear stress cannot be applied to the graphite particles.
- the treatment is longer than 90 minutes, excessive compression shear stress is applied to the graphite particles, and the particle shape is remarkably deformed.
- the blade rotation speed is 500 to 3000 rpm and the treatment time is 10 to 300 minutes.
- the rotational speed is less than 500 rpm, or when the treatment time is less than 10 minutes, sufficient compressive shear stress cannot be applied to the graphite particles.
- the treatment is performed for longer than 300 minutes, excessive compression shear stress is applied to the graphite particles, and the particle shape is remarkably deformed.
- the processing time is 5 to 90 minutes at a peripheral speed of 20 to 60 m / s.
- the process of applying compressive shear stress to graphite particles is a process that cuts the corners of the particles, but the scraped part immediately attaches to the particles and rounds the particles, and the apparent particle size is almost unchanged. It is good to do in. Therefore, it is not pulverization that generates fine powder and reduces the particle size.
- a graphite material having a higher sphericity can be obtained by controlling the temperature during the treatment for applying the compressive shear stress to preferably 60 to 250 ° C. . In particular, it is desirable to operate so that the control temperature during processing is 120 to 200 ° C.
- a step of further heat treatment may be included.
- the heat treatment temperature a temperature range generally used when heat treating the carbon material, for example, 700 ° C. to 3000 ° C. can be employed. By performing such additional heat treatment, dangling bonds exposed on the surface can be further reduced.
- the present invention is a graphite obtained by mixing desulfurized and desulfurized oil as a preferred embodiment of a heavy oil composition, pulverizing and classifying a raw carbon composition having a predetermined H / C atomic ratio and micro strength, and carbonizing and graphitizing. By applying compressive shear stress to the particles, a desired graphite material can be provided.
- the method for producing a negative electrode for a lithium ion secondary battery is not particularly limited, and includes, for example, a graphite material to which the invention according to the present application is applied, a binder (binder), and a conductive auxiliary agent and an organic solvent as necessary.
- the method of pressure-molding a mixture (negative electrode mixture) to a predetermined dimension is mentioned.
- a graphite material to which the invention according to the present application is applied, a binder (binder), a conductive auxiliary agent and the like are kneaded and slurried in an organic solvent, and the slurry is used as a current collector such as a copper foil.
- a method of rolling a coated and dried product (negative electrode mixture) and cutting it into a predetermined size can also be mentioned.
- binder examples include polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polyethylene terate, and SBR (styrene-butadiene rubber).
- the content of the binder in the negative electrode mixture may be appropriately set as required in the battery design, from about 1 to 30 parts by mass with respect to 100 parts by mass of the graphite material.
- the conductive assistant include carbon black, graphite, acetylene black, conductive indium-tin oxide, or conductive polymers such as polyaniline, polythiophene, and polyphenylene vinylene.
- the amount of the conductive aid used is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the graphite material.
- organic solvent examples include dimethylformamide, N-methylpyrrolidone, pyrrolidone, N-methylthiopyrrolidone, hexamethylphosphoamide, dimethylacetamide, isopropanol, toluene and the like.
- the graphite material As a method of mixing the graphite material, the binder, and, if necessary, the conductive aid and the organic solvent, known devices such as a screw type kneader, a ribbon mixer, a universal mixer, and a planetary mixer can be used.
- the mixture is formed by roll pressing or press pressing, and the pressure at this time is preferably about 100 to 300 MPa.
- the material of the current collector can be used without any limitation as long as it does not form an alloy with lithium.
- copper, nickel, titanium, stainless steel, etc. can be mentioned.
- the shape of the current collector can be used without any particular limitation, but as an example, a belt-like shape in the form of foil, perforated foil, mesh, or the like can be given.
- a porous material such as porous metal (foamed metal) or carbon paper can also be used. *
- the method of applying the slurry to the current collector is not particularly limited, for example, metal mask printing method, electrostatic coating method, dip coating method, spray coating method, roll coating method, doctor blade method, gravure coating method, Known methods such as a screen printing method and a die coater method can be used. After coating, it is common to perform a rolling process using a flat plate press, a calender roll, or the like as necessary. Further, the integration of the negative electrode material slurry formed into a sheet shape, a pellet shape, and the like with the current collector can be performed by a known method such as a roll, a press, or a combination thereof.
- the lithium ion secondary battery using the graphite material for the negative electrode of the lithium ion secondary battery according to the present embodiment is, for example, arranged so that the negative electrode and the positive electrode manufactured as described above face each other with a separator interposed therebetween, It can be obtained by injecting an electrolytic solution.
- the active material used for the positive electrode is not particularly limited. For example, a metal compound, metal oxide, metal sulfide, or conductive polymer material that can be doped or intercalated with lithium ions may be used.
- lithium cobaltate LiCoO 2
- lithium nickelate LiNiO 2
- lithium manganate LiMn 2 O 4
- polyacetylene polyaniline
- polypyrrole polythiophene
- electrically conductive polymers such as polyacene, porous carbon or the like and mixtures thereof.
- the separator for example, a nonwoven fabric, a cloth, a microporous film, or a combination thereof, which is mainly composed of polyolefin such as polyethylene or polypropylene, can be used.
- a separator when it is set as the structure where the positive electrode and negative electrode of the lithium ion secondary battery to produce are not in direct contact, it is not necessary to use a separator.
- organic electrolytes As the electrolyte and electrolyte used for the lithium ion secondary battery, known organic electrolytes, inorganic solid electrolytes, and polymer solid electrolytes can be used. Preferably, an organic electrolyte is preferable from the viewpoint of electrical conductivity.
- organic electrolyte examples include dibutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, ethylene glycol phenyl ether, and other ethers, N-methylformamide, N, N-dimethylformamide, N Amides such as ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, sulfur-containing compounds such as dimethylsulfoxide and sulfolane, methyl ethyl ketone, Dialkyl ketones such as methyl isobutyl ketone, cyclic ethers such as tetrahydrofuran and 2-methoxytetrahydrofuran, ethylene carbonate Cyclic carbonates such as butylene carbonate, propylene carbonate and vinyl
- lithium salts can be used as the solute of these solvents.
- Commonly known lithium salts include LiClO 4 , LiBF 4 , LiPF 6 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCl, LiCF 3 SO 3 , LiCF 3 CO 2 , LiN (CF 3 SO 2 ) 2, LiN (C 2 F 5 SO 2 ) 2 and the like.
- polymer solid electrolyte examples include a polyethylene oxide derivative and a polymer containing the derivative, a polypropylene oxide derivative and a polymer containing the derivative, a phosphate ester polymer, a polycarbonate derivative and a polymer containing the derivative. There are no restrictions on the selection of members other than those described above necessary for the battery configuration.
- the structure of the lithium ion secondary battery is not particularly limited, a wound electrode group in which a positive electrode and a negative electrode formed in a strip shape are wound in a spiral shape through a separator is inserted into a battery case and sealed.
- a structure in which a laminated electrode plate group in which a positive electrode and a negative electrode formed in a flat plate shape are sequentially laminated via a separator is enclosed in an exterior body.
- the lithium ion secondary battery is used as, for example, a paper battery, a button battery, a coin battery, a stacked battery, a cylindrical battery, a rectangular battery, or the like.
- the inventors of the present invention have a raw carbon composition in which H / C, which is an atomic ratio of hydrogen atom H to carbon atom C, is 0.30 to 0.50, and micro strength is 7% by mass to 17% by mass.
- a process of carbonizing and graphitizing a composite powder in which calcine coke is embedded on the particle surface, and a structure in which a region with low crystallinity is partially introduced into a highly developed crystal structure, and the particle The relationship that a graphite material with few edge parts exposed on the surface is obtained is considered as follows.
- the calcine coke used in the present invention removes moisture and volatiles by heat-treating petroleum coke, coal pitch coke, etc. in an industrial furnace (calciner such as rotary kiln, shaft kiln, rotary hearth) (1300 ° C-1400 ° C). This means that the crystal structure has been developed (carbon glossary: issued by Agne Jofusha).
- Calcine coke is obtained by pulverizing and classifying the thus obtained calcine coke so as to have an average particle size of 0.1 ⁇ m to 3.0 ⁇ m.
- bottom oil of fluid catalytic cracking equipment fluid catalytic cracking residual oil, FCC DO
- aromatics extracted from fluid catalytic cracking residual oil heavy hydrodesulfurization to heavy oil Treated hydrodesulfurized oil, reduced pressure residue (VR)
- desulfurized desulfurized oil coal liquefied oil, coal solvent extracted oil, atmospheric residue oil, shell oil, tar sand bitumen, naphtha tar pitch, ethylene bottom Oil, coal tar pitch and heavy oil obtained by hydrorefining these oils, or after heat treating a heavy oil composition obtained by blending two or more kinds, coarsely pulverized with a hammer mill, etc.
- Calcine coke can be obtained by carbonizing at 1300 ° C to 1400 ° C.
- a mechanical pulverizer for example, Super Rotor Mill / Nisshin Engineering
- a precision air classifier for example, Turbo Classifier / Nisshin Engineering
- the interface region of these two hexagonal mesh planes in a non-parallel relationship is a region having a lower degree of crystallinity than a region where other crystal structures are highly developed.
- the graphite material obtained by carbonizing and graphitizing composite powder in which calcine coke is embedded on the particle surface of the raw carbon composition has a degree of crystallinity in the graphite material with a highly developed crystal structure.
- the crystal structure has a low region introduced.
- the introduced low crystallinity region has an effect of sterically hindering the co-insertion of the electrolyte solution between the graphite layers.
- the state in which calcine coke is embedded on the surface of the particles of the raw coal composition here means that when the SEM image of 1,000 to 5,000 times is observed, the calcine coke is the raw coal composition. A state in which it is embedded and compounded without substantially protruding from the particle surface.
- the first reason is to suppress an increase in the specific surface area of the particles after graphitization by carbonizing and graphitizing the composite powder in which calcine coke is embedded on the particle surface of the raw carbon composition.
- the surface roughness of the graphite material obtained in this way is extremely small, and the specific surface area is small.
- the contact area between the electrolytic solution and the particle surface of the graphite material is small, so that the electrolytic solution is hardly decomposed in the negative electrode.
- the life characteristics are excellent.
- calcine coke is not embedded in the particle surface of the raw coal composition and carbonized and graphitized only on the composite powder, calcine coke protrudes from the particle surface of the graphite material. A graphite material having a large specific surface area with irregularities on the surface is obtained.
- the second reason why the composite powder is in a state where calcine coke is embedded in the particle surface of the raw coal composition is the interface between the highly developed crystal structure and the low crystallinity region. This is because a chemical bond is formed in order to prevent a crack from occurring at the interface between the two.
- calcine coke In the process in which calcine coke is embedded in the particle surface of the raw coal composition by compressive shear stress, calcine coke has a gap between the hexagonal mesh plane laminate constituting the raw coal composition and the adjacent hexagonal mesh plane laminate. Almost embedded in (void region). This is because the calcine coke breaks the hexagonal mesh plane laminate in the raw coal composition and is embedded in the void region between adjacent hexagonal mesh plane laminates, rather than the energy required to be embedded inside the particles. This is because the energy required for this is smaller. In this void region, unorganized carbon having a structure other than a benzene ring, which is a constituent unit of a hexagonal network plane, exists.
- unorganized carbons are chemically connected to the hexagonal plane planar laminate in the powder of the raw carbon composition, and can form carbon-carbon bonds with other adjacent unorganized carbons.
- unstructured carbon present on the surface of the calcine coke particles can sufficiently come into contact with unstructured carbon in the raw coal composition.
- strong carbon-carbon bonds are formed between the unstructured carbons in contact. Therefore, even in the graphite material obtained after graphitization, the hexagonal mesh plane laminate in calcine coke and the hexagonal mesh plane laminate in graphite are chemically connected to each other without causing cracks.
- the reason why the average particle size of calcine coke mixed with the raw coal composition powder is defined as 0.1 ⁇ m to 3.0 ⁇ m will be described.
- the reason why the lower limit is set to 0.1 ⁇ m is that it is very difficult to obtain calcine coke having an average particle size of less than 0.1 ⁇ m, and it does not match the actual situation.
- the raw carbon composition powder and calcine coke having an average particle size of greater than 3.0 ⁇ m are mixed, the mixed calcine is mixed with respect to the void region between the hexagonal mesh plane laminates of the raw carbon composition.
- the mixed calcine coke is not embedded in the raw coal composition, but only adheres to the particle surface of the raw coal composition, and a composite powder having large irregularities on the particle surface is obtained. .
- the specific surface area of the graphite material obtained by carbonizing and graphitizing this composite powder becomes extremely large.
- the contact area between the electrolyte and the negative graphite material As the electrolyte increases and the electrolyte solution is easily decomposed, the leakage current of the negative electrode increases and the difference from the leakage current with the positive electrode increases, so the operating region of the positive and negative electrode capacities changes and the life characteristics deteriorate. Therefore, it is not preferable.
- a more preferable average particle diameter is 0.5 ⁇ m to 2 ⁇ m.
- the reason why the amount of calcine coke mixed with the powder of the raw coal composition is defined as 0.5 to 10% by mass with respect to the raw coal composition will be described. Obtained by carbonizing and graphitizing a composite powder obtained by mixing a raw material charcoal composition powder and calcine coke of less than 0.5% by mass with respect to the raw material charcoal composition and applying a compressive shear stress.
- a composite powder obtained by mixing a raw material charcoal composition powder and calcine coke of less than 0.5% by mass with respect to the raw material charcoal composition and applying a compressive shear stress.
- the obtained graphite material since the content of calcine coke contained in the composite powder is extremely small, a sufficient contact area between calcine coke and raw coal composition cannot be secured, The interface area becomes extremely small. In this case, the region of low crystallinity introduced into the graphite material becomes extremely small.
- the raw coal composition has an atomic ratio of hydrogen atoms H to carbon atoms C of H / C of 0.30 to 0.50, and a micro strength of 7% by mass to 17% by mass.
- the raw coal composition having such parameters has a void region between appropriate hexagonal mesh plane laminates, it is possible to obtain a composite powder in which calcine coke is embedded in the particle surface of the raw coal composition. Is possible.
- the raw coal composition has an appropriate bond strength between hexagonal mesh plane laminates, in the graphite material obtained after graphitizing the composite powder, calcine coke and hexagonal mesh plane laminate in graphite A strong carbon-carbon bond can be formed between them.
- H / C of the raw coal composition is a ratio of the value obtained by dividing the total hydrogen content (TH (mass%)) by the atomic weight of hydrogen and the value obtained by dividing the total carbon content (TC (mass%)) by the atomic weight of carbon. It is.
- the total hydrogen is measured by completely burning the sample in an oxygen stream at 750 ° C. and determining the amount of water generated from the combustion gas by the coulometric titration method (Karl Fischer method).
- Karl Fischer method an electrolyte containing iodide ions, sulfur dioxide, base (RN) and alcohol as main components is placed in the titration cell in advance, and the sample is placed in the titration cell. Moisture reacts as shown in the following formula (4).
- a sample is measured, for example after cooling in a dry atmosphere after a caulking process.
- the iodine necessary for this reaction can be obtained by electrochemically reacting iodide ions (two-electron reaction) as shown in the following formula (5).
- the constant 96478 is the Faraday constant, and 18.5513 is the molecular weight of water.
- the amount of water can be determined. Furthermore, it converts into the amount of hydrogen from the obtained moisture content, and remove
- the total carbon was measured by burning the sample in an oxygen stream at 1150 ° C., converted into carbon dioxide (partially carbon monoxide), transported to an excess oxygen stream, and CO 2 + CO infrared detector, TC (mass%) is calculated.
- the H / C atomic ratio of the raw coal composition is 0.30 to 0.50.
- the H / C atomic ratio is an index indicating the spread of the hexagonal network plane, that is, the size of the crystallite.
- the ratio of the carbon component contained in the raw coal composition is large, so the spread of the hexagonal mesh plane is large.
- the value of H / C is large, the ratio of hydrogen components contained in the raw coal composition is large, so that the carbon-carbon bond is difficult to form, and the hexagonal mesh plane is small.
- Such raw coal composition contains a large amount of unstructured carbon that does not belong to the hexagonal mesh plane.
- unstructured carbons are incorporated into the hexagonal mesh plane as the hexagonal mesh plane grows in the process of carbonization and graphitization, and are bonded to each other to form a hexagonal mesh plane, or other adjacent carbon materials. It forms a carbon-carbon bond with unorganized carbon.
- Lithium ion secondary batteries using these graphite materials as negative electrodes are prone to decomposition of the electrolyte solution using localized electrons present on the edge as a catalyst, so the leakage current of the negative electrode increases and the leakage current with the positive electrode Therefore, the operating range of the positive and negative electrode capacities is changed, and the life characteristics are deteriorated.
- the H / C of the raw coal composition is limited to 0.30 to 0.50.
- a compressive shear stress is applied to the raw material.
- Composite powder in which calcine coke is appropriately embedded on the particle surface of the charcoal composition can be obtained, and when these composite powders are carbonized and graphitized, strong carbon-carbon bonds are formed, and the particle surface
- Micro strength is a steel cylinder (inner diameter 25.4 mm, length 304.8 mm) with 20 g to 30 mesh sample 2 g and 12 steel balls 5/16 inch (7.9 mm) in diameter.
- Rotate 800 rpm at 25 rpm in the direction perpendicular to the axis ie, rotate the axis horizontally so that the top and bottom can be switched from the upright position, rotate as if the propeller is rotating), and screen with 48 mesh. It is the value which showed the mass on the sieve with respect to the percentage.
- the micro strength of the raw coal composition is 7% by mass to 17% by mass. This micro strength is an index indicating the bond strength between adjacent hexagonal mesh plane laminates.
- the bonding strength of unstructured carbon existing in the void region between the hexagonal mesh plane laminates is extremely weak. Therefore, when calcine coke is embedded in the void region, unorganized carbon bonds existing in the void region are likely to be broken.
- the graphite material obtained by carbonizing and graphitizing the composite powder in such a state an edge surface generated by bond breaking of unstructured carbon existing in the void is exposed to the particle surface.
- Lithium ion secondary batteries using these graphite materials as negative electrodes are prone to decomposition of the electrolyte solution using localized electrons present on the edge as a catalyst, so the leakage current of the negative electrode increases and the leakage current with the positive electrode Therefore, the operating range of the positive and negative electrode capacities is changed, and the life characteristics are deteriorated.
- the specific surface area is greatly increased due to large irregularities on the particle surface.
- the contact area between the electrolytic solution and the negative electrode graphite increases, so that the electrolytic solution is easily decomposed. Therefore, the leakage current of the negative electrode is increased, and the difference from the leakage current with the positive electrode is increased. Therefore, the operating region of the positive / negative electrode capacity is changed, and the life characteristics are deteriorated.
- the micro strength of the raw coal composition is limited to 7% by mass to 17% by mass.
- a raw coal composition having physical properties within this range and pulverized and classified so as to have a predetermined particle size and calcine coke are mixed, and then a compressive shear stress is applied.
- the composite powder in which calcine coke is embedded on the surface of the raw carbon composition particles can be obtained without breaking the bond of the unstructured carbon existing in the void region of the carbon. In this case, it is possible to realize a graphite material in which a region having a very small crystallite edge and a low crystallinity is introduced on the particle surface.
- a graphite material having a structure in which a region having a low degree of crystallinity is introduced in a highly developed crystal structure and having less exposure of edge portions on the particle surface is obtained. Can do.
- the raw coal composition used in the present invention can be obtained by coking a heavy oil composition by a delayed coking process.
- Components of heavy oil composition include bottom oil of fluid catalytic cracking equipment (fluid catalytic cracking residual oil, FCC DO), aromatics extracted from fluid catalytic cracking residual oil, and advanced hydrodesulfurization treatment for heavy oil Hydrodesulfurized oil, vacuum residue (VR), desulfurized desulfurized oil, coal liquefied oil, coal solvent extract oil, atmospheric residual oil, shell oil, tar sand bitumen, naphtha tar pitch, ethylene bottom oil Coal tar pitch and heavy oil obtained by hydrorefining these.
- These heavy oils may be used alone or in a blend of two or more.
- the blending ratio of two or more types of heavy oils may be appropriately adjusted according to the properties of the heavy oils used.
- the properties of heavy oil vary depending on the type of crude oil, the processing conditions for obtaining heavy oil from crude oil, and the like.
- the bottom oil of the fluid catalytic cracking unit is a bottom of the fluidized bed type fluid catalytic cracking unit that uses a vacuum gas oil as a raw material oil and selectively performs a cracking reaction using a catalyst to obtain a high octane FCC gasoline.
- Oil used as the raw material oil is preferably a desulfurized vacuum gas oil obtained by directly desulfurizing an atmospheric distillation residue oil (preferably a sulfur content of 500 ppm by mass or less, a density of 0.8 g / cm 3 or more at 15 ° C. ).
- the aromatic content extracted from the fluid catalytic cracking residual oil is the aromatic content when selectively extracted using dimethylformamide or the like and separated into an aromatic content and a saturated content.
- Hydrodesulfurized oil obtained by subjecting heavy oil to advanced hydrodesulfurization treatment is, for example, sulfur content obtained by hydrodesulfurization treatment of heavy oil having a sulfur content of 1% by mass or more at a hydrogen partial pressure of 10 MPa or more. It is a heavy oil with 0% by mass or less, nitrogen content of 0.5% by mass or less, and aromatic carbon fraction (fa) of 0.1 or more.
- the hydrodesulfurized oil is preferably a hydrodesulfurized oil obtained by hydrodesulfurizing an atmospheric distillation residue in the presence of a catalyst so that the hydrocracking rate is 25% or less.
- the vacuum residual oil (VR) is obtained by subjecting crude oil to an atmospheric distillation apparatus to obtain gas, light oil, and atmospheric residual oil.
- the atmospheric residual oil is heated at the furnace outlet temperature under a reduced pressure of, for example, 10 Torr to 30 Torr.
- This is a bottom oil of a vacuum distillation apparatus obtained by changing the temperature within the range of 320 ° C to 360 ° C.
- Desulfurized desulfurized oil is obtained by, for example, treating oil such as vacuum distillation residue oil with a solvent desulfurization apparatus using propane, butane, pentane, or a mixture thereof as a solvent, and removing the asphaltenes.
- desulfurized oil (DAO) is desulfurized using an indirect desulfurization apparatus (Isomax) or the like, preferably in a range of 0.05 mass% to 0.40 mass% of sulfur content.
- Isomax indirect desulfurization apparatus
- Atmospheric residual oil is obtained by subjecting crude oil to an atmospheric distillation apparatus, for example, heating under normal pressure, and depending on the boiling point of the contained fraction, gas / LPG, gasoline fraction, kerosene fraction, light oil fraction, ordinary oil fraction, One of the fractions obtained when divided into pressure residue oil, and the fraction with the highest boiling point.
- the heating temperature varies depending on the production area of the crude oil and is not limited as long as it can be fractionated into these fractions. For example, the crude oil is heated to 320 ° C.
- Examples of particularly preferred heavy oil compositions include (1) aromatic fraction (aromatic index) fa of 0.3 to 0.65, and (2) normal paraffin content of 5% by mass to 20%. And a heavy oil composition satisfying the three conditions: (3) the desulfurized desulfurized oil is contained in the range of 7% by mass to 15% by mass. it can.
- aromatic fraction aromatic index
- normal paraffin content 5% by mass to 20%.
- the desulfurized desulfurized oil is contained in the range of 7% by mass to 15% by mass. it can.
- a heavy oil component that produces a good bulk mesophase and (2) when the bulk mesophase is polycondensed and carbonized and solidified, the size of the hexagonal mesh plane laminate constituting the mesophase is It is particularly preferable to use a raw oil composition containing a heavy oil component capable of generating a gas having a function of limiting to a small size, and (3) a component that binds the cut hexagonal mesh plane laminates together.
- a heavy oil component that produces a good bulk mesophase is a component that gives an aromatic index fa of 0.3 to 0.65
- a heavy oil component that can generate gas contains normal paraffin This is a desulfurized dewaxed oil containing 5% by mass to 20% by mass of the component, and (3) a component that binds the hexagonal net plane laminates in the range of 7% by mass to 15% by mass.
- the aromatic carbon fraction (aromatic index) (fa) can be determined by the Knight method.
- the carbon distribution is divided into three components (A 1 , A 2 , A 3 ) as an aromatic carbon spectrum by the 13 C-NMR method.
- a 1 is the number of carbon atoms inside the aromatic ring, half of the substituted aromatic carbon and half of the unsubstituted aromatic carbon (corresponding to a peak of about 40 ppm to 60 ppm of 13 C-NMR), and A 2 is substituted
- a 3 is the number of aliphatic carbon (corresponding to a peak of about 130 ppm to 190 ppm of 13 C-NMR), From these, fa is calculated
- the 13 C-NMR method is the best method for quantitatively determining fa, which is the most basic amount of chemical structural parameters of pitches, as described in the literature ("Pitch Characterization II. Chemical Structure” Yokono, Sanada, (Carbon, 1981 (No. 105), p73-81).
- the content of normal paraffin in the heavy oil composition means a value measured by a gas chromatograph equipped with a capillary column. Specifically, after testing with a normal paraffin standard substance, the sample of the non-aromatic component separated by the elution chromatography method is passed through a capillary column and measured. The content based on the total mass of the heavy oil composition can be calculated from this measured value.
- the aromatic index fa of the heavy oil composition is less than 0.3, the yield of coke from the heavy oil composition becomes extremely low, and a good bulk mesophase cannot be formed. It is not preferable because the crystal structure hardly develops even if it is made to be.
- fa exceeds 0.65, a large number of mesophases are generated abruptly in the matrix during the production process of raw coke, and abrupt coalescence of mesophases is mainly repeated rather than single growth of mesophases. For this reason, the rate of coalescence of the mesophases is faster than the rate of gas generation due to the normal paraffin-containing component, which makes it impossible to limit the hexagonal mesh plane of the bulk mesophase to a small size.
- the aromatic index fa of the heavy oil composition is particularly preferably in the range of 0.3 to 0.65.
- fa is susceptible calculated from the density D and the viscosity V of the heavy oil composition, density D is 0.91g / cm 3 ⁇ 1.02g / cm 3, viscosity V is 10 mm 2 / sec. ⁇ 220 mm 2 / sec.
- Particularly preferred are heavy oil compositions having a fa of 0.3 to 0.65.
- the normal paraffin component appropriately contained in the heavy oil composition plays an important role in limiting the size of the bulk mesophase to a small size by generating gas during the coking process. .
- This gas generation also has a function of uniaxially orienting adjacent mesophases limited to a small size and selectively orienting the entire system.
- the content of the normal paraffin-containing component is less than 5% by mass, the mesophase grows more than necessary and a huge carbon hexagonal plane is formed, which is not preferable.
- the normal paraffin content is particularly preferably in the range of 5% by mass to 20% by mass.
- the desulfurized dewaxed oil plays a role of appropriately bonding adjacent hexagonal mesh plane laminates, but the content in the heavy oil composition is in the range of 7% by mass to 15% by mass. It is particularly preferred that When it is less than 7% by mass, or when it exceeds 15% by mass, the micro strength of the heavy oil composition obtained after coking is less than 7% by mass, or may exceed 17% by mass, which is not preferable. .
- the heavy oil composition having such characteristics is coked to form the raw coal composition of the present invention.
- a delayed coking method is preferable. More specifically, a method of obtaining raw coke by heat-treating a heavy oil composition with a delayed coker under conditions where the coking pressure is controlled is preferable.
- preferable operating conditions of the delayed coker are a pressure of 0.1 MPa to 0.8 MPa and a temperature of 400 ° C. to 600 ° C.
- the reason why a preferable range is set for the operating pressure of the coker is that the release rate of the gas generated from the component containing normal paraffin to the outside of the system can be limited by the pressure.
- the residence time of the generated gas in the system is an important control for determining the size of the hexagonal mesh plane. It becomes a parameter.
- the reason why a preferable range is set for the operating temperature of the coker is that the temperature is necessary for growing the mesophase from the heavy oil adjusted to obtain the effect of the present invention.
- the raw coal composition thus obtained is pulverized and classified so as to have a predetermined particle size.
- the average particle size is preferably 30 ⁇ m or less.
- the average particle size is based on measurement by a laser diffraction particle size distribution meter.
- the reason why the average particle size is 30 ⁇ m or less is that the particle size is generally and preferably used as a negative electrode carbon material for lithium ion secondary batteries.
- a preferable average particle diameter is 5 ⁇ m to 30 ⁇ m.
- the method for producing the graphite material used as the negative electrode of the lithium ion secondary battery of the present invention includes a step of mixing the powder of the raw carbon composition and calcine coke and applying a compressive shear stress.
- the compressive shear stress applied at this time includes not only compressive stress and shear stress, but also collision, friction, shear stress, and the like.
- the mechanical energy given by these stresses is larger than the energy obtained by general agitation, and when these energy is given to the particle surface, the mechanochemical phenomenon such as the spheroidization of the particle shape and the composite of the particles The effect called is expressed.
- an apparatus capable of simultaneously applying stresses such as shear, compression, and collision may be used, and the structure and principle of the apparatus are particularly limited. It is not something.
- a ball-type kneader such as a rotary ball mill, a wheel-type kneader such as an edge runner, a hybridization system (manufactured by Nara Machinery Co., Ltd.), mechanofusion (manufactured by Hosokawa Micron), nobilta (manufactured by Hosokawa Micron), COMPOSI (Japan) Coke industry).
- the manufacturing conditions in the process of applying the compressive shear stress vary depending on the apparatus to be used.
- the powder P is formed in the gap 33 between the rotating blade vane (rotating direction R1) 31 and the housing 32 as shown in FIG.
- An apparatus having a structure in which compaction and compressive stress are applied is used.
- the blade rotation speed is 1500 rpm to 5000 rpm and the treatment time is 10 minutes to 180 minutes.
- the rotational speed is less than 1500 rpm, or when the treatment time is less than 10 minutes, sufficient compressive shear stress cannot be imparted to the powder of the raw coal composition.
- the treatment is performed for longer than 180 minutes, an excessive compressive shear stress is imparted to the powder of the raw coal composition, and the particle shape is significantly deformed.
- the processing time is 10 minutes to 180 minutes at a peripheral speed of 50 m / s to 80 m / s.
- the peripheral speed is less than 50 m / s, or when the treatment time is less than 10 minutes, sufficient compressive shear stress cannot be applied to the powder of the raw coal composition.
- the treatment is performed for longer than 180 minutes, an excessive compressive shear stress is imparted to the powder of the raw coal composition, and the particle shape is significantly deformed.
- the blade rotation speed is 500 rpm to 3000 rpm and the treatment time is 10 minutes to 300 minutes.
- the rotational speed is less than 500 rpm, or when the treatment time is less than 10 minutes, sufficient compressive shear stress cannot be applied to the raw material carbon composition powder.
- the treatment is performed for longer than 300 minutes, excessive compression shear stress is imparted to the powder of the raw coal composition, and the particle shape is significantly deformed.
- the processing time is 5 to 180 minutes at a peripheral speed of 40 m / s to 60 m / s. This is because, under this condition, a sufficient compressive shear stress can be applied to the raw material carbon composition powder without significantly changing the particle shape.
- the calcine is preferably applied to the particle surface of the raw coal composition by performing the control temperature at the time of the surface treatment for applying the compressive shear stress, preferably 60 ° C. to 250 ° C.
- a composite powder in which coke is embedded is obtained.
- the composite powder in which calcine coke is embedded in the particle surface of the raw coal composition has an Lc (112) calculated from (112) diffraction lines obtained by the X-ray wide angle diffraction method of 4 nm to 30 nm. It carbonizes and graphitizes so that it may become.
- the method of carbonization and graphitization treatment is not particularly limited.
- the maximum ultimate temperature is 900 ° C. to 1500 ° C. in an inert gas atmosphere such as nitrogen, argon or helium, and the maximum ultimate temperature holding time is 0 hour to 10 hours.
- Lc (112) calculated from the (112) diffraction line obtained by the X-ray wide angle diffraction method of the graphite material is defined as 4 nm to 30 nm in the present invention.
- a graphite material having Lc (112) of less than 4 nm is not preferable because the crystal structure is insufficiently developed, and a lithium ion secondary battery using such a graphite material has a small capacity.
- Lc (112) never exceeded 30 nm, so the upper limit was set to 30 nm.
- the raw coal composition having an H / C atomic ratio of 0.30 to 0.50 and a micro strength of 7% by mass to 17% by mass, calcine coke having an average particle size of 0.1 ⁇ m to 3.0 ⁇ m, Is added to the raw coal composition at a ratio of 0.5 mass% to 10 mass%, and a compressive shear stress is applied to the calcined coke on the particle surface of the raw coal composition.
- the composite powder is carbonized and graphitized, and the crystallite size Lc (112) of the diffraction line (112) measured by the X-ray wide angle diffraction method is 4 nm.
- the present invention mixes desulfurized and desulfurized oil as a preferred embodiment of the heavy oil composition, mixes calcine coke with powder of a raw coal composition having a predetermined H / C atomic ratio and micro strength, and compresses shear stress.
- a desired graphite material can be provided by carbonizing and graphitizing the composite powder obtained by imparting.
- the method for producing a negative electrode for a lithium ion secondary battery is not particularly limited, and includes, for example, a graphite material to which the invention according to the present application is applied, a binder (binder), and a conductive auxiliary agent and an organic solvent as necessary.
- the method of pressure-molding a mixture (negative electrode mixture) to a predetermined dimension is mentioned.
- a graphite material to which the invention according to the present application is applied, a binder (binder), a conductive auxiliary agent and the like are kneaded and slurried in an organic solvent, and the slurry is used as a current collector such as a copper foil.
- a method of rolling a coated and dried product (negative electrode mixture) and cutting it into a predetermined size can also be mentioned.
- binder examples include polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polyethylene terate, and SBR (styrene-butadiene rubber).
- the content of the binder in the negative electrode mixture may be appropriately set as necessary from the viewpoint of battery design from about 1 to 30 parts by mass with respect to 100 parts by mass of the graphite material.
- the conductive assistant examples include carbon black, graphite, acetylene black, conductive indium-tin oxide, or conductive polymers such as polyaniline, polythiophene, and polyphenylene vinylene.
- the amount of the conductive aid used is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the graphite material.
- organic solvent examples include dimethylformamide, N-methylpyrrolidone, pyrrolidone, N-methylthiopyrrolidone, hexamethylphosphoamide, dimethylacetamide, isopropanol, toluene and the like.
- the graphite material As a method of mixing the graphite material, the binder, and, if necessary, the conductive aid and the organic solvent, known devices such as a screw type kneader, a ribbon mixer, a universal mixer, and a planetary mixer can be used.
- the mixture is formed by roll pressure or press pressure, and the pressure at this time is preferably about 100 MPa to 300 MPa.
- the material of the current collector can be used without any limitation as long as it does not form an alloy with lithium.
- copper, nickel, titanium, stainless steel, etc. can be mentioned.
- the shape of the current collector can be used without any particular limitation, but as an example, it may be a strip shape in the form of foil, perforated foil, mesh, or the like.
- a porous material such as porous metal (foamed metal) or carbon paper can also be used.
- the method of applying the slurry to the current collector is not particularly limited, for example, metal mask printing method, electrostatic coating method, dip coating method, spray coating method, roll coating method, doctor blade method, gravure coating method, Known methods such as a screen printing method and a die coater method can be used. After coating, it is common to perform a rolling process using a flat plate press, a calender roll, or the like as necessary. Further, the integration of the negative electrode material slurry formed into a sheet shape, a pellet shape, and the like with the current collector can be performed by a known method such as a roll, a press, or a combination thereof.
- the lithium ion secondary battery using the graphite material for the negative electrode of the lithium ion secondary battery according to the present embodiment is, for example, arranged so that the negative electrode and the positive electrode manufactured as described above face each other with a separator interposed therebetween, It can be obtained by injecting an electrolytic solution.
- the active material used for the positive electrode is not particularly limited. For example, a metal compound, metal oxide, metal sulfide, or conductive polymer material that can be doped or intercalated with lithium ions may be used.
- lithium cobaltate LiCoO 2
- lithium nickelate LiNiO 2
- lithium manganate LiMn 2 O 4
- lithium vanadium compounds V 2 O 5 , V 6 O 13 , VO 2 , MnO 2 , TiO 2, MoV 2 O 8 , TiS 2, V 2 S 5, VS 2, MoS 2, MoS 3, Cr 3 O 8, Cr 2 O
- Olivine LiMPO 4 M: Co, Ni , Mn, Fe
- polyacetylene polyaniline
- polypyrrole polythiophene
- electrically conductive polymers such as polyacene, porous carbon or the like and mixtures thereof.
- the separator for example, a nonwoven fabric, a cloth, a microporous film, or a combination thereof, which is mainly composed of polyolefin such as polyethylene or polypropylene, can be used.
- a separator when it is set as the structure where the positive electrode and negative electrode of the lithium ion secondary battery to produce are not in direct contact, it is not necessary to use a separator.
- organic electrolytes As the electrolyte and electrolyte used for the lithium ion secondary battery, known organic electrolytes, inorganic solid electrolytes, and polymer solid electrolytes can be used. Preferably, an organic electrolyte is preferable from the viewpoint of electrical conductivity.
- organic electrolyte examples include dibutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, ethylene glycol phenyl ether, and other ethers, N-methylformamide, N, N-dimethylformamide, N Amides such as ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, sulfur-containing compounds such as dimethylsulfoxide and sulfolane, methyl ethyl ketone, Dialkyl ketones such as methyl isobutyl ketone, cyclic ethers such as tetrahydrofuran and 2-methoxytetrahydrofuran, ethylene carbonate Cyclic carbonates such as butylene carbonate, propylene carbonate and vinyl
- lithium salts can be used as the solute of these solvents.
- Commonly known lithium salts include LiClO 4 , LiBF 4 , LiPF 6 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCl, LiCF 3 SO 3 , LiCF 3 CO 2 , LiN (CF 3 SO 2 ) 2, LiN (C 2 F 5 SO 2 ) 2 and the like.
- polymer solid electrolyte examples include a polyethylene oxide derivative and a polymer containing the derivative, a polypropylene oxide derivative and a polymer containing the derivative, a phosphate ester polymer, a polycarbonate derivative and a polymer containing the derivative. There are no restrictions on the selection of members other than those described above necessary for the battery configuration.
- the structure of the lithium ion secondary battery is not particularly limited, a wound electrode group in which a positive electrode and a negative electrode formed in a strip shape are wound in a spiral shape through a separator is inserted into a battery case and sealed.
- a structure in which a laminated electrode plate group in which a positive electrode and a negative electrode formed in a flat plate shape are sequentially laminated via a separator is enclosed in an exterior body.
- the lithium ion secondary battery is used as, for example, a paper battery, a button battery, a coin battery, a stacked battery, a cylindrical battery, a rectangular battery, or the like.
- the inventors of the present invention have a raw carbon composition in which H / C, which is an atomic ratio of hydrogen atom H to carbon atom C, is 0.30 to 0.50, and a micro strength is 7% to 17% by mass
- H / C which is an atomic ratio of hydrogen atom H to carbon atom C
- a micro strength is 7% to 17% by mass
- acetylene black is a non-graphitizable carbon material that has a very high purity because it is produced by thermally decomposing acetylene gas and has a structure in which hexagonal planes similar to graphite are formed concentrically. is there.
- Spherical basic particles having a size of about 3 nm to 500 nm are aggregated by Van der Waals force to form an aggregate.
- Aggregates have a complex aggregate structure in which microspherical basic particles are branched into irregular chains, and the degree of fusion between several to several tens of basic particles is called agglomerate. This state is called a structure.
- the growth of crystallites in the basic particles is extremely small compared to the growth of crystallites when graphitizing a graphitizable carbon material. small. Therefore, it can be said that the degree of crystallinity of acetylene black after graphitization is extremely lower than that of graphite material.
- the crystallites in the basic particles of acetylene black are anisotropically oriented so that the c-axis is perpendicular to the surface of the spherical particles. Therefore, there is a feature that the exposure of the crystallite edge is very small in any region of the particle surface. This anisotropic orientation of the crystallites remains in the same state after graphitization.
- the c axis of the crystallite is oriented so as to be perpendicular to the surface of the basic particles. Therefore, there are few edge parts exposed to the particle
- the composite powder in which acetylene black is embedded on the particle surface of the raw coal composition is carbonized and graphitized, so that a region with low crystallinity is partially formed in the highly developed crystal structure.
- a graphite material having an introduced structure and having few edge portions exposed on the particle surface.
- acetylene black is the surface of the particle of the raw coal composition when an SEM image of 1,000 to 5,000 times is observed. It is embedded and compounded without substantially protruding from.
- the first reason is to suppress an increase in the specific surface area of the graphitized particles by carbonizing and graphitizing the composite powder in which acetylene black is embedded on the particle surface of the raw carbon composition.
- a composite powder in which acetylene black is embedded in the particle surface of the raw coal composition since there is little acetylene black protruding from the particle surface of the raw coal composition, such composite powder is obtained by carbonization and graphitization. The unevenness of the surface of the obtained graphite material is extremely small and the specific surface area is small.
- the contact area between the electrolytic solution and the particle surface of the graphite material is small, so that the electrolytic solution is hardly decomposed in the negative electrode.
- the life characteristics are excellent.
- acetylene black is carbonized and graphitized, the acetylene black protrudes from the particle surface of the graphite material when the acetylene black is not embedded in the particle surface of the raw carbon composition and is only adhered to the surface.
- a graphite material having a large specific surface area with unevenness can be obtained.
- the contact area between the electrolytic solution and the particle surface of the graphite material is large, the electrolytic solution is easily decomposed in the negative electrode.
- the difference between the leakage current of the negative electrode and the leakage current of the positive electrode is increased, the operating region of the positive / negative electrode capacity is changed, and the life characteristics are deteriorated.
- the second reason why the composite powder is in a state where acetylene black is embedded in the particle surface of the raw coal composition is the interface between the highly developed crystal structure and the low crystallinity region. This is to prevent the formation of cracks at the interface between the two due to the formation of chemical bonds.
- the acetylene black In the process in which acetylene black is embedded in the particle surface of the raw coal composition by compressive shear stress, the acetylene black has a gap (void) between the hexagonal mesh planar laminate constituting the raw coal composition and the adjacent hexagonal mesh planar laminate. It is easy to be embedded in the area. This is because acetylene black breaks the hexagonal mesh plane laminate in the raw coal composition and is embedded in the void region between adjacent hexagonal mesh plane laminates, rather than the energy required to be embedded inside the particles. This is because the energy required for is smaller.
- unstructured carbon having a structure other than the benzene ring that is a structural unit of the hexagonal mesh plane exists, and these unstructured carbons are chemically connected to the hexagonal mesh plane laminate.
- This unstructured carbon remains after the raw carbon composition is carbonized and / or graphitized, and plays a similar role.
- acetylene black is embedded in such a void region, acetylene black can sufficiently come into contact with unstructured carbon in the raw coal composition, and in the subsequent graphitization process, A strong carbon-carbon bond can be formed. Therefore, even in the graphite material obtained after graphitization, the acetylene black and the crystallites in the graphite are chemically connected without causing cracks.
- the reason why the amount of acetylene black to be mixed with the powder of the raw coal composition is defined as 0.5 to 10% by mass with respect to the raw coal composition will be described. Obtained by carbonizing and graphitizing a composite powder obtained by mixing raw material carbon composition powder and acetylene black of less than 0.5% by mass with respect to the raw material carbon composition and applying compression shear stress.
- a graphite material since the content of acetylene black contained in the composite powder is extremely small, the region of low crystallinity introduced into the graphite material is extremely reduced. Therefore, decomposition of the electrolytic solution due to solvent co-insertion cannot be suppressed.
- the electrolyte solution in the negative electrode is easily decomposed, so that the leakage current of the negative electrode increases and the difference from the leakage current with the positive electrode increases.
- -It is not preferable because the working area of the capacity of the negative electrode changes and the life characteristics deteriorate.
- the raw material carbon composition powder and acetylene black exceeding 10% by mass with respect to the raw material carbon composition are mixed, they are mixed with respect to the void region between the hexagonal net plane laminates of the raw material carbon composition. The amount of acetylene black becomes extremely large.
- the specific surface area of acetylene black is preferably 30 m 2 / g to 300 m 2 / g.
- the specific surface area was measured by BET multipoint method using nitrogen gas adsorption after drying at 180 ° C. for 3 hours using BELSORP-mini II manufactured by Bell Japan.
- BET multipoint method using nitrogen gas adsorption after drying at 180 ° C. for 3 hours using BELSORP-mini II manufactured by Bell Japan.
- the void area in the raw coal composition is extremely small.
- a strong carbon-carbon bond is not formed between acetylene black and the crystallite in graphite when both crystallites grow in the process of carbonization and graphitization. Therefore, it is not preferable.
- the DBP oil absorption of acetylene black is preferably 50 to 200 ml / 100 g.
- the DBP oil absorption is an index indicating the development of the aggregate structure.
- the acetylene black having a DBP oil absorption in this range and the raw carbon composition powder are mixed and then the composite powder obtained by applying compressive shear stress is carbonized and graphitized, acetylene black and graphite
- a graphite material in which a strong carbon-carbon bond is formed between the crystallites can be obtained.
- the DBP oil absorption was an oil absorption per 100 g determined from 70% of the maximum torque when DBP was added to acetylene black using an absorber meter.
- acetylene black having a DBP oil absorption of less than 50 ml / 100 g the structure is not developed and the specific surface area is small.
- acetylene black and raw coal composition powder are mixed and compression shear stress is applied, acetylene black embedded in the void region in the raw coal composition, unstructured carbon existing in the void region, and A composite powder having an extremely small contact area can be obtained.
- a composite powder is carbonized and graphitized, a strong carbon-carbon bond is not formed at the interface between the two during carbonization and graphitization, which is not preferable.
- the structure is highly developed.
- acetylene black and raw coal composition powder are mixed and compressive shear stress is applied, the structure of acetylene black is larger than the volume of the void region of the raw coal composition.
- the acetylene black cannot be embedded in the void region in the raw coal composition.
- a composite powder is obtained in which acetylene black remains attached to the particle surface of the raw carbon composition, and when such a composite powder is carbonized and graphitized, the specific surface area of the graphite particle surface after graphitization is obtained.
- the raw coal composition has an atomic ratio of hydrogen atoms H to carbon atoms C of H / C of 0.30 to 0.50, and a micro strength of 7% by mass to 17% by mass.
- the raw coal composition having such parameters has an appropriate void region between hexagonal net plane laminates, it is possible to obtain a composite powder in which acetylene black is embedded in the particle surface of the raw coal composition. It is.
- the raw coal composition has an appropriate bond strength between hexagonal mesh plane laminates, in the graphite material obtained after graphitizing the composite powder, it is strong between the acetylene black and the crystallites in the graphite. It becomes possible to form a carbon-carbon bond.
- H / C of the raw coal composition is a ratio of the value obtained by dividing the total hydrogen content (TH (mass%)) by the atomic weight of hydrogen and the value obtained by dividing the total carbon content (TC (mass%)) by the atomic weight of carbon. It is.
- the total hydrogen is measured by completely burning the sample in an oxygen stream at 750 ° C. and determining the amount of water generated from the combustion gas by the coulometric titration method (Karl Fischer method).
- Karl Fischer method an electrolyte containing iodide ions, sulfur dioxide, base (RN) and alcohol as main components is placed in the titration cell in advance, and the sample is placed in the titration cell. Moisture reacts as shown in the following formula (4).
- a sample is measured, for example after cooling in a dry atmosphere after a caulking process.
- the iodine necessary for this reaction can be obtained by electrochemically reacting iodide ions (two-electron reaction) as shown in the following formula (5).
- the constant 96478 is the Faraday constant, and 18.5513 is the molecular weight of water.
- the amount of water can be determined. Furthermore, it converts into the amount of hydrogen from the obtained moisture content, and remove
- the total carbon was measured by burning the sample in an oxygen stream at 1150 ° C., converted into carbon dioxide (partially carbon monoxide), transported to an excess oxygen stream, and CO 2 + CO infrared detector, TC (mass%) is calculated.
- the H / C atomic ratio of the raw coal composition is 0.30 to 0.50.
- the H / C atomic ratio is an index indicating the spread of the hexagonal network plane, that is, the size of the crystallite.
- the ratio of the carbon component contained in the raw coal composition is large, so the spread of the hexagonal mesh plane is large.
- the value of H / C is large, since the ratio of hydrogen components contained in the raw coal composition is large, it is difficult to form a carbon-carbon bond, so the hexagonal mesh plane becomes small.
- the spread of the hexagonal mesh plane of the particles in the powder of the raw coal composition obtained by pulverizing and classifying the raw coal composition having an H / C atomic ratio of less than 0.30 is large. Therefore, the void area between the hexagonal plane laminates for acetylene black being embedded is extremely small. Even when acetylene black is mixed with such raw coal composition powder and compression shear stress is applied, the acetylene black is not embedded in the raw coal composition and adheres to the particle surface of the raw coal composition. A composite powder remaining in the state can be obtained. When the composite powder in such a state is carbonized and graphitized, the specific surface area of the surface of the graphite material obtained after graphitization is greatly increased.
- Lithium ion secondary batteries using these graphite materials as negative electrodes are prone to decomposition of the electrolyte solution using localized electrons present on the edge as a catalyst, so the leakage current of the negative electrode increases and the leakage current with the positive electrode Therefore, the operating range of the positive and negative electrode capacities is changed, and the life characteristics are deteriorated.
- the H / C of the raw coal composition is limited to 0.30 to 0.50.
- a compressive shear stress is applied, whereby the raw coal composition Without breaking the bonds between the crystallites present in the void regions in the powder, composite powders in which acetylene black is appropriately embedded on the surface of the raw carbon composition particles can be obtained.
- carbonized and graphitized it is possible to realize a graphite material in which a region having a very small crystallite edge and a low crystallinity is introduced on the particle surface.
- Micro strength is a steel cylinder (inner diameter 25.4 mm, length 304.8 mm) with 20 g to 30 mesh sample 2 g and 12 steel balls 5/16 inch (7.9 mm) in diameter.
- Rotate 800 rpm at 25 rpm in the direction perpendicular to the axis ie, rotate the axis horizontally so that the top and bottom can be switched from the upright position, rotate as if the propeller is rotating), and screen with 48 mesh. It is the value which showed the mass on the sieve with respect to the percentage.
- the micro strength of the raw coal composition is 7% by mass to 17% by mass. This micro strength is an index indicating the bond strength between adjacent hexagonal mesh plane laminates.
- the bonding strength of unstructured carbon existing in the void region between the hexagonal plane laminates is extremely weak. Therefore, when acetylene black is embedded in the void region, the bond of unorganized carbon existing in the void region is likely to be broken.
- the graphite material obtained by carbonizing and graphitizing the composite powder in such a state an edge surface generated by bond breaking of unstructured carbon present in the void is exposed on the particle surface.
- Lithium ion secondary batteries using these graphite materials as the negative electrode are prone to decomposition of the electrolyte solution using the localized electrons present on the edge as a catalyst, so the leakage current of the negative electrode increases and the leakage current with the positive electrode Is not preferable because the operating range of the positive and negative electrode capacities changes and the life characteristics deteriorate. Therefore, in the composite powder in which acetylene black is embedded in the void region, a carbon-carbon bond is not easily formed between acetylene black and unstructured carbon.
- the specific surface area is greatly increased due to large irregularities on the particle surface.
- the contact area between the electrolytic solution and the negative electrode graphite increases, so that the electrolytic solution is easily decomposed. Therefore, the leakage current of the negative electrode is increased, and the difference from the leakage current with the positive electrode is increased. Therefore, the operating region of the positive / negative electrode capacity is changed, and the life characteristics are deteriorated.
- the micro strength of the raw coal composition is limited to 7% by mass to 17% by mass.
- a graphite material having a structure in which a region having a low degree of crystallinity is introduced in a highly developed crystal structure and having less exposure of edge portions on the particle surface is obtained. Can do.
- the raw coal composition used in the present invention can be obtained by coking a heavy oil composition by a delayed coking process.
- Components of heavy oil composition include bottom oil of fluid catalytic cracking equipment (fluid catalytic cracking residual oil, FCC DO), aromatics extracted from fluid catalytic cracking residual oil, and advanced hydrodesulfurization treatment for heavy oil Hydrodesulfurized oil, vacuum residue (VR), desulfurized desulfurized oil, coal liquefied oil, coal solvent extract oil, atmospheric residual oil, shell oil, tar sand bitumen, naphtha tar pitch, ethylene bottom oil Coal tar pitch and heavy oil obtained by hydrorefining these.
- These heavy oils may be used alone or in a blend of two or more.
- the blending ratio of two or more types of heavy oils may be appropriately adjusted according to the properties of the heavy oils used.
- the properties of heavy oil vary depending on the type of crude oil, the processing conditions for obtaining heavy oil from crude oil, and the like.
- the bottom oil of the fluid catalytic cracking unit is a bottom of the fluidized bed type fluid catalytic cracking unit that uses a vacuum gas oil as a raw material oil and selectively performs a cracking reaction using a catalyst to obtain a high octane FCC gasoline.
- Oil used as the raw material oil is preferably a desulfurized vacuum gas oil obtained by directly desulfurizing an atmospheric distillation residue oil (preferably a sulfur content of 500 ppm by mass or less, a density of 0.8 g / cm 3 or more at 15 ° C. ).
- the aromatic content extracted from the fluid catalytic cracking residual oil is the aromatic content when selectively extracted using dimethylformamide or the like and separated into an aromatic content and a saturated content.
- Hydrodesulfurized oil obtained by subjecting heavy oil to advanced hydrodesulfurization treatment is, for example, sulfur content obtained by hydrodesulfurization treatment of heavy oil having a sulfur content of 1% by mass or more at a hydrogen partial pressure of 10 MPa or more. It is a heavy oil with 0% by mass or less, nitrogen content of 0.5% by mass or less, and aromatic carbon fraction (fa) of 0.1 or more.
- the hydrodesulfurized oil is preferably a hydrodesulfurized oil obtained by hydrodesulfurizing an atmospheric distillation residue in the presence of a catalyst so that the hydrocracking rate is 25% or less.
- the vacuum residual oil (VR) is obtained by subjecting crude oil to an atmospheric distillation apparatus to obtain gas, light oil, and atmospheric residual oil.
- the atmospheric residual oil is heated at the furnace outlet temperature under a reduced pressure of, for example, 10 Torr to 30 Torr.
- This is a bottom oil of a vacuum distillation apparatus obtained by changing the temperature within the range of 320 ° C to 360 ° C.
- Desulfurized desulfurized oil is obtained by, for example, treating oil such as vacuum distillation residue oil with a solvent desulfurization apparatus using propane, butane, pentane, or a mixture thereof as a solvent, and removing the asphaltenes.
- desulfurized oil (DAO) is desulfurized using an indirect desulfurization apparatus (Isomax) or the like, preferably in a range of 0.05 mass% to 0.40 mass% of sulfur content.
- Isomax indirect desulfurization apparatus
- Atmospheric residual oil is obtained by subjecting crude oil to an atmospheric distillation apparatus, for example, heating under normal pressure, and depending on the boiling point of the contained fraction, gas / LPG, gasoline fraction, kerosene fraction, light oil fraction, ordinary oil fraction, One of the fractions obtained when divided into pressure residue oil, and the fraction with the highest boiling point.
- the heating temperature varies depending on the production area of the crude oil and is not limited as long as it can be fractionated into these fractions. For example, the crude oil is heated to 320 ° C.
- Examples of particularly preferred heavy oil compositions include (1) aromatic fraction (aromatic index) fa of 0.3 to 0.65, and (2) normal paraffin content of 5% by mass to 20%. And a heavy oil composition satisfying the three conditions: (3) the desulfurized desulfurized oil is contained in the range of 7% by mass to 15% by mass. it can.
- aromatic fraction aromatic index
- normal paraffin content 5% by mass to 20%.
- the desulfurized desulfurized oil is contained in the range of 7% by mass to 15% by mass. it can.
- a heavy oil component that produces a good bulk mesophase and (2) when the bulk mesophase is polycondensed and carbonized and solidified, the size of the hexagonal mesh plane laminate constituting the mesophase is It is particularly preferable to use a raw oil composition containing a heavy oil component capable of generating a gas having a function of limiting to a small size, and (3) a component that binds the cut hexagonal mesh plane laminates together.
- a heavy oil component that produces a good bulk mesophase is a component that gives an aromatic index fa of 0.3 to 0.65
- a heavy oil component that can generate gas contains normal paraffin This is a desulfurized dewaxed oil containing 5% by mass to 20% by mass of the component, and (3) a component that binds the hexagonal net plane laminates in the range of 7% by mass to 15% by mass.
- the aromatic carbon fraction (aromatic index) (fa) can be determined by the Knight method.
- the carbon distribution is divided into three components (A 1 , A 2 , A 3 ) as an aromatic carbon spectrum by the 13 C-NMR method.
- a 1 is the number of carbon atoms inside the aromatic ring, half of the substituted aromatic carbon and half of the unsubstituted aromatic carbon (corresponding to a peak of about 40 ppm to 60 ppm of 13 C-NMR), and A 2 is substituted
- a 3 is the number of aliphatic carbon (corresponding to a peak of about 130 ppm to 190 ppm of 13 C-NMR), From these, fa is calculated
- the 13 C-NMR method is the best method for quantitatively determining fa, which is the most basic amount of chemical structural parameters of pitches, as described in the literature ("Pitch Characterization II. Chemical Structure” Yokono, Sanada, (Carbon, 1981 (No. 105), p73-81).
- the content of normal paraffin in the heavy oil composition means a value measured by a gas chromatograph equipped with a capillary column. Specifically, after testing with a normal paraffin standard substance, the sample of the non-aromatic component separated by the elution chromatography method is passed through a capillary column and measured. The content based on the total mass of the heavy oil composition can be calculated from this measured value.
- the aromatic index fa of the heavy oil composition is less than 0.3, the yield of coke from the heavy oil composition becomes extremely low, and a good bulk mesophase cannot be formed. It is not preferable because the crystal structure hardly develops even if it is made to be.
- fa exceeds 0.65, a large number of mesophases are generated abruptly in the matrix during the production process of raw coke, and abrupt coalescence of mesophases is mainly repeated rather than single growth of mesophases. For this reason, the rate of coalescence of the mesophases is faster than the rate of gas generation due to the normal paraffin-containing component, which makes it impossible to limit the hexagonal mesh plane of the bulk mesophase to a small size.
- the aromatic index fa of the heavy oil composition is particularly preferably in the range of 0.3 to 0.65.
- fa is susceptible calculated from the density D and the viscosity V of the heavy oil composition, density D is 0.91g / cm 3 ⁇ 1.02g / cm 3, viscosity V is 10 mm 2 / sec. ⁇ 220 mm 2 / sec.
- Particularly preferred are heavy oil compositions having a fa of 0.3 to 0.65.
- the normal paraffin component appropriately contained in the heavy oil composition plays an important role in limiting the size of the bulk mesophase to a small size by generating gas during the coking process. .
- This gas generation also has a function of uniaxially orienting adjacent mesophases limited to a small size and selectively orienting the entire system.
- the content of the normal paraffin-containing component is less than 5% by mass, the mesophase grows more than necessary and a huge carbon hexagonal plane is formed, which is not preferable.
- the normal paraffin content is particularly preferably in the range of 5% by mass to 20% by mass.
- the desulfurized dewaxed oil plays a role of appropriately bonding adjacent hexagonal mesh plane laminates, but the content in the heavy oil composition is in the range of 7% by mass to 15% by mass. It is particularly preferred that When it is less than 7% by mass, or when it exceeds 15% by mass, the micro strength of the heavy oil composition obtained after coking is less than 7% by mass or may exceed 17% by mass, which is not preferable. .
- the heavy oil composition having such characteristics is coked to form the raw coal composition of the present invention.
- a delayed coking method is preferable. More specifically, a method of obtaining raw coke by heat-treating a heavy oil composition with a delayed coker under conditions where the coking pressure is controlled is preferable.
- preferable operating conditions of the delayed coker are a pressure of 0.1 MPa to 0.8 MPa and a temperature of 400 ° C. to 600 ° C.
- the reason why a preferable range is set for the operating pressure of the coker is that the release rate of the gas generated from the component containing normal paraffin to the outside of the system can be limited by the pressure.
- the residence time of the generated gas in the system is an important control for determining the size of the hexagonal mesh plane. It becomes a parameter.
- the reason why a preferable range is set for the operating temperature of the coker is that the temperature is necessary for growing the mesophase from the heavy oil adjusted to obtain the effect of the present invention.
- the raw coal composition thus obtained is pulverized and classified so as to have a predetermined particle size.
- the average particle size is preferably 30 ⁇ m or less.
- the average particle size is based on measurement by a laser diffraction particle size distribution meter.
- the reason why the average particle size is 30 ⁇ m or less is that the particle size is generally and preferably used as a negative electrode carbon material for lithium ion secondary batteries.
- a preferable average particle diameter is 5 ⁇ m to 30 ⁇ m.
- the method for producing the graphite material used as the negative electrode of the lithium ion secondary battery of the present invention includes a step of applying a compressive shear stress by mixing the raw carbon composition powder and acetylene black.
- the compressive shear stress applied at this time includes not only compressive stress and shear stress, but also collision, friction, shear stress, and the like.
- the mechanical energy given by these stresses is larger than the energy obtained by general agitation, and when these energies are given to the particle surface, the mechanochemical phenomena such as the spheroidization of particles and the compounding of particles The effect called is expressed.
- a device capable of simultaneously applying stress such as shearing, compression, collision, etc., which is limited to the structure and principle of the device. It is not something.
- a ball-type kneader such as a rotary ball mill, a wheel-type kneader such as an edge runner, a hybridization system (manufactured by Nara Machinery Co., Ltd.), mechanofusion (manufactured by Hosokawa Micron), nobilta (manufactured by Hosokawa Micron), COMPOSI (Japan) Coke industry).
- the manufacturing conditions in the process of applying the compressive shear stress vary depending on the apparatus to be used.
- the powder P is formed in the gap 33 between the rotating blade vane (rotating direction R1) 31 and the housing 32 as shown in FIG.
- An apparatus having a structure in which compaction and compressive stress are applied is used.
- the blade rotation speed is 1500 rpm to 5000 rpm and the treatment time is 10 minutes to 180 minutes.
- the rotational speed is less than 1500 rpm, or when the treatment time is less than 10 minutes, sufficient compressive shear stress cannot be imparted to the powder of the raw coal composition.
- the treatment is performed for longer than 180 minutes, an excessive compressive shear stress is imparted to the powder of the raw coal composition, and the particle shape is significantly deformed.
- the processing time is 10 minutes to 180 minutes at a peripheral speed of 50 m / s to 80 m / s.
- the peripheral speed is less than 50 m / s, or when the treatment time is less than 10 minutes, sufficient compressive shear stress cannot be applied to the powder of the raw coal composition.
- the treatment is performed for longer than 180 minutes, an excessive compressive shear stress is imparted to the powder of the raw coal composition, and the particle shape is significantly deformed.
- the blade rotation speed is 500 rpm to 3000 rpm and the treatment time is 10 minutes to 300 minutes.
- the rotational speed is less than 500 rpm, or when the treatment time is less than 10 minutes, sufficient compressive shear stress cannot be applied to the raw material carbon composition powder.
- the treatment is performed for longer than 300 minutes, excessive compression shear stress is imparted to the powder of the raw coal composition, and the particle shape is significantly deformed.
- the processing time is 5 to 180 minutes at a peripheral speed of 40 m / s to 60 m / s. This is because, under this condition, a sufficient compressive shear stress can be applied to the raw material carbon composition powder without significantly changing the particle shape.
- the control temperature at the time of the surface treatment for applying the compressive shear stress is preferably 60 ° C. to 250 ° C., whereby acetylene black is applied to the particle surface of the raw coal composition.
- a composite powder in which is embedded is obtained.
- Lc (112) calculated from the (112) diffraction lines obtained by the X-ray wide angle diffraction method for the composite powder in which acetylene black is embedded on the particle surface of the raw coal composition is 4 nm to 30 nm. Carbonize and graphitize.
- the method of carbonization and graphitization treatment is not particularly limited.
- the maximum ultimate temperature is 900 ° C. to 1500 ° C. in an inert gas atmosphere such as nitrogen, argon or helium, and the maximum ultimate temperature holding time is 0 hour to 10 hours.
- Lc (112) calculated from the (112) diffraction line obtained by the X-ray wide angle diffraction method of the graphite material is defined as 4 nm to 30 nm in the present invention.
- Graphite particles having an Lc (112) of less than 4 nm hardly develop a crystal structure, and a lithium ion secondary battery using such a graphite material is not preferable because the capacity becomes small.
- Lc (112) never exceeded 30 nm, so the upper limit was set to 30 nm.
- the raw coal composition having an H / C atomic ratio of 0.30 to 0.50 and a micro strength of 7% by mass to 17% by mass, and 0.5% by mass to 10% by mass with respect to the raw coal composition.
- % Of acetylene black is mixed and a compressive shear stress is applied to obtain a composite powder in which acetylene black is embedded on the particle surface of the raw coal composition, and then the composite powder is carbonized and graphitized.
- the crystallite size Lc (112) of the (112) diffraction line measured by the X-ray wide angle diffraction method is 4 nm to 30 nm, and appropriate disturbance is introduced into the crystal structure of the particle surface.
- a graphite material with very little surface exposure can be obtained. And when such a graphite material is used for the negative electrode material of a lithium ion secondary battery, it becomes possible to ensure extremely high reliability.
- a graphite material manufactured using desulfurized and desulfurized oil as a raw material as a negative electrode material of a lithium ion battery.
- desulfurized dewaxed oil is mixed as a preferred embodiment of the heavy oil composition
- acetylene black is mixed with powder of a raw carbon composition having a predetermined H / C atomic ratio and micro strength, and compression shear stress is set.
- a desired graphite material can be provided by carbonizing and graphitizing the composite powder obtained by applying.
- the method for producing a negative electrode for a lithium ion secondary battery is not particularly limited, and includes, for example, a graphite material to which the invention according to the present application is applied, a binder (binder), and a conductive auxiliary agent and an organic solvent as necessary.
- the method of pressure-molding a mixture (negative electrode mixture) to a predetermined dimension is mentioned.
- a graphite material to which the invention according to the present application is applied, a binder (binder), a conductive auxiliary agent and the like are kneaded and slurried in an organic solvent, and the slurry is used as a current collector such as a copper foil.
- a method of rolling a coated and dried product (negative electrode mixture) and cutting it into a predetermined size can also be mentioned.
- binder examples include polyvinylidene fluoride, polytetrafluoroethylene, polyacrylonitrile, polyethylene terate, and SBR (styrene-butadiene rubber).
- the content of the binder in the negative electrode mixture may be appropriately set as necessary from the viewpoint of battery design from about 1 to 30 parts by mass with respect to 100 parts by mass of the graphite material.
- the conductive assistant examples include carbon black, graphite, acetylene black, conductive indium-tin oxide, or conductive polymers such as polyaniline, polythiophene, and polyphenylene vinylene.
- the amount of the conductive aid used is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the graphite material.
- organic solvent examples include dimethylformamide, N-methylpyrrolidone, pyrrolidone, N-methylthiopyrrolidone, hexamethylphosphoamide, dimethylacetamide, isopropanol, toluene and the like.
- the graphite material As a method of mixing the graphite material, the binder, and, if necessary, the conductive aid and the organic solvent, known devices such as a screw type kneader, a ribbon mixer, a universal mixer, and a planetary mixer can be used.
- the mixture is formed by roll pressure or press pressure, and the pressure at this time is preferably about 100 MPa to 300 MPa.
- the material of the current collector can be used without any limitation as long as it does not form an alloy with lithium.
- copper, nickel, titanium, stainless steel, etc. can be mentioned.
- the shape of the current collector can be used without any particular limitation, but as an example, it may be a strip shape in the form of foil, perforated foil, mesh, or the like.
- a porous material such as porous metal (foamed metal) or carbon paper can also be used.
- the method of applying the slurry to the current collector is not particularly limited, for example, metal mask printing method, electrostatic coating method, dip coating method, spray coating method, roll coating method, doctor blade method, gravure coating method, Known methods such as a screen printing method and a die coater method can be used. After coating, it is common to perform a rolling process using a flat plate press, a calender roll, or the like as necessary. Further, the integration of the negative electrode material slurry formed into a sheet shape, a pellet shape, and the like with the current collector can be performed by a known method such as a roll, a press, or a combination thereof.
- the lithium ion secondary battery using the graphite material for the negative electrode of the lithium ion secondary battery according to the present embodiment is, for example, arranged so that the negative electrode and the positive electrode manufactured as described above face each other with a separator interposed therebetween, It can be obtained by injecting an electrolytic solution.
- the active material used for the positive electrode is not particularly limited. For example, a metal compound, metal oxide, metal sulfide, or conductive polymer material that can be doped or intercalated with lithium ions may be used.
- lithium cobaltate LiCoO 2
- lithium nickelate LiNiO 2
- lithium manganate LiMn 2 O 4
- lithium vanadium compounds V 2 O 5 , V 6 O 13 , VO 2 , MnO 2 , TiO 2, MoV 2 O 8 , TiS 2, V 2 S 5, VS 2, MoS 2, MoS 3, Cr 3 O 8, Cr 2 O
- Olivine LiMPO 4 M: Co, Ni , Mn, Fe
- polyacetylene polyaniline
- polypyrrole polythiophene
- electrically conductive polymers such as polyacene, porous carbon or the like and mixtures thereof.
- the separator for example, a nonwoven fabric, a cloth, a microporous film, or a combination thereof, which is mainly composed of polyolefin such as polyethylene or polypropylene, can be used.
- a separator when it is set as the structure where the positive electrode and negative electrode of the lithium ion secondary battery to produce are not in direct contact, it is not necessary to use a separator.
- organic electrolytes As the electrolyte and electrolyte used for the lithium ion secondary battery, known organic electrolytes, inorganic solid electrolytes, and polymer solid electrolytes can be used. Preferably, an organic electrolyte is preferable from the viewpoint of electrical conductivity.
- organic electrolyte examples include dibutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, ethylene glycol phenyl ether, and other ethers, N-methylformamide, N, N-dimethylformamide, N Amides such as ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide, sulfur-containing compounds such as dimethylsulfoxide and sulfolane, methyl ethyl ketone, Dialkyl ketones such as methyl isobutyl ketone, cyclic ethers such as tetrahydrofuran and 2-methoxytetrahydrofuran, ethylene carbonate Cyclic carbonates such as butylene carbonate, propylene carbonate and vinyl
- lithium salts can be used as the solute of these solvents.
- Commonly known lithium salts include LiClO 4 , LiBF 4 , LiPF 6 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCl, LiCF 3 SO 3 , LiCF 3 CO 2 , LiN (CF 3 SO 2 ) 2, LiN (C 2 F 5 SO 2 ) 2 and the like.
- polymer solid electrolyte examples include a polyethylene oxide derivative and a polymer containing the derivative, a polypropylene oxide derivative and a polymer containing the derivative, a phosphate ester polymer, a polycarbonate derivative and a polymer containing the derivative. There are no restrictions on the selection of members other than those described above necessary for the battery configuration.
- the structure of the lithium ion secondary battery is not particularly limited, a wound electrode group in which a positive electrode and a negative electrode formed in a strip shape are wound in a spiral shape through a separator is inserted into a battery case and sealed.
- a structure in which a laminated electrode plate group in which a positive electrode and a negative electrode formed in a flat plate shape are sequentially laminated via a separator is enclosed in an exterior body.
- the lithium ion secondary battery is used as, for example, a paper battery, a button battery, a coin battery, a stacked battery, a cylindrical battery, a rectangular battery, or the like.
- the lithium ion secondary battery using the graphite material of the present invention as a negative electrode material can ensure extremely high reliability as compared with a lithium ion secondary battery using a conventional carbon material, It can be used for industrial purposes such as for automobiles, specifically for hybrid cars, plug-in hybrid cars, electric cars, and power storage for grid infrastructure.
- Raw coal composition and production method thereof (1) Raw coal composition A-1 The atmospheric distillation residue having a sulfur content of 3.1% by mass was hydrodesulfurized in the presence of a catalyst so that the hydrocracking rate was 25% or less to obtain a hydrodesulfurized oil.
- the hydrodesulfurization conditions are a total pressure of 180 MPa, a hydrogen partial pressure of 160 MPa, and a temperature of 380 ° C.
- desulfurized vacuum gas oil (sulfur content: 500 mass ppm, density: 0.88 g / cm 3 at 15 ° C.) was subjected to fluid catalytic cracking to obtain fluid catalytic cracking residual oil.
- the fluid catalytic cracking residual oil was selectively extracted with dimethylformamide, separated into an aromatic component and a saturated component, and the aromatic component was extracted.
- This extracted aromatic component and hydrodesulfurized oil were mixed at a mass ratio of 8: 1, and desulfurized desulfurized oil was added so as to be 19% by mass (100% by mass in the entire mixture including desulfurized desulfurized oil) ),
- a coke raw material oil composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain raw material carbon composition A-1.
- Raw coal composition B-1 Coke is obtained by adding desulfurized dewaxed oil so that the raw oil composition of the raw coal composition A-1 is a mixture of extracted aromatics and hydrodesulfurized oil at a mass ratio of 8: 1 so as to be 11% by mass.
- the raw material oil composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition B-1.
- Raw coal composition C-1 Coke is obtained by adding desulfurized dewaxed oil so that the raw oil composition of the raw coal composition A-1 is a mixture of the extracted aromatic component and the hydrodesulfurized oil in a mass ratio of 8: 1 so as to be 4% by mass.
- the raw material oil composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition C-1.
- Raw coal composition D-1 Coke is obtained by adding desulfurized and desulfurized oil so that the raw material oil composition of the raw coal composition A-1 is a mixture of the extracted aromatic component and the hydrodesulfurized oil in a mass ratio of 6: 1 so as to be 17% by mass.
- the raw material oil composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition D-1.
- Raw coal composition E-1 Coke is obtained by adding desulfurized and desulfurized oil so that the raw material oil composition of the raw coal composition A-1 is a mixture of the extracted aromatic component and the hydrodesulfurized oil in a mass ratio of 6: 1 so as to be 11% by mass.
- the raw material oil composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain raw material carbon composition E-1.
- Raw coal composition F-1 Coke is obtained by adding desulfurized and desulfurized oil so that the raw material oil composition of the raw coal composition A-1 is obtained by mixing the extracted aromatic component and the hydrodesulfurized oil at a mass ratio of 6: 1 so as to be 6% by mass.
- the raw material oil composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition F-1.
- Raw coal composition G-1 Desulfurization and desulfurization so that the hydrodesulfurized oil and the fluid catalytic cracking residual oil, which are the raw materials of the raw oil composition of the raw coal composition A-1, are mixed at a mass ratio of 1: 5 to 15% by mass. Oil was added to obtain a coke feedstock composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition G-1.
- Raw coal composition H-1 Desulfurization and desulfurization of 7% by mass with a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil, which are raw materials of the raw oil composition of raw coal composition A-1, at a mass ratio of 1: 5 Oil was added to obtain a coke feedstock composition.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition H-1.
- Raw coal composition I-1 Desulfurization desulfurization so that it becomes 19 mass% in what mixed the hydrodesulfurization oil used as the raw material of raw material oil composition of raw coal composition A-1, and fluid catalytic cracking residual oil by mass ratio 1: 4. Oil was added to obtain a raw material composition of Oaks. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain raw material charcoal composition I-1.
- Raw coal composition J-1 Desulfurization and desulfurization so that the hydrodesulfurization oil and the fluid catalytic cracking residual oil, which are the raw materials of the raw material oil composition of the raw coal composition A-1, are mixed at a mass ratio of 1: 4 to 16 mass%. Oil was added to obtain a coke feedstock composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain raw material charcoal composition J-1.
- Raw coal composition K-1 Desulfurized desulfurized so that it becomes 11% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil, which are raw materials of the raw material oil composition of raw coal composition A-1, at a mass ratio of 1: 4. Oil was added to obtain a coke feedstock composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition K-1.
- Raw coal composition L-1 Desulfurized and desulfurized so that the hydrodesulfurized oil and the fluid catalytic cracking residual oil, which are the raw materials of the raw oil composition of the raw coal composition A-1, are mixed at a mass ratio of 1: 4 to 5 mass%. Oil was added to obtain a coke feedstock composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition L-1.
- Coking coal composition M-1 Desulfurization and desulfurization of 3% by mass of hydrodesulfurized oil and fluid catalytic cracking residual oil which are raw materials of the raw material oil composition of raw material carbon composition A-1 mixed at a mass ratio of 1: 4 Oil was added to obtain a coke feedstock composition.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition M-1.
- Raw coal composition N-1 Desulfurization and desulfurization so that the hydrodesulfurized oil and the fluid catalytic cracking residual oil, which are the raw materials of the raw oil composition of the raw coal composition A-1, are mixed at a mass ratio of 1: 3 so as to be 14% by mass. Oil was added to obtain a coke feedstock composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition N-1.
- Raw coal composition O-1 Desulfurized and desulfurized so as to be 7% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil, which are raw materials of the raw material oil composition of raw coal composition A-1, at a mass ratio of 1: 3. Oil was added to obtain a coke feedstock composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw carbon composition O-1.
- Raw coal composition P-1 After adding and mixing the same volume of n-heptane to the fluid catalytic cracking residual oil that was the raw material of the raw oil composition of the raw coal composition A-1, it was selectively extracted with dimethylformamide to obtain an aromatic content and a saturated content. Separation was performed, and a saturated portion was selectively extracted. Desulfurized and desulfurized oil was added to a mixture of the fluid catalytic cracking residual oil and the extracted saturated component at a mass ratio of 1: 1 so as to be 16% by mass to obtain a coke raw material oil composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition P-1.
- Raw coal composition Q-1 Desulfurization and desulfurization of 11% by mass in a mixture of the fluid catalytic cracking residual oil, which is the raw material of the raw material oil composition of the raw coal composition P-1, and the extraction saturated component in a mass ratio of 1: 1. Oil was added to obtain a coke feedstock composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition Q-1.
- Raw coal composition R-1 Desulfurization and desulfurization so as to be 6% by mass in a mixture of fluid catalytic cracking residual oil, which is a raw material of the raw material oil composition of the raw coal composition P-1, and an extraction saturated component in a mass ratio of 1: 1. Oil was added to obtain a coke feedstock composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition R-1.
- Raw coal composition S-1 Desulfurized and desulfurized so that it becomes 19% by mass in a mixture of fluid catalytic cracking residual oil, which is a raw material of the raw material oil composition of the raw coal composition P-1, and extraction saturated component in a mass ratio of 1: 2. Oil was added to obtain a coke feedstock composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain raw material carbon composition S-1.
- Raw coal composition T-1 Desulfurized and desulfurized so as to be 10% by mass in a mixture of fluid catalytic cracking residual oil, which is a raw material of the raw material oil composition of the raw material carbon composition P-1, and an extraction saturated component in a mass ratio of 1: 2. Oil was added to obtain a coke feedstock composition. This raw material oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition T-1.
- H / C of the raw coal composition is a ratio of the value obtained by dividing the total hydrogen content (TH (mass%)) by the atomic weight of hydrogen and the value obtained by dividing the total carbon content (TC (mass%)) by the atomic weight of carbon. Calculated with The H / C values of the raw coal compositions A-1 to U-1 are as shown in Table 1.
- a graphite precursor imparted with compressive stress and shear stress was obtained.
- the fine particles to which compressive stress and shear stress were applied were carbonized with a roller hearth kiln manufactured by Takasago Industry Co., Ltd. under a nitrogen gas stream so that the maximum temperature reached 1200 ° C. and the maximum temperature maintained time was 5 hours.
- the obtained carbon material was put into a crucible, placed in an electric furnace, and graphitized at a maximum reached temperature of 2800 ° C. in a nitrogen gas stream at 80 L / min.
- the obtained graphite material is referred to as graphite A-1 to U-1 corresponding to the raw coal compositions A-1 to U-1.
- the obtained carbon material was put into a crucible, placed in an electric furnace, and graphitized at a maximum reached temperature of 2800 ° C. in a nitrogen gas stream at 80 L / min. At this time, the temperature rising rate was 200 ° C./hour, the maximum temperature holding time was 3 hours, the temperature lowering rate was 100 ° C./hour up to 1000 ° C., and then the mixture was allowed to cool to room temperature while maintaining a nitrogen stream.
- the obtained graphite materials are referred to as graphite V-1, W-1, and X-1 corresponding to the raw coal compositions H-1, K-1, and N-1.
- the X-ray diffractometer was D8 ADVANCE (encapsulated tube type) manufactured by Bruker-AXS, the X-ray source was CuK ⁇ ray (using K ⁇ filter Ni), and the applied voltage and current to the X-ray tube were 40 kV and 40 mA.
- the obtained diffraction pattern was also analyzed by a method (carbon 2006, No. 221, P52-60) based on the method defined by the Japan Society for the Promotion of Science 117.
- the measurement data is subjected to smoothing processing, background removal, absorption correction, polarization correction, and Lorentz correction, and using the (422) diffraction line peak position and value width of the Si standard sample, the graphite powder (112)
- the diffraction line was corrected and the crystallite size was calculated.
- the crystallite size was calculated from the half width of the corrected peak using the following Scherrer equation. Measurement and analysis were performed three times each, and the average value was defined as Lc (112).
- the results of measurement of Lc (112) of the graphite powder are as shown in Table 1.
- FIG. 1 is a cross-sectional view of the produced battery.
- the positive electrode is made of lithium nickel oxide having an average particle size of 6 ⁇ m (LiNi 0.8 Co 0.15 Al 0.05 O 2 manufactured by Toda Kogyo Co., Ltd.) and a polyvinylidene fluoride binder (KF # 1320 manufactured by Kureha Co., Ltd.). ), Acetylene black (Denka Black manufactured by Denka) was mixed at a mass ratio of 89: 6: 5, kneaded with N-methyl-2-pyrrolidinone, then pasted into an aluminum foil having a thickness of 30 ⁇ m.
- graphite powders of graphite A-1 to W-1 which are negative electrode materials and polyvinylidene fluoride (Kureha KF # 9310) and acetylene black (Denka black manufactured by Denka) by weight ratio are 91. : 2: 8, mixed with N-methyl-2-pyrrolidinone, kneaded, applied in a paste, coated on one side of 18 ⁇ m thick copper foil, dried and rolled, and the size of the coated part Is a sheet electrode cut to have a width of 32 mm and a length of 52 mm. At this time, the coating amount per unit area was set to 6 mg / cm 2 as the mass of the graphite powder. Part of this sheet electrode is scraped off the negative electrode mixture perpendicularly to the longitudinal direction of the sheet, and the exposed copper foil is connected integrally with the current collector (copper foil) of the coating part, It plays a role as a board.
- the battery was assembled by fully drying the positive electrode, negative electrode, separator, and other components and introducing them into a glove box filled with argon gas having a dew point of ⁇ 100 ° C.
- the drying conditions are such that the positive electrode and the negative electrode are under reduced pressure at 150 ° C. for 12 hours or longer, and the separator and other members are under reduced pressure at 70 ° C. for 12 hours or longer.
- the positive electrode and the negative electrode thus dried are laminated in such a manner that the positive electrode application portion and the negative electrode application portion face each other with a microporous film made of polypropylene (# 2400 manufactured by Celgard) facing each other. Fixed.
- the positive electrode and the negative electrode were positioned so that the peripheral edge of the positive electrode application part projected on the negative electrode application part was surrounded by the inner side of the peripheral part of the negative electrode application part.
- the obtained single-layer electrode body is embedded with an aluminum laminate film, an electrolyte solution is injected, and the laminate film is heat-sealed in a state where the positive and negative electrode lead plates are protruded.
- a layer laminate battery was prepared.
- the electrolyte used was one in which lithium hexafluorophosphate (LiPF 6 ) was dissolved in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 so as to have a concentration of 1 mol / L. .
- the battery voltage was 3.0 V with the same current (15 mA).
- the battery was discharged at a constant current until Let the discharge capacity obtained at this time be the discharge capacity of the first cycle.
- the charge / discharge cycle under the same conditions was repeated 3000 times, and the ratio (%) of the discharge capacity at the 3000th cycle to the discharge capacity at the 1st cycle was calculated to be “capacity maintenance rate after 3000 cycles (%)”.
- Table 1 shows the discharge capacity of the first cycle, the discharge capacity of the 3000th cycle, and the capacity retention rate (%) after 3000 cycles.
- Table 1 shows H / C values and micro strengths of raw coal compositions A-1 to U-1, and graphites A-1 to Z corresponding to the raw coal compositions A-1 to U-1.
- the subsequent capacity retention rate (%) is shown.
- the raw coal composition is within the scope of the present invention, that is, the H / C value is 0.3 to 0.5 and the micro strength is 7 to 17.
- the ones graphitized after applying shear stress (G-1, H-1, K-1, N-1, O-1, Y-1, Z-1) have a discharge capacity retention rate after 3000 cycles. It became 85% or more, and it turned out that a reliable lithium ion secondary battery with little cycle deterioration is realizable.
- the battery using the graphitized material without applying compressive stress and shear stress to the negative electrode has a large cycle deterioration. It has been found that the physical properties being within the scope of the present application and the application of compressive stress and shear stress are necessary conditions for ensuring a capacity retention ratio of at least 85% after 3000 cycles.
- Graphite Y-1 and Z-1 are obtained by setting the graphitization temperature of the raw coal composition K-1 to 2600 ° C. and 2300 ° C.
- the crystallite size Lc (112) of graphite K-1 treated at 2800 ° C. was 7.2 nm
- graphite Y-1 treated at 2600 ° C. was 4 nm
- graphite Z treated at 2300 ° C. -1 was 3.5 nm.
- the physical properties of the raw coal composition are within the scope of the present invention and are graphitized after applying compressive stress and shear stress, so the capacity retention rate after 3000 cycles is 92 % Or more, and can be regarded as a negative electrode graphite material capable of realizing a battery with extremely high cycle stability.
- the crystallite size is small, only a battery with a small capacity can be realized.
- the graphite precursor obtained by applying compressive stress and shear stress to the pulverized and classified raw coal composition is measured by the X-ray wide angle diffraction method (112) Crystalline size of diffraction line Graphite material obtained by graphitization so that the thickness Lc (112) is 4 nm or more, and a raw material carbon composition to be pulverized and classified is subjected to coking treatment of a heavy oil composition by a delayed coking process And having a ratio of hydrogen atom H to carbon atom C, H / C atom ratio of 0.30 to 0.50, and a micro strength of 7 to 17% by mass, the graphite material is used as a negative electrode.
- the lithium ion secondary battery was able to secure a capacity of 16 mAh or more, and the capacity retention rate after 3000 cycles of charge / discharge could achieve 85% or more.
- Raw coal composition and production method thereof (1) Raw coal composition A-2 The atmospheric distillation residue having a sulfur content of 3.1% by mass was hydrodesulfurized in the presence of a catalyst so that the hydrocracking rate was 25% or less to obtain a hydrodesulfurized oil.
- the hydrodesulfurization conditions are a total pressure of 180 MPa, a hydrogen partial pressure of 160 MPa, and a temperature of 380 ° C.
- desulfurized vacuum gas oil (sulfur content: 500 mass ppm, density: 0.88 g / cm 3 at 15 ° C.) was subjected to fluid catalytic cracking to obtain fluid catalytic cracking residual oil.
- the fluid catalytic cracking residual oil was selectively extracted with dimethylformamide, separated into an aromatic component and a saturated component, and the aromatic component was extracted.
- This extracted aromatic component and hydrodesulfurized oil were mixed at a mass ratio of 8: 1, and desulfurized dewaxed oil was added so as to be 19% by mass (100% by mass of the entire mixture including desulfurized desulfurized oil) ),
- a heavy oil composition was obtained.
- This heavy oil composition was introduced into a delayed coker apparatus, and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition A-2.
- Raw coal composition B-2 11% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as the production method of the raw coal composition A-2 and the hydrodesulfurized oil in a mass ratio of 8: 1.
- desulfurized dewaxed oil was added to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition B-2.
- Raw coal composition C-2 4% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as in the production method of the raw coal composition A-2 and the hydrodesulfurized oil at a mass ratio of 8: 1.
- desulfurized dewaxed oil was added to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition C-2.
- Raw coal composition D-2 17% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as the production method of the raw coal composition A-2 and the hydrodesulfurized oil in a mass ratio of 6: 1.
- desulfurized dewaxed oil was added to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition D-2.
- Raw coal composition E-2 11% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as the production method of the raw coal composition A-2 and the hydrodesulfurized oil in a mass ratio of 6: 1.
- desulfurized dewaxed oil was added to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition E-2.
- Raw coal composition F-2 6% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as in the production method of the raw coal composition A-2 and the hydrodesulfurized oil in a mass ratio of 6: 1.
- desulfurized dewaxed oil was added to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition F-2.
- Raw coal composition G-2 A hydrodesulfurized oil obtained in the same manner as in the production method of the raw coal composition A-2 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 5 is desulfurized and dehydrated so as to be 15% by mass. Oil was added to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition G-2.
- Raw coal composition H-2 Desulfurized desulfurized so as to be 7% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-2 at a mass ratio of 1: 5. Oil was added to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition H-2.
- Raw coal composition I-2 A hydrodesulfurized oil obtained in the same manner as in the production method of the raw coal composition A-2 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 4 is desulfurized and dehydrated so as to be 19% by mass. Oil was added to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition I-2.
- Raw coal composition J-2 Desulfurized and desulfurized so that the hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of the raw coal composition A-2 are mixed at a mass ratio of 1: 4 so as to be 16% by mass. Oil was added to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition J-2.
- Raw coal composition K-2 Desulfurized desulfurized so as to be 11% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-2 at a mass ratio of 1: 4. Oil was added to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition K-2.
- Raw coal composition L-2 Desulfurized and desulfurized so as to be 5% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-2 at a mass ratio of 1: 4. Oil was added to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition L-2.
- Raw coal composition M-2 A hydrodesulfurized oil obtained in the same manner as the production method of the raw coal composition A-2 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 4 is desulfurized and dehydrated so as to be 3% by mass. Oil was added to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition M-2.
- Raw coal composition N-2 Desulfurized and desulfurized so as to be 14% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-2 at a mass ratio of 1: 3. Oil was added to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition N-2.
- Raw coal composition O-2 A hydrodesulfurized oil obtained in the same manner as the production method of the raw coal composition A-2 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 3 is desulfurized and dehydrated so as to be 7% by mass. Oil was added to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition O-2.
- Raw coal composition P-2 After adding the same volume of n-heptane to the fluid catalytic cracking residual oil obtained in the same manner as the production method of raw coal composition A-2, the mixture is selectively extracted with dimethylformamide to separate into aromatic and saturated components. The saturated content was selectively extracted.
- a heavy oil composition was obtained by adding desulfurized dewaxed oil to a mixture of the fluid catalytic cracking residual oil and the extracted saturated component at a mass ratio of 1: 1 so as to be 16% by mass. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition P-2.
- Raw coal composition Q-2 Fluid catalytic cracking residual oil obtained in the same manner as the production method of raw coal composition A-2, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-2
- a heavy oil composition was obtained by adding desulfurized dewaxed oil so as to be 11% by mass to a mixture of the extraction saturated content of the mixture of No. 1 and the mixture in a mass ratio of 1: 1.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition Q-2.
- Raw coal composition R-2 Fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-2, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-2
- a heavy oil composition was obtained by adding desulfurized dewaxed oil so as to be 6% by mass to the mixture obtained by mixing the extracted saturated content of the above mixture with a mass ratio of 1: 1.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition R-2.
- Raw coal composition T-2 Fluid catalytic cracking residual oil obtained in the same manner as the production method of raw coal composition A-2, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-2
- a heavy oil composition was obtained by adding desulfurized dewaxed oil so as to be 10% by mass to a mixture of the extraction saturated content of the above mixture and the mixture in a mass ratio of 1: 2. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition T-2.
- H / C of the raw coal composition is a ratio of the value obtained by dividing the total hydrogen content (TH (mass%)) by the atomic weight of hydrogen and the value obtained by dividing the total carbon content (TC (mass%)) by the atomic weight of carbon. Calculated with The H / C values of the raw coal compositions A-2 to U-2 are as shown in Table 2.
- the obtained carbon material was put into a crucible, placed in an electric furnace, and graphitized at a maximum reached temperature of 2800 ° C. in a nitrogen gas stream at 80 L / min. At this time, the rate of temperature increase is 200 ° C./hour, the maximum temperature is maintained for 3 hours, the rate of temperature decrease is up to 1000 ° C./100° C./hour, and then the mixture is allowed to cool to room temperature while maintaining a nitrogen stream.
- Graphite particles were obtained.
- the crystallite size Lc (112) of the (112) diffraction line measured by the X-ray wide angle diffraction method of the obtained graphite particles was 10.9 nm.
- the obtained graphite particles are put into “Nobilta 130 type” manufactured by Hosokawa Micron Corporation so that the filling volume is 500 cc, the rotation speed of the blade is controlled to 1300 rpm, the processing temperature is controlled to about 130 ° C., and the processing time is 15
- the graphite material which gave the compressive shear stress by operating on the conditions of minutes was obtained.
- the X-ray diffractometer was D8 ADVANCE (encapsulated tube type) manufactured by Bruker-AXS, the X-ray source was CuK ⁇ ray (using K ⁇ filter Ni), and the applied voltage and current to the X-ray tube were 40 kV and 40 mA.
- the obtained diffraction pattern was also analyzed by a method (carbon 2006, No. 221, P52-60) based on the method defined by the Japan Society for the Promotion of Science 117.
- the measurement data is subjected to smoothing processing, background removal, absorption correction, polarization correction, and Lorentz correction, and the peak position and value width of the (422) diffraction line of the Si standard sample are used to determine the (112)
- the diffraction line was corrected and the crystallite size was calculated.
- the crystallite size was calculated from the half width of the corrected peak using the following Scherrer equation. Measurement and analysis were performed three times each, and the average value was defined as Lc (112).
- the results of measurement of Lc (112) of the graphite particles are as shown in Table 2.
- FIG. 1 is a cross-sectional view of the battery 10 fabricated.
- FIG. 1 shows a negative electrode 11, a negative electrode current collector 12, a positive electrode 13, a positive electrode current collector 14, a separator 15, and an aluminum laminate outer package 16.
- the positive electrode is made of lithium nickel oxide having an average particle size of 6 ⁇ m (LiNi 0.8 Co 0.15 Al 0.05 O 2 manufactured by Toda Kogyo Co., Ltd.) and a polyvinylidene fluoride binder (KF # 1320 manufactured by Kureha Co., Ltd.).
- Acetylene black (Denka Black manufactured by Denka) was mixed at a mass ratio of 89: 6: 5, kneaded with N-methyl-2-pyrrolidinone, then pasted into an aluminum foil having a thickness of 30 ⁇ m. This is a sheet electrode that is coated on one side, dried and rolled, and cut so that the size of the coated part is 30 mm wide and 50 mm long. At this time, the coating amount per unit area was set to 10 mg / cm 2 as the mass of lithium nickelate.
- the negative electrode is composed of the graphite material obtained in the above Examples and Comparative Examples, which are negative electrode materials, and polyvinylidene fluoride (Kureha KF # 9310) and acetylene black (Denka Black, Denka) in a mass ratio.
- the battery was assembled by fully drying the positive electrode, negative electrode, separator, and other components and introducing them into a glove box filled with argon gas having a dew point of ⁇ 100 ° C.
- the drying conditions are such that the positive electrode and the negative electrode are under reduced pressure at 150 ° C. for 12 hours or longer, and the separator and other members are under reduced pressure at 70 ° C. for 12 hours or longer.
- the positive electrode and the negative electrode thus dried are laminated in such a manner that the positive electrode application portion and the negative electrode application portion face each other with a microporous film made of polypropylene (# 2400 manufactured by Celgard) facing each other. Fixed.
- the positive electrode and the negative electrode were positioned so that the peripheral edge of the positive electrode application part projected on the negative electrode application part was surrounded by the inner side of the peripheral part of the negative electrode application part.
- the obtained single-layer electrode body is embedded with an aluminum laminate film, an electrolyte solution is injected, and the laminate film is heat-sealed in a state where the positive and negative electrode lead plates are protruded.
- a layer laminate battery was prepared.
- the electrolyte used was one in which lithium hexafluorophosphate (LiPF 6 ) was dissolved in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 so as to have a concentration of 1 mol / L. .
- discharge capacity after 30 days at 60 ° C. As an index representing storage characteristics, a ratio (%) of “discharge capacity after 30 days at 60 ° C.” to “initial discharge capacity” is calculated, and “capacity maintenance ratio after holding at 60 ° C. for 30 days (%)” did.
- Table 2 shows the initial discharge capacity, the discharge capacity after holding at 60 ° C. for 30 days, and the capacity retention rate (%) after holding at 60 ° C. for 30 days.
- Table 2 shows the H / C value and micro strength of the raw coal composition in Examples and Comparative Examples, the average particle size of the raw coal composition, Lc (112) of graphite particles, surface treatment conditions, and Initial discharge capacity (mAh) of lithium ion secondary battery using graphite material obtained in Examples and Comparative Examples as negative electrode material, discharge capacity after holding at 60 ° C. for 30 days (mAh), after holding at 60 ° C. for 30 days The capacity maintenance rate (%) of
- the raw coal composition was within the scope of the present invention, that is, the H / C value was 0.3 to 0.5 and the micro strength was 7 to 17 (G-2, H- 2, K-2, N-2, O-2) is pulverized and classified to obtain a raw carbon composition powder, and then carbonized and graphitized, the graphite particles are within the scope of the present invention. That is, the crystallite size Lc (112) calculated from the (112) diffraction line obtained by X-ray wide-angle diffraction satisfied 4 nm to 30 nm.
- a battery using a graphite material obtained by applying a compressive shear stress to these graphite particles as a negative electrode material has a capacity retention rate of 89% or more after being held at 60 ° C. for 30 days, and has excellent storage characteristics. It was found that a secondary battery could be realized.
- the raw coal composition (H-2, K-2, N-2) having an H / C value of 0.3 to 0.5 and a micro strength of 7 to 17 was pulverized.
- the graphite particles obtained by classification and obtaining the raw carbon composition powder and then carbonized and graphitized are within the scope of the present invention, that is, from (112) diffraction lines obtained by X-ray wide angle diffraction.
- the calculated crystallite size Lc (112) satisfied 4 nm to 30 nm.
- the raw coal compositions used in Comparative Examples 1 to 16 do not satisfy the range of the present invention, that is, the H / C value of 0.3 to 0.5 and the micro strength of 7 to 17. Capacity retention rate after holding at 60 ° C. for 30 days of a battery using a graphite material obtained by applying compressive shear stress to graphite particles obtained by pulverizing and classifying these and then carbonizing and graphitizing Became very low.
- a process of pulverizing and classifying a raw coal composition obtained by coking a heavy oil composition by a delayed coking process to obtain a raw coal composition powder, and a powder of the raw coal composition A step of obtaining a carbide by graphitizing the carbide and obtaining a graphite particle having an Lc (112) calculated from a (112) diffraction line obtained by X-ray wide-angle diffraction of 4 nm to 30 nm;
- a ratio of hydrogen atoms H to carbon atoms C as a raw carbon composition, H / C atomic ratio in the range of 0.30 to 0.50 and micro strength in the range of 7 to 17% by mass means that the capacity retention rate after holding at 60 ° C. for 30 days is 89% or higher.
- the graphitization temperature of the raw coal composition K-2 was 2600 ° C and 2300 ° C.
- the crystallite size Lc (112) of graphite particles K-2 (Example 3) treated at 2800 ° C. was 6.9 nm
- the graphite obtained in Comparative Example 17 treated at 2600 ° C. Lc (112) of the particles was 3.9 nm
- Lc (112) of the graphite particles obtained in Comparative Example 18 treated at 2300 ° C. was 3.2 nm.
- the discharge capacity after holding at 60 ° C. for 30 days of a lithium ion secondary battery using these as negative electrodes was 16.4 mAh in Example 3.
- Comparative Example 17 it was 15.0 mAh
- the crystallite size of the graphite used for the negative electrode the smaller the battery capacity.
- the crystallite size Lc (112) of the graphite material used for the negative electrode must be at least 4 nm or more. I understand that.
- the capacity retention rate is 90% or more, and can be regarded as a negative electrode graphite material capable of realizing a battery with extremely high cycle stability. .
- the crystallite size is small, only a battery with a small capacity can be realized.
- the crystallite size Lc (112) of the diffraction line (112) measured by the X-ray wide angle diffraction method obtained by carbonizing and graphitizing the pulverized and classified raw coal composition powder is 4 nm.
- a graphite material for a negative electrode of a lithium ion secondary battery obtained by applying a compressive shear stress to the graphite particles as described above, wherein the raw carbon composition is coke by a delayed coking process.
- the graphite material Lithium-ion secondary batteries using as a negative electrode material can secure a capacity of 16 mAh or more and reach a capacity retention rate of 89% or more after being left in a constant temperature room at 60 ° C. for 30 days. I was able to.
- Raw coal composition and production method thereof (1) Raw coal composition A-3 The atmospheric distillation residue having a sulfur content of 3.1% by mass was hydrodesulfurized in the presence of a catalyst so that the hydrocracking rate was 25% or less to obtain a hydrodesulfurized oil.
- the hydrodesulfurization conditions are a total pressure of 180 MPa, a hydrogen partial pressure of 160 MPa, and a temperature of 380 ° C.
- desulfurized vacuum gas oil (sulfur content: 500 mass ppm, density: 0.88 g / cm 3 at 15 ° C.) was subjected to fluid catalytic cracking to obtain fluid catalytic cracking residual oil.
- the fluid catalytic cracking residual oil was selectively extracted with dimethylformamide, separated into an aromatic component and a saturated component, and the aromatic component was extracted.
- This extracted aromatic component and hydrodesulfurized oil were mixed at a mass ratio of 8: 1, and desulfurized dewaxed oil was added so as to be 19% by mass (100% by mass of the entire mixture including desulfurized desulfurized oil) ),
- a heavy oil composition was obtained.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition A-3.
- Raw coal composition B-3 11% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as the production method of the raw coal composition A-3 and the hydrodesulfurized oil in a mass ratio of 8: 1.
- desulfurized and desulfurized oil was added (100% by mass in the entire mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition B-3.
- Raw coal composition C-3 4% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as the production method of the raw coal composition A-3 and the hydrodesulfurized oil in a mass ratio of 8: 1.
- desulfurized and desulfurized oil was added (100% by mass in the entire mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition C-3.
- Raw coal composition D-3 17% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as in the production method of the raw coal composition A-3 and the hydrodesulfurized oil in a mass ratio of 6: 1.
- desulfurized and desulfurized oil was added (100% by mass in the entire mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition D-3.
- Raw coal composition E-3 11% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as the production method of the raw coal composition A-3 and the hydrodesulfurized oil in a mass ratio of 6: 1. In this way, desulfurized and desulfurized oil was added (100% by mass in the entire mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition E-3.
- Raw coal composition F-3 6% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as the production method of the raw coal composition A-3 and the hydrodesulfurized oil in a mass ratio of 6: 1.
- desulfurized and desulfurized oil was added (100% by mass in the entire mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition F-3.
- Raw coal composition G-3 A hydrodesulfurized oil obtained in the same manner as the production method of the raw coal composition A-3 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 5 is desulfurized and dehydrated so as to be 15% by mass. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition G-3.
- Raw coal composition H-3 Desulfurized desulfurized so as to be 7% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-3 at a mass ratio of 1: 5 Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition H-3.
- Raw coal composition I-3 Desulfurized and desulfurized so as to be 19% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-3 at a mass ratio of 1: 4. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition I-3.
- Raw coal composition J-3 Desulfurized and desulfurized so that the hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of the raw coal composition A-3 are mixed at a mass ratio of 1: 4 to 16 mass%. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition J-3.
- Raw coal composition K-3 A hydrodesulfurized oil obtained in the same manner as the production method of the raw coal composition A-3 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 4 is desulfurized and dehydrated so as to be 11% by mass. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition K-3.
- Raw coal composition L-3 Desulfurized and desulfurized so as to be 5% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-3 at a mass ratio of 1: 4. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition L-3.
- Raw coal composition M-3 A hydrodesulfurized oil obtained in the same manner as in the production method of the raw coal composition A-3 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 4 is desulfurized and dehydrated so as to be 3% by mass. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition M-3.
- Raw coal composition N-3 A hydrodesulfurized oil obtained in the same manner as the production method of the raw coal composition A-3 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 3 is desulfurized and dehydrated so as to be 14% by mass. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition N-3.
- Raw coal composition O-3 A hydrodesulfurized oil obtained in the same manner as in the production method of the raw coal composition A-3 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 3 is desulfurized and dehydrated so as to be 7% by mass. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition O-3.
- Raw coal composition P-3 The same volume of n-heptane is added to and mixed with the fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-3, and then selectively extracted with dimethylformamide to separate into aromatic and saturated components. The saturated content was selectively extracted. Desulfurized and desulfurized oil is added to a mixture of fluid catalytic cracking residual oil and this extraction saturated component at a mass ratio of 1: 1 so that the mass becomes 16% by mass (100 mass in total of the mixture including desulfurized and desulfurized oil). %), A heavy oil composition was obtained. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition P-3.
- Raw coal composition Q-3 Fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-3, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-3 The mixture was mixed with the extraction saturated content of the mixture at a mass ratio of 1: 1, and desulfurized and desulfurized oil was added so as to be 11% by mass (100% by mass of the entire mixture including desulfurized and degassed oil). An oil composition was obtained. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition Q-3.
- Raw coal composition R-3 Fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-3, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-3 The mixture was mixed with the extraction saturated content of the mixture at a mass ratio of 1: 1, and desulfurized and desulfurized oil was added so as to be 6% by mass (100% by mass of the entire mixture including desulfurized and degassed oil). An oil composition was obtained. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition R-3.
- Raw coal composition S-3 Fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-3, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-3
- Desulfurized and desulfurized oil was added to the mixture of the extracted saturated component of the mixture at a mass ratio of 1: 2 so as to be 19% by mass (100% by mass of the entire mixture including the desulfurized and degassed oil).
- An oil composition was obtained.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition S-3.
- Raw coal composition T-3 Fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-3, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-3 Desulfurized and desulfurized oil was added to a mixture of the extraction saturated content of the mixture in a mass ratio of 1: 2 so as to be 10% by mass (100% by mass in the entire mixture including desulfurized and degassed oil), and heavy An oil composition was obtained. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition T-3.
- H / C of the raw coal composition is a ratio of the value obtained by dividing the total hydrogen content (TH (mass%)) by the atomic weight of hydrogen and the value obtained by dividing the total carbon content (TC (mass%)) by the atomic weight of carbon. Calculated with The H / C values of the raw coal compositions A-3 to U-3 are as shown in Table 3.
- the obtained raw coal compositions A-3 to U-3 are pulverized by a mechanical pulverizer (Super Rotor Mill / Nisshin Engineering) and precision air classifier (Turbo Classifier / Nisshin Engineering) To obtain a raw material charcoal composition powder having an average particle size of 14 ⁇ m.
- the average particle size of the powder of the raw coal composition was measured using a laser diffraction / scattering particle size distribution measuring apparatus LA950 manufactured by Horiba.
- the fluid catalytic cracking residual oil was selectively extracted with dimethylformamide, separated into an aromatic component and a saturated component, and the aromatic component was extracted.
- This extracted aromatic component and hydrodesulfurized oil were mixed at a mass ratio of 8: 1 to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere. After coarsely pulverizing to 1 mass%, calcine coke was obtained by carbonizing at 1400 ° C. using a rotary kiln.
- the obtained calcine coke was pulverized with a mechanical pulverizer (Super Rotor Mill / Nisshin Engineering Co., Ltd.) and classified with a precision air classifier (Turbo Classifier / Nisshin Engineering Co., Ltd.). Calcine coke powder having the stated average particle size was obtained.
- the average particle diameter of calcine coke was measured using a laser diffraction / scattering particle size distribution measuring apparatus LA950 manufactured by Horiba.
- Method for Producing Graphite Material of Example 15 The obtained raw coal composition K-3 powder and calcine coke having an average particle size of 2.0 ⁇ m are mixed with the raw coal composition K-3. Is mixed in advance at a ratio of 0.5% by mass, and is charged into the “Nobilta 130” manufactured by Hosokawa Micron Corporation so that the filling volume is 500 cc.
- the composite powder was obtained by controlling and applying compressive shear stress by operating under the condition of a treatment time of 60 minutes. This composite powder was carbonized with a roller hearth kiln manufactured by Takasago Industry Co., Ltd. in a nitrogen gas stream so that the maximum temperature reached 1200 ° C. and the maximum temperature maintained time was 5 hours.
- the obtained carbon material was put into a crucible, placed in an electric furnace, and graphitized at a maximum reached temperature of 2800 ° C. in a nitrogen gas stream at 80 L / min. At this time, the rate of temperature increase is 200 ° C./hour, the maximum temperature is maintained for 3 hours, the rate of temperature decrease is up to 1000 ° C./100° C./hour, and then the mixture is allowed to cool to room temperature while maintaining a nitrogen stream.
- a graphite material was obtained.
- the crystallite size Lc (112) of the (112) diffraction line measured by the X-ray wide angle diffraction method of the obtained graphite material was 7.9 nm.
- Examples 16 to 31 and Comparative Examples 19 to 46 Production methods of graphite materials of Examples 16 to 31 and Comparative Examples 19 to 46
- powders of the raw coal compositions A-3 to U-3 and calcine coke were used. And giving a compressive shear stress to obtain a composite powder, and then carbonized and graphitized under the same conditions as in Example 1 to obtain a graphite material.
- Table 3 shows the conditions for imparting the average particle size and mixing amount of calcine coke and compressive shear stress.
- “Nobilta 130 type” manufactured by Hosokawa Micron Co., Ltd. was used as an apparatus for applying compressive shear stress.
- Example 29 and 30 Nippon Coke Industries “COMPOSI CP-15” manufactured by the company, and “Mechanofusion AMS-Lab” manufactured by Hosokawa Micron Co., Ltd. were used in Example 31.
- Nobilta 130” is abbreviated as “N”
- “Mechanofusion AMS-Lab” as “M” The same apparatus as described in Example 15 was used for all apparatuses other than the apparatus for applying the compressive shear stress.
- the obtained diffraction pattern was also analyzed by a method based on the method (carbon 2006, No. 221, P52-60) defined by the Japan Society for the Promotion of Science 117. Specifically, the measurement data is subjected to smoothing processing, background removal, absorption correction, polarization correction, and Lorentz correction, and using the (422) diffraction line peak position and value width of the Si standard sample, the graphite powder (112) The diffraction line was corrected and the crystallite size was calculated. The crystallite size was calculated from the half width of the corrected peak using the following Scherrer equation. Measurement and analysis were performed three times each, and the average value was defined as Lc (112). The result of measuring Lc (112) of the graphite material is as shown in Table 3.
- FIG. 1 is a cross-sectional view of the battery 10 fabricated.
- FIG. 1 shows a negative electrode 11, a negative electrode current collector 12, a positive electrode 13, a positive electrode current collector 14, a separator 15, and an aluminum laminate outer package 16.
- the positive electrode 13 is made of lithium nickel oxide (LiNi 0.8 Co 0.15 Al 0.05 O 2 manufactured by Toda Kogyo Co., Ltd.) having an average particle diameter of 6 ⁇ m, which is a positive electrode material, and polyvinylidene fluoride (KF) # 1320) and acetylene black (Denka Black manufactured by Denka Co., Ltd.) in a mass ratio of 89: 6: 5, kneaded with N-methyl-2-pyrrolidinone, made into a paste, It is a sheet electrode that is applied to one side of a 30 ⁇ m aluminum foil, dried and rolled, and cut so that the size of the applied part is 30 mm wide and 50 mm long.
- lithium nickel oxide LiNi 0.8 Co 0.15 Al 0.05 O 2 manufactured by Toda Kogyo Co., Ltd.
- KF polyvinylidene fluoride
- acetylene black Denka Black manufactured by Denka Co., Ltd.
- the coating amount per unit area was set to 10 mg / cm 2 as the mass of lithium nickelate.
- a part of this sheet electrode is scraped off the positive electrode mixture perpendicularly to the longitudinal direction of the sheet, and the exposed aluminum foil is connected integrally with the positive electrode current collector 14 (aluminum foil) of the application part. It plays a role as a positive electrode lead plate.
- the negative electrode 11 is made of the graphite materials obtained in Examples 15 to 31 and Comparative Examples 19 to 46, which are negative electrode materials, polyvinylidene fluoride (Kureha KF # 9310), and acetylene black (Denka).
- DENKA BLACK manufactured by mixing at a mass ratio of 91: 2: 8, adding N-methyl-2-pyrrolidinone and kneading, and then applying the paste to one side of a 18 ⁇ m thick copper foil,
- This is a sheet electrode that has been dried and rolled, and cut so that the size of the coating part is 32 mm wide and 52 mm long.
- the coating amount per unit area was set to 6 mg / cm 2 as the mass of the graphite material.
- a part of this sheet electrode is scraped off the negative electrode mixture perpendicularly to the longitudinal direction of the sheet, and the exposed copper foil is integrally connected to the negative electrode current collector 12 (copper foil) of the application part, It plays a role as a negative electrode lead plate.
- the battery 10 was fabricated by sufficiently drying the positive electrode 13, the negative electrode 11, the separator 15, and other components and introducing them into a glove box filled with argon gas having a dew point of ⁇ 100 ° C.
- the drying conditions are such that the positive electrode 13 and the negative electrode 11 are under reduced pressure at 150 ° C. for 12 hours or longer, and the separator 15 and other members are under reduced pressure at 70 ° C. for 12 hours or longer.
- the positive electrode 13 and the negative electrode 11 thus dried are laminated in a state in which the coating portion of the positive electrode 13 and the coating portion of the negative electrode 11 are opposed to each other through a polypropylene microporous film (# 2400 manufactured by Celgard). And fixed with polyimide tape.
- the lamination positional relationship between the positive electrode 13 and the negative electrode 11 was made to oppose so that the peripheral part of the positive electrode application part projected on the application part of the negative electrode 11 was enclosed inside the peripheral part of the negative electrode application part.
- the obtained single-layer electrode body is embedded with an aluminum laminate film, an electrolyte solution is injected, and the laminate film is heat-sealed in a state where the positive and negative electrode lead plates protrude from the sealed single unit electrode.
- a layer laminate battery 10 was produced.
- the electrolyte used was one in which lithium hexafluorophosphate (LiPF 6 ) was dissolved in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 so as to have a concentration of 1 mol / L. .
- a constant current / constant voltage charging was performed with a charging current of 15 mA, a charging voltage of 4.2 V, and a charging time of 3 hours.
- the battery was discharged at a constant current until Charging / discharging under the same conditions was repeated 5 cycles, and the discharge capacity at the 5th cycle was defined as “initial discharge capacity”.
- the battery was charged in the same condition and installed in a constant temperature room at 60 ° C. and left for 60 days. Thereafter, the inside of the temperature-controlled room was set to 25 ° C., and the battery was left for 5 hours and then discharged.
- discharge capacity after 60 days holding As an index representing storage characteristics, a ratio (%) of “discharge capacity after holding at 60 ° C.” with respect to “initial discharge capacity” was calculated as “capacity maintenance ratio after holding for 60 days” (%).
- the graphite materials in Examples 15 to 31 are raw material carbon compositions (G-3, H-3) that satisfy the conditions that H / C is 0.30 to 0.50 and the micro strength is 7% by mass to 17% by mass. , K-3, N-3, O-3) and calcine coke having an average particle size of 0.1 ⁇ m to 3.0 ⁇ m, calsine coke is 0.5 mass% to the raw coal composition. It is obtained by carbonizing and graphitizing a composite powder obtained by mixing at a ratio of 10% by mass and applying compressive shear stress. In these graphite materials, the crystallite size Lc (112) satisfied 4 nm to 30 nm (Table 3).
- the raw coal composition used in Comparative Examples 19 to 34 has either a condition where H / C is 0.3 to 0.5, or a condition where the micro strength is 7% by mass to 17% by mass, or these It is a composition that does not satisfy both conditions.
- the capacity retention rate after 60-day storage of the battery is approximately 74% to 82%, compared with Examples 15 to 31. The values were very low (Table 4).
- a raw coal composition obtained by coking the heavy oil composition by a delayed coking process and an average particle size of 0.5% by mass to 10% by mass with respect to the raw coal composition.
- a method for producing a graphite material for a negative electrode of a lithium ion secondary battery comprising at least a step of forming a graphite material, wherein H / C is 0.30 to 0.50 and the micro strength is 7% by mass.
- the use of the raw material carbon composition in the range of ⁇ 17% by mass is a graphite material for a negative electrode of a lithium ion secondary battery that achieves high storage characteristics with a capacity retention rate of 89% or more after holding at 60 ° C. for 60 days. It can be said that it is an indispensable condition to obtain.
- Comparative Examples 35 and 36 the powder of the raw coal composition K-3 and calcine coke having an average particle size of 2.0 ⁇ m were used, and the calcine coke was 0.2 mass% with respect to the raw coal composition (Comparative Example 35) and mixed at a ratio of 0.4 mass% (Comparative Example 36) to give a compressive shear stress to obtain a composite powder.
- Lc (112) of the graphite material obtained by carbonizing and graphitizing these composite powders was in the range of 4 nm to 30 nm, it was retained for 60 days in a lithium ion secondary battery using these as a negative electrode The subsequent capacity maintenance rate was a little lower than 70%, which was a very low value compared to Examples 15 to 31 (Table 4).
- Comparative Examples 37 and 38 the raw material coal composition K-3 powder and calcine coke having an average particle size of 2.0 ⁇ m were used, and the calcine coke content was 11.0% by mass (comparative example). 37) and 14.0% by mass (Comparative Example 38) and mixed to give a compressive shear stress to obtain a composite powder.
- Lc (112) of the graphite material obtained by carbonizing and graphitizing these composite powders was in the range of 4 nm to 30 nm.
- the capacity retention rate was 70% or less, which was a very low value compared with Examples 15 to 31 (Table 4).
- the reason for this is that when the amount of calcine coke mixed with the raw coal composition powder is more than 10% by mass relative to the raw coal composition, the composite powder obtained by applying compressive shear stress is the raw coal
- the composite powder has calcined coke attached to the particle surface of the composition and has extremely large surface irregularities, and the specific surface area of the graphite material obtained by carbonizing and graphitizing the composite powder becomes extremely large.
- the decomposition of the electrolyte in the negative electrode increases and the leakage current of the negative electrode increases. As a result, the difference from the leakage current with the positive electrode increases. ⁇ It is considered that the operating range of the capacity of the negative electrode changes and the life characteristics deteriorate.
- Comparative Examples 39 and 40 the raw coal composition K-3 powder and calcine coke having an average particle size of 0.1 ⁇ m were used, and the calcined coke content was 12.0% by mass (comparative example). 39) and 0.2% by mass (Comparative Example 40) and mixed to give a compressive shear stress to obtain a composite powder.
- the amount of calcine coke mixed with the raw coal composition powder did not satisfy the range of 0.5% by mass to 10% by mass with respect to the raw coal composition.
- the capacity retention rate was very low as compared with Examples 15 to 31 (Table 4).
- the composite powder As the composite powder, a calcined coke adhered to the particle surface of the raw material carbon composition and the surface unevenness is very large, and when this composite powder is carbonized and graphitized, it is obtained.
- the specific surface area of the obtained graphite material becomes extremely large. Therefore, in lithium ion secondary batteries using these graphite materials, the decomposition of the electrolyte in the negative electrode increases and the leakage current of the negative electrode increases. It is considered that the operating range of the capacity of the negative electrode changes, and the life characteristics deteriorate.
- the raw coal composition powder and calcine coke having an average particle size of 0.1 ⁇ m to 3.0 ⁇ m were obtained.
- Carbonization and graphitization of the composite powder obtained by mixing 5 mass% to 10 mass% and applying compressive shear stress is to achieve high life characteristics with a capacity retention rate of 89% or more. It can be said that it is an indispensable condition.
- the lithium ion secondary battery using the graphite material manufactured by the manufacturing method according to the present invention as the negative electrode was able to achieve high storage characteristics.
- Raw coal composition and production method thereof (1) Raw coal composition A-4 The atmospheric distillation residue having a sulfur content of 3.1% by mass was hydrodesulfurized in the presence of a catalyst so that the hydrocracking rate was 25% or less to obtain a hydrodesulfurized oil.
- the hydrodesulfurization conditions are a total pressure of 180 MPa, a hydrogen partial pressure of 160 MPa, and a temperature of 380 ° C.
- desulfurized vacuum gas oil (sulfur content: 500 mass ppm, density: 0.88 g / cm 3 at 15 ° C.) was subjected to fluid catalytic cracking to obtain fluid catalytic cracking residual oil.
- the fluid catalytic cracking residual oil was selectively extracted with dimethylformamide, separated into an aromatic component and a saturated component, and the aromatic component was extracted.
- This extracted aromatic component and hydrodesulfurized oil were mixed at a mass ratio of 8: 1, and desulfurized dewaxed oil was added so as to be 19% by mass (100% by mass of the entire mixture including desulfurized desulfurized oil) ),
- a heavy oil composition was obtained.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition A-4.
- Raw coal composition B-4 11% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as in the production method of the raw coal composition A-4 and the hydrodesulfurized oil at a mass ratio of 8: 1.
- desulfurized and desulfurized oil was added (100% by mass in the entire mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition B-4.
- Raw coal composition C-4 4% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as in the production method of the raw coal composition A-4 and the hydrodesulfurized oil at a mass ratio of 8: 1.
- desulfurized and desulfurized oil was added (100% by mass in the entire mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition C-4.
- Raw coal composition D-4 17% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as the production method of the raw coal composition A-4 and the hydrodesulfurized oil in a mass ratio of 6: 1.
- desulfurized and desulfurized oil was added (100% by mass in the entire mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition D-4.
- Raw coal composition E-4 11% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as the production method of the raw coal composition A-4 and the hydrodesulfurized oil in a mass ratio of 6: 1.
- desulfurized and desulfurized oil was added (100% by mass in the entire mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition E-4.
- Raw coal composition F-4 6% by mass is obtained by mixing the extracted aromatic content of the fluid catalytic cracking residual oil obtained in the same manner as the production method of the raw coal composition A-4 and the hydrodesulfurized oil in a mass ratio of 6: 1.
- desulfurized and desulfurized oil was added (100% by mass in the entire mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition.
- This heavy oil composition was introduced into a delayed coker apparatus, and coke-treated at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition F-4.
- Raw coal composition G-4 A hydrodesulfurized oil obtained in the same manner as the production method of the raw coal composition A-4 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 5 is desulfurized and dehydrated so as to be 15% by mass. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition G-4.
- Raw coal composition H-4 Desulfurized and desulfurized so as to be 7% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-4 at a mass ratio of 1: 5. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition H-4.
- Raw coal composition I-4 Desulfurized and desulfurized so as to be 19% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-4 at a mass ratio of 1: 4. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition I-4.
- Raw coal composition J-4 Desulfurized and desulfurized so that the hydrodesulfurized oil obtained in the same manner as in the production method of the raw coal composition A-4 and the fluid catalytic cracking residual oil at a mass ratio of 1: 4 is 16% by mass. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition J-4.
- Raw coal composition K-4 A hydrodesulfurized oil obtained in the same manner as in the production method of the raw coal composition A-4 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 4 is desulfurized and dehydrated so as to be 11% by mass. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition K-4.
- Raw coal composition L-4 A hydrodesulfurized oil obtained in the same manner as the production method of the raw coal composition A-4 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 4 is desulfurized and dehydrated so as to be 5% by mass. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition L-4.
- Raw coal composition M-4 A hydrodesulfurized oil obtained in the same manner as the production method of the raw coal composition A-4 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 4 is desulfurized and dehydrated so as to be 3% by mass. Oil was added (100% by mass in total of the mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition M-4.
- Raw coal composition N-4 A hydrodesulfurized oil obtained in the same manner as in the production method of the raw coal composition A-4 and a fluid catalytic cracking residual oil mixed at a mass ratio of 1: 3 is desulfurized and dehydrated so as to be 14% by mass. Oil was added (100% by mass of the total mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition N-4.
- Raw coal composition O-4 Desulfurized desulfurized so as to be 7% by mass in a mixture of hydrodesulfurized oil and fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-4 at a mass ratio of 1: 3. Oil was added (100% by mass of the total mixture including desulfurized and desulfurized oil) to obtain a heavy oil composition. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition O-4.
- Raw coal composition P-4 The same volume of n-heptane is added to and mixed with the fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-4, and then selectively extracted with dimethylformamide to separate into aromatic and saturated components. The saturated content was selectively extracted. Desulfurized and desulfurized oil is added to a mixture of fluid catalytic cracking residual oil and this extraction saturated component at a mass ratio of 1: 1 so that the mass becomes 16% by mass (100 mass in total of the mixture including desulfurized and desulfurized oil). %), A heavy oil composition was obtained. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition P-4.
- Raw coal composition Q-4 Fluid catalytic cracking residual oil obtained in the same manner as the production method of raw coal composition A-4, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-4 The mixture was mixed with the extraction saturated content of the mixture at a mass ratio of 1: 1, and desulfurized and desulfurized oil was added so as to be 11% by mass (100% by mass of the entire mixture including desulfurized and degassed oil). An oil composition was obtained. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain raw coal composition Q-4.
- Raw coal composition R-4 Fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-4, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-4 The mixture was mixed with the extraction saturated content of the mixture at a mass ratio of 1: 1, and desulfurized and desulfurized oil was added so as to be 6% by mass (100% by mass of the entire mixture including desulfurized and degassed oil). An oil composition was obtained. This heavy oil composition was introduced into a delayed coker apparatus, and coke-treated at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition R-4.
- Raw coal composition S-4 Fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-4, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-4 Desulfurized and desulfurized oil was added to the mixture of the extracted saturated component of the mixture at a mass ratio of 1: 2 so as to be 19% by mass (100% by mass of the entire mixture including the desulfurized and degassed oil). An oil composition was obtained. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain raw coal composition S-4.
- Raw coal composition T-4 Fluid catalytic cracking residual oil obtained in the same manner as in the production method of raw coal composition A-4, fluid catalytic cracking residual oil and n-heptane obtained in the same manner as in the production method of raw coal composition P-4 Desulfurized and desulfurized oil was added to a mixture of the extraction saturated content of the mixture in a mass ratio of 1: 2 so as to be 10% by mass (100% by mass in the entire mixture including desulfurized and degassed oil), and heavy An oil composition was obtained. This heavy oil composition was introduced into a delayed coker apparatus and subjected to coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw coal composition T-4.
- H / C of the raw coal composition is a ratio of the value obtained by dividing the total hydrogen content (TH (mass%)) by the atomic weight of hydrogen and the value obtained by dividing the total carbon content (TC (mass%)) by the atomic weight of carbon. Calculated with The H / C values of the raw coal compositions A-4 to U-4 are as shown in Table 5.
- the obtained raw coal compositions A-4 to U-4 were pulverized by a mechanical pulverizer (Super Rotor Mill / Nisshin Engineering) and precision air classifier (Turbo Classifier / Nisshin Engineering) To obtain a raw material charcoal composition powder having an average particle size of 15 ⁇ m.
- the average particle size of the powder of the raw coal composition was measured using a laser diffraction / scattering particle size distribution measuring apparatus LA950 manufactured by Horiba.
- the obtained carbon material was put into a crucible, placed in an electric furnace, and graphitized at a maximum reached temperature of 2800 ° C. in a nitrogen gas stream at 80 L / min. At this time, the rate of temperature increase is 200 ° C./hour, the maximum temperature is maintained for 3 hours, the rate of temperature decrease is up to 1000 ° C./100° C./hour, and then the mixture is allowed to cool to room temperature while maintaining a nitrogen stream.
- a graphite material was obtained.
- the crystallite size Lc (112) of the (112) diffraction line measured by the X-ray wide angle diffraction method of the obtained graphite material was 7.2 nm.
- Examples 33 to 44 and Comparative Examples 47 to 70 powders of raw carbon compositions A-4 to U-4 and acetylene black ( Denka Black) manufactured by Denka Co., Ltd. was applied to give a composite powder by applying compressive shear stress, and then carbonized and graphitized under the same conditions as in Example 32 to obtain a graphite material.
- the amount of acetylene black mixed and the conditions for applying compressive shear stress are as shown in Table 5.
- “Nobilta 130 type” manufactured by Hosokawa Micron Corporation was used as an apparatus for applying compressive shear stress.
- Example 42 Nippon Coke Industries “COMPOSI CP-15” manufactured by KK and “Mechano-Fusion AMS-Lab” manufactured by Hosokawa Micron Corporation were used in Example 44.
- Nobilta 130” is abbreviated as “N”
- N N
- C C
- M Mechanism of Fusion AMS-Lab
- the obtained diffraction pattern was also analyzed by a method based on the method (carbon 2006, No. 221, P52-60) defined by the Japan Society for the Promotion of Science 117. Specifically, the measurement data is subjected to smoothing processing, background removal, absorption correction, polarization correction, and Lorentz correction, and using the (422) diffraction line peak position and value width of the Si standard sample, the graphite powder (112) The diffraction line was corrected and the crystallite size was calculated. The crystallite size was calculated from the half width of the corrected peak using the following Scherrer equation. Measurement and analysis were performed three times each, and the average value was defined as Lc (112). The results of measurement of Lc (112) of the graphite material are as shown in Table 5.
- FIG. 1 is a cross-sectional view of the battery 10 fabricated.
- FIG. 1 shows a negative electrode 11, a negative electrode current collector 12, a positive electrode 13, a positive electrode current collector 14, a separator 15, and an aluminum laminate outer package 16.
- the positive electrode 13 is made of lithium nickel oxide (LiNi 0.8 Co 0.15 Al 0.05 O 2 manufactured by Toda Kogyo Co., Ltd.) having an average particle diameter of 6 ⁇ m, which is a positive electrode material, and polyvinylidene fluoride (KF) # 1320) and acetylene black (Denka Black manufactured by Denka Co., Ltd.) in a mass ratio of 89: 6: 5, kneaded with N-methyl-2-pyrrolidinone, made into a paste, It is a sheet electrode that is applied to one side of a 30 ⁇ m aluminum foil, dried and rolled, and cut so that the size of the applied part is 30 mm wide and 50 mm long.
- lithium nickel oxide LiNi 0.8 Co 0.15 Al 0.05 O 2 manufactured by Toda Kogyo Co., Ltd.
- KF polyvinylidene fluoride
- acetylene black Denka Black manufactured by Denka Co., Ltd.
- the coating amount per unit area was set to 10 mg / cm 2 as the mass of lithium nickelate.
- a part of this sheet electrode is scraped off the positive electrode mixture perpendicularly to the longitudinal direction of the sheet, and the exposed aluminum foil is connected integrally with the positive electrode current collector 14 (aluminum foil) of the application part. It plays a role as a positive electrode lead plate.
- the negative electrode 11 is made of the graphite material obtained in Examples 32 to 44 and Comparative Examples 47 to 70 as negative electrode materials, polyvinylidene fluoride (Kureha KF # 9310), and acetylene black (Denka).
- DENKA BLACK manufactured in a mass ratio of 91: 2: 8, added with N-methyl-2-pyrrolidinone and kneaded, and then pasted into a 18 ⁇ m thick copper foil.
- This is a sheet electrode that has been dried and rolled, and cut so that the size of the coating part is 32 mm wide and 52 mm long. At this time, the coating amount per unit area was set to 6 mg / cm 2 as the mass of the graphite material. A part of this sheet electrode is scraped off the negative electrode mixture perpendicularly to the longitudinal direction of the sheet, and the exposed copper foil is integrally connected to the negative electrode current collector 12 (copper foil) of the application part, It plays a role as a negative electrode lead plate.
- the battery 10 was fabricated by sufficiently drying the positive electrode 13, the negative electrode 11, the separator 15, and other components and introducing them into a glove box filled with argon gas having a dew point of ⁇ 100 ° C.
- the drying conditions are such that the positive electrode 13 and the negative electrode 11 are under reduced pressure at 150 ° C. for 12 hours or longer, and the separator 15 and other members are under reduced pressure at 70 ° C. for 12 hours or longer.
- the positive electrode 13 and the negative electrode 11 thus dried are laminated in a state in which the coating portion of the positive electrode 13 and the coating portion of the negative electrode 11 are opposed to each other through a polypropylene microporous film (# 2400 manufactured by Celgard). And fixed with polyimide tape.
- the lamination positional relationship between the positive electrode 13 and the negative electrode 11 was made to oppose so that the peripheral part of the positive electrode application part projected on the application part of the negative electrode 11 was enclosed inside the peripheral part of the negative electrode application part.
- the obtained single-layer electrode body is embedded with an aluminum laminate film, an electrolyte solution is injected, and the laminate film is heat-sealed in a state where the positive and negative electrode lead plates protrude from the sealed single unit electrode.
- a layer laminate battery 10 was produced.
- the electrolyte used was one in which lithium hexafluorophosphate (LiPF 6 ) was dissolved in a solvent in which ethylene carbonate and ethyl methyl carbonate were mixed at a volume ratio of 3: 7 so as to have a concentration of 1 mol / L. .
- the battery after the preliminary test was placed in a constant temperature room at 60 ° C. and left for 5 hours to start a charge / discharge test.
- the discharge capacity at the first cycle after the start was defined as “initial discharge capacity”. Charging at a constant current at a current of 75 mA until the battery voltage becomes 4.2 V, setting a charge / discharge cycle for discharging at a constant current until the battery voltage reaches 3.0 V at the same current after a pause for 1 minute, This cycle was repeated 2000 times.
- the ratio (%) of the “discharge capacity at the 2000th cycle” with respect to the “initial discharge capacity” was calculated to be “capacity maintenance rate after 2000 cycles” (%).
- the graphite materials in Examples 32 to 44 are raw carbon compositions (G-4, H-4) that satisfy the conditions that H / C is 0.30 to 0.50 and the micro strength is 7% by mass to 17% by mass. , K-4, N-4, O-4) and 0.5% by mass to 10% by mass of acetylene black with respect to the raw coal composition, and applying compressive shear stress. It was obtained by carbonizing and graphitizing the composite powder. In these graphite materials, the crystallite size Lc (112) satisfied 4 nm to 30 nm (Table 5).
- the raw coal composition used in Comparative Examples 47 to 62 has either a condition in which the H / C value is 0.3 to 0.5 or a condition in which the micro strength is 7% by mass to 17% by mass, or these It is a composition that does not satisfy both of the conditions.
- the capacity retention rate after 2000 cycles of the battery is approximately 75% to 82%, compared with Examples 32 to 44. The value was very low (Table 6).
- Lithium ions comprising at least a step of heating to graphitize and making a graphite material having a crystallite size of Lc (112) of 4 nm to 30 nm as a crystallite size of (112) diffraction line measured by an X-ray wide angle diffraction method
- the raw carbon composition has H / C of 0.30 to 0.50 and a micro strength of 7% by mass to 17% by mass.
- Use of a material in the range is an indispensable condition for obtaining a graphite material for a negative electrode of a lithium ion secondary battery that achieves a high life characteristic with a capacity retention rate of 89% or more after 2000 cycles. .
- Comparative Examples 63 and 64 the powder of the raw coal composition K and 0.2% by mass (Comparative Example 63) and 0.4% by mass (Comparative Example 64) of acetylene black are mixed with the raw coal composition. Then, a composite powder was obtained by applying a compressive shear stress. Although Lc (112) of the graphite material obtained by carbonizing and graphitizing these composite powders was in the range of 4 nm to 30 nm, in a lithium ion secondary battery using these as a negative electrode, after 2000 cycles The capacity retention rate was a little lower than 70%, which was a very low value compared to Examples 32-44 (Table 6).
- the reason for this is that when the amount of acetylene black mixed with the powder of the raw coal composition is less than 0.5% by mass with respect to the raw coal composition, the obtained graphite material has a low degree of crystallinity introduced. There is very little area. Therefore, in a lithium ion secondary battery using such a graphite material, the co-insertion of the electrolyte between the graphite layers cannot be suppressed, and the leakage current of the negative electrode increases. It is considered that the operating range of the positive and negative electrode capacities changes and the life characteristics deteriorate.
- Comparative Examples 65 and 66 the powder of the raw coal composition K and 10.2% by mass (Comparative Example 65) and 13.0% by mass (Comparative Example 66) of acetylene black are mixed to give compressive shear stress. As a result, a composite powder was obtained. Although Lc (112) of the graphite material obtained by carbonizing and graphitizing these composite powders was in the range of 4 nm to 30 nm, in a lithium ion secondary battery using these as a negative electrode, after 2000 cycles The capacity retention ratio of the sample was about 70%, which was a very low value compared to Examples 32 to 44 (Table 6).
- the reason for this is that when the amount of acetylene black mixed with the raw coal composition powder is more than 10% by mass with respect to the raw coal composition, the composite powder obtained by applying compressive shear stress is used as the raw coal composition.
- the acetylene black adheres to the particle surface of the product and becomes a composite powder with extremely large surface irregularities, and the specific surface area of the graphite material obtained by carbonizing and graphitizing the composite powder becomes extremely large.
- the decomposition of the electrolyte in the negative electrode increases and the leakage current of the negative electrode increases. As a result, the difference from the leakage current with the positive electrode increases. ⁇ It is considered that the operating range of the capacity of the negative electrode changes and the life characteristics deteriorate.
- Lithium ion secondary batteries using graphite materials obtained by carbonizing and graphitizing composite powders obtained by applying compressive shear stress have a capacity retention rate of 90% or more after 2000 cycles. The value was higher than those of Examples 63 to 66.
- the powder of the raw coal composition and 0.5% by mass to 10% by mass of acetylene black are mixed with the raw coal composition to give a compressive shear stress. It can be said that carbonization and graphitization of the composite powder obtained in this way is an indispensable condition in order to achieve high life characteristics with a capacity retention rate of 89% or more.
- the lithium ion secondary battery using the graphite material manufactured by the manufacturing method according to the present invention as the negative electrode was able to achieve high life characteristics.
- the lithium ion secondary battery using the graphite material manufactured by the manufacturing method according to the present invention secures high storage characteristics as compared with the lithium ion secondary battery using the conventional graphite material. . Therefore, it can be used for industrial purposes such as for automobiles, specifically for hybrid cars, plug-in hybrid cars, electric cars, and power storage for grid infrastructure.
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Abstract
Description
特許文献2によれば、原料炭組成物を粉砕・分級した後、メカノケミカル処理を施すことにより、粒子表層の結晶構造を乱すことができると記載されている(特許文献2の段落[0024])。このような結晶構造の乱れは、最終工程となる黒鉛化後にも未組織炭素として残存するため、負極の初期充放電効率を向上させることは可能(特許文献2の段落[0024])であるが、その後の電池の信頼性まで向上させることはできないという欠点があった。
一般的に、結晶子のエッジ部には、多数のダングリングボンド、即ち価電子結合が飽和せず結合の相手無しに存在する局在電子の状態が多く存在する。充電過程での負極炭素材料の表面、即ち電解液と炭素材料が接触している界面では、リチウムが黒鉛結晶に挿入する本来の充電反応の他に、この局在電子が触媒的に作用し、電解液が還元分解されることに起因した副反応・競争反応が生じることによって、負極の充放電効率が低下すると考えられる。つまり、粒子表面に結晶化度の低い領域を導入することにより、溶媒共挿入による電解液の分解は抑制できたとしても、導入された結晶化度の低い領域における結晶子が等方的な状態であるためにエッジ部が表面に露出することにより、電解液の還元分解が増大し容量劣化が起こるという課題が残る。
本発明者らは、高度に発達した結晶構造中に結晶化度の低い領域が導入された構造を有し、且つ粒子表面に結晶子エッジの露出が少ない黒鉛材料を提供することにより、負極の充放電効率が改善され、リチウムイオン二次電池の保存特性を向上させることが可能となると考え、鋭意検討した結果、本発明に到達した。
本発明に係る第一の形態は、粉砕及び分級された原料炭組成物に、圧縮応力と剪断応力を付与した黒鉛前駆体を黒鉛化して得られ、X線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)が4nm以上であるリチウムイオン二次電池負極用の黒鉛材料であって、上記原料炭組成物が、重質油組成物をディレードコーキングプロセスによってコーキング処理されたものであり、且つ水素原子Hと炭素原子Cの比率、H/C原子比0.30~0.50を有し、且つマイクロ強度7~17質量%を有するリチウムイオン二次電池負極用の黒鉛材料を提供する。
本発明に係る第二の形態は、重質油組成物をディレードコーキングプロセスによってコーキング処理して得られる原料炭組成物を粉砕及び分級する工程と、上記粉砕及び分級された原料炭組成物に圧縮応力と剪断応力を付与して黒鉛前駆体を得る工程と、上記黒鉛前駆体を加熱して黒鉛化し、X線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)が4nm以上となる黒鉛材料を得る工程とを少なくとも含むリチウムイオン二次電池負極用の黒鉛材料の製造方法であって、上記粉砕及び分級される原料炭組成物が、水素原子Hと炭素原子Cの比率、H/C原子比0.30~0.50を有し、且つマイクロ強度7~17質量%を有するリチウムイオン二次電池負極用の黒鉛材料の製造方法を提供する。
本発明に係る第三の形態は、この製造方法によって得られた黒鉛材料を負極材料として使用したリチウムイオン二次電池を提供する。
本発明に係る第五の形態は、この製造方法によって得られた黒鉛材料を負極材料として使用したリチウムイオン二次電池を提供する。
本発明に係る第七の形態は、上記第六の形態の製造方法により製造された黒鉛材料を負極材料として含むリチウムイオン二次電池である。
本発明に係る第九の形態は、上記第八の形態の製造方法により製造された黒鉛材料を負極材料として含むリチウムイオン二次電池である。
そして、本発明の製造方法によって得られる黒鉛材料は、リチウムイオン二次電池の容量維持率の低下を抑制でき、保存特性に優れたリチウムイオン二次電池の負極材料として好適である。
本発明の黒鉛材料は、X線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)を4nm以上とする。4nm以上とする理由は、このように高度に結晶が発達した黒鉛材料は、可逆容量として340mAh/g以上の確保が可能だからであるが、この理由は、この種の電池に使用される負極材料として、高度に結晶が発達した材料が好ましく用いられている理由と全く同じである。結晶が高度に発達するほど高容量が得られる点は公知の事実で、例えば前述の特許文献1の段落[0005]にも記載されている事項である。X線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)が4nm未満の場合は、結晶発達が不十分で小さな可逆容量しか得られないため好ましくない。
全水素の測定は、試料を酸素気流中750℃で完全燃焼させ、燃焼ガスより生成した水分量を電量滴定法(カール・フィッシャー法)で求められる。電量滴定式のカール・フィッシャー法では、予め滴定セルにヨウ化物イオン、二酸化硫黄、塩基(RN)及びアルコールを主成分とする電解液を入れておき、滴定セルに試料を入れることで試料中の水分は、下式(4)の通り反応する。なお、試料は、例えばコーキング処理後、乾燥雰囲気下で冷却した後に測定される。
ヨウ素の発生に要した電気量を測定することで、水分量が求められる。さらに得られた水分量から、水素量に換算し、これを測定に供した試料質量で除することにより、全水素分(TH(質量%))が算出される。
全炭素の測定は、試料を1150℃の酸素気流中で燃焼させ、二酸化炭素(一部一酸化炭素)に変換され過剰の酸素気流に搬送されてCO2+CO赤外線検出器により、全炭素分(TC(質量%))が算出される。
なお、従来、リチウムイオン電池の負極材料として、脱硫脱瀝油を原料として製造された黒鉛材料を使用した例は無い。本発明は、原料油組成の好ましい態様として脱硫脱瀝油を混合し、所定のH/C原子比及びマイクロ強度を有する原料炭組成物を得た後、所望の黒鉛材料を提供できる。
重質油組成物の成分としては、流動接触分解装置のボトム油(流動接触分解残油、FCC DO)、流動接触分解残油から抽出した芳香族分、重質油に高度な水添脱硫処理を施した水素化脱硫油、減圧残油(VR)、脱硫脱瀝油、石炭液化油、石炭の溶剤抽出油、常圧残浚油、シェルオイル、タールサンドビチューメン、ナフサタールピッチ、エチレンボトム油、コールタールピッチ及びこれらを水素化精製した重質油等が挙げられる。これらの重質油を二種類以上ブレンドして重質油組成物を調製する場合、ディレードコーキングプロセスによってコーキング処理した後に得られる原料炭組成物の物性として、H/C原子比が0.30~0.50、且つマイクロ強度が7~17質量%となるように、使用する原料油の性状に応じて配合比率を適宜調整すればよい。なお、原料油の性状は、原油の種類、原油から原料油が得られるまでの処理条件等によって変化する。
流動接触分解残油から抽出した芳香族分は、ジメチルホルムアミド等を用いて選択抽出し、芳香族分と飽和分に分離させたときの芳香族分である。
重質油に高度な水添脱硫処理を施した水素化脱硫油は、例えば、硫黄分1質量%以上の重質油を水素分圧10MPa以上で水素化脱硫処理して得られる硫黄分1.0質量%以下、窒素分0.5質量%以下、芳香族炭素分率(fa)0.1以上の重質油である。水素化脱硫油は、好ましくは、常圧蒸留残油を触媒存在下、水素化分解率が25%以下となるように水素化脱硫して得られる水素化脱硫油である。
減圧残油(VR)は、原油を常圧蒸留装置にかけて、ガス・軽質油・常圧残油を得た後、この常圧残浚油を、例えば、10~30Torrの減圧下、加熱炉出口温度320~360℃の範囲で変化させて得られる減圧蒸留装置のボトム油である。
脱硫脱瀝油は、例えば、減圧蒸留残渣油等の油を、プロパン、ブタン、ペンタン、又はこれらの混合物等を溶剤として使用する溶剤脱瀝装置で処理し、そのアスファルテン分を除去し、得られた脱瀝油(DAO)を、間接脱硫装置(Isomax)等を用いて、好ましくは硫黄分0.05~0.40質量%の範囲までに脱硫したものである。
常圧残浚油は、原油を常圧蒸留装置にかけて、例えば、常圧下、加熱して、含まれる留分の沸点により、ガス・LPGやガソリン留分、灯油留分、軽質油留分、常圧残浚油に分けられる際に得られる留分の一つで、最も沸点高い留分である。加熱温度は、原油の産地等により変動し、これらの留分に分留できるものであれば限定されないが、例えば原油を320℃に加熱する。
重質油は高温処理されることによって、熱分解及び重縮合反応が起こり、メソフェーズと呼ばれる大きな液晶が中間生成物として生成する過程を経て生コークスが製造される。
このとき、(1)良好なバルクメソフェーズを生成する重質油成分と、(2)このバルクメソフェーズが重縮合して炭化及び固化する際に、メソフェーズを構成する六角網平面積層体の大きさを小さく制限する機能を有したガスを生じ得る重質油成分と、更に(3)その切断された六角網平面積層体どうしを結合させる成分が全て含有された原料油組成物を用いることが特に好ましい。(1)良好なバルクメソフェーズを生成する重質油成分が、芳香族指数faとして0.3~0.65を与える成分であり、(2)ガスを生じ得る重質油成分が、ノルマルパラフィン含有率の5~20質量%に相当する成分であり、(3)六角網平面積層体どうしを結合させる成分が7~15質量%の範囲で含有された脱硫脱瀝油である。
このような重質油組成物が本発明の原料炭組成物の原料として好ましく使用される理由は、良好なバルクメソフェーズを生成する重質油成分により形成された六角網平面が、相対的に小さなサイズに制限されることで、コーキング後に形成される六角網平面積層体の隣接網面間の並行度を高く維持できることに加え、脱硫脱瀝油が、隣接する六角網平面積層体を適度に結合させるからである。
また原料油組成物のノルマルパラフィンの含有率は、キャピラリーカラムが装着されたガスクロマトグラフによって測定した値を意味する。具体的には、ノルマルパラフィンの標準物質によって検定した後、上記溶出クロマトグラフィー法によって分離された非芳香族成分の試料をキャピラリーカラムに通して測定する。この測定値から原料油組成物の全質量を基準とした含有率が算出可能である。
このように重質油組成物の芳香族指数faは0.3~0.65の範囲が特に好ましい。faは重質油組成物の密度Dと粘度Vから算出可能であるが、密度Dは0.91~1.02g/cm3、粘度Vは10~220mm2/sec.の範囲の重質油組成物で、faが0.3~0.65となるようなものが特に好ましい。
なお、生コークスの製造に際して、脱硫脱瀝油を添加した例はなく、脱硫脱瀝油の含有が有効であることは驚きである。
コーカーの運転圧力に好ましい範囲が設定されている理由は、ノルマルパラフィン含有成分より発生するガスの系外への放出速度を、圧力で制限することができるからである。前述の通り、メソフェーズを構成する炭素六角網平面のサイズは、発生するガスで制御するため、発生ガスの系内への滞留時間は、前記六角網平面の大きさを決定するための重要な制御パラメータとなる。また、コーカーの運転温度に好ましい範囲が設定されている理由は、本発明の効果を得るために調整された重質油から、メソフェーズを成長させるために必要な温度だからである。
黒鉛化処理の方法は、特に限定されないが、通常は、窒素、アルゴン又はヘリウム等の不活性ガス雰囲気下で最高到達温度900~1500℃、最高到達温度の保持時間0~10時間で炭化(予備焼成)され、次いで同様な不活性ガス雰囲気下、最高到達温度2500~3200℃、最高到達温度保持時間0~100時間の加熱処理する方法を挙げることができる。黒鉛化後はリチウムイオン二次電池の負極として利用することができる。
導電助剤としては、カーボンブラック、グラファイト、アセチレンブラック、又は導電性を示すインジウム-錫酸化物、又は、ポリアニリン、ポリチオフェン、ポリフェニレンビニレン等の導電性高分子を挙げることができる。導電助剤の使用量は、炭素材料100質量部に対して1~15質量部が好ましい。
有機溶媒としては、ジメチルホルムアミド、N-メチルピロリドン、イソプロパノール、トルエン等を挙げることができる。
また、シート状、ペレット状等の形状に成形された負極材スラリーと集電体との一体化は、例えば、ロール、プレス、もしくはこれらの組み合わせ等、公知の方法により行うことができる。
正極に用いる活物質としては、特に制限はなく、例えば、リチウムイオンをドーピング又はインターカレーション可能な金属化合物、金属酸化物、金属硫化物、又は導電性高分子材料を用いればよく、例示するのであれば、コバルト酸リチウム(LiCoO2)、ニッケル酸リチウム(LiNiO2)、マンガン酸リチウム(LiMn2O4)、及び複酸化物(LiCoXNiYMnZO2、X+Y+Z=1)、リチウムバナジウム化合物、V2O5、V6O13、VO2、MnO2、TiO2、MoV2O8、TiS2、V2S5、VS2、MoS2、MoS3、Cr3O8、Cr2O5、オリビン型LiMPO4(M:Co、Ni、Mn、Fe)、ポリアセチレン、ポリアニリン、ポリピロール、ポリチオフェン、ポリアセン等の導電性ポリマー、多孔質炭素等及びこれらの混合物を挙げることができる。
有機電解液としては、ジブチルエーテル、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノメチルエーテル、エチレングリコールフェニルエーテル等のエーテル、N-メチルホルムアミド、N,N-ジメチルホルムアミド、N-エチルホルムアミド、N,N-ジエチルホルムアミド、N-メチルアセトアミド、N,N-ジメチルアセトアミド、N-エチルアセトアミド、N,N-ジエチルアセトアミド等のアミド、ジメチルスルホキシド、スルホラン等の含硫黄化合物、メチルエチルケトン、メチルイソブチルケトン等のジアルキルケトン、テトラヒドロフラン、2-メトキシテトラヒドロフラン等の環状エーテル、エチレンカーボネート、ブチレンカーボネート、プロピレンカーボネート、ビニレンカーボネート等の環状カーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート、メチルプロピルカーボネート等の鎖状カーボネート、γ-ブチロラクトン、γ-バレロラクトン等の環状炭酸エステル、酢酸メチル、酢酸エチル、プロピオン酸メチル、プロピオン酸エチル等の鎖状炭酸エステル、N-メチル2-ピロリジノン、アセトニトリル、ニトロメタン等の有機溶媒を挙げることができる。これらの溶媒は、単独で又は2種以上を混合して使用することができる。
これらの溶媒の溶質としては、各種リチウム塩を使用することができる。一般的に知られているリチウム塩にはLiClO4、LiBF4、LiPF6、LiAlCl4、LiSbF6、LiSCN、LiCl、LiCF3SO3、LiCF3CO2、LiN(CF3SO2)2、LiN(C2F5SO2)2等がある。
なお、上記以外の電池構成上必要な部材の選択についてはなんら制約を受けるものではない。
本発明の黒鉛材料を形成するために用いる原料炭組成物は、水素原子Hと炭素原子Cの比率、H/C原子比が0.30~0.50であり、且つマイクロ強度が7~17質量%である。このような物性を有した原料炭組成物を粉砕・分級して得られた原料炭組成物の粉末を、炭化・黒鉛化して得られた黒鉛粒子は、内部に適度なボイド体積を有し、適度な結晶子間結合強さを有するものを得ることができる。ここでいうボイドとは、黒鉛粒子中において、隣接する結晶子間に形成される隙間のことであり、これらの隙間は粒子内部に均一に分散されている。このような黒鉛粒子に圧縮剪断応力を付与した場合、粒子表面近傍に存在するボイドにより圧縮剪断応力による力学的エネルギーが吸収され、ボイドを介して結晶子にエネルギーが伝播することにより、隣接する結晶子間の相対的位置が変化し、黒鉛粒子表面の結晶組織に乱れが導入される。
ボイド中には、六角網平面の構成単位となるベンゼン環以外の構造を有した未組織炭素が存在する。ボイドにより吸収された力学的エネルギーは、ボイド中に存在する未組織炭素の炭素-炭素結合を切断することなく、結晶子に伝播される。ボイドが吸収し得る最大のエネルギーよりも大きな圧縮剪断応力が付与された場合には、ボイド中の炭素-炭素結合が切断され、その切断面にダングリングボンドを有したエッジ面が露出するため、好ましくない。即ち、ボイドが吸収し得る範囲の大きさの力学的エネルギーが付与された場合、ボイド中の炭素-炭素結合が切断されることなく、隣接する結晶子間の相対位置の変化を誘発することができる。結果として、粒子表面に結晶組織の乱れが導入され、且つ粒子表面に露出する結晶子エッジが極めて少ない黒鉛材料を得ることができる。
全水素の測定は、試料を酸素気流中750℃で完全燃焼させ、燃焼ガスより生成した水分量を電量滴定法(カール・フィッシャー法)で求められる。電量滴定式のカール・フィッシャー法では、予め滴定セルにヨウ化物イオン、二酸化硫黄、塩基(RN)及びアルコールを主成分とする電解液を入れておき、滴定セルに試料を入れることで試料中の水分は、下式(4)の通り反応する。なお、試料は、例えばコーキング処理後、乾燥雰囲気下で冷却した後に測定される。
ヨウ素の発生に要した電気量を測定することで、水分量が求められる。さらに得られた水分量から、水素量に換算し、これを測定に供した試料質量で除することにより、全水素分(TH(質量%))が算出される。
全炭素の測定は、試料を1150℃の酸素気流中で燃焼させ、二酸化炭素(一部一酸化炭素)に変換され過剰の酸素気流に搬送されてCO2+CO赤外線検出器により、全炭素分(TC(質量%))が算出される。
重質油組成物の成分としては、流動接触分解装置のボトム油(流動接触分解残油、FCC DO)、流動接触分解残油から抽出した芳香族分、重質油に高度な水添脱硫処理を施した水素化脱硫油、減圧残油(VR)、脱硫脱瀝油、石炭液化油、石炭の溶剤抽出油、常圧残浚油、シェルオイル、タールサンドビチューメン、ナフサタールピッチ、エチレンボトム油、コールタールピッチ及びこれらを水素化精製した重質油等が挙げられる。これらの重質油を二種類以上ブレンドして重質油組成物を調製する場合、ディレードコーキングプロセスによってコーキング処理した後に得られる原料炭組成物の物性として、H/C原子比が0.30~0.50、且つマイクロ強度が7~17質量%となるように、使用する原料油の性状に応じて配合比率を適宜調整すればよい。なお、原料油の性状は、原油の種類、原油から原料油が得られるまでの処理条件等によって変化する。
流動接触分解残油から抽出した芳香族分は、ジメチルホルムアミド等を用いて選択抽出し、芳香族分と飽和分に分離させたときの芳香族分である。
重質油に高度な水添脱硫処理を施した水素化脱硫油は、例えば、硫黄分1質量%以上の重質油を水素分圧10MPa以上で水素化脱硫処理して得られる硫黄分1.0質量%以下、窒素分0.5質量%以下、芳香族炭素分率(fa)0.1以上の重質油である。水素化脱硫油は、好ましくは、常圧蒸留残油を触媒存在下、水素化分解率が25%以下となるように水素化脱硫して得られる水素化脱硫油である。
減圧残油(VR)は、原油を常圧蒸留装置にかけて、ガス・軽質油・常圧残油を得た後、この常圧残浚油を、例えば、10~30Torrの減圧下、加熱炉出口温度320~360℃の範囲で変化させて得られる減圧蒸留装置のボトム油である。
脱硫脱瀝油は、例えば、減圧蒸留残渣油等の油を、プロパン、ブタン、ペンタン、又はこれらの混合物等を溶剤として使用する溶剤脱瀝装置で処理し、そのアスファルテン分を除去し、得られた脱瀝油(DAO)を、間接脱硫装置(Isomax)等を用いて、好ましくは硫黄分0.05~0.40質量%の範囲までに脱硫したものである。
常圧残浚油は、原油を常圧蒸留装置にかけて、例えば、常圧下、加熱して、含まれる留分の沸点により、ガス・LPGやガソリン留分、灯油留分、軽質油留分、常圧残浚油に分けられる際に得られる留分の一つで、最も沸点高い留分である。加熱温度は、原油の産地等により変動し、これらの留分に分留できるものであれば限定されないが、例えば原油を320℃に加熱する。
重質油は高温処理されることによって、熱分解及び重縮合反応が起こり、メソフェーズと呼ばれる大きな液晶が中間生成物として生成する過程を経て生コークスが製造される。
このとき、(1)良好なバルクメソフェーズを生成する重質油成分と、(2)このバルクメソフェーズが重縮合して炭化及び固化する際に、メソフェーズを構成する六角網平面積層体の大きさを小さく制限する機能を有したガスを生じ得る重質油成分と、更に(3)その切断された六角網平面積層体どうしを結合させる成分が全て含有された重質油組成物を用いることが特に好ましい。(1)良好なバルクメソフェーズを生成する重質油成分が、芳香族指数faとして0.3~0.65を与える成分であり、(2)ガスを生じ得る重質油成分が、ノルマルパラフィン含有率の5~20質量%に相当する成分であり、(3)六角網平面積層体どうしを結合させる成分が7~15質量%の範囲で含有された脱硫脱瀝油である。
なお、生コークスの製造に際して、脱硫脱瀝油を添加した例はなく、脱硫脱瀝油の含有が有効であることは驚きである。
コーカーの運転圧力に好ましい範囲が設定されている理由は、ノルマルパラフィン含有成分より発生するガスの系外への放出速度を、圧力で制限することができるからである。前述の通り、メソフェーズを構成する炭素六角網平面のサイズは、発生するガスで制御するため、発生ガスの系内への滞留時間は、前記六角網平面の大きさを決定するための重要な制御パラメータとなる。また、コーカーの運転温度に好ましい範囲が設定されている理由は、本発明の効果を得るために調整された重質油から、メソフェーズを成長させるために必要な温度だからである。
炭化および黒鉛化処理の方法は、特に限定されないが、通常は、窒素、アルゴン又はヘリウム等の不活性ガス雰囲気下で最高到達温度900~1500℃、最高到達温度の保持時間0~10時間で炭化(予備焼成)され、次いで同様な不活性ガス雰囲気下、最高到達温度2500~3200℃、最高到達温度保持時間0~100時間の加熱処理する方法を挙げることができる。
炭化の後、一旦冷却して再度黒鉛化のために上記熱処理を施してもよい。
導電助剤としては、カーボンブラック、グラファイト、アセチレンブラック、又は導電性を示すインジウム-錫酸化物、又は、ポリアニリン、ポリチオフェン、ポリフェニレンビニレン等の導電性高分子を挙げることができる。導電助剤の使用量は、黒鉛材料100質量部に対して1~15質量部が好ましい。
有機溶媒としては、ジメチルホルムアミド、N-メチルピロリドン、ピロリドン、N-メチルチオピロリドン、ヘキサメチルホスホアミド、ジメチルアセトアミド、イソプロパノール、トルエン等を挙げることができる。
また、シート状、ペレット状等の形状に成形された負極材スラリーと集電体との一体化は、例えば、ロール、プレス、もしくはこれらの組み合わせ等、公知の方法により行うことができる。
正極に用いる活物質としては、特に制限はなく、例えば、リチウムイオンをドーピング又はインターカレーション可能な金属化合物、金属酸化物、金属硫化物、又は導電性高分子材料を用いればよく、例示するのであれば、コバルト酸リチウム(LiCoO2)、ニッケル酸リチウム(LiNiO2)、マンガン酸リチウム(LiMn2O4)、リチウム複合複酸化物(LiCoXNiYMZO2、X+Y+Z=1、MはMn、Al等を示す)、及びこれらの遷移金属の一部が他の元素により置換されたもの、リチウムバナジウム化合物、V2O5、V6O13、VO2、MnO2、TiO2、MoV2O8、TiS2、V2S5、VS2、MoS2、MoS3、Cr3O8、Cr2O5、オリビン型LiMPO4(M:Co、Ni、Mn、Fe)、ポリアセチレン、ポリアニリン、ポリピロール、ポリチオフェン、ポリアセン等の導電性ポリマー、多孔質炭素等及びこれらの混合物を挙げることができる。
有機電解液としては、ジブチルエーテル、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノメチルエーテル、エチレングリコールフェニルエーテル等のエーテル、N-メチルホルムアミド、N,N-ジメチルホルムアミド、N-エチルホルムアミド、N,N-ジエチルホルムアミド、N-メチルアセトアミド、N,N-ジメチルアセトアミド、N-エチルアセトアミド、N,N-ジエチルアセトアミド等のアミド、ジメチルスルホキシド、スルホラン等の含硫黄化合物、メチルエチルケトン、メチルイソブチルケトン等のジアルキルケトン、テトラヒドロフラン、2-メトキシテトラヒドロフラン等の環状エーテル、エチレンカーボネート、ブチレンカーボネート、プロピレンカーボネート、ビニレンカーボネート等の環状カーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート、メチルプロピルカーボネート等の鎖状カーボネート、γ-ブチロラクトン、γ-バレロラクトン等の環状炭酸エステル、酢酸メチル、酢酸エチル、プロピオン酸メチル、プロピオン酸エチル等の鎖状炭酸エステル、N-メチル2-ピロリジノン、アセトニトリル、ニトロメタン等の有機溶媒を挙げることができる。これらの溶媒は、単独で又は2種以上を混合して使用することができる。
これらの溶媒の溶質としては、各種リチウム塩を使用することができる。一般的に知られているリチウム塩にはLiClO4、LiBF4、LiPF6、LiAlCl4、LiSbF6、LiSCN、LiCl、LiCF3SO3、LiCF3CO2、LiN(CF3SO2)2、LiN(C2F5SO2)2等がある。
なお、上記以外の電池構成上必要な部材の選択についてはなんら制約を受けるものではない。
本発明者らは、水素原子Hと炭素原子Cとの原子比であるH/Cが0.30~0.50であり、且つマイクロ強度が7質量%~17質量%である原料炭組成物の粒子表面にカルサインコークスが埋め込まれた複合粉体を炭化及び黒鉛化する工程と、高度に発達した結晶構造に結晶化度の低い領域が部分的に導入された構造を有し、且つ粒子表面に露出するエッジ部が少ない黒鉛材料が得られることの関係を、次のように考えている。
たとえば、重質油組成物の成分として、流動接触分解装置のボトム油(流動接触分解残油、FCC DO)、流動接触分解残油から抽出した芳香族分、重質油に高度な水添脱硫処理を施した水素化脱硫油、減圧残油(VR)、脱硫脱瀝油、石炭液化油、石炭の溶剤抽出油、常圧残浚油、シェルオイル、タールサンドビチューメン、ナフサタールピッチ、エチレンボトム油、コールタールピッチ及びこれらを水素化精製した重質油等を、単独もしくは二種類以上をブレンドして得られた重質油組成物を熱処理した後、ハンマーミルなどで粗粉砕し、その後、1300℃~1400℃で炭化することによりカルサインコークスを得ることができる。得られたカルサインコークスを機械式粉砕機(例えば、スーパーローターミル/日清エンジニアリング製)等で粉砕し、精密空気分級機(例えば、ターボクラシファイヤー/日清エンジニアリング製)等で分級することにより、カルサインコークスが得られる。
カルサインコークスを粉砕及び分級する際には、カルサインコークスの粒子表面には強い力学的エネルギーが付与される。そのため、粒子表面に存在する六角網平面中の炭素-炭素結合が切断され、表面には六角網平面に属さない未組織炭素が多数露出した状態となる。ここで言う未組織炭素とは、六角網平面積層体と化学的に連結した、主に六角網平面の構成単位となるベンゼン環以外の構造を有したものであり、隣接する他の未組織炭素と炭素-炭素結合を形成することができるという特徴を有する。
炭素-炭素結合によりカルサインコークスと原料炭組成物が化学的に連結される場合、カルサインコークス中の六角網平面と原料炭組成物中の六角網平面とは、完全に同一平面上で連結されるわけではない。その理由は、カルサインコークスが原料炭組成物の粉体に埋め込まれた複合粉体において、カルサインコークス中の六角網平面と原料炭組成物中の六角網平面が非平行な状態で複合化されているためである。このような複合粉体を炭化及び黒鉛化した場合、両者の六角網平面の非平行な状態が維持されながら、両者の界面に炭素-炭素結合が形成される。従って、黒鉛化後の黒鉛材料においても、隣接する六角網平面が非平行な状態で連結された結晶構造が残存すると言える。
非平行な関係にある2つの六角網平面が連結された場合、これらは必然的に六角網平面の平行度が低い、すなわち結晶化度の低い領域を介して連結される。これら非平行な関係にある2つの六角網平面の界面領域は、他の結晶構造が高度に発達した領域に比べて、結晶化度の低い領域であると言える。つまり、カルサインコークスが原料炭組成物の粒子表面に埋め込まれた複合粉体を炭化及び黒鉛化することにより得られた黒鉛材料は、結晶構造が高度に発達した黒鉛材料中に、結晶化度の低い領域が導入された結晶構造を有する。導入された結晶化度の低い領域は、黒鉛層間への電解液の共挿入を立体的に阻害する効果を有する。
一つ目の理由は、原料炭組成物の粒子表面にカルサインコークスが埋め込まれた複合粉体を炭化及び黒鉛化することにより、黒鉛化後の粒子の比表面積増大を抑制するためである。
原料炭組成物の粒子表面にカルサインコークスが埋め込まれた複合粉体の場合、原料炭組成物の粒子表面から突出しているカルサインコークスが少ないため、このような複合粉体を炭化及び黒鉛化して得られた黒鉛材料の表面の凹凸は極めて小さく、比表面積の小さい状態となる。このようにして得られた黒鉛材料を負極として用いたリチウムイオン二次電池では、電解液と黒鉛材料の粒子表面との接触面積が小さいために、負極における電解液の分解が起こりにくい。この場合、正・負極の容量の作動領域が変化しにくいため、寿命特性に優れる。
一方、カルサインコークスが原料炭組成物の粒子表面に埋め込まれておらず表面に付着しただけの複合粉体を炭化及び黒鉛化した場合、黒鉛材料の粒子表面にカルサインコークスが突出しているため、表面に凹凸を有する比表面積の大きな黒鉛材料が得られる。これらの黒鉛材料を負極として用いたリチウムイオン二次電池では、電解液と黒鉛材料の粒子表面との接触面積が大きいために、負極における電解液の分解が起こりやすくなる。この場合、負極の漏れ電流と正極の漏れ電流との差が増大するため、正・負極の容量の作動領域が変化し、寿命特性が低下するため好ましくない。
本発明において、複合粉体を原料炭組成物の粒子表面にカルサインコークスが埋め込まれている状態とする二つ目の理由は、高度に発達した結晶構造と結晶化度の低い領域との界面で化学結合が形成されることにより、両者の界面に亀裂が生じるのを防ぐためである。
圧縮剪断応力により、カルサインコークスが原料炭組成物の粒子表面に埋め込まれる過程において、カルサインコークスは、原料炭組成物を構成する六角網平面積層体と隣接する六角網平面積層体との隙間(ボイド領域)に埋め込まれやすい。これは、カルサインコークスが原料炭組成物中の六角網平面積層体を破壊して、粒子内部に埋め込まれるのに必要なエネルギーよりも、隣接する六角網平面積層体間のボイド領域に埋め込まれるのに必要なエネルギーの方が小さいからである。このボイド領域には、主に六角網平面の構成単位となるベンゼン環以外の構造を有した未組織炭素が存在する。これらの未組織炭素は、原料炭組成物の粉体中の六角網平面積層体と化学的に連結しており、隣接する他の未組織炭素と炭素-炭素結合を形成することができる。
このようなボイド領域にカルサインコークスが埋め込まれた場合、カルサインコークスの粒子表面に存在する未組織炭素が、原料炭組成物中の未組織炭素と十分に接触することができるため、その後の炭化及び黒鉛化の過程において、接触する未組織炭素間に強固な炭素-炭素結合が形成される。そのため、黒鉛化後に得られる黒鉛材料においても、カルサインコークス中の六角網平面積層体と黒鉛中の六角網平面積層体の界面には亀裂が生じることなく、両者は化学的に連結される。このようにして、高度に発達した結晶構造に、結晶化度の低い領域が導入された構造を有する黒鉛材料を得ることができる。
一方、カルサインコークスが原料炭組成物の粒子表面に埋め込まれておらず、表面に付着しただけの複合粉体を炭化及び黒鉛化した場合、カルサインコークスの粒子表面に存在する未組織炭素と原料炭組成物中の未組織炭素の接触面積が極めて小さいために、カルサインコークスと原料炭組成物中の未組織炭素間に強固な炭素-炭素結合を形成することは不可能である。このような場合、得られた黒鉛材料においては、カルサインコークス中の六角網平面積層体と黒鉛中の六角網平面積層体との界面に亀裂が生じやすく、その亀裂部には結晶子のエッジ部が露出する。このような黒鉛材料を負極として用いたリチウムイオン二次電池では、黒鉛材料中の亀裂部に露出した結晶子のエッジ部において、電解液が分解されやすくなる。この場合、負極の漏れ電流と正極の漏れ電流との差が増大するため、正・負極の容量の作動領域が変化し、寿命特性が低下するため好ましくない。
まず、0.1μmを下限としたのは、平均粒径0.1μm未満のカルサインコークスを得ることが非常に困難であり、実状に即さないからである。また、原料炭組成物の粉体と、平均粒径3.0μmより大きなカルサインコークスとを混合した場合、原料炭組成物の六角網平面積層体間のボイド領域に対して、混合したカルサインコークスの大きさが極端に大きくなるため、混合したカルサインコークスが原料炭組成物に埋め込まれず、原料炭組成物の粒子表面に付着するに留まり、粒子表面の凹凸の大きな複合粉体が得られる。この複合粉体を炭化及び黒鉛化して得られた黒鉛材料の比表面積は極端に大きくなり、この黒鉛材料を負極として使用したリチウムイオン二次電池では、電解液と負極の黒鉛材料との接触面積が増大し電解液が分解されやすくなるため、負極の漏れ電流が増大し、正極との漏れ電流との差が大きくなるため、正・負極の容量の作動領域が変化し、寿命特性が低下するため好ましくない。より好ましい平均粒径は、0.5μm~2μmである。
原料炭組成物の粉体と、原料炭組成物に対して0.5質量%未満のカルサインコークスとを混合し、圧縮剪断応力を付与して得られる複合粉体を炭化及び黒鉛化して得られた黒鉛材料の場合、複合粉体に含まれるカルサインコークスの含有量が極端に小さいために、カルサインコークスと原料炭組成物との接触面積を十分に確保することができず、両者の界面領域は極端に小さくなる。この場合、黒鉛材料に導入される結晶化度の低い領域が極端に小さくなる。そのため、溶媒共挿入による電解液の分解を抑制することができない。このような黒鉛材料を負極として用いたリチウムイオン二次電池では、負極における電解液の分解が生じ易いため、負極の漏れ電流が増大し、正極との漏れ電流との差が増大するため、正・負極の容量の作動領域が変化し、寿命特性が低下するため好ましくない。
一方、原料炭組成物の粉体と、原料炭組成物に対して10質量%を超えるカルサインコークスとを混合した場合、原料炭組成物の六角網平面積層体間のボイド領域に対して、混合したカルサインコークスの量が極端に多い状態となる。このとき、混合した全てのカルサインコークスが原料炭組成物の粉体に埋め込まれるために必要なボイド領域が極端に不足しているため、多くのカルサインコークスが原料炭組成物に埋め込まれず、原料炭組成物の粒子表面に付着するに留まり、粒子表面の凹凸の大きな複合粉体が得られる。この複合粉体を炭化及び黒鉛化して得られた黒鉛材料の比表面積は極端に大きくなり、この黒鉛材料を負極として使用したリチウムイオン二次電池では、電解液と負極の黒鉛材料との接触面積が増大し電解液が分解されやすくなるため、負極の漏れ電流が増大し、正極との漏れ電流との差が大きくなるため、正・負極の容量の作動領域が変化し、寿命特性が低下する。より好ましいカルサインコークスの量は、1質量%~5質量%である。
このようなパラメータを有した原料炭組成物は、適度な六角網平面積層体間のボイド領域を有するため、カルサインコークスが原料炭組成物の粒子表面に埋め込まれた複合粉体を得ることが可能である。また、当該原料炭組成物は、適度な六角網平面積層体間の結合力を有するため、複合粉体を黒鉛化した後に得られる黒鉛材料において、カルサインコークスと黒鉛中の六角網平面積層体間に強固な炭素-炭素結合を形成することが可能となる。
全水素の測定は、試料を酸素気流中750℃で完全燃焼させ、燃焼ガスより生成した水分量を電量滴定法(カール・フィッシャー法)で求められる。電量滴定式のカール・フィッシャー法では、予め滴定セルにヨウ化物イオン、二酸化硫黄、塩基(RN)及びアルコールを主成分とする電解液を入れておき、滴定セルに試料を入れることで試料中の水分は、下式(4)の通り反応する。なお、試料は、例えばコーキング処理後、乾燥雰囲気下で冷却した後に測定される。
ヨウ素の発生に要した電気量を測定することで、水分量が求められる。さらに得られた水分量から、水素量に換算し、これを測定に供した試料質量で除することにより、全水素分(TH(質量%))が算出される。
このような場合、得られた黒鉛材料においては、カルサインコークスと黒鉛中の六角網平面積層体との界面に亀裂が生じ、その亀裂部には結晶子のエッジ部が露出する。このような黒鉛材料を負極として用いたリチウムイオン二次電池では、黒鉛材料の亀裂部に露出した結晶子のエッジ部において、電解液が分解されやすくなる。この場合、負極の漏れ電流と正極の漏れ電流との差が増大するため、正・負極の容量の作動領域が変化し、寿命特性が低下する。
重質油組成物の成分としては、流動接触分解装置のボトム油(流動接触分解残油、FCC DO)、流動接触分解残油から抽出した芳香族分、重質油に高度な水添脱硫処理を施した水素化脱硫油、減圧残油(VR)、脱硫脱瀝油、石炭液化油、石炭の溶剤抽出油、常圧残浚油、シェルオイル、タールサンドビチューメン、ナフサタールピッチ、エチレンボトム油、コールタールピッチ及びこれらを水素化精製した重質油等が挙げられる。これらの重質油は単独で用いても良く、二種類以上をブレンドして用いても良い。
ディレードコーキングプロセスによってコーキング処理した後に得られる原料炭組成物の物性として、H/C原子比が0.30~0.50であり、且つマイクロ強度が7質量%~17質量%のものを得る場合には、使用する重質油の性状に応じて二種類以上の重質油の配合比率を適宜調整すればよい。なお、重質油の性状は、原油の種類、原油から重質油が得られるまでの処理条件等によって変化する。
流動接触分解残油から抽出した芳香族分は、ジメチルホルムアミド等を用いて選択抽出し、芳香族分と飽和分に分離させたときの芳香族分である。
重質油に高度な水添脱硫処理を施した水素化脱硫油は、例えば、硫黄分1質量%以上の重質油を水素分圧10MPa以上で水素化脱硫処理して得られる硫黄分1.0質量%以下、窒素分0.5質量%以下、芳香族炭素分率(fa)0.1以上の重質油である。水素化脱硫油は、好ましくは、常圧蒸留残油を触媒存在下、水素化分解率が25%以下となるように水素化脱硫して得られる水素化脱硫油である。
減圧残油(VR)は、原油を常圧蒸留装置にかけて、ガス・軽質油・常圧残油を得た後、この常圧残油を、例えば、10Torr~30Torrの減圧下、加熱炉出口温度320℃~360℃の範囲で変化させて得られる減圧蒸留装置のボトム油である。
脱硫脱瀝油は、例えば、減圧蒸留残渣油等の油を、プロパン、ブタン、ペンタン、又はこれらの混合物等を溶剤として使用する溶剤脱瀝装置で処理し、そのアスファルテン分を除去し、得られた脱瀝油(DAO)を、間接脱硫装置(Isomax)等を用いて、好ましくは硫黄分0.05質量%~0.40質量%の範囲までに脱硫したものである。
常圧残浚油は、原油を常圧蒸留装置にかけて、例えば、常圧下、加熱して、含まれる留分の沸点により、ガス・LPGやガソリン留分、灯油留分、軽質油留分、常圧残浚油に分けられる際に得られる留分の一つで、最も沸点の高い留分である。加熱温度は、原油の産地等により変動し、これらの留分に分留できるものであれば限定されないが、例えば原油を320℃に加熱する。
重質油は高温処理されることによって、熱分解及び重縮合反応が起こり、メソフェーズと呼ばれる大きな液晶が中間生成物として生成する過程を経て生コークスが製造される。
このとき、(1)良好なバルクメソフェーズを生成する重質油成分と、(2)このバルクメソフェーズが重縮合して炭化及び固化する際に、メソフェーズを構成する六角網平面積層体の大きさを小さく制限する機能を有したガスを生じ得る重質油成分と、更に(3)その切断された六角網平面積層体どうしを結合させる成分が全て含有された原料油組成物を用いることが特に好ましい。(1)良好なバルクメソフェーズを生成する重質油成分が、芳香族指数faとして0.3~0.65を与える成分であり、(2)ガスを生じ得る重質油成分が、ノルマルパラフィン含有率の5質量%~20質量%に相当する成分であり、(3)六角網平面積層体どうしを結合させる成分が7質量%~15質量%の範囲で含有された脱硫脱瀝油である。
なお、原料炭組成物の製造に際して、脱硫脱瀝油を添加した例はなく、脱硫脱瀝油の含有が有効であることは驚きである。
また重質油組成物のノルマルパラフィンの含有率は、キャピラリーカラムが装着されたガスクロマトグラフによって測定した値を意味する。具体的には、ノルマルパラフィンの標準物質によって検定した後、上記溶出クロマトグラフィー法によって分離された非芳香族成分の試料をキャピラリーカラムに通して測定する。この測定値から重質油組成物の全質量を基準とした含有率が算出可能である。
このように重質油組成物の芳香族指数faは0.3~0.65の範囲が特に好ましい。faは重質油組成物の密度Dと粘度Vから算出可能であるが、密度Dは0.91g/cm3~1.02g/cm3、粘度Vは10mm2/sec.~220mm2/sec.の範囲の重質油組成物で、faが0.3~0.65となるようなものが特に好ましい。
コーカーの運転圧力に好ましい範囲が設定されている理由は、ノルマルパラフィン含有成分より発生するガスの系外への放出速度を、圧力で制限することができるからである。前述の通り、メソフェーズを構成する炭素六角網平面のサイズは、発生するガスで制御するため、発生ガスの系内への滞留時間は、前記六角網平面の大きさを決定するための重要な制御パラメータとなる。また、コーカーの運転温度に好ましい範囲が設定されている理由は、本発明の効果を得るために調整された重質油から、メソフェーズを成長させるために必要な温度だからである。
まず、Lc(112)が4nm未満の黒鉛材料は結晶組織の発達が不十分であり、このような黒鉛材料を用いたリチウムイオン二次電池では容量が小さくなるため好ましくない。また、本発明における原料炭組成物を高温で長時間黒鉛化した場合においても、Lc(112)が30nmを超える大きさになることはなかったため、上限を30nmとした。
導電助剤としては、カーボンブラック、グラファイト、アセチレンブラック、又は導電性を示すインジウム-錫酸化物、又は、ポリアニリン、ポリチオフェン、ポリフェニレンビニレン等の導電性高分子を挙げることができる。導電助剤の使用量は、黒鉛材料100質量部に対して1質量部~15質量部が好ましい。
有機溶媒としては、ジメチルホルムアミド、N-メチルピロリドン、ピロリドン、N-メチルチオピロリドン、ヘキサメチルホスホアミド、ジメチルアセトアミド、イソプロパノール、トルエン等を挙げることができる。
また、シート状、ペレット状等の形状に成形された負極材スラリーと集電体との一体化は、例えば、ロール、プレス、もしくはこれらの組み合わせ等、公知の方法により行うことができる。
正極に用いる活物質としては、特に制限はなく、例えば、リチウムイオンをドーピング又はインターカレーション可能な金属化合物、金属酸化物、金属硫化物、又は導電性高分子材料を用いればよく、例示するのであれば、コバルト酸リチウム(LiCoO2)、ニッケル酸リチウム(LiNiO2)、マンガン酸リチウム(LiMn2O4)、リチウム複合複酸化物(LiCoXNiYMZO2、ここで、X+Y+Z=1であり、MはMn、Al等を示す)、及びこれらの遷移金属の一部が他の元素により置換されたもの、リチウムバナジウム化合物、V2O5、V6O13、VO2、MnO2、TiO2、MoV2O8、TiS2、V2S5、VS2、MoS2、MoS3、Cr3O8、Cr2O5、オリビン型LiMPO4(M:Co、Ni、Mn、Fe)、ポリアセチレン、ポリアニリン、ポリピロール、ポリチオフェン、ポリアセン等の導電性ポリマー、多孔質炭素等及びこれらの混合物を挙げることができる。
有機電解液としては、ジブチルエーテル、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノメチルエーテル、エチレングリコールフェニルエーテル等のエーテル、N-メチルホルムアミド、N,N-ジメチルホルムアミド、N-エチルホルムアミド、N,N-ジエチルホルムアミド、N-メチルアセトアミド、N,N-ジメチルアセトアミド、N-エチルアセトアミド、N,N-ジエチルアセトアミド等のアミド、ジメチルスルホキシド、スルホラン等の含硫黄化合物、メチルエチルケトン、メチルイソブチルケトン等のジアルキルケトン、テトラヒドロフラン、2-メトキシテトラヒドロフラン等の環状エーテル、エチレンカーボネート、ブチレンカーボネート、プロピレンカーボネート、ビニレンカーボネート等の環状カーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート、メチルプロピルカーボネート等の鎖状カーボネート、γ-ブチロラクトン、γ-バレロラクトン等の環状炭酸エステル、酢酸メチル、酢酸エチル、プロピオン酸メチル、プロピオン酸エチル等の鎖状炭酸エステル、N-メチル2-ピロリジノン、アセトニトリル、ニトロメタン等の有機溶媒を挙げることができる。これらの溶媒は、単独で又は2種以上を混合して使用することができる。
これらの溶媒の溶質としては、各種リチウム塩を使用することができる。一般的に知られているリチウム塩にはLiClO4、LiBF4、LiPF6、LiAlCl4、LiSbF6、LiSCN、LiCl、LiCF3SO3、LiCF3CO2、LiN(CF3SO2)2、LiN(C2F5SO2)2等がある。
なお、上記以外の電池構成上必要な部材の選択についてはなんら制約を受けるものではない。
本発明者らは、水素原子Hと炭素原子Cとの原子比であるH/Cが0.30~0.50であり、且つマイクロ強度が7質量%~17質量%である原料炭組成物の粒子表面にアセチレンブラックが埋め込まれた複合粉体を炭化及び黒鉛化する工程と、高度に発達した結晶構造に結晶化度の低い領域が部分的に導入された構造を有し、且つ粒子表面に露出するエッジ部が少ない黒鉛材料が得られることの関係を、次のように考えている。
このような難黒鉛化性のアセチレンブラックを加熱し黒鉛化した場合、基本粒子中の結晶子の成長は、易黒鉛化性炭素材料を黒鉛化した場合の結晶子の成長と比べて、極端に小さい。そのため、黒鉛化後のアセチレンブラックの結晶化度は、黒鉛材料に比べて極めて低いといえる。
また、アセチレンブラックの基本粒子中の結晶子は、c軸が球状粒子の表面に垂直になるように異方的に配向している。そのため、粒子表面のどの領域においても結晶子エッジの露出が非常に少ないという特徴を有する。この結晶子の異方的な配向は、黒鉛化後にも同様の状態で残存する。
また、前述した複合粉体を炭化及び黒鉛化する工程において、原料炭組成物とアセチレンブラックとの界面には炭素-炭素結合が形成される。一方、炭素-炭素結合が形成されない場合には、原料炭組成物とアセチレンブラックとの界面に亀裂が生じるため、その亀裂部分には結晶子のエッジ部が露出し、電解液の還元分解が増大するため好ましくない。
このようにして、高度に発達した結晶構造中に、炭素-炭素結合により連結された結晶化度の低い領域を有する黒鉛材料が得られる。導入された結晶化度の低い領域は、黒鉛層間への電解液の共挿入を立体的に阻害する効果を有する。
一つ目の理由は、原料炭組成物の粒子表面にアセチレンブラックが埋め込まれた複合粉体を炭化及び黒鉛化することにより、黒鉛化後の粒子の比表面積増大を抑制するためである。
原料炭組成物の粒子表面にアセチレンブラックが埋め込まれた複合粉体の場合、原料炭組成物の粒子表面から突出しているアセチレンブラックが少ないため、このような複合粉体を炭化及び黒鉛化して得られた黒鉛材料の表面の凹凸は極めて小さいく、比表面積の小さい状態となる。このようにして得られた黒鉛材料を負極として用いたリチウムイオン二次電池では、電解液と黒鉛材料の粒子表面との接触面積が小さいために、負極における電解液の分解が起こりにくい。この場合、正・負極の容量の作動領域が変化しにくいため、寿命特性に優れる。
一方、アセチレンブラックが原料炭組成物の粒子表面に埋め込まれておらず表面に付着しただけの複合粉体を炭化及び黒鉛化した場合、黒鉛材料の粒子表面にアセチレンブラックが突出しているため、表面に凹凸を有する比表面積の大きな黒鉛材料が得られる。これらの黒鉛材料を負極として用いたリチウムイオン二次電池では、電解液と黒鉛材料の粒子表面との接触面積が大きいために、負極における電解液の分解が起こりやすくなる。この場合、負極の漏れ電流と正極の漏れ電流との差が増大するため、正・負極の容量の作動領域が変化し、寿命特性が低下するため好ましくない。
本発明において、複合粉体を原料炭組成物の粒子表面にアセチレンブラックが埋め込まれている状態とする二つ目の理由は、高度に発達した結晶構造と結晶化度の低い領域との界面で化学結合が形成されることにより、両者の界面に亀裂が生じるのを防ぐためである。
圧縮剪断応力により、アセチレンブラックが原料炭組成物の粒子表面に埋め込まれる過程において、アセチレンブラックは、原料炭組成物を構成する六角網平面積層体と隣接する六角網平面積層体との隙間(ボイド領域)に埋め込まれやすい。これは、アセチレンブラックが原料炭組成物中の六角網平面積層体を破壊して、粒子内部に埋め込まれるのに必要なエネルギーよりも、隣接する六角網平面積層体間のボイド領域に埋め込まれるのに必要なエネルギーの方が小さいからである。このボイド領域には、六角網平面の構成単位となるベンゼン環以外の構造を有した未組織炭素が存在し、これらの未組織炭素は六角網平面積層体と化学的に連結している。この未組織炭素は、原料炭組成物が炭化及び/又は黒鉛化された後も残存し、同様な役割を演じている。
このようなボイド領域にアセチレンブラックが埋め込まれた場合、アセチレンブラックが原料炭組成物中の未組織炭素と十分に接触することができるため、その後の黒鉛化の過程において、接触する未組織炭素と強固な炭素-炭素結合を形成することができる。そのため、黒鉛化後に得られる黒鉛材料においても、アセチレンブラックと黒鉛中の結晶子間は亀裂が生じることなく化学的に連結される。このようにして、高度に発達した結晶構造に、結晶化度の低い領域が導入された構造を有する黒鉛材料を得ることができる。
一方、アセチレンブラックが原料炭組成物の粒子表面に埋め込まれておらず、表面に付着しただけの複合粉体を炭化及び黒鉛化した場合、原料炭組成物中の未組織炭素とアセチレンブラックとの接触面積が極めて小さいために、炭化及び黒鉛化過程において、アセチレンブラックと原料炭組成物中の未組織炭素間に強固な炭素-炭素結合を形成することは不可能である。このような場合、得られた黒鉛材料においては、アセチレンブラックと黒鉛中の結晶子との界面に亀裂が生じやすく、その亀裂部には結晶子のエッジ部が露出する。このような黒鉛材料を負極として用いたリチウムイオン二次電池では、黒鉛材料の亀裂部に露出した結晶子のエッジ部において、電解液が分解されやすくなる。この場合、負極の漏れ電流と正極の漏れ電流との差が増大するため、正・負極の容量の作動領域が変化し、寿命特性が低下する。
原料炭組成物の粉体と原料炭組成物に対して0.5質量%未満のアセチレンブラックとを混合し、圧縮剪断応力を付与して得られる複合粉体を炭化及び黒鉛化して得られた黒鉛材料の場合、複合粉体に含まれるアセチレンブラックの含有量が極端に小さいために、黒鉛材料に導入される結晶化度の低い領域が極端に少なくなる。そのため、溶媒共挿入による電解液の分解を抑制することができない。このような黒鉛材料を負極として用いたリチウムイオン二次電池では、負極における電解液の分解が生じ易いため、負極の漏れ電流が増大し、正極との漏れ電流との差が増大するため、正・負極の容量の作動領域が変化し、寿命特性が低下するため好ましくない。
一方、原料炭組成物の粉体と原料炭組成物に対して10質量%を越えるアセチレンブラックとを混合した場合、原料炭組成物の六角網平面積層体間のボイド領域に対して、混合したアセチレンブラックの量が極端に多い状態となる。このとき、混合した全てのアセチレンブラックが原料炭組成物の粒子表面に埋め込まれるために必要なボイド領域が極端に不足しているため、多くのアセチレンブラックが原料炭組成物に埋め込まれず、原料炭組成物の粒子表面に付着するに留まり、粒子表面の凹凸の大きな複合粉体が得られる。この複合粉体を炭化及び黒鉛化して得られた黒鉛材料の比表面積は極端に大きくなり、この黒鉛材料を負極として使用したリチウムイオン二次電池では、電解液と負極の黒鉛材料との接触面積が増大し電解液が分解されやすくなるため、負極の漏れ電流が増大し、正極との漏れ電流との差が大きくなるため、正・負極の容量の作動領域が変化し、寿命特性が低下する。より好ましいアセチレンブラックの量は、1質量%~5質量%である。
また、比表面積が300m2/gを超えるアセチレンブラックを添加した場合、たとえアセチレンブラックが原料炭組成物に埋め込まれた状態の複合粉体を黒鉛化したとしても、黒鉛化後の黒鉛材料の比表面積が大幅に増大するために、電解液と黒鉛との接触面積が増大し、容量劣化につながるため好ましくない。
DBP吸油量は、アブソープトメーターを使用し、アセチレンブラックにDBPを添加したときの最大トルクの70%から求めた100g当たりの吸油量とした。
DBP吸油量が50ml/100g未満のアセチレンブラックでは、ストラクチャーが発達しておらず、比表面積が小さい。このようなアセチレンブラックと原料炭組成物の粉体とを混合し圧縮剪断応力を付与した場合、原料炭組成物中のボイド領域に埋め込まれたアセチレンブラックと、ボイド領域に存在する未組織炭素との接触面積が極端に小さい複合粉体が得られる。このような複合粉体を炭化及び黒鉛化した場合、炭化及び黒鉛化の過程で両者の界面に強固な炭素-炭素結合が形成されないため、好ましくない。
また、DBP吸油量が200ml/100gを超えるアセチレンブラックでは、ストラクチャーが高度に発達している。このようなアセチレンブラックと原料炭組成物の粉体とを混合し、圧縮剪断応力を付与した場合、原料炭組成物のボイド領域の体積よりも、アセチレンブラックのストラクチャーが大きく発達しているために、アセチレンブラックを原料炭組成物中のボイド領域に埋め込むことができない。この場合、アセチレンブラックが原料炭組成物の粒子表面に付着するに留まった複合粉体が得られ、このような複合粉体を炭化及び黒鉛化した場合、黒鉛化後の黒鉛粒子表面の比表面積が大幅に増大するために、黒鉛粒子表面での電解液の分解が増大し、負極の漏れ電流が増大し、正極との漏れ電流との差が大きくなるため、正・負極の容量の作動領域が変化し、寿命特性が低下するため好ましくない。
このようなパラメータを有した原料炭組成物は、適度な六角網平面積層体間のボイド領域を有するため、アセチレンブラックが原料炭組成物の粒子表面に埋め込まれた複合粉体を得ることが可能である。また、当該原料炭組成物は、適度な六角網平面積層体間の結合力を有するため、複合粉体を黒鉛化した後に得られる黒鉛材料において、アセチレンブラックと黒鉛中の結晶子間に強固な炭素-炭素結合を形成することが可能となる。
全水素の測定は、試料を酸素気流中750℃で完全燃焼させ、燃焼ガスより生成した水分量を電量滴定法(カール・フィッシャー法)で求められる。電量滴定式のカール・フィッシャー法では、予め滴定セルにヨウ化物イオン、二酸化硫黄、塩基(RN)及びアルコールを主成分とする電解液を入れておき、滴定セルに試料を入れることで試料中の水分は、下式(4)の通り反応する。なお、試料は、例えばコーキング処理後、乾燥雰囲気下で冷却した後に測定される。
ヨウ素の発生に要した電気量を測定することで、水分量が求められる。さらに得られた水分量から、水素量に換算し、これを測定に供した試料質量で除することにより、全水素分(TH(質量%))が算出される。
そのため、アセチレンブラックがボイド領域に埋め込まれた複合粉体において、アセチレンブラックと未組織炭素間に炭素-炭素結合が形成されにくい。このような複合粉体を炭化及び黒鉛化して得られた黒鉛材料中では、アセチレンブラックと黒鉛中の結晶子との界面に亀裂が生じやすく、その亀裂部には結晶子のエッジ部が露出する。これらの黒鉛材料を負極として用いたリチウムイオン二次電池では、粒子表面のエッジ部における電解液の分解が起こりやすいため、負極の漏れ電流が増大し、正極との漏れ電流との差が大きくなるため、正・負極の容量の作動領域が変化し、寿命特性が低下するため好ましくない。
重質油組成物の成分としては、流動接触分解装置のボトム油(流動接触分解残油、FCC DO)、流動接触分解残油から抽出した芳香族分、重質油に高度な水添脱硫処理を施した水素化脱硫油、減圧残油(VR)、脱硫脱瀝油、石炭液化油、石炭の溶剤抽出油、常圧残浚油、シェルオイル、タールサンドビチューメン、ナフサタールピッチ、エチレンボトム油、コールタールピッチ及びこれらを水素化精製した重質油等が挙げられる。これらの重質油は単独で用いても良く、二種類以上をブレンドして用いても良い。
ディレードコーキングプロセスによってコーキング処理した後に得られる原料炭組成物の物性として、H/C原子比が0.30~0.50であり、且つマイクロ強度が7質量%~17質量%のものを得る場合には、使用する重質油の性状に応じて二種類以上の重質油の配合比率を適宜調整すればよい。なお、重質油の性状は、原油の種類、原油から重質油が得られるまでの処理条件等によって変化する。
流動接触分解残油から抽出した芳香族分は、ジメチルホルムアミド等を用いて選択抽出し、芳香族分と飽和分に分離させたときの芳香族分である。
重質油に高度な水添脱硫処理を施した水素化脱硫油は、例えば、硫黄分1質量%以上の重質油を水素分圧10MPa以上で水素化脱硫処理して得られる硫黄分1.0質量%以下、窒素分0.5質量%以下、芳香族炭素分率(fa)0.1以上の重質油である。水素化脱硫油は、好ましくは、常圧蒸留残油を触媒存在下、水素化分解率が25%以下となるように水素化脱硫して得られる水素化脱硫油である。
減圧残油(VR)は、原油を常圧蒸留装置にかけて、ガス・軽質油・常圧残油を得た後、この常圧残油を、例えば、10Torr~30Torrの減圧下、加熱炉出口温度320℃~360℃の範囲で変化させて得られる減圧蒸留装置のボトム油である。
脱硫脱瀝油は、例えば、減圧蒸留残渣油等の油を、プロパン、ブタン、ペンタン、又はこれらの混合物等を溶剤として使用する溶剤脱瀝装置で処理し、そのアスファルテン分を除去し、得られた脱瀝油(DAO)を、間接脱硫装置(Isomax)等を用いて、好ましくは硫黄分0.05質量%~0.40質量%の範囲までに脱硫したものである。
常圧残浚油は、原油を常圧蒸留装置にかけて、例えば、常圧下、加熱して、含まれる留分の沸点により、ガス・LPGやガソリン留分、灯油留分、軽質油留分、常圧残浚油に分けられる際に得られる留分の一つで、最も沸点の高い留分である。加熱温度は、原油の産地等により変動し、これらの留分に分留できるものであれば限定されないが、例えば原油を320℃に加熱する。
重質油は高温処理されることによって、熱分解及び重縮合反応が起こり、メソフェーズと呼ばれる大きな液晶が中間生成物として生成する過程を経て生コークスが製造される。
このとき、(1)良好なバルクメソフェーズを生成する重質油成分と、(2)このバルクメソフェーズが重縮合して炭化及び固化する際に、メソフェーズを構成する六角網平面積層体の大きさを小さく制限する機能を有したガスを生じ得る重質油成分と、更に(3)その切断された六角網平面積層体どうしを結合させる成分が全て含有された原料油組成物を用いることが特に好ましい。(1)良好なバルクメソフェーズを生成する重質油成分が、芳香族指数faとして0.3~0.65を与える成分であり、(2)ガスを生じ得る重質油成分が、ノルマルパラフィン含有率の5質量%~20質量%に相当する成分であり、(3)六角網平面積層体どうしを結合させる成分が7質量%~15質量%の範囲で含有された脱硫脱瀝油である。
なお、原料炭組成物の製造に際して、脱硫脱瀝油を添加した例はなく、脱硫脱瀝油の含有が有効であることは驚きである。
また重質油組成物のノルマルパラフィンの含有率は、キャピラリーカラムが装着されたガスクロマトグラフによって測定した値を意味する。具体的には、ノルマルパラフィンの標準物質によって検定した後、上記溶出クロマトグラフィー法によって分離された非芳香族成分の試料をキャピラリーカラムに通して測定する。この測定値から重質油組成物の全質量を基準とした含有率が算出可能である。
このように重質油組成物の芳香族指数faは0.3~0.65の範囲が特に好ましい。faは重質油組成物の密度Dと粘度Vから算出可能であるが、密度Dは0.91g/cm3~1.02g/cm3、粘度Vは10mm2/sec.~220mm2/sec.の範囲の重質油組成物で、faが0.3~0.65となるようなものが特に好ましい。
コーカーの運転圧力に好ましい範囲が設定されている理由は、ノルマルパラフィン含有成分より発生するガスの系外への放出速度を、圧力で制限することができるからである。前述の通り、メソフェーズを構成する炭素六角網平面のサイズは、発生するガスで制御するため、発生ガスの系内への滞留時間は、前記六角網平面の大きさを決定するための重要な制御パラメータとなる。また、コーカーの運転温度に好ましい範囲が設定されている理由は、本発明の効果を得るために調整された重質油から、メソフェーズを成長させるために必要な温度だからである。
Lc(112)が4nm未満の黒鉛粒子では結晶組織が発達し難く、このような黒鉛材料を用いたリチウムイオン二次電池では容量が小さくなるため好ましくない。また、本発明における原料炭組成物を高温で長時間黒鉛化した場合においても、Lc(112)が30nmを超える大きさになることはなかったため、上限を30nmとした。
導電助剤としては、カーボンブラック、グラファイト、アセチレンブラック、又は導電性を示すインジウム-錫酸化物、又は、ポリアニリン、ポリチオフェン、ポリフェニレンビニレン等の導電性高分子を挙げることができる。導電助剤の使用量は、黒鉛材料100質量部に対して1質量部~15質量部が好ましい。
有機溶媒としては、ジメチルホルムアミド、N-メチルピロリドン、ピロリドン、N-メチルチオピロリドン、ヘキサメチルホスホアミド、ジメチルアセトアミド、イソプロパノール、トルエン等を挙げることができる。
また、シート状、ペレット状等の形状に成形された負極材スラリーと集電体との一体化は、例えば、ロール、プレス、もしくはこれらの組み合わせ等、公知の方法により行うことができる。
正極に用いる活物質としては、特に制限はなく、例えば、リチウムイオンをドーピング又はインターカレーション可能な金属化合物、金属酸化物、金属硫化物、又は導電性高分子材料を用いればよく、例示するのであれば、コバルト酸リチウム(LiCoO2)、ニッケル酸リチウム(LiNiO2)、マンガン酸リチウム(LiMn2O4)、リチウム複合複酸化物(LiCoXNiYMZO2、ここで、X+Y+Z=1であり、MはMn、Al等を示す)、及びこれらの遷移金属の一部が他の元素により置換されたもの、リチウムバナジウム化合物、V2O5、V6O13、VO2、MnO2、TiO2、MoV2O8、TiS2、V2S5、VS2、MoS2、MoS3、Cr3O8、Cr2O5、オリビン型LiMPO4(M:Co、Ni、Mn、Fe)、ポリアセチレン、ポリアニリン、ポリピロール、ポリチオフェン、ポリアセン等の導電性ポリマー、多孔質炭素等及びこれらの混合物を挙げることができる。
有機電解液としては、ジブチルエーテル、エチレングリコールモノメチルエーテル、エチレングリコールモノエチルエーテル、エチレングリコールモノブチルエーテル、ジエチレングリコールモノメチルエーテル、エチレングリコールフェニルエーテル等のエーテル、N-メチルホルムアミド、N,N-ジメチルホルムアミド、N-エチルホルムアミド、N,N-ジエチルホルムアミド、N-メチルアセトアミド、N,N-ジメチルアセトアミド、N-エチルアセトアミド、N,N-ジエチルアセトアミド等のアミド、ジメチルスルホキシド、スルホラン等の含硫黄化合物、メチルエチルケトン、メチルイソブチルケトン等のジアルキルケトン、テトラヒドロフラン、2-メトキシテトラヒドロフラン等の環状エーテル、エチレンカーボネート、ブチレンカーボネート、プロピレンカーボネート、ビニレンカーボネート等の環状カーボネート、ジエチルカーボネート、ジメチルカーボネート、メチルエチルカーボネート、メチルプロピルカーボネート等の鎖状カーボネート、γ-ブチロラクトン、γ-バレロラクトン等の環状炭酸エステル、酢酸メチル、酢酸エチル、プロピオン酸メチル、プロピオン酸エチル等の鎖状炭酸エステル、N-メチル2-ピロリジノン、アセトニトリル、ニトロメタン等の有機溶媒を挙げることができる。これらの溶媒は、単独で又は2種以上を混合して使用することができる。
これらの溶媒の溶質としては、各種リチウム塩を使用することができる。一般的に知られているリチウム塩にはLiClO4、LiBF4、LiPF6、LiAlCl4、LiSbF6、LiSCN、LiCl、LiCF3SO3、LiCF3CO2、LiN(CF3SO2)2、LiN(C2F5SO2)2等がある。
なお、上記以外の電池構成上必要な部材の選択についてはなんら制約を受けるものではない。
(1)原料炭組成物A-1
硫黄分3.1質量%の常圧蒸留残油を、触媒存在下、水素化分解率が25%以下となるように水素化脱硫し、水素化脱硫油を得た。水素化脱硫条件は、全圧180MPa、水素分圧160MPa、温度380℃である。また、脱硫減圧軽油(硫黄分500質量ppm、15℃における密度0.88g/cm3)を流動接触分解し、流動接触分解残油を得た。この流動接触分解残油を、ジメチルホルムアミドで選択抽出し、芳香族分と飽和分に分離させ、このうちの芳香族分を抽出した。この抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、19質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、コークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物A-1を得た。
原料炭組成物A-1の原料油組成物が、抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、11質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物B-1を得た。
原料炭組成物A-1の原料油組成物が、抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、4質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物C-1を得た。
原料炭組成物A-1の原料油組成物が、抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、17質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物D-1を得た。
原料炭組成物A-1の原料油組成物が、抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、11質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物E-1を得た。
原料炭組成物A-1の原料油組成物が、抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、6質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物F-1を得た。
原料炭組成物A-1の原料油組成物の原料となった水素化脱硫油と流動接触分解残油とを質量比1:5で混合したものに、15質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物G-1を得た。
原料炭組成物A-1の原料油組成物の原料となった水素化脱硫油と流動接触分解残油とを質量比1:5で混合したものに、7質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物H-1を得た。
原料炭組成物A-1の原料油組成物の原料となった水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、19質量%となるように脱硫脱瀝油を加えークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物I-1を得た。
原料炭組成物A-1の原料油組成物の原料となった水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、16質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物J-1を得た。
原料炭組成物A-1の原料油組成物の原料となった水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、11質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物K-1を得た。
原料炭組成物A-1の原料油組成物の原料となった水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、5質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物L-1を得た。
原料炭組成物A-1の原料油組成物の原料となった水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、3質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物M-1を得た。
原料炭組成物A-1の原料油組成物の原料となった水素化脱硫油と流動接触分解残油とを質量比1:3で混合したものに、14質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物N-1を得た。
原料炭組成物A-1の原料油組成物の原料となった水素化脱硫油と流動接触分解残油とを質量比1:3で混合したものに、7質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物O-1を得た。
原料炭組成物A-1の原料油組成物の原料となった流動接触分解残油に、同体積のn-ヘプタンを加え混合した後、ジメチルホルムアミドで選択抽出し、芳香族分と飽和分に分離させ、このうちの飽和分を選択抽出した。流動接触分解残油と、この抽出飽和分とを質量比1:1で混合したものに、16質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物P-1を得た。
原料炭組成物P-1の原料油組成物の原料となった流動接触分解残油と、抽出飽和分とを質量比1:1で混合したものに、11質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物Q-1を得た。
原料炭組成物P-1の原料油組成物の原料となった流動接触分解残油と、抽出飽和分とを質量比1:1で混合したものに、6質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物R-1を得た。
原料炭組成物P-1の原料油組成物の原料となった流動接触分解残油と、抽出飽和分とを質量比1:2で混合したものに、19質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物S-1を得た。
原料炭組成物P-1の原料油組成物の原料となった流動接触分解残油と、抽出飽和分とを質量比1:2で混合したものに、10質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物T-1を得た。
原料炭組成物P-1の原料油組成物の原料となった流動接触分解残油と、抽出飽和分とを質量比1:2で混合したものに、4質量%となるように脱硫脱瀝油を加えコークスの原料油組成物を得た。この原料油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物U-1を得た。
(1)原料炭組成物のH/C原子比の測定方法
原料炭組成物の全水素の測定は、試料を酸素気流中750℃で完全燃焼させ、燃焼ガスより生成した水分量を電量滴定法(カール・フィッシャー法)で測定した。また原料炭組成物試料を1150℃の酸素気流中で燃焼させ、二酸化炭素(一部一酸化炭素)に変換され過剰の酸素気流に搬送されてCO2+CO赤外線検出器により、全炭素分を測定した。原料炭組成物のH/Cは、全水素分(TH(質量%))を水素の原子量を除した値と、全炭素分(TC(質量%))を炭素の原子量を除した値の比率で算出した。原料炭組成物A-1~U-1のH/C値は表1に示された通りである。
鋼製シリンダー(内径25.4mm、長さ304.8mm)に20~30メッシュの試料2gと直径5/16inch(7.9mm)の鋼球12個を入れ、鉛直面を管と直角方向に25rpmで800回転させたのち(すなわち、シリンダーを立てた状態から上下が入れ替わるように、回転軸を水平にして、あたかもプロペラが回転するように回転させる)、48メッシュでふるい分け、試料に対するふるい上の質量の割合を、パーセントで算出した。原料炭組成物A-1~U-1のマイクロ強度は表1に示された通りである。
得られた原料炭組成物を、機械式粉砕機(スーパーローターミル/日清エンジニアリング社製)で粉砕し、精密空気分級機(ターボクラシファイヤー/日清エンジニアリング社製)で分級することにより、平均粒子径12μmの微粒子材料を得た。次に、この微粒子を、ホソカワミクロン社製の「ノビルタ130型」へ、充填体積が500ccになるように投入し、ブレードの周速度30m/s、両者間の間隙5mm、処理温度は130℃程度にコントロールして、処理時間50分の条件で運転して圧縮応力と剪断応力を付与した黒鉛前駆体を得た。圧縮応力と剪断応力が付与された微粒子を、高砂工業社製のローラーハースキルンで、窒素ガス気流下、最高到達温度が1200℃、最高到達温度保持時間が5時間となるように炭素化した。得られた炭素材料を坩堝に投入し、電気炉に設置して、80L/分の窒素ガス気流中、最高到達温度2800℃で黒鉛化した。このとき昇温速度は200℃/時間、最高到達温度の保持時間は3時間、降温速度は1000℃までが100℃/時間とし、その後窒素気流を保持させた状態で室温まで放冷させた。得られた黒鉛材料は、原料炭組成物A-1~U-1に対応させて、黒鉛A-1~U-1と呼称する。
原料炭組成物H-1、K-1、N-1を各々機械式粉砕機(スーパーローターミル/日清エンジニアリング社製)で粉砕し、精密空気分級機(ターボクラシファイヤー/日清エンジニアリング社製)で分級することにより、平均粒子径12μmの微粒子材料を得た。この微粒子を、圧縮応力と剪断応力を付加すること無しに、高砂工業社製のローラーハースキルンで、窒素ガス気流下、最高到達温度が1200℃、最高到達温度保持時間が5時間となるように炭素化した。得られた炭素材料を坩堝に投入し、電気炉に設置して、80L/分の窒素ガス気流中、最高到達温度2800℃で黒鉛化した。このとき昇温速度は200℃/時間、最高到達温度の保持時間は3時間、降温速度は1000℃までが100℃/時間とし、その後窒素気流を保持させた状態で室温まで放冷させた。得られた黒鉛材料は、原料炭組成物H-1、K-1、N-1に対応させて、黒鉛V-1、W-1、X-1と呼称する。
原料炭組成物K-1を、「3.原料炭組成物A-1~U-1の炭素化及び黒鉛化」に記載された方法と同様に黒鉛化した。ただし黒鉛化の最高到達温度を2600℃としたものを黒鉛Y-1、2300℃としたものを黒鉛Z-1と呼称する。
得られた黒鉛粉末に、内部標準としてSi標準試料を10質量%混合し、ガラス製回転試料ホルダー(25mmφ×0.2mmt)に詰め、日本学術振興会117委員会が定めた方法(炭素2006,No.221,P52-60)に基づき、広角X線回折法で測定を行い、黒鉛粉末の結晶子の大きさLc(112)を算出した。X線回折装置は、Bruker-AXS社製 D8 ADVANCE(封入管型)、X線源はCuKα線(Kβフ
ィルターNiを使用)、X線管球への印可電圧及び電流は40kV及び40mAとした。
得られた回折図形についても、日本学術振興会117委員会が定めた方法に準拠した方法(炭素2006,No.221,P52-60)で解析を行った。具体的には、測定データにスムージング処理、バックグラウンド除去の後、吸収補正、偏光補正、Lorentz補正を施し、Si標準試料の(422)回折線のピーク位置、及び値幅を用いて、黒鉛粉末の(112)回折線に対して補正を行い、結晶子サイズを算出した。なお、結晶子サイズは、補正ピークの半値幅から以下のScherrerの式を用いて計算した。測定・解析は3回ずつ実施し、その平均値をLc(112)とした。黒鉛粉末のLc(112)が測定された結果は、表1に示された通りである。
(1)電池の作製方法
図1に作製した電池の断面図を示す。正極は、正極材料である平均粒子径6μmのニッケル酸リチウム(戸田工業社製LiNi0.8Co0.15Al0.05O2)と結着剤のポリフッ化ビニリデン(クレハ社製KF#1320)、アセチレンブラック(デンカ社製のデンカブラック)を質量比で89:6:5に混合し、N-メチル-2-ピロリジノンを加えて混練した後、ペースト状にして、厚さ30μmのアルミニウム箔の片面に塗布し、乾燥及び圧延操作を行い、塗布部のサイズが、幅30mm、長さ50mmとなるように切断されたシート電極である。このとき単位面積当たりの塗布量は、ニッケル酸リチウムの質量として、10mg/cm2となるように設定した。
このシート電極の一部はシートの長手方向に対して垂直に正極合剤が掻き取られ、その露出したアルミニウム箔が塗布部の集電体(アルミニウム箔)と一体化して繋がっており、正極リード板としての役割を担っている。
負極は、負極材料である黒鉛A-1~W-1の黒鉛粉末と結着剤のポリフッ化ビニリデン(クレハ社製KF#9310)、アセチレンブラック(デンカ社製のデンカブラック)を質量比で91:2:8に混合し、N-メチル-2-ピロリジノンを加えて混練した後、ペースト状にして、厚さ18μmの銅箔の片面に塗布し、乾燥及び圧延操作を行い、塗布部のサイズが、幅32mm、長さ52mmとなるように切断されたシート電極である。このとき単位面積当たりの塗布量は、黒鉛粉末の質量として、6mg/cm2となるように設定した。
このシート電極の一部はシートの長手方向に対して垂直に負極合剤が掻き取られ、その露出した銅箔が塗布部の集電体(銅箔)と一体化して繋がっており、負極リード板としての役割を担っている。
このようにして乾燥された正極及び負極を、正極の塗布部と負極の塗布部とが、ポリポロピレン製のマイクロポーラスフィルム(セルガード社製#2400)を介して対向させる状態で積層し、ポリイミドテープで固定した。なお、正極及び負極の積層位置関係は、負極の塗布部に投影される正極塗布部の周縁部が、負極塗布部の周縁部の内側で囲まれるように対向させた。得られた単層電極体を、アルミラミネートフィルムで包埋させ、電解液を注入し、前述の正・負極リード板がはみ出した状態で、ラミネートフィルムを熱融着することにより、密閉型の単層ラミネート電池を作製した。使用した電解液は、エチレンカーボネートとエチルメチルカーボネートが体積比で3:7に混合された溶媒にヘキサフルオロリン酸リチウム(LiPF6)が1mol/Lの濃度となるように溶解されたものである。
得られた電池を25℃の恒温室内に設置し、以下に示す充放電試験を行った。先ず1.5mAの電流で、電池電圧が4.2Vとなるまで定電流で充電した。10分間休止の後、同じ電流で電池電圧が3.0Vとなるまで定電流で放電する充放電サイクルを10回繰り返した。この充放電サイクルは、電池の異常を検地するためのものであるため、充放電サイクル試験のサイクル数には含まなかった。本実施例で作製された電池は、全て異常がないことを確認した。
次に、充電電流を15mA、充電電圧を4.2V、充電時間を3時間とした定電流/定電圧充電を行い、1分間休止の後、同じ電流(15mA)で電池電圧が3.0Vとなるまで定電流で放電させた。このとき得られた放電容量を、第1サイクル目の放電容量とする。同様な条件の充放電サイクルを3000回繰り返し、第1サイクル目の放電容量に対する第3000サイクル目の放電容量の割合(%)を算出し、「3000サイクル後の容量維持率(%)」とした。第1サイクル目の放電容量、第3000サイクル目の放電容量、及び3000サイクル後の容量維持率(%)を表1中に示す。
表1に原料炭組成物A-1~U-1のH/C値、及びマイクロ強度と、その原料炭組成物A-1~U-1に対応した黒鉛A-1~Z-1の結晶子の大きさLc(112)、及びこれらを負極として使用したリチウムイオン二次電池の第1サイクル目の放電容量(mAh)、第3000サイクル目の放電容量(mAh)、3000サイクル後の容量維持率(%)を示す。
図2及び図3より、原料炭組成物が本発明の範囲内、即ちH/C値が0.3~0.5であり、且つマイクロ強度が7~17であるものに対し、圧縮応力と剪断応力を付与したあと黒鉛化したもの(G-1,H-1,K-1,N-1,O-1,Y-1,Z-1)は、3000サイクル後の放電容量維持率が85%以上となり、サイクル劣化が小さな信頼性の高いリチウムイオン二次電池を実現できることが分かった。なお、図2のグラフ中のX軸に垂直な破線は、X=0.3とX=0.5であり、図3のグラフ中のX軸に垂直な破線は、X=7とX=17である。
また原料炭組成物(H-1,K-1,N-1)を原料とした黒鉛化物の製造方法として、圧縮応力と剪断応力を付与しないで黒鉛化処理したもの(黒鉛V-1,W-1,X-1)を負極に使用した電池は、3000サイクル後の容量維持率が各々70.1%、74.3%、68.4%となり、圧縮応力と剪断応力を付与した対応する黒鉛化物(H-1,K-1,N-1)の場合(85%以上)と比較して、サイクル劣化が著しく大きくなった。原料炭組成物の物性は本出願の範囲内であっても、圧縮応力と剪断応力を付与しないで黒鉛化したものを負極に使用した電池はサイクル劣化が大きかったことから、原料炭組成物の物性が本出願の範囲内であることと、圧縮応力と剪断応力を付与することは、3000サイクル後の容量維持率として85%以上を確保するための必要条件であることが分かった。
(1)原料炭組成物A-2
硫黄分3.1質量%の常圧蒸留残油を、触媒存在下、水素化分解率が25%以下となるように水素化脱硫し、水素化脱硫油を得た。水素化脱硫条件は、全圧180MPa、水素分圧160MPa、温度380℃である。また、脱硫減圧軽油(硫黄分500質量ppm、15℃における密度0.88g/cm3)を流動接触分解し、流動接触分解残油を得た。この流動接触分解残油を、ジメチルホルムアミドで選択抽出し、芳香族分と飽和分に分離させ、このうちの芳香族分を抽出した。この抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、19質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物A-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、11質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物B-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、4質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物C-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、17質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物D-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、11質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物E-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、6質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物F-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:5で混合したものに、15質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物G-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:5で混合したものに、7質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物H-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、19質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物I-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、16質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物J-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、11質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物K-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、5質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物L-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、3質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物M-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:3で混合したものに、14質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物N-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:3で混合したものに、7質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物O-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油に同体積のn-ヘプタンを加え混合した後、ジメチルホルムアミドで選択抽出し、芳香族分と飽和分に分離させ、このうちの飽和分を選択抽出した。流動接触分解残油と、この抽出飽和分とを質量比1:1で混合したものに、16質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物P-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-2の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:1で混合したものに、11質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物Q-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-2の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:1で混合したものに、6質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物R-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-2の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:2で混合したものに、19質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物S-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-2の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:2で混合したものに、10質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物T-2を得た。
原料炭組成物A-2の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-2の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:2で混合したものに、4質量%となるように脱硫脱瀝油を加え重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物U-2を得た。
(1)原料炭組成物のH/C原子比の測定方法
原料炭組成物の全水素の測定は、試料を酸素気流中750℃で完全燃焼させ、燃焼ガスより生成した水分量を電量滴定法(カール・フィッシャー法)で測定した。また原料炭組成物試料を1150℃の酸素気流中で燃焼させ、二酸化炭素(一部一酸化炭素)に変換され過剰の酸素気流に搬送されてCO2+CO赤外線検出器により、全炭素分を測定した。原料炭組成物のH/Cは、全水素分(TH(質量%))を水素の原子量を除した値と、全炭素分(TC(質量%))を炭素の原子量を除した値の比率で算出した。原料炭組成物A-2~U-2のH/C値は表2に示された通りである。
鋼製シリンダー(内径25.4mm、長さ304.8mm)に20~30メッシュの試料2gと直径5/16inch(7.9mm)の鋼球12個を入れ、鉛直面を管と直角方向に25rpmで800回転させたのち(すなわち、シリンダーを立てた状態から上下が入れ替わるように、回転軸を水平にして、あたかもプロペラが回転するように回転させる)、48メッシュでふるい分け、試料に対するふるい上の質量の割合を、パーセントで算出した。原料炭組成物A-2~U-2のマイクロ強度は表2に示された通りである。
得られた原料炭組成物G-2を、機械式粉砕機(スーパーローターミル/日清エンジニアリング社製)で粉砕し、精密空気分級機(ターボクラシファイヤー/日清エンジニアリング社製)で分級することにより、平均粒径10μmの原料炭組成物の粉末を得た。次に、この粉末を、高砂工業社製のローラーハースキルンで、窒素ガス気流下、最高到達温度が1200℃、最高到達温度保持時間が5時間となるように炭化した。得られた炭素材料を坩堝に投入し、電気炉に設置して、80L/分の窒素ガス気流中、最高到達温度2800℃で黒鉛化した。このとき昇温速度は200℃/時間、最高到達温度の保持時間は3時間、降温速度は1000℃までが100℃/時間とし、その後窒素気流を保持させた状態で室温まで放冷させることにより黒鉛粒子を得た。得られた黒鉛粒子のX線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)は10.9nmであった。得られた黒鉛粒子を、ホソカワミクロン社製の「ノビルタ130型」へ、充填体積が500ccになるように投入し、ブレードの回転数を1300rpm、処理温度は130℃程度にコントロールして、処理時間15分の条件で運転して圧縮剪断応力を付与した黒鉛材料を得た。
表2に記載された原料炭組成物を、同表に記載された平均粒径に粉砕・分級し、実施例1に記載したものと同じ条件で炭化・黒鉛化し黒鉛粒子を得た。粉砕・分級および炭化・黒鉛化の装置は、実施例1と同じ装置を用いた。得られた黒鉛粒子に、同表に記載された装置および条件(回転数または周速度、処理時間)で表面処理を施した。
原料炭組成物H-2、K-2、N-2を、同表に記載された平均粒径に粉砕・分級し、実施例1に記載したものと同じ条件で炭化・黒鉛化し黒鉛粒子を得た。粉砕・分級および炭化・黒鉛化の装置は、実施例1と同じ装置を用いた。得られた黒鉛粒子に、同表に記載された装置および条件(回転数または周速度、処理時間)で表面処理を施した。その後、高砂工業社製のローラーハースキルンで、窒素ガス気流下、最高到達温度が1200℃、最高到達温度保持時間が3時間となるように熱処理した。
原料炭組成物K-2を、同表に記載された平均粒径に粉砕・分級し、実施例1に記載したものと同じ条件で炭化・黒鉛化し黒鉛粒子を得た。比較例17では、黒鉛化の最高到達温度を2600℃、比較例18では、2300℃とした。粉砕・分級および炭化・黒鉛化の装置は、実施例1と同じ装置を用いた。得られた黒鉛粒子に、同表に記載された装置および条件(回転数または周速度、処理時間)で表面処理を施した。
得られた黒鉛粒子に、内部標準としてSi標準試料を10質量%混合し、ガラス製回転試料ホルダー(25mmφ×0.2mmt)に詰め、日本学術振興会117委員会が定めた方法(炭素2006,No.221,P52-60)に基づき、広角X線回折法で測定を行い、黒鉛粒子の結晶子の大きさLc(112)を算出した。X線回折装置は、Bruker-AXS社製 D8 ADVANCE(封入管型)、X線源はCuKα線(Kβフ
ィルターNiを使用)、X線管球への印可電圧及び電流は40kV及び40mAとした。
得られた回折図形についても、日本学術振興会117委員会が定めた方法に準拠した方法(炭素2006,No.221,P52-60)で解析を行った。具体的には、測定データにスムージング処理、バックグラウンド除去の後、吸収補正、偏光補正、Lorentz補正を施し、Si標準試料の(422)回折線のピーク位置、及び値幅を用いて、黒鉛粒子の(112)回折線に対して補正を行い、結晶子サイズを算出した。なお、結晶子サイズは、補正ピークの半値幅から以下のScherrerの式を用いて計算した。測定・解析は3回ずつ実施し、その平均値をLc(112)とした。黒鉛粒子のLc(112)が測定された結果は、表2に示された通りである。
(1)電池の作製方法
図1に作製した電池10の断面図を示す。図1には、負極11、負極集電体12、正極13、正極集電体14、セパレータ15、アルミラミネート外装16が示されている。
正極は、正極材料である平均粒子径6μmのニッケル酸リチウム(戸田工業社製LiNi0.8Co0.15Al0.05O2)と結着剤のポリフッ化ビニリデン(クレハ社製KF#1320)、アセチレンブラック(デンカ社製のデンカブラック)を質量比で89:6:5に混合し、N-メチル-2-ピロリジノンを加えて混練した後、ペースト状にして、厚さ30μmのアルミニウム箔の片面に塗布し、乾燥及び圧延操作を行い、塗布部のサイズが、幅30mm、長さ50mmとなるように切断されたシート電極である。このとき単位面積当たりの塗布量は、ニッケル酸リチウムの質量として、10mg/cm2となるように設定した。
このシート電極の一部はシートの長手方向に対して垂直に正極合剤が掻き取られ、その露出したアルミニウム箔が塗布部の集電体(アルミニウム箔)と一体化して繋がっており、正極リード板としての役割を担っている。
負極は、負極材料である前記実施例及び比較例で得られた黒鉛材料と結着剤のポリフッ化ビニリデン(クレハ社製KF#9310)、アセチレンブラック(デンカ社製のデンカブラック)を質量比で91:2:8に混合し、N-メチル-2-ピロリジノンを加えて混練した後、ペースト状にして、厚さ18μmの銅箔の片面に塗布し、乾燥及び圧延操作を行い、塗布部のサイズが、幅32mm、長さ52mmとなるように切断されたシート電極である。このとき単位面積当たりの塗布量は、黒鉛材料の質量として、6mg/cm2となるように設定した。
このシート電極の一部はシートの長手方向に対して垂直に負極合剤が掻き取られ、その露出した銅箔が塗布部の集電体(銅箔)と一体化して繋がっており、負極リード板としての役割を担っている。
このようにして乾燥された正極及び負極を、正極の塗布部と負極の塗布部とが、ポリポロピレン製のマイクロポーラスフィルム(セルガード社製#2400)を介して対向させる状態で積層し、ポリイミドテープで固定した。なお、正極及び負極の積層位置関係は、負極の塗布部に投影される正極塗布部の周縁部が、負極塗布部の周縁部の内側で囲まれるように対向させた。得られた単層電極体を、アルミラミネートフィルムで包埋させ、電解液を注入し、前述の正・負極リード板がはみ出した状態で、ラミネートフィルムを熱融着することにより、密閉型の単層ラミネート電池を作製した。使用した電解液は、エチレンカーボネートとエチルメチルカーボネートが体積比で3:7に混合された溶媒にヘキサフルオロリン酸リチウム(LiPF6)が1mol/Lの濃度となるように溶解されたものである。
得られた電池を25℃の恒温室内に設置し、以下に示す充放電試験を行った。まず充電電流を15mA、充電電圧を4.2V、充電時間を3時間とした定電流/定電圧充電を行い、1分間休止の後、同じ電流(15mA)で電池電圧が3.0Vとなるまで定電流で放電させた。同様の条件の充放電を5サイクル繰り返し、第5サイクル目の放電容量を「初期の放電容量」とした。第6サイクル目は、同様な条件で充電を行った状態で60℃の恒温室内に設置し30日間放置した。その後恒温室内を25℃に設定し、電池を5時間放置したのち放電した。その後前述した条件と同様な条件の充放電サイクルを5回繰り返し、第5サイクル目の放電容量を「60℃30日保持後の放電容量」とした。保存特性を表す指標として、「初期の放電容量」に対する「60℃30日間保持後の放電容量」の割合(%)を算出し、「60℃30日間保持後の容量維持率(%)」とした。初期の放電容量、60℃30日間保持後の放電容量、及び、60℃30日間保持後の容量維持率(%)を表2中に示す。
表2に実施例及び比較例における原料炭組成物のH/C値、及びマイクロ強度と、原料炭組成物の平均粒径、黒鉛粒子のLc(112)、表面処理条件、及び実施例及び比較例において得られた黒鉛材料を負極材料として使用したリチウムイオン二次電池の初期の放電容量(mAh)、60℃30日間保持後の放電容量(mAh)、60℃30日間保持後の容量維持率(%)を示す。
比較例17、18とも、原料炭組成物の物性は本発明の範囲内であるため、容量維持率は90%以上となり、極めてサイクル安定性の高い電池を実現できる負極黒鉛材料と見なすことができる。しかし、その結晶子の大きさが小さいため小さな容量の電池しか実現できないため好ましくないと判断できる。
(1)原料炭組成物A-3
硫黄分3.1質量%の常圧蒸留残油を、触媒存在下、水素化分解率が25%以下となるように水素化脱硫し、水素化脱硫油を得た。水素化脱硫条件は、全圧180MPa、水素分圧160MPa、温度380℃である。また、脱硫減圧軽油(硫黄分500質量ppm、15℃における密度0.88g/cm3)を流動接触分解し、流動接触分解残油を得た。この流動接触分解残油を、ジメチルホルムアミドで選択抽出し、芳香族分と飽和分に分離させ、このうちの芳香族分を抽出した。この抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、19質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物A-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、11質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物B-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、4質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物C-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、17質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物D-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、11質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物E-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、6質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物F-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:5で混合したものに、15質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物G-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:5で混合したものに、7質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物H-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、19質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物I-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、16質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物J-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、11質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物K-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、5質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物L-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、3質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物M-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:3で混合したものに、14質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物N-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:3で混合したものに、7質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物O-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油に同体積のn-ヘプタンを加え混合した後、ジメチルホルムアミドで選択抽出し、芳香族分と飽和分に分離させ、このうちの飽和分を選択抽出した。流動接触分解残油と、この抽出飽和分とを質量比1:1で混合したものに、16質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物P-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-3の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:1で混合したものに、11質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物Q-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-3の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:1で混合したものに、6質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物R-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-3の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:2で混合したものに、19質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物S-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-3の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:2で混合したものに、10質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物T-3を得た。
原料炭組成物A-3の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-3の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:2で混合したものに、4質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物U-3を得た。
(1)原料炭組成物のH/C原子比の測定方法
原料炭組成物の全水素の測定は、試料を酸素気流中750℃で完全燃焼させ、燃焼ガスより生成した水分量を電量滴定法(カール・フィッシャー法)で測定した。また原料炭組成物試料を1150℃の酸素気流中で燃焼させ、二酸化炭素(一部一酸化炭素)に変換され過剰の酸素気流に搬送されてCO2+CO赤外線検出器により、全炭素分を測定した。原料炭組成物のH/Cは、全水素分(TH(質量%))を水素の原子量を除した値と、全炭素分(TC(質量%))を炭素の原子量を除した値の比率で算出した。原料炭組成物A-3~U-3のH/C値は表3に示された通りである。
鋼製シリンダー(内径25.4mm、長さ304.8mm)に20メッシュ~30メッシュの試料2gと直径5/16inch(7.9mm)の鋼球12個を入れ、鉛直面を管と直角方向に25rpmで800回転させたのち(すなわち、シリンダーを立てた状態から上下が入れ替わるように、回転軸を水平にして、あたかもプロペラが回転するように回転させる)、48メッシュでふるい分け、試料に対するふるい上の質量の割合を、パーセントで算出した。原料炭組成物A-3~U-3のマイクロ強度は表13に示された通りである。
次に、カルサインコークスの製造方法を説明する。硫黄分3.1質量%の常圧蒸留残油を、触媒存在下、水素化分解率が25%以下となるように水素化脱硫し、水素化脱硫油を得た。水素化脱硫条件は、全圧180MPa、水素分圧160MPa、温度380℃である。また、脱硫減圧軽油(硫黄分500質量ppm、15℃における密度0.88g/cm3)を流動接触分解し、流動接触分解残油を得た。この流動接触分解残油を、ジメチルホルムアミドで選択抽出し、芳香族分と飽和分に分離させ、このうちの芳香族分を抽出した。この抽出芳香族分と水素化脱硫油とを質量比8:1で混合して重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理した後、SUS304製のハンマーミル(ハンマー直径500mm)を用いて粒径2mm以上の粒子が0.1質量%となるように粗粉砕した後、ロータリーキルンを用い1400℃で炭化することによりカルサインコークスを得た。
得られたカルサインコークスを機械式粉砕機(スーパーローターミル/日清エンジニアリング社製)で粉砕し、精密空気分級機(ターボクラシファイヤー/日清エンジニアリング社製)で分級することにより、表3に記載の平均粒径を有するカルサインコークスの粉体を得た。ここで、カルサインコークスの平均粒径は、堀場製作所製のレーザー回折/散乱式粒度分布測定装置LA950を用いて測定した。
得られた原料炭組成物K-3の粉体と、平均粒径2.0μmのカルサインコークスとを、原料炭組成物K-3に対してカルサインコークスが0.5質量%となる比率で予め混合し、ホソカワミクロン社製の「ノビルタ130型」へ、充填体積が500ccになるように投入し、ブレードの回転数を3500rpm、処理温度は130℃程度にコントロールして、処理時間60分の条件で運転して圧縮剪断応力を付与することにより複合粉体を得た。
この複合粉体を、高砂工業社製のローラーハースキルンで、窒素ガス気流下、最高到達温度が1200℃、最高到達温度保持時間が5時間となるように炭化した。得られた炭素材料を坩堝に投入し、電気炉に設置して、80L/分の窒素ガス気流中、最高到達温度2800℃で黒鉛化した。このとき昇温速度は200℃/時間、最高到達温度の保持時間は3時間、降温速度は1000℃までが100℃/時間とし、その後窒素気流を保持させた状態で室温まで放冷させることにより黒鉛材料を得た。得られた黒鉛材料のX線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)は7.9nmであった。
実施例16~31、および比較例19~46では、原料炭組成物A-3~U-3の粉体と、カルサインコークスとを混合し、圧縮剪断応力を付与して複合粉体を得た後、実施例1と同様の条件により炭化及び黒鉛化して黒鉛材料を得た。カルサインコークスの平均粒径や混合量、圧縮剪断応力を付与する条件は、表3に示すとおりである。ここで、実施例16~28、および比較例19~46については、圧縮剪断応力を付与する装置として、ホソカワミクロン社製の「ノビルタ130型」を使用し、実施例29、30では、日本コークス工業社製の「COMPOSI CP-15」、そして、実施例31では、ホソカワミクロン社製の「メカノフュージョンAMS-Lab」を使用した。尚、表3において、「ノビルタ130型」を「N」と、「COMPOSI CP-15」を「C」、「メカノフュージョンAMS-Lab」を「M」と簡略化して表記した。圧縮剪断応力を付与する装置以外の装置は、全て実施例15に記載したものと同じ装置を使用した。
得られた黒鉛材料に、内部標準としてSi標準試料を5質量%混合し、ガラス製試料ホルダー(25mmφ×0.2mmt)に詰め、日本学術振興会117委員会が定めた方法(炭素2006,No.221,P52-60)に基づき、広角X線回折法で測定を行い、炭素材料の結晶子の大きさLc(112)を算出した。X線回折装置は(株)リガク社製ULTIMA IV、X線源はCuKα線(KβフィルターNiを使用)、X線管球への印可電圧及び電流は40kV及び40mAとした。
得られた回折図形についても、日本学術振興会117委員会が定めた方法(炭素2006,No.221,P52-60)に準拠した方法で解析を行った。具体的には、測定データにスムージング処理、バックグラウンド除去の後、吸収補正、偏光補正、Lorentz補正を施し、Si標準試料の(422)回折線のピーク位置、及び値幅を用いて、黒鉛粉末の(112)回折線に対して補正を行い、結晶子サイズを算出した。なお、結晶子サイズは、補正ピークの半値幅から以下のScherrerの式を用いて計算した。測定・解析は3回ずつ実施し、その平均値をLc(112)とした。黒鉛材料のLc(112)が測定された結果は、表3に示された通りである。
(1)電池の作製方法
図1に作製した電池10の断面図を示す。図1には、負極11、負極集電体12、正極13、正極集電体14、セパレータ15、アルミラミネート外装16が示されている。
正極13は、正極材料である平均粒子径6μmのニッケル酸リチウム(戸田工業社製LiNi0.8Co0.15Al0.05O2)と、結着剤のポリフッ化ビニリデン(クレハ社製KF#1320)、およびアセチレンブラック(デンカ社製のデンカブラック)とを質量比で89:6:5に混合し、N-メチル-2-ピロリジノンを加えて混練した後、ペースト状にして、厚さ30μmのアルミニウム箔の片面に塗布し、乾燥及び圧延操作を行い、塗布部のサイズが、幅30mm、長さ50mmとなるように切断されたシート電極である。このとき単位面積当たりの塗布量は、ニッケル酸リチウムの質量として、10mg/cm2となるように設定した。
このシート電極の一部は、シートの長手方向に対して垂直に正極合剤が掻き取られ、その露出したアルミニウム箔が塗布部の正極集電体14(アルミニウム箔)と一体化して繋がっており、正極リード板としての役割を担っている。
負極11は、負極材料である前記実施例15~31及び比較例19~46で得られた黒鉛材料と、結着剤のポリフッ化ビニリデン(クレハ社製KF#9310)、およびアセチレンブラック(デンカ社製のデンカブラック)とを質量比で91:2:8に混合し、N-メチル-2-ピロリジノンを加えて混練した後、ペースト状にして、厚さ18μmの銅箔の片面に塗布し、乾燥及び圧延操作を行い、塗布部のサイズが、幅32mm、長さ52mmとなるように切断されたシート電極である。このとき単位面積当たりの塗布量は、黒鉛材料の質量として、6mg/cm2となるように設定した。
このシート電極の一部はシートの長手方向に対して垂直に負極合剤が掻き取られ、その露出した銅箔が塗布部の負極集電体12(銅箔)と一体化して繋がっており、負極リード板としての役割を担っている。
このようにして乾燥された正極13及び負極11を、正極13の塗布部と負極11の塗布部とが、ポリプロピレン製のマイクロポーラスフィルム(セルガード社製#2400)を介して対向させる状態で積層し、ポリイミドテープで固定した。なお、正極13及び負極11の積層位置関係は、負極11の塗布部に投影される正極塗布部の周縁部が、負極塗布部の周縁部の内側で囲まれるように対向させた。得られた単層電極体を、アルミラミネートフィルムで包埋させ、電解液を注入し、前述の正・負極リード板がはみ出した状態で、ラミネートフィルムを熱融着することにより、密閉型の単層ラミネート電池10を作製した。使用した電解液は、エチレンカーボネートとエチルメチルカーボネートが体積比で3:7に混合された溶媒にヘキサフルオロリン酸リチウム(LiPF6)が1mol/Lの濃度となるように溶解されたものである。
得られた電池を25℃の恒温室内に設置し、以下に示す充放電試験を行った。
先ず1.5mAの電流で、電池電圧が4.2Vとなるまで定電流で充電した。10分間休止の後、同じ電流で電池電圧が3.0Vとなるまで定電流で放電する充放電サイクルを10回繰り返した。この充放電サイクルは、電池の異常を検知するための予備試験であるため、本実施例および比較例における充放電サイクル試験のサイクル数には含まれない。この予備試験により、本実施例および比較例で作製された電池は、全て異常がないことを確認した上で、以下の本試験を実施した。
本試験として、充電電流を15mA、充電電圧を4.2V、充電時間を3時間とした定電流/定電圧充電を行い、1分間休止の後、同じ電流(15mA)で電池電圧が3.0Vとなるまで定電流で放電させた。同様の条件の充放電を5サイクル繰り返し、第5サイクル目の放電容量を「初期放電容量」とした。第6サイクル目は、同様な条件で充電を行った状態で60℃の恒温室内に設置し60日間放置した。その後恒温室内を25℃に設定し、電池を5時間放置したのち放電した。その後前述した条件と同様な条件の充放電サイクルを5回繰り返し、第5サイクル目の放電容量を「60日間保持後の放電容量」とした。
保存特性を表す指標として、「初期放電容量」に対する「60℃保持後の放電容量」の
割合(%)を算出し、「60日間保持後の容量維持率」(%)とした。
表4に実施例および比較例に記載した黒鉛材料を用いて負極材料評価用セルおよび電池を作製し、電池特性を評価した際の「初期放電容量」(mAh)、「60日間保持後の放電容量」(mAh)、および「60日間保持後の容量維持率」(%)を示す。
この理由として、原料炭組成物の粉体に混合するカルサインコークスの量が原料炭組成物に対して0.5質量%未満の場合、得られた黒鉛材料は、導入された結晶化度の低い領域が極わずかである。そのために、このような黒鉛材料を用いたリチウムイオン二次電池では、電解液の黒鉛層間への共挿入を抑制することができず、負極の漏れ電流が増大する結果、正極との漏れ電流との差が大きくなるため、正・負極の容量の作動領域が変化し、寿命特性が低下するものと考えられる。
この理由として、原料炭組成物の粉体と混合するカルサインコークスの量が原料炭組成物に対して10質量%より多い場合、圧縮剪断応力を付与して得られる複合粉体は、原料炭組成物の粒子表面にカルサインコークスが付着した、表面の凹凸が非常に大きな複合粉体となり、この複合粉体を炭化及び黒鉛化して得られた黒鉛材料の比表面積が極端に大きくなる。そのため、このような黒鉛材料を用いたリチウムイオン二次電池では、負極における電解液の分解が増大し、負極の漏れ電流が増大する結果、正極との漏れ電流との差が大きくなるため、正・負極の容量の作動領域が変化し、寿命特性が低下するものと考えられる。
この理由としては、以下のとおりと考えられる。すなわち、カルサインコークスの平均粒径が3.0μmより大きな場合、圧縮剪断応力を付与してもカルサインコークスが原料炭組成物の粒子表面に埋め込まれない。そのために、複合粉体としては、原料炭組成物の粒子表面にカルサインコークスが付着した、表面の凹凸が非常に大きなものが得られてしまい、この複合粉体を炭化及び黒鉛化すると、得られた黒鉛材料の比表面積が極端に大きくなる。そのため、これらの黒鉛材料を用いたリチウムイオン二次電池では、負極における電解液の分解が増大し、負極の漏れ電流が増大する結果、正極との漏れ電流との差が大きくなるため、正・負極の容量の作動領域が変化し、寿命特性が低下するものと考えられる。
(1)原料炭組成物A-4
硫黄分3.1質量%の常圧蒸留残油を、触媒存在下、水素化分解率が25%以下となるように水素化脱硫し、水素化脱硫油を得た。水素化脱硫条件は、全圧180MPa、水素分圧160MPa、温度380℃である。また、脱硫減圧軽油(硫黄分500質量ppm、15℃における密度0.88g/cm3)を流動接触分解し、流動接触分解残油を得た。この流動接触分解残油を、ジメチルホルムアミドで選択抽出し、芳香族分と飽和分に分離させ、このうちの芳香族分を抽出した。この抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、19質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物A-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、11質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物B-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比8:1で混合したものに、4質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物C-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、17質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物D-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、11質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物E-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油の抽出芳香族分と水素化脱硫油とを質量比6:1で混合したものに、6質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物F-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:5で混合したものに、15質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物G-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:5で混合したものに、7質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物H-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、19質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物I-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、16質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物J-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、11質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物K-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、5質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物L-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:4で混合したものに、3質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物M-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:3で混合したものに、14質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物N-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた水素化脱硫油と流動接触分解残油とを質量比1:3で混合したものに、7質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物O-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油に同体積のn-ヘプタンを加え混合した後、ジメチルホルムアミドで選択抽出し、芳香族分と飽和分に分離させ、このうちの飽和分を選択抽出した。流動接触分解残油と、この抽出飽和分とを質量比1:1で混合したものに、16質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物P-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-4の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:1で混合したものに、11質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物Q-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-4の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:1で混合したものに、6質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物R-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-4の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:2で混合したものに、19質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物S-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-4の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:2で混合したものに、10質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物T-4を得た。
原料炭組成物A-4の製造方法と同様にして得られた流動接触分解残油と、原料炭組成物P-4の製造方法と同様にして得られた流動接触分解残油とn-ヘプタンの混合物の抽出飽和分とを質量比1:2で混合したものに、4質量%となるように脱硫脱瀝油を加え(脱硫脱瀝油を含めた混合物全体で100質量%)、重質油組成物を得た。この重質油組成物をディレードコーカー装置に導入して、不活性ガス雰囲気下、550℃でコーキング処理し、原料炭組成物U-4を得た。
(1)原料炭組成物のH/C原子比の測定方法
原料炭組成物の全水素の測定は、試料を酸素気流中750℃で完全燃焼させ、燃焼ガスより生成した水分量を電量滴定法(カール・フィッシャー法)で測定した。また原料炭組成物試料を1150℃の酸素気流中で燃焼させ、二酸化炭素(一部一酸化炭素)に変換され過剰の酸素気流に搬送されてCO2+CO赤外線検出器により、全炭素分を測定した。原料炭組成物のH/Cは、全水素分(TH(質量%))を水素の原子量を除した値と、全炭素分(TC(質量%))を炭素の原子量を除した値の比率で算出した。原料炭組成物A-4~U-4のH/C値は表5に示された通りである。
鋼製シリンダー(内径25.4mm、長さ304.8mm)に20メッシュ~30メッシュの試料2gと直径5/16inch(7.9mm)の鋼球12個を入れ、鉛直面を管と直角方向に25rpmで800回転させたのち(すなわち、シリンダーを立てた状態から上下が入れ替わるように、回転軸を水平にして、あたかもプロペラが回転するように回転させる)、48メッシュでふるい分け、試料に対するふるい上の質量の割合を、パーセントで算出した。原料炭組成物A-4~U-4のマイクロ強度は表5に示された通りである。
得られた原料炭組成物K-4の粉体と、原料炭組成物K-4に対して0.5質量%のアセチレンブラック(デンカ社製のデンカブラック)とを予め混合し、ホソカワミクロン社製の「ノビルタ130型」へ、充填体積が500ccになるように投入し、ブレードの回転数を3500rpm、処理温度は130℃程度にコントロールして、処理時間60分の条件で運転して圧縮剪断応力を付与することにより複合粉体を得た。
この複合粉体を、高砂工業社製のローラーハースキルンで、窒素ガス気流下、最高到達温度が1200℃、最高到達温度保持時間が5時間となるように炭化した。得られた炭素材料を坩堝に投入し、電気炉に設置して、80L/分の窒素ガス気流中、最高到達温度2800℃で黒鉛化した。このとき昇温速度は200℃/時間、最高到達温度の保持時間は3時間、降温速度は1000℃までが100℃/時間とし、その後窒素気流を保持させた状態で室温まで放冷させることにより黒鉛材料を得た。得られた黒鉛材料のX線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)は7.2nmであった。
実施例33~44、および比較例47~70では、原料炭組成物A-4~U-4の粉体と、アセチレンブラック(デンカ社製のデンカブラック)とを混合し、圧縮剪断応力を付与して複合粉体を得た後、実施例32と同様の条件により炭化及び黒鉛化し黒鉛材料を得た。アセチレンブラックの混合量、圧縮剪断応力を付与する条件は、表5に示すとおりである。ここで、実施例33~41、および比較例47~70については、圧縮剪断応力を付与する装置として、ホソカワミクロン社製の「ノビルタ130型」を使用し、実施例42、43では、日本コークス工業社製の「COMPOSI CP-15」、そして、実施例44では、ホソカワミクロン社製の「メカノフュージョンAMS-Lab」を使用した。尚、表5において、「ノビルタ130型」を「N」と、「COMPOSI CP-15」を「C」、「メカノフュージョンAMS-Lab」を「M」と簡略化して表記した。圧縮剪断応力を付与する装置以外の装置は、全て実施例32に記載したものと同じ装置を使用した。
得られた黒鉛材料に、内部標準としてSi標準試料を10質量%混合し、ガラス製試料ホルダー(25mmφ×0.2mmt)に詰め、日本学術振興会117委員会が定めた方法(炭素2006,No.221,P52-60)に基づき、広角X線回折法で測定を行い、炭素材料の結晶子の大きさLc(112)を算出した。X線回折装置は(株)リガク社製ULTIMA IV、X線源はCuKα線(KβフィルターNiを使用)、X線管球への印可電圧及び電流は40kV及び40mAとした。
得られた回折図形についても、日本学術振興会117委員会が定めた方法(炭素2006,No.221,P52-60)に準拠した方法で解析を行った。具体的には、測定データにスムージング処理、バックグラウンド除去の後、吸収補正、偏光補正、Lorentz補正を施し、Si標準試料の(422)回折線のピーク位置、及び値幅を用いて、黒鉛粉末の(112)回折線に対して補正を行い、結晶子サイズを算出した。なお、結晶子サイズは、補正ピークの半値幅から以下のScherrerの式を用いて計算した。測定・解析は3回ずつ実施し、その平均値をLc(112)とした。黒鉛材料のLc(112)が測定された結果は、表5に示された通りである。
(1)電池の作製方法
図1に作製した電池10の断面図を示す。図1には、負極11、負極集電体12、正極13、正極集電体14、セパレータ15、アルミラミネート外装16が示されている。
正極13は、正極材料である平均粒子径6μmのニッケル酸リチウム(戸田工業社製LiNi0.8Co0.15Al0.05O2)と、結着剤のポリフッ化ビニリデン(クレハ社製KF#1320)、およびアセチレンブラック(デンカ社製のデンカブラック)とを質量比で89:6:5に混合し、N-メチル-2-ピロリジノンを加えて混練した後、ペースト状にして、厚さ30μmのアルミニウム箔の片面に塗布し、乾燥及び圧延操作を行い、塗布部のサイズが、幅30mm、長さ50mmとなるように切断されたシート電極である。このとき単位面積当たりの塗布量は、ニッケル酸リチウムの質量として、10mg/cm2となるように設定した。
このシート電極の一部は、シートの長手方向に対して垂直に正極合剤が掻き取られ、その露出したアルミニウム箔が塗布部の正極集電体14(アルミニウム箔)と一体化して繋がっており、正極リード板としての役割を担っている。
負極11は、負極材料である前記実施例32~44及び比較例47~70で得られた黒鉛材料と、結着剤のポリフッ化ビニリデン(クレハ社製KF#9310)、およびアセチレンブラック(デンカ社製のデンカブラック)とを質量比で91:2:8に混合し、N-メチル-2-ピロリジノンを加えて混練した後、ペースト状にして、厚さ18μmの銅箔の片面に塗布し、乾燥及び圧延操作を行い、塗布部のサイズが、幅32mm、長さ52mmとなるように切断されたシート電極である。このとき単位面積当たりの塗布量は、黒鉛材料の質量として、6mg/cm2となるように設定した。
このシート電極の一部はシートの長手方向に対して垂直に負極合剤が掻き取られ、その露出した銅箔が塗布部の負極集電体12(銅箔)と一体化して繋がっており、負極リード板としての役割を担っている。
このようにして乾燥された正極13及び負極11を、正極13の塗布部と負極11の塗布部とが、ポリプロピレン製のマイクロポーラスフィルム(セルガード社製#2400)を介して対向させる状態で積層し、ポリイミドテープで固定した。なお、正極13及び負極11の積層位置関係は、負極11の塗布部に投影される正極塗布部の周縁部が、負極塗布部の周縁部の内側で囲まれるように対向させた。得られた単層電極体を、アルミラミネートフィルムで包埋させ、電解液を注入し、前述の正・負極リード板がはみ出した状態で、ラミネートフィルムを熱融着することにより、密閉型の単層ラミネート電池10を作製した。使用した電解液は、エチレンカーボネートとエチルメチルカーボネートが体積比で3:7に混合された溶媒にヘキサフルオロリン酸リチウム(LiPF6)が1mol/Lの濃度となるように溶解されたものである。
得られた電池を25℃の恒温室内に設置し、以下に示す充放電試験を行った。
先ず1.5mAの電流で、電池電圧が4.2Vとなるまで定電流で充電した。10分間休止の後、同じ電流で電池電圧が3.0Vとなるまで定電流で放電する充放電サイクルを10回繰り返した。この充放電サイクルは、電池の異常を検知するための予備試験であるため、本実施例および比較例における充放電サイクル試験のサイクル数には含まれない。この予備試験により、本実施例および比較例で作製された電池は、全て異常がないことを確認した上で、以下の本試験を実施した。
本試験としては、上記予備試験後の電池を60℃の恒温室内に設置し5時間放置し、充放電試験を開始した。開始後第1サイクル目の放電容量を「初期放電容量」とした。75mAの電流で、電池電圧が4.2Vとなるまで定電流で充電し、1分間休止の後、同じ電流で電池電圧が3.0Vとなるまで定電流で放電する充放電サイクルを設定し、このサイクルを2000回繰り返した。充放電サイクルの容量維持率として、「初期放電容量」に対する「第2000サイクル目の放電容量」の割合(%)を算出し、「2000サイクル後の容量維持率」(%)とした。
表6に実施例および比較例に記載した黒鉛材料を用いて負極材料評価用セルおよび電池を作製し、電池特性を評価した際の「初期放電容量」(mAh)、「第2000サイクル目の放電容量」(mAh)、「2000サイクル後の容量維持率」(%)を示す。
この理由として、原料炭組成物の粉体と混合するアセチレンブラックの量を原料炭組成物に対して0.5質量%未満の場合、得られた黒鉛材料では、導入された結晶化度の低い領域が極わずかである。そのために、このような黒鉛材料を用いたリチウムイオン二次電池では、電解液の黒鉛層間への共挿入を抑制することができず、負極の漏れ電流が増大する結果、正極との漏れ電流との差が大きくなるため、正・負極の容量の作動領域が変化し、寿命特性が低下するものと考えられる。
この理由として、原料炭組成物の粉体と混合するアセチレンブラックの量が原料炭組成物に対して10質量%より多い場合、圧縮剪断応力を付与して得られる複合粉体は、原料炭組成物の粒子表面にアセチレンブラックが付着した、表面の凹凸が非常に大きな複合粉体となり、この複合粉体を炭化及び黒鉛化して得られた黒鉛材料の比表面積が極端に大きくなる。そのため、このような黒鉛材料を用いたリチウムイオン二次電池では、負極における電解液の分解が増大し、負極の漏れ電流が増大する結果、正極との漏れ電流との差が大きくなるため、正・負極の容量の作動領域が変化し、寿命特性が低下するものと考えられる。
11 正極
12 正極集電体
13 負極
14 負極集電体
15 セパレータ
16 アルミラミネート外装
17 外装
30 装置
31 羽根
32 ハウジング
33 間隙
R1 回転方向
R2 回転方向
P 粉体
Claims (8)
- 重質油組成物をディレードコーキングプロセスによってコーキング処理して得られる原料炭組成物を粉砕及び分級する工程と、
上記粉砕及び分級された原料炭組成物に圧縮応力と剪断応力を付与して黒鉛前駆体を得る工程と、
上記黒鉛前駆体を加熱して黒鉛化し、X線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)が4nm以上となる黒鉛材料を得る工程と
を少なくとも含むリチウムイオン二次電池負極用の黒鉛材料の製造方法であって、
上記粉砕及び分級される原料炭組成物が、水素原子Hと炭素原子Cの比率、H/C原子比0.30~0.50を有し、且つマイクロ強度7~17質量%を有するリチウムイオン二次電池負極用の黒鉛材料の製造方法。 - 重質油組成物をディレードコーキングプロセスによってコーキング処理して得られる原料炭組成物を粉砕及び分級して原料炭組成物の粉体を得る工程と、上記粉砕及び分級された原料炭組成物の粉体を加熱して炭化物を得る工程と、上記炭化物を加熱して黒鉛化し、X線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)が4nm以上となる黒鉛粒子を得る工程と、上記黒鉛粒子に圧縮剪断応力を付与し黒鉛材料を得る工程とを少なくとも含むリチウムイオン二次電池負極用の黒鉛材料の製造方法であって、上記粉砕及び分級される原料炭組成物が、水素原子Hと炭素原子Cの比率、H/C原子比0.30~0.50を有し、且つマイクロ強度7~17質量%を有するリチウムイオン二次電池負極用の黒鉛材料の製造方法。
- 重質油組成物をディレードコーキングプロセスによってコーキング処理して得られる原料炭組成物を粉砕及び分級して原料炭組成物の粉体を得る工程と、上記粉砕及び分級された原料炭組成物の粉体を加熱して炭化物を得る工程と、上記炭化物を加熱して黒鉛化し、X線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)が4nm以上となる黒鉛粒子を得る工程と、上記黒鉛粒子に圧縮剪断応力を付与し黒鉛材料を得る工程と、黒鉛材料に加熱処理を施す工程とを少なくとも含むリチウムイオン二次電池負極用の黒鉛材料の製造方法であって、上記粉砕及び分級される原料炭組成物が、水素原子Hと炭素原子Cの比率、H/C原子比0.30~0.50を有し、且つマイクロ強度7~17質量%を有するリチウムイオン二次電池負極用の黒鉛材料の製造方法。
- 重質油組成物をディレードコーキングプロセスによりコーキング処理して得られ、水素原子Hと炭素原子Cとの原子比であるH/Cが0.30~0.50であり、且つマイクロ強度が7質量%~17質量%である原料炭組成物と、当該原料炭組成物に対して0.5質量%~10質量%の平均粒径0.1μm~3.0μmのカルサインコークスとの混合物に、圧縮剪断応力を付与して、当該原料炭組成物の粒子表面に当該カルサインコークスを埋め込んだ複合粉体を得る工程と、
前記複合粉体を加熱して炭化物を得る工程と、
前記炭化物を加熱して黒鉛化し、X線広角回折法によって測定される(112)回折線の結晶子の大きさであるLc(112)が4nm~30nmである黒鉛材料とする工程と、
を少なくとも含むリチウムイオン二次電池負極用の黒鉛材料の製造方法。 - 重質油組成物をディレードコーキングプロセスによりコーキング処理して得られ、水素原子Hと炭素原子Cとの原子比であるH/Cが0.30~0.50であり、且つマイクロ強度が7質量%~17質量%である原料炭組成物と、当該原料炭組成物に対して0.5質量%~10質量%のアセチレンブラックとの混合物に、圧縮剪断応力を付与して、当該原料炭組成物の粒子表面に当該アセチレンブラックを埋め込んだ複合粉体を得る工程と、
前記複合粉体を加熱して炭化物を得る工程と、
前記炭化物を加熱して黒鉛化し、X線広角回折法によって測定される(112)回折線の結晶子の大きさであるLc(112)が4nm~30nmである黒鉛材料とする工程と、
を少なくとも含むリチウムイオン二次電池負極用の黒鉛材料の製造方法。 - 上記重質油組成物が、水素化脱硫油、流動接触分解残油、及び脱硫脱瀝油からなる群から選ばれる2種類以上を含む請求項1~5のいずれかに記載のリチウムイオン二次電池負極用の黒鉛材料の製造方法。
- 請求項1~6のいずれかに記載の製造方法により製造された黒鉛材料を負極材料として含むリチウムイオン二次電池。
- 粉砕及び分級された原料炭組成物に、圧縮応力と剪断応力を付与した黒鉛前駆体を黒鉛化して得られ、X線広角回折法によって測定される(112)回折線の結晶子の大きさLc(112)が4nm以上であるリチウムイオン二次電池負極用の黒鉛材料であって、
上記原料炭組成物が、重質油組成物をディレードコーキングプロセスによってコーキング処理されたものであり、且つ水素原子Hと炭素原子Cの比率、H/C原子比0.30~0.50を有し、且つマイクロ強度7~17質量%を有するリチウムイオン二次電池負極用の黒鉛材料。
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WO2020149252A1 (ja) * | 2019-01-15 | 2020-07-23 | Jxtgエネルギー株式会社 | 人造黒鉛材料、人造黒鉛材料の製造方法、リチウムイオン二次電池用負極およびリチウムイオン二次電池 |
WO2020149250A1 (ja) * | 2019-01-15 | 2020-07-23 | Jxtgエネルギー株式会社 | 人造黒鉛材料、人造黒鉛材料の製造方法、リチウムイオン二次電池用負極およびリチウムイオン二次電池 |
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JP5615673B2 (ja) * | 2010-11-17 | 2014-10-29 | Jx日鉱日石エネルギー株式会社 | リチウムイオン二次電池負極用非晶質系炭素材料の製造方法及びリチウムイオン二次電池 |
US9384904B2 (en) * | 2012-04-06 | 2016-07-05 | Semiconductor Energy Laboratory Co., Ltd. | Negative electrode for power storage device, method for forming the same, and power storage device |
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2011
- 2011-08-10 KR KR1020137006097A patent/KR20130097181A/ko not_active Application Discontinuation
- 2011-08-10 CN CN201180049246.2A patent/CN103155245B/zh not_active Expired - Fee Related
- 2011-08-10 JP JP2012528709A patent/JP5931727B2/ja not_active Expired - Fee Related
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US11936044B2 (en) | 2014-07-07 | 2024-03-19 | Mitsubishi Chemical Corporation | Carbon material, method for producing carbon material, and non-aqueous secondary battery using carbon material |
WO2016113952A1 (ja) * | 2015-01-16 | 2016-07-21 | 三菱化学株式会社 | 炭素材及び炭素材を用いた非水系二次電池 |
WO2020149252A1 (ja) * | 2019-01-15 | 2020-07-23 | Jxtgエネルギー株式会社 | 人造黒鉛材料、人造黒鉛材料の製造方法、リチウムイオン二次電池用負極およびリチウムイオン二次電池 |
WO2020149250A1 (ja) * | 2019-01-15 | 2020-07-23 | Jxtgエネルギー株式会社 | 人造黒鉛材料、人造黒鉛材料の製造方法、リチウムイオン二次電池用負極およびリチウムイオン二次電池 |
JP2020111489A (ja) * | 2019-01-15 | 2020-07-27 | Jxtgエネルギー株式会社 | 人造黒鉛材料、人造黒鉛材料の製造方法、リチウムイオン二次電池用負極およびリチウムイオン二次電池 |
JP2020111491A (ja) * | 2019-01-15 | 2020-07-27 | Jxtgエネルギー株式会社 | 人造黒鉛材料、人造黒鉛材料の製造方法、リチウムイオン二次電池用負極およびリチウムイオン二次電池 |
JP7178271B2 (ja) | 2019-01-15 | 2022-11-25 | Eneos株式会社 | 人造黒鉛材料、人造黒鉛材料の製造方法、リチウムイオン二次電池用負極およびリチウムイオン二次電池 |
JP7178269B2 (ja) | 2019-01-15 | 2022-11-25 | Eneos株式会社 | 人造黒鉛材料、人造黒鉛材料の製造方法、リチウムイオン二次電池用負極およびリチウムイオン二次電池 |
Also Published As
Publication number | Publication date |
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EP2605318A4 (en) | 2016-05-04 |
JPWO2012020816A1 (ja) | 2013-10-28 |
JP5931727B2 (ja) | 2016-06-08 |
CN103155245A (zh) | 2013-06-12 |
CN103155245B (zh) | 2015-09-16 |
EP2605318A1 (en) | 2013-06-19 |
KR20130097181A (ko) | 2013-09-02 |
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