WO2012046802A1 - 格子歪を有するリチウムイオン二次電池負極用黒鉛材料及びリチウムイオン二次電池 - Google Patents
格子歪を有するリチウムイオン二次電池負極用黒鉛材料及びリチウムイオン二次電池 Download PDFInfo
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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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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- H—ELECTRICITY
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- 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
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
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- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
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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
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- 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
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- the present invention relates to a graphite material used for a negative electrode of a lithium ion secondary battery and a manufacturing method thereof. Specifically, the present invention relates to a graphite material used for a negative electrode of a highly durable lithium ion secondary battery in which capacity deterioration is suppressed, a negative electrode using the graphite material, and a lithium ion secondary battery including the negative electrode.
- lithium secondary batteries are lighter and have higher input / output characteristics than nickel cadmium batteries, nickel metal hydride batteries, and lead batteries, which are conventional secondary batteries.
- 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 secondary batteries are generally divided roughly 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 surfaces of carbon atoms are regularly stacked, and lithium ion insertion / extraction reaction proceeds at the edge of the hexagonal network surface 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.
- reliability is a characteristic related to the lifetime, even when the charge / discharge cycle is repeated, stored in a state charged to a predetermined voltage, or charged continuously at a constant voltage (floating). Even when charged), the charge / discharge capacity and internal resistance hardly change (are not easily deteriorated).
- 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.
- One reason for this is that, because the charge / discharge efficiency of the negative electrode is low, it is theoretically impossible to make the charge / discharge efficiency of the positive electrode reaction (Formula 1) and the negative electrode reaction (Formula 2) exactly the same. Can be mentioned.
- the charge / discharge efficiency is the ratio of the electric capacity that can be discharged to the electric capacity consumed for charging. Below, the reaction mechanism in which a lifetime characteristic deteriorates because the charge / discharge efficiency of a negative electrode reaction is lower is explained in full detail.
- 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 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 also 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 reaction mechanism of capacity degradation has also been reported by academic societies and the like (for example, Non-Patent Document 1 and Non-Patent Document 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 capacity lost due to side reactions / competitive reactions occurring in the charged state that is, the self-discharge amount is larger in the negative electrode than in the positive electrode.
- the battery capacity after storage deteriorates when the operating region changes before and after storage (for example, Non-Patent Document 3).
- 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.
- Patent Document 1 it is described that the crystal structure of the particle surface can be disturbed by pulverizing and classifying the raw carbon composition and then performing a mechanochemical treatment. Such disorder of the crystal structure remains as unstructured carbon even after graphitization, which is the final step, and it is described that the initial charge and discharge efficiency of the negative electrode can be improved (paragraph of Patent Document 1). [0024]).
- the disorder of the crystal structure introduced by the mechanochemical treatment is a so-called isotropic state in which crystallites of unstructured carbon 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 do not saturate a valence bond and exist without a bonding partner exist at the crystallite edge.
- the present invention is to improve the capacity deterioration of the lithium secondary battery as described above, and its purpose is to reduce the capacity deterioration due to repeated charge / discharge cycles, storage in a charged state, and floating charge.
- the present invention intends to provide a negative electrode material for lithium secondary batteries for automobiles, industrial use, and power storage infrastructure that requires high reliability.
- the present inventors provide a graphite material that introduces lattice strain into graphite crystallites, reduces the parallelism of the hexagonal network surface, and provides a graphite material with less exposure of crystallite edges on the particle surface, thereby reducing the charge / discharge efficiency of the negative electrode.
- the present invention has been reached. That is, in order to solve the above-mentioned problem, the first aspect according to the present invention is the ratio of hydrogen atoms H to carbon atoms C, H / C atomic ratio, obtained by coking a heavy oil composition by a delayed coking process.
- a second aspect according to the present invention is a lithium ion secondary battery using the graphite material for a negative electrode of the lithium ion secondary battery described in the first aspect as a negative electrode material.
- a lithium ion secondary battery having high life characteristics can be provided by using a graphite material having an appropriate lattice strain for the negative electrode of the lithium ion secondary battery.
- lattice strain refers to a hexagonal network that occurs when the growth of crystallites is limited to the particle shape in the process of carbonization or graphitization, or by mutual inhibition due to growth between adjacent crystallites. It is an area where the parallelism of the surface is low. In such a lattice strain region, since the parallelism of the hexagonal mesh surface is low, it is difficult for the electrolytic solution to be co-inserted between the graphite layers.
- the inventors of the present invention conducted a coking process on a heavy oil composition by a delayed coking process, the ratio of hydrogen atom H to carbon atom C, the H / C atomic ratio is 0.30 to 0.50, and the micro strength is 7 to After pulverizing and classifying 17% by mass of the raw coal composition, a compressive stress and a shear stress are applied, and a surface treatment is performed so that the average circularity is in the range of 0.91 to 0.97. A lattice strain within a predetermined range is generated.
- the present inventors consider the relationship between the step of applying compressive stress and shear stress before graphitization and the generation of lattice strain after graphitization as follows.
- Coking coal of heavy oil composition by delayed coking process ratio of hydrogen atom H to carbon atom C, H / C atom ratio of 0.30 to 0.50, and micro strength of 7 to 17% by mass It is possible to graphitize the circular powder obtained by pulverizing and classifying the composition and then applying a compressive stress and a shearing stress to the surface treatment so that the average circularity is in the range of 0.91 to 0.97.
- the growth of crystallites occurring during graphitization is equivalent to that occurring in a circular powder having a high average circularity, that is, in a particle having a high surface curvature, that is, in a mold. Will grow while being restricted. That is, crystallite growth varies depending on the shape of the particles.
- crystallites can grow widely and freely along the long axis direction of the particles, whereas in the case of particles having a high surface curvature, the shape of the crystallites increases with respect to the growth direction of the crystallites. Because of the spatial restrictions that are derived, crystallites cannot grow freely. Spatial restriction means that the growth of crystallites is hindered by the energy to maintain the particle shape, and the higher the average circularity of the circular powder, that is, the surface curvature, the more spatial the crystal growth is. The limit is great.
- the effect of the particle shape on the growth of crystallites is collectively expressed as a shape effect.
- the crystallites on the particle surface are oriented along the particle shape, the crystallites arranged on the particle surface have an effect of giving a spatial restriction to the growth of the crystallite inside the particle.
- the graphite is in an antagonistic state between the energy that the crystallites want to grow and the energy that tries to maintain the orientation of the crystallites located closer to the surface.
- lattice strain is introduced into the graphite. That is, even within the particle, the shape effect of the particle is imparted sufficiently and sufficiently.
- the average circularity of the circular powder is less than 0.91, the crystallites can grow freely without being hindered by the particle shape, and the shape effect cannot be imparted. It will not be introduced. On the other hand, it was impossible to make the average circularity of the circular powder more than 0.97 by surface treatment that imparts compressive stress and shear stress to the raw coal composition.
- the crystal structure of the graphite material is strongly dependent on the crystal structure (physical properties) of the raw coal composition that is the precursor raw material.
- Physical properties as described in the first aspect of the present application that is, the ratio of hydrogen atom H to carbon atom C, H / C atomic ratio is 0.30 to 0.50, and the micro strength is 7 to 17 mass.
- the characteristics of the graphite material obtained by graphitizing is that it has a region where the parallelism of the hexagonal network surface is locally low while orderly arranging the crystallites, and that the edge portion on the particle surface is less exposed. is there.
- a graphite material having such characteristics is used as a negative electrode material, so the decomposition of the electrolyte due to the co-insertion with the solvent and the decomposition of the electrolyte at the edge of the particle surface are suppressed, so the leakage of the negative electrode The current is extremely small, and high life characteristics can be realized.
- 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. Is the 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.
- 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). 2I ⁇ ⁇ 2e ⁇ ⁇ I 2 ...
- the micro-strength is as follows: 2 g of 20-30 mesh sample and 12 steel balls with a diameter of 5/16 inch (7.9 mm) are placed in a steel cylinder (inner diameter 25.4 mm, length 304.8 mm), and the vertical surface is tubed. Rotate 800 rpm at 25 rpm in the direction perpendicular to the axis (ie, rotate the rotating shaft 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 H / C atomic ratio in the raw coal composition exceeds 0.50, the structure formation of the carbon skeleton is insufficient, and the crystallite growth is extremely small even when graphitized.
- a lithium ion secondary battery using such a graphite material as a negative electrode is not preferable because the capacity becomes small.
- the H / C of the raw coal composition is limited to 0.30 to 0.50.
- a circular powder obtained by applying a compressive stress and a shear stress to a raw material carbon composition having physical properties within this range and subjecting it to a surface treatment so as to have an average circularity of 0.91 to 0.97 is obtained from graphite. In this case, a graphite material having a moderately grown crystallite and an appropriate lattice strain can be obtained.
- the first invention according to the present application also prescribes that 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 after the raw carbon composition is carbonized and graphitized, and plays a similar role.
- 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.
- the micro strength of the raw carbon composition When the micro strength of the raw carbon composition is less than 7% by mass, it means that the bond strength between adjacent crystallites is extremely weak.
- the micro strength of the raw coal composition is limited to 7 to 17% by mass.
- a graphite material having an extremely small lattice strain and an appropriate lattice strain can be obtained.
- compressive stress and shear stress are imparted to the raw coal composition characterized in that the H / C atomic ratio is 0.30 to 0.50 and the micro strength is 7 to 17% by mass, and the average circularity As long as the circular powder obtained by subjecting the surface treatment to a degree of 0.91 to 0.97 is graphitized, the crystallites develop appropriately and have an appropriate lattice strain, In addition, a graphite material with very few edge portions exposed on the particle surface can be obtained.
- the reason why a circular powder having an average circularity in the range of 0.91 to 0.97 is obtained by applying compressive stress and shear stress to the raw coal composition is as follows.
- the degree of circularity is less than 91, the energy for maintaining the particle shape is extremely small compared to the energy for crystallites to grow in the graphitization step, and a state in which both energies cannot be formed is not formed. . Even if graphitization proceeds in such a state, it is not preferable because it is impossible to introduce lattice strain.
- a circular powder having an average circularity higher than 0.97 could not be obtained.
- the graphite material has an Lc (112) calculated from (112) diffraction lines obtained by X-ray wide-angle diffraction of 4 nm to 30 nm, and (004) diffraction lines and (006).
- Lc (112) calculated from (112) diffraction lines obtained by X-ray wide-angle diffraction of 4 nm to 30 nm, and (004) diffraction lines and (006).
- the reason why the lattice strain calculated from the diffraction line is defined to be in the range of 0.001 to 0.085 will be described.
- 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 degree of graphitization is higher and the parallelism of the hexagonal mesh surface is higher, so that the lattice strain tends to be smaller.
- the graphite material obtained by the conventional manufacturing method could not introduce a lattice strain of 0.001 or more when Lc (112) is in the range of 4 nm to 30 nm. Such a graphite material is not preferable because the parallelism of the hexagonal mesh surface is high, and the electrolyte is easily inserted between graphite layers and decomposed.
- the production method of the present invention that applies compressive stress and shear stress to the raw coal composition introduces a lattice strain of 0.001 or more even in a graphite material having Lc (112) in the range of 4 nm to 30 nm. enable.
- a graphite material is a graphite material with moderately developed crystallites and moderate strain, and in a lithium ion secondary battery in which these graphite materials are used as a negative electrode, an electrolyte solution by co-insertion with a solvent is used. Therefore, the leakage current of the negative electrode is extremely small, and high life characteristics can be realized. Further, in the production method of the present invention, it was impossible to introduce a lattice strain exceeding 0.085 into a graphite material having Lc (112) in the range of 4 nm to 30 nm. It was.
- 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 properties of the raw coal composition obtained after coking the heavy oil composition by a delayed coking process are expressed as H / C atoms. What is necessary is just to adjust a compounding ratio suitably according to the property of the raw material oil used so that ratio may be 0.30-0.50 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 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 reason why such a heavy oil composition is preferably used as a raw material of the raw coal composition of the present invention is that the hexagonal mesh plane formed by the heavy oil component that produces a good bulk mesophase is relatively small. This is because, by being limited by the size, in addition to facilitating the improvement of the average circularity, the desulfurized dewaxed oil appropriately bonds the adjacent hexagonal mesh plane laminates. In order to make the average circularity in the range of 0.91 to 0.97, by reducing the crystallite size, the internal stress of the particles against the compressive stress and shear stress can be relaxed, and the particles can be easily deformed. There is a need to.
- 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 material 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 raw material oil 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. 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 0.6.
- 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 0.6.
- 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 as described above. ing.
- 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 mesh plane laminates, but the content in the heavy oil composition is in the range of 5 to 20% by mass. It is particularly preferred. In the case of less than 5% by mass or in the case of exceeding 20% by mass, the micro strength of the raw coal 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 obtained in this manner was pulverized and classified with a mechanical pulverizer (for example, Super Rotor Mill / Nisshin Engineering Co., Ltd.) to obtain a raw coal composition powder.
- a mechanical pulverizer for example, Super Rotor Mill / Nisshin Engineering Co., Ltd.
- powder of the raw coal composition having an average particle size of 5 to 30 ⁇ m was obtained.
- the average particle size is based on measurement by a laser diffraction particle size distribution meter.
- the reason for setting the average particle size to 5 to 30 ⁇ m is that when the particle size is smaller than 5 ⁇ m, sufficient compressive stress and shear stress cannot be applied to the powder of the raw coal composition, so the average circularity is 0.91 to This is because it is impossible to obtain a circular powder having a range of 0.97.
- the reason why the particle size is 30 ⁇ m or less is that the particle size is generally and preferably used as a negative electrode carbon material for a lithium ion secondary battery.
- the treatment for improving the average circularity of the circular powder is preferably carried out to such an extent that the apparent particle diameter does not substantially change. Also includes potato-like surfaces with bumpy surfaces. Specifically, the surface treatment is performed so that the average circularity of the circular powder is preferably 0.91 to 0.97.
- the average circularity can be measured using a circularity measuring device (for example, a flow type particle image analyzer FPIA-3000 manufactured by Sysmex Corporation).
- the average circularity was calculated from the following formula, and the average value of the circularity of the circular powder was calculated.
- Average circularity L 0 / L (In the formula, L o represents the perimeter of a circle having the same projected area as the particle image, and L represents the perimeter of the particle projected image.)
- 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 process of applying the compressive stress and the shear stress vary depending on the apparatus to be used.
- the blade blade 3 and the housing 5 are rotated relatively, preferably in opposite directions (
- the mechano-fusion apparatus 1 having a structure in which the powder P is compressed and compressive stress is applied to the powder P through the gap 7 between the rotation directions R1 and R2).
- the blade rotation speed is 1500 to 5000 rpm and the processing time is 10 to 180 minutes.
- the rotational speed is less than 1500 rpm, or when the treatment time is less than 10 minutes, sufficient compressive stress and shear stress cannot be applied to the powder of the raw coal composition.
- a treatment longer than 180 minutes is not preferable because excessive compression stress and shear stress are applied to the powder of the raw coal composition, and the particle shape is significantly deformed.
- the processing time is 10 to 180 minutes at a peripheral speed of 50 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 stress and shear stress cannot be imparted to the powder of the raw coal composition.
- a treatment longer than 180 minutes is not preferable because excessive compression stress and shear stress are applied to the powder of the raw coal composition, and the particle shape is significantly 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 stress and shear stress cannot be applied to the powder of the raw coal composition.
- the treatment is performed for longer than 300 minutes, an excessive compressive stress and shear stress are applied 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 to 60 m / s.
- the graphite precursor having a higher average circularity is preferably performed at 60 to 250 ° C. as the control temperature during the surface treatment for applying compressive stress and shear stress. Is obtained. In particular, operation at a control temperature of 120 to 200 ° C. during the surface treatment is desirable.
- 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 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 to 1500 ° C. and a maximum temperature holding time of 0 to 10 hours.
- an inert gas atmosphere such as nitrogen, argon or helium with a maximum temperature of 900 to 1500 ° C. and a maximum temperature holding time of 0 to 10 hours.
- 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.
- the crystallite size Lc (112) calculated from the (112) diffraction line obtained by the X-ray wide angle diffraction is 4 nm to 30 nm, and is calculated from the (004) diffraction line and the (006) diffraction line.
- a graphite material having a lattice strain in the range of 0.001 to 0.085 is obtained.
- the crystal size L is determined by using the half width ⁇ of X-ray diffraction.
- ⁇ ⁇ / L ⁇ cos ⁇ (Formula 7) Is required.
- ⁇ is the X-ray wavelength
- ⁇ is the Bragg angle.
- 1 / L ⁇ ⁇ cos ⁇ / ⁇ (Formula 8) Is obtained.
- ⁇ is the sum of ⁇ (0) based on the true size of the crystallite and the width ⁇ due to lattice distortion (Carbon, 1968, Vol. 52, pages 9-12).
- ⁇ ⁇ (0) + ⁇ (Formula 9) It is expressed.
- ⁇ is attributed to the non-uniformity of the lattice spacing d, and the variation width of the lattice spacing is ⁇ d.
- 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 based on the method (carbon 2006, No. 221, P52-60) 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 method for producing a negative electrode for a lithium secondary battery is not particularly limited.
- a method in which (negative electrode mixture) is pressure-molded to a predetermined size is exemplified.
- a carbon 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 a current collector such as a copper foil.
- a method in which a coated and dried (negative electrode mixture) is rolled and cut into a predetermined size.
- the graphite material for a lithium ion battery of the present invention can be mixed with a binder (binder) to form a negative electrode mixture and applied to a metal foil to form a negative electrode.
- a binder binder
- various binders can be used without particular limitation as long as they are conventionally used binders.
- the binder include polyacrylonitrile (PAN), polyethylene terephthalate, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), polyvinyl fluoride, and SBR (styrene-butadiene rubber).
- the binder is usually used in an amount of 1 to 40 parts by weight, preferably 2 to 25 parts by weight, particularly preferably 5 to 15 parts by weight with respect to 100 parts by weight of the graphite material for the lithium ion battery of the present invention.
- the conductive aid 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 negative electrode mixture is mixed with a solvent to form a slurry.
- the solvent is not particularly limited as long as it is a conventionally used solvent, and various solvents can be used.
- a solvent for example, N-methylpyrrolidone (NMP), pyrrolidone, N-methylthiopyrrolidone, dimethylformamide (DMF), dimethylacetamide, hexamethylphosphoamide, isopropanol, toluene, etc. may be used alone or in combination.
- NMP N-methylpyrrolidone
- DMF dimethylformamide
- dimethylacetamide dimethylacetamide
- hexamethylphosphoamide isopropanol, toluene, etc.
- Can do The solvent is generally used in an amount of 15 to 90 parts by mass, preferably 30 to 60 parts by mass with respect to 100 parts by mass in total of the negative electrode mixture.
- the mixture for the negative electrode needs to be appropriately dispersed as long as the graphite material for the lithium ion battery is not destroyed, and is appropriately mixed and dispersed using a planetary mixer, a ball mill, a screw kneader, or the like.
- the negative electrode mixture and the solvent slurry mixture are applied to a metal foil.
- the metal foil material there are no particular limitations on the metal foil material, and various metal materials can be used. For example, copper, aluminum, titanium, stainless steel, nickel, iron, etc. are mentioned.
- the mixture can be applied to one side or both sides of the metal foil and dried to form an electrode.
- the coating method can be carried out by a conventionally known method. Examples thereof include an extrusion coat, a gravure coat, a curtain coat, a reverse roll coat, a dip coat, a doctor coat, a knife coat, a screen printing, a metal mask printing method, and an electrostatic coating method. After coating, it is common to perform a rolling process using a flat plate press, a calender roll, or the like as necessary.
- the electrode can be produced by applying it to a metal foil and then drying it at a temperature of 50 to 250 ° C.
- a metal foil When applying the mixture to both sides of the metal foil, it is particularly preferable to apply one side, dry at 50 to 250 ° C., and then wash the other side to be applied with water or the like. This cleaning operation can greatly improve the adhesiveness.
- the mixture is applied to one side or both sides of the metal foil, and the paste on the dried metal foil is pressed together with the metal foil to form an electrode.
- the shape of the negative electrode used in the present invention can take various shapes such as a plate shape, a film shape, a columnar shape, or a metal foil depending on the intended battery.
- one formed on a metal foil can be applied to various batteries as a current collector integrated negative electrode.
- the lithium ion secondary battery When the graphite material of the present invention is used as a negative electrode, the lithium ion secondary battery has a negative electrode manufactured as described above and a positive electrode for a lithium ion secondary battery, facing 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.
- a metal compound, metal oxide, metal sulfide, or conductive polymer material that can be doped or inserted with lithium ions may be used.
- lithium cobaltate LiCoO 2
- lithium nickelate LiNiO 2
- lithium manganese acid LiMn 2 O 4
- lithium vanadium compounds V 2 O 5 , V 6 O 13 , VO 2 , MnO 2
- 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 having a polyolefin such as polyethylene or polypropylene as a main component can be used.
- a separator when it is set as the structure where the positive electrode and negative electrode of a lithium ion secondary battery to manufacture do not contact directly, 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, and ethylene glycol phenyl ether; N-methylformamide, N, N-dimethylformamide, N Amides such as ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide and 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 vinylene carbonate
- Lithium salts are used as solutes (electrolytes) for 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.
- the polymer solid electrolyte 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.
- Raw coal composition and production method thereof (1) Raw coal composition A 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 charcoal composition A.
- Raw coal composition B The raw material composition of the raw coal composition A is a mixture of extracted aromatics and hydrodesulfurized oil mixed at a mass ratio of 8: 1, and desulfurized desulfurized oil is added so as to be 11% by mass. An 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.
- Raw coal composition C The raw material composition of raw coal composition A is a mixture of extracted aromatics and hydrodesulfurized oil mixed at a mass ratio of 8: 1, and desulfurized desulfurized oil is added so as to be 4% by mass. An 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.
- Raw coal composition D The raw material oil composition of raw material carbon composition A is a mixture of extracted aromatics and hydrodesulfurized oil mixed at a mass ratio of 6: 1, and desulfurized desulfurized oil is added so as to be 17% by mass, and the raw material of coke An oil composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus, and coking was performed at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition D.
- Raw coal composition E The raw material composition of raw carbon composition A is a mixture of extracted aromatics and hydrodesulfurized oil mixed at a mass ratio of 6: 1, and desulfurized desulfurized oil is added so that the mass becomes 11% by mass. An oil composition was obtained. This raw material oil composition was introduced into a delayed coker apparatus and subjected to a coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition E.
- Raw coal composition F The raw material composition of the raw coal composition A is a mixture of extracted aromatics and hydrodesulfurized oil mixed at a mass ratio of 6: 1, and desulfurized desulfurized oil is added so as to be 6% by mass. An oil composition was obtained. This raw material oil composition was introduced into a delayed coker apparatus, and coking was performed at 550 ° C. in an inert gas atmosphere to obtain a raw carbon composition F.
- Raw coal composition G The desulfurized dewaxed oil is mixed with 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, in a mass ratio of 1: 5 so that the desulfurized desulfurized oil becomes 15% by mass.
- a coke feedstock composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus, and coking was performed at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition G.
- Raw coal composition H The desulfurized dewaxed oil is mixed with 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, in a mass ratio of 1: 5 so that the desulfurized desulfurized oil becomes 7% by mass.
- a coke feedstock composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus, and coking was performed at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition H.
- Raw coal composition I A hydrodesulfurized oil and a fluid catalytic cracking residual oil which are raw materials of the raw material oil composition of the raw coal composition A are mixed at a mass ratio of 1: 4, and desulfurized dewaxed oil is added so as to be 19% by mass. In addition, a coke feedstock composition was obtained. This raw material oil composition was introduced into a delayed coker apparatus, and coking was performed at 550 ° C. in an inert gas atmosphere to obtain a raw material charcoal composition I.
- Coking coal composition J The desulfurized dewaxed oil is mixed with the hydrodesulfurized oil and the fluid catalytic cracking residual oil that are the raw materials of the raw oil composition of the raw coal composition A at a mass ratio of 1: 4 so that the desulfurized desulfurized oil becomes 16% by mass.
- a coke feedstock composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus, and coking was performed at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition J.
- Raw coal composition K The desulfurized dewaxed oil is mixed with 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, in a mass ratio of 1: 4 so as to be 11% by mass.
- a coke feedstock 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 K.
- Raw coal composition L A hydrodesulfurized oil and a fluid catalytic cracking residual oil which are raw materials of the raw material oil composition of the raw coal composition A are mixed at a mass ratio of 1: 4, and desulfurized dewaxed oil is added so as to be 5% by mass.
- a coke feedstock composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to a coking process at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition L.
- Raw coal composition M The hydrodesulfurized oil used as the raw material of the raw material oil composition of the raw coal composition A and the fluid catalytic cracking residual oil are mixed at a mass ratio of 1: 4, and the desulfurized dewaxed oil is added to 3% by mass. In addition, a coke feedstock composition was obtained. This raw material oil composition was introduced into a delayed coker apparatus, and coking was performed at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition M.
- Raw coal composition N The desulfurized dewaxed oil is mixed with 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, in a mass ratio of 1: 3 so that the desulfurized desulfurized oil becomes 14% by mass.
- a coke feedstock 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 N.
- Raw coal composition O The desulfurized dewaxed oil is mixed with 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, in a mass ratio of 1: 3 so that the desulfurized desulfurized oil becomes 7% by mass.
- a coke feedstock composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus, and coking was performed at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition O.
- Raw coal composition P 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 raw coal composition A, it was selectively extracted with dimethylformamide and separated into aromatic and saturated components. Of these, the saturated content 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 coking was performed at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition P.
- Raw coal composition Q A desulfurized dewaxed oil is added to a mixture of the fluid catalytic cracking residual oil, which is a raw material of the raw material oil composition of the raw coal composition P, and the extraction saturated component in a mass ratio of 1: 1 so that the mass becomes 11% by mass.
- a coke feedstock 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 Q.
- Raw coal composition R Desulfurized and desulfurized oil is added to a mixture obtained by mixing the fluid catalytic cracking residual oil that is the raw material of the raw material oil composition of the raw coal composition P and the extraction saturated component at a mass ratio of 1: 1 so as to be 6% by mass.
- a coke feedstock 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 R.
- Coking coal composition S Desulfurized and desulfurized oil is added to a mixture obtained by mixing the fluid catalytic cracking residual oil that is the raw material of the raw material oil composition of the raw coal composition P and the extraction saturated component in a mass ratio of 1: 2, so that the mass becomes 19% by mass.
- a coke feedstock composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to a coking process at 550 ° C. in an inert gas atmosphere to obtain a raw material charcoal composition S.
- Raw coal composition T Desulfurized and desulfurized oil is added to a mixture of the fluid catalytic cracking residual oil that is the raw material of the raw material oil composition of the raw coal composition P and the extraction saturated component in a mass ratio of 1: 2, so that the mass becomes 10% by mass.
- a coke feedstock 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 T.
- Raw coal composition U Desulfurized and desulfurized oil is added to a mixture obtained by mixing fluid catalytic cracking residual oil, which is a raw material of the raw material oil composition of the raw coal composition P, and extraction saturated component in a mass ratio of 1: 2, so that the mass becomes 4% by mass.
- a coke feedstock composition was obtained.
- This raw material oil composition was introduced into a delayed coker apparatus and subjected to a coking treatment at 550 ° C. in an inert gas atmosphere to obtain a raw material carbon composition U.
- the obtained raw coal composition A was pulverized with a mechanical pulverizer (Super Rotor Mill / Nisshin Engineering) and classified by a precision air classifier (Turbo Classifier / Nisshin Engineering).
- a raw material carbon composition powder having a particle size of 10 ⁇ m was obtained.
- the powder was subjected to compressive stress and shear stress using Nobilta 130 manufactured by Hosokawa Micron. At this time, the rotation speed was 3500 rpm, the treatment time was 60 minutes, and the treatment temperature was 130 ° C. After the circularity of the carbon material after treatment was measured using a flow type particle image analyzer FPIA-3000 manufactured by Sysmex Corporation, the maximum temperature reached 1200 ° C.
- Table 1 lists Examples 1 to 14 and Comparative Examples 1 to 22.
- Table 1 shows the raw coal composition, H / C of the raw coal composition, micro strength, average particle size after pulverization / classification, conditions for applying compressive stress and shear stress to the raw coal composition (equipment, rotational speed). Or peripheral speed, treatment time), average circularity of circular powder after applying compressive stress and shear stress, and crystallite size Lc (112) and lattice strain obtained by X-ray wide angle diffraction method of graphite powder The value of ⁇ is shown.
- Example 2 to 14 and Comparative Examples 1 to 17 and 19 to 22 the raw coal composition described in Table 1 was pulverized and classified to the average particle size described in the same table, and described in the same table.
- Surface treatment was performed with the apparatus and conditions (apparatus, rotation speed or peripheral speed, treatment time) to obtain a circular powder having an average circularity described in the same table, and then carbonized / graphite as in Example 1.
- Graphite material was obtained.
- the same apparatus as that described in Example 1 was used for all apparatuses other than the surface treatment apparatus.
- Comparative Example 18 the raw coal composition described in Table 1 was pulverized and classified to the average particle size described in the same table, and carbonized and graphitized in the same manner as in Example 1 without performing surface treatment. A graphite material was obtained. All the devices used were the same as those described in Example 1.
- FIG. 2 shows a cross-sectional view of the battery 20 manufactured.
- the positive electrode 21 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 size of 6 ⁇ m and a polyvinylidene fluoride binder (KF # manufactured by Kureha Co., Ltd.). 1320), acetylene black (Denka Black manufactured by Denka) was mixed at a weight ratio of 89: 6: 5, kneaded after adding N-methyl-2-pyrrolidinone, and pasted into aluminum having a thickness of 30 ⁇ m.
- the sheet electrode is applied to one side of the foil, dried and rolled, and cut so that the size of the application 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. 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 integrally connected to the current collector (aluminum foil) of the coating part, and the positive electrode lead It plays a role as a board.
- the negative electrode 23 is composed of graphite powder obtained in the following Examples or Comparative Examples, which are negative electrode materials, polyvinylidene fluoride as a binder (KF # 9310, manufactured by Kureha), and acetylene black (Denka black, manufactured by Denka). After mixing at a weight ratio of 90: 2: 8, adding N-methyl-2-pyrrolidinone and kneading, paste it, apply it to one side of a 18 ⁇ m thick copper foil, perform drying and rolling operations, The sheet electrode is cut so that the size of the application part is 32 mm in width and 52 mm in length. At this time, the coating amount per unit area was set to 6 mg / cm 2 as the mass of the graphite powder.
- the battery 20 was fabricated by sufficiently drying the positive electrode 21, the negative electrode 23, the separator 25, the outer package 27, and other parts, 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 21 and the negative electrode 23 are under reduced pressure at 150 ° C. for 12 hours or more, and the separator 25 and other members are under reduced pressure at 70 ° C. for 12 hours or more.
- the positive electrode 21 and the negative electrode 23 thus dried were laminated with the positive electrode application portion and the negative electrode application portion facing each other with a microporous film made of polypropylene (Celgard # 2400) facing each other, and polyimide Fixed with tape.
- 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 obtained battery was placed in a constant temperature room at 25 ° C., and the following charge / discharge test was performed. First, it was charged with a constant current at a current of 1.5 mA until the battery voltage reached 4.2V. After a 10-minute pause, a charge / discharge cycle of discharging at a constant current until the battery voltage reached 3.0 V at the same current was repeated 10 times. Since this charge / discharge cycle is for detecting an abnormality of the battery, it was not included in the number of cycles of the charge / discharge cycle test. It was confirmed that all the batteries manufactured in this example were not abnormal. The battery was placed in a constant temperature room at 60 ° C. and left for 5 hours to start a charge / discharge test.
- the first cycle after the start is set as the initial cycle. Charging at a constant current at a current of 75 mA until the battery voltage reaches 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 resting for 1 minute, This cycle was repeated 1000 times. As a capacity retention rate of the charge / discharge cycle, a ratio (%) of the discharge capacity at the 1000th cycle to the initial discharge capacity was calculated.
- a battery was prepared using the graphite materials described in the examples and comparative examples in Table 1, and the discharge capacity (mAh) of the first cycle, the discharge capacity (mAh) of the 1000th cycle when the battery characteristics were evaluated, The capacity retention rate (%) after 1000 cycles is shown.
- 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% by mass (G, H,
- a graphite material obtained by graphitizing a circular powder obtained by subjecting K, N, O) as a raw material to a surface treatment so as to have an average circularity of 0.91 to 0.97 is the scope of the present invention.
- the crystallite size Lc (112) calculated from the (112) diffraction line obtained by X-ray wide-angle diffraction satisfied 4 nm to 30 nm, and the lattice strain ⁇ satisfied 0.001 to 0.085. It has been found that the capacity maintenance rate of the charge / discharge cycle of the battery using these graphite materials as the negative electrode is 91% or more, and a lithium ion secondary battery having excellent life characteristics can be realized.
- Example 14 As the surface treatment apparatus, Nobilta was used in Examples 1 to 11, COMPOSI was used in Examples 12 and 13, and Mechanofusion was used in Example 14. As a result, in any surface treatment apparatus, the Lc (112) and lattice strain values of the obtained graphite material satisfy the claims, and the charge / discharge cycle of the battery using these as negative electrodes It was found that the capacity retention rate showed a high value. By using these surface treatment apparatuses, it is possible to introduce an appropriate lattice strain into the graphite material.
- Lc (112) was less than 4 nm. It can be seen that the smaller the crystallite size Lc (112) of these graphite materials, the smaller the discharge capacity. In order to ensure a capacity of 16 mAh as a battery of this size, it can be understood that the crystallite size Lc (112) of the graphite material used for the negative electrode must be at least 4 nm. In Comparative Examples 1 to 7, the capacity retention rate after 1000 cycles is 91% or more, and can be regarded as a negative electrode graphite material capable of realizing a battery with extremely high cycle stability. However, since the crystallite size is small, only a battery with a small capacity can be realized.
- Lc (112) was 4 nm or more, but the lattice strain ⁇ was less than 0.001.
- the discharge capacity is 17 mAh or more, and can be regarded as a negative electrode material capable of realizing an extremely high discharge capacity.
- the lattice strain ⁇ is small, the capacity retention rate of the charge / discharge cycle is lowered, so it can be determined that it is not preferable.
- the obtained graphite material is within the scope of the present invention, that is, Lc (112) is 4 nm to 30 nm and the lattice strain ⁇ is 0.001 to 0.085, and has a high capacity of 16 mAh or more. It can be said that this is an indispensable condition for achieving a high capacity retention rate of 91% or more.
- a raw carbon composition having a hydrogen atom H to carbon atom C ratio, an H / C atomic ratio of 0.30 to 0.50, and a micro strength of 7 to 17% by mass is used. This can be said to be an indispensable condition for achieving a high capacity maintenance rate of 91% or more.
- Comparative Example 18 was carbonized and graphitized without subjecting the raw carbon composition within the scope of the present invention to surface treatment. Since this graphite material was not subjected to surface treatment, graphitization was likely to proceed, and Lc (112) was as large as 25 nm. However, it was found that the lattice strain ⁇ was a very small value of 0.0002 and no lattice strain was introduced. It was found that the charge / discharge cycle of a battery using this graphite material as a negative electrode was a very low value of 63.3%.
- the raw material charcoal composition within the scope of the present invention was pulverized and classified to an average particle diameter of 4 ⁇ m, and the raw material charcoal composition powder was treated for 90 minutes at a rotational speed of 4000 rpm using a surface treatment apparatus Nobilta.
- the obtained circular powder was graphitized.
- the lattice strain ⁇ was 0.0005, which was smaller than the claims of the present invention.
- the capacity retention rate of the charge / discharge cycle of the lithium ion secondary battery using this graphite material as the negative electrode is 67.2%, which is not preferable because it is a low value.
- Comparative Example 20 the raw coal composition powder obtained by pulverizing and classifying the raw coal composition within the scope of the present invention to an average particle size of 15 ⁇ m was treated with a surface treatment apparatus Nobilta for 120 minutes at a rotational speed of 1450 rpm.
- the obtained circular powder was graphitized.
- the surface treatment could not be sufficiently performed, and thus the lattice strain ⁇ was 0.0007, which was smaller than the claims of the present invention.
- the capacity retention rate of the charge / discharge cycle of the lithium ion secondary battery using this graphite material as the negative electrode is 69.4%, which is not preferable because it is a low value.
- a raw coal composition powder obtained by pulverizing and classifying a raw coal composition within the scope of the present invention to an average particle size of 15 ⁇ m was treated for 90 minutes at a peripheral speed of 45 m / s using a surface treatment apparatus COMPOSI.
- the circular powder obtained was graphitized.
- the lattice strain ⁇ was 0.0009, which was smaller than the claims of the present invention.
- the capacity maintenance rate of the charge / discharge cycle of the lithium ion secondary battery using this graphite material as the negative electrode is 81.9%, which is not preferable because it is a low value.
- Comparative Example 22 a raw material coal composition powder obtained by pulverizing and classifying the raw material coal composition within the scope of the present invention to an average particle size of 15 ⁇ m was treated with a surface treatment apparatus Nobilta for 9 minutes at a rotational speed of 5000 rpm.
- the obtained circular powder was graphitized.
- the surface treatment could not be performed sufficiently, so that the lattice strain ⁇ was 0.0009, which was smaller than the claims of the present invention.
- the capacity retention rate of the charge / discharge cycle of the lithium ion secondary battery using this graphite material as the negative electrode is 79.9%, which is not preferable because it is a low value.
- a raw carbon composition having a hydrogen atom H to carbon atom C ratio, an H / C atom ratio of 0.30 to 0.50, and a micro strength of 7 to 17% by mass, which has been coked by a delayed coking process. Crushing and classification to obtain a raw material coal composition powder, and applying a compressive stress and a shear stress to the raw material carbon composition powder so that the average circularity is 0.91 to 0.97.
- a graphite material obtained by a manufacturing method comprising a step of obtaining a circular powder, a step of heating the circular powder to obtain a carbide, and a step of graphitizing the carbide,
- the crystallite size Lc (112) calculated from the (112) diffraction line obtained by diffraction is 4 nm to 30 nm, and the lattice strain calculated from the (004) diffraction line and the (006) diffraction line is 0.001.
- Lithium ion secondary battery using a negative electrode graphite material for negative electrode of lithium ion secondary battery as a negative electrode can secure a capacity of 16 mAh or more and has a capacity retention rate of 91% after 1000 cycles at 60 ° C. charge / discharge The above has been achieved.
- the lithium secondary battery using the graphite material according to the invention of the present application can ensure a high degree of reliability as compared with a lithium secondary battery using a conventional graphite material. Specifically, it can be used for industrial purposes such as for hybrid vehicles, plug-in hybrid vehicles, electric vehicles, and power storage for grid infrastructure.
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Abstract
Description
一般的に、結晶子エッジには、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、粒子表面に未組織炭素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、導入された未組織炭素の結晶子が等方的な状態であるためにエッジ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。
すなわち、前述した課題を解決するために、本発明に係る第一の態様は、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た、水素原子Hと炭素原子Cの比率、H/C原子比が0.30~0.50、且つマイクロ強度が7~17質量%の原料炭組成物を粉砕・分級し、原料炭組成物の粉体を得る工程と、当該原料炭組成物の粉体を平均円形度が0.91~0.97となるように圧縮応力と剪断応力を付与し、円形粉体を得る工程と、当該円形粉体を加熱して炭化物を得る工程と、当該炭化物を黒鉛化する工程と、を含んだ製造法により得られた黒鉛材料であって、X線広角回折によって得られた(112)回折線から算出される結晶子の大きさLc(112)が4nm~30nm、且つ(004)回折線および(006)回折線から算出される格子歪εが0.001~0.085の範囲である、格子歪みを有するリチウムイオン二次電池負極用黒鉛材料である。
本発明者らは、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た、水素原子Hと炭素原子Cの比率、H/C原子比が0.30~0.50、且つマイクロ強度が7~17質量%の原料炭組成物を粉砕・分級した後、圧縮応力と剪断応力を付与し平均円形度が0.91~0.97の範囲となるように表面処理を施すことによって、黒鉛化後に所定の範囲の格子歪を発生させている。黒鉛化前に圧縮応力と剪断応力を付与する工程と、黒鉛化後の格子歪の発生との関係を、本発明者らは次のように考えている。
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た、水素原子Hと炭素原子Cの比率、H/C原子比が0.30~0.50、且つマイクロ強度が7~17質量%の原料炭組成物を粉砕・分級した後、圧縮応力と剪断応力を付与し平均円形度が0.91~0.97の範囲となるように表面処理を施して得られる円形粉体を黒鉛化することは、黒鉛化途中に起こる結晶子の成長が、平均円形度の高い円形粉体中、すなわち表面の曲率が高い粒子中、言わば鋳型の中で起こることに等しく、結晶子は粒子形状によりその成長方向を制限されながら成長することになる。すなわち、結晶子の成長は、粒子の形状に依存して異なる。
たとえば、扁平状の粒子では、粒子の長軸方向に沿って、結晶子が広く自由に成長できるのに対し、表面の曲率が高い粒子においては、結晶子の成長方向に対して、粒子形状に由来する空間的な制限が付与されるために、結晶子が自由に成長することができない。空間的な制限とは、結晶子の成長が、粒子形状を維持しようとするエネルギーにより阻害されることであり、円形粉体の平均円形度、すなわち表面の曲率が高いほど結晶成長に対する空間的な制限は大きい。ここでは、粒子形状が結晶子の成長に与える効果を総括して形状効果と表現する。
平均円形度が0.91~0.97の範囲である円形粉体の表面部分では、結晶子が成長しようとするエネルギーと、粒子形状を維持しようとするエネルギーとの拮抗状態の中で黒鉛化が進行する。このことは、粒子形状を維持しようとするエネルギーにより結晶子の成長が部分的に阻害されることでもあり、その阻害された部分には六角網面の平行度の低い領域、すなわち格子歪が導入される。このような状態下では、結晶子中に局所的に格子歪が蓄えられながら黒鉛化が進行していく。
一般的に、粒子表面の結晶子の方が、粒子内部の結晶子よりも速く黒鉛化が進行する。粒子表面の結晶子は粒子形状に沿って配向しているため、これら粒子表面に配列した結晶子は、より粒子内部の結晶子の成長に対して空間的な制限を付与する効果を有する。換言すれば、粒子内部の結晶子に対しても、結晶子が成長しようとするエネルギーと、より表面に近い位置に存在する結晶子の配向を維持しようとするエネルギーとの拮抗状態の中で黒鉛化が進行することにより、黒鉛に格子歪が導入される。すなわち、粒子内部であっても粒子の形状効果は波及的且つ十分に付与されるものである。
このような特徴を有する黒鉛材料が負極材料として使用されたリチウムイオン二次電池では、溶媒共挿入による電解液の分解および粒子表面のエッジ部における電解液の分解が抑制されるため、負極の漏れ電流が極めて小さく、高い寿命特性を実現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。
H2O+I2+SO2+CH3OH+3RN
→ 2RN・HI+RN・HSO4CH3 ・・(式4)
この反応に必要なヨウ素は、下式(5)の通りヨウ化物イオンを電気化学的に反応(2電子反応)させることにより得られる。
2I- - 2e- → I2 ・・(式5)
水1モルとヨウ素1モルとが反応することから、水1mgを滴定するのに必要な電気量が、下式(6)の通りファラデーの法則により求められる。
(2×96478)/(18.0153×103)=10.71クーロン ・・(式6)
ここで、定数96478はファラデー常数、18.0153は水の分子量である。
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。
原料炭組成物中のH/C原子比が0.50を超える場合、その炭素骨格の構造形成が不十分であり、黒鉛化した場合においても、結晶子の成長は極端に小さい。このような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容量が小さくなるため好ましくない。
以上の通り原料炭組成物のH/Cは0.30~0.50に限定される。この範囲内の物性を有する原料炭組成物に圧縮応力と剪断応力を付与し、平均円形度0.91~0.97の範囲となるように表面処理を施して得られた円形粉体を黒鉛化した場合、結晶子が適度に発達し、且つ適度な格子歪を有する黒鉛材料が得られる。このような特徴を有する黒鉛材料が負極として使用されたリチウムイオン二次電池では、溶媒共挿入による電解液の分解および粒子表面のエッジ部における電解液の分解が抑制されるため、負極の漏れ電流が極めて小さく、高い寿命特性を実現することが可能となる。
原料炭組成物のマイクロ強度が17質量%を超える場合には、隣接する結晶子間の結合強さが極端に大きくなる。その理由は、隣接した結晶子間に存在する未組織炭素が、その隣接する結晶子と強固な三次元的化学結合を構築するからである。このような原料炭組成物に圧縮応力と剪断応力を付与し、平均円形度を0.91~0.97の範囲になるように表面処理して得られた円形粉体を黒鉛化した場合に、未組織炭素が、結晶子の選択的な配向を妨害するエネルギーが大きいために、粒子の形状効果を十分に付与することができない。そのため、粒子表面の曲率を低減させながら黒鉛化が進行する。このような状態で黒鉛化が進行した場合、適度な格子歪を有した黒鉛材料を得ることは不可能であるため好ましくない。
一方、原料炭組成物に、圧縮応力と剪断応力を付与するという本発明の製造法において、平均円形度が0.97より高い円形粉体を得ることはできなかった。理由は、平均円形度が0.97より高い円形粉体を得るために、原料炭組成物の粉体に非常に強い圧縮応力と剪断応力を付与した場合、粒子表面に大きな亀裂が導入され粒子が崩壊するためである。粒子が崩壊した場合、表面処理後に得られる粉体は、粒径が極端に小さく、大量の微粉を含んだ状態となる。このような粉体を炭化・黒鉛化した場合、比表面積が極端に大きな黒鉛材料が得られる。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、黒鉛と電解液の接触面積が極端に大きく、電解液の分解が増大し、負極の漏れ電流が増大するため好ましくない。
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。
また、本発明の製造法では、Lc(112)が4nm~30nmの範囲である黒鉛材料に対して、0.085を超える格子歪を導入することが不可能であったため、上限を0.085とした。
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、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。
fa=(A1+A2)/(A1+A2+A3)
により求められる。13C-NMR法が、ピッチ類の化学構造パラメータの最も基本的な量であるfaを定量的に求められる最良の方法であることは、文献(「ピッチのキャラクタリゼーション II. 化学構造」横野、真田、(炭素、1981(No.105)、p73~81)に示されている。
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。
平均円形度=L0/L
(式中、Loは、粒子像と同じ投影面積を持つ円の周囲長を表し、Lは粒子投影像の周囲長を表す。)
一般に、結晶サイズLは、X線回折の半価幅βを用いて、
β=λ/L・cosθ (式7)
で求められる。ここで、λはX線の波長、θはブラッグ角である。
式7を変形することにより、
1/L=β・cosθ/λ (式8)
が得られる。
ここで、βは結晶子の真の大きさに基づくβ(0)と格子の歪による幅Δθの和であることが論じられており(炭素、1968年 第52巻第9~12頁)、
β=β(0)+Δθ (式9)
と表される。
β(0)は、結晶子の真の大きさL(0)を用いて、
β(0)=λ/L(0)・cosθ (式10)
と表される。
Δθは、格子面間隔dの不均一性に起因するとされ、格子面間隔の変動幅をΔdとして、
Δθ=(Δd/d)・tanθ=ε・tanθ (式11)
(式中、ε=Δd/d)
で表わされる。このときのεを格子歪という。
式9、式10、式11から、βは以下のように表される。
β=λ/L(0)・cosθ+ε・tanθ (式12)
式12を式8のβに代入することにより、以下の式が得られる。
1/L=1/L(0)+n(ε/2d) (n=1,2,3・・) (式13)
従って、1/L対回折次数nのプロットを取ると直線となり、その直線の傾きが格子歪εに値する。このようにして格子歪を求める方法は、文献(炭素、No.52、P9-12)に示されている。
具体的には、X線解析において、Lc(004)、Lc(006)を求め、それぞれの逆数(1/Lc)を算出する。その値を回折次数に対してプロットした直線の勾配から格子歪εを算出した。回折次数は、(004)ではn=2、(006)ではn=3である。
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、X線広角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(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。
L=K×λ/(β0×cosθB) ・・Scherrerの式
ここで、L:結晶サイズ(nm)
K:形状因子定数(=1.0)
λ:X線の波長(=0.15406nm)
θB:ブラッグ角
β0:半値幅(補正値)
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。
バインダーとしては、従来より使用されているバインダーであれば、特に制限なく各種のバインダーを使用することができる。例えば、バインダーとして、ポリアクリロニトリル(PAN)、ポリエチレンテレフタレート、ポリフッ化ビニリデン(PVDF)、ポリテトラフルオロエチレン(PTFE)、ポリフッ化ビニル、SBR(スチレンーブタジエンラバー)等が挙げられる。
バインダーは、本発明のリチウムイオン電池用の黒鉛材料100質量部に対して、通常、1~40質量部、好ましくは2~25質量部、特に好ましくは5~15質量部の量で使用される。
前記導電助剤としては、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。
溶剤としては、従来より使用されている溶剤であれば特に制限なく、各種の溶剤を使用することができる。このような溶剤としては、例えば、N-メチルピロリドン(NMP)、ピロリドン、N-メチルチオピロリドン、ジメチルホルムアミド(DMF)、ジメチルアセトアミド、ヘキサメチルホスホアミド、イソプロパノール、トルエン等を単独あるいは混合して用いることができる。
溶剤は、負極用混合物の合計100質量部に対して、一般的には、15~90質量部、好ましくは30~60質量部となるように使用される。
塗布の方法は、従来公知の方法によって実施することができる。例えば、エクストルージョンコート、グラビアコート、カーテンコート、リバースロールコート、ディップコート、ドクターコート、ナイフコート、スクリーン印刷、メタルマスク印刷法、静電塗装法等が挙げられる。塗布後は、必要に応じて平板プレス、カレンダーロール等による圧延処理を行うのが一般的である。
電極は、金属箔に塗布のあと、50~250℃の温度で乾燥することにより製造することができる。金属箔の両面に混合物を塗布する場合、片面を塗布し、50~250℃で乾燥した後、塗布しようとする他方の面を水等によって洗浄することが特に好ましい。この洗浄操作によって、接着性を大幅に改善することができる。
金属箔の片面又は両面に混合物が塗布され、乾燥された金属箔上のペーストを金属箔とともにプレスして電極とする。
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挿入可能な金属化合物、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、例えば、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はCo、Ni、Mn又はFeを表す)、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。
セパレータとしては、例えば、ポリエチレン、ポリプロピレン等のポリオレフィンを主成分とした不織布、クロス、微多孔性フィルム又はそれらを組み合わせたものを使用することができる。なお、製造するリチウムイオン二次電池の正極と負極が直接接触しない構造にした場合は、セパレータを使用する必要はない。
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-ピロリドン;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。
高分子固体電解質としては、ポリエチレンオキサイド誘導体及び該誘導体を含む重合体、ポリプロピレンオキサイド誘導体及び該誘導体を含む重合体、リン酸エステル重合体、ポリカーボネート誘導体及び該誘導体を含む重合体等が挙げられる。
1.原料炭組成物とその製造方法
(1)原料炭組成物A
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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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Iを得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物A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を得た。
原料炭組成物P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を得た。
原料炭組成物P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を得た。
原料炭組成物P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を得た。
原料炭組成物P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を得た。
原料炭組成物P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を得た。
比較例18では、表1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、表面処理を施さずに、実施例1と同様にして炭化・黒鉛化し黒鉛材料を得た。使用した装置は全て実施例1に記載したものと同じ装置を使用した。
(1)電池の作製方法
図2に作製した電池20の断面図を示す。正極21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)を重量比で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23は、負極材料である下記実施例又は比較例で得られた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)と、アセチレンブラック(デンカ社製のデンカブラック)とを重量比で90:2:8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。
電池20の作製は、正極21、負極23、セパレータ25、外装27及びその他部品を十分に乾燥させ、露点-100℃のアルゴンガスが満たされたグローブボックス内に導入して組み立てた。乾燥条件は、正極21及び負極23が減圧状態の下150℃で12時間以上、セパレータ25及びその他部材が減圧状態の下70℃で12時間以上である。
このようにして乾燥された正極21及び負極23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、電池の異常を検知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。
この電池を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サイクルを初期サイクルとする。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1000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1000サイクル目の放電容量の割合(%)を算出した。
3 ブレードの羽根
5 ハウジング
7 ブレードとハウジングとの間隙
20 電池
21 対極(正極)
22 正極集電体
23 作用極(負極)
24 負極集電体
25 セパレータ
27 外装
P 粉体
R1、R2 回転方向
Claims (2)
- 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た、水素原子Hと炭素原子Cの比率、H/C原子比が0.30~0.50、且つマイクロ強度が7~17質量%の原料炭組成物を粉砕・分級し、原料炭組成物の粉体を得る工程と、
当該原料炭組成物の粉体を平均円形度が0.91~0.97となるように圧縮応力と剪断応力を付与し、円形粉体を得る工程と、
当該円形粉体を加熱して炭化物を得る工程と、
当該炭化物を黒鉛化する工程とを含んだ製造法により得られた黒鉛材料であって、
X線広角回折によって得られた(112)回折線から算出される結晶子の大きさLc(112)が4nm~30nm、且つ(004)回折線および(006)回折線から算出される格子歪が0.001~0.085の範囲である、格子歪みを有するリチウムイオン二次電池負極用黒鉛材料。 - 請求項1に記載のリチウムイオン二次電池負極用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。
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KR1020137011252A KR20140017496A (ko) | 2010-10-08 | 2011-10-06 | 격자왜곡을 가지는 리튬이온 이차전지 음극용 흑연 재료 및 리튬이온 이차전지 |
EP11830734.7A EP2626933A4 (en) | 2010-10-08 | 2011-10-06 | NETWORK DEFORMATION GRAPHITE MATERIAL USEFUL IN NEGATIVE LITHIUM-ION RECHARGEABLE BATTERY ELECTRODES, AND LITHIUM-ION RECHARGEABLE BATTERY |
US13/858,375 US9214666B2 (en) | 2010-10-08 | 2013-04-08 | Graphite material with lattice distortion for use in lithium-ion secondary battery negative electrodes, and lithium-ion secondary battery |
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EP2869370A4 (en) * | 2012-06-29 | 2016-08-31 | Mt Carbon Co Ltd | GRAPHITE MATERIAL FOR NEGATIVE ELECTRODE OF LITHIUM ION RECHARGEABLE BATTERY, LITHIUM ION RECHARGEABLE BATTERY COMPRISING SAME, AND METHOD FOR PRODUCING GRAPHITE MATERIAL FOR LITHIUM ION RECHARGEABLE BATTERY |
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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 |
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TWI604655B (zh) * | 2014-08-08 | 2017-11-01 | Kureha Corp | Non-aqueous electrolyte secondary battery negative carbonaceous material |
EP3580169A2 (en) * | 2017-02-08 | 2019-12-18 | National Electrical Carbon Products, Inc. | Carbon powders and methods of making same |
KR101957017B1 (ko) * | 2017-05-17 | 2019-03-12 | 서울과학기술대학교 산학협력단 | 전극활물질, 그 제조 방법, 및 이를 포함하는 리튬이차전지 |
JP6816094B2 (ja) * | 2018-12-26 | 2021-01-20 | 住友化学株式会社 | αアルミナ、スラリー、多孔膜、積層セパレータ、並びに非水電解液二次電池及びその製造方法 |
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 |
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 |
TWI756928B (zh) * | 2020-11-19 | 2022-03-01 | 台灣中油股份有限公司 | 人工石墨的製備方法 |
CN116593895B (zh) * | 2023-06-16 | 2024-02-23 | 中国科学技术大学 | 一种基于应变的锂离子电池组电流检测方法及系统 |
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---|---|---|---|---|
EP2869370A4 (en) * | 2012-06-29 | 2016-08-31 | Mt Carbon Co Ltd | GRAPHITE MATERIAL FOR NEGATIVE ELECTRODE OF LITHIUM ION RECHARGEABLE BATTERY, LITHIUM ION RECHARGEABLE BATTERY COMPRISING SAME, AND METHOD FOR PRODUCING GRAPHITE MATERIAL FOR LITHIUM ION RECHARGEABLE BATTERY |
US9831490B2 (en) | 2012-06-29 | 2017-11-28 | Mt Carbon Co., Ltd. | Graphite material for negative electrode of lithium-ion secondary battery, lithium-ion secondary battery including the graphite material, and method of manufacturing graphite material for lithium-ion secondary battery |
Also Published As
Publication number | Publication date |
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EP2626933A1 (en) | 2013-08-14 |
JP2012084360A (ja) | 2012-04-26 |
CN103155244A (zh) | 2013-06-12 |
CN103155244B (zh) | 2016-05-18 |
KR20140017496A (ko) | 2014-02-11 |
EP2626933A4 (en) | 2015-04-01 |
US20130302692A1 (en) | 2013-11-14 |
US9214666B2 (en) | 2015-12-15 |
JP5612428B2 (ja) | 2014-10-22 |
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