WO2012133510A1 - リチウムイオン二次電池の負極用炭素材料の原料炭組成物およびその製造方法 - Google Patents
リチウムイオン二次電池の負極用炭素材料の原料炭組成物およびその製造方法 Download PDFInfo
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- WO2012133510A1 WO2012133510A1 PCT/JP2012/058098 JP2012058098W WO2012133510A1 WO 2012133510 A1 WO2012133510 A1 WO 2012133510A1 JP 2012058098 W JP2012058098 W JP 2012058098W WO 2012133510 A1 WO2012133510 A1 WO 2012133510A1
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- lithium ion
- ion secondary
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
- C01B32/205—Preparation
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B55/00—Coking mineral oils, bitumen, tar, and the like or mixtures thereof with solid carbonaceous material
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- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10B—DESTRUCTIVE DISTILLATION OF CARBONACEOUS MATERIALS FOR PRODUCTION OF GAS, COKE, TAR, OR SIMILAR MATERIALS
- C10B57/00—Other carbonising or coking processes; Features of destructive distillation processes in general
- C10B57/04—Other carbonising or coking processes; Features of destructive distillation processes in general using charges of special composition
- C10B57/045—Other carbonising or coking processes; Features of destructive distillation processes in general using charges of special composition containing mineral oils, bitumen, tar or the like or mixtures thereof
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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
- H01M4/133—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
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/027—Negative electrodes
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
- Y10T428/24479—Structurally defined web or sheet [e.g., overall dimension, etc.] including variation in thickness
Definitions
- the present invention relates to a raw material carbon composition of a carbon material for a negative electrode of a lithium ion secondary battery, and a method for producing the raw material carbon composition.
- Lithium ion secondary batteries are lighter in weight and have superior input / output characteristics compared to conventional secondary batteries such as nickel cadmium batteries, nickel metal hydride batteries, and lead batteries. It is expected as a power source.
- hybrid vehicles for which demand has been increasing, have attracted attention for solving energy and environmental problems because they reduce fuel consumption to 1/2 or less in traffic congestion areas in urban areas. Batteries for hybrid vehicles are discharged when starting or accelerating, and are used to charge regenerative energy (energy acquired by regenerative charging) when a brake is applied. When starting, accelerating, or decelerating, energy is rapidly put in and out (high speed). Therefore, lithium-ion secondary batteries with excellent high-speed charge / discharge characteristics are used as hybrid vehicle batteries. It is desired.
- the battery for the electric vehicle is required to have a high energy density for storing more electric energy.
- the hybrid vehicle does not use only the power of the secondary battery as a power source, the hybrid vehicle battery does not need to have a high energy density as required for the electric vehicle battery.
- a carbon material is used as an active material constituting an electrode of a lithium ion secondary battery, and various studies have been made on carbon materials so far to improve the performance of lithium ion secondary batteries (for example, patents). References 1-2).
- Conventional carbon materials used as negative electrode materials for lithium ion secondary batteries are generally roughly classified into graphite and amorphous materials.
- the graphite-based carbon material has an advantage that the energy density per unit volume is higher than that of the amorphous carbon material. Accordingly, graphite-based carbon materials are generally used as negative electrode materials in lithium ion secondary batteries for mobile phones and notebook computers that are compact but require a large charge / discharge capacity.
- Graphite has a structure in which hexagonal network 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.
- raw cokes various petroleum raw cokes (hereinafter referred to as raw cokes) have been studied (for example, Non-Patent Documents 1 and 3).
- raw cokes various petroleum raw cokes
- the properties of raw coke as a raw coal composition vary greatly depending on the intended use.
- a carbon material for a lithium ion secondary battery negative electrode that requires high-speed charge / discharge characteristics conventional raw coke is not sufficient. Met.
- graphite materials such as natural graphite, synthetic graphite, and expanded graphite as negative electrode carbon materials for lithium ion secondary batteries, carbonized mesocarbon microbeads, mesophase pitch carbon fibers, vapor grown carbon fibers, pyrolysis Carbon materials such as carbon, petroleum coke, pitch coke, and needle coke, and synthetic graphite materials obtained by subjecting these carbon materials to graphitization, or a mixture thereof have been proposed. It was difficult to express high charge / discharge characteristics with good reproducibility.
- the crystallinity of a carbon material has been determined by the crystallinity rule by X-ray diffraction, but it cannot be said that this crystallinity rule necessarily indicates the characteristics of the entire raw coal composition.
- This is in the “Commentary / Carbon Family” written by Michio Inagaki (Agne Jofu Co., Ltd.) “When there is selective orientation of crystallites (almost all carbon materials produce selective orientation) It may be understood from the description that "information about the crystallite may be obtained from X-ray diffraction.” For this reason, the conventional raw coke and the like cannot express the charge / discharge characteristics at a particularly high speed with good reproducibility.
- the object of the present invention has been made in view of such circumstances, and in particular, a lithium ion secondary battery capable of expressing high charge / discharge characteristics with high reproducibility at high speed required for a hybrid vehicle battery and the like. It is to provide carbon materials for use.
- the present inventors provide a raw material carbon composition for a carbon material having a unique structure advantageous for lithium ion diffusion while having excellent uniaxial orientation (crystallinity) for ensuring a reasonable energy density.
- the study was conducted focusing on the generation mechanism.
- needle coke which is a kind of raw coal composition, undergoes thermal decomposition and polycondensation reaction by treating heavy oil at a high temperature to produce liquid crystal spheres called mesophases, which are combined and called bulk mesophases. It is manufactured through a process in which a large liquid crystal is formed as an intermediate product.
- the raw material charcoal composition (raw coke) characterized by the surface of the stripe being curved in an arcuate shape.
- the structure with a striped pattern exhibits a uniaxial orientation along the hole formed when the generated gas escapes from the bulk mesophase when the mesophase is generated and the bulk mesophase is polycondensed in the caulking process, and the laminated surface has an arcuate shape. It is considered to be curved and has a striped structure. Thereby, the crystal structure of raw coke can be in the form of uniaxial orientation that neatly forms a lithium ion diffusion path.
- a lithium ion secondary battery using a carbon material obtained by finely pulverizing and carbonizing such a raw carbon composition, or by further graphitizing after carbonization as a negative electrode material is The present inventor has found that the high charge / discharge characteristics with high reproducibility are expressed with good reproducibility. It is already known that the carbon crystals undergo expansion and contraction when the raw carbon composition is carbonized or further graphitized after the carbonization.
- high charge and discharge characteristics at high speed are characterized by the fact that the raw carbon composition has a uniaxial orientation and is a lump having a striped pattern and the surface of the stripe is curved in an arcuate shape If the raw carbon composition is carbonized or graphitized, the strain due to the expansion and contraction stress increases at the curved portion, so that compared to the conventional raw carbon composition having a flat plate structure, This is probably because many fine gaps are generated and lithium ions are easily diffused.
- the first aspect of the invention is the generation rate (mass%) of generated gas composed of hydrogen gas and C1 to C4 gas generated by coking treatment of heavy oil, and the generation rate of the raw coal composition.
- It is a raw material carbon composition of the carbon material for negative electrodes of a lithium ion secondary battery.
- the raw coal composition according to the first invention is pulverized to an average particle size of 30 ⁇ m or less and then carbonized or further graphitized after carbonization.
- the 4th aspect of the invention which concerns on this application is a lithium ion secondary battery using the carbon material for lithium ion secondary batteries negative electrodes concerning the said 3rd invention.
- a carbon material obtained by carbonizing the raw material charcoal composition of the present invention is used as a negative electrode material, a lithium ion secondary battery that expresses high charge / discharge characteristics at high speed with good reproducibility can be obtained.
- the scanning electron micrograph which observed the surface of the raw coal composition of this invention The scanning electron micrograph which shows the average length L of the vertical direction of the fringe of the raw coal composition of this invention.
- the scanning electron micrograph which shows the average length W and the average height H of the base of the stripe of the raw coal composition of this invention The schematic diagram which shows the relationship of the average length W of the striped base of the raw coal composition of this invention, the average height H, and the average length L of the vertical direction.
- the scanning electron micrograph of the raw material charcoal composition of random structure The scanning electron micrograph of the raw material charcoal composition of random structure. Sectional drawing of a battery.
- Examples of the heavy oil used as the starting material of the raw coal composition of the present invention include, for example, petroleum-based desulfurization and desulfurization oil, hydrodesulfurization heavy oil, bottom oil of fluid catalytic cracking apparatus, vacuum residue oil (VR), Examples include coal liquefied oil, coal solvent extract oil, atmospheric residue oil, shell oil, tar sand bitumen, naphtha tar pitch, coal tar pitch, and heavy oil obtained by hydrotreating these.
- desulfurized and 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 asphalt content.
- the deoiled oil (DAO) obtained after removal is preferably desulfurized to a sulfur content of 0.05 to 0.40 mass%.
- the atmospheric distillation residual oil having a sulfur content of 2.0 to 5.0% by mass is adjusted, for example, at a total pressure of 25% or less in the presence of a catalyst. If hydrodesulfurization is performed under the conditions of 180 MPa, hydrogen partial pressure of 160 MPa, and temperature of 380 ° C., a sulfur content of 0.1 to 0.6% by mass can be obtained.
- the bottom oil of the fluid catalytic cracking apparatus is a bottom oil obtained from a fluid catalytic cracking (abbreviated as FCC) apparatus.
- FCC fluid catalytic cracking
- This apparatus is a fluidized bed type fluid catalytic cracking apparatus 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.
- As the bottom oil of the residual oil fluid catalytic cracker (RFCC) for example, residual oil such as atmospheric residual oil is used in the reactor reaction temperature (ROT) range of 510 to 540 ° C., and the catalyst / oil mass ratio is 6 to 8.
- ROT reactor reaction temperature
- a bottom oil produced by changing the range is mentioned.
- the vacuum residue oil (VR) is a bottom oil of a vacuum distillation apparatus obtained by changing crude oil in a range of 320 to 360 ° C. at a furnace outlet temperature under a reduced pressure of 10 to 30 Torr, for example.
- the delayed coking method is used as a method for converting heavy oil into a raw coal composition by coking treatment.
- the delayed coking method is a method in which heavy oil is heat-treated with a delayed coker under pressurized conditions to obtain a raw coal composition.
- the conditions of the delayed coker are preferably a pressure of 400 to 800 kPa and a temperature of 400 to 600 ° C.
- the ratio of the generation rate (mass%) of the generated gas consisting of hydrogen gas and C1 to C4 gas generated by coking heavy oil according to the present invention and the generation ratio (mass%) of the raw coal composition is as follows:
- the rate of occurrence / generation rate 0.3 to 0.8.
- the generated gas generated by the coking process is hydrogen gas and C1-C4 gas.
- the C1 to C4 gas is a gas composed of a hydrocarbon compound having 1 to 4 carbon atoms, and includes methane (CH 4 ), ethane (C 2 H 6 ), propane (C 3 H 8 ), butane (C 4 H 10 And paraffinic hydrocarbons such as ethylene (C 2 H 4 ), propylene (C 3 H 6 ), butylene (C 4 H 8 ) and the like.
- a single gas such as butane gas or butylene gas or a mixed gas is applicable.
- composition and generation rate of the gas generated by the coking process can be calculated using an integrating gas flow meter, an integrating liquid flow meter, and a process gas chromatograph installed in the delayed coker apparatus.
- production rate of the raw coal composition can be calculated by determining the transition of the volume using a radiation level meter installed in the delayed coker chamber.
- the generated gases hydrogen gas, C1 gas and C2 gas are recovered in a gas state by a coker distillation column OH receiver. C3 and C4 are cooled in the coker gas purification section and recovered as liquids.
- the generation rate (mass%) of hydrogen gas, C1 gas, and C2 gas the generated gas weight is calculated from the amount of gas generated in a certain time (Nm 3 ), the ratio of each component, and the molecular weight of each component. It can be calculated as a ratio to each of the weight of the raw material oil.
- the generation rate (mass%) of C3 gas and C4 gas since it is cooled and recovered as a liquid, the weight is calculated from the volume (KL) generated in a certain time and the density of each component.
- the generated weight is calculated from the raw carbon product volume (m 3 ) and bulk density (ton / m 3 ) measured using a radiation type level meter. It can be calculated as a ratio to the weight of the feed oil that has been applied over a certain period of time.
- the ratio (occurrence rate / production rate) can be controlled by controlling the characteristics of the raw heavy oil and the operating conditions (temperature, pressure) of the delayed coker.
- the relationship between the ratio, the temperature setting in the delayed coker operation, and the feedstock is added.
- the ratio of less than 0.3 occurs when the reaction temperature setting in the delayed coker is lowered to cause a slow decomposition reaction and a polycondensation reaction. In this case, the amount of gas generated by the decomposition / polycondensation reaction is small, and the growth of the mesophase itself generated by causing the decomposition / polycondensation reaction also proceeds slowly.
- the ratio exceeding 0.8 occurs when the reaction temperature setting in the delayed coker is increased to cause an abrupt decomposition reaction or polycondensation reaction.
- the amount of gas generated by the decomposition / polycondensation reaction becomes extremely large, and the generation of the mesophase occurs abruptly and coalesces before the mesophase grows sufficiently.
- the uniaxial orientation is not shown, as shown in FIGS. 3 (a) and 3 (b). Therefore, the structure is not random, and the surface of each stripe is not bowed.
- Such a raw material coal composition having a random structure is inferior in high-speed charge / discharge characteristics.
- the generation rate / generation rate As described above, by setting the generation rate / generation rate to a predetermined ratio, it is possible to obtain a raw carbon composition having a stripe pattern and a structure in which the surface of each stripe is curved in an arc shape.
- selection of the type of raw material oil that is heavy oil, blending of the raw material oil, and operating conditions (pressure, temperature, etc.) of the delayed coker can be appropriately selected.
- the total amount of generated gas from the start of operation to the end of operation, the generated gas composition, and the amount of generated coking coal composition are determined in total, and the value is determined for the next operation. It is desirable to reflect in
- the coking coal composition according to the present invention is a streak-like lump obtained by the delayed coking method under the above-described conditions, and the fringe surface is curved in an arcuate shape.
- the average length of the base in W is W
- the height is H
- the average length in the vertical direction is L
- H / W is 0.15 to 0.40
- L / W is 5.0 or more. is there.
- FIG. 1 is a scanning electron micrograph observing the surface of the lump of the raw coal composition of the present invention.
- the lump could not be observed with the same microscope with the same size, so it was used by breaking and adjusting to the size for measurement.
- This structure which appears to be a striped pattern, shows that during the caulking process, when the bulk mesophase undergoes polycondensation through the generation, growth, and coalescence of the mesophase, the bulk mesophase is formed along the holes formed by the gas generated simultaneously. It is formed by stacking and exhibits uniaxial orientation as indicated by arrows.
- FIG. 2A is an SEM photograph in which the portion X in FIG. 1 is enlarged, and is a scanning electron micrograph showing the average length L in the vertical direction of the stripes of the raw coal composition of the present invention.
- FIG.2 (b) is a scanning electron micrograph which shows the average length W and the average height H of the base of the stripe of the raw coal composition of this invention.
- the raw coal composition of the present invention is a lump having a structure in which a plurality of plates are laminated, and the structure is curved in an arcuate shape. That is, the raw coal composition of the present invention has a structure in which a plurality of plates are laminated, so that the side surface has a structure that looks like a striped pattern shown in FIG. 1, and the surface is curved in an arcuate shape.
- the raw carbon composition is formed by stacking several bulk mesophases and exhibiting uniaxial orientation, and at the same time, the laminated surface is curved in an arcuate shape, which is considered to form a striped pattern on the surface.
- this raw material carbon composition is carbonized, distortion due to expansion and contraction stress due to carbonization or the like occurs between the stacks. In particular, the distortion is increased in a portion that is curved in an arc shape along the generated gas passage hole. For this reason, many fine gaps are generated, and diffusion of lithium ions is facilitated, so that high charge / discharge characteristics at high speed are exhibited.
- FIG. 2 (c) shows the relationship between the base W, height H, and length L attached to FIGS. 2 (a) and 2 (b) as a schematic diagram, and the raw coal composition of the present invention.
- the average arcuate base of the cross section is W
- the average arcuate height is H
- the average length in the vertical direction is L
- H / W is 0.15. ⁇ 0.40
- L / W is 5.0 or more.
- the raw coal composition of the present invention when the average length of the bottom of the stripe is W, the average height is H, and the average length in the stripe direction is L, the raw coal composition of the present invention has an H / W of 0.15 to 0.40. And L / W is 5.0 or more. As shown in FIGS. 2 (a) and 2 (b), the raw coal composition of the present invention has variations in the width of the bottom of the arc, the height of the arc, and the length in the stripe direction. If the average of height and length is taken and H / W and L / W are in the above ranges, the effects of the present invention are exhibited.
- H / W indicates the degree of distortion due to the bow curve. If H / W is less than 0.15, the distortion due to the bow-shaped curvature is small and the gap is small, so that it is difficult to diffuse lithium ions. On the other hand, if H / W exceeds 0.4, the distortion due to the bow-shaped curve is too large, and the structure is likely to break in the subsequent carbonization and graphitization processes.
- L / W affects the battery capacity when a raw material charcoal composition is used to form a lithium ion secondary battery. When L / W is less than 5.0, the uniaxial orientation (crystallinity) is insufficient, and the capacity is inferior because there is no structure for orderly forming a lithium ion diffusion path.
- H / W When H / W is 0.15 to 0.40, the structure is not broken and many fine gaps are generated, so that lithium ions can be easily diffused. And if L / W is 5.0 or more, sufficient battery capacity is securable. As a result, by satisfying these conditions, high charge / discharge characteristics at high speed are exhibited in the lithium ion secondary battery.
- the height of the bow is preferably 1 ⁇ m or more. If it is less than 1 ⁇ m, the capacity and efficiency performance in high-speed charging tends to be slightly inferior. This is thought to be due to the fact that the arcuate curvature is small and the gap in the arcuate curve is reduced during carbonization and graphitization, resulting in poor diffusion of the electrolyte in the case of a lithium ion secondary battery. It is done.
- the length of the bottom of the stripe (the arcuate bottom of the cross section) is preferably 3 to 25 ⁇ m. If it is less than 3 ⁇ m, the pulverization process of the raw coal composition to be performed later is not preferable because pulverization proceeds extremely along the stripe direction. On the other hand, when the base of the stripe exceeds 25 ⁇ m, the average particle diameter of the carbon material used for the lithium ion secondary battery is generally 30 ⁇ m or less, so that the one having an arcuate curve is obtained. The high-speed charge / discharge performance tends to be inferior.
- the raw material carbon composition of the present invention By pulverizing the raw coal composition of the present invention to an average particle size of 30 ⁇ m or less, followed by carbonization or further graphitization treatment, lithium ions having particularly high-speed charge / discharge characteristics superior to conventional products are obtained. It becomes possible to produce a carbon material for a negative electrode of a secondary battery.
- the reason why the raw material carbon composition is pulverized to an average particle size of 30 ⁇ m or less is that the average particle size of the carbon material used in the lithium ion secondary battery is usually 30 ⁇ m or less.
- an average particle diameter can be measured using the measuring apparatus based on a laser diffraction scattering method. Further, after the carbonization treatment, a graphitization treatment may be appropriately performed.
- Carbonization treatment conditions and graphitization treatment conditions are not particularly limited, and the raw carbon composition is fired at 1000 to 1500 ° C. in a rotary kiln, shaft furnace, or the like to obtain calcined (carbonized) coke. Then, if necessary, the calcined coke is graphitized at 2200 to 2800 ° C. in an Atchison furnace or the like.
- a carbon material for a lithium ion secondary battery negative electrode such a carbonized product (calcined product) or a carbonized product after carbonization is used.
- the method for producing a negative electrode for a lithium ion secondary battery is not particularly limited, and examples thereof include a method of pressure-molding a mixture containing a carbon material according to the present invention, a binder, and optionally a conductive additive and an organic solvent. .
- a carbon material, a binder, a conductive additive or the like is slurried in an organic solvent, and the slurry is applied on a current collector and then dried.
- binder examples include polyvinylidene fluoride, polytetrafluoroethylene, SBR (styrene-butadiene rubber), and the like.
- the amount of the binder used is suitably 1 to 30 parts by mass with respect to 100 parts by mass of the carbon material, but is preferably about 3 to 20 parts by mass.
- Examples of the conductive assistant include carbon black, graphite, acetylene black, conductive indium-tin oxide, or conductive polymers such as polyaniline, polythiophene, and polyphenylene vinylene.
- the amount of the conductive aid used is preferably 1 to 15 parts by mass with respect to 100 parts by mass of the carbon material.
- organic solvent examples include dimethylformamide, N-methylpyrrolidone, isopropanol, toluene and the like.
- Examples of the method of mixing the carbon material, the binder, and, if necessary, the conductive additive and the organic solvent include a method using a known apparatus such as a screw kneader, a ribbon mixer, a universal mixer, or a planetary mixer.
- the obtained mixture is molded by roll pressurization and press pressurization.
- the pressure at this time is preferably about 100 to 300 MPa.
- the material and shape of the current collector there are no particular limitations on the material and shape of the current collector, and for example, a strip-shaped material made of aluminum, copper, nickel, titanium, stainless steel, or the like in the form of a foil, a punched foil, or a mesh may be used. Further, a porous material such as porous metal (foamed metal) or carbon paper can be used as the current collector.
- the method of applying the negative electrode material slurry to the current collector is not particularly limited.
- well-known methods, such as a screen printing method are mentioned.
- a rolling process using a flat plate press, a calendar roll or the like is performed as necessary.
- the integration of the slurry formed into a sheet shape, a pellet shape or the like with the current collector can be performed by a known method such as a roll, a press, or a combination thereof.
- a lithium ion secondary battery can be obtained, for example, by placing a negative electrode for a lithium ion secondary battery manufactured as described above and a positive electrode facing each other with a separator interposed therebetween and injecting an electrolytic solution.
- 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 intercalated with lithium ions may be used.
- Lithium oxide (LiCoO 2 ), lithium nickelate (LiNiO 2 ), lithium manganate (LiMnO 2 ), and their double oxides (LiCo X Ni Y Mn Z O 2 , X + Y + Z 1), lithium manganese spinel (LiMn 2) O 4 ), lithium vanadium compound, V 2 O 5 , V 6 O 13 , VO 2 , MnO 2 , TiO 2 , MoV 2 O 8 , TiS 2 , V 2 S 5 , VS 2 , MoS 2 , MoS 3 , Cr 3 O 8 , Cr 2 O 5 , olivine type LiMPO 4 (M: Co, Ni, Mn, Fe), poly Examples thereof include conductive polymers such as acetylene, poly
- the separator for example, a nonwoven fabric, a cloth, a microporous film, or a combination thereof having a polyolefin as a main component such as polyethylene or polypropylene can be used.
- a separator when it is set as the structure where the positive electrode and negative electrode of the lithium ion secondary battery to produce are not in direct contact, it is not necessary to use a separator.
- electrolyte and electrolyte used for the lithium secondary battery known organic electrolytes, inorganic solid electrolytes, and polymer solid electrolytes can be used.
- organic electrolyte is preferable from the viewpoint of electrical conductivity.
- organic electrolyte examples include ethers such as 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-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N-diethylacetamide and other amides, dimethyl sulfoxide, sulfolane and other sulfur-containing compounds, methyl ethyl ketone , Dialkyl ketones such as methyl isobutyl ketone, cyclic ethers such as tetrahydrofuran and 2-methoxytetrahydrofuran, ethylene carbonate DOO, butylene carbonate, diethyl carbonate, di
- preferred examples include ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, propylene carbonate, vinylene carbonate, ⁇ -butyrolactone, diethoxyethane, dimethyl sulfoxide, acetonitrile, tetrahydrofuran, and the like.
- Preferable examples include carbonate-based non-aqueous solvents such as ethylene carbonate and propylene carbonate. These solvents can be used alone or in admixture of two or more.
- Lithium salts are used as solutes (electrolytes) for these solvents.
- the lithium salt include LiClO 4 , LiBF 4 , LiPF 6 , LiAlCl 4 , LiSbF 6 , LiSCN, LiCl, LiCF 3 SO 3 , LiCF 3 CO 2 , and LiN (CF 3 SO 2 ) 2 .
- polymer solid electrolyte examples include a polyethylene oxide derivative and a polymer containing the derivative, a polypropylene oxide derivative and a polymer containing the derivative, a phosphate ester polymer, a polycarbonate derivative and a polymer containing the derivative.
- the structure of the lithium ion secondary battery using the carbon material produced from the raw material carbon composition according to the present invention as the negative electrode material is not particularly limited, usually, a positive electrode and a negative electrode, and a separator provided as necessary, It is common to have a structure in which a coiled plate group is formed by winding in a flat spiral shape, or a laminated plate group is formed by laminating these as a flat plate shape, and these electrode plate groups are enclosed in an exterior body. is there.
- Lithium ion secondary batteries are used as, for example, paper-type batteries, button-type batteries, coin-type batteries, stacked batteries, cylindrical batteries, and the like.
- Example 1 A mixture comprising 30% by mass of desulfurized and desulfurized oil desulfurized to a range of 0.05 to 0.40% by mass of sulfur and 70% by mass of RFCC bottom oil was introduced into a delayed coker apparatus, and under an inert gas atmosphere, A coking process was performed at a pressure of 500 kpa and a temperature of 465 ° C. to obtain a raw coal composition.
- the generation rate of hydrogen gas and C1-C4 generated gas by the coking process was calculated using an integrating gas flow meter, an integrating liquid flow meter and a process gas chromatograph installed in the delayed coker apparatus. Moreover, the production rate of the raw coal composition was calculated by obtaining the transition of the production volume using a radiation type level meter installed in the delayed coker chamber.
- the generation rate of the generated gas and the generation rate of the raw coal composition are as follows. For the generation rates (mass%) of hydrogen gas, C1 gas, and C2 gas, the amount of gas generated in a certain time (Nm 3 ), The generated gas weight was calculated from the ratio and the molecular weight of each component, and was calculated as the ratio of each to the weight of the feed oil spread over a certain period of time.
- the weight is calculated from the volume (KL) generated in a certain time and the density of each component.
- the ratio was calculated as the ratio to the weight of the feed oil that was applied over a certain period of time.
- the generated weight is calculated from the volume (m 3 ) and bulk density (ton / m 3 ) of the raw carbon organism measured using a radiation type level meter. The ratio was calculated as a ratio to the weight of the feed oil that was applied over time.
- a scanning electron micrograph of the obtained raw coal composition is taken by SEM, and is a lump having a striped pattern and the surface of the stripe is curved in an arcuate shape.
- the average length W, height H, and average length L in the vertical direction were measured, and H / W and L / W were calculated.
- the SEM apparatus is Hitachi S-3400N, and the resolution is 3 nm when the acceleration voltage is 30 kV and 10 nm when the acceleration voltage is 3 kV.
- Table 1 shows the feedstock type, the operating conditions of the delayed coker, the ratio of the generation rate / generation rate, H / W, and L / W.
- Example 2 A raw material charcoal composition was obtained by producing under the same conditions as in Example 1 except that the caulking temperature was 470 ° C.
- Example 3 A raw material charcoal composition was obtained by producing under the same conditions as in Example 2 except that the caulking treatment pressure was 550 kpa.
- Example 4 A raw material charcoal composition was obtained under the same conditions as in Example 2 except that the mixture to be caulked was made of 70% by mass of desulfurized and dehydrated oil and 30% by mass of RFCC bottom oil.
- Example 5 A raw material charcoal composition was obtained by producing under the same conditions as in Example 4 except that the coking temperature was 475 ° C.
- Comparative Example 1 A raw material charcoal composition was obtained by producing under the same conditions as in Example 1 except that the coking temperature was 455 ° C.
- Comparative Example 2 A raw material charcoal composition was obtained under the same conditions as in Example 1 except that the caulking temperature was 480 ° C.
- Comparative Example 7 A raw material charcoal composition was obtained under the same conditions as in Example 2 except that the raw material oil to be caulked was changed to 100% by mass of the Middle Eastern decompression residue oil.
- Comparative Example 8 A raw material charcoal composition was obtained under the same conditions as in Comparative Example 7 except that the raw material oil to be caulked was changed to 100% by mass of the Middle Eastern decompression residue oil.
- the rate of temperature increase is 200 ° C./hour
- the maximum temperature is maintained for 10 minutes
- the rate of temperature decrease is 100 ° C./hour up to 1000 ° C.
- the mixture is allowed to cool to room temperature while maintaining a nitrogen stream.
- Graphitization was performed to obtain a carbon material for a negative electrode of a lithium ion secondary battery.
- the average particle diameter was measured using the measuring apparatus based on the laser diffraction scattering method.
- FIG. 5 shows a cross-sectional view of the produced battery 10.
- FIG. 5 shows a negative electrode 11, a negative electrode current collector 12, a positive electrode 13, a positive electrode current collector 14, a separator 15, and an aluminum laminate outer package 16.
- the negative electrode 11 includes a graphitized carbon material obtained in Examples 1 to 5 and Comparative Examples 1 to 9 which are negative electrode materials, a polyvinylidene fluoride binder (KF # 9310 manufactured by Kureha), and a conductive material.
- Acetylene black (Denka Black made by Denka) was mixed in N-methyl-2-pyrrolidone at a mass ratio of 80:10:10 (mass ratio) to form a slurry, and a copper foil having a thickness of 18 ⁇ m
- the sheet electrode was applied to one side, dried for 10 minutes on a hot plate, and then rolled by a roll press, and cut so that the size of the application part was 30 mm wide and 50 mm long. At this time, the coating amount per unit area was set to 6 mg / cm 2 as the mass of the graphite material.
- a part of this sheet electrode is scraped off the negative electrode mixture perpendicularly to the longitudinal direction of the sheet, and the exposed copper foil is integrally connected to the negative electrode current collector 12 (copper foil) of the application part, It plays a role as a negative electrode lead plate.
- the positive electrode 13 is made of lithium nickel oxide having an average particle diameter of 6 ⁇ m (LiNi 0.8 Co 0.15 Al 0.05 O 2 manufactured by Toda Kogyo Co., Ltd.) as a positive electrode material, polyvinylidene fluoride as a binder (KF # 1320 manufactured by Kureha Co.), and conductive
- the material acetylene black (Denka Black made by Denka) was mixed at a mass ratio of 89: 6: 5, added with N-methyl-2-pyrrolidinone, kneaded, then pasted into aluminum having a thickness of 30 ⁇ m.
- the sheet electrode was applied to one side of the foil, dried for 10 minutes on a hot plate, and then rolled by a roll press, and the coated part was cut to have a width of 30 mm and a length of 50 mm. 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 connected integrally with the positive electrode current collector 14 (aluminum foil) of the application part. It plays a role as a positive electrode lead plate.
- the battery 10 was fabricated by sufficiently drying the positive electrode 13, the negative electrode 11, the polyethylene microporous membrane separator 15, and other components and introducing them into a glove box filled with argon gas having a dew point of ⁇ 100 ° C.
- the drying conditions are such that the positive electrode 13 and the negative electrode 11 are under reduced pressure at 150 ° C. for 12 hours or longer, and the separator 15 and other members are under reduced pressure at 70 ° C. for 12 hours or longer.
- the positive electrode 13 and the negative electrode 11 thus dried are laminated in a state in which the coating portion of the positive electrode 13 and the coating portion of the negative electrode 11 are opposed to each other through a polypropylene microporous film (# 2400 manufactured by Celgard). And fixed with polyimide tape.
- the lamination positional relationship between the positive electrode 13 and the negative electrode 11 was made to oppose so that the peripheral part of the positive electrode application part projected on the application part of the negative electrode 11 was enclosed inside the peripheral part of the negative electrode application part.
- the obtained single-layer electrode body is embedded with an aluminum laminate film, an electrolyte solution is injected, and the laminate film is heat-sealed in a state where the positive and negative electrode lead plates protrude from the sealed single unit electrode.
- a layer laminate battery 10 was produced.
- the electrolyte used was one in which lithium hexafluorophosphate (LiPF 6 ) was dissolved in a solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a mass ratio of 3: 7 so that the molar concentration was 1M.
- LiPF 6 lithium hexafluorophosphate
- the raw material carbon compositions of Examples and Comparative Examples except Comparative Example 8 were all a lump having a stripe pattern, and the surface of the stripe was curved in an arcuate shape.
- the raw coal composition of Comparative Example 8 has a random structure as shown in FIGS. 3 (a) and 3 (b), is a lump having a striped pattern, and does not have a structure in which the surface of the stripe is curved in an arcuate shape. It was. Therefore, Comparative Example 8 could not measure the shape of the raw coal composition (Table 1).
- Comparative Examples 5, 7, and 8 use Middle Eastern decompression residue oil.
- the Middle Eastern decompression residue oil is considered to be unable to produce a raw material carbon composition with good crystallinity because the sulfur content is particularly high and the sulfur content inhibits crystallization during the carbonization process among the decompression residue oils.
- Such crystallinity is also one of the factors that cause inferior battery performance.
- the Middle Eastern decompression residue oil was used, and therefore, in Examples 1 to 5, Such a raw material charcoal composition could not be produced, and the battery performance was inferior when compared with the examples.
- the lithium ion secondary battery using the carbon material produced from the raw coal composition according to the present invention for the negative electrode is excellent in high-speed charge / discharge characteristics.
- the lithium ion secondary battery using the carbon material manufactured from the raw coal composition according to the present invention has excellent high-speed charge / discharge characteristics. Therefore, it can be used for industrial purposes such as for automobiles, particularly for hybrid cars and plug-in hybrid cars.
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Abstract
Description
このような発進時や加速時、或は減速時には、急激(高速)にエネルギーを出したり入れたりするので、ハイブリッド車用電池としては、高速での充放電特性に優れたリチウムイオン二次電池が望まれている。
この熱分解及び重縮合反応の過程では、この分解、重縮合を起こすことにより、種々の分解ガスや軽質留分の発生及び重縮合反応に伴う水素ガスの発生が起こる。同時に、これと連動して、分解によるラジカル反応での重合や脱アルキル基、脱水素による重縮合反応により、メソフェーズの生成、成長、合体による生コークスの生成が起こっている。
本発明者らは、原料油の高温処理方法としてディレードコーキング法を採用し、原料油の選択、原料油のブレンドとコーカー運転条件による、コーキング過程での発生ガス量、ガス組成と生成コークス量が化学構造に与える影響について幅広い検討を行った。
鋭意検討を重ねた結果、コーキング過程で、原料油及び運転条件を選択的に行ない、発生ガスの発生率と原料炭組成物の生成量の比率を所定とした、縞模様を有する塊状物であり縞の表面が弓形に湾曲していることを特徴とする原料炭組成物(生コークス)を得るに至った。縞模様を有する構造は、コーキング過程で、メソフェーズの発生、バルクメソフェーズが重縮合する際に、発生したガスがバルクメソフェーズから抜け出す際に出来る孔に沿って、一軸配向を呈し、積層面が弓形に湾曲するものと考えられ、縞模様の構造を呈する。これにより、生コークスの結晶構造は、リチウムイオンの拡散経路を整然と形成させる一軸配向の形態となりうる。
原料炭組成物を炭化処理するか或は炭化処理後さらに黒鉛化処理する際に、炭素結晶が膨張と収縮を起こすことは、既に知られている。すなわち、高速での高い充放電特性の発現は、原料炭組成物が一軸配向を有することに加え、縞模様を有する塊状物であり縞の表面が弓形に湾曲していることを特徴とする構造の原料炭組成物を炭化処理或いは黒鉛化処理すれば、膨張と収縮の応力による歪が、弓形に湾曲する部分で大きくなるために、平板状の構造をとる従来の原料炭組成物に比べ、微細な間隙が多く発生し、リチウムイオンの拡散が容易となっているからであると考えられる。
本出願に係る発明の第二の態様は、ディレードコーキング法による請求項1記載の原料炭組成物の製造方法であって、重質油をコーキング処理することにより発生する水素ガスとC1~C4ガスからなる発生ガスの発生率(質量%)と、原料炭組成物の生成率(質量%)との比率が、発生率/生成率=0.3~0.8であることを特徴とするリチウムイオン二次電池の負極用炭素材料の原料炭組成物の製造方法である。
本出願に係る発明の第三の態様は、前記第一の発明にかかる原料炭組成物を、平均粒子径30μm以下に粉砕した後、炭化処理するか或は炭化処理後さらに黒鉛化処理することを特徴とするリチウムイオン二次電池の負極用炭素材料の製造方法である。
本出願に係る発明の第四の態様は、前記第三の発明にかかるリチウムイオン二次電池負極用炭素材料を用いたリチウムイオン二次電池である。
本発明の原料炭組成物の出発物となる重質油としては、例えば、石油系の脱硫脱歴油や水素化脱硫重質油、流動接触分解装置のボトム油、減圧残渣油(VR)、石炭液化油、石炭の溶剤抽出油、常圧残渣油、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、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。
減圧残渣油(VR)は、原油を、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。
上記コーキング処理により発生する発生ガスは、水素ガスとC1~C4ガスである。C1~C4ガスは、炭素原子数1~4の炭化水素化合物からなるガスであり、メタン(CH4)、エタン(C2H6)、プロパン(C3H8)、ブタン(C4H10)等のようなパラフィン系炭化水素と、エチレン(C2H4)、プロピレン(C3H6)、ブチレン(C4H8)等のようなオレフィン系炭化水素とがある。例えばC4ガスといった場合、ブタンガスやブチレンガス等の単体ガスあるいは混合ガスが該当する。
水素ガス、C1ガスおよびC2ガスの発生率(質量%)については、一定時間に発生したガス量(Nm3)、各成分の比率および各成分の分子量から発生ガス重量が計算され、一定時間に張り込んだ原料油重量に対する各々の比率として算出できる。C3ガスとC4ガスの発生率(質量%)については、冷却され液体で回収されるので一定時間に発生した各々の体積量(KL)と各成分の密度から重量が計算され、上記と同様に一定時間に張り込んだ原料油重量に対する比率として算出できる。
また、原料炭組成物の生成率(質量%)については、放射線式レベル計を用いて計測した原料炭素生物の出来高(m3)とそのかさ密度(トン/m3)から生成重量が計算され、一定時間に張り込んだ原料油重量に対する比率として計算できる。
比率が0.3未満となるのは、ディレードコーカーでの反応温度設定を低くし、緩やかな分解反応、および重縮合反応を起こさせる場合に起こる。この場合、分解・重縮合反応による発生ガス量が少なく、また、分解・重縮合反応を起こすことにより生成するメソフェーズ自体の成長も緩やかに進む。そのため、光学異方性組織の大きなドメインを持つ、バルクメソフェーズが形成されることになり、整然とした結晶の配列が得られる。
しかしながら、ガスの発生も緩やかで少なく、縞の表面が弓形に湾曲した構造を有するものが限られたものとなり、このため、炭化処理時、あるいは黒鉛化処理時に弓形に湾曲する部分で生成する間隙が少ないことから、従来の天然黒鉛等を用いた場合と同等程度の高速充放電特性に留まる。
更に、成長や合体と同時に起こる分解で急激に発生するガスにより、極端な乱流の中でメソフェーズが合体することとなるため、一軸配向を示さず、図3(a)(b)に示すようなランダム構造となり、縞模様を有し各縞の表面が弓形に湾曲した構造とはならない。このようなランダム構造の原料炭組成物は、高速充放電特性が劣るものとなってしまう。
発生率/生成率を所定の比率とするには、重質油である原料油種の選択、原料油のブレンド、ディレードコーカーの運転条件(圧力、温度等)を適宜、選択しえる。
また、より適切に原料炭組成物を得るためには、運転開始から運転終了時点までの発生ガス量、発生ガス組成、原料炭組成物の生成量をトータルして求め、その値を次の運転に反映することが望ましい。
本発明の原料炭組成物は図2(a)、(b)に示すように、弓形の底辺幅や弓形の高さ、縞方向の長さにはバラツキが生じるものの、塊状物中における各底辺や高さ、長さの平均をとり、H/WやL/Wが上記範囲であれば、本発明の効果を奏する。
また、L/Wは、原料炭組成物を用いてリチウムイオン二次電池としたときの電池容量に影響するものである。L/Wが5.0未満では、一軸配向(結晶性)が不足であり、リチウムイオンの拡散経路を整然と形成する構造を持たないために容量が劣る。
H/Wが0.15~0.40であれば、構造が破断することなく、微細な間隙が多く発生するために、リチウムイオンの拡散が容易となる。そして、L/Wが5.0以上であれば、十分な電池容量を確保可能である。結果としてこれらの条件を満たすことで、高速での高い充放電特性がリチウムイオン二次電池に発現することとなる。
ここで、原料炭組成物を平均粒子径30μm以下に粉砕するのは、リチウムイオン二次電池に用いられる炭素材料の平均粒子径が、通常は30μm以下であるからである。なお、平均粒子径は、レーザー回折散乱法に基づく測定装置を用いて測定できる。
また、上記炭化処理後、さらに黒鉛化処理を適宜行ってもよい。
なかでも、エチレンカーボネート、ブチレンカーボネート、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、プロピレンカーボネート、ビニレンカーボネート、γ-ブチロラクトン、ジエトキシエタン、ジメチルスルホキシド、アセトニトリル、テトラヒドロフラン等を好ましい例として挙げることができ、特に好ましい例として、エチレンカーボネート、プロピレンカーボネート等のカーボネート系非水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。
1.原料炭組成物の製造
(1)実施例1
硫黄分0.05~0.40質量%の範囲までに脱硫した脱硫脱歴油30質量%と、RFCCボトム油70質量%からなる混合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、圧力500kpa、温度465℃でコーキング処理し、原料炭組成物を得た。
コーキング処理による水素ガスとC1~C4からなる発生ガスの発生率は、ディレードコーカー装置に設置の積算型ガス流量計、積算型液体流量計及びプロセスガスクロを用いて算出した。また、原料炭組成物の生成率は、ディレードコーカーチャンバー内に設置された放射線式レベル計を用い出来高の推移を求めることで算出した。そして、発生ガスの発生率と原料炭組成物の生成率は、水素ガス、C1ガスおよびC2ガスの発生率(質量%)については、一定時間に発生したガス量(Nm3)、各成分の比率および各成分の分子量から発生ガス重量が計算され、一定時間に張り込んだ原料油重量に対する各々の比率として算出した。C3ガスとC4ガスの発生率(質量%)については、冷却され液体で回収されるので一定時間に発生した各々の体積量(KL)と各成分の密度から重量が計算され、上記と同様に一定時間に張り込んだ原料油重量に対する比率として算出した。原料炭組成物の生成率(質量%)については、放射線式レベル計を用いて計測した原料炭素生物の出来高(m3)とそのかさ密度(トン/m3)から生成重量が計算され、一定時間に張り込んだ原料油重量に対する比率として計算した。
また、得られた原料炭組成物の走査型電子顕微鏡写真をSEMにより撮影し、縞模様を有する塊状物であり縞の表面が弓形に湾曲していることを特徴とする構造において、各縞おける底辺の平均長さW、高さH、縦方向の平均長Lを測定し、H/WとL/Wを算出した。ここで、SEM装置は日立製S-3400Nであり、分解能は加速電圧30kV時3nm、加速電圧3kV時10nmである。
原料油種、ディレードコーカーの運転条件、発生率/生成率の比率、H/W、L/Wを表1に示す。
コーキング処理温度を470℃とする以外は、実施例1と同様の条件により製造し、原料炭組成物を得た。
コーキング処理圧力を550kpaとする以外は、実施例2と同様の条件により製造し、原料炭組成物を得た。
コーキング処理する混合物を、脱硫脱歴油70質量%と、RFCCボトム油30質量%からなる混合物とする以外は、実施例2と同様の条件により作製し、原料炭組成物を得た。
コーキング処理温度を475℃とする以外は、実施例4と同様の条件により製造し、原料炭組成物を得た。
コーキング処理温度を455℃とする以外は、実施例1と同様の条件により製造し、原料炭組成物を得た。
コーキング処理温度を480℃とする以外は、実施例1と同様の条件により製造し、原料炭組成物を得た。
コーキング処理温度を475℃とし、コーキング処理圧力を600kpaとする以外は、実施例4と同様の条件により製造し、原料炭組成物を得た。
コーキング処理温度を465℃とする以外は、実施例4と同様の条件により製造し、原料炭組成物を得た。
コーキング処理する混合物を、中東系減圧残渣油30質量%と、RFCCボトム油70質量%からなる混合物とする以外は、実施例2と同様の条件により製造し、原料炭組成物を得た。
コーキング処理する原料油を、RFCCボトム油100質量%とする以外は、実施例2と同様の条件により製造し、原料炭組成物を得た。
コーキング処理する原料油を、中東系減圧残渣油100質量%とする以外は、実施例2と同様の条件により製造し、原料炭組成物を得た。
コーキング処理する原料油を、中東系減圧残渣油100質量%とする以外は、比較例7と同様の条件により製造し、原料炭組成物を得た。
コーキング処理する原料油を、脱硫脱歴油100質量%とする以外は、実施例5と同様の条件により製造し、原料炭組成物を得た。
各原料炭組成物をSUS304製のハンマーミル(ハンマー直径500mm)を用いて平均粒子径30μm以下に粉砕し、その後ロータリーキルンを用いて1200℃で1時間焼成してか焼コークスを得た。さらにこのか焼コークスを坩堝に投入し、電気炉に設置して、80L/分の窒素ガス気流中、最高到達温度2200℃で黒鉛化した。このとき昇温速度は200℃/時間、最高到達温度の保持時間は10分間、降温速度は1000℃までが100℃/時間とし、その後窒素気流を保持させた状態で室温まで放冷させることにより黒鉛化処理し、リチウムイオン二次電池負極用炭素材料を得た。
なお、平均粒子径は、レーザー回折散乱法に基づく測定装置を用いて測定した。
(1)リチウムイオン二次電池の作製
図5に作製した電池10の断面図を示す。図5には、負極11、負極集電体12、正極13、正極集電体14、セパレータ15、アルミラミネート外装16が示されている。
負極11は、負極材料である前記実施例1~5及び比較例1~9で得られた黒鉛化炭素材料と、結着剤のポリフッ化ビニリデン(クレハ社製KF#9310)、および導電材のアセチレンブラック(デンカ社製のデンカブラック)とを質量比で80:10:10(質量比)の割合で、N-メチル-2-ピロリドン中で混合してスラリーとし、厚さ18μmの銅箔の片面に塗布し、ホットプレートで10分間乾燥した後、ロールプレスで圧延操作を行い、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、黒鉛材料の質量として、6mg/cm2となるように設定した。
このシート電極の一部はシートの長手方向に対して垂直に負極合剤が掻き取られ、その露出した銅箔が塗布部の負極集電体12(銅箔)と一体化して繋がっており、負極リード板としての役割を担っている。
正極13は、正極材料である平均粒子径6μmのニッケル酸リチウム(戸田工業社製LiNi0.8Co0.15Al0.05O2)と、結着剤のポリフッ化ビニリデン(クレハ社製KF#1320)、および導電材のアセチレンブラック(デンカ社製のデンカブラック)とを質量比で89:6:5に混合し、N-メチル-2-ピロリジノンを加えて混練した後、ペースト状にして、厚さ30μmのアルミニウム箔の片面に塗布し、ホットプレートで10分間乾燥した後、ロールプレスで圧延操作を行い、塗布部のサイズが、幅30mm、長さ50mmとなるように切断されたシート電極である。このとき単位面積当たりの塗布量は、ニッケル酸リチウムの質量として、10mg/cm2となるように設定した。
このシート電極の一部は、シートの長手方向に対して垂直に正極合剤が掻き取られ、その露出したアルミニウム箔が塗布部の正極集電体14(アルミニウム箔)と一体化して繋がっており、正極リード板としての役割を担っている。
このようにして乾燥された正極13及び負極11を、正極13の塗布部と負極11の塗布部とが、ポリプロピレン製のマイクロポーラスフィルム(セルガード社製#2400)を介して対向させる状態で積層し、ポリイミドテープで固定した。なお、正極13及び負極11の積層位置関係は、負極11の塗布部に投影される正極塗布部の周縁部が、負極塗布部の周縁部の内側で囲まれるように対向させた。得られた単層電極体を、アルミラミネートフィルムで包埋させ、電解液を注入し、前述の正・負極リード板がはみ出した状態で、ラミネートフィルムを熱融着することにより、密閉型の単層ラミネート電池10を作製した。使用した電解液は、エチレンカーボネートとメチルエチルカーボネートが質量比で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1M体積モル濃度となるように溶解されたものである。
(a)負極の作製
活物質としてリチウムイオン二次電池負極用炭素材料の微粒子、導電材としてアセチレンブラック(AB)、バインダーとしてポリフッ化ビニリデン(PVDF)を80:10:10(質量比)の割合でN-メチル-2-ピロリドン中で混合し、スラリーを作製した。該スラリーを銅箔上に塗布し、ホットプレートで10分間乾燥した後、ロールプレスでプレス成形した。
(b)評価用電池の作製
負極として上記の組成物(30×50mm)、正極としてニッケル酸リチウム(30×50mm)、電解液としてエチレンカーボネート(EC)/メチルエチルカーボネート(MEC)混合液(EC/MEC質量比:3/7、溶質:LiPF6(1M体積モル濃度)、及びセパレータとしてポリエチレン微孔膜を用いた。
(c)高速充放電レート特性の評価
作成した電池の高速充放電特性の測定結果を表2に示した。なお、本評価におけるCレートは10Cとした。利用率%は、10Cでの充放電容量を1Cでの充放電容量で除して求めた。
実施例1~5に示すように、発生率/生成率=0.3~0.8である条件とするディレードコーキング法により得られた、H/Wが0.15~0.40であり、かつ、L/Wが5.0以上である原料炭組成物を用いたリチウムイオン二次電池は、充電容量および放電容量に優れ、利用率も高い80%以上と高い結果を示した(表2)。
一方で、比較例1~9に示すように、発生率/生成率=0.3~0.8である条件や、H/Wが0.15~0.40である条件、およびL/Wが5.0以上である条件のいずれか1つでも満たさない原料炭組成物を用いたリチウムイオン二次電池の場合には、充電容量および放電容量が低く、また利用率も低い結果となった(表2)。
比較例において、比較例5、7、8は、中東系減圧残渣油を用いたものである。中東系減圧残渣油は、減圧残渣油のなかでも、特に硫黄分が高く硫黄分が炭化過程での結晶化を阻害するため、結晶性の良い原料炭組成物が出来ないものと考えられる。こういった結晶性も、電池性能が劣ることとなる要因の一つであり、比較例5、7、8では、中東系減圧残渣油を用いたことに起因して、実施例1~5のような原料炭組成物を製造することはできず、実施例と比較した場合に電池性能に劣る結果となった。
11 負極
12 負極集電体
13 正極
14 正極集電体
15 セパレータ
16 アルミラミネート外装
Claims (5)
- 重質油をコーキング処理することにより発生する水素ガスとC1~C4ガスからなる発生ガスの発生率(質量%)と、原料炭組成物の生成率(質量%)との比率が、発生率/生成率=0.3~0.8である条件とするディレードコーキング法により得られる縞模様の塊状物であり、
前記縞の底辺の平均長さをW、平均高さをH、縦方向の平均長さをLとすると、
H/Wが0.15~0.40であり、かつ、L/Wが5.0以上であることを特徴とするリチウムイオン二次電池の負極用炭素材料の原料炭組成物。 - ディレードコーキング法による請求項1記載の原料炭組成物の製造方法であって、
重質油をコーキング処理することにより発生する水素ガスとC1~C4ガスからなる発生ガスの発生率(質量%)と、原料炭組成物の生成率(質量%)との比率が、発生率/生成率=0.3~0.8であることを特徴とするリチウムイオン二次電池の負極用炭素材料の原料炭組成物の製造方法。 - 請求項1に記載の原料炭組成物を、平均粒子径30μm以下に粉砕した後、炭化処理することを特徴とするリチウムイオン二次電池の負極用炭素材料の製造方法。
- 炭化処理後さらに黒鉛化処理することを特徴とする請求項3記載のリチウムイオン二次電池の負極用炭素材料の製造方法。
- 請求項3または4に記載のリチウムイオン二次電池負極用炭素材料を用いたリチウムイオン二次電池。
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EP12764669.3A EP2693540B1 (en) | 2011-03-30 | 2012-03-28 | Production method of coking coal composition of carbon material for negative electrode of lithium ion secondary battery |
CN201280016752.6A CN103460460B (zh) | 2011-03-30 | 2012-03-28 | 锂离子二次电池的负极用碳材料的原料碳组合物及其制造方法 |
KR1020137026146A KR102008534B1 (ko) | 2011-03-30 | 2012-03-28 | 리튬이온 이차전지의 음극용 탄소재료의 원료탄 조성물 및 그 제조방법 |
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