WO2014058040A1 - 炭素材料、電池電極用炭素材料、及び電池 - Google Patents
炭素材料、電池電極用炭素材料、及び電池 Download PDFInfo
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- WO2014058040A1 WO2014058040A1 PCT/JP2013/077704 JP2013077704W WO2014058040A1 WO 2014058040 A1 WO2014058040 A1 WO 2014058040A1 JP 2013077704 W JP2013077704 W JP 2013077704W WO 2014058040 A1 WO2014058040 A1 WO 2014058040A1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0569—Liquid materials characterised by the solvents
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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
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
- H01M2300/0028—Organic electrolyte characterised by the solvent
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- 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 carbon material, a carbon material for battery electrodes, and a battery. More specifically, the electrode material of the non-aqueous electrolyte secondary battery has a good electrode filling property, a carbon material exhibiting a high energy density and a manufacturing method thereof, and a secondary having a large capacity, charge / discharge cycle characteristics, and high coulomb efficiency. It relates to batteries.
- Lithium ion secondary batteries are used in a variety of applications, ranging from small ones such as portable devices to large ones such as battery electric vehicles (BEV) and hybrid electric vehicles (HEV). Appropriate performance is required. In portable device applications, lithium-ion secondary batteries having higher energy density are required due to the reduction in size and weight of electrical and electronic devices and the increase in power consumption accompanying diversification of functions.
- BEV battery electric vehicles
- HEV hybrid electric vehicles
- the main required characteristics are long-term cycle characteristics over 10 years and high current load characteristics for driving high-power motors, and higher volumetric energy density to further extend the cruising range. Moreover, since a large-sized lithium ion secondary battery is expensive, cost reduction is calculated
- carbon materials such as graphite, hard carbon, and soft carbon are used for the negative electrode active material of the lithium ion secondary battery.
- Hard carbon and soft carbon described in Japanese Patent No. 36553105 (US Pat. No. 5,587,255; Patent Document 1) have excellent large current characteristics and relatively good cycle characteristics. The most widely used is graphite.
- Graphite includes natural graphite and artificial graphite.
- natural graphite is available at a low price, and because of its high degree of graphitization, the discharge capacity and electrode density are high, but the particle shape is scaly, has a large specific surface area, and has a highly reactive graphite edge surface.
- the electrolytic solution is decomposed, the Coulomb efficiency at the first charge / discharge is very low, and gas is generated. Also, the cycle characteristics were not good.
- Japanese Patent No. 3534391 US Pat. No. 6,632,569, Patent Document 2 and the like propose a method of coating carbon on the surface of natural graphite processed into a spherical shape.
- Patent Document 5 In Japanese Patent Application Laid-Open No. 2003-77534 (Patent Document 5), studies have been made for the purpose of charging and discharging at a high speed with a relatively large gap.
- WO2011 / 049199 discloses artificial graphite having excellent cycle characteristics.
- Japanese Patent No. 4945029 discloses an artificial graphite negative electrode produced by adding boron to raw acicular coke having a flow structure.
- Patent Document 8 describes a method of removing boron nitride on the surface of an artificial graphite negative electrode produced by adding boron.
- Japanese Patent No. 36553105 U.S. Pat. No. 5,587,255
- Japanese Patent No. 3534391 Japanese Patent No. 3126030
- Japanese Patent No. 3361510 European Patent No. 0918040
- Japanese Unexamined Patent Publication No. 2003-77534 WO2011 / 049199 U.S. Pat. No. 8,372,373
- Japanese Patent No. 4945029 US Pat. No. 7,141,229
- the negative electrode material described in Patent Document 1 is excellent in characteristics against a large current, but has a low volumetric energy density and a very expensive price, so it is used only for some special large batteries.
- Patent Document 2 The material manufactured by the method described in Patent Document 2 can cope with the high capacity, low current, and medium cycle characteristics required for mobile applications and the like, but the large current and super long cycle of the large battery as described above. It is very difficult to meet requirements such as characteristics.
- the graphitized product described in Patent Document 3 is a negative electrode material with a very good balance, and can produce a battery with a high capacity and a large current. It is difficult to achieve a wide range of cycle characteristics.
- fine powder such as natural graphite can be used in addition to fine powder of artificial graphite raw material, and as a negative electrode material for mobile, very excellent performance is exhibited.
- this material can also handle the high capacity, low current, and medium cycle characteristics required by mobile applications, etc., but it has not yet satisfied the requirements for large currents and ultra-long cycle characteristics of large batteries as described above. .
- Patent Document 5 the capacity is not sufficiently maintained during charging and discharging, and is practically insufficient for use in a secondary battery.
- Patent Document 6 there is room for improvement in the diffusion of active material ions because the graphite structure is dense.
- Patent Document 7 Although the capacity and the initial charge / discharge efficiency are improved compared to the conventional artificial graphite, the raw coke is pulverized and then carbonized by firing, and graphitization is performed in an argon stream. It was expensive and not practical.
- Patent Document 8 the effect of reducing contact resistance is obtained by removing boron nitride generated on the surface by pulverizing and grinding the negative electrode material to which boron is added. Since the number of processes increases, it is expensive and not practical. There is also a problem that the specific surface area is increased by pulverization after graphitization.
- a carbon material containing 0.001 to 0.5 mass% of boron atoms and having an average interplanar spacing (d002) of (002) planes by an X-ray diffraction method of 0.337 nm or less When the optical structure is observed with a polarizing microscope in a rectangular field of view of 480 ⁇ m ⁇ 540 ⁇ m of the cross section of the molded body made of the carbon material, the area is accumulated from a structure having a small area, and the cumulative area is 60% of the total optical structure area.
- SOP is the area of the optical structure when the number of the structures is small, the number of tissues is counted from the structure with a small aspect ratio, the aspect ratio in the 60th tissue of the whole structure is AROP, the volume-based average particle diameter by the laser diffraction method Is D50, 1.5 ⁇ AROP ⁇ 6 and 0.2 ⁇ D50 ⁇ (SOP ⁇ AROP) 1/2 ⁇ 2 ⁇ D50 Carbon material having the relationship [2] The carbon material as described in 1 above, wherein the volume-based average particle diameter (D50) determined by laser diffraction is from 1 ⁇ m to 50 ⁇ m.
- a manufacturing method including a step of performing a heat treatment in an atmosphere containing at least 50% by volume of nitrogen at a temperature of 3000 ° C. or higher and 3600 ° C. or lower.
- the area is accumulated from a small area, and the cumulative area is 60% of the total optical texture area.
- area of the optical tissue when made is at 10 [mu] m 2 or more 5000 .mu.m 2 or less, and the aspect ratio in 60% th tissue small tissue from the counted number of tissues throughout the organization number of the aspect ratio of 1.5 to 6 6.
- a battery electrode carbon material comprising the carbon material as described in any one of 1 to 4 above.
- 100 parts by mass of the carbon material according to any one of 1 to 4 above and 0.01 to 200 parts by mass of natural graphite or artificial graphite, and an average interplanar spacing of the natural graphite or artificial graphite (d002 ) Is a carbon material for battery electrodes having a thickness of 0.3370 nm or less.
- a lithium ion secondary battery including the electrode according to 11 as a constituent element.
- the carbon material of the present invention When the carbon material of the present invention is used as a carbon material for a battery electrode, a battery electrode having a high capacity, a high energy density, a high coulomb efficiency and a low resistance that can be charged / discharged at high speed while maintaining high cycle characteristics is obtained. be able to. Moreover, the carbon material of the present invention is excellent in economic efficiency and mass productivity, and can be produced by a method with improved safety.
- the polarizing microscope photograph (480 micrometers x 540 micrometers) of the calcined coke of Example 2 is shown.
- the black part is resin and the gray part is optical structure.
- the polarizing microscope photograph (480 micrometers x 540 micrometers) of the carbon material of Example 2 is shown.
- the black part is resin and the gray part is optical structure.
- Carbon material The electrode of a rechargeable battery is required to save more electricity per unit volume.
- Graphite is excellent in the Coulomb efficiency of the first charge / discharge, but there is an upper limit to the stoichiometric ratio of lithium atoms to carbon atoms at the time of insertion, and it is difficult to further improve the energy density per mass.
- the active material is coated on a current collector plate and dried, and then pressed to improve the filling property of the negative electrode active material per volume. At this time, if the graphite particles are soft and deformed to some extent with the press, the electrode density can be extremely increased.
- the structure observed in the graphite particles includes a structure that exhibits optical anisotropy due to the development of crystals and the alignment of the graphite network surface, and an optical structure that is not developed or has a large disorder of crystals such as hard carbon. It has long been known that there is an organization that shows direction. For the observation of these structures, it is possible to measure the size of the crystal by using X-ray diffraction method.
- the carbon material in a preferred embodiment of the present invention is a material in which the size and shape of the optical texture are in a specific range, and further has an appropriate degree of graphitization, so that both the crushing characteristics and the battery characteristics as an electrode material are excellent. It becomes.
- the carbon material preferably satisfies the following formula. 1.5 ⁇ AROP ⁇ 6 and 0.2 ⁇ D50 ⁇ (SOP ⁇ AROP) 1/2 ⁇ 2 ⁇ D50
- SOP means that when an optical structure is observed with a polarizing microscope in a rectangular field of view of 480 ⁇ m ⁇ 540 ⁇ m of the cross section of the molded body made of the carbon material, the area is accumulated from a structure with a small area, and the accumulated area is the total optical tissue area. It represents the area of the optical structure when the area is 60%.
- AROP represents the aspect ratio in the tissue that is 60% of the total number of tissues by counting the number of tissues from the tissues having a small aspect ratio.
- D50 represents the 50% cumulative diameter (average particle diameter) measured on a volume basis in a laser diffraction particle size distribution meter, and indicates the apparent diameter of the scaly particles.
- the laser diffraction type particle size distribution analyzer for example, Mastersizer (registered trademark) manufactured by Malvern can be used.
- the carbon material in a preferred embodiment of the present invention has a scale shape.
- the optical structure in the carbon material hardens while flowing, it often has a band shape, and when the cross section of the molded body made of the carbon material is observed, the shape of the optical structure is generally rectangular, and the area is It can be estimated that the minor axis and the major axis of the optical tissue are multiplied.
- the minor axis is the major axis / aspect ratio. If it is assumed that the optical structure to be subjected to the area SOP and the optical structure to be subjected to the aspect ratio AROP are the same, the major axis in the optical structure is (SOP ⁇ AROP) 1/2 . That is, (SOP ⁇ AROP) 1/2 assumes the long diameter of a specific size of optical structure, and the ratio of the average particle diameter (D50) to the optical structure has a certain size or more. Is defined by the above formula.
- (SOP ⁇ AROP) 1/2 assuming the major axis of the optical texture is usually smaller than the average particle diameter D50, but when (SOP ⁇ AROP) 1/2 and D50 are close to each other, This means that the particle is composed of a smaller number of optical structures, and when (SOP ⁇ AROP) 1/2 is small with respect to D50, it means that the particles in the carbon material contain a large number of optical structures. .
- the value of (SOP ⁇ AROP) 1/2 is 0.2 ⁇ D50 or more, there are few boundaries of the optical structure, which is convenient for the diffusion of lithium ions, so that charge / discharge can be performed at a high speed. Moreover, the larger the value, the more lithium ions that can be retained.
- the value is preferably 0.25 ⁇ D50 or more, more preferably 0.28 ⁇ D50 or more, and further preferably 0.35 ⁇ D50 or more.
- the upper limit is less than 2 ⁇ D50, but is preferably 1 ⁇ D50 or less.
- the average particle diameter (D50) of the carbon material in a preferred embodiment of the present invention is 1 ⁇ m or more and 50 ⁇ m or less. In order to make D50 less than 1 ⁇ m, it is necessary to pulverize with special equipment at the time of pulverization, and more energy is required. On the other hand, when D50 is too large, it takes time to diffuse lithium in the negative electrode material, and the charge / discharge rate tends to decrease. More preferable D50 is 5 ⁇ m or more and 35 ⁇ m or less. Since the fine powder has a high surface area and leads to an unintended reaction, it is even more preferable that D50 is 10 ⁇ m or more from the viewpoint that it is better to reduce the fine powder. When it is used for a driving power source such as an automobile that requires generation of a large current, D50 is preferably 25 ⁇ m or less.
- the aspect ratio AROP of the carbon material is more preferably 2.0 or more and 4.0 or less.
- the aspect ratio is larger than the lower limit, it is preferable because the structure slips and a high-density electrode is easily obtained.
- the aspect ratio is lower than the upper limit, the energy required for synthesizing the raw materials is small and preferable.
- the optical tissue observation and analysis method is as follows. [Preparation of observation materials for polarizing microscope]
- “a cross section of a molded body made of a carbon material” is prepared as follows. A double-sided tape is affixed to the bottom of a plastic sample container having an internal volume of 30 cm 3 , and about 2 cups of spatula (about 2 g) are placed on the sample.
- Cold embedding resin (trade name: cold embedding resin # 105, manufacturer: Japan Composite Co., Ltd., sales company: Marumoto Struers Co., Ltd.) and curing agent (trade name: curing agent (M agent), Manufacturing company: Nippon Oil & Fats Co., Ltd., sales company: Marumoto Struers Co., Ltd.) and knead for 30 seconds.
- the obtained mixture (about 5 ml) is slowly poured into the sample container until it reaches a height of about 1 cm, and allowed to stand for 1 day to solidify.
- the solidified sample is taken out and the double-sided tape is peeled off.
- the surface to be measured is polished using a polishing plate rotating type polishing machine.
- Polishing is performed by pressing the polishing surface against the rotating surface.
- the polishing plate is rotated at 1000 rpm.
- the counts of the polishing plates are # 500, # 1000, and # 2000 in order, and finally alumina (trade name: Baikalox (registered trademark) type 0.3CR, particle size 0.3 ⁇ m, manufacturer: Baikowski Polishing using a sales company: Baikowski Japan).
- the polished sample is fixed with clay on a preparation and observed using a polarizing microscope (OLYMPAS, BX51).
- Statistic processing for the detected organization is performed using an external macro.
- the black portion that is, the portion corresponding to the resin portion instead of the optical structure is excluded from the statistical object, and the area and aspect ratio of each structure are calculated for each of the blue, yellow, and red optical structures.
- the carbon material in a preferred embodiment of the present invention contains 0.001% by mass to 0.5% by mass of boron atoms.
- a preferable boron atom content is 0.1% by mass or more and 0.5% by mass or less.
- the content of boron atoms in the carbon material can be measured by ICP emission analysis.
- a carbon material having a large optical structure, a small crystal interlayer distance (d002), which will be described later, and a uniform orientation of the graphite network surface easily develops an edge portion, and the reactivity at that portion becomes high. When such a carbon material is used as an electrode material, a decomposition reaction of the electrolytic solution occurs, and the Coulomb efficiency at the first charge / discharge tends to be low.
- boron is included to increase the SP 3 bond at the particle end face (edge portion), and the defects are uniformly increased, thereby reducing the reactivity at the edge portion, and the initial charge / discharge. It is possible to realize a high value of 90% or more of the coulomb efficiency at the time.
- the boron atom content is in the above range, the increase in electrode potential can be suppressed, and the energy that can be extracted can be increased. In particular, problems tend to arise when the boron atom content increases.
- the carbon material according to a preferred embodiment of the present invention has an average interplanar spacing (d002) of (002) plane of 0.337 nm or less by X-ray diffraction. This increases the amount of lithium insertion / extraction per mass of the carbon material, that is, the weight energy density increases. Further, the thickness (Lc) in the C-axis direction of the crystal is preferably 50 nm or more and 1000 nm from the viewpoint of weight energy density and crushability. If d002 is 0.337 nm or less, most of the optical structure observed with a polarizing microscope is an optically anisotropic structure.
- d002 and Lc can be measured by a known method using a powder X-ray diffraction (XRD) method (Inada Inokichi, Michio Inagaki, Japan Society for the Promotion of Science, 117th Committee Sample, 117-71-A-1 (1963), Michio Inagaki et al., Japan Society for the Promotion of Science, 117th Committee Sample, 117-121-C-5 (1972), Michio Inagaki, “Carbon”, 1963, No. 36, pages 25-34).
- XRD powder X-ray diffraction
- the carbon material in a preferred embodiment of the present invention has a BET specific surface area of 0.4 m 2 / g or more and 5 m 2 / g or less, and more preferably 0.5 m 2 / g or more and 3.5 m 2 / g or less. More preferably not more than 0.5 m 2 / g or more 3.0 m 2 / g.
- the BET specific surface area is measured by a general method of measuring the amount of adsorption / desorption of gas per unit mass.
- NOVA-1200 can be used as the measuring device.
- the carbon material in a preferred embodiment of the present invention has a loose bulk density (0 times tapping) of 0.7 g / cm 3 or more and a powder density (tap density) of 400 g / tap when tapped 400 times. It is cm 3 or more and 1.6 g / cm 3 or less. More preferably, it is 0.9 g / cm 3 or more and 1.6 g / cm 3 or less, and most preferably 1.1 g / cm 3 or more and 1.6 g / cm 3 or less.
- the loose bulk density is a density obtained by dropping 100 g of a sample from a height of 20 cm onto a measuring cylinder and measuring the volume and mass without applying vibration.
- the tap density is a density obtained by measuring the volume and mass of 100 g of powder tapped 400 times using a cantachrome auto tap.
- Examples of the carbon material according to a preferred embodiment of the present invention include a material in which a part of carbon fiber is bonded to the surface.
- a part of the carbon fiber is bonded to the surface of the carbon material, the dispersion of the carbon fiber in the electrode is facilitated, and the cycle characteristics and the current load characteristics are further enhanced by a synergistic effect with the characteristics of the carbon material as the core material.
- the amount of carbon fiber is not particularly limited, but is preferably 0.1 to 5 parts by mass with respect to 100 parts by mass of the carbon material as the core material.
- carbon fibers examples include organic carbon fibers such as PAN-based carbon fibers, pitch-based carbon fibers, and rayon-based carbon fibers, and vapor grown carbon fibers.
- organic carbon fibers such as PAN-based carbon fibers, pitch-based carbon fibers, and rayon-based carbon fibers
- vapor grown carbon fibers having high crystallinity and high thermal conductivity is particularly preferable.
- carbon fibers are bonded to the surface of a carbon material, vapor grown carbon fibers are particularly preferable.
- Vapor-grown carbon fiber is produced, for example, by using an organic compound as a raw material, introducing an organic transition metal compound as a catalyst into a high-temperature reactor together with a carrier gas, and subsequently heat-treating it (Japanese Patent Laid-Open No. No. 60-54998, Japanese Patent No. 2778434, etc.).
- the fiber diameter is 2 to 1000 nm, preferably 10 to 500 nm, and the aspect ratio is preferably 10 to 15000.
- organic compound used as a raw material for carbon fiber examples include gases such as toluene, benzene, naphthalene, ethylene, acetylene, ethane, natural gas, carbon monoxide, and mixtures thereof. Of these, aromatic hydrocarbons such as toluene and benzene are preferred.
- the organic transition metal compound contains a transition metal serving as a catalyst.
- the transition metal include metals of groups IVa, Va, VIa, VIIa, and VIII of the periodic table.
- compounds such as ferrocene and nickelocene are preferable.
- the carbon fiber may be one obtained by pulverizing or pulverizing long fibers obtained by a vapor phase method or the like. Further, the carbon fibers may be aggregated in a flock shape.
- the carbon fiber is preferably one having no thermal decomposition product derived from an organic compound or the like on its surface or one having a high carbon structure crystallinity.
- Carbon fibers to which no pyrolyzate is attached or carbon fibers having a high carbon structure crystallinity are obtained by, for example, firing (heat treatment) carbon fibers, preferably vapor grown carbon fibers, in an inert gas atmosphere. It is done. Specifically, carbon fibers to which no pyrolyzate is attached can be obtained by heat treatment at about 800 to 1500 ° C. in an inert gas such as argon.
- the carbon fiber having high carbon structure crystallinity is preferably obtained by heat treatment in an inert gas such as argon at 2000 ° C. or higher, more preferably 2000 to 3000 ° C.
- the carbon fiber preferably contains a branched fiber. Further, there may be a portion where the entire fiber has a hollow structure communicating with each other. Therefore, the carbon layer which comprises the cylindrical part of a fiber is continuing.
- a hollow structure is a structure in which a carbon layer is wound in a cylindrical shape, and includes a structure that is not a complete cylinder, a structure that has a partial cut portion, and a structure in which two stacked carbon layers are bonded to one layer. .
- the cross section of the cylinder is not limited to a perfect circle, but includes an ellipse or a polygon.
- the carbon fiber has an (002) plane average plane distance d002 of preferably 0.344 nm or less, more preferably 0.339 nm or less, and particularly preferably 0.338 nm or less, as determined by X-ray diffraction.
- a crystal having a thickness (Lc) in the C-axis direction of 40 nm or less is preferable.
- the carbon material in a preferred embodiment of the present invention can be produced by mixing boron or a boron compound with particles obtained by pulverizing calcined coke and then heating.
- a raw material of calcined coke for example, petroleum pitch, coal pitch, coal pitch coke, petroleum coke, and a mixture thereof can be used. Among these, what heated the coke which performed the delayed coking on specific conditions in inert atmosphere is preferable.
- decant oil obtained by removing the catalyst after carrying out fluidized bed catalytic cracking on heavy distillate during refining of crude oil, or coal tar extracted from bituminous coal, etc. has a temperature of 200 ° C or higher. And those having sufficient fluidity by raising the temperature of the tar obtained to 100 ° C. or higher.
- these liquids are heated to 450 ° C. or higher, more preferably 510 ° C. or higher, at least at the entrance to the drum, thereby increasing the residual carbon ratio during coke calcination.
- the pressure in the drum is preferably maintained at normal pressure or higher, more preferably 300 kPa or higher, and further preferably 400 kPa or higher. Thereby, the capacity
- coke is performed under conditions severer than usual, so that the liquid can be reacted more and coke having a higher degree of polymerization can be obtained.
- the obtained coke is cut out from the drum by a jet water flow, and the obtained lump is roughly pulverized to about 5 cm with a hammer.
- a biaxial roll crusher or a jaw crusher can be used, but pulverization is preferably performed so that the amount on a 1 mm sieve is 90% by mass or more. If excessive pulverization is performed to such an extent that fine particles having a particle diameter of 1 mm or less are generated in large quantities, there is a possibility that inconveniences such as soaring after drying or increased burnout may occur in the subsequent heating process.
- the coarsely ground coke is then calcined.
- Calcination refers to heating to remove moisture and organic volatiles. Coke before calcination ignites relatively easily. Therefore, keep it moistened to prevent fire.
- Pre-calcined coke containing water is inferior in handleability, for example, muddy water-containing fine powder contaminates the equipment and surroundings. Calcination is extremely advantageous in terms of handleability. Moreover, when graphitization is performed on the calcined coke, crystals grow more.
- Calcination is performed by heating with electricity or flame heating such as LPG, LNG, kerosene, heavy oil. Since a heat source of 2000 ° C. or less is sufficient for removing moisture and organic volatile components, flame heating, which is a cheaper heat source, is preferable when mass production is performed. Especially when processing on a large scale, the energy cost can be reduced by heating the coke with internal flame or internal heat while burning the organic volatiles of fuel and unheated coke in the rotary kiln. Is possible.
- the calcined coke preferably has a specific optical texture area and aspect ratio in a specific range.
- the area and aspect ratio of the optical structure can be calculated by the above-described method. However, when calcined coke is obtained as a mass of several centimeters in size, it is embedded in the resin as it is, and mirror-finished. Equivalently, the cross section is observed with a polarizing microscope, and the area and aspect ratio of the optical structure are calculated.
- the area is accumulated from a small area structure, and the cumulative area is 60% of the total optical structure area preferably the area of the optical tissues is 10 [mu] m 2 or more 5000 .mu.m 2 or less, more preferably 10 [mu] m 2 or more 1000 .mu.m 2 or less, and more preferably 20 [mu] m 2 or more 500 [mu] m 2 or less.
- graphitized calcined coke in the above range has a sufficiently developed crystal structure, lithium ions can be held at a higher density. Further, it is more preferable that the crystals develop in a more uniform form, and the degree of freedom of the particle shape is high when the electrode is pressed due to slippage caused by fracture of the crystal plane, and the filling property is increased.
- the optical structure of calcined coke is observed in the same manner as described above, the number of tissues is counted from the structure having a small aspect ratio, and the aspect ratio in the 60th structure of the entire structure is 1.5 or more and 6 or less. It is preferable.
- the calcined coke is pulverized.
- pulverize There is no restriction
- the pulverization is preferably performed so that the volume-based average particle diameter (D50) by laser diffraction is 1 ⁇ m or more and 50 ⁇ m or less.
- D50 volume-based average particle diameter
- a large amount of energy is required using special equipment.
- D50 is 5 ⁇ m or more and 35 ⁇ m or less.
- D50 is more preferably 10 ⁇ m or more.
- D50 is more preferably 25 ⁇ m or less.
- Boron or a boron compound is mixed with the pulverized calcined coke particles and then heat-treated. Graphitization occurs by heat treatment.
- a carbon material obtained by heat-treating calcined coke having an optical structure having a specific size and good crushing characteristics has developed edge portions of particles constituting the material. Therefore, there is a problem in that the reactivity with the electrolytic solution at the edge portion is high, and a large amount of electricity is consumed at the first charging, that is, when lithium is inserted, and an excessively thick film is formed. As a result, the reversible lithium insertion / release reaction is inhibited, and the battery life such as cycle characteristics is adversely affected.
- a specific amount of boron or boron compound is mixed with the pulverized calcined coke particles, and then heat treated to increase SP 3 bonds (defects) at the particle end faces (edge portions), thereby reacting with the electrolyte.
- the coulomb efficiency at the first charge / discharge is improved.
- Boron acid, boron oxide, boron carbide, etc. can be used as the boron compound.
- the addition amount is preferably 0.01% by mass or more and 2.0% by mass or less, more preferably 0.1% by mass or more and 1.0% by mass in terms of boron atom with respect to the particles of pulverized calcined coke. It is as follows. If the amount of boron to be added is too small, the effect of adding boron may not be sufficiently exhibited. Moreover, when there is too much boron amount to add, an electrode potential will rise and there exists a tendency for the energy which can be taken out to become small.
- the heat treatment is performed at a temperature of 3000 ° C. or higher and in an atmosphere containing at least 50% by volume of nitrogen. This is because the manufacturing cost can be reduced by carrying out in an atmosphere close to a general atmospheric composition. More preferred is heat treatment in air.
- the nitrogen concentration measured at this time refers to the atmospheric concentration at a distance of about 20 cm from the powder inside the container containing the powder, not in the powder. Since various gases are released from the powder during the heat treatment, it is desirable to perform measurement in a region that is not affected by the gas.
- the conversion temperature is preferably 3600 ° C. or lower. Electrical energy is preferably used to achieve these temperatures. Electrical energy is expensive compared to other heat sources, and consumes extremely large electric power to achieve 2000 ° C. or more. Therefore, it is preferable not to consume electric energy other than graphitization.
- the carbon raw material Prior to graphitization, the carbon raw material is calcined and the organic volatiles are removed, that is, the fixed carbon content is 95% or more, more preferably 98% or more. More preferably, it is 99% or more.
- boron nitride for example, as disclosed in Japanese Patent No. 4945029 (Patent Document 7), a heat treatment at about 2600 to 3000 ° C. is often performed in an argon stream.
- heat treatment in an argon stream requires enormous energy because heat is discharged out of the system, and since argon is used, the cost is extremely high, which is not a practical manufacturing method.
- the boron compound may act as a graphitization catalyst.
- a large amount of boron is added.
- Japanese Patent No. 4014637 European Patent Application Publication No. 0935302
- boron is added to the carbon material after the heat treatment. 3% by mass or more is present.
- the potential of the negative electrode increases, and the energy that can be extracted as a whole battery decreases.
- the heat treatment is not limited as long as it is in the air.
- the carbon raw material is packed in a graphite crucible, and heat is generated by energizing to graphitize. It can be done by the method of.
- the removal method include a method of removing graphite material in a range from a portion in contact with the atmosphere to a predetermined depth. That is, a graphite material having a depth thereafter is obtained.
- the predetermined depth is 2 cm from the surface, more preferably 3 cm, and even more preferably 5 cm.
- the pulverization treatment is not performed after graphitization. However, it can be crushed to such an extent that the particles are not crushed after graphitization.
- the method is not particularly limited.
- the obtained carbon material and carbon fiber are mixed by a mechanochemical method using Mechanofusion (registered trademark) manufactured by Hosokawa Micron, or carbon fiber is further mixed with pulverized calcined coke and boron or a boron compound. And a method of performing graphitization treatment.
- Carbon material for battery electrodes comprises the above carbon material.
- a battery electrode having a high energy density can be obtained while maintaining high capacity, high coulomb efficiency, and high cycle characteristics.
- the carbon material for battery electrodes for example, it can be used as a negative electrode active material and a negative electrode conductivity-imparting material for lithium ion secondary batteries.
- the carbon material for battery electrodes in a preferred embodiment of the present invention only the above carbon material can be used, but spherical natural graphite or artificial graphite having d002 of 0.3370 nm or less with respect to 100 parts by mass of the carbon material.
- a compounding of 0.01 to 120 parts by mass, preferably 0.01 to 100 parts by mass can also be used.
- the mixing can be performed by appropriately selecting a mixed material according to the required battery characteristics and determining the mixing amount.
- carbon fibers can be blended with the carbon material for battery electrodes. Carbon fibers similar to those described above can be used.
- the blending amount is 0.01 to 20 parts by mass, preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the graphite material.
- Electrode paste in a preferred embodiment of the present invention comprises the battery electrode carbon material and a binder.
- This electrode paste is obtained by kneading the carbon material for battery electrodes and a binder.
- known apparatuses such as a ribbon mixer, a screw kneader, a Spartan rewinder, a ladyge mixer, a planetary mixer, and a universal mixer can be used.
- the electrode paste can be formed into a sheet shape, a pellet shape, or the like.
- binder used for the electrode paste examples include fluorine-based polymers such as polyvinylidene fluoride and polytetrafluoroethylene, and rubber-based materials such as SBR (styrene butadiene rubber).
- 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 for battery electrodes, but about 3 to 20 parts by mass is particularly preferable.
- a solvent can be used when kneading.
- the solvent include known solvents suitable for each binder, such as toluene and N-methylpyrrolidone in the case of a fluoropolymer; water in the case of SBR; and dimethylformamide and isopropanol.
- a binder using water as a solvent it is preferable to use a thickener together. The amount of the solvent is adjusted so that the viscosity is easy to apply to the current collector.
- Electrode in a preferred embodiment of the present invention is composed of a molded body of the electrode paste.
- the electrode is obtained, for example, by applying the electrode paste onto a current collector, drying, and pressure-molding.
- the current collector examples include aluminum, nickel, copper, stainless steel foil, mesh, and the like.
- the coating thickness of the paste is usually 50 to 200 ⁇ m. If the coating thickness becomes too large, the negative electrode may not be accommodated in a standardized battery container.
- the method for applying the paste is not particularly limited, and examples thereof include a method in which the paste is applied with a doctor blade or a bar coater and then molded with a roll press or the like.
- Examples of the pressure molding method include molding methods such as roll pressing and press pressing.
- the pressure during pressure molding is preferably about 1 to 3 t / cm 2 .
- the electrode density of the electrode increases, the battery capacity per volume usually increases. However, if the electrode density is too high, the cycle characteristics usually deteriorate.
- the electrode paste according to a preferred embodiment of the present invention is used, a decrease in cycle characteristics is small even when the electrode density is increased, so that an electrode having a high electrode density can be obtained.
- the maximum value of the electrode density of the electrode obtained using this electrode paste is usually 1.6 to 1.9 g / cm 3 .
- the electrode thus obtained is suitable for a negative electrode of a battery, particularly a negative electrode of a secondary battery.
- Electrode Using the electrode as a constituent element (preferably a negative electrode), a battery or a secondary battery can be used.
- a battery or a secondary battery in a preferred embodiment of the present invention will be described by taking a lithium ion secondary battery as a specific example.
- a lithium ion secondary battery has a structure in which a positive electrode and a negative electrode are immersed in an electrolytic solution or an electrolyte.
- the electrode in a preferred embodiment of the present invention is used for the negative electrode.
- a lithium-containing transition metal oxide is usually used as the positive electrode active material, preferably at least selected from Ti, V, Cr, Mn, Fe, Co, Ni, Mo and W.
- An oxide mainly containing at least one transition metal element selected from Fe, Co, and Ni and lithium and having a molar ratio of lithium to transition metal of 0.3 to 2.2 is used.
- Al, Ga, In, Ge, Sn, Pb, Sb, Bi, Si, P, B, or the like may be contained within a range of less than 30 mol% with respect to the transition metal present mainly.
- the value of x is a value before the start of charging / discharging, and increases / decreases by charging / discharging.
- the average particle size of the positive electrode active material is not particularly limited, but is preferably 0.1 to 50 ⁇ m.
- the volume of particles of 0.5 to 30 ⁇ m is preferably 95% or more. More preferably, the volume occupied by a particle group having a particle diameter of 3 ⁇ m or less is 18% or less of the total volume, and the volume occupied by a particle group of 15 ⁇ m or more and 25 ⁇ m or less is 18% or less of the total volume.
- the specific surface area is not particularly limited, but is preferably 0.01 ⁇ 50m 2 / g by BET method, particularly preferably 0.2m 2 / g ⁇ 1m 2 / g.
- the pH of the supernatant when 5 g of the positive electrode active material is dissolved in 100 ml of distilled water is preferably 7 or more and 12 or less.
- a separator may be provided between the positive electrode and the negative electrode.
- the separator include non-woven fabric, cloth, microporous film, or a combination thereof, mainly composed of polyolefin such as polyethylene and polypropylene.
- organic electrolytes As the electrolyte and electrolyte constituting the lithium ion secondary battery in a preferred embodiment of the present invention, known organic electrolytes, inorganic solid electrolytes, and polymer solid electrolytes can be used. From the viewpoint of electrical conductivity, organic electrolytes are used. preferable.
- organic electrolyte examples include diethyl ether, dibutyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethyl 5 glycol monobutyl ether, diethylene glycol dimethyl ether, ethylene glycol phenyl ether.
- Ethers such as formamide, N-methylformamide, N, N-dimethylformamide, N-ethylformamide, N, N-diethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-ethylacetamide, N, N -Diethylacetamide, N, N-dimethylpropionamide, hexamethylphosphoryl
- Amides such as sulfoxides; sulfur-containing compounds such as dimethyl sulfoxide and sulfolane; dialkyl ketones such as methyl ethyl ketone and methyl isobutyl ketone; ethylene oxide, propylene oxide, tetrahydrofuran, 2-methoxytetrahydrofuran, 1,2-dimethoxyethane, 1,3-dioxolane, etc.
- Cyclic ethers of: carbonates such as ethylene carbonate and propylene carbonate; ⁇ -butyrolactone; N-methylpyrrolidone; solutions of organic solvents such as acetonitrile and nitromethane are preferred.
- esters such as ethylene carbonate, butylene carbonate, diethyl carbonate, dimethyl carbonate, propylene carbonate, vinylene carbonate, ⁇ -butyrolactone, ethers such as dioxolane, diethyl ether, diethoxyethane, dimethyl sulfoxide, acetonitrile, tetrahydrofuran, etc.
- Particularly preferred are 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.
- 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 and the like. is there.
- 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.
- Paste preparation An aqueous solution in which styrene-butadiene rubber (SBR) fine particles having a solid content ratio of 40% are dispersed by appropriately adding 0.015 parts by weight of carboxymethyl cellulose (CMC) as a thickener and water to 1 part by weight of the carbon material to adjust the viscosity. 0.038 parts by mass was added and stirred and mixed to prepare a slurry-like dispersion having sufficient fluidity, which was used as the main agent stock solution.
- SBR styrene-butadiene rubber
- CMC carboxymethyl cellulose
- Negative electrode production The main agent stock solution was applied on a high-purity copper foil to a thickness of 150 ⁇ m using a doctor blade, and vacuum-dried at 70 ° C. for 12 hours. After punching out so that the coating area becomes 20 cm 2 , the sheet is sandwiched between super steel press plates, and the press pressure is about 1 ⁇ 10 2 to 3 ⁇ 10 2 N / mm 2 (1 ⁇ 10 3 to 3 ⁇ 10 3 kg / It pressed so that it might become cm ⁇ 2 >), and the negative electrode 1 was produced. Further, after punching out the coated portion to 16 mm ⁇ , it was pressed by the same method as that of the negative electrode 1 so that the pressing pressure was 1 ⁇ 10 2 N / mm 2 (1 ⁇ 10 3 kg / cm 3 ). 2 was produced.
- PVdF polyvinylidene fluoride
- This dispersion was applied onto an aluminum foil having a thickness of 20 ⁇ m by a roll coater so as to have a uniform thickness, dried, and then roll-pressed, and punched out so that the coating part became 20 cm 2 to obtain a positive electrode.
- Electrolyte LiPF 6 was dissolved in an amount of 1 mol / liter as an electrolyte in a mixed solution of 8 parts by mass of EC (ethylene carbonate) and 12 parts by mass of DEC (diethyl carbonate).
- the ratio of the amount of electricity at the time of the first charge / discharge that is, the result of expressing the amount of discharge electricity / the amount of charge as a percentage was defined as the first coulomb efficiency.
- the voltage at the time of discharging 50% of the amount of electricity during discharge was read.
- Measurement test of charge / discharge cycle capacity maintenance rate Tests were performed using a bipolar cell. Charging was carried out at a constant current value of 50 mA (corresponding to 2C) with an upper limit voltage of 4.15 V from the rest potential, and then charged at a cutoff current value of 1.25 mA in the CV mode. The discharge was performed at a lower limit voltage of 2.8 V and 50 mA was discharged in the CC mode. Under the above conditions, 500 cycles of charge and discharge were repeated in a constant temperature bath at 25 ° C.
- Electrode density The main agent stock solution was applied on a high-purity copper foil to a thickness of 150 ⁇ m using a doctor blade, and vacuum dried at 70 ° C. for 12 hours. This was punched to 15 mm ⁇ , the punched electrode was sandwiched with a super steel press plate, and pressed so that the press pressure was 1 ⁇ 10 2 N / mm 2 (1 ⁇ 10 3 kg / cm 3 ) with respect to the electrode, The electrode density was calculated from the electrode weight and electrode thickness.
- Example 1 Crude oil produced in Liaoningzhou, China (API28, wax content 17%, sulfur content 0.66%) is distilled at atmospheric pressure, using a sufficient amount of Y-type zeolite catalyst for heavy fraction, at 510 ° C, Fluidized bed catalytic cracking was performed under pressure. Decant oil 1 was obtained by centrifuging solids such as the catalyst until the obtained oil became clear. This oil was put into a small delayed coking process. The drum inlet temperature was maintained at 505 ° C. and the drum internal pressure was maintained at 600 kPa (6 kgf / cm 2 ) for 10 hours, and then cooled with water to obtain a black lump.
- the calcined coke 1 was observed with a polarizing microscope and subjected to image analysis. The area was accumulated from a small area of the tissue, and the area of the tissue when it was 60% of the total area was 47.4 ⁇ m 2 . In addition, among the detected particles, particles having a small aspect ratio are arranged in order, and the aspect ratio of the portion that is the 60% -th of the whole particles is 2.66.
- the calcined coke 1 was pulverized with a Hosokawa Micron bantam mill, and then coarse powder was cut using a sieve having an opening of 32 ⁇ m.
- Example 2 Bituminous coal-derived coal tar was subjected to atmospheric distillation at 320 ° C. to remove fractions below the distillation temperature. Insoluble matter was removed from the obtained tar with a softening point of 30 ° C. by filtration at 100 ° C. to obtain a viscous liquid 1. This was put into a small delayed coking process.
- the drum inlet temperature was 510 ° C. and the drum internal pressure was maintained at 500 kPa (5 kgf / cm 2 ) for 10 hours, and then cooled with water to obtain a black lump.
- FIG. 1 the polarization microscope photograph (480 micrometers x 540 micrometers) about this calcined coke 2 is shown in FIG.
- the black part is resin and the gray part is optical structure.
- This calcined coke 2 was pulverized by the same method as in Example 1, and then coarse powder was cut using a sieve having an opening of 32 ⁇ m. Next, air classification was performed with a turbo classifier TC-15N manufactured by Nissin Engineering, and powder calcined coke 2 substantially free of particles having a particle size of 1.0 ⁇ m or less was obtained.
- TC-15N manufactured by Nissin Engineering
- FIG. 2 shows a polarizing microscope photograph (480 ⁇ m ⁇ 540 ⁇ m) of the carbon material.
- the black part is resin and the gray part is optical structure.
- Example 3 Municipal crude oil (API30, wax content 2%, sulfur content 0.7%) is distilled at atmospheric pressure, using a sufficient amount of Y-type zeolite catalyst for heavy distillate at 500 ° C and atmospheric pressure Fluidized bed catalytic cracking was performed. Decant oil 2 was obtained by centrifuging solids such as the catalyst until the obtained oil became clear. This oil was put into a small delayed coking process. The drum inlet temperature was maintained at 550 ° C. and the drum internal pressure was maintained at 600 kPa (6 kgf / cm 2 ) for 10 hours, and then cooled with water to obtain a black lump.
- the results are shown in Table 1.
- the calcined coke 3 was pulverized in the same manner as in Example 1 to obtain powder calcined coke 3.
- To the obtained powder calcined coke 0.63% by mass of B 2 O 3 in terms of boron atom was added, and dry-mixing was performed for 30 minutes with a V-type mixer to obtain a mixture.
- This mixture is filled in a graphite crucible, carbonized carbon felt (2 mm) is lightly placed, put into an Atchison furnace in a state where air has been prevented from abruptly flowing, and heat treated at 3150 ° C., and then used as a sample. In order to mix well.
- an electrode was produced in the same manner as in Example 1, and cycle characteristics and the like were measured. The results are shown in Table 1.
- Comparative Example 1 The powder calcined coke 2 described in Example 2 was heat-treated at 3150 ° C. in an Atchison furnace in the same manner as in Example 1, and then mixed well for use as a sample. After measuring various physical properties of the obtained carbon material, an electrode was produced in the same manner as in Example 1, and cycle characteristics and the like were measured. The results are shown in Table 1. In this example, the electrolytic solution reacts at the active edge, the Coulomb efficiency at the first charge / discharge is small, the resistance value is high, the capacity retention rate after cycling is low, and it can be seen that it is not practical.
- Comparative Example 2 To the powder calcined coke 2 described in Example 2, 2.7% by mass of B 4 C in terms of boron atom was added, and after heat treatment at 3150 ° C. in the Atchison furnace as in Example 1, a sample was obtained. Mix well for use. After measuring various physical properties of the obtained carbon material, an electrode was produced in the same manner as in Example 1, and cycle characteristics and the like were measured. The results are shown in Table 1. In this example, since a large amount of boron nitride is generated on the surface, the resistance value is high, the cycle characteristics are deteriorated, and the potential is also increased, so that there is a problem in obtaining a battery with good characteristics. .
- Comparative Example 3 To the powder calcined coke 2 described in Example 2, 0.78% by mass of B 4 C in terms of boron atom was added and heat-treated at 2900 ° C. in an argon stream in a Kurata Giken super high temperature furnace and used as a sample Mix well to do. Table 1 shows the results obtained by measuring the various physical properties of the obtained carbon material and preparing electrodes in the same manner as in Example 1 and measuring the cycle characteristics and the like. In this example, although the generation of boron nitride on the surface is suppressed, the firing temperature is low and boron is not completely removed, and the potential is high. Moreover, since argon is used and it is very costly, it is not practical as a production.
- Comparative Example 4 Residue obtained by vacuum distillation of crude oil from the US West Coast is used as a raw material.
- the properties of this raw material are API18, Wax content 11% by mass, and sulfur content 3.5% by mass. This raw material is put into a small delayed coking process.
- the drum inlet temperature was maintained at 490 ° C. and the drum internal pressure was maintained at 200 kPa (2 kgf / cm 2 ) for 10 hours, and then cooled with water to obtain a black lump.
- Use a rotary kiln (electric heater external heat type, aluminum oxide SSA-S ⁇ 120 mm inner cylinder tube) with the outer wall temperature at the center of the inner cylinder set to 1450 ° C.
- the black lump feed amount and the inclination angle were adjusted so as to be 15 minutes, and heating was performed.
- the obtained red hot sample was cooled in a SUS container by the same method as in Example 1 to obtain a black block sample having a size of about 3 cm at maximum. This was designated as calcined coke 4.
- This calcined coke 4 was observed and image-analyzed with a polarizing microscope in the same manner as in Example 1, and the results are shown in Table 1.
- This calcined coke 4 was pulverized in the same manner as in Example 1 to obtain powder calcined coke 4.
- Comparative Example 5 The powder calcined coke 4 obtained in Comparative Example 4 was filled in a graphite crucible, and carbonized carbon felt (2 mm) was lightly placed on it, placed in an Atchison furnace while preventing air from flowing in suddenly, and heat treated at 3150 ° C. After mixing, well mixed for use as a sample. After measuring various physical properties of the obtained carbon material, an electrode was produced in the same manner as in Example 1, and cycle characteristics and the like were measured. The results are shown in Table 1. In this example, the volume capacity density of the electrodes is low, and it can be seen that there is a problem in obtaining a high-density battery.
- Comparative Example 6 After measuring various physical properties of SFG44 manufactured by Timical, electrodes were prepared in the same manner as in Example 1, and cycle characteristics and the like were measured. The results are shown in Table 1. In this example, the capacity retention rate after cycling is low, and inconvenience arises in order to obtain a long-life battery.
Abstract
Description
携帯機器用途では、電気・電子機器の小型化、軽量化、また機能の多様化に伴う消費電力の増加等により、より高いエネルギー密度を有するリチウムイオン二次電池が求められている。
これらのうち天然黒鉛は安価に入手でき、黒鉛化度が高い為放電容量や電極密度は高いが、粒子形状が鱗片状であり、大きな比表面積を有することや、反応性の高いグラファイトのエッジ面により電解液が分解され、初回充放電時のクーロン効率が非常に低い、ガスが発生する、ということが問題であった。また、サイクル特性も良くはなかった。これらを解決するため、日本国特許第3534391号公報(米国特許第6632569号、特許文献2)等では、球状に加工した天然黒鉛の表面に、カーボンをコーティングする方法が提案されている。
前記炭素材料からなる成形体断面の480μm×540μmの矩形の視野において偏光顕微鏡により光学組織を観察した場合、面積の小さな組織から面積を累積し、その累計面積が全光学組織面積の60%の面積となるときの光学組織の面積をSOPとし、アスペクト比の小さな組織から組織の数を数え組織全体の数の60%番目の組織におけるアスペクト比をAROP、レーザー回析法による体積基準の平均粒子径をD50としたとき、
1.5≦AROP≦6 および
0.2×D50≦(SOP×AROP)1/2<2×D50
の関係を有する炭素材料。
[2]レーザー回析法による体積基準の平均粒子径(D50)が1μm以上50μm以下である前記1に記載の炭素材料。
[3]3000℃以上3600℃以下の温度で、少なくとも窒素を50体積%以上含む雰囲気で熱処理された人造黒鉛である前記1または2に記載の炭素材料。
[4]BET比表面積が0.4m2/g以上5m2/g以下である前記1~3のいずれか1項に記載の炭素材料。
[5]前記1~4のいずれか1項に記載の炭素材料の製造方法であって、か焼コークスを粉砕した粒子に、ホウ素またはホウ素化合物をホウ素原子換算で0.01~2質量%混合した後、3000℃以上3600℃以下の温度で少なくとも窒素を50体積%以上含む雰囲気で熱処理をする工程を含む製造方法。
[6]前記か焼コークスが480μm×540μmの矩形の視野において偏光顕微鏡により光学組織を観察した場合、面積の小さな組織から面積を累積し、その累計面積が全光学組織面積の60%の面積となるときの光学組織の面積が10μm2以上5000μm2以下であり、かつアスペクト比の小さな組織から組織の数を数え組織全体の数の60%番目の組織におけるアスペクト比が1.5以上6以下であるか焼コークスを用いる前記5に記載の製造方法。
[7]前記1~4のいずれか1項に記載の炭素材料を含む電池電極用炭素材料。
[8]前記1~4のいずれか1項に記載の炭素材料100質量部と、天然黒鉛または人造黒鉛を0.01~200質量部含み、該天然黒鉛または該人造黒鉛の平均面間隔(d002)が0.3370nm以下である電池電極用炭素材料。
[9]前記1~4のいずれか1項に記載の炭素材料100質量部と、天然黒鉛または人造黒鉛を0.01~120質量部含み、該天然黒鉛または該人造黒鉛のアスペクト比が2~100であり、該天然黒鉛または該人造黒鉛の平均面間隔(d002)が0.3370nm以下である電池電極用炭素材料。
[10]前記7~9のいずれか1項に記載の電池電極用炭素材料とバインダーとを含む電極用ペースト。
[11]前記10に記載の電極用ペーストの成形体からなる電極。
[12]前記11に記載の電極を構成要素として含む電池。
[13]前記11に記載の電極を構成要素として含むリチウムイオン二次電池。
[14]非水系電解液及び/または非水系ポリマー電解質を含み、前記非水系電解液及び/または非水系ポリマー電解質に用いられる非水系溶媒がエ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、ブチレンカーボネート、γ-ブチロラクトン、及びビニレンカーボネートからなる群から選ばれる少なくとも1種である前記13に記載のリチウムイオン二次電池。
また、本発明の炭素材料は経済性、量産性に優れ、安全性の改善された方法により製造することができる。
充電電池の電極は、単位体積あたりにより多くの電気をためられることが要求されている。黒鉛は、初回の充放電のクーロン効率に優れるが、挿入時の炭素原子に対するリチウム原子の量論比には上限があり、質量あたりのエネルギー密度をこれ以上向上させていくことは困難である。電極のエネルギー密度の向上のためには,電極体積あたりの質量密度の向上が必要となる。このため、一般的に電池の電極として用いるためには活物質を集電板上に塗工乾燥した後、プレスを行い、体積あたりの負極活物質の充填性を向上させる。この際、黒鉛粒子が柔らかく、プレスに伴ってある程度変形すると電極密度を極めて大きくすることが可能である。
1.5≦AROP≦6 および
0.2×D50≦(SOP×AROP)1/2<2×D50
より好ましいD50は5μm以上35μm以下である。微粉は表面積が高く、目的外反応に繋がるために、より減らしたほうがよいとの観点からはD50は10μm以上であることがさらにより好ましい。大電流発生が求められる自動車等駆動電源等の用途に用いる場合にはD50は25μm以下であることが好ましい。
[偏光顕微鏡観察資料作成]
本発明における「炭素材料からなる成形体断面」は以下のようにして調製する。
内容積30cm3のプラスチック製サンプル容器の底に両面テープを貼り、その上にスパチュラ2杯ほど(2g程度)の観察用サンプルを乗せる。冷間埋込樹脂(商品名:冷間埋込樹脂#105、製造会社:ジャパンコンポジット(株)、販売会社:丸本ストルアス(株))に硬化剤(商品名:硬化剤(M剤)、製造会社:日本油脂(株)、販売会社:丸本ストルアス(株))を加え、30秒練る。得られた混合物(5ml程度)を前記サンプル容器に高さ約1cmになるまでゆっくりと流し入れ、1日静置して凝固させる。次に凝固したサンプルを取り出し、両面テープを剥がす。そして、研磨板回転式の研磨機を用いて、測定する面を研磨する。
観察は200倍で行う。偏光顕微鏡で観察した画像は、OLYMPUS製CAMEDIA C-5050 ZOOMデジタルカメラをアタッチメントで偏光顕微鏡に接続し、撮影する。シャッタータイムは1.6秒で行う。撮影データのうち、1200ピクセル×1600ピクセルの画像を解析対象とする。これは480μm×540μmの視野を検討していることに相当する。画像解析はImageJ(アメリカ国立衛生研究所製)を用いて、青色部、黄色部、赤色部、黒色部を判定した。
各色のImageJ使用時に各色を定義したパラメーターは以下の通りである。
光学組織が大きく、後述する結晶層間距離(d002)が小さく黒鉛網面の方向が揃っている炭素材料は、エッジ部が発達し易く、その部分における反応性が高くなる。そのような炭素材料を電極材料として用いると、電解液の分解反応が生じ、初回充放電時のクーロン効率が低くなる傾向がある。本発明の好ましい実施態様においては、ホウ素を含ませることにより粒子端面(エッジ部)のSP3結合を増加させ、均一に欠陥を増加させることにより、エッジ部における反応性を低くし、初回充放電時のクーロン効率が90%以上という高い値を実現することを可能としている。
ホウ素原子の含有量が上記範囲にあることにより、電極電位の上昇を抑制し、取り出せるエネルギーを大きなものとすることができる。特にホウ素原子の含有量が多くなると問題が生じやすい。
ゆるめ嵩密度が0.7g/cm3以上であることにより、電極へ塗工した際の、プレス前の電極密度をより高めることが可能となる。この値により、ロールプレス一回で十分な電極密度を得ることが可能かどうかを予測できる。また、タップ密度が上記範囲内にあることによりプレス時に到達する電極密度を充分高くすることが可能となる。
炭素繊維の量は特に限定されないが、芯材である炭素材料100質量部に対し0.1~5質量部が好ましい。
本発明の好ましい実施態様における炭素材料は、か焼コークスを粉砕した粒子に、ホウ素またはホウ素化合物を混合した後、加熱することにより製造することができる。
か焼コークスの原料としては、例えば、石油ピッチ、石炭ピッチ、石炭ピッチコークス、石油コークスおよびこれらの混合物を用いることができる。これらの中でも、特定の条件下でディレイドコーキングを行ったコークスを、不活性雰囲気で加熱したものが好ましい。
か焼前のコークスは、比較的容易に着火する。そのため、火災の防止のため含水させておく。含水させたか焼前コークスは、泥状の含水微粉が機器および周辺を汚染するなど取り扱い性に劣る。か焼により取り扱い性の点で極めて有利となる。また、か焼を行ったコークスに対して黒鉛化を行うと、結晶がより成長する。
粉砕する手法に特に制限はなく、公知のジェットミル、ハンマーミル、ローラーミル、ピンミル、振動ミル等が用いて行なうことができる。
光学組織が特定の大きさを有し、つぶれ特性が良好なか焼コークスを熱処理して黒鉛化した炭素材料は、材料を構成する粒子のエッジ部が発達している。そのため、エッジ部において電解液に対する反応性が高く、初回の充電すなわちリチウム挿入時に多くの電気量を消費するという問題があり、過剰厚みの皮膜が形成される。その結果、可逆なリチウム挿入脱離反応を阻害し、サイクル特性等、電池の寿命に悪影響を与えることになる。粉砕したか焼コークスの粒子に、特定量のホウ素又はホウ素化合物を混合した後、熱処理することにより、粒子端面(エッジ部)のSP3結合(欠陥)が増加し、それにより電解液に対する反応性が低くなり、初回充放電時のクーロン効率が良好になる。
本発明の好ましい実施態様における電池電極用炭素材料は、上記炭素材料を含んでなる。上記炭素材料を電池電極用炭素材料として用いると、高容量、高クーロン効率、高サイクル特性を維持したまま、高エネルギー密度の電池電極を得ることができる。
本発明の好ましい実施態様における電極用ペーストは、前記電池電極用炭素材料とバインダーとを含んでなる。この電極用ペーストは、前記電池電極用炭素材料とバインダーとを混練することによって得られる。混錬には、リボンミキサー、スクリュー型ニーダー、スパルタンリューザー、レディゲミキサー、プラネタリーミキサー、万能ミキサー等公知の装置が使用できる。電極用ペーストは、シート状、ペレット状等の形状に成形することができる。
本発明の好ましい実施態様における電極は前記電極用ペーストの成形体からなるものである。電極は例えば前記電極用ペーストを集電体上に塗布し、乾燥し、加圧成形することによって得られる。
前記電極を構成要素(好ましくは負極)として、電池または二次電池とすることができる。
なお、実施例及び比較例の炭素材料についての、光学組織に関する観察及びデータ解析、X線回折法による平均面間隔(d002)、平均粒子径(D50)、BET法による比表面積は、本明細書の「発明を実施するための形態」に詳述した方法により測定する。また、その他の物性の測定方法は以下の通り。
試料数十mgを秤量し、マイクロウェーブ専用PTFE(ポリテトラフルオロエチレン)製分解容器に入れ、リン酸、硝酸、硫酸を順に添加し、マイクロウェーブ加熱分解装置にて処理し完全に溶解させた。その後、室温まで放冷し、超純水にて50mlポリ容器へ洗い移し定容を行い、更にその溶液を10倍希釈し、ICP-AES装置にてICP発光分析法により定量を行った。
a)ペースト作製:
炭素材料1質量部に増粘剤としてカルボキシメチルセルロース(CMC)0.015質量部および水を適宜加えて粘度を調節し、固形分比40%のスチレン-ブタジエンゴム(SBR)微粒子の分散した水溶液0.038質量部を加え攪拌・混合し、充分な流動性を有するスラリー状の分散液を作製し、主剤原液とした。
主剤原液を高純度銅箔上でドクターブレードを用いて150μm厚に塗布し、70℃で12時間真空乾燥した。塗布部が20cm2となるように打ち抜いた後、超鋼製プレス板で挟み、プレス圧が約1×102~3×102N/mm2(1×103~3×103kg/cm2)となるようにプレスし、負極1を作製した。また、前記の塗布部を16mmφに打ち抜いた後、負極1と同様の方法で、プレス圧が1×102N/mm2(1×103kg/cm3)となるようにプレスし、負極2を作製した。
Li3Ni1/3Mn1/3Co1/3O290g、導電助剤としてのカーボンブラック(TIMCAL社製、C45)5g、バインダーとしてのポリフッ化ビニリデン(PVdF)5gをN-メチル-ピロリドンを適宜加えながら攪拌・混合し、スラリー状の分散液を作製した。
この分散液を厚み20μmのアルミ箔上に厚さが均一となるようにロールコーターにより塗布し、乾燥後、ロールプレスを行い、塗布部が20cm2となるように打ち抜き、正極を得た。
[二極セル]
上記負極1、正極に対し、それぞれAl箔にAlタブ、Cu箔にNiタブをとりつける。ポリプロピレン製フィルム微多孔膜を介してこれらを対向させ積層、アルミラミネートによりパックし電解液を注液後、開口部を熱融着により封止し、電池を作製した。
[対極リチウムセル]
ポリプロピレン製のねじ込み式フタつきのセル(内径約18mm)内において、上記負極2と16mmφに打ち抜いた金属リチウム箔をセパレーター(ポリプロピレン製マイクロポーラスフィルム(セルガード(登録商標)2400))で挟み込んで積層し、電解液を加えて試験用セルとした。
EC(エチレンカーボネート)8質量部及びDEC(ジエチルカーボネート)12質量部の混合液に、電解質としてLiPF6を1モル/リットル溶解した。
対極リチウムセルを用いて試験を行った。レストポテンシャルから0.002Vまで0.2mAでCC(コンスタントカレント:定電流)充電を行った。次に0.002VでCV(コンスタントボルト:定電圧)充電に切り替え、カットオフ電流値25.4μAで充電を行った。
上限電圧1.5VとしてCCモードで0.2mAで放電を行った。
試験は25℃に設定した恒温槽内行った。この際、初回放電時の容量を放電容量とした。また初回充放電時の電気量の比率、すなわち放電電気量/充電電気量を百分率で表した結果を初回クーロン効率とした。さらに、放電中、放電容量の50%の電気量を放電した際の電圧を読み取った。
二極セルを用いて試験を行った。充電はレストポテンシャルから上限電圧を4.15Vとして定電流値50mA(2C相当)でCCモード充電を行ったのち、CVモードでカットオフ電流値1.25mAで充電を行った。
放電は下限電圧2.8Vとして、CCモードで50mAの放電を行った。
上記条件で、25℃の恒温槽中で500サイクル充放電を繰り返した。
初期電池容量で得られた電池容量(1C=25mAh)を基準として、満充電状態から3時間30分0.1CのCC放電をし(SOC50%)、30分休止後、25mAを5秒放電することによって、電圧降下量からオームの法則(R=ΔV/0.025)により電池内抵抗(DC-IR)を測定した。
主剤原液を高純度銅箔上でドクターブレードを用いて150μm厚に塗布し、70℃で12時間真空乾燥した。これを15mmφに打ち抜き、打ち抜いた電極を超鋼製プレス版ではさみ、プレス圧が電極に対して1×102N/mm2(1×103kg/cm3)となるようにプレスし、電極重量と電極厚みから電極密度を算出した。
中国遼寧省産原油(API28、ワックス含有率17%、硫黄分0.66%)を常圧蒸留し、重質溜分に対して、十分な量のY型ゼオライト触媒を用い、510℃、常圧で流動床接触分解を行った。得られたオイルが澄明となるまで触媒等の固形分を遠心分離し、デカントオイル1を得た。このオイルを小型ディレイドコーキングプロセスに投入した。ドラム入り口温度は505℃、ドラム内圧は600kPa(6kgf/cm2)に10時間維持した後、水冷して黒色塊を得た。得られた黒色塊を最大5cm程度になるように金槌で粉砕した後、内筒中心部外壁温度を1450℃に設定したロータリーキルン(電気ヒーター外熱式、酸化アルミニウムSSA-Sφ 120mm内筒管)を用い、滞留時間が15分となるように黒色塊のフィード量および傾斜角を調整し、加熱を行った。
得られた赤熱サンプルは、SUS容器中で外部を水冷しながら、外気から遮断し、容器内部が負圧にならないように必要量の窒素を供給しながら冷却を行った。黒色で、若干灰色を帯びた最大2cm程度の大きさを持つ塊状サンプルを得た。これをか焼コークス1とした。
か焼コークス1を偏光顕微鏡により観察および画像解析を行い、小さい面積の組織から面積を累積し、総面積の60%となるときの組織の面積を測定したところ、47.4μm2であった。また、検出された粒子のうち、アスペクト比が小さな粒子のものから並べていき、粒子全体の60%番目になった部分のアスペクト比は2.66であった。
このか焼コークス1をホソカワミクロン製バンタムミルで粉砕し、その後32μmの目開きの篩を用いて粗粉をカットした。次に、日清エンジニアリング製ターボクラシファイアーTC-15Nで気流分級し、粒径が1.0μm以下の粒子を実質的に含まない粉末か焼コークス1を得た。
得られた粉末か焼コークス1に対し、ホウ素原子換算で0.78質量%のB4Cを添加し、V型混合機で30分間乾式混合を行い、混合物を得た。
この粉砕された炭素材料を黒鉛るつぼに充填し、炭化したカーボンフェルト(2mm)を軽く載せ、空気が急激に流入することを防いだ。これをアチソン炉において3150℃で熱処理を行った後、試料として使用するためによく混合を行った。
得られた試料について各種物性を測定後、上記のように電極を作製し、サイクル特性等を測定した。結果を表1に示す。
瀝青炭由来コールタールを320℃で常圧蒸留し、蒸留温度以下の留分を除去した。得られた軟化点30℃のタールから、100℃でろ過することにより不溶分を除去して、粘調の液体1を得た。これを小型ディレイドコーキングプロセスに投入した。ドラム入り口温度は510℃、ドラム内圧は500kPa(5kgf/cm2)に10時間維持した後、水冷して黒色塊を得た。得られた黒色塊を最大5cm下程度になるように金槌で粉砕した後、内筒中心部外壁温度を1450℃に設定したロータリーキルン(電気ヒーター外熱式、酸化アルミニウムSSA-Sφ 120mm内筒管)を用い、滞留時間が15分となるように黒色塊のフィード量および傾斜角を調整し、加熱を行った。
得られた赤熱サンプルは、実施例1と同様な手法によりSUS容器中で冷却し、黒色で、最大3cm程度の大きさを持つ塊状サンプルを得た。これをか焼コークス2とした。
このか焼コークス2を実施例1と同様に偏光顕微鏡により観察および画像解析を行い、結果を表1に示す。
また、このか焼コークス2についての偏光顕微鏡写真(480μm×540μm)を図1に示す。黒い部分が樹脂であり、灰色の部分が光学組織である。
このか焼コークス2を実施例1と同様な手法により粉砕し、その後32μmの目開きの篩を用いて粗粉をカットした。次に、日清エンジニアリング製ターボクラシファイアーTC-15Nで気流分級し、粒径が1.0μm以下の粒子を実質的に含まない粉末か焼コークス2を得た。
得られた粉末か焼コークス2に対し、ホウ素原子換算で0.78質量%のB4Cを添加し、V型混合機で30分間乾式混合を行い、混合物を得た。
この混合物を黒鉛坩堝に充填し、炭化したカーボンフェルト(2mm)を軽く乗せ、空気が急激に流入することを防いだ。これをアチソン炉において3150℃で熱処理を行った後、試料として使用するためにV型混合機で30分混合を行った。
得られた炭素材料について各種物性を測定後、実施例1と同様に電極を作製し、サイクル特性等を測定した。結果を表1に示す。
また、その炭素材料についての偏光顕微鏡写真(480μm×540μm)を図2に示す。黒い部分が樹脂であり、灰色の部分が光学組織である。
イラン産原油(API30、ワックス含有率2%、硫黄分0.7%)を常圧蒸留し、重質溜分に対して、十分な量のY型ゼオライト触媒を用い、500℃、常圧で流動床接触分解を行った。得られたオイルが澄明となるまで触媒等の固形分を遠心分離し、デカントオイル2を得た。このオイルを小型ディレイドコーキングプロセスに投入した。ドラム入り口温度は550℃、ドラム内圧は600kPa(6kgf/cm2)に10時間維持した後、水冷して黒色塊を得た。得られた黒色塊を最大5cm下程度になるように金槌で粉砕した後、内筒中心部外壁温度を1450℃に設定したロータリーキルン(電気ヒーター外熱式、酸化アルミニウムSSA-Sφ 120mm内筒管)を用い、滞留時間が15分となるように黒色塊のフィード量および傾斜角を調整し、加熱を行った。
得られた赤熱サンプルは、実施例1と同様の手法によりSUS容器中で冷却し、灰色を帯びた黒色で、最大2cm程度の大きさを持つ塊状サンプルを得た。これをか焼コークス3とした。
このか焼コークス3に対して、実施例1と同様に偏光顕微鏡により観察および画像解析を行った。結果を表1に示す。
このか焼コークス3を実施例1と同様な手法により粉砕し、粉末か焼コークス3を得た。得られた粉末か焼コークスに対し、ホウ素原子換算で0.63質量%のB2O3を添加し、V型混合機で30分間乾式混合を行い、混合物を得た。
この混合物を黒鉛るつぼに充填し、炭化したカーボンフェルト(2mm)を軽く載せ、空気が急激に流入することを防いだ状態でアチソン炉に入れ、3150℃で熱処理を行った後、試料として使用するためによく混合を行った。
得られた炭素材料について各種物性を測定後、実施例1と同様に電極を作製し、サイクル特性等を測定した。結果を表1に示す。
実施例2記載の粉末か焼コークス2を実施例1と同様にアチソン炉で3150℃で熱処理を行った後、試料として使用するためによく混合を行った。
得られた炭素材料について各種物性を測定後、実施例1と同様に電極を作製し、サイクル特性等を測定した。結果を表1に示す。
本例においては、活性なエッジにおいて電解液が反応し、初回充放電時のクーロン効率が小さくなっており、抵抗値が高く、サイクル後容量維持率も低く、実用に耐えないことが分かる。
実施例2記載の粉末か焼コークス2に対し、ホウ素原子換算で2.7質量%のB4Cを添加し、実施例1と同様にアチソン炉で3150℃で熱処理を行った後、試料として使用するためによく混合を行った。
得られた炭素材料について各種物性を測定後、実施例1と同様に電極を作製し、サイクル特性等を測定した。結果を表1に示す。
本例においては表面に窒化ホウ素が多量に生成することにより抵抗値が高く、またサイクル特性が悪化しており、更に電位も上昇しているため、特性の良い電池を得るためには不都合が生じる。
実施例2記載の粉末か焼コークス2に対し、ホウ素原子換算で0.78質量%のB4Cを添加し、倉田技研製超高温炉においてアルゴン気流中、2900℃で熱処理し、試料として使用するためによく混合を行った。
得られた炭素材料について各種物性を測定後、実施例1と同様に電極を作製し、サイクル特性等を測定した結果を表1に示す。
本例においては、表面の窒化ホウ素の生成は抑えられているものの、焼成温度が低くホウ素が抜けきっておらず、電位が高くなっている。また、アルゴンを使用しており非常にコストがかかるため、製造として現実的ではない。
アメリカ西海岸産原油を減圧蒸留した残渣を原料とする。本原料の性状は、API18、Wax分11質量%、硫黄分は3.5質量%である。この原料を、小型ディレイドコーキングプロセスに投入する。ドラム入り口温度は490℃、ドラム内圧は200kPa(2kgf/cm2)に10時間維持した後、水冷して黒色塊を得た。最大5cm下程度になるように金槌で粉砕した後、内筒中心部外壁温度を1450℃に設定したロータリーキルン(電気ヒーター外熱式、酸化アルミニウムSSA-Sφ 120mm内筒管)を用い、滞留時間が15分となるように黒色塊のフィード量および傾斜角を調整し、加熱を行った。
得られた赤熱サンプルは、実施例1と同様な手法によりSUS容器中で冷却し、黒色で、最大3cm程度の大きさを持つ塊状サンプルを得た。これをか焼コークス4とした。
このか焼コークス4を実施例1と同様に偏光顕微鏡により観察および画像解析を行い、結果を表1に示す。
このか焼コークス4を実施例1と同様な手法により粉砕し、粉末か焼コークス4を得た。得られた粉末か焼コークスに対し、ホウ素原子換算で0.78質量%のB4Cを添加し、V型混合機で30分間乾式混合を行い、混合物を得た。
この混合物を黒鉛るつぼに充填し、炭化したカーボンフェルト(2mm)を軽く載せ、空気が急激に流入することを防いだ状態でアチソン炉に入れ、3150℃で熱処理を行った後、試料として使用するためによく混合を行った。
得られた炭素材料について各種物性を測定後、実施例1と同様に電極を作製し、サイクル特性等を測定した。結果を表1に示す。
本例においては、電極の体積容量密度が低く、高密度の電池を得るためには不都合が生じていることがわかる。
比較例4で得た粉末か焼コークス4を黒鉛るつぼに充填し、炭化したカーボンフェルト(2mm)を軽く載せ、空気が急激に流入することを防いだ状態でアチソン炉に入れ、3150℃で熱処理を行った後、試料として使用するためによく混合を行った。
得られた炭素材料について各種物性を測定後、実施例1と同様に電極を作製し、サイクル特性等を測定した。結果を表1に示す。
本例においては、電極の体積容量密度が低く、高密度の電池を得るためには不都合が生じていることがわかる。
ティミカル社製SFG44について各種物性を測定後、実施例1と同様に電極を作製し、サイクル特性等を測定した。結果を表1に示す。
本例においては、サイクル後容量維持率が低く、高寿命の電池を得るためには不都合が生じる。
Claims (14)
- ホウ素原子を0.001~0.5質量%含み、X線回折法による(002)面の平均面間隔(d002)が0.337nm以下である炭素材料であって、
前記炭素材料からなる成形体断面の480μm×540μmの矩形の視野において偏光顕微鏡により光学組織を観察した場合、面積の小さな組織から面積を累積し、その累計面積が全光学組織面積の60%の面積となるときの光学組織の面積をSOPとし、アスペクト比の小さな組織から組織の数を数え組織全体の数の60%番目の組織におけるアスペクト比をAROP、レーザー回析法による体積基準の平均粒子径をD50としたとき、
1.5≦AROP≦6 および
0.2×D50≦(SOP×AROP)1/2<2×D50
の関係を有する炭素材料。 - レーザー回析法による体積基準の平均粒子径(D50)が1μm以上50μm以下である請求項1に記載の炭素材料。
- 3000℃以上3600℃以下の温度で、少なくとも窒素を50体積%以上含む雰囲気で熱処理された人造黒鉛である請求項1または2に記載の炭素材料。
- BET比表面積が0.4m2/g以上5m2/g以下である請求項1~3のいずれか1項に記載の炭素材料。
- 請求項1~4のいずれか1項に記載の炭素材料の製造方法であって、か焼コークスを粉砕した粒子に、ホウ素またはホウ素化合物をホウ素原子換算で0.01~2質量%混合した後、3000℃以上3600℃以下の温度で少なくとも窒素を50体積%以上含む雰囲気で熱処理をする工程を含む製造方法。
- 前記か焼コークスが480μm×540μmの矩形の視野において偏光顕微鏡により光学組織を観察した場合、面積の小さな組織から面積を累積し、その累計面積が全光学組織面積の60%の面積となるときの光学組織の面積が10μm2以上5000μm2以下であり、かつアスペクト比の小さな組織から組織の数を数え組織全体の数の60%番目の組織におけるアスペクト比が1.5以上6以下であるか焼コークスを用いる請求項5に記載の製造方法。
- 請求項1~4のいずれか1項に記載の炭素材料を含む電池電極用炭素材料。
- 請求項1~4のいずれか1項に記載の炭素材料100質量部と、天然黒鉛または人造黒鉛を0.01~200質量部含み、該天然黒鉛または該人造黒鉛の平均面間隔(d002)が0.3370nm以下である電池電極用炭素材料。
- 請求項1~4のいずれか1項に記載の炭素材料100質量部と、天然黒鉛または人造黒鉛を0.01~120質量部含み、該天然黒鉛または該人造黒鉛のアスペクト比が2~100であり、該天然黒鉛または該人造黒鉛の平均面間隔(d002)が0.3370nm以下である電池電極用炭素材料。
- 請求項7~9のいずれか1項に記載の電池電極用炭素材料とバインダーとを含む電極用ペースト。
- 請求項10に記載の電極用ペーストの成形体からなる電極。
- 請求項11に記載の電極を構成要素として含む電池。
- 請求項11に記載の電極を構成要素として含むリチウムイオン二次電池。
- 非水系電解液及び/または非水系ポリマー電解質を含み、前記非水系電解液及び/または非水系ポリマー電解質に用いられる非水系溶媒がエ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、ブチレンカーボネート、γ-ブチロラクトン、及びビニレンカーボネートからなる群から選ばれる少なくとも1種である請求項13に記載のリチウムイオン二次電池。
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CN201380053273.6A CN104718158B (zh) | 2012-10-12 | 2013-10-11 | 碳材料、电池电极用碳材料以及电池 |
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WO2015016182A1 (ja) * | 2013-07-29 | 2015-02-05 | 昭和電工株式会社 | 炭素材料、電池電極用材料、及び電池 |
KR20160145678A (ko) | 2014-05-30 | 2016-12-20 | 쇼와 덴코 가부시키가이샤 | 탄소재료, 그 제조 방법 및 그 용도 |
JPWO2015019994A1 (ja) * | 2013-08-05 | 2017-03-02 | 昭和電工株式会社 | リチウムイオン電池用負極材及びその用途 |
KR20170100606A (ko) | 2015-02-09 | 2017-09-04 | 쇼와 덴코 가부시키가이샤 | 탄소 재료, 그 제조방법 및 그 용도 |
JP2018195560A (ja) * | 2017-05-16 | 2018-12-06 | パナソニックIpマネジメント株式会社 | 非水二次電池用負極活物質、及び、非水二次電池 |
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WO2017129774A1 (de) | 2016-01-29 | 2017-08-03 | Sgl Carbon Se | Katalytisch wirksame additive für petrolstaemmige oder kohlestaemmige kokse |
US11680013B2 (en) * | 2019-05-13 | 2023-06-20 | Carmeuse Lime, Inc. | Calciner using recirculated gases |
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US9406936B2 (en) | 2016-08-02 |
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