WO2016140368A1 - 非水電解質二次電池用混合負極材料の製造方法及びその製造方法によって得られる非水電解質二次電池用混合負極材料 - Google Patents
非水電解質二次電池用混合負極材料の製造方法及びその製造方法によって得られる非水電解質二次電池用混合負極材料 Download PDFInfo
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- WO2016140368A1 WO2016140368A1 PCT/JP2016/057037 JP2016057037W WO2016140368A1 WO 2016140368 A1 WO2016140368 A1 WO 2016140368A1 JP 2016057037 W JP2016057037 W JP 2016057037W WO 2016140368 A1 WO2016140368 A1 WO 2016140368A1
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- carbonaceous material
- graphitizable
- negative electrode
- electrolyte secondary
- secondary battery
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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
- 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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- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
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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
- H01M4/362—Composites
- H01M4/364—Composites as mixtures
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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
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/77—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by unit-cell parameters, atom positions or structure diagrams
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/80—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70
- C01P2002/82—Crystal-structural characteristics defined by measured data other than those specified in group C01P2002/70 by IR- or Raman-data
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/12—Surface area
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/40—Electric properties
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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
Definitions
- the present invention relates to a method for producing a mixed negative electrode material for a nonaqueous electrolyte secondary battery and a mixed negative electrode material for a nonaqueous electrolyte secondary battery obtained by the method.
- a nonaqueous electrolyte secondary battery having high energy density and excellent input / output characteristics can be provided.
- Patent Document 1 a non-aqueous solvent type lithium secondary battery using a carbonaceous material as a negative electrode.
- a lithium ion secondary battery that is a non-aqueous solvent type lithium secondary battery is widely used as a secondary battery having a high energy density, and in order to extend the cruising distance in one charge in EV applications, High energy density and improved input / output characteristics are expected.
- the present inventors have earnestly researched a non-aqueous electrolyte secondary battery having a high energy density and excellent input / output characteristics, and obtained a non-graphitizable carbonaceous material and a graphitizable carbonaceous material and / or a graphite. It has been found that a nonaqueous electrolyte secondary battery exhibiting excellent input / output characteristics can be obtained by using a carbonaceous material mixed with materials. That is, the non-graphitizable carbonaceous material and the carbonaceous material obtained by mixing the easily graphitizable carbonaceous material and / or the graphite material have a high average true density.
- an object of the present invention is to provide a non-aqueous electrolyte secondary battery having high energy density and excellent input / output characteristics in a non-aqueous electrolyte secondary battery using a mixed carbonaceous material.
- the present inventors have found that the increase in the irreversible capacity and the increase in direct current resistance (DC-R) result in moisture absorption during storage of the hardly graphitic material contained in the mixed carbonaceous material. I found out that it was the cause.
- the present inventors have further researched and surprisingly found that the non-graphitizable carbonaceous material obtained by a specific production method has low moisture absorption (Japanese Patent Application No. 2014-039741). And Japanese Patent Application No. 2014-039742).
- the mixed negative electrode material obtained by mixing the non-graphitizable carbonaceous material that absorbs moisture with the graphitizable carbonaceous material and / or the graphite material has an increased DC resistance value.
- the hardly graphitizable carbonaceous material that has absorbed moisture imposes a burden on the easily graphitizable carbonaceous material and / or the graphite material in which Li metal is likely to precipitate.
- the mixed negative electrode material obtained by mixing the non-graphitizable carbonaceous material having low hygroscopicity found by the present inventors with the graphitizable carbonaceous material and / or the graphitic material has a low DC resistance value. And found to have excellent energy density and input / output characteristics.
- the present invention [1] (1) A step of baking a non-graphitizable carbon precursor and a volatile organic substance in an inert gas atmosphere at 800 to 1400 ° C.
- a method for producing a mixed negative electrode material for a non-aqueous electrolyte secondary battery comprising a step of mixing a graphitizable carbonaceous material with an easily graphitizable carbonaceous material and / or a graphite material, and comprising a wide-angle X-ray diffraction is calculated using the Bragg equation at law, it is in the average spacing d 002 in the range of 0.38 ⁇ 0.40 nm in (002) plane of the flame graphitizable carbonaceous material, determined by nitrogen adsorption BET3 point method
- the non-graphitizable carbonaceous material has a specific surface area in the range of 1 to 10 m 2 / g, and the half-width of the peak near 1360 cm ⁇ 1 of the non-graphitizable carbon precursor observed in the Raman spectrum.
- the non-graphitizable carbonaceous material 1360cm difference between the value of the half width of the peak in the vicinity of -1 is 50 ⁇ 84cm -1
- the non-aqueous method for producing electrolyte secondary battery mixing a negative electrode material of charges [2] the value of the half width of the peak around 1360 cm -1 of the flame graphitizable carbonaceous material to be observed in the Raman spectra is in the range of 175 ⁇ 190 cm -1, the non-aqueous electrolyte according to [1] Manufacturing method of mixed negative electrode material for secondary battery, [3]
- the half-value width of the peak near 1360 cm ⁇ 1 of the non-graphitizable carbon precursor observed in the Raman spectrum is in the range of 230 to 260 cm ⁇ 1 .
- a method for producing a mixed negative electrode material for a nonaqueous electrolyte secondary battery [4] (1) A mixture of a non-graphitizable carbon precursor having a specific surface area of 100 to 500 m 2 / g and a volatile organic substance is fired in an inert gas atmosphere at 800 to 1400 ° C. A mixed negative electrode material for a nonaqueous electrolyte secondary battery, comprising: a step of obtaining a material; and (2) a step of mixing the non-graphitizable carbonaceous material with the graphitizable carbonaceous material and / or the graphite material.
- a mixed negative electrode material for a non-aqueous electrolyte secondary battery including a non-graphitizable carbonaceous material and an easily graphitizable carbonaceous material and / or a graphite material, wherein the Bragg formula is expressed by a wide-angle X-ray diffraction method.
- the non-graphitizable carbonaceous material having an average interplanar spacing d 002 of (002) plane in the range of 0.38 to 0.40 nm and calculated by the nitrogen adsorption BET three-point method.
- the half-width value of the peak around 1360 cm ⁇ 1 of the carbon precursor of the non-graphitizable carbonaceous material observed in the Raman spectrum wherein the specific surface area of the carbonaceous material is in the range of 1 to 10 m 2 / g; , wherein the flame difference between the value of the half width of the peak around 1360 cm -1 of the graphitizable carbonaceous material is 50 ⁇ 84cm -1, for a non-aqueous electrolyte secondary battery mixing a negative electrode material, [12]
- the nonaqueous electrolyte according to [11], wherein the half-value width of the peak near 1360 cm ⁇ 1 of the non-graphitizable carbonaceous material observed in the Raman spectrum is in the range of 175 to 190 cm ⁇ 1.
- the half-value width of the peak near 1360 cm ⁇ 1 of the carbon precursor of the non-graphitizable carbonaceous material observed in the Raman spectrum is in the range of 230 to 260 cm ⁇ 1 [11] or [ [12]
- the non-aqueous electrolyte secondary battery using the mixed negative electrode material of the present invention is after storage as compared with a non-aqueous electrolyte secondary battery using a mixed negative electrode material containing a conventional non-graphitizable carbonaceous material.
- the irreversible capacity is small and therefore the DC resistance value is low. That is, the nonaqueous electrolyte secondary battery using the mixed negative electrode material of the present invention exhibits excellent energy density and input / output characteristics.
- the mixed negative electrode material of the present invention has excellent storage characteristics, and the increase in irreversible capacity even when a secondary battery is manufactured after storage in powder or storage after electrode preparation. No increase in DC resistance is observed.
- the mixed negative electrode material of the present invention can reduce the burden on the graphitizable carbonaceous material and / or the graphitic material in which Li metal is likely to precipitate.
- the energy density and input-output characteristic which were excellent compared with the nonaqueous electrolyte secondary battery containing the negative electrode using only a non-graphitizable carbonaceous material are shown.
- it exhibits excellent cycle characteristics as compared with a non-aqueous electrolyte secondary battery including a negative electrode using only a graphitizable carbonaceous material or a graphite material.
- Method for producing mixed negative electrode material for nonaqueous electrolyte secondary battery comprises (1) a non-graphitizable carbon precursor and a volatile organic substance.
- a step of obtaining a non-graphitizable carbonaceous material by firing in an inert gas atmosphere at 800 to 1400 ° C. and (2) the non-graphitizable carbonaceous material, the graphitizable carbonaceous material and / or graphite.
- a non-graphitizable carbonaceous material calculated using the Bragg equation in a wide-angle X-ray diffraction method.
- the average surface distance d 002 of the (002) plane is in the range of 0.38 to 0.40 nm, and the specific surface area of the non-graphitizable carbonaceous material determined by the nitrogen adsorption BET three-point method is 1 to 10 m 2 / g.
- the method for producing a mixed negative electrode material for a non-aqueous electrolyte secondary battery comprises (1) a mixture of a non-graphitizable carbon precursor having a specific surface area of 100 to 500 m 2 / g and a volatile organic substance, 800 to 1400.
- a step of obtaining a non-graphitizable carbonaceous material by firing in an inert gas atmosphere at 0 ° C. and (2) the non-graphitizable carbonaceous material, the graphitizable carbonaceous material and / or the graphitic material, (Hereinafter, may be referred to as “a method for producing a mixed negative electrode material for a nonaqueous electrolyte secondary battery (B)” of the present invention).
- the manufacturing method (A) of the mixed negative electrode material for nonaqueous electrolyte secondary batteries is demonstrated
- the manufacturing method (B) of the mixed negative electrode material for nonaqueous electrolyte secondary batteries is demonstrated.
- Non-graphitizable carbon precursor is a precursor of a non-graphitizable carbonaceous material that supplies a carbon component when producing a non-graphitizable carbonaceous material. Can be used as a raw material.
- char generally indicates a powder-like solid rich in carbon that is not melt-softened, which is obtained when coal is heated, but here it is rich in carbon that is not melt-softened obtained by heating organic matter. Also shown is a powdered solid.
- plant raw material for char derived from plants
- plant raw material For example, coconut husks, coconut beans, tea leaves, sugar cane, fruits (for example, mandarin oranges, bananas), cocoons, shells, hardwoods, conifers, and bamboo can be exemplified.
- waste for example, used tea leaves
- part of plant materials for example, bananas and tangerine peels.
- coconut shells that are easily available in large quantities are preferred.
- the coconut shell is not particularly limited, and examples thereof include palm palm (coconut palm), coconut palm, salak, and palm palm. These coconut shells can be used alone or in combination.
- Palm palm and palm palm coconut shells which are biomass wastes used as foods, detergent raw materials, biodiesel oil raw materials and the like and generated in large quantities, are particularly preferable.
- the method for producing char from the plant raw material is not particularly limited.
- the plant raw material is heat-treated (hereinafter sometimes referred to as “temporary firing”) in an inert gas atmosphere of 300 ° C. or higher.
- temporary firing in an inert gas atmosphere of 300 ° C. or higher.
- char eg, coconut shell char
- the non-graphitizable carbonaceous material produced from plant-derived char can be doped with a large amount of active material, and thus is basically suitable as a negative electrode material for non-aqueous electrolyte secondary batteries.
- plant-derived char contains a large amount of metal elements contained in plants.
- coconut shell char contains about 0.3% potassium and about 0.1% iron element. If such a non-graphitizable carbonaceous material containing a lot of metal elements is used as the negative electrode, it may adversely affect the electrochemical characteristics and safety of the non-aqueous electrolyte secondary battery.
- the plant-derived char also contains alkali metals other than potassium (for example, sodium), alkaline earth metals (for example, magnesium, calcium), transition metals (for example, iron, copper), and other metals. If the non-graphitizable carbonaceous material contains these metals, impurities will elute into the electrolyte during de-doping from the negative electrode of the non-aqueous electrolyte secondary battery, adversely affecting the battery performance and improving safety. There is a possibility of harm.
- alkali metals other than potassium for example, sodium
- alkaline earth metals for example, magnesium, calcium
- transition metals for example, iron, copper
- the deashing method is not particularly limited.
- a method (liquid phase deashing) in which a metal component is extracted and deashed using acid water containing a mineral acid such as hydrochloric acid or sulfuric acid, or an organic acid such as acetic acid or formic acid, hydrogen chloride A method of deashing by exposing to a high temperature gas phase containing a halogen compound such as (gas phase deashing) can be used.
- gas phase deashing that is preferable in that no drying process is required after deashing will be described below.
- halogen compound is not particularly limited, and examples thereof include fluorine, chlorine, bromine, iodine, hydrogen fluoride, hydrogen chloride, hydrogen bromide, chlorine fluoride (ClF), iodine chloride (ICl), iodine bromide (IBr), and chloride. Examples include bromine (BrCl). A compound that generates these halogen compounds by thermal decomposition, or a mixture thereof can also be used. Hydrogen chloride is preferred.
- Vapor phase deashing may be used by mixing a halogen compound and an inert gas.
- the inert gas is not particularly limited as long as it is a gas that does not react with the carbon component constituting the plant-derived char.
- nitrogen, helium, argon, krypton, or a mixed gas thereof can be given. Nitrogen is preferred.
- the mixing ratio of the halogen compound and the inert gas is not limited as long as sufficient deashing can be achieved.
- the amount of the halogen compound with respect to the inert gas is 0.01 to 10%. It is 0.0 volume%, preferably 0.05 to 8.0 volume%, more preferably 0.1 to 5.0 volume%.
- the temperature of the vapor phase demineralization is preferably changed according to the plant-derived char which is the object of demineralization, for example, 500 to 950 ° C., preferably 600 to 940 ° C., more preferably 650 to 940 ° C., and still more preferably. It can be carried out at 850-930 ° C.
- the deashing temperature is too low, the deashing efficiency is lowered and the deashing may not be sufficiently performed. If the deashing temperature is too high, activation by a halogen compound may occur.
- the time for vapor phase demineralization is not particularly limited, but is, for example, 5 to 300 minutes, preferably 10 to 200 minutes, and more preferably 20 to 150 minutes.
- the vapor phase decalcification in the production method of the present invention is to remove potassium, iron and the like contained in plant-derived char.
- the potassium content contained in the non-graphitizable carbon precursor obtained after the vapor phase deashing treatment is preferably 0.1% by weight or less, more preferably 0.05% by weight or less, and further preferably 0.03% by weight or less.
- the iron content contained in the non-graphitizable carbon precursor obtained after the vapor phase deashing treatment is preferably 0.02% by weight or less, more preferably 0.015% by weight or less, and still more preferably 0.01% by weight or less. .
- the dedoping capacity may be reduced in the nonaqueous electrolyte secondary battery using the obtained non-graphitizable carbonaceous material. Also, the undedoped capacity may increase. Furthermore, a short circuit may occur when these metal elements are eluted and re-deposited in the electrolytic solution, which may cause a serious problem in the safety of the nonaqueous electrolyte secondary battery.
- the particle diameter of the plant-derived char that is subject to vapor phase demineralization is not particularly limited. However, if the particle diameter is too small, the gas phase containing removed potassium and the like and the plant-derived char Since it may be difficult to separate, the lower limit of the average particle diameter is preferably 100 ⁇ m or more, more preferably 300 ⁇ m or more, and even more preferably 500 ⁇ m or more. Further, the upper limit of the average particle diameter is preferably 10,000 ⁇ m or less, more preferably 8000 ⁇ m or less, and still more preferably 5000 ⁇ m or less.
- the apparatus used for vapor phase demineralization is not particularly limited as long as it can be heated while mixing plant-derived char and a vapor phase containing a halogen compound.
- a fluidized furnace a continuous or batch type in-bed flow system using a fluidized bed or the like can be used.
- the supply amount (flow amount) of the gas phase is not particularly limited, but, for example, 1 mL / min or more, preferably 5 mL / min or more, more preferably 10 mL / min or more is supplied per 1 g of plant-derived char.
- the concentration of the halogen compound in the vapor phase deashing, the deashing temperature, the deashing time, and the like are not limited as long as sufficient deashing can be achieved.
- the obtained non-graphitizable carbonaceous material What is necessary is just to heat-process so that potassium element content of a material may be 0.1 weight% or less and / or iron element content may be 0.02 weight% or less.
- the higher the concentration of the halogen compound, the longer the deashing temperature, and the longer the deashing time the more the deashing proceeds and the contents of potassium element and iron element decrease. Accordingly, those skilled in the art can appropriately control these conditions so that the non-graphitizable carbonaceous material has a potassium element content of 0.1% by weight or less and / or an iron element content of 0.02% by weight. % Can be heat-treated.
- the half-value width of the peak near 1360 cm ⁇ 1 of the non-graphitizable carbon precursor obtained after vapor phase decalcification is in the range of 230 to 260 cm ⁇ 1. Preferably, it is in the range of 235 to 250 cm ⁇ 1 .
- the half width of the peak near 1360 cm ⁇ 1 of the Raman spectrum is considered to represent the amorphous amount of the non-graphitizable carbonaceous material.
- the half width of the peak is too small, the amount of amorphous material is small, so there are few structures that can be converged by the subsequent firing step, and fine defects possessed by the non-graphitizable carbon precursor are converged.
- the value of the half width is too large, the amount of amorphous that can be converged by the subsequent firing step is too large, and as a result, the non-graphitizable carbonaceous material obtained is not used.
- the electric resistance of the water electrolyte secondary battery may increase.
- the Raman spectrum can be measured using a method described later.
- the half width indicates the full width at half maximum (FWHM).
- a peak near 1360 cm ⁇ 1 is called a D band, and is a peak appearing in a Raman spectrum due to a double resonance effect accompanied by inelastic scattering in a carbon material.
- the non-graphitizable carbon precursor contains plant-derived char having an average particle size of 100 to 10000 ⁇ m in an inert gas atmosphere containing a halogen compound at 500 to 950 ° C., preferably 600 to 940 ° C., more preferably 650 to It may be a non-graphitizable carbon precursor obtained by heat treatment at 940 ° C., more preferably 850 to 930 ° C.
- the method for producing a mixed negative electrode material for a non-aqueous electrolyte secondary battery comprises a plant-derived char having an average particle size of 100 to 10000 ⁇ m in an inert gas atmosphere containing a halogen compound at 500 to 950 ° C., preferably A vapor phase decalcification step wherein heat treatment is performed at 600 to 940 ° C., more preferably 650 to 940 ° C., further preferably 810 to 970 ° C., and further preferably 850 to 930 ° C.
- the manufacturing method of the mixed negative electrode material for nonaqueous electrolyte secondary batteries including the process of mixing a porous material, an easily graphitizable carbonaceous material, and / or a graphite material may be sufficient.
- the average interplanar spacing d 002 of the (002) plane of the non-graphitizable carbonaceous material calculated using the Bragg equation in the wide-angle X-ray diffraction method by the vapor phase decalcification step and the firing step is 0.38.
- the non-graphite that is in the range of ⁇ 0.40 nm, the specific surface area of the non-graphitizable carbonaceous material determined by the nitrogen adsorption BET three-point method is in the range of 1 to 10 m 2 / g, and is observed in the Raman spectrum
- the difference between the half-width value of the peak near 1360 cm ⁇ 1 of the graphitizable carbon precursor and the half-width value of the peak near 1360 cm ⁇ 1 of the non-graphitizable carbonaceous material is 50 to 84 cm ⁇ 1 .
- a non-graphitizable carbonaceous material can be obtained.
- the non-graphitizable carbon precursor is adjusted in average particle size through a pulverization step and a classification step as necessary.
- the pulverization step and the classification step are preferably performed after the decalcification treatment.
- the non-graphitizable carbon precursor is pulverized so that the average particle size after the firing step is in the range of 1 to 30 ⁇ m, for example.
- the non-graphitizable carbonaceous material used in the production method of the present invention is prepared so that the average particle size is in the range of 1 to 30 ⁇ m, for example.
- the order of the pulverization step is not particularly limited as long as it is after the decalcification step. From the viewpoint of reducing the specific surface area of the non-graphitizable carbonaceous material, it is preferably performed before the firing step. However, it does not exclude performing the pulverization step after the firing step.
- the pulverizer used in the pulverization step is not particularly limited, and for example, a jet mill, a ball mill, a hammer mill, or a rod mill can be used. From the viewpoint of generating less fine powder, a jet mill having a classification function is preferable. When using a ball mill, a hammer mill, a rod mill or the like, fine powder can be removed by classification after the pulverization step.
- the average particle size of the non-graphitizable carbonaceous material can be more accurately prepared by the classification process. For example, particles having a particle diameter of 1 ⁇ m or less can be removed.
- the classification method is not particularly limited, and examples thereof include classification using a sieve, wet classification, and dry classification.
- the wet classifier for example, a classifier using principles such as gravity classification, inertia classification, hydraulic classification, centrifugal classification, and the like can be given.
- the dry classifier include a classifier using a principle such as sedimentation classification, mechanical classification, and centrifugal classification.
- the pulverization step and the classification step can be performed using one apparatus.
- the pulverization step and the classification step can be performed using a jet mill having a dry classification function.
- an apparatus in which the pulverizer and the classifier are independent can be used. In this case, pulverization and classification can be performed continuously, but pulverization and classification can also be performed discontinuously.
- a non-graphitizable carbonaceous material used in the production method of the present invention is obtained.
- the specific surface area of the obtained non-graphitizable carbonaceous material can be reduced, and a negative electrode material for a non-aqueous electrolyte secondary battery It can be set as a suitable specific surface area.
- the amount of carbon dioxide adsorbed on the non-graphitizable carbonaceous material can be adjusted.
- the volatile organic substance is preferably an organic substance that is in a solid state at room temperature and has a residual carbon ratio of less than 5%.
- the volatile organic substance is preferably one that generates a volatile substance (for example, hydrocarbon gas or tar) that can reduce the specific surface area of the non-graphitizable carbon precursor produced from plant-derived char.
- a volatile substance for example, hydrocarbon gas or tar
- the content of the volatile substance for example, hydrocarbon gas or tar component
- the specific surface area is not particularly limited.
- volatile organic substances include thermoplastic resins and low molecular organic compounds.
- thermoplastic resin include polystyrene, polyethylene, polypropylene, poly (meth) acrylic acid, poly (meth) acrylic acid ester, and the like.
- (meth) acryl is a general term for methacryl and methacryl.
- low molecular organic compound include toluene, xylene, mesitylene, styrene, naphthalene, phenanthrene, anthracene, and pyrene.
- thermoplastic resin Since those which do not oxidize and activate the surface of the non-graphitizable carbon precursor when volatilized at the firing temperature and thermally decomposed are preferred, polystyrene, polyethylene and polypropylene are preferred as the thermoplastic resin.
- the low molecular weight organic compound preferably has low volatility at room temperature from the viewpoint of safety, and naphthalene, phenanthrene, anthracene, pyrene and the like are preferable.
- the residual carbon ratio is measured by quantifying the carbon content of the ignition residue after the sample is ignited in an inert gas. Ignition is about 1 g of volatile organic matter (this exact weight is set to W1 (g)) in a crucible, and the temperature of the crucible is increased by 10 ° C./min in an electric furnace while flowing 20 L of nitrogen per minute. The temperature is raised from room temperature to 800 ° C. at a temperature rate, and then ignited at 800 ° C. for 1 hour. The residue at this time is regarded as an ignition residue, and its weight is defined as W2 (g).
- the ignition residue can be subjected to elemental analysis in accordance with the method defined in JIS M8819, the carbon weight ratio P1 (%) can be measured, and the residual coal ratio P2 (%) can be calculated.
- the mixture fired in the production method of the present invention is not particularly limited, but is preferably a mixture containing a non-graphitizable carbon precursor and a volatile organic substance in a weight ratio of 97: 3 to 40:60. is there.
- the mixing amount of the non-graphitizable carbon precursor and the volatile organic substance is more preferably 95: 5 to 60:40, still more preferably 93: 7 to 80:20.
- the volatile organic substance is 3 parts by weight or more, the specific surface area can be sufficiently reduced.
- the effect of reducing the specific surface area is saturated, and the volatile organic substances may be consumed in vain, which is not preferable.
- the mixing of the non-graphitizable carbon precursor and the volatile organic substance may be performed at any stage before the pulverization process or after the pulverization process.
- the non-graphitizable carbon precursor and the volatile organic substance are weighed and simultaneously supplied to the pulverizer to simultaneously pulverize and mix.
- the mixing method is a method in which both are uniformly mixed.
- the volatile organic substance is preferably mixed in the form of particles, but the shape and particle diameter of the particles are not particularly limited. From the viewpoint of uniformly dispersing the volatile organic substance in the ground non-graphitizable carbon precursor, the average particle size of the volatile organic substance is preferably 0.1 to 2000 ⁇ m, more preferably 1 to 1000 ⁇ m, and still more preferably 2 ⁇ 600 ⁇ m.
- the above-mentioned mixture may contain other components other than the non-graphitizable carbon precursor and the volatile organic substance.
- natural graphite, artificial graphite, metal-based material, alloy-based material, or oxide-based material can be included.
- the content of other components is not particularly limited, but is preferably 50 parts by weight or less with respect to 100 parts by weight of the mixture of the non-graphitizable carbon precursor and the volatile organic substance, and more preferably 30 parts by weight or less, more preferably 20 parts by weight or less, and most preferably 10 parts by weight or less.
- ⁇ Baking> In the firing step in the production method of the present invention, a mixture of a non-graphitizable carbon precursor and a volatile organic material is fired at 800 to 1400 ° C.
- the firing step may be a firing step in which (a) the pulverized mixture is baked at 800 to 1400 ° C. to perform the main calcination, and (b) the pulverized mixture is pre-baked at 350 ° C. or more and less than 800 ° C. Then, a baking process in which main baking is performed at 800 to 1400 ° C. may be performed.
- the preliminary baking step in the production method of the present invention can be performed, for example, by baking the pulverized mixture at 350 ° C. or higher and lower than 800 ° C.
- Volatile components for example, CO 2 , CO, CH 4 , H 2, etc.
- tar components can be removed by the preliminary firing step.
- production of the volatile matter and tar part in the main baking process implemented after a preliminary baking process can be reduced, and the burden of a baking machine can be reduced.
- the pre-baking step is preferably performed at 350 ° C. or higher, more preferably 400 ° C. or higher.
- the pre-baking step can be performed according to a normal pre-baking procedure. Specifically, the pre-baking can be performed in an inert gas atmosphere. Examples of the inert gas include nitrogen and argon. Further, the pre-baking may be performed under reduced pressure, for example, 10 kPa or less.
- the pre-baking time is not particularly limited, but can be carried out in the range of 0.5 to 10 hours, for example, and more preferably 1 to 5 hours.
- the main baking step can be performed according to a normal main baking procedure. By performing the main firing, a non-graphitizable carbonaceous material for a non-aqueous electrolyte secondary battery can be obtained.
- the specific temperature of the main baking step is 800 to 1400 ° C., preferably 1000 to 1350 ° C., more preferably 1100 to 1300 ° C.
- the main firing is performed in an inert gas atmosphere.
- the inert gas include nitrogen, argon, and the like, and the main calcination can be performed in an inert gas containing a halogen gas.
- this baking process can also be performed under reduced pressure, for example, it is also possible to implement at 10 kPa or less.
- the time for carrying out the main baking step is not particularly limited, but for example, it can be carried out in 0.05 to 10 hours, preferably 0.05 to 8 hours, more preferably 0.05 to 6 hours.
- Non-graphitizable carbonaceous material contained in the negative electrode material of the present invention is not limited, but the non-graphitizable carbonaceous material of the non-graphitizable carbonaceous material calculated using the Bragg equation in the wide angle X-ray diffraction method ( 002)
- the average interplanar spacing d 002 is in the range of 0.38 to 0.40 nm
- the specific surface area of the non-graphitizable carbonaceous material determined by the nitrogen adsorption BET three-point method is in the range of 1 to 10 m 2 / g.
- the value of the half-value width of the peak around 1360 cm -1 of the flame-graphitizable carbon precursor observed in the Raman spectrum the peak around 1360 cm -1 of the flame graphitizable carbonaceous material of the half-value width
- the difference from the value is 50 to 84 cm ⁇ 1 .
- the non-graphitizable carbonaceous material for nonaqueous electrolyte secondary batteries used in the production method of the present invention has a specific surface area determined by a nitrogen adsorption BET three-point method of 1 m 2 / g to 10 m 2 / g, preferably is 1.2m 2 /g ⁇ 9.5m 2 / g, more preferably 1.4m 2 /g ⁇ 9.0m 2 / g.
- the specific surface area is too small, the amount of lithium ions adsorbed on the non-graphitizable carbonaceous material is decreased, and the charge capacity of the nonaqueous electrolyte secondary battery may be decreased.
- the specific surface area is too high, lithium ions may react on the surface of the non-graphitizable carbonaceous material, and the utilization efficiency of lithium ions may be lowered.
- the non-graphitizable carbonaceous material used in the production method of the present invention has an average interplanar spacing d 002 of (002) plane calculated from the wide-angle X-ray diffraction method using the Bragg equation is 0.375 nm or more and 0.00. It is in the range of 40 nm or less, preferably in the range of 0.380 to 0.400 nm, more preferably in the range of 0.381 nm to 0.389 nm. If the average interplanar spacing d002 of (002) plane is too small, the resistance when lithium ions are inserted into the non-graphitizable carbonaceous material may increase, and the resistance during output may increase.
- the input / output characteristics of the lithium ion battery may deteriorate. Further, since the non-graphitizable carbonaceous material repeatedly expands and contracts, the stability as a battery material may be impaired. When the average interplanar distance d 002 is too large, the diffusion resistance of lithium ions decreases, but the volume of the non-graphitizable carbonaceous material increases, and the effective capacity per volume may decrease.
- the amount of nitrogen atoms contained in the non-graphitizable carbonaceous material used in the production method of the present invention is preferably as small as possible, but is usually preferably 0.5% by weight or less from the analytical value obtained by elemental analysis. .
- the amount of nitrogen atoms is too large, lithium ions and nitrogen react to reduce lithium ion efficiency, and may react with oxygen in the air during storage.
- the amount of oxygen atoms contained in the non-graphitizable carbonaceous material used in the production method of the present invention is preferably as small as possible, but is usually preferably 0.25% by weight or less from the analytical value obtained by elemental analysis. . If the amount of oxygen atoms is too large, lithium ions react with oxygen, not only lowering the lithium ion efficiency, but also attracting oxygen and moisture in the air and increasing the probability of reacting with non-graphitizable carbonaceous materials. In addition, when water is adsorbed, the lithium efficiency may decrease, for example, it may not be easily desorbed.
- the half-value width of the peak near 1360 cm ⁇ 1 of the non-graphitizable carbonaceous material obtained after the firing step is preferably in the range of 175 to 190 cm ⁇ 1. More preferably, it is in the range of 175 to 180 cm ⁇ 1 .
- the full width at half maximum of the peak near 1360 cm ⁇ 1 of the non-graphitizable carbonaceous material is in the above range, lithium clusters are easily formed, conductivity can be easily secured, and sufficient discharge characteristics as effective capacity can be obtained. It becomes easy to demonstrate.
- a lithium cluster shows the state which lithium ion gathered by the interaction between lithium ions, and became one lump, and lithium ion is occluded forming a lithium cluster.
- Lithium ions are occluded in the form of lithium ions and lithium clusters, but it is considered that higher battery characteristics can be obtained by forming lithium clusters.
- the value of the half width of the peak around 1360 cm -1 of the Raman spectrum observed by the pre-firing laser Raman spectroscopy non-graphitizable carbon precursor, 1360 cm of non-graphitizable carbonaceous material obtained after calcination -1 The difference from the half-width value of a nearby peak is 50 cm ⁇ 1 or more and 84 cm ⁇ 1 or less.
- the full width at half maximum is more preferably from 55 cm ⁇ 1 to 83 cm ⁇ 1 , and still more preferably from 60 cm ⁇ 1 to 80 cm ⁇ 1 . If the difference in half-value width is 50 cm ⁇ 1 or more, crystals will develop due to the convergence of the carbon structure by firing, and the efficiency in charge and discharge tends to increase.
- the non-graphitizable carbonaceous material used in the production method of the present invention is preferable as the non-graphitizable carbonaceous material for non-aqueous electrolyte secondary batteries.
- the difference between the half widths before and after firing becomes too large, new defects may occur due to the convergence of the carbon structure, and the charge / discharge efficiency may decrease.
- the hygroscopicity of the non-graphitizable carbonaceous material increases, and the generation of acid due to the hydrolysis of the electrolyte and the generation of gas due to water electrolysis may cause problems. Deterioration may occur and storage stability as an electrode material may be reduced.
- the average particle diameter (D v50 ) of the non- graphitizable carbonaceous material used in the production method of the present invention is preferably 1 to 30 ⁇ m.
- the average particle diameter is too small, fine powder increases and the specific surface area of the non-graphitizable carbonaceous material increases.
- the reactivity between the non-graphitizable carbonaceous material and the electrolytic solution is increased, the irreversible capacity is increased, and the proportion of wasted capacity of the positive electrode may be increased.
- the irreversible capacity is a capacity that does not discharge among the capacity charged in the non-electrolyte secondary battery.
- the average particle size of the non-graphitizable carbonaceous material is more preferably 2 ⁇ m or more, and particularly preferably 3 ⁇ m or more. When the average particle size is 30 ⁇ m or less, the lithium free diffusion process in the particles is small, and rapid charge / discharge is possible, which is preferable. Further, in the lithium ion secondary battery, it is important to increase the electrode area for improving the input / output characteristics.
- the upper limit of the average particle diameter is preferably 30 ⁇ m or less, more preferably 19 ⁇ m or less, still more preferably 17 ⁇ m or less, still more preferably 16 ⁇ m or less, and most preferably 15 ⁇ m or less.
- the true density range of the non-graphitizable carbonaceous material used in the production method of the present invention is not particularly limited, but is preferably in the range of 1.45 to 1.70 g / cm 3 , more Preferably it is in the range of 1.45 to 1.65 g / cm 3 , more preferably 1.45 to 1.60 g / cm 3 . 1.45 g / cm 3 less than the doping capacity per unit volume as, and de-doping capacity undesirably decreases.
- the mixing step (2) in the production method of the present invention is a step of mixing the non-graphitizable carbonaceous material, the graphitizable carbonaceous material and / or the graphite material.
- Graphitizable carbon is a general term for non-graphitic carbon that changes to a graphite structure by heat treatment at a high temperature of 2000 ° C. or higher.
- the true density is 1.70 g / cm 3 or more 2
- Non-graphitic carbon of 2 g / cm 3 or less is referred to as graphitizable carbon.
- the true density of the graphitizable carbonaceous material is not particularly limited, but is preferably in the range of 1.80 to 2.18 g / cm 3 , more preferably 1.90 to 2.15 g / cm 3. 3 range.
- the graphitizable carbonaceous material contained in the mixed negative electrode material of the present invention is not limited, but is obtained by firing a graphitizable carbon precursor such as pitch or thermoplastic resin. . That is, the carbon source of the graphitizable carbonaceous material contained in the mixed negative electrode material is not limited as long as the graphitizable carbonaceous material can be produced.
- thermoplastic resin for example, ketone resin, polyvinyl alcohol, polyethylene terephthalate, polyacetal, polyacrylonitrile, styrene / divinylbenzene copolymer
- Coalesced polyimide, polycarbonate, modified polyphenylene ether, polybutylene terephthalate, polyarylate, polysulfone, polyphenylene sulfide, polyether ether ketone, polyimide resin, fluorine resin, aramid resin, or poly Midoimido), it can be mentioned.
- These carbon sources are not infusible by oxidation treatment.
- the graphitizable carbonaceous material can be obtained by firing the graphitizable carbon precursor according to a normal firing procedure.
- the firing may be a firing step in which (a) an easily graphitizable carbon precursor is fired at 800 ° C. or more and less than 2500 ° C. to perform main firing, and (b) an easily graphitizable carbon precursor, 300 ° C. or more and 800 ° C. or more.
- It may be a baking step in which preliminary baking is performed at a temperature lower than °C, and then main baking is performed at 800 ° C. or higher and lower than 2500 ° C. Conditions other than temperature can be performed under the conditions described in the column “ ⁇ Firing”.
- the physical properties of the graphitizable carbonaceous material are not particularly limited, but those having the following physical properties are preferable.
- the average plane distance d 002 of the (002) plane calculated from the graphitizable carbonaceous material using the Bragg equation from a wide-angle X-ray diffraction method is preferably 0.345 nm or more and less than 0.375 nm, Preferably, it is 0.345 nm to 0.360 nm.
- the graphitizable carbonaceous material, specific surface area determined by nitrogen adsorption BET3 point method is a 1m 2 / g ⁇ 10m 2 / g, there preferably 1.2m 2 /g ⁇ 9.5m 2 / g , more preferably 1.4m 2 /g ⁇ 9.0m 2 / g.
- the specific surface area is too small, the amount of lithium ions adsorbed on the carbonaceous material is decreased, and the charge capacity of the nonaqueous electrolyte secondary battery may be decreased.
- the specific surface area is too high, lithium ions may react on the surface of the carbonaceous material, and the utilization efficiency of lithium ions may be reduced.
- the amount of nitrogen atoms in the graphitizable carbonaceous material is preferably as small as possible, but it is usually preferably 0.5% by weight or less from the analytical value obtained by elemental analysis.
- the amount of nitrogen atoms is too large, lithium ions and nitrogen react to reduce lithium ion efficiency, and may react with oxygen in the air during storage.
- the amount of oxygen atoms in the graphitizable carbonaceous material is preferably as small as possible, it is usually preferably 0.25% by weight or less from the analytical value obtained by elemental analysis. If the amount of oxygen atoms is too large, lithium ions and oxygen react to reduce lithium ion efficiency, but also attract oxygen and moisture in the air and increase the probability of reacting with graphitizable carbonaceous materials. In addition, when water is adsorbed, the lithium efficiency may decrease, for example, it may not be easily desorbed.
- the average particle diameter (D v50 ) of the graphitizable carbonaceous material is preferably 3 to 30 ⁇ m. If the average particle size is too small, fine powder increases and the specific surface area of the graphitizable carbonaceous material increases. As a result, the reactivity between the graphitizable carbonaceous material and the electrolytic solution is increased, the irreversible capacity is increased, and the proportion of wasted capacity of the positive electrode may be increased.
- the average particle diameter of the graphitizable carbonaceous material is more preferably 4 ⁇ m or more, and particularly preferably 5 ⁇ m or more. When the average particle size is 30 ⁇ m or less, the lithium free diffusion process in the particles is small, and rapid charge / discharge is possible, which is preferable.
- the upper limit of the average particle diameter is preferably 30 ⁇ m or less, more preferably 19 ⁇ m or less, still more preferably 17 ⁇ m or less, still more preferably 16 ⁇ m or less, and most preferably 15 ⁇ m or less.
- graphite material Although the graphite material contained in the mixed negative electrode material of the present invention is not limited, natural graphite or artificial graphite can be mentioned.
- artificial graphite is not limited, it can be produced by firing (graphitizing) the graphitizable carbon precursor at 2500 to 3000 ° C. in an inert gas atmosphere.
- the graphitization treatment it is possible to continuously raise the carbon precursor to the graphitization treatment temperature (2500 to 3000 ° C.) and continuously perform the carbonization and the graphitization treatment.
- the graphitization process is carried out industrially after carbonization (firing) at a lower temperature, for example, at 500 to 1500 ° C., from the viewpoint of the ease of designing the equipment material, structure, heating method, etc. Often preferred.
- the graphitization treatment is performed by maintaining at a temperature of 2500 to 3000 ° C.
- the graphitization temperature refers to the highest processing temperature that the workpiece is subjected to.
- Graphitization is carried out under reduced pressure or in an inert gas atmosphere, which prevents the raw material from reacting with the atmospheric gas during graphitization.
- the inert gas include argon gas and helium gas.
- an atmosphere in the presence of the above inert gas is preferable.
- the physical properties of the graphite material are not particularly limited, but those having the following physical properties are preferable.
- the theoretical density of graphite is 2.27 g / cm 3
- the true density of the graphite material used in the production method of the present invention is 2.15 g / cm 3 or more, preferably 2.17 g / cm 3. 3 or more, more preferably 2.20 g / cm 3 or more. This is because when the true density is large, the energy density per battery volume can be increased.
- the graphitic material, the average plane spacing d 002 of calculated using the Bragg equation from the wide angle X-ray diffraction (002) plane is preferably 0.336 ⁇ 0.345 nm, more preferably 0.336 ⁇ It is 0.344 nm, and more preferably 0.337 to 0.342 nm.
- a graphite material having d 002 exceeding 0.350 nm may deteriorate the flatness of the discharge curve.
- the crystallite size Lc (002) in the c-axis direction of the graphite material is preferably more than 15 nm and 50 nm or less, more preferably more than 15 nm and 40 nm or less, and still more preferably 20 to 40 nm.
- the graphite material collapses or the electrolyte solution decomposes due to doping and dedoping of the active material. It is easy and not preferable.
- specific surface area determined by nitrogen adsorption BET3 point method is 0.5m 2 / g ⁇ 10m 2 / g, preferably 0.7m 2 /g ⁇ 9.5m 2 / g, more preferably from 1.0m 2 /g ⁇ 9.0m 2 / g.
- specific surface area is too small, the amount of lithium ions adsorbed on the carbonaceous material is decreased, and the charge capacity of the nonaqueous electrolyte secondary battery may be decreased.
- the specific surface area is too high, lithium ions may react on the surface of the carbonaceous material, and the utilization efficiency of lithium ions may be reduced.
- the average particle diameter (D v50 ) of the graphite material is preferably 3 to 30 ⁇ m. If the average particle size is too small, fine powder increases and the specific surface area of the graphite material increases. As a result, the reactivity between the graphite material and the electrolytic solution is increased, the irreversible capacity is increased, and the proportion of wasted capacity of the positive electrode may be increased.
- the average particle diameter of the graphite material is more preferably 4 ⁇ m or more, and particularly preferably 5 ⁇ m or more. When the average particle size is 30 ⁇ m or less, the lithium free diffusion process in the particles is small, and rapid charge / discharge is possible, which is preferable.
- the upper limit of the average particle diameter is preferably 30 ⁇ m or less, more preferably 19 ⁇ m or less, still more preferably 17 ⁇ m or less, still more preferably 16 ⁇ m or less, and most preferably 15 ⁇ m or less.
- the mixing ratio of the non-graphitizable carbonaceous material and the graphitizable carbonaceous material and / or the graphite material in the mixing step of the present invention is not limited as long as the effect of the present invention is obtained.
- the non-graphitizable carbonaceous material is 20% by mass to 80% by mass, preferably 25% by mass to 75% by mass, and more preferably 30% by mass with respect to the total mass of the obtained mixed negative electrode material. % By mass to 70% by mass.
- the graphitizable carbonaceous material is 20% by mass to 80% by mass with respect to the total mass of the obtained mixed negative electrode material, preferably 25% by mass to 75% by mass, and more preferably 30% by mass to 70% by mass.
- the graphite material is 20% by mass to 80% by mass, preferably 25% by mass to 75% by mass, and more preferably 30% by mass to 70% by mass with respect to the total mass of the obtained mixed negative electrode material. is there.
- the specific surface area of the non-graphitizable carbon precursor after pulverization is 100 to 500 m 2 / g, preferably 200 to 500 m 2 / g, for example 200 to 400 m 2. / G. If the specific surface area is too small, the micropores of the non-graphitizable carbonaceous material may not be sufficiently reduced even after the firing step described later, and the hygroscopicity of the non-graphitizable carbonaceous material is reduced. It may be difficult.
- the generation of acid accompanying the hydrolysis of the electrolytic solution and the generation of gas due to the electrolysis of water may cause problems. Further, the oxidation of the non-graphitizable carbonaceous material progresses in an air atmosphere, and the battery performance may change greatly. If the specific surface area becomes too large, the specific surface area of the carbonaceous material will not be reduced even after the firing step described later, and the utilization efficiency of lithium ions in the nonaqueous electrolyte secondary battery may be reduced.
- the specific surface area of the non-graphitizable carbon precursor can be prepared by controlling the temperature of vapor phase decalcification.
- the specific surface area means a specific surface area (BET specific surface area) determined by a BET method (nitrogen adsorption BET three-point method). Specifically, it can measure using the method mentioned later.
- the non-graphitizable carbon precursor used in the method (B) for producing the mixed negative electrode material for nonaqueous electrolyte secondary batteries has a specific surface area of 100 to 500 m 2 / g as described above.
- the other features of the non-graphitizable carbon precursor and the adjustment method thereof are not limited, but are substantially “" Non-graphite graphite "in the method (A) for producing a mixed negative electrode material for a non-aqueous electrolyte secondary battery. It may be the same as the non-graphitizable carbon precursor described in the column of “graphitizable carbonaceous precursor” ”.
- the volatile organic substance used in the production method (B) of the present invention is substantially the same as that described in the column “ ⁇ Volatile organic substance” in the production method (A) of the mixed negative electrode material for a nonaqueous electrolyte secondary battery. Volatile organic materials can be used.
- Non-graphitizable carbonaceous material used in the production method (B) of the present invention is substantially as long as it is obtained by firing a non-graphitizable carbon precursor having a specific surface area of 100 to 500 m 2 / g.
- it may be the same as the non-graphitizable carbonaceous material described in the column “ ⁇ Non-graphitizable carbonaceous material >>” in the manufacturing method (A) of the mixed negative electrode material for nonaqueous electrolyte secondary batteries.
- the mixing step (2) in the production method (B) of the present invention is substantially the description in the column “ ⁇ Mixing step (2) >>” of the production method (A) of the mixed negative electrode material for a nonaqueous electrolyte secondary battery. Can be done according to.
- the mixed negative electrode material for nonaqueous electrolyte secondary battery of the present invention comprises a non-graphitizable carbonaceous material, an easily graphitizable carbonaceous material and / or a graphite material.
- the difference between the half-width value of the peak near 1360 cm ⁇ 1 of the carbon precursor of the non-graphitizable carbonaceous material and the half-width value of the peak near 1360 cm ⁇ 1 of the non-graphitizable carbonaceous material is 50 to 84 cm ⁇ 1 .
- the mixed negative electrode material for a nonaqueous electrolyte secondary battery of the present invention is not limited.
- the mixed negative electrode material for a nonaqueous electrolyte secondary battery of the present invention is manufactured by the manufacturing method (A) or (B). can do.
- the specific surface area determined by the nitrogen adsorption BET three-point method of the mixed negative electrode material for a nonaqueous electrolyte secondary battery of the present invention is not particularly limited, but is preferably 1 m 2 / g to 10 m 2 / g, preferably a 1.2m 2 /g ⁇ 9.5m 2 / g, more preferably 1.4m 2 /g ⁇ 9.0m 2 / g.
- the true density of the mixed negative electrode material for a non-aqueous electrolyte secondary battery of the present invention is not particularly limited, but is preferably 1.45 to 2.10 g / cm 3 , more preferably 1.50 to 2 a .05g / cm 3, more preferably from 1.50 ⁇ 2.00g / cm 3.
- the average particle diameter (D v50 ) of the mixed negative electrode material for a nonaqueous electrolyte secondary battery of the present invention is not particularly limited, but is preferably 3 to 30 ⁇ m.
- the lower limit of the average particle diameter is more preferably 4 ⁇ m or more, and particularly preferably 5 ⁇ m or more.
- the upper limit of the average particle diameter is more preferably 19 ⁇ m or less, further preferably 17 ⁇ m or less, further preferably 16 ⁇ m or less, and most preferably 15 ⁇ m or less.
- Non-graphitizable carbonaceous material The average interplanar spacing d 002 of the (002) plane of the non-graphitizable carbonaceous material contained in the mixed negative electrode material for a nonaqueous electrolyte secondary battery of the present invention is calculated using the Bragg equation in the wide angle X-ray diffraction method, It is in the range of 0.38 to 0.40 nm.
- the specific surface area of the non-graphitizable carbonaceous material determined by the nitrogen adsorption BET three-point method is in the range of 1 to 10 m 2 / g.
- the difference from the half width value of the peak is 50 to 84 cm ⁇ 1 , more preferably 55 cm ⁇ 1 to 83 cm ⁇ 1 , and still more preferably 60 cm ⁇ 1 to 80 cm ⁇ 1 .
- the non-graphitizable carbonaceous material, the graphitizable carbonaceous material, and the graphite material contained in the mixed negative electrode material (carbon material mixture) of the present invention can be separated by the true density by the density pipe method.
- the carbon fiber-density test method JIS R7603-1999
- non-graphitizable carbon contained in the carbon material mixture easily graphitizable carbonaceous material, and Graphite materials
- the carbonaceous material is separated from the negative electrode for the non-aqueous electrolyte secondary battery that is formed including a binder, and the non-graphitizable carbonaceous material and graphitizable property are similarly obtained by the true density by the density pipe method. It is possible to separate the carbonaceous material and the graphite material.
- Negative electrode for nonaqueous electrolyte secondary battery Manufacture of negative electrode
- a binder binder
- an appropriate amount of an appropriate solvent is added and kneaded to form an electrode mixture, and then a current collector plate made of a metal plate or the like is used. It can be produced by pressure molding after coating and drying.
- the mixed negative electrode material of the present invention an electrode having high conductivity can be produced without particularly adding a conductive auxiliary agent. However, the electrode combination is necessary for the purpose of imparting higher conductivity.
- a conductive aid can be added.
- the binder is not particularly limited as long as it does not react with an electrolytic solution such as PVDF (polyvinylidene fluoride), polytetrafluoroethylene, and a mixture of SBR (styrene-butadiene rubber) and CMC (carboxymethylcellulose).
- PVDF polyvinylidene fluoride
- SBR styrene-butadiene rubber
- CMC carbboxymethylcellulose
- the preferred addition amount of the binder varies depending on the type of binder used, but is preferably 3 to 13% by weight, more preferably 3 to 10% by weight for the PVDF-based binder.
- a binder using water as a solvent is often used by mixing a plurality of binders such as a mixture of SBR and CMC, and the total amount of all binders used is preferably 0.5 to 5% by weight, The amount is preferably 1 to 4% by weight.
- the electrode active material layer is basically formed on both sides of the current collector plate, but may be on one side if necessary. A thicker electrode active material layer is preferable for increasing the capacity because fewer current collector plates and separators are required. However, the larger the electrode area facing the counter electrode, the better the input / output characteristics, and the thicker the active material layer. Too much is not preferable because the input / output characteristics deteriorate.
- the thickness of the active material layer (per one side) is not limited and is in the range of 10 to 1000 ⁇ m, preferably 10 to 80 ⁇ m, more preferably 20 to 75 ⁇ m, and particularly preferably 20 to 60 ⁇ m. is there.
- the negative electrode usually has a current collector.
- As the negative electrode current collector for example, SUS, copper, nickel, or carbon can be used, and among them, copper or SUS is preferable.
- Non-aqueous electrolyte secondary battery When the negative electrode of the non-aqueous electrolyte secondary battery is formed using the mixed negative electrode material of the present invention, other materials constituting the battery such as a positive electrode material, a separator, and an electrolytic solution are particularly limited. It is possible to use various materials conventionally used or proposed as a nonaqueous solvent secondary battery.
- the positive electrode includes a positive electrode active material, and may further include a conductive additive, a binder, or both.
- the mixing ratio of the positive electrode active material and other materials in the positive electrode active material layer is not limited as long as the effect of the present invention is obtained, and can be determined as appropriate.
- the positive electrode active material can be used without limiting the positive electrode active material.
- a layered oxide system (expressed as LiMO 2 , where M is a metal: for example, LiCoO 2 , LiNiO 2 , LiMnO 2 , or LiNi x Co y Mn z O 2 (where x, y, z are composition ratios)
- Olivine-based represented by LiMPO 4 , M is a metal: for example LiFePO 4
- spinel-based represented by LiM 2 O 4
- M is a metal: for example LiMn 2 O 4
- Compounds may be mentioned, and these chalcogen compounds may be mixed as necessary.
- a ternary system [Li (Ni-Mn-Co) in which a part of cobalt of lithium cobaltate is replaced with nickel and manganese, and the stability of the material is improved by using three of cobalt, nickel, and manganese.
- NCA-based materials [Li (Ni—Co—Al) O 2 ] using aluminum instead of O 2 ] and the ternary manganese are known, and these materials can be used.
- the positive electrode can further contain a conductive additive and / or a binder.
- a conductive support agent acetylene black, ketjen black, or carbon fiber can be mentioned, for example.
- the content of the conductive assistant is not limited, but is, for example, 0.5 to 15% by weight.
- a binder fluorine-containing binders, such as PTFE or PVDF, can be mentioned, for example.
- the content of the conductive assistant is not limited, but is, for example, 0.5 to 15% by weight.
- the thickness of the positive electrode active material layer is not limited, but is, for example, in the range of 10 to 1000 ⁇ m.
- the positive electrode active material layer usually has a current collector.
- the negative electrode current collector for example, SUS, aluminum, nickel, iron, titanium, and carbon can be used, and among these, aluminum or SUS is preferable.
- the nonaqueous solvent electrolyte used in combination of these positive electrode and negative electrode is generally formed by dissolving an electrolyte in a nonaqueous solvent.
- the non-aqueous solvent include organic solvents such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, dimethoxyethane, diethoxyethane, ⁇ -butyllactone, tetrahydrofuran, 2-methyltetrahydrofuran, sulfolane, or 1,3-dioxolane. These can be used alone or in combination of two or more.
- the electrolyte LiClO 4 , LiPF 6 , LiBF 4 , LiCF 3 SO 3 , LiAsF 6 , LiCl, LiBr, LiB (C 6 H 5 ) 4 , or LiN (SO 3 CF 3 ) 2 is used.
- the positive electrode layer and the negative electrode layer formed as described above are generally immersed in an electrolytic solution with a liquid-permeable separator made of nonwoven fabric or other porous material facing each other as necessary. It is formed by.
- a non-woven fabric usually used for a secondary battery or a permeable separator made of another porous material can be used.
- a solid electrolyte made of a polymer gel impregnated with an electrolytic solution can be used instead of or together with the separator.
- vm was determined by a three-point method by nitrogen adsorption at liquid nitrogen temperature, and the specific surface area of the sample was calculated by the following equation.
- v m adsorption amount necessary to form a monomolecular layer on the surface of the sample (cm 3 / g)
- v adsorption amount is measured (cm 3 / g)
- p 0 saturation vapor pressure
- p Absolute pressure
- c is a constant (reflecting the heat of adsorption)
- N is Avogadro's number 6.022 ⁇ 1023
- a (nm 2 ) is an area occupied by the adsorbate molecule on the sample surface (molecular occupation cross section).
- the amount of nitrogen adsorbed on the carbon material at the liquid nitrogen temperature was measured as follows using “BELL Sorb Mini” manufactured by BELL JAPAN. A carbon material pulverized to a particle size of about 5 to 50 ⁇ m is filled into a sample tube, and the sample tube is cooled to ⁇ 196 ° C., and the pressure is once reduced. %) Is adsorbed. The amount of nitrogen adsorbed on the sample when the equilibrium pressure was reached at each desired relative pressure was defined as the amount of adsorbed gas v.
- the residual carbon ratio was measured by quantifying the carbon content of the ignition residue after the sample was ignited in an inert gas. Ignition is about 1 g of volatile organic matter (this exact weight is W 1 (g)) in a crucible, and the crucible is heated at 10 ° C./min in an electric furnace while flowing 20 L of nitrogen per minute. The temperature was raised from room temperature to 800 ° C. at a temperature rate, and then ignited at 800 ° C. for 1 hour. The residue at this time was regarded as an ignition residue, and its weight was defined as W 2 (g). Next, the ignition residue was subjected to elemental analysis in accordance with the method defined in JIS M8819, and the carbon weight ratio P 1 (%) was measured. The residual coal rate P 2 (%) was calculated by the following formula.
- distilled water excluding the gas that has been boiled and dissolved immediately before use is placed in a specific gravity bottle, immersed in a constant temperature water bath as before, and the mass (m 5 ) is measured after aligning the marked lines.
- the true density ( ⁇ Bt ) is calculated by the following formula. (Where d is the specific gravity of water at 30 ° C. (0.9946))
- a dispersing agent cationic surfactant “SN Wet 366” (manufactured by San Nopco)
- SALD-3000J particle size distribution measuring device
- the negative electrode material was vacuum-dried at 200 ° C. for 12 hours, and then 1 g of this negative electrode material was spread on a petri dish having a diameter of 8.5 cm and a height of 1.5 cm so as to be as thin as possible.
- a constant temperature and humidity chamber controlled to a constant atmosphere at a temperature of 25 ° C and a humidity of 50% for 100 hours, remove the petri dish from the constant temperature and humidity chamber and use a Karl Fischer moisture meter (Mitsubishi Chemical Analytech / CA-200). The moisture absorption was measured using The temperature of the vaporization chamber (VA-200) was 200 ° C.
- the carbon material mixture of the present invention is suitable for constituting the negative electrode of a non-aqueous electrolyte secondary battery, but the discharge capacity (de-doping amount) and irreversible capacity (non-reduction capacity) of the battery active material.
- discharge capacity de-doping amount
- irreversible capacity non-reduction capacity
- a 16 mm diameter stainless steel mesh disk was spot welded to the outer lid of a CR2016 size coin-shaped battery can beforehand, and then a 0.8 mm thick metal lithium sheet was punched into a 15 mm diameter disk shape.
- an electrode counter electrode
- a pair of electrodes manufactured in this manner was used, and an electrolyte solution was obtained by adding LiPF 6 at a rate of 1.2 mol / L to a mixed solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 3: 7.
- a 2016-size coin-type non-aqueous electrolyte lithium secondary battery was assembled in an Ar glove box using a polyethylene gasket as a separator of a microporous membrane made of borosilicate glass fiber having a diameter of 19 mm. .
- the lithium doping reaction on the carbon electrode will be described as “charging”.
- “discharge” is a charging reaction in the test batteries prepared in (a) to (b), but it is described as “discharge” for convenience because it is a dedoping reaction of lithium from a carbonaceous material.
- the charging method adopted here is a constant current / constant voltage method. Specifically, constant current charging is performed at a current density of 0.5 mA / cm 2 until the terminal voltage reaches 50 mV, and constant when the voltage reaches 50 mV. Charging was continued with the voltage maintained until the current value reached 20 ⁇ A. After completion of charging, the battery circuit was opened for 30 minutes and then discharged.
- the discharge was a constant current discharge at 0.5 mA / cm 2 and the final voltage was 1.5V.
- the positive electrode was 94 parts by weight of LiNi 1/3 Co 1/3 Mn 1/3 O 2 (Cumcore MX6 manufactured by umicore), carbon black (Supercal manufactured by TIMCAL). NMP was added to 3 parts by weight and 3 parts by weight of polyvinylidene fluoride (Kureha KF # 7200) to form a paste, which was uniformly coated on the aluminum foil. After drying, the coated electrode was punched onto a disk having a diameter of 14 mm and pressed to obtain an electrode. The amount of LiNi 1/3 Co 1/3 Mn 1/3 O 2 in the electrode was adjusted to about 15 mg.
- a negative electrode was produced in the same procedure as in the above (a), except that the weight of the carbonaceous material in the negative electrode was adjusted to 95% of the charge capacity of the negative electrode active material. Note that to calculate the capacity of LiNi 1/3 Co 1/3 Mn 1/3 O 2 as 165 mAh / g, and 1C and (C represents the time rate) and 2.475MA. Using the pair of electrodes prepared in this manner, an electrolytic solution obtained by adding LiPF 6 at a ratio of 1.2 mol / L to a mixed solvent in which ethylene carbonate and methyl ethyl carbonate were mixed at a volume ratio of 3: 7 was used.
- a 2032 size coin-type non-aqueous electrolyte lithium secondary battery was assembled in an Ar glove box using a polyethylene gasket as a separator for a microporous membrane made of borosilicate glass fiber having a diameter of 17 mm. .
- (E) 50% charged state input / output test and direct current resistance value test The non-aqueous electrolyte secondary battery having the configuration of (d) above was subjected to a battery test using a charge / discharge tester (“TOSCAT” manufactured by Toyo System). It was. After aging first, an input / output test and a direct current resistance test were started in a 50% state of charge. The aging procedures (e-1) to (e-3) are shown below.
- Aging procedure (e-1) Using the constant current constant voltage method, constant current charging is performed at a current value of C / 10 until the battery voltage reaches 4.2 V, and then the battery voltage is maintained at 4.2 V (held at a constant voltage). While) the current value was attenuated and charging was continued until the current value became C / 100 or less. After completion of charging, the battery circuit was opened for 30 minutes. Aging procedure (e-2) The battery was discharged at a constant current value of C / 10 until the battery voltage reached 2.75V. After completion of charging, the battery circuit was opened for 30 minutes. The irreversible capacity was calculated from the difference between the charge capacity of the aging procedure (e-1) and the discharge capacity of the aging procedure (e-2). Aging procedure (e-3) Aging procedures (e-1) to (e-2) were repeated two more times.
- the I / O test and the DC resistance test were conducted in Matsushita Battery Industry 2005-2006 NEDO Results Report. Lithium Battery Technology Development for Fuel Cell Vehicles, etc. Automotive Lithium Battery Technology Development (High I / O / Long Life Lithium Ion Battery) (Technology Development) 3) -1
- the input / output test and DC resistance value test procedures (e-4) to (e-7) are shown below.
- Input / output test and DC resistance test procedure (e-4) In a charged state of 50% with respect to the discharge capacity, discharging was performed at a current value of 1 C for 10 seconds, and then the battery circuit was opened for 10 minutes.
- Input / output test and DC resistance test procedure (e-5) After charging at a current value of 1 C for 10 seconds, the battery circuit was opened for 10 minutes.
- Input / output test and DC resistance test procedure (e-6) Change the charge / discharge current values in the input / output test procedures (e-4) and (e-5) to 2C and 3C, and perform the input / output test procedures (e-4) to (e-5) in the same way. It was.
- Input / output test and DC resistance test procedure (e-7) On the charge side, the voltage at 10 seconds was plotted against each current value, and an approximate straight line was obtained by the method of least squares. By extrapolating this approximate straight line, the current value when the upper limit voltage on the charging side was 4.2 V was calculated.
- Input / output test and DC resistance test procedure (e-8)
- Input / output test and DC resistance test procedure (e-9)
- the voltage at 10 seconds on the discharge side was plotted against each current value, and an approximate straight line was obtained by the least square method. By extrapolating this approximate straight line, the current value when the lower limit voltage on the discharge side was 2.75 V was calculated.
- Input / output test and DC resistance test procedure (e-10) The product of the obtained current value (A) and the lower limit voltage (V) is the output value (W), and the unit is W / cm 3 divided by the volume of the positive electrode and the negative electrode (excluding the volume of both current collectors). The output value per volume is shown.
- Aging procedure (g-1) Using the constant current constant voltage method, constant current charging is performed at a current value of C / 20 until the battery voltage reaches 4.1 V, and then the battery voltage is maintained at 4.1 V (held at a constant voltage). While) the current value was attenuated and charging was continued until the current value became C / 100 or less. After completion of charging, the battery circuit was opened for 30 minutes. Aging procedure (g-2) The battery was discharged at a constant current value of C / 20 until the battery voltage reached 2.75V. After completion of charging, the battery circuit was opened for 30 minutes. Aging procedure (g-3) In the aging procedure (g-1), the battery voltage is changed to 4.2 V, and the current values of (g-1) and (g-2) are changed from C / 20 to C / 5. g-2) was repeated twice.
- Preparation Example 1 The coconut shell was crushed and dry-distilled at 500 ° C. to obtain coconut shell char having a particle size of 2.360 to 0.850 mm (containing 98% by weight of particles having a particle size of 2.360 to 0.850 mm).
- a vapor phase deashing process was performed for 50 minutes at 870 ° C. while supplying nitrogen gas containing 1% by volume of hydrogen chloride gas at a flow rate of 10 L / min to 100 g of this coconut shell char. Thereafter, only the supply of hydrogen chloride gas was stopped, and while supplying nitrogen gas at a flow rate of 10 L / min, vapor phase deoxidation treatment was further performed at 870 ° C. for 30 minutes to obtain a carbon precursor.
- the obtained carbon precursor was coarsely pulverized to an average particle size of 10 ⁇ m using a ball mill, and then pulverized and classified using a compact jet mill (manufactured by Seishin Enterprise Co., Ltd., Kodget System ⁇ -mkIII). About 6 ⁇ m of carbon precursor was obtained. The specific surface area of the obtained carbon precursor was 350 m 2 / g.
- the prepared carbon precursor 9.1 g and 0.9 g of polystyrene (manufactured by Sekisui Plastics Co., Ltd., average particle size 400 ⁇ m, residual carbon ratio 1.2%) were mixed.
- Adjustment example 2 an easily graphitizable carbonaceous material was prepared.
- a 70 kg petroleum pitch with a softening point of 205 ° C. and an H / C atomic ratio of 0.65 and 30 kg of naphthalene are charged into a 300 L internal pressure vessel equipped with stirring blades and outlet nozzles, and heated, melted and mixed at 190 ° C. After cooling to 80 to 90 ° C., the inside of the pressure vessel was pressurized with nitrogen gas, and the contents were extruded from the outlet nozzle to obtain a string-like molded body having a diameter of about 500 ⁇ m.
- this string-like molded body was pulverized so that the ratio (L / D) of the diameter (D) to the length (L) was about 1.5, and the obtained crushed material was heated to 93 ° C.
- the solution was poured into an aqueous solution in which 53% by weight of polyvinyl alcohol (saponification degree: 88%) was dissolved, stirred and dispersed, and cooled to obtain a spherical pitch molded body slurry. After most of the water was removed by filtration, naphthalene in the pitch molding was extracted and removed with n-hexane, which was about 6 times the weight of the spherical pitch molding.
- the porous spherical pitch obtained in this manner was heated to 150 ° C. while passing through heated air using a fluidized bed, and was maintained at 150 ° C. for 1 hour for oxidation to obtain a porous spherical oxidized pitch.
- the oxidation pitch was raised to 650 ° C. in a nitrogen gas atmosphere (normal pressure), and kept at 650 ° C. for 1 hour to carry out preliminary carbonization to obtain a carbon precursor.
- the obtained carbon precursor was pulverized to obtain a powdery carbon precursor having an average particle size of about 4 ⁇ m. 10 g of this powdery carbon precursor is deposited on a graphite board, placed in a horizontal tubular furnace having a diameter of 100 mm, heated to 1200 ° C.
- Adjustment example 4 The carbonaceous material 4 was obtained by repeating the operation of Adjustment Example 1 except that the temperature of the vapor phase decalcification treatment was changed to 980 ° C. instead of 870 ° C. Table 1 shows the full width at half maximum around 1360 cm ⁇ 1 and the difference between the Raman spectra measured before and after firing.
- Adjustment Example 5 The carbonaceous material 5 was obtained by repeating the operation of Adjustment Example 1 except that the temperature of the vapor phase decalcification treatment was changed to 800 ° C. instead of 870 ° C. Table 1 shows the full width at half maximum around 1360 cm ⁇ 1 and the difference between the Raman spectra measured before and after firing.
- Example 1 60% by mass of the carbonaceous material 1 obtained in Preparation Example 1 and 40% by mass of the graphitizable carbonaceous material obtained in Preparation Example 2 were mixed using a planetary kneader. A test battery using the obtained carbon material mixture 1 as a negative electrode active material was produced.
- Example 2 The procedure of Example 1 was repeated except that 80% by mass of the carbonaceous material 1 obtained in Preparation Example 1 and 20% by mass of the graphitizable carbonaceous material obtained in Preparation Example 2 were used. Then, a carbon material mixture 2 was prepared, and a test battery was produced.
- Example 3 60% by mass of the carbonaceous material 1 obtained in Preparation Example 1 and 40% by mass of the graphite material obtained in Preparation Example 3 were mixed using a planetary kneader. A test battery using the obtained carbon material mixture 3 as a negative electrode active material was produced.
- Example 4 The procedure of Example 3 was repeated except that 80% by mass of the carbonaceous material 1 obtained in Preparation Example 1 and 20% by mass of the graphite material obtained in Preparation Example 3 were used. Mixture 4 was prepared to produce a test battery.
- Example 1 The procedure of Example 1 was repeated except that 60% by mass of the carbonaceous material 4 obtained in Preparation Example 4 and 40% by mass of the graphitizable carbonaceous material obtained in Preparation Example 2 were used. Thus, a carbon material mixture was prepared to prepare a test battery.
- Example 2 The procedure of Example 1 was repeated except that 80% by mass of the carbonaceous material 5 obtained in Preparation Example 5 and 20% by mass of the graphite material obtained in Preparation Example 3 were used. A mixture was prepared and a test battery was made.
- the secondary batteries using the negative electrode of the carbon material mixture obtained in Examples 1 to 4 had a small irreversible capacity after electrode storage and a low DC resistance value. That is, it showed excellent energy density and input / output characteristics. Further, the moisture absorption of the carbon material mixtures obtained in Examples 1 to 4 was very low and excellent. Furthermore, the secondary battery using the negative electrode of the carbon material mixture showed excellent cycle characteristics. In contrast, the carbonaceous materials of Preparation Examples 4 and 5 in which the difference between the half-width value of the peak near 1360 cm ⁇ 1 between the carbon precursor and the carbonaceous material was not included in 50 to 84 cm ⁇ 1 were used. The carbon material mixture obtained in Comparative Examples 1 and 2 had a high moisture absorption, a large irreversible capacity after electrode storage, and a high DC resistance value.
- the non-aqueous electrolyte secondary battery using the carbonaceous material of the present invention has a good resistance to oxidative degradation as well as a good charge / discharge capacity. Therefore, it can be used particularly for in-vehicle applications such as hybrid vehicles (HEV) and electric vehicles (EV) that require a long life.
- HEV hybrid vehicles
- EV electric vehicles
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Abstract
Description
従って、本発明の目的は、混合炭素質材料を用いる非水電解質二次電池において高エネルギー密度及び優れた入出力特性を有する非水電解質二次電池を提供することである。
本発明は、こうした知見に基づくものである。
従って、本発明は、
[1](1)難黒鉛化性炭素前駆体と揮発性有機物とを800~1400℃の不活性ガス雰囲気下で焼成し、難黒鉛化性炭素質材料を得る工程、及び(2)前記難黒鉛化性炭素質材料と、易黒鉛化性炭素質材料及び/又は黒鉛質材料とを混合する工程、を含む非水電解質二次電池用混合負極材料の製造方法であって、広角X線回折法においてBragg式を用いて算出される、前記難黒鉛化性炭素質材料の(002)面の平均面間隔d002が0.38~0.40nmの範囲にあり、窒素吸着BET3点法により求めた前記難黒鉛化性炭素質材料の比表面積が1~10m2/gの範囲にあり、そしてラマンスペクトルにおいて観察される前記難黒鉛化性炭素前駆体の1360cm-1付近のピークの半値幅の値と、前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値との差が50~84cm-1である、非水電解質二次電池用混合負極材料の製造方法、
[2]ラマンスペクトルにおいて観察される前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値が、175~190cm-1の範囲にある、[1]に記載の非水電解質二次電池用混合負極材料の製造方法、
[3]ラマンスペクトルにおいて観察される前記難黒鉛化性炭素前駆体の1360cm-1付近のピークの半値幅の値が、230~260cm-1の範囲にある、
[1]又は[2]に記載の非水電解質二次電池用混合負極材料の製造方法、
[4](1)比表面積100~500m2/gの難黒鉛化性炭素前駆体と揮発性有機物との混合物を800~1400℃の不活性ガス雰囲気下で焼成し、難黒鉛化性炭素質材料を得る工程、及び(2)前記難黒鉛化性炭素質材料と、易黒鉛化性炭素質材料及び/又は黒鉛質材料とを混合する工程、を含む非水電解質二次電池用混合負極材料の製造方法、
[5]広角X線回折法においてBragg式を用いて算出される、前記難黒鉛化性炭素質材料の(002)面の平均面間隔d002が0.38~0.40nmの範囲にあり、そして
窒素吸着BET3点法により求めた前記難黒鉛化性炭素質材料の比表面積が1~10m2/gの範囲にある、[4]に記載の非水電解質二次電池用混合負極材料の製造方法、
[6]前記難黒鉛化性炭素前駆体が植物由来である、[1]~[5]のいずれかに記載の非水電解質二次電池用混合負極材料の製造方法、
[7]前記揮発性有機物が、常温で固体状態であり、そして残炭率が5重量%未満であって、前記残炭率は、前記揮発性有機物1gを、不活性ガス中で常温から10℃/分の昇温速度で800℃まで昇温した後、800℃で1時間灰化して得た残存物の重量と前記残存物の炭素含有率との積により定まる数値である、[1]~[6]のいずれかに記載の非水電解質二次電池用混合負極材料の製造方法、
[8]前記[1]~[7]のいずれかに記載の製造方法によって得ることのできる、非水電解質二次電池用混合負極材料、
[9]前記[8]に記載の混合負極材料を含む非水電解質二次電池用負極、及び
[10]前記[9]に記載の負極を含む、非水電解質二次電池、
に関する。
本明細書は、
[11]難黒鉛化性炭素質材料と易黒鉛化性炭素質材料及び/又は黒鉛質材料とを含む非水電解質二次電池用混合負極材料であって、広角X線回折法においてBragg式を用いて算出される、前記難黒鉛化性炭素質材料の(002)面の平均面間隔d002が0.38~0.40nmの範囲にあり、窒素吸着BET3点法により求めた前記難黒鉛化性炭素質材料の比表面積が1~10m2/gの範囲にあり、そしてラマンスペクトルにおいて観察される難黒鉛化性炭素質材料の炭素前駆体の1360cm-1付近のピークの半値幅の値と、前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値との差が50~84cm-1である、非水電解質二次電池用混合負極材料、
[12]ラマンスペクトルにおいて観察される前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値が、175~190cm-1の範囲にある、[11]に記載の非水電解質二次電池用混合負極材料、
[13]ラマンスペクトルにおいて観察される前記難黒鉛化性炭素質材料の炭素前駆体の1360cm-1付近のピークの半値幅の値が、230~260cm-1の範囲にある、[11]又は[12]に記載の非水電解質二次電池用混合負極材料、又は
[14]前記難黒鉛化性炭素質材料の炭素源が植物由来である、[11]~[13]のいずれかに記載の非水電解質二次電池用混合負極材料、
を開示する。
また、本発明の混合負極材料によれば、難黒鉛化性炭素質材料のみを用いた負極を含む非水電解質二次電池と比較して優れたエネルギー密度及び入出力特性を示す。また、易黒鉛化性炭素質材料又は黒鉛質材料のみを用いた負極を含む非水電解質二次電池と比較して、優れたサイクル特性を示す。
本発明の非水電解質二次電池用混合負極材料の製造方法は、(1)難黒鉛化性炭素前駆体と揮発性有機物とを800~1400℃の不活性ガス雰囲気下で焼成し、難黒鉛化性炭素質材料を得る工程、及び(2)前記難黒鉛化性炭素質材料と、易黒鉛化性炭素質材料及び/又は黒鉛質材料とを混合する工程、を含む非水電解質二次電池用混合負極材料の製造方法であって、広角X線回折法においてBragg式を用いて算出される、前記難黒鉛化性炭素質材料の(002)面の平均面間隔d002が0.38~0.40nmの範囲にあり、窒素吸着BET3点法により求めた前記難黒鉛化性炭素質材料の比表面積が1~10m2/gの範囲にあり、そしてラマンスペクトルにおいて観察される前記難黒鉛化性炭素前駆体の1360cm-1付近のピークの半値幅の値と、前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値との差が50~84cm-1である製造方法(以下、本発明の「非水電解質二次電池用混合負極材料の製造方法(A)」と称することがある)であってもよい。
また、本発明の非水電解質二次電池用混合負極材料の製造方法は、(1)比表面積100~500m2/gの難黒鉛化性炭素前駆体と揮発性有機物との混合物を800~1400℃の不活性ガス雰囲気下で焼成し、難黒鉛化性炭素質材料を得る工程、及び(2)前記難黒鉛化性炭素質材料と、易黒鉛化性炭素質材料及び/又は黒鉛質材料とを混合する工程、を含む製造方法(以下、本発明の「非水電解質二次電池用混合負極材料の製造方法(B)」と称することがある)であってもよい。
以下に、非水電解質二次電池用混合負極材料の製造方法(A)を説明し、続いて非水電解質二次電池用混合負極材料の製造方法(B)を説明する。
《焼成工程(1)》
焼成工程(1)においては、難黒鉛化性炭素前駆体と揮発性有機物とを800~1400℃の不活性ガス雰囲気下で焼成する。
(炭素源)
難黒鉛化性炭素前駆体は、難黒鉛化性炭素質材料を製造する際に炭素成分を供給する難黒鉛化性炭素質材料の前駆体であり、植物由来の炭素材(以下、「植物由来のチャー」と称することがある)を原料に用いて製造することができる。なお、チャーとは、一般的には、石炭を加熱した際に得られる溶融軟化しない炭素分に富む粉末状の固体を示すが、ここでは有機物を加熱して得られる溶融軟化しない炭素分に富む粉末状の固体も示す。
植物由来のチャーから製造された難黒鉛化性炭素質材料は、多量の活物質をドープ可能であることから、非水電解質二次電池の負極材料として基本的には適している。しかし、植物由来のチャーには、植物に含まれていた金属元素が多く含有されている。例えば、椰子殻チャーでは、カリウムを0.3%程度、鉄元素を0.1%程度含んでいる。このような金属元素を多く含んだ難黒鉛化性炭素質材料を負極として用いると、非水電解質二次電池の電気化学的な特性や安全性に好ましくない影響を与えることがある。
前記の気相脱灰工程及び焼成工程により、広角X線回折法においてBragg式を用いて算出される、前記難黒鉛化性炭素質材料の(002)面の平均面間隔d002が0.38~0.40nmの範囲にあり、窒素吸着BET3点法により求めた前記難黒鉛化性炭素質材料の比表面積が1~10m2/gの範囲にあり、そしてラマンスペクトルにおいて観察される前記難黒鉛化性炭素前駆体の1360cm-1付近のピークの半値幅の値と、前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値との差が50~84cm-1である、難黒鉛化性炭素質材料を得ることができる。
難黒鉛化性炭素前駆体は、必要に応じて粉砕工程、分級工程を経て、平均粒子径を調製される。粉砕工程、分級工程は、脱灰処理の後、実施することが好ましい。
難黒鉛化性炭素前駆体と揮発性有機物との混合物を焼成することによって、本発明の製造方法で用いる難黒鉛化性炭素質材料が得られる。難黒鉛化性炭素前駆体と揮発性有機物とを混合して焼成することにより、得られる難黒鉛化性炭素質材料の比表面積を低減させることができ、非水電解質二次電池用の負極材として好適な比表面積とすることができる。更に、難黒鉛化性炭素質材料への二酸化炭素の吸着量を調整することができる。
本発明の製造方法における焼成工程は、難黒鉛化性炭素前駆体と揮発性有機物との混合物を800~1400℃で焼成する。
本発明の製造方法における予備焼成工程は、例えば粉砕された混合物を350℃以上800℃未満で焼成することによって行うことができる。予備焼成工程によって、揮発分(例えばCO2、CO、CH4、H2等)とタール分とを除去できる。予備焼成工程後に実施する本焼成工程における揮発分やタール分の発生を軽減でき、焼成機の負担を軽減することができる。
本焼成工程は、通常の本焼成の手順に従って行うことができる。本焼成を行うことにより、非水電解質二次電池用の難黒鉛化性炭素質材料を得ることができる。
本発明の負極材料に含まれる難黒鉛化性炭素質材料は、限定されるものではないが、広角X線回折法においてBragg式を用いて算出される、前記難黒鉛化性炭素質材料の(002)面の平均面間隔d002が0.38~0.40nmの範囲にあり、窒素吸着BET3点法により求めた前記難黒鉛化性炭素質材料の比表面積が1~10m2/gの範囲にあり、ラマンスペクトルにおいて観察される前記難黒鉛化性炭素前駆体の1360cm-1付近のピークの半値幅の値と、前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値との差が50~84cm-1である。
本発明の製造方法における混合工程(2)は、前記難黒鉛化性炭素質材料と、易黒鉛化性炭素質材料及び/又は黒鉛質材料とを混合する工程である。
易黒鉛化性炭素とは、2000℃以上の高温で熱処理することにより黒鉛構造に変化する非黒鉛質炭素の総称であるが、本明細書においては、真密度が1.70g/cm3以上2.2g/cm3以下の非黒鉛質炭素を易黒鉛化性炭素と称する。易黒鉛化性炭素質材料の真密度は、特に限定されるものではないが、好ましくは1.80~2.18g/cm3の範囲にあり、より好ましくは1.90~2.15g/cm3の範囲である。
焼成は、(a)易黒鉛化性炭素前駆体を、800℃以上2500℃未満で焼成し、本焼成を行う焼成工程、でもよく、(b)易黒鉛化性炭素前駆体、300℃以上800℃未満で予備焼成し、その後800℃以上2500℃未満で本焼成を行う焼成工程、でもよい。
温度以外の条件は、前記「《焼成》」の欄に記載の条件で行うことができる。
前記易黒鉛化性炭素質材料の、広角X線回折法からBragg式を用いて算出される(002)面の平均面間隔d002は、好ましくは0.345nm以上0.375nm未満であり、更に好ましくは0.345nm~0.360nmである。
本発明の混合負極材料に含まれる黒鉛質材料は、限定されるものではないが、天然黒鉛又は人造黒鉛を挙げることができる。
黒鉛化処理は、炭素前駆体を連続して黒鉛化処理温度(2500~3000℃)まで昇温して炭素化と黒鉛化処理を連続して行うことも可能であるが、一旦黒鉛化処理温度より低い温度で、例えば500~1500℃で炭素化(焼成)した後、黒鉛化処理することが工業的に実施する場合は装置の材質、構造、加熱方法等の設計の容易さ等の点から好ましい場合が多い。
黒鉛化処理は不活性ガス雰囲気中又は減圧下に2500~3000℃の温度に数分~数時間程度保持することによって行う。黒鉛化温度とは被処理物が受ける最高の処理温度をいう。黒鉛化は減圧下又は不活性ガス雰囲気中で行うが、これは黒鉛化時に原料が雰囲気ガスと反応することを防止するものである。不活性ガスとしてはアルゴンガス、ヘリウムガス等を挙げることができる。又減圧下の黒鉛化においては上記不活性ガス共存下の雰囲気が好ましい。
黒鉛の理論密度は、2.27g/cm3であるが、本発明の製造方法において使用される黒鉛質材料の真密度は、2.15g/cm3以上であり、好ましくは2.17g/cm3以上であり、更に好ましくは2.20g/cm3以上である。真密度が大きい場合、電池容積当たりのエネルギー密度を高くすることができるからである。
黒鉛質材料の、広角X線回折法からBragg式を用いて算出される(002)面の平均面間隔d002は、好ましくは0.336~0.345nmであり、より好ましくは0.336~0.344nmであり、更に好ましくは0.337~0.342nmである。d002が0.350nmを超える黒鉛質材料は、放電曲線の平坦性が悪化することがある。
黒鉛質材料の、c軸方向の結晶子の大きさLc(002)は、好ましくは15nmを超え50nm以下であり、より好ましくは15nmを超え40nm以下であり、更に好ましくは20~40nmである。Lc(002)が50nmを超えるような黒鉛構造の発達した黒鉛質材料を負極材料として用いた二次電池においては、活物質のドープ及び脱ドープによる黒鉛質物質の崩壊や電解液の分解が起り易く、好ましくない。
本発明の混合工程における前記難黒鉛化性炭素質材料と、易黒鉛化性炭素質材料及び/又は黒鉛質材料との混合比は、本発明の効果が得られる限りにおいて、限定されるものではないが、難黒鉛化性炭素質材料は、得られる混合負極材料の総質量に対して20質量%~80質量%であり、好ましくは25質量%~75質量%であり、更に好ましくは、30質量%~70質量%である。易黒鉛化性炭素質材料は、得られる混合負極材料の総質量に対して20質量%~80質量%であり、好ましくは25質量%~75質量%であり、更に好ましくは、30質量%~70質量%である。黒鉛質材料は、得られる混合負極材料の総質量に対して20質量%~80質量%であり、好ましくは25質量%~75質量%であり、更に好ましくは、30質量%~70質量%である。
《焼成工程(1)》
前記製造方法(B)における焼成工程(1)においては、比表面積100~500m2/gの難黒鉛化性炭素前駆体と揮発性有機物との混合物を800~1400℃の不活性ガス雰囲気下で焼成する。
本発明の製造方法(B)において、粉砕後の難黒鉛化性炭素前駆体の比表面積は、100~500m2/gであり、好ましくは200~500m2/gであり、例えば200~400m2/gである。比表面積が小さすぎると、後述する焼成工程を経ても、難黒鉛化性炭素質材料の微細孔を十分に低減することができないことがあり、難黒鉛化性炭素質材料の吸湿性が低下しにくくなることがある。難黒鉛化性炭素質材料に水分が存在すると、電解液の加水分解に伴う酸の発生や水の電気分解によるガスの発生が問題を引き起こすことがある。また、空気雰囲気下で難黒鉛化性炭素質材料の酸化が進み、電池性能が大きく変化することもある。比表面積が大きくなりすぎると、後述する焼成工程を経ても炭素質材料の比表面積が小さくならず、非水電解質二次電池のリチウムイオンの利用効率が低下することがある。難黒鉛化性炭素前駆体の比表面積は、気相脱灰の温度の制御によって調製することが可能である。なお、本明細書において、比表面積はBET法(窒素吸着BET3点法)により定まる比表面積(BET比表面積)を意味する。具体的には後述する方法を用いて測定することができる。
非水電解質二次電池用混合負極材料の製造方法(B)で使用する難黒鉛化性炭素前駆体は、前記の通り、比表面積100~500m2/gである。それ以外の難黒鉛化性炭素前駆体の特徴及び調整方法などは、限定されるものではないが、実質的に非水電解質二次電池用混合負極材料の製造方法(A)の「《難黒鉛化性炭素質前駆体》」の欄に記載の難黒鉛化性炭素前駆体と同様であってもよい。
本発明の製造方法(B)において使用される揮発性有機物は、実質的に前記非水電解質二次電池用混合負極材料の製造方法(A)の「《揮発性有機物》」の欄に記載の揮発性有機物を用いることができる。
本発明の製造方法(B)における焼成は、比表面積100~500m2/gの難黒鉛化性炭素前駆体を用いる限りにおいて、実質的に前記非水電解質二次電池用混合負極材料の製造方法(A)の「《焼成》」の欄に記載に従って、行うことができる。
本発明の製造方法(B)において使用される難黒鉛化性炭素質材料は、比表面積100~500m2/gの難黒鉛化性炭素前駆体を焼成して得られたものである限り、実質的に前記非水電解質二次電池用混合負極材料の製造方法(A)の「《難黒鉛化性炭素質材料》」の欄に記載の難黒鉛化性炭素質材料と同様のものでもよい。
本発明の製造方法(B)における混合工程(2)は、実質的に前記非水電解質二次電池用混合負極材料の製造方法(A)の「《混合工程(2)》」の欄の記載に従って、行うことができる。
本発明の非水電解質二次電池用混合負極材料は、難黒鉛化性炭素質材料と易黒鉛化性炭素質材料及び/又は黒鉛質材料とを含む非水電解質二次電池用混合負極材料であって、広角X線回折法においてBragg式を用いて算出される、前記難黒鉛化性炭素質材料の(002)面の平均面間隔d002が0.38~0.40nmの範囲にあり、窒素吸着BET3点法により求めた前記難黒鉛化性炭素質材料の比表面積が1~10m2/gの範囲にあり、そしてラマンスペクトルにおいて観察される難黒鉛化性炭素質材料の炭素前駆体の1360cm-1付近のピークの半値幅の値と、前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値との差が50~84cm-1である。本発明の非水電解質二次電池用混合負極材料は、限定されるものではないが、例えば本発明の非水電解質二次電池用混合負極材料の製造方法(A)又は(B)によって、製造することができる。
本発明の非水電解質二次電池用混合負極材料に含まれる難黒鉛化性炭素質材料の(002)面の平均面間隔d002は、広角X線回折法においてBragg式を用いて算出され、0.38~0.40nmの範囲にある。前記難黒鉛化性炭素質材料の窒素吸着BET3点法により求めた比表面積は1~10m2/gの範囲にある。前記難黒鉛化性炭素質材料の難黒鉛化性炭素前駆体のラマンスペクトルにおいて観察される1360cm-1付近のピークの半値幅の値と、前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値との差が50~84cm-1であり、より好ましくは55cm-1~83cm-1であり、更に好ましくは60cm-1~80cm-1である。
本発明の混合負極材料(炭素材混合物)に含まれる難黒鉛化性炭素質材料、易黒鉛化性炭素質材料、及び黒鉛質材料は、密度こう配管法による真密度によって分離することができる。具体的には、炭素繊維-密度の試験方法(JISR7603-1999)の密度こう配管法に準拠して操作を行い、炭素材混合物に含まれる非黒鉛性炭素(易黒鉛化性炭素質材料、及び黒鉛質材料)を分離し、測定された真密度から、それらを同定することができる。
更に、バインダー等を含み成形された非水電解質二次電池用負極から、炭素質材料を分離し、同じように密度こう配管法による真密度によって、難黒鉛化性炭素質材料、易黒鉛化性炭素質材料、及び黒鉛質材料を分離することが可能である。
《負極電極の製造》
本発明の混合負極材料を用いる負極電極は、炭素質材料に結合剤(バインダー)を添加し適当な溶媒を適量添加、混練し、電極合剤とした後に、金属板等からなる集電板に塗布・乾燥後、加圧成形することにより製造することができる。本発明の混合負極材料を用いることにより特に導電助剤を添加しなくとも高い導電性を有する電極を製造することができるが、更に高い導電性を賦与することを目的に必要に応じて電極合剤を調製時に、導電助剤を添加することができる。導電助剤としては、アセチレンブラック、ケッチェンブラック、カーボンナノファイバー、カーボンナノチューブ、又はカーボンファイバーなどを用いることができ、添加量は使用する導電助剤の種類によっても異なるが、添加する量が少なすぎると期待する導電性が得られないので好ましくなく、多すぎると電極合剤中の分散が悪くなるので好ましくない。このような観点から、添加する導電助剤の好ましい割合は0.5~15重量%(ここで、活物質(混合負極材料)量+バインダー量+導電助剤量=100重量%とする)であり、更に好ましくは0.5~7重量%、特に好ましくは0.5~5重量%である。結合剤としては、PVDF(ポリフッ化ビニリデン)、ポリテトラフルオロエチレン、およびSBR(スチレン・ブタジエン・ラバー)とCMC(カルボキシメチルセルロース)との混合物等の電解液と反応しないものであれば特に限定されない。中でもPVDFは、活物質表面に付着したPVDFがリチウムイオン移動を阻害することが少なく、良好な入出力特性を得るために好ましい。PVDFを溶解しスラリーを形成するためにN-メチルピロリドン(NMP)などの極性溶媒が好ましく用いられるが、SBRなどの水性エマルジョンやCMCを水に溶解して用いることもできる。結合剤の添加量が多すぎると、得られる電極の抵抗が大きくなるため、電池の内部抵抗が大きくなり電池特性を低下させるので好ましくない。また、結合剤の添加量が少なすぎると、負極材料粒子相互および集電材との結合が不十分となり好ましくない。結合剤の好ましい添加量は、使用するバインダーの種類によっても異なるが、PVDF系のバインダーでは好ましくは3~13重量%であり、更に好ましくは3~10重量%である。一方、溶媒に水を使用するバインダーでは、SBRとCMCとの混合物など、複数のバインダーを混合して使用することが多く、使用する全バインダーの総量として0.5~5重量%が好ましく、更に好ましくは1~4重量%である。電極活物質層は集電板の両面に形成するのが基本であるが、必要に応じて片面でもよい。電極活物質層が厚いほど、集電板やセパレータなどが少なくて済むため高容量化には好ましいが、対極と対向する電極面積が広いほど入出力特性の向上に有利なため活物質層が厚すぎると入出力特性が低下するため好ましくない。好ましい活物質層(片面当たり)の厚みは、限定されるものではなく10~1000μmの範囲内であるが、好ましくは10~80μmであり、更に好ましくは20~75μm、特に好ましくは20~60μmである。
負極電極は、通常集電体を有する。負極集電体としては、例えば、SUS、銅、ニッケル又はカーボンを用いるができ、中でも、銅又はSUSが好ましい。
本発明の混合負極材料を用いて、非水電解質二次電池の負極を形成した場合、正極材料、セパレータ、電解液など電池を構成する他の材料は特に限定されることなく、非水溶媒二次電池として従来使用され、あるいは提案されている種々の材料を使用することが可能である。
正極電極は、正極活物質を含み、更に導電助剤、バインダー、又はその両方を含んでもよい。正極活物質層における正極活物質と、他の材料との混合比は、本発明の効果が得られる限りにおいて、限定されるものではなく、適宜決定することができる。
正極活物質は、正極活物質を限定せずに用いることができる。例えば、層状酸化物系(LiMO2と表されるもので、Mは金属:例えばLiCoO2、LiNiO2、LiMnO2、又はLiNixCoyMnzO2(ここでx、y、zは組成比を表す))、オリビン系(LiMPO4で表され、Mは金属:例えばLiFePO4など)、スピネル系(LiM2O4で表され、Mは金属:例えばLiMn2O4など)の複合金属カルコゲン化合物を挙げることができ、これらのカルコゲン化合物を必要に応じて混合してもよい。
また、コバルト酸リチウムのコバルトの一部をニッケルとマンガンで置換し、コバルト、ニッケル、マンガンの3つを使用することで材料の安定性を高めた三元系〔Li(Ni-Mn-Co)O2〕や前記三元系のマンガンの代わりにアルミニウムを使用するNCA系材料〔Li(Ni-Co-Al)O2〕が知られており、これらの材料を使用することができる。
正極活物質層は、通常集電体を有する。負極集電体としては、例えば、SUS、アルミニウム、ニッケル、鉄、チタンおよびカーボンを用いるができ、中でも、アルミニウム又はSUSが好ましい。
これら正極と負極との組み合わせで用いられる非水溶媒型電解液は、一般に非水溶媒に電解質を溶解することにより形成される。非水溶媒としては、例えばプロピレンカーボネート、エチレンカーボネート、ジメチルカーボネート、ジエチルカーボネート、ジメトキシエタン、ジエトキシエタン、γ-ブチルラクトン、テトラヒドロフラン、2-メチルテトラヒドロフラン、スルホラン、又は1,3-ジオキソランなどの有機溶媒の一種又は二種以上を組み合わせて用いることができる。また、電解質としては、LiClO4、LiPF6、LiBF4、LiCF3SO3、LiAsF6、LiCl、LiBr、LiB(C6H5)4、又はLiN(SO3CF3)2などが用いられる。二次電池は、一般に上記のようにして形成した正極層と負極層とを必要に応じて不織布、その他の多孔質材料などからなる透液性セパレータを介して対向させ電解液中に浸漬させることにより形成される。セパレータとしては、二次電池に通常用いられる不織布、その他の多孔質材料からなる透過性セパレータを用いることができる。あるいはセパレータの代わりに、もしくはセパレータと一緒に、電解液を含浸させたポリマーゲルからなる固体電解質を用いることもできる。
なお、以下に炭素前駆体、揮発性有機物、炭素質材料、及び混合負極材料等の物性値の測定法を記載するが、実施例を含めて、本明細書中に記載する物性値は、以下の方法により求めた値に基づくものである。
以下にBETの式から誘導された近似式を記す。
「株式会社リガク製MiniFlexII」を用い、炭素質材料粉末を試料ホルダーに充填し、Niフィルターにより単色化したCuKα線を線源とし、X線回折図形を得た。回折図形のピーク位置は重心法(回折線の重心位置を求め、これに対応する2θ値でピーク位置を求める方法)により求め、標準物質用高純度シリコン粉末の(111)面の回折ピークを用いて補正した。CuKα線の波長を0.15418nmとし、以下に記すBraggの公式によりd002を算出した。
株式会社堀場製作所製、LabRAM ARAMISを用い、レーザー波長532nmの光源を用いて、ラマンスペクトルを測定した。試験は、各サンプルにおいて無作為に3箇所の粒子をサンプリングし、更にサンプリングした各粒子内から2箇所について測定した。測定条件は、波長範囲50~2000cm-1、積算回数1000回であり、計6箇所の平均値を計測値として算出した。
半値幅は、上記測定条件にて得られたスペクトルに対し、Dバンド(1360cm-1付近)とGバンド(1590cm-1付近)とのピーク分離を、ガウス関数でフィッティングして実施した後、測定した。
残炭率は、試料を不活性ガス中で強熱した後の強熱残分の炭素量を定量することにより測定した。強熱は、揮発性有機物およそ1g(この正確な重量をW1(g)とする)を坩堝にいれ、1分間に20Lの窒素を流しながら坩堝を電気炉にて、10℃/分の昇温速度で常温から800℃まで昇温、その後800℃で1時間強熱した。このときの残存物を強熱残分とし、その重量をW2(g)とした。
次いで上記強熱残分について、JIS M8819に定められた方法に準拠して元素分析を行い、炭素の重量割合P1(%)を測定した。残炭率P2(%)は以下の式により算出した。
JIS R7212に定められた方法に準拠し、ブタノールを用いて測定した。概要を以下に記す。
内容積約40mLの側管付比重びんの質量(m1)を正確に量る。次に、その底部に試料を約10mmの厚さになるように平らに入れた後、その質量(m2)を正確に量る。これに1-ブタノールを静かに加えて、底から20mm程度の深さにする。次に比重びんに軽い振動を加えて、大きな気泡の発生がなくなったのを確かめた後、真空デシケーター中に入れ、徐々に排気して2.0~2.7kPaとする。その圧力に20分間以上保ち、気泡の発生が止まった後取り出して、更に1-ブタノールで満たし、栓をして恒温水槽(30±0.03℃に調節してあるもの)に15分間以上浸し、1-ブタノールの液面を標線に合わせる。次に、これを取り出して外部をよくぬぐって室温まで冷却した後、質量(m4)を正確に量る。次に同じ比重びんに1-ブタノールだけを満たし、前記と同じようにして恒温水槽に浸し、標線を合わせた後、質量(m3)を量る。また、使用直前に沸騰させて溶解した気体を除いた蒸留水を比重びんにとり、前と同様に恒温水槽に浸し、標線を合わせた後質量(m5)を量る。真密度(ρBt)は次の式により計算する。
試料約0.1gに対し、分散剤(カチオン系界面活性剤「SNウェット366」(サンノプコ社製))を3滴加え、試料に分散剤を馴染ませる。次に、純水30mLを加え、超音波洗浄機で約2分間分散させたのち、粒径分布測定器(島津製作所製「SALD-3000J」)で、粒径0.05~3000μmの範囲の粒径分布を求めた。
得られた粒径分布から、累積容積が50%となる粒径をもって平均粒径Dv50(μm)とした。
測定前に、負極材料を200℃で12時間、真空乾燥させ、その後、この負極材料1gを直径8.5cm、高さ1.5cmのシャーレに、できる限り薄い厚みとなるように広げた。温度25℃、湿度50%の一定雰囲気に制御した恒温恒湿槽内に、100時間、放置した後、恒温恒湿槽からシャーレを取り出し、カールフィッシャ水分計(三菱化学アナリテック/CA-200)を用いて吸湿量を測定した。気化室(VA-200)の温度は200℃とした。
炭素質材料又は炭素材混合物を用いて、以下の(a)~(g)の操作を行い、負極電極及び非水電解質二次電池を作製し、そして電極性能の評価を行った。
(a)負極電極の作製
炭素質材料94重量部、ポリフッ化ビニリデン(株式会社クレハ製「KF#9100」)6重量部にNMPを加えてペースト状にし、銅箔上に均一に塗布した。乾燥した後、銅箔より直径15mmの円板状に打ち抜き、これをプレスして電極とした。なお、電極中の炭素質材料の量は約10mgになるように調整した。
本発明の炭素材混合物は、非水電解質二次電池の負極電極を構成するのに適しているが、電池活物質の放電容量(脱ドープ量)及び不可逆容量(非脱ドープ量)を、対極の性能のバラツキに影響されることなく精度良く評価するために、特性の安定したリチウム金属を対極として、上記で得られた電極を用いてリチウム二次電池を構成し、その特性を評価した。
リチウム極の調製は、Ar雰囲気中のグローブボックス内で行った。予めCR2016サイズのコイン型電池用缶の外蓋に直径16mmのステンレススチール網円盤をスポット溶接した後、厚さ0.8mmの金属リチウム薄板を直径15mmの円盤状に打ち抜いたものをステンレススチール網円盤に圧着し、電極(対極)とした。
このようにして製造した電極の対を用い、電解液としてはエチレンカーボネートとメチルエチルカーボネートを容量比で3:7で混合した混合溶媒に1.2mol/Lの割合でLiPF6を加えたものを使用し、直径19mmの硼珪酸塩ガラス繊維製微細細孔膜のセパレータとして、ポリエチレン製のガスケットを用いて、Arグローブボックス中で、2016サイズのコイン型非水電解質系リチウム二次電池を組み立てた。
上記構成のリチウム二次電池について、充放電試験装置(東洋システム製「TOSCAT」)を用いて充放電試験を行った。炭素極へのリチウムのドープ反応を定電流定電圧法により行い、脱ドープ反応を定電流法で行った。ここで、正極にリチウムカルコゲン化合物を使用した電池では、炭素極へのリチウムのドープ反応が「充電」であり、本発明の(a)~(b)で作製した試験電池のように対極にリチウム金属を使用した電池では、炭素極へのドープ反応が「放電」と呼ぶことになり、用いる対極により同じ炭素極へのリチウムのドープ反応の呼び方が異なる。そこでここでは、便宜上炭素極へのリチウムのドープ反応を「充電」と記述することにする。逆に「放電」とは(a)~(b)で作製した試験電池では充電反応であるが、炭素質材料からのリチウムの脱ドープ反応であるため便宜上「放電」と記述することにする。
ここで採用した充電方法は、定電流定電圧法であり、具体的には端子電圧が50mVに達するまで0.5mA/cm2の電流密度で定電流充電を行い、50mVに達した時点で一定電圧のまま充電を行い、電流値が20μAに達するまで充電を継続した。
充電終了後、30分間電池回路を開放し、その後放電を行った。放電は0.5mA/cm2で定電流放電を行い、終止電圧を1.5Vとした。このときの放電した電気量を放電容量と定義し、炭素質材料電極の体積(集電体の体積を除く)で除したmAh/cm3を単位として、体積当たりの放電容量を示した。特性測定は25℃で行った。同一試料を用いて作製した試験電池について、n=3の測定値を平均して放電容量を決定した。
正極は、LiNi1/3Co1/3Mn1/3O2(UMICORE製Cellcore MX6)94重量部、カーボンブラック(TIMCAL製Super P)3重量部、ポリフッ化ビニリデン(クレハ製KF#7200)3重量部にNMPを加えてペースト状にし、アルミニウム箔上に均一に塗布した。乾燥した後、塗工電極を直径14mmの円板上に打ち抜き、これをプレスし電極とした。なお、電極中のLiNi1/3Co1/3Mn1/3O2の量は約15mgになるように調整した。
負極は、負極活物質の充電容量の95%となるよう負極電極中の炭素質材料の重量を調整した以外、上記(a)と同様の手順で負極電極を作製した。なお、LiNi1/3Co1/3Mn1/3O2の容量を165mAh/gとして計算し、1C(Cは時間率を表す)を2.475mAとした。
このようにして調製した電極の対を用い、電解液としてはエチレンカーボネートとメチルエチルカーボネートを容量比で3:7で混合した混合溶媒に1.2mol/Lの割合でLiPF6を加えたものを使用し、直径17mmの硼珪酸塩ガラス繊維製微細細孔膜のセパレータとして、ポリエチレン製のガスケットを用いて、Arグローブボックス中で、2032サイズのコイン型非水電解質系リチウム二次電池を組み立てた。
上記(d)の構成の非水電解質二次電池について、充放電試験機(東洋システム製「TOSCAT」)を用いて電池試験を行った。はじめにエージングを行った後、50%充電状態で入出力試験および直流抵抗値試験を開始した。以下にエージング手順(e-1)~(e-3)を示す。
定電流定電圧法を用いて、電池電圧が4.2VになるまではC/10の電流値で定電流充電を行い、その後、電池電圧を4.2Vに保持するように(定電圧に保持しながら)電流値を減衰させて電流値がC/100以下になるまで充電を継続した。充電終了後、30分間電池回路を開放した。
エージング手順(e-2)
電池電圧が2.75Vに達するまでC/10の定電流値で放電を行った。充電終了後、30分間電池回路を開放した。
不可逆容量は、前記エージング手順(e-1)の充電容量とエージング手順(e-2)の放電容量との差から計算した。
エージング手順(e-3)
エージング手順(e-1)~(e-2)を更に2回繰り返した。
入出力試験および直流抵抗値試験手順(e-4)
上記放電容量に対する50%の充電状態において、1Cの電流値で放電を10秒間行った後、10分間電池回路を開放した。
入出力試験および直流抵抗値試験手順(e-5)
1Cの電流値で充電を10秒間行った後、10分間電池回路を開放した。
入出力試験および直流抵抗値試験手順(e-6)
入出力試験手順(e-4)と(e-5)における充放電の電流値を、2C、3Cに変更して、同様に入出力試験手順(e-4)~(e-5)を行った。
入出力試験および直流抵抗値試験手順(e-7)
充電側において10秒目の電圧を各電流値に対してプロットし、最小二乗法によって近似直線を得た。この近似直線を外挿して充電側の上限電圧を4.2Vとした際の電流値を算出した。
入出力試験および直流抵抗値試験手順(e-8)
得られた電流値(A)と上限電圧(V)との積を入力値(W)とし、正極および負極の体積(両方の集電体の体積を除く)で除したW/cm3を単位として、体積当たりの入力値を示した。
入出力試験および直流抵抗値試験手順(e-9)
同様に、放電側において10秒目の電圧を各電流値に対してプロットし、最小二乗法によって近似直線を得た。この近似直線を外挿して放電側の下限電圧を2.75Vとした際の電流値を算出した。
入出力試験および直流抵抗値試験手順(e-10)
得られた電流値(A)と下限電圧(V)との積を出力値(W)とし、正極および負極の体積(両方の集電体の体積を除く)で除したW/cm3を単位として、体積当たりの出力値を示した。
入出力試験および直流抵抗値試験手順(e-11)
放電側において電流印加停止から10分後までの電圧差を各電流値に対してプロットし、最小二乗法によって近似直線を得た。この近似直線の傾きを直流抵抗値(Ω)とした。
上記(d)で作製した負極を温度25℃、湿度50%の一定雰囲気に制御した恒温恒湿槽内に、7日間(168時間)、放置した後、恒温恒湿槽から取り出し、上記(d)~(e)と同様の手順で評価用電池の作製および直流抵抗値試験を行った。保存後の直流抵抗値を保存前の直流抵抗値で除し、保存前後の直流抵抗変化率(%)とした。また、(e-1)及び(e-2)から得られた充電容量と放電容量の差から、不可逆容量を計算した。保存後の不可逆容量を保存前の不可逆容量で除し、保存前後の不可逆容量変化率(%)とした。
LiNi1/3Co1/3Mn1/3O2正極との組み合わせ電池における、50℃で100サイクル後の初回放電量に対する容量維持率(%)として求めた。
評価用電池は、上記(d)と同様の手順で作製した。
上記(d)の構成の非水電解質二次電池について、充放電試験機(東洋システム製「TOSCAT」)を用いて電池試験を行った。はじめにエージングを行った後、サイクル特性試験を開始した。以下にエージング手順(g-1)~(g-5)を示す。
定電流定電圧法を用いて、電池電圧が4.1VになるまではC/20の電流値で定電流充電を行い、その後、電池電圧を4.1Vに保持するように(定電圧に保持しながら)電流値を減衰させて電流値がC/100以下になるまで充電を継続した。充電終了後、30分間電池回路を開放した。
エージング手順(g-2)
電池電圧が2.75Vに達するまでC/20の定電流値で放電を行った。充電終了後、30分間電池回路を開放した。
エージング手順(g-3)
エージング手順(g-1)の電池電圧を4.2Vに、(g-1)と(g-2)の電流値をC/20からC/5に変更して、(g-1)~(g-2)を2回繰り返した。
この充放電方法を50℃で100サイクル繰り返した。100サイクル目の放電容量を1サイクル目の放電容量で除し、容量維持率(%)とした。
椰子殻を破砕し、500℃で乾留して、粒径2.360~0.850mmの椰子殻チャー(粒径2.360~0.850mmの粒子を98重量%含有)を得た。この椰子殻チャー100gに対して、塩化水素ガスを1体積%含む窒素ガスを10L/分の流量で供給しながら870℃で50分間気相脱灰処理を実施した。その後、塩化水素ガスの供給のみを停止し、窒素ガスを10L/分の流量で供給しながら、更に870℃で30分間気相脱酸処理を実施し、炭素前駆体を得た。
得られた炭素前駆体を、ボールミルを用いて平均粒子径10μmに粗粉砕した後、コンパクトジェットミル(株式会社セイシン企業製、コジェットシステムα-mkIII)を用いて粉砕及び分級し、平均粒径約6μmの炭素前駆体を得た。得られた炭素前駆体の比表面積は、350m2/gであった。
調製した炭素前駆体9.1gと、ポリスチレン0.9g(積水化成品工業株式会社製、平均粒径400μm、残炭率1.2%)とを混合した。この混合物10gを黒鉛製容器(縦100mm、横100mm、高さ50mm)に入れ、株式会社モトヤマ製高速昇温炉中、毎分5Lの窒素流量下、毎分60℃の昇温速度で1290℃まで昇温した後、24分間保持し、自然冷却した。炉内温度が200℃以下に低下したことを確認し、炉内から炭素質材料1を取り出した。回収された炭素質材料1は8.1gであり、炭素前駆体に対する回収率は89%であった。
本調整例では、易黒鉛化性炭素質材料の調製を行った。
軟化点205℃、H/C原子比0.65の石油系ピッチ70kgと、ナフタレン30kgとを、撹拌翼および出口ノズルのついた内容積300Lの耐圧容器に仕込み、190℃で加熱溶融混合を行った後、80~90℃に冷却し、耐圧容器内を窒素ガスにより加圧して、内容物を出口ノズルから押出し、直径約500μmの紐状成型体を得た。次いで、この紐状成型体を直径(D)と長さ(L)の比(L/D)が約1.5になるように粉砕し、得られた破砕物を93℃に加熱した0.53重量%のポリビニルアルコール(ケン化度88%)を溶解した水溶液中に投入し、撹拌分散し、冷却して球状ピッチ成型体スラリーを得た。大部分の水をろ過により取り除いた後、球状ピッチ成形体の約6倍量の重量のn-ヘキサンでピッチ成形体中のナフタレンを抽出除去した。このようにして得た多孔性球状ピッチを、流動床を用いて、加熱空気を通じながら、150℃まで昇温し、150℃に1時間保持して酸化し、多孔性球状酸化ピッチを得た。
次に酸化ピッチを窒素ガス雰囲気中(常圧)で650℃まで昇温し、650℃で1時間保持して予備炭素化を実施し、炭素前駆体を得た。得られた炭素前駆体を粉砕し、平均粒子径約4μmの粉末状炭素前駆体とした。
この粉末状炭素前駆体10gを黒鉛ボードに堆積し、直径100mmの横型管状炉に入れ、250℃/hの速度で1200℃まで昇温し、1200℃で1時間保持して、易黒鉛化性炭素質材料を得た。なお、本焼成は、流量10L/minの窒素雰囲気下で行った。
焼成前及び焼成後のラマンスペクトル測定による1360cm-1付近の半値幅及びそれらの差を表1に示す。
人造黒鉛(上海杉杉製CMS-G10)を黒鉛質材料とした。
気相脱灰処理の温度を870℃に代えて980℃で行った以外は調整例1の操作を繰り返して、炭素質材料4を得た。焼成前及び焼成後のラマンスペクトル測定による1360cm-1付近の半値幅及びそれらの差を表1に示す。
気相脱灰処理の温度を870℃に代えて800℃で行った以外は調整例1の操作を繰り返して、炭素質材料5を得た。焼成前及び焼成後のラマンスペクトル測定による1360cm-1付近の半値幅及びそれらの差を表1に示す。
調製例1で得られた60質量%の炭素質材料1、及び調製例2で得られた40質量%の易黒鉛化性炭素質材料を遊星型混練機によって混合した。得られた炭素材混合物1を、負極活物質として用いた試験電池を作製した。
調製例1で得られた80質量%の炭素質材料1及び調製例2で得られた20質量%の易黒鉛化性炭素質材料を用いたことを除いては、実施例1の操作を繰り返して、炭素材混合物2を調製し、試験電池を作製した。
調製例1で得られた60質量%の炭素質材料1、及び調製例3で得られた40質量%の黒鉛質材料を遊星型混練機によって混合した。得られた炭素材混合物3を、負極活物質として用いた試験電池を作製した。
調製例1で得られた80質量%の炭素質材料1及び調製例3で得られた20質量%の黒鉛質材料を用いたことを除いては、実施例3の操作を繰り返して、炭素材混合物4を調製し、試験電池を作製した。
調製例4で得られた60質量%の炭素質材料4及び調製例2で得られた40質量%の易黒鉛化性炭素質材料を用いたことを除いては、実施例1の操作を繰り返して、炭素材混合物を調製し、試験電池を作製した。
調製例5で得られた80質量%の炭素質材料5及び調製例3で得られた20質量%の黒鉛質材料を用いたことを除いては、実施例1の操作を繰り返して、炭素材混合物を調製し、試験電池を作製した。
以上、本発明を特定の態様に沿って説明したが、当業者に自明の変形や改良は本発明の範囲に含まれる。
Claims (14)
- (1)難黒鉛化性炭素前駆体と揮発性有機物とを800~1400℃の不活性ガス雰囲気下で焼成し、難黒鉛化性炭素質材料を得る工程、及び
(2)前記難黒鉛化性炭素質材料と、易黒鉛化性炭素質材料及び/又は黒鉛質材料とを混合する工程、を含む非水電解質二次電池用混合負極材料の製造方法であって、
広角X線回折法においてBragg式を用いて算出される、前記難黒鉛化性炭素質材料の(002)面の平均面間隔d002が0.38~0.40nmの範囲にあり、
窒素吸着BET3点法により求めた前記難黒鉛化性炭素質材料の比表面積が1~10m2/gの範囲にあり、そして
ラマンスペクトルにおいて観察される前記難黒鉛化性炭素前駆体の1360cm-1付近のピークの半値幅の値と、前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値との差が50~84cm-1である、
非水電解質二次電池用混合負極材料の製造方法。 - ラマンスペクトルにおいて観察される前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値が、175~190cm-1の範囲にある、
請求項1に記載の非水電解質二次電池用混合負極材料の製造方法。 - ラマンスペクトルにおいて観察される前記難黒鉛化性炭素前駆体の1360cm-1付近のピークの半値幅の値が、230~260cm-1の範囲にある、
請求項1又は2に記載の非水電解質二次電池用混合負極材料の製造方法。 - (1)比表面積100~500m2/gの難黒鉛化性炭素前駆体と揮発性有機物との混合物を800~1400℃の不活性ガス雰囲気下で焼成し、難黒鉛化性炭素質材料を得る工程、及び
(2)前記難黒鉛化性炭素質材料と、易黒鉛化性炭素質材料及び/又は黒鉛質材料とを混合する工程、を含む非水電解質二次電池用混合負極材料の製造方法。 - 広角X線回折法においてBragg式を用いて算出される、前記難黒鉛化性炭素質材料の(002)面の平均面間隔d002が0.38~0.40nmの範囲にあり、そして
窒素吸着BET3点法により求めた前記難黒鉛化性炭素質材料の比表面積が1~10m2/gの範囲にある、
請求項4に記載の非水電解質二次電池用混合負極材料の製造方法。 - 前記難黒鉛化性炭素前駆体が植物由来である、請求項1~5のいずれか一項に記載の非水電解質二次電池用混合負極材料の製造方法。
- 前記揮発性有機物が、常温で固体状態であり、そして残炭率が5重量%未満であって、前記残炭率は、前記揮発性有機物1gを、不活性ガス中で常温から10℃/分の昇温速度で800℃まで昇温した後、800℃で1時間灰化して得た残存物の重量と前記残存物の炭素含有率との積により定まる数値である、
請求項1~6のいずれか一項に記載の非水電解質二次電池用混合負極材料の製造方法。 - 難黒鉛化性炭素質材料と易黒鉛化性炭素質材料及び/又は黒鉛質材料とを含む非水電解質二次電池用混合負極材料であって、
広角X線回折法においてBragg式を用いて算出される、前記難黒鉛化性炭素質材料の(002)面の平均面間隔d002が0.38~0.40nmの範囲にあり、
窒素吸着BET3点法により求めた前記難黒鉛化性炭素質材料の比表面積が1~10m2/gの範囲にあり、そして
ラマンスペクトルにおいて観察される難黒鉛化性炭素質材料の炭素前駆体の1360cm-1付近のピークの半値幅の値と、前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値との差が50~84cm-1である、非水電解質二次電池用混合負極材料。 - ラマンスペクトルにおいて観察される前記難黒鉛化性炭素質材料の1360cm-1付近のピークの半値幅の値が、175~190cm-1の範囲にある、
請求項9に記載の非水電解質二次電池用混合負極材料。 - ラマンスペクトルにおいて観察される前記難黒鉛化性炭素前駆体の1360cm-1付近のピークの半値幅の値が、230~260cm-1の範囲にある、
請求項8又は9に記載の非水電解質二次電池用混合負極材料。 - 前記難黒鉛化性炭素質材料の炭素源が植物由来である、請求項8~10のいずれか一項に記載の非水電解質二次電池用混合負極材料
- 前記請求項1~7のいずれか一項に記載の製造方法によって得ることのできる、非水電解質二次電池用混合負極材料。
- 前記請求項12に記載の混合負極材料を含む非水電解質二次電池用負極。
- 前記請求項13に記載の負極を含む、非水電解質二次電池。
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WO2020071547A1 (ja) * | 2018-10-04 | 2020-04-09 | 株式会社クラレ | 炭素質材料、非水電解質二次電池用負極、非水電解質二次電池および炭素質材料の製造方法、並びに炭化物および炭化物の製造方法 |
WO2020141574A1 (ja) * | 2019-01-04 | 2020-07-09 | 日立化成株式会社 | リチウムイオン二次電池用負極材、リチウムイオン二次電池用負極材の製造方法、リチウムイオン二次電池用負極及びリチウムイオン二次電池 |
WO2020141607A1 (ja) * | 2019-01-04 | 2020-07-09 | 日立化成株式会社 | リチウムイオン二次電池用負極材、リチウムイオン二次電池用負極材の製造方法、リチウムイオン二次電池用負極及びリチウムイオン二次電池 |
JPWO2020141607A1 (ja) * | 2019-01-04 | 2021-09-27 | 昭和電工マテリアルズ株式会社 | リチウムイオン二次電池用負極材、リチウムイオン二次電池用負極材の製造方法、リチウムイオン二次電池用負極及びリチウムイオン二次電池 |
JP7004093B2 (ja) | 2019-01-04 | 2022-01-21 | 昭和電工マテリアルズ株式会社 | リチウムイオン二次電池用負極材、リチウムイオン二次電池用負極材の製造方法、リチウムイオン二次電池用負極及びリチウムイオン二次電池 |
WO2021215397A1 (ja) * | 2020-04-20 | 2021-10-28 | 株式会社クラレ | 炭素質材料、その製造方法、および電気化学デバイス |
EP4140948A4 (en) * | 2020-04-20 | 2024-06-05 | Kuraray Co., Ltd. | CARBON MATERIAL, METHOD OF PRODUCING THE SAME, AND ELECTROCHEMICAL DEVICE |
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KR101992668B1 (ko) | 2019-06-26 |
KR20170131407A (ko) | 2017-11-29 |
CN107431205A (zh) | 2017-12-01 |
JP6456474B2 (ja) | 2019-01-23 |
JPWO2016140368A1 (ja) | 2018-02-22 |
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