WO2014038492A1 - 非水電解質二次電池負極用炭素質材料及びその製造方法、並びに前記炭素質材料を用いた負極および非水電解質二次電池 - Google Patents
非水電解質二次電池負極用炭素質材料及びその製造方法、並びに前記炭素質材料を用いた負極および非水電解質二次電池 Download PDFInfo
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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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- 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
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/056—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes
- H01M10/0564—Accumulators with non-aqueous electrolyte characterised by the materials used as electrolytes, e.g. mixed inorganic/organic electrolytes the electrolyte being constituted of organic materials only
- H01M10/0566—Liquid materials
- H01M10/0567—Liquid materials characterised by the additives
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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
- H01M2220/00—Batteries for particular applications
- H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M2300/00—Electrolytes
- H01M2300/0017—Non-aqueous electrolytes
- H01M2300/0025—Organic electrolyte
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
- Y02T10/00—Road transport of goods or passengers
- Y02T10/60—Other road transportation technologies with climate change mitigation effect
- Y02T10/70—Energy storage systems for electromobility, e.g. batteries
Definitions
- the present invention relates to a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery that has been subjected to an oxidation treatment and a method for producing the same.
- Non-graphitizable carbon is suitable for use in automobile applications from the viewpoint of low expansion and contraction of particles due to lithium doping and dedoping reactions and high cycle durability (Patent Document 1).
- pitches, polymer compounds, plant-based organic substances, and the like have been studied as carbon sources for non-graphitizable carbon.
- pitches There are petroleum-based and coal-based pitches, which contain many metal impurities, so that they must be removed during use.
- These pitches have a property of generating graphitizable carbon (such as coke) by heat treatment, and a crosslinking treatment is essential for producing non-graphitizable carbon. Thus, many steps are required to prepare non-graphitizable carbon from pitches.
- Non-graphitizable carbon can be obtained by heat-treating a polymer compound, particularly a thermosetting resin such as a phenol resin or a furan resin.
- a polymer compound particularly a thermosetting resin such as a phenol resin or a furan resin.
- a thermosetting resin such as a phenol resin or a furan resin.
- Patent Document 2 a carbon source derived from plant-derived organic matter is promising as a negative electrode material because it can be doped with a large amount of active material.
- Patent Document 3 ash such as potassium and calcium elements present in the organic raw material is doped and dedoped with the carbonaceous material used as the negative electrode. Therefore, there has been proposed a method for reducing the content of potassium element by subjecting plant-derived organic matter to deashing treatment by acid cleaning (hereinafter referred to as liquid phase demineralization) (patent) References 2 and 3).
- Patent Document 4 discloses deashing with warm water using waste coffee beans that have not been heat-treated at 300 ° C. or higher.
- the potassium content can be reduced to 0.1% by mass or less even when using raw materials having a particle diameter of 1 mm or more, and the filterability is also improved. Is done.
- JP-A-8-64207 JP-A-9-161801 Japanese Patent Laid-Open No. 10-21919 JP 2000-268823 A
- Carbonaceous materials made from plant-derived organic materials as described above have been desired to be industrialized because the raw materials are easily available.
- the present inventors have determined that a plant-derived organic substance having an average particle diameter of 100 ⁇ m or more is detarred. It has been found that potassium and calcium can be removed by performing a decalcification treatment in an acidic solution having a pH of 3.0 or less.
- the carbonaceous material from the plant-derived organic material prepared by the above method has a high order of crystal structure and a small average layer spacing between d (002) planes contributing to lithium doping and dedoping.
- the true density of the obtained carbonaceous material is increased.
- the structural characteristics are liable to occur due to the expansion and contraction of the crystal due to repeated doping and undoping of lithium, so that the cycle characteristics are low. Therefore, when the operating temperature is high, the mobility of lithium in the electrolyte also increases, so that lithium doping and undoping is more likely to occur, structural breakdown is accelerated, and high-temperature cycle characteristics are significantly reduced. Had.
- the first object of the present invention is carbon for a non-aqueous electrolyte secondary battery negative electrode, which is made from plant-derived organic materials, has an alkali metal such as potassium element sufficiently decalcified, has high purity, and has excellent high-temperature cycle characteristics.
- An object of the present invention is to provide a quality material and a lithium ion secondary battery using the same.
- a second object of the present invention is to provide a method for stably and efficiently producing a carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery excellent in high temperature cycle characteristics.
- the present inventors have found that in the above-described oxidation treatment, heat is generated by the oxidation reaction of the raw material and the system temperature rapidly rises, so that the system temperature needs to be appropriately controlled.
- the temperature in the system rises at an accelerated rate, and the gas generated by the thermal decomposition of the raw material and the oxidizing gas react to cause combustion of the raw material and thermal runaway in the system. There was a cause. Therefore, in order to suppress an excessive rise in system temperature due to oxidation heat generated by drying or oxidation treatment, water is supplied into the system, and the system temperature is appropriately adjusted by cooling the system with the latent heat of vaporization of water. There was a need to control.
- the method is an inefficient but inevitable step from a manufacturing point of view.
- a coffee extraction residue an organic substance derived from coffee beans
- deoxidation organic matter derived from demineralized coffee beans
- demineralized product organic material derived from deashed coffee beans
- a carbonaceous material obtained by carbonizing a plant-derived organic substance, the atomic ratio (H / C) of hydrogen atoms to carbon atoms by elemental analysis is 0.1 or less, and the average particle diameter Dv50 is 2 ⁇ m 50 ⁇ m or less, 002 plane average plane spacing determined by powder X-ray diffraction method is 0.365 nm to 0.400 nm, potassium element content is 0.5 mass% or less, calcium element content is 0.02 mass%
- a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery having a true density determined by a pycnometer method using butanol of 1.44 g / cm 3 or more and less than 1.54 g / cm 3 [2]
- the plant-derived organic material includes a coffee bean-derived organic material, the carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to [1], [3]
- the average particle diameter Dv 50 is 2
- a method for producing an intermediate for producing a carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery comprising: an oxidation treatment step; and a step of detarring the organic substance after the oxidation treatment at 300 ° C. or more and 1000 ° C. or less, [5] A step of deashing an organic substance derived from coffee beans having an average particle size of 100 ⁇ m or more, and an oxidizing gas atmosphere while introducing and mixing the organic substance derived from the deashed coffee beans An oxidation treatment step of heating and drying at 200 ° C. to 400 ° C.
- a non-aqueous electrolyte secondary battery negative electrode comprising: a step of deashing the organic matter derived from the coffee beans; and a step of detarring the organic matter derived from the deashed coffee beans at a temperature of 300 ° C. to 1000 ° C.
- Production method [9] The method according to any one of [4] to [8], further comprising a step of pulverizing the decalcified organic matter, [10] An intermediate obtained by the method according to any one of [4] to [9], [11] A step of firing the intermediate produced by the method according to any one of [4] to [8] at 1000 ° C. or higher and 1500 ° C.
- a method for producing a carbonaceous material for a non-aqueous electrolyte secondary battery comprising: [12] A method for producing a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery, comprising a step of firing the intermediate produced by the method according to [9] at 1000 ° C or higher and 1500 ° C or lower, [13] A carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery obtained by the production method according to [11] or [12], [14] A negative electrode for a non-aqueous electrolyte secondary battery comprising the carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode according to any one of [1] to [3] and [13], [15] The negative electrode for a nonaqueous electrolyte secondary battery according to [14], comprising a water-soluble polymer, [16] A nonaqueous electrolyte secondary battery
- the present invention provides [19] The carbonaceous material for a non-aqueous electrolyte secondary battery negative electrode according to any one of [1] to [3], wherein the halogen content is 50 ppm or more and 10,000 ppm or less, [20] The carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to [1] or [2], wherein the average particle diameter Dv 50 is 2 ⁇ m or more and 50 ⁇ m or less, and the particles of 1 ⁇ m or less are 2% by volume or less.
- the average particle diameter Dv 50 is at 2 ⁇ m or more 8 ⁇ m or less, 1 [mu] m or less of the particles is 10% or less
- the non-aqueous electrolyte secondary battery negative electrode carbon materials as described in, [22] The method for producing an intermediate for producing a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode according to any one of [4] to [9], wherein the detarring is performed in an oxygen-containing atmosphere, [23] An intermediate obtained by the method according to any one of [4] to [9] and [22], [24] A non-pulverized intermediate produced by the method according to [22], including a step of firing at 1000 ° C. or higher and 1500 ° C.
- a method for producing a carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery comprising a step of firing the pulverized intermediate produced by the method according to [22] at 1000 ° C or higher and 1500 ° C or lower, [26] The carbon for a nonaqueous electrolyte secondary battery negative electrode according to any one of [11], [12], [24], and [25], wherein the firing is performed in an inert gas containing a halogen gas.
- the method for producing a carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery of the present invention by performing an oxidation treatment before detarring, the carbonaceous material is free of impurity ions, specifically, potassium element.
- impurity ions specifically, potassium element.
- the true density is adjusted within a specific range, when used as a battery, the high temperature cycle characteristics can be improved while maintaining the characteristics as non-graphitizable carbon.
- a plant-derived carbonaceous material for a negative electrode excellent in electrical characteristics as a negative electrode can be obtained industrially and in large quantities. .
- Non-aqueous electrolyte secondary battery negative electrode carbonaceous material The nonaqueous electrolyte secondary battery negative electrode carbonaceous material of the present invention (hereinafter sometimes simply referred to as a carbonaceous material) is carbonized plant-derived organic matter.
- the atomic ratio (H / C) of hydrogen atoms to carbon atoms is 0.1 or less
- the average particle diameter Dv50 is 2 to 50 ⁇ m
- the average spacing of the 002 planes was 0.365 nm to 0.400 nm
- the potassium element content was 0.5 mass% or less
- the calcium element content was 0.02 mass% or less
- the pycnometer method using butanol was used.
- the true density is 1.44 g / cm 3 or more and less than 1.54 g / cm 3 .
- the carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode of the present invention preferably has an average particle diameter Dv 50 of 2 to 8 ⁇ m.
- the carbonaceous material of the present invention uses plant-derived organic matter as a carbon source, and is therefore a non-graphitizable carbonaceous material.
- Non-graphitizable carbon has small cycle expansion and contraction due to lithium doping and dedoping reactions, and has high cycle durability.
- Such plant-derived organic substances will be described in detail in the description of the production method of the present invention.
- H / C of the carbonaceous material of the present invention is measured by elemental analysis of hydrogen atoms and carbon atoms. Since the hydrogen content of the carbonaceous material decreases as the degree of carbonization increases, H / C is It tends to be smaller. Therefore, H / C is effective as an index representing the degree of carbonization.
- H / C of the carbonaceous material of this invention is not limited, it is 0.1 or less, More preferably, it is 0.08 or less. Especially preferably, it is 0.05 or less. If the ratio H / C of hydrogen atoms to carbon atoms exceeds 0.1, many functional groups are present in the carbonaceous material, and the irreversible capacity may increase due to reaction with lithium, which is not preferable.
- the average particle size (volume average particle size: D v50 ) of the carbonaceous material of the present invention is preferably 2 to 50 ⁇ m.
- the average particle size is less than 2 ⁇ m, the fine powder increases, the specific surface area increases, the reactivity with the electrolyte increases, the irreversible capacity that does not discharge even when charged increases, and the capacity of the positive electrode increases. This is not preferable because a waste rate increases.
- a negative electrode is manufactured, one gap formed between the carbonaceous materials is reduced, and movement of lithium in the electrolytic solution is suppressed, which is not preferable.
- the lower limit is preferably 2 ⁇ m or more, more preferably 3 ⁇ m or more, particularly preferably 4 ⁇ m or more (specifically, 8 ⁇ m or more).
- the average particle size is 50 ⁇ m or less, the lithium free diffusion process in the particles is small, and rapid charge / discharge is possible.
- the upper limit of the average particle diameter is preferably 50 ⁇ m or less, more preferably 40 ⁇ m or less, still more preferably 30 ⁇ m or less, particularly preferably 25 ⁇ m or less, and most preferably 20 ⁇ m or less.
- the carbonaceous material may have an average particle size (volume average particle size: Dv 50 ) of 1 to 8 ⁇ m, preferably 2 to 8 ⁇ m.
- the average particle diameter is 1 to 8 ⁇ m, the resistance of the electrode can be lowered, and thereby the irreversible capacity of the battery can be reduced.
- the lower limit of the average particle diameter is preferably 1 ⁇ m, more preferably 3 ⁇ m.
- the average particle size is 8 ⁇ m or less, the lithium free diffusion process in the particles is small, and rapid charge / discharge is possible. Furthermore, in a lithium ion secondary battery, it is important to increase the electrode area in order to improve input / output characteristics.
- the coating thickness of the active material on the current collector plate during electrode preparation it is necessary to reduce the coating thickness of the active material on the current collector plate during electrode preparation.
- the particle diameter of the active material it is necessary to reduce the particle diameter of the active material.
- the upper limit of the average particle diameter is preferably 8 ⁇ m or less, more preferably 7 ⁇ m or less. If the thickness exceeds 8 ⁇ m, the surface area of the active material increases and the electrode reaction resistance increases, which is not preferable.
- the carbonaceous material of the present invention is preferably one from which fine powder has been removed.
- the carbonaceous material from which the fine powder has been removed is used as the negative electrode of the non-aqueous electrolyte secondary battery, the irreversible capacity is reduced and the charge / discharge efficiency is improved.
- the active material can be sufficiently adhered with a small amount of binder. That is, the carbonaceous material containing a large amount of fine powder cannot sufficiently adhere the fine powder, and may be inferior in long-term durability.
- the amount of fine powder contained in the carbonaceous material of the present invention is not limited, but in the case of an average particle diameter of 2 to 50 ⁇ m (preferably an average particle diameter of 8 to 50 ⁇ m), a ratio of particles of 1 ⁇ m or less is preferable. Is 2% by volume or less, more preferably 1% by volume or less, and still more preferably 0.5% by volume or less. When a carbonaceous material having a ratio of particles of 1 ⁇ m or less of more than 2% is used, the irreversible capacity of the obtained battery is increased and the cycle durability may be inferior.
- the ratio of particles of 1 ⁇ m or less is preferably 10% by volume or less, more preferably 8% by volume or less, although it is not limited. More preferably, it is 6% by volume or less.
- a carbonaceous material having a ratio of particles of 1 ⁇ m or less of more than 10% is used, the irreversible capacity of the obtained battery is increased and the cycle durability may be inferior.
- a carbonaceous material having an average particle diameter of 10 ⁇ m a carbonaceous material containing 0.0 vol% of fine powder of 1 ⁇ m or less and a carbonaceous material containing 2.8 vol% of fine powder of 1 ⁇ m or less are used.
- the irreversible capacities of the manufactured secondary batteries they were 65 (mAh / g) and 88 (mAh / g), respectively, and it was found that the irreversible capacity was reduced due to the small amount of fine powder.
- the present invention is a carbonaceous material obtained by carbonizing a plant-derived organic substance, and the atomic ratio (H / C) of hydrogen atoms to carbon atoms by elemental analysis is 0.1 or less, and the average particle diameter D v50 is 2 to 50 ⁇ m, the average spacing of 002 planes determined by powder X-ray diffraction method is 0.365 nm to 0.400 nm, the content of potassium element is 0.5 mass% or less, and the ratio of particles of 1 ⁇ m or less is 2%.
- the present invention relates to a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery whose true density determined by a pycnometer method using butanol is 1.44 g / cm 3 or more and less than 1.54 g / cm 3 .
- the present invention also relates to a carbonaceous material obtained by carbonizing a plant-derived organic material, wherein an atomic ratio (H / C) of hydrogen atoms to carbon atoms by elemental analysis is 0.1 or less, and an average particle diameter D v50 is 1 to 8 ⁇ m, the average spacing of 002 planes determined by powder X-ray diffraction method is 0.365 nm to 0.400 nm, the content of potassium element is 0.5% by mass or less, and the proportion of particles having 1 ⁇ m or less is 10%.
- an atomic ratio (H / C) of hydrogen atoms to carbon atoms by elemental analysis is 0.1 or less
- an average particle diameter D v50 is 1 to 8 ⁇ m
- the average spacing of 002 planes determined by powder X-ray diffraction method is 0.365 nm to 0.400 nm
- the content of potassium element is 0.5% by mass or less
- the proportion of particles having 1 ⁇ m or less is 10%.
- the present invention relates to a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery whose true density determined by a pycnometer method using butanol is 1.44 g / cm 3 or more and less than 1.54 g / cm 3 .
- Plant-derived organic substances contain alkali metals (for example, potassium and sodium), alkaline earth metals (for example, magnesium or calcium), transition metals (for example, iron and copper), and other elements, and these metals It is also preferable to reduce the content of the species. This is because if these metals are contained, impurities are eluted into the electrolytic solution during dedoping from the negative electrode, and the battery performance and safety are likely to be adversely affected.
- alkali metals for example, potassium and sodium
- alkaline earth metals for example, magnesium or calcium
- transition metals for example, iron and copper
- the potassium element content in the carbonaceous material of the present invention is 0.5% by mass or less, more preferably 0.2% by mass or less, and further preferably 0.1% by mass or less.
- the dedoping capacity may decrease and the undoping capacity may increase.
- the content of calcium in the carbonaceous material of the present invention is 0.02% by mass or less, more preferably 0.01% by mass or less, and further preferably 0.005% by mass or less.
- a non-aqueous electrolyte secondary battery using a carbonaceous material for a negative electrode having a high calcium content there is a possibility of generating heat due to a short circuit. Moreover, there is a possibility that the doping characteristics and the dedoping characteristics are adversely affected.
- halogen content contained in the carbonaceous material of the present invention fired with a halogen gas-containing non-oxidizing gas described later is not limited, but is 50 to 10,000 ppm, more preferably 100 to 5000 ppm. Yes, more preferably from 200 to 3000 ppm.
- the present invention is a carbonaceous material obtained by carbonizing a plant-derived organic substance, and the atomic ratio (H / C) of hydrogen atoms to carbon atoms by elemental analysis is 0.1 or less, and the average particle diameter D v50 is 2 to 50 ⁇ m, the mean spacing of 002 planes determined by powder X-ray diffraction method is 0.365 nm to 0.400 nm, potassium element content is 0.5 mass% or less, halogen content is 50 to 10000 ppm,
- the present invention relates to a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery having a true density determined by a pycnometer method using butanol of 1.44 g / cm 3 or more and less than 1.54 g / cm 3 .
- the average layer spacing of the (002) plane of the carbonaceous material shows a smaller value as the crystal perfection is higher, that of an ideal graphite structure shows a value of 0.3354 nm, and the value increases as the structure is disturbed. Tend. Therefore, the average layer spacing is effective as an index indicating the carbon structure.
- the average interplanar spacing of the 002 plane determined by the X-ray diffraction method of the carbonaceous material for a non-aqueous electrolyte secondary battery of the present invention is 0.365 nm or more, more preferably 0.370 nm or more, and further 0.375 nm or more. preferable.
- the average spacing is 0.400 nm or less, more preferably 0.395 nm or less, and still more preferably 0.390 nm or less.
- the 002 plane spacing is less than 0.365 nm, the dope capacity decreases when used as a negative electrode of a non-aqueous electrolyte secondary battery, or the expansion and contraction associated with lithium doping and dedoping increases. Since voids are generated between them and the conductive network between the particles is blocked, the repetitive characteristics are inferior. On the other hand, if it exceeds 0.400 nm, the undedoped capacity increases, which is not preferable.
- true density of carbonaceous material The true density of the carbonaceous material of the present invention was determined by a pycnometer method using butanol.
- the true density of the graphite material having an ideal structure is 2.2 g / cm 3 , and the true density tends to decrease as the crystal structure is disturbed. Therefore, the true density can be used as an index representing the structure of carbon.
- True density of the carbonaceous material of the present invention is less than 1.44 g / cm 3 or more 1.54 g / cm 3, the lower limit is more preferably 1.47 g / cm 3 or more, 1.50 g / cm 3 or more is more preferable.
- the upper limit of the true density is preferably 1.53 g / cm 3 or less, and more preferably 1.52 g / cm 3 or less.
- the high-temperature cycle characteristics are inferior.
- the true density is less than 1.44 g / cm 3 , the electrode density is lowered, and thus the volume energy density of the battery is lowered. Therefore, it is not preferable.
- the specific surface area (hereinafter sometimes referred to as “SSA”) determined by the BET method of nitrogen adsorption of the carbonaceous material of the present invention is not limited, but is preferably 13 m 2 / g or less, more preferably 12 m. 2 / g or less, still more preferably not more than 10 m 2 / g.
- the lower limit of the specific surface area is preferably 1 m 2 / g or more, more preferably 1.5 m 2 / g or more, and still more preferably 2 m 2 / g or more. If a carbonaceous material having an SSA of less than 1 m 2 / g is used, the discharge capacity of the battery may be reduced.
- Plant-derived organic substances are heated at 200 to 400 ° C. in an oxidizing gas atmosphere to oxidize the terminal end of the cyclic structure in the plant-derived organic substance to produce oxygen-containing functional groups with oxygen atoms added. To do. Thereafter, in the process of passing through the firing step, the cyclization reaction proceeds and an aromatic compound is generated. At the same time, a crosslinked structure is generated starting from the oxygen-containing functional group. As a result of this action, it is considered that the carbonaceous material obtained from the plant-derived organic matter subjected to the oxidation treatment forms a disordered state of crystals and increases the d (002) plane spacing.
- Increased d (002) plane spacing suppresses the expansion and contraction of crystals due to lithium doping and dedoping in a room temperature environment or a high temperature environment, improving cycle characteristics, particularly high temperature cycle characteristics. it is conceivable that.
- the carbonaceous material obtained from the organic substance of the coffee residue has a relatively high crystal structure order among the carbon structures classified as non-graphitizable carbon, and contributes to doping and dedoping of lithium d ( (002)
- the average layer spacing of the plane is small. For this reason, structural destruction is likely to occur due to expansion and contraction of the crystal due to repeated lithium doping and dedoping, resulting in low cycle characteristics.
- the deterioration of the cycle characteristics is significantly accelerated compared to room temperature. Therefore, in particular, by the oxidation treatment in which the coffee residue is heated in an oxidizing gas atmosphere, a crosslinked structure is generated from the organic substance derived from the coffee residue starting from the oxygen-containing functional group, and the crystal of the carbonaceous material obtained by this action is more By forming a disordered state and maintaining a large d (002) plane spacing, the expansion and contraction of the crystal due to lithium doping and dedoping is suppressed under normal temperature environment or high temperature environment, and cycle characteristics, particularly high temperature It is considered that the cycle characteristics are improved.
- Method for producing carbonaceous material for negative electrode of nonaqueous electrolyte secondary battery uses a plant-derived organic material having an average particle size of 100 ⁇ m or more as a raw material. At least (1) a step of deashing using an acidic solution (hereinafter, sometimes referred to as “liquid phase deashing step”), (2) the deashed organic substance is 200 to 400 in an oxidizing gas atmosphere.
- a step of deashing using an acidic solution hereinafter, sometimes referred to as “liquid phase deashing step”
- the deashed organic substance is 200 to 400 in an oxidizing gas atmosphere.
- An oxidation treatment step (hereinafter sometimes referred to as an “oxidation treatment step”) heated at a temperature of 3 ° C., and (3) a step of detarring the organic substance after the oxidation treatment at 300 to 1000 ° C. (hereinafter referred to as a “detarring step”).
- a method for producing a carbonaceous material is preferably an average of either (4) deashed organic matter or carbonized product (carbonized product after detarring or carbonized product after main firing).
- a step of pulverizing to a particle size of 2 to 50 ⁇ m (hereinafter sometimes referred to as “grinding step”) and / or (5) a step of firing at 1000 to 1500 ° C. in a non-oxidizing atmosphere (hereinafter referred to as “firing step”). May be called). Therefore, the method for producing a carbonaceous material for a negative electrode of a nonaqueous electrolyte secondary battery according to the present invention includes a liquid phase decalcification step (1), an oxidation treatment step (2), and a detarring step (3), preferably a pulverization step. (4) and / or a baking process (5) are included.
- the plant as a raw material is not particularly limited. There may be mentioned hardwoods, conifers, bamboo, or rice husks. These plant-derived organic substances can be used alone or in combination of two or more.
- the extraction residue obtained by extracting the beverage coffee component from the coffee beans has some minerals extracted and removed when extracting the coffee component, and in particular, the coffee extraction that has been industrially extracted The residue is particularly preferred because it is moderately ground and available in large quantities.
- the carbonaceous material for negative electrode manufactured from these plant-derived organic substances can be doped with a large amount of active material
- the negative electrode material of the non-aqueous electrolyte secondary battery Useful as.
- plant-derived organic substances contain many metal elements, and particularly contain a lot of potassium and calcium.
- a carbonaceous material produced from a plant-derived organic material containing a large amount of metal elements has an undesirable effect on electrochemical characteristics and safety when used as a negative electrode. Therefore, it is preferable to reduce the content of potassium element or calcium element contained in the carbonaceous material for negative electrode as much as possible.
- the plant-derived organic material used in the present invention is preferably not heat-treated at 500 ° C. or higher.
- the heat treatment is performed at 500 ° C. or higher, deashing may not be sufficiently performed due to carbonization of the organic matter.
- the plant-derived organic material used in the present invention is preferably not heat-treated.
- 400 ° C. or lower is preferable, 300 ° C. or lower is more preferable, 200 ° C. or lower is further preferable, and 100 ° C. or lower is most preferable.
- heat treatment at about 200 ° C. may be performed by roasting, but it can be sufficiently used as a plant-derived organic substance used in the present invention.
- the plant-derived organic material used in the present invention is preferably one that has not been spoiled.
- microorganisms may grow and organic substances such as lipids and proteins may be decomposed by storing for a long time in a state of containing a lot of water. Some of these organic substances undergo a cyclization reaction during the carbonization process, and become aromatic compounds to form a carbon structure. Therefore, when organic substances are decomposed by decay, the final carbon structure will be different. There is a case. When the coffee extraction residue which has progressed aerobic decay is used, the true density of the obtained carbonaceous material may be lowered.
- the irreversible capacity may increase when used in a battery, which is not preferable. Moreover, since the water absorption of the carbonaceous material also increases, the degree of deterioration due to atmospheric exposure increases.
- the deashing step in the production method of the present invention is basically a liquid phase deashing step in which plant-derived organic matter is treated in an acidic solution having a pH of 3.0 or less before detarring.
- a liquid phase decalcification potassium element, calcium element and the like can be efficiently removed, and calcium element can be efficiently removed as compared with the case where no acid is particularly used. Further, other alkali metals, alkaline earth metals, and transition metals such as copper and nickel can be removed.
- a secondary battery using a carbonaceous material obtained by liquid phase decalcification at 0 ° C. or more and 80 ° C. or less is particularly excellent in discharge capacity and efficiency.
- any method such as liquid phase deashing or gas phase demineralization can be used as the deashing method.
- Deashing is possible at any stage from the raw material stage to after making the carbonaceous material. It is preferable to deash in the liquid phase before carrying out detarring.
- the content of metal elements such as potassium element is efficiently reduced by treating the coffee extraction residue in the aqueous phase before detarring.
- water can be used as a condition for the aqueous phase in the liquid phase decalcification step, it is preferably treated in an acidic solution having a pH of 3.0 or less.
- Potassium element and calcium element can be efficiently removed by liquid phase demineralization in an acidic solution having a pH of 3.0 or less, and in particular, calcium element can be removed more efficiently than when no acid is used. Can do. Further, other alkali metals, alkaline earth metals, and transition metals such as copper and nickel can be efficiently removed.
- the acid used for the liquid phase decalcification is not particularly limited, and examples thereof include strong acids such as hydrochloric acid, hydrofluoric acid, sulfuric acid and nitric acid, weak acids such as citric acid and acetic acid, and mixtures thereof. Preferably, it is hydrochloric acid or hydrofluoric acid.
- the plant-derived organic substance used in the present invention is preferably not heat-treated at 500 ° C. or higher. However, when the carbonization of the organic substance is proceeding at 500 ° C. or higher, hydrofluoric acid should be used. It is possible to sufficiently deash.
- the coffee extraction residue is detarred at 700 ° C., then subjected to liquid phase decalcification with 35% hydrochloric acid for 1 hour, then washed with water three times, dried, pulverized to 10 ⁇ m, and then calcined at 1250 ° C.
- 409 ppm of potassium and 507 ppm of calcium remained.
- potassium and calcium were below the detection limit (10 ppm or less) in the fluorescent X-ray measurement.
- the pH in liquid phase demineralization is not limited as long as sufficient demineralization is achieved, but the pH is preferably 3.0 or less, more preferably 2.5 or less, and even more preferably 2 0.0 or less. If the pH exceeds 3.0, it is disadvantageous because sufficient decalcification cannot be performed (particularly, calcium element cannot be sufficiently decalcified).
- the treatment temperature in the liquid phase demineralization of the present invention is not particularly limited, but is performed at 0 ° C. or more and 100 ° C. or less, preferably 80 ° C. or less, more preferably 40 ° C. or less, and still more preferably. Room temperature (0-40 ° C).
- the treatment temperature is 80 ° C. or lower, the true density of the carbonaceous material increases, and when the battery is used, the discharge capacity and efficiency of the battery are improved.
- the deashing temperature is low, it may take a long time to perform sufficient deashing. If the deashing temperature is high, a short treatment time is required, but the true density using butanol, a carbonaceous material. Is unfavorable because it decreases.
- the time for liquid phase decalcification varies depending on the pH and processing temperature and is not particularly limited, but the lower limit is preferably 1 minute, more preferably 3 minutes, still more preferably 5 minutes, Preferably it is 10 minutes, most preferably 30 minutes.
- the upper limit is preferably 300 minutes, more preferably 200 minutes, and even more preferably 150 minutes. If the length is short, decalcification cannot be sufficiently achieved, and if the length is long, it is inconvenient in terms of work efficiency.
- the liquid phase demineralization step (1) in the present invention is a step for removing potassium and calcium contained in plant-derived organic substances.
- 0.5 mass% or less is preferable, as for potassium content after a liquid phase demineralization process (1), 0.2 mass% or less is more preferable, and 0.1 mass% or less is still more preferable.
- the calcium content is preferably 0.02% by mass or less, more preferably 0.01% by mass or less, and further preferably 0.005% by mass or less.
- the dedoping capacity is reduced, This is because not only the undoped capacity is increased, but also these metal elements are eluted into the electrolytic solution, and when they are re-deposited, a short circuit is caused, which may cause a serious problem in safety.
- the particle diameter of the plant-derived organic substance used for liquid phase demineralization is not particularly limited. However, if the particle size is too small, the permeability of the solution during filtration after decalcification is lowered, so the lower limit of the particle size is preferably 100 ⁇ m or more, more preferably 300 ⁇ m or more, and even more preferably 500 ⁇ m or more.
- the upper limit of the particle diameter is preferably 10,000 ⁇ m or less, more preferably 8000 ⁇ m or less, and still more preferably 5000 ⁇ m or less.
- the plant-derived organic matter Prior to the liquid phase decalcification, the plant-derived organic matter can be pulverized to an appropriate average particle size (preferably 100 to 50,000 ⁇ m, more preferably 100 to 10,000 ⁇ m, still more preferably 100 to 5000 ⁇ m). This pulverization is different from the pulverization step (2) in which the average particle size after firing is 2 to 50 ⁇ m.
- Oxidation treatment step In the production method of the present invention, an oxidation treatment step of heating the deashed organic substance at 200 to 400 ° C. in an oxidizing gas atmosphere before detarring is essential. This oxidation treatment lowers the order of the crystals of the resulting carbonaceous material and reduces the true density to an appropriate level, thereby reducing expansion and shrinkage during lithium doping and dedoping. Can be improved. Moreover, you may further oxidize to the organic substance derived from the plant which carried out liquid phase decalcification and detarred.
- the yield of carbonaceous material is improved and the ordering of its crystal structure is reduced, especially when organic matter is simply detarred. Can be improved.
- the oxidation treatment increases the proportion of the organic matter contained in the raw material that is not distilled off by detarring because the cross-linking through the oxygen-containing functional group proceeds to polymerize and become non-volatile.
- oxygen cross-linking of organic matter by oxidation treatment reduces the order of the carbon crystal structure derived from them, and the expansion of the average layer spacing suppresses expansion and contraction due to lithium doping and dedoping during charging and discharging. is there.
- the oxidation treatment of the present invention is performed by heating a carbon source in an oxidizing gas atmosphere.
- the oxidizing gas used for the oxidation treatment is not particularly limited.
- a gaseous state containing an element such as oxygen, sulfur, and nitrogen is preferable.
- a gas containing oxygen is preferable.
- An atmosphere is preferred.
- Air may be used as the oxidizing gas.
- it may be a mixed gas with a non-oxidizing gas such as nitrogen, helium, or argon.
- a mixed gas atmosphere containing oxygen and nitrogen is preferable from the viewpoint of handleability.
- the temperature of the oxidation treatment is not particularly limited, and the optimum temperature varies depending on the oxidizing gas and the oxidation treatment time.
- the oxidation treatment temperature is preferably 200 to 400 ° C, more preferably 220 to 360 ° C, and further preferably 240 to 320 ° C.
- the reaction temperature is preferably controlled at 200 to 400 ° C.
- the reaction temperature of oxidation treatment is less than 200 ° C., drying and oxidation may not be sufficient, which is not preferable.
- the temperature exceeds 400 ° C. the treatment temperature is high, and therefore, oxidative decomposition is more likely to occur than the addition of oxygen by oxidation, and the specific surface area of the resulting carbonaceous material increases, which is not preferable.
- the reaction temperature exceeds 400 ° C. it is difficult to lower the temperature that rises due to heat generation, and the rate of oxidative decomposition of the carbon source increases, so the yield in the oxidation step decreases.
- the maximum temperature of the oxidation reaction temperature is not particularly limited in the range of 200 to 400 ° C., but is preferably 350 ° C. or less, more preferably 300 ° C. or less from the viewpoint of the yield of the oxidation step.
- the time for the oxidation treatment is not particularly limited, and the optimum time varies depending on the oxidation treatment temperature and the oxidizing gas. For example, in the case of oxidation treatment at 240 to 320 ° C. in a gas atmosphere containing oxygen, 10 minutes to 3 hours are preferable, 30 minutes to 2 hours 30 minutes are more preferable, and 50 minutes to 1 hour 30 minutes are even more preferable.
- the lower limit of the particle diameter is preferably 100 ⁇ m or more, more preferably 300 ⁇ m or more, and further preferably 500 ⁇ m.
- the upper limit of the particle diameter is preferably 10,000 ⁇ m or less, more preferably 8000 ⁇ m or less, and still more preferably 5000 ⁇ m or less.
- coffee extraction residue organic matter derived from coffee beans
- deashed coffee extraction residue decalcified Before detarring the organic matter derived from coffee beans
- an oxidation treatment step of heating in an oxidizing gas atmosphere is essential. That is, the oxidation treatment step (2) can be performed before the deashing step or after the deashing step.
- the coffee extraction residue or its liquid phase demineralized product contains a large amount of moisture, and it is necessary to dry it for smooth storage and transportation to the next process. In the present invention, by performing this drying together with the oxidation treatment, the process can be shortened and energy can be saved.
- the production method of the present invention does not exclude the provision of a separate drying step in addition to the above oxidation treatment step, and may include a step of drying as necessary in each step.
- the water content of the coffee extraction residue or its liquid phase demineralized product is not particularly limited, but is preferably about 10 to 70%. If there is too much moisture, the processing time required for oxidation and drying will become longer, the range of adjustment of the introduction amount when adding residue for cooling will be small and temperature control will be difficult, and the amount of gas required And is not preferable in that the amount of heat increases.
- a vertical furnace or a horizontal furnace having a raw material supply means and an oxidizing gas supply means can be used for the oxidation treatment of the present invention.
- a method for introducing the raw material powder for example, a known method such as supplying the raw material powder cut from the table feeder from the raw material supply pipe may be used.
- the gas flow rate or temperature may be set to a constant value during the process, but the temperature in the raw material powder, etc. is monitored, and the gas flow rate or the temperature in the reaction system is adjusted and controlled to manage the process temperature. This is preferable.
- the mixing method in the reaction system in the oxidation treatment in the present invention is not particularly limited, but the mixing may be performed by an oxidizer equipped with a stirrer using a stirring blade, or a similar mechanical stirrer is used. May be. Moreover, it can implement also with the form with which the inside of a reaction system is mixed by introduce
- Detarring step In the production method of the present invention, the carbon source is detarred to form a carbonaceous precursor.
- the heat treatment for modifying the carbonaceous precursor to carbonaceous is called firing. Firing may be performed in one stage, or may be performed in two stages of low temperature and high temperature. In this case, firing at a low temperature is called preliminary firing, and firing at a high temperature is called main firing. In this specification, the main purpose is not to remove volatile components from a carbon source to form a carbonaceous precursor (detarring) or to reform the carbonaceous precursor to carbonaceous (firing). The case is called “non-carbonization heat treatment” and is distinguished from “detarring” and “calcination”.
- Non-carbonization heat treatment means, for example, heat treatment at less than 500 ° C. More specifically, roasting of coffee beans at about 200 ° C. is included in the non-carbonization heat treatment.
- the plant-derived organic material used in the present invention is preferably not heat-treated at 500 ° C. or higher. That is, the plant-derived organic material used in the present invention should be non-carbonized heat-treated. it can.
- Detarring is performed by firing a carbon source at 300 ° C. or higher and 1000 ° C. or lower. More preferably, it is 500 degreeC or more and less than 900 degreeC. Detarring removes volatile components such as CO 2 , CO, CH 4 , and H 2 and tar components, reduces the generation of these in the main firing, and reduces the burden on the calciner. . When the detarring temperature is less than 300 ° C., the detarring becomes insufficient, and there is a large amount of tar and gas generated in the main firing step after pulverization, which may adhere to the particle surface. This is not preferable because it cannot be maintained and the battery performance is lowered.
- the detarring temperature exceeds 1000 ° C.
- the tar generation temperature range is exceeded, and the energy efficiency to be used is lowered, which is not preferable.
- the generated tar causes a secondary decomposition reaction, which adheres to the intermediate and may cause a decrease in performance, which is not preferable.
- the atmosphere of detarring is not particularly limited, but for example, it is carried out in an inert gas atmosphere, and examples of the inert gas include nitrogen or argon. Moreover, detarring can also be performed under reduced pressure, for example, it can be performed at 10 KPa or less.
- the time for detarring is not particularly limited, however, for example, 0.5 to 10 hours can be used, and 1 to 5 hours is more preferable. Moreover, you may perform a grinding
- a step of pulverizing the raw material, intermediate or final processed product, and a step of firing the intermediate may be added as appropriate according to the purpose.
- the average particle diameter Dv 50 is preferably 2 to 63 ⁇ m, and more preferably 1 to 10 ⁇ m. If the average particle diameter is set within this range, the particle size of the carbonaceous material can be made within the scope of the present invention after shrinking through the subsequent firing step (preliminary firing, main firing). Moreover, it is preferable to adjust so that content of potassium and calcium may be 0.5 mass% or less and 0.02 mass% or less, respectively, in the intermediate. If it exists in this range, the density
- detarring in oxygen-containing atmosphere can also be performed in an oxygen-containing atmosphere.
- the oxygen-containing atmosphere is not limited.
- air can be used, but it is preferable that the oxygen content is small.
- the oxygen content in the oxygen-containing atmosphere is preferably 20% by volume or less, more preferably 15% by volume or less, still more preferably 10% by volume or less, and most preferably 5% by volume or less.
- the oxygen content may be, for example, 1% by volume or more.
- the present invention preferably includes a liquid phase decalcification step (1), an oxidation treatment step (2), a detarring step (3), a pulverization step (4), and a calcination step (5).
- the present invention relates to a method for producing a carbonaceous material for a non-aqueous electrolyte secondary battery, wherein 3) is performed in an oxygen-containing atmosphere.
- the detarring step (3) when the detarring step (3) is performed in an oxygen-containing atmosphere using plant-derived organic matter (eg, coconut shell char) that has been heat-treated at 600 ° C., the carbonaceous matter that has undergone the firing step (4) thereafter.
- the specific surface area of the material was 60 m 2 / g, but the detarring step (3) was performed in an oxygen-containing atmosphere using plant-derived organic matter (for example, coffee residue) that was not heat-treated at 500 ° C. or higher.
- the specific surface area of the carbonaceous material that had undergone the firing step (4) was 8 m 2 / g, and no increase in the specific surface area was observed. This is a numerical value equivalent to that of a carbonaceous material that has been detarred under an inert gas atmosphere.
- detarring is possible in an oxygen-containing atmosphere in the present invention. Since the plant-derived organic substance used in the present invention is not heat-treated at a high temperature, a large amount of tar and gas are generated in the detarring step. The generated tar content, gas, and oxygen are preferentially consumed by the oxidation reaction, and oxygen that reacts with plant-derived organic matter is depleted, so that it is assumed that activation does not occur.
- detarring is possible in an oxygen-containing atmosphere, so that the atmosphere control can be simplified. Furthermore, the manufacturing cost can be reduced by reducing the amount of inert gas such as nitrogen.
- Pulverization step The pulverization step in the production method of the present invention includes an organic substance from which potassium and calcium have been removed (decalcified organic substance), an oxidized organic substance, or a carbonized substance (carbonized substance after detarring or carbonized substance after main firing). ) Is pulverized so that the average particle size after firing becomes 2 to 50 ⁇ m. That is, the average particle diameter of the obtained carbonaceous material is adjusted to 2 to 50 ⁇ m by the pulverization step. In the pulverization step, pulverization is performed so that the average particle size after firing is preferably 1 to 8 ⁇ m, more preferably 2 to 8 ⁇ m.
- the carbonaceous material to be obtained is prepared so as to have an average particle diameter of 1 to 8 ⁇ m, more preferably 2 to 8 ⁇ m by the pulverization step.
- the “carbonaceous precursor” or “intermediate” means the product after the detarring step. That is, in the present specification, the “carbonaceous precursor” and the “intermediate” are used in substantially the same meaning, and include those that are pulverized and those that are not pulverized.
- the pulverizer used for pulverization is not particularly limited.
- a jet mill, a ball mill, a hammer mill, a rod mill, or the like can be used, or a combination of these can be used.
- a jet mill having a classification function is preferable in that it has a small amount.
- fine powder can be removed by classification after pulverization.
- classification by sieve As classification, classification by sieve, wet classification, or dry classification can be mentioned.
- the wet classifier include a classifier using a principle such as gravity classification, inertia classification, hydraulic classification, or centrifugal classification.
- the dry classifier include a classifier using the principle of sedimentation classification, mechanical classification, or centrifugal classification.
- pulverization and classification can be performed using one apparatus.
- pulverization and classification 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.
- the pulverized intermediate (carbonaceous precursor) can be fired by a firing process. Depending on the firing conditions, shrinkage of about 0 to 20% occurs. Therefore, when the pulverization is performed before firing and the firing step is performed, the nonaqueous electrolyte secondary battery having an average particle diameter Dv50 of 2 to 50 ⁇ m is finally obtained.
- Dv50 average particle diameter of the pulverized intermediate in the range of about 0 to 20%.
- the average sphere diameter after pulverization is not limited as long as the average particle diameter of the finally obtained carbonaceous material is 2 to 50 ⁇ m. Specifically, the average particle diameter Dv50 is 2 to 63 ⁇ m.
- the average particle diameter of the pulverized carbonaceous precursor is in the range of about 0 to 20%. It is preferable to prepare larger.
- the average sphere diameter after pulverization is not limited as long as the average particle diameter of the finally obtained carbonaceous material is 2 to 8 ⁇ m.
- the average particle diameter Dv 50 is 1 to 10 ⁇ m. It is preferable to prepare in the range of 1 to 9 ⁇ m.
- the carbonaceous material of the present invention is preferably one from which fine powder has been removed.
- the method for removing the fine powder is not particularly limited, and the fine powder can be removed in the pulverization step using, for example, a pulverizer such as a jet mill having a classification function.
- a pulverizer such as a jet mill having a classification function.
- fine powder can be removed by classification after pulverization.
- fine powder can be recovered using a cyclone or a bag filter.
- the firing step in the production method of the present invention is a step of firing the intermediate to make it carbonaceous. For example, it is performed at 1000 ° C. to 1500 ° C., and is generally called “main firing” in the technical field of the present invention. Moreover, in the baking process of this invention, preliminary baking can be performed before this baking as needed.
- Calcination in the production method of the present invention can be performed according to a normal procedure, and a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode can be obtained by performing calcination.
- the firing temperature is 1000 to 1500 ° C.
- a calcination temperature of less than 1000 ° C. is not preferable because many functional groups remain in the carbonaceous material and the H / C value increases, and the irreversible capacity increases due to reaction with lithium.
- the minimum of the calcination temperature of this invention is 1000 degreeC or more, More preferably, it is 1100 degreeC or more, Most preferably, it is 1150 degreeC or more.
- the upper limit of the firing temperature of the present invention is 1500 ° C. or less, more preferably 1450 ° C. or less, and particularly preferably 1400 ° C. or less.
- Calcination is preferably performed in a non-oxidizing gas atmosphere.
- the non-oxidizing gas include helium, nitrogen, and argon, and these can be used alone or in combination.
- the main calcination can be performed in a gas atmosphere in which a halogen gas such as chlorine is mixed with the non-oxidizing gas.
- the supply amount (circulation amount) of the gas is not limited, but is 1 mL / min or more, preferably 5 mL / min or more, more preferably 10 mL / min or more per 1 g of decalcified carbon precursor.
- baking can also be performed under reduced pressure, for example, it can also be performed at 10 KPa or less.
- the firing time is not particularly limited.
- the residence time at 1000 ° C. or higher can be 0.05 to 10 hours, preferably 0.05 to 3 hours, and 0.05 to 1 Time is more preferred.
- preliminary firing can be performed.
- the preliminary firing is performed by firing the carbon source at 300 ° C. or higher and lower than 1000 ° C., preferably 300 ° C. or higher and lower than 900 ° C.
- Pre-baking removes volatile components that remain even after the detarring process, such as CO 2 , CO, CH 4 , and H 2 , and tar components, and reduces the generation of these in the main firing, The burden on the vessel can be reduced. That is, in addition to the detarring step, CO 2 , CO, CH 4 , H 2 , or tar content may be further removed by preliminary calcination.
- Pre-baking is performed in an inert gas atmosphere, and examples of the inert gas include nitrogen and argon. Pre-baking can also be performed under reduced pressure, for example, 10 KPa or less.
- the pre-baking time is not particularly limited, but can be performed, for example, in 0.5 to 10 hours, and more preferably 1 to 5 hours. Moreover, you may perform the said grinding
- the pre-calcination removes volatile components remaining after the detarring step, such as CO 2 , CO, CH 4 , and H 2 , and tar components, and reduces the generation of them in the main firing. , The burden on the calciner can be reduced.
- the firing or preliminary firing in the present invention can be performed in a non-oxidizing gas containing a halogen gas.
- a halogen gas used include chlorine gas, bromine gas, iodine gas, and fluorine gas, and chlorine gas is particularly preferable.
- a substance that easily releases halogen at a high temperature such as CCl 4 or Cl 2 F 2 , can be supplied using an inert gas as a carrier. Firing or pre-firing with a halogen gas-containing non-oxidizing gas may be performed at the temperature of main baking (1000 to 1500 ° C.), but may be performed at a temperature lower than the main baking (for example, 300 ° C.
- the temperature range is preferably 800 to 1400 ° C. As a minimum of temperature, 800 ° C is preferred and 850 ° C is still more preferred.
- the upper limit is preferably 1400 ° C, more preferably 1350 ° C, and most preferably 1300 ° C.
- the raw organic material When the raw organic material is heated and carbonized, it is carbonized through a process of heating in a halogen gas-containing atmosphere such as chlorine gas, whereby the obtained carbonaceous material shows an appropriate halogen content, and It has a fine structure suitable for occlusion of lithium. Thereby, a large charge / discharge capacity can be obtained.
- a halogen gas-containing atmosphere such as chlorine gas
- a mixed gas obtained by adding 0.04 L / min of chlorine gas to 0.2 L / min of nitrogen gas is supplied.
- the discharge capacity increased by 7%.
- the halogen content contained in the carbonaceous material of the present invention fired with a halogen gas-containing non-oxidizing gas is not limited, but is 50 to 10,000 ppm, more preferably 100 to 5000 ppm, and still more preferably. Is 200 to 3000 ppm.
- a carbonaceous material for a negative electrode of a non-aqueous electrolyte secondary battery having a large charge / discharge capacity can be obtained by firing with a non-oxidizing gas containing halogen gas or preliminary firing is not clear, but halogen and hydrogen atoms in the carbonaceous material It is thought that carbonization proceeds in a state where hydrogen is rapidly removed from the carbonaceous material.
- the halogen gas also has an effect of reducing residual ash by reacting with ash contained in the carbonaceous material. If the halogen content contained in the carbonaceous material is too small, hydrogen is not sufficiently removed in the course of the manufacturing process, and as a result, the charge / discharge capacity may not be sufficiently improved. Then, there may be a problem that the remaining halogen reacts with lithium in the battery to increase the irreversible capacity.
- the present invention preferably includes a liquid phase demineralization step (1), an oxidation treatment step (2), a pulverization step (3), a detarring step (4), and a calcination step (5). It is related with the manufacturing method of the carbonaceous material for nonaqueous electrolyte secondary batteries performed in the inert gas containing this.
- the method for producing an intermediate (carbonaceous precursor) according to the present invention includes a step of decalcifying a plant-derived organic material having an average particle size of 100 ⁇ m or more (decalcification step), and the decalcified organic material. And an oxidization treatment step of heating at 200 to 400 ° C. in an oxidizing gas atmosphere, and a detarring step (detarring step) of the organic substance after the oxidation treatment at 300 to 1000 ° C.
- the method further includes a step of crushing the ashed organic substance (crushing step). Furthermore, it is preferable to perform the said liquid phase demineralization process at the temperature of 0 degreeC or more and 80 degrees C or less.
- the deashing step, the oxidation treatment step, the detarring step, and the pulverization step are the deashing step, the detarring step, the oxidation treatment step, and the pulverization step in the method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode of the present invention. It is the same.
- the pulverization step can be performed after the liquid phase decalcification step or after the detarring step. Note that the intermediate (carbonaceous precursor) obtained by the detarring step may be pulverized or not pulverized.
- a step of deashing an organic matter derived from coffee beans having an average particle size of 100 ⁇ m or more
- a step of detarring at 300 to 1000 ° C. (detarring step).
- an organic substance derived from coffee beans having an average particle size of 100 ⁇ m or more is introduced and mixed in an oxidizing gas atmosphere.
- the deashing step, the oxidation treatment step, the detarring step, and the pulverization step are the deashing step, the oxidation treatment step, the detarring step, and the pulverization in the method for producing a carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode of the present invention. It is the same as the process.
- Nonaqueous electrolyte secondary battery negative electrode of the present invention includes the carbonaceous material for a nonaqueous electrolyte secondary battery negative electrode of the present invention.
- a binder (binder) is added to the carbonaceous material, and an appropriate solvent is added and kneaded to form an electrode mixture. It can be produced by pressure molding after coating and drying.
- a conductive aid can be added.
- the conductive assistant conductive carbon black, vapor grown carbon fiber (VGCF), nanotube, etc. can be used, and the amount added varies depending on the type of conductive assistant used, but the amount added is too small.
- 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 amount of the binder added is preferably 3 to 13% by mass, more preferably 3 to 10% by mass for the PVDF binder, although it varies depending on the type of binder used.
- 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 mass. The amount is preferably 1 to 4% by mass.
- 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 side) is preferably 10 to 80 ⁇ m, more preferably 20 to 75 ⁇ m, and particularly preferably 20 to 60 ⁇ m.
- a water-soluble polymer can be mentioned as a binder used for the preferable nonaqueous electrolyte secondary battery negative electrode of this invention.
- a water-soluble polymer for the negative electrode of the non-aqueous electrolyte secondary battery of the present invention a non-aqueous electrolyte secondary battery whose irreversible capacity is not reduced by an exposure test can be obtained.
- a nonaqueous electrolyte secondary battery having excellent cycle characteristics can be obtained.
- Such a water-soluble polymer can be used without particular limitation as long as it is soluble in water.
- cellulosic compounds include cellulosic compounds, polyvinyl alcohol, starch, polyacrylamide, poly (meth) acrylic acid, ethylene-acrylic acid copolymer, ethylene-acrylamide-acrylic acid copolymer, polyethyleneimine, etc. and their derivatives or Salt.
- cellulose compounds, polyvinyl alcohol, poly (meth) acrylic acid and derivatives thereof are preferable.
- CMC carboxymethyl cellulose
- the mass average molecular weight of the water-soluble polymer of the present invention is 10,000 or more, more preferably 15,000 or more, and still more preferably 20,000 or more. If it is less than 10,000, the dispersion stability of the electrode mixture is inferior or it is easy to elute into the electrolytic solution, which is not preferable.
- the mass average molecular weight of the water-soluble polymer is 6,000,000 or less, more preferably 5,000,000 or less. When the mass average molecular weight exceeds 6,000,000, the solubility in a solvent is lowered, which is not preferable.
- a water-insoluble polymer can be used in combination as a binder. These are dispersed in an aqueous medium to form an emulsion.
- Preferred water-insoluble polymers include diene polymers, olefin polymers, styrene polymers, (meth) acrylate polymers, amide polymers, imide polymers, ester polymers, and cellulose polymers.
- thermoplastic resins used as the binder for the negative electrode can be used without particular limitation as long as they have a binding effect and have resistance to the non-aqueous electrolyte used and resistance to electrochemical reaction at the negative electrode. .
- the two components of the water-soluble polymer and the emulsion are often used.
- the water-soluble polymer is mainly used as a dispersibility imparting agent or a viscosity modifier, and the emulsion is important for imparting the binding property between the particles and the flexibility of the electrode.
- preferred examples include homopolymers or copolymers of conjugated diene monomers and acrylate (including methacrylate) monomers, and specific examples thereof include polybutadiene, polyisoprene, and polymethyl.
- a polymer (rubber) having rubber elasticity is particularly preferably used.
- PVDF polyvinylidene fluoride
- PTFE polytetrafluoroethylene
- SBR styrene butadiene rubber
- water-insoluble polymers those having a polar group such as a carboxyl group, a carbonyloxy group, a hydroxyl group, a nitrile group, a carbonyl group, a sulfonyl group, a sulfoxyl group, and an epoxy group are listed as preferred examples in terms of binding properties. It is done. Particularly preferred examples of the polar group are a carboxyl group, a carbonyloxy group, and a hydroxyl group.
- the content of the water-soluble polymer in the previous binder is preferably 8 to 100% by mass. If it is less than 8% by mass, the water absorption resistance is improved, but the cycle durability of the battery is not sufficient.
- the preferred amount of binder to be added varies depending on the type of binder used, but binders that use water as a solvent often use a mixture of a plurality of binders, such as a mixture of SBR and CMC, and use all of them.
- the total amount of the binder is preferably 0.5 to 10% by mass, and more preferably 1 to 8% by mass.
- the solvent that can be used is not particularly limited as long as it can dissolve the binder and can disperse the carbonaceous material satisfactorily.
- one kind or two or more kinds selected from water, methyl alcohol, ethyl alcohol, propyl alcohol, N-methylpyrrolidone (NMP) and the like can be used.
- 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 collectors and separators are required.
- the thickness of the active material layer (per side) is preferably 10 to 80 ⁇ m, more preferably 20 to 75 ⁇ m, and particularly preferably 20 to 60 ⁇ m.
- the press pressure in the production of the electrode using the carbonaceous material of the present invention is not particularly limited. However, it is preferably 2.0 to 5.0 tf / cm 2 , more preferably 2.5 to 4.5 tf / cm 2 , and still more preferably 3.0 to 4.0 tf / cm 2 .
- the contact between the active materials is improved by applying the press pressure described above, and the conductivity is improved. Therefore, an electrode excellent in long-term cycle durability can be obtained.
- the pressing pressure is too low, the contact between the active materials becomes insufficient, so that the resistance of the electrode is increased, and the coulomb efficiency is lowered, so that long-term durability may be inferior. If the press pressure is too high, the electrode may be bent by rolling, and winding may be difficult.
- Nonaqueous electrolyte secondary battery of the present invention includes the negative electrode of the nonaqueous electrolyte secondary battery of the present invention.
- the nonaqueous electrolyte secondary battery using the negative electrode for a nonaqueous electrolyte secondary battery using the carbonaceous material of the present invention exhibits excellent output characteristics and excellent cycle characteristics.
- non-aqueous electrolyte secondary batteries Manufacture of non-aqueous electrolyte secondary batteries
- other materials constituting the battery such as a positive electrode material, a separator, and an electrolytic solution are not particularly limited, and are nonaqueous solvents.
- Various materials conventionally used or proposed as a secondary battery can be used.
- the cathode material one represented layered oxide (LiMO 2, M is a metal: for example, LiCoO 2, LiNiO 2, LiMnO 2, or LiNi x Co y Mo z O 2 (where x, y, z represents a composition ratio), olivine system (represented by LiMPO 4 , M is a metal: for example, LiFePO 4 ), spinel system (represented by LiM 2 O 4 , M is a metal: for example, LiMn 2 O 4, etc.
- LiMPO 4 olivine system
- M is a metal: for example, LiFePO 4
- spinel system represented by LiM 2 O 4
- M is a metal: for example, LiMn 2 O 4, etc.
- the composite metal chalcogen compound is preferable, and these chalcogen compounds may be mixed if necessary, and these positive electrode materials are molded together with an appropriate binder and a carbonaceous material for imparting conductivity to the electrode, A positive electrode is formed by forming a layer on a conductive current collector.
- 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.
- the LUMO value calculated by using the semi-empirical molecular orbital AM1 (Austin Model 1) calculation method for the electrolyte is in the range of ⁇ 1.10 to 1.11 eV.
- the nonaqueous electrolyte secondary battery using the negative electrode for a nonaqueous electrolyte secondary battery using the carbonaceous material and additive of the present invention has high dope and dedope capacity and exhibits excellent high temperature cycle characteristics.
- a solid electrolyte film (SEI) is formed by reductive decomposition of an organic electrolyte solution at the first charge.
- SEI solid electrolyte film
- LUMO Large Unoccupied Molecular Orbital
- LUMO represents a molecular orbital function having no electrons at the lowest energy level, and when a molecule accepts electrons, the electrons are buried in this energy level, and this value determines the degree of reduction. The lower the LUMO value, the higher the reduction property, and the higher the LUMO value, the reduction resistance.
- the LUMO value of the compound added to the electrolytic solution was obtained by using the AM1 calculation method in the semi-empirical molecular orbital method, which is one of the quantum chemical calculation methods.
- Semi-empirical calculation methods include AM1, PM3 (Parametric method 3), MNDO (Modified Negative of Different Overlap), CNDO (Complementary OverDifferential), depending on the types of assumptions and parameters. It is classified into MINDO (Modified Intermediate Neighbor of Differential Overlap) and the like.
- the AM1 calculation method was developed in 1985 by Dewer et al. By partially improving the MNDO method so as to be suitable for hydrogen bond calculation.
- the AM1 method in the present invention is provided by the computer program package Gaussian 03 (Gaussian), but is not limited thereto.
- Gaussian 03 Gaussian
- the operation procedure for calculating the LUMO value using Gaussian 03 is shown below.
- the visualization function installed in the drawing program GaussView 3.0 was used for modeling of the molecular structure in the pre-calculation stage. After creating a molecular structure and optimizing the structure in the ground state, charge “0”, spin “singlet”, and solvent effect “none” using the AM1 method for the Hamiltonian, one-point calculation of energy at the same level went.
- the LUMO value determined by the AM1 calculation method in the quantum chemistry calculation method is ⁇ 1.1 to 1.11 eV, more preferably ⁇ 0.6 to 1.0 eV, and more preferably 0 to 1. 0 eV is more preferable.
- An LUMO value of 1.11 eV or more is not preferable because it may not act as an additive. Further, if the LUMO value is ⁇ 1.1 eV or less, side reactions may occur on the positive electrode side, which is not preferable.
- additives having a LUMO value of ⁇ 1.10 to 1.11 eV include fluoroethylene carbonate (FEC, 0.9829 eV), trimethylsilyl phosphate (TMSP, 0.415 eV), lithium tetrafluoroborate (LiBF 4, 0.2376 eV), chloroethylene carbonate (ClEC, 0.1056 eV), propane sultone (PS, 0.0656 eV), ethylene sulfite (ES, 0.0248 eV), vinylene carbonate (VC, 0.0155 eV), vinyl ethylene carbonate (VEC, -0.5736 eV), dioxathiolane dioxide (DTD, -0.7831 eV), lithium bis (oxalato) borate (LiBOB, -1.0427 eV), and the like.
- FEC fluoroethylene carbonate
- TMSP trimethylsilyl phosphate
- TMSP trimethylsilyl phosphate
- the battery includes a positive electrode, a separator, and an electrolyte solution, in addition to containing at least vinylene carbonate or fluoroethylene carbonate in the electrolyte.
- the other materials to be used are not particularly limited, and various materials conventionally used or proposed as non-aqueous solvent secondary batteries can be used.
- the electrolyte used for the nonaqueous electrolyte secondary battery of the present invention has a LUMO value calculated using the AM1 calculation method in the semi-empirical molecular orbital method in the range of ⁇ 1.10 to 1.11 eV.
- Additives are included and can be used alone or in combination of two or more.
- the content in the electrolytic solution is preferably 0.1 to 6% by mass, and more preferably 0.2 to 5% by mass. If the content is less than 0.1% by mass, a film derived from the reductive decomposition of the additive is not sufficiently formed, so that the high-temperature cycle characteristics are not improved, and if it exceeds 6% by mass, a thick film is formed on the negative electrode. As a result, resistance increases and input / output characteristics deteriorate.
- 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.
- the lithium secondary battery of the present invention is suitable as a battery (typically a lithium secondary battery for driving a vehicle) mounted on a vehicle such as an automobile.
- the vehicle according to the present invention can be targeted without particular limitation, such as a vehicle normally known as an electric vehicle, a hybrid vehicle with a fuel cell or an internal combustion engine, and at least a power supply device including the battery, An electric drive mechanism that is driven by power supply from the power supply device and a control device that controls the electric drive mechanism are provided. Further, a mechanism for charging the lithium secondary battery by converting the energy generated by braking into electricity by providing a power generation brake or a regenerative brake may be provided.
- the true density was measured by a butanol method according to a method defined in JIS R 7212.
- the mass (m 1 ) of a specific gravity bottle with a side tube having an internal volume of about 40 mL is accurately measured.
- the sample is placed flat on the bottom so as to have a thickness of about 10 mm, and its mass (m 2 ) is accurately measured.
- light vibration is applied to the specific gravity bottle, and it is confirmed that large bubbles are not generated.
- the bottle is placed in a vacuum desiccator and gradually evacuated to 2.0 to 2.7 kPa.
- d is the specific gravity of water at 30 ° C. (0.9946).
- ⁇ H (True density by helium method)
- the measuring device has a sample chamber and an expansion chamber, and the sample chamber has a pressure gauge for measuring the pressure in the chamber.
- the sample chamber and the expansion chamber are connected by a connecting pipe having a valve.
- a helium gas introduction pipe having a stop valve is connected to the sample chamber, and a helium gas discharge pipe having a stop valve is connected to the expansion chamber.
- the volume of the sample chamber (V CELL ) and the volume of the expansion chamber (V EXP ) are measured in advance using a calibration sphere with a known volume.
- the sample is placed in the sample chamber, fills the system with helium, the system pressure at that time and P a. Then closing the valve, is increased to a pressure P 1 added sample chamber only helium gas. After that, when the valve is opened and the expansion chamber and the sample chamber are connected, the system pressure decreases to P 2 due to expansion.
- the volume of the sample (V SAMP ) is calculated by the following equation. Therefore, if the sample mass is W SAMP , the density is It becomes.
- the amount of nitrogen adsorbed on the carbonaceous material at the liquid nitrogen temperature was measured as follows.
- the sample tube is then returned to room temperature.
- the amount of nitrogen desorbed from the sample was measured with a thermal conductivity detector, and the amount of adsorbed gas v was obtained.
- An X-ray diffraction pattern is obtained by filling a carbonaceous material powder into a sample holder and using CuK ⁇ rays monochromated by a Ni filter as a radiation source.
- the peak position of the diffraction pattern is obtained by the barycentric method (a method of finding the barycentric position of the diffraction line and determining the peak position with the corresponding 2 ⁇ value), and using the diffraction peak on the (111) plane of the high-purity silicon powder for standard substances.
- the wavelength of the CuK ⁇ ray is set to 0.15418 nm, and d (002) is calculated by the Bragg formula described below.
- ⁇ : X-ray wavelength (CuK ⁇ m 0.15418 nm)
- Dispersant Surfactant SN wet 366 (manufactured by San Nopco)
- SALD-3000S particle size distribution measuring instrument
- a carbon sample containing a predetermined potassium element and calcium element is prepared in advance, and the intensity of the potassium K ⁇ ray and the potassium content are measured using a fluorescent X-ray analyzer.
- a calibration curve was created for the relationship and the relationship between the calcium K ⁇ line intensity and the calcium content.
- strength of the potassium K alpha ray and calcium K alpha ray in a fluorescent X ray analysis was measured about the sample, and potassium content and calcium content were calculated
- Fluorescence X-ray analysis was performed using LAB CENTER XRF-1700 manufactured by Shimadzu Corporation under the following conditions. Using the upper irradiation system holder, the sample measurement area was within the circumference of 20 mm in diameter. The sample to be measured was placed by placing 0.5 g of the sample to be measured in a polyethylene container having an inner diameter of 25 mm, pressing the back with a plankton net, and covering the measurement surface with a polypropylene film for measurement. The X-ray source was set to 40 kV and 60 mA.
- LiF (200) was used as the spectroscopic crystal and a gas flow proportional coefficient tube was used as the detector, and 2 ⁇ was measured in the range of 90 to 140 ° at a scanning speed of 8 ° / min.
- LiF (200) was used as the spectroscopic crystal, and a scintillation counter was used as the detector, and 2 ⁇ was measured in the range of 56 to 60 ° at a scanning speed of 8 ° / min.
- Reference Example 3 The coffee residue after extraction was dried in a nitrogen gas atmosphere, and then detarred at 700 ° C. for preliminary carbonization. Add 100 g of 1% hydrochloric acid to 100 g of the pre-carbonized coffee residue, stir at 100 ° C. for 1 hour, filter, repeat the washing operation of adding 300 g of boiling water and washing with water three times to deash, A deashed coffee extraction residue was obtained. This was pulverized using a rod mill to obtain carbon precursor fine particles. Next, this carbon precursor was fully fired at 1250 ° C. for 1 hour to obtain a reference carbonaceous material 3 having an average particle diameter of 10 ⁇ m.
- Reference Example 4 The coffee residue after extraction was dried in a nitrogen gas atmosphere, and then detarred at 700 ° C. for preliminary carbonization. This was pulverized using a rod mill to obtain a fine powder. Add 100 g of 1% hydrochloric acid to 100 g of finely ground coffee residue that has been pre-carbonized, stir at 100 ° C. for 1 hour, filter, repeat the washing operation of adding 300 g of boiling water and washing with water three times to deash. The deashed coffee extraction residue was obtained by processing. Next, this carbon precursor was fully fired at 1250 ° C. for 1 hour to obtain a reference carbonaceous material 4 having an average particle diameter of 10 ⁇ m.
- Reference Example 5 A reference carbonaceous material 5 was obtained in the same manner as in Reference Example 1 except that only washing with water was repeated without using an acid during deashing.
- Electrode preparation NMP was added to 90 parts by mass of the carbonaceous material and 10 parts by mass of polyvinylidene fluoride (“KF # 1100” manufactured by Kureha Co., Ltd.) to form a paste, which was uniformly applied on the copper foil. After drying, it was punched out from a copper foil into a disk shape having a diameter of 15 mm and pressed to obtain an electrode. In addition, it prepared so that the quantity of the carbonaceous material in an electrode might be set to about 10 mg.
- the carbonaceous material 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-desorption) of the battery active material.
- a lithium secondary battery is configured using the electrode obtained above, using lithium metal with stable characteristics as a counter electrode, Its characteristics were evaluated.
- the lithium electrode was prepared in a glove box in an Ar atmosphere.
- a 16 mm diameter stainless steel mesh disk is spot-welded to the outer lid of a 2016 coin-sized battery can, and then a 0.8 mm thick metal lithium sheet is punched into a 15 mm diameter disk shape.
- the electrode pair thus produced was used, and as the electrolyte, LiPF 6 was mixed at a rate of 1.5 mol / L in a mixed solvent in which ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate were mixed at a volume ratio of 1: 2: 2.
- a polyethylene gasket is used as a separator of a borosilicate glass fiber fine pore membrane having a diameter of 19 mm, and a 2016 coin-sized non-aqueous electrolyte lithium secondary battery is used in an Ar glove box. The next battery was assembled.
- the lithium doping reaction on the carbon electrode will be described as “charging”.
- “discharge” is a charging reaction in the test battery, but is referred to as “discharge” for convenience because it is a dedoping reaction of lithium from the carbonaceous material.
- the charging method adopted here is a constant current constant voltage method. Specifically, constant current charging is performed at 0.5 mA / cm 2 until the terminal voltage reaches 0 mV, and after the terminal voltage reaches 0 mV, the terminal voltage is increased. The constant voltage charge was performed at 0 mV, and the charge was continued until the current value reached 20 ⁇ A.
- the value obtained by dividing the supplied amount of electricity by the mass of the carbonaceous material of the electrode was defined as the charge capacity (mAh / g) per unit mass of the carbonaceous material.
- 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.
- a value obtained by dividing the quantity of electricity discharged at this time by the mass of the carbonaceous material of the electrode is defined as a discharge capacity (mAh / g) per unit mass of the carbonaceous material.
- the irreversible capacity is calculated as charge capacity-discharge capacity.
- Tables 1 to 3 show the decalcification and firing conditions of the reference carbonaceous materials 1 to 5 prepared in Reference Examples 1 to 5, the ion content contained in the obtained carbonaceous materials, and the battery characteristics, respectively. .
- the decalcification efficiency of the potassium element and the calcium element is lowered when the plant-derived organic matter is detarred before the liquid phase decalcification step. I understand. Moreover, even if those materials are pulverized and the decalcification particle size is reduced, it is understood that the reduction efficiency of calcium element is low if the organic matter is detarred before the liquid phase demineralization step. That is, it can be beneficial to perform liquid phase deashing before the ordering of the crystal structure is increased by detarring.
- Example 1 171 g of 35% hydrochloric acid (special grade manufactured by Junsei Chemical Co., Ltd.) and 5830 g of pure water were added to 2000 g of coffee residue (water content 65%) after extraction to adjust the pH to 0.5. After stirring at a liquid temperature of 20 ° C. for 1 hour, the mixture was filtered to obtain an acid-treated coffee extraction residue. Thereafter, 6000 g of pure water was added to the acid-treated coffee extraction residue, and the water washing operation of stirring for 1 hour was repeated three times for deashing treatment to obtain a deashed coffee extraction residue.
- 35% hydrochloric acid special grade manufactured by Junsei Chemical Co., Ltd.
- the obtained deashed coffee extraction residue was dried at 150 ° C. in a nitrogen gas atmosphere, and then detarred at 380 ° C. for 1 hour in a tubular furnace to obtain a detarned deashed coffee extraction residue.
- 50 g of the resulting detar-decalcified coffee extraction residue was put in an alumina case and subjected to an oxidation treatment at 220 ° C. for 1 hour in an air stream in an electric furnace to obtain an oxidation-treated coffee extraction residue.
- Example 2 A carbonaceous material 2 was obtained in the same manner as in Example 1 except that the oxidation treatment temperature in Example 1 was set to 260 ° C.
- Example 3 A carbonaceous material 3 was obtained in the same manner as in Example 1 except that the oxidation treatment temperature in Example 1 was changed to 300 ° C.
- Example 4 A carbonaceous material 4 was obtained in the same manner as in Example 1 except that the oxidation treatment temperature in Example 1 was changed to 350 ° C.
- Example 5 A carbonaceous material 5 was obtained in the same manner as in Example 1 except that the oxidation treatment temperature in Example 1 was set to 400 ° C.
- the deashed coffee extraction residue 50 g was detarred in a tube furnace under a nitrogen stream at 700 ° C. for 1 hour for preliminary carbonization. This was pulverized with a rod mill to obtain carbon precursor fine particles. Next, 10 g of the carbon precursor fine particles were placed in a horizontal tubular furnace, and carbonized by being held at 1250 ° C. for 1 hour while flowing nitrogen gas, to obtain a comparative carbonaceous material 1 having an average particle diameter of 10 ⁇ m.
- Example 2 A comparative carbonaceous material 2 was obtained in the same manner as in Example 1 except that the oxidation treatment temperature in Example 1 was changed to 190 ° C.
- Comparative Example 3 A comparative carbonaceous material 3 was obtained in the same manner as in Example 1 except that the oxidation treatment temperature in Example 1 was 410 ° C.
- Electrode preparation NMP was added to 94 parts by mass of the carbonaceous material and 6 parts by mass of polyvinylidene fluoride (“KF # 9100” manufactured by Kureha Co., Ltd.) to form a paste, which was uniformly applied on the copper foil. After drying, it was punched out from a copper foil into a disk shape having a diameter of 15 mm and pressed to obtain an electrode. In addition, it prepared so that the quantity of the carbonaceous material in an electrode might be set to about 10 mg.
- the carbonaceous material 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-desorption) of the battery active material.
- a lithium secondary battery is configured using the electrode obtained above, using lithium metal with stable characteristics as a counter electrode, Its characteristics were evaluated.
- the lithium electrode was prepared in a glove box in an Ar atmosphere.
- a 16 mm diameter stainless steel mesh disk is spot-welded to the outer lid of a 2016 coin-sized battery can, and then a 0.8 mm thick metal lithium sheet is punched into a 15 mm diameter disk shape.
- the electrode pair thus produced was used, and as the electrolyte, LiPF 6 was mixed at a rate of 1.5 mol / L in a mixed solvent in which ethylene carbonate, dimethyl carbonate, and methyl ethyl carbonate were mixed at a volume ratio of 1: 2: 2.
- a polyethylene gasket is used as a separator of a borosilicate glass fiber fine pore membrane having a diameter of 19 mm, and a 2016 coin-sized non-aqueous electrolyte lithium secondary battery is used in an Ar glove box. The next battery was assembled.
- the lithium doping reaction on the carbon electrode will be described as “charging”.
- “discharge” is a charging reaction in the test battery, but is referred to as “discharge” for convenience because it is a dedoping reaction of lithium from the carbonaceous material.
- the charging method adopted here is a constant current constant voltage method. Specifically, constant current charging is performed at 0.5 mA / cm 2 until the terminal voltage reaches 0 mV, and after the terminal voltage reaches 0 mV, the terminal voltage is increased. The constant voltage charge was performed at 0 mV, and the charge was continued until the current value reached 20 ⁇ A.
- the value obtained by dividing the supplied amount of electricity by the mass of the carbonaceous material of the electrode was defined as the charge capacity (mAh / g) per unit mass of the carbonaceous material.
- 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.
- a value obtained by dividing the quantity of electricity discharged at this time by the mass of the carbonaceous material of the electrode is defined as a discharge capacity (mAh / g) per unit mass of the carbonaceous material.
- the irreversible capacity is calculated as charge capacity-discharge capacity.
- LiCoO 2 (“CELLSEED C5-H” manufactured by Nippon Chemical Industry Co., Ltd.) was used as the positive electrode material (active material), 94 parts by mass of this positive electrode material, 3 parts by mass of acetylene black, and polyvinylidene fluoride binder (stock) It was mixed with 3 parts by mass of “KF # 1300” manufactured by Kureha Co., Ltd., added with N-methyl-2-pyrrolidone (NMP) to form a paste, and uniformly applied to one side of a strip-shaped aluminum foil having a thickness of 20 ⁇ m.
- NMP N-methyl-2-pyrrolidone
- the negative electrode (carbon electrode) was made into a paste by adding NMP to 94 parts by mass of each of the negative electrode materials produced in the examples or comparative examples described above and 6 parts by mass of polyvinylidene fluoride (“KF # 9100” manufactured by Kureha Corporation), It apply
- the obtained sheet-like electrode was punched into a disk shape having a diameter of 15 mm, and this was pressed to obtain a negative electrode.
- the quantity of the negative electrode material (carbonaceous material) in an electrode might be about 10 mg.
- the electrolyte was LiPF at a ratio of 1.5 mol / L in a mixed solvent in which ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 2: 2.
- a coin type nonaqueous electrolyte-based lithium 2016 A secondary battery was assembled. In the lithium ion secondary battery having such a configuration, a charge / discharge test was performed. Charging was performed by a constant current constant voltage method.
- Charging conditions are set to 4.2V for the upper limit of charging voltage and 2C for charging current value (that is, the current value necessary for charging in 30 minutes). After reaching 4.2V, the current is attenuated with a constant voltage. Thus, charging was terminated when the current reached 1/100 C. Subsequently, a current was passed in the reverse direction to discharge. The discharge was performed at a current value of 2C, and the discharge was terminated when the voltage reached 2.75V. Such charging and discharging were repeated in a 50 ° C. constant temperature bath to evaluate the high temperature cycle characteristics. In the evaluation of the high-temperature cycle characteristics, the discharge capacity after 150 cycles was divided by the discharge capacity at the first cycle to obtain the discharge capacity retention rate (%) after 150 cycles.
- Table 4 shows the physical properties of the carbonaceous materials 1 to 5 and the comparative carbonaceous materials 1 to 3, and Table 5 shows the performance of lithium ion secondary batteries manufactured using these carbonaceous materials. Moreover, the change of the discharge capacity retention with respect to the number of charge / discharge cycles of the carbonaceous material 2 and the comparative carbonaceous material 1 is shown in FIG.
- d (002) plane is obtained by performing an oxidation treatment. Since the interval increased and ⁇ Bt decreased, it can be seen that the oxidation treatment made the crystal order disorder and increased the pores (Table 4).
- Comparative Example 2 since the oxidation treatment temperature is as low as 190 ° C., the d (002) plane spacing is small and ⁇ Bt is also large, so the effect of the oxidation treatment is small.
- Comparative Example 3 since the oxidation treatment temperature is as high as 410 ° C., the decomposition reaction by oxidation is promoted, and the specific surface area is increased. When the specific surface area is increased, the number of electrochemical reaction sites is increased, so that the amount of the solid electrolyte membrane formed by the decomposition reaction of the electrolytic solution during charging increases, and the irreversible capacity may increase due to lithium consumption. Therefore, an oxidation treatment temperature higher than this is not preferable.
- Example 6 A washing operation of adding 300 g of 1% hydrochloric acid to 100 g of coffee residue after extraction of roasted coffee beans having a grain size of 1 mm, stirring at 20 ° C. for 1 hour, filtering, adding 300 g of water at 20 ° C. and washing with water 3 The deashing process was repeated repeatedly to obtain a deashed coffee extraction residue.
- the deashed coffee residue subjected to the oxidation treatment was detarred in a tubular furnace under a nitrogen stream at 700 ° C. for 1 hour to perform preliminary carbonization. This was pulverized using a rod mill to obtain carbon precursor fine particles. Next, this carbon precursor was fully fired at 1250 ° C. for 1 hour to obtain a carbonaceous material 6 having an average particle diameter of 10 ⁇ m.
- Example 7 A carbonaceous material 7 was obtained in the same manner as in Example 6 except that drying and oxidation were performed at 260 ° C.
- Example 8 A carbonaceous material 8 was obtained in the same manner as in Example 6 except that drying and oxidation were performed at 300 ° C.
- Example 9 A carbonaceous material 9 was obtained in the same manner as in Example 6 except that drying and oxidation were performed at 260 ° C. in a horizontal furnace with a feeder.
- Example 10 A carbonaceous material 10 was obtained in the same manner as in Example 6 except that a vertical furnace was used and drying and oxidation were separately performed in this order. When adjusting the oxidation temperature to the set temperature, water was introduced into the vertical furnace to adjust the temperature.
- Example 10 prepared by the same method as Examples 1 to 5, 131 g of introduced water was required for adjusting the set temperature in the oxidation step.
- Table 6 shows the oxidation conditions and the content and characteristics of ions contained in the obtained carbonaceous material.
- NMP was added to 94 parts by mass of lithium cobalt oxide (LiCoO 2 ), 3 parts by mass of carbon black, and 3 parts by mass of polyvinylidene fluoride (Kureha KF # 1300) to form a paste, which was uniformly coated on the aluminum foil. After drying, the coated electrode is punched onto a disk having a diameter of 14 mm. The amount of lithium cobaltate in the positive electrode was adjusted so as to be 95% of the charge capacity of the negative electrode active material measured in (c). At this time, the capacity of lithium cobaltate was calculated as 150 mAh / g.
- LiCoO 2 lithium cobalt oxide
- carbon black carbon black
- Kureha KF # 1300 polyvinylidene fluoride
- the electrolyte used was the same as that used in the active material dope-dedope test, and a borosilicate glass fiber microporous membrane having a diameter of 19 mm 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.
- (B) Cycle test Charging is performed with constant current and constant voltage. Charging is performed with a constant current (2C) until 4.2V, and then the current value is attenuated so that the voltage is maintained at 4.2V (while maintaining a constant voltage). Charging is continued until (1/100) C is reached. After completion of charging, the battery circuit was opened for 30 minutes and then discharged. Discharging was performed at a constant current (2C) until the battery voltage reached 2.75V. The first three cycles were performed at 25 ° C., and the subsequent cycles were performed in a constant temperature bath at 50 ° C.
- Table 7 shows the battery characteristics of the lithium secondary battery prepared by the above manufacturing method.
- Reference Example 7 A reference carbonaceous material 7 was obtained in the same manner as the reference carbonaceous material 6 except that the used coffee residue was extracted from Brazil beans (Arabica seeds) with different roasting degrees.
- Reference Example 8 A reference carbonaceous material 8 was obtained in the same manner as the reference carbonaceous material 6, except that a coffee bean residue used was obtained by extracting Vietnamese beans (canephora species).
- the obtained deashed coffee extraction residue was dried at 150 ° C. in a nitrogen gas atmosphere, and then detarred at 380 ° C. for 1 hour in a tubular furnace to obtain a detarned deashed coffee extraction residue.
- 50 g of the resulting detar-decalcified coffee extraction residue was put in an alumina case and subjected to an oxidation treatment at 260 ° C. for 1 hour in an air stream in an electric furnace to obtain an oxidation-treated coffee extraction residue.
- Reference carbonaceous material 10 was obtained in the same manner as in Reference Example 6 except that the average particle size was changed to 11 ⁇ m.
- Reference carbonaceous material 11 was obtained in the same manner as in Reference Example 6 except that the main firing temperature was 800 ° C.
- Table 8 shows the resistance values measured by the methods shown below and battery characteristics measured in the same manner as described above, by preparing negative electrodes using the carbonaceous materials of Reference Examples 6 to 11.
- NMP was added to 94 parts by mass of each of the carbonaceous materials obtained in Reference Examples 6 to 11 and 6 parts by mass of polyvinylidene fluoride (Kureha KF # 9100) to form a paste, which was uniformly applied onto the copper foil. After drying, the coated electrode was punched into a disk shape having a diameter of 15 mm, and this was pressed to produce a negative electrode.
- NMP was added to 94 parts by mass of lithium cobaltate (LiCoO 2 , “Cellseed C-5H” manufactured by Nippon Chemical Industry Co., Ltd.), 3 parts by mass of carbon black and 3 parts by mass of polyvinylidene fluoride (Kureha KF # 1300) to form a paste. It applied uniformly on the aluminum foil. After drying, the coated electrode is punched onto a disk having a diameter of 14 mm. The amount of lithium cobaltate in the positive electrode was adjusted so as to be 95% of the charge capacity of the negative electrode active material measured in (c). The capacity of lithium cobaltate was calculated as 150 mAh / g.
- the electrode pair thus prepared was used, and the electrolyte was LiPF at a ratio of 1.5 mol / liter in a mixed solvent in which ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 2: 2.
- a mixed solvent in which ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 2: 2.
- aging is performed by repeating charging and discharging twice. Conversion of the current value in aging to the C rate was calculated from the electric capacity and mass of the lithium cobalt oxide defined above.
- Charging is performed with constant current and constant voltage. Charging is performed at a constant current of 0.2 C (current value necessary for charging in 1 hour is defined as 1 C) until 4.2 V is reached, and then the voltage is maintained at 4.2 V The current value is attenuated (while maintaining a constant voltage) and charging is continued until the current value reaches (1/100) C. After completion of charging, the battery circuit was opened for 30 minutes and then discharged. Discharging was performed at a constant current of 0.2 C until the battery voltage reached 2.75V. In the second charge / discharge, the current value was set to 0.4C.
- pulse charging / discharging was performed in a low-temperature incubator (at 0 ° C. atmosphere). Pulse charge / discharge is measured at each current of 0.5C, 1C, and 2C, with 600 seconds open circuit after charging for 10 seconds at a constant current, 10 seconds after discharge, and 600 seconds open circuit as one set. The voltage change with respect to each current was plotted, and the slope of the linear approximation was calculated as the DC resistance.
- the resistance of the negative electrode using the carbonaceous materials of Reference Examples 6 to 9 having a small particle diameter is small, and the irreversible capacity of the battery using this is also small.
- the carbonaceous material of the present invention having particularly high purity and specific physical properties is useful as a secondary battery for a hybrid vehicle (HEV) that requires high input / output characteristics that repeat supply and acceptance of large currents at the same time. It turns out that it is.
- HEV hybrid vehicle
- the coffee bean residue and coconut shell are made into a carbonaceous material powder for a negative electrode by the following method.
- the carbonaceous material powder made from plant-derived organic material is prepared by the following method.
- Reference Example 13 A reference carbonaceous material 13 was obtained in the same manner as in Reference Example 12 except that a coffee beans residue was used to extract lightly roasted Brazilian beans. Table 10 shows various characteristics of the obtained carbonaceous material.
- Reference Example 14 A reference carbonaceous material 14 was obtained in the same manner as in Reference Example 12, except that a deep roasted Brazilian bean was used as the used coffee residue. Table 10 shows various characteristics of the obtained carbonaceous material.
- Reference carbonaceous material 15 was obtained in the same manner as in Reference Example 12 except that the firing temperature was 800 ° C. Table 10 shows various properties of the obtained carbonaceous material.
- the coconut shell char was calcined at 600 ° C. for 1 hour in a nitrogen gas atmosphere (normal pressure) and then pulverized to obtain a powdery carbon precursor having an average particle size of 19 ⁇ m. Next, this powdery carbon precursor is immersed in 35% hydrochloric acid for 1 hour, and then washed with boiling water for 1 hour to repeat deashing treatment twice to obtain a deashed powdery carbon precursor. It was. 10 g of the obtained decalcified powdery carbon precursor was placed in a horizontal tubular furnace and subjected to main firing at 1200 ° C. for 1 hour in a nitrogen atmosphere to obtain a reference carbonaceous material 16. Table 10 shows various characteristics of the obtained reference carbonaceous material 16.
- Electrode preparation A solvent was added to the carbonaceous material and the binder to form a paste, which was uniformly coated on the copper foil. After drying, it was punched out from a copper foil into a disk shape having a diameter of 15 mm and pressed to obtain electrodes of Reference Examples 17-24. Table 11 shows the carbonaceous material used, the binder, and the blending ratio.
- surface is as follows.
- SBR Styrene-butadiene rubber
- CMC Carboxymethylcellulose
- PAA Polyacrylate
- PVDF Polyvinylidene fluoride (“KF # 9100” manufactured by Kureha Corporation)
- Example carbon 1 (E) Cycle test (Preparation of negative electrode)
- the electrode mixture of Example carbon 1 was uniformly applied on one side of a copper foil having a thickness of 18 ⁇ m, and this was heated and dried at 120 ° C. for 25 minutes. After drying, it was punched into a disk shape having a diameter of 15 mm and pressed to produce a negative electrode.
- the mass of the active material which a disk shaped negative electrode has was adjusted so that it might be set to 10 mg.
- NMP is added to 94 parts by mass of lithium cobaltate (Nippon Chemical Industrial “Cellseed C-5”), 3 parts by mass of carbon black, 3 parts by mass of polyvinylidene fluoride (KF # 1300 manufactured by Kureha Corporation), and 3 parts by mass of carbon black. And mixed to prepare a positive electrode mixture.
- the obtained mixture was uniformly applied onto an aluminum foil having a thickness of 50 ⁇ m. After drying, the coated electrode was punched into a disk shape having a diameter of 14 mm to produce a positive electrode.
- the amount of lithium cobaltate in the positive electrode was adjusted so as to be 95% of the charge capacity per unit mass of the active material in Reference Example 17 measured by the method described above. The capacity of lithium cobaltate was calculated as 150 mAh / g.
- LiPF6 was mixed at a rate of 1.5 mol / liter in a mixed solvent in which ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate were mixed at a volume ratio of 1: 2: 2 as an electrolyte.
- Table 12 shows the exposure test and cycle characteristics of the prepared lithium secondary battery.
- charge / discharge test was done using the charge / discharge test apparatus ("TOSCAT" by Toyo System), and charge / discharge was performed by the constant current constant voltage method.
- charge is a discharge reaction in the test battery, but in this case, it is a lithium insertion reaction into the carbonaceous material, and therefore “charge” is described for convenience.
- discharge is a charge reaction in a test battery, but is a lithium desorption reaction from a carbonaceous material, and is therefore referred to as “discharge” for convenience.
- the constant current / constant voltage method employed here is charged at a constant current density of 0.5 mA / cm 2 until the battery voltage reaches 0V, and then maintains the voltage at 0V (while maintaining the constant voltage). ) Continue charging until the current value reaches 20 ⁇ A by continuously changing the current value. A value obtained by dividing the amount of electricity supplied at this time by the mass of the carbonaceous material of the electrode was defined as a charge capacity (doping capacity) (mAh / g) per unit mass of the carbonaceous material. After completion of charging, the battery circuit was opened for 30 minutes and then discharged.
- Discharging is performed at a constant current density of 0.5 mA / cm 2 until the battery voltage reaches 1.5 V, and the value obtained by dividing the amount of electricity discharged at this time by the mass of the carbonaceous material of the electrode is per unit mass of the carbonaceous material.
- Discharge capacity (de-doped capacity) (mAh / g).
- the irreversible capacity (non-dedoped capacity) (mAh / g) is calculated as charge amount ⁇ discharge amount, and the efficiency (%) is calculated as (discharge capacity / charge capacity) ⁇ 100.
- NMP was added to 94 parts by mass of lithium cobaltate (LiCoO 2 , “Cellseed C-5H” manufactured by Nippon Chemical Industry Co., Ltd.), 3 parts by mass of carbon black and 3 parts by mass of polyvinylidene fluoride (Kureha KF # 1300) to form a paste. It applied uniformly on the aluminum foil. After drying, the coated electrode is punched into a disk shape having a diameter of 14 mm. The amount of lithium cobaltate in the positive electrode was adjusted so as to be 95% of the charge capacity of the negative electrode active material measured in (c). At this time, the capacity of lithium cobaltate was calculated as 150 mAh / g.
- the electrolyte used was the same as that used in the active material dope-dedope test, and a borosilicate glass fiber microporous membrane having a diameter of 19 mm 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.
- VC vinylene carbonate (0.0155 eV)
- FEC Fluoroethylene carbonate (0.9829 eV)
- CIEC Chloroethylene carbonate (0.1056eV)
- PC Propylene carbonate (1.3132 eV)
- Electrolyte and LUMO EC ethylene carbonate (1.2417 eV)
- DMC Dimethyl carbonate (1.1366 eV)
- EMC Ethyl methyl carbonate (1.1301 eV)
- Non-water including an oxidation treatment step including a step of drying in an oxidizing gas atmosphere while introducing and mixing a coffee extraction residue or a deashed product thereof, and a step of detarring the oxidation treatment product
- Method for producing intermediate for producing carbonaceous material for electrolyte secondary battery [2] The method according to [1], wherein the temperature of the oxidizing gas is controlled to be 200 ° C. or higher and 400 ° C. or lower.
- the method according to [1] or [2] further comprising a step of decalcifying the coffee extraction residue using an acidic solution having a pH of 3.0 or less at a temperature of 0 ° C. or higher and 100 ° C. or lower.
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Abstract
Description
[1]植物由来の有機物を炭素化して得られる炭素質材料であって、元素分析による水素原子と炭素原子との原子比(H/C)が0.1以下、平均粒子径Dv50が2μm以上50μm以下、粉末X線回折法により求めた002面の平均面間隔が0.365nm以上0.400nm以下、カリウム元素含有量が0.5質量%以下、カルシウム元素含有量が0.02質量%以下、ブタノールを用いたピクノメータ法により求めた真密度が1.44g/cm3以上1.54g/cm3未満である非水電解質二次電池負極用炭素質材料、
[2]前記植物由来の有機物は、コーヒー豆由来の有機物を含む[1]に記載の非水電解質二次電池負極用炭素質材料、
[3]平均粒子径Dv50が2μm以上8μm以下である[1]又は[2]に記載の非水電解質二次電池負極用炭素質材料、
[4]平均粒子径が100μm以上である植物由来の有機物に対し、脱灰を行う工程と、前記脱灰をされた有機物を、酸化性ガス雰囲気下にて200℃以上400℃以下で加熱する酸化処理工程と、酸化処理後の前記有機物を300℃以上1000℃以下で脱タールする工程と、を含む非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法、
[5]平均粒子径が100μm以上であるコーヒー豆由来の有機物に対し、脱灰を行う工程と、前記脱灰をされたコーヒー豆由来の有機物を導入及び混合しながら、酸化性ガス雰囲気下にて200℃以上400℃以下で加熱及び乾燥する酸化処理工程と、前記酸化処理されたコーヒー豆由来の有機物を300℃以上1000℃以下で脱タールする工程と、を含む、[4]に記載の非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法、
[6]平均粒子径が100μm以上であるコーヒー豆由来の有機物を導入及び混合しながら、酸化性ガス雰囲気下にて200℃以上400℃以下で加熱及び乾燥する酸化処理工程と、前記酸化処理されたコーヒー豆由来の有機物に対し、脱灰を行う工程と、前記脱灰されたコーヒー豆由来の有機物を300℃以上1000℃以下で脱タールする工程と、を含む、非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法、
[7]前記脱灰は、pHが3.0以下の酸性溶液を用いて行う[4]から[6]のいずれかに記載の非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法、
[8]前記脱灰工程を、0℃以上80℃以下の温度で行う、[4]から[7]のいずれかに記載の非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法、
[9]前記脱灰をされた有機物を粉砕する工程を更に含む[4]から[8]のいずれかに記載の方法、
[10][4]から[9]のいずれかに記載の方法によって得られる中間体、
[11][4]から[8]のいずれか一項に記載の方法で製造した前記中間体を、1000℃以上1500℃以下で焼成する工程と、前記中間体又はその焼成物を粉砕する工程を含む非水電解質二次電池用炭素質材料の製造方法、
[12][9]に記載の方法で製造した前記中間体を、1000℃以上1500℃以下で焼成する工程を含む非水電解質二次電池負極用炭素質材料の製造方法、
[13][11]又は[12]に記載の製造方法によって得られる非水電解質二次電池負極用炭素質材料、
[14][1]から[3]及び[13]のいずれか一項に記載の非水電解質二次電池負極用炭素質材料を含む非水電解質二次電池用負極電極、
[15]水溶性高分子を含む、[14]に記載の非水電解質二次電池用負極電極、
[16][14]又は[15]に記載の非水電解質二次電池用負極電極を備える非水電解質二次電池、
[17]半経験的分子軌道法のAM1(Austin Model 1)計算法を使用して算出したLUMOの値が-1.10eV以上1.11eV以下の範囲である添加剤を含む電解液を含む[16]に記載の非水電解質二次電池、
[18][16]又は[17]に記載の非水電解質二次電池を搭載した車両、
に関する。
[19]ハロゲン含有量が50ppm以上10000ppm以下である[1]から[3]のいずれかに記載の非水電解質二次電池負極用炭素質材料、
[20]平均粒子径Dv50が2μm以上50μm以下であり、かつ1μm以下の粒子が2体積%以下である、[1]又は[2]に記載の非水電解質二次電池負極用炭素質材料、
[21]平均粒子径Dv50が2μm以上8μm以下であり、1μm以下の粒子が10%以下である[3]に記載の非水電解質二次電池負極用炭素質材料、
[22]前記脱タールを、酸素含有雰囲気下で行う、[4]から[9]のいずれかに記載の非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法、
[23][4]から[9]及び[22]のいずれかに記載の方法によって得られる中間体、
[24][22]に記載の方法で製造した粉砕されていない前記中間体を、1000℃以上1500℃以下で焼成する工程と、前記中間体又はその焼成物を粉砕する工程と、を含む非水電解質二次電池用炭素質材料の製造方法、
[25][22]に記載の方法で製造した粉砕された前記中間体を、1000℃以上1500℃以下で焼成する工程を含む非水電解質二次電池負極用炭素質材料の製造方法、
[26]前記焼成を、ハロゲンガスを含有する不活性ガス中で行う、[11]、[12]、[24]、及び[25]のいずれかに記載の非水電解質二次電池負極用炭素質材料の製造方法、
[27][11]、[12]、[24]から[26]のいずれかに記載の製造方法によって得られる非水電解質二次電池負極用炭素質材料、
[28][1]から[3]及び[27]のいずれかに記載の非水電解質二次電池負極用炭素質材料を含む非水電解質二次電池用負極電極、
[29]水溶性高分子を含む、[28]に記載の非水電解質二次電池用負極電極、
[30]プレス圧が2.0~5.0tf/cm2で製造された、[14]、[15]、[28]及び[29]のいずれかに記載の非水電解質二次電池用負極電極、
[31][14]、[15]、[28]から[30]のいずれかに記載の非水電解質二次電池用負極電極を備える非水電解質二次電池、
[32]半経験的分子軌道法のAM1(Austin Model 1)計算法を使用して算出したLUMOの値が-1.10eV以上1.11eV以下の範囲である添加剤を含む電解液を含む[31]に記載の非水電解質二次電池、及び
[33][16]、[17]、[31]、及び[32]のいずれかに記載の非水電解質二次電池を搭載した車両、
に関する。
本発明の非水電解質二次電池負極用炭素質材料(以下、単に炭素質材料ということもある。)は、植物由来の有機物を炭素化して得られる炭素質材料であって、元素分析による水素原子と炭素原子の原子比(H/C)が0.1以下、平均粒子径Dv50が2~50μm、粉末X線回折法により求めた002面の平均面間隔が0.365nm~0.400nmであり、カリウム元素含有量が0.5質量%以下、カルシウム元素含有量が0.02質量%以下、ブタノールを用いたピクノメータ法により求めた真密度が1.44g/cm3以上1.54g/cm3未満であることを特徴とする。また、本発明の非水電解質二次電池負極用炭素質材料は、好ましくは平均粒子径Dv50が2~8μmである。
本発明の炭素質材料は、微粉が除去されているものが好ましい。微粉が除去された炭素質材料を非水電解質二次電池の負極として用いると、不可逆容量が低下し、充放電効率が向上する。微粉が少ない炭素質材料の場合、少量のバインダーで活物質を十分に接着させることができる。すなわち、微粉を多く含む炭素質材料は、微粉を十分に接着することができず、長期の耐久性に劣ることがある。
平均粒子径10μmの炭素質材料において、1μm以下の微粉を0.0体積%含む(ほとんど含んでいない)炭素質材料と、1μm以下の微粉を2.8体積%含む炭素質材料とを用いて製造した二次電池の不可逆容量を比較すると、それぞれ65(mAh/g)及び88(mAh/g)であり、微粉が少ないことにより、不可逆容量が低下することがわかった。
また、本発明は、植物由来の有機物を炭素化して得られる炭素質材料であって、元素分析による水素原子と炭素原子との原子比(H/C)が0.1以下、平均粒子径Dv50が1~8μm、粉末X線回折法により求めた002面の平均面間隔が0.365nm~0.400nm、カリウム元素含有量が0.5質量%以下、1μm以下の粒子の割合が10%以下であるブタノールを用いたピクノメータ法により求めた真密度が1.44g/cm3以上1.54g/cm3未満である非水電解質二次電池負極用炭素質材料に関する。
植物由来の有機物は、アルカリ金属(例えば、カリウム、ナトリウム)、アルカリ土類金属(例えばマグネシウム、又はカルシウム)、遷移金属(例えば、鉄や銅)及びその他の元素類を含んでおり、これらの金属類の含有量も減少させることが好ましい。これらの金属を含んでいると負極からの脱ドープ時に不純物が電解液中に溶出し、電池性能や安全性に悪影響を及ぼす可能性が高いからである。
炭素質材料の(002)面の平均層面間隔は、結晶完全性が高いほど小さな値を示し、理想的な黒鉛構造のそれは、0.3354nmの値を示し、構造が乱れるほどその値が増加する傾向がある。したがって、平均層面間隔は、炭素の構造を示す指標として有効である。本発明の非水電解質二次電池用炭素質材料のX線回折法により求めた002面の平均面間隔は、0.365nm以上であり、0.370nm以上がより好ましく、0.375nm以上が更に好ましい。同じく、上記平均面間隔は、0.400nm以下であり、0.395nm以下がより好ましく、0.390nm以下が更に好ましい。002面の面間隔が0.365nm未満であると、非水電解質二次電池の負極として用いた場合にドープ容量が小さくなるため、あるいはリチウムのドープ、脱ドープに伴う膨張収縮が大きくなり、粒子間に空隙を生じてしまい、粒子間の導電ネットワークを遮断してしまうことから、繰り返し特性に劣るため、特に自動車用途として好ましくない。また0.400nmを超えると非脱ドープ容量が大きくなるため好ましくない。
本発明の炭素質材料の真密度は、ブタノールを用いたピクノメータ法により求めた。理想的な構造を有する黒鉛質材料の真密度は2.2g/cm3であり、結晶構造が乱れるに従い真密度が小さくなる傾向がある。したがって、真密度は炭素の構造を表す指標として用いることができる。本発明の炭素質材料の真密度は、1.44g/cm3以上1.54g/cm3未満であり、下限は1.47g/cm3以上がより好ましく、1.50g/cm3以上が更に好ましい。真密度の上限は1.53g/cm3以下が好ましく、1.52g/cm3以下がより好ましい。真密度が1.54g/cm3以上であると電池に使用した場合、高温サイクル特性が劣り、1.44g/cm3未満では、電極密度が低下するため、電池の体積エネルギー密度の低下をもたらすので好ましくない。
本発明の炭素質材料の窒素吸着のBET法により求めた比表面積(以下「SSA」と記すことがある)は、限定されるものではないが、好ましくは13m2/g以下、より好ましくは12m2/g以下、更に好ましくは10m2/g以下である。SSAが13m2/gより大きい炭素質材料を用いると、得られる電池の不可逆容量が大きくなることがある。また、その比表面積はの下限は、好ましくは1m2/g以上、より好ましくは1.5m2/g以上、更に好ましくは、2m2/g以上である。SSAが1m2/g未満の炭素質材料を使用すると、電池の放電容量が小さくなることがある。
本発明の非水電解質二次電池負極用炭素質材料の製造方法は、平均粒径100μm以上の植物由来の有機物を原料とし、少なくとも(1)酸性溶液を用いて脱灰する工程(以下、「液相脱灰工程」と称することがある)、(2)脱灰された有機物を、酸化性ガス雰囲気下にて200~400℃で加熱する酸化処理工程(以下、「酸化処理工程」と称することがある)、及び(3)酸化処理後の前記有機物を300~1000℃で脱タールする工程(以下、「脱タール工程」と称することがある)を含む、炭素質材料の製造方法である。非水電解質二次電池負極用炭素質材料の製造方法は、好ましくは(4)脱灰した有機物、あるいは炭素化物(脱タール後の炭素化物、又は本焼成後の炭素化物)のいずれかを平均粒子径が2~50μmに粉砕する工程(以下、「粉砕工程」と称することがある)、及び/又は(5)非酸化性雰囲気下1000~1500℃で焼成する工程(以下、「焼成工程」と称することがある)を含む。従って、本発明の非水電解質二次電池負極用炭素質材料の製造方法は、液相脱灰工程(1)、酸化処理工程(2)及び脱タール工程(3)を含み、好ましくは粉砕工程(4)及び/又は焼成工程(5)を含む。
本発明に用いることのできる植物由来の有機物において、原料となる植物は、特に限定されるものではないが、例えば、コーヒー豆、ヤシ殻、茶葉、サトウキビ、果実(みかん、又はバナナ)、藁、広葉樹、針葉樹、竹、又は籾殻を挙げることができる。これらの植物由来の有機物を、単独で又は2種以上組み合わせて使用することができる。前記植物由来の有機物の中で、コーヒー豆から飲料コーヒー成分を抽出した抽出残渣はコーヒー成分を抽出する際に一部のミネラル分が抽出除去されており、中でも工業的に抽出処理されたコーヒー抽出残渣は適度に粉砕されており、且つ大量に入手可能であることから特に好ましい。
好気性腐敗が進んだコーヒー抽出残渣を用いると、得られた炭素質材料の真密度が低下することがある。炭素質材料の真密度が低下すると、電池に用いた場合に不可逆容量が大きくなることがあるので好ましくない。また炭素質材料の吸水性も高くなるため、大気暴露による劣化の度合いが大きくなる。
本発明の製造方法における脱灰工程は、基本的に植物由来の有機物を、脱タールの前に、pH3.0以下の酸性溶液中で処理する液相脱灰工程である。この液相脱灰によって、カリウム元素及びカルシウム元素などを効率よく除去することができ、特に酸を用いない場合と比較して、カルシウム元素を効率よく除去することができる。また、他のアルカリ金属、アルカリ土類金属、更には銅やニッケルなどの遷移金属を除去することが可能である。液相脱灰工程においては、植物由来の有機物を、0℃以上80℃以下のpH3.0以下の酸性溶液中で処理することが好ましい。0℃以上80℃以下で液相脱灰することによって得られた炭素質材料を用いた二次電池は、放電容量及び効率において特に優れている。
本発明の特定の実施態様である前記項目[5]及び項目[6]の製造方法においては、脱灰の方法としては、液相脱灰、気相脱灰などいずれの方法でも可能である。脱灰は、原料段階から炭素質材料とした後までのいずれの段階においても可能であるが、カリウム元素含有量およびカルシウム元素含有量を極力低下させるためには、原料となるコーヒー抽出残渣を、脱タールを実施する前に液相で脱灰することが好ましい。液相脱灰工程は、コーヒー抽出残渣を、脱タールの前に、水相中で処理することにより、カリウム元素などの金属元素含有量を効率よく低下させるものである。液相脱灰工程における水相の条件として、水の使用も可能であるが、pH3.0以下の酸性溶液中で処理することが好ましい。pH3.0以下の酸性溶液中での液相脱灰によって、カリウム元素及びカルシウム元素などを効率よく除去することができ、特に酸を用いない場合と比較して、カルシウム元素を効率よく除去することができる。また、他のアルカリ金属、アルカリ土類金属、更には銅やニッケルなどの遷移金属を効率よく除去することが可能である。
本発明に用いる植物由来の有機物は、500℃以上で熱処理されていないものが好ましいが、500℃以上で熱処理されて有機物の炭素化が進行している場合には、フッ化水素酸を用いることで十分に脱灰を行うことが可能である。例えば、コーヒー抽出残渣を700℃で脱タールした後、35%塩酸を用いて1時間液相脱灰を行い、その後3回水洗し、乾燥させた後に10μmに粉砕してから1250℃本焼成した場合、カリウムが409ppm、カルシウムが507ppm残存した。一方、8.8%塩酸+11.5%フッ化水素酸混合溶液を用いた場合、蛍光X線測定においてカリウムとカルシウムは検出限界以下(10ppm以下)であった。
なお、液相脱灰の前に、植物由来の有機物を適当な平均粒子径(好ましくは100~50000μm、より好ましくは100~10000μm、更に好ましくは100~5000μm)に粉砕することができる。この粉砕は、焼成後の平均粒子径を2~50μmになるように粉砕する粉砕工程(2)とは、異なるものである。
本発明の製造方法では、脱灰された有機物を、脱タールする前に、酸化性ガス雰囲気下にて200~400℃で加熱する酸化処理工程を必須とする。この酸化処理によって、得られる炭素質材料の結晶の秩序性を低くし、真密度が適度に低くなることによって、リチウムのドープ、脱ドープ時の膨張収縮を低減することができ、高温サイクル特性を改善することができる。また、液相脱灰し、脱タールした植物由来の有機物にさらに酸化処理を施してもよい。
本発明の製造方法においては、炭素源に対し脱タールを行い炭素質前駆体を形成する。また、炭素質前駆体を炭素質へ改質するための熱処理を、焼成という。焼成は一段階で行ってもよいし、低温及び高温の二段階で行うこともできる。この場合、低温における焼成を予備焼成と呼び、高温における焼成を本焼成と呼ぶ。なお、本明細書においては、炭素源から揮発分などを除去し炭素質前駆体を形成すること(脱タール)や炭素質前駆体を炭素質へ改質すること(焼成)を主目的としない場合を「非炭素化熱処理」といい、「脱タール」や「焼成」と区別する。非炭素化熱処理とは、例えば500℃未満の熱処理を意味する。より具体的には、200℃程度でのコーヒー豆の焙煎などが非炭素化熱処理に含まれる。前記のように、本発明に用いる植物由来の有機物は、500℃以上で熱処理されていないものが好ましいが、すなわち本発明に用いる植物由来の有機物は、非炭素化熱処理されてものを用いることができる。
本発明においては、脱タールを含酸素雰囲気中で行うことも可能である。含酸素雰囲気は限定されるものではなく、例えば空気を用いることができるが、酸素含有量が少ないほうが好ましい。従って、含酸素雰囲気中の酸素含有量は、好ましくは20容量%以下であり、より好ましくは15容量%以下であり、更に好ましくは10容量%以下であり、最も好ましくは5容量%以下である。なお、酸素含有量は、例えば1容量%以上であってよい。
賦活発生の有無は脱タール後に焼成工程(4)を経た炭素質材料の比表面積から推測が可能であり、賦活が生じた材料では比表面積が増大する。例えば、600℃で熱処理された植物由来の有機物(例えば、椰子殻チャー)を用いて、脱タール工程(3)を含酸素雰囲気中で行った場合、その後に焼成工程(4)を経た炭素質材料の比表面積は60m2/gであったが、500℃以上で熱処理されていない植物由来の有機物(例えば、コーヒー残渣)を用いて、脱タール工程(3)を含酸素雰囲気中で行った場合、焼成工程(4)を経た炭素質材料の比表面積は8m2/gであり、比表面積の増加が見られなかった。これは不活性ガス雰囲気下で脱タールを行った炭素質材料と同等の数値である。
本発明の製造方法における粉砕工程は、カリウム及びカルシウムを除去した有機物(脱灰した有機物)、酸化処理された有機物、あるいは炭素化物(脱タール後の炭素化物、又は本焼成後の炭素化物)を、焼成後の平均粒子径が2~50μmになるように粉砕する工程である。すなわち、粉砕工程によって、得られる炭素質材料の平均粒子径が2~50μmとなるように調製する。粉砕工程は、焼成後の平均粒子径が好ましくは1~8μm、より好ましくは2~8μmになるように粉砕する。すなわち、粉砕工程によって、得られる炭素質材料の平均粒子径が1~8μm、より好ましくは2~8μmとなるように調製する。なお、本明細書において「炭素質前駆体」又は「中間体」とは、脱タール工程を終えたものを意味する。すなわち、本明細書において「炭素質前駆体」及び「中間体」は、実質的に同じ意味で用いられ、粉砕されたもの及び粉砕されていないものを含む。
本発明の炭素質材料は、微粉が除去されているものが好ましい。微粉を除去することにより、二次電池の長期の耐久性を上昇させることができる。また、二次電池の不可逆容量を低下させることができる。
微粉を除去する方法としては、特に限定されるものではなく、例えば分級機能を備えたジェットミルなどの粉砕機を用いて、粉砕工程において、微粉を除去することができる。一方、分級機能を持たない粉砕機を用いる場合は、粉砕後に分級を行うことで微粉を除くことができる。更には粉砕の後、もしくは分級の後にサイクロンやバグフィルターを用いて微粉を回収することができる。
本発明の製造方法における焼成工程は、中間体を焼成して炭素質とする工程である。例えば、1000℃~1500℃で行われ、本発明の技術分野において、通常「本焼成」と呼ばれるものである。また、本発明の焼成工程においては、必要に応じて、本焼成の前に予備焼成を行うことができる。
本発明の製造方法においては、予備焼成を行うことができる。予備焼成は、炭素源を300℃以上1000℃未満、好ましくは300℃以上900℃未満で焼成することによって行う。予備焼成は、脱タール工程をへても残存する揮発分、例えばCO2、CO、CH4、及びH2などと、タール分とを除去し、本焼成において、それらの発生を軽減し、焼成器の負担を軽減することができる。すなわち、脱タール工程に加えて、更にCO2、CO、CH4、H2、又はタール分を予備焼成により除去してもよい。
本発明における焼成又は予備焼成は、ハロゲンガスを含有した非酸化性ガス中で行うことができる。用いるハロゲンガスとしては、塩素ガス、臭素ガス、ヨウ素ガス、又はフッ素ガスを挙げることができるが、塩素ガスが特に好ましい。更に、CCl4、Cl2F2のような高温で容易にハロゲンを放出する物質を、不活性ガスをキャリアとして供給することも可能である。
ハロゲンガス含有非酸化性ガスによる焼成又は予備焼成は、本焼成の温度(1000~1500℃)で行ってもよいが、本焼成よりも低い温度(例えば、300℃~1000℃)で行うこともできる。その温度域は好ましくは800~1400℃である。温度の下限としては800℃が好ましく、850℃が更に好ましい。上限としては1400℃が好ましく、1350℃が更に好ましく、1300℃が最も好ましい。
ハロゲンガス含有非酸化性ガスによる焼成又は予備焼成を行うことにより充放電容量が大きい非水電解質二次電池負極用炭素質材料が得られる理由は定かでないが、ハロゲンと炭素質材料中の水素原子とが反応し、炭素質材料から速やかに水素が除去された状態で炭素化が進むためと考えられる。またハロゲンガスは炭素質材料中に含まれる灰分とも反応し、残存灰分を低減させる効果もあると考えられる。なお、炭素質材料に含まれるハロゲン含有量が過小であると、その製造プロセスの過程で十分に水素が除去されず、結果的に充放電容量が十分に向上しないおそれがある一方、過大であると、残存するハロゲンが電池内でリチウムと反応し不可逆容量が増加するという問題があり得る。
本発明の中間体(炭素質前駆体)の製造方法は、平均粒子径が100μm以上である植物由来の有機物に対し、脱灰を行う工程(脱灰工程)と、前記脱灰をされた有機物を、酸化性ガス雰囲気下にて200~400℃で加熱する酸化処理工程、及び酸化処理後の前記有機物を300~1000℃で脱タールする工程(脱タール工程)とを含み、好ましくは前記脱灰された有機物を粉砕する工程(粉砕工程)を更に含むものである。更には、前記液相脱灰工程を、0℃以上80℃以下の温度で行うことが好ましい。
脱灰工程、酸化処理工程、脱タール工程、及び粉砕工程は、本発明の非水電解質二次電池負極用炭素質材料の製造方法における脱灰工程、脱タール工程、酸化処理工程、及び粉砕工程と同様である。本発明の中間体の製造方法においては、粉砕工程を液相脱灰工程の後、又は脱タール工程の後に行うことができる。なお、脱タール工程によって得られる中間体(炭素質前駆体)は、粉砕されていても、粉砕されていなくてもよい。
更に、本発明の製造方法特定の実施態様である前記項目[6]の製造方法においては、平均粒子径が100μm以上であるコーヒー豆由来の有機物を導入及び混合しながら、酸化性ガス雰囲気下にて200~400℃で加熱及び乾燥する酸化処理工程と、前記酸化処理されたコーヒー豆由来の有機物に対し、脱灰を行う工程(脱灰工程)と、前記脱灰されたコーヒー豆由来の有機物を300~1000℃で脱タールする工程(脱タール工程)と、を含む。
前記脱灰工程、酸化処理工程、脱タール工程、及び粉砕工程は、本発明の非水電解質二次電池負極用炭素質材料の製造方法における脱灰工程、酸化処理工程、脱タール工程、及び粉砕工程と同様である。
本発明の非水電解質二次電池負極は、本発明の非水電解質二次電池負極用炭素質材料を含むものである。
本発明の炭素質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、金属板など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。本発明の炭素質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、導電性のカーボンブラック、気相成長炭素繊維(VGCF)、ナノチューブ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0.5~10質量%(ここで、活物質(炭素質材料)量+バインダー量+導電助剤量=100質量%とする)であり、更に好ましくは0.5~7質量%、特に好ましくは0.5~5質量%である。
本発明の好ましい非水電解質二次電池負極に用いるバインダーとして水溶性高分子をあげることができる。本発明の非水電解質二次電池負極に水溶性高分子を用いることによって、暴露試験によって不可逆容量が低下しない非水電解質二次電池を得ることができる。また、サイクル特性の優れた非水電解質二次電池を得ることができる。
このような水溶性高分子としては、水に溶解するものであれば特に限定されることなく使用できる。具体例には、セルロース系化合物、ポリビニルアルコール、スターチ、ポリアクリルアミド、ポリ(メタ)アクリル酸、エチレン-アクリル酸共重合体、エチレン-アクリルアミド-アクリル酸共重合体、ポリエチレンイミン等及びそれらの誘導体又は塩が挙げられる。これらのなかでも、セルロース系化合物、ポリビニルアルコール、ポリ(メタ)アクリル酸及びそれらの誘導体が好ましい。また、カルボキシメチルセルロース(CMC)誘導体、ポリビニルアルコール誘導体、ポリアクリル酸塩を用いることが、更に好ましい。これらは、単独または2種類以上を組み合わせて使用することができる。
本発明の炭素質材料を用いた電極の製造におけるプレス圧は、特に限定されるものではない。しかしながら、好ましくは2.0~5.0tf/cm2であり、より好ましくは2.5~4.5tf/cm2であり、更に好ましくは3.0~4.0tf/cm2である。炭素質材料を塗工、乾燥した後に、前記のプレス圧をかけることで活物質同士の接触が良くなり導電性が向上する。従って、長期のサイクル耐久性に優れた電極を得ることができる。なお、プレス圧力が低すぎる場合は、活物質同士の接触が不十分となるため電極の抵抗が高くなり、クーロン効率が低下するため長期の耐久性に劣ることがある。また、プレス圧力が高すぎる場合は、圧延により電極が湾曲し、捲回が困難になることがある。
本発明の非水電解質二次電池は、本発明の非水電解質二次電池負極を含むものである。本発明の炭素質材料を使用した非水電解質二次電池用負極電極を用いた非水電解質二次電池は、優れた出力特性及び優れたサイクル特性を示す。
本発明の負極材料を用いて、非水電解質二次電池の負極電極を形成した場合、正極材料、セパレータ、及び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。
本発明の非水電解質二次電池は、好ましくは電解質に半経験的分子軌道法のAM1(Austin Model 1)計算法を使用して算出したLUMOの値が-1.10~1.11eVの範囲である添加剤を含むものである。本発明の炭素質材料及び添加剤を使用した非水電解質二次電池用負極電極を用いた非水電解質二次電池は、高いドープ、脱ドープ容量を有し、優れた高温サイクル特性を示す。
半経験的計算方法としては、仮定及びパラメータの種類によってAM1、PM3(Parametric method 3)、MNDO(Modified Neglect of Differential Overlap)、CNDO(Complete Neglect of Differential Overlap)、INDO(Intermediate Neglect of Differential Overlap)、MINDO(Modified Intermediate Neglect of Differential Overlap)などに分類される。AM1計算法は、1985年Dewerらが水素結合計算に適するようにMNDO法を部分的に改善して開発したものである。本発明におけるAM1法は、コンピュータプログラムパッケージGaussian03(Gaussian社)により提供されたものであるが、これに限定されるものではない。
以下に、Gaussian03を使用してLUMO値を計算する操作手順を示す。計算の前段階における分子構造のモデリングには描画プログラムGaussView3.0に搭載されている可視化機能を使用した。分子構造を作成し、ハミルトニアンにAM1法を用いて「基底状態」、電荷「0」、スピン「Singlet」、溶媒効果「なし」にて構造最適化を行った後、同じレベルでエネルギー一点計算を行った。構造最適化によって得られた全電子エネルギーの値が最も小さい構造を最安定構造とし、その分子構造における最低空軌道に対応する数値をLUMO値とした。結果は単位が原子単位で与えられるため、1a.u.=27.2114eVを用いて電子ボルトに換算した。
本発明の負極材料を用いて、非水電解質二次電池の負極電極を形成した場合、電解質に少なくともビニレンカーボネート又はフルオロエチレンカーボネートを含むこと以外に,正極電極、セパレータ、及び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。
本発明のリチウム二次電池は、例えば自動車などの車両に搭載される電池(典型的には車両駆動用リチウム二次電池)として好適である。
真密度は、JIS R 7212に定められた方法に従い、ブタノール法により測定した。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いれた後、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いれ、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に、取り出し、更に1-ブタノールを満たし、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。
ρHの測定は、島津製作所社製乾式自動密度計アキュピック1330を用いた。試料は予め200℃で5時間以上乾燥してから測定を行った。10cm3のセルを用い、試料を1g入れ、周囲温度は23℃で行った。パージ回数は5回とし、体積値が繰り返し測定で0.5%以内で一致することを確認したn=5の平均値をρHとした。
試料室の容積(VCELL)及び膨張室の容積(VEXP)は体積既知の校正球を使用して予め測定しておく。試料室に試料を入れ、系内をヘリウムで満たし、その時の系内圧力をPaとする。次にバルブを閉じ、試料室のみヘリウムガスを加え圧力P1まで増加させる。その後バルブを開け、膨張室と試料室を接続すると、膨張により系内圧力はP2まで減少する。
このとき試料の体積(VSAMP)は次式で計算する。
したがって、試料の質量をWSAMPとすると密度は
となる。
以下にBETの式から誘導された近似式を記す。
上記の近似式を用いて、液体窒素温度における、窒素吸着による1点法(相対圧力x=0.3)によりvmを求め、次式により試料の比表面積を計算した。
このとき、vmは試料表面に単分子層を形成するに必要な吸着量(cm3/g)、vは実測される吸着量(cm3/g)、xは相対圧力である。
JIS M8819に定められた方法に準拠し測定した。CHNアナライザーによる元素分析により得られる試料中の水素及び炭素の質量割合から、水素/炭素の原子数の比として求めた。
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線回折図形を得る。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値でピーク位置をもとめる方法)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する。CuKα線の波長を0.15418nmとし、以下に記すBraggの公式によりd(002)を算出する。
λ:X線の波長(CuKαm=0.15418nm),θ:回折角
試料に分散剤(界面活性剤SNウェット366(サンノプコ社製))を加え馴染ませる。次に純水を加えて、超音波により分散させた後、粒径分布測定器(島津製作所社製「SALD-3000S」)で、屈折率を2.0-0.1iとし、粒径0.5~3000μm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、平均粒子径Dv50とした。
カリウム元素含有率及びカルシウム含有率の測定のために、予め所定のカリウム元素及びカルシウム元素を含有する炭素試料を調製し、蛍光X線分析装置を用い、カリウムKα線の強度とカリウム含有量との関係、及びカルシウムKα線の強度とカルシウム含有量との関係に関する検量線を作成した。ついで試料について蛍光X線分析におけるカリウムKα線及びカルシウムKα線の強度を測定し、先に作成した検量線よりカリウム含有量及びカルシウム含有量を求めた。
抽出後のコーヒー残渣100gに対して1%塩酸300gを加え、100℃で1時間撹拌した後ろ過し、沸騰水300gを加えて水洗する洗浄操作を3回繰り返して脱灰処理し、脱灰コーヒー抽出残渣を得た。得られた脱灰コーヒー抽出残渣を窒素ガス雰囲気中で乾燥させたのち、700℃で脱タールして予備炭素化を行った。これをロッドミルを用いて粉砕し、炭素前駆体微粒子とした。次にこの炭素前駆体を1250℃で1時間本焼成し、平均粒子径10μmの参考炭素質材料1を得た。
酸による脱灰工程を行わなかった以外は、参考例1と同様にして参考炭素質材料2を得た。
抽出後のコーヒー残渣を窒素ガス雰囲気中で乾燥させたのち、700℃で脱タールして予備炭素化を行った。予備炭素化を行ったコーヒー残渣100gに対して1%塩酸300gを加え、100℃で1時間撹拌した後ろ過し、沸騰水300gを加えて水洗する洗浄操作を3回繰り返して脱灰処理し、脱灰コーヒー抽出残渣を得た。これをロッドミルを用いて粉砕し、炭素前駆体微粒子とした。次にこの炭素前駆体を1250℃で1時間本焼成し、平均粒子径10μmの参考炭素質材料3を得た。
抽出後のコーヒー残渣を窒素ガス雰囲気中で乾燥させたのち、700℃で脱タールして予備炭素化を行った。これをロッドミルを用いて粉砕し、微粉状とした。予備炭素化を行った微粉状のコーヒー残渣100gに対して1%塩酸300gを加え、100℃で1時間撹拌した後ろ過し、沸騰水300gを加えて水洗する洗浄操作を3回繰り返して脱灰処理し、脱灰コーヒー抽出残渣を得た。次にこの炭素前駆体を1250℃で1時間本焼成し、平均粒子径10μmの参考炭素質材料4を得た。
脱灰時に酸を用いず水洗のみ繰り返した以外は、参考例1と同様にして参考炭素質材料5を得た。
参考例1~5で得られた参考炭素質材料1~5を用いて、以下の(a)~(c)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。
上記炭素質材料90質量部、ポリフッ化ビニリデン(株式会社クレハ製「KF#1100」)10質量部に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になるように調製した。
本発明の炭素質材料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。
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0mVになるまで0.5mA/cm2で定電流充電を行い、端子電圧を0mVに達した後、端子電圧0mVで定電圧充電を行い電流値が20μAに達するまで充電を継続した。このとき、供給した電気量を電極の炭素質材料の質量で除した値を炭素質材料の単位質量当たりの充電容量(mAh/g)と定義した。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。このとき放電した電気量を電極の炭素質材料の質量で除した値を炭素質材料の単位質量当たりの放電容量(mAh/g)と定義する。不可逆容量は、充電容量-放電容量として計算される。同一試料を用いて作製した試験電池についてのn=3の測定値を平均して充放電容量及び不可逆容量を決定した。表3に電池特性を示す。
抽出後のコーヒー残渣2000g(含水率65%)に対して、35%塩酸(純正化学株式会社製 特級)171g、純水5830gを加え、pH0.5とした。液温20℃で1時間撹拌した後、ろ過し、酸処理コーヒー抽出残渣を得た。その後、酸処理コーヒー抽出残渣に、純水6000gを加え、1時間攪拌する水洗操作を3回繰り返して脱灰処理し、脱灰コーヒー抽出残渣を得た。
実施例1における酸化処理温度を260℃にした以外は、実施例1と同様にして炭素質材料2を得た。
実施例1における酸化処理温度を300℃にした以外は、実施例1と同様にして炭素質材料3を得た。
実施例1における酸化処理温度を350℃にした以外は、実施例1と同様にして炭素質材料4を得た。
実施例1における酸化処理温度を400℃にした以外は、実施例1と同様にして炭素質材料5を得た。
抽出後のコーヒー残渣2000g(含水率65%)に対して、35%塩酸(純正化学株式会社製 特級)171g、純水5830gを加え、液温20℃で1時間撹拌した後、ろ過し、酸処理コーヒー抽出残渣を得た。その後、酸処理コーヒー抽出残渣に、純水6000gを加え、1時間攪拌する水洗操作を3回繰り返して脱灰処理し、脱灰コーヒー抽出残渣を得た。
実施例1における酸化処理温度を190℃にした以外は、実施例1と同様にして比較炭素質材料2を得た。
実施例1における酸化処理温度を410℃にした以外は、実施例1と同様にして比較炭素質材料3を得た。
(a)電極作製
上記炭素質材料94質量部、ポリフッ化ビニリデン(株式会社クレハ製「KF#9100」)6質量部に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になるように調製した。
本発明の炭素質材料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。
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0mVになるまで0.5mA/cm2で定電流充電を行い、端子電圧を0mVに達した後、端子電圧0mVで定電圧充電を行い電流値が20μAに達するまで充電を継続した。このとき、供給した電気量を電極の炭素質材料の質量で除した値を炭素質材料の単位質量当たりの充電容量(mAh/g)と定義した。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。このとき放電した電気量を電極の炭素質材料の質量で除した値を炭素質材料の単位質量当たりの放電容量(mAh/g)と定義する。不可逆容量は、充電容量-放電容量として計算される。同一試料を用いて作製した試験電池についてのn=3の測定値を平均して充放電容量及び不可逆容量を決定した。
LiCoO2正極との組み合わせ電池における、50℃で150サイクル後の放電容量を、初回放電容量に対する%容量維持率として求めた。その詳細は以下のとおりである。
正極材料(活物質)としてLiCoO2(日本化学工業(株)製「セルシードC5-H」)を用い、この正極材料を94質量部、アセチレンブラック3質量部を、結着材ポリフッ化ビニリデン(株式会社クレハ製「KF#1300」)3質量部と混合し、N-メチル-2-ピロリドン(NMP)を加えてペースト状にし、厚さ20μmの帯状アルミニウム箔の片面に均一に塗布した。乾燥した後、得られたシート状電極を直径14mmの円板状に打ち抜き、これをプレスして正極とした。
負極(炭素極)は、前述した実施例または比較例で製造した負極材料各94質量部、ポリフッ化ビニリデン(株式会社クレハ製「KF#9100」)6質量部に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、得られたシート状電極を直径15mmの円板状に打ち抜き、これをプレスして負極とした。なお、電極中の負極材料(炭素質材料)の量は約10mgになるように調製した。
上記のようにして調製した正極と負極を用い、電解液としてはエチレンカーボネートとジメチルカーボネートとメチルエチルカーボネートを容量比で1:2:2で混合した混合溶媒に1.5mol/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。このような構成のリチウムイオン二次電池において、充放電試験を行った。
充電は定電流定電圧法により行った。充電条件は、充電上限電圧を4.2V、充電電流値を2C(すなわち30分間で充電するために必要な電流値)に設定し、4.2Vに到達後、一定電圧のまま電流を減衰させて、1/100Cの電流になった時点で充電終了とした。続いて逆方向に電流を流し放電を行った。放電は、2Cの電流値で行い2.75Vに達した時点で放電終了とした。このような充電および放電を50℃の恒温槽中で繰り返して行い、高温サイクル特性の評価を行った。
上記高温サイクル特性の評価において、150サイクル後の放電容量を、1サイクル目の放電容量で除し、150サイクル後放電容量保持率(%)とした。
粒経1mmの焙煎コーヒー豆の抽出後のコーヒー残渣100gに対して1%塩酸300gを加え、20℃で1時間撹拌した後ろ過し、20℃の水300gを加えて水洗する洗浄操作を3回繰り返して脱灰処理し、脱灰コーヒー抽出残渣を得た。
乾燥及び酸化を260℃でおこなった以外は、実施例6と同様にして炭素質材料7を得た。
乾燥及び酸化を300℃でおこなった以外は、実施例6と同様にして炭素質材料8を得た。
乾燥及び酸化をフィーダー付横型炉中、260℃でおこなった以外は、実施例6と同様にして炭素質材料9を得た。
縦型炉を用い、乾燥及び酸化をこの順で別々に行った以外は、実施例6と同様にして炭素質材料10を得た。酸化温度を設定温度に調節するに際、縦型炉中に水を導入して温度調節を行った。
実施例6~10で得られた炭素質材料6~10を用いて、前記活物質のドープ-脱ドープ試験の(a)~(c)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)測定セルの作成方法
上記炭素質材料94質量部、ポリフッ化ビニリデン(クレハ製KF#9100)6質量部に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、塗工電極を直径15mmの円板状に打ち抜き、これをプレスすることで負極電極を作製した。
充電は定電流定電圧により行う。充電条件は4.2Vになるまで一定の電流(2C)で充電を行い、その後、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(1/100)Cに達するまで充電を継続する。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。放電は電池電圧が2.75Vに達するまで一定の電流(2C)で行った。初めの3サイクルは25℃で行い、以降のサイクルは50℃の恒温槽内で行った。
抽出後のコーヒー残渣100gに対して1%塩酸300gを加え、20℃で1時間攪拌した後ろ過し、20℃の水300gを加えて水洗する洗浄操作を3回繰り返して脱灰処理し、脱灰コーヒー抽出残渣を得た。得られた脱灰コーヒー抽出残渣を窒素ガス雰囲気中150℃で乾燥させたのち、管状炉で窒素気流下、700℃で1時間脱タールして予備炭素化を行った。これをロッドミルを用いて粉砕した後、38μmの篩で篩分し、粗大粒子をカットして炭素前駆体微粒子とした。次にこの炭素前駆体を横型管状炉に入れ、窒素ガスを流しながら、1250℃で1時間保持して炭素化し、平均粒子径6.1μmの参考炭素質材料6を得た。
使用コーヒー残渣として、焙煎度の異なるブラジル豆(アラビカ種)を抽出したものを使用した以外は、参考炭素質材料6と同様にして、参考炭素質材料7を得た。
使用コーヒー残渣として、ベトナム豆(カネフォラ種)を抽出したものを使用した以外は、参考炭素質材料6と同様にして、参考炭素質材料8を得た。
抽出後のコーヒー残渣2000g(含水率65%)に対して、35%塩酸(純正化学株式会社製 特級)171g、純水5830gを加え、pH0.5とした。液温20℃で1時間攪拌した後、ろ過し、酸処理コーヒー抽出残渣を得た。その後、酸処理コーヒー抽出残渣に、純水6000gを加え、1時間攪拌する水洗操作を3回繰り返して脱灰処理し、脱灰コーヒー抽出残渣を得た。
平均粒子径を11μmにした以外は、参考例6と同様にして参考炭素質材料10を得た。
(参考例11)
本焼成温度を800℃とした以外は参考例6と同様にして、参考炭素質材料11を得た。
上記参考例6~11で得られた炭素質材料各94質量部、ポリフッ化ビニリデン(クレハ製KF#9100)6質量部に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、塗工電極を直径15mmの円板状に打ち抜き、これをプレスすることで負極電極を作製した。
はじめに2回充放電を繰り返してエージングを行う。エージングにおける電流値のCレートへの換算は、先に規定したコバルト酸リチウムの電気容量と質量から算出した。充電は定電流定電圧により行う。充電条件は4.2Vになるまで一定の電流0.2C(1時間で充電するために必要な電流値が1Cと定義される)で充電を行い、その後、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(1/100)Cに達するまで充電を継続する。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。放電は電池電圧が2.75Vに達するまで一定の電流0.2Cで行った。2回目の充放電は電流値をそれぞれ0.4Cとした。
本参考例においては、コーヒー豆残渣及びヤシガラを以下の方法で負極用炭素質材料粉末とする。植物由来の有機物を原料とする炭素質材料粉末は、以下の方法で作成する。
抽出後のブレンドコーヒー残渣100gに対して1%塩酸300gを加え、20℃で1時間攪拌した後ろ過した。次に20℃の水300gを加えて1時間攪拌した後ろ過する水洗操作を3回繰り返して脱灰処理し、脱灰コーヒー抽出残渣を得た。得られた脱灰コーヒー抽出残渣を窒素ガス雰囲気中で乾燥させたのち、700℃で脱タールして予備炭素化を行った。これをロッドミルを用いて粉砕し、炭素前駆体微粒子とした。次にこの炭素前駆体を1250℃で1時間本焼成し、平均粒子径10μmの参考炭素質材料12を得た。検討した炭素質材料の諸特性を、表10にそれぞれ示す。
使用コーヒー残渣として、浅煎りブラジル豆を抽出したものを使用した以外は、参考例12と同様にして、参考炭素質材料13を得た。得られた炭素質材料の諸特性を、表10に示す。
使用コーヒー残渣として、深煎りブラジル豆を抽出したものを使用した以外は参考例12と同様にして、参考炭素質材料14を得た。得られた炭素質材料の諸特性を、表10に示す。
(参考例15)
焼成温度を800℃とした以外は参考例12と同様にして、参考炭素質材料15を得た。得られた炭素質材料の諸特性を、表10にそれぞれ示す。
椰子殻チャーを窒素ガス雰囲気中(常圧)で600℃で1時間仮焼成した後、粉砕し、平均粒径19μmの粉末状炭素前駆体とした。次に、この粉末状炭素前駆体を、35%塩酸に1時間浸漬した後、沸騰した水で1時間洗浄する洗浄操作を2回繰り返して脱灰処理し、脱灰粉末状炭素前駆体を得た。得られた脱灰粉末状炭素前駆体10gを、横型管状炉中に置き、窒素雰囲気下、1200℃で1時間本焼成を行い、参考炭素質材料16を得た。得られた参考炭素質材料16の諸特性を表10に示す。
(a)電極作製
上記炭素質材料とバインダに溶媒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、これをプレスして参考例17~24の電極とした。表11に、用いた炭素質材料およびバインダ、配合比をそれぞれ示す。
SBR:スチレン・ブタジエン・ラバー
CMC:カルボキシメチルセルロース
PVA:ポリビニルアルコール
PAA:ポリアクリル酸塩
PVDF:ポリフッ化ビニリデン(株式会社クレハ製「KF#9100」)
上記構成のリチウム二次電池について、25℃、50%RH、空気中に1週間放置した。試験電池の作製と電池容量の測定は、暴露後の電極を試験極として用いた以外は暴露前の試験と同様に行った。
(負極電極の作製)
実施炭素1の電極合剤を厚み18μmの銅箔の片面上に均一に塗布し、これを120℃25分加熱・乾燥した。乾燥後、直径15mmの円盤状に打ち抜き、これをプレスすることで負極電極を作製した。なお円盤状負極電極が有する活物質の質量は10mgとなるように調整した。
(正極電極の作製)
コバルト酸リチウム(日本化学工業性「セルシードC-5」)94質量部、カーボンブラック3質量部、ポリフッ化ビニリデン(株式会社クレハ製KF#1300)3質量部、カーボンブラック3質量部にNMPを添加し、混合して正極用合剤を調製した。得られた合剤を厚さ50μmのアルミ箔上に均一に塗布した。乾燥した後、塗工電極を直径14mmの円盤状に打ち抜き、正極電極を作製した。なお、前述に記載の方法で測定した参考例17における活物質の単位質量あたりの充電容量の95%となるよう正極電極中のコバルト酸リチウムの量を調整した。コバルト酸リチウムの容量を150mAh/gとして計算した。
(活物質のドープ-脱ドープ試験)
(a)電極作製
前記各参考例で製造した負極材料を用いて、以下のようにして非水電解液二次電池を作成し、その特性を評価した。本発明の負極材料は非水電解質二次電池の負極として適しているが、電池活物質の放電容量及び不可逆容量を、対極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、前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。
上記正極及び負極を用い、電解液としてはエチレンカーボネートとジメチルカーボネートとメチルエチルカーボネートを容量比1:2:2で混合した混合溶媒に1.5mol/Lの割合でLiPF6を、1あるいは3wt%の割合で表5に示した添加剤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雰囲気のグローブボックス内で2016サイズのコイン型非水電解質リチウム二次電池を組み立てた。また、添加剤を用いない以外は同様のものを、比較電解質とし、参考例(表13)にて使用した。
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い、充放電は定電流定電圧法により行った。ここで、「充電」は試験電池では放電反応であるが、この場合は炭素質材料へのリチウム挿入反応であるので、便宜上「充電」と記述する。逆に「放電」とは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離反応であるため、便宜上「放電」と記述することにする。ここで採用した定電流定電圧法は、電池電圧が0Vになるまで一定の電流密度0.5mA/cm2で充電を行い、その後、電圧を0Vに保持するように(定電圧を保持しながら)電流値を連続的に変化させて電流値が20μAに達するまで充電を継続する。このとき供給した電気量を電極の炭素質材料の質量で除した値を炭素質材料の単位質量あたりの充電容量(ドープ容量)(mAh/g)と定義した。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。放電は電池電圧が1.5Vに達するまで一定の電流密度0.5mA/cm2で行い、このとき放電した電気量を電極の炭素質材料の質量で除した値を炭素質材料の単位質量あたりの放電容量(脱ドープ容量)(mAh/g)と定義する。不可逆容量(非脱ドープ容量)(mAh/g)は、充電量-放電量として計算され、効率(%)は(放電容量/充電容量)×100として算出される。同一試料を用いて作製した試験電池についてのn=3の測定値を平均して充放電容量及び不可逆容量を決定した。
(a)測定セルの作成方法
上記炭素質材料94質量部、ポリフッ化ビニリデン(クレハ製KF#9100)6質量部に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、塗工電極を直径15mmの円板状に打ち抜き、これをプレスすることで負極電極を作製した。
充電は定電流定電圧により行う。充電条件は4.2Vになるまで一定の電流(2C;1時間で充電するために必要な電流値が1Cと定義される)で充電を行い、その後、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(1/100)Cに達するまで充電を継続する。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。放電は電池電圧が2.75Vに達するまで一定の電流(2C)で行った。初めの3サイクルは25℃で行い、以降のサイクルは50℃の恒温槽内で行った。
サイクル特性の評価は、50℃の恒温槽に移した初めの充放電を1サイクル目として、150サイクル後の放電容量を1サイクル目の放電容量で除した値を放電容量維持率(%)として行った。
VC:ビニレンカーボネート(0.0155eV)
FEC:フルオロエチレンカーボネート(0.9829eV)
CIEC:クロロエチレンカーボネート(0.1056eV)
PC:プロピレンカーボネート(1.3132eV)
電解液とLUMO
EC:エチレンカーボネート(1.2417eV)
DMC:ジメチルカーボネート(1.1366eV)
EMC:エチルメチルカーボネート(1.1301eV)
[1]コーヒー抽出残渣又はその脱灰物を導入及び混合しながら、酸化性ガス雰囲気下にて乾燥を行う工程を含む酸化処理工程と、酸化処理物を脱タールする工程と、を含む非水電解質二次電池用炭素質材料製造用の中間体の製造方法、
[2]前記酸化性ガスの温度を200℃以上400℃以下に制御する[1]に記載の方法、
[3]前記コーヒー抽出残渣を、0℃以上100℃以下の温度でpHが3.0以下の酸性溶液を用いて脱灰する工程を更に含む[1]又は[2]に記載の方法、
[4]前記脱灰をされた原料組成物(コーヒー抽出残渣)を粉砕する工程を更に含む[3]に記載の方法、
[5][1]から[3]のいずれかに記載の方法で製造した前記中間体を、1000℃以上1500℃以下で焼成する工程と、前記中間体又はその被熱処理物(焼成物)を粉砕する工程と、を含む非水電解質二次電池負極用炭素質材料の製造方法、
[6][4]に記載の方法で製造した前記中間体を、1000℃以上1500℃以下で焼成する工程を含む非水電解質二次電池用炭素質材料の製造方法、
[7][5]又は[6]に記載の方法で製造される非水電解質二次電池用炭素質材料を含む非水電解質二次電池用負極電極、
[8][7]に記載の非水電解質二次電池用負極電極を備える非水電解質二次電池、又は
[9][8]に記載の非水電解質二次電池が搭載された車両、
を開示する。
Claims (18)
- 植物由来の有機物を炭素化して得られる炭素質材料であって、元素分析による水素原子と炭素原子との原子比(H/C)が0.1以下、平均粒子径Dv50が2μm以上50μm以下、粉末X線回折法により求めた002面の平均面間隔が0.365nm以上0.400nm以下、カリウム元素含有量が0.5質量%以下、カルシウム元素含有量が0.02質量%以下、ブタノールを用いたピクノメータ法により求めた真密度が1.44g/cm3以上1.54g/cm3未満である非水電解質二次電池負極用炭素質材料。
- 前記植物由来の有機物は、コーヒー豆由来の有機物を含む請求項1に記載の非水電解質二次電池負極用炭素質材料。
- 平均粒子径Dv50が2μm以上8μm以下である請求項1又は2に記載の非水電解質二次電池負極用炭素質材料。
- 平均粒子径が100μm以上である植物由来の有機物に対し、脱灰を行う工程と、
前記脱灰をされた有機物を、酸化性ガス雰囲気下にて200℃以上400℃以下で加熱する酸化処理工程と、
酸化処理後の前記有機物を300℃以上1000℃以下で脱タールする工程と、
を含む非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法。 - 平均粒子径が100μm以上であるコーヒー豆由来の有機物に対し、脱灰を行う工程と、
前記脱灰をされたコーヒー豆由来の有機物を導入及び混合しながら、酸化性ガス雰囲気下にて200℃以上400℃以下で加熱及び乾燥する酸化処理工程と、
前記酸化処理されたコーヒー豆由来の有機物を300℃以上1000℃以下で脱タールする工程と、
を含む、請求項4に記載の非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法。 - 平均粒子径が100μm以上であるコーヒー豆由来の有機物を導入及び混合しながら、酸化性ガス雰囲気下にて200℃以上400℃以下で加熱及び乾燥する酸化処理工程と、
前記酸化処理されたコーヒー豆由来の有機物に対し、脱灰を行う工程と、
前記脱灰されたコーヒー豆由来の有機物を300℃以上1000℃以下で脱タールする工程と、
を含む、非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法。 - 前記脱灰は、pHが3.0以下の酸性溶液を用いて行う請求項4から6のいずれか一項に記載の非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法。
- 前記脱灰工程を、0℃以上80℃以下の温度で行う、請求項4から7のいずれか一項に記載の非水電解質二次電池負極用炭素質材料製造用の中間体の製造方法。
- 前記脱灰をされた有機物を粉砕する工程を更に含む請求項4から8のいずれか一項に記載の方法。
- 請求項4から9のいずれか一項に記載の方法によって得られる中間体。
- 請求項4から8のいずれか一項に記載の方法で製造した前記中間体を、1000℃以上1500℃以下で焼成する工程と、
前記中間体又はその焼成物を粉砕する工程を含む非水電解質二次電池負極用炭素質材料の製造方法。 - 請求項9に記載の方法で製造した前記中間体を、1000℃以上1500℃以下で焼成する工程を含む非水電解質二次電池負極用炭素質材料の製造方法。
- 請求項11又は12に記載の製造方法によって得られる非水電解質二次電池負極用炭素質材料。
- 請求項1から3及び請求項13のいずれか一項に記載の非水電解質二次電池負極用炭素質材料を含む非水電解質二次電池用負極電極。
- 水溶性高分子を含む、請求項14に記載の非水電解質二次電池用負極電極。
- 請求項14又は15に記載の非水電解質二次電池用負極電極を備える非水電解質二次電池。
- 半経験的分子軌道法のAM1(Austin Model 1)計算法を使用して算出したLUMOの値が-1.10eV以上1.11eV以下の範囲である添加剤を含む電解液を含む請求項16に記載の非水電解質二次電池。
- 請求項16又は17に記載の非水電解質二次電池を搭載した車両。
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CN201380033933.4A CN104412426A (zh) | 2012-09-06 | 2013-08-30 | 非水电解质二次电池负极用碳质材料及其制造方法,以及使用所述碳质材料的负极及非水电解质二次电池 |
KR1020157001246A KR101700048B1 (ko) | 2012-09-06 | 2013-08-30 | 비수 전해질 2차 전지 음극용 탄소질 재료 및 이의 제조 방법 과 상기 탄소질 재료를 이용한 음극 및 비수 전해질 2차 전지 |
US14/420,412 US20150180020A1 (en) | 2012-09-06 | 2013-08-30 | Carbonaceous material for anode of nanaqueous electrolyte secondary battery, process for producing the same, and anode and nonaqueous electrolyte secondary battery obtained using the carbonaceous material |
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JPWO2018034155A1 (ja) * | 2016-08-16 | 2019-01-10 | 株式会社クラレ | 非水電解質二次電池の負極活物質用の炭素質材料、非水電解質二次電池用負極、非水電解質二次電池ならびに炭素質材料の製造方法 |
WO2018034155A1 (ja) * | 2016-08-16 | 2018-02-22 | 株式会社クラレ | 非水電解質二次電池の負極活物質用の炭素質材料、非水電解質二次電池用負極、非水電解質二次電池ならびに炭素質材料の製造方法 |
US11345601B2 (en) | 2016-08-16 | 2022-05-31 | Kuraray Co., Ltd. | Carbonaceous material for negative pole active substance of nonaqueous electrolyte secondary battery, negative pole for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery, and method for producing carbonaceous material |
WO2019009333A1 (ja) * | 2017-07-06 | 2019-01-10 | 株式会社クラレ | 非水電解質二次電池の負極活物質用の炭素質材料、非水電解質二次電池用負極、非水電解質二次電池ならびに炭素質材料の製造方法 |
WO2019009332A1 (ja) * | 2017-07-06 | 2019-01-10 | 株式会社クラレ | 非水電解質二次電池の負極活物質用の炭素質材料、非水電解質二次電池用負極、非水電解質二次電池ならびに炭素質材料の製造方法 |
US11492260B2 (en) | 2017-07-06 | 2022-11-08 | Kuraray Co., Ltd. | Carbonaceous material for negative electrode active material for non-aqueous electrolyte secondary batteries, non-aqueous electrolyte secondary battery negative electrode, non-aqueous electrolyte secondary battery, and production method of carbonaceous material |
US11637286B2 (en) | 2017-07-06 | 2023-04-25 | Kuraray Co., Ltd. | Carbonaceous material for negative electrode active material for non-aqueous electrolyte secondary batteries, non-aqueous electrolyte secondary battery negative electrode, non-aqueous electrolyte secondary battery, and production method of carbonaceous material |
WO2022059646A1 (ja) * | 2020-09-15 | 2022-03-24 | 株式会社クラレ | 蓄電デバイスの負極活物質に適した炭素質材料、蓄電デバイス用負極、蓄電デバイス |
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KR101700048B1 (ko) | 2017-01-26 |
US20150180020A1 (en) | 2015-06-25 |
KR20150030731A (ko) | 2015-03-20 |
TW201421787A (zh) | 2014-06-01 |
CN104412426A (zh) | 2015-03-11 |
TWI543431B (zh) | 2016-07-21 |
JPWO2014038492A1 (ja) | 2016-08-08 |
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