Classifications

• • 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
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/20—Graphite
  • C01B32/205—Preparation
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
  • C01B32/00—Carbon; Compounds thereof
  • C01B32/20—Graphite
  • C01B32/21—After-treatment
• • 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
• • 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
• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
  • H01M4/00—Electrodes
  • H01M4/02—Electrodes composed of, or comprising, active material
  • H01M4/36—Selection of substances as active materials, active masses, active liquids
  • H01M4/362—Composites
  • H01M4/366—Composites as layered products
• • C—CHEMISTRY; METALLURGY
  • C01—INORGANIC CHEMISTRY
  • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
  • C01P2004/00—Particle morphology
  • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
  • C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
  • C01P2004/84—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases one phase coated with the other
• • 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
• • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
  • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
  • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
  • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
  • Y02E60/10—Energy storage using batteries

Definitions

• the present invention relates to a lithium ion secondary battery having a large discharge capacity and a high initial charge / discharge efficiency, and a constituent material thereof. More specifically, the present invention relates to a composite graphite material comprising at least three types of graphite having different crystallinities and a method for producing the same, as well as a negative electrode material, a negative electrode, and a lithium ion secondary battery using the composite graphite material.
• Lithium-ion rechargeable batteries are attracting attention because they can be used at higher voltages than other rechargeable batteries and can increase the energy density.
• a lithium ion secondary battery has a negative electrode, a positive electrode, and a non-aqueous electrolyte as main components. Lithium ions generated from the nonaqueous electrolyte move between the negative electrode and the positive electrode during the discharging and charging processes, and become a secondary battery. '.
• Irreversible capacity Initial charge capacity-Initial discharge capacity.
• two layers are formed by using graphite of high crystallinity, which is advantageous for increasing the discharge capacity, as a nucleus, and covering the surface with graphite or carbon of low crystallinity, which is advantageous for improving the initial charge and discharge efficiency. Structured methods have been proposed. This is because low-crystalline carbon has a low discharge capacity but a low reactivity to the electrolyte.
• Carbon that can be converted to black tin by baking at around 3000 ° C (also referred to as “easy graphitization '! Raw carbon” in this application), such as raw coats, is converted to a gas phase in an oxidizing atmosphere. Is a liquid phase which is oxidized at about 300 ° C. and then graphitized (JP-A-10-326661, JP-A-10-218615).
• the above methods (1) and (4) have a problem in productivity because the production process is complicated and costly from the viewpoint of industrial production.
• it is difficult to control / control the thickness of the low-crystalline carbon on the surface so that powder characteristics such as specific surface area and bulk density, and battery characteristics such as discharge capacity and initial charge / discharge efficiency become unstable.
• the method (2) described above is that, when firing at about 100 ° C., the low-crystalline carbon in the surface layer is fused together, and when this is broken down, the low-crystalline carbon in the surface layer is reduced.
• it is exfoliated from graphite as a core, and powder characteristics such as specific surface area and bulk density, and battery characteristics such as initial charge / discharge efficiency are reduced.
• the nucleus graphite and the surface crystalline carbon have different expansion and contraction behaviors due to charge and discharge.
• Low-crystalline carbon may flake off and cause similar problems as above.
• the discharge capacity of a battery largely depends on the discharge capacity per volume of graphite constituting the negative electrode. Therefore, in order to increase the discharge capacity of the battery, it is advantageous to fill graphite with a large discharge capacity per unit weight (mAh / g) at a high density.
• the above-mentioned methods (1) and (2) tend to have insufficient adhesion between the graphite and the low-crystalline carbon of the catalyst layer. Then, the low-crystalline carbon film is peeled off from the graphite, the surface of the graphite having high reactivity with the electrolyte is exposed, and the initial charge / discharge efficiency may decrease.
• An object of the present invention is to obtain a lithium-ion secondary battery that has a trade-off performance when graphite is used as a negative electrode material of a lithium-ion secondary battery, that is, a large discharge capacity and a high initial charge / discharge efficiency.
• an object of the present invention is to provide a composite graphite material capable of satisfying both of these properties and a method for producing the same, and a negative electrode material, a negative electrode, and a lithium ion secondary battery using the composite graphite material.
• the present invention has a black bell B having a lower crystallinity than the graphite A outside the black I & A, and at least a part of an outer surface of the black bell B has a lower crystallinity than the graphite B.
• the composite graphite material preferably has a structure in which the graphite A is covered with the graphite bell B, and the graphite B is further covered with the graphite C. '
• any of the above composite graphite materials is a spherical or ellipsoidal granule.
• the plane spacing (d oo 2 ) of the carbon mesh layer is 0.3365 nm or less, and the size of the crystallite in the C-axis direction (L c ) Is 4
• the graphite A is flaky graphite.
• the graphite A has an interplanar (d 002 ) force of not more than SO.358 nm of the carbon netting layer.
• the graphite B has a plane spacing (d 002 ) of the carbon netting layer of 0.337 Onm or less. .
• the present invention also provides an invention of a negative electrode material for a lithium ion secondary battery containing any of the above composite graphite materials. Further, the present invention also provides an invention of a negative electrode for a lithium ion secondary battery containing any of the above composite graphite materials.
• the present invention also provides a lithium ion secondary battery having any one of the above-described negative electrodes.
• the invention also provides a method for producing a composite graphite material.
• the graphite is preferably flake graphite. Further, in any of the above production methods, it is preferable that the graphite has a plane interval (d oo 2 ) of the carbon netting layer of 0.3358 nm or less. .
• the graphitizable carbon is at least one selected from the group consisting of tar and pitch. Further, it is preferable that any of the above-mentioned production methods includes a step of granulating the graphite before the attaching step.
• the graphitizable carbon is made into a liquid state by at least one method selected from melting, dissolving and dispersing in the decocting and attaching step, and the method is used to attach the graphitizable carbon to the graphite. Is preferred.
• any of the above production methods it is preferable that in the primary firing step, 2.0% by mass or more and less than 20% by mass of the volatile component of the graphitizable carbon remain. Further, it is preferable that any of the above-mentioned production methods includes a step of disagglomerating aggregates of secondary aggregation or more after the primary firing step.
• FIG. 1 is a schematic diagram illustrating the structure of an evaluation battery used in Examples and Comparative Examples of the present invention. It is a formula sectional view.
• FIG. 2 (a) is a diagram illustrating an operation mechanism of a reforming treatment device for applying mechanical energy used in the present invention, and (b) is a schematic diagram illustrating a configuration of the device.
• FIG. 3 is a schematic view of a reforming treatment apparatus for applying another mechanical energy used in the present invention.
• FIG. 4 is a scanning electron micrograph of the composite graphite material produced according to Example 2. -Best mode for carrying out the invention
• the composite graphite material of the present invention has graphite B 'having a lower crystallinity than the graphite A on the outside of the graphite A, and at least a part of the outer surface of the graphite B has a higher crystallinity than the graphite B. It has a structure in which graphite C exists.
• the composite graphite material of the present invention has, as a primary structure, graphite B having a lower crystallinity than graphite A outside graphite A.
• the “outside of graphite A” here may be the entire outer surface of the black I0A or a part thereof. Therefore, the primary structure may be such that the graphite B wraps a plurality of the graphite A from the outside.
• the two graphites A may be surrounded by the graphite B in a dumbbell shape. In any of these cases, a portion of the graphite B may be omitted, or a portion of the graphite bell may be exposed without any loss.
• the embodiments of the primary structure are collectively illustrated below. '
• the graphite C constituting the composite graphite material of the present invention only needs to be present on at least a part of the outer surface of the graphite B having the primary structure. In particular, it is desirable that it be present on the entire outer surface of graphite B and be integrated with graphite B.
• graphite referred to in the present invention includes, in addition to graphite itself, a carbonaceous material that binds graphite to one another, and includes what is called “graphitic material” by those skilled in the art.
• graphite A has higher crystallinity than graphite B. Examples of graphite A include artificial graphite, natural graphite, expanded graphite, graphite carbon fiber, and graphite carbon black.
• mesophase calcined carbon (Balta mesophase), tartar and pitch as raw materials, sophase microspheres, coke (raw cotas, green coke, pitch coaters, needle coaters, petroleum coaters, etc.).
• carbonized graphite at around 300 ° C.
• those having high crystallinity are preferable from the viewpoint of obtaining a large discharge capacity, and natural black bell is more preferable.
• the crystallinity of black bells can be determined from the plane spacing ( d.02 ) of the carbon netting layer in X-ray wide-angle diffraction. That is,! ! ! !
• the crystallinity of graphite A is not particularly limited as long as it is relatively higher than graphite B, but preferably d. 02 is equal to or less than 0.33 5 8 im.
• Examples of the shape of the black bell A include those having various shapes such as a sphere, an ellipsoid, a scale, a block, a plate, a fiber, and a particle. Lumpy, processed graphite may be used. In particular, as the graphite A, scaly graphite is preferable. Among them, it is more preferable that a plurality of flaky black bells are aggregated or granulated to form a spherical or ellipsoidal shape.
• graphite A may be arranged in a spherical or ellipsoidal shape in the composite graphite material finally obtained, but a plurality of flaky graphites are granulated in advance to obtain a dense spherical or elliptical shape. It is more desirable to form graphite A in the form of a body.
• the densely granulated spherical or ellipsoidal graphite A preferably has a porosity of 50 volume% or less, more preferably 30 volume% or less. . If the porosity of the granulated material is 50% by volume or less, the amount of easily graphitizable carbon to be attached in the next step is suitable, and a sufficient discharge capacity is easily obtained. In addition, voids are less likely to remain inside the composite graphite material, and there is no danger that the composite graphite material will be broken and the initial charge / discharge efficiency will be reduced even when a negative electrode is manufactured at a high density.
• the particle diameter of graphite A is preferably an average particle in terms of volume.
• the diameter is 110 m, more preferably 2 to 30 / in.
• the ratio of graphite ⁇ to graphite ⁇ is preferably 50 to 100 parts by mass with respect to graphite B 100 parts by mass, more preferably 100 to 100 parts by mass graphite A. The ratio is 200 parts by mass.
• the graphite B of the present invention may be any graphite as long as it has lower crystallinity than graphite A. Examples of the graphite B include black IfH territories of easily graphitizable carbon. Graphitizable carbon is carbon that can be converted to graphite by firing at about 300 ° C.
• the composite graphite material of the present invention has a small outer surface of graphite B constituting the primary structure. At least in part, black age C with lower crystallinity than graphite B exists.
• This graphite C is, for example, converted to graphitizable carbon, which is a raw material of graphite B, after being subjected to a reforming treatment that imparts mechanical energy such as compression, shear, impact, and Z or friction. Thus, it can be manufactured or formed.
• the graphitizable carbon Since the graphitizable carbon has at least a part of its crystal structure disturbed by this modification treatment, the crystallinity of graphite C obtained by graphitization after that is lower than that of graphite B. Become.
• the graphite C constituting the composite material of the present invention can be formed on at least a part of the outer surface of the graphite B constituting the primary structure by such a method.
• graphite C obtained separately can be made to exist by means such as bonding or insertion. From the viewpoint of production efficiency, it is preferable to form the graphite C integrally with the surface of black rather than to manufacture graphite C separately.
• the composite graphite material of the present invention is not particularly limited, as long as it can produce a composite graphite material having the above-mentioned form.
• a part of the manufacturing method of the present invention will be described below as an example of a method for manufacturing such a composite graphite material.
• the manufacturing method of the present application is a step of adhering graphitizable carbon to the outside of graphite; a step of first firing the adhered body to such an extent that the graphitizable carbon is not substantially graphitized; Modifying the primary fired body by applying mechanical energy without substantially crushing it; and removing the modified body until the graphitizable carbon is substantially graphitized.
• This is a method for producing a composite graphite material having a structure in which a part exists.
• the method of the present invention it is referred to as “the method of the present invention”.
• the composite graphite material of the present invention having high crystallinity in the order of mA >> graphite c can be easily obtained.
• Graphite C is relatively less crystalline than graphite B.
• graphite bell C is formed by the above-mentioned manufacturing method, the boundary between graphite B and graphite C is not clear, so that the thickness of graphite C cannot be clearly defined, but the thickness of graphite C is 0.0. About 1 to 5 m is preferable.
• the crystallinity of graphite A, graphite B and graphite C be higher in the order of A>B> C.
• the crystallinity of the outer surface of the composite graphite material, ie, graphite C can be evaluated by Raman spectrum using an argon laser.
• the intensity ratio R is preferably R ⁇ 0.05. This is probably because the crystallization of the surface layer is moderately disturbed and the decomposition reaction of the electrolyte on the surface of the composite graphite material is suppressed. Further, R is preferably R ⁇ 0.30 from the viewpoint of minimizing a decrease in discharge capacity.
• the crystallinity of the entire composite graphite material can be evaluated as an average value by the X-ray wide-angle diffraction method in the same manner as described above. . Can be determined from the spacing of the carbon net plane layer (d. 02) Oyopi formation. Crystallites in the C-axis direction size. (L c). In other words, using Cu K ⁇ -rays as an X-ray source and high-purity silicon as a standard material 2) Measure the diffraction peak and calculate doo 2 and L c respectively from the peak position and its half width.
• the entire composite graphite material of the present invention preferably has d 002 of not more than 0.3365 nm and L c of not less than 40 nm. It is particularly preferred that d 002 is not more than 0.3362 nm and L c is not less than 50 nm. d. If 02 is 0.3365 nm or less, and if c is 40 nm or more, the average graphite structure of the composite graphite material is sufficiently developed, so the composite graphite material is used as a negative electrode material for a lithium ion secondary battery. When used, the doping amount of lithium increases, so that a large discharge capacity can be obtained.
• the average particle size of the composite graphite material of the present invention is appropriately selected depending on the application. When used as an electrode material, the average particle size may be adjusted according to the design thickness of the electrode, adjustment of battery characteristics, and the like. When the composite graphite material of the present invention is used as a negative electrode material of a lithium ion secondary battery, the average particle diameter is preferably 5 to 100 m, particularly preferably 5 to 30 ⁇ m. .
• the composite graphite material of the present invention + is preferably as spherical as possible and preferably shaped.
• a spherical or ellipsoidal composite graphite material is preferable as a negative electrode material for a lithium ion secondary battery because it has excellent electrolyte injectability and retention, and contributes to rapid discharge efficiency and improved cycle characteristics.
• flake graphite granules represented by natural graphite are used as graphite A, it is easy to make the composite graphite material into a nearly spherical shape.
• the average graphite ratio of the composite graphite material of the present invention is preferably 3 or less, and particularly preferably 2 or less.
• the bulk density is preferably at least 0.5 gZcm 3 , and particularly preferably at least 0.7 g, cm 3 . More preferably, it is 1.0 gZcm 3 or more.
• the specific surface area of the composite graphite material of the present invention depends on the characteristics of the lithium ion secondary battery and the negative electrode composite. It can be arbitrarily designed according to the properties of the agent paste. A surface area of less than 20 m 2 / g in terms of BE ratio is preferred from the viewpoint of safety of the lithium ion secondary battery. Generally, the BET specific surface area is preferably 0.3 to 5 m 2 Z g, and particularly preferably 3 m 2 / g or less. More preferably, it is not more than lm 2 Z g. The above-described production method invention of the present application will be described in more detail.
• easily curable carbon is attached to the outside of graphite. That is, one or more graphites may be interposed in the graphitizable carbon.
• This graphite corresponds to graphite A of the composite graphite material of the present invention. It is preferable that the graphite used has a carbon mesh layer having a plane spacing ( d.02 ) of 0.3358 nm or less.
• the graphitizable carbon is at least one selected from the group consisting of tar, pitch and mesophase.
• at least one of petroleum-based or coal-based heavy oils such as tar and pitch is used as a starting material, and a mesophase is generated in the next primary firing step.
• the graphitizable carbon is liquidized by at least one of at least two methods selected from melting, dissolving and dispersing, and is attached to the graphite.
• at least two methods selected from melting, dissolving and dispersing, and is attached to the graphite.
• a small amount of graphitizable carbon in a molten state may be added to graphite and granulated to adjust to a desired particle shape.
• the solution of the graphitizable carbon and the graphite may be mixed, and the solvent may be removed by a method such as heating, reduced pressure, or spray drying alone or in combination.
• the graphite-based charcoal, such as tar and pitch is dissolved in benzene, toluene, quinoline, medium tar oil, heavy tar oil, etc. to form a solution, and the graphite is immersed in the solution, heated, and decompressed. By doing so, the solvent is removed at the same time that the easily curable carbon is attached to the graphite.
• the obtained graphite to which the graphitizable carbon has adhered may not necessarily be uniform, and may have different volatile components between the center and the surface. No.
• the method further comprises a step of granulating the graphite before the attaching step.
• the composite graphite material of the present invention preferably has a spherical or ellipsoidal shape, graphite bells giving these shapes, that is, the graphite A is preferably a spherical or ellipsoidal one.
• the one formed by granulating a plurality of flaky graphite is more preferable.
• a method of granulating graphite a conventional method of granulating a plurality of flaky graphite by a dry method or a wet method can be applied.
• a binder component may be used.
• the binder component the above-mentioned easily graphitic carbon can also be used.
• the binder component may disappear in a subsequent secondary firing step. Further, even if a graphite structure is not formed by secondary firing, it can be used as long as the effects of the present invention are not impaired. '-'...
• tar or pitch is used as the easily graphitic carbon, it is preferable to further contain fine particles. By blending the fine particles, there is an advantage that fusion after primary firing can be suppressed, and even if fusion is performed, crushing becomes easy. If the fusion after the primary firing is suppressed, the outside of the graphite can be completely covered with graphitizable carbon, which contributes to further improvement of the initial charge and discharge efficiency of the finally obtained composite graphite material.
• the fine particles preferably have low adhesion to the lipophilic tar / pitch and the mesophase formed by primary baking of these. In the case of having adhesiveness, the effect of improving the crushability is small.
• the fine particles preferably have hydrophilicity.
• the fine particles may react with carbon during firing, or may remain in the composite graphite material finally obtained, but the fine particles and their reaction products It is desirable that it be vaporized and decomposed by the time of secondary firing and not remain in the composite graphite material.
• the preferred average particle size of the fine particles is 1 // m or less. If it is less than lm, it is not necessary to add a large amount of fine particles, and the battery performance such as discharge capacity will not be reduced.
• the amount of the fine particles is preferably in the range of 0.01 to 10% by mass, and particularly preferably in the range of 0.05 to 3% by mass, based on graphite B of the obtained composite graphite material.
• the content is 0.01% by mass or more, the effect of improving the crushability is increased, and when the content is 10% by mass or less, the specific surface area of the finally obtained composite graphite material becomes suitable, The diameter is also suitable, and the initial charge / discharge efficiency is unlikely to decrease.
• Fine particles satisfying the above preferred conditions include inorganic fine powders such as silica, alumina, and titanium oxide, metal oxides, carbonaceous particles such as oxidized carbon black, iron black, graphite, zinc yellow, yellow iron oxide, and the like.
• '' Pigments such as loess, titanium yellow, red iron, zinc red, zinc white, lead white, lead sulfate, lithobon, titania, antimony oxide, anolemina white, gloss white, satin white, plaster, kaolin clay, wax stone Clay, calcined clay, aluminum silicates such as hydrated aluminum silicate composites, calcium carbonates such as chalk, chalk, calcium-magnesium carbonates such as dolomite powder, magnesite powder, magnesium carbonates such as basic magnesium carbonate Calcium silicate such as wollastonite, hydrous calcium silicate synthetic , Magnesium silicate such as barrel click, My force, quartz powder, fine powder silicic acid, silicic acid such as diatomaceous earth, etc. resin beads are
• the above-mentioned particles may be used alone or in combination of two or more.
• inorganic fine powders such as silica, alumina, titanium oxide and the like, which do not react with graphitizable carbon and which are obtained by a gas phase method, are particularly suitable.
• the method of mixing the fine particles with the graphitizable carbon is not particularly limited, but a method of dispersing the fine particles in a medium, injecting the dispersion into a molten tar or pitch, and stirring + Is exemplified.
• the solvent the above-mentioned solvents can be used.
• the adhered body is fired to such an extent that the graphitizable carbon is not substantially graphitized.
• the degree to which substantially no graphite is present means a state in which the crystal structure can be disturbed in the subsequent reforming step, and a state in which the molecular structure has mobility.
• the polycondensation reaction of the graphitizable carbon slightly proceeds.
• This state can show a suitable range by the volatile content of the remaining graphitizable carbon.
• the volatile matter contained in the graphitizable carbon after the primary firing is preferably 2.0% by mass or more and less than 20% by mass. More preferably, it is from 4% by mass or more to less than 15% by mass.
• the volatile content is measured according to the following method in accordance with the fixed carbon method of JIS K 2425.
• Measuring method of volatile content of graphitizable carbon Sample (graphitizable carbon) Weigh lg into crucible and heat in electric furnace at 43.0 ° C for 30 minutes without lid I do. Then, it is made into a double crucible and heated at 800 ° C for 30 minutes to remove volatile components, and the weight loss rate is determined as volatile components.
• the easy black H dangling carbon after primary firing by another index is a solid having a softening point (Mettler method) of about 360 ° C or more, and a quinoline insoluble matter (QI) of more than 50% by mass. To less than 100% by mass, and more preferably from 80% by mass to 99.5% by mass. '
• Q.I is measured by the following filtration method in accordance with JIS K 2425. .
• QI measurement method Dissolve powdered carbon material (easily graphitizable carbon) in quinoline, heat at 7 ⁇ 5 ° C for 30 minutes, and then filter by suction while hot. The residue is washed with quinoline and acetate in this order until the respective filtrates become visually colorless, then dried and weighed to give QI (Quinoline insoluble). Diatomaceous earth is used as a filter aid. As the filter, a bottle-type filter 1 G4 specified in JIS'R3503 is used.
• Graphitizable carbon with high volatile content or low QI shows meltability when graphitized by secondary firing.
• Such an easily graphitic dangling carbon has a shape during the secondary firing. It may change or cause fusion of the materials. Therefore, when the volatile content is less than 20% by mass even after the primary firing, the crystal structure of the surface layer is likely to be disordered by the reforming process that imparts mechanical energy, and the graphite is also graphitized in the subsequent secondary firing. Ease ,.
• the easily graphitizable carbon used in the present invention suppress the volatile content within the preferred range by primary firing.
• graphitizable carbon with low volatile content or high QI does not exhibit the above-mentioned melting properties.
• the volatile content is 2.0% by mass or more, it is easy to apply mechanical energy to disturb the crystal structure of the outer surface of the easily-curable carbon, and after the secondary firing, It is suitable for forming low crystalline graphite C. Therefore, in the present invention, it is preferable that the volatile matter of the graphitizable carbon be adjusted to 2.0% by mass or more and less than 20% by mass by primary firing. ⁇
• the next baking may be performed under reduced pressure, normal pressure or pressurization.
• the temperature for the primary firing is usually in the range of 3.0.0 to 1200 ° C., preferably 350 to 600 ° C.
• the atmosphere is non-oxidizing. Desirably, heat treatment may be performed in a slightly acidic atmosphere.
• the primary baking may be performed in a plurality of times. The baking time is not particularly limited, but may be 0.5. It is about 100 hours.
• the shape of the fired product after the subsequent firing is not particularly limited, and may be any of granules, scales, spheres, needles, and fibrous shapes, but is preferably spherical or ellipsoidal. -If the product is slightly fused by the subsequent firing, the fused product can be crushed using various known mills. '' As the crushing method, for example, various types of sales powder roller, such as roller type, impact type, friction type, compression type, stone mill type, moving body collision type, eddy current type, air flow type, shearing type and vibration type Can be used.
• the primary fired body obtained by the primary firing described above is subjected to the modification treatment by applying mechanical energy without substantially pulverizing the primary fired body. ⁇
• graphite B having relatively low crystallinity is provided outside graphite A having high crystallinity, and at least a part of the outer surface of graphite B has a relatively lower graphite B.
• a composite graphite material having a structure in which crystalline graphite C is present can be obtained.
• the primary fired body be disagglomerated (disagglomerated) to be adjusted to a shape close to a final product, and then mechanical energy be applied.
• mechanical energy it is possible to apply mechanical energy continuously at the same time as unsealing the fused material composed of multiple lead and graphitizable carbon.
• the mechanical energy referred to in the present invention means various kinds of stress such as compression, shear, collision, and friction.
• the mechanical energy is preferably applied to the outer surface of the primary fired graphitizable carbon. This operation is also commonly referred to as mechanochemical treatment, and the applied mechanical energy is usually greater than the force applied by ordinary agitation.
• the primary fired body at least the graphite particles (ie, graphite A) constituting the primary fired body, is not substantially destroyed. Excessive destruction tends to lower the initial charge and discharge efficiency. Specifically, it is preferable to suppress the rate of decrease in the average particle diameter of the primary fired body due to the application of mechanical energy to 20% or less.
• the reforming treatment may be any device that can apply mechanical energy to the outer surface of the primary fired body, and the structure and type are not particularly limited.
• a device for applying mechanical energy include a kneader such as a pressure kneader and a two-roll machine, a rotating pole mill, a hybridization system (manufactured by Nara Machinery Co., Ltd.), Mekano Micros (Nara Machinery Co., Ltd.) and Mechanofusion System (Hosoka Micron Co., Ltd.) can be used. a kneader such as a pressure kneader and a two-roll machine, a rotating pole mill, a hybridization system (manufactured by Nara Machinery Co., Ltd.), Mekano Micros (Nara Machinery Co., Ltd.) and Mechanofusion System (Hosoka Micron Co., Ltd.) can be used. '
• a device that simultaneously applies a shearing force and a compressive force by utilizing a difference in rotational speed is preferable.
• a mechanofusion system manufactured by Hosoka Micron Co., Ltd. whose schematic structure is shown in FIGS. 2 (a) and 2 (b), is preferable. That is, as shown in FIG. 2 (b), the rotating drum 11, an internal member (inner piece) 12 having a different rotating speed from the rotating drum 11, a circulation mechanism 14 for the primary fired body 13 and a discharge It can be performed using a device ft having the mechanism 15.
• FIG. 2 (a) while applying centrifugal force to the primary fired body 13 supplied between the rotating drum 11 and the internal member 12, 1 Due to speed difference from 1
• the reforming treatment can be performed by simultaneously and repeatedly applying the compressive force and the shearing force.
• a hybridization system manufactured by Nara Machinery Co., Ltd. whose schematic structure is shown in FIG. 3, can also be used. That is, a device having a fixed drum 21, a rotor 22 rotating at a high speed, a circulation mechanism 24 and a discharge mechanism 25 of the “” next-baked body 23, a blade 26, a stator 27, and a jacket 28 is provided.
• the primary fired body 23 is supplied between the fixed drum 21 and the rotor 22, and the compression force and the shearing force caused by the speed difference between the fixed drum 21 and the rotor 22 are used for the primary fired body 23.
• the reforming treatment may be performed using a device added to the above.
• the conditions for the reforming treatment vary depending on the equipment used, and cannot be generally specified. However, it is preferable to set such that the rate of decrease in the average particle size of the composite graphite material due to the treatment is suppressed to 20% or less.
• the peripheral speed difference between the rotating drum and the inner part is 5 to 50 mZ s, and the distance between the two is 1 to: L 0 It is preferably performed under the conditions of 0 mm and a processing time of 5 to 60 minutes. '
• the primary fired body subjected to the modification treatment (also referred to as a modified body in the present application) is subjected to secondary treatment until the graphitizable carbon contained therein is substantially graphitized. Bake. .
• the secondary sintering temperature is not particularly limited, but may be used to increase the degree of graphite sintering. The higher the value, the better.
• the temperature is preferably higher than 1500 ° C., more preferably 250 ° C. or higher.
• the upper limit is about 330 ° C., preferably 280 to 320 ° C., from the viewpoint of heat resistance of the apparatus and prevention of sublimation of graphite. Heat to such a high temperature for 0.5 to 50 hours, preferably 2 to 20 hours.
• the graphite material of the present invention can be obtained.
• this is used as the negative electrode material, a lithium ion secondary battery having a large discharge capacity can be obtained.
• the secondary firing of the present invention no fusion or fusion deformation between solids occurs. For this reason, if the composite is provided in a desired product shape, it is not necessary to newly form the desired shape after the secondary firing, and the process is simplified. Further, since the low-crystallized surface generated by the modification step ′ can be maintained, the effects of the present invention can be further achieved.
• the disintegration after the primary firing may be any step as long as it is after the primary firing. For example, even after secondary firing. It is preferable that at least the graphite that becomes graphite A is not powdered, and that the secondary aggregate that exceeds the particle diameter of the desired composite black material is broken down. ⁇ ''
• the obtained composite graphite material preferably has a nucleus composed of highly crystalline graphite A and a coating layer composed of graphite B having relatively low crystallinity.
• Graphite C which is less volatile, is present. Since both graphite A and graphite B are graphitic, the interface between them is firmly adhered. In particular, when graphite B covers a plurality of granules of graphite A, the adhesion between graphite A and graphite B is extremely high due to the anchor effect.
• graphite C is formed by modifying a part of graphite B, and is in one piece. Therefore, graphite A, graphite B, and graphite C are hardly exfoliated, and can achieve both a large capacity derived from graphite A and a high initial charge / discharge efficiency derived from graphite C. It is extremely useful as a negative electrode material for pumion secondary batteries.
• the R value of the composite lead material of the present invention shows a small value as compared with the R value of the prior art. Although this mechanism is not clear, it is a phenomenon that can be achieved by a new technique of applying mechanical energy only to the outer surface of easily graphitizable carbon and then performing graphite.
• the present application also provides a negative electrode material containing any of the composite graphite materials described above.
• the composite graphite material of the present invention can be diverted to applications other than the negative electrode, for example, conductive materials for fuel cell separators and graphite for refractories, taking advantage of its characteristics. It is suitable as a negative electrode material.
• the negative electrode material of the present invention is required to contain at least the above-described composite graphite material. Therefore, the composite graphite material of the present invention is also a negative electrode material of the present invention.
• the composite graphite material of the present invention and a binder were mixed together.Anode mixture> A paste of a negative electrode obtained by further adding a solvent. And the like are also within the scope of the negative electrode material of the present invention.
• & material of the present invention as a negative electrode material, and a lithium ion secondary battery will be described.
• the present application also provides an invention of a negative electrode for a lithium ion secondary battery having any of the negative electrode materials of the present invention '.
• the negative electrode of the present invention is obtained by solidifying or shaping the above-described negative electrode material of the present invention.
• the negative electrode can be formed according to a normal molding method. However, the performance of the graphitized material can be sufficiently extracted, the shape of the powder can be high, and the negative electrode can be chemically and electrochemically stable.
• the method is not limited as long as the method can obtain the following.
• a negative electrode mixture obtained by adding a binder to a composite graphite material. You. It is desirable to use a binder having chemical stability and electrochemical stability with respect to the electrolyte and the electrolyte solvent.
• fluororesins such as polyvinylidene fluoride and polytetrafluoroethylene, polyethylene, polyvinyl alcohol, styrene butadiene rubber, and carboxymethyl cellulose are used. These can be used in combination.
• the binder in an amount of about 1 to 20% by mass based on the whole amount of the negative electrode mixture.
• the negative electrode mixture layer is prepared by mixing a composite graphite material adjusted to an appropriate particle size by classification or the like with a binder to prepare a negative electrode mixture. It can be formed by applying to one or both surfaces of a current collector. At this time, an ordinary solvent can be used, and the negative electrode mixture is dispersed in the solvent to form a paste, and then applied to the current collector and dried, so that the negative electrode mixture layer is uniformly and firmly collected. A negative electrode attached to the body can be obtained.
• the paste can be prepared by stirring with various mixers. .
• the composite graphite material of the present invention and a fluororesin powder such as polytetrafluoroethylene may be mixed and kneaded in a solvent such as isopropyl alcohol, and then applied to form a negative electrode mixture layer.
• a solvent such as isopropyl alcohol
• the composite graphite material of the present invention and a fluorine-containing resin powder such as polyvinylidene fluoride or a water-soluble binder such as carboxymethyl cellulose are mixed with a solvent such as ⁇ -methylpyrrolidone, dimethylformamide or water or alcohol. After mixing to form a slurry, the mixture may be applied to form a negative electrode mixture layer.
• the thickness of the negative electrode mixture comprising the mixture of the composite graphite material and the binder of the present invention when applied to the current collector is preferably 10 to 300 ⁇ .
• pressure bonding such as press pressure can further increase the adhesive strength between the negative electrode mixture layer and the current collector.
• the shape of the current collector used for the negative electrode is not particularly limited, but may be a foil shape, a mesh, or a mesh such as a kissed metal. And the like are used.
• the current collector include copper, stainless steel, and nickel.
• the thickness of the current collector is preferably about 520 m in the case of a foil.
• the present invention further provides a lithium ion secondary battery using any one of the above-described negative electrodes.
• Lithium-ion secondary battery is usually composed of a negative electrode, a positive electrode, and a non-aqueous electrolyte.
• Each of the positive electrode and the negative electrode serves as a lithium ion carrier. This is a battery mechanism in which lithium ions are doped into the negative electrode during charging and dedoped from the negative electrode during discharging.
• the lithium ion secondary battery of the present invention is not particularly limited except that a negative electrode obtained from a negative electrode material containing the composite graphite material of the present invention is used.
• Other components are the same as those of a general lithium ion secondary battery element.
• the material of the positive electrode (positive electrode active material) it is preferable to select a material capable of doping / dedoping a sufficient amount of lithium.
• a positive electrode active material include a composite chalcogenide of lithium and a transition metal, in particular, a composite oxide of lithium and a transition metal.
• the composite oxide of lithium and a transition metal may be a solid solution of lithium and two or more transition metals.
• L i M (1) M (2) 3 ⁇ 4 0 2 where X is a numerical value in the range of 0 ⁇ X ⁇ 1, and M (1) M (2) is at least one type of transition metal.
• L i M (1) M (2) 0 4 where Y is a number in the range of 0 ⁇ Y ⁇ 1 and ⁇ (1) ⁇ (2) is at least one transition metal element Consists of).
• examples of the transition metal element represented by ⁇ include CoNi, Mn, CrTi, VFeZnAl, In, Sn and the like.
• the above-mentioned lithium-containing transition metal oxide is prepared, for example, by using Li, an oxide or a salt of a transition metal as a starting material, mixing these starting materials according to the composition, and mixing the starting material in an atmosphere containing oxygen at 600 ° C. It can be obtained by firing in a temperature range of up to 100 ° C.
• the starting material is not limited to acids or salts, and can be synthesized from a hydroxide or the like.
• the positive electrode active material may be used alone or in combination of two or more kinds”.
• a carbonate such as lithium carbonate can be added to the positive electrode.
• a positive electrode mixture consisting of the positive electrode material, a binder, and a conductive agent for imparting conductivity to the electrode is applied to both surfaces of the current collector.
• a positive electrode mixture layer is formed.
• the binder any of those exemplified for the production of the negative electrode can be used.
• the conductive agent for example, a carbon material, graphite, and carbon black are used.
• the shape of the current collector is not particularly limited, and a foil shape or a mesh shape such as mesh, mesh, and expanded metal is used.
• examples of the current collector include an aluminum foil, a stainless steel foil, and a nickel foil.
• the thickness is preferably from 10 to 40 / zm. ''
• the positive electrode mixture is dispersed in a solvent to form a paste, and the paste-like positive electrode mixture is applied to a current collector and dried to form a positive electrode.
• a mixture layer may be formed, and after the positive electrode mixture layer is formed, press-fitting such as pressing may be further performed. Thereby, the positive electrode mixture layer is uniformly and firmly adhered to the current collector.
• an organic electrolyte composed of a solvent and an electrolyte salt, a polymer electrolyte composed of a polymer and an electrolyte salt, and the like can be used as the electrolyte used in the present invention.
• the electrolytic Shitsushio for example L i PF S s L i BF 4, L i A s F 6, L i C 1 Q 4 , L i B (Ce H 5 ), L i C 1, L i B r, L i CF 3 SOs, L i CH 3 S0 3, L i N (CF 3 S0 2) 2, L i C (CFs SO 2 ) 3 , L i N (C, F CH 2 OSO 2 ) 2 , L i N (CFs CF 2 0S0 2 ) 2 , L i N (HCF 2 CF 2 CH 2 0S0 2 ) 2 , L i N (( CFs) 2 CHOS0 2 ) 2 , L i B
• L i A 1 and C can be used as L i S i F e.
• Li PFe and Li BF 4 are preferably used from the viewpoint of oxidation stability.
• the concentration of the electrolyte salt in the organic electrolyte is preferably from 0.1 to 5 mol / liter, more preferably from 0.5 to 3.0 mol / liter.
• Solvents for organic electrolytes include ethylene carbonate, propylene carbonate, dimethyl / recarbonate, ethynolecarbonate, ethy / lemethinorecarbonate, 1,1,1- or 1,2-dimethoxetane, 1, 2-diethoxytan, tetrahydrofuran, 2-methyltetrahydrofuran, ⁇ , butyrolataton, 1,3-dioxolan, 4-methyl-1,3-dioxolan, aniso-nore, jetinoreetenore, snoreholane, methylsulfolane Acetonitrile, chloronitrile, propionitol-tolyl, trimethyl borate, tetramethyl silicate, nitromethane, dimethylformamide, methionolepyrrolidone, ethyl acetate, trimethyl orthoformate, nitrobenzene, benzoyl chloride, benzoyl bromide
• a non-aqueous electrolyte When a non-aqueous electrolyte is used as a polymer electrolyte, it contains a matrix polymer gelled with a plasticizer (non-aqueous electrolyte).
• the matrix polymer may be an ether-based polymer such as polyethylene oxide or a crosslinked product thereof.
• Molecules, fluoropolymers such as polymethacrylate, polyacrylate, polyvinylidenefluoride / vinylidenefluoride hexafluoropropylene copolymers, etc. can be used alone or in combination. .
• a fluorine-containing polymer such as polyvinylidene fluoride or • vinylidene fluoride-> xafluoropropylene copolymer from the viewpoint of acid reduction stability.
• electrolyte salt and the solvent constituting the plasticizer contained in the polymer electrolyte any of those described above can be used.
• 0.1-5 mol Z liter is preferred, and 0.5-'2.0 mol Z liter is more preferred.
• the method for producing such a polymer electrolyte is not particularly limited, and examples thereof include a method of mixing a polymer compound forming a matrix, a lithium salt and a solvent, and heating and melting the mixture. Further, a method in which a polymer compound, a lithium salt and a solvent are dissolved in an appropriate organic solvent for mixing, and then the organic solvent for mixing is evaporated. In addition, a method of mixing a monomer, a lithium salt and a solvent, and irradiating the mixture with ultraviolet light, an electron beam, or a molecular beam to form a polymer can be used.
• the proportion of the solvent added in the polymer electrolyte is preferably 10 to 9 p% by mass, more preferably 30 to 80% by mass.
• the content is 10 to 90% by mass, the conductivity is high, the mechanical strength is high, and the film is formed. .
• a separator may be used. .
• the separator is not particularly limited.
• woven fabric, non-woven fabric, synthetic resin microporous membrane and the like can be mentioned.
• a synthetic resin microporous membrane is preferably used.
• a polyolefin-based microporous film is preferable in terms of thickness, film strength, and film resistance.
• 'It is a microporous membrane that combines these.
• a polymer electrolyte can be used because of its high initial charge / discharge efficiency.
• a lithium-ion secondary battery using a polymer electrolyte is generally called a polymer battery.
• a negative electrode containing the composite graphite material of the present invention can be composed of a polymer electrolyte.
• it is configured by laminating a negative electrode, a polymer monoelectrolyte, and a positive electrode in this order, and housing the battery in a battery exterior material.
• a polymer electrolyte may be further provided outside the negative electrode and the positive electrode.
• propylene carbonate can be contained in the polymer electrolyte.
• propylene carbonate has a strong electrolysis reaction with graphite, but has a low decomposition reactivity with the composite graphite material of the present invention.
• the structure of the lithium ion secondary battery according to the present invention is arbitrary, and its shape and form are not particularly limited. It can be arbitrarily selected from cylindrical type, square type, coin type, button type, etc.
• a structure in which the battery is sealed in a laminate film may be used.
• a button-type secondary battery for evaluation having the structure shown in FIG. 1 was prepared and evaluated.
• an actual battery can be manufactured according to a known method based on the concept of the present invention.
• the working electrode was expressed as the negative electrode
• the counter electrode was expressed as the positive electrode.
• the above-mentioned negative electrode mixture paste was applied on a copper foil (current collector) in a uniform thickness, further ripened in vacuum at 90 ° C to evaporate the solvent, and dried.
• the negative electrode mixture applied on the copper foil is pressed by a roller press, and the copper foil t is punched together with the copper foil into a circular shape having a diameter of 15.5 m.
• a negative electrode 2 composed of a negative electrode mixture layer closely adhered to b was produced.
• a lithium metal foil is pressed against a nickel net and punched out into a cylindrical shape having a diameter of 15.5 mm.
• a current collector 7 a made of a nickel net and a positive electrode 4 made of a lithium metal foil adhered to the current collector 4 a was manufactured. ⁇
• LiPF 6 was dissolved in a mixed solvent of 33 vol% of ethylene carbonate and 67 vol% of ethyl methyl carbonate at a concentration of 1 mol / dm 3 to prepare a non-aqueous electrolyte.
• the obtained non-aqueous electrolyte was impregnated into a porous polypropylene body to produce a separator 5 impregnated with the electrolyte.
• a potane type secondary battery having the structure shown in FIG. 1 was produced as an evaluation battery.
• a separator 5 impregnated with an electrolyte solution is laminated between the negative electrode 2 adhered to the current collector 7b and the positive electrode 4 adhered to the current collector 7a.
• the outer cup 1 and the outer can 3 are combined so that the negative electrode current collector 7 b is accommodated in the outer can 1 and the positive electrode current collector 7 a is accommodated in the outer can 3.
• an insulating gasket 6 was interposed between the outer edges of the outer cup 1 and the outer can 3. No.
• the following charge / discharge test was performed on the evaluation battery manufactured as described above at a temperature of 25 ° C.
• the following charge / discharge test was conducted at a temperature of 25 ° C for the evaluation battery manufactured as described above. ⁇ Charge / discharge test>
• Constant current charging is performed with a current value of 0.9 mA until the circuit voltage reaches OmV. Next, switch to constant voltage charging when the circuit voltage reaches O mV, and continue charging until the current value reaches 20 ⁇ . After that, it was paused for 120 minutes.
• Table 2 shows the measured battery characteristics such as the measured discharge capacity (mA / g) and initial charge / discharge efficiency (g) per 1 g of the composite graphite material powder.
• the lithium ion secondary battery using the composite graphite material of the present invention for + negative S shows a large discharge capacity and high initial charge / discharge efficiency.
• constant current discharging was performed at a current value of 18 mA until the circuit voltage reached 2.5 V.
• the rapid discharge efficiency was evaluated from the discharge capacity in the first cycle and the discharge capacity in the second cycle according to the following equation.
• Rapid discharge efficiency (%) ; ⁇ ⁇ ": ⁇ X 100
• Coal tar pitch containing about 40% by mass of volatile matter KP-QL, manufactured by Kawasaki Steel Co., Ltd.
• KP-QL Melted 80 parts by mass of natural graphite (BF5A, manufactured by Chuetsu Graphite Industry Co., Ltd., average) (Particle size 5 ⁇ ) 50 parts by mass was added and kneaded using a heating kneader.
• the softening point (Mettler method) of the graphitizable carbon portion obtained by primary firing the coal tar pitch was 445 ° C.
• the obtained primary fired product contained 50 parts by weight of the primary fired coal tar pitch and 50 parts by weight of natural graphite.
• This primary fired body was crushed by an eddy-type mill, and was prepared into massive particles having an average particle diameter of 20 m.
• the agglomerate particles were introduced into a reformer (Mechanofusion, System, manufactured by Hosokawa Micron Co., Ltd.), whose structure is shown in Fig. 2 (a) and (b), to impart mechanical energy.
• a reformer Mechanism offusion, System, manufactured by Hosokawa Micron Co., Ltd.
• Fig. 2 (a) and (b) to impart mechanical energy.
• compressive force and shear force were repeatedly applied under the conditions of a rotating drum of 20 m / s, a processing time of 10 minutes, and a distance of 5 mm between the rotating drum and internal members.
• the average particle size of the primary fired product after the modification treatment was 19 m.
• the modified primary fired body was placed in a graphite crucible, and the surroundings of the crucible were filled with coke please and secondary fired at 300 ° C. for 5 hours to obtain a composite graphite material. No fusion or deformation was observed in the obtained composite graphite material, and the particle shape was maintained.
• an evaluation battery was manufactured using the obtained composite graphite material, and the battery characteristics were evaluated. Table 2 shows the measured values of discharge capacity (mAh / g), initial charge / discharge efficiency (%), rapid discharge efficiency (%), and cycle characteristics (%) per 1 g of the composite graphite particles measured for crystallinity.
• Example 2 Shown in ⁇ ⁇ ⁇ As shown in Table 2, the composite graphite material obtained in Example 1 (Example of the present invention) has a larger discharge capacity than the material of Comparative Example 1 which does not contain natural black and is not subjected to a modification treatment. And the initial charge / discharge efficiency is remarkably high. In addition, it has better initial charge / discharge efficiency, rapid discharge efficiency, and cycle characteristics than Comparative Example 2 which contains natural graphite but is not modified. It was confirmed that the surface of the composite graphite material of Example 1 was reduced in crystallinity by the modification treatment. (Example 2).
• Natural graphite (HG30A, manufactured by Chuetsu Graphite Industry Co., Ltd., average particle size 30 ⁇ ) was granulated to obtain a dense spherical or ellipsoidal graphite granule.
• the graphite granules have an average particle size of
• the cross section of the obtained graphite granules was polished, and the porosity (area ratio) in the particles was measured using a scanning electron microscope. As a result, it was about 15% by volume.
• the adhered material was primarily fired at 450 ° C. for 20 hours under an inert gas flow.
• the fired body was in a state where the easily graphitizable carbon on the surface of the graphite granule was slightly fused to each other.
• the primary fired body was crushed by an impact type powder.
• the primary fired body obtained by crushing had an average particle diameter of 22 ⁇ and an aspect ratio of 1.7.
• the primary fired body was charged into a reforming treatment apparatus (Mechano Fusion System, manufactured by Hosokawa Micron Co., Ltd.) shown in FIGS. 2 (a) and 2 (b), and mechanical energy was applied. That is, a compressive force and a shear force were repeatedly applied under the conditions of a rotating drum of 2 Oms, a processing time of 30 minutes, and a distance of 5 mm between the rotating drum and the internal member.
• the average particle size of the primary fired product after the modification treatment was 22 ⁇ m, and the aspect ratio was 1.7, and there was no change in the average particle size and the aspect ratio before and after the modification.
• the obtained modified treated body was filled in a graphite crucible, and the periphery of the crucible was filled with coke blaze and heated at 3000 ° C. for 5 hours to be graphitized to obtain a composite graphite material. No fusion or deformation was observed in the composite graphite material, and the particle shape was maintained.
• the average particle size of the composite graphite material was 22 / im, the aspect ratio was 1.7, the specific surface area was 0.5 m 2 g, and the bulk density was 1.02 gZcm 3 .
• Figure 4 shows a scanning electron microscope photograph of the manufactured and manufactured composite graphite material.
• Example 2 In 100 parts by mass of the coal tar pitch solution used in Example 2, an anhydrous silica fine powder ("AE ROSIL 300", manufactured by Nippon Aerosil Co., Ltd., average particle diameter of 7) obtained in advance by a gas phase method was used. nm) was added, and the mixture was subjected to primary baking to change the volatile content of graphitizable carbon. The other conditions were the same as in Example 2 to produce a composite graphite material. In the crushing process after the primary firing, the load on the crusher was reduced and crushing was easy. Various evaluations were performed on the obtained composite graphite material. Table 2 shows the results of the crystal cell characteristics. '
• the evaluation battery using the composite graphite materials of Examples 2-5 showed large discharge capacity close to the theoretical capacity of graphite (3 7 2 mA h / / g), and high initial It has the initial charge power efficiency.
• the initial charge / discharge efficiency of Examples 3 to 5 in which anhydrous silica fine powder obtained by a gas phase method was added to easily graphitizable carbon was added to easily graphitizable carbon. This is considered to be an effect of facilitating unframing of the fused graphitizable carbon, thereby suppressing the exfoliation of the graphitizable carbon film.
• it has excellent rapid discharge efficiency and cycle characteristics. In particular, it has excellent rapid discharge efficiency and cycle characteristics even when the electrode density is set high. .,
• the black materials were fused to each other after the secondary firing, and could not maintain the shape at the time of the crushing performed after the primary firing. Therefore, the fused graphite material was crushed to a certain degree to adjust the average particle size to ⁇ 19 ⁇ , and then a battery for evaluation was fabricated using it.
• Table 2 shows the results of evaluating the characteristics of the crystalline semiconductor battery.
• Comparative Example 1 which is a graphite material that does not contain natural graphite and that has not been modified, are extremely small.
• Example 2 A graphite material was produced in the same manner as in Example 1 except that the modification treatment in Example 1 was omitted.
• the graphite materials were slightly fused to each other by the secondary firing, and could not retain the shape at the time of crushing performed after the primary firing. Therefore, the fused graphite material was disintegrated again to adjust the average particle diameter to 19 ⁇ m, and then used to make a battery for evaluation.
• Table 2 shows the results of evaluating the crystallinity and battery characteristics.
• a graphite material was manufactured in the same manner as in Example 1 except that the secondary firing temperature in Example 1 was changed to 130 ° C.
• the obtained graphite material corresponds to a conventional product, and natural graphite is included in the non-graphitic material. In addition, little fusion was observed in the obtained material, and the crushed shape was maintained. Using this, a battery for evaluation was produced in the same manner as in Example 1. Table 2 shows the results of evaluating the crystallinity and battery characteristics.
• An evaluation battery was prepared using natural graphite (BF10A, manufactured by Chuetsu Graphite Industry Co., Ltd., average particle size: 1 ⁇ ) as it was.
• the method of Example 1 was applied to the production of the evaluation battery and the evaluation of the battery characteristics.
• Table 2 shows the characteristics of the crystalline semiconductor battery. --As shown in Table 2, in the case of Comparative Example 5 using natural graphite alone, the discharge capacity was large, but the initial charge / discharge efficiency, rapid discharge efficiency, and cycle characteristics were low. When the electrode density is increased, these characteristics are significantly reduced.
• a graphite material was produced in the same manner as in Example 2 except that the modification treatment in Example 2 was omitted.
• Table 2 shows the results of evaluating the crystallinity and battery characteristics.
• Comparative Example 6 is a graphite material manufactured without any modification treatment. Note that the R value of Example 2 is larger than that of Comparative Example 6, which indicates that the surface of the graphite material is selectively crystallized to be low.
• the composite graphite material of the present invention is suitable as a negative electrode or a negative electrode material.
• a lithium ion secondary battery using this as the negative electrode can achieve both high initial charge / discharge efficiency and large discharge capacity, which were difficult to achieve in the past.
• the composite graphite material can be manufactured with high productivity while suppressing fusion or the like at the time of graphitization. Therefore, the composite graphite material of the present invention can satisfy the recent demand for higher density of battery energy.
• the device equipped with the negative electrode material, the negative electrode and the lithium secondary battery of the present invention can be reduced in size and improved in performance, and can contribute to society widely.

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