WO2012137770A1 - 改質天然黒鉛粒子 - Google Patents
改質天然黒鉛粒子 Download PDFInfo
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- WO2012137770A1 WO2012137770A1 PCT/JP2012/059059 JP2012059059W WO2012137770A1 WO 2012137770 A1 WO2012137770 A1 WO 2012137770A1 JP 2012059059 W JP2012059059 W JP 2012059059W WO 2012137770 A1 WO2012137770 A1 WO 2012137770A1
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- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/74—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by peak-intensities or a ratio thereof only
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/10—Solid density
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/11—Powder tap density
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/19—Oil-absorption capacity, e.g. DBP values
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/90—Other properties not specified above
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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
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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
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Definitions
- the present invention relates to modified natural graphite particles useful as a negative electrode active material in a negative electrode plate of a non-aqueous electrolyte secondary battery, particularly a lithium ion secondary battery.
- a negative electrode plate of a nonaqueous electrolyte secondary battery typified by a lithium ion secondary battery includes applying a negative electrode mixture formed by mixing at least a negative electrode active material and a binder to a current collector and then compacting the mixture. Manufactured by the method.
- the current collector is often a foil made of copper or a copper alloy.
- the negative electrode active material a material that can occlude cations such as lithium ions during charging is used, and a typical material includes a graphite material that has a layered crystal structure and can occlude cations between layers.
- Graphite materials are roughly classified into natural graphite and artificial graphite. In general, natural graphite is less expensive than artificial graphite.
- natural graphite natural graphite with a high aspect ratio due to its flat shape has a high degree of graphitization that represents crystallinity, and therefore has a high charge / discharge capacity as a negative electrode active material (hereinafter simply referred to as “capacity”). Is expected to be obtained.
- natural graphite with such a high aspect ratio has the problems that the shape is anisotropic, so that it is oriented when applied to a current collector, the initial irreversible capacity is large, and the packing density is low. Have. For this reason, natural graphite having a high aspect ratio is not used as an active material as it is, but is usually used after a shape adjustment treatment.
- Patent Document 1 and Non-Patent Document 1 disclose a method of making a particle shape into a disk shape using Mechano-Fusion (registered trademark) as a method for adjusting the shape of graphite particles.
- Patent Document 2 discloses a method of making a particle shape spherical using a jet mill.
- Patent Documents 3 and 4 disclose a method of making a particle shape spherical using a pin mill.
- the binder which is another essential component of the negative electrode mixture, serves to bond the negative electrode active materials to each other or between the negative electrode active material and the current collector. It is desirable that the utilization efficiency of the binder is high as long as the adhesiveness can be secured. In particular, in recent years, there has been a demand for higher electrode density (increased capacity per unit volume of the negative electrode mixture), so that the negative electrode active materials or between the negative electrode active material and the current collector are not involved. In order to minimize the amount of the binder existing between the graphite particles and inhibiting the densification of the electrodes, there is a tendency to reduce the amount of binder used as a whole.
- JP 2007-169160 A Japanese Patent Laid-Open No. 11-263612 Japanese Patent Laid-Open No. 2003-238135 JP 2008-24588 A
- the negative electrode mixture used for the production of the negative electrode plate of the nonaqueous electrolyte secondary battery simply reducing the amount of binder used decreases the bonding strength between the negative electrode active materials or between the negative electrode active material and the current collector, and the negative electrode plate
- the negative electrode mixture falls off from the current collector or the negative electrode plate.
- the production or assembly speed is increased, the bending force or tensile force applied to the negative electrode mixture layer or the negative electrode plate formed on the current collector tends to increase. The phenomenon tends to occur.
- the loss of the negative electrode mixture not only causes a decrease in product quality, but also a significant decrease in productivity such as a decrease in yield and line stoppage. While non-aqueous electrolyte secondary batteries are being developed not only for consumer use but also for automobile use and power storage use, cost reduction by improving productivity is an important issue.
- This invention makes it a subject to provide the natural graphite material which can solve said problem and can bring about the negative electrode plate excellent in adhesive strength.
- the present invention completed based on the above findings is defined by the following equation, which has a circularity of 0.92 or more and is obtained by measurement of a CK edge X-ray absorption spectrum using synchrotron radiation as an excitation light source.
- the circularity is expressed by the following formula, and the upper limit is 1.
- (Circularity) (Perimeter of a circle having the same area as the projected shape) / (Perimeter of the projected shape)
- the “projection shape” is a shape obtained by projecting particles to be measured on a two-dimensional plane.
- the circumference of a circle having the same area as the projection shape and the circumference of the projection shape are images of the projection shape. It is calculated by processing.
- the modified natural graphite particles according to the present invention satisfy at least one of the following conditions (a) to (c): (a) the true specific gravity is 2.25 g / cm 3 or more; (b) The tap density is 1.0 g / cm 3 or more and 1.4 g / cm 3 or less; (c) linseed oil absorption is less than 20 cm 3/100 g or more 50 cm 3/100 g.
- the present invention also provides carbon-attached graphite particles comprising the modified natural graphite particles and a carbonaceous material attached to at least a part of the surface thereof. Since the modified natural graphite particles according to the present invention have a sufficiently smooth surface, a negative electrode having sufficient adhesive strength between the negative electrode mixture and the current collector even if the amount of binder used is suppressed A board is obtained. Such a negative electrode plate has high quality and high productivity. Therefore, the nonaqueous electrolyte secondary battery including the negative electrode plate using the modified natural graphite particles according to the present invention is high in quality and high in productivity.
- FIG. 3A is a diagram showing a CK edge NEXAFS spectrum when radiated light is incident on carbon at different incident angles (0 °, 30 °, and 60 °), and FIG. In the case of a certain HOPG (Highly Oriented Pyrolytic Graphite), FIG. 3B shows a case where the carbon is an amorphous carbon deposition film (film thickness: 10 nm).
- HOPG Highly Oriented Pyrolytic Graphite
- FIG. 5 (A) is an explanatory view conceptually showing a process in which natural graphite is granulated by spheronization in the production of modified natural graphite particles according to the present invention
- FIG. 5 (B) is spheroidized.
- An SEM observation image of the spheroidized graphite in the middle of the processing is shown
- FIG. 5C shows an optical microscope observation image of the cross section of the spheroidized graphite in the middle of the spheroidizing processing.
- grains after a spheroidization process is shown.
- grains based on this invention obtained by performing the smoothing process after a spheronization process is shown.
- Natural graphite particles as a raw material of the modified natural graphite particles according to the present invention are scaly graphite (specifically, scaly graphite or scaly graphite described below). Thus, it has not been subjected to modification treatment or heat treatment.
- the modified natural graphite particles according to the present invention can be produced, for example, by subjecting the natural graphite particles to a shape adjustment treatment described later.
- Natural graphite is classified according to its appearance and properties into flake graphite, flake graphite (also known as bulk graphite), and amorphous graphite.
- Scaly graphite and scaly graphite show nearly perfect crystals, and earthy graphite has lower crystallinity than them.
- the quality of natural graphite is determined by the main production areas and veins. Scaly graphite is produced in Madagascar, China, Brazil, Ukraine, Canada, Vietnam, Australia, etc. Scaly graphite is mainly produced in Sri Lanka. Soil graphite is produced in the Korean peninsula, China, Mexico, etc.
- the modified natural graphite particles according to the present invention are required to have a high capacity, scaly graphite and scaly graphite having high crystallinity are suitable as the raw material graphite.
- a true specific gravity is mentioned as a scale for evaluating the crystallinity of the graphite particles, and the raw graphite preferably has a true specific gravity of 2.25 g / cm 3 or more. Since the true specific gravity hardly changes in the mechanical modification treatment, it is preferable that the obtained modified natural graphite particles have a true specific gravity of 2.25 g / cm 3 or more.
- the shape and size of the raw graphite are not particularly limited. Moreover, you may comprise raw material graphite by mixing 2 or more types of graphites with different origins and types.
- the particle shape is evaluated by using circularity as an index of sphericity. The degree of circularity is obtained by the following equation regarding the projection shape.
- Circularity (perimeter of a circle having the same area as the projected shape) / (perimeter of the projected shape) If the projected shape is a perfect circle, the circularity is 1. Therefore, the maximum value of circularity is 1. When the degree of circularity is 1, the degree of sphere when the particle is evaluated three-dimensionally is considered to be particularly high. Therefore, the higher the degree of circularity (closer to 1), the higher the degree of sphericity of the particle. I can say that.
- the projected shape can be obtained from an observation image obtained using an optical microscope, a scanning electron microscope, or the like.
- the circularity of the raw graphite is usually around 0.85 and rarely exceeds 0.90.
- the raw material graphite may have such a low circularity, and the circularity of the raw material graphite is not particularly specified.
- modified natural graphite particles having a circularity of 0.92 or more are obtained after the modification treatment.
- the “average particle diameter” is used as the median diameter in the volume-based particle size distribution obtained by the light scattering diffraction method.
- This particle size distribution can be measured, for example, with a laser diffraction / scattering particle size distribution meter (LA-910) manufactured by Horiba, Ltd.
- the raw material graphite preferably has an average particle size of 5 mm or less, particularly preferably 200 ⁇ m or less.
- the average particle size of the raw graphite is preferably 3 ⁇ m or more, and particularly preferably 5 ⁇ m or more.
- modified natural graphite particles have a circularity of 0.92 or more, and the incident angle dependence S 60/0 of the peak intensity ratio in the CK edge X-ray absorption spectrum (for details) (Described later) is 0.5 or more and 0.7 or less.
- the modified natural graphite particles according to the present invention have a circularity of 0.92 or more. When the circularity is less than 0.92, the graphite particles have a flat shape with a large aspect ratio, and problems such as orientation during coating and a decrease in capacity as a battery are likely to occur.
- the upper limit of the circularity is 1.0 when the particle shape is a true sphere, that is, 1.0.
- the circularity is preferably 0.93 or more.
- the modified natural graphite particles according to the present invention have the following formula when measuring the CK-edge X-ray absorption spectrum of a powder using synchrotron radiation as an excitation light source.
- the incident angle dependence S 60/0 of the peak intensity ratio defined by is 0.5 or more and 0.7 or less.
- B 60 From the C-1s level to the ⁇ * level (that is, the antibonding orbital of sp3 bond: ⁇ C in the CK edge X-ray absorption spectrum of the particle measured with the incident angle of the emitted light being 60 ° Absorption peak intensity attributed to the transition to -C-).
- a 0 Absorption peak intensity attributed to the transition from the C-1s level to the ⁇ * level in the CK edge X-ray absorption spectrum of the particle, measured with the incident angle of the emitted light being 0 °.
- B 0 Absorption peak intensity attributed to the transition from the C-1s level to the ⁇ * level in the CK edge X-ray absorption spectrum of the particle measured with the incident angle of the emitted light being 0 °.
- the CK edge X-ray absorption spectrum used in the present invention is also called a CK edge NEXAFS (Near Edge X-ray Absorbance Fine Structure) spectrum, and the core level of an occupied carbon atom ( An absorption spectrum observed when electrons (K-shell inner electrons) existing in the (1s orbit) absorb energy of the irradiated X-rays and are excited to various vacant levels in an unoccupied state. is there.
- FIG. 1 The measurement principle of this X-ray absorption spectroscopy is shown in FIG. 1 in comparison with X-ray photoelectron spectroscopy (XPS).
- XPS X-ray photoelectron spectroscopy
- an energy variable light source in the soft X-ray region (280 eV to 320 eV) is necessary. Since S 60/0 is based on the premise that the linear polarization of the excitation light source is high, the CK edge NEXAFS spectrum according to the present invention uses emitted light as the excitation light source.
- the vacant levels at which electrons in the core level are excited include the ⁇ * level attributed to the antibonding orbitals of sp2 bonds that reflect the crystallinity (basal plane, orientation, etc.) in natural graphite, and crystals ⁇ * level attributed to antibonding orbitals of sp3 bonds that reflect disorder of properties (edge surface, non-orientation, etc.), or antibonding orbitals such as CH bonds and CO bonds There are empty levels.
- the surface is a plane of a hexagonal network surface (AB surface described later) is a basal surface, and a surface on which the end of the hexagonal network appears. Is the edge surface. On the edge surface, carbon often takes sp3 bonds.
- the CK edge NEXAFS spectrum reflects the local structure in the vicinity of the carbon atom including the excited inner electrons, and in addition, the escape depth of electrons emitted from the solid into the vacuum by the irradiated light. Since the thickness is about 10 nm, only the measured surface structure of the graphite particles is reflected. Therefore, by using the CK edge NEXAFS spectrum, the crystalline state (orientation) of graphite existing on the surface of the modified natural graphite particles can be measured, thereby evaluating the roughness of the graphite surface. it can.
- the method for fixing the modified natural graphite particles to be measured to the sample stage is not particularly limited. It is preferable to adopt a method such as supporting on the copper substrate with In (indium) foil or supporting on the copper substrate with carbon tape so that an excessive load is not applied to the graphite particles and the surface properties thereof are not changed. .
- the sample is irradiated with radiation light having a fixed incident angle with respect to the sample. Then, while scanning the energy of radiated light from 280 eV to 320 eV, the total electron yield method is used to measure the sample current flowing into the sample in order to complement the photoelectrons emitted from the sample.
- the basic configuration of this measurement method is shown in FIG.
- 3 (A) and 3 (B) are diagrams showing CK edge NEXAFS spectra when radiated light is incident on carbon at different incident angles (0 °, 30 °, and 60 °), respectively.
- 3A shows the case where carbon is a single crystal HOPG (highly oriented pyrolytic graphite)
- FIG. 3B shows the case where carbon is an amorphous carbon vapor deposition film (film thickness: 10 nm). Show.
- HOPG which is a single crystal
- the absorption peak intensity attributed to the transition from the C-1s level to the ⁇ * level when the incident angle is increased from 0 ° to 60 °.
- the profile of the HOPG CK edge NEXAFS spectrum varies greatly depending on the incident angle.
- the profile of the CK edge NEXAFS spectrum of the amorphous carbon vapor deposition film shown in FIG. 3B hardly depends on the incident angle, and the profile does not change even when the incident angle changes. Almost no change.
- the graphite crystals existing in the vicinity of the surface of the material are regularly arranged, that is, when the orientation is high and, on the contrary, the ratio I does not depend on the incident angle, the material
- the graphite crystals existing in the vicinity of the surface are irregularly arranged and have low orientation. Then, by quantifying the incident angle dependency of the ratio I between the absorption intensities A and B, the orientation of graphite crystals existing in the vicinity of the surface of the graphite-based material can be quantitatively evaluated.
- FIG. 4 is a diagram for explaining the method for quantitative evaluation of the orientation of surface graphite crystals according to the present invention, using HOPG as a sample.
- the modified natural graphite particles according to the present invention are obtained from scaly raw material graphite and have a circularity of 0.92 or more. .
- a process for obtaining the above circularity by making the shape of the entire raw graphite close to a sphere (hereinafter referred to as “spheronization process”) is performed.
- Specific examples of the spheroidizing process include those disclosed in Patent Documents 2 to 4.
- the scale-shaped graphite used as a raw material has many hexagonal mesh planes (AB planes) in which carbon atoms regularly form a network structure and spread in a plane, and has a thickness in the C-axis direction perpendicular to the AB plane. It is a crystal. Since the bonding force (van der Waals force) between the laminated AB surfaces is much smaller than the bonding force in the in-plane direction of the AB surface, peeling between the AB surfaces is likely to occur. Therefore, since the thickness of the laminate is small with respect to the spread of the AB surface, the scale shape is exhibited as a whole.
- the raw graphite having the scale shape is subjected to the spheronization treatment, as shown in FIGS. 5 (A) to 5 (C), the raw graphite which was originally substantially flat is folded or another particle is folded. It is taken in when it is applied, or adheres to the surface of another particle.
- spheroidized graphite particles graphite particles obtained by spheroidizing raw material graphite (hereinafter referred to as “spheroidized graphite particles”) with the surface (AB surface) of the raw material graphite being flat as it is. Covers most of the surface. Therefore, the AB surface is considered to be dominant on the surface of the spheroidized graphite particles.
- FIG. 6 if the spheroidized graphite particles are enlarged and observed, the end surfaces of the folded particles and the end surfaces of the adhered particles, that is, the edge surfaces are exposed on the surface. There are irregularities. From a microscopic viewpoint, the impact force during the spheroidizing process causes peeling at some points on the AB surface and bending, generating a portion where the edge surface appears on the surface.
- the surface of the spheroidized graphite particles Due to the unevenness of the surface, the surface of the spheroidized graphite particles has a rough surface. For this reason, the bond axis of the sp2 bond in the graphite crystal existing in the vicinity of the surface of the spheroidized graphite particles is directed in a random direction as a whole. Therefore, the spheroidized graphite particles have a circularity of 0.92 or more, but S 60/0 is in the vicinity of 1.
- Spherical graphite particles having a surface texture roughened by spheronization treatment in other words, spheroidized graphite particles having a circularity of 0.92 or more and S 60/0 in the vicinity of 1, and a negative electrode active material. Then, only the protruding portion of the rough surface of the spheroidized graphite particles becomes a contact portion between the negative electrode active materials and a contact portion between the negative electrode active material and the current collector.
- the binder that is contained together with the negative electrode active material and constitutes the negative electrode mixture is originally bonded to the negative electrode active materials or the negative electrode active material and the current collector by being supplied to such a contact portion,
- the obtained negative electrode mixture has low adhesiveness and is easily dropped from the current collector.
- the modified natural graphite particles according to the present invention have a circularity of 0.92 or more and S 60/0 of 0.7 or less, so that the particles are subjected to spheronization treatment.
- the surface graphite crystals are oriented to some extent. In the oriented portion of the surface graphite crystal, there is little defect such as bending, and the AB surface has high planarity. Therefore, the negative electrode active material made of these particles is relatively wide with the adjacent negative electrode active material or current collector. A contact portion can be formed.
- the modified natural graphite particles according to the present invention as the negative electrode active material, it is possible to obtain a negative electrode mixture that has high adhesiveness and does not easily fall off from the current collector.
- the lower limit of S 60/0 of the modified natural graphite particles according to the present invention is not particularly limited as long as the circularity is 0.92 or more, but 0.5 is a substantial lower limit. When S 60/0 is less than 0.5, it is practically extremely difficult to set the circularity to 0.92 or more.
- the modified natural graphite particles according to the present invention have a tap density of 1.0 g / cm 3 or more and 1.4 g / cm 3 or less measured using a container having a volume of 100 cm 3 as tapping frequency of 180 times. It is preferable that
- the packing density of the negative electrode active material in the negative electrode plate is increased.
- the tap density is preferably 1.05 g / cm 3 or more. Since the graphite particles obtained by spheroidizing raw material graphite have a rough surface, the tap density is difficult to increase.
- the tap density is preferably higher, but in reality, the upper limit is 1.4 g / cm 3 .
- a modified natural graphite particle according to the present invention is linseed that is measured using an absorbent meter in accordance with an oil absorption measurement method generally defined in JIS K6217-4: 2008. It is preferred oil absorption is less than 20 cm 3/100 g or more 50 cm 3/100 g.
- Graphite particles obtained by spheroidizing raw material graphite tend to have a high linseed oil absorption because the surface is excessively rough.
- the amount of linseed oil absorbed is excessively high, the utilization efficiency of the binder is lowered and it is difficult to increase the capacity. Therefore, it is preferable linseed oil absorption is 50 cm 3/100 g or less. Oil absorption is preferably smaller, but in practice the lower limit is 20 cm 3/100 g.
- modified natural graphite particles according to the present invention having the above characteristics may be carbon-attached graphite particles having a carbonaceous material attached to the surface thereof. This improves battery characteristics.
- carbonaceous material means a material mainly composed of carbon, and the structure thereof is not particularly limited.
- the carbonaceous material may be attached to a part of the surface of the modified natural graphite particles, or may be attached so as to substantially cover the entire surface.
- the carbonaceous material preferably has a lower crystallinity than modified natural graphite particles serving as a core material and / or a high sp3 bond composition ratio in all carbon-carbon bonds. Since such a carbonaceous material has a higher bulk hardness than the graphite particles, the presence of the carbonaceous material attached to the surface of the modified natural graphite particles increases the hardness of the entire particles. As a result, in the manufacturing process of the negative electrode plate, particularly in the compression process, the possibility that the closed pores are formed inside the electrode, which is the negative electrode active material, and charge acceptability is reduced is reduced.
- the specific surface area of the graphite particles is reduced due to carbon adhesion, and thus the reactivity with the electrolytic solution is suppressed. Therefore, the negative electrode plate using the carbon-attached graphite particles as an active material has improved charge / discharge efficiency and improved battery capacity.
- turbostratic structure carbon refers to a carbon substance having a laminated structure parallel to the hexagonal plane direction but composed of carbon atoms whose crystallographic regularity cannot be measured in the three-dimensional direction.
- Amorphous carbon is exemplified as a carbonaceous material having a lower crystallinity than modified natural graphite particles serving as a core material and a high constituent ratio of sp3 bonds.
- amorphous carbon is a carbon material having short-range order (several to tens of atoms) but not long-range order (hundreds to thousands of atoms).
- the method for adhering the carbonaceous material to the surface of the modified natural graphite particles as a core material and the method for coating are not particularly limited.
- a surface treatment method and a deposition method using a vacuum film forming technique are exemplified.
- the surface treatment method is a method in which an organic compound such as pitch is attached to at least a part of the surface of the graphite powder in advance or is coated, and then the organic compound is carbonized by heat treatment.
- a carbonaceous material composed of a turbostratic carbon is obtained.
- a carbonaceous material made of amorphous carbon can be attached to the surface of the core material.
- the modified natural graphite particles according to the present invention may be produced by any production method as long as they have the above properties. Next, a method capable of stably and efficiently producing modified natural graphite particles satisfying the above characteristics will be described. Conditions in each processing step are appropriately adjusted so that the modified natural graphite particles according to the present invention are obtained.
- the raw natural graphite particles can be spheroidized.
- the raw graphite particles collide with pins or the like at a high speed, and as shown in FIGS. 5 (A) to 5 (C), the laminated AB surface is bent or other graphite particles are adhered. As a result, the aspect ratio of the graphite particles decreases.
- the mechanical attrition treatment is a treatment performed to round the corners of the particles and smooth the fine irregularities on the particle surface.
- a device that repeatedly gives mechanical action to particles such as compression, friction, and shear, including particle interaction, can be used.
- a powder processing apparatus (circulation type mechanofusion system, AMS-Lab) manufactured by Hosokawa Micron Co., Ltd., a theta composer manufactured by Deoksugaku Kosakusho, etc. can be used.
- a strong sliding force in the in-plane direction is applied to the surface of the graphite particles by allowing the graphite particles to pass through a gap formed by two solids (for example, a rotor and an inner piece) that move in close proximity to each other. .
- the crystal passing through the gap is oriented in the sliding direction at the sliding portion.
- the exposed end surfaces of the folded particles and the end surfaces of the adhered particles also slip between the AB surface layers and are covered with the AB surface.
- the portion where the edge portion is directed to the surface direction due to peeling and bending existing in various places on the AB surface is also compressed and oriented.
- modified natural graphite particles according to the present invention having a circularity of 0.92 or more and S60 / 0 of 0.7 or less can be obtained.
- a negative electrode plate of a nonaqueous electrolyte secondary battery can be produced.
- the binder and current collector used for the production of the negative electrode are not particularly limited, and may be those conventionally used.
- the surface of the graphite particles as the active material is smooth, and the contact area between the graphite particles or between the graphite particles and the current collector is increased, so that the amount of the binder can be reduced as compared with the prior art. This makes it possible to manufacture higher density and higher capacity electrodes.
- Examples 1 to 4 and Comparative Examples 1 to 4 (1) Production of modified natural graphite particles Graphite particles made from Hosokawa Micron Co., Ltd. (ACM pulperizer, ACM-) against raw natural graphite particles (Chinese scale graphite, true specific gravity is 2.26 g / cm 3 ) The spheronization treatment was performed using 10A). The treatment was repeated 15 times. Furthermore, fine powder was removed by air classification. Spheroidized graphite particles shown as Comparative Examples 1 to 4 in Table 1 having four different particle sizes were obtained by appropriately performing spheronization at different pulverization rotational speeds and classification rotational speeds.
- a negative electrode active material composed of spheroidized graphite particles or modified natural graphite particles obtained by the above method and a binder are mixed to prepare two types of negative electrode mixtures (negative electrode mixtures 1 and 2). Prepared.
- Negative electrode mixture 2 A binder composed of polyvinylidene fluoride (PVdF) and graphite particles were mixed to prepare a negative electrode mixture.
- Each negative electrode mixture was applied onto an electrolytic copper foil (thickness: 17 ⁇ m) serving as a current collector and dried (75 ° C. ⁇ 20 minutes for negative electrode mixture 1, 100 ° C. ⁇ 20 minutes for negative electrode mixture 2), and uniaxial It consolidated by the press and the negative electrode plate was obtained.
- the negative electrode mixture layer in the obtained negative electrode plate was 9 mg / cm 2 in all cases, and the density was 1.6 g / cm 3 .
- the peel strength of each negative electrode plate was measured by the method described later, and the results are shown in Table 1.
- the CK edge NEXAFS spectrum measuring apparatus installed in BL7B and BL9, the CK edge NEXAFS spectrum was measured for the graphite particles according to the examples and the comparative examples, and the obtained incident angles were 0 ° and 60 °. S 60/0 was calculated from the spectrum profile at °. The details of the measurement principle and the measurement method are as described above. In foil was used as a carrier for supporting sample particles.
- Average particle diameter (denoted as d50 in Table 1)
- the volume-based particle size distribution of each graphite particle was determined by a light scattering diffraction method using a laser diffraction / scattering particle size distribution analyzer (LA-910) manufactured by Horiba, Ltd.
- the median diameter in the obtained particle size distribution was defined as the average particle diameter of each graphite particle.
- each graphite particle was measured using a flow type particle image analyzer FPIA-2100 manufactured by Sysmex Corporation. Specifically, 5,000 or more particles constituting each graphite particle are taken as measurement samples, and a flat sample flow is taken as an ion exchange water dispersion medium to which polyoxylen sorbitan monourarate is added as a surfactant, Each particle image obtained was determined by image processing.
- FPIA-2100 flow type particle image analyzer
- Peel strength Peel strength was determined in accordance with JIS C6481. Specifically, a negative electrode plate cut into a strip shape having a width of 15 mm was placed on the table so that the negative electrode mixture was on the lower surface, and fixed to the table with double-sided tape (NW-K15 manufactured by Nichiban Co., Ltd.). . The negative electrode current collector forming the upper surface of the fixed negative electrode plate was pulled 50 mm at a speed of 50 mm / min in the direction perpendicular to the upper surface of the table to separate the negative electrode current collector from the negative electrode mixture. The peel load at this time was continuously measured, and the lowest value among the obtained measurement loads was defined as the peel strength (unit: N / m).
- the strength ratio in Table 1 is the ratio of the peel strength after the smoothing treatment to the peel strength before the smoothing treatment, and specifically, (peel strength of Example 1) / (peel strength of Comparative Example 1). This is what I asked for.
- the graphite particles of Comparative Examples 1 to 4 obtained by spheronization treatment have a circularity of 0.92 or more, but S60 / 0 is as large as 0.75 to 0.88, and linseed oil absorption the amount was also not exceed 50cm 3 / 100g.
- the graphite particles of Examples 1 to 4 received a smoothing process becomes small as S 60/0 is from 0.51 to 0.68, linseed oil absorption amount is smaller than 50 cm 3/100 g.
- the tap density was higher in the example when the corresponding comparative example and the example (example, example 1 and comparative example 1) were compared.
- the modified natural graphite particles of Examples 1 to 4 according to the present invention have a peel strength of 1.72 to 1.88 in the mixture 1 compared to the spheroidized graphite particles of Comparative Examples 1 to 4 before the smoothing treatment. In the case of Mixture 2, it is 2.11-7.50 times higher, indicating that the peel strength is remarkably improved.
- Example 5 and Comparative Example 5 Each of the graphite particles obtained in Example 2 and Comparative Example 2 was mixed with coal-based pitch powder having an average particle size of 15 ⁇ m in an amount of 20% by mass with respect to the graphite particles, and the mixture was mixed at 1000 ° C. in a nitrogen stream. By heat-treating for 1 hour, carbon-attached graphite particles having a turbulent structure carbon attached to the surface were obtained. The average particle diameter, specific surface area, tap density, and linseed oil absorption of the obtained carbon-attached graphite particles were determined in the same manner as in Examples 1 to 4. The results are shown in Table 2.
- the negative electrode active material composed of carbon-attached graphite particles thus obtained and PVdF were mixed at a mass ratio of 95: 5 to prepare a negative electrode mixture.
- negative electrode plates were produced in the same manner as in Examples 1 to 4.
- the peel strength of the obtained negative electrode plate was measured in the same manner as in Examples 1 to 4, and the strength ratio and the strength ratio are also shown in Table 2.
- Example 5 in which the core material was modified natural graphite particles according to the present invention, a peel strength 2.28 times higher than that in Comparative Example 5 in which the core material was spheroidized graphite particles was obtained. .
- the carbon adhesion treatment significantly reduces the specific surface area of the graphite particles and increases the tap density, but the average particle diameter hardly increases.
- the amount of coal-based pitch powder used to form the carbonaceous material is relatively large, it is considered that most of the surfaces of the graphite particles are covered with the carbonaceous material (turbulent structure carbon). Thereby, since the micro unevenness was filled, the specific surface area was remarkably reduced.
- Example 6 and Comparative Example 6 Each of the graphite particles obtained in Example 3 and Comparative Example 3 was mixed with a coal-based pitch powder having an average particle diameter of 15 ⁇ m in an amount of 2% by mass with respect to the graphite particles, and then in a nitrogen stream at 1000 ° C. for 1 hour. By carrying out heat treatment, carbon-attached graphite particles having a turbulent structure carbon attached to the surface were obtained. The average particle diameter, specific surface area, tap density, and linseed oil absorption of the obtained carbon-attached graphite particles were determined in the same manner as in Examples 1 to 4. The results are shown in Table 3.
- the negative electrode active material comprising the carbon-attached graphite particles thus obtained, SBR, and CMC were mixed at a mass ratio of 98: 1: 1 to prepare a negative electrode mixture.
- negative electrode plates were produced in the same manner as in Examples 1 to 4.
- the peel strength of the obtained negative electrode plate was measured in the same manner as in Examples 1 to 4. As a result, the strength ratio is also shown in Table 3.
- Example 6 in which the core material was modified natural graphite particles according to the present invention, a peel strength 1.89 times higher than that in Comparative Example 6 in which the core material was spheroidized graphite particles was obtained. .
- the carbonaceous material of the turbulent structure carbon adheres to only part of the surface of the graphite particles. It is thought that there is. Even in this case, the specific surface area of the graphite particles was somewhat reduced. This is presumably because the molten pitch preferentially adhered to the edge surface having a larger surface area than the basal surface.
Abstract
Description
本発明者らは、上記課題を解決するために検討を行った結果、次の新たな知見を得た。
(D)黒鉛粒子表面の粗さを定量的に評価するための手段として、C-K端X線吸収スペクトルによる黒鉛粒子の配向の程度の計測および黒鉛粒子による亜麻仁油の吸収量を計測することが好ましい。
S60/0=I60/I0
ここで、
I60=B60/A60
I0=B0/A0
A60:放射光の入射角を60°として測定した、粒子のC-K端X線吸収スペクトルにおける、C-1s準位からπ*準位への遷移に帰属される吸収ピーク強度;
B60:放射光の入射角を60°として測定した、粒子のC-K端X線吸収スペクトルにおける、C-1s準位からσ*準位への遷移に帰属される吸収ピーク強度;
A0:放射光の入射角を0°として測定した、粒子のC-K端X線吸収スペクトルにおける、C-1s準位からπ*準位への遷移に帰属される吸収ピーク強度;
B0:放射光の入射角を0°として測定した、粒子のC-K端X線吸収スペクトルにおける、C-1s準位からσ*準位への遷移に帰属される吸収ピーク強度。
(円形度)=(投影形状と同一の面積を有する円の周囲長)/(投影形状の周囲長)
「投影形状」とは測定に係る粒子を二次元平面に投影して得られる形状であり、投影形状と同一の面積を有する円の周囲長および投影形状の周囲長は、投影形状の画像を画像処理することにより求められる。
(a)真比重が2.25g/cm3以上である;
(b)タップ密度が1.0g/cm3以上1.4g/cm3以下である;
(c)亜麻仁油吸収量が20cm3/100g以上50cm3/100g以下である。
本発明に係る改質天然黒鉛粒子は、その表面が十分に平滑化されているため、バインダ使用量を抑制しても、負極合剤と集電体との間に十分な接着強度を有する負極板が得られる。そのような負極板は品質が高い上に生産性が高い。したがって、本発明に係る改質天然黒鉛粒子を用いた負極板を備える非水電解質二次電池も品質が高くかつ生産性が高い。
1.天然黒鉛粒子
本発明に係る改質天然黒鉛粒子の原料となる天然黒鉛粒子(以下「原料黒鉛」という)は、鱗片形状の黒鉛(具体的には次に述べる鱗片状黒鉛または鱗状黒鉛)であって、改質処理や熱処理を受けていないものである。この天然黒鉛粒子に、例えば、後述する形状調整処理を施すことにより、本発明に係る改質天然黒鉛粒子を製造することができる。
本発明では、球形度の指標として円形度を用いることにより粒子形状を評価する。円形度は投影形状に関する次の式により求められる。
投影形状が真円をなす場合には円形度は1となる。従って、円形度の最大値は1である。円形度が1である場合、その粒子を3次元的に評価した場合における球形の程度も特に高いと考えられることから、円形度が高いほど(1に近づくほど)、粒子の球形度も高いといえる。投影形状は、光学顕微鏡や走査型電子顕微鏡などを用いて得られた観察像から求めることができる。
本発明に係る改質天然黒鉛粒子は、円形度が0.92以上であり、C-K端X線吸収スペクトルにおけるピーク強度比の入射角依存性S60/0(詳細は後述)が0.5以上0.7以下である。
(1)円形度
本発明に係る改質天然黒鉛粒子の円形度は0.92以上である。円形度が0.92未満であると、黒鉛粒子はアスペクト比が大きな扁平形状をなしているため、塗布時の配向、電池としての容量低下などの問題が生じやすくなる。円形度の上限は粒子形状が真球となる場合の円形度、つまり1.0である。円形度は好ましくは0.93以上である。
本発明に係る改質天然黒鉛粒子は、放射光を励起光源とする粉体のC-K端X線吸収スペクトルを測定したときに下記式により定義されるピーク強度比の入射角依存性S60/0が0.5以上0.7以下である。
ここで、
I60=B60/A60
I0=B0/A0
A60:放射光の入射角を60°として測定した、粒子のC-K端X線吸収スペクトルにおける、C-1s準位からπ*準位(即ち、sp2結合の反結合性軌道:-C=C-)への遷移に帰属される吸収ピーク強度。
B0:放射光の入射角を0°として測定した、粒子のC-K端X線吸収スペクトルにおける、C-1s準位からσ*準位への遷移に帰属される吸収ピーク強度。
i)測定方法
本発明において用いるC-K端X線吸収スペクトルは、C-K端NEXAFS(Near Edge X-ray Absorbance Fine Structure)スペクトルとも称され、占有状態である炭素原子の内殻準位(1s軌道)に存在する電子(K殻内殻電子)が、照射されたX線のエネルギーを吸収して、非占有状態である種々の空準位に励起されることにより観測される吸収スペクトルである。
結合エネルギーが283.8eVである炭素の内殻準位から種々の空準位への電子遷移を観測するためには、軟X線領域(280eV~320eV)におけるエネルギー可変光源が必要であること、およびS60/0の定量性は励起光源の直線偏光性が高いことを前提としていることから、本発明に係るC-K端NEXAFSスペクトルでは励起光源として放射光を用いる。
次に説明するように、S60/0を測定することにより、測定された改質天然黒鉛粒子の表面近傍の黒鉛結晶(以下、「表面黒鉛結晶」という)の配向性を定量的に評価することができる。
なお、S60/0を求めるにあたり、In箔やカーボンテープを用いて試料粒子を担持する場合には、これらの担体のC-K端NEXAFSスペクトルをブランクスペクトルとして測定しておき、試料粒子を測定して得られたC-K端NEXAFSスペクトルの強度をこのブランクスペクトルを用いて補正して各遷移の吸収ピーク強度を算出する。
本発明に係る改質天然黒鉛粒子は鱗片形状の原料黒鉛から得られるものであって、その円形度が0.92以上である。原料黒鉛全体の形状を球形に近づけ、前記円形度を得るための処理(以下、「球形化処理」という)が施されている。この球形化処理として、具体的には特許文献2から4に開示されるような処理が例示される。
本発明に係る改質天然黒鉛粒子のS60/0の下限は、円形度が0.92以上である限り特に限定されないが、0.5が実質的な下限となる。S60/0が0.5未満である場合には円形度を0.92以上とすることは現実的にきわめて困難である。
本発明に係る改質天然黒鉛粒子は、容積100cm3の容器を用いてタッピング回数180回として測定されるタップ密度が、1.0g/cm3以上1.4g/cm3以下であることが好ましい。
本発明に係る改質天然黒鉛粒子は、概ねJIS K6217-4:2008に規定されるオイル吸収量測定方法に準拠して、アブソープドメータを用いて測定される亜麻仁油吸収量が20cm3/100g以上50cm3/100g以下であることが好ましい。
上記の特性を備える本発明に係る改質天然黒鉛粒子は、その表面に炭素質材料を付着させた炭素付着黒鉛粒子としてもよい。こうすると電池特性が向上する。
本発明に係る改質天然黒鉛粒子は上記の特性を有する限り、いかなる製造方法により製造されていてもよい。上記の特性を満たす改質天然黒鉛粒子を安定的かつ効率的に生産することができる方法を次に説明する。各処理工程における条件は、本発明に係る改質天然黒鉛粒子が得られるように、適宜調整される。
ジェットミル、ピンミルなどで例示される衝撃式の粉砕手段を用いることにより、原料の天然黒鉛粒子を球形化することができる。この手段において、原料黒鉛粒子は高速でピンなどと衝突することによって、図5(A)~図5(C)に示されるように、積層されたAB面は折れ曲がったり、他の黒鉛粒子が付着したりして、黒鉛粒子のアスペクト比は低下する。
上記の球状化黒鉛粒子に対して、機械的摩砕処理を適用することにより、黒鉛粒子の表面を平滑化し、本発明の改質天然黒鉛粒子を得ることができる。
(1)改質天然黒鉛粒子黒鉛粒子の製造
原料天然黒鉛粒子(中国産鱗片状黒鉛、真比重は2.26g/cm3)に対して、ホソカワミクロン(株)製粉砕装置(ACMパルペライザ、ACM-10A)を用いて球形化処理を行った。処理は15回繰り返した。さらに風力分級により微粉を除去した。適宜異なった粉砕回転数、分級回転数で球形化処理を行うことにより、粒度の異なる4種類の表1に比較例1から4として示す球状化黒鉛粒子を得た。
ロータとインナーピースとの隙間:5mm
回転数:2600rpm
処理時間:15分間
この平滑化処理により、表1に実施例1から4として示す改質天然黒鉛粒子を得た。
上記方法により得られた球状化黒鉛粒子または改質天然黒鉛粒子からなる負極活物質とバインダとを混合して2種類の負極合剤(負極合剤1および2)を調製した。
スチレン-ブダジエンゴム(SBR)およびカルボキシメチルセルロースナトリウム(CMC)からなるバインダと黒鉛粒子とを混合して負極合剤を調製した。負極合剤の配合比(質量比)は次のとおりであった:
負極活物質:SBR:CMC=98:1:1。
ポリフッ化ビニリデン(PVdF)からなるバインダと黒鉛粒子とを混合して負極合剤を調製した。負極合剤の配合比(質量比)は次のとおりであった:
負極活物質:PVdF=9:1。
i)S60/0
C-K端NEXAFSスペクトルの測定は、兵庫県が大型放射光施設Spring-8の敷地内に設置し、兵庫県立大学高度産業科学技術研究所が運営している、放射光施設ニュースバルのビームラインBL7BおよびBL9において行った。加速電圧1.0GeV~1.5GeV、蓄積電流80~350mAで蓄積リングに蓄積された電子が、アンジュレーターと呼ばれる挿入光源を蛇行して通過する際に放出される放射光を励起光源とした。BL7BおよびBL9に設置されているC-K端NEXAFSスペクトル測定装置を用いて、各実施例および比較例に係る黒鉛粒子についてC-K端NEXAFSスペクトルを測定し、得られた入射角0°および60°におけるスペクトルプロファイルからS60/0を算出した。測定原理および測定方法の詳細については前述のとおりである。試料粒子を担持するための担体としてはIn箔を用いた。
(株)堀場製作所製レーザー回折/散乱式粒度分布計(LA-910)を用いて光散乱回折法により各黒鉛粒子の体積基準の粒度分布を求めた。得られた粒度分布におけるメジアン径を各黒鉛粒子の平均粒径とした。
シスメックス(株)製フロー式粒子画像分析装置FPIA-2100を用いて、各黒鉛粒子の円形度を測定した。具体的には、各黒鉛粒子を構成する5000個以上の粒子を測定対象試料とし、界面活性剤としてポリオキシレンソルビタンモノウラレートを添加したイオン交換水分散媒とする扁平な試料流を撮影し、得られた各粒子像を画像処理することにより求めた。
ユアサアイオニクス(株)製カンタソープを用いて、各黒鉛粒子の比表面積をBET1点法により求めた。
ホソカワミクロン(株)製パウダテスタ(登録商標)PT-N型を用い、容積100cm3の容器を用いてタッピング回数180回として固め見掛け比重を各黒鉛粒子について測定し、これを各黒鉛粒子のタップ密度とした。
(株)あさひ総研製アブソープドメータ(S-410)を用い、概ねJIS K6217-4:2008に規定されるオイル吸収量測定法に準拠して、各黒鉛粒子の亜麻仁油吸収量を測定した。具体的には、2枚羽根によってかき混ぜられている黒鉛粒子に4cm3/minの速度で亜麻仁油を添加した。このときの粘度特性の変化をトルク検出器によってトルクの変化として検出した。発生した最大トルクの100%時点のトルクに対応する亜麻仁油添加量を、黒鉛粒子100gあたりに換算して亜麻仁油吸収量を求めた。
剥離強度は、概ねJIS C6481に準拠して求めた。具体的には、幅15mmの短冊状に切り取った負極板を、負極合剤が下面になるようにテーブル上に配置して、両面テープ(ニチバン(株)製NW-K15)でテーブルに固定した。固定された負極板の上面をなす負極集電体を、テーブル上面に対して垂直方向に50mm/minの速さで50mm引っ張ることにより負極集電体と負極合剤とを剥離させた。このときの剥離荷重を連続的に測定し、得られた測定荷重のうちの最低値を剥離強度(単位:N/m)とした。
実施例2および比較例2で得られた黒鉛粒子のそれぞれに、平均粒径15μmの石炭系ピッチ粉末を黒鉛粒子に対して20質量%の量で混合し、混合物を窒素気流中、1000℃で1時間熱処理することにより、表面に乱層構造炭素が付着した炭素付着黒鉛粒子を得た。得られた炭素付着黒鉛粒子の平均粒径、比表面積、タップ密度、および亜麻仁油吸収量を実施例1~4と同様の方法で求めた。結果を表2に示す。
実施例3および比較例3で得られた黒鉛粒子のそれぞれに、平均粒径15μmの石炭系ピッチ粉末を黒鉛粒子に対して2質量%の量で混合し、窒素気流中、1000℃で1時間熱処理することにより、表面に乱層構造炭素が付着した炭素付着黒鉛粒子を得た。得られた炭素付着黒鉛粒子の平均粒径、比表面積、タップ密度、および亜麻仁油吸収量を実施例1~4と同様の方法で求めた。結果を表3に示す。
Claims (5)
- 円形度が0.92以上であって、放射光を励起光源としたC-K端X線吸収スペクトルの測定により求められる、下記式により定義されるピーク強度比の入射角依存性S60/0が0.5以上0.7以下である、ことを特徴とする改質天然黒鉛粒子:
S60/0=I60/I0
ここで、
I60=B60/A60
I0=B0/A0
A60:放射光の入射角を60°として測定した、粒子のC-K端X線吸収スペクトルにおける、C-1s準位からπ*準位への遷移に帰属される吸収ピーク強度。
B60:放射光の入射角を60°として測定した、粒子のC-K端X線吸収スペクトルにおける、C-1s準位からσ*準位への遷移に帰属される吸収ピーク強度。
A0:放射光の入射角を0°として測定した、粒子のC-K端X線吸収スペクトルにおける、C-1s準位からπ*準位への遷移に帰属される吸収ピーク強度。
B0:放射光の入射角を0°として測定した、粒子のC-K端X線吸収スペクトルにおける、C-1s準位からσ*準位への遷移に帰属される吸収ピーク強度。 - 真比重が2.25g/cm3以上である請求項1記載の改質天然黒鉛粒子。
- タップ密度が1.0g/cm3以上1.4g/cm3以下である請求項1または2記載の改質天然黒鉛粒子。
- 亜麻仁油吸収量が20cm3/100g以上50cm3/100g以下である、請求項1から3のいずれかに記載の改質天然黒鉛粒子。
- 請求項1から4のいずれかに記載される改質天然黒鉛粒子の表面の少なくとも一部に炭素質材料が付着してなる、炭素付着黒鉛粒子。
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CN103596881A (zh) | 2014-02-19 |
JPWO2012137770A1 (ja) | 2014-07-28 |
US20140093781A1 (en) | 2014-04-03 |
EP2695857A1 (en) | 2014-02-12 |
KR101562724B1 (ko) | 2015-10-22 |
KR20140002793A (ko) | 2014-01-08 |
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JP5814347B2 (ja) | 2015-11-17 |
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