WO2013141041A1 - Composite graphitic particles and method for manufacturing same - Google Patents

Abstract

The purpose of the present invention is to provide composite graphitic particles that can form a dense conductive network in an electrode when forming an electrode of a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery or the like, and to provide a method for manufacturing the same. These composite graphitic particles can include graphite, conductive carbonaceous fine particles, and non-graphitic carbon. The graphite is preferably natural graphite, and more preferably is a spherical graphite granule formed by aggregating a plurality of natural graphite flakes. Furthermore, the graphite is preferably smoothed. The conductive carbonaceous fine particles are directly adhered to the graphite. The non-graphitic carbon is at least partially adhered to the conductive carbonaceous fine particles and the graphite. Furthermore, when a predetermined external force is applied to the composite graphitic particles, the conductive carbonaceous fine particles detach from the graphite.

Description

Composite graphite particles and method for producing the same

The present invention relates to composite graphite particles and a method for producing the same.

In the past, composite particles containing the following graphite and conductive carbonaceous fine particles have been proposed as electrode active material materials for lithium ion secondary batteries.

A carbonaceous layer having a lower crystallinity than the graphite granule is filled and / or coated on the internal voids and / or the outer surface of the graphite granule formed by aggregating a plurality of scaly graphites, Composite graphite particles in which carbonaceous fine particles are added to a carbonaceous layer (for example, see JP-A-2004-066331).

On the surface of the graphite powder having an average particle diameter of 5 to 30 μm and an average lattice spacing d (002) of less than 0.3360 nm, the average particle diameter is 0.05 to 2 μm and the average lattice spacing d (002) is 0.3360 nm. The above amorphous carbon powder is bound and coated with carbide of binder pitch, the nitrogen adsorption specific surface area is 3 to 7 m ² / g, the average particle diameter is 7 to 40 μm, and the Raman spectral intensity ratio 11360/11580. A composite particle having a core-shell structure having a particle diameter of 0.6 or more (see, for example, pamphlet of International Publication No. 2008/56820).

A graphite carbon material with a mechanochemical treatment of an amorphous carbon material (see JP 2009-238657 A).

JP 2004-066331 A International Publication No. 2008/56820 Pamphlet JP 2009-238657 A

By the way, when forming an electrode by binding only the composite graphite particles as described above with a binder (binder), a conductive network is formed by the point contact of the composite graphite particles within the electrode. Will be. Thus, the conductive network formed by the point contact between the composite graphite particles is likely to collapse due to the expansion / contraction of the composite graphite particles accompanying charge / discharge. For this reason, it is considered that the composite graphite particles as described above cannot contribute to the improvement of the charge / discharge cycle characteristics of the lithium ion secondary battery. Therefore, it is expected in the future that composite graphite particles capable of forming a dense conductive network that does not easily collapse due to expansion / contraction associated with charge / discharge are expected.

An object of the present invention is to provide composite graphite particles capable of forming a dense conductive network in an electrode when forming an electrode of a non-aqueous electrolyte secondary battery such as a lithium ion secondary battery, and a method for producing the same. is there.

The composite graphite particles according to one aspect of the present invention include graphite, conductive carbonaceous fine particles, and non-graphitic carbon. The graphite is preferably natural graphite. When the graphite is natural graphite, the natural graphite is preferably a spherical graphite granule formed by aggregating a plurality of scaly natural graphites. The graphite is preferably smoothed. When the graphite is a spherical graphite granule, the circularity is 0.92 or more and 1.00 or less, and the incident angle dependence S _60/0 of the peak intensity ratio in the _CK edge X-ray absorption spectrum is _0.00 . It is preferable that it is 7 or less. The conductive carbonaceous fine particles are directly attached to the graphite. Non-graphitic carbon is at least partially attached to the conductive carbonaceous fine particles and graphite.

If the composite graphite particles are configured as described above, a part or all of the conductive carbonaceous fine particles can be detached from the graphite by applying a predetermined external force. For this reason, if composite graphite particles are formed so that part or all of the conductive carbonaceous fine particles are desorbed from graphite with a force applied when preparing an electrode mixture slurry, Conductive carbonaceous fine particles can be uniformly dispersed. That is, if this composite graphite particle is used, a dense conductive network mainly composed of graphite and conductive carbonaceous fine particles can be formed in the electrode when forming the electrode of the nonaqueous electrolyte secondary battery.

The ratio of "predetermined specific surface area after an external force is applied (m 2 ^{/ g)"} "The specific surface area value before the predetermined force is applied (m 2 ^{/ g)"} for the composite graphite particles described above It is preferably in the range of 1.10 or more and 2.00 or less. This is because such composite graphite particles can release a sufficient amount of conductive carbonaceous fine particles into the slurry during slurry preparation.

In the above composite graphite particles, the mass ratio of the conductive carbonaceous fine particles to graphite is preferably in the range of 0.3% to 2.0%. The mass ratio of non-graphitic carbon to the sum of graphite and conductive carbonaceous fine particles is preferably in the range of 0.8% to 15.0%. By making the composition of the composite graphite particles in this way, the conductive carbonaceous fine particles can be satisfactorily adhered to the graphite before the preparation of the electrode mixture slurry, and the conductive carbonaceous fine particles are prepared during the preparation of the electrode mixture slurry. This is because can be released from graphite.

The method for producing composite graphite particles according to another aspect of the present invention includes a primary composite particle preparation step and a composite graphite particle preparation step. In the primary composite particle preparation step, the conductive composite particles are prepared by directly attaching the conductive carbonaceous fine particles to the graphite. The graphite is preferably natural graphite. When the graphite is natural graphite, the natural graphite is preferably a spherical graphite granule formed by aggregating a plurality of scaly natural graphites. The graphite is preferably smoothed. When the graphite is a spherical graphite granule, the circularity is 0.92 or more and 1.00 or less, and the incident angle dependence of the peak intensity ratio in the CK edge X-ray absorption spectrum is 0.7 or less. It is preferable. In the primary composite particle preparation step, it is preferable that a mechanochemical treatment is performed on the conductive carbonaceous fine particles and graphite. In the composite graphite particle preparation step, non-graphitic carbon is partially or wholly attached to the primary composite particles to prepare composite graphite particles.

By this composite graphite particle production method, composite graphite particles in which part or all of the conductive carbonaceous fine particles are detached from the graphite by applying a predetermined external force can be constituted. For this reason, if the composite graphite particles are formed so that part or all of the conductive carbonaceous fine particles are detached from the graphite with a force applied when preparing the electrode mixture slurry, Conductive carbonaceous fine particles can be uniformly dispersed. That is, if this composite graphite particle is used, a dense conductive network can be formed in the electrode when forming the electrode of the nonaqueous electrolyte secondary battery.

In the above-described method for producing composite graphite particles, in the composite graphite particle preparation step, primary composite particles and non-graphitic carbon raw material powder are mixed and then heated. As a result, the non-graphitic carbon raw material powder is converted into non-graphitic carbon, and the non-graphitic carbon is partially or entirely attached to the primary composite particles.

The above-described composite graphite particles can be used as an active material constituting an electrode, particularly an electrode of a nonaqueous electrolyte secondary battery. Nonaqueous electrolyte secondary batteries are represented by lithium ion secondary batteries.

2 is a scanning electron micrograph of composite graphite particles according to an embodiment of the present invention. 2 is a scanning electron micrograph of composite graphite particles after ultrasonic treatment of the composite graphite particles shown in FIG. It is a figure which shows the measurement principle of X-ray absorption spectroscopy by contrast with X-ray photoelectron spectroscopy (XPS). It is a figure which shows the basic composition of the measuring method of the X-ray absorption spectroscopy by synchrotron radiation. Different incident angles (0 °, 30 ° and 60 °) for single crystal HOPG (highly oriented pyrolytic graphite) (left) and amorphous carbon deposited film (film thickness: 10 nm) (right) FIG. 6 is a diagram illustrating a CK end NEXAFS spectrum when radiant light is incident on the line. It is a figure explaining the case where HOPG is made into the sample for the quantitative evaluation method of the orientation of surface graphite crystal.

The composite graphitic particles according to the embodiment of the present invention are mainly composed of graphite, conductive carbonaceous fine particles, and non-graphitic carbon.

The graphite may be natural graphite or artificial graphite, but is preferably natural graphite. As the graphite, a mixture of natural graphite and artificial graphite may be used. The graphite is preferably a spherical graphite granule formed by aggregating a plurality of scaly graphites. As scale-like graphite, natural graphite, artificial graphite, mesophase calcined carbon (bulk mesophase) made from tar pitch, coke (raw coke, green coke, pitch coke, needle coke, petroleum coke, etc.), etc. Graphitized, etc., and those granulated using a plurality of natural graphites having high crystallinity are particularly preferable. One graphite granule is usually formed by collecting 2 to 100, preferably 3 to 20, scaly graphite, but can be made spherical by folding one graphite. . The graphite is preferably smoothed. When the graphite is a spherical graphite granule, the circularity is 0.92 or more and 1.00 or less, and the incident angle dependence S _60/0 of the peak intensity ratio in the _CK edge X-ray absorption spectrum is _0.00 . It is preferable that it is 7 or less. The lower limit of the incident angle dependence S _60/0 of the peak intensity ratio in the _CK edge X-ray absorption spectrum is preferably 0.5, that is, 0.5 or more. If the circularity of the graphite granule is 0.92 or more, since the graphite granule is relatively spherical, the graphite granule is not oriented when the electrode mixture slurry is applied. Is less likely to cause problems such as a decrease in capacity of the nonaqueous electrolyte secondary battery. Further, when the incident angle dependence S _60/0 of the peak intensity ratio in the _CK edge X-ray absorption spectrum is 0.7 or less, the surface of the graphite granule becomes sufficiently smooth and an external force is applied. In addition, the conductive carbonaceous fine particles are easily detached from the graphite.

Hereinafter, the incident angle dependence of the peak intensity ratio in the _CK edge X-ray absorption spectrum used as an index of the surface smoothness of the graphite granulated product is S _60/0 (hereinafter, simply referred to as “S _60/0 ”). Exist).

The CK-edge X-ray absorption spectrum is also called a CK-edge NEXAFS (Near Edge X-ray Absorption Fine Structure) spectrum, which is an electron existing in the core level (1s orbital) of an occupied carbon atom (1s orbital). K-shell inner-shell electrons) are absorption spectra that are observed when the irradiated X-ray energy is absorbed and excited to various vacant levels in an unoccupied state.

The measurement principle of this X-ray absorption spectroscopy is shown in FIG. 3 in comparison with X-ray photoelectron spectroscopy (XPS).
In order to observe electronic transitions from the core level of carbon having a binding energy of 283.8 eV to various vacant levels, an energy variable light source in the soft X-ray region (280 eV to 320 eV) is necessary. _Since the quantitative property of S _60/0 is based on the premise that the linear polarization property of the excitation light source is high, synchrotron radiation is used as the excitation light source in the CK edge NEXAFS spectrum.

The vacant levels at which electrons in the inner core level are excited include π ^* levels attributed to antibonding orbitals of sp2 bonds that reflect the crystallinity (basal plane, orientation, etc.) in natural graphite, crystals Σ ^* level attributed to anti-bonding orbitals of sp3 bonds that reflect disorder of properties (edge surface, non-orientation, etc.), or anti-bonding orbitals such as CH bonds and CO bonds There are empty levels. In graphite having a crystal structure in which hexagonal network structures by sp2 bonds are laminated, the surface is a plane of a hexagonal network surface (AB surface described later) is a basal surface, and a surface on which an end of the hexagonal network appears. Is the edge surface. On the edge surface, carbon often has an sp3 bond (because there is a possibility that —C═O or the like is present at the terminal).

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, it is possible to measure the crystalline state (orientation) of graphite on the surface of the graphite granulated product, thereby evaluating the roughness of the surface of the graphite granulated product. it can.

The method for fixing the graphite granule to be measured to the sample stage is not particularly limited. It is preferable to employ a method of supporting the graphite particles on the copper substrate with In foil or supporting it on the copper substrate with carbon tape so that an excessive load is not applied to the graphite particles.

Measure the CK edge NEXAFS spectrum by irradiating the sample with radiated 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.

As described below, by measuring S _60/0 , the orientation of the graphite crystals in the vicinity of the surface of the measured graphite granulated product (hereinafter referred to as “surface graphite crystal”) can be quantitatively evaluated. it can.

Since synchrotron radiation is highly linearly polarized, when the incident direction of synchrotron radiation is parallel to the bond axis direction of the sp2 bond (-C = C-) of the surface graphite crystal, the C-1s level to the π ^* level The absorption peak intensity attributed to the transition to becomes larger, and conversely when the two are orthogonal, the absorption peak intensity decreases.

Therefore, when the graphite crystal forming sp2 bonds in the vicinity of the surface is highly oriented, such as highly oriented pyrolytic graphite (HOPG, single crystal graphite), the incident angle of the radiated light to the sample is If the sample is a sample with a low orientation of a carbon material that forms sp2 bonds in the vicinity of the surface, such as a carbon vapor deposition film (non-graphite), the incident angle of the emitted light to the sample changes. Even if is changed, the spectrum shape hardly changes.

FIG. 5 shows CK-edge NEXAFS spectra when radiated light is incident on carbon at different incident angles (0 °, 30 °, and 60 °). The graph on the left side shows a case where HOPG (highly oriented pyrolytic graphite) in which carbon is a single crystal, and the graph on the right side shows a carbon deposited film in which carbon is non-graphitic ( The case of film thickness: 10 nm) is shown. As shown in the graph on the left side of FIG. 5, in HOPG which is a single crystal, when the incident angle is increased from 0 ° to 60 °, it belongs to the transition from the C-1s level to the π ^* level. The absorption peak intensity A is increased, and the absorption peak intensity B attributed to the transition from the C-1s level to the σ ^* level is decreased. Therefore, the profile of the HOPG CK edge NEXAFS spectrum varies greatly depending on the incident angle. On the other hand, the profile of the CK edge NEXAFS spectrum of the non-graphitic carbon deposited film shown in the graph on the right side of FIG. 5 hardly depends on the incident angle, and the incident angle changes. But the profile hardly changes.

[Correction 21.05.2013 based on Rule 91]
Therefore, as a result of measuring the CK edge NEXAFS spectrum at a different incident angle for a certain graphite-based material, the ratio I (= B / A) of the absorption peak intensity B to the absorption peak intensity A varies depending on the incident angle. In this case, the graphite crystals existing in the vicinity of the surface of the material are regularly arranged, that is, when the orientation is high and the incidence angle dependence is not seen in the ratio I, the surface of the material The graphite crystals present in the vicinity are irregularly arranged and have low orientation. Then, by quantifying the incident angle dependence of the ratio I of the absorption peak intensity B to the absorption peak intensity A, the orientation of the graphite crystals existing in the vicinity of the surface of the graphite-based material can be quantitatively evaluated. Become.

[Correction 21.05.2013 based on Rule 91]
Therefore, here, the incident angle dependence S _{60/0 of the} peak intensity ratio derived using the ratios I ₆₀ and I ₀ of the absorption peak intensity B to the absorption peak intensity A in the case of two incident angles 60 ° and 0 °. (= I ₆₀ / I ₀ ) is used to quantitatively evaluate the orientation of the surface graphite crystals. FIG. 6 is a diagram for explaining the quantitative evaluation method for the orientation of the surface graphite crystal, taking HOPG as a sample as an example.

When S _60/0 is in the vicinity of 1, the orientation of the surface graphite crystal is low, and as S _60/0 approaches 1 to 0 (FIG. 6), the orientation of the surface graphite crystal is high.

In _obtaining S _60/0 , when sample particles are supported using In foil or carbon tape, the CK edge NEXAFS spectra of these carriers are measured as blank spectra, and the sample particles are measured. The intensity of the obtained CK edge NEXAFS spectrum is corrected using this blank spectrum, and the absorption peak intensity of each transition is calculated.

Examples of the method of forming a graphite granulated product by aggregating a plurality of graphites include, for example, a method of mixing a plurality of scaly graphites in the presence of a binder of a graphite raw material, and a method of applying mechanical external force to a plurality of scaly graphites And a method using the above-mentioned two methods in combination. Among these methods, a method of granulating by applying a mechanical external force without using a binder component is particularly preferable. As an apparatus for applying a mechanical external force, for example, a counter jet mill AFG (manufactured by Hosokawa Micron Corporation, registered trademark), a current jet (manufactured by Nissin Engineering Co., Ltd., registered trademark), and an ACM pulverizer (Hosokawa Micron Corporation). A pulverizer such as “manufactured registered trademark”, a hybridization system (manufactured by Nara Machinery Co., Ltd., registered trademark), mechano hybrid (manufactured by Nippon Coke Industries, Ltd., registered trademark), and the like can be used.

As a method of smoothing graphite, for example, a method of applying mechanical external force to graphite can be mentioned. As a device for applying a mechanical external force, for example, a shear compression processing machine such as a mechanofusion system (manufactured by Hosokawa Micron Corporation, “Mechanofusion” is a registered trademark) can be used.

The conductive carbonaceous fine particles are directly attached to the graphite. The conductive carbonaceous fine particles are, for example, carbon black such as Ketjen Black (registered trademark), furnace black, acetylene black, carbon nanotube, carbon nanofiber, carbon nanocoil and the like. Among these conductive carbonaceous fine particles, acetylene black is particularly preferable. The conductive carbonaceous fine particles may be a mixture of different types of carbon black or the like. The mass ratio of the conductive carbonaceous fine particles to graphite is preferably in the range of 0.3% to 2.0%, more preferably in the range of 0.5% to 2.0%, More preferably, it is in the range of 0.7% or more and 2.0% or less, and particularly preferably in the range of 1.0% or more and 2.0% or less.

Non-graphitic carbon is at least partially adhered to the conductive carbonaceous fine particles and graphite. Non-graphitic carbon is at least one of amorphous carbon and turbostratic carbon.

As used herein, “amorphous carbon” refers to carbon that has short-range order (on the order of several to tens of atoms) but does not have long-range order (on the order of hundreds to thousands of atoms). Say.

Here, “turbulent structure carbon” refers to carbon composed of carbon atoms having a turbulent structure parallel to the hexagonal plane direction, but having no crystallographic regularity in the three-dimensional direction. In the X-ray diffraction pattern, hkl diffraction lines corresponding to the 101 plane and the 103 plane do not appear. However, since the composite graphite particles according to the embodiment of the present invention have strong diffraction lines of graphite as a base material, it is difficult to confirm the existence of the turbostratic carbon by X-ray diffraction. For this reason, it is preferable that the turbostratic structure carbon is confirmed with a transmission electron microscope (TEM) or the like.

This turbostratic carbon is obtained by firing a raw material of non-graphitic carbon. The raw material of non-graphitic carbon is an organic compound such as tar, petroleum-based pitch powder, coal-based pitch powder, and resin powder. The non-graphitic carbon raw material may be a mixture of different types of pitches. Among these, coal-based pitch powder is particularly preferable. As an example of the heat treatment conditions in the firing, the heat treatment temperature may be in the range of 800 ° C to 1200 ° C. This heat treatment time is appropriately determined in consideration of the heat treatment temperature and the characteristics of the organic compound, and is typically about 1 hour. The atmosphere during the heat treatment is preferably a non-oxidizing atmosphere (inert gas atmosphere, vacuum atmosphere), and a nitrogen atmosphere is preferred from an economic viewpoint.

Amorphous carbon can be formed, for example, by a vapor phase method such as a vacuum deposition method or a plasma CVD method.

The mass ratio of non-graphitic carbon to the sum of graphite and conductive carbonaceous fine particles is preferably in the range of 0.8% to 15.0%, and in the range of 2.0% to 14.0%. More preferably, it is more preferably within the range of 4.0% or more and 12.0% or less, and particularly preferably within the range of 6.0% or more and 10.0% or less.

When an external force such as ultrasonic waves is applied to the composite graphite particles according to the embodiment of the present invention, some or all of the conductive carbonaceous fine particles are detached from the graphite (see FIGS. 1 and 2). The force required for this desorption is the various settings of the mechanochemical (registered trademark) processing device and mechanofusion (registered trademark) processing device, the type of non-graphitic carbon raw material powder, and the composition , And can be adjusted depending on the amount added.

The ratio of the "predetermined specific surface area after an external force is applied (m 2 ^{/ g)"} "The specific surface area value before the predetermined force is applied (m 2 ^{/ g)"} for 1.10 or 2. It is preferably in the range of 00 or less, more preferably in the range of 1.20 or more and 2.00 or less, further preferably in the range of 1.30 or more and 2.00 or less, and 1.40. More preferably, it is in the range of 2.00 or less and particularly preferably in the range of 1.50 or more and 2.00 or less.

Such composite graphite particles can be used as an active material constituting an electrode, particularly a negative electrode of a nonaqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery is represented by a lithium ion secondary battery.

<Manufacture of composite graphite particles>
The composite graphite particles according to the embodiment of the present invention are manufactured through a primary composite particle preparation step and a composite graphite particle preparation step. In the primary composite particle preparation step, the conductive composite particles are directly attached to the graphite by a process such as a mechanochemical (registered trademark) process or a mechanofusion (registered trademark) process to produce primary composite particles. In the composite graphite particle preparation step, the primary composite particles and the non-graphitic carbon raw material powder are mixed and then heated. As a result, the non-graphitic carbon raw material powder is converted into non-graphitic carbon, and the non-graphitic carbon is partially or entirely attached to the primary composite particles.

<Characteristics of composite graphite particles>
When a predetermined external force is applied to the composite graphite particles according to the embodiment of the present invention, some or all of the conductive carbonaceous fine particles are detached from the graphite. For this reason, if this composite graphite particle | grain is utilized, electroconductive carbonaceous microparticles | fine-particles can be disperse | distributed uniformly in an electrode mixture slurry at the time of electrode mixture slurry preparation. That is, if this composite graphite particle is used, a dense conductive network can be formed in the electrode when forming the electrode of the nonaqueous electrolyte secondary battery.

<Examples and Comparative Examples>
Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples.

<Manufacture of composite graphite particles>
(1) Smoothing treatment of spherical natural graphite powder Spherical natural graphite powder (average particle diameter 19.5 μm, specific surface area 5.0 m ² / g, tap density 1.02 g / cm ³ , oil absorption 50.8 mL / 100 g) 600 g was weighed and put into a mechanofusion (AMS-Lab manufactured by Hosokawa Micron Co., Ltd.) in which the gap between the rotor and the inner piece was 5 mm, and the spherical natural graphite powder was smoothed at a rotational speed of 2600 rpm for 20 minutes. Hereinafter, this spherical natural graphite powder is referred to as “smoothed spherical natural graphite powder”. In the present specification, the average particle diameter means a particle diameter (D50) at a volume fraction of 50% in the cumulative particle size distribution unless otherwise specified.

The smoothed spherical natural graphite powder has a circularity of 0.92 or more and 1.00 or less, and the incident angle dependence S _60/0 of the peak intensity ratio in the _CK edge X-ray absorption spectrum is 0.67. Was confirmed.

The circularity was measured using a flow type particle image analyzer FPIA-2100 ("FPIA" is a registered trademark) manufactured by Sysmex Corporation. (Circularity) is a value obtained by dividing (perimeter of a circle having the same area as the projection shape) by (perimeter of the projection shape). Here, the “projection shape” is a shape obtained by projecting the particles to be measured onto a two-dimensional plane, and the circumference length of a circle having the same area as the projection shape and the circumference length of the projection shape are It is obtained by image processing of an image.

The CK edge X-ray absorption spectrum was measured using synchrotron radiation facility NEWVAL beam lines BL7B and BL9. During this measurement, emitted light is emitted when electrons accumulated in the storage ring with an acceleration voltage of 1.0 GeV to 1.5 GeV and an accumulation current of 80 to 350 mA meander through an insertion light source called an undulator. Was used as an excitation light source. In addition, the C-K edge X-ray absorption spectrum of the smooth spherical natural graphite powder was measured using a CK edge NEXAFS (Near Edge X-ray Absorbance Fine Structure) installed in the beam lines BL7B and BL9. The peak intensity ratio S _60/0 was calculated from the _measured spectrum profiles at incident angles of 0 ° and 60 °. Note that S _60/0 = I ₆₀ / I ₀ . Here, I ₆₀ = B ₆₀ / A ₆₀ and I ₀ = B ₀ / A ₀ . A ₆₀ is the C-1s level to π ^* level (ie, anti-bonding property of sp2 bond) 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 orbit: -C = C-). B ₆₀ is the C-1s level to σ ^* level (that is, the antibonding orbital of sp3 bond in the CK edge X-ray absorption spectrum of the particle measured with the incident angle of the emitted light being 60 °: It is the absorption peak intensity attributed to the transition to -CC-). A ₀ is the absorption peak intensity attributed to the transition from the C-1s level to the π ^* level in the CK edge X-ray absorption spectrum of the particle, measured with the incident angle of the emitted light being 0 °. is there. B ₀ is the absorption peak intensity attributed to the transition from the C-1s level to the σ ^* level in the CK edge X-ray absorption spectrum of the particle, measured with the incident angle of the emitted light being 0 °. is there.

(2) Compounding of smoothed spherical natural graphite powder and acetylene black Smoothed spherical natural graphite powder (average particle size 19.4 μm, specific surface area 5.0 m ² / g, tap density 1.06 g / cm ³ , oil absorption 41.6 mL / 100 g) and acetylene black (Denka Black (registered trademark) manufactured by Denki Kagaku Kogyo Co., Ltd., powdered product) and a smooth spherical natural graphite powder so that the mass ratio is 100.0: 0.5 600 g of mixed powder was prepared by mixing with acetylene black. 600 g of this mixed powder was put into a mechano-fusion system (AMS-Lab made by Hosokawa Micron) with a gap of 5 mm between the rotor and the inner piece, and then the mixed powder was processed at a rotational speed of 2600 rpm for 5 minutes to make it smooth Spherical natural graphite powder and acetylene black were combined. Hereinafter, this composite is referred to as “primary composite powder”.

(3) Composite of primary composite powder and non-graphitic carbon Primary composite powder and coal so that the mass ratio of primary composite powder and coal-based pitch powder (average particle size 20 μm) is 100.5: 2.0. After mixing with the system pitch powder, the mixed powder was heat-treated at 1000 ° C. for 1 hour under a nitrogen stream to obtain the desired composite graphite particles. During this heat treatment, the coal-based pitch powder changed to non-graphitic carbon. Moreover, it confirmed that the pitch residual carbon rate was 50% from the mass change before and behind heat processing. Further, the mass ratio of the smoothed spherical natural graphite powder, acetylene black and non-graphitic carbon in the composite graphite particles was 98.5: 0.5: 1.0 (see Table 1).

<Characteristic evaluation of composite graphite particles>
(1) Measurement of average particle size (D50) The volume-based particle size distribution of the composite graphite particles was measured by a light scattering diffraction method using a laser diffraction / scattering particle size distribution analyzer (LA-910, manufactured by Horiba, Ltd.). . Then, using the obtained particle size distribution, the particle diameter (median diameter) at a volume fraction of 50% was determined, and this was used as the average particle diameter. As a result, the average particle diameter was 19.5 μm (see Table 1).

(2) Evaluation of separation characteristics of acetylene black Using a canter soap manufactured by Yuasa Ionics Co., Ltd., the specific surface area of the composite graphite particles was determined by the BET one-point method. As a result, the BET specific surface area of the composite graphite particles was 4.34 m ² / g (see Table 2).

Next, after 1.2 g of the composite graphite particles described above were put into a 20 mL beaker, 10 mL of ethanol was poured into the beaker. Then, the contents of the beaker were lightly stirred with a spoon, and the composite graphite particles were allowed to settle. Then, the beaker was placed in an ultrasonic cleaner equipped with water (Sono Cleaner 100a (CA-3481), AC100V, 0.8A manufactured by Kaijo Corporation), and then the ultrasonic cleaner was operated for 20 minutes. Thereafter, the beaker was allowed to stand for 2 minutes and then decanted. Next, 20 mL of ethanol was again poured into the beaker, and the contents of the beaker were gently stirred with a spoon. The operation from ultrasonic cleaning to decantation was repeated twice thereafter.

After the above-described repeated operation, the contents of the beaker were filtered. And after fully drying the filtrate, the specific surface area was calculated | required by the BET 1-point method using the canta soap by Yuasa Ionics. As a result, the BET specific surface area of the composite graphite particles after the ultrasonic treatment was 3.81 m ² / g (see Table 2). That is, the ratio of the BET specific surface area before the ultrasonic treatment to the BET specific surface area after the ultrasonic treatment was 1.14 (see Table 2).

(3) Battery characteristics evaluation (3-1) Electrode preparation After mixing CMC (carboxymethylcellulose sodium) powder with the composite graphite particles described above, and adding an aqueous dispersion of SBR (styrene-butadiene rubber) to the mixed powder The mixture was stirred to obtain an electrode mixture slurry. Here, CMC and SBR are binders. The compounding ratio of the composite graphite particles, CMC and SBR was 98.0: 1.0: 1.0 by mass ratio. The solid content concentration of this electrode mixture slurry was 55.7% by mass. Then, this electrode mixture slurry was applied onto a copper foil (current collector) having a thickness of 17 μm by a doctor blade method (the coating amount was 10 to 11 mg / cm ² ). After drying the coating solution to obtain a coating film, the coating film was punched into a disk shape having a diameter of 13 mm. Thereafter, the disk was pressed with a press molding machine so that the density of the disk was 1.60 g / cm ³ , thereby producing an electrode.

(3-2) Battery Preparation An electrode assembly was prepared by disposing the above electrode and a counter Li metal foil on both sides of a polyolefin separator. And the electrolyte solution was inject | poured in the inside of the electrode assembly, and the coin type non-aqueous test cell was produced. The composition of the electrolytic solution was ethylene carbonate (EC): ethyl methyl carbonate (EMC): dimethyl carbonate (DMC): vinylene carbonate (VC): fluoroethylene carbonate (FEC): LiPF ₆ = 23: 4: 48: 1: 8 : 16 (mass ratio).

[Correction 21.05.2013 based on Rule 91]
(3-3) Evaluation of discharge capacity, charge / discharge efficiency and charge / discharge cycle In this non-aqueous test cell at an environmental temperature of 23 ° C., first, a potential difference of 0 (zero) with respect to the counter electrode at a current value of 0.325 mA After constant current doping until V is reached (equivalent to insertion of lithium ions into the electrode and charging of the lithium ion secondary battery), while maintaining 0 V, the constant electrode is doped with constant voltage until 5 μA Then, the doping capacity was measured. Next, dedoping (corresponding to detachment of lithium ions from the electrode and discharging of the lithium ion secondary battery) was performed at a constant current of 0.325 mA until the potential difference became 1.5 V, and the dedoping capacity was measured. The doping capacity and the dedoping capacity at this time correspond to the charging capacity and discharging capacity when this electrode is used as the negative electrode of the lithium ion secondary battery, and these were used as the charging capacity and discharging capacity. The discharge capacity of the non-aqueous test cell according to this example was 367 mAh / g (see Table 2). Since the ratio of dedoping capacity / doping capacity corresponds to the ratio of discharge capacity / charge capacity of the lithium ion secondary battery, this ratio was defined as charge / discharge efficiency. The charge / discharge efficiency of the non-aqueous test cell according to this example was 93.3% (see Table 2).

Cycle characteristics were measured using a coin-type non-aqueous test cell configured in the same manner as described above. In this test cell, the above-described charging / discharging was performed, and from this, a “discharge capacity at the first dedoping” was obtained. Subsequently, after doping with a constant current of 1.56 mA until the potential difference became 5 mV with respect to the counter electrode (corresponding to charging), doping was continued at a constant voltage until 50 μA was maintained while maintaining 5 mV. Next, undoping was performed at a constant current of 1.56 mA until the potential difference became 1.5 V (corresponding to discharge), and the dedoping capacity was measured. The dedope capacity at this time was defined as the discharge capacity.

Doping and dedoping are repeated 49 times under the same conditions as described above, and the cycle characteristics are determined by the ratio (capacity maintenance ratio) of "discharge capacity at undoping in the 49th cycle" to "discharge capacity at undoping at the first cycle". Evaluated. If this capacity maintenance rate is 90% or more, it can be regarded as a good practical battery. The capacity maintenance rate of the non-aqueous test cell according to this example was 94.6% (see Table 2).

Smoothed spherical natural graphite powder so that the mass ratio of smoothed spherical natural graphite powder and acetylene black is 100.0: 1.0 in “(2) Composite of smoothed spherical natural graphite powder and acetylene black” And acetylene black are mixed so that the mass ratio of primary composite powder to coal-based pitch powder is 101.0: 2.0 in “(3) Composite of primary composite powder and non-graphitic carbon”. Except for mixing the primary composite powder and the coal-based pitch powder, the target composite graphite particles were obtained in the same manner as in Example 1, and the characteristics of the composite graphite particles were evaluated in the same manner as in Example 1. The mass ratio of the smoothed spherical natural graphite powder, acetylene black and non-graphitic carbon in the composite graphite particles was 98.0: 1.0: 1.0 (see Table 1).

The average particle size of the composite graphite particles was 19.5 μm (see Table 1). The BET specific surface area before ultrasonic treatment of the composite graphite particles was 4.54 m ² / g (see Table 2), and the BET specific surface area after ultrasonic treatment of the particles was 3.73 m ² / g ( (See Table 2). That is, the ratio of the BET specific surface area before the ultrasonic treatment to the BET specific surface area after the ultrasonic treatment was 1.22 (see Table 2). The solid content concentration of the electrode mixture slurry was 55.1% by mass (see Table 2). The discharge capacity of the non-aqueous test cell was 365 mAh / g (see Table 2), the charge / discharge efficiency was 92.8% (see Table 2), and the capacity retention rate was 98.6% (see Table 2). ).

Smoothed spherical natural graphite powder so that the mass ratio of smoothed spherical natural graphite powder and acetylene black is 100.0: 1.5 in “(2) Composite of smoothed spherical natural graphite powder and acetylene black” And acetylene black are mixed so that the mass ratio of primary composite powder and coal-based pitch powder is 101.5: 2.0 in “(3) Composite of primary composite powder and non-graphitic carbon”. Except for mixing the primary composite powder and the coal-based pitch powder, the target composite graphite particles were obtained in the same manner as in Example 1, and the characteristics of the composite graphite particles were evaluated in the same manner as in Example 1. The mass ratio of the smoothed spherical natural graphite powder, acetylene black and non-graphitic carbon in the composite graphite particles was 97.5: 1.5: 1.0 (see Table 1).

The average particle size of the composite graphite particles was 19.5 μm (see Table 1). The BET specific surface area before ultrasonic treatment of the composite graphite particles was 4.67 m ² / g (see Table 2), and the BET specific surface area after ultrasonic treatment of the particles was 3.48 m ² / g ( (See Table 2). That is, the ratio of the BET specific surface area before the ultrasonic treatment to the BET specific surface area after the ultrasonic treatment was 1.34 (see Table 2). The solid content concentration of the electrode mixture slurry was 53.9% by mass (see Table 2). The discharge capacity of the non-aqueous test cell was 364 mAh / g (see Table 2), the charge / discharge efficiency was 92.5% (see Table 2), and the capacity retention rate was 99.3% (see Table 2). ).

Smoothed spherical natural graphite powder so that the mass ratio of smoothed spherical natural graphite powder and acetylene black is 100.0: 2.0 in “(2) Composite of smoothed spherical natural graphite powder and acetylene black” And acetylene black are mixed so that the mass ratio of primary composite powder to coal-based pitch powder is 102.0: 2.0 in “(3) Composite of primary composite powder and non-graphitic carbon”. The target composite graphite particles were obtained in the same manner as in Example 1 except that the primary composite powder and the coal-based pitch powder were mixed together, and the characteristics of the composite graphite particles were evaluated in the same manner as in Example 1. . The mass ratio of the smoothed spherical natural graphite powder, acetylene black and non-graphitic carbon in the composite graphite particles was 97.1: 1.9: 1.0 (see Table 1).

The average particle size of the composite graphite particles was 19.6 μm (see Table 1). The BET specific surface area before ultrasonic treatment of the composite graphite particles was 4.94 m ² / g (see Table 2), and the BET specific surface area after ultrasonic treatment of the particles was 3.40 m ² / g ( (See Table 2). That is, the ratio of the BET specific surface area before the ultrasonic treatment to the BET specific surface area after the ultrasonic treatment was 1.45 (see Table 2). The solid content concentration of the electrode mixture slurry was 53.0% by mass (see Table 2). The discharge capacity of the non-aqueous test cell was 362 mAh / g (see Table 2), the charge / discharge efficiency was 91.9% (see Table 2), and the capacity retention rate was 99.5% (see Table 2). ).

Smoothed spherical natural graphite powder so that the mass ratio of smoothed spherical natural graphite powder and acetylene black is 100.0: 1.0 in “(2) Composite of smoothed spherical natural graphite powder and acetylene black” And acetylene black are mixed so that the mass ratio of the primary composite powder to the coal-based pitch powder is 101.0: 10.0 in “(3) Composite of primary composite powder and non-graphitic carbon”. Except for mixing the primary composite powder and the coal-based pitch powder, the target composite graphite particles were obtained in the same manner as in Example 1, and the characteristics of the composite graphite particles were evaluated in the same manner as in Example 1. The mass ratio of the smoothed spherical natural graphite powder, acetylene black and non-graphitic carbon in the composite graphite particles was 94.3: 0.9: 4.8 (see Table 1).

The average particle size of the composite graphite particles was 19.7 μm (see Table 1). The BET specific surface area before ultrasonic treatment of the composite graphite particles was 1.60 m ² / g (see Table 2), and the BET specific surface area after ultrasonic treatment of the particles was 1.40 m ² / g ( (See Table 2). That is, the ratio of the BET specific surface area before the ultrasonic treatment to the BET specific surface area after the ultrasonic treatment was 1.14 (see Table 2). The solid content concentration of the electrode mixture slurry was 54.9% by mass (see Table 2). The discharge capacity of the non-aqueous test cell was 355 mAh / g (see Table 2), the discharge efficiency was 92.3% (see Table 2), and the capacity retention rate was 97.4% (see Table 2). .

Smoothed spherical natural graphite powder so that the mass ratio of smoothed spherical natural graphite powder and acetylene black is 100.0: 1.0 in “(2) Composite of smoothed spherical natural graphite powder and acetylene black” And acetylene black are mixed so that the mass ratio of primary composite powder and coal-based pitch powder is 101.0: 20.0 in “(3) Composite of primary composite powder and non-graphitic carbon”. Except for mixing the primary composite powder and the coal-based pitch powder, the target composite graphite particles were obtained in the same manner as in Example 1, and the characteristics of the composite graphite particles were evaluated in the same manner as in Example 1. The mass ratio of the smoothed spherical natural graphite powder, acetylene black and non-graphitic carbon in the composite graphite particles was 90.0: 0.9: 9.1 (see Table 1).

The average particle size of the composite graphite particles was 19.9 μm (see Table 1). The BET specific surface area of the composite graphite particles before ultrasonication was 1.00 m ² / g (see Table 2), and the BET specific surface area of the particles after ultrasonic treatment was 0.90 m ² / g ( (See Table 2). That is, the ratio of the BET specific surface area before the ultrasonic treatment to the BET specific surface area after the ultrasonic treatment was 1.11 (see Table 2). The solid content concentration of the electrode mixture slurry was 55.3 mass% (see Table 2). The discharge capacity of the non-aqueous test cell was 340 mAh / g (see Table 2), the discharge efficiency was 91.9% (see Table 2), and the capacity retention rate was 94.2% (see Table 2). .

Smoothed spherical natural graphite powder so that the mass ratio of smoothed spherical natural graphite powder and acetylene black is 100.0: 0.2 in “(2) Composite of smoothed spherical natural graphite powder and acetylene black” And acetylene black are mixed so that the mass ratio of primary composite powder to coal-based pitch powder is 100.2: 2.0 in “(3) Composite of primary composite powder and non-graphitic carbon”. Except for mixing the primary composite powder and the coal-based pitch powder, the target composite graphite particles were obtained in the same manner as in Example 1, and the characteristics of the composite graphite particles were evaluated in the same manner as in Example 1. The mass ratio of the smoothed spherical natural graphite powder, acetylene black and non-graphitic carbon in the composite graphite particles was 98.8: 0.2: 1.0 (see Table 1).

The average particle size of the composite graphite particles was 19.6 μm (see Table 1). The BET specific surface area before ultrasonic treatment of the composite graphite particles was 3.98 m ² / g (see Table 2), and the BET specific surface area after ultrasonic treatment of the particles was 3.66 m ² / g ( (See Table 2). That is, the ratio of the BET specific surface area before the ultrasonic treatment to the BET specific surface area after the ultrasonic treatment was 1.09 (see Table 2). The solid content concentration of the electrode mixture slurry was 56.6% by mass (see Table 2). The discharge capacity of the non-aqueous test cell was 367 mAh / g (see Table 2), the discharge efficiency was 93.5% (see Table 2), and the capacity retention rate was 84.6% (see Table 2). .

Smoothed spherical natural graphite powder so that the mass ratio of smoothed spherical natural graphite powder and acetylene black is 100.0: 3.0 in “(2) Composite of smoothed spherical natural graphite powder and acetylene black” And acetylene black are mixed so that the mass ratio of primary composite powder to coal-based pitch powder is 103.0: 2.0 in “(3) Composite of primary composite powder and non-graphitic carbon”. Except for mixing the primary composite powder and the coal-based pitch powder, the target composite graphite particles were obtained in the same manner as in Example 1, and the characteristics of the composite graphite particles were evaluated in the same manner as in Example 1. The mass ratio of the smoothed spherical natural graphite powder, acetylene black and non-graphitic carbon in the composite graphite particles was 96.1: 2.9: 1.0 (see Table 1).

The average particle size of the composite graphite particles was 19.6 μm (see Table 1). The BET specific surface area before ultrasonic treatment of the composite graphite particles was 5.44 m ² / g (see Table 2), and the BET specific surface area after ultrasonic treatment of the particles was 3.48 m ² / g ( (See Table 2). That is, the ratio of the BET specific surface area before ultrasonic treatment to the BET specific surface area after ultrasonic treatment was 1.56 (see Table 2). The solid concentration of the electrode mixture slurry was 51.4% by mass (see Table 2). The discharge capacity of the non-aqueous test cell was 359 mAh / g (see Table 2), the discharge efficiency was 91.2% (see Table 2), and the capacity retention rate was 99.7% (see Table 2). .

“(1) Smoothing of spherical natural graphite powder” is not performed, and the smoothed spherical natural graphite powder is replaced with spherical natural graphite powder in “(2) Compounding of smoothed spherical natural graphite powder and acetylene black”. The smoothed spherical natural graphite powder and acetylene black were mixed so that the mass ratio of the spherical natural graphite powder and acetylene black was 100.0: 1.0, and “(3) primary composite powder and non-graphitic carbon were mixed. Except that the primary composite powder and the coal-based pitch powder were mixed so that the mass ratio of the primary composite powder and the coal-based pitch powder was 101.0: 2.0 Thus, the target composite graphite particles were obtained, and the characteristics of the composite graphite particles were evaluated in the same manner as in Example 1. The mass ratio of the spherical natural graphite powder, acetylene black, and non-graphitic carbon in the composite graphite particles was 98.0: 1.0: 1.0 (see Table 1).

The average particle size of the composite graphite particles was 19.5 μm (see Table 1). BET specific surface area before sonication composite graphite particles is 4.50 m ² / g (see Table 2), the BET specific surface area after sonication of the same particles was 4.15m ² / g ( (See Table 2). That is, the ratio of the BET specific surface area before ultrasonic treatment to the BET specific surface area after ultrasonic treatment was 1.08 (see Table 2). The solid content concentration of the electrode mixture slurry was 55.3 mass% (see Table 2). The discharge capacity of the non-aqueous test cell was 365 mAh / g (see Table 2), the discharge efficiency was 98.5% (see Table 2), and the capacity retention rate was 86.3% (see Table 2). .

(Comparative Example 1)
“(2) Smoothing spherical natural graphite powder and acetylene black are not composited”, and “(3) Primary composite powder and non-graphitic carbon are composited”. The control was carried out in the same manner as in Example 1 except that the smoothed spherical natural graphite powder and the coal-based pitch powder were mixed so that the mass ratio with the powder (average particle size 20 μm) was 100.0: 2.0. A powder was obtained, and the control powder was evaluated in the same manner as in Example 1. In this control powder, the mass ratio of the smoothed spherical natural graphite powder, acetylene black and non-graphitic carbon was 99.0: 0.0: 1.0 (see Table 1).

The average particle size of the composite graphite particles was 19.6 μm (see Table 1). The BET specific surface area before ultrasonic treatment of the composite graphite particles was 3.83 m ² / g (see Table 2), and the BET specific surface area after ultrasonic treatment of the particles was 3.60 m ² / g ( (See Table 2). That is, the ratio of the BET specific surface area before ultrasonic treatment to the BET specific surface area after ultrasonic treatment was 1.06 (see Table 2). The solid content concentration of the electrode mixture slurry was 57.2% by mass (see Table 2). The discharge capacity of the non-aqueous test cell was 367 mAh / g (see Table 2), the discharge efficiency was 93.9% (see Table 2), and the capacity retention rate was 78.8% (see Table 2). .

(Comparative Example 2)
Smoothed spherical natural graphite powder so that the mass ratio of smoothed spherical natural graphite powder and acetylene black is 100.0: 1.0 in “(2) Composite of smoothed spherical natural graphite powder and acetylene black” And acetylene black were mixed, and a control powder was obtained in the same manner as in Example 1 except that “(3) Composite of primary composite powder and non-graphitic carbon” was not performed. The control powder was characterized. The mass ratio of the smoothed spherical natural graphite powder, acetylene black and non-graphitic carbon in this control powder was 99.0: 1.0: 0.0 (see Table 1).

The average particle size of the composite graphite particles was 19.5 μm (see Table 1). The BET specific surface area of the composite graphite particles before ultrasonic treatment was 6.80 m ² / g (see Table 2), and the BET specific surface area of the particles after ultrasonic treatment was 5.48 m ² / g ( (See Table 2). That is, the ratio of the BET specific surface area before ultrasonic treatment to the BET specific surface area after ultrasonic treatment was 1.24 (see Table 2). The solid content concentration of the electrode mixture slurry was 57.2% by mass (see Table 2). The discharge capacity of the non-aqueous test cell was 364 mAh / g (see Table 2), the discharge efficiency was 89.8% (see Table 2), and the capacity retention rate was 98.3% (see Table 2). .

From the above results, in the composite graphite particles according to the present invention, when the ratio of the BET specific surface area before ultrasonic treatment to the BET specific surface area after ultrasonic treatment is 1.10 or more, the capacity retention rate is at a high level. It was found to be maintained. It was also found that the larger the mass ratio of acetylene black to non-graphitic carbon, the greater the ratio of the BET specific surface area before ultrasonic treatment to the BET specific surface area after ultrasonic treatment.

In Japanese Patent Laid-Open No. 2004-066331, the ratio of the discharge capacity of the 10th cycle to the discharge capacity of the 1st cycle is expressed as a percentage as an evaluation index of charge / discharge cycle characteristics. As the performance of secondary batteries increases, evaluation of discharge capacity of about 10 cycles is not sufficient for practical use.

The non-aqueous test cell according to this example (hereinafter referred to as “non-aqueous test cell of the present application”) has a non-aqueous test cell (hereinafter referred to as “conventional non-aqueous test cell”) disclosed in Japanese Patent Application Laid-Open No. 2004-066331. It is difficult to simply compare the two non-aqueous test cells, but the non-aqueous test cell of the present application is more severe than the conventional non-aqueous test cell. Since the charge / discharge cycle characteristics are evaluated, it is considered that the non-aqueous test cell of the present application is superior in charge / discharge cycle characteristics than the conventional non-aqueous test cell.

Claims (10)

1. Graphite,
   Conductive carbonaceous fine particles directly attached to the graphite;
   Composite graphite particles comprising the conductive carbonaceous fine particles and non-graphitic carbon that adheres at least partially to the graphite.
2. The composite graphitic particles according to claim 1, wherein a part or all of the conductive carbonaceous fine particles are detached from the graphite when a predetermined external force is applied.
3. The ratio of the “specific surface area value before the external force is applied (m ² / g)” to the “specific surface area value after the external force is applied (m ² / g)” is 1.10 or more. 2. Composite graphite particles described in 1.
4. The graphite is spherical, has a circularity of 0.92 or more, and an incident angle dependency S _60/0 of a peak intensity ratio in a _CK edge X-ray absorption spectrum is 0.7 or less. 4. The composite graphite particle according to any one of 3.
5. The mass ratio of the conductive carbonaceous fine particles to the graphite is in the range of 0.3% to 2.0%,
   The composite graphite according to any one of claims 1 to 4, wherein a mass ratio of the non-graphitic carbon to a sum of the graphite and the conductive carbonaceous fine particles is in a range of 0.8% to 15.0%. Particle.
6. A primary composite particle preparation step of preparing primary composite particles by directly attaching conductive carbonaceous fine particles to graphite;
   A method for producing composite graphite particles, comprising: a composite graphite particle preparation step of preparing composite graphite particles by partially or entirely attaching non-graphitic carbon to the primary composite particles.
7. The method for producing composite graphite particles according to claim 6, wherein in the composite graphite particle preparation step, the primary composite particles and the non-graphitic carbon raw material powder are mixed and then heated.
8. Composite graphite particles obtained by the method for producing composite graphite particles according to claim 6 or 7.
9. An electrode using the composite graphite particles according to any one of claims 1, 2, 3, 4, 5, and 8 as an active material.
10. A nonaqueous electrolyte secondary battery comprising the electrode according to claim 9.

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