JP2003119014A - Reformed graphite particle, production method therefor, and electrode material for secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide reformed graphite particles with a special particle structure which have more improved performance as that of an electrode material for a secondary battery by further improving the spheroidized reformed particles shown in No.1999-263612 in published application by the applicant, to provide a production method therefor, and to provide an electrode material for a secondary battery consisting of the reformed graphite particles obtained thereby. SOLUTION: Raw material particles (x) consisting of flaky graphite particles or the particles obtained by reforming the same particles are mixed with raw material spheroidized particles (y) with a cabbagelike appearance in which graphite cut pieces go toward various directions by microscopic observation in the broken-out section, and they are collided in a flowing state. Thus, the spheroidized particles with a structure where small-sized graphidized particles (a) with a cabbagelike apparance in which graphite cut pieces go toward various directions by microscopic observation in the broken-out section are numerously contained in the internal gaps can be obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a modified graphite particle having a special particle structure and having excellent secondary battery performance when used as an electrode material for a secondary battery, and a method for producing the same. Is. The present invention also relates to an electrode material for a secondary battery using the modified graphite particles obtained in this way.

[0002]

2. Description of the Related Art In recent years, from the viewpoint of miniaturization of electronic equipment, high-capacity batteries replacing lead-acid batteries and nickel-cadmium batteries, especially lithium-ion secondary batteries, have been attracting attention and put to practical use. Among them, the one using a carbon material for the negative electrode is advantageous in terms of high safety, high capacity, high voltage, etc., and these materials are used as the material for the negative electrode.

Natural graphite and artificial graphite can be used as an electrode material for secondary batteries, especially as a negative electrode material for lithium ion secondary batteries. In particular, scaly natural graphite is suitable for this purpose.

When scaly natural graphite is used for this purpose, it is often the case that scaly natural graphite is mixed with a solvent and a binder to form a slurry, which is then applied to an object. In this case, since the scaly natural graphite literally has a scaly (plate-like) shape, the fluidity when mixed with a solvent and a binder is poor, and it is necessary to use a large amount of solvent to obtain a predetermined viscosity. In some cases, a coating layer having a predetermined thickness cannot be formed. Therefore, in order to improve the fluidity, conventionally, a method of pulverizing to a particle size of several μm, a method of adding various surfactants to ensure fluidity, a method of vigorous stirring for a long time, etc. have been adopted. Was there.

However, in the method of finely pulverizing the scaly natural graphite in order to secure the fluidity, it is actually not easy to set the particle size to 5 μm or less because the graphite is slippery, and more than that. The effect of improving liquidity is small. Then, depending on the application, there is a limit to making the particle diameter excessively small, but in such a case, it cannot be dealt with. Although the addition of a surfactant is effective in improving the fluidity, it is often difficult to balance the selection of the surfactant and the mixing amount thereof, and it is often difficult to maintain the optimum state. Further, the addition of the surfactant is limited depending on the application, which makes it unsuitable for such application. The method of improving fluidity by vigorous stirring for a long time requires time and labor, which is unavoidable from an industrial disadvantage, and that the fluidity required cannot be obtained even by vigorous stirring for a long time. There are many.

[0006] Therefore, the applicant of the present invention, while maintaining the goodness of the raw material flake-like natural graphite particles, modified it,
We have proposed flake-shaped natural graphite modified particles consisting of spherical particles with unique structure and properties. That is, Japanese Patent Laid-Open No. 11-263612 discloses a spherical particle obtained by modifying scaly natural graphite particles so as to approximate a spherical shape, and the spherical particle has a circularity of 0.86 or more, In the microscopic observation of the fracture surface, the graphite slices have a cabbage-like appearance facing various directions, and the 002 plane (with the graphite layer) by X-ray diffraction (reflection method), which is an index of orientation randomness. Horizontal surface) and 110 surface (surface vertical to the graphite layer)
Peak intensity ratio Ih ₁₁₀ / Ih ₀₀₂ is 0.0050
The scaly natural graphite-modified particles satisfying all the above requirements are disclosed.

[0007]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
The scale-like natural graphite-modified particles disclosed in Japanese Patent No. 63612,
When this is used as an electrode material for a secondary battery, due to its unique structure, it has properties of good slurry characteristics and small reduction in discharge capacity at large discharge current values.

However, the scaly natural graphite-modified particles have a unique structure in which the graphite pieces have a cabbage-like appearance in various directions. It was found that voids composed of a plurality of graphite layers were generated, and the performance as an electrode material for a secondary battery had a certain limit.

Under such a background, the present invention further improves the spheroidized modified particles disclosed in Japanese Patent Application Laid-Open No. 11-263612 of the applicant of the present invention.
PROBLEM TO BE SOLVED: To provide a modified graphite particle having a special particle structure with further improved performance as an electrode material for a secondary battery and a method for producing the same, and a secondary battery comprising the modified graphite particle thus obtained. The purpose is to provide a material for electrodes.

[0010]

The modified graphite particles of the present invention are spheroidized modified graphite particles obtained by modifying scaly graphite particles so that they are close to spherical, and the spheroidized modified graphite particles are Microscopic observation of fracture surface makes graphite slices in various directions In the internal voids of large spherical particles (A) that have a cabbage-like appearance. It is characterized by having a structure in which a large number of small-diameter spherical particles (a) having an outward cabbage-like appearance are included.

The method for producing modified graphite particles of the present invention is a cabbage in which graphite slices are directed in various directions on a raw material particle (x) made of scaly graphite particles or particles obtained by modifying the scaly graphite particles by observing the fracture surface with a microscope. By mixing the raw material spheroidized particles (y) having a circular appearance and making them collide in a fluidized state, a graphite section has a cabbage-like appearance in which various directions are observed by microscopic observation of the fracture surface. Spheroidized particles having a structure in which a large number of small-sized spherical particles (a) having a cabbage-like appearance in which graphite sections face in various directions by microscopic observation of fracture surfaces are included in the internal voids of the spherical particles (A). It is characterized by obtaining.

The secondary battery electrode material of the present invention is characterized by comprising the above-mentioned modified graphite particles.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.

<Modified Graphite Particles> The modified graphite particles of the present invention are spheroidized modified graphite particles obtained by modifying scaly graphite particles so as to approximate a spherical shape, and have the following special particle structure. . That is, the modified graphite particles of the present invention have a fracture surface in the internal voids of large-diameter spherical particles (A) having a cabbage-like appearance in which graphite sections face in various directions by microscopic observation of the fracture surface. In a microscopic observation, the graphite section has a structure in which a large number of small-sized spherical particles (a) having a cabbage-like appearance in various directions are included.

<Method of Producing Modified Graphite Particles> In the internal voids of the modified graphite particles having the above-mentioned special particle structure, that is, large-diameter spherical particles (A) having a cabbage-like appearance,
The modified graphite particles having a structure in which a large number of small-sized spherical particles (a) having a cabbage-like appearance are included are typically flaky graphite particles or raw material particles (x ) Is mixed with raw material spheroidized particles (y) having a cabbage-like appearance in which the graphite section faces in various directions by microscopic observation of the fracture surface, and the particles are collided in a fluidized state.

First, as the scaly graphite particles which are the raw material particles (x), scaly natural graphite is preferably used.
Since the flake-like natural graphite is usually available in a purity of 85% to 99% or more, the purity can be further increased by an appropriate means if necessary. The particle size of the flake graphite particles cannot be unconditionally determined because it depends on the application, but when used as an electrode material of a secondary battery, the average particle size is about 1 to 200 μm, particularly about 10 to 100 μm. Often. As the flake graphite particles that are the raw material particles (x), flake artificial graphite can also be used.

As the raw material particles (x), in addition to the scaly graphite particles, scaly graphite particles obtained by spheroidizing and modifying by any method can be used.

Next, the raw material spheroidized particles (y) having a cabbage-like appearance in which the graphite sections face in various directions by microscopic observation of the fracture surface are obtained by using scaly graphite particles as a raw material. It can be obtained by carrying out the method disclosed in JP-A No. 11-263612 or a method similar thereto.

That is, using a tank (1) having a collision area and a flow area where jet streams collide with each other, flake graphite particles as a raw material are charged from the feeder (2) into the tank (1) and the tank ( By injecting a jet stream from a counter nozzle (3) provided on the lower side of 1), particles collide with each other in the lower collision area of the tank (1), and the upper flow area of the tank (1). Then, the particles are circulated and flowed, while fine powder below the classification limit is discharged to the outside of the tank by a classifier (4) provided in the upper part of the tank (1). This operation is preferably performed in batch. As a result, spheroidized particles (y) having a cabbage-like appearance in which the graphite sections are oriented in various directions can be obtained by microscopic observation of the fracture surface. This method will be described in more detail with reference to FIG. 1 described later.

As the above-mentioned tank (1), for example, a fluidized bed type counter jet mill available on the market can be diverted,
It can be used by improving it for the purpose of the present invention. From the feeder (2), flake graphite particles as a raw material are charged into the tank (1). The feeder (2)
The hopper type is preferably installed at an appropriate place in the tank (1), and in that case, the feeder (2) can be used as an outlet for the spheroidized graphite particles (y). Further, the feeder (2) can be provided in the lower part of the tank (1) as a screw type. The amount of the flake graphite particles as a raw material charged into the tank (1) is determined in consideration of the effective space of the tank (1), but not so strict. However, when the charged amount is extremely small, the particles do not flow smoothly, and when the charged amount is extremely large, the particles are excessively crushed and it is difficult to obtain the target raw material spherical particles (y). Become.

A counter nozzle (3) is provided on the lower side of the tank (1) so as to penetrate the tank wall, and a jet stream is blown from the counter nozzle (3) to collide with the lower collision area in the tank (1). Then, the particles that have entered the airflow collide with each other. It is preferable to dispose a plurality of counter nozzles (3), especially three nozzles. The velocity of the jet stream blown from the opposed nozzle (3), the amount of blown gas, the tank pressure, etc. are set so that smooth collision and flow can be achieved, and the desired degree of spheroidization can be achieved by appropriately setting the operation time. Be prepared.

Particles collide with each other in the lower collision area of the tank (1), but circulating flow of particles occurs in the upper flow area of the tank (1). In the steady state, the particles generally blow up in the center of the tank (1) and descend along the wall of the tank (1).

A classifier (4) is provided above the tank (1),
Discharge fine powder below the classification limit to the outside of the tank. Classifier (4)
Usually uses a high-speed rotary classifier. The amount discharged at this time varies depending on the particle size of the flake graphite particles as a raw material.

The above operation is preferably performed in batch. The operation was carried out continuously like ordinary jet mill crushing, the flake graphite particles as the raw material were continuously supplied, and the crushed particles were continuously taken out from the upper part of the tank. The compound particles (y) cannot be obtained.

By performing the above operation under controlled conditions, the raw material spherical particles (y) can be obtained. The particle size of the raw material spherical particles (y) is about 1 to 200 μm in average particle diameter,
Especially, it is often about 10 to 100 μm. The raw material spherical particles (y) are the raw material particles (x) described above.
The average particle size should be smaller than that.

In the present invention, the raw material spherical particles (y) (obtained as described above) are added to the raw material particles (x) which are composed of the above-described scaly graphite particles or the spherically modified particles thereof. The raw material spheroidized particles (y) having a cabbage-like appearance in which graphite sections are oriented in various directions by microscopic observation of fracture surfaces are mixed and collided in a fluidized state.

The conditions at this time can be the same as in the above-mentioned method for producing the raw material spherical particles (y). However, a mixture of the raw material particles (x) and the raw material spherical particles (y) is used instead of the flaky graphite particles that are the raw material when the raw material spherical particles (y) are obtained. The tank (1) may be charged after mixing both, or may be charged separately.

When the total amount of the raw material particles (x) and the raw material spherical particles (y) is 100 parts by weight, the raw material particles (x) are 95-40 parts by weight (preferably 9 parts by weight).
0 to 45 parts by weight) and the raw material spherical particles (y) are preferably 5 to 60 parts by weight (preferably 10 to 55 parts by weight). When the amount of the raw material particles (x) is excessive (the amount of the raw material spheroidized particles (y) is insufficient), the voids inside the target modified graphite particles are not sufficiently filled, and thus the conductivity tends to be insufficient. On the other hand, if the amount of raw material particles (x) is too small (the amount of raw material spherical particles (y) is too large), there is still excess even if the voids are filled. There is a possibility that physical properties such as a decrease in the particle size of the fine graphite particles may be significantly changed.

In this way, the microscopic observation of the fractured surface is observed in the internal voids of the large-diameter spherical particles (A) having a cabbage-like appearance in which the graphite section faces in various directions in the microscopic observation of the fractured surface. It is possible to obtain spheroidized particles (modified graphite particles) in which a large number of small-diameter spheroidized particles (a) having a cabbage-like appearance in which the graphite pieces are oriented in various directions are included.
The average particle size of the spherical particles (modified graphite particles) is about 1 to 200 μm, preferably about 10 to 100 μm. Spherical particles (modified graphite particles)
The particle size of can be adjusted arbitrarily by a classification operation.

<Use, secondary battery electrode material, secondary battery>
The modified graphite particles thus obtained are useful as an electrode material for a secondary battery, particularly as a negative electrode material for a lithium ion secondary battery. In addition to a negative electrode material for lithium ion secondary batteries, it can also be used as an electrode material for polymer batteries (paper batteries) and the like. Not limited to such electrode materials, it can be used for various applications such as conductive paints, sliding materials for brake discs, and particles of electrorheological fluid.

Examples of the positive electrode material in the lithium ion secondary battery include modified MnO _{2, LiCoO 2} and L.
iNiO ₂ , LiNi _1-y Co _y O ₂ , LiMn
O ₂ , LiMn ₂ O ₄ , LiFeO ₂ or the like is used. As the electrolytic solution, for example, an organic solvent such as ethylene carbonate or a low boiling point solvent such as dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxymethane or ethoxymethoxyethane. LiPF ₆ , Li in the mixed solvent
A solution in which an electrolytic solution solute such as BF ₄ , LiClO ₄ , or LiCF ₃ SO ₃ is dissolved is used.

The charging / discharging reaction in the case of a lithium ion secondary battery is as follows (reaction from left side to right side is charging reaction, reaction from right side to left side is discharging reaction), and lithium ion is positive electrode and negative electrode. Go back and forth between C + LiCoO ₂ = CLi _x + Li _1-x CoO ₂
(0 <X <1)

<Function> The modified graphite particles (spherical particles) of the present invention are large-diameter spherical particles (having a cabbage-like appearance in which graphite sections are oriented in various directions by microscopic observation of fracture surfaces ( It has a peculiar structure in which a large number of small spherical particles (a) having a cabbage-like appearance in which graphite sections face in various directions by microscopic observation of fracture surfaces are included in the internal voids of A). .

Due to the unique particle structure, the void volume of particles, the density of particles, and the hardness of particles are controlled within the optimum ranges, and the modified graphite particles (spherical particles) of the present invention are used for secondary batteries. When used as an electrode material (particularly, a negative electrode material for lithium ion secondary batteries) of JP-A-11-26361
Compared with the modified graphite particles disclosed in Japanese Patent Publication No. 2, the conductivity and the cycle characteristics are further improved, and the particles are less likely to be crushed when they are made into an electrode plate, so that the absorption of the electrolytic solution is improved. Also, the load characteristics are improved.

[0035]

EXAMPLES The present invention will be further described with reference to examples. Hereinafter, "parts" means "parts by weight".

(Manufacturing Device) FIG. 1 is a schematic view of a manufacturing device for spherical particles. This test device consists of a cylindrical tank (1), and on the lower side of the tank (1) are three opposed nozzles (3).
(Nozzle inner diameter 2.5 mm) is arranged so as to face the center (only one of them is shown in FIG. 1), and as an example of a classifier (4) at the top of the tank (1) The high-speed rotary classifier is installed. The feeder (2) is provided on the side wall of the tank (1), and the blowing nozzle (5) is provided at the bottom of the tank (1).

(Production of Spherical Particles) Scale-like natural graphite produced in China (particle size: 100 mesh, 90% or more passed, purity: 9
(9% or more) was pulverized with a counter type jet mill until the average particle size became 60 μm, and subjected to high purification treatment with a purity of 99.9% or more, and then used as raw material flake graphite particles. .

The scaly graphite particles were charged into the tank (1) from the feeder (2), and air was blown from each of the three opposed nozzles (3) to modify the particles for a predetermined time. Meanwhile, from the classifier (4) installed at the top,
Along with the exhaust of the blown air, fine powder of about 5 μm or less was discharged. The conditions during the modification process were set as follows. Raw material charge: 200 g Nozzle discharge air pressure: 0.13 MPa Operating time: 30 min

After the above operation, the particles were taken out of the tank (1) and classified to obtain spherical particles having an average particle diameter of 10 μm, which were used as the raw spherical graphite particles (y).

Examples 1 to 3 and Comparative Example 1 (Production of Modified Graphite Particles) As raw material particles (x), the same average particle diameter of 60 μm as that of the raw flake graphite particles used in the production of the above spheroidized particles was used. Particles were used. Then, the raw material particles (x) were mixed with the spherical particles (raw material spherical particles (y)) having an average particle diameter of 10 μm obtained above.
The mixing ratio of (x) :( y) is 50 parts: 50 parts (Example 1), 70 parts: 30 parts (Example 2), 85 parts: 15 parts (Example 3), 100 parts: 0 parts. It was set to (Comparative Example 1).

The modification operation was carried out under the same conditions as in the production of the spheronized particles described above, except that these mixtures were used. The spheroidized particles (modified graphite particles) after the completion of the modification process were taken out of the tank (1), and a classification operation was performed to make the particle sizes uniform, to obtain a sample having an average particle size of 44 μm.

(Appearance) The fractured surfaces of the obtained spherical particles (modified graphite particles) were observed with a microscope. That is,
Fix spherical particles (modified graphite particles) with epoxy resin,
After freezing and solidifying with liquid nitrogen, it fractured and the fracture surface was judged by a micrograph.

The spheroidized particles (modified graphite particles) obtained in Examples 1 to 3 all had a cabbage-like appearance in which the graphite sections were oriented in various directions by microscopic observation of fracture surfaces. Having a structure in which a large number of small-sized spherical particles (a) having a cabbage-like appearance in which graphite sections face in various directions by microscopic observation of fracture surfaces are included in the internal voids of the spherical particles (A) Was there. FIG. 2 shows a micrograph of the spherical particles (modified graphite particles) obtained in Example 1. The magnification is 2000 times.

On the other hand, the spheroidized particles (modified graphite particles) obtained in Comparative Example 1 had a cabbage-like appearance in which graphite sections were oriented in various directions by microscopic observation of fracture surfaces, but many voids were present. Included. FIG. 3 shows a micrograph of the modified graphite particles of Comparative Example 1. The magnification is 2000 times.

The modified graphite particles of each of Examples 1 to 3 and Comparative Example 1 had a cabbage-like appearance in which the graphite pieces were oriented in various directions, and contained the layered structure of scaly natural graphite. , It was common in that the structure was modified to be chimeric. By the way, microscopic observation was also performed on the flaky graphite particles that were the raw material used for the production of the spheroidized particles described in the first operation, but the graphite slices were layered only in almost the same direction. .

(Properties, Electrode Properties) Properties (average particle size, peak intensity ratio, surface area, degree of conductivity (electrical resistance)) and electrodes of the modified graphite particles obtained in Examples 1 to 3 and Comparative Example 1. The performance (discharge capacity, initial efficiency, load characteristics, charging characteristics) was examined. The results are shown separately in Table 1 and Table 2.

[0047]

[Table 1]

[0048]

[Table 2]

(Peak intensity ratio) The peak intensity ratio Ih of the 002 plane (plane parallel to the graphite layer) and the 110 plane (plane perpendicular to the graphite layer) by X-ray diffraction (reflection method), which is an index of orientation randomness. ₁₁₀ / Ih ₀₀₂ (see paragraph 0045 of Japanese Patent Application Laid-Open No. 11-263612) filed by the present applicant.

(Surface area) "AS manufactured by Shimadzu Corporation
AP-2405 ".

(Electrical Resistance) The area of the upper and lower surfaces of the sample was 0.
12 cm ² , height 2 cm, density 1.25 g / cm ³
The molded product is obtained by compression molding into a cylindrical body, and the electrical resistance between the upper and lower surfaces of the molded product is measured.

(Electrode Performance) 100 parts by weight of the negative electrode material, 3 parts by weight of polyvinylidene fluoride as a binder, and an appropriate amount of N-methylpyrrolidone as a solvent were mixed and uniformly stirred in a liquid phase. The obtained slurry was applied onto a copper foil, dried, and then pressure-molded with a press to prepare a negative electrode plate, which was then vacuum dried at 150 ° C. for 6 hours. Next, a lithium foil was pressure-bonded to a stainless steel plate, which was used as a counter electrode via a separator to assemble a bipolar cell. The assembly was performed in a dry box adjusted to have a water content of 20 ppm or less, and 1 M-LiPF ₆ / (EC
+ DEC (1: 1)), that is, LiPF ₆ dissolved in a mixed solvent of ethylene carbonate and diethyl carbonate at a volume ratio of 1: 1 at a ratio of 1M was used.

Charging is performed at 0.2 mA / cm ² (0.05
After charging until the constant current value of C) became 0 V, it was performed at a constant potential of 0 V until the current value became 0.01 mA / cm ² . The discharge was performed at a current value of 0.2 mA / cm ² to 1 V. The initial efficiency (%) = 100 × discharge capacity / charge capacity was calculated from the charge capacity and discharge capacity at the first time of each sample.

The load characteristic is the ratio (%) of the discharge capacity discharged in 30 minutes to the discharge capacity discharged in 10 hours.

The charge characteristic is the ratio (%) of the constant current charge capacity charged in 1 hour to the constant current charge capacity charged in 10 hours.

[0056]

The modified graphite particles of the present invention are basically
Since it has a spherical shape and has a cabbage-like appearance, it should have a viscosity suitable for coating even if the solid content concentration is increased during slurry formation (that is, the amount of solvent used is reduced). In addition, the slurry has good operability, and the coating property and the binding property when the electrode plate is prepared by coating it on a copper foil or the like are easy.

Moreover, the modified graphite particles of the present invention have a large diameter of spherical particles (A) having a cabbage-like appearance in which graphite sections face in various directions by microscopic observation of fracture surfaces. , Small-diameter spherical particles (a) having a cabbage-like appearance in which graphite sections face in various directions by microscopic observation of fracture surfaces
Since it has a special particle structure in which a large number of particles are included, the void volume of particles, the density of particles, and the hardness of particles are controlled within the optimum range, and these modified graphite particles are used as electrodes for secondary batteries. When used as a material (particularly as a negative electrode material for a lithium ion secondary battery), compared with the modified graphite particles disclosed in Japanese Patent Application Laid-Open No. 11-263612, conductivity, load characteristics, cycle characteristics, etc. The performance as an electrode material for secondary batteries is further improved. Furthermore, since the particles are less likely to be crushed when the electrode plate is manufactured, the liquid permeability of the electrolytic solution is improved.

[Brief description of drawings]

FIG. 1 is a schematic view of an apparatus for producing spherical particles.

FIG. 2 is a micrograph of spherical particles (modified graphite particles) obtained in Example 1 (magnification: 2000 times).

FIG. 3 is a micrograph of the modified graphite particles of Comparative Example 1 (magnification: 2000 times).

[Explanation of symbols]

(1) ... tank, (2) ... feeder, (3) ... Counter nozzle, (4) ... Classifier, (5) ... Blow-up nozzle

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Shingo Asada             2-8-6 Tomogaoka, Sanda City, Hyogo Prefecture (72) Inventor Junichi Yasumaru             4-9-9 Tsutsujigaoka Minami, Sanda City, Hyogo Prefecture F-term (reference) 4G046 EA05 EB13 EC02 EC06                 5H050 AA02 AA19 BA17 CA07 CB08                       FA12 FA17 FA19 GA02 GA05                       GA06 HA05 HA13

Claims (3)

[Claims] 1. A sphere-shaped modified graphite particle obtained by modifying scaly graphite particles so as to be closer to a sphere, wherein the sphere-shaped modified graphite particles have graphite slices in various directions observed by a microscopic observation of a fracture surface. In the internal voids of the large-diameter spherical particles (A) having a cabbage-like appearance, a small-diameter spherical particle having a cabbage-like appearance in which the graphite section faces in various directions by microscopic observation of a fracture surface ( Modified graphite particles having a structure including a large number of a). 2. A raw material spherical particle (x) having a cabbage-like appearance in which a graphite section is oriented in various directions by microscopic observation of a fracture surface of a raw material particle (x) composed of scaly graphite particles or modified particles thereof ( By mixing y) and making them collide in a fluidized state, it is possible to observe in a microscopic observation of the fracture surface that the graphite slices have cabbage-like appearances in various directions, into the internal voids of large spherical particles (A). A modified graphite having a structure in which a large number of small-diameter spherical particles (a) having a cabbage-like appearance in which graphite sections face in various directions by microscopic observation of fracture surfaces are obtained. Particle manufacturing method. 3. A secondary battery electrode material comprising the modified graphite particles of claim 1.