JPH08337411A - Graphite particle, its production and lithium ion secondary battery - Google Patents

Abstract

PURPOSE: To make it possible to form an electrode having a high packing density and excellent charging and discharging efficiency by using graphite particles which are spheroidal particles having a diameter within a prescribed range, have a specific grain size distribution curve and has an inter-crystal layer distance and the size of the crystallize in a C-axis direction within a prescribed range as a battery material. CONSTITUTION: This graphite particles are obtd. by subjecting a catalyst metal source component (e.g.: transition metal component) and carbon source component (e.g.: org. compd.) to a thermal decomposition treatment at 950 to 1200 deg.C in an atmosphere of an inert gas (e.g.: hydrogen enriched gas) and contains the transition metal at 100 to 10,000ppm. The diameter of these particles is 0.3 to 3pm; the 50% diameter in the grain size distribution curve is 3 to 60μm; the 10% diameter/50% diameter (ratio) is 0.1 to 0.3; the 90% diameter/50% diameter (ratio) is 2 to 6; the inter-crystal layer distance is 0.337nm at the largest' the size of the crystallite in the C-axis direction is 50nm at the smallest and the specific surface area is <=15m<2> /g. The charging and discharging efficiency is :>=90% initially and is >=95% at the good time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to graphite particles, a method for producing graphite particles, and a lithium ion secondary battery, and more specifically, crystallinity, that is, a crystal interlayer distance (d).
₀₀₂ ) and the crystallite size in the C-axis direction (L _c ), and can be suitably used as a battery material. When used as a battery material, an electrode having a high packing density and excellent charge / discharge efficiency can be obtained. Graphite particles that can be formed, a method that can efficiently and economically produce the graphite particles, and a lithium-ion secondary battery that has a large charge / discharge capacity, high voltage, excellent charge / discharge efficiency, and is safe Regarding

[0002]

2. Description of the Related Art In a lithium ion secondary battery, carbon or graphite is used for the negative electrode, and lithium compounds such as cobalt acid, nickel acid, manganic acid (LiCoO ₂ , LiNiO ₂₎ are used for the positive electrode. , L
iMn ₂ O ₄ ) is used. In this lithium ion secondary battery, lithium ions are inserted between carbon or graphite layers during charging to form an intercalation compound, while lithium ions are released from the carbon or graphite layers during discharging. Due to such a charging / discharging mechanism, the lithium ion secondary battery has the features of large capacity, high voltage, and safety. Therefore, the lithium ion secondary battery is expected to be used in various fields.

By the way, a lithium ion secondary battery using a vapor-grown carbon fiber (hereinafter sometimes referred to as "VGCF") obtained by using a transition metal as a catalyst or a graphite obtained by graphitizing the fiber is used as a negative electrode. It has been reported that the charge and discharge capacity is large and the performance is high. As such a lithium ion secondary battery, for example, JP-A-3-129
No. 664 discloses that the X-ray diffraction peak has a half width of 1 ° or less, specifically a diameter of 1 μm or less and a length of 500 μm.
A lithium ion secondary battery using the following fine fibrous graphite as a negative electrode is described. JP-A-5-182666
The publication describes a lithium ion secondary battery using a flat ribbon-shaped carbon fiber as a negative electrode. JP-A-6
JP-A-84517 describes a lithium ion secondary battery in which VGCF is graphitized and then crushed to a predetermined length and used as a negative electrode. Japanese Unexamined Patent Publication No. 6-119922 discloses a lithium ion secondary battery using a carbon fiber-implanted metal molding having a structure as if carbon fibers were implanted on the surface of a metal as a negative electrode.

However, since the negative electrode in these lithium ion secondary batteries is formed of fibers or fibrous graphite having a large aspect ratio, its density is not high.
Therefore, in these lithium ion secondary batteries, the absolute amount of the negative electrode and the packing density are not sufficient,
There is a problem that large capacity and high voltage cannot be realized.

Under these circumstances, it may be possible to solve the above problems by using a crushed product obtained by crushing fibers or fibrous graphite having a large aspect ratio as the negative electrode. For example, in Japanese Unexamined Patent Publication (Kokai) No. Hei 5-221622, large surface area vapor-grown carbon obtained by subjecting graphitized vapor-grown carbon fiber to oxidation treatment, heat treatment, and pulverization is crystalline, that is, crystalline. Interlayer distance (d ₀₀₂ )
And that the crystallite size (L _c ) in the C-axis direction is excellent. Further, JP-A-6-81218 describes that vapor phase grown carbon for forming an intercalation compound, which is obtained by substantially graphitizing VGCF and then pulverizing it, has excellent crystallinity. Therefore, it is expected that a high-performance lithium ion secondary battery that solves the above problems can be obtained by using these pulverized products for the negative electrode.

However, when the graphitized vapor grown carbon fiber is crushed and shortened, fine powder is generated due to the crushing,
The fiber has a fracture surface. Therefore, when this pulverized product is used as a negative electrode in a lithium ion secondary battery, the fine powder or the fractured surface reacts with the electrolytic solution, so that the initial charge / discharge efficiency is 90% or less, especially when finely pulverized. Has the problem that it will drop to the 70% range.

An object of the present invention is to solve the above-mentioned conventional problems. INDUSTRIAL APPLICABILITY The present invention is excellent in crystallinity, that is, the distance between crystal layers (d ₀₀₂ ) and the size of crystallites in the C-axis direction (L _c ), can be suitably used as a battery material, and when used as a battery material, It is an object of the present invention to provide graphite particles having a high packing density and capable of forming an electrode having excellent charge / discharge efficiency. Another object of the present invention is to provide a method capable of efficiently and economically producing the graphite particles. Further, another object of the present invention is to provide a lithium ion secondary battery which has a large charge / discharge capacity, a high voltage, excellent charge / discharge efficiency, and is safe.

[0008]

The invention for solving the above problems is as follows, and the invention according to claim 1 is
The spherical particles having a diameter of 0.3 to 3 μm are connected in a chain shape, the 50% diameter in the particle size distribution curve is 3 to 60 μm, and the ratio of the 10% diameter to the 50% diameter in the particle size distribution curve (10 % Diameter / 50% diameter) is 0.1 to 0.3, the ratio of 90% diameter to 50% diameter (90% diameter / 50% diameter) in the particle size distribution curve is 2 to 6, and Distance (d ₀₀₂ )
Is 0.337 nm at most, and the size (L _c ) of the crystallite in the C-axis direction is at most 50 nm. Graphite particles characterized in that the invention according to claim 2 is an inert gas. Transition metal, which is obtained by subjecting the catalytic metal source component and the carbon source component to thermal decomposition treatment in an atmosphere of
The method for producing graphite particles according to claim 1, wherein the carbonaceous particles contained in an amount of ˜10,000 ppm are heat treated, and the invention according to claim 3 is characterized in that the catalyst metal source component is transitional. The method for producing graphite particles according to claim 2, which is a metal compound and the carbon source component is an organic compound, and the invention according to claim 4 is that the catalyst metal source component and the carbon source component are both transition metal compounds. The method for producing the graphite particles according to claim 2, wherein the invention according to claim 5 is the method for producing the graphite particles according to any one of claims 2 to 4, wherein the inert gas is a hydrogen-enriched gas. In the invention according to claim 6, the thermal decomposition treatment has a thermal decomposition temperature of 950 to 1,200.
The method for producing the graphite particles according to any one of claims 2 to 5, wherein the invention according to claim 7 comprises a negative electrode formed using the graphite particles according to claim 1. It is a lithium ion secondary battery characterized by the above.

The graphite particles, the method for producing the graphite particles, and the lithium ion secondary battery of the present invention will be described in detail below.

-Graphite particles-The graphite particles in the present invention have a structure in which spherical particles having a diameter of 0.3 to 3 µm are connected in a chain. Regarding the structure of the graphite particles, the size and connection state of individual particles can be observed by SEM. In the graphite particles of the present invention, individual spherical particles are firmly bonded.

In the graphite particles of the present invention, the 50% diameter in the particle size distribution curve is usually 3 to 60 μm, preferably 5
To 50 μm, more preferably 10 to 40 μm, the ratio of 10% diameter to 50% diameter (10% diameter / 50% diameter) in the particle size distribution curve is 0.1 to 0.3, and the particle size distribution is The particle size distribution curve has a ratio of 90% diameter to 50% diameter (90% diameter / 50% diameter) of 2 to 6 in the curve. When the graphite particles have the above-mentioned specific particle size distribution curve, the object of the present invention can be effectively achieved. In particular,
When the 50% diameter is within the above range, an electrode having a sufficient density and capable of being thinned can be obtained. Also, 1
When the ratio of the 0% diameter to the 50% diameter and the ratio of the 90% diameter to the 50% diameter are within the above ranges, the packing density is high and an electrode having a large capacity, a high charge / discharge efficiency and a high cycle characteristic is obtained. be able to. The particle size distribution curve can be measured using Microtrac.

The graphite particles in the present invention have a crystal layer distance (d ₀₀₂ ) of usually 0.337 nm or less, preferably 0.3354 to 0.3369 nm. When the distance between crystal layers (d ₀₀₂ ) is within the above range, the object of the present invention can be effectively achieved. Specifically, the discharge capacity can be increased to a theoretical value of 372 mAh / g as C ₆ Li. The crystallite size (L _c ) in the C-axis direction is usually 50 nm or more, preferably 60 to
It is 100 nm or more. In addition, although described as "100 nm or more" here, the crystallinity is measured by "Gakushin method".
It is performed by line diffraction, and when L _c exceeds 100 nm in calculation, it is expressed as 100 nm or more. When the crystallite size (L _c ) in the C-axis direction is within the above range,
The object of the present invention can be effectively achieved. Specifically, the theoretical value is 372 mA when the discharge capacity is C ₆ Li.
It can be as high as h / g. Crystal layer distance (d
₀₀₂ ) and the crystallite size (L _c ) in the C-axis direction is X
It can be measured by line diffraction.

The graphite particles in the present invention have a specific surface area of usually 15 m ² / g or less, preferably 0.1-10.
m ² / g, particularly preferably 0.3 to ³ m ² / g. When the specific surface area is within the above range, the object of the present invention can be effectively achieved. Specifically, the initial charge / discharge efficiency can be increased to 90% or more, and to 95% or more when the efficiency is good. The specific surface area is the BET method (N
₂ ) can be measured.

The graphite particles in the present invention are excellent in crystallinity, that is, the distance between crystal layers (d ₀₀₂ ) and the size of crystallites in the C-axis direction (L _c ), and can be suitably used as a battery material. Further, when used as a battery material, it is possible to form an electrode having a high packing density and excellent charge / discharge efficiency. Therefore, the graphite particles can be suitably used particularly as a negative electrode forming material in a lithium ion secondary battery.

-Method of Producing Graphite Particles-The graphite particles of the present invention can be produced by the method of producing graphite particles of the present invention. In the method for producing the graphite particles, a transition metal is contained in an amount of 100 to 10,000 ppm, which is obtained by subjecting a catalytic metal source component and a carbon source component to thermal decomposition treatment in an inert gas atmosphere. The carbonaceous particles are heat treated.

As the inert gas, a hydrogen-rich gas can be preferably mentioned. The hydrogen-rich gas may be hydrogen gas itself, or other than hydrogen gas, for example, N ₂ gas, CO gas, CO ₂ gas, noble gas such as H
Other gases such as e, Ne, Ar, Kr, Xe, etc., such as air, may be contained. When the hydrogen-enriched gas contains other gas, the mixing ratio of the other gas to the hydrogen gas (other gas / hydrogen gas) is usually 1/3 or less, preferably 1/5 or less.

Further, in some cases, any value or 0 of the mixing ratios used in Examples described later is set as a lower limit value,
It is also possible to adopt any one of the mixing ratios adopted in the examples described later or a mixing ratio having an upper limit value of 1/3.
The hydrogen-enriched gas functions as a carrier gas, and has a role of keeping the ultrafine metal particles precipitated by the decomposition of the catalyst source component in an active state and controlling the rate of decomposition of the carbon source component.

The catalyst metal source component (A) is not particularly limited as long as it is a substance which releases the catalyst metal into a gas state in the temperature range of the thermal decomposition treatment, and examples thereof include transition metal compounds. . The transition metal compound is not particularly limited as long as it is a compound containing a transition metal such as iron, copper, nickel, chromium, tungsten and molybdenum, and an organic transition metal compound and an inorganic transition metal compound can be mentioned. Among these, especially Fe and N
Compounds containing a Group VIII element typified by i and Co are preferable.

Examples of the organic transition metal compound include metallocenes such as ferrocene and nickelocene, metal carbonyls such as iron carbonyl, iron hydrocarbonyl, cobalt carbonyl and nickel carbonyl, iron acetylacetonate, nickel acetylacetonate and nickel acetate. Can be mentioned.

When the catalytic metal component (A) is an organic transition metal compound having sufficient carbon content in its molecule to form graphite particles, the catalytic metal component (A) is It also functions as a carbon source component. That is, the organic transition metal compound may serve as a catalyst metal component and a carbon source component.

Examples of the inorganic transition metal compound include iron chloride, titanium chloride, nickel chloride, molybdenum chloride and tungsten chloride.

In the present invention, among these catalyst metal source components, the compounds used in the examples described later and the metallocenes are preferable.

The carbon source component (B) is not particularly limited as long as it is an organic compound which becomes a gas state in the temperature range of the thermal decomposition treatment. For example, a hydrocarbon compound, N,
Organic compounds containing atoms such as O, S and halogen atoms,
Examples thereof include organic compounds containing a metal atom such as Na.

Examples of the hydrocarbon compound include aliphatic hydrocarbons and aromatic hydrocarbons.

Examples of the aliphatic hydrocarbon include, for example,
Saturated aliphatic hydrocarbons such as methane, ethane, propane, butane, pentane and hexane; unsaturated aliphatic hydrocarbons such as ethylene, propylene, butene, pentene and hexene;
Examples thereof include alicyclic hydrocarbons such as cyclopropane, cyclobutane, cyclopentane, cyclohexane, cycloheptane, cyclopentene, cyclohexene, adamantane, decalin and bornane.

The aromatic hydrocarbon is benzene,
Examples thereof include xylene, toluene, cumene, naphthalene, anthracene, phenol, biphenyl, biphenylene, indene and styrene.

Examples of the compounds containing atoms such as N, O, S and halogen atoms include N atoms such as aniline, pyrrole, imidazole, pyrazole, pyridine, piperidine, pyridazine, pyrimidine, pyrazine, quinoline, isoquinoline and purine. A compound containing C;
O, CO ₂ , acetone, alkyl ketone, tetrahydropyran, pyran, ethylene oxide, tetrahydrofuran, furan, alcohols such as ethanol, monosaccharides such as phenol and glucose, disaccharides of maltose sugar, oligosaccharides such as cyclodextrin, etc. O-containing compounds such as sugars, fatty acids, etc .; S-containing compounds such as thiols and thiophenes; dihalobenzenes such as p-dichlorobenzene; halogen-containing compounds such as dihaloalkanes such as dichloroethane; Other compounds such as oxazole, isoxazole, thiazole, 1,2,3-thiadiazole, xanthine, uric acid;
And so on.

Further, examples of the carbon source component (B) include gasoline, light oil, kerosene, heavy oil, anthracene oil, natural gas, naphtha and the like.

The carbon string component (B) may be used alone or in combination of two or more.

In the present invention, among these carbon source components, the compounds used in Examples described later, and toluene and thiophene are preferable.

Catalyst metal source component (A) and carbon source component (B)
The mixing ratio (mol number of A / mol number of B) is usually 0.1 / 99.9 to 50/50, and preferably 0.1.
5 / 99.5 to 30/70, particularly preferably 1 /
It is 99 to 10/90. Further, depending on the case, any value of the mixing ratios or 0.
It is also possible to adopt a content range in which 1 / 99.9 is one end value and one of the mixing ratios adopted in Examples described later or the other end value is 50/50. When the mixing ratio is within the above range, the object of the present invention can be efficiently achieved. On the other hand, if the catalytic metal component is less than the above range, the crystallinity of the graphite particles will be low, and conversely, if it is more than the above range, the effect may not be seen despite the high cost of the raw material ratio. .

The ratio of the inert gas to the mixed gas of the catalytic metal source component (A) and the carbon source component (B) (the number of the inert gas / the number of the mixed gas) is usually 30/7.
0 to 90/10, preferably 40/60 to 80 /
20 and particularly preferably 50/50 to 70/30. Further, in some cases, one of the values or 30/70 of the mixing ratios used in the examples described below is set as one end value, and any value of the mixing ratios used in the examples described below or 90/10 is set as the other end. It is also possible to adopt a content range to be a value. When the mixing ratio is within the above range, the proportion of vapor grown carbon fiber which is a by-product can be reduced, and the crystallinity of graphite particles can be maintained at a good value.

In the thermal decomposition treatment of the present invention, the thermal decomposition temperature is usually 950 to 1,200 ° C., preferably 98.
0 to 1,150 ° C., particularly preferably 1,000 to
It is carried out under conditions that are 1100 ° C. Further, in some cases, any value of the thermal decomposition temperatures adopted in the examples described below or 950 ° C. is set as a lower limit value, and any value of the thermal decomposition temperatures adopted in the examples described below or 1,200 ° C.
It is also possible to adopt a thermal decomposition temperature having an upper limit of. When the thermal decomposition temperature is within the above range, the object of the present invention can be efficiently achieved. Specifically, the production amount of carbonaceous particles does not decrease, and the crystallinity of the graphite particles can be maintained at a good value. The thermal decomposition treatment is performed using a conventionally known apparatus that has been used for producing a vapor-grown carbon fiber, for example, which has a structure in which a reaction tube is arranged in an electric furnace or a combustion furnace. You can

As a result of the thermal decomposition treatment, carbonaceous particles can be obtained.

The carbonaceous particles have a diameter of 0.3 to 3 μm.
Which has a structure in which spherical particles are bound in a chain. With respect to the structure of the carbonaceous particles, the size and connection state of individual particles can be observed by SEM. In the carbonaceous particles, the individual spherical particles are firmly bonded.

The carbonaceous particles generally contain 100 to 10,000 ppm, preferably 200 to 2,000 ppm of a transition metal when a transition metal compound is used as a catalyst metal source component. There is. Further, in some cases, any value of the transition metal content in the examples described below or 100 ppm is set as the lower limit value, and any value of the transition metal content in the examples described below or 10,000 ppm is set as the upper limit value. The transition metal is contained within the range.

The content of the catalyst metal can be measured by burning the carbonaceous particles and quantifying the residual oxide. When the carbonaceous particles contain the catalyst metal within the above range, the object of the present invention can be effectively achieved.
Specifically, when graphitizing carbonaceous particles by high-temperature heat treatment, the degree of graphitization of particles is increased. In addition to metals, it may be desirable to contain a small amount of sulfur and the like.

According to the thermal decomposition treatment, vapor-grown carbon fibers are produced as by-products in addition to carbonaceous particles. The content of vapor grown carbon fiber in the reaction product of the thermal decomposition treatment is usually 30.
It is not more than 20% by weight, preferably not more than 20% by weight.
When the content of the vapor grown carbon fiber is within the above range, the density of the negative electrode of the battery can be increased.

The heat treatment in the present invention is usually 2,000 ° C. or higher, preferably 2,500 ° C. or more by conducting heating, dielectric heating or the like in N ₂ gas or a rare gas for several minutes to several tens of minutes.
It can be carried out under the condition that the heat treatment temperature is 3,000 ° C. In some cases, any value of the heat treatment temperatures used in the examples described below or 2,000 ° C. is set as a lower limit value, and any value of the heat treatment temperatures used in the examples described below or 3,000 ° C. is set. It is also possible to adopt a thermal decomposition temperature that is the upper limit value. By this heat treatment, the carbonaceous particles are graphitized to obtain the graphite particles.

According to the method for producing graphite particles of the present invention,
The graphite particles of the present invention can be efficiently and simply used, and the proportion of vapor-grown carbon fibers, which is a by-product, can be suppressed low.

—Lithium Ion Secondary Battery— The lithium ion secondary battery of the present invention comprises a negative electrode formed using the graphite particles.

The negative electrode can be formed, for example, by integrally molding the graphite particles and the thermoplastic resin by pressing or the like.

The thermoplastic resin is not particularly limited and may be a resin known per se. For example, polyolefin such as polyethylene, polyethylene terephthalate, polybutylene terephthalate, polyamide, polycarbonate, polytetrafluoroethylene and other fluorine may be used. Resin, polyoxymethylene, polyphenylene oxide, vinyl acetate, polyvinyl acetal, AB
Examples thereof include S resin, polyimide, polyacrylonitrile, and phenol resin. Polyolefin, fluororesin, etc. are particularly preferable.

The lithium-ion secondary battery further comprises a positive electrode, a solvent, an electrolyte and the like in addition to the negative electrode.

The positive electrode can be formed by using a material known per se as a positive electrode material in a lithium ion secondary battery. For example, LiCoO ₂ .V ₂ O
₅ , Li _x MnO ₅ .V ₂ O ₅ or the like can be used.

Examples of the solvent include ethylene carbonate, propylene carbonate, diethyl carbonate, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxolane, sulfolane, anisole, γ-butyrolactone, 1,2-diethoxyethane, and two or more of these. Examples thereof include the above-mentioned various solvents containing a mixture of the above or a small amount of additives.

The electrolyte is not particularly limited, but examples thereof include LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAs.
F _{6 and the} like can be mentioned.

The form of the lithium ion secondary battery is as follows.
There is no particular limitation and it can be appropriately determined according to the purpose,
For example, it may be of a button type, or may be of a cylindrical type, a rectangular type, or a large-sized battery formed by stacking a plurality of cells.

The lithium ion secondary battery of the present invention has a large charge / discharge capacity and a high voltage, is excellent in charge / discharge efficiency, and is safe. Therefore, the lithium ion secondary battery of the present invention can be suitably used in various fields.

[0050]

Embodiments of the present invention will be described below.
It should be noted that the present invention is not limited to the following embodiments, and can be appropriately modified within a range not impairing the object of the present invention.

Example 1 5 g of ferrocene was added to 1 part of benzene.
It was dissolved in 00 ml. This solution was vaporized, mixed with hydrogen gas, and supplied to an alumina reaction tube having a diameter of 85 mm and a heating length of 1,200 mm. 1,0 in this reaction tube
A thermal decomposition treatment was performed at 50 ° C.

The amount of the solution supplied was 2.48 ml /
min, the supply amount of hydrogen gas was 4.95 mol%, and the composition in the mixed gas was 1.1 mol of ferrocene.
%, Benzene 49.4 mol%, hydrogen 49.5 mol%
And the total gas flow rate is 1,27 l / m at room temperature.
in, and the average residence time of the gas was 55 seconds.

After 30 minutes, the supply of the solution and hydrogen gas was stopped. As a result, 33 g of carbonaceous particles were obtained. The carbonaceous particles contained 250 ppm of ultrafine iron particles.

Then, the carbonaceous particles were placed in a graphite container and heat-treated at 2,800 ° C. for 10 minutes in an N ₂ atmosphere. As a result, graphite particles were obtained.

The obtained graphite particles have a crystal interlayer distance (d
₀₀₂ ) was 0.3367 nm, and the crystallite size (L _c ) in the C-axis direction was 82 nm. The BET specific surface area was 2.1 m ² / g. Furthermore, the 50% diameter in the particle size distribution curve measured by Microtrac is 2
4.43 μm, 10% diameter 5.63 μm, 90%
The diameter was 80.37 μm. SE obtained graphite particles
As a result of observation with an M photograph, it was confirmed that particles of 0.3 to 1 μm were fixed to each other in a chain shape with carbon. The obtained graphite particles contained about 15% by weight of vapor grown carbon fiber having a diameter of about 2 μm as a by-product.

Next, the graphite particles were NM together with PVDF.
An electrode was formed by mixing with P, coating this on a nickel mesh, and drying. Using the obtained electrode,
Using a Li thin film as the counter reference electrode of this electrode, 1M LiC
A glass cell lithium ion secondary battery was manufactured using an electrolytic solution containing 10 ₄ and ethylene carbonate (EC) and diethyl carbonate (DEC) in a ratio of 1: 1.

Regarding the obtained lithium ion secondary battery,
It tested by the three-electrode method. The results are shown in Table 1.

Example 2 In Example 1, the heat treatment decomposition temperature was set to 1,100 ° C., and the solution supply amount was 2.98 ml.
/ Min, the hydrogen gas supply rate is 0.43 liters / m
nitrogen gas 0.08 liter / m
Graphite particles were prepared in the same manner as in Example 1 except that the amount of in was added, and a lithium ion secondary battery was manufactured.
The results are shown in Table 1.

The composition of the mixed gas is as follows: ferrocene 1.1 mol%, benzene 49.4 mol%, hydrogen 3
It was 3.7 mol% and nitrogen 6.7 mol%. Also,
The obtained graphite particles did not contain a vapor-grown carbon fiber as a by-product.

Example 3 In Example 1, the heat treatment decomposition temperature was set to 1,000 ° C. and the solution supply amount was set to 5.0 ml /
The supply amount of hydrogen gas is 0.63 liters / mi per min.
Graphite particles were prepared in the same manner as in Example 1 except that the supply time was changed to n and the supply time was changed to 80 minutes to manufacture a lithium ion secondary battery. The results are shown in Table 1.

The composition of the mixed gas was as follows: ferrocene 1.5 mol%, benzene 65.3 mol%, hydrogen 3
It was 3.2 mol%. Further, the obtained graphite particles contained about 5% by weight of vapor grown carbon fiber having a diameter of about 2 μm as a by-product.

Comparative Example 1 Graphite particles were prepared in the same manner as in Example 1 except that nitrogen gas was used instead of hydrogen gas to manufacture a lithium ion secondary battery. The results are shown in Table 1.

Comparative Example 2 Graphite particles were prepared in the same manner as in Example 3 except that a solution of benzene alone to which ferrocene was not added was used to produce a lithium ion secondary battery. The results are shown in Table 1.

Comparative Example 3 A lithium ion secondary battery was manufactured in the same manner as in Example 1 except that the vapor grown carbon fiber (2 μm) described in JP-A-6-84517 was used. Table 1 shows the results.

(Comparative Example 4) A lithium ion secondary battery was manufactured in the same manner as in Example 1 except that synthetic high-purity graphite powder (SPG-2, manufactured by SEC) having an average diameter of 2 µm was used. Table 1 shows the results.

(Example 4) The graphite particles prepared in Example 1 were mixed with 5% by weight of PVDF and NMP (N-methylpyrrolidone) to prepare a slurry. This is 10
After coating on a copper foil having a thickness of μm, it was dried and pressed to form a negative electrode. Similarly, 5% by weight of acetylene black and 5% by weight of PVDF were added to the lithium cobalt oxide particles.
A positive electrode was formed by applying the mixture of and on an aluminum foil having a thickness of 20 μm, drying and pressing. In addition, 1
A single 3 cylindrical lithium ion secondary battery was manufactured using an electrolyte solution containing M LiPF ₆ and ethylene carbonate (EC) and diethyl carbonate (DEC) in a ratio of 1: 1.

As a result of testing the obtained lithium ion secondary battery, the initial charge / discharge capacity was 800 mA, the initial charge / discharge efficiency was 95%, the average discharge voltage was 3.8 V, and the capacity retention rate after 250 cycles was 87%. It was

[0068]

[Table 1]

[0069]

According to the present invention, the above-mentioned conventional problems can be solved. According to the invention,
It is excellent in crystallinity, that is, the distance between crystal layers (d ₀₀₂ ) and the size of crystallites in the C-axis direction (L _c ), and can be suitably used as a battery material. When used as a battery material, the packing density is high. It is possible to provide graphite particles capable of forming an electrode having excellent charge / discharge efficiency. Further, according to the present invention, it is possible to provide a method capable of efficiently and economically producing the graphite particles. Furthermore, according to the present invention, it is possible to provide a lithium-ion secondary battery that has a large charge / discharge capacity, a high voltage, excellent charge / discharge efficiency, and is safe.

Continuation of front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location B01J 23/38 B01J 23/38 M 23/70 23/70 M 23/745 H01M 4/58 H01M 4/58 B01J 23/74 301M

Claims (7)

[Claims] 1. Spherical particles having a diameter of 0.3 to 3 μm are connected in a chain shape, the 50% diameter in the particle size distribution curve is 3 to 60 μm, and the 10% diameter and the 50% diameter in the particle size distribution curve. And the ratio (10% diameter / 50% diameter) is 0.1 to 0.
3, the ratio of 90% diameter to 50% diameter (90% diameter / 50% diameter) in the particle size distribution curve is 2 to 6, and the crystal interlayer distance (d ₀₀₂ ) is 0.337 nm at most. C
Even if the crystallite size (L _c ) in the axial direction is small, it is 50 nm.
Graphite particles characterized by: 2. A catalyst metal source component and a carbon source component obtained by thermal decomposition treatment in an atmosphere of an inert gas,
The method for producing graphite particles according to claim 1, wherein the carbonaceous particles containing the transition metal in an amount of 100 to 10,000 ppm are heat-treated. 3. The method for producing graphite particles according to claim 2, wherein the catalyst metal source component is a transition metal compound and the carbon source component is an organic compound. 4. The method for producing graphite particles according to claim 2, wherein both the catalyst metal source component and the carbon source component are transition metal compounds. 5. The method for producing graphite particles according to claim 2, wherein the inert gas is a hydrogen-enriched gas. 6. The thermal decomposition treatment has a thermal decomposition temperature of 950 to 1,
It is 200 degreeC, The manufacturing method of the graphite particle in any one of Claims 2-5. 7. A lithium ion secondary battery comprising a negative electrode formed by using the graphite particles according to claim 1.