JP2001126726A - Nonaqueous electrolytic secondary cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic secondary cell which has high inflammability, can generate a high voltage and has a good charge discharge performance. SOLUTION: A nonaqueous electrolytic secondary cell comprises a negative electrode using a core of a carbon particle and a carbon-carbon composite material, formed by coating a surface of the core with a carbon layer as a negative active material and a positive electrode containing a positive active material and a nonaqueous electrolyte comprising a nonaqueous solvent containing a phosphate ester compound and an electrolyte. It is preferably that the volume average particle diameter of the core comprising a carbon particle be 100 μm or smaller, the specific surface area of the complex material be 5 cm2/g or smaller. Trimethyl phosphate, triethyl phosphate and the like can be used as the phosphate ester compound. This cell is suitable as a lithium ion secondary cell.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a secondary battery using a non-aqueous electrolyte. More specifically, the present invention relates to a lithium ion secondary battery containing a non-aqueous electrolyte having high flame retardancy, capable of generating a high voltage, and having excellent charge / discharge characteristics of the battery.

[0002]

BACKGROUND OF THE INVENTION Non-aqueous electrolyte secondary batteries are used as energy storage devices using non-aqueous electrolytes such as lithium batteries. These devices have high voltage, high energy density, and high reliability. Because of their high cost, they are widely used as power sources for consumer electronic devices.

[0003] A non-aqueous electrolyte is composed of a non-aqueous solvent and an electrolyte. Examples of the non-aqueous solvent include propylene carbonate, γ-butyrolactone, and organic solvents having a high dielectric constant.
Sulfolane or low-viscosity organic solvents such as dimethyl carbonate, dimethoxyethane, tetrahydrofuran, and 1,3-dioxolan are used. LiBF ₄ , LiPF ₆ , LICLO ₄ , Li
ASF ₆ , LiCF ₃ SO ₃ , LiAlCl ₄ , LiSiF
₆ etc. are used.

Recently, in the field of secondary batteries, there is a strong need for batteries with higher energy density, and research on high-voltage batteries has been promoted. For example, there is a rocking chair type secondary battery in which a composite oxide of lithium and a transition metal such as LiCoO ₂ , LiNiO ₂ , and LiMn ₂ O ₄ is used for a positive electrode of a battery and a carbon material is used for a negative electrode. This battery can generate a battery voltage of 4 V or more, and has no deposition of metallic lithium, so that overcharging,
Excellent results have been obtained by experiments such as external shorts, nail penetration, and crushing, and are distributed for consumer use.

However, further increase in energy density and size are expected in the future, and in order to realize this, it is necessary to provide self-extinguishing properties to a flammable non-aqueous electrolyte from the viewpoint of safety. Is required. As one of the methods, Japanese Patent Application Laid-Open No. 4-184870 proposes adding a phosphate ester known as a compound having self-extinguishing properties to an electrolytic solution.

However, when a general phosphate such as triethyl phosphate is added to the electrolytic solution, the flame retardancy is improved.
A phenomenon is seen in which the charge / discharge efficiency of the battery, the energy density of the battery, and the battery life are reduced. Accordingly, Japanese Patent Application Laid-Open No.
No. 40 proposes to limit the amount of phosphate ester added.

[0007] By taking measures against these electrolytes, the flame retardancy, charge / discharge efficiency, energy density, battery life, etc. of the battery have been improved. Is required.

[0008]

SUMMARY OF THE INVENTION In order to meet the above demand, the present invention provides a non-aqueous electrolyte secondary battery having high flame retardancy, high voltage, and excellent battery charge / discharge performance. Aim.

[0009]

SUMMARY OF THE INVENTION The present invention provides a negative electrode using a carbon-carbon composite material obtained by coating a nucleus composed of carbon particles and a surface thereof with a carbon layer as a negative electrode active material, a positive electrode containing a positive electrode active material, Provided is a non-aqueous electrolyte secondary battery having a non-aqueous electrolyte including a non-aqueous solvent containing a phosphate ester compound and an electrolyte.

A preferred embodiment of the present invention is a non-aqueous electrolyte secondary battery in which the phosphate compound is a phosphate represented by the following general formulas [1] to [3].

[0011]

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[0012]

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[0013]

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(In the formula, R ^{1 to} R ⁴ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms or a fluorine-substituted alkyl group; Or a branched or branched hydrocarbon group, k, s, t, and u represent the number of carbon atoms, k is an integer of 2 to 8, and s, t, and u may be the same or different. It is a good integer of 0 to 12, and at least one of s, t, and u is an integer of 1 or more.)

A non-aqueous electrolyte secondary battery in which the electrolyte is a lithium salt is also a preferred embodiment of the present invention.

A non-aqueous electrolyte secondary battery having a positive electrode containing at least one selected from the group consisting of a composite oxide of lithium and a transition metal, a carbon material, and a mixture thereof as the positive electrode active material is also provided. This is a preferred embodiment of the present invention.

Further, the present invention provides a non-aqueous electrolyte secondary battery further comprising at least one of a cyclic carbonate and a chain carbonate in the non-aqueous solvent.

[0018]

Next, the non-aqueous electrolyte secondary battery according to the present invention will be described in detail. Negative electrode active material The negative electrode according to the present invention uses, as a negative electrode active material, a nucleus made of carbon particles and a carbon-carbon composite material whose surface is covered with a carbon layer. The core of the carbon particles has an average particle diameter (volume average particle diameter) of 100 μm or less, preferably 50 μm or less, and a specific surface area of the carbon-carbon composite material of 5 m ² / g or less. . further,
It is desirable that the equilibrium adsorption water content of the carbon-carbon composite material is 0.3% by weight or less.

As the carbon particles serving as the nucleus, non-graphitizable carbon obtained by firing a pulverized product of natural graphite, a pulverized product of expanded graphite, a condensate of an aromatic sulfonic acid or a salt thereof by a methylene type bond, or the like is used. be able to.

Such a composite material is disclosed in, for example,
012241 or JP-A-9-326254
It can be manufactured with reference to the description in Japanese Patent Publication No. As a method for coating the surface of the carbon particles in the present invention, for example, heating the carbon particles, introducing an organic vapor into the carbon particles, and carbonizing and depositing the thermally decomposed organic vapor on the carbon particle surface.
It is preferable to use a so-called chemical vapor deposition method. The chemical vapor deposition temperature at this time is preferably 700 to 1300 ° C., and the thickness of the coated carbon layer is 0.1 to 2 μm.
m is desirable.

Examples of organic substances used as a pyrolytic carbon source for chemical vapor deposition include benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, diphenyl, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, cumarone and pyridine. , Anthracene, phenanthrene, or a mixture thereof, and gas or light oil obtained in the tar distillation step, creosote oil, anthracene oil, naphtha cracked tar oil, acetylene, ethylene, propylene, isopropylene, butadiene, and the like. .

By using these negative electrode active materials as the negative electrode, the charge / discharge efficiency and load characteristics of the battery may be reduced when a nonaqueous solvent containing a phosphate compound is used as a solvent for the nonaqueous electrolyte. And a non-aqueous electrolyte secondary battery having high flame retardancy, high voltage generation, and excellent battery charge / discharge performance and load characteristics can be obtained.

The nonaqueous electrolytic solution according to the present invention the non-aqueous electrolytic solution, a nonaqueous solvent containing a phosphoric acid ester compound, which consists of an electrolyte, are explained in detail below for each.

Phosphate ester compound As the phosphate ester compound used in the present invention, phosphoric esters represented by the following general formulas [1] to [3] are preferably used.

[0025]

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[0026]

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[0027]

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(In the formula, R ^{1 to} R ⁴ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms or a fluorine-substituted alkyl group; Or a branched or branched hydrocarbon group, k, s, t, and u represent the number of carbon atoms, k is an integer of 2 to 8, and s, t, and u may be the same or different. It is a good integer of 0 to 12, and at least one of s, t, and u is an integer of 1 or more.)

Specific examples of the phosphate represented by the formula [1] include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, dimethylethyl phosphate, methyl diethyl phosphate and the like.

As the phosphate represented by the formula [2], specifically, methyl ethylene phosphate,

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Methyltrimethylene phosphate,

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As the phosphoric ester represented by the formula [3], specifically,

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[0033]

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Trimethylolethane phosphate,

Embedded image And the like.

Of these, trimethyl phosphate and triethyl phosphate are preferred because of their great effect in imparting flame retardancy, and trimethyl phosphate is particularly preferred.

Other Nonaqueous Solvent In the present invention, only the phosphate compound may be used as the nonaqueous solvent, or another solvent may be added to the phosphate compound. As the other solvent to be added to the non-aqueous solvent composed of the phosphate compound, an organic solvent having a high dielectric constant is usually used. Of these, the use of carbonates such as cyclic carbonates and chain carbonates is preferred. By using carbonates, the charge / discharge efficiency and load characteristics of the battery can be improved. As a suitable cyclic carbonate, a compound represented by the following general formula [4] is selected.

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Here, R ⁵ and R ⁶ represent a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, which may be the same or different from each other. Examples of the alkyl group include a methyl group, an ethyl group, and an n-propyl group.

Examples of the cyclic carbonate represented by the formula [4] include ethylene carbonate, propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-
Pentylene carbonate and the like. These cyclic carbonates may be used as a mixture of two or more kinds. In particular, ethylene carbonate, propylene carbonate, or a mixed solvent of ethylene carbonate and propylene carbonate having a high dielectric constant and a low viscosity and a low freezing point is preferably used. When these cyclic carbonates are contained, the solubility of the electrolyte at a low temperature can be increased, the transport of the electrolyte is facilitated, and the electric conductivity of the electrolyte can be improved.

On the other hand, suitable chain carbonates include
Examples thereof include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, and ethyl propyl carbonate. These chain carbonates are 2
You may mix and use more than one kind.

When such a chain carbonate is contained in the non-aqueous solvent, the viscosity of the non-aqueous electrolyte can be reduced, the solubility of the electrolyte can be further increased, and the electric conductivity at normal temperature or low temperature can be improved. It is possible to obtain an electrolytic solution having excellent properties.
A chain carbonate, particularly dimethyl carbonate, has an effect of enhancing the self-extinguishing property of the electrolytic solution, and thus can be suitably used.

When a cyclic carbonate and / or a chain carbonate is used, the mixing ratio of the cyclic carbonate and the chain carbonate represented by the general formula [4] in the non-aqueous solvent is by weight. Expressing the cyclic carbonate:
When the chain carbonate is 0: 100 to 100: 0, preferably 5:95 to 95: 5, particularly preferably 20:80 to
85:15. When the cyclic carbonate is contained in the non-aqueous solvent at such a quantitative ratio, the electric conductivity of the non-aqueous electrolyte can be increased. A non-aqueous electrolyte excellent in fire extinguishing properties can be obtained.

The following compounds can be mentioned as other solvents that can be used in addition to the carbonate ester. 1) chain esters such as methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate and ethyl propionate; 2) chain ethers such as dimethoxyethane; 3) tetrahydrofuran and the like Cyclic ethers, 4) amides such as dimethylformamide,

5) Chain force-bamates such as methyl-N, N-dimethylcarbamate 6) Cyclic esters such as γ-butyrolactone 7) Cyclic sulfones such as sulfolane 8) N-methyloxasolidinone Cyclic carbamates such as 9) cyclic amides such as N-methylpyrrolidone; 10) cyclic ureas such as N, N-dimethylimidazolidone.

[0044] Specific examples of the electrolyte electrolyte, LiPF _6, LiBF _4, Li
_{ClO 4, LiAsF 6, LiSiF 6} , LiC 4 F 9 S
Lithium salts such as O ₃ and LiC ₈ F ₁₇ SO ₃ are mentioned. Further, a lithium salt represented by the following general formula can also be used. LiOSO ₂ R ⁷ , LiN (SO ₂ R ⁸ ) (S
O ₂ R ⁹ ), LiN (SO ₂ R ¹⁰ ) (SO ₂ R ¹¹ ), LiN
(SO ₂ R ¹² ) (SO ₂ R ¹³ ) (SO ₂ R ¹⁴ ) [wherein R ⁷
To R ¹⁴ may be the same or different and are perfluoroalkyl groups having 1 to 6 carbon atoms]. These lithium salts may be used alone or as a mixture of two or more.

Of these, in particular, LiPF₆, LiB
F_Four, LiOSO_TwoR⁷, LiN (SO _TwoR⁸) (SO
_TwoR⁹), LiN (SO_TwoR^Ten) (SO_TwoR¹¹), LiN
(SO_TwoR¹²) (SO_TwoR¹³) (SO_TwoR¹⁴) Is preferred
No. Of these lithium salts, LiPF ₆And LiB
F_FourIs more flame retardant due to the synergistic action with phosphate ester
It is particularly preferable because the layer becomes high.

The non-aqueous electrolytic solution according to the present invention comprises a non-aqueous solvent containing a phosphate compound and an electrolyte. Preferably, the other solvent described above may be further added. These components are blended in the following proportions.

The phosphate compound is used in an amount of usually 0.1 to 100% by weight, preferably 0.1 to 9% by weight, based on the total amount of the nonaqueous solvent.
It is used in a proportion of 9.9% by weight, more preferably 1-90% by weight, most preferably 3-60% by weight. When the phosphate compound is contained in the nonaqueous solvent in such an amount ratio, flame retardancy can be imparted to the nonaqueous electrolyte. The remainder can be used by further mixing another solvent such as a cyclic carbonate or a chain carbonate.

The electrolyte is usually 0.1 to 3 mol / l, preferably 0.1 to 3 mol / l, based on the total volume of the phosphate compound, other non-aqueous solvent and the electrolyte.
It is desirable that it be contained in the non-aqueous electrolyte at a concentration of 5 to 2 mol / l. In addition, other additives can be blended within a range that does not impair the object of the present invention.

The secondary battery according to the secondary batteries present invention, for example, lithium ion secondary battery, a negative electrode, a positive electrode is configured to include basically a non-aqueous electrolyte solution of the, and typically the negative electrode A separator is provided between the positive electrode and the positive electrode. As described above, a carbon-carbon composite material in which a nucleus composed of carbon particles and the surface thereof are covered with a carbon layer is used as the negative electrode active material constituting the negative electrode.

As the positive electrode active material constituting the positive electrode, Mo is used.
S_Two, TiS_Two, MnO_Two, V_TwoO_FiveTransition metal sulfides
Or transition metal oxide, LiCoO_Two, LiMnO_Two, Li
Mn _TwoO_Four, LiNiO_TwoFrom lithium and transition metals
Composite oxides, carbon materials and the like. In these
However, especially composite oxides composed of lithium and transition metals
preferable. In addition, a composite of lithium and a transition metal is used as the positive electrode.
A mixture of a composite oxide and a carbon material can also be used.

The separator is a porous membrane, and usually a microporous polymer film is suitably used. In particular, a porous polyolefin film is preferable, and specific examples thereof include a porous polyethylene film, a porous polypropylene film, and a multilayer film of a porous polyethylene film and polypropylene.

A secondary battery containing such a non-aqueous electrolyte is
It can be formed in a cylindrical shape, a coin shape, a square shape, or any other shape. However, the basic structure of the battery is the same regardless of the shape, and the design can be changed according to the purpose. Next, the structures of the cylindrical type and coin type batteries will be described. The negative electrode active material, the positive electrode active material, and the separator constituting each battery can be commonly used.

For example, in the case of a cylindrical secondary battery, a negative electrode obtained by applying a negative electrode active material to a negative electrode current collector and a positive electrode obtained by applying a positive electrode active material to a positive electrode current collector are injected with a nonaqueous electrolyte. And wound in a battery can in a state where insulating plates are placed above and below the wound body.

The secondary battery according to the present invention can be applied to a coin-type secondary battery. In a coin-type battery, a disk-shaped negative electrode, a separator, a disk-shaped positive electrode, and a stainless steel plate are housed in a coin-type battery can in a state of being stacked in this order.

[0055]

Next, the present invention will be described in detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

(Example 1) <Preparation of non-aqueous electrolyte> Ethylene carbonate (EC),
Mixed solvent of dimethyl carbonate (DMC) and trimethyl phosphate (TMPA) (weight ratio EC: DMC: TMP)
A = 37.8: 57.0: 5.2) and the electrolyte LiPF
₆ was dissolved to prepare a non-aqueous electrolyte having an electrolyte concentration of 1.0 mol / liter.

<Preparation of Negative Electrode> 95 parts by weight of a graphite negative electrode material (trade name: GDA-MT-2-3) manufactured by Mitsui Mining Co., Ltd. and 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder were used. The mixture was mixed and dispersed in N-methylpyrrolidone as a solvent to prepare a negative electrode mixture slurry (paste). The negative electrode material is obtained by using a crushed product of natural graphite as a nucleus and coating the surface thereof with pyrolytic carbon by a chemical vapor deposition (CVD) method. The properties are shown in Table 1.

[0058]

[Table 1] * Measuring instrument: MICROTRAC 93 manufactured by Leeds Northrup
20-X10C ** D ₁₀ indicates that up to 10% smaller particles are included in diameters up to 7.8 .mu.m. D ₅₀ and D ₉₀
The same applies to.

This negative electrode mixture slurry was applied to a negative electrode current collector made of a 20-μm-thick strip-shaped copper foil, and dried to obtain a strip-shaped carbon negative electrode. The thickness of the negative electrode mixture after drying is 25 μm
Met. Further, after punching out this strip-shaped electrode into a disk shape having a diameter of 15 mm, compression molding was performed to obtain a negative electrode.

<Preparation of Positive Electrode> L manufactured by Honjo Chemical Co., Ltd.
iCoO ₂ (product name: HLC-21, average particle size 8 μm)
91 parts by weight of fine particles, 6 parts by weight of graphite as a conductive material, and 3 parts by weight of polyvinylidene fluoride as a binder are mixed to prepare a positive electrode mixture, and then dispersed in N-methylpyrrolidone to form a positive electrode mixture. An agent slurry was obtained.

The slurry was applied to a 20 μm-thick positive electrode current collector made of aluminum foil, dried, and compression molded to obtain a positive electrode strip. The thickness of the positive electrode mixture after drying is 40μ.
m. Further, this strip-shaped electrode was punched into a disk having a diameter of 15 mm to obtain a positive electrode.

<Preparation of Battery> The disk-shaped negative electrode, disk-shaped positive electrode, and separator (thickness: 25 μm) thus obtained were obtained.
m, a microporous polypropylene film having a diameter of 19 mm) were laminated on a stainless steel battery can of 2032 size in the order of negative electrode, separator, and positive electrode. Thereafter, the non-aqueous electrolyte was injected into the separator, and a stainless steel plate (thickness 2.4
mm, diameter 15.4 mm). The airtightness in the battery is maintained by caulking the battery can (lid) via a polypropylene gasket, and the diameter is 20 mm and the height is 3.
A 22 mm coin-type non-aqueous electrolyte secondary battery was produced.

<Measurement of Discharge Capacity> The charge / discharge capacity of the secondary battery thus manufactured was measured. In the present embodiment, the current direction in which the negative electrode is doped with Li ⁺ is charged, and the current direction in which the negative electrode is undoped is discharge. Charging is 4.2V,
1mA constant current constant voltage charging method, charging current is 50μ
When it became A or less, it was terminated. The discharge was performed at a constant current of 1 mA, and was terminated when the voltage reached 2.7 V. From the charge capacity and discharge capacity of this charge / discharge cycle,
The charge / discharge efficiency was calculated by the following equation, and the results are shown in Table 1. Charge / discharge efficiency (%) = [{discharge capacity (mAh / g)} /
{Charging capacity (mAh / g)}] × 100

<Evaluation of self-extinguishing property of non-aqueous electrolyte> 15 mm, 30 cm length was placed in a beaker containing the non-aqueous electrolyte
The separator was cut into strips and was soaked in a 0.04 mm-thick manila sheet for separator for 1 minute or more. Excess non-aqueous electrolyte dripping from the manila paper is wiped with a beaker wall, and the manila paper is removed by 2.5 times.
The sample was fixed horizontally by piercing the support needle of a sample table having the support needle at an interval of cm. 25 sample stands with fixed Manila paper
cm × 25cm × 50cm placed in a metal box, ignited one end with a lighter, measured the burned length of the separator paper, if the burning length is less than 1cm, it is evaluated as self-extinguishing, The results are shown in Table 1.

Example 2 In Example 1, a mixed solvent (weight ratio EC: DMC: TMPA = 3) was used as a mixed solvent.
1.7: 47.8: 20.5), and the charge / discharge efficiency of the battery and the self-extinguishing property of the electrolyte were evaluated in the same manner as in Example 1. The results are shown in Table 1.

Comparative Example 1 A mixed solvent containing no TMPA as a mixed solvent in Example 1 (weight ratio EC: DM)
The charge and discharge efficiency of the battery and the self-extinguishing property of the electrolytic solution were evaluated in the same manner as in Example 1 except that C = 40.1: 59.9) was used. The results are shown in Table 1.

Comparative Example 2 In Example 1, a mesophase pitch carbon fiber (MCF) (trade name: Membron Milled, d.
002 = 0.336 nm, density 2.21 g / cm ³ ), and the charge / discharge efficiency of the battery and the self-extinguishing property of the electrolyte were evaluated in the same manner as in Example 1. The results are shown in Table 1.

(Comparative Example 3) In Example 2, a mesophase pitch carbon fiber (MCF) (trade name: Membron Milled, d.
002 = 0.336 nm, density 2.21 g / cm ³ ), and the charge / discharge efficiency of the battery and the self-extinguishing property of the electrolyte were evaluated in the same manner as in Example 2. The results are shown in Table 1.

[0069]

[Table 2]

[0070]

The non-aqueous electrolyte secondary battery according to the present invention has excellent flame retardancy, can generate a high voltage, has excellent charge / discharge characteristics, and can be used as a lithium ion secondary battery. It is suitable.

 ──────────────────────────────────────────────────続 き Continued on front page F term (reference) 5H003 AA01 AA10 BA00 BA01 BA04 BB01 BB12 BC01 BC05 BD00 BD02 BD05 5H014 AA01 AA06 BB00 BB01 CC07 EE01 EE08 HH00 HH06 5H029 AJ02 AJ12 AK02 AK03 C05 DJ12 DJ16 EJ11 HJ02 HJ05 HJ07 HJ12

Claims (12)

[Claims] 1. A negative electrode using a carbon-carbon composite material obtained by coating a nucleus composed of carbon particles and a surface thereof with a carbon layer as a negative electrode active material, a positive electrode containing a positive electrode active material, and a non-aqueous solution containing a phosphate compound A non-aqueous electrolyte secondary battery comprising a non-aqueous electrolyte comprising a solvent and an electrolyte. 2. The method according to claim 1, wherein the average particle diameter (volume average particle diameter) of the nuclei comprising the carbon particles is 100 μm or less, and the specific surface area of the carbon-carbon composite material is 5 m ² / g or less. The non-aqueous electrolyte secondary battery according to claim 1. 3. The non-aqueous electrolyte secondary battery according to claim 1, wherein the carbon layer is formed by a chemical vapor deposition method. 4. The non-aqueous electrolyte secondary battery according to claim 1, wherein a ground material of natural graphite is used as the carbon particles. 5. The non-aqueous electrolyte secondary battery according to claim 1, wherein a pulverized product of expanded graphite is used as the carbon particles. 6. The non-graphitizable carbon obtained by firing a condensate of a methylene type bond of an aromatic sulfonic acid or a salt thereof as the carbon particles. A non-aqueous electrolyte secondary battery according to any of the above items. 7. The non-aqueous electrolysis according to claim 1, wherein the phosphate compound is a phosphate ester represented by the following general formulas [1] to [3]. Liquid secondary battery. Embedded image Embedded image Embedded image (Wherein, R ^{1 to} R ⁴ may be the same or different and each represents an alkyl group having 1 to 6 carbon atoms or a fluorine-substituted alkyl group, and-(C)-represents a linear or branched , S, t, and u represent the number of carbon atoms, k is an integer of 2 to 8, and s, t, and u may be the same or different from each other. An integer of 12, s, t,
At least one of u is an integer of 1 or more. ) 8. The phosphate ester compound is selected from the group consisting of trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, dimethyl ethyl phosphate, methyl diethyl phosphate, methyl trimethylene phosphate, and trimethylol ethane phosphate. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery is at least one compound. 9. The non-aqueous electrolyte secondary battery according to claim 1, wherein the phosphate compound is trimethyl phosphate or triethyl phosphate. 10. The non-aqueous electrolyte secondary battery according to claim 1, wherein the electrolyte is a lithium salt. 11. The positive electrode active material is at least one selected from the group consisting of a composite oxide of lithium and a transition metal, a carbon material, and a mixture thereof. The non-aqueous electrolyte secondary battery according to any one of the above. 12. The non-aqueous electrolyte secondary battery according to claim 10, wherein the non-aqueous electrolyte secondary battery is a lithium ion secondary battery.