JP2017168406A - Methods for manufacturing nonaqueous electrolyte secondary battery negative electrode active material, negative electrode, and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery negative electrode active material which is superior in load characteristic while retaining advantages of a silicon-based active material, including a high battery capacity and a low volumetric expansion coefficient.SOLUTION: A method for manufacturing a nonaqueous electrolyte secondary battery negative electrode active material including particles of a silicon compound, and a carbon coating formed on the surface of each particle and having open pores in the carbon coating comprises: the step of performing a carbon coating-forming reaction, which causes the thermal decomposition of an organic material gas, twice to four times on the surface of each of particles of a silicon compound (SiOx, where 0.5≤x<1.6).SELECTED DRAWING: None

Description

  The present invention relates to a non-aqueous electrolyte secondary battery negative electrode active material, a negative electrode, and a battery manufacturing method.

  In recent years, with the remarkable development of portable electronic devices, communication devices, etc., secondary batteries with high energy density are strongly demanded from the viewpoints of economy and downsizing and weight reduction of devices.

Conventionally, as a measure for increasing the capacity of this type of secondary battery, for example, a method of using an oxide such as V, Si, B, Zr, Sn, or a composite oxide thereof as a negative electrode material (see Patent Documents 1 and 2) , A method of applying a molten and quenched metal oxide as a negative electrode material (see Patent Document 3), a method of using silicon oxide as a negative electrode material (see Patent Document 4), and Si ₂ N ₂ O and Ge ₂ N ₂ O as negative electrode materials There is known a method using the method (see Patent Document 5).

  In addition, for the purpose of imparting conductivity to the negative electrode material, a method of carbonizing SiO after graphite and mechanical alloying (see Patent Document 6), a method of coating a carbon layer on the surface of silicon particles by a chemical vapor deposition method (Patent Document 7). And a method of coating the surface of silicon oxide particles with a carbon layer by chemical vapor deposition (see Patent Document 8).

  However, in the above conventional method, although the charge / discharge capacity is increased and the energy density is increased, the cycleability is insufficient, or the required characteristics of the market are still insufficient, and are not always satisfactory. However, further improvement in energy density has been desired.

  In particular, Patent Document 4 uses silicon oxide as a negative electrode material for a lithium ion secondary battery to obtain a high-capacity electrode. However, as far as the present inventors know, the irreversible capacity during the initial charge / discharge is still large. There is a problem that the cycle performance has not reached the practical level, and there is room for improvement.

Further, the technique of imparting conductivity to the negative electrode material also has a problem in Patent Document 6 that a uniform carbon film is not formed because of solid-solid fusion, and the conductivity is insufficient.
In the method of Patent Document 7, although a uniform carbon film can be formed, since Si is used as a negative electrode material, the expansion / contraction at the time of adsorption / desorption of lithium ions is too large. As a result, the battery cannot be put into practical use, and the cycle performance is degraded.

  In the method of Patent Document 8, although improvement in cycle performance is confirmed, the number of cycles of charge / discharge is increased due to insufficient deposition of fine silicon crystals, integration of the carbon coating structure and the base material. As a result, there is a problem that the capacity gradually decreases and then rapidly decreases after a certain number of times, which is still insufficient for a secondary battery.

JP-A-5-174818 JP-A-6-60867 JP 10-294112 A Japanese Patent No. 2999741 JP-A-11-102705 JP 2000-243396 A JP 2000-215887 A JP 2002-42806 A

  An object of this invention is to provide the negative electrode active material for lithium ion secondary batteries excellent in load characteristics, maintaining the advantage of the high battery capacity of a silicon type active material, and a low volume expansion coefficient.

  As a result of intensive studies to achieve the above object, the present inventors have conducted a carbon film forming reaction for thermally decomposing an organic gas on the particle surface made of a silicon compound (SiOx: 0.5 ≦ x <1.6). It has been found that an opening is formed in the carbon film by performing the above process 4 times, and the above problem can be solved, and the present invention has been made.

Accordingly, the present invention provides the following production method.
[1]. Carbon particles are formed on the surface of the particles made of the silicon compound, including a step of performing a carbon film forming reaction for thermally decomposing an organic gas 2 to 4 times on the surface of the particles made of a silicon compound (SiOx: 0.5 ≦ x <1.6). A method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery in which a film is formed and the carbon film has pores.
[2]. The negative electrode active material of the nonaqueous electrolyte secondary battery according to [1], wherein the BET specific surface area of the negative electrode active material of the nonaqueous electrolyte secondary battery by a nitrogen gas adsorption method is 3.3 to 7.5 m ² / g. A method for producing a substance.
[3]. The non-aqueous electrolyte secondary battery negative electrode active material according to [2], wherein the negative electrode active material of the non-aqueous electrolyte secondary battery has a BET specific surface area by a nitrogen gas adsorption method of 3.6 to 7.3 m ² / g. A method for producing a substance.
[4]. Production of the negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of [1] to [3], wherein the average pore diameter of the pores calculated by a nitrogen gas adsorption method is 9.8 to 26.0 nm Method.
[5]. The opening volume of the opening calculated by the nitrogen gas adsorption method is 0.9 × 10 ^{−2 to} 5.7 × 10 ⁻² cm ³ / g [1] to [4] The manufacturing method of the nonaqueous electrolyte secondary battery negative electrode active material in any one of these.
[6]. The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to any one of [1] to [5], wherein the carbon coating amount of the non-aqueous electrolyte secondary battery negative electrode active material is 0.5 to 19% by mass.
[7]. The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to [6], wherein the carbon coating amount is 1 to 15% by mass.
[8]. The volume resistivity when the nonaqueous electrolyte secondary battery negative electrode active material is compressed to a density of 1.5 cm ³ / g is 0.01 to 190 Ω · cm, according to any one of [1] to [7] A method for producing a negative electrode active material for a water electrolyte secondary battery.
[9]. The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to [8], wherein the volume resistivity is 0.01 to 100 Ω · cm.
[10]. The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to any one of [1] to [9], wherein the non-aqueous electrolyte secondary battery negative electrode active material contains silicon carbide.
[11]. Content of silicon carbide in nonaqueous electrolyte secondary battery negative electrode active material is 1.6 mass% or less, The manufacturing method of the nonaqueous electrolyte secondary battery negative electrode active material as described in [10] characterized by the above-mentioned.
[12]. The method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery according to [11], wherein the content of silicon carbide is 1% by mass or less.
[13]. The ratio of the carbon film thickness Anm formed in the first carbon coating process to the carbon film thickness Bnm formed in the second and subsequent carbon coating processes is 0.3 ≦ B / A <1.7. [1] A method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery according to any one of [12].
[14]. The said ratio is 0.4 <= B / A <1.4, The manufacturing method of the nonaqueous electrolyte secondary battery active material as described in [13] characterized by the above-mentioned.
[15]. The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to any one of [1] to [14], wherein the thermal decomposition temperature is 600 ° C to 1,200 ° C in the carbon film forming reaction.
[16]. A method for producing a nonaqueous electrolyte secondary battery negative electrode, comprising using the nonaqueous electrolyte secondary battery active material obtained by the production method according to any one of [1] to [15].
[17]. A step of producing a slurry using the nonaqueous electrolyte secondary battery active material obtained by the production method according to any one of [1] to [15], and a step of applying and drying the slurry to the negative electrode current collector The manufacturing method of the nonaqueous electrolyte secondary battery negative electrode containing.
[18]. [16] A method for producing a nonaqueous electrolyte secondary battery, comprising using the negative electrode obtained by the production method of [17].
[19]. [16] or [17] The negative electrode obtained by the production method and the positive electrode are laminated or wound via a separator to form a wound body, and the wound body is enclosed in a film, A method for producing a non-aqueous electrolyte secondary battery, comprising a step of introducing an electrolytic solution and vacuum impregnation, and a step of fusing the film.

  According to the production method of the present invention, it is possible to provide a negative electrode active material for a lithium ion secondary battery excellent in load characteristics while maintaining the advantages of a high battery capacity and a low volume expansion coefficient of a silicon-based active material. Moreover, the manufacturing method of the negative electrode and nonaqueous electrolyte secondary battery using this can be provided.

Hereinafter, the present invention will be described in detail.
[Method for producing non-aqueous electrolyte secondary battery negative electrode active material]
The carbon film formation reaction (CVD) that thermally decomposes organic gas is performed 2 to 4 times on the particle surface made of silicon compound (SiOx: 0.5 ≦ x <1.6). This is a method for producing a nonaqueous electrolyte secondary battery negative electrode active material having pores (silicon compound particles on which a carbon film is formed: hereinafter may be referred to as negative electrode active material particles).

  As the particles made of a silicon compound, the silicon compound particles represented by the general formula SiOx: 0.5 ≦ x <1.6 are composite particles having a structure in which silicon oxide particles and silicon fine particles are dispersed in a silicon compound. Is also included. x is preferably 0.5 ≦ x <1.5, more preferably 0.8 ≦ x <1.3, and still more preferably 0.8 ≦ x ≦ 1.0. As the composition of the silicon compound, x is preferably close to 1 from the viewpoint of obtaining high cycle characteristics. The silicon compound in the present invention does not necessarily mean 100% purity, and may contain a trace amount of impurity elements.

The physical properties of the particles made of the silicon compound are appropriately selected depending on the physical properties of the target negative electrode active material. An average particle diameter can be 0.01-50 micrometers, 0.1-20 micrometers is preferable and 0.5-15 micrometers is more preferable. In addition, an average particle diameter can be represented by the volume average particle diameter in the particle size distribution measurement by a laser beam diffraction method. Further, BET specific surface area is preferably 0.1~30m ² / g, more preferably 0.1~25m ² / g, more preferably 0.2~20m ² / g. The BET specific surface area is a value measured by the BET one-point method evaluated by the N ₂ gas adsorption amount.

  In the present invention, silicon oxide is a general term for amorphous silicon oxides obtained by cooling and precipitating silicon monoxide gas generated by heating a mixture of silicon dioxide and metal silicon. It can be represented by the formula SiOx (0.5 ≦ x <1.6). As a method for producing silicon oxide, for example, a raw material that generates silicon oxide gas is heated in a temperature range of 900 ° C. to 1,600 ° C. in the presence of an inert gas or under reduced pressure to generate silicon oxide gas, which is generated. There is a method of depositing silicon oxide gas on an adsorption plate. The deposit is taken out with the temperature in the reactor lowered, and pulverized and powdered using a ball mill, jet mill or the like.

  In the composite particles having a structure in which silicon fine particles are dispersed in a silicon-based compound (hereinafter may be abbreviated as composite particles), the silicon-based compound is preferably inactive, and silicon dioxide is easy to manufacture. Is preferred. Moreover, it is preferable that this particle | grain has the following property.

i. In X-ray diffraction (Cu-Kα) using copper as the counter-cathode, a diffraction peak attributed to Si (111) centered around 2θ = 28.4 ° is observed, and based on the broadening of the diffraction line The particle diameter of silicon fine particles (crystals) determined by the Scherrer equation is preferably 1 to 500 nm, more preferably 2 to 200 nm, and still more preferably 2 to 20 nm. If the size of the silicon fine particles is smaller than 1 nm, the charge / discharge capacity may be reduced. Conversely, if the silicon fine particles are larger than 500 nm, the expansion / contraction during charge / discharge increases, and the cycle performance may be deteriorated. The size of the silicon fine particles can also be measured by a transmission electron micrograph.

ii. In solid-state NMR ( ²⁹ Si-DDMAS) measurement, there is a broad silicon dioxide peak whose spectrum is centered around −110 ppm, and a peak characteristic of Si diamond crystal is present near −84 ppm. This spectrum is completely different from ordinary silicon oxide (SiO _x : x = 1.0 + α), and the structure itself is clearly different. Further, it is confirmed by transmission electron microscope that silicon crystals are dispersed in amorphous silicon dioxide.

  The dispersion amount of the silicon fine particles (Si) in the composite particles (Si / silicon compound) is preferably 2 to 36% by mass, particularly preferably 10 to 30% by mass. If the amount of dispersed silicon is less than 2% by mass, the charge / discharge capacity may be reduced, and conversely if it exceeds 36% by mass, the cycle performance may be reduced.

The above composite particles, for example, the general formula _{SiO x (0.5 ≦ x <1.6} ) of silicon oxide particles represented by an inert gas atmosphere, in a temperature range of 800～1,400 ° C. heat treatment It can obtain by the method of giving disproportionation.

  The carbon film forming reaction is not particularly limited, but it is preferable to use thermal CVD. In thermal CVD, silicon oxide powder is set in a furnace, and then the furnace is filled with a hydrocarbon gas to raise the temperature in the furnace. The hydrocarbon gas is thermally decomposed to form a carbon film on the surface of the silicon oxide particles.

  The number of times of carbon film formation is defined as the number of times of exposure to a hydrocarbon atmosphere in which a carbon film can be formed by dividing the number of reactions by exposure to an atmosphere other than the hydrocarbon atmosphere in which the carbon film can be formed. That is, after the carbon film forming reaction, when the temperature is lowered and exposed to the atmosphere, the temperature is raised again and the carbon film forming atmosphere is formed to form the carbon film, the number of carbon film forming reactions is two. Also, in the case of a two-stage reaction in which an inert gas atmosphere is passed after an atmosphere in which a carbon film can be formed in a high temperature state and an atmosphere in which a carbon film can be formed again, the number of carbon film formation reactions is 2 times. When silicon oxide particles represented by the general formula SiOx (0.5 ≦ x <1.6) are used as raw materials, the disproportionation reaction proceeds by chemical vapor deposition (CVD), and silicon fine particles In some cases, the surface of particles having a fine structure dispersed in a silicon compound is coated with graphite.

  At this time, as the hydrocarbon used as the carbon source, aliphatic hydrocarbons, aromatic hydrocarbons, and tar fractions can be used singly or in appropriate combination of two or more.

Examples of the aliphatic hydrocarbon include methane, ethane, ethylene, acetylene, propane, butane, butene, pentane, isobutane, hexane, and propylene. Among these C _n H _m compositions, 3 ≧ n is particularly preferable. This is because the production cost is low and the physical properties of the product by thermal decomposition are good.

  Examples of the aromatic hydrocarbon include benzene, toluene, xylene, styrene, ethylbenzene, diphenylmethane, naphthalene, phenol, cresol, nitrobenzene, chlorobenzene, indene, coumarone, pyridine, anthracene, phenanthrene, and mesitylene.

  Examples of the fraction obtained in the tar distillation step include gas light oil, creosote oil, anthracene oil, and naphtha cracked tar oil.

  The temperature at which the organic gas is thermally decomposed to form the carbon film is preferably 600 to 1,200 ° C., more preferably 800 to 1,150 ° C., still more preferably 800 to 1,050 ° C., and 800 to 950 ° C. Particularly preferred. When the film forming temperature is within the above range, a negative electrode active material having excellent load characteristics, a high capacity retention rate, and a high initial efficiency can be provided. The reaction pressure is preferably 500 to 50,000 Pa, and more preferably 1,000 to 10,000 Pa. The treatment time is appropriately selected depending on the target carbon coating amount, treatment temperature, gas (organic gas) concentration (flow rate), introduction amount, and the like, but usually the residence time in the maximum temperature range is 1 to 100 hours. In particular, it is economically efficient for 1 to 50 hours and 1 to 30 hours.

  The frequency | count of the carbon film formation reaction which thermally decomposes organic substance gas is 2-4 times, and 2 to 3 times is more preferable. By setting the number of times of CVD to a plurality of times, the carbon coating has suitable pores, and the retention of the electrolyte is improved when the battery is made. Therefore, the nonaqueous electrolyte with excellent battery characteristics, particularly load characteristics, is obtained. It becomes a secondary battery negative electrode active material.

  The present invention is characterized in that the carbon film forming reaction for thermally decomposing the organic gas is performed 2 to 4 times, but the carbon film thickness Anm formed in the first carbon coating step and the second and subsequent carbon coating steps. The ratio of the formed carbon film thickness Bnm can be in the range of 0.3 ≦ B / A <1.7, preferably in the range of 0.4 ≦ B / A <1.4, More preferably, 0.4 ≦ B / A ≦ 1.0. If the thickness of the carbon coating on the silicon compound is within the above range, a carbon coating having voids in the coating can be produced more efficiently, and the load characteristics are further improved. When it is smaller than the above range, the base is only buried in the second and subsequent steps, and the voids may not be formed efficiently. Moreover, when larger than the said range, since the formed space | gap is filled, there exists a possibility that a space | gap may not be formed efficiently. In order to obtain the carbon film thickness as described above, the total carbon film thickness is preferably 30 to 100 nm, preferably 40 to 70 nm, and the carbon film formed by the first time is preferably 10 to 50 nm. It is preferable to control at 20 to 40 nm. Similarly, the total carbon film thickness formed after the second time is preferably 10 to 50 nm, and preferably controlled at 20 to 40 nm. In addition, the said ratio and film thickness can be adjusted by selecting the hydrocarbon seed | species and reaction time at the time of thermal decomposition CVD. The ratio and film thickness are measured with a transmission electron microscope TEM.

[Nonaqueous electrolyte secondary battery negative electrode active material]
The method for producing a negative electrode active material for a non-aqueous electrolyte secondary battery according to the present invention is characterized by having voids in a carbon film formed by performing a pyrolysis step 2 to 4 times. By performing the pyrolysis step in multiple steps, voids are efficiently formed between the carbon surface as a base and the carbon film formed on the surface, and these voids serve to retain the electrolyte. Bear. Thereby, especially the load characteristic of a battery improves. In this case, occlusion / release of lithium ions may be performed in at least a part of the carbon coating layer by the carbon component. Moreover, the same effect is acquired also in the electronic device using the secondary battery using the nonaqueous electrolyte secondary battery negative electrode material of this invention. Hereinafter, the negative electrode active physical properties of the nonaqueous electrolyte secondary battery obtained by the above production method will be described. These physical properties can be obtained by adjusting hydrocarbon species, reaction pressure, and reaction time in a carbon film forming reaction in which organic gas is thermally decomposed.

BET specific surface area may be a 3.3~7.5m ² / g, preferably from ^{3.6~7.3m 2 / g, 4.3~6.9m 2 /} g is more preferable. If it is such, the space | gap is formed and the negative electrode active material which has a high load characteristic is provided. If the BET is too low, the load characteristics may be deteriorated because the voids are small, and if the BET is too high, the side reaction proceeds, which may cause a decrease in initial efficiency. The BET specific surface area can be adjusted by selecting the hydrocarbon species, reaction pressure, and reaction time during pyrolysis CVD. The measurement conditions of the BET specific surface area are adsorbate: nitrogen, adsorption temperature: 77K, and can be measured by, for example, BELSORP-mini manufactured by Microtrack Bell Co., Ltd.

  The average pore diameter calculated by the nitrogen gas adsorption method in the opening can be 9.8 to 26.0 nm, preferably 10.0 to 24.0 nm, and more preferably 15.0 to 19.0 nm. . When the average pore diameter is in the above range, the retention property of the electrolyte is improved, and the load characteristics are further improved. When the average pore diameter is too small, the retention property is poor and the load characteristics may be deteriorated. Moreover, when too large, there exists a possibility of becoming a factor of initial efficiency fall by side reaction. The average pore diameter can be adjusted by selecting the hydrocarbon species, reaction pressure, and reaction time during pyrolysis CVD. The average pore diameter can be calculated by analyzing the isothermal adsorption line obtained by the nitrogen gas adsorption method using the BET method.

The opening volume calculated by the nitrogen gas adsorption method in the opening can be 0.9 × 10 ^{−2 to} 5.7 × 10 ⁻² cm ³ / g, and 0.9 × 10 ⁻² to 5.4 × 10 ⁻² cm ³ / g is preferable, and 1.8 × 10 ^{−2 to} 3.5 × 10 ⁻² cm ³ / g is more preferable. When the pore volume is in the above range, the retention property of the electrolyte is improved, and the load characteristics are improved. When the average pore diameter is smaller than the above range, the retention property is poor and the load characteristics may be deteriorated. Moreover, when too large, there exists a possibility of becoming a factor of initial efficiency fall by side reaction. The pore volume can be adjusted by selecting the hydrocarbon species, reaction pressure, reaction time, and number of CVDs during pyrolysis CVD. The pore volume can be calculated by analyzing the isothermal adsorption line obtained by the nitrogen gas adsorption method using the BET method.

  The carbon coating amount of the non-aqueous electrolyte secondary battery negative electrode active material (carbon amount relative to the whole negative electrode active material) can be 0.5 to 19% by mass, preferably 1 to 15% by mass, and 4 to 10% by mass. Is more preferable. Since favorable electroconductivity can be taken in the range of 1 to 15% by mass, battery characteristics are further improved. If the amount is too small, the conductivity may be insufficient, which causes a decrease in battery characteristics. On the other hand, if the amount is too large, the carbon component having no capacity increases, and the effect of adding SiOx may be reduced. The carbon coating amount can be adjusted by selecting the hydrocarbon species, reaction time, and reaction temperature during each pyrolysis CVD. The carbon coating amount can be measured with a carbon analyzer such as a carbon analyzer manufactured by Horiba.

The volume resistivity when compressed to a density of 1.5 cm ³ / g can be 0.01 to 190 Ω · cm, preferably 0.01 to 100 Ω · cm. When the volume resistivity is in the above range, good conductivity is obtained and the battery characteristics are improved. If the volume resistivity is too small, the conductivity of the battery is too high, which causes a short circuit due to charge concentration and the like, which is a problem in terms of safety. On the other hand, if the volume resistivity is too high, charge transfer is hindered, which may adversely affect battery characteristics. The volume resistivity can be adjusted by selecting the hydrocarbon species, the reaction time, and the reaction temperature during each pyrolysis CVD. The volume resistivity when compressed to the density of 1.5 cm ³ / g can be measured with a resistivity meter, for example, a resistivity meter manufactured by Mitsubishi Analytech. The measurement conditions are (i) device example: Loresta, (ii) measurement method: 4-terminal 4-probe method).

  In the present invention, the lower the crystallinity of the Si component of the silicon compound, the better, and the half width (2θ) of the diffraction peak due to the Si (111) crystal plane obtained by X-ray diffraction is 1.2 ° or more. At the same time, the crystallite size attributable to the crystal plane is preferably 7.5 nm or less. This is because the deterioration of battery characteristics due to the presence of the Si crystal can be suppressed by reducing the presence of the Si crystal.

  It is preferable that the non-aqueous electrolyte secondary battery negative electrode active material (or part thereof) contains silicon carbide. In addition, the interface between the silicon compound and the carbon coating is fixed by a chemical bond, so that the carbon coating is prevented from peeling and detaching due to expansion and contraction of the active material during charging and discharging, and the conductivity of the active material can be secured even after cycling. Therefore, the capacity maintenance rate is improved. The content of the non-aqueous electrolyte secondary battery negative electrode active material can be 1.6% by mass or less, and preferably 1% by mass or less. The lower limit is preferably 0.1% by mass. Silicon carbide is an insulator and does not occlude Li. For this reason, if the amount is too large, the conductivity of the active material may be lowered, which may hinder Li movement. The amount of silicon carbide can be adjusted by selecting the hydrocarbon species, reaction time, and reaction temperature during each pyrolysis CVD. The amount of silicon carbide can be measured with a carbon analyzer such as a carbon analyzer manufactured by Horiba.

  Content of the organic substance component extracted with toluene in the non-aqueous electrolyte secondary battery negative electrode active material can be 50 to 1,900 ppm, preferably 50 to 1,000 ppm, and more preferably 80 to 800 ppm. When the content of the organic compound extracted by the extraction operation with toluene is less than the above range, good SEI cannot be formed, which may cause a decrease in battery characteristics. Moreover, when too large, there exists a possibility that it may become a cause of a fall of initial efficiency by side reaction. As for the content of the organic component, 500 mL of toluene is added to 100 g of a nonaqueous electrolyte secondary battery negative electrode active material (with a carbon film formed on the surface of a silicon compound), and the mixture is stirred at room temperature in a sealed container, and then the solution is filtered. The toluene solution is concentrated using a rotary evaporator or the like. This operation is repeated 6 times, and the final concentrated product is dried under reduced pressure by heating at 100 ° C./2 hours with a vacuum dryer or the like. Thereafter, the mass of the extract is measured, and the ratio of the organic compound in the silicon compound is calculated.

  In addition, it is desirable that a particulate carbon-based compound having a median diameter smaller than that of the silicon compound is included around the non-aqueous electrolyte secondary battery negative electrode active material particles. Thereby, it is possible to improve the electrical conductivity between the negative electrode active material particles. The carbon-based compound can be present around the negative electrode active material particles by, for example, physical mixing with the negative electrode active material particles.

  The median diameter of the nonaqueous electrolyte secondary battery negative electrode active material particles is not particularly limited, but is preferably 0.5 μm to 20 μm. This is because lithium ions are easily occluded and released during charging and discharging, and the particles are difficult to break. When the median diameter is 0.5 μm or more, the surface area does not become too large, and an increase in battery irreversible capacity can be prevented. Furthermore, if the median diameter is 20 μm or less, the particles are difficult to break and a new surface is difficult to appear. The average particle diameter is based on particle size distribution measurement by a laser light diffraction method.

  Examples of the negative electrode binder include one or more of polymer materials, synthetic rubbers, and the like. Examples of the polymer material include polyvinylidene fluoride, polyimide, polyamideimide, aramid, polyacrylic acid, lithium polyacrylate, and carboxymethylcellulose. The synthetic rubber is, for example, styrene butadiene rubber, fluorine rubber, ethylene propylene diene, or the like.

  Examples of the negative electrode conductive assistant include one or more carbon materials such as carbon black, acetylene black, graphite, ketjen black, carbon nanotube, and carbon nanofiber.

  The negative electrode active material layer may be formed in a mixed state of the negative electrode material of the present invention and a carbon material (carbon-based negative electrode material). By mixing the carbon-based negative electrode material with the silicon-based negative electrode material of the present invention, it is possible to reduce the electrical resistance of the negative electrode active material layer and to reduce the expansion stress accompanying charging. Examples of the carbon-based negative electrode material include pyrolytic carbons, cokes, glassy carbon fibers, organic polymer compound fired bodies, and carbon blacks.

  Furthermore, it is preferable that the median diameter Y of the silicon compound and the median diameter X of the carbon-based negative electrode material satisfy the relationship of X / Y ≧ 1. Thus, by using the negative electrode material further comprising the carbon compound negative electrode material together with the negative electrode material composed of the silicon compound containing the Li compound and the coating layer, it is possible to prevent the negative electrode from being damaged due to the volume change. In particular, this effect is effectively exhibited when the carbon-based negative electrode material is equal to or larger than the silicon compound.

[Nonaqueous electrolyte secondary battery negative electrode]
A non-aqueous electrolyte secondary battery negative electrode using the non-aqueous electrolyte secondary battery negative electrode active material (silicon compound particles on which a carbon film is formed) of the present invention will be described. The negative electrode is configured to have a negative electrode active material layer on a negative electrode current collector. This negative electrode active material layer may be provided on both surfaces or only one surface of the negative electrode current collector. Furthermore, as long as the negative electrode active material of the present invention is used, the negative electrode current collector may be omitted.

[Negative electrode current collector]
The negative electrode current collector is an excellent conductive material and is made of a material having excellent mechanical strength. Examples of the conductive material that can be used for the negative electrode current collector include copper (Cu) and nickel (Ni). This conductive material is preferably a material that does not form an intermetallic compound with lithium (Li).

  The negative electrode current collector preferably contains carbon (C) and sulfur (S) in addition to the main element. This is because the physical strength of the negative electrode current collector is improved. In particular, in the case of having an active material layer that expands during charging, if the current collector contains the above-described element, there is an effect of suppressing electrode deformation including the current collector. Although content of said content element is not specifically limited, Especially, it is preferable that it is 100 ppm or less. This is because a higher deformation suppressing effect can be obtained.

  The surface of the negative electrode current collector may be roughened or not roughened. The roughened negative electrode current collector is, for example, a metal foil subjected to electrolytic treatment, embossing treatment, or chemical etching. The non-roughened negative electrode current collector is, for example, a rolled metal foil.

  The negative electrode active material layer includes a plurality of negative electrode active material particles capable of occluding and releasing lithium ions, and further includes other materials such as a negative electrode binder (binder) and a conductive aid in terms of battery design. Also good. The nonaqueous electrolyte secondary battery negative electrode material of the present invention is a material constituting the negative electrode active material layer.

[Production method of negative electrode]
It includes a step of producing a slurry using a nonaqueous electrolyte secondary battery active material (negative electrode active material particles) and a step of applying and drying the slurry to a negative electrode current collector. Specifically, the negative electrode active material particles, the negative electrode binder, and other materials such as a conductive additive are mixed to form a negative electrode mixture, and then an organic solvent or water is added to form a slurry.

  Next, a mixture slurry is applied to the surface of the negative electrode current collector and dried to form a negative electrode active material layer. At this time, you may perform a heat press etc. as needed.

  In addition, if the negative electrode current collector contains 90 ppm or less of carbon and sulfur, a higher effect can be obtained.

[Lithium ion secondary battery]
Next, as a specific example of the non-aqueous electrolyte secondary battery using the above-described negative electrode, a lithium ion secondary battery, particularly a laminate film type secondary battery will be described.

[Configuration of laminated film type secondary battery]
A laminate film type secondary battery is one in which a wound electrode body is accommodated mainly in a sheet-like exterior member. This wound body has a separator between a positive electrode and a negative electrode and is wound. There is also a case where a separator is provided between the positive electrode and the negative electrode and a laminate is accommodated. In both electrode bodies, a positive electrode lead is attached to the positive electrode and a negative electrode lead is attached to the negative electrode. The outermost peripheral part of the electrode body is protected by a protective tape.

  For example, the positive and negative electrode leads are led out in one direction from the inside of the exterior member to the outside. The positive electrode lead is formed of a conductive material such as aluminum, and the negative electrode lead is formed of a conductive material such as nickel and copper.

  The exterior member is, for example, a laminate film in which a fusion layer, a metal layer, and a surface protective layer are laminated in this order, and this laminate film is a fusion of two films so that the fusion layer faces the electrode body. The outer peripheral edges of the layers are bonded together with an adhesive or an adhesive. The fused part is a film such as polyethylene or polypropylene, and the metal part is an aluminum foil or the like. The protective layer is, for example, nylon.

  An adhesion film is inserted between the exterior member and the positive and negative electrode leads to prevent intrusion of outside air. This material is, for example, polyethylene, polypropylene, or polyolefin resin.

[Positive electrode]
The positive electrode has a positive electrode active material layer on both surfaces or one surface of a positive electrode current collector, for example, similarly to the negative electrode.

  The positive electrode current collector is formed of, for example, a conductive material such as aluminum.

  The positive electrode active material layer includes one or more of positive electrode materials capable of occluding and releasing lithium ions, and includes other materials such as a binder, a conductive additive, and a dispersant depending on the design. You can leave. In this case, details regarding the binder and the conductive additive are the same as, for example, the negative electrode binder and the negative electrode conductive additive already described.

As the positive electrode material, a lithium-containing compound is desirable. Examples of the lithium-containing compound include a composite oxide composed of lithium and a transition metal element, or a phosphate compound having lithium and a transition metal element. Among these described positive electrode materials, compounds having at least one of nickel, iron, manganese, and cobalt are preferable. These chemical formulas are represented by, for example, Li _x M ₁ O ₂ or Li _y M ₂ PO ₄ . In the formula, M ₁ and M ₂ represent at least one transition metal element. The values of x and y vary depending on the battery charge / discharge state, but are generally expressed as 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Examples of the composite oxide having lithium and a transition metal element include lithium cobalt composite oxide (Li _x CoO ₂ ) and lithium nickel composite oxide (Li _x NiO ₂ ). Examples of the phosphate compound having lithium and a transition metal element include a lithium iron phosphate compound (LiFePO ₄ ) or a lithium iron manganese phosphate compound (LiFe _1-u Mn _u PO ₄ (0 <u <1)). Is mentioned. This is because, when these positive electrode materials are used, a high battery capacity can be obtained and excellent cycle characteristics can be obtained.

[Negative electrode]
The negative electrode has, for example, a negative electrode active material layer on both sides of the current collector. The negative electrode preferably has a negative electrode charge capacity larger than the electric capacity (charge capacity as a battery) obtained from the positive electrode active material agent. This is because the deposition of lithium metal on the negative electrode can be suppressed.

  The positive electrode active material layer is provided on part of both surfaces of the positive electrode current collector, and the negative electrode active material layer is also provided on part of both surfaces of the negative electrode current collector. In this case, for example, the negative electrode active material layer provided on the negative electrode current collector is provided with a region where there is no opposing positive electrode active material layer. This is for a stable battery design.

  In the non-opposing region, that is, the region where the negative electrode active material layer and the positive electrode active material layer are not opposed to each other, there is almost no influence of charge / discharge. Therefore, the state of the negative electrode active material layer is maintained as it is immediately after formation. This makes it possible to accurately examine the composition and the like with good reproducibility without depending on the presence or absence of charge and discharge, such as the composition of the negative electrode active material.

[Separator]
The separator separates the positive electrode and the negative electrode, and allows lithium ions to pass through while preventing current short-circuiting due to bipolar contact. This separator is formed of a porous film made of, for example, a synthetic resin or ceramic, and may have a laminated structure in which two or more kinds of porous films are laminated. Examples of the synthetic resin include polytetrafluoroethylene, polypropylene, and polyethylene.

[Electrolyte]
At least a part of the active material layer or the separator is impregnated with a liquid electrolyte (electrolytic solution). This electrolytic solution has an electrolyte salt dissolved in a solvent, and may contain other materials such as additives.

  For example, a non-aqueous solvent can be used as the solvent. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, methyl propyl carbonate, 1,2-dimethoxyethane, and tetrahydrofuran. Among these, it is desirable to use at least one of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, and ethyl methyl carbonate. This is because better characteristics can be obtained. In this case, more advantageous characteristics can be obtained by combining a high viscosity solvent such as ethylene carbonate or propylene carbonate and a low viscosity solvent such as dimethyl carbonate, ethyl methyl carbonate, or diethyl carbonate. This is because the dissociation property and ion mobility of the electrolyte salt are improved.

  The solvent additive preferably contains an unsaturated carbon bond cyclic carbonate. This is because a stable film is formed on the surface of the negative electrode during charging and discharging, and the decomposition reaction of the electrolytic solution can be suppressed. Examples of the unsaturated carbon bond cyclic ester carbonate include vinylene carbonate and vinyl ethylene carbonate.

  The solvent additive preferably contains sultone (cyclic sulfonic acid ester). This is because the chemical stability of the battery is improved. Examples of sultone include propane sultone and propene sultone.

  Furthermore, it is preferable that the solvent contains an acid anhydride. This is because the chemical stability of the electrolytic solution is improved. Examples of the acid anhydride include propanedisulfonic acid anhydride.

The electrolyte salt can include, for example, any one or more of light metal salts such as a lithium salt. Examples of the lithium salt include lithium hexafluorophosphate (LiPF ₆ ) and lithium tetrafluoroborate (LiBF ₄ ).

  The content of the electrolyte salt is preferably 0.5 mol / kg or more and 2.5 mol / kg or less with respect to the solvent. This is because high ionic conductivity is obtained.

[Production method of laminated film type secondary battery]
A step of laminating or winding a negative electrode and a positive electrode via a separator to form a wound body, a step of encapsulating the wound body in a film, charging an electrolyte, and vacuum impregnation, and the film Including the step of fusing. Specifically, it is shown below.

  First, a positive electrode is manufactured using the positive electrode material described above. First, a positive electrode active material and, if necessary, a binder, a conductive additive and the like are mixed to form a positive electrode mixture, and then dispersed in an organic solvent to form a positive electrode mixture slurry. Subsequently, the mixture slurry is applied to the positive electrode current collector with a coating apparatus such as a die coater having a knife roll or a die head, and dried with hot air to obtain a positive electrode active material layer. Finally, the positive electrode active material layer is compression-molded with a roll press machine or the like. You may heat at this time.

  Next, a negative electrode is produced by forming a negative electrode active material layer on the negative electrode current collector using the same operation procedure as that for producing the negative electrode for a lithium ion secondary battery described above.

  When producing the positive electrode and the negative electrode, respective active material layers are formed on both surfaces of the positive electrode and the negative electrode current collector. At this time, the active material application length of both surface portions may be shifted in either electrode.

  Subsequently, an electrolytic solution is prepared. The positive electrode lead is attached to the positive electrode current collector and the negative electrode lead is attached to the negative electrode current collector by ultrasonic welding or the like. Then, a positive electrode and a negative electrode are laminated | stacked or wound through a separator, a wound electrode body is produced, and a protective tape is adhere | attached on the outermost periphery part. Next, the wound body is molded so as to have a flat shape. Subsequently, after sandwiching the wound electrode body between the folded film-shaped exterior members, the insulating portions of the exterior members are bonded to each other by a heat fusion method, and the wound electrode body is opened in only one direction. Encapsulate. An adhesion film is inserted between the positive electrode lead and the negative electrode lead and the exterior member. A predetermined amount of the adjusted electrolytic solution is introduced from the release portion, and vacuum impregnation is performed. After the impregnation, the release part is fused by a vacuum heat fusion method. As described above, a laminated film type secondary battery can be manufactured.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not restrict | limited to the following Example.

[Example 1-1]
A laminate film type secondary battery was produced by the following procedure.
First, a positive electrode was produced. The positive electrode active material was prepared by mixing 95 parts by mass of lithium cobalt oxide (LiCoO ₂ ), 2.5 parts by mass of a positive electrode conductive additive and 2.5 parts by mass of a positive electrode binder (polyvinylidene fluoride, PVDF). An agent was used. Subsequently, the positive electrode mixture was dispersed in an organic solvent (N-methyl-2-pyrrolidone, hereinafter also referred to as NMP) to obtain a paste slurry. Then, the slurry was apply | coated to both surfaces of the positive electrode electrical power collector with the coating device which has a die head, and it dried with the hot air type drying apparatus. At this time, a positive electrode current collector having a thickness of 15 μm was used. Finally, compression molding was performed with a roll press.

Next, a negative electrode was produced as described below.
First, the negative electrode active material particles contained in the negative electrode material of the present invention were prepared as follows.
First, a raw material mixed with metal silicon and silicon dioxide is placed in a reaction furnace, and vaporized in a 10 Pa vacuum atmosphere is deposited on an adsorption plate, cooled sufficiently, and then the deposit is taken out and ball milled. Crushed with. After adjusting the particle size, the obtained silicon oxide powder was set in the furnace, and then the furnace gas was filled with a hydrocarbon gas to raise the furnace temperature. A carbon film is formed on the surface of the silicon oxide particles by thermally decomposing methane. The in-furnace temperature was 1,000 ° C. and 2,000 Pa, and one time was 10 hours. After completion of the reaction, the temperature was lowered to 400 ° C. and exposed to the atmosphere, and a carbon film was formed again by the same method as described above.

At this time, in the negative electrode active material particles, the value of x of the silicon compound represented by SiO _x was 0.9, and the median diameter D ₅₀ of the silicon compound was 4 μm. Moreover, the coating amount of the carbon coating layer was 5% by mass with respect to the total of the silicon compound and the carbon coating layer.

  Subsequently, negative electrode active material particles and natural graphite were blended at a mass ratio of 10:90. After mixing the blended active material, carbon-based conductive additive, carbon-based conductive additive, and negative electrode binder (polyimide) precursor at a dry weight ratio of 80-83: 10: 2: 5-8, Diluted with NMP to obtain a paste-like negative electrode mixture slurry. In this case, NMP was used as a solvent for the polyamic acid. Subsequently, the negative electrode mixture slurry was applied to both surfaces of the negative electrode current collector with a coating apparatus and then dried. As this negative electrode current collector, an electrolytic copper foil (thickness = 15 μm) was used. Finally, baking was performed in a vacuum atmosphere at 400 ° C. for 1 hour. Thereby, a negative electrode binder (polyimide) is formed.

Next, after mixing a solvent (4-fluoro-1,3-dioxolan-2-one (FEC), ethylene carbonate (EC) and dimethyl carbonate (DMC)), an electrolyte salt (lithium hexafluorophosphate: LiPF) ₆ ) was dissolved to prepare an electrolytic solution. In this case, the composition of the solvent was FEC: EC: DMC = 10: 20: 70 as a deposition ratio, and the content of the electrolyte salt was 1.2 mol / kg with respect to the solvent.

  Next, a secondary battery was assembled as follows. First, an aluminum lead was ultrasonically welded to one end of the positive electrode current collector, and a nickel lead was welded to the negative electrode current collector. Subsequently, a positive electrode, a separator, a negative electrode, and a separator were laminated in this order and wound in the longitudinal direction to obtain a wound electrode body. The end portion was fixed with a PET protective tape. As the separator, a laminated film of 12 μm sandwiched between a film mainly composed of porous polyethylene and a film mainly composed of porous polypropylene was used. Subsequently, after sandwiching the electrode body between the exterior members, the outer peripheral edges except for one side were heat-sealed, and the electrode body was housed inside. As the exterior member, a nylon film, an aluminum foil, and an aluminum laminate film in which a polypropylene film was laminated were used. Subsequently, the prepared electrolyte was injected from the opening, impregnated in a vacuum atmosphere, and then heat-sealed and sealed.

The following evaluation was performed about the obtained negative electrode active material particle (silicon compound coated with carbon).
[BET specific surface area]
The measurement conditions of the BET one-point method and BET specific surface area evaluated by the N ₂ gas adsorption amount are adsorbate: nitrogen, adsorption temperature: 77K, and were measured by BELSORP-mini manufactured by Microtrac Bell Co., Ltd.
[Average hole diameter, hole volume]
The isothermal adsorption line obtained by the nitrogen gas adsorption method was calculated by the BET analysis.
[Carbon coverage, silicon carbide content]
It was measured with a Horiba carbon analyzer.
[Volume resistivity when compressed to a density of 1.5 cm ³ / g]
Measured with a resistivity meter manufactured by Mitsubishi Analitech Co., Ltd. (measurement conditions (i) device example: Loresta, (ii) measurement method: 4-terminal 4-probe method)
[Carbon film thickness]
The silicon compound covered with carbon was embedded in a resin, thinned with FIB, and the carbon film thickness of 30 particles was measured using a transmission electron microscope, and the average value was used.

The battery was evaluated as follows.
[Cycle characteristics]
The cycle characteristics were examined as follows. First, in order to stabilize the battery, charge / discharge was performed for 2 cycles in an atmosphere at 25 ° C., and the discharge capacity at the second cycle was measured. Subsequently, charge and discharge were performed until the total number of cycles reached 100, and the discharge capacity was measured each time. Finally, the discharge capacity at the 100th cycle was divided by the discharge capacity at the 2nd cycle and multiplied by 100 for% display, and the capacity maintenance rate (hereinafter, sometimes simply referred to as the maintenance rate) was calculated. As a cycle condition, the battery was charged at a current value of 0.2 C until 4.2 V was reached, and charged at a stage where the voltage reached 4.2 V until a utility pole value of 0.05 C was reached at a constant voltage of 4.2 V. During discharge, the battery was discharged at a current value of 0.2 C until the voltage reached 2.5V.

[Capacity maintenance ratio (%), initial efficiency (%), load characteristics]
For the initial charge / discharge characteristics, the initial efficiency (hereinafter sometimes referred to as initial efficiency) was calculated. The initial efficiency was calculated from an equation represented by initial efficiency (%) = (initial discharge capacity / initial charge capacity) × 100. The ambient temperature was the same as when the cycle characteristics were examined. The charge / discharge conditions were 0.2 times the cycle characteristics.
Regarding the load characteristics, after the initial discharge capacity measurement, constant voltage charging was performed under the same conditions as in the initial capacity measurement. Subsequently, each battery after charging was discharged at a current value of 4C until the voltage reached 2.5V, and the capacity at that time (4C capacity) was measured. For each battery, the 4C capacity was divided by the initial capacity, multiplied by 100 for% display, and the capacity maintenance rate was calculated. The higher the capacity retention rate, the better the load characteristics of the battery.

[Examples 1-2 to 1-4, Comparative examples 1-1 to 1-3]
Example 1-2 Except that the reaction pressure was changed to 1,500 Pa, the procedure was the same as in Example 1-1. Otherwise, the number of thermal decomposition CVD (carbon film formation reaction for thermally decomposing machine gas) was shown in the following table. Except for the above, a carbon-coated silicon compound (negative electrode active material particles) was obtained in the same manner as in Example 1-1.

  By performing the thermal decomposition CVD process 2 to 4 times, the capacity retention rate and the initial efficiency were high, and excellent load characteristics were exhibited. By carrying out the process a plurality of times, voids are formed in the carbon film, and the retention of the electrolytic solution is improved. In one process, voids are not easily formed in the carbon film, and thus the above effects are not observed. If it was performed 5 times or more, the load characteristics deteriorated. It is thought that the voids increase and the surface deposits are caused by side reactions.

[Examples 2-1 to 2-8]
A carbon-coated silicon compound (negative electrode active material particles) was obtained in the same manner as in Example 1-1 except that the hydrocarbon species, reaction pressure, and reaction time during pyrolysis CVD were as follows. The results of Example 1-1 are also shown.

By controlling the BET specific surface area in the range of 3.6 to 7.3 m ² / g, the capacity retention ratio, initial efficiency and load characteristics were all improved. When the BET specific surface area is 7.3 or more, the load characteristics are improved, but the initial efficiency tends to decrease due to the side reaction on the surface.

[Examples 3-1 to 3-3]
A silicon compound (negative electrode active material particles) coated with carbon was obtained in the same manner as in Example 1-1 except that the reaction time in pyrolysis CVD was as follows. The results of Example 1-1 are also shown.

  When the carbon coating amount is small, the battery characteristics tend to be lowered because of insufficient conductivity. In addition, when the amount of silicon carbide is small, SiOx and the carbon film form a chemical bond, and the effect of suppressing exfoliation of the carbon film derived from the expansion and contraction of the active material during charge and discharge is reduced, so the capacity maintenance rate is reduced. Resulting in. On the other hand, when the carbon coating amount is more than 15% by mass, the conductivity can be sufficiently ensured, but the capacity merit of SiO is lowered, which is not realistic. Moreover, when there is more silicon carbide than 1 mass%, since silicon carbide becomes a resistance component this time, there exists a possibility that it may interfere with a battery characteristic. From the above, the capacity retention rate, initial efficiency and load characteristics were all improved by setting the carbon amount to 1 to 15% by mass, the volume resistivity to 0.01 to 100Ω · cm or less, and silicon carbide to 1% by mass or less. .

[Examples 4-1 to 4-6]
A silicon compound coated with carbon (negative electrode active material particles) was obtained in the same manner as in Example 1-1 except that the hydrocarbon species and reaction time during pyrolysis CVD were as follows. The results of Example 1-1 are also shown.

  By controlling B / A in the range of 0.4 to 1.4, the capacity retention rate, initial efficiency, and load characteristics were all improved.

[Examples 5-1 to 5-4]
A silicon compound (negative electrode active material particles) coated with carbon was obtained in the same manner as in Example 1-1 except that the reaction temperature during pyrolysis CVD was as follows. The results of Example 1-1 are also shown.

  Even if the reaction temperature was changed, good battery characteristics were obtained by performing pyrolysis CVD a plurality of times. In particular, capacity retention ratios and load characteristics were improved under low temperature conditions of 800 ° C. and 900 ° C., and initial efficiency was improved under high temperature conditions of 1,100 ° C. and 1,200 ° C.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Claims (19)

  Carbon particles are formed on the surface of the particles made of the silicon compound, including a step of performing a carbon film forming reaction for thermally decomposing an organic gas 2 to 4 times on the surface of the particles made of a silicon compound (SiOx: 0.5 ≦ x <1.6). A method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery in which a film is formed and the carbon film has pores. The non-aqueous electrolyte secondary battery negative electrode active material according to claim 1, wherein the non-aqueous electrolyte secondary battery negative electrode active material has a BET specific surface area by a nitrogen gas adsorption method of 3.3 to 7.5 m ² / g. A method for producing a substance. The negative electrode active material of a nonaqueous electrolyte secondary battery according to claim ² , wherein the BET specific surface area of the negative electrode active material of the nonaqueous electrolyte secondary battery by a nitrogen gas adsorption method is 3.6 to 7.3 m ² / g. A method for producing a substance.   The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to any one of claims 1 to 3, wherein an average pore diameter of the pores calculated by a nitrogen gas adsorption method is 9.8 to 26.0 nm. . The opening volume of the opening calculated by the nitrogen gas adsorption method is 0.9 × 10 ^{−2 to} 5.7 × 10 ⁻² cm ³ / g. The negative electrode active material of a non-hydrolyzed secondary battery according to claim 1.   The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to any one of claims 1 to 5, wherein the non-aqueous electrolyte secondary battery negative electrode active material has a carbon coating amount of 0.5 to 19% by mass.   The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to claim 6, wherein the carbon coating amount is 1 to 15 mass%. The non-aqueous electrolyte according to any one of claims 1 to 7, wherein the non-aqueous electrolyte secondary battery negative electrode active material has a volume resistivity of 0.01 to 190 Ω · cm when compressed to a density of 1.5 cm ³ / g. A method for producing an electrolyte secondary battery negative electrode active material.   The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to claim 8, wherein the volume resistivity is 0.01 to 100 Ω · cm.   The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to any one of claims 1 to 9, wherein the non-aqueous electrolyte secondary battery negative electrode active material contains silicon carbide.   The method for producing a negative electrode active material for a nonaqueous electrolyte secondary battery according to claim 10, wherein the content of silicon carbide in the negative electrode active material for the nonaqueous electrolyte secondary battery is 1.6% by mass or less.   The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to claim 11, wherein the content of silicon carbide is 1% by mass or less.   The ratio of the carbon film thickness Anm formed in the first carbon coating process to the carbon film thickness Bnm formed in the second and subsequent carbon coating processes is 0.3 ≦ B / A <1.7. The manufacturing method of the nonaqueous electrolyte secondary battery active material of any one of Claims 1-12.   The said ratio is 0.4 <= B / A <1.4, The manufacturing method of the nonaqueous electrolyte secondary battery active material of Claim 13 characterized by the above-mentioned.   The method for producing a non-aqueous electrolyte secondary battery negative electrode active material according to any one of claims 1 to 14, wherein in the carbon film forming reaction, a thermal decomposition temperature is 600 ° C to 1,200 ° C.   The manufacturing method of the nonaqueous electrolyte secondary battery negative electrode characterized by using the nonaqueous electrolyte secondary battery active material obtained by the manufacturing method of any one of Claims 1-15.   The process which produces a slurry using the nonaqueous electrolyte secondary battery active material obtained by the manufacturing method of any one of Claims 1-15, and the process of apply | coating and drying a slurry to a negative electrode collector. A method for producing a non-aqueous electrolyte secondary battery negative electrode.   A method for producing a non-aqueous electrolyte secondary battery, wherein the negative electrode obtained by the production method according to claim 16 or 17 is used.   A step of forming a wound body by laminating or winding the negative electrode obtained by the manufacturing method of claim 16 or 17 and a positive electrode via a separator, and encapsulating the wound body in a film, A method for producing a non-aqueous electrolyte secondary battery, which includes a step of charging and vacuum impregnating, and a step of fusing the film.