JP5131429B2 - Negative electrode for nonaqueous electrolyte secondary battery and method for producing the same - Google Patents

Description

  The present invention relates to a negative electrode for a nonaqueous electrolyte secondary battery and a method for producing the same, and more particularly to a negative electrode for a lithium ion secondary battery and a method for producing the same.

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 (JP-A-5-174818) JP-A-6-60867: Patent Documents 1 and 2), a method of applying a molten metal quenching metal oxide as a negative electrode material (JP-A-10-294112: Patent Document 3), silicon oxide as a negative electrode material A method of using (Patent No. 2999741: Patent Document 4), a method of using Si ₂ N ₂ O and Ge ₂ N ₂ O as a negative electrode material (Patent No. 2999741: Patent Document 5), and the like are known.

  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.

Among them, the method using silicon oxide as the negative electrode material (Patent Document 4) tends to damage the negative electrode film due to expansion and contraction, although a lithium ion secondary battery with good battery characteristics can be obtained.
For example, Patent Document 6 (Japanese Patent Laid-Open No. 2006-172901) is known as a negative electrode to which a fibrous product or a needle-like filler is added.

JP-A-5-174818 JP-A-6-60867 JP 10-294112 A Japanese Patent No. 2999741 Japanese Patent No. 2999741 JP 2006-172901 A

  The present invention has been made in view of the above circumstances, and provides a negative electrode for a non-aqueous electrolyte secondary battery suitable as a negative electrode for a lithium ion secondary battery with little damage to the negative electrode film and a high capacity retention rate, and a method for producing the same The purpose is to do.

As a result of intensive studies to achieve the above object, the present inventors have determined that the particle size distribution is a laser diffraction scattering type particle size distribution measuring method as a negative electrode active material containing silicon capable of occluding and releasing lithium ions. the particle diameter corresponding to cumulative 50% cumulative particle size from fine side when the D _50, with selected so D ₅₀ is in the range of 0.1 to 30 [mu] m, is added to the negative active material according to fiber length of the fibrous polymeric material selected to be a negative electrode active material particle diameter D ₅₀ or more containing silicon, the fibrous polymer material with respect to the negative electrode active material from 0.2 to 30 wt% In this case, it has been found that it is effective to achieve the above object by using an added material, in particular, by firing a mixture containing these at 200 ° C. or higher, and the present invention has been made.

Accordingly, the present invention provides the following negative electrode for a non-aqueous electrolyte secondary battery and a method for producing the same.
[1]. (1), (2) and (3) below
(1) High-purity silicon powder having a metal impurity concentration of 1 ppm or less, chemical-grade silicon powder, metallurgically refined metal silicon processed into powder, alloys thereof, lower oxides of silicon and partial oxidation , Silicon nitride and partial nitride,
(2) The above (1) is further mixed with a carbon material, alloyed, coated with a conductive material, carbon precipitated with an organic gas, carbonized resin, carbon black on resin And carbonized after adding
(3) It is possible to occlude and release lithium ions selected from particles having a structure in which silicon microcrystals having a size of 1 to 500 nm are dispersed in a silicon-based compound and those coated with carbon. A negative electrode for a non-aqueous electrolyte secondary battery, comprising: a negative electrode active material containing silicon; and a negative electrode material containing 0.2 to 30% by mass of a fibrous polymer material with respect to the negative electrode active material, When the particle size distribution of the negative electrode active material containing a particle diameter corresponding to 50 mass% cumulative from the fine particle side is D ₅₀ by the cumulative particle diameter measured by the laser diffraction scattering particle size distribution measurement method, D ₅₀ is 0.1 to 30 μm. The mixture of the negative electrode active material containing silicon and the fibrous polymer material is 200 ° C., and the fiber length of the fibrous polymer material is not less than the particle diameter D _{50 of} the negative electrode active material containing silicon. Obtained by firing above Negative electrode for a nonaqueous electrolyte secondary battery characterized in that it.
[2]. The fibrous polymer substance is a polymer fibrous product selected from cellulose resin, phenol resin, polyvinyl alcohol resin, furan resin, polystyrene resin, polyimide resin, polyamide resin and acrylic resin [1. ] The negative electrode for nonaqueous electrolyte secondary batteries of description.
[3]. A negative electrode active material containing silicon capable of inserting and extracting lithium ions, particles having a structure in which microcrystals of silicon having a size of 1 to 500 nm are dispersed in a silicon-based compound, and this are coated with carbon The negative electrode for a nonaqueous electrolyte secondary battery according to [1] or [2], wherein the negative electrode is selected from those described above.
[4]. The negative electrode for a non-aqueous electrolyte secondary battery according to [1], [2] or [3], characterized by having a space.
[5]. (1), (2) and (3) below
(1) High-purity silicon powder having a metal impurity concentration of 1 ppm or less, chemical-grade silicon powder, metallurgically refined metal silicon processed into powder, alloys thereof, lower oxides of silicon and partial oxidation , Silicon nitride and partial nitride,
(2) The above (1) is further mixed with a carbon material, alloyed, coated with a conductive material, carbon precipitated with an organic gas, carbonized resin, carbon black on resin And carbonized after adding
(3) Particles having a structure in which silicon microcrystals having a size of 1 to 500 nm are dispersed in silicon-based compounds, and those coated with carbon
As a negative electrode active material containing silicon that can occlude / release lithium ions, the particle size distribution is 50 mass% cumulative from the fine particle side by the particle size distribution measured by the laser diffraction scattering particle size distribution measurement method. when the particle diameter corresponding to a D ₅₀ to, together with selected so D ₅₀ is in the range of 0.1 to 30 [mu] m, containing a fiber length of silicon fibrous polymer material to be added to the anode active material The negative electrode active material is selected so as to have a particle diameter D ₅₀ or larger, and a mixture containing 0.2 to 30% by mass of the fibrous polymer material added to the negative electrode active material is fired at 200 ° C. or higher. A method for producing a negative electrode for a non-aqueous electrolyte secondary battery.
[6]. The fibrous polymer substance is a polymeric fibrous product selected from cellulose resin, phenol resin, polyvinyl alcohol resin, furan resin, polystyrene resin, polyimide resin, polyamide resin and acrylic resin [5. ] The manufacturing method of the negative electrode for nonaqueous electrolyte secondary batteries of description.

  According to the present invention, it is possible to produce a nonaqueous electrolyte secondary battery, in particular, a negative electrode for a lithium ion secondary battery, which is less damaged, has a high capacity retention rate, is excellent in cycle characteristics, and is advantageous in terms of cost.

  The negative electrode for a non-aqueous electrolyte secondary battery according to the present invention contains 0.2 to 30% by mass of a fibrous polymer material with respect to a negative electrode active material containing silicon capable of occluding and releasing lithium ions. Is.

  Here, examples of the negative electrode active material include an active material containing silicon capable of inserting and extracting lithium ions. Specifically, chemical-grade silicon from which metal impurities are removed by washing with high-purity silicon powder or hydrochloric acid with a metal impurity concentration of 1 ppm or less and then treating with hydrofluoric acid or a mixture of hydrofluoric acid and nitric acid. Powders and metallurgically refined metal silicon processed into powder, their alloys, lower oxides and partial oxides of silicon, silicon nitrides and partial nitrides, and further for conducting a conductive treatment Mixed with carbon materials, alloyed by mechanical alloying, etc., coated with a conductive material such as metal by sputtering or plating, deposited carbon with organic gas, carbonized resin or resin Including carbon black added and carbonized. In this case, the negative electrode active material is a particle having a structure in which silicon microcrystals having a size of 1 to 500 nm are dispersed in a silicon-based compound, particularly silicon dioxide, as described in JP-A-2004-47404. Those having a surface coated with carbon are preferred. These active materials have a charge / discharge capacity higher than that of conventionally used graphite, but there is a problem that the electrodes are damaged by volume expansion and contraction that occur when charge / discharge is repeated. In particular, lower oxides of silicon exhibit much smaller volume expansion and contraction when repeated charge / discharge than when silicon itself is used, and the cycle characteristics are good, but there is still room for improvement. It was.

From this point, in the present invention, as the negative electrode active material containing silicon, the particle size distribution is a particle size corresponding to a cumulative particle size by the laser diffraction scattering type particle size distribution measurement method of 50% by mass from the fine particle side. _{When 50} , D ₅₀ is in the range of 0.1 to 30 μm.

A negative electrode using a negative electrode active material containing silicon capable of occluding and releasing lithium ions has a larger expansion / shrinkage due to lithium doping and dedoping compared to graphite, so that the expansion / shrinkage of the electrode is uniform. It is preferable that each particle is uniform. That is, when the negative electrode active material containing silicon has a cumulative particle diameter measured by the laser diffraction scattering particle size distribution measurement method as a particle diameter corresponding to a cumulative 50 mass% from the fine particle side as D ₅₀ , D ₅₀ is 0.1 to 30 μm. A negative electrode material with uniform expansion and contraction can be obtained by using a negative electrode active material containing silicon having a particle size distribution of 0.5 to 20 μm.

  In order to obtain a predetermined particle diameter, a well-known pulverizer and a well-known classifier are used. The crusher, for example, moves the grinding media such as balls and beads, and uses the impact force, friction force, and compression force due to the kinetic energy to crush the material to be crushed, the media agitation mill, and the compression force by the roller. Rolling mill that uses pulverization, jet mill that pulverizes the crushed material against the lining material at high speed, and pulverization using the impact force, and impact force caused by rotation of a rotor with a hammer, blade, pin, etc. A hammer mill, a pin mill, a disk mill, a colloid mill using a shearing force, a high-pressure wet opposed collision type disperser “Ultimizer”, or the like is used. For pulverization, both wet and dry processes are used. In order to adjust the particle size distribution after pulverization, dry classification, wet classification or sieving classification is used. In the dry classification, the process of dispersion, separation (separation of fine particles and coarse particles), collection (separation of solid and gas), and discharge are performed sequentially or simultaneously, mainly using air flow. Pre-classification (adjustment of moisture, dispersibility, humidity, etc.) is performed before classification so that the classification efficiency is not reduced due to the shape, air flow disturbance, velocity distribution, static electricity, etc. Used by adjusting moisture and oxygen concentration. In the type in which the dry classifier is integrated with the jet mill, pulverization and classification are performed at a time, and a desired particle size distribution can be obtained.

Furthermore, in the present invention, in order to hold the negative electrode material, it has a fiber length that is at least equal to the particle diameter D ₅₀ of the negative electrode active material containing silicon, more preferably a fiber length that is not less than 2 times and not more than 10 times. The organic compound polymer fibrous product (fibrous polymer material) is 0.2 to 30% by mass, preferably 0.2 to 20% after the drying (firing) step in producing the negative electrode material with respect to the negative electrode active material. It is contained by mass%, more preferably 1 to 20 mass%, still more preferably 2 to 15 mass%. When a fibrous product having a fiber length exceeding 10 times the particle diameter D ₅₀ of the negative electrode active material is used, it is difficult to produce a uniform paste during electrode production or to apply uniformly. There is a risk of becoming. On the other hand, if the content is too small, the effect of adding the fibrous product is not recognized. If the content is too large, the content of the active material is reduced and the charge / discharge capacity is lowered.

  In this case, the conventional fibrous products include conductive carbon fibers, single-walled and multi-walled carbon nanotubes, such as VGCF (fiber diameter 150 nm, fiber length 10 μm) of Showa Denko KK or the like. Although it is mentioned as a carbon nanotube, there exist the problem of a micro short circuit and the problem of cost as it exists in patent document 6, and the careful attention was required for the use of carbon fiber.

  On the other hand, the fibrous polymer material suitably used in the present invention is a high polymer selected from at least one of cellulose resin, phenol resin, polyvinyl alcohol resin, furan resin, polystyrene resin, polyimide resin, polyamide resin, and acrylic resin. It is a fibrous product of a molecular substance, particularly preferably a cellulose fiber, which may be partially or wholly carbonized in the firing step as long as it has a fibrous structure.

  Cellulose is used as a negative electrode active material as a baked product of crystalline cellulose in JP-A-2-54866, and cellulose carbonized at a high temperature can be used as a negative electrode material for lithium secondary batteries having excellent characteristics. is there. A method of consolidating the electrode in order to improve the capacity per volume at the time of electrode preparation is general, but when using a negative electrode active material containing silicon that has a large expansion and contraction, there are problems such as difficulty in consolidating the electrode was there. On the other hand, the electrode compacted using cellulose fibers is 200 ° C. or higher (usually 200 to 500 ° C.), preferably 200 to 400 ° C., more preferably 200 to 350 ° C., and even more preferably about 200 to 300 ° C. By firing, it becomes possible to create an appropriate space, and the effect of alleviating expansion and contraction, and further increasing the temperature to retain and carbonize the fibrous structure of cellulose, ensuring a conductive path and relaxation during expansion and contraction Thus, it is possible to produce a negative electrode that is effective as a role.

  The negative electrode for a non-aqueous electrolyte secondary battery according to the present invention can be used as a positive electrode, a negative electrode, a separator, a secondary battery provided with a non-aqueous electrolyte, particularly a negative electrode of a lithium ion secondary battery.

Here, examples of the positive electrode active material include oxides, sulfides, and organic polymer compounds capable of occluding and releasing lithium ions, and any one or more of these are used. Specifically, for example, TiS ₂ , MoS ₂ , NbS ₂ , ZrS ₂ , VS ₂ , V ₂ O ₅ , MoO ₃ , Mg (V ₃ O ₈ ) ₂ and other metal sulfides and oxides not containing lithium, or lithium composite oxide is exemplified containing lithium and a composite metal such as NbSe ₂ can also be mentioned. Among these, in order to increase the energy density, a lithium composite oxide mainly composed of Li (Met) _x O ₂ is preferable. Specifically, Met is preferably at least one of cobalt, nickel, iron, and manganese, and x is usually a value in the range of 0.05 ≦ x ≦ 1.10. Specific examples of such a lithium composite oxide include LiCoO ₂ , LiNiO ₂ , LiFeO ₂ , Li _x Ni _y Co _1-y O ₂ having a layer structure (where 0.05 ≦ x ≦ 1.10, 0 ≦ y ≦ 1), spinel-structured LiMn ₂ O ₄ and orthorhombic LiMnO ₂ . Furthermore, substituted spinel manganese compounds LiMet _x Mn _1-x O ₄ (where 0 ≦ x ≦ 1) are also used as high-voltage compatible types, where Met is titanium, chromium, iron, cobalt, copper, zinc, etc. Is mentioned.

  The lithium composite oxide is obtained by, for example, grinding lithium carbonate, nitrate, chloride or hydroxide and transition metal carbonate, nitrate, oxide or hydroxide according to a desired composition. It is prepared by mixing and baking at a temperature in the range of 600 to 1,000 ° C. in an oxygen atmosphere.

  Furthermore, an organic polymer compound can also be used as the positive electrode active material. Illustrative examples include high molecular compounds such as conductive polymers such as polyacetylene, polypyrrole, polyparaphenylene, polyaniline, polythiophene, polyacene, and polysulfide compounds.

  There is no restriction | limiting in particular about the preparation methods of a positive electrode and a negative electrode. In general, an active material, a binder, a conductive agent or the like is added to a solvent to form a slurry, which is applied to a current collector sheet, dried and pressed.

  Examples of the binder generally include polyvinylidene fluoride, polytetrafluoroethylene, styrene / butadiene rubber, isoprene rubber, various polyimides, and polyamide resins. In particular, various polyimides and polyamide resins are particularly preferable for shrinking cellulose fibers at high temperatures and using them as relaxation of expansion and contraction. The amount used thereof is usually 20% by mass or less (0 to 20% by mass), preferably 2 to 20% by mass, and more preferably about 5 to 15% by mass with respect to the entire positive electrode or negative electrode.

  Examples of the conductive agent generally include carbon-based materials such as graphite and carbon black, and metal materials such as copper and nickel. The usage-amount can be made into about 50 mass% or less (0-50 mass%) with respect to the whole positive electrode or a negative electrode.

  Examples of the current collector include aluminum or an alloy thereof for the positive electrode, and a metal such as copper, stainless steel, nickel, or an alloy thereof for the negative electrode.

In the present invention, for the production of the negative electrode, a slurry is prepared by adding the negative electrode active material, the fibrous polymer material, the binder, and, if necessary, a conductive agent to the current collector sheet. after the one was applied and dried, pressure 0~5ton / cm ^2, in particular crimped in 0~2ton / cm ^2, 200 ℃ or higher, preferably 250 to 500 ° C., more preferably at 250 to 450 ° C. , 0.5 to 20 hours, particularly 1 to 10 hours are preferably used.

  In addition, the separator used between the positive electrode and the negative electrode is not particularly limited as long as it is stable with respect to the electrolytic solution and has excellent liquid retention, but generally a porous sheet of polyolefin such as polyethylene and polypropylene, Or a nonwoven fabric is mentioned.

  The shape of the battery is arbitrary and is not particularly limited. In general, a coin type in which an electrode punched into a coin shape and a separator are stacked, a cylinder type in which an electrode sheet and a separator are spiraled, and the like can be given.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated concretely, this invention is not limited to the following Example. In the following examples,% indicates mass%.

[Example 1]
[Preparation of negative electrode active material (conductive silicon composite)]
A conductive silicon composite as a negative electrode active material was produced based on the method described in JP-A-2004-47404. The production method is described below.
A mixed powder prepared by mixing silicon dioxide powder (BET specific surface area = 200 m ² / g) and metal silicon powder for chemical grade (BET specific surface area = 4 m ² / g) at an equimolar ratio was 1,350 ° C., 0.1 Torr. Then, the generated SiO _x gas was deposited on a SUS substrate. Next, this precipitate was collected and then pulverized with a jet mill (manufactured by Hosokawa Micron Corporation), and oxidation of D ₅₀ = 4.8 μm and D ₁₀ = 2.5 μm (D ₅₀ / D ₁₀ = 1.9). Silicon powder (SiO _x : x = 1.02) was obtained. The powder obtained here was subjected to X-ray diffraction using Cu-Kα rays, and it was confirmed that the obtained powder was amorphous silicon oxide (SiO _x ) powder.

The obtained silicon oxide powder of D ₅₀ = 4.8 μm was mixed with a non-uniform silicon oxide using a rotary kiln type reactor under conditions of 1,150 ° C. and average residence time of about 2 hours under a methane-argon mixed gas flow. At the same time, thermal CVD was performed. After the operation was completed, the temperature was lowered and black powder was recovered. The amount of deposited carbon of the obtained black powder is 5.2%. From the X-ray diffraction pattern, the obtained black powder is different from the silicon oxide powder in that Si (111) around 2θ = 28.4 °. ), And the crystal size is obtained from the half-value width of this diffraction line by the Scherrer method. The size of the silicon crystal dispersed in silicon dioxide is 11 nm. A conductive silicon composite powder having a D ₅₀ = 4.8 μm in which fresh silicon (Si) crystals are dispersed in silicon dioxide (SiO ₂ ) was prepared.

[Production of negative electrode]
The negative electrode was produced according to the following procedure.
Weigh the powder of cellulose fiber (fiber diameter 1 μm, fiber diameter 5-30 μm, average particle diameter D ₅₀ = 6.0 μm) into the conductive silicon composite powder of D ₅₀ = 4.8 μm at a mass ratio of 95: 5. Add 10% polyimide to this, add N-methylpyrrolidone to make a slurry, apply this slurry to a 20 μm thick copper foil, vacuum dry at 80 ° C. for 1 hour, then press-mold the electrode by roller press Then, it was vacuum-dried (fired) at 400 ° C. for 1 hour, punched out to 2 cm ² and used as a negative electrode.

[Production of battery]
Here, in order to evaluate the charge / discharge characteristics of the obtained negative electrode, a lithium foil was used as a counter electrode, and lithium hexafluoride was mixed with 1/1 (volume ratio) of ethylene carbonate and diethyl carbonate as a non-aqueous electrolyte. A lithium ion secondary battery for evaluation using a non-aqueous electrolyte solution dissolved at a concentration of 1 mol / L and a polyethylene microporous film having a thickness of 30 μm as a separator was prepared.

The prepared lithium ion secondary battery was allowed to stand at room temperature overnight, and then charged with a secondary battery charge / discharge tester (manufactured by Nagano Co., Ltd.) until the test cell voltage reached 0 V at 0.5 mA / cm ² . Charging was performed at a constant current, and after reaching 0V, charging was performed by decreasing the current so as to keep the cell voltage at 0V. The charging was terminated when the current value fell below 0.1 mA / cm ² . Discharging was performed at a constant current of 0.5 mA / cm ² , and discharging was terminated when the cell voltage exceeded 2.0 V, and the discharge capacity was determined. The above charge / discharge test was repeated 100 times, and the cycle retention after 100 cycles was determined. The results are shown in Table 1.

Moreover, the differential thermal analysis (Tg-DTA) of the used cellulose fiber was calculated | required in 100-500 degreeC, the temperature increase rate of 5.0 degree-C / min, and nitrogen atmosphere under atmospheric pressure. The results are shown in FIG.
It can be seen from FIG. 1 that the used cellulose fibers have a mass reduction from around 300 ° C. and a mass of about 10% at 400 ° C.
Furthermore, the specific resistance was calculated | required by the four-terminal method what used the cellulose fiber separately heat-processed at 400 degreeC. The specific resistance was 0.1 Ω · cm.

[Example 2]
[Production of negative electrode]
The same procedure was followed except that the drying (firing) temperature of the negative electrode of Example 1 was 250 ° C. The results are shown in Table 1.
Moreover, the specific resistance was calculated | required by the four-terminal method what used the cellulose fiber separately heat-processed at 250 degreeC. The specific resistance was 10 ⁷ Ω · cm or more.

[Comparative Example 1]
Using the negative electrode active material (conductive silicon composite powder) prepared in Example 1, 10% of polyimide was added, N-methylpyrrolidone was further added to form a slurry, and this slurry was applied to a copper foil having a thickness of 20 μm. After vacuum drying at 80 ° C. for 1 hour, the electrode was press-molded with a roller press, vacuum dried at 400 ° C. for 1 hour, punched out to 2 cm ² and used as a negative electrode.
A lithium ion secondary battery was produced in the same manner as in Example 1, and the cycle characteristics were determined. The results are shown in Table 1.

It is a figure which shows the differential thermal analysis (Tg-DTA) of a cellulose fiber.

Claims (6)

(1), (2) and (3) below
(1) High-purity silicon powder having a metal impurity concentration of 1 ppm or less, chemical-grade silicon powder, metallurgically refined metal silicon processed into powder, alloys thereof, lower oxides of silicon and partial oxidation , Silicon nitride and partial nitride,
(2) The above (1) is further mixed with a carbon material, alloyed, coated with a conductive material, carbon precipitated with an organic gas, carbonized resin, carbon black on resin And carbonized after adding
(3) It is possible to occlude and release lithium ions selected from particles having a structure in which silicon microcrystals having a size of 1 to 500 nm are dispersed in a silicon-based compound and those coated with carbon. A negative electrode for a non-aqueous electrolyte secondary battery, comprising: a negative electrode active material containing silicon; and a negative electrode material containing 0.2 to 30% by mass of a fibrous polymer material with respect to the negative electrode active material, When the particle size distribution of the negative electrode active material containing a particle diameter corresponding to 50 mass% cumulative from the fine particle side is D ₅₀ by the cumulative particle diameter measured by the laser diffraction scattering particle size distribution measurement method, D ₅₀ is 0.1 to 30 μm. The mixture of the negative electrode active material containing silicon and the fibrous polymer material is 200 ° C., and the fiber length of the fibrous polymer material is not less than the particle diameter D _{50 of} the negative electrode active material containing silicon. Obtained by firing above Negative electrode for a nonaqueous electrolyte secondary battery characterized in that it.   The fibrous polymer substance is a polymer fibrous product selected from cellulose resin, phenol resin, polyvinyl alcohol resin, furan resin, polystyrene resin, polyimide resin, polyamide resin and acrylic resin. 1. A negative electrode for a non-aqueous electrolyte secondary battery according to 1.   A negative electrode active material containing silicon capable of inserting and extracting lithium ions, particles having a structure in which microcrystals of silicon having a size of 1 to 500 nm are dispersed in a silicon-based compound, and this are coated with carbon The negative electrode for a non-aqueous electrolyte secondary battery according to claim 1 or 2, wherein the negative electrode is selected from those described above.   The negative electrode for a nonaqueous electrolyte secondary battery according to claim 1, wherein the negative electrode has a space. (1), (2) and (3) below
(1) High-purity silicon powder having a metal impurity concentration of 1 ppm or less, chemical-grade silicon powder, metallurgically refined metal silicon processed into powder, alloys thereof, lower oxides of silicon and partial oxidation , Silicon nitride and partial nitride,
(2) The above (1) is further mixed with a carbon material, alloyed, coated with a conductive material, carbon precipitated with an organic gas, carbonized resin, carbon black on resin And carbonized after adding
(3) Particles having a structure in which silicon microcrystals having a size of 1 to 500 nm are dispersed in silicon-based compounds, and those coated with carbon
As a negative electrode active material containing silicon that can occlude / release lithium ions, the particle size distribution is 50 mass% cumulative from the fine particle side by the particle size distribution measured by the laser diffraction scattering particle size distribution measurement method. when the particle diameter corresponding to a D ₅₀ to, together with selected so D ₅₀ is in the range of 0.1 to 30 [mu] m, containing a fiber length of silicon fibrous polymer material to be added to the anode active material The negative electrode active material is selected so as to have a particle diameter D ₅₀ or larger, and a mixture containing 0.2 to 30% by mass of the fibrous polymer material added to the negative electrode active material is fired at 200 ° C. or higher. A method for producing a negative electrode for a non-aqueous electrolyte secondary battery. The fibrous polymer substance is a polymer fibrous product selected from cellulose resin, phenol resin, polyvinyl alcohol resin, furan resin, polystyrene resin, polyimide resin, polyamide resin and acrylic resin. 5. A method for producing a negative electrode for a nonaqueous electrolyte secondary battery according to 5 .

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