JP2010244767A - Method for manufacturing anode for lithium secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing an anode for a lithium secondary battery not only having remarkably excellent cycle characteristics but also having large capacity which stands a practical use as an electrode for a lithium secondary battery. <P>SOLUTION: In the method for manufacturing a lithium secondary battery anode by adhering active material particles on a collector with the use of solid high-speed collision method, the active material particles are complexes made by integrating with a first substance of one or more kinds selected from a group consisting of silicon, silicon alloy, tin and tin alloy, and a second substance of one or more kinds selected from a group consisting of tin, copper, magnesium, iron, cobalt, nickel, zinc, aluminum, germanium, indium and carbon. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

The present invention relates to a method for producing a negative electrode for a lithium secondary battery used as a power storage device such as a mobile phone or a notebook computer.

2. Description of the Related Art In recent years, lithium secondary batteries that are charged and discharged by moving lithium ions between a positive electrode and a negative electrode are widely used as power storage devices used in mobile applications such as mobile phones and power storage applications for automobiles. Recently, with the improvement in performance of mobile phones and the like, higher capacity of lithium secondary batteries has been increasingly demanded. However, the graphite material, which is currently the mainstream of negative electrode active materials, has already reached almost the theoretical capacity, and there is a strong demand for a shift to higher capacity active materials. In order to meet this demand, silicon, which is a high-capacity metal active material, has attracted attention as an electrode material. It has been pointed out that silicon, which is a high-capacity active material, has poor cycle characteristics because the silicon itself pulverizes and peels off from the current collector by repeated expansion and contraction during the insertion and release of lithium ions during charge and discharge. It was. For example, when silicon particles are applied to a current collector by a coating method using a slurry mixture that is usually used in the manufacture of lithium secondary battery electrodes, the adhesion between the silicon particles and the current collector is improved. It cannot be raised sufficiently. Therefore, peeling of silicon from the current collector could not be sufficiently suppressed, and cycle characteristics could not be improved.

Thus, various attempts have been made to improve the adhesion between the silicon particles and the current collector in the electrode for the lithium secondary battery. For example, in Patent Documents 1 and 2, silicon particles are dispersed in an air stream without being melted or evaporated, and the air stream is blown onto a current collector to cause the silicon particles to collide with the current collector at high speed. A method of depositing silicon particles on a current collector using a cold spray method, which is one of the solid high-speed collision methods for bringing silicon particles into close contact with the current collector surface, is disclosed. According to the method, for a lithium secondary battery, the silicon particles are in direct contact with the current collector surface in a state in which the bottom surface portion is embedded in a recess formed by an impact that collides with the current collector surface. An electrode can be manufactured. The electrode for the lithium secondary battery has high adhesion between the silicon particles and the current collector, and has remarkably good cycle characteristics as compared with an electrode manufactured by a conventional slurry coating method.

JP-A-2005-310502 JP 2005-332797 A

By the way, even if the adhesion between the silicon particles and the current collector is increased and the cycle characteristics are enhanced as in Patent Documents 1 and 2, it is generally used at present for use as an electrode for a lithium secondary battery. If it is intended to face the lithium cobalt oxide positive electrode, it is expected that the capacity per unit area is 3 mAh / cm ² or more. If only one layer of silicon is deposited on the current collector, the capacity does not reach 1 mAh / cm ² . Therefore, for practical use, it is necessary to deposit at least four silicon layers. However, silicon cannot be deposited directly on silicon deposited on the current collector even by the solid high-speed collision method. Therefore, in Patent Document 2, a mixture of silicon particles and other particles, for example, tin, copper, magnesium, iron, cobalt, nickel, zinc, aluminum, germanium, or indium particles is placed on a current collector by a cold spray method. It has been proposed to deposit. However, for example, in a mixture of silicon powder and copper powder, there is a difference in impact force at the time of collision due to the difference in specific gravity, particle size, and shape of the both, and only copper powder is selectively deposited in part. The harmful effect of forming a uniform film of only copper occurs. Since copper is inactive to lithium, when a uniform film of copper is formed, the movement of lithium is inhibited, and the silicon layer formed below the copper film cannot react with lithium. The capacity cannot be increased.

Therefore, the problem to be solved by the present invention is not only a cycle characteristic is remarkably good, but also a method for producing a negative electrode for a lithium secondary battery having a capacity large enough to be put into practical use as an electrode for a lithium secondary battery. It is to provide.

The present inventors firstly mixed silicon particles with other particles such as tin, copper, magnesium, iron, cobalt, nickel, zinc, aluminum, germanium or indium particles as described in Patent Document 2. Was attempted to be deposited on the current collector evenly by, for example, a cold spray method. However, as is remarkable with the mixture of silicon particles and copper particles, depending on the deposition properties of each material, it causes uneven deposition of each material, and an ideal randomly deposited state can be achieved. After all, it was not easy to increase the battery capacity. Therefore, the present inventors have thought that if silicon particles and other particles are pre-combined in a random state, it is possible to prevent the bias that occurs during deposition and increase the battery capacity. It came. However, it was not easy to combine these particles in a random state. The inventors of the present invention have made various studies to achieve this, and when these particles are processed using an appropriate powder secondary processing method, for example, an apparatus capable of applying a shearing force such as an attritor or a ball mill is provided. They found that if used and processed, they could be compounded in a random state. If the composite is brought into close contact with the current collector by a solid high-speed collision method, for example, cold spray, the composite can be firmly brought into close contact with the current collector and cycle characteristics can be improved. The present inventors have found that this can be done and have completed the present invention.

That is, the present invention
(1) A method for producing a negative electrode for a lithium secondary battery by bringing active material particles into close contact with a current collector using a solid high-speed collision method, wherein the active material particles include silicon, silicon alloy, tin, and One or more first substances selected from the group consisting of tin alloys and one or more second substances selected from the group consisting of tin, copper, magnesium, iron, cobalt, nickel, zinc, aluminum, germanium, indium and carbon It is a manufacturing method characterized by being a composite united with a substance.

As a preferred embodiment,
(2) The production method according to the above (1), wherein the mass ratio of the first substance to the second substance is 5:95 to 95: 5,
(3) The production method according to the above (1), wherein the mass ratio of the first substance to the second substance is 7:93 to 75:25,
(4) The production method according to the above (1), wherein the mass ratio of the first substance to the second substance is 10:90 to 50:50,
(5) The production method according to any one of (1) to (4), wherein in the particle size distribution of the composite, particles having a particle size of 50 μm or less are 95% by volume or more,
(6) The production method according to any one of (1) to (4), wherein in the particle size distribution of the composite, particles having a particle size of 1 to 50 μm are 95% by volume or more,
(7) The production method according to any one of (1) to (4) above, wherein in the particle size distribution of the composite, particles having a particle size of 5 to 25 μm are 95% by volume or more,
(8) The manufacturing method according to any one of (1) to (7), wherein the first substance is silicon or a silicon alloy, and the second substance is copper.
(9) The manufacturing method according to any one of (1) to (8), wherein the current collector surface is made of copper, a copper alloy, iron, nickel, zinc, or stainless steel.
(10) The manufacturing method according to any one of (1) to (8), wherein the current collector surface is made of copper or a copper alloy.
(11) The production method according to any one of (1) to (10), wherein the composite is produced by a powder secondary processing method,
(12) The production method according to the above (11), wherein the powder secondary processing method is performed by an attritor or a ball mill.

In the production method of the present invention, one or more first substances selected from the group consisting of silicon, silicon alloy, tin and tin alloy, and tin, copper, magnesium, iron, cobalt, nickel, zinc, aluminum, A composite with one or more second substances selected from the group consisting of germanium, indium, and carbon is manufactured and deposited on the current collector by a solid high-speed collision method. It can be made to adhere to the body, thereby giving a capacity large enough to be put into practical use as a negative electrode for a lithium secondary battery. In addition, since the composite particles are applied by the solid high-speed collision method, the adhesion between the particles and the current collector is high, and extremely good cycle characteristics are provided.

FIG. 1 is an explanatory view showing a schematic structure of a complex. FIG. 2 is an electron micrograph (reflected electron image) of a composite composed of silicon and copper. (Example 1) FIG. 3 is an electron micrograph (reflected electron image) of a composite composed of silicon and copper. (Example 2) FIG. 4 is an explanatory diagram showing the configuration of the apparatus used for the solid high-speed collision method used in the examples and comparative examples. FIG. 5 is an electron micrograph of an electrode cross section in which a composite made of silicon and copper is deposited by a solid high-speed collision method. (Example 1) FIG. 6 is an electron micrograph of a cross section of an electrode deposited by a composite solid high-speed collision method composed of silicon and copper. (Example 2) FIG. 7 is an electron micrograph of an electrode cross section in which only silicon particles are deposited by a solid high-speed collision method. (Comparative Example 1) FIG. 8 is an electron micrograph of an electrode cross section in which a simple mixture of silicon particles and copper particles is deposited by a solid high-speed collision method. (Comparative Example 2) FIG. 9 is an electron micrograph of an electrode cross section in which a simple mixture of silicon particles and iron particles is deposited by a solid high-speed collision method. (Comparative Example 3)

The active material particles used in the production method of the present invention are one or more first substances selected from the group consisting of silicon, silicon alloys, tin and tin alloys, tin, copper, magnesium, iron, cobalt, nickel, zinc , Aluminum, germanium, indium, and carbon. Here, the composite refers to a particulate material in which the particles of the first substance and the particles of the second substance are integrated by physical and / or chemical action. The composite can be produced by blending the particles of the first substance and the particles of the second substance, and processing by a powder secondary processing method. After the treatment by the powder secondary processing method, heat treatment can also be performed in a non-oxidizing atmosphere. In order to explain the complex, a schematic structure of the complex is shown in FIG. As shown in FIG. 1, the composite of the present invention has a structure in which, for example, silicon particles (Si) and particles of other substances, for example, copper particles (Cu) are randomly present and integrated with each other. is doing. In FIG. 1, dark portions indicate silicon particles (Si), and light portions indicate copper particles (Cu).

The processing itself by the powder secondary processing method is known. For example, the compounding of the particles of the first substance and the particles of the second substance may be combined (may be partially alloyed) while being repeatedly mixed and adhered by mechanical bonding force. Can do. As an apparatus to be used, a mixer, a disperser, a pulverizer and the like which are usually used in the field of powder can be used. For example, an attritor, a reiki machine, a ball mill, a vibration mill, an agitator mill, and the like can be given. In particular, in order to make each particle randomly present in the obtained composite and to reduce the stacking of particles of a specific substance, the particles that are overlapped or aggregated during the composite operation are separated for each particle. Since it is necessary to disperse efficiently, it is preferable to use an apparatus capable of applying a shearing force. For example, a dry attritor or a planetary ball mill is preferably used. The operation conditions of these apparatuses are not particularly limited as long as they can be combined.

The conditions for the optional heat treatment are not particularly limited as long as they are in a non-oxidizing atmosphere. The heat treatment can promote the alloying of the particles of the first substance and the particles of the second substance, if necessary. For example, heat treatment can be performed at a temperature of 250 ° C. or lower in an inert gas atmosphere such as argon gas. The heat treatment time can be appropriately determined depending on the heat treatment temperature.

As the substance that forms a complex with the first substance, copper, iron, cobalt, and nickel, which are difficult to alloy with lithium among the second substances, are preferable. More preferably, a composite of silicon and copper is used.

The mass ratio of the first substance to the second substance is preferably 5:95 to 95: 5, more preferably 7:93 to 75:25, and still more preferably 10:90 to 50: 50. If the first material is too much, the cycle characteristics tend to be lowered, while if the second material is too much, the battery capacity is remarkably lowered.

In the particle size distribution, the particle size of the composite is preferably 95% by volume or more of particles having a particle size of 50 μm or less, more preferably 95% by volume or more of particles having a particle size of 1 to 50 μm, and more preferably, Particles having a particle size of 5 to 25 μm are 95% by volume or more. If the particle diameter exceeds the above upper limit, when particles are applied to the current collector by the solid high-speed collision method, clogging may occur in the powder supply path in the apparatus, or the deposited film may become non-uniform. To do. Below the above lower limit, when the high-speed air flow in the solid high-speed collision method collides with the current collector, the composite may be blown away by the shock wave generated on the surface, and the current may not sufficiently collide with the current collector. May decrease. Here, the particle size distribution of the composite is measured by a laser diffraction / scattering method. The particle size of the composite is one or more first substances selected from the group consisting of silicon, silicon alloys, tin and tin alloys used as raw materials, and tin, copper, magnesium, iron, cobalt, nickel, zinc Depends on the particle size and other characteristics of one or more second substances selected from the group consisting of aluminum, germanium, indium, and carbon, and the type and conditions of the powder secondary processing method, such as processing time, It can adjust by changing these suitably.

It is known to adhere active material particles onto a current collector using a solid high-speed collision method. Here, the solid high-speed collision method referred to in the present invention is to disperse the particles in a high-speed air current without melting or evaporating the particles, and spray the high-speed air current to the current collector to cause the particles to collide with the current collector at high speed. This is a method of bringing particles into close contact with the current collector surface with this impact force. For example, it can be carried out using the cold spray method described in Patent Documents 1 and 2. The cold spray method is a method in which metal or ceramic particles are dispersed in a high-speed air current, and the high-speed air current is collided with a base material used as a current collector at high speed so that the particles adhere to the base material. . For example, a gas such as nitrogen, helium, or air heated to 100 to 1,000 ° C. is introduced into a supersonic nozzle to adjust the speed to a supersonic flow, and particles are introduced into the flow to accelerate it. Then, it is made to collide with the base material in the solid state. In addition, examples of the solid high-speed collision method include a shot peening method, a method of reducing the pressure on the substrate side during lamination, for example, an AD (aerosol deposition) method, and the like. The particle collision speed can be 100 m / second or more. In the present invention, the close contact means a state where the current collector and the composite are in contact with each other at a point or a surface.

The current collector of the present invention is preferably formed of a material having ductility and / or malleability, the surface of which can be plastically deformed by an impact force. Examples of the material include copper, copper alloy, iron, nickel, aluminum, zinc, and stainless steel. Of these, copper or a copper alloy is more preferable. Further, the current collector surface is preferably roughened, whereby the area of the current collector surface can be increased and the amount of the composite particles attached can be increased.

A lithium secondary battery having a negative electrode for a lithium secondary battery produced by the production method of the present invention can be produced by assembling the negative electrode, a positive electrode, an electrolytic solution, a separator and the like according to a known method.

A well-known thing can be used as a positive electrode of a lithium secondary battery. Examples thereof include lithium-containing transition metal oxides such as lithium cobaltate, lithium nickelate, and lithium manganate. In addition to these, there is no particular limitation as long as it can be used as a positive electrode of a lithium secondary battery.

A well-known thing can also be used for the solvent of electrolyte solution. Examples thereof include cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and vinylene carbonate, and chain carbonates such as dimethyl carbonate, methyl ethyl carbonate, and diethyl carbonate. When a cyclic carbonate is present in the solvent of the nonaqueous electrolyte, a high-quality film excellent in lithium ion conductivity is particularly easily formed on the surface of the active material particles, and thus the cyclic carbonate is preferably used. In particular, ethylene carbonate and propylene carbonate are preferable. A mixed solvent of cyclic carbonate and chain carbonate can also be used. Such a mixed solvent particularly preferably contains ethylene carbonate or propylene carbonate and diethyl carbonate.

Examples of the solute of the electrolyte include LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ( _{C 4 F 9 SO 2),} LiC (CF 3 SO 2) 3, LiC (C 2 F 5 SO 2) 3, LiAsF 6, LiClO 4, Li 2 B 10 Cl 10, Li 2 B 12 Cl 12 and their A mixture is mentioned. In particular, LiXF _y (wherein X is P, As, Sb, B, Bi, Al, Ga or In, and when X is P, As or Sb, y is 6 and X is B, Bi, Al) , the y when the Ga or in is 4), lithium perfluoroalkyl sulfonic acid imide _{LiN (C m F 2m + 1} SO 2) (C n F 2n + 1 SO 2) ( wherein, m and n are, respectively independently, an integer of 1 to 4), lithium perfluoroalkyl sulfonic acid methide _{LiC (C p F 2p + 1} SO 2) (C q F 2q + 1 SO 2) (C r F 2r + 1 SO 2) Solutes such as (wherein p, q and r are each independently an integer of 1 to 4) are preferred. Among these, LiPF ₆ is particularly preferably used. Furthermore, examples of the electrolyte include a gel polymer electrolyte obtained by impregnating a polymer electrolyte such as polyethylene oxide and polyacrylonitrile with an electrolytic solution, and an inorganic solid electrolyte such as LiI and Li ₃ N. The electrolyte of a lithium secondary battery can be used without restriction unless the lithium compound as a solute that develops ionic conductivity and the solvent that dissolves and retains the lithium compound does not decompose at the time of charging, discharging or storing the battery. be able to.

EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited by these Examples.

Examples 1-5
(Manufacture of complex)
As raw materials, silicon particles having an average particle diameter d50 = 18 μm and copper particles having an average particle diameter d50 = 5 μm were used. This was mixed at each mass ratio shown in Table 1, and a composite was manufactured using a dry attritor (MA1D type manufactured by Mitsui Mining Co., Ltd.). The specifications and operating conditions of the used attritor are as follows. In addition, the particle diameter and particle size distribution of the raw material and the composite are both measured using a laser diffraction / scattering particle size distribution measuring apparatus (MT-3300EX manufactured by Nikkiso Co., Ltd.).

<Attritor specifications and operating conditions>
Pot material: SUS304
Pot capacity: 1.8 liters Ball dimensions: 3/8 inch Ball material: SUJ2
Ball weight: 17.5kg
Rotation speed: 300rpm
Processing time: 10 minutes Atmospheric gas: Argon raw material charge: 1 liter

An electron micrograph (reflection electron image, magnification 1,000 times) of the obtained composite is shown in FIG. 2 (Example 1) and FIG. 3 (Example 2). As is clear from each figure, composites with various particle diameters were observed, copper particles (the white portion shown by the Cu arrow in the photograph) and silicon particles (the gray portion shown by the Si arrow in the photograph). It can be seen that and are randomly scattered to form one composite particle.

(Manufacture of electrodes)
FIG. 4 shows a cold spray apparatus (KM-CDS3.0 manufactured by Inovati) used for manufacturing the electrode. First, the composite (1) produced above was charged into the hopper (2) in the sample supply unit (A). Next, the composite (1) was transported to the powder mixing section (B) by helium gas from the helium gas supply pipe (4) while being cut out by the feeder (3). Separately, helium gas from the helium gas supply pipe (6) heated by the gas heating device (5) in the gas heating unit (C) is supplied to the powder mixing unit (B), and the composite (1) is supplied. In the powder heating section (7), the mixture was heated with heated helium gas, then combined with the flow of the composite (1), mixed and accelerated. The accelerated composite (1) was accelerated in the nozzle (9), sprayed from the tip of the nozzle (9), and deposited on the copper foil (11) used as a current collector to produce an electrode. The dimensions of the copper foil (11) were 90 mm long, 120 mm wide and 18 μm thick. The operation of depositing the composite (1) on the copper foil (11) is performed by sweeping the nozzle (9) in the lateral (longitudinal) direction of the copper foil (11) at an interval of 1 mm, so that the copper foil (11) is entirely exposed. The composite (1) was carried out so as to deposit uniformly. The operating conditions of the cold spray device are as follows.

<Operation conditions of cold spray device>
Distance from nozzle tip to copper foil: 10mm
Nozzle sweep speed: 400 mm / sec Composite injection pressure: 345 kPa
Complex heating temperature: 116 ° C
Composite injection amount: 1.6 g / min

An electron micrograph (secondary electron image, magnification of 3,000 times) of the obtained electrode cross section is shown in FIG. 5 (Example 1) and FIG. 6 (Example 2). As is clear from each figure, it can be seen that composite particles in which copper particles and silicon particles are randomly scattered are adhered and deposited on a copper foil as a base material.

(Charge / discharge cycle test)
A test electrode prepared by punching the electrode manufactured as described above into a circle having a diameter of 12 mm was prepared. On the other hand, a lithium foil having a diameter of 12 mm and a thickness of 500 μm was prepared as a counter electrode. Separately, LiPF ₆ was dissolved at a ratio of 1.0 mol / liter in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1 to prepare an electrolytic solution. Next, a positive electrode and a negative electrode were placed opposite to each other with a separator (polyolefin resin microporous membrane) and a glass filter interposed therebetween, and impregnated with an electrolytic solution to prepare a 2032 type coin cell. Using this coin cell, a cycle test was conducted by charging and discharging at a 0.2C rate (the 0.2C rate indicates charging or discharging the battery capacity in 5 hours). The results are shown in Table 1.

Comparative Example 1
An electrode was produced in the same manner as in Example 1 except that instead of the composite of silicon and copper, only silicon particles having an average particle diameter d50 = 18 μm used in Example 1 were used without being combined. Then, a charge / discharge cycle test was conducted.

The electron micrograph (secondary electron image, magnification of 3,000 times) of the obtained electrode cross section is shown in FIG. As apparent from FIG. 7, it can be seen that silicon particles are deposited on the copper foil as the base material. The results of the cycle test are shown in Table 1.

Comparative Example 2
An electrode was produced in the same manner as in Example 1 except that silicon and copper were not used as a composite but used as a simple mixture, and a charge / discharge cycle test was performed. An electron micrograph (secondary electron image, magnification of 3,000 times) of the obtained electrode cross section is shown in FIG. As can be seen from FIG. 8, the silicon particles and the copper particles are not randomly deposited, but the copper particles form a partially uniform film and are deposited on the copper foil as the base material. The results of the cycle test are shown in Table 1.

Comparative Example 3
An electrode was produced in the same manner as in Comparative Example 2 except that iron having an average particle diameter d50 = 5 μm was used instead of copper, and a charge / discharge cycle test was performed. An electron micrograph (secondary electron image, magnification of 3,000 times) of the obtained electrode cross section is shown in FIG. Although it is not possible to confirm iron particles in the secondary electron image of FIG. 9, it is recognized that silicon particles are unevenly deposited on the substrate, and the silicon particles and iron particles are on the copper foil as the substrate. It is presumed that they are deposited randomly rather than randomly. The results of the cycle test are shown in Table 1.

Comparative Example 4
The charge / discharge cycle test was carried out in the same manner as in Example 1 except that only silicon particles having an average particle diameter d50 = 18 μm used in Example 1 were used as they were without being complexed and an electrode was produced by a slurry coating method. Carried out.

Comparative Example 5
A charge / discharge cycle test was conducted in the same manner as in Example 1 except that the electrode was produced by a slurry coating method instead of the cold spray method.

The production of the electrode by the coating method using the slurry mixture in Comparative Examples 4 and 5 was performed as follows. Polyvinylidene fluoride (PVDF) was dissolved in N-methyl-2-pyrrolidone (NMP) to produce a 12% by mass PVDF paste. Next, 10% by mass of the paste, 85% by mass of silicon particles in Comparative Example 4 or 85% by mass of the composite prepared in Example 1 in Comparative Example 5, and acetylene black (average particle diameter d50 = 36 nm) 5% by mass was mixed to prepare a slurry mixture. The slurry was applied to a copper foil having the same dimensions as those used in Example 1, and the surface was smoothed using a doctor blade to form a sheet. The sheet was dried at 80 ° C. for 30 minutes to remove NMP, and then tightly bonded using a roll press to produce the electrode for the charge / discharge cycle test. The results of the cycle test are shown in Table 1.

In Table 1, each discharge capacity retention rate (%) is obtained by dividing the initial discharge capacity value, the discharge capacity value after 50 cycles, and the discharge capacity value after 100 cycles by the initial discharge capacity value. Further, each of the composites obtained in Examples 1 to 5 had a total particle size of 50 μm or less.

In Examples 1 to 5, a composite made of silicon and copper adhered to a copper foil by a cold spray method was used as a negative electrode for a lithium secondary battery. In the composite, a combination of silicon and copper was used. The ratio is changed. All showed high initial discharge capacity values. Moreover, since the initial discharge capacity value was high, it was found that a negative electrode for a lithium secondary battery that exhibits a sufficiently high discharge capacity value and can withstand practical use even after 50 and 100 cycles was obtained. In particular, in Examples 2 and 3, extremely high discharge capacity values were shown. In addition, the discharge capacity retention rate (the discharge capacity after the cycle has been normalized by the initial discharge capacity) was better as the silicon content in the composite decreased. From Examples 1 to 5, even when the silicon amount ratio in the composite was increased and the copper amount ratio was decreased, the discharge capacity was kept relatively good and the discharge capacity retention rate was kept good. On the other hand, it was found that the discharge capacity retention ratio was further improved when the silicon ratio in the composite was decreased and the copper ratio was increased.

On the other hand, Comparative Example 1 uses only silicon particles adhered to a copper foil by a cold spray method as a negative electrode for a lithium secondary battery. Although the discharge capacity retention rate was high, the initial discharge capacity was extremely small and could not be practically used. In Comparative Examples 2 and 3, a mixture of silicon and copper particles and a mixture of silicon and iron particles were used as a negative electrode for a lithium secondary battery without being combined and directly attached to a copper foil by a cold spray method. It is a thing. After all, although the discharge capacity retention rate was high, the initial discharge capacity was extremely small and could not withstand practical use. The comparative example 4 uses what adhered only the silicon particle to the copper foil by the slurry application | coating method as a negative electrode for lithium secondary batteries. Although it is possible to increase the initial discharge capacity by changing the thickness of the slurry to be applied, the adhesion to the copper foil is poor, and the discharge capacity retention rate is extremely low and cannot be practically used. Further, from the results of Comparative Example 5, even when the composite made of silicon and copper was adhered to the copper foil by the slurry coating method, the discharge capacity retention rate was also extremely poor.

One or more first substances selected from the group consisting of silicon, silicon alloys, tin and tin alloys manufactured by the manufacturing method of the present invention, tin, copper, magnesium, iron, cobalt, nickel, zinc, aluminum, A negative electrode for a lithium secondary battery provided with a composite obtained by integrating at least one second substance selected from the group consisting of germanium, indium, and carbon has a large capacity and extremely good cycle characteristics. Therefore, it is extremely useful as an alternative to the currently used negative electrode for lithium secondary batteries of carbon materials such as graphite.

DESCRIPTION OF SYMBOLS 1 Composite 2 Hopper 3 Feeder 4 Helium gas supply pipe 5 Gas heating apparatus 6 Helium gas supply pipe 7 Powder heating part 8 Flow-rate restricting part 9 Nozzle 10 Powder gas mixing part 11 Copper foil A Sample supply part B Powder mixing part C Gas heating Part

Claims (4)

A method for producing a negative electrode for a lithium secondary battery by adhering active material particles on a current collector using a solid high-speed collision method, wherein the active material particles are made of silicon, a silicon alloy, tin and a tin alloy. One or more first substances selected from the group consisting of, and one or more second substances selected from the group consisting of tin, copper, magnesium, iron, cobalt, nickel, zinc, aluminum, germanium, indium, and carbon. A manufacturing method characterized by being an integrated composite. The manufacturing method according to claim 1, wherein a mass ratio of the first substance to the second substance is 5:95 to 95: 5. The manufacturing method according to claim 1, wherein the first substance is silicon or a silicon alloy, and the second substance is copper. The manufacturing method according to claim 1, wherein the composite is manufactured by a powder secondary processing method.