JP2005340028A - Activator particle for nonaqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide activator particles for a nonaqueous electrolyte secondary battery having high electron conductivity, in a simple manufacturing method. <P>SOLUTION: The activator particles for the nonaqueous electrolyte secondary battery are composed of core particles made of silicon or a silicon alloy, on the surface of which a metal deposited by chemical plating is adhered. The activator particles are obtained by adding the core particles made of silicon or a silicon alloy in alkaline solution of pH7 or higher containing metal in an ionic state, and depositing the metal on the surface of the core particles. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to active material particles for non-aqueous electrolyte secondary batteries. The present invention also relates to a method for producing an electroless plated article including the active material particles.

  Currently, lithium ion secondary batteries are mainly used as secondary batteries for mobile phones and personal computers. This is because the battery has a higher energy density than other secondary batteries. With the recent increase in functionality of mobile phones and personal computers, their power consumption has increased remarkably, and large capacity secondary batteries are increasingly required. However, as long as the current electrode active material is used, it will be difficult to meet the needs in the near future.

  In general, graphite is used as a negative electrode active material of a lithium ion secondary battery. Currently, active materials composed of Si-based materials having a capacity potential 5 to 10 times that of graphite are being actively developed. However, since Si-based materials have poor electron conductivity, a conductive additive is added for the purpose of imparting electron conductivity between the current collector and the active material.

In addition, it has been proposed to secure the electron conductivity between the current collector and the active material by increasing the electron conductivity of the Si-based active material itself. For example, it has been proposed that metal material particles having a particle size of 0.0005 to 10 μm are attached to the surface of Si-based active material particles (see Patent Document 1). Further, it has been proposed that the core particles containing silicon are coated with a silicon solid solution such as Mg ₂ Si, CoSi, NiSi, and the surface thereof is further coated with a conductive material such as graphite or acetylene black (Patent Document). 2).

  According to these proposals, the electronic conductivity of the Si-based active material particles is increased, but the production is complicated and not economical.

JP-A-11-250896 JP 2000-285919 A

  Accordingly, an object of the present invention is to provide a Si-based active material that can eliminate various drawbacks of the above-described prior art.

  The present invention provides the active material particles for a non-aqueous electrolyte secondary battery, characterized in that a metal deposited by electroless plating is attached to the surface of core particles made of silicon or a silicon alloy. The goal has been achieved.

  Further, the present invention is characterized in that a base material made of silicon or a silicon alloy is introduced into an alkaline solution having a pH of 7 or more in which the metal exists in an ionic state, and the metal is deposited on the surface of the base material. A method for producing an electroless plated product is provided.

  ADVANTAGE OF THE INVENTION According to this invention, the active material particle for nonaqueous electrolyte secondary batteries with high electronic conductivity can be manufactured with a simple manufacturing method. Moreover, according to this invention, various metals can be deposited on the surface of the silicon | silicone or silicon-type base material which is not easy to perform electroless plating.

  Hereinafter, the present invention will be described based on preferred embodiments thereof. The active material particles for a non-aqueous electrolyte secondary battery of the present invention (hereinafter also simply referred to as active material particles) are configured by attaching metal to the surface of core particles made of silicon or a silicon alloy. (Hereinafter, this metal is referred to as an attached metal). The deposited metal is deposited on the surface of the core particle by electroless plating.

  Core particles made of silicon or a silicon-based alloy cannot easily deposit metal by electroless plating. The reason for this is that silicon dissolves in an alkaline solution, but other metals form hydroxides in the alkaline solution, and precipitation due to electroless plating utilizing the difference in ionization tendency from silicon does not occur. Because. On the other hand, in this invention, a metal can be made to adhere to the surface of the core particle which consists of a silicon | silicone or a silicon-type alloy by using the electroless-plating method mentioned later.

  The attached metal does not completely cover the entire surface of the core particle, but the attached metal is attached so that ultrafine particles of the attached metal are randomly attached to the surface of the core particle and a part of the surface of the core particle is exposed. Preferably it is. If the adhered metal completely covers the surface of the core particle, the electrolyte cannot contact the core particle and a desired electrochemical reaction cannot be caused. However, if the amount of the attached metal is too small, the desired electron conductivity cannot be imparted to the active material particles. From these viewpoints, when the supported adhered metal is represented by the content in the active material, it is preferably 1 to 40% by weight, particularly 5 to 25% by weight.

  There are no particular limitations on the type of the attached metal as long as it can be deposited on the surface of the core particles by the electroless plating method described later. When the active material particles are used as, for example, a negative electrode active material for a lithium ion secondary battery, it is preferable that the deposited metal has a low ability to form a lithium compound. Examples of such metals include nickel, copper, iron, cobalt, and the like. An alloy of these metals can also be used as the deposited metal.

  As the core particle, silicon or a silicon alloy is used as described above. Use of a silicon alloy is advantageous because it can further increase the electronic conductivity of the active material particles. It is also possible to prevent the core particles from being oxidized.

The density of silicon or silicon-based alloy, which is a constituent material of the core particle, is smaller than the density of the deposited metal, and the deposited metal coats the surface of the core particle thinly and discontinuously. Therefore, even if the deposited metal is deposited on the surface of the core particle, there is no significant difference between the particle size of the active material particle of the present invention and the particle size of the core particle. Both have a maximum particle size of preferably 50 μm or less, more preferably 20 μm or less. Moreover, when the particle diameter of the particle is expressed by a D ₅₀ value, it is preferably 0.1 to 8 μm, particularly preferably 1 to 5 μm. When the maximum particle size is more than 50 μm, the particles are likely to fall off from the electrode, and the life of the electrode may be shortened. There is no particular limitation on the lower limit of the particle size, and the smaller the better. In view of the method for producing the particles, the lower limit is about 0.01 μm. The particle size of the particles is measured by microtrack and electron microscope observation (SEM observation).

  When the core particle is made of a silicon-based alloy, examples of the metal contained in the alloy include Ni, Cu, Fe, Co, Cr, Ag, Zn, B, Al, Ge, Sn, Li, In, V, Ti, and Y. , Zr, Nb, Ta, W, La, Ce, Pr, Pd, Nd, or the like is used. Ni, Cu, Fe, and Co are particularly preferable. The amount of silicon in the silicon-based alloy is preferably 40 to 90% by weight. On the other hand, the amount of metal contained in the alloy is preferably 10 to 60% by weight.

  Silicon-based alloys are manufactured by, for example, a rapid cooling method such as a mold casting method or a roll casting method, so that the crystallites of the alloy have a fine size and are uniformly dispersed, so that the pulverization of active material particles is suppressed. From the viewpoint of maintaining electronic conductivity. Instead of the rapid cooling method, a gas atomizing method, an arc melting method, or a mechanical milling method can also be used.

  The active material particles of the present invention are particularly useful as a negative electrode active material for a lithium ion secondary battery. In order to produce an electrode using the active material particles of the present invention, for example, a negative electrode mixture formed by mixing the active material particles with a binder or a conductive auxiliary agent is formed, and the mixture is used on one side or both sides of the current collector. You just apply to. In this case, since the electronic conductivity of the active material particles per se is high, the amount of the conductive auxiliary compounded in the negative electrode mixture can be reduced as compared with the conventional negative electrode. As a result of reducing the amount of the conductive additive, the amount of the active material can be increased as compared with the conventional negative electrode. As a result, there is an advantage that the capacity of the battery is increased and the energy density is also increased.

  The active material particles of the present invention can also be applied to the electrode 10 shown in FIG. In FIG. 1, only one surface side of the electrode 10 is shown and the other surface side is not shown, but the structure of the other surface side is substantially the same. The electrode 10 shown in FIG. 1 is particularly useful as a negative electrode for a lithium ion secondary battery, and has a first surface and a second surface (not shown) which are a pair of front and back surfaces in contact with the electrolytic solution. doing. The electrode 10 includes an active material layer 4 including active material particles 5 between both surfaces. The active material layer 4 is continuously covered with a pair of current collecting surface layers 3 (one current collecting surface layer is not shown) 3 formed on each surface of the layer 4. Each surface layer includes a first surface and a second surface, respectively. Further, as is apparent from FIG. 1, the electrode 10 does not have a current collecting thick film conductor (for example, a metal foil) called a current collector, which has been used for conventional electrodes.

  The current collecting surface layer 3 has a current collecting function in the electrode 10. The surface layer 3 is also used to prevent the active material contained in the active material layer 4 from falling off due to expansion and / or contraction due to an electrode reaction. The surface layer 3 is made of a metal that can be a current collector of a secondary battery. As such a metal, one having a low ability to form a lithium compound is used. Examples include Cu, Ni, Fe, Co, or alloys thereof. In order to improve the corrosion resistance, Cr may be added. The two surface layers may have the same constituent material or may be different.

  Each surface layer 3 is thinner than the thick film conductor for current collection used in conventional electrodes. Specifically, a thin layer of about 0.3 to 20 μm, particularly about 0.3 to 10 μm, particularly about 0.5 to 5 μm is preferable. As a result, the active material layer 4 can be continuously covered almost uniformly with the minimum necessary thickness. As a result, it is possible to prevent the active material particles 5 from falling off. In addition, by making such a thin layer and not having a thick film conductor for current collection, the ratio of the active material to the entire electrode becomes relatively high, and per unit volume and unit weight. Energy density can be increased. In the conventional electrode, the ratio of the thick film conductor for current collection to the entire electrode is high, so there is a limit to increasing the energy density. The thin surface layer 3 in the above range is preferably formed by electrolytic plating. The two surface layers 3 may have the same thickness or may be different.

  As described above, the electrode 10 includes a first surface and a second surface, respectively. When the electrode 10 is incorporated in a battery, the first surface and the second surface are in contact with the electrolytic solution and participate in the electrode reaction. In contrast, a thick film conductor for collecting current in a conventional electrode is not in contact with the electrolyte solution when the active material layer is formed on both sides thereof, and does not participate in the electrode reaction. Even when an active material layer is formed on one side, only one side is in contact with the electrolyte. In other words, the electrode 10 does not have the current collecting thick film conductor used in the electrode, and the layer located on the outermost surface of the electrode, that is, the surface layer 3 is involved in the electrode reaction and the current collecting function. And the function of preventing the active material from falling off.

  Each surface layer 3 including each of the first surface and the second surface has a current collecting function. Therefore, when the electrode 10 is incorporated in a battery, any surface layer 3 is used for current extraction. There is an advantage that lead wires can be connected.

  As shown in FIG. 1, the electrode 10 has a large number of fine voids 5 that are open in the first surface and the second surface and communicate with the active material layer 4. The fine gap 6 exists in the surface layer 3 so as to extend in the thickness direction of each current collecting surface layer 3. By forming the fine voids 6, the electrolytic solution can sufficiently penetrate into the active material layer 4, and the reaction with the active material particles 5 occurs sufficiently. The fine void 6 is a fine one having a width of about 0.1 μm to about 10 μm when the surface layer 3 is observed in cross section. Although it is fine, the fine gap 6 has a width that allows the electrolyte solution to penetrate. The fine voids 6 are preferably formed simultaneously with the formation of the surface layer 3 by electrolytic plating.

When the first surface and the second surface are viewed in plan by electron microscope observation, the average pore area of the fine void 6 on at least one surface is preferably about 0.1 to 100 μm ² , more preferably 1 About 10 μm ² . By setting the opening area within this range, it is possible to effectively prevent the active material particles 5 from falling off while ensuring sufficient permeation of the electrolytic solution. Further, the charge / discharge capacity can be increased from the initial stage of charge / discharge. From the viewpoint of more effectively preventing the active material particles 5 from dropping off, the average pore area is preferably 5 to 70%, particularly 10 to 40% of the maximum cross-sectional area of the active material particles 5.

  The active material layer 4 located between the first surface and the second surface contains the active material particles 5 of the present invention. Since the active material layer 4 is covered with the two surface layers 3, it is effectively prevented that the active material particles 5 fall off due to expansion and / or contraction due to the electrode reaction. Since the active material particles 5 can come into contact with the electrolytic solution through the fine gaps 6, the electrode reaction is not hindered.

  If the amount of the active material relative to the entire electrode is too small, it is difficult to sufficiently improve the energy density of the battery. Conversely, if the amount is too large, the active material tends to fall off. Considering these, the amount of the active material particles 5 is preferably 10 to 90% by weight, more preferably 20 to 80% by weight, and still more preferably 40 to 80% by weight with respect to the entire electrode. The thickness of the active material layer 4 can be appropriately adjusted according to the ratio of the amount of the active material particles 5 to the whole electrode and the particle size of the active material particles 5, and is not particularly critical in the present embodiment. It is about 1 to 200 μm, particularly about 10 to 100 μm. The active material layer 4 is preferably formed by applying a conductive slurry containing the active material particles 5. The total thickness of the electrode including the surface layer 3 and the active material layer 4 is preferably about 1 to 500 μm, particularly about 1 to 250 μm, especially about 10 to 150 μm, in consideration of increasing the strength and energy density of the electrode.

  In the active material layer 4, it is preferable that the material constituting each surface layer 3 including each of the first surface 1 and the second surface penetrates over the entire thickness direction of the active material layer 4. The active material particles 5 are preferably present in the permeated material. That is, it is preferable that the active material particles 5 are not substantially exposed on the surface of the electrode 10 and are embedded in the surface layer 3. As a result, the adhesion between the active material layer 4 and the surface layer 3 becomes strong, and the falling off of the active material is further prevented. In addition, since electronic conductivity is ensured between the surface layer 3 and the active material particles 5 through the material that has penetrated into the active material layer 4, it is possible to generate an electrically isolated active material, in particular, the active material layer 4 The generation of an electrically isolated active material in the deep part of the substrate is effectively prevented, and the current collecting function is maintained. As a result, the function deterioration as an electrode is suppressed. In addition, the life of the electrode can be extended. In particular, since the active material particles 5 have an attached metal on the surface thereof, the electron conductivity between the surface layer 3 and the active material particles 5 is further increased.

  The material constituting the current collecting surface layer 3 preferably penetrates the active material layer 4 in the thickness direction and is connected to both surface layers 3. As a result, the two surface layers 3 are electrically connected through the material, and the electron conductivity of the entire electrode is further increased. That is, the electrode 10 shown in FIG. 1 has a current collecting function as a whole. The fact that the material constituting the current collecting surface layer 3 penetrates over the entire thickness direction of the active material layer and the two surface layers are connected to each other can be obtained by electron microscope mapping using the material as a measurement object. .

When the active material particles of the present invention are applied to the various negative electrodes described above, the configuration of a non-aqueous electrolyte secondary battery using the negative electrode is as follows. That is, the positive electrode used in a pair with the negative electrode is prepared by suspending a positive electrode active material and, if necessary, a conductive agent and a binder in an appropriate solvent to prepare a positive electrode mixture, applying this to a current collector, and drying. It is obtained by roll rolling, pressing, further cutting and punching. As the positive electrode active material, conventionally known positive electrode active materials such as lithium nickel composite oxide, lithium manganese composite oxide, and lithium cobalt composite oxide are used. As the separator disposed between the negative electrode and the positive electrode, a synthetic resin nonwoven fabric, polyethylene, polypropylene porous film, or the like is preferably used. In the case of a lithium secondary battery, the nonaqueous electrolytic solution is a solution in which a lithium salt that is a supporting electrolyte is dissolved in an organic solvent. The lithium salt, for _{example, LiC1O 4, LiA1Cl 4, LiPF} 6, LiAsF 6, LiSbF 6, LiSCN, LiC1, LiBr, LiI, etc. _{LiCF 3 SO 3, LiC 4 F} 9 SO 3 are exemplified.

  Next, the preferable manufacturing method of the active material particle of this invention is demonstrated below. The production method described below is preferable as the production method of the active material particles of the present invention. However, other objects, that is, various metals are formed on the surface of various shapes of the base material made of silicon or silicon alloy. It is also useful as a method for producing an electroless plated product that adheres.

  As the plating bath in this production method, an alkaline solution having a pH of 7 or more in which the metal exists in an ionic state is used. Examples of the metal include copper, nickel, iron, cobalt and the like described above. These metals generally form hydroxides in a solution made alkaline by an alkali metal hydroxide or an alkaline earth metal hydroxide and cannot be used for electroless plating. Therefore, in this production method, a solution system in which these metals do not form hydroxides even when the pH is in the alkaline region is used. This is a feature of the present manufacturing method.

  In this production method, it is preferable to use an aqueous solution of a salt of a weak acid as a solution system in which the metal does not form a hydroxide in the alkaline region. As the salt of the weak acid, a salt of acetic acid or pyrophosphoric acid can be used. The salt is preferably a sodium salt or a potassium salt. In particular, it is preferable to use an aqueous sodium acetate solution as an aqueous solution of a weak acid salt because no impurities are produced. A salt of a weak acid, such as sodium acetate, dissolves in water and exhibits alkalinity. As a result of the examination by the present inventors, it was found that when a metal salt is dissolved in this solution, the metal does not form a hydroxide and exists in the solution in an ionic state. Here, “exists in an ionic state” includes that the metal exists in a complex ion state.

  As the metal salt, for example, when the metal is nickel, nickel chloride, nickel sulfate, or the like can be used. In the case of copper, copper chloride, copper sulfate, etc. can be used. In the case of iron, iron chloride, iron sulfate, etc. can be used. In the case of cobalt, cobalt chloride, cobalt sulfate, etc. can be used.

  By adding the core particles to an alkaline solution in which the metal exists in an ionic state, silicon in the core particles dissolves in the solution and emits electrons. By a substitution reaction with this, metal ions receive electrons and are reduced and deposited on the surfaces of the core particles. From the viewpoint of successfully reducing and precipitating metal ions, the pH of the solution is preferably 6.5 to 12, particularly preferably 7.0 to 9.0. As for the concentration of metal ions in the solution, a metal salt corresponding to a predetermined amount of metal adhesion may be dissolved. The amount of deposited metal is desirably 5 to 25% by weight with respect to the weight of silicon or silicon-based alloy.

  The reaction is preferably carried out while stirring the solution. Depending on the type of metal used, an impurity precipitation reaction may proceed in addition to the reduction precipitation reaction. Therefore, in order to suppress the impurity precipitation and promote the reduction precipitation reaction, for example, the reaction is started from 40 to 60 ° C., and heated at a rate of temperature increase of 1 to 10 ° C./min, to 70 to 90 ° C. For 5 minutes to 4 hours. Appropriate processing is performed by this operation.

  When a predetermined amount of metal is deposited on the surface of the core particles and desired active material particles are obtained, the particles are filtered and washed with water. The obtained particles are in a fresh state in which the surface oxide is dissolved, and on the contrary, they are easily oxidized when exposed to the atmosphere. In order to suppress the reoxidation, a benzotriazole (BTA) treatment after washing with water is effective because the reoxidation is suppressed.

  The manufacturing method described above is for the case where the core particles are used as a base material on which metal is reduced and deposited. However, this manufacturing method can be applied to a base material made of various granular materials other than the core particles. Further, as described above, the present manufacturing method can be applied to a base material having a shape other than the granular material. For example, this manufacturing method can be applied using various bulk bodies including a plate-shaped body and a rod-shaped body as a base material.

  As another method of this production method, an alkali metal hydroxide or an alkaline earth metal hydroxide can be used as an agent for making the aqueous solution alkaline with a pH of 7 or higher. However, as described above, if the pH of the liquid is higher than that of an alkali metal hydroxide or an alkaline earth metal hydroxide, the metal becomes a hydroxide under normal conditions and is not reduced and precipitated. However, when the plating solution is heated to a predetermined temperature, the metal hydroxide is dissolved and the metal is present in an ion state in the solution. By introducing the core particles under the state, reduction precipitation of the metal occurs and the metal adheres to the surface of the core particle.

  Hereinafter, the present invention will be described in more detail with reference to examples. Unless otherwise specified, “%” means “% by weight”.

[Example 1]
Core particles having a composition of Si 80% -Ni 20% having an average particle diameter D ₅₀ of 1.5 μm were obtained by a roll casting method. The core particles were charged into an aqueous solution containing 10 g / l sodium acetate and 2.5 g / l nickel sulfate and having a pH of 7.8 while stirring the aqueous solution. The liquid temperature was 50 ° C. at the time of charging. The input amount was 5 g / l. Thereafter, the mixture was heated at a rate of temperature increase of 1 ° C./min. The pH at that time was 5.6.
As a result, nickel was reduced and deposited on the surfaces of the core particles to obtain active material particles. The content of nickel in the obtained active material particles was 10%.

[Examples 2 to 5]
Active material particles were obtained in the same manner as in Example 1 except that the types of core particles and the nickel content were as shown in Table 1. Si ₈₀ Co ₂₀ and Si particles were produced by the roll casting method in the same manner as in Example 1.

Example 6
Core particles were charged into an aqueous solution containing 2.5 g / l potassium pyrophosphate and 2.0 g / l nickel chloride and having a pH of 9.0 while stirring the aqueous solution. The core particles had an average particle diameter D ₅₀ of 1.5 μm and a composition of Si 80% -Ni 20%. The liquid temperature was kept at 80 ° C. As a result, nickel was reduced and deposited on the surfaces of the core particles to obtain active material particles. The content of nickel in the obtained active material particles was 10%.

[Examples 7 to 10]
Active material particles were obtained in the same manner as in Example 1 except that the types of core particles and the nickel content were as shown in Table 1.

[Performance evaluation]
Using the active material particles obtained in each Example, a negative electrode for a lithium ion secondary battery was produced by the method shown in FIG. A lithium ion secondary battery was produced by the following method using the produced negative electrode. The capacity maintenance rate at 200 cycles of this battery was measured and calculated by the following method. These results are shown in Table 1 below.

(1) Formation of Release Layer As shown in FIG. 2A, an electrolytic copper foil having a thickness of 35 μm was used as the carrier foil 1. The carrier foil 1 was washed in a pickling solution at room temperature for 30 seconds. Subsequently, it was washed with pure water at room temperature for 30 seconds. Next, the carrier foil 1 was immersed for 30 seconds in a 3 g / l carboxybenzotriazole solution kept at 40 ° C. to form a release layer 2 as shown in FIG. Further, it was washed with pure water for 15 seconds at room temperature.

(2) Formation of first surface layer The carrier foil 1 is immersed in a nickel plating bath having the following bath composition for electrolysis, and as shown in FIG. A surface layer 3a was formed. The first surface layer 3a was formed on the release layer 2 formed on the glossy surface side of the carrier foil. The current density was 5 A / dm ² and the bath temperature was 50 ° C. A nickel electrode was used as the anode. A DC power source was used as the power source. The film thickness of the first surface layer 3a was 3 μm.

The slurry composition was active material: acetylene black: PVdF = 94: 1: 5.
NiSO ₄ · 6H ₂ O 250g / l
NiCl ₂ · 6H ₂ O 45g / l
H ₃ BO ₃ 30 g / l

(3) Formation of active material layer After the formation of the first surface layer 3a, it was washed with pure water for 30 seconds and then dried in the atmosphere. Next, on the first surface layer 3a, the slurry containing the active material particles 5 obtained in the respective examples is applied, and as shown in FIG. 2D, the active material layer 4 having a film thickness of 15 μm is formed. Formed. The slurry contained the active material particles 5, acetylene black and polyvinylidene fluoride (hereinafter referred to as PVdF). The slurry composition was active material particles: acetylene black: PVdF = 94: 1: 5.

(4) Formation of Second Surface Layer As shown in FIG. 2 (e), a second surface layer 3 b made of an ultrathin nickel foil was formed on the active material layer 4 by electrolysis. The electrolysis conditions were the same as the formation conditions of the first surface layer 3a. The film thickness was 3 μm.

(5) Peeling of the electrode The electrode 10 thus obtained was peeled from the carrier foil 1 as shown in FIG. 2 (f) to obtain a negative electrode.

(6) Production of Lithium Ion Secondary Battery The negative electrode obtained above was used as a working electrode, LiCoO ₂ was used as a counter electrode, and both electrodes were opposed via a separator. A lithium ion secondary battery was produced by a conventional method using a mixed solution (1: 1 volume ratio) of LiPF ₆ / ethylene carbonate and diethyl carbonate as a non-aqueous electrolyte.

[Capacity maintenance rate at 200 cycles]
The discharge capacity at the 200th cycle was measured, the value was divided by the maximum negative electrode discharge capacity, and multiplied by 100.

  As is clear from the results shown in Table 1, it can be seen that the lithium ion secondary battery using the active material particles of each example has a high capacity retention rate at 200 cycles.

It is a schematic diagram which shows the structure of the electrode containing the active material particle of this invention. FIG. 2A to FIG. 2F are process diagrams showing an example of a method for producing an electrode including active material particles of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Carrier foil 2 Release layer 3, 3a, 3b Current collecting surface layer 4 Active material layer 5 Active material particle 6 Fine void

Claims (10)

  An active material particle for a nonaqueous electrolyte secondary battery, wherein a metal deposited by electroless plating is attached to the surface of a core particle made of silicon or a silicon alloy.   The negative electrode for nonaqueous electrolyte secondary batteries containing the active material particle of Claim 1.   A non-aqueous electrolyte secondary battery comprising the negative electrode according to claim 2.   Electroless plating characterized by introducing a base material made of silicon or a silicon alloy into an alkaline solution having a pH of 7 or more in which the metal exists in an ionic state, and depositing the metal on the surface of the base material Manufacturing method.   The production method according to claim 4, wherein the alkaline solvent contains a salt of a weak acid and has a pH of 7 or more.   6. The process according to claim 5, wherein the salt of the weak acid is a salt of acetic acid or pyrophosphoric acid.   The manufacturing method according to claim 4, wherein the base material is a granular material.   The manufacturing method according to claim 4, wherein the base material is a plate-like body.   The manufacturing method according to claim 4, wherein the metal is nickel, copper, iron, or cobalt. The manufacturing method according to claim 4, wherein the alkaline solution is kept at 50 to 100 ° C. to deposit the metal.

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