WO2005117168A1

WO2005117168A1 - Active material particle for nonaqueous electrolyte secondary battery

Info

Publication number: WO2005117168A1
Application number: PCT/JP2005/008777
Authority: WO
Inventors: Yoshiki Sakaguchi; Hitohiko Honda; Kiyotaka Yasuda
Original assignee: Mitsui Mining & Smelting Co., Ltd.
Priority date: 2004-05-27
Filing date: 2005-05-13
Publication date: 2005-12-08
Also published as: JP2005340028A; JP4829483B2

Abstract

Active material particles for nonaqueous electrolyte secondary batteries are characterized by having such a constitution wherein a metal deposited by electroless plating adheres to the surfaces of core particles which are composed of silicon or an silicon alloy. Such active material particles can be obtained by putting core particles composed of silicon or an silicon alloy in an alkaline solution having a pH of not less than 7 in which a metal is present in the form of ions, and having the metal deposit on the surfaces of the core particles. The alkaline solution preferably contains a weak acid salt so as to have a pH of not less than 7, and a salt of acetic acid or pyrophoric acid is preferably used as the weak acid salt.

Description

Specification

Active material particles for non-aqueous electrolyte secondary batteries

Technical field

The present invention relates to active material particles for a non-aqueous electrolyte secondary battery. Further, the present invention relates to a method for producing an electroless plated material including the active material particles.

Background art

[0002] Currently, lithium ion secondary batteries are mainly used as secondary batteries for mobile phones and personal computers. The reason is that this battery has a higher energy density than other secondary batteries. In recent years, the power consumption of these mobile phones and personal computers has increased significantly due to their multifunctionality, and large-capacity secondary batteries are increasingly required. However, as long as the current electrode active material is used, it is expected that it will be difficult to meet the needs in the near future.

[0003] Graphite is generally used as a negative electrode active material of a lithium ion secondary battery.

At present, active materials with Si-based material strength, which has a capacity potential 5 to 10 times that of graphite, are being actively developed. However, since the Si-based material has poor electron conductivity, a conductive assistant is added for the purpose of imparting electron conductivity between the current collector and the active material when using the Si-based material.

[0004] Further, it has been proposed that the electron conductivity between the current collector and the active material be ensured by increasing the electron conductivity of the Si-based active material itself. For example, it has been proposed to attach particles of a metal material having a particle diameter of 0.0005 to 10 m on the surface of Si-based active material particles (see Japanese Patent Application Laid-Open No. 11-250896). In addition, Mg Si, CoSi, NiSi

2

It has been proposed to cover the surface with a silicon solid solution such as that described above, and further cover the surface with a conductive material such as graphite or acetylene black (see US Pat. No. 6,548,208).

[0005] According to these proposals, the electron conductivity of the Si-based active material particles is increased, but the production thereof is complicated and not economical.

[0006] Accordingly, an object of the present invention is to provide a Si-based active material capable of solving the above-mentioned various disadvantages of the related art. Disclosure of the invention

[0007] The present invention provides an active material particle for a nonaqueous electrolyte secondary battery, characterized in that a metal precipitated by electroless plating adheres to the surface of a core particle which also has a silicon or silicon alloy force. This object has been achieved by providing a child.

[0008] In the present invention, a base material having a silicon or silicon alloy force is introduced into an alkaline solution having a pH of 7 or more which exists in a state of a metal force ion, and the metal is precipitated on the surface of the base material. It is intended to provide a method for producing an electroless plated product characterized by the above.

Brief Description of Drawings

FIG. 1 is a schematic diagram showing a structure of an electrode including active material particles of the present invention.

FIGS. 2 (a) to 2 (f) are process diagrams showing an example of a method for producing an electrode containing active material particles of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

[0010] Hereinafter, the present invention will be described based on preferred embodiments. 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 formed by attaching a metal to the surface of a core particle which also has a silicon or silicon alloy force. (Hereinafter, this metal is referred to as an adhering metal). The deposited metal was deposited on the surface of the core particles by electroless plating.

[0011] Silicon or silicon-based alloy core particles cannot easily deposit metal by electroless plating. The reason is that silicon dissolves in an alkaline solution, and other metals form hydroxides in an alkaline solution. This is because no precipitation due to is caused. On the other hand, in the present invention, the metal can be attached to the surface of the core particle which also has silicon or a silicon-based alloy by using an electroless plating method described later.

[0012] The adhered metal does not completely cover the entire surface of the core particle, but ultra-fine particles of the adhered metal adhere randomly to the core particle surface and adhere so that a part of the core particle surface is exposed. U, then prefer. If the adhered metal completely covers the surface of the core particles, the electrolyte cannot contact the core particles, and a desired electrochemical reaction cannot be caused. However, if the amount of the attached metal is too small, the desired electron conductivity is given to the active material particles. Can not do it. From these viewpoints, when the amount of the deposited adhered metal is represented by the content in the active material, it is preferably 1 to 40% by weight, particularly preferably 5 to 25% by weight.

[0013] The type of the adhering metal is not particularly limited as long as it can be deposited on the surface of the core particle by an electroless plating method described later. When the active material particles are used, for example, as a negative electrode active material for a lithium ion secondary battery, the adhered metal preferably has a low ability to form a lithium compound. Examples of such a metal include nickel, copper, iron, and cobalt. Also, alloys of these metals can be used as the adhering metal.

[0014] As described above, silicon or a silicon alloy is used as the core particles. The use of a silicon alloy is advantageous because the electron conductivity of the active material particles can be further increased. It is also possible to prevent the core particles from being oxidized.

[0015] The density of silicon or a silicon-based alloy, which is a constituent material of the core particles, is smaller than the density of the adhered metal, and the adhered metal thinly and discontinuously coats the surface of the core particles. Therefore, even if the adhered metal is deposited on the surface of the core particles, there is no significant difference between the particle size of the active material particles of the present invention and the particle size of the core particles. Both have a maximum particle size of preferably 50 m or less, more preferably 20 m or less. When the particle size is represented by the D value, 0

50

It is preferably from 1 to 8 μm, particularly preferably from 1 to 5 μm. If the maximum particle size is more than 50 μm, particles may easily 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 value, 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 a laser diffraction scattering method and electron microscope observation (SEM observation).

[0016] When the core particles also have a silicon-based alloy force, examples of metals contained in the alloy include Ni, Cu, Fe, Co, Cr, Ag, Zn, B, Al, Ge, Sn, Li, In, V, One or more of Ti, Y, Zr, Nb, Ta, W, La, Ce, Pr, Pd, Nd and the like are used. Particularly, Ni, Cu, Fe and Co are 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.

[0017] Since silicon-based alloys are manufactured by a quenching method such as a 铸 -type manufacturing method or a roll-type manufacturing method, the crystallites of the alloy have a fine size and are uniformly dispersed. It is preferable because the pulverization of the material particles is suppressed and the electron conductivity is maintained. Instead of the rapid cooling method, a gas atomizing method, an arc melting method, or a mechanical milling method can 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. To produce an electrode using the active material particles of the present invention, for example, a negative electrode mixture is prepared by mixing the active material particles with a binder and a conductive auxiliary, and the mixture is formed on one or both surfaces of a current collector. It is good to apply to. In this case, since the electron conductivity of the active material particles themselves 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 being able to reduce the amount of the conductive auxiliary agent, it is possible to increase the compounding amount of the active material as compared with the conventional negative electrode. As a result, there is an advantage that the capacity of the battery increases and the energy density also increases.

The active material particles of the present invention can also be applied to the electrode 10 shown in FIG. In FIG. 1, only one side of the electrode 10 is shown and the other side is not shown, but the structure of the other side is almost 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 that are in contact with the electrolyte. are doing. The electrode 10 has an active material layer 4 containing active material particles 5 between both surfaces. The active material layer 4 is continuously covered by 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. As is clear from FIG. 1, the electrode 10 has a thick current collector (eg, a metal foil) for current collection called a current collector that has been used for a conventional electrode!

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, a metal having a low ability to form a lithium compound is used. Examples include Cu, Ni, Fe, Co or alloys thereof. Cr may be added to improve the corrosion resistance. The two surface layers may be made of the same material or different materials.

[0021] Each surface layer 3 has a thickness S thinner than that of a thick current collector for current collection used in a conventional electrode. Specifically, about 0.3 to 20 / ζπι, especially about 0.3 to: LO / zm, The thickness is preferably about 0.5 to 5 m. Thus, the active material layer 4 can be coated almost uniformly and continuously with a minimum necessary thickness. As a result, it is possible to prevent the active material particles 5 from falling off. In addition, having a thin layer of such a degree and having a thick film conductor for current collection, the ratio of the active material to the entire electrode becomes relatively high, so that the weight per unit volume and the unit weight is increased. Per unit energy density can be increased. In the conventional electrode, the ratio of the thick film conductor for current collection to the entire electrode was high, so that there was a limit in increasing the energy density. It is preferable that the thin surface layer 3 in the above range is formed by electrolytic plating. Note that the two surface layers 3 may have the same thickness or may have different thicknesses.

[0022] As described above, the electrode 10 includes the first surface and the second surface, respectively. When the electrode 10 is incorporated in a battery, the first surface and the second surface become surfaces that come into contact with the electrolytic solution and participate in the electrode reaction. In contrast to this, the thick film conductor for current collection in the conventional electrode does not come into contact with the electrolytic solution when the active material layer is formed on both surfaces thereof and does not participate in the electrode reaction, and Even when the active material layer is formed on one side, only one side is in contact with the electrolyte. That is, the electrode 10 does not have a thick-film conductor for current collection used in the conventional electrode, and the layer located on the outermost surface of the electrode, that is, the surface layer 3 participates in the electrode reaction and collects. It has both an electrical function and a function to prevent the active material from falling off.

Each of the surface layers 3 including the first surface and the second surface has a current collecting function. Therefore, when the electrode 10 is incorporated in a battery, any of the surface layers 3 Also, there is an advantage that a lead wire for extracting current can be connected.

As shown in FIG. 1, the electrode 10 has a large number of fine voids 5 that are open on the first surface and the second surface and communicate with the active material layer 4. The fine voids 6 are present in the surface layer 3 so as to extend in the thickness direction of each current collecting surface layer 3. The formation of the fine voids 6 allows the electrolytic solution to sufficiently penetrate into the active material layer 4 and sufficiently reacts with the active material particles 5. The fine voids 6 have a width of about 0: L m to about 10 IX m when the cross section of the surface layer 3 is observed. Although it is fine, the minute gap 6 has a width that allows the electrolyte to penetrate. The fine voids 6 are preferably formed at the same time when the surface layer 3 is formed by electroplating. When the first surface and the second surface are viewed in plan by electron microscope observation, the average open area of the fine voids 6 on at least one surface is preferably about 0.1 to: LOO / zm ² . There, the more preferably 1: ² approximately LO / zm. By setting the opening area in this range, it is possible to effectively prevent the active material particles 5 from falling off while ensuring sufficient penetration of the electrolytic solution. In addition, the initial stage charge / discharge capacity of charge / discharge can be increased. From the viewpoint of more effectively preventing the active material particles 5 from falling off, the average opening area is preferably 5 to 70%, particularly preferably 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, the active material particles 5 are effectively prevented from falling off due to expansion and Z or contraction due to an electrode reaction. Since the active material particles 5 can come into contact with the electrolytic solution through the fine voids 6, the electrode reaction is not hindered.

[0027] When the amount of the active material relative to the entire electrode is too small, the energy density of the battery is not sufficiently improved, whereas when it 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 based on the whole 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 entire electrode and the particle size of the active material particles 5, and is not particularly critical in the present embodiment. . About 1 to 200 111, especially about 10: LOO / zm. 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 should be 1 to 500 / ζπι, particularly 1 to 250 111, and especially about 10 to 150 m, considering the strength and energy density of the electrode. Riko

In the active material layer 4, the material constituting each surface layer 3 including the first surface 1 and the second surface may penetrate throughout the thickness of the active material layer 4. Like,. It is preferable that the active material particles 5 exist in the permeated material. That is, it is preferable that the active material particles 5 are not substantially exposed to the surface of the electrode 10 but 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, Material shedding is further prevented. Further, electron conductivity is ensured between the surface layer 3 and the active material particles 5 through the material penetrated into the active material layer 4, so that an electrically isolated active material is generated. Generation of an electrically isolated active material in the deep part of 4 is effectively prevented, and the current collecting function is maintained. As a result, a decrease in the function of the electrode is suppressed. Further, the life of the electrode can be extended. In particular, since the active material particles 5 have an attached metal on the surface, the electron conductivity between the surface layer 3 and the active material particles 5 is further increased.

It is preferable that the material constituting the current-collecting surface layer 3 penetrates the active material layer 4 in the thickness direction and is connected to both surface layers 3. Thereby, the two surface layers 3 become electrically conductive through the material, and the electron conductivity of the electrode as a whole is further increased. That is, the electrode 10 shown in FIG. 1 has a current collecting function as a whole as a whole. The fact that the material constituting the current-collecting surface layer 3 penetrates over the entire area in the thickness direction of the active material layer and that the two surface layers are connected to each other is determined by electron microscope mapping using the material as a measurement target. It comes out.

When the active material particles of the present invention are applied to the above-described various types of negative electrodes, the configuration of a non-aqueous electrolyte secondary battery using the negative electrodes is as follows. That is, the positive electrode used as 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 the mixture to a current collector, and drying the mixture. , Roll rolling, pressing, and further cutting and punching. As the positive electrode active material, a conventionally known positive electrode active material such as a lithium nickel composite oxide, a lithium manganese composite oxide, and a lithium cobalt composite oxide is used. As the separator disposed between the negative electrode and the positive electrode, a synthetic resin nonwoven fabric, a polyethylene or polypropylene porous film, or the like is preferably used. In the case of a lithium secondary battery, the nonaqueous electrolyte is composed of a solution in which a lithium salt as a supporting electrolyte is dissolved in an organic solvent. Examples of lithium salts include LiCIO, LiAlCl, LiPF, LiAsF,

4 4 6 6

LiSbF, LiSCN, LiCl, LiBr, Lil, LiCFSO, LiCFSO and the like are exemplified.

6 3 3 4 9 3

Next, a preferred method for producing the active material particles of the present invention will be described below. The production method described below is preferable as the method for producing the active material particles of the present invention. However, other objects, that is, various metals are formed on the surface of the base material having various shapes of silicon or silicon alloy. It is also useful as a method for producing an electroless plated product having the particles adhered thereto. [0032] As a plating bath in the present production method, an alkaline solution having a pH of 7 or more in which a metal exists in an ion 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 rendered alkaline by an alkali metal hydroxide or an alkaline earth metal hydroxide and cannot be subjected to electroless plating. Therefore, in the present production method, even if the pH is in an alkaline range, these metals do not form hydroxides, and a solution system is used. This is a feature of this manufacturing method.

[0033] In the present 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 solution of sodium acetate as an aqueous solution of a salt of a weak acid since impurities are not generated. Salts of weak acids, such as sodium acetate, dissolve in water and exhibit alkaline properties. When the metal salt was dissolved in this solution, the present inventors found that the metal did not form a hydroxide and was present in the solution in an ion state. Here, “existing in the ion state” includes that the metal exists in a complex ion state.

[0034] As the above-mentioned 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 or the like can be used. In the case of iron, iron chloride, iron sulfate or the like can be used. In the case of konoleto, cobalt chloride, cobalt sulfate or the like can be used.

[0035] By adding the core particles to the alkaline solution that exists in the state of metal ions, the silicon in the core particles dissolves in the solution and emits electrons. By the substitution reaction with this, the metal ions receive the electrons and are reduced and deposited on the surface of the core particles. The pH of the solution is preferably 6.5 to 12, particularly preferably 7.0 to 9.0, from the viewpoint of successfully reducing and depositing metal ions. Regarding the concentration of the metal ion in the solution, a metal salt corresponding to a predetermined amount of the deposited metal may be dissolved. It is desirable that the amount of deposited metal is 5 to 25% by weight based on the weight of silicon or silicon-based alloy.

[0036] The reaction is preferably performed while stirring the solution. Depending on the type of metal used, an impurity precipitation reaction may proceed in addition to the reduction precipitation reaction. So, that impure In order to suppress precipitation and promote the reduction precipitation reaction, for example, start the reaction at 40 to 60 ° C, heat at a rate of 1 to 10 ° C Zmin, and heat at 70 to 90 ° C. U, preferably to hold for minutes to 4 hours. Appropriate processing is performed by this operation.

[0037] When a predetermined amount of metal is precipitated on the surface of the core particles to obtain desired active material particles, the particles are separated by filtration and washed with water. The obtained particles are in a fresh state by dissolving the surface oxidized substance, and are in a state easily oxidized when exposed to the air. If benzotriazole (BTA) treatment is carried out after washing with water to suppress the reoxidation, reoxidation is suppressed, which is more effective.

[0038] The above-described production method is a force when the above-described core particles are used as the base material on which the metal is reduced and precipitated. This production method can be applied to a base material having various granular strengths 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, the present manufacturing method can be applied to various kinds of barta bodies such as plate bodies and rod bodies as base materials.

[0039] As an alternative to the present manufacturing method, an aqueous solution as agent for the _P H7 or alkaline it may be used Mizusani匕alkali metal or Mizusani匕alkaline earth metals. However, as described above, when the pH of the solution is made higher than that of the alkali metal hydroxide or the alkaline earth metal, 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 hydroxide of the metal is dissolved, and the metal is present in the solution in an ionic state. When the core particles are put in this state, reduction precipitation of the metal occurs, and the metal adheres to the surface of the core particle.

Example

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

Example 1

The composition of Si80% -Ni20% with an average particle size D of 1.5 m

50

The obtained core particles were obtained. The core particles were added to an aqueous solution containing 10 gZl of sodium acetate and 2.5 gZl of nickel sulfate and having a pH of 7.8 while stirring the aqueous solution. The liquid temperature was 50 ° C at the time of introduction. The input amount was 5 gZl. Then heat at the heating rate of CZmin, 8 When the temperature reached 0 ° C, the temperature was maintained for 30 minutes. The pH at that time was 5.6. As a result, nickel was reduced and precipitated on the surfaces of the core particles to obtain active material particles. The nickel content 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 type of the core particles and the nickel content were as shown in Table 1. The particles of Si Co and Si were prepared as in Example 1.

80 20

Manufactured by the Ruzo method.

Example 6

The core particles were added to an aqueous solution containing 2.5 gZl of potassium pyrophosphate and 2.OgZl of nickel chloride and having ρΗ of 9.0 while stirring the aqueous solution. The core particles have an average particle size D of 1.

50 and had a composition of 80% Si—20% Ni. The liquid temperature was kept at 80 ° C. As a result, nickel was reduced and precipitated on the surface of the core particles to obtain active material particles. The nickel content 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 type of the core particles and the nickel content were as shown in Table 1.

[Performance evaluation]

Using the active material particles obtained in each of the examples, a negative electrode for a lithium ion secondary battery was produced by the method shown in FIG. Using the produced negative electrode, a lithium ion secondary battery was produced in the following manner. The capacity retention of the battery at 200 cycles was measured and calculated by the following method. The 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. Carrier foil 1 was washed in a pickling solution at room temperature for 30 seconds. Subsequently, pure water washing was performed at room temperature for 30 seconds. Next, the carrier foil 1 was immersed in a 3 gZl carboxybenzotriazole solution kept at 40 ° C. for 30 seconds to form a release layer 2 as shown in FIG. 2 (b). Further, the resultant was washed with pure water at room temperature for 15 seconds.

(2) Formation of First Surface Layer The carrier foil 1 was immersed in a nickel plating bath having the following bath composition, and electrolysis was performed to form a first surface layer 3a of an ultra-thin nickel foil as shown in FIG. 2 (c). The first surface layer 3a was formed on the release layer 2 formed on the glossy side of the carrier foil. The current density was 5AZdm ² and the bath temperature was 50 ° C. A nickel electrode was used for the anode. DC power supply was used. The thickness of the first surface layer 3a was 3 m.

[0048] The slurry composition was: active material: acetylene black: PVdF = 94: 1: 5.

(3) Formation of Active Material Layer

After the formation of the first surface layer 3a, the substrate was washed with pure water for 30 seconds and then dried in the air. Next, a slurry containing the active material particles 5 obtained in each example was applied on the first surface layer 3a, and as shown in FIG. Formed four. The slurry contained active material particles 5, acetylene black, and polyvinylidene fluoride (hereinafter referred to as PVdF!). The slurry composition was as follows: active material particles: acetylene black: PVdF = 94: 1: 5.

(4) Formation of Second Surface Layer

As shown in FIG. 2E, on the active material layer 4, a second surface layer 3b, which is also a very thin nickel foil, was formed by electrolysis. The conditions for the electrolysis were the same as the conditions for forming the first surface layer 3a. The film thickness was 3 m.

(5) Separation of electrodes

The electrode 10 thus obtained was peeled off 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 the working electrode, LiCoO was used as the counter electrode, and both electrodes were used as separators.

2

Were opposed to each other. LiPF as non-aqueous electrolyte

A lithium ion secondary battery was fabricated by a conventional method using a mixed solution of 6Z ethylene carbonate and getyl carbonate (1: 1 volume ratio). [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 to calculate.

[Table 1]

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

Industrial applicability

As described above in detail, according to the present invention, active material particles for a nonaqueous electrolyte secondary battery having high electron conductivity can be manufactured by a simple manufacturing method. Further, according to the present invention, various metals can be deposited on the surface of silicon or a silicon-based base material, which facilitates electroless plating.

Claims

The scope of the claims

[1] An active material particle for a non-aqueous electrolyte secondary battery, wherein a metal precipitated by electroless plating adheres to the surface of a core particle which also has a silicon or silicon alloy force.

[2] A negative electrode for a non-aqueous electrolyte secondary battery, comprising the active material particles according to claim 1.

[3] A non-aqueous electrolyte secondary battery comprising the negative electrode according to claim 2.

[4] A base material made of silicon or silicon alloy powder is put into an alkaline solution having a pH of 7 or more that exists in the state of a metal ion, and the metal is deposited on the surface of the base material. A method for producing an electroless plating.

5. The production method according to claim 4, wherein the alkaline solution contains a salt of a weak acid, whereby the pH is adjusted to 7 or more.

6. The method according to claim 5, wherein the salt of the weak acid is a salt of acetic acid or pyrophosphoric acid.

7. The method according to claim 4, wherein the base material is a granular material.

[8] The method according to claim 4, wherein the base material is a plate.

[9] The method according to claim 4, wherein the metal is nickel, copper, iron or cobalt.

[10] The method according to claim 4, wherein the metal is deposited while keeping the alkaline solution at 50 to 100 ° C.