JP2003151544A - Negative electrode active substance and its manufacturing method as well as nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress deterioration of cycle characteristics due to fine powder formation in a lithium alloy series negative electrode active substance. SOLUTION: By using a negative electrode active substance wherein a metal M capable of having an electrochemical reaction with lithium contains carbon inside, and wherein a metal R having no electrochemical reaction with carbon or the lithium is adhered, reduction can be suppressed in electronic conduction of the metal M capable of having the electrochemical reaction with the lithium at the inside and at the surface, even if the fine powder formation due to swelling and contraction during the electrochemical reaction occurs.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a negative electrode active material containing a metal capable of electrochemically reacting with lithium and a method for producing the same.
It also relates to a non-aqueous electrolyte secondary battery using the negative electrode active material.

[0002]

2. Description of the Related Art Recently, a VTR with a built-in camera, a mobile phone,
Many portable electronic devices such as laptop computers have appeared, and their size and weight have been reduced. As a portable power source for these electronic devices, research and development for improving the energy density of batteries, especially secondary batteries, have been actively promoted.

Among them, the lithium ion secondary battery has a great advantage because it can obtain a larger energy density than the lead battery and the nickel cadmium battery which are the conventional aqueous electrolyte secondary batteries.

As a negative electrode active material used in a lithium ion secondary battery, carbonaceous negative electrode active materials such as non-graphitizable carbon and graphite are widely used because they have a relatively high capacity and exhibit good cycle characteristics. It is used.

[0005]

With the increase in capacity in recent years, it has become a problem to further increase the capacity of carbon-based negative electrode active materials. For example, in Japanese Patent Application Laid-Open No. 8-315825, high capacity is achieved with a carbonaceous material negative electrode by selecting a carbonization raw material and production conditions.

However, the negative electrode discharge potential was 0.8 V to 1.0 V with respect to lithium, the battery discharge voltage when the battery was constructed was low, and a significant improvement in battery energy density could not be expected. Further, there is a drawback that the charge / discharge curve shape has a large hysteresis and the energy efficiency in each charge / discharge cycle is low.

On the other hand, as a high-capacity negative electrode, a material has been extensively studied, which is applied to the fact that a certain kind of metal is electrochemically alloyed with lithium and reversibly produced / decomposed. For example, a high-capacity negative electrode using a Li-Al alloy has been widely studied, and US Pat. No. 4,950,566 discloses a high-capacity negative electrode using a Si alloy. However, the Li-Al or Li-Si alloy expands and contracts with charge and discharge, and the negative electrode is pulverized each time the charge and discharge cycle is repeated, resulting in extremely poor cycle characteristics.

One of the main causes of deterioration of cycle characteristics is that such pulverization hinders the electronic connection between the negative electrode materials and the current collector and makes it difficult for the charge / discharge reaction to proceed. is there.

The present invention has been proposed in view of the above conventional circumstances, and is a negative electrode active material having improved cycle characteristics, a method for producing the same, and a non-aqueous electrolyte secondary using the negative electrode active material. The purpose is to provide a battery.

[0010]

The negative electrode active material of the present invention comprises:
The metal M capable of electrochemically reacting with lithium contains carbon, and carbon or a metal R that does not electrochemically react with lithium is fixed to the surface of the metal M.

In the negative electrode active material according to the present invention as described above, since the metal M contains carbon, and the carbon or the metal R is fixed on the surface of the metal M, the expansion during the electrochemical reaction. Even if it is pulverized due to contraction, it is possible to suppress a decrease in electron conduction inside and on the surface of the metal M that can electrochemically react with lithium.

The method for producing the negative electrode active material of the present invention is
In producing a negative electrode active material in which a metal M capable of electrochemically reacting with lithium contains carbon, and carbon or a metal R that does not electrochemically react with lithium is fixed to the surface of the metal M, In the process of encapsulating carbon in the metal M, the method is characterized by having a step of processing in a non-oxidizing atmosphere.

In the method for producing a negative electrode active material according to the present invention as described above, in the process of encapsulating carbon in the metal M, there is a step of treating in a non-oxidizing atmosphere.
Oxidation of carbon is suppressed.

The non-aqueous electrolyte secondary battery of the present invention is L
iM _x O _y (M is Co, Ni, Mn, Fe, Cr, A
At least one element selected from l and Ti. )
A positive electrode having a lithium composite oxide represented by as a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte interposed between the positive electrode and the negative electrode. It is characterized in that the metal M capable of chemically reacting contains carbon and a metal R that does not electrochemically react with carbon or lithium is fixed to the surface of the metal M.

In the non-aqueous electrolyte secondary battery according to the present invention as described above, the metal M contains carbon, and the negative electrode active material in which carbon or the metal R is fixed on the surface of the metal M is used. Therefore, even if it is pulverized by expansion and contraction during the electrochemical reaction, it is possible to suppress a decrease in electron conduction inside and on the surface of the metal M that can electrochemically react with lithium.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of a negative electrode active material to which the present invention is applied, a method for producing the same, and a non-aqueous electrolyte secondary battery using the negative electrode active material will be specifically described with reference to the drawings. explain.

FIG. 1 is a vertical cross-sectional view showing one structural example of the non-aqueous electrolyte secondary battery of the present invention. This non-aqueous electrolyte battery 1
Is a film-shaped positive electrode 2 and a film-shaped negative electrode 3,
A wound layer electrode body wound in a close contact state via the separator 4 is loaded inside the battery can 5.

The positive electrode 2 is prepared by applying a positive electrode mixture containing a positive electrode active material and a binder onto a current collector and drying it. A metal foil such as an aluminum foil is used for the current collector.

As the positive electrode active material, a metal oxide, a metal sulfide or a specific polymer can be used depending on the type of the intended battery.

Specifically, for example, TiS ₂ , MoS ₂ ,
Lithium-free metal sulfides or oxides such as NbSe ₂ , V ₂ O ₅ and Li _x MO ₂ (wherein M represents one or more transition metals, x varies depending on the charge / discharge state of the battery, It is possible to use a lithium composite oxide mainly composed of 0.05 ≦ x ≦ 1.10.
As the transition metal M constituting the lithium composite oxide, Co, Ni, Mn and the like are preferable.

Specific examples of such a lithium composite oxide and
Then LiCoO_Two, LiNiO _Two, Li_xNi_yC
o_1-yO_Two(In the formula, x and y depend on the charging / discharging state of the battery.
Is different, usually 0 <x <1, 0.7 <y <1.02
is there. ), A lithium manganese compound having a spinel structure
The compound oxide and the like can be increased. These lithium composites
Oxide can generate high voltage and is excellent in energy density.
It becomes a positive electrode active material. The positive electrode contains these positive electrode active materials.
You may mix and use two or more types.

As the binder for the above-mentioned positive electrode mixture, a known binder which is usually used in a positive electrode mixture for batteries can be used. In addition to the above-mentioned positive electrode mixture, a conductive agent or the like is also known. Additives can be added.

The negative electrode 3 is produced by applying a negative electrode mixture containing a negative electrode active material and a binder onto a current collector and drying it. For the current collector, a metal foil such as a copper foil is used.

Here, in the present invention, as the negative electrode active material,
A metal M that can electrochemically react with lithium has carbon contained therein, and carbon or a metal R that does not electrochemically react with lithium is fixed to the surface of the metal.

The inventors of the present invention have made extensive studies to solve the above-mentioned problems, and as a result, in the process of producing the metal M capable of electrochemically reacting with lithium, carbon particles are included and the surface of the metal M is included. By using the negative electrode active material to which the metal R that does not electrochemically react with carbon or lithium is fixed, even if the metal R capable of electrochemically reacting with lithium is pulverized due to expansion and contraction during the electrochemical reaction, It was found that the decrease in electron conduction can be suppressed. Thereby, cycle deterioration of the non-aqueous electrolyte battery 1 can be suppressed.

Examples of the metal M capable of electrochemically forming an alloy with lithium include elemental elements and their alloy compounds. The alloy compound here means a chemical formula M _x M ′ _y , where M is a metal element capable of forming an alloy with lithium.
Li _z (where M ′ is one or more metal elements other than the Li element and the M element, x is a numerical value greater than 0, and y, z
Is a numerical value of 0 or more. ) Is a compound represented by.

Furthermore, in the present specification, elements such as B, Si, As, which are semiconductor elements, are also included in the metal M.
For example, Hg, B, Al, Ga, In, Si,
Ge, Sn, Pb, Sb, Bi, Cd, Ag, Zn, H
f, Zr, Y metals and their alloy compounds, Li-A
1, Li-Al-M (M is composed of one or more of 2A, 3B, and 4B transition metal elements.) AlSb, CuMgS
b, etc.

As the metal M capable of forming an alloy with lithium, it is preferable to use a group 3B typical element, preferably Si or Sn, and more preferably Si. For example, a compound represented by M _x N _y Si (M is one or more metal elements other than Si or Sn), and specifically, SiB ₄ , SiB ₆ , and Hg ₂ Si,
Hg ₂ Sn, Ni ₂ Si, TiSi ₂ , MoSi ₂ , C
_{oSi 2, NiSi 2, CaSi 2} , CrSi 2, Cu
₅ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaS
i ₂ , VSi ₂ , WSi ₂ , ZnSi _{2 and the} like can be mentioned. Further, a combination of a plurality of kinds of metals is possible, and these include metals that do not electrochemically form an alloy with lithium.

As the carbon to be contained in the metal M as described above, at least one kind of hard carbon, soft carbon, graphite and carbon black can be used. Further, as the shape, fibrous, spherical,
At least one kind of granular or scale-like can be used.

In the present invention, the purpose of encapsulating carbon in the metal M is to ensure electron conductivity even in finely divided metal, so carbon can be appropriately selected depending on the usage form of the metal. For example, highly crystalline graphite is preferable in order to obtain higher electron conductivity, and hard carbon is preferable in order to suppress expansion and contraction. Also,
Fibrous carbon is preferable for suppressing structural destruction, and carbon black is preferable for improving dispersibility.
Further, the shape thereof is preferably granular or spherical so as to enhance the carbon filling property. Furthermore, in order to obtain the effect of the above combination, two or more kinds can be mixed and used appropriately.

Such a carbon content can be used within a range in which the capacity of the negative electrode exceeds that of the carbon-based negative electrode. The content with respect to the metal M is preferably in the range of 0.3% by weight to 90% by weight. A more preferable range is 0.
It is 5% to 80% by weight, and the most preferable range is 1% to 70% by weight.

The carbon fixed to the surface of the metal M is
It is preferable that the metal M has a characteristic similar to that of the carbon contained therein.

As the metal R fixed to the surface of the metal M, any metal can be used as long as it does not electrochemically react with lithium. Specifically, Cr,
Mn, Fe, Co, Ni, Cu, Ag, Mo, Nb, N
Examples of the metal include d, Sm, Ta, Ti, and V. Further, the metal R does not necessarily have to be an elemental simple substance, and may be an alloy or an intermetallic compound. It is also possible to mix two or more of them. That is, any metal R can be suitably used as long as it does not react electrochemically with lithium and has electronic conductivity.

Carbon or metal R fixed to the surface of metal M
Is preferably in the range of 0.5% by weight to 20% by weight, more preferably 1% by weight to 1% with respect to the metal M.
It is in the range of 0% by weight. Further, the carbon or the metal R may cover the entire surface of the metal M or only a part thereof.

The method of encapsulating carbon in the metal M can be performed by any method, but industrially, the method of dispersing the carbon in the metal in a molten state is preferable. At that time, mechanical stirring may be performed, or self-stirring action such as induction heating may be used.

As a matter of course, since the metal melts at a considerably high temperature, carbon may be oxidized or burned. Therefore, in any of the manufacturing processes, it is preferable to manufacture in a non-oxidizing atmosphere when carbon may be exposed to the metal and oxidized.

When the metals are mixed by a dry method before melting, the atmosphere may be replaced with a vacuum or a non-oxidizing atmosphere before heating.

As a method of fixing the metal R to the surface of the metal M, there are a method of mechanically fixing such as hybridization and mechanofusion, a method of fixing with a certain kind of binder, and a method of plating. Can be mentioned.

Further, after the metal R is fixed to the surface of the metal M, the temperature is 50 ° C. to 100 ° C. lower than the lower one of the melting points of the metal M and the metal R, and in a vacuum or non-oxidizing atmosphere. The heat treatment in the inside is preferable because the metal R and the metal M are more firmly fixed to each other and the electron conductivity is further improved.

Whether the carbon is contained in the metal M or whether the carbon or the metal R is fixed to the metal M is determined by, for example, cutting the metal by any method and observing the cross section with an analysis electron microscope or the like. It can be confirmed by doing. Here, the definition of "encapsulation" in the present invention is that carbon is fixed in the metal, and the effect can be obtained even when the carbon is exposed from the metal surface.

The negative electrode active material of the present invention obtained as described above may be used as a mixture with a carbon-based negative electrode material, and can be used within a range in which the capacity of the negative electrode is superior to that of the carbon-based negative electrode. As the function of carbon in this case, a function as a conductive auxiliary agent and a function as a negative electrode material are considered,
It can be used in any combination of two or more kinds in order to obtain predetermined battery characteristics.

As such a carbon material, at least one of hard carbon, soft carbon, graphite and carbon black can be used. Also,
As the shape, at least one kind of fibrous, spherical, granular, and scaly can be used. Further, the mixing amount of the carbon material is preferably in the range of 1 wt% to 95 wt% with respect to the metal component.

When a negative electrode is manufactured using such a negative electrode active material, the binder of the negative electrode mixture is
Known binders that are commonly used in the negative electrode mixture of lithium ion batteries can be used, and known additives and the like can be added to the above negative electrode mixture.

Doping lithium into the negative electrode may be performed electrochemically in the battery after the battery is manufactured, and may be electrochemically supplied from the positive electrode or a lithium source other than the positive electrode after the battery is manufactured or before the battery is manufactured. It may be doped. Alternatively, it may be synthesized as a lithium-containing material during material synthesis and included in the negative electrode during battery production.

The non-aqueous electrolytic solution is prepared by dissolving an electrolyte in a non-aqueous solvent.

As the electrolyte, it is possible to use a known electrolyte that is usually used in a battery electrolyte. Specifically, LiClO ₄ , LiAsF ₆ , LiPF ₆ , L
iBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li,
_{CF 3 SO 3 Li, LiCl,} LiBr , and the like.

As the non-aqueous solvent, various non-aqueous solvents conventionally used for non-aqueous electrolytes can be used. For example, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-ptyrolactone, tetrahydrofuran, 2
-Methyltetrahydrofuran, 1,3-dioxolane,
4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, acetonitrile,
Examples thereof include propionitrile, anisole, acetic acid ester, butyric acid ester, propionic acid ester and the like. These non-aqueous solvents may be used alone or in combination of two or more.

The positive electrode 2 and the negative electrode 3 as described above are in close contact with each other via the separator 4 and are wound in a spiral shape many times to form a wound layer electrode body. An insulating plate 6 is arranged at the bottom of the battery case 5 made of iron and having nickel plating inside, and the wound layer electrode body is housed on the insulating plate 6.

Then, one end of a negative electrode lead 7 made of, for example, nickel for collecting the current of the negative electrode is pressure-bonded to the negative electrode 3, and the other end is welded to the battery can 5. As a result, the battery can 5 becomes conductive with the negative electrode 3 and serves as an external negative electrode of the non-aqueous electrolyte battery 1.

Further, one end of a positive electrode lead 8 made of, for example, aluminum for collecting the current of the positive electrode 2 is attached to the positive electrode 2, and the other end is connected to the battery cover 1 via a thin plate 9 for interrupting current.
It is electrically connected to 0. This current interrupting thin plate 9
Is to interrupt the current according to the internal pressure of the battery. As a result, the battery lid 10 becomes conductive with the positive electrode 2,
It serves as an external positive electrode of the non-aqueous electrolyte battery 1.

A non-aqueous electrolytic solution is poured into the battery can 5 to immerse the wound body. Then, the battery can 5 is caulked via the insulating sealing gasket 11 coated with asphalt, whereby the battery lid 10 is fixed.

In this non-aqueous electrolyte battery 1,
As shown in FIG. 1, a center pin 12 connected to the negative electrode lead 7 and the positive electrode lead 8 is provided, and a safety valve device for venting internal gas when the internal pressure of the battery becomes higher than a predetermined value. 13 and a PTC element 14 for preventing a temperature rise inside the battery.

As described above, in the non-aqueous electrolyte battery 1 according to the present invention, carbon particles are included in the metal M capable of electrochemically reacting with lithium as the negative electrode active material, and the metal M Since a metal R that does not electrochemically react with carbon or lithium is fixed to the surface,
Even if the negative electrode active material is pulverized due to expansion and contraction during the electrochemical reaction, it is possible to suppress a decrease in electron conduction inside and on the surface of the metal M that can electrochemically react with lithium. As a result, the non-aqueous electrolyte battery 1 can suppress an increase in battery internal resistance due to electrode deterioration, suppress cycle deterioration, and have high capacity and excellent cycle characteristics.

In the above-mentioned embodiments, the case where the non-aqueous electrolyte is a non-aqueous electrolyte prepared by dissolving an electrolyte salt in a non-aqueous solvent has been described as an example. However, the present invention is not limited to this. However, any of a solid electrolyte containing an electrolyte salt and a gel electrolyte in which a matrix polymer is impregnated with the above nonaqueous electrolytic solution can be used.

As the solid electrolyte, either an inorganic solid electrolyte or a polymer solid electrolyte can be used as long as it has lithium ion conductivity. Examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. A solid polymer electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. The polymer compound may be an ether polymer such as poly (ethylene oxide) or a cross-linked polymer thereof, a poly (methacrylate) ester system, or an acrylate system. They can be used alone, or can be copolymerized or mixed in the molecule.

As the matrix polymer of the gel electrolyte, various polymers can be used as long as they absorb the above non-aqueous electrolyte and gel. For example, poly (vinylidene fluoride) and poly (vinylidene fluoride)-
Fluorine-based polymers such as co-hexafluoropropylene), ether-based polymers such as poly (ethylene oxide) and cross-linked products thereof, and poly (acrylonitrile) can be used. In particular, it is desirable to use a fluoropolymer because of its redox stability.

The battery shape of the battery of the present invention is not particularly limited. Various shapes and sizes such as a cylinder type, a square type, a coin type, and a button type can be used. Further, all the lithium present in the battery system does not necessarily have to be supplied from the positive electrode or the negative electrode, and may be electrochemically doped into the positive electrode or the negative electrode during the manufacturing process of the electrode or the battery.

[0058]

EXAMPLES Examples and comparative examples conducted to confirm the effects of the present invention will be described below. It should be noted that in the following description, specific substance names, numerical values, etc. are given for explanation, but it goes without saying that the present invention is not limited to these examples.

<Example 1> First, a negative electrode was prepared as follows.

Si powder which is a metal M capable of electrochemically reacting with lithium is heated and melted at 1500 ° C. in a non-oxidizing atmosphere, and as carbon to be encapsulated therein, 10 parts by weight of MCM6-28 (based on Si powder) is used. (Made by Osaka Gas Chemicals)
Was added without changing the atmosphere and mixed for a while. Then, it atomized in Ar gas atmosphere and obtained the atomized powder. 97 parts by weight of the obtained powder and 3 parts by weight of acetylene black were put into a hybridization device,
Atomized powder having acetylene black fixed on the surface was obtained. The obtained powder was classified with 200 mesh, and the bottom of the sieve was used as a metal negative electrode active material.

This metallic negative electrode active material and scaly graphite (KS-44 manufactured by Timical) were mixed at a weight ratio of 50:50,
As a binder, 8 parts by weight of polyvinylidene fluoride was added to the above mixture, and N-methylpyrrolidone was further added as a solvent to obtain a slurry-like negative electrode mixture. This negative electrode mixture was uniformly applied to both sides of a strip-shaped copper foil current collector, dried, and compression-molded with a roll press to obtain a strip-shaped negative electrode.

On the other hand, a positive electrode was prepared as follows.

In order to obtain a positive electrode active material (LiCoO ₂ ), lithium carbonate and cobalt carbonate were mixed in a ratio of 0.5 mol: 1 mol, and the mixture was baked in air at 900 ° C. for 5 hours.
Next, 91 parts by weight of the obtained LiCoO ₂ , 6 parts by weight of graphite as a conductive agent, and 3 parts by weight of polyvinylidene fluoride (PVdF) as a binder were mixed, and this was further mixed with N-methyl- It was dispersed in 2-pyrrolidone to obtain a slurry-like positive electrode mixture.

Then, this positive electrode mixture was uniformly applied on both sides of a 20 μm thick aluminum foil, which is a strip-shaped positive electrode current collector, dried, and compression-molded by a roll press machine to obtain a strip-shaped positive electrode.

A separator made of a strip-shaped negative electrode, a strip-shaped positive electrode and a microporous polypropylene film having a thickness of 25 μm was laminated in this order on the negative electrode, the separator, the positive electrode, and the separator, and then this laminated body was spirally wound many times to form the outermost periphery. The final end of the separator was fixed with tape to produce a wound layer electrode body.

The wound-layer electrode body thus manufactured was nickel-plated with a diameter of 18 mm and a height of 65 m.
m iron battery can (inner diameter: 17.38 mm, can thickness: 0.31)
mm). Insulating plates were arranged on both upper and lower end surfaces of the wound layer electrode body. Further, the aluminum positive electrode lead was led out from the positive electrode current collector and welded to the battery lid, and the nickel negative electrode lead was led out from the negative electrode current collector and welded to the battery can. An electrolytic solution was injected into the battery can. This electrolytic solution was prepared by dissolving LiPF _{6 in a} mixed solvent of equal volumes of ethylene carbonate and dimethyl carbonate at a ratio of 1 mol / 1.

The battery lid was fixed by caulking the battery can through the insulating sealing gasket whose surface was coated with asphalt, and the airtightness inside the battery was maintained. As described above, a cylindrical non-aqueous electrolyte secondary battery was produced.

Example 2 A cylindrical non-aqueous solution was inserted in the same manner as in Example 1 except that a metal negative electrode active material was prepared by hybridizing atomized powder and Cu powder. An electrolyte secondary battery was produced.

Example 3 Since the melting point of Si is 1414 ° C. and the melting point of Cu is 1085 ° C., the atomized powder having Cu adhered to the surface produced in Example 2 is 1000 After heat treatment at ℃ for 5 hours, it was pulverized and classified with 200 mesh, and the under sieve was obtained as a metal negative electrode active material. Other than using this metal negative electrode active material,
A cylindrical non-aqueous electrolyte secondary battery was produced in the same manner as in Example 2.

Comparative Example 1 A cylindrical non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that the metal negative electrode active material in which carbon was not included in the metal M was used.

Comparative Example 2 Cylindrical non-aqueous electrolytic solution was prepared in the same manner as in Example 1 except that a metal negative electrode active material in which acetylene black was not hybridized was used around the metal M containing carbon. A secondary battery was produced.

A charging / discharging cycle test was conducted on the batteries of Examples and Comparative Examples produced as described above, and the cycle characteristics were evaluated.

First, for each battery, the maximum voltage 4.2
A charging / discharging cycle was repeated in which constant-current constant-voltage charging was performed under the conditions of V, constant current 1A, and charging time 5h, and then discharging at a constant current 1A to a final voltage of 2.5V. The discharge capacity of the first cycle was defined as the initial capacity, and the discharge capacity maintenance ratio (%) at the 50th cycle was calculated when the initial capacity was 100.

Table 1 shows the initial capacity and the capacity maintenance rate at the 50th cycle for each battery.

[0075]

[Table 1]

As is clear from Table 1, the batteries of Comparative Example 1 in which carbon is not included in the metal M and Comparative Example 2 in which carbon is not fixed around the metal M have poor electron conductivity. Metal M that cannot be charged or discharged from the first cycle of charging
Will start to occur. It can be seen that the amount of the metal M that cannot be charged and discharged increases with the cycle, and the initial capacity and the capacity maintenance rate are inferior.

On the other hand, when the metal M contains carbon, the metal M
In the batteries of Examples 1 to 3 using the metal negative electrode active material in which the carbon or the metal R is fixed around, since the electron conductivity of the metal negative electrode active material is sufficiently ensured,
It can be seen that the initial capacity is large and the capacity maintenance rate is also high. In particular, the battery of Example 3 in which sufficient electron conductivity was ensured by heat treatment showed the largest initial capacity and high capacity maintenance rate.

From the above results, by using the metal M containing carbon particles and having the surface of the metal M fixed with carbon or metal R as the negative electrode active material, the negative electrode active material undergoes an electrochemical reaction. Even if it is pulverized by the expansion and contraction of
It is possible to suppress a decrease in electron conduction inside and on the surface of the metal M that can electrochemically react with lithium. Then, a non-aqueous electrolyte battery using such a negative electrode active material is capable of suppressing an increase in battery internal resistance due to electrode deterioration, suppressing cycle deterioration, and having high capacity and excellent cycle characteristics. I understood it.

[0079]

INDUSTRIAL APPLICABILITY In the present invention, as a negative electrode active material, carbon particles are included in a metal M capable of electrochemically reacting with lithium, and the surface of the metal M does not electrochemically react with carbon or lithium. Since the material to which the metal R is adhered is used, even if the negative electrode active material is pulverized due to expansion and contraction during the electrochemical reaction, it is possible to suppress a decrease in electron conduction inside and on the surface of the metal M capable of electrochemically reacting with lithium. be able to.

As a result, according to the present invention, it is possible to suppress an increase in battery internal resistance due to electrode deterioration, suppress cycle deterioration, and realize a non-aqueous electrolyte secondary battery having high capacity and excellent cycle characteristics. You can

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view showing one structural example of a non-aqueous electrolyte battery of the present invention.

[Explanation of symbols]

1 non-aqueous electrolyte battery, 2 positive electrode, 3 negative electrode, 4
Separator, 5 battery cans, 6 insulating plates, 7 negative electrode leads, 8 positive electrode leads, 9 current cut thin plates,
10 Battery lid, 11 Insulation sealing gasket, 12
Center pin, 13 safety valve device, 14 PTC element

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01M 10/40 H01M 10/40 ZF term (reference) 5H029 AJ03 AJ05 AK03 AL12 AM03 AM04 AM05 AM07 BJ02 BJ14 CJ02 CJ07 CJ28 DJ08 DJ15 DJ16 EJ01 EJ04 HJ05 5H050 AA07 AA08 BA16 CA07 CB12 DA03 DA10 EA02 EA03 EA04 EA05 EA08 FA05 FA16 FA17 FA18 GA02 GA06 GA09 GA27 HA05

Claims (18)

[Claims] 1. A metal M capable of electrochemically reacting with lithium.
However, the negative electrode active material contains carbon, and a metal R that does not electrochemically react with carbon or lithium is fixed to the surface of the metal M. 2. The negative electrode active material according to claim 1, wherein the metal M is a mixture of a metal that electrochemically reacts with lithium and a metal that does not react with lithium. 3. The negative electrode active material according to claim 1, wherein the carbon contained in the metal M is at least one of hard carbon, soft carbon, graphite and carbon black. 4. The negative electrode active material according to claim 1, wherein the shape of the carbon contained in the metal M is at least one of fibrous, spherical, granular, and scaly. 5. The carbon fixed to the surface of the metal M is hard carbon, soft carbon, graphite,
The negative electrode active material according to claim 1, which is at least one kind of carbon black. 6. The metal R is Cr, Mn, Fe, C
o, Ni, Cu, Ag, Mo, Nb, Nd, Sm, T
The negative electrode active material according to claim 1, which is a mixture or alloy compound of at least one metal selected from a, Ti, and V. 7. A metal M capable of electrochemically reacting with lithium
In producing a negative electrode active material in which carbon is included and a metal R that does not electrochemically react with carbon or lithium is fixed to the surface of the metal M, in the process of including carbon in the metal M A method for producing a negative electrode active material, comprising a step of treating in a non-oxidizing atmosphere. 8. The method for producing a negative electrode active material according to claim 7, wherein a mixture of a metal that electrochemically reacts with lithium and a metal that does not react is used as the metal M. 9. The method for producing a negative electrode active material according to claim 7, wherein at least one of hard carbon, soft carbon, graphite, and carbon black is used as carbon contained in the metal M. 10. The carbon contained in the metal M,
The method for producing a negative electrode active material according to claim 7, wherein at least one of fibrous, spherical, granular, and scale-like shapes is used. 11. The carbon fixed to the surface of the metal M is hard carbon, soft carbon, graphite,
The method for producing a negative electrode active material according to claim 7, wherein at least one kind of carbon black is used. 12. The metal R is Cr, Mn, F.
e, Co, Ni, Cu, Ag, Mo, Nb, Nd, S
The method for producing a negative electrode active material according to claim 7, wherein a mixture or alloy compound of at least one metal selected from m, Ta, Ti, and V is used. 13. LiM _x O _y (M is Co, Ni, M
It is at least one element selected from the group consisting of n, Fe, Cr, Al, and Ti. ), A positive electrode having a lithium composite oxide as a positive electrode active material, a negative electrode having a negative electrode active material, and a non-aqueous electrolyte interposed between the positive electrode and the negative electrode, wherein the negative electrode active material is lithium. A non-aqueous electrolyte secondary battery characterized in that a metal M capable of electrochemical reaction contains carbon and a metal R that does not electrochemically react with carbon or lithium is fixed to the surface of the metal M. . 14. The non-aqueous electrolyte secondary battery according to claim 13, wherein the metal M is a mixture of a metal that electrochemically reacts with lithium and a metal that does not react with lithium. 15. The non-aqueous electrolyte secondary battery according to claim 13, wherein the carbon contained in the metal M is at least one of hard carbon, soft carbon, graphite, and carbon black. 16. The non-aqueous electrolyte secondary battery according to claim 13, wherein the shape of the carbon contained in the metal M is at least one of fibrous, spherical, granular, and scaly. 17. The non-aqueous electrolyte secondary battery according to claim 13, wherein the carbon fixed to the surface of the metal M is at least one of hard carbon, soft carbon, graphite and carbon black. . 18. The metal R is Cr, Mn, Fe, C
o, Ni, Cu, Ag, Mo, Nb, Nd, Sm, T
14. The non-aqueous electrolyte secondary battery according to claim 13, which is a mixture or alloy compound of at least one metal selected from a, Ti, and V.