JP2001196052A - Negative electrode and nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict deterioration in charging/discharging cycles and achieve a high capacity and a long life. SOLUTION: This battery comprises a positive electrode containing a lithium composite oxide, a negative electrode containing a metal capable of forming an alloy with lithium or its alloy and fiber carbon or carbon black and a nonaqueous electrolyte laid between the positive electrode and the negative electrode.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a negative electrode and a non-aqueous electrolyte battery using the same.

[0002]

2. Description of the Related Art In recent years, many portable electronic devices such as a camera-integrated video tape recorder, a portable telephone, and a laptop computer have appeared, and their size and weight have been reduced. Research and development for improving the energy density of batteries, particularly secondary batteries, as portable power sources for these electronic devices are being actively pursued. Above all, lithium ion secondary batteries are expected to have a large energy density as compared with conventional aqueous electrolyte secondary batteries such as lead batteries and nickel cadmium batteries.

As negative electrode materials used in lithium ion batteries, non-graphitizable carbon and carbonaceous materials such as graphite are widely used because they exhibit a relatively high capacity and exhibit good cycle characteristics.

[0004]

However, with the recent increase in capacity, there has been an issue of further increasing the capacity of the negative electrode material. JP-A-8-315825 discloses that a carbonaceous material negative electrode achieves high capacity by selecting a carbonized material and manufacturing conditions. However, the negative electrode discharge potential was 0.8 V to 1.0 V with respect to lithium potential, the battery discharge voltage at the time of configuring the battery was low, and no significant improvement in battery energy density could be expected. Further, there is a disadvantage that the hysteresis is large in the shape of the charge / discharge curve and the energy efficiency in each charge / discharge cycle is low.

On the other hand, as a high load capacity, a material which utilizes the fact that a certain kind of lithium alloy is electrochemically reversibly formed / decomposed has been widely studied.

A high capacity negative electrode using a Li-Al alloy has been widely studied, and US-Patent Number 4950566 proposes a high capacity negative electrode using a Si alloy. However, the Li-Al alloy or Li-Si alloy expands and contracts with charge and discharge, and each time the charge and discharge cycle is repeated, the negative electrode is pulverized to give a battery with extremely poor cycle characteristics. In order to improve the cycle characteristics, a method of adding an element which does not participate in expansion and contraction accompanying doping and undoping of lithium into a material has been studied. For example, JP-A-6-325765 discloses Li _x SiO _y (x ≧ 0, 2>y> 0), and JP-A-7-230800 discloses Li _x Si _(1-y) M _y O
_z (x ≧ 0, 1>y> 0, 0 <z <2), and
No. 288130 proposes a Li-Ag-Te alloy.

However, even with these methods, the charge / discharge cycle deterioration resulting from the expansion and contraction of the alloy is large,
The fact is that the features of high capacity loads are not fully utilized.

A high-capacity negative electrode using a Group 4B compound other than carbon, which contains one or more nonmetallic elements, is disclosed in JP-A-11-102.
As reported in Japanese Unexamined Patent Publication No. 705, there is a problem that charge / discharge cycle deterioration is large as in the case described above.

The present invention has been proposed in view of the above-described conventional circumstances, and has a negative electrode which suppresses deterioration of charge / discharge cycles and achieves high capacity and long life, and a non-aqueous electrolyte battery using the same. The purpose is to provide.

[0010]

The negative electrode according to the present invention has a pole active material layer containing a metal capable of forming an alloy with lithium or an alloy of the metal, and fibrous carbon or carbon black. I do.

In the above-described negative electrode according to the present invention, by including fibrous carbon or carbon black in the negative electrode active material layer, a conductive path in the negative electrode is formed stably, and lithium is doped and dedoped. The change in volume of the negative electrode due to this is suppressed.

Further, the negative electrode of the present invention has a negative electrode active material layer containing a group 4B compound other than carbon, which contains one or more nonmetallic elements, and fibrous carbon or carbon black. .

In the above-described negative electrode according to the present invention, by including fibrous carbon or carbon black in the negative electrode active material layer, a conductive path in the negative electrode is formed stably, and lithium is doped and dedoped. The change in volume of the negative electrode due to this is suppressed.

Further, the nonaqueous electrolyte battery of the present invention comprises a positive electrode containing a lithium composite oxide and a negative electrode containing a metal capable of forming an alloy with lithium or an alloy of the metal and fibrous carbon or carbon black. A negative electrode having a material layer;
A nonaqueous electrolyte interposed between the positive electrode and the negative electrode.

In the non-aqueous electrolyte battery according to the present invention as described above, by including fibrous carbon or carbon black in the negative electrode active material layer, a conductive path in the negative electrode is formed stably, and lithium is doped. -A change in the volume of the negative electrode due to undoping is suppressed. The non-aqueous electrolyte battery according to the present invention using such a negative electrode has excellent cycle characteristics.

Further, the non-aqueous electrolyte battery of the present invention comprises a positive electrode containing a lithium composite oxide, a group 4B compound other than carbon containing one or more nonmetallic elements, and fibrous carbon or carbon black. And a non-aqueous electrolyte interposed between the positive electrode and the negative electrode.

In the nonaqueous electrolyte battery according to the present invention as described above, by including fibrous carbon or carbon black in the negative electrode active material layer, the conductive path in the negative electrode is formed stably, and lithium is doped. -A change in the volume of the negative electrode due to undoping is suppressed. The non-aqueous electrolyte battery according to the present invention using such a negative electrode has excellent cycle characteristics.

[0018]

Embodiments of the present invention will be described below.

FIG. 1 shows an example of the configuration of a nonaqueous electrolyte battery according to the present invention. This non-aqueous electrolyte battery 1 includes a negative electrode 2,
A negative electrode can 3 containing the negative electrode 2, a positive electrode 4, a positive electrode can 5 containing the positive electrode 4, a separator 6 disposed between the positive electrode 4 and the negative electrode 2, and an insulating gasket 7; The positive electrode can 5 is filled with a non-aqueous electrolyte.

The negative electrode 2 is formed by forming a negative electrode active material layer containing the above-mentioned negative electrode active material on a negative electrode current collector. As the negative electrode current collector, for example, a nickel foil or the like is used. And in the nonaqueous electrolyte battery 1 of the present invention, as described later,
The negative electrode 2 contains fibrous carbon or carbon black.

Examples of the negative electrode active material include a metal capable of forming an alloy with lithium and an alloy compound of the metal.
The alloy compound referred to here is a chemical formula M _x M ′ _y Li where M is a metal element capable of forming an alloy with lithium.
_z (M ′ is one or more metal elements other than the Li element and the M element. Further, x is a numerical value greater than 0, and y and z are numerical values of 0 or more.) is there. Further, in the present invention, semiconductor elements such as B, Si, and As are included in the metal elements.

As the negative electrode active material, specifically, Mg, B,
Al, Ga, In, Si, Ge, Sn, Pb, Sb, B
i, Cd, Ag, Zn, Hf, Zr, Y and their alloy compounds, that is, for example, Li-Al, Li-
Al-M (M is composed of at least one of transition metal elements of Group 2A, 3B and 4B), AlSb, CuMgSb and the like.

Among the above-mentioned elements, it is preferable to use an element such as Si or Sn or an alloy thereof in addition to the group 3B typical element. Among them, Si or Si alloy is particularly preferred. Specifically, as Si or a Si alloy, M _x Si,
A compound represented by M _x Sn (M is one or more metal elements excluding Si or Sn), specifically, SiB ₄ , Si
B ₆ , Mg ₂ Si, Mg ₂ Sn, Ni ₂ Si, TiSi ₂ ,
MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrS
i ₂ , Cu ₅ Si, FeSi ₂ , MnSi ₂ , NbSi ₂ ,
TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi _{2 and the} like can be mentioned.

Further, in the non-aqueous electrolyte battery 1 of the present invention,
Group 4B elements other than carbon, including one or more nonmetallic elements, can also be used as the negative electrode active material. The material may contain one or more group 4B carbons. Further, a metal element other than Group 4B including lithium may be contained. For example, SiC, Si ₃ N ₄ , Si ₂ N ₂ O, Ge ₂ N ₂ O,
SiO _x (where 0 <x ≦ 2), SnO _x (where 0 <x ≦ 2), LiSiO, LiSnO, and the like.

The group 4B element other than carbon, including one or more non-metallic elements, is electrochemically doped with lithium.
Must have the ability to undope. Preferably 40
0 mAh / cm ³ or more, more preferably 500 mAh / cm ³
It preferably has a charge / discharge capacity of at least cm ³ . When calculating the charge / discharge capacity per volume, the true specific gravity of the compound is used.

The method of preparing the negative electrode active material as described above is not limited, but a mechanical ironing method, a method of mixing raw material compounds and performing a heat treatment in an inert atmosphere or a reducing atmosphere may be employed.

The doping of the negative electrode active material with lithium may be performed electrochemically in the battery after the battery is prepared. After or before the battery is prepared, the lithium may be supplied from a positive electrode or a lithium source other than the positive electrode. It may be doped. Alternatively, it may be synthesized as a lithium-containing material at the time of material synthesis, and may be contained in the negative electrode at the time of battery production.

The negative electrode active material as described above may be used after being pulverized, or may be used without being pulverized.

When the negative electrode active material is used after being pulverized, it may be pulverized so that the maximum particle diameter is smaller than the thickness of the negative electrode active material layer. The method of pulverization is not limited. Ball mill pulverization, jet mill pulverization and the like can be mentioned. Specifically, the average particle diameter (volume average particle diameter) of the pulverized negative electrode active material is preferably 50 μm or less, and more preferably 20 μm or less.

When the negative electrode active material is used without being pulverized, the negative electrode active material layer is formed by chemical vapor deposition, sputtering,
It can be manufactured as a molded body by hot pressing or the like.

As the binder contained in the negative electrode active material layer, a known resin material or the like which is generally used as a binder for the negative electrode active material layer of this type of nonaqueous electrolyte battery can be used. .

In the non-aqueous electrolyte battery 1 of the present invention,
The negative electrode active material layer contains fibrous carbon or carbon black.

By including fibrous carbon or carbon black in the negative electrode active material layer, a conductive path in the negative electrode can be formed stably, and a change in the volume of the negative electrode due to doping and undoping of lithium can be suppressed. As a result, the nonaqueous electrolyte battery 1 has excellent cycle characteristics.

The fibrous carbon is obtained by heat-treating a precursor made of a polymer or pitch spun into a fibrous form, and an organic vapor such as benzene is placed on a substrate at a temperature of about 1000 ° C. There is a vapor-grown carbon or the like obtained by directly flowing and growing a carbon crystal using iron fine particles or the like as a catalyst.

When fibrous carbon is obtained by heat treatment, examples of the polymer precursor include polyacrylonitrile and rayon. Further, polyamide, lignin, polyvinyl alcohol and the like can be used.

As the pitch, tars obtained by high-temperature pyrolysis of coal tar, ethylene bottom oil, crude oil, etc., and asphalt are distilled (vacuum distillation, atmospheric distillation,
There are also those obtained by operations such as steam distillation), thermal polycondensation, extraction, and chemical polycondensation, and other pitches formed during wood carbonization. As the starting material for the above pitch,
Examples include polyvinyl chloride resin, polyvinyl acetate, polyvinyl butyrate, and 3,5-dimethylphenol resin.

During the carbonization, these coals and pitches exist as liquids at a maximum of about 400 ° C., and when held at that temperature, aromatic rings are condensed and polycyclic to form a laminated orientation. At temperatures above this level, a solid carbon precursor, semicoke, is formed. Such a process is called a liquid phase carbonization process and is a typical production process of graphitizable carbon.

In addition, condensed polycyclic hydrocarbon compounds such as naphthalene, phenanthrene, anthracene, triphenylene, pyrene, perylene, pentaphen, and pentacene, other derivatives (eg, carboxylic acids, carboxylic anhydrides, carboxylic imides, etc.), or Mixtures, condensed heterocyclic compounds such as acenaphthylene, indole, isoindole, quinoline, isoquinoline, quinoxaline, phthalazine, carbazole, acridine, phenazine, phenanthridine, and derivatives thereof can also be used as raw materials for fibrous carbon.

Both the polymer-based precursor and the pitch-based precursor undergo a process of infusibility or stabilization, and are then heat-treated at a higher temperature to form fibrous carbon.

The infusibilizing or stabilizing step is a step of oxidizing the fiber surface with an acid, oxygen, ozone, or the like so that the polymer or the like does not melt or thermally decompose during carbonization. It is. At this time, the treatment method can be appropriately selected depending on the type of the precursor. However, the processing temperature needs to be selected below the melting point of the precursor. Further, the processing may be repeated a plurality of times as necessary to ensure sufficient stabilization.

In order to obtain fibrous carbon, the infusibilized or stabilized polymer precursor or pitch precursor is heated at a temperature of 300 ° C. in an inert gas stream such as nitrogen.
After carbonization at ~ 700 ° C, in an inert gas stream, the temperature is raised at a rate of 1 ° C to 100 ° C per minute, ultimate temperature of 900 ° C to 1500 ° C,
It is obtained by calcining under conditions of a holding time at the ultimate temperature of about 0 to 30 hours. Of course, carbonization may be omitted in some cases.

On the other hand, when fibrous carbon is obtained by a vapor phase growth method, any organic substance which can be gaseous as a starting material may be used. For example, ethylene or propane which exists in a gaseous state at normal temperature or an organic substance which can be heated and vaporized at a temperature lower than the thermal decomposition temperature can be used.

The vaporized organic substance is crystallized as fibrous carbon by being directly discharged onto a high-temperature substrate. The temperature at this time is preferably about 400 ° C. to 1500 ° C., and is appropriately selected depending on the type of the organic material as the starting material.

At this time, a catalyst may be used to promote crystal growth. As the catalyst, fine particles of iron, nickel, or a mixture thereof can be used. In addition, a metal called a graphitization catalyst or an oxide thereof also functions as a catalyst. These catalysts are appropriately selected depending on the kind of the organic substance as a starting material.

The outer diameter and length of the fibrous carbon can be appropriately selected depending on the preparation conditions.

For example, when a polymer is used as a raw material, an appropriate fiber diameter and length can be obtained depending on the inner diameter of a blowing nozzle for forming into a fiber shape and the blowing temperature.
In the case of the vapor phase growth method, an optimum fiber diameter can be obtained by appropriately selecting the size of a portion that becomes a nucleus of crystal growth such as a substrate and a catalyst. In addition, ethylene as a raw material,
The fiber diameter and linearity can be appropriately selected by regulating the supply amount of an organic substance such as propane.

The obtained fibrous carbon was further heated in an inert gas stream at a rate of 1 to 100 ° C./min.
The graphitization treatment may be performed under the conditions of 000 ° C. or more, preferably 2500 ° C. or more, and a holding time at the ultimate temperature of about 0 to 30 hours.

The obtained fibrous carbon may be pulverized in accordance with the thickness of the electrode, the particle size of the active material, and the like, and a single fiber obtained during spinning may be used. In addition, grinding is performed before and after carbonization and calcining, or during the heating process before graphitization.
Either may be performed.

In order to include such fibrous carbon in the negative electrode active material layer, when preparing the negative electrode mixture by mixing the negative electrode active material and the binder, the fibrous carbon is contained in the negative electrode mixture. What is necessary is just to add carbon.

The negative electrode active material layer preferably contains the above-mentioned fibrous carbon in the range of 0.2% by weight or more and 10% by weight or less based on the whole negative electrode active material layer. When the amount of the fibrous carbon is less than 0.2% by weight, when the negative electrode active material expanded at the time of charging contracts at the time of discharging, sufficient conductivity cannot be imparted and the cycle characteristics cannot be improved. . On the other hand, if the amount of fibrous carbon is more than 10% by weight, the amount of the negative electrode active material decreases accordingly, and the discharge capacity decreases.

Therefore, when the amount of fibrous carbon is in the range of 0.2% by weight or more and 10% by weight or less with respect to the entire negative electrode active material layer, charge / discharge is maintained while maintaining a high discharge capacity. Cycle characteristics can be improved.

On the other hand, the carbon black added to the negative electrode active material layer is not particularly limited, and various carbon blacks can be used.
Examples include those produced by an acetylene decomposition method, a contact method, a lamp / pine smoke method, a gas furnace method, and an oil furnace method. Specific examples of the carbon black produced by the above production method include, for example, acetylene black, Ketjen black, thermal black, furnace black and the like.

In order to include such carbon black in the negative electrode active material layer, when preparing the negative electrode mixture by mixing the negative electrode active material and the binder, the carbon black is contained in the negative electrode mixture. What is necessary is just to add.

The negative electrode active material layer preferably contains the above-mentioned carbon black in a range of 0.5% by weight or more and 10% by weight or less based on the whole negative electrode active material layer. If the amount of carbon black is less than 0.5% by weight, the contact state between the negative electrode active material and the carbon black is lost when the negative electrode active material expands, and when the negative electrode active material expanded during charging contracts during discharging, The conductivity cannot be sufficiently imparted, and the cycle characteristics cannot be improved.

The amount of carbon black is 10% by weight.
If the amount is too large, the amount of the negative electrode active material decreases accordingly, and the discharge capacity decreases. Further, the cycle characteristics are rather deteriorated. This is because the amount of carbon black is large, so that when the negative electrode active material expands, the carbon black follows and the conductivity is secured, but when the negative electrode active material contracts, the carbon black shrinks to the stage before the negative electrode active material expands. It is considered difficult. In the initial stage of repeating charge and discharge, the contact between the negative electrode active material and the carbon black is maintained, but when the negative electrode active material repeats expansion and contraction, the contact state between the negative electrode active material and the carbon black deteriorates. It is considered that it becomes difficult to impart conductivity to the negative electrode active material.

Therefore, by setting the amount of carbon black in the range of 0.2% by weight or more and 10% by weight or less with respect to the whole negative electrode active material layer, it is possible to maintain a high discharge capacity while maintaining a high discharge capacity. Cycle characteristics can be improved.

The negative electrode can 3 accommodates the negative electrode 2 and serves as an external negative electrode of the nonaqueous electrolyte battery 1.

The positive electrode 4 is formed by forming a positive electrode active material layer containing a positive electrode active material on a positive electrode current collector. As the positive electrode current collector, for example, an aluminum foil or the like is used.

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

Specifically, as the positive electrode active material, Ti
Lithium-free metal sulfides or oxides such as S ₂ , MoS ₂ , NbSe ₂ , V ₂ O ₅ , or Li _x MO ₂ (where M represents one or more transition metals, and x represents the charge of the battery. It depends on the state of discharge, and usually satisfies 0.05 ≦ x ≦ 1.10).

As the transition metal M constituting the lithium composite oxide, Co, Ni, Mn and the like are preferable. As a specific example of such a lithium composite oxide, LiCoO
₂ , LiNiO ₂ , Li _x Ni _y Co _1-y O ₂ (where x, y
Depends on the charge / discharge state of the battery, and usually 0 <x <1,
0.7 <y <1.02. A) Lithium manganese composite oxide having a spinel structure. These lithium composite oxides can generate high voltage,
It becomes a positive electrode active material excellent in energy density. A plurality of these positive electrode active materials may be mixed and used for the positive electrode.

In forming a positive electrode using the above-described positive electrode active material, a known conductive material, a binder and the like can be added.

The positive electrode can 5 accommodates the positive electrode 4 and serves as an external positive electrode of the nonaqueous electrolyte battery 1.

The separator 6 separates the positive electrode 4 and the negative electrode 2 from each other, and can be formed of a known material usually used as a separator of this type of nonaqueous electrolyte battery. A polymer film is used. Also, from the relationship between lithium ion conductivity and energy density, it is necessary that the thickness of the separator be as small as possible. Specifically, the thickness of the separator is suitably, for example, 50 μm or less.

The insulating gasket 7 is integrated into the negative electrode can 3. The insulating gasket 7 is for preventing the leakage of the nonaqueous electrolyte filled in the negative electrode can 3 and the positive electrode can 5.

As the non-aqueous electrolyte, a solution in which an electrolyte is dissolved in an aprotic non-aqueous solvent is used.

Any non-aqueous solvent can be used as long as it is used for this type of battery. For example, propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate,
1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolan, 4-
Methyl-1,3-dioxolan, diethyl ether, sulfolane, methylsulfolane, acetonitrile, propionitrile, anisole, acetate, butyrate, propionate and the like.

As the electrolyte, any electrolyte can be used as long as it is used for this type of battery.
For example, LiClO ₄ , LiAsF ₆ , LiPF
₆ , LiBF ₄ , LiB (C ₆ H ₅ ) ₄ , CH ₃ SO ₃ Li,
CF ₃ SO ₃ Li, LiCl, LiBr and the like can be mentioned.

In the nonaqueous electrolyte battery 1 of the present invention having the above-described structure, since the negative electrode active material layer contains fibrous carbon or carbon black, the conductive path in the negative electrode is formed stably. In addition, a change in the volume of the negative electrode due to doping and undoping of lithium is suppressed. As a result, the nonaqueous electrolyte battery 1 of the present invention has excellent cycle characteristics.

In the above-described embodiment, a non-aqueous electrolyte battery using a non-aqueous electrolyte has been described as an example. However, the present invention is not limited to this. Solid electrolyte battery using a solid electrolyte in which a non-aqueous solvent and an electrolyte salt are impregnated in an organic polymer or a gel using a gel electrolyte in which a matrix polymer is impregnated with a non-aqueous solvent and an electrolyte salt The present invention is also applicable to a solid electrolyte battery.

As the solid electrolyte, any of inorganic solid electrolyte and polymer solid electrolyte can be used as long as the material has lithium ion conductivity. Examples of the inorganic solid electrolyte include lithium nitride and lithium iodide. The polymer solid electrolyte is composed of an electrolyte salt and a polymer compound that dissolves the electrolyte salt. Examples of the polymer compound include an ether polymer such as poly (ethylene oxide) and its crosslinked product, and an ester polymer such as poly (methacrylate). A polymer, an acrylate-based polymer, or the like can be used alone, or 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 non-aqueous electrolyte and gel. Specific examples of the matrix polymer include poly (vinylidene fluoride)
And poly (vinylidene fluoride-co-hexafluoropropylene), such as fluorine-based polymers, ether-based polymers such as poly (ethylene oxide) and crosslinked products thereof, and poly (acrylonitrile). In particular, it is preferable to use a fluoropolymer from the viewpoint of oxidation-reduction stability. Ionic conductivity is imparted by including an electrolyte salt.

Further, in the above-described embodiment, the description has been given by taking the secondary battery as an example. However, the present invention is not limited to this, and can be applied to a primary battery. In addition, the battery of the present invention has a cylindrical shape, a square shape, a coin shape, a button shape, and the like, and its shape is not particularly limited,
In addition, various sizes such as a thin type and a large size can be used.

[0074]

EXAMPLES In order to confirm the effects of the present invention, a battery having the above-mentioned structure was manufactured and its characteristics were evaluated.

First, in Examples 1 to 5 and Comparative Example 1 described below, the effect when fibrous carbon was added to the negative electrode was examined.

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

Mg ₂ Si was pulverized to an average particle size of 15 μm. 54.9 parts by weight of this Mg ₂ Si powder, 0.1 part by weight of vapor-grown carbon fiber (manufactured by Showa Denko KK) as fibrous carbon, 35 parts by weight of artificial graphite, and polyfluoride as a binder 10 parts by weight of vinylidene chloride was mixed with a negative electrode mixture, and this was further dispersed in n-methylpyrrolidone to form a slurry.

Next, the obtained slurry was uniformly applied to both surfaces of a copper foil as a negative electrode current collector, dried, compression-molded by a roll press, and punched into a pellet having a diameter of 15.5 mm.

Next, a positive electrode was prepared as follows.

LiCoO ₂ as a positive electrode active material was obtained by mixing lithium carbonate and cobalt carbonate at a molar ratio of 0.5: 1 and calcining 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 material, and 3 parts by weight of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. This was further dispersed in N-methyl-2-pyrrolidone to form a slurry.

Next, the obtained slurry was uniformly applied to both sides of a 20 μm-thick aluminum foil serving as a positive electrode current collector, dried, and then compression-molded by a roll press to obtain a slurry having a diameter of 15 μm.
Punched into 5 mm pellets.

On the other hand, LiPF ₆ was added to a mixed solvent of ethylene carbonate and diethyl carbonate in an equal volume of 1.0.
A non-aqueous electrolyte was prepared by dissolving at a concentration of mol / l.

Then, the obtained negative electrode was accommodated in a negative electrode can,
The positive electrode is accommodated in a positive electrode can, and a thickness of 25 mm is provided between the negative electrode and the positive electrode.
A separator made of a μm polypropylene porous membrane was provided. A coin-type non-aqueous electrolyte battery having a diameter of 20 mm and a height of 2.5 mm is obtained by injecting a non-aqueous electrolyte into the negative electrode can and the positive electrode can and caulking and fixing the negative electrode can and the positive electrode can via an insulating gasket. Was completed.

Example 2 The negative electrode mixture was composed of 54.8 parts by weight of Mg ₂ Si powder, 0.2 part by weight of vapor grown carbon fiber (manufactured by Showa Denko KK) as fibrous carbon, and 35 parts by weight of graphite and 1 part of polyvinylidene fluoride as a binder
A coin-type non-aqueous electrolyte battery was produced in the same manner as in Example 1, except that the mixture was prepared by mixing 0 parts by weight.

Example 3 The negative electrode mixture was composed of 45 parts by weight of Mg ₂ Si powder, 10 parts by weight of vapor grown carbon fiber (manufactured by Showa Denko KK) as fibrous carbon, and 35 parts by weight of artificial graphite. And a coin-type nonaqueous electrolyte battery was produced in the same manner as in Example 1, except that the mixture was prepared by mixing 10 parts by weight of polyvinylidene fluoride as a binder.

Example 4 The negative electrode mixture was composed of 44 parts by weight of Mg ₂ Si powder, 11 parts by weight of vapor grown carbon fiber (manufactured by Showa Denko KK) as fibrous carbon, and 35 parts by weight of artificial graphite. And a coin-type nonaqueous electrolyte battery was produced in the same manner as in Example 1, except that the mixture was prepared by mixing 10 parts by weight of polyvinylidene fluoride as a binder.

Example 5 Mg ₂ S was used as a negative electrode active material.
Example 2 except that Si ₂ N ₂ O was used instead of i.
In the same manner as in the above, a coin-type nonaqueous electrolyte battery was produced.

Comparative Example 1 55 parts by weight of Mg ₂ Si powder and 3 parts of artificial graphite were added without adding fibrous carbon to the negative electrode mixture.
5 parts by weight and 10 parts by weight of polyvinylidene fluoride as a binder
A coin-type non-aqueous electrolyte battery was produced in the same manner as in Example 1 except that the mixture was prepared by mixing the same with the same weight part.

The cycle characteristics of each battery obtained as described above were evaluated.

First, each battery was subjected to constant current and constant voltage discharge at 20 ° C. and 1 mA up to an upper limit of 4.2 V.
Was discharged to a final voltage of 2.5 V. The above process was defined as one cycle, and this was repeated 100 cycles. Then, the discharge capacity retention rate (%) at the 100th cycle was determined, where the discharge capacity at the first cycle was 100.

Table 1 shows the measurement results of the discharge capacity retention ratio for the batteries of Examples 1 to 5 and Comparative Example 1.

[0093]

[Table 1]

As is clear from Table 1, the batteries of Examples 1 to 4 in which fibrous carbon was added to the negative electrode active material layer were compared with the batteries of Comparative Example 1 in which no fibrous carbon was added. In each case, the discharge capacity and the discharge capacity retention rate after 100 cycles are improved.

However, it cannot be said that the battery of Example 1 in which the amount of fibrous carbon was 0.1% by weight had a discharge capacity retention ratio satisfying the characteristics. This is presumably because the amount of the fibrous carbon added was small and the negative electrode active material expanded during charging contracted during discharging, so that sufficient conductivity could not be imparted. In addition, in the battery of Example 5 in which the amount of fibrous carbon added was 11% by weight, the discharge capacity retention ratio was high, but the initial discharge capacity was reduced.
This is considered to be because if the amount of the fibrous carbon added is too large, the amount of the negative electrode active material decreases accordingly, and the discharge capacity decreases.

On the other hand, in the battery of Example 2 in which the amount of fibrous carbon added was 0.2% by weight based on the whole negative electrode active material layer, the amount of fibrous carbon added was 0.2% by weight based on the whole negative electrode active material layer. In the battery of Example 3 with 10% by weight, the initial discharge capacity and 10%
Both of the discharge capacity retention rates after 0 cycles can be satisfied.

Therefore, by setting the amount of fibrous carbon in the range of 0.2% by weight or more and 10% by weight or less with respect to the entire negative electrode active material layer, charge and discharge can be performed while maintaining a high discharge capacity. Cycle characteristics can be improved.

Further, from the results of Example 5, it can be seen that the effect of the present invention can be obtained also in a battery using Si ₂ N ₂ O as a negative electrode active material instead of Mg ₂ Si.

Next, the following Embodiments 6 to 12 will be described.
In Comparative Example 2, the effect of adding carbon black to the negative electrode was examined.

Example 6 First, a negative electrode was manufactured as follows.

Mg ₂ Si was pulverized to an average particle size of 15 μm. A negative electrode mixture was prepared by mixing 54.6 parts by weight of this Mg ₂ Si powder, 0.4 parts by weight of acetylene black, 35 parts by weight of artificial graphite, and 10 parts by weight of polyvinylidene fluoride as a binder. This was further dispersed in n-methylpyrrolidone to form a slurry.

Next, the obtained slurry was uniformly applied to both surfaces of a copper foil as a negative electrode current collector, dried, compression-molded by a roll press, and punched into a pellet having a diameter of 15.5 mm.

Next, a positive electrode was produced as follows.

LiCoO ₂ as a positive electrode active material was obtained by mixing lithium carbonate and cobalt carbonate at a molar ratio of 0.5: 1 and firing 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 material, and 3 parts by weight of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. This was further dispersed in N-methyl-2-pyrrolidone to form a slurry.

Next, the obtained slurry was uniformly applied to both sides of a 20 μm-thick aluminum foil serving as a positive electrode current collector, dried, and then compression-molded by a roll press to obtain a slurry having a diameter of 15 μm.
Punched into 5 mm pellets.

On the other hand, LiPF ₆ was added to a mixed solvent of ethylene carbonate and diethyl carbonate in an equal volume of 1.0.
A non-aqueous electrolyte was prepared by dissolving at a concentration of mol / l.

Then, the obtained negative electrode was housed in a negative electrode can,
The positive electrode is accommodated in a positive electrode can, and a thickness of 25 mm is provided between the negative electrode and the positive electrode.
A separator made of a μm polypropylene porous membrane was provided. A coin-type non-aqueous electrolyte battery having a diameter of 20 mm and a height of 2.5 mm is obtained by injecting a non-aqueous electrolyte into the negative electrode can and the positive electrode can and caulking and fixing the negative electrode can and the positive electrode can via an insulating gasket. Was completed.

Example 7 A negative electrode mixture was composed of 54.5 parts by weight of Mg ₂ Si powder, 0.5 part by weight of acetylene black, 35 parts by weight of artificial graphite, and polyvinylidene fluoride as a binder. Was prepared in the same manner as in Example 6, except that it was mixed with 10 parts by weight of a nonaqueous electrolyte battery.

Example 8 The negative electrode mixture was composed of 54 parts by weight of Mg ₂ Si powder, 1 part by weight of acetylene black, 35 parts by weight of artificial graphite, and 10 parts by weight of polyvinylidene fluoride as a binder. A coin-type non-aqueous electrolyte battery was manufactured in the same manner as in Example 6, except that the mixture was prepared by mixing.

Example 9 The negative electrode mixture was composed of 47 parts by weight of Mg ₂ Si powder, 8 parts by weight of acetylene black, 35 parts by weight of artificial graphite, and 10 parts by weight of polyvinylidene fluoride as a binder. A coin-type non-aqueous electrolyte battery was manufactured in the same manner as in Example 6, except that the mixture was prepared by mixing.

Example 10 The negative electrode mixture was composed of 45 parts by weight of Mg ₂ Si powder, 10 parts by weight of acetylene black, 35 parts by weight of artificial graphite, and 10 parts by weight of polyvinylidene fluoride as a binder. A coin-type non-aqueous electrolyte battery was manufactured in the same manner as in Example 6, except that the mixture was prepared by mixing.

Example 11 The negative electrode mixture was composed of 44 parts by weight of Mg ₂ Si powder, 11 parts by weight of acetylene black, 35 parts by weight of artificial graphite, and 10 parts by weight of polyvinylidene fluoride as a binder. A coin-type non-aqueous electrolyte battery was manufactured in the same manner as in Example 6, except that the mixture was prepared by mixing.

Example 12 Mg ₂ was used as the negative electrode active material.
A coin-type nonaqueous electrolyte battery was manufactured in the same manner as in Example 7, except that Si ₂ N ₂ O was used instead of Si.

Comparative Example 2 Without adding acetylene black to the negative electrode mixture, 55 parts by weight of Mg ₂ Si powder, 35 parts by weight of artificial graphite, and 10 parts by weight of polyvinylidene fluoride as a binder were used. Was prepared in the same manner as in Example 6 except that the mixture was prepared by mixing the above.

The cycle characteristics of each of the batteries obtained as described above were evaluated by the same method as described above.

Table 2 shows the measurement results of the discharge capacity retention rates of the batteries of Examples 6 to 12 and Comparative Example 2.

[0118]

[Table 2]

As is clear from Table 2, in the batteries of Examples 6 to 11 in which carbon black was added to the negative electrode active material layer, Comparative Example 1 in which no carbon black was added was used.
It can be seen that the discharge capacity and the discharge capacity retention rate after 100 cycles are improved as compared to the batteries of No.

However, when the amount of carbon black added was 0.1%.
In the battery of Example 6 with 4% by weight, it cannot be said that the discharge capacity maintenance ratio satisfying the characteristics was obtained. This is because if the amount of carbon black is small, the contact state between the negative electrode active material and the carbon black is lost when the negative electrode active material expands,
When the negative electrode active material expanded during charging contracts during discharging,
This is probably because conductivity cannot be sufficiently imparted.

Further, in the battery of Example 11 in which the addition amount of carbon black was 11% by weight, both the discharge capacity retention ratio and the initial discharge capacity were reduced. This is because, because of the large amount of carbon black, the carbon black follows during the expansion of the negative electrode active material, ensuring conductivity.
This is probably because the carbon black hardly shrinks to the stage before the negative electrode active material expands when the negative electrode active material shrinks. That is, at the initial stage of repeating charge and discharge, the contact between the negative electrode active material and the carbon black is maintained,
It is considered that when the negative electrode active material repeats expansion and contraction, the contact state between the negative electrode active material and the carbon black deteriorates, and it becomes difficult to impart conductivity to the negative electrode active material.

On the other hand, in the batteries of Examples 7 to 10 in which the addition amount of carbon black was in the range of 0.5% by weight or more and 10% by weight or less based on the whole negative electrode active material layer, the initial discharge capacity and Both of the discharge capacity retention rates after 100 cycles can be satisfied.

Therefore, by setting the amount of carbon black in the range of 0.5% by weight or more and 10% by weight or less based on the whole negative electrode active material layer, the charge / discharge cycle can be maintained while maintaining a high discharge capacity. Characteristics can be improved.

Further, from the results of Example 12, it was found that Mg ₂ Si
It can be seen that the effect of the present invention can also be obtained for a battery using Si ₂ N ₂ O as the negative electrode active material instead of the above.

[0125]

According to the present invention, by including fibrous carbon or carbon black in the negative electrode active material layer, the conductive path in the negative electrode can be formed stably, and the volume change of the negative electrode due to doping and undoping of lithium. Thus, it is possible to realize a negative electrode in which the density is suppressed.

In the present invention, by using the above-described negative electrode, a non-aqueous electrolyte battery having excellent cycle characteristics can be realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a configuration example of a nonaqueous electrolyte battery according to the present invention.

[Explanation of symbols]

1 non-aqueous electrolyte battery, 2 negative electrode, 3 negative electrode can, 4
Positive electrode, 5 Positive electrode can, 6 Separator, 7 Insulating gasket

 ────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Atsushi Komaru 1-1-1 Shimosugishita, Takakura, Hiwada-cho, Koriyama-shi, Fukushima Prefecture Sony Energy Tech Co., Ltd. F term (reference) 5H003 AA04 BB02 BB04 BB05 BB15 BC02 BD04 5H014 AA02 EE05 EE07 HH01 HH04 5H029 AJ05 AK02 AK03 AK05 AL01 AL02 AL03 AL11 AM00 AM02 AM03 AM04 AM05 AM07 AM12 AM16 DJ08 DJ15 EJ04 HJ01 HJ19

Claims (14)

[Claims] 1. A negative electrode comprising a negative electrode active material layer containing a metal capable of forming an alloy with lithium or an alloy of the metal, and fibrous carbon or carbon black. 2. The negative electrode according to claim 1, wherein the negative electrode active material layer contains the fibrous carbon in a range of 0.2% by weight or more and 10% by weight or less. 3. The negative electrode according to claim 1, wherein the negative electrode active material layer contains the carbon black in a range of 0.5% by weight or more and 10% by weight or less. 4. A negative electrode comprising a negative electrode active material layer containing a Group 4B compound other than carbon, which contains one or more nonmetallic elements, and fibrous carbon or carbon black. 5. The negative electrode according to claim 4, wherein the negative electrode active material layer contains the fibrous carbon in a range of 0.2% by weight or more and 10% by weight or less. 6. The negative electrode according to claim 4, wherein the negative electrode active material layer contains the carbon black in a range of 0.5% by weight or more and 10% by weight or less. 7. The Group 4B compound other than carbon, including one or more non-metallic elements, electrochemically converts lithium to 400.
5. The negative electrode according to claim 4, wherein the negative electrode can be doped and de-doped at mAh / cm ³ or more. 8. A negative electrode comprising a positive electrode containing a lithium composite oxide, a metal capable of forming an alloy with lithium or an alloy of the metal, and a negative electrode active material layer containing fibrous carbon or carbon black; A nonaqueous electrolyte battery comprising a nonaqueous electrolyte interposed between a positive electrode and the negative electrode. 9. The nonaqueous electrolyte battery according to claim 8, wherein the negative electrode active material layer contains the fibrous carbon in a range of 0.2% by weight or more and 10% by weight or less. 10. The non-aqueous electrolyte battery according to claim 8, wherein the negative electrode active material layer contains the carbon black in a range of 0.5% by weight or more and 10% by weight or less. 11. A positive electrode containing a lithium composite oxide, and a negative electrode having a negative electrode active material layer containing a group 4B compound other than carbon and fibrous carbon or carbon black containing at least one nonmetallic element. A nonaqueous electrolyte battery comprising: a nonaqueous electrolyte interposed between the positive electrode and the negative electrode. 12. The nonaqueous electrolyte battery according to claim 11, wherein the negative electrode active material layer contains the fibrous carbon in a range of 0.2% by weight or more and 10% by weight or less. 13. The nonaqueous electrolyte battery according to claim 11, wherein the negative electrode active material layer contains the carbon black in a range of 0.5% by weight or more and 10% by weight or less. 14. The group 4B compound other than carbon, including one or more nonmetallic elements, electrochemically converts lithium to 40%.
12. The non-aqueous electrolyte battery according to claim 11, wherein the non-aqueous electrolyte battery can be doped / dedoped at 0 mAh / cm ³ or more.