JP2002203548A - Positive electrode active substance and nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery wherein decomposition reaction of nonaqueous electrolyte is suppressed and gas generation is being suppressed in an excessive charge and under high temperature environments exceeding 60 deg.C. SOLUTION: This battery has electrode 4 containing the positive electrode active substance wherein lithium complex oxide is the main body and the content of halide ion is not more than 10 ppm for the weight of the positive electrode active substance, a negative electrode 5 containing a negative electrode active substance, and the solid electrolyte 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a positive electrode active material mainly composed of a lithium composite oxide, a positive electrode containing the positive electrode active material, a negative electrode containing a lithium-doped / dedopable negative electrode active material, and A nonaqueous electrolyte battery including the nonaqueous electrolyte.

[0002]

2. Description of the Related Art There has been active research and development into thinning, miniaturization, and weight reduction of various electronic devices, and cordless and portable electronic devices such as cellular phones and portable personal computers have become widespread. ing.

Power supplies for driving these electronic devices include aqueous secondary batteries such as lead-acid batteries, nickel-cadmium batteries, nickel-metal hydride batteries, lithium metals, lithium alloys, and the like.
Alternatively, a nonaqueous electrolyte battery using a material capable of doping / dedoping lithium as a negative electrode active material and a lithium composite oxide as a positive electrode active material, that is, a so-called lithium battery is known.

In particular, lithium-based batteries have the advantages of high output, high energy density, and light weight as compared with conventional aqueous secondary batteries, and have high performance. It is expected as a battery having.

[0005]

SUMMARY OF THE INVENTION Lithium-based batteries include:
Lithium batteries utilizing lithium dissolution / precipitation, lithium ion batteries utilizing lithium ion doping / undoping, etc. are known. In any battery, a non-aqueous electrolyte is used depending on a use environment and a combination of members. Are decomposed, and a gas resulting from this decomposition reaction may be generated. For example, when a lithium-based battery is stored in a high-temperature environment exceeding 60 ° C. or is overcharged, the non-aqueous electrolyte is decomposed on the surface of the positive electrode active material, and gas is generated by the decomposition reaction. is there. The gas generation phenomenon in the lithium ion secondary battery is described by Ku
A detailed study has been made by mai et al. (Reference: Journal of Power Sources 81-82 (1999) 715-71).
9)).

Conventionally, in a lithium ion battery using a battery can as an exterior material, for example, Japanese Unexamined Patent Publication No.
As described in Japanese Patent No. 270011, as a safety measure at the time of overcharging, many methods have been proposed in which gas generation is promoted to operate a safety valve.

However, in the case of a lithium ion battery using a flexible laminate film as an exterior material, even if a small amount of gas is generated, the laminate film swells and the battery exterior shape is deformed. There is a problem.

[0008] Therefore, the present invention is not limited to overcharging or 60 ° C.
The object of the present invention is to provide a positive electrode active material in which the decomposition reaction of the non-aqueous electrolyte is suppressed even during storage in a high-temperature environment exceeding that, gas generation is suppressed, and a non-aqueous electrolyte battery using the same. It is a proposal.

[0009]

Means for Solving the Problems In order to achieve the above object, the present inventors have conducted intensive studies. As a result, when a positive electrode active material mainly composed of a lithium composite oxide is used, By controlling the content of halogen ions that can be mixed, the decomposition reaction of the non-aqueous electrolyte that proceeds on the surface of the positive electrode active material is suppressed during overcharge or storage in a high-temperature environment exceeding 60 ° C. It has been found that the generation is suppressed.

The cathode active material according to the present invention has been completed on the basis of the above findings, and is mainly composed of a lithium composite oxide, and has a halogen ion content of 10 ppm or less based on the weight of the cathode active material. There is a feature.

In general, the surface of a positive electrode active material mainly composed of a lithium composite oxide is extremely activated in a charged state. Therefore, on the surface of the charged positive electrode active material,
The decomposition reaction of the non-aqueous electrolyte easily proceeds. In particular, when a highly reactive halogen ion is mixed in the positive electrode active material to a certain degree or more, the decomposition reaction of the nonaqueous electrolyte is accelerated during overcharge or storage in a high-temperature environment exceeding 60 ° C. there is a possibility.

In the positive electrode active material according to the present invention, since the content of the halogen ions is limited to the above range, the decomposition reaction of the non-aqueous electrolyte by the halogen ions is remarkably suppressed. Therefore, according to the positive electrode active material according to the present invention,
Even during overcharge or storage in a high-temperature environment exceeding 60 ° C., a nonaqueous electrolyte battery in which the decomposition reaction of the nonaqueous electrolyte is suppressed and gas generation is suppressed is realized.

In order to achieve the above object, the present inventors have conducted intensive studies. As a result, when a positive electrode active material mainly composed of a lithium composite oxide is used in the positive electrode, the positive electrode active material is mixed in the positive electrode active material. It has been found that by controlling the content of halogen ions, the decomposition reaction of the nonaqueous electrolyte that proceeds on the surface of the positive electrode active material during charging is suppressed, and gas generation is suppressed.

The non-aqueous electrolyte battery according to the present invention has been completed based on the above findings, and is mainly composed of a lithium composite oxide and has a halogen ion content of 10 ppm or less based on the weight of the positive electrode active material. A positive electrode containing a positive electrode active material, a negative electrode containing a negative electrode active material, and a non-aqueous electrolyte.

In general, the surface of a positive electrode active material mainly composed of a lithium composite oxide is extremely activated in a charged state. Therefore, on the surface of the charged positive electrode active material,
The decomposition reaction of the non-aqueous electrolyte easily proceeds. In particular, when highly reactive halogen ions are mixed in the positive electrode active material,
During overcharge or storage in a high-temperature environment exceeding 60 ° C., the decomposition reaction of the non-aqueous electrolyte may be accelerated.

In the nonaqueous electrolyte battery according to the present invention, the content of halogen ions in the positive electrode active material contained in the positive electrode is limited to the above range, so that the decomposition reaction of the nonaqueous electrolyte by the halogen ions is remarkable. Is suppressed. Therefore, according to the non-aqueous electrolyte battery according to the present invention, even during overcharging or storage in a high temperature environment exceeding 60 ° C.,
The decomposition reaction of the non-aqueous electrolyte is suppressed, and gas generation is suppressed.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a positive electrode active material and a nonaqueous electrolyte battery according to the present invention will be described in detail with reference to the drawings.

The solid electrolyte battery 1 to which the present invention is applied is a non-aqueous electrolyte battery using a solid electrolyte as the non-aqueous electrolyte. In this solid electrolyte battery 1, as shown in FIG. 1, a laminate film 2 is used as an exterior material, and a battery element 3 is sealed in the laminate film 2.

FIG. 2 shows a cross section of the solid electrolyte battery 1 cut along the line AA 'shown in FIG. The battery element 3 included in the solid electrolyte battery 1 includes, as shown in FIG.
A positive electrode 4 containing a positive electrode active material and a negative electrode 5 containing a negative electrode active material are wound in the longitudinal direction via a solid electrolyte 6.

The laminate film 2 enclosing the battery element 3 is formed by laminating a plastic film on both sides or one side of a metal thin film. As the metal thin film, any material can be used as long as the material has good adhesiveness to the plastic film, and usually aluminum or the like is used. The plastic film is intended for sealing by heat fusion when enclosing the battery element 3, and any thermoplastic plastic material can be used.
Specifically, polyethylene, polypropylene, polyethylene terephthalate, or the like can be used as the plastic film.

As shown in FIG. 3, the cathode 4 has a cathode active material layer 12 formed on both sides of a cathode current collector 11 made of a metal foil such as an aluminum foil.
A positive terminal 13 is connected to one end of 1. Also,
On the positive electrode active material layer 12 of the positive electrode 4, a solid electrolyte 6a
Are formed.

The positive electrode active material layer 12 is made of a paste-like positive electrode mixture containing a positive electrode active material and a binder.
1 and dried.

The positive electrode active material is mainly composed of a lithium composite oxide, and has a halogen ion content of 10 ppm or less based on the weight of the positive electrode active material.

In general, lithium cobalt oxide (LiCoO)
The surface of the positive electrode active material mainly composed of a lithium composite oxide such as ₂ ) is very activated in a charged state. For this reason, the decomposition reaction of the nonaqueous electrolyte easily proceeds on the surface of the charged positive electrode active material. In particular, when highly reactive halogen ions are mixed in the positive electrode active material, overcharging or 6
During storage in a high-temperature environment exceeding 0 ° C., the decomposition reaction of the non-aqueous electrolyte may be accelerated.

For example, when a nonaqueous electrolyte containing propylene carbonate is used and chloride ions are excessively mixed as halogen ions in the positive electrode active material, the battery containing the nonaqueous electrolyte may be overcharged. When stored in a high-temperature environment exceeding 60 ° C., propylene carbonate is decomposed, and gases such as CO ₂ , C ₃ H ₈ , and C ₃ H ₇ Cl are generated.

When lithium hexafluorophosphate (LiPF ₆ ) is used as an electrolyte salt and chloride ions are excessively mixed as halogen ions in the positive electrode active material, a battery containing this nonaqueous electrolyte is used. Overcharging or 60 ℃
When stored in a high-temperature environment exceeding, lithium hexafluorophosphate undergoes a halogen exchange reaction with chloride ions and is decomposed, so that hydrofluoric acid is generated. Then, this hydrofluoric acid causes a decomposition reaction similar to the above-described decomposition reaction of propylene carbonate, and the above-mentioned gas is generated.

On the other hand, according to the positive electrode active material to which the present invention is applied, since the content of halogen ions is limited to 10 ppm or less, the solid electrolyte battery 1 can be overcharged,
Even when stored in a high-temperature environment exceeding 0 ° C., the decomposition reaction of the non-aqueous electrolyte is suppressed, and gas generation is suppressed.

When the content of the halogen ion exceeds 10 ppm based on the weight of the positive electrode active material, the decomposition reaction of the nonaqueous electrolyte cannot be suppressed, and a gas is generated by the decomposition reaction. Accordingly, in the solid electrolyte battery 1, by using a positive electrode active material mainly composed of a lithium composite oxide such as lithium cobalt oxide and having a halogen ion content of 10 ppm based on the weight of the positive electrode active material,
Even during overcharge or storage in a high temperature environment exceeding 60 ° C., the decomposition reaction of the nonaqueous electrolyte is suppressed, and gas generation is suppressed. The halogen ion content is more preferably 1 ppm based on the weight of the positive electrode active material.

Examples of the lithium composite oxide consisting mainly of the positive electrode active material, the general formula _{Li x M 1-y N y} O 2-z ( wherein, M represents, Co, represents Ni or Mn, N is, M And at least one element selected from the group consisting of transition metal elements or elements having an atomic number of 11 or more.
Represents a number within the range of 2 ≦ x ≦ 1.2, and y is 0 ≦ y ≦
Represents a number in the range of 0.5, and z represents a number in the range of 0 ≦ z ≦ 1.0. ), Specifically, a lithium composite oxide containing cobalt, nickel, manganese, niobium, or the like.

Among these lithium composite oxides, it is preferable to use lithium cobalt oxide as a main component of the positive electrode active material. In particular, the content of lithium cobaltate is preferably 90% or more. When the content of lithium cobaltate is 90% or more, the gas generation suppressing action is most effectively obtained.

Incidentally, lithium cobaltate is obtained by firing a mixture of tricobalt tetroxide and lithium carbonate. When producing this cobalt trioxide,
As a starting material, cobalt chloride, cobalt sulfate or the like is used.

When cobalt trichloride is produced using cobalt chloride as a starting material, and a mixture of this cobalt trioxide and lithium carbonate is fired to produce lithium cobalt oxide, halogen ions contained in cobalt chloride, specifically Specifically, chloride ions mainly remain in lithium carbonate, and as a result, chloride ions may be mixed as impurities in the final product lithium cobaltate.

Therefore, in the process of producing lithium cobalt oxide from cobalt chloride, the firing temperature and the firing atmosphere are controlled so that the content of chloride ions in the lithium cobalt oxide becomes 10 ppm or less. in this way,
If halogen ions are removed in the process of producing the positive electrode active material and the content of halogen ions in the finally obtained positive electrode active material is set to 10 ppm or less, the starting material containing halogen ions such as chloride ions can be used. Can be used even if there is.

When tricobalt tetroxide is produced using cobalt sulfate as a starting material and lithium cobaltate is produced from the tricobalt tetroxide, since cobalt sulfate does not contain halogen ions, it cannot be used as a final product. There is no possibility that halogen ions are mixed in a certain lithium cobalt oxide.

The cathode active material layer 12 is made of a material capable of inserting and extracting lithium ions or cations, such as a conjugated polymer such as polypyrrole or polyaniline, or vanadium pentoxide, as a cathode active material other than the lithium composite oxide. (V ₂ O ₅ ) and the like can be contained.

As the binder, a known resin material or the like which is usually used as a binder for the positive electrode active material layer in this type of solid electrolyte battery can be used.

As shown in FIG. 4, the negative electrode 5 has a negative electrode active material layer 22 formed on both sides of a negative electrode current collector 21 made of a metal foil such as a copper foil. Is connected to the negative electrode terminal 23. The negative electrode 5
On the negative electrode active material layer 22, a solid electrolyte 6b is formed.

The negative electrode active material layer 22 is made of a paste-like negative electrode mixture containing a negative electrode active material and a binder,
1 and dried.

As the negative electrode active material, a carbon material or a transition metal compound capable of doping / dedoping lithium ions can be used. In this case, the solid electrolyte battery 1
A lithium ion battery using lithium ion doping / dedoping is obtained.

The carbon material and the transition metal compound are not particularly limited as long as they can dope lithium ions. Examples of the carbon material include a PAN-based carbon material, a pitch-based carbon material, a vapor-grown carbon material, and a carbon fiber. In the case of natural graphite and transition metal compounds, complex chalcogenides can be used.

As the negative electrode active material, a lithium compound capable of inserting and extracting lithium, such as metallic lithium and a lithium alloy, can be used. In this case, the solid electrolyte battery 1 is a lithium battery utilizing the dissolution / precipitation of lithium. When these lithium compounds are used as the negative electrode active material, a simple substance of the lithium compound is used as the negative electrode.

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

As the solid electrolyte, any of a gel electrolyte obtained by swelling a polymer matrix with a non-aqueous electrolyte comprising an electrolyte salt and a lubricating solvent, an inorganic solid electrolyte, a polymer solid electrolyte and the like can be used.

As the electrolyte salt of the non-aqueous electrolyte, for example, L
iPF₆, LiBF₄, LiAsF ₆, LiCF₃SO
₃, LiN (CF₃SO₂)₂, LiC (CF₃S
O₂)₃, LiClO₄, LiF, LiBr, etc., alone
Alternatively, they can be used in combination. Among these electrolyte salts
Also especially LiPF₆It is preferred to use Electrolytes
LiPF as salt₆The use of charge and discharge characteristics and heat stability
The properties are better.

As the lubricating solvent for the non-aqueous electrolyte, a solvent that does not easily cause a decomposition reaction within the operating potential range of the solid electrolyte battery 1 is desirable. For example, propylene carbonate, ethylene carbonate, cyclic carbonates such as vinylene carbonate, cyclic esters such as γ-butyrolactone, dimethyl carbonate, chain carbonates such as ethyl methyl carbonate, chain ethers such as dimethoxyethane, chains such as methyl propionate. Esters, dimethyl sulfoxide, acetonitrile and derivatives thereof can be used.

Examples of the polymer matrix include polyethers such as polyethylene oxide and polypropylene oxide, halogen-containing polymer compounds such as polytetrafluoroethylene, polyvinylidene fluoride and polyvinylidene chloride, polymethacrylic acid and various esters thereof. And polymer compounds mainly composed of polyacrylamide, polycarbonate, polysulfone, polyethersulfone, and the like, derivatives, copolymers, and mixtures thereof.

Among these polymer matrices, it is preferable to use polyvinylidene fluoride as a main component.
It is preferable that poly (vinylidene fluoride-co-hexafluoropropylene) obtained by block copolymerization be used as a main component.

When a solid electrolyte layer containing poly (vinylidene fluoride-co-hexafluoropropylene) as a main component obtained by block copolymerization is formed, the composition ratio of hexafluoropropylene is preferably 7% by weight or less. . Also, when forming a gel electrolyte,
80% by weight of non-aqueous electrolyte comprising salt and solvent
It is preferable to make the above. If the composition ratio of hexafluoropropylene is 7% by weight or more, the crystallinity of the polymer is reduced, and the strength as a membrane is reduced, so that the function as a diaphragm may not be sufficiently exhibited, which is not preferable.

When the composition ratio of hexafluoropropylene is 7% by weight or less, the molecular weight of the polymer matrix is preferably from 300,000 to 3,000,000, more preferably from 550,000 to 1,000,000. Is more preferred. Further, it contains two components, a polymer matrix having a molecular weight of 300,000 to 550,000 and a polymer matrix having a molecular weight of 550,000 to 1,000,000, and the weight ratio thereof is 0:10 to
Most preferably, it is 7: 3.

When the molecular weight of the polymer matrix is less than 300,000, the positive electrode active material layer 12 and the negative electrode active material layer 22
There is a possibility that the adhesion strength of the solid electrolyte layer to be bonded thereon is low and insufficient.

The molecular weight of the polymer matrix is 5
Although it is considered better to be 50,000 or more, some of the esters, ethers, and carbonates used as the non-aqueous electrolyte component of the present invention have a polymer matrix having a molecular weight exceeding 1,000,000. Is not sufficiently compatible, and it may be difficult to prepare a suitable solution. Therefore, compatibility is improved by blending a polymer matrix having a molecular weight of 300,000 to 550,000.

The solid electrolyte battery 1 configured as described above
Thus, even when overcharged or stored in a high-temperature environment exceeding 60 ° C., the decomposition reaction of the nonaqueous electrolyte on the surface of the positive electrode active material is suppressed, and gas generation is suppressed. Therefore, the solid electrolyte battery 1 does not have a possibility of deforming the battery outer form due to gas generation, and can use the flexible laminated film 2 as the outer material, and has high reliability.

Next, another nonaqueous electrolyte battery to which the present invention is applied will be described. Note that the same members as those of the solid electrolyte battery 1 described above are denoted by the same reference numerals and description thereof will be omitted.

A nonaqueous electrolyte battery according to another embodiment to which the present invention is applied is a nonaqueous electrolyte battery using a nonaqueous electrolyte as a nonaqueous electrolyte. In this non-aqueous electrolyte battery 31,
As shown in FIG.
The battery element 32 is sealed in the laminated film 2.

FIG. 6 shows a cross section of the nonaqueous electrolyte battery 31 cut along the line BB 'shown in FIG. The battery element 32 includes a belt-shaped positive electrode 4 containing a positive electrode active material.
And a strip-shaped negative electrode 5 containing a negative electrode active material are wound in the longitudinal direction with a separator 33 interposed therebetween. The battery element 32 is impregnated with a non-aqueous electrolyte. That is, the positive electrode active material layer 12, the negative electrode active material layer 22, and the separator 33 are impregnated with the non-aqueous electrolyte.

The separator 33 is a polymer microporous film usually used in this type of non-aqueous electrolyte battery. The separator 33 is impregnated with the electrolyte and can form a partition wall between the positive electrode 4 and the negative electrode 5. Any material can be used.
Specifically, a film formed of a high molecular compound mainly composed of polyethylene, polypropylene, polyacrylonitrile, polytetrafluoroethylene, polyamide or the like or a derivative thereof can be used.

As the non-aqueous electrolyte, a non-aqueous electrolyte obtained by dissolving an electrolyte salt in a lubricating solvent in the solid electrolyte battery 1 described above can be used similarly.

In the nonaqueous electrolyte battery 31 to which the present invention is applied as configured above, the positive electrode whose main component is a lithium composite oxide and whose halogen ion content is 10 ppm or less with respect to the weight of the positive electrode active material. Since the positive electrode 4 containing the active material is provided, the same effects as those of the solid electrolyte battery 1 described above can be obtained. That is, in the non-aqueous electrolyte battery 31, the decomposition reaction of the non-aqueous electrolyte is suppressed even during overcharge or storage in a high-temperature environment exceeding 60 ° C., and gas generation is suppressed. In addition, the nonaqueous electrolyte battery 31 has high reliability because there is no possibility that the battery outer form is deformed due to gas generation, and the flexible laminated film 2 can be used as the outer material. .

In the above-described solid electrolyte battery 1 and non-aqueous electrolyte battery 31, the case where the laminate film 2 is used as the exterior material has been described. However, the present invention is not limited to this. It is also applicable when using a can or the like as an exterior material.

[0060]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail based on specific experimental results.

Example 1 [Preparation of Positive Electrode] First, a positive electrode active material was prepared as follows.

[0063] Tricobalt tetroxide is produced using cobalt sulfate as a starting material, and a mixture of this and lithium carbonate is calcined to give a lithium cobaltate component ratio of 99%.
The positive electrode active material A described above was obtained.

When the content of halogen ions contained in the positive electrode active material A was measured by chromatography using water extraction, it was confirmed that this content was not more than the detection limit of 0.01 ppm or less.

Next, 91 parts by weight of the positive electrode active material A and 6 parts by weight of graphite as a conductive material were used as components of the positive electrode mixture.
10 parts by weight of poly (vinylidene fluoride-co-hexafluoropropylene) was weighed as a binder. Next, these components were dispersed in N-methyl-2-pyrrolidone to prepare a slurry-like positive electrode mixture.

Next, the positive electrode mixture was uniformly applied to both surfaces of a positive electrode current collector having a thickness of 20 μm and made of aluminum foil to form a positive electrode active material layer. Then, after drying the positive electrode active material layer in a wet state, a positive electrode sheet was prepared by pressing with a roll press machine, and the positive electrode sheet was cut out to obtain a strip-shaped positive electrode having a length of 50 mm and a width of 280 mm. The positive electrode active material area density per unit area of the positive electrode was 40 mg / cm ² .

At one end of the positive electrode, a positive electrode active material layer having a length of 50 mm and a width of 5 mm was cut off from above the positive electrode current collector to form a lead weld. Then, a lead made of aluminum was welded to the lead welded portion to form a positive electrode terminal.

[Preparation of Negative Electrode] First, 90 parts by weight of graphite powder as a negative electrode active material and 10 parts by weight of poly (vinylidene fluoride-co-hexafluoropropylene) as a binder were used as components of a negative electrode mixture. Was weighed. Next, these components were dispersed in N-methyl-2-pyrrolidone to prepare a slurry-like negative electrode mixture.

Next, the negative electrode mixture was uniformly applied to both surfaces of a negative electrode current collector having a thickness of 10 μm and made of copper foil to form a negative electrode active material layer. Then, after drying the negative electrode active material layer in a wet state, a negative electrode sheet is produced by pressing with a roll press machine, and this negative electrode sheet is cut out and vertically cut.
A strip-shaped negative electrode having a width of 2 mm and a width of 300 mm was used.

At one end of the negative electrode, a negative electrode active material layer having a length of 52 mm and a width of 5 mm was cut off from above the negative electrode current collector to form a lead weld. Then, a lead made of nickel was welded to the lead welded portion to form a negative electrode terminal.

[Preparation of Nonaqueous Electrolyte] First, as a nonaqueous solvent, 35 parts by weight of ethylene carbonate and 35 parts by weight of propylene carbonate were used.
15 parts by weight of γ-butyrolactone and 15 parts by weight of LiPF ₆ as an electrolyte salt were mixed in the mixed non-aqueous solvent to prepare a non-aqueous electrolyte.

[Preparation of Nonaqueous Electrolyte Battery] Next, the positive electrode and the negative electrode obtained as described above were laminated via a polypropylene porous film having a thickness of 25 μm as a separator, and wound in the longitudinal direction. A winding type battery element having dimensions of 5 cm in length, 4 cm in width, and 0.4 cm in height was obtained.

Next, the battery element was housed in a bag-like laminate film, and 3 cc of a non-aqueous electrolyte was injected into the laminate film, and the battery element was impregnated with the non-aqueous electrolyte in vacuum. Then, the battery element was sealed in the laminate film by closing the opening of the bag-like laminate film under reduced pressure. In closing, the degree of decompression was 10 mmHg, the decompression time was 30 sec, the sealing temperature was 200 ° C., and the sealing time was 5 sec. Also, as the laminated film, polypropylene, aluminum,
A three-layer laminated film obtained by laminating nylon in this order was used.

As described above, a non-aqueous electrolyte battery was manufactured. Note that the positive electrode terminal and the negative electrode terminal are led out of the laminate film.

Example 2 First, a positive electrode and a negative electrode were produced in the same manner as in Example 1.

Next, an electrolyte solution was prepared as described below.

As the components of the plasticizer constituting the gel electrolyte, 35 parts by weight of ethylene carbonate, 35 parts by weight of propylene carbonate, 15 parts by weight of γ-butyrolactone, and 15 parts by weight of LiPF ₆ as an electrolyte salt were used as lubricating solvents. After weighing, these components were mixed to prepare a plasticizer. Next, 30 parts by weight of the above plasticizer, 10 parts by weight of poly (vinylidene fluoride-co-hexafluoropropylene) as a polymer matrix, and 60 parts by weight of diethyl carbonate were mixed and dissolved to prepare an electrolyte solution. .

The electrolyte solution thus prepared is
The solution was applied and impregnated on the positive electrode active material layer and the negative electrode active material layer, and allowed to stand at room temperature for 8 hours to vaporize and remove diethyl carbonate. Thus, a gel electrolyte layer having a thickness of 30 μm was formed on the positive electrode active material and the negative electrode active material.

Next, a strip-shaped positive electrode and a strip-shaped negative electrode provided with a gel electrolyte layer are laminated and wound in the longitudinal direction, and the winding type battery element having an outer dimension of 5 cm in length, 4 cm in width, and 0.4 cm in height. I got

Next, this battery element was sandwiched between laminated films used as exterior materials. Then, the outer peripheral edge of the laminate film was sealed by heat sealing under reduced pressure, and the battery element was sealed in the laminate film by performing a reduced pressure pack (10 mmHg, 30 sec). As the laminate film, a laminate film having a three-layer structure in which polypropylene, aluminum, and nylon were laminated in this order was used.

As described above, a gel electrolyte battery was manufactured. Note that the positive electrode terminal and the negative electrode terminal are led out of the laminate film.

Example 3 When preparing a positive electrode active material, tricobalt tetroxide was produced using cobalt chloride as a starting material, and a mixture of this and lithium carbonate was fired, so that the lithium cobalt oxide component ratio was 99%. % Of the positive electrode active material B was obtained. When the content of the halogen ions contained in the positive electrode active material B was measured by chromatography using water extraction, the content was 55 ppm.

Therefore, 1 g of the positive electrode active material B is
Washing with stirring was performed for 1 hour with 00 volumes of pure water. The content of halogen ions contained in the positive electrode active material B after stirring and washing (hereinafter, referred to as positive electrode active material B ′) was measured by chromatography with water extraction, and the content was 7 ppm. Next, the positive electrode active material B ′ is
It was heated and vacuum dried for 15 hours under an environment of 200 ° C. and less than 1 mmHg.

The procedure of Example 2 was repeated, except that the dried positive electrode active material B ′ was used in place of the positive electrode active material A.
A gel electrolyte battery was manufactured.

COMPARATIVE EXAMPLE 1 In preparing a positive electrode active material, cobalt chloride and cobalt sulfate were mixed at a weight ratio of 1: 1 as starting materials, and tricobalt tetroxide was produced using this mixture. By firing the mixture with lithium carbonate, a positive electrode active material C having a lithium cobaltate component ratio of 99% or more was obtained.
When the content of the halogen ions contained in the positive electrode active material C was measured by chromatography using water extraction, the content was 24 ppm.

A gel electrolyte battery was manufactured in the same manner as in Example 2 except that the positive electrode active material C was used instead of the positive electrode active material A.

Comparative Example 2 For 100 g of the positive electrode active material A prepared in Example 1,
After adding 50 cc of a 10% aqueous potassium chloride solution and mixing well, the mixture was heated and vacuum-dried under an environment of less than 1 mmHg and 200 ° C. for 15 hours to prepare a positive electrode active material D to which a halide was added. The content of the halogen ions contained in the positive electrode active material D was measured by chromatography using water extraction, and the content was 51 ppm.

A gel electrolyte battery was manufactured in the same manner as in Example 2 except that the positive electrode active material D was used instead of the positive electrode active material A.

Comparative Example 3 The same procedure as in Example 2 was carried out except that the positive electrode active material B ′ which had not been washed with stirring, that is, the positive electrode active material B having a halogen ion content of 55 ppm was used in place of the positive electrode active material A. Thus, a gel electrolyte battery was produced.

Comparative Example 4 For 100 g of the positive electrode active material A prepared in Example 1,
After adding 50 cc of a 10% aqueous potassium bromide solution and mixing well, the mixture was dried under heating at 200 ° C. under an environment of less than 1 mmHg for 15 hours to prepare a positive electrode active material E to which a halide was added. When the content of the halogen ions contained in the positive electrode active material E was measured by chromatography using water extraction, the content was 50 ppm.

A gel electrolyte battery was manufactured in the same manner as in Example 2 except that the positive electrode active material E was used instead of the positive electrode active material A.

The batteries of Examples 1 to 3 and Comparative Examples 1 to 4 manufactured as described above were subjected to the following battery evaluation tests to evaluate the battery characteristics.

<Battery Evaluation Test 1> First, 1
100 mA constant current / 4.2 V constant voltage charging
A, the discharge capacity at 3 V cut was measured. Next, as a high-temperature storage test, a battery fully charged at a constant current of 100 mA / a constant voltage of 4.2 V was stored for 6 hours in a temperature environment of 90 ° C., and then stored for 6 hours in a temperature environment of 25 ° C. A heat cycle test was performed with this storage as one cycle,
The thickness of the battery was measured, and the gas generation status was observed.

FIG. 7 shows the above measurement results. FIG.
In the graph, the horizontal axis indicates the number of cycles (unit: times) of the heat cycle test, and the vertical axis indicates the thickness (unit: cm) of the battery.

FIG. 7 shows that in the batteries of Examples 1 to 3, the thickness of the batteries did not change much after the heat cycle test. On the other hand, in the batteries of Comparative Examples 1 to 4, the heat cycle test shows that the thickness of the batteries was significantly expanded.

Therefore, by using a positive electrode active material mainly composed of a lithium composite oxide and having a halogen ion content of 10 ppm or less, gas generation can be largely suppressed even when stored under a high temperature environment. confirmed.

<Battery Evaluation Test 2> First, 1
100 mA constant current / 4.2 V constant voltage charging
A, the discharge capacity at 3 V cut was measured. After that, as a high-temperature continuous charge test, the battery was stored in a 60 ° C. constant temperature bath, continuously charged at a constant voltage of 4.2 V, the thickness of the battery was measured over time, and the gas generation status of each sample was observed. did.

FIG. 8 shows the above measurement results. FIG.
In the graph, the horizontal axis indicates time (unit: minute), and the vertical axis indicates battery thickness (unit: cm).

FIG. 8 shows that in the batteries of Examples 1 to 3, the thickness of the batteries did not change much even after the high-temperature continuous charging test. On the other hand, in the batteries of Comparative Examples 1 to 4, it can be seen that the thickness of the batteries was greatly expanded by the high-temperature continuous charging test.

Therefore, by using a positive electrode active material mainly composed of a lithium composite oxide and having a halogen ion content of 10 ppm or less with respect to the weight of the positive electrode active material, charge and discharge can be repeated under a high temperature environment. It was confirmed that gas generation was significantly suppressed.

From the above battery evaluation tests, it was found that the nonaqueous electrolyte battery uses a positive electrode active material mainly composed of a lithium composite oxide and having a halogen ion content of 10 ppm or less based on the weight of the positive electrode active material. Overcharge or 60 ℃
It was found that the decomposition reaction of the non-aqueous electrolyte was suppressed and the generation of gas was suppressed even during storage in a high-temperature environment exceeding the above.

[0101]

As is clear from the above description, the positive electrode active material according to the present invention is mainly composed of a lithium composite oxide and has a halogen ion content of 10 ppm or less. In this case, the decomposition reaction of the non-aqueous electrolyte by the halogen ions is significantly suppressed. Therefore, according to the positive electrode active material of the present invention, the nonaqueous electrolyte battery in which the decomposition reaction of the nonaqueous electrolyte is suppressed even during overcharge or storage in a high temperature environment exceeding 60 ° C., and gas generation is suppressed. Can be realized.

In the non-aqueous electrolyte battery according to the present invention, since the above-described positive electrode active material is used, the decomposition reaction of the non-aqueous electrolyte by halogen ions during charging is significantly suppressed. Therefore, in the nonaqueous electrolyte battery according to the present invention, the decomposition reaction of the nonaqueous electrolyte is suppressed even during overcharge or storage in a high-temperature environment exceeding 60 ° C., and gas generation is suppressed. Further, in the nonaqueous electrolyte battery according to the present invention, since there is no possibility that the battery exterior form is deformed, a flexible laminated film can be used as the exterior material.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration example of a solid electrolyte battery to which the present invention is applied.

FIG. 2 is a cross-sectional view of the solid electrolyte battery taken along line AA ′ shown in FIG.

FIG. 3 is a schematic diagram showing one configuration example of a positive electrode.

FIG. 4 is a schematic diagram illustrating a configuration example of a negative electrode.

FIG. 5 is a schematic diagram showing a configuration example of a nonaqueous electrolyte battery to which the present invention is applied.

FIG. 6 is a cross-sectional view of the nonaqueous electrolyte battery taken along line BB ′ shown in FIG.

FIG. 7 is a characteristic diagram showing a measurement result of a battery evaluation test 1.

FIG. 8 is a characteristic diagram showing measurement results of a battery evaluation test 2.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Solid electrolyte battery, 2 Laminated film, 3 Battery element, 4 Positive electrode, 5 Negative electrode, 6, 6a, 6b Solid electrolyte, 31 Non-aqueous electrolyte battery, 32 Battery element, 33 Separator

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yusuke Suzuki 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Tomoyuki Nakamura 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation F term (reference) 5H029 AJ02 AJ04 AK03 AL07 AM00 AM03 AM05 AM07 BJ04 DJ08 EJ03 HJ01 HJ02 5H050 AA03 AA10 BA17 CA08 CA09 CB08 DA09 EA11 EA24 FA05 HA01 HA02

Claims (13)

[Claims] 1. A lithium composite oxide as a main component, wherein the content of halogen ions is 10 pp with respect to the weight of the positive electrode active material.
m or less. 2. The positive electrode active material according to claim 1, wherein the halogen ion is a chloride ion. 3. The lithium composite oxide has a general formula Li
_{x M 1-y N y O} 2- z ( wherein, M represents, Co, represents Ni or Mn, N is selected from the group consisting of transition metal elements or atomic number 11 or more elements different from M 1 Represents at least one kind of element, x represents a number in the range of 0.2 ≦ x ≦ 1.2, y represents a number in the range of 0 ≦ y ≦ 0.5,
z represents a number in the range of 0 ≦ z ≦ 1.0. The positive electrode active material according to claim 1, wherein the compound is represented by the following formula: 4. The general formula Li _x M _1-y N _y O _2-z
Compound represented by the positive electrode active material according to claim 3, characterized in that the LiCoO _2. 5. The positive electrode active material according to claim 4, wherein the content of LiCoO ₂ is 90% or more. 6. A lithium composite oxide as a main component, wherein the content of halogen ions is 10 pp with respect to the weight of the positive electrode active material.
A non-aqueous electrolyte battery comprising: a positive electrode containing a positive electrode active material of not more than m; a negative electrode containing a negative electrode active material; and a non-aqueous electrolyte. 7. The non-aqueous electrolyte battery according to claim 6, wherein the halogen ion is a chloride ion. 8. The lithium composite oxide of the general formula Li
_{x M 1-y N y O} 2- z ( wherein, M represents, Co, represents Ni or Mn, N is selected from the group consisting of transition metal elements or atomic number 11 or more elements different from M 1 X represents a number in the range of 0.2 ≦ x ≦ 1.2, y represents a number in the range of 0 ≦ y ≦ 0.5,
z represents a number in the range of 0 ≦ z ≦ 1.0. 7. The non-aqueous electrolyte battery according to claim 6, which is a compound represented by the formula: 9. The compound represented by the general formula Li _x M _1-y N _y O _2-z
Compound represented by the non-aqueous electrolyte battery according to claim 8, wherein it is LiCoO _2. 10. The content of LiCoO ₂ is 90%.
The non-aqueous electrolyte battery according to claim 9, wherein: 11. The non-aqueous electrolyte battery according to claim 6, wherein the non-aqueous electrolyte is a non-aqueous electrolyte. 12. The non-aqueous electrolyte battery according to claim 6, wherein the non-aqueous electrolyte is a solid electrolyte. 13. The non-aqueous electrolyte battery according to claim 6, wherein a laminate film is used as the exterior material.