JP2006054167A - Non-aqueous electrolyte secondary battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a non-aqueous electrolyte secondary battery that has a high reliability in which occurrence of a gas inside the battery is reduced even after it is stored in a charged state under high temperatures, battery characteristic is well maintained after the storage while suppressing effect of temperature elevation is maintained, and furthermore a recycling characteristic is superior. <P>SOLUTION: This has an electrodes group, a non-aqueous electrolyte, and an outer package that houses the electrodes group and the non-aqueous electrolyte, while the electrodes group has anodes, cathodes, and separators that are interposed between the anodes and the cathodes, in which a prescribed bromine compound having an aromatic ring is made to be contained in the non-aqueous electrolyte, in order to provide the non-aqueous electrolyte secondary battery of high reliability which has a superior safety. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to a highly reliable non-aqueous electrolyte secondary battery excellent in safety and including a predetermined bromine compound having an aromatic ring in a non-aqueous electrolyte.

  A non-aqueous electrolyte secondary battery typified by a lithium ion secondary battery has a feature that it has a high energy density and can be reduced in size and weight. A nonaqueous electrolyte secondary battery generally has the following structure.

  The nonaqueous electrolyte secondary battery has an electrode group, a nonaqueous electrolyte, and an outer package that houses the electrode group and the nonaqueous electrolyte. The electrode group includes a positive electrode, a negative electrode, and a separator (insulating layer) interposed between the positive electrode and the negative electrode. In many cases, the positive electrode and the negative electrode are spirally wound via a separator.

The positive electrode includes a positive electrode current collector and a positive electrode mixture layer supported thereon, and the negative electrode includes a negative electrode current collector and a negative electrode mixture layer supported thereon. The positive electrode mixture contains a positive electrode active material. As the positive electrode active material, a composite metal oxide is mainly used, and in particular, a lithium-containing transition metal oxide such as lithium cobaltate (LiCoO ₂ ) is used. The negative electrode mixture contains a negative electrode active material. As the negative electrode active material, a material capable of occluding and releasing lithium ions, for example, a carbon material such as graphite is used.

  As the separator, a microporous film mainly made of a polyolefin resin such as polyethylene or polypropylene is used. A polymer film containing polyethylene oxide, polyvinylidene fluoride, polyacrylate or the like is also used as a separator.

As the nonaqueous electrolyte, a nonaqueous solvent in which a solute is dissolved, a gel electrolyte, or the like is used. The gel electrolyte is obtained by holding a nonaqueous solvent in which a solute is dissolved in a polymer matrix (network structure). For example, a lithium salt such as lithium hexafluorophosphate (LiPF ₆ ) is used as the solute. There are a wide variety of non-aqueous solvents, and for example, those containing carbonates such as ethylene carbonate and dimethyl carbonate are used.

  Since the nonaqueous electrolyte is flammable, it is necessary to ensure safety. Therefore, for example, a high-capacity lithium ion secondary battery is generally provided with a protection circuit for preventing overcharge and overdischarge.

  The nonaqueous electrolyte secondary battery can be charged to a high voltage and can increase the energy density. However, since it has a high voltage and a high energy density, oxidative decomposition of the nonaqueous electrolyte tends to occur on the positive electrode side. Moreover, since the negative electrode side has an electrochemically very low potential, reductive decomposition of the nonaqueous electrolyte is likely to occur. These decomposition reactions are more likely to occur at higher temperatures, and a large amount of gas is generated while the battery is stored at a high temperature of 60 to 85 ° C.

  The nonaqueous electrolyte secondary battery is used as a power source for driving electronic devices such as notebook computers. The temperature inside the notebook computer is usually 45 to 60 ° C. Under such temperature conditions, the battery is charged at a constant voltage of 4.2 V and may be maintained in a charged state for a long time. When a charged battery is stored at a high temperature, gas generation is likely to occur inside the battery as compared with a case where an open circuit battery is stored at a high temperature. When the pressure inside the battery rises due to gas generation during high-temperature storage, the protection circuit is activated, the current is cut off, and the function of the battery may be lost.

  In order to improve battery characteristics during high-temperature storage, a battery in which a bromine compound is contained in the positive electrode has been proposed (Patent Document 1). In addition, a bromine compound having an aromatic ring, which is a flame retardant material, is included in the electrode in order to suppress the heat generation of the electrode from accelerating the temperature rise when the battery temperature rises to a high temperature, such as in an overcharge test. It is proposed to include. For example, a battery in which a bromine compound is included in an electrode has been proposed (Patent Document 2). In addition, a battery in which a non-aqueous electrolyte is mixed with a flame retardant such as hexabromobenzene that is liquid at room temperature has been proposed (Patent Document 3).

By including a flame retardant material in the electrode, it is possible to suppress the acceleration of the temperature rise of the battery, and by mixing hexabromobenzene or the like with a non-aqueous electrolyte, an improvement in safety can be obtained. it can.
JP-A-6-231753 Japanese Patent Laid-Open No. 10-172615 Japanese Patent No. 3305035

  However, when the flame retardant material is included in the electrode, there is a problem that the flame retardant material acts as a resistance component and the electrode plate resistance is remarkably increased. In addition, flame retardant materials are thought to form a film that suppresses gas generation on the electrode, but when the flame retardant material is included in the electrode, it is difficult to efficiently generate the film, and gas generation is suppressed. May not be effective. Furthermore, when the bromine compound which is an insulator is contained in the electrode, there is a problem that it becomes an inhibition factor of diffusion of electrons and ions, that is, a charge transfer reaction, and the cycle characteristics are deteriorated. Further, even if hexabromobenzene or the like is mixed with the nonaqueous electrolyte, a good quality film cannot be formed on the electrode.

  The present invention maintains the effect of suppressing the temperature rise of the battery, generates little gas inside the battery even when stored at a high temperature in a charged state, has good battery characteristics after storage, and cycle characteristics Another object of the present invention is to provide a highly reliable non-aqueous electrolyte secondary battery.

  That is, the present invention has an electrode group, a nonaqueous electrolyte, and an exterior body that accommodates the electrode group and the nonaqueous electrolyte, and the electrode group includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The non-aqueous electrolyte contains a bromine compound having an aromatic ring, and the bromine compound has the formula (1):

(Wherein, X _{1 to} X ₁₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom), formula (2):

(Wherein, X _{11 to} X ₂₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom), formula (3):

(In the formula, X _{21 to} X ₃₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 1 to 4), Formula (4):

(Wherein X _{31 to} X ₃₄ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom), formula (5):

(Wherein X _{35 to} X ₃₈ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. R ₁ and R ₂ each independently contains a carbon atom, A group containing at least one selected from the group consisting of an atom and an oxygen atom, and the number of carbon atoms is 1 to 6.), Formula (6)

(In the formula, X _{39 to} X ₄₆ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 0 to 4), Formula (7)

(In the formula, X _{47 to} X ₅₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. R ₃ and R ₄ each independently include a carbon atom and a hydrogen atom. And a group containing at least one selected from the group consisting of a bromine atom and an oxygen atom, and the number of carbon atoms is 1 to 6.), Formula (8):

(Wherein, X _{51 to} X ₅₆ are each independently a bromine atom or a hydrogen atom, at least one is a bromine atom. N is 2 to 10), Formula (9):

(Wherein, X _{57 to} X ₆₀ are each independently a bromine atom or a hydrogen atom, at least one is a bromine atom. N is 1 to 100), formula (10):

(Wherein, X _{61 to} X ₆₅ are each independently a bromine atom or a hydrogen atom, at least one is a bromine atom. N is 10 to 30), Formula (11):

(Wherein, X _{66 to} X ₇₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 100 to 200), Formula (12):

(. Wherein, X ₇₁ to X ₇₅ each independently represents a bromine atom or a hydrogen atom, at least one is bromine atom .n is 200-600), formula (13):

(Wherein, x, y and z represent the number of bromine atoms bonded to the aromatic ring, respectively, the sum of x, y and z is 1 to 6 and n is 1 to 5), (14):

(Wherein x represents the number of bromine atoms bonded to the aromatic ring and x is 1 to 5), formula (15):

(Wherein x represents the number of bromine atoms bonded to the aromatic ring and x is 1 to 5), formula (16):

(Wherein x represents the number of bromine atoms bonded to the aromatic ring, x is 1 to 5) and formula (17):

(Wherein x, y and z each represent the number of bromine atoms bonded to the aromatic ring, and x, y and z are each 1 to 5) The present invention relates to a secondary battery.

  The amount of bromine atoms contained in the bromine compound having an aromatic ring with respect to the nonaqueous electrolytic mass (that is, the amount of bromine atoms contained in the bromine compound having an aromatic ring added to the nonaqueous electrolyte at the time of manufacturing the battery) is 0. It is preferable that it is 003-0.1 mol / L, and it is still more preferable that it is 0.003-0.05 mol / L.

  By including a bromine compound having an aromatic ring as described above in the non-aqueous electrolyte, the effect of suppressing the temperature rise of the battery is obtained, and when the charged battery is stored at a high temperature, the gas generation is suppressed. be able to. Further, the battery characteristics after storage are also good, and the cycle characteristics are also good. Therefore, according to the present invention, a highly reliable non-aqueous electrolyte secondary battery excellent in safety can be provided.

  Examples of the non-aqueous electrolyte secondary battery of the present invention include a lithium ion secondary battery, a polymer secondary battery using a gel electrolyte, a magnesium secondary battery, an aluminum secondary battery, and a sodium secondary battery. There are no particular limitations on the shape or package of the nonaqueous electrolyte secondary battery.

The non-aqueous electrolyte secondary battery of the present invention has an electrode group, a non-aqueous electrolyte, and an exterior body that houses the electrode group and the non-aqueous electrolyte.
The electrode group includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The electrode group includes a columnar electrode group in which a positive electrode and a negative electrode are wound through a separator, and an electrode group in which a plurality of positive electrodes and negative electrodes are stacked in a stack through a separator, respectively.

The non-aqueous electrolyte includes a non-aqueous solvent in which a solute is dissolved. As the solute, an alkali metal salt is preferably used. For example, a fluorine-containing inorganic anion salt or a lithium imide salt can be used. Examples of the fluorine-containing inorganic anion salts, and the like _{LiPF 6, LiBF 4, LiAsF 6} , LiSbF 6, NaPF 6, NaBF 4. Examples of the lithium imide salt include LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) (C ₄ F ₉ SO ₂ ), LiN (CF ₃ SO ₂ ) _2. And so on. A solute may be used individually by 1 type, and may be used in combination of 2 or more type.

  Non-aqueous solvents include, for example, cyclic carbonates, acyclic carbonates, lactones or derivatives thereof, furans or derivatives thereof, ethers or derivatives thereof, glymes or derivatives thereof, amides, alcohols, esters, Phosphoric acids or phosphate esters, dimethyl sulfoxide, sulfolane or derivatives thereof, dioxolane or derivatives thereof, and the like can be used. Although a non-aqueous solvent can also be used individually by 1 type, it is preferable to use combining 2 or more types.

  Examples of the cyclic carbonate include propylene carbonate, ethylene carbonate, butylene carbonate, vinylene carbonate and the like. Examples of the acyclic carbonate include dimethyl carbonate, diethyl carbonate, and methyl ethyl carbonate. Examples of lactones or derivatives thereof include γ-butyrolactone, γ-valerolactone, and δ-valerolactone. Examples of furans or derivatives thereof include tetrahydrofuran and 2-methyltetrahydrofuran. Examples of ethers or derivatives thereof include 1,2-dimethoxyethane and 1,2-diethoxyethane. Examples of the glymes or derivatives thereof include diglyme, triglyme, and tetraglyme. Examples of amides include n, n-dimethylformamide and n-methylpyrrolidinone. Examples of alcohols include ethylene glycol and propylene glycol. Examples of the esters include methyl acetate, ethyl acetate, methyl propionate, and ethyl propionate.

  Various additives generally used conventionally, such as cyclohexylbenzene and propane sultone, may be added to the non-aqueous solvent.

  The exterior body that accommodates the electrode group and the nonaqueous electrolyte is, for example, a battery can of various shapes, a case made of an aluminum laminate film, or the like. The aluminum laminate film is obtained by bonding an aluminum foil and a resin film.

The nonaqueous electrolyte included in the nonaqueous electrolyte secondary battery of the present invention includes a bromine compound having an aromatic ring. The bromine compound having an aromatic ring is represented by any one of formulas (1) to (17). In addition, the bromine compound represented by Formula (1)-(17) may be used individually by 1 type, and may be used in combination of 2 or more type.
Formula (17):

（式中、Ｘ₁〜Ｘ₁₀は、それぞれ独立に、臭素原子または水素原子であり、少なくとも１つは臭素原子である。）
式（２）：

(Wherein X _{1 to} X ₁₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom.)
Formula (2):

(Wherein, X _{11 to} X ₂₀ each independently represents a bromine atom or a hydrogen atom, and at least one is a bromine atom.)
Formula (3):

(In the formula, X _{21 to} X ₃₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 1 to 4.)
Formula (4):

(Wherein X _{31 to} X ₃₄ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom.)
Formula (5):

(Wherein X _{35 to} X ₃₈ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. R ₁ and R ₂ each independently contains a carbon atom, (It is a group containing at least one selected from the group consisting of an atom and an oxygen atom, and the number of carbon atoms is 1 to 6.)
Formula (6)

(In the formula, X _{39 to} X ₄₆ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 0 to 4.)
Formula (7)

(In the formula, X _{47 to} X ₅₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. R ₃ and R ₄ each independently include a carbon atom and a hydrogen atom. And a group containing at least one selected from the group consisting of a bromine atom and an oxygen atom, and the number of carbon atoms is 1 to 6.)
Formula (8):

(In the formula, X _{51 to} X ₅₆ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 2 to 10.)
Formula (9):

(In the formula, X _{57 to} X ₆₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 1 to 100.)
Formula (10):

(In the formula, X _{61 to} X ₆₅ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 10 to 30.)
Formula (11):

(In the formula, X _{66 to} X ₇₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 100 to 200.)
Formula (12):

(In the formula, X _{71 to} X ₇₅ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 200 to 600.)
Formula (13):

(In the formula, x, y and z each represent the number of bromine atoms bonded to the aromatic ring, and the sum of x, y and z is 1 to 6. n is 1 to 5.)
Formula (14):

(In the formula, x represents the number of bromine atoms bonded to the aromatic ring, and x is 1 to 5.)
Formula (15):

(In the formula, x represents the number of bromine atoms bonded to the aromatic ring, and x is 1 to 5.)
Formula (16):

(In the formula, x represents the number of bromine atoms bonded to the aromatic ring, and x is 1 to 5.) Formula (17):

(In the formula, x, y and z each represent the number of bromine atoms bonded to the aromatic ring, and x, y and z are each 1 to 5).

The bromine compounds represented by the formulas (1) to (3) are biphenyl compounds in which at least some of the hydrogen atoms are substituted with bromine.
Specific examples of the bromine compound represented by the formula (1) include decabromodiphenyl, nonabromodiphenyl, octabromodiphenyl, heptabromodiphenyl, hexabromodiphenyl, pentabromodiphenyl, tetrabromodiphenyl, tribromodiphenyl, dibromodiphenyl and mono Bromodiphenyl. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Specific examples of the bromine compound represented by the formula (2) include decabromodiphenyl ether, nonabromodiphenyl ether, octabromodiphenyl ether, heptabromodiphenyl ether, hexabromodiphenyl ether, pentabromodiphenyl ether, tetrabromodiphenyl ether, tribromodiphenyl ether, dibromodiphenyl ether and monobromodiphenyl ether. Bromodiphenyl ether. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Specific examples of the bromine compound represented by the formula (3) include decabromodiphenoxyethane, nonabromodiphenoxyethane, octabromodiphenoxyethane, heptabromodiphenoxyethane, hexabromodiphenoxyethane, pentabromodiphenoxyethane, Tetrabromodiphenoxyethane, tribromodiphenoxyethane, dibromodiphenoxyethane, hexabromodiphenoxymethane, hexabromodiphenoxypropane, hexabromodiphenoxybutane and the like. These may be used individually by 1 type and may be used in combination of 2 or more type.

Bromine compounds represented by the formulas (4) to (6) are compounds based on phthalic anhydride.
Specific examples of the bromine compound represented by the formula (4) are tetrabromophthalic anhydride, tribromophthalic anhydride, dibromophthalic anhydride, monobromophthalic anhydride, and the like.

The bromine compound represented by the formula (5) is a diester compound of tetrabromophthalic acid, tribromophthalic acid, dibromophthalic acid or monobromophthalic acid. R ₁ and R ₂ are various.

  Specific examples of the bromine compound represented by the formula (6) are bistetrabromophthalimide, methylene bistetrabromophthalimide, ethylene bistetrabromophthalimide, propylene bistetrabromophthalimide, butylene bistetrabromophthalimide, ethylene bistribromophthalimide, ethylene bis Dibromophthalimide, ethylenebismonobromophthalimide and the like.

The bromine compound represented by formula (7) is a compound based on bisphenol A.
Specific examples of the bromine compound represented by the formula (7) include tetrabromobisphenol A-bis- (2,3-dibromopropyl ether), tetrabromobisphenol A-bis- (2-hydroxyethyl ether), and tetrabromobisphenol A. -Bis- (allyl ether), dibromobisphenol A-bis- (2,3-dibromopropyl ether), dibromobisphenol A-bis- (2-hydroxyethyl ether) and the like.

  The bromine compound represented by the formula (8) is a carbonate oligomer containing tetrabromobisphenol A in the main skeleton. There are various bromine compounds represented by the formula (8).

  The bromine compound represented by the formula (9) is an epoxy resin containing tetrabromobisphenol A in the main skeleton. There are various bromine compounds represented by the formula (9). For example, a compound represented by the formula (9) in which n is 1 to 6, about 65, about 80, or about 100 is easily available commercially.

  The bromine compounds represented by the formulas (10) to (13) are oligomers or polymers containing a benzene ring in which at least part of hydrogen atoms are substituted with bromine.

  The bromine compound represented by the formula (10) is polydibromophenylene oxide, and the bromine compound represented by the formula (10) is various. For example, a compound represented by formula (10) wherein n is about 10, about 20, or about 30 can be mentioned. These are readily available commercially.

  A specific example of the bromine compound represented by the formula (11) is poly (pentabromobenzyl) acrylate, and examples thereof include a bromine compound represented by the formula (11) in which n is about 100, about 140, or about 200. . These are readily available commercially.

  Specific examples of the bromine compound represented by the formula (12) are polypentabromostyrene, polytetrabromostyrene, polytribromostyrene, polydibromostyrene, and polymonobromostyrene. There are various compounds represented by the formula (12) depending on the n value representing the degree of polymerization. For example, n is about 200, about 320, about 440, or about 600 compounds. These are readily available commercially.

  A specific example of the bromine compound represented by the formula (13) is polybrominated acetonaphthylene. There are various compounds represented by the formula (13) depending on the n value, x, y, z value representing the degree of polymerization. For example, compounds having n of 2 to 5 are easily commercially available.

Formulas (14) to (16) are compounds having one benzene ring in which at least a part of hydrogen atoms is substituted with bromine.
Specific examples of the bromine compound represented by the formula (14) are monobromophenylmaleimide, dibromophenylmaleimide, tribromophenylmaleimide, tetrabromophenylmaleimide and pentabromophenylmaleimide.

  Specific examples of the bromine compound represented by the formula (15) are monobromobenzyl acrylate, dibromobenzyl acrylate, tribromobenzyl acrylate, tetrabromobenzyl acrylate, and pentabromobenzyl acrylate.

  Specific examples of the bromine compound represented by the formula (16) are monobromostyrene, dibromostyrene, tribromostyrene, tetrabromostyrene, and pentabromostyrene.

The bromine compound represented by the formula (17) is a compound having an isocyanurate structure and three benzene rings in which at least a part of hydrogen atoms are substituted with bromine.
Specific examples of the bromine compound represented by the formula (17) include tris (monobromobenzyl) isocyanurate, tris (dibromobenzyl) isocyanurate, tris (tribromobenzyl) isocyanurate, tris (tetrabromobenzyl) isocyanurate, tris. (Pentabromobenzyl) isocyanurate, bis (pentabromobenzyl) mono (tribromobenzyl) isocyanurate, mono (monobromobenzyl) mono (tribromobenzyl) mono (pentabromobenzyl) isocyanurate and the like.

Next, the effect | action of the bromine compound which has an aromatic ring is demonstrated.
A bromine compound having an aromatic ring is a film containing an aromatic ring and a bromine atom on the surface of the negative electrode active material and the surface of the positive electrode active material at the time of initial charge for activating the battery (a film containing a bromine compound decomposition component). Is considered to generate. Since this coating is stable, it is considered that the decomposition reaction of the nonaqueous electrolyte hardly occurs even when the battery is stored in a charged state, and gas generation is suppressed. Moreover, since this film contains bromine, it also has a flame retardant effect and can suppress an increase in battery temperature during overcharge or internal short circuit.

  When a bromine compound having no aromatic ring is used, a flame retardant effect is obtained, but the effect of suppressing gas generation is not observed, or it is extremely compared with the case of using a bromine compound having an aromatic ring. Get smaller. That is, the effect of suppressing gas generation is a characteristic effect when a bromine compound having an aromatic ring is used. This is considered to be related to the fact that the coating containing the bromine compound decomposition component contains an aromatic ring.

  In order to produce a film containing an aromatic ring and a bromine atom (a film containing a bromine compound decomposition component) on the surface of the negative electrode active material and the surface of the positive electrode active material during the initial charge for activating the battery, A bromine compound having an aromatic ring needs to be present in the vicinity of the material surface. For this purpose, the bromine compound needs to exist in a state where it can move to some extent. Therefore, it is most effective to add the bromine compound to the non-aqueous electrolyte from the viewpoint of film formation.

  Even when a gel electrolyte in which a nonaqueous solvent in which a solute is dissolved is used in a polymer matrix (network structure) is used, the bromine compound can move to some extent in the gel electrolyte. It is possible to form a film containing a decomposition component. For example, a gel electrolyte containing a bromine compound having an aromatic ring is obtained by dissolving a solute and retaining a nonaqueous solvent to which a bromine compound having an aromatic ring is added in a polymer matrix. There is also a method of obtaining a gel electrolyte by mixing a solution of a monomer that is a raw material of a polymer matrix and a nonaqueous solvent in which a solute is dissolved and a bromine compound having an aromatic ring is added, and then the monomer is polymerized. .

  The bromine compound is preferably included in the non-aqueous electrolyte so that the total number of moles of bromine atoms is 0.003 to 0.1 mol / L with respect to the non-aqueous electrolytic mass. If the amount of bromine atoms relative to the nonaqueous electrolyte is less than 0.003 mol / L, the amount of gas generated during high temperature storage may increase, or the discharge characteristics of the battery after storage may deteriorate. On the other hand, when the amount of bromine atoms relative to the non-aqueous electrolyte is more than 0.1 mol / L, the amount of gas generated during high-temperature storage is suppressed, but a relatively large amount of bromine compound is present in the non-aqueous electrolyte. The bromine compound acts as a resistance component, and the rapid discharge characteristics may deteriorate. Therefore, it is preferable to include the bromine compound in the nonaqueous electrolyte so that the concentration of bromine atoms is 0.003 to 0.1 mol / L with respect to the nonaqueous electrolyte.

  The bromine compound may be dissolved in the nonaqueous electrolyte or may be dispersed without being completely dissolved. Even if the bromine compound is not completely dissolved in the non-aqueous electrolyte and is dispersed, it does not become a large resistance component and does not particularly affect the battery characteristics.

  For the separator, a microporous film obtained by molding a resin or a resin composition into a sheet and further stretching is preferably used. The resin that is a raw material for such a separator is not particularly limited, and for example, polyolefin resins such as polyethylene and polypropylene, polyamide, polyethylene terephthalate (PET), polyamideimide, polyimide, and the like are used. Of these, a microporous membrane made of polyolefin is preferable.

The positive electrode active material is not particularly limited, for example, lithium cobalt oxide (LiCoO _2), lithium nickelate (LiNiO _2), lithium manganate _{(LiMn 2 O 4, LiMnO 2} ), such as lithium (LiFeO ₂₎ ferrate Lithium-containing transition metal oxides are preferably used. Among these lithium-containing transition metal oxides, composite oxides in which a part of the transition metal is replaced with another transition metal or a typical metal such as tin or aluminum is also preferably used. In addition, lithium compounds having an olivine structure, transition metal oxides, transition metal sulfides, polymers, and the like can be used as the positive electrode active material. Examples of lithium compounds having an olivine structure include lithium iron phosphate (LiFePO ₄ ), lithium manganese phosphate (LiMnPO ₄ ), lithium cobalt phosphate (LiCoPO ₄ ), and the like. Examples of the transition metal oxide include vanadium oxide (V ₂ O ₅ ), manganese dioxide (MnO ₂ ), molybdenum oxide (MoO ₂ ), and the like. Examples of transition metal sulfides include iron sulfate (FeSO ₄ ), titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ , MoS ₃ ), and iron sulfide (FeS ₂ ). Examples of the polymers include polyaniline, polypyrrole, polythiophene and the like. A positive electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.

The negative electrode active material is not particularly limited, and a material that can occlude and release alkali metal ions (for example, lithium ions and sodium ions), a material that can be alloyed with alkali metal ions, and the like are used. Examples of materials that can occlude and release alkali metal ions include carbon materials, metal oxides, and intermetallic compounds. Examples of the carbon material include amorphous carbon, artificial graphite, and natural graphite. Examples of the metal oxide include oxides of lead (Pb), tin (Sn), bismuth (Bi), and silicon (Si). Examples of the intermetallic compound include alkali metal interstitial insertion type cubic AlSb, Mg ₂ Si, NiSi _{2 and the} like. Examples of materials that can be alloyed with alkali metal ions include metals such as aluminum (Al), lead (Pb), tin (Sn), bismuth (Bi), silicon (Si), and alloys containing these metals. In addition, a lithium nitrogen compound represented by the general formula Li _3-x M _x N (M is a transition metal), a titanium spinel compound (Li ₄ TiO ₁₂ ), a lithium vanadium oxide, or the like can also be used. A negative electrode active material may be used individually by 1 type, and may be used in combination of 2 or more type.

  EXAMPLES Next, although this invention is demonstrated concretely based on an Example, a following example does not limit this invention.

<< Examples 1-8 >>
(I) Production of positive electrode Li ₂ CO ₃ , Co ₃ O ₄ and MgCO ₃ were mixed so that the molar ratio of Li: Co: Mg was 1: 0.97: 0.03, and the resulting mixture was And calcining at 900 ° C. for 10 hours to obtain LiMg _0.03 Co _0.97 O ₂₋ δ (0 ≦ δ ≦ 1) which is a lithium-containing transition metal oxide.

3 parts by weight of acetylene black as a conductive agent and 7 parts by weight of “BM-400B (trade name)” (100 parts by weight of LiMg _0.03 Co _0.97 O ₂₋ δ powder (positive electrode active material)) An aqueous dispersion containing 40% by weight of a styrene-butadiene copolymer (manufactured by Nippon Zeon Co., Ltd.) and an appropriate amount of an aqueous carboxymethyl cellulose solution were mixed to prepare a positive electrode mixture paste.

  The obtained positive electrode mixture paste was applied to both sides of a positive electrode current collector made of an aluminum foil having a thickness of 30 μm, dried, and the dried coating film was rolled to obtain a positive electrode having a thickness of 0.18 mm. A positive electrode lead made of aluminum was welded to the positive electrode current collector.

(Ii) Production of Negative Electrode 100 parts by weight of artificial graphite powder (negative electrode active material) is mixed with 5 parts by weight of a styrene-butadiene copolymer as a binder and an appropriate amount of an aqueous solution of carboxymethyl cellulose, and a negative electrode mixture paste. Got.

  The obtained negative electrode mixture paste was applied to both sides of a negative electrode current collector made of a copper foil having a thickness of 20 μm, dried, and the dried coating film was rolled to obtain a negative electrode having a thickness of 0.19 mm. A negative electrode lead made of nickel was welded to the negative electrode current collector.

(Iii) Preparation of non-aqueous electrolyte Ethylene carbonate, ethyl methyl carbonate, and diethyl carbonate were mixed at a volume ratio of 1: 2: 1 to obtain a non-aqueous solvent. In the obtained non-aqueous solvent, lithium hexafluorophosphate (LiPF ₆ ) was dissolved as a solute at a concentration of 1.2 mol / L, and the bromine compounds (decabromodiphenyl) shown in Table 1 were listed in Table 1. The nonaqueous electrolyte was obtained.

  The amount of decabromodiphenyl contained in the nonaqueous electrolyte was changed in the range of 0.008 to 1.572 wt%. That is, the concentration of bromine atoms contained in the nonaqueous electrolyte was changed in the range of 0.001 to 0.2 mol / L.

(Iv) Battery assembly As shown in FIG. 1, a cylindrical lithium ion secondary battery having a diameter of 18 mm, a height of 65 mm, a nominal voltage of 3.6 V, and a nominal capacity of 2400 mAh was produced.
First, the positive electrode 2 and the negative electrode 3 were wound through a separator 1 made of a polyethylene microporous film (thickness 25 μm) to form a columnar electrode group. The electrode group was accommodated in the inner space of a battery can (exterior body) 7 also serving as a negative electrode terminal in a state where an upper insulating ring 8 and a lower insulating ring 6 for preventing a short circuit were arranged. A separator 1 was interposed between the electrode group and the battery can 7. Note that the end of the positive electrode lead 4 was welded to the back surface of the battery lid 10 also serving as the positive electrode terminal, and the end of the negative electrode lead 5 was welded to the inner bottom surface of the battery can 7. Next, a non-aqueous electrolyte was injected into the battery can, and the electrode group was impregnated with the non-aqueous electrolyte. The opening of the battery can 7 was closed with the battery lid 10. The opening end of the battery can 7 was caulked to the periphery of the battery lid 10 via the insulating packing 9.

(V) Activation of Battery The assembled battery was repeatedly charged and discharged under the following conditions three times alternately at an environmental temperature of 25 ° C.
Constant current charging: Current 480 mA (equivalent to 0.2 C), end-of-charge voltage 4.1 V
Constant current discharge: Current 480 mA (equivalent to 0.2 C), discharge end voltage 3.0 V
Next, a fourth charge was performed under the above conditions, and then the charged battery was left at 60 ° C. for 2 days to finish the battery.

<< Comparative Example 1 >>
A battery was fabricated in the same manner as in Example 1 except that decabromodiphenyl was not added to the nonaqueous electrolyte.

<< Comparative Example 2 >>
3 parts by weight of acetylene black as a conductive agent and 7 parts by weight of “BM-400B (trade name)” (100 parts by weight of LiMg _0.03 Co _0.97 O ₂₋ δ powder (positive electrode active material)) An aqueous dispersion containing 40% by weight of a styrene-butadiene copolymer (manufactured by Nippon Zeon Co., Ltd.), an appropriate amount of carboxymethylcellulose aqueous solution, and decabromodiphenyl were mixed to prepare a positive electrode mixture paste.

  A battery was fabricated in the same manner as in Example 1 except that the obtained positive electrode mixture paste containing decabromodiphenyl was used and no decabromodiphenyl was added to the nonaqueous electrolyte.

  The content of decabromodiphenyl contained in the positive electrode mixture (the content of decabromodiphenyl in the total of the positive electrode active material, the conductive agent, the binder, the CMC, and decabromodiphenyl) was 0. .15 wt%.

<< Comparative Example 3 >>
To 100 parts by weight of artificial graphite powder (negative electrode active material), 5 parts by weight of a styrene-butadiene copolymer, an appropriate amount of carboxymethylcellulose aqueous solution, and decabromodiphenyl are mixed as a binder, and a negative electrode mixture paste is prepared. Obtained.

  A battery was fabricated in the same manner as in Example 1 except that the obtained negative electrode mixture paste containing decabromodiphenyl was used and no decabromodiphenyl was added to the nonaqueous electrolyte.

  The content of decabromodiphenyl contained in the negative electrode mixture (the content of decabromodiphenyl in the total of the negative electrode active material, the binder, CMC, and decabromodiphenyl) was 0.15 wt%. did.

<< Comparative Example 4 >>
A battery was fabricated in the same manner as in Example 1, except that decabromodiphenyl was not added to the nonaqueous electrolyte, and hexabromobenzene was added as a bromine compound.
The content of hexabromobenzene contained in the nonaqueous electrolyte was 2 wt%. That is, the concentration of bromine atoms contained in the nonaqueous electrolyte was 0.26 mol / L.

<< Comparative Example 5 >>
A battery was fabricated in the same manner as in Example 1, except that decabromodiphenyl was not added to the nonaqueous electrolyte, and hexabromocyclododecane was added as a bromine compound.
The content of hexabromocyclododecane contained in the nonaqueous electrolyte was 2 wt%. That is, the concentration of bromine atoms contained in the nonaqueous electrolyte was 0.22 mol / L.

[Evaluation]
After confirming the initial discharge capacity, the batteries of Examples 1 to 8 and Comparative Examples 1 to 5 were each used for 10 cells to determine the initial discharge capacity. A high rate discharge test and a high temperature charge storage test were conducted. The high rate discharge test was conducted on all the batteries before the high temperature charge storage test. Of the 10 cells after high temperature storage, 5 cells were used for measurement of the amount of gas generated after storage. The remaining 5 cells were used for the measurement of discharge capacity for obtaining the recovery rate before and after storage. Furthermore, in order to confirm the safety of the battery, 10 cells were used for each battery, and an overcharge test and a cycle test were performed. All the values shown in the table are average values of 10 cells or 5 cells.

(Initial discharge capacity)
Prior to testing, the discharge capacity of each battery was measured.
First, the battery charged at the time of activation was discharged at an environmental temperature of 25 ° C. at a constant current of 1200 mA (corresponding to 0.5 C) until a final discharge voltage of 2.5 V was reached.
Next, charging and discharging under the following conditions were repeated for 3 cycles at an environmental temperature of 25 ° C., the discharge capacity at the third cycle was measured, and the average value of 10 cells was obtained.
Constant current charging: Current 1680 mA (equivalent to 0.7 C), end-of-charge voltage 4.2 V
Constant voltage charge: Voltage 4.2V, Charging period 2.5 hours Constant current discharge: Current 1200mA (equivalent to 0.5C), discharge end voltage 2.5V

(High rate discharge test (High rate discharge characteristics (2C / 0.5C)))
The battery whose initial discharge capacity was confirmed was charged and discharged under the following conditions at an environmental temperature of 25 ° C. to obtain a 2C discharge capacity.
Constant current charging: Current 1680 mA (equivalent to 0.7 C), end-of-charge voltage 4.2 V
Constant voltage charge: voltage 4.2V, charge period 2.5 hours Constant current discharge: current 4800mA (equivalent to 2C), discharge end voltage 2.5V

Thereafter, the battery was further charged and discharged under the following conditions at an environmental temperature of 25 ° C. to obtain a 0.5 C discharge capacity.
Constant current charging: Current 1680 mA (equivalent to 0.7 C), end-of-charge voltage 4.2 V
Constant voltage charge: Voltage 4.2V, Charging period 2.5 hours Constant current discharge: Current 1200mA (equivalent to 0.5C), discharge end voltage 2.5V
The ratio of 2C discharge capacity to 0.5C discharge capacity was calculated as a percentage to obtain high rate discharge characteristics (2C / 0.5C).

(High temperature charge storage test)
(I) Recovery rate before and after storage The battery after the high rate discharge test was charged under the following conditions at an environmental temperature of 25 ° C.
Constant current charging: Current 1680 mA (equivalent to 0.7 C), end-of-charge voltage 4.25 V
Constant voltage charging: Voltage 4.25 V, charging period 2.5 hours Thereafter, the charged battery was stored at an environmental temperature of 60 ° C. for 20 days.
The battery after storage was discharged at an environmental temperature of 25 ° C. under the following conditions.
Constant current discharge: current 1200mA (equivalent to 0.5C), discharge end voltage 2.5V

Next, charging and discharging under the following conditions were repeated for 3 cycles at an environmental temperature of 25 ° C., and the discharge capacity at the third cycle was measured as the discharge capacity after storage.
Constant current charging: Current 1680 mA (equivalent to 0.7 C), end-of-charge voltage 4.2 V
Constant voltage charge: Voltage 4.2V, Charging period 2.5 hours Constant current discharge: Current 1200mA (equivalent to 0.5C), discharge end voltage 2.5V
The ratio of the discharge capacity after storage to the initial discharge capacity was calculated as a percentage and used as the recovery rate.

(Ii) Gas amount after storage A battery and a push pin after storage were placed in a Teflon (registered trademark) bag, and the bag was filled with a known amount of argon gas, and the bag was sealed. Inside the bag, a push pin was used to make a hole in the battery sealing plate, and the gas inside the battery was collected in the bag. The amount of gas collected was determined by gas chromatography.

(Overcharge test)
The battery whose initial discharge capacity was confirmed was charged at the environmental temperature of 25 ° C. under the following conditions.
Constant current charging: Current 1680 mA (equivalent to 0.7 C), end-of-charge voltage 4.2 V
Constant voltage charging: voltage of 4.2 V, charging period of 2.5 hours Next, whether the battery temperature exceeds 120 ° C. by continuously charging the charged battery at an environmental temperature of 25 ° C. and a current of 2400 mA equivalent to 1C. I observed how. The number of batteries exceeding 120 ° C. was counted.

(Cycle test)
The battery whose initial discharge capacity was confirmed was charged and discharged under the following conditions for three cycles at an environmental temperature of 25 ° C., and the discharge capacity at the third cycle was measured.
Constant current charging: Current 1680 mA (equivalent to 0.7 C), end-of-charge voltage 4.2 V
Constant voltage charge: Voltage 4.2V, Charging period 2.5 hours Constant current discharge: Current 1200mA (equivalent to 0.5C), discharge end voltage 2.5V
Thereafter, charging and discharging under the following conditions were repeated 496 cycles at an environmental temperature of 25 ° C.
Constant current charging: current 2400 mA (equivalent to 1 C), end-of-charge voltage 4.2 V
Constant voltage charge: Voltage 4.2V, Charging period 2.5 hours Constant current discharge: Current 2400mA (equivalent to 1C), discharge end voltage 2.5V

Next, charge / discharge at the 500th cycle was performed under the following conditions.
Constant current charging: Current 1680 mA (equivalent to 0.7 C), end-of-charge voltage 4.2 V
Constant voltage charge: Voltage 4.2V, Charging period 2.5 hours Constant current discharge: Current 1200mA (equivalent to 0.5C), discharge end voltage 2.5V
The ratio of the discharge capacity at the 500th cycle to the discharge capacity at the 3rd cycle was obtained as a percentage, and was defined as the capacity maintenance rate.

  Table 2 shows the results of the high rate discharge test, the high temperature charge storage test, the overcharge test, and the cycle test.

  As Table 2 shows, the batteries of Examples 1 to 8 had less gas generation after storage than the batteries of Comparative Examples 1 to 5. Among the batteries of Examples 1 to 8, it was observed that the gas generation amount tended to decrease particularly when the concentration of bromine atoms contained in the nonaqueous electrolyte was 0.003 mol / L or more. Further, the recovery rate before and after storage tended to improve as the amount of bromine compound was increased, but the recovery rate decreased when the concentration of bromine atoms contained in the non-aqueous electrolyte was 0.01 mol / L or more. There was a trend. Therefore, from the viewpoint of the balance between the gas generation amount and the recovery rate, the concentration of bromine atoms contained in the nonaqueous electrolyte is preferably 0.003 to 0.1 mol / L, more preferably 0.003 to 0.05 mol / L. It can be seen that it is.

  In the overcharge test, in Comparative Example 1, the temperature of the 3/10 cell exceeded 120 ° C, whereas in Examples 1 to 8, none of the batteries reached 120 ° C. From this, it was found that the safety of the battery can be improved by including a bromine compound in the nonaqueous electrolyte.

  The batteries of Examples 1 to 8 also had good high rate discharge characteristics and good capacity retention after 500 cycles. This is considered to be the effect of the coating film containing the decomposition product of the bromine compound formed on the positive electrode and the negative electrode.

  In Comparative Examples 2 and 3 in which decabromodiphenyl was mixed in the positive electrode or the negative electrode, safety was improved as compared with Comparative Example 1, but almost no effect of suppressing gas generation was observed. Further, the high rate discharge characteristics and the capacity retention after 500 cycles were lower than those of Comparative Example 1. When a bromine compound having an aromatic ring is mixed in the electrode as in Comparative Examples 2 and 3, it is considered that the safety improvement effect is recognized, but the high rate discharge characteristics and cycle characteristics are adversely affected. This is presumably because an insulator such as a bromine compound having an aromatic ring remains in the electrode.

  The hexabromobenzene used in Comparative Example 4 and the hexabromocyclododecane used in Comparative Example 5 are relatively low-molecular molecules and exist as liquids at room temperature. Therefore, there is a feature that it can be easily mixed with a non-aqueous electrolyte. However, in Comparative Examples 4 and 5, safety and high rate discharge characteristics were good, but the effect of suppressing gas generation after storage was not obtained, and the capacity recovery rate after storage was also low. This is presumably because the film formed on the positive electrode and the negative electrode is non-uniform. Since the hexabromobenzene of Comparative Example 4 has a relatively low molecular weight, it is considered that a good film is not generated even when decomposed. Since the hexabromocyclododecane of Comparative Example 5 does not have an aromatic ring, It is considered that the effect of suppressing the occurrence does not appear.

<< Examples 9 to 132 >>
The bromine compounds shown in Tables 3A to F were prepared in the same manner as in Example 1 except that the bromine compounds contained in the nonaqueous electrolyte were added to the nonaqueous electrolyte so that the bromine atoms contained in the nonaqueous electrolyte had the concentrations shown in Tables 3A to F. The batteries of Examples 9 to 132 were produced and evaluated in the same manner as described above.

Hereinafter, information is captured for some of the bromine compounds shown in Tables 3A-F.
<1> The tetrabromobisphenol A-carbonate oligomer used in Examples 24-26 (Table 3A) is a bromine compound represented by the formula (8), X _{51 to} X ₅₆ are all hydrogen atoms, and n = 5.
<2> The tetrabromobisphenol A-based epoxy resin used in Examples 27 to 29 (Table 3A) is a bromine compound represented by the formula (9), and X _{57 to} X ₆₀ are all bromine atoms. n = 1.

<3> The polydibromophenylene oxide used in Examples 30 to 32 (Table 3B) is a bromine compound represented by the formula (10), X _{61 to} X ₆₅ are all bromine atoms, and n = 20 is there.
<4> The poly (pentabromobenzyl) acrylate used in Examples 33 to 35 (Table 3B) is a bromine compound represented by the formula (11), X _{66 to} X ₇₀ are all bromine atoms, n = 140.

<5> The brominated polystyrene used in Examples 36 to 38 (Table 3B) is a bromine compound represented by the formula (12), X _{71 to} X ₇₅ are all bromine atoms, and n = 440. .
<6> The polybrominated acetonaphthylene used in Examples 39 to 41 (Table 3B) is a bromine compound represented by the formula (13), x + y + z = 6, and n = 2.

<7> The tetrabromobisphenol A-carbonate oligomer 1 used in Example 92 (Table 3D) is a bromine compound represented by the formula (8), and X _{51 to} X ₅₆ are all bromine atoms, and n = 5 It is.
<8> The tetrabromobisphenol A-carbonate oligomer 2 used in Example 93 (Table 3D) is a bromine compound represented by the formula (8), X _{51 to} X ₅₆ are all hydrogen atoms, and n = 2 It is.

<9> The tetrabromobisphenol A-carbonate oligomer 3 used in Example 94 (Table 3D) is a bromine compound represented by the formula (8), X _{51 to} X ₅₆ are all hydrogen atoms, and n = 7 It is.
<10> The tetrabromobisphenol A-carbonate oligomer 4 used in Example 95 (Table 3D) is a bromine compound represented by the formula (8), X _{51 to} X ₅₆ are all hydrogen atoms, and n = 10 It is.

<11> The tetrabromobisphenol A-based epoxy resin 1 used in Example 96 (Table 3D) is a bromine compound represented by the formula (9), and X _{57 to} X ₆₀ are all bromine atoms, and n = 2.
<12> The tetrabromobisphenol A-based epoxy resin 2 used in Example 97 (Table 3D) is a bromine compound represented by the formula (9), and X _{57 to} X ₆₀ are all bromine atoms, and n = 5.

<13> The tetrabromobisphenol A-based epoxy resin 3 used in Example 98 (Table 3D) is a bromine compound represented by the formula (9), and X _{57 to} X ₆₀ are all bromine atoms, and n = 65.
<14> The tetrabromobisphenol A-based epoxy resin 4 used in Example 99 (Table 3E) is a bromine compound represented by the formula (9), and X _{57 to} X ₆₀ are all bromine atoms, and n = 80.

<15> The tetrabromobisphenol A-based epoxy resin 5 used in Example 100 (Table 3E) is a bromine compound represented by the formula (9), and X _{57 to} X ₆₀ are all bromine atoms, and n = 100.
<16> The tetrabromobisphenol A-based epoxy resin 6 used in Example 101 (Table 3E) is a bromine compound represented by the formula (9), and X _{57 to} X ₆₀ are all hydrogen atoms, and n = 1.

<17> The tetrabromobisphenol A-based epoxy resin 7 used in Example 102 (Table 3E) is a bromine compound represented by the formula (9), and X _{57 to} X ₆₀ are all hydrogen atoms, and n = 5.
<18> The polydibromophenylene oxide 1 used in Example 103 (Table 3E) is a bromine compound represented by the formula (10), and X _{61 to} X ₆₅ are all bromine atoms and n = 10. .

<19> The polydibromophenylene oxide 2 used in Example 104 (Table 3E) is a bromine compound represented by the formula (10), and X _{61 to} X ₆₅ are all bromine atoms, and n = 30. .
<20> The polydibromophenylene oxide 3 used in Example 105 (Table 3E) is a bromine compound represented by the formula (10), and X _{61 to} X ₆₅ are all hydrogen atoms and n = 10. .

<21> The polydibromophenylene oxide 4 used in Example 106 (Table 3E) is a bromine compound represented by the formula (10), and X _{61 to} X ₆₅ are all hydrogen atoms and n = 20. .
<22> The poly (pentabromobenzyl) acrylate 1 used in Example 107 (Table 3E) is a bromine compound represented by the formula (11), X _{66 to} X ₇₀ are all bromine atoms, and n = 100.

<23> The poly (pentabromobenzyl) acrylate 2 used in Example 108 (Table 3E) is a bromine compound represented by the formula (11), and X _{66 to} X ₇₀ are all bromine atoms, and n = 200.
<24> The poly (pentabromobenzyl) acrylate 3 used in Example 109 (Table 3E) is a bromine compound represented by the formula (11), X _{66 to} X ₇₀ are all bromine atoms, and n = 140.

<25> The poly (2,4,6-tribromobenzyl) acrylate used in Example 110 (Table 3E) is a bromine compound represented by the formula (11), and X ₆₆ , X ₆₈ and X ₇₀ are A bromine atom, X ₆₇ and X ₆₉ are hydrogen atoms, and n = 100.
<26> The poly (3,5-dibromobenzyl) acrylate used in Example 111 (Table 3E) is a bromine compound represented by the formula (11), X ₆₇ and X ₆₉ are bromine atoms, ₆₆ , X ₆₈ and X ₇₀ are hydrogen atoms, and n = 100.

<27> Polypentabromostyrene 1 used in Example 112 (Table 3E) is a bromine compound represented by the formula (12), and n = 200.
<28> Polypentabromostyrene 2 used in Example 113 (Table 3E) is a bromine compound represented by the formula (12), and n = 600.

<29> The poly (2,4,6-tribromo) styrene used in Example 114 (Table 3E) is a bromine compound represented by the formula (12), and n = 200.
<30> The poly (3,5-dibromo) styrene used in Example 115 (Table 3E) is a bromine compound represented by the formula (12), and n = 200.

<31> The polybrominated acetonaphthylene 1 used in Example 116 (Table 3E) is a bromine compound represented by the formula (13), x + y + z = 6, and n = 3.
<32> The polybrominated acetonaphthylene 2 used in Example 117 (Table 3E) is a bromine compound represented by the formula (13), x + y + z = 6, and n = 5.

<33> The polybrominated acetonaphthylene 3 used in Example 118 (Table 3E) is a bromine compound represented by the formula (13), x + y + z = 4, and n = 2.
<34> The polybrominated acetonaphthylene 4 used in Example 119 (Table 3E) is a bromine compound represented by the formula (13), x + y + z = 2, and n = 2.

  Tables 4A to 4F show the results of high rate discharge characteristics, initial discharge capacity, recovery rate before and after storage, and gas amount after storage.

  As Tables 4A to F show, the batteries of Examples 9 to 132 had less gas generation after storage than the battery of Comparative Example 1 that did not contain a bromine compound. In all of the Examples, the discharge capacity and the recovery rate after storage were also good. In addition, as in Examples 1 to 8, all the batteries had good safety, and high rate discharge characteristics and cycle characteristics were good.

In addition, although the said Example demonstrated some bromine compounds, even if it uses any bromine compound represented by Formula (1)-(17), the same effect is acquired.
In the above-described embodiments, the lithium ion secondary battery has been described. However, other non-aqueous electrolyte secondary batteries, for example, polymer secondary batteries using a gel electrolyte, magnesium secondary batteries, aluminum secondary batteries, sodium secondary batteries. Similar effects can be obtained in batteries and the like.

  Moreover, although the said Example demonstrated the battery containing the electrode group which wound the positive electrode and the negative electrode through the separator, the form of the electrode group of a battery is not limited to this. A similar effect can be obtained even in a battery including an electrode group in which a positive electrode and a negative electrode are stacked in a stack via a separator.

  Further, the shape of the nonaqueous electrolyte secondary battery is not limited to the cylindrical shape as described above. The same effect can be obtained in a rectangular or coin-type battery using a battery can as an exterior body, a sheet-type battery using an aluminum laminate film as an exterior body, or the like.

  As described above, according to the present invention, the temperature rise of the battery is suppressed, and when the charged battery is stored at a high temperature, gas generation can be suppressed. Further, the battery characteristics after storage are also good, and the cycle characteristics are also good. Therefore, according to the present invention, a highly reliable non-aqueous electrolyte secondary battery excellent in safety can be provided. The nonaqueous electrolyte secondary battery of the present invention is useful as a drive power source for electronic devices such as notebook computers, mobile phones, and digital still cameras.

It is a fragmentary longitudinal cross-sectional view of an example of the cylindrical lithium ion secondary battery which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Separator 2 Positive electrode 3 Negative electrode 4 Positive electrode lead 5 Negative electrode lead 6 Lower insulating ring 7 Battery can 8 Upper insulating ring 9 Insulating packing 10 Battery lid

Claims (2)

An electrode group, a non-aqueous electrolyte, and an exterior body that houses the electrode group and the non-aqueous electrolyte;
The electrode group has a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode,
The non-aqueous electrolyte contains a bromine compound having an aromatic ring,
The bromine compound is represented by the formula (1):

(Wherein, X _{1 to} X ₁₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom), formula (2):

(Wherein, X _{11 to} X ₂₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom), formula (3):

(In the formula, X _{21 to} X ₃₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 1 to 4), Formula (4):

(Wherein X _{31 to} X ₃₄ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom), formula (5):

(Wherein X _{35 to} X ₃₈ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. R ₁ and R ₂ each independently contains a carbon atom, A group containing at least one selected from the group consisting of an atom and an oxygen atom, and the number of carbon atoms is 1 to 6.), Formula (6)

(In the formula, X _{39 to} X ₄₆ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 0 to 4), Formula (7)

(In the formula, X _{47 to} X ₅₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. R ₃ and R ₄ each independently include a carbon atom and a hydrogen atom. And a group containing at least one selected from the group consisting of a bromine atom and an oxygen atom, and the number of carbon atoms is 1 to 6.), Formula (8):

(Wherein, X _{51 to} X ₅₆ are each independently a bromine atom or a hydrogen atom, at least one is a bromine atom. N is 2 to 10), Formula (9):

(Wherein, X _{57 to} X ₆₀ are each independently a bromine atom or a hydrogen atom, at least one is a bromine atom. N is 1 to 100), formula (10):

(Wherein, X _{61 to} X ₆₅ are each independently a bromine atom or a hydrogen atom, at least one is a bromine atom. N is 10 to 30), Formula (11):

(Wherein, X _{66 to} X ₇₀ are each independently a bromine atom or a hydrogen atom, and at least one is a bromine atom. N is 100 to 200), Formula (12):

(. Wherein, X ₇₁ to X ₇₅ each independently represents a bromine atom or a hydrogen atom, at least one is bromine atom .n is 200-600), formula (13):

(Wherein, x, y and z represent the number of bromine atoms bonded to the aromatic ring, respectively, and the sum of x, y and z is 1 to 6. n is 1 to 5), (14):

(Wherein x represents the number of bromine atoms bonded to the aromatic ring and x is 1 to 5), formula (15):

(Wherein x represents the number of bromine atoms bonded to the aromatic ring, and x is 1 to 5), formula (16):

(Wherein x represents the number of bromine atoms bonded to the aromatic ring, x is 1 to 5) and formula (17):

(Wherein, x, y and z each represent the number of bromine atoms bonded to the aromatic ring, and x, y and z are each 1 to 5) Secondary battery. The nonaqueous electrolyte secondary battery according to claim 1, wherein an amount of bromine atoms of the bromine compound is 0.003 to 0.1 mol / L with respect to the nonaqueous electrolytic mass.

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