WO2016063865A1

WO2016063865A1 - Film pack battery and battery module provided with same

Info

Publication number: WO2016063865A1
Application number: PCT/JP2015/079548
Authority: WO
Inventors: 登吉田; 志村　健一; 井上　和彦
Original assignee: 日本電気株式会社
Priority date: 2014-10-21
Filing date: 2015-10-20
Publication date: 2016-04-28
Also published as: JPWO2016063865A1; JP6597631B2

Abstract

This film pack secondary battery is provided with: a battery element which comprises a positive electrode and a negative electrode that are laminated with a separator being interposed therebetween; a nonaqueous electrolyte which contains a lithium salt; and a film package which contains the battery element and the nonaqueous electrolyte. a: The nonaqueous electrolyte contains a redox shuttle agent that consumes excess energy at the time of overcharging. b: The separator has (b1) a melting point of 180°C or more and (b2) a Gurley value of 100 [sec/100 cc] or less.

Description

Film exterior battery and battery module including the same

The present invention relates to a film-clad battery and the like, and in particular, the separator is not deformed due to heat during operation of the redox shuttle agent, and the positive electrode and the negative electrode are not short-circuited, and the redox shuttle agent can efficiently consume energy. The present invention relates to a film-clad battery or the like that has improved safety.

Non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries have already been put to practical use as batteries for notebook computers and mobile phones due to their advantages such as high energy density, low self-discharge, and excellent long-term reliability. Yes. However, in recent years, electronic devices have been enhanced in functionality and used in electric vehicles, and development of lithium ion secondary batteries with higher energy density has been demanded.

In order to realize a cell having a high energy density, it is effective to use a positive electrode such as NCA (lithium nickel cobalt aluminum oxide) or LNO (lithium nickel oxide). However, these positive electrodes may cause thermal runaway with oxygen release during overcharge or high temperature. As one of techniques for ensuring safety during overcharge, a technique using a redox shuttle agent has been proposed.

The overcharge prevention mechanism using the redox shuttle agent is roughly as follows. In other words, by adding a redox shuttle agent that reacts at a higher voltage than the normal operating voltage of the cell to the electrolyte, the redox shuttle agent consumes current when the cell voltage rises during overcharge. This is to prevent the active material from being overcharged. As a secondary battery using such an overcharge prevention mechanism using a redox shuttle agent, a battery as disclosed in Patent Document 1 can be cited as an example.

JP 2007-287445 A

However, since the redox shuttle agent generates heat during operation, if the melting point of the separator is low, the separator may melt and the positive electrode and the negative electrode may be short-circuited. In addition, it is desirable that energy consumption by the redox shuttle agent be efficiently continued even under overcharge conditions.

Accordingly, an object of the present invention relates to a film-clad battery using a redox shuttle agent, and the separator is not deformed due to heat during operation of the redox shuttle agent, so that the positive electrode and the negative electrode are not short-circuited. The object is to provide a film-clad battery or the like that can be consumed and has improved safety.

In order to achieve the above object, a battery according to an embodiment of the present invention is as follows:
A battery element having a positive electrode and a negative electrode laminated via a separator;
A non-aqueous electrolyte containing a lithium salt;
A film exterior body for housing them,
a: the non-aqueous electrolyte includes a redox shuttle agent that consumes excess energy when overcharged;
b: The separator is
(B1) Its melting point is 180 ° C. or higher,
(B2) Gurley value is 100 [sec / 100cc] or less,
Film outer battery.

(Explanation of terms)
A “film-clad battery” refers to a battery in which a battery element is accommodated in a film-clad body together with an electrolytic solution, and generally has a flat shape as a whole. For example, a battery for an electric vehicle is required to have a large capacity, a low internal resistance, a high heat dissipation, and the like, and a film-covered battery is advantageous in these respects. One film-clad battery may be referred to as a “battery cell” or simply a “cell”.
-“Film exterior” refers to an exterior that is made of a flexible film and contains battery elements, and seals battery elements by placing two films facing each other and welding them together. Alternatively, the battery element may be sealed by folding back one film and welding the opposed surfaces.
-Regarding the numerical range, for example, the range “a to b” means the range from a to b.

The present invention relates to a film-clad battery or the like using a redox shuttle agent, so that the separator is not deformed due to heat during operation of the redox shuttle agent and the positive electrode and the negative electrode are short-circuited. A film-clad battery or the like that can be consumed and has improved safety can be provided.

It is a perspective view which shows the basic structure of the film-clad battery of one form of this invention. It is sectional drawing which shows a part of cross section of the battery of FIG. It is a schematic diagram for demonstrating the internal structure of a film-clad battery (plan view). It is sectional drawing which shows the internal structure of a film-clad battery typically. It is a schematic diagram of the battery module which accommodated the film exterior battery in the module container. It is a figure which shows typically the mechanism which applies a pressure with respect to a film-clad battery.

1. Basic structure of film-clad battery A basic structure of a film-clad battery 50 according to an embodiment of the present invention will be described with reference to FIGS. As a matter of course, the film-clad battery 50 of the present invention may have other structures (for example, a gas release mechanism), but only the basic configuration of the battery is shown in FIGS.

As shown in FIGS. 1 and 2, the film-clad battery 50 includes a battery element 20, a film-clad body 10 that accommodates the battery element 20 together with a non-aqueous electrolyte, and a battery element 20 that is connected to the outside of the film-clad body 10. A positive electrode tab 21 and a negative electrode tab 25 (hereinafter simply referred to as “electrode tabs”) are provided.

The battery element 20 is formed by alternately laminating a plurality of positive electrodes and a plurality of negative electrodes made of metal foils each coated with an electrode material on both sides of a separator. Although the overall external shape of the battery element 20 is not particularly limited, in this example, it is a flat and substantially rectangular parallelepiped. Details of each part constituting the battery element 20 will be described later.

<Film outer package>
As the material of the film outer package, any material may be used as long as it is stable to the electrolytic solution and has a sufficient water vapor barrier property. For example, in the case of a laminated laminate type secondary battery, it is preferable to use, as an example, a laminate film of aluminum and resin as the outer package. An exterior body may be comprised with a single member and may be comprised combining several members. In the present embodiment, as shown in FIG. 1, the film outer package 10 may be composed of a first film 11 and a second film 12 disposed to face the first film 11.

The outline shape of the film outer package 10 is not particularly limited, but may be a quadrangle, which is a rectangle in this example. Both the films 11 and 12 are heat-welded to each other around the battery element 20 and joined. Thereby, the peripheral part of the film exterior body 10 becomes the heat welding part 15. A positive electrode tab 21 and a negative electrode tab 25 are drawn from one side of the short side of the heat-welded portion 15. Various materials can be adopted as the

electrode tabs

21 and 25. As an example, the positive electrode tab 21 is aluminum or an aluminum alloy, and the negative electrode tab 25 is copper or nickel. When the material of the negative electrode tab 25 is copper, the surface may be nickel-plated.

In addition, about the extraction position of the

electrode tabs

21 and 25, the tab may be pulled out from one side of the long side. Moreover, the positive electrode tab 21 and the negative electrode tab 25 may be pulled out from different sides. As this example, the structure by which the positive electrode tab 21 and the negative electrode tab 25 are pulled out in the opposite direction from the opposing side is mentioned.

As illustrated in FIG. 3, each of the positive electrode and the negative electrode may have an extension part (see

reference numerals

31 a and 35 a) partially protruding from a part of the outer periphery, and the positive electrode extension part and the negative electrode extension part Are arranged in staggered positions so that they do not interfere with each other when the positive and negative electrodes are stacked. The extension portions of the positive electrodes are stacked and connected to each other to form a current collector 31a, and the positive electrode tab 21 is connected to the current collector 31a. Similarly, regarding the negative electrode, the extension portions are stacked and connected to each other to form the current collecting portion 35a, and the negative electrode tab 25 is connected to the current collecting portion 35a. The connection between the electrode tab and the current collector may be performed by welding, for example.

FIG. 4 is a cross-sectional view schematically showing the internal structure of the film-clad battery, in which a state in which the positive electrode 31 and the negative electrode 35 are stacked via the separator 38 is depicted. In an actual film-clad battery, a plurality of positive electrodes 31 and negative electrodes 35 are alternately stacked via separators 38.

For each element of the battery element, specifically, the following may be adopted.
<Separator>
As the separator in this embodiment, a separator having a melting point of 180 ° C. or higher and high air permeability is used. Specifically, the Gurley value (sec / 100 cc) is preferably 100 or less, more preferably 50 or less, and even more preferably 20 or less with respect to the air permeability.

Examples of materials having a melting point of 180 ° C. or higher include polyethylene terephthalate (PET), cellulose, aramid, polyimide, polyphenylene sulfide (PPS) and the like as polymer materials. Moreover, glass fiber is mentioned with an inorganic material.

A high air permeability separator made of a porous film, a woven fabric, or a nonwoven fabric made of these materials can be suitably used in the present invention. Among them, a separator made of woven fabric or non-woven fabric is particularly preferable because of high air permeability. Specifically, a glass fiber, an aramid fiber, a polyimide fiber, etc. are mentioned.

The separator may have a coat layer made of a material having higher heat resistance than the base material. As a material for the coating layer, a high heat resistant resin, an oxide such as aluminum, silicon, titanium, or a nitride can be used.

The thickness of the separator is preferably in the range of 12 μm to 40 μm, for example. When thickness is less than 12 micrometers, the intensity | strength of a separator falls and handleability at the time of manufacture etc. will fall. On the other hand, when the thickness exceeds 40 μm, the energy density of the battery is lowered. In particular, in the present invention, the redox shuttle agent is used, and the energy consumption effect by the shuttle agent is lowered. there is a possibility. This is due to the following reason. That is, the redox shuttle agent performs an oxidation-reduction reaction while repeating reciprocating movement between the positive electrode (reference numeral 31 in FIG. 4) and the negative electrode (reference numeral 35 in FIG. 4) in the electrolyte solution, so that the current during overcharge is reduced. Is to consume. Therefore, when the separator is too thick (in other words, the distance between the electrodes is increased), the movement / reaction of the redox shuttle agent between the electrodes is reduced, and as a result, the energy consumption effect of the shuttle agent is reduced. In view of the relationship between the shuttle agent and the separator thickness, the thickness of the separator is preferably 30 μm or less, and preferably 20 μm or less.

In the present invention, it is important that the redox shuttle agent moves and reacts in the separator between the electrodes. In order for the redox shuttle agent to reciprocate well between the electrodes and exert its effect, it is necessary that the thickness of the separator is not too thick and the air permeability of the separator is sufficiently high. Therefore, it is preferable that the separator has the above thickness and air permeability in that efficient energy consumption by the shuttle agent can be realized.

For the above characteristics, a parameter of “thickness” × “Gurley value” can be used as an index. As an example, this value is preferably in the range of 10 to 1500 (sec / 100 cc · μm), and more preferably in the range of 10 to 500 (sec / 100 cc · μm).

<Negative electrode>
The negative electrode has a negative electrode current collector formed of a metal foil, and a negative electrode active material coated on both surfaces of the negative electrode current collector. The negative electrode active material is bound so as to cover the negative electrode current collector with a negative electrode binder. The negative electrode current collector is formed to have an extension connected to the negative electrode terminal, and the negative electrode active material is not applied to the extension.

The negative electrode active material in the present embodiment is not particularly limited. For example, a carbon material that can occlude and release lithium ions, a metal that can be alloyed with lithium, a metal oxide that can occlude and release lithium ions, and the like. Is mentioned.

Examples of the carbon material include carbon, amorphous carbon, diamond-like carbon, carbon nanotube, or a composite thereof. Here, carbon with high crystallinity has high electrical conductivity, and is excellent in adhesiveness and voltage flatness with a negative electrode current collector made of a metal such as copper. On the other hand, since amorphous carbon having low crystallinity has a relatively small volume expansion, it has a high effect of relaxing the volume expansion of the entire negative electrode, and deterioration due to non-uniformity such as crystal grain boundaries and defects hardly occurs.

A negative electrode containing a metal or metal oxide is preferable in that it can improve the energy density and increase the capacity per unit weight or unit volume of the battery.

Examples of the metal include Al, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, and alloys of two or more thereof. Moreover, you may use these metals or alloys in mixture of 2 or more types. These metals or alloys may contain one or more non-metallic elements.

Examples of the metal oxide include silicon oxide, aluminum oxide, tin oxide, indium oxide, zinc oxide, lithium oxide, and composites thereof. In this embodiment, it is preferable that tin oxide or silicon oxide is included as a negative electrode active material, and it is more preferable that silicon oxide is included. This is because silicon oxide is relatively stable and hardly causes a reaction with other compounds. In addition, one or more elements selected from nitrogen, boron and sulfur may be added to the metal oxide, for example, 0.1 to 5% by mass. By carrying out like this, the electrical conductivity of a metal oxide can be improved.

Also, the negative electrode active material can be used by mixing a plurality of materials without using a single material. For example, the same kind of materials such as graphite and amorphous carbon may be mixed, or different kinds of materials such as graphite and silicon may be mixed.

The binder for the negative electrode is not particularly limited. For example, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, vinylidene fluoride-tetrafluoroethylene copolymer, styrene-butadiene copolymer Rubber, polytetrafluoroethylene, polypropylene, polyethylene, polyimide, polyamideimide, polyacrylic acid, or the like can be used. The amount of the binder for the negative electrode used is 0.5 to 25 parts by mass with respect to 100 parts by mass of the negative electrode active material from the viewpoints of “sufficient binding force” and “high energy” which are in a trade-off relationship. Is preferred.

As the negative electrode current collector, aluminum, nickel, stainless steel, chromium, copper, silver, and alloys thereof are preferable in view of electrochemical stability. Examples of the shape include foil, flat plate, and mesh.

<Positive electrode>
The positive electrode has a positive electrode current collector formed of a metal foil, and a positive electrode active material coated on both surfaces of the positive electrode current collector. The positive electrode active material is bound so as to cover the positive electrode current collector with a positive electrode binder. The positive electrode current collector is formed to have an extension connected to the positive electrode terminal, and the positive electrode active material is not applied to the extension.

The positive electrode active material is not particularly limited as long as it is a material that can occlude and release lithium, and can be selected from several viewpoints. From the viewpoint of increasing the energy density, it is preferable to include a high-capacity compound. Examples of the high-capacity compound include nickel-lithium oxide (LiNiO ₂ ) or lithium-nickel composite oxide obtained by substituting a part of nickel in nickel-lithium oxide with another metal element. The layered structure represented by the following formula (A) Lithium nickel composite oxide is preferred.

Li _y Ni _(1-x) M _x O ₂ (A)
(However, 0 ≦ x <1, 0 <y ≦ 1.2, and M is at least one element selected from the group consisting of Co, Al, Mn, Fe, Ti, and B.)

From the viewpoint of high capacity, the Ni content is high, that is, in the formula (A), x is preferably less than 0.5, and more preferably 0.4 or less. Examples of such compounds include Li _α Ni _β Co _γ Mn _δ O ₂ (0 ≦ α ≦ 1.2, preferably 1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.7, γ ≦ 0. .2), Li _α Ni _β Co _γ Al _δ O ₂ (0 ≦ α ≦ 1.2, preferably 1 ≦ α ≦ 1.2, β + γ + δ = 1, β ≧ 0.6, preferably β ≧ 0.7, γ ≦ 0.2), etc., especially LiNi _β Co _γ Mn _δ O ₂ (0.75 ≦ β ≦ 0.85, 0.05 ≦ γ ≦ 0.15, 0.10 ≦ δ ≦ 0.20). ). More specifically, for example, LiNi _0.8 Co _0.05 Mn _0.15 O ₂ , LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , LiNi _0.8 Co _0.15 Al _0.05 O _2, _LiNi 0.8 _Co 0.1 _Al can be preferably used 0.1 _{O 2} or the like.

From the viewpoint of thermal stability, it is also preferable that the Ni content does not exceed 0.5, that is, in the formula (A), x is 0.5 or more. It is also preferred that the number of specific transition metals does not exceed half. Such compounds include Li _α Ni _β Co _γ Mn _δ O ₂ (0 ≦ α ≦ 1.2, preferably 1 ≦ α ≦ 1.2, β + γ + δ = 1, 0.2 ≦ β ≦ 0.5, 0 0.1 ≦ γ ≦ 0.4, 0.1 ≦ δ ≦ 0.4). More specifically, LiNi _0.4 Co _0.3 Mn _0.3 O ₂ (abbreviated as NCM433), LiNi _1/3 Co _1/3 Mn _1/3 O ₂ , LiNi _0.5 Co _0.2 Mn _0.3 O ₂ (abbreviated as NCM523), LiNi _0.5 Co _0.3 Mn _0.2 O ₂ (abbreviated as NCM532), etc. (however, the content of each transition metal in these compounds varies by about 10%) Can also be included).

In addition, two or more compounds represented by the formula (A) may be used as a mixture. For example, NCM532 or NCM523 and NCM433 range from 9: 1 to 1: 9 (typically 2 It is also preferable to use a mixture in 1). Furthermore, in the formula (A), a material having a high Ni content (x is 0.4 or less) and a material having a Ni content not exceeding 0.5 (x is 0.5 or more, for example, NCM433) are mixed. As a result, a battery having a high capacity and high thermal stability can be formed.

Other than the above, as the positive electrode active material, for example, LiMnO ₂ , Li _x Mn ₂ O ₄ (0 <x <2), Li ₂ MnO ₃ , Li _x Mn _1.5 Ni _0.5 O ₄ (0 <x < 2) Lithium manganate having a layered structure or spinel structure such as LiCoO ₂ or a part of these transition metals replaced with another metal; Li in these lithium transition metal oxides more than the stoichiometric composition And those having an olivine structure such as LiFePO ₄ . Furthermore, a material in which these metal oxides are partially substituted with Al, Fe, P, Ti, Si, Pb, Sn, In, Bi, Ag, Ba, Ca, Hg, Pd, Pt, Te, Zn, La, etc. Can also be used. Any of the positive electrode active materials described above can be used alone or in combination of two or more.

Also, radical materials or the like can be used as the positive electrode active material.

As the positive electrode binder, the same as the negative electrode binder can be used. The amount of the positive electrode binder to be used is preferably 2 to 15 parts by mass with respect to 100 parts by mass of the positive electrode active material from the viewpoints of “sufficient binding force” and “high energy” which are in a trade-off relationship. .

As the positive electrode current collector, for example, aluminum, nickel, silver, or an alloy thereof can be used. Examples of the shape of the positive electrode current collector include a foil, a flat plate, and a mesh. As the positive electrode current collector, an aluminum foil can be suitably used.

<Electrolyte>
The electrolytic solution in the present embodiment is a non-aqueous electrolytic solution including a lithium salt (supporting salt) and a non-aqueous solvent that dissolves the supporting salt, and the ratio of the low boiling point solvent is set to be relatively low. It is preferable. This is because when gas is generated between the electrodes due to vaporization of the low boiling point solvent, the redox shuttle agent cannot move at that location, and energy consumption by the shuttle agent is not performed.

Specifically, the electrolyte solution preferably contains 20% by volume or more of a solvent having a boiling point of 160 ° C. or higher, and more preferably 30% or more when the volume of all the solvents is 100%. Preferably, it contains 50% or more.

Examples of the non-aqueous solvent include carbonic acid esters (chain or cyclic carbonates), carboxylic acid esters (chain or cyclic carboxylic acid esters), ethers (chain or cyclic ethers), or fluorine-substituted compounds thereof, phosphoric acid esters, and the like. Protic organic solvents can be used.

Examples of carbonate solvents include cyclic carbonates such as propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), and vinylene carbonate (VC); dimethyl carbonate (DMC), diethyl carbonate (DEC), and ethyl methyl carbonate. (EMC), chain carbonates such as dipropyl carbonate (DPC); and propylene carbonate derivatives.

Examples of the carboxylic acid ester solvent include aliphatic carboxylic acid esters such as methyl formate, methyl acetate, and ethyl propionate; and lactones such as γ-butyrolactone.

Among these, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), vinylene carbonate (VC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate Carbonic acid esters (cyclic or chain carbonates) such as (DPC) are preferred.

Examples of the phosphate ester include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, trioctyl phosphate, triphenyl phosphate, and the like.

Other solvents that can be contained in the non-aqueous electrolyte include, for example, ethylene sulfite (ES), propane sultone (PS), butane sultone (BS), dioxathilane-2,2-dioxide (DD), and sulfolene. 3-methylsulfolene, sulfolane (SL), succinic anhydride (SUCAH), propionic anhydride, acetic anhydride, maleic anhydride, diallyl carbonate (DAC), dimethyl 2,5-dioxahexanoate, 2,5 Dimethyl hexane hexanoate, furan, 2,5-dimethylfuran, diphenyl disulfide (DPS), dimethoxyethane (DME), dimethoxymethane (DMM), diethoxyethane (DEE), ethoxymethoxyethane, chloroethylene carbonate , Dimethyl ether, methyl Tyl ether, methyl propyl ether, ethyl propyl ether, dipropyl ether, methyl butyl ether, diethyl ether, phenyl methyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran (2-MeTHF), tetrahydropyran (THP), 1,4-dioxane (DIOX), 1,3-dioxolane (DOL), methyl acetate, ethyl acetate, propyl acetate, isopropyl acetate, butyl acetate, methyl difluoroacetate, methyl propionate, ethyl propionate, propyl propionate, methyl formate , Ethyl formate, ethyl butyrate, isopropyl butyrate, methyl isobutyrate, methyl cyanoacetate, vinyl acetate, diphe Rudisulfide, dimethyl sulfide, diethyl sulfide, adiponitrile, valeronitrile, glutaronitrile, malononitrile, succinonitrile, pimonitrile, suberonitrile, isobutyronitrile, biphenyl, thiophene, methyl ethyl ketone, fluorobenzene, hexafluorobenzene, glyme, ether, There are acetonitrile, propiononitrile, γ-butyrolactone, γ-valerolactone, dimethyl sulfoxide (DMSO) ionic liquid, phosphazene.

The fluorinated carbonate is represented by the formula (1). In the formula (1), R ₁ and R ₂ each independently represents an alkyl group or a fluorine-substituted alkyl group, and at least one of R ₁ and R ₂ Is a fluorine-substituted alkyl group. For example, there are bis (2,2,2-trifluoroethyl) carbonate in which a part of hydrogen in DEC is substituted with fluorine, and fluoroethylene carbonate (FEC) in which a part of hydrogen in EC is substituted with fluorine.

Specific examples of the fluorinated carboxylic acid ester include, for example, ethyl pentafluoropropionate, ethyl 3,3,3-trifluoropropionate, methyl 2,2,3,3-tetrafluoropropionate, acetic acid 2, 2-difluoroethyl, methyl heptafluoroisobutyrate, methyl 2,3,3,3-tetrafluoropropionate, methyl pentafluoropropionate, methyl 2- (trifluoromethyl) -3,3,3-trifluoropropionate , Ethyl heptafluorobutyrate, methyl 3,3,3-trifluoropropionate, 2,2,2-trifluoroethyl acetate, isopropyl trifluoroacetate, tert-butyl trifluoroacetate, 4,4,4-trifluorobutyric acid Ethyl,

methyl

4,4,4-trifluorobutyrate, 2,2-difluoroacetic acid Chill, ethyl difluoroacetate, n-butyl trifluoroacetate, 2,2,3,3-tetrafluoropropyl acetate, ethyl 3- (trifluoromethyl) butyrate, methyl tetrafluoro-2- (methoxy) propionate, 3, 3,3-trifluoropropionic acid 3,3,3 trifluoropropyl, methyl difluoroacetate, 2,2,3,3-tetrafluoropropyl trifluoroacetate, 1H, 1H-heptafluorobutyl acetate, methyl heptafluorobutyrate, Examples thereof include ethyl trifluoroacetate and ethyl 3,3,3-trifluoropropionate.

The chain fluorinated ether compound is represented by the formula (2). In the formula (2), R _a and R _b each independently represents an alkyl group or a fluorine-substituted alkyl group, and at least one of Ra and Rb Is a fluorine-substituted alkyl group. For example, CF ₃ OCH ₃ , CF ₃ OC ₂ H ₆ , F (CF ₂ ) ₂ OCH ₃ , F (CF ₂ ) ₂ OC ₂ H ₅ , F (CF ₂ ) ₃ OCH ₃ , F (CF ₂ ) ₃ OC _{_{_{2 H 5, F (CF 2}}} ) 4 OCH 3, F (CF 2) 4 OC 2 H 5, F (CF 2) 5 OCH 3, F (CF 2) 5 OC 2 H 5, F (CF 2) 8OCH _{_{3, F (CF 2) 8OC}} 2 H 5, F (CF 2) 9OCH 3, CF 3 CH 2 OCH 3, CF 3 CH 2 OCHF 2, CF 3 CF 2 CH 2 OCH 3, CF 3 CF 2 CH 2 OCHF ₂ , CF ₃ CF ₂ CH ₂ O (CF ₂ ) ₂ H, CF ₃ CF ₂ CH ₂ O (CF ₂ ) ₂ F, HCF ₂ CH ₂ OCH ₃ , H (CF ₂ ) ₂ OCH ₂ CH ₃ , H ( _{_{_{_{CF 2) 2 OCH 2 CF 3}}}} , H (CF 2) 2 CH 2 OCHF 2, H (CF 2) 2 CH 2 O (CF 2) 2 H, H (CF 2) 2 CH 2 _{_{(CF 2) 3 H, H}} (CF 2) 3 CH 2 O (CF 2) 2 H, (CF 3) 2 CHOCH 3, (CF 3) 2 CHCF 2 OCH 3, CF 3 CHFCF 2 OCH 3, CF 3 CHFCF ₂ OCH ₂ CH ₃ , CF ₃ CHFCF ₂ CH ₂ OCHF ₂ , H (CF ₂ ) ₂ CH ₂ OCF ₂ CHFCF ₃ , CHF ₂ —CH ₂ —O—CF ₂ CFH—CF ₃ , F (CF ₂ ) ₂ such as CH _₂ OCF ₂ CFHCF ₃ and the like.

As the supporting salt in the present embodiment, LiPF ₆ , LiAsF ₆ , LiAlCl ₄ , LiClO ₄ , LiBF ₄ , LiSbF ₆ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN ( CF ₃ SO _{₂₎ 2} normal lithium salt which can be used in lithium ion batteries or the like can be used. The supporting salt can be used alone or in combination of two or more.

<Redox shuttle agent>
As the redox shuttle agent, a compound that can be uniformly dissolved or dispersed in the non-aqueous electrolyte and has an oxidation potential higher than the maximum (SOC 100%) potential normally used for the positive electrode active material is used. it can. However, the redox shuttle agent is preferably selected as appropriate according to the maximum potential used by the positive electrode active material. The oxidation potential of the redox shuttle agent is preferably 0.1 to 2 V higher than the maximum potential of the positive electrode, and more preferably 0.2 to 1 V higher. When the oxidation potential of the redox shuttle agent is within the above range, the reaction of the redox shuttle agent can be suppressed when the secondary battery is operated at a normal voltage, and the redox shuttle agent can be quickly reduced in the event of an abnormality such as overcharge. The shuttle agent reacts to stop the operation of the secondary battery.

Examples of redox shuttle agents include aromatic compounds, heterocyclic complexes, metallocene complexes such as ferrocene, Ce compounds, and radical compounds. Moreover, a redox shuttle agent can also be used individually by 1 type, or can also be used in combination of 2 or more type.

Specific examples of the compound include 3,4-difluoroanisole, 2,4-difluoroanisole, 1-methoxy-2,3,4,5,6-pentafluorobenzene, 2,3,5,6-tetra Fluoroanisole, 4- (trifluoromethoxy) anisole, 3,4-dimethoxybenzonitrile, 1,2,3,4-tetrachloro-5,6-dimethoxybenzene, 1,2,4,5-tetrachloro-3 , 6-Dimethoxybenzene 4-fluoro-1,2-dimethoxybenzene, 4-bromo-1,2-dimethoxybenzene, 2-bromo-1,4-dimethylbenzene, 1-bromo-3-fluoro-4-methoxybenzene 2-bromo-1,3-difluoro-5-methoxybenzene, 4,5-difluoro-1,2-dimethoxybenzene, 2,5-diflu B-1,4-dimethoxybenzene, 1,2,3,4-tetrachloro-5,5-dimethoxycyclopentadiene, 1,2,4-trimethoxybenzene, 1,2,3-trimethoxybenzene, 2, 5-di-tert-butyl-1,4-dimethoxybenzene, 4-tert-butyl-1,2-dimethoxybenzene, 1,4-ditetrabutyl-2,5-trifluoromethoxybenzene, 1,2-ditetrabutyl-4 Monocyclic compounds having one or more electron-withdrawing or electron-donating substituents such as 4-chloro-1,2-methylenedioxybenzene, 4-bromo-1 , 2-methylenedioxybenzene, 3,4-methylenedioxybenzonitrile, 4-nitro-1,2-methylenedioxybenzene, 2-chloro- -A heterocyclic compound such as methoxypyrazine; a radical compound such as a nitroxyl radical compound; a cerium compound such as cerium nitrate; a metallocene complex such as a ferrocene complex; it can.

Of these, aromatic compounds (methoxybenzenes and dimethoxybenzenes) having one or more alkoxy groups can be preferably used. Since these compounds are excellent in the chemical stability of the oxidant produced by the oxidation reaction, it is possible to suppress a decrease in battery performance due to side reactions or the like. Moreover, the compound which has a halogen atom can be used more preferably. Such a compound can be applied to a positive electrode having a high oxidation potential and a higher redox potential, that is, a secondary battery having a higher energy density.

<Battery capacity>
In one embodiment, the battery capacity of the film-clad battery is preferably 4 Ah or more, more preferably 6 Ah or more, and further preferably 8 Ah or more. A large battery capacity means a large charging current at the time of charging. When charging is performed with a large current, the battery tends to be hot. Therefore, the technical idea of the present invention can be particularly suitably applied to such a large film-clad battery.

<Viewpoint of heat dissipation>
If the heat dissipation of the film-clad battery is too high, the battery will not rise to a predetermined temperature (the trigger temperature at which the safety mechanism operates) unless the charging voltage is increased to some extent. From the viewpoint of safety, it is preferable to raise the battery to a predetermined temperature and operate the safety mechanism while the voltage is relatively low (in other words, in a relatively safe state). Based on this concept, it is also preferable to design the heat dissipation of the film-clad battery to be relatively low. Therefore, the surface area per capacity of the battery may be set to 5000 mm ² / Ah or less, preferably 4000 mm ² / Ah or less, more preferably 2500 mm ² / Ah or less.

In addition, said "surface area" means the surface area (a seal part of a peripheral part is included) of a film exterior body. In the film outer package, the end face of the film also has an area, but since the proportion of the entire surface area is extremely small, the area of the end face may not be included in the “surface area”.

2. Storage of Film-Exterior Battery in Container FIG. 5 shows an example of a battery module using the film-exterior battery of the present embodiment. The battery module 1 includes one or a plurality of film-clad batteries 50 and a module container 71 that accommodates them.

The module container 71 may be configured as a hard case, and the material may be any of resin, metal, a combination thereof, and the like. The module container 71 may be made of a nonflammable material. As an example, the module container 71 may be configured as an incombustible container such as an aluminum alloy.

The arrangement of the film-clad battery 50 in the container is not particularly limited, and various arrangements can be made. For example, it may be arranged in a single layer state as shown in FIG. Or you may arrange | position in the lamination | stacking state like FIG.5 (b). With respect to the orientation of the film-clad battery 50, the battery module 1 may be in an orientation when in use, such that the film-clad battery 50 may be substantially horizontal (horizontal placement), or may be substantially vertical (vertical placement). Or may be inclined or a combination thereof.

Furthermore, the battery module 1 according to one embodiment of the present invention includes pressing members 61 and 62 (see FIG. 5A) for pressing the battery in the thickness direction in order to prevent the film-clad battery 50 from expanding. It may be a thing. The holding

members

61 and 62 may have any size and shape as long as they have a pressing surface for pressing at least a part of the outer surface of the film-clad battery 50. The pressing surface may be such that it entirely contacts the outer surface of the film-clad battery (precisely, the flat surface of the raised portion corresponding to the shape of the battery element). The pressing surface is formed as a flat surface by way of example. As a specific example, the

pressing members

61 and 62 may be plate members. As an embodiment, the pressing surface may be formed in an uneven shape.

The

pressing members

61 and 62 do not necessarily have to be pressed against the film-clad battery 50 (biased by a biasing member such as a spring). In the initial state, the

pressing members

61 and 62 are simply in contact with or close to the film-clad battery 50, and when the film-clad battery 50 begins to expand, they are in close contact to prevent further deformation of the battery. If it is. Even if it is such a structure, it is because the expansion | swelling of the electrode laminated body inside a battery accompanying gas generation mentioned later can be prevented.

In the case of the battery arrangement as shown in FIG. 5B, one pressing member 62 may be disposed between the film-clad

batteries

50 and 50, and the

pressing members

61 and 63 may be disposed on both sides thereof. Regarding the shape and the like of the pressing member 63, the above description regarding the

pressing members

61 and 62 can be used as it is. In the above description, the configuration in which the pressing members are arranged on both sides of the film-clad battery 50 has been described, but one or both are omitted and the outer surface of the film-clad battery 50 is pressed by the inner surface of the module container 71. It is also possible.

By providing the

pressing members

61 and 62 as described above, the outer surface of the film exterior battery 50 is pressed by the

pressing members

61 and 62 when the expansion of the film exterior body 10 starts, thereby The deformation of the electrode laminate (battery element 20 in FIG. 2) inside the battery is prevented. If no member for constraining the outer shape of the film-clad battery 50 is provided, the film-clad body 10 and the battery element 20 can expand to some extent freely. For example, the distance between the electrodes is increased by the gas generated between the electrodes. There is also the possibility of spreading. An increase in the distance between the electrodes means that the energy consumption function of the redox shuttle agent in that portion is reduced. On the other hand, when a pressing member that holds the outer surface of the film-clad battery 50 and prevents deformation is provided as in this embodiment, the distance between the electrodes is within a predetermined range even in a situation where gas is generated. Therefore, the energy consumption function by the redox shuttle agent can be kept good. The pressing member may be a member whose pressing surface abuts against the entire outer surface (maximum area surface) of the film exterior body, but as another aspect, for example, 50% or more of the same surface, preferably It may be one that suppresses an area of 75% or more.

In FIG. 5, as an example, it is illustrated that both sides of the vertically mounted film-covered battery 50 are held by pressing

members

61, 62, etc., but the film-covered battery 50 can be pressed from the outside to prevent its expansion. As long as it is a thing, various other mechanisms are employable.

FIG. 6 schematically shows a mechanism for applying pressure to the film-clad battery 50. Specifically, the film-clad battery 50 is disposed on the first member 65, and the second member 69 that holds the battery is disposed on the film-clad battery 50. In FIG. 6, the film-clad battery 50 is placed horizontally, but here, it is not an essential difference whether the battery is placed horizontally or vertically. It is a more important point whether to do or to energize.

As the member corresponding to the first member 65, for example, a module case, another laminated film battery, or a base member constituting a part of a device on which the battery is mounted may be used.

As what corresponds to the 2nd member 69, the other film-clad battery laminated | stacked, the pressing member which presses a film-clad battery, etc. may be sufficient, for example, it is a film using together biasing means, such as a spring. It is also preferable that the outer battery is pressed. In addition, when laminating | stacking a film-clad battery, since a lower film-clad battery will be pressed by the dead weight of a battery, it may not be necessary to use an urging means together.

In addition, it is good also as a structure which presses both a 1st member and a 2nd member with respect to a battery. On the other hand, in the initial state, the first member and / or the second member are not in close contact with the film-clad battery (for example, arranged with a slight gap), It is good also as a structure which closely_contact | adheres when a battery begins to expand | swell, and fulfill | performs the function as a pressing member substantially.

According to the film-clad battery according to an embodiment of the present invention configured as described above, (i) since the redox shuttle agent is included in the electrolyte, the battery is in a charged state that causes overcharge. Even in such a case, excessive current is consumed by the action of the redox shuttle agent, so that the positive electrode active material is not overcharged.
(Ii) Even if the electrolyte becomes hot due to the operation of the redox shuttle agent, the separator has a melting point of 180 ° C. or higher, so that the separator is not deformed or melted. Safety is ensured without a short circuit.
(Iii) Furthermore, since the separator has a Gurley value of air permeability of 100 (sec / 100 cc) or less, the redox shuttle agent operates well in the separator and can consume excessive current well. .

Although several configurations as one aspect of the present invention have been described above, the items (technical features) described above can be combined as appropriate without departing from the scope of the present invention.

Hereinafter, the embodiments of the present invention will be specifically described by way of examples, but the present invention is not limited to these examples.

(Example 1)
<Negative electrode>
Natural graphite was used as the negative electrode active material. 96: 2: 1: This negative electrode active material, styrene-butadiene copolymer rubber (SBR) as a negative electrode binder, carboxymethyl cellulose (CMC) as a thickener, and acetylene black as a conductive auxiliary material. Weighed at a mass ratio of 1. In addition, as SBR, the rubber particle dispersion (solid content 40 mass%) was used, and it measured and used so that the solid content of the binder might become the said mass ratio.

And these were mixed with water and the negative electrode slurry was prepared. After applying the negative electrode slurry to a copper foil having a thickness of 10 μm, it was dried by performing a heat treatment at 80 ° C. for 8 hours in a nitrogen atmosphere. The obtained negative electrode was stored in an environment with a dew point of −10 ° C. for 3 hours to obtain a negative electrode.

<Positive electrode>
LiNi _0.8 Co _0.15 Al _0.05 O ₂ was used as the positive electrode active material. This positive electrode active material, carbon black as a conductive auxiliary material, and polyvinylidene fluoride as a positive electrode binder were weighed at a mass ratio of 90: 5: 5. These were mixed with N-methylpyrrolidone to prepare a positive electrode slurry. The positive electrode slurry was applied to an aluminum foil having a thickness of 20 μm, dried, and further pressed to produce a positive electrode.

<Separator>
Aramid having a nonwoven fabric structure with a thickness of 25 μm, a porosity of 70%, and a Gurley value of 1.4 seconds / 100 cc was used. The thermal decomposition temperature of aramid is 400 ° C. or higher.

<Electrode laminate>
The obtained positive electrode and negative electrode were laminated via a separator. The ends of the positive electrode current collector not covered with the positive electrode active material and the negative electrode current collector not covered with the negative electrode active material were welded. Furthermore, the positive electrode terminal made from aluminum and the negative electrode terminal made from nickel were each welded to the welding location, and the electrode laminated body which has a planar laminated structure was obtained. The number of layers was adjusted so that the initial charge capacity of the cell was 10 Ah.

<Electrolyte>
A mixed solvent of EC and DEC (volume ratio: EC / DEC = 30/70) was used as the non-aqueous solvent. Into this, LiPF ₆ as a supporting salt was added so that the concentration in the electrolyte was 1M. Further, 1,2-difluoro-4,5-dimethoxybenzene was added as a redox shuttle agent so that the concentration in the electrolytic solution was 0.1 M, to prepare an electrolytic solution.

<Secondary battery>
The electrode laminate was accommodated in an aluminum laminate film as an exterior body, and an electrolyte solution was injected into the exterior body. Thereafter, the outer package was sealed while reducing the pressure to 0.1 atm, and a lithium ion secondary battery was produced. The surface area of the secondary battery was 36000 mm ² .

<Evaluation>
(Overcharge test)
An overcharge test in which the manufactured secondary battery was charged at a constant current up to 10 V at 1 C was performed. The test was performed in a state where the battery laminate was fixed at a fixed size according to the thickness of the battery with a flat pressing plate. Prior to the test, no pressure was applied to the laminate by the pressing plate. Table 1 summarizes the maximum temperature reached on the cell surface and the presence or absence of smoke from the secondary battery.

(Example 2)
Aramid having a microporous structure having a thickness of 15 μm, a porosity of 65%, and a Gurley value of 90 seconds / 100 cc was used as a separator. Other than that, a secondary battery was prepared and evaluated in the same procedure as in Example 1. The results are shown in Table 1.

(Example 3)
As the separator, cellulose having a nonwoven fabric structure with a thickness of 25 μm, a porosity of 70%, and a Gurley value of 2.2 seconds / 100 cc was used. Other than that, a secondary battery was prepared and evaluated in the same procedure as in Example 1. The thermal decomposition temperature of cellulose is about 300 ° C. The results are shown in Table 1.

Example 4
A microporous polyimide having a thickness of 20 μm, a porosity of 80%, and a Gurley value of 60 seconds / 100 cc was used as a separator. Other than that, a secondary battery was prepared and evaluated in the same procedure as in Example 1. The thermal decomposition temperature of polyimide is about 500 ° C. or higher. The results are shown in Table 1.

(Comparative Example 1)
As the separator, polypropylene having a nonwoven fabric structure having a thickness of 25 μm, a porosity of 70%, and a Gurley value of 1.7 seconds / 100 cc was used. Other than that, a secondary battery was prepared and evaluated in the same procedure as in Example 1. The melting point of polypropylene is 160 ° C. The results are shown in Table 1.

(Comparative Example 2)
A microporous polypropylene having a thickness of 25 μm, a porosity of 55%, and a Gurley value of 200 seconds / 100 cc was used as a separator. Other than that, a secondary battery was prepared and evaluated in the same procedure as in Example 1. The results are shown in Table 1.

(Comparative Example 3)
Aramid having a microporous structure having a thickness of 45 μm, a porosity of 65%, and a Gurley value of 270 seconds / 100 cc was used as a separator. Other than that, a secondary battery was prepared and evaluated in the same procedure as in Example 1. The results are shown in Table 1.

As shown in Table 1, in the secondary battery (Comparative Examples 1 and 2) having a polypropylene separator having a melting point of 160 ° C., the cell surface temperature rose to about 270 ° C., and smoke was seen from the laminate outer package. It was. This is because the internal temperature of the cell reached 160 ° C., the separator melted and contracted, and the positive and negative electrodes were short-circuited.

Further, even in the case of an aramid microporous separator having a thermal decomposition temperature exceeding 400 ° C., in the secondary battery having a film thickness of 45 μm and a Gurley value of 270 seconds / 100 cc (Comparative Example 3), the cell surface temperature Rose to 280 ° C., and smoke was seen from the laminate outer package. This is because the operability of the redox shuttle agent is reduced due to the increase in the film thickness and the Gurley value, the positive electrode is overcharged, and thermal runaway occurs.

On the other hand, a secondary battery (Examples 1 and 2) including a separator made of aramid having a pyrolysis temperature exceeding 400 ° C. and having a Gurley value of 100 seconds / 100 cc or less, or cellulose having a pyrolysis temperature of about 300 ° C. In a secondary battery comprising a separator made of (Example 3) and a secondary battery comprising a polyimide separator having a thermal decomposition temperature of 500 ° C. or higher, the ultimate temperature is only about 130 ° C., and smoke is seen from the laminate outer package. I couldn't. This is presumably because the short circuit between the positive and negative electrodes was suppressed because the redox shuttle agent normally consumed current and the separator did not melt or shrink.

(Appendix)
The present application discloses the following inventions.
1. A battery element having a positive electrode and a negative electrode laminated via a separator, a non-aqueous electrolyte containing a lithium salt, and a film outer package containing them,
a: The non-aqueous electrolyte contains a redox shuttle agent that consumes excess energy when overcharged,
b: The separator is
(B1) Its melting point is 180 ° C. or higher,
(B2) A film-clad battery having a Gurley value of 100 [sec / 100 cc] or less.
Note that the separator may be “whose melting point or thermal decomposition temperature is 180 ° C. or higher” instead of “the melting point is 180 ° C. or higher”.

2. 2. The film-clad battery according to 1 above, wherein the separator has a thickness in the range of 12 μm to 40 μm.

3. 3. The film-clad battery according to 1 or 2, wherein the separator is a woven fabric or a nonwoven fabric.

4). 4. The film-clad battery according to 3 above, wherein the separator is selected from glass fiber, aramid fiber, and polyimide fiber.

5. 5. The film-clad battery according to any one of 1 to 4 above, wherein the surface area of the film-clad body per capacity is 5000 mm ² / Ah or less.

6). 6. The film-clad battery according to any one of 1 to 5 above, having a capacity of 4 Ah or more.

7). A battery module comprising the film-clad battery according to any one of 1 to 6 above and a module container that accommodates the battery (also referred to as “assembled battery”).

8). Further, a pressing member (61, 62, etc.) that is disposed in contact with or close to the film-clad battery and that prevents the battery element from being deformed by pressing the battery from the outside when gas is generated inside the battery. 8. The battery module according to 7 above.

The secondary battery according to one embodiment of the present invention can be used in, for example, all industrial fields that require a power source. As an example, it can be used as a power source for mobile devices such as mobile phones and laptop computers; it can be used as a power source for electric vehicles such as electric cars, hybrid cars, electric bikes, and electric assist bicycles; transport for transportation such as trains, satellites, and submarines It can be used as a power source for mediums; it can be used as a power storage system for storing electric power.

DESCRIPTION OF SYMBOLS 1 Battery module 10 Film exterior body 11, 12 Film 15 Heat welding part 18 Gas discharge | release mechanism 20

Battery element

21, 25 Electrode tab 31 Positive electrode 35 Negative electrode 31a, 35b Current collector 38 Separator 50 Film exterior battery 61-63

Holding member

65, 69 member 71 module case

Claims

A battery element having a positive electrode and a negative electrode laminated via a separator;
A non-aqueous electrolyte containing a lithium salt;
A film exterior body for housing them,
a: the non-aqueous electrolyte includes a redox shuttle agent that consumes excess energy when overcharged;
b: The separator is
(B1) Its melting point is 180 ° C. or higher,
(B2) Gurley value is 100 [sec / 100cc] or less,
Film outer battery.
2. The film-clad battery according to claim 1, wherein the separator has a thickness in the range of 12 μm to 40 μm.
The film-clad battery according to claim 1 or 2, wherein the separator is a woven fabric or a non-woven fabric.
The film-clad battery according to claim 3, wherein the separator is selected from glass fiber, aramid fiber, and polyimide fiber.
The film-clad battery according to any one of claims 1 to 4, wherein the surface area of the film-clad body per capacity is 5000 mm 2 / Ah or less.
The film-clad battery according to any one of claims 1 to 5, having a capacity of 4 Ah or more.
The film-clad battery according to any one of claims 1 to 6,
A module container for housing it,
A battery module comprising:
further,
It is disposed in contact with or close to the film-clad battery, and includes a pressing member that prevents the battery element from being deformed by pressing the battery from the outside when gas is generated inside the battery.
The battery module according to claim 7.