JP2002373704A - Nonaqueous electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery having high security and high battery performance. SOLUTION: The nonaqueous electrolyte secondary battery comprises generating elements wrapped in a jacket, the generating elements including a nonaqueous electrolyte having a cold molten salt, a positive electrode, a negative electrode and a separator. The cold molten salt is composed of a quaternary ammonium organic cation represented by the formula 1 or 2 and an anion consisting solely of nonmetallic elements. The nonaqueous electrolyte contains a lithium salt in a concentration of 0.5 mol/l or more, the lithium salt being composed of lithium ion and an anion consisting solely of nonmetallic elements. The nonaqueous electrolyte contains a cyclic ester having a π-bond.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte battery containing a room temperature molten salt in an electrolyte, and to an improvement of the non-aqueous electrolyte.

[0002]

2. Description of the Related Art In recent years, non-aqueous electrolyte batteries using various non-aqueous electrolytes capable of obtaining a high energy density have been developed as power supplies for electronic equipment, power storage, and power supplies for electric vehicles, which have been improved in performance and miniaturization. Attention has been paid.

In general, a non-aqueous electrolyte battery uses a lithium metal oxide for a positive electrode, a lithium metal or a lithium alloy or a carbonaceous material for absorbing and releasing lithium ions for a negative electrode, and a lithium salt for a liquid organic solvent at room temperature for an electrolyte. Is used. Examples of the organic solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, γ-butyrolactone,
Examples include propiolactone, valerolactone, tetrahydrofuran, dimethoxyethane, diethoxyethane, methoxyethoxyethane, and the like.

[0004] However, the above-mentioned organic solvents are all classified as flammable substances, are easily volatilized, and have high flammability. Therefore, especially for relatively large non-aqueous electrolyte batteries used for power storage power supplies, electric vehicle power supplies, and the like, sufficient safety is ensured at the time of abuse such as overcharging, overdischarging or short-circuit, or in a high temperature environment. It wasn't.

Therefore, non-aqueous electrolyte batteries which do not contain a flammable substance such as an organic solvent as a main component and are excellent in safety are disclosed in JP-A-4-349365, JP-A-10-92467, and JP-A-11-86905. Publication, Japanese Patent Application Laid-Open No. 11-2
No. 60400 proposes a non-aqueous electrolyte battery using a room temperature molten salt having a lithium salt and a quaternary ammonium organic cation as an electrolyte. The room temperature molten salt shown in the above publication has almost no volatility while being liquid at room temperature, and has flame retardancy or noncombustibility.
A battery with excellent safety can be provided.

[0006]

However, the above-described nonaqueous electrolyte battery has the following problems. That is, the operating potential of the negative electrode material of the nonaqueous electrolyte lithium secondary battery is generally the metal lithium potential (in the case of an aqueous solution, -3.
045V vs. 045V NHE) and very lowly. However, room-temperature molten salts having quaternary ammonium organic cations generally have a relatively noble reduction potential, so that quaternary ammonium organic cations and the like in the electrolyte are reductively decomposed, resulting in low charge / discharge efficiency and low charge / discharge efficiency. This was a cause of deterioration in cycle characteristics.

Japanese Patent Application Laid-Open No. 4-349365 discloses a non-aqueous electrolyte battery using a room-temperature molten salt having aluminum halide ions. However, this battery has the following problems. That is, there is a problem that the corrosiveness of aluminum halide ions (for example, AlCl ₄ ⁻ ) deteriorates battery performance. In addition, since aluminum halide generally has severe reactivity, there is a problem in that it is difficult to handle during production, which leads to an increase in production cost.

The present invention has been made in view of the above problems, and has as its object to provide a non-aqueous electrolyte battery having high safety and high battery performance.

[0009]

In order to solve the above-mentioned problems, the present invention provides a power generating element comprising a non-aqueous electrolyte having a normal temperature molten salt, a positive electrode, a negative electrode, and a separator, as described in claim 1. In the non-aqueous electrolyte battery included in the material, the room-temperature molten salt comprises at least a quaternary ammonium organic cation having a skeleton represented by the following formula (1):
Formed with an anion consisting only of a non-metallic element, and
The non-aqueous electrolyte has a lithium salt formed of lithium ions and an anion consisting of only a non-metallic element of 0.5 m
The non-aqueous electrolyte battery is contained at a concentration of ol / l or more, and the non-aqueous electrolyte contains a cyclic ester having a π bond.

[0010]

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According to such a configuration, the non-aqueous electrolyte comprises:
Since it contains a room temperature molten salt having a quaternary ammonium organic cation as a main component, it has a property of a room temperature molten salt such as being liquid at room temperature, having little volatility, and having flame retardancy or nonflammability. It will surely be prepared. Therefore, a battery provided with such a non-aqueous electrolyte is excellent in safety at the time of abuse such as overcharging, overdischarging or short-circuit, and safety under a high temperature environment.

Further, since the anions forming the molten salt at room temperature consist only of non-metallic elements and do not contain highly corrosive aluminum halide ions or the like, deterioration of battery performance due to the corrosiveness and handling during manufacture are also considered. The difficulty does not arise. In addition, since the lithium salt is formed using an anion consisting of only the nonmetallic element, even when the lithium salt that is solid at room temperature coexists with the molten salt at room temperature, the nonaqueous electrolyte containing both is solid. Since the characteristics of the room-temperature molten salt that is liquid at room temperature are reliably maintained without any risk of being converted, the non-aqueous electrolyte containing the room-temperature molten salt suitably maintains a liquid state.

[0013] Further, by incorporating a lithium salt into the non-aqueous electrolyte, the reduction potential as a non-aqueous electrolyte is low even when a room temperature molten salt having a quaternary ammonium organic cation whose reduction potential is generally relatively noble is used. The phenomenon of shifting to a high potential is observed. In the present invention, since the non-aqueous electrolyte contains the lithium salt in an amount of 0.5 mol / l or more, the reduction potential of the non-aqueous electrolyte is shifted to a potential equal to or lower than the potential of metallic lithium. For this reason, reductive decomposition of quaternary ammonium organic cations and the like in the non-aqueous electrolyte is prevented, so that a high charge / discharge efficiency is obtained and a battery having excellent charge / discharge cycle characteristics can be provided.

When the content of the lithium salt in the non-aqueous electrolyte is less than 0.5 mol / l, the shift of the reduction potential of the non-aqueous electrolyte is not sufficient, and the effect of the present invention can be sufficiently obtained. Can not. Conversely, when the content of the lithium salt in the non-aqueous electrolyte exceeds 3 mol / l, the melting point of the non-aqueous electrolyte increases, and it is difficult to maintain a liquid state at normal temperature. Therefore, the content of lithium ions in the non-aqueous electrolyte is 0.1%.
It is preferably in the range of 5 to 3 mol / l, and more preferably in the range of 0.5 to 2 mol / l.

Further, the non-aqueous electrolyte used in the battery of the present invention can further contain a cyclic ester having a π bond, thereby lowering the viscosity and freezing point of the non-aqueous electrolyte. In addition to improving the low-temperature characteristics, a part of the cyclic ester is reduced during the initial charge of the battery, and a lithium ion-permeable protective film is formed on the surface of the negative electrode material. Reductive decomposition of organic cations is suppressed, and charge / discharge efficiency can be improved. Further, since the cyclic ester has an effect of accelerating the dissociation of the lithium salt, the ratio of the lithium salt existing in an ionic state is increased, and various performances of the battery can be further improved. However, since the cyclic ester having a π bond is flammable as described above, if the amount added is too large, the nonaqueous electrolyte may be flammable, and not only may the safety be insufficient, but also the positive electrode side , It may be oxidatively decomposed to deteriorate battery performance, which is not preferable. Therefore, in consideration of compatibility between battery performance and safety, the content of the cyclic ester having a π bond in the nonaqueous electrolyte is preferably in the range of 1 to 10% by volume, and more preferably in the range of 1 to 5% by volume. It is preferable that

A room temperature molten salt is a salt that is at least partially liquid at room temperature. The normal temperature is a temperature range in which the battery is assumed to normally operate. The upper limit is about 100 ° C, and in some cases, about 60 ° C, and the lower limit is −50 ° C.
About -20 ° C in some cases.

On the other hand, "Molten salt and heat technology research group.
Fundamentals of Thermal Technology, Agne Technology Center, 1993, 313p. (ISBN
4-900041-24-6)), an inorganic molten salt such as Li ₂ CO ₃ —Na ₂ CO ₃ —K ₂ CO ₃ used for various electrodepositions has a melting point of 300 ° C. Most of the above are not present in a liquid state within a temperature range in which the battery is normally expected to operate, and are not included in the room temperature molten salt in the present invention.

Examples of the quaternary ammonium organic cation having a skeleton represented by Chemical Formula 1 include imidazolium ions such as dialkyl imidazolium ion and trialkyl imidazolium ion, tetraalkyl ammonium ion, pyridinium ion, pyrazolium ion, and pyrrolium ion. Ion, pyrrolium ion, pyrrolidinium ion, piperidinium ion and the like. In particular, either an imidazolium cation having a skeleton represented by (Chemical Formula 2) or a pyridinium cation having a skeleton represented by (Chemical Formula 3) is preferable.

The tetraalkylammonium ion includes, but is not limited to, trimethylethylammonium, trimethylpropylammonium, trimethylhexylammonium, tetrapentylammonium, and the like.

The anion consisting only of a nonmetallic element refers to an anion that is not an anion containing a metallic element, such as an aluminum halide ion. Specific examples of the combination in which a quaternary ammonium organic cation and an anion consisting only of a nonmetal element form a room-temperature molten salt include the combinations shown in the following (1) to (4). It is not limited. (1) A combination of an N-butylpyridinium cation, a tetrafluoroborate anion (BF ₄ ⁻ ), a trifluoromethanesulfonic acid anion (CF ₃ SO ₃ ⁻ ), and the like. (2) Trimethylhexylammonium cation and trifluoromethanesulfonylamide anion (N (C
^{_{F 3 SO 2) 2 -)}} , bis pentafluoroethane sulfonyl amide anion _{(N (C 2 F 5 SO} 2) 2 -) combined with such. (3) 1-ethyl-3-methylimidazolium cation, tetrafluoroborate anion (BF ₄ ⁻ ), trifluoromethanesulfonate anion (CF ₃ SO ₃ ⁻ ), trifluoromethanesulfonylamide anion (N (C
^{_{F 3 SO 2) 2 -)}} , bis pentafluoroethane sulfonyl amide anion _{(N (C 2 F 5 SO} 2) 2 -) combined with such. (4) A combination of a 1-methyl-3-butylimidazolium cation, a tetrafluoroborate anion (BF ₄ ⁻ ), a hexafluorophosphate anion (PF ₆ ⁻ ), and the like.

The anion of the lithium salt contained in the nonaqueous electrolyte of the battery of the present invention may be the same as or different from the anion of the room temperature molten salt. That is, as the lithium salt, for example, LiBF ₄ , LiPF ₆ , LiClO ₄ , L
iCF ₃ SO ₃ , 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 ), L
Examples thereof include iC (CF ₃ SO ₂ ) ₃ and LiC (C ₂ F ₅ SO ₂ ) ₃ , but are not limited thereto. Among them, LiBF ₄ is preferable. These may be used alone or as a mixture of two or more.

The cyclic ester having a π bond refers to a cyclic ester having an unsaturated bond or an aromatic ring in the molecule. In particular, a cyclic carbonate having an unsaturated bond or an aromatic ring in the molecule is preferable, and examples thereof include vinylene carbonate, styrene carbonate, vinylethylene carbonate, 1-phenylvinylene carbonate, and 1,2-diphenylvinylene carbonate. Among them, vinylene carbonate and styrene carbonate are preferred. These may be used alone or as a mixture of two or more.

The non-aqueous electrolyte of the battery of the present invention may be used by adding an organic solvent which is liquid at normal temperature, in addition to a lithium salt, a normal temperature molten salt and a cyclic ester having a π bond. Here, as the organic solvent, an organic solvent generally used for an electrolyte for a non-aqueous electrolyte battery can be used. Examples include, but are not limited to, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, diphenyl carbonate, tetrahydrofuran, dimethoxyethane, diethoxyethane, methoxyethoxyethane, and the like. However, since these organic solvents are flammable as described above, if the added amount is too large, the non-aqueous electrolyte may become flammable, and sufficient safety may not be obtained. Therefore, the content of the organic solvent including the cyclic carbonate having a π bond in the nonaqueous electrolyte is preferably in the range of 1 to 50% by volume, and more preferably in the range of 5 to 30% by volume. preferable. Further, a phosphate ester, which is a flame-retardant solvent generally added to an electrolyte for a non-aqueous electrolyte battery, can also be used. For example, trimethyl phosphate, triethyl phosphate, ethyl dimethyl phosphate, diethyl methyl phosphate, tripropyl phosphate, tributyl phosphate, tri (trifluoromethyl) phosphate, tri (trifluoroethyl) phosphate, trifluoroethyl phosphate (Tripperfluoroethyl) and the like, but are not limited thereto. These may be used alone or as a mixture of two or more.

The non-aqueous electrolyte of the battery of the present invention may be solidified into a gel by compounding a polymer. Here, as the polymer, for example, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, various acrylic monomers, methacrylic monomers, acrylamide monomers, allyl monomers, styrene monomers Examples thereof include polymers, but are not limited thereto. These may be used alone or as a mixture of two or more.

Further, according to the present invention, as described in claim 2, the quaternary ammonium organic cation is represented by the following formula (2).
Or a pyridinium cation having a skeleton represented by the following formula (3).

[0026]

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[0027]

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According to such a configuration, not only the mobility of lithium ions in the non-aqueous electrolyte can be sufficiently ensured, but also the safety during abuse such as overcharging, overdischarging or short-circuiting or in a high temperature environment. Can be sufficiently obtained, and the above operation can be effectively obtained.

Examples of the imidazolium cation include, for example, dialkyl imidazolium ions of 1,
3-dimethylimidazolium ion, 1-ethyl-3-
Methyl imidazolium ion, 1-methyl-3-ethyl imidazolium ion, 1-butyl-3-methyl imidazolium ion, and the like, and trialkyl imidazolium ions include 1,2,3-trimethyl imidazolium ion, Examples include, but are not limited to, 2-dimethyl-3-ethylimidazolium ion, 1,2-dimethyl-3-propylimidazolium ion, 1-butyl-2,3-dimethylimidazolium ion, and the like. .

The alkylpyridinium ion includes N-methylpyridinium ion, N-ethylpyridinium ion, N-propylpyridinium ion,
-Butylpyridinium ion 1-ethyl-2-methylpyridinium, 1-butyl-4-methylpyridinium, 1
-Butyl-2,4-dimethylpyridinium and the like, but are not limited thereto.

Incidentally, these room temperature molten salts having a cation may be used alone or in combination of two or more.

Further, according to the present invention, there is provided a non-aqueous electrolyte battery characterized in that the non-aqueous electrolyte contains at least a tetrafluoroborate anion.

According to such a configuration, the viscosity and the freezing point of the room temperature molten salt are particularly low, so that the mobility of lithium ions in the non-aqueous electrolyte can be sufficiently ensured.
The above operation can be obtained effectively.

According to a fourth aspect of the present invention, there is provided a non-aqueous electrolyte battery characterized in that the cyclic ester contains at least one of vinylene carbonate and styrene carbonate. is there.

According to such a configuration, the nonaqueous electrolyte contains at least one of vinylene carbonate and styrene carbonate, so that when the battery is initially charged, the nonaqueous electrolyte contains vinylene carbonate or styrene carbonate. Partially reduced, a lithium ion permeable protective film is formed on the surface of the negative electrode material. Since the protective coating made of a reducing substance of vinylene carbonate or styrene carbonate is dense and has excellent lithium ion permeability, reductive decomposition of quaternary ammonium organic cations in the second and subsequent cycles is effectively suppressed. In addition, the charging and discharging efficiency can be improved.

According to the present invention, there is provided a non-aqueous electrolyte battery characterized in that a carbonaceous material is used as a negative electrode material.

According to such a configuration, the operating potential of the carbonaceous material is reduced to the metallic lithium potential (in the case of an aqueous solution, -3.045).
V vs. NHE), it is possible to obtain a non-aqueous electrolyte battery having a high operating voltage and a high energy density. Examples of the carbonaceous material include mesophase carbon microbeads, natural graphite, artificial graphite, resin fired carbon material, carbon black, carbon fiber, and the like. These may be used alone or as a mixture of two or more.

According to a sixth aspect of the present invention, there is provided a non-aqueous electrolyte battery characterized in that a metal resin composite material is used for the exterior material.

According to such a configuration, the non-aqueous electrolyte battery can be reduced in size and weight because it is lighter than a case using a metal battery case and can be easily formed into a thin shape.
As the metal resin composite material, for example, a known aluminum laminated film can be exemplified.

The method and procedure for producing the non-aqueous electrolyte battery of the present invention are not limited. For example, a power generating element composed of a positive electrode, a negative electrode, and a separator may be placed in a battery package as an exterior material. Then, a method of injecting a non-aqueous electrolyte into a battery package and finally sealing the battery may be used. Also, for example, as in a coin-type battery, a positive electrode, a negative electrode, and a separator may be used. The battery package having a positive electrode storage section, a negative electrode storage section, and a separator storage section is independently stored in each of the storage sections, and then a non-aqueous electrolyte is injected into a battery package made of an exterior material, and finally sealed. It is also possible to use a method obtained by stopping.

The positive electrode used in the nonaqueous electrolyte battery of the present invention contains a positive electrode active material as a main component, and the positive electrode active material is preferably an oxide capable of intercalating / deintercalating lithium ions. No. The oxide is preferably a lithium-containing composite oxide,
For example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , Li
V ₂ O ₅ , Li _m [Ni _{2-n Mn} O ₄ ] (M is one or more Ni
Excluding transition metal elements. For example, Mn, Co, Zn, F
e, V, etc. 0 ≦ m ≦ 1.1, 0.75 ≦ n ≦ 1.8
0. )), But is not limited thereto. These may be used alone or as a mixture of two or more. The positive electrode active material is preferably a powder having an average particle size of about 1 to 40 microns.

It is preferable that the positive electrode and the negative electrode are formed using a conductive agent and a binder in addition to the active material which is a main component.

The conductive agent is not limited as long as it is an electron conductive material which does not adversely affect battery characteristics.
Natural graphite (flaky graphite, flaky graphite, earthy graphite, etc.), artificial graphite, carbon black, acetylene black, ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, A conductive material such as a metal fiber and a conductive ceramic material can be included as one type or a mixture thereof.

Among these, acetylene black is preferred as the conductive agent from the viewpoints of conductivity and coatability. The amount of the conductive agent to be added is 1 to 5 with respect to the total weight of the positive electrode or the negative electrode.
0% by weight is preferable, and particularly preferably 2% by weight to 30% by weight. These mixing methods are physical mixing, and ideally, uniform mixing. Therefore, dry or wet mixing using a powder mixer such as a V-type mixer, an S-type mixer, a grinder, a ball mill, and a planetary ball mill may be mentioned.

Examples of the binder include thermoplastic resins such as polytetrafluoroethylene, polyvinylidene fluoride, polyethylene and polypropylene, ethylene-propylene diene terpolymer (EPDM), and sulfonated EPD.
M, a polymer having rubber elasticity such as styrene-butadiene rubber (SBR) or fluororubber, or a polysaccharide such as carboxymethylcellulose can be used alone or as a mixture of two or more. When a binder having a functional group that reacts with lithium, such as a polysaccharide, is used, it is desirable to deactivate the functional group by, for example, methylation. The addition amount of the binder is preferably from 1 to 50% by weight, particularly preferably from 2 to 30% by weight, based on the total weight of the positive electrode or the negative electrode.

A positive electrode and a negative electrode are suitably produced by kneading a positive electrode active material or a negative electrode material, a conductive agent and a binder by adding an organic solvent such as toluene or water, kneading, shaping into an electrode shape, and drying. it can.

It is preferable that the positive electrode active material is in close contact with the positive electrode current collector and the negative electrode material is in close contact with the negative electrode current collector. Examples of the positive electrode current collector include aluminum and titanium. In addition to stainless steel, nickel, calcined carbon, conductive polymer, conductive glass, etc., the surface of aluminum, copper, etc. is coated with carbon, nickel, titanium or silver for the purpose of improving adhesiveness, conductivity and oxidation resistance. And the like can be used. As the negative electrode current collector, besides copper, nickel, iron, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., adhesiveness, conductivity, oxidation resistance For the purpose of improvement, a product obtained by treating the surface of copper or the like with carbon, nickel, titanium, silver, or the like can be used. The surface of these materials may be oxidized.

Regarding the shape of the current collector, in addition to a foil shape, a film shape, a sheet shape, a net shape, a punched or expanded material, a lath body, a porous body, a foamed body, a formed fiber group, and the like are used. be able to. The thickness of the current collector is not limited, but a thickness of 1 to 500 μm is used. Among these current collectors, as a positive electrode current collector,
Aluminum foil with excellent oxidation resistance, as a negative electrode current collector, is stable in a reduction field, and has excellent conductivity, and is an inexpensive copper foil, nickel foil, iron foil, and an alloy containing a part thereof. It is preferred to use foil. Further, it is preferable that the foil has a rough surface roughness of 0.2 μm Ra or more, whereby the adhesion between the positive electrode and the negative electrode and the current collector becomes excellent. Therefore, it is preferable to use an electrolytic foil because of having such a rough surface. In particular, an electrolytic foil subjected to a napping treatment is most preferable.

[0049]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail, but the present invention is not limited by these descriptions.

(Example 1) FIG. 1 shows a sectional view of a battery of the present invention. The battery of the present invention shown in FIG. 1 includes a positive electrode group 1, a negative electrode 2, and a separator 3, a nonaqueous electrolyte, and a metal resin composite film 5. The positive electrode 1 has a positive electrode mixture 11 applied on a positive electrode current collector 12, and the negative electrode 2 has a negative electrode mixture 21 applied on a negative electrode current collector 22. The non-aqueous electrolyte is impregnated in the pole group 4. The metal-resin composite film 5 covers the electrode group 4, and the four sides are sealed by heat welding.

Next, a method for manufacturing the nonaqueous electrolyte battery having the above-described structure will be described.

The positive electrode 1 was obtained as follows. First, LiCoO ₂ that is a positive electrode active material and acetylene black that is a conductive agent are mixed, and an N-methyl-2-pyrrolidone solution of polyvinylidene fluoride is further mixed as a binder,
This mixture was applied to one side of a positive electrode current collector 12 made of aluminum foil, and then dried, and the thickness of the positive electrode mixture 11 was 0.1 mm.
Pressed to be. The positive electrode 1 was obtained by the above steps.

The negative electrode 2 was obtained as follows. First, graphite, which is a negative electrode material, and Ketjen Black, which is a conductive agent, are mixed, and further, an N-methyl-2-pyrrolidone solution of polyvinylidene fluoride is mixed as a binder,
The mixture was applied to one surface of a negative electrode current collector 22 made of copper foil, dried, and pressed so that the negative electrode mixture 21 had a thickness of 0.1 mm. A negative electrode 2 was obtained through the above steps.

The separator 3 was obtained as follows. First, an ethanol solution was prepared by dissolving 3% by weight of a bifunctional acrylate monomer having the structure represented by Chemical Formula 4, and a porous substrate made of a polyethylene microporous membrane (average pore diameter 0.1 μm, porosity 50%) 23 μm thick, 12.52 g / m ² in weight, 89 seconds / 100 ml in air permeability), and then irradiating the monomer with electron beam to form an organic polymer layer, and drying at 60 ° C. for 5 minutes I let it. Through the above steps, the separator 3 was obtained. The obtained separator 3 has a thickness of 24 microns and a weight of 13.
04 g / m ² , air permeability 103 sec / 100 ml, and the weight of the organic polymer layer is about 4% based on the weight of the porous material.
% By weight, the thickness of the crosslinked body layer was about 1 micron, and the pores of the porous substrate were maintained almost as they were.

[0055]

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The electrode group 4 was constructed by arranging and stacking the positive electrode and the negative electrode such that the positive electrode mixture 11 and the negative electrode mixture 21 face each other with the separator 3 interposed therebetween.

[0057] The non-aqueous electrolyte, 1-ethyl-3-methylimidazolium ion (EMI ⁺⁾ and tetrafluoroborate (BF ₄ ^-) consisting of ionic liquid (EMIB
F ₄ ), ethylene carbonate, γ-butyrolactone, and vinylene carbonate in a volume ratio of 80: 9: 9: 2 in a ratio of 1 liter to 1 mol of LiBF
Obtained by dissolving ₄ .

Next, the electrode group 4 was immersed in the non-aqueous electrolyte to impregnate the electrode group 4 with the non-aqueous electrolyte. further,
The electrode group 4 was covered with the metal resin composite film 5, and the four sides were sealed by heat welding.

The battery obtained by the above method is referred to as Battery A of the present invention. The design capacity of the battery A of the present invention was 10 m.
Ah.

Example 2 As a non-aqueous electrolyte, a room temperature molten salt (BPyBF ₄ ) composed of N-butylpyridinium ion (BPy ⁺ ) and BF ₄ ⁻ , ethylene carbonate, γ
-Butyrolactone and vinylene carbonate in a volume ratio of 8
A nonaqueous electrolyte was prepared using the same raw materials and manufacturing method as in Example 1 except that 1 mol of LiBF ₄ was dissolved in 1 liter of a liquid mixed at a ratio of 0: 9: 9: 2. I got a battery. This is designated as Battery B of the invention.

Example 3 As a non-aqueous electrolyte, room temperature molten salt (EMIBF ₄ ) composed of 1-ethyl-3-methylimidazolium ion (EMI ⁺ ) and tetrafluoroborate ion (BF ₄ ⁻ ), ethylene The volume ratio of carbonate, γ-butyrolactone and styrene carbonate is 80:
For 1 liter of the liquid mixed in the ratio of 9: 9: 2, 1
A non-aqueous electrolyte battery was obtained by the same raw materials and manufacturing method as in Example 1, except that a solution in which moles of LiBF ₄ was dissolved was used. This is designated as Battery C of the invention.

Comparative Example 1 As a non-aqueous electrolyte, ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1.
Except that 1 mol of LiBF ₄ was used for 1 liter of the mixed solvent.
A non-aqueous electrolyte battery was obtained using the same raw materials and manufacturing method as in Example 1. This is designated as Comparative Battery D.

Comparative Example 2 As a non-aqueous electrolyte, a room-temperature molten salt (EMIBF ₄ ) composed of 1-ethyl-3-methylimidazolium ion (EMI ⁺ ) and tetrafluoroborate ion (BF ₄ ⁻ ) and diethyl carbonate Is mixed with 1 liter of a liquid obtained by mixing at a volume ratio of 80:20.
A non-aqueous electrolyte battery was obtained by the same raw materials and manufacturing method as in Example 1, except that a solution in which moles of LiBF ₄ was dissolved was used. This is designated as Comparative Battery E.

[0064] (Comparative Example 3) as the non-aqueous electrolytic solution, 1-ethyl-3-methylimidazolium ion (EMI ⁺⁾ and tetrafluoroborate (BF ₄ ^-) ionic liquid (EMIBF ₄₎ consisting of 1 liter A non-aqueous electrolyte battery was obtained by the same raw material and manufacturing method as in Example 1 except that a solution in which 1 mol of LiBF ₄ was dissolved was used. This is designated as Comparative Battery F.

(Charge / Discharge Cycle Test) Battery A of the present invention
A charge / discharge cycle test was performed using B and C and comparative batteries D, E and F. The test temperature was 20 ° C. The charging was performed at a constant current of 1 mA and a final voltage of 4.2 V. The discharge was a constant current discharge at a current of 1 mA and a final voltage of 2.7 V. The percentage of the amount of discharge electricity with respect to the design capacity of the battery was defined as the discharge capacity (%). FIG. 2 shows the charge / discharge cycle characteristics of the batteries A, B, and C of the present invention and the comparative batteries D, E, and F.

As is clear from FIG. 2, the comparative batteries E and F
In this case, the initial discharge capacity was only about 80% of the designed capacity, and the charge / discharge efficiency was about 85%. On the other hand, in the batteries A, B, and C of the present invention and the comparative battery D, the discharge capacity was almost 100% of the design capacity, and the charge and discharge efficiency was almost 100%.
%Met.

Further, in the comparative batteries E and F, the discharge capacity sharply decreases with the passage of the number of charge / discharge cycles. The discharge capacity of the comparative battery F at the 100th cycle and the discharge capacity at the 120th cycle of the comparative battery E reach the designed capacity. It fell below 60%. On the other hand, in the batteries A, B, and C of the present invention and the comparative battery D,
Even after 200 cycles, the discharge capacity was maintained at 80% or more of the designed capacity.

(High Temperature Storage Test) Using the batteries A, B, and C of the present invention and the comparative batteries D, E, and F, a high temperature storage test was performed. The charge and discharge conditions were as described above. After confirming the initial capacity, the battery was charged, stored at 100 ° C. for 3 hours, and then stored at room temperature for 21 hours. The discharge capacity after storage under the conditions was measured. The percentage of the difference between the discharge capacity before storage and the discharge capacity after storage relative to the discharge capacity before storage was defined as the self-discharge rate (%).

The battery thickness was measured before and after the high-temperature storage test, and the change in the battery thickness was examined. Table 1 shows the results.

[0070]

[Table 1]

As shown in Table 1, not only the self-discharge of the comparative battery D was large but also the battery thickness was greatly changed. On the other hand, in the batteries A, B, and C of the present invention and the comparative batteries E and F, not only the self-discharge was relatively small, but also the change in the battery thickness was hardly observed. However, the comparative batteries E and F had a low self-discharge rate because the discharge capacity before the high-temperature storage was already low, but the discharge capacity after the high-temperature storage was lower than that of the batteries A, B, and C of the present invention. It was low.

(Combustion Test) Further, the batteries A, B, and
A combustion test was performed using C and comparative batteries D, E, and F. After confirming the initial capacity under the charge / discharge conditions as described above, the battery was forcibly charged at 10 mA for 9 hours to make it overcharged, and then the battery was placed at a position about 2 cm above the flame of the gas burner.

As a result, the comparative battery D burned explosively by igniting the electrolyte while the aluminum laminate film as the outer package burned. However, in the batteries A, B, C of the present invention and the comparative batteries E, F, The aluminum laminate film burned, but no electrolyte combustion was observed.

From the results of the above three tests, the battery A of the present invention,
B and C were found to have better battery performance and higher safety than the comparative batteries D, E and F.

[0075]

According to the present invention, as described above, the non-aqueous electrolyte contains a room-temperature molten salt as a main component, thereby maintaining excellent battery performance. High safety can be achieved even during abuse such as overcharging, overdischarging or short-circuiting or in a high temperature environment.

The non-aqueous electrolyte contains lithium salt of 0.5 m
Since the content is at least ol / l, the charge / discharge rate of the battery is increased, and the charge / discharge cycle characteristics are excellent.

Further, since the non-aqueous electrolyte contains a cyclic ester having a π bond in addition to the lithium salt and the room-temperature molten salt, the high-rate discharge characteristics and the low-temperature characteristics of the battery are improved, and the charge / discharge efficiency is improved. Can be done.

Further, according to the configuration of the second aspect, higher safety can be exhibited at the time of abuse such as overcharging, overdischarging or short-circuiting or in a high temperature environment.

According to the third aspect of the present invention, the mobility of lithium ions in the non-aqueous electrolyte can be sufficiently ensured, and the above operation can be effectively obtained.

According to the fourth aspect of the present invention, when the non-aqueous electrolyte contains at least one of vinylene carbonate and styrene carbonate, the quaternary ammonium organic compound cations in the second and subsequent cycles can be effectively prepared. Can be suppressed, and the charge / discharge efficiency can be improved.

According to the structure of the fifth aspect, a non-aqueous electrolyte battery having a high operating voltage and a high energy density can be easily obtained.

According to the structure of the sixth aspect, the size and weight of the nonaqueous electrolyte battery can be reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view of a battery of the present invention.

FIG. 2 is a diagram showing charge / discharge cycle characteristics of a battery of the present invention and a comparative battery.

[Explanation of symbols]

 Reference Signs List 1 positive electrode 11 positive electrode mixture 12 positive electrode current collector 2 negative electrode 21 negative electrode mixture 22 negative electrode current collector 3 separator 4 electrode group 5 metal resin composite film

Continued on front page F term (reference) 5H011 AA09 BB04 CC02 CC06 CC10 5H029 AJ01 AJ12 AK02 AK03 AL06 AL07 AL08 AM03 AM04 AM05 AM07 BJ03 DJ02 DJ09 HJ02 HJ10 5H050 AA15 BA17 CA07 CA08 CA09 CB07 CB08 DA13 HA02 HA10

Claims (6)

[Claims] 1. A non-aqueous electrolyte having a room temperature molten salt, a positive electrode,
In a non-aqueous electrolyte battery in which a power generation element having a negative electrode and a separator is included in an exterior material, the room-temperature molten salt is
The non-aqueous electrolyte is formed of at least a quaternary ammonium organic cation having a skeleton represented by (Chemical Formula 1) and an anion composed of only a non-metallic element, and the non-aqueous electrolyte includes a lithium ion and an anion composed of only a non-metallic element. A non-aqueous electrolyte battery containing the lithium salt formed in the above at a concentration of 0.5 mol / l or more, and wherein the non-aqueous electrolyte contains a cyclic ester having a π bond. Embedded image 2. The quaternary ammonium organic cation contains at least one of an imidazolium cation represented by Chemical Formula 2 and a pyridinium cation having a skeleton represented by Chemical Formula 3. The non-aqueous electrolyte battery according to claim 1, wherein Embedded image Embedded image 3. The non-aqueous electrolyte battery according to claim 1, wherein the anion composed of only the non-metallic element includes at least a tetrafluoroborate anion. 4. The non-aqueous electrolyte battery according to claim 1, wherein the cyclic ester contains at least one of vinylene carbonate and styrene carbonate. 5. The non-aqueous electrolyte battery according to claim 1, wherein the negative electrode material used for the negative electrode is a carbonaceous material. 6. The non-aqueous electrolyte battery according to claim 1, wherein a metal resin composite material is used for the exterior material.