JP2005044685A - Nonaqueous electrolyte battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte battery having excellent battery performance even though a normal temperature molten salt is used for a nonaqueous electrolyte. <P>SOLUTION: The nonaqueous electrolyte battery has positive and negative poles. In the nonaqueous electrolyte, the normal temperature molten salt and a lithium salt are used. The normal temperature molten salt is formed by at least quaternary ammonium organic material cation and anion composed of a non-metallic element only. The lithium salt is formed by a lithium ion and the anion composed of the non-metallic element only. In the nonaqueous electrolyte battery, the concentration of lithium salt is at least 0.5mol/1 and an acid anhydride should be contained. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  In recent years, non-aqueous electrolyte batteries using various non-aqueous electrolytes capable of obtaining a high energy density have attracted attention as power supplies for electronic devices, power storage power supplies, electric vehicle power supplies, etc., which are becoming higher performance and smaller. .

Currently, commercially available lithium ion batteries use lithium cobaltate (LiCoO ₂ ) for the positive electrode, use a carbon material that absorbs and releases lithium ions for the negative electrode, and use, for example, room temperature such as ethylene carbonate or diethyl carbonate as a nonaqueous electrolyte. A nonaqueous electrolytic solution in which a lithium salt is dissolved in a liquid organic solvent is used.

On the other hand, there is a lithium battery using a room temperature molten salt as a non-aqueous electrolyte. By using a room temperature molten salt as a non-aqueous electrolyte, flame retardancy is imparted to the electrolyte, so that a battery suitable for applications that require particularly high safety can be obtained. As the cation of the room temperature molten salt, for example, a cyclic quaternary ammonium organic cation having an aromatic ring typified by an imidazolium cation is used. Patent Documents 1 to 3 describe batteries using a carbon material for the negative electrode. However, the cyclic quaternary ammonium organic cation has a reductive decomposition potential that is relatively nobler than that of a general non-aqueous electrolyte component, and is easily decomposed at a potential of 1 V (vs Li ^/ Li ⁺ ) or less. Due to the nature, when a carbonaceous material that operates at a potential of 1 V or less is used for the negative electrode, there has been a problem that the battery performance is greatly deteriorated.

In order to avoid this problem, as described in Patent Document 4, the operating potential of lithium titanate (Li _4/3 Ti _5/3 O ₄ ) is nobler than 1 V with respect to the potential of metallic lithium. It was necessary to use a negative electrode active material. However, since the negative electrode operating potential is noble, there is a problem that a battery having a high energy density cannot be obtained.

JP-A-10-92467 JP-A-11-86905 JP-A-11-260400 JP 2001-319688 A Study Group of Molten Salt / Thermal Technology “Basics of Molten Salt / Thermal Technology”, Agne Technology Center, 1993, 313p (ISBN 4-900041-24-6)

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a nonaqueous electrolyte battery excellent in battery performance while using a room temperature molten salt as a nonaqueous electrolyte.

  The present inventors diligently studied to solve the above problems, and surprisingly surprisingly, by making the configuration of the non-aqueous electrolyte specific in the non-aqueous electrolyte battery using the room temperature molten salt, Thus, the present inventors have found that a nonaqueous electrolyte battery having excellent battery performance can be provided even when a negative electrode material operating at a base potential, which could not be used as a negative electrode substantially, has been achieved. That is, the configuration of the present invention is as follows. However, the action mechanism includes estimation, and the success or failure of the action mechanism does not limit the present invention.

According to the first aspect of the present invention, in the nonaqueous electrolyte battery including the positive electrode, the negative electrode, and the nonaqueous electrolyte, the nonaqueous electrolyte is a quaternary ammonium organic substance having a skeleton represented by at least (Chemical Formula 1). A normal temperature molten salt formed with a cation and an anion consisting only of a nonmetallic element and a lithium salt formed with a lithium ion and an anion consisting only of a nonmetallic element are used, and the lithium salt concentration is 0 The nonaqueous electrolyte battery is characterized in that the nonaqueous electrolyte contains acid anhydride.

  That is, according to the present invention, in a nonaqueous electrolyte battery having a room temperature molten salt composed of a quaternary ammonium organic cation, a negative electrode that operates at a base potential can be produced by containing an acid anhydride in an electrolyte. It is possible to remarkably suppress the decrease in battery performance observed when used.

  Although it is not necessarily clear about this effect, the present inventors guess as follows.

In a lithium ion battery using a general non-aqueous electrolyte that does not have a room temperature molten salt, a film formed by the decomposition of the organic solvent in the non-aqueous electrolyte mainly on the negative electrode surface during the initial charging process It is thought that the further decomposition of the non-aqueous electrolyte is suppressed. On the other hand, when a room temperature molten salt composed of a quaternary ammonium organic cation is used for a non-aqueous electrolyte, the quaternary ammonium organic cation is similarly decomposed on the negative electrode surface in the initial charging process. Since it does not become a protective film that can sufficiently suppress further decomposition of the quaternary ammonium organic cation, it is considered that decomposition of the non-aqueous electrolyte proceeds as charging proceeds. However, according to the present invention, when the non-aqueous electrolyte contains an acid anhydride, a part of the acid anhydride is reduced at a potential nobler than the decomposition potential of the quaternary ammonium organic cation, and the surface of the negative electrode material is quaternized. Since a protective film capable of suppressing the decomposition of the ammonium organic cation is formed, the negative electrode is set to 1V v. s. It is considered that good performance was able to be exhibited even when operated below Li / Li ⁺ .

  The content of the acid anhydride in the nonaqueous electrolyte is preferably in the range of 0.1 to 10% by volume. By setting the content to 0.1% or more, an effect of forming a protective film capable of suppressing decomposition of the quaternary ammonium organic cation on the surface of the negative electrode material can be effectively exhibited. By setting it as 10 volume% or less, a possibility that the electrode interface resistance by the protective film formed may become high too much can be reduced. Furthermore, the content of the acid anhydride in the nonaqueous electrolyte is more preferably in the range of 0.1 to 5% by volume.

  The type of acid anhydride is not limited, but for example, chain acid anhydrides such as acetic anhydride, propionic anhydride, butyric anhydride, succinic anhydride, methyl succinic anhydride, 2,2-dimethyl succinic anhydride 2,3-dimethyl succinic anhydride, maleic anhydride, methyl maleic anhydride, 2,3-dimethyl maleic anhydride, phenyl maleic anhydride, itaconic anhydride, glutaric anhydride, 3-methyl glutaric anhydride, anhydrous 2 , 2-dimethylglutaric acid, anhydrous 3,3-dimethylglutaric acid, citraconic anhydride, glutaconic anhydride, phthalic anhydride, tetrahydrophthalic anhydride, diglycolic anhydride, homophthalic anhydride, and the like. However, it is not limited to these. These may be used alone or in combination of two or more. In particular, it preferably contains a cyclic acid anhydride.

  The concentration of the lithium salt used for the non-aqueous electrolyte is preferably in the range of 0.5 to 3 mol / l. By including a lithium salt in the non-aqueous electrolyte, the reduction potential of the non-aqueous electrolyte can be shifted to a base potential even though the reduction potential of the quaternary ammonium organic cation is relatively noble. Here, by setting the lithium salt concentration to 0.5 mol / l or more, the reduction potential of the nonaqueous electrolyte can be shifted to a sufficiently low potential. By this effect, the effect | action which suppresses decomposition | disassembly of the quaternary ammonium organic substance cation in a nonaqueous electrolyte is exhibited more effectively. In addition, by setting the lithium salt concentration to 3 mol / l or less, it is possible to reduce the possibility that the melting point of the nonaqueous electrolyte rises and solidifies. The concentration of the lithium salt used for the nonaqueous electrolyte is more preferably 0.5 to 2 mol / l.

  Examples of the quaternary ammonium organic cation having a skeleton represented by (Chemical Formula 1) include imidazolium ions such as dialkylimidazolium ions and trialkylimidazolium ions, tetraalkylammonium ions, pyridinium ions, pyrazolium ions, pyrrolium ions, pyrroles. Examples thereof include a nium ion, a pyrrolidinium ion, and a piperidinium ion. Of these, either an imidazolium cation or a pyridinium cation is preferable.

  Examples of the tetraalkylammonium ion include, but are not limited to, trimethylethylammonium, trimethylpropylammonium, trimethylhexylammonium, and tetrapentylammonium.

The anion which consists only of the said nonmetallic element means what is not an anion containing a metallic element like an aluminum halide ion, for example. Specific examples of combinations in which a quaternary ammonium organic cation and an anion consisting only of a nonmetallic 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 and a tetrafluoroborate anion (BF ₄ ⁻ ), a trifluoromethanesulfonate anion (CF ₃ SO ₃ ⁻ ), or the like.
(2) Combination of trimethylhexylammonium cation with trifluoromethanesulfonylamide anion (N (CF ₃ SO ₂ ) ₂ ⁻ ), bispentafluoroethanesulfonylamide anion (N (C ₂ F ₅ SO ₂ ) ₂ ⁻ ), etc. .
(3) 1-ethyl-3-methylimidazolium cation, tetrafluoroborate anion (BF ₄ ⁻ ), trifluoromethanesulfonate anion (CF ₃ SO ₃ ⁻ ), trifluoromethanesulfonylamide anion (N (CF ₃ SO ₂ ) In combination with ₂ ⁻ ), bispentafluoroethanesulfonylamide anion (N (C ₂ F ₅ SO ₂ ) ₂ ⁻ ) and the like.
(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 , LiCF 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 ), LiC (CF ₃ SO ₂ ) ₃ , LiC (C ₂ F ₅ SO ₂ ) _{3 and the} like are exemplified, but not limited thereto. Of these, LiBF ₄ is preferable. These may be used alone or in combination of two or more.

Further, in the present invention, as described in claim 2, the quaternary ammonium organic cation is an imidazolium cation represented by (Chemical Formula 2) or a pyridinium cation having a skeleton represented by (Chemical Formula 3). This is a non-aqueous electrolyte battery.

  According to such a configuration, not only can the mobility of lithium ions in the non-aqueous electrolyte be sufficiently ensured, but also safety at the time of abuse such as overcharge, overdischarge and short circuit and in a high temperature environment is sufficiently obtained. It is possible to obtain the above-mentioned action effectively.

  Examples of the imidazolium cation represented by (Chemical Formula 2) include 1,3-dimethylimidazolium ion, 1-ethyl-3-methylimidazolium ion, 1-butyl-3-methylimidazole as dialkylimidazolium ions. Examples of trialkylimidazolium ions include 1,2,3-trimethylimidazolium ions, 1,2-dimethyl-3-ethylimidazolium ions, 1,2-dimethyl-3-propylimidazolium ions, Examples include 1-butyl-2,3-dimethylimidazolium ion, but are not limited thereto.

  In addition, the normal temperature molten salt which has these cations may be used independently, and may be used in mixture of 2 or more types.

  According to a third aspect of the present invention, in the nonaqueous electrolyte battery according to the third aspect, the nonaqueous electrolyte contains at least a tetrafluoroborate anion.

  According to such a configuration, since the viscosity and freezing point of the room temperature molten salt are lowered, the mobility of lithium ions in the non-aqueous electrolyte can be sufficiently ensured, and the above action can be effectively obtained. It becomes possible. The method for producing a non-aqueous electrolyte containing a tetrafluoroborate anion is not limited, but it can be achieved by using at least one of a room temperature molten salt or a lithium salt formed from a tetrafluoroborate anion. As shown in the examples described later, both the room temperature molten salt and the lithium salt are formed from tetrafluoroborate anions so that the anion contained in the non-aqueous electrolyte contains only the tetrafluoroborate anions. It may be configured.

  According to a fourth aspect of the present invention, in the nonaqueous electrolyte battery according to the fourth aspect, the acid anhydride is a cyclic acid anhydride.

  According to such a configuration, by selecting the acid anhydride from a cyclic acid anhydride, formation of a protective film that can suppress decomposition of the quaternary ammonium organic cation at the negative potential negative electrode during the initial charge of the battery Is made effective.

  Moreover, this invention is a nonaqueous electrolyte battery characterized by using a carbonaceous material as a negative electrode active material as described in Claim 5.

According to the present invention, while using a room temperature molten salt, 1 V (vs.
Even when an active material that operates at a potential of (Li / Li ⁺ ) or lower is used, good battery performance is exhibited. Accordingly, the negative electrode active material used for the negative electrode of the battery of the present invention is preferably selected to have a flat portion of the discharge curve of the active material at 1 V (vs Li / Li ⁺ ) or less. That is, an active material in which the main part of the potential at which the negative electrode transitions during an effective discharge process of the battery is 1 V (vs. Li / Li ⁺ ) or less is preferable. Specifically, the amount of lithium ions that the negative electrode active material can release in the entire potential region is Q1, and the amount of lithium ions that the negative electrode active material can release in the potential region of 1 V (vs Li / Li ⁺ ). Is preferably a negative electrode active material having a Q2 / Q1 value of at least 0.2, preferably 0.5 or more, and more preferably 0.8 or more. Thereby, a high battery voltage can be obtained while using a room temperature molten salt, and a nonaqueous electrolyte battery that can be used stably can be provided. Examples of the negative electrode active material include lithium metal, lithium alloys (lithium metal-containing alloys such as lithium-aluminum, lithium-lead, lithium-tin, lithium-aluminum-tin, lithium-gallium, and wood alloys), and lithium. An alloy capable of occluding and releasing carbon, a carbon material (for example, graphite, hard carbon, low-temperature fired carbon, amorphous carbon, etc.) and the like can be mentioned. Among them, it is preferable to use a carbon material. This is due to the following reason. The carbon material has a natural electrode potential that greatly exceeds 1 V (vs. Li / Li ⁺ ) when the battery is manufactured, and a potential at which decomposition of a cyclic quaternary ammonium organic cation having an aromatic ring starts (for example, 1-ethyl In the case of the -3-methylimidazolium cation, it is nobler than about 1.1 V), and the negative electrode potential gradually changes in the base direction in the initial charging process performed at the time of manufacturing the battery. Is formed. Therefore, the physical properties of the protective coating can be arbitrarily designed by devising the initial charge conditions (initial charge rate, initial charge current waveform, initial charge process (intermittent charge, etc.), initial charge temperature, etc.). Therefore, it is very preferable. For the same reason, a negative electrode active material mainly composed of silicon is also preferable in that the physical properties of the protective coating can be arbitrarily designed.

  On the other hand, when metallic lithium or a lithium alloy is used, the apparent initial efficiency value is observed to be high, but the coating as described above is rapidly formed in the process of initial charging, so that the quaternary ring having an aromatic ring is formed. It is difficult to be a protective film that can effectively suppress decomposition of ammonium organic cation. Furthermore, since the construction / disintegration of the coating is repeated each time the charge / discharge cycle is repeated, the charge / discharge cycle performance tends to be inferior.

  Moreover, this invention is a nonaqueous electrolyte battery using the metal resin composite material for the said exterior material as described in Claim 6.

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

  ADVANTAGE OF THE INVENTION According to this invention, the nonaqueous electrolyte battery excellent in battery performance can be provided, using normal temperature molten salt for a nonaqueous electrolyte.

  The present invention is described in detail below, but the present invention is not limited to these descriptions.

  First, the room temperature molten salt used in the nonaqueous electrolyte battery of the present invention will be described in detail.

In the present specification, the room temperature molten salt refers to 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., in some cases about 60 ° C., and the lower limit is about −50 ° C., and in some cases about −20 ° C. On the other hand, an inorganic molten salt such as Li ₂ CO ₃ —Na ₂ CO ₃ —K ₂ CO ₃ used for various electrodepositions as described in Non-Patent Document 1 has a melting point of 300 ° C. or higher. However, it is not a liquid in the temperature range in which the battery is normally assumed to operate, and is not included in the room temperature molten salt in the present invention.

  The non-aqueous electrolyte according to the present invention has a room temperature molten salt having a quaternary ammonium organic cation, so that it is liquid at room temperature and has almost no volatility, and has flame retardancy or nonflammability. It will surely have the characteristics of molten salt. Therefore, a battery equipped with such a non-aqueous electrolyte is excellent in safety during overuse such as overcharge, overdischarge and short circuit, and in a high temperature environment.

  Furthermore, since the anion forming the room temperature molten salt consists of only non-metallic elements and does not contain highly corrosive aluminum halide ions, etc., the battery performance deteriorates due to the corrosiveness and is difficult to handle during production. Does not occur. In addition, since the lithium salt is formed using an anion composed only of a non-metallic element, the non-aqueous electrolyte containing both is solid even when the lithium salt that is solid at room temperature coexists with the room temperature molten salt. Therefore, the non-aqueous electrolyte containing the room temperature molten salt maintains a liquid state satisfactorily.

  You may add and use the organic solvent which is liquid at normal temperature to the nonaqueous electrolyte which this invention battery comprises. Here, as said organic solvent, the organic solvent generally used for the electrolyte solution for nonaqueous electrolyte batteries 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 addition amount is too large, the non-aqueous electrolyte may be flammable and sufficient safety may not be obtained, which is not preferable. Therefore, the content of the organic solvent in the non-aqueous electrolyte is preferably in the range of 1 to 50% by volume, and more preferably in the range of 5 to 30% by volume. Moreover, the phosphate ester which is a flame-retardant solvent generally added to the electrolyte solution for nonaqueous electrolyte batteries 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, triphosphate (Triperfluoroethyl) and the like may be mentioned, but are not limited thereto. These may be used alone or in combination of two or more.

  In addition, the nonaqueous electrolyte of the battery of the present invention may be solidified in a gel form by complexing a polymer. Here, examples of the polymer include, for example, polyethylene oxide, polypropylene oxide, polyacrylonitrile, polymethyl methacrylate, polyvinylidene fluoride, various acrylic monomers, methacrylic monomers, acrylamide monomers, allyl monomers, and styrene monomers. Examples include, but are not limited to, polymers. These may be used alone or in combination of two or more.

  The method and procedure for producing the nonaqueous electrolyte battery of the present invention is not limited.For example, a power generation element composed of a positive electrode, a negative electrode, and a separator is placed in a battery package that is an exterior material. Then, a method may be used in which a nonaqueous electrolyte is injected into the battery package and finally sealed, and the positive electrode, the negative electrode, and the separator are connected to the positive electrode storage portion, for example, like a coin-type battery. , A negative electrode storage portion, a separator storage portion, and a battery package, each of which is stored independently, and then a nonaqueous electrolyte is injected into the battery package made of an exterior material, and finally sealed. An obtaining method may be used.

The positive electrode used in the nonaqueous electrolyte battery of the present invention has a positive electrode active material as a main component, and examples of the positive electrode active material preferably include oxides capable of intercalating and deintercalating lithium ions. The oxide is preferably a lithium-containing composite oxide. For example, LiCoO ₂ , LiMn ₂ O ₄ , LiNiO ₂ , LiV ₂ O ₅ , Li _m [Ni _2−n MnO ₄ ] (M is one or more kinds). Transition metal elements other than Ni, such as Mn, Co, Zn, Fe, V, etc. (0 ≦ m ≦ 1.1, 0.75 ≦ n ≦ 1.80) and the like, but are not limited thereto is not. These may be used alone or in combination of two or more. The positive electrode active material is preferably a powder having an average particle size of about 1 to 40 μm.

  The positive electrode and the negative electrode are preferably prepared using a conductive agent and a binder as constituent components in addition to the active material which is a main constituent component.

  The conductive agent is not limited as long as it is an electron conductive material that does not adversely affect the battery characteristics. Usually, natural graphite (such as scaly graphite, scaly graphite, earthy graphite), artificial graphite, carbon black, acetylene black, Conductive materials such as ketjen black, carbon whisker, carbon fiber, metal (copper, nickel, aluminum, silver, gold, etc.) powder, metal fiber, and conductive ceramic material can be included as one kind or a mixture thereof. .

  Among these, as the conductive agent, acetylene black is desirable from the viewpoints of conductivity and coating properties. The addition amount of the conductive agent is preferably 1 to 50% by weight, particularly 2 to 30% by weight, based on the total weight of the positive electrode or the negative electrode. These mixing methods are physical mixing, and the ideal is uniform mixing. Therefore, it is possible to use dry or wet mixing using a powder mixer such as a V-type mixer, S-type mixer, grinding machine, ball mill, or planetary ball mill.

  As the binder, usually, thermoplastic resins such as polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and polypropylene, ethylene-propylene diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluorine rubber, and the like These polymers having rubber elasticity, polysaccharides such as carboxymethylcellulose, and the like can be used as one kind or a mixture of two or more kinds. Moreover, when using the binder which has a functional group which reacts with lithium like polysaccharide, it is desirable to deactivate the functional group, for example by methylating. The addition amount of the binder is preferably 1 to 50% by weight, particularly preferably 2 to 30% by weight, based on the total weight of the positive electrode or the negative electrode.

  The positive electrode active material or the negative electrode material, the conductive agent and the binder are added with an organic solvent such as toluene or water, kneaded, formed into an electrode shape, and dried, whereby the positive electrode and the negative electrode can be suitably prepared.

  The positive electrode active material is preferably in close contact with the positive electrode current collector, and the negative electrode material is preferably in close contact with the negative electrode current collector. Examples of the positive electrode current collector include aluminum, titanium, and stainless steel. In addition to nickel, baked carbon, conductive polymer, conductive glass, etc., the surface of aluminum, copper, etc. is treated with carbon, nickel, titanium, silver, etc. for the purpose of improving adhesion, conductivity and oxidation resistance. Can be used. In addition to copper, nickel, iron, stainless steel, titanium, aluminum, calcined carbon, conductive polymer, conductive glass, Al-Cd alloy, etc., as negative electrode current collector, adhesiveness, conductivity, oxidation resistance For the purpose of improvement, a material 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 the 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 body of a fiber group, and the like can be used. . The thickness of the current collector is not limited, but one having a thickness of 1 to 500 μm is used. Among these current collectors, an aluminum foil excellent in oxidation resistance is used as a positive electrode current collector, and copper as a negative electrode current collector is stable in a reduction field and has excellent conductivity and is inexpensive. It is preferable to use foil, nickel foil, iron foil, and alloy foil containing a part thereof. Furthermore, the foil preferably has a rough surface surface roughness of 0.2 μm Ra or more, whereby the adhesion between the positive and negative electrodes and the current collector is excellent. Therefore, it is preferable to use an electrolytic foil because it has such a rough surface. In particular, an electrolytic foil that has been subjected to a cracking treatment is most preferable.

  The present invention is described in detail below, but the present invention is not limited to these descriptions.

  A cross-sectional view of the nonaqueous electrolyte battery according to the example is shown in FIG. The electrode group 4 includes a positive electrode 1, a negative electrode 2, and a separator 3, a nonaqueous electrolyte, and a metal resin composite film 5. The positive electrode 1 is formed by applying a positive electrode mixture 11 on a positive electrode current collector 12, and the negative electrode 2 is formed by applying a negative electrode mixture 21 on a negative electrode current collector 22. The nonaqueous electrolyte is impregnated in the pole group 4. The metal resin composite film 5 covers the pole group 4 and is sealed on all four sides by heat welding.

  Next, a method for manufacturing the nonaqueous electrolyte battery having the above configuration 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, and this mixture is made of an aluminum foil. After applying to one side of the positive electrode current collector 12, it was dried and pressed so that the thickness of the positive electrode mixture 11 was 0.1 mm. The positive electrode 1 was obtained by the above process.

  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 an N-methyl-2-pyrrolidone solution of polyvinylidene fluoride is further mixed as a binder, and this mixture is a negative electrode made of copper foil. After apply | coating to the single side | surface of the electrical power collector 22, it dried and it pressed so that the negative mix 21 might be set to 0.1 mm. The negative electrode 2 was obtained by the above process.

Separator 3 was obtained as follows. First, an ethanol solution in which 3% by weight of a bifunctional acrylate monomer having a structure represented by (Chemical Formula 4) was dissolved was prepared, and a porous substrate made of a polyethylene microporous membrane (average pore size 0.1 μm, porosity 50%) And coated with a thickness of 23 μm, weight of 12.52 g / m ² , air permeability of 89 seconds / 100 ml), and then an organic polymer layer is formed by effecting the monomer by electron beam irradiation and dried at a temperature of 60 ° C. for 5 minutes. It was. The separator 3 was obtained by the above process. The obtained separator 3 has a thickness of 24 μm, a weight of 13.04 g / m ² , and an air permeability of 103 seconds / 100 ml. The weight of the organic polymer layer is about 4% by weight with respect to the weight of the porous material. The thickness of the crosslinked layer was about 1 μm, and the pores of the porous base material were maintained as they were.

The pole group 4 was configured by arranging and laminating the positive electrode and the negative electrode so that the positive electrode mixture 11 and the negative electrode mixture 21 face each other with the separator 3 interposed therebetween.
Next, the electrode group 4 was impregnated with the non-aqueous electrolyte by immersing the electrode group 4 in the non-aqueous electrolyte. Furthermore, the pole group 4 was covered with the metal resin composite film 5, and the four sides were sealed by heat welding. As a result, a nonaqueous electrolyte battery having a design capacity of 10 mAh was obtained.

(Example 1)
1 mol of LiBF ₄ is dissolved in 1 liter of room temperature molten salt (EMIBF ₄ ) composed of 1-ethyl-3-methylimidazolium ion (EMI ⁺ ) and tetrafluoroborate ion (BF ₄ ⁻ ), and A non-aqueous electrolyte was obtained by dissolving 1% by weight of succinic anhydride. Using this nonaqueous electrolyte, a nonaqueous electrolyte battery was obtained by the above procedure.

(Example 2)
As a non-aqueous electrolyte, 1 mol of LiBF ₄ is dissolved in 1 liter of a room temperature molten salt (BPyBF ₄ ) composed of N-butylpyridinium ion (BPy ⁺ ) and BF ₄ ^−, and 1% by weight of glutaric anhydride is further dissolved. By doing so, a non-aqueous electrolyte was obtained. Using this nonaqueous electrolyte, a nonaqueous electrolyte battery was obtained by the above procedure.

(Example 3)
As a non-aqueous electrolyte, 1 mol of LiBF ₄ was added to 1 liter of a room temperature molten salt (EMIBF ₄ ) composed of 1-ethyl-3-methylimidazolium ion (EMI ⁺ ) and tetrafluoroborate ion (BF ₄ ⁻ ). The nonaqueous electrolyte was obtained by dissolving and further dissolving 1% by weight of maleic anhydride. Using this nonaqueous electrolyte, a nonaqueous electrolyte battery was obtained by the above procedure.

(Example 4)
As a non-aqueous electrolyte, 1 mol of LiBF ₄ was added to 1 liter of a room temperature molten salt (EMIBF ₄ ) composed of 1-ethyl-3-methylimidazolium ion (EMI ⁺ ) and tetrafluoroborate ion (BF ₄ ⁻ ). The nonaqueous electrolyte was obtained by dissolving and further dissolving 1% by weight of acetic anhydride. Using this nonaqueous electrolyte, a nonaqueous electrolyte battery was obtained by the above procedure.

(Comparative Example 1)
As a non-aqueous electrolyte, 1 mol of LiBF ₄ was added to 1 liter of a room temperature molten salt (EMIBF ₄ ) composed of 1-ethyl-3-methylimidazolium ion (EMI ⁺ ) and tetrafluoroborate ion (BF ₄ ⁻ ). By dissolving it, a nonaqueous electrolyte was obtained. Using this nonaqueous electrolyte, a nonaqueous electrolyte battery was obtained by the above procedure.

(Reference example)
As a non-aqueous electrolyte, 1 mol of LiBF ₄ was dissolved in 1 liter of a mixed solvent in which ethylene carbonate and diethyl carbonate were mixed at a volume ratio of 1: 1 to obtain a non-aqueous electrolyte. Using this nonaqueous electrolyte, a nonaqueous electrolyte battery was obtained by the above procedure.

(Initial discharge capacity test)
These batteries were subjected to an initial discharge capacity test. The test temperature was 20 ° C. The charging was a constant current charging with a current of 1 mA and a final voltage of 4.2V. The discharge was a constant current discharge with a current of 1 mA and a final voltage of 2.7 V. The obtained battery capacity was defined as the initial discharge capacity.

(High temperature storage test)
Subsequently, a high temperature storage test was conducted. Each battery was charged again at 20 ° C. under the same conditions as described above, and then a temperature cycle of 100 ° C. for 3 hours to room temperature for 21 hours was repeated for 30 days. Next, discharging under the same conditions as described above was performed at 20 ° C. The discharge capacity at this time was defined as the remaining discharge capacity after storage. Further, the battery thickness was measured before and after the high temperature storage test, and the battery thickness increase rate was determined.

  The test results are shown in Table 1.

  From Table 1, it was found that the batteries 1 to 4 of the present invention had a larger initial capacity and a remaining capacity after storage than the comparative battery 1, and the increase in battery thickness due to high temperature storage was also suppressed. Furthermore, since the battery of the present invention uses a room temperature molten salt having flame retardancy, it goes without saying that the battery has high safety.

It is sectional drawing of the nonaqueous electrolyte battery which concerns on an Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 11 Positive electrode mixture 12 Positive electrode collector 2 Negative electrode 21 Negative electrode mixture 22 Negative electrode collector 3 Separator 4 Electrode group 5 Metal resin composite film

Claims (6)

In a non-aqueous electrolyte battery including a positive electrode, a negative electrode, and a non-aqueous electrolyte, 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 only of a non-metallic element. Room temperature molten salt and a lithium salt formed of an anion consisting only of lithium ions and a non-metallic element, the lithium salt concentration is 0.5 mol / l or more, and the non-water A nonaqueous electrolyte battery characterized in that the electrolyte contains an acid anhydride.

The quaternary ammonium organic cation includes 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 nonaqueous electrolyte battery as described.

The non-aqueous electrolyte battery according to claim 1, wherein the non-aqueous electrolyte includes at least a tetrafluoroborate anion. The non-aqueous electrolyte battery according to claim 1, wherein the acid anhydride is a cyclic acid anhydride. The nonaqueous electrolyte battery according to claim 1, wherein a carbonaceous material is used as a negative electrode active material. The non-aqueous electrolyte battery according to claim 1, wherein a metal resin composite material is used for the exterior material.

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