JP2006032300A - Electrolyte and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of improving cycle property by improving stability of a solvent, and to provide an electrolyte used for the same. <P>SOLUTION: An anode 22 contains a single body, an alloy or a compound of a metal element, or a single body, an alloy or a compound of a semi-metal element capable of storing and releasing lithium. Electrolyte solution with electrolyte salt dissolved in a solvent is impregnated in a separator 23. The solvent contains fluorocarboxylic ester as a low-viscosity solvent together with a high-dielectric constant solvent. As the electrolyte salt, bis-(trifluoromethane sulfone)imide lithium or the like is preferable. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery including an electrolyte solution together with a positive electrode and a negative electrode, in particular, lithium (Li) or the like as an electrolytic reactant, and an electrolyte solution used therefor.

  In recent years, many portable electronic devices such as a camera-integrated VTR (video tape recorder), a digital still camera, a mobile phone, a portable information terminal, or a notebook computer have appeared, and their size and weight have been reduced. Accordingly, as a portable power source for electronic devices, research and development for improving the energy density of batteries, particularly secondary batteries, are being actively promoted. Among these, lithium ion secondary batteries using a carbon material for the negative electrode, a composite material of lithium and a transition metal for the positive electrode, and a carbonate ester for the electrolytic solution are larger than conventional lead batteries and nickel cadmium batteries. Since energy density can be obtained, it is widely used.

Recently, with the improvement in performance of portable electronic devices, further improvement in capacity has been demanded, and it is considered to use tin (Sn) or silicon (Si) instead of carbon material as the negative electrode active material. Has been. This is because the theoretical capacity of tin is 994 mAh / g and the theoretical capacity of silicon is 4199 mAh / g, which is much larger than the theoretical capacity of graphite, 372 mAh / g, and an improvement in capacity can be expected. In particular, it has been reported that a negative electrode in which a thin film of tin or silicon is formed on a current collector can maintain a relatively large discharge capacity without pulverization of the negative electrode active material even by insertion and extraction of lithium ( For example, see Patent Document 1).
International Publication No. WO01 / 031724 Pamphlet

  However, a tin alloy or a silicon alloy that occludes lithium has a strong activity. For example, when a cyclic carbonate that is a high dielectric constant solvent and a chain carbonate that is a low-viscosity solvent are used as an electrolyte, a chain carbonate is particularly preferable. Since the ester is decomposed and the lithium is inactivated, there is a problem that the charge / discharge efficiency is lowered when charge / discharge is repeated.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a battery with high electrolyte stability and improved cycle characteristics, and an electrolyte used therefor.

  The electrolytic solution of the present invention contains the fluorocarboxylic acid ester shown in Chemical Formula 1 and a high dielectric constant solvent.

（式中、Ｒ１は、炭素数１から５であるアルキル基の少なくとも一部の水素をフッ素基で置換した基を表す。Ｒ２は、炭素数１から４のアルキル基あるいはそれらの少なくとも一部の水素をフッ素で置換した基を表す。）

(In the formula, R1 represents a group in which at least a part of hydrogen of an alkyl group having 1 to 5 carbon atoms is substituted with a fluorine group. R2 represents an alkyl group having 1 to 4 carbon atoms or at least a part of them. (Represents a group in which hydrogen is substituted with fluorine.)

  The battery of the present invention is provided with an electrolytic solution together with a positive electrode and a negative electrode, and the electrolytic solution contains the fluorocarboxylic acid ester shown in Chemical Formula 2 and a high dielectric constant solvent.

（式中、Ｒ１は、炭素数１から５であるアルキル基の少なくとも一部の水素をフッ素基で置換した基を表す。Ｒ２は、炭素数１から４のアルキル基あるいはそれらの少なくとも一部の水素をフッ素で置換した基を表す。）

(In the formula, R1 represents a group in which at least a part of hydrogen of an alkyl group having 1 to 5 carbon atoms is substituted with a fluorine group. R2 represents an alkyl group having 1 to 4 carbon atoms or at least a part of them. (Represents a group in which hydrogen is substituted with fluorine.)

  According to the electrolytic solution and battery of the present invention, since the fluorocarboxylic acid ester shown in Chemical Formula 1 and the high dielectric constant solvent are included, the decomposition reaction of the solvent in the negative electrode can be suppressed, and the cycle characteristics can be improved. Can be improved.

  In particular, as a negative electrode active material capable of occluding and releasing an electrode reactant in the negative electrode, at least one member selected from the group consisting of simple elements, alloys and compounds of metal elements and simple metals, alloys and compounds of metalloid elements It is effective when including.

  If the high dielectric constant solvent includes at least one member selected from the group consisting of cyclic carbonates and cyclic carbonate derivatives obtained by substituting some of these hydrogens with halogen, cycle characteristics can be further improved. In particular, if 4-fluoro-1,3-dioxolan-2-one or 4-chloro-1,3-dioxolan-2-one is used, a high effect can be obtained.

  Furthermore, if an anion having a structure in which a perfluoroalkyl group having 1 to 8 carbon atoms or a perfluoroalkylene group having 2 to 4 carbon atoms is bonded to an O═S═O group is contained, the fluorocarboxylic acid ester is increased. A high dielectric constant solvent can be mixed at a ratio, and high ionic conductivity can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a cross-sectional structure of a secondary battery according to an embodiment of the present invention. This secondary battery is a so-called cylindrical type, and is a wound electrode in which a strip-like positive electrode 21 and a negative electrode 22 are laminated and wound inside a substantially hollow cylindrical battery can 11 via a separator 23. It has a body 20. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 are arranged perpendicular to the winding peripheral surface so as to sandwich the winding electrode body 20.

  At the open end of the battery can 11, a battery lid 14, a safety valve mechanism 15 provided inside the battery lid 14 and a heat sensitive resistance element (Positive Temperature Coefficient; PTC element) 16 are interposed via a gasket 17. It is attached by caulking, and the inside of the battery can 11 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the heat sensitive resistance element 16, and the disk plate 15A is reversed when the internal pressure of the battery exceeds a certain level due to an internal short circuit or external heating. Thus, the electrical connection between the battery lid 14 and the wound electrode body 20 is cut off. When the temperature rises, the heat sensitive resistance element 16 limits the current by increasing the resistance value and prevents abnormal heat generation due to a large current. The gasket 17 is made of, for example, an insulating material, and asphalt is applied to the surface.

  For example, a center pin 24 is inserted in the center of the wound electrode body 20. A positive electrode lead 25 made of aluminum (Al) or the like is connected to the positive electrode 21 of the spirally wound electrode body 20, and a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded to and electrically connected to the battery can 11.

  FIG. 2 shows an enlarged part of the spirally wound electrode body 20 shown in FIG. The positive electrode 21 includes, for example, a positive electrode current collector 21A having a pair of opposed surfaces and a positive electrode active material layer 21B provided on both surfaces or one surface of the positive electrode current collector 21A. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil. The positive electrode active material layer 21B includes, for example, a positive electrode material that can occlude and release lithium as an electrode reactant as a positive electrode active material.

As a cathode material capable of inserting and extracting lithium, for example, lithium cobalt oxide, a solid solution containing lithium nickelate, or these _{(Li (Ni x Co y Mn} z) O 2)) (x, y and z Of 0 <x <1, 0 <y <1, 0 <z <1, x + y + z = 1), or lithium composite oxide such as manganese spinel (LiMn ₂ O ₄ ), or lithium iron phosphate A phosphate compound having an olivine structure such as (LiFePO ₄ ) is preferred. This is because a high energy density can be obtained. Examples of positive electrode materials capable of inserting and extracting lithium include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as iron disulfide, titanium disulfide and molybdenum sulfide, polyaniline or Examples also include conductive polymers such as polythiophene. As the positive electrode material, one kind may be used alone, or two or more kinds may be mixed and used.

  The positive electrode active material layer 21B also contains, for example, a conductive agent, and may further contain a binder as necessary. Examples of the conductive agent include carbon materials such as graphite, carbon black, and ketjen black, and one or more of them are used in combination. In addition to the carbon material, a metal material or a conductive polymer material may be used as long as it is a conductive material. Examples of the binder include synthetic rubbers such as styrene butadiene rubber, fluorine rubber or ethylene propylene diene rubber, or polymer materials such as polyvinylidene fluoride, and one or more of them are mixed. Used. For example, when the positive electrode 21 and the negative electrode 22 are wound as shown in FIG. 1, it is preferable to use a styrene butadiene rubber or a fluorine rubber having high flexibility as the binder.

  The negative electrode 22 includes, for example, a negative electrode current collector 22A having a pair of opposed surfaces, and a negative electrode active material layer 22B provided on both surfaces or one surface of the negative electrode current collector 22A.

  In some cases, the negative electrode current collector 22A is preferably made of a metal material containing at least one metal element that does not form an intermetallic compound with lithium. When an intermetallic compound is formed with lithium, it expands and contracts with charge and discharge, structural destruction occurs, and current collecting performance is reduced. In addition, the ability to support the negative electrode active material layer 22B is reduced, and the negative electrode active material layer 22B becomes a negative electrode. This is because the current collector 22A may fall off. Note that in this specification, the metal material includes not only a single metal element but also an alloy composed of two or more metal elements or one or more metal elements and one or more metalloid elements. Examples of the metal element that does not form an intermetallic compound with lithium include copper (Cu), nickel, titanium (Ti), iron, and chromium (Cr).

  The negative electrode active material layer 22B is, for example, as a negative electrode active material, a simple substance, an alloy and a compound of a metal element capable of inserting and extracting lithium as an electrode reactant, and a half capable of inserting and extracting lithium. It contains at least one negative electrode material selected from the group consisting of simple elements, alloys and compounds of metal elements. Thereby, this secondary battery can obtain a high energy density. Note that in this specification, alloys include those composed of one or more metal elements and one or more metalloid elements in addition to those composed of two or more metal elements. Moreover, the nonmetallic element may be included. There are structures in which a solid solution, a eutectic (eutectic mixture), an intermetallic compound, or two or more of them coexist.

  Examples of metal elements or metalloid elements constituting the negative electrode material include magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), silicon, germanium (Ge), tin, lead (Pb). , Bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd) or platinum (Pt). These may be crystalline or amorphous.

As the alloy or compound of these metal element or a metalloid element, for example, those represented by the chemical formula Ma _s Mb _t Li _u or a chemical formula Ma _p Mc _q Md _r,. In these chemical formulas, Ma represents at least one of a metal element and a metalloid element capable of forming an alloy with lithium, and Mb represents at least one of a metal element and a metalloid element other than lithium and Ma. , Mc represents at least one of non-metallic elements, and Md represents at least one of metallic elements and metalloid elements other than Ma. The values of s, t, u, p, q, and r are s> 0, t ≧ 0, u ≧ 0, p> 0, q> 0, and r ≧ 0, respectively.

  Among these, the negative electrode material is preferably a simple substance, alloy or compound of a group 4B metal element or semimetal element in the short-period type periodic table, particularly preferably a simple substance of silicon or tin, or an alloy or compound thereof. . This is because silicon, tin simple substance, alloys and compounds have a large ability to occlude and release lithium, and depending on the combination, the energy density of the anode 22 can be made higher than that of conventional graphite.

Specific examples of such alloys or compounds include SiB ₄ , SiB ₆ , Mg ₂ Si, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoSi ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ Si. FeSi ₂ , MnSi ₂ , NbSi ₂ , TaSi ₂ , VSi ₂ , WSi ₂ , ZnSi ₂ , SiC, Si ₃ N ₄ , Si ₂ N ₂ O, SiO _v (0 <v ≦ 2), SnO _w (0 < v ≦ 2), SnSiO ₃ , LiSiO, LiSnO, Mg ₂ Sn, or an alloy containing tin and cobalt.

  The negative electrode active material layer 22B may be formed by a vapor phase method, a liquid phase method, or a baking method, or may be formed by coating. The firing method is a method in which a particulate negative electrode active material is mixed with a binder or a solvent and molded, and then heat-treated at a temperature higher than the melting point of the binder, for example. Among these, in the case of the vapor phase method, the liquid phase method, or the firing method, the negative electrode active material layer 22B and the negative electrode current collector 22A are preferably alloyed at least at a part of the interface. Specifically, it is preferable that the constituent element of the negative electrode current collector 22A is diffused in the negative electrode active material layer 22B, the constituent element of the negative electrode active material is diffused in the negative electrode current collector 22A, or they are mutually diffused at the interface. This is because breakage due to expansion / contraction of the negative electrode active material layer 22B due to charging / discharging can be suppressed, and electronic conductivity between the negative electrode active material layer 22B and the negative electrode current collector 22A can be improved. .

  In the case of coating, in addition to the negative electrode active material, other materials such as a binder such as polyvinylidene fluoride and a conductive agent may be included. The same applies to the case of the firing method.

  As the negative electrode active material, a carbon material such as graphite, non-graphitizable carbon or graphitizable carbon may be used, and these carbon materials and the negative electrode material described above may be used together. Also good. The carbon material has very little change in the crystal structure that occurs during charging and discharging. For example, if used together with the negative electrode material described above, a high energy density can be obtained and excellent cycle characteristics can be obtained. This is preferable because it can function as a conductive agent.

  The separator 23 separates the positive electrode 21 and the negative electrode 22 and allows lithium ions to pass through while preventing a short circuit of current due to contact between the two electrodes. The separator 23 is made of, for example, a porous film made of synthetic resin made of polytetrafluoroethylene, polypropylene, polyethylene or the like, or a multi-hard film made of ceramic, and these two or more kinds of porous films are laminated. It may be made the structure.

  For example, the separator 23 is impregnated with an electrolytic solution that is a liquid electrolyte. The electrolytic solution contains, for example, a solvent and an electrolyte salt dissolved in the solvent.

  As the solvent, it is preferable to use a mixture of a high dielectric constant solvent having a relative dielectric constant of 30 or more and a low viscosity solvent having a viscosity of 1 mPa · s or less. This is because high ion conductivity can be obtained.

  Examples of the high dielectric constant solvent include cyclic compounds such as cyclic carbonates such as ethylene carbonate, propylene carbonate or butylene carbonate, 4-fluoro-1,3-dioxolan-2-one shown in Chemical Formula 3, A cyclic carbonate derivative having a halogen atom such as 4-chloro-1,3-dioxolan-2-one or 4-trifluoromethyl-1,3-dioxolan-2-one represented by Chemical Formula 4, γ-butyrolactone or Cyclic carboxylic acid esters such as γ-valerolactone, cyclic amides such as 1-methyl-2-pyrrolidinone, cyclic carbamates such as 3-methyl-2-oxozaridinone, cyclic sulfur compounds such as tetramethylene sulfone or γ-propane sultone Is mentioned. Among them, a cyclic carbonate or a cyclic carbonate derivative having a halogen atom is preferable, a cyclic carbonate derivative having a halogen atom is more preferable, and 4-fluoro-1,3-dioxolan-2-one is particularly desirable. This is because the effect of suppressing the decomposition reaction of the solvent is high. A high dielectric constant solvent may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  As the low-viscosity solvent, the fluorocarboxylic acid ester shown in Chemical formula 5 is preferable, and among them, the fluorocarboxylic acid ester shown in Chemical formula 6 or the fluorocarboxylic acid ester shown in Chemical formula 7 is desirable. This is because the decomposition reaction of the solvent in the negative electrode 22 can be suppressed. In particular, when a single element, alloy or compound of a metal element or a metalloid element is used for the negative electrode 22 as a negative electrode active material capable of inserting and extracting an electrode reactant, it is preferable because a high effect can be obtained. A low viscosity solvent may be used individually by 1 type, and 2 or more types may be mixed and used for it.

（式中、Ｒ１は、炭素数１から５であるアルキル基の少なくとも一部の水素をフッ素基で置換した基を表す。Ｒ２は、炭素数１から４のアルキル基あるいはそれらの少なくとも一部の水素をフッ素で置換した基を表す。Ｒ１およＲ２は、同一であってもよいし異なっていてもよい。）

(In the formula, R1 represents a group in which at least a part of hydrogen of an alkyl group having 1 to 5 carbon atoms is substituted with a fluorine group. R2 represents an alkyl group having 1 to 4 carbon atoms or at least a part of them. (Represents a group in which hydrogen is substituted with fluorine. R1 and R2 may be the same or different.)

（式中、Ｒ２は、炭素数１から４のアルキル基あるいはそれらの少なくとも一部の水素をフッ素で置換した基を表す。Ｒ１１は、水素基，フッ素基，炭素数１から４のアルキル基あるいはそれらの少なくとも一部の水素をフッ素で置換した基を表す。Ｒ２およびＲ１１は、同一であってもよいし異なっていてもよい。）

(In the formula, R2 represents an alkyl group having 1 to 4 carbon atoms or a group in which at least a part of hydrogen thereof is substituted with fluorine. R11 represents a hydrogen group, a fluorine group, an alkyl group having 1 to 4 carbon atoms, or (Represents a group in which at least a part of hydrogen is substituted with fluorine. R2 and R11 may be the same or different.)

（式中、Ｒ２は、炭素数１から４のアルキル基あるいはそれらの少なくとも一部の水素をフッ素で置換した基を表す。Ｒ１２，Ｒ１３およびＲ１４は、トリフルオロエチル基，ペンタフルオロエチル基を表すが、それらのうちの２つまたは全部がトリフルオロエチル基である。Ｒ２，Ｒ１２，Ｒ１３およびＲ１４は、同一であってもよいし異なっていてもよい。）

(In the formula, R2 represents an alkyl group having 1 to 4 carbon atoms or a group in which at least a part of hydrogen thereof is substituted with fluorine. R12, R13 and R14 each represents a trifluoroethyl group or a pentafluoroethyl group. And two or all of them are trifluoroethyl groups, and R2, R12, R13 and R14 may be the same or different.)

Examples of the fluorocarboxylic acid ester shown in Chemical Formula 6 include trifluoroacetic acid esters such as methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, and butyl trifluoroacetate, methyl pentafluoropropionate, and pentafluoropropion. Examples thereof include pentafluoropropionic acid esters such as ethyl acid, propyl pentafluoropropionate, and butyl pentafluoropropionate, heptafluorobutyric acid ester, and nonafluorovaleric acid ester. Examples of the fluorocarboxylic acid ester shown in Chemical Formula 7 include trifluoromethyl acetate such as (CF ₃ ) ₃ CCOOCF ₃ .

  The content of the fluorocarboxylic acid ester shown in Chemical Formula 5 is preferably 25% by mass or more with respect to the entire electrolytic solution. This is because high cycle characteristics can be obtained within this range.

  As the electrolyte salt, it is preferable to use a metal salt having a structure in which a perfluoroalkyl group having 1 to 8 carbon atoms or a perfluoroalkylene group having 2 to 4 carbon atoms is bonded to an O═S═O group. That is, the electrolytic solution preferably contains an anion having such a structure. Since the above-mentioned fluorocarboxylic acid ester has high hydrophobicity, it is difficult to mix with a high dielectric constant solvent, and it is difficult to mix with a high dielectric constant solvent at a high ratio, but by using this electrolyte salt, a high ratio is obtained. This is because they can be mixed uniformly.

  Examples of such anions include those shown in Chemical Formula 8 to Chemical Formula 11.

（式中、Ｒ３は、炭素数１から８のパーフルオロアルキル基を表す。）

(In the formula, R3 represents a perfluoroalkyl group having 1 to 8 carbon atoms.)

（式中、Ｒ４，Ｒ５は、炭素数１から８のパーフルオロアルキル基を表す。Ｒ４およびＲ５は、同一であってもよいし異なっていてもよい。）

(In the formula, R4 and R5 each represent a perfluoroalkyl group having 1 to 8 carbon atoms. R4 and R5 may be the same or different.)

（式中、Ｒ６，Ｒ７およびＲ８は、炭素数１から８のパーフルオロアルキル基を表す。Ｒ６，Ｒ７およびＲ８は、同一であってもよいし異なっていてもよい。）

(In the formula, R6, R7 and R8 represent a perfluoroalkyl group having 1 to 8 carbon atoms. R6, R7 and R8 may be the same or different.)

（式中、Ｒ９は、炭素数２から４のパーフルオロアルキレン基を表す。）

(In the formula, R9 represents a perfluoroalkylene group having 2 to 4 carbon atoms.)

  Specific examples of such metal salts that generate anions include lithium trifluoromethanesulfonate shown in Chemical formula 12, bis (trifluoromethanesulfone) imidolithium shown in Chemical formula 13, and bis ( Pentafluoroethanesulfone) imidolithium, tris (trifluoromethanesulfone) methidelithium shown in Chemical Formula 15, 1,1,2,2,3,3-hexafluoropropanedisulfonimide lithium shown in Chemical Formula 16 and the like.

In addition to these metal salts, other metal salts may be used as the electrolyte salt. Examples of the other metal salts include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium perchlorate (LiClO ₄ ), and lithium hexafluorate (LiAsF ₆ ). Of these, lithium hexafluorophosphate is preferred. This is because higher ionic conductivity can be obtained. Another metal salt may be used individually by 1 type, and 2 or more types may be mixed and used for it.

  For example, the secondary battery can be manufactured as follows.

  First, for example, the positive electrode active material layer 21B is formed on the positive electrode current collector 21A to produce the positive electrode 21. The positive electrode active material layer 21B is prepared, for example, by mixing a positive electrode active material powder, a conductive agent, and a binder to prepare a positive electrode mixture, and then using the positive electrode mixture in a solvent such as N-methyl-2-pyrrolidone. The positive electrode mixture slurry is dispersed to form a positive electrode mixture slurry, and the positive electrode mixture slurry is applied to the positive electrode current collector 21A, dried, and compression molded.

  Further, for example, the negative electrode active material layer 22B is formed on the negative electrode current collector 22A to produce the negative electrode 22. The negative electrode active material layer 22B may be formed by, for example, any one of a vapor phase method, a liquid phase method, a baking method, and coating, or a combination of two or more thereof. When formed by a vapor phase method, a liquid phase method, or a firing method, the negative electrode active material layer 22B and the negative electrode current collector 22A may be alloyed at least at a part of the interface at the time of formation. An alloy may be formed by heat treatment under a non-oxidizing atmosphere.

  As the vapor phase method, for example, a physical deposition method or a chemical deposition method can be used. Specifically, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, a thermal CVD (Chemical Vapor Deposition) A chemical vapor deposition method) or a plasma CVD method can be used. As the liquid phase method, a known method such as electrolytic plating or electroless plating can be used. As for the firing method, a known method can be used. For example, an atmosphere firing method, a reaction firing method, or a hot press firing method can be used. In the case of application, it can be formed in the same manner as the positive electrode 21.

  Next, the positive electrode lead 25 is attached to the positive electrode current collector 21A by welding or the like, and the negative electrode lead 26 is attached to the negative electrode current collector 22A by welding or the like. Subsequently, the positive electrode 21 and the negative electrode 22 are wound through the separator 23, and the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the tip of the negative electrode lead 26 is welded to the battery can 11. The positive electrode 21 and the negative electrode 22 are sandwiched between a pair of insulating plates 12 and 13 and stored in the battery can 11. After the positive electrode 21 and the negative electrode 22 are accommodated in the battery can 11, the electrolytic solution is injected into the battery can 11 and impregnated in the separator 23. After that, the battery lid 14, the safety valve mechanism 15, and the heat sensitive resistance element 16 are fixed to the opening end of the battery can 11 by caulking through a gasket 17. Thereby, the secondary battery shown in FIG. 1 is completed.

  In this secondary battery, when charged, for example, lithium ions are released from the positive electrode 21 and inserted in the negative electrode 22 through the electrolytic solution. On the other hand, when discharging is performed, for example, lithium ions are separated from the negative electrode 22 and inserted into the positive electrode 21 through the electrolytic solution. At that time, since the electrolytic solution contains the fluorocarboxylic acid ester shown in Chemical Formula 5 and the high dielectric constant solvent, the decomposition reaction of the solvent in the negative electrode 22 is suppressed.

  FIG. 3 shows a configuration of a secondary battery according to another embodiment of the present invention. In this secondary battery, a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached is accommodated in a film-like exterior member 40, and can be reduced in size, weight, and thickness. ing.

  The positive electrode lead 31 and the negative electrode lead 32 are led out from the inside of the exterior member 40 to the outside, for example, in the same direction. The positive electrode lead 31 and the negative electrode lead 32 are each made of a metal material such as aluminum, copper, nickel, or stainless steel, and each have a thin plate shape or a mesh shape.

  The exterior member 40 is made of, for example, a rectangular aluminum laminated film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. For example, the exterior member 40 is disposed so that the polyethylene film side and the wound electrode body 30 face each other, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive. An adhesive film 41 is inserted between the exterior member 40 and the positive electrode lead 31 and the negative electrode lead 32 to prevent intrusion of outside air. The adhesion film 41 is made of a material having adhesion to the positive electrode lead 31 and the negative electrode lead 32, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 40 may be made of a laminated film having another structure, a polymer film such as polypropylene, or a metal film instead of the above-described aluminum laminated film.

  FIG. 4 shows a cross-sectional structure taken along line II of the spirally wound electrode body 30 shown in FIG. The electrode winding body 30 is obtained by laminating a positive electrode 33 and a negative electrode 34 via a separator 35 and an electrolyte layer 36 and winding them, and the outermost periphery is protected by a protective tape 37.

  The positive electrode 33 has a structure in which a positive electrode active material layer 33B is provided on one or both surfaces of a positive electrode current collector 33A. The negative electrode 34 has a structure in which a negative electrode active material layer 34B is provided on one surface or both surfaces of a negative electrode current collector 34A, and the negative electrode active material layer 34B side is disposed so as to face the positive electrode active material layer 33B. Yes. The configurations of the positive electrode current collector 33A, the positive electrode active material layer 33B, the negative electrode current collector 34A, the negative electrode active material layer 34B, and the separator 35 are respectively the positive electrode current collector 21A, the positive electrode active material layer 21B, and the negative electrode current collector 22A. The same as the negative electrode active material layer 22B and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution and a polymer compound serving as a holding body that holds the electrolytic solution, and has a so-called gel shape. A gel electrolyte is preferable because it can obtain high ionic conductivity and can prevent battery leakage or swelling at high temperatures. The structure of the electrolytic solution (that is, the solvent and the electrolyte salt) is the same as that of the cylindrical secondary battery shown in FIG. The holding body is made of, for example, a polymer material. Examples of the polymer material include, for example, an ether polymer compound such as polyethylene oxide or a crosslinked product containing polyethylene oxide, an ester polymer compound such as polymethacrylate, or an acrylate polymer compound, or polyvinylidene fluoride or vinylidene fluoride. Examples thereof include polymers of vinylidene fluoride such as a copolymer with hexafluoropropylene, and any one of these or a mixture of two or more thereof is used. In particular, from the viewpoint of redox stability, it is desirable to use a fluorine-based polymer compound such as a vinylidene fluoride polymer.

  For example, the secondary battery can be manufactured as follows.

  First, a precursor solution containing a solvent, an electrolyte salt, a polymer compound, and a mixed solvent is applied to each of the positive electrode 33 and the negative electrode 34, and the mixed solvent is volatilized to form the electrolyte layer 36. After that, the positive electrode lead 31 is attached to the end of the positive electrode current collector 33A by welding, and the negative electrode lead 32 is attached to the end of the negative electrode current collector 34A by welding. Next, the positive electrode 33 and the negative electrode 34 on which the electrolyte layer 36 is formed are laminated via a separator 35 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and a protective tape 37 is adhered to the outermost peripheral portion. Thus, the wound electrode body 30 is formed. Finally, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edges of the exterior members 40 are sealed and sealed by heat fusion or the like. At that time, the adhesion film 41 is inserted between the positive electrode lead 31 and the negative electrode lead 32 and the exterior member 40. Thereby, the secondary battery shown in FIGS. 3 and 4 is completed.

  Further, this secondary battery may be manufactured as follows. First, the positive electrode 33 and the negative electrode 34 are prepared as described above, and after the positive electrode lead 31 and the negative electrode lead 32 are attached to the positive electrode 33 and the negative electrode 34, the positive electrode 33 and the negative electrode 34 are stacked via the separator 35 and wound. Rotate and adhere the protective tape 37 to the outermost periphery to form a wound body that is a precursor of the wound electrode body 30. Next, the wound body is sandwiched between the exterior members 40, and the outer peripheral edge portion excluding one side is heat-sealed to form a bag shape, and is stored inside the exterior member 40. Subsequently, an electrolyte composition including a solvent, an electrolyte salt, a monomer that is a raw material of the polymer compound, a polymerization initiator, and other materials such as a polymerization inhibitor as necessary is prepared, and the exterior member Inject into 40.

  After injecting the electrolyte composition, the opening of the exterior member 40 is heat-sealed and sealed in a vacuum atmosphere. Next, heat is applied to polymerize the monomer to obtain a polymer compound, thereby forming a gel electrolyte layer 36, and assembling the secondary battery shown in FIG.

  The operation of this secondary battery is the same as that of the cylindrical secondary battery shown in FIG.

  As described above, according to the battery according to the present embodiment, the electrolyte contains the fluorocarboxylic acid ester shown in Chemical Formula 5 and the high dielectric constant solvent, so that the decomposition reaction of the solvent in the negative electrodes 22 and 34 is suppressed. And cycle characteristics can be improved.

  In particular, the negative electrode active material capable of inserting and extracting electrode reactants into and from the negative electrodes 22 and 34 is selected from the group consisting of simple elements, alloys and compounds of metal elements and simple elements, alloys and compounds of metalloid elements. It is effective when at least one kind is included.

  If the high dielectric constant solvent includes at least one member selected from the group consisting of cyclic carbonates and cyclic carbonate derivatives obtained by substituting some of these hydrogens with halogen, cycle characteristics can be further improved. In particular, if 4-fluoro-1,3-dioxolan-2-one or 4-chloro-1,3-dioxolan-2-one is used, a high effect can be obtained.

  Furthermore, if an anion having a structure in which a perfluoroalkyl group having 1 to 8 carbon atoms or a perfluoroalkylene group having 2 to 4 carbon atoms is bonded to an O═S═O group is contained, the fluorocarboxylic acid ester is increased. A high dielectric constant solvent can be mixed at a ratio, and high ionic conductivity can be obtained.

  Further, specific embodiments of the present invention will be described in detail.

(Examples 1-1 to 1-5)
The coin-type secondary battery shown in FIG. 5 was produced. This secondary battery is formed by laminating a positive electrode 51 and a negative electrode 52 via a separator 53 impregnated with an electrolytic solution, sandwiching between an outer can 54 and an outer cup 55 and caulking via a gasket 56. is there. First, after mixing 94 parts by mass of lithium cobalt composite oxide (LiCoO ₂ ) as a positive electrode active material, 3 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder, N-methyl-2 -Pyrrolidone was added to obtain a positive electrode mixture slurry. Next, the obtained positive electrode mixture slurry was uniformly applied to a positive electrode current collector 51A made of an aluminum foil having a thickness of 20 μm and dried to form a positive electrode active material layer 51B having a thickness of 70 μm. After that, the positive electrode current collector 51A on which the positive electrode active material layer 51B was formed was punched into a circle having a diameter of 16 mm to produce the positive electrode 51.

  A negative electrode active material layer 52B made of silicon having a thickness of 5 μm was formed on the negative electrode current collector 52A made of copper foil having a thickness of 15 μm by sputtering. After that, the negative electrode current collector 52A on which the negative electrode active material layer 52B was formed was punched into a circle having a diameter of 16 mm to produce the negative electrode 52.

  Next, the positive electrode 51 and the negative electrode 52 are laminated via a separator 53 made of a microporous polypropylene film having a thickness of 25 μm, and then 0.1 g of an electrolytic solution is injected into the separator 53, and these are made of an exterior cup 55 made of stainless steel. And the outer can 54 and caulked them to obtain the secondary battery shown in FIG. In Examples 1-1 to 1-5, the electrolyte solution includes a high dielectric constant solvent, a low viscosity solvent, bis (trifluoromethanesulfone) imide lithium as an electrolyte salt, and lithium hexafluorophosphate. Dielectric constant solvent: low-viscosity solvent: bis (trifluoromethanesulfone) imidolithium: lithium hexafluorophosphate = 36: 36: 26: 2 mixed at a mass ratio was used. At that time, the high dielectric constant solvent was ethylene carbonate in Example 1-1, 4-chloro-1,3-dioxolan-2-one in Example 1-2, and 4-chloro in Examples 1-3 to 1-5. Fluoro-1,3-dioxolan-2-one was used. The low viscosity solvent was isopropyl trifluoroacetate in Examples 1-1 to 1-3, ethyl trifluoroacetate in Example 1-4, and methyl pentafluoropropionate in Example 1-5.

  As Comparative Example 1-1 with respect to Examples 1-1 to 1-5, except that the high dielectric constant solvent was ethylene carbonate and the low-viscosity solvent was diethyl carbonate, the others were the same as those of Examples 1-1 to 1-5. Similarly, a coin-type secondary battery was produced. Further, as Comparative Example 1-2, Examples 1-1 to 1 were otherwise performed except that the high dielectric constant solvent was 4-fluoro-1,3-dioxolan-2-one and the low viscosity solvent was diethyl carbonate. A coin-type secondary battery was produced in the same manner as in -5. Furthermore, as Comparative Example 1-3, ethylene carbonate as a high dielectric constant solvent, isopropyl trifluoroacetate as a low viscosity solvent, lithium hexafluorophosphate as an electrolyte salt, ethylene carbonate: isopropyl trifluoroacetate: six Although an electrolytic solution was prepared with a mass ratio of lithium fluorophosphate = 42: 42: 16, the solvent was not mixed uniformly and could not be used as the electrolytic solution.

  For the obtained secondary batteries of Examples 1-1 to 1-5 and Comparative examples 1-1 and 1-2, the battery was charged at 1.77 mA with 4.2 V as the upper limit for 12 hours, and then rested for 10 minutes. Charging / discharging of discharging until it reached 2.5 V at .77 mA was repeated, and the discharge capacity maintenance rate at the 50th cycle was determined. The discharge capacity retention rate at the 50th cycle was calculated as (discharge capacity at the 50th cycle / initial discharge capacity) × 100. The obtained results are shown in Table 1.

  As can be seen from Table 1, according to Examples 1-1 and 1-3 using isopropyl trifluoroacetate which is a fluorocarboxylic acid ester shown in Chemical Formula 5 as a low-viscosity solvent, Comparative Example 1 in which this was not used The discharge capacity retention ratios were improved from -1 and 1-2, respectively. Further, Examples 1-2 and 1-3 using cyclic carbonate derivatives in which a part of hydrogen is substituted with halogen are more preferable than Example 1-1 using cyclic carbonate as a high dielectric constant solvent. Discharge capacity maintenance rate improved. Furthermore, in Examples 1-4 and 1-5 in which another fluorocarboxylic acid ester was used instead of isopropyl trifluoroacetate, the discharge capacity retention ratio was improved.

  That is, if the fluorocarboxylic acid ester shown in Chemical Formula 5 is used as the low-viscosity solvent, cycle characteristics can be improved, and a cyclic carbonate derivative in which a part of hydrogen is substituted with halogen can be used as the high dielectric constant solvent. It has been found that the cycle characteristics can be further improved.

(Examples 2-1 to 2-5, 3-1 to 3-5, 4-1)
As Examples 2-1 to 2-5, a negative electrode active material layer 52B made of tin having a thickness of 5 μm was formed on a negative electrode current collector 52A made of copper foil having a thickness of 15 μm by vacuum vapor deposition using tin as the negative electrode active material. Except for the formation, coin-type secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-5.

  As Examples 3-1 to 3-5, a tin-cobalt alloy having a mass ratio of tin: cobalt = 72: 28 was used as the negative electrode active material, 94 parts by mass of this tin-cobalt alloy, and 3 parts by mass of graphite as a conductive agent. And 3 parts by mass of polyvinylidene fluoride as a binder, N-methyl-2-pyrrolidone is added, and uniformly applied to a negative electrode current collector 52A made of a copper foil having a thickness of 15 μm and dried. A coin-type secondary battery was fabricated in the same manner as in Examples 1-1 to 1-5, except that the negative electrode active material layer 52B having a thickness of 70 μm was formed by the above.

  As Example 4-1, using graphite as the negative electrode active material, mixing 97 parts by mass of this graphite and 3 parts by mass of polyvinylidene fluoride as a binder, adding N-methyl-2-pyrrolidone, A coin-type battery is formed in the same manner as in Example 1-3 except that the negative electrode active material layer 52B having a thickness of 70 μm is formed by uniformly applying and drying the negative electrode current collector 52A made of a copper foil having a thickness of 15 μm. A secondary battery was prepared.

  As Comparative Examples 2-1 and 3-1 for these examples, except that the high dielectric constant solvent was ethylene carbonate and the low viscosity solvent was diethyl carbonate, that is, the same electrolytic solution as in Comparative Example 1-1 was used. Otherwise, coin-type secondary batteries were fabricated in the same manner as in Examples 2-1 to 2-5 and 3-1 to 3-5. Further, as Comparative Examples 2-2, 3-2 and 4-1, except that the high dielectric constant solvent was 4-fluoro-1,3-dioxolan-2-one and the low viscosity solvent was diethyl carbonate, Other than using the same electrolytic solution as in Comparative Example 1-2, other than the coin type secondary as in Examples 2-1 to 2-5, 3-1 to 3-5, 4-1. A battery was produced.

  Regarding the fabricated secondary batteries of Examples 2-1 to 2-5, 3-1 to 3-5, 4-1, and Comparative Examples 2-1, 2-2, 3-1, 3-2, 4-1. Also, the discharge capacity retention ratio at the 50th cycle was determined in the same manner as in Examples 1-1 to 1-5. The results are shown in Tables 2-4.

  As can be seen from Tables 2 to 4, according to Examples 2-1 to 2-5, 3-1 to 3-5, 4-1, similarly to Examples 1-1 to 1-5, Comparative Example 2 -1,2-2,3-1, 3-2, 4-1, higher discharge capacity retention rate was obtained, and in particular, a cyclic carbonate derivative in which a part of hydrogen was substituted with halogen as a high dielectric constant solvent It was able to be improved more in the used Examples 2-2 to 2-5, 3-2 to 3-5. That is, even when other negative electrode active materials are used, if the fluorocarboxylic acid ester shown in Chemical Formula 5 is used as the low viscosity solvent, the cycle characteristics can be improved, and a part of the high dielectric constant solvent can be used. It has been found that cycle characteristics can be further improved by using a cyclic carbonate derivative in which hydrogen is substituted with halogen.

  Further, as can be seen by comparing Tables 1 to 4, Examples 1-1 to 1-1 using a metal element or a semi-metal element as a simple substance, an alloy, or a compound as a negative electrode active material capable of occluding and releasing an electrode reactant. According to -5, 2-1 to 2-5, 3-1 to 3-5, compared with Comparative Examples 1-1, 1-2, 2-1, 2-2, 3-1, 3-2 While the discharge capacity retention rate could be greatly improved, Example 4-1 using a carbon material could only improve slightly.

  That is, when a single element, alloy or compound of a metal element or metalloid element is used as a negative electrode active material capable of occluding and releasing an electrode reactant, the fluorocarboxylic acid ester shown in Chemical Formula 5 is used as a low viscosity solvent. It was found that a high effect can be obtained.

(Examples 5-1, 5-2, 6-1, 6-2, 7-1, 7-2)
Except for replacing the electrolyte salt with lithium tris (trifluoromethanesulfone) methide lithium and lithium hexafluorophosphate, or lithium bis (pentafluoroethanesulfone) imido, Example 1-3, Example 2-3, or A coin-type secondary battery was produced in the same manner as in Example 3-3. In Examples 5-1, 6-1 and 7-1, the composition of the electrolytic solution was, by mass ratio, 4-fluoro-1,3-dioxolan-2-one: isopropyl trifluoroacetate: tris (trifluoromethanesulfone). Lithium methide: lithium hexafluorophosphate = 33: 33: 32: 2. In Examples 5-2, 6-2, and 7-2, by mass ratio, 4-fluoro-1,3-dioxolan-2-one: isopropyl trifluoroacetate: bis (pentafluoroethanesulfone) imide lithium = 33:33:34.

  The fabricated secondary batteries of Examples 5-1, 5-2, 6-1, 6-2, 7-1, 7-2 were the same as in Examples 1-3, 2-3, and 3-3. The discharge capacity retention rate at the 50th cycle was determined. The results are shown in Tables 5 to 7 together with the results of Example 1-3, Example 2-3, or Example 3-3.

  As can be seen from Tables 5 to 7, in place of bis (trifluoromethanesulfone) imide lithium, an implementation using an electrolyte salt generated by dissociation of an anion having a structure in which another perfluoroalkylene group is bonded to an O═S═O group Also in Examples 5-1, 6-1 and 7-1, the capacity retention rate was improved in the same manner as in Examples 1-3, 2-3 and 3-3. In addition, the capacity retention rate was similarly improved in Examples 5-2, 6-2, and 6-3 that did not use lithium hexafluorophosphate.

  That is, if an electrolyte salt produced by dissociation of an anion having a structure in which a perfluoroalkylene group is bonded to an O═S═O group is used, cycle characteristics can be improved. It turned out that it may mix.

(Examples 8-1, 9-1, 10-1)
Except for changing the content of isopropyl trifluoroacetate, that is, changing the composition of the electrolytic solution, the others were as in Example 1-3, Example 2-3, or Example 3-3. Similarly, a coin-type secondary battery was produced. The compositions of the electrolyte solutions of Examples 8-1, 9-1, and 10-1 are, by mass ratio, 4-fluoro-1,3-dioxolan-2-one: isopropyl trifluoroacetate: bis (pentafluoromethanesulfone). Imidolithium: lithium hexafluorophosphate = 48: 24: 26: 2.

  For the fabricated secondary batteries of Examples 8-1, 9-1, and 10-1, the discharge capacity retention ratio at the 50th cycle was determined in the same manner as in Examples 1-3, 2-3, and 3-3. . The results are shown together with the results of Examples 1-3, 5-1, 5-2, Examples 2-3, 6-1, 6-2, or Examples 3-3, 7-1, 7-2. Shown in 8-10.

  As can be seen from Tables 8 to 10, the discharge capacity retention rate increased as the content of isopropyl trifluoroacetate increased, and then decreased after showing the maximum value. That is, it was found that the content of the fluorocarboxylic acid ester shown in Chemical Formula 5 is preferably 25% by mass or more.

  Although the present invention has been described with reference to the embodiments and examples, the present invention is not limited to the embodiments and examples, and various modifications can be made. For example, in the above-described embodiments and examples, a coin-type secondary battery and a wound-structure secondary battery have been specifically described. However, the present invention is not limited to a square-type, sheet-type or card-type, or The present invention can be similarly applied to a secondary battery having a stacked structure in which a plurality of positive electrodes and negative electrodes are stacked. Further, the present invention is not limited to the secondary battery, and can be similarly applied to other batteries such as a primary battery.

  In addition, in the above embodiments and examples, the case where lithium is used as the electrode reactant has been described. However, other group 1 elements in the long-period periodic table such as sodium (Na) or potassium (K), or The present invention can also be applied to the case of using elements of Group 2 in the long-period periodic table such as magnesium or calcium (Ca), other light metals such as aluminum, lithium, or alloys thereof. An effect can be obtained. At that time, a negative electrode material, a positive electrode material, a non-aqueous solvent, or the like that can occlude and release the electrode reactant is selected according to the electrode reactant.

It is sectional drawing showing the structure of the secondary battery which concerns on one embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG. It is a disassembled perspective view showing the structure of the secondary battery which concerns on other embodiment of this invention. It is sectional drawing along the II line | wire of the winding electrode body shown in FIG. It is sectional drawing showing the structure of the secondary battery produced in the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Battery can, 12, 13 ... Insulation board, 14 ... Battery cover, 15 ... Safety valve mechanism, 15A ... Disc board, 16 ... Heat sensitive resistance element, 17, 56 ... Gasket, 20, 30 ... Winding electrode body, 21 , 33, 51 ... positive electrode, 21A, 33A, 51A ... positive electrode current collector, 21B, 33B, 51B ... positive electrode active material layer, 22, 34, 52 ... negative electrode, 22A, 34A, 52A ... negative electrode current collector, 22B, 34B, 52B ... negative electrode active material layer, 23, 35, 53 ... separator, 24 ... center pin, 25, 31 ... positive electrode lead, 26, 32 ... negative electrode lead, 36 ... electrolyte, 37 ... protective tape, 40 ... exterior member, 41 ... Adhesion film, 54 ... Exterior can, 55 ... Exterior cup

Claims (15)

An electrolytic solution comprising the fluorocarboxylic acid ester represented by Chemical Formula 1 and a high dielectric constant solvent.

(In the formula, R1 represents a group in which at least part of hydrogen of an alkyl group having 1 to 5 carbon atoms is substituted with fluorine. R2 represents an alkyl group having 1 to 4 carbon atoms or at least part of hydrogen thereof. Represents a group substituted with fluorine.)   2. The electrolytic solution according to claim 1, comprising 25 mass% or more of the fluorocarboxylic acid ester.   The fluorocarboxylic acid ester is methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, methyl pentafluoropropionate, ethyl pentafluoropropionate, propyl pentafluoropropionate and butyl pentafluoropropionate The electrolytic solution according to claim 1, comprising at least one member selected from the group consisting of:   2. The electrolytic solution according to claim 1, wherein the high dielectric constant solvent includes at least one member selected from the group consisting of cyclic carbonates and cyclic carbonate derivatives obtained by substituting some of their hydrogens with halogens.   The electrolytic solution according to claim 4, wherein the cyclic carbonate derivative contains at least one of 4-fluoro-1,3-oxolane-one and 4-chloro-1,3-oxolane-one.   2. The anion having a structure in which a perfluoroalkyl group having 1 to 8 carbon atoms or a perfluoroalkylene group having 2 to 4 carbon atoms is bonded to an O═S═O group. Electrolytic solution. The electrolytic solution according to claim 6, wherein the anion contains at least one of the anions shown in Chemical Formulas 2 to 5.

(In the formula, R3 represents a perfluoroalkyl group having 1 to 8 carbon atoms.)

(In the formula, R4 and R5 each represent a perfluoroalkyl group having 1 to 8 carbon atoms.)

(In the formula, R6, R7 and R8 represent a perfluoroalkyl group having 1 to 8 carbon atoms.)

(In the formula, R9 represents a perfluoroalkylene group having 2 to 4 carbon atoms.) A battery comprising an electrolyte solution together with a positive electrode and a negative electrode,
The battery characterized in that the electrolytic solution contains the fluorocarboxylic acid ester shown in Chemical Formula 6 and a high dielectric constant solvent.

(In the formula, R1 represents a group in which at least part of hydrogen of an alkyl group having 1 to 5 carbon atoms is substituted with fluorine. R2 represents an alkyl group having 1 to 4 carbon atoms or at least part of hydrogen thereof. Represents a group substituted with fluorine.)   The battery according to claim 8, wherein the electrolytic solution contains 25% by mass or more of the fluorocarboxylic acid ester.   The fluorocarboxylic acid ester is methyl trifluoroacetate, ethyl trifluoroacetate, propyl trifluoroacetate, butyl trifluoroacetate, methyl pentafluoropropionate, ethyl pentafluoropropionate, propyl pentafluoropropionate and butyl pentafluoropropionate The battery according to claim 8, comprising at least one member selected from the group consisting of:   9. The battery according to claim 8, wherein the high dielectric constant solvent includes at least one member selected from the group consisting of cyclic carbonates and cyclic carbonate derivatives obtained by substituting some of the hydrogen atoms with halogens.   12. The battery according to claim 11, wherein the cyclic carbonate derivative includes at least one of 4-fluoro-1,3-oxolane-one and 4-chloro-1,3-oxolane-one.   The electrolyte solution further includes an anion having a structure in which a perfluoroalkyl group having 1 to 8 carbon atoms or a perfluoroalkylene group having 2 to 4 carbon atoms is bonded to an O═S═O group. Item 9. The battery according to Item 8. The battery according to claim 13, wherein the anion contains at least one of the anions shown in Chemical Formula 7 to Chemical Formula 10.

(In the formula, R3 represents a perfluoroalkyl group having 1 to 8 carbon atoms.)

(In the formula, R4 and R5 each represent a perfluoroalkyl group having 1 to 8 carbon atoms.)

(In the formula, R6, R7 and R8 represent a perfluoroalkyl group having 1 to 8 carbon atoms.)

(In the formula, R9 represents a perfluoroalkylene group having 2 to 4 carbon atoms.) The negative electrode is at least one member selected from the group consisting of simple elements, alloys and compounds of metal elements and simple elements, alloys and compounds of metalloid elements as negative electrode active materials capable of inserting and extracting electrode reactants. The battery according to claim 8, comprising:

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