JP4826128B2 - Secondary battery electrolyte and secondary battery - Google Patents

Description

The present invention relates to a secondary battery using the electrolyte and for a secondary battery comprising a fluoride carbonate.

  In recent years, many portable electronic devices such as notebook portable computers, mobile phones, camera-integrated VTRs (video tape recorders), digital cameras, silicon audio, and hard disk players have appeared, and their size and weight have been reduced. Accordingly, as a power source for these portable electronic devices, development of a secondary battery that is lightweight and capable of obtaining a high energy density is in progress. As a secondary battery capable of obtaining a high energy density, for example, a lithium secondary battery is known.

  In these lithium secondary batteries, in order to improve various battery characteristics, for example, improvement of the electrolytic solution is performed. For example, use of 4-fluoro-1,3-dioxolan-2-one has been studied in order to improve cycle characteristics and the like (see, for example, Patent Document 1).

In addition, in order to suppress abnormal heat generation during overcharge, for example, the use of aromatic compounds has been studied. For example, Patent Documents 2 to 6 discuss the use of anisole derivatives, biphenyl, 4,4′-dimethylbiphenyl, 3-R-thiophene, 3-chlorothiophene, furan, and the like. Patent Document 7 discusses the use of a nonionic aromatic compound having an alkyl group. Further, Patent Document 8 discusses the use of 2,2-diphenylpropane and the like.
Japanese Patent Laid-Open No. 7-240232 JP-A-7-302614 JP 2000-156243 A JP-A-9-106835 JP-A-9-171840 JP-A-10-32258 JP-A-10-275632 Japanese Patent Laid-Open No. 11-162512

  By the way, in recent years, these secondary batteries are often used in a high-temperature environment, and the development of an electrolytic solution that can improve high-temperature characteristics such as high-temperature storage characteristics or high-temperature cycle characteristics is eagerly desired. It was.

The present invention has been made in view of such problems, and an object of the present invention is to provide an electrolytic solution for a secondary battery that can improve high-temperature characteristics while maintaining safety during overcharging, and a secondary battery using the same. Is to provide.

The first electrolyte for a secondary battery according to the present invention comprises at least one member selected from the group consisting of tert-alkylbenzene, cycloalkylbenzene and m-phenylcyclohexylbenzene as an aromatic compound, and 4-fluoro-1,3-dioxolane. 2-one is contained, the content of the aromatic compound is 0.1% by mass or more and 8.0% by mass or less, and the content of 4-fluoro-1,3-dioxolan-2-one is 16. 8 mass% or more and those under 59.5% by mass or.

The second electrolyte for a secondary battery according to the present invention contains 2,4-difluoroanisole and 4-fluoro-1,3-dioxolan-2-one, and the content of 2,4-difluoroanisole is or less 0.1 wt% or more 14.7% by weight, 4-fluoro-1, the content of 3-dioxolan-2-one is of under 59.5% by mass or more 16.8 wt%.

A first secondary battery according to the present invention includes an electrolyte solution together with a positive electrode and a negative electrode, and the electrolyte solution is selected from the group consisting of tert-alkylbenzene, cycloalkylbenzene, and m-phenylcyclohexylbenzene as an aromatic compound. And at least one kind of 4-fluoro-1,3-dioxolan-2-one, and the content of the aromatic compound in the electrolytic solution is 0.1% by mass or more and 8.0% by mass or less. 4-fluoro-1 in the liquid, 3-content of dioxolan-2-one is of under 59.5% by mass or more 16.8 wt%.

A second secondary battery according to the present invention includes an electrolyte solution together with a positive electrode and a negative electrode, and the electrolyte solution includes 2,4-difluoroanisole and 4-fluoro-1,3-dioxolan-2-one. The content of 2,4-difluoroanisole in the electrolytic solution is 0.1% by mass or more and 14.7% by mass or less, and the amount of 4-fluoro-1,3-dioxolan-2-one in the electrolytic solution is the content is of under 59.5% by mass or more 16.8 wt%.

According to the secondary battery electrolyte of the present invention, at least one member selected from the group consisting of tert-alkylbenzene, cycloalkylbenzene, and m-phenylcyclohexylbenzene is 0.1% by mass or more and 8.0% by mass or less, 4- Fluoro-1,3-dioxolan-2-one is contained in the range of 16.8 % to 59.5 % by mass, or 2,4-difluoroanisole is 0.1% to 14.7 % by mass. % Or less, and 4-fluoro-1,3-dioxolan-2-one is contained within the range of 16.8 % by mass or more and 59.5 % by mass or less. Can also improve the chemical stability. Thus, lever by the secondary battery of the present invention using the electrolytic solution, while maintaining safety, it is possible to improve the high temperature properties.

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

  The electrolytic solution according to an embodiment of the present invention includes, for example, a solvent, an electrolyte salt dissolved in the solvent, and an additive.

  The solvent contains 4-fluoro-1,3-dioxolan-2-one. Thereby, the decomposition reaction of the solvent can be suppressed.

  As the solvent, in addition to 4-fluoro-1,3-dioxolan-2-one, one or more kinds of other solvents may be mixed and used. Other solvents include, for example, cyclic carbonates such as ethylene carbonate (1,3-dioxolan-2-one), propylene carbonate (4-methyl-1,3-dioxolan-2-one) or butylene carbonate, or 4 -Trifluoromethyl-1,3-dioxolan-2-one, 4,4-difluoro-1,3-dioxolan-2-one, 4,5-difluoro-1,3-dioxolan-2-one, 4,4 , 5-trifluoro-1,3-dioxolan-2-one, 4,4,5,5-tetrafluoro-1,3-dioxolan-2-one, 4-fluoromethyl-1,3-dioxolan-2-one Cyclic carbonate derivatives having halogen atoms such as ON or 4-difluoromethyl-1,3-dioxolan-2-one, or dimethyl carbonate, diethyl carbonate, methyl carbonate Chain carbonates such as ethyl, di (i-propyl) carbonate, di (n-propyl) carbonate, di (n-butyl) carbonate or di (tert-butyl) carbonate, or γ-butyrolactone or γ-valerolactone Or a chain carboxylic acid ester such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate or ethyl propionate, or tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, 1,3-dioxolane, 4-methyl-1 , 3-dioxolane, 1,3-dioxane, 4-methyl-1,3-dioxane or cyclic ethers such as 1,3-benzodioxole, or 1,2-dimethoxyethane, 1,2-diethoxyethane , Diglyme, triglyme, tetraglyme or diechi Chain ethers such as ether, or sulfur compounds such as ethylene sulfite, propane sultone, sulfolane, methyl sulfolane or diethyl sulfine, or nitriles such as acetonitrile or propionitrile, or methyl N, N-dimethylcarbamate, N, Chain carbamate such as methyl N-diethylcarbamate, or 1,3-dioxol-2-one, 4,5-diphenyl-1,3-dioxol-2-one, 4-vinyl-1,3-dioxolane Examples include carbonates having an unsaturated bond such as 2-one, allylmethyl carbonate, or diallyl carbonate.

  Among these, it is preferable to mix with a low viscosity solvent having a viscosity of 1 mPa · s or less. Since 4-fluoro-1,3-dioxolan-2-one is a high dielectric constant solvent having a relative dielectric constant of 30 or more, the ion conductivity can be further improved by mixing with one or more low viscosity solvents. Because you can. Examples of the low-viscosity solvent include chain carbonate ester, chain carboxylate ester, chain ether, or chain carbamate ester among the above-mentioned solvents, and dimethyl carbonate, diethyl carbonate or methyl ethyl carbonate is particularly preferable.

As the electrolyte salt, _{e.g., LiPF 6, LiBF 4, LiClO} 4, LiAsF 6, LiSbF 6, CF 3 SO 3 Li, (CF 3 SO 2) 2 NLi, (CF 3 SO 2) 3 CLi, (C 2 F ₅ SO ₂ ) ₂ NLi, LiCl, LiBr, LiI, LiB (C ₆ H ₅ ) ₄ , LiPF ₄ (CF ₃ ) ₂ , LiPF ₃ (C ₂ F ₅ ) ₃ , LiPF ₃ (CF ₃ ) ₃ , LiPF ₃ (Iso-C ₃ F ₇ ) ₃ , LiPF ₅ (iso-C ₃ F ₇ ), lithium bisoxalate borate (LiB (C ₂ O ₄ ) ₂ ), difluoro [oxolato-O, O ′] lithium borate, etc. Lithium salt.

  As an additive, an aromatic compound is included. Thereby, the temperature rise by overcharge, etc. are suppressed.

  As the aromatic compound, those having 1, 2, or 3 benzene rings are preferable. It is because it will become difficult to melt | dissolve in electrolyte solution when there are many.

  Specifically, benzene, or a benzene derivative such as fluorobenzene, or biphenyl, or 4-fluorobiphenyl, 4-methylbiphenyl, 2-fluorobiphenyl, 3,3′-difluorobiphenyl, 4,4′-difluorobiphenyl, 2-methylbiphenyl, 3-methylbiphenyl, 3,3′-dimethylbiphenyl, 4,4′-dimethylbiphenyl, biphenyl derivatives such as 2-phenoxybiphenyl or 4-tert-butylbiphenyl, or cycloalkylbenzenes such as cyclohexylbenzene, Or a cycloalkylbenzene derivative such as m-phenylcyclohexylbenzene, or dibenzofuran or a derivative thereof, terphenyl, 3-cyclohexylbiphenyl, 1,3-diphenyl Hexane, 3-phenylbicyclohexyl or 1,3-dicyclohexylbenzene, a compound obtained by hydrogenating a part of terphenyl, diphenyl ether or a derivative thereof, 2-chloro-p-xylene, 4-chloro-o-xylene, 4 -Xylene derivatives such as bromo-m-xylene or 2-fluoro-p-xylene, or anisole, or 4-chloroanisole, 2,4-difluoroanisole, 3,5-difluoroanisole, 4-fluoroanisole, 4-bromo Anisole derivatives such as anisole, 2-chloroanisole, 3-chloroanisole, 3-fluoroanisole or 2,3,5,6-tetrafluoro-4-methylanisole, or dimethoxybenzene, or 2-dimethoxy-4-bromoben 1,4-dimethoxy-2-fluorobenzene, 1,3-dimethoxy-5-chlorobenzene, 3,5-dimethoxy-1-fluorobenzene, 1,3-dimethoxy-4-bromobenzene, 2,5-dimethoxy -1-bromobenzene or dimethoxybenzene derivatives such as 1,2,4,5-tetrafluoro-3,6-dimethoxybenzene, or 1,2-diphenoxyethane, 1- (4-biphenyloxy) -2-phenoxy Phenoxyethoxybenzene or a derivative thereof such as ethane or 1- (2-biphenyloxy) 2-phenoxyethane, or diphenoxybenzene or a derivative thereof such as 1,4-diphenoxybenzene or 1,3-diphenoxybenzene, or diphenylmethane 1,2-diphenylethane or Include diphenylalkanes such as 2,2-diphenylpropane or derivatives thereof, or tert-alkylbenzenes such as tert-pentylbenzene, iso-pentylbenzene, tert-butylbenzene or iso-butylbenzene, or iso-alkylbenzenes.

  Among these, those having a fluorine atom are preferable. Specific examples include fluorinated benzene or fluorinated anisole, among which fluorobenzene or 2,4-difluoroanisole is preferred. This is because a high effect can be obtained.

  Further, cycloalkylbenzene or a derivative thereof, or tert-alkylbenzene is also preferred, and among them, cyclohexylbenzene, m-phenylcyclohexylbenzene or tert-pentylbenzene is preferred. Furthermore, biphenyl or terphenyl is also preferred.

  The content of 4-fluoro-1,3-dioxiran-2-one in the electrolytic solution is in the range of 4.2% by mass or more and 85.8% by mass or less, and is 9.1% by mass or more and 68.2% by mass. The following range is preferable, and it is particularly preferable if it is within the range of 16.8% by mass or more and 59.5% by mass or less. Moreover, if the content of the aromatic compound is 2,4-difluoroanisole, it is 14.7% by mass or less, and more preferably 0.8% by mass or more. On the other hand, if it is an aromatic compound other than 2,4-difluoroanisole, it is 8.0 mass% or less, and more preferably 0.8 mass% or more. If the aromatic compound is included within this range, the temperature rise due to overcharge can be further suppressed, but the aromatic compound alone is likely to be decomposed in a high-temperature environment, so that 4-fluoro- It is because decomposition | disassembly of an aromatic compound can be suppressed now by including 1, 3- dioxirane-2-one in this range. Moreover, it is because the temperature rise by overcharge etc. can be suppressed further.

  This electrolytic solution is used for a secondary battery as follows, for example.

(First secondary battery)
FIG. 1 shows a cross-sectional configuration of a first secondary battery using the electrolytic solution according to the present embodiment. This secondary battery is a so-called lithium ion secondary battery in which the capacity of the negative electrode is represented by a capacity component due to insertion and extraction of lithium as an electrode reactant. This secondary battery is a so-called cylindrical type, and a wound electrode body 20 in which a belt-like positive electrode 21 and a negative electrode 22 are wound through a separator 23 inside a substantially hollow cylindrical battery can 11. have. 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, 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 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. 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, one or more of positive electrode materials capable of inserting and extracting lithium as a positive electrode active material, and a conductive material such as a carbon material and a binder as necessary. An agent may be included. The positive electrode material capable of inserting and extracting lithium does not contain lithium such as titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ), niobium selenide (NbSe ₂ ), or vanadium oxide (V ₂ O ₅ ). Examples include chalcogenides and lithium-containing compounds containing lithium.

Among these, lithium-containing compounds are preferable because some compounds can obtain a high voltage and a high energy density. Examples of such a lithium-containing compound include a composite oxide containing lithium and a transition metal element, or a phosphate compound containing lithium and a transition metal element. In particular, cobalt (Co), nickel and manganese (Mn Among these, those containing at least one of them are preferred. This is because a higher voltage can be obtained. The chemical formula is represented by, for example, Li _x MIO ₂ or Li _y MIIPO ₄ . In the formula, MI and MII represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state of the battery, and are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

Specific examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (Li _x CoO ₂ ), lithium nickel composite oxide (Li _x NiO ₂ ), and lithium nickel cobalt composite oxide (Li _x Ni _1-z Co _z O ₂ (z <1)), lithium nickel cobalt manganese composite oxide (Li _x Ni _1-vw Co _v Mn _w O ₂ (v + w <1)), or lithium manganese having a spinel structure Examples include composite oxide (LiMn ₂ O ₄ ). Among these, a composite oxide containing nickel is preferable. This is because a high capacity can be obtained and excellent cycle characteristics can also be obtained. Specific examples of the phosphate compound containing lithium and a transition metal element include, for example, a lithium iron phosphate compound (LiFePO ₄ ) or a lithium iron manganese phosphate compound (LiFe _1-u Mn _u PO ₄ (u <1)). Can be mentioned.

  Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride and chlorotrifluoroethylene, a copolymer of vinylidene fluoride and hexafluoropropylene, or vinylidene fluoride and hexafluoro. Examples include a copolymer of propylene and tetrafluoroethylene.

  The negative electrode 22 has, for example, a structure in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A having a pair of opposed surfaces. The negative electrode current collector 22A is made of, for example, a metal foil such as a copper (Cu) foil, a nickel foil, or a stainless steel foil.

  The negative electrode active material layer 22B includes, for example, any one or more of negative electrode materials capable of inserting and extracting lithium as a negative electrode active material. Examples of the negative electrode material capable of inserting and extracting lithium include a material containing tin or silicon as a constituent element. This is because tin and silicon have a large ability to occlude and release lithium, and a high energy density can be obtained.

  As such a negative electrode material, specifically, a simple substance, an alloy, or a compound of tin, a simple substance, an alloy, or a compound of silicon, or a material having one or more phases thereof at least in part. Is mentioned. In the present invention, alloys include those containing 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.

  As an alloy of tin, for example, as a second constituent element other than tin, silicon, nickel, copper, iron, cobalt, manganese, zinc (Zn), indium (In), silver (Ag), titanium (Ti), Examples include those containing at least one selected from the group consisting of germanium (Ge), bismuth (Bi), antimony (Sb), and chromium (Cr). As an alloy of silicon, for example, as a second constituent element other than silicon, among the group consisting of tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony and chromium And those containing at least one of the following.

  Examples of the tin compound or silicon compound include those containing oxygen (O) or carbon (C), and may contain the second constituent element described above in addition to tin or silicon.

  Among these, as this negative electrode material, tin, cobalt, and carbon are included as constituent elements, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the total of tin and cobalt is A CoSnC-containing material having a cobalt ratio Co / (Sn + Co) of 30% by mass to 70% by mass is preferable. This is because a high energy density can be obtained in such a composition range, and excellent cycle characteristics can be obtained.

  This CoSnC-containing material may further contain other constituent elements as necessary. As other constituent elements, for example, silicon, iron, nickel, chromium, indium, niobium (Nb), germanium, titanium, molybdenum (Mo), aluminum, phosphorus (P), gallium (Ga) or bismuth is preferable. It may contain more than seeds. This is because the capacity or cycle characteristics can be further improved.

  This CoSnC-containing material has a phase containing tin, cobalt, and carbon, and this phase preferably has a low crystallinity or an amorphous structure. In this CoSnC-containing material, it is preferable that at least a part of carbon as a constituent element is bonded to a metal element or a semimetal element as another constituent element. The decrease in cycle characteristics is thought to be due to the aggregation or crystallization of tin or the like, but this is because such aggregation or crystallization can be suppressed by combining carbon with other elements. .

  As a measuring method for examining the bonding state of elements, for example, X-ray photoelectron spectroscopy (XPS) can be cited. In XPS, the peak of the carbon 1s orbital (C1s) appears at 284.5 eV in an energy calibrated apparatus so that the peak of the gold atom 4f orbital (Au4f) is obtained at 84.0 eV if it is graphite. . Moreover, if it is surface contamination carbon, it will appear at 284.8 eV. On the other hand, when the charge density of the carbon element increases, for example, when carbon is bonded to a metal element or a metalloid element, the C1s peak appears in a region lower than 284.5 eV. That is, when the peak of the synthetic wave of C1s obtained for the CoSnC-containing material appears in a region lower than 284.5 eV, at least a part of the carbon contained in the CoSnC-containing material is a metal element or a half of other constituent elements. Combined with metal elements.

  In XPS measurement, for example, the C1s peak is used to correct the energy axis of the spectrum. Usually, since surface-contaminated carbon exists on the surface, the C1s peak of the surface-contaminated carbon is set to 284.8 eV, which is used as an energy standard. In the XPS measurement, the waveform of the C1s peak is obtained as a shape including the surface contamination carbon peak and the carbon peak in the CoSnC-containing material. For example, by analyzing using a commercially available software, the surface contamination The carbon peak and the carbon peak in the CoSnC-containing material are separated. In the waveform analysis, the position of the main peak existing on the lowest bound energy side is used as the energy reference (284.8 eV).

  As a negative electrode material capable of inserting and extracting lithium, for example, a material containing another metal element or other metalloid element capable of forming an alloy with lithium as a constituent element can also be used. Such metal elements or metalloid elements include magnesium (Mg), boron (B), aluminum, gallium, indium, germanium, lead (Pb), bismuth, cadmium (Cd), silver, zinc, hafnium (Hf). , Zirconium (Zr), yttrium (Y), palladium (Pd), or platinum (Pt).

  Examples of negative electrode materials capable of inserting and extracting lithium include cokes, glassy carbons, graphites, non-graphitizable carbons, pyrolytic carbons, carbon fibers, or organic polymer compound combustors. Such carbon materials may be used, and these carbon materials and the negative electrode material described above may be used together. The carbon material has very little change in crystal structure due to insertion and extraction of lithium. For example, when used together with the negative electrode material described above, a high energy density and excellent cycle characteristics can be obtained. It is also preferable because it functions as a conductive agent.

  The negative electrode active material layer 22B may also include other materials that do not contribute to charging, such as a conductive agent, a binder, or a viscosity modifier. Examples of the conductive agent include graphite fiber, metal fiber, and metal powder. Examples of the binder include polyvinylidene fluoride, polytetrafluoroethylene, a copolymer of vinylidene fluoride and chlorotrifluoroethylene, a copolymer of vinylidene fluoride and hexafluoropropylene, or vinylidene fluoride and hexafluoropropylene. Examples thereof include a copolymer with tetrafluoroethylene, styrene butadiene rubber, ethylene-propylene rubber, nitrile rubber, or butadiene rubber. Examples of the viscosity modifier include carboxymethylcellulose.

Note that in this embodiment, by adjusting the amount of the positive electrode active material and the negative electrode material capable of inserting and extracting lithium, lithium can be stored and released rather than the charge capacity of the positive electrode active material. possible as towards the charge capacity due to the anode material increases, lithium metal is not a precipitated on the anode 22 even at the time of full charge.

  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.

  The separator 23 is impregnated with the electrolytic solution according to the present embodiment. As a result, the high temperature characteristics can be improved while maintaining safety during overcharge.

  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, in the same manner as the positive electrode 21, the negative electrode active material layer 22 </ b> B is formed on the negative electrode current collector 22 </ b> A to produce the negative electrode 22.

  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 FIGS. 1 and 2 is completed.

  In the secondary battery, when charged, for example, lithium ions are extracted 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 extracted from the negative electrode 22 and inserted in the positive electrode 21 through the electrolytic solution. At that time, since the electrolyte solution contains 4-fluoro-1,3-dioxolan-2-one and the aromatic compound in the above-described ratio, a temperature increase due to overcharge is suppressed, and the like. High temperature characteristics are improved.

  As described above, according to the present embodiment, the electrolyte contains 8.0% by mass or less of aromatic compound and 4-fluoro-1,3-dioxolan-2-one of 4.2% by mass or more and 85.8% by mass. It is included within the following range, or 2,4-difluoroanisole is 14.7% by mass or less, and 4-fluoro-1,3-dioxolan-2-one is 4.2% by mass or more and 85.8% by mass or less. Thus, the chemical stability can be improved even at high temperatures by acting synergistically. Therefore, high temperature characteristics can be improved while maintaining safety.

(Secondary secondary battery)
The second secondary battery has the same configuration and operation as the first secondary battery except that the configuration of the negative electrode is different, and can be manufactured in the same manner. Therefore, with reference to FIG. 1 and FIG. 2, the same code | symbol is attached | subjected to a corresponding component and description of the same part is abbreviate | omitted.

  Similar to the first secondary battery, the negative electrode 22 has a structure in which a negative electrode active material layer 22B is provided on both surfaces of a negative electrode current collector 22A. The negative electrode active material layer 22B contains, for example, a negative electrode active material containing tin or silicon as a constituent element. Specifically, for example, it contains a simple substance, an alloy, or a compound of tin, or a simple substance, an alloy, or a compound of silicon, and may contain two or more of them.

  The negative electrode active material layer 22B is formed using, for example, a vapor phase method, a liquid phase method, a firing method, or two or more of these methods. The negative electrode active material layer 22B and the negative electrode current collector 22A are formed. Are preferably alloyed in at least 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. .

  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 chemical vapor deposition ( Examples include CVD (Chemical Vapor Deposition), plasma chemical vapor deposition, and thermal spraying. As the liquid phase method, a known method such as electroplating or electroless plating can be used. The firing method is, for example, a method in which a particulate negative electrode active material is mixed with a binder, dispersed in a solvent, applied, and then heat-treated at a temperature higher than the melting point of the binder. A known method can also be used for the firing method, for example, an atmospheric firing method, a reactive firing method, or a hot press firing method.

(Third secondary battery)
The third secondary battery is a so-called lithium metal secondary battery in which the capacity of the negative electrode 22 is represented by a capacity component due to precipitation and dissolution of lithium as an electrode reactant. This secondary battery has the same configuration as the first secondary battery except that the negative electrode active material layer 22B is made of lithium metal, and can be manufactured in the same manner. Therefore, with reference to FIG. 1 and FIG. 2, the same code | symbol is attached | subjected to a corresponding component and description of the same part is abbreviate | omitted.

  That is, this secondary battery uses lithium metal as a negative electrode active material, and thereby can obtain a high energy density. The negative electrode active material layer 22B may be configured to be already provided from the time of assembly, but may be configured by lithium metal which is not present at the time of assembly and is deposited during charging. Alternatively, the negative electrode active material layer 22B may be used as a current collector, and the negative electrode current collector 22A may be deleted.

  In the secondary battery, when charged, for example, lithium ions are extracted from the positive electrode 21 and deposited as lithium metal on the surface of the negative electrode current collector 22A through the electrolytic solution. When the discharge is performed, for example, lithium metal is eluted as lithium ions from the negative electrode active material layer 22B, and is occluded in the positive electrode 21 through the electrolytic solution. Thus, in this secondary battery, the deposition and dissolution of lithium metal are repeated in the negative electrode 22, so that the activity of the negative electrode 22 is very high. In this embodiment, 4-fluoro-1, Since 3-dioxolan-2-one and an aromatic compound are contained in the above-described ratio, a temperature increase due to overcharging is suppressed and high temperature characteristics are improved.

(Fourth secondary battery)
In the fourth secondary battery, the capacity of the negative electrode includes a capacity component due to insertion and extraction of lithium as an electrode reactant, and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof. This secondary battery has the same configuration as that of the first secondary battery except that the configuration of the negative electrode active material layer 22B is different, and can be manufactured in the same manner. Therefore, with reference to FIG. 1 and FIG. 2, the same code | symbol is attached | subjected to a corresponding component and description of the same part is abbreviate | omitted.

  The negative electrode active material layer 22B includes one or more negative electrode materials capable of inserting and extracting lithium as a negative electrode active material, and may include a binder as necessary. As such a negative electrode material, for example, a carbon material described in the first secondary battery, or a material containing a metal element or a metalloid element capable of forming an alloy with lithium as a constituent element can be given. Among these, it is preferable to use a carbon material because excellent cycle characteristics can be obtained.

  The amount of the negative electrode material capable of inserting and extracting lithium is adjusted so that the charge capacity of the negative electrode material is smaller than the charge capacity of the positive electrode 21. As a result, in the secondary battery, lithium metal starts to deposit on the negative electrode 22 at the time when the open circuit voltage (that is, the battery voltage) is lower than the overcharge voltage in the charging process.

  The overcharge voltage refers to the open circuit voltage when the battery is overcharged. For example, the “lithium secondary battery” is one of the guidelines established by the Japan Storage Battery Industry Association (Battery Industry Association). Refers to a voltage that is higher than the open circuit voltage of a “fully charged” battery as defined and defined in the “Safety Evaluation Criteria Guidelines” (SBA G1101). In other words, it refers to a voltage higher than the open circuit voltage after charging using the charging method, standard charging method, or recommended charging method used when determining the nominal capacity of each battery. For example, when full charge occurs when the open circuit voltage is 4.2 V, lithium metal is formed on the surface of the negative electrode material capable of inserting and extracting lithium in a part of the open circuit voltage in the range of 0 V to 4.2 V. Is deposited. Therefore, in this secondary battery, both the negative electrode material capable of occluding and releasing lithium and lithium metal function as the negative electrode active material, and the negative electrode material capable of occluding and releasing lithium is a base material on which the lithium metal is deposited. It has become. Thereby, in this secondary battery, the characteristics of both a so-called lithium ion secondary battery and a so-called lithium metal secondary battery can be obtained. That is, high energy density can be obtained, and cycle characteristics and quick charge characteristics can be improved.

  In the secondary battery, when charged, lithium ions are released from the positive electrode 21 and are first inserted into the negative electrode material capable of inserting and extracting lithium contained in the negative electrode 22 through the electrolytic solution. When charging is further continued, lithium metal begins to deposit on the surface of the negative electrode material capable of inserting and extracting lithium in a state where the open circuit voltage is lower than the overcharge voltage. After that, lithium metal continues to deposit on the negative electrode 22 until charging is completed. Next, when discharging is performed, first, lithium metal deposited on the negative electrode 22 is eluted as ions, and is occluded in the positive electrode 21 through the electrolytic solution. When the discharge is further continued, lithium ions are released from the negative electrode material capable of inserting and extracting lithium in the negative electrode 22 and inserted into the positive electrode 21 through the electrolytic solution. Thus, in this secondary battery as well, since the deposition and dissolution of lithium metal are repeated in the negative electrode 22, the activity of the negative electrode 22 is very high, but in this embodiment, 4-fluoro-1, Since 3-dioxolan-2-one and an aromatic compound are contained in the above-described ratio, a temperature increase due to overcharging is suppressed and high temperature characteristics are improved.

(Fifth secondary battery)
FIG. 3 shows the configuration of the fifth secondary battery. This secondary battery is a so-called laminate film type, and has a wound electrode body 30 to which a positive electrode lead 31 and a negative electrode lead 32 are attached accommodated in a film-shaped exterior member 40.

  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 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 both surfaces of a negative electrode current collector 34A, and the negative electrode active material layer 34B and the positive electrode active material layer 33B are arranged to face each other. The configuration 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 is the same as that of the positive electrode current collector 21A, positive electrode active This is the same as the material layer 21B, the negative electrode current collector 22A, the negative electrode active material layer 22B, and the separator 23.

  The electrolyte layer 36 includes an electrolytic solution according to the present embodiment and a polymer compound that serves as a holding body that holds the electrolytic solution, and has a so-called gel shape. A gel electrolyte is preferable because high ion conductivity can be obtained and battery leakage can be prevented. Examples of the polymer compound 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 an electrolytic solution, 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. Next, the positive electrode lead 31 is attached to the positive electrode current collector 33A, and the negative electrode lead 32 is attached to the negative electrode current collector 34A. Subsequently, 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 the protective tape 37 is attached to the outermost peripheral portion. The wound electrode body 30 is formed by bonding. After that, for example, the wound electrode body 30 is sandwiched between the exterior members 40, and the outer edge portions of the exterior members 40 are sealed and sealed by thermal 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 an electrolytic solution, 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 interior of the exterior member 40 Then, the opening of the exterior member 40 is heat-sealed and sealed. Thereafter, heat is applied to polymerize the monomer to obtain a polymer compound, thereby forming the gel electrolyte layer 36, and assembling the secondary battery shown in FIGS.

  The operation of this secondary battery is the same as that of the first to fourth secondary batteries described above.

  Thus, according to the present embodiment, since the 4-fluoro-1,3-dioxolan-2-one and the aromatic compound are included in the above-described ratio, the second to fifth secondary batteries are included. In the same manner as in the first secondary battery, these can act synergistically to improve chemical stability even at high temperatures, and to improve high-temperature characteristics while maintaining safety. .

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

( Experimental Examples 1-1 to 1-7)
A battery in which the capacity of the negative electrode 22 is represented by a capacity component due to insertion and extraction of lithium, a so-called lithium ion secondary battery was manufactured. At that time, the battery was as shown in FIG.

First, lithium carbonate (Li ₂ CO ₃ ) and cobalt carbonate (CoCO ₃ ) are mixed at a ratio of Li ₂ CO ₃ : CoCO ₃ = 0.5: 1 (molar ratio), and 5 ° C. at 900 ° C. in the air. After firing for a time, lithium-cobalt composite oxide (LiCoO ₂ ) as a positive electrode material was obtained. Next, 91 parts by mass of this lithium / cobalt composite oxide, 6 parts by mass of graphite as a conductive agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a positive electrode mixture. Subsequently, this positive electrode mixture is dispersed in N-methyl-2-pyrrolidone as a solvent to form a positive electrode mixture slurry, which is uniformly applied to both surfaces of a positive electrode current collector 21A made of a strip-shaped aluminum foil having a thickness of 20 μm and dried. Then, the cathode active material layer 21B was formed by compression molding with a roll press machine, and the cathode 21 was produced. After that, an aluminum positive electrode lead 25 was attached to one end of the positive electrode current collector 21A.

  Further, 80 parts by mass of CoSnC-containing material powder as a negative electrode material, 11 parts by mass of graphite (KS-15 manufactured by Lonza) and 1 part by mass of acetylene black as a conductive agent, and 8 parts by mass of polyvinylidene fluoride as a binder, After being dispersed in N-methyl-2-pyrrolidone, the negative electrode current collector 22A made of a copper foil having a thickness of 10 μm was uniformly applied and dried to form the negative electrode active material layer 22B, thereby preparing the negative electrode 22. After that, a nickel negative electrode lead 26 was attached to one end of the negative electrode current collector 22A. At that time, the filling amount of the positive electrode material and the negative electrode material was adjusted so that the capacity of the negative electrode 22 was represented by a capacity component due to insertion and extraction of lithium.

  Furthermore, the CoSnC-containing material powder was synthesized using a mechanochemical reaction by mixing cobalt-tin alloy powder and carbon powder. When the composition of the obtained CoSnC-containing material was analyzed, the content of cobalt was 29.3 mass%, the content of tin was 49.9 mass%, the content of carbon was 19.8 mass%, The ratio Co / (Sn + Co) of cobalt to the total with cobalt was 37% by mass. The carbon content was measured by a carbon / sulfur analyzer, and the cobalt and tin contents were measured by ICP (Inductively Coupled Plasma) emission analysis. Further, when X-ray diffraction was performed on the obtained CoSnC-containing material, a diffraction peak having a wide half-width with a diffraction angle 2θ of 1.0 ° or more was observed between diffraction angles 2θ = 20 ° to 50 °. It was. Further, when XPS was performed on the CoSnC-containing material, a peak P1 was obtained as shown in FIG. When the peak P1 was analyzed, a peak P2 of surface contamination carbon and a peak P3 of C1s in the CoSnC-containing material on the lower energy side than the peak P2 were obtained. This peak P3 was obtained in a region lower than 284.5 eV. That is, it was confirmed that carbon in the CoSnC-containing material was bonded to other elements.

  After each of the positive electrode 21 and the negative electrode 22 was prepared, a separator (manufactured by Ube Industries) 23 composed of a polypropylene-polyethylene-polypropylene film having a thickness of 25 μm was prepared. The laminated body was wound many times in a spiral shape, and the winding end portion was fixed with an adhesive tape to produce a wound electrode body 20.

  After producing the wound electrode body 20, the wound electrode body 20 is sandwiched between the pair of insulating plates 12 and 13, the negative electrode lead 26 is welded to the battery can 11, and the positive electrode lead 25 is welded to the safety valve mechanism 15. The wound electrode body 20 was housed inside a nickel-plated iron battery can 11. After that, an electrolytic solution was injected into the battery can 11 by a reduced pressure method to produce a cylindrical secondary battery having a diameter of 18 mm and a height of 65 mm.

In the electrolyte solution, 4-fluoro-1,3-dioxolan-2-one (FEC), ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (DMC), methyl ethyl carbonate (MEC), carbonic acid as a solvent. diethyl (DEC) and 1,3-dioxol-2-one (VC) in the solvent in a mixing ratio shown in Table 1, those of LiPF ₆ was dissolved as an electrolyte salt was added an aromatic compound as a further additive It was. The LiPF ₆ content in the electrolytic solution was 11.8% by mass, and the additive content was 1.0% by mass. Further, the additive, and in Examples 1-1 biphenyl (BP), in Examples 1-2 cycloheteroalkyl as cyclohexyl benzene (CHB), and in Examples 1-3 tert-pentyl benzene (TPB), experimental examples and 1-4 in terphenyl (TP), and fluorobenzene in examples 1-5 (FB), and in examples 1-6 m-phenyl cyclohexylbenzene (pCHB), in experimental example 1-7 2,4 -Difluoroanisole (DFA).

As Comparative Example 1-1 with respect to Experimental Examples 1-1 to 1-7, except that 4-fluoro-1,3-dioxolan-2-one and an additive were not used, the others were Experimental Example 1-1. A secondary battery was produced in the same manner as ˜1-7. Further, as Comparative Example 1-2, a secondary battery was fabricated in the same manner as in Experimental Examples 1-1 to 1-7, except that no additive was used. Further, as Comparative Examples 1-3 to 1-9, except that 4-fluoro-1,3-dioxolan-2-one was not used, the rest was the same as in Experimental Examples 1-1 to 1-7. A secondary battery was produced. The composition of the solvent and the content of the electrolyte salt in the electrolytic solution were as shown in Table 1.

For the fabricated secondary batteries of Experimental Examples 1-1 to 1-7 and Comparative Examples 1-1 to 1-9, the high-temperature storage characteristics, the high-temperature cycle characteristics, and the overcharge characteristics were examined. The results are shown in Table 1.

  The high temperature storage characteristics were examined as follows. First, constant current charging was performed at 23 ° C. at a constant current density of 0.2 C until the battery voltage reached 4.2 V, and then constant voltage charging was performed at a constant voltage of 4.2 V for 3 hours to obtain a fully charged state. Next, constant current discharge was performed at 23 ° C. at a constant current density of 0.2 C until the battery voltage reached 2.5V. This charge / discharge was further performed for one cycle, and the discharge capacity before storage was determined. Subsequently, constant current and constant voltage charging was performed under the same conditions, and after standing for 30 days in a constant temperature bath at 60 ° C., constant current discharging was performed at 23 ° C. under the same conditions to obtain a discharge capacity after storage. . The high-temperature storage characteristics were determined from the ratio of the discharge capacity after storage to the discharge capacity before storage, that is, (discharge capacity after storage / discharge capacity before storage) × 100 (%).

  The high temperature cycle characteristics were examined as follows. First, two cycles of charge / discharge were performed under the conditions described above, and the discharge capacity (discharge capacity at 23 ° C.) was determined. Subsequently, 100 cycles of charge and discharge were performed under the same conditions in a thermostat at 60 ° C., and the discharge capacity at the 100th cycle was determined. The high-temperature cycle characteristics were determined from the discharge capacity maintenance ratio at the 100th cycle at 60 ° C. (discharge capacity at the 100th cycle at 60 ° C./discharge capacity at the 23 ° C.) × 100 (%) with respect to the discharge capacity at 23 ° C.

  Furthermore, the overcharge characteristics were examined as follows. First, a fully charged state was obtained by performing constant current constant voltage charging at 23 ° C. under the above-described conditions. Subsequently, overcharging was performed by passing a constant current of 2 C between the positive electrode 21 and the negative electrode 22. For the overcharge characteristic, the maximum value of the battery temperature until the safety valve mechanism 15 was operated was obtained.

As can be seen from Table 1, according to Experimental Examples 1-1 to 1-7 using 4-fluoro-1,3-dioxolan-2-one and an aromatic compound, 4-fluoro-1,3- More than Comparative Example 1-1 that does not use dioxolan-2-one and an aromatic compound, or Comparative Example 1-2 that does not use an aromatic compound, or 4-fluoro-1,3-dioxolane-2 -Compared with Comparative Examples 1-3 to 1-9 using no ON, both storage characteristics at high temperatures, cycle characteristics, and overcharge characteristics could be improved.

  That is, it was found that if 4-fluoro-1,3-dioxolan-2-one and an aromatic compound are included in the electrolytic solution, both high temperature characteristics and safety can be improved.

( Experimental Examples 2-1 to 2-36)
Except that the content of 4-fluoro-1,3-dioxolan-2-one in the electrolytic solution was changed within the range of 4.2% by mass to 85.8% by mass, others were experimental examples 1-1 to 1-1. A secondary battery was made in the same manner as 1-7. At that time, in Experimental Examples 2-1 to 2-12, the solvent is 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate, and dimethyl carbonate, methyl ethyl carbonate or diethyl carbonate as a low viscosity solvent. If necessary, 1,3-dioxol-2-one was mixed. In Experimental Examples 2-13 to 2-19, 4-fluoro-1,3-dioxolan-2-one, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate or diethyl carbonate as a low-viscosity solvent, and 1,3-dioxole- 2-one was mixed. In Experimental Examples 2-20 to 2-31, 4-fluoro-1,3-dioxolan-2-one, ethylene carbonate and propylene carbonate, dimethyl carbonate, methyl ethyl carbonate or diethyl carbonate as a low viscosity solvent, and as necessary And 1,3-dioxol-2-one. In Experimental Examples 2-32 to 2-36, 4-fluoro-1,3-dioxolan-2-one was mixed with dimethyl carbonate as a low viscosity solvent and 1,3-dioxol-2-one as necessary. It was supposed to be. In these experimental examples, the content of other solvents was changed as the amount of 4-fluoro-1,3-dioxolan-2-one increased. As the aromatic compound, biphenyl, cyclohexylbenzene, and tert-pentylbenzene were mixed and used. Tables 2 and 3 show the solvent composition, LiPF ₆ content, and aromatic compound content in the electrolytic solution.

As Comparative Examples 2-1 to 2-5 with respect to Experimental Examples 2-1 to 2-36, except that 4-fluoro-1,3-dioxolan-2-one was not used, the others were Experimental Examples 2-1 to A secondary battery was fabricated in the same manner as in 2-36. Moreover, as Comparative Example 2-6, except that the content of 4-fluoro-1,3-dioxolan-2-one in the electrolytic solution was 1.7% by mass, the others were Experimental Examples 2-1 to 2- A secondary battery was produced in the same manner as in Example 36. In each comparative example, the composition of the solvent, the content of LiPF _{6 and} the content of the aromatic compound in the electrolytic solution were as shown in Table 3.

For the secondary batteries of experiments were prepared Examples 2-1～2-36 and Comparative Examples 2-1 to 2-6, high temperature storage characteristics in the same manner as in Experiment Example 1-1 to 1-7, the high-temperature cycle characteristics and overcharge The characteristics were investigated. The results are shown in Tables 2 and 3.

As can be seen from Tables 2 and 3, Experimental Examples 2-1 to 2-36 containing 4-fluoro-1,3-dioxolan-2-one within the range of 4.2 mass% to 85.8 mass% According to Comparative Example 2-1, which does not contain 4-fluoro-1,3-dioxolan-2-one or the content of 4-fluoro-1,3-dioxolan-2-one is less than 4.2% by mass Both the storage characteristics at high temperatures, the cycle characteristics, and the overcharge characteristics were improved over ˜2-6. In particular, the content of 4-fluoro-1,3-dioxolan-2-one is in the range of 9.1% by mass to 68.2% by mass, and more preferably 16.8% by mass to 59.5% by mass. A high effect was obtained within the range.

  That is, if 4-fluoro-1,3-dioxolan-2-one is contained within the range of 4.2% by mass or more and 85.8% by mass or less, both high temperature characteristics and safety can be improved. In particular, it was found that the content in the range of 9.1% by mass to 68.2% by mass is preferable, and that the content is preferably in the range of 16.8% by mass to 59.5% by mass.

( Experimental examples 3-1 to 3-15)
Except that the content of biphenyl, cyclohexylbenzene, tert-pentylbenzene, terphenyl, fluorobenzene or m-phenylcyclohexylbenzene in the electrolytic solution was 0.1% by mass or 8.0% by mass, other experiments were conducted. Secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-6. Further, except that the content of 2,4-difluoroanisole in the electrolytic solution was 0.1% by mass, 8.0% by mass or 14.7% by mass, the other two were performed in the same manner as in Experimental Example 1-7. A secondary battery was produced. At that time, in each experimental example, the composition of the solvent and the content of LiPF ₆ in the electrolytic solution were as shown in Tables 4 and 5.

As Comparative Examples 3-1 to 3-13 for Experimental Examples 3-1 to 3-15, biphenyl, cyclohexylbenzene, tert-pentylbenzene, terphenyl, fluorobenzene, m-phenylcyclohexylbenzene, or 2 in the electrolytic solution , 4-difluoroanisole is 11.4% by mass, 11.5% by mass or 17.6% by mass, or 4-fluoro-1,3-dioxolan-2-one in the electrolyte solution A secondary battery was fabricated in the same manner as in Experimental Examples 3-1 to 3-15, except that the content was 1.6% by mass. In each comparative example, the composition of the solvent, the content of LiPF _{6 and} the content of the aromatic compound in the electrolytic solution are as shown in Tables 4 and 5.

For the secondary batteries of experiments were prepared Examples 3-1～3-15 and Comparative Examples 3-1～3-13, high-temperature storage characteristics in the same manner as in Experiment Example 1-1 to 1-7, the high-temperature cycle characteristics and overcharge The characteristics were investigated. The results are shown in Tables 4 and 5 together with the results of Experimental Examples 1-1 to 1-7 and Comparative Example 1-2.

As can be seen from Tables 4 and 5, Experimental Example 1 containing biphenyl, cyclohexylbenzene, tert-pentylbenzene, terphenyl, fluorobenzene or m-phenylcyclohexylbenzene in a range of 8.0% by mass or less. -1 to 1-6, 3-1 to 3-12, or experimental examples 1-7, 3-13 to contain 2,4-difluoroanisole in the range of 14.7% by mass or less According to 3-15, these contents are more than 8.0% by mass, or more than 14.7% by mass, or the content of 4-fluoro-1,3-dioxolan-2-one is 4.2%. Both the storage characteristics at high temperature, the cycle characteristics, and the overcharge characteristics were improved as compared with Comparative Examples 1-2 and 3-1 to 3-13 which are less than mass%.

  That is, 4-fluoro-1,3-dioxolan-2-one is contained in the range of 4.2% by mass or more and 85.8% by mass or less, and 2,4-difluoroanisole is contained in the range of 14.7% by mass or less. It has been found that both high temperature characteristics and safety can be improved if it is included or if other aromatic compounds other than 2,4-difluoroanisole are included within the range of 8.0% by mass or less. .

( Experimental examples 4-1 to 4-8)
Two or more of biphenyl, cyclohexylbenzene, tert-pentylbenzene, terphenyl, fluorobenzene, m-phenylcyclohexylbenzene and 2,4-difluoroanisole were mixed so as to have the contents shown in Table 6. Other than the above, secondary batteries were fabricated in the same manner as in Experimental Examples 1-1 to 1-7. At that time, the composition of the solvent and the content of LiPF ₆ in the electrolytic solution were as shown in Table 6.

As Comparative Examples 4-1 and 4-2 for Experimental Examples 4-1 to 4-8, except that 4-fluoro-1,3-dioxolan-2-one was not used, or 4-fluoro-in the electrolyte solution A secondary battery was fabricated in the same manner as in Experimental Examples 4-1 to 4-8, except that the content of 1,3-dioxolan-2-one was 1.7% by mass. At that time, Table 6 shows the composition of the solvent, the content of LiPF _{6 in} the electrolytic solution, and the content of the aromatic compound.

For the secondary batteries of Experimental Examples 4-1 to 4-8 and Comparative Examples 4-1 and 4-2 were produced, the high-temperature storage characteristics in the same manner as in Experiment Example 1-1 to 1-7, the high-temperature cycle characteristics and overcharge The characteristics were investigated. The results are shown in Table 7.

As can be seen from Tables 6 and 7, using two or more of biphenyl, cyclohexylbenzene, tert-pentylbenzene, terphenyl, fluorobenzene, m-phenylcyclohexylbenzene and 2,4-difluoroanisole, According to Experimental Examples 4-1 to 4-8 containing fluoro-1,3-dioxolan-2-one in the range of 4.2% by mass or more and 85.8% by mass or less, it is less than 4.2% by mass. Compared with Comparative Examples 4-1 and 4-2, storage characteristics at high temperatures, cycle characteristics, and overcharge characteristics could be improved.

  That is, it was found that even when any two or more of the aromatic compounds are mixed, both the high temperature characteristics and the safety can be improved.

( Experimental Examples 5-1 to 5-7)
Except that silicon was used as the negative electrode material, silicon was deposited on the negative electrode current collector 22B made of copper foil by electron beam evaporation, and the negative electrode active material layer 22A was formed by heating and drying, thereby producing the negative electrode 22. Otherwise, secondary batteries were fabricated in the same manner as in Experimental Examples 1-1 to 1-7. At that time, the filling amount of the positive electrode material and the negative electrode material was adjusted so that the capacity of the negative electrode 22 was represented by a capacity component due to insertion and extraction of lithium.

As Comparative Example 5-1 with respect to Experimental Examples 5-1 to 5-7, except that 4-fluoro-1,3-dioxolan-2-one and an additive were not used, that is, Comparative Example 1-1 A secondary battery was fabricated in the same manner as in Experimental Examples 5-1 to 5-7 except that the same electrolytic solution was used. Further, as Comparative Example 5-2, except that the additive was not used, that is, except that the same electrolytic solution as Comparative Example 1-2 was used, the others were as Experimental Examples 5-1 to 5-7. Similarly, a secondary battery was produced. Further, as Comparative Examples 5-3 to 5-9, except that 4-fluoro-1,3-dioxolan-2-one was not used, that is, the same electrolytic solution as Comparative Examples 1-3 to 1-9 A secondary battery was fabricated in the same manner as in Experimental Examples 5-1 to 5-7 except that was used.

For the secondary batteries of experiments were prepared Examples 5-1～5-7 and Comparative Examples 5-1 to 5-9, high temperature storage characteristics in the same manner as in Experiment Example 1-1 to 1-7, the high-temperature cycle characteristics and overcharge The characteristics were investigated. The results are shown in Table 8.

As can be seen from Table 8, the same results as in Experimental Examples 1-1 to 1-7 were obtained. That is, even when other negative electrode materials are used, if the electrolyte contains 4-fluoro-1,3-dioxolan-2-one and an aromatic compound, both high temperature characteristics and safety are improved. I found out that

( Experimental examples 6-1 to 6-29)
Except for changing the content of 4-fluoro-1,3-dioxolan-2-one in the electrolytic solution, that is, Experimental Examples 2-1 to 2-12, 2-20 to 2-31,2-32 A secondary battery was fabricated in the same manner as in Experimental Examples 5-1 to 5-7, except that the same electrolytic solution as in ˜2-36 was used.

As Comparative Examples 6-1 to 6-5 to Experimental Examples 6-1 to 6-29, except that 4-fluoro-1,3-dioxolan-2-one was not used, that is, Comparative Examples 2-1 to 2-1 A secondary battery was fabricated in the same manner as in Experimental Examples 6-1 to 6-27, except that the same electrolytic solution as in 2-5 was used. Further, as Comparative Example 6-6, except that the content of 4-fluoro-1,3-dioxolan-2-one in the electrolytic solution was 1.7% by mass, that is, the same as Comparative Example 6-6 A secondary battery was fabricated in the same manner as in Experimental Examples 6-1 to 6-27, except that the electrolytic solution was used.

For the secondary batteries of experiments were prepared Examples 6-1～6-27 and Comparative Examples 6-1 to 6-6, high temperature storage characteristics in the same manner as in Experiment Example 1-1 to 1-7, the high-temperature cycle characteristics and overcharge The characteristics were investigated. The results are shown in Tables 9 and 10.

As can be seen from Tables 9 and 10, the same results as in Experimental Examples 2-1 to 2-36 were obtained. That is, even when other negative electrode materials are used, if 4-fluoro-1,3-dioxolan-2-one is contained in the range of 4.2% by mass or more and 85.8% by mass or less, the temperature is high. It was found that both the characteristics and safety can be improved, and the range of 9.1% by mass to 68.2% by mass is particularly preferable.

( Experimental examples 7-1 to 7-15)
Except that the content of biphenyl, cyclohexylbenzene, tert-pentylbenzene, terphenyl, fluorobenzene, or m-phenylcyclohexylbenzene in the electrolytic solution was 0.1% by mass or 8.0% by mass, ie, an experiment A secondary battery was fabricated in the same manner as in Experimental Examples 5-1 to 5-7, except that the same electrolytic solution as in Examples 3-1 to 3-12 was used. Further, except that the content of 2,4-difluoroanisole in the electrolytic solution was 0.1% by mass, 8.0% by mass or 14.7% by mass, ie, Experimental Examples 3-13 to 3-15 and A secondary battery was fabricated in the same manner as in Experimental Examples 5-1 to 5-7, except that the same electrolytic solution was used.

As Comparative Examples 7-1 to 7-13 to Experimental Examples 7-1 to 7-15, biphenyl, cyclohexylbenzene, tert-pentylbenzene, terphenyl, fluorobenzene, m-phenylcyclohexylbenzene, or 2 in the electrolytic solution , 4-difluoroanisole is 11.4% by mass, 11.5% by mass or 17.6% by mass, or 4-fluoro-1,3-dioxolan-2-one in the electrolyte solution Except that the content was set to 1.6% by mass, that is, except that the same electrolytic solution as in Comparative Examples 3-1 to 3-13 was used, and the others were the same as in Experimental Examples 7-1 to 7-15. Thus, a secondary battery was produced.

For the secondary batteries of experiments were prepared Examples 7-1～7-15 and Comparative Examples 7-1～7-13, high-temperature storage characteristics in the same manner as in Experiment Example 1-1 to 1-7, the high-temperature cycle characteristics and overcharge The characteristics were investigated. The results are shown in Tables 11 and 12.

As can be seen from Tables 11 and 12, the same results as in Experimental Examples 3-1 to 3-15 were obtained. That is, when other negative electrode materials are used, 4-fluoro-1,3-dioxolan-2-one is contained in the range of 4.2% by mass or more and 85.8% by mass or less, and 2,4-difluoro If anisole is included in the range of 14.7% by mass or less, or other aromatic compound other than 2,4-difluoroanisole is included in the range of 8.0% by mass or less, the high temperature characteristics and It has been found that both safety can be improved.

( Experimental examples 8-1 to 8-8)
Two or more of biphenyl, cyclohexylbenzene, tert-pentylbenzene, terphenyl, fluorobenzene, m-phenylcyclohexylbenzene and 2,4-difluoroanisole were mixed so as to have the contents shown in Table 13. In other words, a secondary battery was fabricated in the same manner as in Experimental Examples 5-1 to 5-7 except that the same electrolytic solution as in Experimental Examples 4-1 to 4-8 was used.

As Comparative Examples 8-1 and 8-2 for Experimental Examples 8-1 to 8-8, except that 4-fluoro-1,3-dioxolan-2-one was not used, or 4-fluoro- 1, the content of 3-dioxolan-2-one except that the 1.7 wt%, i.e., except for using the same electrolyte as in Comparative example 4-1 and 4-2, other experiments Secondary batteries were fabricated in the same manner as in Examples 5-1 to 5-7.

For the secondary batteries of experiments were prepared Examples 8-1～8-8 and Comparative Examples 8-1 and 8-2, high temperature storage characteristics in the same manner as in Experiment Example 1-1 to 1-7, the high-temperature cycle characteristics and overcharge The characteristics were investigated. The results are shown in Table 14.

As can be seen from Tables 13 and 14, the same results as in Experimental Examples 4-1 to 4-8 were obtained. That is, it was found that even when any two or more of the aromatic compounds are mixed, both the high temperature characteristics and the safety can be improved.

( Experimental examples 9-1 to 9-10, 10-1 to 10-10)
As Experimental Examples 9-1 to 9-10, a negative electrode active material layer 22B made of silicon was formed by sputtering on a negative electrode current collector 22B made of copper foil having a thickness of 35 μm using silicon as the negative electrode material. A secondary battery was fabricated in the same manner as in Experimental Examples 1-1 to 1-7, except for the fabrication. At that time, the solvent composition, the content of LiPF ₆ , the type and content of the additive in the electrolytic solution were as shown in Table 15. Moreover, the filling amount of the positive electrode material and the negative electrode material was adjusted so that the capacity of the negative electrode 22 was represented by a capacity component due to insertion and extraction of lithium.

As Experimental Examples 10-1 to 10-10, silicon was used as a negative electrode material, silicon powder having an average particle diameter of 1 μm, polyvinylidene fluoride as a binder, and N-methyl-2-pyrrolidone as a solvent were dispersed. After that, it was applied to a negative electrode current collector 22A made of a copper foil having a thickness of 18 μm, dried and pressurized, and further heat-treated at 400 ° C. for 12 hours in a vacuum atmosphere to form a negative electrode active material layer 22B. A secondary battery was fabricated in the same manner as in Experimental Examples 1-1 to 1-7, except that the negative electrode 22 was fabricated. At that time, silicon powder and polyvinylidene fluoride were mixed at a mass ratio of silicon powder: polyvinylidene fluoride = 90: 10. In addition, the solvent composition, the content of LiPF ₆ , the type and content of additives in the electrolytic solution were as shown in Table 16. Furthermore, the filling amount of the positive electrode material and the negative electrode material was adjusted so that the capacity of the negative electrode 22 was represented by a capacity component due to insertion and extraction of lithium.

As Comparative Examples 9-1 to 9-10 and 10-1 to 10-10 with respect to Experimental Examples 9-1 to 9-10 and 10-1 to 10-10, 4-fluoro-1,3-dioxolan-2-one A secondary battery was fabricated in the same manner as in Experimental Examples 9-1 to 9-10 and 10-1 to 10-10, except that was not used. Tables 15 and 16 show the solvent composition, LiPF ₆ content, additive type and content in the electrolytic solution.

For the secondary batteries of Experimental Examples 9-1～9-10,10-1～10-10 and Comparative Example 9-1～9-10,10-1～10-10 was produced, Experimental Example 1-1-1 The high temperature storage characteristics, high temperature cycle characteristics, and overcharge characteristics were examined in the same manner as in -7. The results are shown in Tables 15 and 16.

  As can be seen from Tables 15 and 16, 4-fluoro-1,3-dioxolan-2-one is contained in the range of 4.2 mass% to 85.8 mass%, and 2,4-difluoroanisole is 14. If it is contained within the range of 7% by mass or less, or other aromatic compound other than 2,4-difluoroanisole is contained within the range of 8.0% by mass or less, both high temperature characteristics and safety are achieved. It has been found that it can be improved.

( Experimental examples 11-1 to 11-14, 12-1 to 12-14, 13-1 to 13-14)
As Experimental Examples 11-1 to 11-14, after using artificial graphite powder as a negative electrode material, and dispersing this artificial graphite powder and polyvinylidene fluoride as a binder in N-methyl-2-pyrrolidone as a solvent was applied to the anode current collector 22A made of a copper foil, dried to form the anode active material layer 22B, except that the anode 22 was formed, the other in the same manner as in experimental example 1-1 to 1-7 A secondary battery was produced. At that time, the solvent composition, the content of LiPF ₆ , the type and content of the additive in the electrolytic solution were as shown in Table 17. Moreover, the filling amount of the positive electrode material and the negative electrode material was adjusted so that the capacity of the negative electrode 22 was represented by a capacity component due to insertion and extraction of lithium.

As experimental examples 12-1 to 12-14, except that the negative electrode 22 was prepared by attaching a lithium metal foil to a negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 15 μm, the other experimental examples 1-1 to 1-1 A secondary battery was fabricated in the same manner as in -7. That is, a lithium metal secondary battery in which the capacity of the negative electrode 22 is expressed by precipitation and dissolution of lithium was produced. At that time, the solvent composition, the content of LiPF ₆ , the type and content of the additive in the electrolytic solution were as shown in Table 18.

As Experimental Examples 13-1 to 13-14, artificial graphite was used as a negative electrode material, and after artificial graphite powder and polyvinylidene fluoride as a binder were dispersed in N-methyl-2-pyrrolidone as a solvent, was applied to the anode current collector 22A made of a copper foil, dried to form the anode active material layer 22B, except that the anode 22 was formed, the other in the same manner as in experimental example 1-1 to 1-7 two A secondary battery was produced. At this time, the filling amount of the positive electrode material and the negative electrode material is such that the capacity of the negative electrode 22 includes a capacity component due to insertion and extraction of lithium and a capacity component due to precipitation and dissolution of lithium, and is represented by the sum thereof. Designed. Table 19 shows the solvent composition, LiPF ₆ content, additive type and content in the electrolytic solution.

As Comparative Examples 11-1 to 11-13, 12-1 to 12-13, 13-1 to 13-13 with respect to this experimental example, 4-fluoro-1,3-dioxolan-2-one was not used. Except that the aromatic compound was not used, or the aromatic compound was not used, or both of these were not used, the others were experimental examples 11-1 to 11-14, 12-1 to 12-14, 13-1 A secondary battery was fabricated in the same manner as 13-14. Tables 17, 18, and 19 show the solvent composition, LiPF ₆ content, additive type and content in the electrolytic solution.

About the produced secondary battery of the experimental example and the comparative example, it carried out similarly to Experimental example 1-1 to 1-7, and investigated the high temperature storage characteristic, the high temperature cycling characteristic, and the overcharge characteristic. The results are shown in Tables 17-19.

  As can be seen from Tables 17 to 19, a lithium ion battery using artificial graphite as a negative electrode material, or a lithium metal secondary battery in which the capacity of the negative electrode 22 is represented by precipitation and dissolution of lithium, or the capacity of the negative electrode 22 is lithium. In the case of a secondary battery that includes a capacity component due to occlusion and release and a capacity component due to precipitation and dissolution of lithium and is expressed as a sum thereof, 4-fluoro-1,3-dioxolan-2-one is also represented by 4 .2 mass% or more and 85.8 mass% or less, 2,4-difluoroanisole is contained in the range of 14.7 mass% or less, or other fragrance other than 2,4-difluoroanisole It was found that both high temperature characteristics and safety can be improved by including a group compound in the range of 8.0% by mass or less.

( Experimental examples 14-1 to 14-3)
Secondary batteries were fabricated in the same manner as in Experimental Examples 5-1 to 5-7, except that a square container having a width of 30 mm, a height of 48 mm, and a thickness of 5 mm was used. At that time, the solvent composition, the LiPF ₆ content, the type and content of the additive in the electrolytic solution were as shown in Table 20. The negative electrode 22 is obtained by forming a negative electrode active material layer 22B made of silicon by an electron beam evaporation method.

As Comparative Examples 14-1 and 14-2 with respect to Experimental Examples 14-1 to 14-3, except that 4-fluoro-1,3-dioxolan-2-one was not used, the others were Experimental Examples 14-1 to 14-1. A secondary battery was fabricated in the same manner as 14-3. Table 20 shows the solvent composition, the content of LiPF ₆ , the type and content of additives in the electrolytic solution.

For the secondary batteries of experiments were prepared Examples 14-1 to 14-3 and Comparative Examples 14-1 and 14-2, the high-temperature storage characteristics in the same manner as in Experiment Example 1-1 to 1-7, the high-temperature cycle characteristics and overcharge The characteristics were investigated. The results are shown in Table 20.

  As can be seen from Table 20, even when other exterior members are used, 4-fluoro-1,3-dioxolan-2-one is included in the range of 4.2% by mass or more and 85.8% by mass or less, 2,4-difluoroanisole may be contained within a range of 14.7% by mass or less, or other aromatic compound other than 2,4-difluoroanisole may be contained within a range of 8.0% by mass or less. It has been found that both high temperature characteristics and safety can be improved.

( Experimental Examples 15-1 to 15-3)
The secondary battery shown in FIGS. 3 and 4 was produced. First, the positive electrode 33 and the negative electrode 34 were produced in the same manner as in Experimental Examples 5-1 to 5-7.

  Next, a block copolymer of vinylidene fluoride and hexafluoropropylene was prepared as a polymer compound, and the block copolymer, an electrolytic solution, and a mixed solvent were mixed to prepare a precursor solution. The ratio of hexafluoropropylene in the copolymer was 7% by mass. The composition of the electrolytic solution was as shown in Table 21.

  The obtained precursor solution was applied to both surfaces of the positive electrode 33 and the negative electrode 34, and then the mixed solvent was volatilized to form a gel electrolyte layer 36.

  After that, the positive electrode 33 and the negative electrode 34 respectively formed with the electrolyte layer 36 were laminated via a separator 35 made of a microporous polyethylene film having a thickness of 25 μm and wound to form a wound electrode body 30.

  The obtained wound electrode body 30 was sealed under reduced pressure in an exterior member 40 made of a laminate film, and the secondary battery shown in FIGS. 3 and 4 was produced.

As Comparative Examples 15-1 and 15-2 for Experimental Examples 15-1 to 15-3, except that 4-fluoro-1,3-dioxolan-2-one was not used, the others were Experimental Examples 15-1 to 15-1. A secondary battery was fabricated in the same manner as in 15-3. Table 21 shows the solvent composition, LiPF ₆ content, additive type and content in the electrolytic solution.

For the fabricated secondary batteries of Experimental Examples 15-1 to 15-3 and Comparative Examples 15-1 and 15-2, high temperature storage characteristics, high temperature cycle characteristics, and overcharge were performed in the same manner as in Experimental Examples 1-1 to 1-7. The characteristics were investigated. The results are shown in Table 21.

  As can be seen from Table 21, even when a gel electrolyte is used, 4-fluoro-1,3-dioxolan-2-one is contained in the range of 4.2% by mass to 85.8% by mass, 2,4-difluoroanisole may be contained within a range of 14.7% by mass or less, or other aromatic compound other than 2,4-difluoroanisole may be contained within a range of 8.0% by mass or less. It has been found that both high temperature characteristics and safety can be improved.

  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, the case where an electrolytic solution is used as an electrolyte or the case where a gel electrolyte in which an electrolytic solution is held in a polymer compound is used has been described. However, other electrolytes may be used. Good. Other electrolytes include, for example, a mixture of an ion conductive inorganic compound such as ion conductive ceramics, ion conductive glass or ionic crystal and an electrolytic solution, or a mixture of another inorganic compound and an electrolytic solution. Or a mixture of these inorganic compounds and a gel electrolyte.

  In the above embodiment and examples, a battery using lithium as an electrode reactant has been described. However, other alkali metals such as sodium (Na) or potassium (K), or alkalis such as magnesium or calcium (Ca) are used. The present invention can also be applied to the case of using an earth metal or another light metal such as aluminum. At that time, the negative electrode active material described in the above embodiment, for example, a material containing tin or silicon as a constituent element, or a carbon material can be used in the same manner for the negative electrode.

Further, in the above-described embodiment or example, a cylindrical type, a square type, or a laminated film type secondary battery has been specifically described. However, the present invention is not limited to a coin type or a button type. next battery or Ru can be similarly applied to secondary batteries having other structures, such as a multilayer structure.

It is sectional drawing showing the structure of the 1st secondary battery using the electrolyte solution 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 5th secondary battery using the electrolyte solution which concerns on one embodiment of this invention. It is sectional drawing showing the structure along the II line of the winding electrode body shown in FIG. An example of the peak obtained by the X-ray photoelectron spectroscopy which concerns on the negative electrode material produced in the Example is represented.

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 ... Gasket, 20, 30 ... Winding electrode body, 21, 33 ... Positive electrode, 21A, 33A ... Positive electrode current collector, 21B, 33B ... Positive electrode active material layer, 22, 34 ... Negative electrode, 22A, 34A ... Negative electrode current collector, 22B, 34B ... Negative electrode active material layer, 23, 35 ... Separator , 24 ... Center pin, 25, 31 ... Positive electrode lead, 26, 32 ... Negative electrode lead, 36 ... Electrolyte layer, 37 ... Protective tape, 40 ... Exterior member, 41 ... Adhesion film.

Claims (14)

Containing at least one member selected from the group consisting of tert-alkylbenzene, cycloalkylbenzene and m-phenylcyclohexylbenzene as an aromatic compound, and 4-fluoro-1,3-dioxolan-2-one;
The content of the aromatic compound is 0.1% by mass or more and 8.0% by mass or less,
The 4-fluoro-1, the content of 3-dioxolan-2-one is 59.5 wt% or less than 16.8 wt%, the electrolyte solution for a secondary battery. The tert-alkylbenzene is tert-pentylbenzene or tert-butylbenzene,
The cycloalkylbenzene is cyclohexylbenzene.
The electrolyte solution for secondary batteries according to claim 1. The electrolyte solution for secondary batteries of Claim 1 used for a lithium secondary battery. 2,4-difluoroanisole and 4-fluoro-1,3-dioxolan-2-one,
The content of 2,4-difluoroanisole is 0.1% by mass or more and 14.7% by mass or less,
The 4-fluoro-1, the content of 3-dioxolan-2-one is 59.5 wt% or less than 16.8 wt%, the electrolyte solution for a secondary battery. The electrolyte solution for secondary batteries of Claim 4 used for a lithium secondary battery. Bei example a cathode, an anode,
The electrolytic solution contains at least one member selected from the group consisting of tert-alkylbenzene, cycloalkylbenzene and m-phenylcyclohexylbenzene as an aromatic compound, and 4-fluoro-1,3-dioxolan-2-one,
The content of the aromatic compound in the electrolytic solution is 0.1% by mass or more and 8.0% by mass or less,
The content of 4-fluoro-1, 3-dioxolan-2-one in the electrolytic solution is 59.5 wt% or less than 16.8 mass%, the secondary battery. The tert-alkylbenzene is tert-pentylbenzene or tert-butylbenzene,
The cycloalkylbenzene is cyclohexylbenzene.
The secondary battery according to claim 6. The negative electrode has a negative electrode current collector provided with a negative electrode active material layer containing a negative electrode material,
The negative electrode material contains silicon or tin as a constituent element,
The secondary battery according to claim 6. The negative electrode has a negative electrode current collector provided with a negative electrode active material layer containing a negative electrode material,
The negative electrode material includes a CoSnC-containing material containing tin, cobalt, and carbon as constituent elements,
In the CoSnC-containing material, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co)) is 30 mass% or more and 70 The half-width of the diffraction peak obtained by X-ray diffraction is 1 ° or more, and not more than mass%.
The secondary battery according to claim 6. The secondary battery according to claim 6, which is a lithium secondary battery. Bei example a cathode, an anode,
The electrolytic solution contains 2,4-difluoroanisole and 4-fluoro-1,3-dioxolan-2-one,
The content of 2,4-difluoroanisole in the electrolytic solution is 0.1% by mass or more and 14.7% by mass or less,
The content of 4-fluoro-1, 3-dioxolan-2-one in the electrolytic solution is 59.5 wt% or less than 16.8 mass%, the secondary battery. The negative electrode has a negative electrode current collector provided with a negative electrode active material layer containing a negative electrode material,
The negative electrode material contains silicon or tin as a constituent element,
The secondary battery according to claim 11. The negative electrode has a negative electrode current collector provided with a negative electrode active material layer containing a negative electrode material,
The negative electrode material includes a CoSnC-containing material containing tin, cobalt, and carbon as constituent elements,
In the CoSnC-containing material, the carbon content is 9.9 mass% or more and 29.7 mass% or less, and the ratio of cobalt to the total of tin and cobalt (Co / (Sn + Co)) is 30 mass% or more and 70 The half-width of the diffraction peak obtained by X-ray diffraction is 1 ° or more, and not more than mass%.
The secondary battery according to claim 11. The secondary battery according to claim 11, wherein the secondary battery is a lithium secondary battery.

Images