JP5002952B2 - battery - Google Patents

Description

  The present invention relates to a battery using a negative electrode active material containing silicon (Si) as a constituent element.

  In recent years, many portable electronic devices such as a camera-integrated VTR (Videotape Recorder), a digital still camera, a mobile phone, a portable information terminal, or a notebook personal computer have appeared, and the size and weight of the portable electronic device have been reduced. Accordingly, development of secondary batteries that are lightweight and can obtain a high energy density as a power source for these electronic devices is underway. Among them, lithium ion secondary batteries using a carbon material for the negative electrode, a composite material of lithium (Li) and a transition metal for the positive electrode, and a carbonate ester for the electrolyte are compared with conventional lead batteries and nickel cadmium batteries. Since a large energy density can be obtained, it is widely used.

In recent years, with the improvement in performance of portable electronic devices, further improvement in capacity has been demanded, and the use of silicon or the like as a negative electrode active material instead of a carbon material has been studied. This is because the theoretical capacity of silicon is 4199 mAh / g, which is much larger than the theoretical capacity of 372 mAh / g of graphite, and an improvement in capacity can be expected. In particular, it has been reported that a negative electrode formed with a silicon thin film on a current collector can retain a relatively large discharge capacity even when lithium (Li) is occluded and released without pulverizing the negative electrode active material. (For example, refer to Patent Document 1).
International Publication No. WO01 / 031724 Pamphlet

  However, as portable electronic devices are increasingly used, recently, they are often placed under high temperature conditions during transportation or use, resulting in a problem of deterioration of battery characteristics. Accordingly, it has been desired to develop a battery capable of obtaining excellent characteristics not only at room temperature but also at high temperatures.

  The present invention has been made in view of such problems, and an object thereof is to provide a battery capable of improving high temperature characteristics.

The battery of the present invention includes an electrolyte together with a positive electrode and a negative electrode, the negative electrode contains a negative electrode active material containing silicon as a constituent element, and the electrolyte includes a cation shown in Chemical Formula 1, N ⁻ (CF ₃ SO ₂ ) ₂ and a room temperature molten salt.

（Ｒ１は、炭素数１から４の直鎖状あるいは分岐状のアルキレン基を表す。Ｒ２は、アルキル基，アリル基またはアルコキシアルキル基を表す。）

(R1 represents a linear or branched alkylene group having 1 to 4 carbon atoms. R2 represents an alkyl group, an allyl group, or an alkoxyalkyl group.)

According to the battery of the present invention, since the electrolyte contains a room temperature molten salt composed of the cation shown in Chemical Formula 1 and N ⁻ (CF ₃ SO ₂ ) ₂ , the decomposition reaction of the electrolyte is suppressed even at a high temperature. Even if left under a high temperature condition or used under a high temperature condition, excellent characteristics can be obtained.

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

(First embodiment)
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. One positive electrode material may be used alone, or a plurality of positive electrode materials may be mixed and used.

  The positive electrode active material layer 21 </ b> B also includes, for example, a conductive material, and may further include a binder as necessary. Examples of the conductive material 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.

  The anode 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. This is because when lithium and an intermetallic compound are formed, they expand and contract with charge / discharge, structural breakdown occurs, current collection performance decreases, and the ability to support the negative electrode active material layer 22B decreases. 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 includes, for example, a negative electrode material capable of inserting and extracting lithium as an electrode reactant as a negative electrode active material.

  A negative electrode material capable of inserting and extracting lithium contains a material containing silicon as a constituent element. This is because a high energy density can be obtained. The negative electrode material may be a simple substance of silicon, an alloy, or a compound, or may have one or more of these phases in at least a part thereof. 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.

  Examples of the silicon alloy include tin (Sn), nickel, copper, iron, cobalt (Co), manganese (Mn), zinc (Zn), indium (In), silver as the second constituent element other than silicon. Examples include those containing at least one member selected from the group consisting of (Ag), titanium, germanium (Ge), bismuth (Bi), antimony (Sb), and chromium. Examples of the silicon compound include those containing oxygen (O) or carbon (C), and may contain the second constituent element described above in addition to silicon.

  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. Examples of the vapor phase method include a physical deposition method or a chemical deposition method. Specifically, a vacuum deposition method, a sputtering method, an ion plating method, a laser ablation method, or a CVD (Chemical Vapor Deposition; chemical vapor phase). (Growth) method. Examples of the liquid phase method include electrolytic plating or electroless plating. The firing method is a method in which, for example, a particulate negative electrode active material is mixed with a binder or a solvent as necessary, and then heat-treated at a temperature higher than the melting point of the binder. 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 and a conductive material such as polyvinylidene fluoride may be included. The same applies to the case of the firing method.

  As the negative electrode material, in addition to a material containing silicon as a constituent element, a carbon material capable of inserting and extracting lithium may be mixed and used. The carbon material has very little change in crystal structure that occurs during charging and discharging, and if used together with the above-described material containing silicon as a constituent element, a high energy density can be obtained and an excellent cycle can be obtained. It is preferable because characteristics can be obtained and it also functions as a conductive material.

  Examples of such carbon materials include non-graphitizable carbon, graphitizable carbon, graphite, pyrolytic carbons, cokes, glassy carbons, organic polymer compound fired bodies, activated carbon, and carbon black. 1 type (s) or 2 or more types can be used. Among these, cokes include pitch coke, needle coke, and petroleum coke. Organic polymer compound fired bodies are carbonized by firing polymer compounds such as phenol resin and furan resin at an appropriate temperature. What you did.

  Further, as the negative electrode material, in addition to a material containing silicon as a constituent element, a material containing at least one of other metalloid elements and metal elements as a constituent element may be mixed and used. Examples of other metalloid elements and metal elements include tin, magnesium (Mg), boron (B), aluminum, gallium (Ga), indium, germanium, lead (Pb), bismuth, which can form an alloy with lithium. Examples thereof include cadmium (Cd), silver, zinc, hafnium (Hf), zirconium (Zr), yttrium (Y), palladium (Pd), and platinum (Pt). These may be crystalline or amorphous.

  The separator 23 is made of, for example, a porous film made of synthetic resin such as polytetrafluoroethylene, polypropylene, or polyethylene, or a porous film made of ceramic, and has a structure in which two or more kinds of porous films are laminated. May be. Among these, a porous film made of polyolefin is preferable because it is excellent in short-circuit preventing effect and can improve the safety of the battery due to the shutdown effect. In particular, polyethylene is preferable as a material constituting the separator 23 because a shutdown effect can be obtained within a range of 100 ° C. or higher and 160 ° C. or lower and the electrochemical stability is excellent. Polypropylene is also preferable, and any other resin having chemical stability can be used by copolymerizing or blending with polyethylene or polypropylene.

  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.

The solvent is selected from the cation shown in Chemical Formula ₂ , N ⁻ (CF ₃ SO ₂ ) ₂ , CF ₃ SO ₃ ⁻ , N ⁻ (C ₂ F ₅ SO ₂ ) ₂ , BF ₄ ⁻ and BF ₃ (CF ₃ ) ^−. , BF ₃ (C ₂ F ₅ ) ⁻ , BF ₃ (C ₃ F ₇ ) ⁻ and PF ₆ ⁻ . This is because the decomposition reaction of the electrolytic solution can be suppressed even at high temperatures, and excellent characteristics can be obtained even when left under high temperature conditions or when used under high temperature conditions. A room temperature molten salt may be used alone or in combination of two or more.

（Ｒ１は、炭素数１から４の直鎖状あるいは分岐状のアルキレン基を表す。Ｒ２は、アルキル基，アリル基，アリール基，複素環基，アラルキル基，アルコキシアルキル基を表す。）

(R1 represents a linear or branched alkylene group having 1 to 4 carbon atoms. R2 represents an alkyl group, an allyl group, an aryl group, a heterocyclic group, an aralkyl group, or an alkoxyalkyl group.)

  Examples of such cations include N, N-dimethylpyrrolidinium, N-methyl-N-ethylpyrrolidinium, N-methyl-N-butylpyrrolidinium, N-methyl-N-arylpyrrolidinium, N -Methyl-N-benzylpyrrolidinium, N-methyl-N-hexylpyrrolidinium, N-methyl-N-vinylpyrrolidinium, N-methyl-N-methoxyethylpyrrolidinium, N-methyl-N- Methoxymethylpyrrolidinium, N-methyl-N-pentamethylphenylpyrrolidinium, N-methyl-N-ethylpiperidinium, N-methyl-N-butylpiperidinium, N, N-dimethylpiperidinium, N-methyl-N-propylpiperidinium, N-methyl-N-arylpiperidinium, N-methyl-N-benzylpiperidinium, -Methyl-N-hexylpiperidinium, N-methyl-N-vinylpiperidinium, N-methyl-N-methoxyethylpiperidinium, N-methyl-N-methoxymethylpiperidinium, N-methyl-N -Pentamethylphenylpiperidinium, N, N-dimethyladipinium, N-methyl-N-ethyladipinium, N-methyl-N-butyladipinium, N-methyl-N-aryladipinium, N-methyl-N-benzyladipinium, N-methyl-N-hexyladipinium, N-methyl-N-vinyladipinium, N-methyl-N-methoxymethyladipinium, N-methyl-N There are cations of -methoxyethyl adipium or N-methyl-N-pentamethylphenyladipium.

  The content of the room temperature molten salt is preferably in the range of 1% by volume to 40% by volume. This is because if the content is small, the effect of suppressing the decomposition reaction of the electrolytic solution at high temperature is not sufficient, and if the content is large, the viscosity of the electrolytic solution increases and the battery characteristics deteriorate.

  The solvent preferably contains a cyclic carbonate derivative having a halogen atom in addition to these room temperature molten salts, and among them, the cyclic carbonate derivative shown in Chemical Formula 3 is desirable. This is because the decomposition reaction of the electrolytic solution in the negative electrode 22 can be suppressed, and battery characteristics such as cycle characteristics can be improved. A cyclic carbonate derivative may be used individually by 1 type, and may mix and use multiple types.

（Ｒ３，Ｒ４，Ｒ５およびＲ６は、メチル基，エチル基あるいはそれら少なくとも一部の水素（Ｈ）をフッ素（Ｆ）若しくは塩素（Ｃｌ）で置換した基、または水素、またはフッ素、または塩素を表す。Ｒ３，Ｒ４，Ｒ５およびＲ６のうちの少なくとも一つはハロゲンを有する基である。Ｒ３，Ｒ４，Ｒ５およびＲ６は、互いに同一であってもよいし、異なっていてもよい。）

(R3, R4, R5 and R6 represent a methyl group, an ethyl group or a group in which at least a part of hydrogen (H) is substituted with fluorine (F) or chlorine (Cl), or hydrogen, fluorine, or chlorine. At least one of R3, R4, R5 and R6 is a halogen-containing group, and R3, R4, R5 and R6 may be the same or different.

  Specific examples of the cyclic carbonate derivative shown in Chemical formula 3 are shown in Chemical formulas (1-1) to (1-14) and Chemical formula 5 (1-15) to (1-23). Compounds. Of these, 4-fluoro-1,3-dioxolan-2-one shown in (1-1) of Chemical Formula 4 is preferable. This is because a higher effect can be obtained.

  The content of the cyclic carbonate derivative in the solvent is preferably 50% by volume or less. This is because a higher effect can be obtained.

  In addition to these, various conventionally used solvents can be mentioned, for example, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, γ-butyrolactone, γ-valerolactone, 1,2-dimethoxy. Ethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxolane, 4-methyl-1,3-dioxolane, methyl acetate, methyl propionate, ethyl propionate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, acetonitrile, glutaro Nitrile, adiponitrile, methoxyacetonitrile, 3-methoxypropionitrile, N, N-dimethylformamide, N-methylpyrrolidinone, N-methyloxazolidinone, N, N′-dimethylimidazolidinone, nitromethane, nitroethane, sulfolane, Examples thereof include dimethyl sulfoxide and trimethyl phosphate. Among these, in order to realize excellent charge / discharge capacity characteristics and charge / discharge cycle characteristics, it is preferable to use at least one selected from the group consisting of ethylene carbonate, propylene carbonate, vinylene carbonate, dimethyl carbonate, and ethyl methyl carbonate. These solvents may be used alone or in combination of two or more.

  The electrolyte salt preferably contains a light metal salt shown in Chemical formula 6. This is because this light metal salt can form a stable film on the surface of the negative electrode 22, suppress the decomposition reaction of the solvent, and improve battery characteristics such as cycle characteristics. The light metal salt shown in Chemical Formula 6 may be used alone or in combination of two or more.

（Ｒ１１は、化７，化８または化９に示した基を表し、Ｒ１２は、ハロゲン，アルキル基，ハロゲン化アルキル基，アリール基またはハロゲン化アリール基を表し、Ｘ１１およびＸ１２は、酸素または硫黄（Ｓ）をそれぞれ表し、Ｍ１１は、遷移金属元素または短周期型周期表における３Ｂ族元素，４Ｂ族元素あるいは５Ｂ族元素を表し、Ｍ２１は、短周期型周期表における１Ａ族元素あるいは２Ａ族元素またはアルミニウムを表し、ａは１から４の整数であり、ｂは０から８の整数であり、ｃ，ｄ，ｅおよびｆはそれぞれ１から３の整数である。）

(R11 represents the group shown in Chemical formula 7, Chemical formula 8 or Chemical formula 9, R12 represents a halogen, an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, and X11 and X12 represent oxygen or sulfur. M11 represents a transition metal element or a group 3B element, a group 4B element or a group 5B element in the short periodic table, and M21 represents a group 1A element or a group 2A element in the short periodic table Or a represents aluminum, a is an integer from 1 to 4, b is an integer from 0 to 8, and c, d, e, and f are each an integer from 1 to 3.)

（Ｒ２１は、アルキレン基，ハロゲン化アルキレン基，アリーレン基またはハロゲン化アリーレン基を表す。）

(R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group.)

（Ｒ２２，Ｒ２３は、アルキル基，ハロゲン化アルキル基，アリール基またはハロゲン化アリール基を表す。Ｒ２２，Ｒ２３は、同一であっても異なっていてもよい。）

(R22 and R23 represent an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group. R22 and R23 may be the same or different.)

  As the light metal salt shown in Chemical formula 6, for example, the compound shown in Chemical formula 10 is preferable.

（Ｒ１１は、化１１，化１２または化１３に示した基を表し、Ｒ１３は、ハロゲンを表し、Ｍ１２は、リン（Ｐ）またはホウ素を表し、Ｍ２１は短周期型周期表における１Ａ族元素あるいは２Ａ族元素またはアルミニウムを表し、ａ１は１から３の整数であり、ｂ１は０，２または４であり、ｃ，ｄ，ｅおよびｆはそれぞれ１から３の整数である。）

(R11 represents the group shown in Chemical formula 11, Chemical formula 12 or Chemical formula 13, R13 represents halogen, M12 represents phosphorus (P) or boron, M21 represents a group 1A element in the short-period periodic table or Represents a group 2A element or aluminum, a1 is an integer of 1 to 3, b1 is 0, 2 or 4, and c, d, e and f are each an integer of 1 to 3.)

（Ｒ２１は、アルキレン基，ハロゲン化アルキレン基，アリーレン基またはハロゲン化アリーレン基を表す。）

(R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group.)

（Ｒ２２，Ｒ２３は、アルキル基，ハロゲン化アルキル基，アリール基またはハロゲン化アリール基を表す。Ｒ２２，Ｒ２３は、同一であっても異なっていてもよい。）

(R22 and R23 represent an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group. R22 and R23 may be the same or different.)

  Specifically, lithium difluoro [oxolato-O, O ′] lithium borate shown in Chemical formula 14, lithium tetrafluoro [oxolato-O, O ′] lithium phosphate shown in Chemical formula 15, difluorobis [ Oxolato-O, O ′] lithium phosphate, difluoro [3,3,3-trifluoro-2-oxide-2-trifluoromethylpropionate (2-)-O, O ′] boric acid shown in Chemical formula 17 Lithium, bis [3,3,3-trifluoro-2-oxide-2-trifluoromethylpropionate (2-)-O, O ′] lithium borate shown in Chemical Formula 18, and bis shown in Chemical Formula 19 [Oxolato-O, O ′] lithium borate and the like.

Examples of the electrolyte salt include LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) _2, or LiN (C ₄ F ₉ SO ₂ ) ( A lithium salt represented by Chemical Formula 20 such as CF ₃ SO ₂ ), a lithium salt represented by Chemical Formula 21 such as LiC (CF ₃ SO ₂ ) ₃ , or a cyclic imide salt represented by Chemical Formula 22 or a chemical formula 23 A cyclic imide salt is also preferred.

（ｍおよびｎは、１以上の整数である。）

(M and n are integers of 1 or more.)

（ｐ，ｑおよびｒは、１以上の整数である）

(P, q and r are integers of 1 or more)

（Ｍ１は短周期型周期表における１Ａ族元素，２Ａ族元素またはアルミニウムを表す。Ｒ７は、炭素数２から５の直鎖状あるいは分岐状のアルキレン基、また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。ｔは、１, ２または３である。）

(M1 represents a group 1A element, a group 2A element or aluminum in the short periodic table. R7 represents a linear or branched alkylene group having 2 to 5 carbon atoms, or at least a part of hydrogen atoms thereof as fluorine. And t is 1, 2 or 3.

（Ｍ２は、短周期型周期表における１Ａ族元素，２Ａ族元素またはアルミニウムを表す。Ｒ８は、炭素数２から５の直鎖状あるいは分岐状のアルキレン基、また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。ｕは、１, ２または３である。）

(M2 represents a group 1A element, a group 2A element or aluminum in the short periodic table. R8 represents a linear or branched alkylene group having 2 to 5 carbon atoms, or at least a part of hydrogen atoms thereof. Represents a group substituted with fluorine, u is 1, 2 or 3)

  Examples of the cyclic imide salt represented by Chemical Formula 22 and the cyclic imide salt represented by Chemical Formula 23 include 1,2-perfluoroethanedisulfonylimide lithium represented by Chemical Formula 24 (1), and Chemical Formula 24 (2). 1,3-perfluoropropanedisulfonylimide lithium shown, 1,3-perfluorobutanedisulfonylimide lithium shown in Chemical Formula 24 (3), 1,4-perfluorobutanedi shown in Chemical Formula 24 (4) Examples thereof include sulfonylimidolithium and lithium perfluoroheptanenidate shown in Chemical Formula 24 (5).

In particular, LiPF ₆ , a light metal salt represented by Chemical Formula ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , a lithium salt represented by Chemical Formula 20, a lithium salt represented by Chemical Formula 21, a cyclic imide salt represented by Chemical Formula 22, and It is preferable to use a mixture of at least one selected from the group consisting of cyclic imide salts shown in Chemical Formula 23. This is because ion conductivity can be improved, decomposition reaction of the electrolytic solution can be further suppressed, and battery characteristics such as cycle characteristics can be improved.

In addition to these, electrolyte salts include LiB (C ₆ H ₅ ) ₄ , LiCH ₃ SO ₃ , LiCF ₃ SO ₃ , LiAlCl ₄ , LiSiF ₆ , LiCl, or LiBr. You may use, and may mix and use multiple types.

  The content (concentration) of the electrolyte salt is preferably in the range of 0.3 mol / kg or more and 3.0 mol / kg or less with respect to the solvent. Outside this range, there is a risk that sufficient battery characteristics may not be obtained due to an extreme decrease in ionic conductivity. Among them, the content of the light metal salt shown in Chemical Formula 6 is preferably in the range of 0.01 mol / kg to 2.0 mol / kg with respect to the solvent. This is because a higher effect can be obtained within this range.

  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 material, 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. When discharging is performed, for example, lithium ions are released from the negative electrode 22 and inserted in the positive electrode 21 through the electrolytic solution. At that time, since the above-mentioned room temperature molten salt is contained in the electrolytic solution, the decomposition reaction of the electrolytic solution is suppressed even at a high temperature.

As described above, according to the present embodiment, the cation shown in Chemical Formula ₂ , N ⁻ (CF ₃ SO ₂ ) ₂ , CF ₃ SO ₃ ⁻ , N ⁻ (C ₂ F ₅ SO ₂ ) ₂ , BF ₄ ⁻ , A room temperature molten salt comprising one anion of the group consisting of BF ₃ (CF ₃ ) ⁻ , BF ₃ (C ₂ F ₅ ) ⁻ , BF ₃ (C ₃ F ₇ ) ⁻ and PF ₆ ⁻ As a result, the decomposition reaction of the electrolyte can be suppressed even at a high temperature, and excellent characteristics can be obtained even when left under a high temperature condition or used under a high temperature condition.

(Second Embodiment)
FIG. 3 illustrates the configuration of the secondary battery according to the second embodiment. 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 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 the same as those of the positive electrode current collector 21A and the positive electrode active material layer 21B in the first embodiment described above. , The same as the anode current collector 22A, the anode 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 high ion conductivity can be obtained and battery leakage can be prevented. The configuration of the electrolytic solution is the same as that of the first embodiment. 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, and other materials such as a polymerization initiator or a polymerization inhibitor as necessary is prepared, and the interior of the exterior member 40 is prepared. After the injection, the opening of the exterior member 40 is heat-sealed and sealed. After that, if necessary, heat is applied to polymerize the monomer to form a polymer compound, thereby forming the gel electrolyte layer 36 and assembling the secondary battery shown in FIGS.

  This secondary battery acts in the same manner as the secondary battery according to the first embodiment, and can obtain the same effect.

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

(Examples 1-1 to 1-14)
The cylindrical secondary battery shown in FIG. 1 was produced. First, 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 material, and 3 parts by mass of polyvinylidene fluoride as a binder were prepared to prepare a positive electrode mixture. After that, it was dispersed in N-methyl-2-pyrrolidone as a solvent to obtain a positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry was uniformly applied to a positive electrode current collector 21A made of an aluminum foil having a thickness of 20 μm, dried, and then compression molded to form a positive electrode active material layer 21B. After that, an aluminum positive electrode lead 25 was attached to one end of the positive electrode current collector 21A.

  Also, silicon was used as the negative electrode active material, and the negative electrode active material layer 22B made of silicon was formed on the negative electrode current collector 22A made of a copper foil having a thickness of 15 μm by an electron beam vapor deposition method to produce the negative electrode 22. After that, a nickel negative electrode lead 26 was attached to one end of the negative electrode current collector 22A.

  After preparing the positive electrode 21 and the negative electrode 22, a separator 23 made of a microporous polypropylene film having a thickness of 25 μm is prepared, and the negative electrode 22, the separator 23, the positive electrode 21, and the separator 23 are stacked in this order to form a spiral structure. The wound electrode body 20 was produced by winding a number of times.

  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.

In Examples 1-1 to 1-7, the electrolytic solution was ethylene carbonate (EC), diethyl carbonate (DEC), and room temperature molten salt, ethylene carbonate: diethyl carbonate: room temperature molten salt = 35: 60: 5. A solution in which LiPF ₆ was dissolved as an electrolyte salt at a concentration of 1.0 mol / kg was used in a solvent mixed at a volume ratio of In Examples 1-8 to 1-14, 4-fluoro-1,3-dioxolan-2-one (FEC), which is a cyclic carbonate derivative having a halogen atom, diethyl carbonate, room temperature molten salt, Was mixed with 4-fluoro-1,3-dioxolan-2-one: diethyl carbonate: room temperature molten salt = 35: 60: 5 in a volume ratio of LiPF ₆ as an electrolyte salt at a concentration of 1.0 mol / kg. What was dissolved in was used. The room temperature molten salt was a compound shown in Chemical Formula 25 to Chemical Formula 31 consisting of a cation shown in Chemical Formula ₂ and an anion consisting of N ⁻ (CF ₃ SO ₂ ) ₂ .

  After injecting the electrolyte into the battery can 11, the battery lid 14 was caulked to the battery can 11 via the gasket 17 to obtain a cylindrical secondary battery.

  As Comparative Examples 1-1 and 1-2 for Examples 1-1 to 1-14, except that no room temperature molten salt was used, other examples 1-1 to 1-7 and 1-8 to 1- In the same manner as in Example 14, a secondary battery was produced. At that time, in Comparative Example 1-1, the solvent is a mixture of ethylene carbonate and diethyl carbonate in a volume ratio of ethylene carbonate: diethyl carbonate = 40: 60. In Comparative Example 1-2, 4-fluoro- 1,3-dioxolan-2-one and diethyl carbonate were mixed at a volume ratio of 4-fluoro-1,3-dioxolan-2-one: diethyl carbonate = 40: 60.

  In addition, as Comparative Examples 1-3 to 1-6, secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-14, except that a carbon material was used as the negative electrode active material. At that time, the negative electrode is mixed with a carbon material and polyvinylidene fluoride as a binder, and N-methyl-2-pyrrolidone as a solvent is added and uniformly applied to a negative electrode current collector made of a strip-shaped copper foil. It was prepared by drying and compression molding with a roll press to form a negative electrode active material layer. The electrolytic solution was the same as in Examples 1-2 and 1-9 or Comparative Examples 1-1 and 1-2.

  For the fabricated secondary batteries of Examples 1-1 to 1-14 and Comparative examples 1-1 to 1-6, the high-temperature storage characteristics and the high-temperature cycle characteristics were examined as follows.

  First, at 23 ° C., two cycles of charge / discharge were performed, and the discharge capacity at the second cycle (discharge capacity before storage) was determined. Subsequently, the battery was charged again and stored for 10 days in a constant temperature bath at 80 ° C., and then discharged at 23 ° C. to determine the discharge capacity after storage. At that time, the charge was 0.2 C constant current and constant voltage charge up to the upper limit voltage of 4.20 V, and the discharge was 0.2 C constant current discharge to the end voltage of 2.50 V. 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 results are shown in Tables 1 and 2. 0.2 C is a current value at which the theoretical capacity can be discharged in 5 hours.

  Moreover, at 23 degreeC, charging / discharging was performed 2 cycles, and the discharge capacity of the 2nd cycle (discharge capacity of the 2nd cycle in 23 degreeC) was calculated | required. Subsequently, 100 cycles of charge / discharge were performed in a thermostat at 60 ° C., and the discharge capacity at the 100th cycle (discharge capacity at the 100th cycle at 60 ° C.) was obtained. At that time, the charge was 0.2 C constant current and constant voltage charge up to the upper limit voltage of 4.20 V, and the discharge was 0.2 C constant current discharge to the end voltage of 2.50 V. The high-temperature cycle characteristic is the ratio of the discharge capacity at the 100th cycle at 60 ° C to the discharge capacity at the second cycle at 23 ° C, that is, the discharge capacity at the 100th cycle at 60 ° C / the discharge capacity at the second cycle at 23 ° C. It calculated | required from x100 (%). The results are shown in Tables 1 and 2.

  As shown in Table 1 and Table 2, according to Examples 1-1 to 1-7 and 1-8 to 1-14 using silicon as a negative electrode active material and using a normal temperature molten salt, The high-temperature storage characteristics and the high-temperature cycle characteristics were dramatically improved as compared with Comparative Examples 1-1 and 1-2 that were not used. On the other hand, in Comparative Examples 1-3 to 1-6 using a carbon material as the negative electrode active material, the effect of improving the high-temperature storage characteristics and the high-temperature cycle characteristics due to the inclusion of the room temperature molten salt was not observed.

  Furthermore, according to Examples 1-8 to 1-14 using 4-fluoro-1,3-dioxolan-2-one, it was stored at a higher temperature than Examples 1-1 to 1-7 without using it. Both characteristics and high-temperature cycle characteristics were improved.

That is, if a negative electrode active material containing silicon as a constituent element is used, and the electrolyte solution contains a room temperature molten salt composed of a cation shown in Chemical Formula ₂ and an anion composed of N ⁻ (CF ₃ SO ₂ ) _2. Even when left under high temperature conditions or when used under high temperature conditions, excellent characteristics can be obtained. In particular, it is preferable if the electrolyte contains a cyclic carbonate derivative having a halogen atom. I understood that.

(Examples 2-1 to 2-15)
In Examples 2-1 to 2-7, in addition to LiPF ₆ , lithium difluoro [oxolato-O, O ′] lithium borate shown in Chemical Formula 14 as a light metal salt shown in Chemical Formula ₆ was used as an electrolyte salt. Other than the above, secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-7. At that time, the concentration of LiPF _{6 in} the electrolytic solution was 0.8 mol / kg, and the concentration of lithium difluoro [oxolato-O, O ′] lithium borate was 0.2 mol / kg.

Further, in Examples 2-8 to 2-14, in addition to LiPF ₆ as an electrolyte salt, bis [oxolato-O, O ′] lithium borate shown in Chemical formula 19 which is a light metal salt shown in Chemical formula 6 is used. Except for the above, secondary batteries were fabricated in the same manner as in Examples 1-1 to 1-7. At that time, the concentration of LiPF _{6 in} the electrolytic solution was 0.8 mol / kg, and the concentration of lithium bis [oxolato-O, O ′] lithium borate was 0.2 mol / kg.

Further, in Example 2-15, in addition to LiPF ₆ as an electrolyte salt, lithium bis [oxolato-O, O ′] lithium borate shown in Chemical formula 19 which is a light metal salt shown in Chemical formula 6, and cyclic imide salt A secondary battery was fabricated in the same manner as in Example 1-2 except that 1,3-perfluoropropanedisulfonylimide lithium shown in Chemical Formula 24 (2) was used. At that time, the concentration of LiPF _{6 in} the electrolyte was 0.8 mol / kg, the concentration of lithium bis [oxolato-O, O ′] lithium borate was 0.2 mol / kg, and 1,3-perfluoropropanedisulfonylimide. The concentration of lithium was 0.1 mol / kg.

  As Comparative Example 2-1 with respect to Examples 2-1 to 2-15, secondary batteries were fabricated in the same manner as in Examples 2-1 to 2-15, except that the room temperature molten salt was not used. At that time, the solvent is a mixture of ethylene carbonate and diethyl carbonate in a volume ratio of ethylene carbonate: diethyl carbonate = 40: 60, and the type and concentration of the electrolyte salt are the same as in Examples 2-1 to 2-7. I made it.

  In Comparative Example 2-2, a secondary battery was fabricated in the same manner as in Examples 2-1 to 2-15 except that a carbon material was used as the negative electrode active material and no room temperature molten salt was used. . At that time, the negative electrode was manufactured in the same manner as in Comparative Examples 1-3 to 1-6. The solvent is a mixture of ethylene carbonate and diethyl carbonate in a volume ratio of ethylene carbonate: diethyl carbonate = 40: 60, and the type and concentration of the electrolyte salt are the same as in Examples 2-1 to 2-7. did.

  For the fabricated secondary batteries of Examples 2-1 to 2-15 and Comparative Examples 2-1 and 2-2, the high-temperature storage characteristics and the high-temperature cycle characteristics were examined in the same manner as in Examples 1-1 to 1-14. . The results are shown in Table 3 and Table 4.

As shown in Table 3 and Table 4, in addition to LiPF ₆ as the electrolyte salt, implementation using lithium difluoro [oxolato-O, O ′] lithium borate or difluoro [oxolato-O, O ′] lithium borate According to Examples 2-1 to 2-7 and 2-8 to 2-14, both the high-temperature storage characteristics and the high-temperature cycle characteristics are improved as compared with Examples 1-1 to 1-7 not using these, Moreover, the high temperature storage characteristic and the high temperature cycling characteristic improved rather than the comparative example 2-1 which does not use normal temperature molten salt. Furthermore, according to Example 2-15 using 1,3-perfluoropropanedisulfonylimide lithium in addition to LiPF ₆ and difluoro [oxolato-O, O ′] lithium borate, 1,3-perfluoro Both the high-temperature storage characteristics and the high-temperature cycle characteristics were improved as compared with Example 2-2 that did not use propanedisulfonylimide lithium. In addition, in Comparative Example 2-2 using a carbon material as the negative electrode active material, the effect of using lithium difluoro [oxolato-O, O ′] lithium borate in addition to LiPF ₆ was observed, but the effect was low. It was.

That is, the light metal salt shown in Chemical formula ₆ , LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , the lithium salt shown in Chemical formula 20, the lithium salt shown in Chemical formula 21, the cyclic imide salt shown in Chemical formula 22 and the chemical formula 23 It was found that it was preferable to use at least one member selected from the group consisting of the cyclic imide salts shown in FIG.

(Examples 3-1 to 3-4)
The laminate type secondary battery shown in FIGS. 3 and 4 was produced. At that time, a liquid electrolyte solution was used instead of the gel electrolyte layer 36.

  First, the positive electrode 33 and the negative electrode 34 were produced in the same manner as in Examples 1-1 to 1-14, and the positive electrode lead 31 and the negative electrode lead 32 were attached. At that time, the positive electrode current collector 33A was a strip-shaped aluminum foil having a thickness of 12 μm.

  After that, the positive electrode 33 and the negative electrode 34 are stacked via the separator 35 so that the positive electrode active material layer 33B and the negative electrode active material layer 34B face each other, and wound to be a precursor of the wound electrode body 30. A gyrus was formed.

  The obtained wound body is sandwiched between exterior members 40 made of a laminate film, and the outer peripheral edge except for one side is heat-sealed into a bag shape, accommodated inside the exterior member 40, and the electrolytic solution of the exterior member 40 Injected inside. The same electrolyte solution as in Examples 1-1, 1-2, 1-8, 1-9 was used. The laminate film was made of nylon-aluminum-unstretched polypropylene from the outside, and the thicknesses thereof were 30 μm, 40 μm, and 30 μm, respectively, for a total of 100 μm.

  After injecting the electrolytic solution, the opening of the exterior member 40 was heat-sealed and sealed in a vacuum atmosphere to produce a laminate film type secondary battery.

  As Comparative Examples 3-1 and 3-2 with respect to Examples 3-1 to 3-4, a laminate film type was obtained in the same manner as in Examples 3-1 to 3-4 except that no room temperature molten salt was used. A secondary battery was prepared. At that time, the electrolytic solution was the same as in Comparative Examples 1-1 and 1-2.

  For the fabricated secondary batteries of Examples 3-1 to 3-4 and Comparative examples 3-1 and 3-2, the high-temperature storage characteristics and the high-temperature cycle characteristics were examined in the same manner as in Examples 1-1 to 1-14. . The results are shown in Table 5.

As shown in Table 5, the same results as in Examples 1-1 to 1-14 were obtained. That is, in the case of a battery having another shape, a negative electrode active material containing silicon as a constituent element is used, and the cation shown in Chemical formula 2 and an anion made of N ⁻ (CF ₃ SO ₂ ) ₂ are used in the electrolytic solution. By including a room temperature molten salt consisting of the above, it is possible to obtain excellent characteristics even when left under high temperature conditions or when used under high temperature conditions. It has been found preferable to include a carbonate ester derivative.

(Examples 4-1 to 4-5)
In Examples 4-1 and 4-2, in addition to LiPF ₆ , lithium difluoro [oxolato-O, O ′] lithium borate shown in Chemical formula 14 as a light metal salt shown in Chemical formula ₆ was used as an electrolyte salt. A secondary battery was fabricated in the same manner as in Examples 3-1 and 3-2 except for. At that time, the electrolytic solution was the same as in Examples 2-1 and 2-2.

Further, in Examples 4-3 and 4-4, in addition to LiPF ₆ as an electrolyte salt, bis [oxolato-O, O ′] lithium borate shown in Chemical formula 19, which is a light metal salt shown in Chemical formula 6, is used. A secondary battery was fabricated in the same manner as in Examples 3-1 and 3-2 except for the above. At that time, the electrolytic solution was the same as in Examples 2-8 and 2-9.

Further, in Example 4-5, in addition to LiPF ₆ as an electrolyte salt, lithium bis [oxolato-O, O ′] lithium borate shown in Chemical formula 19 which is a light metal salt shown in Chemical formula 6, and cyclic imide salt A secondary battery was fabricated in the same manner as in Example 3-2 except that 1,3-perfluoropropanedisulfonylimide lithium shown in Chemical Formula 24 (2) was used. At that time, the electrolytic solution was the same as in Example 2-15.

  As Comparative Example 4-1 for Examples 4-1 to 4-5, secondary batteries were fabricated in the same manner as in Examples 4-1 to 4-5, except that the room temperature molten salt was not used. At that time, the electrolytic solution was the same as in Comparative Example 2-1.

  For the fabricated secondary batteries of Examples 4-1 to 4-5 and Comparative example 4-1, high temperature storage characteristics and high temperature cycle characteristics were examined in the same manner as in Examples 1-1 to 1-14. The results are shown in Table 6.

As shown in Table 6, the same results as in Examples 2-1 to 2-15 were obtained. That is, even in the case of batteries having other shapes, the light metal salt shown in Chemical formula ₆ , LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , the lithium salt shown in Chemical formula 20, the lithium salt shown in Chemical formula 21, It was found that it was preferable to use at least one member selected from the group consisting of the cyclic imide salt shown in Chemical Formula 22 and the cyclic imide salt shown in Chemical Formula 23.

(Examples 5-1 to 5-4)
A secondary battery was fabricated in the same manner as in Examples 1-1 to 1-14, except that a rectangular container having a width of 30 mm, a height of 48 mm, and a thickness of 5 mm was used. At that time, the positive electrode current collector was a strip-shaped aluminum foil having a thickness of 12 μm. The same electrolyte solution as in Examples 1-1, 1-2, 1-8, 1-9 was used.

  As Comparative Examples 5-1 and 5-2 for Examples 5-1 to 5-4, secondary batteries were the same as those of Examples 5-1 to 5-4 except that no room temperature molten salt was used. Was made. At that time, the electrolytic solution was the same as in Comparative Examples 1-1 and 1-2.

  Regarding the fabricated secondary batteries of Examples 5-1 to 5-4 and Comparative Examples 5-1 and 5-2, the high-temperature storage characteristics and the high-temperature cycle characteristics were examined in the same manner as in Examples 1-1 to 1-14. . The results are shown in Table 7.

As shown in Table 7, the same results as in Examples 1-1 to 1-14 were obtained. That is, in the case of a battery having another shape, a negative electrode active material containing silicon as a constituent element is used, and the cation shown in Chemical formula 2 and an anion made of N ⁻ (CF ₃ SO ₂ ) ₂ are used in the electrolytic solution. By including a room temperature molten salt consisting of the above, it is possible to obtain excellent characteristics even when left under high temperature conditions or when used under high temperature conditions. It has been found preferable to include a carbonate ester derivative.

(Examples 6-1 to 6-5)
In Examples 6-1 and 6-2, in addition to LiPF ₆ , lithium difluoro [oxolato-O, O ′] lithium borate shown in Chemical formula 14, which is a light metal salt shown in Chemical formula _6, was used as the electrolyte salt. Other than the above, secondary batteries were fabricated in the same manner as in Examples 5-1 and 5-2. At that time, the electrolytic solution was the same as in Examples 2-1 and 2-2.

Further, in Examples 6-3 and 6-4, in addition to LiPF ₆ as an electrolyte salt, bis [oxolato-O, O ′] lithium borate shown in Chemical formula 19, which is a light metal salt shown in Chemical formula 6, is used. A secondary battery was fabricated in the same manner as in Examples 5-1 and 5-2 except for the above. At that time, the electrolytic solution was the same as in Examples 2-8 and 2-9.

Further, in Example 6-5, in addition to LiPF ₆ as an electrolyte salt, lithium bis [oxolato-O, O ′] lithium borate shown in Chemical formula 19 which is a light metal salt shown in Chemical formula 6, and cyclic imide salt A secondary battery was fabricated in the same manner as in Example 5-2 except that 1,3-perfluoropropanedisulfonylimide lithium shown in Chemical Formula 24 (2) was used. At that time, the electrolytic solution was the same as in Example 2-15.

  As Comparative Example 6-1 with respect to Examples 6-1 to 6-5, secondary batteries were fabricated in the same manner as in Examples 6-1 to 6-5, except that the room temperature molten salt was not used. At that time, the electrolytic solution was the same as in Comparative Example 2-1.

  For the fabricated secondary batteries of Examples 6-1 to 6-5 and Comparative Example 6-1, high temperature storage characteristics and high temperature cycle characteristics were examined in the same manner as in Examples 1-1 to 1-14. The results are shown in Table 8.

As shown in Table 8, the same results as in Examples 2-1 to 2-15 were obtained. That is, even in the case of batteries having other shapes, the light metal salt shown in Chemical formula ₆ , LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , the lithium salt shown in Chemical formula 20, the lithium salt shown in Chemical formula 21, It was found that it was preferable to use at least one member selected from the group consisting of the cyclic imide salt shown in Chemical Formula 22 and the cyclic imide salt shown in Chemical Formula 23.

  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 the electrolyte solution or the gel electrolyte in which the polymer solution is held in the polymer compound is used as the electrolyte has been described, but other electrolytes may be used. 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. In that case, a positive electrode active material etc. can be suitably selected according to an electrode reaction material.

  Further, in the above embodiment or example, a cylindrical type, laminated film type or square type secondary battery has been specifically described, but the present invention has other shapes such as a button type or a coin type. The present invention can be similarly applied to a secondary battery or a secondary battery having another structure such as a laminated structure. Further, the present invention is not limited to the secondary battery, and can be similarly applied to other batteries such as a primary battery.

It is sectional drawing showing the structure of the secondary battery which concerns on the 1st 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 the 2nd Embodiment of this invention. It is sectional drawing showing the structure along the II line of the winding electrode body shown in FIG.

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 (7)

Bei example a cathode, an anode,
The negative electrode contains a negative electrode active material containing silicon (Si) as a constituent element,
The electrolyte, the cation represented by Chemical Formula ^1, N - containing (CF ₃ SO _{2) 2} and become more ambient temperature molten salt batteries.

(R1 represents a linear or branched alkylene group having 1 to 4 carbon atoms. R2 represents an alkyl group, an allyl group, or an alkoxyalkyl group.) The electrolyte contains a solvent comprising a cyclic carbonate derivative having halogen atoms, battery according to claim 1, wherein. The cyclic carbonate derivative comprises a compound represented by Chemical Formula 2, a battery according to claim 2, wherein.

(R3, R4, R5 and R6 represent a methyl group, an ethyl group or a group in which at least a part of hydrogen (H) is substituted with fluorine (F) or chlorine (Cl), or hydrogen, fluorine, or chlorine. At least one of R3, R4, R5 and R6 is a group having a halogen.) The cyclic carbonate derivatives include 4-fluoro-1,3-dioxolan-2-one, battery of claim 2 wherein. The electrolyte includes a light metal salt shown in Chemical formula ₃ , LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , a lithium salt shown in Chemical formula 4, a lithium salt shown in Chemical formula 5, a cyclic imide salt shown in Chemical formula ₆ and including at least one kind of battery of claim 1, wherein one of the group consisting of the cyclic imide salt shown in Chemical formula 7.

(R11 represents a -C (= O) -R21-C (= O)-group (R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group), or -C (= O). -C (R23) (R24)-group (R23 and R24 represent an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group), or -C (= O) -C (= O)- R12 represents a halogen, an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group, X11 and X12 each represent oxygen (O) or sulfur (S), and M11 represents a transition metal Represents an element or a group 3B element, a group 4B element or a group 5B element in a short periodic table, and M21 represents a group 1A element, a group 2A element or an element in the short period periodic table Represents bromide (Al), a is an integer from 1 4, b is an integer from 0 to 8, c, d, e and f are the respective 1 3 integer.)

(M and n are integers of 1 or more.)

(P, q and r are integers of 1 or more)

(M1 represents a group 1A element, a group 2A element or aluminum in the short periodic table. R7 represents a linear or branched alkylene group having 2 to 5 carbon atoms, or at least a part of hydrogen atoms thereof as fluorine. And t represents 1, 2 or 3.

(M2 represents a group 1A element, a group 2A element or aluminum in the short periodic table. R8 represents a linear or branched alkylene group having 2 to 5 carbon atoms, or at least a part of hydrogen atoms thereof. Represents a group substituted with fluorine, u is 1, 2 or 3) The electrolyte comprises a compound represented by Chemical Formula 8, the battery of claim 1, wherein.

(R11 represents a -C (= O) -R21-C (= O)-group (R21 represents an alkylene group, a halogenated alkylene group, an arylene group or a halogenated arylene group), or -C (= O). -C (R23) (R24)-group (R23 and R24 represent an alkyl group, a halogenated alkyl group, an aryl group or a halogenated aryl group), or -C (= O) -C (= O)- R13 represents a halogen, M12 represents phosphorus (P) or boron (B), M21 represents a Group 1A element, a Group 2A element or aluminum in the short-period periodic table, and a1 is from 1 3 is an integer, b1 is 0, 2 or 4, and c, d, e and f are each an integer of 1 to 3.) The electrolytes include difluoro [oxolato-O, O ′] lithium borate shown in Chemical Formula 9, tetrafluoro [oxolato-O, O ′] lithium phosphate shown in Chemical Formula 10, difluorobis [oxolato shown in Chemical Formula 11 -O, O '] lithium phosphate, difluoro [3,3,3-trifluoro-2-oxide-2-trifluoromethylpropionate (2-)-O, O'] lithium borate shown in Chemical formula 12 Bis [3,3,3-trifluoro-2-oxide-2-trifluoromethylpropionate (2-)-O, O ′] lithium borate shown in Chemical Formula 13, and bis [ oxalate -O, O '] includes at least one of the group consisting of lithium borate, battery according to claim 1, wherein.

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