JP2007257959A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery improvable in charge/discharge efficiency. <P>SOLUTION: A cathode 21 and an anode 22 are arranged in opposition through a separator 23. The anode 22 contains natural graphite. The separator 23 is impregnated with an electrolyte solution. The electrolyte solution contains a cyclic imide salt such as a lithium (tetrafluoroethylene) sulfonimide, a lithium (hexafluoropropene) sulfonimide, a lithium (octafluorobutene) sulfonimide, a lithium tetrafluoro succinic acid imide, or a lithium hexafluoro glutaric acid imide. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a battery including natural graphite in a negative electrode.

  In recent years, many portable electronic devices such as a camera-integrated VTR (video tape recorder), a digital still camera, a mobile phone, a portable information terminal, or a notebook computer have appeared, and their size and weight have been reduced. Accordingly, as a portable power source for electronic devices, research and development for improving the energy density of batteries, particularly secondary batteries, are being actively promoted. Among them, a lithium ion secondary battery using a carbon material as a negative electrode active material, a composite oxide containing lithium (Li) and a transition metal as a positive electrode active material, and using a carbonate ester as an electrolytic solution is a conventional aqueous electrolysis. Compared to lead batteries or nickel cadmium batteries, which are liquid secondary batteries, a large energy density is obtained, so that they are widely put into practical use.

Carbon materials that have been studied in such lithium ion secondary batteries include synthetic graphite and natural graphite. Among these, natural graphite has a larger discharge capacity and lower cost than synthetic graphite. (For example, see Patent Documents 1 and 2).
JP-A-6-290781 JP-A-8-213020

  However, in order to use natural graphite mined from a mine as a negative electrode active material, it is necessary to pulverize large natural graphite crystals, which increases the reactivity of the pulverized cross-section and causes the electrolyte to decompose. There was a problem that the discharge efficiency was lowered.

  This invention is made | formed in view of this problem, The objective is to provide the battery which can improve charging / discharging efficiency.

  The battery according to the present invention is provided with an electrolytic solution together with a positive electrode and a negative electrode, the negative electrode contains natural graphite, and the electrolytic solution contains a cyclic imide salt.

  According to the battery of the present invention, since the electrolytic solution contains a cyclic imide salt, the decomposition reaction of the electrolytic solution can be suppressed and the charge / discharge efficiency can be improved even if the negative electrode contains natural graphite. be able to.

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

  FIG. 1 shows a cross-sectional configuration of a secondary battery according to an embodiment of the present invention. 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 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 of the positive electrode current collector 21A. The positive electrode current collector 21A is made of a metal material such as aluminum, nickel, or stainless steel, for example. 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 polyfluoride as necessary. A binder such as vinylidene may be included.

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 manganese spinel (LiMn ₂ O ₄ ) or its solid solution (Li (Mn _2−v Ni _v ) O ₄ ) (value of v is v <2) or a phosphate compound having an olivine structure such as lithium iron phosphate (LiFePO ₄ ) is preferable. This is because a high energy density can be obtained. Examples of the positive electrode material capable of occluding and releasing lithium include oxides such as titanium oxide, vanadium oxide and manganese dioxide, disulfides such as iron disulfide, titanium disulfide and molybdenum disulfide, and sulfur. And conductive polymers such as polyaniline and polythiophene.

  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 anode current collector 22A is made of, for example, a metal material such as copper (Cu), nickel, or stainless steel.

  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.

  The negative electrode material capable of inserting and extracting lithium includes natural graphite. This is because the discharge capacity is large and the battery capacity can be increased.

  Further, the negative electrode material capable of inserting and extracting lithium may contain other negative electrode active materials in addition to natural graphite. Examples of other negative electrode active materials include artificial graphite. In addition, a material including a metal element or a metalloid element capable of forming an alloy with lithium as a constituent element can be given. For example, silicon (Si), tin (Sn), magnesium (Mg), boron (B), aluminum, gallium (Ga), indium (In), germanium (Ge), lead (Pb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr), yttrium Examples include materials containing (Y), palladium (Pd), or platinum (Pt). Furthermore, the material containing the element which forms complex oxide with lithium, such as titanium (Ti), is also mentioned. As the other negative electrode active material, one kind may be used alone, or two or more kinds may be mixed and used.

  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 porous film made of ceramic, and these two or more kinds of porous films are laminated. It may be made the structure.

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

  The solvent contains a high dielectric constant solvent having a relative dielectric constant of 30 or more. This is because the number of lithium ions can be increased.

  Examples of the high dielectric constant solvent include cyclic carbonates such as ethylene carbonate, propylene carbonate, and butylene carbonate, or fluoroethylene carbonate (4-fluoro-1,3-dioxolan-2-one), chloroethylene carbonate (4-chloro -1,3-dioxolan-2-one) or cyclic carbonate derivatives such as ethylene trifluorocarbonate, lactones such as γ-butyrolactone or γ-valerolactone, or lactams such as N-methyl-2-pyrrolidone, or Examples thereof include cyclic carbamates such as N-methyl-2-oxazolidinone, and sulfone compounds such as tetramethylene sulfone. As the high dielectric constant solvent, one kind may be used alone, or a plurality of kinds may be mixed and used.

  Moreover, it is preferable to mix and use a low-viscosity solvent having a viscosity of 1 mPa · s or less as the high dielectric constant solvent. This is because high ion conductivity can be obtained. Examples of the low-viscosity solvent include chain carbonate esters such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate or methyl propyl carbonate, or methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, Chain carboxylic acid ester such as methyl trimethylacetate or ethyl trimethylacetate, chain amide such as N, N-dimethylacetamide, or chain formula such as methyl N, N-diethylcarbamate or ethyl N, N-diethylcarbamate Carbamates or ethers such as 1,2-dimethoxyethane, tetrahydrofuran, tetrahydropyran or 1,3-dioxolane can be mentioned. One low viscosity solvent may be used alone, or a plurality of low viscosity solvents may be mixed and used.

  As the solvent, it is preferable to include a carbonate having a multiple bond such as vinylene carbonate or vinyl ethylene carbonate. This is because the decomposition reaction of the electrolytic solution can be suppressed, and the charge / discharge efficiency can be improved. One type of carbonate ester having multiple bonds may be used alone, or a plurality of types may be mixed and used.

  The electrolyte salt includes a cyclic imide salt. It is considered that the cyclic imide salt can be opened during charging to form a film on the negative electrode 22, and even if the negative electrode 22 contains natural graphite, the decomposition of the electrolyte solution is increased. This is because the reaction can be suppressed and the charge / discharge efficiency can be improved. Moreover, it is because a high effect can be obtained even in a high temperature environment.

  As such a cyclic imide salt, an alkali metal salt of a cyclic perfluoroalkanoic acid imide is preferably exemplified, and examples thereof include an alkali metal salt of perfluoroalkanesulfonimide or an alkali metal salt of perfluorocarboxylic acid imide. . One kind of cyclic imide salt may be used alone, or a plurality of kinds may be mixed and used.

  Examples of the alkali metal salt of perfluoroalkanesulfonimide or the alkali metal salt of perfluorocarboxylic acid imide include the compound shown in Chemical Formula 1 (1) and the compound shown in Chemical Formula 1 (2).

（式中、Ｒ１およびＲ２は、炭素数２から４のパーフルオロアルキレン基を表す。Ｍ１およびＭ２は、リチウム，ナトリウム（Ｎａ），カリウム（Ｋ），ルビジウム（Ｒｂ），セシウム（Ｃｓ）などのアルカリ金属を表す。）

(In the formula, R1 and R2 represent perfluoroalkylene groups having 2 to 4 carbon atoms. M1 and M2 are lithium, sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), etc.) Represents an alkali metal.)

  Specific examples of the compound shown in Chemical Formula 1 (1) or the compound shown in Chemical Formula 1 (2) include lithium (tetrafluoroethylene) sulfonimide and Chemical Formula 2 shown in Chemical Formula 2 (1). Lithium (hexafluoropropene) sulfonimide shown in (2), lithium (octafluorobutene) sulfonimide shown in chemical formula 2 (3), lithium tetrafluorosuccinimide shown in chemical formula 2 (4) or chemical formula And lithium hexafluoroglutarimide shown in (2) of 2 above.

  Moreover, it is preferable that content of cyclic imide salt is 0.1 to 10 mass% in electrolyte solution. This is because a higher effect can be obtained.

The electrolyte salt may contain other electrolyte salt in addition to the cyclic imide salt. Examples of other electrolyte salts include lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), and lithium hexafluoroantimonate (LiSbF). ₆ ), an inorganic lithium salt such as lithium perchlorate (LiClO ₄ ), lithium tetrachloroaluminate (LiAlCl ₄ ), lithium trifluoromethanesulfonate (CF ₃ SO ₃ Li), lithium bis (trifluoromethanesulfone) imide ( (CF ₃ SO ₂ ) ₂ NLi), lithium bis (pentafluoroethanesulfone) imide ((C ₂ F ₅ SO ₂ ) ₂ NLi), lithium tris (trifluoromethanesulfone) methide ((CF ₃ SO ₂ ) ₃ CLi) And lithium salts of perfluoroalkanesulfonic acid derivatives. One kind of other electrolyte salt may be used alone, or a plurality of kinds may be mixed and used.

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

  First, for example, a positive electrode active material, a conductive material, and a binder are mixed to prepare a positive electrode mixture, and the positive electrode mixture is dispersed in a solvent such as N-methyl-2-pyrrolidone to obtain a paste-like material. A positive electrode mixture slurry is obtained. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector 21A and the solvent is dried. Then, the positive electrode active material layer 21B is formed by compression molding using a roll press or the like, and the positive electrode 21 is manufactured.

  Further, for example, a negative electrode mixture is prepared by mixing natural graphite, if necessary, another negative electrode active material, and a binder, and this negative electrode mixture is mixed with a solvent such as N-methyl-2-pyrrolidone. Disperse to obtain a paste-like negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, and the solvent is dried. Then, the negative electrode active material layer 22B is formed by compression molding using a roll press or the like, and the negative electrode 22 is manufactured.

  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. Here, natural graphite is contained in the negative electrode 22 and the reactivity is high. However, since the cyclic imide salt is contained in the electrolytic solution, the reactivity of the negative electrode 22 is reduced and the electrolytic solution is decomposed. The reaction is suppressed.

  As described above, according to the present embodiment, since the cyclic imide salt is included in the electrolytic solution, the decomposition reaction of the electrolytic solution can be suppressed even when the negative electrode 22 includes natural graphite. Efficiency can be improved.

  Further, if the content of the cyclic imide salt in the electrolytic solution is 0.1% by mass or more and 10% by mass or less, a higher effect can be obtained.

  Furthermore, if the electrolytic solution contains a carbonate having a multiple bond, the charge / discharge efficiency can be further improved, and the content thereof is 0.5% by mass or more and 5% by mass or less in the electrolytic solution. If so, a higher effect can be obtained.

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

(Examples 1-1 to 1-5)
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 mixed, and then N-methyl as a solvent. -2-Pyrrolidone was added to obtain a positive electrode mixture slurry. Subsequently, the obtained positive electrode mixture slurry was 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 to form a positive electrode active material layer 21B. After that, the positive electrode current collector 21A on which the positive electrode active material layer 21B was formed was cut into a shape having a width of 50 mm and a length of 300 mm to produce the positive electrode 21.

  Moreover, after mixing 97 mass parts of natural graphite as a negative electrode active material and 3 mass parts of polyvinylidene fluoride as a binder, N-methyl-2-pyrrolidone was added as a solvent to obtain a negative electrode mixture slurry. The obtained negative electrode mixture slurry was uniformly applied to both surfaces of a negative electrode current collector 22A made of a strip-shaped copper foil having a thickness of 15 μm and dried to form a negative electrode active material layer 22B. After that, the negative electrode current collector 22A on which the negative electrode active material layer 22B was formed was cut into a shape having a width of 50 mm and a length of 300 mm to produce the negative electrode 22.

  After preparing the positive electrode 21 and the negative electrode 22, a separator 23 made of a microporous polyethylene 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 the electrolyte solution, ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and vinylene carbonate as solvents, lithium hexafluorophosphate and cyclic imide salt as electrolyte salts, ethylene carbonate: propylene carbonate: dimethyl carbonate: Ethyl methyl carbonate: vinylene carbonate: lithium hexafluorophosphate: cyclic imide salt = a mixture of 12: 9: 55: 4: 2: 16: 2 in a mass ratio. In Example 1-1, lithium (hexafluoropropene) sulfonimide shown in Chemical Formula 2 (2) was used, and in Example 1-2, lithium (tetrafluoroethylene) sulfonimide shown in Chemical Formula 2 (1) was used. In 1-3, the lithium (octafluorobutene) sulfonimide shown in Chemical Formula 2 (3) was used. In Example 1-4, the lithium shown in Chemical Formula 2 (4) was used. And tiger fluoro succinimide was lithium hexafluoro glutaric acid imide shown in Example 1-5 In Formula 2 (5).

  After injecting the electrolyte into the battery can 11, the battery lid 14 was caulked to the battery can 11 via a gasket 17 having asphalt coated on the surface, thereby obtaining a cylindrical secondary battery having a diameter of 18 mm.

  As Comparative Example 1-1 with respect to Examples 1-1 to 1-5, a secondary battery was fabricated in the same manner as in Examples 1-1 to 1-5, except that a cyclic imide salt was not used. . Specifically, the electrolyte includes ethylene carbonate, propylene carbonate, dimethyl carbonate, ethyl methyl carbonate, vinylene carbonate, and lithium hexafluorophosphate as an electrolyte salt, ethylene carbonate: propylene carbonate: dimethyl carbonate: ethyl methyl carbonate. : Vinylene carbonate: lithium hexafluorophosphate = 12: 9: 57: 4: 2: 16 mixed at a mass ratio was used.

  Regarding the secondary batteries of Examples 1-1 to 1-5 and Comparative Example 1-1, 300 cycles of charge / discharge were performed in an environment of 23 ° C. or 45 ° C., and the cycle characteristics were examined. The results are shown in Table 1. The charging is performed at 2200 mA for 4.2 hours with 4.2 V as the upper limit, the discharging is performed at 2200 mA up to 3.0 V, and the cycle characteristic is the maintenance ratio of the discharge capacity at the 300th cycle relative to the discharge capacity at the first cycle, that is, , (Discharge capacity at the 300th cycle / discharge capacity at the first cycle) × 100 (%).

  As shown in Table 1, according to Examples 1-1 to 1-5 using a cyclic imide salt, the discharge capacity maintenance rate at 23 ° C. was dramatically higher than that of Comparative Example 1-1 using no cyclic imide salt. Improved. In Example 1-1 using a cyclic imide salt, the discharge capacity retention rate at 45 ° C. was also high.

  That is, even when the negative electrode 22 contains natural graphite, it has been found that charging and discharging efficiency can be improved if the electrolyte contains a cyclic imide salt. It was also found that a high effect can be obtained even in a high temperature environment.

(Examples 2-1 and 2-2)
A secondary battery was made in the same manner as Example 1-1 except that the content of lithium (hexafluoropropene) sulfonimide in the electrolytic solution was 10% by mass or 0.1% by mass. Specifically, ethylene carbonate: propylene carbonate: dimethyl carbonate: ethyl methyl carbonate: vinylene carbonate: lithium hexafluorophosphate: lithium (hexafluoropropene) sulfonimide (mass ratio) is 12 in Example 2-1. : 9: 47: 4: 2: 16: 10, and in Example 2-2, it was set to 12: 9: 56.9: 4: 2: 16: 0.1.

  For the secondary batteries of Examples 2-1 and 2-2, cycle characteristics were examined in an environment at 23 ° C. in the same manner as in Examples 1-1 to 1-5. The results are shown in Table 2 together with the results of Example 1-1 and Comparative example 1-1.

  As shown in Table 2, in Examples 1-1, 2-1, and 2-2 in which the content of lithium (hexafluoropropene) sulfonimide in the electrolytic solution was 0.1% by mass or more and 10% by mass or less, A high discharge capacity retention rate was obtained.

  That is, it has been found that it is preferable if the content of the cyclic imide salt in the electrolytic solution is 0.1% by mass or more and 10% by mass or less.

(Examples 3-1 and 3-2)
A secondary battery was fabricated in the same manner as in Example 1-1, except that the content of vinylene carbonate in the electrolytic solution was 5 mass% or 0.5 mass%. Specifically, ethylene carbonate: propylene carbonate: dimethyl carbonate: ethyl methyl carbonate: vinylene carbonate: lithium hexafluorophosphate: lithium (hexafluoropropene) sulfonimide (mass ratio) is 9 in Example 3-1. : 9: 55: 4: 5: 16: 2 and in Example 3-2, 13.5: 9: 55: 4: 0.5: 16: 2.

  As Comparative Examples 3-1 and 3-2 with respect to Examples 3-1 and 3-2, except that lithium (hexafluoropropene) sulfonimide was not used, the others were the same as Examples 3-1 and 3-2 Thus, a secondary battery was produced. Specifically, ethylene carbonate: propylene carbonate: dimethyl carbonate: ethyl methyl carbonate: vinylene carbonate: lithium hexafluorophosphate (mass ratio) is 9: 9: 57: 4: 5 in Comparative Example 3-1. 16 and 13.5: 9: 57: 4: 0.5: 16 in Comparative Example 3-2.

  For the secondary batteries of Examples 3-1 and 3-2, cycle characteristics were examined in an environment at 23 ° C. in the same manner as in Examples 1-1 to 1-5. The results are shown in Table 3 together with the results of Example 1-1 and Comparative example 1-1.

  As shown in Table 3, it was found that even if the content of vinylene carbonate was changed, the charge / discharge efficiency could be improved if the electrolyte contained a cyclic imide salt.

  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 embodiments and examples, a battery using lithium as an electrode reactant has been described. However, other alkali metals such as sodium or potassium, alkaline earth metals such as magnesium or calcium (Ca), or aluminum The present invention can also be applied to cases where other light metals such as are used. At that time, the positive electrode active material capable of inserting and extracting the electrode reactant is selected according to the electrode reactant.

  In the above embodiments and examples, the cylindrical type secondary battery has been specifically described. However, the present invention is not limited to a coin type, a button type, a square type, an elliptical type, a polygon type, or a laminate film type. The present invention can be similarly applied to secondary batteries having other shapes such as those described above or secondary batteries having other structures such as a stacked structure. Furthermore, the present invention is not limited to the secondary battery, and can be similarly applied to other batteries such as a primary battery.

  Furthermore, in the above embodiments and examples, the case where a liquid electrolytic solution is used as the electrolyte has been described. However, a gel electrolyte in which the electrolytic solution is held by a holding body such as a polymer compound may be used. Good. Examples of such a polymer compound include polyacrylonitrile, polyvinylidene fluoride, a copolymer of vinylidene fluoride and hexafluoropropylene, polytetrafluoroethylene, polyhexafluoropropylene, polyethylene oxide, polypropylene oxide, and polyphosphazene. , Polysiloxane, polyvinyl acetate, polyvinyl alcohol, polymethyl methacrylate, polyacrylic acid, polymethacrylic acid, styrene-butadiene rubber, nitrile-butadiene rubber, polystyrene or polycarbonate. In particular, polyacrylonitrile, polyvinylidene fluoride, polyhexafluoropropylene, or polyethylene oxide is preferable from the viewpoint of electrochemical stability.

It is sectional drawing showing the structure of the secondary battery which concerns on one embodiment of this invention. It is sectional drawing which expands and represents a part of winding electrode body in the secondary battery shown in FIG.

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 ... Winding electrode body, 21 ... Positive electrode, 21A DESCRIPTION OF SYMBOLS ... Positive electrode collector, 21B ... Positive electrode active material layer, 22 ... Negative electrode, 22A ... Negative electrode collector, 22B ... Negative electrode active material layer, 23 ... Separator, 24 ... Center pin, 25 ... Positive electrode lead, 26 ... Negative electrode lead.

Claims (6)

A battery comprising an electrolyte solution together with a positive electrode and a negative electrode,
The negative electrode includes natural graphite,
The battery includes a cyclic imide salt.   The battery according to claim 1, wherein the cyclic imide salt includes an alkali metal salt of cyclic perfluoroalkanoic acid imide. 2. The battery according to claim 1, wherein the cyclic imide salt includes at least one selected from the group consisting of a compound represented by Chemical Formula (1) and a compound represented by Chemical Formula (2). .

(In the formula, R 1 and R 2 represent a perfluoroalkylene group having 2 to 4 carbon atoms. M 1 and M 2 represent an alkali metal.)   The imide salt is selected from the group consisting of lithium (tetrafluoroethylene) sulfonimide, lithium (hexafluoropropene) sulfonimide, lithium (octafluorobutene) sulfonimide, lithium tetrafluorosuccinimide and lithium hexafluoroglutarimide. The battery according to claim 1, comprising at least one of the following.   2. The battery according to claim 1, wherein a content of the cyclic imide salt in the electrolytic solution is 0.1% by mass or more and 10% by mass or less. The battery according to claim 1, wherein the electrolytic solution further contains a carbonate ester having a multiple bond.

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