JP2008027837A - Electrolyte and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of reducing bulge by suppressing a decomposition reaction of an electrolyte even in a high-temperature environment. <P>SOLUTION: This electrolyte 24 contains an electrolytic solution containing a cyclic carbonate derivative such as trans-4, 5-difluoro-1, 3-dioxolan-2-on or cis-4, 5-difluoro-1, 3-dioxolan-2-on, and sultone such as 1, 3-propene sultone or 1, 3-propane sultone. Thereby, the decomposition of the electrolyte 24 is suppressed even in a high-temperature environment, and the bulge of this battery can be reduced. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an electrolyte containing a cyclic carbonate derivative having a halogen atom and a battery using the same.

  In recent years, many portable electronic devices such as a camera-integrated VTR (video tape recorder), a digital still camera, a mobile phone, a portable information terminal, or a notebook computer have appeared, and their size and weight have been reduced. Accordingly, as a portable power source for electronic devices, research and development for improving the energy density of batteries, particularly secondary batteries, are being actively promoted. Among these, lithium ion secondary batteries using a carbon material for the negative electrode, a composite material of lithium (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.

  As such a lithium ion secondary battery, for example, since it is lightweight and has a high energy density, a battery using a laminate film as an exterior member has been put into practical use. In particular, an electrolytic solution is held in a polymer compound. A so-called gel is widely used since it can suppress deformation of the exterior member.

In these lithium ion secondary batteries, it has been proposed to add various additives to the electrolyte in order to improve battery characteristics such as cycle characteristics. For example, in Patent Documents 1 and 2 listed below, trans-4,5-difluoro-1,3-dioxolan-2-one or cis-4,5-difluoro-1,3-dioxolan-2-one (hereinafter referred to as electrolyte) is used as an electrolyte. In addition, a lithium ion secondary battery having a high capacity and excellent cycle characteristics is obtained by containing difluoroethylene carbonate (DFEC).
JP 2003-168480 A JP 2004-319317 A

  By the way, in said electronic device, there exists a tendency for power consumption to increase, and the emitted-heat amount is also increasing in connection with it. Since an electrolyte containing difluoroethylene carbonate (DFEC) is easily decomposed during high-temperature storage, the swelling of the exterior member tends to increase when such an electrolyte is used.

  The present invention has been made in view of such problems, and its purpose is to provide an electrolyte capable of suppressing a decomposition reaction even under a high temperature environment, and such an electrolyte, and using a film-like exterior member. Another object is to provide a battery capable of suppressing swelling.

  The electrolyte of the present invention comprises a solvent containing a cyclic carbonate derivative having two or more halogen atoms and a compound having a sulfone structure having a cyclic bond or a carbon-carbon multiple bond, and an electrolyte salt. It is.

  The battery of the present invention is a battery comprising a positive electrode and a negative electrode together with an electrolyte containing a solvent and an electrolyte salt, and the electrolyte includes a cyclic carbonate derivative having two or more halogen atoms and a cyclic bond or carbon-carbon multiple. And a solvent containing a compound having a sulfone structure having a bond.

  According to the electrolyte of the present invention and the battery including the electrolyte, the solvent includes a cyclic carbonate derivative having two or more halogen atoms and a compound having a sulfone structure having a cyclic bond or a carbon-carbon multiple bond. Therefore, the decomposition reaction of the electrolyte can be suppressed even in a high temperature environment. Therefore, even if a film-like exterior member is used, the swelling can be suppressed, and the safety as a battery can be ensured.

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

  FIG. 1 shows an exploded view of a secondary battery as an embodiment of the present invention. This secondary battery is a so-called laminate film type, and has a wound electrode body 20 to which a positive electrode lead 11 and a negative electrode lead 12 are attached accommodated in a film-shaped exterior member 30.

  The positive electrode lead 11 and the negative electrode lead 12 are each led out from the inside of the exterior member 30 to the outside, for example, in the same direction. The positive electrode lead 11 and the negative electrode lead 12 are each made of a metal material such as aluminum (Al), copper (Cu), nickel (Ni), or stainless steel, and each have a thin plate shape or a mesh shape.

  The exterior member 30 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. The exterior member 30 is disposed, for example, so that the polyethylene film side and the wound electrode body 20 face each other, and the outer edge portions are in close contact with each other by fusion or an adhesive. An adhesion film 31 is inserted between the exterior member 30 and the positive electrode lead 11 and the negative electrode lead 12 to prevent intrusion of outside air. The adhesion film 31 is made of a material having adhesion to the positive electrode lead 11 and the negative electrode lead 12, for example, a polyolefin resin such as polyethylene, polypropylene, modified polyethylene, or modified polypropylene.

  The exterior member 30 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. 2 shows a cross-sectional structure taken along line II-II of the spirally wound electrode body 20 shown in FIG. The wound electrode body 20 is obtained by laminating a positive electrode 21 and a negative electrode 22 via a separator 23 and an electrolyte 24 and winding them, and the outermost periphery is protected by a protective tape 25.

  The positive electrode 21 is, for example, provided with a positive electrode active material layer 21B on both surfaces or one surface of a positive electrode current collector 21A having a pair of opposed surfaces. 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, any one or more of positive electrode materials capable of occluding and releasing lithium, which is an electrode reactant, as a positive electrode active material. A conductive agent and a binder such as polyvinylidene fluoride 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 f Co g Mn} h) O 2)) (f, g and h 0 <f <1, 0 <g <1, 0 <h <1, f + g + h = 1.), Or manganese spinel (LiMn ₂ O ₄ ) or its solid solution (Li (Mn _2−z Ni _z) ) O ₄ ) (the value of z is z <2) or a lithium composite oxide, 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 positive electrode materials 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 sulfide, sulfur, Examples thereof include 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 or one surface of a negative electrode current collector 22A having a pair of opposed surfaces. The negative electrode current collector 22A is made of, for example, a metal material such as copper, nickel, or stainless steel.

  The negative electrode active material layer 22B includes, for example, one or more negative electrode materials capable of inserting and extracting lithium as an electrode reactant as a negative electrode active material. Examples of the negative electrode material capable of inserting and extracting lithium include a carbon material. Examples of such carbon materials include non-graphitizable carbon, pyrolytic carbons, cokes, graphites, glassy carbon fibers, organic polymer compound fired bodies, carbon fibers, activated carbon, and carbon blacks. Among these, coke includes pitch coke, needle coke, petroleum coke, and the like, and the organic polymer compound fired body is obtained by firing and carbonizing a phenol resin or a furan resin at an appropriate temperature. .

  Examples of the negative electrode material capable of inserting and extracting lithium also include a material containing at least one of a metal element and a metalloid element capable of forming an alloy with lithium as a constituent element. The negative electrode material may be a single element, alloy or compound of a metal element or metalloid element, or may have at least a part of one or more of these phases. In addition, in addition to what consists of 2 or more types of metal elements, an alloy is set as the concept also including what has 1 or more types of metal elements and 1 or more types of metalloid 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 such metal elements or metalloid elements include tin (Sn), lead (Pb), aluminum, indium (In), silicon (Si), zinc (Zn), antimony (Sb), and bismuth (Bi). , Gallium (Ga), germanium (Ge), arsenic (As), silver (Ag), hafnium (Hf), zirconium (Zr) and yttrium (Y). Among them, a group 14 metal element or metalloid element in the long-period type periodic table is preferable, and silicon or tin is particularly preferable. This is because silicon and tin have a large ability to occlude and release lithium, and a high energy density can be obtained.

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

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

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

  The electrolyte 24 contains an electrolytic solution in which an electrolyte salt is dissolved in a solvent. In particular, the electrolyte 24 is desirably in a so-called gel state by holding the electrolytic solution in a polymer compound. This is because by making the electrolyte 24 into a gel, it is possible to obtain high ionic conductivity and to prevent battery leakage.

  Examples of the solvent include trans-4,5-difluoro-1,3-dioxolan-2-one (trans-difluoroethylene carbonate) shown in Chemical Formula 1 and cis-4,5-difluoro-1, shown in Chemical Formula 2, A cyclic carbonate derivative having two or more halogen atoms such as 3-dioxolan-2-one (cis-difluoroethylene carbonate) is used. Such a cyclic carbonate derivative is called a high dielectric constant solvent having a relative dielectric constant of 30 or more.

  Examples of the solvent include, as a high dielectric constant solvent, cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, and vinyl ethylene carbonate, in addition to the above-described cyclic carbonate derivatives having two or more halogen atoms. Ester, lactone such as γ-butyrolactone or γ-valerolactone, lactam such as N-methyl-2-pyrrolidone, cyclic carbamate such as N-methyl-2-oxazolidinone, and sulfone compound such as tetramethylene sulfone are further added. You may do it.

  A low-viscosity solvent having a viscosity of 1 mPa · s or less may be further added to the solvent. In particular, when these low-viscosity solvents are mixed and used, ion conductivity may be improved.

  Examples of the low-viscosity solvent include chain carbonate esters such as dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and methyl propyl carbonate, methyl acetate, ethyl acetate, methyl propionate, ethyl propionate, methyl butyrate, methyl isobutyrate, and trimethyl. Chain carboxylic acid ester such as methyl acetate or ethyl trimethylacetate, chain amide such as N, N-dimethylacetamide, chain carbamic acid ester such as methyl N, N-diethylcarbamate or ethyl N, N-diethylcarbamate 1,2-dimethoxyethane, tetrahydrofuran, tetrahydropyran or ether such as 1,3-dioxolane.

  The solvent further contains, as an additive, a compound having a sulfone structure having a cyclic bond or a carbon-carbon multiple bond, specifically, sultone (cyclic sulfonate ester). Thereby, a good film is formed on the surface of the electrode, ion conductivity in the electrode is improved, and decomposition reaction of the electrolyte 24 is suppressed even in a high temperature environment.

  Examples of such sultone include the compounds shown in Chemical Formulas 3 to 6.

（式中、Ｒ１は、Ｃ_ｍＨ_２ｍ−ｎＦ_ｎまたはＣ_ｐＨ_{２ｐ−ｑ−２}Ｆ_ｑを表す。ｍ，ｎ，ｐ，ｑは、２≦ｍ≦５，０≦ｎ≦２ｍ，２≦ｐ≦５，０≦ｑ≦２ｐ−２の範囲内の整数を表す。）

(Wherein, R1 _{is, C m H 2m-n F} n or _C p .m representing the _{H 2p-q-2 F q} , n, p, q are, 2 ≦ m ≦ 5,0 ≦ n ≦ 2m, (It represents an integer in the range of 2 ≦ p ≦ 5, 0 ≦ q ≦ 2p−2.)

（式中、Ｒ２は、Ｃ_ｒＨ_２ｒ−２Ｆ_s またはＣ_ｔＨ_{２ｔ−ｕ−２}Ｆ_ｕを表す。ｒ，ｓ，ｔ，ｕは、１≦ｒ≦４，０≦ｓ≦２ｒ，１≦ｔ≦４，０≦ｕ≦２ｔ−２の範囲内の整数を表す。Ｒ３，Ｒ４，Ｒ５およびＲ６は、水素基，アルキル基，アリール基，ハロゲン基，水酸基またはアミノ基を表す。Ｒ３，Ｒ４，Ｒ５およびＲ６は、同一のものがあっても、すべてが異なっていてもよい。）

(Wherein, R2 _is, .r representing the C _{r H 2r-2} F _s or _{C t H 2t-u-2} F u, s, t, u is, 1 ≦ r ≦ 4,0 ≦ s ≦ 2r, R represents an integer in the range of 1 ≦ t ≦ 4, 0 ≦ u ≦ 2t−2, R3, R4, R5 and R6 each represents a hydrogen group, an alkyl group, an aryl group, a halogen group, a hydroxyl group or an amino group. , R4, R5 and R6 may be the same or all different.)

（式中、Ｒ７〜Ｒ１２は、水素基，アルキル基，アリール基，ハロゲン基，水酸基またはアミノ基を表す。これらは、同一のものがあっても、すべてが異なっていてもよい。）

(Wherein R7 to R12 represent a hydrogen group, an alkyl group, an aryl group, a halogen group, a hydroxyl group or an amino group. These may be the same or all different.)

（式中、Ｒ１３〜Ｒ１６は、水素基，アルキル基，アリール基，ハロゲン基，水酸基またはアミノ基を表す。これらは、同一のものがあっても、すべてが異なっていてもよい。）

(Wherein R13 to R16 represent a hydrogen group, an alkyl group, an aryl group, a halogen group, a hydroxyl group or an amino group. These may be the same or all different.)

  Specific examples of such compounds include 1,3-propane sultone (3-hydroxypropanesulfonic acid γ-sultone) shown in Chemical formula 7 (1), 1,3 shown in Chemical formula 7 (2). -Propene sultone (3-hydroxypropene sulfonic acid γ-sultone) or divinyl sulfone shown in Chemical formula 7 (3).

  In this secondary battery, a phosphorus compound having hydrogen that can be dissociated as protons may be further added to the solvent. By doing so, the decomposition reaction of the electrolyte 24 can be more effectively suppressed.

  Examples of such phosphorus compounds include the compounds shown in Chemical Formulas 8 to 10.

（式中、Ｒ１７，Ｒ１８は、Ｃ_ｖＨ_２ｖ＋１またはＣ_ｗＨ_２ｗ−７を表す。ｖ，ｗは、０≦ｖ≦４，６≦ｗ≦１１の範囲内の整数を表す。）

(In the formula, R17 and R18 represent C _v H _{2v + 1} or C _w H _2w-7 . V and w represent integers in the range of 0 ≦ v ≦ 4, 6 ≦ w ≦ 11.)

（式中、Ｒ１９，Ｒ２０は、Ｃ_ｖＨ_２ｖ＋１またはＣ_ｗＨ_２ｗ−７を表す。ｖ，ｗは、０≦ｖ≦４，６≦ｗ≦１１の範囲内の整数を表す。）

(In the formula, R19 and R20 represent C _v H _{2v + 1} or C _w H _2w-7 . V and w represent integers in the range of 0 ≦ v ≦ 4, 6 ≦ w ≦ 11.)

（式中、Ｒ２１，Ｒ２２は、Ｃ_ｖＨ_２ｖ＋１またはＣ_ｗＨ_２ｗ−７を表す。ｖ，ｗは、０≦ｖ≦４，６≦ｗ≦１１の範囲内の整数を表す。）

(In the formula, R21 and R22 represent C _v H _{2v + 1} or C _w H _2w-7 . V and w represent integers in the range of 0 ≦ v ≦ 4, 6 ≦ w ≦ 11.)

  More specifically, phosphorous acid shown in Chemical formula 11 (1) or diphenyl phosphate shown in Chemical formula 11 (2) can be used. In addition, phosphoric acid, phenylphosphonic acid or phenylphosphinic acid may be added.

As the electrolyte salt, e.g., lithium hexafluorophosphate (LiPF _6), lithium tetrafluoroborate (LiBF _4), lithium hexafluoroarsenate (LiAsF _6), lithium hexafluoro antimonate (LiSbF ₆₎ Inorganic lithium salts 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), etc. Lithium lithium of fluoroalkanesulfonic acid derivatives Salt and the like. One electrolyte salt may be used alone, or a plurality of electrolyte salts may be mixed and used.

  As the polymer compound for holding the electrolytic solution, a polymer of vinylidene fluoride such as polyvinylidene fluoride containing a structural unit of formula 12 or a copolymer of vinylidene fluoride and hexafluoropropylene is preferably exemplified. This is because the redox stability is high.

  Examples of the polymer compound include those formed by polymerizing a polymerizable compound. Examples of the polymerizable compound include those containing a vinyl group or a group obtained by substituting a part of hydrogen with a substituent such as a methyl group. Specifically, monofunctional acrylates such as acrylic acid esters, monofunctional methacrylates such as methacrylic acid esters, polyfunctional acrylates such as diacrylic acid esters or triacrylic acid esters, and polyfunctional acrylates such as dimethacrylic acid esters or trimethacrylic acid esters. There are functional methacrylate, acrylonitrile, methacrylonitrile, and the like. Among them, an ester having an acrylate group or a methacrylate group is preferable. This is because the polymerization proceeds easily and the reaction rate of the polymerizable compound is high. Moreover, as a polymeric compound, what does not contain an ether group is preferable. This is because if an ether group is present, lithium ions are coordinated to the ether group, thereby reducing the ionic conductivity. As such a polymer compound, for example, polyacrylic acid ester containing a structural unit represented by Chemical Formula 13 can be given.

（式中、Ｒ２３は、Ｃ_ｊＨ_２ｊ−１Ｏ_ｋを表す。ｊ，ｋは、１≦ｊ≦８，０≦ｋ≦４の範囲内の整数である。）

(In the formula, R23 represents C _j H _2j-1 O _k. J and k are integers in the range of 1 ≦ j ≦ 8, 0 ≦ k ≦ 4.)

  Any one of the polymerizable compounds may be used alone, but it is desirable to mix a monofunctional compound and a polyfunctional compound, or to use a polyfunctional compound singly or in combination of two or more. . This is because such a configuration makes it easy to achieve both the mechanical strength of the polymer compound formed by polymerization and the electrolyte solution retention.

  Furthermore, as a high molecular compound, what has a structure which superposed | polymerized at least 1 sort (s) of the group which consists of polyvinyl acetal and its derivative (s) is preferable.

  Polyvinyl acetal is a compound containing a structural unit containing an acetal group shown in Chemical formula 14 as a repeating unit. Specific examples thereof include polyvinyl formal in which R24 shown in Chemical formula 14 is hydrogen.

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

  First, a positive electrode active material, a binder, and a conductive agent are mixed to prepare a positive electrode mixture, and dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a positive electrode mixture slurry. Next, the positive electrode mixture slurry is applied to both surfaces or one surface of the positive electrode current collector 21A, dried, and compression-molded to form the positive electrode active material layer 21B to produce the positive electrode 21. Subsequently, the positive electrode lead 11 is joined to the positive electrode current collector 21A by ultrasonic welding, spot welding, or the like.

  On the other hand, a negative electrode active material and a binder are mixed to prepare a negative electrode mixture, and dispersed in a solvent such as N-methyl-2-pyrrolidone to prepare a negative electrode mixture slurry. Next, this negative electrode mixture slurry is applied to both surfaces or one surface of the negative electrode current collector 22A, dried, and compression molded to form the negative electrode active material layer 22B, whereby the negative electrode 22 is produced. Subsequently, the negative electrode lead 12 is joined to the negative electrode current collector 22A by ultrasonic welding, spot welding, or the like.

  After that, the positive electrode 21 and the negative electrode 22 are laminated and wound via the separator 23, and the protective tape 25 is adhered to the outermost peripheral portion to form a wound body that is a precursor of the wound electrode body 20. Next, the wound body is sandwiched between the exterior members 30, and the outer peripheral edge portion excluding one side is heat-sealed to form a bag shape, and is stored inside the exterior member 30. Subsequently, after injecting the electrolyte into the exterior member 30, the opening of the exterior member 30 is heat-sealed and sealed. At that time, the adhesion film 31 is inserted between the positive electrode lead 11 and the negative electrode lead 12 and the exterior member 30. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  Moreover, when making electrolyte solution hold | maintain to a high molecular compound, it is good to manufacture as follows.

  First, the precursor of the wound electrode body 20 formed by the above-described method is sandwiched between the exterior members 30, and the outer peripheral edge except one side is heat-sealed to form a bag shape, which is then stored inside the exterior member 30. Subsequently, an electrolyte composition including an electrolytic solution, a monomer that is a raw material of the polymer compound, a polymerization initiator and other materials such as a polymerization inhibitor, if necessary, is prepared, and the interior of the exterior member 30 Then, the opening of the exterior member 30 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 24 and assembling the secondary battery shown in FIGS.

  Instead of injecting the electrolyte composition after producing the wound body, for example, the electrolyte composition is applied on the positive electrode 21 and the negative electrode 22 and then wound and enclosed in the exterior member 30. Further, the electrolyte 24 may be formed by heating as necessary. Alternatively, the electrolyte composition may be applied on the positive electrode 21 and the negative electrode 22, heated as necessary to form the electrolyte 24, wound, and sealed in the exterior member 30. However, it is preferable that the electrolyte 24 is formed after being enclosed in the exterior member 30. This is because interfacial bonding between the electrolyte 24 and the separator 23 can be sufficiently improved, and an increase in internal resistance can be suppressed.

  In addition, it is preferable to use polyvinyl acetal or a derivative thereof as a monomer because the ratio of the electrolytic solution in the electrolyte 24 can be increased and ion conductivity can be improved.

  Moreover, you may manufacture this secondary battery as follows. First, after producing the positive electrode 21 as described above, the positive electrode lead 11 is joined to the positive electrode current collector 21A. After that, a precursor solution containing an electrolytic solution, a polymer compound, and a mixed solvent is prepared and applied on the positive electrode active material layer 21B, that is, on both sides or one side of the positive electrode 21, and the mixed solvent is volatilized to obtain an electrolyte. 24 is formed.

  On the other hand, after producing the negative electrode 22 as described above, the negative electrode lead 12 is joined to the negative electrode current collector 22A, and the negative electrode active material layer 22B, that is, on both sides or one side of the negative electrode 22, is made in the same manner as the positive electrode 21. Thus, the electrolyte 24 is formed.

  Subsequently, the positive electrode 21 and the negative electrode 22 on which the electrolyte 24 is formed are laminated via a separator 23 to form a laminated body, and then the laminated body is wound in the longitudinal direction, and the protective tape 25 is bonded to the outermost peripheral portion. Thus, the wound electrode body 20 is formed. After that, for example, the wound electrode body 20 is sandwiched between the exterior members 30, and the outer edges of the exterior members 30 are brought into close contact by thermal fusion or the like and sealed. Even in such a case, the secondary battery shown in FIGS. 1 and 2 can be manufactured.

  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 electrolyte 24. On the other hand, when discharging is performed, lithium ions are released from the negative electrode 22 and inserted into the positive electrode 21 through the electrolyte 24. At that time, since sultone is contained in the electrolyte 24, a good film is formed on the surface of the electrode, ion conductivity is improved, and decomposition reaction of the electrolyte 24 is suppressed even in a high temperature environment. When the electrolyte 24 further contains a phosphorus compound having hydrogen that can be dissociated as protons, such as phosphorous acid or diphenyl phosphate, the decomposition reaction of the electrolyte 24 is more effectively suppressed. .

  Thus, according to the present embodiment, trans-4,5-difluoro-1,3-dioxolan-2-one or cis-4,5-difluoro-1,3-dioxolan-2-one is used as the electrolyte 24. Since sultone is contained together with a cyclic carbonate derivative such as the above, a good film can be formed on the surface of the electrode, ion conductivity at the electrode can be improved, and the decomposition reaction of the electrolyte 24 can be performed. Can be suppressed. Therefore, even under a high temperature environment, swelling can be suppressed even when the film-shaped exterior member 30 is used while maintaining good cycle characteristics.

  Further, if the electrolyte 24 contains a phosphorus compound having hydrogen that can be dissociated as protons, such as phosphorous acid or diphenyl phosphate, a higher effect can be obtained.

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

[First embodiment]
(Example 1-1)
In this example, a secondary battery corresponding to the above embodiment mode was manufactured. 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 agent, and 3 parts by mass of polyvinylidene fluoride as a binder were mixed, and N— Methyl-2-pyrrolidone was added to obtain a positive electrode mixture slurry. Next, the obtained positive electrode mixture slurry was uniformly applied to both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 20 μm and dried to form a positive electrode active material layer. The area density of the positive electrode active material layer was 18 mg / cm ² per side. After that, the positive electrode current collector on which the positive electrode active material layer was formed was cut into a shape having a width of 50 mm and a length of 300 mm to produce a positive electrode.

On the other hand, after mixing 97 parts by mass of graphite as a negative electrode active material and 3 parts by mass of polyvinylidene fluoride as a binder, N-methyl-2-pyrrolidone was added as a solvent to obtain a negative electrode mixture slurry. Next, the obtained negative electrode mixture slurry was uniformly applied to both surfaces of a negative electrode current collector 22A made of a copper foil having a thickness of 15 μm and dried to form a negative electrode active material layer 22B. The area density of the negative electrode active material layer 22B was 10 mg / cm ² per side. After that, the negative electrode current collector on which the negative electrode active material layer was formed was cut into a shape having a width of 50 mm and a length of 300 mm to produce a negative electrode.

  After preparing the positive electrode and the negative electrode, the positive electrode lead made of aluminum is attached to the positive electrode, the negative electrode lead made of nickel is attached to the negative electrode, and the positive electrode and the negative electrode are laminated via a separator made of a microporous polyethylene film having a thickness of 12 μm. And wound to prepare a wound body.

  Next, after sandwiching the wound body between the exterior members made of the aluminum laminate film, the outer edges of the exterior members were bonded to form a bag shape with one side remaining. At that time, the positive electrode lead and the negative electrode lead were led out of the exterior member.

  Subsequently, about 2 g of electrolyte was injected into the exterior member from the open side, and the open side of the exterior member was bonded by thermal fusion to produce the secondary battery shown in FIGS.

  As the electrolyte 24, a solvent obtained by mixing ethylene carbonate, diethyl carbonate, trans-difluoroethylene carbonate, and 1,3-propane sultone in order at a mass ratio of 30: 64.5: 5: 0.5, and an electrolyte salt A solution prepared by mixing and dissolving lithium hexafluorophosphate at a mass ratio of 86:14 was used.

(Example 1-2)
A secondary battery as Example 1-2 was fabricated in the same manner as in Example 1-1 except that 1,3-propene sultone was used instead of 1,3-propane sultone.

(Example 1-3)
Same as Example 1-1 except that 1,3-propene sultone was used instead of 1,3-propane sultone and cis-difluoroethylene carbonate was used instead of trans-difluoroethylene carbonate Thus, a secondary battery as Example 1-3 was produced.

(Example 1-4)
A secondary battery as Example 1-4 was fabricated in the same manner as in Example 1-1 except that divinyl sulfone was used instead of 1,3-propane sultone.

(Example 1-5)
A secondary battery as Example 1-5 was made in the same manner as Example 1-1 except that phosphorous acid was used as an additive in the electrolyte. At that time, the content of phosphorous acid was 0.2% of the whole solvent, and the content of diethyl carbonate was reduced to 64.3%.

(Example 1-6)
A secondary battery as Example 1-6 was made in the same manner as Example 1-1 except that diphenyl phosphate was used as an additive in the electrolyte. At that time, the content of diphenyl phosphate was 0.5% of the whole solvent, and the content of diethyl carbonate was reduced to 64.0% accordingly.

(Comparative Example 1-1)
As Comparative Example 1-1 with respect to Examples 1-1 to 1-6, a secondary battery was fabricated in the same manner as Example 1-1 except that sultone was not added.

  After the obtained secondary batteries of Examples 1-1 to 1-6 and Comparative Example 1-1 were charged at a constant current and a constant voltage for 3 hours with an upper limit of 4.2 V at 700 mA in a 45 ° C. environment, The swelling of the exterior member was measured when stored at 90 ° C. for 4 hours. The results are shown in Table 1. In the column of “bulge after storage at 90 ° C. for 4 hours” in Table 1, the thickness of the (initial) secondary battery at the time of production is taken as a reference value, and the ratio of the thickness after high-temperature storage to the reference value Indicates. In addition, when the capacity | capacitance in each battery was investigated, all were 700 mAh.

  As can be seen from Table 1, according to Examples 1-1 to 1-6 to which sultone was added, swelling was able to be significantly reduced as compared with Comparative Example 1-1 to which this was not added. From the comparison of Example 1-1, Example 1-2, and Example 1-4, it was found that the addition of propene sultone was particularly effective in reducing blistering.

  Further, from comparison between Example 1-2 and Example 1-3, it can be said that the use of trans-difluoroethylene carbonate tends to suppress swelling more than cis-difluoroethylene carbonate.

  Furthermore, from the comparison of Example 1-2, Example 1-5, and Example 1-6, when a phosphorus compound having hydrogen that can be dissociated as a proton, such as phosphorous acid or diphenyl phosphate, is included, the swelling is reduced. It was found to be particularly effective.

[Second Embodiment]
(Examples 2-1 to 2-6)
Except having used silicon (Si) as a negative electrode active material, the secondary battery as Example 2-1 to 2-6 was produced similarly to Example 1-1 to 1-6, respectively. The negative electrode was prepared by forming a negative electrode active material layer made of silicon on a negative electrode current collector made of a copper foil having a thickness of 15 μm by using an electron beam evaporation method.

(Comparative Example 2-1)
As Comparative Example 2-1 with respect to Examples 2-1 to 2-6, a secondary battery was fabricated in the same manner as in Example 2-1, except that sultone was not added.

  For the fabricated secondary batteries of Examples 2-1 to 2-6 and Comparative Example 2-1, the swelling of the exterior member was measured in the same manner as in Examples 1-1 to 1-6. The results are shown in Table 2.

  As can be seen from Table 2, in the second example, the same effect as in the first example was confirmed. That is, according to Examples 2-1 to 2-6 to which sultone was added, swelling was able to be significantly reduced as compared with Comparative Example 2-1 to which this was not added. From comparison of Example 2-1, Example 2-2, and Example 2-4, it was found that the incorporation of propene sultone was extremely effective in reducing blistering.

  Moreover, from the comparison between Example 2-2 and Example 2-3, it can be said that the use of trans-difluoroethylene carbonate tends to suppress swelling more than cis-difluoroethylene carbonate.

  Further, from the comparison between Example 2-2, Example 2-5 and Example 2-6, it is possible to reduce swelling when a phosphorus compound having hydrogen that can dissociate as a proton, such as phosphorous acid or diphenyl phosphate, is contained. It was found to be particularly effective.

[Third embodiment]
(Examples 3-1 to 3-6)
Except having used Sn alloy as a negative electrode active material, the secondary battery as Example 3-1 to 3-6 was produced similarly to Example 1-1 to 1-6, respectively. The negative electrode was produced as follows.

  First, a negative electrode active material was prepared in the following manner. A mixture was obtained by dry-mixing tin / cobalt / indium / titanium alloy powder and carbon powder. After 10 g of this mixture was set in a reaction vessel of a planetary ball mill manufactured by Ito Seisakusho together with about 400 g of steel balls having a diameter of 9 mm, the reaction vessel was replaced with an argon atmosphere and operated for 10 minutes at a rotational speed of 250 revolutions per minute. The pause for 10 minutes was repeated until the total operation time was 20 hours. Thereafter, the synthesized negative electrode active material powder was taken out by cooling the reaction vessel to room temperature, and coarse powder was removed through a 280 mesh sieve. As a result, a CoSnC-containing material containing tin, cobalt, indium, titanium, and carbon in a mass ratio of 48: 23: 5: 2: 20 was obtained.

  94 parts by weight of the negative electrode active material made of the CoSnC-containing material thus prepared, 3 parts by weight of graphite as a conductive material, and 8 parts by weight of polyvinylidene fluoride as a binder are mixed, and N— which is a solvent is mixed. A negative electrode mixture slurry was prepared by dispersing in methyl-2-pyrrolidone. Subsequently, the negative electrode mixture slurry is uniformly applied to both sides of a negative electrode current collector made of a strip-shaped copper foil having a thickness of 15 μm, dried, and compression molded at a constant pressure to form a negative electrode active material layer having a thickness of 50 μm on one side. After forming, the negative electrode was produced by cutting to a size of 50 mm in width and 300 mm in length. After that, a negative electrode lead made of nickel was attached to one end of the negative electrode current collector. The filling amount of the positive electrode active material and the CoSnC-containing material was adjusted so that lithium metal did not deposit on the negative electrode during charging.

(Comparative Example 3-1)
As Comparative Example 3-1 with respect to Examples 3-1 to 3-6, a secondary battery was fabricated in the same manner as in Example 3-1, except that sultone was not added.

  For the fabricated secondary batteries of Examples 3-1 to 3-6 and Comparative Example 3-1, the swelling of the exterior member was measured in the same manner as in Examples 1-1 to 1-6. The results are shown in Table 3.

  As can be seen from Table 3, in the third example, the same effects as in the first and second examples were confirmed. That is, according to Examples 3-1 to 3-6 to which sultone was added, swelling was able to be significantly reduced as compared with Comparative Example 3-1 in which this was not added. From a comparison of Example 3-1, Example 3-2 and Example 3-4, it was found that the incorporation of propene sultone was particularly effective in reducing blistering.

  Further, from comparison between Example 3-2 and Example 3-3, it can be said that the use of trans-difluoroethylene carbonate tends to suppress swelling more than cis-difluoroethylene carbonate.

  Furthermore, from the comparison of Example 3-2, Example 3-5 and Example 3-6, when a phosphorus compound having hydrogen that can dissociate as a proton, such as phosphorous acid or diphenyl phosphate, is contained, swelling is reduced. It was found to be particularly effective.

[Fourth embodiment]
(Examples 4-1 to 4-6)
Examples 1-1 to 1-6 are the same as those of Examples 1-1 to 1-6, except that polyvinylidene fluoride was applied to both surfaces of a separator made of a microporous polyethylene film having a thickness of 7 μm so as to have a thickness of 2 μm. Similarly, secondary batteries as Examples 4-1 to 4-6 were produced.

(Comparative Example 4-1)
As Comparative Example 4-1 for Examples 4-1 to 4-6, a secondary battery was fabricated in the same manner as in Example 2-1, except that sultone was not added.

  For the fabricated secondary batteries of Examples 4-1 to 4-6 and Comparative Example 4-1, the swelling of the exterior member was measured in the same manner as in Examples 1-1 to 1-6. The results are shown in Table 4.

  As can be seen from Table 4, in the fourth example, the same effects as in the first to third examples were confirmed. That is, according to Examples 4-1 to 4-6 to which sultone was added, swelling was able to be greatly reduced as compared with Comparative Example 4-1 to which this was not added. From a comparison of Example 4-1, Example 4-2 and Example 4-4, it was found that the addition of propene sultone was particularly effective in reducing blistering.

  Further, from comparison between Example 4-2 and Example 4-3, it can be said that the use of trans-difluoroethylene carbonate tends to suppress swelling more than cis-difluoroethylene carbonate.

  Further, from the comparison of Example 4-2, Example 4-5 and Example 4-6, when a phosphorus compound having hydrogen that can be dissociated as a proton, such as phosphorous acid or diphenyl phosphate, is included, the swelling is reduced. It was found to be particularly effective.

[Fifth embodiment]
(Examples 5-1 to 5-6)
Except having used silicon (Si) as a negative electrode active material, the secondary battery as Example 5-1 to 5-6 was produced similarly to Example 4-1 to 4-6, respectively. The negative electrode was prepared by forming a negative electrode active material layer made of silicon on a negative electrode current collector made of a copper foil having a thickness of 15 μm by using an electron beam evaporation method.

(Comparative Example 5-1)
As Comparative Example 5-1 with respect to Examples 5-1 to 5-6, a secondary battery was fabricated in the same manner as in Example 5-1, except that sultone was not added.

  For the fabricated secondary batteries of Examples 5-1 to 5-6 and Comparative Example 5-1, the swelling of the exterior member was measured in the same manner as in Examples 1-1 to 1-6. The results are shown in Table 5.

  As can be seen from Table 5, in the fifth example, the same effects as in the first to fourth examples were confirmed. That is, according to Examples 5-1 to 5-6 to which sultone was added, swelling was able to be significantly reduced as compared with Comparative Example 5-1 to which this was not added. From a comparison of Example 5-1, Example 5-2 and Example 5-4, it was found that the addition of propene sultone was particularly effective in reducing blistering.

  Further, from comparison between Example 5-2 and Example 5-3, it can be said that the use of trans-difluoroethylene carbonate tends to suppress swelling more than cis-difluoroethylene carbonate.

  Furthermore, from the comparison between Example 5-2, Example 5-5 and Example 5-6, it is possible to reduce swelling when a phosphorus compound having hydrogen that can dissociate as a proton, such as phosphorous acid or diphenyl phosphate, is contained. It was found to be particularly effective.

[Sixth embodiment]
(Examples 6-1 to 6-6)
Rechargeable batteries as Examples 6-1 to 6-6 were prepared in the same manner as in Examples 1-1 to 1-6, except that an Sn alloy was used as the negative electrode active material. The negative electrode was produced in the same manner as in Examples 3-1 to 3-6.

(Comparative Example 6-1)
As Comparative Example 6-1 with respect to Examples 6-1 to 6-6, a secondary battery was fabricated in the same manner as Example 6-1 except that sultone was not added.

  For the fabricated secondary batteries of Examples 6-1 to 6-6 and Comparative Example 6-1, the swelling of the exterior member was measured in the same manner as in Examples 1-1 to 1-6. The results are shown in Table 6.

  As can be seen from Table 6, in the sixth example, the same effects as in the first to fifth examples were confirmed. That is, according to Examples 6-1 to 6-6 to which sultone was added, swelling was able to be significantly reduced as compared with Comparative Example 6-1 to which this was not added. From comparison of Example 6-1, Example 6-2, and Example 6-4, it was found that inclusion of propene sultone was extremely effective in reducing blistering.

  Further, from comparison between Example 6-2 and Example 6-3, it can be said that the use of trans-difluoroethylene carbonate tends to suppress swelling more than cis-difluoroethylene carbonate.

  Further, from the comparison between Example 6-2, Example 6-5 and Example 6-6, it is possible to reduce swelling when a phosphorus compound having hydrogen that can dissociate as a proton, such as phosphorous acid or diphenyl phosphate, is contained. It was found to be particularly effective.

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

  Furthermore, in the above-described embodiment or example, the laminated film type secondary battery has been specifically described, but the present invention has other shapes such as a cylindrical type, a coin type, a button type, or a square 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 a disassembled perspective view showing the structure of the secondary battery which concerns on one embodiment of this invention. It is sectional drawing showing the structure along the II-II line of the winding electrode body shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Positive electrode lead, 12 ... Negative electrode lead, 20 ... Winding electrode body, 21 ... Positive electrode, 21A ... 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 ... electrolyte, 25 ... protective tape, 30 ... exterior member, 31 ... adhesion film.

Claims (16)

Including a solvent and an electrolyte salt,
The solvent includes a cyclic carbonate derivative having two or more halogen atoms and a compound having a sulfone structure having a cyclic bond or a carbon-carbon multiple bond.   The electrolyte according to claim 1, wherein the halogen atom is fluorine.   2. The electrolyte according to claim 1, wherein the compound having the sulfone structure is a cyclic sulfonic acid ester. The cyclic carbonate derivative is trans-4,5-difluoro-1,3-dioxolan-2-one (trans-difluoroethylene carbonate) or cis-4,5-difluoro-1,3-dioxolan-2-one. (Cis-difluoroethylene carbonate),
The electrolyte according to claim 3, wherein the cyclic sulfonic acid ester is 1,3-propene sultone.   The electrolyte according to claim 1, wherein the solvent further contains a phosphorus compound having hydrogen that can dissociate as protons.   6. The electrolyte according to claim 5, wherein the phosphorus compound includes at least one of phosphoric acid, phosphorous acid, diphenyl phosphate, phenylphosphonic acid, and phenylphosphinic acid. A battery comprising an electrolyte containing a solvent and an electrolyte salt together with a positive electrode and a negative electrode,
The battery includes a solvent containing a cyclic carbonate derivative having two or more halogen atoms and a compound having a sulfone structure having a cyclic bond or a carbon-carbon multiple bond.   The battery according to claim 7, wherein the halogen atom is fluorine.   The battery according to claim 7, wherein the compound having the sulfone structure is a cyclic sulfonate ester. The cyclic carbonate derivative is trans-4,5-difluoro-1,3-dioxolan-2-one (trans-difluoroethylene carbonate) or cis-4,5-difluoro-1,3-dioxolan-2-one. (Cis-difluoroethylene carbonate),
The battery according to claim 9, wherein the cyclic sulfonate ester is 1,3-propene sultone.   The battery according to claim 7, wherein the solvent further includes a phosphorus compound having hydrogen that can dissociate as protons.   The battery according to claim 11, wherein the phosphorus compound is phosphoric acid, phosphorous acid, diphenyl phosphate, phenylphosphonic acid, or phenylphosphinic acid.   The battery according to claim 7, wherein the negative electrode contains a metal element or a semimetal element belonging to Group 14 of the periodic table in the long-period periodic table.   The battery according to claim 7, further comprising an encapsulating member made of a laminate film including an aluminum layer.   The battery according to claim 7, wherein the electrolyte includes an electrolytic solution and a polymer compound as a holding body that holds the electrolytic solution.   The battery according to claim 15, wherein the polymer compound is polyvinyl formal, polyacrylic acid ester, or polyvinylidene fluoride.

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