JP2008159496A - Gel electrolyte, lithium-ion secondary battery, and manufacturing method of gel electrolyte - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a gel electrolyte capable of suppressing deterioration in capacity while suppressing liquid leakage, a lithium ion secondary battery, and a manufacturing method of the gel electrolyte. <P>SOLUTION: The gel electrolyte contains an electrolyte salt, a solvent, a polymer compound having a structure in which polyvinyl acetal and its derivative or the like are polymerized, and a compound or the like containing a group III element and a group IV element of the periodic table. The lithium ion secondary battery using the gel electrolyte has a composition constituted of polyvinyl acetal comprising 65 mol% or more by a vinyl formal unit and 20 mol% or less by a vinyl alcohol unit. The gel electrolyte is manufactured by dissolving polyvinyl acetal, a support electrolyte, and the compound or the like as a cross-linking promoter containing the group III element and the group IV element of the periodic table into an electrolytic solution solvent, and by forming a cross-linked polymer having the structure in which polyvinyl acetal and its derivative or the like are polymerized from polyvinyl acetal in the solution using the support electrolyte and the cross-linking promoter as the catalyst. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a gel electrolyte, a lithium ion secondary battery, and a method for producing a gel electrolyte, and more particularly to a gel electrolyte having a structure obtained by polymerizing polyvinyl acetal or a derivative thereof, a lithium ion secondary battery, and a method for producing a gel electrolyte.

  In recent years, many portable electronic devices such as a camera-integrated VTR (videotape recorder), a mobile phone, or a portable computer have appeared, and their size and weight have been reduced. Along with this, development of batteries, particularly secondary batteries, has been actively promoted as portable power sources for electronic devices. In particular, lithium ion secondary batteries are attracting attention as being capable of realizing a high energy density, and many studies have been made on thin and high-flexible shapes that can be bent.

  Such batteries with a high degree of freedom include a solid polymer electrolyte in which an electrolyte salt is dissolved in a polymer compound, and a gel polymer electrolyte in which an electrolyte is held in a polymer compound. It is used. In particular, gel polymer electrolytes have an electrolyte solution, so they have better contact with the active material and ionic conductivity than all solids, and they have a higher leakage than electrolytes. It is attracting attention because it has the feature that it hardly occurs.

  As for the polymer used in the gel polymer electrolyte, various substances such as ether-based polymers, methyl methacrylate, polyvinylidene fluoride and the like have been studied. Among them, polyvinyl formal or polyvinyl butyral There are those using polyvinyl acetal.

For example, Patent Document 1 describes a primary battery using polyvinyl acetal. Moreover, about the electrolyte using polyvinyl acetal, the ion conductive solid body composition using polyvinyl butyral is described in patent documents 2 and 3, and the gel containing polyvinyl formal and electrolyte solution in patent documents 4-6. A state electrolyte is described.
However, sufficient ionic conductivity is not obtained because the content of the electrolytic solution is low. Therefore, in Patent Document 7, it is studied to increase the amount of the electrolytic solution by adjusting the amount of hydroxyl group contained in polyvinyl formal. Patent Document 8 describes the use of a Lewis acid or a Lewis acid salt having a fluorine atom as a crosslinking accelerator.
JP-A-52-115332 JP-A-57-143355 JP-A-57-143356 JP-A-3-43909 Japanese Patent Laid-Open No. 3-43910 Japanese Patent Laid-Open No. 10-50141 Japanese Patent Laid-Open No. 2001-200126 Japanese Patent Laid-Open No. 2005-50808

  However, even with the method described in Patent Document 7, it is necessary to contain 10% or more of polyvinyl acetal, and there is a problem that it is difficult to obtain sufficient ion conductivity in consideration of current load characteristics. In addition, when the crosslinking accelerator described in Patent Document 8 is used, there is a problem that the capacity is greatly deteriorated although the crosslinking is promoted.

  The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide a gel electrolyte and a lithium ion secondary battery that can suppress deterioration of capacity while suppressing leakage. A secondary battery and a method for producing a gel electrolyte are provided.

  As a result of intensive studies to solve the above problems, the present inventors have found that the above object can be achieved by using a compound containing a Group 3 element or a Group 4 element in the periodic table as a crosslinking accelerator. The invention has been completed.

That is, the gel electrolyte of the present invention comprises an electrolyte salt and a solvent,
A polymer compound having a structure obtained by polymerizing at least one selected from the group consisting of polyvinyl acetal and derivatives thereof;
1 type or 2 types or more of the compound containing a periodic table group 3 element and / or a group 4 element,
It is characterized by including.

The lithium ion secondary battery of the present invention includes an electrolyte salt and a solvent,
A polymer compound having a structure obtained by polymerizing at least one selected from the group consisting of polyvinyl acetal and derivatives thereof;
1 type or 2 types or more of the compound containing a periodic table group 3 element and / or a group 4 element,
A lithium ion secondary battery using a gel electrolyte comprising
The polyvinyl acetal has a composition of 65 mol% or more of vinyl formal units and 20 mol% or less of vinyl alcohol units.

Furthermore, the method for producing a gel electrolyte of the present invention includes an electrolyte solution solvent,
1 type or 2 types or more of the compound containing a polyvinyl acetal, electrolyte salt, and a periodic table group 3 element and / or group 4 element as a crosslinking accelerator,
Dissolve
A cross-linked polymer having a structure obtained by polymerizing at least one selected from the group consisting of polyvinyl acetal and derivatives thereof from an acetal salt and a cross-linking accelerator as a catalyst is formed from the polyvinyl acetal in the solution. And

  According to the present invention, since a compound containing a group 3 element or a group 4 element in the periodic table is used as the crosslinking accelerator, the gel electrolyte and lithium ion that can suppress the deterioration of the capacity while suppressing the liquid leakage A method for producing a secondary battery and a gel electrolyte can be provided.

  Hereinafter, the gel electrolyte of the present invention will be described. In the present specification and claims, “%” for concentration, content, etc. represents mass percentage unless otherwise specified.

（式中のＲは水素原子又は炭素数１〜３のアルキル基を示す）
で表されるアセタール基を含む構成単位と、以下の化学式４

で表される水酸基を含む構成単位と、以下の化学式５

で表されるアセチル基を含む構成単位とを繰り返し単位に含む高分子化合物である。
具体的には、例えば、化３に示すＲが水素のポリビニルホルマール、又はＲがプロピル基のポリビニルブチラールが挙げられる。 As described above, the gel electrolyte of the present invention includes a polymer compound having a structure obtained by polymerizing one or more kinds arbitrarily selected from polyvinyl acetal and derivatives thereof, and an electrolytic solution, and is in a so-called gel form. ing.
Polyvinyl acetal has the following chemical formula 3

(R in the formula represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms)
A structural unit containing an acetal group represented by the following chemical formula 4

A structural unit containing a hydroxyl group represented by the following chemical formula 5

And a structural unit containing an acetyl group represented by the formula:
Specifically, for example, R shown in Chemical formula 3 is hydrogen formal polyvinyl or R is propyl group polyvinyl butyral.

Here, it is preferable that the ratio of the acetal group in this polyvinyl acetal or its derivative (s) is 60 mol% or more, and it is more preferable if it is in the range of 65 mol% to 85 mol%. The proportion of vinyl alcohol units is preferably 20 mol% or less. Moreover, it is preferable that the molecular weight of polyvinyl acetal exists in the range of 10000-500000 in a weight average molecular weight.
If it is in these ranges, while being able to improve the solubility with a solvent, stability of a polymer electrolyte can be improved more.

  The polymer compound may be a polymer obtained by polymerizing only polyvinyl acetal or one of its derivatives, or a polymer obtained by polymerizing two or more of them, and a copolymer of monomers other than polyvinyl acetal and its derivatives. It may be combined. The content of the polymer compound is preferably in the range of 0.5% to 5%. If it is less than this, the electrolytic solution cannot be sufficiently retained, and if it is more than this, sufficient ionic conductivity may not be obtained.

  Further, the polymer compound is obtained by polymerizing a compound containing either one or both of Group 3 elements and Group 4 elements of the periodic table as a crosslinking accelerator, whereby the polymerization is promoted, and the electrolyte solution has a small content. Can be held. Any one of these crosslinking accelerators may be used alone, or two or more thereof may be mixed and used.

（式中のＭ１は周期表３族元素、Ｒ１，Ｒ２，Ｒ３はアルコキシ基、ハロゲン基、ＲｆＳＯ３‐、（ＲｆＳＯ２）２Ｎ‐又は（ＲｆＳＯ２）３Ｃ‐（Ｒｆは炭化水素基の水素のうち少なくとも１つがフッ素で置換されているもの）で表される置換基を有し、Ｒ１，Ｒ２，Ｒ３のそれぞれは同じでも異なってもよい）
で表される構造を有する化合物（Ｍ１化合物）が挙げられる。
具体的なＭ１化合物としては、例えば、スカンジウム（Ｓｃ）、イットリウム（Ｙ）等の周期律表３族元素を含む化合物、例えば、スカンジウムクロライド，スカンジウムトリフルオロメタンスルホンイミド，スカンジウムトリフルオロメタンスルホネート，イットリウムクロライド，イットリウムフルオライド，イットリウムトリフルオロメタンスルホネートなどが挙げられる。 As a compound containing a group 3 element of the periodic table, typically, the following chemical formula 6

(In the formula, M1 is a group 3 element of the periodic table, R1, R2, and R3 are alkoxy groups, halogen groups, RfSO3-, (RfSO2) 2N-, or (RfSO2) 3C- (Rf is at least one of hydrogens of a hydrocarbon group). One of which is substituted with fluorine), and each of R1, R2, and R3 may be the same or different)
The compound (M1 compound) which has a structure represented by these is mentioned.
Specific examples of the M1 compound include compounds containing Group 3 elements of the periodic table such as scandium (Sc) and yttrium (Y), such as scandium chloride, scandium trifluoromethanesulfonimide, scandium trifluoromethanesulfonate, yttrium chloride, Examples thereof include yttrium fluoride and yttrium trifluoromethanesulfonate.

（式中のＭ２は周期表４族元素、Ｒ４，Ｒ５，Ｒ６，Ｒ７はアルコキシ基、ハロゲン基、ＲｆＳＯ３‐、（ＲｆＳＯ２）２Ｎ‐又は（ＲｆＳＯ２）３Ｃ‐（Ｒｆは炭化水素基の水素のうち少なくとも１つがフッ素で置換されているもの）で表される置換基を有し、Ｒ４，Ｒ５，Ｒ６，Ｒ７のそれぞれは同じでも異なってもよい）
で表される構造を有する化合物（Ｍ２化合物）が挙げられる。
具体的なＭ２化合物としては、チタン（Ｔｉ）、ジルコニウム（Ｚｒ）、ハフニウム（Ｈｆ）等の周期律表４族元素を含む化合物、例えば、ジルコニウムテトラエトキシド、ジルコニウムテトラｎ‐プロポキシド、ジルコニウムテトライソプロポキシド、ジルコニウムテトラｎ‐ブトキシド、ジルコニウムテトラｔ‐ブトキシド等のジルコニウムアルコキシド；四塩化ジルコニウム、四臭化ジルコニウム、四ヨウ化ジルコニウム等のジルコニウムハライド；トリフルオロメタンスルホニル基、ＲｆＳＯ３、（ＲｆＳＯ２）２Ｎ、（ＲｆＳＯ２）３Ｃ等スルホン基含有のジルコニウム塩が挙げられる。なお、Ｒｆは炭化水素基の水素のうち少なくとも１つがフッ素で置換されているものである。 Moreover, as a compound containing a periodic table 4 group element, typically, following Chemical formula 7

(Wherein M2 is a Group 4 element of the periodic table, R4, R5, R6, and R7 are alkoxy groups, halogen groups, RfSO3-, (RfSO2) 2N- or (RfSO2) 3C- (Rf is a hydrocarbon group hydrogen) At least one of which is substituted with fluorine), and each of R 4, R 5, R 6 and R 7 may be the same or different)
The compound (M2 compound) which has a structure represented by these is mentioned.
Specific examples of the M2 compound include compounds containing Group 4 elements of the periodic table such as titanium (Ti), zirconium (Zr), hafnium (Hf), such as zirconium tetraethoxide, zirconium tetra n-propoxide, zirconium tetra Zirconium alkoxide such as isopropoxide, zirconium tetra n-butoxide, zirconium tetra t-butoxide; zirconium halide such as zirconium tetrachloride, zirconium tetrabromide, zirconium tetraiodide; trifluoromethanesulfonyl group, RfSO3, (RfSO2) 2N, (RfSO2) 3C and other sulfone group-containing zirconium salts. Rf is one in which at least one of the hydrogen atoms of the hydrocarbon group is substituted with fluorine.

  The addition amount of such a crosslinking accelerator is preferably in the range of 0.01% to 5.0% in terms of the ratio to the gel electrolyte including the additive. Within this range, a higher effect can be obtained. However, this crosslinking accelerator does not need to be decomposed during polymerization and remain in the gel electrolyte. Further, it may be polymerized with polyvinyl acetal and derivatives thereof to constitute a polymer compound.

  Moreover, the electrolyte solution contained in the gel electrolyte of the present invention is obtained by dissolving an electrolyte salt in a solvent. However, various additives may be included as necessary.

Examples of the solvent include lactone solvents such as γ-butyrolactone, γ-valerolactone, δ-valerolactone, and ε-caprolactone, ethylene carbonate, propylene carbonate, butylene carbonate, vinylene carbonate, dimethyl carbonate, ethyl methyl carbonate, or carbonate. Carbonate ester solvents such as diethyl, ether solvents such as 1,2-dimethoxyethane, 1-ethoxy-2-methoxyethane, 1,2-diethoxyethane, tetrahydrofuran or 2-methyltetrahydrofuran, nitrile solvents such as acetonitrile And non-aqueous solvents such as sulfolane-based solvents, phosphoric acids, phosphate ester solvents, and pyrrolidones.
In addition, the said solvent may be used individually by 1 type, and may mix and use 2 or more types.

The electrolyte salt is not particularly limited as long as it dissolves in the solvent and generates ions, and may be used alone or in combination of two or more.
For example, if it is a lithium salt, lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), lithium perchlorate (LiClO4), trifluoromethanesulfonic acid Lithium (LiCF3SO3), bis (trifluoromethanesulfonyl) imide lithium (LiN (CF3SO2) 2), bis (perfluoroethanesulfonyl) imide lithium (LiN (C2F5SO2) 2), tris (trifluoromethanesulfonyl) methyllithium (LiC (CF3SO2) 3), tris (perfluoroethanesulfonyl) methyllithium (LiC (C2F5SO2) 3), lithium tetrachloroaluminate (LiAlCl4), or lithium hexafluorosilicate (LiSiF6).
Among these, it is preferable to use lithium hexafluorophosphate because both high reactivity and ion conductivity in the crosslinking reaction can be achieved. Further, it is preferable to use lithium tetrafluoroborate because the leakage resistance of the gel electrolyte can be improved by further promoting the crosslinking reaction.

Next, the lithium ion secondary battery of the present invention will be described.
The lithium ion secondary battery of the present invention is characterized by using the above-mentioned gel electrolyte, wherein the polyvinyl acetal has a composition having a vinyl formal unit of 65 mol% or more and a vinyl alcohol unit of 20 mol% or less.

  Here, the above-mentioned gel electrolyte is used for a lithium ion secondary battery as follows, for example. In the present embodiment, a battery using lithium as an electrode reactant will be described.

FIG. 1 is an exploded perspective view showing a secondary battery according to an embodiment of the lithium ion secondary battery of the present invention.
In the secondary battery, a battery element 20 to which a positive electrode terminal 11 and a negative electrode terminal 12 are attached is enclosed in a film-shaped exterior member 30. The positive electrode terminal 11 and the negative electrode terminal 12 are led out from the inside of the exterior member 30 to the outside, for example, in the same direction. The positive electrode terminal 11 and the negative electrode terminal 12 are each made of a metal material such as aluminum (Al), copper (Cu), nickel (Ni), or stainless steel.

  The exterior member 30 is made of, for example, a rectangular laminate film in which a nylon film, an aluminum foil, and a polyethylene film are bonded together in this order. For example, the exterior member 30 is disposed so that the polyethylene film side and the battery element 20 face each other, and the outer edge portions are in close contact with each other by fusion bonding or an adhesive. An adhesion film 31 is inserted between the exterior member 30 and the positive electrode terminal 11 and the negative electrode terminal 12 to prevent intrusion of outside air. The adhesion film 31 is made of a material having adhesion to the positive electrode terminal 11 and the negative electrode terminal 12. For example, when the positive electrode terminal 11 and the negative electrode terminal 12 are made of the metal material described above, polyethylene, polypropylene, It is preferably composed of a polyolefin resin such as modified polyethylene or modified polypropylene.

  The exterior member 30 may be configured by a laminated film having another structure, a polymer film such as polypropylene, a metal film, or the like instead of the above-described laminated film.

  FIG. 2 shows a cross-sectional structure taken along line II of the battery element 20 shown in FIG. In the battery element 20, the positive electrode 21 and the negative electrode 22 are positioned so as to face each other via the gel electrolyte 23 and the separator 24 described above, and the outermost peripheral portion is protected by a protective tape 25. .

  The positive electrode 21 has, for example, a structure in which a positive electrode active material layer 21B is provided on both surfaces of a positive electrode current collector 21A having a pair of opposed surfaces. The positive electrode current collector 21A is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless steel foil.

  The positive electrode active material layer 21B includes, for example, any one or more of positive electrode materials capable of inserting and extracting lithium as a positive electrode active material, and a conductive agent and a binder as necessary. May be included. Examples of the positive electrode material capable of inserting and extracting lithium include chalcogenides containing no lithium such as titanium sulfide (TiS2), molybdenum sulfide (MoS2), niobium selenide (NbSe2), or vanadium oxide (V2O5), Alternatively, a lithium-containing compound containing lithium, or a polymer compound such as polyacetylene or polypyrrole can be given.

  Among these, lithium-containing compounds are preferable because some compounds can obtain a high voltage and a high energy density. Examples of such a lithium-containing compound include a composite oxide containing lithium and a transition metal element, or a phosphate compound containing lithium and a transition metal element. In particular, cobalt (Co), nickel, manganese (Mn And those containing at least one of iron (Fe). This is because a higher voltage can be obtained. The chemical formula is represented by, for example, LixMIO2 or LiyMIIPO4. In the formula, MI and MII represent one or more transition metal elements. The values of x and y vary depending on the charge / discharge state of the battery, and are generally 0.05 ≦ x ≦ 1.10 and 0.05 ≦ y ≦ 1.10.

  Specific examples of the composite oxide containing lithium and a transition metal element include lithium cobalt composite oxide (LixCoO2), lithium nickel composite oxide (LixNiO2), and lithium nickel cobalt composite oxide (LixNi1-zCozO2 (z <1). ), Or lithium manganese composite oxide (LiMn2O4) having a spinel structure. Specific examples of the phosphate compound containing lithium and a transition metal element include, for example, a lithium iron phosphate compound (LiFePO4) or a lithium iron manganese phosphate compound (LiFe1-vMnvPO4 (v <1)).

  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, as with the positive electrode 21. The negative electrode current collector 22A is made of, for example, a metal foil such as a copper foil, a nickel foil, or a stainless steel foil.

  The negative electrode active material layer 22B includes, for example, any one or more of a negative electrode material capable of inserting and extracting lithium or metallic lithium as a negative electrode active material, and a conductive agent as necessary. And a binder may be included. Examples of the negative electrode material capable of inserting and extracting lithium include a carbon material, a metal oxide, and a polymer compound. Examples of the carbon material include non-graphitizable carbon materials or graphite-based materials. More specifically, pyrolytic carbons, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers Or there is activated carbon. Among these, cokes include pitch coke, needle coke, and petroleum coke, and organic polymer compound fired bodies are carbonized by firing polymer materials such as phenol resin and furan resin at an appropriate temperature. Say things. Examples of the metal oxide include iron oxide, ruthenium oxide, and molybdenum oxide, and examples of the polymer compound include polyacetylene and polypyrrole.

  Examples of the negative electrode material capable of sucking and releasing lithium 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 a metalloid element, or may have at least a part of one or more of these phases. In the present invention, the alloy includes an alloy containing one or more metal elements and one or more metalloid elements in addition to an alloy 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 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 the tin alloy include, as the second constituent element other than tin, silicon, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium (Ti), germanium, bismuth, antimony, or chromium (Cr ), And those related to any combination thereof. As an alloy of silicon, for example, as a second constituent element other than silicon, tin, nickel, copper, iron, cobalt, manganese, zinc, indium, silver, titanium, germanium, bismuth, antimony or chromium, and any of these Including those related to the combination.

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

  The separator 24 has a high ion permeability and a predetermined mechanical strength, such as a porous film made of a polyolefin-based synthetic resin such as polypropylene or polyethylene, or a porous film made of an inorganic material such as a ceramic nonwoven fabric. It is comprised by the insulating thin film which has, and may be set as the structure which laminated | stacked these 2 or more types of porous films. Among these, a polyolefin-based porous film is preferable because it is excellent in separability between the positive electrode 21 and the negative electrode 22 and can further reduce internal short circuit and a decrease in open circuit voltage.

Next, the secondary battery described above can be manufactured, for example, as follows.
First, the positive electrode 21 is produced. For example, when a particulate positive electrode active material is used, a positive electrode mixture is prepared by mixing the positive electrode active material and, if necessary, a conductive agent and a binder, and dispersed such as N-methyl-2-pyrrolidone. A positive electrode mixture slurry is prepared by dispersing in a medium. Next, the positive electrode mixture slurry is applied to the positive electrode current collector 21A, dried, and compression molded to form the positive electrode active material layer 21B.

  Moreover, the negative electrode 22 is produced. For example, when a particulate negative electrode active material is used, a negative electrode active material is mixed with a conductive agent and a binder as necessary to prepare a negative electrode mixture, and dispersion of N-methyl-2-pyrrolidone or the like A negative electrode mixture slurry is prepared by dispersing in a medium. Next, the negative electrode mixture slurry is applied to the negative electrode current collector 22A, dried, and compression molded to form the negative electrode active material layer 22B.

  Subsequently, after attaching the positive electrode terminal 11 to the positive electrode 21 and attaching the negative electrode terminal 12 to the negative electrode 22, the separator 24, the positive electrode 21, the separator 24, and the negative electrode 22 are sequentially stacked and wound, and the protective tape 25 is wound on the outermost peripheral portion. Are bonded to form a wound electrode body. Thereafter, the wound electrode body is sandwiched between the exterior members 30, and the outer peripheral edge except one side is heat-sealed to form a bag shape.

  Next, an electrolyte composition comprising at least one monomer of the above-mentioned polyvinyl acetal and derivatives thereof, at least one crosslinking accelerator in the group of compounds including the group 3 and 4 elements, an electrolyte salt, and a solvent. An object is prepared and injected into the wound electrode body from the opening of the exterior member 30, and the opening of the exterior member 30 is heat-sealed and sealed. Thereafter, in the exterior member 30, the monomer is polymerized using a crosslinking accelerator to form the gel electrolyte 23. In the polymerization, the electrolyte salt may act as a catalyst. Thereby, the secondary battery shown in FIGS. 1 and 2 is completed.

  In addition, you may manufacture this secondary battery as follows. For example, instead of injecting the electrolyte composition after producing the wound electrode body, the electrolyte composition is applied on the positive electrode 21 and the negative electrode 22 and then wound and sealed in the exterior member 30. Also good. Alternatively, at least one monomer of polyvinyl acetal and derivatives thereof may be applied on the positive electrode 21 and the negative electrode 22, wound, and stored in the exterior member 30, and then the electrolyte may be injected.

  In the secondary battery, when charged, for example, lithium ions are separated from the positive electrode active material layer 21 </ b> B and inserted into the negative electrode active material layer 22 </ b> B through the gel electrolyte 23. When discharging is performed, for example, lithium ions are separated from the negative electrode active material layer 22 </ b> B and inserted into the positive electrode active material layer 21 </ b> B through the gel electrolyte 23. At that time, the mobility of lithium ions depends on the electrolyte contained in the gel electrolyte 23. In the present embodiment, polymerization of the polymer compound is promoted by using an organic titanium compound, a polyfunctional carboxylic acid or a polyfunctional carboxylic acid derivative, and a cross-linking accelerator that is arbitrarily combined with these compounds. It is possible to hold the electrolytic solution even if the ratio is small. Therefore, movement of lithium ions is facilitated, and high ionic conductivity is obtained. In addition, the gel electrolyte 23 (this secondary battery) has high shape stability, so that the cycle characteristics are also improved.

  As described above, according to the embodiment, since the organic titanium compound, the polyfunctional carboxylic acid or the polyfunctional carboxylic acid derivative, and the crosslinking accelerator arbitrarily combined with these are used, the polyvinyl acetal and the derivative thereof can be used. Polymerization can be promoted and the content of the polymer compound can be reduced. Moreover, high shape stability can also be obtained. Therefore, while suppressing leakage, it is possible to improve current load characteristics, suppress capacity deterioration, and improve battery characteristics such as cycle characteristics. Moreover, if the positive electrode 21 and the negative electrode 22 are accommodated in the exterior member 30 and then the electrolyte composition is added to polymerize the monomer, the battery according to the present embodiment can be easily manufactured with a small number of steps. Can do.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in full detail, this invention is not limited to these Examples.

  A laminate film type secondary battery as shown in FIGS. First, 0.5 mol of lithium carbonate and 1 mol of cobalt carbonate were mixed, and this mixture was fired in air at 900 ° C. for 5 hours to synthesize a lithium cobalt composite oxide (LiCoO 2) as a positive electrode active material. Next, 85 parts by mass of this lithium cobalt composite oxide powder, 5 parts by mass of graphite powder as a conductive agent, and 10 parts by mass of polyvinylidene fluoride as a binder were prepared to prepare a positive electrode mixture, and then dispersed. A positive electrode mixture slurry was prepared by dispersing in N-methyl-2-pyrrolidone as a medium. Subsequently, this positive electrode mixture slurry was applied to both surfaces of 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. Thereafter, the positive electrode terminal 11 was attached to the positive electrode 21.

  Further, after using the pulverized graphite powder as a negative electrode active material, 90 parts by mass of this graphite powder and 10 parts by mass of polyvinylidene fluoride as a binder were mixed to prepare a negative electrode mixture, and then N as a dispersion medium A negative electrode mixture slurry was prepared by dispersing in -methyl-2-pyrrolidone. Subsequently, the negative electrode mixture slurry was applied to both surfaces of a negative electrode current collector 22A made of a copper foil having a thickness of 15 μm, dried, and then compression molded to form a negative electrode active material layer 22B, whereby the negative electrode 22 was produced. Thereafter, the negative electrode terminal 12 was attached to the negative electrode 22.

  Next, the produced positive electrode 21 and negative electrode 22 are closely attached via a separator 24 made of a microporous polyethylene film having a thickness of 25 μm, wound in the longitudinal direction, and a protective tape 25 is adhered to the outermost peripheral portion to form a wound electrode body. Was made. Subsequently, the wound electrode body was sandwiched between the exterior members 30, and then the outer peripheral edge of the exterior member 30 was formed into a bonded bag shape except for one side. For the exterior member 30, a moisture-proof aluminum laminate film in which a 25 μm thick nylon film, a 40 μm thick aluminum foil, and a 30 μm thick polypropylene film were laminated in order from the outermost layer was used.

  Then, the secondary battery shown in FIGS. 1 and 2 was produced by injecting the electrolyte composition from the opening of the exterior member 30 and thermally sealing and sealing the opening under reduced pressure to form the gel electrolyte 23. .

(Examples 1-7)
In the electrolyte composition, polyvinyl formal and an electrolytic solution are mixed and dissolved at a mass ratio of polyvinyl formal: electrolyte = 2.0: 98.0 to prepare a mixed solution, and then a crosslinking accelerator is added to the mixed solution. The one to which was added was used. An electrolytic solution is obtained by dissolving lithium hexafluorophosphate at a concentration of 1.0 mol / l in a solvent obtained by mixing ethylene carbonate and ethyl methyl carbonate in a mass ratio of ethylene carbonate: ethyl methyl carbonate = 3: 7. did. A polyvinyl formal having a weight average molecular weight of about 70000 and a molar ratio of formal group, hydroxyl group and acetyl group of about formal group: hydroxyl group: acetyl group = 80: 7: 13 was used.

  Moreover, the kind and addition amount of the additive were changed as shown in Table 1 in Examples 1 to 7, respectively. In addition, the addition amount is a ratio with respect to the whole gel electrolyte including the additive. Specifically, in Example 1 and Example 2, hafnium trifluoromethanesulfonic acid, which is a hafnium compound, was added. In Example 3, 0.5% of scandium trifluoromethanesulfonic acid, which is a scandium compound, was added. In Example 4, 0.5% of an yttrium compound was added. In Example 5, 0.5% of scandium trifurylimide was added. In Example 6, 0.5% of scandium trifurylmethide was added. In Example 7, 0.5% by weight of tanranoid triflate was added.

  About the produced secondary battery of Examples 1-7, when the battery was disassembled and the gel electrolyte 23 was taken out and the weight average molecular weight of the polymer compound was measured, all were larger than the weight average molecular weight of the used polyvinyl formal. It was confirmed that the polymerized.

(Comparative Examples 1-6)
As Comparative Example 1 with respect to Examples 1 to 7, secondary batteries were fabricated in the same manner as in Examples 1 to 7, except that no crosslinking accelerator was added. As Comparative Examples 2-6, secondary batteries were fabricated in the same manner as in Examples 1-7, except that the type and amount of additive were changed as shown in Table 1. Specifically, in Comparative Example 2, 0.1% of aluminum chloride, which is an inorganic aluminum compound, was added. In Comparative Example 3, 0.5% of aluminum triflate salt was added. In Comparative Example 4, trifluoromethanesulfonic acid was 0.5%. In Comparative Examples 5 and 6, trimethylsilyl phosphate was 0.5% and 0.25, respectively. % Was added.

(Evaluation test)
About the produced secondary battery of Examples 1-7 and Comparative Examples 1-6, while performing the leak test, it charged / discharged and investigated discharge capacity and cycling characteristics.
In the liquid leakage test, 20 secondary batteries of Examples 1 to 7 and Comparative Examples 1 to 6 were produced, and immediately after production, a hole with a diameter of 0.5 mm was formed in the exterior member 30 at a pressure of 9.8 MPa. The number of batteries that were pressed and the electrolyte leaked was determined.
The discharge capacity was determined by performing a constant current / constant voltage charge of 500 mA at 23 ° C. to an upper limit of 4.2 V for 2 hours, and then performing a constant current discharge of 100 mA to a final voltage of 3.0 V. The cycle characteristics are as follows: charge / discharge is repeated 100 cycles at 23 ° C. after 500 mA constant current / constant voltage charge up to an upper limit of 4.2V for 2 hours and 500 mA constant current discharge to a final voltage of 3.0V. The discharge capacity retention rate at the 100th cycle when the discharge capacity was 100%, that is, (discharge capacity at the 100th cycle in 500 mA discharge / discharge capacity at the first cycle in 500 mA discharge) × 100 (%) . The obtained results are shown in Table 1.

As shown in Table 1, in Examples 1 to 7 in which polyvinyl formal was polymerized using a compound containing groups 3 and 4 of the periodic table, the electrolyte solution did not leak, whereas a crosslinking accelerator was used. In Comparative Example 1 that was not used, electrolyte leakage occurred. Alternatively, when 0.25% of fonium triflate was used, the electrolyte solution did not leak, whereas when trimethylsilyl phosphate was used, the electrolyte solution was added when 0.25% was added. (Comparative Example 6). This is considered to be because in Examples 1 to 7, a network of polymer compounds was generated, and the leakage resistance was improved.
In Examples 1 to 7, high cycle characteristics of 70% or more were obtained, whereas in Comparative Examples 2 to 4, a decrease in cycle characteristics was observed. This is considered to be because in Comparative Examples 2 to 4, the gel electrolyte 23 was deteriorated due to a side reaction accompanying charging / discharging of the crosslinking accelerator, and the ionic conductivity was lowered.

Although the present invention has been described with reference to some embodiments, the present invention is not limited to these embodiments, and various modifications can be made within the scope of the gist of the present invention.
For example, in the above embodiment, a laminate type non-aqueous electrolyte secondary battery is manufactured, but the present invention is similarly applied to a battery using a can as an exterior member, a battery having other shapes such as a so-called cylindrical type, a square type, and a button type. The invention can be applied. Furthermore, it is applicable not only to a secondary battery but also to a primary battery.

It is a disassembled perspective view which shows one Embodiment of the nonaqueous electrolyte battery of this invention. It is sectional drawing which shows the battery element of the nonaqueous electrolyte battery of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Positive electrode terminal, 12 ... Negative electrode terminal, 20 ... Battery element, 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 ... Gel electrolyte composition layer, 24 ... Separator, 25 ... Masking tape, 30 ... Exterior member, 31 ... Adhesion film

Claims (7)

An electrolyte salt and a solvent;
A polymer compound having a structure obtained by polymerizing at least one selected from the group consisting of polyvinyl acetal and derivatives thereof;
A gel electrolyte comprising one or more compounds containing a group 3 element and / or a group 4 element in the periodic table. The compound containing the group 3 element of the periodic table is represented by the following chemical formula 1,

(In the formula, M1 is a group 3 element of the periodic table, R1, R2, and R3 are alkoxy groups, halogen groups, RfSO3-, (RfSO2) 2N-, or (RfSO2) 3C- (Rf is at least one of hydrogens of a hydrocarbon group). One of which is substituted with fluorine), and each of R1, R2, and R3 may be the same or different)
The gel electrolyte according to claim 1, wherein the gel electrolyte has a structure represented by: The compound containing the Group 4 element of the periodic table has the following chemical formula:

(Wherein M2 is a Group 4 element of the periodic table, R4, R5, R6, and R7 are alkoxy groups, halogen groups, RfSO3-, (RfSO2) 2N- or (RfSO2) 3C- (Rf is a hydrocarbon group hydrogen) At least one of which is substituted with fluorine), and each of R 4, R 5, R 6 and R 7 may be the same or different)
The gel electrolyte according to claim 1, wherein the gel electrolyte has a structure represented by:   The gel electrolyte according to claim 1, wherein the polyvinyl acetal or a derivative thereof has a composition of 65 mol% or more of vinyl formal units and 20 mol% or less of vinyl alcohol units. An electrolyte salt and a solvent;
A polymer compound having a structure obtained by polymerizing at least one selected from the group consisting of polyvinyl acetal and derivatives thereof;
1 type or 2 types or more of the compound containing a periodic table group 3 element and / or a group 4 element,
A lithium ion secondary battery using a gel electrolyte comprising
A lithium ion secondary battery, wherein the polyvinyl acetal has a composition of 65 mol% or more of vinyl formal units and 20 mol% or less of vinyl alcohol units.   6. The lithium ion secondary battery according to claim 5, wherein the gel electrolyte contains an ionic compound containing at least one selected from LiBF4 and LiPF6 as an electrolyte salt. In the electrolyte solvent,
1 type or 2 types or more of the compound containing a polyvinyl acetal, electrolyte salt, and a periodic table group 3 element and / or group 4 element as a crosslinking accelerator,
Dissolve
A cross-linked polymer having a structure obtained by polymerizing at least one selected from the group consisting of polyvinyl acetal and derivatives thereof from an acetal salt and a cross-linking accelerator as a catalyst is formed from the polyvinyl acetal in the solution. A method for producing a gel electrolyte.

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