JP2012119091A - Nonaqueous electrolytic solution, electrode, and electrochemical device comprising nonaqueous electrolytic solution and electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolytic solution improving safety of an electrochemical device by reducing the heating value in an electrode active material layer while maintaining the discharge capacity, an electrode, and an electrochemical device comprising the nonaqueous electrolytic solution and the electrode.SOLUTION: A nonaqueous electrolytic solution contains a fluorine-containing (meth)acrylic acid derivative represented by the formula (I), a nonaqueous solvent, and an electrolyte. In the formula (I), X represents a hydrogen atom or a methyl group, and Rrepresents a C1-C26 hydrocarbon group in which at least one hydrogen atom is substituted by a fluorine atom.

Description

  The present invention relates to a non-aqueous electrolyte solution, an electrode, and an electrochemical device including the non-aqueous electrolyte solution and the electrode.

  In order to improve the performance of electrochemical devices using non-aqueous electrolytes, such as capacity, storage characteristics, cycle characteristics, safety, etc., addition of organic compounds such as methyl methacrylate to the electrolyte has been studied (patent) Reference 1-6). In addition, it is disclosed that a fluorine-containing polymer compound modified with a modifying substance such as acrylic acid is used as a binder of an electrode (see Patent Documents 7 to 10).

JP 2000-223154 A JP 2000-149989 A JP 2006-216276 A JP 2010-027616 A JP 2001-015158 A JP 2009-123498 A Japanese Patent No. 3982221 Japanese Patent No. 3726899 JP 2003-263987 A JP 2004-095264 A

  By the way, in terms of safety, an electrochemical device using a non-aqueous electrolytic solution is a material that is generally flammable, such as an electrode active material and an electrolytic solution. If the temperature rises (abnormal heat generation), there is a risk that the electrochemical device body burns.

  In order to solve such problems, for example, the use of olivine-type lithium iron phosphate, lithium titanate, or the like as the electrode active material, or the use of, for example, an ionic liquid as the electrolytic solution has been studied. However, employing these materials is not preferable in terms of energy density reduction and cost. In addition, an additive is added to the electrolyte solution to reduce abnormal heat generation of the electrochemical device. However, paying attention to heat generation in the electrode active material layer under a high temperature environment, the heat generation amount is suppressed. Has not yet been fully studied.

  Therefore, the present invention includes a non-aqueous electrolyte solution, an electrode, and the non-aqueous electrolyte solution and the electrode that reduce the calorific value in the electrode active material layer and improve the safety of the electrochemical device while maintaining the discharge capacity. An object is to provide an electrochemical device.

式（Ｉ）中、Ｘは水素原子又はメチル基を示し、Ｒ¹は、少なくとも１つの水素原子がフッ素原子で置換された、炭素数１〜２６の炭化水素基を示す。 The present invention provides a nonaqueous electrolytic solution containing a fluorine-containing (meth) acrylic acid derivative represented by the formula (I), a nonaqueous solvent, and an electrolyte.

In formula (I), X represents a hydrogen atom or a methyl group, and R ¹ represents a hydrocarbon group having 1 to 26 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom.

  The non-aqueous electrolyte contains the fluorine-containing (meth) acrylic acid derivative represented by the above formula (I), thereby reducing the calorific value in the electrode active material layer under a high temperature environment while maintaining the discharge capacity. Can do. Thereby, the temperature rise of an electrochemical device can be suppressed and the safety | security of an electrochemical device can be improved.

Here, in the formula (I), the fluorine atom bonded to the carbon skeleton in the hydrocarbon group represented by R ¹ is 50 mol based on the total amount of hydrogen atoms and fluorine atoms bonded to the carbon skeleton in the hydrocarbon group. % Or more is preferable.

  Thereby, the effect of the said invention can be acquired more reliably.

  Moreover, it is preferable that this invention contains 0.01 mass%-8.0 mass% of fluorine-containing (meth) acrylic acid derivatives represented by Formula (I).

  When the content of the fluorine-containing (meth) acrylic acid derivative represented by the formula (I) is less than 0.01% by mass in the non-aqueous electrolyte solution of the present invention, the effect of reducing the calorific value in the electrode active material layer is not good. There is a tendency to be sufficient. On the other hand, when the content is more than 8.0% by mass, the effect of reducing the amount of heat generated in the electrode active material layer is improved, but the discharge capacity tends to be reduced. By containing 0.01% by mass or more and 8.0% by mass or less of the fluorine-containing (meth) acrylic acid derivative represented by the formula (I), the effect of the present invention can be obtained more reliably.

式（Ｉ）中、Ｘは水素原子又はメチル基を示し、Ｒ¹は、少なくとも１つの水素原子がフッ素原子で置換された、炭素数１〜２６の炭化水素基を示す。 The present invention also includes a current collector, an active material, a binder, and a polymer of a fluorine-containing (meth) acrylic acid derivative represented by formula (I), and an active material layer formed on the surface of the current collector, An electrode is provided.

In formula (I), X represents a hydrogen atom or a methyl group, and R ¹ represents a hydrocarbon group having 1 to 26 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom.

  As a result, it is possible to obtain an electrode in which the discharge capacity is sufficiently maintained and the calorific value in a high temperature environment is reduced.

  Moreover, this invention provides an electrochemical device provided with said non-aqueous electrolyte solution, and an electrochemical device provided with said electrode.

  Thereby, an electrochemical device with improved safety can be obtained.

  According to the present invention, a non-aqueous electrolyte solution, an electrode, and a non-aqueous electrolyte solution and an electrode that reduce the calorific value in the electrode active material layer and improve the safety of the electrochemical device while maintaining the discharge capacity. An electrochemical device can be provided.

FIG. 1 is a schematic cross-sectional view showing an electrochemical device according to this embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings as necessary. In addition, the dimensional ratio of drawing is not restricted to the ratio of illustration.

First, the non-aqueous electrolyte used for the electrochemical device according to this embodiment will be described.
[Non-aqueous electrolyte]
The nonaqueous electrolytic solution of the present invention contains a fluorine-containing (meth) acrylic acid derivative represented by the formula (I), a nonaqueous solvent, and an electrolyte.

式（Ｉ）中、Ｘは水素原子又はメチル基を示し、Ｒ¹は、少なくとも１つの水素原子がフッ素原子で置換された、炭素数１〜２６の炭化水素基を示す。炭素数１〜２６の炭化水素基としては、例えば、直鎖アルキル基、分岐アルキル基、シクロアルキル基、アリール基、或いは、直鎖アルキレン基又は分岐アルキレン基がシクロアルキル基と結合した基、シクロアルキレン基が直鎖アルキル基又は分岐アルキル基と結合した基、直鎖アルキレン基、分岐アルキレン基、又はシクロアルキレン基がアリール基と結合した基、アリーレン基が直鎖アルキル基、分岐アルキル基、又はシクロアルキル基と結合した基が挙げられる。これらの炭化水素基における炭素骨格に結合した水素原子は、少なくとも１つがフッ素原子で置換されていればよい。

In formula (I), X represents a hydrogen atom or a methyl group, and R ¹ represents a hydrocarbon group having 1 to 26 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom. Examples of the hydrocarbon group having 1 to 26 carbon atoms include a linear alkyl group, a branched alkyl group, a cycloalkyl group, an aryl group, a group in which a linear alkylene group or a branched alkylene group is bonded to a cycloalkyl group, A group in which an alkylene group is bonded to a linear alkyl group or a branched alkyl group, a group in which a linear alkylene group, a branched alkylene group, or a cycloalkylene group is bonded to an aryl group, an arylene group is a linear alkyl group, a branched alkyl group, or And a group bonded to a cycloalkyl group. At least one hydrogen atom bonded to the carbon skeleton of these hydrocarbon groups may be substituted with a fluorine atom.

  The fluorine-containing (meth) acrylic acid derivative includes a fluorine-containing acrylic acid derivative in which X is a hydrogen atom and a fluorine-containing methacrylic acid derivative in which X is a methyl group.

When the hydrocarbon group having 1 to 26 carbon atoms in which at least one hydrogen atom in R ¹ is substituted with a fluorine atom is a linear or branched alkyl group, the fluorine-containing (meth) acrylic acid derivative is: For example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, pentyl (meth) acrylate, hexyl (meth) acrylate, heptyl (meth) acrylate , Octyl (meth) acrylate, nonyl (meth) acrylate, decyl (meth) acrylate, undecyl (meth) acrylate, dodecyl (meth) acrylate, tridecyl (meth) acrylate, tetradecyl (meth) acrylate, Pentadecyl (meth) acrylate, hexadecyl (meth) acrylate, heptadecyl (meth) acrylate Octadecyl (meth) acrylate, Nonadecyl (meth) acrylate, Icosyl (meth) acrylate, Henicosyl (meth) acrylate, Docosyl (meth) acrylate, Tricosyl (meth) acrylate, Tetracosyl (meth) acrylate, ( Examples thereof include compounds in which at least one hydrogen atom in a linear or branched alkyl group such as pentacosyl acrylate and hexacosyl (meth) acrylate is substituted with a fluorine atom.

  When the hydrocarbon group having 1 to 26 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom is a cycloalkyl group, examples of the fluorine-containing (meth) acrylic acid derivative include cyclopropyl (meth) acrylate, Cyclobutyl (meth) acrylate, cyclopentyl (meth) acrylate, cyclohexyl (meth) acrylate, cycloheptyl (meth) acrylate, cyclooctyl (meth) acrylate, cyclononyl (meth) acrylate, cyclodecyl (meth) acrylate , Cycloundecyl (meth) acrylate, cyclododecyl (meth) acrylate, cyclotridecyl (meth) acrylate, cyclotetradecyl (meth) acrylate, cyclopentadecyl (meth) acrylate, (meth) acrylic acid Cyclohexadecyl, cyclo (meth) acrylate Putadecyl, cyclooctadecyl (meth) acrylate, cyclononadecyl (meth) acrylate, cycloicosyl (meth) acrylate, cyclohenicosyl (meth) acrylate, cyclodocosyl (meth) acrylate, cyclotricosyl (meth) acrylate, Examples include compounds in which at least one hydrogen atom in a cycloalkyl group such as cyclotetracosyl (meth) acrylate, cyclopentacosyl (meth) acrylate, or cyclohexacosyl (meth) acrylate is substituted with a fluorine atom.

  When the hydrocarbon group having 1 to 26 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom is an aryl group, examples of the fluorine-containing (meth) acrylic acid derivative include phenyl (meth) acrylate, (meth ) A compound obtained by substituting at least one hydrogen atom in an aryl group such as naphthyl acrylate with a fluorine atom.

When the hydrocarbon group having 1 to 26 carbon atoms, in which at least one hydrogen atom is substituted with a fluorine atom, is a group in which a linear alkylene group or a branched alkylene group is bonded to a cycloalkyl group, fluorine-containing (meth) As the acrylic acid derivative, R ¹ in formula (I) is a group in which at least one hydrogen atom is removed from the linear alkyl group or branched alkyl group and the cycloalkyl group, Examples include compounds in which the total number of carbon atoms in the carbon skeleton of the group is in the range of 1 to 26, and at least one hydrogen atom in the group is a group substituted with a fluorine atom.

When the hydrocarbon group having 1 to 26 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom is a group in which a cycloalkylene group and a linear alkyl group or a branched alkyl group are bonded, fluorine-containing (meth) As the acrylic acid derivative, R ¹ in formula (I) is a group in which at least one hydrogen atom is removed from the cycloalkyl group, and the linear alkyl group or branched alkyl group is bonded, Examples include compounds in which the total number of carbon atoms in the carbon skeleton of the group is in the range of 1 to 26, and at least one hydrogen atom in the group is a group substituted with a fluorine atom.

When at least one hydrogen atom is substituted with a fluorine atom and the hydrocarbon group having 1 to 26 carbon atoms is a group in which a linear alkylene group, branched alkylene group, or cycloalkylene group is bonded to an aryl group, fluorine-containing (meta ) Acrylic acid derivatives in which R ¹ in formula (I) is a group in which at least one hydrogen atom is removed from the linear alkyl group, branched alkyl group, or cycloalkyl group and the aryl group is bonded In addition, a compound in which the total number of carbon atoms in the carbon skeleton of the group is in the range of 1 to 26, and at least one hydrogen atom in the group is a group substituted with a fluorine atom. Specific examples include benzyl (meth) acrylate and trityl (meth) acrylate.

When at least one hydrogen atom is substituted with a fluorine atom and the hydrocarbon group having 1 to 26 carbon atoms is a group in which an arylene group is bonded to a linear alkyl group, a branched alkyl group, or a cycloalkyl group, fluorine As the containing (meth) acrylic acid derivative, R ¹ in the formula (I) is a group in which at least one hydrogen atom is removed from the aryl group, and the linear alkyl group, branched alkyl group, or cycloalkyl group. A compound in which the total number of carbon atoms of the carbon skeleton of the group is in the range of 1 to 26 and at least one hydrogen atom in the group is substituted with a fluorine atom. Specific examples include tolyl (meth) acrylate and xylyl (meth) acrylate.

  Among these, at least one hydrogen atom is used from the viewpoint of reacting the double bond portion of (meth) acrylic acid with the surface of the active material or the surface of the binder to form a polymer of (meth) acrylic acid on these surfaces. The hydrocarbon group having 1 to 26 carbon atoms in which is substituted with a fluorine atom is preferably a linear alkyl group, a branched alkyl group or a cycloalkyl group having no double bond, more preferably a linear alkyl group or a branched alkyl group. preferable. Moreover, from the viewpoint of allowing the polymer formation without delay, the number of carbon atoms of the hydrocarbon group is preferably 1 to 12 in order to reduce steric hindrance.

When atoms with greatly different electronegativity are adjacent to each other, the polarization becomes stronger, and the atoms tend to be ionized and easily desorbed (Non-Patent Document Fluoropolymer Handbook edited by Takaomi Satokawa, Nikkan Kogyo Shimbun, 1990). Therefore, in R ¹ , when a hydrogen atom and a fluorine atom having greatly different electronegativity are adjacent to each other like —CH—CF—, the hydrogen atom or the fluorine atom is easily ionized and desorbed. Therefore, in the hydrocarbon group represented by R ¹ , it is better that the number of hydrogen atoms bonded to the carbon skeleton and the number of fluorine atoms adjacent to each other is smaller, and it is better to increase the proportion of fluorine atoms. The fluorine atom bonded to the skeleton is preferably 50 mol% or more, more preferably 65 mol% or more, more preferably 80 mol% or more based on the total amount of hydrogen atoms and fluorine atoms bonded to the carbon skeleton. Is more preferable, and it is particularly preferable that all hydrogen atoms bonded to the alkyl skeleton are substituted with fluorine atoms (100 mol%). From the viewpoint of stability, it is more preferable to substitute the hydrogen atom bonded to the terminal portion of the carbon skeleton with a fluorine atom.

  When the non-aqueous electrolyte contains the fluorine-containing (meth) acrylic acid derivative represented by the above formula (I), an electrochemical device using the non-aqueous electrolyte can be used in a high temperature environment while maintaining the discharge capacity. The amount of heat generated in the electrode active material layer can be reduced. Thereby, the temperature rise of an electrochemical device can be suppressed and the safety | security of an electrochemical device can be improved.

  The fluorine-containing (meth) acrylic acid derivative represented by the formula (I) is preferably contained in an amount of 0.01% by mass to 8.0% by mass based on the total amount of the non-aqueous electrolyte solution, and 0.05% by mass. It is more preferable that it is contained to 5.0% by mass, further preferably 0.08% to 3.0% by mass, and particularly preferably 0.08% to 1.5% by mass. preferable. If the content of the fluorine-containing (meth) acrylic acid derivative represented by the formula (I) is less than the lower limit, the effect of reducing the calorific value in the electrode active material layer tends to be insufficient. On the other hand, when the amount is larger than the above upper limit value, the effect of reducing the calorific value in the electrode active material layer is improved, but the discharge capacity tends to decrease. By adjusting the content of the fluorine-containing (meth) acrylic acid derivative represented by the formula (I) to a value within the above numerical range, the effect of the present invention can be obtained more reliably.

As the electrolyte, when the electrochemical device is a lithium secondary battery, a lithium salt is used. Examples of the lithium salt include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCF ₃ CF ₂ SO ₃ , LiC (CF ₃ SO ₂ ) ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN _{(CF 3 CF 2 SO 2)} 2, LiN (CF 3 SO 2) (C 4 F 9 SO 2), LiN (CF 3 CF 2 CO) 2 , and the like.

When the electrochemical device is an electric double layer capacitor, for example, a quaternary ammonium salt such as tetraethylammonium tetrafluoroborate (TEA ⁺ BF ₄ ⁻ ) or triethyl monomethyl ammonium tetrafluoroborate (TEMA ⁺ BF ₄ ⁻ ) is used. An electrolytic solution dissolved in an organic solvent is used.

  In addition, these salts may be used individually by 1 type, and may use 2 or more types together.

  Moreover, as an organic solvent, if the fluorine-containing (meth) acrylic acid derivative represented by the above formula (I) and the above electrolyte can be dissolved, a solvent used in a known electrochemical device can be used. Can be used. For example, ethylene carbonate, propylene carbonate, butylene carbonate, γ-butyrolactone, γ-valerolactone, dimethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, 1,3-dioxylene, 4-methyl-1,3 -Dixylene, methyl formate, methyl acetate, methyl propionate, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, acetonitrile, sulfolane, 2-methyl sulfolane, dimethyl sulfoxide, N, N-dimethylformamide, N-methyloxazolidinone, etc. . These solvents can be used alone or in combination. Moreover, you may add about the amount of additives, such as vinyl carbonate and vinylene carbonate.

  The nonaqueous electrolytic solution of the present invention may be gelled by adding a polymer or the like as long as the effects of the present invention can be obtained.

  Subsequently, the electrode and the electrochemical device according to the present embodiment will be described with reference to FIG. Specifically, the case where the electrochemical device is a lithium secondary battery will be described.

[Lithium ion secondary battery]
The lithium ion secondary battery 100 mainly includes a laminate 30, a case 50 that accommodates the laminate 30 in a sealed state, and a pair of leads 60 and 62 connected to the laminate 30.

  The laminated body 30 is configured such that a pair of the positive electrode 10 and the negative electrode 20 are opposed to each other with the separator 18 interposed therebetween. The positive electrode 10 is obtained by providing a positive electrode active material layer 14 on a plate-like (film-like) positive electrode current collector 12. The negative electrode 20 is obtained by providing a negative electrode active material layer 24 on a plate-like (film-like) negative electrode current collector 22. The positive electrode active material layer 14 and the negative electrode active material layer 24 are in contact with both sides of the separator 18. Leads 60 and 62 are connected to the end portions of the positive electrode current collector 12 and the negative electrode current collector 22, respectively, and the end portions of the leads 60 and 62 extend to the outside of the case 50.

  Hereinafter, the positive electrode 10 and the negative electrode 20 are collectively referred to as electrodes 10 and 20, and the positive electrode current collector 12 and the negative electrode current collector 22 are collectively referred to as current collectors 12 and 22, and the positive electrode active material layer 14 and the negative electrode The active material layers 24 are collectively referred to as active material layers 14 and 24.

[electrode]
The electrodes 10 and 20 will be specifically described. The electrodes 10 and 20 include current collectors 12 and 22, and active material layers 14 and 24 containing active materials and binders formed on the surfaces of the current collectors 12 and 22, and the active material layer further includes the above A polymer of a fluorine-containing (meth) acrylic acid derivative represented by the formula (I) is included.

(Positive electrode 10)
The positive electrode current collector 12 may be a conductive plate material, and for example, a thin metal plate of aluminum, copper, or nickel foil can be used.
The positive electrode active material layer 14 includes the active material according to the present embodiment, a binder, and a conductive material in an amount necessary.

  The binder bonds the active materials to each other and bonds the active material to the positive electrode current collector 12.

The positive electrode active material may be any compound that contains lithium ions and can occlude and release lithium ions. For example, LiCoO ₂ , LiNiO ₂ , LiMn ₂ O ₄ , Li (Co _x Ni _y Mn _z ) O ₂ Li-containing metal oxides such as Li (Ni _x Co _y Al _z ) O ₂ , Li ( _M n _x Al _y ) ₂ O ₄ , Li [Li _w Mn _x Ni _y Co _z ] O ₂ , LiVOPO ₄ , LiFePO ₄ Is mentioned.

  The material of the binder is not particularly limited as long as the above-described bonding is possible. For example, polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene. -Perfluoroalkyl vinyl ether copolymer (PFA), ethylene-tetrafluoroethylene copolymer (ETFE), polychlorotrifluoroethylene (PCTFE), ethylene-chlorotrifluoroethylene copolymer (ECTFE), polyvinyl fluoride ( Fluorine resin such as PVF).

  In addition to the above, as the binder, for example, vinylidene fluoride-hexafluoropropylene-based fluororubber (VDF-HFP-based fluororubber), vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene-based fluororubber (VDF-HFP-) TFE fluorine rubber), vinylidene fluoride-pentafluoropropylene fluorine rubber (VDF-PFP fluorine rubber), vinylidene fluoride-pentafluoropropylene-tetrafluoroethylene fluorine rubber (VDF-PFP-TFE fluorine rubber), Vinylidene fluoride-perfluoromethyl vinyl ether-tetrafluoroethylene fluoro rubber (VDF-PFMVE-TFE fluoro rubber), vinylidene fluoride-chlorotrifluoroethylene fluoro rubber The containing rubbers (VDF-CTFE-based fluorine rubber) vinylidene fluoride-based fluorine rubbers such as may be used.

  In addition to the above, for example, polyethylene, polypropylene, polyethylene terephthalate, aromatic polyamide, cellulose, styrene / butadiene rubber, isoprene rubber, butadiene rubber, ethylene / propylene rubber, and the like may be used as the binder. Also, thermoplastic elastomeric polymers such as styrene / butadiene / styrene block copolymers, hydrogenated products thereof, styrene / ethylene / butadiene / styrene copolymers, styrene / isoprene / styrene block copolymers, and hydrogenated products thereof. May be used. Further, syndiotactic 1,2-polybutadiene, ethylene / vinyl acetate copolymer, propylene / α-olefin (carbon number 2 to 12) copolymer may be used.

  Alternatively, an electron conductive conductive polymer or an ion conductive conductive polymer may be used as the binder. Examples of the electron conductive conductive polymer include polyacetylene. In this case, since the binder also functions as a conductive material, it is not necessary to add a conductive material.

As the ion-conductive conductive polymer, for example, those having ion conductivity such as lithium ion can be used. For example, polymer compounds (polyether-based polymer compounds such as polyethylene oxide and polypropylene oxide) A crosslinked polymer of a polyether compound, polyepichlorohydrin, polyphosphazene, polysiloxane, polyvinylpyrrolidone, polyvinylidene carbonate, polyacrylonitrile, etc.) monomers, and LiClO ₄ , LiBF ₄ , LiPF ₆ , LiAsF ₆ , LiCl, LiBr, Examples include Li (CF ₃ SO ₂ ) ₂ N, LiN (C ₂ F ₅ SO ₂ ) ₂ lithium salt, or a composite of alkali metal salt mainly composed of lithium. Examples of the polymerization initiator used for the combination include a photopolymerization initiator or a thermal polymerization initiator that is compatible with the above-described monomer.

  It is preferable that the content rate of the binder contained in the positive electrode active material layer 14 is 0.5-6 mass% on the basis of the mass of an active material layer. When the binder content is less than 0.5% by mass, the amount of the binder is too small and a tendency to fail to form a strong active material layer increases. Moreover, when the content rate of a binder exceeds 6 mass%, the quantity of the binder which does not contribute to an electrical capacity will increase, and the tendency for it to become difficult to obtain sufficient volume energy density becomes large. In this case, particularly, when the electronic conductivity of the binder is low, the electric resistance of the active material layer is increased, and there is a tendency that a sufficient electric capacity cannot be obtained.

  Examples of the conductive material include carbon powder such as carbon black, carbon nanotube, carbon material, fine metal powder such as copper, nickel, stainless steel and iron, a mixture of carbon material and fine metal powder, and conductive oxide such as ITO. It is done.

(Negative electrode 20)
The negative electrode current collector 22 may be a conductive plate material, and for example, a thin metal plate of aluminum, copper, or nickel foil can be used.
The negative electrode active material may be any compound that can occlude and release thium ions, and known negative electrode active materials for batteries can be used. Examples of the negative electrode active material include carbon materials such as graphite (natural graphite, artificial graphite) capable of inserting and extracting lithium ions, carbon nanotubes, non-graphitizable carbon, graphitizable carbon, low-temperature calcined carbon, Al, Si, and the like. And particles containing a metal that can be combined with lithium such as Sn, an amorphous compound mainly composed of an oxide such as SiO ₂ and SnO ₂ , lithium titanate (Li ₄ Ti ₅ O ₁₂ ), and the like. .
As the binder and the conductive material, the same materials as those for the positive electrode can be used.

Next, a method for manufacturing the electrodes 10 and 20 according to this embodiment will be described.
(Method for manufacturing electrodes 10 and 20)
The method for manufacturing the electrodes 10 and 20 according to the present embodiment includes a step of applying a coating material, which is a raw material of the electrode active material layers 14 and 24, onto the aggregate (hereinafter, also referred to as “coating step”), and a collector. The step of removing the solvent in the paint applied on the electric body to form an electrode active material layer (hereinafter sometimes referred to as “solvent removal step”), and the surface of the electrode active material layer, A step of forming a polymer of a fluorine-containing (meth) acrylic acid derivative represented by I) (hereinafter also referred to as “polymer forming step”).

(Coating process)
An application process for applying the paint to the current collectors 12 and 22 will be described. The paint contains the active material, a binder, and a solvent. In addition to these components, the coating material may contain, for example, a conductive material for increasing the conductivity of the active material. As the solvent, for example, N-methyl-2-pyrrolidone, N, N-dimethylformamide and the like can be used.

  The mixing method of the components constituting the paint such as the active material, the binder, the solvent, and the conductive material is not particularly limited, and the mixing order is not particularly limited. For example, first, an active material, a conductive material, and a binder are mixed, and N-methyl-2-pyrrolidone is added to and mixed with the obtained mixture to prepare a coating material.

  The paint is applied to the current collectors 12 and 22. There is no restriction | limiting in particular as an application | coating method, The method employ | adopted when producing an electrode normally can be used. Examples thereof include a slit die coating method and a doctor blade method.

(Solvent removal step)
Subsequently, the solvent in the paint applied on the current collectors 12 and 22 is removed. The removal method is not particularly limited, and the current collectors 12 and 22 to which the paint is applied may be dried, for example, in an atmosphere of 80 ° C. to 150 ° C.

  Then, the electrodes on which the active material layers 14 and 24 are formed in this way may then be pressed by a roll press device or the like as necessary. The linear pressure of the roll press can be, for example, 10 to 50 kgf / cm.

  Through the above steps, the electrode active material layers 14 and 24 are formed on the current collectors 12 and 22, and the fluorine-containing (meth) acrylic represented by the above formula (I) is formed on the surfaces of the electrode active material layers 14 and 24. An electrode before the polymer of the acid derivative is formed (hereinafter referred to as “electrode before polymer formation”) can be produced.

(Polymer formation process)
Subsequently, the positive electrode and the negative electrode before polymer formation are laminated via the separator 18. For example, by immersing this laminate in the non-aqueous electrolyte solution of the present invention, connecting the leads 60 and 62 to a charge / discharge tester and charging / discharging at least once, the positive electrode active material layer before polymer formation, and The polymer of the fluorine-containing (meth) acrylic acid derivative represented by the above formula (I) can be formed on the negative electrode active material layer before polymer formation, and the positive electrode 10 and the negative electrode 20 can be produced. The existence state of the polymer is not necessarily clear, but it is attached to the surface of the active material or the binder or bonded to the active material or the binder to cover the surfaces of the electrode active material layers 14 and 24. Inferred.

The polymer can be prepared under the conditions set during the charge / discharge test using a charge / discharge tester used in a normal charge / discharge test, and is not particularly limited as long as it is a normal charge / discharge condition. For example, at a voltage of 3.0 to 4.3 V, a current density of 0.001 to 10 mA / cm ² and a temperature of 20 to 30 ° C., the battery may be charged to about 80 to 100% at full charge and discharged to 3.0 V. .

  In the polymer forming step, the positive electrode or the negative electrode and the lithium metal sheet are laminated via a separator, a half cell laminate is prepared for each of the positive electrode and the negative electrode, and the half cell laminate according to the present invention. Fluorine-containing represented by the above formula (I) on the surface of the positive electrode active material layer and the surface of the negative electrode active material layer by immersing in an electrolytic solution and charging and discharging at least once each under the above charge and discharge conditions A polymer of a (meth) acrylic acid derivative may be formed, and the positive electrode 10 and the negative electrode 20 may be produced separately.

  Here, another component of the lithium ion secondary battery 100 using the electrode manufactured as described above will be described.

  The separator 18 is an electrically insulating porous body, for example, a single layer of a film made of polyethylene, polypropylene or polyolefin, a stretched film of a laminate or a mixture of the above resins, or a group consisting of cellulose, polyester and polypropylene. Examples thereof include a nonwoven fabric made of at least one selected constituent material.

  The case 50 seals the laminated body 30 and the electrolytic solution therein. The case 50 is not particularly limited as long as it can prevent leakage of the electrolytic solution to the outside and entry of moisture and the like into the electrochemical device 100 from the outside. For example, as the case 50, as shown in FIG. 1, a metal laminate film in which a metal foil 52 is coated with a polymer film 54 from both sides can be used. For example, an aluminum foil can be used as the metal foil 52 and a film such as polypropylene can be used as the polymer film 54. For example, the material of the outer polymer film 54 is preferably a polymer having a high melting point such as polyethylene terephthalate (PET) or polyamide, and the material of the inner polymer film 54 is polyethylene (PE) or polypropylene (PP). preferable.

  The leads 60 and 62 are made of a conductive material such as aluminum.

  Then, the leads 60 and 62 are welded to the positive electrode current collector 12 and the negative electrode current collector 22 by a known method, respectively, and a separator is provided between the positive electrode active material layer 14 of the positive electrode 10 and the negative electrode active material layer 24 of the negative electrode 20. 18 may be inserted into the case 50 together with the electrolytic solution with the 18 interposed therebetween, and the entrance of the case 50 may be sealed.

  As mentioned above, although non-aqueous electrolyte of this invention, an electrode, a lithium ion secondary battery provided with the said electrolyte and electrode, and suitable one Embodiment of those manufacturing methods were demonstrated in detail, this invention is the above-mentioned. It is not limited to the embodiment.

  For example, the electrolytic solution and electrode of the present invention can be used for electrochemical devices other than lithium ion secondary batteries. Electrochemical devices include secondary batteries other than lithium ion secondary batteries such as metallic lithium secondary batteries (using the above active material as the cathode and metallic lithium as the anode), and electrochemical capacitors such as lithium capacitors. Etc. These electrochemical elements can be used for power sources such as self-propelled micromachines and IC cards, and distributed power sources arranged on or in a printed circuit board. In the case of an electrochemical device other than a lithium ion secondary battery, a material suitable for each electrochemical device may be used as the electrode active material. For example, in the case of an electrochemical capacitor, acetylene black, graphite, graphite, activated carbon, or the like is used as the active material contained in the positive electrode active material-containing layer and the negative electrode active material-containing layer.

[Function and effect]
The reason why the effect of the present invention is obtained is not necessarily clear, but the present inventors infer the reason why the above effect is obtained as follows. When the electrochemical device is charged and discharged for the first time, the surface of the electrode active material layer in contact with the electrolytic solution, for example, the surface of the active material or the surface of the binder, the fluorine-containing (meth) acrylic acid derivative represented by the above formula (I) A polymer is formed. Since the C—F bond has a bond distance as small as 1.317 mm and a bond energy as large as 116 kcal / mol, the fluorine-containing (meth) acrylic acid attractant polymer represented by the above formula (I) is resistant to heat and resistance. It is considered that the chemical properties are excellent, and for example, it is considered that the reaction between the electrolytic solution and the electrode active material can be effectively suppressed, and the amount of heat generated in the electrode active material layer can be reduced during abnormal heat generation.

  EXAMPLES Hereinafter, although this invention is demonstrated more concretely based on an Example and a comparative example, this invention is not limited to a following example.

Example 1
[Creation of negative electrode]
Artificial graphite as a negative electrode active material, styrene-butadiene rubber as a binder, carboxymethyl cellulose as a thickener, and water as a solvent were mixed to prepare a paint. This paint was applied to a copper foil (thickness: 15 μm) as a current collector by a doctor blade method, dried at 80 ° C., and then rolled to form a positive electrode active material layer on the surface of the copper foil. The copper foil was provided with a portion to which no paint was applied in order to connect the external lead terminal. As the external lead terminal, a nickel foil wound with polypropylene grafted with maleic anhydride was prepared for the purpose of improving the sealing performance with the exterior body. The nickel foil and the copper foil after the coating material was applied and dried were ultrasonically welded.

[Creation of positive electrode]
Li (Ni _0.82 Co _0.15 Al _0.03 ) O ₂ as a positive electrode active material, polyvinylidene fluoride as a binder, carbon black and graphite as a conductive additive, N-methylpyrrolidone as a solvent, and a paint Created. This paint was applied to an aluminum foil (thickness 20 μm) as a current collector by a doctor blade method, dried at 100 ° C., and then rolled to form a positive electrode active material layer on the surface of the aluminum foil. The aluminum foil was provided with a portion to which no paint was applied in order to connect the external lead terminal. As an external lead terminal, for the purpose of improving the sealing property with the exterior body, an aluminum foil wrapped with polypropylene grafted with maleic anhydride was prepared. This aluminum foil and the aluminum foil after the coating material was applied and dried were ultrasonically welded.

[Creation of electrolyte]
LiPF ₆ was dissolved at a concentration of 1 M in a solution obtained by mixing ethylene carbonate at a ratio of 30 vol% and diethyl carbonate at a ratio of 70 vol% to prepare an electrolytic solution. This electrolyte solution, the fluorine-containing acrylic acid derivative _{(CH 2 CHCOO- (CH 2)} 2 -C 8 F 17) was added 0.1 wt% was dissolved.

[Create half-cell]
(Preparation of positive electrode half cell)
The positive electrode produced as described above and a separator (polyolefin microporous membrane, manufactured by Asahi Kasei Corporation, (trade name) SV722) were cut into predetermined dimensions. A positive electrode, a separator, and a lithium metal were laminated in this order to produce a positive electrode half-cell laminate. The outer package of the battery enclosing the laminate was made of an aluminum laminate material, and the configuration thereof was polyethylene terephthalate (12 μm) / Al (40 μm) / polypropylene (50 μm). At this time, bags were made so that PP was on the inside. The laminate was placed in the outer package, an appropriate amount of the electrolyte prepared as described above was added, and the outer package was vacuum-sealed to produce a positive electrode half cell.

(Preparation of negative electrode half cell)
A negative electrode half cell was produced in the same manner as the production method of the positive electrode half cell except that the negative electrode, the separator, and the lithium metal were laminated in this order to produce a laminate for the negative electrode half cell.

<Measurement of discharge capacity>
When the positive electrode half cell and the negative electrode half cell prepared as described above were subjected to a charge / discharge tester (manufactured by Hokuto Denko Corporation, (product name) HJ1001SM8A) with a discharge rate of 0.1 C (constant current discharge at 25 ° C.) The discharge capacity (unit: mAh / g) was measured when the current value reached the end of discharge in 10 hours. Table 1 shows the discharge capacity of the positive electrode and the discharge capacity of the negative electrode.
Incidentally, the electrolytic solution recovered from the battery after charging and _{discharging, PO 2 F-O- (CH} 2) 2 -C 8 F 17, CH 3 CH 2 O- (CH 2) 2 COO- (CH 2) 2 and _{-C 8 F 17, C 8 F} 18 detects trace amounts. This is a substance produced by decomposition of a part of the additive and reaction with a part of the solvent or the supporting salt, and the performance of the battery was not impaired.

<Measurement of calorific value of positive electrode active material layer>
After the charge / discharge test, the positive electrode half cell was disassembled, a part of the positive electrode active material layer was taken out, about 1 mg was put in a SUS container having a diameter of 5 mm and sealed with a SUS lid, and then a differential scanning calorimeter (Rigaku Corporation) The calorific value was measured by (Product name: Thermo plus DSC8230). The measurement range was 25 ° C. to 500 ° C., the rate of increase was 10 ° C./min, and the reference material was alumina (attached to a differential scanning calorimeter). The exotherm began at about 230 ° C.

(Example 2)
Fluorine-containing acrylic acid derivative _{(CH 2 CHCOO- (CH 2)} 2 -C 8 F 17) a fluorine-containing methacrylic acid derivative in place of _{(CH 2 CCH 3 COO-CH} 2 -CF 3) except for adding Example 1 In the same manner, a positive electrode half cell and a negative electrode half cell were produced.

(Example 3)
A positive electrode half cell and a negative electrode half cell were produced in the same manner as in Example 1 except that 1.0% by mass of a fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ) was added.

Example 4
Instead of 0.1% by mass of a fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ), a fluorine-containing methacrylic acid derivative (CH ₂ CCH ₃ COO—CH ₂ —CF ₃ ) is used. A positive electrode half cell and a negative electrode half cell were produced in the same manner as in Example 1 except that 1.0% by mass was added.

(Example 5)
Instead of 0.1% by mass of a fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ), a fluorine-containing methacrylic acid derivative (CH ₂ CCH ₃ COO—CH ₂ —CF ₃ ) 3 A positive electrode half cell and a negative electrode half cell were produced in the same manner as in Example 1 except that 0.0 mass% was added.

(Example 6)
Instead of 0.1% by mass of fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ), 5.0% of methacrylic acid derivative (CH ₂ CCH ₃ COO—CH ₂ —CF ₃ ) is added. A positive electrode half cell and a negative electrode half cell were produced in the same manner as in Example 1 except that the addition by mass% was performed.

(Example 7)
Instead of 0.1% by mass of fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ), 0.05% of methacrylic acid derivative (CH ₂ CCH ₃ COO—CH ₂ —CF ₃ ) was added. A positive electrode half cell and a negative electrode half cell were produced in the same manner as in Example 1 except that the addition by mass% was performed.

(Example 8)
Instead of 0.1% by mass of a fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ), a methacrylic acid derivative (CH ₂ CCH ₃ COO—CH ₂ —CF ₃ ) is used at 5.5. A positive electrode half cell and a negative electrode half cell were produced in the same manner as in Example 1 except that the addition by mass% was performed.

(Comparative Example 1)
A positive electrode half cell and a negative electrode half cell were produced in the same manner as in Example 1 except that no additive was used in the electrolytic solution.

(Comparative Example 2)
The same procedure as in Example 1 was conducted except that 1.0% by mass of methyl methacrylate was added instead of 0.1% by mass of the fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ). A positive electrode half cell and a negative electrode half cell were prepared.

(Comparative Example 3)
The same procedure as in Example 1 was performed except that 1.0% by mass of ethyl methacrylate was added instead of 0.1% by mass of the fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ). Thus, a positive electrode half cell and a negative electrode half cell were produced.

(Comparative Example 4)
A positive electrode half cell and a negative electrode half cell were produced in the same manner as in Example 1 except that methyl methacrylate was added instead of the fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ).

(Comparative Example 5)
A positive electrode half cell and a negative electrode half cell were produced in the same manner as in Example 1 except that ethyl methacrylate was added instead of the fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ).

(Comparative Example 6)
Instead of 0.1% by mass of a fluorine-containing acrylic acid derivative (CH ₂ CHCOO— (CH ₂ ) ₂ —C ₈ F ₁₇ ), vinylene carbonate (VC) and propane sultone (PS) in total 1.0% by mass A positive electrode half cell and a negative electrode half cell were produced in the same manner as in Example 1 except for the addition.

  In Examples 2 to 9 and Comparative Examples 1 to 6, similarly to Example 1, the discharge capacities of the positive electrode and the negative electrode were measured for the positive electrode half cell and the negative electrode half cell. Further, as in Example 1, the calorific value of the positive electrode active material layer was measured. Table 1 shows the positive electrode discharge capacity, the negative electrode discharge capacity, and the positive electrode active material layer calorific value of Examples 1 to 9 and Comparative Examples 1 to 6.

  In the examples, the effect of reducing the calorific value was sufficiently obtained even with the addition amount of 0.1% by mass. On the other hand, as shown in the comparative example, the electrolyte solution to which methyl methacrylate, ethyl methacrylate, or a mixture of VC and PS was added had a low heating value reduction effect unless 1.0% by mass or more was added.

  DESCRIPTION OF SYMBOLS 10,20 ... Electrode, 12 ... Positive electrode collector, 14 ... Positive electrode active material layer, 18 ... Separator, 22 ... Negative electrode collector, 24 ... Negative electrode active material layer, 30 ... Laminate, 50 ... Case, 52 ... Metal Foil, 54 ... polymer film, 60, 62 ... lead, 100 ... lithium ion secondary battery.

Claims (6)

A nonaqueous electrolytic solution containing a fluorine-containing (meth) acrylic acid derivative represented by the formula (I), a nonaqueous solvent, and an electrolyte.

[In formula (I), X represents a hydrogen atom or a methyl group, and R ¹ represents a hydrocarbon group having 1 to 26 carbon atoms in which at least one hydrogen atom is substituted with a fluorine atom. ] In the formula (I), the fluorine atom bonded to the carbon skeleton in the hydrocarbon group represented by R ¹ is 50 mol based on the total amount of hydrogen atoms and fluorine atoms bonded to the carbon skeleton in the hydrocarbon group. The non-aqueous electrolyte solution according to claim 1, which is at least%.   The non-aqueous electrolyte solution of Claim 1 or 2 which contains 0.01 mass%-8.0 mass% of fluorine-containing (meth) acrylic acid derivatives represented by the said formula (I). A current collector,
An active material layer comprising an active material, a binder and a polymer of a fluorine-containing (meth) acrylic acid derivative represented by the formula (I), and formed on the surface of the current collector;
Electrode.

  An electrochemical device comprising the nonaqueous electrolytic solution according to any one of claims 1 to 3. An electrochemical device comprising the electrode according to claim 4.

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