JP2017183248A - Binder composition for electrode of lithium ion secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a lithium ion secondary battery electrode which is low in battery resistance at a low temperature, hard to form a pin hole or a crack in the surface of the active material layer, and superior in durability against bending and folding even in the case of increasing a coating amount of an active material layer for the purpose of increasing the battery capacity of a lithium ion secondary battery.SOLUTION: A binder composition is used for a composition for an electrode to form an active material layer of a lithium ion secondary battery electrode. The binder composition comprises: a compound having a sulfonyl group and an oxycarbonyl group; a resin component; and a solvent.SELECTED DRAWING: None

Description

  The present invention relates to a binder composition for an electrode of a lithium ion secondary battery. More specifically, the present invention is suitable for a lithium ion secondary battery electrode having a low battery resistance at low temperature, having no defects in the appearance of the active material layer, and having excellent bending resistance, and the lithium ion secondary battery electrode. A composition for an electrode of a lithium ion secondary battery that can be used for the electrode, a binder composition for an electrode of a lithium ion secondary battery that can be suitably used for the composition for an electrode of the lithium ion secondary battery, and the above The present invention relates to a lithium ion secondary battery having an electrode for a lithium ion secondary battery.

  Conventionally, various binders and binder compositions for electrodes of lithium ion secondary batteries have been proposed. Among them, a binder for an electrode composition containing a water-soluble polymer compound containing a structural unit derived from an ethylenically unsaturated carboxylate monomer and a structural unit derived from an ethylenically unsaturated carboxylic acid ester monomer, It has been attracting attention because it is excellent in dispersibility of the active material and the conductive additive and has excellent binding properties between the active materials and between the active material and the current collector (see, for example, Patent Document 1). The binder for electrode compositions is excellent in the dispersibility of the active material and the conductive auxiliary agent, and is excellent in the binding properties between the active materials and between the active material and the current collector.

In recent years, it has been studied to increase the thickness of the active material layer in order to increase the battery capacity of the lithium ion secondary battery. However, regarding the positive electrode, generally, when the coating amount of the active material layer of the lithium ion secondary battery is 12 mg / cm ² or more, the rate characteristics are lowered and the battery resistance is increased. Further, since the use of the lithium ion secondary battery may be limited by the environmental temperature, pinholes or cracks may occur on the surface of the active material layer, or the active material layer may be bent. May deteriorate.

  Therefore, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and pinholes and cracks are formed on the surface of the active material layer. Therefore, development of an electrode for a lithium ion secondary battery excellent in bending resistance is awaited.

JP 2015-188776 A

  The present invention has been made in view of the above prior art, and battery resistance at a low temperature even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. Lithium ion secondary battery electrode, which is low in resistance, hardly causes pinholes and cracks on the surface of the active material layer, and has excellent bending resistance, and lithium that can be suitably used for the lithium ion secondary battery electrode Composition for electrode of ion secondary battery, binder composition for electrode of lithium ion secondary battery that can be suitably used for electrode composition of lithium ion secondary battery, and electrode for lithium ion secondary battery It is an object of the present invention to provide a lithium ion secondary battery having:

The present invention
(1) A binder composition used in an electrode composition for forming an active material layer of an electrode for a lithium ion secondary battery, comprising a compound having a sulfonyl group and an oxycarbonyl group, a resin component, and a solvent. A binder composition for an electrode of a lithium ion secondary battery,
(2) A composition for an electrode of a lithium ion secondary battery comprising the binder composition for an electrode according to (1) and an active material,
(3) An electrode having a current collector and an active material layer, wherein the active material layer is formed from the electrode composition for a lithium ion secondary battery according to (2). An electrode, and (4) The present invention relates to a lithium ion secondary battery having the electrode for a lithium ion secondary battery according to (3).

  According to the present invention, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and the surface of the active material layer is reduced. An electrode for a lithium ion secondary battery that does not easily cause pinholes and cracks and has excellent bending resistance, and a composition for an electrode of a lithium ion secondary battery that can be suitably used for the electrode for a lithium ion secondary battery, Provided are a binder composition for an electrode of a lithium ion secondary battery that can be suitably used for the electrode composition of the lithium ion secondary battery, and a lithium ion secondary battery having the electrode for a lithium ion secondary battery. The

  As described above, the binder composition for an electrode of a lithium ion secondary battery of the present invention is a binder composition used for an electrode composition that forms an active material layer of an electrode for a lithium ion secondary battery, and is a sulfonyl group. And a compound having an oxycarbonyl group, a resin component, and a solvent.

  Since the binder composition for an electrode of a lithium ion secondary battery of the present invention contains a compound having a sulfonyl group and an oxycarbonyl group, the active material layer of the lithium ion secondary battery is increased in order to increase the battery capacity of the lithium ion secondary battery. Even when the coating amount is increased, the battery resistance at low temperature is low, and it is difficult to generate pinholes and cracks on the surface of the active material layer. Thus, a lithium ion secondary battery electrode that has low battery resistance, hardly generates pinholes and cracks on the surface of the active material layer, and has excellent bending resistance can be obtained.

  Examples of the compound having a sulfonyl group and an oxycarbonyl group include aromatic compounds having a sulfonyl group and an oxycarbonyl group. Among aromatic compounds having a sulfonyl group and an oxycarbonyl group, the battery resistance at low temperature even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is low, does not easily cause pinholes and cracks on the surface of the active material layer, and has excellent bending resistance, the formula (I):

[Wherein, R ¹ and R ² each independently represent a hydrogen atom, an alkali metal atom, an ammonium group, an alkylammonium group or an alkanolammonium group, and —OR ¹ and —OR ² are combined into an ether bond. (-O-) may be formed]
The compound represented by is more preferable.

In the formula (I), R ¹ and R ² have low battery resistance at low temperature even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is less prone to pinholes and cracks on the surface of the active material layer and has excellent bending resistance, each of them is independently a hydrogen atom, an alkali metal atom, an ammonium group, or an alkylammonium. A group or an alkanol ammonium group, and —OR ¹ and —OR ² may be combined to form an ether bond (—O—).

  Examples of the alkali metal atom include lithium, sodium, potassium, and the like. Among these, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and the pin is not pinned on the surface of the active material layer. From the viewpoint of obtaining an electrode for a lithium ion secondary battery that hardly causes holes and cracks and has excellent bending resistance, sodium and lithium are preferable, and lithium is more preferable.

  Examples of the alkylammonium group include a monoethylammonium group, a diethylammonium group, and a triethylammonium group, but the present invention is not limited to such examples.

  Examples of the alkanol ammonium group include a monoethanol ammonium group, a diethanol ammonium group, a triethanol ammonium group, and the like, but the present invention is not limited to such examples.

Among R ¹ and R ² , even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and the active material layer From the viewpoint of obtaining an electrode for a lithium ion secondary battery in which pinholes and cracks are unlikely to occur on the surface of the metal, R ¹ and R ² are each independently a hydrogen atom, an alkali metal atom or ammonium. Or —OR ¹ and —OR ² are preferably combined to form an ether bond (—O—), and R ¹ and R ² are both hydrogen atoms, or It is more preferable that —OR ¹ and —OR ² are integrated to form an ether bond (—O—).

In the formula (I), the position where the —SO ₂ —OR ¹ group bonded to the benzene ring and —CO—OR ² are bonded is an active material for increasing the battery capacity of the lithium ion secondary battery. Even when the coating amount of the layer is increased, the battery resistance at low temperature is low, pinholes and cracks do not occur on the surface of the active material layer, and the lithium ion secondary battery has excellent bending resistance. From the viewpoint of obtaining an electrode, the ortho position is preferred.

  Specific examples of the compound represented by the formula (I) include 2-sulfobenzoic acid, monosodium 2-sulfobenzoate, disodium 2-sulfobenzoate, monolithium 2-sulfobenzoate, and dilithium 2-sulfobenzoate. 2-sulfobenzoic acid monoammonium, 2-sulfobenzoic acid diammonium, 2-sulfobenzoic anhydride, 3-sulfobenzoic acid, 3-sulfobenzoic acid monosodium, 3-sulfobenzoic acid disodium, 3-sulfo Examples include monolithium benzoate, dilithium 3-sulfobenzoate, and 4-sulfobenzoic acid, but the present invention is not limited to such examples. These compounds may be used alone or in combination of two or more. Among these compounds, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and the surface of the active material layer From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is less prone to pinholes and cracks and has excellent bending resistance, 2-sulfobenzoic acid, monosodium 2-sulfobenzoate, disodium 2-sulfobenzoate, 2-sulfobenzoic acid monolithium, 2-sulfobenzoic acid dilithium, 2-sulfobenzoic acid monoammonium, 2-sulfobenzoic acid diammonium and 2-sulfobenzoic anhydride are preferred, and 2-sulfobenzoic anhydride is more preferred. preferable.

  The content of the compound having a sulfonyl group and an oxycarbonyl group in the nonvolatile content of the binder composition for an electrode of the present invention increases the coating amount of the active material layer in order to increase the battery capacity of the lithium ion secondary battery. From the viewpoint of obtaining a lithium ion secondary battery electrode that has low battery resistance at low temperatures, does not easily cause pinholes and cracks on the surface of the active material layer, and has excellent bending resistance. 1% by mass or more, more preferably 2% by mass or more, and further preferably 3% by mass or more, in the case where the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. However, from the viewpoint of obtaining a lithium ion secondary battery electrode that has low battery resistance at low temperatures, does not easily cause pinholes and cracks on the surface of the active material layer, and has excellent bending resistance. Properly 30 wt% or less, more preferably 20 wt% or less, more preferably 15 wt% or less, even more preferably 10 mass% or less.

  The binder composition for electrodes of the present invention contains a resin component and a solvent. Examples of the form of the resin component and the solvent include a dispersion in which resin particles are dispersed in a solvent and a resin solution in which a resin is dissolved in a solvent. However, the present invention is limited only to such examples. is not. Among the resin components and solvents, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and the active material From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is resistant to pinholes and cracks on the surface of the layer and has excellent bending resistance, a dispersion in which resin particles are dispersed in a solvent is preferable, and contains emulsion particles. A resin emulsion is more preferable.

  The emulsion particles contained in the resin emulsion can be obtained, for example, by emulsion polymerization of a monomer component. Among the monomer components, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and the active material layer From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is resistant to pinholes and cracks on the surface and has excellent bending resistance, an alkyl (meth) acrylate having 1 to 3 carbon atoms and a polyfunctional monomer Monomer components containing the body are preferred.

  In the present specification, “(meth) acrylate” means “acrylate” or “methacrylate”, “(meth) acryl” means “acryl” or “methacryl”, and “(meth) acryloyl”. "Means" acryloyl "or" methacryloyl "and" (meth) acryloyloxy "means" acryloyloxy "or" methacryloyloxy ".

  Examples of the alkyl (meth) acrylate having 1 to 3 carbon atoms include methyl (meth) acrylate, ethyl (meth) acrylate, and propyl (meth) acrylate. These alkyl (meth) acrylates may be used alone or in combination of two or more. Among these alkyl (meth) acrylates, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and Methyl (meth) acrylate and ethyl (meth) acrylate are preferred from the viewpoint of obtaining an electrode for a lithium ion secondary battery that is resistant to pinholes and cracks on the surface of the material layer and has excellent bending resistance, and methyl (meth) Acrylate is more preferred.

  The content of the alkyl (meth) acrylate having 1 to 3 carbon atoms in the monomer component was the case where the coating amount of the active material layer was increased in order to increase the battery capacity of the lithium ion secondary battery. However, from the viewpoint of obtaining a lithium ion secondary battery electrode that has low battery resistance at low temperatures, hardly generates pinholes and cracks on the surface of the active material layer, and is excellent in bending resistance, preferably 25% by mass or more. More preferably, it is 30% by mass or more, more preferably 35% by mass or more, even at a low temperature even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. From the viewpoint of obtaining an electrode for a lithium ion secondary battery that has low battery resistance, does not easily cause pinholes and cracks on the surface of the active material layer, and is excellent in bending resistance, preferably 80% by mass or less, Ri is preferably not more than 75 wt%.

  Examples of the polyfunctional monomer include a monomer having a (meth) acryloyl group and a crosslinkable group, and a monomer having two or more (meth) acryloyl groups. It is not limited to only. The crosslinkable group is a functional group that undergoes a crosslinking reaction under conditions such as heating, acidity, and basicity.

  Examples of the monomer having a (meth) acryloyl group and a crosslinkable group include amide groups such as N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, and Nn-butoxymethyl (meth) acrylamide. Containing polyfunctional monomer; epoxy group containing polyfunctional monomer such as glycidyl (meth) acrylate; γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane, γ- ( Alkoxysilyl group-containing (meth) acrylates such as (meth) acryloyloxypropylmethyldiethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, and the like can be mentioned, but the present invention is not limited to such examples. Absent. These monomers may be used alone or in combination of two or more.

  Examples of the monomer having two or more (meth) acryloyl groups include ethylene glycol diacrylate, ethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tripropylene glycol diacrylate, and tripropylene glycol diacrylate. Examples include methacrylate, trimethylolpropane triacrylate, trimethylolpropane trimethacrylate, pentaerythritol tetraacrylate, pentaerythritol tetramethacrylate, and the like, but the present invention is not limited to such examples. These monomers may be used alone or in combination of two or more.

  Among the polyfunctional monomers, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and the active material layer From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is less prone to pinholes and cracks on the surface of the resin, an amide group-containing polyfunctional monomer is preferred, and N-methylol (meth) acrylamide is more preferred. preferable.

  The content of the polyfunctional monomer in the monomer component is such that the battery resistance at low temperature is increased even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. From the viewpoint of obtaining a lithium ion secondary battery electrode that is low and does not easily cause pinholes and cracks on the surface of the active material layer and has excellent bending resistance, it is preferably 0.5% by mass or more, more preferably 1% by mass. %, More preferably 1.5% by mass or more, and the battery resistance at low temperature is increased even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. From the viewpoint of obtaining a lithium ion secondary battery electrode that is low and does not easily cause pinholes and cracks on the surface of the active material layer and has excellent bending resistance, it is preferably 5% by mass or less, more preferably 4% by mass or less. Even better It is properly 3 mass% or less.

  The monomer component includes an alkyl (meth) having 1 to 3 carbon atoms in the alkyl group so that the total amount of monomers used in the monomer component is 100% by mass. In the remainder other than the acrylate and the polyfunctional monomer, other monomers (hereinafter referred to as other monomers) other than the alkyl (meth) acrylate having the alkyl group having 1 to 3 carbon atoms and the polyfunctional monomer. ) Can be used.

  Other monomers include, for example, alkyl (meth) acrylates having an alkyl group with 4 to 18 carbon atoms, carboxyl group-containing monomers, nitrile group-containing monomers, and nitrogen other than nitrile group-containing monomers. Atom-containing monomer, monomer having alicyclic structure, hydroxyl group-containing (meth) acrylate, carbonyl group-containing monomer, aromatic monomer, silicon atom-containing monomer, fluorine atom-containing monomer, etc. However, the present invention is not limited to such examples. These monomers may be used alone or in combination of two or more. Among these monomers, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and the active material layer From the viewpoint of obtaining an electrode for a lithium ion secondary battery in which pinholes and cracks are unlikely to occur on the surface of the resin, and the alkyl group contains 4 to 18 alkyl (meth) acrylates and carboxyl groups Monomers and nitrile group-containing monomers are preferred.

  Examples of the alkyl (meth) acrylate having an alkyl group having 4 to 18 carbon atoms include n-butyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, and sec-butyl (meth) acrylate. And alkyl (meth) acrylates having 4 to 18 carbon atoms in the ester group such as 2-ethylhexyl (meth) acrylate, tridecyl (meth) acrylate, n-octyl (meth) acrylate, and n-lauryl (meth) acrylate. However, the present invention is not limited to such examples. These alkyl (meth) acrylates may be used alone or in combination of two or more. Among these alkyl (meth) acrylates, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, and From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is resistant to pinholes and cracks on the surface of the material layer and has excellent bending resistance, an alkyl group having 4 to 12 carbon atoms, especially 4 to 8 carbon atoms. (Meth) acrylate is preferable, and n-butyl (meth) acrylate, tert-butyl (meth) acrylate and 2-ethylhexyl (meth) acrylate are more preferable.

  The content of the alkyl (meth) acrylate having 4 to 18 carbon atoms of the alkyl group in the monomer component increased the coating amount of the active material layer in order to increase the battery capacity of the lithium ion secondary battery. Even in this case, the battery resistance at low temperature is low, pinholes and cracks are hardly generated on the surface of the active material layer, and from the viewpoint of obtaining an electrode for a lithium ion secondary battery excellent in bending resistance, preferably 10 It is a case where the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, more preferably 15% by mass or more, more preferably 20% by mass or more. However, from the viewpoint of obtaining a lithium ion secondary battery electrode that has low battery resistance at low temperatures, hardly causes pinholes and cracks on the surface of the active material layer, and has excellent bending resistance, preferably 7 Mass% or less, more preferably 65 wt% or less, more preferably not more than 60 wt%.

  Examples of the carboxyl group-containing monomer include (meth) acrylic acid, maleic acid, fumaric acid, itaconic acid, and the like, but the present invention is not limited to such examples. These carboxyl group-containing monomers may be used alone or in combination of two or more. Among the carboxyl group-containing monomers, the battery resistance at low temperature is low even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, and the active material (Meth) acrylic acid is preferred from the viewpoint of obtaining an electrode for a lithium ion secondary battery that hardly causes pinholes and cracks on the surface of the layer and has excellent bending resistance.

  Even if the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the content of the carboxyl group-containing monomer in the monomer component is low battery resistance. From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is low, does not easily cause pinholes and cracks on the surface of the active material layer, and has excellent bending resistance, it is preferably 0.3% by mass or more, more preferably 0%. 5% by mass or more, more preferably 1% by mass or more, and battery resistance at low temperature even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is low, does not easily cause pinholes and cracks on the surface of the active material layer, and has excellent bending resistance, it is preferably 15% by mass or less, more preferably 10% by mass. , More preferably not more than 5 wt%.

  Examples of the nitrile group-containing monomer include (meth) acrylonitrile, but the present invention is not limited to such examples. These nitrile group-containing monomers may be used alone or in combination of two or more. Among the nitrile group-containing monomers, the battery resistance at low temperature is low even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, and the active material From the viewpoint of obtaining an electrode for a lithium ion secondary battery that hardly causes pinholes and cracks on the surface of the layer and has excellent bending resistance, acrylonitrile is preferred.

  The content of the nitrile group-containing monomer in the monomer component is 0% by mass or more. However, in order to increase the cohesive strength of the emulsion particles and increase the battery capacity of the lithium ion secondary battery, the active material layer is applied. Even when the amount of work is increased, the battery resistance at low temperature is low, the pinhole and crack are hardly generated on the surface of the active material layer, and an electrode for a lithium ion secondary battery excellent in bending resistance is obtained. From the viewpoint, it is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass or more. The coating of the active material layer is performed in order to increase the battery capacity of the lithium ion secondary battery. Even when the amount of work is increased, the battery resistance at low temperature is low, the pinhole and crack are hardly generated on the surface of the active material layer, and an electrode for a lithium ion secondary battery excellent in bending resistance is obtained. From the perspective Preferably 15 wt% or less, more preferably 10 wt% or less, more preferably not more than 5 wt%.

  Examples of nitrogen atom-containing monomers other than nitrile group-containing monomers include (meth) acrylamide compounds such as (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, and dimethylaminoethyl (meth) acrylate. And nitrogen atom-containing (meth) acrylates such as diethylaminoethyl (meth) acrylate, and the like, but the present invention is not limited to such examples. These nitrogen atom-containing monomers may be used alone or in combination of two or more. Among the nitrogen atom-containing monomers, the battery resistance at low temperature is low even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, and From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is resistant to pinholes and cracks on the surface of the material layer and has excellent bending resistance, a (meth) acrylamide compound and a nitrogen atom-containing (meth) acrylate are preferred, ) An acrylamide compound is more preferable, and (meth) acrylamide is more preferable.

  The content of the nitrogen atom-containing monomer other than the nitrile group-containing monomer in the monomer component is 0% by mass or more, but in order to increase the battery capacity of the lithium ion secondary battery, the active material layer is applied. Even when the amount of work is increased, the battery resistance at low temperature is low, the pinhole and crack are hardly generated on the surface of the active material layer, and an electrode for a lithium ion secondary battery excellent in bending resistance is obtained. From the viewpoint, it is preferably 0.3% by mass or more, more preferably 0.5% by mass or more, and still more preferably 1% by mass or more. The coating of the active material layer is performed in order to increase the battery capacity of the lithium ion secondary battery. Even when the amount of work is increased, the battery resistance at low temperature is low, the pinhole and crack are hardly generated on the surface of the active material layer, and an electrode for a lithium ion secondary battery excellent in bending resistance is obtained. From the viewpoint, preferred 20 mass% or less, more preferably 15 wt% or less, more preferably 10 mass% or less.

  In the monomer having an alicyclic structure, the alicyclic structure is preferably a cycloalkyl group having 4 to 20 carbon atoms, more preferably a cycloalkyl group having 4 to 10 carbon atoms. Examples of the monomer having an alicyclic structure include cycloalkyl (meth) acrylate and cycloalkylalkyl (meth) acrylate, and these monomers may be used alone or in combination of two or more. May be used in combination. Moreover, these monomers may have a substituent. Examples of the substituent include an alkyl group such as a methyl group and a tert-butyl group, a nitro group, a nitrile group, an alkoxyl group, an acyl group, a sulfone group, a hydroxyl group, and a halogen atom. It is not limited to illustration only.

  As the cycloalkyl (meth) acrylate, for example, a cycloalkyl group such as isobornyl (meth) acrylate, cyclohexyl (meth) acrylate and the like preferably has 4 to 20 carbon atoms, more preferably 4 to 10 cycloalkyl (meth) acrylates. However, the present invention is not limited to such examples. These cycloalkyl (meth) acrylates may be used alone or in combination of two or more. Examples of the cycloalkylalkyl (meth) acrylate include carbon numbers of cycloalkyl groups such as cyclohexylmethyl (meth) acrylate, cyclohexylethyl (meth) acrylate, cyclohexylpropyl (meth) acrylate, and 4-methylcyclohexylmethyl (meth) acrylate. Is preferably 4 to 20, more preferably 4 to 10, and examples thereof include cycloalkylalkyl (meth) acrylates having 1 to 4 carbon atoms in the alkyl group. These cycloalkylalkyl (meth) acrylates are Each may be used alone or in combination of two or more.

  Among the monomers having an alicyclic structure, the battery resistance at low temperature is low even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is resistant to pinholes and cracks on the surface of the active material layer and has excellent bending resistance, a cycloalkyl (meth) having a cycloalkyl group having 4 to 20 carbon atoms. An acrylate is preferable, a cycloalkyl (meth) acrylate having a cycloalkyl group having 4 to 10 carbon atoms is more preferable, and isobornyl (meth) acrylate and cyclohexyl (meth) acrylate are more preferable.

  Examples of the hydroxyl group-containing (meth) acrylate include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 4-hydroxy Examples include hydroxyl group-containing (meth) acrylates having 1 to 18 carbon atoms in ester groups such as butyl (meth) acrylate and glycerin mono (meth) acrylate, but the present invention is not limited to such examples. . These monomers may be used alone or in combination of two or more. Among these hydroxyl group-containing (meth) acrylates, even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low. 2-hydroxyethyl (meth) acrylate and glycerin mono (meth) acrylate are preferred from the viewpoint of obtaining an electrode for a lithium ion secondary battery that is resistant to pinholes and cracks on the surface of the active material layer and has excellent bending resistance. 2-hydroxyethyl (meth) acrylate is more preferable.

  Examples of the carbonyl group-containing monomer include acrolein, methacrolein, humylstyrene, vinyl ethyl ketone, acryloxyalkyl propenal, methacryloxyalkyl propenal, acetonyl acrylate, acetonyl methacrylate, diacetone acrylate, diacetone. Methacrylate, diacetone acrylamide, diacetone methacrylamide, 2-hydroxypropyl acrylate acetyl acetate, 2-hydroxypropyl methacrylate acetyl acetate, butanediol-1,4-acrylate acetyl acetate, 2- (acetoacetoxy) ethyl acrylate, 2- ( Acetoacetoxy) ethyl methacrylate and the like, but the present invention is not limited to such examples. . These carbonyl group-containing monomers may be used alone or in combination of two or more.

  Examples of the aromatic monomer include divinyl compounds such as styrene, α-methylstyrene, p-methylstyrene, tert-methylstyrene, chlorostyrene, aralkyl (meth) acrylate, vinyltoluene, and divinylbenzene. However, the present invention is not limited to such examples. Examples of the aralkyl (meth) acrylate include aralkyl having 7 to 18 carbon atoms such as benzyl (meth) acrylate, phenylethyl (meth) acrylate, methylbenzyl (meth) acrylate, naphthylmethyl (meth) acrylate and the like. Although (meth) acrylate etc. are mentioned, this invention is not limited only to this illustration. These aromatic monomers may be used alone or in combination of two or more.

  Examples of the silicon atom-containing monomer include vinyltrichlorosilane, vinyltris (β-methoxyethoxy) silane, vinyltrimethoxysilane, and vinyltriethoxysilane, but the present invention is limited to such examples. It is not a thing. These monomers may be used alone or in combination of two or more.

  Examples of the fluorine atom-containing monomer include fluorine atom-containing alkyl having 2 to 6 carbon atoms in an ester group such as trifluoroethyl (meth) acrylate, tetrafluoropropyl (meth) acrylate, and octafluoropentyl (meth) acrylate. Although (meth) acrylate etc. are mentioned, this invention is not limited only to this illustration. These monomers may be used alone or in combination of two or more.

  As a method for emulsion polymerization of the monomer component, for example, an aqueous medium containing a water-soluble organic solvent such as methanol and a lower alcohol, and water, an emulsifier is dissolved in a medium such as water, and a single amount is obtained under heating and stirring. A method of dropping a body component and a polymerization initiator, a method of dropping a monomer component previously emulsified with an emulsifier and water, into water or an aqueous medium, and the like. It is not limited. In addition, what is necessary is just to set the quantity of a medium suitably in consideration of the non volatile matter amount contained in the resin emulsion obtained.

  Examples of the emulsifier include an anionic emulsifier, a nonionic emulsifier, a cationic emulsifier, an amphoteric emulsifier, a polymer emulsifier, and a reactive emulsifier. These emulsifiers may be used alone or in combination of two or more. May be.

  Examples of the anionic emulsifier include alkyl sulfate salts such as ammonium dodecyl sulfate and sodium dodecyl sulfate; alkyl sulfonate salts such as ammonium dodecyl sulfonate and sodium dodecyl sulfonate; alkyl aryl sulfonate salts such as ammonium dodecyl benzene sulfonate and sodium dodecyl naphthalene sulfonate; Polyoxyethylene alkyl sulfate salts; polyoxyethylene alkyl aryl sulfate salts; dialkyl sulfosuccinates; aryl sulfonic acid-formalin condensates; fatty acid salts such as ammonium laurate, sodium stearate, polyoxyethylene polycyclic phenyl ether sulfates However, the present invention is limited to such examples. Not intended to be.

  Nonionic emulsifiers include, for example, polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, condensate of polyethylene glycol and polypropylene glycol, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, fatty acid monoglyceride, ethylene oxide and aliphatic Although the condensate with an amine etc. are mentioned, this invention is not limited only to this illustration.

  Examples of the cationic emulsifier include alkylammonium salts such as dodecylammonium chloride, but the present invention is not limited to such examples.

  Examples of amphoteric emulsifiers include betaine ester type emulsifiers, but the present invention is not limited to such examples.

  Examples of the polymer emulsifier include poly (meth) acrylates such as sodium polyacrylate; polyvinyl alcohol; polyvinyl pyrrolidone; polyhydroxyalkyl (meth) acrylates such as polyhydroxyethyl acrylate; single polymers constituting these polymers. Although the polymer etc. which use a 1 or more types of monomer of a monomer as a copolymerization component are mentioned, this invention is not limited only to this illustration.

  As the reactive emulsifier, for example, propenyl-alkylsulfosuccinic acid ester salt, (meth) acrylic acid polyoxyethylene sulfonate salt, (meth) acrylic acid polyoxyethylene phosphonate salt [for example, manufactured by Sanyo Chemical Industries, Ltd., Product name: Eleminol RS-30, etc.], polyoxyethylene alkylpropenyl phenyl ether sulfonate salt [for example, product name: Aqualon HS-10, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.], allyloxymethylalkyloxypolyoxyethylene Sulfonate salt [eg, Daiichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon KH-10, etc.], Sulphonate salt of allyloxymethylnonylphenoxyethylhydroxypolyoxyethylene [eg, ADEKA Corporation, trade name: ADEKA Rear soap SE-10 Allyloxymethylalkoxyethylhydroxy polyoxyethylene sulfate ester salt [for example, manufactured by ADEKA, trade name: Adekaria soap SR-10, SR-30, etc.], bis (polyoxyethylene polycyclic phenyl ether) Methacrylated sulfonate salts [for example, manufactured by Nippon Emulsifier Co., Ltd., trade name: Antox MS-60, etc.], allyloxymethylalkoxyethylhydroxypolyoxyethylene [for example, manufactured by ADEKA Corporation, trade name: Adeka Soap ER -20, etc.], polyoxyethylene alkylpropenyl phenyl ether [for example, manufactured by Daiichi Kogyo Seiyaku Co., Ltd., trade name: Aqualon RN-20, etc.], allyloxymethylnonylphenoxyethylhydroxypolyoxyethylene [for example, Co., Ltd. Made by ADEKA, quotient Name: Adeka such REASOAP NE-10) but the like, the present invention is not limited only to those exemplified.

  The amount of the emulsifier per 100 parts by mass of the monomer component is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more from the viewpoint of improving the monopolymerization stability. The battery of the lithium ion secondary battery Even when the coating amount of the active material layer is increased in order to increase the capacity, battery resistance at low temperature is low, pinholes and cracks do not easily occur on the surface of the active material layer, and bending resistance is improved. From the viewpoint of obtaining an excellent electrode for a lithium ion secondary battery, it is preferably 10 parts by mass or less, more preferably 7 parts by mass or less, and still more preferably 5 parts by mass or less.

  Examples of the polymerization initiator include azobisisobutyronitrile, 2,2-azobis (2-methylbutyronitrile), 2,2-azobis (2,4-dimethylvaleronitrile), 2,2-azobis ( Azo compounds such as 2-diaminopropane) hydrochloride, 4,4-azobis (4-cyanovaleric acid), 2,2-azobis (2-methylpropionamidine); persulfates such as ammonium persulfate and potassium persulfate; Examples of the peroxide include peroxides such as hydrogen peroxide, benzoyl peroxide, parachlorobenzoyl peroxide, lauroyl peroxide, and ammonium peroxide. However, the present invention is not limited to such examples. These polymerization initiators may be used alone or in combination of two or more.

  The amount of the polymerization initiator per 100 parts by mass of the monomer component is preferably 0.05 parts by mass or more, more preferably 0 from the viewpoint of increasing the polymerization rate and reducing the residual amount of the unreacted monomer component. .1 part by mass or more, and even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery, the battery resistance at low temperature is low, From the viewpoint of obtaining an electrode for a lithium ion secondary battery that hardly causes pinholes and cracks on the surface and has excellent bending resistance, it is preferably 1 part by mass or less, more preferably 0.5 part by mass or less.

  The method for adding the polymerization initiator is not particularly limited. Examples of the addition method include batch charging, divided charging, and continuous dripping. From the viewpoint of advancing the completion time of the polymerization reaction, a part of the polymerization initiator may be added to the flask before or after the monomer component is added to the reaction system.

  In order to accelerate the decomposition of the polymerization initiator, for example, an appropriate amount of a reducing agent such as sodium disulfite or sodium hydrogen sulfite, or a decomposition agent of a polymerization initiator such as transition metal salt such as ferrous sulfate in the reaction system. May be added.

  In addition, if necessary, additives such as chain transfer agents such as compounds having a thiol group such as tert-dodecyl mercaptan, pH buffering agents, chelating agents, and film-forming aids are added to the reaction system. May be. The amount of the additive per 100 parts by mass of the monomer component varies depending on the type and cannot be determined unconditionally, but is usually preferably 0.01 to 5 parts by mass, more preferably 0.1 to 3 parts. Part by mass.

  The atmosphere for emulsion polymerization of the monomer component is not particularly limited, but is preferably an inert gas such as nitrogen gas from the viewpoint of increasing the efficiency of the polymerization initiator.

  Although the polymerization temperature at the time of carrying out emulsion polymerization of a monomer component does not have limitation, Usually, Preferably it is 50-100 degreeC, More preferably, it is 60-95 degreeC. The polymerization temperature may be constant or may be changed during the polymerization reaction.

  The polymerization time for emulsion polymerization of the monomer component is not particularly limited and may be appropriately set according to the progress of the polymerization reaction, but is usually about 2 to 9 hours.

  Emulsion particles are obtained by emulsion polymerization of the monomer component as described above.

  The polymer constituting the emulsion particles may have a crosslinked structure. The weight average molecular weight of the polymer is preferably 100,000 or more, more preferably 300,000 or more, further preferably 550,000 or more, from the viewpoint of improving the binding properties between the active materials and the active material and the current collector. More preferably, it is 600,000 or more. The upper limit of the weight average molecular weight of the polymer is not particularly limited because it is difficult to measure the weight average molecular weight when it has a crosslinked structure, but when it does not have a crosslinked structure, it should be 5 million or less. Is preferred.

  In addition, in this specification, the weight average molecular weight of a polymer uses gel permeation chromatography [manufactured by Tosoh Corporation, product number: HLC-8120GPC, column: TSKgel G-5000HXL and TSKgel GMHXL-L in series. ] Is used to mean the weight average molecular weight (in terms of polystyrene) measured.

  The average particle diameter of the emulsion particles is preferably 50 nm or more, more preferably 100 nm or more, from the viewpoint of improving the mechanical stability of the emulsion particles themselves, and the binding properties between the active materials and between the active material and the current collector. From the viewpoint of improving the thickness, it is preferably 300 nm or less, more preferably 200 nm or less.

  In the present specification, the average particle size of the emulsion particles is measured using a particle size distribution measuring instrument (manufactured by Particle Sizing Systems, trade name: NICOMP Model 380) by a dynamic light scattering method. It means the volume average particle diameter.

  The nonvolatile content in the resin emulsion is preferably 30% by mass or more, more preferably 40% by mass or more from the viewpoint of improving productivity, and preferably 70% by mass or less, more preferably from the viewpoint of improving handleability. 60% by mass or less.

The non-volatile content in the resin emulsion was determined by weighing 1 g of the resin emulsion and drying it with a hot air dryer at a temperature of 150 ° C. for 30 minutes.
[Non-volatile content in resin emulsion (mass%)]
= ([Residue mass] / [resin emulsion 1 g]) × 100
Means the value obtained based on

  The content of the emulsion particles in the nonvolatile content of the binder composition for an electrode of the present invention is low even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. From the viewpoint of obtaining an electrode for a lithium ion secondary battery that has low battery resistance, has no pinholes and cracks on the surface of the active material layer, and has excellent bending resistance, it is preferably 70% by mass or more, more preferably Is 80% by mass or more, more preferably 85% by mass or more, and still more preferably 90% by mass or more, when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery Even in such a case, the battery resistance at low temperature is low, the surface of the active material layer is hard to cause pinholes and cracks, and an electrode for a lithium ion secondary battery having excellent bending resistance is obtained. From the viewpoint, preferably 99 wt% or less, more preferably 98 wt% or less, more preferably not more than 97 wt%.

  As described above, a resin emulsion containing emulsion particles can be obtained.

  The electrode binder composition of the present invention includes, for example, a compound having a sulfonyl group and an oxycarbonyl group represented by the formula (I), a resin component and a resin emulsion containing emulsion particles in the form of a solvent and optionally other components. Etc. can be easily prepared by mixing them.

  The electrode binder composition of the present invention may contain other resin components, emulsion particles, and the like as long as the object of the present invention is not impaired.

  The composition for electrodes of the lithium ion secondary battery of the present invention contains the binder composition for electrodes of the present invention and an active material. Since the composition for an electrode of a lithium ion secondary battery of the present invention contains the binder composition for an electrode of the present invention and an active material, the active material layer is applied to increase the battery capacity of the lithium ion secondary battery. Even when the amount of work is increased, battery resistance at low temperatures is low, pinholes and cracks are hardly generated on the surface of the active material layer, and the bending resistance is excellent.

  The composition for electrodes of the lithium ion secondary battery of the present invention can be prepared, for example, by mixing the binder composition for electrodes of the present invention, an active material, and other components as necessary.

  The composition for electrodes of the lithium ion secondary battery of the present invention includes a composition for positive electrodes and a composition for negative electrodes. The binder composition for an electrode of the present invention has a low battery resistance at a low temperature even when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. From the viewpoint of obtaining an electrode for a lithium ion secondary battery that is less prone to pinholes and cracks on the surface of the layer and has excellent bending resistance, it can be suitably used for any composition.

  The binder composition for electrodes and the conductive additive of the present invention can be used for the positive electrode composition of the lithium ion secondary battery. A conductive support agent is used in order to improve the output of a lithium ion secondary battery. As the conductive assistant, conductive carbon is mainly used. Examples of the conductive carbon include carbon black, fiber-like carbon, and graphite. However, the present invention is not limited to such examples. Among these conductive assistants, carbon black is preferable. Examples of carbon black include ketjen black and acetylene black, but the present invention is not limited to such examples.

  The positive electrode active material used for the positive electrode composition of the lithium ion secondary battery is preferably a positive electrode active material capable of occluding or releasing lithium ions. Examples of the compound capable of inserting or extracting lithium ions include lithium-containing metal oxides. Examples of the metal oxide containing lithium include lithium cobalt oxide, lithium iron phosphate, lithium manganese phosphate, lithium manganate, lithium nickel manganese cobalt oxide, and lithium nickel cobalt aluminum composite oxide. The invention is not limited to such examples. These positive electrode active materials may be used alone or in combination of two or more.

  In the composition for the positive electrode of the lithium ion secondary battery, as other components, if necessary, for example, (meth) acrylic polymer, nitrile polymer, non-fluorine polymer such as diene polymer, polytetrafluoroethylene, etc. Polymers such as fluoropolymers, surfactants such as anionic surfactants, nonionic surfactants, and cationic surfactants; dispersants such as polymer dispersants such as styrene-maleic acid copolymers and polyvinylpyrrolidone , Thickeners, preservatives and the like may be included.

  From the viewpoint of improving the output characteristics and electrical characteristics of the lithium ion secondary battery, the content of the nonvolatile content of the electrode binder composition in the nonvolatile content of the aqueous positive electrode composition for a lithium ion secondary battery is preferably 0.2 to 7 mass%, More preferably, it is 0.5-5 mass%, The content rate of a positive electrode active material becomes like this. Preferably it is 60-98.9 mass%, More preferably, it is 70-98.8 mass%, More preferably, it is 80 ˜98.3 mass%. The content of the conductive assistant in the nonvolatile content of the aqueous positive electrode composition for a lithium ion secondary battery is preferably 0.5 to 30% by mass from the viewpoint of improving the output characteristics and electrical characteristics of the lithium ion secondary battery. Preferably it is 1-20 mass%, More preferably, it is 1.5-10 mass%. The content of other components in the nonvolatile content of the aqueous positive electrode composition for a lithium ion secondary battery is preferably 0 to 20% by mass, more preferably from the viewpoint of improving the output characteristics and electrical characteristics of the lithium ion secondary battery. It is 0-15 mass%, More preferably, it is 0-10 mass%.

  The viscosity of the electrode composition for a lithium ion secondary battery measured using a viscometer [manufactured by Toki Sangyo Co., Ltd., product number: TVB-10] at a temperature of 25 ± 1 ° C. and 30 rpm is the electrode From the viewpoint of accurately coating the dispersion stability of the composition and the desired coating amount, the viscosity is preferably 500 to 5000 mPa · s, more preferably 1000 to 3000 mPa · s.

  Moreover, the pH at 25 ° C. of the positive electrode composition of the lithium ion secondary battery is preferably 5 to 11 and more preferably 6 to 10 from the viewpoint of suppressing corrosion of the current collector. The pH is a value measured using a glass electrode type hydrogen ion thermometer [manufactured by Horiba, Ltd., product number: F-21].

  The composition for the positive electrode of the lithium ion secondary battery is, for example, mixed with a binder composition for an electrode, an active material, a conductive additive and other components as necessary, and dispersed using a bead mill, a ball mill, a stirring type mixer, or the like. Can be obtained.

  The binder composition for electrodes of the present invention and the conductive auxiliary agent can be used for the negative electrode composition of the lithium ion secondary battery.

  Examples of the negative electrode active material used in the negative electrode composition of a lithium ion secondary battery include carbon materials such as graphite, natural graphite, and artificial graphite, polyacene conductive polymers, composite metal oxides such as lithium titanate, lithium Although an alloy etc. are mentioned, this invention is not limited only to this illustration. These negative electrode active materials may be used alone or in combination of two or more. Among these negative electrode active materials, a carbon material and lithium titanate are preferable. The content of the carbon material and / or lithium titanate in the negative electrode active material is preferably 50 to 100% by mass, more preferably 70 to 100% by mass, and still more preferably 80 to 100% by mass.

  If necessary, the composition for negative electrode of a lithium ion secondary battery may contain, for example, a conductive additive, a dispersant, a thickener, a preservative, and the like.

  The content of the non-volatile content of the electrode binder composition in the non-volatile content of the negative electrode composition of the lithium ion secondary battery is preferably 0.3 to from the viewpoint of improving the rate characteristics and electrical characteristics of the lithium ion secondary battery. It is 7 mass%, More preferably, it is 0.5-5 mass%. The content of the negative electrode active material in the nonvolatile content of the negative electrode composition of the lithium ion secondary battery is preferably 60 to 99.9% by mass from the viewpoint of improving the rate characteristics and electrical characteristics of the lithium ion secondary battery. Preferably it is 70-99.7 mass%, More preferably, it is 80-99.5 mass%. The content of the conductive additive in the nonvolatile content of the negative electrode composition of the lithium ion secondary battery is preferably 0.5 to 30% by mass from the viewpoint of improving rate characteristics and electrical characteristics of the lithium ion secondary battery. Preferably it is 1-20 mass%, More preferably, it is 1.5-10 mass%. The content of other components in the nonvolatile content of the negative electrode composition of the lithium ion secondary battery is preferably 0 to 20% by mass, more preferably from the viewpoint of improving the rate characteristics and electrical characteristics of the lithium ion secondary battery. It is 0-15 mass%, More preferably, it is 0-10 mass%.

  Moreover, the pH at 25 degreeC of the composition for negative electrodes of a lithium ion secondary battery is 5-11, preferably 6-10 from a viewpoint of stabilizing the dispersion state of an active material. The pH is a value measured using a glass electrode type hydrogen ion thermometer [manufactured by Horiba, Ltd., product number: F-21].

  The composition for the negative electrode of the lithium ion secondary battery is, for example, mixed with a binder composition for an electrode, a negative electrode active material, a conductive auxiliary agent and other components as necessary, and dispersed using a bead mill, a ball mill, a stirring type mixer, etc. Can be obtained.

  The electrode for a lithium ion secondary battery of the present invention is an electrode having a current collector and an active material layer, and the active material layer is formed from the composition for an electrode of the lithium ion secondary battery of the present invention.

  Since the electrode composition for a lithium ion secondary battery of the present invention is used for the active material layer constituting the electrode, the electrode for the lithium ion secondary battery of the present invention has a battery capacity of the lithium ion secondary battery. Even when the coating amount of the active material layer is increased in order to increase the resistance, the battery resistance at low temperature is low, pinholes and cracks do not easily occur on the surface of the active material layer, and the bending resistance is excellent. ing.

  In addition, a positive electrode and a negative electrode are used for the lithium ion secondary battery of this invention. The positive electrode has a positive electrode active material layer formed on the surface of the positive electrode current collector, and the negative electrode has a negative electrode active material layer formed on the surface of the negative electrode current collector. Examples of the positive electrode current collector include aluminum, aluminum alloys, SUS (stainless steel), and conductive metals such as titanium. However, the present invention is not limited to such examples. Among these, aluminum is preferable from the viewpoints of workability and economy. Examples of the negative electrode current collector include conductive metals such as copper, iron, nickel, silver, and stainless steel (SUS). However, the present invention is not limited to such examples. Among these, copper is preferable from the viewpoint of workability.

  The electrode for a lithium ion secondary battery of the present invention can be produced, for example, by forming an active material layer made of the composition for an electrode of the lithium ion secondary battery of the present invention on the surface of a current collector.

  Examples of a method for producing an electrode in which an active material layer made of the composition for an electrode of the lithium ion secondary battery of the present invention is formed on the surface of a current collector include, for example, a cast coating method, a spin coating method, and a blade coating method. The electrode composition of the lithium ion secondary battery of the present invention is collected by a printing method such as dip coating method, roll coating method, bar coating method, die coating method, ink jet method, relief printing, intaglio printing, planographic printing, screen printing After coating on one side of the body and forming a coating film, it is dried using a hot plate, oven, etc. if necessary, and further stretched uniaxially or multiaxially using a roll press etc. However, the present invention is not limited to such examples.

From the viewpoint of increasing the battery capacity of the lithium ion secondary battery, the coating weight after drying of the positive electrode active material layer formed on the surface of the current collector is preferably 12 mg / cm ² or more, more preferably 14 mg / cm ^2. cm ^{2 or} more, even when increasing the coat weight of the active material layer in order to increase the battery capacity of the lithium ion secondary battery, low battery resistance at low temperatures, the surface of the active material layer From the viewpoint of obtaining an electrode for a lithium ion secondary battery that hardly causes pinholes or cracks and has excellent bending resistance, it is preferably 30 mg / cm ² or less, more preferably 26 mg / cm ² or less. In the positive electrode of the present invention, even if the coating weight of the active material layer is large as described above, pinholes and cracks do not easily occur on the surface of the active material layer and are excellent in bending resistance. Therefore, the battery capacity of the lithium ion secondary battery can be increased because the coating weight of the active material layer can be increased as compared with the coating weight (about 8 to 10 mg / cm ² ).

The coating weight after drying of the negative electrode active material layer formed on the surface of the current collector is preferably 6 mg / cm ² or more, more preferably 8 mg / cm ² from the viewpoint of increasing the battery capacity of the lithium ion secondary battery. cm ^{2 or} more, even when increasing the coat weight of the active material layer in order to increase the battery capacity of the lithium ion secondary battery, low battery resistance at low temperatures, the surface of the active material layer From the viewpoint of obtaining an electrode for a lithium ion secondary battery that hardly causes pinholes or cracks and has excellent bending resistance, it is preferably 15 mg / cm ² or less, more preferably 12 mg / cm ² or less. In the negative electrode according to the present invention, even if the coating weight of the active material layer is large as described above, the surface of the active material layer hardly causes pinholes and cracks, and has excellent bending resistance. can be increased in comparison with the coat weight of the active material layer (3-5 mg / cm ² or so), it is possible to increase the battery capacity of the lithium ion secondary battery.

  The electrode of the present invention obtained as described above is not liable to cause pinholes and cracks on the surface of the active material layer, and is excellent not only in bending resistance but also in low battery resistance at low temperatures. It can use suitably for the electrode of a secondary battery.

  The lithium ion secondary battery of this invention has the said electrode for lithium ion secondary batteries. Since the electrode for a lithium ion secondary battery is used as the electrode of the lithium ion secondary battery of the present invention, the lithium ion secondary battery has a large battery capacity and a low battery resistance at low temperatures. Can be obtained.

  In the lithium ion secondary battery of the present invention, the lithium ion secondary battery electrode may be used for the positive electrode or the negative electrode, and may be used for both the positive electrode and the negative electrode. From the viewpoint of obtaining a lithium ion secondary battery that is large and has low battery resistance at low temperatures, it is preferably used for at least the positive electrode.

  The lithium ion secondary battery of the present invention is, for example, stored in a battery case with the electrode for the lithium ion secondary battery of the present invention and the counter electrode facing each other through a separator impregnated with an electrolytic solution. However, the present invention is not limited to such examples.

As the electrolytic solution, an electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent can be used. Examples of the supporting electrolyte include lithium salts. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi , (FSO ₂ ) ₂ NLi, (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) ₂ NLi, and the like, but the present invention is not limited to such examples. These supporting electrolytes may be used alone or in combination of two or more.

  Examples of the organic solvent include carbonates such as dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, diethyl carbonate, propylene carbonate, butylene carbonate, and methyl ethyl carbonate, esters such as γ-butyrolactone and methyl formate, and 1,2-dimethoxyethane. And ethers such as tetrahydrofuran, and the like, but the present invention is not limited to such examples. These organic solvents may be used alone or in combination of two or more.

  In addition, as the solvent, for example, a viscosity-adjusting polymer or a gelling agent and a highly viscous one or a gelled one can be used. Examples of the viscosity adjusting polymer include polyacrylonitrile, carboxymethylcellulose, polyvinyl chloride, polyethylene oxide, polypropylene oxide, polyurethane, polyacrylate, polymethacrylate, polyamide, polyacrylamide, polyester, and polyvinylidene fluoride. The invention is not limited to such examples. These polymers for adjusting viscosity may be used alone or in combination of two or more.

  Examples of the separator include cotton, rayon, acetate, nylon, glass, polyester, polyethylene, polypropylene, polyimide, fluororesin, and epoxy resin, but the present invention is not limited to such examples.

  Since the lithium ion secondary battery of the present invention obtained as described above uses the lithium ion secondary battery electrode of the present invention, the battery capacity of the lithium ion secondary battery is large and the battery resistance at low temperature is high. Has the advantage of low.

  In addition, the electric capacity maintenance factor after 50 cycles after repeating 50 times of charge / discharge of the lithium ion secondary battery of this invention becomes like this. Preferably it is 85% or more, More preferably, it is 95% or more.

  EXAMPLES Next, although this invention is demonstrated further in detail based on an Example, this invention is not limited only to this Example.

Preparation Example 1
In a four-necked separable flask equipped with a stirrer, a thermometer, a cooler, a nitrogen gas inlet tube and a dropping funnel, 494.5 parts by mass of ion-exchanged water was charged. While maintaining the internal temperature of the flask at 75 ° C., nitrogen gas was gently allowed to flow into the flask under stirring to completely replace the inside of the flask with nitrogen gas.

  It consists of 366.3 parts by mass of an aqueous 2.7% by mass polyoxyethylene polycyclic phenyl ether sulfate ester salt, 705 parts by mass of methyl acrylate, 250 parts by mass of butyl acrylate, 20 parts by mass of acrylic acid and 25 parts by mass of N-methylolacrylamide. A pre-emulsion was prepared by mixing the monomer components so as to have a uniform composition.

  Using ammonium persulfate as a polymerization initiator, 3.5 parts by mass of ammonium persulfate was dissolved in 66.5 parts by mass of ion-exchanged water to prepare an aqueous ammonium persulfate solution. Moreover, using sodium disulfite as a reducing agent, 1.5 parts by mass of sodium disulfite was dissolved in 58.5 parts by mass of ion-exchanged water to prepare a sodium disulfite aqueous solution.

  While maintaining the temperature in the flask at 75 ° C., the pre-emulsion, the ammonium persulfate aqueous solution and the sodium disulfite aqueous solution obtained above were uniformly dropped into the flask over 2 hours. After completion of the dropwise addition, stirring was continued for 1.5 hours while maintaining the internal temperature of the flask at 75 ° C., and then the reaction was terminated by cooling to obtain a resin emulsion X having a nonvolatile content of 50% by mass. It was.

Production Example 1
While stirring the resin emulsion X obtained above, the mass ratio of the resin emulsion X to the sulfobenzoic anhydride aqueous solution (resin emulsion X / sulfobenzoic anhydride aqueous solution) is 10 mass% sulfobenzoic anhydride aqueous solution. After mixing so that it may become 100/25, the binder for electrodes whose pH in 25 degreeC is 6.7 is mixed by mixing the obtained mixture, 5% lithium hydroxide monohydrate aqueous solution, and ion-exchange water. Composition A was obtained.

  In addition, pH at 25 degreeC of the binder composition A for electrodes was measured using the glass electrode type hydrogen ion thermometer [Corporation | KK Horiba, product number: F-21].

  Moreover, when the non volatile matter content in the electrode binder composition A obtained above was measured, the said non volatile matter content was 33 mass%.

The nonvolatile content in each resin emulsion and each electrode binder composition was measured by weighing about 1 g of the resin emulsion or electrode binder composition in an aluminum dish and drying it in a hot air dryer at 150 ° C. for 30 minutes. From the mass before and after, the formula:
[Non-volatile content (mass%)] = [(mass after drying) ÷ (mass before drying)] × 100
It is a value when calculated based on.

  Next, the viscosity of the electrode binder composition A obtained above was measured using a viscometer [manufactured by Toki Sangyo Co., Ltd., product number: TVB-10] under the condition of 30 rpm at a temperature of 25 ± 1 ° C. did. As a result, the viscosity of the binder composition A for electrodes was 50 mPa · s.

Comparative production example 1
An electrode binder composition B was obtained by adding an aqueous solution of 5% lithium hydroxide monohydrate and ion-exchanged water to the resin emulsion X obtained above and stirring.

  It was 6.7 when pH at 25 degrees C of the binder composition B for electrodes obtained above was measured like manufacture example 1. When the viscosity at 25 ± 1 ° C. of the electrode binder composition B obtained above was measured in the same manner as in Production Example 1, the viscosity was 2310 mPa · s. Moreover, when the non-volatile content of the binder composition B for electrodes obtained above was measured in the same manner as in Production Example 1, the non-volatile content was 40% by mass.

Example 1
2 parts by mass of carboxymethylcellulose [Daiichi Kogyo Seiyaku Co., Ltd., trade name: Cellogen BSH-6] 75 parts by mass of aqueous solution and 7 parts by mass of acetylene black powder [Denki Kagaku Kogyo Co., Ltd.] have a uniform composition. To obtain a mixture.

  100 parts by mass of lithium nickel manganese cobaltate [trade name: Cellseed NMC111] manufactured by Nippon Kagaku Kogyo Co., Ltd. is added to the mixture obtained above, and mixed to obtain a uniform composition, and ion-exchanged water is added. After adjusting so that the non-volatile content of a mixture might be 50-60 mass%, the composition for electrodes was obtained by adding 4.5 mass parts of binder composition A for electrodes to the said mixture.

Next, using an aluminum foil as a current collector, the electrode composition obtained above was applied to one surface of the aluminum foil with an applicator so that the thickness at the time of application was 180 μm, and the inside temperature was After drying for 10 minutes in a hot air oven set at 80 ° C., the active material having a coating amount of 12 mg / cm ² after drying on the surface of the aluminum foil is pressed with a roll press at a linear pressure of 5 kN. A sheet-like electrode having a layer formed thereon was obtained.

Comparative Example 1
In Example 1, a sheet-like electrode was produced in the same manner as in Example 1 except that the electrode binder composition B was used instead of the electrode binder composition A.

  Next, using the electrodes obtained in Example 1 and Comparative Example 1, the appearance, bending resistance and battery resistance at low temperature of the active material layer of the electrodes were examined based on the following methods.

[Appearance of active material layer]
The appearance of the active material layer of the electrode was visually observed and evaluated based on the following evaluation criteria.

(Evaluation criteria)
A: No abnormality in the appearance of the active material layer B: Pinhole-like defects are observed in the appearance of the active material layer.
Δ: In addition to pinhole-like defects, small cracks are observed in the appearance of the active material layer.
X: In addition to pinhole-like defects, large cracks are recognized in the appearance of the active material layer.

[Bending resistance]
A test piece was produced by cutting the electrode into a rectangle 3 cm long and 5 cm wide. After the test piece was bent at an angle of 180 degrees, it was returned to its original state, the appearance at that time was visually observed, and the bending resistance was evaluated based on the following evaluation criteria.

(Evaluation criteria)
(Double-circle): The coating film does not fall off by bending a test piece.
○: Slight dropout of the coating film due to bending of the test piece is observed.
X: The fall of the coating film by bending of a test piece is clearly recognized.

[Battery resistance at low temperature]
(1) Production of coin cell type lithium ion secondary battery A positive electrode is produced by punching the electrode obtained above into a circle having a diameter of 12 mm, and a negative electrode is produced by punching a metal lithium plate into a circle having a diameter of 14 mm. A separator was prepared by punching a polyethylene film (thickness: 16 μm) into a circle having a diameter of 16 mm.

  Next, coin-type battery parts [manufactured by Hosen Co., Ltd., product number: CR2032, positive electrode case (material: SUS304L), negative electrode cap (material: SUS316L), spacer (thickness: 1 mm, material: SUS316L), wave washer (Material: SUS316L), gasket (material: polypropylene)] was used to produce a coin-type lithium battery.

More specifically, a negative electrode cap equipped with a gasket, a wave washer, a spacer, and a negative electrode are stacked in this order, non-aqueous electrolyte [manufactured by Kishida Chemical Co., Ltd., product number: LBG-94893, electrolyte: LiPF ₆ (1 mol / L) Solvent: mixed solvent consisting of 30% by volume of ethylene carbonate and 70% by volume of ethyl methyl carbonate] After 35 μL was dropped on the negative electrode surface, a polyethylene separator was placed, and 35 μL of the non-aqueous electrolyte solution was placed on the surface of the separator. It was dripped.

  Next, the positive electrode was placed so that the active material layer faced the separator, and the positive electrode case was stacked thereon and crimped with a crimping machine, thereby producing a coin cell type lithium ion secondary battery.

(2) Measurement of battery resistance at low temperature Using a charge / discharge measuring device [manufactured by Asuka Electronics Co., Ltd., product number: ACD-001], the coin cell type lithium ion secondary battery obtained above in an atmosphere at 25 ° C. Is charged at a current value of C rate 0.2 and a constant voltage of 4.2V until the current value drops to C rate 0.02, and then a constant current discharge is performed to a current value of C rate 0.2 to 2.7V. I did it.

  Next, after charging again under the above conditions, constant current discharge was performed for 0.5 hour at a C rate of 1.0, and the state of charge capacity was adjusted to 50%. Thereafter, the temperature of the atmosphere was changed to −20 ° C., and after sufficient time for the temperature to stabilize, discharging was performed at a C rate of 0.2 seconds for 10 seconds, thereby obtaining current and voltage measurement data. In the same manner as described above, by discharging for 10 seconds at C rate 0.5, discharging for 10 seconds at C rate 1, discharging for 10 seconds at C rate 2, and discharging for 10 seconds at C rate 3, current and voltage at each C rate Measurement data was obtained.

  The current of each C rate obtained above is plotted on the x-axis, the voltage when discharged at each C rate is plotted on the y-axis, and a linear approximation curve (y = Ax + B) is created from the plotted points. The resistance value was determined from the absolute value of the slope A of the curve.

  The battery resistance at low temperature of the electrode obtained in Example 1 based on the battery resistance at low temperature of the electrode obtained in the conventional Comparative Example 1 was relatively evaluated based on the following evaluation criteria.

(Evaluation criteria)
A: Low temperature resistance value is less than 65% of the low temperature resistance value of Comparative Example 1. B: Low temperature resistance value is 65% or more and less than 75% of the low temperature resistance value of Comparative Example 1. Δ: Low temperature resistance value is the low temperature resistance of Comparative Example 1. 75% or more of value, less than 100% x: Low temperature resistance value is 100% or more of low temperature resistance value of Comparative Example 1

  From the above results, in the electrode obtained in Example 1, the external appearance evaluation is ◎, the bending resistance evaluation is ◎, and the low-temperature resistance evaluation compared with the battery obtained in Comparative Example 1 is Whereas, the electrode obtained in Comparative Example 1 had an evaluation of the appearance of x, and the evaluation of the bending resistance was x.

  Therefore, the electrode obtained in Example 1 is compared with the electrode obtained in Comparative Example 1 when the coating amount of the active material layer is increased in order to increase the battery capacity of the lithium ion secondary battery. However, the battery resistance at low temperature is low, pinholes and cracks do not easily occur on the surface of the active material layer, and it is excellent in bending resistance. Therefore, it can be suitably used for a lithium ion secondary battery. I understand that I can do it.

Claims (4)

  A binder composition used for an electrode composition for forming an active material layer of an electrode for a lithium ion secondary battery, comprising a compound having a sulfonyl group and an oxycarbonyl group, a resin component, and a solvent. A binder composition for an electrode of a lithium ion secondary battery.   The composition for electrodes of the lithium ion secondary battery formed by containing the binder composition for electrodes of Claim 1, and an active material.   The electrode for lithium ion secondary batteries which is an electrode which has a collector and an active material layer, Comprising: The said active material layer is formed from the composition for electrodes of the lithium ion secondary battery of Claim 2.   The lithium ion secondary battery which has an electrode for lithium ion secondary batteries of Claim 3.