WO2018037867A1 - 非水系二次電池機能層用組成物、非水系二次電池用機能層、非水系二次電池、および非水系二次電池用電極の製造方法 - Google Patents
非水系二次電池機能層用組成物、非水系二次電池用機能層、非水系二次電池、および非水系二次電池用電極の製造方法 Download PDFInfo
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- H—ELECTRICITY
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- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/04—Processes of manufacture in general
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- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/058—Construction or manufacture
- H01M10/0585—Construction or manufacture of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
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- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H01M10/4235—Safety or regulating additives or arrangements in electrodes, separators or electrolyte
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- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
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- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
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- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
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- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
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- H—ELECTRICITY
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- H01M50/00—Constructional details or processes of manufacture of the non-active parts of electrochemical cells other than fuel cells, e.g. hybrid cells
- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/451—Separators, membranes or diaphragms characterised by the material having a layered structure comprising layers of only organic material and layers containing inorganic material
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- H01M50/46—Separators, membranes or diaphragms characterised by their combination with electrodes
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- H01M50/40—Separators; Membranes; Diaphragms; Spacing elements inside cells
- H01M50/409—Separators, membranes or diaphragms characterised by the material
- H01M50/449—Separators, membranes or diaphragms characterised by the material having a layered structure
- H01M50/454—Separators, membranes or diaphragms characterised by the material having a layered structure comprising a non-fibrous layer and a fibrous layer superimposed on one another
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- the present invention relates to a non-aqueous secondary battery functional layer composition, a non-aqueous secondary battery functional layer, a non-aqueous secondary battery, and a non-aqueous secondary battery electrode including a functional layer for a non-aqueous secondary battery. It is about the method.
- Non-aqueous secondary batteries such as lithium ion secondary batteries (hereinafter sometimes simply referred to as “secondary batteries”) have the characteristics of being small and light, having high energy density, and capable of repeated charge and discharge. Yes, it is used for a wide range of purposes.
- the non-aqueous secondary battery generally includes a battery member such as a positive electrode, a negative electrode, and a separator that separates the positive electrode and the negative electrode and prevents a short circuit between the positive electrode and the negative electrode.
- a battery member having a functional layer that imparts desired performance (for example, heat resistance and strength) to the battery member is used.
- a separator in which a functional layer is formed on a separator base material, or an electrode in which a functional layer is formed on an electrode base material in which an electrode mixture layer is provided on a current collector It is used as a battery member.
- a functional layer that can improve the heat resistance and strength of the battery member a functional layer made of a porous film layer formed by binding non-conductive particles with a binder is used.
- this functional layer apply
- a binder comprising a polymer unit of a vinyl monomer having a hydrophilic acidic group, a non-conductive organic particle having a functional group capable of crosslinking with the hydrophilic acidic group,
- a porous film By forming a porous film using a slurry for a secondary battery porous film containing a solvent, non-conductive organic particles are prevented from falling off (pouring off) from the porous film, and the flexibility of the porous film is reduced. Improvement techniques have been proposed.
- the functional layer is required to exhibit battery characteristics (such as cycle characteristics and output characteristics) excellent in the secondary battery.
- the functional layer formed using the functional layer composition of Patent Document 1 described above cannot exhibit excellent battery characteristics for the secondary battery.
- the organic particles used in the functional layer composition of Patent Document 1 are likely to elute in the electrolytic solution, and the shape thereof may not be sufficiently maintained. Therefore, the functional layer formed using the composition for the functional layer cannot exhibit sufficient adhesion in the electrolytic solution, and the battery characteristics (particularly, cycle characteristics) of the non-aqueous secondary battery are deteriorated.
- the functional layer composition of Patent Document 1 has room for improvement in terms of enhancing the adhesion of the functional layer after immersion in the electrolyte and exhibiting excellent battery characteristics for the secondary battery. .
- the present invention provides a non-aqueous secondary battery capable of forming a functional layer for a non-aqueous secondary battery that is excellent in adhesiveness after immersion in an electrolyte and that can exhibit excellent cycle characteristics and output characteristics in a non-aqueous secondary battery. It aims at providing the composition for secondary battery functional layers. Another object of the present invention is to provide a functional layer for a non-aqueous secondary battery that can exhibit excellent cycle characteristics and output characteristics of the non-aqueous secondary battery. And an object of this invention is to provide the non-aqueous secondary battery which is excellent in cycling characteristics and output characteristics. Furthermore, an object of the present invention is to provide a method for producing an electrode for a non-aqueous secondary battery that can exhibit excellent cycle characteristics and output characteristics for the non-aqueous secondary battery.
- the present inventor has intensively studied for the purpose of solving the above problems. Then, the present inventor has a functional layer containing, as non-conductive particles, organic particles whose elution amount with respect to an electrolytic solution under a predetermined condition (hereinafter referred to as “electrolytic solution elution amount”) is within a predetermined range.
- electrolytic solution elution amount organic particles whose elution amount with respect to an electrolytic solution under a predetermined condition
- the present inventors have found that the use of the composition for use can improve the adhesion of the obtained functional layer after immersion in the electrolyte and improve the battery characteristics of the secondary battery.
- the present invention aims to advantageously solve the above problems, and the composition for a non-aqueous secondary battery functional layer of the present invention includes organic particles and a functional layer binder,
- the electrolyte solution elution amount of the organic particles is 0.001% by mass or more and 5.0% by mass or less.
- a functional layer having excellent adhesion after immersion in the electrolyte solution can be obtained. If this functional layer is used, the secondary battery can exhibit excellent cycle characteristics and output characteristics.
- the “electrolytic solution elution amount” of the organic particles can be measured using the method described in the examples of the present specification.
- the organic particles contain 5.0% by mass or more and 85% by mass or less of a crosslinkable monomer unit.
- the organic particles include the crosslinkable monomer unit in the above-described ratio, the adhesiveness of the functional layer after being immersed in the electrolytic solution can be further improved, and the cycle characteristics and output characteristics of the secondary battery can be further improved.
- the polymer such as organic particles “contains a monomer unit” means “a polymer-derived structural unit is contained in a polymer obtained using the monomer. "Means.
- the nonaqueous secondary battery functional layer composition of the present invention preferably has a volume average particle diameter D A of the organic particles is preferably at 0.01 ⁇ m or 2.0 ⁇ m or less.
- D A (D50) of the organic particles is within the above range, the metal such as lithium is prevented from being deposited on the electrode surface, and the cycle characteristics and output characteristics of the secondary battery are further improved. be able to.
- the “volume average particle diameter” of the organic particles can be measured using the method described in the examples of the present specification.
- the content of the organic particles is 1% by mass or more and 99% by mass or less of the total content of the organic particles and the functional layer binder. It is preferable that If the ratio of the content of the organic particles in the total content of the organic particles and the binder for the functional layer is within the above range, the adhesion of the functional layer before immersion in the electrolyte solution is ensured to prevent powder falling. On the other hand, when the battery member having the functional layer is stored and transported, the battery member is prevented from sticking through the functional layer (that is, the blocking resistance of the battery member having the functional layer is improved). be able to. And while suppressing metal, such as lithium, depositing on the electrode surface, the cycling characteristics and output characteristics of a secondary battery can be improved further.
- the nonaqueous secondary battery functional layer composition of the present invention preferably has a volume average particle diameter D A of the organic particles is preferably the functional layer binder volume average particle size D B above . If the volume of the organic particles having an average particle diameter D A (D50) and volume-average particle diameter of the functional layer binder D B (D50) is satisfied the above relation, to increase the blocking resistance of the battery element comprising a functional layer The adhesiveness of the functional layer after immersion in the electrolytic solution can be further improved. And the cycle characteristic and output characteristic of a secondary battery can be improved further.
- the “volume average particle diameter” of the binder for functional layers can be measured using the method described in the examples of the present specification.
- the composition for non-aqueous secondary battery functional layers of this invention contains an inorganic particle further. If organic particles and inorganic particles having a predetermined electrolyte solution elution amount are used in combination as the non-conductive particles, the blocking resistance of the battery member including the functional layer can be improved and the heat resistance of the functional layer can be improved.
- the functional layer for non-aqueous secondary batteries of this invention is either of the composition for non-aqueous secondary battery functional layers mentioned above. It was formed using.
- the functional layer formed using the functional layer composition described above is excellent in adhesiveness after immersion in the electrolyte, and can exhibit excellent cycle characteristics and output characteristics in the secondary battery.
- the present invention aims to solve the above-mentioned problem advantageously, and the non-aqueous secondary battery of the present invention is characterized by comprising the above-described functional layer for a non-aqueous secondary battery.
- the secondary battery including the above-described functional layer is excellent in battery characteristics such as cycle characteristics and output characteristics.
- the non-aqueous secondary battery of the present invention is preferably a stacked type. If the non-aqueous secondary battery of the present invention is a laminated type, the volume energy density can be improved, and battery characteristics such as cycle characteristics and output characteristics can be further enhanced.
- the present invention aims to advantageously solve the above-mentioned problems, and the method for producing an electrode for a non-aqueous secondary battery according to the present invention comprises the above-described functional layer and electrode base for a non-aqueous secondary battery. It includes a step of laminating materials, and a step of adhering the above-described functional layer for a non-aqueous secondary battery and an electrode substrate by applying pressure. By using such a procedure, it is possible to efficiently produce a large electrode that exhibits excellent cycle characteristics and output characteristics for the secondary battery at high speed.
- the electrode base material includes a binder for the electrode mixture layer, and the binder for the electrode mixture layer is an aromatic vinyl monomer. It preferably contains a body unit and an aliphatic conjugated diene monomer unit. If an electrode is produced using a binder for an electrode mixture layer containing an aromatic vinyl monomer unit and an aliphatic conjugated diene monomer unit, the cycle characteristics and output characteristics of the secondary battery can be further enhanced. .
- a non-aqueous secondary battery capable of forming a functional layer for a non-aqueous secondary battery that is excellent in adhesiveness after immersion in an electrolyte and can exhibit excellent cycle characteristics and output characteristics in a non-aqueous secondary battery.
- a composition for a secondary battery functional layer can be provided.
- the functional layer for non-aqueous secondary batteries which can exhibit the cycling characteristics and output characteristics which were excellent in the non-aqueous secondary battery can be provided.
- the non-aqueous secondary battery which is excellent in cycling characteristics and output characteristics can be provided.
- the manufacturing method of the electrode for non-aqueous secondary batteries which can exhibit the cycling characteristics and output characteristics which were excellent in the non-aqueous secondary battery can be provided.
- the composition for non-aqueous secondary battery functional layers of the present invention is used as a material for preparing a functional layer for non-aqueous secondary batteries.
- the functional layer for non-aqueous secondary batteries of this invention is formed using the composition for non-aqueous secondary battery functional layers of this invention.
- the nonaqueous secondary battery of this invention is provided with the functional layer for nonaqueous secondary batteries of this invention at least.
- the manufacturing method of the electrode for non-aqueous secondary batteries of this invention is used when producing the electrode for non-aqueous secondary batteries provided with the functional layer for non-aqueous secondary batteries of this invention.
- composition for functional layer of non-aqueous secondary battery contains organic particles as non-conductive particles and a binder for functional layers, and can optionally be contained in inorganic particles as non-conductive particles and other functional layers.
- This is a slurry composition containing water and the like as a dispersion medium.
- the composition for a functional layer of the present invention is characterized in that the amount of organic particles eluted from the electrolyte is 0.001% by mass or more and 5.0% by mass or less.
- the organic particles contained in the functional layer composition of the present invention have an electrolyte solution elution amount of 0.001% by mass or more, and thus sufficiently retain wettability with the electrolyte solution.
- the organic particles have an electrolyte solution elution amount of 5.0% by mass or less, so that they do not elute excessively in the electrolyte solution and can maintain their shape sufficiently even after being immersed in the electrolyte solution for a long time. it can. Therefore, the functional layer formed from the composition for a functional layer of the present invention containing organic particles whose electrolyte solution elution amount is within the above range exhibits excellent adhesiveness even after the electrolyte solution is immersed, The cycle characteristics and output characteristics of the secondary battery can be improved.
- Organic particles are particles used as non-conductive particles that can increase the heat resistance and strength of the functional layer, and are usually made of a polymer that does not have a binding ability. And since a nonelectroconductive particle is electrochemically stable, it exists stably in a functional layer under the use environment of a secondary battery.
- the electrolyte solution elution amount of the organic particles needs to be 0.001% by mass or more and 5.0% by mass or less, preferably 0.005% by mass or more, and 0.01% by mass or more. Is more preferable, 0.1% by mass or more is further preferable, 0.7% by mass or more is particularly preferable, 4.5% by mass or less is preferable, and 4.0% by mass or less is preferable. More preferred is 3.7% by mass or less.
- the elution amount of the organic particles in the electrolyte solution is less than the lower limit, the wettability of the organic particles with respect to the electrolyte solution cannot be ensured, and the output characteristics of the secondary battery deteriorate.
- the elution amount of the organic particles in the electrolyte exceeds the above upper limit, it becomes difficult for the organic particles to maintain their shape sufficiently in the electrolyte, and the adhesion of the functional layer after immersion in the electrolyte is ensured. I can't. Therefore, the cycle characteristics of the secondary battery are deteriorated.
- the cause is not certain, when the amount of the electrolyte solution elution of the organic particles exceeds the above upper limit value, the blocking resistance tends to decrease.
- the electrolytic solution elution amount can be adjusted by changing the composition of the organic particles.
- the electrolyte solution elution amount can be decreased, and if the content ratio of the crosslinkable monomer unit is decreased, the electrolyte solution elution amount can be increased.
- the amount of electrolytic solution eluted can be further reduced by using a dispersion stabilizer.
- the elution amount of the electrolyte solution can be reduced, and the epoxy group-containing monomer unit and / or Alternatively, the elution amount of the electrolyte can be increased by increasing the content of the alkoxysilyl group-containing monomer unit.
- the volume average particle diameter D A (D50) of the organic particles is preferably 0.01 ⁇ m or more, more preferably 0.03 ⁇ m or more, further preferably 0.05 ⁇ m or more, 0 0.1 ⁇ m or more is more preferable, 2.0 ⁇ m or less is preferable, 1.0 ⁇ m or less is more preferable, and 0.6 ⁇ m or less is still more preferable. If the volume average particle diameter D A of the organic particles less than the above lower limit, the Gurley value of the function layer is increased (i.e., ions decreases conduction) to prevent the, on a metal such as lithium electrodes While suppressing precipitation, the cycle characteristics and output characteristics of the secondary battery can be further improved.
- the volume average particle diameter D A of the organic particles is preferably not less than the volume average particle diameter D B of the functional layer binder to be described later, and more preferably greater than the volume average particle diameter D B.
- the volume average particle diameter D A of the organic particles, if functional layer binder volume average a particle size D B above, to increase the blocking resistance of the cell components with a functional layer, after the electrolyte immersing the functional layer The adhesiveness of can be further improved. And the cycle characteristic and output characteristic of a secondary battery can be improved further.
- the glass transition temperature of the organic particles is preferably 30 ° C. or higher, and more preferably 50 ° C. or higher. If the glass transition temperature of the organic particles is equal to or higher than the above lower limit value, the deformation of the organic particles during the operation of the secondary battery can be suppressed, and the heat resistance and strength of the functional layer can be ensured.
- the glass transition temperature of the organic particles is not particularly limited, but is usually 250 ° C. or lower. In the present invention, the “glass transition temperature” of the organic particles can be measured by differential scanning calorimetry according to JIS K7121.
- composition of organic particles is not particularly limited, but the organic particles preferably include a crosslinkable monomer unit.
- the organic particles can contain monomer units other than the crosslinkable monomer units (other monomer units).
- the crosslinkable monomer capable of forming a crosslinkable monomer unit is a monomer having two or more polymerizable double bonds (for example, olefinic double bonds) per molecule.
- Examples of the crosslinkable monomer include a bifunctional crosslinkable monomer, a trifunctional crosslinkable monomer, and a tetrafunctional crosslinkable monomer.
- Bifunctional crosslinkable monomers include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and 1,3-butylene glycol di (Meth) acrylate, 1,4-butylene glycol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate (preferably molecular weight 500-1200), 2,2-bis (4- (acryloxypropyloxy) phenyl) propane, 2,2-bis (4- (acryloxydiethoxy) phenyl) propane, dipropylene glycol diallyl ether, diethyl Glycol diallyl ether, triethylene glycol divinyl ether, trimethylolpropane - diallyl ether, methylenebisacryl
- Examples of the trifunctional crosslinkable monomer include triallylamine and trimethylolpropane tri (meth) acrylate.
- Examples of tetrafunctional crosslinkable monomers include tetraallyloxyethane, tetramethylolmethane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, tetramethylolmethane tetra (meth) acrylate, and pentaerythritol tetra (meth) acrylate.
- (meth) acrylate means acrylate and / or methacrylate.
- crosslinkable monomers may be used alone or in combination of two or more.
- divinylbenzene, ethylene glycol dimethacrylate, and trimethylolpropane trimethacrylate are preferred from the viewpoint of further improving the adhesiveness of the functional layer after immersion in the electrolyte, and the cycle characteristics and output characteristics of the secondary battery.
- Divinylbenzene is more preferred.
- the proportion of the crosslinkable monomer units contained in the organic particles is preferably 5.0% by mass or more, preferably 10% by mass or more, with the total monomer unit amount being 100% by mass. Is more preferably 15% by mass or more, particularly preferably 60% by mass or more, preferably 85% by mass or less, more preferably 80% by mass or less, and 75% by mass. More preferably, it is as follows. If the ratio of the crosslinkable monomer unit contained in the organic particles is not less than the above lower limit value, the amount of the organic particles eluted from the electrolyte may be reduced, and the organic particles may sufficiently maintain their shape in the electrolyte. it can.
- the adhesiveness after immersion of the functional layer in the electrolyte and the cycle characteristics of the secondary battery can be further improved.
- the ratio of the crosslinkable monomer unit contained in the organic particles is not more than the above upper limit value, the wettability of the organic particles with the electrolytic solution is increased, and the output characteristics of the secondary battery can be further improved.
- the monomer unit other than the crosslinkable monomer unit that can be contained in the organic particles is not particularly limited, but is an aromatic monovinyl monomer unit, a (meth) acrylic acid ester monomer unit, an acid group-containing monomer. Examples thereof include a unit, a hydroxyl group-containing monomer unit, an epoxy group-containing monomer unit, and an alkoxysilyl group-containing monomer unit.
- the other monomer units are monomer units other than the crosslinkable monomer unit as described above. Therefore, the monomer corresponding to the crosslinkable monomer described above is not included in other monomers that can form other monomer units.
- “(meth) acryl” means acryl and / or methacryl.
- aromatic monovinyl monomer that can form an aromatic monovinyl monomer unit
- aromatic monovinyl monomer examples include styrene, ⁇ -methylstyrene, vinyltoluene, 4- (tert-butoxy) styrene, ethylvinylbenzene, fluorostyrene, and vinylpyridine. Etc. These may be used alone or in combination of two or more. Of these, styrene and ethyl vinylbenzene are preferred.
- the proportion of aromatic monovinyl monomer units contained in the organic particles is preferably 5.0% by mass or more, preferably 10% by mass or more, with the total monomer unit amount being 100% by mass. More preferably, the content is 15% by mass or more, further preferably 90% by mass or less, more preferably 70% by mass or less, and further preferably 40% by mass or less. If the ratio of the aromatic monovinyl monomer unit contained in the organic particles is within the above range, the organic particles can sufficiently maintain their shape in the electrolytic solution, and the functional layer is bonded after being immersed in the electrolytic solution. And the cycle characteristics of the secondary battery can be further improved.
- Examples of the (meth) acrylate monomer that can form a (meth) acrylate monomer unit include, for example, methyl acrylate, ethyl acrylate, n-propyl acrylate, isopropyl acrylate, n-butyl acrylate, and t-butyl.
- Acrylic acid alkyl esters such as acrylate, pentyl acrylate, hexyl acrylate, heptyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, lauryl acrylate, n-tetradecyl acrylate, stearyl acrylate; methyl methacrylate, ethyl methacrylate, n -Propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, t-butyl methacrylate, pentyl Methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, lauryl methacrylate, n- tetradec
- the ratio of the (meth) acrylic acid ester monomer unit contained in the organic particles is preferably 0.1% by mass or more, with the total monomer unit amount being 100% by mass, It is more preferably at least mass%, more preferably at least 1.0 mass%, preferably at most 60 mass%, more preferably at most 20 mass%, and at most 5.0 mass%. More preferably, it is more preferably 4.0% by mass or less. If the proportion of the (meth) acrylic acid ester monomer unit contained in the organic particles is within the above range, the flexibility of the functional layer and the adhesiveness after immersion in the electrolyte are ensured, and the cycle characteristics of the secondary battery Can be further improved.
- a monomer having an acid group for example, a monomer having a carboxylic acid group, a monomer having a sulfonic acid group, and Examples thereof include a monomer having a monomer having a phosphate group.
- Examples of the monomer having a carboxylic acid group include monocarboxylic acid and dicarboxylic acid.
- Examples of the monocarboxylic acid include acrylic acid, methacrylic acid, and crotonic acid.
- Examples of the dicarboxylic acid include maleic acid, fumaric acid, itaconic acid and the like.
- Examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, methyl vinyl sulfonic acid, (meth) allyl sulfonic acid, (meth) acrylic acid-2-ethyl sulfonate, 2-acrylamido-2-methyl. Examples thereof include propanesulfonic acid and 3-allyloxy-2-hydroxypropanesulfonic acid.
- examples of the monomer having a phosphoric acid group include phosphoric acid-2- (meth) acryloyloxyethyl phosphate, methyl-2- (meth) acryloyloxyethyl phosphate, and ethyl phosphate- (meth) acryloyloxyethyl phosphate.
- Etc. “(meth) allyl” means allyl and / or methallyl
- “(meth) acryloyl” means acryloyl and / or methacryloyl.
- These acid group-containing monomers may be used alone or in combination of two or more.
- a monomer having a carboxylic acid group is preferable, a monocarboxylic acid is more preferable, and (meth) acrylic acid is still more preferable.
- the ratio of the acid group-containing monomer unit contained in the organic particles is preferably 0.2% by mass or more, with the total monomer unit amount being 100% by mass, and preferably 1.0% by mass or more. More preferably, it is 1.5% by mass or more, more preferably 10% by mass or less, more preferably 8.0% by mass or less, and 6.0% by mass or less. More preferably it is. If the ratio of the acid group-containing monomer units contained in the organic particles is within the above range, the secondary battery cycle is suppressed by suppressing the aggregation of the organic particles and reducing the amount of moisture remaining in the functional layer. The characteristics and output characteristics can be further improved.
- Examples of the hydroxyl group-containing monomer that can form a hydroxyl group-containing monomer unit include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, N-hydroxymethyl acrylamide (N- Methylolacrylamide), N-hydroxymethylmethacrylamide, N-hydroxyethylacrylamide, N-hydroxyethylmethacrylamide and the like. These may be used alone or in combination of two or more. Of these, 2-hydroxyethyl methacrylate is preferred.
- the ratio of the hydroxyl group-containing monomer units contained in the organic particles is preferably 0.1% by mass or more, with the amount of all monomer units being 100% by mass, preferably 0.3% by mass or more. More preferably, it is preferably 3.0% by mass or less, more preferably 2.0% by mass or less, and further preferably 1.0% by mass or less.
- Examples of the epoxy group-containing monomer capable of forming an epoxy group-containing monomer unit include those described as “monomer having an epoxy group” in International Publication No. 2012/046843. These may be used alone or in combination of two or more. If organic particles containing an epoxy group-containing monomer unit are used, it is possible to form a functional layer that is excellent in flexibility and suppressed from falling off. On the other hand, organic particles containing an epoxy group-containing monomer unit tend to have high wettability to an electrolytic solution and increase the amount of electrolytic solution eluted.
- the ratio of the epoxy group-containing monomer units contained in the organic particles is the total monomer units.
- the amount is 100% by mass, it is preferably less than 0.4% by mass, more preferably less than 0.2% by mass, and still more preferably less than 0.1% by mass.
- alkoxysilyl group-containing monomer capable of forming an alkoxysilyl group-containing monomer unit examples include those described as “monomers having an alkoxysilane group” in International Publication No. 2012/046843. These may be used alone or in combination of two or more. If organic particles containing an alkoxysilyl group-containing monomer unit are used, a functional layer excellent in flexibility and suppressed from falling off can be formed. On the other hand, organic particles containing an alkoxysilyl group-containing monomer unit tend to have high wettability to an electrolytic solution and increase the amount of electrolytic solution eluted.
- the proportion of the alkoxysilyl group-containing monomer units contained in the organic particles is the total monomer units. Is preferably less than 1.7% by mass, more preferably less than 0.4% by mass, still more preferably less than 0.2% by mass, and 0.1% by mass. It is particularly preferred that it is less than%.
- the organic particles can be produced by polymerizing a monomer composition containing the above-described monomer in an aqueous solvent such as water. Under the present circumstances, the content rate of each monomer in a monomer composition can be defined according to the content rate of each repeating unit (monomer unit) in an organic particle.
- the polymerization mode is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used.
- any reaction such as ionic polymerization, radical polymerization, and living radical polymerization can be used.
- seed polymerization may be performed using seed particles.
- the polymerization conditions can be appropriately adjusted according to the polymerization method and the like.
- additives such as an emulsifier, a polymerization initiator, a polymerization aid, a dispersion stabilizer, and an auxiliary stabilizer can be used.
- the emulsifier, the polymerization initiator, and the polymerization aid commonly used ones can be used, and the amount used thereof can also be a commonly used amount.
- the dispersion stabilizer is not particularly limited.
- the dispersion stabilizer is a polymer containing at least one selected from the group consisting of a hydroxyl group, a carbonyl group, an amino group, and an epoxy group (however, a binder for organic particles or a functional layer).
- dispersion stabilizer examples include polyvinyl alcohol, carboxymethyl cellulose, polyacrylate, rosin resin, polyvinyl pyrrolidone, and poly (meth) acrylate. Among these, those that are water-soluble are preferable, those that are water-soluble and nonionic are preferable. Examples of water-soluble and nonionic dispersion stabilizers include polyvinyl alcohol and polyvinyl pyrrolidone.
- the amount of the dispersion stabilizer used is not particularly limited, but preferably per 100 parts by weight of the monomer used for polymerization (including seed monomer used for seed particle preparation when seed polymerization is used for organic particle preparation).
- an auxiliary stabilizer can be used in addition to the dispersion stabilizer. By using an auxiliary stabilizer, it is possible to increase the dispersion stability of the crosslinkable monomer and to proceed the polymerization more stably.
- an auxiliary stabilizer by using an auxiliary stabilizer, the film-forming property of the composition for a functional layer containing organic particles is enhanced, and the tear resistance of a battery member (particularly a separator) provided with the resulting functional layer is enhanced.
- an anionic surfactant a nonionic surfactant, a quaternary ammonium salt, a long chain alcohol, or the like is used. Specific examples include sodium di (2-ethylhexyl) sulfosuccinate, nonylphenoxypolyethoxyethanol, methyl tricapryl ammonium chloride, cetyl alcohol and the like.
- the functional layer binder holds the components such as the organic particles contained in the functional layer so as not to be detached from the functional layer.
- the functional layer binder is usually made of a polymer having binding ability.
- a particulate polymer is preferably used as the binder used for the functional layer composition.
- the particulate polymer is usually a water-insoluble polymer.
- the polymer being “water-insoluble” means that at 25 ° C., when 0.5 g of the polymer is dissolved in 100 g of water, the insoluble content becomes 90% by mass or more.
- the volume average particle diameter D B (D50) of the functional layer binder is preferably 0.01 ⁇ m or more, more preferably 0.05 ⁇ m or more, and 0.5 ⁇ m or less. It is preferable that it is 0.35 ⁇ m or less. If the volume average particle diameter D B of the functional layer binder is equal to or greater than the lower limit, the Gurley value of the function layer is increased (i.e., ion conductivity decreases) the by suppressing, metal such as lithium Can be prevented from being deposited on the electrode, and the cycle characteristics and output characteristics of the secondary battery can be further improved. On the other hand, if the volume average particle diameter D B of the functional layer binder is less than the upper limit value, to improve the adhesion of the electrolytic solution before immersion functional layer, it is possible to suppress dusting.
- the glass transition temperature of the functional layer binder is preferably ⁇ 30 ° C. or more, more preferably ⁇ 20 ° C. or more, preferably 20 ° C. or less, and 15 ° C. or less. Is more preferable. If the glass transition temperature of the binder for functional layers is more than the said lower limit, the blocking resistance of a battery member provided with a functional layer can be ensured. On the other hand, if the glass transition temperature of the functional layer binder is equal to or lower than the above upper limit value, the functional layer binder exhibits excellent binding ability, before the functional layer is immersed in the electrolyte and after the electrolyte is immersed It is possible to ensure sufficient adhesion. Therefore, the cycle characteristics and output characteristics of the secondary battery can be further improved.
- the particulate polymer that is a binder for the functional layer is not particularly limited, and can be used when forming a functional layer such as a thermoplastic resin, a thermosetting resin, and a synthetic rubber.
- Known particulate polymers can be used.
- a polymer containing a conjugated diene monomer unit conjugated diene polymer
- SBR styrene-butadiene copolymer
- a polymer (acrylic polymer) containing a monomer unit is preferably exemplified. Among these, acrylic polymers are more preferable.
- particulate polymers may be used individually by 1 type, and may be used in combination of 2 or more types.
- suitable composition of the acrylic polymer which is a particulate polymer is demonstrated as an example, the binder for functional layers is not limited to this.
- Suitable particulate polymers include (meth) acrylate monomer units and aromatic monovinyl monomer units, and optionally other monomer units.
- (Meth) acrylic acid ester monomer unit examples include the same as those described above in the section of “Organic particles”. These may be used alone or in combination of two or more.
- the alkyl group bonded to the non-carbonyl oxygen atom has 4 or more carbon atoms
- the ratio of the (meth) acrylic acid ester monomer unit contained in the particulate polymer is preferably 35% by mass or more, with the amount of all monomer units being 100% by mass, preferably 40% by mass. More preferably, it is more preferably 45% by mass or more, more preferably 80% by mass or less, more preferably 75% by mass or less, and still more preferably 70% by mass or less. 65 mass% or less is particularly preferable, and 60 mass% or less is most preferable. If the proportion of the (meth) acrylic acid ester monomer unit contained in the particulate polymer is within the above range, the binding ability of the particulate polymer is enhanced and the particulate polymer is eluted into the electrolytic solution. Can be suppressed. Therefore, the cycle characteristics and output characteristics of the secondary battery can be further improved.
- aromatic monovinyl monomer that can form an aromatic monovinyl monomer unit
- aromatic monovinyl monomer that can form an aromatic monovinyl monomer unit
- organic particles These may be used alone or in combination of two or more. Of these, styrene is preferred.
- the ratio of the aromatic monovinyl monomer unit contained in the particulate polymer is preferably 20% by mass or more, and 25% by mass or more, with the total monomer unit amount being 100% by mass. More preferably, it is more preferably 30% by mass or more, particularly preferably 35% by mass or more, preferably 65% by mass or less, more preferably 64.9% by mass or less, More preferably, it is 60 mass% or less, and it is especially preferable that it is 50 mass% or less. If the ratio of the aromatic monovinyl monomer unit contained in the particulate polymer is within the above range, the elution of the particulate polymer into the electrolytic solution is suppressed and the amount of moisture brought into the functional layer is reduced. be able to. Therefore, the adhesiveness after immersion of the functional layer in the electrolyte can be further improved, and the cycle characteristics and output characteristics of the secondary battery can be further improved.
- the monomer unit other than the (meth) acrylic acid ester monomer unit and the aromatic monovinyl monomer unit that can be included in the particulate polymer is not particularly limited. Examples include a unit of a monomer.
- Examples of the acid group-containing monomer capable of forming the acid group-containing monomer unit include the same as those described above in the section of “Organic particles”. These may be used alone or in combination of two or more. Among these, itaconic acid and maleic acid are preferable from the viewpoint of improving the output characteristics of the secondary battery.
- the ratio of the acid group-containing monomer units contained in the particulate polymer is preferably 0.1% by mass or more, with the total monomer unit amount being 100% by mass, and 0.2% by mass. % Or more, more preferably 0.3% by mass or more, further preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and 2.0% or less.
- the content is more preferably no more than mass%, and particularly preferably no more than 1.0 mass%. If the ratio of the acid group-containing monomer unit contained in the particulate polymer is equal to or higher than the lower limit, the adhesive property of the functional layer after immersion in the electrolyte is improved, and the cycle characteristics and output characteristics of the secondary battery are improved. Further improvement can be achieved. On the other hand, if the ratio of the acid group-containing monomer unit is not more than the above upper limit value, the amount of moisture remaining in the functional layer can be reduced to further improve the cycle characteristics of the secondary battery.
- crosslinkable monomer that can form a crosslinkable monomer unit
- examples of the crosslinkable monomer that can form a crosslinkable monomer unit include the crosslinkable monomers described above in the section of “Organic particles”. These may be used alone or in combination of two or more. Among these, ethylene glycol dimethacrylate and divinylbenzene are preferable from the viewpoint of reducing the amount of moisture remaining in the functional layer and further improving the cycle characteristics of the secondary battery.
- the proportion of the crosslinkable monomer units contained in the particulate polymer is preferably 0.01% by mass or more, with the total monomer units being 100% by mass, preferably 0.1% by mass. More preferably, it is more preferably 0.5% by mass or more, more preferably 5.0% by mass or less, and even more preferably 4.0% by mass or less, and 3.0% by mass. % Or less is more preferable. If the ratio of the crosslinkable monomer unit contained in the particulate polymer is not less than the above lower limit value, the elution of the functional layer binder into the electrolytic solution is suppressed, and the functional layer is immersed in the electrolytic solution. Adhesiveness can be further increased. Therefore, the cycle characteristics of the secondary battery can be further improved.
- the functional layer binder exhibits excellent binding ability, and the functional layer electrolyte Adhesiveness before immersion and after immersion in the electrolyte can be sufficiently ensured. Therefore, the cycle characteristics and output characteristics of the secondary battery can be further improved.
- the method for preparing the functional layer binder is not particularly limited.
- the particulate polymer as the binder for the functional layer can be produced by polymerizing the monomer composition containing the above-described monomer in an aqueous solvent such as water.
- the content rate of each monomer in a monomer composition can be defined according to the content rate of each repeating unit (monomer unit) in a particulate polymer.
- the polymerization mode is not particularly limited, and any method such as a solution polymerization method, a suspension polymerization method, a bulk polymerization method, and an emulsion polymerization method can be used.
- any reaction such as ionic polymerization, radical polymerization, and living radical polymerization can be used.
- additives such as an emulsifier used for superposition
- the amount of these additives used may also be a commonly used amount.
- the polymerization conditions can be appropriately adjusted according to the polymerization method and the type of polymerization initiator.
- the content ratio of the organic particles and the functional layer binder in the functional layer composition is not particularly limited, but the organic particle content is 1 mass of the total content of the organic particles and the functional layer binder. % Or more, preferably 25% by weight or more, more preferably 50% by weight or more, still more preferably 60% by weight or more, and particularly preferably 75% by weight or more. 99% by mass or less, more preferably 98% by mass or less, and still more preferably 97% by mass or less. If the ratio of the organic particles in the total of the organic particles and the binder for the functional layer is equal to or higher than the above lower limit, the blocking resistance of the battery member including the functional layer is secured and a metal such as lithium is on the electrode.
- Precipitation can be suppressed.
- the cycle characteristics and output characteristics of the secondary battery can be further improved.
- the ratio of the organic particles in the total of the organic particles and the binder for the functional layer is equal to or less than the above upper limit value, the adhesiveness of the functional layer before and after immersion in the electrolyte should be sufficiently secured. Can do.
- inorganic particles are preferably used as non-conductive particles in addition to the organic particles described above. If organic particles and inorganic particles are used in combination, the blocking resistance and heat resistance of the battery member provided with the functional layer can be improved.
- the inorganic particles aluminum oxide (alumina), aluminum oxide hydrate (boehmite (AlOOH ), Gibbsite (Al (OH) 3 ), silicon oxide, magnesium oxide (magnesia), calcium oxide, titanium oxide (titania), barium titanate (BaTiO 3 ), ZrO, alumina-silica composite oxide and other oxide particles
- Nitride particles such as aluminum nitride and boron nitride
- Covalent crystal particles such as silicon and diamond
- Slightly soluble ion crystal particles such as barium sulfate, calcium fluoride and barium fluoride
- Clay fine particles such as talc and montmorillonite;
- these particles are Substituted, surface treatment, among may.
- the inorganic particles boehmite particles, barium sulfate particles, alumina particles are preferred.
- the inorganic particle mentioned above may be used individually by 1 type, and may be used in combination of 2 or more types.
- the volume average particle diameter (D50) of the inorganic particles is preferably 0.1 ⁇ m or more, more preferably 0.3 ⁇ m or more, preferably 2.0 ⁇ m or less, and 1.5 ⁇ m or less. More preferably. If the volume average particle diameter of the inorganic particles is equal to or greater than the lower limit, the Gurley value of the functional layer is suppressed from increasing (that is, the ionic conductivity is decreased), and the output characteristics of the secondary battery can be further improved. it can. On the other hand, if the volume average particle diameter of the non-conductive particles is not more than the above upper limit value, the density of the functional layer can be increased, and the protective function (for example, heat resistance) of the functional layer can be ensured. In the present invention, the “volume average particle diameter of inorganic particles” can be measured using the method described in the examples of the present specification.
- the content of the inorganic particles in the functional layer composition is preferably 2 parts by mass or more, more preferably 5 parts by mass or more, and 100 parts by mass or less per 100 parts by mass of the organic particles. It is preferably 50 parts by mass or less.
- the content of the inorganic particles is set to the above lower limit value or more, the blocking resistance and heat resistance of the battery member including the functional layer can be further improved.
- the content of the inorganic particles is less than or equal to the above upper limit value, if the content is less than or equal to the above upper limit value, the wettability of the functional layer to the electrolytic solution is ensured, and the output characteristics of the secondary battery can be further improved. it can.
- the composition for functional layers may contain arbitrary other components in addition to the components described above.
- the other components are not particularly limited as long as they do not affect the battery reaction, and known components can be used. Moreover, these other components may be used individually by 1 type, and may be used in combination of 2 or more types.
- known additives such as a dispersing agent and a wetting agent, are mentioned, for example.
- Dispersion medium for the functional layer composition of the present invention, water is usually used.
- the mixture of water and another solvent can also be used.
- the other solvent is not particularly limited.
- cycloaliphatic hydrocarbon compounds such as cyclopentane and cyclohexane
- aromatic hydrocarbon compounds such as toluene and xylene
- ketones such as ethyl methyl ketone and cyclohexanone.
- ester compounds such as ethyl acetate, butyl acetate, ⁇ -butyrolactone, ⁇ -caprolactone
- nitrile compounds such as acetonitrile and propionitrile
- ether compounds such as tetrahydrofuran and ethylene glycol diethyl ether
- Alcohol compounds such as ethylene glycol monomethyl ether
- amide compounds such as N-methylpyrrolidone (NMP) and N, N-dimethylformamide
- the functional layer composition of the present invention is not particularly limited, and the organic particles, the functional layer binder, and the inorganic particles and additives that can be optionally used are present in the presence of a dispersion medium such as water. Can be obtained by mixing below.
- the mixing method and mixing order of the components described above are not particularly limited, but it is preferable to perform mixing using a disperser as a mixing device in order to disperse each component efficiently.
- a disperser is an apparatus which can disperse
- the disperser include a ball mill, a sand mill, a pigment disperser, a crusher, an ultrasonic disperser, a homogenizer, and a planetary mixer.
- the functional layer for a non-aqueous secondary battery of the present invention is formed from the above-described composition for a non-aqueous secondary battery functional layer.
- the functional layer composition described above is applied to the surface of an appropriate substrate. After forming the coating film by coating, it can be formed by drying the formed coating film. That is, the functional layer for a non-aqueous secondary battery of the present invention is composed of a dried product of the above-described composition for a non-aqueous secondary battery functional layer, contains organic particles and a binder for the functional layer, and is optionally inorganic. Contains particles and additives.
- the polymer containing the crosslinkable monomer unit is a composition for a nonaqueous secondary battery functional layer. May be crosslinked at the time of drying, or at the time of heat treatment optionally performed after drying (that is, the functional layer for non-aqueous secondary battery is composed of the organic particles and / or the binder for functional layer described above). It may contain a cross-linked product).
- the functional layer for non-aqueous secondary batteries of this invention is formed using the composition for non-aqueous secondary battery functional layers mentioned above, it is excellent in the adhesiveness after electrolyte solution immersion. And if the battery member provided with the functional layer for non-aqueous secondary batteries of this invention is used, the cycling characteristics and output characteristics which were excellent in the secondary battery can be exhibited.
- a functional layer composition coating film is formed on the surface of a release substrate, and the coating film is dried to form a functional layer.
- the release substrate may be peeled off from the functional layer.
- the functional layer peeled off from the release substrate can be used as a self-supporting film for forming a battery member of a secondary battery.
- the functional layer peeled off from the release substrate may be laminated on the separator substrate to form a separator having the functional layer, or the functional layer peeled off from the release substrate may be used as the electrode substrate.
- An electrode provided with a functional layer may be formed by stacking on the substrate.
- a separator substrate or an electrode substrate as the substrate.
- the functional layer provided on the separator substrate and the electrode substrate can be suitably used as a protective layer for improving the heat resistance and strength of the separator and the electrode.
- the organic separator substrate is a porous member made of an organic material.
- examples of the organic separator substrate include a microporous membrane or a nonwoven fabric containing a polyolefin resin such as polyethylene or polypropylene, an aromatic polyamide resin, etc., and since it is excellent in strength, a polyethylene microporous membrane or nonwoven fabric is used. Is preferred.
- Mw weight average molecular weight
- a separator substrate made of a mixture (polyethylene composition) containing 30% by mass or more and 70% by mass or less of (high density) polyethylene having an Mw of 1 ⁇ 10 4 or more and less than 8 ⁇ 10 5 is more preferable.
- Mw of polyethylene can be measured using gel permeation chromatography (Gel Permeation Chromatography: GPC).
- the thickness of the separator substrate can be any thickness, preferably 3 ⁇ m or more and 30 ⁇ m or less, more preferably 4 ⁇ m or more and 20 ⁇ m or less, and further preferably 5 ⁇ m or more and 18 ⁇ m or less. If the thickness of the separator substrate is 3 ⁇ m or more, sufficient safety can be obtained. Moreover, if the thickness of the separator base material is 30 ⁇ m or less, it is possible to suppress the decrease in ionic conductivity and the low temperature output characteristics of the secondary battery from being decreased, and the heat of the separator base material. Heat resistance can be improved by suppressing the shrinkage force from increasing.
- Electrode substrate Although it does not specifically limit as an electrode base material (a positive electrode base material and a negative electrode base material), The electrode base material with which the electrode compound-material layer was formed on the electrical power collector is mentioned.
- the method for forming the electrode mixture layer on the current collector is not particularly limited, and for example, the method described in JP2013-145663A can be used.
- the binder for the electrode mixture layer is a polymer containing an aromatic vinyl monomer unit and an aliphatic conjugated diene monomer unit from the viewpoint of further improving the cycle characteristics and output characteristics of the secondary battery.
- the binder for electrode mixture layers containing an aromatic vinyl monomer unit and an aliphatic conjugated diene monomer unit further contains a monomer unit having a carboxylic acid group.
- the binder for the electrode mixture layer may contain a monomer unit other than the aromatic vinyl monomer unit, the aliphatic conjugated diene monomer unit, and the monomer unit having a carboxylic acid group. Good.
- aromatic vinyl monomer that can form an aromatic vinyl monomer unit
- examples of the aromatic vinyl monomer that can form an aromatic vinyl monomer unit include styrene, ⁇ -methylstyrene, vinyl toluene, and divinylbenzene. These may be used alone or in combination of two or more. Among these, styrene is preferable.
- the ratio of the aromatic vinyl monomer unit contained in the binder for the electrode mixture layer is preferably 50% by mass or more, with the total monomer unit amount being 100% by mass, and 55% by mass. % Or more, more preferably 60% by mass or more, further preferably 75% by mass or less, more preferably 70% by mass or less, and further preferably 65% by mass or less. preferable.
- Examples of the aliphatic conjugated diene monomer that can form an aliphatic conjugated diene monomer unit include 1,3-butadiene, 2-methyl-1,3-butadiene, 2,3-dimethyl-1,3-butadiene, Examples include 2-chloro-1,3-butadiene, substituted linear conjugated pentadienes, substituted and side chain conjugated hexadienes, and the like. These may be used alone or in combination of two or more. Of these, 1,3-butadiene is preferred.
- the proportion of the aliphatic conjugated diene monomer unit contained in the binder for the electrode mixture layer is preferably 20% by mass or more, with the amount of all monomer units being 100% by mass, 25 More preferably, it is more preferably 30% by mass or more, further preferably 45% by mass or less, more preferably 40% by mass or less, and more preferably 35% by mass or less. Further preferred.
- Examples of the monomer having a carboxylic acid group capable of forming a monomer unit having a carboxylic acid group include those described above in the section of “Organic particles”. These may be used alone or in combination of two or more. Of these, itaconic acid is preferred.
- the ratio of the monomer unit which has a carboxylic acid group contained in the binder for electrode compound-material layers is 0.5 mass% or more by making the quantity of all the monomer units into 100 mass%.
- it is 1% by mass or more, more preferably 2% by mass or more, further preferably 10% by mass or less, more preferably 7% by mass or less, and 5% by mass or less. More preferably it is.
- Examples of other monomers that can form other monomer units contained in the binder for electrode mixture layers include monomers copolymerizable with the above-described monomers.
- other monomers include a hydroxyl group-containing monomer such as 2-hydroxyethyl acrylate, a fluorine-containing monomer such as a fluorine-containing (meth) acrylate monomer; acrylamide-2-methyl Sulfate ester group-containing monomers such as propanesulfonic acid; Amide group-containing monomers such as acrylamide and methacrylamide; Crosslinkable monomers such as allyl glycidyl ether, allyl (meth) acrylate, N-methylol acrylamide; ethylene, Olefins such as propylene; halogen atom-containing monomers such as vinyl chloride and vinylidene chloride; vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate and vinyl benzoate; methyl vinyl ether, ethyl vinyl ether,
- Vinyl ethers methyl vinyl ketone, Vinyl ketones such as ruvinyl ketone, butyl vinyl ketone, hexyl vinyl ketone and isopropenyl vinyl ketone; heterocyclic compounds containing heterocycles such as N-vinyl pyrrolidone, vinyl pyridine and vinyl imidazole; containing amino groups such as aminoethyl vinyl ether and dimethylaminoethyl vinyl ether Monomers; ⁇ , ⁇ -unsaturated nitrile monomers such as acrylonitrile and methacrylonitrile; and the like. These other monomers may be used alone or in combination of two or more.
- preparation method of the binder for electrode compound-material layers is not specifically limited, For example, the method similar to the "preparation method of the binder for functional layers" mentioned above can be used.
- Examples of the method for forming a functional layer on a substrate such as the separator substrate and electrode substrate described above include the following methods. 1) A method in which the composition for a functional layer of the present invention is applied to the surface of a separator substrate or an electrode substrate (in the case of an electrode substrate, the surface on the electrode mixture layer side, the same shall apply hereinafter) and then dried; 2) A method of drying a separator substrate or an electrode substrate after immersing the separator substrate or electrode substrate in the functional layer composition of the present invention; 3) A method for applying the composition for a functional layer of the present invention on a release substrate, drying to produce a functional layer, and transferring the obtained functional layer to the surface of a separator substrate or an electrode substrate; Among these, the method 1) is particularly preferable because the layer thickness of the functional layer can be easily controlled. Specifically, the method 1) includes a step of applying a functional layer composition on a substrate (application step) and a functional layer formed by
- the method for coating the functional layer composition on the substrate is not particularly limited.
- the doctor blade method, the reverse roll method, the direct roll method, the gravure method, the extrusion method, the brush coating The method of the method etc. is mentioned.
- a functional layer formation process it does not specifically limit as a method of drying the composition for functional layers on a base material.
- a well-known method can be used. Examples of the drying method include drying with warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with infrared rays, electron beams, or the like.
- the drying conditions are not particularly limited, but the drying temperature is preferably 50 to 150 ° C., and the drying time is preferably 5 to 30 minutes.
- the thickness of the functional layer formed using the composition for non-aqueous secondary battery functional layers of the present invention is preferably 0.1 ⁇ m or more, more preferably 0.5 ⁇ m or more, and 5 ⁇ m. Or less, more preferably 3 ⁇ m or less. If the thickness of the functional layer is not less than the above lower limit value, the protective function can be further enhanced, so that the heat resistance and tear resistance of the battery member provided with the functional layer can be improved. Moreover, if the thickness of the functional layer is equal to or less than the above upper limit value, the output characteristics excellent in the secondary battery can be exhibited.
- the battery member (separator and electrode) provided with the functional layer of the present invention is not limited to the separator base or electrode base and the functional layer of the present invention as long as the effects of the present invention are not significantly impaired. You may provide components other than a functional layer.
- constituent elements other than the functional layer of the present invention are not particularly limited as long as they do not correspond to the functional layer of the present invention, and are provided on the functional layer of the present invention for bonding between battery members. Examples thereof include an adhesive layer used.
- the electrode provided with the functional layer as an example of the battery member provided with the functional layer can be manufactured using, for example, the method for manufacturing the electrode for non-aqueous secondary battery of the present invention.
- the manufacturing method of the electrode for non-aqueous secondary batteries of this invention includes the process of laminating
- the method for producing an electrode for a non-aqueous secondary battery according to the present invention is such that a functional layer and an electrode base material are laminated, and they are bonded together by pressure, whereby the functional layer and the electrode base material are pressed.
- the aspect will not be specifically limited.
- the functional layer the self-supporting film described above in the section “Base material” may be used, or a functional layer provided on the separator base material may be used. (More specifically, the separator provided with the functional layer and the electrode base material may be laminated so that the functional layer of the separator provided with the functional layer is in contact with the electrode base material).
- an electrode base material the thing similar to the electrode base material mentioned above by the term of the "base material” can be used.
- the pressurization may be performed in the battery container or in the presence of the electrolytic solution (more specifically, the functional layer is provided in the battery container).
- a separator and an electrode base material may be disposed, and the functional layer and the electrode base material may be adhered by applying pressure after injecting the electrolyte into the battery container.
- adhesion by pressurization of a functional layer and an electrode base material can be performed using a known pressurization adhesion technique.
- the non-aqueous secondary battery of the present invention includes the above-described functional layer for a non-aqueous secondary battery of the present invention. More specifically, the non-aqueous secondary battery of the present invention includes a positive electrode, a negative electrode, a separator, and an electrolyte solution, and the functional layer for the non-aqueous secondary battery described above is a battery member of the positive electrode, the negative electrode, and the separator. Included in at least one. And the non-aqueous secondary battery of this invention can exhibit the outstanding battery characteristic (for example, cycling characteristics, output characteristics).
- At least one of the positive electrode, the negative electrode, and the separator used for the secondary battery of the present invention includes the functional layer of the present invention.
- a positive electrode and a negative electrode having a functional layer an electrode in which the functional layer of the present invention is provided on an electrode substrate formed by forming an electrode mixture layer on a current collector can be used.
- a separator which has a functional layer the separator which provides the functional layer of this invention on a separator base material can be used.
- an electrode base material and a separator base material the thing similar to what was mentioned by the term of the "functional layer for non-aqueous secondary batteries" can be used.
- the positive electrode, the negative electrode, and the separator that do not have a functional layer are not particularly limited, and an electrode made of the above-described electrode base material and a separator made of the above-described separator base material can be used.
- an electrode made of the above-described electrode base material and a separator made of the above-described separator base material can be used.
- a separator substrate made of a mixture (polyethylene composition) is more preferred.
- an organic electrolytic solution in which a supporting electrolyte is dissolved in an organic solvent is usually used.
- a lithium salt is used in a lithium ion secondary battery.
- 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 , (CF 3 SO 2 ) 2 NLi, (C 2 F 5 SO 2 ) NLi, and the like.
- LiPF 6 , LiClO 4 , and CF 3 SO 3 Li are preferable because they are easily dissolved in a solvent and exhibit a high degree of dissociation.
- electrolyte may be used individually by 1 type and may be used in combination of 2 or more types.
- the lithium ion conductivity tends to increase as the supporting electrolyte having a higher degree of dissociation is used, so that the lithium ion conductivity can be adjusted depending on the type of the supporting electrolyte.
- the organic solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte.
- dimethyl carbonate (DMC) dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC).
- Carbonates such as propylene carbonate (PC), butylene carbonate (BC), and methyl ethyl carbonate (MEC); esters such as ⁇ -butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfolane, Sulfur-containing compounds such as dimethyl sulfoxide; are preferably used.
- carbonates are preferable because they have a high dielectric constant and a wide stable potential region.
- the lower the viscosity of the solvent used the higher the lithium ion conductivity tends to be, so the lithium ion conductivity can be adjusted depending on the type of solvent.
- the concentration of the electrolyte in the electrolytic solution can be adjusted as appropriate.
- the non-aqueous secondary battery of the present invention described above includes, for example, a positive electrode and a negative electrode that are stacked via a separator, and are pressure-bonded as necessary, and directly or wound or folded into a battery container. It can be manufactured by injecting an electrolytic solution into a container and sealing it.
- the non-aqueous secondary battery of the present invention is a laminate obtained by stacking a positive electrode and a negative electrode through a separator from the viewpoint of further improving battery characteristics such as cycle characteristics and output characteristics while increasing volume energy density. It is preferable that the non-aqueous secondary battery includes a body (that is, does not perform operations such as winding and folding after stacking).
- At least one member is a member with a functional layer.
- an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate, or the like may be placed in the battery container to prevent an increase in pressure inside the battery or overcharge / discharge.
- the shape of the battery may be any of a coin shape, a button shape, a sheet shape, a cylindrical shape, a square shape, a flat shape, and the like.
- the amount of electrolyte solution elution of organic particles, the volume average particle diameter of organic particles, inorganic particles, and functional layer binders, the glass transition temperature of organic particles and functional layer binders, and the functional layer The blocking resistance and tear resistance of the battery member provided, the adhesion of the functional layer before and after immersion in the electrolyte, lithium deposition on the electrode surface, and the cycle characteristics and output characteristics of the secondary battery were measured by the following methods. And evaluated.
- ⁇ Electrolytic solution elution amount> The obtained aqueous dispersion of organic particles was dried to remove water, and then pressurized under conditions of 185 ° C. for 2 minutes to produce a film having a thickness of 3 ⁇ 0.3 mm.
- the produced film was cut into 5 mm squares to prepare a plurality of film pieces. About 1 g of these film pieces was accurately weighed. The mass of the precisely weighed film piece was defined as W0.
- Electrolytic solution elution amount (%) 100 ⁇ (W1 / W0) ⁇ 100 ⁇ Volume average particle diameter> [Binder for organic particles and functional layer (particulate polymer)] Measure the particle size distribution (volume basis) of organic particles and functional layer binder (particulate polymer) in aqueous dispersion using a laser diffraction particle size distribution analyzer (SALD-7100, manufactured by Shimadzu Corporation) did.
- the particle diameter at which the cumulative volume calculated from the small diameter side becomes 50% was defined as the volume average particle diameter (D50).
- the inorganic particles were dispersed in a 0.2% by mass sodium hexametaphosphate aqueous solution and subjected to ultrasonic irradiation for 1 minute to obtain an aqueous dispersion. Except for using this aqueous dispersion, the particle size distribution (volume basis) was measured in the same manner as the organic particles and functional layer binder (particulate polymer) described above, and the volume average particle size (D50) was determined. Were determined.
- the DSC curve was measured according to JISK7121 using the differential thermal-analysis measuring apparatus (the SII nanotechnology company make, EXSTAR DSC6220). Specifically, 10 mg of the dried measurement sample was weighed into an aluminum pan, an empty aluminum pan was used as a reference, and the DSC was performed at a temperature increase rate of 20 ° C./min between a measurement temperature range of ⁇ 100 ° C. to 200 ° C. The curve was measured.
- the baseline immediately before the endothermic peak of the DSC curve where the differential signal (DDSC) becomes 0.05 mW / min / mg or more and the tangent line of the DSC curve at the first inflection point after the endothermic peak The glass transition temperature of the organic particles and the functional layer binder was determined from the intersection with ⁇ Blocking resistance>
- the produced single-sided separator was cut into a square with a side of 5 cm and a square with a side of 4 cm, and two sets of test pieces were obtained with two sheets. Then, a sample obtained by simply superimposing two test pieces (a sample in an unpressed state) and a sample placed under pressure at a temperature of 40 ° C.
- a notch with a length of 50 mm extending in the length direction of the test piece was formed from the center of one short side of the test piece.
- a tear test was conducted with the end portion (width: 14 mm) divided into two pieces fixed to the upper and lower chucks of about 10 mm.
- a digital force gauge manufactured by Imada, ZTS-5N was used for the measurement, and the moving speed of the chuck was set to 400 mm / min.
- the tear strength was calculated as an average load until the moving distance of the chuck reached 60 mm.
- tear resistance was evaluated according to the following criteria. It shows that a functional layer is excellent in tear resistance, so that tear strength is large.
- Tear strength is 35 g ⁇ m / s 2 or more
- B Tear strength is 25 g ⁇ m / s 2 or more and less than 35 g ⁇ m / s 2
- C Tear strength is 15 g ⁇ m / s 2 or more and less than 25 g ⁇ m / s 2
- D Tear strength is less than 15 g ⁇ m / s 2 ⁇ Adhesiveness before electrolytic solution immersion>
- the produced single-sided positive electrode and single-sided separator were each cut to a width of 10 mm, stacked one by one so that the functional layer of the single-sided separator and the positive electrode composite material layer of the positive electrode face each other, and heated and pressed at a temperature of 85 ° C.
- Peel strength P1 is 20 N / m or more
- B Peel strength P1 is 15 N / m or more and less than 20 N / m
- C Peel strength P1 is 10 N / m or more and less than 15 N / m
- D Peel strength P1 is less than 10 N / m ⁇ electrolysis Adhesiveness after immersion in liquid> The produced single-sided negative electrode and single-sided separator were each cut out into a strip shape of 10 mm ⁇ 100 mm.
- the negative electrode mixture layer of a single-sided negative electrode on the surface of the functional layer of a single-sided separator, it heat-presses for 6 minutes at the temperature of 85 degreeC and the pressure of 0.5 MPa, and prepares the laminated body provided with a single-sided negative electrode and a single-sided separator.
- the laminate was used as a test piece. This test piece was put into a laminate packaging material with about 400 ⁇ l of an electrolyte solution. After 1 hour, the test piece was pressed together with the laminate packaging material at 60 ° C. and a pressure of 0.5 MPa for 15 minutes. After pressing, the temperature was maintained at 60 ° C. for 1 day.
- EC / DEC / VC volume mixing ratio at 25 ° C.
- LiPF 6 dissolved at a concentration of 1 mol / L was used.
- the test piece was taken out and the electrolytic solution adhering to the surface was wiped off.
- the cellophane tape was affixed on the surface of the single-sided negative electrode for this test piece with the current collector-side surface of the single-sided negative electrode facing down.
- a cellophane tape defined in JIS Z1522 was used.
- the cellophane tape was fixed on a horizontal test bench. And the stress when one end of the single-sided separator was pulled upward at a pulling speed of 50 mm / min and peeled was measured. This measurement was performed three times, and the average value of the stress was determined as the peel strength P2 and evaluated according to the following criteria. The larger the peel strength P2, the better the adhesion of the functional layer in the electrolytic solution, indicating that the separator and the electrode are firmly bonded.
- the metal deposition rate on the electrode during charging of the secondary battery was measured as a lithium deposition area ratio on the negative electrode by the following method. Specifically, the manufactured lithium ion secondary battery was fully charged to a depth of charge (SOC) of 100% at a constant current of 1 C in a 20 ° C. environment.
- SOC depth of charge
- Lithium precipitation area ratio (%) (Area of precipitated lithium / Area of surface of negative electrode composite material layer) ⁇ 100 Calculated according to And it evaluated on the following references
- Lithium deposition area ratio is less than 2%
- the manufactured lithium ion secondary battery was allowed to stand for 24 hours in an environment at 25 ° C., and then charged to 4.35 V at a charge rate of 0.1 C in an environment at 25 ° C., and a discharge rate of 0.1 C.
- the charge / discharge operation for discharging to 2.75 V was performed, and the initial capacity C0 was measured. Thereafter, the same charge / discharge operation was repeated under an environment of 60 ° C., and the capacity C1 after 1000 cycles was measured.
- a larger value of the capacity retention ratio ⁇ C indicates that the secondary battery has better high-temperature cycle characteristics and a longer life.
- Capacity maintenance ratio ⁇ C is 84% or more
- the manufactured lithium ion secondary battery was allowed to stand for 24 hours in an environment of 25 ° C., and then charged for 5 hours at a charge rate of 0.1 C in an environment of 25 ° C., and the voltage V0 at that time was Was measured. Thereafter, a discharge operation was performed at a discharge rate of 1 C in an environment of ⁇ 15 ° C., and the voltage V1 15 seconds after the start of discharge was measured.
- a smaller voltage change ⁇ V indicates that the secondary battery is more excellent in low temperature output characteristics.
- Example 1 ⁇ Preparation of organic particles>
- 10 parts of polystyrene particles weight average molecular weight: 17,000, average particle diameter: 0.21 ⁇ m
- 4 parts of sodium dodecylbenzenesulfonate as an emulsifier 4 parts of sodium dodecylbenzenesulfonate as an emulsifier
- a crosslinkable monomer 70 parts of divinylbenzene as a body 1 part of sodium persulfate as a polymerization initiator
- 800 parts of ion-exchanged water were charged, followed by polymerization at 80 ° C. for 1 hour with stirring while blowing nitrogen gas.
- a monomer composition was obtained by mixing 40 parts of styrene as a monomer, 0.8 part of itaconic acid as an acid group-containing monomer, and 1.0 part of ethylene glycol dimethacrylate as a crosslinkable monomer. .
- This monomer composition was continuously added to the reaction vessel over 4 hours for polymerization. During the addition, the reaction was carried out at 60 ° C.
- ⁇ Preparation of functional layer composition For 100 parts of barium sulfate particles (volume average particle diameter: 0.6 ⁇ m, specific surface area: 6.0 m 2 / g) as inorganic particles, polycarboxylic acid-based dispersant (San Nopco, SN Dispersant 5020) Add 2.5 parts, and add water to make the solid content 50%, then use the media-less dispersion device (product name "Inline Crusher MKO" manufactured by IKA) A dispersion of barium sulfate particles in water was prepared by passing the solution twice.
- polycarboxylic acid-based dispersant San Nopco, SN Dispersant 5020
- a separator base material As a separator base material, an organic separator base material made of polyethylene (manufactured by a sequential biaxial stretching method. Thickness: 7 ⁇ m. 40% by mass of ultra high molecular weight polyethylene having a Mw of 2.4 ⁇ 10 6 and Mw of 2.6 ⁇ And a polyethylene composition composed of 10 5 high-density polyethylene (60% by mass).
- the functional layer composition obtained as described above was applied to one side of the prepared organic separator substrate and dried at 60 ° C. for 10 minutes. Thereby, a separator (single-sided separator) provided with a functional layer (thickness: 1 ⁇ m) on one side was obtained.
- the functional layer composition obtained as described above was applied to both surfaces of an organic separator substrate prepared in the same manner and dried at 60 ° C. for 10 minutes. This obtained the separator (double-sided separator) provided with a functional layer (thickness: 1 micrometer) on both surfaces. Using the obtained single-sided and double-sided separators, blocking resistance, tear resistance, and adhesion before and after immersion in the electrolyte were evaluated. The results are shown in Table 1.
- a 5% aqueous sodium hydroxide solution was added to the mixture containing the binder for the negative electrode mixture layer to adjust the pH to 8. Subsequently, after removing the unreacted monomer by heating under reduced pressure, it was cooled to 30 ° C. or lower to obtain an aqueous dispersion containing the desired binder for the negative electrode mixture layer.
- the mixed solution 1.5 parts of the binder for the negative electrode mixture layer and ion-exchanged water corresponding to the solid content are added, adjusted so that the final solid content concentration is 52%, and further mixed for 10 minutes. did. This was defoamed under reduced pressure to obtain a slurry composition for a secondary battery negative electrode having good fluidity.
- the obtained negative electrode slurry composition was applied on a copper foil having a thickness of 20 ⁇ m, which was a current collector, with a comma coater so that the film thickness after drying was about 150 ⁇ m, and dried. This drying was performed by conveying the copper foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C.
- the negative electrode raw material before pressing was rolled with a roll press to obtain a negative electrode after pressing with a negative electrode mixture layer thickness of 80 ⁇ m (single-sided negative electrode).
- a negative electrode mixture layer is formed on both sides, and rolled by a roll press, and the thickness of the negative electrode mixture layer is 80 ⁇ m after pressing.
- a negative electrode was obtained (double-sided negative electrode).
- the obtained positive electrode slurry composition was applied onto a 20 ⁇ m-thick aluminum foil as a current collector by a comma coater so that the film thickness after drying was about 150 ⁇ m and dried. This drying was performed by transporting the aluminum foil in an oven at 60 ° C. at a speed of 0.5 m / min for 2 minutes. Thereafter, heat treatment was performed at 120 ° C. for 2 minutes to obtain a positive electrode raw material before pressing.
- the positive electrode raw material before pressing was rolled with a roll press to obtain a positive electrode after pressing with a positive electrode mixture layer thickness of 80 ⁇ m (single-sided positive electrode).
- a positive electrode was obtained (double-sided positive electrode).
- the single-sided positive electrode obtained above is cut out to 5 cm ⁇ 15 cm, and the double-sided separator cut out to 6 cm ⁇ 16 cm is arranged on the top (the composite material layer side) so that one functional layer of the separator faces the single-sided positive electrode. did.
- the double-sided negative electrode cut out to 5.5 cm x 15.5 cm was arrange
- a double-sided separator cut out to 6 cm ⁇ 16 cm was disposed so that one functional layer of the separator faces the double-sided negative electrode.
- a double-sided positive electrode cut out to 5 cm ⁇ 15 cm was stacked on the other functional layer side of the double-sided separator.
- a double-sided separator cut out to 6 cm ⁇ 16 cm on the double-sided positive electrode was further arranged so that one functional layer of the separator was opposed to the double-sided positive electrode.
- a single-sided negative electrode cut out to 5.5 cm ⁇ 5.5 cm is laminated on the other functional layer of the double-sided separator so that the negative electrode composite material layer faces the functional layer of the double-sided separator, and laminate B Got.
- the obtained battery outer packaging was flat-pressed at 100 ° C. for 2 minutes at 100 kgf to produce a 1000 mAh stacked lithium ion secondary battery. did.
- the obtained secondary battery lithium deposition on the electrode surface, cycle characteristics, and output characteristics were evaluated. The results are shown in Table 1.
- Examples 2 and 3 In the same manner as in Example 1 except that the composition of organic particles and the amount of inorganic particles used (in Example 3, no inorganic particles were used) were changed as shown in Table 1, organic particles and particulate polymers (functions) Layer binder), a functional layer composition, a separator, a positive electrode, a negative electrode, and a secondary battery. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. In addition, it was confirmed that the glass transition temperature of the organic particles used in Examples 2 and 3 was 100 ° C. or higher.
- Example 4 The amount of inorganic particles was changed as shown in Table 1, and the particulate polymer (binder for functional layer) was used in the same manner as in Example 1 except that organic particles prepared as follows were used. , A functional layer composition, a separator, a positive electrode, a negative electrode, and a secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. In addition, it confirmed that the glass transition temperature of the organic particle used for Example 4 was 100 degreeC or more.
- Example 5 The amount of inorganic particles was changed as shown in Table 1, and the particulate polymer (binder for functional layer) was used in the same manner as in Example 1 except that organic particles prepared as follows were used. , A functional layer composition, a separator, a positive electrode, a negative electrode, and a secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. In addition, it confirmed that the glass transition temperature of the organic particle used for Example 5 was 100 degreeC or more.
- Example 6 When preparing the organic particles, the composition of the organic particles was changed as shown in Table 1, and the amount of sodium dodecylbenzenesulfonate as an emulsifier was changed to 1.5 parts without using polyvinyl alcohol as a stabilizer during dispersion. Except that, organic particles, particulate polymer (functional layer binder), functional layer composition, single-sided and double-sided separator, positive electrode, negative electrode, and secondary battery were produced in the same manner as Example 5. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. In addition, it confirmed that the glass transition temperature of the organic particle used for Example 6 was 100 degreeC or more.
- Examples 7 and 8 In the same manner as in Example 6, except that the organic particles prepared as described below were used, and the amounts of the organic particles, inorganic particles, and functional layer binder were changed as shown in Table 1. A polymer (binder for functional layer), a composition for functional layer, a separator, a positive electrode, a negative electrode, and a secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1. In addition, it confirmed that the glass transition temperature of the organic particle used for Example 7 and 8 was 100 degreeC or more.
- Example 9 Except for changing the amount of inorganic particles used as shown in Table 1 and changing the amount of sodium lauryl sulfate as an emulsifier to 0.1 part when preparing the particulate polymer (binder for functional layer), In the same manner as in Example 6, organic particles, particulate polymer (functional layer binder), functional layer composition, separator, positive electrode, negative electrode, and secondary battery were produced. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.
- Example 10 The amount of sodium lauryl sulfate as an emulsifier was changed to 6 parts at the time of preparation of organic particles, and the amount of sodium lauryl sulfate as an emulsifier was changed to 0.8 parts at the time of preparation of a particulate polymer (binder for functional layer). Except for changing to, organic particles, particulate polymer (binder for functional layer), functional layer composition, separator, positive electrode, negative electrode and secondary battery were produced in the same manner as in Example 6. Various evaluations were performed in the same manner as in Example 1. The results are shown in Table 1.
- Example 11 and 12 When preparing the functional layer composition, instead of barium sulfate particles as inorganic particles, alumina particles (volume average particle size: 0.8 ⁇ m) and boehmite particles (volume average particle size: 0.9 ⁇ m) are used, respectively. And except having changed the usage-amount of inorganic particle
- TMPT divinylbenzene unit
- EDMA trimethylolpropane trimethacrylate units
- ST indicates a styrene unit
- EVB indicates an ethylvinylbenzene unit
- BA represents an n-butyl acrylate unit
- MMA indicates methyl methacrylate unit
- MAA indicates a methacrylic acid unit
- 2HEMA refers to 2-hydroxyethyl methacrylate units
- PST indicates polystyrene
- PVA refers to polyvinyl alcohol
- PVP refers to polyvinylpyrrolidone
- ACL indicates an acrylic polymer.
- a non-aqueous secondary battery capable of forming a functional layer for a non-aqueous secondary battery that is excellent in adhesiveness after immersion in an electrolyte and can exhibit excellent cycle characteristics and output characteristics in a non-aqueous secondary battery.
- a composition for a secondary battery functional layer can be provided.
- the functional layer for non-aqueous secondary batteries which can exhibit the cycling characteristics and output characteristics which were excellent in the non-aqueous secondary battery can be provided.
- the non-aqueous secondary battery which is excellent in cycling characteristics and output characteristics can be provided.
- the manufacturing method of the electrode for non-aqueous secondary batteries which can exhibit the cycling characteristics and output characteristics which were excellent in the non-aqueous secondary battery can be provided.
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Abstract
Description
具体的には、例えば特許文献1では、親水性酸性基を有するビニルモノマーの重合単位を含んでなる結着材と、親水性酸性基と架橋し得る官能基を有する非導電性有機粒子と、溶媒とを含む二次電池多孔膜用スラリーを用いて多孔膜を形成することにより、多孔膜から非導電性有機粒子が脱落する(粉落ちする)のを抑制すると共に、多孔膜の柔軟性を向上させる技術が提案されている。
すなわち、上記特許文献1の機能層用組成物には、機能層の電解液浸漬後の接着性を高めて、二次電池に優れた電池特性を発揮させるという点において、改善の余地があった。
また、本発明は、非水系二次電池に優れたサイクル特性および出力特性を発揮させうる非水系二次電池用機能層を提供することを目的とする。
そして、本発明は、サイクル特性および出力特性に優れる非水系二次電池を提供することを目的とする。
更に、本発明は、非水系二次電池に優れたサイクル特性および出力特性を発揮させうる非水系二次電池用電極の製造方法を提供することを目的とする。
なお、本発明において、有機粒子の「電解液溶出量」は、本明細書の実施例に記載の方法を用いて測定することができる。
なお、本発明において、有機粒子などの重合体が「単量体単位を含む」とは、「その単量体を用いて得た重合体中に単量体由来の構造単位が含まれている」ことを意味する。
なお、本発明において、有機粒子の「体積平均粒子径」は、本明細書の実施例に記載の方法を用いて測定することができる。
なお、本発明において、機能層用結着材の「体積平均粒子径」は、本明細書の実施例に記載の方法を用いて測定することができる。
また、本発明によれば、非水系二次電池に優れたサイクル特性および出力特性を発揮させうる非水系二次電池用機能層を提供することができる。
そして、本発明によれば、サイクル特性および出力特性に優れる非水系二次電池を提供することができる。
更に、本発明によれば、非水系二次電池に優れたサイクル特性および出力特性を発揮させうる非水系二次電池用電極の製造方法を提供することができる。
ここで、本発明の非水系二次電池機能層用組成物は、非水系二次電池用機能層を調製する際の材料として用いられる。そして、本発明の非水系二次電池用機能層は、本発明の非水系二次電池機能層用組成物を用いて形成される。また、本発明の非水系二次電池は、少なくとも本発明の非水系二次電池用機能層を備えるものである。更に、本発明の非水系二次電池用電極の製造方法は、本発明の非水系二次電池用機能層を備える非水系二次電池用電極を作成する際に用いられる。
本発明の機能層用組成物は、非導電性粒子としての有機粒子と、機能層用結着材とを含有し、任意に、非導電性粒子としての無機粒子、機能層に含有されうるその他の成分(添加剤など)を更に含有する、水などを分散媒としたスラリー組成物である。ここで、本発明の機能層用組成物は、有機粒子の電解液溶出量が、0.001質量%以上5.0質量%以下であることを特徴とする。
有機粒子は、機能層の耐熱性や強度を高めうる非導電性粒子として用いられる粒子であり、通常、結着能を有さない重合体からなる。そして、非導電性粒子は、電気化学的に安定であるため、二次電池の使用環境下で機能層中に安定に存在する。
有機粒子の電解液溶出量は、0.001質量%以上5.0質量%以下であることが必要であり、0.005質量%以上であることが好ましく、0.01質量%以上であることがより好ましく、0.1質量%以上であることが更に好ましく、0.7質量%以上であることが特に好ましく、4.5質量%以下であることが好ましく、4.0質量%以下であることがより好ましく、3.7質量%以下であることが更に好ましい。有機粒子の電解液溶出量が上記下限値未満となると、有機粒子の電解液に対する濡れ性を確保することができず、二次電池の出力特性が低下する。一方、有機粒子の電解液溶出量が上記上限値を超えると、電解液中で有機粒子がその形状を十分に維持することが困難となり、機能層の電解液浸漬後の接着性を確保することができない。そのため、二次電池のサイクル特性が低下する。また、原因は定かではないが、有機粒子の電解液溶出量が上記上限値を超えると、耐ブロッキング性が低下する傾向がある。
なお、電解液溶出量は、有機粒子の組成を変更することで調整することができる。例えば、有機粒子中の架橋性単量体単位の含有割合を増やせば電解液溶出量を低下させることができ、架橋性単量体単位の含有割合を減らせば電解液溶出量を高めることができる。ここで、架橋性単量体単位を含む有機粒子を重合する際、分散安定剤を用いることで電解液溶出量を一層低下させることができる。また、有機粒子中のエポキシ基含有単量体単位および/またはアルコキシシリル基含有単量体単位の含有割合を減らせば電解液溶出量を低下させることができ、エポキシ基含有単量体単位および/またはアルコキシシリル基含有単量体単位の含有割合を増やせば電解液溶出量を高めることができる。
そして、有機粒子の体積平均粒子径DAは、後述する機能層用結着材の体積平均粒子径DB以上であることが好ましく、体積平均粒子径DBよりも大きいことがより好ましい。有機粒子の体積平均粒子径DAが、機能層用結着材の体積平均粒子径DB以上であれば、機能層を備える電池部材の耐ブロッキング性を高めると共に、機能層の電解液浸漬後の接着性を更に向上させることができる。そして、二次電池のサイクル特性および出力特性を一層向上させることができる。
なお、本発明において、有機粒子の「ガラス転移温度」は、JIS K7121に準拠し、示差走査熱量分析により測定することができる。
重合体である有機粒子の組成は、特に限定されないが、有機粒子は、架橋性単量体単位を含むことが好ましい。そして、有機粒子は、架橋性単量体単位以外の単量体単位(その他の単量体単位)を含むことができる。
架橋性単量体単位を形成し得る架橋性単量体は、1分子あたり2つ以上の重合可能な二重結合(例えば、オレフィン性二重結合)を有する単量体である。ここで架橋性単量体としては、例えば、2官能架橋性単量体、3官能架橋性単量体、4官能架橋性単量体が挙げられる。
2官能架橋性単量体としては、エチレングリコールジ(メタ)アクリレート、ジエチレングリコールジ(メタ)アクリレート、トリエチレングリコールジ(メタ)アクリレート、テトラエチレングリコールジ(メタ)アクリレート、1,3-ブチレングリコールジ(メタ)アクリレート、1,4-ブチレングリコールジ(メタ)アクリレート、1,6-ヘキサンジオールジ(メタ)アクリレート、ネオペンチルグリコールジ(メタ)アクリレート、ポリプロピレングリコールジ(メタ)アクリレート(好ましくは、分子量が500~1200)、2,2-ビス(4-(アクリロキシプロピロキシ)フェニル)プロパン、2,2-ビス(4-(アクリロキシジエトキシ)フェニル)プロパン、ジプロピレングリコールジアリルエーテル、ジエチレングリコールジアリルエーテル、トリエチレングリコールジビニルエーテル、トリメチロールプロパン-ジアリルエーテル、メチレンビスアクリルアミド、ジビニルベンゼン、アリル(メタ)アクリレートなどが挙げられる。
3官能架橋性単量体としては、トリアリルアミン、トリメチロールプロパントリ(メタ)アクリレートなどが挙げられる。
4官能架橋性単量体としては、テトラアリルオキシエタン、テトラメチロールメタントリ(メタ)アクリレート、ジトリメチロールプロパンテトラ(メタ)アクリレート、テトラメチロールメタンテトラ(メタ)アクリレート、ペンタエリスリトールテトラ(メタ)アクリレートなどが挙げられる。
なお、本発明において、「(メタ)アクリレート」とは、アクリレートおよび/またはメタクリレートを意味する。
有機粒子が含みうる架橋性単量体単位以外の単量体単位としては、特に限定されないが、芳香族モノビニル単量体単位、(メタ)アクリル酸エステル単量体単位、酸基含有単量体単位、水酸基含有単量体単位、エポキシ基含有単量体単位、アルコキシシリル基含有単量体単位などが挙げられる。ここで、その他の単量体単位は、上述したように架橋性単量体単位以外の単量体単位である。そのため、上述した架橋性単量体に該当する単量体は、その他の単量体単位を形成しうるその他の単量体には含まれないものとする。
なお、本発明において、「(メタ)アクリル」とは、アクリルおよび/またはメタクリルを意味する。
また、スルホン酸基を有する単量体としては、例えば、ビニルスルホン酸、メチルビニルスルホン酸、(メタ)アリルスルホン酸、(メタ)アクリル酸-2-スルホン酸エチル、2-アクリルアミド-2-メチルプロパンスルホン酸、3-アリロキシ-2-ヒドロキシプロパンスルホン酸などが挙げられる。
更に、リン酸基を有する単量体としては、例えば、リン酸-2-(メタ)アクリロイルオキシエチル、リン酸メチル-2-(メタ)アクリロイルオキシエチル、リン酸エチル-(メタ)アクリロイルオキシエチルなどが挙げられる。
なお、本発明において、「(メタ)アリル」とは、アリルおよび/またはメタリルを意味し、「(メタ)アクリロイル」とは、アクリロイルおよび/またはメタクリロイルを意味する。
有機粒子は、上述した単量体を含む単量体組成物を、例えば水などの水系溶媒中で重合することにより、製造し得る。この際、単量体組成物中の各単量体の含有割合は、有機粒子中の各繰り返し単位(単量体単位)の含有割合に準じて定めることができる。
そして、重合様式は、特に制限なく、溶液重合法、懸濁重合法、塊状重合法、乳化重合法などのいずれの方法も用いることができる。また、重合反応としては、イオン重合、ラジカル重合、リビングラジカル重合などいずれの反応も用いることができる。重合に際しては、シード粒子を採用してシード重合を行ってもよい。重合条件は、重合方法などに応じて適宜調整しうる。
また、重合には、乳化剤、重合開始剤、重合助剤、分散安定剤、補助安定剤などの添加剤を使用しうる。
乳化剤、重合開始剤、重合助剤としては、一般に用いられるものを使用することができ、これらの使用量も、一般に使用される量としうる。
そして、分散安定剤としては、特に限定されず、例えば、水酸基、カルボニル基、アミノ基、およびエポキシ基からなる群から選択される少なくとも1つを含む重合体(但し、有機粒子や機能層用結着材に該当するものを除く)を使用することができる。このような分散安定剤としては、例えば、ポリビニルアルコール、カルボキシメチルセルロース、ポリアクリル酸塩、ロジン樹脂、ポリビニルピロリドン、ポリ(メタ)アクリル酸エステルなどが挙げられる。これらの中でも、水溶性であるものが好ましく、水溶性であり且つ非イオン性のものが好ましい。水溶性であり且つ非イオン性の分散安定剤としては、ポリビニルアルコールおよびポリビニルピロリドンが挙げられる。分散安定剤の使用量は、特に限定されないが、重合に用いる単量体(有機粒子の調製にシード重合を用いる場合、シード粒子の調製に使用した単量体を含む)100質量部当たり、好ましくは0.1質量部以上30質量部以下であり、より好ましくは0.8質量部以上25質量部以下である。分散安定剤の使用量が上記下限値を下回ると、重合安定性が悪化して電解液溶出量が高まる虞がある。一方、分散安定剤の使用量が上記上限値を上回ると、得られる有機粒子が着色するなどの問題が生じる虞がある。
ここで、有機粒子の調製に架橋性単量体を使用する場合、上記分散安定剤に加え補助安定剤を用いることもできる。補助安定剤を用いることで、特に架橋性単量体の分散安定性を高めて重合を一層安定的に進行させることができる。また補助安定剤を用いることで、有機粒子を含む機能層用組成物の成膜性を高めて、得られる機能層を備える電池部材(特にセパレータ)の耐引裂き性を高める効果がある。このような補助安定剤としては、アニオン性界面活性剤、ノニオン性界面活性剤、4級アンモニウム塩、長鎖アルコール等が用いられる。具体的には、ジ(2-エチルヘキシル)スルホコハク酸ナトリウム、ノニルフェノキシポリエトキシエタノール、メチルトリカプリルアンモニウムクロリド、セチルアルコール等を挙げることができる。
機能層用結着材は、機能層に含まれる上記有機粒子などの成分が機能層から脱離しないように保持する。そして、機能層用結着材は、通常、結着能を有する重合体からなる。機能層用組成物に用いる結着材としては、例えば、粒子状重合体を用いることが好ましい。ここで、通常、粒子状重合体は、非水溶性の重合体である。なお、本発明において、重合体が「非水溶性」であるとは、25℃において、その重合体0.5gを100gの水に溶解した際に、不溶分が90質量%以上となることをいう。
機能層用結着材(粒子状重合体)の体積平均粒子径DB(D50)は、0.01μm以上であることが好ましく、0.05μm以上であることがより好ましく、0.5μm以下であることが好ましく、0.35μm以下であることがより好ましい。機能層用結着材の体積平均粒子径DBが上記下限値以上であれば、機能層のガーレー値が上昇する(即ち、イオン伝導性が低下する)のを抑制して、リチウムなどの金属が電極上に析出するのを抑制すると共に、二次電池のサイクル特性および出力特性を更に向上させることができる。一方、機能層用結着材の体積平均粒子径DBが上記上限値以下であれば、電解液浸漬前の機能層の接着性を向上させて、粉落ちを抑制することができる。
ここで、機能層用結着材である粒子状重合体としては、特に限定されることなく、熱可塑性樹脂、熱硬化性樹脂、および合成ゴムなどの、機能層を形成する際に使用し得る既知の粒子状重合体を用いることができる。具体的には、粒子状重合体としては、スチレン-ブタジエン共重合体(SBR)などの、共役ジエン単量体単位を含む重合体(共役ジエン系重合体)や、(メタ)アクリル酸エステル単量体単位を含む重合体(アクリル系重合体)が好適に挙げられる。これらの中でも、アクリル系重合体がより好適である。そして、これらの粒子状重合体は、1種類を単独で使用してもよいし、2種類以上を組み合わせて用いてもよい。
以下、一例として、粒子状重合体であるアクリル系重合体の好適組成について説明するが、機能層用結着材はこれに限定されるものではない。好適な粒子状重合体は、(メタ)アクリル酸エステル単量体単位および芳香族モノビニル単量体単位を含み、任意にその他の単量体単位を含む。
(メタ)アクリル酸エステル単量体単位を形成しうる(メタ)アクリル酸エステル単量体としては、「有機粒子」の項で上述したものと同様のものが挙げられる。これらは、1種類を単独で用いてもよく、2種類以上を組み合わせて用いてもよい。そしてこれらの中でも、機能層中に残留する水分の量を低減して、二次電池のサイクル特性を向上させる観点からは、非カルボニル性酸素原子に結合するアルキル基の炭素数が4以上の(メタ)アクリル酸アルキルエステル(2-エチルヘキシルアクリレート、n-ブチルアクリレート、t-ブチルアクリレート、オクチルアクリレートなど)が好ましく、同炭素数が5以上の(メタ)アクリル酸アルキルエステル(2-エチルヘキシルアクリレート、オクチルアクリレートなど)がより好ましい。
芳香族モノビニル単量体単位を形成しうる芳香族モノビニル単量体としては、「有機粒子」の項で上述したものと同様のものが挙げられる。これらは、1種類を単独で用いてもよく、2種類以上を組み合わせて用いてもよい。そしてこれらの中でも、スチレンが好ましい。
粒子状重合体が含みうる(メタ)アクリル酸エステル単量体単位および芳香族モノビニル単量体単位以外の単量体単位としては、特に限定されないが、酸基含有単量体単位、架橋性単量体単位などが挙げられる。
機能層用結着材の調製方法は、特に限定されない。例えば、機能層用結着材としての粒子状重合体は、上述した単量体を含む単量体組成物を、例えば水などの水系溶媒中で重合することにより、製造し得る。この際、単量体組成物中の各単量体の含有割合は、粒子状重合体中の各繰り返し単位(単量体単位)の含有割合に準じて定めることができる。
そして、重合様式は、特に制限なく、溶液重合法、懸濁重合法、塊状重合法、乳化重合法などのいずれの方法も用いることができる。また、重合反応としては、イオン重合、ラジカル重合、リビングラジカル重合などいずれの反応も用いることができる。
また、重合に使用される乳化剤、分散剤、重合開始剤、重合助剤などの添加剤は、一般に用いられるものを使用しうる。これらの添加剤の使用量も、一般に使用される量としうる。重合条件は、重合方法および重合開始剤の種類などに応じて適宜調整しうる。
機能層用組成物中の有機粒子と機能層用結着材の含有量比は、特に限定されないが、有機粒子の含有量が、有機粒子と機能層用結着材の合計含有量の1質量%以上であることが好ましく、25質量%以上であることが好ましく、50質量%以上であることがより好ましく、60質量%以上であることが更に好ましく、75質量%以上であることが特に好ましく、99質量%以下であることが好ましく、98質量%以下であることがより好ましく、97質量%以下であることが更に好ましい。有機粒子と機能層用結着材の合計中に占める有機粒子の割合が上記下限値以上であれば、機能層を備える電池部材の耐ブロッキング性を確保すると共に、リチウムなどの金属が電極上に析出するのを抑制することができる。そして、二次電池のサイクル特性および出力特性を更に向上させることができる。一方、有機粒子と機能層用結着材の合計中に占める有機粒子の割合が上記上限値以下であれば、機能層の電解液浸漬前および電解液浸漬後の接着性を十分に確保することができる。
本発明の機能層用組成物は、非導電性粒子として、上述した有機粒子に加えて、無機粒子を用いることが好ましい。有機粒子と無機粒子を併用すれば、機能層を備える電池部材の耐ブロッキング性および耐熱性を向上させることができる
無機粒子としては、酸化アルミニウム(アルミナ)、酸化アルミニウムの水和物(ベーマイト(AlOOH)、ギブサイト(Al(OH)3)、酸化ケイ素、酸化マグネシウム(マグネシア)、酸化カルシウム、酸化チタン(チタニア)、チタン酸バリウム(BaTiO3)、ZrO、アルミナ-シリカ複合酸化物等の酸化物粒子;窒化アルミニウム、窒化ホウ素等の窒化物粒子;シリコン、ダイヤモンド等の共有結合性結晶粒子;硫酸バリウム、フッ化カルシウム、フッ化バリウム等の難溶性イオン結晶粒子;タルク、モンモリロナイト等の粘土微粒子;などが挙げられる。また、これらの粒子は、必要に応じて元素置換、表面処理、固溶体化等が施されていてもよい。これらの中でも、無機粒子としては、ベーマイト粒子、硫酸バリウム粒子、アルミナ粒子が好ましい。
なお、上述した無機粒子は、1種類を単独で使用してもよいし、2種類以上を組み合わせて用いてもよい。
なお、本発明において、「無機粒子の体積平均粒子径」は、本明細書の実施例に記載の方法を用いて測定することができる。
機能層用組成物は、上述した成分以外にも、任意のその他の成分を含んでいてもよい。前記その他の成分は、電池反応に影響を及ぼさないものであれば特に限られず、公知のものを使用することができる。また、これらのその他の成分は、1種類を単独で使用してもよいし、2種類以上を組み合わせて用いてもよい。
前記その他の成分としては、例えば、分散剤や濡れ剤などの既知の添加剤が挙げられる。
本発明の機能層用組成物の分散媒としては、通常、水が用いられる。なお、分散媒としては、水と他の溶媒との混合物も用いることができる。ここで、他の溶媒としては、特に限定されることなく、例えば、シクロペンタン、シクロヘキサン等の環状脂肪族炭化水素化合物;トルエン、キシレン等の芳香族炭化水素化合物;エチルメチルケトン、シクロヘキサノン等のケトン化合物;酢酸エチル、酢酸ブチル、γ-ブチロラクトン、ε-カプロラクトン等のエステル化合物;アセトニトリル、プロピオニトリル等のニトリル化合物;テトラヒドロフラン、エチレングリコールジエチルエーテル等のエーテル化合物;メタノール、エタノール、イソプロパノール、エチレングリコール、エチレングリコールモノメチルエーテル等のアルコール化合物;N-メチルピロリドン(NMP)、N,N-ジメチルホルムアミド等のアミド化合物;などが挙げられる。これらは、1種類を単独で用いてもよく、2種類以上を任意の比率で組み合わせて用いてもよい。
本発明の機能層用組成物は、特に限定されることなく、上述した有機粒子、機能層用結着材、並びに、任意に使用されうる無機粒子および添加剤を、水などの分散媒の存在下で混合して得ることができる。
本発明の非水系二次電池用機能層は、上述した非水系二次電池機能層用組成物から形成されたものであり、例えば、上述した機能層用組成物を適切な基材の表面に塗布して塗膜を形成した後、形成した塗膜を乾燥することにより、形成することができる。即ち、本発明の非水系二次電池用機能層は、上述した非水系二次電池機能層用組成物の乾燥物よりなり、有機粒子および機能層用結着材を含有し、任意に、無機粒子および添加剤を含有する。なお、上述した有機粒子および/または機能層用結着材が架橋性単量体単位を含む場合は、当該架橋性単量体単位を含む重合体は、非水系二次電池機能層用組成物の乾燥時、或いは、乾燥後に任意に実施される熱処理時などに架橋されていてもよい(即ち、非水系二次電池用機能層は、上述した有機粒子および/または機能層用結着材の架橋物を含んでいてもよい)。
ここで、機能層用組成物を塗布する基材に制限は無く、例えば離型基材の表面に機能層用組成物の塗膜を形成し、その塗膜を乾燥して機能層を形成し、機能層から離型基材を剥がすようにしてもよい。このように、離型基材から剥がされた機能層を自立膜として二次電池の電池部材の形成に用いることもできる。具体的には、離型基材から剥がした機能層をセパレータ基材の上に積層して機能層を備えるセパレータを形成してもよいし、離型基材から剥がした機能層を電極基材の上に積層して機能層を備える電極を形成してもよい。
しかし、機能層を剥がす工程を省略して電池部材の製造効率を高める観点からは、基材としてセパレータ基材または電極基材を用いることが好ましい。セパレータ基材および電極基材上に設けられた機能層は、セパレータおよび電極の耐熱性や強度などを向上させる保護層として好適に使用することができる。
セパレータ基材としては、特に限定されないが、有機セパレータ基材などが挙げられる。有機セパレータ基材は、有機材料からなる多孔性部材である。ここで、有機セパレータ基材の例としては、ポリエチレン、ポリプロピレン等のポリオレフィン樹脂、芳香族ポリアミド樹脂などを含む微多孔膜または不織布などが挙げられ、強度に優れることからポリエチレン製の微多孔膜や不織布が好ましい。そして、セパレータ基材の強度を高めることで機能層塗工時の搬送を安定化させるため、重量平均分子量(Mw)が1×106以上の超高分子量ポリエチレンを30質量%以上70質量%以下と、Mwが1×104以上8×105未満の(高密度)ポリエチレンを30質量%以上70質量%以下含む混合物(ポリエチレン組成物)からなるセパレータ基材がより好ましい。なお、ポリエチレンのMwは、ゲル浸透クロマトグラフィー(Gel Permeation Chromatography:GPC)を用いて測定することができる。
また、セパレータ基材の厚さは、任意の厚さとすることができ、好ましくは3μm以上30μm以下であり、より好ましくは4μm以上20μm以下であり、更に好ましくは5μm以上18μm以下である。セパレータ基材の厚さが3μm以上であれば、十分な安全性が得られる。また、セパレータ基材の厚さが30μm以下であれば、イオン伝導性が低下するのを抑制し、二次電池の低温出力特性が低下するのを抑制することができると共に、セパレータ基材の熱収縮力が大きくなるのを抑制して耐熱性を高めることができる。
電極基材(正極基材および負極基材)としては、特に限定されないが、集電体上に電極合材層が形成された電極基材が挙げられる。
集電体、電極合材層中の電極活物質(正極活物質、負極活物質)および電極合材層用結着材(正極合材層用結着材、負極合材層用結着材)、並びに、集電体上への電極合材層の形成方法としては、特に限定されないが、例えば特開2013-145763号公報に記載のものを用いることができる。
ここで、電極合材層用結着材は、二次電池のサイクル特性および出力特性を更に高める観点から、芳香族ビニル単量体単位および脂肪族共役ジエン単量体単位を含む重合体であることが好ましい。また、芳香族ビニル単量体単位および脂肪族共役ジエン単量体単位を含む電極合材層用結着材は、さらにカルボン酸基を有する単量体単位を含むことが好ましい。なお、電極合材層用結着材は、芳香族ビニル単量体単位および脂肪族共役ジエン単量体単位、並びにカルボン酸基を有する単量体単位以外の単量体単位を含んでいてもよい。
上述したセパレータ基材、電極基材などの基材上に機能層を形成する方法としては、以下の方法が挙げられる。
1)本発明の機能層用組成物をセパレータ基材または電極基材の表面(電極基材の場合は電極合材層側の表面、以下同じ)に塗布し、次いで乾燥する方法;
2)本発明の機能層用組成物にセパレータ基材または電極基材を浸漬後、これを乾燥する方法;
3)本発明の機能層用組成物を離型基材上に塗布し、乾燥して機能層を製造し、得られた機能層をセパレータ基材または電極基材の表面に転写する方法;
これらの中でも、前記1)の方法が、機能層の層厚制御をしやすいことから特に好ましい。前記1)の方法は、詳細には、機能層用組成物を基材上に塗布する工程(塗布工程)と、基材上に塗布された機能層用組成物を乾燥させて機能層を形成する工程(機能層形成工程)を含む。
そして、塗布工程において、機能層用組成物を基材上に塗布する方法としては、特に制限は無く、例えば、ドクターブレード法、リバースロール法、ダイレクトロール法、グラビア法、エクストルージョン法、ハケ塗り法などの方法が挙げられる。
また、機能層形成工程において、基材上の機能層用組成物を乾燥する方法としては、特に限定されず公知の方法を用いることができる。乾燥法としては、例えば、温風、熱風、低湿風による乾燥、真空乾燥、赤外線や電子線などの照射による乾燥が挙げられる。乾燥条件は特に限定されないが、乾燥温度は好ましくは50~150℃で、乾燥時間は好ましくは5~30分である。
そして、本発明の非水系二次電池機能層用組成物を用いて形成される機能層の厚さは、0.1μm以上であることが好ましく、0.5μm以上であることがより好ましく、5μm以下であることが好ましく、3μm以下であることがより好ましい。機能層の厚さが上記下限値以上であれば、保護機能を更に高めることができるので、機能層を設けた電池部材の耐熱性や耐引裂き性を向上させることができる。また、機能層の厚さが上記上限値以下であれば、二次電池に優れた出力特性を発揮させることができる。
本発明の機能層を備える電池部材(セパレータおよび電極)は、本発明の効果を著しく損なわない限り、セパレータ基材または電極基材と、本発明の機能層との他に、上述した本発明の機能層以外の構成要素を備えていてもよい。
ここで、機能層を備える電池部材の一例としての機能層を備える電極は、例えば、本発明の非水系二次電池用電極の製造方法を用いて製造することができる。そして、本発明の非水系二次電池用電極の製造方法は、本発明の機能層と電極基材を積層する工程と、本発明の機能層と電極基材を加圧により接着させる工程を含む。このような手順を用いれば、二次電池に優れたサイクル特性および出力特性を発揮させる大型の電極を高速で効率よく製造することができる。ここで、本発明の非水系二次電池用電極の製造方法は、機能層と電極基材が積層され、それらが加圧により接着されることで、機能層と電極基材の加圧積層体である電極を得ることができれば、その態様は特に限定されない。
例えば、機能層と電極基材の積層に際して、機能層としては、「基材」の項で上述した自立膜を用いてもよいし、セパレータ基材上に設けられた機能層を用いてもよい(より具体的には、機能層を備えるセパレータの機能層が電極基材と接するように、機能層を備えるセパレータと電極基材を積層してもよい)。なお、電極基材としては、「基材」の項で上述した電極基材と同様のものを用いることができる。
また例えば、機能層と電極基材の加圧による接着に際して、加圧は、電池容器内、電解液の存在下で行ってもよい(より具体的には、電池容器内に、機能層を備えるセパレータと電極基材を配置し、電池容器内に電解液を注入した後に加圧することで、機能層と電極基材を接着させてもよい)。そして、機能層と電極基材の加圧による接着は、既知の加圧接着手法を用いて行うことができる。
本発明の非水系二次電池は、上述した本発明の非水系二次電池用機能層を備えるものである。より具体的には、本発明の非水系二次電池は、正極、負極、セパレータ、および電解液を備え、上述した非水系二次電池用機能層が、電池部材である正極、負極およびセパレータの少なくとも一つに含まれる。そして、本発明の非水系二次電池は、優れた電池特性(例えば、サイクル特性、出力特性)を発揮し得る。
本発明の二次電池に用いる正極、負極およびセパレータは、少なくとも一つが本発明の機能層を含む。具体的には、機能層を有する正極および負極としては、集電体上に電極合材層を形成してなる電極基材の上に本発明の機能層を設けてなる電極を用いることができる。また、機能層を有するセパレータとしては、セパレータ基材の上に本発明の機能層を設けてなるセパレータを用いることができる。なお、電極基材およびセパレータ基材としては、「非水系二次電池用機能層」の項で挙げたものと同様のものを用いることができる。
また、機能層を有さない正極、負極およびセパレータとしては、特に限定されることなく、上述した電極基材よりなる電極および上述したセパレータ基材よりなるセパレータを用いることができるが、上述したMwが1×106以上の超高分子量ポリエチレンを30質量%以上70質量%以下と、Mwが1×104以上8×105未満の(高密度)ポリエチレンを30質量%以上70質量%以下含む混合物(ポリエチレン組成物)からなるセパレータ基材がより好ましい。
電解液としては、通常、有機溶媒に支持電解質を溶解した有機電解液が用いられる。支持電解質としては、例えば、リチウムイオン二次電池においてはリチウム塩が用いられる。リチウム塩としては、例えば、LiPF6、LiAsF6、LiBF4、LiSbF6、LiAlCl4、LiClO4、CF3SO3Li、C4F9SO3Li、CF3COOLi、(CF3CO)2NLi、(CF3SO2)2NLi、(C2F5SO2)NLiなどが挙げられる。なかでも、溶媒に溶けやすく高い解離度を示すので、LiPF6、LiClO4、CF3SO3Liが好ましい。なお、電解質は1種類を単独で用いてもよく、2種類以上を組み合わせて用いてもよい。通常は、解離度の高い支持電解質を用いるほどリチウムイオン伝導度が高くなる傾向があるので、支持電解質の種類によりリチウムイオン伝導度を調節することができる。
なお、電解液中の電解質の濃度は適宜調整することができる。また、電解液には、既知の添加剤を添加してもよい。
上述した本発明の非水系二次電池は、例えば、正極と負極とをセパレータを介して重ね合わせ、これを必要に応じて圧着し、そのまま、又は巻く、折るなどして電池容器に入れ、電池容器に電解液を注入して封口することで製造することができる。ここで、本発明の非水系二次電池は、体積エネルギー密度を高めつつ、サイクル特性および出力特性などの電池特性を更に高める観点から、正極と負極とをセパレータを介して重ね合わせて得られる積層体(すなわち、重ね合わせ後に巻く、折るなど操作を行わない)を含む積層型の非水系二次電池であることが好ましい。なお、正極、負極、セパレータのうち、少なくとも一つの部材を機能層付きの部材とする。また、電池容器には、必要に応じてエキスパンドメタルや、ヒューズ、PTC素子などの過電流防止素子、リード板などを入れ、電池内部の圧力上昇、過充放電の防止をしてもよい。電池の形状は、例えば、コイン型、ボタン型、シート型、円筒型、角形、扁平型など、何れであってもよい。
また、複数種類の単量体を共重合して製造される重合体において、ある単量体を重合して形成される単量体単位の前記重合体における割合は、別に断らない限り、通常は、その重合体の重合に用いる全単量体に占める当該ある単量体の比率(仕込み比)と一致する。
実施例および比較例において、有機粒子の電解液溶出量、有機粒子、無機粒子および機能層用結着材の体積平均粒子径、有機粒子および機能層用結着材のガラス転移温度、機能層を備える電池部材の耐ブロッキング性および耐引裂き性、機能層の電解液浸漬前および浸漬後の接着性、電極表面のリチウム析出、並びに、二次電池のサイクル特性および出力特性は、下記の方法で測定および評価した。
得られた有機粒子の水分散液を乾燥して水を除去した後、185℃2分の条件で加圧して、厚さ3±0.3mmのフィルムを作製した。作製したフィルムを5mm角に裁断して複数のフィルム片を用意した。これらのフィルム片の約1gを精秤した。精秤したフィルム片の質量をW0とした。このフィルム片を、100gの電解液(EC、MEC、DECの混合溶媒(EC/MEC/DEC(25℃における体積混合比)=30/20/50))に60℃で24時間浸漬した。その後、電解液からフィルム片を引き揚げた。引き揚げたフィルム片をメタノールで洗浄し、次いで105℃で3時間真空乾燥して、その重量(不溶分の質量)W1を計測した。そして、以下の式に従って、有機粒子の電解液溶出量(%)を算出した。
電解液溶出量(%)=100-(W1/W0)×100
<体積平均粒子径>
[有機粒子および機能層用結着材(粒子状重合体)]
レーザー回折式粒度分布測定装置(島津製作所社製、SALD-7100)を用いて水分散液中の有機粒子および機能層用結着材(粒子状重合体)の粒子径分布(体積基準)を測定した。そして、測定された粒子径分布において、小径側から計算した累積体積が50%となる粒子径を体積平均粒子径(D50)とした。
[無機粒子]
無機粒子を0.2質量%ヘキサメタリン酸ナトリウム水溶液に分散させ、1分間超音波照射を施して水分散液を得た。この水分散液を使用した以外は、上述した有機粒子および機能層用結着材(粒子状重合体)と同様にして粒子径分布(体積基準)を測定し、体積平均粒子径(D50)を決定した。
<ガラス転移温度>
有機粒子および機能層用結着材について、示差熱分析測定装置(エスアイアイ・ナノテクノロジー社製、EXSTAR DSC6220)を用い、JIS K7121に従ってDSC曲線を測定した。具体的には、乾燥させた測定試料10mgをアルミパンに計量し、リファレンスとして空のアルミパンを用い、測定温度範囲-100℃~200℃の間で、昇温速度20℃/分で、DSC曲線を測定した。この昇温過程で、微分信号(DDSC)が0.05mW/分/mg以上となるDSC曲線の吸熱ピークが出る直前のベースラインと、吸熱ピーク後に最初に現れる変曲点でのDSC曲線の接線との交点から、有機粒子および機能層用結着材のガラス転移温度を求めた。
<耐ブロッキング性>
作製した片面セパレータを、一辺が5cmの正方形と、一辺が4cmの正方形とに切って、2枚で一組の試験片を2組得た。そして、2枚の試験片を単に重ね合わせたサンプル(未プレスの状態のサンプル)と、2枚の試験片を重ね合わせた後に温度40℃、圧力10g/cm2の加圧下に置いたサンプル(プレスしたサンプル)とを作製した。その後、これらのサンプルを、それぞれ24時間放置した。
そして、24時間放置後のサンプルにおいて、各サンプルのセパレータ同士の接着状態(ブロッキング状態)を確認し、下記の基準で評価した。
A:未プレス状態のサンプルおよびプレスしたサンプルの双方においてセパレータ同士が張り付かなかった。
B:未プレス状態のサンプルではセパレータ同士は張り付かなかったが、プレスしたサンプルではセパレータ同士が張り付いた。
<耐引裂き性>
作製した両面セパレータ(各機能層の厚み:1μm)を、長さ150mm、幅28mmの長方形に切り出し試験片とした。この試験片の一方の短辺中心から、試験片長さ方向に伸びる長さ50mmの切り欠きを形成した。二つに分かれた端部(幅14mm)をテンシロンの上下のチャックに約10mm程度固定して引裂き試験を行った。測定にはデジタルフォースゲージ(イマダ社製、ZTS-5N)を用い、チャックの移動速度は400mm/分とした。引裂き強度は、チャックの移動距離が60mmとなるまでの平均荷重として算出した。そして、耐引裂き性を下記の基準で評価した。引裂き強度が大きいほど、機能層が耐引裂き性に優れることを示す。
A:引裂き強度が35g・m/s2以上
B:引裂き強度が25g・m/s2以上35g・m/s2未満
C:引裂き強度が15g・m/s2以上25g・m/s2未満
D:引裂き強度が15g・m/s2未満
<電解液浸漬前の接着性>
作製した片面正極および片面セパレータをそれぞれ10mm幅に切り出して、片面セパレータの機能層と正極の正極合材層が向かい合うように1枚ずつ重ね、温度85℃、圧力0.5MPaで6分間加熱プレスして試験片とした。この試験片を、正極の集電体側表面を下にして、正極の表面にセロハンテープを貼り付けた。この際、セロハンテープはJIS Z1522に規定されるものを用いた。また、セロハンテープは水平な試験台に固定しておいた。その後、片面セパレータの一端を鉛直上方に引張り速度50mm/分で引っ張って剥がしたときの応力を測定した。この測定を3回行い、応力の平均値を求めて、当該平均値をピール強度P1とした。ピール強度P1が大きいほど、機能層が電解液浸漬前の接着性に優れることを示す。
A:ピール強度P1が20N/m以上
B:ピール強度P1が15N/m以上20N/m未満
C:ピール強度P1が10N/m以上15N/m未満
D:ピール強度P1が10N/m未満
<電解液浸漬後の接着性>
作製した片面負極と片面セパレータとを、それぞれ、10mm×100mmの短冊状に切り出した。そして、片面セパレータの機能層の表面に片面負極の負極合材層を沿わせた後、温度85℃、圧力0.5MPaで6分間加熱プレスし、片面負極および片面セパレータを備える積層体を調製し、この積層体を試験片とした。
この試験片を、電解液約400μlと共にラミネート包材に入れた。1時間経過後、試験片を、ラミネート包材ごと60℃、圧力0.5MPaで15分間プレスした。プレス後、温度60℃で1日間保持した。ここで、電解液としては、EC、DECおよびビニレンカーボネート(VC)の混合溶媒(EC/DEC/VC(25℃における体積混合比)=68.5/30/1.5)に対し、支持電解質としてLiPF6を1mol/Lの濃度で溶かしたものを用いた。
その後、試験片を取り出し、表面に付着した電解液を拭き取った。次いで、この試験片を、片面負極の集電体側の面を下にして、片面負極の表面にセロハンテープを貼り付けた。この際、セロハンテープとしては、JIS Z1522に規定されるものを用いた。また、セロハンテープは、水平な試験台に固定しておいた。そして、片面セパレータの一端を鉛直上方に引張り速度50mm/分で引っ張って剥がしたときの応力を測定した。この測定を3回行い、応力の平均値をピール強度P2として求め、下記の基準で評価した。ピール強度P2が大きいほど、電解液中における機能層の接着性が優れており、セパレータと電極とが強固に接着していることを示す。
A:ピール強度P2が5.0N/m以上
B:ピール強度P2が3.0N/m以上5.0N/m未満
C:ピール強度P2が1.0N/m以上3.0N/m未満
D:ピール強度P2が1.0N/m未満
<電極表面のリチウム析出>
二次電池の充電時における電極上での金属析出率を、以下の方法により、負極上でのリチウム析出面積割合として測定した。具体的には、製造したリチウムイオン二次電池を、20℃環境下、1Cの定電流で充電深度(SOC)100%まで満充電した。そして、満充電した二次電池を解体して負極を取り出し、負極合材層の表面上に析出したリチウムの面積割合を、以下の算出式:
リチウム析出面積割合(%)=(析出したリチウムの面積/負極合材層の表面の面積)×100
に従って算出した。そして、以下の基準で評価した。リチウム析出面積割合が低いほど、二次電池として良好であることを示す。
A:リチウム析出面積割合が2%未満
B:リチウム析出面積割合が2%以上5%未満
C:リチウム析出面積割合が5%以上10%未満
D:リチウム析出面積割合が10%以上
<サイクル特性>
製造したリチウムイオン二次電池を、25℃の環境下で24時間静置させた後、25℃の環境下において、0.1Cの充電レートで4.35Vまで充電し、0.1Cの放電レートで2.75Vまで放電する充放電の操作を行い、初期容量C0を測定した。その後、更に、60℃の環境下で、同様の充放電の操作を繰り返し、1000サイクル後の容量C1を測定した。
そして、サイクル前後での容量維持率ΔC(=(C1/C0)×100%)を算出し、下記の基準で評価した。容量維持率ΔCの値が大きいほど、二次電池が高温サイクル特性に優れ、長寿命であることを示す。
A:容量維持率ΔCが84%以上
B:容量維持率ΔCが80%以上84%未満
C:容量維持率ΔCが70%以上80%未満
D:容量維持率ΔCが70%未満
<出力特性>
製造したリチウムイオン二次電池を、25℃の環境下で24時間静置させた後、25℃の環境下において、0.1Cの充電レートで5時間の充電の操作を行い、その時の電圧V0を測定した。その後、-15℃の環境下で、1Cの放電レートにて放電の操作を行い、放電開始15秒後の電圧V1を測定した。そして、電圧変化ΔV(=V0-V1)を求め、下記の基準で評価した。この電圧変化ΔVが小さいほど、二次電池が低温出力特性に優れていることを示す。
A:電圧変化ΔVが350mV未満
B:電圧変化ΔVが350mV以上500mV未満
C:電圧変化ΔVが500mV以上600mV未満
D:電圧変化ΔVが600mV以上
<有機粒子の調製>
撹拌機を備えた反応容器に、シード粒子としてのポリスチレン粒子(重量平均分子量:17,000、平均粒子径:0.21μm)10部、乳化剤としてのドデシルベンゼンスルホン酸ナトリウム4部、架橋性単量体としてのジビニルベンゼン70部、重合開始剤としての過硫酸ナトリウム1部、イオン交換水800部を仕込み、その後窒素ガスを吹き込みながら撹拌下80℃で1時間重合した。次いで、重合開始剤としての過硫酸ナトリウム0.5部、芳香族モノビニル単量体としてのスチレン15部、酸基含有単量体としてのメタクリル酸4.5部、水酸基含有単量体としての2-ヒドロキシエチルメタクリレート0.5部、分散安定剤としてのポリビニルアルコール(重合度:2000、ケン化度:87~89)の2.5%水溶液1部(固形分相当)、イオン交換水20部を混合してエマルションを調製し、このエマルションを80℃で3時間にわたり連続的に反応容器に添加して、重合を完結させ有機粒子を得た。得られた有機粒子の体積平均粒子径DAおよびガラス転移温度を測定した。有機粒子のガラス転移温度は、100℃以上であることを確認した。また、体積平均粒子径DAの測定結果を表1に示す。
<粒子状重合体(機能層用結着材)の調製>
撹拌機を備えた反応容器に、イオン交換水70部、乳化剤としてのラウリル硫酸ナトリウム(花王ケミカル社製、「エマール(登録商標)2F」)0.15部、および過流酸アンモニウム0.5部を、それぞれ供給し、気相部を窒素ガスで置換し、60℃に昇温した。
一方、別の容器でイオン交換水50部、乳化剤としてのドデシルベンゼンスルホン酸ナトリウム0.5部、そして(メタ)アクリル酸エステル単量体としての2-エチルヘキシルアクリレート58.2部、芳香族モノビニル単量体としてのスチレン40部、酸基含有単量体としてのイタコン酸0.8部、架橋性単量体としてのエチレングリコールジメタクリレート1.0部を混合して単量体組成物を得た。この単量体組成物を4時間かけて前記反応容器に連続的に添加して重合を行った。添加中は、60℃で反応を行った。添加終了後、さらに70℃で3時間撹拌して反応を終了し、粒子状重合体(アクリル系重合体)を含む水分散液を製造した。得られた粒子状重合体の体積平均粒子径DBおよびガラス転移温度を測定した。結果を表1に示す。
<機能層用組成物の調製>
無機粒子としての硫酸バリウム粒子(体積平均粒子径:0.6μm、比表面積:6.0m2/g)100部に対し、ポリカルボン酸系の分散剤(サンノプコ株式会社製、SNディスパーサント5020)2.5部を添加し、更に固形分濃度が50%となるように水を添加して得た粗分散液を、メディアレス分散装置(IKA社製、製品名「インライン型粉砕機MKO」)に2回通過させて分散処理することにより、硫酸バリウム粒子の水分散液を準備した。
そして、無機粒子としての硫酸バリウム粒子の水分散液を5部(固形分相当)と、機能層用結着材としての粒子状重合体の水分散液を7部(固形分相当)とを、イオン交換水と混合して分散させた。次いで、上述の有機粒子の水分散液を93部(固形分相当)、および濡れ剤としてのポリエチレングリコール型界面活性剤(サンノプコ株式会社製、製品名「サンノプコ(登録商標)SNウェット366」)0.2部を更に混合し、固形分濃度を40%に調整して機能層用組成物を得た。
<機能層および機能層付きセパレータの製造>
セパレータ基材として、ポリエチレン製の有機セパレータ基材(逐次二軸延伸法により製造。厚さ:7μm。Mwが2.4×106の超高分子量ポリエチレン40質量%と、Mwが2.6×105の高密度ポリエチレン60質量%とで構成されるポリエチレン組成物からなる。)を用意した。用意した有機セパレータ基材の片面に、上述のようにして得られた機能層用組成物を塗布し、60℃で10分乾燥させた。これにより、機能層(厚さ:1μm)を片面に備えるセパレータ(片面セパレータ)を得た。
同様にして用意した有機セパレータ基材の両面に、上述のようにして得られた機能層用組成物を塗布し、60℃で10分乾燥させた。これにより、機能層(厚さ:1μm)を両面に備えるセパレータ(両面セパレータ)を得た。
得られた片面および両面セパレータを用いて、耐ブロッキング性、耐引裂き性、並びに電解液浸漬前および浸漬後の接着性を評価した。結果を表1に示す。
<負極の製造>
攪拌機付き5MPa耐圧容器に、1,3-ブタジエン33部、イタコン酸3.5部、スチレン63.5部、乳化剤としてのドデシルベンゼンスルホン酸ナトリウム0.4部、イオン交換水150部及び重合開始剤として過硫酸カリウム0.5部を入れ、十分に攪拌した後、50℃に加温して重合を開始した。重合転化率が96%になった時点で冷却し反応を停止して、負極合材層用結着材(SBR)を含む混合物を得た。上記負極合材層用結着材を含む混合物に、5%水酸化ナトリウム水溶液を添加して、pH8に調整した。次いで、加熱減圧蒸留によって未反応単量体の除去を行った後、30℃以下まで冷却し、所望の負極合材層用結着材を含む水分散液を得た。
負極活物質としての人造黒鉛(平均粒子径:15.6μm)100部、水溶性重合体としてのカルボキシメチルセルロースナトリウム塩(日本製紙社製「MAC350HC」)の2%水溶液を固形分相当で1部、およびイオン交換水を混合して固形分濃度68%に調製した後、25℃で60分間さらに混合した。さらにイオン交換水で固形分濃度を62%に調製した後、25℃で15分間さらに混合した。上記混合液に、上記の負極合材層用結着材を固形分相当で1.5部、及びイオン交換水を入れ、最終固形分濃度が52%となるように調整し、さらに10分間混合した。これを減圧下で脱泡処理して流動性の良い二次電池負極用スラリー組成物を得た。
得られた負極用スラリー組成物を、コンマコーターで、集電体である厚さ20μmの銅箔の上に、乾燥後の膜厚が150μm程度になるように塗布し、乾燥させた。この乾燥は、銅箔を0.5m/分の速度で60℃のオーブン内を2分間かけて搬送することにより行った。その後、120℃にて2分間加熱処理してプレス前の負極原反を得た。このプレス前の負極原反をロールプレスで圧延して、負極合材層の厚さが80μmのプレス後の負極を得た(片面負極)。
また、前記プレス前の負極原反の裏面に同様の塗布を実施し、両面に負極合材層を形成し、ロールプレスで圧延して、負極合材層の厚さが各80μmのプレス後の負極を得た(両面負極)。
<正極の製造>
正極活物質としての体積平均粒子径12μmのLiCoO2を100部、導電材としてのアセチレンブラック(電気化学工業社製、「HS-100」)を2部、正極合材層用結着材としてのポリフッ化ビニリデン(クレハ社製、「#7208」)を固形分相当で2部と、N-メチルピロリドンとを混合し全固形分濃度が70%となる量とした。これらを混合し、正極用スラリー組成物を調製した。
得られた正極用スラリー組成物を、コンマコーターで、集電体である厚さ20μmのアルミ箔の上に、乾燥後の膜厚が150μm程度になるように塗布し、乾燥させた。この乾燥は、アルミ箔を0.5m/分の速度で60℃のオーブン内を2分間かけて搬送することにより行った。その後、120℃にて2分間加熱処理して、プレス前の正極原反を得た。このプレス前の正極原反をロールプレスで圧延して、正極合材層の厚さが80μmのプレス後正極を得た(片面正極)。
また、前記プレス前の正極原反の裏面に同様の塗布を実施し、両面に正極合材層を形成し、ロールプレスで圧延して、正極合材層の厚さが各80μmのプレス後の正極を得た(両面正極)。
<二次電池の製造>
上記で得られた片面正極を5cm×15cmに切り出し、その上(合材層側)に、6cm×16cmに切り出した両面セパレータを、当該セパレータの一方の機能層が片面正極と対向するように配置した。さらにその両面セパレータのもう一方の機能層側に、5.5cm×15.5cmに切り出した両面負極を配置し、積層体Aを得た。この積層体Aの両面負極側に、6cm×16cmに切り出した両面セパレータを、当該セパレータの一方の機能層が両面負極と対向するように配置した。さらにその両面セパレータのもう一方の機能層側に、5cm×15cmに切り出した両面正極を重ねた。次いで、さらにその両面正極の上に6cm×16cmに切り出した両面セパレータを、当該セパレータの一方の機能層が両面正極と対向するように配置した。最後に、その両面セパレータのもう一方の機能層上に、5.5cm×5.5cmに切り出した片面負極を、負極合材層が両面セパレータの機能層と対向するように積層し、積層体Bを得た。この積層体Bを、電池の外装としてのアルミ包材外装で包み、電解液(EC、DECおよびVCの混合溶媒(EC/DEC/VC(25℃における体積比)=68.5/30/1.5)に対し、支持電解質としてLiPF6を1mol/Lの濃度で溶かしたもの)を空気が残らないように注入した。さらに、150℃のヒートシールをしてアルミ包材外装を閉口したのちに、得られた電池外装体を100℃、2分間、100Kgfで平板プレスし、1000mAhの積層型リチウムイオン二次電池を製造した。
得られた二次電池を用いて、電極表面のリチウム析出、サイクル特性、出力特性を評価した。結果を表1に示す。
有機粒子の組成および無機粒子の使用量(実施例3では無機粒子を使用せず)を表1のように変更した以外は、実施例1と同様にして、有機粒子、粒子状重合体(機能層用結着材)、機能層用組成物、セパレータ、正極、負極および二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を表1に示す。なお、実施例2および3に用いた有機粒子のガラス転移温度が、何れも100℃以上であることを確認した。
無機粒子の使用量を表1のように変更し、また以下のようにして調製した有機粒子を使用した以外は、実施例1と同様にして、粒子状重合体(機能層用結着材)、機能層用組成物、セパレータ、正極、負極および二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を表1に示す。なお、実施例4に用いた有機粒子のガラス転移温度が100℃以上であることを確認した。
<有機粒子の調製>
撹拌機を備えた反応容器に、架橋性単量体としてのジビニルベンゼン55部、芳香族モノビニル単量体としてのエチルビニルベンゼン45部、分散安定剤としてのポリビニルピロリドン22部、重合開始剤としての2,2’-アゾビスイソブチロニトリル10部および過酸化ベンゾイル4.5部、メチルアルコール1300部を入れ、窒素ガス雰囲気下、73℃で28時間、撹拌しながら重合を完結させ、有機粒子を得た。この重合反応における重合転化率は96%であった。そして、得られたメチルアルコール分散液中のメチルアルコールをイオン交換水に置換した。
無機粒子の使用量を表1のように変更し、また以下のようにして調製した有機粒子を使用した以外は、実施例1と同様にして、粒子状重合体(機能層用結着材)、機能層用組成物、セパレータ、正極、負極および二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を表1に示す。なお、実施例5に用いた有機粒子のガラス転移温度が100℃以上であることを確認した。
<有機粒子の調製>
撹拌機を備えた反応容器に、架橋性単量体としてのジビニルベンゼン70部、芳香族モノビニル単量体としてのスチレン25部、(メタ)アクリル酸エステル単量体としてのn-ブチルアクリレート2部、酸基含有単量体としてのメタクリル酸3部、重合開始剤としての過硫酸ナトリウム1部、乳化剤としてのドデシルベンゼンスルホン酸ナトリウム6部、およびイオン交換水900部を仕込み、攪拌下80℃で1時間重合して、有機粒子を得た。
有機粒子の調製に際し、有機粒子の組成を表1のように変更すると共に、分散時安定剤としてのポリビニルアルコールを使用せず、乳化剤としてのドデシルベンゼンスルホン酸ナトリウムの量を1.5部に変更した以外は、実施例5と同様にして、有機粒子、粒子状重合体(機能層用結着材)、機能層用組成物、片面および両面セパレータ、正極、負極並びに二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を表1に示す。なお、実施例6に用いた有機粒子のガラス転移温度が100℃以上であることを確認した。
以下のようにして調製した有機粒子を使用すると共に、有機粒子、無機粒子および機能層用結着材の使用量を表1のように変更した以外は、実施例6と同様にして、粒子状重合体(機能層用結着材)、機能層用組成物、セパレータ、正極、負極および二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を表1に示す。なお、実施例7および8に用いた有機粒子のガラス転移温度は、100℃以上であることを確認した。
<有機粒子の調製>
撹拌機を備えた反応容器に、シード粒子としてのポリスチレン粒子(重量平均分子量:17,000、平均粒子径:0.21μm)を10部、分散安定剤としてポリビニルアルコール(重合度:2000、ケン化度:87~89)の2.5%水溶液を7.5部(固形分相当)、(メタ)アクリル酸エステル単量体としてのメチルメタクリレート50部、架橋性単量体としてのトリメチロールプロパントリメタクリレート40部を加え、次いで、昇温して65℃で8時間重合を行った。重合転化率は99%であり、また凝固物の発生は殆どなかった。
無機粒子の使用量を表1のように変更し、また粒子状重合体(機能層用結着材)の調製時に、乳化剤であるラウリル硫酸ナトリウムの量を0.1部に変更した以外は、実施例6と同様にして、有機粒子、粒子状重合体(機能層用結着材)、機能層用組成物、セパレータ、正極、負極および二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を表1に示す。
有機粒子の調製時に、乳化剤であるラウリル硫酸ナトリウムの量を6部に変更し、粒子状重合体(機能層用結着材)の調製時に、乳化剤であるラウリル硫酸ナトリウムの量を0.8部に変更した以外は、実施例6と同様にして、有機粒子、粒子状重合体(機能層用結着材)、機能層用組成物、セパレータ、正極、負極および二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を表1に示す。
機能層用組成物の調製時に、無機粒子としての硫酸バリウム粒子に替えて、それぞれアルミナ粒子(体積平均粒子径:0.8μm)、ベーマイト粒子(体積平均粒子径:0.9μm)を使用し、かつ無機粒子の使用量を表1のように変更した以外は、実施例1と同様にして、有機粒子、粒子状重合体(機能層用結着材)、機能層用組成物、セパレータ、正極、負極および二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を表1に示す。
有機粒子の組成を表1のように変更し、機能層用組成物の調製時に、無機粒子としての硫酸バリウム粒子に替えて、アルミナ粒子(体積平均粒子径0.8μm)を使用し、かつ無機粒子の使用量を表1のように変更した以外は、実施例1と同様にして、有機粒子、粒子状重合体(機能層用結着材)、機能層用組成物、セパレータ、正極、負極および二次電池を製造した。そして、実施例1と同様にして各種評価を行った。結果を表1に示す。
「DVB」は、ジビニルベンゼン単位を示し、
「TMPT」は、トリメチロールプロパントリメタクリレート単位を示し、
「EDMA」は、エチレングリコールジメタクリレート単位を示し、
「ST」は、スチレン単位を示し、
「EVB」は、エチルビニルベンゼン単位を示し、
「BA」は、n-ブチルアクリレート単位を示し、
「MMA」は、メチルメタクリレート単位を示し、
「MAA」は、メタクリル酸単位を示し、
「2HEMA」は、2-ヒドロキシエチルメタクリレート単位を示し、
「PST」は、ポリスチレンを示し、
「PVA」は、ポリビニルアルコールを示し、
「PVP」は、ポリビニルピロリドンを示し、
「ACL」は、アクリル系重合体を示す。
また、本発明によれば、非水系二次電池に優れたサイクル特性および出力特性を発揮させうる非水系二次電池用機能層を提供することができる。
そして、本発明によれば、サイクル特性および出力特性に優れる非水系二次電池を提供することができる。
更に、本発明によれば、非水系二次電池に優れたサイクル特性および出力特性を発揮させうる非水系二次電池用電極の製造方法を提供することができる。
Claims (11)
- 有機粒子および機能層用結着材を含み、
前記有機粒子の電解液溶出量が、0.001質量%以上5.0質量%以下である、非水系二次電池機能層用組成物。 - 前記有機粒子が、架橋性単量体単位を5.0質量%以上85質量%以下含む、請求項1に記載の非水系二次電池機能層用組成物。
- 前記有機粒子の体積平均粒子径DAが、0.01μm以上2.0μm以下である、請求項1又は2に記載の非水系二次電池機能層用組成物。
- 前記有機粒子の含有量が、前記有機粒子と前記機能層用結着材との合計含有量の1質量%以上99質量%以下である、請求項1~3の何れかに記載の非水系二次電池機能層用組成物。
- 前記有機粒子の体積平均粒子径DAが、前記機能層用結着材の体積平均粒子径DB以上である、請求項1~4の何れかに記載の非水系二次電池機能層用組成物。
- 更に無機粒子を含む、請求項1~5の何れかに記載の非水系二次電池機能層用組成物。
- 請求項1~6の何れかに記載の非水系二次電池機能層用組成物を用いて形成した、非水系二次電池用機能層。
- 請求項7に記載の非水系二次電池用機能層を備える、非水系二次電池。
- 積層型である、請求項8に記載の非水系二次電池。
- 請求項7に記載の非水系二次電池用機能層と電極基材を積層する工程と、前記非水系二次電池用機能層と前記電極基材を加圧により接着させる工程を含む、非水系二次電池用電極の製造方法。
- 前記電極基材が電極合材層用結着材を含み、
前記電極合材層用結着材が、芳香族ビニル単量体単位および脂肪族共役ジエン単量体単位を含む、請求項10に記載の非水系二次電池用電極の製造方法。
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EP17843353.8A EP3506394B1 (en) | 2016-08-25 | 2017-08-02 | Composition for nonaqueous secondary battery functional layers, functional layer for nonaqueous secondary batteries, nonaqueous secondary battery, and method for producing electrode for nonaqueous secondary batteries |
CN201780047858.5A CN109565020B (zh) | 2016-08-25 | 2017-08-02 | 非水系二次电池功能层用组合物、非水系二次电池用功能层、非水系二次电池和非水系二次电池用电极的制造方法 |
KR1020197002882A KR102407601B1 (ko) | 2016-08-25 | 2017-08-02 | 비수계 이차 전지 기능층용 조성물, 비수계 이차 전지용 기능층, 비수계 이차 전지, 및 비수계 이차 전지용 전극의 제조 방법 |
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PL17843353.8T PL3506394T3 (pl) | 2016-08-25 | 2017-08-02 | Kompozycja dla warstw funkcjonalnych niewodnej baterii akumulatorowej, warstwa funkcjonalna dla niewodnych baterii akumulatorowych, niewodna bateria akumulatorowa i sposób wytwarzania elektrody dla niewodnych baterii akumulatorowych |
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JP7517150B2 (ja) | 2018-08-24 | 2024-07-17 | 日本ゼオン株式会社 | 非水系二次電池機能層用スラリー組成物、非水系二次電池用セパレータおよび非水系二次電池 |
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KR102407601B1 (ko) | 2022-06-10 |
CN109565020B (zh) | 2023-04-04 |
KR20190042554A (ko) | 2019-04-24 |
JPWO2018037867A1 (ja) | 2019-06-20 |
CN109565020A (zh) | 2019-04-02 |
US20190207189A1 (en) | 2019-07-04 |
JP7020416B2 (ja) | 2022-02-16 |
US10930912B2 (en) | 2021-02-23 |
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