JP2015138687A - Adhesive agent coating liquid for collector coat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adhesive agent coating liquid for a collector coat that enables the manufacturing of an electrochemical element having excellent characteristics.SOLUTION: The adhesive agent coating liquid for a collector coat includes a binder, a water soluble fluorescent material, a surfactant, and water. Concentration of the water soluble fluorescent material is equal to or more than 0.01 wt.% and less than 3 wt.%. Concentration of the surfactant is equal to or more than 0.1 wt.% and less than 1 wt.%.

Description

  The present invention relates to a current collector coating adhesive coating solution used for producing an electrochemical device.

  Electrochemical elements such as lithium ion secondary batteries that are small and lightweight, have high energy density, and can be repeatedly charged and discharged are rapidly expanding their demands by taking advantage of their characteristics. Lithium ion secondary batteries are used in fields such as mobile phones, notebook personal computers, and electric vehicles because of their relatively high energy density.

  With the expansion and development of applications, these electrochemical elements are required to be further improved, such as lowering resistance, increasing capacity, improving mechanical properties and productivity. Under such circumstances, there has been a demand for a more productive manufacturing method for electrochemical element electrodes, and various improvements have been made regarding a manufacturing method capable of high-speed molding and a material for electrochemical element electrodes suitable for the manufacturing method. It has been broken.

  Electrochemical element electrodes are usually formed by laminating an electrode active material layer formed by binding an electrode active material and a conductive agent used as necessary with a binder on a current collector. It is. As a method for forming such an electrode active material layer, Patent Document 1 discloses that a particulate electrode material is obtained by spray-drying a slurry containing an electrode active material, rubber particles, and a dispersion medium. A method of forming an electrode active material layer using a material is disclosed.

Japanese Patent No. 4219705

Incidentally, in order to improve the adhesion between the electrode active material layer and the current collector, an intermediate layer such as an adhesive layer is provided between the electrode active material layer and the current collector. However, when the electrode active material layer is formed on the part where the coating liquid for providing the adhesive layer is not applied as in the method disclosed in Patent Document 1, the resistance of the battery is increased, and the capacity retention rate is increased. Battery performance deteriorates, such as falling.
This invention is providing the adhesive agent coating liquid for collector coating which can manufacture the electrochemical element which has favorable performance.

  As a result of intensive studies, the present inventors have found that the above object can be achieved by using a water-soluble phosphor, and have completed the present invention.

That is, according to the present invention,
(1) It contains a binder, a water-soluble phosphor, a surfactant, and water, and the concentration of the water-soluble phosphor is 0.01 wt. % Or more and 3 wt. %, And the surfactant concentration is 0.1 wt. % Or more and 1 wt. % Current collector coating adhesive coating solution,
(2) The adhesive coating liquid for current collector coating according to (1), wherein the binder is a particulate binder,
(3) The adhesive coating liquid for current collector coating according to (1) or (2), wherein the binder contains an acrylic polymer.

  According to the adhesive coating liquid for current collector coating according to the present invention, an electrochemical device having good performance can be produced.

  Hereinafter, the adhesive coating liquid for current collector coating of the present invention will be described. The adhesive coating liquid for current collector coating of the present invention comprises a binder, a water-soluble phosphor, a surfactant, and water, and the concentration of the water-soluble phosphor is 0.01 wt. % Or more and 3 wt. %, And the surfactant concentration is 0.1 wt. % Or more and 1 wt. %.

(Binder)
The binder used in the present invention is a component for adhering the electrode active materials to each other, and the current collector and other components and the electrode active material. Usually, the polymer particles having binding properties are dispersed in water. The dispersion is used in the form of a dispersion (binder aqueous dispersion) or in the form of a solution in which a polymer having binding properties is dissolved in water (binder solution).

  Examples of the polymer used for the binder aqueous dispersion include a diene polymer, an acrylic polymer, a fluorine polymer, and a silicone polymer.

  Among these, a diene polymer or an acrylic polymer is preferable because of excellent adhesion between the current collector and the electrode active material layer. In addition, since the adhesive layer obtained from the current collector coating adhesive coating solution is used in the positive electrode and the negative electrode, high redox stability is required, and in particular, the oxidation stability at the positive electrode is high. To acrylic polymers are most preferred.

(Diene polymer)
The diene polymer is a polymer containing monomer units obtained by polymerizing conjugated dienes such as butadiene and isoprene. The proportion of monomer units obtained by polymerizing conjugated diene in the diene polymer is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more. Examples of the polymer include homopolymers of conjugated dienes such as polybutadiene and polyisoprene; and copolymers of monomers that are copolymerizable with conjugated dienes. Examples of the copolymerizable monomer include α, β-unsaturated nitrile compounds such as acrylonitrile and methacrylonitrile; unsaturated carboxylic acids such as acrylic acid and methacrylic acid; styrene, chlorostyrene, vinyltoluene, and t-butyl. Styrene monomers such as styrene, vinyl benzoic acid, methyl vinyl benzoate, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, α-methyl styrene, divinylbenzene; olefins such as ethylene, propylene; vinyl chloride, vinylidene chloride Halogen atom-containing monomers such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate, etc .; vinyl ethers such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; methyl vinyl ketone, ethyl vinyl Vinyl ketones such as ketone, butyl vinyl ketone, hexyl vinyl ketone, and isopropenyl vinyl ketone; and heterocyclic ring-containing vinyl compounds such as N-vinyl pyrrolidone, vinyl pyridine, and vinyl imidazole.

(Acrylic polymer)
The acrylic polymer is a polymer containing a monomer unit obtained by polymerizing an acrylic ester and / or a methacrylic ester. The proportion of monomer units obtained by polymerizing acrylic acid ester and / or methacrylic acid ester in the acrylic polymer is usually 40% by weight or more, preferably 50% by weight or more, more preferably 60% by weight or more. . Examples of the polymer include homopolymers of acrylic acid esters and / or methacrylic acid esters, and copolymers with monomers copolymerizable therewith. Examples of the copolymerizable monomer include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, and fumaric acid; two or more carbons such as ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, and trimethylolpropane triacrylate. -Carboxylic acid ester having a carbon double bond; styrene, chlorostyrene, vinyl toluene, t-butyl styrene, vinyl benzoic acid, vinyl benzoate methyl, vinyl naphthalene, chloromethyl styrene, hydroxymethyl styrene, α-methyl styrene, Styrene monomers such as divinylbenzene; Amide monomers such as acrylamide, N-methylol aquaylamide, and acrylamide-2-methylpropanesulfonic acid; α, β- such as acrylonitrile and methacrylonitrile Saturated nitrile compounds; olefins such as ethylene and propylene; diene monomers such as butadiene and isoprene; monomers containing halogen atoms such as vinyl chloride and vinylidene chloride; vinyl acetate, vinyl propionate, vinyl butyrate, vinyl benzoate Vinyl esters such as methyl vinyl ether, ethyl vinyl ether, butyl vinyl ether; vinyl ketones such as methyl vinyl ketone, ethyl vinyl ketone, butyl vinyl ketone, hexyl vinyl ketone, isopropenyl vinyl ketone; N-vinyl pyrrolidone, vinyl Heterocycle-containing vinyl compounds such as pyridine and vinylimidazole can be mentioned.

  Examples of the polymer used for the binder solution include hydroxyethyl cellulose (HEC), polyethylene glycol (PEG), polyethylene oxide (PEO), polyvinyl alcohol (PVA), polyvinyl pyrrolidone (PVP), and polyoxyethylene polyoxypropylene block copolymer. Combined (PPP), polyacrylamide (PMMA), poly N-vinylformamide (PNVF), polyacrylic acid (PAA), sodium polyacrylate (PAA-Na), ammonium polyacrylate (PAA-NH4), polystyrene sulfonic acid Sodium (PSS-Na), sodium carboxymethylcellulose (CMC-Na), polyethyleneimine (PEI), etc. are mentioned.

  The binder used in the present invention is preferably obtained through a particulate metal removal step of removing particulate metal contained in the binder aqueous dispersion or the binder solution in the production process. When the content of the particulate metal component contained in the binder is 10 ppm or less, there is little concern about increased self-discharge due to internal short circuit of the battery or dissolution / precipitation during charging, improving the cycle characteristics and safety of the battery. To do.

  The method for removing the particulate metal component from the binder aqueous dispersion or the binder solution in the particulate metal removal step is not particularly limited. For example, the removal method by filtration using a filtration filter, the removal method using a vibrating sieve, and centrifugation. And a method of removing by magnetic force. Especially, since the removal object is a metal component, the method of removing by magnetic force is preferable. The method for removing by magnetic force is not particularly limited as long as it is a method that can remove the metal component. However, in consideration of productivity and removal efficiency, it is preferable to place a magnetic filter in the binder production line. Is called.

  The shape of the binder in the binder aqueous dispersion used in the present invention is not particularly limited, but is preferably particulate. By being particulate, the binding property is good, and it is possible to suppress deterioration of the capacity of the manufactured electrode and deterioration due to repeated charge and discharge. Examples of the particulate binder include those in which binder particles such as latex are dispersed in water, and powders obtained by drying such a dispersion.

  The average particle size of the binder in the binder aqueous dispersion is preferably 50 to 500 nm, more preferably 70 to 400 nm.

  The glass transition temperature (Tg) of the binder is appropriately selected according to the purpose of use, but is usually −150 to + 100 ° C., preferably −50 to + 25 ° C., more preferably −35 to + 5 ° C. .

  The solid content concentration of the binder aqueous dispersion is preferably 15 to 70 wt.% From the viewpoint of good workability in the production of the current collector coating adhesive coating solution. %, More preferably 20 to 65 wt. %, More preferably 30-60 wt. %.

(Water-soluble phosphor)
The water-soluble phosphor used in the present invention is not particularly limited as long as it is a water-soluble fluorescent dye. For example, Acid Yellow 7 (CI-56205), Basic Yellow (Basic Yellow) HG (C.I.-46040), Eosin (C.I.-45385), Eosin Yellowish (C.I.-45380), Rhodamine 6G (C.I. -45160) and Rhodamine B (C.I.-45170) can be preferably used, and rhodamine-based fluorescent dyes such as rhodamine 6G and rhodamine B can be more preferably used from the viewpoint of dispersibility. .

  The concentration of the water-soluble phosphor in the current collector coating adhesive coating liquid of the present invention is such that the content of the water-soluble phosphor in the adhesive coating liquid is the current collector coating adhesive coating liquid on the current collector. From the viewpoint of easy inspection of whether or not the coating is applied, preferably 0.02 to 2.5 wt. %, More preferably 0.05 to 2 wt. %. When the content of the water-soluble phosphor is too large, the resistance of the obtained (lithium ion secondary) battery increases. Moreover, when there is too little content of water-soluble fluorescent substance, it will become impossible to test | inspect the coating condition of the adhesive coating liquid for collector coating on a collector.

(Surfactant)
The surfactant used in the present invention is not particularly limited as long as it imparts wettability to the current collector of the current collector coating adhesive coating solution, but a nonionic surfactant is preferably used. Nonionic surfactants include polyoxyalkylene alkyl aryl ether surfactants, polyoxyalkylene alkyl ether surfactants, polyoxyalkylene fatty acid ester surfactants, sorbitan fatty acid ester surfactants, silicone surfactants, acetylenes Examples include alcohol surfactants and fluorine-containing surfactants.

  Examples of the polyoxyalkylene alkyl aryl ether surfactant include polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, and polyoxyethylene dodecyl phenyl ether.

  Examples of the polyoxyalkylene alkyl ether surfactant include polyoxyethylene oleyl ether and polyoxyethylene lauryl ether.

  Examples of the polyoxyalkylene fatty acid ester surfactant include polyoxyethylene oleate, polyoxyethylene laurate, and polyoxyethylene distearate.

Examples of the sorbitan fatty acid ester surfactant include sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate.
Examples of silicone surfactants include dimethylpolysiloxane.

Examples of the acetylene alcohol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5- Examples thereof include dimethyl-1-hexyne-3ol.
Examples of fluorine-containing surfactants include fluorine alkyl esters.

  The concentration of the surfactant in the current collector coating adhesive coating liquid of the present invention is preferably 0.2 to 0.8 wt.% As the content in the adhesive coating liquid. %. When there is too much content of surfactant, the resistance of the lithium ion secondary battery obtained will rise. Moreover, when there is too little content of surfactant, the adhesive coating liquid for collector coating cannot be applied on a collector.

(Adhesive coating solution for current collector coating)
The method for producing the current collector coating adhesive coating liquid of the present invention is not particularly limited, and any means may be used as long as each solid component can be dispersed in a dispersion medium. For example, a binder aqueous dispersion containing a binder, a water-soluble phosphor and a surfactant are mixed together, and then a dispersion medium is added if necessary, and water is added to reduce the solid content concentration of the dispersion. You may adjust. Further, at least one of the water-soluble phosphor and the surfactant may be added in a state of being dissolved or dispersed in water.

  The adhesive coating liquid for current collector coating is in the form of a slurry, and its viscosity depends on the coating method, but from the viewpoint of forming a uniform adhesive layer on the current collector, it is preferably 10 to 10,000 mPa. · S, more preferably 20 to 5,000 mPa · s, still more preferably 50 to 2,000 mPa · s.

(Current collector with adhesive layer)
By applying the adhesive coating liquid for current collector coating of the present invention onto the current collector, a current collector with an adhesive layer in which an adhesive layer is formed on the current collector can be obtained.

  The material of the current collector is, for example, metal, carbon, conductive polymer, etc., and metal is preferably used. As the current collector metal, aluminum, platinum, nickel, tantalum, titanium, stainless steel, copper, other alloys and the like are usually used. Among these, it is preferable to use copper, aluminum, or an aluminum alloy in terms of conductivity and voltage resistance.

  The thickness of the current collector is preferably 5 to 100 μm, more preferably 8 to 70 μm, and still more preferably 10 to 50 μm.

  The method for applying the adhesive layer is not particularly limited. For example, the adhesive layer is formed on the current collector by a doctor blade method, a dip method, a reverse roll method, a direct roll method, a gravure method, an extrusion method, a die coating method, brushing, or the like. Further, after forming an adhesive layer on the release paper, it may be transferred to a current collector.

  The coated adhesive layer may be dried, and examples of the drying method include drying with warm air, hot air, low-humidity air, vacuum drying, and drying by irradiation with (far) infrared rays or electron beams. It is done. Of these, a drying method using hot air and a drying method using irradiation with far infrared rays are preferable. The drying temperature and the drying time are preferably a temperature and a time at which the solvent in the current collector coating adhesive coating solution coated on the current collector can be completely removed, and the drying temperature is usually 50 to 300 ° C., preferably 80 ~ 250 ° C. The drying time is usually 2 hours or less, preferably 5 seconds to 30 minutes. In addition, it is preferable that the adhesive bond layer formed with the adhesive agent coating liquid for collector coating of this invention has a tack | tuck, without heating after the coating to a collector.

  The thickness of the adhesive layer is 0.5 to 5 μm, preferably 0.5 to 4 μm, particularly preferably from the viewpoint of obtaining an electrode having good adhesion to the electrode active material layer described later and having a low resistance. Is 0.5 to 3 μm.

  The adhesive layer has a composition corresponding to the solid content composition of the current collector coating adhesive coating solution, and includes a binder, a water-soluble phosphor, and a surfactant.

(Uncoated part detection process)
In the present invention, since the adhesive coating liquid for current collector coating contains a water-soluble phosphor, the current collector on the current collector is examined by inspecting the current collector with an adhesive layer using ultraviolet light. An uncoated portion of the coating adhesive coating solution, that is, a region where the adhesive layer is not formed can be detected.

(Electrochemical element electrode)
An electrochemical element electrode can be obtained by forming an electrode active material layer on the current collector with an adhesive layer. Although the formation method of an electrode active material layer is not specifically limited, It is preferable to laminate | stack an electrode active material layer on an electrical power collector with an adhesive layer using the composite particle containing an electrode active material.

  When laminating the electrode active material layer on the current collector with the adhesive layer, the composite particles may be formed into a sheet and then laminated on the current collector with the adhesive layer. A method in which the composite particles are directly pressure-molded on the current collector is preferred. As a method for pressure molding, for example, a roll type pressure molding apparatus provided with a pair of rolls is used, and a composite particle is rolled by a supply device such as a screw feeder while feeding the current collector with an adhesive layer by the roll. By supplying to the pressure forming device, roll pressure forming method for forming the electrode active material layer on the current collector with the adhesive layer, or by dispersing the composite particles on the current collector with the adhesive layer, For example, a method of adjusting the thickness with a blade or the like, and then forming with a pressurizing apparatus, a method of filling composite particles into a mold, and pressing the mold to form. Among these, the roll pressure molding method is preferable. In particular, since the composite particles of the present invention have high fluidity, they can be molded by roll press molding due to the high fluidity, thereby improving productivity.

  The roll temperature at the time of roll press molding is preferably 25 to 200 ° C., more preferably from the viewpoint of ensuring sufficient adhesion between the electrode active material layer and the current collector with the adhesive layer. 50-150 degreeC, More preferably, it is 80-120 degreeC. Moreover, the press linear pressure between rolls at the time of roll press molding is preferably 10 to 1000 kN / m, more preferably 200 to 900 kN / m, from the viewpoint of improving the uniformity of the thickness of the electrode active material layer. More preferably, it is 300-600 kN / m. Moreover, the molding speed at the time of roll pressure molding is preferably 0.1 to 20 m / min, more preferably 4 to 10 m / min.

  Further, post-pressurization may be further performed as necessary in order to eliminate variations in the thickness of the formed electrochemical element electrode and increase the density of the electrode active material layer to increase the capacity. The post-pressing method is preferably a pressing process using a roll. In the roll pressing step, two cylindrical rolls are arranged vertically in parallel with a narrow interval, each is rotated in the opposite direction, and pressure is applied by interposing an electrode therebetween. In this case, the temperature of the roll may be adjusted as necessary, such as heating or cooling.

(Composite particles)
The composite particles can be obtained by granulating using other components such as an electrode active material, a binder, a water-soluble polymer added as necessary, and a conductive additive. The method for producing the composite particles is not particularly limited, and the slurry for composite particles containing other components such as an electrode active material, a binder, and a conductive auxiliary agent added as necessary is used for spray drying granulation, rolling Layer granulation method, compression granulation method, stirring granulation method, extrusion granulation method, crushing granulation method, fluidized bed granulation method, fluidized bed multifunctional granulation method, and melt granulation method, etc. It can be obtained by a manufacturing method. Among these, the spray-drying granulation method is preferable from the viewpoint that the composite particles can be produced relatively easily.

(Slurry for composite particles)
The slurry for composite particles used for the manufacture of composite particles is obtained by dispersing or dissolving an electrode active material, a conductive agent, a binder, and other components added as necessary, in a dispersion medium.

(Electrode active material)
When the electrochemical element is a lithium ion secondary battery, examples of the electrode active material (positive electrode active material) for the positive electrode of the lithium ion secondary battery include metal oxides capable of reversibly doping and dedoping lithium ions. It is done. Examples of the metal oxide include lithium cobaltate, lithium nickelate, lithium manganate, and lithium iron phosphate. In addition, the positive electrode active material illustrated above may be used independently according to a use, and may be used in mixture of multiple types.

  Examples of the negative electrode active material (negative electrode active material) as the counter electrode of the lithium ion secondary battery positive electrode include low crystalline carbon (amorphous) such as graphitizable carbon, non-graphitizable carbon, and pyrolytic carbon. Carbon), graphite (natural graphite, artificial graphite), alloy materials such as tin and silicon, oxides such as silicon oxide, tin oxide, and lithium titanate. In addition, the negative electrode active material illustrated above may be used independently according to a use suitably, and multiple types may be mixed and used for it.

  The shape of the electrode active material for a lithium ion secondary battery electrode is preferably a granulated particle. When the shape of the particles is granular, a higher-density electrode can be formed during electrode molding.

  The volume average particle diameter of the electrode active material for a lithium ion secondary battery electrode is usually 0.1 to 100 μm, preferably 0.5 to 50 μm, more preferably 0.8 to 30 μm for both the positive electrode and the negative electrode.

(Conductive agent)
Specific examples of the conductive agent used in the present invention include conductive carbon black such as furnace black, acetylene black, and ketjen black (registered trademark of Akzo Nobel Chemicals Bethloten Fennaut Shap). Among these, acetylene black and furnace black are more preferable.
These conductive agents can be used alone or in combination of two or more.

(Binder)
As the binder used for the production of the composite particles, the same binder as that used in the above-described current collector coating adhesive coating solution can be used.

(Other ingredients)
The composite particle slurry may contain other components such as a dispersant as required. Specific examples of the dispersant include cellulose polymers such as carboxymethyl cellulose and methyl cellulose, and ammonium or alkali metal salts thereof. These dispersants can be used alone or in combination of two or more.

(Manufacture of composite particles)
The composite particles can be obtained, for example, by spray drying the slurry containing the electrode active material, the conductive agent, the binder, and other components added as necessary. Here, the composite particle includes at least an electrode active material, a conductive agent, and a binder. However, each of the composite particles does not exist as an independent particle, but is an electrode active material that is a constituent, a binder. One particle is formed by two or more components including an agent. Specifically, a plurality of (more preferably several to several tens of) electrode active materials are formed by combining a plurality of the individual particles of the two or more components to form secondary particles. It is preferable that the particles are bound to form particles.

  The average particle diameter of the composite particles is preferably 0.1 to 200 μm, more preferably 1 to 150 μm, and still more preferably 10 to 80 μm, from the viewpoint that an electrode active material layer having a desired thickness can be easily obtained. In addition, in this invention, an average particle diameter is a volume average particle diameter measured and calculated with the laser diffraction type particle size distribution measuring apparatus (for example, SALD-3100; Shimadzu Corporation make).

(Electrochemical element)
Examples of usage of the electrochemical element electrode include a lithium ion secondary battery and a lithium ion capacitor using such an electrode, and a lithium ion secondary battery is preferable. For example, a lithium ion secondary battery uses an electrochemical element electrode obtained as described above as at least one of a positive electrode and a negative electrode, and further includes a separator and an electrolytic solution.

  In the present invention, when an electrochemical device electrode is produced, even if an uncoated portion of the adhesive coating liquid for the current collector coating is detected by the uncoated portion detection step, the current collector An electrode active material layer is formed on the body. After that, when manufacturing an electrochemical element such as a lithium ion secondary battery, an electrode active material formed on the uncoated part, including an uncoated part detected by the uncoated part detection step. Remove with layer. Thereby, the electrochemical element using the electrochemical element electrode which does not contain the uncoated part of the adhesive agent coating liquid for collector coating can be obtained.

(Separator)
As the separator, for example, a polyolefin resin such as polyethylene or polypropylene, a microporous film or a nonwoven fabric containing an aromatic polyamide resin, a porous resin coat containing an inorganic ceramic powder, or the like can be used.

  The thickness of the separator is preferably 0.5 to 40 μm, more preferably from the viewpoint of reducing resistance due to the separator in the lithium ion secondary battery and excellent workability when manufacturing the lithium ion secondary battery. It is 1-30 micrometers, More preferably, it is 1-25 micrometers.

(Electrolyte)
The electrolytic solution is not particularly limited. For example, a solution obtained by dissolving a lithium salt as a supporting electrolyte in a non-aqueous solvent can be used. Examples of the lithium salt include LiPF ₆ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlCl ₄ , LiClO ₄ , CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, CF ₃ COOLi, (CF ₃ CO) ₂ NLi , (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) NLi, and other lithium salts. In particular, LiPF ₆ , LiClO ₄ , and CF ₃ SO ₃ Li that are easily soluble in a solvent and exhibit a high degree of dissociation are preferably used. These can be used alone or in admixture of two or more. The amount of the supporting electrolyte is usually 1 wt. % Or more, preferably 5 wt. % Or more, and usually 30 wt. % Or less, preferably 20 wt. % Or less. If the amount of the supporting electrolyte is too small or too large, the ionic conductivity is lowered, and the charging characteristics and discharging characteristics of the battery are degraded.

  The solvent used in the electrolytic solution is not particularly limited as long as it can dissolve the supporting electrolyte. Usually, dimethyl carbonate (DMC), ethylene carbonate (EC), diethyl carbonate (DEC), propylene carbonate (PC), butylene. Alkyl carbonates such as carbonate (BC) and methyl ethyl carbonate (MEC); esters such as γ-butyrolactone and methyl formate; ethers such as 1,2-dimethoxyethane and tetrahydrofuran; sulfolane and dimethyl sulfoxide Sulfur-containing compounds are used. In particular, dimethyl carbonate, ethylene carbonate, propylene carbonate, diethyl carbonate, and methyl ethyl carbonate are preferable because high ion conductivity is easily obtained and the use temperature range is wide. These can be used alone or in admixture of two or more. Moreover, it is also possible to use an electrolyte containing an additive. The additive is preferably a carbonate compound such as vinylene carbonate (VC).

Examples of the electrolytic solution other than the above include a gel polymer electrolyte in which a polymer electrolyte such as polyethylene oxide and polyacrylonitrile is impregnated with the electrolytic solution, lithium sulfide, LiI, Li ₃ N, Li ₂ S—P ₂ S ₅ glass ceramic, etc. An inorganic solid electrolyte can be mentioned.

  A lithium ion secondary battery is obtained by stacking a negative electrode and a positive electrode through a separator, winding this according to the shape of the battery, folding it into a battery container, pouring the electrolyte into the battery container and sealing it. It is done. Further, if necessary, an expanded metal, an overcurrent prevention element such as a fuse or a PTC element, a lead plate and the like can be inserted to prevent an increase in pressure inside the battery and overcharge / discharge. The shape of the battery may be any of a laminated cell type, a coin type, a button type, a sheet type, a cylindrical type, a square type, a flat type, and the like.

EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples. However, the present invention is not limited to the following examples, and may be arbitrarily changed without departing from the gist and equivalent scope of the present invention. Can be implemented. In the following description, “%” and “parts” representing amounts are based on weight unless otherwise specified.
In the examples and comparative examples, the end scraping test, the internal resistance, and the capacity retention rate were evaluated as follows.

<Scraping test>
Lithium ion secondary battery electrodes obtained in Examples and Comparative Examples (negative electrode in Example 6 and positive electrode in other Examples and Comparative Examples) were cut into 100 mm × 2000 mm and used as test pieces. The test piece was wound around a φ300 mm roll by a half turn and reciprocated 500 mm back and forth from the center at a tension of 10 N and a speed of 1 m / min. This test was performed on 10 test pieces, and the presence or absence of powder falling was determined by comparing the weights of the test pieces before and after the test. In addition, when the weight change before and after performing the test was 0.1% or more, it was determined that there was powder falling. The evaluation was performed according to the following criteria.
A: The number of test pieces that have fallen off is 0 B: The number of test pieces that have fallen down is 1 or more and less than 3 C: The number of test pieces that have fallen off is 3 or more and less than 10 D: The test that has fallen off 10 pieces

<Internal resistance>
About the lithium ion secondary battery obtained by the Example and the comparative example, it charged with constant current until it became 4.2V by the constant current method which was made into the charge rate 0.2C at 25 degreeC, and then rated voltage The battery was charged at a constant voltage. Thereafter, the discharge rate was set to 0.2 C and discharged to 3.0 V. The amount of voltage drop 10 seconds after the start of discharge was taken as ΔV. Then, the discharge rate is changed from 0.2 C to 10 C, the voltage drop amount ΔV is measured in the same manner, the discharge current value I (A) and the voltage drop amount ΔV (V) are plotted, and the straight line The inclination was defined as internal resistance, and the following criteria were used for judgment.
A: Internal resistance is less than 3.0Ω B: Internal resistance is 3.0Ω or more and less than 3.5Ω C: Internal resistance is 3.5Ω or more and less than 4.0Ω D: Internal resistance is 4.0Ω or more, 4.5Ω Less than E: Internal resistance is 4.5Ω or more

<Capacity maintenance rate>
About the lithium ion secondary battery obtained by the Example and the comparative example, it charged by constant current until it became 4.2V by the constant current constant voltage charging method of 0.5C at 60 degreeC, and it charged by constant voltage after that. Then, a charge / discharge cycle test was performed in which the battery was discharged to 3.0 V at a constant current of 0.5 C. The charge / discharge cycle test was conducted up to 100 cycles. The ratio of the discharge capacity at the 100th cycle to the initial discharge capacity was determined as the capacity retention rate. In each example and comparative example, 10 samples were produced, and the sample having the smallest capacity retention rate among the 10 samples was determined according to the following criteria. It shows that the capacity | capacitance reduction by repeated charge / discharge is so small that this value is large.
A: Capacity maintenance rate is 90% or more B: Capacity maintenance rate is 80% or more and less than 90% C: Capacity maintenance rate is 70% or more and less than 80% D: Capacity maintenance rate is 60% or more and less than 70% E: Capacity maintenance rate is less than 60%

  The adhesive coating liquid for current collector coating, the positive electrode for lithium ion secondary battery, the negative electrode for lithium ion secondary battery and the lithium ion secondary battery of Examples and Comparative Examples were prepared as follows.

Example 1
(Manufacture of binder)
In an autoclave equipped with a stirrer, 300 parts of ion exchange water, 93.8 parts of n-butyl acrylate, 2 parts of acrylonitrile, 1.0 part of allyl glycine ether, 2.0 parts of methacrylic acid, 1.2 parts of N-methylol acrylamide and molecular weight adjustment After adding 0.05 part of t-dodecyl mercaptan as an agent and 0.3 part of potassium persulfate as a polymerization initiator and stirring sufficiently, the mixture was heated to 70 ° C. for polymerization, and a solid content concentration of 40% as a binder. An aqueous dispersion of a binder (acrylate binder) containing an acrylic polymer was obtained. The polymerization conversion rate determined from the solid content concentration was approximately 99%.

(Manufacture of adhesive coating liquid for current collector coating)
The binder is 20 wt. %, Rhodamine B is 0.5 wt. %, Dispanol TOC (manufactured by NOF Corporation), which is a nonionic surfactant, is 0.5 wt. The binder coating solution for current collector coating was obtained by mixing the binder, the water-soluble phosphor, the surfactant, and water so as to be in a percentage.

(Manufacture of composite particles)
92 parts of lithium cobaltate (LiCoO ₂ , hereinafter referred to as “LCO”) (particle diameter: 6 μm) as the positive electrode active material, 2.0 parts of the above binder in terms of solid content, and acetylene black (electric Denka black powder product manufactured by Kagaku Kogyo Co., Ltd .: particle size 35 nm, specific surface area 68 m ^{2 /} g) 5.0 parts, 1.5% aqueous solution of carboxymethyl cellulose (DN-800H: manufactured by Daicel Chemical Industries) as a dispersant 1.0 part by volume in terms of the amount was mixed, and ion-exchanged water was further added so that the solid content concentration would be 40%, and mixed and dispersed to obtain a composite particle slurry for the positive electrode. This positive electrode composite particle slurry is spray-dried (manufactured by Okawara Chemical Co., Ltd.), is rotated at a rotational speed of 25,000 rpm, hot air temperature is 150 ° C. Spray drying granulation was performed at a temperature of 90 ° C. to obtain composite particles. The average volume particle diameter of the composite particles was 50 μm.

(Formation of adhesive layer)
A current collector coating adhesive coating solution is applied to a 10 μm thick aluminum current collector by a gravure coating method at a molding speed of 20 m / min, dried at 120 ° C. for 2 minutes, and then collected. A current collector with an adhesive layer in which an adhesive layer having a thickness of 1.2 μm was formed on the electric body was obtained.

(Manufacture of lithium ion secondary battery positive electrode)
The current collector with an adhesive layer is conveyed at a speed of 2 m / min, and is positively charged by a roll (rolling rough surface hot roll, manufactured by Hirano Giken Kogyo Co., Ltd.) roll (roll temperature 100 ° C., press linear pressure 4 kN / cm). The active material layer was formed into a sheet shape on the current collector with an adhesive layer to obtain a lithium ion secondary battery positive electrode having a thickness of 60 μm.

(Manufacture of negative electrode slurry and lithium ion secondary battery negative electrode)
Artificial graphite as the negative electrode active material (average particle size: 24.5 μm, graphite interlayer distance ((002) plane spacing (d value): 0.354 nm by X-ray diffraction method) 96 parts, styrene-butadiene copolymer latex ( BM-400B) is 3.0 parts in terms of solid content, and 1.5 parts of a carboxymethylcellulose 1.5% aqueous solution (DN-800H: manufactured by Daicel Chemical Industries) as a dispersant is mixed in 1.0 part in terms of solid content. Further, ion exchange water was added so as to have a solid content concentration of 50%, and mixed and dispersed to obtain a negative electrode slurry, which was applied to a copper foil having a thickness of 18 μm and dried at 120 ° C. for 30 minutes. Thereafter, roll pressing was performed to obtain a negative electrode having a thickness of 50 μm.

(Preparation of separator)
A single-layer polypropylene separator (width 65 mm, length 500 mm, thickness 25 μm, manufactured by dry method, porosity 55%) was cut into a 5 × 5 cm ² square.

(Manufacture of lithium ion secondary batteries)
An aluminum packaging exterior was prepared as the battery exterior. The positive electrode for a lithium ion secondary battery obtained above was cut into a 4 × 4 cm ² square and placed so that the current collector-side surface was in contact with the aluminum packaging exterior. On the surface of the positive electrode active material layer of the positive electrode for a lithium ion secondary battery, the square separator obtained above was disposed. Further, the negative electrode for a lithium ion secondary battery obtained above was cut into a square of 4.2 × 4.2 cm ² and arranged on the separator so that the surface on the negative electrode active material layer side faced the separator. Further, containing the vinylene carbonate 2.0%, was charged with LiPF ₆ solution having a concentration of 1.0 M. The solvent of this LiPF ₆ solution is a mixed solvent (EC / EMC = 3/7 (volume ratio)) of ethylene carbonate (EC) and ethyl methyl carbonate (EMC). Furthermore, in order to seal the opening of the aluminum packaging material, heat sealing was performed at 150 ° C. to close the aluminum exterior, and a laminate type lithium ion secondary battery (laminated cell) was manufactured.

(Example 2)
In the production of the current collector coating adhesive coating solution, the concentration of rhodamine B as the water-soluble phosphor is 0.05 wt. %, Manufacturing of an adhesive coating solution for current collector coating, for lithium ion secondary batteries, except that the binder, water-soluble phosphor, surfactant and water were mixed so that A positive electrode, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were produced.

(Example 3)
In the production of the current collector coating adhesive coating solution, the concentration of rhodamine B as the water-soluble phosphor is 1.5 wt. %, Manufacturing of an adhesive coating solution for current collector coating, for lithium ion secondary batteries, except that the binder, water-soluble phosphor, surfactant and water were mixed so that A positive electrode, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were produced.

Example 4
In the production of the current collector coating adhesive coating solution, the concentration of Dispanol TOC as the surfactant was 0.2 wt. %, Manufacturing of an adhesive coating solution for current collector coating, for lithium ion secondary batteries, except that the binder, water-soluble phosphor, surfactant and water were mixed so that A positive electrode, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were produced.

(Example 5)
In the production of the current collector coating adhesive coating solution, the concentration of Dispanol TOC as the surfactant was 0.8 wt. %, Manufacturing of an adhesive coating solution for current collector coating, for lithium ion secondary batteries, except that the binder, water-soluble phosphor, surfactant and water were mixed so that A positive electrode, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were produced.

(Example 6)
(Manufacture of adhesive coating liquid for current collector coating)
In the production of the current collector coating adhesive coating solution, instead of the above binder as a binder, styrene-butadiene copolymer latex (BM-400B) (hereinafter sometimes referred to as “SBR binder”). ) Was used to mix a binder, a water-soluble phosphor, a surfactant, and water to obtain an adhesive coating solution for current collector coating.

(Manufacture of composite particles)
Artificial graphite as the negative electrode active material (average particle size: 24.5 μm, graphite interlayer distance (plane distance (d value) of (002) by X-ray diffraction method (d value): 9254 nm), 92 parts), styrene-butadiene copolymer latex (BM-400B) is 2.0 parts in terms of solid content, and 1.0 part of a 1.5% aqueous solution of carboxymethyl cellulose (DN-800H: manufactured by Daicel Chemical Industries, Ltd.) is used as the dispersant. Further, ion-exchanged water was added so as to have a solid content concentration of 40%, and mixed and dispersed to obtain a composite particle slurry for a negative electrode, which was then spray-dried (Okawara Chemical Co., Ltd.). Made by using a rotating disk type atomizer (diameter 65 mm), rotating at 25,000 rpm, hot air temperature 150 ° C., and particle recovery outlet temperature 90 ° C. To obtain a composite particle. The average volume particle size of the composite particles was 50 [mu] m.

(Production of slurry for positive electrode and positive electrode for lithium ion secondary battery)
92 parts of LiCoO ₂ having a spinel structure as a positive electrode active material (hereinafter sometimes abbreviated as “LCO”), polyvinylidene fluoride (PVDF; “KF-1100” manufactured by Kureha Chemical Co., Ltd.) as a positive electrode binder 6 parts of acetylene black (“HS-100” manufactured by Denki Kagaku Kogyo Co., Ltd.) and 20 parts of N-methylpyrrolidone are added and mixed with a planetary mixer. A slurry was obtained. This positive electrode slurry was applied to an aluminum foil having a thickness of 18 μm, dried at 120 ° C. for 30 minutes, and then roll-pressed to obtain a positive electrode for a lithium ion secondary battery having a thickness of 60 μm.

(Manufacture of lithium ion secondary batteries)
A separator similar to that in Example 1 was prepared, and the lithium ion secondary battery negative electrode and lithium ion secondary battery positive electrode obtained in Example 6 were used in the same procedure as in Example 1 to form a laminated lithium ion secondary battery. A battery (laminated cell) was produced.

(Example 7)
In the production of the current collector coating adhesive coating solution, the binder, water-soluble phosphor, surfactant and water were mixed using polyethylene oxide instead of the binder as the binder. Produced the adhesive coating liquid for current collector coating, the positive electrode for lithium ion secondary battery, the negative electrode for lithium ion secondary battery, and the lithium ion secondary battery in the same manner as in Example 1.

(Comparative Example 1)
In the production of the current collector coating adhesive coating solution, the concentration of rhodamine B as the water-soluble phosphor is 0.005 wt. %, Manufacturing of an adhesive coating solution for current collector coating, for lithium ion secondary batteries, except that the binder, water-soluble phosphor, surfactant and water were mixed so that A positive electrode, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were produced.

(Comparative Example 2)
In the production of the current collector coating adhesive coating solution, the concentration of rhodamine B as the water-soluble phosphor is 5 wt. %, Manufacturing of an adhesive coating solution for current collector coating, for lithium ion secondary batteries, except that the binder, water-soluble phosphor, surfactant and water were mixed so that A positive electrode, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were produced.

(Comparative Example 3)
In the production of the current collector coating adhesive coating solution, the concentration of Dispanol TOC as the surfactant was 0.05 wt. %, Manufacturing of an adhesive coating solution for current collector coating, for lithium ion secondary batteries, except that the binder, water-soluble phosphor, surfactant and water were mixed so that A positive electrode, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were produced.

(Comparative Example 4)
In the production of the current collector coating adhesive coating solution, the concentration of Dispanol TOC as the surfactant was 2 wt. %, Manufacturing of an adhesive coating solution for current collector coating, for lithium ion secondary batteries, except that the binder, water-soluble phosphor, surfactant and water were mixed so that A positive electrode, a negative electrode for a lithium ion secondary battery, and a lithium ion secondary battery were produced.

(Comparative Example 5)
In the production of the current collector coating adhesive coating solution, the current collector coating adhesive was the same as in Example 1 except that the binder and water were mixed without using the water-soluble phosphor and surfactant. Manufacture of the coating liquid, the positive electrode for lithium ion secondary batteries, the negative electrode for lithium ion secondary batteries, and the lithium ion secondary battery were manufactured.

  As shown in Table 1, it contains a binder, a water-soluble phosphor, a surfactant, and water, and the concentration of the water-soluble phosphor is 0.01 wt. % Or more and 3 wt. %, And the surfactant concentration is 0.1 wt. % Or more and 1 wt. Less than 10% in the end scraping test of a lithium ion secondary battery electrode using a current collector coating adhesive coating solution that is less than 15%, and lithium ion using a current collector coating adhesive coating solution The internal resistance of the lithium ion secondary battery including the secondary battery electrode was low, and the capacity retention rate was good.

Claims (3)

A binder, a water-soluble phosphor, a surfactant, and water;
The concentration of the water-soluble phosphor is 0.01 wt. % Or more and 3 wt. %, And
The surfactant concentration is 0.1 wt. % Or more and 1 wt. % Current collector coating adhesive coating solution.   The adhesive coating liquid for current collector coating according to claim 1, wherein the binder is a particulate binder.   The adhesive coating liquid for current collector coating according to claim 1 or 2, wherein the binder contains an acrylic polymer.