CN109075290B - Polyurethane resin aqueous dispersion for secondary battery separator, and secondary battery - Google Patents

Polyurethane resin aqueous dispersion for secondary battery separator, and secondary battery Download PDF

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Publication number
CN109075290B
CN109075290B CN201680084420.XA CN201680084420A CN109075290B CN 109075290 B CN109075290 B CN 109075290B CN 201680084420 A CN201680084420 A CN 201680084420A CN 109075290 B CN109075290 B CN 109075290B
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secondary battery
polyurethane resin
polyol
separator
polyolefin
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CN109075290A (en
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金子文弥
渡边聪哉
宫村岳志
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DKS Co Ltd
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Dai Ichi Kogyo Seiyaku Co Ltd
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/417—Polyolefins
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/40—High-molecular-weight compounds
    • C08G18/62—Polymers of compounds having carbon-to-carbon double bonds
    • C08G18/6204—Polymers of olefins
    • C08G18/6208—Hydrogenated polymers of conjugated dienes
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/67—Unsaturated compounds having active hydrogen
    • C08G18/69—Polymers of conjugated dienes
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/423—Polyamide resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M50/411—Organic material
    • H01M50/414—Synthetic resins, e.g. thermoplastics or thermosetting resins
    • H01M50/426—Fluorocarbon polymers
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • 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
    • H01M50/443—Particulate material
    • 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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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Electrochemistry (AREA)
  • General Chemical & Material Sciences (AREA)
  • Health & Medical Sciences (AREA)
  • Medicinal Chemistry (AREA)
  • Polymers & Plastics (AREA)
  • Organic Chemistry (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Polyurethanes Or Polyureas (AREA)
  • Cell Separators (AREA)
  • Secondary Cells (AREA)

Abstract

According to the present invention, it is possible to obtain a polyurethane resin aqueous dispersion for a secondary battery separator, which has good mixing stability with a thickener, good electrolyte resistance, strength retention before and after impregnation with an electrolyte solution, and good dynamic viscoelasticity and adhesion. An aqueous dispersion of a polyurethane resin for a secondary battery separator is used, the polyurethane resin being a reaction product of at least a polyolefin-based polyol (excluding a hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in 1 molecule) (A) and a polyisocyanate compound (B).

Description

Polyurethane resin aqueous dispersion for secondary battery separator, and secondary battery
Technical Field
The invention relates to a polyurethane resin aqueous dispersion for a secondary battery separator, and a secondary battery.
Background
In recent years, mobile terminals such as notebook personal computers, mobile phones, and pdas (personal Digital assistants) have been spread remarkably. Secondary batteries used as power sources of these portable terminals are often secondary batteries typified by lithium-ion secondary batteries. On the other hand, polyurethane resins are also used in a wide range of fields due to their characteristics, and secondary batteries are also used (patent document 1).
Documents of the prior art
Patent document
Patent document 1: japanese laid-open patent publication No. 2012 and 003841
Disclosure of Invention
However, the resin described in the patent document does not necessarily satisfy the performance when used as a secondary battery separator.
In order to solve the above problems, the present invention relates to:
(1) an aqueous dispersion of a polyurethane resin for a secondary battery separator, the polyurethane resin being a reaction product of at least a polyolefin-based polyol (wherein a hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in 1 molecule) and a polyisocyanate compound (B) are excluded,
(2) the aqueous polyurethane resin dispersion for a secondary battery separator according to (1), wherein (A) is one or more selected from the group consisting of a polybutadiene polyol (A1), a polyisoprene polyol (A2), a hydrogenated polybutadiene polyol (A3) and a hydrogenated polyisoprene polyol (A4) in which the hydroxyl group in 1 molecule is 2 or more,
(3) a secondary battery separator obtained by using the aqueous polyurethane resin dispersion according to (1) or (2),
(4) a secondary battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the separator is the separator for a secondary battery according to (3).
According to the present invention, the coating film obtained from the polyurethane resin aqueous dispersion has good electrolyte resistance, strength retention before and after impregnation with an electrolyte, dynamic viscoelasticity, and adhesion, and therefore, the coating film is suitable for use as a separator for a secondary battery.
Detailed Description
Preferred embodiments of the present invention will be described below.
< aqueous polyurethane resin dispersion >
The polyurethane resin of the present invention is a reaction product of at least a polyolefin polyol (excluding a hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in 1 molecule) (a) and a polyisocyanate compound (B). By using the polyolefin polyol, the polarity of the polyurethane resin is lowered, and thus the electrolyte resistance, the strength retention ratio before and after the impregnation with the electrolyte solution, the dynamic viscoelasticity, and the adhesion are excellent.
Preferably obtained by the following operations: the urethane prepolymer is obtained by reacting a polyol containing a polyolefin polyol (excluding a hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in 1 molecule) (a), a polyisocyanate compound (B), and, if necessary, a hydrophilic group-containing compound, and if necessary, neutralizing or quaternizing the hydrophilic group contained therein with a quaternizing agent, emulsifying the urethane prepolymer with water, and further performing a chain extension reaction with water or/and a polyamine.
In the present invention, the polyolefin polyol (excluding a hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in 1 molecule) (A) refers to a compound containing a hydroxyl group in a polymer or copolymer of a C4-12 diolefin such as butadiene or isoprene, or a copolymer of a C4-12 diolefin and a C2-22 α -olefin. The method for containing a hydroxyl group is not particularly limited, and for example, there is a method of reacting a diene monomer with hydrogen peroxide. Further, saturated aliphatation may be performed by hydrogenating the remaining double bonds. Examples of such polyolefin polyols include "NISSO-PB G" series manufactured by Nippon Kao corporation, "Poly bd" series manufactured by shinghua corporation, and "Epol". Among these, from the viewpoints of electrolyte resistance, strength retention before and after immersion in an electrolyte solution, dynamic viscoelasticity, and adhesion, polybutadiene polyol (a1), polyisoprene polyol (a2), hydrogenated polybutadiene polyol (A3) and hydrogenated polyisoprene polyol (a4) in which the number of hydroxyl groups in 1 molecule is 2 or more are preferable. One or two or more of them may be used.
In the present invention, polyols other than the polyolefin polyol (not including the hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in 1 molecule) (a) may be used in combination. The other polyol is not particularly limited as long as it is a compound having 2 or more hydroxyl groups in the molecule, and examples thereof include compounds having 2 or more hydroxyl groups at the molecular end or in the molecule, such as polyols, polyether polyols, polyester polyols, polyetherester polyols, polycarbonate polyols, polyacrylic polyols, polyacetal polyols, polybutadiene polyols, polysiloxane polyols, fluorine polyols, and the like. The polyhydric alcohol is not particularly limited, and examples thereof include ethylene glycol, diethylene glycol, butanediol, propylene glycol, hexanediol, bisphenol a, bisphenol B, bisphenol S, hydrogenated bisphenol a, dibromobisphenol a, 1, 4-cyclohexanedimethanol, dihydroxyethyl terephthalate, hydroquinone dihydroxyethyl ether, trimethylolpropane, glycerol, pentaerythritol, and the like. The polyether polyol is not particularly limited, and examples thereof include alkylene derivatives of polyols, polytetramethylene glycol, polythioether polyols, and the like. The polyester polyol and polyether polyol are not particularly limited, and examples thereof include esterified products derived from polyhydric alcohols, polycarboxylic acids, polycarboxylic acid anhydrides, polyether polyols, polycarboxylic acid esters, castor oil polyols, polycaprolactone polyols, and the like. Among these, polyether polyols and polyester polyols are preferable. One or two or more of them may be used. Further, a compound having 1 hydroxyl group may be used in combination.
In the present invention, the number average molecular weight of the polyol component is not particularly limited, but is preferably 50 to 10000, more preferably 500 to 5000, from the viewpoint of the compounding stability with the thickener and the physical properties.
In the present invention, the polyisocyanate compound (B) is not particularly limited, and examples thereof include organic polyisocyanates such as aromatic, aliphatic, alicyclic and aromatic-aliphatic polyisocyanates. Among these, from the viewpoints of electrolyte resistance, strength retention before and after immersion in an electrolyte solution, dynamic viscoelasticity, and adhesion, organic polyisocyanates such as aliphatic, alicyclic, and aromatic fats, and their polymeric modifications (dimers, trimers, and the like), and biuret modifications produced by the reaction of the above organic polyisocyanates with water are preferable. More preferred are organic polyisocyanates such as 4, 4' -dicyclohexylmethane diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate [ bis (isocyanatomethyl) cyclohexane ], hexamethylene diisocyanate, lysine diisocyanate, norbornane diisocyanate, xylylene diisocyanate and the like, and modified products thereof. Further, 4' -dicyclohexylmethane diisocyanate and isophorone diisocyanate are more preferable. One or two or more of them may be used.
In the present invention, the ratio (molar equivalent ratio) of the isocyanate group to the hydroxyl group for obtaining the urethane prepolymer is not particularly limited as long as it is 1.1 or more to 1: 1 (isocyanate group: hydroxyl group), and is preferably 1.5 to 3.0:1, more preferably 1.6 to 2.2:1, from the viewpoint of enabling the urethane prepolymer (b) to have a low viscosity and to obtain a stable emulsion. When the amount is within these ranges, the stability of the mixture with the thickener is good.
In the present invention, the average molecular weight of the urethane prepolymer is preferably 5000 or less, more preferably 4000 or less, from the viewpoint of emulsifiability and emulsion stability. The average molecular weight herein means a theoretical value calculated from the number average molecular weight of the charged raw materials.
In the present invention, the hydrophilic group may be any of the anionic group, cationic group, or nonionic group, and is not particularly limited, and among them, from the viewpoint of the blending stability with a thickener and the coating performance, an anionic group or cationic group is preferable.
The hydrophilic group compound containing and introducing the hydrophilic group is not particularly limited, and examples thereof include (di) alkanol carboxylic acid or sulfonic acid neutralized products of tertiary amines or alkali metals, (methoxy) polyalkylene oxides, and (di) alkanol amines neutralized products of organic and inorganic acids, and quaternary ammonium salts obtained by reacting these with alkyl halides or dialkyl sulfuric acids. Among them, preferred are (di) alkanol carboxylic acid or sulfonic acid tertiary amine or alkali metal neutralized product, (di) alkanol amine organic/inorganic acid neutralized product, and quaternary ammonium salt obtained by reacting them with alkyl halide or dialkyl sulfuric acid. The (methoxy) polyalkylene oxide may contain at least ethylene oxide as an alkylene oxide, and may contain alkylene oxides other than ethylene oxide, such as propylene oxide and butylene oxide. The addition form (hydrophilic group introduction form) when a (methoxy) polyalkylene oxide containing a plurality of alkylene oxides is used may be either block addition or random addition.
Examples of the compound into which these hydrophilic groups can be introduced include the following compounds.
Examples of the anion type include salts obtained by neutralizing a carboxylic acid compound such as dimethylolpropionic acid, dimethylolbutyric acid, lactic acid, or glycine, a sulfonic acid compound such as aminoethylsulfonic acid, or a polyester diol composed of sulfoisophthalic acid and a diol, with a tertiary alkanolamine such as triethylamine, NaOH, or dimethylaminoethanol. Among them, dimethylolpropionic acid, glycine and sodium salt of aminoethylsulfonic acid are preferable from the viewpoints of compounding stability with a thickener and film performance.
Examples of the cation type include salts obtained by neutralizing alkanolamines such as dimethylaminoethanol and methyldiethanolamine with organic carboxylic acids such as formic acid and acetic acid, and inorganic acids such as hydrochloric acid and sulfuric acid, and compounds obtained by quaternizing alkanolamines such as methyl chloride and methyl bromide, and dialkylsulfuric acids such as dimethylsulfuric acid. Among them, a combination of methyldiethanolamine and an organic carboxylic acid and a combination of methyldiethanolamine and dimethylsulfuric acid are preferable for reasons of easy industrial production.
The content of the hydrophilic group in the urethane prepolymer (b) is not particularly limited. For example, the content is preferably 0.07 to 2.10mmol/g, more preferably 0.12 to 1.80mmol/g, and still more preferably 0.17 to 1.60 mmol/g. If the amount is within the above range, the amount is preferably in view of the stability of blending with a thickener and the performance of the coating film.
In the above chain extension, water or polyamine may be used. The polyamine is not particularly limited, and for example, aliphatic polyamines such as ethylenediamine, trimethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine, and the like, aromatic polyamines such as m-xylylenediamine, tolylenediamine, diaminodiphenylmethane, and the like, alicyclic polyamines such as piperazine, isophoronediamine, and the like, and polyhydrazides such as hydrazine, adipic acid dihydrazide, and the like can be used. The polyamine compounds can be used alone, also can be used in combination of 2 or more.
The solid content of the polyurethane resin in the aqueous polyurethane resin dispersion of the present invention is not particularly limited, and is, for example, preferably 1 to 60 mass%, more preferably 3 to 55 mass%, and still more preferably 4 to 50 mass% with respect to the aqueous dispersion. When the amount is within these ranges, the amount is preferably in view of stability of blending with a thickener and workability.
In addition, various additives generally used may be used as needed in the aqueous dispersion of the present invention. Examples of such additives include weather-resistant agents, antibacterial agents, antifungal agents, pigments, fillers, rust-proofing agents, pigments, dyes, film-forming aids, inorganic crosslinking agents, organic crosslinking agents (e.g., blocked isocyanate crosslinking agents, epoxy crosslinking agents, carbodiimide crosslinking agents, and the like),
Figure BDA0001821530700000051
Oxazoline-based crosslinking agents, melamine-based crosslinking agents), silane coupling agents, antiblocking agents, viscosity modifiers, leveling agents, defoamers, dispersion stabilizers, light stabilizers, antioxidants, ultraviolet absorbers, inorganic and organic fillers, plasticizers, lubricants, antistatic agents, and the like.
< Secondary Battery separator >
The secondary battery separator of the present invention is obtained using the above-described aqueous polyurethane resin dispersion. The porous body is not particularly limited, and preferably includes insulating fine particles stable to the nonaqueous electrolytic solution and an organic binder.
In the separator of the present invention, an organic binder is used for the purpose of binding the insulating fine particles to each other. The organic binder may be any organic binder that is electrochemically stable, stable to an electrolytic solution, and capable of favorably binding insulating fine particles and the like, but the aqueous polyurethane resin dispersion is preferably used from the viewpoint of maintaining the storage elastic modulus at high temperatures of dynamic viscoelasticity. Examples of the other material include EVA (having 20 to 35 mol% of a structural unit derived from vinyl acetate), ethylene-acrylic ester copolymers such as ethylene-ethyl acrylate copolymers, fluorine-based rubbers, Styrene Butadiene Rubbers (SBR), carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyvinyl pyrrolidone (PVP), polyurethane, and epoxy resins, and these may be used alone or in combination of 2 or more.
As the porous body, a porous film having ion conductivity, high resistance to a nonaqueous electrolytic solution, and a fine pore diameter is used, although it has no electron conductivity. Examples thereof include a microporous membrane made of a resin such as a polyolefin (polyethylene, polypropylene, polybutylene, or polyvinyl chloride) or a mixture or copolymer thereof, a microporous membrane made of a resin such as polyethylene terephthalate, polycycloolefin, polyether sulfone, polyamide, polyimide amide, aramid, polycycloolefin, nylon, or polytetrafluoroethylene, a woven fabric obtained by weaving polyolefin fibers, a nonwoven fabric thereof, and an aggregate of insulating material particles. Among them, a microporous film made of a polyolefin resin is preferable in order to reduce the thickness of the secondary battery separator and increase the ratio of the electrode active material layer in the battery to increase the capacity per unit volume.
The thickness of the porous body is preferably 0.5 to 40 μm, more preferably 1 to 30 μm, and particularly preferably 1 to 10 μm. When the amount is within the above range, the resistance of the porous body in the battery is reduced, and the workability in manufacturing the battery is excellent.
For the purpose of improving tear strength and puncture strength, the porous body may have a multilayer structure having 2 or more layers that can be used as the porous body. Specifically, a laminate of a polyethylene microporous membrane and a polypropylene microporous membrane, a laminate of a nonwoven fabric and a polyolefin separator, and the like can be given.
The insulating fine particles serve as a main component of the secondary battery separator of the present invention, and have an effect of suppressing the occurrence of short circuits due to lithium dendrites. The insulating fine particles are not particularly limited as long as they have electrical insulating properties and electrochemical stability, are stable with respect to the electrolyte solution and the solvent used in the composition for forming a separator (composition containing a solvent), and do not dissolve in the electrolyte solution in a high-temperature state.
In the present specification, the "insulating fine particles stable to a nonaqueous electrolytic solution" refers to insulating fine particles that are not deformed or chemically changed in a nonaqueous electrolytic solution (a nonaqueous electrolytic solution used as an electrolytic solution of a lithium secondary battery). The "high temperature state" referred to in the present specification is specifically a temperature of 150 ℃ or higher, and may be stable particles that do not deform or change in chemical composition in the electrolyte at such a temperature. In the present specification, "electrochemically stable" means that no chemical change occurs during charge and discharge of the battery.
Specific examples of such insulating fine particles include iron oxide and SiO2、Al2O3、TiO2、BaTiO2Oxide fine particles such as ZrO; nitride fine particles such as aluminum nitride and silicon nitride; insoluble ionic crystal particles such as calcium fluoride, barium fluoride and barium sulfate; covalently bonded crystalline fine particles of silicon, diamond, or the like; clay fine particles such as talc and montmorillonite; and mineral resource-derived substances such as boehmite, zeolite, apatite, kaolin, mullite, spinel, olivine, sericite, and bentonite, and artificial products thereof. In addition, the metal fine particles may be formed by using a material having electrical insulation (for example, a material constituting the above-described electrically insulating fine particles); SnO2Oxide fine particles such as Indium Tin Oxide (ITO); fine particles having electrical insulation properties obtained by surface-treating the surfaces of conductive fine particles such as carbonaceous fine particles of carbon black, graphite, and the like. These insulating fine particles may be used alone in 1 kind, or may be used in combination in 2 or more kinds.
The form of the insulating fine particles may be any form such as spherical, particulate, plate-like, and preferably plate-like. The plate-like particles include various commercially available products, for example, "sunlovely" (SiO) available from Asahi glass SI-Tech2) Pulverized product of "NST-B1" manufactured by Shigaku industries Ltd. (TiO)2) "H series" and "HL series" of barium sulfate prepared by Sakai chemical industry, Inc., "Micron White" (talc) prepared by Linghuazai chemical Co., Ltd, "Bengel" (bentonite) prepared by Linghuai chemical Co., Ltd, "BMM" (boehmite) prepared by Hehe lime Co., Ltd, "Ser" (boehmite) prepared by Hehe lime Co., Ltdrasur BMT-B' [ alumina (Al)2O3)]"Seraph" (alumina) manufactured by Kinseimatec, and "HIKAWA-Mica Z-20" (sericite) manufactured by Fizeau mining, and the like.
< Secondary Battery >
The secondary battery of the present invention is not particularly limited as long as it has the separator of the present invention and includes a positive electrode, a negative electrode, a separator, and an electrolyte, and other configurations and structures can be adopted as long as they are conventionally known. In the present invention, the secondary battery is preferably a nonaqueous electrolyte secondary battery, and more preferably a lithium ion secondary battery.
< Process for producing aqueous polyurethane resin dispersion >
The urethane polymer of the present invention can be produced by a known method, but is not particularly limited to, for example, a method in which a polyol, an isocyanate compound and, if necessary, a hydrophilic group-containing compound are reacted at 30 to 130 ℃ for about 0.5 to 10 hours, and the resulting reaction product is cooled to 5 to 45 ℃ if necessary to neutralize the hydrophilic group contained therein or quaternized with a quaternizing agent to obtain a urethane prepolymer. As the solvent, acetone, methyl ethyl ketone, tetrahydrofuran, or dioxane can be used
Figure BDA0001821530700000071
An optional organic solvent such as an alkane, ethyl acetate, or butyl acetate. The urethane prepolymer is further emulsified and chain-extended to produce a polyurethane resin aqueous dispersion. The water used for the emulsification is preferably added in an amount of 100 to 900 parts by weight based on 100 parts by weight of the urethane polymer.
< method for producing secondary battery separator >
The method for producing the secondary battery separator of the present invention is not particularly limited, and can be obtained by, for example, first coating a slurry containing insulating fine particles and an organic binder on a porous body and drying the coated slurry. The slurry is produced by mixing a dispersion medium, the insulating fine particles as the solid component, an organic binder, and optional components. As the viscosity modifier for slurrying, a thickener such as a water-soluble polymer may be used. Specifically, there may be used cellulose compounds selected from carboxymethyl cellulose salts, methyl cellulose, ethyl cellulose, hydroxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxyethylmethyl cellulose and the like; polycarboxylic acid compounds such as polyacrylic acid and sodium polyacrylate; compounds having a vinylpyrrolidone structure such as polyvinylpyrrolidone; 1 or more than 2 of polyacrylamide, polyethylene oxide, polyvinyl alcohol, sodium alginate, xanthan gum, carrageenan, guar gum, agar, starch and the like, wherein carboxymethyl cellulose salt is preferred. In the present invention, by using the above components, a slurry in which insulating fine particles are highly dispersed can be obtained regardless of the mixing method and the mixing procedure. The secondary battery separator of the present invention is obtained using the above-described aqueous polyurethane resin dispersion. The porous body is not particularly limited, but preferably includes insulating fine particles stable to the nonaqueous electrolytic solution and an organic binder. The dispersion medium is not particularly limited as long as the solid component can be uniformly dispersed. Both water and organic solvents can be used. Examples of the organic solvent include cyclic aliphatic hydrocarbons such as cyclopentane and cyclohexane; aromatic hydrocarbons such as toluene, xylene, and ethylbenzene; ketones such as acetone, methyl ethyl ketone, diisopropyl ketone, cyclohexanone, methylcyclohexane, and ethylcyclohexane; chlorine-based aliphatic hydrocarbons such as methylene chloride, chloroform and carbon tetrachloride; esters such as ethyl arylacetate, butyl acetate, gamma-butyrolactone, and epsilon-caprolactone; nitriles such as acetonitrile and propionitrile; ethers such as tetrahydrofuran and ethylene glycol diethyl ether, alcohols such as methanol, ethanol, isopropanol, ethylene glycol and ethylene glycol monomethyl ether; amides such as N-methylpyrrolidone and N, N-dimethylformamide.
< method for manufacturing secondary battery >
Specific examples of a method for producing a secondary battery include a method in which a positive electrode and a negative electrode are stacked with the separator for a secondary battery of the present invention interposed therebetween to obtain a laminate, the laminate is wound or bent in accordance with the shape of the battery and placed in a battery container, and an electrolyte solution is injected into the battery container and sealed. In order to obtain the laminate, the laminate is preferably hot-pressed. Hot pressing is a method of heating and pressing simultaneously. The pressing is performed by a roll press, a flat press, or the like using a metal roll, an elastic roll, or the like. Examples of the pressing method include batch pressing and continuous rolling, and the continuous rolling is preferable in terms of improving productivity.
< physical Properties, etc.)
The stability of the aqueous dispersion of the present invention in combination with a thickener by the method described in examples is preferably such that no separation is observed, and more preferably no separation is observed at all.
The electrolyte resistance of the coating film obtained from the aqueous polyurethane resin dispersion of the present invention is preferably not dissolved by the method described in the examples, and is preferably 50% or less, more preferably 40% or less.
The strength of the coating film obtained from the aqueous polyurethane resin dispersion of the present invention before and after the impregnation with an electrolyte is preferably 5 (N/mm) by the method described in examples2)1 (N/mm) above2) Above, more preferably 8 (N/mm)2)2 (N/mm) above2) The above.
The dynamic viscoelasticity of the coating film obtained from the aqueous polyurethane resin dispersion of the present invention is preferably 0.5 (10) in the method described in the examples6Pa) or more, more preferably 1.0 (10)6Pa) or more.
The adhesiveness of the coating film obtained from the aqueous polyurethane resin dispersion of the present invention is preferably 0.17(N/cm) or more, and more preferably 0.15(N/cm) or more in the method described in examples.
Examples
The present invention will be described in further detail below with reference to examples, but the present invention is not limited to these examples.
(example 1)
74.3 parts by weight of polyolefin polyol (A1) (KRASOLLBH-P3000 (CRAY VALLEY Co., Ltd., polybutadiene polyol)) and 4.2 parts by weight of dimethylolpropionic acid (Bis-MPA), 21.5 parts by weight of polyisocyanate compound (B-1) (hydrogenated diphenylmethane diisocyanate) and 100 parts by weight of methyl ethyl ketone were charged into a four-necked flask equipped with a stirrer, a reflux condenser, a thermometer and a nitrogen blowing tube, and reacted at 75 ℃ for 2 hours to obtain a methyl ethyl ketone solution of a polyurethane prepolymer. The content of free isocyanate groups based on the nonvolatile content of the solution was 2.2%. Subsequently, the solution was cooled to 45 ℃ and 3.2 parts by weight of triethylamine was added to neutralize the solution, and then emulsion reaction was performed using a homogenizer while slowly adding 186 parts by weight of water. To the obtained emulsion dispersion, an aqueous solution of 1.6 parts by weight of diethylenetriamine dissolved in 27 parts by weight of water was added and reacted for 1 hour, and then methyl ethyl ketone as a reaction solvent was distilled under reduced pressure to obtain an aqueous composition having a nonvolatile content (solid content) concentration of 35% by weight.
(examples 2 to 6, comparative example)
Synthesis was performed in the same manner as in example 1, except that the composition was changed to the composition shown in table 1.
The compounds used are shown below.
Polyolefin polyol (A2): Poly ip (polyisoprene polyol having a functional group number of 2.3, manufactured by Shixinghua Co., Ltd.)
Polyolefin polyol (A3) polyether H (hydrogenated polybutadiene polyol with a functional group number of 2.3, manufactured by Mitsubishi chemical corporation)
Polyolefin polyol (A4): Epol (hydrogenated polyisoprene polyol having a functional group number of 2.3, manufactured by shingling Co., Ltd.)
Other polyol (A') ETERNACOLL UH-100 (polycarbonate polyol, product of Yu Ming Co., Ltd.)
Polyisocyanate Compound (B-2) Isophorone diisocyanate
Neutralizing salt (Li) lithium hydroxide monohydrate (manufactured by Nakalai Tesque Co., Ltd.)
(stability of blending with thickener)
A slurry was obtained by mixing the aqueous polyurethane resin dispersion and carboxymethylcellulose (serigen WS-C, thickening agent) at 100/1 (weight ratio) under stirring at 200rpm for 10 minutes, and the state of the obtained slurry after standing at 20 ℃ for 24 hours was visually confirmed, and evaluated as follows.
Complete absence of separation
Separation is seen
The following electrolyte solutions were used for evaluation.
The impregnation liquid is mixed solution of ethylene carbonate/propylene carbonate/dimethyl carbonate/methyl ethyl carbonate/diethyl carbonate (mass ratio) 1/1/1/1/1
(electrolyte resistance)
A coating film was produced using the aqueous polyurethane resin dispersion under the following conditions.
The coating film formation conditions were 40 ℃ for 15 hours, 80 ℃ for 6 hours, 120 ℃ for 20 minutes
Dried film thickness 300 μm and weight 0.2g
The weight of the prepared film before immersion was measured, and then the film was immersed in an electrolyte solution at 60 ℃ for 3 days, and then returned to room temperature, and the immersion solution on the surface was wiped off, and the weight after immersion was measured. The weight gain (%) was calculated based on the following formula.
Weight increase (%) (weight after impregnation-weight before impregnation)/weight before impregnation
(Strength before and after impregnation with electrolyte)
The film immersed under the above conditions was measured at a drawing speed of 100mm/min in accordance with JIS-K-6301.
(dynamic viscoelasticity)
The coating film thus produced was measured using a dynamic viscoelasticity apparatus manufactured by Rheogel-E4000 UBM at a temperature rise rate of 4 ℃/min).
(Adhesivity)
After adjusting to 30% resin solid content by adding distilled water, the resin was applied to a separator made of a polyethylene porous membrane by a bar coater so that the dry film thickness became 10 μm. In the state where the coated surface of the obtained coated film was fixed to the support, one end of the separator was subjected to stretch peeling in a 180 ° direction at a stretching speed of 100mm/min, and adhesion was evaluated.
[ Table 1]
Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Comparative example
Polyolefin polyol (A1) 74.30 77.4
Polyolefin polyol (A2) 70.8
Polyolefin polyol (A3) 74.30 74.30
Polyolefin polyol (A4) 70.8
Other polyols (A') 71.1
Bis-MPA 4.20 4.20 4.20 4.20 4.20 4.20 6.10
Polyisocyanate Compound (B-1) 21.50 25.0 21.5 21.5 25.0 22.8
Polyisocyanate Compound (B-2) 18.4
Amine elongation agent DETA DETA DETA DETA DETA DETA DETA
Neutralizing salt TEA TEA TEA Li TEA TEA TEA
Compounding stability of thickener ○ ○ ○ ○ ○ ○ ×
Electrolyte resistance (%) 29 29 16 14 19 32 Dissolution
Strength (N/mm) before impregnation with electrolyte2) 11 18 13 17 13 14 25
Strength (N/mm) after immersion in electrolyte2) 3.3 5.4 5.7 8.5 5.1 2.9 Dissolution
Dynamic viscoelasticity (10)6Pa) 2.9 1.5 6.7 29.8 1.7 1.8 0.2
Adhesives (N/cm) 0.2 0.21 0.2 0.19 0.2 0.21 0.15
As is clear from table 1, the aqueous polyurethane resin dispersion of the present invention has good mixing stability of the slurry, and the obtained coating film has good electrolyte resistance, strength retention before and after impregnation with an electrolyte, dynamic viscoelasticity, and adhesion. On the other hand, it is found that the comparative examples which did not use the polyolefin polyol (excluding the hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in 1 molecule) (a) were inferior in all of electrolyte resistance, dynamic viscoelasticity and adhesiveness. The mixing stability of the slurry was evaluated by using SBR (styrene butadiene rubber), and found to be X.
Industrial applicability
The polyurethane resin aqueous dispersion of the present invention has good mixing stability with a thickener, and the obtained coating film has good electrolyte resistance, strength retention before and after impregnation with an electrolyte, dynamic viscoelasticity, and adhesion, and therefore, can be suitably used as a separator for a secondary battery. In addition, the secondary battery separator using the same can also be applied to a secondary battery.

Claims (4)

1. An aqueous polyurethane resin dispersion for a secondary battery separator, the polyurethane resin being a reaction product of at least a polyolefin-based polyol (A) and a polyisocyanate compound (B), the polyolefin-based polyol (A) not including a hydrogenated polybutadiene polyol having less than 2 hydroxyl groups in 1 molecule.
2. The aqueous polyurethane resin dispersion for a secondary battery separator according to claim 1, wherein the polyolefin polyol (A) is one or more selected from the group consisting of a polybutadiene polyol (A1), a polyisoprene polyol (A2), a hydrogenated polybutadiene polyol (A3) having 2 or more hydroxyl groups in 1 molecule, and a hydrogenated polyisoprene polyol (A4).
3. A secondary battery separator obtained by using the aqueous polyurethane resin dispersion according to claim 1 or 2.
4. A secondary battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the separator is the separator for a secondary battery according to claim 3.
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