Polymer solid electrolyte

Abstract

A polymer solid electrolyte obtained by blending (1) a polyether copolymer having a main chain derived form ethylene oxide and an oligooxyethylene side chain, (2) an electrolyte salt compound, and (3) a plasticizer of an aprotic organic solvent or a derivative or metal salt of a polyalkylene glycol having a number-average molecular weight of 200 to 5,000 or a metal salt of the derivative is superior in ionic conductivity and also superior in processability, moldability and mechanical strength to a conventional solid electrolyte. A secondary battery is constructed by using the polymer solid electrolyte in combination with a lithium metal negative electrode and a lithium cobaltate positive electrode.

1 . A polymer solid electrolyte comprising: 
 (1) an optionally crosslinked polyether copolymer having a number-average molecular weight of 10,000 to 2,000,000 and comprising: 
 (A) 1 to 99% by mol of a repeating unit derived from a monomer represented by the formula (I):  
                     
  wherein R 1  is a group selected from an alkyl group having 1 to 12 carbon atoms, an alkenyl group having 2 to 8 carbon atoms, a cycloalkyl group having 3 to 8 carbon atoms, an aryl group having 6 to 14 carbon atoms, an aralkyl group having 7 to 12 carbon atom and a tetrahydropyranyl group; and n is a numeral of 1 to 12;  
 (B) 99 to 1% by mol of a repeating unit derived from a monomer represented by the formula (II):  
                     
  ; and  
 (C) 0 to 15% by mol of a repeating unit derived from a monomer having one epoxy group and at least one reactive functional group;  
   (2) an electrolyte salt compound; and    (3) a plasticizer selected from the group consisting of an aprotic organic solvent, and a derivative or metal salt of a straight-chain or branched polyalkylene glycol having a number-average molecular weight of 200 to 5,000 or a metal salt of the derivative.    
     
     
         2 . The polymer solid electrolyte according to  claim 1 , wherein the glass transition temperature and fusion heat of the polyether copolymer measured by a differential scanning calorimeter (DSC) are not more than −60° C. and not more than 90 J/g, respectively.  
     
     
         3 . The polymer solid electrolyte according to  claim 1 , the reactive functional group in the constituent unit (C) is (a) a reactive silicon group, (b) an epoxy group, (c) an ethylenically unsaturated group or (d) a halogen atom.  
     
     
         4 . The polymer solid electrolyte according to  claim 1 , wherein the repeating unit (C) is derived from a monomer of the formula (III-1) or (III-2):  
       
         
           
           
               
               
           
         
       
       wherein R 2  and R 3  represent a group having a reactive functional group.  
     
     
         5 . The polymer solid electrolyte according to  claim 1 , wherein the monomer having a reactive silicon group, which constitutes the repeating unit (C), is represented by the formula (III-a-1-1), (III-a-1-2) or (III-a-2-1):  
       
         
           
           
               
               
           
         
       
       wherein R 4 , R 5  and R 6  may be the same or different, and at least one of them represents an alkoxy group and the remainder represents an alkyl group; and m represents 1 to 6.  
     
     
         6 . The polymer solid electrolyte according to  claim 1 , wherein the monomer having a reactive silicon group, which constitutes the repeating unit (C), is 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 4-(1,2-epoxy)butyltrimethoxysilane, 5-(1,2-epoxy)pentyltrimethoxysilane or 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane.  
     
     
         7 . The polymer solid electrolyte according to  claim 1 , wherein the monomer having two epoxy groups, which constitutes the repeating unit (C), is represented by the formula (III-b):  
       
         
           
           
               
               
           
         
       
       wherein R 7  is a divalent organic group.  
     
     
         8 . The polymer solid electrolyte according to  claim 7 , wherein R 7  in the formula (III-b) is 
       —CH 2 —O—(CHA 1 —CHA 2 —O) m —CH 2 —,—(CH 2 ) m —, 
       or 
       —CH 2 O—Ph—OCH 2 — 
       wherein A 1  and A 2  represent hydrogen or a methyl group; Ph represents a phenylene group; and m represents a numeral of 0 to 12.  
     
     
         9 . The polymer solid electrolyte according to  claim 1 , wherein the monomer having two epoxy groups, which constitutes the repeating unit (C), is 2,3-epoxypropyl-2′,3′-epoxy-2′-methyl propyl ether or ethylene glycol-2,3-epoxypropyl-2′,3′-epoxy-2′-methyl propyl ether.  
     
     
         10 . The polymer solid electrolyte according to  claim 1 , wherein the monomer having an ethylenically unsaturated group, which constitutes the repeating unit (C), is represented by the formula (III-c):  
       
         
           
           
               
               
           
         
       
       wherein R 8  is a group having an ethylenically unsaturated group.  
     
     
         11 . The polymer solid electrolyte according to  claim 1 , wherein the monomer having an ethylenically unsaturated group, which constitutes the repeating unit (C), is allyl glycidyl ether, 4-vinylcyclohexyl glycidyl ether, α-terpinyl glycidyl ether, cyclohexenylmethyl glycidyl ether, p-vinylbenzyl glycidyl ether, allylphenyl glycidyl ether, vinyl glycidyl ether, 3,4-epoxy-1-butene, 3,4-epoxy-1-pentene, 4,5-epoxy-2-pentene, 1,2-epoxy-5,9-cyclododecadiene, 3,4-epoxy-1-vinylcyclohexene, 1,2-epoxy-5-cyclooctene, glycidyl acrylate, glycidyl methacrylate, glycidyl sorbate, glycidyl cinnamate, glycidyl crotonate, glycidyl-4-hexenoate, oligoethylene glycol glycidyl ether acrylate having 1 to 12 oxyethylene chains, oligoethylene glycol glycidyl ether methacrylate having 1 to 12 oxyethylene chains, oligoethylene glycol allyl glycidyl ether having 1 to 12 oxyethylene chains, or  
       
         
           
           
               
               
           
         
       
       (n=1-12).  
     
     
         12 . The polymer solid electrolyte according to  claim 1 , wherein the monomer having a halogen atom, which constitutes the repeating unit (C), is represented by the formula (III-d):  
       
         
           
           
               
               
           
         
       
       wherein R 9  is a group having at least one halogen atom.  
     
     
         13 . The polymer solid electrolyte according to  claim 1 , wherein the monomer having a halogen atom is  
       
         
           
           
               
               
           
         
       
       wherein X represents a bromine atom (Br) or an iodine atom (I).  
     
     
         14 . The polymer solid electrolyte according to  claim 1 , wherein the polyether copolymer comprises 3 to 99% by mol of the repeating unit (A), 95 to 1% by mol of the repeating unit (B) and 0 to 5% by mol of the repeating unit (C).  
     
     
         15 . The polymer solid electrolyte according to  claim 1 , wherein the electrolyte salt compound is a compound comprising a cation selected from a metal cation, an ammonium ion, an amidinium ion and a guanidium ion, and an anion selected from a chlorine ion, a bromine ion, a iodine ion, a perchlorate ion, a thiocyanate ion, a tetrafluoroborate ion, a nitrate ion, AsF 6   − , PF 6   − , a stearylsulfonate ion, an octylsulfonate ion, a dodecylbenzenesulfonate ion, a naphthalenesulfonate ion, a dodecylnaphthalenesulfonate ion, a 7,7,8,8-tetracyano-p-quinodimethane ion, X 1 SO 3   − , (X 1 SO 2 )(X 2 SO 2 )N − , (X 1 SO 2 ) (X 2 SO 2 ) (X 3 SO 2 )C −  and (X 1 SO 2 ) (X 2 SO 2 ) YC −  (wherein X 1 , X 2 , X 3  and Y respectively represent an electron attractive group).  
     
     
         16 . The polymer solid electrolyte according to  claim 15 , wherein X 1 , X 2  and X 3  independently represent a perfluoroalkyl having 1 to 6 carbon atoms or a perfluoroaryl group and Y represents a nitro group, a nitroso group, a carbonyl group, a carboxyl group or a cyano group.  
     
     
         17 . The polymer solid electrolyte according to  claim 15 , wherein the metal cation is a cation of a metal selected from Li, Na, K, Rb, Cs, Mg, Ca and Ba metals.  
     
     
         18 . The polymer solid electrolyte according to  claim 15 , wherein the metal cation is a cation of a transition metal.  
     
     
         19 . The polymer solid electrolyte according to  claim 15 , wherein the metal cation is a cation of a metal selected from Mn, Fe, Co, Ni, Cu, Zn and Ag metals.  
     
     
         20 . The polymer solid electrolyte according to  claim 1 , wherein the formulation ratio of the electrolyte salt compound to the polyether copolymer is so that a value of a molar ratio of the number of moles of the electrolyte salt compound to the total number of moles of oxyethylene units in the copolymer is from 0.0001 to 5.  
     
     
         21 . The polymer solid electrolyte according to  claim 1 , wherein the aprotic organic solvent is an aprotic organic solvent selected from ethers or esters.  
     
     
         22 . The polymer solid electrolyte according to  claim 1 , wherein the aprotic organic solvent is an organic solvent selected from propylene carbonate, γ-butyrolactone, butylene carbonate and 3-methyl-2-oxazolidone.  
     
     
         23 . The polymer solid electrolyte according to  claim 1 , wherein the aprotic organic solvent is an organic solvent selected from triethylene glycol dimethyl ether, triethylene glycol diethyl ether, tetraethylene glycol dimethyl ether and tetraethylene glycol diethyl ether.  
     
     
         24 . The polymer solid electrolyte according to  claim 1 , wherein the number-average molecular weight of the polyalkylene glycol is from 200 to 2000.  
     
     
         25 . The polymer solid electrolyte according to  claim 1 , wherein the polyalkylene glycol is polyethylene glycol or polypropylene glycol.  
     
     
         26 . The polymer solid electrolyte according to  claim 1 , wherein the derivative of the polyalkylene glycol is an ether derivative or an ester derivative.  
     
     
         27 . The polymer solid electrolyte according to  claim 26 , wherein the ether derivative of the polyalkylene glycol is any one of polyethylene glycol dimethyl ether, polyethylene glycol diethyl ether and polyethylene glycol diallyl ether.  
     
     
         28 . The polymer solid electrolyte according to  claim 26 , wherein the ester derivative of the polyalkylene glycol is any one of polyethylene glycol dimethacrylate ester, polyethylene glycol diacrylate ester and polyethylene glycol acetate ester.  
     
     
         29 . The polymer solid electrolyte according to  claim 1 , wherein the metal salt of the polyalkylene glycol is any one of a sodium salt, a lithium salt and a dialkylaluminum salt.  
     
     
         30 . The polymer solid electrolyte according to  claim 1 , wherein the metal salt of the polyalkylene glycol is any one of a lithium salt of polyethylene glycol and a dialkylaluminum salt of polyethylene glycol.  
     
     
         31 . The polymer solid electrolyte according to  claim 1 , wherein the metal salt of the polyalkylene glycol is any one of a lithium salt of polyethylene glycol monomethyl ether, a lithium salt of polyethylene glycol monoethyl ether and a lithium salt of polyethylene glycol monoallyl ether.  
     
     
         32 . The polymer solid electrolyte according to  claim 1 , wherein the metal salt of the polyalkylene glycol derivative is any one of a dioctylaluminum salt of polyethylene glycol monomethyl ether, a dioctylaluminum salt of polyethylene glycol monoethyl ether and a dioctylaluminum salt of polyethylene glycol monoallyl ether.  
     
     
         33 . The polymer solid electrolyte according to  claim 1 , wherein the amount of the plasticizer is from 1 to 2,000 parts by weight based on 100 parts by weight of the polyether copolymer.  
     
     
         34 . A battery comprising the polymer solid electrolyte of  claim 1 , a positive electrode and a negative electrode.