TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Property: The equilibrium moisture of electrolytic membrane is 5-80%. The redox flow secondary battery uses sulfuric acid electrolyte solution, vanadium as positive electrode and negative electrode electrolyte solution.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The ion exchange resin composition contains additive chosen from cerium type additive, cobalt-type additive and molybdenum-type additive.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The fluoropolymer electrolyte polymer contains polymer of formula:(CF2CX1X2)a-(CF2CF(CF2-O-(CFR1)b-(CFR2)c-X3))g- having repeating unit of formula (I) and repeating unit of formula (II) and further has repeating unit comprising tetrafluoroethylene. The fluoropolymer electrolyte polymer contains copolymer containing repeating unit based on monomer (A) and repeating unit based on monomer (B). The monomer (A) is perfluoro monomer which is radically polymerized to obtain polymer which has repeating unit having ring structure in a principal chain and the monomer (B) is perfluoro vinyl ether of formula: CF2=CF-(OCF2CFY1)m-Op-(CF2)n-SO2Y2. The monomer (A) contains repeating unit(s) of formula (III-VI).X1,X2=halo or 1-3C perfluoroalkyl;X3=COOZ', SO3Z', PO3Z'2 or PO3HZ';Z'=H, alkaline-metal, alkaline-earth metal, or amine chosen from NH4, NH3R1, NH2R1R2, NHR1R2R3R4;R3,R4=alkyl or arene;R1,R2=halo, 1-10C perfluoroalkyl and fluorochloro alkyl;a=0-1 (excluding 1);g=0-1 (excluding 0);or a+g=1;b=0-8;c=0 or 1;Q1=perfluoro alkylene having ethereal oxygen;Q2=single bond or perfluoro alkylene having ethereal oxygen;X=O, N or C;s=0 or 1;Rf2=perfluoro alkyl;Z=F or monovalent perfluoro organic group;t=0-3;Y1=F or trifluoromethyl;m=0-3;n=1-12;p=0 or 1;Y2=OH or NHSO2Z;Z=1-6C perfluoroalkyl having ethereal oxygen;or m+p=less than 0;n=1-4;Rf=1-8C perfluoroalkyl or perfluoroalkyl;andX4,X5=F or trifluoromethyl.(i) When a is 0, X is oxygen; (ii) When a is 1, X is nitrogen; and (iii) When a is 2, X is carbon. An ion exchange resin composition contains 0.1-200 parts mass polyazole type compound with respect to 100 parts mass fluoropolymer electrolyte polymers. The electrolytic membrane has a reinforcing material which consists of a fluorine-type microporous film. The polyazole type compound is chosen from polymers of heterocyclic compounds containing one or more nitrogen atoms in the ring and polymers of heterocyclic compounds containing sulfur and oxygen and/or one or more nitrogen atoms in the ring. The polyazole type compound is preferably chosen from polyimidazole compound, polybenzimidazole type compound, polybenzobis-imidazole compound, polybenzoxazole type compound, polyoxazole type compound, polythiazole type compound and polybenzothiazole type compound. An ion exchange resin composition contains 0.1-20 parts mass polyphenylene-ether resin and/or polyphenylene sulfide resin with respect to 100 parts mass fluoropolymer electrolyte polymers. Preferred Process: The fluoropolymer electrolyte polymer is obtained by copolymerizing comonomers compound of perfluoro unsaturated compound which has two double bonds (C), perfluoro ethene or perfluoro(alkylvinyl ether) which has bromine atom (D), polyfluoro ethene or the polyfluoro (alkylvinyl ether) which has a carboxylic acid group (carboxylate group, or carboxylate-ester group) (E), polyfluoro ethene or polyfluoro (alkylvinyl ether) which has hydroxyl group (F), perfluoro ethene or perfluoro(alkylvinyl ether) which has cyano group (G), or perfluoro ethene or perfluoro(alkylvinyl ether) which has cyanato group (H). The fluoropolymer electrolyte polymer and the polyazole type compound forms the ionic bond.