ELECTROLYTE MEMBRANE FOR REDOX FLOW BATTERY, REDOX FLOW BATTERY, AND METHOD FOR PRODUCING ELECTROLYTE MEMBRANE

The present invention provides an electrolyte membrane for a redox flow battery, comprising a perfluorocarbon polymer having an ion-exchange group, wherein the perfluorocarbon polymer has equivalent weight EW of the ion-exchange group of 600 g/eq or more and 2000 g/eq or less, a craze area ratio of the electrolyte membrane is 1.5% or less, and a relative dimension of the electrolyte membrane in at least one of a X direction and a Y direction is 80% or more and less than 100% in the following relative dimension by dipping in 2 M aqueous sulfuric acid solution.