▎ 摘　　要

NOVELTY - Preparing a graphene oxide coating material comprises: preparing a graphene oxide using a natural graphite as a starting material; forming a graphene oxide dispersed solution by adding the graphene oxide into water in an ultrasonic reactor; and adding nafion to the graphene oxide dispersed solution to prepare a coating solution in an ultrasonic reaction tub. USE - The method is useful for preparing a graphene oxide coating material useful in an electrolyte membrane of a redox flow battery (all claimed). ADVANTAGE - The formation of the vanadate ion is reduced so as to reduce a crossover phenomenon, so that the performance of the redox flow battery is increased. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for: (1) an electrolyte membrane coated with nafion solution coating material coated on both sides; and (2) a redox flow battery.