Efforts to build a renewable energy to environmental problems caused by the depletion of fossil energy and CO2 emissions are concentrated. to solve this problem, such as the Smart Grid and the ESS has been introduced. Because of redox flow batteries can operate at room temperature and burden on maintenance costs and environmental issues are relatively small, It is advantageous for the energy storage system. But the biggest problem is capacity loss of redox flow battery and lifetime degradation due to cross contamination. In this study, in order to prevent cross contamination in the vanadium redox flow battery, sulfonated silica was dispersed in Nafion solution. and it was prepared by casting a solution of Nafion membrane. By changing the amount of silica was to evaluate the performance of the produced silica/Nafion composite membrane. These membranes for dimensional change, conductivity, impedance, the change in performance was observed over a silica content in accordance with the charge/ discharge test.