Abstract:Membrane is the key factor confining the wide use of all-vanadium flow battery. Now Nation membranes were usually adopted because of its good electrochemical performance and long life. But Nation can not be used widely in China because of high permeation of V ion and high cost. A domestic membrane was selected and modified. Electrochemical results show that this modified low-cost membrane by the way of soak in Nation solution has good electrochemical performance and high current efficiency. But voltage efficiency decrease obviously with the current density increase. Meanwhile, this modified membrane has low permeation of V ion, but the chemical stability need to be improved.