Vanadium Species in CH3SO3H and H2SO4 Mixed Acid as the Supporting Electrolyte for Vanadium Redox Flow Battery

Cyclic voltammetry (CV) and electrochemical impedance spectroscopies (EIS) of 2M V (IV) electrolyte in CH3SO3H and H2SO4 mixed acid solution (MAS sample) and in H2SO4 (Pristine sample) as the positive electrolyte in vanadium redox flow battery (VRFB) were investigated. CV results revealed that the MAS sample had a higher reversible redox reaction than Prisinte sample. EIS showed that. The performance of a VRFB with MAS sample as positive electrolyte was investigated with the charge-discharge technique. At 120 mA/cm2, VRFB with MAS sample exhibited the higher energy density (39.87 Wh/L) in comparison of Pristine sample. Cycling tests indicated that VRFB with the mixed acid system possessed a stable cycling performance during 30 cycles.