For improvement of vanadium redox flow battery (VRB) performance, novel amphoteric semi-interpenetrating membranes (ASIPN) were prepared using poly(ether ether ketone) (PEEK) and polysulfone (PSf), the former bearing sulfonic groups and the latter imidazolium. These two groups form ionic crosslinks between PEEK and PSf; meanwhile, covalent cross links were built between PSf chains with addition of N-(3-aminopropyl)-imidazole. The amphoteric nature of the membrane allows facile proton and anion transport; the IPN structure and the presence of imidazolium cation effectively suppress vanadium ion crossover through the membrane. Therefore, the ASIPN based VRBs show higher Coulombic efficiency and energy efficiency than that assembled with pristine SPEEK and Nafion 212 membranes. Our work demonstrates that the ASIPN membranes are promising for VRB applications.