A H3PO4 preswelling strategy to enhance the proton conductivity of a H2SO4-doped polybenzimidazole membrane for vanadium flow batteries. Issue 28 (1st March 2016) - Peng, Sangshan
Abstract : A H3 PO4 preswelling strategy is proposed to prepare H2 SO4 -doped polybenzimidazole (PBI) membranes with improved ADL and proton conductivity for vanadium flow battery. Abstract : A H3 PO4 preswelling strategy is proposed to prepare H2 SO4 -doped polybenzimidazole (PBI) membranes for vanadium flow batteries (VFB). Before being immersed in 3.0 M H2 SO4, PBI membranes are preswelled by immersion in concentrated H3 PO4, which leads to a higher H2 SO4 doping level, thereby dramatically reducing the area resistance of the PBI membrane to 0.43 Ω cm 2, which is close to that of Nafion 212 (0.35 Ω cm 2 ) and much lower than that of Fumasep®FAP-450 (0.64 Ω cm 2 ). Meanwhile, the substantially high selectivity is maintained. The VFB assembled with the H3 PO4 preswelled PBI membrane displays high energy efficiencies (EE: 80.9–89.2%) over a current density range of 20–80 mA cm −2, much higher than those of the non-preswelled PBI membrane (EE: 66.8–84.5%), Nafion 212 (EE: 63.1–75.6%) and Fumasep®FAP-450 (EE: 75.5–82.6%). The stable performance over 50 charge–discharge cycles demonstrates the good physicochemical stability of the preswelled PBI membrane. Considering the above results, the H3 PO4 preswelling strategy proposed herein is facile and efficient for fabricating high-performance PBI membranes for VFB.