PVA-Silica Composite Membrane for Aqueous Hybrid Flow Battery

Abstract

The use of redox flow batteries (RFBs) has become popular for preserving renewable energy. For widespread commercialization, the appropriate selection of redox-active species and ion exchange membranes (IEM) is essential. Herein, we synthesized a robust PVA-Silica (PVA-SiO2) composite membrane and demonstrated its essential use in an aqueous hybrid RFB. A proton-conducting, chemically and physically stable membrane was created by combining the traditional hydrophilicity of PVA with well-defined interconnecting ion-conducting channels produced by uniformly distributed silica particles. We believe that thermal crosslinking ensured substantial dimensional and chemical durability, whereas silica permitted good ionic conductivity. The utility of the membrane was proved in a hybrid redox flow battery consisting of newly synthesized 1,4-phenoxy bis-propane sulfonic acid (PPS) and vanadium (III) salt in 2 M H2SO4. A detailed battery analysis was carried out with a rate performance study, cycling test, polarization curve, and OCV. Over 100 charge/discharge cycles, it demonstrated 95% coulombic efficiency, 61% voltage efficiency, and 57% energy efficiency at a current density of 50 mA cm-2, indicating the best utility of an oxidatively susceptible functional group-free robust proton conducting membrane.