Performance of the vanadium redox-flow battery (VRB) for Si-PWA/PVA nanocomposite membrane

Abstract

The performance of Si-PWA/PVA nanocomposite membrane in vanadium redox-flow battery (VRB) is reported. Structurally, the membrane consisted of a dispersion of sub-micron-sized silica immobilized phosphotungstic acid (Si-PWA) inorganic ion-exchanging phase in the continuous phase of cross-linked poly(vinyl alcohol) (PVA). SEM micrographs indicated the defect-free top surface of membrane with similar morphology of Nafion-115. Good ion selectivity and availability of ion-exchangeable sites were observed as indicated by higher transport number (0.89) and ion-exchange capacity (IEC) (1.20 meq g−1), respectively. Oxidative stability of the membrane was good in vanadium ion species (V4+, V3+, and V2+) but its stability in V5+ solution and Fenton’s reagent was slightly lower than Nafion-115. Vanadium ion permeability (0.69 × 10−7 cm min−1) of Si-PWA/PVA membrane was significantly lower than Nafion-115. Suitability for VRB with Si-PWA/PVA membrane was assessed from open-circuit voltage (OCV) decay which was lower compared to Nafion-115. Single-cell VRB with Si-PWA/PVA membrane exhibited lower voltage during charge and higher during discharge with excellent cyclic stability compared to VRB with Nafion-115.