Nafion/SiO2 hybrid membrane for vanadium redox flow battery

Sol–gel derived Nafion/SiO2 hybrid membrane is prepared and employed as the separator for vanadium redox flow battery (VRB) to evaluate the vanadium ions permeability and cell performance. Nafion/SiO2 hybrid membrane shows nearly the same ion exchange capacity (IEC) and proton conductivity as pristine Nafion 117 membrane. ICP-AES analysis reveals that Nafion/SiO2 hybrid membrane exhibits dramatically lower vanadium ions permeability compared with Nafion membrane. The VRB with Nafion/SiO2 hybrid membrane presents a higher coulombic and energy efficiencies over the entire range of current densities (10–80 mA cm−2), especially at relative lower current densities (<30 mA cm−2), and a lower self-discharge rate compared with the Nafion system. The performance of VRB with Nafion/SiO2 hybrid membrane can be maintained after more than 100 cycles at a charge–discharge current density of 60 mA cm−2. The experimental results suggest that the Nafion/SiO2 hybrid membrane approach is a promising strategy to overcome the vanadium ions crossover in VRB.