Sustainability of vanadium redox-flow batteries: Benchmarking electrolyte synthesis procedures

This work focuses on the assessment, in terms of effectiveness, feasibility and sustainability, of three different procedures for the synthesis of vanadium-based mixed-acid electrolytes to be used in vanadium redox-flow batteries (VRFBs). Procedures considered consisted in: a) the mere mixing of suitable vanadium precursors (Electrolyte A); b) the chemical reduction of V2O5 by oxalic acid (Electrolyte B); c) the electrochemical reduction of V2O5 using a home-made “H-shaped” electrolysis cell (Electrolyte C). VRFB properties such as energy efficiency, mean charge-discharge voltages, cycle duration as well as stability and conductivity of the electrolyte were analysed and compared with the state-of-the-art. Experimental tests carried out on a laboratory scale VRFB battery comprised: thermal stability test, cyclic voltammetry, electrochemical impedance spectroscopy measurements and charge-discharge tests. A Life Cycle Assessment of the three electrolytes is also presented for benchmarking purposes.