Sulfonated Poly(ether ether ketone) membrane optimization for the set-up of an in-house built small-sized Vanadium Redox-Flow Battery

Vanadium redox flow battery (VRFB) has been considered as one of the most promising large-scale electrical energy storage systems due to a partition between energy and power rating, a fast response, a room working temperature, and an extremely long life.1 The commercialization of the VRFB is still hindered by the low stability of vanadium precursors which compose the electrolyte and the high costs of some key components such as the membranes. In this contribution, sulfonated poly(ether ether ketone) (SPEEK) membranes with different sulphonation degrees and filler contents were prepared and tested in a lab-scale VRFB system. An optimized mixed sulphuric/hydrochloric acid was used as electrolyte.2 Electrochemical impedance spectroscopy (EIS) measurements and consecutive charge-discharge cycles permitted to select the suitable membrane to configure an in-house built small-sized VRFB. The performance of the configured small-sized VRFB was evaluated by means of consecutive charge-discharge cycles carried out at different current densities.