Investigating a Bromide Supported Electrolyte for an All-Copper Flow Battery

Abstract

This work investigates a bromide supported electrolyte for use in an all-copper flow battery (CuFB). In this battery, halide ions stabilize the cuprous ion. During charge, the cuprous halide complex is reduced to copper metal at the negative electrode and the complex is oxidized to a cupric halide complex at the positive electrode. Our measurements indicated that the CuFB utilizing a bromide electrolyte can achieve a higher open circuit potential (OCP) as compared to using a chloride electrolyte. The CuFB has negligible hydrogen and bromine evolution indicating that high coulombic efficiencies are achievable. A bromide supported all-CuFB with graphitic porous felt electrodes was demonstrated and the OCP after the initial charge was observed to be 0.81 V. The cell was cycled with a geometric current density of 150 mA cm−2 for 50 cycles with state of charge swings of 0 to 60%, and had a voltaic efficiency (∑i=1jVdischargej∑i=1kVchargek) of 64%, however, copper electrodeposits were nodular and non-adherent to the substrate. We conclude that further understanding of plating morphology and the effect of substrates are necessary to take advantage of this chemistry in a conventional hybrid battery configuration, and that this system could benefit from a slurry electrode.