The performance of a redox flow battery based on chlorocuprates dissolved in an ionic liquid analogue is reported at 50 degrees C. The kinetics of the positive electrode reaction at a graphite electrode are favourable with a heterogeneous rate constant, k(0) of 9.5 x 10(-4) cm s(-1). Coulombic efficiency was typically 94% and independent of current density. The small cell potential of 0.75 V and slow mass transport result in energy efficiencies of only 52% and 62% at current densities of 10 and 7.5 mA/cm(2) respectively. The successful development of a separator by jellifying the electrolyte using polyvinyl alcohol is reported. (C) 2013 Elsevier Ltd. All rights reserved.