The performance of a redox flow battery based on chlorocuprates dissolved in an ionic liquid analogue is reported at 50°C. The kinetics of the positive electrode reaction at a graphite electrode are favourable with a heterogeneous rate constant, k 0, of 9.5×10−4 cms−1. Coulombic efficiency was typically 94% and independent of current density. The small cell potential of 0.75V and slow mass transport result in energy efficiencies of only 52% and 62% at current densities of 10 and 7.5mA/cm2 respectively. The successful development of a separator by jellifying the electrolyte using polyvinyl alcohol is reported.