Lead Pb/Ru pyrochlore (Pb2Ru2O6.5) was synthesized as a new electrode material for aqueous-electrolyte capacitors. This material was characterized using X-ray diffraction, BET area anhgalysis and cyclic voltammetry. Small laboratory-scale prototype capacitors were fabricated with Pb2Ru2O6.5 oxide electrodes and tested for their electrochemical performance in terms of capacitance, rate-capabilities, and energy–power performance. These laboratory cells exhibited excellent performance under constant power discharge delivering >5Wh/kg specific energy at 750W/kg power level based on electrode and electrolyte masses only.