Capacitive energy storage has long been relied upon for fulfilling the need for short bursts of electrical power. Such needs have usually been met with either electrolytic or electrostatic capacitors. Where very high energy densities are required, neither of these technologies is suitable and instead rechargeable pile-type batteries have been employed. Electrochemical capacitors offer the capability of bridging the gap between conventional capacitors and rechargeable batteries, and fall into two categories, namely double layer capacitors which rely solely on interfacial charge separation, across the electrical double layer, and pseudocapacitors, which have enhanced charge storage derived from Faradaic charge transfer reactions, in parallel with the double layer. In this program, the feasibility of high surface areas, and thereby low (esr), bipolar electrochemical capacitors, having superior energy and power densities is being demonstrated. The technical approach includes double layer and pseudcapacitive electrode materials. The objective is fabrication of small research prototype cells demonstrating superior pulse-discharge capability. Successful development of high power/high energy density electrochemical capacitors would provide an attractive alternative to the use of conventional energy storage capacitors. Specific areas might include: applications where multiple high energy pulses are desired following a single charge; applications demanding superior charge retention; and, hybrid systems together with relatively low power density, but high energy density, rechargeable batteries.
