Ultrahigh specific power electrochemistry, exemplified by Al/MnO4- and Cd/AgO redox chemistry

An unusual charge transfer domain for electrochemical processes is investigated. Criteria are described which facilitate an ultrahigh specific power domain. This domain is defined for faradaic processes that are long when compared to the electrochemical double layer charging time, as a specific power over 10000 W/kg occurring at a specific energy over 1 Wh/kg. Traditionally compared to capacitors, faradaic processes can achieve high specific energy, >1 Wh/kg, but limited specific power, (1000 W/kg. Experimental evidence and examples of irreversible and quasi-reversible processes which occur in the ultrahigh power domain are presented. Each has a specific power approaching one million W/kg. The irreversible example establishes electrochemical control of the chemically reactive couple: Al + MnO4- + 2H(2)O --> Al(OH)(4)(-) + MnO2, E-cell = 2.9 V. The quasi-reversible (secondary) example utilizes a conventional macroscopic silver/cadmium couple systematically reduced to the submicron and micron microelectrochemical cross section domain (submicron Ag and Cd electrodes separated by a 5 mu m interelectrode gap).