Batteries/Iron-metal hydride 050805
Nickel or iron metal electrodes nominally accept 1 electron per ion, but hexavalent or superoxidized iron can accept three electrons per ion, substantially increasing the energy producible. Prototypes made before the turn of the century employed sand grain sized particles, but new work at the Israel institute of Technology has achieved nano scale superoxidized iron with 200 cycle life. The technology is a promising step in the increasing capability of batteries, but it will require years of continued development.
Chemical Communications 6, March 10, 2004, pp. 628-629