Enhanced Fe(VI) cathode conductance and charge transfer: effects on the super-iron battery

Cathodes comprising Fe(VI) salts are capable of three-electron reduction, a nd are useful for the formation of energetic 'super-iron' batteries. Materi al additions to the Fe(VI) cathode can be used to enhance the conductance a nd the efficiency of charge transfer to the cathode, and control the charac teristics of the electrochemical storage. Whereas several common carbons ar e ineffective as conductive matrices for Fe(VI) reduction, several others s uch as small particle ( 1 mu m) graphite, compressed carbon black, and fluo rinated polymer graphites support efficient Fe(VI) 3e(-) reduction. Several inorganic salts also sustain Fe(VI) reduction, but at lower current densit ies. Titanates and other salts added to a K2FeO4 cathode improve the farada ic efficiency of Fe(VI) reduction at higher ( similar to 3 mA cm(-2)) disch arge current densities. Fluorinated polymer graphites provide an unusual ad ditive to the Fe(VI) cathode mix, and at a low level ( 10 wt.%) addition ca n support efficient Fe(VI) reduction. (C) 2000 Elsevier Science S.A. All ri ghts reserved.