The super-iron boride battery

A high-capacity alkaline redox storage chemistry is explored based on an environmentally benign zirconia-stabilized Fe6+/B2- chemistry. This super-iron boride battery sustains an electrochemical potential matched to the pervasive, conventional MnO2-Zn battery chemistry, but with a much higher electrochemical storage capacity. Whereas a conventional alkaline battery pairs the 2e(-) zinc anode with a 1e(-) MnO2 cathode, the new alkaline cell couples an 11e(-) boride anode, such as VB2, with a 3e- storage hexavalent iron cathode. The cell has an open circuit and discharge potential comparable to the conventional, commercial alkaline battery. Based on VB2 (72.6 g mol(-1) and the Fe (VI) salt K2FeO4 (198.0 g mol(-1)), the super-iron boride cell has an 11 Faraday theoretical capacity of 369 mAh g(-1). Added AgO mediates and further facilitates the 3e(-) K2FeO4 reductive charge transfer, and we demonstrate for super-iron boride that over 300 mAh g(-1) is approached experimentally, which is substantially higher than the conventional Zn/MnO2 alkaline battery with an experimental capacity (to 0.8 V) of 160 mAh g(-1) and a theoretical capacity of 224 mAh g(-1). (c) 2008 The Electrochemical Society.