Chemistry of the Fe6+/B2- Super-iron Boride Battery: An Overview of Primary Alkaline Fe6+ Cathodic Charge Storage Including the New B2- Anode

Abstract

An overview of progress on primary alkaline Super-Iron batteries, first introduced in 1999, is presented. The batteries are based on an unusual Fe(VI) redox couple and multiple electron cathodic charge storage. Such Fe(VI) cathodes can be "green", cost effective and store considerably higher charge than conventional cathode materials. For example, the Fe(VI) salt K2FeO4 holds 406 mA/g, is readily prepared, and the ferric oxide discharge product is environmentally benign. Fe(VI) salts that have been synthesized and demonstrated as Super-Iron cathodes include compounds with a 3-electron cathodic charge capacity, such as Li2FeO4, Na2FeO4, K2FeO4, Rb2FeO4, Cs2FeO4 (alkali Fe(VI) salts), as well as alkali earth Fe(VI) salts BaFeO4, SrFeO4, and also a transition metal Ag2FeO4 salt. Configuration optimization, enhancement and mediation of Fe(VI) alkaline cathode charge transfer are summarized. Composite Fe(VI)/Mn(IV or VII), Fe(VI)/Ag(II), and zirconia coating stabilized, and boride anode batteries effects are also illustrated.