Reversible lithium intercalation in amorphous iron borate

Upon electrochemical reduction in a lithium cell, calcite-type FeBO3 gives an amorphous compound which can intercalate 3 Li per formula at 1.1 V, ending with metallic iron for full discharge to 0.9 V. The amorphous phase can be cycled reversibly at 1.5-3 V with capacities as high as 300 Ah/kg. This material was successfully tested as an inexpensive negative electrode for Li-ion batteries with LiCoO2 as the positive electrode. Its behaviour is quite different from that of Fe2O3, both in intercalation potential and cyclability.