Preparation of Mn-substituted LiFeO2: A solid solution of LiFeO2 and LixMnO2

A new type of LiFeO₂–Li_xMnO₂ solid solution was synthesized at 350 °C under argon flow by a solid-state reaction. The doped Mn ions in the LiMn_xFe_1?xO₂ (0<x?0.5) obtained at 150 °C were regarded as an impurity in the orthorhombic LiFeO₂ structure and failed to form a perfect substitution form due to the low synthesis temperature. However, the LiFeO₂–Li_xMnO₂ solid solutions with various Mn contents (Mn/(Fe + Mn)=0.1–0.5) were successfully obtained by calcination at 350 °C. Especially, the XRD pattern of the 50% Mn-substituted LiFeO₂ material was very similar to that of a lithiated Li_xMnO₂ compound. The Li/50% Mn-substituted LiFeO₂ cell exhibited not only a distinct increased voltage plateau in the 2.8 V region, but also an excellent cycling performance upto 50 cycles. We believe that this LiFeO₂–Li_xMnO₂ solid solution type compound has a unique electrochemical property in the cycling process.