Enhanced Electrochemical Performance of Monoclinic LiMnBO₃-Based Li Storage Material Via Partial Substitution

We developed a new electrochemically active Li storage material based on a polyanionic framework. By replacing a portion of Mn with Fe and Mg in monoclinic lithium manganese borate (LiMnBO 3 ), a phase-pure LiMn 0.5 Fe 0.4 Mg 0.1 BO 3 was successfully synthesized. A C/50-rate galvanostatic discharge delivered a near theoretical capacity of 201 mAh g -1 at room temperature with much improved rate capability, 120 mAh g -1 at a 1C discharge, compared to other borate chemistries. We explained this superior Li storage activity in relation to the topological effect of substitution, which leads to facile Li diffusion and stabilizes the structure. Combining with the inherent stability of the borate group against oxygen evolution, we believe that the enhanced electrochemical properties achieved in this study makes the LiMn 0.5 Fe 0.4 Mg 0.1 BO 3 compound a strong contender as a new cathode material for Li-ion batteries and will bring more attention to the lithium transition metal borate chemistry.