Recent Advances of Mn-Rich LiFe_1-_yMn_yPO₄ (0.5 ≤ y < 1.0) Cathode Materials for High Energy Density Lithium Ion Batteries

LiMnPO₄ (LMP) is one of the most potential candidates for high energy density (≈700 W h kg⁻¹) lithium ion batteries (LIBs). However, the intrinsically low electronic conductivity and lithium ion diffusion coefficient of LMP result in its low performance. To overcome these challenges, it is an effective approach to prepare nanometer-sized Fe-doping LMP (LFMP) materials through optimization of the preparation routes. Moreover, surface coating can improve the ionic and electronic conductivity, and decrease the interfacial side reactions between the nanometer particles and electrolyte. Thus, a uniform surface coating will lead to a significant enhancement of the electrochemical performance of LFMP. Currently, considerable efforts have been devoted to improving the electrochemical performance of LiFe_1-yMn_yPO₄ (0.5 ≤ y < 1.0) and some important progresses have been achieved. Here, a general overview of the structural features, typical electrochemical behavior, delithiation/lithiation mechanisms, and thermodynamic properties of LiFe_1-yMn_yPO₄-based materials is presented. The recent developments achieved in improvement of the electrochemical performances of LiFe_1-yMn_yPO₄-based materials are summarized, including selecting the synthetic methods, nanostructuring, surface coating, optimizing Fe/Mn ratios and particle morphologies, cation/anion doping, and rational designing of LFMP-based full cells. Finally, the critical issues at present and future development of LiFe_1-yMn_yPO₄-based materials are discussed.