Lithium transition-metal phosphates of LiMPO4 (M = Fe, Mn, Co, Ni) with olivine structure have attracted much attention as promising cathode materials for next generation of lithium ion batteries. Compared with the traditional transition- metal oxide cathode, LiMPO4 possesses the merits of lower toxicity, cost-effectiveness, environmental friendliness and high safety. LiMnPO4 provides a moderate working voltage compatible to the present electrolyte systems and a higher energy density on account of the relatively high redox potential of ~ 4.1 V for Mn~(3+)/Mn~(2+) couple. However, the pristine LiMnPO4 shows a poor electrochemical performance due to the sluggish lithium diffusion kinetics within the grains caused by the low intrinsic electronic and ionic conductivity. Additionally, LiMnPO4 also suffers from instability of the charged phase (MnPO4), Jahn-Teller distortion of the Mn~(3+), the large volume change between LiMnPO4 and MnPO4 during charge-discharge process, which results in the lower capacity and limited rate capability. Many efforts have been made to overcome these drawbacks so as to improve the electrochemical performance of LiMnPO4 by particle-size minimization, carbon coating and cation doping.
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