(692d) Synthesis and Electrochemical Performance of LiMnPO4 Nano Materials As a Cathode Material for Lithium-Ion Batteries

Exploring novel cathode materials is crucial to meet the demand of high-performance lithium ion battery. The increasing research interests have been focused on the new active materials to replace the typical LiCoO2 regarding to the costs and the toxicity of cobalt. The potential alternatives are lithium transition metal phosphates, such as LiFePO4 or LiMnPO4, thanks to their thermal and electrochemical stability, low toxicity, low costs and their environmental friendly. The low operating potential of LiFePO4 indicates the low energy density which limits its application for electric vehicles. The successful commercialization of LiFePO4 has stimulated the search for other olivine's such as LiMnPO4. LiMnPO4 exhibits an operating voltage of about 4.1 V vs. Li+/Li, making the theoretical energy density ( 171 mAh·g-1× 4.1 V= 701 Wh·kg-1 ) 1.2 times larger than that of LiFePO4 ( 170 mAh·g-1× 3.45 V= 586.5 Wh·kg-1 ). However, the electrochemical performance of LiMnPO4 is poor due to the slow lithium diffusion kinetics within the grains and the low intrinsic electronic conductivity, even much worse than those of LiFePO4. Excellent electrochemical performance, especially the rate capability of the material can be obtained by particle-size minimization, carbon coating, cation substitution and morphology control.

LiMnPO4 is prepared by a hydrothermal method with different solvents such as PEG 400, NMP and EG, different surfactants such as SDBS, CTAB and PVP, different kinds of carbon coating to find the higher performance.