Synthesis And Electrochemical Performance Of Nano-LiMnPO₄/C Coated By Double Carbon

Lithium manganese phosphate has been investigated as a new generation of high energy density cathode material due to its high energy density (697Wh·kg-1), low cost and good environment compatibility. However, lithium manganese phosphate suffers from low electronic conductivity and slow ionic diffusion, leading to the low electrochemical activity, which limits its practical application.A double carbon coating LiMnPO4nano-sized powder was synthesized by a double ball-milled with a double heated method using lithium carbonate, manganese oxalate and ammonium dihydrogen phosphate as raw material, the L-Ascorbic acid as the reducing agent and the carbon source, and PEG400as a dispersant. The effects of processe parameters on the structure, morphology and the electrochemical properties of the prepared material were characterized by XRD, SEM, TGA, HRTEM, EDS, CV, EIS and constant current charge/discharge technology.The results show that the LiMnPO4with pure phase and olivine structure at the conditions of550℃calcined for3h and650℃calcined for10h. The material particle size can reach20～40nm. The products exhibited the initial charge capacity of110mAh·g-1, the discharge capacity of87mAh·g-1and the first efficiency was79%at0.1C. After50cycles, the discharge capacity retention rate remained98%, with a certain cycle stability.The double coated carbon can increase the carbon in the manganese phosphate on the surface of the force, it also can reduce the damage to the structure produced in acid materials from electrolyte, which achieve the goal of prolong the cycle life of lithium manganese phosphate. At the same time, carbon coated layer can also provide ion diffusion channels for lithium manganese phosphate, in order to promote ions diffusion in lithium manganese phosphate. Lithium manganese phosphate materials by nanometer can reduce particle size of lithium manganese phosphate, shorten the diffusion path of lithium ions, and then improve the diffusion rate of lithium ions, in order to improve the electrochemical properties of lithium manganese phosphate.