A facile solvothermal synthesis of Mn-doped LiFePO 4 nanoplates with improved electrochemical performances

Using diethylene glycol as a solvent and manganese salts as doping sources, respectively, manganese doping and morphology control of olivine LiFePO 4 as a cathode for Li-ion battery were simultaneously achieved by a facile solvothermal approach to alleviate the sluggish Li-ion diffusion kinetics. By the contrast to pure LiFePO 4 nanoplates, the preferential growth of Mn-doped LiFePO 4 particles was unchanged during the solvothermal synthesis procedure, and the plate morphology with a thickness of about 40 nm and a lateral size of 120–200 nm was kept, which was verified by XRD, SEM, and XPS characterizations. Moreover, it was demonstrated that the cell volume of as-synthesized LiFePO 4 nanoplates with a reduced size along b -axial gradually was enlarged as the doping level of manganese increased. When assembled to a coin cell, electrochemical tests showed that Mn-doped LiFePO 4 nanoplates delivered an excellent capacity of 165 mAh/g at a rate of 0.1 C, by comparison with pure LiFePO 4 nanoplates with a capacity of 147 mAh/g 1 . Even at a high charging/discharging rate of 10 C, a capacity of 139 mAh/g was maintained. Additionally, Mn-doped LiFePO 4 nanoplates also manifested a satisfactory cyclability with a capacity retention of 98.2% after 100 cycles at a rate of 10 C. The higher capacity, excellent rate capability, and cyclability of LiFePO 4 were explained by the improved Li-ion intercalation/extraction kinetics and diffusion rate, as evidenced by cyclic voltammetry and electrochemical impedance spectroscopy, which was attributed to Mn doping and morphology tuning of LiFePO 4 .