Effect of doped Mn on improving the electrochemical performance of LiFePO4

Abstract

A series of LiFe1−xMnxPO4/C composites were successfully synthesized through a simple hydrothermal method. The effects of doped Mn on their micro-structures and electrochemical performances were investigated. The XRD results indicate that Mn doping cannot change the olivine lattice type of LiFePO4. Appropriate Mn doping can reduce the particle size of LiFePO4. The electrochemical performance data show that the electrochemical performances of the composite materials are enhanced at first and then decrease as the doping amount of Mn increases. Both the CV and EIS results illustrate that a small amount of doped Mn will reduce the electrode polarization and electrochemical impedance of the samples and simultaneously improve the electrochemical performance. Among all the samples, the LiFe0.98Mn0.02PO4/C sample has a desirable electrochemical performance, with its specific discharge capacity reaching 156.0 mAh g−1 at a rate of 0.1 C. Even at a high rate of 5 C, it can still reach 110.0 mAh g−1. All the results indicate that an appropriate amount of doped Mn has an emphatic effect on the electrochemical performance of LiFePO4/C.