Positive Effect of Minor Manganese Doping on the Electrochemical Performance of LiFePO4/C under Extreme Conditions

Uniform minor Mn-doped LiFePO4/C cathode materials are synthesized and their electrochemical performances are investigated systematically. Via tuning the doping amount of Mn, it is found that the well crystallized LiFePO4/C doped with 11000 ppm Mn gives the highest discharge capacity of 165 mAh g−1 at 0.1 C at room temperature. Remarkably, it holds a quite stable cycling performance at 45 °C, with capacity retention of 97.4% after 200 cycles using a high rate of 3.0 C, and its low-temperature (−20 °C) specific capacity maintains at high up to 131.4 mAh g−1 at 0.1 C, higher than that of the majority reports. The higher or lower Mn-doping amount than 11000 ppm is found to have less positive impact on the performance of LiFePO4/C. Such phenomenon may be attributed to the negative cooperative effect of Mn doping, which enlarges the crystal space for improving the Li+ transfer under low dose due to the large radius of Mn, but increases the charge transfer resistance and declines the performance under high dose owing to its poor intrinsic kinetics.