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 degrees C, with capacity retention of 97.4% after 200 cycles using a high rate of 3.0 C, and its low-temperature (-20 degrees 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. (C) 2015 Elsevier Ltd. All rights reserved.