Enhanced low-temperature performance of slight Mn-substituted LiFePO_4/C cathode for lithium ion batteries

Low temperature performance of LiFePO4/C cathode was remarkably improved by slight Mn-substitution. Electrochemical measurements showed that about 95% of the discharge capacity of LiFe0.98Mn0.02PO4/C cathode at 20°C was obtained at 0°C, compared to 85% of that of LiFePO4/C cathode. The LiFe0.98Mn0.02PO4/C sample also presented enhanced rate performance at –20°C with the discharge capacities of 124.4 mA h/g (0.1C), 99.8 mA h/g (1C), 80.7mAh/g (2C) and 70 mA h/g (5C), respectively, while pristine LiFePO4/C only delivered capacities of 120.5 mA h/g (0.1C), 90.7 mA h/g (1C), 70.4 mA h/g (2C) and 52.2 mA h/g (5C). Cyclic voltammetry measurements demonstrated an obvious improvement of the lithium insertion-extraction process of the LiFePO4/C cathode by slight Mn-substitution. The results of FSEM observation and electrical conductivity measurement indicated that slight Mn-substitution minimized the particle size of LiFe0.98Mn0.02PO4/C and also obviously improved the electrical conductivity of the compound, thus obviously enhances the interface reaction process on the cathode.