Co-substituted α-Ni(OH)2 was synthesized by a novel microwave homogeneous precipitation method in the presence of urea. LiNi0.8Co0.2O2 cathode material was synthesized by calcining Co-substituted α-Ni(OH)2 precursor and LiOH·H2O at 900℃ for 10 h in flowing oxygen. XRD, FTIR, FESEM and electro- chemical tests were used to study the physical and the electrochemical performances of the materials. The results show that the prepared LiNi0.8Co0.2O2 compound has a good layered hexagonal structure. Moreover, the LiNi0.8Co0.2O2 cathode material demonstrates stable cyclability with a high initial specific discharge capacity of 183.9 mAh/g. The good electrochemical performance could be attributed to the uniform distribution of Ni2+ and Co2+ ions in the crystal structure and a minimal cation mixing in LiNi0.8Co0.2O2 host structure.
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.
ZENG LingJie GONG Qiang LIAO XiaoZhen HE Li HE YuShi MA ZiFeng
