Electrochemically-active FePO4 was introduced for surface modification of spinel LiMn2O4 cathode material to improve the electrochemical performance. Optimal technique for the LiMn2O4/FePO4 composites was specified. With proper content of FePO4 and annealing temperature, significant improvement in capacity and cyclability was obtained at room temperature and 60 °C. As compared with the LiMn2O4 coated with other oxides such as Al2O3, SiO2 and ZrO2, the FePO4 incorporated LiMn2O4 shows both enhanced initial capacity and cyclability. Examined by impedance measurement, the FePO4 incorporation in LiMn2O4 significantly suppresses the increase of charge-transfer impedance.
Oxalic-acid-based co-precipitation method was employed to prepare LiNi 2/3 Mn 1/3 O 2 sample with a high-ordered structure. Li + , Ni 2+ and Mn 2+ acetates were used as starting materials. The influence of the amount of lithium source in the starting materials on Li + content, disorder of Li + -Ni 2+ ions, and electrochemical performance has been investigated. Rietveld refinement shows that the sample prepared with 20% excess Li-source in the starting materials exhibits a perfect ordered structure. A specific discharge capacity is as high as 172 mAh/g at C/20 in the voltage range of 4.35−2.7 V. However, the cyclability is not satisfactory: about 25.3% fade in capacity was observed over 50 cycles.
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