Cathode performance of LiMnPO 4/C nanocomposites prepared by a combination of spray pyrolysis and wet ball-milling followed by heat treatment

Abstract

LiMnPO 4/C nanocomposites could be prepared by a combination of spray pyrolysis and wet ball-milling followed by heat treatment in the range of spray pyrolysis temperature from 200 to 500 °C. The ordered LiMnPO 4 olivine structure without any impurity phase could be identified by X-ray diffraction analysis for all samples. It could be also confirmed from scanning electron microscopy and transmission electron microscopy observations that the final samples were the LiMnPO 4/C nanocomposites with approximately 100 nm in primary particles size. The LiMnPO 4/C nanocomposite samples were used as cathode active materials for lithium batteries, and the electrochemical tests were carried out for the cell Li|1 M LiPF 6 in EC:DMC = 1:1|LiMnPO 4/C at various charge/discharge rates in three charge modes. As a result, the final sample which was synthesized at 300 °C by spray pyrolysis showed the best electrochemical performance due to the largest specific surface area, the smallest primary particle size and a well distribution of carbon. At galvanostatic charge/discharge rates of 0.05 C, the cell delivered first discharge capacities of 123 and 165 mAh g −1 in correspondence to charge cutoff voltages of 4.4 and 5.0 V, respectively. Furthermore, in a constant current–constant voltage charge mode at 4.4 V, the cells also exhibited initial discharge capacities of 147 mAh g −1 at 0.05 C, 145 mAh g −1 at 0.1 C, 123 mAh g −1 at 1 C and 65 mAh g −1 at 10 C. Moreover, the cells showed fair good cycleability over 100 cycles.