Influence of calcined temperatures on the microstructure and electrochemical properties of LiFePO4/C nano-particles with a core-shell structure and It's thermal stability study

摘要

Influence of calcined temperatures on the microstructure and electrochemical properties of LiFePO4/C nano-particles as well as it's thermal stability were studied using HRTEM, XRD, electrochemical workstation and TGA. The results indicated that when calcined at 973 K, the LiFePO4/C nano-particles consisted of a well-crystalline LiFePO4 core with size of 58.6-80.1 nm and an amorphous carbon shell with thickness of 2 nm. With the increase of calcined temperature, the electrochemical properties of LiFePO4/C materials increased first and then decreased, it reached maximum when temperature equaled to 973 K. The initial discharge capacity of the sample was 142 mAh/g, the discharge capacity of it maintained 132 mAh/g with capacity retention of 93.0% after 40 cycles. The decomposition reaction of LiFePO4/C material calcined at 973 K occurred at 938.38-1194.52 K under 10 K . min(-1) in N-2 atmosphere and corresponded to approximately 5.8% of the total weight. The decomposition mechanism of it consisted of three stages: the first stage was controlled by gas diffusion in carbon shell; the second stage was controlled by chemical reaction and gas diffusion; the third stage was controlled by chemical reaction.