Effect of Nb2O5 nanocoating on the thermal stability and electrochemical performance of LiNi0.6Co0.2Mn0.2O2 cathode materials for lithium ion batteries

摘要

The electrochemical properties and thermal stability of the LiNi0.6Co0.2Mn0.2O2 (NCM622) material have been significantly improved by Nb2O5 nanocoating. The electrochemical properties were researched systematically by various electrochemical tests, and the molar ratio of Nb2O5 to NCM622 was evaluated as 0.5 mol%. Results showed that Nb2O5 nanocoated sample exhibited good cyclic performance, whose capacity retention was 92.36%, whereas that of the bare NCM was only 87.59% after 200 cycles under 1C at 25 degrees C. In addition, the Nb2O5 surface-coated sample exhibited a good discharge capacity of 164.05 mAh g & minus;1 after 200 cycles under 1C at 60 degrees C. The result owing to the nano coating of Nb2O5, which greatly increased the thermal stability, thereby maintaining remarkable specific capacity even in high-temperature environments. The modified sample could maintain a relatively complete structure after cycling, whereas the bare sample had already collapsed. Based on the transmission electron microscopic images, the thickness of the coating layer was about 15 nm. The nanocoating of Nb2O5 was prepared by solid-phase reaction. This method is simple and convenient, which is conducive to industrial production and commercialisation promotion. The Nb2O5 surface coating can enhance the electrochemical properties of the cathode materials, as well as strengthen the thermal and structural stability, which can extend the battery life.