Enhancement of the high-voltage electrochemical performance of an LiNi_(0.5)Co_(0.2)Mn_(0.3)O_2 cathode via WO_3 coating

摘要

Inspired by the WO3 transition metal semiconductor, a simple liquid phase WO3 coating strategy is introduced to improve the surface stability of LiNi0.5Co0.2Mn0.3O2. The electrochemical performance of WO3-coated LiNi0.5Co0.2Mn0.3O2 is improved at both a high cut-off voltage (4.5 V) and high temperature (50 degrees C). With the WO3 (0.6 wt%) coating amount optimized, the material capacity retention is maintained at 138 mAh g(-1) and 170.9 mAh g(-1) at 25 degrees C and 50 degrees C after 200 cycles compared with 107.8 mAh g(-1) and 143.9 mAh g(-1), respectively, for pristine NCM523. The WO3-coated sample also exhibits a better rate capability, maintaining 126 mAh g(-1) at 25 degrees C in the voltage range of 3-4.5 V at the current density of 5 C. The enhanced properties of the WO3-coated LiNi0.5Co0.2Mn0.3O2 due to the WO3 coating layer result from the interface that prevents immediate contact between the electrolyte and the active material as well as the lower polarization and electrochemical resistance of the battery. SEM, TEM, XPS and EIS further reveal these improved electrochemical performances, which indicate the success of the approach for regenerating NCM523.