Construction of a robust lithium cobalt phosphate layer for enhancement of the electrochemical performance of LiNi0.8Co0.1Mn0.1O2 at high voltage

The low cycling stability of LiNi0.8Co0.1Mn0.1O2 (NCM811) is due to structural instability during lithium insertion and removal and strong surface reactivity, and it limits widespread application. In this study, a layer of LiCoPO4 was coated on NCM811, and electrochemical tests showed that the material had excellent high-voltage electrochemical properties. The NCM811 sample coated with 1.0 wt% LiCoPO4 (NCM-LCP1) had a capacity of 156.5 mAh g-1 after 100 cycles at 3-4.6 V and a retention rate of 87.47%. In contrast, the capacity of unmodified NCM811 was only 96.9 mAh g-1, with a retention rate of 55.9%. An NCM-LCP1/graphite full cell demonstrated a capacity retention rate of 87.46% over 200 cycles at 3-4.3 V. By combining EIS and postcycle analyses, the stability and protection mechanism of the LiCoPO4 layer under high voltage was confirmed. The LiCoPO4 layer effectively prevented particle fragmentation and kept the structure stable. It also suppressed side reactions on the cathode surface. This work offers a new methodology for modifying NCM811 materials operated at 4.6 V.