Stabling LiNi0.8Co0.1Mn0.1O2 by PVP-assisted LiF-LaF3 layer for lithium ion batteries with improved electrochemical properties at high cut-off voltage

LiNi0.8Co0.1Mn0.1O2 (NCM811) has gradually become a research hotspot for the high-energy density. However, it is troubled by the residual lithium during the preparation process and its subsequent effect on the electrochemical performance in the following charge and discharge. Polyvinylpyrrolidone (PVP)-assisted LiFLaF3 coated NCM811 materials are prepared by in-situ method to reduce the residual lithium, improve the interface and electrochemical performance of the NCM811. Results show that the content of Li2CO3 (from 6610 ppm to 2230 ppm) and LiOH (from 3260 ppm to 1870 ppm) is greatly reduced, and the modified NCM811 cathode maintains exceptional capacity retention of 91.17% (159.2 mAh g(-1)/173.6 mAh g(-1)) and 81.78% (122.1 mAh g(-1)/149.3 mAh g(-1)) at high cut-off voltage of 2.8-4.6 V after 100 cycles, at 5C and 10C, respectively, which are much higher than that of the bare NCM811. The structural and compositional characterization (XRD, XPS and EIS) further reveal the electrochemical mechanism and kinetics of the designed NCM811 cathode, indicate that the improved cycling and rate performance of LiF-LaF3 coated NCM811 is mainly due to the reduction of residual lithium, the suppression of interfacial side reactions and the enhancement of thermal stability. (C) 2020 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.