Understanding the surface decoration on primary particles of nickel-rich layered LiNi0.6Co0.2Mn0.2O2 cathode material with lithium phosphate

Abstract

Phase transition and structural degradation of nickel-rich cathode materials are harmful to electrochemical stability, which is unfavorable for the application in high energy density lithium-ion batteries. In this study, the decorated LiNi0.6Co0.2Mn0.2O2 with reconstructed surface on the primary particles is obtained simultaneously during the synthesis process of the material with a facile one-step method. The surface of primary particles decorated with Li3PO4 is well understood to clarify the decoration role in enhancing the charge/discharge performance of the high nickel cathode material. Detailed analysis of LiNi0.6Co0.2Mn0.2O2 cathode surface structure during the charge-discharge process is implemented by high resolution transmission electron microscopy, electron energy-loss spectroscopy, X-ray photoelectron spectrometer et al. It is indicated that the decorated LiNi0.6Co0.2Mn0.2O2 material is stabilized by a spine phase hindering the transformation of layered structure towards rock-salt phase on the surface with cycling. As a result, the decorated LiNi0.6Co0.2Mn0.2O2 material displays outstanding electrochemical performance. It delivers a good capacity retention of 95.3% and 94.3% after 50 cycles at 2C and 5C under high cutoff voltage (2.7–4.5V), respectively, and it is much higher than that of the pristine samples, 87.8% and 86.5%.