Enhanced rate performance and cycle stability of LiNi0.6Co0.2Mn0.2O2 at high cut-off voltage by Li6.1La3Al0.3Zr2O12 surface modification

Abstract A stable surface structure is vital for Ni-rich cathode materials to achieve an excellent electrochemical performance, especially rate performance and cyclic stability. In this work, Li6.1La3Al0.3Zr2O12 (LLAZO) modified LiNi0.6Co0.2Mn0.2O2 (NCM) was successfully synthesized via in-situ wet coating and synchronous lithiation strategy. X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy with EDS element mapping and transmission electron microscopy confirm the existence of LLAZO on the surface of NCM. According to the results, the 1 wt% LLAZO modified NCM (1-NCM) delivers a reversible capacity of 165.5 mAh g−1 at 2C from 2.7 to 4.5 V at 25℃, and the capacity retention rate is as high as 84.6%, whereas NCM delivers only 141.5 mAh g−1 and 54.7%, respectively. Furthermore, the 1-NCM delivers higher rate capacities of 172mAh g−1 at 1C and 125 mAh g−1 at 10C than those of NCM (162 and 102 mAh g−1), respectively. The enhanced electrochemical performance of LLAZO modified NCM is mainly due to: (1) the structure of NCM host is stabilized by LLAZO shell; (2) Li+ transport speed is enhanced on NCM surface after LLAZO modification. It is hopeful for LLAZO or others materials with higher ionic conductivity to enhance the electrochemical performance of Ni-rich cathode materials.