A novel approach to improve the electrochemical performances of layered LiNi1/3Co1/3Mn1/3O2 cathode by YPO4 surface coating

Layered LiNi1/3Co1/3Mn1/3O2 (LNCMO) is surface coated with different contents of YPO4 (0.5wt.%, 1wt.% and 3wt.%) through simple chemical deposition method. The pristine and YPO4-coated LNCMO are characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). It is found that the YPO4 surface coating layers do not change the bulk structure of LNCMO. The investigation in their cycling performances demonstrates that 1wt.% YPO4-coated LNCMO exhibits the best cycling stability, with capacity retention ratio of 88.6% after 50 cycles, much better than that of the pristine material (only 80.1%). Furthermore, the 1wt.% YPO4 surface modification improves the rate performance and thermal stability of layered LNCMO. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and Fourier transform infrared (FTIR) measurements of pristine and 1wt.% YPO4-coated LNCMO are also measured and compared. It has been proved that the coated YPO4 inhibits the growth of solid electrolyte interfacial (SEI) film in repeated cycling, which partly explains the improved capacity retention in electrochemical tests.