Effects of MnO nanolayer coating on Li3V2(PO4)3/C cathode material for lithium-ion batteries

Abstract

Abstract The MnO-coated Li3V2(PO4)3/C (LVP/C) cathode material was successfully synthesized by a sol–gel method. The nanolayer structure of MnO coating on the surface of LVP/C is demonstrated by the transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) etc. It indicates that the manganese oxide in the coating layer appears in the form of MnO. The MnO coating prevents the preferential growth of LVP at the (1 2 0) crystal plane. The key function of MnO modification is to improve the structure of SEI film. The as-prepared 4% MnO-coated LVP/C has the best electrochemical behavior. The MnO coating greatly enhances the stability of the SEI structure and Li+ ion conductivity, and reduces the electrode polarization, so the as-prepared 4% MnO-coated LVP/C has excellent rate capability and cycle performance. Its apparent Li+ diffusion coefficient (DLi+) reaches 4.0 × 10−9 cm2 s−1. In the range of 3.0–4.3 V, its specific capacities are 121.4 and 108.4 mAh g−1 in the 1st and 300th cycles at 10C rate, respectively. Its capacity retention reaches 89.3%, but it is only 75.6% for LVP/C without MnO coating.