Synergistic effect of doping and surface engineering on LiNi0.5Mn1.5O4 and its application as a high-performance cathode material for Li-ion batteries

Abstract

In this study, we synthesize V5+-doped LiNi0.5Mn1.5O4 (LNMO) and subject it to SiO2 surface modification using a coprecipitation method. The synergistic effect of ion doping and interfacial engineering improves the electrochemical properties of LNMO by accelerating its redox kinetics and prolonging its cycling life. The experimental results and density functional theory simulation data indicate that V5+-ion doping caused the Fermi level of LNMO to shift toward the conduction band, thereby narrowing the bandgap of LNMO because of the n-type doping effect. However, the introduction of V5+ ions prevents Li + -ion migration in LNMO, which hinders the ion intercalation–deintercalation process of LNMO cathodes. Therefore, the V5+-doped LNMO compound with optimal V5+-ion doping concentration was expected to present the highest rate capability. In addition, SiO2 surface modification provides a protective layer that inhibits metal dissolutions and significantly improves cathode cycling stability. Owing to the synergistic effect of doping and interfacial modification, the fabricated LNMO cathode presented remarkable energy storage capacity with discharge capacities of 133/118.8 mAh/g at 0.2/10 C and a capacity retention of 87.9% after 200 cycles at 4 C.