Surface-reinforced NCM811 with enhanced electrochemical performance for Li-ion batteries

Effective and uniform surface modification is very important for improving the properties of LiNi0.8Co0.1Mn0.1O2 (NCM811). Here, we used a liquid-phase assisted method to modify the surface of NCM811 via ammonium metatungstate to synthesize 1 W@NCM811. This step reduced surface residual lithium and led to in situ WO3/Li2WO4 coating. The uniform WO3/Li2WO4 coating acted as an ideal protective layer and physically prevented direct contact between the NCM811 lattice and the electrolyte, thus stabilizing the cathode/electrolyte interface and passivating detrimental reactions. Moreover, the coating enhanced the electrochemical kinetics in terms of the impedance of Li+ through a solid electrolyte film (Rsf) and charge transfer resistance (Rct). The strong W-O bond can effectively improve the thermal stability of the material. As a result, the 1 W@NCM811-based cathode exhibits significantly enhanced structural stability, electrochemical performance, and thermodynamic properties. At 0.5 C (1 C = 200 mAh g−1) in the voltage range of 3.0–4.3 V, the 1 W@NCM811-based cathode delivers excellent capacity retention of 97.36% and 88.92% after 100 cycles at 25 °C and 55 °C, respectively. According to the analysis of 1 W@NCM811-based cathode, a better layered lattice, fewer by-products, and less heat generation prove that this approach provides an effective means for the development of NCM811.