Enhanced electrochemical properties of SiO2-Li2SiO3-coated NCM811 cathodes by reducing surface residual lithium

Ni-rich LiNi0.8Co0.1Mn0.1O2 (NCM811) cathode has advantages of large specific capacity, low cost, and environmental friendliness. However, it is easy to generate residual lithium on the surface during synthesis and storage, resulting in rapid capacity attenuation and inferior rate capability. Surface coating is considered as effective route to improve electrochemical performance of NCM-based cathodes. Herein, residual lithium is induced to react with Si on the surface of polysiloxane (EPS)-coated NCM811 and generate SiO2-Li2SiO3 coating layer. The mechanisms of improved electrochemical performance are mainly attributed to the physical barrier of SiO2 and the three-dimensional Li+ diffusion channels of Li2SiO3, which discussed based on the results of XRD, SEM, TEM, EDS and XPS. Results reveal that SiO2-Li2SiO3 layer can effectively reduce residual lithium and significantly stabilize surface phase transition, resulting in excellent capacity retention (92.0 %, 100 cycles and 1 C) and superior rate performance (131.1 mAh/g at 10 C). Proposed strategy can effectively improve electrochemical performance of cathode materials for lithium-ion batteries.