Constructing LiF@spinel dual shell to suppress interfacial side reactions of Li-rich cathode materials

Li-rich oxides are considered as promising candidate cathode materials for high-energy Li-ion batteries due to their high specific capacity. However, the widespread adoption of Li-rich materials is hindered because of the lack of a stable surface structure to inhibit interfacial side reactions. In this study, a stable LiF@spinel dual shell was constructed on the surface of Li-rich materials, in which spinel is formed by in situ surface reconstruction, and LiF is bonded to the spinel through the Ni–F bond. The spinel serves as a buffer layer between the LiF coating and the Li-rich oxide, providing a three-dimensional Li-ion diffusion channel to improve the Li-ion diffusion coefficient, while the outer LiF plays a critical role in isolating the cathode from the electrolyte. Under the abovementioned dual effect, the interfacial side reactions of Li-rich materials are inhibited, thereby improving their cycle stability. The obtained LiF@spinel-coated Li-rich cathode exhibits an enhanced capacity retention of 81.5% after 150 cycles at a current density of 2 C, which is better than the pristine Li-rich sample (63.2%). These findings indicate that the construction of the LiF@spinel dual shell is a successful strategy for the modification of Li-rich materials.