Tailoring the interface of high-voltage lithium metal batteries with a functional silicone additive through compatible film-forming reactions

High-voltage lithium metal batteries with high energy density are still hindered by the unstable electrode/ electrolyte interface. Additive incorporated electrolyte is effective in creating a protective interface film through pre-REDOX of free additive and REDOX of desolvated molecules. However, the compatibility of the two film forming processes is less researched but essential for establishing a dense and stable interface film. Herein, we introduce a silicone electrolyte additive (3-methacrylamidopropyl) triethoxysilane (MCAPTS) to protect the high-voltage LiNi0.5Mn1.5O4 (LNMO) cathode and lithium anode simultaneously. MCAPTS can freely exist in the solvent and contribute to the formation of interfacial film through its pre-REDOX. Moreover, MCAPTS can enter the Li+ solvation sheath to regulate solvation structure via hydrogen bonding and coordination effects of its acrylamide (AM) group, and participate in film construction through REDOX after desolvation. The concurrent involvement of MCAPTS in both film-forming reactions enhances their compatibility, ultimately, a highly conductive and stable interface film containing F, N and Si is produced. The cycle life of LNMO/Li battery is improved under harsh operating conditions at 3.5-4.9 V and 50 degrees C, with a high capacity retention of 73.9% after the 400th cycle. This work offers ingenious insights for designing electrolytes and high-voltage Li metal batteries.