Fully Methylated Siloxane-Based Electrolyte for Practical Lithium Metal Batteries

Developing solvents with balanced physicochemical properties for high-voltage cathodes and lithium metal anodes is crucial for a sustainable and intelligent future. Herein, we report fully methylated tetramethyl-1,3-dimethoxydisiloxane (TMMS) as a single solvent for lithium metal batteries. We demonstrate that the fully methylated structure and Si–O bonds within TMMS can effectively elevate the dehydrogenation energy barrier, migrating the oxidation decomposition of the electrolyte. Additionally, the weak solvating power of TMMS favors the formation of an anion-rich solvation structure that induces the generation of an inorganic-rich electrode/electrolyte interphase layer at both the cathode and anode. Accordingly, the formulated electrolyte exhibits remarkable stability against high-voltage cathodes and lithium metal anodes. Notably, LiNi0.8Co0.1Mn0.1O2||Li (NCM811||Li) full cells with TMMS-based electrolytes realize a significant improvement in capacity retention compared with a dimethoxyethane-based electrolyte at both room temperature and 50 °C. This work provides insight into full methylation and the Si–O bond strategy and paves the way for the development of high-voltage lithium metal batteries.