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.