Electrolyte Engineering via Fluorinated Siloxane Solvent for Achieving High-Performance Lithium-Metal Batteries

Advanced solvent is of important significance to develop an excellent electrolyte that simultaneously maintains a high ionic conductivity, wide electrochemical window, and good compatibility with electrodes for high-performance lithium-metal batteries (LMBs). To realize a stable electrode/electrolyte interface and a uniform lithium (Li) deposition process, an optimal fluorinated siloxane (3,3,3-trifluoropropyltrimethoxysilane, TFTMS) is proposed as a cosolvent with 1,2-dimethoxyethane (DME) and highly antioxidative fluoroethylene carbonate (FEC) to formulate a Li-metal compatibility electrolyte. The TFTMS-based electrolyte presents high oxidization stability, high Li+ conductivity, and high Li+ transfer number, contributing to the accelerated reaction kinetics, homogeneous Li deposition behavior, and stable interfacial chemistry. Therefore, high Li stripping/plating reversibility (similar to 99%) and stable cycling (1400 h) are achieved in the TFTMS-based electrolyte, giving rise to the excellent electrochemical performance of practical Li-metal full cells. Moreover, an industrial 4 Ah NCM811|Gr pouch cell with the TFTMS-based electrolyte is demonstrated to display similar cycling performance with the commercial carbonate electrolyte in 120 cycles at 1 C. This work offers an approach toward high-performance LMBs through rational electrolyte design with fluorinated siloxane solvent.