Electrolyte engineering via non-fluorinated solvent for high-performance lithium metal batteries.

Lithium metal batteries (LMBs) employing high-voltage cathode present a promising pathway toward high-energy-density energy storage systems. However, critical challenges have hindered their practical application, including lithium dendrite proliferation, unstable solid-electrolyte interphase (SEI), and limited oxidative stability of conventional 1,2-dimethoxyethane (DME)-based electrolytes. Herein, we rationally design a siloxane-based electrolyte system featuring enhanced oxidative stability through solvent molecular engineering. The Si-O bonding in siloxanes demonstrates superior bond energy compared to conventional C-O bonds in DME, which enables remarkable oxidative stability and the compatibility of high-voltage LMBs. Through in-operando Raman spectroscopy and molecular dynamics simulations, we reveal that more FSI- anion coordinates with Li+ to construct the solvation sheath in siloxane-based electrolyte. This unique coordination environment facilitates anion-derived SEI formation dominated by LiF/Li3N inorganic components, effectively suppressing dendrite growth and enhancing interfacial stability. The optimized electrolyte (DMS-3) enables exceptional electrochemical performance: Li||Cu cells achieve a high Coulombic efficiency of 99.4 % for 1000 cycles (0.5 mA cm-2) and 98.8 % for 800 cycles (1.0 mA cm-2). Li||LiNi0.8Co0.1Mn0.1O2 full cell with 89.82 % capacity retention after 500 cycles at 1.0 C. The practical validation using 1.2 Ah Li||LiNi0.8Co0.1Mn0.1O2 pouch cell demonstrated 92.26 % capacity retention after 110 cycles (0.3/0.5 C). This work establishes a molecular design paradigm for electrolyte engineering, providing critical insights for developing high-voltage LMBs.