Hydrogen-bond-mediated cross-sheath associations couple Li+ solvation with interfacial chemistry in lithium metal batteries

Extending the lifetime of lithium metal batteries requires electrolyte strategies that coordinate Li⁺ solvation with interfacial chemistry. Here, we introduce hydrogen-bond-mediated cross-sheath molecular association as a design principle for an ether-based localized high-concentration electrolyte. Spectroscopic analyses, noncovalent-interaction calculations and ab initio molecular dynamics simulations indicate that 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE) and fluoroethylene carbonate (FEC) reside predominantly in the outer solvation environment, whereas 1,2-diethoxyethane (DEE) remains an important inner-shell solvent. The pre-associated FEC–TTE motif exhibits a stronger overall association with DEE than isolated TTE, providing a plausible molecular bridge between the outer and primary solvation environments. This cross-sheath association contributes to weaker average Li⁺–DEE coordination and increased participation of bis(fluorosulfonyl)imide (FSI⁻) and isosorbide dinitrate (ISDN), yielding a compact, anion-enriched local solvation structure. At the electrode interface, the reconstructed solvation environment cooperates with the reduction chemistry of FEC, FSI⁻ and ISDN to suppress excessive solvent decomposition and promote a homogeneous LiN_xO_y/LiF-rich solid electrolyte interphase. Consequently, Li||Li symmetric cells sustain stable plating/stripping for approximately 1354 h at 1 mA cm⁻² and 1 mAh cm⁻², while high-loading Li||LiFePO₄ cells cycle for approximately 1188 cycles at 1 C. Unlike conventional approaches focused primarily on direct regulation of the first Li⁺ solvation shell, this work demonstrates that engineering molecular associations across solvation environments offers an effective route to couple solvation redistribution with interfacial film formation.