Hierarchical Solvation Chemistry via Ether–Ester–Cosolvent Synergy Enables High‐Performance Lithium‐Metal Batteries at a Low Temperature

Abstract

ABSTRACT Lithium metal batteries (LMBs) offer high energy densities but are frequently plagued by rapid degradation under extreme conditions, such as low temperatures or high C‐rates. This performance decay stems primarily from sluggish Li + transport kinetics and high desolvation energy penalties imposed by conventional electrolytes. Herein, we engineer a hierarchically solvating electrolyte system comprising a weakly coordinating ether (tetrahydropyran, THP), a strongly coordinating ester (methyl propionate, MP), and lithium difluoro(oxalato)borate (LiDFOB). This molecular configuration fosters an anion‐enriched primary solvation sheath, effectively minimizing the activation energy required for Li + desolvation. Furthermore, the incorporation of trifluorotoluene (TFT) as a non‐solvating diluent modulates the local solvation structure toward aggregate dominance, thereby promoting the formation of a compact and homogeneous solid electrolyte interphase (SEI). Through precise compositional tuning, we achieve a robust SEI architecture characterized by the uniform distribution of ductile organic matrices and high‐modulus inorganic species. This mosaic structure provides an optimal mechanical balance of rigidity and elasticity, preserving interfacial integrity during prolonged cycling at cryogenic temperatures. Consequently, Li||Li symmetric cells exhibit ultrastable cycling for over 6000 h at −25°C. In Li||LiCoO 2​ full cells, the electrolyte supports 400 stable cycles, retaining 85.5% and 66.2% of the nominal room‐temperature capacity at −25°C and −45°C, respectively. These findings offer critical design principles for tailoring solvation chemistry to enable high‐performance LMBs in extreme environments.