High-energy lithium metal batteries (LMBs) require electrolytes that simultaneously stabilize the lithium metal anodes and high-voltage cathodes (>4.5 V vs. Li/Li+). Conventional carbonate electrolytes fail due to the unstable organic interphases formed under such aggressive conditions. Here we address these challenges through the topological design of fluorinated carboxylate esters (FCEs) as electrolyte co-solvents, combined with a rationally designed ternary-salt configuration. Critically, our systematic manipulation of the fluorination topology and alkyl chain length of FCEs establishes the descriptor-guided correlations between the molecular structure, Li+ solvation thermodynamics, and interphase formation behaviors within the studied FCE family. Furthermore, the interplay between weakly and strongly coordinating anions in the FCE electrolytes regulates ion transport while promoting inorganic-rich interphases at both electrodes. The designed electrolyte with carbonate as the baseline solvent enables 98.8% Coulombic efficiency for the lithium metal anode and 4.6-V cycling of Li||LiNi0.8Co0.1Mn0.1O2 full cells over 100 cycles with a capacity retention of 88.9% at a current density of 2.20 mA cm-2. This work reveals the molecular-level structure-performance relationship that provides useful guidance on the co-solvents and salts for LMB electrolytes, paving the way for the engineering of next-generation high-energy LMBs.
Ma et al. (Wed,) studied this question.