Solvation Cluster Engineering of Non-Fluorinated Ethers toward High-Energy Lithium Metal Batteries

Abstract Lithium metal batteries (LMBs) can provide high energy density for next-generation energy storage, yet their cycle life remains limited by interfacial incompatibility between electrolyte species and electrodes. Conventional electrolytes based on polar or fluorinated solvents often suffer from sluggish transport kinetics, high cost, and even environmental concerns. Herein, we rationally modulate the polarity and coordination ability of nonfluorinated solvents and report a fluorine-free host–guest synergy electrolyte (HGSE) constructed by tailoring the intermolecular interaction between a long-chain multidentate ether and a monodentate ether solvent. The weak Hδ+–Oδ− intermolecular interaction between these solvents tunes the electrolyte coordination ability and solvation cluster size, leading to a contact ion pair-dominated solvation cluster structure with enhanced ionic conductivity. Meanwhile, the optimized solvation cluster in HGSE promotes anion decomposition while suppressing electrode side reactions, resulting in anion-derived LiF-rich interphases and minimized cathode cracking. More notably, the HGSE electrolyte enables a Li||NCM811 pouch cell to deliver a high energy density of 472.5 Wh kg–1, while a 20 Ah-level anode-free Cu||Ni90 pouch cell with a lean electrolyte (1.5 g Ah–1) achieves a superior energy density of 525 Wh kg–1 with 71.6% capacity retention over 120 cycles. These findings elucidate the role of intermolecular interactions and solvation cluster engineering in high-energy and sustainable LMBs.