Rational Design of Ether-Based Localized Weak Solvation Liquid Electrolyte for Practical Lithium Metal Batteries

Although localized high concentration electrolytes (LHCEs) exhibit compatibility with state-of-the-art high-voltage cathodes and lithium metal anodes, their practical implementation is hindered by the excessive volume fraction of fluorinated diluents and suboptimal ionic conductivity. Herein, a localized weak solvation strategy is proposed to preserve electrode interfacial stability while reducing fluorinated diluent content. Specifically, ethylene glycol dibutyl ether (DBE) is identified as a weakly coordinating solvent due to its steric hindrance effect, which preferentially facilitates contact ion pair formation at reduced salt concentrations. Furthermore, the non-coordinating (trifluoromethyl) cyclohexane (TFMH) diluent synergistically enhances anion-cation interactions while maintaining residual free solvent molecules as ion transport sites. Benefiting from this rational electrolyte design, the 9 mg cm⁻² NCM811-Li cell demonstrates exceptional cycling stability under 4.4 V cutoff voltage, achieving 91.3% capacity retention and 99.9% average Coulombic efficiency over 400 cycles. Remarkably, even under practical conditions employing a high cathode loading (21 mg cm⁻²) and ultrathin Li metal anode (50 µm), the NCM811-Li full cell maintains stable operation for 160 cycles.