Localized High-Concentration Electrolytes With Semi-Solvated Hexafluoroisopropyl Methyl Ether Diluent for...

Conventional electrolytes in lithium metal batteries (LMBs) suffer from irreversible interfacial degradation at elevated temperatures and sluggish Li⁺ desolvation/transport kinetics under cryogenic conditions. Herein, we present an innovative semi-solvated hexafluoroisopropyl methyl ether (HFME) diluent in localized high-concentration electrolytes (LHCEs) that strategically addresses these limitations. Li⁺ hopping networks within the electrolyte can be preserved even at low temperatures due to the coordination of lithiophilic groups in HFME molecules with Li⁺. Simultaneously, lithiophobic group induced spatial confinement effects promote the formation of anion-cation aggregates (AGGs), significantly optimizing Li⁺ desolvation kinetics and boosting the formation of inorganic-dominated solid electrolyte interphase (SEI) with exceptional thermal stability. Li||LiFePO₄ (LFP) cell with the diluent-coordinated LHCEs (DCL) can deliver 125.4 mA h g^-1 initial capacity at -20 °C with 92.2% retention after 150 cycles. Under elevated temperatures (65 °C), the DCL-based Li||LFP cell can maintain the capacity retention of 91.3% over 60 cycles. The Li||NCM811 pouch cell (10 cm × 6.5 cm, capacity: 1000 mA h) based on the DCL exhibits outstanding cycling stability, retaining 91.6% of its initial capacity after 75 cycles. This work pioneers a solvent chemistry paradigm through spatially modulated solvation structures, establishing fundamental design principles for electrolyte for wide-temperature-range LMBs.