Tailoring and unveiling the stable solvent structure dependence of interfacial chemistry for extremely high-temperature lithium metal batteries

Traditionally, the construction of stable interphases relies on solvent structures dominated by aggregated anionic structures (AGG/AGG+). Nonetheless, we find that the construction of stable interphases in high-temperature environments is based on contact ion pairs (CIPs) dominated solvation structure here. In detail, in the long-chain phosphate ester-based electrolyte, the spatial site-blocking effect enables the strong solvation co-solvent ether (diethylene glycol dimethyl ether, G2) to exhibit strong ion-dipole interactions, further multicomponent competitive coordination maintaining the CIP, balancing electrode kinetics, and optimizing the high-temperature interphases. High-temperature in-situ Raman spectroscopy monitors the changes in the stable solvent structure during charge/discharge processes for the first time, and time of flight secondary ion mass spectrometry (TOF-SIMS) reveals the stable solid electrolyte interphase (SEI) with full-depth enrichment of the inorganic component. Benefiting from the high-temperature interfacial chemistry-dependent solvent structure, the advanced electrolyte enables stable cycling of 1.6 Ah 18650 batterie at 100–125 °C and discharging with high current pulses (∼1.83 A) at 150 °C, which has rarely been reported so far. In addition, pin-pricking of 18650 batteries at 100% state of charge (SoC) without fire or smoke and the moderate thermal runaway temperature (187 °C) tested via the accelerating rate calorimetry (ARC) demonstrate the excellent safety of the optimized electrolyte.