γ-Valerolactone-Based Anion-Dominated Loose Solvation Electrolyte Enables Stable Lithium Metal Batteries from -60°C...

Integrating high-nickel cathodes with lithium metal anodes enables ultrahigh-energy-density batteries but remains challenged by electrolyte instability under extreme temperatures. Here, we design an anion-dominated loose solvation structure, where fluorine-rich weak solvents occupy coordination sites. γ-Valerolactone (GVL) serves as the primary solvent, assisted by two weakly coordinating co-solvents: difluoroethylene carbonate (DFEC) to modulate solvation and ethyl trifluoroacetate (ETFA) to reduce viscosity and freezing point. This balanced solvation environment enhances ionic transport, interfacial stability, and desolvation kinetics. Consequently, Li||NCM811 cells deliver stable cycling at 100°C, exceeding 90 cycles, negligible capacity loss at -40°C, and 90.4 mAh g^-1 at -60°C. Full cells (N/P ≈ 1.8) retain 90.3% capacity after 130 cycles. This work offers a viable solvation design for high-voltage lithium metal batteries operating across extreme temperatures.