Weakly dissociated lithium salt decouples solvent–anion interfacial dynamics for wide-temperature lithium-ion batteries

Abstract

Developing lithium-ion batteries (LIBs) operable across extreme temperatures (−40 to 60 °C) is imperative for electric vehicles and space technologies, yet hindered by incompatible interphasial requirements: cathode–electrolyte interphase (CEI) degradation at high temperatures and anode solid-electrolyte interphase (SEI) impedance surge under subzero conditions. Here, we report a novel dual-salt electrolyte composed of weakly dissociated LiPO₂F₂ (LiDFP) and commonly used LiPF₆ in an ethyl acetate (EA)/ethylene carbonate (EC) co-solvent, enabling wide-temperature LIB operation with exceptional interphasial stability. LiDFP with elevated solubility renders contact ion pairs and aggregates surrounding Li⁺, enriching PO₂F₂⁻ coordination within the Li⁺ solvation shell. This unique solvation structure promotes the preferential decomposition of PO₂F₂⁻ anions at electrode surfaces, forming thin, dense CEI/SEI layers dominated by Li₃PO₄ and LiF, which simultaneously enhance interphasial robustness and Li⁺ transport. As a result, 5 Ah NCM613‖graphite pouch cells deliver over 80% capacity retention after 200 cycles at 60 °C and maintain 57% reversible capacity at −40 °C, while the cell using the LiPF₆-EC electrolyte retains 80% capacity after only 200 cycles at 45 °C. By decoupling anion-mediated interfacial regulation from solvent-centric limitations, this work establishes a universal electrolyte paradigm to achieve intrinsically stable, wide-temperature LIBs.