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 at subzero conditions. Here, we report a novel dual-salt electrolyte composed of weakly-dissociated LiPO2F2 (LiDFP) and common-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 LiPF6-EC electrolyte retain 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.