Enabling low-temperature sodium metal batteries via a multifunctional electrolyte additive

Tetrahydrofuran (THF) excels as a low-temperature electrolyte solvent for sodium metal batteries. However, trace water can often induce the ring-opening polymerization of THF, leading to gelation/loss of conductivity and deterioration of interfacial charge transfer kinetics. Accordingly, we introduced tris(pentafluorophenyl)borane to inhibit polymerization, improve Na⁺ migration, and optimize the interphase, achieving stable Na deposition/stripping (2.0 mA cm^-2, 1000 hours, and -20 °C). Under 10.0 A g^-1, the Na₃V₂ (PO₄)₃/Na full cell maintains a capacity of 66.0 mAh g^-1 after 1000 cycles at -20 °C.