Low-Temperature and Fast-Charge Sodium Metal Batteries

Low-temperature operation of sodium metal batteries (SMBs) at the high rate faces challenges of unstable solid electrolyte interphase (SEI), Na dendrite growth, and sluggish Na+ transfer kinetics, causing a largely capacity curtailment. Herein, low-temperature and fast-charge SMBs are successfully constructed by synergetic design of the electrolyte and electrode. The optimized weak-solvation dual-salt electrolyte enables high Na plating/stripping reversibility and the formation of NaF-rich SEI layer to stabilize sodium metal. Moreover, an integrated copper sulfide electrode is in situ fabricated by directly chemical sulfuration of copper current collector with micro-sized sulfur particles, which significantly improves the electronic conductivity and Na+ diffusion, knocking down the kinetic barriers. Consequently, this SMB achieves the reversible capacity of 202.8 mAh g-1 at -20 degrees C and 1 C (1 C = 558 mA g-1). Even at -40 degrees C, a high capacity of 230.0 mAh g-1 can still be delivered at 0.2 C. This study is encouraging for further exploration of cryogenic alkali metal batteries, and enriches the electrode material for low-temperature energy storage. A low-temperature and fast-charge sodium metal battery is successfully constructed by simultaneous design of both the electrolyte and electrode. A weakly solvated dual-salt electrolyte enables fast ion desolvation and the formation of NaF-rich solid electrolyte interphase (SEI) layer to stabilize sodium metal, and meanwhile, CuS as the active material is simply prepared by in situ chemical sulfuration of copper current collector, knocking downg the kinitic barrier in electrode. This synergetic strategy could be extended to other cryogenic alkali metal batteries. image