Ionic-Liquid Additive Enabled Interfacial Stabilization for Dendrite-Free and Low-Temperature Zn Metal Batteries

Interfacial instability at the Zn metal anode, manifested by uncontrolled dendritic growth, parasitic hydrogen evolution, and corrosion/passivation, fundamentally limits the reversibility of Zn metal batteries, particularly under high-depth-of-discharge (DOD) and low-temperature conditions. Here, we developed an ionic-liquid-modified organic electrolyte by introducing 1-butyl-3-methylimidazolium hexafluorophosphate (BMFP-ZBF) to regulate the Zn/electrolyte interfacial chemistry. The ionic-liquid additive reconstructed the local interfacial environment, promoted the formation of a robust solid electrolyte interphase (SEI), and induced uniform Zn deposition beneath the interphase, thereby simultaneously suppressing dendrite growth, hydrogen evolution, and corrosion. As a result, the optimized BMFP-ZBF electrolyte delivers substantially improved Zn reversibility and interfacial durability compared with both the aqueous electrolyte and the additive-free organic electrolyte. Zn || Zn symmetric cells operated stably for 4000 h at 0.5 mA cm –2 /0.5 mAh cm –2, 680 h at 3 mA cm –2 /3 mAh cm –2 (51% DOD), and 182 h at 80% DOD. Zn || Cu cells also exhibited markedly prolonged cycling and enhanced reversibility. Notably, the BMFP-ZBF electrolyte remains unfrozen at –20 °C and enables stable Zn || Zn cycling for 2230 h under subzero conditions. Moreover, Zn || ZnVO full cells can be stably cycled for 6000 cycles at 5 A g –1 . This work offers an effective electrolyte-engineering strategy for achieving highly stable Zn metal batteries under practically relevant harsh operating conditions.