A corrosion-free zinc metal battery with an ultra-thin zinc anode and high depth of discharge

Abstract

Zinc metal batteries featuring high capacity, low cost, and environmental benignity have been receiving more attention than ever. Regrettably, due to the intrinsic thermodynamic instability of metallic zinc in conventional aqueous electrolytes, giant challenges still remain before its broad application. Herein, we report a corrosion-free zinc metal battery with an ultra-thin zinc anode and high depth of discharge by rational electrolyte engineering. This weakly coordinated aprotic electrolyte endows the metallic zinc with excellent thermodynamic stability in static storage by avoiding the generation of H⁺ and the zinc foil experienced no evident corrosion even after soaking for two weeks, which provides an important benchmark for employing an ultra-thin metallic zinc anode down to 10 μm-thick. Besides, benefiting from its distinctive weakly-coordinated solvation structure (i.e., [Zn(DMI)₃]²⁺ and [Zn(DMI)₄]²⁺), this electrolyte endows the zinc metal battery with superior electrochemical performance at a high depth of discharge. 10 μm Zn‖10 μm Zn symmetric cells stably cycled for 7220 hours at the current density of 1 mA cm⁻² and 10 μm Zn‖15.3 mg cm⁻² PANI full cells stably ran for 1700 cycles at the current density of 50 mA g⁻¹, exhibiting a high capacity retention of 82.5%. Lastly, we revealed that the superior dynamic performance of the aqueous electrolyte is attributed to the faster mass transfer in the electrolyte rather than a lower de-solvation energy in the electrode/electrolyte interphase. This work illustrates a potential pathway for the commercial application of zinc metal batteries.