Interfacial H₂O Structure Matters: Realizing Stable Zinc Anodes with Trace Acesulfame-K in Aqueous Electrolyte

The stability of Zinc metal anodes (ZMAs) significantly limits the electrochemical performance and practical application of aqueous Zn-ion batteries (ZIBs). An efficient and economical solution is the use of trace additives. However, efforts on trace additives are sparse, and essential uncertainties remain concerning their role in the stabilization of ZMAs. Herein, a low-cost ZnSO4-based aqueous electrolyte containing trace amounts of Acesulfame-K (AK) (only 1.0 mg mL(-1)) is reported, which effectively suppresses the parasitic reactions occurring on the ZMA surface to realize a dendrite-free Zn2+ deposition process, an ultra-long cycle life over 1600 h and a high Coulombic efficiency of 99.86%. Accordingly, the practical Zn//NH4V4O10 full cell with AK also exhibits a high discharge capacity and capacity retention. In situ spectroscopies coupled with theoretical calculations reveal that the trace AK tends to accumulate at the ZMA/electrolyte interface to alleviate electrolyte corrosion. More importantly, the adsorbed AK can regulate the interfacial H2O structures (i.e., disrupting the interfacial H-bonds to form more isolated H2O) to reduce the proton/hydroxides transport, thus suppressing the parasitic hydrogen evolution reaction and improving low-temperature acclimation. This study provides design inspiration for trace additives expected to enable low-cost and practical ZIBs with long lifespans.