Electrolyte-Tailored Heterostructured Zinc Metal Anodes with Tunable Electric Double Layer for Fast-Cycling Aqueous Zinc Batteries

The structures and properties of the electric double layer (EDL) on zinc (Zn) anodes significantly influence the cycling and rate performance of aqueous Zn batteries (ZBs). Here, a strategy is reported to regulate the EDL structure through work function (Wf) engineering to effectively enhance the electrochemical performance of ZBs, which is enabled by electrolyte-tailored growth of heterogenous metal with a large Wf on the Zn anode. The metal-to-metal charge transfer in heterostructured Zn metal induced by the disparity of Wf increases the surface charge density, which enriches the Zn ions and shortens the thickness of EDL. The compressed EDL weakens the repulsive force of Zn deposits to achieve a tightly stacked and dendrite-free Zn deposition. Besides, the formed H2O-deficient EDL structure enables the inorganic-rich solid electrolyte interphase (SEI) with high Zn-ion conductivity to inhibit the notorious parasitic reactions and improve the electrode reaction kinetics. Consequently, the Zn||Zn symmetric cells demonstrate an ultra-long cycling life over 2700 cycles (the cumulative capacity reaches 5400 mA h cm-2) at a high current density of 50 mA cm-2. The Zn anodes show a high average Coulombic efficiency of 99.70% over 3650 cycles. The Zn||MnO2 full cells exhibit excellent practical-level performance under cyclic continuous mode (3000-cycle life at high rates) and cyclic intermittent mode (1170-cycle life with 83.05% capacity retention). Practical pouch cells are also demonstrated with outstanding cycling performance. The surface charge modulation by work function (Wf) engineering realizes compressed electric double layer (EDL) to weaken the repulsion of Zn deposits and achieve dense Zn deposition. The formed H2O-deficient EDL structure inhibits parasitic reactions and induces stable inorganic-rich solid/electrolyte interphase. Benefiting from these features, zinc batteries demonstrate exceptional cycling and rate performance even under challenging conditions. image