A single ion conductive "plasticine-like" solid electrolyte combined with a modulated d-band center of interfacial zinc atoms for highly reversible zinc metal anodes

Highly concentrated salts, like 30 m ZnCl₂, can reduce free water molecules in aqueous electrolytes but also increase acidity, causing severe acid-catalyzed corrosion of the Zn anode, current collector, and encapsulation layer. Here, we develop a “plasticine-like” solid electrolyte (PLSE) by mutual solubilization of PAN and (ZnCl₄)²⁻. The weak solvation structure contributes a high Zn²⁺ ion transfer number of 0.9, much higher than that of the 30 m ZnCl₂ aqueous electrolyte (0.6). Furthermore, an anti-catalytic indium-rich solid electrolyte interphase (In-rich SEI) is constructed by incorporating trace amounts of InCl₃ in the PLSE, which boosts Zn²⁺ ion adsorption by modulating the d-band center. The combination of proton shielding by the “plasticine-like” electrolyte and the anti-catalytic effect of the In-rich SEI expands the stabilized voltage window to 6.8 V (2.8 V for 30 m ZnCl₂) and significantly suppresses hydrogen generation. As a result, the Zn‖Zn symmetric cell can continuously cycle for 10 000 h at a current density of 0.5 mA cm⁻² and the Zn‖Cu symmetric cell achieves over 8000 cycles with an average coulombic efficiency of >99.4%. Meanwhile, the four-electron-transfer Zn‖I₂ battery delivers specific capacities of 370 mA h g⁻¹ at room temperature and 483 mA h g⁻¹ at 50 °C. The battery can operate over a wide temperature range of −50 to 60 °C and achieve impressive cycling stability over 1200 cycles with 89.28% initial capacity retained. In addition, the Zn‖Br₂ cell with a higher charge/discharge plateau successfully achieved 3500 cycles at 1.5 A g⁻¹ and provided a high specific capacity of 245 mA h g⁻¹ with 85.31% capacity retention. The PLSE and anti-catalytic interphase provide valuable insights into the design of electrolytes for highly reversible zinc metal anodes.