Boosting Cathode Activity and Anode Stability of Zn‐S Batteries in Aqueous Media Through Cosolvent‐Catalyst Synergy

Aqueous Zn−S battery with high energy density represents a promising large‐scale energy storage technology, but its application is severely hindered by the poor reversibility of both S cathode and Zn anode. Herein, we develop a “cocktail optimized” electrolyte containing tetraglyme (G4) and water as co‐solvents and I2 as additive. The G4‐I2 synergy could activate efficient polar I3−/I− catalyst couple and shield the cathode from water, thus facilitating the conversion kinetics of S and suppressing the interfacial side reactions. Simultaneously, it could stabilize Zn anode by forming an organic–inorganic interphase upon cycling. With boosted electrodes reversibility, the Zn−S cell delivers a high capacity of 775 mAh g−1 at 2 A g−1, and retains over 70 % capacity after 600 cycles at 4 A g−1. The advances can also be readily generalized to other ethers/water hybrid electrolytes, showing the universality of the “cocktail optimized” electrolyte design strategy. The reversible Zn−S chemistry in aqueous media is realized by introducing tetraglyme cosolvent and iodine catalyst. The cosolvent‐catalyst synergy can not only activate the polar I3−/I− catalyst couple for S conversion but also generate an organic–inorganic interphase on Zn in situ, thus resulting in boosted cathode activity and anode stability. The strategy presents a new paradigm to stabilize aqueous Zn−S batteries.