Acetonitrile‐Induced Iodine Mediation Enables High‐Rate Aqueous Zn‐S Batteries

Aqueous Zn‐S batteries exhibit great potential owing to their intrinsic safety, cost‐effectiveness, and eco‐friendly nature. However, their advancement faces persistent challenges, including sluggish redox kinetics, parasitic side reactions, and poor cathode wettability. Herein, we propose a hybrid electrolyte composed of acetonitrile (ACN) ‐ H 2 O solvents, with an iodine (I 2 ) redox mediator, to address these issues. Compared to H 2 O, the ACN molecules exhibit a higher adsorption affinity toward sulfur, thereby facilitating the formation of an ACN‐enriched interfacial layer on the cathode. This layer mediates I 2 transport to the sulfur cathode, while I 2 ensures efficient sulfur redox conversion, synergistically promoting the reversible S/ZnS reactions. Notably, the I 2 concentration critically influences reaction kinetics and rate capability. Moreover, incorporating ACN enhances cathode wettability and mitigates side reactions, thereby improving cathode stability. Consequently, the Zn‐S battery delivers a high specific capacity of 1535 mAh g −1 at 0.1 C and a high energy density of 912 Wh kg −1 . Notably, it demonstrates exceptional rate capability, retaining a substantial capacity of 899 mAh g −1 at a high current density of 10 C (16.75 A g −1 ), while maintaining considerable cycling stability.