A Durable Zns Cathode for Aqueous Zn-S Batteries

Traditional aqueous zinc-ion batteries suffer from an unsatisfactory energy density due to the limited specific capacity of cathode. Zn-S battery shows a high energy density due to the high theoretical capacity of S (1675 mAh g−1). However, the sluggish redox kinetics and large volume evolution hinder its practical application. To tackle these problems, we propose a nanoscale ZnS packed and connected by carbon sheath (ZnS@CF) as the cathode. By introducing iodinated thiourea as a redox mediator, the activation barrier of ZnS@CF is reduced to 1.26 V. The ZnS@CF cathode delivers an extraordinary capacity of 465 mAh gZnS−1, a high specific energy density of 274 Wh kgZnS−1 (832 Wh kgS−1) and excellent rate performance (197 mAh gZnS−1 at 9.04 C). This work provides a promising high performance cathode and strategies to improve the kinetics and cycle stability of Zn-S batteries.