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 g_ZnS⁻¹, a high specific energy density of 274 Wh kg_ZnS⁻¹ (832 Wh kg_S⁻¹) and excellent rate performance (197 mAh g_ZnS⁻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.