Trace Selenium Doping for Improving the Reaction Kinetics of ZnS Cathode for Aqueous Zn–S Batteries

Aqueous Zinc–sulfur (Zn–S) batteries are promising for the field of energy storage due to their low cost, high theoretical capacity, and safety. However, the large volume expansion and the inherently poor conductivity of sulfur would result in electrode cracking and sluggish reaction kinetics, limiting the practical application of Zn–S batteries. Herein, commercial zinc sulfide (ZnS) is employed instead of S as cathode and proposed a doping modification strategy to solve the above problems. The designed ZnS_0.93Se_0.07 cathode shows good cycle stability and much-improved reaction kinetics, which is due to the smaller bandgap of ZnS_0.93Se_0.07 (1.40 eV) compared to ZnS (1.86 eV). As a result, the obtained ZnS_0.93Se_0.07 cathode exhibits a high specific capacity of 552 mAh g⁻¹ (1672.6 mAh g⁻¹ based on S) at 0.1 A g⁻¹ and 330 mAh g⁻¹ (1000 mAh g⁻¹ based on S) at 2 A g⁻¹. Moreover, the ZnS_0.93Se_0.07 cathode can provide a high areal capacity of 3.8 mAh cm⁻² at a high mass loading of 10 mg cm⁻² and limited electrolyte (4 µL mg⁻¹). This work provides a simple and effective cathode modification strategy, which is conducive to promoting the practical application of Zn–S batteries.