Internal Electron Donor Accelerated Sulfur Redox for Aqueous Zn─S Batteries

Abstract Improving the electrical conductivity of sulfur cathode while ensuring its high affinity to catalyst holds the key to facilitate the reaction kinetics of aqueous zinc–sulfur batteries. Herein, the sulfur redox in aqueous electrolyte is accelerated by introducing selenium–sulfur bonds into the sulfur structure to build an internal electron transport path. The Se with less electronegativity can act as an electron donor to accelerate the binding between S and Zn²⁺. Meanwhile, the bonded Se in the electron‐poor state endows the modified sulfur cathode with a strong affinity to the I₃⁻ catalyst, which further facilitates the conversion efficiency. Thus, the internal electron donor assisted sulfur cathode delivers excellent electrochemical performance in terms of high reversible capacity (1490 mAh g⁻¹ at 0.5 A g⁻¹), competitive rate performance (1010 mAh g⁻¹ at 4 A g⁻¹), as well as outstanding cycle stability (735 mAh g⁻¹ at 4 A g⁻¹ after 500 cycles).