Interface Chemistry and Reaction Pathway Regulation for Boosted Redox Kinetics in Aqueous Zn–S Batteries

Aqueous Zn-S batteries are promising candidates for large-scale energy storage applications due to their high specific capacity and energy density. However, their performance is extremely plagued by the sluggish redox kinetics. Here, an interface chemistry regulator is proposed for both electrodes to facilitate reaction kinetics and promote stability. The tetramethylurea (TTMU) is selected as the electrolyte additive. It first preferentially adsorbs on the sulfur cathode surface and coordinates to Zn²⁺, thereby altering their reaction pathway. This reduces the energy barrier and promotes uniform ZnS nucleation, which accelerates reaction kinetics. At the same time, the additive induces an effective solid-electrolyte interphase on the anode and enhances the reversibility and stability of Zn plating/stripping. With the help of 10% TTMU additive, the Zn-S battery delivers a high capacity of 1620 mAh g^-1 with a low overpotential of 0.37 V at 0.1 A g^-1, which is superior to 1138 mAh g^-1/0.65 V in the benchmark Zn(OAc)₂/ZnI₂ electrolyte. With the increase of current density to 5 A g^-1, the additive also significantly enhances the capacity from 48 to 913 mAh g^-1. Promoted cycling stabilities are further achieved for both Zn electrode and Zn-S cells in the TTMU containing electrolyte.