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

## TL;DR

A new electrolyte additive improves the performance of aqueous zinc-sulfur batteries by speeding up chemical reactions and enhancing stability.

## Contribution

The use of tetramethylurea as an interface chemistry regulator to enhance redox kinetics in aqueous Zn–S batteries is introduced.

## Key findings

- Tetramethylurea reduces energy barriers and promotes uniform ZnS nucleation on the sulfur cathode.
- The additive forms a solid-electrolyte interphase on the anode, improving Zn plating/stripping reversibility.
- With 10% TTMU, the battery achieves 1620 mAh g−1 capacity and 0.37 V overpotential at 0.1 A g−1.

## Abstract

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.

The reaction properties of both electrodes in aqueous Zn‐S batteries is regulated by a tetramethylurea electrolyte additive. It preferentially adsorbs on the sulfur surface and coordinates to Zn2+, thereby altering their reaction process. The energy barrier is reduced and nucleation is promoted, which accelerates reaction kinetics. It also induces an SEI layer on the anode, enhancing Zn plating/stripping reversibility. This strategy significantly boosts the electrochemical performance of Zn‐S batteries.