Trace amount of taurine leveling agent for stable Zn anode†

Abstract

Aqueous zinc-ion batteries are highly praised for their cost-effectiveness, environmental friendliness, and high safety, making them an ideal choice for next-generation energy storage systems. However, the practical application of Zn metal anodes is constrained by well-known challenges such as dendrite growth and significant interfacial side reactions. This study introduces a trace amount of taurine (TAU) as a leveling additive into the electrolyte to optimize the microstructure of the electrolyte and the anode interface chemistry. On one hand, the preferential adsorption of TAU on the Zn surface promotes the in situ formation of a stable, protective molecular interfacial layer on the anode, which helps to refine the deposited grains and guide the uniform deposition of Zn²⁺. On the other hand, the introduction of TAU can regulate the hydrogen bond structure in the electrolyte, reduce the activity of water, thereby significantly inhibiting the occurrence of side reactions such as hydrogen evolution. Consequently, the Zn//Zn symmetric cell system demonstrates an extended cycle life of over 1150 cycles at a current density of 1 mA cm⁻² and maintains stable cycling performance for over 600 cycles at 10 mA cm⁻². Moreover, the Zn//Cu asymmetric cell system achieves over 1400 cycles of reversible deposition/dissolution at a current density of 1 mA cm⁻², with a coulombic efficiency of 99.4%. The incorporation of TAU further enhances the cycle stability of the Zn//MnO₂ full cell. These innovative achievements have laid a solid foundation for the broader industrial adoption of aqueous zinc-ion batteries.