Position-selective modulation of carboxyl groups on thiophene rings for dendrite-free zinc metal anodes

Abstract

Introducing additives into electrolytes represents an effective approach to suppress dendrite growth in zinc-ion batteries (ZIBs). However, the influence of the coordination environment of functional groups in regulating the detrimental effects on the Zn surface remains inadequately understood. Herein, as a prototype, 3-thiophenecarboxylic acid (3TA) and 2-thiophenecarboxylic acid (2TA) with carboxyl groups on different sites of the thiophene ring were employed as additives of conventional electrolytes to explore the influence of the coordination environment of functional groups on battery performance. In comparison with 2TA, 3TA with carboxyl groups at the 3rd position of the thiophene ring is more conducive to facilitating the desolvation of hydrated Zn²⁺. Meanwhile, 3TA is preferentially adsorbed onto Zn foil to prevent direct contact between active water and the anode, promoting plating/stripping kinetics of Zn²⁺. As a result, electrodeposition/dissolution cycling of the Zn‖Zn symmetric cell with the assistance of the 3TA additive can reach 4900 h at 1 mA cm⁻². The reversibility of the Zn electrode in electrolyte containing 3TA endows Zn‖carbon-cloth@MnO₂ ZIBs with long cycle life, significantly surpassing that without an additive or with a 2TA additive. The work proves that the coordination environment of functional groups has a significant effect on enhancing the stability of Zn anodes, broadening the scope of regulation.