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 thiophene ring were employed as additives of conventional electrolytes to explore the influence of 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 are 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 Zn||Zn symmetric cell with the assistance of 3TA additive can reach 4900 h at 1 mA cm-2. The reversibility of Zn electrode in electrolyte containing 3TA endows Zn||carbon-cloth@MnO2 ZIBs with long cycle life, significantly surpassing that without additive or with 2TA additive. The work testifies that the coordination environment of functional groups have significant effect on enhancing the stability of Zn anode, broadening the scope of regulation.