Highly reversible and stable Zn metal anodes realized using a trifluoroacetamide electrolyte additive

Abstract

The practical application of aqueous zinc-ion batteries (AZIBs) is limited due to the inherent side reactions and dendrite growth of Zn anodes. Herein, we propose a solution to the issue of AZIBs by creating a versatile electrolyte through the addition of trifluoroacetamide (TFA). The CO group of TFA interacts strongly with Zn²⁺, leading to a change in the inherent structure of Zn(H₂O)₆²⁺ and an enhancement in the transport of Zn²⁺. The interaction between TFA and H₂O disrupts the H bond network structure of H₂O, resulting in a reduction of active H₂O and stabilization of the electrolyte's pH value. Moreover, TFA, with a low LUMO value, breaks down into Zn₄CO₃(OH)₆·H₂O and ZnF₂, forming a robust SEI that results in uniform Zn²⁺ deposition and improved Zn²⁺ transport kinetics. As a result, Zn//Zn symmetric cells with the TFA electrolyte remain stable for over 1360 h and 800 h at high current densities of 5 mA cm⁻² and 40 mA cm⁻², respectively. The TFA electrolyte also enables Zn//5,7,12,14-pentacenetetrone full cells and Zn//active carbon capacitors to perform steadily for 10 000 cycles at 25 °C and 70 °C, respectively. This research provides valuable insights into the use of electrolyte additives and promotes the long-term stability of AZIBs even at ultra-high current densities.