Microenvironment regulation of anode-electrolyte interface enables highly stable Zn anodes

Abstract

H₂O-induced side reactions and dendrite growth occurring at the Zn anode-electrolyte interface (AEI) limit the electrochemical performances of aqueous zinc ion batteries. Herein, methionine (Met) is introduced as an electrolyte additive to solve the above issues by three aspects: Firstly, Met is anchored on Zn anode by amino/methylthio groups to form a H₂O-poor AEI, thus increasing the overpotential of hydrogen evolution reaction (HER); secondly, Met serves as a pH buffer to neutralize the HER generated OH⁻, thereby preventing the formation of by-products (e.g. Zn₄SO₄(OH)₆⋅xH₂O); thirdly, Zn²⁺ could be captured by carboxyl group of the anchored Met through electrostatic interaction, which promotes the dense and flat Zn deposition. Consequently, the Zn||Zn symmetric cell obtains a long cycle life of 3200 h at 1.0 mA cm⁻², 1.0 mAh cm⁻², and 1400 h at 5.0 mA cm⁻², 5.0 mAh cm⁻². Moreover, Zn||VO₂ full cell exhibits a capacity retention of 91.0% after operating for 7000 cycles at 5.0 A g⁻¹. This study offers a novel strategy for modulating the interface microenvironment of AEI via integrating the molecular adsorption, pH buffer, and Zn²⁺ capture strategies to design advanced industrial-oriented batteries.