Gradient fluorinated and hierarchical selective adsorption coating for Zn-Based aqueous battery

Abstract

Rechargeable aqueous zinc-ion batteries (ZIBs) are considered as one of the most promising large-scale energy storage system due to their high energy density, low cost and inherent safety. However, the notorious dendrite growth and severe side reactions, impede their practical application. Herein, we constructed a multifunctional gradient composite fluorinated coating with insulating ZnF2 outside and Zn/Sn alloy inside. ZnF2 outside and Zn/Sn alloy inside perform their own functions and solve the dendrites and side reactions jointly. Density functional theory (DFT) calculations and Molecular dynamics (MD) simulations demonstrate that the electronically insulating ZnF2 layer on the surface can regulate the transport of Zn2+ cations, limit the free H2O molecules and improve the dissolution of Zn2+, at the same time, the zincophilicity Zn/Sn alloy inside work as the favorable nucleation sites for Zn atoms and lowers the Zn2+ diffusion energy barrier. As a result, the ZnF2-Sn@Zn electrode in a symmetrical cell exhibits a long cycle life of about 1400 h, as well as 91 % capacity retention after 1400 cycles at 1 A/g in the ZnF2-Sn@Zn//MnO2@CNT full batteries. This work provides a practically promising strategy and new insights for the electrolyte and anode interface design.