Multifunctional Interface Layer Constructed by Trace Zwitterions for Highly Reversible Zinc Anodes

Abstract

The inhomogeneous plating/stripping of Zn anode, attributed to dendrite growth and parasitic reactions at the electrode/electrolyte interface, severely restricts its cycling life-span. Here, trace zwitterions (trifluoroacetate pyridine, TFAPD) are introduced into the aqueous electrolyte to construct a multifunctional interface that enhances the reversibility of Zn anode. The TFA⁻ anions with strong specific adsorption adhere onto the Zn surface to reconstruct the inner Helmholtz plane (IHP), preventing the hydrogen evolution and corrosion side reactions caused by free H₂O. The Py⁺ cations accumulate on the outer Helmholtz plane (OHP) of Zn anode with the force of electric field during Zn²⁺ plating, forming a shielding layer to uniformize the deposition of Zn²⁺. Besides, the adsorbed TFA⁻ and Py⁺ promote the desolvation process of Zn²⁺ resulting in fast reaction kinetics. Thus, the Zn||Zn cells present an outstanding cycling performance of more than 10000 hours. And even at 85 % utilization rate of Zn, it can stably cycle for over 200 hours at 10 mA cm⁻² and 10 mAh cm⁻². The Zn||I₂ full cell exhibits a capacity retention of over 95 % even after 30000 cycles. Remarkably, the Zn||I₂ pouch cells (95 mAh) deliver a high-capacity retention of 99 % after 750 cycles.