Hydrogel Electrolyte with Electron/Ion Dual Regulation Mechanism for Highly Reversible Flexible Zinc Batteries

Abstract

Hydrogel electrolytes have been extensively developed for flexible zinc-ion batteries (FZIBs) owing to their rich ion transfer channels, mechanical stability and intrinsic safety. However, the single ion regulation in traditional hydrogel electrolytes still remains a great challenge to effectively inhibit the growth of Zn dendrites and the occurrence of side reactions, leading to limited performance level in FZIBs. To address this, herein, the unique electron/ion dual regulation mechanism is established in the hydrogel electrolyte by integrating polyacrylamide (PAM) network and carboxylated multi-walled carbon nanotubes (MWCNTs) for high performance and stable FZIBs. The negatively charged carbonyl groups within PAM chains and high conductivity of MWCNTs trigger an associated synergistic regulation mechanism to achieve unifrom ionic/electronic field for highly reversible Zn anode. As a result, the well-designed hydrogel electrolyte showcases a high Zn2+ ions transference number of 0.712 and a high ionic conductivity of 22.02 mS cm-1 at room temperature as well as high battery performance, including a high Coulombic efficiency of 98.2%, over 3600 h of lifespan, and superior mechanical/electrochemical stability for flexible Zn//MnO2 pouch cells. This unique electron/ion dual regulation strategy to challenge traditional hydrogel electrolytes and aqueous Zn chemistry may open up a new avenue for building better FZIBs and beyond.