Advanced hydrogel electrolyte with enhanced interfacial adhesion and low-temperature resistant for flexible zinc-ion batteries

Flexible zinc-ion batteries (ZIBs) have great potential in wearable devices due to their excellent mechanical properties, safety and high energy density. However, the poor adhesion of the electrodes in bending, folding and low-temperature environments remains a challenge. In this study, we developed a dual-network hydrogel electrolyte (C-PAM@TA) by incorporating tannic acid (TA) into a cross-linked polyacrylamide (PAM) network. The C-PAM@TA hydrogel electrolyte exhibits strong interfacial adhesion, high ion conductivity, and low-temperature frost resistance. Through experimental and theoretical analyses, we demonstrate that TA helps regulate anion/cation transport channels, weakens the solvation of zinc ions and enables stable and uniform plating/stripping behavior of the zinc metal anode. As a result, the Zn//Zn symmetric cell employing the C-PAM@TA hydrogel electrolyte exhibits outstanding cycling stability (2000 h) at 0.5 mA cm−2. Furthermore, the assembled Zn//C-PAM@TA//fcc@PANI flexible ZIBs can undergo 7000 cycle stability tests, withstand 4500 bending tests and operate normally in a low-temperature environment of −18 ℃. This study successfully develops high-performance, low-temperature resistant flexible ZIBs, providing valuable insights for the design of multifunctional flexible energy storage and wearable electronic devices.