A New Low-Rate Stable Hydrogel Cathode for Aqueous Zn-ion Batteries.

Abstract

Aqueous Zn-ion batteries (ZIBs) are attractive candidates for large-scale energy storage owing to the abundance, low cost, and intrinsic safety of Zn metal. However, their practical application is hindered by poor cycle stability, especially at low current densities, due to cathode dissolution and limited electrochemically active sites (EAS). Herein, a hydrogel-based cathode comprising ammonium vanadate, carbon black, and a Zn-ion-conducting carboxymethyl chitosan-acrylamide hydrogel matrix doped with Zn(ClO₄)₂ is reported. This design establishes a continuous Zn-ion-conducting network, thereby maximizing EAS density throughout the electrode volume. The ZIB with the hydrogel cathode exhibits outstanding cycling stability, with 77% capacity retention after 2000 cycles at 1 A g^-1 and 75% retention after 1400 cycles at 0.5 A g^-1, far surpassing conventional polyvinylidene fluoride-based cathodes. In addition to retaining high EAS density, the hydrogel matrix also suppresses active material dissolution. These results demonstrate a new strategy for stabilizing ZIB cathodes and advancing long-duration energy storage.