Topology-engineered hydrogel with cellulose nanosheets for robust and high-capacity zinc-ion batteries

Aqueous zinc-ion batteries (ZIBs) are regarded as a promising candidate for the next-generation energy storage system. As a gel electrolyte with tunable chemistry, polyacrylamide hydrogels suffer from insufficient mechanical strength and limited capability to regulate Zn²⁺ transport. Herein, we address this challenge by incorporating 2D cellulose nanosheets (CNS) into a polyacrylamide network, constructing a composite gel electrolyte with heterogeneous synergistic effects. The CNS reinforces the gel through physical cross-linking with polyacrylamide chains, significantly improving its mechanical properties, while the CNS increases the transference number of Zn²⁺ and suppresses side reactions, thereby favoring uniform zinc deposition and reversible stripping. Benefiting from this cooperative mechanism, the composite hydrogel enables stable cycling in Zn||Zn symmetric cells, operating for over 2800 h at 0.5 mA cm⁻² and 0.5 mAh cm⁻², and the assembled Zn||MnO₂ full cell demonstrates a high-capacity retention of 88.5% after 2500 cycles at 0.5 A g⁻¹. Furthermore, the assembled flexible battery exhibited stable specific capacity under repeated bending, confirming its excellent mechanical flexibility. This work establishes a novel system for long-life and high-safety gel electrolyte for ZIBs, while validating the considerable promise of 2D biomass-derived nanomaterials for advanced energy storage systems.