Ordered Hierarchical Hydrogel Electrolyte for Long-Life Zinc-Ion Batteries

Hydrogel electrolytes show significant promise for mitigating critical issues of Zn anodes, yet reconciling ionic conductivity with mechanical strength remains challenging. To resolve this trade-off, an ordered hierarchical hydrogel electrolyte (OHHE) is engineered by inducing the directional alignment of bacterial cellulose (BC) nanofibers. The ordered channels for fast Zn²⁺ migration result in a high ionic conductivity (36.19 mS cm^-1) and Zn²⁺ transference number (0.75), facilitating homogenization of Zn²⁺ flux. Furthermore, a hierarchical interfibrous interface integrating nanofiber interlocking and enhanced hydrogen-bond network bridging achieves mechanical reinforcement through energy dissipation (a tensile strength of 27.35 MPa, Young's modulus of 127.81 MPa, and toughness of 5.60 MJ m^-3) to physically suppress dendrite penetration. Concurrently, this dense hydrogen-bond network firmly immobilizes free water at the Zn-OHHE interface, thereby suppressing side reactions. Benefiting from this triple-synergy mechanism, Zn//Zn symmetric cells deliver stable cycling for over 1600 h at 3 mA cm^-2/3 mAh cm^-2 and over 1400 h at a depth-of-discharge of 42%. Additionally, full cells with NaV₃O₈·1.5H₂O cathodes exhibit 82.47% capacity retention even after 3800 cycles at 5 A g^-1. This tailored structural design offers novel insights for realizing high-performance and long-life aqueous zinc-ion batteries.