A green bacterial cellulose/PAF hydrogel electrolyte guiding ordered Zn2+ transport for dendrite-free zinc batteries

Abstract

Rechargeable aqueous zinc-ion batteries (ZIBs) represent a promising class of energy storage devices, prized for their inherent safety, low cost and environmental compatibility. Their widespread adoption, however, has been hampered by persistent challenges including zinc dendrite growth and detrimental interfacial side reactions, which severely compromise cycling life and reversibility. Herein, a synergistic material design that simultaneously achieved breakthrough electrochemical performance and intrinsic green material attributes was reported. A robust cross-linked hydrogel electrolyte (PAM/BC/PAF-6) was fabricated by incorporating a functional, triazine-based porous aromatic framework (PAF-6) into a bacterial cellulose (BC)-reinforced polyacrylamide (PAM) network. This unique architecture delivered exceptional mechanical properties (tensile strength: 80.6 kPa; elongation: 316.7%), arising from the rigid framework and extensive hydrogen-bonding interactions. Crucially, the polar-rich hierarchical structure of the composite orchestrated superior ion dynamics: it significantly lowered the desolvation energy barrier for hydrated Zn²⁺, confined their surface diffusion, and guided the homogeneous three-dimensional ion flux. This resulted in a dendrite-free Zn plating/stripping process with uniform interfacial environment. Concurrently, the hydrophilic network effectively mitigated water activity, thereby suppressing the hydrogen evolution and corrosion reactions. The optimized hydrogel (30% PAF-6) exhibited an ionic conductivity of 2.94 S m⁻¹ and high Zn²⁺ transference number of 0.69. When deployed in batteries, it enabled an ultralong-cycling Zn∥Zn symmetric cell (>7000 h, 0.5 mA cm⁻²) and high-capacity Zn∥V₂O₅ full cell (412.4 mAh g⁻¹ after 600 cycles at 1 A g⁻¹), both coupled with remarkable flexibility. This work demonstrated that the advanced functionality and sustainable material design are not mutually supportive, and can be powerfully co-engineered. It provided a compelling blueprint for developing durable, high-performance and environmentally considerate hydrogel electrolytes for next-generation energy storage.