Bio-based supramolecular dual-network gel electrolytes with synergistic mechanical robustness and ionic conductivity for high-performance flexible Zn-ion batteries

Gel electrolytes offer attractive potential for flexible Zn-ion batteries due to their safety, structural flexibility, and ionic conductivity. However, challenges persist in achieving sufficient mechanical strength to prevent dendrite growth, ensuring efficient ion transport, and mitigating side reactions between electrodes and sustainable gel electrolytes. We present a supramolecular gel electrolyte (CS-gel) developed through ethanol-induced molecular assembly of cellulose and silk fibroin. The CS-gel features interwoven hydrogen-bond (H-bond) networks and β-sheet domains, achieving an ionic conductivity of 14.39 mS cm⁻¹ and a tensile strength of 1.14 MPa. The polar groups (-OH, -NH₂, -COOH) within the gel interact dynamically with Zn²⁺ ions, reorganizing solvation structures to inhibit dendrite formation and reduce parasitic reactions. In a flexible Zn//MnO₂ battery, the CS-gel retains 97.67 % capacity after 1500 cycles at a discharge rate of 0.5 A g⁻¹, demonstrating stable long-term cycling performance under bending and at temperatures as low as -20 °C. This supramolecular design, integrating natural biopolymers, presents an effective and sustainable approach to high-performance flexible energy storage devices.