Hyperquaternized Biomass‐Derived Solid Electrolytes: Architecting Superionic Conduction for Sustainable Flexible Zinc‐Air Batteries

ABSTRACT Flexible zinc‐air batteries are pivotal next‐generation energy storage solutions but face critical solid‐state electrolyte challenges: resource scarcity, low ionic conductivity (<0.05 S cm ⁻¹ ), and poor cycling stability (<100 h). Urgently needed are sustainable electrolytes combining high ion transport, material abundance, and durability. This study develops a chitosan (CS)‐based membrane with exceptional quaternization (109%), biodegradability, and superionic conductivity (0.196 S cm ⁻¹ at 25°C). Simulations reveal hydroxide ion (OH ⁻ ) transport follows the Grotthuss mechanism, with a supplementary contribution from the vehicle mechanism. The resulting solid‐state battery achieves a stable 1.2 V discharge plateau at 10 mA cm ⁻² , 90 mW cm ⁻² peak power density, and 6000‐min cycle life. Crucially, the biomass‐derived membrane degrades fully within 9 weeks, yielding N/K/Zn‐rich residues as eco‐fertilizers—validating a closed‐loop “energy‐storage‐to‐nutrient” pathway. This work advances highly quaternized chitosan electrolytes, delivering record conductivity and lifecycle sustainability while enhancing zinc‐air battery performance and environmental compatibility.