Inspired by the morphology of elm fruit, this study constructed a chitosan-based solid-state electrolyte membrane (QHTCC@SPI) with ultrahigh ionic conductivity for zinc-air batteries. Using chitosan extracted from shrimp/crab shells as the raw material, a two-step quaternization strategy is proposed to graft quaternary ammonium groups onto the amino and hydroxyl groups of chitosan, thereby increasing the density of quaternary ammonium cations and obtaining highly quaternized chitosan (QHTCC). This work provides critical insights into highly quaternized chitosan and establishes a sustainable electrolyte platform for high-performance 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.