Zwitterion-modified chitosan anion exchange membranes with balanced conductivity and stability for high-performance...

The commercialization of rechargeable zinc-air batteries (RZABs) is still limited by the conductivity-stability trade-off in anion exchange membranes (AEMs). To address this challenge, a series of zwitterionic sulfobetaine-modified chitosan AEMs (CS@SBAx) were synthesized via covalent grafting, and the effect of sulfobetaine (SBA) loading on the comprehensive performance of the membranes was systematically investigated. FT-IR and XPS confirms the successful modification, and electrostatic interactions among the zwitterionic side-chains constructs a physical crosslinking network that effectively inhibits membrane swelling. Among all prepared membranes, CS@SBA150 delivers a high OH^- conductivity of 81.0 mS cm^-1 at 80 °C and a suppressed swelling ratio of 26.2%. Impressively, it exhibits remarkable long-term alkaline stability, with 94.1% of the initial conductivity preserved after 216 h exposure to 6 M KOH solution at 25 °C. Molecular dynamics simulations and density functional theory calculations reveal that surface hopping, synergistically assisted by Grotthuss transfer and a weak Vehicle-type transport, endows the CS@SBA150 membrane with elevated conductivity at low water uptake. RZABs assembled with the CS@SBA150 membrane delivers a peak power density of 150.4 mW cm^-2, maintains stable discharge at 1.20 V for over 3 h, and exhibits a charge-discharge cycle life of 14 h. This work provides a green and effective strategy for the design of biomass-derived AEMs with balanced conductivity and stability.