Imidazolium-based AEMs with high dimensional and alkaline-resistance stabilities for extended temperature range of alkaline fuel cells

Anion exchange membranes prepared from imidazolium cations still need to overcome the drawbacks of water solubility and chemical stability in strong base. Here, we use density functional theory (DFT) to focus on alkaline stability of imidazolium-based monomers with different C4/C5-position substituents and analyze their degradation mechanism when treated with 10 M NaOH. On the basis, we select methyl-substituted imidazolium (MeIM) cationic compound to construct ether-free main-chain type polymers via superacid-catalytic reaction, together with the introduction of branched monomer to inhibit water swelling of membrane. The optimized branched structure maintains stable dimension performance under 80 °C compared to linear polymer dissolved in water. Meanwhile, the alkaline-resisted membrane with branched structure expands the operating temperature range of fuel cell to 90 °C and maintains long-term durability.