Microcrystalline-Induced Physical-Cross-linking toward a High Performance Hyper-Branched Anion Exchange Membrane

An anion exchange membrane (AEM) is the core component of the low-cost anion exchange membrane fuel cell (AEMFC). To realize the commercial application of AEMFC, extremely low swelling of AEM is vital for the membrane electrode assembly preparation and cell integrity, except for high hydroxide conductivity, strength, and chemical stability. However, it is hard to achieve an extremely low swelling ratio while maintaining high conductivity, especially for a homogeneous membrane. Herein, a series of quaternized poly(trans-1,2-diphenylethylene-co-terphenyl-N,N′-dimethyl piperidinium) with a sophisticated structure are synthesized for AEM to address such dilemma. The physical-cross-linking induced by microcrystalline effectively restricts the swelling of AEM (<6.2%@80 °C). Moreover, a hyper-branched structure is also introduced in order to increase the free volume in the polymer membrane, resulting in a high conductivity of up to 275.6 mS cm–1 at 80 °C. Accordingly, excellent fuel cell performance with a peak power density of 1.13 W cm–2 for H2–O2 at 80 °C is attained.