High Ion Conductivity and Diffusivity in the Anion Exchange Membrane Enabled by Tethering with Multication Strings on the Poly(biphenyl alkylene) Backbone

• DOI: 10.1021/acsaem.0c00409
• Publication Date: 2020-06-05T22:32:28Z
• Authors: Lijuan Li; Jujia Zhang; Tao Jiang; Xiaoqian Sun; Yulu Li; Xueliang Li; Shanzhong Yang; Shanfu Lu; Haibing Wei; Yunsheng Ding
• Keywords: Side chain; Biphenyl

Aryl ether-free polyaromatics tethered with quaternary ammoniums (QAs) offer a promising candidate as an anion exchange membrane (AEM) for use in alkaline fuel cells. However, the traditional trade-off dilemma between ion conductivity and water swelling of AEM still remains. Herein, we report series poly(biphenyl alkylene) (PBPA) polymers multiple QAs per side chain that combine advantages high conductivity, diffusion coefficient, suppressed uptake. Upon increasing number on each chain, degree phase separation resulting increased, thereby improving coefficient from 2.03 × 10–6 cm2 s–1 single-QA-based PBPA100-1QA to 2.26 triple-QA-based PBPA35-3QA. The triply-charged membranes show much improved performances. Specifically, at given capacity (IEC) 2.5 mmol g–1, despite notably low uptake was observed, PBPA35-3QA exhibited ∼40% higher than PBPA100-1QA. highest observed PBPA50-3QA (IEC = 3.1 g–1), achieving 63 mS cm–1 chloride 80 °C, while corresponding well-suppressed within 116 wt %. Owing diffusivity well uptake, cell fabricated 25 μm thick showed high-frequency resistance 0.03 Ω cm2. 18% cation degradation after aging 300 h 2 M NaOH which is significantly inferior value those counterparts chains.