title: An effective approach for alleviating cation-induced backbone degradation in aromatic ether-based alkaline polymer electrolytes.
abstract: Aromatic ether-based alkaline polymer electrolytes (APEs) are one of the most popular types of APEs being used in fuel cells. However, recent studies have demonstrated that upon being grafted by proximal cations some polar groups in the backbone of such APEs can be attacked by OH(-), leading to backbone degradation in an alkaline environment. To resolve this issue, we performed a systematic study on six APEs. We first replaced the polysulfone (PS) backbone with polyphenylsulfone (PPSU) and polyphenylether (PPO), whose molecular structures contain fewer polar groups. Although improved stability was seen after this change, cation-induced degradation was still obvious. Thus, our second move was to replace the ordinary quaternary ammonia (QA) cation, which had been closely attached to the polymer backbone, with a pendant-type QA (pQA), which was linked to the backbone through a long side chain. After a stability test in a 1 mol/L KOH solution at 80 °C for 30 days, all pQA-type APEs (pQAPS, pQAPPSU, and pQAPPO) exhibited as low as 8 wt % weight loss, which is close to the level of the bare backbone (5 wt %) and remarkably lower than those of the QA-type APEs (QAPS, QAPPSU, and QAPPO), whose weight losses under the same conditions were >30%. The pQA-type APEs also possessed clear microphase segregation morphology, which led to ionic conductivities that were higher, and water uptakes and degrees of membrane swelling that were lower, than those of the QA-type APEs. These observations unambiguously indicate that designing pendant-type cations is an effective approach to increasing the chemical stability of aromatic ether-based APEs.
authors.affiliation: College of Chemistry and Molecular Sciences, Hubei Key Lab of Electrochemical Power Sources, and ‡Institute for Advanced Studies, Wuhan University , Wuhan 430072, China.
authors.forename: Juanjuan
authors.initials: J
authors.lastname: Han
authors.forename: Qiong
authors.initials: Q
authors.lastname: Liu
authors.forename: Xueqi
authors.initials: X
authors.lastname: Li
authors.forename: Jing
authors.initials: J
authors.lastname: Pan
authors.forename: Ling
authors.initials: L
authors.lastname: Wei
authors.forename: Ying
authors.initials: Y
authors.lastname: Wu
authors.forename: Hanqing
authors.initials: H
authors.lastname: Peng
authors.forename: Ying
authors.initials: Y
authors.lastname: Wang
authors.forename: Guangwei
authors.initials: G
authors.lastname: Li
authors.forename: Chen
authors.initials: C
authors.lastname: Chen
authors.forename: Li
authors.initials: L
authors.lastname: Xiao
authors.forename: Juntao
authors.initials: J
authors.lastname: Lu
authors.forename: Lin
authors.initials: L
authors.lastname: Zhuang
keywords: alkaline polymer electrolyte; backbone degradation; chemical stability; fuel cell application; pendant-type quaternary ammonia cation; phase separation