Partially methylated polybenzimidazoles as coating for alkaline zinc anodes

Anastasiia Konovalova, Daniel Stock, Steffen Schröder, Hyun S. Park, Jong Hyun Jang, Hyoung Juhn Kim, Jonghee Han, Daniel Schröder, Dirk Henkensmeier

    Research output: Contribution to journalArticlepeer-review

    17 Citations (Scopus)

    Abstract

    Hydroxide ion conductive polymer coatings with a low permeability for zinc species reduce shape change and dendrite formation of zinc anodes, and reduce the capacity fade over charge/discharge cycles. Herein we focus on the material properties and aim to minimize the permeability of polybenzimidazole (PBI) for zincate ions by methylating its imidazole NH groups. This reduces the volume swelling in 4 M KOH solution from 104% for PBI to 20% for a PBI with 1.3 methyl groups per repeat unit. Similarly, materials with a degree of methylation (DOM) between 0.96 and 1.2 show very low uptake of KOH. Above a DOM of 1.7 decreasing alkaline stability is observed, presumably because a fraction of the imidazole groups is permethylated to benzmidazolium ions. Most importantly, membranes with a DOM around 1–1.2 revealed the lowest permeation for zincate ions, with permeability coefficients P of 0.9–1.5 10−9 cm2 s−1, 3000 times lower than for PBI. At higher DOM slightly higher P values were observed. In a Zn/NiOOH cell an optimized anode coating with 0.96MePBI led to better cycling stability than with PBI, and an initial capacity of 265 mAh (g anode)−1.

    Original languageEnglish
    Article number118254
    JournalJournal of Membrane Science
    Volume610
    DOIs
    Publication statusPublished - 2020 Sept 1

    Bibliographical note

    Publisher Copyright:
    © 2020 Elsevier B.V.

    Keywords

    • Alkylated polybenzimidazole
    • Anode coating
    • Hydroxide ion conductivity
    • Zinc oxygen battery
    • Zincate ion permeability

    ASJC Scopus subject areas

    • Biochemistry
    • General Materials Science
    • Physical and Theoretical Chemistry
    • Filtration and Separation

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