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    Downplaying the role of water in the rheological changes of conducting polymers by using water-in-salt electrolytes

    Year: 2021

    Journal: Phys. Chem. Chem. Phys., Volume 23, JUN 7, page 12251–12259

    Authors: Obana, Thiago T.; Leite, Marina M.; Martins, Vitor L.; Torresi, Roberto M.

    Organizations: FAPESP [2015/26308-7, 2017/10046-9, 2013/22748-7, 2019/02669-1, 2020/07768-5]

    Volumetric changes associated with solvent/electrolyte exchange in electronic conducting polymers (ECPs) play an important role in the mechanical stability of the polymers, as these changes are a critical factor in ECP-based energy storage devices. Thus, the present work explores the hindering of such volumetric deformations for polypyrrole films doped with dodecylbenzenesulphonate (PPy(DBS)) by employing highly concentrated aqueous electrolytes (or water-in-salt electrolytes, WiSEs), and their effects over the corresponding electrochemical capacitor cell energy retention. Electrochemical quartz crystal microbalance with dissipation monitoring measurements for thin PPy(DBS) films in the WiSEs revealed negligible dissipation changes (Delta D-n approximate to 0), in contrast with those in dilute aqueous electrolyte (Delta D-n not equal 0), indicating inexpressive structural deformation of PPy(DBS) in the WiSE. This phenomenon is observed for thick freestanding PPy(DBS) films, which presented a maximum bending angle decay from similar to 56 degrees (diluted aqueous electrolyte) to 3.5 degrees when working in the WiSE, thus proving the hindering of film bending. The observed trends are reflected in the PPy(DBS) cell energy retention, where the use of a WiSE decreased cell energy fading by 30% after 600 cycles, in comparison with cells based on diluted electrolytes.
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