Enhanced Capacitive Energy Storage in Polyoxometalate‐Doped Polypyrrole

Abstract

High-performance batteries and supercapacitors require the molecular-level linkage of charge transport components and charge storage components. This study shows how redox-tunable Lindqvist-type molecular metal oxide anions [V n M 6-n O 19 ] (2+n)− (M = W(VI) or Mo(VI); n = 0, 1, 2) can be incorporated in cationic polypyrrole (PPy) conductive polymer films by means of electrochemical polymerization. Electron microscopy and (spectro-)electrochemistry show that the electroactivity and morphology of the composites can be tuned by Lindqvist anion incorporation. Reductive electrochemical "activation" of the Lindqvist-PPy composites leads to significantly increased electrical capacitance (range: ≈25-38 F g −1 , increase up to ≈25×), highlighting that this general synthetic route gives access to promising capacitive materials with suitable long-term stability. Electrochemical, electron microscopic, and Raman spectroscopic analyses together with density functional theory (DFT) calculations provide molecular-level insight into the effects of Lindqvist anion incorporation in PPy films and their role during reductive activation. The study therefore provides fundamental understanding of the principles governing the bottom-up integration of molecular components into nanostructured composites for electrochemical energy storage.The ORCID identification number(s) for the author(s) of this article can be found under http://dx.The combination of in situ (spectro-)electrochemistry and theoretical calculations allows us to provide initial molecular level understanding of the underlying activation mechanism. The study therefore provides new molecular design principles for capacitive charge storage devices.

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