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Open AccessArticle

Immobilization of Polyiodide Redox Species in Porous Carbon for Battery-Like Electrodes in Eco-Friendly Hybrid Electrochemical Capacitors

1
Institute for Chemistry and Technology of Materials, Graz University of Technology, 8010 Graz, Austria
2
Graz Centre for Electron Microscopy, Steyrergasse 17, 8010 Graz, Austria
3
Institute of Electron Microscopy and Nanoanalysis, NAWI Graz, Graz University of Technology, Steyrergasse 17, 8010 Graz, Austria
4
Institute for Applied Materials (IAM), Karlsruhe Institute of Technology (KIT), Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
*
Author to whom correspondence should be addressed.
The author is currently on leave from Poznan University of Technology, Poland.
Nanomaterials 2019, 9(10), 1413; https://doi.org/10.3390/nano9101413
Received: 16 September 2019 / Revised: 29 September 2019 / Accepted: 30 September 2019 / Published: 3 October 2019
(This article belongs to the Special Issue Nano Carbon for Batteries Applications)
Hybrid electrochemical capacitors have emerged as attractive energy storage option, which perfectly fill the gap between electric double-layer capacitors (EDLCs) and batteries, combining in one device the high power of the former and the high energy of the latter. We show that the charging characteristics of the positive carbon electrode are transformed to behave like a battery operating at nearly constant potential after it is polarized in aqueous iodide electrolyte (1 mol L−1 NaI). Thermogravimetric analysis of the positive carbon electrode confirms the decomposition of iodides trapped inside the carbon pores in a wide temperature range from 190 °C to 425 °C, while Raman spectra of the positive electrode show characteristic peaks of I3 and I5 at 110 and 160 cm−1, respectively. After entrapment of polyiodides in the carbon pores by polarization in 1 mol L−1 NaI, the positive electrode retains the battery-like behavior in another cell, where it is coupled with a carbon-based negative electrode in aqueous NaNO3 electrolyte without any redox species. This new cell (the iodide-ion capacitor) demonstrates the charging characteristics of a hybrid capacitor with capacitance values comparable to the one using 1 mol L−1 NaI. The constant capacitance profile of the new hybrid cell in aqueous NaNO3 for 5000 galvanostatic charge/discharge cycles at 0.5 A g−1 shows that iodide species are confined to the positive battery-like electrode exhibiting negligible potential decay during self-discharge tests, and their shuttling to the negative electrode is prevented in this system. View Full-Text
Keywords: hybrid electrochemical capacitor; redox active electrolyte; polyiodide immobilizaton; battery-like electrode; charge transfer; activated carbon hybrid electrochemical capacitor; redox active electrolyte; polyiodide immobilizaton; battery-like electrode; charge transfer; activated carbon
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MDPI and ACS Style

Abbas, Q.; Fitzek, H.; Schröttner, H.; Dsoke, S.; Gollas, B. Immobilization of Polyiodide Redox Species in Porous Carbon for Battery-Like Electrodes in Eco-Friendly Hybrid Electrochemical Capacitors. Nanomaterials 2019, 9, 1413.

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