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Elaborating the Iodine/Polyiodide Equilibrium Effects in Nanoporous Carbon-based Battery Electrode via Extreme Mass Asymmetry in Hybrid Cells.

H SchrangerS KhosraviH FitzekQ Abbas
Published in: ChemElectroChem (2021)
This article discusses the conversion of electrodeposited iodine to polyiodides within the nanopores of carbon electrodes that affect the performance of iodide electrolyte-based electrochemical cells. Here, carbon electrodes have been polarized in aqueous sodium iodide electrolyte to store charge in the form of solid iodine via highly reversible reaction (2I-⇌I2+2e-). The stored iodine within the pores interacts with free iodide ions present in the bulk electrolyte via comproportionation reactions leading to polyiodide (I3 - and I5 -) formations. By tuning the mass asymmetry of carbon electrodes in hybrid cells and using the in-situ Raman spectroscopy on positive battery electrode, we show the influence of iodine/polyiodides equilibrium shifts on the self-discharge and voltage rebounds during open circuit conditions. This study provides insights into the charging mechanisms of carbon electrodes for iodine-based hybrid supercapacitors and battery systems.
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