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Persistent and Reversible Solid Iodine Electrodeposition in Nanoporous Carbons

  • Aqueous iodine based electrochemical energy storage is considered a potential candidate to improve sustainability and performance of current battery and supercapacitor technology. It harnesses the redox activity of iodide, iodine and polyiodide species in the confined geometry of nanoporous carbon electrodes. However, current descriptions of the electrochemical reaction mechanism to interconvert these species are elusive. Here we show that in nanoporous carbons electrochemical oxidation of iodide forms persistent solid iodine deposits. Confinement slows down dissolution into triiodide and pentaiodide, responsible for otherwise significant self-discharge via shuttling. The main tools for these insights are in situ Raman spectroscopy and in situ small and wide angle X-ray scattering (in situ SAXS/WAXS). In-situ Raman confirms the reversible formation of triiodide and pentaiodide. In situ SAXS/WAXS indicates remarkable amounts of solid iodine deposited in the carbon nanopores. Combined with stochastic modelling, in situ SAXS allows quantifying the solid iodine volume fraction and visualizing the iodine structure on 3D lattice models at the sub-nanometer scale. Based on the derived mechanism we demonstrate strategies for improved iodine pore filling capacity and prevention of self-discharge, applicable to hybrid supercapacitors and batteries.

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Document Type:Preprint
Author:Christian PrehalORCiD, Harald FitzekORCiD, Gerald KothleitnerORCiD, Volker PresserORCiD, Berhard GollasORCiD, Stefan A. FreunbergerORCiD, Qamar AbbasORCiD
Parent Title (English):chemRxiv
Issue:Version 1 23.04.2020 ; Version 2 02.09.2020
First Page:1
Last Page:19
Date of first Publication:2020/04/23
Release Date:2023/01/20
Tag:Iodine battery; hybrid supercapacitor; in situ Raman spectroscopy; in situ small angle x-ray scattering; nanoporous carbon
Funding Information:Lise Meitner project M 2576-N37 ERC starting grant OMICON, grant agreement no. 636069
Research Departments:Energie-Materialien
DDC classes:500 Naturwissenschaften und Mathematik / 540 Chemie
Open Access:Open Access
Signature:INM 2020/099_preprint
Licence (German):License LogoCreative Commons - CC BY - Namensnennung 4.0 International