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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 electrochemical oxidation of iodide in nanoporous carbons 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 modeling, 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:Article
Author:Christian PrehalORCiD, Harald FitzekORCiD, Gerald KothleitnerORCiD, Volker PresserORCiD, Bernhard GollasORCiD, Stefan A. FreunbergerORCiD, Qamar AbbasORCiD
Parent Title (English):Nature Communications
First Page:4838
Year of first Publication:2020
Release Date:2022/11/18
Tag:batteries; electrochemistry; supercapacitors
Impact:14.919 (2020)
Funding Information:European Union’s Horizon 2020 research and innovation program (grant agreement no. 636069) and the Austrian Federal Ministry of Science, Research and Economy and the Austrian Research Promotion Agency (grant No. 845364)
Research Departments:Energie-Materialien
Open Access:Open Access
Signature:INM 2020/099 INM 2020/099_correction
Licence (German):License LogoCreative Commons - CC BY - Namensnennung 4.0 International