Capacitance enhancement of hybrid electrochemical capacitor with asymmetric carbon electrodes configuration in neutral aqueous electrolyte

Przygocki, Patryk; Abbas, Qamar; Béguin, François

doi:10.1016/j.electacta.2018.03.016

Cited by 37 publications

(30 citation statements)

References 40 publications

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“…With increasing cell voltage, the widths of the G-and D-modes increase, while they are slightly red-and blue-shifted, respectively and the I D -to-I G ratio is lowered. This can be explained by a superposition of charge transfer and an increase of defects [34][35][36][37] , which is qualitatively consistent with ex situ results reported earlier 18,38 .…”

Section: Resultssupporting

confidence: 91%

Persistent and reversible solid iodine electrodeposition in nanoporous carbons

et al. 2020

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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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Section: Resultssupporting

confidence: 91%

Persistent and reversible solid iodine electrodeposition in nanoporous carbons

et al. 2020

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“…With increasing cell voltage, the widths of the G-and D-modes increase, while they are slightly redand blue-shifted, respectively and the ID-to-IG ratio is lowered. This can be explained by a superposition of charge transfer and an increase of defects [33][34][35][36] , which is qualitatively consistent with ex situ results reported earlier 18,37 .…”

Section: In Situ Raman Spectroscopysupporting

confidence: 91%

Persistent and Reversible Solid Iodine Electrodeposition in Nanoporous Carbons

Prehal¹,

Fitzek²,

Kothleitner³

et al. 2020

Preprint

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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.<br>

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“…Similarly, hybrid capacitors with aqueous vanadyl sulfate (VOSO 4 ) show high capacitance and a cell voltage of up to 1.4 V [20]. In order to simultaneously obtain a large potential window and high cell capacitance, redox species are mixed with a supporting aqueous electrolyte of near neutral pH [15,21,22,23,24]. The redox active species that work better in the presence of a supporting electrolyte are iodide salts mixed with aqueous lithium sulfate (Li 2 SO 4 ) [15], aqueous choline chloride or choline nitrate-based supporting electrolyte [24].…”

Section: Introductionmentioning

confidence: 99%

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

Abbas

Fitzek

Schröttner³

et al. 2019

Nanomaterials

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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.

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Capacitance enhancement of hybrid electrochemical capacitor with asymmetric carbon electrodes configuration in neutral aqueous electrolyte

Cited by 37 publications

References 40 publications

Persistent and reversible solid iodine electrodeposition in nanoporous carbons

Persistent and reversible solid iodine electrodeposition in nanoporous carbons

Persistent and Reversible Solid Iodine Electrodeposition in Nanoporous Carbons

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

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