Quantification of ion confinement and desolvation in nanoporous carbon supercapacitors with modelling and in situ X-ray scattering

Prehal, Christian; Koczwara, Christian; Jäckel, Nicolas; Schreiber, Anna; Burian, Max; Amenitsch, Heinz; Hartmann, Markus; Presser, Volker; Paris, Oskar

doi:10.1038/nenergy.2016.215

Cited by 247 publications

(222 citation statements)

References 56 publications

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“…Frequently used nanoporous electrodes for supercapacitors are activated and carbidederived carbons [62]. Such electrodes do not consist of perfectly aligned monodisperse slits, but they are random porous media, containing interconnected pores of various shapes and sizes [69][70][71][72][73]. Clearly, our model is not directly applicable to these electrodes.…”

Section: Nanoporous Electrodesmentioning

confidence: 98%

Superionic liquids in conducting nanoslits: A variety of phase transitions and ensuing charging behavior

Dudka

Kondrat

Bénichou

et al. 2019

The Journal of Chemical Physics

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South Kensington Campus, London SW7 2AZ, United Kingdom ‡ 7 Interdisciplinary Scientific Center J-V Poncelet, UMI CNRS 2615, 11 Bol. Vlassievsky per., Moscow, Russia §We develop a theory of charge storage in ultra-narrow slit-like pores of nanostructured electrodes. Our analysis is based on the Blume-Capel model in external field, which we solve analytically on a Bethe lattice. The obtained solutions allow us to explore the complete phase diagram of confined ionic liquids in terms of the key parameters characterising the system, such as pore ionophilicity, interionic interaction energy and voltage. The phase diagram includes the lines of first and second-order, direct and re-entrant, phase transitions, which are manifested by singularities in the corresponding capacitance-voltage plots. To test our predictions experimentally requires mono-disperse, conducting, ultra-narrow slit pores, permitting only one layer of ions, and thick pore walls, preventing interionic interactions across the pore walls. However, some qualitative features, which distinguish the behavior of ionophilic and arXiv:1909.13089v1 [cond-mat.soft] 28 Sep 2019 ionophobic pores, and its underlying physics, may emerge in future experimental studies of more complex electrode structures.

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Section: Nanoporous Electrodesmentioning

confidence: 98%

Superionic liquids in conducting nanoslits: A variety of phase transitions and ensuing charging behavior

Dudka

Kondrat

Bénichou

et al. 2019

The Journal of Chemical Physics

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“…While in situ x-ray and neutron experiments now provide information at various scales on the localization of ions inside the electrodes [20,21], quantitative predictions of the ionic concentrations, or equivalently the capacitance and salt adsorption, essentially rely on models of the electric double layer (EDL). The most commonly used models in these contexts are Debye-Hückel (DH) and Poisson-Boltzmann (PB)-possibly including excluded volume effects-theories [22][23][24][25][26][27][28][29], as well as modified Donnan (mD) models [30].…”

Section: Introductionmentioning

confidence: 99%

Blue Energy and Desalination with Nanoporous Carbon Electrodes: Capacitance from Molecular Simulations to Continuous Models

et al. 2018

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Capacitive mixing (CapMix) and capacitive deionization (CDI) are currently developed as alternatives to membrane-based processes to harvest blue energy-from salinity gradients between river and sea waterand to desalinate water-using charge-discharge cycles of capacitors. Nanoporous electrodes increase the contact area with the electrolyte and hence, in principle, also the performance of the process. However, models to design and optimize devices should be used with caution when the size of the pores becomes comparable to that of ions and water molecules. Here, we address this issue by simulating realistic capacitors based on aqueous electrolytes and nanoporous carbide-derived carbon (CDC) electrodes, accounting for both their complex structure and their polarization by the electrolyte under applied voltage. We compute the capacitance for two salt concentrations and validate our simulations by comparison with cyclic voltammetry experiments. We discuss the predictions of Debye-Hückel and Poisson-Boltzmann theories, as well as modified Donnan models, and we show that the latter can be parametrized using the molecular simulation results at high concentration. This then allows us to extrapolate the capacitance and salt adsorption capacity at lower concentrations, which cannot be simulated, finding a reasonable agreement with the experimental capacitance. We analyze the solvation of ions and their confinement within the electrodes-microscopic properties that are much more difficult to obtain experimentally than the electrochemical response but very important to understand the mechanisms at play. We finally discuss the implications of our findings for CapMix and CDI, both from the modeling point of view and from the use of CDCs in these contexts.

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“…It has been shown that the maximum volumetric capacitance was achieved when the carbon pore size matched that of the adsorbing electrolyte ions . The development of in situ experimental techniques, including the electrochemical quartz crystal microbalance (EQCM) and small‐angle X‐ray scattering (SAXS), has radically modified understanding of charge storage mechanisms and ion dynamics in nanoporous carbon‐based supercapacitors in aqueous electrolytes. Recently, Prehal et al used SAXS to characterize ion adsorption mechanisms in confined pores and the effects of different microporous carbons on the capacitance.…”

Section: Introductionmentioning

confidence: 99%

“…The development of in situ experimental techniques, including the electrochemical quartz crystal microbalance (EQCM) and small‐angle X‐ray scattering (SAXS), has radically modified understanding of charge storage mechanisms and ion dynamics in nanoporous carbon‐based supercapacitors in aqueous electrolytes. Recently, Prehal et al used SAXS to characterize ion adsorption mechanisms in confined pores and the effects of different microporous carbons on the capacitance. Their results showed that the pore size of the carbon material decreased from 1.3 to 0.65 nm, while the volumetric capacitance considerably increased from 80 to 180 F cm −3 .…”

Section: Introductionmentioning

confidence: 99%

Nitrogen Codoped Unique Carbon with 0.4 nm Ultra‐Micropores for Ultrahigh Areal Capacitance Supercapacitors

Zhou

Hou

Luan

et al. 2018

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A full understanding of ion transport in porous carbon electrodes is essential for achieving effective energy storage in their applications as electrochemical supercapacitors. It is generally accepted that pores in the size range below 0.5 nm are inaccessible to electrolyte ions and lower the capacitance of carbon materials. Here, nitrogen-doped carbon with ultra-micropores smaller than 0.4 nm with a narrow size distribution, which represents the first example of electrode materials made entirely from ultra-microporous carbon, is prepared. An in situ electrochemical quartz crystal microbalance technique to study the effects of the ultra-micropores on charge storage in supercapacitors is used. It is found that ultra-micropores smaller than 0.4 nm are accessible to small electrolyte ions, and the area capacitance of obtained sample reaches the ultrahigh value of 330 µF cm , significantly higher than that of previously reported carbon-based materials. The findings provide a better understanding of the correlation between ultra-micropore structure and capacitance and open new avenues for design and development of carbon materials for the next generation of high energy density supercapacitors.

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Quantification of ion confinement and desolvation in nanoporous carbon supercapacitors with modelling and in situ X-ray scattering

Cited by 247 publications

References 56 publications

Superionic liquids in conducting nanoslits: A variety of phase transitions and ensuing charging behavior

Superionic liquids in conducting nanoslits: A variety of phase transitions and ensuing charging behavior

Blue Energy and Desalination with Nanoporous Carbon Electrodes: Capacitance from Molecular Simulations to Continuous Models

Nitrogen Codoped Unique Carbon with 0.4 nm Ultra‐Micropores for Ultrahigh Areal Capacitance Supercapacitors

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