Modeling the structural evolution of carbide-derived carbons using quenched molecular dynamics

Palmer, Jeremy C.; Llobet, Anna; Yeon, Sun-Hwa; Fischer, J. E.; Shi, Yunfeng; Gogotsi, Yury; Gubbins, Keith E.

doi:10.1016/j.carbon.2009.11.033

Cited by 191 publications

(220 citation statements)

References 18 publications

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“…The details of the simulation cells are provided in Supplementary Table S2. The carbon structure for the porous electrodes was obtained through quenched molecular dynamics 15 and corresponds to the experimental structure of a CDC synthesized at 1,200°C, with an average pore size of 0.9 nm.…”

Section: Methodsmentioning

confidence: 99%

“…In this model, the local charges on the atoms of the electrode vary dynamically in response to the electrical potential caused by the ions and molecules in the electrolyte. The electrode structure mimics that of a carbide-derived carbon (CDC) 14,15 and two different electrolytes were studied: the first consists of the pure ionic liquid 1-butyl-3-methylimidazolium (BMI þ ) hexafluorophosphate (PF À 6 ) at 400 K and the second of the same ionic species dissolved in acetonitrile (ACN), with a concentration of 1.5 M, at 298 K. As in our previous work, we use the coarse-grained models described in the Methods section for these liquids. These have been shown to reproduce their bulk and interfacial properties extremely well: in particular, we have shown that, when combined with the model porous carbons, this setup yields much higher capacitances than the ones obtained at planar electrodes 9 and in good agreement with experimental values.…”

Section: Supercapacitors Simulationsmentioning

confidence: 99%

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Highly confined ions store charge more efficiently in supercapacitors

et al. 2013

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Liquids exhibit specific properties when they are adsorbed in nanoporous structures. This is particularly true in the context of supercapacitors, for which an anomalous increase in performance has been observed for nanoporous electrodes. This enhancement has been traditionally attributed in experimental studies to the effect of confinement of the ions from the electrolyte inside sub-nanometre pores, which is accompanied by their partial desolvation. Here we perform molecular dynamics simulations of realistic supercapacitors and show that this picture is correct at the microscopic scale. We provide a detailed analysis of the various environments experienced by the ions. We pick out four different adsorption types, and we, respectively, label them as edge, planar, hollow and pocket sites upon increase of the coordination of the molecular species by carbon atoms from the electrode. We show that both the desolvation and the local charge stored on the electrode increase with the degree of confinement.

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Section: Methodsmentioning

confidence: 99%

Section: Supercapacitors Simulationsmentioning

confidence: 99%

Highly confined ions store charge more efficiently in supercapacitors

et al. 2013

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“…Indeed, quenched molecular dynamics simulations predict highly disordered and discontinuous structures for CDCs produced at low chlorination temperatures. 28 In such materials, the reduced electron delocalization would be expected to result in a reduced ring current shift for in-pore species.…”

Section: Understanding Pore Size Effects On Electrolyte Adsorptionmentioning

confidence: 99%

Solid-state NMR studies of supercapacitors

Griffin

Forse

Grey

2016

Solid State Nuclear Magnetic Resonance

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Electrochemical double-layer capacitors, or 'supercapacitors' are attracting increasing attention as high-power energy storage devices for a wide range of technological applications. These devices store charge through electrostatic interactions between liquid electrolyte ions and the surfaces of porous carbon electrodes. However, many aspects of the fundamental mechanism of supercapacitance are still not well understood, and there is a lack of experimental techniques which are capable of studying working devices. Recently, solid-state NMR has emerged as a powerful tool for studying the local environments and behaviour of electrolyte ions in supercapacitor electrodes. In this Trends article, we review these recent developments and applications. We first discuss the basic principles underlying the mechanism of supercapacitance, as well as the key NMR observables that are relevant to the study of supercapacitor electrodes.We then review some practical aspects of the study of working devices using ex situ and in situ methodologies and explain the key advances that these techniques have allowed on the study of supercapacitor charging mechanisms. NMR experiments have revealed that the pores of the carbon electrodes contain a significant number of electrolyte ions in the absence of any charging potential. This has important implications for the molecular mechanisms of supercapacitance, as charge can be stored by different ion adsorption/desorption processes. Crucially, we show how in situ NMR experiments can be used to quantitatively study and characterise the charging mechanism, with the experiments providing the most detailed picture of charge storage to date, offering the opportunity to design enhanced devices. Finally, an outlook for future directions for solid-state NMR in supercapacitor research is offered.3

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“…They do not have cylindrical pores either: They are 3D amorphous networks. Gubbins's group produced models of carbide-derived ( Figure 4a-c ) and activated carbons, 20 and Salanne's group performed MD simulations showing how ions enter the pores of disordered carbons. 41 In the case of ionic liquids, the simulations showed that negative ions drag positive ions along and vice versa ( Figure 7 ), so that there are always counterions penetrating into pores.…”

Section: Applications Of Graphenementioning

confidence: 99%

Not just graphene: The wonderful world of carbon and related nanomaterials

Gogotsi

2015

MRS Bull.

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Carbon, with its variety of allotropes and forms, is the most versatile material, and virtually any combination of mechanical, optical, electrical, and chemical properties can be achieved with carbon by controlling its structure and surface chemistry. The goal of this article is to help readers appreciate the variety of carbon nanomaterials and to describe some engineering applications of the most important of these. Many different materials are needed to meet a variety of performance requirements, but they can all be built of carbon. Considering the example of supercapacitor electrodes, zero-and onedimensional nanoparticles, such as carbon onions and nanotubes, respectively, deliver very high power because of fast ion sorption/desorption on their outer surfaces. Twodimensional (2D) graphene offers higher charge/discharge rates than porous carbons and a high volumetric energy density. Three-dimensional porous activated, carbide-derived, and templated carbon networks, with high surface areas and porosities in the angstrom or nanometer range, can provide high energy densities if the pore size is matched with the electrolyte ion size. Finally, carbon-based nanostructures further expand the range of available nanomaterials: Recently discovered 2D transition-metal carbides (MXenes) have already grown into a family with close to 20 members in about four years and challenge graphene in some applications.

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Modeling the structural evolution of carbide-derived carbons using quenched molecular dynamics

Cited by 191 publications

References 18 publications

Highly confined ions store charge more efficiently in supercapacitors

Highly confined ions store charge more efficiently in supercapacitors

Solid-state NMR studies of supercapacitors

Not just graphene: The wonderful world of carbon and related nanomaterials

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