Multinuclear in situ magnetic resonance imaging of electrochemical double-layer capacitors

Ilott, Andrew J.; Trease, Nicole M.; Grey, Clare P.; Jerschow, Alexej

doi:10.1038/ncomms5536

Cited by 74 publications

(55 citation statements)

References 38 publications

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“…7,8 However, historically, MRI of bulk metals has been very rare (as detailed in supplementary material Section S2), due to challenges posed by the physics of propagation of radiofrequency (r.f.) magnetic field (B 1 ) in bulk metals.…”

Section: Introductionmentioning

confidence: 99%

Visualizing electromagnetic fields in metals by MRI

Chandrashekar¹,

Shellikeri

Chandrashekar

et al. 2017

AIP Advances

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Based upon Maxwell’s equations, it has long been established that oscillating electromagnetic (EM) fields incident upon a metal surface, decay exponentially inside the conductor, leading to a virtual absence of EM fields at sufficient depths. Magnetic resonance imaging (MRI) utilizes radiofrequency (r.f.) EM fields to produce images. Here we present a visualization of a virtual EM vacuum inside a bulk metal strip by MRI, amongst several findings. At its simplest, an MRI image is an intensity map of density variations across voxels (pixels) of identical size (=Δx Δy Δz). By contrast in bulk metal MRI, we uncover that despite uniform density, intensity variations arise from differing effective elemental volumes (voxels) from different parts of the bulk metal. Further, we furnish chemical shift imaging (CSI) results that discriminate different faces (surfaces) of a metal block according to their distinct nuclear magnetic resonance (NMR) chemical shifts, which holds much promise for monitoring surface chemical reactions noninvasively. Bulk metals are ubiquitous, and MRI is a premier noninvasive diagnostic tool. Combining the two, the emerging field of bulk metal MRI can be expected to grow in importance. The findings here may impact further development of bulk metal MRI and CSI.

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Section: Introductionmentioning

confidence: 99%

Visualizing electromagnetic fields in metals by MRI

Chandrashekar¹,

Shellikeri

Chandrashekar

et al. 2017

AIP Advances

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“…experiments to enable independent yet simultaneous observation of both electrodes. 77 Using in situ MRI, the electrodes can be studied individually in the standard 'parallel plate' geometry, without the need for the shifted cell design. By using a specially-designed PTFE cell and deuterated solvent, …”

Section: In Situ Nmr Of Supercapacitors: Experimental Considerationsmentioning

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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“…Imaging results can also be combined with spectroscopic information provided by NMR, providing spatially resolved chemical information. Recently, Ilott et al [16]presented the first in situ experiments showing localized information of the electrolyte ions in real time for a working capacitor of standard geometry. It has also been shown that MRI is able to map concentration gradients and visualise electrochemical processes in electrochemical cells containing bulk metals [17].…”

Section: Introductionmentioning

confidence: 99%