Paramagnetic electrodes and bulk magnetic susceptibility effects in the in situ NMR studies of batteries: Application to Li1.08Mn1.92O4 spinels

Zhou, Lina; Leskes, Michal; Ilott, Andrew J.; Trease, Nicole M.; Grey, Clare P.

doi:10.1016/j.jmr.2013.05.011

Cited by 72 publications

(111 citation statements)

References 31 publications

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“…Similar assignments have also been made in battery systems, where Li-microstructures growing perpendicular to the surface of the electrode have been shown to display a significant shift away from the bulk metal peak [19,21], and where orientation-dependent bulk magnetic susceptibility effects have been explored [39]. In non-conducting samples, the latter leads to a broadening of the spectrum as the shifts vary continuously from one part of the sample to another.…”

Section: Resultssupporting

confidence: 53%

Visualizing skin effects in conductors with MRI: 7Li MRI experiments and calculations

Ilott

Chandrashekar

Klöckner

et al. 2014

Journal of Magnetic Resonance

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While experiments on metals have been performed since the early days of NMR (and DNP), the use of bulk metal is normally avoided. Instead, often powders have been used in combination with low fields, so that skin depth effects could be neglected. Another complicating factor of acquiring NMR spectra or MRI images of bulk metal is the strong signal dependence on the orientation between the sample and the radio frequency (RF) coil, leading to non-intuitive image distortions and inaccurate quantification. Such factors are particularly important for NMR and MRI of batteries and other electrochemical devices. Here, we show results from a systematic study combining RF field calculations with experimental MRI of 7 Li metal to visualize skindepth effects directly and to analyze the RF field orientation effect on MRI of bulk metal. It is shown that a certain degree of selectivity can be achieved for particular faces of the metal, simply based on the orientation of the sample. By combining RF field calculations with bulk magnetic susceptibility calculations accurate NMR spectra can be obtained from first principles. Such analyses will become valuable in many applications involving battery systems, but also metals, in general.

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Section: Resultssupporting

confidence: 53%

Visualizing skin effects in conductors with MRI: 7Li MRI experiments and calculations

Ilott

Chandrashekar

Klöckner

et al. 2014

Journal of Magnetic Resonance

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“…[12][13][14]17,[22][23][24] Interestingly, the 3d CSI sheds new light on previous bulk metal NMR studies. For instance, in an earlier study, 12 a similar shift difference between NMR peaks was observed at and ⊥ orientations (relative to B 0 ) of the major faces of a thinner metal strip, by carrying out two separate experiments.…”

Section: Csimentioning

confidence: 88%

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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“…However, recently researchers have shifted their interest to in situ NMR studies of cathode materials. This is quite challenging due to the signal broadening and peak shifting, which results from the paramagnetic nature of most cathode materials and the inability to use in situ magic angle spinning to overcome these limitations [78]. Detailed practical aspects associated with in situ [75,78].…”

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%

“…This is quite challenging due to the signal broadening and peak shifting, which results from the paramagnetic nature of most cathode materials and the inability to use in situ magic angle spinning to overcome these limitations [78]. Detailed practical aspects associated with in situ [75,78]. Shimoda and co-workers [79] were able to observe the lithium extraction/insertion from/in LiCoO 2 by optimization of the cell components and increasing the magnetic field strength.…”

Section: Nuclear Magnetic Resonance Spectroscopymentioning

confidence: 99%