Скачать или смотреть Paramagnetic NMR: Motion, Migration, Charge Compensation in a Na+ Battery | Euan Bassey | Session 44

During the 44th session of the Global NMR Discussion Meetings held on March 8th, 2022 via Zoom, Euan Bassey from Prof. Clare Grey's research group at the University of Cambridge gave a talk on the topic below. The recording serves as a tutorial.

Topic: Motion, Migration and Charge Compensation in a Na+ Ion Battery Cathode: Tales from the Paramagnetic NMR Storybook

Abstract:
Sodium-ion batteries (NIBs) are a more sustainable and significantly cheaper energy storage alternative to lithium-ion batteries (LIBs) and as such are poised to play a vital role in future grid-based energy storage. To date, the capacities and rate capabilities of NIBs—limited by the cathode—are too low for many real-world applications, and the sources of NIB degradation during charge and discharge have not received the attention that LIBs have. If we are to address the energy storage problem and improve the electrochemical performance of NIB cathodes, we must understand the sources of energy losses of this poor rate behaviour in terms of the changes to the chemical structure of the cathode during charge and discharge.

Solid-state NMR (ss-NMR) is ideally suited to studying such structural changes; variable-temperature 23Na ss-NMR is invaluable in assessing the extent of Na+ ion mobility (and hence the charge-discharge rates possible in NIB cathodes), whilst 17O NMR provides a local handle on the charge compensation scheme. Amongst the families of NIB cathode materials, layered NIB cathodes are particularly attractive, owing to their high Na+ mobility and good gravimetric capacities.

In this presentation, we provide an overview of paramagnetic NMR, the effect of motion on NMR spectra and the assignment of highly paramagnetic NMR spectra. We introduce Na0.67[Mg0.28Mn0.72]O2, a high-capacity, high-rate Na+-ion cathode and go on to report the changes in Na+ ion dynamics during its first charge-discharge cycle. Using a combination of variable temperature 23Na NMR and ab initio calculations of the NMR shifts and energy barriers, we assess the mobility of Na+ ions in the structure and hopping routes of these ions. For the first time, we elucidate the superstructure of P2-Na0.67[Mg0.28Mn0.72]O2 through powder synchrotron X-ray diffraction, powder neutron diffraction and pair distribution function analysis. We examine the structural changes in this material using 25Mg and 17O NMR and use these to develop a mechanism for charge compensation.

Speaker's biography:
Euan completed his BA(Cantab) and MSci in Natural Sciences at the University of Cambridge. Having fallen in love with magnetic resonance techniques and solid-state chemistry, he is currently pursuing a PhD in Chemistry, supervised by Prof. Clare Grey. Now in his fourth year, he wishes to enthuse and inspire others to use magnetic resonance techniques to understand novel systems.

Twitter: @EuanBassey
Website: https://www.ch.cam.ac.uk/person/eb599

Current organizers:
Adrian Draney (Creighton University Chemistry)
Amrit Venkatesh (Lyndon Emsley Lab, EPFL)
Asif Equbal (Wasielewski lab, Northwestern University)
Blake Wilson (Robert Tycko Lab, NIH)
Michael Hope (Lyndon Emsley Lab, EPFL)
Mohamed Sabba (Malcolm Levitt Lab, UK)
Mouzhe Xie (Maurer Lab, Uni. Chicago)
Nino Wili (Niels Chr Nielsen Lab, Aarhus University)
Pinelopi Moutzouri (Lyndon Emsley Lab, EPFL)