Critical Role of the Interphase at Magnesium Electrodes in Chloride-Free, Simple Salt Electrolytes

Holc, Conrad; Dimogiannis, Konstantinos; Hopkinson, Emily; Johnson, Lee R.

Abstract

Magnesium (Mg) batteries are a potential beyond lithium-ion technology but currently suffer from poor cycling performance, partly due to the interphase formed when magnesium electrodes react with electrolytes. The use of magnesium bis(trifluoromethanesulfonyl)imide (Mg(TFSI)2) electrolytes would enable high-voltage intercalation cathodes, but many reports identify poor Mg plating/stripping in the electrolyte solution due to a passivating interphase. Here, we have assessed the Mg plating/stripping mechanism at bulk Mg electrodes in a Mg(TFSI)2-based electrolyte by cyclic voltammetry, ex situ Fourier-transform infrared spectroscopy, and electron microscopy and compared this to the cycling of a Grignard-based electrolyte. Our studies indicate a nontypical cycling mechanism at Mg surfaces in Mg(TFSI)2-based electrolytes that occurs through Mg deposits rather than the bulk electrode. Fourier-transform infrared spectroscopy demonstrates an evolution in the interphase chemistry during conditioning (repeated cycling) and that this is a critical step for stable cycling in the Mg(TFSI)2-tetraglyme (4G) electrolyte. The fully conditioned electrode in Mg(TFSI)2-4G is able to cycle with an overpotential of

• Journal Article Type: Article
• Acceptance Date: Jun 4, 2021
• Online Publication Date: Jun 18, 2021
• Publication Date: Jun 30, 2021
• Deposit Date: Jul 15, 2021
• Publicly Available Date: Jun 19, 2022
• Journal: ACS Applied Materials and Interfaces
• Print ISSN: 1944-8244
• Electronic ISSN: 1944-8252
• Publisher: American Chemical Society (ACS)
• Peer Reviewed: Peer Reviewed
• Volume: 13
• Issue: 25
• Pages: 29708-29713
• DOI: https://doi.org/10.1021/acsami.1c06130
• Keywords: General Materials Science
• Public URL: https://nottingham-repository.worktribe.com/output/5693519
• Publisher URL: https://pubs.acs.org/doi/10.1021/acsami.1c06130
• Additional Information: This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Materials & Interfaces, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://doi.org/10.1021/acsami.1c06130