Operando monitoring of the solution-mediated discharge and charge processes in a Na-O2 battery using liquid-electrochemical Transmission Electron Microscopy

Lutz, Lukas; Dachraoui, Walid; Demorti�re, Arnaud; Johnson, Lee R.; Bruce, Peter G.; Grimaud, Alexis; Tarascon, Jean-Marie

Abstract

Despite the fact that in sodium-oxygen (Na-O2) batteries show promise as high-energy storage systems, this technology is still the subject of intense fundamental research, owing to the complex reaction by which it operates. To understand the formation mechanism of the discharge product, sodium superoxide (NaO2), advanced experimental tools must be developed. Here we present for the first time the use of a Na-O2 micro-battery using a liquid aprotic electrolyte coupled with fast imaging transmission electron microscopy to visualize, in real time, the mechanism of NaO2 nucleation/growth. We observe that the formation of NaO2 cubes during reduction occurs by a solution-mediated nucleation process. Furthermore, we unambiguously demonstrate that the subsequent oxidation of NaO2, of which little is known, also proceeds via a solution mechanism. We also provide insight into the cell electrochemistry via the visualization of an outer shell of parasitic reaction product, formed through chemical reaction at the interface between the growing NaO2 cubes and the electrolyte, and suggest that this process is responsible for the poor cyclability of Na-O2 batteries. The assessment of the discharge- charge mechanistic in Na-O2 batteries through operando electrochemical TEM visualization should facilitate the development of this battery technology.

Citation

Lutz, L., Dachraoui, W., Demortière, A., Johnson, L. R., Bruce, P. G., Grimaud, A., & Tarascon, J.-M. (in press). Operando monitoring of the solution-mediated discharge and charge processes in a Na-O2 battery using liquid-electrochemical Transmission Electron Microscopy. Nano Letters, 18(2), https://doi.org/10.1021/acs.nanolett.7b04937

• Journal Article Type: Article
• Acceptance Date: Jan 11, 2018
• Online Publication Date: Jan 22, 2018
• Deposit Date: Mar 27, 2018
• Publicly Available Date: Jan 23, 2019
• Journal: Nano Letters
• Print ISSN: 1530-6984
• Electronic ISSN: 1530-6992
• Publisher: American Chemical Society
• Peer Reviewed: Peer Reviewed
• Volume: 18
• Issue: 2
• DOI: https://doi.org/10.1021/acs.nanolett.7b04937
• Keywords: Na-O2 battery; Solution-mediated mechanism; Discharge and charge processes; Operando TEM; Parasitic product formation
• Public URL: https://nottingham-repository.worktribe.com/output/906476
• Publisher URL: https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.7b04937
• Additional Information: This document is the Accepted Manuscript version of a Published Work that appeared in final form in Nano Letters, copyright © American Chemical Society after peer review and technical editing by the publisher. To access the final edited and published work see https://pubs.acs.org/doi/abs/10.1021/acs.nanolett.7b04937
• Contract Date: Mar 27, 2018