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Elucidating the Sodiation Mechanism in Hard Carbon by Operando Raman Spectroscopy

Weaving, JS; Lim, A; Millichamp, J; Neville, TP; Ledwoch, D; Kendrick, E; McMillan, PF; ... Brett, DJL; + view all (2020) Elucidating the Sodiation Mechanism in Hard Carbon by Operando Raman Spectroscopy. ACS Applied Energy Materials , 3 (8) pp. 7474-7484. 10.1021/acsaem.0c00867. Green open access

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Abstract

Operando microbeam Raman spectroscopy is used to map the changes in hard carbon during sodiation and desodiation in unprecedented detail, elucidating several important and unresolved aspects of the sodiation mechanism. On sodiation a substantial, reversible decrease in G-peak energy is observed, which corresponds directly to the sloping part of the voltage profile and we argue can only be due to steady intercalation of sodium between the turbostratic layers of the hard carbon. The corresponding reversibility of the D-peak energy change is consistent with intercalation rather than representing a permanent increase in disorder. No change in energy of the graphitic phonons occurs over the low-voltage plateau, indicating that intercalation saturates before sodium clusters form in micropores in this region. At the start of the initial sodiation there is no change in G- and D-peak energy as the solid electrolyte interphase (SEI) forms. After SEI formation, the background slope of the spectra increases irreversibly due to fluorescence. The importance of in situ/operando experiments over ex situ studies is demonstrated; washing the samples or air exposure causes the G- and D-peaks to revert back to their original states because of SEI removal and sodium deintercalation and confirms no permanent damage to the carbon structure.

Type: Article
Title: Elucidating the Sodiation Mechanism in Hard Carbon by Operando Raman Spectroscopy
Open access status: An open access version is available from UCL Discovery
DOI: 10.1021/acsaem.0c00867
Publisher version: https://doi.org/10.1021/acsaem.0c00867
Language: English
Additional information: This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions.
Keywords: operando Raman spectroscopy, hard carbon, sodium-ion batteries, sodiation mechanism, energy storage
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Engineering Science > Dept of Chemical Engineering
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery.ucl.ac.uk/id/eprint/10109126
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