Wang, Yanfang 
ORCID: 0000-0002-5837-7674
(2024).
Breaking the ceiling of capacity limit via anion redox reactions.
University of Birmingham.
Ph.D.
|
Wang2024PhD.pdf
Text - Accepted Version Available under License All rights reserved. Download (17MB) | Preview |
Abstract
Anion redox reactions (ARRs) in lithium rich cathode materials (LRCMs) have attracted great attention due to their potential for delivering extra capacities beyond traditional cation redox activities. This thesis presents a study to stabilize the ARRs in LRCMs via developing the understanding of the nature of the oxygen redox activities and tailoring rational local structures to suppress the ARR-induced structural degradations (i.e., oxygen loss and transition metal (TM) migration).
Chapter 1 introduces a background to the field, including basic knowledge about lithium-ion batteries (LIBs), previous understanding of ARRs, and challenges for their future success in practical utilizations. The characterization techniques and experimental details are described in Chapter 2.
Monitoring the local coordination evolutions induced by ARRs and Ru redox reactions was carried out on the archetypal Li2RuO3 by using in-situ Raman spectroscopy. As detailed in Chapter 3, both the Raman-active Ru-Ru motions and the emergence of the O-O dimers were tracked and interpreted in combination with multimodal characterization techniques.
A F-doping study was conducted on Li2RuO3, as described in Chapter 4. Although F-dopants did not stabilize the ARRs, trace amount of F-doping improved the cycling stability of the Ru redox reactions. Such a performance enhancement was attributed to the effects of F-dopants on relaxing the interlayer repulsions and altering the preferential orientations.
In Chapter 5, a metastable O6-phase was reported to demonstrate stable cation and anion redox reactions under long-term operation. The hidden mechanisms underneath its structural stability were investigated by using a plenty of techniques including ex-situ/ in-situ X-ray diffraction (XRD), ex-situ X-ray absorption spectroscopy (XAS), ex-situ/ in-situ Raman spectroscopy, ex-situ electromagnetic resonance spectroscopy (EPR), ex-situ X-ray photoelectron spectroscopy (XPS), and electrochemical analyses. Unlike the edge-sharing local structures in the traditional O3-phase, the O6-phase presented the face-sharing geometry between the TMO2 and LiO2 slabs, in which the interlayer TM migration was suppressed.
An interferometric scattering microscopy (iSCAT) setup was introduced in Appendix C, which was built to track the ARR-induced evolutions at the single particle level via using nondestructive visible light as the probe.
| Type of Work: | Thesis (Doctorates > Ph.D.) | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Award Type: | Doctorates > Ph.D. | |||||||||||||||
| Supervisor(s): |
|
|||||||||||||||
| Licence: | All rights reserved | |||||||||||||||
| College/Faculty: | Colleges (2008 onwards) > College of Engineering & Physical Sciences | |||||||||||||||
| School or Department: | School of Chemistry | |||||||||||||||
| Funders: | None/not applicable | |||||||||||||||
| Subjects: | Q Science > Q Science (General) Q Science > QD Chemistry |
|||||||||||||||
| URI: | http://etheses.bham.ac.uk/id/eprint/14536 |
Actions
 |
Request a Correction |
 |
View Item |
Downloads
Downloads per month over past year