The Library
Metal oxides for high-rate, high-capacity anodes for Li-ion batteries
Tools
Wheeler-Jones, Evangeline (2022) Metal oxides for high-rate, high-capacity anodes for Li-ion batteries. PhD thesis, University of Warwick.
|
PDF
WRAP_Theses_Wheeler-Jones_2022.pdf - Submitted Version - Requires a PDF viewer. Download (18Mb) | Preview |
Official URL: http://webcat.warwick.ac.uk/record=b3910180
Abstract
This work synthesised a range of Nb2O5 and MoO2 materials and produced a selection of novel composites through the combination of these oxides. These materials were characterised using a number of experimental techniques and their properties towards Li-ion storage were investigated to assess their use in Li-ion battery technology. All materials were produced via a simple hydrothermal preparation at 225 C and in some cases, the use of a subsequent short heat-treatment step up to 1300 C. The structure of the materials were characterised using X-ray diffraction and the particle properties were studied by microscopy, particle size analysis, thermal gravimetric analysis and N2 adsorption analysis. All materials were cast into electrodes and tested against Li to establish their electrochemical abilities via cycling, cyclic voltammetry, and impedance spectroscopy.
Within the Nb2O5 family of materials an anisotropically crystalline, orthorhombic (T-) and monoclinic (H-) forms were produced. All materials show high-rate capability, although T-Nb2O5 has been favoured in the previous literature. This work presents H-Nb2O5 as a more capable high-rate anode, where long-term cycling at 100 C gave capacities of 50 mAhg-1 after 400 cycles. As for MoO2, the nature of the Li-ion storage mechanism is investigated using a range of electrochemical tests and ex-situ X-ray diffraction on cycled electrodes, where evidence of conversion, intercalation and pseudocapacitive mechanisms was apparent. Moreover, the activation process that MoO2 exhibits was determined to be from a change in symmetry from monoclinic to tetragonal. The MoO2 materials struggle to reach the high capacities expected from previous literature, yet significant knowledge is gained from their electrochemical characterisation. A range of composite oxides are synthesised with the ratios, 10:90, 20:80, 50:50, 80:20 and 90:10 of Nb2O5:MoO2. The 50:50 composite shows the most promising electrochemical results, where heat-treatment was used to improve the electrochemical properties significantly. As such, capacities of 515 mAhg-1 were achieved after low rates (200 cycles at 1C) and 105 mAhg-1 at high rates (400 cycles at 100C). In summary, this thesis studies structural and electrochemical properties of Nb2O5 and MoO2 and presents novel composite materials for high capacities and high charging rates in an anode material for potential use in Li-ion batteries.
Item Type: | Thesis (PhD) | ||||
---|---|---|---|---|---|
Subjects: | T Technology > TK Electrical engineering. Electronics Nuclear engineering | ||||
Library of Congress Subject Headings (LCSH): | Lithium ion batteries, Anodes -- Materials, Storage batteries, Metallic oxides, Electric batteries -- Electrodes | ||||
Official Date: | March 2022 | ||||
Dates: |
|
||||
Institution: | University of Warwick | ||||
Theses Department: | Warwick Manufacturing Group | ||||
Thesis Type: | PhD | ||||
Publication Status: | Unpublished | ||||
Supervisor(s)/Advisor: | Loveridge, Melanie ; Walton, Richard I. | ||||
Format of File: | |||||
Extent: | 301 pages : colour illustrations, charts | ||||
Language: | eng |
Request changes or add full text files to a record
Repository staff actions (login required)
View Item |