Thesis
Improving charge transport in integrated MoO₃/C electrode materials for water-in-salt energy storage systems by incorporating oxygen vacancies
Master of Science (M.S.), Drexel University
Jun 2023
DOI:
https://doi.org/10.17918/00001693
Abstract
Improvements in the charge storage properties of [alpha]-MoO₃ used as an electrode with a 30 m ZnCl₂ water-in-salt electrolyte have been achieved by enhancements in electron and ion transport enabled by an inventive synthesis route. Electron transport was improved through the integration of MoO₃ with dopamine-derived carbon via a chemical preintercalation route, and enhanced ion transport was achieved by incorporating oxygen vacancies in MoO₃ structure through ethanol reduction under hydrothermal conditions. The presence of carbon was confirmed by corresponding D and G bands observed in Raman spectroscopy measurements. The presence of oxygen vacancies was proven through correlated XPS, TGA, Raman spectroscopy and XRD analyses, with the introduction of oxygen vacancies leading to an expanded interlayer region. Four-point probe measurements provided evidence of increased electronic conductivity due to the incorporation of carbon, and cyclic voltammetry-based charge storage mechanism analyses revealed increases in ion transport kinetics due to oxygen vacancy formation. The MoO_[3-x]/C electrode that was hydrothermally treated in the presence of chemically preintercalated dopamine and 50[mu]L of ethanol showed the highest discharge capacity and capacity retention of 243 mAh g⁻¹ and 99%, respectively, after 100 cycles at 1,000 mA g⁻¹; and the best rate capability, with a discharge capacity of 214 mA g⁻¹ at 2,000 mA g⁻¹. Tuning the oxygen vacancy concentration is critical, as excessive concentrations of these point defects leads to structural instability and poor capacity retention. This work demonstrates the combined potential of carbon and oxygen vacancies in moderate concentrations to enhance the charge storage properties of transition metal oxides. The strategies developed in this study offer a path to the development of promising materials for high-rate, high-capacity, and long-duration electrochemical energy storage technologies.
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Details
- Title
- Improving charge transport in integrated MoO₃/C electrode materials for water-in-salt energy storage systems by incorporating oxygen vacancies
- Creators
- Darrell Emake Mbeng Omo-Lamai
- Contributors
- Ekaterina Pomerantseva (Advisor)
- Awarding Institution
- Drexel University
- Degree Awarded
- Master of Science (M.S.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xix, 91 pages
- Resource Type
- Thesis
- Language
- English
- Academic Unit
- Materials (Science and) Engineering (Metallurgical Engineering) (1970-2026); College of Engineering (1970-2026); Drexel University
- Other Identifier
- 991020879311904721