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Continuous Hydrothermal Flow Synthesized Transition Metal Oxides and Chalcogenides for Secondary Energy Storage Systems

Xu, Yijie; (2022) Continuous Hydrothermal Flow Synthesized Transition Metal Oxides and Chalcogenides for Secondary Energy Storage Systems. Doctoral thesis (Ph.D), UCL (University College London). Green open access

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Abstract

Efficient energy storage is the key to faciltating the widespread use of portable electronics, electric and hybrid vehicles, and residential energy storage. Recently, technologies such as Li-ion, Na-ion and Zn-air batteries have been identified as suitable solutions for energy storage devices. Li-ion and Na-ion -based systems have the capability to provide high gravimetric and volumetric energy densities together with the ability to supply energy for demanding, high-power applications. Zn-air batteries combine the best aspects of fuel-cell and a conventional redox battery in a single package, providing high volumetric energy density, improved safety aspects, ease of transportation, and the ability to work in an open-system under atmospheric conditions. However, existing synthesis methods may not be optimal for industrial applications, where a continuous, scaleable, environmentally-friendly, and consistent approach is desirable. To meet such requirements, Continuous Hydrothermal Flow Synthesis (CHFS) provides a suitable approach that allows for the scaleable production of nanomaterials, such as metal oxides, sulfides, or composite materials, with high physical consistency and narrow size distributions. Moreover, CHFS is particularly suited for combinatorial studies on the effects of dopant introduction and compositional variation on compounds of interest, as the output formulaic composition can be finely-tuned through control over the precursor concentration and flow rates. In this study, CHFS has been utilized to produce phase-pure nanostructured electrode materials for the first time. In Li-ion and Na-ion half-cells, nanostructured sodium titanate and cobalt nickel sulfide were investigated as an insertion and conversion anode materials, respectively. The high surface area sodium titanates exhibited additional pseudocapacitive charge storage mechanisms the became more pronounced in Na-ion half-cells. For the cobalt nickel sulfides, in-situ carbon-coating and post-synthesis heat-treatments were shown to increase cycling stability and specific capacity of the anode material, with the former introducing pseudocapacitive charge storage mechanisms and aiding in buffering destructive volume change, while the latter aiding in the evolution of structurally stable monometallic phases capable of synergistic interactions with bimetallic sulfide components. Cobalt nickel sulfides were also evaluated as bifunctional electrocatalysts and as air-cathodes for Zn-air batteries, where their performance was optimized by altering their formulaic composition through varying the proportion of its metallic precursors, and the introduction of tertiary transition-metal dopants. The improved performance was attributed to the high surface area, the favourable tuning of existing nickel and cobalt cation ratios, and the inherent activity of the dopant cations themselves.

Type: Thesis (Doctoral)
Qualification: Ph.D
Title: Continuous Hydrothermal Flow Synthesized Transition Metal Oxides and Chalcogenides for Secondary Energy Storage Systems
Open access status: An open access version is available from UCL Discovery
Language: English
Additional information: Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) Licence (https://creativecommons.org/licenses/by-nc/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.
UCL classification: 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
UCL
URI: https://discovery.ucl.ac.uk/id/eprint/10142829
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