Abstract
The fast-moving development of emerging portable electronics and the rise of electric transportation with smart grids promote the ever-growing demand for sustainable, environmentally-friendly, safe and large-scale electrochemical energy storage technologies. Notwithstanding lithium-ion batteries (LIBs) have dominated the current market as commonly used energy storage devices, the limited resources of lithium and the soaring costs have greatly restricted their long-lasting applications in the future.As a cost-effective successor to LIBs, sodium- and potassium-ion batteries (SIBs/PIBs) have aroused wide public concern because of their abundant reserves and identical rocking-chair mechanisms for facilitating large-scale implementations using the existing infrastructure for LIBs. However, SIBs/PIBs undergo unsatisfactory rate capability and poor cycling stability of carbonaceous anodes due to the large ionic radii, which impedes their practical applications. In this thesis, the first subject investigates the feasibility of ice-templated cellulose nanocrystals /poly(ethylene oxide) (CNCs/PEO)- derived carbon aerogels as anodes for SIBs/PIBs via studying the optimum parameters (e.g., suspension concentration, ice-templating directions, cooling rate, carbonisation temperature) of the ice-templating strategy. By tuning the cooling rate of the unidirectional ice-templating technique, the second subject focuses on developing vertically-aligned carbon aerogels with hierarchically tailored channels as anodes with high reversible capacities (~298 mAh g⁻¹ for SIBs and ~258 mAh g⁻¹ PIBs at 0.1 C) and excellent cyclabilities over 1000 cycles for SIBs/PIBs.
Sodium metal holds considerable promise as an anode material for high-energy density energy storage systems. However, the major impediments to the development of sodium-metal batteries (SMBs) are associated with uncontrolled dendrite growth, degradation of battery cycle life and an ultimate short-circuit when Na dendrites penetrate the separator to reach the cathode. Therefore, the third subject probes the employment of a novel bifunctional CNC-based nanofibrous separator with abundant sodiophilic functional groups and uniaxially-aligned arrays via a controllable alignment degree for SMBs, which achieves unprecedented long-term cycling performances at high current densities (≥ 1000 h at 1 and 3 mA cm⁻², ≥ 700 h at 5 mA cm⁻²) of symmetric cells in additive-free carbonate electrolytes. The organic-sodium full cells assembled with our separator also demonstrated its practical implementation.
These above-mentioned works both possess the additional merits of the sustainability of the precursors (i.e., renewable CNCs) and scalable availability at comparatively low cost in a one-step fabrication process, which also opens up unique avenues for the rational design of tailored aligned microstructures. Moreover, these unique strategies offer design guidelines to be readily extended to other metallic-based batteries for the large-scale implementation of sustainable energy storage technologies.
| Date of Award | 24 Jan 2023 |
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| Original language | English |
| Awarding Institution |
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| Supervisor | Steve Eichhorn (Supervisor) & Byung Chul (Eric) Kim (Supervisor) |