Novel Electrodes for Enhanced Selective Lithium Recovery from Brines via Capacitive Deionization

Yu, Hanwei

Novel Electrodes for Enhanced Selective Lithium Recovery from Brines via Capacitive Deionization

Yu, Hanwei

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Publication Type:: Thesis
Issue Date:: 2025

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Field	Value	Language
dc.contributor.author	Yu, Hanwei
dc.date.accessioned	2026-04-28T01:07:30Z
dc.date.available	2026-04-28T01:07:30Z
dc.date.issued	2025
dc.identifier.uri	http://hdl.handle.net/10453/194814
dc.description	University of Technology Sydney. Faculty of Engineering and Information Technology.	en_US.UTF-8
dc.description.abstract	The growing global demand for lithium (Li), driven by its critical role in energy storage systems, necessitates exploring sustainable and efficient methods for Li extraction from alternative aqueous resources. However, the low concentration of Li and the presence of competing ions pose significant challenges for selective Li extraction from brines. Capacitive deionization (CDI), an emerging electrochemical separation technology, offers advantages such as low energy consumption, mild operational conditions, and environmental compatibility. Nevertheless, conventional CDI suffers from poor ion selectivity, especially for Li recovery from complex ionic matrices. This thesis addresses the challenge of enhancing Li selectivity in CDI by systematically investigating three material-based strategies: (i) size-sieving effect using metal-organic framework (MOF) coatings, (ii) Donnan effect via sulfonated membrane integration, and (iii) structural memory effect using Li-ion sieve (LIS) materials. Commercial AC electrodes were first modified with ZIF-8-based composite coatings to evaluate Li selectivity enhancement through subnano-scale size exclusion. Results showed that the presence of ZIF-8-PDA significantly improved Li selectivity and removal percentages in Li/Na and Li/K systems, with selectivity values reaching 1.50 and 1.85 under 0.5 V, respectively. To investigate charge-based selectivity, sulfonated poly ether ketone (SPEK) membranes with varying degrees of sulfonation were coated onto AC electrodes. In the Li/K system, Li removal percentages increased by 2.12–2.86 times, and Li selectivity improved by 1.21–1.56 times compared to unmodified AC electrodes. While sulfonation degree had little influence in monovalent systems, it had notable impact in divalent systems, with SPEK-60 enabling sequential Li recovery. Nevertheless, overall selectivity was lower than the size-sieving approach, indicating that the external electric field in CDI suppresses the Donnan effect. Recognizing these limitations, finally, LIS materials based on Li₂TiO₃-type lithium titanate oxide (LTO) were fabricated into CDI electrodes to leverage their structural memory effect for selective Li capture. When tested using simulated SWDB, the LTO-based electrodes exhibited superior Li selectivity above 100 over 10 cycles. These results confirmed that structurally selective materials outperform conventional AC modifications under practical CDI conditions. In summary, this thesis advances the development of selective CDI technologies for Li recovery by systematically comparing three ion separation mechanisms. The research demonstrates that among the strategies investigated, the use of LIS-based electrodes provides the most promising pathway toward scalable, energy-efficient, and high-selectivity Li extraction from diluted aqueous resources. The thesis concludes with recommendations for future work, emphasizing pilot-scale validation, cycling stability, and regeneration optimization to enhance CDI-based Li recovery from complex, low-grade brines.	en_US.UTF-8
dc.format	Thesis (PhD)
dc.language.iso	en_US	en_US.UTF-8
dc.relation	https://opus.lib.uts.edu.au/bitstream/10453/194814/1/thesis.pdf
dc.rights	info:eu-repo/semantics/openAccess
dc.rights	The author owns the copyright in this thesis including all reproduction and reuse rights for the work. The work may not be altered without the permission of the copyright owner. Attribution is essential when quoting or paraphrasing from this thesis.
dc.rights	© 2025 Hanwei Yu
dc.rights	au.edu.uts.lib/cph
dc.title	Novel Electrodes for Enhanced Selective Lithium Recovery from Brines via Capacitive Deionization	en_US.UTF-8
dc.type	Thesis
utslib.copyright.status	open_access	*
utslib.copyright.embargo	2026-02-20T00:00:00+1000

Abstract:

The growing global demand for lithium (Li), driven by its critical role in energy storage systems, necessitates exploring sustainable and efficient methods for Li extraction from alternative aqueous resources. However, the low concentration of Li and the presence of competing ions pose significant challenges for selective Li extraction from brines. Capacitive deionization (CDI), an emerging electrochemical separation technology, offers advantages such as low energy consumption, mild operational conditions, and environmental compatibility. Nevertheless, conventional CDI suffers from poor ion selectivity, especially for Li recovery from complex ionic matrices. This thesis addresses the challenge of enhancing Li selectivity in CDI by systematically investigating three material-based strategies: (i) size-sieving effect using metal-organic framework (MOF) coatings, (ii) Donnan effect via sulfonated membrane integration, and (iii) structural memory effect using Li-ion sieve (LIS) materials. Commercial AC electrodes were first modified with ZIF-8-based composite coatings to evaluate Li selectivity enhancement through subnano-scale size exclusion. Results showed that the presence of ZIF-8-PDA significantly improved Li selectivity and removal percentages in Li/Na and Li/K systems, with selectivity values reaching 1.50 and 1.85 under 0.5 V, respectively. To investigate charge-based selectivity, sulfonated poly ether ketone (SPEK) membranes with varying degrees of sulfonation were coated onto AC electrodes. In the Li/K system, Li removal percentages increased by 2.12–2.86 times, and Li selectivity improved by 1.21–1.56 times compared to unmodified AC electrodes. While sulfonation degree had little influence in monovalent systems, it had notable impact in divalent systems, with SPEK-60 enabling sequential Li recovery. Nevertheless, overall selectivity was lower than the size-sieving approach, indicating that the external electric field in CDI suppresses the Donnan effect. Recognizing these limitations, finally, LIS materials based on Li₂TiO₃-type lithium titanate oxide (LTO) were fabricated into CDI electrodes to leverage their structural memory effect for selective Li capture. When tested using simulated SWDB, the LTO-based electrodes exhibited superior Li selectivity above 100 over 10 cycles. These results confirmed that structurally selective materials outperform conventional AC modifications under practical CDI conditions. In summary, this thesis advances the development of selective CDI technologies for Li recovery by systematically comparing three ion separation mechanisms. The research demonstrates that among the strategies investigated, the use of LIS-based electrodes provides the most promising pathway toward scalable, energy-efficient, and high-selectivity Li extraction from diluted aqueous resources. The thesis concludes with recommendations for future work, emphasizing pilot-scale validation, cycling stability, and regeneration optimization to enhance CDI-based Li recovery from complex, low-grade brines.

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