Design, synthesis, and characterisation of transition-metal dicarboxylate anodes for lithium-ion batteries

Batteries play an increasingly critical role in the functioning of contemporary society. Current battery technology suffers from a number of shortcomings, including use of performance limited, expensive, non-renewable, and toxic materials. To ensure future proofing of battery technology, new materials and methods that overcome the current shortcomings need to be developed. The work in this thesis develops the use of transition-metal dicarboxylates as anode materials for Li ion batteries. A holistic approach to this development was taken, exploring the interdependency of the numerous parameters that affect the overall electrochemical performance. Specifically examined were how the chemical and physical properties of the active material and the electrode formulation impact the nano and microstructure of the electrodes and the mechanism of Li insertion. This project addresses the ambiguity in the organic electrode material (OEM) literature, with regards to the composition of reported dicarboxylic acid electrodes. The reaction between the acid and the copper current collector was considered and characterised, which led to the investigation into and development of the use of the metal-carboxylates. Chapter 1 details the general theory and principles behind batteries, with further exploration into the limitations of current lithium-ion battery technology. Subsequently, OEMs and metal organic frameworks (MOFs) are introduced and explored as emerging electrode materials that present the opportunity to combat some of these limitations. Chapter 2 provides the background theory and principles behind the analytical techniques and instrumentation used in this thesis. These techniques include small and ultra-small angle neutron ii scattering (SANS and USANS), X-ray diffraction (XRD), X-ray absorption spectroscopy (XAS), X-ray photoelectron spectroscopy (XPS), Mossbauer spectroscopy (MBS), nuclear magnetic resonance spectroscopy (NMR) and scanning electron microscopy (SEM). Techniques not commonly used in battery materials research and development are discussed in detail. Chapter 3 explores the electrochemistry of copper tartrate as a Li ion anode material. Insights into its unusual capacity increase with cycle number and high specific capacity of 744 mAhg-1 were gained through in depth characterisation of the electrode system. It was revealed that the capacity gain was likely related to the activation of electrochemical processes that were delayed due to the nano and microstructure of the electrode, specifically the large particle size distribution of the active material. Subsequently a novel formulation technique utilising the parent acid of copper tartrate, tartaric acid, is employed to improve the electrode nano and microstructure ultimately resulting in superior electrochemical performance. Chapter 4 dives deeper into the novel formulation techniques introduced in Chapter 3, expanding the range of acids, and consequently the range of copper dicarboxylates, that can be utilised. Here, the physical and chemical properties of the acids and the formulation methodology were demonstrated to impact the composition and nano and microstructure of the final electrode. These effects were then correlated to the observed differences in the electrochemical performance, namely, high solubility of the acid in the formulation solvent improved the electrode nano and microstructure, ultimately improving the electrochemical performance. The picture of the composition-structure-performance relationship was subsequently built to an extent that allowed a rational approach to acid and copper selection. Chapter 5 focuses on expanding the transition metal from copper to a wider range of transition-metal dicarboxylates. These were made using the syntheses techniques previously demonstrated. The effects of the electrode nano and microstructure on the electrochemical performance were further explored, which revealed significant correlation between the two. Subsequently, novel formulation techniques were employed to tune the electrode nano and microstructure and hence improve the electrochemical performance. Namely, utilising a formulation solvent that the active material was soluble in to decrease the active material particle size and increase the homogeneity in the electrode. iii This ultimately led to an iron (ii) tartrate electrode that achieved a specific capacity of 870 mAhg-1 Chapter 6 summarises the findings of Chapters 3, 4 and 5. Additionally, several key avenues of future work are discussed, drawing on preliminary results. These include assessment of the suitability of the metal-dicarboxylates for use in sodium ion batteries, further investigation into the mechanism of Li storage of the metal-dicarboxylates, optimisation of the active material loading and optimisation of the metal dicarboxylate syntheses. Overall, this work has resulted in an Australian Provisional Patent 2022902762 and a deeper understanding of the use of metal-dicarboxylates as anode materials for Li ion batteries.

Grantor dc:publisher

UNSW, Sydney

Year dc:date

2023

Author dc:creator

• Teusner, Matthew ; https://orcid.org/0000-0002-1480-6801

• Batteries
• materials characterisation
• electrochemistry
• anzsrc-for: 3403 Macromolecular and materials chemistry
• anzsrc-for: 3401 Analytical chemistry

Statement dc:rights

• open access
• CC BY 4.0
• free_to_read

Licence

• https://purl.org/coar/access_right/c_abf2
• https://creativecommons.org/licenses/by/4.0/

Language dc:language

en

Identifier

https://doi.org/10.26190/unsworks/24961

OAI identifier oai:identifier

oai:unsworks.library.unsw.edu.au:1959.4/101254