High voltage positive electrodes for high energy lithium-ion batteries

Abstract

Lithium-ion high voltage cathode materials are discussed within this thesis, with LiCoPO4 as a composite electrode evaluated for use as the active compound within lithium half-cells. A comprehensive literature review on lithium containing cathode materials with a focus on high voltage materials is provided. The majority of the materials within this work were synthesised using solvothermal techniques, which were characterised through XRD and SEM. Composite type electrodes were prepared through mainly using PTFE as the binder material, and different electrolytes were also investigated.

Composite electrodes were electrochemically evulated with competitive capacites obtained compared to the literature. The performance of the LiCoPO4 composite electrodes was found to be significantly different and attributed to the use of different synthesis solvents and heating conditions used for synthesis. The rate performance and electrochemical cycling was found to depend highly on the surface area and particle size of the composite electrode. XANES and in-situ XRD was performed at Diamond Light Source (UK synchrotron), where the LiCoPO4 charge profile was fully characterised. It was found that LiCoPO4 undergoes transient lattice parameter changes during charging, and that phase recovery during any relaxations was observed.

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ORCID for Andrew Hector: orcid.org/0000-0002-9964-2163

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