Brownrigg, A. et al. (2015). In situ Fe K-edge X-ray absorption spectroscopy study during cycling of Li2FeSiO4 and Li2.2Fe0.9SiO4 Li ion battery materials. Journal of Materials Chemistry A[Online]3:7314-7322.
In situ X-ray Absorption Spectroscopy (XAS) results are presented for Li2FeSiO4 and Li2.2Fe0.9SiO4, promising cathode materials for lithium-ion batteries. The aims are to establish the valence and local structure of Fe during charge and discharge to understand if the Fe3+/Fe4+ redox pair can be reached in the current battery design. It is found that the valence state changes between Fe2+ and Fe3+, with no evidence of Fe4+ before the onset of electrolyte degradation. There is a reversible contraction and extension of the FeO bond lengths during cycling while the FeSi distance remains constant, which underlines the stability of the Li2FeSiO4 material. The same observations apply to Li2.2Fe0.9SiO4 cathode material indicating that changing the stoichiometry does not provide any additional structural stability.
Kossoff, D. et al. (2014). Mine tailings dams: Characteristics, failure, environmental impacts, and remediation. Applied Geochemistry[Online]51:229-245.
Electrochromic (EC) performances of Ni3 + containing NiO thin films, called modified NiO thin films, prepared either by pulsed laser deposition or by chemical route are reported. When cycled in lithium based electrolyte, the comparison of the EC behavior of nonstoichiometric NiO thin films points out a larger optical contrast for the films synthesized by chemical route with the absence of an activation period on early electrochemical cycling due in particular to a larger porosity. Herein we demonstrate faster kinetics for modified NiO thin films cycled in lithium ion free electrolyte. Finally, X-ray absorption spectroscopy is used for a preliminary understanding of the mechanism involved in this original EC behavior linked to the film characteristics including their disorder character, the presence of Ni3 + and their porous morphology.
Vidal-Abarca, C. et al. (2012). Improving the cyclability of sodium-ion cathodes by selection of electrolyte solvent. Journal of Power Sources[Online]197:314-318.
A composite material containing orthorhombic Na1.8FePO4F and carbon is prepared by mechanical activation and ceramic procedures. The material is studied in sodium test cells as a potential candidate for sodium-ion battery cathodes. The effect of the solvents in the electrolyte on the electrochemical performance is analysed by X-ray absorption spectroscopy. The structural changes on cycling are small, while the changes in the oxidation state of iron agree with the sodium insertionextraction processes. The oxidation state is especially affected by the upper limit of the voltage window, and the discharge capacity is strongly affected when using propylene carbonate solvent. Capacity and capacity retention are higher for sodium cells using mixtures of ethylene carbonate and diethyl carbonate as the solvent of NaPF6 electrolytes.
Conference or workshop item
Woods, M. et al. (2014). Integrated Antenna-Battery for Low-profile Short Range Communications. in:EuCAP 2014.
An integrated antenna-battery was designed in order to function at 2.45GHz, with short range Bluetooth applications considered. The model was derived from a previous study in which an integrated system was first explored. The tan was investigated for the substrate and this new structure was found to give favourable gains and efficiencies compared to the previous study. Experimental parameters were also applied to the model in the presence of a dielectric material. These experimental