Separating ion and electron transport kinetics in aqueous ion storage battery materials

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The proposed project seeks to employ novel time resolved X-ray spectroscopic and structural characterisation techniques to follow the oxidation state changes and (for some stored ions) the ion transport in real time, providing a detailed understanding of how these processes are interrelated and their effects on the structural integrity of the PBA based battery electrodes. Such information will enable a deeper understanding of the mechanisms of charging, discharge, and degradation of the PBA battery electrodes. These aims will be accomplished through completion of the following work packages and objectives:(i) Synthetic preparation of a series of PBA electrode materials and physical characterisation of these materials using conventional XRD and Raman analysis, followed fabrication of the materials into battery cathodes and characterisation of their charge/discharge capacities and rates for the storage of Na+, Mg2+, Ca2+, and Zn2+ in aqueous electrolytes. The objectives of this package are to benchmark the materials prepared against the best known in the literature and further understanding of the roles of PBA composition and structure on the storage capacities and charging rates of the electrode materials.(ii) Design and testing of an electrochemical cell to enable operando X-ray absorption spectroscopic (XAS) and X-ray diffraction (XRD) studies of the PBA battery electrodes, with the objective of ensuring that the operando XAS and XRD measurements to be conducted in (iii) and (iv) are representative of the ideal electrochemical cell geometry used in part (i).(iii) Collection of time-resolved X-ray absorption spectroscopic data using the operando cell, which will require interface of the electrochemical control system (a potentiostat) with the beamline hardware and software. The data acquired will uniquely enable understanding of the relative rates of the oxidation state changes of each of the metal ions in the PBA materials. (iv) Collection of operando XRD data to compliment the time resolved XAS conducted in part (iii), which will enable a deeper understanding of any accompanying structural changes to the PBA materials during ion storage and discharge as well as the effects of cycling (degradation). Accomplishing this objective will require implementation of an XRD detector and development of the data acquisition protocols.