My research takes place at the interface between advanced materials and manufacturing, and concerns a wide range of structural and functional materials. Current activity includes structured electrodes for supercapacitors and batteries, 3D printed materials with spatially varying electromagnetic properties for microwave devices, and advanced metallics for power generation. Recent work has also concerned X-ray imaging of microstructural evolution, especially of solidifying alloys.
My research uses manufacturing techniques used in industry, such as vacuum plasma spraying and field assisted sintering, alongside in-house developed novel processes such as spray deposition of multi-suspensions and 3D printing of dielectric materials. We make use of numerical modelling for device design, to provide insights into underlying process physics, and to understand how heat and mass flows control the final microstructure and properties. All the research involves close collaboration with industry and other universities across the UK and the world.
4D Bragg Edge Tomography of Directional Ice Templated Graphite Electrodes
Journal of Imaging
<jats:p>Bragg edge tomography was carried out on novel, ultra-thick, directional ice templated graphite electrodes for Li-ion battery cells to visualise the distribution of graphite and stable lithiation phases, namely LiC12 and LiC6. The four-dimensional Bragg edge, wavelength-resolved neutron tomography technique allowed the investigation of the crystallographic lithiation states and comparison with the electrode state of charge. The tomographic imaging technique provided insight into the crystallographic changes during de-/lithiation over the electrode thickness by mapping the attenuation curves and Bragg edge parameters with a spatial resolution of approximately 300 µm. This feasibility study was performed on the IMAT beamline at the ISIS pulsed neutron spallation source, UK, and was the first time the 4D Bragg edge tomography method was applied to Li-ion battery electrodes. The utility of the technique was further enhanced by correlation with corresponding X-ray tomography data obtained at the Diamond Light Source, UK.</jats:p>
High energy lithium ion capacitors using hybrid cathodes comprising electrical double layer and intercalation host multi-layers
Energy Storage Materials
© 2020 Elsevier B.V. The ability to recharge and to deliver high capacity quickly is required for the next generation of lithium ion storage technologies, especially for pure electric vehicles. A new type of hybrid positive electrode for lithium ion capacitors is investigated that comprises discrete layers of high power capacitive activated carbon and high capacity insertion-type LiFePO4, with the aim of boosting energy density towards that of a lithium ion battery while preserving capacitor-like power capability over thousands of charge/discharge cycles. The electrochemical performance of these hybrid electrodes was investigated both as a function of the LiFePO4 weight fraction (its thickness in the multi-layered electrode arrangement) and its location within the multi-layer. The best performing hybrid positive electrode architecture delivered an attractive balance of an energy density of ~ 90 Wh/kg and a power density of ~ 15 kW/kg in a full lithium ion capacitor configuration, which outperformed other combinations of the same materials. The ability to produce a double-sided configuration of the hybrid layered electrode over 20 × 20 cm2 was demonstrated, confirming the potential scalability of layer-by-layer manufacture.
In situ mapping of chemical segregation using synchrotron x-ray imaging