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.
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.
Electron microscopy and atom probe tomography of nanoindentation deformation in oxide dispersion strengthened steels
Scalable Multilayer Printing of Graphene Interfacial Layers for Ultrahigh Power Lithium-Ion Storage
© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim A low resistance graphene-based interfacial layer is developed for multilayered lithium-ion capacitor electrodes using a layer-by-layer printing approach, with the goal of boosting energy storage performance at ultrafast charge/discharge rates (≥100 C). The electrochemical behavior of spray printed Li4Ti5O12-based heterostructure electrodes is investigated as a thin, discrete graphene layer is placed: 1) at the base of the Li4Ti5O12 (at the electrode/current collector interface); 2) on the top of the Li4Ti5O12 (at the electrode/separator junction); and 3) both at the base and on the top of the Li4Ti5O12 (sandwich configuration), with marked improved electrode performance at >50 C when the graphene layer is interleaved at the Li4Ti5O12/current collector interface. This best performing heterostructure negative electrode is then coupled with a spray printed activated carbon positive electrode in a lithium-ion capacitor configuration, showing an attractive power density of ≈8000 W kg−1 at 350 C. The fabrication of double-sided graphene/Li4Ti5O12 multilayered heteroelectrodes is successfully demonstrated over areas of 20 cm × 15 cm and in various patterned configurations.
Effect of the sintering temperature on the microstructure and superconducting properties of MgB2 bulks manufactured by the field assisted sintering technique