My primary research interests are in the fields of solid state chemistry and electrochemistry; particularly solid state ionics, which embraces ionically conducting solids and intercalation compounds. I am interested in the fundamental science of ionically conducting solids (ceramic and polymeric materials) and intercalation compounds, in the synthesis of new materials with new properties or combinations of properties, in understanding these properties and in exploring their applications in new devices, especially energy storage devices such as rechargeable lithium batteries. Although ionically conducting solids represent the starting point for much of our research, we have extended our interests well beyond the confines of this subject alone.
Lithium intercalation into solid hosts is the fundamental mechanism underpinning the operation of electrodes in rechargeable lithium batteries. We seek to synthesise new lithium intercalation compounds with unusual properties or combinations of properties. We are especially interested in nanomaterials (e.g. mesoporous solids and inorganic nanotubes) since the nanoscale can enhance the intercalation properties.
Structure is the foundation on which much of modern chemistry is based. In the absence of single crystals it is important to be able to solve structures ab initio from powder X-ray or neutron diffraction data. We developed powerful direct space methods by which this can be achieved. Nanomaterials are important but establishing their structure (atomic arrangement) is difficult because the breakdown of long range order due to the confined dimensions negates the use of conventional crystallographic methods. We are exploring alternative approaches including Debye methods, which relate the atomic arrangement to the diffraction data without recourse to symmetry. All of the above methods allow access to the structures of compounds with a wealth of properties within and beyond materials chemistry.
Since the discovery of crown ethers and cryptands by Pederson, Cram and Lahn (for which they received the Nobel Prize in 1987), the significance of molecules containing the repeat units -CH2-CH2-O- as coordinating ligands for metal cations has been recognised. By combining salts and polyethers such as polyethylene oxide (-CH2-CH2-O-)n, it is possible to synthesise thousands of metal-polyether complexes, alternatively known as polymer electrolytes. Such materials are co-ordination compounds in the solid state and support ionic conductivity. For 30 years it was believed that ionic conductivity was confined to amorphous polymers above Tg and that crystalline polymers were insulators. We overturned this view with the discovery of crystalline polymer electrolytes. We are engaged in understanding the mechanism of ionic conductivity, increasing the conductivity by doping/modifying the polymers and exploring their applications in devices such as all-solid-state rechargeable lithium and sodium batteries.
THE Li-AIR BATTERY
Energy storage is critical to addressing climate change. The rechargeable lithium-ion battery has revolutionised portable electronics, it will be key to electrifying transport and to delivering secure and stable renewable electricity. However the highest energy density possible for Li-ion batteries is only double that of today and this is insufficient to meet future demands. The Li-air battery can exceed this energy density. We are investigating some of the exciting and interesting fundamental scientific challenges facing the Li-air battery.
SELECTED RECENT PUBLICATIONS
School of Chemistry, University of St Andrews, North Haugh, St Andrews, Scotland KY16 9ST.
Tel : +44 (0)1334 463 800, Fax : +44 (0)1334 463 808
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