New assembled heterogeneous layered materials as high capacity rechargeable battery materials

This joint research studentship (Oxford University, Diamond Light Source, EPSRC) is for research and development of novel prototype battery systems based on new assembled inorganic heterogeneous layered materials to store energy from renewable sources (wind or solar) by reversibly intercalating Li or Na metal atoms therein. This approach offers considerable potential for the practical capture of renewable energy and release (or buffer) to electrical devices/appliances in the period of no light or wind. Hence this project falls within the EPSRC 'energy' research area. When it comes to this kind of large-scale renewable power system, we are particularly interested in those that operate on Na ions. In contrast to lithium, sodium is one of the most abundant elements in the Earth's crust and is hence economically more desirable than lithium for realizing large scale power source. Using the experience and expertise of advanced material synthesis, the Oxford group will produce MoS2 and related layered structures with desirable properties (high capacity and durable, short charge/discharge cycle) for battery application. It is exciting to assemble 2-D layer materials of different nature (MoS2-graphene; MoS2-WS2) into functional 3-D materials for battery applications since new interactions may be tailored between layers of different structural or electronic influence. Particularly, conjugated linker molecules may be used to allow re-stacking of these layer structures (i.e. filling of sulphur vacancies of MoS2 by conjugated dithio-compounds). The Tsang group at Oxford University has recently reported some new chemical methods to synthesize single molecular layer oxide and sulphide materials. Also of note is a recent breakthrough from the group to identify a range of surface sites for metal ions on single layer MoS2 (Nature Chem., 2016 accepted). Preliminary data show that re-stacked single layers of MoS2 offers much higher energy density storage without deactivation than bulk during cycling alkali metal. It is important to collect high quality structural data for detailed material characterisation. This will be done by the student supervised by beamline scientists at Diamond using high-resolution powder diffraction (I11) for structural-electrochemical data for refinements, as well as XANES to work out electronic changes, and EXAFS (B18) to determine local structures and molecular spectroscopy to estimate the organic linker species for structural details. Most importantly, in operando experiments are required to correlate the structural changes and electrochemistry using coil cells containing the assembled structures. Battery coin cells will be produced from selected samples to be used for operando time-resolved powder diffraction, long duration and X-ray absorption studies. Our ambitious programme will generate high quality science from the synthesis and in operando synchrotron studies. High impact publications and conference presentations from Diamond facilities are expected including technological spin-off from the prototype development.