In-situ studies of Li ion electrode surfaces

The continued development and deployment of batteries and in particular Lithium-ion batteries is essential to decarbonising the global energy economy. They are needed for future transport systems and stabilising electrical grids with high penetrations of renewable generation. The University of Sheffield has recently constructed the world's largest Lithium Titanate (LTO) battery connected to the UK's electrical grid at Willenhall. This batter comprises 23,000 20AH Toshiba SCiB cells, all of which need to be monitored individually. Understanding the aging of these cells is essential to device operation and safety.

Perhaps the most sensitive aspect of any Li-ion battery is the formation of a Solid Electrolyte Interface SEI) at both the positive and negative terminals. Without this interface L-ion batteries would be chemically unstable. Yet as batteries age the SEI contributes increasingly to internal impedance and results in decreased efficiency and the increasing likelihood of run-away heating and explosion. The objective of this proposal is to use advanced X-ray and other characterisation techniques to understand the structure and chemistry of SEIs in LTO batteries, and how these change in time. We propose to use batteries from Sheffield's grid connected battery for part of the project, thus contributing to a much larger international project.

This PhD programme will develop model electrode interfaces (replicating current research chemistries and materials) which are designed to allow for in-situ investigations using neutron and x-ray scattering techniques. Experiments will be conducted on large (cm2) planar interfaces using neutron and x-ray reflectivity whilst bulk phase studies will be conducted using neutron and x-ray small angle and wide angle scattering. Both will seek to yield structural and chemical information on the angstrom to nanometre lengthscale.
The research will therefore involve access to large scale experimental facilities such as the Diamond Synchrotron and Rutherford neutron labs (Oxford) and The European Synchrotron and ILL (Grenoble, France).

The results of this study will provide a greater understanding of the structural and chemical changes which occur during the devices life cycle and will help shape the development of future energy storage systems.