CDT Advanced Materials Characterisation

Correlative X-ray and Neutron Studies of Li-ion Battery Performance and Degradation

Supervisor	Professor Paul Shearing
University	University College London
Industry Co-Sponsor	Diamond Light Source
Project Description	The Li-ion battery was one of the transformative technologies of the 20th century and promises to have wider impact in the 21st century with the rapid uptake of electric vehicles. Battery degradation remains one of the most pressing issues facing vehicle electrification and is also critical across a range of industries from consumer electronics to aerospace. The increasingly demanding applications for Li-ion batteries mandate an improved understanding of the performance, degradation and failure of both materials and devices, and moreover motivates the exploration of new chemistries for post Li-ion batteries. To advance this understanding, researchers have a portfolio of microscopy, spectroscopy, diffraction and analytical tools, and the increasing trends towards multi-modal and in-situ or operando characterisation provides an opportunity probe the highly correlated physio-chemical phenomena associated with battery operation and degradation. For example, neutron techniques provide a high degree of complementarity to X-ray tools with their sensitivity to nuclear and electron density respectively. In this programme, the student will develop combined neutron imaging and diffraction tools, alongside novel X-ray imaging techniques – in concert, these tools provide an understanding of battery operation and degradation from the ‘atom to the device’ level. Leveraging the world leading capabilities across Diamond, ISIS and UCL, there is a unique opportunity to understand and explain degradation phenomena that arise during battery operation (for example as a function of voltage, temperature or cycle life), which will inform new approaches to materials and device, design and operation.
Key Techniques	Our recent work using high resolution X-ray imaging has yielded significant insight into the changing morphology of these materials at sub-micron length scales. However, these investigations are limited; firstly by the field of view (FoV) for high resolution X-ray computed tomography (CT) (FoV <1 mm) which necessitate the use of miniaturized bespoke cells, and secondly the high X-ray attenuation of NMC for large samples making the investigation of commercial cells challenging. This project will leverage the unique capabilities of both Diamond Light Source and ISIS to address these challenges: advanced X-ray imaging approaches (including laminography) will enable us to improve the physical size of the cell investigated whilst retaining high resolution, whilst neutron imaging and diffraction will provide the sensitivity to light elements, where the relative neutron transparency of common cell construction materials will allow investigation of technologically relevant form factors. These techniques will provide significant complementarity; in terms of sensitivity to the numerous components inside commercial cells (neutron sensitivity to nuclear density, and X-ray sensitivity to electron density); the time and length scales that can be resolved (from unit cell to full device), and the ability to quantify and correlate morphology, chemistry and crystallography. The effective combination of these techniques will provide a platform for numerous investigations of cell performance and degradation, these include evaluation of cell lifetime as a function of operational variables including rate, temperature and voltage window. Neutron imaging will allow us to isolate areas of enhanced/diminished electrochemical activity and/or gas generation, which are signatures of cell degradation. This study will provide a macroscopic view of the cell performance (for example reconciling activity as a function of distance to current collector tab). X-ray imaging including laminography will extend the temporal and spatial resolution of the measurements to examine electrode morphology evolution. In combination the imaging tools will also provide a priori information to inform higher resolution quantitative studies using neutron diffraction; for example quantifying the local crystallography/chemistry of NMC cathodes as a function of voltage and cycle life.

For information on how to apply for this project please visit cdt-acm.org/phd-opportunities

Joshua Bailey
Being part of the CDT-ACM was an all-round fantastic experience; I not only received great training in a range of advanced characterisation techniques, but I also made strong links with industry and strong bonds with my cohort which have both led to fruitful collaborations.