Advanced diffraction methods for characterisation of li-ion battery materials
The development of ‘NMC’ cathode materials (generic formula LiNixMnyCozO2) is centred on the reduction in cobalt concentration driven by cost, safety and sustainability factors. However, departures from the traditional 111 ratio to high Ni contents (811 an beyond), has proven problematic owing to enhanced degradation rates, and requirements for more complex processing. Whilst the phase changes associated with lithiation of high Ni content cathodes remains the subject of on-going debate, the long term cycling performance is barely understood.
Here we propose to utilise a combination of high throughput XRD afforded by the ESRF upgrade to rapidly map the chemical and crystallographic changes associated with charge cycling. Meanwhile XRD-CT are used to provide spatially reconciled crystallographic and morphological information to improve understanding of the degradation processes occurring over extended cycling. Whilst much of this work is conducted using bespoke operando cells, we also explore the application of these diffraction techniques to larger format, technologically relevant cells (for example the ubiquitous 18650 geometry) to understand macroscopic chemical and thermal gradients.
Working in partnership with Johnson Matthey, we proactively translate these new methods to industry, providing new benchmarks to evaluate cathode materials, and understand their operation and degradation behaviour. We anticipate extensive academic impact through journal publications and conference presentations, alongside unique mobility benefits for the students, which include opportunities at JM, and NREL.