Polaris

Description

The Polaris instrument at ISIS is a high intensity, medium resolution powder diffractometer. It is optimised for the rapid characterisation of structures, the study of small amount of materials (as little as ~1mm³), the collection of data sets in rapid time (with data collection times down to ~5 minutes), and the study of materials under non-ambient conditions.

Neutrons are ideal for the characterisation of materials with light elements i.e. H, Li as well as materials containing elements of similar mass i.e. Mn and Fe, while the high count rate of Polaris is well suited for time-resolved in-situ and in-operando studies. This combination makes Polaris the ideal instrument for structural characterisation of battery materials during cycling. In addition to standard diffraction experiments, Polaris is ideal for total scattering measurements due to its fast count rate, low instrumental background, and the wide angle detector coverage that provides a large accessible Q-range.

A relevant case study demonstrates the use of a custom made electrochemical cell with coin cell geometry on Polaris. The in situ study shows the structural evolution of the cathode material LiCoO₂ during charge. Excellent signal-to-noise allows Rietveld refinements of the data, and the cell has electrochemical performance comparable to commercial coin cells. Bo Dong et al. 2018 J. Electrochem. Soc. 165 A793.

Additional Resources

For more details on the instrument see https://www.isis.stfc.ac.uk/Pages/polaris.aspx

For more details on the instrument capability see https://aip.scitation.org/doi/pdf/10.1063/1.5099568