Case Study: Resolving the chemistry inside commercial cylindrical Li-ion batteries with X-ray diffraction computed tomography (XRD-CT)

Companies involved:

Finden Ltd, University College London, DESY, Alan A. Coelho, STFC’s SciML

Challenge:

Li-ion batteries (LiBs) have dominated the energy storage market finding applications in portable electronic devices, electric vehicles and grid storage. Over the past decade, X-ray imaging techniques have attracted a lot of interest as diagnostic tools for LiBs however conventional methods most often fail to resolve the chemistry inside commercial devices.

Sample:

Commerical NMC532 Li-ion battery cells

Solution:

Synchrotron high-energy X-ray diffraction computed tomography (XRD-CT) was employed to investigate, for the first time, commercial cylindrical Li-ion batteries electrochemically cycled over the two cycling rates of C/2 and C/20. This technique yielded maps of the crystalline components and chemical species as a cross-section of the cell with high spatiotemporal resolution (550 x 550 images with 20 x 20 x 3 µm³ voxel size in ca. 1 h). The recently developed Direct Least-Squares Reconstruction algorithm was used to overcome the well-known parallax problem and led to accurate lattice parameter maps for the device cathode.

Benefits:

Chemical heterogeneities were revealed at both electrodes and were attributed to uneven Li and current distributions in the cells. It was shown that the XRD-CT technique has the potential to become an invaluable diagnostic tool for real-world commercial batteries and for their characterization under operating conditions, leading to unique insights into “real” battery degradation mechanisms as they occur.