Complete 3D picture of next-generation solid-state batteries unveiled

Solid-state batteries are lined up to be the next-generation energy storage devices, providing higher energy density and improved safety over traditional lithium-ion batteries. However, they face challenges in terms of long-term performance and reliability and therefore, are still not commercially available. 

Until today, scientists had only been able to visualize cracks in these kinds of batteries. But a team led by Partha Paul from the Henry Royce Institute (now at Stanford University), Alex Rettie from University College London (UCL) and Marco DI Michiel from ESRF has unveiled not only the chemistry of these batteries but also the mechanical properties. “The changes in both chemistry and mechanics of the batteries, what is called electrochemomechanics, are key to a better design of these promising batteries, so that they can reach the market in the near future”, explains Rettie.

The researchers combined complementary 3D in situ X-ray techniques, primarily on beamline ID15A but also on ID19, on new and cycled-to-failure cells. First, they used micro-computed tomography imaging to analyse the morphological degradation in the solid electrolyte (voids, pores and cracks). Then, they applied 3D resolved X-ray diffraction computed tomography (XRD-CT) to gather insights into the chemistry of the battery. Finally, XRD-CT analysed the volumetric stress, and relate degradation to deformation globally and locally, around degradation hotspots.

Marco Di Michiel, scientist in charge of ID15A, on the beamline. Credits: S. Candé.

The experiments showed that stress concentrations around cracks and voids, in particular at the interfaces between lithium and solid electrolyte materials, are critical to understanding why the device fails. The results were unexpected, Rettie explains: “We were surprised to see different impurity phases than those we expected and the strain profiles around the cracks still puzzle us. Here we have a whole 3D volume of the cell, with millions XRD patterns and tens of cracks, where we see a hierarchy of processes that occur and that haven’t been disclosed previously”.

“To our knowledge, it is the first time that XRD-CT has been used in solid state batteries, as well as the combination of the micro-CT with XRD-CT to correlate degradation mechanisms”, says Paul.

The next step for the team is to use these techniques in batteries in operando, i.e. as they are cycled. Paul highlights the importance of the new EBS in the upcoming experiments: “The capabilities of EBS are crucial for our future in situ experiments, because the time resolution is not so much faster, with so much flux that you can do experiments in the time-frame that is close to in situ/operando, which would not be possible anywhere else”.

This research was funded by the EPSRC for the International Center to Center Collaboration grant, awarded to the Henry Royce Institute.

Reference:

Ji Hu, et. el, Advanced Energy Materials, first published: 04 December 2024. https://doi.org/10.1002/aenm.202404231

Text by Montserrat Capellas Espuny