Visualization of Electrochemical Reactions in Battery Materials with X-ray Microscopy and Mapping

Abstract

Unlocking the full performance capabilities of battery materials will require a thorough understanding of the underlying electrochemical mechanisms at a variety of length scales. A broad arsenal of X-ray microscopy and mapping techniques is now available to probe these processes down to the nanoscale. The tunable nature of X-ray sources allows for the extraction of chemical states through spectromicroscopy. The addition of phase contrast imaging can retrieve the complex-valued refraction of the material, giving an even more nuanced chemical picture. Tomography and coherent Bragg diffraction imaging provide a reconstructed three-dimensional volume of the specimen, as well as internal strain information from the latter. Many recent insights into battery materials have been achieved through the creative use of these, and similar, methods. Experiments performed while the battery is being actively cycled reveal behavior that differs significantly from what is observed at equilibrium and metastable conditions. Planned improvements to X-ray source brightness and coherence will extend these techniques by alleviating the current trade-off in time, chemical, and spatial resolution.

Synchrotron‐Based X‐ray Absorption Fine Structures, X‐ray Diffraction, and X‐ray Microscopy Techniques Applied in the Study of Lithium Secondary Batteries

“…XRD is a powerful technique to determine crystallographic information of crystalline materials, including cell parameters, strain, and microstructural information and has been widely applied in lithium secondary batteries. [132,133] Based on different working principles, there are three typical X-ray diffraction techniques, including X-ray powder and single-crystal diffraction and X-ray Laue diffraction. While the first two techniques use monochromatic X-ray, the last one can apply polychromatic X-ray to test materials combined with 2D detectors.…”

Fast operando X-ray pair distribution function using the DRIX electrochemical cell

“…Bragg diffraction has offered insights into the structural changes of crystalline phases (Johnsen & Norby, 2013;Peterson et al, 2017), and when used in combination with computed tomography methods can allow 3D crystallographic mapping within a battery (Finegan et al, 2020). Imaging methods allow for the direct visualization of battery components in terms of microstructure, morphology and chemical composition (Wolf et al, 2017;Ulvestad et al, 2014). The speed of modern synchrotron imaging even allows data to be collected during catastrophic cell failures, and combination with suitable in situ apparatus allows concurrent collection of calorimetric data and ejected media from explosive events (Finegan et al, 2019).…”

Best practices for operando depth-resolving battery experiments

“…Operando studies of electrochemical reactions based on scattering, spectroscopy and imaging are widely used to interrogate battery performance and limitations (Wolf et al, 2017;Lin et al, 2017). The operando modality is key to capturing dynamic species and states that can relax when the system is allowed to rest.…”