Tracking Electrochemical Active Material Transport with Simultaneous Neutron and X-Ray Tomography

In situ tracking of electrochemical active species is critical to understanding the complex transport mechanisms in electrochemical devices such as fuel cells, electrolyzers, and batteries. Many probes available to track electrochemical processes often require significant modifications to the devices to allow probe access to the reaction sites. These modifications can strongly influence the reaction by altering mass and charge transport, thermal gradients, and mechanical stresses. Additionally, the layered materials in electrochemical devices are not flat and can have a wavy interface which requires three-dimensional analysis to fully capture these interfaces. Two penetrating nondestructive probes that resolve three-dimensional structures are neutron tomography and X-ray tomography. Neutrons excel at detecting hydrogen and lithium while X-rays of sufficient energy to penetrate larger samples are sensitive to solid structures and high-Z components. The NIST-NeXT system combines these two probes together for truly simultaneous neutron and X-ray tomography that can gain greater information about the sample than either mode on its own. Recent advances in how NIST-NeXT data are analyzed has significantly reduced the acquisition time of a tomography scan. This reduction will produce scan times in the <15 minute range which is critical for tracking performance evolution in electrochemical devices. This talk will give an overview of the NIST-NeXT system with example studies from fuel cells, electrolyzers, and lithium-ion batteries to demonstrate the system’s unique characterization capabilities for electrochemical devices.