Probing Multiscale Transport and Inhomogeneity in a Lithium-Ion Pouch Cell Using In Situ Neutron Methods

We demonstrate the lithiation process in graphitic anodes using in situ neutron radiography and diffraction in a single-layer pouch cell. The variation in neutron absorption contrast in graphite shows a direct correlation between the degree of lithiation and the discharge potential. The experimental neutron attenuation line profiles across the graphite electrode at various discharge times (potentials) were compared with lithium concentration profiles computed using a 3D electrochemical transport model. In conjunction with imaging/radiography, in situ neutron diffraction was carried out to obtain information about the local structural changes during various stages of lithiation in carbon. Combined in situ radiography and diffraction supported by 3D multiscale electrochemical modeling opens up a powerful nondestructive tool that can be utilized to understand the multiscale nature of lithium transport as well as observe various inhomogeneities at a cell level.