Uniformity of Flat Li-Ion Batteries Studied by Diffraction and Imaging of X-rays and Neutrons

A combination of high-resolution neutron powder diffraction, energy-dependent cold-neutron radiography, and synchrotron-based X-ray diffraction radiography on two pouch bag cells of different dimensions and cell chemistries, LiCoO2 vertical bar graphite and LiNi0.5Mn0.2Co0.3O2 vertical bar graphite, is applied. The evolution of the crystal structure in cell electrodes and its uniformity are probed by in operando neutron diffraction on the permanently rotated pouch bag cells by applying slip ring contact. A rhombohedral-to-monoclinic phase transition is detected for both LiCoO2 and LiNi0.5Mn0.2Co0.3O2 cathodes utilized in custom-built cells. X-ray diffraction radiography performed for both cells in the charged state reveals heterogeneous lithium distribution in the graphite anode and LiCoO2 and LiNi0.5Mn0.2Co0.3O2 cathodes.

Automated summary

This study utilized a combination of high-resolution neutron powder diffraction, energy-dependent cold-neutron radiography, and synchrotron-based X-ray diffraction radiography on pouch bag cells to probe the crystal structure evolution and uniformity in cell electrodes. A phase transition from rhombohedral to monoclinic was detected in both custom-built cells utilizing LiCoO2 and LiNi0.5Mn0.2Co0.3O2 cathodes. X-ray diffraction radiography revealed heterogeneous lithium distribution in the graphite anode and cathodes.