(300d) Operando Study Electronic and Magnetic Transitions in Lithium and Sodium Batteries Using X-Ray Emission/Absorption Spectroscopy

Tracking the change in electronic and local structure is crucial to investigate and improve the stability and performance of rechargeable batteries. Doing so under operando conditions is challenging but, if done correctly and complementarily with ex-situ studies, can reveal the intimate connections between local point-group structure/symmetry, the oxidation states of the constituent elements and their spin states. We will discuss the advances in both lab-based and synchrotron-based x-ray absorption and high-energy-resolution x-ray emission spectroscopy that we used to study not just the internal reactions within batteries during charge and discharge, but also the intrinsic property changes (e.g. magnetic) induced in the active materials by these reactions. The cases that will be examined are lithium and sodium iron phosphates (LFP/NFP), lithium nickel manganese cobalt oxide of various stoichiometries (NMC 622 and NMC 811), iron oxide (Fe₂O₃), and lithium cobalt oxide (LCO). As NMC and LCO are structural siblings, we will specifically look at the connections and subtle differences between them as they undergo electrochemically induced chemical and physical changes.