Kazushi Hoshi | Searcharxiv

arXiv2021

Redox oscillations in 18650-type lithium-ion cell revealed by in operando Compton scattering imaging

Compton scattering imaging using high-energy synchrotron x-rays allows the visualization of the spatio-temporal lithiation state in lithium-ion batteries probed in-operando. Here, we apply this imaging technique to the commercial 18650-type cylindrical lithium-ion battery. Our analysis of the lineshapes of the Compton scattering spectra taken from different electrode layers reveals the emergence of inhomogeneous lithiation patterns during the charge-discharge cycles. Moreover, these patterns exhibit oscillations in time where the dominant period corresponds to the time scale of the charging curve.

physics.app-ph↗

arXiv2019

Identification of ferrimagnetic orbitals preventing spinel degradation by charge ordering in Li$_x$Mn$_2$O$_4$

Spinel Li$_x$Mn$_2$O$_4$ is a key cathode material that is used extensively in commercial Li-ion batteries. A challenge with this material has been that the capacity of the battery fades with cycling, an effect that can be traced to the presence of an anti-ferromagnetic insulator phase in the fully lithiated LiMn$_2$O$_4$ (LMO) and the associated charge disproportionation that drives distortions of the MnO$_6$ octahedra. Here, by combining x-ray magnetic Compton scattering experiments with parallel first-principles computations, we show that the anti-ferromagnetic phase of LMO is surrounded by a robust ferrimagnetic metallic phase, which becomes stable when even a small amount of Li is removed from or added to the charge-ordered LMO. In this surprising ferrimagnetic state, charge-ordering and octahedral distortions are found to be strongly suppressed. We identify the nature of the ferrimagnetic orbitals involved through theoretical and experimental analyses of the magnetic Compton scattering spectra.

cond-mat.mtrl-sci↗