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arXiv · 1911.11183

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

Hasnain Hafiz·Kosuke Suzuki·Bernardo Barbiellini·Yuki Orikasa·Stanislaw Kaprzyk·Naruki Tsuji·Kentaro Yamamoto·Ayumu Terasaka·Kazushi Hoshi·Yoshiharu Uchimoto·Yoshiharu Sakurai·Hiroshi Sakurai·Arun Bansil
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Abstract

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.

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Hasnain Hafiz, Kosuke Suzuki, Bernardo Barbiellini, Yuki Orikasa, Stanislaw Kaprzyk, Naruki Tsuji, Kentaro Yamamoto, Ayumu Terasaka, Kazushi Hoshi, Yoshiharu Uchimoto, Yoshiharu Sakurai, Hiroshi Sakurai, Arun Bansil. 2019-11-25. Identification of ferrimagnetic orbitals preventing spinel degradation by charge ordering in Li$_x$Mn$_2$O$_4$. https://doi.org/10.1103/physrevb.100.205104

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