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Download fileStructural Investigation of Quaternary Layered Oxides upon Na-Ion Deinsertion
journal contribution
posted on 20.05.2020, 11:35 authored by Angelo Mullaliu, Kazutoshi Kuroki, Marlou Keller, Kei Kubota, Daniel Buchholz, Shinichi Komaba, Stefano PasseriniNa-ion
batteries are emerging alternatives to Li-ion chemistries for large-scale
energy storage applications. Quaternary layered oxide Na0.76Mn0.5Ni0.3Fe0.1Mg0.1O2 offers outstanding electrochemical performance in Na-ion
batteries compared to pure-phase layered oxides because of the synergistic
effect of the P/O-phase mixing. The material is indeed constituted
by a mixture of P3, P2, and O3 phases, and a newly identified Na-free
phase, i.e., nickel magnesium oxide phase, which improves heat removal
and enhances the electrochemical performance. Herein, we structurally
investigate, through synchrotron-radiation X-ray diffraction, the
modifications occurring after full desodiation, detailing the material
structural rearrangement upon Na removal and revealing the effect
of two different charging protocols, i.e., constant current (CC) and
constant current–constant voltage (CCCV). While the Na-free
phase is electrochemically inactive, likely helping in homogenization
of the thermal gradient in the electrode during cycling, O–P
intergrown phases appear during the extraction of Na ions from interslab
layers, and they are dependent on the desodiation level. The application
of a constant voltage step at the end of the galvanostatic charge
is responsible for a shortening of the interslab distance and a significant
volume contraction (−11.9%).