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In Situ X‐Ray Diffraction Studies on Structural Changes of a P2 Layered Material during Electrochemical Desodiation/Sodiation
Author(s) -
Jung Young Hwa,
Christiansen Ane S.,
Johnsen Rune E.,
Norby Poul,
Kim Do Kyung
Publication year - 2015
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201500469
Subject(s) - materials science , electrochemistry , transition metal , x ray absorption spectroscopy , ternary operation , diffraction , redox , phase transition , absorption spectroscopy , stacking , xanes , lattice constant , crystallography , spectroscopy , electrode , chemistry , metallurgy , catalysis , thermodynamics , quantum mechanics , programming language , biochemistry , physics , organic chemistry , computer science , optics
Sodium layered oxides with mixed transition metals have received significant attention as positive electrode candidates for sodium‐ion batteries because of their high reversible capacity. The phase transformations of layered compounds during electrochemical reactions are a pivotal feature for understanding the relationship between layered structures and electrochemical properties. A combination of in situ diffraction and ex situ X‐ray absorption spectroscopy reveals the phase transition mechanism for the ternary transition metal system (Fe–Mn–Co) with P2 stacking. In situ synchrotron X‐ray diffraction using a capillary‐based microbattery cell shows a structural change from P2 to O2 in P2–Na 0.7 Fe 0.4 Mn 0.4 Co 0.2 O 2 at the voltage plateau above 4.1 V on desodiation. The P2 structure is restored upon subsequent sodiation. The lattice parameter c in the O2 structure decreases significantly, resulting in a volumetric contraction of the lattice toward a fully charged state. Observations on the redox behavior of each transition metal in P2–Na 0.7 Fe 0.4 Mn 0.4 Co 0.2 O 2 using X‐ray absorption spectroscopy indicate that all transition metals are involved in the reduction/oxidation process.