Details

Autor(en) / Beteiligte

• Jung, Young Hwa
• Christiansen, Ane S.
• Johnsen, Rune E.
• Norby, Poul
• Kim, Do Kyung

Titel

In Situ X-Ray Diffraction Studies on Structural Changes of a P2 Layered Material during Electrochemical Desodiation/Sodiation

Ist Teil von

• Advanced functional materials, 2015-06, Vol.25 (21), p.3227-3237

Ort / Verlag

Blackwell Publishing Ltd

Erscheinungsjahr

2015

Quelle

Wiley-Blackwell Journals

Beschreibungen/Notizen

• 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–Na0.7Fe0.4Mn0.4Co0.2O2 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–Na0.7Fe0.4Mn0.4Co0.2O2 using X‐ray absorption spectroscopy indicate that all transition metals are involved in the reduction/oxidation process. The phase transition of a sodium layered material with P2 stacking during electro­chemical desodiation/sodiation is studied by in situ synchrotron X‐ray diffraction using a capillary‐based microcell. P2–Na0.7Fe0.4Mn0.4Co0.2O2 is transformed to an O2 structure in the voltage plateau at 4.1 V, and the O2 phase shows a rapid change in the c lattice until a fully charged state.