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

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

Research output: Contribution to journalJournal articleResearchpeer-review

Abstract

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.
Original languageEnglish
JournalAdvanced Functional Materials
Volume25
Issue number21
Pages (from-to)3227-3237
Number of pages11
ISSN1616-301X
DOIs
Publication statusPublished - 2015

Keywords

  • in situ XRD
  • layered structures
  • positive electrode materials
  • sodium‐ion batteries

Cite this