Journal Article

PUBDB-2026-01700

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Interplay Between Phase Evolution, Fe Migration, and Oxygen Redox in O3‐Type Na_xFe_yMn_1−yO₂ Cathodes

Johansen, M.Extern*DESY* ; Schou Hansen, M.Extern* ; Dunker, J.Extern* ; Klemmt, R.Extern* ; Bomholdt Ravnsbaek, D. (Corresponding author)Extern*

2026
Wiley-VCH Weinheim

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Please use a persistent id in citations: doi:10.1002/adfm.75994

Abstract: In the development of sustainable Na-ion battery cathodes, the use of earth-abundant elements, such as iron, is essential to reduce costs and mitigate reliance on scarce transition metals. However, Fe-based layered oxides frequently exhibit complex redox behavior and structural instability, making it crucial to understand how Fe affects the redox properties and phase evolution during cycling. Here, we use Fe-rich O3-type layered Na_xFe_yMn_1−yO₂ (y = 0.5–0.8) as a model system to elucidate the role of Fe by combining cyclic voltammetry, operando X-ray absorption spectroscopy, and stacking-fault-sensitive operando powder X-ray diffraction. Increasing Fe content shifts the high-potential redox response to lower potentials and promotes earlier Fe³⁺ migration into tetrahedral sites in O-type NaO₂ layers during charge. This migration strongly influences the phase evolution: While moderate-Fe compositions complete the O3→P3→OP2→O3 sequence in the first electrochemical cycle, Fe-rich materials remain confined to stacking-faulted O3-like structures due to early structural “pinning” of the O-type layers. The findings clarify the mechanistic role of Fe in the interplay between cationic and anionic redox processes and establish why Fe content exerts such a strong, composition-dependent influence on the structural stability of O3-type Na-ion cathodes.

Note: This is an "Early View Online Version of Record before inclusion in an issue e75994" as written on the website.

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Contributing Institute(s):

1. DOOR-User (DOOR ; HAS-User)
2. PETRA-D (FS-PETRA-D)

Research Program(s):

1. 632 - Materials – Quantum, Complex and Functional Materials (POF4-632) (POF4-632)
2. 6G3 - PETRA III (DESY) (POF4-6G3) (POF4-6G3)
3. FS-Proposal: I-20230207 EC (I-20230207-EC) (I-20230207-EC)
4. FS-Proposal: I-20250737 EC (I-20250737-EC) (I-20250737-EC)

Experiment(s):

1. PETRA Beamline P02.1 (PETRA III)

Appears in the scientific report 2026

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Database coverage:
; Clarivate Analytics Master Journal List ; Current Contents - Electronics and Telecommunications Collection ; Current Contents - Engineering, Computing and Technology ; Current Contents - Physical, Chemical and Earth Sciences ; DEAL Wiley ; Ebsco Academic Search ; Essential Science Indicators ; IF >= 15 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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