The ion‑exchange study by LiMn2O4 for Na‑ion cathodes: an investigation of structural and electrochemical performance

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Doğan E., Arshad M., Altın E., Altundağ S., Altın S.

JOURNAL OF APPLIED ELECTROCHEMISTRY, pp.1-12, 2025 (SCI-Expanded)

  • Publication Type: Article / Article
  • Publication Date: 2025
  • Doi Number: 10.1007/s10800-025-02270-9
  • Journal Name: JOURNAL OF APPLIED ELECTROCHEMISTRY
  • Journal Indexes: Science Citation Index Expanded (SCI-EXPANDED), Scopus, Academic Search Premier, Aerospace Database, Applied Science & Technology Source, Aquatic Science & Fisheries Abstracts (ASFA), Chemical Abstracts Core, Communication Abstracts, Compendex, Computer & Applied Sciences, INSPEC, Metadex, Civil Engineering Abstracts
  • Page Numbers: pp.1-12
  • Inonu University Affiliated: Yes

Abstract

The sodium manganese oxide phase was synthesized by an ion-exchange process in the glovebox using LiMn2O4

electrodes.

For this process, LiMn2O4

cathodes were discharged at specific voltage values that correspond to the redox reaction values

in cycling voltammetry measurements and then the cell was disassembled, and the cathode was used for Na-ion cell by Na

metal. The newly assembled cell was discharged to 1.5 V for the ion-exchange process. To understand the mechanism during

the ion-exchange process, the cells were disassembled in each redox voltage during the charging and discharging of the cell

for structural analysis. The XRD patterns of each electrode were analyzed by Rietveld refinement and the possible reaction

mechanism for the ion-exchange process was investigated. It was found that there are λ-MnO2, Li2MnO3,

and NaMn2O4

phases in the electrodes which formed at different cut of voltages. According to Fourier Transform Infrared Spectroscopy

measurements, the presence of Na–O bands was confirmed the successful ion-exchange within the materials. Structural

properties were further examined using Scanning Electron Microscopy combined with Energy Dispersive X-ray analysis dot

mapping and X-ray photoelectron spectroscopy analysis, supported by X-ray diffraction experimental results. The electrochemical

performance of the ion-exchanged electrodes was investigated by cyclic voltammetry, electrochemical impedance

spectroscopy, galvanostatic cycling, and C-rate measurements. The results showed that there was a significant change in

the redox reaction mechanism by the ion-exchange process. According to galvanostatic measurements, the ion-exchanged

electrodes showed better performance up to 50 cycles, but a phase change in the electrodes during the cycling caused a

sharp decrease in capacity. Ex-situ XRD analysis after 100 cycles revealed the formation of the Na2Mn3O7

phase which is electrochemically inactive, and it has Mn4+ ions in the structure. The results suggest that the ion-exchange mechanism is a

successful method, but the crystal structure has a crucial role in the cycling process of the cells.