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ORIGINAL RESEARCH article

Front. Batter. Electrochem.
Sec. Next Generation Batteries and Technologies
Volume 3 - 2024 | doi: 10.3389/fbael.2024.1433241
This article is part of the Research Topic Women in Battery Science and Technology View all 13 articles

Ion-intercalation Mechanism and Structural Relaxation in Layered Iron Phosphate Na 3 Fe 3 (PO 4 ) 4 Cathodes

Provisionally accepted
Christian L. Jakobsen Christian L. Jakobsen 1Morten Johansen Morten Johansen 2Tore Ericsson Tore Ericsson 3Lennart Häggström Lennart Häggström 3Christian K. Christensen Christian K. Christensen 1Ida Nielsen Ida Nielsen 3William R. Brant William R. Brant 3Dorthe Bomholdt Ravnsbæk Dorthe Bomholdt Ravnsbæk 2*
  • 1 University of Southern Denmark, Odense, Denmark
  • 2 Aarhus University, Aarhus, Denmark
  • 3 Uppsala University, Uppsala, Uppsala, Sweden

The final, formatted version of the article will be published soon.

    Layered Na3Fe3(PO4)4 can function as a positive electrode for both Li-and Na-ion batteries and may hold advantages from both classical layered and phosphate-based electrode materials. Using a combination of ex-situ and operando synchrotron radiation powder X-ray diffraction, void space analysis, and Mössbauer spectroscopy, we herein investigate the structural evolution of the Na3Fe3(PO4)4 framework during Li-and Na-ion intercalation. We show that during discharge, Li-and Na-intercalation into Na3Fe3(PO4)4 occurs via a solid solution reaction wherein Na-ions appear to be preferentially intercalated into the intralayer sites. The intercalation causes an expansion of the unit cell volume, however at open circuit conditions after ion-intercalation (i.e., after battery discharge), Na3+xFe3(PO4)4 and LixNa3Fe3(PO4)4 undergo a structural relaxation, wherein the unit volume contracts below that of the pristine material. Rietveld refinement suggests that the ion intercalated into the intralayer sites diffuse to the sites in the inter-layer space during the relaxation. This behavior brings new perspectives to understanding structural relaxation and deviations between structural evolution observed under dynamic and static conditions.

    Keywords: Li- and Na-ion batteries, Cathode materials, Structural relaxation, Operando PXRD, Polyanionic electrode, Ion-intercalation

    Received: 16 May 2024; Accepted: 22 Jul 2024.

    Copyright: © 2024 Jakobsen, Johansen, Ericsson, Häggström, Christensen, Nielsen, Brant and Bomholdt Ravnsbæk. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Dorthe Bomholdt Ravnsbæk, Aarhus University, Aarhus, Denmark

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