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The production and electrochemical performance analysis of an O3-NaTi0.2Mn0.2Fe0.2Ni0.2Co0.2O2 high-entropy oxide cathode for Na-ion batteries

Topal, Ali ; Naveed, Abdul ; Hetherington, Crispin LU orcid ; Gouttebaron, Rachel ; Sahinbay, Sevda and Altin, Serdar (2026) In RSC Advances 16(31). p.28366-28375
Abstract

In this study, we report the suppression of degradative transformations observed in Na-ion batteries by utilizing five different transition-metal cations at a single crystallographic site, which is expected to impart entropy-induced stabilization, resulting in enhanced structural stability. We successfully synthesized phase-pure O3-NaTi0.2Mn0.2Fe0.2Ni0.2Co0.2O2 through a facile solid-state sintering method. In this compound, Co3+, Fe3+, and Ni2+ provide charge compensation for capacity, Mn4+ acts as a structure former, and Ti4+ helps stabilize the overall structure. The synthesized material was successfully... (More)

In this study, we report the suppression of degradative transformations observed in Na-ion batteries by utilizing five different transition-metal cations at a single crystallographic site, which is expected to impart entropy-induced stabilization, resulting in enhanced structural stability. We successfully synthesized phase-pure O3-NaTi0.2Mn0.2Fe0.2Ni0.2Co0.2O2 through a facile solid-state sintering method. In this compound, Co3+, Fe3+, and Ni2+ provide charge compensation for capacity, Mn4+ acts as a structure former, and Ti4+ helps stabilize the overall structure. The synthesized material was successfully characterized using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), inductively coupled plasma mass spectroscopy (ICP-MS), X-ray photo-electron spectroscopy (XPS), and transmission electron microscopy (TEM). The configurational entropy was calculated to be ∼1.6 R, which is consistent with a high-entropy oxide. The material revealed a single phase with R3̄m symmetry, which matches well with the O3-type layered structure. SEM revealed irregular 1–3 µm particles, while EDX mapping confirmed uniform elemental dispersion. ICP provided the composition as Na0.94(Ti0.18Mn0.20Fe0.20Ni0.21Co0.21)O2. The XPS analysis showed mixed-valence chemistry for each component (Ti is predominantly Ti4+ with minor metallic Ti; Mn is consistent with Mn4+; Fe exhibits Fe2+/Fe3+ coexistence; Co exhibits Co2+/Co3+ coexistence; and Ni exhibits Ni2+/Ni3+ coexistence), which can be explained by a charge compensation mechanism. Transmission electron microscopy and selected area electron diffraction (TEM-SAEED) analysis confirmed the formation of an R3̄m structure, and the interlayer separation was also calculated. The electrochemical properties were systematically evaluated, and the capacity of the cells was found to be 120 mA h g−1 at a C/3-rate, which demonstrates the promising potential of this composition for sodium-ion battery applications.

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author
; ; ; ; and
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
RSC Advances
volume
16
issue
31
pages
10 pages
publisher
Royal Society of Chemistry
external identifiers
  • pmid:42211358
  • scopus:105039972448
ISSN
2046-2069
DOI
10.1039/d6ra02449a
language
English
LU publication?
yes
id
b0080f37-8bce-47c4-a2de-92897e5b834e
date added to LUP
2026-09-21 14:54:25
date last changed
2026-10-06 13:06:05
@article{b0080f37-8bce-47c4-a2de-92897e5b834e,
  abstract     = {{<p>In this study, we report the suppression of degradative transformations observed in Na-ion batteries by utilizing five different transition-metal cations at a single crystallographic site, which is expected to impart entropy-induced stabilization, resulting in enhanced structural stability. We successfully synthesized phase-pure O3-NaTi<sub>0.2</sub>Mn<sub>0.2</sub>Fe<sub>0.2</sub>Ni<sub>0.2</sub>Co<sub>0.2</sub>O<sub>2</sub> through a facile solid-state sintering method. In this compound, Co<sup>3+</sup>, Fe<sup>3+</sup>, and Ni<sup>2+</sup> provide charge compensation for capacity, Mn<sup>4+</sup> acts as a structure former, and Ti<sup>4+</sup> helps stabilize the overall structure. The synthesized material was successfully characterized using X-ray diffraction (XRD), scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM/EDX), inductively coupled plasma mass spectroscopy (ICP-MS), X-ray photo-electron spectroscopy (XPS), and transmission electron microscopy (TEM). The configurational entropy was calculated to be ∼1.6 R, which is consistent with a high-entropy oxide. The material revealed a single phase with R3̄m symmetry, which matches well with the O3-type layered structure. SEM revealed irregular 1–3 µm particles, while EDX mapping confirmed uniform elemental dispersion. ICP provided the composition as Na<sub>0.94</sub>(Ti<sub>0.18</sub>Mn<sub>0.20</sub>Fe<sub>0.20</sub>Ni<sub>0.21</sub>Co<sub>0.21</sub>)O<sub>2</sub>. The XPS analysis showed mixed-valence chemistry for each component (Ti is predominantly Ti<sup>4+</sup> with minor metallic Ti; Mn is consistent with Mn<sup>4+</sup>; Fe exhibits Fe<sup>2+</sup>/Fe<sup>3+</sup> coexistence; Co exhibits Co<sup>2+</sup>/Co<sup>3+</sup> coexistence; and Ni exhibits Ni<sup>2+</sup>/Ni<sup>3+</sup> coexistence), which can be explained by a charge compensation mechanism. Transmission electron microscopy and selected area electron diffraction (TEM-SAEED) analysis confirmed the formation of an R3̄m structure, and the interlayer separation was also calculated. The electrochemical properties were systematically evaluated, and the capacity of the cells was found to be 120 mA h g<sup>−1</sup> at a C/3-rate, which demonstrates the promising potential of this composition for sodium-ion battery applications.</p>}},
  author       = {{Topal, Ali and Naveed, Abdul and Hetherington, Crispin and Gouttebaron, Rachel and Sahinbay, Sevda and Altin, Serdar}},
  issn         = {{2046-2069}},
  language     = {{eng}},
  number       = {{31}},
  pages        = {{28366--28375}},
  publisher    = {{Royal Society of Chemistry}},
  series       = {{RSC Advances}},
  title        = {{The production and electrochemical performance analysis of an O3-NaTi<sub>0.2</sub>Mn<sub>0.2</sub>Fe<sub>0.2</sub>Ni<sub>0.2</sub>Co<sub>0.2</sub>O<sub>2</sub> high-entropy oxide cathode for Na-ion batteries}},
  url          = {{http://dx.doi.org/10.1039/d6ra02449a}},
  doi          = {{10.1039/d6ra02449a}},
  volume       = {{16}},
  year         = {{2026}},
}