Alluaudite Na<inf>2</inf>Co<inf>2</inf>Fe(PO<inf>4</inf>)<inf>3</inf> as an electroactive material for sodium ion batteries

Rachid Essehli, I. Belharouak, Hamdi Yahia, Kenza Maher, Ali Abouimrane, B. Orayech, S. Calder, X. L. Zhou, Z. Zhou, Y. K. Sun

Research output: Contribution to journalArticle

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Abstract

The electroactive orthophosphate Na<inf>2</inf>Co<inf>2</inf>Fe(PO<inf>4</inf>)<inf>3</inf> was synthesized using a solid state reaction. Its crystal structure was solved using the combination of powder X-ray- and neutron-diffraction data. This material crystallizes according to the alluaudite structure (S.G. C2/c). The structure consists of edge sharing [MO<inf>6</inf>] octahedra (M = Fe, Co) resulting in chains parallel to [-101]. These chains are linked together via the [PO<inf>4</inf>] tetrahedra to form two distinct tunnels in which sodium cations are located. The electrochemical properties of Na<inf>2</inf>Co<inf>2</inf>Fe(PO<inf>4</inf>)<inf>3</inf> were evaluated by galvanostatic charge-discharge cycling. During the first discharge to 0.03 V, Na<inf>2</inf>Co<inf>2</inf>Fe(PO<inf>4</inf>)<inf>3</inf> delivers a specific capacity of 604 mA h g<sup>-1</sup>. This capacity is equivalent to the reaction of more than seven sodium ions per formula unit. Hence, this is a strong indication of a conversion-type reaction with the formation of metallic Fe and Co. The subsequent charge and discharge involved the reaction of fewer Na ions as expected for a conversion reaction. When discharged to 0.9 V, the material intercalated only one Na<sup>+</sup>-ion leading to the formation of a new phase Na<inf>3</inf>Co<inf>2</inf>Fe(PO<inf>4</inf>)<inf>3</inf>. This phase could then be cycled reversibly with an average voltage of 3.6 V vs. Na<sup>+</sup>/Na and a capacity of 110 mA h g<sup>-1</sup>. This result is in good agreement with the theoretical capacity expected from the extraction/insertion of two sodium atoms in Na<inf>3</inf>Co<inf>2</inf>Fe(PO<inf>4</inf>)<inf>3</inf>.

Original languageEnglish
Pages (from-to)7881-7886
Number of pages6
JournalDalton Transactions
Volume44
Issue number17
DOIs
Publication statusPublished - 7 May 2015

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Conversion Disorder
Sodium
Ions
Neutron Diffraction
Neutron diffraction
Solid state reactions
Electrochemical properties
X-Ray Diffraction
Powders
Cations
Tunnels
Crystal structure
Phosphates
X ray diffraction
Atoms
Electric potential

ASJC Scopus subject areas

  • Inorganic Chemistry

Cite this

Alluaudite Na<inf>2</inf>Co<inf>2</inf>Fe(PO<inf>4</inf>)<inf>3</inf> as an electroactive material for sodium ion batteries. / Essehli, Rachid; Belharouak, I.; Yahia, Hamdi; Maher, Kenza; Abouimrane, Ali; Orayech, B.; Calder, S.; Zhou, X. L.; Zhou, Z.; Sun, Y. K.

In: Dalton Transactions, Vol. 44, No. 17, 07.05.2015, p. 7881-7886.

Research output: Contribution to journalArticle

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abstract = "The electroactive orthophosphate Na2Co2Fe(PO4)3 was synthesized using a solid state reaction. Its crystal structure was solved using the combination of powder X-ray- and neutron-diffraction data. This material crystallizes according to the alluaudite structure (S.G. C2/c). The structure consists of edge sharing [MO6] octahedra (M = Fe, Co) resulting in chains parallel to [-101]. These chains are linked together via the [PO4] tetrahedra to form two distinct tunnels in which sodium cations are located. The electrochemical properties of Na2Co2Fe(PO4)3 were evaluated by galvanostatic charge-discharge cycling. During the first discharge to 0.03 V, Na2Co2Fe(PO4)3 delivers a specific capacity of 604 mA h g-1. This capacity is equivalent to the reaction of more than seven sodium ions per formula unit. Hence, this is a strong indication of a conversion-type reaction with the formation of metallic Fe and Co. The subsequent charge and discharge involved the reaction of fewer Na ions as expected for a conversion reaction. When discharged to 0.9 V, the material intercalated only one Na+-ion leading to the formation of a new phase Na3Co2Fe(PO4)3. This phase could then be cycled reversibly with an average voltage of 3.6 V vs. Na+/Na and a capacity of 110 mA h g-1. This result is in good agreement with the theoretical capacity expected from the extraction/insertion of two sodium atoms in Na3Co2Fe(PO4)3.",
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AU - Yahia, Hamdi

AU - Maher, Kenza

AU - Abouimrane, Ali

AU - Orayech, B.

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AU - Zhou, Z.

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N2 - The electroactive orthophosphate Na2Co2Fe(PO4)3 was synthesized using a solid state reaction. Its crystal structure was solved using the combination of powder X-ray- and neutron-diffraction data. This material crystallizes according to the alluaudite structure (S.G. C2/c). The structure consists of edge sharing [MO6] octahedra (M = Fe, Co) resulting in chains parallel to [-101]. These chains are linked together via the [PO4] tetrahedra to form two distinct tunnels in which sodium cations are located. The electrochemical properties of Na2Co2Fe(PO4)3 were evaluated by galvanostatic charge-discharge cycling. During the first discharge to 0.03 V, Na2Co2Fe(PO4)3 delivers a specific capacity of 604 mA h g-1. This capacity is equivalent to the reaction of more than seven sodium ions per formula unit. Hence, this is a strong indication of a conversion-type reaction with the formation of metallic Fe and Co. The subsequent charge and discharge involved the reaction of fewer Na ions as expected for a conversion reaction. When discharged to 0.9 V, the material intercalated only one Na+-ion leading to the formation of a new phase Na3Co2Fe(PO4)3. This phase could then be cycled reversibly with an average voltage of 3.6 V vs. Na+/Na and a capacity of 110 mA h g-1. This result is in good agreement with the theoretical capacity expected from the extraction/insertion of two sodium atoms in Na3Co2Fe(PO4)3.

AB - The electroactive orthophosphate Na2Co2Fe(PO4)3 was synthesized using a solid state reaction. Its crystal structure was solved using the combination of powder X-ray- and neutron-diffraction data. This material crystallizes according to the alluaudite structure (S.G. C2/c). The structure consists of edge sharing [MO6] octahedra (M = Fe, Co) resulting in chains parallel to [-101]. These chains are linked together via the [PO4] tetrahedra to form two distinct tunnels in which sodium cations are located. The electrochemical properties of Na2Co2Fe(PO4)3 were evaluated by galvanostatic charge-discharge cycling. During the first discharge to 0.03 V, Na2Co2Fe(PO4)3 delivers a specific capacity of 604 mA h g-1. This capacity is equivalent to the reaction of more than seven sodium ions per formula unit. Hence, this is a strong indication of a conversion-type reaction with the formation of metallic Fe and Co. The subsequent charge and discharge involved the reaction of fewer Na ions as expected for a conversion reaction. When discharged to 0.9 V, the material intercalated only one Na+-ion leading to the formation of a new phase Na3Co2Fe(PO4)3. This phase could then be cycled reversibly with an average voltage of 3.6 V vs. Na+/Na and a capacity of 110 mA h g-1. This result is in good agreement with the theoretical capacity expected from the extraction/insertion of two sodium atoms in Na3Co2Fe(PO4)3.

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