Alluaudite Na2Co2Fe(PO4)(3) as an electroactive material for sodium ion batteries
- Authors
- Essehli, R.; Belharouak, I.; Ben Yahia, H.; Maher, K.; Abouimrane, A.; Orayech, B.; Calder, S.; Zhou, X. L.; Zhou, Z.; Sun, Yang Kook
- Issue Date
- Mar-2015
- Publisher
- ROYAL SOC CHEMISTRY
- Citation
- DALTON TRANSACTIONS, v.44, no.17, pp.7881 - 7886
- Indexed
- SCIE
SCOPUS
- Journal Title
- DALTON TRANSACTIONS
- Volume
- 44
- Number
- 17
- Start Page
- 7881
- End Page
- 7886
- URI
- https://scholarworks.bwise.kr/hanyang/handle/2021.sw.hanyang/25621
- DOI
- 10.1039/c5dt00971e
- ISSN
- 1477-9226
- 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 Na2Co2Fe(PO4)(3).
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