Alluaudite Na2Co2Fe(PO4)(3) as an electroactive material for sodium ion batteries

Title
Alluaudite Na2Co2Fe(PO4)(3) as an electroactive material for sodium ion batteries
Authors
선양국
Keywords
BOND-VALENCE PARAMETERS; LITHIUM BATTERIES; ELECTRODE MATERIALS; ANODE MATERIAL; CAPACITY; CATHODE; STABILITY; PHOSPHATE; NA2FEPO4F; PHASES
Issue Date
2015-05
Publisher
ROYAL SOC CHEMISTRY
Citation
DALTON TRANSACTIONS, v. 44, NO 17, Page. 7881-7886
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).
URI
http://pubs.rsc.org/en/Content/ArticleLanding/2015/DT/C5DT00971E#!divAbstracthttp://hdl.handle.net/20.500.11754/24786
ISSN
1477-9226; 1477-9234
DOI
http://dx.doi.org/10.1039/c5dt00971e
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > DEPARTMENT OF ENERGY ENGINEERING(에너지공학과) > Articles
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