A neutron powder diffraction study of electrochemically lithiated R-Li3+xFe2(PO4)3 for x=1.8

被引：11

作者：

Eyob, P ^{[1
]}

Andersson, AS ^{[1
]}

Thomas, JO ^{[1
]}

机构：

[1] Uppsala Univ, Angstrom Lab, Dept Chem Mat, SE-75121 Uppsala, Sweden

来源：

JOURNAL OF MATERIALS CHEMISTRY | 2002年 / 12卷 / 08期

关键词：

D O I：

10.1039/b203059d

中图分类号：

O64 [物理化学（理论化学）、化学物理学];

学科分类号：

070304 ; 081704 ;

摘要：

The electrochemically lithiated form of R-Li3Fe2(PO4)(3), synthesised by ion exchange of fine powders of Na3Fe2(PO4)(3) in a concentrated aqueous solution of LiNO3 at a slightly elevated temperature (40 degreesC), has been investigated by a combination of ex situ X-ray and neutron diffraction to probe particularly the lithium-ion distribution in the structure. Li3+xFe2(PO4)(3) samples were extracted from discharged electrochemical cells with a Li-metal anode; their structure was refined by the Rietveld method. Approximately 1.8 Li per formula unit can be inserted reversibly into the structure, corresponding to the reduction of almost all Fe3+ to Fe-2. Ex situ X-ray powder diffraction shows the Fe-2(PO4)(3) framework to remain intact during lithiation. The Li(18f) site in R-Li3Fe2(PO4)(3) (space group: R (3) over bar) is totally vacated in R-Li3+xFe2(PO4)(3), 0 less than or equal to x less than or equal to 1.8, with the lithium ions moving into two new general (18f) positions, Li(l) and Li(2), with 74(4)% and 86(4)% occupation, respectively. This corresponds to the Li+ ions moving cooperatively from pairs of layers (alternate separations: 2.2 and 5.4 Angstrom) for x = 0 to equally spaced layers (separation: 3.8 Angstrom) for x = 1.8.

引用

页码：2343 / 2347

页数：5

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