Reinvestigation of trilithium divanadium(III) tris­(orthophosphate), Li3V2(PO4)3, based on single-crystal X-ray data

Yongho Kee; Hoseop Yun

doi:10.1107/S1600536813001499

. 2013 Jan 19;69(Pt 2):i11–i12. doi: 10.1107/S1600536813001499

Reinvestigation of trilithium divanadium(III) tris(orthophosphate), Li₃V₂(PO₄)₃, based on single-crystal X-ray data

Yongho Kee ^a, Hoseop Yun ^a,^*

PMCID: PMC3569174 PMID: 23424392

Abstract

The structure of Li₃V₂(PO₄)₃ has been reinvestigated from single-crystal X-ray data. Although the results of the previous studies (all based on powder diffraction data) are comparable with our redetermination, all atoms were refined with anisotropic displacement parameters in the current study, and the resulting bond lengths are more accurate than those determined from powder diffraction data. The title compound adopts the Li₃Fe₂(PO₄)₃ structure type. The structure is composed of VO₆ octahedra and PO₄ tetrahedra by sharing O atoms to form the three-dimensional anionic framework _∞ ³[V₂(PO₄)₃]³⁻. The positions of the Li⁺ ions in the empty channels can vary depending on the synthetic conditions. Bond-valence-sum calculations showed structures that are similar to the results of the present study seem to be more stable compared with others. The classical charge balance of the title compound can be represented as [Li⁺]₃[V³⁺]₂[P⁵⁺]₃[O²⁻]₁₂.

Related literature

For the isotypic Li₃Fe₂(PO₄)₃ structure, see: Patoux et al. (2003 ▶). Structural studies of Li₃V₂(PO₄)₃ based on powder diffraction data have been reported previously by Yin et al. (2003 ▶); Patoux et al. (2003 ▶); Kuo et al. (2008 ▶); Yang et al. (2010 ▶); Fu et al. (2010 ▶). For ionic radii, see: Shannon (1976 ▶). For bond-valence calculations, see: Adams (2001 ▶). For the Inorganic Crystal Structure Database, see: ICSD (2012 ▶).

Experimental

Crystal data

Li₃V₂(PO₄)₃
M _r = 407.61
Monoclinic,
a = 8.6201 (4) Å
b = 8.6013 (4) Å
c = 14.7465 (7) Å
β = 125.204 (3)°
V = 893.39 (7) Å³
Z = 4
Mo Kα radiation
μ = 2.70 mm⁻¹
T = 290 K
0.08 × 0.04 × 0.04 mm

Data collection

Rigaku R-AXIS RAPID diffractometer
Absorption correction: multi-scan (ABSCOR; Higashi, 1995 ▶) T _min = 0.741, T _max = 1.000
8328 measured reflections
2031 independent reflections
1772 reflections with I > 2σ(I)
R _int = 0.031

Refinement

R[F ² > 2σ(F ²)] = 0.024
wR(F ²) = 0.062
S = 1.08
2031 reflections
181 parameters
Δρ_max = 0.58 e Å⁻³
Δρ_min = −0.49 e Å⁻³

Data collection: RAPID-AUTO (Rigaku, 2006 ▶); cell refinement: RAPID-AUTO; data reduction: RAPID-AUTO; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: DIAMOND (Brandenburg, 1999 ▶); software used to prepare material for publication: WinGX (Farrugia, 2012 ▶).

Supplementary Material

Click here for additional data file.^{(16.4KB, cif)}

Crystal structure: contains datablock(s) global, I. DOI: 10.1107/S1600536813001499/wm2716sup1.cif

e-69-00i11-sup1.cif^{(16.4KB, cif)}

Click here for additional data file.^{(97.9KB, hkl)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536813001499/wm2716Isup2.hkl

e-69-00i11-Isup2.hkl^{(97.9KB, hkl)}

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Table 1. Selected bond lengths (Å).

Li1—O4	1.930 (6)
Li1—O5	1.940 (6)
Li1—O3ⁱ	2.094 (6)
Li1—O10ⁱⁱ	2.215 (6)
Li2—O3	1.968 (6)
Li2—O1	1.974 (6)
Li2—O7	2.004 (6)
Li2—O9	2.153 (7)
Li3—O6	1.944 (5)
Li3—O10	1.946 (5)
Li3—O11	1.994 (5)
Li3—O9	2.014 (6)
V1—O2	1.9040 (19)
V1—O8	1.954 (2)
V1—O1ⁱ	2.0163 (19)
V1—O7	2.0168 (18)
V1—O5	2.0450 (18)
V1—O3ⁱ	2.1172 (18)
V2—O12ⁱⁱⁱ	1.9099 (19)
V2—O6	1.9810 (18)
V2—O4	2.0012 (18)
V2—O11	2.0316 (18)
V2—O10ⁱⁱ	2.0343 (19)
V2—O9ⁱⁱ	2.0618 (18)
P1—O2^iv	1.5199 (19)
P1—O4^v	1.5297 (19)
P1—O1	1.5310 (19)
P1—O6	1.5400 (18)
P2—O8^vi	1.492 (2)
P2—O9	1.5419 (19)
P2—O7	1.5458 (18)
P2—O10ⁱⁱ	1.5497 (19)
P3—O12	1.5101 (19)
P3—O11	1.5343 (19)
P3—O5^vii	1.5454 (19)
P3—O3ⁱⁱ	1.5506 (18)

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) ; (iv) ; (v) ; (vi) ; (vii) .

Acknowledgments

This research was supported by the Basic Science Research Program through the National Research Foundation of Korea funded by the Ministry of Education, Science and Technology (grant No. 2011–0011309).

supplementary crystallographic information

Comment

Trilithium divanadium(III) tris(orthophosphate), Li₃V₂(PO₄)₃, has been investigated as a cathode material of secondary batteries (Yin et al., 2003) and its structure has been reported based on powder diffraction data (Yin et al., 2003; Patoux et al., 2003; Kuo et al., 2008; Yang et al., 2010; Fu et al., 2010). In an attempt to prepare new mixed-metal phosphates using LiCl as a flux, we were able to isolate crystals of Li₃V₂(PO₄)₃, and report here the results of the structure analysis based on single-crystal X-ray diffraction data.

The title compound adopts the Li₃Fe₂(PO₄)₃ structure type. The general structural features of this compound are the same as reported previously (Patoux et al., 2003; Fu et al., 2010). However, as would be expected, the bond lengths found here from single-crystal diffraction data are more accurate than those reported previously from powder diffraction data. For example, the V—O distances (Table 1) reported by Kuo et al. (2008) range from 1.846 (3) to 2.258 (4) Å compared with 1.904 (2)–2.117 (2) Å here. Figure 1 shows the local coordination environment of the V and P atoms. In the structure, VO₆ octahedra are joined to PO₄ tetrahedra forming a [V₂(PO₄)₃] unit. These units share a terminal oxygen atom to construct the anionic three-dimensional framework, _∞³[V₂(PO₄)₃]^3- (Fig. 2). The V—O distances are in good agreement with those calculated from their ionic radii (1.99 Å, Shannon, 1976), assuming a valence of +III for V.

The Li⁺ ions in the empty channels are surrounded by four O atoms in distorted tetrahedral coordination sites. There are three crystallographically independent Li sites for this phase. It has been reported that the positions of the Li atoms can vary depending on the synthetic conditions while those of the V, P, and O atoms comprising the rigid framework remain intact (Yang et al., 2010). The Li positions found from the present single-crystal study are consistent with those reported by Patoux et al.(2003) and of a sample treated with microwave radiation at 1123 K for 3 min by Yang et al. (2010). According to bond valence sum calculations (Adams, 2001) for the various structure determinations, our study gives the lowest global instability index, Gii = 0.027. The Gii values of structures with Li positions similar to ours are likewise relatively low (i.e. 0.079; Yang et al., 2010), while those with Li positions considerably different as those from the present structures are much higher (i.e. 0.175; Yin et al., 2003).

The classical charge balance of the title compound can be represented as [Li⁺]₃[V³⁺]₂[P⁵⁺]₃[O^2-]₁₂.

Experimental

The title compound, Li₃V₂(PO₄)₃, was prepared by the reaction of the elements with the use of the reactive halide-flux technique. A combination of the pure elements, Nb powder (Alfa Aesar 99.8%), V powder (STREM CHEMICALS 99.5%) and P powder (CERAC 99.5%) were mixed in a fused silica tube in a molar ratio of Nb:V:P = 1:1:3 and then LiCl (Sigma-Aldrich 99%) was added. The mass ratio of the reactants and the halide was 1:5. The tube was evacuated to 0.133 Pa, sealed, and heated gradually (150 K/h) to 1123 K, where it was kept for 12 h. The tube was cooled to room temperature at a rate of 3 K/h. The excess halide was removed with water and colourless block-shaped crystals were obtained. The crystals are stable in air and water. A qualitative X-ray fluorescence analysis of selected crystal indicated the presence of V, P, and O. The composition of the compound was determined by single-crystal X-ray diffraction.