LiMnVO4

Acta Cryst.(2003). E59, i161±i163 DOI: 10.1107/S1600536803023742 Masahiko Sugaharaet al. LiMnVO₄

i161

inorganic papers

Acta Crystallographica Section E Structure Reports Online

ISSN 1600-5368

LiMnVO

Masahiko Sugahara,* Akira Yoshiasa, Takamitu Yamanaka and Humihiko Takei

Department of Earth and Space Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama, Toyonaka, Osaka 560-0043, Japan

Correspondence e-mail: [email protected]

Key indicators Single-crystal X-ray study

T= 297 K

Mean(V±O) = 0.001 AÊ

Rfactor = 0.022

wRfactor = 0.033

Data-to-parameter ratio = 64.0

For details of how these key indicators were automatically derived from the article, see http://journals.iucr.org/e.

#2003 International Union of Crystallography Printed in Great Britain ± all rights reserved

The crystal structure of lithium manganese vanadate, LiMnVO4, is characterized by chains of edge-sharing MnO6

octahedra, bridged by pairs of edge-sharing LiO4 and VO4

tetrahedra. Cation±cation repulsions displace the V and Li ions from the tetrahedral centres and deform the tetrahedra further by shortening the mutually shared OÐO edges. The smallest r.m.s. atomic displacements in thermal motion for Li and Vare parallel to the shortest Li V vector with maximum vibrational motion normal to that direction. Cation±cation interactions between the Li and V tetrahedral sites play an important role.

Comment

LixMn2O4(0 <x< 2) and vanadium oxides such as V2O5and

LiV3O8 have been widely investigated as candidates for

cathode materials in lithium batteries. The LiMnVO4 phase

has been found in the pseudo-binary system of LiMn2O4±

LiV2O4. The structure of the phase was proposed by Rietveld

analysis (Sato & Kano, 1994), and consists of an arrangement of edge-sharing MnO6octahedral chains, linked by VO4and

LiO4tetrahedra sharing a common edge.

The lithium ion, which has a low mass and is monovalent, usually exhibits a large anisotropic thermal motion in ionic conductors. However, although the displacement modes contain much information about possible lithium migration

Received 23 September 2003 Accepted 20 October 2003 Online 8 November 2003

Figure 1

Perspective view of the LiMnVO4structure. Displacement ellipsoids are

inorganic papers

i162

paths, no detailed single-crystal structure analysis of LiMnVO4

has been published. In this study, we have succeeded in synthesizing a large single crystal of LiMnVO4 and the

structure re®nement with full anisotropic displacement parameters is reported. The large anisotropic thermal motion of Li in the edge-sharing LiO4tetrahedral site is discussed.

Sato & Kano (1994), Sato et al. (1996), and Padhi et al. (1997) have investigated the crystal structure of LiMnVO4via

the Rietveld method, with an isotropic displacement model for all atoms. We ®nd good agreement between the atomic coordinates of their powder determination and those of our single-crystal study.

The crystal structure of LiMnVO4(Fig. 1) is characterized

by chains of edge-sharing MnO6octahedra, running parallel to

thecaxis. These chains are bridged by pairs of LiO4and VO4

tetrahedra. Both tetrahedral sites are linked to each other by sharing an edge. Both the Mn Mn [3.1815 (2) AÊ] and V Li [2.684 (6) AÊ] distances parallel to the c andb axes, respec-tively, are relatively short, resulting in a strong repulsion between cations.

Interatomic distances for the MnO6, VO4and LiO4

poly-hedra are listed in Table 1. The distances of O1 O1iv

between MnO6octahedra themselves and O1 O1iii

shared-edges between VO4 and LiO4 tetrahedra are 2.992 (1) and

2.772 (1) AÊ, respectively (symmetry codes as in Table 1). The O1 O1iii _{edges are shortened, due to cation±cation}

repul-sion, which accompanies the signi®cant off-centering of V and Li in each tetrahedral site.

An additional measure of the distortion of the VO4 and

LiO4tetrahedra is given by the deviation of the bond angles

from the ideal 109.48_.

Fig. 1 shows the r.m.s. displacements of Mn, V, Li and O atoms rendered as ellipsoids. The smallest Li atom mean atomic displacements are oriented along the Li V vectors and the maximal displacement vector is normal to this direc-tion. The cation±cation interaction between the Li and V tetrahedral sites play an important role.

Many Li cathode materials, such as the spinel-type structure and layer structure (Sato & Kano, 1994), have an Li-ion conduction path in the structure. On the other hand, the Li sites in this LiMnVO4 structure are widely separated from

each other and no vacant site which the Li ion could occupy is located near the Li site, though the amplitude and anisotropy of thermal vibration for Li is large enough. It is, therefore, inferred that this phase does not suit a cathode material. This phase transforms to a spinel-type phase (Padhiet al., 1997) under high pressure and temperature. The spinel-type phase should be appropriate for a cathode material. It is emphasized that the largest amplitude of the Li ion in this phase corres-ponds to the direction of displacement in the transition from this phase to the spinel-type phase, and the transition is achieved only by the displacement of Li ions.

Experimental

A single crystal of LiMnVO4 was grown using an LiVO3¯ux. A

mixture of Li2CO3(0.1 mol), V2O5(0.1 mol) and MnCO3(0.05 mol)

was heated at 1570 K for 24 h under atmospheric conditions. After slow cooling to 1070 K at a rate of 1 K hÿ1_{, the product was}

quen-ched. A ¯at LiMnVO4single crystal of 10101 mm was ground

into a sphere. The stoichiometric composition was con®rmed by an ICP emission spectrochemical analysis.

Crystal data

LiMnVO4 Mr= 176.82 Orthorhombic,Cmcm a= 5.7640 (3) AÊ

b= 8.7418 (9) AÊ

c= 6.3629 (3) AÊ

V= 320.61 (4) AÊ3 Z= 4

Dx= 3.663 Mg mÿ3

MoKradiation Cell parameters from 25

re¯ections

= 39.4±49.0

= 6.68 mmÿ1 T= 297 K Sphere, brown 0.08 mm (radius)

Data collection

Rigaku AFC-5Sdiffractometer

/2scans

Absorption correction: sphere (International Tables, Vol C, Table 6.3.3.3)

Tmin= 0.330,Tmax= 0.343

1759 measured re¯ections 944 independent re¯ections 902 re¯ections withF> 3(F)

Rint= 0.014

max= 50.0 h= 0!12

k=ÿ18!0

l=ÿ13!13 3 standard re¯ections

every 150 re¯ections intensity decay: none

Re®nement

Re®nement onF R= 0.022

wR= 0.033

S= 1.95 1663 re¯ections 26 parameters

w= 1/[2_{(Fo) + (0.013936Fo)}2_]

(/)max< 0.001 max= 0.18 e AÊÿ3 min=ÿ1.19 e AÊÿ3

Extinction correction:RADY89 (Sasaki, 1989)

Extinction coef®cient: 0.057 (4)

Table 1

Selected geometric parameters (AÊ,_). LiÐO1 2.123 (4) LiÐO2i _{1.962 (2)}

MnÐO1ii _{2.1909 (6)}

MnÐO2 2.1602 (10) VÐO1 1.7544 (9) VÐO2 1.6896 (10)

O1ÐLiÐO1iii _{81.5 (2)}

O1ÐLiÐO2iv _{107.7 (2)}

O2i_ÐLiÐO2iv _{132.5 (3)}

O1v_ÐMnÐO1vi _{86.12 (6)}

O1v_{ÐMnÐO2 90.65 (6)}

O1ÐVÐO1iii _{104.35 (10)}

O1ÐVÐO2 110.55 (2) O2ÐVÐO2vii _{110.2 (1)} Symmetry codes: (i) ÿx;1ÿy;1

2‡z; (ii) 12ÿx;12ÿy;ÿz; (iii) ÿx;y;12ÿz; (iv)

x;1ÿy;ÿz; (v)1

2ÿx;yÿ12;12ÿz; (vi)xÿ21;yÿ12;z; (vii)x;y;12ÿz.

Precession photographs showed an orthorhombic unit cell with systematic absences ofhkl;h+k= 2n+ 1 andh0l;handl= 2n+ 1. The possible space groups were thereforeCmcm, Cmc21andC2cm.

The space group was initially assumed to be Cmcm before the remaining two space groups were tested. Calculations gave the reliability factorR= 0.0217 forCmcm, R= 0.0217 forCmc21andR=

0.0223 forC2cm, all with anisotropic displacement parameters. Since all structure models converged to the Cmcm model and were essentially identical, within errors, the space group Cmcm was adopted. The minimum electron-density peak was located near the position (0, 0.08, 0). All atoms are located on special positions. Crystallographically equivalent re¯ections were averaged.

Data collection: MSC Software (Rigaku, 1996); cell re®nement:

MSC Software; data reduction:MSC Software; program(s) used to

solve structure:RADY89 (Sasaki, 1989); program(s) used to re®ne structure: RADY89; molecular graphics: ORTEP-3 for Windows

We thank Associate Professor Nobuo Ishizawa for his help.

References

Farrugia, L. J. (1997).J. Appl. Cryst.30, 565.

Padhi, A. K., Archibald, W. B., Nanjundaswamy, K. S. & Goodenough, J. B. (1997).J. Solid State Chem.128, 267±272.

Rigaku (1996).MSC Software. Version 4.4.1. Rigaku, Tokyo, Japan. Sasaki, S. (1989).RADY89. Tokyo Institute of Technology, Japan. Sato, M. & Kano, S. (1994).Chem. Lett.3, 427±430.

Sato, M., Kano, S., Tamaki, S., Misawa, M., Shirakawa, Y. & Ohashi, M. (1996).

J. Mater. Chem.6, 1191±1194.

Acta Cryst.(2003). E59, i161±i163 Masahiko Sugaharaet al. LiMnVO₄

i163

supporting information

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Acta Cryst. (2003). E59, i161–i163

supporting information

Acta Cryst. (2003). E59, i161–i163 [https://doi.org/10.1107/S1600536803023742]

LiMnVO

Masahiko Sugahara, Akira Yoshiasa, Takamitu Yamanaka and Humihiko Takei

lithium manganese vanadate

Crystal data

LiMnVO4 Mr = 176.82

Orthorhombic, Cmcm

Hall symbol: -C 2c 2

a = 5.7640 (3) Å

b = 8.7418 (9) Å

c = 6.3629 (3) Å

V = 320.61 (4) Å3 Z = 4

F(000) = 332.0

Dx = 3.663 Mg m−3

Mo Kα radiation, λ = 0.71069 Å Cell parameters from 25 reflections

θ = 39.4–49.0°

µ = 6.68 mm−1 T = 297 K Sphere, brown 0.08 mm (radius)

Data collection

Rigaku AFC-5S diffractometer

Radiation source: X-ray tube Graphite monochromator

θ/2θ scans

Absorption correction: for a sphere International Tables Vol C Table 6.3.3.3

Tmin = 0.330, Tmax = 0.343

1759 measured reflections

944 independent reflections 902 reflections with F > 3σ(F)

Rint = 0.014

θmax = 50.0°, θmin = 4.2° h = 0→12

k = −18→0

l = −13→13

3 standard reflections every 150 reflections intensity decay: none

Refinement

Refinement on F

Least-squares matrix: full

R[F2 _{> 2σ(F}2_{)] = 0.022} wR(F2_{) = 0.033} S = 1.83 1663 reflections 26 parameters 0 restraints

0 constraints

w = 1/[σ2_(F

o) + (0.013936Fo)2]

(Δ/σ)max < 0.001

Δρmax = 0.18 e Å−3

Δρmin = −1.19 e Å−3

Extinction correction: RADY89 (Sasaki, 1989) Extinction coefficient: 0.057 (4)

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2₎

x y z Uiso*/Ueq

Li 0.0000 0.6637 (7) 0.2500 0.0241 (11)

Mn 0.0000 0.0000 0.0000 0.00856 (4)

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Acta Cryst. (2003). E59, i161–i163

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

Li 0.033 (3) 0.0183 (19) 0.021 (2) 0.000 0.000 0.000 Mn 0.00905 (9) 0.00916 (9) 0.00747 (9) 0.000 0.000 0.00023 (5) V 0.00621 (8) 0.00740 (9) 0.00766 (9) 0.000 0.000 0.000 O1 0.0097 (3) 0.0122 (3) 0.0107 (3) −0.0030 (2) 0.000 0.000 O2 0.0133 (3) 0.0109 (3) 0.0107 (3) 0.000 0.000 −0.0023 (2)

Geometric parameters (Å, º)

Li—O1 2.123 (4) Mn—O2viii _{2.1602 (10)}

Li—O1i _{2.123 (4) V—O1 1.7544 (9)}

Li—O2ii _{1.962 (2) V—O1}i _{1.7544 (9)}

Li—O2iii _{1.962 (2) V—O2 1.6896 (10)}

Mn—O1iv _{2.1909 (6) V—O2}i _{1.6896 (10)}

Mn—O1v _{2.1909 (6) O1—O1}i _{2.772 (1)}

Mn—O1vi _{2.1909 (6) O1—O1}ix _{2.992 (1)}

Mn—O1vii _{2.1909 (6) O1—O1}iii _{3.2011 (2)}

Mn—O2 2.1602 (10)

O1—Li—O1i _{81.5 (2) O2—Mn—O2}x ₁₈₀

O1—Li—O2iii _{107.7 (2) O1—V—O1}i _{104.35 (10)}

O2ii_—Li—O2iii _{132.5 (3) O1—V—O2 110.55 (2)}

O1vii_—Mn—O1vi _{86.12 (6) O2—V—O2}xi _{110.2 (1)}

O1vii_{—Mn—O2 90.65 (6)}