LiNi0 66Fe0 34PO4

inorganic papers

Acta Cryst.(2007). E63, i73–i74 doi:10.1107/S1600536807007507 Lianget al. _LiNi

0.66Fe0.34PO4

i73

Structure Reports

Online

ISSN 1600-5368

LiNi

Fe

PO

Gan Liang,aRonald E. Benson,b* Jiying Li,cDavid Vaknincand Lee M. Danielsb

a_{Department of Physics, Sam Houston State}

University, Huntsville, Texas 77341, USA, b_{Rigaku Americas Corporation, 9009 New Trails}

Drive, The Woodlands, TX 77381, USA, and c_{Ames Laboratory and Department of Physics &}

Astronomy, Iowa State University, Ames, Iowa 50011, USA

Correspondence e-mail: [email protected]

Key indicators

Single-crystal X-ray study

T= 150 K

Mean(P–O) = 0.002 A˚ Disorder in main residue

Rfactor = 0.020

wRfactor = 0.043 Data-to-parameter ratio = 8.0

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

Received 30 January 2007 Accepted 13 February 2007

#2007 International Union of Crystallography All rights reserved

Lithium nickel(II) iron(II) phosphate, LiNi0.66Fe0.34PO4, was

crystallized from an LiCl melt. The structure is closely related

to the known phase LiFePO4but with mixed occupancy at the

metal atom site of approximately 66% nickel and 34% iron. The Ni/Fe atom is octahedrally coordinated by six O atoms. The P atoms are tetrahedrally coordinated by four O atoms.

Comment

The solid-state phase LiFePO4 was first structurally

char-acterized by X-ray diffraction in 1938 (Bjo¨rling & Westgren, 1938). However, the potential use of this olivine phase as a

cathode material was not reported until 1997 (Padhi et al.,

1997). Currently, the material is the focus of research and development of lithium ion batteries. The late arrival of

LiFePO4 and related structures as candidates for possible

cathode materials is primarily due to their low inherent elec-trical conductivity. Most prior scientific investigations were focused on materials with edge-shared transition metal octa-hedra, often exhibited in spinel structures (Tarascon & Armand, 2001). Transition metal oxides with edge-shared octahedra are more efficient ion conductors and tend to retain

their structure better during reduction. Although LiFePO4

contains both edge-shared and corner-shared polyhedra, marked increases in conductivity are observed by intercalating

LiFePO4with multivalent cations such as Mg, Ti, W, and Al

(Thackeray, 2002). A partially nickel-substituted compound,

Figure 1

The asymmetric unit of LiNi0.66Fe0.34PO4 with additional atoms to complete the coordination environments. Displacement ellipsoids are drawn at the 80% probability level. [Symmetry codes (i)x+1

2,y,z 1 2, (ii)x+1

2,y+ 1 2,z

1

2, (iii)x,y,z1, (iv)x,y+ 1

2,z, (v)x 1 2,y+

1 2,

z+1

LiNi0.66Fe0.34PO4has been characterized and its structure is

presented here.

The title compound is isostructural with LiFePO4. It

featuresMO6octahedra (M= Fe, Ni) and PO4tetrahedra that

form alternating ‘chains’ of corner-sharing and edge-sharing polyhedra along the [100] and [001] directions. Conversely, in the (010) plane there is a discrete layer of edge-sharing polyhedra followed by a discrete layer of corner-sharing polyhedra as one moves down the [100] axis. Lithium cations

reside in the cavities between the polyhedra, yielding LiO6

octahedra. Approximately 66 (4)% of the metal-atom sites in the structure are occupied by Ni, which is somewhat lower than the 80 mol-% in the starting mixture. In the flux growth,

the chemical reaction of the NiCl2in certain portions of the

starting mixture might not be fully completed, resulting in an Ni concentration in the analyzed crystal which is different from that in the starting mixture.

TheMO6 octahedra are severely distorted [cis-O—Ni—O

angles between 68.53 (8) _{and 114.22 (9)]. Even the LiO}

6

octahedra are rather distorted [cis-O—Li—O 71.82 (7)_–

108.18 (7)_{]. Similar distortions, albeit to a lesser extent, are}

observed in the PO4 tetrahedra, with angles in the range

102.69 (2)–113.90 (8)The site occupation factors of Fe and

Ni were refined with the constraintxNi= 1xFe.

Experimental

Synthesis: LiNi0.66Fe0.34PO4 single crystals were grown in sealed platinum crucibles by standard flux-growth techniques with LiCl as the flux. High purity FeCl2 (99.999% Aldrich), NiCl2 (99.999% Aldrich) and Li3PO4(99.999% Aldrich) powders were mixed with a molar ratio of 1:4:5. A small hole of about 50mm diameter was drilled in the crucible to release the pressure from the high vapor pressure of LiCl. The mixture was pre-melted at 800 K for 2 h, heated to 890 K over 5 h, soaked at 890 K for 10 h, slowly cooled to 710 K at a rate of 0.7 K h1and then further cooled to 650 K at 1.5 K h1. The furnace was turned off at 650 K. The crystals were extracted from the mixture

red–brown color and a volume of about 0.1 mm3. Powder X-ray diffraction of the crushed single crystals revealed a single-phase product.

Crystal data

LiNi0.66Fe0.34PO4

Mr= 159.63

Orthorhombic,Pnma a= 10.0871 (16) A˚

b= 5.8845 (10) A˚

c= 4.6820 (8) A˚

V= 277.91 (8) A˚3

Z= 4

MoKradiation

= 6.84 mm1

T= 150 (2) K 0.190.180.14 mm

Data collection

Rigaku SCXmini diffractometer Absorption correction: multi-scan

(ABSCOR; Higashi, 1995)

Tmin= 0.568,Tmax= 0.692

(expected range = 0.309–0.376)

2026 measured reflections 345 independent reflections 328 reflections withI> 2(I)

Rint= 0.033

Refinement

R[F2_{> 2(F}2_{)] = 0.020}

wR(F2) = 0.044

S= 1.18 345 reflections

43 parameters

max= 0.37 e A˚

3 min=0.47 e A˚

3

Table 1

Selected bond lengths (A˚ ).

Ni1—O2 2.051 (2) Ni1—O3i

2.0557 (15) Ni1—O1ii

2.111 (2) Ni1—O3iii 2.1599 (15)

P1—O1 1.523 (2)

P1—O2iv 1.538 (2) P1—O3iii

1.5572 (16) Li1—O2iv

2.0844 (15) Li1—O3v 2.1327 (15) Li1—O1vi

2.1464 (16)

Symmetry codes: (i) xþ1 2;y;z

1

2; (ii) x;y;z1; (iii) x;yþ 1 2;z; (iv)

x1 2;yþ

1 2;zþ

1

2; (v)x;y;z; (vi)x;y;zþ1.

Data collection: PROCESS-AUTO (Rigaku, 1998); cell refine-ment:SCXmini Benchtop Crystallography System Software(Rigaku, 2006); data reduction:CrystalStructure (Rigaku, 2005); program(s) used to solve structure: SHELXS97(Sheldrick, 1997); program(s) used to refine structure: SHELXL97 (Sheldrick, 1997); molecular graphics:SCXmini Benchtop Crystallography System Software; soft-ware used to prepare material for publication:CrystalStructure.

The work at Sam Houston State University is supported by a grant from the SHSU EGR program. The work at Ames Laboratory is supported by the Department of Energy, Office of Basic Energy Sciences under contract number W-7405-Eng-82.

References

Bjo¨rling, C. O. & Westgren, A. (1938).Stockholm Fo¨rhandlingar60, 67–72. Higashi, T. (1995).ABSCOR. Rigaku Corporation, Tokyo, Japan.

Padhi, A. K., Najundaswamy, K. S. & Goodenough, J. B. (1997). J.

Electrochem. Soc.144, 1188–1194.

Rigaku (1998).PROCESS-AUTO. Rigaku Corporation, Tokyo, Japan. Rigaku (2005).Crystal Structure. Version 3.7. Rigaku Americas Corporation,

The Woodlands, Texas, USA.

Rigaku (2006).SCXmini Benchtop Crystallography System Software, Version 1.0. Rigaku Americas Corporation, The Woodlands, Texas, USA. Sheldrick, G. M. (1997).SHELXS97andSHELXL97. Unversity of Go¨ttingen,

Figure 2

supporting information

sup-1 Acta Cryst. (2007). E63, i73–i74

supporting information

Acta Cryst. (2007). E63, i73–i74 [https://doi.org/10.1107/S1600536807007507]

LiNi

Fe

PO

Gan Liang, Ronald E. Benson, Jiying Li, David Vaknin and Lee M. Daniels

Lithium ferrous nickel phosphate

Crystal data

LiNi0.66Fe0.34PO4

Mr = 159.63

Orthorhombic, Pnma

Hall symbol: -P 2ac 2n

a = 10.0871 (16) Å

b = 5.8845 (10) Å

c = 4.6820 (8) Å

V = 277.91 (8) Å3

Z = 4

F(000) = 416

Dx = 3.815 Mg m−3

Dm = 3.749 Mg m−3

Dm measured by floatation Mo Kα radiation, λ = 0.71075 Å Cell parameters from 50 reflections

θ = 1.0–27.5°

µ = 6.84 mm−1

T = 150 K

Block, dark amber-brown 0.19 × 0.18 × 0.14 mm

Data collection

Rigaku SCXmini diffractometer

Radiation source: fine-focus sealed tube Graphite monochromator

Detector resolution: 4900 pixels mm-1 data collected from ω scans

Absorption correction: multi-scan (ABSCOR; Higashi, 1995)

Tmin = 0.568, Tmax = 0.692

2026 measured reflections 345 independent reflections 328 reflections with I > 2σ(I)

Rint = 0.033

θmax = 27.5°, θmin = 4.0°

h = −13→12

k = −7→7

l = −6→5

Refinement

Refinement on F2 Least-squares matrix: full

R[F2 _{> 2σ(F}2_{)] = 0.020}

wR(F2_{) = 0.044}

S = 1.18 345 reflections 43 parameters 0 restraints

Primary atom site location: structure-invariant direct methods

Secondary atom site location: difference Fourier map

w = 1/[σ2_(F

o2) + (0.0162P)2 + 0.3281P] where P = (Fo2 + 2Fc2)/3

(Δ/σ)max < 0.001 Δρmax = 0.37 e Å−3 Δρmin = −0.47 e Å−3

Special details

Experimental. high-temperature flux

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 _{against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F}2_, conventional R-factors R are based on F, with F set to zero for negative F2_{. The threshold expression of F}2 _{> σ(F}2_{) is used} only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

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

x y z Uiso*/Ueq Occ. (<1)

Ni1 0.27649 (4) 0.2500 −0.01877 (8) 0.0034 (2) 0.66

Fe1 0.27649 (4) 0.2500 −0.01877 (8) 0.0034 (2) 0.34

P1 0.09411 (8) 0.2500 0.41781 (17) 0.0041 (2)

O1 0.0988 (2) 0.2500 0.7429 (5) 0.0058 (5)

O2 0.4521 (2) 0.2500 0.2019 (5) 0.0051 (5)

O3 0.16550 (14) 0.0433 (3) 0.2782 (3) 0.0058 (4)

Li1 0.0000 0.0000 0.0000 0.0050 (11)

Atomic displacement parameters (Å2₎

U11 _U22 _U33 _U12 _U13 _U23

Ni1 0.0031 (3) 0.0022 (3) 0.0048 (3) 0.000 −0.00022 (14) 0.000

Fe1 0.0031 (3) 0.0022 (3) 0.0048 (3) 0.000 −0.00022 (14) 0.000

P1 0.0040 (4) 0.0033 (4) 0.0049 (4) 0.000 0.0003 (3) 0.000

O1 0.0061 (11) 0.0050 (10) 0.0063 (11) 0.000 −0.0006 (9) 0.000

O2 0.0043 (11) 0.0043 (10) 0.0067 (11) 0.000 0.0005 (9) 0.000

O3 0.0070 (8) 0.0044 (7) 0.0060 (7) 0.0007 (6) 0.0014 (6) 0.0001 (5)

Li1 0.006 (3) 0.005 (2) 0.004 (3) −0.004 (2) −0.0009 (18) −0.0013 (18)

Geometric parameters (Å, º)

Ni1—O2 2.051 (2) O1—Li1vi _{2.1464 (16)}

Ni1—O3i _{2.0557 (15) O2—P1}vii _{1.538 (2)}

Ni1—O3ii _{2.0557 (15) O2—Li1}viii _{2.0844 (15)}

Ni1—O1iii _{2.111 (2) O2—Li1}ix _{2.0844 (15)}

Ni1—O3iv _{2.1599 (15) O3—Fe1}x _{2.0557 (15)}

Ni1—O3 2.1600 (15) O3—Ni1x _{2.0557 (15)}

Ni1—P1 2.7501 (10) O3—Li1 2.1327 (15)

Ni1—Li1 3.1544 (5) Li1—O2v _{2.0844 (15)}

Ni1—Li1iv _{3.1544 (5) Li1—O2}xi _{2.0844 (15)}

P1—O1 1.523 (2) Li1—O3xii _{2.1327 (15)}

P1—O2v _{1.538 (2) Li1—O1}xiii _{2.1464 (16)}

P1—O3iv _{1.5572 (16) Li1—O1}iii _{2.1464 (16)}

supporting information

sup-3 Acta Cryst. (2007). E63, i73–i74

P1—Li1iv _{2.6253 (7) Li1—Li1}xiv _{2.9423 (5)}

O1—Fe1vi _{2.111 (2) Li1—Ni1}xii _{3.1544 (5)}

O1—Ni1vi _{2.111 (2) Li1—Fe1}xii _{3.1544 (5)}

O2—Ni1—O3i _{89.26 (5) Fe1}x_—O3—Ni1x _{0.000 (19)}

O2—Ni1—O3ii _{89.26 (5) P1—O3—Li1 89.30 (7)}

O3i_—Ni1—O3ii _{114.22 (9) Fe1}x_{—O3—Li1 113.88 (7)}

O2—Ni1—O1iii _{178.34 (8) Ni1}x_{—O3—Li1 113.88 (7)}

O3i_—Ni1—O1iii _{89.84 (5) P1—O3—Ni1 94.03 (7)}

O3ii_—Ni1—O1iii _{89.84 (5) Fe1}x_{—O3—Ni1 128.53 (7)}

O2—Ni1—O3iv _{97.09 (6) Ni1}x_{—O3—Ni1 128.53 (7)}

O3i_—Ni1—O3iv _{156.63 (7) Li1—O3—Ni1 94.59 (6)}

O3ii_—Ni1—O3iv _{88.42 (4) O2}v_—Li1—O2xi _{180.00 (9)}

O1iii_—Ni1—O3iv _{84.28 (6) O2}v_{—Li1—O3 71.82 (7)}

O2—Ni1—O3 97.09 (6) O2xi_{—Li1—O3 108.18 (7)}

O3i_{—Ni1—O3 88.42 (4) O2}v_—Li1—O3xii _{108.18 (7)}

O3ii_{—Ni1—O3 156.63 (7) O2}xi_—Li1—O3xii _{71.82 (7)}

O1iii_{—Ni1—O3 84.28 (6) O3—Li1—O3}xii _180.0

O3iv_{—Ni1—O3 68.53 (8) O2}v_—Li1—O1xiii _{90.04 (6)}

O2—Ni1—P1 101.74 (6) O2xi_—Li1—O1xiii _{89.96 (6)}

O3i_{—Ni1—P1 122.29 (4) O3—Li1—O1}xiii _{95.91 (7)}

O3ii_{—Ni1—P1 122.29 (4) O3}xii_—Li1—O1xiii _{84.09 (7)}

O1iii_{—Ni1—P1 79.92 (6) O2}v_—Li1—O1iii _{89.96 (6)}

O3iv_{—Ni1—P1 34.39 (4) O2}xi_—Li1—O1iii _{90.04 (6)}

O3—Ni1—P1 34.39 (4) O3—Li1—O1iii _{84.09 (7)}

O2—Ni1—Li1 138.57 (4) O3xii_—Li1—O1iii _{95.91 (7)}

O3i_{—Ni1—Li1 82.70 (4) O1}xiii_—Li1—O1iii _{180.00 (10)}

O3ii_{—Ni1—Li1 131.01 (4) O2}v_{—Li1—P1 35.84 (6)}

O1iii_{—Ni1—Li1 42.62 (4) O2}xi_{—Li1—P1 144.16 (6)}

O3iv_{—Ni1—Li1 77.66 (4) O3—Li1—P1 36.38 (4)}

O3—Ni1—Li1 42.37 (4) O3xii_{—Li1—P1 143.62 (4)}

P1—Ni1—Li1 52.252 (16) O1xiii_{—Li1—P1 97.70 (5)}

O2—Ni1—Li1iv _{138.57 (4) O1}iii_{—Li1—P1 82.30 (5)}

O3i_—Ni1—Li1iv _{131.01 (4) O2}v_—Li1—P1xii _{144.16 (6)}

O3ii_—Ni1—Li1iv _{82.70 (4) O2}xi_—Li1—P1xii _{35.84 (6)}

O1iii_—Ni1—Li1iv _{42.62 (4) O3—Li1—P1}xii _{143.62 (4)}

O3iv_—Ni1—Li1iv _{42.37 (4) O3}xii_—Li1—P1xii _{36.38 (4)}

O3—Ni1—Li1iv _{77.66 (4) O1}xiii_—Li1—P1xii _{82.30 (5)}

P1—Ni1—Li1iv _{52.252 (16) O1}iii_—Li1—P1xii _{97.70 (5)}

Li1—Ni1—Li1iv _{55.597 (13) P1—Li1—P1}xii _180.0

O1—P1—O2v _{113.17 (13) O2}v_—Li1—Li1iv _{45.11 (4)}

O1—P1—O3iv _{113.90 (8) O2}xi_—Li1—Li1iv _{134.89 (4)}

O2v_—P1—O3iv _{106.12 (8) O3—Li1—Li1}iv _{83.13 (4)}

O1—P1—O3 113.90 (8) O3xii_—Li1—Li1iv _{96.87 (4)}

O2v_{—P1—O3 106.12 (8) O1}xiii_—Li1—Li1iv _{133.27 (4)}

O3iv_{—P1—O3 102.69 (12) O1}iii_—Li1—Li1iv _{46.73 (4)}

O1—P1—Li1 139.12 (5) P1—Li1—Li1iv _{55.919 (11)}

O3iv_{—P1—Li1 106.98 (7) O2}v_—Li1—Li1xiv _{134.89 (4)}

O3—P1—Li1 54.32 (6) O2xi_—Li1—Li1xiv _{45.11 (4)}

O1—P1—Li1iv _{139.12 (5) O3—Li1—Li1}xiv _{96.87 (4)}

O2v_—P1—Li1iv _{52.53 (6) O3}xii_—Li1—Li1xiv _{83.13 (4)}

O3iv_—P1—Li1iv _{54.32 (6) O1}xiii_—Li1—Li1xiv _{46.73 (4)}

O3—P1—Li1iv _{106.98 (7) O1}iii_—Li1—Li1xiv _{133.27 (4)}

Li1—P1—Li1iv _{68.16 (2) P1—Li1—Li1}xiv _{124.082 (11)}

O1—P1—Ni1 136.23 (9) P1xii_—Li1—Li1xiv _{55.918 (11)}

O2v_{—P1—Ni1 110.61 (9) Li1}iv_—Li1—Li1xiv _180.0

O3iv_{—P1—Ni1 51.58 (6) O2}v_—Li1—Ni1xii _{96.07 (5)}

O3—P1—Ni1 51.58 (6) O2xi_—Li1—Ni1xii _{83.93 (5)}

Li1—P1—Ni1 71.82 (2) O3—Li1—Ni1xii _{136.96 (4)}

Li1iv_{—P1—Ni1 71.82 (2) O3}xii_—Li1—Ni1xii _{43.04 (4)}

P1—O1—Fe1vi _{123.70 (13) O1}xiii_—Li1—Ni1xii _{41.77 (6)}

P1—O1—Ni1vi _{123.70 (13) O1}iii_—Li1—Ni1xii _{138.23 (6)}

Fe1vi_—O1—Ni1vi _{0.000 (18) P1—Li1—Ni1}xii _{124.08 (2)}

P1—O1—Li1xv _{123.10 (8) P1}xii_—Li1—Ni1xii _{55.92 (2)}

Fe1vi_—O1—Li1xv _{95.61 (8) Li1}iv_—Li1—Ni1xii _{117.799 (7)}

Ni1vi_—O1—Li1xv _{95.61 (8) Li1}xiv_—Li1—Ni1xii _{62.201 (7)}

P1—O1—Li1vi _{123.10 (8) O2}v_—Li1—Fe1xii _{96.07 (5)}

Fe1vi_—O1—Li1vi _{95.61 (8) O2}xi_—Li1—Fe1xii _{83.93 (5)}

Ni1vi_—O1—Li1vi _{95.61 (8) O3—Li1—Fe1}xii _{136.96 (4)}

Li1xv_—O1—Li1vi _{86.53 (8) O3}xii_—Li1—Fe1xii _{43.04 (4)}

P1vii_{—O2—Ni1 128.37 (13) O1}xiii_—Li1—Fe1xii _{41.77 (6)}

P1vii_—O2—Li1viii _{91.63 (8) O1}iii_—Li1—Fe1xii _{138.23 (6)}

Ni1—O2—Li1viii _{122.50 (7) P1—Li1—Fe1}xii _{124.08 (2)}

P1vii_—O2—Li1ix _{91.63 (8) P1}xii_—Li1—Fe1xii _{55.92 (2)}

Ni1—O2—Li1ix _{122.50 (7) Li1}iv_—Li1—Fe1xii _{117.799 (7)}

Li1viii_—O2—Li1ix _{89.79 (8) Li1}xiv_—Li1—Fe1xii _{62.201 (7)}

P1—O3—Fe1x _{126.39 (9) Ni1}xii_—Li1—Fe1xii _{0.000 (16)}

P1—O3—Ni1x _{126.39 (9)}