inorganic compounds\(\def\hfill{\hskip 5em}\def\hfil{\hskip 3em}\def\eqno#1{\hfil {#1}}\)

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ISSN: 2056-9890

A novel lithium copper iron phosphate with idealized formula Li5Cu22+Fe3+(PO4)4: crystal structure and distribution of defects

aChemistry and Materials, SUNY Binghamton, Binghamton, NY, USA, and bDepartment of Geology, Moscow State University, Moscow, Russian Federation
*Correspondence e-mail: stanwhit@gmail.com

(Received 6 March 2011; accepted 30 March 2011; online 7 April 2011)

Gray–green single crystals were obtained under high-pressure, high-temperature hydro­thermal conditions. A refinement of atom occupancies gave the composition Li3.68Cu2+Fe3+(Cu0.55Li0.45)2Fe2+0.15(PO4)4. The structure is built from triplets of edge-sharing (Cu,Li)O5–FeO6–(Cu,Li)O5 polyhedra, CuO4 quadrilaterals and PO4 tetra­hedra. In the (Cu,Li)O5 polyhedra the Cu and Li positions are statistically occupied in a 0.551 (2):0.449 (2) ratio. Both FeO6 and CuO4 polyhedra exhibit [\overline1] symmetry. The positions of additional Li atoms with vacancy defects are in the inter­stices of the framework.

Related literature

For a related structure, see: Yakubovich et al. (2006[Yakubovich, O. V., Massa, W., Kireev, V. V. & Urusov, V. S. (2006). Dokl. Phys. 51, 474-480.]). For related materials with low concentration of Cu atoms at Fe sites, see: Amine et al. (2000[Amine, K., Yasuda, H. & Yamachi, M. (2000). Proc. Electrochem. Soc. 99, 311-325.]); Heo et al. (2009[Heo, J. B., Lee, S. B., Cho, S. H., Kim, J., Park, S. H. & Lee, Y. S. (2009). Mater. Lett. 63, 581-583.]); Ni et al. (2005[Ni, J. F., Zhou, H. H., Chen, J. T. & Zhang, X. X. (2005). Mater. Lett. 59, 2361-2365.]); Yang et al. (2009[Yang, R., Song, X., Zhao, M. & Wang, F. (2009). J. Alloys Compd, 468, 365-369.]). For information on bond-valence calculations, see: Pyatenko (1972[Pyatenko, Yu. A. (1972). Sov. Phys. Crystallogr. 17, 677-682.]).

Experimental

Crystal data
  • Cu2.10Fe1.15Li4.59(PO4)4

  • Mr = 609.63

  • Triclinic, [P \overline 1]

  • a = 4.8950 (14) Å

  • b = 7.847 (2) Å

  • c = 8.388 (2) Å

  • α = 69.472 (5)°

  • β = 89.764 (6)°

  • γ = 75.501 (5)°

  • V = 290.88 (13) Å3

  • Z = 1

  • Mo Kα radiation

  • μ = 5.87 mm−1

  • T = 298 K

  • 0.27 × 0.23 × 0.19 mm

Data collection
  • Bruker SMART APEX diffractometer

  • Absorption correction: multi-scan (SADABS; Bruker, 2000[Bruker (2000). SADABS. Bruker AXS Inc., Madison, Wisconsin, USA.]) Tmin = 0.235, Tmax = 0.332

  • 100441 measured reflections

  • 1775 independent reflections

  • 1647 reflections with I > 2σ(I)

  • Rint = 0.023

Refinement
  • R[F2 > 2σ(F2)] = 0.031

  • wR(F2) = 0.086

  • S = 1.20

  • 1708 reflections

  • 143 parameters

  • Δρmax = 0.66 e Å−3

  • Δρmin = −0.63 e Å−3

Table 1
Selected bond lengths (Å)

Cu1—O4i 1.936 (2)
Cu1—O6 1.9430 (19)
Fe1—O1 1.931 (2)
Fe1—O5 2.038 (2)
Fe1—O2 2.041 (2)
Cu2—O8 1.969 (2)
Cu2—O7 1.998 (2)
Cu2—O6 2.003 (2)
Cu2—O5 2.075 (2)
Cu2—O2ii 2.171 (2)
Li1—O3 1.967 (8)
Li1—O4iii 2.028 (7)
Li1—O8iv 2.045 (7)
Li1—O3v 2.124 (8)
Fe2—O3 1.891 (6)
Fe2—O8vi 2.063 (6)
Fe2—O7vii 2.133 (7)
Fe2—O6vi 2.236 (7)
Fe2—O4iii 2.334 (6)
Li3—O7 1.909 (8)
Li3—O3viii 1.916 (7)
Li3—O2viii 2.183 (11)
Li3—O8ix 2.183 (10)
Symmetry codes: (i) -x-1, -y+2, -z+2; (ii) -x, -y+2, -z+1; (iii) -x, -y+1, -z+2; (iv) -x, -y+2, -z+2; (v) -x+1, -y+1, -z+2; (vi) x+1, y-1, z; (vii) x, y-1, z; (viii) x, y+1, z; (ix) x+1, y, z.

Data collection: SMART (Bruker, 2001[Bruker (2001). SMART. Bruker AXS Inc., Madison, Wisconsin, USA.]); cell refinement: SAINT (Bruker, 2002[Bruker (2002). SAINT. Bruker AXS Inc., Madison, Wisconsin, USA.]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008[Sheldrick, G. M. (2008). Acta Cryst. A64, 112-122.]); molecular graphics: DIAMOND (Brandenburg, 2006[Brandenburg, K. (2006). DIAMOND. Crystal Impact GbR, Bonn, Germany.]); software used to prepare material for publication: publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Comment top

There has been much interest in understanding the chemical and physical behavior of a new class of materials that shows reversible intercalation of lithium in the crystalline lattice for use in the next generation of Li ion batteries. Here we report a new type of Li containing solid which could be of great interest to electrochemists.

The asymmetric unit of the triclinic structure (Fig. 1) includes two tetrahedral P sites, both on the general position. The Cu1 – O distances around the square–planar Cu2+ cation at the center of symmetry (1d site) are 1.936 (2) and 1.943 (2) Å. Fe3+ cations in 1b Wyckoff site are surrounded by six O atoms, forming octahedral configuration with Fe—O bond lengths in the interval 1.931 (2) – 2.041 (2) Å. The cation-anion distances in five-vertex polyhedra, occupied by Cu and Li atoms in nearly equivalent amounts change from 1.969 (2) to 2.171 (2) Å; thus, the mixed occupation of the polyhedron by Cu2+ and Li+ cations explains why the Jahn-Teller distorton of the polyhedron is not so evident. Two Li sites with vacancy defects adopt five-vertex coordination, each with four closest oxygen atoms (Table 1), and one oxygen atom at longer distances of 2.739 (11) Å (Li3 –O8) and 2.778 (8) Å (Li1 – O3). In addition, a position of low occupancy for Fe2+ (Fe2) atoms has been found at 0.99 (1) Å from the Li3 site. Bond-valance sum data (Pyatenko, 1972) are consistent with the assumed oxidation state of Cu and Fe.

The basic features of the crystal structure consist of triplets of edge sharing (Cu,Li)2 – Fe1 –(Cu,Li)2 polyhedra (Fig.2) and Cu1 quadrilaterals, that form a three-dimensional framework by sharing oxygen vertices. The PO4 tetrahedra strengthen this framework by sharing all vertices with Fe1 octahedra and/or (Cu,Li)2 polyhedra (P1), while P2 tetrahedron shares one vertex with Fe1 and (Cu,Li)2 polyhedra, two vertices with Cu1 quadrilaterals, and one vertex (O3) remains unshared with the cationic framework and participates in the coordination of Li atoms (Table 2). Li1 and Li3 atoms occupy interstices of the structure; they form tetra groups of five-vertex polyhedra sharing edges (Fig.3). The structure may be described using an idealized formula Li5Cu2+2Fe3+(PO4)4; a similar lithium saturated iron phosphate with isomorphous and vacancy defects in the position of Li atoms, having an idealized formula Li5Fe3+(PO4)2F2 was studied in (Yakubovich et al., 2006). There are many reports in literature for crystal structures with low concentration of Cu atoms in Fe sites (Amine et al., 2000; Heo et al., 2009, Yang et al., 2009, Ni et al., 2005), however, the present structure seems to be a rare example of Cu rich three-dimensional matrix with Li+ ions in the interstices.

Related literature top

For a related structure, see: Yakubovich et al. (2006). For related materials with low concentration of Cu atoms at Fe sites, see: Amine et al. (2000); Heo et al. (2009); Ni et al. (2005); Yang et al. (2009). For information on bond-valence calculations, see Pyatenko (1972).

Experimental top

Single crystals were grown under high-temperature high-pressure hydrothermal conditions in the LiH2PO4—Fe2O3—H3PO4 system. Fe2O3 and LiH2PO4, weight ratio 5:1, were placed in a copper ampule of 120 ml volume with 5, 10, 20, 30 or 40% water solution of H3PO4. The reaction was conducted at 400 °C, 1000 bar (1 bar = 10 5 Pa) for 100 h. The reaction product was a mixture of brown, grayish-green, and blue-green crystals, white powder and copper chunks in a ratio dependant upon phosphoric acid concentration. The crystals were hand picked under an optical microscope, washed with water and isopropyl alcohol, dried and subjected to single-crystal x-ray diffraction analysis. The obtained crystals were also analyzed with a Jeol 8900 Electron Microprobe for EDS elemental content. The conditions were optimized with an acceleration potential of 15 kV and acurrent of 10 mA. The average result of 15 analyses showed the Cu: Fe: P ratio equal to 0.47: 0.28: 1, which is close to the ratio 0.52: 0.29: 1 determined from single-crystal X-ray refinement.

Refinement top

Refinement of site occupancies showed that Cu2 and Li2 atoms share one position in the structure, in the proportion of 0.551 (2): 0.449. During the refinement, the displacement parameters of Cu2 and Li2 were constrained to be equal. The oxidation states of Fe atoms in 1b and 2i Wyckoff sites were fixed in accordance with Fe - O distances and confirmed by bond valence calculation (Pyatenko, 1972).

Computing details top

Data collection: SMART (Bruker, 2001); cell refinement: SAINT (Bruker, 2002); data reduction: SAINT (Bruker, 2002); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: DIAMOND (Brandenburg, 2006); software used to prepare material for publication: publCIF (Westrip, 2010).

Figures top
[Figure 1] Fig. 1. The main structural elements of the title compound. Displacement ellipsoids are drawn at the 50% probability level. [Symmetry codes: (i) x, y - 1, z; (ii) -x, 1 - y, 1 - z; (v) 1 - x, 1 - y, 1 - z].
[Figure 2] Fig. 2. The crystal structure of the title compound projected onto the plane cb.
[Figure 3] Fig. 3. The structure fragment showing the groups of five-vertex Li polyhedra sharing edges.
Pentalithium dicopper iron tetraphosphate top
Crystal data top
Cu2.10Fe1.15Li4.59(PO4)4Z = 1
Mr = 609.63F(000) = 293.9
Triclinic, P1Dx = 3.480 Mg m3
Hall symbol: -P 1Mo Kα radiation, λ = 0.71073 Å
a = 4.8950 (14) ÅCell parameters from 8918 reflections
b = 7.847 (2) Åθ = 2.4–28.3°
c = 8.388 (2) ŵ = 5.87 mm1
α = 69.472 (5)°T = 298 K
β = 89.764 (6)°Block, green
γ = 75.501 (5)°0.27 × 0.23 × 0.19 mm
V = 290.88 (13) Å3
Data collection top
Bruker SMART APEX
diffractometer
1775 independent reflections
Radiation source: fine-focus sealed tube1647 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.023
ϕ scans, and ω scansθmax = 30.6°, θmin = 2.6°
Absorption correction: multi-scan
(SADABS; Bruker, 2000)
h = 77
Tmin = 0.235, Tmax = 0.332k = 1111
100441 measured reflectionsl = 1212
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.031 w = 1/[σ2(Fo2) + (0.040P)2 + 0.5P]
where P = (Fo2 + 2Fc2)/3
wR(F2) = 0.086(Δ/σ)max = 0.001
S = 1.20Δρmax = 0.66 e Å3
1708 reflectionsΔρmin = 0.63 e Å3
143 parametersExtinction correction: SHELXL97 (Sheldrick, 2010), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
0 restraintsExtinction coefficient: 0.008 (3)
Crystal data top
Cu2.10Fe1.15Li4.59(PO4)4γ = 75.501 (5)°
Mr = 609.63V = 290.88 (13) Å3
Triclinic, P1Z = 1
a = 4.8950 (14) ÅMo Kα radiation
b = 7.847 (2) ŵ = 5.87 mm1
c = 8.388 (2) ÅT = 298 K
α = 69.472 (5)°0.27 × 0.23 × 0.19 mm
β = 89.764 (6)°
Data collection top
Bruker SMART APEX
diffractometer
1775 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2000)
1647 reflections with I > 2σ(I)
Tmin = 0.235, Tmax = 0.332Rint = 0.023
100441 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.031143 parameters
wR(F2) = 0.0860 restraints
S = 1.20Δρmax = 0.66 e Å3
1708 reflectionsΔρmin = 0.63 e Å3
Special details top

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 F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) 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) top
xyzUiso*/UeqOcc. (<1)
Cu10.50001.00001.00000.00809 (14)
Fe10.00001.00000.50000.00691 (15)
Cu20.09925 (13)1.25406 (8)0.71583 (7)0.0080 (2)0.551 (2)
Li20.09925 (13)1.25406 (8)0.71583 (7)0.0080 (2)0.449 (2)
P10.37011 (14)1.70119 (10)0.53149 (9)0.00622 (16)
P20.08696 (15)0.80671 (10)0.91211 (8)0.00607 (16)
Li10.3243 (15)0.3973 (10)1.1070 (9)0.023 (2)0.92 (3)
Fe20.3834 (13)0.4186 (9)0.8189 (9)0.014 (2)0.076 (3)
Li30.262 (2)1.5161 (15)0.7187 (13)0.040 (2)0.924 (3)
O10.2556 (4)1.1578 (3)0.4209 (3)0.0106 (4)
O20.3006 (4)0.7643 (3)0.5056 (3)0.0090 (4)
O30.2355 (5)0.6208 (3)0.8948 (3)0.0132 (4)
O40.2135 (4)0.7997 (3)0.9644 (3)0.0111 (4)
O50.0858 (5)0.9747 (3)0.7461 (3)0.0104 (4)
O60.2511 (4)1.1666 (3)0.9440 (2)0.0076 (4)
O70.2528 (4)1.3249 (3)0.6291 (3)0.0108 (4)
O80.2947 (5)1.5157 (3)0.6891 (3)0.0133 (4)
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cu10.0056 (2)0.0073 (2)0.0128 (2)0.00214 (17)0.00253 (17)0.00512 (18)
Fe10.0061 (3)0.0056 (3)0.0090 (3)0.00124 (19)0.00114 (19)0.0029 (2)
Cu20.0102 (3)0.0052 (3)0.0078 (3)0.0007 (2)0.0029 (2)0.0023 (2)
Li20.0102 (3)0.0052 (3)0.0078 (3)0.0007 (2)0.0029 (2)0.0023 (2)
P10.0052 (3)0.0056 (3)0.0076 (3)0.0011 (2)0.0007 (2)0.0023 (2)
P20.0054 (3)0.0060 (3)0.0067 (3)0.0009 (2)0.0008 (2)0.0026 (2)
Li10.026 (4)0.019 (4)0.025 (4)0.002 (3)0.001 (3)0.011 (3)
Fe20.014 (3)0.012 (3)0.018 (4)0.004 (2)0.006 (2)0.008 (3)
Li30.058 (6)0.050 (6)0.036 (5)0.024 (5)0.013 (5)0.037 (5)
O10.0101 (9)0.0133 (10)0.0120 (9)0.0062 (8)0.0023 (7)0.0069 (8)
O20.0052 (9)0.0095 (9)0.0134 (9)0.0009 (7)0.0001 (7)0.0063 (8)
O30.0153 (10)0.0115 (10)0.0134 (9)0.0000 (8)0.0017 (8)0.0079 (8)
O40.0066 (9)0.0084 (9)0.0186 (10)0.0015 (7)0.0033 (8)0.0055 (8)
O50.0160 (10)0.0091 (9)0.0069 (8)0.0058 (8)0.0003 (7)0.0023 (7)
O60.0075 (9)0.0101 (9)0.0080 (8)0.0053 (7)0.0013 (7)0.0044 (7)
O70.0105 (9)0.0128 (10)0.0127 (9)0.0055 (8)0.0056 (7)0.0075 (8)
O80.0139 (10)0.0088 (10)0.0117 (9)0.0013 (8)0.0017 (8)0.0003 (8)
Geometric parameters (Å, º) top
Cu1—O4i1.936 (2)P2—O51.545 (2)
Cu1—O61.9430 (19)P2—O6v1.554 (2)
Fe1—O11.931 (2)Li1—O31.967 (8)
Fe1—O52.038 (2)Li1—O4vi2.028 (7)
Fe1—O22.041 (2)Li1—O8v2.045 (7)
Cu2—O81.969 (2)Li1—O3vii2.124 (8)
Cu2—O71.998 (2)Fe2—O31.891 (6)
Cu2—O62.003 (2)Fe2—O8viii2.063 (6)
Cu2—O52.075 (2)Fe2—O7ix2.133 (7)
Cu2—O2ii2.171 (2)Fe2—O6viii2.236 (7)
P1—O7iii1.521 (2)Fe2—O4vi2.334 (6)
P1—O1iii1.524 (2)Li3—O71.909 (8)
P1—O81.545 (2)Li3—O3x1.916 (7)
P1—O2iv1.555 (2)Li3—O2x2.183 (11)
P2—O31.515 (2)Li3—O8xi2.183 (10)
P2—O41.542 (2)
O4i—Cu1—O688.35 (9)O5—Cu2—O2ii78.90 (8)
O1—Fe1—O5ii88.97 (8)O7iii—P1—O1iii111.94 (12)
O1—Fe1—O292.27 (9)O7iii—P1—O8112.64 (12)
O5ii—Fe1—O282.88 (8)O1iii—P1—O8106.40 (12)
O8—Cu2—O792.29 (9)O7iii—P1—O2iv109.52 (12)
O8—Cu2—O688.84 (9)O1iii—P1—O2iv110.70 (12)
O7—Cu2—O6136.25 (9)O8—P1—O2iv105.43 (12)
O8—Cu2—O5176.89 (9)O3—P2—O4108.60 (12)
O7—Cu2—O590.75 (9)O3—P2—O5111.10 (12)
O6—Cu2—O589.40 (9)O4—P2—O5112.78 (12)
O8—Cu2—O2ii99.79 (9)O3—P2—O6v109.26 (12)
O7—Cu2—O2ii102.81 (8)O4—P2—O6v108.23 (12)
O6—Cu2—O2ii120.07 (8)O5—P2—O6v106.78 (11)
Symmetry codes: (i) x1, y+2, z+2; (ii) x, y+2, z+1; (iii) x, y+3, z+1; (iv) x1, y+1, z; (v) x, y+2, z+2; (vi) x, y+1, z+2; (vii) x+1, y+1, z+2; (viii) x+1, y1, z; (ix) x, y1, z; (x) x, y+1, z; (xi) x+1, y, z.

Experimental details

Crystal data
Chemical formulaCu2.10Fe1.15Li4.59(PO4)4
Mr609.63
Crystal system, space groupTriclinic, P1
Temperature (K)298
a, b, c (Å)4.8950 (14), 7.847 (2), 8.388 (2)
α, β, γ (°)69.472 (5), 89.764 (6), 75.501 (5)
V3)290.88 (13)
Z1
Radiation typeMo Kα
µ (mm1)5.87
Crystal size (mm)0.27 × 0.23 × 0.19
Data collection
DiffractometerBruker SMART APEX
diffractometer
Absorption correctionMulti-scan
(SADABS; Bruker, 2000)
Tmin, Tmax0.235, 0.332
No. of measured, independent and
observed [I > 2σ(I)] reflections
100441, 1775, 1647
Rint0.023
(sin θ/λ)max1)0.716
Refinement
R[F2 > 2σ(F2)], wR(F2), S 0.031, 0.086, 1.20
No. of reflections1708
No. of parameters143
Δρmax, Δρmin (e Å3)0.66, 0.63

Computer programs: SMART (Bruker, 2001), SAINT (Bruker, 2002), SHELXS97 (Sheldrick, 2008), SHELXL97 (Sheldrick, 2008), DIAMOND (Brandenburg, 2006), publCIF (Westrip, 2010).

Selected bond lengths (Å) top
Cu1—O4i1.936 (2)Li1—O8iv2.045 (7)
Cu1—O61.9430 (19)Li1—O3v2.124 (8)
Fe1—O11.931 (2)Fe2—O31.891 (6)
Fe1—O52.038 (2)Fe2—O8vi2.063 (6)
Fe1—O22.041 (2)Fe2—O7vii2.133 (7)
Cu2—O81.969 (2)Fe2—O6vi2.236 (7)
Cu2—O71.998 (2)Fe2—O4iii2.334 (6)
Cu2—O62.003 (2)Li3—O71.909 (8)
Cu2—O52.075 (2)Li3—O3viii1.916 (7)
Cu2—O2ii2.171 (2)Li3—O2viii2.183 (11)
Li1—O31.967 (8)Li3—O8ix2.183 (10)
Li1—O4iii2.028 (7)
Symmetry codes: (i) x1, y+2, z+2; (ii) x, y+2, z+1; (iii) x, y+1, z+2; (iv) x, y+2, z+2; (v) x+1, y+1, z+2; (vi) x+1, y1, z; (vii) x, y1, z; (viii) x, y+1, z; (ix) x+1, y, z.
 

Acknowledgements

We thank the US Department of Energy, Office of Vehicle Technologies, for their financial support through the BATT program at LBNL. Financial support from the National Science Foundation, DMR 0705657, is greatly appreciated. Olga Yakubovich thanks the Russian Fund for Basic Researches (Grant N 10–05-01068a) for the financial support.

References

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