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

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Lithium cobalt(II) pyrophosphate, Li1.86CoP2O7, from synchrotron X-ray powder data

aChemistry and Materials, SUNY Binghamton, Binghamton, NY, USA
*Correspondence e-mail: stanwhit@gmail.com

(Received 30 August 2011; accepted 19 September 2011; online 30 September 2011)

Structure refinement of high-resolution X-ray powder diffraction data of the title compound gave the composition Li1.865CoP2O7, which is also verified by the ICP measurement. Two Co sites exist in the structure: one is a CoO5 square pyramid and the other is a CoO6 octa­hedron. They share edges and are further inter­connected through P2O7 groups, forming a three-dimensional framework, which exhibits different kinds of inter­secting tunnels containing Li cations and could be of great inter­est in Li ion battery chemistry. The structure also exhibits cation disorder with 13.5% Co residing at the lithium (Li1) site. Co seems to have an average oxidation state of 2.135, as obtained from the strutural stochiometry that closely supports the magnetic susceptibility findings.

Related literature

For related structures, see: Adam et al. (2008[Adam, L., Guesdon, A. & Raveau, B. (2008). J. Solid State Chem. 181, 3110-3115.]); Nishimura et al. (2010[Nishimura, S., Nakamura, M., Natsui, R. & Yamada, A. (2010). J. Am. Chem. Soc. 132, 13596-13597.]); Zhou et al. (2011[Zhou, H., Upreti, S., Chernova, N., Hautier, G., Ceder, G. & Whittingham, M. S. (2011). Chem. Mater. 23,293-300.]). For related materials with Na+ and K+ cations, see: Erragh et al. (1991[Erragh, F., Boukhari, A., Elouadi, B. & Holt, E. M. (1991). J. Cryst. Spect. Res. 21, 321-326.]); Sanz et al. (1999[Sanz, F., Parada, C., Rojo, J. M., Reuiz-Valero, C. & Saez-Puche, R. (1999). J. Solid State Chem. 145, 604-611.]); Beaury et al. (2004[Beaury, L., Derouet, J., Binet, J., Sanz, F. & Ruiz-Valero, C. (2004). J. Solid State Chem. 177, 1437-1443.]); Gopalakrishna et al. (2005[Gopalakrishna, G. S., Mahesh, M. J., Ashamanjari, K. G. & Shashidharaprasad, J. (2005). J. Cryst. Growth, 281, 604-610.]); Bih et al. (2006[Bih, H., Saadoune, I. & Mansori, M. (2006). Moroc. J. Condens. Matter, 7, 74-76.]); Guesmi et al. (2007[Guesmi, A., Ouerfelli, N., Mazza, D. & Driss, A. (2007). Acta Cryst. A63, s277-s278.]). For related structural frameworks, see: Beaury et al. (2004[Beaury, L., Derouet, J., Binet, J., Sanz, F. & Ruiz-Valero, C. (2004). J. Solid State Chem. 177, 1437-1443.]); Fagginani & Calvo (1976)[Fagginani, R. & Calvo, C. (1976). Can. J. Chem., 54, 3319-3324.]; Sandström et al. (2003[Sandström, M., Fischer, A. & Boström, D. (2003). Acta Cryst. E59, i139-i141.]); Etheredge & Hwu (1995[Etheredge, K. M. S. & Hwu, S. J. (1995). Inorg. Chem. 34, 1495-1499.]); El Maadi et al. (1995[El Maadi, A., Boukhari, A. & Holt, E. M. (1995). J. Chem. Crystallogr. 25, 531-536.]); Huang & Hwa (1998[Huang, Q. & Hwu, S. J. (1998). Inorg. Chem. 37, 5869-5874.]); Sanz et al. (1999[Sanz, F., Parada, C., Rojo, J. M., Reuiz-Valero, C. & Saez-Puche, R. (1999). J. Solid State Chem. 145, 604-611.]); Erragh et al. (1998[Erragh, F., Boukhari, A., Sadel, A. & Holt, E. M. (1998). Acta Cryst. C54, 1373-1376.]). Pseudovoigt profile coefficients as parameterized in Thompson et al. (1987[Thompson, P., Cox, D. E. & Hastings, J. B. (1987). J. Appl. Cryst. 20, 79-83.]) and Finger et al. (1994[Finger, L. W., Cox, D. E. & Jephcoat, A. P. (1994). J. Appl. Cryst. 27, 892-900.]).

Experimental

Crystal data
  • CoLi1.865O7P2

  • Mr = 245.82

  • Monoclinic, P 21 /a

  • a = 9.76453 (4) Å

  • b = 9.69622 (4) Å

  • c = 10.95952 (4) Å

  • β = 101.7664 (2)°

  • V = 1015.83 (1) Å3

  • Z = 8

  • Synchrotron radiation, λ = 0.413988 Å

  • μ = 0.89 mm−1

  • T = 297 K

  • irregular shape, 15 × 13 mm

Data collection
  • Advanced Photon Source diffractometer

  • Specimen mounting: kapton capillary

  • Data collection mode: transmission

  • Scan method: continuous

Refinement
  • Rp = 0.057

  • Rwp = 0.080

  • Rexp = 0.049

  • R(F2) = 0.04534

  • χ2 = 2.624

  • 24500 data points

  • 269 parameters

Data collection: Advance Photon Source Argonne National Laboratory; cell refinement: GSAS (Larson & Von Dreele, 2000[Larson, A. C. & Von Dreele, R. B. (2000). GSAS. Report LAUR 86-748. Los Alamos National Laboratory, New Mexico, USA.]); data reduction: Powder4 (Dragoe, 2001[Dragoe, N. (2001). J. Appl. Cryst. 34, 535.]); program(s) used to solve structure: GSAS; program(s) used to refine structure: GSAS; molecular graphics: CrystalMaker (Palmer, 2005[Palmer, D. (2005). CrystalMaker. CrystalMaker Software Ltd, Yarnton, England.]); software used to prepare material for publication: publCIF (Westrip, 2010[Westrip, S. P. (2010). J. Appl. Cryst. 43, 920-925.]).

Supporting information


Comment top

A2MP2O7 is a large family, in which various frameworks are encountered consisting of MO6 octahedra (Fagginani et al., 1976; Sandström et.al., 2003) and MO4 polyhedra (Etheredge et al., 1995; Erragh et al., 1998; Sanz et al., 1999) interconnected through P2O7 groups (Fig. 1). Dimeric M2O10 units, built up of two edge-sharing MO6 octahedra, are only observed for some A2MP2O7 pyrophosphates (El Maadi et al. 1995; Huang et al. 1998) and dimeric M2O11 units(corner-shared MO6) seem to be much more rare, just observed for Na2CoP2O7 (Erragh et al. 1991). Two forms of structures were found for Na2CoP2O7 by Erragh et al. 1991: one is triclinic and another one is orthorhombic. The tetragonal structure of Na2CoP2O7 was reported by Sanz et al. 1999 and they found that the tetragonal form could be a derivative of the orthorhombic form, with a higher point symmetry for the former. In addition, the tetragonal structured Na2CoP2O7 was described by Guesmi et al. 2007. To our knowledge, the A2CoP2O7 with Li as cation has never been reported.

Here, we report a new Li containing solid with a three-dimensional framework (Fig. 2) crystallizing in the monoclinic space group P21/a. Its structure is similar to the recently reported Li2MnP2O7 (Adam et al. 2008), a new member of the A2MP2O7 family: original M2O9 units, built up of one MO5 trigonal bipyramid sharing one edge with one MO6 octahedron, sharing corners with P2O7 pyrophosphate groups to form undulating (M4P8O32) layers. A 3-D framework results from the interconnection between metal oxide and pyrophosphate groups, and the lithium cations are located in the tunnels thus formed (Fig 2). The structure of the related Fe-compound has been studied by us (Zhou et al. 2011) and Nishimura et al. (2010), as well as the electrochemical properties, which showed that it is a good candidate for the cathode material of lithium-ion batteries. The title compound also has the potential to work as the cathode material for lithium-ion batteries. We present here its crystal structure, as determined and refined from synchrotron powder X-ray diffraction data (Fig. 3).

Related literature top

For related structures, see: Adam et al. (2008); Nishimura et al. (2010); Zhou et al. (2011). For related materials with Na and K cations, see: Erragh et al. (1991); Sanz et al. (1999); Beaury et al. (2004); Gopalakrishna et al. (2005); Bih et al. (2006); Guesmi et al. (2007). For related structural frameworks, see: Beaury et al. (2004); Fagginani & Calvo (1976); Sandström et al. (2003); Etheredge & Hwu (1995); El Maadi et al. (1995); Huang et al. (1998); Sanz et al. (1999); Erragh et al. (1998);

Experimental top

The powder sample was synthesized through a "wet" method based on mixing stoichiometric aqueous solutions of the precursors followed by thermal treatments. The general procedure involves the mixing of soluble precursors in distilled water followed by a slow evaporation through continuous stirring to dryness before annealing the resultant solids. The precursors for the synthesis were Li(CH3COO),Co(CH3COO)2. 4H2O,and NH4H2PO4, which were dissolved in 100 ml distilled water in a molar ratio of 2:1:2 (1.32 g, 2.49 g and 2.3 g respectively) to give a 0.02 molar lithium solution. The self-adjusted pH of all the solutions were found to be around 4.5. The solution was stirred and evaporated on a hot-plate in the hood followed by vacuum oven drying overnight at 363 K. The resulting solid was preheated in a H2/He (8.5°/91.5° by volume) atmosphere at 673 K for 4h to decompose the precursors followed by reheating under the same atmosphere up to 873 K for 16h with intermittent grinding to obtain the pink colored powder as final product. The sample was also analyzed with a Perkin-Elmer ICP-OES Optima 7000 DV for the elemental content. The average result of 3 analyses showed that the ratio of Li: Co: P is 1.85: 0.996:2. In addition, the SQUID magnetic study on the sample using a Quantum Design MPMS XL SQUID magnetometer showed that the effective magnetic moment of it is 5.23mBwhich is typical divalent Co.

Refinement top

During structural refinement, occupancy factor for Li1 and Co3 were refined using constrains for atomic coordinate, atomic displacement parameter, and keeping the sum of occupancy facter equals to unity, which later were fixed to their close refined values as 0.73 and 0.27 respectively. Occupancy for Co1 was also observed to be deficient and fixed to it's closely refined value of 0.739 to 0.73, in final refinement cycles.

Structure description top

A2MP2O7 is a large family, in which various frameworks are encountered consisting of MO6 octahedra (Fagginani et al., 1976; Sandström et.al., 2003) and MO4 polyhedra (Etheredge et al., 1995; Erragh et al., 1998; Sanz et al., 1999) interconnected through P2O7 groups (Fig. 1). Dimeric M2O10 units, built up of two edge-sharing MO6 octahedra, are only observed for some A2MP2O7 pyrophosphates (El Maadi et al. 1995; Huang et al. 1998) and dimeric M2O11 units(corner-shared MO6) seem to be much more rare, just observed for Na2CoP2O7 (Erragh et al. 1991). Two forms of structures were found for Na2CoP2O7 by Erragh et al. 1991: one is triclinic and another one is orthorhombic. The tetragonal structure of Na2CoP2O7 was reported by Sanz et al. 1999 and they found that the tetragonal form could be a derivative of the orthorhombic form, with a higher point symmetry for the former. In addition, the tetragonal structured Na2CoP2O7 was described by Guesmi et al. 2007. To our knowledge, the A2CoP2O7 with Li as cation has never been reported.

Here, we report a new Li containing solid with a three-dimensional framework (Fig. 2) crystallizing in the monoclinic space group P21/a. Its structure is similar to the recently reported Li2MnP2O7 (Adam et al. 2008), a new member of the A2MP2O7 family: original M2O9 units, built up of one MO5 trigonal bipyramid sharing one edge with one MO6 octahedron, sharing corners with P2O7 pyrophosphate groups to form undulating (M4P8O32) layers. A 3-D framework results from the interconnection between metal oxide and pyrophosphate groups, and the lithium cations are located in the tunnels thus formed (Fig 2). The structure of the related Fe-compound has been studied by us (Zhou et al. 2011) and Nishimura et al. (2010), as well as the electrochemical properties, which showed that it is a good candidate for the cathode material of lithium-ion batteries. The title compound also has the potential to work as the cathode material for lithium-ion batteries. We present here its crystal structure, as determined and refined from synchrotron powder X-ray diffraction data (Fig. 3).

For related structures, see: Adam et al. (2008); Nishimura et al. (2010); Zhou et al. (2011). For related materials with Na and K cations, see: Erragh et al. (1991); Sanz et al. (1999); Beaury et al. (2004); Gopalakrishna et al. (2005); Bih et al. (2006); Guesmi et al. (2007). For related structural frameworks, see: Beaury et al. (2004); Fagginani & Calvo (1976); Sandström et al. (2003); Etheredge & Hwu (1995); El Maadi et al. (1995); Huang et al. (1998); Sanz et al. (1999); Erragh et al. (1998);

Computing details top

Data collection: Advance Photon Source Argonne National Laboratory; cell refinement: GSAS (Larson & Von Dreele, 2000); data reduction: Powder4 (Dragoe, 2001); program(s) used to solve structure: GSAS (Larson & Von Dreele, 2000); program(s) used to refine structure: GSAS (Larson & Von Dreele, 2000); molecular graphics: publCIF (Westrip, 2010); software used to prepare material for publication: CrystalMaker (Palmer, 2005).

Figures top
[Figure 1] Fig. 1. Thermal ellipsoid view of Li1.86CoP2O7 framework, having edge shared CoO5 and CoO6 interconnected through P2O7 moities.
[Figure 2] Fig. 2. Polyhedral view of unit cell packing showing tunneled structures containing Li ions, viewed along [100].
[Figure 3] Fig. 3. X-ray Rietveld refinement profiles for Li1.86CoP2O7, data recorded at room temperature. Triangles mark the experimental points (red), solid line is the calculated profile (blue) and bottom trace shows the difference curve (green).
Lithium cobalt(II) pyrophosphate top
Crystal data top
CoLi1.865O7P2F(000) = 948.7
Mr = 245.82Dx = 3.214 Mg m3
Monoclinic, P21/aMelting point: 1023 K
Hall symbol: -P 2yabSynchrotron radiation, λ = 0.413988 Å
a = 9.76453 (4) ŵ = 0.89 mm1
b = 9.69622 (4) ÅT = 297 K
c = 10.95952 (4) ÅParticle morphology: block
β = 101.7664 (2)°pink
V = 1015.83 (1) Å3irregular, 15 × 13 mm
Z = 8Specimen preparation: Prepared at 873 K and 101.325 kPa
Data collection top
Advanced Photon Source
diffractometer
Specimen mounting: kapton capillary
Radiation source: SynchrotronData collection mode: transmission
Si monochromatorScan method: continuous
Refinement top
Least-squares matrix: fullExcluded region(s): Reflections exceeding 2-theta 30 were omitted for the ease of refinement.
Rp = 0.057Profile function: CW Profile function number 3 with 19 terms Pseudovoigt profile coefficients as parameterized in Thompson et al., (1987) and Finger et al. (1994).
#1(GU) = 6.454 #2(GV) = -0.998 #3(GW) = 0.075 #4(GP) = 0.000 #5(LX) = 0.327 #6(LY) = 0.000 #7(S/L) = 0.0011 #8(H/L) = 0.0014 #9(trns) = 0.00 #10(shft)= 0.0000 #11(stec)= 0.00 #12(ptec)= 0.00 #13(sfec)= 0.00 #14(L11) = 0.067 #15(L22) = 0.070 #16(L33) = 0.058 #17(L12) = 0.010 #18(L13) = 0.010 #19(L23) = -0.004 Peak tails are ignored where the intensity is below 0.0010 times the peak Aniso. broadening axis 0.0 0.0 1.0
Rwp = 0.080269 parameters
Rexp = 0.0490 restraints
R(F2) = 0.04534(Δ/σ)max = 0.03
24500 data pointsBackground function: GSAS Background function number 1 with 36 terms. Shifted Chebyshev function of 1st kind 1: 165.338 2: -31.4210 3: -8.19118 4: 6.28432 5: -10.8524 6: 14.3842 7: -8.22810 8: -0.949190 9: 13.3092 10: -14.8044 11: 4.75285 12: -1.09442 13: -0.739293 14: 5.47743 15: -2.87265 16: 1.05489 17: -3.22764 18: 1.21714 19: 0.537209 20: -3.25962 21: 2.18736 22: -1.12437 23: -2.15219 24: 3.41374 25: -3.88852 26: 1.14500 27: 3.06741 28: -3.05038 29: 0.529274 30: 0.298855 31: -4.06399 32: 1.50867 33: 1.15056 34: -2.20673 35: 0.550944 36: 5.540140E-02
Crystal data top
CoLi1.865O7P2V = 1015.83 (1) Å3
Mr = 245.82Z = 8
Monoclinic, P21/aSynchrotron radiation, λ = 0.413988 Å
a = 9.76453 (4) ŵ = 0.89 mm1
b = 9.69622 (4) ÅT = 297 K
c = 10.95952 (4) Åirregular, 15 × 13 mm
β = 101.7664 (2)°
Data collection top
Advanced Photon Source
diffractometer
Data collection mode: transmission
Specimen mounting: kapton capillaryScan method: continuous
Refinement top
Rp = 0.05724500 data points
Rwp = 0.080269 parameters
Rexp = 0.0490 restraints
R(F2) = 0.04534
Special details top

Experimental. Data was collected with powder sample packed in Kapton capillary

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/UeqOcc. (<1)
Co10.25281 (15)0.71550 (15)0.18010 (14)0.0137 (4)*0.73
Co20.30165 (11)0.43043 (11)0.32719 (10)0.0095 (3)*
P10.3790 (2)0.6536 (2)0.5771 (2)0.0078 (5)*
P20.0613 (2)0.9265 (2)0.24116 (18)0.0089 (5)*
P30.0210 (2)0.4551 (2)0.75861 (19)0.0103 (5)*
P40.6144 (2)0.7956 (2)0.1113 (2)0.0117 (6)*
O10.1615 (5)0.8210 (5)0.3113 (5)0.0130 (14)*
O20.4709 (5)0.7806 (5)0.0792 (4)0.0106 (12)*
O30.3911 (5)0.8599 (4)0.1472 (5)0.0107 (13)*
O40.0302 (5)0.8437 (5)0.5592 (4)0.0116 (14)*
O50.4330 (5)0.4292 (5)0.1033 (4)0.0168 (13)*
O60.1790 (5)0.8356 (5)0.1511 (4)0.0115 (13)*
O70.0189 (5)0.4120 (4)0.6224 (4)0.0087 (13)*
O80.1866 (5)0.2976 (4)0.4146 (4)0.0047 (12)*
O90.1013 (5)0.6017 (4)0.7747 (4)0.0116 (13)*
O100.3827 (5)0.5734 (5)0.7087 (4)0.0061 (12)*
O110.4152 (5)0.5900 (4)0.2661 (4)0.0085 (13)*
O120.2775 (5)0.5646 (5)0.4803 (4)0.0134 (13)*
O130.3713 (5)1.0314 (5)0.2124 (5)0.0205 (15)*
O140.2204 (5)0.6299 (5)0.0018 (4)0.0094 (13)*
Li11.3433 (3)0.9255 (3)0.0397 (3)0.0087 (7)*0.73
Li20.0807 (17)0.1083 (15)0.0261 (15)0.009 (4)*
Li30.6728 (15)0.0711 (14)0.5465 (14)0.029 (4)*
Li40.400 (2)0.246 (2)0.5725 (17)0.065 (7)*
Co31.3433 (3)0.9255 (3)0.0397 (3)0.0087 (7)*0.27
Geometric parameters (Å, º) top
Co1—O12.105 (5)P2—O5v1.524 (4)
Co1—O32.028 (4)P2—O10iv1.584 (5)
Co1—O112.067 (4)P2—O11vi1.516 (5)
Co1—O13i2.226 (5)P3—O3ii1.514 (5)
Co1—O142.123 (5)P3—O71.546 (5)
Co2—O4ii2.030 (5)P3—O91.616 (4)
Co2—O6i2.180 (5)P3—O13vii1.563 (5)
Co2—O82.068 (4)P4—O21.519 (5)
Co2—O112.091 (4)P4—O6iii1.524 (4)
Co2—O122.173 (4)P4—O9viii1.582 (5)
Co2—O13i2.128 (5)P4—O14iii1.589 (5)
P1—O4iii1.529 (5)Co3—O2ix1.983 (5)
P1—O8iv1.547 (4)Co3—O3ix2.104 (6)
P1—O101.633 (5)Co3—O6ix2.006 (6)
P1—O121.556 (4)Co3—O13ix2.220 (5)
P2—O11.512 (5)Co3—O14x2.154 (5)
O1—Co1—O3100.14 (19)O8—Co2—O11169.24 (17)
O1—Co1—O11111.53 (19)O8—Co2—O13i96.85 (19)
O1—Co1—O14145.9 (2)O11—Co2—O13i83.05 (18)
O3—Co1—O1190.63 (18)O8iv—P1—O10108.2 (3)
O3—Co1—O1494.6 (2)O8iv—P1—O12109.1 (3)
O11—Co1—O1498.73 (18)O10—P1—O12103.6 (3)
O4ii—Co2—O884.60 (18)O1—P2—O5v111.4 (3)
O4ii—Co2—O1195.03 (18)O1—P2—O10iv106.9 (3)
O4ii—Co2—O13i177.0 (2)O5v—P2—O10iv104.4 (3)
Symmetry codes: (i) x+1/2, y1/2, z; (ii) x+1/2, y1/2, z+1; (iii) x+1/2, y+3/2, z; (iv) x+1/2, y+1/2, z+1; (v) x+1/2, y+1/2, z; (vi) x1/2, y+3/2, z; (vii) x1/2, y+3/2, z+1; (viii) x+1/2, y+3/2, z1; (ix) x+1, y, z; (x) x+3/2, y+1/2, z.

Experimental details

Crystal data
Chemical formulaCoLi1.865O7P2
Mr245.82
Crystal system, space groupMonoclinic, P21/a
Temperature (K)297
a, b, c (Å)9.76453 (4), 9.69622 (4), 10.95952 (4)
β (°) 101.7664 (2)
V3)1015.83 (1)
Z8
Radiation typeSynchrotron, λ = 0.413988 Å
µ (mm1)0.89
Specimen shape, size (mm)Irregular, 15 × 13
Data collection
DiffractometerAdvanced Photon Source
Specimen mountingKapton capillary
Data collection modeTransmission
Scan methodContinuous
2θ values (°)2θmin = ? 2θmax = ? 2θstep = ?
Refinement
R factors and goodness of fitRp = 0.057, Rwp = 0.080, Rexp = 0.049, R(F2) = 0.04534, χ2 = 2.624
No. of parameters269

Computer programs: Advance Photon Source Argonne National Laboratory, GSAS (Larson & Von Dreele, 2000), Powder4 (Dragoe, 2001), publCIF (Westrip, 2010), CrystalMaker (Palmer, 2005).

 

Acknowledgements

Use of the Advanced Photon Source at the Argonne National Laboratory was supported by the US Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE–AC02-06CH11357. The research at Binghamton was supported by the Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies of the US Department of Energy under Contract No. DE–AC02-05CH11231, under the Batteries for Advanced Transportation Technologies (BATT) Program subcontract # 6807148.

References

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