Synthesis, crystal structure and lithium ion conduction of Li 3BP2O8

Article abstract of DOI:10.1039/c3dt52917g

Single crystals of Li₃BP₂O₈ were prepared by heating a mixture of starting materials with a Li : B : P molar ratio of 22 : 11 : 13 at 933 K in air and by cooling at a rate of -10 K h^-1. The X-ray diffraction (XRD) reflections of a single crystal were indexed with triclinic cell parameters: a = 5.1888(5) A, b = 7.4118(7) A, c = 7.6735(7) A, α = 101.18(1)°, β = 105.07(1)°, γ = 90.34(1)° (space group P1 (no. 2)). In the crystal structure of Li₃BP₂O₈, BO₄ and PO₄ tetrahedra share O atoms and form one-dimensional 1∞[BP₂O ₈]^3- chains along the c-axis direction. A polycrystalline Li₃BP₂O₈ bulk sample was synthesized by the solid state reaction of Li₄P₂O₇ and LiPO ₃ prepared from the starting materials in advance with H ₃BO₃ at 923 K. The lithium ion conductivities measured for the polycrystalline sample by the AC impedance and DC methods were 1.5 × 10^-5 S cm^-1 at 583 K and 6.0 × 10^-8 S cm^-1 at 423 K, respectively.

Full text of DOI:10.1039/c3dt52917g

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Synthesis, crystal structure and lithium ion
conduction of Li3BP2O8†
Cite this: Dalton Trans., 2014, 43,
2294
Toru Hasegawa and Hisanori Yamane*
Single crystals of Li3BP2O8 were prepared by heating a mixture of starting materials with a Li : B : P molar
ratio of 22 : 11 : 13 at 933 K in air and by cooling at a rate of −10 K h−1. The X-ray diffraction (XRD) reflec-
tions of a single crystal were indexed with triclinic cell parameters: a = 5.1888(5) Å, b = 7.4118(7) Å, c =
7.6735(7) Å, α = 101.18(1)°, β = 105.07(1)°, γ = 90.34(1)° (space group P¯1 (no. 2)). In the crystal structure of
1
Li3BP2O8, BO4 and PO4 tetrahedra share O atoms and form one-dimensional ∞[BP2O8]3− chains along
Received 16th October 2013,
Accepted 11th November 2013
the c-axis direction. A polycrystalline Li3BP2O8 bulk sample was synthesized by the solid state reaction of
Li4P2O7 and LiPO3 prepared from the starting materials in advance with H3BO3 at 923 K. The lithium ion
conductivities measured for the polycrystalline sample by the AC impedance and DC methods were
1.5 × 10−5 S cm−1 at 583 K and 6.0 × 10−8 S cm−1 at 423 K, respectively.
DOI: 10.1039/c3dt52917g
www.rsc.org/dalton
prepared in autoclaves at 553 K using boric acid or sodium
dihydrogen phosphate as the flux.7
Introduction
Borophosphates, containing complex anionic groups built
Borates and phosphates are known to be glass forming
of BO4 and/or BO3 and PO4, have been studied due to their materials, and formation of borophosphate glass in the Li2O–
rich structural chemistry and potential applications. The struc- B2O3–P2O5 system was reported by Tien and Hummel.5 The
tural chemistry of borophosphate anions extends from isolated structure and electrical conductivity of lithium borophosphate
species, oligomers, rings and chains to layers and glasses with the composition of 50Li2O–xB2O3–(1 − x)P2O5 (x =
frameworks.1–3 A concept for the classification of crystalline 2–25 mol%) was investigated,8 and a lithium ion conductivity
borophosphates in terms of structural chemistry has been pro- of 1.6 × 10−7 S cm−1 at room temperature was measured for a
posed by Gurbanova et al.2 and Ewald et al.3 Most borophos- glass of 0.45Li2O–0.275B2O3–0.275P2O5 composition.9
phates have been synthesized under hydrothermal conditions,
In the present study, the crystalline phase of Li3BP2O8 was
and OH− and/or H2O are contained in the structures. Anhy- synthesized in the Li2O–B2O3–P2O5 system. The crystal struc-
drous borophosphates are rare and usually prepared by high- ture of Li3BP2O8 was determined by single crystal X-ray diffrac-
temperature solid state reaction.3,4
tion (XRD), and the electrical properties were characterized for
Anhydrous alkali metal borophosphates reported in pre- polycrystalline bulk samples.
6
vious studies are Li22B11P13O60, Li2B3PO8,5 Na5B2P3O13
,
Na3B6PO13 and Na3BP2O8.7 Li22B11P13O60 and Li2B3PO8 were
found by X-ray diffraction (XRD) in the study of the Li2O–
B2O3–P2O5 system.5 Powder XRD data of these compounds
have been reported, but the crystal structures have not been
analyzed. Na5B2P3O13 was prepared by heating stoichiometric
amounts of NaH2PO4·H2O and NaBO2·H2O at 1073 K. Loop-
branched chains of [B2P3O13] are contained in the structure
of Na5B2P3O13.6 Na3B6PO13 and Na3BP2O8, consisting of
1∞[B6PO13]3− chains and ∞1 [BP2O8]3− chains, respectively, were
Experimental
H3BO3 (99.5%, Wako Pure Chemical Ind.), Li2CO3 (99.0%,
Wako Pure Chemical Ind.) and NH4H2PO4 (99.0%, Wako Pure
Chemical Ind.) were used as starting powders. To prepare
Li22B11P13O60 reported in the previous study,5 the starting
powders were weighed with a molar ratio of Li : B : P =
22 : 11 : 13, mixed in an agate mortar with a pestle and pressed
into a pellet. The pellet was placed on a platinum plate and
heated at 473 K for 9 h in air with an electric furnace. After
cooling, the product was powdered, pelletized and heated at
823 K for 12 h. The crystalline phases in the obtained sample
were identified by powder XRD using CuKα radiation with a
graphite monochromator mounted on a powder diffractometer
(Rigaku, Model RINT2000).
Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-
1 Katahira, Aoba-ku, Sendai 980-8577, Japan. E-mail: yamane@tagen.tohoku.ac.jp;
Fax: +81 22 217 5813
†CCDC 966781. For crystallographic data in CIF or other electronic format see
DOI: 10.1039/c3dt52917g
2294 | Dalton Trans., 2014, 43, 2294–2300
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For the preparation of single crystals, the pellet sample
obtained by heating at 823 K was heated again at 933 K for 1 h,
cooled to 873 K for 6 h and then cooled to room temperature
in the furnace. The product was crushed and a single crystal
for crystal structure analysis was picked up, fixed to the tip of a
glass fiber with epoxy resin and set to a goniometer of a
single-crystal X-ray diffractometer (Rigaku, R-AXIS RAPID-II).
X-ray diffraction data of the single crystal were collected using
MoKα radiation with a graphite monochromator and an
imaging plate. Unit cell refinement and absorption collection
were performed by the programs PROCESS-AUTO10 and
NUMABS,11 respectively. The crystal structure was solved by
direct methods using the SIR2004 program12 and structure
parameters were refined by full-matrix least-squares on F2
using the SHELXL-97 program.13 Crystal structure illustration
and Madelung energy calculation were carried out using the
VESTA program.14
Polycrystalline Li3BP2O8 samples for electrical conductivity
measurement were synthesized with a mixture of Li4P2O7 and
LiPO3 powders prepared in advance and H3BO3 powder. A
powder mixture of Li2CO3 and NH4H2PO4 with a molar ratio of
Li : P = 2 : 1 was calcined at 473 K for 9 h. Li4P2O7 was syn-
thesized by heating the calcined mixture at 823 K for 12 h. For
the synthesis of LiPO3, a mixture of Li2CO3 and NH4H2PO4
with a molar ratio of Li : P = 1 : 1 was calcined at 423 K for
12 h. The calcined powder was ground and heated again at
473 K for 12 h, and then heated at 823 K for 12 h.
The powders of Li4P2O7, LiPO3 and H3BO3 weighed with a
molar ratio of Li : B : P = 3 : 1 : 2 were mixed, pressed into
pellets, and heated on a Pt plate two times at 923 K for 12 h
with intermediate pulverization and pelletization. The
obtained polycrystalline samples were powdered and the crys-
talline phases in the samples were analyzed by powder XRD.
Rietveld analysis of the powder XRD pattern was performed
using the RIETAN-FP program.15 Chemical analysis of the poly-
crystalline sample was carried out using an inductively
coupled plasma-optical (ICP) emission spectrometer
(SPECTRO, SPECTRO ARCOS).
The electrical conductivity of the polycrystalline sample was
measured by the AC impedance method using an impedance
analyzer (WAYNE KERR, LCR METER 4100) in a frequency
range of 20 Hz–1 MHz in a temperature range of 473–583 K.
Graphite or Ag paste was used as the electrode. The electromo-
tive force of a cell Li|Li3BP2O8|C was measured with a galvano-
stat (HOKUTO DENKO, POTENTIOSTAT/GALVANOSTAT
HAB-151). Two-probe DC electrical conductivity measurement
using Li or C as the electrode was carried out using a digital
multimeter.
Fig. 1 Powder XRD patterns of samples prepared by heating starting-
powder mixtures with a molar ratio of Li : B : P = 22 : 11 : 13 at 823 K for
12 h (a) and such mixtures with a molar ratio of Li : B : P = 2 : 3 : 1 at
923 K for 12 h (b).
a
Table 1 Crystal data and refinement results for Li3BP2O8
Chemical formula
Formula weight, Mr
Temperature, T
Crystal system
Li3BP2O8
221.57 g mol−1
293(2) K
Triclinic
ˉ
Space group
P1 (no. 2)
Unit cell dimensions
a = 5.1888(5) Å, α = 101.18(1)°
b = 7.4118(7) Å, β = 105.07(1)°
c = 7.6735(7) Å, γ = 90.34(1)°
279.06(5) Å3
Unit cell volume, V
Z
2
Calculated density, Dcal
Radiation wavelength, λ
Crystal form, color
Absorption correction
Absorption coefficient, μ
Crystal size
2.637 Mg m−3
0.71075 Å (MoKα)
Colorless
Numerical
0.784 mm−1
0.176 × 0.168 × 0.072 mm3
−6 ≤ h ≤ 6
Limiting indices
−9 ≤ k ≤ 9
−9 ≤ l ≤ 9
F000
216
θ range for data collection
Reflections collected/unique
Rint
Data/restraints/parameters
Weight parameters, a, b
Goodness-of-fit on F2, S
R1, wR2 (I > 2σ(I))
3.545°–27.49°
1265/1067
0.0272
1265/0/127
0.0304, 0.5296
1.063
0.0329, 0.0748
0.0407, 0.0809
0.560, −0.543 e Å−3
R1, wR2 (all data)
Largest diff. peak and hole, Δρ
2
a R1 = ∑||Fo| − |Fc||/∑|Fo|. wR2 = [∑w(Fo − Fc2)2/∑(wFo2)2]1/2, w =
1/[σ2(Fo2) + (aP)2 + bP], where Fo is the observed structure factor,
2
Fc is the calculated structure factor, σ is the standard deviation of Fc
,
and P = (Fo + 2Fc2)/3. S = [∑w(Fo − Fc2)2/(n − p)]1/2, where n is the
number of reflections and p is the total number of parameters refined.
2
2
Results and discussion
823 K for 12 h. Besides the XRD reflections of Li22B11P13O60
reported by Tien and Hummel,5 reflections of Li3PO4 and
H3BO3 were observed. H3BO3 was probably formed by the reac-
tion of B2O3 with moisture in the air. This polycrystalline
Fig. 1(a) shows the powder XRD pattern of the sample pre-
pared by heating a starting mixture of Li2CO3, H3BO3 and
NH4H2PO4 with a molar ratio of Li : B : P = 22 : 11 : 13 at 473 K
for 9 h, followed by powdering, pelletizing and heating at
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multi-phase sample changed to a colorless transparent glass coordinates, anisotropic displacement parameters and
phase on heating at 973 K. Crystalline phases could not be selected bond lengths of Li3BP2O8 are listed in Tables 2–4.
obtained by slow cooling of the glass phase from 973 K. The
Fig. 2 shows the coordination environment of Li3BP2O8
multi-phase crystalline sample obtained at 823 K was annealed using the refined structural parameters. Four O atoms coordi-
at 873 K for 100 h, but no grain growth or a change in the com- nate to the B1 atom and form a boron-centered tetrahedron
bination of the crystalline phases was observed. However, by [BO4]. The B1–O distances vary from 1.455(3) to 1.484(3) Å. P
heating the multi-phase sample at 933 K, grain growth in atoms at P1 and P2 sites are coordinated by four O atoms and
partial melt conditions was recognized. Single crystals with a in the oxygen tetrahedra [PO4] with P1–O distances 1.4995(19)–
size of about 0.2 mm were obtained by cooling from 933 K to 1.5786(18) Å, and P2–O distances 1.4957(19)–1.5717(18) Å.
873 K at a rate of −10 K h−1
.
O–B1–O, O–P1–O and O–P2–O angles are in the ranges
The XRD reflections of a single crystal were indexed with tri- 105.0–111.4°, 103.6–114.3° and 106.2–112.4°, respectively. The
clinic unit-cell parameters of a = 5.1888(5) Å, b = 7.4118(7) Å, Li1 atom is coordinated by five O atoms. Four of the Li1–O dis-
c = 7.6735(7) Å, α = 101.18(1)°, β = 105.07(1)°, γ = 90.34(1)°. tances range from 1.970(6) to 2.180(6) Å and the Li1–O5 dis-
Considering the cell volume of 279.06(5) Å3, the element tance is 2.609(6) Å. Li2 and Li3 atoms are at the 4-fold
numbers in the unit cell were postulated to be Li6B3P3O15, coordination sites with Li2–O and Li3–O distances of 1.876(5)–
which is about 1/4 of Li22B11P13O60, for the calculation to solve 1.965(5) Å and 1.890(6)–2.213(9) Å, respectively. The bond
the crystal structure with the space group using the SIR2004 valence sums for the atoms at the sites of B1, P1, P2, Li1, Li2
program. An obtained structure model was improved by re- and Li3, calculated with the bond lengths and the bond valence
labeling some atoms and by searching missing atoms from the parameters presented by Brece and O’Keeffe,16 were 3.05, 4.97,
results of differential Fourier synthesis using the SHELXL-97 5.00, 0.82, 1.15 and 0.91, respectively (Table 4). These values are
program. The structural chemical formula of the single crystal comparable with the valences of the elements.
was finally determined to be Li3BP2O8 (Z = 2) by refinement
The value of the Madelung energy for Li3BP2O8 calculated
with an R1-value (all data) of 4.07% (Table 1). The atomic with the structure parameters was −60 600 kJ mol−1, which
Table 2 Atomic coordinates and equivalent isotropic displacement parameters (Ueq) for Li3BP2O8
Atom
Site
Occ.
x
y
z
Ueq a/Å2
Li1
Li2
Li3
B1
P1
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0.7757(12)
0.6698(9)
0.1387(11)
0.2584(5)
0.37120(12)
0.11689(12)
0.0529(3)
0.4736(3)
0.9397(4)
0.2023(3)
0.2817(3)
0.3045(4)
0.1831(3)
0.6000(3)
0.1333(8)
0.4796(7)
0.5327(9)
0.9615(4)
0.21492(9)
0.25094(9)
0.8131(3)
0.1125(2)
0.3047(3)
0.3680(2)
0.0826(2)
0.4066(3)
0.0641(2)
0.2751(3)
0.3078(8)
0.1455(6)
0.3879(10)
0.2316(4)
0.55001(9)
0.05505(9)
0.1482(2)
0.7151(2)
0.1836(2)
0.6055(2)
0.1061(2)
0.0591(3)
0.3957(2)
0.4847(2)
0.0311(12)
0.0193(10)
0.0468(18)
0.0108(6)
0.01021(18)
0.01017(18)
0.0137(4)
0.0127(4)
0.0152(4)
0.0135(4)
0.0129(4)
0.0169(4)
0.0113(4)
0.0145(4)
P2
O1
O2
O3
O4
O5
O6
O7
O8
a Ueq = (∑i ∑j Uij ai*a*j ai·aj)/3.
Table 3 Anisotropic displacement parameters (Uij/Å) for Li3BP2O8
Atom
Site
U11
U22
U33
U23
U13
U12
Li1
Li2
Li3
B1
P1
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
2i
0.037(3)
0.015(2)
0.020(3)
0.025(3)
0.025(3)
0.037(4)
0.039(3)
0.015(2)
0.066(5)
0.006(2)
0.025(3)
0.0006(18)
0.004(3)
0.003(2)
0.0041(18)
−0.001(2)
−0.0001(10)
0.0019(2)
0.0010(2)
−0.0037(7)
0.0043(7)
0.0059(7)
0.0035(7)
0.0045(7)
−0.0030(7)
0.0003(7)
−0.0004(7)
0.0024(19)
−0.022(3)
0.0008(11)
0.0012(2)
0.0018(2)
0.0013(7)
0.0034(7)
0.0033(8)
0.0010(7)
0.0060(7)
0.0058(8)
0.0004(7)
0.0004(7)
0.0093(13)
0.0099(3)
0.0106(3)
0.0146(9)
0.0119(8)
0.0167(9)
0.0135(9)
0.0146(9)
0.0156(9)
0.0112(8)
0.0129(9)
0.0124(14)
0.0101(3)
0.0096(3)
0.0147(10)
0.0142(9)
0.0166(10)
0.0119(9)
0.0126(9)
0.0138(10)
0.0119(9)
0.0150(10)
0.0094(13)
0.0104(3)
0.0102(3)
0.0106(9)
0.0132(9)
0.0142(9)
0.0148(9)
0.0147(9)
0.0197(10)
0.0109(9)
0.0149(9)
0.0015(11)
0.0030(2)
0.0028(2)
0.0022(7)
0.0046(7)
0.0071(8)
0.0041(7)
0.0073(7)
0.0004(8)
0.0044(7)
0.0046(7)
P2
O1
O2
O3
O4
O5
O6
O7
O8
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two BO4 tetrahedra. The fundamental building unit (FBU) can
Table 4 Selected bond lengths and bond valence sums (Vi), for
Li3BP2O8
a
3
□
□
□ □
be expressed by the description of Ewald et al. as 6
: <4 > .
Similar 1∞[BP2O8]3− chains have been reported in the crystal
Li1–O8
Li1–O3
Li1–O7i
Li1–O2ii
Li1–O5
VLi1
1.970(6)
2.031(6)
2.143(6)
2.180(6)
2.609(6)
0.82
B1–O1
B1–O5vii
B1–O2iv
B1–O7vii
VB
1.455(3)
1.463(3)
1.484(3)
1.484(3)
3.05
structures of Na3BP2O8 (space group C2/c)7 and RbZnBP2O8
20
ˉ
(space group P1).
Li1 sites are in the layers of 1∞[BP2O8]3− chains, and Li2
and Li3 sites align on the a–c plane at y = 0.41–0.59 (Fig. 3(b)),
forming zigzag chains along the a + c direction (Fig. 3(c)). The
distances of Li2–Li2, Li2–Li3 and Li3–Li3 are in the range
2.531(5)–2.624(7) Å (Fig. 3(c)). The Li–Li distances between the
zigzag chains are 3.688(7)–4.588(6) Å. The relatively short Li–Li
interatomic distances in the chains may suggest a lithium ion
conduction path of Li3BP2O8.
Li2–O6
Li2–O3
Li2–O6iii
Li2–O4iv
VLi2
1.876(5)
1.919(5)
1.953(5)
1.965(5)
1.15
P1–O8
P1–O4
P1–O7
P1–O2
VP1
1.4995(19)
1.5018(18)
1.5742(18)
1.5786(18)
4.97
Li3–O8iv
Li3–O4v
Li3–O3vi
Li3–O4
VLi3
1.890(6)
1.930(6)
2.119(6)
2.213(9)
0.91
P2–O6
P2–O3vi
P2–O1viii
P2–O5
VP2
1.4957(19)
1.5164(19)
1.5578(18)
1.5717(18)
5.00
In order to reveal Li ion conduction, preparation of
Li3BP2O8 bulk samples was attempted. Fig. 1(b) shows the
powder XRD pattern of the sample prepared by heating the
starting powders of H3BO3, Li2CO3 and NH4H2PO4 with a Li :
B : P molar ratio of 3 : 1 : 2 at 473 K for 9 h, followed by grind-
ing, pelletizing and heating two times at 923 K for 12 h with
intermediate pulverization and pelletization. In this powder
XRD pattern, the reflection peaks of BPO4 and Li4P2O7 were
seen besides the peaks of Li3BP2O8 indexed with the lattice
parameters determined by the single crystal XRD analysis.
BPO4 is a stable compound with a melting point of about
1673 K. Once BPO4 was crystallized in the sample, it was
difficult to react BPO4 completely with Li4P2O7. The single
phase of Li3BP2O8 was prepared from Li4P2O7 (m.p.: 1149 K),
LiPO3 (m.p.: 929 K) and H3BO3 (decomposed to B2O3 at 458 K,
m.p. of B2O3: 753 K) as starting materials.
a Symmetry codes: (i) x + 1, y, z; (ii) −x + 1, −y, −z + 1; (iii) −x + 1, −y +
1, −z; (iv) −x + 1, −y + 1, −z + 1; (v) −x, −y + 1, −z + 1; (vi) x − 1, y, z;
(vii) x, y + 1, z; (viii) −x, −y + 1, −z. Bond valence parameters: Li+:
1.466 Å, B3+: 1.371 Å, P5+: 1.617 Å.16
Fig. 4 shows the result of Rietveld refinement for the
powder XRD pattern of the Li3BP2O8 sample using the crystal
structure model presented by the single crystal XRD. All peaks
were indexed with the lattice parameters refined by the Riet-
veld analysis: a = 5.18971(18) Å, b = 7.41030(26) Å, c =
7.67204(29) Å, α = 101.14(1)°, β = 105.05(1)° and γ = 90.34(1)°,
which agreed with those of single crystal XRD (Table 1). The
final R-factors defined in ref. 21 were Rwp = 0.112, Rp
=
0.083, RB = 0.030, RF = 0.017 and S = 2.243. As listed in Table 5,
the d values and intensities of the XRD peaks reported for
Li22B11P13O60 by Tien and Hummel5 are comparable to the
data for L3BP2O8 revealed in the present study. The polycrystal-
line bulk sample of Li3BP2O8 was dissolved in an HCl water
solution, and the contents of Li2O, B2O3 and P2O5 analyzed by
ICP spectrometry were 19.4, 15.7 and 62.4 mass% (total
97.5%), respectively, which were fairly consistent with the ideal
compositions (Li2O: 20.2%, B2O3: 15.7%, P2O5: 64.1%).
Fig. 2 Atomic arrangement around Li, B, P and O atoms in the structure
of Li3BP2O8. Displacement ellipsoids are drawn at the 90% probability
level. Symmetry codes: (i) x + 1, y, z; (ii) −x + 1, −y, −z + 1; (iii) −x + 1, −y
+ 1, −z; (iv) −x + 1, −y + 1, −z + 1; (v) −x, −y + 1, −z + 1; (vi) x − 1, y, z;
(vii) x, y + 1, z; (viii) −x, −y + 1, −z.
The electrical conductivity was measured by the AC impe-
dance method with the electrodes of graphite or Ag paste
coated on both sides of the sample disk. The relative density
of the polycrystalline Li3BP2O8 bulk sample disk (diameter:
6.01 mm, thickness: 1.02 mm) was approximately 74%. Fig. 5
shows plots of the impedance measured at 453, 513, 553 and
583 K. The semicircles of the impedance plots could not be
separated into intra-grain and grain-boundary parts. The total
resistances of the Li3BP2O8 polycrystalline bulk sample
measured at 453, 513, 553 and 583 K were 1560, 213, 61 and
was almost identical to the value of −59 900 kJ mol−1 (differ-
ence Δ = 1.1%) of the Madelung energies: Li2O −3500 kJ
mol−1 17 B2O3 −2190 kJ mol−1 18 and P2O5 −43 700 kJ mol−1 19
,
with the formula Li3BP2O8 = 3/2Li2O + 1/2B2O3 + P2O5.
As shown in Fig. 3(a), all oxygen atoms of the BO4 tetra-
hedron are shared by four PO4 tetrahedra. One-dimensional
1∞[BP2O8]3− chains are formed in the c-axis direction by
linking the four-membered rings composed of two PO4 and
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Fig. 3 Projective views of the crystal structure of Li3BP2O8 along the a axis (a), the c axis (b) and the b axis (y = 0.41–0.59) (c).
a
Table 5 XRD data for Li22B11P13O60 5 and Li3BP2O8
5
Li22B11P13O60
Li3BP2O8
d[Å]
I/I0
h
k
l
dcal
Iobs
Ical
43
100
26
47
54
4
7.25
4.75
4.25
4.11
4.00
3.83
3.69
3.63
3.55
3.40
3.27
3.11
3.02
2.92
2.88
2.80
2.69
2.62
2.59
2.42
2.38
2.32
2.23
2.12
1.969
1.895
75
100
22
44
41
20
19
58
11
13
8
15
41
19
25
44
10
25
9
1
1
1
1
1
1
1
0
0
1
1
1
0
1
0
1
1
1
2
1
2
2
0
2
1
2
0
0
1
7.258
4.751
4.239
4.120
4.009
3.844
3.686
3.629
3.544
3.398
3.269
3.108
3.012
2.916
2.872
2.799
2.687
2.624
2.586
2.415
2.376
2.310
2.231
2.116
1.967
1.896
45
100
25
47
53
4
16
32
8
14
11
11
34
23
35
43
11
15
2
−1
−1
0
1
1
−1
0
−1
−1
0
2
1
0
1
1
1
1
0
16
33
8
−2
−2
−2
1
14
11
12
36
24
37
45
11
17
2
29
6
7
11
18
12
6
Fig. 4 Observed, calculated and difference XRD profiles for Li3BP2O8.
The observed data are indicated by dots and the profiles calculated by
Rietveld refinement and the differences between the observed and cal-
culated patterns are shown by solid lines. The short vertical lines below
the profiles mark the positions of all possible Bragg reflections.
2
−1
−2
−2
1
2
−2
2
−2
0
0
2
0
1
2
2
2
2
−1
1
−2
−2
−3
−1
2
26
13
12
15
25
9
28
6
7
11
18
12
6
24 kΩ, respectively, which were converted to electrical conduc-
tivities of 2.3 × 10−7, 1.7 × 10−6, 5.9 × 10−6 and 1.5 × 10−5
S
cm−1, respectively. No difference was observed between the
conductivities measured with the graphite electrodes and the
Ag paste electrodes.
10
−1
−3
Fig. 6 shows a logarithmic plot of the electrical conduc-
tivities measured by the AC impedance method as a function
of reciprocal measurement temperatures. The results of the
DC measurement with Li metal electrodes added in the plot
a Refined lattice parameters of Li3BP2O8: a = 5.18971(18) Å, b =
7.41030(26) Å, c = 7.67204(29) Å, α = 101.14(1)°, β = 105.05(1)°, γ =
90.34(1)°.
2298 | Dalton Trans., 2014, 43, 2294–2300
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0.265B2O3–0.265P2O5: 51 kJ mol−1), and lower than that of
Li3BO3 (167 kJ mol−1) and Li3PO4 (93 kJ mol−1). The Li ion
conductivity of Li3BP2O8 was larger than the conductivities of
Li3BO3 and Li3PO4 in the low temperature region.
As described by the results of crystal structure analysis, a
diffusion path was expected in the a + c-axis direction.
Li3BP2O8 might exhibit anisotropy of Li ion conduction, and
higher conductivities would be expected for a single crystal
bulk, or a polycrystalline bulk and a film with preferred
orientation.
Summary
Lithium borophosphate, Li22B11P13O60, reported in a previous
study5 was revealed to be Li3BP2O8 which crystallizes in the tri-
ˉ
clinic space group P1 (no. 2). B and P atoms are located at
Fig. 5 Complex impedance plots for a polycrystalline Li3BP2O8 sample
tetrahedral sites of O atoms and form 1∞[BP2O8]3− chains by
sharing the vertex oxygen atoms of the tetrahedra. A polycrys-
talline bulk sample of single-phase Li3BP2O8 was prepared by
using a powder mixture of Li4P2O7, LiPO3 and H3BO3. Li ion
conduction of Li3BP2O8 was confirmed by AC impedance and
DC measurements. The ionic conductivity measured for
the polycrystalline Li3BP2O8 sample was 1.5 × 10−5 S cm−1
at 583 K.
at 453, 513, 553 and 583 K.
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