Synthesis, crystal structure and lithium ion conduction of Li3BP2O8

Abstract

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) 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 (no. 2)). In the crystal structure of Li₃BP₂O₈, BO₄ and PO₄ tetrahedra share O atoms and form one-dimensional ¹_∞[BP₂O₈]³⁻ chains along 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.