A new lithium manganese phosphate with an original tunnel structure in the A2MP2O7 family

A new member of the A2MP2O7 diphosphate family, Li2MnP2O7, has been synthesized by solid-state reaction and characterized using single-crystal X-ray diffraction. Li2MnP2O7 crystallizes in the monoclinic space group P21/a (#14) with the cell parameters a=9.9158(6) Å, b=9.8289(6) Å, c=11.1800(7) Å, β=102.466(5)°, Z=8 and V=1063.9(1) Å3. Its mixed framework exhibits an original Mn2O9 unit, built up of one MnO5 trigonal bipyramid sharing one edge with one MnO6 octahedron. These Mn2O9 units are sharing corners with P2O7 diphosphate groups, forming the undulating [Mn4P8O32]∞ layers. The [MnP2O7]∞ 3D framework, resulting from the interconnection of the undulating [Mn4P8O32]∞ layers, exhibits different kinds of intersecting tunnels containing the Li cations.