Structure Determination of the Crystalline LiPON Model Structure Li5+xP2O6−xN1+x with x≈0.9

Abstract

Non-crystalline lithium oxonitridophosphate (LiPON) is used as solid electrolyte in all-solid-state batteries. Crystalline lithium oxonitridophosphates are important model structures to retrieve analytical information that can be used to understand amorphous phases better. The new crystalline lithium oxonitridophosphate Li5+xP2O6−xN1+x was synthesized as an off-white powder by ampoule synthesis at 750–800 °C under Ar atmosphere. It crystallizes in the monoclinic space group P21/c with a=15.13087(11) Å, b=9.70682(9) Å, c=8.88681(7) Å, and β=106.8653(8)°. Two P(O,N)4 tetrahedra connected by an N atom form the structural motif [P2O6−xN1+x](5+x)−. The structure was elucidated from X-ray diffraction data and the model corroborated by NMR and infrared spectroscopy, and elemental analyses. Measurements of ionic conductivity show a total ionic conductivity of 6.8×10−7 S cm−1 at 75 °C with an activation energy of 0.52±0.01 eV.