Structure Determination from Powder Diffraction Data of Some Moisture-sensitive Network Coordination Compounds

A series of new compounds was discovered during the study of a novel solid lithium-ion battery electrolyte system based on succinonitrile. The phases LiX(succinonitrile)2 (X = PF6, AsF6, ClO4) were identified as undesirable phases that formed at low salt concentrations in succinonitrile. The silver analogues of these systems also exist as crystalline phases, but the lithium salts do not share the same structure. The crystal structures of the Li salts were solved from laboratory X-ray diffraction data. The AsF6 and PF6 adducts are isostructural, with the monoclinic space group, P2. The ClO4 adduct has a doubled unit cell volume compared to the AsF6 and PF6 materials and has the orthorhombic space group Pba2. The lithium coordination in these adducts helps explain why plastic crystal electrolytes using LiPF6 and LiClO4 salts have poor ionic conductivity at room temperature.