A Novel Class of All Inorganic Solid State Lithium Ion Conductors

Most commercial lithium batteries use electrolytes that are organic solutions of lithium salts, the classic example being the lithium hexafluorophosphate (LiPF₆). Although those electrolytes satisfy the requirements of high conductivity and practical chemical window, there are numerous safety issues (including leakage and flammability) that call for alternative materials. In this work, we present a novel class of all inorganic, solid state lithium-ion conductors with very high conductivities (on the order of 6 mS.cm^-1 at room temperature) made from inexpensive materials. The new materials are rotator phases in which lithium is the most mobile species. The all inorganic nature of the new compounds result in a higher operating temperature range than that achieved when organic solvents are used, and the new materials retain competitive conductivities even at very low temperatures (46 µS.cm^-1 at -30^oC). The new materials were characterized by magic angle spinning solid-state nuclear magnetic resonance (MAS NMR), Raman spectroscopy, powder X-ray diffraction, differential scanning calorimetry and electrochemical impedance spectroscopy (EIS).