Probing the electrochemical behaviour of lithium imide as an electrolyte for solid-state batteries.

All-solid-state batteries utilising a Li-metal anode have long promised to be the next-generation of high-performance energy storage device, with a step-change in energy density, cycling stability and cell safety touted as potential advantages compared to conventional Li-ion battery cells. A key to enabling this technology is the development of solid-state electrolytes with the elusive combination of high ionic conductivity, wide electrochemical stability and the ability to form a conductive and stable interface with Li metal. Presently, oxide and sulfide-based materials, particularly garnet and argyrodite-type structures, have proved most promising for this application. However, these still suffer from a number of challenges, including resistive lithium metal interfaces, poor lithium dendrite suppression (at high current density) and low voltage stability. Here we report the first application of lithium imide, an antifluorite-structured material, as a solid electrolyte in a Li-metal battery. Low-temperature synthesis of lithium imide produces promising Li-ion conductivity, reaching >1 mS cm