Beyond garnets, phosphates and phosphosulfides solid electrolytes: New ceramic perspectives for all solid lithium metal batteries

Lithium-ion battery technology has been steadily approaching its intrinsic limits of energy density and cycling capacity, and solid-state electrolytes offer a more performant solution when compared with traditional organic electrolytes in terms of affinity with Li-metal electrodes and global battery safety. Oxide and sulfide-based solid electrolytes have been abundantly reported in literature owing to their peculiar chemical properties which made them the favourite candidates for practical applications. However, some significant limitations, such as sensitivity against moisture, partial incompatibility with active materials and relatively high costs, lead current research interest towards a series of alternative chemistries and configurations which may overcome their deficiences. Among these new families of Li-superionic conductors halides and hydrides stand out the most for their appealing qualities, including, foremost, values of ionic conductivities above and beyond 10−3 S cm−1 at room temperature. Some of the most promising outcomes in research are reported and discussed in the present review, along with a brief outlook of the crucial challenges to face in the field of solid-state batteries and the future developments prospected for energy storage systems.