Just saying that solid electrolytes ("superionic conductors" is just a synonym) have been around for a long time: https://en.wikipedia.org/wiki/Fast_ion_conduct

Just saying that solid electrolytes ("superionic conductors" is just a synonym) have been around for a long time: https://en.wikipedia.org/wiki/Fast_ion_conductor https://en.wikipedia.org/wiki/Fast_ion_conductor There's the zirconia oxygen-sensitive electrode in your car's exhaust system, beta-alumina (used in various high-temperature batteries), the high-temperature modification of silver iodide, and others. Fascinating subject, some of these are almost as conductive as metals!