at larger scales (electric vehicle or gridscale energy storage) has been hampered by insufficient energy densities, prohibitive material costs, and safety concerns. [2] While significant progress has been made in the development of high energy density battery materials, the implementation of these materials in practical systems without sacrificing cell longevity or safety remains a pressing scientific challenge. One of the best studied approaches to improve the energy density of LIBs is to replace existing graphitic anodes (372 mA h g −1 capacity) with metallic lithium (3860 mA h g −1 capacity). [3] Unfortunately, uneven lithium plating and stripping in conventional organic liquid electrolytes promotes the growth of lithium dendrites, accelerating the formation of internal short-circuits. Additionally, the low thermal stability of electrolyte solvents (often mixtures of cyclic and linear carbonates) incurs exothermic decomposition of the electrolyte in the event of cell failure, often resulting in catastrophic thermal runaway. [4-6] While many approaches have been explored to address these issues, one of the most promising options is the elimination of the liquid electrolyte in favor of a solid electrolyte. [7] Transitioning from conventional liquid electrolytes to Li +conducting solid electrolytes (SEs) presents two primary advantages. The high mechanical rigidity of inorganic SEs may act to suppress the formation of dendrites at lithium anodes, reducing the possibility of internal short circuits. [8] Additionally, the negligible flammability of most SEs dramatically lowers the risk of uncontrolled thermal runaway in the event of cell failure. [9,10] These potential benefits motivate the search for materials with sufficiently high ionic conductivities to serve as replacements for their liquid counterparts. Among the known SE formulations, the thiophosphate class of superionic conductors exhibit exceptionally fast lithium transport at room temperature. [11] Specifically, Li 10 GeP 2 S 12 (LGPS) demonstrates an ionic conductivity of ≈10 mS cm −1 , comparable to conductivities achievable in conventional liquid electrolytes. [12] Despite the favorable ionic conductivity of LGPS, its poor chemical and electrochemical stabilities remain key challenges for practical application. The narrow window of electrochemical stability of LGPS and many other thiophosphate