Conventional lithium-ion batteries are reaching their theoretical limits in term of energy density and rely on flammable liquid electrolytes. 1 2 A promising alternative for the next generation of energy storage device are all-solid-state batteries (ASSBs), which may enable the next step-up in terms of energy density and safety required for the ongoing energy transition and the electrification of transport. Numerous solid electrolytes (SEs) have been developed, reaching Li-ion conductivities of up to 10 -2 S cm - 1 , are comparable with liquid electrolytes. However, the interfacial stability of SEs with both lithium metal (LM) and common high-voltage cathodes remains a tremendous challenge and hampers their application in ASSBs. A LM anode may be indispensable for ASSBs to surpass conventional lithium-ion batteries in terms of energy density 3 thus stable LM/SE interfaces are crucial for the full-scale commercialization of ASSBs.