Lithium-metal penetration is one of the main modes of cell failure in solid-state batteries and limits the plating rate during charging . While some researchers have described lithiummetal structures penetrating the electrolyte as "dendrites", the morphology of the lithium metal is not necessarily tree-like . As an alternative, we here use the term "intrusions", defined as lithium-metal growth that electrochemically propagates within the solid-state electrolyte.