A lithium-metal battery, includes: a substrate; a cathode disposed on the substrate; a garnet solid-state electrolyte disposed on the cathode; and a lithium anode disposed on the garnet solid-state electrolyte, such that a discoloration layer is disposed at an interface of the lithium anode and garnet solid-state electrolyte, the discoloration layer includes: a first portion; and a second portion, such that the first portion has a lithium component and the second portion has a garnet component. A method of forming a lithium-metal battery, includes: stacking a garnet source with at least one lithium source; and heating the stack at a temperature of at least 300° C. for a time in a range of 1 sec to 20 min to form a discoloration layer, such that the discoloration layer is disposed at an interface of the garnet source and the lithium source.