Batteries include a cathode, an interlayer disposed on the cathode, a solid-state electrolyte disposed on the interlayer, and a lithium anode disposed on the solid-state electrolyte. The interlayer includes a deep-eutectic-solvent-based electrolyte including a lithium salt and a sulfone compound. Methods of forming a battery comprising disposing a deep-eutectic-solvent-based electrolyte comprising a lithium salt and a sulfone compound on a first major surface of a cathode. Methods further comprising disposing a solid-state electrolyte over the first major surface of the cathode. The deep-eutectic-solvent-based electrolyte is positioned between the cathode and the solid-state electrolyte.