Methods, systems, and compositions for the solution-phase deposition of thin films comprising one or more artificial solid-electrolyte interphase (SEI) layers. The thin films can be coated onto the surface of porous components of electrochemical devices, such as solid-state electrolytes employed in rechargeable batteries. The methods and systems provided herein involve exposing the component to be coated to different liquid reagents in sequential processing steps, with optional intervening rinsing and drying steps. Processing may occur in a single reaction chamber or multiple reaction chambers.