While solid state electrolytes hold promise for safer batteries, the lithium/solid-state electrolyte interface has presented challenges. Herein, we report a fully self-forming solid state rechargeable battery based on the Li/I-2 couple using LiI rich lithium iodide-(3-hydroxyproprionitrile)(2) electrolyte. Effective charge-discharge cycling was demonstrated, showing promise for future generations of high energy density self-forming, self-healing batteries. (C) 2018 The Electrochemical Society.