A review of solid-state lithium metal batteries through in-situ solidification

High-energy-density lithium metal batteries are the next-generation battery systems of choice, and replacing the flammable liquid electrolyte with a polymer solid-state electrolyte is a prominent conduct towards realizing the goal of high-safety and high-specific-energy devices. Unfortunately, the inherent intractable problems of poor solid-solid contacts between the electrode/electrolyte and the growth of Li dendrites hinder their practical applications. The in-situ solidification has demonstrated a variety of advantages in the application of polymer electrolytes and artificial interphase, including the design of integrated polymer electrolytes and asymmetric polymer electrolytes to enhance the compatibility of solid-solid contact and compatibility between various electrolytes, and the construction of artificial interphase between the Li anode and cathode to suppress the formation of Li dendrites and to enhance the high-voltage stability of polymer electrolytes. This review firstly elaborates the history of in-situ solidification for solid-state batteries, and then focuses on the synthetic methods of solidified electrolytes. Furthermore, the recent progress of in-situ solidification technology from both the design of polymer electrolytes and the construction of artificial interphase is summarized, and the importance of in-situ solidification technology in enhancing safety is emphasized. Finally, prospects, emerging challenges, and practical applications of in-situ solidification are envisioned.