Contributing to the Revolution of Electrolyte Systems via In Situ Polymerization at Different Scales: A Review

Abstract Solid‐state batteries have become the most anticipated option for compatibility with high‐energy density and safety. In situ polymerization, a novel strategy for the construction of solid‐state systems, has extended its application from solid polymer electrolyte systems to other solid‐state systems. This review summarizes the application of in situ polymerization strategies in solid‐state batteries, which covers the construction of polymer, the formation of the electrolyte system, and the design of the full cell. For the polymer skeleton, multiple components and structures are being chosen. In the construction of solid polymer electrolyte systems, the choice of initiator for in situ polymerization is the focus of this review. New initiators, represented by lithium salts and additives, are the preferred choice because of their ability to play more diverse roles, while the coordination with other components can also improve the electrical properties of the system and introduce functionalities. In the construction of entire solid‐state battery systems, the application of in situ polymerization to structure construction, interface construction, and the use of separators with multiplex functions has brought more possibilities for the development of various solid‐state systems and even the perpetuation of liquid electrolytes.