Synergistic Composite Solid Electrolyte Based on Multifunctional Polymer Networks for High‐Performance Lithium Metal Batteries

Abstract The advancement of polymer‐based solid‐state electrolytes (SPEs) is essential for the development of high energy density (ED) and long‐operation durability lithium–metal batteries (LMBs). However, conventional poly (ethylene oxide) (PEO)‐based electrolytes suffer from insufficient ionic conductivity (IC) at room temperature (RT) and limited capability to suppress lithium (Li) dendrite growth, particularly under high‐rate operations. These challenges arise from unfavorable anion‐solvate structures, which lead to a reduced Li‐ion transference number (LITN) and hinder efficient ion transport. Here, a facile and scalable strategy is presented to design a self‐healing composite polymer electrolyte by incorporating iminoboronate‐functionalized networks. By succinonitrile (SN) into an anion‐trapping polymer matrix, this approach enhances LITN while preserving overall IC. The resulting electrolyte facilitates rapid, selective, and uniform Li‐ion transport, enabling stable LMB operation at 1 C for 480 cycles with an impressive 88% capacity retention. Moreover, the exceptional self‐healing capacity of the iminoboronate‐based polymer electrolyte (I‐SHPE) significantly reinforces the mechanical properties of PEO‐based electrolytes. The SN‐embedded I‐SHPE (I‐SN‐SHPE) exhibits a synergistic combination of high IC, anion‐capture ability, and rapid self‐healing properties. This work provides a promising strategy to overcome the intrinsic limitations of conventional PEO‐based electrolytes, paving the way for safer and more durable LMBs.