A Fast Na‐Ion Conduction Polymer Electrolyte via Triangular Synergy Strategy for Quasi‐Solid‐State Batteries

Polymer electrolytes provide a visible pathway for the construction of high‐safety quasi‐solid‐state batteries due to their high interface compatibility and processability. Nevertheless, sluggish ion transfer at room temperature seriously limits their applications. Herein, a triangular synergy strategy is proposed to accelerate Na‐ion conduction via the cooperation of polymer‐salt, ionic liquid, and electron‐rich additive. Especially, PVDF‐HFP and NaTFSI salt acted as the framework to stably accommodate all the ingredients. An ionic liquid (Emim+‐FSI−) softened the polymer chains through a weakening molecule force and offered additional liquid pathways for ion transport. Physicochemical characterizations and theoretical calculations demonstrated that electron‐rich Nerolin with π‐cation interaction facilitated the dissociation of NaTFSI and effectively restrained the competitive migration of large cations from EmimFSI, thus lowering the energy barrier for ion transport. The strategy resulted in a thin F‐rich interphase dominated by NaTFSI salt's decomposition, enabling rapid Na+ transmission across the interface. These combined effects resulted in a polymer electrolyte with high ionic conductivity (1.37×10−3 S cm−1) and tNa+ (0.79) at 25 °C. The assembled cells delivered reliable rate capability and stability (200 cycles, 99.2 %, 0.5 C) with a good safety performance. A fast Na‐ion conduction polymer electrolyte was designed through a triangular synergy strategy, which limits the migration of ionic liquid and facilitates the dissociation of salt, resulting in a faster Na+ conduction in the polymer electrolyte. The modified polymer electrolyte led to a salt‐decomposition dominated interphase, which effectively suppressed gas evolution from ionic liquid decomposition, ensuring battery safety.