Synergistically Enhancing Li + Transference and Conductivity: Anion‐Regulating Gel Electrolyte With In Situ SEI for Stable Lithium Metal Batteries

ABSTRACT Lithium metal batteries are hindered by dendrite growth, largely due to low Li + transference numbers (t Li + ) in conventional electrolytes that accelerate concentration polarization. Raising t Li + without sacrificing ionic conductivity remains challenging because most approaches trade one transport limitation for another. Here, we design an in situ polymerized gel electrolyte incorporating a porphyrin‐based porous organic polymer (PPOP) as a multifunctional filler to synergistically regulate anion migration, Li + transport, and interfacial stability. PPOP is expected to interact with DFOB − ‐derived species through its polar framework, thereby restricting long‐range anion migration and increasing t Li + from 0.41 to 0.87 while maintaining an ionic conductivity of 1.01 mS cm − 1 . According to the classical Sand‐type scaling, the increased t Li + is expected to delay diffusion‐limited Li + depletion under idealized transport conditions. Meanwhile, EMP‐5‐0.5 promotes the formation of a dense SEI, which further stabilizes the electrode/electrolyte interface. Benefiting from the combined regulation of bulk ion transport and interfacial chemistry, Li||Li symmetric cells with EMP‐5‐0.5 achieve stable cycling for over 9000 h at 0.25 mA cm − 2 . This work demonstrates a synergistic strategy that couples bulk anion regulation with interfacial SEI stabilization for stable lithium metal batteries.