Molecularly Dispersed Bismuth Anodes in Fluorinated Triazine Frameworks for High-Capacity and Long-Life Potassium-Ion...

Potassium-ion batteries (PIBs) demand anodes that couple high capacity with long cycling durability, yet bismuth suffers from large volume fluctuations, and fully fluorinated triazine frameworks (F-CTFs) are too chemically inert to host metal species effectively. Here, we report a low-temperature molten-salt strategy using a vacuum reactor, in which BiCl₃ functions simultaneously as the molten medium and reactive precursor. Under mild conditions (250 °C), vacuum-assisted capillary infiltration drives molten BiCl₃ into the pores of a highly fluorinated triazine framework (HFCTF), enabling molecular-level dispersion of bismuth and forming strong Bi-F-C interfacial bonds. The resulting Bi@HFCTF/S-275 composite exhibits an interconnected porous network for efficient ion transport and strain accommodation, along with interface-induced electronic restructuring that imparts metalloid-like electronic character and rapid charge-transfer kinetics. As a PIB anode, it delivers 364 mAh·g^-1 at 0.1 A·g^-1 with >95% retention after 500 cycles and exhibits excellent Li-ion storage performance. This work establishes a safe, scalable, low-temperature route for integrating highly inert fluorinated frameworks with active metals, offering a new paradigm for advanced electrode design.