Self-Reconstructing, Conductive Bismuth Organic Framework Enables Effective Alloying and High-Capacity Potassium-Ion Anodes.

Abstract

Conversion-type anodes can deliver high capacities for potassium-ion batteries (PIBs), but practical deployment is hindered by severe alloying-induced volume expansion that destabilizes electrode interphases. Meanwhile, many porous host materials are electronically insulating and require substantial carbon additives, which dilute the active mass and reduce practical capacity and kinetics. Here, we report a high-performing PIB anode based on thin 2D crystals of an intrinsically conductive bismuth metal-organic framework (MOF) built from π-conjugated hexahydroxytriphenylene (HHTP) ligands. Electronic coupling between the HHTP ligands and Bi nodes yields markedly higher conductivity than analogous 3D carboxylate Bi-MOFs. Atomically accessible Bi sites on the 2D sheets enable extensive, highly confined K-Bi alloying, which drives reversible framework disassembly during potassiation and reassembly upon depotassiation, as revealed by operando X-ray diffraction (XRD). The electrode delivers high reversible capacity from efficient alloying/dealloying, complemented by ligand-mediated pseudocapacitive storage at higher potentials. Confinement of the alloying reaction buffers strain and limits electrode expansion by fourfold compared with Bi powder. Bi-HHTP outperforms 3D Bi-MOFs and conductive Cu-, Ni-, and Co-HHTP analogues across all tested current densities, establishing conductive Bi-HHTP as a top-performing MOF-based anode for PIBs and providing design guidelines for future alloy-type electrodes.