Atomically tailored heteroatom-doped hard carbon from structure-engineered coordination-crosslinked polymers for potassium-ion storage

Hard carbon (HC) possesses large interlayer spacing, abundant defects, and porous structures, enabling efficient storage of large-radius K + ions. Nevertheless, its highly disordered nature renders the microstructure challenging to precisely regulate, which disrupts electronic conductivity and introduces irreversible active sites. Herein, conjugated poly(bithiophene) and phytic acid were employed as ligands to construct a lamellar precursor with reinforced interlayer support through Fe 3+ coordination and crosslinking. Upon optimized pyrolysis, the derived HC exhibits a high reversible capacity of 407 mAh g −1 , long-term cycling stability (1800 cycles at 1 A g −1 ), and excellent rate capability (200 mAh g −1 at 1 A g −1 ) in potassium-ion batteries. Thermogravimetry-mass spectrometry (TG-MS) analysis was conducted to investigate the structural evolution mechanisms of the precursor during pyrolysis. Furthermore, ex-situ characterization combined with density functional theory (DFT) calculations elucidated the intrinsic origin of the superior reversibility and activity associated with S–C and P–C doped configuration. These findings offer new insights into precursor engineering and controlled heteroatom doping for the development of high-performance HC anodes, providing both fundamental understanding and practical guidance for next-generation energy storage and conversion.