In Situ Composite Strategy of O/F-Dual-Doped Soft–Hard Carbon Anode Promotes Ultrafast and Highly Durable Potassium Storage Performance

Soft-hard carbon has been regarded as a suitable anode material for potassium-ion batteries (PIBs) due to synergistic effects between hard carbon (HC) and soft carbon. However, the cost-effective and precise structural control of these carbons remains a significant challenge. In this study, O/F-dual-doped soft-hard carbon (OFPC) composite materials with a porous honeycomb-like structure are simply synthesized by using an in situ, low-temperature pyrolysis strategy. It is observed that the outer wall of HC is uniformly and closely wrapped by a soft carbon layer, ensuring excellent electrical conductivity and charge-transfer kinetics. Furthermore, O/F codoping in soft-hard carbon can preserve rich defects and active sites while enlarging the interlayer spacing (0.413 nm). As an anode for PIBs, OFPC demonstrates obviously reducing polarization, long-life cycling stability (93% capacity retention rate over 3000 cycles at 1 A g^-1), and rapid K⁺ transport kinetics (reversible capacity retention of 47.1% at 5 A g^-1 compared to that at 0.1 A g^-1). Particularly noteworthy is the continuous structural self-optimization during the cyclic charge/discharge process to adapt to the large radius of K⁺, which can be monitored and quantified by kinetic analysis and in situ/ex situ Raman spectra. This work provides a facile strategy to develop promising carbon anodes for advanced PIBs.