Synergistic structural engineering and fluorine doping strategy in hard carbon for fast and stable potassium-ion storage

Structural design and heteroatom doping of hard carbon are crucial strategies for enhancing their potassium-ion storage performance. Herein, fluorine-doped hollow porous hard carbon spheres (FHCS) are synthesized via an in-situ template coupled with fluorination strategy. The hollows carbon spherical architecture of FHCS provides abundant porosity and defects for potassium-ion adsorption while effectively mitigating volume expansion during K + insertion/extraction. Moreover, the high-content doping of fluorine element further increases the defect density of FHCS. These characteristics guarantee that the FHCS anode exhibits a predominantly adsorption-driven K + storage mechanism, contributing 81.8 % of the total capacity at 1.0 mV s −1 . As a result, the FHCS anode delivers exceptional reversible capacity (381 mAh g −1 at 0.1 A g −1 ), outstanding rate capability (194 mAh g −1 at 10 A g −1 ), and remarkable cycling stability of 83.8 % capacity retention after 3000 cycles. Furthermore, the potassium-ion hybrid capacitor assembled with FHCS anode exhibits high energy density (104 Wh kg −1 ). This study provides an effective strategy for the rational design of hard carbon and the advancement of high-performance K + storage.