Design of free-standing porous carbon fibers anode with high-efficiency potassium-ion storage

Designing porous structures is emerging as a promising approach to prominently improve the potassium storage performance of carbonaceous materials. In this work, we design free-standing porous carbon fibers (PCF) by electrospinning for highly potassium-ion storage. With the introduction of Zn in the electrospinning precursor, the PCF was obtained after the evaporation of Zn during the heat treatment. After bending and folding, the free-standing PCF also presents excellent flexibility. As the free-standing anode for potassium-ion battery (KIB), it is found that the PCF presents an enhanced potassium-ion storage performance with a reversible specific capacity of 256 mAh/g after 80 cycles at 50 mA g−1. Even at the current density of 1 A/g, our PCF still remains a high reversible specific capacity of 149 mAh/g after 3300 cycles for KIBs. According to the density functional theory calculation and finite element analysis, we find that K-ions can also inset into the carbon layer during the fully potassiation state for the porous structure of PCF. In addition, due to the strong adsorption characteristics of K-ions, the porous structure of porous carbon fibers also can accommodate K-clusters in the pore defects. The common effects of the K-intercalation and K cluster contribute to the improvement of the K-ion storage performance of porous carbon fibers.