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 freestanding 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 Kions, 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.