Porous Carbon Tubes Constructing Freestanding Flexible Electrodes for Symmetric Potassium-Ion Hybrid Capacitors

Developing electrode materials to apply in anodes and cathodes with superior kinetics and high specific capacity still remains a serious challenge for potassium-ion hybrid capacitors (PIHCs). Herein, a well-designed flexible freestanding electrode consisting of porous carbon tubes (FSF-PCTs) that functioned as both an anode and a cathode for PIHCs presents favorable energy storage performance. Based on this fully carbon-based FSF-PCTs electrode, symmetrical freestanding potassium-ion hybrid capacitors (SPIHCs) are developed. Moreover, SPIHCs deliver good practical application in terms of a high power density of 8109.9 W kg(-1) (at 39.2 W h kg(-1)), a high energy density of 117.8 W h kg(-1) (at 450 W kg(-1)), and a great cycle stability of 51 W h kg(-1) at 1 A g(-1) after 1500 cycles as well as ultrafast charge and slow discharge characteristics (full charge in only 1 min and the discharge time lasting for 15 min). Moreover, systematic characterization analysis in half potassium-ion batteries (PIBs) reveals that the K+ storage mechanism in anode FSF-PCTs is a synergistic effect of intercalation and surface capacitance, and the operating principle of FSF-PCTs as a cathode is an adsorption behavior of PF6- on its surface.

Automated summary

The study developed a novel carbon-based electrode material that functions as both an anode and cathode for potassium-ion hybrid capacitors, demonstrating excellent energy storage performance. The developed symmetrical freestanding potassium-ion hybrid capacitors exhibit impressive performance in terms of power density, energy density, and cyclic stability.