An Ultrastable Nonaqueous Potassium‐Ion Hybrid Capacitor

Abstract

Abstract Potassium‐ion hybrid capacitors (PIHCs) show great potential in large‐scale energy storage due to the advantages of electrochemical capacitors and potassium‐ion batteries. However, their development remains at the preliminary stage and is mainly limited by the kinetic imbalance between the two electrodes. Herein, an architecture of NbSe 2 nanosheets embedded in N, Se co‐doped carbon nanofibers (NbSe 2 /NSeCNFs) as flexible, free‐standing, and binder‐free anodes for PIHCs is reported. The NbSe 2 /NSeCNFs with hierarchically porous structure and N, Se co‐doping afford highly efficient channels for fast transportation of potassium ions and electrons during repeated cycling process. Furthermore, excellent electrochemical reversibility of the NbSe 2 /NSeCNFs electrode is demonstrated through in situ XRD, in situ Raman, ex situ transmission electron microscopy and element mapping. Thus, PIHCs with the NbSe 2 /NSeCNFs anode and active carbon cathode achieve a high energy of 145 W h kg −1 at a current density of 50 mA g −1 , as well as an ultra‐long cycle life of over 10 000 cycles at a high current density of 2 A g −1 . These results indicate that the assembled PIHCs display great potential for applications in the field of ultra‐long cycling energy storage devices.