Rational Construction of Nitrogen-Doped Hierarchical Dual-Carbon for Advanced Potassium-Ion Hybrid Capacitors

Potassium-ion hybrid capacitors (PIHCs), elaborately integrate the advantages of high output power as well as long lifespan of supercapacitors and the high energy density of batteries, and exhibit great possibilities for the future generations of energy storage devices. The critical next step for future implementation lies in exploring a high-rate battery-type anode with an ultra-stable structure to match the capacitor-type cathode. Herein, a dual-carbon is constructed, in which a three-dimensional nitrogen-doped microporous carbon polyhedron (NMCP) derived from metal-organic frameworks is tightly wrapped by two-dimensional reduced graphene oxide (NMCP@rGO). Benefiting from the synergistic effect of the inner NMCP and outer rGO, the NMCP@rGO exhibits a superior K-ion storage capability with a high reversible capacity of 386 mAh g(-1) at 0.05 A g(-1) and ultra-long cycle stability with a capacity of 151.4 mAh g(-1) after 6000 cycles at 5.0 A g(-1). As expected, the as-assembled PIHCs with a working voltage as high as 4.2 V present a high energy/power density (63.6 Wh kg(-1) at 19 091 W kg(-1)) and excellent capacity retention of 84.7% after 12 000 cycles. This rational construction of advanced PIHCs with excellent performance opens a new avenue for further application and development.