Uniform Hollow Mesoporous Nickel Cobalt Sulfide Microdumbbells: A Competitive Electrode with Exceptional Gravimetric/Volumetric Pseudocapacitance for High‐Energy‐Density Hybrid Superapacitors

In this contribution, a facile two‐step hydrothermal protocol to prepare hierarchical uniform hollow mesoporous NiCo 2 S 4 microdumbbells (NCS‐MDs) for advanced supercapacitors is developed. Physicochemical investigations reveal that the as‐obtained NCS‐MDs with mesoporous channels in nanoshells possess high‐content Co(III) and Ni(III) species, large surface area (≈80 m 2 g −1 )/pore volume (≈0.12 m 3 g −1 ), and high tap density (≈0.8 g cm −3 ). When evaluated as an attractive pseudocapacitive electrode, the unique NCS‐MDs with mass loading of 7 mg cm −2 exhibit remarkable gravimetric/volumetric specific capacitances of ≈912 F g −1 (≈729 F cm −3 ) at 3 A g −1 , and even ≈767 F g −1 (≈613 F cm −3 ) at high current density of 10 A g −1 . Additionally, capacitive degradations of ≈13% and ≈18% are observed over 5000 continous cycles at current rates of 6 and 10 A g −1 , respectively. Furthermore, a high‐energy‐density hybrid device is fabricated by using hollow NCS‐MDs and biomass‐derived activated carbon as positive and negative electrodes, respectively, and delivers striking energy density of ≈35.4 Wh kg −1 at power density of ≈381.2 W kg −1 , and excellent electrochemical stability at various rates over 11 000 consecutive cycles. These fascinating features strongly highlight that the as‐resulted hollow mesoporous NCS‐MDs could be highly anticipated as a promising electrode platform for next‐generation hybrid supercapacitors.