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

Abstract

In this contribution, a facile two‐step hydrothermal protocol to prepare hierarchical uniform hollow mesoporous NiCo2S4 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 m2 g−1)/pore volume (≈0.12 m3 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.

Hierarchical mesoporous Co3O4@ZnCo2O4 hybrid nanowire arrays supported on Ni foam for high-performance asymmetric supercapacitors

“…5e. The ASCs can deliver a high energy density of 37.3 W h kg −1 at a power density of 800 W kg −1 and still maintain as high as 21.3 W h kg −1 while at a high power density of 8 kW kg −1 , which is higher than previously reported ASCs [45][46][47][48][49]. The cycling performance of the Co 3 O 4 @ZnCo 2 O 4 ||AC ASCs was performed at a current density of 5 A g −1 (Fig.…”

Mixed Metal Sulfides for Electrochemical Energy Storage and Conversion

“…Ternary nickel cobalt sulfides with various crystal structures (such as NiCo 2 S 4 , [27,33,74,103,108,121] CoNi 2 S 4 , [93,98,111,117] Ni 1.5 Co 1.5 S 4 , [122] Co 0.9 Ni 0.1 S 2 , [123] Ni 3.5 Co 3.5 S 8 , [88] and Ni 3 Co 6 S 8 [124] ) and diverse nanostructures (such as nanoparticles, [92][93][94][95][96] nanotubes, [99] nanosheets, [100] and hierarchical porous/hollow nanostructures [28,74,75,79,83,99,[103][104][105][125][126][127][128] ) have been widely investigated and proved to possess superior electrochemical performance for energy storage and conversion. In this section, the application of nanostructured ternary nickel cobalt sulfides in HSCs, LIBs/SIBs, and electrocatalysis will be thoroughly summarized and discussed.…”

“…Especially, the self-template method is an efficient approach to generate MMSs with hollow nanostructures. [28,30,75,79,82,83,87] When synthesizing Mo-or W-containing MMSs using these solutionbased methods, (NH 4 ) 2 Mo(W)S 4 is generally used as both Mo(W) and S sources. [29,48,63,89] The gas sulfidation method is another facile approach to synthesize MMSs.…”

“…In general, a self-template method involves the synthesis of template precursors and subsequent sulfidation treatment process through ion-exchange reactions and/or Kirkendall effect. Up to present, numerous intriguing templates have been developed, including mixed metal oxide, [72,73] mixed metal hydroxide, [74,75] layered double hydroxide (LDH), [76,77] mixed metal carbonate, [78,79] mixed metal glycerate, [28,80,81] mixed metal carbonate hydroxide, [27,82] mixed metal acetate hydroxide, [83] mixed metal silicate, [84,85] and metal-organic frameworks (MOFs). [86][87][88] These self-engaged templates could directly determine the shape, size, and composition of the resultant MMSs.…”

“…[28,72,75,[78][79][80][81][82][83][84][85][130][131][132][133][134] Up to now, various strategies have been developed to synthesize hollow nanostructured nickel cobalt sulfides with diverse nanostructures. Temple-engaged approach is probably the most effective strategy to construct hollow nanostructured nickel cobalt sulfides with controlled composition, size, morphology, shell thickness, internal void size, and interior complexity.…”