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We have prepared hybrid supercapacitors (HSCs) based on metal oxide/nickel cobalt sulfide composite electrodes decorated with an ultrathin carbon layer (Co3O4@C@CoNi2S4). This ultrathin carbon laye...

In this work, hierarchically porous MnO/carbon (MnO/C) microsphere materials were fabricated by a facile two-step approach. The MnO precursors and the polymerization of dopamine were synthesized simultaneously by chemical solution method at room temperature. The dopamine plays a key role in the formation of MnO/C, which guides the growth of porous spherical structures and acts as a carbon source. The enhancement of electrochemical properties and electrical conductivity strongly depend on the porous structure of the composite electrodes. Benefiting from the unique structures, the optimized MnO/C electrode delivered a high specific capacitance of 378 F·g−1 at 0.1 A·g−1 and retained over 96.66% of its initial capacitance after 1000 cycles at 1 A·g−1, suggesting that MnO/C hybrid material has promising potential for practical supercapacitors.

The rational design of positive electrodes for hybrid supercapacitors is profound for applications in energy storage and conversion. Herein, we designed porous-hollow Co9S8/NiCo-Mo one-dimensional (1D) hetero-nanostructures on carbon cloth as battery-type electrodes. In particular, Ni–Co double hydroxide and Mo oxide grow on the surface of hollow Co9S8 nanowires, providing rich active sites. Meanwhile, the hollow structure of the Co9S8 nanowires is beneficial for electrolyte penetration and slows down the volume change caused by the continuous charge and discharge process. Moreover, the Co9S8/NiCo-Mo oxide/hydroxide electrode exhibits a remarkable areal capacity of 3.07 mA h cm−2 (1 mA cm−2), and a hybrid supercapacitor based on Co9S8/NiCo-Mo nanostructures and activated carbon (AC) can output a high specific energy of 37.6 W h kg−1 at a specific power of 228.7 W kg−1 with decent cycling stability (capacity retention of 87.7% after 10 000 cycles). Two connected HSCs can light up a red-light emitting diode (LED) and make the motor turn for more than 5 min. The results indicate that the unique integrated Co9S8/NiCo-Mo nanostructure shows great potential as a novel battery-type electrode for supercapacitors.

The unique feather-like arrays composing of ultrathin secondary nanowires are fabricated on nickel foam (NF) through a facile hydrothermal strategy. Thus, the enhancement of electrochemical properties especially the low charge transfer resistance strongly depends on more active sites and porosity of the morphology. Benefiting from the unique structure, the optimized NiCo2O4 electrode delivers a significantly lower charge transfer resistance of 0.32 Ω and a high specific capacitance of 450 F·g−1 at 0.5 A·g−1, as well as a superior cycling stability of 139.6% capacitance retention. The improvement of the electrochemical energy storage property proves the potential of the fabrication of various binary metal oxide electrodes for applications in the electrochemical energy field.

Although ternary cobalt nickel sulfide is a promising electrode material for supercapacitors, its wide application is limited by its relatively poor electrochemical stability, low rate capacity and inefficient nanostructure. Here, we demonstrate that the electrochemical activity of cobalt nickel sulfide can be significantly improved by synergy from a Co-MOF-derived Co3O4 skeleton. We design and fabricate petal-like Co3O4@CoNi2S4 nanowall arrays combined with carbon cloth as an excellent self-standing electrode for asymmetric supercapacitors. The Co3O4@CoNi2S4 electrode exhibits a high specific capacitance of 244.4 mA h g−1 at a current density of 1 A g−1 and an excellent rate capability of 81.3% at 16 A g−1. Furthermore, the assembled Co3O4@CoNi2S4//AC asymmetric supercapacitor (ASC) shows a high energy density of 55.6 W h kg−1 at a power density of 884.4 W kg−1, and the capacitance retention of Co3O4@CoNi2S4 is up to 86% after 10 000 cycles. It is believed that the presented work opens up a new strategy to fabricate high-performance supercapacitor electrodes.

Three-dimensional (3D) carbon nanospheres and two-dimensional (2D) carbon layer co-decorated dendritic nickel sulfide (Ni3S2) is fabricated on a nickel foam via a two-step hydrothermal process. The carbon nanospheres with the diameters ranging from 150 to 200 nm embellished on the “treetop” and the carbon layer coated uniformly on the “trunk”, which enhance the capacitive performance of the composite electrode. Herein, the amorphous carbon can further provide more efficient electron conduction path for the electrodes. With its unique superstructure, the as-fabricated carbon decorated Ni3S2 electrode exhibits a high specific capacity of 297.2 mAh g−1 at 5 mA cm−2, remarkable cycling stability (84.1% of the initial capacity) for 10,000 cycles at 10 mA cm−1. The hybrid supercapacitor fabricates by carbon decorated Ni3S2 and active carbon, which achieves a high specific energy of 62.5 Wh kg−1 at a specific power of 241.5 W kg−1. The encouraging results of the electrode make it as a potential candidate for energy storage.