Rational Design of Carbon Layer-Decorated Metal Oxide/Nickel Cobalt Sulfide-Based Composite with Faster Energy Storage and Long Cyclic Life

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 layer serves as an “expressway” for enhanced electron and ion transport, and the horizontally aligned nanosheet structure prevents the electrodes from structural collapse during electrochemical reaction processes. The obtained Co3O4@C@CoNi2S4 hierarchical composites exhibit a higher gravimetric specific discharge capacity (400.6 mA h·g–1 at 1 A·g–1). More importantly, as a HSC based on Co3O4@C@CoNi2S4//active carbon (AC), a high specific energy of 46.5 W h·kg–1 at a specific power of 1052.8 W h·kg–1 was obtained (95.6% capacitance retention after 10,000 charge/discharge cycles). The result indicates that such Co3O4@C@CoNi2S4 heterostructures may show significant promise for application of electrochemistry in the energy field.