Ultrathin porous hierarchically textured NiCo₂O₄–graphene oxide flexible nanosheets for high-performance supercapacitors

Abstract

The ultimate goal of supercapacitor research industries is to develop devices which could be used as flexible, portable, ultrathin and highly-efficient power sources. However, the bulk NiCo 2 O 4 materials prevent the achievement of high energy density as well as immense rate performance due to the limited electroactive surface area. In this work, we proposed a new breakthrough strategy to develop highly porous hierarchical flexible nanosheets of NiCo 2 O 4 -graphene oxide (NiCo 2 O 4 -GO) on nickel foam by a facile electrochemical deposition method. The morphogenesis of the NiCo 2 O 4 -GO hybrid nanostructurebased electrode exhibits hierarchical porous flexible nanosheet-like structures. The electrochemical properties of these electrodes were investigated by cyclic voltammetry and galvanostatic charge-discharge measurements in 3 M KOH electrolyte. The obtained results exhibit that this new hybrid nanostructure has a specific capacitance of 1078 F g À1 at a discharge current of 1 mA with great cyclic stability. These excellent capacitive performances of NiCo 2 O 4 -GO can be attributed to its hierarchical porous nanosheet-like unique structure. This unique structure provides efficient ion transport that is highly desirable for superior rate capability and excellent cycling stability. Hence, our method provides a promising facile and binder-free nanostructure electrode for next generation high-performance supercapacitor applications.

Flexible Supercapacitors: A Materials Perspective

“…For example, the ternary oxide NiCo 2 O 4 is highly suitable for supporting multiple electrochemical processes as it contains mixed valence metals (Zhang and Lou, 2013;Zhang D. et al, 2014). NiCo 2 O 4 nanocrystals grown on different substrates such as carbon fiber paper, nickel foam, and titanium sheets have shown good cyclic stability and high capacitance (Zhang et al, 2012;Huang et al, 2013;Mitchell et al, 2015). Recently, a highly flexible quasi solid-state supercapacitor device was fabricated by sandwiching electrodes of flower-shaped NiCo 2 O 4 nanocrystals on graphene oxide (GO) substrate (Gupta et al, 2015).…”

Layered ternary sulfide CuSbS2 nanoplates for flexible solid-state supercapacitors

“…18 These characteristics make them attractive for use in electrical vehicles, consumer electronics, memory back-up systems and other applications where a burst supply of energy is required. 24,25,26 In contrast, layered materials that are separated by weak van der Waals forces can withstand large volume changes and can also host a variety of foreign atoms or ions between layers. 21 A significant improvement in energy density can be achieved by use of metal oxide pseudocapacitors.…”

Highly stable hollow bifunctional cobalt sulfides for flexible supercapacitors and hydrogen evolution

“…Supercapacitors are electrochemical energy storage devices primarily appealing for their excellent power density and long cycle life. [4][5][6][7] Carbon based electrodes are suitable for delivering high power density but have low energy density. 8 Nevertheless, in recent years, the energy density of supercapacitors has been boosted by the use of metal oxides, which in turn sacrices the cycle life.…”