Two-Dimensional, Porous Nickel–Cobalt Sulfide for High-Performance Asymmetric Supercapacitors

Abstract

High specific surface area, high electrical conductivity, and abundant channels have been recognized to favor pseudocapacitors, but their realization at the same time is still a great challenge. Here, we report on nickel-cobalt sulfide nanosheets (NSs) with both ultrathin thickness and nanoscale pores for supercapacitors. The porous Ni-Co sulfide NSs were facilely synthesized through micelle-confined growth and subsequent sulfuration. The NSs are as thin as several nanometers and have a large number of pores with a mean size of ∼7 nm, resulting in ultrahigh atom ratio at surface with unique chemical and electronic structure. Therefore, fast diffusion of ions, facile transportation of electrons and high activity make great synergistic contributions to the surface-dependent reversible redox reactions. In the resulted supercapacitors, a specific capacitance of 1304 F g(-1) is achieved at a current density of 2 A g(-1) with excellent rate capability that 85.6% of the original capacitance is remained at 20 A g(-1). The effects of crystallinity and self-doping are optimized so that 93.5% of the original capacitance is obtained after 6000 cycles at a high current density of 8 A g(-1). Finally, asymmetric supercapacitors with a high energy density of 41.4 Wh/kg are achieved at a power density of 414 W/kg.

Holey 2D Nanomaterials for Electrochemical Energy Storage

“…Li et al reported the facile synthesis of ultrathin nickel-cobalt sulfide nanosheets through the micelle confined growth and further sulfuration. [40] The as-synthesized nickel-cobalt sulfide nanosheets can be as thin as several nanometers and with an average pore size of ≈7 nm (Figure 6d,e). The ultrathin nickelcobalt sulfide nanosheets tended to assemble into a 3D hierarchical structure (Figure 6d).…”

Facile synthesis of CoNi 2 S 4 /Co 9 S 8 composites as advanced electrode materials for supercapacitors

“…Shen et al [27] used a hydrothermal method to prepare CoNi2S4/CNT/graphene composites which had high specific capacitance (710 F/g at 20 A/g) and the capacity retained 82% after 2000 charging-discharging cycles. Li et al [28] reported a solvothermal method to synthesize NiCo2S4 which had high specific capacitance of 1304 F/g at 2 A/g, excellent rate capability of 1116 F/g at 20 A/g. However, the disadvantages of the hydrothermal method such as long reaction time, high reaction pressure/temperature, and low production level greatly hinder large-scale production of NCS [29].…”

Hydrothermal assisted in situ growth of CoSe onto graphene nanosheets as a nanohybrid positive electrode for asymmetric supercapacitors

“…The CoSe-GkAC ASC has superior energy and power densities than that of other metal-chalcogenides based ASCs in aqueous electrolyte, such as NiTekAC (33.6 57 The high energy and power densities of CoSe-GkAC ASC could be assigned to (i) a synergistic effect between graphene and CoSe nanoparticles in the hybrid and (ii) a well developed large interfacial contact between the interfaces. Therefore, the newer CoSe-GkAC based ASC offers a potential energy storage applications.…”