Zinc Cobalt Sulfide Microspheres as a High‐Performance Electrode Material for Supercapacitors

Abstract

Fast charging/discharging rate, sustained cycle life, and high power density are irreplaceable virtues of supercapacitors (SCs), and these merits can be achieved by selecting suitable active materials and designing the rational microstructure. In this work, zinc cobalt sulfde (ZCS) microspheres have been synthesized by a simple two‐step method involving an ethylene glycol (EG) mediated solvothermal approach and subsequent sulfidation treatment. The formation mechanism of the microspheres is also proposed in detail by analyzing the time‐dependent SEM observations. Compared to ZCS nanosheets, ZCS microspheres achieve better electrochemical storage performance due to their satisfactory mesoporous feature, conductivity, and effective transport/diffusion paths for ions and electrons. When used as the electrode material of supercapacitor, ZCS microspheres not only obtain a large specific capacitance of 1516 F g−1 (211 mAh g−1) at 1 A g−1 with good rate capability of 1080 F g−1 (150 mAh g−1) at 10 A g−1, but also exhibit exceptional cycling stability with a capacitance reduced 6% of the initial specific capacitance at 10 A g−1 after 4000 cycles. An asymmetric supercapacitor using ZCS microspheres as the cathode and activated carbon (AC) as the anode is assembled, which achieves high specific capacitance (489.3 F g−1), energy density (152.9 Wh kg−1), and power density (750 W kg−1) at 1 A g−1 with the capacitance retention of 79% at 5 A g−1 after 2000 cycles. This work illustrates the promising application potential of the ZCS microspheres as the electrode material for electrochemical capacitors.

Practical Synthesis for N‐doped Carbon Microsphere Coated with Zn0.76Co0.24S Nanoparticles towards High‐performance Supercapacitors

“…As we know, the specific capacitance of the material is positively correlated with the measure of area in CV curves. [18] It is found that the area of the closed region of NÀ C@ZCS-55 % is perspicuous larger than the others. And the material without carbon addition exhibits the minimum area, indicating the addition of carbon material has a qualitative improvement on the properties of the composite.…”

Facile Construction of Sandwich‐like Co3O4/CNTs Complex for High‐performance Asymmetric Supercapacitors

“…The intersection of the high frequency intercept on the real axis (Z’‐axis) represents the series resistance ( R s ), including the contact resistance of the electrode/electrolyte interface and electrolyte resistance. The semicircles in higher frequency region represent the constant phase element (CPE) and charge‐transfer resistance ( R ct ) at the CE/electrolyte interface which resembles to the frequency requirement of the ion diffusion/transport in the electrolyte . A sharp Nernst diffusion plot in lower frequency range related to the Warburg diffusion impedance represents good capacitance behavior of the electrode materials, which signify the fast diffusion of ions towards the electrode .…”

A Review of Cobalt-Based Metal Hydroxide Electrode for Applications in Supercapacitors

“…Zinc-cobalt-sulfde (ZCS) disc microspheres were synthesized at three levels of sulfdation using ethylene glycol (EG) as an additive by a co-reduction reaction of zinc and cobalt picolinate [15]. Te presence of this ordered structure provides evidence supporting the use of orderedmesoporous flm prepared by electrochemical deposition as solid acid catalysts [16].…”