CoNi₂S₄ Nanosheet Arrays Supported on Nickel Foams with Ultrahigh Capacitance for Aqueous Asymmetric Supercapacitor Applications

Abstract

We report that CoNi2S4 nanosheet arrays exhibit ultrahigh specific capacitance of 2906 F g(-1) and areal capacitance of 6.39 F cm(-2) at a current density of 5 mA cm(-2), as well as good rate capability and cycling stability, and superior electrochemical performances with an energy density of 33.9 Wh kg(-1) at a power density of 409 W kg(-1) have been achieved in an assembled aqueous asymmetric supercapacitor. The CoNi2S4 nanosheet arrays were in situ grown on nickel foams by a facile two-step hydrothermal method. The formation mechanism of the CoNi2S4 nanosheet arrays was based on an anion-exchange reaction involving the pseudo Kirkendall effect. The two aqueous asymmetric supercapacitors in series using the CoNi2S4 nanosheet arrays as the positive electrodes can power four 3-mm-diameter red-light-emitting diodes. The outstanding supercapacitive performance of CoNi2S4 nanosheet arrays can be attributed to ravine-like nanosheet architectures with good mechanical and electrical contact, low crystallinity and good wettability without an annealing process, rich redox reactions, as well as high conductivity and transport rate for both electrolyte ions and electrons. Our results demonstrate that CoNi2S4 nanosheet arrays are promising electrode materials for supercapacitor applications.

Investigation of the Electrochemical Properties of CoAl-Layered Double Hydroxide/Ni(OH)2

“…Three typical peaks, marked with asterisks, originate from nickel foam. 26 As can be seen from the figure, the peaks at 11.4…”

“…26,28 To determine the ion transport properties of electrode materials for supercapacitor applications, electrochemical impedance spectroscopy (EIS) tests were investigated over frequency ranges of 0.01 Hz to 100 kHz. Nyquist plots of different mixture electrodes are shown in Fig.…”

Electrochemically Synthesis of Nickel Cobalt Sulfide for High‐Performance Flexible Asymmetric Supercapacitors

“…Figure 6d shows the Ragone plot relating the energy density to the power density of ASC devices. Notably, the energy density of ASC devices is comparable or superior than that of Ni‐Co sulfide nanowire//activated carbon cells (25 Wh kg −1 at 3.57 kW kg −1 ),38 carbon/CoNi 3 O 4 //activated carbon cells (19.2 Wh kg −1 at 13 kW kg −1 ),39 graphene–nickel cobaltite nanocomposite//activated carbon (7.6 Wh kg −1 at 5.6 kW kg −1 ),40 Ni–Co oxide//activated carbon (7.4 Wh kg −1 at 1.9 kW kg −1 ),41 Co x Ni 1− x O/reduced G–O//reduced G–O cells (28 Wh kg −1 at 3614 W kg −1 ),42 Ni–Co hydroxides/Zn 2 SnO 4 //activated carbon (AC) devices (23.7 Wh kg −1 at 284 W kg −1 ),43 Ni–Co–S/cloth//GF (60 Wh kg −1 at 1.8 kW kg −1 ),44 and CoNi 2 S 4 nanosheet arrays on NF//AC devices (33.9 Wh kg −1 at 409 W kg −1 ) 45. The electrochemical properties of nickel cobalt sulfide‐based ASCs are generalized in Table S2 (Supporting Information).…”

Mixed Metal Sulfides for Electrochemical Energy Storage and Conversion

“…To well address the above-mentioned issues, an intriguing strategy is to grow electroactive materials on conductive current collectors. Recently, nanoarrays of MMSs have been directly grown on conductive substrates, such as NF, [30,[111][112][113][114][115][116] carbon cloth (CC), [65,117,118] carbon fiber paper (CFP), [73,119,120] and so on, to construct 3D electrodes. Such binder-free and conductive-agent-free integrated electrodes can avoid the "dead surface" and the tedious process in preparing traditional slurry-coating electrodes and significantly improve the utilization rate of electroactive materials.…”