Binder‐free preparation of bimetallic oxide vertical nanosheet arrays toward high‐rate performance and energy density supercapacitors

Abstract

Fabrication of binder-free electrode materials with vertical nanoarchitecture is the prominent approach to achieve exalted energy storage performance.Herein, we synthesized NiCo 2 O 4 (NCO) zigzag-patterned vertical nanosheet arrays (ZNSAs) directly over the nickel foam substrate by adopting a facile one-step solvothermal method, which is followed by a calcining process. The effect of ethanol and water solvents on the development of ZNSAs was studied by varying their volume concentration. Among the samples, the NCO ZNSA electrode prepared with an equal volume proportion of ethanol and water solvents revealed the highest electrochemical performance with the areal capacity of 146.1 μAh/cm 2 at 4 mA/cm 2 due to the well-developed NSAs with hierarchical and open-porous texture. Moreover, the NCO ZNSA electrode exhibited remarkable stability (97.6% retention) after the cycling process of 4000 cycles.A hybrid supercapacitor (HSC) device was also constructed with NCO ZNSAs and activated carbon as the cathode and anode, respectively. At 2 mA/cm 2 , the HSC showed a notable areal capacitance of 173.5 mF/cm 2 . Furthermore, the HSC exhibited a maximum energy density of 52.7 μWh/cm 2 and power density of 10500 μW/cm 2 . With the energy storage capabilities, the HSC demonstrated its practical applicability by glowing light-emitting diodes and powering up a motor fan. K E Y W O R D Sbinder-free growth, energy storage performance, hybrid supercapacitor, nickel cobalt oxides, zigzag-patterned vertical nanosheet arrays

Supercapacitor performance evaluation of nanostructured Ag‐decoratedCo‐Co3O4composite thin film electrode material

“…The GCD curves of the Co‐Co 3 O 4 /NF electrode (Figure 5A) are similar to those of the Ag/Co‐Co 3 O 4 /NF electrode as observed in the CV analysis. The shape of the curves, deviated from the ideal triangular shape of EDLC electrode materials together with voltage plateaus, further confirms the Faradaic reactions of battery‐type behaviors complementing the observations on the CV curves 33,40‐42 . When the specific current was increased from 1 to 20 A/g, the shape of the curves obtained from the individual electrodes remained unchanged, indicating that the as‐prepared electrodes have high stability 40 .…”

“…In addition, it can be noticed that there is a peak shift in the oxidation peaks toward higher potential and 33,[40][41][42] When the specific current was increased from 1 to 20 A/g, the shape of the curves obtained from the individual electrodes remained unchanged, indicating that the as-prepared electrodes have high stability. 40 Furthermore, it can be observed that the discharge times decreased with increasing specific currents in both cases.…”

“…To investigate the performance of the thin films as potential electrodes for supercapacitor applications, CV, The deviation of the shape of all the CV curves from the ideal rectangular shape of electrical double-layer capacitor (EDLC) electrode materials, and the presence of redox peaks suggests that the specific capacitance arises mainly from Faraday redox reactions indicating battery-type storage properties. 4,15,32,33 1). 5,10,17,34 Similarly, the redox pair (A3 [0.47 V], C3 [0.36 V]) is also attributed to the redox reaction of Co 3+ / Co 4+ according to Equation (2).…”

Investigation of magnetron sputtered Ni@Cu/ WS 2 as an electrode material for potential supercapattery devices

“…The prime electrochemical characteristics of the supercapattery including energy and power density represented by E d and P d have been further calculated using the equations as follows: Here, in Equations () and () the “ E d ” and “ P d ” symbolize energy density (Wh/kg) and power density (W/kg), respectively, whereas “ Q S ” signify specific capacity (C/g), “Δ V ” denotes the voltage window () while “Δ t ” defines the discharging time ( s ). To illustrate the energy and power characteristics in comparison to the reported literature a Ragone plot showing excellent performance of the hybrid device has been revealed in Figure 9C 53‐56 . In this plot, the supercapattery exhibits the high E d of 43.9 Wh/kg while sustaining P d of 425 W/kg at 0.5 A/g.…”

“…To illustrate the energy and power characteristics in comparison to the reported literature a Ragone plot showing excellent performance of the hybrid device has been revealed in Figure 9C. [53][54][55][56] In this plot, the supercapattery exhibits the high E d of 43.9 Wh/kg while sustaining P d of 425 W/kg at 0.5 A/g. However, at 8 A/g the device procured a maximum P d of 6800 W/kg.…”