Hybrid Supercapacitors Based on Interwoven CoO‐NiO‐ZnO Nanowires and Porous Graphene Hydrogel Electrodes with Safe Aqueous Electrolyte for High Supercapacitance

Abstract

pollution. [6,7] The electrode material is an important factor to determine the performance of supercapacitors. [8] At present, electrode materials are roughly classified into four categories: metal oxides, carbon materials, conductive polymers, metal sulfides, and others. Compared with the other materials, metal oxides are favored by researchers because of their low cost and extremely high theoretical specific capacitance. [9] Various metal oxides, such as CoO, [10] NiO, [11] ZnO, [12,13] Co 3 O 4 , [14] Fe 2 O 3 , [15] and MnO 2 [16,17] have been used as electrode materials for supercapacitors. ZnO is one of the typical semiconductor materials. Due to its good electrochemical activity, large specific surface area, low cost, easy manufacturing, and high mechanical flexibility, it is considered to be a promising electrode material for supercapacitors. [12] However, the theoretical specific capacitance of ZnO limits its application in energy storage fields such as supercapacitor. [18] CoO is applied as electrode widely due to its ultra-high theoretical specific capacitance and high redox activity. [19,20] However, the high electrical resistance and poor electrical conductivity during charge and discharge restrict the cycle stability of CoO. As one of the materials currently used in supercapacitor electrode materials, NiO has the advantages of high theoretical specific capacitance and large specific surface area, but it is well known that its cycle stability and rate performance are poor. [21] Therefore, the composite materials obtained by combining several of them can also take advantage of their long complements and fully exert their synergistic effects, so that the comprehensive electrochemical performance is improved significantly so as to solve the problems of single metal oxide electrode. [22,23] For example, the surface/volume ratio of the nanostructures can increase the specific capacitance exponentially. The urchinlike CoO nanostructures were selected as the framework for depositing NiO nanosheets to construct a graded core/shell CoO@NiO hybrid nanostructure. [24] Unfortunately, although it has a good specific capacitance and energy density, its cycle stability is poor. ZnO/CoO composite in situ grown on Ni foam was produced, although the cycle stability is improved, the general specific capacitance is less satisfactory. [25] Compared with the single metal oxides, the energy density, power density, Metal oxides-based supercapacitors have attracted much attention due to their easy fabrication and ultra-high theoretical specific capacitance. Here, a novel ternary metal oxide (CoO-NiO-ZnO, CNZO) in situ grown on Ni foam (CNZO@Ni foam) is prepared by one-pot hydrothermal synthesis and a subsequent annealing method. Compared with the corresponding binary and single metal oxides of CoO-ZnO, NiO-ZnO, CoO-NiO, CoO, NiO, and ZnO, this ternary metal oxide shows an ultra-high specific capacitance (areal capacitance) of 2115.5 F g −1 (4.23 F cm −2 ) at a current density of 1 A g −1 (2 mA cm −2 ). Further, a hybrid sup...

Interior and Exterior Decoration of Transition Metal Oxide Through Cu0/Cu+ Co-Doping Strategy for High-Performance Supercapacitor

“…Carbon materials, conducting polymers and transition metal oxides (TMOs) are the most widely used electrode materials in SCs [10][11][12]. Particularly, TMOs, such as CoO [13,14], Co 3 O 4 [15], NiO [16] and Fe 3 O 4 [17], deliver much higher specific capacitance than that of carbon materials and conductive polymers benefiting from the multiple reversible faradaic redox reactions.…”

Rational Design of Hierarchical CoO/NiO Nanosheets on Conductive Polypyrrole Nanotubes for Peroxidase Mimicking and Sensing Application

“…The typical diffraction bands are located between that of CoO (JCPDS 48–1719) and NiO (JCPDS 47–1049), demonstrating the composite of CoO and NiO (Figure a and Figure S5). , However, a diffraction peak appears at around 36.8° when there is no or little Ni content, which can be indexed as the (311) crystal plane of the Co 3 O 4 (JCPDS 42–1467). The XRD result implies that the introduction of Ni promotes the formation of the CoO phase in the PPy@CoO/NiO NTs.…”

A Powder Self‐Healable Hydrogel Electrolyte for Flexible Hybrid Supercapacitors with High Energy Density and Sustainability

“…Compared with most previously reported hydrogel electrolyte-based supercapacitors, the Ragone plot of SPMA-ZHS exhibits a higher energy density of 164.13 Wh kg −1 at the power density of 1283.44 Wh kg −1 (Figure 3G, Table S2, Supporting Information). [52][53][54][55][56][57][58][59][60][61][62][63] Cycling performance is an important indicator for the supercapacitors. Cycling stability and coulombic efficiency of SPMA-ZHS were investigated at 10 A g −1 for 5000 charge-discharge cycles.…”