Advanced Asymmetric Supercapacitors Based on Ni(OH)₂/Graphene and Porous Graphene Electrodes with High Energy Density

Abstract

Hierarchical flowerlike nickel hydroxide decorated on graphene sheets has been prepared by a facile and cost‐effective microwave‐assisted method. In order to achieve high energy and power densities, a high‐voltage asymmetric supercapacitor is successfully fabricated using Ni(OH)2/graphene and porous graphene as the positive and negative electrodes, respectively. Because of their unique structure, both of these materials exhibit excellent electrochemical performances. The optimized asymmetric supercapacitor could be cycled reversibly in the high‐voltage region of 0–1.6 V and displays intriguing performances with a maximum specific capacitance of 218.4 F g−1 and high energy density of 77.8 Wh kg−1. Furthermore, the Ni(OH)2/graphene//porous graphene supercapacitor device exhibits an excellent long cycle life along with 94.3% specific capacitance retained after 3000 cycles. These fascinating performances can be attributed to the high capacitance and the positive synergistic effects of the two electrodes. The impressive results presented here may pave the way for promising applications in high energy density storage systems.

NiCo2S4 Nanosheets Grown on Nitrogen‐Doped Carbon Foams as an Advanced Electrode for Supercapacitors

“…The mass ratio of NiCo 2 S 4 to OMC/NCF was controlled at about 0.21 in the ASCs based on the principle of charge balance at 5 mV s −1 for both electrode (see experiment methods). Referring to previous reports, the carbon material exhibits a typical characteristic of a electric double-layer capacity in an electrolyte of KOH aqueous solution within the range −1.0−0 V. [41][42][43] NiCo 2 S 4 based material display excellent electrochemical reversibility within a potential window of −0.1−0.6 V. [ 23,27 ] Therefore, it is expected that the work voltage of ASCs device can be extended to 1.6 V. We performed a series of CV and charge/ discharge measurements with increasing voltage windows to estimate the best operating potential of the designed ASCs device ( Figure S8a,c, Supporting Information). More capacitive response from Faradaic reactions will occur with the increasing operating potential.…”

Microstructural tunability of co-continuous bijel-derived electrodes to provide high energy and power densities

“…The initial drop in capacitance could be explained by poor wettability of the electrode in the electrolyte as well as a decrease in electrical contact between the current collector and active material. 32 The ensuing slow increase in capacitance could be caused by an activation process within the electrolytically active material that allows trapped ions to slowly diffuse out as well as an increasing improvement in the wettability of the electrodes surface by the electrolyte during subsequent cycles. 32 Aer 1000 cycles, the specic capacitance was maintained at 93% of its original value.…”

“…32 The ensuing slow increase in capacitance could be caused by an activation process within the electrolytically active material that allows trapped ions to slowly diffuse out as well as an increasing improvement in the wettability of the electrodes surface by the electrolyte during subsequent cycles. 32 Aer 1000 cycles, the specic capacitance was maintained at 93% of its original value. Furthermore, SEM images of the sample revealed that its microstructure remained intact aer the cycling test (ESI Fig.…”

“…On a gravimetric basis, we exceed the best values reported in the literature, providing at least a 1.5Â and up to a 10Â improvement in energy density at comparable specic powers for all reported values. 24,26,[32][33][34] This is again afforded by the unique architecture of our electrode, which allows for rapid energy delivery to and from the entirety of the active material, enabling battery-type specic energies and rate performances equivalent to or surpassing that of the best supercapacitors.…”

Ni@NiO core/shell dendrites for ultra-long cycle life electrochemical energy storage

“…1 Nickel based materials have been identied as promising electrode materials for electrochemical energy storage devices because of their high theoretical specic capacitance ($2584 F g À1 for NiO and 2082 F g À1 for Ni(OH) 2 ), environmental friendliness and low cost. 2,3 With the aim to provide a larger reaction area and shorten ion diffusion paths, many fabrication methods including chemical precipitation, 4,5 hydrothermal synthesis, [6][7][8][9][10][11] sol-gel, 12,13 thermal oxidation [14][15][16] and anodization 17,18 have been used to produce various kinds of nickel-based nanostructures, such as amorphous Ni(OH) 2 nanoboxes, 5 Ni-Co oxide nanowires, 6,19 Ni(OH) 2 nanosheets, 7,11 NiO nanobelts, 8 nanosized rambutan-like NiO, 9 urchin-like NiCo 2 O 4 , 10 spinel nickel cobaltite aerogels, 12 NiO nanoowers, 13 NiO nanoblocks 14 and sponge-like Ni(OH) 2 -NiF 2 composites. 18 Apart from the above methods, electrodeposition has gained more and more attention because the electroactive material can be directly grown on a current collector without the need for using any binder or conducting agent.…”