A High‐Energy Density Asymmetric Supercapacitor Based on Fe₂O₃ Nanoneedle Arrays and NiCo₂O₄/Ni(OH)₂ Hybrid Nanosheet Arrays Grown on SiC Nanowire Networks as Free‐Standing Advanced Electrodes

Abstract

environmentally friendly energy storage devices. As an emerging energy powering sources, supercapacitors (SCs) hold a vital and individual position owing to their high power density, excellent cycling stability, fast charge/discharge process as well as noticeable reliability, tremendously bridging the gap between rechargeable batteries and traditional capacitors in terms of energy density and power density. [1][2][3][4] Nevertheless, their commercial applications are still seriously impeded since energy densities of SCs are far lagging behind rechargeable batteries. [5,6] In the light of the critical parameters that decide the energy density (E = 1/2CV 2 ) of supercapacitor devices, [7][8][9] substantial efforts have been dedicated to maximizing the energy density via elevating the overall cell voltage (V) and total specific capacitance (C) governed by negative and positive electrodes. Configuration of asymmetric supercapacitors (ASCs) has emerged as a desirable strategy because of the expanded V arised from the absolutely opposite potential window of the two dissimilar electrode materials. [10][11][12] Accordingly, considerable research interest has been invested in constructing highly capacitive negative and positive electrode materials.Until now, transition metal oxides, hydroxides, or phosphides, especially Ni-Co compounds with low cost, natural abundance, and environmentally benign, are mostly employed as positive electrode materials in ASCs because they can present variable oxidation states, favorable electrochemical activity, and large theoretical-specific capacitance based on redox reactions, so they have received extensive attentions as perfect candidates in ASCs. [13][14][15][16][17][18] However, in comparison of the extraordinary advancement obtained by positive electrode materials, the lack of desired negative electrodes restricts the progress of high-performance ASCs. Previously, carbonaceous materials are still the most widely used as negative electrode, giving rise to low-specific capacitance of 100-250 F g −1 . [19][20][21][22][23] In this regard, pseudocapacitive negative electrode materials are proposed to be hopeful alternatives, whereas the restricted studies and poor , even when charging the device within 6.5 s, the energy density can still maintain as high as 45 W h kg −1 at 26.1 kW kg −1 , and the ASC manifests long cycling lifespan with 86.6% capacitance retention even after 5000 cycles. This pioneering work not only offers an attractive strategy for rational construction of high-performance SiC NW-based nanostructured electrodes materials, but also provides a fresh route for manufacturing next-generation high-energy storage and conversion systems.

Hollow 3D Frame Structure Modified with NiCo2S4 Nanosheets and Spinous Fe2O3 Nanowires as Electrode Materials for High‐Performance All‐Solid‐State Asymmetric Supercapacitors

“…The low‐magnification TEM image shown in Figure g clearly shows that vertical Fe 2 O 3 nanowires are uniformly assembled on the surface of MF/PPY, which is consistent with the SEM results. Furthermore, the HRTEM image in Figure i reveals the well‐ordered lattice planes with an average spacing of 0.25 nm, which can be attributed to the (110) lattice spacing of Fe 2 O 3 . Fe 2 O 3 @MF/PPY also shows a typical polycrystalline nature, as indicated by the SAED pattern.…”

Reversible ternary nickel‐cobalt‐iron catalysts for intermittent water electrolysis

“…Upon the application of a deposition potential at −1.0 V vs Ag/AgCl, the nitrate ions are reduced to OH − ions and increase the local pH value (Equation 1). The OH − ions then reacted with the Ni 2+ , Co 2+ , and/or Fe 3+ forming bimetallic or trimetallic hydroxide composites on the surface of NF (Equation 2, see details in Methods) . Figure A shows the scanning electron microscopy (SEM) image of the NiCo bimetallic composite deposited on nickel foam (NiCo/NF) from the electrolyte containing equal molar (2.5 mM) of Ni 2+ and Co 2+ .…”

“…The deposited NiCo film exhibits a nanoporous structure with highly curved and rippled, but interconnected nanoflakes/nanosheets. The nanopores have sizes ranging from 100‐200 nm, which is known to enhance the contact between electrolytes and the active catalysts surface area . Incorporating of iron into the NiCo composite induces no significant morphological change of the deposits on NF.…”

High‐Performance Flexible Asymmetric Supercapacitors Facilitated by N‐doped Porous Vertical Graphene Nanomesh Arrays

“…In general, the conductive scaffold or robust skeletons can be mainly divided into two major categories, i. e., metallic conductive substrates (e. g., nickel foam, Ti plate) and carbon‐based substrates . Commercially available carbon cloth (CC) as a commonly used flexible substrate have many favorable properties such as ultralight weight, outstanding mechanical strength and good processability, which makes them advantageous as versatile current collectors for applications in flexible energy storage systems . Nevertheless, They have some bottlenecks to be solved immediately: (1) Intrinsic low surface area makes it easy to generate “dead mass”, and difficult to achieve high mass loading of active substances.…”