Ultrathin Mesoporous NiCo₂O₄ Nanosheets Supported on Ni Foam as Advanced Electrodes for Supercapacitors

Abstract

A facile two‐step method is developed for large‐scale growth of ultrathin mesoporous nickel cobaltite (NiCo2O4) nanosheets on conductive nickel foam with robust adhesion as a high‐performance electrode for electrochemical capacitors. The synthesis involves the co‐electrodeposition of a bimetallic (Ni, Co) hydroxide precursor on a Ni foam support and subsequent thermal transformation to spinel mesoporous NiCo2O4. The as‐prepared ultrathin NiCo2O4 nanosheets with the thickness of a few nanometers possess many interparticle mesopores with a size range from 2 to 5 nm. The nickel foam supported ultrathin mesoporous NiCo2O4 nanosheets promise fast electron and ion transport, large electroactive surface area, and excellent structural stability. As a result, superior pseudocapacitive performance is achieved with an ultrahigh specific capacitance of 1450 F g−1, even at a very high current density of 20 A g−1, and excellent cycling performance at high rates, suggesting its promising application as an efficient electrode for electrochemical capacitors.

Porous nanoarchitectures of spinel-type transition metal oxides for electrochemical energy storage systems

“…Given that the electrochemical properties of spinel-type transition metal oxides are highly sensitive to their material characteristics, a large number of low-temperature synthesis procedures have been developed for the fabrication of spinel-type transition metal oxides with controlled composition, crystal structures, surface morphologies, and porous structures. 50,[81][82][83][84][85][86][87][88] Although Section 3 provides details of the preparation of spinel-type transition metal oxides and their applications in specific ESSs, here, we highlight the most recent progress in the synthesis of spinel-type transition metal oxides with controlled phases and porous/morphological characteristics.…”

“…In particular, the shape and size control of the spinel-type transition metal oxides has been regarded as a useful strategy to improve the electrochemical performance of ESSs. To date, various spineltype transition metal oxides with diverse shapes in micro-and nano-scale forms, including nanoparticles, [46][47][48] nanoneedles, 49 nanosheets, [49][50][51] nanowires, [52][53][54][55][56] nanorods, 57 nanocubes, 58,94 nanofibres, 59 nanotubes, 60,61 polyhedral structures, 62,63,93 hierarchical structures, 58,92 hollow structures, 58,64,97 and core-shell structures, 65,96,97 have been synthesised and utilised as electroactive materials for ESSs. 98 The porous nanoarchitectures constructed by various morphological strategies have proved to be highly desirable for energy storage materials used for practical ESSs.…”

Two-dimensional NiCo2O4nanosheet-coated three-dimensional graphene networks for high-rate, long-cycle-life supercapacitors

“…13,39 Third, the thin NiCo 2 O 4 NS connected with each other to form a nanosheet network with highly open space can serve as an "ion-buffering reservoir" for OH − ions, ensuring a sufficient Faradaic reaction occurring even at very high current density. 46 Lastly, the strong coupling between NiCo 2 O 4 NS and 3DGN renders good mechanical adhesion and electrical connection, avoiding the use of polymer binders and conductive additives and leading to enhanced electrochemical kinetics, which is good for high-rate capability and long-term cycling performance of supercapacitors. 12,22,27 In summary, we have successfully fabricated high-capacitance, high-rate, and long-cycle-life supercapacitors by synthesis of thin 2D NiCo 2 O 4 NS with a thickness of ∼6.4 nm on 3DGN.…”

Hybrid system of nickel–cobalt hydroxide on carbonised natural cellulose materials for supercapacitors

“…2 and 3, respectively. The XRD peak labels correspond to the standard powder diffraction patterns of Ni(OH) 2 (JCPDS card no.14-0117), Co(OH) 2 (JCPDS card no.JCPDS74-1057) and other references [9,[19][20][21]29]. The diffraction peaks of electrodeposited Ni(OH) 2 are weak and broad, suggesting low crystallinity.…”

“…Another method is the substitution of nickel by other metals to enhance conductivity; cobalt is usually used because it shares a similar crystal structure with Ni [17]. The co-deposition of Ni and Co can reach a high supercapacitance of 1920 F g −1 , consistently higher than the counterpart of Ni or Co modified alone [14,[17][18][19][20][21]. Intensive research has focussed on the structure of Ni-Co compounds.…”