Asymmetric Hybrid Capacitor Based on NiCo₂O₄ Nanosheets Electrode

Abstract

The looming global energy crisis and ever-increasing energy demands have catalyzed the development of renewable energy storage systems. In this regard, supercapacitors (SCs) have attracted widespread attention because of their advantageous attributes such as high power density, excellent cycle stability, and environmental friendliness. However, SCs exhibit low energy density and it is important to optimize electrode materials to improve the overall performance of these devices. Among the various electrode materials available, spinel nickel cobaltate (NiCo2O4) is particularly interesting because of its excellent theoretical capacitance. Based on the understanding that the performances of the electrode materials strongly depend on their morphologies and structures, in this study, we successfully synthesized NiCo2O4 nanosheets on Ni foam via a simple hydrothermal route followed by calcination. The structures and morphologies of the as-synthesized products were characterized by X-ray diffraction, scanning electron microscopy, and Brunauer-Emmett-Teller (BET) surface area analysis, and the results showed that they were uniformly distributed on the Ni foam support. The surface chemical states of the elements in the samples were identified by X-ray photoelectron spectroscopy. The as-synthesized NiCo2O4 products were then tested as cathode materials for supercapacitors in a traditional three-electrode system. The electrochemical performances of the NiCo2O4 electrode materials were studied and the area capacitance was found to be 1.26 C•cm −2 at a current density of 1 mA•cm −2 . Furthermore, outstanding cycling stability with 97.6% retention of the initial discharge capacitance after 10000 cycles and excellent rate performance (67.5% capacitance retention with the current density from 1 to 14 mA•cm −2 ) were achieved. It was found that the Ni foam supporting the NiCo2O4 nanosheets increased the conductivity of the electrode materials. However, it is worth noting that the contribution of nickel foam to the areal capacitance of the electrode materials was almost zero during the charge and discharge processes. To further investigate the practical application of the assynthesized NiCo2O4 nanosheets-based electrode, a device was assembled with the as-prepared samples as the positive electrode and active carbon (AC) as the negative electrode. The assembled supercapacitor showed energy densities of 0.14 and 0.09 Wh•cm −3 at 1.56 and 4.5 W•cm −3 , respectively. Furthermore, it was able to maintain 95% of its initial specific capacitance after 10000 cycles. The excellent electrochemical performance of the NiCo2O4 nanosheets could be ascribed to their unique spatial structure composed of interconnected ultrathin nanosheets, which facilitated electron transportation and ion penetration, suggesting their potential applications as electrode materials for high performance supercapacitors. The present synthetic route can be extended to other ternary transition metal oxides/sulfides for future energy storage devices and systems.

Core–Shell Structured C@SiO2 Hollow Spheres Decorated with Nickel Nanoparticles as Anode Materials for Lithium‐Ion Batteries

“…of 2p 3/2 and 2p 1/2 were observed at 858.3 and 875.8 eV, respectively. [50][51][52][53] The Si 2p core-level spectrum (Figure 4c) showed the peak at 103.7 eV, ascribed to the characteristic of tetravalent silicon. [54] The XPS spectrum of C 1s was deconvoluted into several peaks (Figure S5d To investigate the lithium-ion storage performance of Ni-SiO 2 /C HS, coin cell was assembled by using Ni-SiO 2 /C HS electrode and lithium disk as working electrode and counter electrode, respectively.…”

Co3O4@NiMoO4 composite electrode materials for flexible hybrid capacitors

“…In Fig. 3e, O 1 s peaks at 531.8, 530.6 and 529.4 eV correspond to defect oxygen, O 2− and OH − , respectively [26]. In Fig.…”

3D Carbon Electrode with Hierarchical Nanostructure Based on NiCoP Core‐Layered Double Hydroxide Shell for Supercapacitors and Hydrogen Evolution

“…Due to the energy crisis and increasing environmental pollution accompanying economic development, rational design and effective combination of new energy conversion equipment and energy storage devices would be a promising strategy to reduce the use of fossil fuels. [1][2][3][4][5][6][7][8] Compared with batteries and traditional physical capacitors, supercapacitors are mainly characterized by high power density, long cycle life, low maintenance cost and reliable safety. But lower energy density limits its large-scale application.…”