Nickel–cobalt layered double hydroxides (Ni–Co-LDH) have recently been examined for their potential as battery-type hybrid supercapacitors made from metal hydroxide electrode materials, due to their unique spatial structure, excellent electrochemical activity, and good electrical conductivity. However, the main disadvantage restricting the application of Ni–Co-LDHs is their low electronic conductivity, which results in low capacitance. To address this problem, we used different concentrations of ammonium fluoride to control the Ni–Co-LDH surface morphology and direct growth on Ni foam (NF). We created Ni–Co-LDH composite electrode materials with different morphologies that showed large surface areas, high conductivity, and high electrochemical performance. Results showed that the samples prepared with ammonium fluoride additive had a higher specific capacity of about 1445 F g⁻¹ at a current density of 2 A g⁻¹, a good specific capacitance rate of about 59.5% from 2 A g⁻¹ to 40 A g⁻¹, and good capacity retention of up to 99% when the current density was enhanced to 30 A g⁻¹, suggesting promise for future applications.

In this study, we synthesized binder-free NiCo₂O₄@NiCo₂O₄ nanostructured materials on nickel foam (NF) by combined hydrothermal and cyclic voltammetry deposition techniques followed by calcination at 350 °C to attain high-performance supercapacitors. The hierarchical porous NiCo₂O₄@NiCo₂O₄ structure, facilitating faster mass transport, exhibited good cycling stability of 83.6% after 5000 cycles and outstanding specific capacitance of 1398.73 F g⁻¹ at the current density of 2 A·g⁻¹, signifying its potential for energy storage applications. A solid-state supercapacitor was fabricated with the NiCo₂O₄@NiCo₂O₄ on NF as the positive electrode and the active carbon (AC) was deposited on NF as the negative electrode, delivering a high energy density of 46.46 Wh kg⁻¹ at the power density of 269.77 W kg⁻¹. This outstanding performance was attributed to its layered morphological characteristics. This study explored the potential application of cyclic voltammetry depositions in preparing binder-free NiCo₂O₄@NiCo₂O₄ materials with more uniform architecture for energy storage, in contrast to the traditional galvanostatic deposition methods.

Layered double hydroxides (LDH) as active electrode materials have become the focus of research in energy storage applications. The manufacturing of excellent electrochemical performance of the LDH electrode is still a challenge. In this paper, the production of CoAl-LDH@Ni(OH)₂ is carried out in two steps, including hydrothermal and electrodeposition techniques. The prominent features of this electrode material are shown in the structural and morphological aspects, and the electrochemical properties are investigated by improving the conductivity and cycle stability. The core of this experimental study is to investigate the properties of the materials by depositing different amounts of nickel hydroxide and changing the loading of the active materials. The experimental results show that the specific capacity is 1810.5F·g⁻¹ at 2 A/g current density and the cycle stability remained at 76% at 30 A g⁻¹ for 3000 cycles. Moreover, a solid-state asymmetric supercapacitor with CoAl-LDH@Ni(OH)₂ as the positive electrode and multi-walled carbon nanotube coated on the nickel foam as the negative electrode delivers high energy density (16.72 Wh kg⁻¹ at the power density of 350.01 W kg⁻¹). This study indicates the advantages of the design and synthesis of layered double hydroxides, a composite with excellent electrochemical properties that has potential applications in energy storage.

Battery-type electrodes of three-dimensional (3D) hierarchical cobalt hydroxide carbonate arrays on Ni foam were fabricated using a hydrothermal method for use in supercapacitors. X-ray diffraction analysis, scanning electron microscopy, and transmission electron microscopy were used to characterize their structures and morphologies. The cobalt hydroxide carbonate synthesized with 10 h reaction time showed the highest specific capacitance (1381 F g⁻¹ at a current density of 2 A g⁻¹) and excellent cycling stability (92% capacitance retention after 5000 cycles). Moreover, its capacitance increased by 33% at 2 A g⁻¹ and by 10% at 20 A g⁻¹ after 5000 charge–discharge cycles. This cobalt hydroxide carbonate composite is a promising candidate for electrochemical energy-related applications.

In this study, to fabricate a non-binder electrode, we grew nickel–cobalt sulfide (NCS) nanotubes (NTs) on a Ni foam substrate using a hydrothermal method through a two-step approach, namely in situ growth and an anion-exchange reaction. This was followed by the electrodeposition of double-layered nickel-cobalt hydroxide (NCOH) over a nanotube-coated substrate to fabricate NCOH core-shell nanotubes. The final product is called NCS@NCOH herein. Structural and morphological analyses of the synthesized electrode materials were conducted via SEM and XRD. Different electrodeposition times were selected, including 10, 20, 40, and 80 s. The results indicate that the NCSNTs electrodeposited with NCOH nanosheets for 40 s have the highest specific capacitance (SC), cycling stability (2105 Fg⁻¹ at a current density of 2 Ag⁻¹), and capacitance retention (65.1% after 3,000 cycles), in comparison with those electrodeposited for 10, 20, and 80 s. Furthermore, for practical applications, a device with negative and positive electrodes made of active carbon and NCS@NCOH was fabricated, achieving a high-energy density of 23.73 Whkg⁻¹ at a power density of 400 Wkg⁻¹.