In situ growth of nickel-cobalt oxyhydroxide/oxide on carbon nanotubes for high performance supercapacitors

Composite of CoS1.97 nanoparticles decorated CuS hollow cubes with rGO as thin film electrode for high-performance all solid flexible supercapacitors

Stretchable flexible thin-film electrodes are extensively explored for developing new wearable energy storage devices. However, traditional carbon-based materials used in such independent electrodes have limited practical applications owing to their low energy storage capacity and energy density. To address this, a unique structure and remarkable mechanical stability thin-film flexible positive electrode comprising CoS1.97 nanoparticles decorated hollow CuS cubes and reduced graphene oxide (rGO), hereinafter referred to as CCSrGO, is prepared. Transition metal sulfide CoS1.97 and CuS shows high energy density owing to the synergistic effects of its active components. The electrode can simultaneously meet the high-energy density and safety requirements of new wearable energy storage devices. The electrode has excellent electrochemical performance (1380 F/g at 1 A/g) and ideal capacitance retention (93.8 % after 10,000 cycles) owing to its unique three-dimensional hollow structure and polymetallic synergies between copper and cobalt elements, which are attributed to their different energy storage mechanisms. Furthermore, a flexible asymmetric supercapacitor (FASC) was constructed using CCSrGO as the positive electrode and rGO as the negative electrode (CCSrGO//rGO), which delivers an energy density of 100 Wh kg-1 and a corresponding power density of 2663 W kg-1 within a voltage window of 0-1.5 V. The resulting FASC can power a light-emitting diode (LED) at different bending and twisting angles, exerting little effect on the capacitance. Therefore, the prepared CCSrGO//rGO FASC devices show great application prospects in energy storage.

Hierarchical NiMn-LDH Hollow Spheres as a Promising Pseudocapacitive Electrode for Supercapacitor Application

Layered double hydroxides (LDH) are regarded as attractive pseudocapacitive materials due to their impressive capacitive qualities that may be adjustable to their morphological features. However, the layered structure of LDH renders them susceptible to structural aggregation, which inhibits effective electrolyte transport and limits their practical applicability after limited exposure to active areas. Herein, we propose a simple template-free strategy to synthesize hierarchical hollow sphere NiMn-LDH material with high surface area and exposed active as anode material for supercapacitor application. The template-free approach enables the natural nucleation of Ni-Mn ions resulting in thin sheets that self-assemble into a hollow sphere, offering expended interlayer spaces and abundant redox-active active sites. The optimal NiMn-LDH-12 achieved a specific capacitance of 1010.4 F g-1 at a current density of 0.2 A g-1 with capacitance retention of 70% at 5 A g-1 after 5000 cycles with lower charge transfer impedance. When configured into an asymmetric supercapacitors (ASC) device as NiMn-LDH//AC, the material realized a specific capacitance of 192.4 F g-1 at a current density of 0.2 A g-1 with a good energy density of 47.9 Wh kg-1 and a power density of 196.8 W kg-1. The proposed morphological-tuning route is promising for designing template-free NiMn-LDHs spheres with practical pseudocapacitive characteristics.

Reduced Mo-doped NiCo2O4 with rich oxygen vacancies as advanced electrode material in supercapacitors

Reduced Mo-doped NiCo2O4 (R-Mo-NiCo2O4) was facilely prepared through a dual-defect strategy. Mo-doped NiCo layered double hydroxide (Mo-NiCo-LDH) was used as the precursor and calcined in an air atmosphere, and the...

Capacitive performance of electrochemically deposited Co/Ni oxides/hydroxides on polythiophene-coated carbon-cloth

Cobalt, nickel, and their mixed hydroxides were electrochemically deposited on polythiophene-coated carbon-cloth substrate to develop new pseudo-capacitive electrodes for energy storage devices. Thiophene was electro-polymerized on carbon-cloth by the potentiodynamic method in acetonitrile containing 1-butyl-2,3-dimethylimidazolium hexafluorophosphate ionic-liquid as supporting electrolyte. The scanning-electron-microscopy images imply that flower-like Co(OH)2 microstructures deposited on bamboo-like polythiophene coatings on carbon-fibers but they are covered by net curtain like thin Ni(OH)2 layer. The Co-Ni layered-double-hydroxide deposited from their equimolar sulfate solutions is composed of large aggregates. The electron-dispersive-spectrum exhibits that Co/Ni ratio equals unity in the layered-double-hydroxide. The capacitances of Co, Ni, and Co-Ni hydroxide-coated PTh electrodes are 100, 569, and 221 F/g at 5 mA/cm2 in 1 M KOH solution, respectively. Their corresponding oxides obtained by calcination at 450 °C in de-aerated medium possess higher capacitance up to 911, 643, and 696 F/g at 2 A/cm2. The shape of cyclic-voltammetry and galvanostatic-charge-discharge curves, as well as the Nyquist plots derived from electrochemical-impedance-spectroscopy measurements, reveal that hydroxide coatings on the polythiophene-coated carbon-cloth are more promising electrode materials for supercapacitor applications. The mixed hydroxide-coated electrode shows good cyclic stability of 100% after 400 cycles at 5 mA/cm2.

Biomass-derived O, N-codoped hierarchically porous carbon prepared by black fungus and Hericium erinaceus for high performance supercapacitor

Biomass-derived carbon materials have been widely researched due to their advantages such as low cost, environmental friendliness, readily available raw materials. Black fungus and Hericium erinaceus contain many kinds of amino acids. In this paper, unique O, N-codoped black fungus-derived activated carbons (FAC X ), and Hericium erinaceus-derived activated carbons (HAC X ) were prepared by KOH chemical activation under different temperatures without adding additional reagents containing nitrogen and oxygen functional groups, respectively. As electrode materials of symmetric supercapacitors, FAC2 and HAC2 calcined at 800 °C exhibited the highest specific capacitance of 209.3 F g-1 and 238.6 F g-1 at 1.0 A g-1 in the two-electrode configuration with 6.0 M KOH as the electrolyte, respectively. The X-ray photoelectron spectroscopy confirmed that the as-synthesized FAC X and HAC X contained small amounts of nitrogen and oxygen elements. Moreover, heteroatom-doped FAC2 and HAC2 electrode materials shown excellent rate performance (84.1% and 75.0% capacitance retention at 20 A g-1, respectively). By comparison, the oxygen-rich hierarchical porous carbon (HAC2) shows higher specific capacitance and energy density and longer cycling performance. Nevertheless, carbon-rich hierarchical porous carbon (FAC2) indicates excellent rate performance. Biomass-derived heteroatom self-doped porous carbons are expected to become ideal active materials for high performance supercapacitor.

Electrochemical properties of NiCoO2 synthesized by hydrothermal method

NiCoO₂ microspheres were successfully synthesized via an easy hydrothermal method, followed by an annealing process at 350 °C under a nitrogen atmosphere.

A comparative study of Ni–Mn layered double hydroxide/carbon composites with different morphologies for supercapacitors

A variety of carbon materials varying from 0D to 2D, i.e. 0D nanoparticles, 1D carbon nanotubes (CNTs) and 2D reduced graphene oxide (rGO) are selected to in situ combine with Ni–Mn layered double hydroxide (LDH) to prepare electrode materials for supercapacitors.

CoOOH ultrafine nanoparticles for supercapacitors

CoOOH ultrafine nanoparticles with a high surface area were prepared by a novel route to achieve enhanced electrochemical performances.

Controllable synthesis of Ni(OH)2/Co(OH)2 hollow nanohexagons wrapped in reduced graphene oxide for supercapacitors

Reduced graphene oxide (rGO) wrapped hollow nanohexagons comprised of nickel hydroxide and cobalt hydroxide have been synthesized via in situ wet chemical approach.