Preparation of Nickel Cobalt Sulfide Hollow Nanocolloids with Enhanced Electrochemical Property for Supercapacitors Application

Potential transition and post-transition metal sulfides as efficient electrodes for energy storage applications: review

Electrochemical energy storage has attracted much attention due to the common recognition of sustainable energy development. Transition metal sulfides and post-transition metal sulfides have been intensively been focused on due to their potential as electrode materials for energy storage applications in different types of capacitors such as supercapacitors and pseudocapacitors, which have high power density and long cycle life. Herein, the physicochemical properties of transition and post-transition metal sulfides, their typical synthesis, structural characterization, and electrochemical energy storage applications are reviewed. Various perspectives on the design and fabrication of transition and post-transition metal sulfides-based electrode materials having capacitive applications are discussed. This review further discusses various strategies to develop transition and/or post-transition metal sulfide heterostructured electrode-based self-powered photocapacitors with high energy storage efficiencies.

Electrochemical energy storage has attracted much attention due to the common recognition of sustainable energy development.

Solid Solution Metal Chalcogenides for Sodium-Ion Batteries: The Recent Advances as Anodes

The sodium-ion battery (SIB) has attracted ever growing attention as a promising alternative of the lithium-ion battery (LIB). Constructing appropriate anode materials is critical for speeding up the application of SIB. This review aims at guiding anode design from the material's perspective, and specifically focusing on solid solution metal chalcogenide anode. The sodium ion storage mechanisms of a solid solution metal chalcogenide anode is overviewed on basis of the elements it is composed of, and discusses how the solid solution character alters the electrochemical performances through diffusion and surface-controlled processes. In addition, by classifying solid solution metal chalcogenide as cation and anion, their recent applications are updated, and understanding the roles of guest elements in improving the electrochemical behaviors of a solid solution metal chalcogenide is carried out. After that, discussion of possible strategies to further optimize these anode materials in the future, flowing from crystal structure design to morphology control and finally to the intimacy improvement between conductive matrix and solid solution metal chalcogenide are also provided.

Three-dimensional flower-like nickel doped cobalt phosphate hydrate microarchitectures for asymmetric supercapacitors

Development of asymmetric supercapacitors (ASCs) using hierarchical three-dimensional (3D) morphologies is becoming crucial in energy storage applications due to the greater power density rather than batteries. Herein, 3D flower-like Co₃(PO₄)₂·8H₂O (CPH) and nickel doped CPH (Ni-CPH) microarchitectures were synthesized by a silicone oil bath method at low temperatures without calcination. The synthesized microarchitectures-based electrodes (bare CPH and Ni-CPH) revealed battery-like properties during the electrochemical study. Importantly, the Ni-CPH electrode showed improved electrochemical performance compared to the bare CPH electrode material. The specific capacity values of the CPH and Ni-CPH electrode materials were calculated to be 74 and 108 mAh g^-1 at 0.5 A g^-1, respectively. Furthermore, for the Ni-CPH electrode, 78% of capacity retention was obtained after 9000 cycles at 5 A g^-1. Additionally, an ASC was developed while employing the optimized Ni-CPH electrode (positive-type) and activated carbon (negative-type) and it showed superior electrochemical results. The ASC device exhibited excellent capacity retention (94%) after 9000 cycles at 2 A g^-1. Also, this device delivered a high energy density of 23.4 Wh kg^-1 and a power density of 2103 W kg^-1. Finally, several portable electronic devices were successfully tested using the obtained good energy and power density results from the ASC device for energy storage applications.

Rational Design of Porous Structured Nickel Manganese Sulfides Hexagonal Sheets-in-Cage Structures as an Advanced Electrode Material for High-Performance Electrochemical Capacitors

The design of hierarchical electrodes comprising multiple components with a high electrical conductivity and a large specific surface area has been recognized as a feasible strategy to remarkably boost pseudocapacitors. Herein, we delineate hexagonal sheets-in-cage shaped nickel-manganese sulfides (Ni-Mn-S) with nanosized open spaces for supercapacitor applications to realize faster redox reactions and a lower charge-transfer resistance with a markedly enhanced specific capacitance. The hybrid was facilely prepared through a two-step hydrothermal method. Benefiting from the synergistic effect between Ni and Mn active sites with the improvement of both ionic and electric conductivity, the resulting Ni-Mn-S hybrid displays a high specific capacitance of 1664 F g^-1 at a current density of 1 A g^-1 and a capacitance of 785 F g^-1 is maintained at a current density of 50 A g^-1 , revealing an outstanding capacity and rate performance. The asymmetric supercapacitor device assembled with the Ni-Mn-S hexagonal sheets-in-cage as the positive electrode delivers a maximum energy density of 40.4 Wh kg^-1 at a power density of 750 W kg^-1 . Impressively, the cycling retention of the as-fabricated device after 10 000 cycles at a current density of 10 A g^-1 reaches 85.5 %. Thus, this hybrid with superior capacitive performance holds great potential as an effective charge-storage material.

Novel approach to synthesize NiCo2S4 composite for high-performance supercapacitor application with different molar ratio of Ni and Co

Here, we developed a new approach to synthesize NiCo2S4 thin films for supercapacitor application using the successive ionic layer adsorption and reaction (SILAR) method on Ni mesh with different molar ratios of Ni and Co precursors. The five different NiCo2S4 electrodes affect the electrochemical performance of the supercapacitor. The NiCo2S4 thin films demonstrate superior supercapacitance performance with a significantly higher specific capacitance of 1427 F g-1 at a scan rate of 20 mV s-1. These results indicate that ternary NiCo2S4 thin films are more effective electrodes compared to binary metal oxides and metal sulfides.

Recent advances in metal sulfides: from controlled fabrication to electrocatalytic, photocatalytic and photoelectrochemical water splitting and beyond

This review describes an in-depth overview and knowledge on the variety of synthetic strategies for forming metal sulfides and their potential use to achieve effective hydrogen generation and beyond.

Effect of Time on a Hierarchical Corn Skeleton-Like Composite of CoO@ZnO as Capacitive Electrode Material for High Specific Performance Supercapacitors

CoO–ZnO-based composites have attracted considerable attention for the development of energy storage devices because of their multifunctional characterization and ease of integration with existing components. This paper reports the synthesis of CoO@ZnO (CZ) nanostructures on Ni foam by the chemical bath deposition (CBD) method for facile and eco-friendly supercapacitor applications. The formation of a CoO@ZnO electrode functioned with cobalt, zinc, nickel and oxygen groups was confirmed by X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), low and high-resolution scanning electron microscopy (SEM), and transmission electron microscopy (TEM) analysis. The as-synthesized hierarchical nanocorn skeleton-like structure of a CoO@ZnO-3h (CZ3h) electrode delivered a higher specific capacitance (Cs) of 1136 F/g at 3 A/g with outstanding cycling performance, showing 98.3% capacitance retention over 3000 cycles in an aqueous 2 M KOH electrolyte solution. This retention was significantly better than that of other prepared electrodes, such as CoO, ZnO, CoO@ZnO-1h (CZ1h), and CoO@ZnO-7h (CZ7h) (274 F/g, 383 F/g, 240 F/g and 537 F/g). This outstanding performance was attributed to the excellent surface morphology of CZ3h, which is responsible for the rapid electron/ion transfer between the electrolyte and the electrode surface area. The enhanced features of the CZ3h electrode highlight potential applications in high performance supercapacitors, solar cells, photocatalysis, and electrocatalysis.

Facile synthesis of NiCo2S4/CNTs nanocomposites for high-performance supercapacitors

Herein, porous NiCo2S4/CNTs nanocomposites were synthesized via a simple hydrothermal method followed by the sulphurization process using different sulfide sources. By comparing two different sulfur sources, the samples using thioacetamide as sulfide source delivered more remarkable electrochemical performance with a high specific capacitance of 1765 F g-1 at 1 A g-1 and an admirable cycling stability with capacitance retention of 71.7% at a high current density of 10 A g-1 after 5000 cycles in 2 M KOH aqueous electrolyte. Furthermore, an asymmetric supercapacitor (ASC) device was successfully fabricated with the NiCo2S4/CNTs electrode as the positive electrode and graphene as the negative electrode. The device provided a maximum energy density of 29.44 W h kg-1 at a power density of 812 W kg-1. Even at a high power density of 8006 W kg-1, the energy density still reaches 16.68 W h kg-1. Moreover, the ASC presents 89.8% specific capacitance retention after 5000 cycles at 5 A g-1. These results reveal its great potential for supercapacitors in electrochemical energy storage field.

Hierarchically Porous Fe2 CoSe4 Binary-Metal Selenide for Extraordinary Rate Performance and Durable Anode of Sodium-Ion Batteries

Owing to high energy capacities, transition metal chalcogenides have drawn significant research attention as the promising electrode materials for sodium-ion batteries (SIBs). However, limited cycle life and inferior rate capabilities still hinder their practical application. Improvement of the intrinsic conductivity by smart choice of elemental combination along with carbon coupling of the nanostructures may result in excellence of rate capability and prolonged cycling stability. Herein, a hierarchically porous binary transition metal selenide (Fe2 CoSe4 , termed as FCSe) nanomaterial with improved intrinsic conductivity was prepared through an exclusive methodology. The hierarchically porous structure, intimate nanoparticle-carbon matrix contact, and better intrinsic conductivity result in extraordinary electrochemical performance through their synergistic effect. The synthesized FCSe exhibits excellent rate capability (816.3 mA h g-1 at 0.5 A g-1 and 400.2 mA h g-1 at 32 A g-1 ), extended cycle life (350 mA h g-1 even after 5000 cycles at 4 A g-1 ), and adequately high energy capacity (614.5 mA h g-1 at 1 A g-1 after 100 cycles) as anode material for SIBs. When further combined with lab-made Na3 V2 (PO4 )3 /C cathode in Na-ion full cells, FCSe presents reasonably high and stable specific capacity.

Bimetallic CoNiSx nanocrystallites embedded in nitrogen-doped carbon anchored on reduced graphene oxide for high-performance supercapacitors

Exploring high-performance and low-priced electrode materials for supercapacitors is important but remains challenging. In this work, a unique sandwich-like nanocomposite of reduced graphene oxide (rGO)-supported N-doped carbon embedded with ultrasmall CoNiS_x nanocrystallites (rGO/CoNiS_x/N-C nanocomposite) has been successfully designed and synthesized by a simple one-step carbonization/sulfurization treatment of the rGO/Co-Ni precursor. The intriguing structural/compositional/morphological advantages endow the as-synthesized rGO/CoNiS_x/N-C nanocomposite with excellent electrochemical performance as an advanced electrode material for supercapacitors. Compared with the other two rGO/CoNiO_x and rGO/CoNiS_x nanocomposites, the rGO/CoNiS_x/N-C nanocomposite exhibits much enhanced performance, including a high specific capacitance (1028.2 F g^-1 at 1 A g^-1), excellent rate capability (89.3% capacitance retention at 10 A g^-1) and good cycling stability (93.6% capacitance retention over 2000 cycles). In addition, an asymmetric supercapacitor (ASC) device based on the rGO/CoNiS_x/N-C nanocomposite as the cathode and activated carbon (AC) as the anode is also fabricated, which can deliver a high energy density of 32.9 W h kg^-1 at a power density of 229.2 W kg^-1 with desirable cycling stability. These electrochemical results evidently indicate the great potential of the sandwich-like rGO/CoNiS_x/N-C nanocomposite for applications in high-performance supercapacitors.

NiO/NixCo3−xO4 porous ultrathin nanosheet/nanowire composite structures as high-performance supercapacitor electrodes

The demand for a new generation of high-safety, long-lifespan, and high-capacity power sources increases rapidly with the growth of energy consumption in the world. Here we report a facile method for preparing architecture materials made of NiO/Ni_xCo_3−xO₄ porous nanosheets coupled with NiO/Ni_xCo_3−xO₄ porous nanowires grown in situ on nickel foams using a hydrothermal method without any binder followed by a heat treatment process. The nanosheet-shaped NiO/Ni_xCo_3−xO₄ species in the nanosheet matrix function well as a scaffold and support for the dispersion of the Ni_xCo_3−xO₄ nanowires, resulting in a relatively loose and open structure within the electrode matrix. Among all composite electrodes prepared, the one annealed in air at 300 °C displays the best electrochemical behavior, achieving a specific capacitance of 270 mF cm⁻² at 5 mA cm⁻² while maintaining excellent stability (retaining ≈ 89% of the max capacitance after 20 000 cycles), demonstrating its potential for practical application in power storage devices.

Porous ultrathin nanosheet/nanowire composite structures are prepared as high-performance supercapacitor electrodes which exhibit excellent stability.

Influence of solvents in the preparation of cobalt sulfide for supercapacitors

In this study, cobalt sulfide (CoS) electrodes are synthesized using various solvents such as water, ethanol and a combination of the two via a facile chemical bath deposition method on Ni foam. The crystalline nature, chemical states and surface morphology of the prepared CoS nanoparticles are characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transition electron microscopy. The electrochemical properties of CoS electrodes are also evaluated using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. When used as an electrode for a supercapacitor, CoS prepared with ethanol as a solvent exhibits a capacitance of 41.36 F g^-1 at 1.5 A g^-1, which is significantly better than that prepared using water and water/ethanol-based solvents (31.66 and 18.94 F g^-1 at 1.5 A g^-1, respectively). This superior capacitance is attributed to the ideal surface morphology of the solvent, which allows for easy diffusion of electrolyte ions into the inner region of the electrode. High electrical conduction enables a high rate capability. These results suggest that CoS nanoparticles are highly promising for energy storage applications as well as photocatalysis, electrocatalysis, water splitting and solar cells, among others. These results show that CoS is a promising positive electrode material for practical supercapacitors.

Galvanic displacement assembly of ultrathin Co3O4 nanosheet arrays on nickel foam for a high-performance supercapacitor

High-performance supercapacitors are very desirable for many portable electronic devices, electric vehicles and high-power electronic devices. Herein, a facile and binder-free synthesis method, galvanic displacement of the precursor followed by heat treatment, is used to fabricate ultrathin Co₃O₄ nanosheet arrays on nickel foam substrate. When used as a supercapacitor electrode the prepared Co₃O₄ on nickel foam exhibits a maximum specific capacitance of 1095 F g^-1 at a current density of 1 A g^-1 and good cycling stability of 71% retention after 2000 cycling tests. This excellent electrochemical performance can be ascribed to the high specific surface area of each Co₃O₄ nanosheet that comprises numerous nanoparticles.

Interconnected hierarchical NiCo2O4 microspheres as high-performance electrode materials for supercapacitors

Hierarchical NiCo₂O₄ microspheres with large tunnels and abundant mesopores have been prepared, and they exhibit excellent performance in supercapacitor applications.