MOF assistance synthesis of nanoporous double-shelled CuCo2O4 hollow spheres for hybrid supercapacitors

Zeolitic imidazolate framework-67-derived chalcogenides as electrode materials for supercapacitors

With the rapid development of new energy technologies, hybrid supercapacitors have received widespread attention owing to their advantages of high power density, fast charging/discharging rate and long cycle life. In this case, the selection and design of electrode materials are the key to improving the energy storage performance of supercapacitors. Herein, zeolitic imidazolate framework-67 (ZIF-67) is presented as a good candidate material for the fabrication of supercapacitor electrodes because of its controllable pore size, constant cavity size and large specific area. Moreover, pristine ZIF-67 and ZIF-67-derived porous carbon have shown exemplary performances in supercapacitors. However, they belong to the class of electric double layer capacitor materials and have a lower magnitude of energy storage compared with pseudocapacitor materials. Therefore, to improve the energy density of hybrid supercapacitors, other ZIF-67 derivatives need to be explored, especially chalcogenides. This review mainly reports the application of ZIF-67-derived transition metal chalcogenides (TMCs, C including Oxide, Sulfide, Selenide, Telluride) in supercapacitors. Moreover, the strategies for the preparation of ZIF-67-derived TMCs and their electrochemical performance in supercapacitors are further discussed. Finally, the remaining challenges and future perspectives are highlighted.

Recent Trend and Future Aspects of Metal-organic Framework-derived Multi-Shelled Nanomaterials for Energy Storage

Metal-organic frameworks (MOFs) have gained prominence through reticular chemistry, connecting building blocks to create specific structures. MOFs offer high surface areas, porosity, stability, and diverse functionalities. This makes them easily modifiable for various applications, evolving into complex architectures. Recent advancements in MOF-derived multi-shelled nanostructures are summarized herein. The advantages and disadvantages of these nanostructures over bare MOFs and single-shelled structures are discussed. The recent progress and potential of multi-shelled structures in energy storage applications are comprehensively explored. Challenges and prospects in this area are also outlined.

Facile and controllable synthesis of sea urchin-like CuCo2O4 on Ni foam for high-performance supercapacitors

CuCo2O4 is considered to be an attractive electrode material for supercapacitors due to its low toxicity, high theoretical capacity and low cost. However, the low specific capacity, poor cycling performance and low intrinsic conductivity limit the further application of CuCo2O4. In this research, CuCo2O4 arrays with different morphologies (rods, sea urchin-like and flakes) were synthesized on the surface of nickel foam (NF) via a solvothermal method and calcination. The controllable preparation of CuCo2O4 morphology was achieved by changing the solvent. Vertically grown sea urchin-like CuCo2O4 has large open channels that promote rapid electron transport, and the abundance of active sites allows more electrochemical reactions to occur simultaneously. As a result, the sea urchin-like CuCo2O4 exhibited the best electrochemical performance with a specific capacitance of 1426.2 F g-1 at 1 A g-1 and a capacitance retention of 96.78% after 10 000 cycles at 10 A g-1. In addition, an asymmetric supercapacitor with a CuCo2O4 anode and a reduced graphene oxide (RGO) cathode was fabricated. At a power density of 802.3 W kg-1, the CuCo2O4//RGO device exhibited an energy density of 59.6 W h kg-1. This research provides insights into modulating the morphostructure of CuCo2O4 to improve its electrochemical properties.

Hierarchical Ni3V2O8@N-Doped Carbon Hollow Double-Shell Microspheres for High-Performance Lithium-Ion Storage

Transition metal oxides (TMOs) are highly dense in energy and considered as promising anode materials for a new generation of alkaline ion batteries. However, their electrode structure is disrupted due to significant volume changes during charging and discharging, resulting in the short cycle life of batteries. In this paper, the hierarchical Ni3V2O8@N-doped carbon (Ni3V2O8@NC) hollow double-shell microspheres were prepared and used as electrode materials for lithium-ion batteries (LIBs). The utilization efficiency and ion transfer rate of Ni3V2O8 were improved by the hollow microsphere structure formed through nanoparticle self-assembly. Furthermore, the uniform N-doped carbon layer not only enhanced the structural stability of Ni3V2O8, but also improved the overall electrical conductivity of the composite. The Ni3V2O8@NC electrode has an initial discharge capacity of up to 1167.3 mAh g-1 at a current density of 0.3 A g-1, a reversible capacity of up to 726.5 mAh g-1 after 200 cycles, and still has a capacity of 567.6 mAh g-1 after 500 cycles at a current density of 1 A g-1, indicating that the material has good cycle stability and high-rate capability. This work presents new findings on the design and fabrication of complex porous double-shell nanostructures.

Benign-by-design plant extract-mediated preparation of copper oxide nanoparticles for environmentally related applications

A facile, cost-competitive, scalable and novel synthetic approach is used to prepare copper oxide (CuO) nanoparticles (NPs) using Betel leaf (Piper betle) extracts as reducing, capping, and stabilizing agents. CuO-NPs were characterized using various analytical techniques, including Fourier-transform infrared (FTIR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), as well as photoluminescence (PL) measurements. The activity of CuO-NPs was investigated towards Congo red dye degradation, supercapacitor energy storage and antibacterial activity. A maximum of 89% photodegradation of Congo red dye (CR) was obtained. The nanoparticle modified electrode also exhibited a specific capacitance (Csp) of 179 Fg-1. Furthermore, the antibacterial potential of CuO NPs was evaluated against Bacillus subtilis and Pseudomonas aeruginosa, both strains displaying high antibacterial performance.

Hollow Ni3S4@Co3S4 with core-satellite nanostructure derived from metal-organic framework (MOF)-on-MOF hybrids as an electrode material for supercapacitors

Metal-organic frameworks (MOFs) have found wide applications in the field of supercapacitors due to their highly controllable porous structure, big specific surface area, and abundant chemical functional groups. MOF-on-MOF hybrids not only enhance the composition of MOFs (such as ligands and/or metal centers) but also provide greater structural diversity. By utilizing MOFs as precursors for preparing sulfides, the unique characteristics and inherent structure of MOFs are preserved but their conductivity and capacitance are enhanced. This study successfully synthesized hollow-structured Ni3S4@Co3S4 derived from an Ni-MOF@ZIF-67 hybrid structure, where the Ni-MOF serves as the core and ZIF-67 as the satellite. The Ni3S4@Co3S4 electrode demonstrated a specific capacity as high as 747.3 C g-1 at 1 A g-1, and it could still maintain 77% of its initial capacity at 10 A g-1. Furthermore, the assembled Ni3S4@Co3S4//AC hybrid supercapacitor (HSC) device achieved a maximum energy density of 30.8 W h kg-1 when the power density was 750 W kg-1. The device exhibited remarkable cycling durability, retaining 85.4% of its initial capacitance after 5000 cycles. Therefore, the derived functional materials based on MOF-on-MOF provide a more scalable and promising approach for the preparation of efficient electrode materials.

Unveiling the redox electrochemical kinetics of interconnected wrinkled microspheres of binary Cu2-xSe/Ni1-xSe as battery-type electrode for advanced supercapatteries

Developing a rational design of nanoarchitechtures with excellent electrochemical behaviors is an ultimate and unique strategy to enhance the redox electrokinetics of battery-type electrode materials. Herein, we demonstrate a hierarchical composite comprising interconnected wrinkled micro-solid sphere (ICWMS)-like binary copper selenide/nickel selenide over nickel foam (Cu2-xSe/Ni1-xSe/NF) prepared via a wet chemical synthetic protocol and utilized as an effective positrode for improved supercapaterry performance. The binary Cu2-xSe/Ni1-xSe/NF electrode considerably improved the electroactive surface area and facilitated ultrafast redox electrochemistry in an alkaline electrolyte medium. Remarkably, the binary Cu2-xSe/Ni1-xSe/NF electrode afforded the highest specific capacity of 368 ± 1C/g at 1 A/g greater than that of pristine single selenide electrodes (Cu2Se and NiSe) in a three-electrode setup which might be attributed to its large surface area, synergism between Ni and Cu, and specific morphology. Moreover, a coin cell supercapattery with the binary Cu2-xSe/Ni1-xSe/NF positrode and a porous activated carbon-on-nickel-foam negatrode was constructed, which exhibited excellent energy-storage characteristics in terms of capacity (87.5 ± 1 mAh/g), specific energy (39.3 Wh kg-1), specific power (450 W kg-1), and capacity retention (91.8 %). This simple fabrication approach of hierarchically designed Cu2-xSe/Ni1-xSe/NF paves the way for utilizing it as the promising positrode for high-performance supercapattery.

Engineering Rich-Cation Vacancies in CuCo2O4 Hollow Spheres with a Large Surface Area Derived from a Template-Free Approach for Ultrahigh Capacity and High-Energy Density Supercapacitors

Intriguing cationic defects with hollow nano-/microstructures are a critical challenge but a potential strategy to discover electrochemical energy conversion and storage devices with improved electrochemical performances. Herein, we successfully produced a highly porous, and large surface area of self-templated CuCo₂O₄ hollow spheres (CCOHSs) with cationic defects via a solvothermal route. We hypothesized that the inside-out Ostwald ripening mechanism of the template-free strategy was the framework for forming the CCOHSs. Cationic defects (Cu) within the CCOHSs were identified by employing various analytical techniques, including energy-dispersive X-ray spectroscopy analysis of both scanning and transmission electron microscopy, X-ray photon spectroscopy, and inductively coupled plasma-atomic emission spectroscopy. The resulting CCOHSs had significant properties, such as a high specific surface area of 98.32 m² g^-1, rich porosity, and battery-type electrode behavior in supercapacitor applications. Notably, the CCOHSs demonstrated an outstanding specific capacity of 1003.7 C g^-1 at 1 A g^-1, with excellent structural integrity and cycle stability. Moreover, the fabricated asymmetric CCOHS//activated carbon device exhibited a high energy density of 65.2 Wh kg^-1 at a power density of 777.8 W kg^-1.

Metal-Organic Framework Materials for Electrochemical Supercapacitors

Exploring new materials with high stability and capacity is full of challenges in sustainable energy conversion and storage systems. Metal-organic frameworks (MOFs), as a new type of porous material, show the advantages of large specific surface area, high porosity, low density, and adjustable pore size, exhibiting a broad application prospect in the field of electrocatalytic reactions, batteries, particularly in the field of supercapacitors. This comprehensive review outlines the recent progress in synthetic methods and electrochemical performances of MOF materials, as well as their applications in supercapacitors. Additionally, the superiorities of MOFs-related materials are highlighted, while major challenges or opportunities for future research on them for electrochemical supercapacitors have been discussed and displayed, along with extensive experimental experiences.

Facile design and synthesis of a nickel disulfide/zeolitic imidazolate framework-67 composite material with a robust cladding structure for high-efficiency supercapacitors

In this paper, a core-shell structure nickel disulfide and ZIF-67 composite electrode material (NiS2/ZIF-67) was synthesized by a two-step method. Firstly, spherical NiS2 was synthesized by a hydrothermal method, dispersed in methanol, then reacted and coated by adding cobalt ions and 2-methylimidazole to obtain the NiS2/ZIF-67 core-shell composite. The NiS2/ZIF-67 composite shows a high specific capacitance (1297.9 F g-1 at 1 A g-1) and excellent cycling durability (retaining 110.0% after 4000 cycles at 5 A g-1). Furthermore, the corresponding hybrid supercapacitor (NiS2/ZIF-67//AC HSC) has an energy density of 9.5 W h kg-1 at 411.1 W kg-1 (6 M KOH) and remarkable cycling stability (maintaining 133.3% after 5000 cycles). Its excellent electrochemical performance may be due to the core-shell structure and the synergistic effect between the transition metal sulfide and metal-organic framework. These results indicate that the NiS2/ZIF-67 composite as an electrode material with a core-shell structure has potential application in high-efficiency supercapacitors.

PPy coated nanoflower like CuCo2O4based onin situgrowth of nanoporous copper for high-performance supercapacitor electrodes

General CuCo₂O₄electrodes suffer a very low reversible capacity and poor cycling stability because of easily fading phenomena and volume change during cycling. To optimize the electrode, a facile method is conducted to fabricate a novel electrode of Cu@CuCo₂O₄@polypyrrole nanoflowers. Due to larger specific surface area and more electrochemical reactive areas of CuCo₂O₄@polypyrrole nanoflowers, the pseudocapacitance of thein situgrown CuCo₂O₄@polypyrrole (912 F g^-1at 2 A g^-1) is much higher than the pristine CuCo₂O₄(618 F g^-1at 2 A g^-1). Remarkably, the CuCo₂O₄@polypyrrole (cathode) and active carbon (anode) are used to assemble an asymmetric supercapacitor, which exhibits a relatively high energy density of 90 Wh kg^-1at a power density of 2519 W kg^-1and 35 Wh kg^-1at a high-power density of 9109 W kg^-1, and excellent cycling stability (about 90.4% capacitance retention over 10 000 cycles). The prominent performance of CuCo₂O₄@polypyrrole makes it as a potential electrode for supercapacitor.

High-performance quasi-solid-state flexible supercapacitors based on a flower-like NiCo metal–organic framework

NiCo metal–organic framework (MOF) electrodes were prepared by a simple hydrothermal method. The flower-like NiCo MOF electrode exhibited an exciting potential window of 1.2 V and an excellent specific capacitance of 927.1 F g⁻¹ at 1 A g⁻¹. The flower-like NiCo MOF//activated carbon (AC) device delivered a high energy density of 28.5 W hkg⁻¹ at a power density of 400.5 W kg⁻¹ and good cycle stability (95.4% after 5000 cycles at 10 A g⁻¹). Based on the flower-like NiCo MOF electrode, the asymmetric quasi-solid-state flexible supercapacitor (AFSC) was prepared and exhibited good capacitance retention after bending (79% after 100 bends and 64.4% after 200 bends). Furthermore, two AFSCs in series successfully lit up ten parallel red LED lights, showing great application potential in flexible and wearable energy storage devices.

The flower-like NiCo MOF prepared by a hydrothermal has a specific capacitance of 927.1 F g⁻¹ at 1 A g⁻¹ and a capacitance retention of 69.7% from 1 A g⁻¹ to 10 A g⁻¹, showing excellent electrochemical performance.

General metal-organic framework-derived strategy to synthesize yolk-shell carbon-encapsulated nickelic spheres for sodium-ion batteries

Transition-metal compounds have attracted enormous attention as potential energy storage materials for their high theoretical capacity and energy density. However, the most present transition-metal compounds still suffer from severe capacity decay and limited rate capability due to the lack of robust architectures. Herein, a general metal-organic framework-derived route is reported to fabricate hierarchical carbon-encapsulated yolk-shell nickelic spheres as anode materials for sodium-ion batteries. The nickelic metal-organic framework (Ni-MOF) precursors can be in situ converted into hierarchical carbon-encapsulated Ni₂P (Ni₂P/C), NiS₂ (NiS₂/C) and NiSe₂ (NiSe₂/C) by phosphorization, sulfuration, and selenation reaction, respectively, and maintain their yolk-shell sphere-like morphology. The as-synthesized Ni₂P/C sample can deliver much lower polarization and discharge platform, smaller voltage gap, and faster kinetics in comparison with that of the other two counterparts, and thus achieve higher initial specific capacity (3222.1/1979.3 mAh g^-1) and reversible capacity of 765.4 mAh g^-1 after 110 cycles. This work should provide new insights into the phase and structure engineering of carbon-encapsulated transition-metal compound electrodes via MOFs template for advanced battery systems.

Metal organic framework derived porous carbon materials excel as an excellent platform for high-performance packaged supercapacitors

Designing and synthesizing new materials with special physical and chemical properties are the key steps to assembling high performance supercapacitors. Metal organic framework (MOF) derived porous carbon materials have drawn great attention in supercapacitors because of their large specific surface area, high chemical/thermal stability and tunable pore structure. Thus, the recent development of porous carbon as an electrode material for supercapacitors is reviewed. The types, design and synthesis strategies of porous carbon are systematically summarized. This review will be divided into three main parts: (1) the design and synthesis of MOF precursors and templates for MOF-derived porous carbon materials; (2) the application of different types of MOF-derived carbon in supercapacitors; and (3) the design of typical structures of porous carbon composites for supercapacitors. Finally, the problems and challenges confronted when using porous carbon are assessed and elaborated, and some suggestions on future research directions are proposed.

CuCo2O4 nanoparticles wrapped in a rGO aerogel composite as an anode for a fast and stable Li-ion capacitor with ultra-high specific energy

To meet practical application requirements, high specific energy and specific power and excellent cyclability are highly desired.

MWCNT-mesoporous silica nanocomposites inserted in a polyhedral metal–organic framework as an advanced hybrid material for energy storage device

Hybridizing of trimetallic HKUST-1 with mesoporous SBA/CNT is highly desirable fot the improvement of energy and power densities in supercapacitors.

Comprehensive Insight into the Mechanism, Material Selection and Performance Evaluation of Supercapatteries

Electrochemical energy storage devices (EESs) play a crucial role for the construction of sustainable energy storage system from the point of generation to the end user due to the intermittent nature of renewable sources. Additionally, to meet the demand for next-generation electronic applications, optimizing the energy and power densities of EESs with long cycle life is the crucial factor. Great efforts have been devoted towards the search for new materials, to augment the overall performance of the EESs. Although there are a lot of ongoing researches in this field, the performance does not meet up to the level of commercialization. A further understanding of the charge storage mechanism and development of new electrode materials are highly required. The present review explains the overview of recent progress in supercapattery devices with reference to their various aspects. The different charge storage mechanisms and the multiple factors involved in the performance of the supercapattery are described in detail. Moreover, recent advancements in this supercapattery research and its electrochemical performances are reviewed. Finally, the challenges and possible future developments in this field are summarized.

Dual-functional NiCo2S4 polyhedral architecture with superior electrochemical performance for supercapacitors and lithium-ion batteries

Dual-functional NiCo₂S₄ polyhedral architectures with outstanding electrochemical performance for supercapacitors and lithium-ion batteries (LIBs) have been rationally designed and successfully synthesized by a hydrothermal method. The as-synthesized NiCo₂S₄ electrode for supercapacitor exhibits an outstanding specific capacitance of 1298Fg^-1 at 1Ag^-1 and an excellent rate capability of ~80.4% at 20Ag^-1. Besides, capacitance retention of 90.44% is realized after 8000 cycles. In addition, the NiCo₂S₄ as anode in LIBs delivers high initial charge/discharge capacities of 807.6 and 972.8mAhg^-1 at 0.5C as well as good rate capability. In view of these points, this work provides a feasible pathway for assembling electrodes and devices with excellent electrochemical properties in the next generation energy storage applications.

Metal–organic-framework-derived hierarchical Co/CoP-decorated nanoporous carbon polyhedra for robust high-energy storage hybrid supercapacitors

Electrode materials exhibiting nanostructural design, high surface area, tunable pore size, and efficient ion diffusion/transportation are essential for achieving improved electrochemical performance.

CuCo2O4 nanoneedle array with high stability for high performance asymmetric supercapacitors

Cycling performance is very important to device application. Herein, a facile and controllable approach is proposed to synthesize high stability CuCo₂O₄ nanoneedle array on a conductive substrate. The electrode presents excellent performances in a large specific capacitance up to 2.62 F cm⁻² (1747 F g⁻¹) at 1 mV s⁻¹ and remarkable electrochemical stability, retaining 164% even over 70 000 cycles. In addition, the asymmetric supercapacitor assembled with the optimized CuCo₂O₄ nanoneedle array (cathode) and active carbon (anode), which exhibits superior specific capacity (146 F g⁻¹), energy density (57 W h kg⁻¹), and cycling stability (retention of 83.9% after 10 000 cycles). These outstanding performances are mainly ascribed to the ordered binder-free nanoneedle array architecture and holds great potential for the new-generation energy storage devices.

The CuCo₂O₄ nanoneedle array with enhanced electrochemical performance especially high stability is due to the hierarchical porosity framework with the high mesoporous nanoneedle array.

A rational design of nanoporous Cu–Co–Ni–P nanotube arrays and CoFe2Se4 nanosheet arrays for flexible solid-state asymmetric devices

A facile method was developed to synthesize nanoporous Cu–Co–Ni–P nanotube arrays and hierarchical CoFe₂Se₄ nanosheet arrays for a flexible asymmetric device.

Reduced graphene/nanostructured cobalt oxide nanocomposite for enhanced electrochemical performance of supercapacitor applications

We demonstrate the preparation of nanostructures cobalt oxide/reduced graphene oxide (Co₃O₄/rGO) nanocomposites by a simple one-step cost-effective hydrothermal technique for possible electrode materials in supercapacitor application. The X-ray diffraction patterns were employed to confirm the nanocomposite crystal system of Co₃O₄/rGO by demonstrating the existence of normal cubic spinel structure of Co₃O₄ in the matrix of Co₃O₄/rGO nanocomposite. FTIR and FT-Raman studies manifested the structural behaviour and quality of prepared Co₃O₄/rGO nanocomposite. The optical properties of the nanocomposite Co₃O₄/rGO have been investigated by UV absorption spectra. The SEM/TEM images showed that the Co₃O₄ nanoparticles in the Co₃O₄/rGO nanocomposites were covered over the surface of the rGO sheets. The electrical properties were analyzed in terms of real and imaginary permittivity, dielectric loss and AC conductivity. The electrocatalytic activities of synthesized Co₃O₄/rGO nanocomposites were determined by cyclic voltammetry and charge-discharge cycle to evaluate the supercapacitive performance. The specific capacitance of 754 Fg^-1 was recorded for Co₃O₄/rGO nanocomposite based electrode in three electrode cell system. The electrode material exhibited an acceptable capability and excellent long-term cyclic stability by maintaining 96% after 1000 continuous cycles. These results showed that the prepared sample could be an ideal candidate for high-energy application as electrode materials. The synthesized Co₃O₄/rGO nanocomposite is a versatile material and can be used in various application such as fuel cells, electrochemical sensors, gas sensors, solar cells, and photocatalysis.