Asymmetric Hybrid Supercapacitor Research Articles

Rational design of the binder-free polythiophene nanofibers deposited nickel foam for the high-performance aqueous asymmetric supercapacitor

Development of the binder-free electrode materials and employing in the supercapacitor is the essential footstep for high energy storage. The present study highlights the cost-effective synthesis strategy for the binder-free growth of the amorphous polythiophene nanofibers over the nickel foam substrate. The presence of functional bonds like CC, C-H, and C-S has confirmed the deposition of the polythiophene nanofibers on the nickel foam, while elemental mapping analysis detected the uniform distribution of Carbon and Sulfur elements over nanofibers. The surface structure of the polythiophene is transformed from nanofibers to a wire-like structure as the result of the monomer concentration variation. The optimized polythiophene film exhibited the highest areal capacitance of 1263.2 mF/cm2 at 2 mA/cm2 with 90.03% capacitance retention after 5000 cycles. Moreover, the aqueous asymmetric device (PTh//AC) is fabricated which delivered 31.5 F/g at 10 mA/cm2. The highest specific energy of PTh//AC device was 6.3 Wh/kg. Also, it showed good retention capability with 82.3% retention. Based on these results, the present investigation provides the performance metrics of the polythiophene nanofibers and highlights the potential utilization of the polythiophene-based supercapacitor in practical energy storage systems.

The construction of an asymmetric hybrid supercapacitor with 2D materials MXene and perovskite

The construction of an asymmetric hybrid supercapacitor with 2D materials MXene and perovskite

NiFe2O4@NiCo2O4 hollow algae-like microspheres enabled by Mott-Schottky for electrochemical energy storage

Designing hybrid structure of transition metal oxides (TMOs) with controlled morphology can adjust the electronic structure and create more kinetics reactions. Herein, a new kind of NiFe2O4@NiCo2O4 nanocomposite was synthesized with one pot hydrothermal route. The unique hollow algae-like microspheres with plenty nanowires and the synergistic effect factors promote high electroactive sites and generate a built-in electric field. The constituted Mott-Schottky heterostructure creates strong interfacial interaction, paves the way for the electrolyte ions diffusion and results high charges transfer abilities by reducing the energy barriers in the heterointerfaces. As cathode material, the NiFe2O4@NiCo2O4 presents satisfactory specific capacity of 996C·g−1 at 0.5 A·g−1 and maintains ultrahigh capacity retention of 81 % at 30 A·g−1 with marvellous stability of only 6 % loss during 20,000 cycles. Interestingly, asymmetric hybrid supercapacitor device based NiFe2O4@NiCo2O4//active carbon (AC) provides tremendous energy density of 117.6 Wh·kg−1 at 438 W·kg−1 power density. What’s more, all-solid-state device offers ultra-low self-discharge process of 9.5 % through 24 h. Therefore, the combination of NiFe2O4@NiCo2O4 to form Mott-Schottky heterojunction was a promising strategy to develop electrode material with high energy storage performance.

Enhancing the Electrochemical Performance of ZnO-Co3O4 and Zn-Co-O Supercapacitor Electrodes Due to the In Situ Electrochemical Etching Process and the Formation of Co3O4 Nanoparticles

Zinc oxide (ZnO) and materials based on it are often used to create battery-type supercapacitor electrodes and are considered as promising materials for hybrid asymmetric supercapacitors. However, when creating such electrodes, it is necessary to take into account the instability and degradation of zinc oxide in aggressive environments with a non-neutral pH. To the best of our knowledge, studies of the changes in the properties of ZnO-containing electrodes in alkaline electrolytes have not been carried out. In this work, changes in the structure and properties of these electrodes under alkaline treatment were investigated using the example of ZnO-containing composites, which are often used for the manufacturing of supercapacitor electrodes. Supercapacitor electrodes made of two materials containing ZnO were studied: (i) a heterogeneous ZnO-Co3O4 system, and (ii) a hexagonal h-Zn-Co-O solid solution. A comparison was made between the structure and properties of these materials before and after in situ electrochemical oxidation in the process of measuring cyclic voltammetry and galvanostatic charge/discharge. It has been shown that the structure of both nanoparticles of the heterogeneous ZnO-Co3O4 system and the h-Zn-Co-O solid solution changes due to the dissolution of ZnO in the alkaline electrolyte 3.5 M KOH, with the short-term alkaline treatment producing cobalt and zinc hydroxides, and long-term exposure leading to electrochemical cyclic oxidation–reduction, forming cobalt oxide Co3O4. Since the resulting cobalt oxide nanoparticles are immobilized in the electrode structure, a considerable specific capacity of 446 F g−1 or 74.4 mA h g−1 is achieved at a mass loading of 0.0105 g. The fabricated hybrid capacitor showed a good electrochemical performance, with a series resistance of 0.2 Ohm and a capacitance retention of 87% after 10,000 cycles.

Tweaking the Efficiency of Asymmetric Hybrid Supercapacitors with Mechanochemically Synthesized Mixed‐Metal–Organic Framework‐Derived Metal Oxides

Novel electrode and electrolyte materials are crucial for enhancing supercapacitor efficiency. Metal–organic frameworks (MOFs) have gained attention owing to their high porosity and surface area. However, their low capacity limits their usage. To tackle this, a highly effective mechanochemical annealing strategy is implemented to improve their efficiency. Three different forms of metal oxides NiCo2O4 are derived from bimetallic MOFs by incorporating Ni2+ and Co2+ with linkers 1,3,5‐benzene tricarboxylic acid (MO‐1), 2,6‐naphthalene dicarboxylic acid (MO‐2), and 1,2,4,5‐benzene tetracarboxylic acid (MO‐3). The synthesized metal oxides have different morphologies due to different linkers and displayed remarkable electrochemical performance, attributed to favorable charge transport paths and enhanced electrochemical double‐layer capacitance with an enlarged specific surface area. These metal oxides exhibit specific capacitance values of 913.3, 43.4, and 210 F g−1 at operating voltages of 0.55, 0.55, and 0.6 V for MO‐1, MO‐2, and MO‐3, respectively. Notably, MO‐1 shows extended discharging time and demonstrates the characteristic behavior of battery‐type supercapacitors, making it versatile. The fabricated hybrid supercapacitor (bimetal hybrid supercapacitor) shows pseudocapacitive behavior, reaching up to 1.5 V with a specific capacitance of 65.6 F g−1, energy density of 73.83 W h kg−1, and power density of 1181.2 W kg−1.

All-functionalized-graphene ribbon films for flexible asymmetric supercapacitors with ultrahigh energy and power densities

Asymmetric (hybrid) supercapacitors (ASCs) based on different positive and negative pseudocapacitance materials can deliver more energy density than electric double layer capacitors (EDLCs). Yet, few pseudocapacitive materials can provide high energy and power density, simultaneously, due to their poor conductivity and unfavorable reaction kinetics under fast charge/discharge rates. Here, we graft sulphur- and oxygen- functionalized into interconnected graphene ribbons to improve the accessibility of ion and enhance redox-active sites. The prepared sulphur- and oxygen- functionalized interconnected graphene ribbon (S-IGR and O-IGR) films as positive electrode and negative electrode, respectively, for high energy density flexible ASCs. Benefiting from the more “active sites” for the graphene ribbons, the S-IGR and O-IGR films connect more sulphur and oxygen groups. As a result, the S-IGR and O-IGR films exhibit ultra-high specific capacitance of 1660 F g−1 (1.66 F cm−2) and 428 F g−1 (0.43 F cm−2), respectively. More importantly, the assembled O-IGR//S-IGR ASCs based on aqueous and gel electrolytes exhibit ultra-high energy densities of 106.6 Wh kg−1 and 35.6 Wh kg−1, respectively. With the ultrafast charging and discharging capability, the ASCs based on aqueous electrolytes can be charge/discharged within 0.53 s to deliver high energy density of 15.0 Wh kg−1 and ultrahigh-power density of 101.4 kW kg−1. Thus, this strategy could possibly be used as designing and fabricating new generation of all grphene-based ASCs with high energy and power densities.

Ni/Co-MOFs derived NiS2/Co3S4 heterostructured microspheres for high-performance asymmetric supercapacitors

Despite the relatively mature state with respect to the technology for synthesizing transition metal sulfide structure, preparation of heterostructured transition metal sulfides with superior structure and high specific capacitance is still challenging. Herein, we prepared NiS2/Co3S4 heterostructured microspheres by the two-part hydrothermal method using bimetallic MOFs as precursors. By constructing this heterostructure, we aimed to modify the electronic structure of electrode materials to enhance the electrochemical performance. We did not need carbonization in the preparation process and showed good electrochemical properties with a great appearance. Experimental and characterization analysis demonstrated the successful synthesis of NiS2/Co3S4 heterostructured microspheres. The NiS2/Co3S4 electrode manifests a specific capacity of 252.3 mAh/g at 1 A/g. Furthermore, the hybrid asymmetric supercapacitor with NiS2/Co3S4 as the positive electrode has the energy density of 4.29 Wh kg−1 at the power density of 61.99 W kg−1 according to the stack volume. These heterostructured mixed metal sulfide electrode materials with high specific capacity and high rate provide new ideas for research.

A new streamlined electrochemical assembly procedure to improve conductive polymer-based metal chalcogenide electrodes for innovative energy systems

Reliable, effective, and environmentally friendly supercapacitors still need development despite the progress made in many nanoscale electrode materials. In this area, composite materials made of organic polymers with high electrical conductivity and metal sulfides with various oxidation states were more attractive. This article describes the design and synthesis of zinc sulfide and polyaniline nanocomposites employing a fast and straightforward electrochemical deposition method and their use as electrode materials for supercapacitors. The structural investigation showed clumped spherical for pAni, hexagonal for pure ZnS, and coexisting hexagonal and spherical phases for ZnS@pAni nanocomposites. The ZnS@pAni nanocomposite demonstrated remarkable electrochemical efficiency and faradaic energy storage capabilities with practical reversibility. Also, an impedance inquiry found that the ZnS@pAni composite has better conductivity and a lower charge transfer resistance than its bulk components. ZnS@pAni//AC was used to create a hybrid asymmetric supercapacitor and displayed a large voltage window up to 2.06 V, 235.24 F g−1 specific capacity, and an ultimate energy density of 144.08 Wh kg−1. Also, when energy density drops to 22 Wh kg−1, substantial power delivery is achieved at 6.3 kW kg−1. Moreover, 88.05% of the capacitance was retained after the device completed 5000 cycles, suggesting good ZnS@pAni//AC asymmetric supercapacitor stability.

High performance MnNbS@MXene hybrid electrode for battery-supercapacitor hybrid device and biomedical applications

Hybrid energy storage devices have obtained a lot of interest because of their remarkable capacitance, high stability and multiple applications. The energy-storage capabilities of transition metal sulfides, such as MnNbS, have expanded beyond the domain of oxide-based materials. Transition metal sulfides and the MXene-based nano-architecture materials have been praised because of their synergistically enhanced conductivity and redox flexibility. Manganese niobium sulfide (MnNbS) binary electrode material was synthesized using the hydrothermal method. The MnNbS-MXene nanocomposite electrode was designed to improve the electrochemical characteristics. It exhibited a superior specific capacity (Qs) of 1094 C/g or 1562.85F/g at 1.5 A/g. The hybrid material (MnNbS-MXene) and activated carbon (AC) were used to make the asymmetric hybrid supercapacitors (MNS-MXene//AC). The hybrid device delivered extraordinary Qs of 153.23 C/g, energy density of 35.77 Wh/kg, and power density of 2800 W/kg. To estimate the capacity retention (CR), the device was measured up to 6000 cycles. It also revealed an astonishing CR of 91 %, which is much greater than that of pure MXene//AC and MnNbS//AC. Besides, the MnNbS-MXene//AC nanocomposite electrode is used as a chemical sensor to detect hydrogen peroxide (H2O2). The MnNbS-MXene showed high sensitivity against the H2O2. The device showed the response up to a wide range of H2O2 (1 mM-5mM). Our research presents a perspective and practical application for producing high-performance electrode material based on transition metal sulfide composites and chemical sensors to detect cancerous cells in the body.

RuxV2−xO5 nanowire/templated carbon composite electrodes for supercapacitors

V2O5 nanowires were doped with Ru4+ using a hydrothermal process. RuxV2−xO5 composites were characterized by x-ray diffraction, energy-dispersive x-ray analysis, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). The electrochemical performance of the RuxV2−xO5 nanowires/carbon composites were evaluated by cyclic voltammetry and galvanostatic charge-discharge techniques. The RuxV2−xO5/carbon exhibited a maximum specific capacitance of 351 F·g−1 at a scan rate of 5 mV/s in a symmetric coin cell device. The asymmetric hybrid supercapacitor device achieved a specific cell capacitance of 237 F·g−1 at a scan rate of 5 mV/s, which delivers a high energy and power of 74.8 Wh·kg−1 and 5994.5 W·kg−1, respectively.

Utilization of lead-based saturated adsorbents for the fabrication of battery-like hybrid asymmetric supercapacitors

Utilization of lead-based saturated adsorbents for the fabrication of battery-like hybrid asymmetric supercapacitors

Advanced High-Energy All-Solid-State Hybrid Supercapacitor with Nickel-Cobalt-Layered Double Hydroxide Nanoflowers Supported on Jute Stick-Derived Activated Carbon Nanosheets.

Developing efficient, lightweight, and durable all-solid-state supercapacitors is crucial for future energy storage systems. The study focuses on optimizing electrode materials to achieve high capacitance and stability. This study introduces a novel two-step pyrolysis process to synthesize activated carbon nanosheets from jute sticks (JAC), resulting in an optimized JAC-2 material with a high yield (≈24%) and specific surface area (≈2600m2g-1). Furthermore, an innovative in situ synthesis approach is employed to synthesize hybrid nanocomposites (NiCoLDH-1@JAC-2) by integrating JAC nanosheets with nickel-cobalt-layered double hydroxide nanoflowers (NiCoLDH). These nanocomposites serve as positive electrode materials and JAC-2 as the negative electrode material in all-solid-state asymmetric hybrid supercapacitors (HSCs), exhibiting remarkable performance metrics. The HSCs achieve a specific capacitance of 750Fg-1, a specific capacity of 209mAhg-1 (at 0.5Ag-1), and an energy density of 100Whkg-1 (at 250Wkg-1) using PVA/KOH solid electrolyte, while maintaining outstanding cyclic stability. Importantly, a density functional theory framework is utilized to validate the experimental findings, underscoring the potential of this novel approach for enhancing HSC performance and enabling the large-scale production of transition metal-based layered double hydroxides.

Attaining high energy density using metal-organic framework-derived NiO/Co3O4/NiCo2O4 as an electrode in asymmetric hybrid supercapacitor

This study investigates the potential of hybrid NiO/NiCo2O4/Co3O4 composite as electrode for high-performance supercapacitors. Hydrothermally synthesized Ni(BDC) and Co(BDC) as sacrificial templates with different mass ratios are used to obtain NiO/NiCo2O4/Co3O4 nanocomposite. Notably, the electrochemical studies revealed that NiO/NiCo2O4/Co3O4 derived from a 4:1 mass ratio of Ni-MOF and Co-MOF displayed the highest specific capacity value of 1108.9C g−1 at 2 A g−1 with enhanced rate capability and excellent electrochemical stability, with 95.3 % retention up to 5000 cycles at 10 A g−1. The enhancement of specific capacity is attributed to the multiple metal oxidation states (Ni2+, Ni3+, Co2+, Co3+), surface oxygen defects, and the reduced solvation effect due to mesoporous structure and higher specific surface area. The assembled hybrid asymmetric supercapacitor (NiO/NiCo2O4/Co3O4 //Carbon Black) demonstrated a remarkable specific capacity of 416.95C g−1 at 0.5 Ag−1 with 89.1 % retention up to 5000 cycles at 10 A g−1 and an exceedingly high energy density of 89.81 W h kg−1 at a power density of 387.49 W kg−1. Even at a high-power density value of 7740 W kg−1, the device maintained an impressive energy density of 72.43 W h kg−1.

Exploring the synergistic effect of temperature on hydrothermally synthesized tungsten oxide (WO3) nanostructures and its role in asymmetric liquid-state hybrid supercapacitors

The objective of this study was to produce non-uniform nanostructures (NSs) with different crystalline structures of the tungstate oxide (WO3) using the simple hydrothermal method for the supercapacitor application to overcome the critical energy crisis. In these aspects, the prepared WO3-NSs have been thoroughly examined using various physio-chemical methods likely Thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) and Raman spectroscopy, Scanning electron microscope (SEM), transmission electron microscope (TEM), and X-ray photoelectron spectroscopy (XPS). The supercapacitive characteristics of WO3-NSs Ni-foam (NF) based electrodes were studied using an aqueous 2 M KOH electrolyte. According to the findings, the W3-NF electrode exhibits a higher specific capacitance (Cs) of 750 F/g and capacity (Csp) of 94 mAh/g with moderate specific energy (Ed), power densities (Pd) of 22 Wh/kg, and 600 W/kg at 5 mA/cm2, as well as capacitive retention of 91% after 5000 cycles. Furthermore, an asymmetric liquid state hybrid device (ASH) was fabricated using WO3-NF and GO-NF as the positive and negative materials respectively. The ASH device delivers a maximum Ed of 32 Wh/kg and Pd of 1170 W/kg while maintaining capacitive retention of 90% over the 4000 cycles of charging and discharging. Therefore, the findings have sparked significant interest in exploring the synthesis, and performance evaluation of WO3-NSs for SCs applications.

Urchin-like structure and nanowire arrays of NiCo2O4/NiCoSe2 as a binder-free electrode material for high-performance supercapacitor

Hybrid structures targeted at high-performance electrochemical applications circumvent great challenges. Nanostructures with high porosity facilitating electrolyte penetration and providing fast ion and electron transfer are suitable candidates for constructing hybrid structured electrode materials. Here in, an architecture composed of nanowires and urchin-like structures of NiCo2O4 covered by NiCoSe2 nanosheets is successfully constructed on Ni foam through hydrothermal treatment in association with electrodeposition. The fabricated NiCo2O4/NiCoSe2 hybrid electrode demonstrates areal capacitance of 12.09 F cm-2 at current density of 5 mA cm-2, surpassing that of pristine NiCo2O4. Furthermore, the electrode evidences cycling stability with 87.6% capacitance retention over 3000 cycles. An asymmetric hybrid supercapacitor, assembled by the NiCo2O4/NiCoSe2 as a positive electrode and activated carbon as a negative electrode, represents areal capacitance of 3.07 F cm-2 at 5 mA cm−2. The as-fabricated device with excellent cycling stability (90.9% capacitance retention over 2000 cycles) delivers an energy density of 66.13 Wh kg-1 at a power density of 233 W kg-1. Our results convey a promising synthesis method of the core-shell structure of NiCo2O4/NiCoSe2 nanowire arrays for application in supercapacitors.

Optimizing performance: Achieving high capacitance and cycling durability in alkaline electrolyte with SnO2/SnSe||AC/KOH-based aqueous hybrid supercapacitor

A facile wet-chemical assisted synthesis route is adapted to prepare a novel SnO2/SnSe nanocomposite for the time to construct an aqueous asymmetric hybrid supercapacitor (AAHSC). The detailed characterization reveals the appropriate formation of micro flower-like SnO2-SnSe nanocomposite-covered with SnSe network to provide a conductive support and facilitate charge transport during the electrochemical processs. Compared with pure SnO2 micro flowers and SnSe electrodes, the SnO2-SnSe nanocomposite electrode delivers a brilliant charge storage performance. A rapid charge transport pathways was accomplished due to the lowest charge transfer resistance, resulting in a high capacitance and improved charge storage properties in an aqueous alkaline electrolyte solution with incredible reversibility and rate capability. Inspired by the excellent charge storage and capacitive properties, a two-cell mode-based AAHSC was built with SnO2-SnSe nanocomposite (cathode) and activated carbon (AC) as an anode (symbolized as SnO2-SnSe||AC/KOH) displayed the highest energy of 33.4 Wh/kg at a maximum power of 4003.7 W/kg, operating in a voltage of 1.6 V with excellent cycling stability of 89.5 %.

Enhanced high energy and power density hybrid asymmetric supercapacitor based on 2D layered MoS2/g-C3N4 electrode materials

Enhanced high energy and power density hybrid asymmetric supercapacitor based on 2D layered MoS2/g-C3N4 electrode materials

Enhancing the electrochemical performance of hybrid supercapacitors with in-situ grown ultrasound-mediated heterostructure bi-metallic and dual-linker MOF nanoarchitecture by harnessing charge storage mechanisms

In the present technological era, energy storage devices like batteries and supercapacitors hold immense importance, and their hybrid variants have gained notable interest. The aim of this study was to develop a dual-linker MOF capable of selectively capturing cobalt and vanadium ions using two distinct organic ligands. The ultrasonication-assisted hydrothermal technique was demonstrated to be a resounding success in achieving the synthesis of the bimetallic and dual-linker metal-organic framework (MOF). The outcome of the electrochemical analysis demonstrated that the Co-V-capacitance MOF contributes to the battery-type process by diffusion control at 88.52 %, while 11.48 % of the process is capacitive-controlled, in an aqueous electrolyte (1 M KOH). Additionally, the upgraded Co-V-MOF electrode displayed an impressive specific capacity of 1711.1 F/g. The utilization of Co-V-MOF in the hybrid Asymmetric supercapacitor resulted in an outstanding specific capacitance of 187.5 F/g, with energy and power densities of 70.65 Wh/kg and 835 W/kg, respectively. It is important to mention that the Co-V-MOF hybrid supercapacitor exhibited excellent and consistent performance for 10,000 cycles (92.21 %). The outstanding specific capacitance performances produced in this study represent the most significant findings reported to date for bi-metallic and dual-linker MOFs based on vanadium-cobalt.

CoSe2@ZnS microsphere arrays with remarkable electrochemical performance for hybrid asymmetric supercapacitor

This study presents a simple hydrothermal synthesis method for preparing CoSe2, ZnS, and their nanohybrid combinations (ZnS-70 % CoSe2 and ZnS-50 % CoSe2, referred to as ZC-1 and ZC-2) for the first time. These materials are intended for application in a supercapacitor (SC) and are synthesized through an ex-situ wet-chemical approach. The research thoroughly examines the electrochemical properties of as-prepared electrodes and how they relate to their structure and morphology to understand their charge storage mechanism better. The detailed characterization reveals that a one-step hydrothermal reaction obtains the cubic crystal structure of the ZnS with microsphere morphology, and the CoSe2 presents a snow crystals-like morphology with a highly smooth and transparent surface appearance. The systematic electrochemical examination declares the typical pseudocapacitive charge storage response owing to fast Faradaic redox reactions with good reversibility and rate capability. Notably, a high capacitance of CoSe2-ZnS nanohybrid (denoted as ZC-2) is realized by the synergistic effect between ZnS and CoSe2 supported by the impedance, cyclic voltammetry, and charge/discharge studies. High specific energy with a power of 46.71 Wh/kg (899.21 W/kg) and 9 Wh/kg (5400 W/kg) is realized by adding an optimal voltage and capacitance simultaneously by fabricating a hybrid asymmetric HASCs (ZC-2||AC HASC) in aqueous solution. This study believes that metal sulfide and selenide-based nanohybrids can be effective candidates for competing in the growing electrochemical energy storage demand.

Hydrothermally synthesized three-dimensional hierarchical CuO nanomaterials for energy storage applications

Copper oxide is a promising material for various applications because it exhibits excellent properties in different nanostructures. Highly porous nanomaterials are better suited to a variety of applications, including charge storage supercapacitors. In this research article, the binder-free, flower-like three-dimensional hierarchical copper oxide (3Dh-CuO) nanomaterials on stainless steel (SS) substrates via a hydrothermal technique for charge storage supercapacitor applications has been studied. The flower-like 3Dh-CuO monoclinic polycrystalline structures were confirmed by morphological and structural analysis. The quantum confinement effect was observed on a flower-like 3Dh-CuO nanomaterial. The Quantum Confinement Semiconductor (QCS) exhibits excellent charge storage electrochemical performance. The maximum specific capacitance of binder-free, flower-like 3Dh-CuO nanomaterials is 1312.8 Fg−1 at a 2 mVs−1 sweep rate and 1301.3 Fg−1 at a 1.0 mA cm−2 current density in 1 M KOH electrolyte. The maximum energy density (ED) is 152.73 Wh kg−1 and the power density (PD) is 4.33 kW kg−1. The Solid Asymmetric Hybrid Supercapacitor (SAsHSc)device of the flower-like 3Dh-CuO shows a capacitance of 172.8 Fg-1 at 10 mVs−1 in the 1.6 V potential, with the highest cycling stability up to 3000 cycles having 77.66% retention. The binder-free, flower-like 3Dh-CuO electrodes have been considered a potential candidate material for electrochemical supercapacitors.