Supercapacitor Electrode Research Articles

Construction of Moiré-like TiO2/polypyrrole electrodes for high performance photo-assisted supercapacitors

There is currently a need for research into using external energy to increase the performance of the supercapacitor in energy storage systems because of their poor energy density. This paper reports the effective creation of photo-assisted supercapacitors with moiré-like morphology using polypyrrole (PPy) and titanium dioxide nano powder to replicate the surface of inexpensive and widely available CD discs. The composite material combines the moiré-like superstructure's strong light trapping property with titanium dioxide's high photo-sensitivity, achieving the aims of boosting light absorption, extending the optical route, and improving capacitor performance under light. By combining morphology construction and external energy interventions to improve capacitor performance, the specific capacitance under light is 509.0 F g−1 at 1 A g−1, 13.1 % higher than the same material without moiré-like morphology (449.9 F g−1). When assemble into a sandwich-structured symmetric supercapacitor, it has an area specific capacitance of 99.42 mF cm−2 and an energy density of 7.28 Wh kg−1 at a power density of 217.4 W kg−1, outperforming typical photo-assisted supercapacitors. The current work suggests a practical and straightforward method for increasing the light absorption efficiency and performance of photo-assisted supercapacitors.

High Performance MXene/MnCo2O4 Supercapacitor Device for Powering Small Robotics.

The development of advanced energy storage devices is critical for various applications including robotics and portable electronics. The energy storage field faces significant challenges in designing devices that can operate effectively for extended periods while maintaining exceptional electrochemical performance. Supercapacitors, which bridge the gap between batteries and conventional capacitors, offer a promising solution due to their high power density and rapid charge-discharge capabilities. This study focuses on the fabrication and evaluation of a MXene/MnCo2O4 nanocomposite supercapacitor electrode using a simple and cost-effective electrodeposition method on a copper substrate. The MXene/MnCo2O4 nanocomposite exhibits superior electrochemical properties, including a specific capacitance of 668 F g-1, high energy density (35 Wh kg-1), and excellent cycling stability (94.6% retention over 5000 cycles). The combination of MXene and MnCo2O4 enhances the redox activity, electronic conductivity, and structural integrity of the electrode. An asymmetric supercapacitor device, incorporating MXene/MnCo2O4 as the positive electrode and Bi2O3 as the negative electrode, demonstrates remarkable performance in powering small robotics and small electronics. This work underscores the potential of MXene-based nanocomposites for high-performance supercapacitor applications, paving the way for future advancements in energy storage technologies.

Construction of hierarchical and core-shell structured Co3O4@MnO2@NiO nanoarrays as binder-free electrodes for high-performance asymmetric supercapacitors

Remarkable specific capacity and excellent cycle stability of the electrode materials are vital prerequisites for their practical applications. Transition metal oxide-based materials have been extensively explored and employed as electrode materials for asymmetric supercapacitors. However, the actual specific capacitances of these materials are still far lower than their theoretically predicted values. Thus, it is essential to design transition metal oxide with novel structures in order to maximize their specific capacity and cycle stability. Herein, we constructs hierarchical and core-shell structured Co3O4@MnO2@NiO arrays on nickel foam (Co3O4@MnO2@NiO/NF) through a three-step hydrothermal-annealing process, and use them as a direct binder-free electrode for pseudocapacitors. The as-prepared layered hierarchical Co3O4@MnO2@NiO/NF electrode exhibits an impressive specific capacitance of 6.42 F cm−2 (2054 F g−1) at 1 mA cm−2 in a three-electrode configuration, which is largely because of the synergistic effect among Co3O4, MnO2 and NiO. Furthermore, the 3D nanoarray structure can provides a larger specific surface area, a rapid diffusion path, and more active sites that allow to achieve improved electrochemical performance. In addition, the assembled Co3O4@MnO2@NiO/NF//AC/NF ASC all-solid-state asymmetric supercapacitor (ASC) displays a remarkable energy density (30.7 Wh kg−1 at 400.4 W kg−1), demonstrating that this all-solid-state ASC owns considerable potential for practical applications in such high-performance energy storage devices.

Synergistic interface engineering of ZnCo2O4/NiMnCo-layered double hydroxides for boosted reactivity in advanced supercapacitor electrodes

NiMn layered double hydroxide (LDH) exhibits high redox activity as a cathode material for hybrid supercapacitors, but it has the disadvantages of low conductivity and poor stability. In this work, the electrochemical properties of NiMnCo-LDH with different Co contents prepared by electrodeposition were tested. The results showed that the addition of an appropriate amount Co increased the adsorption of OH− on NiMn-LDH and improved the reactivity of the material. ZnCo-MOF grown on carbon cloth was transformed into flake ZnCo2O4 by calcination, and NiMnCo-LDH was electrodeposited on it to prepare ZnCo2O4/NiMnCo-LDH composite electrode. The core-shell structure increases the reaction area between the LDH material and the electrolyte. Physical characterization and density functional theory (DFT) calculations show that the structure and electronic distribution of ZnCo2O4/NiMnCo-LDH at the heterogeneous interface are reconstructed, which increases the valence state of Co and Mn elements, and finally exhibits enhanced electrochemical performance. Due to the existence of this synergistic effect, the specific capacity of the electrode is as high as 231.5 mAh g−1, with excellent stability demonstrated after 5000 cycles compared to the NiMnCo-LDH. The assembled hybrid supercapacitor exhibits a high energy density of 39.4 Wh kg−1, and has high cycle stability (90 % after 5000 cycles).

Optical and electrochemical performance of NdVO4 nanorods

Tetragonal structured NdVO4 nanorods were prepared by simple solvothermal route with various temperatures. An optimized NdVO4 sample was characterized through XRD, FTIR, RAMAN, UV–Visible, PL, SEM, HRTEM and EDX techniques. Electrochemical performance of NdVO4 electrodes were analyzed by CV instrument. From XRD, it is confirmed that the prepared samples were perfectly formed in pure tetragonal structured NdVO4 nanoparticles with the crystallite size of 41.08 nm, 44.92 nm and 54.78 nm for the temperature of 240 °C, 260 °C, and 280 °C, respectively. In UV–Visible absorption spectrum, there are seven peaks raised for NdVO4. The XPS shows the three elements that are Nd, V and O with the corresponding electronic configuration states of 3d, 2p and 1 s, respectively. SEM and HRTEM picture the nanorod morphology of the prepared NdVO4 nanoparticles. The electrochemical performance of the NV1 electrode showed pseudocapacitive existence with the current density of 10 mV/s (362F/g) and it will act as well behaved electrode in supercapacitors.

One-step pulsed laser deposition of carbon/metal oxynitride composites for supercapacitor application

Abstract Advanced material composite of nanocarbons and metal-based materials provides a synergistic effect to obtain excellent electrochemical charge-storage performance and other properties. Herein, 3D porous carbon-metal oxynitride nanocomposites with tunable carbon/metal and oxygen/nitrogen ratio are synthesized uniquely by simultaneous ablation from two different targets by single-step pulsed laser deposition at room temperature. Co-ablation of titanium and vanadium nitride targets together with graphite allowed us to synthesize carbon-metal oxynitride porous nanocomposite and exploit them as a binder-free thin film supercapacitor electrode in aqueous electrolyte. We show that the elemental composition ratio and hence the structural properties can be tuned by selecting target configuration and by manipulating the ablation position. We investigate how this tuning capability impacts their charge-storage performances. We anticipate the utilization of as-synthesized various composites in a single PLD production run as next-generation active materials for flexible energy storage and optoelectronic applications.

Green synthesised Mn3O4 and poly (o-phenylenediamine) for antimicrobial textile-based supercapacitor applications

The advancement of wearable supercapacitors (SCs) has recently garnered a lot of attention owing to their ease of fabrication into textiles, low cost, long cycle life, fast charging and discharging, high efficiency, and ability to bridge the energy and power gap between conventional capacitors and batteries. The present study focuses on the development of wearable textile-based SC electrodes using green-synthesised manganese oxide nanoparticles functionalised on poly(o-phenylenediamine) reinforced to a polymer nanocomposite. The prepared nanocomposite was characterized using spectroscopic techniques such as UV-visible spectroscopy, Fourier transform infrared spectroscopy, x-ray diffraction studies, and scanning electron microscopy to validate the incorporation of metal oxide nanoparticles into the polymer matrix. The thermal properties were studied using thermogravimetric analysis and differential scanning calorimetry. The electrochemical performance of the bare polymer and the nanocomposite was evaluated using cyclic voltammetry, galvanostatic charge-discharge, and impedance spectroscopy techniques. An impressive specific capacitance of 213 Fg-1was achieved at a current density of 1 Ag-1for the polymer nanocomposite and even after 1000 cycles a capacitance retention of 89% was observed. Enhanced antimicrobial activity was also observed for the nanocomposite against both gram-negative and gram-positive bacteria. Based on these attributes, the fabricated device can be used as an efficient antimicrobial wearable SC.

Electrochemical measurements, structural and morphological studies of electrodeposited polypyrrole supercapacitor electrode

This study presented the electrochemical deposition of potassium nitrate-doped polypyrrole (Ppy:KNO3) on stainless steel (SS), graphite sheet (GRs), and carbon fiber (CF) substrates, Ppy:KNO3/SS, Ppy:KNO3/GRs, and Ppy:KNO3/CF supercapacitor electrodes. Structural, morphological, and molecular analyses were conducted using X-ray diffraction (XRD), scanning electronic microscope (SEM), and Fourier transform infrared spectroscopy (FTIR). SEM images exhibited distinct morphologies of Ppy:KNO3 films, varying with cycles, scan rates, and Ppy:KNO3 concentrations. Ppy:KNO3/CF film displayed a unique structure with minimal particle aggregation. Electrochemical performance was assessed through Cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) measurements and electrochemical impedance spectroscopy (EIS). Notably, Ppy:KNO3/CF demonstrated a specific capacitance of 1020 F/g at 1 A/g. It exhibited 92 % capacitance retention after 1000 cycles, along with impressive power and energy densities of 310 W/kg and 71.2 Wh/kg, respectively. These results represented a significant progress in the development of high-performance, durable supercapacitors.

Shape tailored nano-ceria as high performance supercapacitor electrode material

Electrochemical energy storage devices herald a brighter future, offering efficient and sustainable solutions to meet the escalating global energy demands. The current work investigates the development and characterization of different ceria nanostructures (nanorod, nanocube, and nanopolyhedra) as effective electrode materials for supercapacitor applications. The electrode materials are systematically characterized using various spectroscopic and non-spectroscopic techniques. Galvanostatic charge-discharge, electrochemical impedance spectroscopy, and cyclic voltammetry techniques are used to evaluate the electrochemical performance of the electrode materials. The optimum material for the said application is cerium nanorod which has the maximum specific capacitance of 437.27 F/g in acid electrolytes. The current-voltage (I-V) characteristics of the ceria nanostructures exhibit hysteresis behavior; ceria nanorod showing coexistence of memristive and memcapacitive nature. The loop area of the hysteresis curve, derived from the ratio of OFF resistance to ON resistance (ROFF/RON) at 4 V, yields approximate values of 1.08, 1.33, and 1.57 for ceria nanocubes, ceria nanopolyhedra, and ceria nanorods, respectively. Impedance vs. frequency analysis of the samples was also carried out to study their electrical and transport properties. The results obtained from electrochemical analyses are complimented by electrical studies.

Electrospun Mn1-xCoxFe2O4 (x=0–0.7) nanofibers for supercapacitors and oxygen evolution reaction

Cobalt manganese ferrite nanofibers (Mn1-xCoxFe2O4; x = 0, 0.3, 0.5, 0.7), were synthesized using sol-gel electrospinning technique. The impact of cobalt incorporation on physical and electrochemical properties of manganese ferrite nanofibers was investigated. The XRD peaks confirmed the formation of a cubic spinel phase and lattice parameter decreased gradually with increasing cobalt concentration. SEM analysis revealed the nanofibers with diameters in the range of 30–60 nm. VSM analysis showed that magnetic parameters such as coercivity, and saturation magnetization were enhanced by cobalt substitution and the sample Mn0.3Co0.7Fe2O4 showed the highest saturation magnetization and coercivity. DRS analysis exhibited that the incorporation of cobalt in the manganese ferrite reduced the band gap energy. The supercapacitive performance of Mn1-xCoxFe2O4 electrodes was investigated using CV, GCD and EIS in 3 M KOH electrolyte solution. The highest specific capacitance (453 F g−1) was obtained with long cycling stability (94.6 % retention after 4000th cycles) for Mn0.7Co0.3Fe2O4. Furthermore, an asymmetric supercapacitor (ASC) was made with reduced graphene oxide (rGO) and Mn0.7Co0.3Fe2O4 as anode and cathode electrodes, respectively. The Mn–CoFe2O4//rGO ASC revealed an impressive energy density of 50.2 Wh kg−1 at a power density of 750 W kg−1. The electrocatalytic oxygen evolution reaction (OER) performance of the Mn0.7Co0.3Fe2O4 and MnFe2O4 catalysts were also investigated in 1 M KOH alkaline electrolyte. Experiments demonstrated that the Mn0.7Co0.3Fe2O4 nanofiber catalyst had a lower overpotential (201 mV) at 10 mA cm−2, a small Tafel slope (106 mV dec−1), a larger ECSA (176 cm2), a greater TOF (7.68 × 10−4 s−1), and better long-term durability (96.3 % for 12 h) than MnFe2O4 for OER. This highlights the potential of the synthesized Mn0.7Co0.3Fe2O4 electrode for supercapacitor and oxygen evolution reaction.

FeCl3 induced catalytic activation prepared porous carbon with carbon nanotube skeleton from coal for supercapacitor electrodes

Poor conductivity and pore utilization of porous carbon (PC) have limited its use for supercapacitor electrodes. A simple FeCl3 induced catalytic KOH activation method was used to adjust the pore structure and graphitic carbon skeleton of coal-based PC. Under atmosphere of activation, the Fe component can be transformed into Fe3C, and then the Fe3C may act as catalysts for the deposition of activated gases, such as CO and CH4, to form carbon nanotubes (CNTs). As a result, the CNTs as graphite skeleton in situ growth in the PC (PC-CNTs), which enhances the conductivity and stability of the materials. The PC-CNTs sample shows hierarchical porous structure with surface area (SBET) of 2178.11 m2 g−1. As supercapacitor electrode, it exhibits a specific capacitance of 224.41 F g−1 at a current density of 1 A g−1, and maintains 182.66 F g−1 at 10 A g−1. Furthermore, a PC-CNTs//PC-CNTs symmetrical supercapacitor retains 98 % of its initial capacitance after 20,000 cycles at 1 A g−1. This study employed in situ pyrolysis gas from coal as a carbon source to prepare CNTs for adjusting the pore structure and graphitization of PC, which provides new insights for the utilization of low-rank coal in supercapacitor applications.

Cornstarch as a green binder in supercapacitors: Understanding the effect of binder on the charge storage mechanism

This study used a scalable process to fabricate activated carbon (AC) supercapacitor electrodes with cornstarch as a green binder. A vital aspect of this study was comparing its performance with synthetic binders like polyvinylidene fluoride (PVDF) and Nafion. The chemical and physical properties of the AC were characterized using Brunauer-Emmett-Teller (BET), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), Raman spectroscopy, and Field Emission Scanning Electron Microscopy (FE-SEM). Water contact angle measurements evaluated the hydrophilicity of AC-based electrodes with different binders. Their electrochemical characteristics were studied using open circuit potential (OCP), cyclic voltammetry (CV), galvanic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 1 M NaSO4 electrolyte, and the charge storage mechanism was discussed in detail. The starch binder significantly facilitated the charge storage mechanism by suppressing diffusion limitations compared to other binders. The fabricated symmetric supercapacitor device of starch-based electrodes exhibited the highest Cs of 120 F/g at a specific current of 1 A g-1 with a high energy density of 135 Wh/kg and an exact power density of 750 W/kg. The starch-based supercapacitor device exhibited a capacitance retention of 104 % and 65.5 % at specific currents of 2 A g-1 and 10 A g-1 after 10,000 cycles of charging/discharging, respectively.

Strategic design of MXene/CoFe2O4/g-C3N4 electrode for high-energy asymmetric supercapacitors

MXenes are emerging as the next-generation materials for energy storage due to their substantial surface area, exceptional conductivity, and abundant surface-terminating groups. However, the tortuous path for ion transfer within the restacked layers significantly limits the electrochemical performance of multilayered MXenes. To overcome this, interlayer spacers have been introduced. These spacers help mitigate ion diffusion barriers and enhance the accessibility of active sites, thereby improving the overall efficiency and longevity of MXene-based supercapacitors and related devices. In this study, a rational material is designed by incorporating CoFe2O4 and g-C3N4 into the layers of MXene through ultrasonication for supercapacitor application. The physicochemical properties of the synthesized materials have been comprehensively characterized using diverse techniques, revealing that MXene/CoFe2O4/g-C3N4 has successfully evolved into a multilayered structure possessing enhanced surface area, low restacking tendency, high pore diameter, and excellent pore volume. Leveraging these properties, it performs as a viable material for fabricating the working electrode with a specific capacitance (Csp) of 1506.2 F g−1 at a current density of 5 A g−1 in 3 M KOH. It shows good stability with 89 % capacitance retention over 7000 cycles. An asymmetric supercapacitor (ASC) constructed with MXene/CoFe2O4/g-C3N4 as positive electrode and activated carbon as negative electrode exhibits an energy density of 79.8 Wh Kg−1 and power density of 1343.3 W Kg−1. Furthermore, it shows a capacitive retention of 91 % over 10,000 cycles. This MXene based composite, with excellent capacitance and outstanding stability, offers an appreciable performance in the field of sustainable energy storage.

One-step rapid prototyping of recyclable ultrathin CNF/MWCNT/Fe-based spinel oxide asymmetric interdigital nanopaper electrodes for high performance flexible supercapacitors

Flexible asymmetric supercapacitors (FASCs) are potential energy storage devices for wearable electronics, considering that these have a wide operating voltage window, high specific capacity, and high energy density. However, achieving high energy density through the optimization of structure and electrode remains a challenge. Herein, two electrode inks with exceptional homogeneity nature and stability are prepared by using in-situ grown Fe-based spinel oxide (MFe2O4 = Fe3O4/MnFe2O4) on multi-walled carbon nanotubes (MWCNT) combined with eco-friendly and renewable cellulose nanofiber (CNF). Meanwhile, ultrathin flexible asymmetric interdigital nanopaper electrodes (NFT@MnFe and NFT@Fe) with customized patterns are fabricated through a one-step mask-assisted vacuum filtration strategy by using the obtained electrode inks. The planar interdigital FASC device based on the NFT@MnFe cathode and the NFT@Fe anode has excellent area specific capacity (309.8 mF cm−2), energy density (110.2 μW h cm−2), and power density (0.47 mW cm−2). The FASC maintain over 95 % of the original capacity after 5000 charge/discharge cycles. Noteworthy, a stacked interdigital FASC can be achieved with an energy density of up to 273.8 μW h cm−2 at 0.47 mW cm−2 power density, combining the structural benefits of planar interdigital and sandwich-type devices.

Reutilization of Silver-Impregnated Activated Carbon (SAC) Cartridges with Surface Modification for Supercapacitor Electrodes for Large-Scale Energy-Storage Applications

The strategy of converting waste materials into new functional materials is a promising approach for energy-storage applications, particularly in the case of silver-impregnated activated carbon (SAC). SAC, which is typically derived from coconut shells, is primarily used for water purification in home-based filters due to its excellent antibacterial properties. However, the silver concentration is low, and it tends to leach out after a certain period, resulting in waste. To address this issue, SAC was used as a precursor for electrodes in supercapacitor applications. Additional surface treatments, such as heteroatom doping, are also being employed to improve the electrical conductivity and wettability of SAC. Nitrogen was introduced using urea as a precursor to enhance the properties of SAC. XRD analysis confirmed the structural analysis of activated carbon and nitrogen-activated carbon. Morphological analysis revealed the formation of micropores on the surface of the samples. FTIR analysis confirmed the presence of functional groups in the samples. Raman spectra showed the presence of defects after the introduction of nitrogen atoms into the carbon lattice, with higher relative [Formula: see text] compared to AC. Multipoint bet analysis was conducted, and the surface area of the sample was found to be approximately 815[Formula: see text]m2g[Formula: see text], with pore sizes of 810[Formula: see text]m2g[Formula: see text]. Electrochemical analysis was carried out in both three- and two-electrode configurations. The specific capacitance of NAC in cyclic voltammetry and galvanostatic charge–discharge analysis was found to be higher than that of AC because the nitrogen atoms reduced the ionic charge transfer resistance between the electrode and electrolyte surface. Electrochemical impedance spectroscopy (EIS) was also conducted, confirming the solution resistance with 1.5[Formula: see text]Ohm.

Insights of oxygen vacancies engineered structural, morphological, and electrochemical attributes of Cr-doped Co3O4 nanoparticles as redox active battery-type electrodes for hybrid supercapacitors

The global warming issue is spurring the development of renewable energy solutions, where supercapacitors are emerging as promising options for energy storage. Despite advancements in battery-type materials, doping is a practical approach to enhancing electrochemical performance. In this study, using the solution combustion method, we synthesized spinel Co3O4 nanoparticles doped with chromium (Cr) at 2.5 % and 5 % concentrations. The addition of Cr significantly modifies the structural, morphological, surface, and electrochemical properties of Co3O4 nanoparticles. Raman and X-ray photoelectron spectroscopy confirm that this doping method effectively regulates the oxygen vacancy defect level. Moreover, Cr dopants and oxygen vacancies modify electronic states, facilitating more accessible contact to active sites, improving electrical conductivity and more intricate redox chemistry. Notably, the 2.5 % Cr-doped Co3O4 configuration demonstrates substantially enhanced specific capacity (334.64 C g−1/92.95 mAh g−1 at 1 A g−1) and rate performance (59 %), surpassing those of 5 % Cr-doped Co3O4 and undoped Co3O4. Furthermore, the as-fabricated 2.5 % Cr-doped Co3O4//activated carbon (AC) hybrid supercapacitor (HSC) device exhibits a noteworthy energy density of 42.5 Wh kg−1 at 1295.73 W kg−1, withstanding 33.54 Wh kg−1 even at a power density of 5720.46 W kg−1. The HSC device showcases outstanding cyclic performance with 100 % capacity retention after 5000 cycles. Therefore, our work offers a viable way to improve the efficiency of hybrid supercapacitors by providing essential insights into the design of defect-engineered battery-type electrode materials.

Effect of processing parameters on the properties of carbon paper as a free-standing supercapacitor electrode

As newly emerging energy storage devices, supercapacitors are being investigated thoroughly by researchers. Free-standing electrode is one of the major research focuses in this area, which not only avoids the use of resistive binders but also simplifies device assembly. The study describes the synthesis and study of carbon fiber-based carbon carbon composite paper (heat treated to different temperatures) as a free-standing supercapacitor electrode. Due to the inert nature of carbon paper, it was activated to create defect sites and to increase the specific surface area. Electrochemical studies suggested that activated carbon paper heat treated to 750°C (ACP-750) exhibited the highest areal capacitance of 11.4 F/cm2 (422.2 F/g) at the current density 2.5 mA/cm2 (0.09 A/g), probably due to the generation of larger number of defect sites (as depicted by XRD and RAMAN studies). ACP-750 electrode was used to fabricate the solid-state symmetric supercapacitor device that exhibited an energy density 0.77 Wh/cm2 at a power density of 2.34 W/cm2. The electrode was allowed to age (ACPA-750), after which it exhibited enhanced specific capacitance of 16.8 F/cm2 (622.2 F/g) at a current density 2.5 mA/cm2. ACPA-750//ACPA-750 device delivered maximum energy density of 1.66Wh/cm2 at a power density of 3 W/cm2. The device exhibited a coulombic efficiency of 96.1% and capacitance retention of 89% after 10,000 cycles.

Facile synthesis of MWCNT hexagonal needles grown on interconnected honeycombs like MnCo2O4/MnO2 nanoporous electrode for high-performance asymmetric supercapacitor

The construction of a honeycomb-like structure composed of MnCo2O4/MnO2was effectively achieved using a combination of hydrothermal processing and heat treatment. The whole surface of the MnCo2O4/MnO2 honeycomb is coated with neatly arranged hexagonal nano needles made of MWCNT, leading to a substantial enhancement in the specific surface area. At 1 A/g, the supercapacitor electrode composed of MnCo2O4/MnO2@MWCNT composite exhibited an exceptional specific capacitance of around 1539 F/g. Furthermore, it maintained approximately 95.5 % of its capacity even after undergoing 10,000 cycles. The asymmetric capacitor device, with MnCo2O4/MnO2@MWCNT and AC electrode, has a power density of 1537.8 W kg−1 and an energy density of 48.78 Wh kg−1. The MnCo2O4/MnO2composite exhibits exceptional rate performance, significant capacitance, and excellent cycle performance due to the synergistic effect between MnCo2O4/MnO2 and MWCNT, as well as the high specific surface area and unique structure. Consequently, it presents a viable option for the advancement of high-efficiency electrochemical super capacitors in the next generation.

The enhanced properties of ZnCoNi-S electrode by magnetron sputtering of Au nanoparticles for high performance supercapacitors

In this work, the distinctive effect of Au nanoparticles on shape preservation and properties enhancement during the preparation of transition metal sulfides is explored for the first time. After zeolitic imidazolate framework-67 (ZIF-67) is uniformly covered on nickel foam (NF), ZnCo layered double hydroxides (ZnCo-LDH) are compounded with ZIF-67 via hydrothermal method. The surface of compound is then coated with Au by magnetron sputtering. The final electrode is produced through sulfidation reaction. Benefiting from the excellent inertness and electrical conductivity of Au, the flake structure remains stable during the following sulfidation, and transfer impedance of the obtained Au/ZnS@Co3S4@Ni3S2 (Au/ZCN-S) electrode decreases significantly. In contrast, magnetron sputtered Ag or Cu nanoparticles react to Ag2S or CuS2 and cannot protect the refined structure of electrode as Au does. The Au/ZCN-S electrode shows a low transfer impedance of 0.0785 Ω and enables a specific capacity of 302.6 mAh g−1. Furthermore, the asymmetric supercapacitor constructed by Au/ZCN-S and activated carbon (AC) achieves a remarkable energy density of 104.09 Wh kg−1 with a high capacitance retention rate of 91.184 % after 10000 cycles. This work provides a new approach to optimize the morphology and performance of transition metal sulfides electrode for supercapacitors.

Se-doped cobalt-nickel sulfide hollow nanospheres with heterostructure and engineered defects as high-performance electrode for supercapacitors

Porous structures with heterogeneous interfaces and defects are an important way to enhance electrochemically active sites and facilitate electron transfer, while also improving the permeability of the electrolyte and the rate of ion transport. In this study, Se-doped cobalt-nickel sulfide (Se-CoNi2S4) hollow nanospheres with heterostructure and defects were prepared from CoNi metal-organic framework (MOF) as substrate by sequential sulfidation and selenization treatments. Notably, the hollow structure not only offers additional ion transport channels to promote rapid transfer of ions in the electrolyte but also provides an increased number of electrochemically active sites. The morphology and electrochemical performance of Se-CoNi2S4 nanospheres with different levels of Se doping were compared. From the results, Se doping not only enhances the conductivity of CoNi2S4 but also increases its charge storage capacity. As an electrode material, the synthesized Se-CoNi2S4 composite that was synthesized demonstrated a notable specific capacitance of 1260 F g−1 at 1 A g−1. Additionally, when Se-CoNi2S4 was utilized as the anode and activated carbon served as the cathode in an asymmetric supercapacitor, it achieved an energy density of 44.6 Wh kg−1 at a power density of 827 W kg−1. After undergoing 10,000 cycles, this device demonstrated exceptional cycling stability, retaining 80.2 % of its initial capacitance. Therefore, the synthesized electrode material Se-CoNi2S4 has significant potential for energy storage applications.