High-performance Asymmetric Supercapacitors Research Articles

Preparation of Zirconium-Based MOF-Derived Phosphide on GO/MXene Double Substrates for High-Performance Asymmetric Supercapacitors.

At present, it is very necessary to select and prepare suitable positive and negative electrode materials to fabricate high-performance asymmetric supercapacitors. Metal-organic frameworks (MOFs) have garnered significant attention in the energy storage field due to their high conductivity. As a branch, the zirconium organic framework (UIO-66) is a promising porous material due to its large specific surface area and abundant Zr centers. Graphene oxide (GO) and MXene are very suitable as substrate materials for conducting an MOF due to their abundant active sites and adjustable interlayer distance. The GO/MXene@NiZrP prepared through an in situ composite of GO and Mxene with the hydrothermal method and calcining method showed excellent electrochemical performance. Compared with the precursor UIO-66, the specific capacitance of the final product GO/MXene@NiZrP increases more than ten times, mainly because of its special layered porous structure, and GO/MXene@NiZrP has a larger specific surface area, pore volume, and surface defects caused by unstable Zr4+ than those of UIO-66. Using GO/MXene@NiZrP as the positive electrode and biochar (BC) as the negative electrode, an asymmetric supercapacitor, BC//GO/MXene@NiZrP, is assembled. After 10,000 cycles at a current density of 10 A g-1, the capacitance retention remains at 83.3%, showing excellent cycle stability.

Tuning capacitance of bimetallic ZnCo2O4 using anionic, cationic and non-ionic surfactants by hydrothermal synthesis for high-performance asymmetric supercapacitor

Surface properties of nanomaterials are directly related to their electrochemical performance, with surfactants playing an essential role in their cost-effective synthesis as structure-directing agents and templates. This research article discusses the effects of neutral, cationic, and anionic surfactants on the capacitance of bimetallic ZnCo2O4 nanomaterial, synthesized via a straightforward hydrothermal-annealing method. We investigated how cationic (cetyl-trimethyl ammonium bromide), anionic (sodium dodecyl sulphate), and non-ionic (urea) surfactants influence the electrochemical characteristics of ZnCo2O4 nano-powders. All three surfactant-based ZnCo2O4 electrodes exhibited Faradaic behaviour during electrochemical tests. The ionic nature of the surfactants significantly impacted the charge-storage mechanism, with specific capacitance values rising in the order of Urea (550 Fg−1) < C-TAB (740 Fg−1) < SDS (980 Fg−1) at a 1 Ag−1 in half-cell studies. The ZnCo2O4-SDS displayed the highest surface redox reactivity and superior electrochemical performance, with 426 Fg−1 in full-cell studies, energy density of 230 WhKg−1 (1 Ag−1), power density of 18,213.9 WKg−1 (10 Ag−1), and 93 % capacitance retention is observed over 50,000 cycles (50 Ag−1).

NiCoP@amorphous carbon composites with 3D core-shell structure for high-performance asymmetric supercapacitors

In this paper, a facile bio-templating method is proposed to prepare NiCoP coated on amorphous carbon (NiCoP@AC) composite electrode materials with using bagasse as template and carbon source. NiCoP nanowire network arrays precursors coating on bagasse substrate with high yield were prepared via a novel synthesis strategy utilizing the toluene-water interface reaction process, which subsequently formed as NiCoP@AC composite electrode materials after phosphating process. The assembled core-shell structure attenuated the volume expansion during charging and discharging, additionally, the overall electrical conductivity of the composite was also improved owing to the characteristic of bagasse biochar. The NiCoP@AC electrode exhibited high specific capacitance (1706 F g−1 at 1 A g−1), outstanding rate capability (82.1 % capacity retention from 1 to 20 A g−1) and good cycling stability (retaining 80.0 % capacitance over 5000 cycles). In addition, bagasse biomass activated carbon (BAC) was prepared via a typical alkaline activation process for the use as negative electrode. The as-fabricated NiCoP@AC//BAC supercapacitor displayed a high energy density of 46.2 Wh kg−1 at a power density of 807.3 W kg−1, and an excellent capacitance retention rate (88.5 % after 5000 cycles), suggesting that the as-prepared NiCoP@AC electrode materials have wide application prospects in high-performance supercapacitors.

NiCo layered double hydroxides/carbon dots composites with S-doing for high-performance asymmetric supercapacitors

The pursuit of high-performance electrode materials for supercapacitors has led to the exploration of transition metal layered double hydroxides (LDH), which boast an impressive theoretical specific capacitance. However, their intrinsic limitations, such as poor electronic conductivity and slow diffusion kinetics, have posed significant challenges for their practical implementation. In this work, a NiCo LDH/carbon dots (CDs) composite with S-doping has been meticulously designed to overcome the aforementioned limitations through a synergistic combination of heteroatom doping and carbon incorporation. Utilizing a one-pot hydrothermal method, the composite electrode for the application of asymmetric supercapacitors have been in-situ growth on Ni foam substrate, which not only serves as a robust support but also contributes to the formation of NiCo LDH by providing a uniform Ni source, thereby ensuring strong adhesion and structural integrity. The morphology and microstructures of composites could be finely modulated by adjusting CDs amount. With moderate CDs contents, the optimum electrode S-LDH/CDs-2 exhibits distinctive 3D needle-like spherical morphology, coupled with the ample space for ion diffusion. Consequently, the electrode demonstrates outstanding electrochemical performance, featuring a high areal capacitance of 5157 mF cm−2 at a current density of 2 mA cm−2. Additionally, it exhibits noteworthy rate performance and maintains excellent cycling stability. Integrating the innovative electrode into asymmetric supercapacitors configuration, superior energy density (0.24–0.45 mWh cm−2) and power density (4–20 mW cm−2) as well as good stability have been achieved for the S-LDH/CDs-2//AC device. These results indicate that S-doped NiCo LDH/CDs composite electrode has the desirable potential to be a candidate for energy storage devices.

Eu-viologen based bimetal–organic frameworks nanosheets with Mn atoms anchored on Eu-µ-O skeletons as high-performance negative electrode for flexible asymmetric supercapacitors

Exploring advanced negative electrode materials is imperative to develop high-performance asymmetric supercapacitors for breaking through current energy density limits of supercapacitors, but remains challenging. Herein, a strategy is proposed to create a novel negative electrode by anchoring Mn single-atoms on Eu-viologen metal–organic frameworks (EV-Mn MOFs) nanosheets flowery architectures that self-supported on oxidized carbon cloths (OCC). Such EV-Mn/OCC achieves a negative broadened voltage window (−1 ∼ 0 V) and boosted areal capacitance (840.82 mF cm−2), which is four folds of the isostructural EV/OCC without Mn atoms and surpasses most of currently reported negative electrodes. Also, the EV-Mn/OCC manifests good cycling stability (∼80 % retention for 10,000 cycles). As deduced by the thorough studies of X-ray absorption fine spectra and X-ray photoelectron spectroscopies, the enhanced pseudocapacitance of EV-Mn/OCC definitely correlates to the valence modulation of Mn and Eu through internal electron transfer via Eu-O-Mn bonds on Eu-µ-O skeleton in EV-Mn MOFs. Subsequently, the constructed flexible all-solid-state symmetric supercapacitors employing EV-Mn/OCC as negative electrode can deliver a high energy density (86.89 μWh cm−2) at 1600 μW cm−2, outperforming many asymmetric devices based on traditional negative electrode materials. This work can spur the development of single-atom metallic electronic-modulation strategy for MOFs negative electrode material (MOFs-NEM), and accelerate their applications in flexible energy conversion and storage devices.

Synergistic effects of haematite/hausmannite anchored graphene hybrids in high-energy density asymmetric supercapacitors

Addressing the critical demand for advanced energy storage systems (ESSs) amid escalating global energy needs and population growth, this study pioneers the synthesis of graphene-supported haematite and hausmannite (Gr@Mn3O4@Fe2O3/NF) ternary composite cathodes. These cathodes are tailored for high-performance asymmetric supercapacitors (ASCs), leveraging an economically viable process of fabrication. This innovation represents a significant leap forward, employing cost-effective techniques without compromising efficiency. Synchrotron X-ray absorption spectroscopy (XAS) analysis reveals a distinct blend of Fe and Mn valences, confirming the composite's unique structure. Electrochemical assessment underscores the superior capability of the electrodes, registering an unprecedented specific capacitance of ∼854 F/g in aqueous electrolytes, far surpassing traditional electrodes. Additionally, the composite electrodes maintain ∼70 % capacitance retention and about ∼94 % coulombic efficiency under a high current density of 4 A/g. In an ASC configuration, pairing the Gr@Mn3O4@Fe2O3/NF cathode with an anode made of AC, the ASC achieves the highest capacitance of ∼139 F/g, an energy density of ∼156.3 Wh/kg at a power density of ∼1439 W/kg, coupled with outstanding cyclability in a 1.5 V. This research delineates a scalable pathway for fabricating cost-efficient, high-energy density SCs, heralding a new era of portable electronic devices with enhanced energy storage capabilities.

Facile synthesis of MnMoO4 nanostructures arrays as novel electrode materials for high-performance symmetric and asymmetric supercapacitor

Facile synthesis of MnMoO4 nanostructures arrays as novel electrode materials for high-performance symmetric and asymmetric supercapacitor

Core-shell structured MgCo2O4@Ni(OH)2 nanorods as electrode materials for high-performance asymmetric supercapacitors

In the field of energy storage, supercapacitors have received extensive attention in recent years. However, achieving the expected electrochemical performance and energy density of supercapacitors is still a huge challenge. The design and synthesis of binder-free composite electrode with core–shell structure is an effective strategy to improve the electrochemical performance of supercapacitors. In this paper, a heterogeneous core–shell structured and binder-free electrode material MgCo2O4@Ni(OH)2 (MCO@NH) grown on nickel foam (NF) is prepared by a simple hydrothermal and oil bath method. The unique core–shell structure makes the MCO@NH have a large specific surface area, which provides abundant active sites for ion transport and storage, thereby improving the electrochemical performance. The MCO@NH/NF nanocomposite demonstrates a high specific capacitance (Cs) of 1583 F g−1 at 1 A/g. A solid-state asymmetric supercapacitor (ASC) assembled with MCO@NH/NF and active carbon (AC) exhibits excellent energy density (45 Wh kg−1 at 457.5 W kg−1) and outstanding capacitance (89.51 %) and coulombic efficiency (97.8 %) after 12,000 cycles, evidencing its good operation stability and potential practical applications. Therefore, the prepared core–shell MCO@NH/NF electrode can be a promising candidate for energy storage devices.

Green Synthesis of ZnO Nanoparticles and Ag-Doped ZnO Nanocomposite Utilizing Sansevieria trifasciata for High-Performance Asymmetric Supercapacitors.

This study provides a comprehensive analysis of a biofabricated nanomaterial derived from Sansevieria trifasciata root extract, evaluating its structural, morphological, and optical properties for use in asymmetric supercapacitors. The nanomaterial comprises pristine ZnO nanoparticles (ZnO NPs) and a 1% Ag-doped ZnO nanocomposite (Ag@ZnO NC), synthesized through a green-assisted sol-gel autocombustion method. Employing techniques such as X-ray diffraction, ultraviolet-visible near-infrared, scanning electron microscopy-energy-dispersive X-rayspectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy, the study confirms a hexagonal wurtzite structure and nanocrystallites with spherical and hexagonal shapes (30 nm). Optical analysis reveals a red shift in the band gap with Ag doping, indicating improved conductivity. The material shows potential applications in solar cells, optoelectronics, spintronics, wastewater treatment, and high-performance asymmetric supercapacitors. Raman spectra validate the wurtzite phase and identify intrinsic defects. Electrochemical tests demonstrate remarkable supercapacitive behavior with a 94% capacitance retention after 10,000 cycles, highlighting its promise as advanced asymmetric supercapacitors.

High-performance asymmetric supercapacitor based on hierarchical hydrothermally grown CuS nanostructures

In this work, various hierarchical CuS were fabricated via an efficient one-step hydrothermal process with different surfactants (polyvinyl pyrrolidine (CS-P), Citric acid (CS-C), Oleic acid (CS-O)) and examined as electrode materials for supercapacitors. XRD, FESEM, HRTEM and BET analysis reveal the fabrication of a hexagonal crystal structure with porous microspheres of CuS-PVP having a BJH pore diameter of 16.241 nm. Among these, the CS-P electrode exhibits a superior specific capacitance of 414.28F/g at 1 A/g of current density in the KOH electrolyte. Additionally, an asymmetric supercapacitor built with CS-P as positive and Activated carbon as negative electrodes exhibited a specific energy of 27.95 Wh/kg at 624.96 W/kg of specific power at 2 A/g and demonstrated outstanding cycling stability with 80.6 % persistence of capacitance for 2500 GCD cycles at 10 A/g. Additionally, an ASC device created for use in real life and tested by charging it for 30 s managed to reach a 3-minute 50-second self-discharging duration. Hence, these favourable electrochemical findings indicate that the hydrothermally grown hierarchical CuS-PVP electrode is a bright potential material in energy storage applications.

Photo-assisted charging of heterostructured NiCo2S4@NiCo-LDH composite electrode with remarkable photoelectronic memory effect for high-performance asymmetric supercapacitor

Rational establishment of photo-assisted supercapacitor represents a viable strategy for achieving solar energy conversion and storage. In this study, NiCo2S4@NiCo-LDH (NCS@NC-LDH) composite electrode was effectively synthesized for a highly efficient asymmetric supercapacitor (ASC). Specific capacitance of NCS@NC-LDH under light condition (3286.25 F g−1 at 1 A g−1) demonstrated notable improvement in contrast to that under dark condition (2171.5 F g−1 at 1 A g−1). Meanwhile, NCS@NC-LDH displayed strong photoelectronic memory, as a merely 3 % specific capacitance decreased when discharged under dark compared to that of continuous illumination. Additionally, the assembled aqueous ASC (NCS@NC-LDH//AC) exhibited substantial energy density (83.2 Wh kg−1 at 800 W kg−1) under light condition. Density functional theory (DFT) calculation further demonstrated that the formed matched band facilitated efficient generation-transfer of photoinduced electrons/holes and thus improved the energy storage behavior. We anticipated that this work may offer new perspectives on developing multi-component composite electrodes tailored for high-performance solar-driven electrochemical energy storage.

Controlled preparation of carbon cloth decorated with nanostructured Mn(OH)2/Mn3O4 electrodes for high-performance asymmetric supercapacitors

Environmentally friendly aqueous asymmetric supercapacitors are expected to exhibit excellent energy storage properties, stable performance, and facile production protocols. This study focused on the fabrication and characterisation of an asymmetric supercapacitor (ASC) with a commercial activated carbon (AC) negative electrode and Mn(OH)2/Mn3O4 composite on carbon cloth (hCC) positive electrode. The Mn-based electrode was synthesised using a one-step electrodeposition process. The morphology and crystalline structure of the composite electrode were modified by varying the deposition time of the Mn(OH)2/Mn3O4 nanostructures on carbon cloth substrate which greatly influence the electrochemical performance of the asymmetric systems. The best ASC used the AC electrode and a Mn(OH)2/Mn3O4@hCC electrode prepared using electrodeposition over an optimised time of 3 h. It exhibited a remarkable specific energy density of 40.7 Wh kg−1 at a power density of 100 W kg−1. In addition, this ASC demonstrated stable long-term performance, retaining 88 % of its capacitance after 5000 charge–discharge cycles, showing its great application potential in the field of supercapacitors.

Enhancing heterojunction interface charge transport efficiency in NiCo-LDHs@Co/CoO-CNFs for high-performance asymmetric and zinc-ion hybrid supercapacitors

The lack of active groups and poor dispersion of pristine carbon substrates lead to their inability to composite with other materials effectively, so that the electron transfer between them is inefficient. Therefore, in order to design carbon-based composites with high conductivity and electrochemical properties, the electron transfer between them must be enhanced first. Herein, the Co/CoO quantum dots doped carbon nanofiber (Co/CoO–CNF) materials with mesopore, high degree of graphitization and mechanical flexibility are synthesized via an electrospinning method. Then, ultrathin NiCo-LDHs are uniformly loaded on the Co/CoO-CNFs in situ to form NiCo-LDHs@Co/CoO-CNFs. Benefiting from the Fermi energy level difference and heterointerface between Co/CoO-CNFs (EF = −4.44 eV) and NiCo-LDHs (EF = −2.12 eV), electrons can be tansfered rapidly from NiCo-LDHs to Co/CoO-CNFs during the electrochemical reaction, so that NiCo-LDHs@Co/CoO-CNFs exhibit the excellent specific capacitance of 2055 F g−1 at 1 A g−1. When using in a flexible asymmetric supercapacitor, NiCo-LDHs@Co/CoO-CNFs shows a high energy density of 54.0 W h kg−1 at 760.0 W kg−1. Furthermore, assembled as the Zn-ion hybrid supercapacitor, NiCo-LDHs@Co/CoO-CNFs can also display an ultra-high energy density of 108 W h kg−1 at 914.8 W kg−1, as well as outstanding work durability (the capacitance of 98.2 % after 10,000 cycles).

Polytoluidine blue-coated multiwalled carbon nanotubes: In-situ polymerization based hybrid nanostructure for high performance asymmetric supercapacitors

In this work, a series of multiwalled carbon nanotubes/polytoluidine blue (MWCNTs/PTB) with network structure are synthesized by in-situ oxidative polymerization. Electrochemical performance of MWCNTs/PTB are optimized through precise control of mass ratio between two components. Field emission scanning electron microscope analysis reveals a more homogeneous dispersion of network structure under the mass ratio of 1:3. Prepared MWCNTs/PTB-3 electrode exhibits the highest specific capacity of 232.7C g−1 and satisfactory specific capacity retention of 91.9 % after 5000 charge/discharge cycles in 1.0 M H2SO4 electrolyte. Additionally, the assembled asymmetric supercapacitor exhibits energy density of 13.4 Wh kg−1 at power density of 600 W kg−1 and maintains exceptional cyclic stability. In conclusion, constructing carbon nanotube-supported conductive polymer composite proves to be an effective approach for enhancing the energy storage performance.

High-performance pristine ZIF-67 asymmetric supercapacitor device with excellent energy and power density for energy storage application

The current work describes a simple and safe method for creating ZIF-67 (zeolitic imidazolate framework-67) nanostructures. X-ray diffraction (XRD) patterns reveal that the material exhibits a cubic phase free from contaminating impact. The synthesized material has a notable porosity, a high specific surface area (SSA) of ∼ 1071 m2 g−1, and a clearly defined hexagonal shape with high-resolution transmission electron microscope (HRTEM) analysis. Moreover, the electrochemical analysis in the three-electrode setup shows an extraordinary specific capacitance (CS) of 472 F g−1 and exceptional cyclic performance of 91.6 % retention in a 6 M NaOH aqueous electrolyte. Furthermore, activated carbon (AC) is being used as the negative electrode and ZIF-67 as the positive electrode to design a device with a wide potential window (1.50 V). The outstanding performance of the Asymmetric supercapacitor (ASC) device is evident in its exceptional CS (358 F g−1). This, coupled with its remarkable energy (22 Wh kg−1) and power density (4164 W kg−1), highlights its suitability for demanding energy storage applications. Notably, the device demonstrates extraordinary cyclic stability, retaining over 132 % of its initial capacitance after 5000 charge-discharge cycles, solidifying its long-term reliability. Finally, LEDs (Light Emitting Diodes) of various colors are being illuminated using three series-connected devices. Hence, the recent work is illustrating the possible practical benefit of the ongoing development of supercapacitive energy storage systems.

Stepwise Construction of MoS2@CoAl-LDH/NF 3D Core-Shell Nanoarrays with High Hole Mobility for High-Performance Asymmetric Supercapacitors.

Supercapacitors (SCs) have received widespread attention as excellent energy storage devices, and the design of multicomponent electrode materials and the construction of ingenious structures are the keys to enhancing the performance of SCs. In this paper, MoS2 nanorods were used as the carrier structure to induce the anchoring of CoAl-LDH nanosheets and grow on the surface of nickel foam (NF) in situ, thus obtaining a uniformly distributed MoS2 nanorod@CoAl-LDH nanosheet core-shell nanoarray material (MoS2@CoAl-LDH/NF). On the one hand, the nanorod-structured MoS2 as the core provides high conductivity and support, accelerates electron transfer, and avoids agglomeration of CoAl-LDH nanosheets. On the other hand, CoAl-LDH nanosheet arrays have abundant interfacially active sites, which accelerate the electrolyte penetration and enhance the electrochemical activity. The synergistic effect of the two components and the unique core-shell nanostructure give MoS2@CoAl-LDH/NF a high capacity (14,888.8 mF cm-2 at 2 mA cm-2) and long-term cycling performance (104.4% retention after 5000 charge/discharge cycles). The integrated MoS2@CoAl-LDH/NF//AC device boasts a voltage range spanning from 0 to 1.5 V, achieving a peak energy density of 0.19 mW h cm-2 at 1.5 mW cm-2. Impressively, it maintains a capacitance retention rate of 84.6% after enduring 10,000 cycles, demonstrating exceptional durability and stability.

Application of Fe-based nanocomposites for the preparation of high-performance asymmetric supercapacitors

Application of Fe-based nanocomposites for the preparation of high-performance asymmetric supercapacitors

Facile Synthesis of 3D Cu(OH)2@NiCo-Binary Hydroxide Core–Shell Nanotube Arrays with High Mass Loading for High-Performance Asymmetric Supercapacitors

Facile Synthesis of 3D Cu(OH)₂@NiCo-Binary Hydroxide Core–Shell Nanotube Arrays with High Mass Loading for High-Performance Asymmetric Supercapacitors

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.

Microcubes of ZnSe–SnSe2 Encapsulated within Graphene for High-Performance Asymmetric Supercapacitors

Microcubes of ZnSe–SnSe₂ Encapsulated within Graphene for High-Performance Asymmetric Supercapacitors