Asymmetric Device Research Articles

Mesoporous NiMoO4 nanorod electrode materials for flexible and asymmetric energy storage devices.

Recently, ternary metal oxides as cathode materials have been the focus of research into supercapacitors owing to their high power density and cost-efficient features. The development of excellent electrode materials is the key to improving supercapacitor total performance. Herein, we report several kinds of NiMoO4 nanostructures grown on nickel foam using a simple hydrothermal strategy. The assembled hybrid devices show an energy density of 35.9 W h kg-1 at a power density of 2708 W kg-1. After repeated charging and discharging cycling and bending tests, they show excellent durability performance and mechanical stability performance.

Synthesis of reduced graphene oxide (rGO)/polyaniline (PANI) composite electrode for energy storage: Aqueous asymmetric supercapacitor

Composite materials have gained significant interest for energy storage applications due to their possible synergistic effects. This work describes the synthesis of reduced graphene oxide (rGO)/polyaniline (PANI) composite thin films using chemical bath deposition (CBD) method. A field-emission scanning electron microscope revealed that PANI spikes coated on rGO sheets in rGO/PANI composite. The electrochemical studies of a rGO/PANI composite electrode showed a specific capacitance (Cs) of 1130F/g Cs at a scan rate of 5 mV/s in 1 M H2SO4 electrolyte. The combined effect of rGO with PANI, a aqueous asymmetric supercapacitor device (ASC) with configuration of rGO/PANI/H2SO4/WO3 produced 97F/g Cs at a 5 mV/s scan rate and retained 82 % capacitance after 5,000 galvanostatic charge–discharge cycles. The ASC achieved a high specific energy of 23 Wh kg−1 at a specific power of 732 W kg−1. The electrochemical properties of rGO/PANI composite indicate a feasible method for creating asymmetric supercapacitors.

Synergistic Effects in BFO@NiCoS@CNT//AC Nanocomposite for High-Capacity Energy Storage Systems

Here, we synthesized a nanocomposite electrode material for high-performance asymmetric supercapacitor devices (ASCD) made of bismuth ferrite (BFO) nanocomposite and nickel cobalt sulfide with carbon nanotubes (NiCoS@CNT). To fabricate the BFO@NiCoS@CNT nanocomposite, a simple hydrothermal process was used. Electrochemical impedance spectroscopy, galvanostatic charge/discharge measurements, and cyclic voltammetry were used to evaluate the electrochemical experiments. At a scan speed of 5 mVs−1, the BFO@NiCoS@CNT nanocomposite exhibited a specific capacitance of 2890 Fg−1, surpassing pure BFO@NiCoS. Furthermore, the nanocomposite displayed excellent cyclic stability, retaining around 87.8% of its capacity retention even after 5000 cycles. Another notable property is its energy density (Ed) of 71 Whkg−1 at the power density (Pd) of 2400 Wkg−1. Based on these promising findings, BFO@NiCoS@CNT nanocomposite might be used to fabricate electrodes for high-performance hybrid supercapacitors. Our research indicates that this is the first report of a BFO@NiCoS@CNT nanocomposite used as an asymmetric supercapacitor.

Development of Flexible High‐Efficient Aluminum ion Supercapacitors With 2D Niobium MXene Electrode

ABSTRACTA high‐performance aluminum‐ion supercapacitor is fabricated using 2D few‐layered Nb2CTx MXene, as an active electrode material and Al2(SO4)3 electrolyte for efficient energy storage. Nb2CTx MXene has been synthesized from Nb2AlC MAX phase using HF. Nb2CTx MXene coated on carbon cloth (Nb@CC) displays a capacitance of 307 F g−1 with 90% coulombic efficiency. The specific capacitance of Nb@CC in Al2(SO4)3 electrolyte is exceptionally high compared to those (≤32.2 F g−1) in H2SO4, Na2SO4, and MgSO4 electrolytes. Both symmetric and asymmetric aluminum ion supercapacitors are fabricated with Nb@CC electrode. The Nb@CC//Nb@CC symmetric device exhibits a capacitance of 122 F g−1 with a high energy density (Ed) of 33.2 Wh kg−1 at 1.41 kW kg−1 power density (Pd). An asymmetric supercapacitor device (ASC), Nb@CC//CNT@CC, with carbon nanotube (CNT@CC) cathode delivers a maximum Ed of 24.7 Wh kg−1 at 3.41 kW kg−1 Pd and excellent stability with 90% capacitance retention after 4000 cycles. A remarkably high Pd of 34 kW kg−1 is maintained with 13.2 Wh kg−1 Ed, and the rate capability is 53% for a 10‐fold increase in current density. These results offer the feasibility of efficient aqueous supercapacitors with Al‐ion as guest species, presenting new possibilities for supercapacitors.

Graphene-enhanced manganese dioxide functional ink infused with polyaniline for high-performance screen-printed micro supercapacitor

In the world of miniature advancements in technology, a current champion has emerged: the micro supercapacitors. In order to fabricate these micro-supercapacitors, we have developed a promising and user-friendly approach for printing a conductive functional ink containing a ternary composite of manganese dioxide (MnO2) nanoparticles, Graphene, and polyaniline (PANI) as a dopant. Screen-printing technique was employed to fabricate micro-supercapacitors using the nanocomposite conductive ink. The performance of the energy storage device was examined using flexible symmetric and asymmetric, with an aqueous 1 M KOH electrolyte. According to this strategy, the characterisation and electrochemical study results revealed that doping PANI into both symmetric and asymmetric devices significantly increased the material’s capacitive performance of areal capacitance 167 mFcm−2 for MnO2/Graphene/PANI-5 composite (MGP-5) and 292.5 mFcm−2 for asymmetric supercapacitor (ASSC) at 5 mVs−1. Furthermore, the asymmetric supercapacitor displayed outstanding cyclic stability, retaining 93.6% of its capacitance after 10000 cycles. This underscores the possibility of incorporating polyaniline (PANI) into MnO2 and graphene matrices as efficient blueprints for the development of superior electrode materials. The improvement represents a significant step forward, opening avenues for the future development of novel devices and their integration into top-of-the-line flexible energy storage systems.

Enhancing capacitive performance of MoS2 through Fe doping: Synthesis, characterization, and electrochemical evaluation for supercapacitor applications

The capacitive performance of bare MoS2 is limited due to its poor electronic conductivity. Therefore, we tried to dope different weight percentages (2 %, 4 %, 6 %, 8 %, and 10 %) of Iron (Fe) into the MoS2 to promote more active sites to improve its energy storage capacity. Given this, we have synthesized bare MoS2 and Fe-doped MoS2 using the hydrothermal method for electrochemical charge storage application. The effect of doping was well assessed using different physicochemical tests. The electrochemical properties of the bare MoS2 and Fe-doped MoS2 were evaluated using a three-electrode setup in a 3 M KOH aqueous electrolyte. As a result, the 8 % Fe-doped MoS2 electrode material demonstrates the maximum specific capacitance (CSP) of 545 F/g @ 1 A/g with 84.8 % capacitive retention over 2000 cycles at 5 A/g. Additionally, we fabricated an asymmetric solid-state supercapacitor device, which reveals a high CSP of 74.28 F/g at 4 A/g with an energy density of 72.79 Wh/kg and a power density of 10.07 kW/kg. The results asserted that the Fe-doped MoS2 is a potential electrode material for supercapacitor application.

Conjugated cobalt‐based metal complex nanosheet for fabricating high‐performance supercapacitor electrode

AbstractIn order to cope with the increasingly serious problem of energy shortage, supercapacitors have been developed as a clean and renewable energy source, and the supercapacitors with excellent energy density and long cycle life are imperative. Here, by employing a facile liquid–liquid (L‐L) interfacial method at room temperature (RT), a set of two‐dimensional (2D) metal complex nanosheets N1‐N3 have been synthesized by the facile coordination between Co2+ ion and 2,3,6,7,10,11‐hexaiminotriphenylene (HITP). Given the layered superstructure with well‐ordered nanopores, the N1‐N3 electrodes displayed excellent capacities of 4751.9, 5770.9 and 6075.2 F g−1 at 1 A g−1, and a good cyclic stability with 92.1% capacity retention after 1000 cycles for the N3 electrode. The asymmetric supercapacitor device with N3 as the positive electrode delivers a maximum energy density of 238.2 Wh kg−1 at a power density of 1610.1 W kg−1 and an excellent cycling stability with a capacitance retention of 109.1% after 5000 cycles. This is the best electroactive bottom‐up metal complex nanosheet reported so far for use in supercapacitor, which greatly expands the applicability of this 2D nanomaterial in energy device applications.image

Room temperature and rapid synthesis of ZnMn2O4 nanostructured spinel using deep eutectic solvent for high energy asymmetric supercapacitors

Recently, binary metal oxides have drawn significant attention due to their interesting physico-chemical characteristics, makes them suitable for supercapacitor application. In the present work, high surface area spinel ZnMn2O4 is prepared using a reaction of deep eutectic solvent (DES) containing zinc chloride, choline chloride and glycerol with manganese precursor (KMnO4). The DES serves as both precursor and template for the growth of ZnMn2O4. Interestingly, the spinel structure of ZnMn2O4 is prepared within one-minute time at room temperature using DES route makes this process cost-effective. The reaction between DES and manganese precursors can be halted at any stage with the addition of water to the reaction mixture as it reduces existing bonding interaction between the reactants. With this advantage, we have varied reaction time between DES and KMnO4 and further studied the effect of reaction time on surface area and electrochemical properties of the obtained ZnMn2O4. The ZnMn2O4 sample, where DES and KMnO4 reacted for 10 min (ZnMnO-10) showed highest surface area of 118.5 m2/g with a pore volume of 0.19 cm3/g. Further, the ZnMnO-10 sample showed a good specific capacitance of 499.58 F/g at 0.1 A/g in a neutral electrolyte (1 M Na2SO4). The symmetric supercapacitor device fabricated using ZnMnO-10//ZnMnO-10 with energy and power density of 39.40 Wh/kg and 7.06 kW/kg, respectively. Further, the asymmetric supercapacitor device is also assembled using ZnMn2O4 and agro waste-derived carbon (HBC-800) showed an excellent Csp of 331.24 F/g at 0.2 A/g with energy density and power density of 74.50 Wh/kg and 5.4 kW/kg, respectively. The current work proposes the rapid and facile synthesis of spinel ZnMn2O4 utilizing green DES and the obtained ZnMn2O4 showed good specific capacitance and energy density for both symmetric and asymmetric supercapacitor devices.

High-Energy–Density Fiber Supercapacitors Based on Transition Metal Oxide Nanoribbon Yarns for Comprehensive Wearable Electronics

AbstractFiber supercapacitors (FSs) based on transition metal oxides (TMOs) have garnered considerable attention as energy storage solutions for wearable electronics owing to their exceptional characteristics, including superior comfortability and low weights. These materials are known to exhibit high energy densities, high specific capacitances, and fast redox reactions. However, current fabrication methods for these structures primarily rely on chemical deposition, often resulting in undesirable material structures and necessitating the use of additives, which can degrade the electrochemical performance of such structures. Herein, physically deposited TMO nanoribbon yarns generated via delamination engineering of nanopatterned TMO/metal/TMO trilayer arrays are proposed as potential high-performance FSs. To prepare these arrays, the target materials were initially deposited using a nanoline mold, and subsequently, the nanoribbon was suspended through selective plasma etching to obtain the desired twisted yarn structures. Because of the direct formation of TMOs on Ni electrodes, a high energy/power density and excellent electrochemical stability were achieved in asymmetric FS devices incorporating CoNixOy nanoribbon yarns and graphene fibers. Furthermore, a triboelectric nanogenerator, pressure sensor, and flexible light-emitting diode were synergistically combined with the FS. The integration of wearable electronic components, encompassing energy harvesting, energy storage, and powering sensing/display devices, is promising for the development of future smart textiles. Graphical Abstract

High Performance Flexible Supercapacitor Based on Single Precursor Derived NiFe2O4 Spinel with Tailored Cationic Distribution and Oxygen Vacancies in Acidic Medium

AbstractSpinel metal oxides are extensively studied for supercapacitors (SCs) in alkaline electrolytes, where charge storage capacity is limited by surface site availability due to surface reconstruction forming metal hydroxides/oxyhydroxides. The use of an acidic medium, which can boost the charge storage capacity of spinel oxides offering an additional channel of intercalation‐deintercalation of protons, is underexplored. Moreover, the impact of chemical compositions and the cationic distributions is crucial on the electrocatalysis performance of spinel oxides, however, such a correlation is first time reported for charge storage properties of spinel ferrite NiFe2O4 nanoparticles (NFO NPs). Besides, a low‐cost and scalable synthesis of NFO NPs involving the thermal decomposition of Ni‐Fe glycolate, followed by controlled air‐calcination is reported. Thus crafted NFO NPs‐based device shows impressive specific capacitance (2112 F g−1 at 10 A g−1) in half‐cell configuration. A flexible all‐solid‐state asymmetric device (full‐cell) configuration depicts impressive energy density (20.7 Wh kg−1), power density (4000 W kg−1), gravimetric capacitance (140 F g−1 at 2 A g−1), and retention of its performance (≈75% after 10,000 charging/discharging cycles). The results depict a new insight toward the tuning of electronic and charge storage properties in NFO, which otherwise are predominately attributed to only the crystallite size and morphological effects.

Superior Electrochemical Performance and Cyclic Stability of WS2@CoMgS//AC Composite on the Nickel-Foam for Asymmetric Supercapacitor Devices

Two-dimensional (2D) sulfide-based transition metal dichalcogenides (TMDs) have shown their crucial importance in energy storage devices. In this study, the tungsten disulfide (WS2) nanosheets were combined with hydrothermally synthesized cobalt magnesium sulfide (CoMgS) nanocomposite for use as efficient electrodes in supercapattery energy storage devices. The characteristics of the WS2@CoMgS nanocomposite were better than those of the WS2 and CoMgS electrodes. XRD, SEM, and BET analyses were performed on the nanocomposite to examine its structure, morphology, and surface area in depth. In three-electrode assemblies, the composite (WS2@CoMgS) electrode showed a high specific capacity of 874.39 C g−1 or 1457.31 F g−1 at 1.5 A g−1. The supercapattery device (WS2@CoMgS//AC) electrode demonstrated a specific capacity of 325 C g−1 with an exceptional rate capability retention of 91% and columbic efficiency of 92% over 7000 cycles, according to electrochemical studies. Additionally, the high energy storage capacity of the WS2@CoMgS composite electrode was proved by structural and morphological investigations.

Biocompatible Janus microparticle synthesis in a microfluidic device.

Janus particles are popular in recent years due to their anisotropic physical and chemical properties. Even though there are several established synthesis methods for Janus particles, microfluidics-based methods are convenient and reliable due to low reagent consumption, monodispersity of the resultant particles and efficient control over reaction conditions. In this work a simple droplet-based microfluidic technique is utilized to synthesize magnetically anisotropic TiO2-Fe2O3 Janus microparticles. Two droplets containing reagents for Janus particle were merged by using an asymmetric device such that the resulting droplet contained the constituents within its two hemispheres distinct from each other. The synthesized Janus particles were observed under the optical microscope and the scanning electron microscope. Moreover, a detailed in vitro characterization of these particles was completed, and it was shown that these particles have a potential use for biomedical applications.

Quantum Graphene Asymmetric Devices for Harvesting Electromagnetic Energy.

We present here the fabrication at the wafer level and the electrical performance of two types of graphene diodes: ballistic trapezoidal-shaped graphene diodes and lateral tunneling graphene diodes. In the case of the ballistic trapezoidal-shaped graphene diode, we observe a large DC current of 200 µA at a DC bias voltage of ±2 V and a large voltage responsivity of 2000 v/w, while in the case of the lateral tunneling graphene diodes, we obtain a DC current of 1.5 mA at a DC bias voltage of ±2 V, with a voltage responsivity of 3000 v/w. An extended analysis of the defects produced during the fabrication process and their influences on the graphene diode performance is also presented.

Synergy of Charge Storage Properties of CuO and Polypyrrole in Composite CuO-Polypyrrole Electrodes for Asymmetric Supercapacitor Devices

Synergy of Charge Storage Properties of CuO and Polypyrrole in Composite CuO-Polypyrrole Electrodes for Asymmetric Supercapacitor Devices

Synthesis of Binder-Free, Low-Resistant Randomly Orientated Nanorod/Sheet ZnS-MoS2 as Electrode Materials for Portable Energy Storage Applications.

The scientific community needs to conduct research on novel electrodes for portable energy storage (PES) devices like supercapacitors (S-Cs) and lithium-ion batteries (Li-ion-Bs) to overcome energy crises, especially in rural areas where no electrical poles are available. Herein, the nanostructured MoS2 and ZnS-MoS2 E-Ms consisting of nanoparticles/rods/sheets (N-Ps-Rs-Ss) are deposited on hierarchical nickel foam by a homemade chemical vapor deposition (H-M CVD) route. The X-ray diffraction patterns confirm the formation of polycrystalline films growing along various orientations, whereas the field-emission scanning electron microscope analysis confirms the formation of N-Ps-Rs-Ss. The change in structural and microstructural parameters indicates the existence of defects improving the energy storage ability of the deposited ZnS-MoS2@Ni-F electrodes. The specific capacitances of MoS2@Ni-F and ZnS-MoS2@Ni-F electrodes are found to be 1763 and 3565 F/g at 0.5 mV/s and 1451 and 3032 F/g at 1 A/g, respectively. The growing behavior of impedance graphs indicates their capacitive nature; however, the shifting of impedance curves toward y-axis indicates that the increasing diffusion rates due to the formation of nanostructures of ZnS-MoS2 results in low impedance. An excellent energy storage performance, minimum capacity fading, and improved electrical conductivity of the deposited E-Ms are due to the combined contributions of the electrical double layer and pseudocapacitor nature, which is again confirmed by theoretical Dunn's model. The absence of charge transfer resistance and good capacitance retention (95%) even after 10,000 cycles indicates that the deposited E-Ms are better for PES devices like S-Cs and Li-ion-Bs than MoS2 E-Ms. The assembled asymmetric supercapacitor device exhibited the maximum specific capacitance = 996 F/g, energy density = 354-285 W h/kg, power density = 2400-24,000 W/kg, capacitance retention = 95% and Coulombic efficiency = 100% even after a long charging-discharging of 10,000 cycles.

Hierarchical NiCo2O4 needle-like heterostructure arrays anchored on WO3 as high- performance asymmetric supercapacitors for energy storage applications

The current work employs a novel approach to construct a composite nanostructure to improve the capacitive performance of a supercapacitor device. The work involved preparing cube-shaped WO3 particles and depositing them onto the surface of NiCo2O4 needles using a microwave technique. The structure of the composites enables efficient paths for ion transport and electron diffusion in supercapacitors. The hybrid composite electrode demonstrates a specific capacitance of 716 F g−1 at a current density of 5 Ag−1. The asymmetric capacitor device, which utilizes NiCo2O4@WO3 as the positive electrode and AC as the negative electrode, exhibits an energy density of 48.57 Wh kg−1 at a power density of 1120 W kg−1. In addition, the NiCo2O4@WO3//AC device has a favourable cycle life, maintaining 85.7 % of its capacitance retention after 10,000 cycles. The findings demonstrate the potential of NiCo2O4@WO3//AC to be used in the development of advanced hybrid electrodes for improved supercapacitors.

Designing high-performance hybrid supercapacitors and electrochemical sensors with carbon nanotube-embedded silver manganese sulfide@AC@NF composites

Recently, there has been a lot of interest in hybrid supercapacitors due to their amazing capacity to store energy, surpassing the energy storage capability of both conventional supercapacitors and batteries. In this work, physical integration of silver manganese sulphide (AgMnS) into carbon nanotubes was achieved using hydrothermal synthesis. A comprehensive evaluation was conducted on the material's electrical characteristics. With this composite functioning as the positive electrode and activated carbon (AC) acting as the negative, an asymmetric device configuration was used. The AgMnS@CNT composite demonstrated a notable specific capacity of 358.0C/g at a 2.0 A/g rate. The material demonstrated a remarkable 49.5 Wh/kg energy density and a remarkable 1505.0 W/kg power density. 83.3 % of the initial capacity of the composite material remained even after 5000 cycles. This illustrates its continued stability and suggests that its operating lifetime may be increased. Besides; the hybrid electrode is used to detect the glucose in the specimen up to 0 mM to 2 mM. The electrochemical device showed a remarkable value of sensitivity of 1402 μA·cm−2 mM−1. As the field of energy storage technology develops, this dynamic composite may reveal completely new and exciting options.

Handy preparation of a carbon-Ni/NiO/Ni(OH)2 composite and its application in high-performance supercapacitors

The growing demand for energy storage is required with the development of the intermittent renewable energy. Supercapacitors are a promising energy storage equipment, but their capacitive performance mainly depend on the electrode material. To obtain a high-performance electrode material for supercapacitors, in this work, a carbon-Ni/NiO/Ni(OH)2 composite was prepared from pine sawdust as the carbon precursor by integrating CO2 gasification and electrochemical deposition. It is found that the carbon-ternary nickel composite shows good electrochemical performance due to synergistic effect of the unique hierarchical structure and components involving porous carbon skeleton, Ni0 and NiO nanoparticles, and Ni(OH)2 microspheres. The composite displays the specific capacitance of 1875.6 F/g (or 937.8 C/g) at a current density of 1 A/g in a traditional three-electrode system. The assembled asymmetric supercapacitor device presents a potential window of 1.6 V, along with the energy density of 38.24 Wh/kg at the power density of 400 W/kg (or 22.60 Wh/kg at 2000 W/kg). After 6000 charge-discharge cycles, the capacitance retention ratio of the assembled supercapacitor reaches up to 105 %, exhibiting a good application potential. This work provides a novel and handy strategy for preparation of ternary nickel-based composite for advanced supercapacitors.

Room temperature thermal rectification in suspended asymmetric graphene ribbon

Thermal rectifiers are essential in optimizing heat dissipation in solid-state devices to enhance energy efficiency, reliability, and overall performance. In this study, we experimentally investigate the thermal rectification phenomenon in suspended asymmetric graphene ribbons (GRs). The asymmetry within the graphene is introduced by incorporating periodic parallel nanoribbons on one side of the GR while maintaining the other side in a pristine form. Our findings reveal a substantial thermal rectification effect in these asymmetric graphene devices, reaching up to 45% at room temperature and increasing further at lower environmental temperatures. This effect is attributed to a significant thermal conductivity contrast between pristine graphene and nanoribbon graphene within the asymmetric structure. We observe that the incorporation of nanoribbons leads to a notable reduction in thermal conductivity, primarily due to phonon scattering and bottleneck effects near the nanoribbon edges. These findings suggest that graphene structures exhibiting asymmetry, facilitated by parallel nanoribbons, hold promise for effective heat management at the nanoscale level and the development of practical phononic devices.

Surface active sites enriched CoNiFe-Manganite: An effective electrode for high-performance supercapacitors

The electrochemical performance of ternary metal oxide electrodes exhibiting faradic battery-type characteristics, represents a promising and desirable solution for addressing the ongoing energy crisis. In the current investigation, we present the optimized solution-combustion synthesis of Co0.03Ni0.97FeγMn2-γO4 nanoparticles, with varying Fe concentrations (γ=0.01, 0.05, 0.10 %), specifically tailored for application in supercapacitors. The Styrofoam-natured (CNMFO:1) exhibited outstanding specific capacitance, reaching 489.12 Fg−1 at a scan rate of 50 mVs−1. Moreover, validation through galvanostatic charge-discharge (GCD) investigations substantiated a notable specific capacitance of 391.41 Fg−1, achieved at a current density of 1Ag−1. In addition, the CNMFO:1 electrode demonstrated remarkable cyclic stability, retaining 83.87 % of its initial performance over 6000 cycles. Similarly, the fabricated asymmetric device of (CNMFO:1||AC) also demonstrated a maximum specific capacitance of 33.86 Fg−1 under a current density of 1Ag−1, which exhibits good energy and power density of 10.52 Wh Kg−1 and 749.34 W Kg−1 respectively. From the overall observation, the CNMFO:1 electrode exhibited notable cyclic stability and electrochemical reversibility. This research recommends that CNMFO:1 nanocomposite have an extraordinary potential for evolution of active electrode materials forthcoming supercapacitors in energy storage system.