High-performance Asymmetric Supercapacitors Research Articles

Wire-shaped, all-solid-state, high-performance flexible asymmetric supercapacitors based on (Mn,Fe) oxides/reduced graphene oxide/oxidized carbon nanotube fiber hybrid electrodes

Wire-shaped flexible supercapacitors (FSCs) have attracted tremendous attention due to their tiny volume, lightweight, high flexibility, and wearability. In the present study, we report the MnO2- or Fe2O3-loaded three-dimensional (3D) nanostructure networks of reduced graphene oxide (rGO) composite on oxidized CNT (denoted as the OCNTF/3D-rGO/MnO2 and OCNTF/3D-rGO/Fe2O3) fibers as the cathode and anode, respectively, for the fabrication of a high-performance, wire-shaped, all-solid-state, flexible asymmetric supercapacitor (FASC). To this end, the 3D-rGO/OCNTF hierarchical structure was electrochemically fabricated, followed by further pulse electrodeposition of MnO2 and Fe2O3, respectively, into the 3D porous graphene networks and the insides of the OCNTF. As such, they were restricted to nano-sized particles and linked by the graphene and the OCNTF. The OCNTF/3D-rGO/MnO2 as the cathode was assembled with the OCNTF/3D-rGO/Fe2O3 as the anode with the carboxymethyl cellulose sodium (CMC)-Na2SO4 gel electrolyte, producing a wire-shaped, all-solid-state FASC that achieved a high specific capacitance of 59.2 F·cm−3 (171 mF·cm−2) and an exceptional energy density of 26.7 mWh·cm−3. The FASC device also showed good flexibility and cyclability, promising to advance power sources for wearable electronics.

Design and preparation of hierarchical porous carbon-based materials with bionic “ant nest” structure for high performance asymmetric supercapacitors

Rational design of electrodes to broaden the working potential window is an attractive approach to improve the energy density of asymmetric supercapacitors. Herein, a simple non-solvent-induced phase separation method was used to construct a bionic "ant nest" three-dimensional hierarchical porous carbon (HPC) without any template, realizing a three-dimensional interlaced interconnection network structure similar to that of a natural ant nest, which adsorbs more ions through a larger accessible area and facilitates the bi-continuous transport of ions and electrons. Further, the aqueous asymmetric supercapacitor assembled with MnO2-modified HPC (HPC/MnO2) as the positive electrode and nitrogen-doped HPC (NHPC) as the negative electrode has an energy density as high as 21 Wh kg−1 at a power density of 410 W kg−1, and as high as 17 Wh kg−1 even at a power density of 13 kW kg−1. The device exhibits an excellent electrochemical performance over a potential window of 0–1.6 V.

Oxygen-doped NiCoP derived from Ni-MOFs for high performance asymmetric supercapacitor.

Oxygen doping strategy is one of the most effective methods to improve the electrochemical properties of nickel-cobalt phosphide (NiCoP)-based capacitors by adjusting its inherent electronic structure. In this paper, O-doped NiCoP microspheres derived from porous nanostructured nickel metal-organic frameworks (Ni-MOFs) were constructed through solvothermal method followed by phosphorization treatment. The O-doping concentration has a siginificant influence on the rate performance and cycle stability. The optimized O-doped NiCoP electrode material shows a specific capacitance of 632.4 F-g-1at 1 A-g-1and a high retention rate of 56.9% at 20 A g-1. The corresponding NiCoP-based asymmetric supercapacitor exhibits a high energy density of 30.1 Wh kg-1when the power density is 800.9 W kg-1, and can still maintain 82.1% of the initial capacity after 10 000 cycles at 5 A g-1.

Construction of high-performance solid-state asymmetric supercapacitor based on Ti3C2Tx MXene/CuS positive electrode and Fe2O3@rGO negative electrode

The reasonable and logical construction of electrode materials along with greater electrochemical features and solid architectural design is an effective strategy for boosting the electrochemical performance of supercapacitors. In this paper, Ti3C2Tx MXene/CuS composites have been synthesized using an electrostatic attraction connection of negatively charged 2D few-layered Ti3C2Tx MXene sheets with positively charged CuS nanoparticles and are investigated as an asymmetric supercapacitor active material. The addition of MXene enhances the conductivity and specific surface area of the MXene/CuS electrode compared to their individual components. The as-prepared MXene/CuS electrode exhibits a high specific capacity (1541.6C g−1 (2569.3 F g−1)) at 1 A g−1 and an excellent cycle performance with 93.5 % capacity retention after 10,000 cycles. Furthermore, Fe2O3 nanoparticles/reduced graphene oxide (rGO) nanosheets (Fe2O3@rGO) composite electrode is also produced. The designed Fe2O3@rGO negative electrode with a wide operation voltage window of 1.1 V can deliver a capacity of 255.6C g−1 at 1 A g−1. Ultimately, the MXene/CuS//Fe2O3@rGO device displays energy density of 74.1 Wh kg−1 and power density of 849.8 W kg−1. In addition, the ASC shows excellent cycling stability of 91.3 % capacity retention after 10,000 cycles.

Novel 2D CeO2 nanoflakes as a high-performance asymmetric supercapacitor electrode material

Enhancing the performance and durability of benchmarked metal catalysts using nanostructured non-metallic materials is an active area of research that is exciting from both a fundamental and an application perspective. The 2D CeO2 nanoflakes are characterized using structural and electrochemical techniques. Galvanostatic charge-discharge (GCD) revealed that the material delivers a specific capacitance of 1801 F/g at 1 A/g, among the best-reported values for transition and rare earth metal oxide electrode material. Due to its nanoflake-like structure, the sample has a modest surface area (12.6 m2/g). Asymmetric supercapacitor device (CeO2//AC) fabricated delivered an energy density of 57.6 Wh/kg and a power density of 771 W/kg with 83 % capacitance retention after 1000 cycles in 3 M KOH. This study reveals that CeO2 is a promising electrode material for energy storage applications.

Controllable synthesis of MnSe2/Co0.85Se nanosheets as a binder-free electrode for high-performance asymmetric supercapacitors

With the increasingly serious environmental pollution and depletion of natural resources, it is necessary to develop efficient and environmentally friendly energy storage equipments to alleviate the problem of resource shortage. In this study, a novel MnSe2/Co0.85Se (MCSe) electrode was successfully prepared using a simple, green and environmentally friendly electrodeposition method. The MCSe electrode exhibited good electrochemical performance, and possesses a high specific capacity (Cs) of 1380C/g at a current density (CD) of 1 A/g. An asymmetric supercapacitor (ASC) assembled using a positive electrode (the MCSe electrode) and a negative electrode (active carbon (AC) electrode) delivered a high specific energy density (Es) of 49.63 Wh/kg at a specific power density (Ps) of 750 W/kg. Hence, this study provides a new approach for designing metal selenides for energy storage and conversion.

A novel sustainable cornstalk-derived porous carbon composited with in-situ polymerized polyaniline nanowires for high-performance asymmetric supercapacitors

In this work, a novel renewable cornstalk-derived porous carbon/polyaniline (PC/PANI) composite used as the electrode material for high-performance asymmetric supercapacitors is synthesized by a facile in-situ polymerization of aniline in the presence of cornstalk-derived PC. The three-dimensional hierarchical PC is successfully prepared by a KOH activation route combined with sodium chloride (NaCl) and potassium chloride (KCl) as the salt templates and cornstalk as carbon source, which the specific surface area reaches 1181.6 m2·g−1. As an electrode material, the PC/PANI possess a high specific capacitance of 1041.2 F·g−1 at 0.5 A g−1 in 1 M H2SO4 electrolyte, compared with the bare PC (234.1 F·g−1) or single PANI (335.6 F·g−1). Moreover, what is noteworthy is that the asymmetric supercapacitor based on PC/PANI electrode exhibits high energy density (31.2 Wh·kg−1) and power density (8135.2 W·kg−1) in a voltage window of 0–1.8 V, as well as an excellent cycling stability (91.2 % capacitance retention over more than 10,000 cycles), revealing that the superior properties of PC/PANI electrode have a substantial promotion for the development of high-performance supercapacitors.

Synthesis of NiCoMn ternary metal–organic frameworks with a hollow spherical structure for high-performance asymmetric supercapacitors

Synthesis of NiCoMn ternary metal–organic frameworks with a hollow spherical structure for high-performance asymmetric supercapacitors

Alpha-Ni(OH)2 nanoflakes incorporated on MOF derived ZnO hybrid Faradaic arrays for high-performance asymmetric supercapacitor

Elegant transition metal oxide nanocomposites with modified structures are required to enhance specific capacitance of supercapacitors. A core–shell embedded ZnO@Ni(OH)2 nanocomposite electrode with porous nano-flakes morphology has been synthesised by low temperature wet chemical method. Ni(OH)2 nano flakes are decorated on ZnO derived from Zeolitic Imidazolate Framework-8 (ZIF-8) by a facile technique. The wurtzite hexagonal phase of ZnO and α-Ni(OH)2 are evidenced by XRD analysis. FTIR spectral analysis confirms the Zn-O, Ni-OH and interlamellar hydrogen bonded Ni(OH)2 layers of the ZnO @Ni(OH)2 sample. FESEM and elemental mapping results reveal core–shell embedded architecture of ZnO@Ni(OH)2. The presence of primary elements such as Zn, Ni, and O of ZnO, Ni(OH)2 and their oxidation states are confirmed in XPS results with the existence of binding energies corresponding to Zn 2P3/2, Zn 2P1/2, Ni 2P3/2, Ni 2P1/2, and O 1s peaks. The ZnO@Ni(OH)2 nanocomposite electrode in a three electrode system exhibits a high specific capacitance of 510F g−1 at 1 A g−1 and a good cyclability for 2000 cycles at 10 A g−1 with 77% capacity retention. Also, in the case of an asymmetrical supercapacitor, it was delivered the specific capacitance of 45F g−1 at 1 A g−1. Furthermore, a good cyclability for 10,000 cycles with capacity retention of 76.25%, and a high power density of 1595.5 W kg−1 are obtained. The excellent electrochemical behaviour of ZnO@Ni(OH)2 nanocomposite favoured by the core–shell embedded architecture is discussed as a futuristic pseudocapacitor energy storage material.

Preparation of high-performance asymmetric supercapacitors based on NiCo2S4 nanospheres and CuO-MOF nanosheets on carbon fibers

Highly efficient and low-cost supercapacitors (SCs) with excellent energy storing capacity are highly demanded to fabricate modern portable and wearable electronic devices. Herein, NiCo2S4 nanospheres and CuO-MOF nanosheets were fabricated on flexible carbon fibers (CF) by one-step hydrothermal solvent method, employed as two effective electrode materials. Accordingly, the cathode (CuO-MOF@CF) and anode (NiCo2S4@CF) plays a prominent role in energy storage properties due to large specific surface areas, by providing comparative capacities of 953 F/g and 1571 F/g, respectively. Remarkably, benefited from the synergistic effect, the designed asymmetric supercapacitor (SC) CuO-MOF@CF//NiCo2S4@CF exhibits a voltage window of ∼3.0 V, which demonstrates an impressive specific capacitance of 2426.6 F/g at a current density of 700 mA/g, the maximum energy density (ED) of 164.85 Wh/kg, as well as an excellent power density (PD) of 3780 W/kg. Even after 10,000 cycles of charge and discharge, the specific capacitance retention rate still reaches 96.43 %. This study offers a cost-effective and simple strategy for rational design of energy storage configurations for favorable electrochemical performances, emphasizing great potentials in next-generation supercapacitors application.

Hydrothermal synthesis of rGO/ZnCoS composite for high performance asymmetric supercapacitor and HER applications

Here, we describe the successful hydrothermal synthesis of zinc cobalt sulfide (ZCS) and reduced graphene oxide/zinc cobalt sulfide (rZCS) nanoparticles (NPs). X-Ray diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (TEM) characterizations were used to test ZCS and rZCS NPs. Through the use of cyclic voltammetry (CV), galvanostatic charge and discharge (GCD), and electrochemical impedance (EIS), the electrochemical performance of the produced materials was examined. Electrochemical hydrogen evolution reactions and supercapacitor applications required the development of ZCS and rZCS electrodes. 10 mA cm−2 is driven by rZCS electrodes at 132 mV HER overpotential. High specific capacitance of 891 F g−1 at 1 A g−1 current density and 99 % cyclic stability are displayed by the rZCS electrode even after 5000 cycles. The specific capacitance of (181 F g−1 at 1 A g−1 current density), capacitance retention of (92 % after 10,000 cycles at 1 A g−1, and energy and power density of (29 Wh kg−1 and 2215 W kg−1), respectively, are recommended for asymmetric supercapacitors made from cells using rZCS and rGO. Given this, the produced electrodes material holds potential for use in energy storage technologies.

A rational preparation strategy of phase tuned MoO3 nanostructures for high-performance all-solid asymmetric supercapacitor

In this work, phase and morphology-tuned MoO3 nanostructures are synthesized through a novel modified co-precipitation method, and their electrochemical properties are investigated. For the first time, such a simple surfactant-assisted synthesis process aided by minor temperature variations is reported which results in phase transition of the nanoparticles from h-MoO3 nano-rods to α-MoO3 nano-flakes. The nanostructures thus developed are highly porous and crystalline with significantly large specific surface area as compared to previous literature. The theoretical bandgap energy of the optimized sample calculated using Perdew-Zunger local density approximation (LDA) is in good agreement with the experimental findings. An overall structural, morphological, and surface-behavioural analysis predicts the electrochemical superiority in 2D α-MoO3. The cyclic voltammetry and galvano-potentiometry measurements of 2D α-MoO3 in the potential window of −0.6 V to +0.2 V present the highest pseudo-supercapacitive response with a maximum specific capacitance of 829 F g−1 at 2 A g−1 as compared to h-MoO3 (452 F g−1) and h@α-MoO3(783 F g−1). Thus, the MoO3 2D nanostructures synthesized through our novel synthesis technique display excellent specific capacitance as compared to previous reported data. Additionally, α-MoO3 exhibits a galvanostatic charging-discharging cyclic stability of about 91% after 2000 cycles, indicating that it can serve as an excellent electrode material for supercapacitors. A solid-state asymmetric supercapacitor device is successfully constructed using α-MoO3 which can light up 4 red LEDs for 10 s. The specific energy density of the device reaches a maximum value of 36.3 W h kg−1 at the power density of 50 W kg−1.

Controlled synthesis of 2H-WSe2@rGO nanocomposites: An efficient electrode material for high performance asymmetric supercapacitor device application

In this article, 2H-WSe2 (WSe2) and 2H-WSe2@rGO (WSe2@rGO) nanocomposite are synthesized using one-step solvothermal method. The synthesized materials are characterized using different experimental techniques. The specific capacitance (SC) of WSe2@rGO electrode is calculated to be 1371 Fg−1 at 0.5 Ag−1 in 3 M KOH electrolyte. The value of SC of WSe2@rGO electrode is twice than that of the value of SC of WSe2 electrode. The WSe2@rGO electrode retains 88.0% of its initial SC after 3000 cycles. An asymmetric supercapacitor (WSe2@rGO//AC) device is fabricated by taking activated carbon (AC) and WSe2@rGO as negative and positive electrodes, respectively. The energy density of the fabricated device is calculated to be 51.5 Whkg−1 at the power density of 2133.3 Wkg−1. The WSe2@rGO//AC device retains 82.0% of its initial value of SC at 7 Ag−1 current density after 3000 cycles. The WSe2@rGO//AC device illuminates red, green, and blue light emitting diode (LEDs) for 20, 10, and 5 min, respectively after being charged for 30 s. Thus, the WSe2@rGO may be used as an effective electrode material for fabricating efficient and stable energy storage devices.

Synthesis of flower-like Mn-Co-MoS2 compounds for high-performance asymmetric supercapacitors

Synthesis of flower-like Mn-Co-MoS2 compounds for high-performance asymmetric supercapacitors

Rice straw-derived activated carbon/nickel cobalt sulfide composite for high performance asymmetric supercapacitor

Rice straw (RS) is a biomass waste that causes environmental and health issues. In this paper, the rice straw-derived activated carbon (RSAC) was obtained by KOH chemical activation method using RS as a raw material. The NiCo2S4/RSAC composite was synthesized via a facile two-step controlled sulfurization route. Nanostructural NiCo2S4 species were anchored on RSAC to form a 3D network structure. NiCo2S4 provides higher capacitance for the composite electrode and RSAC supplies high conductivity, large specific surface area, and 3D porous structure, which are beneficial to the fast electron and ion transport for composite electrode. The layered porous nanostructure of RSAC can also act as an ion buffer storage layer and shorten the ion diffusion path. The composites were systematically characterized and studied as electrode materials for supercapacitors. The results show that the NiCo2S4/RSAC composite electrode has high specific capacitance (643.4 F g−1 at 1 A g−1) and good rate capability (329.7 F g−1 at 20 A g−1). The assembled NiCo2S4/RSAC//RSAC asymmetric supercapacitor exhibits a stable potential window of 0–1.6 V, delivers a high energy density of 24.5 W h kg−1 at a power density of 700 W kg−1, and 19.06 Wh kg−1 at a high power density of 7001.6 W kg−1, which are higher than those of reported similar devices. These results indicate that the as-prepared NiCo2S4/RSAC composite has potential applications in the field of practical energy storage.

Carboxymethylcellulose/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate membrane after dimethyl sulfoxide treatment for flexible and high electrochemical performance asymmetric supercapacitors

As the requirements for wearable electronic devices continue to increase, the development of bendable and foldable supercapacitors is becoming critical. However, it is still challenging to design free-standing electrodes with flexibility and high electrical conductivity. Herein, using carboxymethylcellulose (CMC) as the biological template and poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as the electroactive material, a flexible CMC/PEDOT:PSS membrane with a cross-linked mesh structure was firstly synthesized by a facile in-situ polymerization and vacuum filtration process. Subsequently, the CMC/PEDOT:PSS membrane was further treated with dimethyl sulfoxide (DMSO) to remove the excess PSS, thereby enhancing their electrochemical performance. The results showed that the best performing hybrid membrane had good mechanical properties (tensile strength of 48.1 MPa) and high electrical conductivity (45.1 S cm−1). The assembled asymmetric supercapacitor (ASC) is capable of delivering an energy density of 181.9 μW h cm−2 at a power density of 750 μW cm−2 and maintains an initial capacitance of 93.4 % and a coulombic efficiency of 100 % after 10,000 GCD cycles, demonstrating an ultra-long cycle life. Moreover, good electrochemical properties can be retained even in the bent and folded state. Therefore, the hybrid membrane electrode with both flexibility and high electrochemical performance has great potential for application in wearable electronics.

Synthesis of dandelion-like bimetallic nickel‑cobalt metal-organic framework as an efficient cathode for high-performance asymmetric supercapacitors

This study employed pyromellitic acid (PMA) to synthesize a NiCo metal-organic framework (MOF) for supercapacitors. The resultant, NiCo-MOF (PMA), revealed a dandelion-like structure with a surface area reaching 500.7 m2 g−1. At the current density of 1 A g−1, the NiCo-MOF (PMA) produced an impressive specific capacitance value of 918.8 F g−1. It retained 61.1 % of the capacitance obtained at 1 A g−1 even after increasing the current density to 10 A g−1. Moreover, the 64.3 % capacitance retention was achieved even after 10,000 cycles of charging/discharging at 10 A g−1. More importantly, the asymmetric supercapacitor (ASC) based on the NiCo-MOF (PMA) cathode demonstrated a specific capacitance of 83.47 F g−1 at 0.5 A g−1, and 80.34 % of its initial capacitance was still maintained after 5000 cycles at 5 A g−1. The ASC delivered an energy density of 23.88 Wh kg−1 at a power density of 750 W kg−1. Two ASCs in a series successfully powered 120 green LED lights for 21 min, illustrating its potential practical applications.

Insight into the synergistic effect of 2D/2D layered metal selenides wrapped nickel boride nanoparticles based ternary heterostructure for constructing asymmetric supercapacitors with excellent energy density

Tuning the structural and electronic properties of layered metal selenides is a highly feasible approach for developing high-performance asymmetric supercapacitors (ASCs). In this work, a ternary heterostructure of yttrium diselenide/molybdenum diselenide (YSe2/MoSe2) with amorphous nickel boride nanoparticles (NixB NPs) was prepared by a simple hydrothermal method followed by a liquid phase route. Interestingly, this ternary heterostructure consists of multiple layers of YSe2/MoSe2 nanosheets uniformly wrapped by NixB NPs over the entire surface. The characterization results by X-ray diffraction, Raman, and X-ray photoelectron spectroscopy showed that the strong synergism between YSe2/MoSe2 and NixB NPs indicates an obvious electron transfer from NixB to the YSe2/MoSe2 hybrid, which contributes to the enhancement of the electrical conductivity of the electrode. Due to its exclusive heterostructure network, the single YSe2/MoSe2/NixB electrode achieved a specific capacitance of 893.3 F/g at 1 A/g and a capacity retention of 128.17% over 5000 cycles. In addition, the asymmetric YSe2/MoSe2/NixB||rGO device with a working potential of 1.6 V showed an impressive energy density of 39.5 Wh kg−1 with a power density of 800 W kg−1 and excellent cycling stability with 85.60% capacity retention after 5000 cycles in aqueous electrolyte. This result of the designed ASC device encourages the development of a new platform for the design of electrode materials based on metal selenides and metal borides.

Synthesis of nanosphere-like vanadium selenide cathode for high performance asymmetric hybrid supercapacitors

Vanadium selenide electrodes exhibit promising candidates for supercapacitor application, owing to their exotic electronic properties. Exploring more facile synthesis strategies undoubtedly promote the development of vanadium selenide electrodes that from laboratory to practical application, while it was still a challenging. In this work, we provided a facile electrodeposition method to prepare vanadium selenide cathodes for asymmetric hybrid supercapacitors. By controlling the deposition technique, nanosphere-like vanadium selenide cathode or microrod-like selenium were achieved. Electrochemical tests indicated that the prepared vanadium selenide cathode exhibited high capacitance feature (921.6 F/g at a current density of 1 A/g), due to the high ion diffusion ability in the vanadium selenide nanosphere electrode. The charge storage mechanism and reaction kinetics of the prepared vanadium selenide were further investigated and results indicated a mixed effect of pseudocapacitance and battery-type together contributed to the energy storage, meaning a hybrid capacitor. The further assembly hybrid supercapacitor exhibited excellent rate performance and good cycling stability. Moreover, density functional theory calculations demonstrated that the electrode material possessed appropriate adsorption energy of OH− with a low ion diffusion barrier.

The configuration of BiFe-PBA derived Bi2O3/BiFeO3 rectangular nanorods and NiCo-LDH/rGO for high-performance asymmetric hybrid supercapacitor with high energy density

The rectangular nanorods microstructure with abundant pores can reduce structural damage caused by the volume contraction during charging-discharging processes and enhance the specific capacitance. In this work, to enhance the energy density and accelerate the marketable applications of supercapacitors, Bi2O3/BiFeO3 rectangular nanorods with rich mesoporous structure derived from the iron‑bismuth based Prussian blue analogue are rationally designed to achieve a large specific capacitance through precipitation and annealing measures. There are a huge specific capacity of 741 F g−1 and long cycle life. The NiCo-LDH/rGO (954 F g−1) demonstrated an impressive stability of 86 % after 10,000 cycles and is utilized to establish asymmetric supercapacitor device. Amazingly, the NiCo-LDH/rGO//Bi2O3/BiFeO3 device achieves an enormous energy density of 59.7 Wh kg−1 at 800 W kg−1. In addition, the capacity retention ratio is 79.3 % after 7000 cycles. The work has suggested that Bi2O3/BiFeO3 has great potential as a negative electrode of supercapacitors.