High-performance Asymmetric Supercapacitors Research Articles

Design of high-performance asymmetric supercapacitors (Cu-BDC@Ni1.5Mn0.5-LDH//V2O3/C@Fe0.75Mn0.65O) and study of electrode materials

Based on the idea of increasing the energy storage capacity of MOFs material and improving the LDH arrangement distribution, an electrode material with large specific surface area and high electrochemical performance is designed with MOFs as the core and LDH as the shell. In this paper, the spherical flower-shaped core-shell material Cu-BDC@Ni1.5Mn0.5-LDH (N1.5M0.5C) is synthesized using simple solvothermal and hydrothermal methods. The material has a specific capacitance of 2252 F/g at a current density of 1 A/g and a capacitance retention of 90.14 % after 10,000 charge and discharge cycles at a current density of 10 A/g. In addition, the supercapacitor cathode material V2O3/C@Fe0.75Mn0.65O (FMVO) with good performance is constructed by growing Fe0.75Mn0.65O with large specific capacitance on the surface of V2O3/C with good conductivity. The FMVO negative electrode material can achieve a specific capacitance of 1261.3 F/g (at a current density of 1 A/g), while the material has a capacitance retention of 89.13 % (4 A/g) after 5000 charge/discharge cycles. The two electrode materials are assembled into an asymmetric supercapacitor (ASC), which achieves an energy density of 137.4 Wh/kg at a power density of 800 W/kg. The capacity retention rate is 81.17 % after 10,000 charges and discharges (10 A/g). We connect two Cu-BDC@Ni1.5Mn0.5-LDH//V2O3/C@Fe0.75Mn0.65O coin cell batteries in series, which can light up the LED light bulb for 50 min, indicating that it has good practical application potential.

Superhydrophilic nickel hydroxide ultrathin nanosheets enable high-performance asymmetric supercapacitors

Superhydrophilic nickel hydroxide ultrathin nanosheets enable high-performance asymmetric supercapacitors

Facile preparation of CoMoO4/NiCo2O4 nano-sphere anode materials and their performance in asymmetric supercapacitors

CoMoO4/NiCo2O4 electrodes with a three-dimensional nano-sphere structure have been successfully prepared by a combination of hydrothermal and calcination methods. The electrode material exhibits a high specific capacitance of 1175 F g−1 at 1 A/g, excellent multiplicative performance (74.2 % capacity at 15 A/g) and good cycling stability (85.9 % specific capacitance retention after 10,000 cycles). The asymmetric supercapacitor was constructed using activated carbon (AC) as the negative electrode, showing excellent energy density (27.7 wh kg−1) and power density (806 W kg−1). It also has an extremely long operating life, maintaining a specific capacitance of 78.3 % after 5000 cycles at current densities up to 6 A/g. The results indicate that the synthesized mixed transition metal oxides CoMoO4/NiCo2O4 are promising as composite electrode materials for high-performance asymmetric supercapacitors.

High-performance aqueous asymmetric supercapacitors based on a cathode of carbon nanotube/NiCo2O4 nanograss-supported MnCoP nanosheets on Ni foam

In this paper, we report a cathode with the good comprehensive electrochemical performance by electrochemically growing MnCoP nanosheets on NiCo2O4 nanograss hydrothermally grown on carbon nanotube (CNT)-coated Ni foam. A capacitance of 4787.3 mF cm−2 at 1 mA cm−2, high rate performance (3126.2 mF cm−2 at 30 mA cm−2), as well as good cycle stability is delivered by the cathode. By employing this cathode, the anode of activated carbon on carbon cloth, and the electrolyte of 2 M KOH aqueous solution, we assembled an aqueous asymmetric supercapacitor, which exhibits an energy density of 0.390 mWh cm−2 at 0.825 mW cm−2 and good cycle stability of 85.7 % capacitance retention after 20,000 cycles at 10 mA cm−2.

Green synthesis of MnO2 via plant extracts and its composite with exfoliated graphene for high-performance asymmetric supercapacitors

Pure MnO2 nanostructure oxides were synthesized by a green synthesis method using purified natural extracts of watercress (MW) and spinach (MS) as benign and economical reducing agents for KMnO4. The MnO2/graphene composites (GMW and GMS) were prepared through a physical mixing process, in which MnO2 oxide was uniformly loaded on graphene sheets. The composition, morphology, and microstructure of the as-prepared oxides and composites were characterized using X-ray diffraction (XRD), Thermal gravimetric analysis (TGA), Raman, Scanning electron microscope (SEM), and Transmission electron microscope (TEM). Additionally, the supercapacitive performance was examined by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and galvanostatic charge/discharge (GCD). The results imply that the composites GMS and GMW exhibit specific capacitances of 334 and 500 F/g at 1 A/g, respectively, and GMW shows a capacitance retention of 71 % after 7000 cycles at 200 mV/s. Herein, the charge storage mechanism in MnO2/graphene composites is discussed in detail. An asymmetric supercapacitor (ASC) was assembled using the GMW composite and graphene as positive and negative electrodes, respectively. The as-assembled ASC device GMW//GE was scanned reversibly at a voltage of 0–1.8 V and showed a specific capacitance of 167 F/g at 0.5 A/g with a rate capability of 77 % (128.3 F/g at 5 A/g). Moreover, the ASC exhibited excellent cycle stability of 94 % after 2000 cycles and an energy density of 18.9 Wh/kg at a power density of 2.25 kW/kg. These encouraging results showed enormous potential in developing supercapacitors with enhanced performance for practical applications.

Facile synthesis of synergetic MoO2/MoS2@GO nanohybrid as energy-efficient electrode material for high-performance asymmetric supercapacitor applications

Rechargeable batteries and supercapacitors have been unitized extensively for energy storage applications, but each possesses its downsides, such as gradual charge transfer and low energy density, respectively. Hybrid supercapacitors are gaining extreme consideration due to their versatility in merging both power density and energy storage performance to an optimum level. Still, increasing energy and power density requires significant attention for their utilization in industrial applications. For this purpose, a prospective MoO2/MoS2@GO ternary nanohybrid is synthesized by employing a wet-chemical-aided approach and used as a synergistic electrode for high-performance asymmetric supercapacitor applications. FESEM images revealed that the enriched active sites, provided by highly porous shape, MoS2-covered MoO2 nanoparticles interconnected with large area GO sheets facilitate quicker ions transport along with an exceptional surface area. From half-cell measurements, the integrated electrode displayed a high specific capacitance of 1530 F/g at a current density of 2 A/g. For practical applications, an asymmetric device (ASC) device MoO2/MoS2@GO||AC||KOH was assembled which displayed the specific energy and specific power of 76 Wh/kg and 825 W/kg, respectively, in conjunction with excellent capacitance retention of 91.3 % after 10,000 continuous cycles. The theoretical Dunn model was used to validate experimental findings by quantitatively analyzing the maximum diffusive and capacitive contribution of 78 % (10 mV/s) and 72 % (100 mV/s) to overall ASC device capacity, respectively. These fascinating results show that graphene-hybridized metal oxide/sulfide composites could potentially be a great choice for high-performance energy and power applications in industrial, biomedical, and sensing technologies.

Solvent triggering assembly of self-supported MXene hydrogel for high performance asymmetric supercapacitors

Constructing 3D porous structure of MXene (Ti3C2Tx) is an efficient approach to prevent nanosheets restacking and realize prominent electrochemical functionality. However, the assembly of self-supported 3D Ti3C2Tx architecture is difficult due to the inherent rigidity and superior hydrophilicity of Ti3C2Tx nanosheets. Herein, a solvent-triggering gelation strategy is developed using polar aprotic N,N-Dimethylformamide and polar protic H2O as co-solvent to enhance hydrogen bonding and Ti-O-Ti covalent bonding between Ti3C2Tx nanosheets. Thereby, self-supported Ti3C2Tx hydrogel (MH12/5:5) in absence of any crosslinkers or substrates has been successfully fabricated. The MH12/5:5 hydrogel exhibits excellent specific capacitance of 384.4 F g1 and superb rate capability of 61 % in a broad current density range of 1–100 A g−1. Asymmetric supercapacitor has been assembled using MH12/5:5 hydrogel as negative electrode and a polyaniline hydrogel as positive electrode, which presents high energy density of 21.2 Wh kg−1. This solvent-triggering gelation strategy points toward a promising direction to develop self-supported MXene hydrogels for high performance energy storage devices.

Construction of binder-free 3-D porous NiMn LDH electrode materials for high performance asymmetric supercapacitors using dynamic hydrogen bubbles as template

Three-dimensional porous Ni/NiMn layered double hydroxides (3-D Ni/NiMn LDH) with enhanced specific capacitance and superior cycle stability were loaded on nickel foam (NNM/NF) by combining dynamic hydrogen bubble template (DHBT) and electrodeposition methods. The optimized NNM-2/NF electrode for supercapacitors (SCs) possessed high specific capacitance (2755.36 F g–1 at 1 A g–1) and considerable capacitance retention (71.25% after 5000 consecutive cycles at 20 A g–1). When NNM-2/NF and active carbon (AC) were used to construct an asymmetric supercapacitor (ASC) device, it achieves a high specific energy density of 41.75 Wh kg–1 at a power density of 2700.09 W kg–1 and an excellent cycling performance (109.85% capacitance retention after 5000 cycles at 20 A g–1). The practical energy storage applicability of this device was demonstrated by the lighting of an LED bulb when two NNM-2/NF//AC devices were connected in series. This work provided potential strategy to promote the further application of porous Ni/NiMn LDH electrodes in new-generation energy storage.

Ni0.5Co0.5WO4@f-MWCNTs/GO nanocomposite with improved supercapattery activity as the electrode for asymmetric supercapacitor device

Developing electrode materials that possess both high capacitance and cycling stability is a significant challenge for creating high-performance asymmetric supercapacitors. In this study, the invariant hierarchical mesoporous 3D urchin-like Ni0.5Co0.5WO4@f-MWCNTs/GO composite as electrode material was synthesized through a straightforward hydrothermal process and characterized by spectroscopic and electrochemical methods and its supercapattery activity was tested. The restricted-Hartree Fock/semiempirical parametrization method (RHF/PM6) was used to perform calculations and optimization of the structures of various materials. The synthesized catalyst showed a high capacitance of 1166.7 F g−1 at 1 A g−1. Moreover, the assembled solid-state asymmetric supercapacitor (ASC) supplies a high specific capacity of 266.25 F g−1 at 1 A g−1, a power density of 703.12 W kg−1, and an energy density of 83.33 Wh kg−1. Long-term cycling tests showed that the device retained around 87 % of its capacitance after 5000 charge-discharge cycles at a current density of 5 A g−1. The superior performance of the composite can be attributed to its mesoporous structure, the synergistic effect of its components, and stability. This study presents a novel approach for constructing a 3D structure using binary metal tungstate and carbon-based materials, which holds great potential for use in next-generation energy storage devices.

Optimized 3D interconnected foam-like NiO@rGO composite as a binder-free electrode for high-performance asymmetric supercapacitor

Bonding of transition metal oxides and highly conductive carbon materials to exploit the synergistic effect of both materials has been proven to be an efficient means to develop high-capacity electrode materials. A unique interconnected foam-like NiO@rGO structure was constructed by loading the NiO nanoparticles onto rGO frameworks as a binder-free supercapacitor electrode via three steps including hydrothermal reaction, electrodeposition and heating treatment. The morphology and crystallinity were tuned by controlling the electrodeposition time and heating temperature, and the electrochemical properties of the NiO@rGO composites were systematically investigated. The optimized NiO@rGO-250 composite showed excellent electrochemical properties (1399 F g−1 at 1 A g−1) and superior cycling stability. Furthermore, an asymmetric supercapacitor using NiO@rGO and active carbon as two electrodes achieved a high specific energy of 40.4 Wh k g−1 at a specific power of 750 W k g−1.

Chemisynthesized tungsten oxide (WO3) electrodes for high-performance asymmetric supercapacitor application: effect of deposition time

Chemisynthesized tungsten oxide (WO3) electrodes for high-performance asymmetric supercapacitor application: effect of deposition time

Integrating V-doped CoP on Ti3C2Tx MXene-incorporated hollow carbon nanofibers as a freestanding positrode and MOF-derived carbon nanotube negatrode for flexible supercapacitors

Novel architectural electrode materials that are freestanding and exhibit improved electrochemical performances in flexible asymmetric supercapacitors are urgently needed; however, designing these materials is challenging. Herein, a Ti3C2TX MXene-aligned hollow carbon fiber (MX/HCF) is engineered and vanadium-doped cobalt phosphide nanorod arrays are grown on it (V-CoP@MX/HCF) and applied for supercapacitor positrode. V doping modulates the surface structure and electronic environment of CoP nanorods grown over conductive and flexible MX/HCFs. As expected, the optimized V-CoP@MX/HCF exhibits a better electrochemical performance (1896.8Fg−1) than that of CoP@MX/HCF and CoP@HCF. For the negative electrode, zeolitic imidazolate framework-67 (ZIF-67) grown on electrospun polyacrylonitrile (PAN) fibers is converted to cobalt nanoparticle-encapsulated nitrogen-doped carbon nanotubes at carbon nanofibers (Co-CNT@CNF) by a simple heat treatment without the burden of external catalysts and reducing gases. The as-designed freestanding Co-CNT@CNF delivers a specific capacitance of 405.5Fg−1 with superior cycling stability. A flexible asymmetric supercapacitor (V-CoP@MX/HCF//Co-CNT@CNF) is designed that unveil remarkable electrochemical properties, such as a high energy density of 72.4 Wh kg−1 at 800.12 W kg−1 and good capacitance retention (91.4 %) after 10,000 charge/discharge cycles. Furthermore, the device can maintain a consistent performance regardless of the bending degree. More importantly, this work provides new opportunities to rationally design novel freestanding cathodes and anodes for high-performance flexible asymmetric supercapacitors.

Composite electrode materials based on nickel cobalt sulfide/carbon nanotubes to enhance the Redox activity for high performance Asymmetric supercapacitor devices

Asymmetric supercapacitor or supercapattery, is a unique device that combines the best features of both supercapacitors and batteries. Specifically, it offers improved cycle life and specific power, which are the strengths of supercapacitors, along with the high energy density that batteries are known for. This technology represents a significant advancement in energy storage and has the potential to revolutionize various industries. In this work, nickel cobalt sulfide (NiCoS) was synthesized through a hydrothermal process and then physically mixed with carbon nanotubes (CNTs). The electrical characteristics of the material were analyzed using a three-electrode and a two-electrode setup. In a three-electrode system, NiCoS/CNTs composite showed a specific capacity of 1542.1 Cg−1 at 2.5 Ag−1. In an asymmetric device, the negative and positive electrode was activated carbon (AC) and NiCoS/CNTs, respectively. The composite of NiCoS/CNTs exhibited a specific capacity of 161.3 Cg−1, which is noteworthy. Additionally, the material demonstrated an exceptional energy density of 35.5 Whkg−1 and a power density of 1800 Wkg−1. The capacity retention of the composite material was 84.0% after 5000 cycles. The composite electrode materials of transition metal sulfide and CNT in a 90/10 wt. ratio provides an opportunity to develop high-performance energy storage devices.

Preparation of a High-Performance Asymmetric Supercapacitor by Recycling Aluminum Paper and Filter Components of Heated Tobacco.

In this study, Al paper and cellulose acetate (CA) filters derived from heated tobacco waste were successfully converted into current collectors and active materials for a supercapacitor device. Typically, heated tobacco contains electrically discontinuous Al paper. First, Al was extracted from the tobacco waste using HCl to produce Lewis acid (AlCl3). This acid was then used in an Al electrodeposition process utilizing the chloroaluminate ionic liquid reaction between the acid and the base (RCl) at room temperature. To enhance the conductivity, a supplementary coating of Al metal was applied to the Al paper through electrodeposition, thus re-establishing the electrical continuity of the discontinuous parts and forming an Al-coated current collector. Moreover, the CA filters were carbonized under a nitrogen atmosphere, yielding carbon precursors (C-CA) for the supercapacitor electrodes. To further enhance the electrochemical performance, nickel oxide (NiO) was incorporated into C-CA, resulting in C-CA@NiO with pseudocapacitance. The specific surface area of CA increased with carbonization and the subsequent incorporation of NiO. The as-synthesized C-CA and C-CA@NiO materials were applied to an Al-coated current collector to obtain C-CA- and C-CA@NiO-based electrodes, exhibiting stable electrochemical behavior in the voltage range of -1.0 to 0 V and 0 to 1.0 V, respectively. An asymmetric supercapacitor (ASC) device was assembled with C-CA@NiO and C-CA as the positive and negative electrodes, respectively. This ASC device demonstrated a high specific capacitance of 40.8 F g-1, while widening the operating voltage window to 2.0 V. The high electrochemical performance of the device is attributed to the successful Al electrodeposition, which facilitates the electrical conductivity and increased porosity of the C-CA@NiO and C-CA materials. To the best of our knowledge, this is a pioneering study in regards to the conversion of biomass waste into current collectors and active materials to fabricate a practical ASC device. Our findings highlight the potential of reusing Al paper and CA filters from heated tobacco waste as essential components of energy storage devices.

Sugar gourd-like NiCo layered double hydroxide @ NiMoO4 hierarchical core-shell material for high-performance asymmetric supercapacitors

As one of the strategies for preparing electrode materials with excellent electrochemical properties, reasonable structural design has been widely used to improve the performance of electrode materials. In this work, a core-shell structure with a unique sugar gourd-like appearance is designed, in which NiMoO4 (NMO) nanorods string together multiple NiCo-LDH (NCL) hollow nanocages to form NCL@NMO/NF composite electrode. The unique structure and the synergistic effect between the two substances give it high cycle stability and excellent capacity. DFT calculations show that the electronic structure at the NCL@NMO heterogeneous interface changes after compounding, so that electrons are transferred from the NCL to the NMO surface, and the difference in the work function promotes the transfer of electrons and accelerates the reaction rate. When used as the positive electrode of asymmetric supercapacitor (ASC), the material exhibits a specific capacity of 1186 C g−1 at a current density of 1 A g−1, and a capacity retention rate of 85.5 % after 5000 cycles at 5 A g−1. In addition, the assembled NCL@NMO/NF//AC ASC exhibits a high energy density of 80.38 Wh kg−1 at a power density of 800 W kg−1, and has high cycle stability (89.2 % after 5000 cycles).

Utilization mild and green oxidation method to fabricate skin-core structure derived from non melting-shrinkage PPS carbon fibers with ultra-thin nanosheets for high performance asymmetric supercapacitor

Two crucial elements that aid in the development of supercapacitors are the usage of distinctive components and the creation of optimal structures. In view of this, polyphenylene sulfide (PPS) non-woven fibers prepared by melt-blast process are used as carbon precursor, and oxidized polyphenylene sulfide (O-PPS) was prepared by an innovative and environmentally friendly oxidation method, which overcame the melting and shrinkage of PPS at high temperatures. After carbonization, flexible carbon fibers (SCFs) with high specific surface area were formed by O-PPS. Then, polypyrrole (PPy) and metal-organic framework material (Co-MOF) are successively grown on the SCFs, and the Co-MOF is transformed into layered double hydroxide (NiCo-LDH) ultra-thin nanosheets (ca. 4 nm) with rich electrochemical active sites under nickel nitrate etching, which obtains the “skin-core” structure composite electrode. This materials' high specific capacitance of 1705.6 F g−1 at 1 A g−1, and the electrode reaction process is governed by the pseudocapacitance characteristic. Asymmetric supercapacitors assembled with porous carbon possesses 46.96 Wh kg−1 at 725 W kg−1, and the capacitance retention rate is 81.47% after 8500 cycles. This research provides a new combination of ultra-thin NiCo-LDH nanosheets with carbon fiber for energy storage while improving the energy density of supercapacitors.

Scalable synthesis of K+/Na+ pre-intercalated α-MnO2 via Taylor fluid flow-assisted hydrothermal reaction for high-performance asymmetric supercapacitors

In this work, a two-step synthetic method: Couette-Taylor flow mixing, and hydrothermal method have been used to synthesize α-manganese oxide pre-intercalated with sodium and potassium ions (Na+/K+@α-MnO2) for supercapacitor application. In addition, the effects of different aqueous electrolytes on the energy storage properties of the Na+/K+@α-MnO2 nanowires are investigated. The results show that KOH is a better electrolyte than NaOH and Na2SO4, with Na+/K+@α-MnO2 nanowires exhibiting a higher specific capacitance of 124 Fg−1 in KOH electrolyte. This is attributed to the high ionic conductivity and smaller hydrate ion of K+ ions. DFT calculations reveal that K+ ions have a higher adsorption energy and a higher partial density of states than Na+ ions, indicating more favourable pseudocapacitive behaviour for K+ ions compared to Na+ ions. Furthermore, the asymmetric capacitor device based on N-CNTs@CF//Na+/K+@α-MnO2 delivers a specific energy density of 21 Wh kg−1 and a specific power density of 450 W kg−1, with excellent cycling performance (∼94 % capacity retention after 5,000 cycles). Our findings demonstrate that the pre-intercalation of α-MnO2 nanowires account for enhanced cycling stability, as well as higher capacitance.

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.