High-performance Hybrid Supercapacitors Research Articles

In-situ growth of series-connected CoNi2S4 hollow nanocages strung by carbon nanotubes for high-performance hybrid supercapacitors

For supercapacitors (SCs), there is an urgent need to develop positive materials with excellent electrochemical performance. In this work, in-situ growth of series-connected CoNi2S4 hollow nanocages derived from zeolitic imidazolate framework-67 (ZIF-67) and strung by carboxylated carbon nanotubes (C-CNTs) were successfully synthesized through a two-step ordered ion etching/exchange procedure. The special connection structure and synergistic effect between CoNi2S4 nanocages and C-CNTs greatly improve the electrochemical performance of the hybrid (CoNi2S4/C-CNTs), in which porous CoNi2S4 hollow nanocages offer electrochemical active sites and fast ion diffusion channels, while C-CNTs provide electron transport paths. The optimized hybrid, CoNi2S4/C-CNTs20, exhibits excellent electrochemical performance with a high specific capacity (1314.6C g−1 at 1 A g−1) and an impressive rate capability (72.1 % retention at 20 A g−1). Furthermore, the hybrid supercapacitor (HSC) using CoNi2S4/C-CNTs20 and active rice husk carbon (ARHC) as the positive and negative electrodes, respectively, demonstrates an outstanding energy density of 47.9 Wh kg−1 at a power density of 800 W kg−1 and remarkable cycling stability of 90 % at 5 A g−1 after 8500 cycles. Our work will open up a brand-new strategy to oriented design electrode materials for various energy storage devices.

Rational design of hierarchical reduced graphene oxide/Ni(OH)2 heterojunction with long cycle life for high-performance hybrid supercapacitors

As a promising electrode material for supercapacitors, Ni(OH)2 is very attractive owing to its superior theoretical specific capacitance; however, its inferior cycling stability remains a barrier. Herein, we constructed a reduced graphene oxide (rGO)/Ni(OH)2 heterojunction via a facile electrostatic self-assembly route, in which Ni(OH)2 nanoflakes were planted on the surface of the rGO substrate, resulting in an increased specific surface area and accelerated electron/ion transport while inheriting the outstanding cycling stability of rGO. The optimal rGO/Ni(OH)2 electrode afforded a great specific capacitance of 2251.6 F/g at 2 A/g and a remarkable cycling stability of ∼104.9 % after 5000 cycles. The rGO/Ni(OH)2//activated carbon hybrid supercapacitor (HSC) achieved an outstanding energy density of 35.4 Wh/kg at 775 W/kg and a cycling durability of ∼98.8 % after 10,000 cycles. Furthermore, two HSCs were connected in series to light 27 parallel red LEDs for more than 210 s, exhibiting enormous application prospects in supercapacitors.

Synthesis of Fe₃O₄/FeS₂ composites via MOF-templated sulfurization for high-performance hybrid supercapacitors

The development of advanced anode materials for supercapacitors is crucial for driving innovation in the field of new energy technologies. Although iron-based materials exhibit significant potential, their electrical conductivity and cyclic stability remain challenges. In this study, Fe3O4/FeS2 composites were successfully synthesized using a sacrificial MOF template and a solid-state sulfurization process. The composite preserved the original morphology of Fe-MOF, while numerous nanoscale particles were generated through heterogeneous sulfurization. Notably, the SMFO-2 composite exhibited a specific capacity of 208.5 mAh g−1 at a current density of 1 A g⁻¹. When integrated into a hybrid supercapacitor (HSC) with SMFO-2 serving as the anode and super-electric activated carbon (AC) as the cathode, the device exhibited excellent electrochemical performance. Specifically, it achieved a capacity retention rate of 78.6 % after 10,000 charge-discharge cycles at 2 A g⁻¹. Furthermore, the HSC achieved an optimal energy density of 28.8 Wh kg⁻¹ at a power density of 375 W kg⁻¹, successfully powering a small bulb, highlighting its strong potential of the Fe3O4/FeS2 composite for real-world practical applications.

Yolk@shell layered NiCo hydroxide: Controllable synthesis, sulfuration and electrochemical applications for hybrid supercapacitors

Developing electrode materials with rational structures is an important strategy for constructing high-performance hybrid supercapacitors (HSCs). Herein, designing a yolk@shell structure composed of layered nickel-cobalt hydroxide with a Ni/Co feed ratio of 4:1 (denoted as layered Ni4Co1 hydroxide) and nickel-cobalt sulfide with a sulfuration duration of 2 h (labeled as Ni4Co1S-2h) to enhance the capacity and stabilize the cyclic performances of HSCs was conducted. The yolk@shell structured microspheres of layered Ni4Co1 hydroxide were synthesized using a cetyltriethylammonium bromide (CTAB) template-assisted solvothermal treatment. Subsequently, nickel-cobalt sulfide microspheres with the unique yolk@shell structure were prepared from layered Ni4Co1 hydroxide precursor. Notably, yolk@shell Ni4Co1S-2h microspheres feature a large specific surface area and an interspace between the yolk and shell, facilitating charge transfer but also effectively alleviating volume expansion during ion transport and electron transfer. The resultant Ni4Co1S-2h material demonstrates a superior capacity of 902.2 C·g−1 at 3·A g−1, while the assembled Ni4Co1S-2h//porous carbon (PC) HSC shows a relatively higher energy density (83.1 Wh·kg−1) and power density (15000 W·kg−1). The design of yolk@shell structured layered Ni4Co1 hydroxide and Ni4Co1S-2h electrode materials holds significant implications for the advancement of high-performance HSCs.

Construction of ultra-thin NiMo3S4 nanosheet sphere electrode for high-performance hybrid supercapacitor

The construction of electrode materials with rational morphology and structure based on bimetallic sulfides is crucial to improve the performance of supercapacitors. Ultra-thin three-dimensional nickel molybdenum sulfide nanosheet spheres (NiMo3S4 NSSs) are grown on nickel foam (NF) using a one-step hydrothermal synthesis. NiMo3S4 NSSs have a diameter of ∼ 5 μm and nanosheet thickness of 200 nm. The effects of increasing the hydrothermal synthesis time and molar concentration ratios of Ni2+ to MoO42- on the morphologies of the NiMo3S4 are investigated. Due to the synergistic effect of NiMo3S4 NSSs and bimetallic ions which can provide a larger solution contact areas and improve the redox activity, the electrode exhibits good electrochemical properties. The specific capacity of NiMo3S4 NSSs/NF electrode can reach 1002.4 C/g (1 A/g). After being assembled into a hybrid supercapacitor (HSC) with activated carbon (AC), the energy density can reach 72.1 Wh/kg at the power density of 749.9 W/kg. In addition, the HSC shows an excellent stability of 89 % after 10, 000 charge-discharge cycles (10 A/g).

Sodium anthraquinone-2-sulfonate combined with biomass porous carbon for high-performance zinc-ion hybrid supercapacitors

Zinc ion hybrid supercapacitors (ZIHSCs) can have their energy density raised by coupling high-capacity molecules with porous carbon, as demonstrated by research. However, few studies on the effect of introduction strategies of these molecules have been conducted on ZIHSC performance. Herein, sodium anthraquinone-2-sulfonate (AQS) are introduced into porous carbon (TAC) by one-step hydrothermal strategy to prepare the composites (TAC/AQS (W)). TAC/AQS (M) composites synthesized by physical mixing method as control samples. When used as the cathode material for aqueous ZIHSCs, TAC/AQS-1 (W) with the best mass ratio of AQS and TAC has a high specific capacitance of 310.89 mAh g−1 at 0.2 A g−1 and retains 89.17 % of its capacity after 20,000 cycles of the charge and discharge test, while those of TAC/AQS-0.5 (M) is 284.60 mAh g−1 and 10.09 %. Furthermore, TAC/AQS-1 (W) can achieve energy density of 295.35 Wh kg−1 and that of TAC/AQS-0.5 (M) is only 256.14 Wh kg−1. These results demonstrate that the way of introducing AQS affect the electrochemical properties of ZIHSC. The main reason for the difference in performance of two approaches is that the hydrothermal method makes AQS and TAC combine into a single solid phase with π-π non-covalent bonds, while the physical method is only a simple mechanical mixing of two phases.

Architecture of interconnected cubic NiCo2S4 decorated mesoporous carbon with self-doped nitrogen based-hydrogel for high performance hybrid supercapacitor

Although the transition metal sulfides have shown persuasive proof and stellar traits for energy storage applications, their real applications still possess some obstacles such as prolonged ionic and electronic transport. Hence, NiCo2S4 decorated a pyrolyzed hydrogel (NiCo2S4@PHG) via facile synthesis is considered a promising electrocatalyst for energy storage devices. The prepared electrode materials were characterized utilizing different analysis techniques like XPS, XRD, FT-IR, TGA, SEM, TEM, elemental mapping and EDX that reveal the crucial role of the hydrogel pyrolysis in creating a homogenous nitrogen-doped carbon matrix. The as-fabricated 0.5 NiCo2S4@PHG nanocomposite was electrochemically examined in a sealed workstation cell and showed a clear battery-type supercapacitor behavior attributed to various redox reactions, porosity, and conductivity that was enhanced by self-doped nitrogen. In contrast, composites based on nickel and cobalt sulfides individually with pure hydrogel demonstrated the superiority of binary metal composites. The 0.5 NiCo2S4@PHG electrode exposed a marvelous specific capacity of 317.9 mAh g−1 and capacitance of 2728.5 F g−1 at a current density of 1 A g−1. A hybrid asymmetric supercapacitor was established by 0.5 NiCo2S4@PHG (cathode) and activated carbon (AC, anode), which brought large energy and power densities of 32.8 Wh kg−1 and 750 W kg−1, respectively. The fabricated cell manifests ultra-high retention of 82.6% at a current density of 20 A g−1 after 10,000 cycles. These outstanding accomplishments hold significant potential for practical energy storage and conversion applications.

Calcination synthesized and self-assembled “rough bark-like” cobalt pyrophosphate for the high-performance hybrid supercapacitor as cathode materials

Transition-metal phosphate/pyrophosphate always exhibits promising theoretical electrochemical performance and has essential prospects in supercapacitors. In this study, “rough bark-like” Co2P2O7 is successfully synthesized via calcination method using ammonium cobalt phosphate as raw material. By investigating the effect of calcination temperature on the morphology of Co2P2O7, the pure cobalt pyrophosphate piece could be prepared at 600 °C (CPO-600). Due to the unique morphology and mesoporous presence, the CPO-600 exhibits a good affinity and infiltration interface with the electrolyte and displays a specific capacitance of 544 F g−1 at 1 A g−1 in 3 M KOH, which has excellent rate performance. After 10,000 cycles at 20 A g−1, it still maintains the good cycle stability with 81.48 % initial specific capacitance. Furthermore, the hybrid asymmetric aqueous supercapacitor of CPO-600//AC delivers remarkable energy densities of 10.6 Wh kg−1 at power densities of 559 W kg−1. And its gel electrolyte device also provides higher electrochemical properties and good comprehensive performance.

Ni2P nanosheet-coated N-doped carbon hollow tubes for high-performance hybrid supercapacitors

Ni2P shows significant potential for energy storage devices due to its high capacitance and long-term cyclic stability. However, its poor electrical conductivity and porosity limit its effectiveness in electrode battery-type (BT) applications for hybrid supercapacitors (HSCs). In this study, the Ni2P nanosheet-coated N-doped carbon hollow tubes (Ni2P/NCHTs) derived from polypyrrole (PPy) have been developed. These Ni2P/NCHTs form a unique one-dimension (1D) core-shell structure through a synergetic carbonization and phosphorization process. The resulting Ni2P/NCHTs exhibit a remarkable specific capacitance of up to 150.83 mAh·g−1 (1086 F g−1) at 1 A g−1 in an aqueous electrolyte (2 M KOH) using a three-electrode system. In an HSC device, with Ni2P/NCHTs as the positive electrode and an active carbon fiber (ACF) as the negative electrode, an energy density of 46.53 W h kg−1 is achieved at a power density of 1125 W kg−1 with high cycle stability (99.45 % retention after 5000 cycles). Therefore, Ni2P/NCHTs present a promising candidate for energy storage devices.

Mangenese Copper Selenide Nanosheet Arrays Derived from Metal-Organic Frameworks for Efficient Solid-State Asymmetric Supercapacitors

Metal chalcogenide nanostructures, particularly metal selenides, have unique properties, such as high electrical conductivity, large specific surface area, exclusive porous networks, and exceptional electrochemical properties compared to traditional nanostructures.1 2 A novel strategy is proposed to design and fabricate hierarchical Manganese copper selenide nanosheet (MnCuSe NS) arrays from metal-organic frameworks (MOFs). The hierarchical MnCuSe NS arrays can deliver enriched electroactive sites and shorten the ion/electron diffusion pathways. When evaluated as positive electrodes for supercapacitor (SC), the MnCuSe NS electrode displayed remarkable electrochemical properties with ultra-high specific capacity of ≈350.4 mA h g− 1 and an areal capacity of ≈0.94 mA h cm− 2 at a current density of 3 mA cm− 2, exceptional rate capability (≈79.5% of the capacity retention at a higher current density of 50 mA cm− 2), and outstanding cyclic stability (≈95.4 % of capacity retention after 10 000 cycles). Most importantly, the assembled MnCuSe NS//FeMnO/NG solid-state asymmetric SC exhibited a wide operating potential window of 1.6 V with an ultra-high volumetric capacity of ≈2.4 mA h cm− 3 at a current density of 3 mA cm− 2, an excellent energy density of ≈71.6 Wh Kg− 1 at a power density of ≈794 W Kg− 1, and ultra-long cycle life (≈93.4 % of capacity retention after 10 000 cycles). This proposed method provides a general protocol to design and fabricate metal selenide nanosheet arrays with superior electrochemical energy storage properties and exceptional cyclic stability, holding significant potential for future energy storage devices in commercial aspects. Keywords: Hierarchical, Metal-organic frameworks, Metal chalcogenide, Energy density, Asymmetric supercapacitorsReference:(1) Han, J. H.; Kwak, M.; Kim, Y.; Cheon, J. Recent Advances in the Solution-Based Preparation of Two-Dimensional Layered Transition Metal Chalcogenide Nanostructures. Chem. Rev. 2018, 118 (13), 6151–6188. https://doi.org/10.1021/acs.chemrev.8b00264.(2) Karuppasamy, K.; Vikraman, D.; Hussain, S.; Kumar Veerasubramani, G.; Santhoshkumar, P.; Lee, S.-H.; Bose, R.; Kathalingam, A.; Kim, H.-S. Unveiling a Binary Metal Selenide Composite of CuSe Polyhedrons/CoSe2 Nanorods Decorated Graphene Oxide as an Active Electrode Material for High-Performance Hybrid Supercapacitors. Chemical Engineering Journal 2022, 427, 131535. https://doi.org/10.1016/j.cej.2021.131535.

Cellulose-doped ternary composites for high-performance hybrid supercapacitor

This study presents the cellulose fiber doped ternary composite of different transition diselenides. The ternary composites were prepared via a hydrothermal-assisted physical blending route. The ternary composite of CoSe2-based symmetric cell provided higher electrochemical performance than the other ternary composites. The energy and power density provided by the same cell is around 144 W h kg-1 and 989 W kg-1 at 1 A g-1 for a 1.6 V. The stabilization of the CAC-5 material was investigated for 10,000 cycles at 2 A g-1. The real-time use of the CAC-5 symmetric cell was successfully verified via the illuminating 26-red LED panel for 1 h 40 min. Additionally, the schematic depiction of the charge storage mechanism connected with the CAC-5 symmetric cell during the charging/discharging process has been proposed in this work. The results highlight the potential of CAC-5 material for its application in the energy storage field.

Hydrothermal Synthesis of β-NiS Nanoparticles and Their Applications in High-Performance Hybrid Supercapacitors.

In this work, β-NiS nanoparticles (NPs) were efficiently prepared by a straightforward hydrothermal process. The difference in morphology between these NiS NPs was produced by adding different amounts of thiourea, and the corresponding products were denoted as NiS-15 and NiS-5. Through electrochemical tests, the specific capacity (Cs) of NiS-15 was determined to be 638.34 C g-1 at 1 A g-1, compared to 558.17 C g-1 for NiS-5. To explore the practical application potential of such β-NiS NPs in supercapacitors, a hybrid supercapacitor (HSC) device was assembled with activated carbon (AC) as an anode. Benefitting from the high capacity of the NiS cathode and the large voltage window of the device, the NiS-15//AC HSC showed a high energy density (Ed) of 43.57 W h kg-1 at 936.92 W kg-1, and the NiS-5//AC HSC provided an inferior Ed of 37.89 W h kg-1 at 954.79 W kg-1. Both HSCs showed excellent cycling performance over 6000 cycles at 10 A g-1. The experimental findings suggest that both NiS-15 and NiS-5 in this study can serve as potential cathodes for high-performance supercapacitors. This current synthesis method is simple and can be extended to the preparation of other transition metal sulfide (TMS)-based electrode materials with exceptional electrochemical properties.

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.

In situ grown heterostructures based on MAX-derived TaO2F nanorod and TaC (MXene) nanosheet for high-performance hybrid supercapacitors

Two-dimensional MXene-based interface heterostructures have an undeniable position in the energy storage systems, particularly supercapacitors, due to their unique microstructure and electrochemical properties. However, the selection of materials in heterogeneous structures and the assembly strategy often have often have a significant impact on the properties of heterogeneous structures. This study proposes a in situ grown strategy for constructing TaO2F@TaC nano-heterostructures consisting of one-dimensional TaO2F nanorods combined with two-dimensional TaC nanosheets derived from the precursor MAX phase. The complex etching and growth mechanism from MAX to 1D/2D TaO2F@TaC is reasonably inferred. The construction of TaO2F@TaC nano-heterostructures effectively addresses the issue of MXene to restack and improves the poor conductivity of TaO2F. Density functional theory (DFT) calculations validated the electronic structure and charge distribution at the heterostructure interface, demonstrating its capability for electron conduction and ion transport. Moreover, the hybrid supercapacitor (HSC) based on TaO2F@TaC exhibited superior energy density (153.4 μWh cm−2 at a power density of 222.2 μW cm−2) and excellent cycle stability. The prepared quasi-solid-state supercapacitor (QSC) also shows a capacitance of 457.4 mF cm−2, and retains 99.38 % capacity after 8200 cycles. This work innovatively bypasses the multi-step process of preparing MXene heterostructures and provides a new approach for developing MXene-based electrode materials to enhance the performance of hybrid supercapacitors.

Zeolitic Imidazolate Framework-8 enhanced with tungsten carbide for high-performance hybrid supercapacitors and hydrogen evolution

A promising metal-organic framework (MOF) called Zeolitic Imidazolate Framework-8 (ZIF-8) stands out for its electrochemical applications. Its versatility in physicochemical properties makes it a strong candidate for breakthroughs in energy storage and electrochemical water splitting. The electrode nanomaterials lower specific capacity, small charging/discharging rate, and low conductivity limit its supercapacitor and hydrogen evaluation reaction (HER) applications. The ZIF-8 zeolite structure was decorated with tungsten carbide (WC) to overcome these issues. These modifications result in improved porosity, surface area, density, and pore size, shape, and structure. These characteristics contribute significantly to enhanced electrochemical activity. ZIF-8 MOF/WC nanocomposites have excellent dispersion and stability due to their porosity and strong connection between embedded WC nanoclusters and the framework. The prepared electrode showed a 118.11 mV overpotential and 36.45 mV/dec Tafel slope throughout HER activity. ZIF-8 MOF/WC was used for electrochemical studies and to make a hybrid energy storage device using activated carbon (AC). The hybrid supercapacitor had higher energy and power densities (87 W h/kg and 850 W/kg). The theoretical technique (Dunn model) was also employed to analyze experimental results more thoroughly.

Zirconium doping facilitates a vertically aligned NiCoZr-layered hydroxide nanoneedle arrays electrode for hybrid supercapacitors exhibiting a 90,000 cycle durability

LDHs (Layered Double Hydroxides) are a kind of promising cathode material for high-performance hybrid supercapacitor. Nevertheless, it suffers quick capacitance decay after only thousands of cycles, which greatly prevents it from further application. In this contribution, zirconium (Zr) is introduced to the host layer of NiCo-LDH via a simple one-pot hydrothermal process. Owing to the strong bonding energy of ZrO (760 kJ mol−1) and special electronic structure (fully empty 4d orbits), the doped Zr could not only act as a structural stabilized element, but also change the mechanism of the energy storage process to alleviate the Jahn-Teller distortion of NiCo-LDH. Moreover, the introduction of Zr boosts an orderly growth of the LDHs, changing from disorder stack structure to vertically aligned nanoneedle arrays, which improve their structural stability. By controlling a varying level of Zr content, the electrode NiCoZr-LDH@CC with a Zr content ratio of 6.4 % delivers the best comprehensive electrochemical performance with a specific capacitance of 1758 F g−1 and good rate performance (73 % capacitance retention at 10 A g−1). The assembled asymmetric supercapacitor shows a highest energy density of 42.3 Wh kg−1 at 504 W kg−1 and an ultralong cycling lifespan beyond 90,000 cycles with a 97 % capacitance retention. The results exhibit the great potential of NiCoZr-LDH as a qualified candidate for high-performance hybrid supercapacitors.

Chemical Route Synthesis of Nanohybrid Mo–V Oxide and rGO for High-Performance Hybrid Supercapacitors

Chemical Route Synthesis of Nanohybrid Mo–V Oxide and rGO for High-Performance Hybrid Supercapacitors

Developing a high-performance hybrid supercapacitor with the controlled assembly of a hierarchical 3D flower-like NiCo double hydroxide nano/microarchitecture electrode material

The design of hierarchical nano/microarchitectures containing multiple elemental compositions has attracted significant interest due to their ability to offer morphological, enhanced conductive, and exceptional electrochemical capabilities in the field of energy storage. Herein, a 3D flower-like porous nano/microarchitecture of NiCo double hydroxide (NCDH-1) was synthesized using a facile hydrothermal technique for supercapacitor electrode materials. The 3D hierarchical structure formed by the network arrangement of 2D nanosheets comprises of many open spaces between the nanosheets. These nanosheets lead to a large specific surface area, abundant active sites, and multiple channels for the transport of electrons/ions. These factors boost redox processes and facilitate the rapid transfer of electrons/ions into the electrode material. The NCDH-1 electrode material, with its hierarchical 3D nano/microarchitecture, exhibits the supreme capacitance (Csp) of 2199 F g−1 at 1 A g−1 and demonstrates excellent rate capability, retaining 58.2 % at 20 A g−1. The hybrid supercapacitor configured using 3D flower-like NCDH-1 and commercial grade activated carbon (AC; MSP-20) electrodes demonstrates an impressive Csp of 232 F g−1 at 1 A g−1, a superior energy density of 72.5 Wh kg−1, and an excellent cycle lifetime. Thus, the approach outlined in this work offers a promising strategy for developing 3D nano/microarchitecture metal hydroxides with potential applications in energy storage systems.

Molybdenum trioxide/carbon nanotubes/poly (5-carboxylindole) (MoO3/MWCNT-COOH/P5ICA) nanocomposites as an electrode material for high-performance hybrid supercapacitors

Molybdenum trioxide/carboxyl functionalized carbon multi-wall nanotubes/poly(5-carboxylindole) (MoO3/MWCNT-COOH/P5ICA) ternary composites were prepared as supercapacitor electrodes by hydrothermal and electrochemical polymerization methods. When three materials are composite used as electrodes for supercapacitors, the advantages of each material can be effectively integrated, resulting in low impedance and high capacitance characteristics. After optimizing the electrochemical polymerization time of P5ICA, the maximum specific capacitance of the composite electrode can reach 165.6 mF cm−2. The symmetric supercapacitor constructed with composite electrodes demonstrates a maximum specific capacitance of 61.0 mF cm−2, and the area specific capacitance can remain 74 % of the original after 1000 charge and discharge cycles. This study provides a feasible scheme for preparing high performance supercapacitor materials.

Graphene-wrapped (Ni,Co)Se2 carbon nanowires toward high performance hybrid supercapacitors

To probe the next generation of flexible supercapacitors for practical application, small size, excellent electrical conductivity, low cost, Eco-friendly and excellent capacitance are prerequisites. However, due to dissatisfied electrical conductivity, limited surface area and low porosity, which results in few active sites and long ion transport channels, electrochemical improvements are needed for bimetallic selenide-based flexible supercapacitors. Hence, novel three dimensional graphene (3DG) encapsulated cobalt-nickel selenide carbon nanowires [3DG/(Co,Ni)Se2 CNWs] composite aerogels was successfully fabricated through a modified self-templating approach. The assembled 3DG/(Co,Ni)Se2 CNWs electrode showcases outstanding electrochemical performance, achieving a high specific capacitance of 1286 F g−1 at 1 A g−1 attributed to its combination structure of carbon based materials and nanowires. It demonstrates excellent cycling stability, with a capacity retention of 88 % after 3000 cycles at 2 A g−1. The prepared 3DG/(Co,Ni)Se2 CNWs//active carbon (AC) asymmetric flexible all-solid-state supercapacitors demonstrates outstanding electrochemical properties, achieving an energy density of up to 28 Wh kg−1 at a power density of 800 W kg−1. Even after 6000 cycles at 5 A g−1, it retains 84.15 % of its specific capacitance, thus presenting a new direction for energy storage applications.