Metallic Fabrics as the Current Collector for High-Performance Graphene-Based Flexible Solid-State Supercapacitor

Carbon carrier-based rapid Joule heating technology: a review on the preparation and applications of functional nanomaterials

Compared to conventional heating techniques, the carbon carrier-based rapid Joule heating (CJH) method is a new class of technologies that offer significantly higher heating rates and ultra-high temperatures. Over the past few decades, CJH technology has spawned several techniques with similar principles for different application scenarios, including ultra-fast high temperature sintering (UHS), carbon thermal shock (CTS), and flash Joule heating (FJH), which have been widely used in material preparation research studies. Functional nanomaterials are a popular direction of research today, mainly including nanometallic materials, nanosilica materials, nanoceramic materials and nanocarbon materials. These materials exhibit unique physical, chemical, and biological properties, including a high specific surface area, strength, thermal stability, and biocompatibility, making them ideal for diverse applications across various fields. The CJH method is a remarkable approach to producing functional nanomaterials that has attracted attention for its significant advantages. This paper aims to delve into the fundamental principles of CJH and elucidate the efficient preparation of functional nanomaterials with superior properties using this technique. The paper is organized into three sections, each dedicated to introducing the process and characteristics of CJH technology for the preparation of three distinct material types: carbon-based nanomaterials, inorganic non-metallic materials, and metallic materials. We discuss the distinctions and merits of the CJH method compared to alternative techniques in the preparation of these materials, along with a thorough examination of their properties. Furthermore, the potential applications of these materials are highlighted. In conclusion, this paper concludes with a discussion on the future research trends and development prospects of CJH technology.

Self-assembled monolayers of reduced graphene oxide for robust 3D-printed supercapacitors

Herein, additive manufacturing, which is extremely promising in different sectors, has been adopted in the electrical energy storage field to fabricate efficient materials for supercapacitor applications. In particular, Al2O3-, steel-, and Cu-based microparticles have been used for the realization of 3D self-assembling materials covered with reduced graphene oxide to be processed through additive manufacturing. Functionalization of the particles with amino groups and a subsequent "self-assembly" step with graphene oxide, which was contextually partially reduced to rGO, was carried out. To further improve the electrical conductivity and AM processability, the composites were coated with a polyaniline-dodecylbenzene sulfonic acid complex and further blended with PLA. Afterward, they were extruded in the form of filaments, printed through the fused deposition modeling technique, and assembled into symmetrical solid-state devices. Electrochemical tests showed a maximum mass capacitance of 163 F/g, a maximum energy density of 15 Wh/Kg at 10 A/g, as well as good durability (85% capacitance retention within 5000 cycles) proving the effectiveness of the preparation and the efficiency of the as-manufactured composites.

MOF/graphene oxide based composites in smart supercapacitors: a comprehensive review on the electrochemical evaluation and material development for advanced energy storage devices

The surge in interest surrounding energy storage solutions, driven by the demand for electric vehicles and the global energy crisis, has spotlighted the effectiveness of carbon-based supercapacitors in meeting high-power requirements. Concurrently, metal-organic frameworks (MOFs) have gained attention as a template for their integration with graphene oxide (GO) in composite materials which have emerged as a promising avenue for developing high-power supercapacitors, elevating smart supercapacitor efficiency, cyclic stability, and durability, providing crucial insights for overcoming contemporary energy storage obstacles. The identified combination leverages the strengths of both materials, showcasing significant potential for advancing energy storage technologies in a sustainable and efficient manner. In this research, an in-depth review has been presented, in which properties, rationale and integration of MOF/GO composites have been critically examined. Various fabrication techniques have been thoroughly analyzed, emphasizing the specific attributes of MOFs, such as high surface area and modifiable porosity, in tandem with the conductive and stabilizing features of graphene oxide. Electrochemical characterizations and physicochemical mechanisms underlying MOF/GO composites have been examined, emphasizing their synergistic interaction, leading to superior electrical conductivity, mechanical robustness, and energy storage capacity. The article concludes by identifying future research directions, emphasizing sustainable production, material optimization, and integration strategies to address the persistent challenges in the field of energy storage. In essence, this research article aims to offer a concise and insightful resource for researchers engaged in overcoming the pressing energy storage issues of our time through the exploration of MOF/GO composites in smart supercapacitors.

Resent Development of Binder-Free Electrodes of Transition Metal Oxides and Nanohybrids for High Performance Supercapacitors - A Review

The entire world is aware of the serious issue of global warming and therefore utilizing renewable energy sources is the most encouraging steps toward solving energy crises, and as a result, energy storage solutions are necessary. The supercapacitors (SCs) have a high-power density and a long cycle life, they are promising as an electrochemical conversion and storage device. In order to achieve high electrochemical performance, electrode fabrication must be implemented properly. Electrochemically inactive and insulating binders are utilized in the conventional slurry coating method of making electrodes to provide adhesion between the electrode material and the substrate. This results in an undesirable "dead mass," which lowers the overall device performance. In this review, we focused on binder-free SCs electrodes based on transition metal oxides and composites. With the best examples providing the critical aspects, the benefits of binder-free electrodes over slurry-coated electrodes are addressed. Additionally, different metal-oxides used in the fabrication of binder-free electrodes are assessed, taking into account the various synthesis methods, giving an overall picture of the work done for binder-free electrodes. The future outlook is provided along with the benefits and drawbacks of binder-free electrodes based on transition metal oxides.

Smart Electronic Textile-Based Wearable Supercapacitors

Electronic textiles (e-textiles) have drawn significant attention from the scientific and engineering community as lightweight and comfortable next-generation wearable devices due to their ability to interface with the human body, and continuously monitor, collect, and communicate various physiological parameters. However, one of the major challenges for the commercialization and further growth of e-textiles is the lack of compatible power supply units. Thin and flexible supercapacitors (SCs), among various energy storage systems, are gaining consideration due to their salient features including excellent lifetime, lightweight, and high-power density. Textile-based SCs are thus an exciting energy storage solution to power smart gadgets integrated into clothing. Here, materials, fabrications, and characterization strategies for textile-based SCs are reviewed. The recent progress of textile-based SCs is then summarized in terms of their electrochemical performances, followed by the discussion on key parameters for their wearable electronics applications, including washability, flexibility, and scalability. Finally, the perspectives on their research and technological prospects to facilitate an essential step towards moving from laboratory-based flexible and wearable SCs to industrial-scale mass production are presented.

Performance comparison of distinct bismuth molybdate single phases for asymmetric supercapacitor applications

The enticing features of metal molybdates make them an attractive candidate for energy storage systems. This report describes the synthesis of three distinct single-phase bismuth molybdates (Bi₂Mo_xO_y; α-Bi₂Mo₃O₁₂, β-Bi₂Mo₂O₉, and γ-Bi₂MoO₆) using the gel matrix particle growth method and their application in high-performance asymmetric supercapacitors. The single phase and purity of the synthesized Bi₂Mo_xO_y particles were confirmed by X-ray diffraction (XRD) and further verified by Raman analysis. The UV-visible spectra show the electronic and optical behaviours of the as-synthesized α, β, and γ Bi₂Mo_xO_y. The morphologies of the as-synthesized three different Bi₂Mo_xO_y phases were analysed using scanning electron microscopy (SEM). The particle formation was further investigated by transmission electron microscopy (TEM), and the interplanar spacings of the Bi₂Mo_xO_y phases were in accordance with the planes. The surface area and pore volume of the prepared samples were analysed using Brunauer-Emmett-Teller (BET) analysis. The electrochemical properties of the products were confirmed by various tests, including cyclic voltammetry (CV), galvanostatic charge discharge (GCD), and electrochemical impedance spectroscopy (EIS) in 3 M KOH. Among the three phases, α-Bi₂Mo₃O₁₂ exhibits a huge specific capacitance (Cs) of 714 F g^-1 at a current density of 1 A g^-1. Furthermore, it displays an admirable cycling stability of 86.55% after 5000 cycles. The chosen α-Bi₂Mo₃O₁₂ electrode possesses an increased energy density of 47.5 W h kg^-1 at 1 A g^-1 with a capacitive retention rate of 71.90% at 5 A g^-1 after 10 000 cycles. A remarkable electrochemical performance of Bi₂Mo₃O₁₂ with an exceptional power density of 750 W kg^-1 was observed for the prepared asymmetric device. Bismuth molybdate's notable performance indicates that it can be an active material for energy storage applications.

A Biodegradable Polymer-Based Plastic Chip Electrode as a Current Collector in Supercapacitor Application

Here, we report the performance of a biodegradable polymer-based Plastic chip Electrode (PCE) as a current collector in supercapacitor applications. Its production was evaluated using two redox materials (conducting polymers polyaniline and poly(3,4-ethylene dioxythiophene)) and a layered material, rGO. The conducting polymers were directly deposited over the Eco-friendly PCE (EPCE) using the galvanostatic method. The rGO was prepared in the conventional way and loaded over the EPCE using a binder. Both conducting polymers and rGO showed proper specific capacitance compared to previous studies with regular current collectors. Electrodes were found highly stable during experiments in high acidic medium. The supercapacitive performance was evaluated with cyclic voltammetry, charge–discharge measurements, and impedance spectroscopy. The supercapacitive materials were also characterized for their electrical and microscopic properties. Polyaniline and PEDOT were deposited over EPCEs showing >150 Fg−1 and >120 Fg−1 specific capacitance, respectively, at 0.5 Ag−1. rGO continued to show higher particular capacitance of >250 Fg−1 with excellent charge–discharge cyclic stability. The study concludes that EPCs can be used as promising electrodes for electrical energy storage applications.

Compact 3D Metal Collectors Enabled by Roll-to-Roll Nanoimprinting for Improving Capacitive Energy Storage

Reducing the contact resistance between active materials and current collectors is of engineering importance for improving capacitive energy storage. 3D current collectors have shown extraordinary promise for reducing the contact resistance, however, there is a major obstacle of being bulky or inefficient fabrication before they become viable in practice. Here a roll-to-roll nanoimprinting method is demonstrated to deform flat aluminum foils into 3D current collectors with hierarchical microstructures by combining soft matter-enhanced plastic deformation and template-confined local surface nanocracks. The generated 3D current collectors are inserted by and interlocked with active electrode materials such as activated carbon, decreasing the contact resistance by at least one order of magnitude and quadrupling the specific capacitance at high current density of 30 A g^-1 for commercial-level mass loading of 5 mg cm^-2 . The 3D current collectors are so compact that they have a low volume percentage of 7.8% in the entire electrode film, resulting in energy and power density of 29.1 Wh L^-1 and 12.8 kW L^-1 , respectively, for stack cells in organic electrolyte. Furthermore, roll-to-roll nanoimprinting of metal microstructures is low-cost, high-throughput, and can be extended to other systems that involve the microstructured metal interface, such as batteries and thermal management.

Unraveling CoNiP-CoP2 3D-on-1D Hybrid Nanoarchitecture for Long-Lasting Electrochemical Hybrid Cells and Oxygen Evolution Reaction

Evolving cost-effective transition metal phosphides (TMPs) using general approaches for energy storage is pivotal but challenging. Besides, the absence of noble metals and high electrocatalytic activity of TMPs allow their applicability as catalysts in oxygen evolution reaction (OER). Herein, CoNiP-CoP₂ (CNP-CP) composite is in situ deposited on carbon fabric by a one-step hydrothermal technique. The CNP-CP reveals hybrid nanoarchitecture (3D-on-1D HNA), i.e., cashew fruit-like nanostructures and nanocones. The CNP-CP HNA electrode delivers higher areal capacity (82.8 μAh cm^-2 ) than the other electrodes. Furthermore, a hybrid cell assembled with CNP-CP HNA shows maximum energy and power densities of 31 μWh cm^-2 and 10.9 mW cm^-2 , respectively. Exclusively, the hybrid cell demonstrates remarkable durability over 30 000 cycles. In situ/operando X-ray absorption near-edge structure analysis confirms the reversible changes in valency of Co and Ni elements in CNP-CP material during real-time electrochemical reactions.  Besides, a quasi-solid-state device unveils its practicability by powering electronic components. Meanwhile, the CNP-CP HNA verifies its higher OER activity than the other catalysts by revealing lower overpotential (230 mV). Also, it exhibits relatively small Tafel slope (38 mV dec^-1 ) and stable OER activity over 24 h. This preparation strategy may initiate the design of advanced TMP-based materials for multifunctional applications.

Chitosan-based oxygen-doped activated carbon/graphene composite for flexible supercapacitors

Flexible supercapacitors have attracted widespread attention from many researchers as a type of portable energy storage device. As a unique carbon material, graphene has shown great potential in supercapacitor electrodes, mainly due to its large theoretical specific surface area, high conductivity and chemical stability. Therefore, reasonable design of graphene-based hydrogels with low cost, high specific surface area, and excellent mechanical properties is of great significance for flexible and wearable energy storage device applications. Oxygen-doped activated carbon/graphene composite hydrogels have been fabricated using a one-step hydrothermal method. In the hybrid hydrogel, the activated carbon derived from chitosan with high specific surface area and oxygen-containing groups which were introduced by using a facile room-temperature oxidation strategy with HNO₃ are assembled into the framework of reduced graphene oxide (rGO) to effectively prevent the restacking of rGO nanosheets and result in high specific surface area and high conductivity of the composite hydrogels, thereby leading to an excellent energy storage performance. The optimal sample displayed a high specific capacitance of 375.7 F g⁻¹ in 1 M H₂SO₄ electrolyte at a current density of 1 A g⁻¹. Furthermore, the assembled flexible supercapacitor showed an ideal cycling stability of 83% after 5000 charge/discharge cycles at 10 A g⁻¹. The facile strategy developed in this work is of significance for the performance improvement of supercapacitor electrode materials.

An activated carbon/graphene hydrogel for supercapacitors was prepared by using chitosan-based activated carbon and graphene oxide via a hydrothermal process.

Low cost, high efficiency flexible supercapacitor electrodes made from areca nut husk nanocellulose and silver nanoparticle embedded polyaniline

Energy storage is a key aspect in the smooth functioning of the numerous gadgets that aid easy maneuvering through modern life. Supercapacitors that store energy faradaically have recently emerged as potential inventions for which mechanical flexibility is an absolute requirement for their future applications. Flexible supercapacitors based on nanocellulose extracted from easily available waste materials via low cost methods have recently garnered great attention. In the present work, we discuss the construction of flexible, binder-free supercapacitive electrodes using nanocellulose extracted from locally available areca nut husks and polyaniline embedded with silver nanoparticles. The prepared electrodes were characterized using SEM, TEM, XRD, FTIR, EDX and electrochemical characterization techniques such as CV, galvanostatic charge–discharge, chronoamperometry and EIS. A specific capacitance of 780 F g⁻¹ was obtained for the silver nanoparticle embedded polyaniline–nanocellulose (Ag–PANI–NC) substrate supported electrodes, which is ∼4.2 times greater than that of bare polyaniline–nanocellulose electrodes. We attributed this enhancement to a lowering of the activation energy barrier of correlated electron hopping among localized defect states in the composite matrix by the Ag nanoparticles. An energy density value of 15.64 W h kg⁻¹ and a power density of 244.8 W kg⁻¹ were obtained for the prepared electrodes. It was observed that the Ag–PANI–NC based electrode can retain ∼98% of its specific capacitance upon recovery from mechanical bending to extreme degrees.

Energy storage is a key aspect in the smooth functioning of the numerous gadgets that aid easy maneuvering through modern life. Utilization of waste materials for energy storage applications enables the sustainable development of energy field.

Carbon-Based Polymer Nanocomposite for High-Performance Energy Storage Applications

In recent years, numerous discoveries and investigations have been remarked for the development of carbon-based polymer nanocomposites. Carbon-based materials and their composites hold encouraging employment in a broad array of fields, for example, energy storage devices, fuel cells, membranes sensors, actuators, and electromagnetic shielding. Carbon and its derivatives exhibit some remarkable features such as high conductivity, high surface area, excellent chemical endurance, and good mechanical durability. On the other hand, characteristics such as docility, lower price, and high environmental resistance are some of the unique properties of conducting polymers (CPs). To enhance the properties and performance, polymeric electrode materials can be modified suitably by metal oxides and carbon materials resulting in a composite that helps in the collection and accumulation of charges due to large surface area. The carbon-polymer nanocomposites assist in overcoming the difficulties arising in achieving the high performance of polymeric compounds and deliver high-performance composites that can be used in electrochemical energy storage devices. Carbon-based polymer nanocomposites have both advantages and disadvantages, so in this review, attempts are made to understand their synergistic behavior and resulting performance. The three electrochemical energy storage systems and the type of electrode materials used for them have been studied here in this article and some aspects for example morphology, exterior area, temperature, and approaches have been observed to influence the activity of electrochemical methods. This review article evaluates and compiles reported data to present a significant and extensive summary of the state of the art.

Facile synthesis of battery waste-derived graphene for transparent and conductive film application by an electrochemical exfoliation method

Low defect ratio graphene with promising conductivity and transparency can be obtained from the spent graphite in Zn–C battery waste.

A flexible and conductive metallic paper-based current collector with energy storage capability in supercapacitor electrodes

The development of flexible current collectors as an indispensable component in energy storage devices has been in strong demand for the ever-growing market of flexible and wearable electronics. Herein, flexible and conductive paper-based current collectors are fabricated by directly depositing a metallic Ni layer composed of spiny Ni nanospheres of 400 nm diameter on the surface of filter paper via electroless deposition. The metallic paper shows excellent electric and mechanical properties: the sheet resistance is 2.7 Ω cm^-2 (R₀ = 0.8 Ω cm^-2) after 5000 bending cycles and the mass density is only 0.35 g cm^-3. MnO₂ is selected as an electrode active material to explore the role of flexible and conductive paper-based current collectors in supercapacitors. Electrochemical results reveal that the largest areal specific capacitance is 1095 mF cm^-2 at 1 mA cm^-2 and the excellent electrochemical performance can be attributed to the hierarchical porous fibre structure of paper and the lower contact resistance between the active material and the current collector. Note that the approach can be applied to an enlarged size of metallic conductive paper or textile, presenting a simple and feasible method to fabricate flexible current collectors in a large scale.

Three-dimensional nickel vanadium layered double hydroxide nanostructures grown on carbon cloth for high-performance flexible supercapacitor applications

This study reports the synthesis of ultrathin Ni-V layered double hydroxide nanosheets on carbon cloth (NVL@CC) through adopting a facile and cost-effective method for flexible supercapacitor applications. The as-synthesized NVL@CC possesses a uniform, mechanically strong and highly ordered porous network with connected pores, ensuring high specific capacitance and enhanced cyclability. A high specific capacity of 1226 C g^-1 (2790 F g^-1) was obtained at 1 A g^-1, and it remained at 430 C g^-1 (1122 F g^-1) even at a higher current density of 10 A g^-1. A hybrid supercapacitor (HSC) was assembled with the NVL@CC electrode as the positive electrode and activated carbon coated carbon cloth as the negative electrode (NVL@CC//AC HSC). The devices showed an excellent energy density of 0.69 mW h cm^-3 at a power density of 2.5 mW cm^-3 with 100% of the original capacitance being retained at a current density of 5 mA cm^-2. Furthermore, the devices exhibited an energy density of 0.24 mW h cm^-3 even at a higher power density of 214.4 mW cm^-3, surpassing the performances observed for many recently reported flexible supercapacitors. Importantly, the electrochemical performance of the solid-state flexible supercapacitors showed a negligible change upon bending and twisting of the devices. The devices showed no decay in specific capacitance and coulombic efficiency up to 5000 charge-discharge cycles, confirming the excellent cycle life of the HSC device. The performance of NVL@CC indicates the great potential of the material for future flexible energy storage devices.

Hybrid carbon nanostructured fibers: stepping stone for intelligent textile-based electronics

The journey of smart textile-based wearable technologies first started with the attachment of sensors to fabrics, followed by embedding sensors in apparels. Presently, garments themselves can be transformed into sensors, which demonstrates the tremendous growth in the field of smart textiles. Wearable applications demand flexible materials that can withstand deformation for their practical use on par with conventional textiles. To address this, we explore the potential reasons for the enhanced performance of wearable devices realized from the fabrication of carbon nanostructured fibers with the use of graphene, carbon nanotubes and other two-dimensional materials. This review presents a brief introduction on the fabrication strategies to form carbon-based fibers and the relationship between their properties and characteristics of the resulting materials. The likely mechanisms of fiber-based electronic and storage devices, focusing mainly on transistors, nano-generators, solar cells, supercapacitors, batteries, sensors and therapeutic devices are also presented. Finally, the future perspectives of this research field of flexible and wearable electronics are discussed. The present study supplements novel ideas not only for beginners aiming to work in this booming area, but also for researchers actively engaged in the field of fiber-based electronics, dealing with advanced electronics and wide range of functionalities integrated into textile fibers.

Metal–organic framework derived small sized metal sulfide nanoparticles anchored on N-doped carbon plates for high-capacity energy storage

ZnS nanoparticles embedded in N-doped mesoporous carbon plates are prepared and exhibit high energy storage performance.

Towards flexible solid-state supercapacitors for smart and wearable electronics

Flexible solid-state supercapacitors (FSSCs) are frontrunners in energy storage device technology and have attracted extensive attention owing to recent significant breakthroughs in modern wearable electronics. In this study, we review the state-of-the-art advancements in FSSCs to provide new insights on mechanisms, emerging electrode materials, flexible gel electrolytes and novel cell designs. The review begins with a brief introduction on the fundamental understanding of charge storage mechanisms based on the structural properties of electrode materials. The next sections briefly summarise the latest progress in flexible electrodes (i.e., freestanding and substrate-supported, including textile, paper, metal foil/wire and polymer-based substrates) and flexible gel electrolytes (i.e., aqueous, organic, ionic liquids and redox-active gels). Subsequently, a comprehensive summary of FSSC cell designs introduces some emerging electrode materials, including MXenes, metal nitrides, metal-organic frameworks (MOFs), polyoxometalates (POMs) and black phosphorus. Some potential practical applications, such as the development of piezoelectric, photo-, shape-memory, self-healing, electrochromic and integrated sensor-supercapacitors are also discussed. The final section highlights current challenges and future perspectives on research in this thriving field.

New amphiphilic block copolymer-modified electrodes for supercapacitors

Herein, amphiphilic block copolymer-modified film electrodes were fabricated using poly(acrylic acid)-b-poly(acrylonitrile)-b-poly(acrylic acid) as a surface modifier, polyethersulfone as a matrix polymer, and activated carbon as an active substance by the phase separation method to enhance the wettability of the electrodes.

Flexible and integrated supercapacitor with tunable energy storage

A flexible integrated supercapacitor based on three dimensional reduced graphene oxide/graphene oxide/reduced graphene oxide (RGO-GO-RGO) foam has been fabricated via a laser direct writing strategy. The supercapacitor with outstanding mechanical properties shows a high capacitance performance which can be easily regulated by controlling the compressive state of the electrodes. This work provides a new platform for potential applications in the next-generation intelligent power supply of electronics.

Phytic acid-assisted electrochemically synthesized three-dimensional O, P-functionalized graphene monoliths with high capacitive performance

Three-dimensional functionalized graphene monoliths (3DFGMs) have attracted intensive attention as energy storage materials due to their unique interconnected porous structure, good electrical conductivity, excellent mechanical strength, and pseudocapacitive characteristic. Herein, we report a facile, green and low-cost strategy through a simple, one-step electrochemical process in a phytic acid solution to fabricate a 3DFGM. The 3D porous structure and functionalization of graphene can be obtained simultaneously. The as-obtained 3DFGM that consists of 3D porous O, P-functionalized few-layer graphene shows high specific surface area and good electrical conductivity. The 3DFGM with these characteristics exhibits excellent electrochemical performance, including an ultrahigh specific areal capacitance of 485 mF cm^-2, superior rate performance, and outstanding cycling stability. Most importantly, the assembled 3DFGM//3DFGM symmetric supercapacitor exhibits a high specific areal capacitance of 225 mF cm^-2 and delivers a maximum energy density of 1.2 W h L^-1 and a power density of 560 W L^-1 in aqueous electrolyte. Therefore, this work provides a promising method for the future design and fabrication of high performance 3D functionalized graphene-based electrodes for energy storage devices.

One-Dimensional Assembly of Conductive and Capacitive Metal Oxide Electrodes for High-Performance Asymmetric Supercapacitors

A one-dimensional morphology comprising nanograins of two metal oxides, one with higher electrical conductivity (CuO) and the other with higher charge storability (Co₃O₄), is developed by electrospinning technique. The CuO-Co₃O₄ nanocomposite nanowires thus formed show high specific capacitance, high rate capability, and high cycling stability compared to their single-component nanowire counterparts when used as a supercapacitor electrode. Practical symmetric (SSCs) and asymmetric (ASCs) supercapacitors are fabricated using commercial activated carbon, CuO, Co₃O₄, and CuO-Co₃O₄ composite nanowires, and their properties are compared. A high energy density of ∼44 Wh kg^-1 at a power density of 14 kW kg^-1 is achieved in CuO-Co₃O₄ ASCs employing aqueous alkaline electrolytes, enabling them to store high energy at a faster rate. The current methodology of hybrid nanowires of various functional materials could be applied to extend the performance limit of diverse electrical and electrochemical devices.

Flexible Fiber-Shaped Supercapacitor Based on Nickel-Cobalt Double Hydroxide and Pen Ink Electrodes on Metallized Carbon Fiber

Flexible fiber-shaped supercapacitors (FSSCs) are recently of extensive interest for portable and wearable electronic gadgets. Yet the lack of industrial-scale flexible fibers with high conductivity and capacitance and low cost greatly limits its practical engineering applications. To this end, we here present pristine twisted carbon fibers (CFs) coated with a thin metallic layer via electroless deposition route, which exhibits exceptional conductivity with ∼300% enhancement and superior mechanical strength (∼1.8 GPa). Subsequently, the commercially available conductive pen ink modified high conductive composite fibers, on which uniformly covered ultrathin nickel-cobalt double hydroxides (Ni-Co DHs) were introduced to fabricate flexible FSSCs. The synthesized functionalized hierarchical flexible fibers exhibit high specific capacitance up to 1.39 F·cm^-2 in KOH aqueous electrolyte. The asymmetric solid-state FSSCs show maximum specific capacitance of 28.67 mF·cm^-2 and energy density of 9.57 μWh·cm^-2 at corresponding power density as high as 492.17 μW·cm^-2 in PVA/KOH gel electrolyte, with demonstrated high flexibility during stretching, demonstrating their potential in flexible electronic devices and wearable energy systems.

Design and synthesis of graphene/activated carbon/polypyrrole flexible supercapacitor electrodes

A ternary composite of graphene/activated carbon/polypyrrole (GN/AC/PPy) used as an electrode active material for supercapacitors has been synthesized via vacuum filtration and anodic constant current deposition methods.

Synthesis and characterization of free-standing activated carbon/reduced graphene oxide film electrodes for flexible supercapacitors

Free-standing, binder-free and flexible activated carbon/reduced graphene oxide (AC/rGO) composite films with various ratios were fabricated via a facile vacuum-filtration process.

High Efficient Photo-Fenton Catalyst of α-Fe2O3/MoS2 Hierarchical Nanoheterostructures: Reutilization for Supercapacitors

A novel three-dimensional (3D) α-Fe₂O₃/MoS₂ hierarchical nanoheterostructure is effectively synthesized via a facile hydrothermal method. The zero-dimensional (0D) Fe₂O₃ nanoparticles guide the growth of two-dimensional (2D) MoS₂ nanosheets and formed 3D flower-like structures, while MoS₂ facilitates the good dispersion of porous Fe₂O₃ with abundant oxygen vacancies. This charming 3D-structure with perfect match of non-equal dimension exhibits high recyclable photo-Fenton catalytic activity for Methyl orange pollutant and nice specific capacity in reusing as supercapacitor after catalysis. The synergistic effect between Fe₂O₃ and MoS₂, the intermediate nanointerfaces, the 3D porous structures, and the abundant oxygen vacancies both contribute to highly active catalysis, nice electrochemical performance and stable cycling. This strategy is simple, cheap, and feasible for maximizing the value of the materials, as well as eliminating the secondary pollution.