Paper or flexible supercapacitor*

By virtue of its narrow pulse width and high peak power, the femtosecond pulsed laser can achieve high-precision material modification, material additive or subtractive, and other forms of processing. With additional good material adaptability and process compatibility, femtosecond laser-induced application has achieved significant progress in flexible electronics in recent years. These advancements in the femtosecond laser fabrication of flexible electronic devices are comprehensively summarized here. This review first briefly introduces the physical mechanism and characteristics of the femtosecond laser fabrication of various electronic microdevices...

Electrochromic devices (ECD) are widely used to regulate the transmittance of sunlight by applying a small voltage, but the drawbacks like complex layer-by-layer preparation procedures and inconvenient assembling process still exist. To address these problems, gel or solution-type all-in-one ECDs were recently developed for the simple structure, however, the leakage risk and absence of flexible large-area production have limited real applications. Herein, a novel all-solid-state and all-in-one flexible ECD was reported by originally developed polymer dispersed electrochromic device (PDECD) strategy...

The severe Zn-dendrite growth and insufficient carbon-based cathode performance are two critical issues that hinder the practical applications of flexible Zn-ion micro-ssupercapacitors (FZCs). Herein, a self-adaptive electrode design concept of the synchronous improvement on both the cathode and anode is proposed to enhance the overall performance of FZCs. Polypyrrole doped with anti-expansion graphene oxide and acrylamide (PPy/GO-AM) on the cathode side can exhibit remarkable electrochemical performance, including decent capacitance and cycling stability, as well as exceptional mechanical properties...

Hydrogel electrolyte can endow supercapacitors with excellent flexibility, which has developed rapidly in recent years. However, the water-rich structures of hydrogel electrolyte are easy to freeze at subfreezing and dry at high temperatures, which will affect its energy storage characteristics. The low energy density of micro supercapacitors also hinders their development. Herein, a strategy is proposed to reduce the free water activity in the hydrogel to improve the operating voltage and the energy density of the device, which is achieved through the synergistic effect of the hydrogel skeleton, N, N'-dimethylformamide (DMF), NaClO4 and water...

As a promising green and sustainable coating material, gum was extracted from durian seed to produce eutectogel, which the properties were tunable using natural deep eutectic solvent (NADES). Ten different eutectogels were successfully synthesized using durian seed gum (DSG) and xanthan gum (XG) gelators at different composition (5, 10, 15 %) to gel choline chloride-glucose (1:1), choline chloride-fructose (1:2) and betaine-glucose-water (1:1:1) NADESs. Results revealed that eutectogel was non-Newtonian and weak gel material with excellent thermostability up to 200 °C...

Supercapacitors demonstrate promising potential for flexible, multi-functional energy storage devices; however, their widespread adoption is confronted by fabrication challenges. To access a combination of desirable device qualities such as flexibility, lightweight, structural stability, and enhanced electrochemical performance, carbon fiber (CF) can be utilized as a current collector, alongside graphene as an electrochemically active material. Yet achieving a cost-effective, large-scale graphene production, particularly on CF, remains challenging...

Developing a highly efficient electrochromic energy storage device with sufficient color fluctuation and significant electrochemical performance is highly desirable for practical energy-saving applications. Here, to achieve a highly stable material with a large electrochemical storage capacity, a W18 O49 NW/Ti3 C2 Tx composite has been fabricated and deposited on a pre-assembled Ag and W18 O49 NW conductive network by Langmuir-Blodgett technique. The resulting hybrid electrode composed of 15 layers of W18 O49 NW/Ti3 C2 Tx composite exhibits an areal capacitance of 125 mF cm-2 , with a fast and reversible switching response...

The advancement of aqueous micro-supercapacitors offers an enticing prospect for a broad spectrum of applications, spanning from wearable electronics to micro-robotics and sensors. Unfortunately, conventional micro-supercapacitors are characterized by low capacity and slopy voltage profiles, limiting their energy density capabilities. To enhance the performance of these devices, the use of 2D MXene-based compounds has recently been proposed. Apart from their capacitive contributions, these structures can be loaded with redox-active nanowires which increase their energy density and stabilize their operation voltage...

The reuse of waste papers by conversion into valuable carbon materials has received considerable attention for diverse applications such as energy storage and water purification. However, traditional methods for converting waste papers into materials with suitable properties for specific applications are often complex and ineffective, involving consecutive carbonization and activation steps. Herein, we propose a simple one-step microwave (MW)-assisted synthesis for preparing waste paper-derived porous carbons (WPCs) for energy storage and water purification...

Carbonaceous materials are attractive active materials for the manufacture of flexible electrochemical double-layer capacitors (EDLCs) because of their high electrical conductivity, large surface area, and inherent resilience against deformation. However, compared to pseudocapacitors, which store electrochemical energy via faradaic redox reactions, EDLCs generally exhibit inferior energy density. One potential approach to addressing this issue is to incorporate highly porous and electrically conductive materials into carbonaceous material-based EDLCs...

Hydrogel polymer electrolytes (GPEs), as an important component of flexible energy storage devices, have gradually received wide attention compared with traditional liquid electrolytes due to their advantages of good mechanical, bending, and safety properties. In this paper, two cross-linked GPEs of poly(acrylic acid-co-acrylamide) or poly(acrylic acid-co-N-methylolacrylamide) with NaNO3 aqueous solution (P(AA-co-AM)/NaNO3 or P(AA-co-HAM)/NaNO3 ) were successfully prepared using radical polymerization, respectively, using acrylic acid (AA) as the monomer, N-methylolacrylamide (HAM) or acrylamide (AM) as the comonomer, and N, N-methylenebisacrylamide (MBAA) as the cross-linking agent...

Flexible supercapacitors (FSCs) with high electrochemical and mechanical performance are inevitably necessary for the fabrication of integrated wearable systems. Conducting polymers with intrinsic conductivity and flexibility are ideal active materials for FSCs. However, they suffer from poor cycling stability due to huge volume variations during operation cycles. Two-dimensional (2D) materials play a critical role in FSCs, but restacking and aggregation limit their practical application. Nanocomposites of conducting polymers and 2D materials can mitigate the above-mentioned drawbacks...

The burgeoning demand for miniaturized energy storage devices compatible with the miniaturization trend of electronic technologies necessitates advancements in micro-supercapacitors (MSCs) that promise safety, cost efficiency, and high-speed charging capabilities. However, conventional aqueous MSCs face a significant limitation due to their inherently narrow electrochemical potential window, which restricts their operational voltage and energy density compared to their organic and ionic liquid counterparts...

The development of electrode materials with excellent performance serves as the key for researchers to enhance the energy density of supercapacitors. Cobalt molybdate (CoMoO4 ) nanomaterials have been regarded as one of the most prospective electrode materials for supercapacitors due to their high theoretical capacitance and excellent electrical conductivity. In this paper, three kinds of CoMoO4 nanorods were prepared directly via simple and environmentally friendly solid-phase chemical reactions with solid inorganic salts as raw materials...

Based on MnO2 /carbon cloth (CC) composite materials, an Ag-doped MnO2 nanowire, self-assembled, urchin-like structure was synthesized in situ on the surface of CC using a simple method, and a novel and efficient flexible electrode material for supercapacitors was developed. The morphology, structure, elemental distribution, and pore distribution of the material were analyzed using SEM, TEM, XRD, XPS, and BET. The electrochemical performance was tested using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD)...

Hydrogel electrolyte is an ideal candidate material for flexible energy storage devices due to its excellent softness and conductivity properties. However, challenges such as the inherent mechanical weakness, the susceptibility to be frozen in low-temperature environments, and the insufficiency of hydrogel-electrode contact persist. Herein, a "Multi in One" strategy is employed to effectively conquer these difficulties by endowing hydrogels with high strength, freeze-resistance, and self-adhesive ability. Multiple hydrogen bond networks and ion crosslinking networks are constructed within the hydrogel electrolyte (PVA/PAAc/XG) containing polyvinyl alcohol (PVA), acrylic acid (AAc), and xanthan gum (XG), promoting the enhanced mechanical property, and the adhesion to electrode materials is also improved through abundant active groups...

Polymeric foams, also known as three-dimensional (3D) polymeric sponges, are lightweight, flexible, compressible, and possess a high surface area compared with other bulk polymers. These sponges have traditionally been used for mattresses or seat cushions in homes, offices, aircraft, automobiles, and trains, and to insulate against heat, electricity, and noise. Recently, the demand for modern materials has expanded the application of polymeric foams to various high-value technologies, including in areas that need high flame retardancy, flame sensors, oil/water separation, metal adsorption, solar steam generation, piezoresistivity, electromagnetic interference shielding, thermal energy storage, catalysis, supercapacitors, batteries, and triboelectric energy harvesting...

Supercapacitors have become one of the most popular energy-storage devices for high power density and fast charging/discharging capability. Polyaniline is a class of conductive polymer materials with ultra-high specific capacitance, and the excellent mechanical properties will play a key role in the research of flexible supercapacitors. The synergistic effect between polyaniline and graphene is often used to overcome their respective inherent shortcomings, thus the high-performance polyaniline-graphene based nanocomposite electrode materials can be prepared...

Polybenzoxazines (Pbzs) are advanced forms of phenolic resins that possess many attractive properties, including thermal-induced self-curing polymerization, void-free polymeric products and absence of by-product formation. They also possess high Tg (glass transition temperature) and thermal stability. But the produced materials are brittle in nature. In this paper, we present our attempt to decrease the brittleness of Pbz by blending it with polyvinylalcohol (PVA). Benzoxazine monomer (Eu-Ed-Bzo) was synthesized by following a simple Mannich condensation reaction...

The bottleneck in the preparation of supercapacitors is how to develop high-energy and high-power-density devices by using appropriate materials. Herein, a novel Ni x Co3- x -B/GO heterostructure material was synthesized through a simple ultrasonic and precipitation method. The prepared Ni x Co3- x -B/GO heterostructure exhibits significant improvements in supercapacitor performance than Ni x Co3- x -B. The presence of GO effectively suppresses the excessive growth and accumulation of Ni x Co3- x -B; therefore, Ni2...