High-performance Flexible Supercapacitors Research Articles

Co9S8@MnO2 core–shell defective heterostructure for High-Voltage flexible supercapacitor and Zn-ion hybrid supercapacitor

Flexible and wearable energy storage devices have drawn increasing attention owing to the rapid development of smart and portable electronic gadgets. Herein, vertically oriented Co9S8@MnO2 core–shell heterostructure nanotube arrays are in situ grown on the carbon cloth surface and activated by oxygen vacancy engineering via a fast NaBH4 reduction method. The introduction of oxygen vacancy can effectively improve the conductivity, reaction kinetics and thus increase the capacitance performance. The as-prepared high-active electrode material can assemble into high-performance flexible supercapacitor and Zn-ion hybrid supercapacitor. The assembled flexible all-solid asymmetric supercapacitors (AAS) show a wide potential window of 2.4 V, the excellent areal capacitance of 0.8058F cm−2 at 2 mA cm−2, high energy density of 92.14 Wh kg−1 and power density of 342.86 W kg−1. Further, the assembled Zn-ion hybrid supercapacitor has a higher energy density of 198.857 Wh kg−1, which is about twice than that of AAS devices. This work provides a rational strategy for design energy storage devices with high energy density and voltage window.

Co-MOF@MXene-carbon nanofiber-based freestanding electrodes for a flexible and wearable quasi-solid-state supercapacitor

Freestanding and flexible electrodes are crucial for advancing flexible and wearable energy storage devices (FW-ESD). However, the significant trade-off between mechanical flexibility and electrochemical performance of electrodes limits the development of high-performance FW-ESD. Therefore, flexible and freestanding multi-component hybrid electrodes with improved electrochemical properties are in high demand. This work reports a rational design of cobalt-metal organic framework (Co-MOF) structures on a highly flexible and electroconductive MXene-carbon nanofiber mat (MX-CNF). Further, the Co-MOF@MX-CNF was used as a starting material to derive capacitive-type Co-PC@MX-CNF and battery-type MnO2@Co3O4-PC@MX-CNF functional multi-component electrodes for a high-performance flexible wearable hybrid supercapacitor (FW-HSC). Owing to their high specific surface area (SSA), wettability, conductivity, and abundant active sites, Co-PC@MX-CNF and MnO2@Co3O4-PC@MX-CNF exhibited a specific capacitance of 426.7 F g−1 and a specific capacity of 475.4 mAh g−1 at 1 A g−1, respectively, with excellent mechanical flexibility. Moreover, the two electrodes were used to fabricate an FW-HSC with an operating voltage window of 1.5 V, delivering an energy density of 72.5 Wh kg−1 at a power density of 832.4 W kg−1 with long-term stability (90.36 % capacitance retention). Furthermore, a series connection of two identical FW-HSC devices could power a digital clock and light up a green LED, demonstrating its potential as a power source for various wearable devices.

In situ anodic electrodeposition of two-dimensional conductive metal-organic framework@nickel foam for high-performance flexible supercapacitor

Owing to their large specific surface area and well-defined porosity, metal-organic frameworks (MOFs) have long been considered as promising materials for energy storage. Unfortunately, their straightforward utilization in supercapacitors was hindered for years due to poor conductivity until the emergence of 2D conductive MOF materials. To date, several 2D conductive MOF-based supercapacitors have been reported. Nevertheless, almost all these supercapacitors were fabricated from MOF powders through a slurry coating method or dense packing method, which negatively affected their capacitor performance. Herein, we have developed an anodic electrodeposition (AED) approach to fabricate a uniformly deposited 2D conducting MOF on nickel foam and use it directly as electrodes for supercapacitors without any additives. The superior performance of the 2D conducting MOF on nickel foam in both aqueous and organic electrolytes was then disclosed by a series of electrochemical measurements, demonstrating the significant advantages of the AED approach over traditional methods.

Coupling of graphene quantum dots with MnO2 nanosheets for boosting capacitive storage in ionic liquid electrolyte

Utilizing ionic liquid (IL) as electrolyte to fabricate supercapacitor is an effective strategy for increasing its operating voltage and energy density. Although manganese dioxide (MnO2) can exhibit pseudocapacitive storage behavior in some specific IL electrolytes, it still suffers from low specific capacitance as well as unsatisfactory kinetics. Herein, a new design of graphene quantum dots (GQDs) integrated with MnO2 nanosheets is proposed to construct a GQDs@MnO2 composite electrode for IL-based supercapacitor. Synergistically coupling of GQDs with MnO2 nanosheets provides a 3D nanoflower architecture with increased surface area, enhanced electrochemical kinetics and excellent structural integrity. The GQDs play an important role in modifying the density of state and energy bandgap as well as enhance the electronic conductivity of GQDs@MnO2 electrode. These properties endow the superior capacitive storage, rapid charge–discharge response and high electrochemical reversibility for GQDs@MnO2 electrode in IL electrolyte. For real-life application, a high-performance flexible IL-based supercapacitor is assembled, which can deliver a high energy density (82.2 Wh kg−1), a high power density (11.6 kW kg−1), and long-term cycle performance upon the straight and bent states, suggesting its great potential in energy-related technologies and portable electronics.

Well-defined tetraaniline deposited graphene via mixed self-assembly for high-performance flexible supercapacitor application

Graphene-based flexible supercapacitors have been widely developed for wearable devices. To enhance the electrochemical property, various electroactive materials have been incorporated into the graphene-based electrodes. Here, tetraaniline (TA) was used to fabricate the high-performance flexible electrodes for supercapacitors, owing to its high electroactivity and good processability. The well-defined tetraaniline deposited graphene was optimized by investigating the effects of the kinds of graphene, fabrication methods, and the feeding ratios between the two components. The symmetric supercapacitors based on the optimized one (TA-rPGO) via the one-step mixed self-assembly of TA in presence of porous expandable graphene oxide (PGO) possessed specific capacitance of 85.6 F/g, energy density of 7.9 Wh/kg, and power density of 87.6 W/kg at 0.10 A/g respectively, with excellent flexibility and cycling stability.

Biowaste-derived electrode and electrolyte materials for flexible supercapacitors

One of the key challenges in the development of energy storage devices relates to material sourcing in harmony with clean technologies. Herein, cellulose nanocrystals (CNC) extracted from brewery residues are used as transparent hydrogel electrolyte after physical cross-linking with aluminum ions (Al3+). The hydrogel electrolyte (Al-CNC) exhibits an ultrahigh ionic conductivity (∼24.9 mS cm−1), high optical transmittance (∼92.9% at 550 nm wavelength), outstanding compression strength (3.9 MPa at a 70% strain), and tolerates to various deformations (e.g., twisting, folding, rolling). Meanwhile, animal bone biowaste is used to synthesize porous carbon (PC) electrodes (∼879 m2 g−1) that are effective in delivering an outstanding specific capacitance (∼804 F g−1 at 1 A g−1). A fully renewable flexible symmetric supercapacitor is assembled by sandwiching the Al-CNC hydrogel between two bone-derived PC electrodes (PC//Al-CNC//PC). The obtained flexible device displays a high energy density (18.2 Wh kg−1 at 1 425 W kg−1), exceptional power density (20 833 W kg−1 at 7.1 Wh kg−1), and ∼92% capacitance retention after 6 000 cycles at 5 A g−1. We further demonstrated the biowaste-derived high-performance flexible supercapacitors for their mechanical durability and reliable electrochemical performance under bending cycles. All combined, the devices are shown to be ideally suited for renewable energy storage applications.

High-Performance Flexible Solid-State Supercapacitors Based on MnO2-Decorated Carbon Nanotube Sponge with Ultra-high Capacitance, Long Cycling Life, and Enhanced Mechanical Strength

High-Performance Flexible Solid-State Supercapacitors Based on MnO₂-Decorated Carbon Nanotube Sponge with Ultra-high Capacitance, Long Cycling Life, and Enhanced Mechanical Strength

One-step microwave synthesis of CoSb for high-performance wearable flexible supercapacitor

The activated carbon felt with uniform loading of CoSb nanomaterials is obtained by microwave radiation. Impressively, electrochemical tests show that the capacitance value of CoSb at 1 A g[Formula: see text] is 1311.0 F g[Formula: see text], and after 20,000 cycles, the capacitance retention rate is 81.5%. The assembled asymmetric flexible capacitor has a voltage window of 1.8 V. The energy density and power density of the device are 24.3 W h Kg[Formula: see text] and 921.0 W kg[Formula: see text], respectively. The electrochemical performance of the device is not affected under bending conditions.

Growth of yolk-shell CuCo2S4 on NiO nanosheets for high-performance flexible supercapacitors

A poor electrical conductivity and short cycle life limits the wide application of transition metal oxides in energy storage applications. In this study, yolk-shell structured CuCo 2 S 4 was grown on NiO nanosheets (NiO@CuCo 2 S 4 ) via a hydrothermal method and vulcanization, which combined the synergistic interactions between Ni, Co, and Cu. The effect of varying the amount of the vulcanizing agent (thiourea) on the electrochemical performance of NiO@CuCo 2 S 4 was also investigated. Moreover, the amount of thiourea not only tuned the morphology of the composite, but significantly influenced its electrochemical performance. When the Cu 2+ : Co 2+ : thiourea molar ratio in the precursor solution was 1:2:6, the obtained NiO@CuCo 2 S 4 exhibited the best electrochemical performance of the various systems examined, with a specific capacitance of 1658 F g −1 being achieved at 1 A g −1 . Density functional theory calculations further confirmed the excellent synergistic effect between NiO and CuCo 2 S 4 . In addition, the asymmetric supercapacitor composed of a NiO@CuCo 2 S 4 positive electrode reached an ultrahigh energy density of 73 Wh kg −1 at a power density of 802 W kg −1 , as well as excellent cycling stability (i.e., 91% capacitance retention after 5000 cycles). These results suggest that NiO@CuCo 2 S 4 is a promising candidate for use in energy storage applications.

Nitrogen-doped graphene fiber electrodes with optimal micro-/meso-/macro-porosity ratios for high-performance flexible supercapacitors

The introduction of graphene fiber-based supercapacitors as important power storage components in wearable electronic products has attracted increasing attention because of their lightweight, good flexibility, high power density, long lifecycle and excellent charge/discharge capacity. However, their capacitance and energy density are greatly confined as a result of the dense graphene stacking, hydrophobicity and poor electrical conductivity of graphene fiber electrodes. Here we report a nitrogen-doped graphene fiber electrode with optimal micro-/meso-/macro-porosity ratios to improve the utilization efficiency of fiber inner interface for accumulated charge storage and boosted ion transport. Urea is employed as both nitrogen doping source and self-removed template for graphene fibers to tune the hierarchically porous architecture, wettability, nitrogen content, and electrical conductivity for improved electrochemical performance. The resulting supercapacitors display superior areal capacitance of 1,217 mF/cm 2 (486.3 F/g) and high energy density of 27 μW h/cm 2 (10.8 W h/Kg) in polyvinyl alcohol/H 3 PO 4 gel electrolyte. These metrics represent the highest values to date among existing all-solid-state fiber-based supercapacitors based on inorganic electrolyte. Moreover, the fiber-based supercapacitors show good rate capability and excellent cyclic performance. Our work also provides an understanding of the effect of fiber structure on electrochemical activity and highlights the importance of full utilization of graphene interior interface. • Hierarchically structured nitrogen-doped graphene fibers are fabricated. • The utilization efficiency of fiber inner interface is improved. • Nitrogen doping improves wettability, nitrogen content and electrical conductivity. • The all-solid-state flexible fiber-based supercapacitors have been fabricated. • Fiber-based supercapacitors exhibit outstanding electrochemical performance.

High performance flexible carbon cloth-based solid-state supercapacitors with redox-mediated gel electrolytes

The electrochemical performance of supercapacitors is mainly determined by both the electrodes and electrolytes. By integration of the flexible electrodes with redox-mediated gel electrolytes, high performance solid state supercapacitors were designed in the present work. The flexible carbon cloth (CC)-based electrodes were prepared by covalent immobilization of tetraaniline (TA) onto the oxidized carbon cloth (OCC). Hydroquinone (HQ) and p-phenylenediamine (PPD) were used as redox additive respectively to enhance the electrochemical property of the PVA-H2SO4 gel electrolyte. After optimization, high performance flexible solid-state symmetric supercapacitors (SSSCs) were obtained with specific capacitance of 834.0 mF/cm2, retention of 93.69% after 10,000 CV cycles and 108.5% after 500 cycles of 180°-bending, and energy density of 74.2 mWh/cm2 at power density of 405.3 mW/cm2. Such outstanding comprehensive performance makes them promising potential for practical application.

PANI-MnO2 and Ti3C2Tx (MXene) as electrodes for high-performance flexible asymmetric supercapacitors

Polyaniline (PANI) and manganese dioxide (MnO2) are forward-looking electrode materials due to their high specific capacitance. But poor cyclic stability of PANI and low power density of MnO2 limit their development. In this paper, PANI and MnO2 were synthesized on carbon cloth (CC) by electrochemical polymerization with the addition of LiClO4. The capacitance of CC/PANI-MnO2 increases to 634.0 F g−1 (380.4 C g−1) at 1 A g−1. And its decent electrochemical performances can be ascribed to the synergistic effect of PANI and MnO2. Moreover, an asymmetric supercapacitor based on CC/PANI-MnO2 as positive electrode and CC/MXene as negative electrode were assembled to broaden the potential range. The device has capacitance of 21.1 F g−1 at 0.5 A g−1 and the capacitance retention of 83% after 4000 cycles. The device shows an energy density of 47.25 μWh cm−2 at a power density of 2.40 mW cm−2. Furthermore, the ductility of the device was explored to resist the bending and stretching from external forces. The research of flexible asymmetric supercapacitors herein further improves the practical application of energy storage devices.

NiCo2O4 nanoneedle-nanosheet hybrid structure on CC substrate for high-performance flexible supercapacitors

In this paper, three different morphologies of NiCo2O4 nanoarrays, namely, nanosheet (S-NiCo2O4), nanoneedle (N-NiCo2O4) and their hybrid nanostructure (M-NiCo2O4) were successfully prepared on flexible carbon cloth (CC) by a hydrothermal method. The structures, surface morphologies and compositions of the samples were respectively characterized by XRD, SEM, EDS, and XPS, and the effect of NiCo2O4 morphologies on the electrochemical performances was systematically investigated. It is found that the M-NiCo2O4/CC electrode demonstrates the best supercapacitive performance among the three kinds of samples, typically its specific capacitance is 1347.4 F/g at 1 A/g (1509.1 F/cm2 at 1 mA/cm2), much higher than that of S-NiCo2O4 (938.4 F/g at 1 A/g) and N-NiCo2O4 (1022.4 F/g at 1 A/g). Meanwhile, the M-NiCo2O4/CC sample exhibits excellent rate capability (81.6%, from 1 A/g to 15 A/g) and cycling stability (92.4% retention after 10,000 cycles). In addition, an flexible solid-state asymmetric supercapacitor (ASC) with M-NiCo2O4/CC as positive electrode manifests great capacity retention (94% after 5000 cycles) and outstanding energy density of 41.7 Wh/kg at the power density of 750 W/kg. Moreover, the charge-discharge time shows no significant change after 2000 bends, demonstrating its application potential in the field of flexible SCs. The excellent performance is attributed to the unique hybrid porous structure of one-dimensional (1D) nanoneedles and two-dimensional (2D) nanosheets.

Bimetallic Heterojunction Effectively Constructs Porous Surface Engineering for High Performance Flexible Asymmetric Supercapacitors

Bimetallic Heterojunction Effectively Constructs Porous Surface Engineering for High Performance Flexible Asymmetric Supercapacitors

Hydrogen Peroxide-Assisted Synthesis of Nitrogen/Sulfur Co-Doped Activated Carbon for High-Performance All-Printed Flexible Supercapacitor

Hydrogen Peroxide-Assisted Synthesis of Nitrogen/Sulfur Co-Doped Activated Carbon for High-Performance All-Printed Flexible Supercapacitor

A high-performance flexible energy storage device from biomass-derived porous carbon supported MnCo2O4 nanorods and MnO2 nanoscales

MCO-MnO2-PC||PC as a high-performance flexible asymmetric supercapacitor device.

Hybrid Carbon Nanofiller/Polymer Composites as Self-Healable Current Collector Electrodes for Use in High-Performance Flexible Metal-Free Supercapacitors

Hybrid Carbon Nanofiller/Polymer Composites as Self-Healable Current Collector Electrodes for Use in High-Performance Flexible Metal-Free Supercapacitors

Fabrication of High-Performance Flexible Printed Supercapacitor Using Cobalt Hydroxide Nanowires

Fabrication of High-Performance Flexible Printed Supercapacitor Using Cobalt Hydroxide Nanowires

Carbon Quantum Dot-Induced Robust Ε-Mno2 Electrode by Synergistic Engineering of Oxygen Vacancy and Low Crystallinity for High-Performance Flexible Asymmetric Supercapacitor

Carbon Quantum Dot-Induced Robust Ε-Mno2 Electrode by Synergistic Engineering of Oxygen Vacancy and Low Crystallinity for High-Performance Flexible Asymmetric Supercapacitor

Facile preparation of graphene@polyaniline nanofiber network/oxidized carbon cloth composites for high-performance flexible solid-state supercapacitors.

The complicated preparation process and low energy density of polyaniline (PANI)-based electrodes limit their wide applications in flexible energy storage devices. In this work, a reduced graphene (rGO)-wrapped polyaniline nanofiber network (PANI-NFN)/oxidized carbon cloth (OCC) (rGO@PANI-NFN/OCC) composite was prepared by a facile impregnation method using reactive templates of MnO2 on the surface of OCC. The as-prepared rGO@PANI-NFN/OCC composite exhibited a high area specific capacitance of 4438 mF cm-2 and maintained an initial capacitance of 88.2% after 3000 GCD cycles. It can be used as an independent electrode to construct flexible solid-state supercapacitors (FSSCs), and the FSSCs based on rGO@PANI-NFN/OCC also exhibit a high energy density of 117.9 μW h cm-2 and 88.39% retention after 500 bending cycles, which shows a great prospect for flexible energy storage device applications. The enhanced performance of rGO@PANI-NFN/OCC composites is mainly attributed to the synergistic effect of PANI-NFN structures with a large specific surface area and a rGO wrap layer to reduce the swelling and shrinking of PANI.