Flexible High-performance Supercapacitors Research Articles

Waste-Cotton-Cloth-Derived Sustainable and Flexible High-Performance Supercapacitor

Waste-Cotton-Cloth-Derived Sustainable and Flexible High-Performance Supercapacitor

High-performance VO2/CNT@PANI with core–shell construction enable printable in-planar symmetric supercapacitors

As a progressive electronic energy storage device, the flexible supercapacitor holds tremendous promise for powering wearable/portable electronic products. Of various pseudocapacitor materials, vanadium dioxide (VO2) has garnered extensive attention due to its impressive theoretical capacitance. However, the challenges of inferior cycling life and lower energy density to be addressed. Herein, we prepare VO2 nanorods with winding carbon nanotubes (CNT) via a facile solvothermal route, followed by in situ polymerization of polyaniline (PANI) shell. Taking full advantage of the synergistic effect, the VO2/CNT@PANI composite delivers a high specific capacitance of 354.2F/g at 0.5 A/g and a long cycling life of ∼ 88.2 % over 5000 cycles resulting from the enhanced conductivity of CNT and stabilization of PANI shell. By screen printing the formulated inks with outstanding rheological behaviours, we manufacture an in-planar VO2/CNT@PANI symmetric supercapacitor (VO2/CNT@PANI SSC) device featuring an orderly arrangement structure. This device yields a remarkable areal energy density of 99.57 μWh/cm2 at a power density of 387.5 μW/cm2 while retaining approximately ∼ 87.6 % of its initial capacitance after prolonged use. Furthermore, we successfully powered a portable game machine for more than 2 min using two SSCs connected in series with ease. Therefore, this work presents a universal strategy that utilises combination and coating to boost electrochemical performance for flexible high-performance supercapacitors.

A mild one-step synthesis of sodium pre-intercalated δ-MnO2@CC for flexible high-performance supercapacitors with ultralong cycle life

Cation ion intercalated δ-MnO2 has been considered as a promising candidate for flexible energy storage devices. Herein, we fabricated Na ion pre-intercalated δ-MnO2 immobilized on flexible carbon cloth (CC) for symmetric supercapacitors via a mild one-step cyclic voltammetry (CV) electrodeposition method. Compared to that of NaxMnO2–32 without NH4+additive, NaxMnO2–32-N with NH4+ additive obtained a larger Cs (1208 mF·cm−2) with a 40 % increase and a maintained Cm (208 F·g−1 at 1 mA·cm−2). In addition, NaxMnO2–32-N exhibited more remarkable capacitive behavior and better rate capability. Based on the XPS, BET, TEM and SEM results, the increase of specific surface area, Na+ ion pre-embedded content and deposition mass were deduced to be the dominant role in optimizing electrochemical properties of δ-MnO2. A flexible symmetric supercapacitor was assembled by NaxMnO2–32-N electrodes to evaluate its applications and demonstrated a high energy density of 117.74 μW·h·cm−2 (at a power density of 225 μW·cm−2) and power density of 3375 μW·cm−2 (at an energy density of 12.35 μW·h·cm−2) with good flexibility. Furthermore, it showed excellent capacity retention rate (97 %) and coulomb efficiency (105 %) after 80,000 long-term charging/recharging cycles.

Porous prussian blue analogs derived nickel-iron bimetallic phosphide nanocubes on conductive hollow mesoporous carbon nanospheres for stable and flexible high-performance supercapacitor electrode

Nickel-iron bimetallic phosphide (Ni-Fe-P) is the ideal battery-type materials for supercapacitor in virtue of high theoretical specific capacitance. Nevertheless, its actual adhibition is astricted on account of inferior rate capability and cyclic stability. Herein, we constructed hierarchical core–shell nanocomposites with hollow mesoporous carbon nanospheres (HMCS) packaged via prussian blue analogs derived Ni-Fe-P nanocubes (Ni-Fe-P@HMCS), as a positive electrode for hybrid supercapacitor (HSC). Profiting from the cooperative effects of Ni-Fe-P nanocubes with small size and good dispersibility, and HMCS with continuously conductive network, the Ni-Fe-P@HMCS composite electrode with abundantly porous architectures presents an ultrahigh gravimetric specific capacity for 739.8 C g−1 under 1 A g−1. Specially, the Ni-Fe-P@HMCS electrode presents outstanding rate capability of 78.4% (1 A g−1 to 20 A g−1) and cyclic constancy for 105% after 5000 cycles. Density functional theory implies that the composite electrode possesses higher electrical conductivity than bare Ni-Fe-P electrode by reason of the incremental charge density, and the electrons transferring from NiFe3P4 to HMCS layers. Additionally, the assembled Ni-Fe-P@HMCS//HMCS HSC facility delivers the high energy density for 64.1 Wh kg−1, remarkable flexibility and mechanical stability. Thus, this work proffers a viable and efficacious measure to construct ultra-stability electrode for high-performance portable electronic facilities.

A review of flexible high-performance supercapacitors for the internet of things (IoT) and artificial intelligence (ai) applications

The Internet of Things (IoT) is a new area of modern technology today. Transportation, agriculture, healthcare, manufacturing, wearables, smart grid, energy-saving technologies, smart homes, smart management systems, and other fields of engineering, technology, and real-time management all have IoT applications. Moreover, artificial intelligence (AI) has broad applications in the car industry, surveillance, security, education, entertainment, gaming, e-commerce, portable gadgets, robotics, medicinal devices, etc. They require efficient energy to operate for an extended period. These devices necessitate offline and online energy storage devices that discharge for an extended period of time or require less time to charge advanced electrical energy storage devices such as supercapacitors. This review article reveals advanced energy storage devices such as supercapacitors and their applications in IoT and AI-based devices. A supercapacitor is an electrochemical capacitor that has high energy density and better performance efficiency.

A New Strategy for Fabricating Well-Distributed Polyaniline/Graphene Composite Fibers toward Flexible High-Performance Supercapacitors.

Fiber-shaped supercapacitors are promising and attractive candidates as energy storage devices for flexible and wearable electric products. However, their low energy density (because their microstructure lacks homogeneity and they have few electroactive sites) restricts their development and application. In this study, well-distributed polyaniline/graphene composite fibers were successfully fabricated through a new strategy of self-assembly in solution combined with microfluidic techniques. The uniform assembly of polyaniline on graphene oxide sheets at the microscale in a water/N-methyl-2-pyrrolidone blended solvent was accompanied by the in situ reduction of graphene oxides to graphene nanosheets. The assembled fiber-shaped supercapacitors with gel-electrolyte exhibit excellent electrochemical performance, including a large specific areal capacitance of 541.2 mF cm−2, along with a high energy density of 61.9 µW h cm−2 at a power density of 294.1 µW cm−2. Additionally, they can power an electronic device and blue LED lights for several minutes. The enhanced electrochemical performance obtained is mainly attributed to the homogeneous architecture designed, with an increased number of electroactive sites and a synergistic effect between polyaniline and graphene sheets. This research provides an avenue for the synthesis of fiber-shaped electrochemically active electrodes and may promote the development of future wearable electronics.

Brush-electroplated rGO@MnO2 composite supported on carbon cloth for flexible high-performance supercapacitor electrodes

Brush-electroplated rGO@MnO2 composite supported on carbon cloth for flexible high-performance supercapacitor electrodes

A Strong, Anti-Freezing, Anti-Swelling and High Ionic Conductive Hydrogel Electrolyte Based on Bacterial Cellulose Aerogel Reinforced Pana/Koh Hydrogel for Flexible High Performance Supercapacitor

A Strong, Anti-Freezing, Anti-Swelling and High Ionic Conductive Hydrogel Electrolyte Based on Bacterial Cellulose Aerogel Reinforced Pana/Koh Hydrogel for Flexible High Performance Supercapacitor

CuCo-Layered Double Hydroxide Nanosheet-Based Polyhedrons for Flexible Supercapacitor Cells

Herein, a flexible high-performance supercapacitor cell using nanostructured CuCo-layered double hydroxide (LDH) as power source electrode material is reported for the first time, where the CuCo-LD...

Direct laser writing of pure lignin on carbon cloth for highly flexible supercapacitors with enhanced areal capacitance

A facile approach was developed to synthesize pure lignin-derived porous carbon for highly flexible high-performance supercapacitor electrodes.

3D self-supporting heterostructure NiCo-LDH/ZnO/CC electrode for flexible high-performance supercapacitor

Two kinds of nanostructured ZnO, namely nanorods (ZnO NR) and nanoflakes (ZnO NF) were first prepared on conductive flexible carbon cloth (CC) by a hydrothermal route. Then nickel cobalt layered double hydroxide (NiCo-LDH) nanoflakes were directly hydrothermally deposited on them to construct three-dimensional (3D) self-supporting heterostructure NiCo-LDH/ZnO NR/CC and NiCo-LDH/ZnO NF/CC flexible electrodes. The effects of different nanostructured ZnO on morphology, structure and electrochemical performance of NiCo-LDH/ZnO/CC composite materials were investigated. It is found that NiCo-LDH nanoflakes grown on ZnO NF/CC substrate are more compact and uniform than those on ZnO NR/CC substrate. Moreover, NiCo-LDH/ZnO NF/CC electrode presents better electrochemical properties than NiCo-LDH/ZnO NR/CC electrode with 2.6 times higher specific capacitance (1577.6 F g−1 at 1 A g−1), 2.2 times better rate capability, and 1.5 time greater cycle stability, which may be attributed to the larger contact area and more redox-active sites provided by the NiCo-LDH NFs grown on ZnO NFs. Furthermore, the as-assembled solid-state flexible NiCo-LDH/ZnO NF//AC (active carbon) asymmetric supercapacitor (ASC) delivers a maximal energy density of 51.39 Wh kg−1 (800 W kg−1) with a high operating window of 1.6 V, and exhibits great cyclic stability with 87.3% capacitance retaining after 1000 cycles, which is higher than many reported ASCs. Finally, two packaged ASCs in series successfully lighted a red light-emitting diode (LED, 2.2 V/20 mA), evincing the potentiality of practical application.

Self-supported core-shell heterostructure MnO2/NiCo-LDH composite for flexible high-performance supercapacitor

Nickel cobalt layered double hydroxides (NiCo-LDHs) nanosheets (NSs) were synthesized on a flexible carbon cloth (CC) substrate by a simple hydrothermal method. Then the manganese dioxide (MnO2) NSs were directly deposited on the NiCo-LDH/CC to form three-dimensional (3D) self-supported core-shell MnO2/NiCo-LDH/CC flexible electrodes. The MnO2 NSs with three different loading amount on NiCo-LDH/CC substrate, named MnO2-1/NiCo-LDH/CC, MnO2-2/NiCo-LDH/CC and MnO2-3/NiCo-LDH/CC, were hydrothermally synthesized in 0.01 M, 0.02 M and 0.03 M potassium permanganate (KMnO4) solution, respectively. The morphology and electrochemical performance of these obtained composite electrodes were observed and analyzed. The MnO2-2/NiCo-LDH/CC electrode exhibits a capacitive performance of 312 F g−1 at 0.2 A g−1 (937 mF cm−2 at 1 mV s−1) and maintains 97% of the original capacitance after 5000 charge-discharge cycles. The good mechanical stability and excellent cycle performance of MnO2-2/NiCo-LDH/CC electrode is benefit from the numerous channels for rapid electron transport provided by the large specific surface area and self-supported of NiCo-LDH nanoflakes. Therefore, the MnO2-2/NiCo-LDH/CC composite electrode is a potential candidate in wearable energy storage device.

Soft conducting polymer hydrogels in situ doped by sulfonated graphene quantum dots for enhanced electrochemical activity

Electrode materials play a crucial role in determining the comprehensive performance of the constructed flexible supercapacitors. Herein, a simple synthesis method was reported to fabricate soft polypyrrole (PPy) hydrogels with in situ-doped sulfonated graphene quantum dots (sGQD). The sulfonic acid groups rimming the graphene quantum dots (GQD) can protonate the nitrogen groups of PPy and form electrostatic interactions, leading to PPy chains cross-linking to form a three-dimensional network which can be gelated into a hydrogel. It is found that sGQD can form transport channels to facilitate fast solvated ion diffusion during charge and discharge process that can contribute to the performance improvement. Since both electrochemical activity and excellent conductivity are reserved, the as-prepared PPy/sGQD-160 hydrogel electrode exhibits an extremely higher specific capacitance (641 F g−1 at current density of 0.2 A g−1) and superior cycle stability compared with PPy hydrogel. In addition, the electrochemical performance of PPy/sGQD hydrogels is gradually improved with the increment of sGQD, which can be ascribed to the high conductivity of sGQD dopant. These results indicate that the obtained PPy/sGQD hydrogels can be considered as a promising electrode material for flexible high-performance supercapacitors.

In-situ temperature regulation of flexible supercapacitors by designing intelligent electrode with microencapsulated phase change materials

Benefiting from the on-going update of wearable electrical devices, flexible supercapacitors have attracted extensive attention in energy storage devices. However, the challenge still exists in achieving high electrochemical performance and cycling stability at high operating temperatures. Herein, an innovative in-situ thermal management system by rationally implanting microencapsulated phase change materials (MPCMs) into three-dimensional porous reduced graphene oxide/polyaniline (GP) frameworks on the surface of carbon nanotube film (CNF) was developed for flexible all-solid-state supercapacitors via facile one-pot electrochemical co-deposition method. The flexible sandwich-shaped all-solid-state supercapacitors using hybrid CNF/GP/MPCMs as electrodes and PVA-H2SO4 as the gel electrolyte were successfully assembled. The incorporation of MPCMs effectively suppressed the temperature fluctuation of the supercapacitor and promoted its operation stability at high temperatures. The supercapacitor containing MPCMs showed superior long-term cyclic stability in comparison with the counterpart without MPCMs. Moreover, the as-prepared supercapacitor was capable of enduring deformations of various angles and maintained 94.1% of the initial capacitance after 500 bending cycles, manifesting excellent mechanical performance. The study paves a feasible way of facilely constructing temperature regulation mechanism based on MPCMs for flexible high-performance supercapacitors.

Highly porous structured polyaniline nanocomposites for scalable and flexible high-performance supercapacitors.

Recently, flexible energy devices have been used to power up portable electronics such as E-skins, smart clothes, and bendable displays. However, the usage of rigid and inactive components in electrode materials limits the application in flexible energy devices. Here, we report a novel method to fabricate porous polyaniline composites (Pt_CPPy/PANI:CSA) using Pt decorated carboxyl polypyrrole nanoparticles (Pt_CPPyNPs) as a nucleating agent for electrodes of supercapacitors. The specific capacitance and electrical conductivity of the Pt_CPPy/PANI:CSA film are 325.0 F g-1 and 814 S cm-1, respectively, which are much higher than those of the pristine PANI:CSA film. Furthermore, the porous PANI:CSA composites exhibit excellent rate capability and cycling stability as the pores in the PANI structure enhance the active surface area between PANI and the ions of the electrolytes. This unique fabrication technique is an effective approach for preparing large scale highly porous polyaniline nanomaterials for diverse electrochemical applications.

Electrochemical synthesis of NiCo layered double hydroxide nanosheets decorated on moderately oxidized graphene films for energy storage.

The introduction of oxygenous functional groups onto graphene can provide additional pseudocapacitance for supercapacitors. However, how to balance the amount of introduced oxygenous functional groups and the reduced electrical conductivity arising from the disruption of the conjugated system remains a big challenge. Here, a controllable strategy is reported to prepare moderately oxidized reduced graphene oxide (MORGO) via an electrochemical oxidation process. The MORGO not only has oxygenous groups with appropriate quantities, but also preserves the highly crystalline structure of the π-π conjugated carbon framework. As a result, the MORGO films showed superior electrochemical properties to the pristine RGO films and other previously reported RGO films. Furthermore, the oxygenous groups and the conductivity of MORGO films can be easily adjusted by controlling the oxidation time. A hierarchical composite of NiCo-layered double hydroxide nanosheet arrays on MORGO films (MORGO/NiCo-LDH) was also constructed via electrochemical deposition to combine the advantages of electric double-layer electrode materials and faradaic electrode materials. The flexible solid-state supercapacitor fabricated with MORGO/NiCo-LDH film electrodes exhibits a high energy density (0.51 mW h cm-3), as well as a long cycle life (88.2% capacitance retention after 10 000 cycles).

Polypyrrole-Decorated Hierarchical NiCo2O4 Nanoneedles/Carbon Fiber Papers for Flexible High-Performance Supercapacitor Applications

A novel polyprrole (PPy)-decorated hierarchical NiCo2O4 nanoneedles was grown on highly conductive carbon fiber paper (CFP) for high performance asymmetric supercapacitor applications. The PPy-decorated hierarchical NiCo2O4 nanoneedle on CFP (PPy-NiCo2O4@CPF) was grown by two steps. At first, NiCo2O4 nanoneedle was grown by hydrothermal process and followed by the deposition of PPy through electrochemical method. The fabricated PPy-NiCo2O4@CPF electrode displayed the higher electrochemical performance. The specific capacitance was ∼910F g-1 at a current density of 1Ag−1 and cyclic stability was ∼88% after 10,000 cycles. To explore real performance of the electrode, we have fabricated solid state asymmetric supercapacitor using PPy-NiCo2O4@CFP as positive and nitrogen doped reduced graphene oxide (N-rGO) as negative electrodes. The fabricated asymmetric device delivered a specific capacitance of 118.6F g-1 at a current density of 1.0Ag−1 with a maximum energy density of 40.81WhKg−1 (at a power density of 738.27WKg−1) and maximum power density of 3746.77WKg−1 (at an energy density of 13.53WhKg−1). The impressive results suggest that flexible PPy-NiCo2O4@CFPs can be a promising electrode material for supercapacitor applications.

Transparent and flexible high-performance supercapacitors based on single-walled carbon nanotube films

Transparent and flexible energy storage devices have garnered great interest due to their suitability for display, sensor and photovoltaic applications. In this paper, we report the application of aerosol synthesized and dry deposited single-walled carbon nanotube (SWCNT) thin films as electrodes for an electrochemical double-layer capacitor (EDLC). SWCNT films exhibit extremely large specific capacitance (178 F g−1 or 552 μF cm−2), high optical transparency (92%) and stability for 10 000 charge/discharge cycles. A transparent and flexible EDLC prototype is constructed with a polyethylene casing and a gel electrolyte.

CuO Nanoflowers growing on Carbon Fiber Fabric for Flexible High-Performance Supercapacitors

A hierarchical CuO nano-structure is prepared by directly growing CuO nanoflowers on carbon fiber fabric (CuO/CFF) via a hydrothermal method. The CuO/CFF is used as the electrode material of a supercapacitor for electrochemical energy storage. The supercapacitor displays superior electrochemical performance in aqueous electrolyte with the specific capacitance of 839.9F/g at the scan rate of 1mV/s, energy density of 10.05 Wh/kg and power density of 1798.5W/kg, which are the highest values for the CuO/CFF electrodes. Moreover, a flexible symmetric solid-state symmetric supercapacitor is also fabricated by using the CuO/CFF as electrodes. The solid-state supercapacitor exhibits a specific capacitance of 131.34F/g at the scan rate of 1mV/s with a power density of 145.12W/kg, and 95.8% capacitance retention after 2000 charge-discharge cycles.

Stacked Bilayer Graphene and Redox-Active Interlayer for Transparent and Flexible High-Performance Supercapacitors

Fabrication of a transparent and flexible supercapacitor requires electrode materials that are optically transparent and mechanically flexible. Although chemical vapor deposition (CVD)-grown graphene is a promising electrode material, its use in supercapacitor applications is greatly limited by the low area-specific capacitance of the fabricated supercapacitor. Here, we demonstrate transparent and flexible high-performance supercapacitor using stacked bilayer graphene and an ultrathin redox-active interlayer. By inserting the redox-active layer between stacked bilayer graphene, we achieved an almost 20-fold enhancement of the area-specific capacitance (from 5.6 μF/cm2 to 101 μF/cm2) with a thickness of electrode material for each electrode less than 2 nm. In addition, the fabricated supercapacitor exhibited excellent transparency of 75% (including the substrate’s transparency) and flexibility (bending radius down to 5 mm) by virtue of the outstanding transparency and flexibility of the stacked bilayer gra...