High-performance Flexible Solid-state Supercapacitors Research Articles

A wearable system based on core-shell structured peptide-Co9S8 supercapacitor and triboelectric nanogenerator

We report a new core-shell structure of peptide-Co9S8 nanobricks for supercapacitor electrode. The nanostructured peptide is intrinsically flexible and biocompatible, which is highly suited for wearable supercapacitor electrodes. However, the application of the nanostructured peptide is often limited by its generally low power density and energy density, and its long-term stability is also a concern. Herein, the core-shell structure of peptide-Co9S8 nanobricks is synthesized by conformally coating a thin shell layer of Co9S8 via atomic layer deposition (ALD) onto self-assembled peptide nanobricks. The shell layer can not only protect the peptide material from being attacked by the electrolyte but also contribute extra capacitance to the supercapacitor. The supercapacitors made of the peptide-Co9S8 nanobricks exhibit a high capacitance of 1.3 F/cm2 at 0.7 mA/cm2 and a much improved cycling stability of 96% capacitance retention after 5000 charge-discharge cycling. High-performance flexible solid-state asymmetric supercapacitor (SC) can be also made from the core-shell peptide-Co9S8 nanobricks with activated carbon. The flexible asymmetric supercapacitor can also be coupled with a triboelectric nanogenerator (TENG) to afford a flexible self-powered TENG/SC system. The TENG/SC system with 2.7-h continuously charging by TENG can power a red LED for 21 min, which demonstrates its excellent performance of self-charging and energy-supplying, and therefore it is of great promise for future wearable electronics applications.

High performance flexible solid-state asymmetric supercapacitor composed of a polyaniline/PEDOT/polyaniline/ultralarge reduced graphene oxide tetralayer film and a PEDOT/MoS2 composite film

A flexible solid-state asymmetric supercapacitor (ASC) was assembled with a polyaniline (PANi)/PEDOT/PANi/ultralarge reduced graphene oxide (UrGO) tetralayer film (denoted as PPPrG, used as the positive electrode) and a PEDOT/MoS2 film (denoted as PMo, used as the negative electrode) on a flexible polyethylene terephthalate (PET) substrate with polyvinyl alcohol/H2SO4 gel electrolyte. The PPPrG tetralayers were fabricated on PET via a layer-by-layer self-assembly method, whereas the PMo electrode was fabricated on PET using a drop-coating approach. The ASC exhibited a maximum energy density of 5.4 mW h/cm3 at a power density of 110 mW/cm3, demonstrating excellent electrochemical performance without performance loss despite various deformation states due to high conductivity and flexibility of the multilayer film electrodes, which act as both the active electrode and the current collector. The ASC retained an energy density of 4.0 mW h/cm3 at a power density of 265 mW/cm3 with an optimized cell voltage of 0.8 V. The excellent performance of this ASC was ascribed mainly to the conductivity of the multilayer film electrodes, which was improved by the combination of PANi, UrGO and PEDOT layers, which functioned as conducting networks in the nanostructured composite films. This flexible ASC system based on multilayer film electrodes with superior capacitive performance offers substantial promise for use in grid-scale energy storage devices integrated into portable and bio-implantable microelectronic devices.

Facile strategy for mass production of polymer-supported film electrodes for high performance flexible symmetric solid-state supercapacitors

Free-standing electrodes have been widely investigated for high performance flexible supercapacitors, especially those with polymer films as flexible substrates. However, the most widely used technique for the polymer-supported electrodes, in-situ solution polymerization, restricts their mass production. Here, a facile strategy was established for the mass production of flexible polymer-supported film electrode for high performance flexible symmetric solid-state supercapacitor via a two-step coating approach, with polylactic acid (PLA) as biodegradable and flexible substrate and polyaniline (PANI) as electroactive materials. Under the optimized condition, high specific capacitance of 615 F/g (areal capacitance of 143 mF/cm2) was achieved with the flexible film electrode at a current density of 1 A/g in 1.0 M H2SO4. It possessed excellent cycling stability (109.6% of its original specific capacitance after 5000 CV cycles), flexible stability (105.6% capacitance retention after 180°-bending 1000 times), and mechanical strength (tensile strength up to 16.89 MPa), owing to the inlay structure. The flexible symmetric solid-state supercapacitor (SSC) based on the composite film electrodes showed good comprehensive performance.

Highly microporous carbon with nitrogen-doping derived from natural biowaste for high-performance flexible solid-state supercapacitor

Highly microporous carbon material with nitrogen doping has been synthesized via a facile one-step approach by employing natural biowaste miscellaneous wood fibers derived hydrochar as precursor and melamine as nitrogen source respectively. The added melamine not only results in the incorporation of some nitrogen into the carbon framework but also increases the specific surface area of carbon material. Such resultant N-doped microporous carbon possesses the functionalized nitrogen doping (1.75 at. %), a large specific surface area (∼1807 m2 g−1) and abundant highly interconnected micropores. Benefiting from the synergistic effect of high specific surface area, well-developed pore size distribution and functionalized groups, this carbon material delivers a high specific capacitance of 345 F g−1 at 0.5 A g−1, an excellent capacitance retention with 270 F g−1 at up to 30 A g−1, and a remarkable cycle ability with 91.3% retention after 10,000 cycles at 5.0 A g−1. Based on it, the as-developed flexible symmetric solid-state supercapacitor delivers a high energy density of 7.92 W h kg−1 at the power density of 250 W kg−1. Evidently, this work provides a facile and cost-effective route for functionalized natural biowaste-based carbon materials and further opens up a way for highly value-added recycling of biowaste-like materials.

High performance flexible solid-state symmetric supercapacitors based on laser induced porous reduced graphene oxide-graphene oxide hybrid nanostructure devices

Materials with a porous structure and high surface area have gained tremendous research interests in the design of advanced high energy density supercapacitors because of their great capacitance and chemical stability. Herein, an effective method is introduced to achieve a large-scale production of porous graphene network by laser irradiation of graphene oxide films with a short span of time. Interestingly, this method introduces a porous structure, high surface area and promising electrochemical properties which significantly enhances the reversible capacitance behaviour. Notably, laser irradiated graphene oxide films electrodes show excellent areal capacitance of 149.7 mF cm−2 at 3 mV s−1 with a maximum energy density of 7.5 mWhcm−3. Also, these electrodes demonstrate an outstanding cycling stability, which retains above 85% capacitance of its initial capacitance after 5000 charge-discharge cycles shows a significant enhancement over other values reported in the literature. Furthermore, the bending tests confirms that the superior flexible performance of the laser irradiated graphene oxide electrodes holds a great potential for the development of wearable electronic devices.

Interlaced NiMn-LDH nanosheet decorated NiCo2O4 nanowire arrays on carbon cloth as advanced electrodes for high-performance flexible solid-state hybrid supercapacitors.

The development of flexible energy storage devices for portable and wearable electronics has aroused increasing interest. In this work, three-dimensional hierarchical NiCo2O4@NiMn-LDH nanowire/nanosheet arrays have been successfully fabricated on carbon cloth through a facile hydrothermal and calcination synthetic method. Benefiting from the sophisticated hybrid nanoarchitectures with desirable structure and components, the optimized NiCo2O4@NiMn-LDH hybrid electrode is found to deliver a remarkable specific capacity of 278 mA h g-1 at 2 mA cm-2 and a good rate capability of 89.1% retention at 20 mA cm-2. Detailed analysis of the reaction kinetics for the hybrid electrode clearly indicates the dominant diffusion-controlled contribution to the total capacity. In addition, a flexible solid-state hybrid supercapacitor is assembled by taking NiCo2O4@NiMn-LDH and activated carbon as the cathode and anode, respectively, which manifests a maximum energy density of 47 W h kg-1 at a power density of 357 W kg-1 as well as an excellent long-term cycling stability (95.6% retention after 5000 cycles over 8 mA cm-2). Our work demonstrates the great potential of this core/shell hybrid nanostructure as an advanced battery-type electrode for high-performance flexible energy storage devices.

Optimal structuring of nitrogen-doped hybrid-dimensional nanocarbons for high-performance flexible solid-state supercapacitors

Nitrogen-doped hybrid-dimensional nanocarbons are architectured into special structures and used for fabrication of solid-state flexible supercapacitors showing high-performance energy storage capacity.

Graphene-Wrapped Polyaniline Nanowire Array Modified Functionalized of Carbon Cloth for High-Performance Flexible Solid-State Supercapacitor

Graphene-wrapped polyaniline (PANI) nanowire array modified functionalized carbon cloth (fCC) (fCC-PANI array-rGO) is successfully fabricated and served as free-standing electrode for assembling fl...

High-Performance Biomass-Based Flexible Solid-State Supercapacitor Constructed of Pressure-Sensitive Lignin-Based and Cellulose Hydrogels

Employing renewable, earth-abundant, environmentally friendly, low-cost natural materials to design flexible supercapacitors (FSCs) as energy storage devices in wearable/portable electronics represents the global perspective to build sustainable and green society. Chemically stable and flexible cellulose and electroactive lignin have been employed to construct a biomass-based FSC for the first time. The FSC was assembled using lignosulfonate/single-walled carbon nanotubeHNO3 (Lig/SWCNTHNO3) pressure-sensitive hydrogels as electrodes and cellulose hydrogels as an electrolyte separator. The assembled biomass-based FSC shows high specific capacitance (292 F g-1 at a current density of 0.5 A g-1), excellent rate capability, and an outstanding energy density of 17.1 W h kg-1 at a power density of 324 W kg-1. Remarkably, the FSC presents outstanding electrochemical stability even suffering 1000 bending cycles. Such excellent flexibility, stability, and electrochemical performance enable the designed biomass-based FSCs as prominent candidates in applications of wearable electronic devices.

Hierarchical nanothorns MnCo2O4 grown on porous/dense Ni bi-layers coated Cu wire current collectors for high performance flexible solid-state fiber supercapacitors

Cu wires are coated by porous/dense Ni bi-layers as current collectors through electroless plating and hydrogen bubble dynamic template electrodepostion methods. The unique coaxial composite current collectors can be beneficial from the high electrical/thermal conductivity of metal Cu core and high corrosion resistance of dense metal Ni coating as well as porous Ni substrate for growth of active materials. Furthermore, the metal wire current collectors have excellent flexibility and mechanical strength. Highly flexible solid-state fiber supercapacitors are then fabricated by binder-free integrated electrodes of hierarchical MnCo2O4 nanothorns grown on porous/dense Ni bi-layers coated Cu wires. The fiber supercapacitors reach capacitance of 20.6 mF cm−1 (54.8 mF cm−2) and energy density of 4.8 μWh cm−1 (12.8 μWh cm−2) at a power density of 32.25 μW cm−1 (110 μW cm−2). Moreover, the twist fiber supercapacitors show good rate capability and cycling stability. The outstanding performances of the fiber supercapacitors might be attributed to the hierarchically nanothorns MnCo2O4 active materials and the unique porous/dense Ni coated Cu wire current collectors. Our results can provide a novel strategy to design flexible nanostructure fiber supercapacitors for energy storage applications in future wearable electronics.

3D porous binary-heteroatom doped carbon nanosheet/electrochemically exfoliated graphene hybrids for high performance flexible solid-state supercapacitors

3D porous carbon nanosheet/electrochemically exfoliated graphene hybrids with abundant nitrogen- and sulfur-containing functional groups and high specific surface area were prepared and evaluated as electrode materials.

Biowaste-derived 3D honeycomb-like porous carbon with binary-heteroatom doping for high-performance flexible solid-state supercapacitors

N and S-co-doped activated corncob sponge of honeycomb-like porous carbon with the interconnected micro-meso-macropores and the large specific surface area was evaluated as an electrode material for flexible solid-state supercapacitors, exhibiting high specific capacitance, high energy–power density, and great cyclic stability.

High electrochemical performance flexible solid-state supercapacitor based on Co-doped reduced graphene oxide and silk fibroin composites

Abstract A simple method for the preparation of flexible supercapacitor based on Co-doped reduced graphene oxide (rGO) and silk fibroin composites film is reported. The facile and cost-effective green pathways are chosen to reduce the exfoliated graphite oxide using a microbial strain, at room temperature. Doping process is performed by using in-situ precipitation technique. The Co-doped reduced graphene oxide (Co-rGO) is characterized by X-ray diffraction, Raman spectroscopy and Scanning Electron Microscopy (SEM). The as-prepared Co-rGO and silk fibroin are used to prepare flexible electrode for supercapacitor device. Electrochemical performance of the electrode is examined using cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The fabricated supercapacitor shows the specific capacitance of 104 F g−1 at a current density of 0.5 A g−1 in ionic liquid electrolyte (EMIm+BF4−). After a charge–discharge rate of 1 A g−1 for 10,000 cycles, the Co-rGO film exhibits remarkable electrochemical stability with the capacitance retention ratio of 89%. Furthermore, the Co-rGO film based supercapacitor achieves high energy density up to 28.31 Wh kg−1 at a power density of 78.24 kW kg−1 by using the ionic liquid electrolyte. The results shown in this work indicate that our proposed Co-rGO-silk fibroin composites film is a promising electrode material for manufacturing flexible supercapacitors.

N-doped porous reduced graphene oxide as an efficient electrode material for high performance flexible solid-state supercapacitor

Supercapacitors (SCs) are energy storage devices with an immense potential to resolve energy related issues. Being a low cost, durable and multifunctional material, graphene and its derivatives are the most promising candidates for SCs. Here, we report the synthesis of N-doped porous reduced graphene (N-pGr) and its use for the fabrication of all-solid-state supercapacitor (ASSC) device. The N-pGr exhibited a specific capacitance of 230Fg−1 at 1Ag−1 current density and good capacitance retention up to ∼88% even after 10,000 galvanostatic charge–discharge cycles recorded at 5Ag−1 fabricated in a solid-state supercapacitor. The synergistic effect of the porosity and N-doping is believed to be the underlying principle for the improved charge storage ability when compared to other reports. Significantly, the porous nature of N-pGr contributes in increasing the electroactive surface area for the formation of electrical double layer as well as facilitating the faster movement of electrolyte ions inside the electrode network. N-doping is believed to change the electrical properties of the electrode material and also to participate in the pseudo-capacitance which helped to boost the overall capacitance of the fabricated device. The good capacitance retention provides the room for making robust flexible solid-state supercapacitor (FSSC) with the N-pGr material.

A high-performance flexible solid-state supercapacitor based on Li-ion intercalation into tunnel-structure iron sulfide

A flexible solid-state supercapacitor based on iron sulfide (FeS2) nanospheres supported on carbon-paper is fabricated, which exhibits excellent electrochemical performance such as, high capacitance of 484Fg−1 at a scan rate of 5mVs−1, good rate capability, and excellent cycling stability (95.7% after 5000 cycles). The supercapacitor achieves high energy density of 44Whkg−1 at power density of 175Wkg−1 with high coulombic efficiency (97%). Three charged supercapacitors connected in series can power 12 green-color light-emitting-diodes (LED, 3.0V, 20mA) for 5.5minutes. To understand the detailed electrochemistry, we have carried out both experimental and theoretical investigations. The pseudocapacitive characteristics of the FeS2 nanospheres are systematically investigated by a single electrode in aqueous electrolyte. According to our structural analysis, the FeS2 nanospheres have orthorhombic structure, where Fe atoms are surrounded by 6S atoms to form a FeS6 octahedron. These octahedrons are connected to form a network structure, which provide tunnels (2.55×4.77Å). With all the evidence, we believe that the FeS2 nanospheres could be a promising material for supercapacitor electrodes.

High-performance flexible all-solid-state supercapacitors based on densely-packed graphene/polypyrrole nanoparticle papers

Graphene-based all-solid-state supercapacitors (ASSSCs) have received increasing attention. It’s a great challenge to fabricate high-performance flexible solid-state supercapacitors with high areal and volumetric energy storage capability, superior electron and ion conductivity, robust mechanical flexibility, as well as long term stability. Herein, we report a facile method to fabricate flexible ASSSCs based on densely-packed reduced graphene oxide (rGO)/polypyrrole nanoparticle (PPy NP) hybrid papers with a sandwich framework, which consists of well-separated and continuously-aligned rGO sheets. The incorporation of PPy NPs not only provides pseudocapacitance but also facilitates the infiltration of gel electrolyte. The assembled ASSSCs possess maximum areal and volumetric specific capacitances of 477mF/cm2 and 94.9F/cm3 at 0.5mA/cm2. They also exhibit little capacitance deviation under different bending states, excellent cycling stability, small leakage current and low self-discharge characteristics. Additionally, the maximum areal and volumetric energy densities of 132.5μWh/cm2 and 26.4mWh/cm3 are achieved, which indicate that this hybrid paper is a promising candidate for high-performance flexible energy storage devices.

Conducting polymer hydrogel materials for high-performance flexible solid-state supercapacitors

Different from solid electrodes, conducting polymer hydrogel electrodes swollen with water and ions, can reach contact with the electrolyte solution at the molecular level, which will result in more efficient electrochemical process of supercapacitors. Besides, the inherent soft nature of hydrogel material offers the electrode superior flexibility, which benefits to gain high flexibility for devices. Here, this perspective briefly introduces the current research progress in the field of conducting polymer hydrogel electrodes-based flexible solid-state supercapacitor and gives an outlook on the future trend of research.

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

Flexible solid-state supercapacitors attract more and more attention as the power supply for wearable electronics. To fabricate such devices, the flexible and economical current collectors are needed. In this paper, we report the stainless steel fabrics as the current collector for high-performance graphene-based supercapacitors. The stainless steel fabrics have superior properties compared with the widely used flexible current collectors. The flexible supercapacitors show large specific capacitance of 180.4 mF/cm(2), and capacitance retention of 96.8% after 7500 charge-discharge cycles. Furthermore, 96.4% of the capacitance is retained after 800 repeating stretching-bending cycles. The high performance is related to the excellent conductivity, good mechanical flexibility, and high electrochemical stability of the stainless steel fabrics. The achievement of such high-performance and flexible supercapacitor can open up exciting opportunities for wearable electronics and energy storage applications.

Three-dimensional skeleton networks of graphene wrapped polyaniline nanofibers: an excellent structure for high-performance flexible solid-state supercapacitors.

Thin, robust, lightweight, and flexible supercapacitors (SCs) have aroused growing attentions nowadays due to the rapid development of flexible electronics. Graphene-polyaniline (PANI) hybrids are attractive candidates for high performance SCs. In order to utilize them in real devices, it is necessary to improve the capacitance and the structure stability of PANI. Here we report a hierarchical three-dimensional structure, in which all of PANI nanofibers (NFs) are tightly wrapped inside reduced graphene oxide (rGO) nanosheet skeletons, for high-performance flexible SCs. The as-fabricated film electrodes with this unique structure showed a highest gravimetric specific capacitance of 921 F/g and volumetric capacitance of 391 F/cm3. The assembled solid-state SCs gave a high specific capacitance of 211 F/g (1 A/g), a high area capacitance of 0.9 F/cm2, and a competitive volumetric capacitance of 25.6 F/cm3. The SCs also exhibited outstanding rate capability (~75% retention at 20 A/g) as well as excellent cycling stability (100% retention at 10 A/g for 2000 cycles). Additionally, no structural failure and loss of performance were observed under the bending state. This structure design paves a new avenue for engineering rGO/PANI or other similar hybrids for high performance flexible energy storage devices.

High-Performance Flexible Solid-State Supercapacitor with an Extended Nanoregime Interface through in Situ Polymer Electrolyte Generation.

Here, we report an efficient strategy by which a significantly enhanced electrode-electrolyte interface in an electrode for supercapacitor application could be accomplished by allowing in situ polymer gel electrolyte generation inside the nanopores of the electrodes. This unique and highly efficient strategy could be conceived by judiciously maintaining ultraviolet-triggered polymerization of a monomer mixture in the presence of a high-surface-area porous carbon. The method is very simple and scalable, and a prototype, flexible solid-state supercapacitor could even be demonstrated in an encapsulation-free condition by using the commercial-grade electrodes (thickness = 150 μm, area = 12 cm(2), and mass loading = 7.3 mg/cm(2)). This prototype device shows a capacitance of 130 F/g at a substantially reduced internal resistance of 0.5 Ω and a high capacitance retention of 84% after 32000 cycles. The present system is found to be clearly outperforming a similar system derived by using the conventional polymer electrolyte (PVA-H3PO4 as the electrolyte), which could display a capacitance of only 95 F/g, and this value falls to nearly 50% in just 5000 cycles. The superior performance in the present case is credited primarily to the excellent interface formation of the in situ generated polymer electrolyte inside the nanopores of the electrode. Further, the interpenetrated nature of the polymer also helps the device to show a low electron spin resonance and power rate and, most importantly, excellent shelf-life in the unsealed flexible conditions. Because the nature of the electrode-electrolyte interface is the major performance-determining factor in the case of many electrochemical energy storage/conversion systems, along with the supercapacitors, the developed process can also find applications in preparing electrodes for the devices such as lithium-ion batteries, metal-air batteries, polymer electrolyte membrane fuel cells, etc.