摘要 :
Limited by 2D geometric morphology and low bulk packing density, developing graphene-based flexible/compressible supercapacitors with high specific capacitances (gravimetric/volumetric/areal), especially at high rates, is an outst...
展开
Limited by 2D geometric morphology and low bulk packing density, developing graphene-based flexible/compressible supercapacitors with high specific capacitances (gravimetric/volumetric/areal), especially at high rates, is an outstanding challenge. Here, a strategy for the synthesis of free-standing graphene ribbon films (GRFs) for high-performance flexible and compressible supercapacitors through blade-coating of interconnected graphene oxide ribbons and a subsequent thermal treatment process is reported. With an ultrahigh mass loading of 21 mg cm(-2), large ion-accessible surface area, efficient electron and ion transport pathways as well as high packing density, the compressed multilayer-folded GRF films (F-GRF) exhibit ultrahigh areal capacitance of 6.7 F cm(-2) at 5 mA cm(-2), high gravimetric/volumetric capacitances (318 F g(-1), 293 F cm(-3)), and high rate performance (3.9 F cm(-2) at 105 mA cm(-2)), as well as excellent cycling stability (109% of capacitance retention after 40 000 cycles). Furthermore, the assembled F-GRF symmetric supercapacitor with compressible and flexible characteristics, can deliver an ultrahigh areal energy density of 0.52 mWh cm(-2) in aqueous electrolyte, almost two times higher than the values obtained from symmetric supercapacitors with comparable dimensions.
收起
摘要 :
The inception of flexible supercapacitors that can work steadily under large deformation has been a research hotspot in recent years. To improve the device's stability, one needs to find innovative solutions to inevitable delamina...
展开
The inception of flexible supercapacitors that can work steadily under large deformation has been a research hotspot in recent years. To improve the device's stability, one needs to find innovative solutions to inevitable delaminations of electroactive components, which are resulted by relative displacement under external force. Herein, an extensive all-in-one hydrogel-based supercapacitor is designed. Based on the special physical properties of hydrogels, the polypyrrole-polyvinyl alcohol/dilute sulphuric acid-polypyrrole (PHP) sandwiched device shows the harmonious mechanical and electrical properties. When the tensile strain of PHP reaches to 110%, the areal capacitance still maintains at 90%. Similarly, the high areal capacitance retention under compression and twisting also verifies that the PPy active layer tightly permeates and adheres to the PVA-H2SO4 electrolyte layer. In addition to the fascinating mechanical properties, the undetectable contact angle reveals a superhydrophilic surface which is beneficial to provide an easy access for electrolyte ions, thus enhancing the electrochemical performance. Moreover, a stable cycle performance (97% after 10000 cycles) is obtained due to the excellent water retention ability which prevents the loss of electrolyte. The maximum extended voltage window is 1 V with the power density of 500 mu W cm(-2) (the energy density of 6.94 mu W h cm(-2)). These hydrogel-based supercapacitors can be immune to the harm caused by external forces and maintain good mechanical integrity and electrochemical stability. Developing the hydrogel-based supercapacitors can provide a fresh perspective on multifunction applications and herald a new territory for flexible energy storage devices. (C) 2019 Elsevier B.V. All rights reserved.
收起
摘要 :
Compressible supercapacitors are particularly important in wearable energy storage because they can maintain desired levels of performance during repeated compressing and recovering process. However, it is still challenging for a ...
展开
Compressible supercapacitors are particularly important in wearable energy storage because they can maintain desired levels of performance during repeated compressing and recovering process. However, it is still challenging for a compressible supercapacitor to maintain excellent electrochemical performances under highly compressive strain. Herein, a highly compressible reduced graphene oxide-polypyrrole-reduced graphene oxide melamine sponge (G-PPy-G-MS) electrode is prepared via coating polypyrrole and a double layer of reduced graphene oxide on the melamine sponge. Polypyrrole provides the capability of high redox pseudocapacitive charge storage for the electrode, the electronic conductivity of the sample is greatly promoted by the double layer of reduced graphene oxide, and the melamine sponge ensures remarkable compressive properties. As a result, under the high compressive strain of 80 %, the G-PPy-G-MS electrode possesses a high specific capacitance of 464.10 F g(-1), superior rate performance with 44.47 % retention from 0.5 A g(-1) to 10 A g(-1), and desirable cycling stability (remains 85.43 % after 5000 cycles). Moreover, the all-solid-state symmetric super capacitor constructed by G-PPy-G-MS maintains 97.48 % specific capacitance after 100 compressing-recovering cycles at the high strain of 80 %. This work develops a novel and feasible strategy to fabricate composite electrodes with high electrochemical and mechanical performances for compressible supercapacitors.
收起
摘要 :
Design and fabrication of compressible electrode for energy storage devices are highly demanded due to their wide applications. Here, compressible graphene/polypyrrole (PPy)/Ag composite electrodes were fabricated by one step hydr...
展开
Design and fabrication of compressible electrode for energy storage devices are highly demanded due to their wide applications. Here, compressible graphene/polypyrrole (PPy)/Ag composite electrodes were fabricated by one step hydrothermal treatment of pyrrole (Py) and silver nitrate (AgNO3) in graphene oxide (GO) aqueous solution. The resulting composite electrodes are characterized by scanning electron microscope (SEM), X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), transmission electron microscope (TEM) and X-ray photoelectron spectroscopy (XPS) and indicate that PPy and Ag nanoparticles are absorbed on graphene sheets. The capacitive behavior of the composite is investigated by using cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy. The electrochemical properties can be controlled by tuning the mass ratio of GO, Py monomer and AgNO3. The maximum specific mass capacitance of the electrode is 447 F g(-1). Importantly, the resulting electrode can be compressed both in dried state and in aqueous electrolyte. The assembled supercapacitor can be compressed up to 50% strain and maintains its original capacitance when released. This work indicates that it is possible to build high performance compressive conductors and supercapacitors by using graphene networks coated with conductive polymer and silver nanoparticles. (C) 2019 Elsevier B.V. All rights reserved.
收起
摘要 :
Developing flexible and deformable supercapacitors electrodes based on porous materials is of high interest in energy related fields. We propose a novel approach called "soaking-squeezing-calcining" to fabricate a unique carbon na...
展开
Developing flexible and deformable supercapacitors electrodes based on porous materials is of high interest in energy related fields. We propose a novel approach called "soaking-squeezing-calcining" to fabricate a unique carbon nanotubes melamine sponge electrode, and demonstrate its application as a highly compressible supercapacitor electrode with high performance. Our supercapacitor electrode consists of three-dimensional melamine sponge as flexible skeleton and conductive skeleton, the carbon nanotubes filled in the sponge skeleton by physical adsorption and calcination process to enhance the overall conductivity and mechanical properties. After adding carbon nanotubes, the volume specific capacity of the supercapacitors increases by 3 times and the mass specific capacity is basically unchanged. Furthermore, it is found that its capacity retention rate could still reach 91% after the device is compressed by 50% for 1000 cycles of charging and discharging and 88% in the original uncompressed state for 5000 cycles of charging and discharging, respectively, which deeply proves that the carbon nanotubes reinforced sponge electrode has excellent electrochemical stability. Most importantly, the mechanical strength of the electrode increases by 5 times compared with that without carbon nanotubes. The results indicate that this electrode has the potential to fabricate deformable, robust supercapacitors with stable performance and many other energy devices. (C) 2019 Elsevier B.V. All rights reserved.
收起
摘要 :
Most developed flexible energy storage devices lack sufficient softness and toughness to tolerate various deformations, such as stretching, compressing, twisting, folding and puncturing, meanwhile guarantee a stable energy output ...
展开
Most developed flexible energy storage devices lack sufficient softness and toughness to tolerate various deformations, such as stretching, compressing, twisting, folding and puncturing, meanwhile guarantee a stable energy output required for the soft human-machine interfaces and intelligent wearable electronics. In this work, all-hydrogel soft supercapacitors consisting of reversibly deformable hydrogel electrodes and electrolyte are constructed without using additional stretchable substrate or separator membrane. Both electrode and electrolyte contain the same polyacrylamide/sodium alginate dual-network hydrogel matrix, making them possess superb self-adhesion due to hydrophilic interaction/hydrogen bonds, and highly softness/toughness thanks to the energy-dissipative mechanism. After adding carbon nanotube conductive network/electrode active material and electrolyte salt/redox couple in the hydrogel matrix, the newly developed supercapacitor with all-in-one architecture is intrinsically highly stretchable/compressible and can even be deformed arbitrarily under various severe stress-strain deformation conditions at device level, simultaneously deliver high areal capacitance (232 mF cm(-2) at 5 mV s(-1) and 128 mF cm(-2) at 1 mA cm(-2)) and maintain stable energy output. The simple device architecture, novel structural components, steady mechanical properties combined with excellent electrochemical properties make the soft supercapacitors promising for truly wearable applications.
收起
摘要 :
The progress in flexible/stretchable electronics has increased the demand to develop highly reliable and efficient devices and systems for energy storage, which likely experience large mechanical stresses/deformation. In this work...
展开
The progress in flexible/stretchable electronics has increased the demand to develop highly reliable and efficient devices and systems for energy storage, which likely experience large mechanical stresses/deformation. In this work, we systematically investigate the effects of compressive stress on the electrochemical performance of symmetrical supercapacitor cells with xylose-derived activated-carbon spheres as electrode materials under different current densities. The electrolytes are aqueous solutions with different Na2SO4 concentrations; the compressive stress is in a range of 2.55 to 40.75 MPa. Increasing the compressive stress from 2.55 to 40.75 MPa leads to the increase of the specific gravimetric capacitance from 123.6 to 238.1 F g(-1) under a current density of 1 A g(-1) and the decrease of IR drop from 0.18 to 0.04 V. A power-law relationship between the specific gravimetric capacitance and the compressive stress is derived under the framework of mechanical deformation. This relationship is qualitatively in accord with the experimental results. There exists stress-assisted diffusion of ions in the activated carbon spheres during electrochemical cycling, and the nominal diffusion coefficient of ions in the activated carbon spheres is an exponential function of the compressive stress. The results reveal that increasing the compaction of activated carbon can increase the charge storage in supercapacitors. (C) 2020 Elsevier Ltd. All rights reserved.
收起
摘要 :
Portable and wearable electronics are undergoing rapid development, but these flexible devices may break and fail to work under high compressive strains. Here, presented is a new free-standing compressible carbon nanotube array (C...
展开
Portable and wearable electronics are undergoing rapid development, but these flexible devices may break and fail to work under high compressive strains. Here, presented is a new free-standing compressible carbon nanotube array (CCNA) with a unique gradually crosslinking structure, which mimics the gradient structure of the beak of the giant squid. The CCNAs can tolerate various compressive strains and demonstrate high reversible compressibility up to 1 & x202f;00 & x202f;000 cycles with high electrical conductivities. On the basis of the CCNA, a novel all-solid-state compression-sensing supercapacitor (CSS) that can store energy and tolerate and sense the external strain change is produced. It demonstrates a high capacitance of 93.2 mF cm(-2)and can be maintained by 94% even after 3000 continuous compressing cycles at a strain of 60%. In addition, it also shows superior strain sensing capability and stability up to 1900 compressive cycles. These flexible CSSs promise a wide range of applications including electronic skins and advanced bioelectronic devices.
收起
摘要 :
With overwhelming development of electronic technology, flexible electronic devices are spring up in modern today. For fulfilling the trendy and artistic designing of electronic devices, mechanical toughness and self-healable all-...
展开
With overwhelming development of electronic technology, flexible electronic devices are spring up in modern today. For fulfilling the trendy and artistic designing of electronic devices, mechanical toughness and self-healable all-solid-state supercapacitors play an essential role of modern electronics. However, the saw-of-the-art polyvinyl alcohol-based electrolyte for all-solid-state supercapacitors neither has tough physical performance nor self-healing, which is hard to implant into special-shaper and repeated-deformation device for energy supplier. A novel electrolyte with mechanical robust and endowed self-healing is prepared by micelle co-polymerization of acrylic acid and octadecyl methacrylate in vinyl-treated sponge (S-PAA). The 3D interconnected skeleton of sponge serves as stress buffers to dissipate energy when physical impact (stretch and compress) is applied, solving the intrinsically poor mechanical performance and easy cracking under repeated-deformation drawbacks of state-of-the-art supercapacitors. The supercapacitor equipped with newly type of electrolyte can be worked under compressing, bending and stretching station. Moreover, the electrochemical performances have no evidence loss even using self-healed fragment electrolyte.
收起
摘要 :
Abstract Graphene oxide nanosheets can be assembled into multifunctional graphene aerogels for sensing and energy storage applications. However, due to strong van der Waals forces, reduced graphene oxide nanosheets often stack tog...
展开
Abstract Graphene oxide nanosheets can be assembled into multifunctional graphene aerogels for sensing and energy storage applications. However, due to strong van der Waals forces, reduced graphene oxide nanosheets often stack together, significantly compromising their performance. Here, we demonstrate high-performance multifunctional hybrid carbon aerogels by hybridizing graphene oxide nanosheets with functionalized carbon fibers using a hydrothermal assembly method followed by two-step freezing, natural drying, and annealing. We compared the difference between carbon microfibers and carbon nanofibers. Our results show that flexible carbon nanofibers can enable more bindings with graphene nanosheets, creating stabler three-dimensional structures and enabling more efficient electron transfer. The resulting hybrid graphene aerogels have a high compressive strength of 56.7?kPa at 50% strain, an electrical conductivity of 3.072 S m?1, and a strain-responsive electrical response sensitivity of 11.3?k?Pa?1 in a low-pressure range of 0–0.15?kPa. These hybrid carbon aerogels were applied in strain sensors to detect various human bio-signals. Furthermore, they were used as free-standing electrodes in flexible supercapacitors, demonstrating satisfactory energy storage performances. Overall, we show that three-dimensional graphene-carbon nanofiber hybrid aerogels have excellent multifunctional properties for applications in flexible electronics and energy storage devices.Graphical abstract
收起
原文获取