Graphene Micro-supercapacitors Research Articles

Fabrication of flexible nitrogen-doped graphene micro-supercapacitors by laser-induced self-made precursors

Fabrication of flexible nitrogen-doped graphene micro-supercapacitors by laser-induced self-made precursors

Enhanced pseudocapacitive behaviour in laser-written graphene micro-supercapacitors decorated with nickel cobalt sulphide nanoparticles

The next generation of energy storage technologies requires enhanced fabrication techniques such as the use of CO2 infrared lasers to pattern micro-supercapacitor (MSC) electrodoes. This study reports direct-writen laser-induced graphene (LIG) micro-supercapacitors with electrodepositated NiCo2S4- nanoparticles on commercial polyimide sheets. X-ray photoelectron spectroscopy (XPS) combined with transmission electron microscopy (TEM) showed NiCo2S4 nanoparticles decorating the graphene, within a highly porous carbon-based electrode. The LIG/NiCo2S4 exhibited outstanding properties with a specific capacitance of 30.4 mF cm−2 at 0.75 mA cm−2 and an energy density of 16.9 µWh cm−2 at a power density of 367.5 µW cm−2. High capacitance retention of 1.22-fold was measured after 5000 cycles of charge/discharge, and of ∼90% when bent to 120˚ angle. Here, it is demonstrated that surface decoration is an effective route in improving LIG MSC storage properties, and that the LIG/NiCo2S4 MSC is suitable for use in next generation of flexible and miniaturized portable devices.

Laser-Induced Graphene Microsupercapacitors: Structure, Quality, and Performance.

Laser-induced graphene (LIG) is a graphenic material synthesized from a polymeric substrate through point-by-point laser pyrolysis. It is a fast and cost-effective technique, and it is ideal for flexible electronics and energy storage devices, such as supercapacitors. However, the miniaturization of the thicknesses of the devices, which is important for these applications, has still not been fully explored. Therefore, this work presents an optimized set of laser conditions to fabricate high-quality LIG microsupercapacitors (MSC) from 60 µm thick polyimide substrates. This is achieved by correlating their structural morphology, material quality, and electrochemical performance. The fabricated devices show a high capacitance of 22.2 mF/cm2 at 0.05 mA/cm2, as well as energy and power densities comparable to those of similar devices that are hybridized with pseudocapacitive elements. The performed structural characterization confirms that the LIG material is composed of high-quality multilayer graphene nanoflakes with good structural continuity and an optimal porosity.

Laser Induced Graphene Microsupercapacitors: Structure, Quality and Performance

Laser Induced Graphene Microsupercapacitors: Structure, Quality and Performance

Sand-Milling Fabrication of Screen-Printable Graphene Composite Inks for High-Performance Planar Micro-Supercapacitors.

Rational engineering and simplified production of printable graphene inks are essential for building high-energy and flexible graphene micro-supercapacitors (MSCs). However, few graphene-based MSCs show impressive areal capacitance and energy density, especially based on additive-manufacturing, cost-effective, and printable inks. Herein, a new-style and solution-processable graphene composite ink is ingeniously formulated for scalable screen printing MSCs. More importantly, the as-formulated inks consist of interwoven two-dimensional graphene and activated carbon nanofillers, which are delaminated by one-step sand-milling turbulent flow exfoliation. Notably, embedding the activated carbon nanoplatelets into graphene layers drastically boosts the electrochemical performance of screen-printed micro-supercapacitors (denoted as Gr/AC-MSCs), such as an outstanding areal capacitance of 12.5 mF cm-2 (about 20 times than pure graphene). The maximum energy density, maximum power density, and exceptional cyclability are 1.07 μW h cm-2, 0.004 mW cm-2, and 88.1% after 5000 cycles, respectively. As such, the as-printed MSCs on paper display high resolution and pronounced energy-storage performance. Furthermore, the packaged and optimized Gr/AC-MSCs showcase remarkable mechanical flexibility even under highly folded and excellent water resistance, maintaining 91.8% capacitance retention after being washed for 90 min. The versatile methodology highlights the promise of graphene and analogous 2D nanosheet functional inks for scalable fabrication of flexible energy-storage devices.

Capacity Enhancement of Low-Cost and Flexible Micro-Supercapacitors By a Redox-Active Electrolyte and Laser-Induced Fibrous Graphene

Graphene-based nanomaterials are very promising for wearable and flexible electronics because of their unique electrical and mechanical properties. However, their difficult chemical synthesis has limited wide-spread commercial adoption. In particular, energy storage devices such as micro-supercapacitors require a porous morphology for large specific surface area and patterning such as interdigitated designs, which traditionally requires multiple complex fabrication steps. Laser-induced graphene (LIG) is a recently developed method that solves this problem by simultaneously generating and patterning porous graphene electrodes. Laser irradiation of a polyimide (PI) substrate selectively transforms the PI into graphene. This method shows promise to fabricate miniaturized energy storage devices at low cost and on a flexible substrate. However, the capacitance of LIG micro-supercapacitors needs to be improved by developing novel charge storage mechanisms compatible with LIG electrodes. Typically, energy storage mechanisms are classified as either electrochemical double-layer capacitance (EDLC) or pseudocapacitance. EDLC is enhanced by facile adsorption of electrolyte ions on the electrode material. Therefore, light weight carbon-based materials such as activated carbon, carbon nanotubes, graphene and their different combinations are suitable for EDLC but ultimately their performance is limited by their specific surface area. Pseudocapacitance allows further charge to be stored beyond the limitations imposed by the electrode’s surface area utilizing redox reactions of the electrode material with the electrolyte ions. There has been extensive interest in enhancing pseudocapacitance using various redox reactions between electrode materials such as transition metal oxides, conducting polymers and electrolyte ions. Carbon-based large-scale supercapacitors have been reported with improved performance by adding redox species, which can undergo redox reactions with the carbon-based electrodes, to the electrolyte. Reports on micro-supercapacitors using redox electrolytes have been limited to electrodes fabricated by complex multi-step fabrication processes. Here, we report graphene micro-supercapacitors fabricated by one-step laser scribing with enhanced capacitance utilizing a redox electrolyte. Hydroquinone (HQ) is a promising candidate as a redox additive in the electrolyte owing to its double charge transfer mechanism i.e. loss of 2H+ and 2e- during the charging process, which results in benzoquinone (BQ). Similarly, BQ is reduced to HQ by gaining 2H+ and 2e- during discharging. HQ (0.5 mol/L) was added to the aqueous H2SO4 (1 mol/L) electrolyte, which was deposited onto interdigitated LIG electrodes. The laser parameters were optimized to achieve LIG with a fibrous morphology. Fig.1a shows a scanning electron microscope (SEM) image of the cross-section of the fibrous LIG on PI. The addition of HQ as a redox-active additive enhanced specific capacitance approximately 5 times compared to devices without the HQ additive. The unmodified H2SO4 electrolyte exhibited an areal capacitance of 0.8 mF/cm2. Addition of HQ raised the total capacitance to 3.9 mF/cm2 as calculated from the area under the cyclic voltammetry curve in Fig.1b. Cyclic voltammetry of the device with HQ electrolyte showed very strong peaks due to oxidation and reduction of HQ and BQ as shown in Fig. 1b. A typical cyclic voltammetry graph with rectangular shape due to EDLC was observed in H2SO4 at 10 mV/s scan rate. It remained stable even at a high scan rate of 1000 mV/s as shown in Fig.1c-d. These results demonstrate the conductive nature of the engraved graphene and facile adsorption of the H+ ions. The device was further tested at higher scan rates after the introduction of HQ (10-1000 mV/s as shown in Fig.1e-f. The redox peaks were found very stable at higher scan rates and their peak values move towards extreme potentials at higher scan rates. To further investigate the motion of electrolyte ions within the pores of the fibrous graphene, electrochemical impedance spectroscopy (EIS) was performed with and without HQ in H2SO4 (see Fig.1g-j). A semi circle at low frequencies was observed (see Fig.1j), which indicates only 3 Ω charge-transfer resistance owing to facile motion of the electrolyte ions. In conclusion, we report a facile method to increase the capacitance of micro-supercapacitors with laser-induced graphene electrodes. The method only requires the addition of one redox-active component to the electrolyte. Combined with the one-step fabrication and patterning of graphene by LIG, this method shows promise for low-cost flexible energy storage devices. Figure 1

Flash foam stamp-inspired fabrication of flexible in-plane graphene integrated micro-supercapacitors on paper

Developing patterning techniques with practicability, cost-effectiveness and safety are essential for shape-confirmable integrated energy storage devices. Herein we design a novel flash foam stamp-inspired technique for simple fabrication of flexible high energy in-plane micro-supercapacitors based on interdigital electrodes of self-depositing electrochemically exfoliated graphene on paper substrates. This technique is an attractive and novel bottom-up microfabrication technology due to its advantages of simplicity and low-cost. These novelly developed all-solid-state, paper-based in-plane graphene micro-supercapacitors exhibit excellent electrochemical performances, such as high area specific capacitance of ∼4.02 mF cm−2 and excellent cycling stability (95.6% retention at 0.08 mA cm−2 for 5000 cycles). And these solid-state flexible micro-supercapacitors are observed non-obvious structural change and loss of performance under bending state, suggesting remarkable flexibility and mechanical stability. Therefore, such all-solid-state, flexible paper-based graphene micro-supercapacitors can potentially be used for wearable and portable electronics.

Plasma functionalisation of few-layer graphenes and carbon nanotubes for graphene microsupercapacitors

Plasma processing, as a commercial and large-scale technology, was used to functionalize few-layer graphene (FLG) and multi-walled carbon nanotubes (MWCNT). The successful functionalities of FLG and MWCNT have been confirmed by elemental microanalysis, X-ray photoelectron spectroscopy, acid-base titration and zeta potential measurements. With the assistance of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT/PSS), a water-dispersible and conductive polymer, a composite of functionalized FLG and MWCNT was fabricated into large-size flexible films and also interdigitated microelectrodes for microsupercapacitor application via simple and scalable techniques (i.e. doctor blading and laser-etching). When normalised by volume and area, the devices made from FLG(NH3)-MWCNT(Acid) (19.9 F cm−3 at 5 mV s−1 and 12.2 F cm−3 at 200 mV s−1) and FLG-MWCNT(Acid) (19.5 mF cm−2 at 5 mV s−1 and 12.8 mF cm−2 at 200 mV s−1) show the best performing composites, respectively, indicating how effective functionalization of FLG and MWCNT is for the enhancement of electrochemical capacitance. In-situ Raman microscopy confirmed the reversible pseudo-capacitive behaviour of electrode materials and the stable electrochemical performance of the devices. The facile techniques used in this work and the good device performances show their great potential for wearable applications.

Wet Transfer of Inkjet Printed Graphene Micro-Supercapacitors

In terms of mechanical and electronic characteristics, graphene is a fascinating discovery and certainly deserves the nickname of “wonder” material. As a matter of fact, this 2-dimensional carbon allotrope holds a number of record qualities1,2 which grant benefits in a plethora of applications. Biomedical devices,3 transistors,4 energy storage and conversion5 and solar cells6 are all proved uses of graphene and, consequently, the research community has high expectations for the real-world future of this disruptive technology. Moreover, where surface area, high throughput and easiness of fabrication are preferred like in energy storage devices, sensors and solar cells, graphene can be produced through the liquid-phase exfoliation of graphite which yields graphene flakes.7 As for graphene flakes deposition methods, inkjet printing has the main advantage in the fact that the patterning is direct and happens during the deposition. The technology also boasts micro-scale resolution and good substrate versatility as compared to other printing techniques.8 However, the choice of substrate is still not entirely straightforward as wetting and other surface properties of the substrate affect the printed film significantly and post-treatment of the inks is required. Herein, we demonstrate a wet transfer technique of inkjet printed graphene enabling the production of graphene patterns with a fine resolution on a range of substrates. Inspired by wet transfer methods of mostly CVD-grown graphene which have been subject of research since 2007, this process aims to expand their uses and capabilities through their implementation with inkjet printed graphene. The versatility of the technique allows depositing devices on a number of substrates, including plastics, silicon dioxide, plastics, paper (Figure 1a) and 3D objects. From the SEM images (Figure 1b) the protruding graphene flakes are visible, which are typical of inkjet printed graphene and greatly increase the surface area of the film. It can also be seen that the thin films maintain their structural integrity during the process. The cyclic voltammetry curves show that the energy storage mechanism is purely based on electrical double layer capacitance (Figure 1c), with an areal capacitance of about 120 µF/cm2. Because of its versatility, low cost and substrate compatibility, we expect this technique to boost the use of graphene for a number of applications such as epidermal electronics, human monitoring and environmental sensors. Bibliography A. C. Ferrari, F. Bonaccorso, V. Fal'ko, K. S. Novoselov, S. Roche, P. Bøggild, S. Borini, F. H. L. Koppens, V. Palermo, N. Pugno, J. A. Garrido et al., Nanoscale, 2015, 7, 4598–4810.K. S. Novoselov, V. I. Fal′ko, L. Colombo, P. R. Gellert, M. G. Schwab and K. Kim, Nature, 2012, 490, 192–200.K. Kostarelos and K. S. Novoselov, Science, 2014, 344, 261–263.F. Schwierz, Nature Nanotechnology, 2010, 5, 487–496.R. Raccichini, A. Varzi, S. Passerini and B. Scrosati, Nature Materials, 2014, 14, 271–279.Z. Yin, J. Zhu, Q. He, X. Cao, C. Tan, H. Chen, Q. Yan and H. Zhang, Advanced Energy Materials, 2013, 4, 1300574.V. Nicolosi, M. Chhowalla, M. G. Kanatzidis, M. S. Strano and J. N. Coleman, Science, 2013, 340, 1226419–1226419.J. Li, F. Ye, S. Vaziri, M. Muhammed, M. C. Lemme and M. Östling, Advanced Materials, 2013, 25, 3985–3992. Figure 1. a)Optical image of micro-supercapacitor on common paper. b)SEM image of the graphene film. c)Cyclic voltammetry performance of micro-supercapacitors on paper at scan rates from 5 to 250 mV/s. Figure 1

Transfer Printing of Sub-5 μm Graphene Electrodes for Flexible Microsupercapacitors.

Printed graphene microsupercapacitors (MSCs) are attractive for scalable and low-cost on-chip energy storage for distributed electronic devices. Although electronic devices have experienced significant scaling to smaller formats, the corresponding miniaturization of energy storage components has been limited, with a typical resolution of ∼30 μm for printed graphene patterns to date. Transfer printing is demonstrated here for patterning graphene electrodes with fine line and spacing resolution less than 5 μm. The resulting devices exhibit an exceptionally small footprint (∼0.0067 mm2), which provides, to the best of our knowledge, the smallest printed graphene MSCs. Despite this, the devices retain excellent performance with a high areal capacitance of ∼6.63 mF/cm2 along with excellent electrochemical stability and mechanical flexibility, resulting from an efficient nonplanar electrode structure and an optimized two-step photoannealing method. As a result, this miniaturization strategy facilitates the on-chip integration of printed graphene MSCs to power emerging electronic devices.

Scalable High-Performance Ultraminiature Graphene Micro-Supercapacitors by a Hybrid Technique Combining Direct Writing and Controllable Microdroplet Transfer.

Miniaturization of energy storage devices can significantly decrease the overall size of electronic systems. However, this miniaturization is limited by the reduction of electrode dimensions and the reproducible transfer of small electrolyte drops. This paper reports first a simple scalable direct writing method for the production of ultraminiature microsupercapacitor (MSC) electrodes, based on femtosecond laser reduced graphene oxide (fsrGO) interlaced pads. These pads, separated by 2 μm spacing, are 100 μm long and 8 μm wide. A second stage involves the accurate transfer of an electrolyte microdroplet on top of each individual electrode, which can avoid any interference of the electrolyte with other electronic components. Abundant in-plane mesopores in fsrGO induced by a fs laser together with ultrashort interelectrode spacing enables MSCs to exhibit a high specific capacitance (6.3 mF cm-2 and 105 F cm-3) and ∼100% retention after 1000 cycles. An all graphene resistor-capacitor (RC) filter is also constructed by combining the MSC and a fsrGO resistor, which is confirmed to exhibit highly enhanced performance characteristics. This new hybrid technique combining fs laser direct writing and precise microdroplet transfer easily enables scalable production of ultraminiature MSCs, which is believed to be significant for practical application of micro-supercapacitor microelectronic systems.

Combustion-Assisted Photonic Annealing of Printable Graphene Inks via Exothermic Binders.

High-throughput and low-temperature processing of high-performance nanomaterial inks is an important technical challenge for large-area, flexible printed electronics. In this report, we demonstrate nitrocellulose as an exothermic binder for photonic annealing of conductive graphene inks, leveraging the rapid decomposition kinetics and built-in energy of nitrocellulose to enable versatile process integration. This strategy results in superlative electrical properties that are comparable to extended thermal annealing at 350 °C, using a pulsed light process that is compatible with thermally sensitive substrates. The resulting porous microstructure and broad liquid-phase patterning compatibility are exploited for printed graphene microsupercapacitors on paper-based substrates.

Scalable Fabrication and Integration of Graphene Microsupercapacitors through Full Inkjet Printing.

A simple full-inkjet-printing technique is developed for the scalable fabrication of graphene-based microsupercapacitors (MSCs) on various substrates. High-performance graphene inks are formulated by integrating the electrochemically exfoliated graphene with a solvent exchange technique to reliably print graphene interdigitated electrodes with tunable geometry and thickness. Along with the printed polyelectrolyte, poly(4-styrenesulfonic acid), the fully printed graphene-based MSCs attain the highest areal capacitance of ∼0.7 mF/cm2, substantially advancing the state-of-art of all-solid-state MSCs with printed graphene electrodes. The full printing solution enables scalable fabrication of MSCs and effective connection of them in parallel and/or in series at various scales. Remarkably, more than 100 devices have been connected to form large-scale MSC arrays as power banks on both silicon wafers and Kapton. Without any extra protection or encapsulation, the MSC arrays can be reliably charged up to 12 V and retain the performance even 8 months after fabrication.

Inkjet printed highly transparent and flexible graphene micro-supercapacitors.

Modern energy storage devices for portable and wearable technologies must fulfill a number of requirements, such as small size, flexibility, thinness, reliability, transparency, manufacturing simplicity and performance, in order to be competitive in an ever expanding market. To this end, a comprehensive inkjet printing process is developed for the scalable and low-cost fabrication of transparent and flexible micro-supercapacitors. These solid-state devices, with printed thin films of graphene flakes as interdigitated electrodes, exhibit excellent performance versus transparency (ranging from a single-electrode areal capacitance of 16 μF cm-2 at transmittance of 90% to a capacitance of 99 μF cm-2 at transmittance of 71%). Also, transparent and flexible devices are fabricated, showing negligible capacitance degradation during bending. The ease of manufacturing coupled with their great capacitive properties opens up new potential applications for energy storage devices ranging from portable solar cells to wearable sensors.

Flexible Boron-Doped Laser-Induced Graphene Microsupercapacitors.

Heteroatom-doped graphene materials have been intensely studied as active electrodes in energy storage devices. Here, we demonstrate that boron-doped porous graphene can be prepared in ambient air using a facile laser induction process from boric acid containing polyimide sheets. At the same time, active electrodes can be patterned for flexible microsupercapacitors. As a result of boron doping, the highest areal capacitance of as-prepared devices reaches 16.5 mF/cm(2), 3 times higher than nondoped devices, with concomitant energy density increases of 5-10 times at various power densities. The superb cyclability and mechanical flexibility of the device are well-maintained, showing great potential for future microelectronics made from this boron-doped laser-induced graphene material.

Flexible and stackable laser-induced graphene supercapacitors.

In this paper, we demonstrate that by simple laser induction, commercial polyimide films can be readily transformed into porous graphene for the fabrication of flexible, solid-state supercapacitors. Two different solid-state electrolyte supercapacitors are described, namely vertically stacked graphene supercapacitors and in-plane graphene microsupercapacitors, each with enhanced electrochemical performance, cyclability, and flexibility. Devices with a solid-state polymeric electrolyte exhibit areal capacitance of >9 mF/cm2 at a current density of 0.02 mA/cm2, more than twice that of conventional aqueous electrolytes. Moreover, laser induction on both sides of polyimide sheets enables the fabrication of vertically stacked supercapacitors to multiply its electrochemical performance while preserving device flexibility.

Mass Production on a DVD

Optik & PhotonikVolume 8, Issue 1 p. 26-26 Research & TechnologyFree Access Mass Production on a DVD UCLA researchers develop new technique to scale up production of graphene micro-supercapacitors First published: 15 April 2013 https://doi.org/10.1002/opph.201390006AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article. Volume8, Issue1April 2013Pages 26-26 RelatedInformation

Scalable fabrication of high-power graphene micro-supercapacitors for flexible and on-chip energy storage

The rapid development of miniaturized electronic devices has increased the demand for compact on-chip energy storage. Microscale supercapacitors have great potential to complement or replace batteries and electrolytic capacitors in a variety of applications. However, conventional micro-fabrication techniques have proven to be cumbersome in building cost-effective micro-devices, thus limiting their widespread application. Here we demonstrate a scalable fabrication of graphene micro-supercapacitors over large areas by direct laser writing on graphite oxide films using a standard LightScribe DVD burner. More than 100 micro-supercapacitors can be produced on a single disc in 30 min or less. The devices are built on flexible substrates for flexible electronics and on-chip uses that can be integrated with MEMS or CMOS in a single chip. Remarkably, miniaturizing the devices to the microscale results in enhanced charge-storage capacity and rate capability. These micro-supercapacitors demonstrate a power density of ~200 W cm-3, which is among the highest values achieved for any supercapacitor.