On-chip Micro-supercapacitors Research Articles

Excellent electrochemical performance of all-solid-state planar on-chip micro-supercapacitors with narrow interdigital electrode configuration

As a popular direction of research in micro-energy storage devices, improving the comprehensive performance of all-solid-state planar on-chip micro-supercapacitors (MSCs) has received increasing attention. Graphene quantum dots (GQDs) are a new type of nano-scale electrode materials that can improve the electrochemical performance of devices. In addition, the doping of nitrogen/oxygen heteroatoms can further improve the electrochemical activity of the electrode materials. In this paper, nitrogen-oxygen co-doped graphene quantum dots (NO-GQDs) were used as electrode materials, and a modified liquid-air interface self-assembly method was used to fabricate the electrode films. Finally, the MSCs with narrow interdigital electrode configuration were prepared by photolithography with an electrode width/interdigital gap of 3 μm/1 μm. The prepared MSCs have excellent electrochemical performance, including an area capacitance of 150.63 μF cm−2, an energy density of 20.92 nWh cm−2, a power density of 175.49 μW cm−2, a relaxation time constant of 3.53 μs, and a capacitance retention of 90.42%. As shown by the results, the combination of NO-GQDs and narrow interdigital electrode configuration provides a significant improvement in the comprehensive electrochemical performance of the all-solid-state planar on-chip MSCs.

Effect of Weight Ratio of Graphene Oxide and Carbon Nanotubes on Electrochemical Performance of Planar On-Chip Micro-Supercapacitors

With the wide popularization of 5 G network, the application of miniaturized electronic equipment is being gradually developed, but limited by energy storage technology. Micro-supercapacitors (MSCs) have become the possible direction to solve this problem because of their unique properties. Graphene oxide and carbon nanotubes are very suitable materials for preparing MSCs. However, graphene oxide will overlap due to van der Waals force, and carbon nanotubes will be entangled. In order to solve these problems, reduced graphene oxide and carbon nanotube composite films were prepared by liquid-air interface self-assembly and hydroiodic acid reduction. Planar MSCs with weight ratios of 5:1, 10:1 and 15:1 were prepared by photolithography, and the MSCs of 15:1 show the best comprehensive performance with the area capacitance of 0.905 μF cm−2, the energy density of 0.125 nWh cm−2, the power density of 2263.31 nW cm−2, the time constant of 38 ms, and the capacitance retention of 91.2%.

Planar on-chip micro-supercapacitors based on reduced graphene oxide and carbon nanotube by liquid–air interface self-assembly and photolithography

Recently, the development of miniaturized electronic devices has accelerated the demand for the rate capability of planar on-chip micro-supercapacitors (POMSs). The POMSs based on reduced graphene oxide and carbon nanotube (rGO/CNT) composite electrodes (rGO/CNT-POMSs) were manufactured in the work and detailed electrochemical tests of devices were carried out over a wide range of scanning rates (0.01–10000 V s−1). The rGO/CNT composite electrode films without binder were prepared on silicon substrates by a modified liquid–air interface self-assembly method and a hydroiodic acid reduction method. The electrodes were fabricated into interdigital structure with 50 μm width of electrode and gap of electrode by photolithography. Interdigital POMSs based on different electrodes were prepared by gold sputtering on the electrode lugs. The area capacitance of the rGO/CNT-POMSs was 28.62 μF cm−2. They also had 0.004 μWh cm−2 of energy density and 1.068 μW cm−2 of power density. In addition, the charge–discharge time constant of the device was only 5.6 μs, and the charge–discharge rate was very quick. After 10,000 cycles of charge–discharge, the capacitance retention rate was still above 88%. At the ultra-high scan rate of 10000 V s−1, the devices still worked well. Compared with the POMSs based on reduced graphene oxide electrodes (rGO-POMSs) and the POMSs based on carbon nanotube electrodes (CNT-POMSs), the introduction of the CNT significantly increased the area capacitance, energy density and power density of rGO/CNT-POMSs, and significantly shortened the charge–discharge time constant. This indicated that the rGO/CNT composite electrodes had a good application prospect in the micro-chip accumulator devices.

Photolithographic Fabrication of Planar On-Chip Micro-Supercapacitors Based on Aminated Graphene Quantum Dots with Comprehensive Electrochemical Performance

Nowadays, more and more electrode materials were used to fabricate micro-supercapacitors (MSCs). The graphene quantum dots were widely used due to the abundant edge defects, good conductivity, multiple active sites and other excellent characteristics. The aminated graphene quantum dots (A-GQDs) not only had the above characteristics, but also further improved the ion channel between the electrolyte and the electrode surface, and increased the transmission rate between the electrode interface. In this work, a modified liquid-air interface self-assembly method was used to fabricate the A-GQDs films on the silicon wafer for MSCs. Cyclic voltammetry measurements showed that the energy density of the MSCs was 10.21 nWh cm−2 at 0.1 V s−1 and the power density was 113.55 μW cm−2. The flat design of interdigitated electrodes can improve the frequency response with time constant as low as 1.23 μs. There is still a high areal capacitance (73.5 μF cm−2) which benefit from the narrow electrode width and the film thickness on the order of 101 nanometers. It can be seen that A-GQDs can be used as a new type of high-activity, low-cost electrode materials, suitable for high performance supercapacitors.

Outstanding Electrochemical Performance of Planar On-chip Micro-supercapacitors Based on Nitrogen and Oxygen Co-doped Graphene Quantum Dots at High Scan Rates

In recent years, researchers continue optimizing and innovating in the selection of supercapacitor electrode materials and fabrication processes. In this paper, the fabrication process and electrochemical performance of an all-solid-state planar on-chip micro-supercapacitors (POMSs) with nitrogen and oxygen co-doped graphene quantum dots as electrode material will be demonstrated. Graphene quantum dots (GQDs) electrode films were prepared by a modified liquid-air interface self-assembly method, and patterned by photolithography. The resulting POMSs achieved an area capacitance of 25.53 μFcm−2, and its areal energy density and areal power density are 3.55nWh cm−2 and 8.79 μW cm−2 correspondingly. It is worth noting that the POMSs have excellent rate capability and can maintain outstanding performance at ultrahigh scan rate of 10000 V s−1. The POMSs have a short time constant which is 3.16 μs, and the capacitance characteristics can be maintained over 99.1% in 10000 cycles of charge and discharge at a scan rate of 5000 V s−1 in the cyclic stability test.

Direct mask-free fabrication of patterned hierarchical graphene electrode for on-chip micro-supercapacitors

• Functionalized membrane with customized pattern is prepared by fast laser carving. • Selective permeable membrane complemented with vacuum filtration is used to develop intact interdigital thin film. • Macroscopic assembly based on size effect rationally guide the structural design and precise fabrication of flexible electrode with expected high performances. • Flexible high-performance on-chip micro-supercapacitors with planar arbitrary shape are fabricated. Graphene-based electrodes with rational structural design have shown extraordinary prospect for enhanced electrical double-layer capacitance of micro-supercapacitors (MSCs). Herein, a facile fabrication method for flexible planar MSCs based on hierarchical graphene was demonstrated by using a laser-treated membrane for electrode patterning, complemented with hierarchical electrode configuration taking full advantages of size-determined functional graphene. The in-plane interdigital shape of MSCs was defined through vacuum filtration with the assistance of the functionalized polypropylene (PP) membrane. The hierarchical graphene films were built by macroscopic assembly based on size effect of different lateral sized graphene sheets (rGO-LSL). The sample of MSCs based on rGO-LSL (MSCs-LSL) exhibited excellent volumetric capacitance of 6.7 F cm −3 and high energy density of 0.37 mWh cm −3 . The MSCs-LSL presented superb flexibility and cycling stability with no capacitance deteroriated after 2000 cycles. This newly developed fabrication strategy is of good scalability and designability to manufacture flexible electrode for MSCs with customized shapes, while the construction of hierarchical graphene can enlighten the structural design of analogous two-dimensional materials for potential advanced electronics. A facile mask-free filtration approach is developed for the fabrication of patterned onchip micro-supercapacitors based on hierarchical graphene. The use of the functionalized membrane complemented with macroscopic assembly based on size effect provides the control over the planar configuration of micro-supercapacitors, and rationally guide the structural design of flexible electrode with expected high performances.

Advanced Three-Dimensional Microelectrode Architecture Design for High-Performance On-Chip Micro-Supercapacitors.

The rapid development of miniaturized electronic devices has greatly stimulated the endless pursuit of high-performance on-chip micro-supercapacitors (MSCs) delivering both high energy and power densities. To this end, an advanced three-dimensional (3D) microelectrode architecture design offers enormous opportunities due to high mass loading of active materials, large specific surface areas, fast ion diffusion kinetics, and short electron transport pathways. In this review, we summarize the recent advances in the rational design of 3D architectured microelectrodes including 3D dense microelectrodes, 3D nanoporous microelectrodes, and 3D macroporous microelectrodes. Furthermore, the emergent microfabrication strategies are discussed in detail in terms of charge storage mechanisms and structure-performance correlation for on-chip MSCs. Finally, we conclude with a perspective on future opportunities and challenges in this thriving field.

Hierarchical polypyrrole@cobalt sulfide-based flexible on-chip microsupercapacitors with ultrahigh energy density for self-charging system

Hierarchical polypyrrole@cobalt sulfide-based flexible on-chip microsupercapacitors with ultrahigh energy density for self-charging system

Facile fabrication of 2D porous carbon nano-flake electrodes for high-performance flexible on-chip micro-supercapacitors

Graphene has been continuously investigated as electrode material for flexible micro-supercapacitors (MSCs). However, owing to the lack of in-plane ion transport channels and low specific surface area caused by restacking of graphene sheets, its electrochemical performance is unsatisfactory. To solve this problem, herein, we present a novel strategy for preparing 2D porous carbon nano-flake (PCF) through simple chlorine-etching MXene (Ti3C2). Distinctly different from the commonly graphene sheets, the prepared PCF shows high specific surface area (1239 m2 g−1) and abundant ion transport channels in c-axis direction, thus enhancing electrochemical performance. When the prepared PCF is used as the electrode for MSCs, the MSCs behaves excellent electrochemical performances. The areal capacitance and the energy density is up to 102.1 mF cm−2 (at current density of 0.2 mA cm−2) and 13.2 μWh cm−2 (at 0.1 mW cm−2 power density), respectively, which, to the best of our knowledge, are both among the highest values reported for MSCs with the graphene electrodes. In addition, the fabricated MSCs also show excellent mechanical flexibility and easy-adjustment in the voltage and capacitance by connecting multiple MSCs in series and parallel. These results indicate that the prepared PCF has great application potential in micro electrochemical energy storage devices.

Photolithographic fabrication and electrochemical characterization of planar on-chip micro-supercapacitors based on nitrogen and oxygen co-doped graphene quantum dots with superior capacitance retention rates

Compared with graphene, nitrogen and oxygen co-doped graphene quantum dots can make up for the limitation of graphene active sites. Here, we demonstrated the fabrication of planar on-chip micro-supercapacitors based on nitrogen and oxygen co-doped graphene quantum dots. The interdigital micro-electrodes were prepared on the surface of the electrode thin film by the photolithographic technique. Notably, the electrochemical performance of the micro-supercapacitors had significantly increased. The area capacitance was 18.74 μF cm−2. Furthermore, this work offered the areal energy density of 2.60 nWh cm−2 and the areal power density of 116.43 μW cm−2. After 10,000 cycles at 5000 Vs−1, the capacitance retention rate of 99.23% was obtained. Meantime, the corresponding time constant was 10.03 μs.

Planar on-chip microsupercapacitors based on aminated graphene quantum dots with high areal power density and rapid frequency response capability

Planar on-chip microsupercapacitors (POMSs) with a finger width and a gap width of 10 μm were fabricated based on aminated graphene quantum dots electrode films by modified liquid-air interface self-assembly method, photolithography and oxygen plasma etching, and they had the areal power density of 154.14 μWcm−2 and energy density of 0.01 μWhcm−2. Moreover, the POMSs showed rapid frequency response capability, the frequency at phase angle of −45° was 0.18 MHz and the corresponding time constant was 5.57 μs. After 10000 charge and discharge cycles, the capacitance retention rate was 93%. Doping of nitrogen can improve the conductivity of the electrode films and the presence of amino groups can improve surface modification of the electrode films.

On-Chip Planar Interdigital Micro-Supercapacitors Based on Reduced Graphene Oxide with Superior Rate and Charge-Discharge Capabilities

Reduced graphene oxide (RGO) thin films were prepared on silicon substrates by a modified liquid-air interface self-assembly method and a hydroiodic acid reduction method. Planar on-chip micro-supercapacitors with interdigital structure electrodes (RGO-POMSs) were prepared by photolithography and gold sputtering on the electrode lugs. Area capacitance of interdigital RGO-POMSs was 51.72 μF cm−2. They also had 0.0072 μW h cm−2 of energy density and 59.78 μW cm−2 of power density. Due to the short ion transport path caused by interdigital electrodes, the charge discharge time constant of the device was only 0.029 ms, which could realize rapid charge discharge. In addition, they also had good cycle stability and could maintain 82% capacitance after 4500 cycles of charge and discharge. The cyclic voltammetry test showed that the device still worked well at the ultra-high scan rate of 10,000 V s−1. This showed that RGO-POMSs had considerable prospects in the research field of micro energy storage devices.

Ultrafast response planar on-chip micro-supercapacitors based on nitrogen and oxygen co-doped graphene quantum dots with both ultrahigh power and energy densities

Great results had been achieved in the research of graphene-based planar on-chip micro-supercapacitors. The performances of fabricated micro-supercapacitors had been greatly improved. However, the energy characteristics of graphene-based planar on-chip micro-supercapacitors are generally low due to few active sites of graphene. Nitrogen and oxygen co-doped graphene quantum dots have the nanometer size, more active sites, and rich edge defects, are conducive to ion adsorption and desorption, and can solve the above-mentioned disadvantages of graphene. In this article, all-solid-state planar on-chip micro-supercapacitors based on nitrogen and oxygen co-doped graphene quantum dots with both ultrahigh power and energy densities were fabricated by modified liquid–air interface self-assembly and photolithography for the first time. Planar on-chip electrodes were provided with a nanoscale thickness of 6 nm and an interdigital electrode width of 3 μm. Energy density of 11.49 mWh cm−3, power density of 41.42 W cm−3, and time constant of 3.16 μs were demonstrated. It should be emphasized that the above-mentioned energy density and power density are the highest for the planar on-chip micro-supercapacitors based on nitrogen and oxygen co-doped graphene quantum dots reported to date. The capacitance retention was 99% after 10000 cycles at 5000 V s−1.

All-solid-state planar on-chip micro-supercapacitors with excellent areal power performance at ultrahigh scan rates by photolithography

All-solid-state planar on-chip micro-supercapacitors (MSCs), as a new type of energy storage device, can be well integrated with micro-nano devices and exhibit good practical performance. Nitrogen and oxygen co-doped graphene quantum dots (GQDs), as one of the electrode materials for fabricating supercapacitors, exhibiting novel chemical/physical properties including nanometer-size, abundant edge defects, good conductivity and better surface grafting. In this article, the GQDs film was prepared by modified liquid–air interface self-assembly method and fabricated interdigital electrodes with electrode width and interdigital gap of 6 μm by simple photolithography technology. Electrochemical measurements revealed that the obtained GQDs electrodes for all-solid-state MSCs exhibited the areal power density of up to 0.107 mW cm−2 at the scan rate of 10,000 V s−1 and 95.6% capacitance after charging and discharging for 10,000 cycles. Specially, there was still the ultra-fast charging-discharging time (4.17 μs). The favorable performances make the GQDs film interdigital electrodes prepared by photolithography have good application prospects.

Tunable Capacitive Behavior in Metallopolymer-based Electrochromic Thin Film Supercapacitors.

Volumetric capacitance is a more critical performance parameter for rechargeable power supply in lightweight and microelectronic devices as compared to gravimetric capacitance in larger devices. To this end, we report three electrochromic metallopolymer-based electrode materials containing Fe2+ as the coordinating metal ion with high volumetric capacitance and energy densities in a symmetric two-electrode supercapacitor setup. These metallopolymers exhibited volumetric capacitance up to 866.2 F cm-3 at a constant current density of 0.25 A g-1. The volumetric capacitance (poly-Fe-L2: 544.6 F cm-3 > poly-Fe-L1: 313.8 F cm-3 > poly-Fe-L3: 230.8 F cm-3 at 1 A g-1) and energy densities (poly-Fe-L2: 75.5 mWh cm-3 > poly-Fe-L1: 43.6 mWh cm-3 > poly-Fe-L3: 31.2 mWh cm-3) followed the order of the electrical conductivity of the metallopolymers and are among the best values reported for metal-organic systems. The variation in the ligand structure was key toward achieving different electrical conductivities in these metallopolymers with excellent operational stability under continuous cycling. High volumetric capacitances and energy densities combined with tunable electro-optical properties and electrochromic behavior of these metallopolymers are expected to contribute to high performance and compact microenergy storage systems. We envision that the integration of smart functionalities with thin film supercapacitors would warrant the surge of miniaturized on-chip microsupercapacitors integrated in-plane with other microelectronic devices for wearable applications.

All-solid-state planar on-chip micro-supercapacitors based on reduced graphene oxide with ultrahigh energy characteristics

Planar on-chip micro-supercapacitors are recognized as one of the most competitive energy sources for electronics. Here, we showed ultrahigh performance all-solid-state planar on-chip micro-supercapacitors with photolithographic interdigital electrodes based on modified liquid-air interface self-assembly technique. The electrode width which is narrower than other existing lithography is only on the order of 10° μm (electrode width is 4 μm and the gap width is 4 μm). Planar on-chip micro-supercapacitors prepared with reduced graphene oxide films as electrodes had the energy density of 124.4 mWh cm−3, the corresponding time constant of 2.15 μs and the displayed stack capacitance of 895.74 F cm−3. In addition, it exhibited excellent cycle stability with a capacitance retention of 98.9% after 10,000 cycles. The demonstrated planar on-chip micro-supercapacitors have a good application foreground in the preparation of high-performance integrated micro-devices.

Fabrication and Characterization of Planar on-Chip Micro-Supercapacitors Based on Nitrogen and Oxygen Co-Doped Graphene Quantum Dots by Modified Liquid-Air Interface Self-Assembly Method

Planar micro-supercapacitors stand out among micro/nano energy storage components for their high power, high energy, long life and fast time response. In this paper, all-solid-state planar on-chip micro-supercapacitors with high power characteristics were prepared by modified liquid-air interface self-assembly method, photolithography and sputtering gold. The nitrogen and oxygen co-doped graphene quantum dots electrode films are continuous and uniform, and the surface contains a large number of nitrogen and oxygen chemical bonds and functional groups. The finger width of the supercapacitors is 50 μm, the gap width is 50 μm and a number of electrode fingers is 100. In terms of performance, the supercapacitors had a very short time constant (2.16 μs), high power density (15.80 μW cm−2) and excellent cycle stability (94.5% capacity retention after 10000 cycles).

In-situ exfoliation and integration of vertically aligned graphene for high-frequency response on-chip microsupercapacitors

Fast response on-chip micro-supercapacitors (MSCs) with large energy storage capabilities are highly in demand for high-frequency circuits and systems such as alternating current (AC) line filters. Devices with vertically aligned graphene thin-film electrodes were shown to be promising in maintaining close-to-ideal capacitive behavior at high frequencies due to low ionic and electric resistances. This study investigates a novel in-situ integration of vertically aligned graphene layers with micro-sized gold current collectors in which a modified bipolar electrochemistry method has been applied. The electrochemical analysis revealed a high average capacitance of 640 μF cm−2 (C.V−1cm−2) at a scan rate of 2 mV s−1 for the fabricated MSCs and their excellent stability even after 50000 successive charge-discharge cycles by constant current. Most notably, the electrochemical impedance spectroscopy results revealed that the MSCs exhibited very fast response and close-to-ideal capacitive behavior even at around 1000 Hz. Specifically, the phase angle and specific capacitance measured at 120 Hz were −81.2 deg and 65.2 μF cm−2, respectively, in addition to a cut-off frequency of 3486 Hz at which the impedance angle is −45 deg. The device was tested as the capacitive energy storage component in a standard AC line filter, and its performance was found comparable to a commercial off-the-shelf aluminum electrolytic capacitor.

Interfacial synthesis of crystalline quasi-two-dimensional polyaniline thin films for high-performance flexible on-chip micro-supercapacitors

Quasi-two-dimensional (q2D) conducting polymer thin film synergizes the advantageous features of long-range molecular ordering and high intrinsic conductivity, which are promising for flexible thin film-based micro-supercapacitors (MSCs). Herein, we present the high-performance flexible MSCs based on highly ordered quasi-two-dimensional polyaniline (q2D-PANI) thin film using surfactant monolayer assisted interfacial synthesis (SMAIS). Owing to high electrical conductivity, rich redox chemistry, and thin-film morphology, the q2D-PANI MSCs show high volumetric specific capacitance (ca. 360 F/cm3) and energy density (17.9 mWh/cm3), which outperform the state-of-art PANI thin-film based MSCs and promise for future flexible electronics.

Micro-nanoscale all-solid-state planar on-chip micro-supercapacitors based on nitrogen and oxygen Co-doped graphene quantum dots with excellent areal power and energy characteristics

As a new quasi-zero-dimensional nanomaterial, graphene quantum dots (GQDs) can solve the impact of carbon materials that have low specific surface area and few active sites, improving the performance of planar on-chip micro-supercapacitors (POMSs) by reducing the interdigital width. In this article, nitrogen and oxygen co-doped GQDs (N-O-GQDs) as an electrode material and narrow electrode width and gap are both 6 μm make the POMS possess a power density of 28.1 μW cm−2 and an energy density of 15.11 nWh cm−2. Importantly, the capacitance retention rate is as high as 96.1% after 10,000 cycles of charging and discharging.