Solid-state Micro-supercapacitors Research Articles

Synergistic effect of solvent addition and temperature treatment on conductivity enhancement of MWCNTs: PEDOT:PSS composite ink for electrodes in all printed solid-state micro-supercapacitors

All solid-state micro-supercapacitors (S-MSCs) are pivotal for modern wearables as they offer rapid energy storage and release, with seamless integration into small, lightweight wearables. Developing all printed S-MSCs is a cost-effective alternative to traditional S-MSCs and can potentially revolutionize wearable energy storage technologies. This manuscript presents an innovative, substrate-friendly approach to enhance the conductivity and electrochemical performance of screen-printed electrodes for S-MSCs using multi-walled carbon nanotubes (MWCNTs): PEDOT:PSS (poly(3,4-ethylene dioxythiophene): poly(styrene sulfonate)) composite ink. By incorporating various polar solvents into the ink formulation and optimizing printing and drying parameters, a four-fold increase in conductivity (5.5 × 103 S/m) was achieved. The synergy of polar solvent addition and temperature treatment on the dielectric screening, preferential solvation, and partial segregation of PSS were identified as the principal reason behind this enhancement. The optimally formulated ink was employed to create supercapacitor electrodes, demonstrating hybrid capacitive behavior with both liquid and gel electrolytes. An impressive 97.5 % decrease in charge transfer resistance (RCT) and a corresponding increase in areal capacitance and energy density were observed for these supercapacitors due to the segregation of PEDOT and PSS achieved by the synergistic effect. All printed S-MSCs were also fabricated with an impressive areal capacitance of 9.82 mF/cm2 @ 60 µA/cm2 and areal energy density of 1.964 µWh/cm2 at an areal power density of 63 µW/cm2. The fabricated S-MSCs exhibited impeccable capacitance retention of 99.7 % after 6,000 operation cycles and impressive stability upto 10,000 bending cycles, making them promising energy storage solutions for flexible and wearable devices.

Printed flexible solid-state microsupercapacitor with highly-stable aqueous cobalt-based inks

Cobalt-based nanomaterials are among the most noticed candidates for manufacturing supercapacitive electrodes. Inkjet-printing is an emerging technique for fabricating miniaturized devices. In this work, highly flexible microsupercapacitors (MSCs) are manufactured, using a pseudocapacitive (C = 900 F‌ g−1 at 1 A g−1) Co-oxide-hydroxide water-based and ultra-stable (up to 12 months) ink on paper. The synthesized capacitive active material consists of cobalt-oxide nanocubes and cobalt-hydroxide hexagonal nanoflakes. Conductive (Rs = 13 Ω/□) silver nanowire networks serve as current collectors, and the morphology of cobalt oxide-hydroxide structures and the developed ink features, allow for printing well-detailed and homogeneous patterns. The inkjet-printed symmetric and asymmetric devices show notable areal specific capacitances of 35.68 mF cm−2 and 23.60 mF cm−2 at a current density of 0.1 mA cm−2, respectively. The asymmetric devices deliver impressive energy and power densities of 2.76 μW h cm−2 (4.10 W h kg−1) and 646 μW cm−2 (959 W kg−1), respectively. A thorough study on the cyclic and mechanical stability of the flexible devices resulted in perfect capacitance maintenance of 94.3 % after 10,000 charge and discharge cycles and retention of over 80 % even after 1000 cycles of successive bending and folding. The extensive study of capacitance retention following folding under various obtuse and reflex angles, which can be regarded as an important step toward characterizing flexible devices suitable for being utilized in wearable electronics, is carried out for the first time to the best of our knowledge. The findings of this study clearly illustrate the prospects of using the inkjet-printing technique to fabricate high-performance MSC devices appropriate for integration with flexible and wearable electronics.

Paper-Based Solid-State Micro-supercapacitors Fabricated by Hydrophobic Wax Barrier Printing

Paper-Based Solid-State Micro-supercapacitors Fabricated by Hydrophobic Wax Barrier Printing

3D Printed Stamps for Transfer Printing of Flexible and Wearable Supercapacitors

In recent times, there has been an increasing demand for portable, lightweight, and flexible electronic devices. These electronic devices are required in healthcare, robotics, sports, defence, and other applications. Energy storage unit is one of the key requirements of these electronics and solid-state micro-supercapacitors (MSCs) are preferred for flexible and wearable electronics.[1,2] However, conventional methods of manufacturing MSCs are complex, time-consuming, and costly. This work aims to explore an alternative approach to developing MSCs by transferring electronic inks onto paper, textiles, and other flexible substrates using 3D-printed stamps. Different in-plane MSCs with varying finger widths and interspace gaps were fabricated to find the optimum electrochemical properties. The developed devices exhibit excellent electrochemical performance including high power density, high energy density, excellent lifetime, and excellent flexibility under different mechanical deformation conditions (such as bending, rolling, folding, etc.). This approach has a huge potential for fabrication of next-generation electronics for flexible and wearable electronic applications.

Flexible interdigitated symmetric solid-state micro-supercapacitors with higher energy density for wearable electronics

Planar interdigitated solid-state supercapacitors are one of the most promising energy storage devices as they offer the merit of fast ionic transportation with minimal charge transfer resistance due to the narrow gap between the interdigitated isolated electrode fingers. This study focuses on fabricating flexible symmetric solid-state supercapacitor devices with high energy and power densities. Specifically, a symmetric SnO2‖PVA-LiClO4‖SnO2 solid-state supercapacitor (SSC) device was fabricated using the electron beam evaporation (e-beam) technique on thin, flexible electrodes in interdigitated (ISSC) and stacked (SSSC) configurations and their electrochemical performances were compared. The ISSC exhibiting pseudo-capacitive behavior achieved a maximum volumetric capacitance of 439.5 F cm−3 at a scan rate of 5 mV S−1. Quantitative calculation of the device's charge storage dynamics reveals that the diffusion-limited Lithium insertion processes predominantly contribute to the capacitance of ISSC. Comparatively, the ISSC outperformed the SSSC with a diffusion coefficient of 2.55 × 10−13 m2s−1 and ac conductivity of 2.2 × 10−2 S m−1, demonstrating excellent energy density and power density values. Furthermore, the ISSC with no adverse effect on its capacitance even when bent at various angles suggesting its suitability for flexible wearable electronic devices.

In-situ crosslinking of polysiloxane electrolyte within Al2O3@SiNWs for quasi-solid-state micro-supercapacitors

Developing flexible solid-state micro-supercapacitors with large potential window is crucial for many technologies. The present study focuses on the synthesis and elaboration of quasi-solid-state (QSS) electrolytes with an electrochemical stability greater than 3.0 V based on functionalized polysiloxane. Their electrochemical behavior was studied with silicon nanowires electrodes. The polysiloxane was functionalized with both ammonium and cross-linkable functions. The nanostructured electrodes were impregnated with a mixture of ionic liquid and functionalized polysiloxane. The crosslinking of the polymer electrolyte was then performed by thermal curing directly within the nanostructured electrodes. The quasi-solid system exhibits very high stability upon galvanostatic cycling i.e. during 100 000 cycles with a cell potential of 3.0 V only a capacitance loss of 2.10−5% per cycle was registered. The performance of this QSS with safe electrolyte is remarkable.

Tailoring ion dynamics in energy storage conductors for ultra-stable, high-performance solid-state microsupercapacitor array

All-solid-state electrochemical energy storage (EES) devices with prolonged lifetime, operational stability, and mechanical flexibility can be a promising route to powering up wearable electronics. However, conventional EES devices have been often hindered by a gradual decrease in energy capacity due to low ionic conducting electrolytes, non-suitable electrode materials, or poor electrode/electrolyte interfaces. Herein, we propose a harmonization of the molecular-level tailoring of ionic gel polymer electrolyte (IGPE) and graphene-based electrodes, significantly improving and sustaining the electrochemical performance (11.9 μWh cm−2) of EES microsupercapacitor (MSC) devices. Our optimized MSC device based on ethyl-3-methylimidazolium bis(fluorosulfonyl)imide (EMIM-FSI) and interdigitated reduced-graphene oxide (rGO) electrode array maintains 99 % of the initial electrochemical capacity even after 20,000 cycles, also demonstrating the excellent mechanical flexibility (bending radius up to 4 mm) and environmental stability (>30 days) of the MSC-based array. Molecular-level simulation and spectroscopic atomic analysis revealed noticeably lower residual ionic liquid (IL) molecules of EMIM-FSI, compared to EMIM-trifluoromethyl FSI, between the graphene-based layers of electrodes during the charge/discharge cycles. Therefore, our optimization strategy and findings will pave the way to accomplish next-generation of all-solid-state EES devices with ultra-high operational stability, powering wearable electronics.

PEDOT:PSS/regenerated cellulose composite microelectrode for high-performance micro-supercapacitor

Ecofriendly electronic and energy storage devices are critical for addressing the issues regarding the limited energy resources and environmental pollution. Conductive micropatterns on biodegradable substrates are key components for the development of green energy storage devices. In this study, we report a facile strategy for constructing highly conductive and flexible poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) micropatterns on regenerated cellulose (RC) substrates via a simple vacuum-assisted filtration with a 3D printed shadow mask and dimethyl sulfoxide (DMSO) post-treatment. Theshadow maskwas effectively used in a vacuum filtration process to create various PEDOT:PSS micropatterns on RC substrates (PEDOT:PSS/RCs). The RC substrates present the advantages of being both synthetic and natural polymers such as high uniformity, good solution-processability, mechanical property, and biodegradability. The PEDOT:PSS patterns on the RC substrates show a sheet resistance of 4.2 Ω/cm2, an electrical conductivity of 327 S/cm, good adhesion stability and excellent bending durability. Furthermore, the PEDOT:PSS micropatterns on the RC substrates were successfully used for fabricating a solid-state micro-supercapacitor (MSC) device. The MSC sandwich structure based on PEDOT:PSS/RCs has a good specific capacitance of 65.55 mF/cm2 and an excellent cycling stability over 4000 cycles.

MXene decorated 3D-printed carbon black-based electrodes for solid-state micro-supercapacitors

Three-dimensional (3D) printing offers a unique approach to fabricating free-standing and complex structured electrodes for high-performance micro-supercapacitors (MSCs).

N/O co-doped micropores carbon derived from a solvent-free synthesized polymer for high-performance supercapacitor

BackgroundHeteroatom-doped porous carbons have attracted widespread concern as promising electrode materials for supercapacitors. Polymers are considered as the promising carbon sources because their derived carbons possess the unique advantages of inherited uniform heteroatoms doping, high purity, and good reproducibility. While the synthesis process of polymers usually involves solvents, which will bring a pollution of the environment and increase the consumption of cost and energy. MethodsHerein, nitrogen/oxygen co-doped porous carbons (NOPCs) with predominant micropores were prepared via carbonization and activation of a solvent-free synthesized polymer using 2-aminophenol, hexamethylenetetramine as monomers. Kinetics studies and density functional theory (DFT) simulations reveal that N/O heteroatoms credibly introduces pseudocapacitance and greatly improves the chemisorption of K+, leading to an outstanding electrochemical performance. Significant findingsThe obtained NOPCs exhibit interconnected microporous structure, large specific surface area (3297 m2 g−1), narrow pore size distribution (ca. < 1 nm), suitable heteroatoms content (N: 4.13%, O: 13.06%) and high carbon yield of 48 wt%. Benefitting from these features, the optimal NOPC-800 delivers a remarkable specific capacitance of 410 F g−1 at 1 A g−1 and retains 270 F g−1 at 50 A g−1. The solid-state micro-supercapacitors fabricated from the NOPCs presents areal capacitance up to 29.7 mF cm−2 and energy density up to 0.97 μWh cm−2.

Biocompatible Parylene-C Laser-Induced Graphene Electrodes for Microsupercapacitor Applications.

Laser irradiation of polymeric materials has drawn great attention as a fast, simple, and cost-effective method for the formation of porous graphene films that can be subsequently fabricated into low-cost and flexible electronic and energy-storage devices. In this work, we report a systematic study of the formation of laser-induced graphene (LIG) with sheet resistances as low as 9.4 Ω/sq on parylene-C ultrathin membranes under a CO2 infrared laser. Raman analysis proved the formation of the multilayered graphenic material, with ID/IG and I2D/IG peak ratios of 0.42 and 0.65, respectively. As a proof of concept, parylene-C LIG was used as the electrode material for the fabrication of ultrathin, solid-state microsupercapacitors (MSCs) via a one-step, scalable, and cost-effective approach, aiming at future flexible and wearable applications. The produced LIG-MSC on parylene-C exhibited good electrochemical behavior, with a specific capacitance of 1.66 mF/cm2 and an excellent cycling stability of 96% after 10 000 cycles (0.5 mA/cm2). This work allows one to further extend the knowledge in LIG processes, widening the group of precursor materials as well as promoting future applications. Furthermore, it reinforces the potential of parylene-C as a key material for next-generation biocompatible and flexible electronic devices.

Three-Dimensional Carbon Foam Based Asymmetric Assembly of Metal Oxides Electrodes for High-Performance Solid-State Micro-Supercapacitor

Micro-supercapacitors hold great attention as one of the promising energy storage devices satisfying the increasing quest for miniaturized and portable devices. Despite having impressive power density, superior cyclic lifetime, and high charge-discharge rates, micro-supercapacitors still suffer from low energy density, limits their practical application. The energy density (E=1/2CV2) can be increased either by increasing specific capacitance (C) or voltage range (V). Asymmetric micro-supercapacitors have attracted great attention by using two different electrode materials to expand the voltage window and thus increase the energy density. Currently, versatile fabrication technologies such as inkjet printing, lithography, laser scribing, etc., are used to directly or indirectly pattern the electrode material; these techniques still suffer from scalable production and cost inefficiency. Here, we demonstrate the scalable production of a three-dimensional (3D) carbon foam (CF) based asymmetric micro-supercapacitor by spray printing technique on an array of interdigital electrodes. The solid-state asymmetric micro-supercapacitor comprised of CF-MnO positive electrode and CF-Fe2O3 negative electrode achieves a high areal capacitance of 18.4 mF/cm2 (2326.8 mF/cm3) at 5 mV/s and a wider potential window of 1.4 V. Consequently, a superior energy density of 5 µWh/cm2 is obtained, and high cyclic stability is confirmed with retention of the initial capacitance by 86.1% after 10000 electrochemical cycles. The optimized decoration of pseudocapacitive metal oxides in the 3D carbon network helps in high electrochemical utilization of materials where the 3D interconnected network of carbon provides overall electrical conductivity and structural integrity. The research provides a simple and scalable spray printing method to fabricate an asymmetric micro-supercapacitor using a custom-made mask that can be integrated on a large scale.

Nanometric Amorphous TiO2 As an Extrinsic Pseudo-Capacitive Electrode for All-Solid-State Asymmetric Hybrid Micro-Supercapacitors: Effects on the Electrochemical Performance

On-chip solid-state micro-supercapacitors (MSCs) have gained widespread attention owing to their versatile benefits, including high power density and long cycle life1,2. Recently asymmetric hybrid microsupercapacitors (AsHMSCs) introducing a charge storage mechanism based on both faradaic reaction and electric double-layer phenomena have been considered to increase the energy density. Within this context, the selection of electrode materials and their interaction at the interface with the electrolyte is a key issue to optimize the AsHMSC electrochemical performance.In this work, nanometric (5-20 nm thick) amorphous TiO2 films have been elaborated and characterized in liquid and solid-state electrolyte (LiPON) half-cell configurations. Interestingly, TiO2 films after LiPON deposition exhibited a constant initial amount of intercalated lithium ions for all considered thicknesses and did not require a first activation process, in comparison to the liquid electrolyte configuration. For all considered configurations, the specific capacity extracted from cyclic voltammetry and galvanostatic cycling within [0.5-3V] potential range correspond to the theoretical value expected for the Lix=1TiO2 phase at low current density. Furthermore, the cooperative effects of high Li ion intercalation kinetics and Low interfacial charge transfer resistance for 5nm TiO2 electrode (extracted from electrochemical impedance spectroscopy analysis) exhibit an outstanding specific capacity of 2mC.cm-2 at 1µA.cm-2, and high rate performance with 60% capacity holding ratio at 100µA.cm-2, thus highlighting the extrinsic pseudo-capacitive behavior of the sub 10nm electrodes.A TiO2 5nm/LiPON 100nm/Pt AsHMSC is successfully fabricated, which achieves an operating voltage window of 3V and a specific capacity of 0.3mC.cm-2 at 1mA.cm-2.In addition, the device also exhibited a 100% coulombic efficiency even after cycling for 6000 continuous charge-discharge cycles. This work offers an approach to tune the Li ion storage properties of TiO2 by nano-engineering and gives insights into the enhancement of pseudocapacitance-assisted lithium-storage capacity.References Kyeremateng et al., Nature Nanotech 12, 7–15 (2017). https://doi.org/10.1038/nnano.2016.196Sallaz et al., J. Power Sources 451, 227786 (2020), doi: 10.1016/j.jpowsour.2020.227786. Figure 1

High-Performance Solid-State Micro-Supercapacitor of Sharp-Edged Electrode Geometry from Metal-Oxide Nanoparticles Loaded Carbon Foam

The demand for miniaturization of energy storage systems has accelerated development of on-chip micro-power devices, for integration into portable electronic devices. Micro-supercapacitors can suitably cater to this need by functioning as efficient miniaturized energy storage devices with high power density, fast charge-discharge rates, and long cyclic lifetime. The parameters that affect performance metrics of micro-supercapacitors are electrode materials, electrolytes, device architecture, and microfabrication techniques. By effective utilisation and tuning of these critical parameters, we report a novel sharp-edged electrode geometry for the in-plane micro-supercapacitors by spray coating of porous carbon foam loaded with iron-oxide nanoparticles (Fe2O3). The high specific surface area of carbon foam facilitated extensive mass loading of metal oxide nanoparticles to exhibit both pseudocapacitance and electric double-layer capacitance. Also, it is imperative to rationally design electrodes with sharp edges as it would lead to an increase of charge density at the corners due to curved surfaces. Utilising this concept of edging effect, we have designed a sharp-edged electrode geometry that exhibited a 68% enhancement of the electric field at the electrodes' corner edges compared to conventional interdigitated electrodes as obtained by COMSOL multiphysics simulation. This increase in the electric field contributed to a high areal capacitance of 12.4 mF/cm2 at 5 mV/s with an enhancement of 235% as compared to conventional interdigitated electrodes. Also, excellent cyclic stability (~ 99.5%) over 10000 charge-discharge cycles was achieved. More notably, the sharp-edged micro-supercapacitor show an excellent areal energy density of 1.73 µWh/cm2 and areal power density of 1425 µW/cm2. Thus, this high-performance in-plane architecture of sharp-edged electrodes possesses enormous potential for numerous energy storage applications.

Photopatternable hydroxide ion electrolyte for solid-state micro-supercapacitors

<h2>Summary</h2> Electrochemical energy storage (EES) devices that provide high power and energy for micropower systems are considered to be essential for developing micro/nano electronics such as nanorobotics, environmental sensors, and connected smart electronics. One promising research direction in this field has been to develop on-chip EES devices whose length scales integrate with those of miniaturized electronic devices. In the work described here, we provide the first report of a hydroxide-ion-conducting solid electrolyte that can be patterned using standard lithography. By combining a negative photoresist with a polymerizable ionic liquid, we obtain a thermally and dimensionally stable, hydroxide-ion-conducting solid electrolyte with a conductivity of 10 mS cm⁻¹. Patterning the solid electrolyte directly on interdigitated vanadium nitride (VN) electrodes enables a scalable fabrication approach for producing high-resolution, solid-state VN micro-supercapacitors (MSC) in both single and multiple devices.

Three-dimensional carbon foam-metal oxide-based asymmetric electrodes for high-performance solid-state micro-supercapacitors.

A three-dimensional carbon foam (CF)-based asymmetric planar micro-supercapacitor is fabricated by the direct spray patterning of active materials on an array of interdigital electrodes. The solid-state asymmetric micro-supercapacitor comprises the CF network with pseudocapacitive metal oxides (manganese oxide (MnO), iron oxide (Fe2O3)), where CF-MnO composite as a positive electrode, and CF-Fe2O3 as negative electrode for superior electrochemical performance. The micro-supercapacitor, CF-MnO//CF-Fe2O3, attains an ultrahigh supercapacitance of 18.4 mF cm-2 (2326.8 mF cm-3) at a scan rate of 5 mV s-1. A wider potential window of 1.4 V is achieved with a high energy density of 5 μW h cm-2. The excellent cyclic stability is confirmed by 86.1% capacitance retention after 10 000 electrochemical cycles.

Ultra-thick 3D graphene frameworks with hierarchical pores for high-performance flexible micro-supercapacitors

Constructing 3D graphene frameworks with ultra-thickness and rich ion transport paths is of great significance for the practical application of graphene supercapacitors. Herein, 3D porous graphene frameworks, with thickness up to 320 μm, are directly grown by laser induction on the synthesized polyimide by optimizing the thermal sensitivity of polyimide to increase laser penetration depth. Simultaneously, hierarchical pores are obtained due to fast liberation of gaseous products during laser radiation, which facilitates fast ion transport. Coupled with its conductive interconnection network, the as-prepared 3D graphene delivers a high specific capacitance of 132.2 mF cm−2 at 0.5 mA cm−2, which is nearly one order of magnitude larger than that of most reported laser induced graphene electrodes. Pseudocapacitive polypyrrole is further introduced into the graphene frameworks to prepare composite electrodes, which show specific capacitances as high as 2412.2 mF cm−2 at 0.5 mA cm−2. Accordingly, flexible solid-state micro-supercapacitors are constructed, with a high energy density of 134.4 μW h cm−2 at a power density of 325 μW cm−2. Furthermore, 95.6% of initial capacitance is retained after 10,000 cycles, indicating superior cycling stability. These results suggest that the ultra-thick hierarchical porous graphene frameworks have promising prospects for high-performance flexible micro-supercapacitors.

Controllable layer-by-layer assembly of metal-organic frameworks/polyaniline membranes for flexible solid-state microsupercapacitors

We report a new type of flexible solid-state microsupercapacitors (MSCs) with high power density, excellent cycle life, and good mechanical flexibility. The MSCs are fabricated through the layer-by-layer (LBL) electrodeposition of porous polyaniline (PANI) and the metal-organic frameworks (MOFs) crystals on laser-induced graphene (LIG) substrate. Owing to the synergic effect of MOFs with highly porous structure and the PANI chains with the excellent conductivity, the resulting MSCs exhibit layer-dependent capacitance performance with the largest areal specific capacitance of 719.2 mF cm−2 at a current density of 0.5 mA cm−2, which is almost 370 times higher than that of MSCs prepared by the bare LIG. Meanwhile, the prepared MSCs retain more than 87.6% of their capacitances after 6000 cycles of charge-discharging test, demonstrating their promising cycling stability. Furthermore, the application of MSCs for the lighting of the light-emitting diode (LED) and their stable mechanical flexibility reveals their remarkable capability as the power supply for the small and wearable devices.

Liquid and solid states on-chip micro-supercapacitors using silicon nanowire-graphene nanowall-pani electrode based on microfabrication technology

Liquid and solid states on-chip micro-supercapacitors based on polyaniline (PANI) coated on graphene nanowalls which grown on silicon nanowires were reported in this work. Novel micro-fabrication technologies were investigated to create three dimension (3D) hierarchical electrodes. High aspect ratio silicon nanowires were produced by metal-assisted chemical etching (MACE). 3D hierarchical graphene nanowalls were grown on silicon nanowire surface by a microwave plasma-enhanced chemical vapor deposition (PECVD). Graphene nanowalls were subsequently coated by conductive PANI. Both of liquid and solid state micro-supercapacitors were successfully fabricated with symmetric face to face high density nanowire arrays separated by liquid and gel electrolytes, respectively. The areal energy and power density of the liquid-state on-chip micro-supercapacitor are 11.7 μWh/cm2 and 0.42 mW/cm2, respectively, while those of the solid-state on-chip micro-supercapacitor are 10.8 μWh/cm2 and 0.78 mW/cm2.

All Two-Dimensional Pseudocapacitive Sheet Materials for Flexible Asymmetric Solid-State Planar Microsupercapacitors with High Energy Density.

With the rapid development of portable devices and wireless protocols, miniaturized energy storage units have become an important prerequisite. Although in-plane microsupercapacitors are emerging as competitive candidate devices, their practical applications have been severely hindered by their low energy density. Here, employing pseudocapacitive active materials working in complementary voltage windows, namely, manganese oxide (MnO2) and titanium carbide (Ti3C2), both in the two-dimensional sheet morphology, a flexible asymmetric interdigitated solid-state microsupercapacitor was assembled. Profiting from the perfect voltage complementarity of the two types of sheets, the high exposure of electrochemically active sites and the maximized utilization of the sheets due to the planar ion transport, the designed device achieved excellent electrochemical performance even when using a gel electrolyte. In particular, the device obtained a high specific capacitance of 106 F g-1 (295 mF cm-2), a wide potential window (2 V), an ultrahigh rate performance (retaining 83% even with a 20-fold in current density to 20 A g-1), an excellent cycling stability (87% retention after 104 cycles at 10 A g-1), and a competitive energy density of 58 W h kg-1 (162 μW h cm-2) that are even comparable to those of some microbatteries, while maintaining a high power density of 985 W kg-1 (2.7 mW cm-2). Importantly, this outstanding electrochemical performance was also stably maintained under various bending conditions. These results indicate that two-dimensional pseudocapacitive sheet materials have a plethora of possibilities for constructing flexible and wearable devices.