Areal Power Density Research Articles

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.

Flexible thermoelectric generator with high Seebeck coefficients made from polymer composites and heat-sink fabrics

Light and flexible thermoelectric generators working around room temperature and within a small temperature range are much desirable for numerous applications of wearable microelectronics, internet of things, and waste heat recovery. Herein, we report a high performance flexible thermoelectric generator made of polymeric thermoelectric composites and heat sink fabrics. The thermoelectric composites comprise n- and p-type Bi2Te3 particles and poly(3,4-ethylenedioxythiophene) polystyrene sulfonate, exhibiting a synergic effect that results in Seebeck coefficients higher than those of the constituent alloys and conductive polymer. The flexible and light thermoelectric generator produces an output power of 9.0 mW, a specific output power of 2.3 mW/g, and an areal power density of 6.5 W/m2 at ΔT = 45 K. By using the heat sink fabrics to maintain a large and uniform distribution of temperature difference across the generator, a three-fold increment of the output power is obtained.

Single‐Molecule Confinement Induced Intrinsic Multi‐Electron Redox‐Activity to Enhance Supercapacitor Performance

Aggregation of polyoxometalates (POM) is largely responsible for the reduced performance of POM‐based energy‐storage systems. To address this challenge, here, the precise confinement of single Keggin‐type POM molecule in a porous carbon (PC) of unimodal super‐micropore (micro‐PC) is realized. Such precise single‐molecule confinement enables sufficient activity center exposure and maximum electron‐transfer from micro‐PC to POM, which well stabilizes the electron‐accepting molecules and thoroughly activates its inherent multi‐electron redox‐activity. In particular, the redox‐activities and electron‐accepting properties of the confined POM molecule are revealed to be super‐micropore pore size‐dependent by experiment and spectroscopy as well as theoretical calculation. Meanwhile, the molecularly dispersed POM molecules confined steadily in the “cage” of micro‐PC exhibit unprecedented large‐negative‐potential stability and multiple‐peak redox‐activity at an ultra‐low loading of ~11.4 wt%. As a result, the fabricated solid‐state supercapacitor achieves a remarkable areal capacitance, ultrahigh energy and power density of 443 mF cm−2, 0.12 mWh cm−2 and 21.1 mW cm−2, respectively. This work establishes a novel strategy for the precise confinement of single POM molecule, providing a versatile approach to inducing the intrinsic activity of POMs for advanced energy‐storage systems.

Microsupercapacitive Stone Module for Natural Energy Storage

Increasing accessibility of energy storage platforms through user interface is significant in realizing autonomous power supply systems because they can be expanded in multidimensional directions to enable pervasive and customized energy storage systems (ESSs) for portable and miniaturized electronics. Herein, we implemented a high-performance asymmetric microsupercapacitor (MSC) on a natural stone surface, which represents a class of omnipresent, low-cost, ecofriendly, and recyclable energy storage interface for sustainable and conveniently accessible ESSs. Highly conductive and porous Cu electrodes were robustly fabricated on a rough marble substrate via explosive reduction-sintering of cost-effective CuO nanoparticles by using instantaneous, inexpensive, and simple laser-material interaction (LMI) technology. Faradaic Fe3O4 and capacitive Mn3O4 were sequentially electroplated on the surface of the porous Cu interdigitated electrodes to demonstrate hybrid MSC with a high-potential window and specific area. Despite the irregular geometry of the stone interface, the laser-induced MSC module produced high areal energy density and power density (6.55 μWh cm-2 and 1.2 mW cm-2, respectively) without the use of complex integrated circuit fabrication methods, such as photolithography, vacuum deposition, or chemical etching. The fabricated MSC stone cells were successfully scaled up via serial or parallel connections to achieve the concept of a scalable energy storage wall applicable as a three-dimensional energy station inside or outside a whole-building interface. The excellent durability of the MSC wall was confirmed by harsh-impact tests, and it was attributed to the robustness of the LMI-derived Cu current collectors and electroplated MSC metal oxides. Furthermore, a natural stone substrate with high mechanical toughness could be recycled by grinding the MSC conductors and active layers, thus considerably reducing the environmental pollutants and helping to realize green electronics.

Composite Assembling of Oxide-Based Optically Transparent Electrodes for High-Performance Asymmetric Supercapacitors.

Simultaneously achieving a transparent and high-energy density supercapacitor is a major challenge because of the trade-off between energy storage capacity and optical transparency of active electrode materials. Herein, we demonstrate a novel approach to construct an optically transparent asymmetric supercapacitor (Trans-ASC) by assembling positive (ZnO-SnO2) and negative (TiO2-SnO2) composite thin-film electrodes on a conductive indium-doped tin oxide substrate via reactive DC magnetron cosputtering. The optical transmittance for both composite thin films is found to be 68% (ZnO-SnO2) and 64% (TiO2-SnO2). Furthermore, electrochemical kinematics of the primed transparent electrodes are scrutinized in 0.5 M KOH electrolyte without affecting the transparency of active electrodes. The structural reliability of the electrodes aids the superb electrochemical performance to construct a Trans-ASC, TiO2-SnO2//ZnO-SnO2, which works at a voltage of +1.2 V and attains a higher areal capacitance of 44.6 mF cm-2 at 2 mA cm-2. The assembled Trans-ASC delivers a maximum areal energy density of 8.75 μW h cm-2 with an optimal areal power density of 570 μW cm-2. Additionally, the capacitance retention of 81.6% and transparency of both electrodes remain almost the same (up to 60% for ZnO-SnO2 and 62% for TiO2-SnO2) even after 10,000 charging-discharging cycles. These remarkable electrochemical properties and outstanding cycling stability of the designed Trans-ASC device make it a potential candidate for storing energy and for further use in transparent electronic devices.

Fabrication of Binder‐Free TiO2 Nanofibers@Carbon Cloth for Flexible and Ultra‐Stable Supercapacitor for Wearable Electronics

AbstractFor the realization of the miniaturized devices for flexible/wearable electronics systems in the current electronics industry; flexible, safe, and compatible energy storage devices are of great research interest. Herein, carbon cloth (CC) textile is coated by TiO2 nanofibers (NFs) through a safe and facile electrophoretic deposition (EPD) technique for flexible/wearable supercapacitor (SC) application. The modified microstructure of the flexible and binder‐free electrode fabricated via EPD shows a high areal capacitance of 1651 mF cm−2 at 1 mA cm−2 current density. Moreover, the electrode shows the high cyclability with 100% capacitance retention after 15 000 cycles at 10 mA cm−2 current density, presents the ultra‐high stability for the fabricated electrode. Further, a fully flexible symmetric SC device is fabricated utilizing the fabricated electrodes assembled with the gel electrolyte. The device delivers an areal capacitance of 468 mF cm−2 at 1 mA cm−2 current density with 97% capacitance retention after 30 000 successive cycles and 98% retention after 2000 bending cycles at 5 mA cm−2. Moreover, the SC device delivers the maximum areal energy density and areal power density of 0.14 mWh cm−2 and 3.6 mW cm−2, respectively.

Upscalable ultra thick rayon carbon felt based hybrid organic‐inorganic electrodes for high energy density supercapacitors

AbstractLow weight, small footprint, and high performances are essential requisites for the implementation of energy storage devices within consumer electronics. One way to achieve these goals is to increase the thickness of the active material layer. In this work, carbonized and graphitized rayon felt, a cellulose‐derived material, is used as a three‐dimensional current collector scaffold to enable the incorporation of large amount of active energy storage materials and ionic liquid‐based gel electrolyte in the supercapacitor devices. PEDOT:PSS, alone or in combination with active carbon, has been used as the active material. Three‐dimensional supercapacitors with high per unit area capacitance (more than 1.1 F/cm2) have been achieved owing to the loading of large amount of active material in the felt matrix. Areal energy density of more than 101 μWh/cm2 and areal power density of more than 5.9 mW/cm2 have been achieved for 0.8 V operating voltage at a current density of 1 mA/cm2. A nanographite material was found to be beneficial in reducing the internal serial resistance of the supercapacitor to lower than 1.7 Ω. Furthermore, it was shown that even after 2000 times cycling test, the devices could still retain its performance with at least 88% coulombic efficiency for all the devices. All the materials are readily available commercially, environmentally sustainable and the process can potentially be upscaled with industrial process.

Data-driven and validated dimensional analysis for rational scale-up of a dual-chamber microbial fuel cell system for water-energy nexus exploitation

Mathematical modelling of microbial fuel cells (MFC) facilitates their scale-up by maintaining dimensionless parameters across reactor volumes for consistent performance. This study developed data-driven correlations to predict areal power density for a batch-fed dual-chamber MFC using hybridised first-principle mechanistic model and Buckingham’s Pi theorem. The established correlations were validated using experimentally-derived data for pre-enriched electroactive biofilm from mixed cultures. The biochemical model parameters are infilled with stoichiometric and thermodynamics estimations. Results showed that the correlations using logistic kinetics (Nash-Sutcliffe Efficiency, NSE = 0.59) outperformed Monod kinetics (NSE = 0.52) as the latter was not suitable for representing the first-order biochemical kinetics under limited substrate conditions. Sensitivity analysis on varying pH and bicarbonate concentration improved model predictions by ± 50%, though relative absolute error was ± 20% due to inherent error of estimated biochemical parameters. The application of hybridised approach for modelling MFC provides renewed perspectives for their rational design and scale-up applications.

Macro‐ and Nano‐Porous 3D‐Hierarchical Carbon Lattices for Extraordinarily High Capacitance Supercapacitors

AbstractSupercapacitors, which can be charged/discharged rapidly, play important roles in a sustainable society. Thick electrodes can reduce the ratio of inactive components in the overall cell while simultaneously improving energy and power densities. However, thick electrodes induce longer ion diffusion pathways, and capacitance drops dramatically after a certain thickness. To overcome this, precisely designed macro‐ and nano‐porous 3D‐hierarchical carbon lattices, where ions can diffuse freely inside the electrode, are prepared by combining an inexpensive stereolithography‐type 3D printer, whose resolution is 50 µm, with a simple CO2 activation process. The activated 3D carbon lattice with a 66% burn‐off ratio (3D‐CL‐A66%) has ordered macropores (≈150 µm) and uniform nanopores (2–3 nm), exhibiting a maximum areal capacitance of 5251 mF cm–2 at 3 mA cm–2. Furthermore, manganese oxide is electrochemically deposited on 3D‐CL‐A16% for 8 min (3D‐CL‐A16%‐MnO2‐8 min), increasing the areal capacitance by 2.5‐times. Finally, an all‐3D‐printed asymmetric 1.8 V supercapacitor is prepared by combining 3D‐CL‐A16%‐MnO2‐8 min and 3D‐CL‐A66% as the positive and negative electrodes, respectively, demonstrating a maximum energy density of 0.808 mWh cm–2 at a power density of 2.48 mW cm–2. The achieved values are one of the highest areal energy and power densities reported so far.

Strategic Modulation of Target-Specific Isolated Fe,Co Single-Atom Active Sites for Oxygen Electrocatalysis Impacting High Power Zn-Air Battery.

An effective modulation of the active sites in a bifunctional electrocatalyst is essentially desired, and it is a challenge to outperform the state-of-the-art catalysts toward oxygen electrocatalysis. Herein, we report the development of a bifunctional electrocatalyst having target-specific Fe-N4/C and Co-N4/C isolated active sites, exhibiting a symbiotic effect on overall oxygen electrocatalysis performances. The dualism of N-dopants and binary metals lower the d-band centers of both Fe and Co in the Fe,Co,N-C catalyst, improving the overpotential of the overall electrocatalytic processes (ΔEORR-OER = 0.74 ± 0.02 V vs RHE). Finally, the Fe,Co,N-C showed a high areal power density of 198.4 mW cm-2 and 158 mW cm-2 in the respective liquid and solid-state Zn-air batteries (ZABs), demonstrating suitable candidature of the active material as air cathode material in ZABs.

Integrated piezo-tribo hybrid acoustic-driven nanogenerator based on porous MWCNTs/PVDF-TrFE aerogel bulk with embedded PDMS tympanum structure for broadband sound energy harvesting

In this work, a novel type of acoustic-driven nanogenerator (ANG) that integrates piezoelectric and triboelectric effects is reported for broadband sound energy harvesting. With an internal structure combining beam-like porous multi-walled carbon nanotubes/polyvinylidene fluoride-trifluoroethylene (MWCNTs/PVDF-TrFE) aerogel and polydimethylsiloxane (PDMS) tympanum, the integrated MWCNTs/PVDF-TrFE/PDMS (MCPP) ANG achieves efficient collection of acoustic energy through the enhanced vibration and friction generated internally. Besides, by eliminating the need for a contact separation structure or an external resonator cavity, this design greatly simplifies the structure and contributes to the flexibility and durability of the device. The MCPP ANG, with 20 wt% sodium carboxymethyl cellulose (SCMC), 2 wt% MWCNTs and 5% w/v PDMS, reaches an optimal output of 34.4 V and 1.74 μA under 150 Hz and 115 dB sound stimulation, corresponding to an areal power density of 11.62 mW/m2. It possesses a broad working bandwidth from 110 Hz to 400 Hz, and can directly illuminate 7 light-emitting diodes (LEDs) in series. Employing a novel, simple and effective structural design, the ANG proposed here achieves flexible and stable acoustic collection, offering a promising path toward sound spectrum analysis, noise detection and power supply for various low-power sensors.

Nanocoating of microbial fuel cell electrodes for enhancing bioelectricity generation from wastewater

Microbial fuel cells (MFCs) are devices where bacteria generate electrical energy by oxidizing organic matter in wastewater. The implementation of MFCs on a commercial scale is limited due to electrode resistances, which are one of the key factors limiting electricity generation. This study presents a method to maximize the electrical power production from MFCs by coating the electrodes using nanomaterials which leads to prototyping novel electrodes having higher electrical conductivity than common electrodes. The voltage reached 1.234 V directly after operating the MFCs, with nanocoated electrodes, and showed voltage stability till the end of the 140 h interval with a peak value of 1.367 V with a maximum areal power density of 116 mW m−2 and a maximum volumetric power density of 15.6 mW m−3. However, the voltage of the control (without coating) was steadily increased to 0.616 V after 22 h with a maximum areal power density of 23.6 mW m−2 and a maximum volumetric power density of 3.2 mW m−3 then showed voltage stability till the end of the 140 h interval. It was found that the coulombic efficiency of the MFCs where its electrodes are coated with graphitic carbon nitride nanosheets was higher than graphene, carbon nanotubes, and the control in a descending order, respectively. By this method, it is possible to improve the electrical conductivity of the MFCs which results in increasing the generated electrical power by 4.9 times the conventional method.

Sludge Derived Carbon Modified Anode in Microbial Fuel Cell for Performance Improvement and Microbial Community Dynamics.

The conversion of activated sludge into high value-added materials, such as sludge carbon (SC), has attracted increasing attention because of its potential for various applications. In this study, the effect of SC carbonized at temperatures of 600, 800, 1000, and 1200 °C on the anode performance of microbial fuel cells and its mechanism are discussed. A pyrolysis temperature of 1000 °C for the loaded electrode (SC1000/CC) generated a maximum areal power density of 2.165 ± 0.021 W·m−2 and a current density of 5.985 ± 0.015 A·m−2, which is 3.017- and 2.992-fold that of the CC anode. The addition of SC improves microbial activity, optimizes microbial community structure, promotes the expression of c-type cytochromes, and is conducive to the formation of electroactive biofilms. This study not only describes a technique for the preparation of high-performance and low-cost anodes, but also sheds some light on the rational utilization of waste resources such as aerobic activated sludge.

Oxynitride-Encapsulated Silver Nanowire Transparent Electrode with Enhanced Thermal, Electrical, and Chemical Stability.

Silver nanowire (AgNW) networks have been explored as a promising technology for transparent electrodes due to their solution-processability, low-cost implementation, and excellent trade-off between sheet resistance and transparency. However, their large-scale implementation in applications such as solar cells, transparent heaters, and display applications has been hindered by their poor thermal, electrical, and chemical stability. In this work, we present reactive sputtering as a method for fast deposition of metal oxynitrides as an encapsulant layer on AgNWs. Because O2 cannot be used as a reactive gas in the presence of oxidation-sensitive materials such as Ag, N2 is used under moderate sputtering base pressures to leverage residual H2O on the sample and chamber to deposit Al, Ti, and Zr oxynitrides (AlOxNy, TiOxNy, and ZrOxNy) on Ag nanowires on glass and polymer substrates. All encapsulants improve AgNW networks' electrical, thermal, and chemical stability. In particular, AlOxNy-encapsulated networks present exceptional chemical stability (negligible increase in resistance over 7 days at 80% relative humidity and 80 °C) and transparency (96% for 20 nm films on AgNWs), while TiOxNy demonstrates exceptional thermal and electrical stability (stability up to over temperatures 100 °C more than that of bare AgNW networks, with a maximum areal power density of 1.72 W/cm2, and no resistance divergence at up to 20 V), and ZrOxNy presents intermediate properties in all metrics. In summary, a novel method of oxynitride deposition, leveraging moderate base pressure reactive sputtering, is demonstrated for AgNW encapsulant deposition, which is compatible with roll-to-roll processes that are operated at commercial scales, and this technique can be extended to arbitrary, vacuum-compatible substrates and device architectures.

Novel 3D grid porous Li4Ti5O12 thick electrodes fabricated by 3D printing for high performance lithium-ion batteries

Three-dimensional (3D) grid porous electrodes introduce vertically aligned pores as a convenient path for the transport of lithium-ions (Li-ions), thereby reducing the total transport distance of Li-ions and improving the reaction kinetics. Although there have been other studies focusing on 3D electrodes fabricated by 3D printing, there still exists a gap between electrode design and their electrochemical performance. In this study, we try to bridge this gap through a comprehensive investigation on the effects of various electrode parameters including the electrode porosity, active material particle diameter, electrode electronic conductivity, electrode thickness, line width, and pore size on the electrochemical performance. Both numerical simulations and experimental investigations are conducted to systematically examine these effects. 3D grid porous Li4Ti5O12 (LTO) thick electrodes are fabricated by low temperature direct writing technology and the electrodes with the thickness of 1085 µm and areal mass loading of 39.44 mg·cm−2 are obtained. The electrodes display impressive electrochemical performance with the areal capacity of 5.88 mAh·cm−2@1.0 C, areal energy density of 28.95 J·cm−2@1.0 C, and areal power density of 8.04 mW·cm−2@1.0 C. This study can provide design guidelines for obtaining 3D grid porous electrodes with superior electrochemical performance.

Heteroatom-doped porous carbon nanoparticle-decorated carbon cloth (HPCN/CC) as efficient anode electrode for microbial fuel cells (MFCs)

Developing high-performance anode materials is critical for improving microbial fuel cells (MFCs) performance. Carbon nanoparticles derived from plant polyphenols (tannic acid) have attracted our attention due to excellent biocompatibility, great conductivity, easy functionalization, and low cost. In this work, we prepared heteroatom-doped (N, P, S, Co) porous carbon nanoparticles (HPCNs). The HPCNs decorated carbon cloth-based MFCs exhibited areal power density of 1.72 W m−2 and the areal current density of 4.52 A m−2, which was 1.82 times and 1.44 times higher than the carbon cloth (CC) anode. Moreover, the extracellular electron transfer (EET) and cell viability of the electroactive biofilms were substantially enhanced by the proposed anode. Microbial community structure analysis demonstrated that more electrochemically active microorganism types were enriched on the studied anode, and their synergistic effect promoted the EET process. Nanoscale and porous structure of HPCNs can promote biofilm formation. The doping of heteroatoms makes the materials have high conductivity, good biocompatibility and abundant electrochemically active sites, which promote the EET process. This work provides a method for the preparation of anode materials with adjustable structure and excellent properties, and provides a strategy for application of high performance anode in MFCs.

High Mass Loading Asymmetric Micro-supercapacitors with Ultrahigh Areal Energy and Power Density.

High mass loading asymmetric micro-supercapacitors (MSCs) are key components for the development of high-performance energy and power supply systems. Here, a concept for achieving high mass loading electrodes is presented and applied to high mass loading micro-supercapacitors with ultrahigh areal energy and power density. The positive electrode is made from porous carbon with birnessite coverage and multiwalled carbon nanotubes (CNTs) as conducting additives (PIC-CNTs-MnO2). The negative electrode is prepared from hierarchically porous active carbon mixed with CNTs (PICK-CNTs). Both positive and negative electrode materials are tailored to ensure a high content of macro- and mesopores. MSCs with an optimized mass loading of 13.9 mg·cm-2 (maximum: 23.6 mg·cm-2) provide an ultrahigh areal capacitance of 1.13 F·cm-2 (volumetric capacitance: 22.6 F·cm-3), an outstanding energy of 627.8 μWh·cm-2, and a maximum power density of 64 mW·cm-2. About 85% of the initial capacitance remained after 5000 cycles. Moreover, shunt and tandem device testing confirmed a high uniformity of these MSCs, meeting the requirements of adjustable output currents and voltages in microchips.

SWCNT/ZnO nanocomposite decorated with carbon dots for photoresponsive supercapacitor applications

In this work, we report the fabrication of an optically responsive hybrid supercapacitor. The hybrid electrode material for the supercapacitor was synthesized by attaching carbon dots (CDs) on the SWCNT/ZnO nanocomposites. The optical properties of CDs and ZnO have been explored by operating the supercapacitor under illuminated conditions (UV light). It was observed that the areal capacitance of the fabricated supercapacitor got enhanced by ∼ 41.38% at 50 mV/s scan rate under UV light. The photo-charging and galvanostatic discharging of the device were also examined. The maximum photo-charged areal capacitance value was calculated to be 1.53 mF/cm2 at a current density of 1.25 μA/cm2, whereas the values of areal energy density and areal power density at this current density value were 19.85×10-3 μWh/cm2, and 0.0953 μW/cm2, respectively. The working mechanism of the supercapacitive system has also been explored. It is observed that the overall capacitance of the hybrid electrode is a combination of both electric double layer capacitance (EDLC) and pseudocapacitance. The EDLC and pseudocapacitance contributions were confirmed by using the Dunn method, and the values of the individual capacitance contributions are 69.35 and 30.65% for EDLC and pseudocapacitance, respectively. Further, it was observed that the pseudocapacitance phenomenon was dominated by the diffusion of the ions in the electrode material. The diffusivity of the electrolytic ions was calculated to be 0.13 and 0.14 mm2/s for the oxidation peaks, whereas 1 and 0.07 mm2/s for the reduction peaks, respectively. Moreover, the reaction mechanism of the system has also been explored, and the occurrence of intercalation of K+ ions in the defects of ZnO has been confirmed with justified explanations.

Water-Evaporation-Induced Electric Generator Built from Carbonized Electrospun Polyacrylonitrile Nanofiber Mats.

Electricity has been generated from evaporation-driven water flow in films of carbon soot particles and other porous media. This paper reports the placement of carbon nanofiber mats (CNMs) on fiberglass screens for the construction of efficient water-evaporation-induced generators (WEIGs). These CNMs are prepared from carbonizing electrospun polyacrylonitrile nanofiber mats and then treating them with oxygen plasma. After electrode attachment to the two ends of a CNM, one electrode is immersed into water. Water rises in the mat due to capillary action and evaporates from the mat surface due to thermal energy provided by the environment. The steady rise of water pushes the dissociated ions of the surface functionalities upward, resulting in a streaming current and an electric potential. This paper investigates how the generated short-circuit current, Is, and open-circuit voltage, Vo, of the WEIG change with structural parameters of the CNMs. Under optimized conditions, these CNMs produce electricity at an areal power density of 83 nW/cm2, which is almost 10 times those offered by some existing ones. Thus, the easy-to-handle CNMs are an attractive porous scaffold for WEIGs.

Pristine Graphene Inks for 3D Printed Supercapacitors with High Capacitance

The 3D printing of 2D materials, such as graphene, transition metal dichalcogenides and M-Xenes, offers a cost-efficient and sustainable route for the fabrication of integrated electronics and advanced energy devices with arbitrarily complex architectures. In particular, the assembly of 2D materials into rationally designed three-dimensional electrodes can enhance the charge transport kinetic and increase the electrochemically-active surface area, resulting in superior electrochemical performance.Graphene has long been considered a promising active material for carbon-based supercapacitors, owing to its high intrinsic capacitance, superior mechanical strength and flexibility, and excellent electrical conductivity. However, because of the limited processability of pristine graphene in water, the 3D printing of graphene supercapacitors has either relied on inks containing high boiling solvents and electrochemically inactive binders, or on aqueous dispersions of graphene oxide, which must be thermally reduced at elevated temperatures (>1000°C) after printing.In this work we demonstrate a new class of 3D printed supercapacitors obtained from aqueous inks of pristine graphene, without the need of functional additives or high-temperature processing to achieve high capacitance. With an electrical conductivity of ~1370 S m-1 and rationally designed architectures, the symmetric supercapacitors can achieve an exceptional areal capacitance of 1.57 F cm-2 at 2 mA cm-2 which is retained over 72% after repeated voltage holding test. The areal power density (0.968 mW cm-2) and areal energy density (51.2 μWh cm-2) outperform many carbon-based supercapacitors previously reported, indicating the feasibility of this approach for the fabrication of efficient energy storage devices.