Micro-supercapacitors Research Articles

Laser-machined micro-supercapacitors: from microstructure engineering to smart integrated systems.

With the rapid development of portable and wearable electronic devices, there is an increasing demand for miniaturized and lightweight energy storage devices. Micro-supercapacitors (MSCs), as a kind of energy storage device with high power density, a fast charge/discharge rate, and a long service life, have attracted wide attention in the field of energy storage in recent years. The performance of MSCs is mainly related to the electrodes, so there is a need to explore more efficient methods to prepare electrodes for MSCs. The process is cumbersome and time-consuming using traditional fabrication methods, and the development of laser micro-nano technology provides an efficient, high-precision, low-cost, and convenient method for fabricating supercapacitor electrodes, which can achieve finer mask-less nanofabrication. This work reviews the basics of laser fabrication of MSCs, including the laser system, the structure of MSCs, and the performance evaluation of MSCs. The application of laser micro-nanofabrication technology to MSCs and the integration of MSCs are analyzed. Finally, the challenges and prospects for the development of laser micro-nano technology for manufacturing supercapacitors are summarized.

Direct ink writing 3D printing of low-dimensional nanomaterials for micro-supercapacitors.

Micro-supercapacitors (MSCs) have attracted significant attention for potential applications in miniaturized electronics due to their high power density, rapid charge/discharge rates, and extended lifespan. Despite the unique properties of low-dimensional nanomaterials, which hold tremendous potential for revolutionary applications, effectively integrating these attributes into MSCs presents several challenges. 3D printing is rapidly emerging as a key player in the fabrication of advanced energy storage devices. Its ability to design, prototype, and produce functional devices incorporating low-dimensional nanomaterials positions it as an influential technology. In this review, we delve into recent advancements and innovations in micro-supercapacitor manufacturing, with a specific focus on the incorporation of low-dimensional nanomaterials using direct ink writing (DIW) 3D printing techniques. We highlight the distinct advantages offered by low-dimensional nanomaterials, from quantum effects in 0D nanoparticles that result in high capacitance values to rapid electron and ion transport in 1D nanowires, as well as the extensive surface area and mechanical flexibility of 2D nanosheets. Additionally, we address the challenges encountered during the fabrication process, such as material viscosity, printing resolution, and seamless integration of active materials with current collectors. This review highlights the remarkable progress in the energy storage sector, demonstrating how the synergistic use of low-dimensional nanomaterials and 3D printing technologies not only overcomes existing limitations but also opens new avenues for the development and production of advanced micro-supercapacitors. The convergence of low-dimensional nanomaterials and DIW 3D printing heralds the advent of the next generation of energy storage devices, making a significant contribution to the field and laying the groundwork for future innovations.

Sub-mm3 dimensional scaling of fully-integrated additively-fabricated microsupercapacitors for embedded energy storage applications

Microsupercapacitors (MSCs) are attractive energy devices for applications in IoT, wireless sensors, and other microelectronic systems due to their small footprints.

Scalable synthesis of N, O co-doped hierarchical porous carbon for high energy density supercapacitors

Rational design of hierarchical porous architecture with abundant pseudocapacitive sites is highly desirable for carbon electrode materials. However, the lengthy production process and high economic input limit its broader application. Herein, we successfully prepared N, O co-doped hierarchical porous carbon (NOHC) through hydrothermal carbonization (HTC) of chitin biomass with the assist of NH4Cl and subsequent carbonization with NaNH2. The optimal NOHC600 exhibits a remarkable hierarchical porous structure and an ultrahigh specific surface area (SSA) of 2555 m2 g−1. Furthermore, it showcases a significant content of N, O co-doping, thereby providing abundant defects and additional active sites for ion adsorption. The aforementioned characteristics ensure outstanding capacitance performance of NOHC600. In the three-electrode system, NOHC600 exhibits a remarkable specific capacitance of up to 455 F g−1 at a current density of 0.5 A g-1. The symmetric supercapacitors (SCs) based on NOHC600 achieve an impressive energy density of 30.4 Wh kg−1 at a power density of 180 W kg−1. Moreover, the all-solid-state NOHC600 microsupercapacitors (MSCs) demonstrate an exceptional areal capacitance of 78.2 mF cm−2 and an areal energy density of up to 10.8 μWh cm−2. Accordingly, this facile and scalable strategy shows a great potential for producing high-heteroatom-doped porous carbon materials from chitin biomass, which can be applied in practical energy-related applications.

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.

Phosphorus-Doped Nickel Oxide Micro-Supercapacitor: Unleashing the Power of Energy Storage for Miniaturized Electronic Devices.

For an uninterrupted self-powered network, the requirement of miniaturized energy storage device is of utmost importance. This study explores the potential utilization of phosphorus-doped nickel oxide (P-NiO) to design highly efficient durable micro-supercapacitors. The introduction of P as a dopant serves to enhance the electrical conductivity of bare NiO, leading to 11-fold augmentation in volumetric capacitance to 841.92 Fcm-3 followed by significant enhancement of energy and power density from 6.71 to 42.096 mWhcm-3 and 0.47 to 1.046 Wcm-3, respectively. Theoretical calculations used to determine the adsorption energy of OH- ions, revealing higher in case of bare NiO (1.52eV) as compared to phosphorus-doped NiO (0.64eV) leading to high electrochemical energy storage performance. The as-designed micro-supercapacitor (MSC) device demonstrates a facile integration with the photovoltaic system for renewable energy storage and smooth transfer to external loads for enlightening the blue LED for ≈1min. The choice of P-NiO/Ni not only contributes to cost reduction but also ensures minimal lattice mismatch at the interface facilitating high durability up to 15 K cycles along with capacitive retention of ≈100% and coulombic efficiency of 93%. Thus, the heterostructure unveils the possibilities of exploring miniaturized energy storage devices for portable electronics.

Laser-Induced Electron Synchronization Excitation for Photochemical Synthesis and Patterning Graphene-Based Electrode.

Micro-supercapacitors (MSCs) represent a pressing requirement for powering the forthcoming generation of micro-electronic devices. The simultaneous realization of high-efficiency synthesis of electrode materials and precision patterning for MSCs in a single step presents an ardent need, yet it poses a formidable challenge. Herein, a unique shaped laser-induced patterned electron synchronization excitation strategy has been put forward to photochemical synthesis RuO2 /reduced graphene oxide (rGO) electrode and simultaneously manufacture the micron-scale high-performance MSCs with ultra-high resolution. Significantly, the technique represents a noteworthy advancement over traditional laser direct writing (LDW) patterning and photoinduced synthetic electrode methods. It not only improves the processing efficiency for MSCs and the controllability of laser-induced electrode material but also enhances electric fields and potentials at the interface for better electrochemical performance. The resultant MSCs exhibit excellent area and volumetric capacitance (516mFcm-2 and 1720Fcm-3 ), and ultrahigh energy density (0.41Whcm-3 ) and well-cycle stability (retaining 95% capacitance after 12000 cycles). This investigation establishes a novel avenue for electrode design and underscores substantial potential in the fabrication of diverse microelectronic devices.

Highly stable aqueous carbon-based conductive ink for screen-printed planar flexible micro-supercapacitor

In this study, we have successfully developed a series of low-cost, environmentally friendly, and high-performance carbon-based conductive inks with a three-dimensional micro-nano structure through a simple dispersion and ball-milling process, offering an array of desirable characteristics. Significantly, the carbon-based conductive inks remained stable even after a 30-day settling period. Furthermore, the conductive film, produced using screen printing techniques, demonstrated an impressive conductivity of 1.99 × 103 S/m. This remarkable conductivity highlights the ability of the films to consistently maintain a robust conductivity network, even when subjected to 5000 mechanical bending/releasing tests. Expanding on the success of our carbon-based conductive inks, we harnessed their potential in the production of all-solid-state flexible Micro-supercapacitors (MSCs) with an interdigital structure, utilizing screen-printing technology. The resulting MSCs exhibited outstanding performance metrics, including a notable areal energy density of 1.47 µWh cm-2 and an area power density of 0.2 mW cm-2. Moreover, these MSCs demonstrated remarkable cycle stability, retaining 96.3% of their capacitance after 20,000 cycles. Additionally, their excellent mechanical flexibility was evident as they experienced only a minor 2.98% capacitance degradation after undergoing 5000 bending/releasing cycles. These findings highlight the enormous potential of our work in facilitating the scalable production of wearable and portable electronic products.

Sustainable Ketjenblack‐Based Carbon Ink for 3D Extrusion Micro‐Printing to Fabricate Flexible Supercapacitors

Abstract3D printing has attracted much attention in industry and academia because it offers simple, low‐cost, versatile and environmentally‐friendly manufacturing technologies and has been utilized to fabricate flexible electronics like supercapacitors, batteries and sensors. Finding a suitable printable ink is the most challenging task for 3D printing. Carbon materials have been widely used in 3D printing of flexible electronics due to their high electrical conductivity, chemical stability, non‐toxicity, and high surface area with versatile pore structure. However, mostly toxic solvents like NMP and DMF as well as non‐biodegradable polymer binders such as PVDF and PTFE were used to fabricate printable inks. Herein, a sustainable carbon ink highly suitable for 3D extrusion printing for well‐defined, flexible in‐plane all‐solid‐state micro‐supercapacitors (MSC) using only non‐toxic and biodegradable ingredients is presented. The MSCs show high areal capacitances of up to 13.41 mF cm−2 and 35.10 F cm−3 for 5 mV s−1 as well as excellent cycle stability even when mechanically stressed. Various suspension additives are explored for tuning the rheological behavior, conductivity, and electrochemical performance of MSCs.

Multilayer Superlattices of Monolayer Mesoporous Carbon Framework‐Intercalated MXene for Efficient Capacitive Energy Storage

AbstractIncorporating conductive and porous components as pillaring materials into the interlayers of two‐dimensional (2D) materials offers a solution to the restacking issue and enables the creation of multifunctional hetero‐superstructures. Here, multilayer MXene superlattices intercalated with monolayer mesoporous carbon frameworks (MMCFs) are synthesized by colloidal co‐assembly of MXene Ti3C2Tx nanosheets and Fe3O4 nanoparticles. The intercalated MMCFs not only increase interlayer spacing and create porous channels for fast mass transport but also act as conductive pillars to facilitate electron transfer along the z‐direction. These unique structural features allow for the full utilization of unilamellar MXene, making the resulting Ti3C2Tx/MMCF superlattices particularly suitable for capacitive energy storage in organic electrolytes containing bulky ions. As a demonstration, supercapacitors made from Ti3C2Tx/MMCFs exhibit a volumetric capacitance of 317 F cm−3 in a tetraethylammonium tetrafluoroborate/propylene carbonate electrolyte. Furthermore, on‐chip micro‐supercapacitors (MSCs) fabricated from Ti3C2Tx/MMCFs, using the ionic liquid 1‐ethyl‐3‐methylimidazolium tetrafluoroborate as an electrolyte, achieve an areal energy density of 0.10 mWh cm−2, surpassing that of most state‐of‐the‐art MXene‐based MSCs developed to date. This study not only highlights the significant potential of Ti3C2Tx/MMCFs for efficient capacitive energy storage in organic electrolytes but also introduces a new method for synthesizing 2D porous hetero‐superstructures for various applications.

Flexible micro-supercapacitors with organic gel electrolytes based on screen-printable CuO-ink

In recent years, due to the increase in the demand for miniaturized devices, there has been a massive increase in research to develop flexible, thin and scalable rechargeable energy storage micro-devices. Micro-supercapacitors (MSCs) with high charge-discharge rates and power density are excellent options for small, lightweight, easy-to-incorporate, flexible energy storage devices. However, the main problem with modern MSCs is their low energy density and money-intensive, time taking, sophisticated construction methods. Screen-printing is a simple, cost-effective and scalable method for fabricating MSCs. Using silver as the current collector, copper oxide as the active material, and gel electrolyte, we present a screen-printable method for constructing flexible MSCs on a PET substrate. The printed MSC was found to give 10.13 mA h cm−3 of volumetric specific capacity and energy density of 10.1 mW h cm−3 with an excellent stability of 99.5% over 3000 cycles and very small capacity degradation even with 120° bending deformation, suggesting outstanding mechanical flexibility and operation stability. Additionally, by connecting numerous MSC devices in series and parallel, the output voltage and current are intelligently adjusted to meet the requirements of varied applications. This study offers an efficient and economical approach to generate MSCs characterized by a substantial energy density. This breakthrough opens avenues for incorporating these MSCs into upcoming wearable technologies.

Wood‐Like Low‐Tortuosity Thick Electrode for Micro‐Redoxcapacitor with Ultrahigh Areal Energy Density and Steady Power Output

AbstractConventional MXene‐based thick electrodes with stacked and tortuous microstructures suffer from sluggish charge transport and low‐utilization of active substances, thus a limited boost in areal energy density of the assembled micro‐supercapacitors (MSCs). Herein, the duplication of wood‐like microstructure is realized in MXene/Ag‐nanowires (AgNWs) hybrid aerogel electrode (WL‐M/A‐AE) via directional freeze‐drying technique. Benefitting from the uniform 3D vertically‐aligned microchannels as the highways for ions transport throughout the matrix, the WL‐M/A‐AE with a thickness of up to 2000 µm can achieve a 50‐times higher of Cl− diffusion coefficient relative to closely restacked film electrode with the same mass loading of MXene. Furthermore, the evenly interspersed AgNWs serving as percolation network within the electrode matrix can facilitate horizontal electrons transmission between vertically‐aligned loose MXene flakes, while reversibly capture/release Cl− ions via phase conversion (Ag⇔AgCl) to raise the charge storage capacity of the WL‐M/A‐AE. Thus, when coupling with Zn anode, the assembled micro‐redoxcapacitor adopting polyacrylamide/ZnCl2+NH4Cl hydrogel electrolyte can deliver an areal energy density up to 292.5 µWh cm−2 in a more stable way (a smooth discharge plateau contributing 40.9% of the energy). The demonstrated hybrid thick electrode with wood‐like low‐tortuosity microstructure promises an effective avenue for tackling the performance bottlenecks facing traditional MSCs.

Analysis of the potential of nickel selenide micro-supercapacitors as energy storage device

Microsupercapacitors (MSCs) are emerging as compelling electrochemical energy storage solutions, particularly for miniaturized portable electronics. Their appeal lies in their high-power density and exceptional cycling stability, making them promising alternatives to traditional batteries. However, current microfabrication techniques often involve costly steps that result in materials with structural defects, ultimately limiting their energy density. This research introduces an innovative approach by harnessing screen-printing technology, which offers an additive and cost-effective production process while reducing waste generation. The study centers on the assessment of three distinct electrode materials—NiSe2, Ni3Se4, and NiSe—synthesized via a hydrothermal process for their suitability in supercapacitor applications. Among these materials, NiSe emerges as a standout candidate, showcasing remarkable energy storage capabilities. It achieves an impressive specific capacity of 93.3 mAh g−1 at a current density of 12 A g−1 in three-electrode measurements and demonstrates outstanding cycling stability, retaining 98 % of its capacity over an impressive 30,000 charge-discharge cycles. The resulting flexible symmetric micro-supercapacitor (NiSe-MSC) exhibits a remarkable volumetric capacitance of 81.44 F cm−3 at a current density of 6 A g−1, accompanied by impressive power density (822.86 W cm−3) and energy density (5.28 mWh cm−3).

Enhancing energy storage performance in flexible all-solid-state laser-induced graphene-based microsupercapacitors through the addition of carbon black and Prussian blue

In this study, we present an efficient and scalable method for the stepwise modification of polyimide (PI)-based laser-induced graphene using environmentally friendly additives. The as-prepared composite materials were applied as flexible electrodes for high-performance all-solid-state microsupercapacitors (MSCs). The electrochemical deposition of carbon black (CB) microparticles and Prussian blue (PB) inorganic redox dye onto the laser-induced graphene electrode surface significantly enhanced the electrochemical performance of the devices. The areal capacitance of MSCs increased by 116 % after the addition of CB to the electrode composition, 201 % after the modification of the electrode surface with PB, and 325 % after incorporating both CB and PB (CB-PB). The exhibited capacitance values at an applied current density of 0.1 mA·cm−2 are equal to 27.6, 38.5 and 54.4 mF·cm−2 upon incorporating CB, PB and CB-PB, respectively. Furthermore, the use of a PVA/H2SO4 gel electrolyte led to a large stability electrochemical window of 3.0 V, resulting in an energy density as high as 68.1 μWh·cm−2 with a power density of 0.3 mW·cm−2 at 0.10 mA·cm−2. Additionally, the MSCs modified with CB-PB showed an excellent electrochemical stability, retaining over 95.8 % of their initial capacitance after 6000 galvanostatic charge-discharge cycles. Overall, this study presents a facile, convenient, and scalable approach for designing cost-effective and high-performance MSCs with a low-carbon footprint suitable for powering low-energy-consuming electronics.

3D-printed, high-energy-density, current collector-free flexible micro-supercapacitors based on CNT@V2O5 nanowires

Herein, we present current collector-free, high-performance micro-supercapacitors (MSCs) fabricated by 3D extrusion-based printing. To this end, we develop printable hybrid electrode inks by combining V2O5 nanowires (NWs) and carbon nanotubes (CNTs). The performance of the hybrid electrodes is optimized by rationally tailoring the V2O5 NW-to-CNT ratio. Owing to the high conductivity of the hybrid electrodes, the resulting MSCs could operate even without a current collector. Additionally, we improve the areal capacitance by increasing the mass loading per unit area through multiple printing in the vertical direction. The final multilayered MSCs exhibit outstanding energy-storage characteristics, including a high areal capacitance (18.98 mF/cm2 at 0.05 mA/cm2), a high energy density of 5.93 μWh/cm2 at a power density of 39.99 μW/cm2, excellent cycle stability (10,000 cycles), and reliable operation under mechanical deformation.

The Effect of Anion Modification on the Conductive Polymer/Ag‐Interdigitated Electrodes Micro‐Supercapacitor

Due to their outstanding electrical conductivity, simplicity of synthesis, and exceptional flexibility, conductive polymers are the most attractive electrode materials for micro‐supercapacitors (MSCs). However, when used as an electrode material alone, its poor capacitive performance and cycle‐life hinder the wide engineering applications. Herein, a polypyrrole (PPy)/Ag‐interdigitated electrodes MSCs is proposed, and the impact of aromatic sulfonic acid group anion modification on the electrochemical properties and flexibility of PPy/Ag MSCs is investigated. In the results, it is shown that different aromatic sulfonic‐acid‐based anionic dopants have different effects on the properties of PPy films. Among the prepared three PPy/Ag MSCs devices, PPy:anthraquinone‐2‐sulfonic acid/Ag MSCs have the highest areal capacitance (198.8 mF cm−2) at a current density of 0.5 mA cm−2, surpassing PPy:2‐naphthalenesulfonic acid/Ag MSCs (114.3 mF cm−2) and PPy:p‐toluenesulfonic acid monohydrate/Ag MSCs (89.7 mF cm−2). Furthermore, at a power density of 0.25 mW cm−2, the PPy:AQS/Ag MSCs exhibit a high energy density of 27.61 μWh cm−2, which is above the most of the previously reported PPy‐based MSCs. Therefore, in this research, the groundwork is provided for improving properties of flexible MSCs based on PPy.

“Additive fabrication of fully-integrated high-performance millimeter-scale microsupercapacitors: Fine-tuning chemistry to maximize performance’’

Microsupercapacitors (MSCs) are attractive for use as energy devices to power wearables, IoT, and other small microsystems. Additive fabrication of these devices will facilitate easy integration into a range of ubiquitous microsystem platforms. In this work, MSCs with lateral sizes < 0.5 cm2 (full package: 7 mm × 7 mm and charge storage active area: 4 mm × 3.5 mm) and total height of ∼2 mm with remarkable electrochemical performance are fully 3D printed via a combination of FDM printing and 3D extrusion-based printing. By fine-tuning the chemistries of the components of the MSCs, a combination of high energy density of 16.1 μWh.cm−2, power density of ∼3028 mW.cm−2, areal capacitance of ∼323 mF.cm−2, and ∼91.3% capacitance retention after 21000 cycles are realized. These performance levels are achieved using novel inks for the electrodes, electrolytes, and current collectors in addition to provision of proper packaging and encapsulation of the devices. The demonstrated performance of these encapsulated millimeter-scale fully additively fabricated MSCs with thick electrodes (i.e., ∼300 μm) thus makes them attractive for use as integrated energy sources for powering microsystems, wearables, and IoT.

High-performance fractal microsupercapacitors based on Ti3C2Tx MXene for kHz alternating current line-filtering applications

Microsupercapacitors (MSCs) are attracting attention as vital filter capacitors for microscale power conversion in alternating current (AC) line-filtering circuits due to their rapid frequency response characteristics. This study demonstrates the wafer-scale fabrication of Ti3C2Tx MXene-based MSCs with a high-potential device structure incorporating fractal microelectrodes. The experimental and simulation results show that the new structure enables increased ion-transport rates through increased absorption sites and a strong electric field, resulting in improved energy storage and frequency response performance. Therefore, by optimizing the size of the microelectrodes, the fractal MSCs (FMSCs) achieve a high specific capacitance of 615.3 μF cm−2 at 1 V s−1 and their highest frequency characteristic (f0) can reach kHz. Notably, the FMSCs exhibit excellent filtering performance in AC line-filtering circuits by successfully filtering different AC waveforms at a high frequency of 20 kHz into direct current.

Architectural engineering of vertically expanded graphene-CoMn2O4 compounds based interdigital electrode for in-plane micro-supercapacitor

Structurally engineered carbon allotropes and their composites are widely applicable in various electronic/electrochemical devices including energy storage. Herein, we develop an efficient method to fabricate graphene/ceramic hybrid nanostructure based in-plane micro-supercapacitors (MSCs). Via CO2-laser irradiation method, MSCs patterns consisting of CoMn2O4 nanoparticles incorporated in vertically structured laser-induced graphene (CMOLIG) were formed on a freestanding graphene oxide film. The process is extremely convenient, since the laser irradiated CMOLIG patterns serve as the in-plane MSCs electrode, while the untreated graphene oxide acts as the substrate. MSCs with enhanced performance can be fabricated with the CMOLIG hybrid electrode patterns that are made of CoMn2O4 nanoparticles with pseudocapacitive properties anchored on vertically structured high-quality graphene film with excellent electrical property and high surface area. Notably, the CMOLIG electrode patterns exhibit enhanced specific capacitance with fast redox kinetics. Using the technique, customized in-plane MSCs arrays are also fabricated, which demonstrated controllable output voltage and capacitance depending on the array configuration to suit the requirements of various wearable microelectronics.

Co3 O4 Quantum Dots Intercalation Liquid-Crystal Ordered-Layered-Structure Optimizing the Performance of 3D-Printing Micro-Supercapacitors.

The effects of near surface or surface mechanisms on electrochemical performance (lower specific capacitance density) hinders the development of 3D printed micro supercapacitors (MSCs). The reasonable internal structural characteristics of printed electrodes and the appropriate intercalation material can effectively compensate for the effects of surface or near-surface mechanisms. In this study, a layered structure is constructed inside an electrode using an ink with liquid-crystal characteristics, and the pore structure and oxidation active sites of the layered electrode are optimized by controlling the amount of Co3 O4 -quantum dots (Co3 O4 QDs). The Co3 O4 QDs are distributed in the pores of the electrode surface, and the insertion of Co3 O4 QDs can effectively compensate for the limitations of surface or near-surface mechanisms, thus effectively improving the pseudocapacitive characteristics of the 3D-printed MSCs. The 3D printed MSC exhibits a high area capacitance (306.13 mF cm-2 ) and energy density (34.44 µWh cm-2 at a power density of 0.108mW cm-2 ). Therefore, selecting the appropriate materials to construct printable electrode structures and effectively adjusting material ratios for efficient 3D printing are expected to provide feasible solutions for the construction of various high-energy storage systems such as MSCs.