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MXenes, a novel class of 2D materials, exhibit great potential for energy storage due to their unique layered structure and excellent electrical conductivity. However, improving the intrinsic electrochemical storage capacity of MXenes remains a significant challenge, often requiring the incorporation of other Faradaic materials. Oxidation, in particular, poses a key issue that impacts the capacity of MXene devices. In this study, controlled oxidation is employed to create nanoscale holes within MXene, transforming them into holey MXene (H‐MXene) nanosheets. These porous structures shorten ion transport distances and increase ion transport pathways, thereby significantly enhancing the electrochemical storage capacity of MXenes. The resulting H‐MXene micro‐supercapacitors (MSCs) demonstrate exceptional performance, achieving an aerial capacitance 2.5 times that of unmodified MXene electrodes, along with excellent cycling stability, retaining 91.7% of their capacitance after 10 000 cycles. Additionally, a flexible integrated system combining energy storage and sensing functionalities is developed, showcasing its scalability in self‐powered sensing applications. The incorporation of self‐healing polyurethane (PU) enables the device to retain 90% of its storage capacity after undergoing self‐healing. This study presents a novel approach for developing high‐performance MXene‐based energy storage devices and provides valuable insights into efficient ion transport and storage in 2D materials. [ABSTRACT FROM AUTHOR]

The limited energy density of micro‐supercapacitors (MSCs) and challenges in their integration significantly impede the advancement of MSCs in wearable electronic devices. Here, this work designs a robust and wrinkled liquid metal‐CNT‐PEDOT:PSS film with high capacity and self‐healing properties (defined as LM‐CNT‐PEDOT:PSS). The wrinkled structure further enhances tensile properties of LM‐CNT‐PEDOT:PSS and increases its active specific surface area per unit. Simultaneously, the incorporation of liquid metal (LM) enhances both the mechanical and healing properties of the LM‐CNT‐PEDOT:PSS electrode. The flexible and self‐healing MSC based on wrinkled LM‐CNT‐PEDOT:PSS shows a remarkable specific capacitance of 114.29 mF cm−2 and a high areal energy density of 15.47 µW h cm−2. Furthermore, the electrochemical performance of the healed MSC retained 90.01% of its initial performance, and the MSC unit can be arbitrarily integrated according to various energy and voltage requirements through the healing properties of LM‐CNT‐PEDOT:PSS, widening the range of applications in next‐generation microelectronic devices. The wrinkled LM‐CNT‐PEDOT:PSS film is utilized for the fabrication of a highly sensitive strain sensor. Simultaneously, the prepared sensor can be seamlessly integrated with wireless charging and MSC to facilitate convenient monitoring of physiological signals, thereby offering an effective solution for the advancement of wearable technology and self‐powered systems. [ABSTRACT FROM AUTHOR]

2D Ti3C2Tx‐MXenes have gained attention as highly promising materials owing to their distinctive characteristics. Even so, the limited ionic kinetics and active site exposure of these materials are hindered by the significant degradation caused by oxidation, as well as the challenges in ink formulation processability and nanosheet restacking. Here, this study presents a single‐step and economical method to embellish cysteine onto titanium carbide (MX‐C) nanosheets. Cysteine is found to facilitate the tuning of the interlayer spacing in MXene nanosheets. The idea is then applied in the development of micro‐supercapacitors (MSCs) and the removal of toxic metal ions, specifically lead. In addition, the investigation reveals that MX‐C exhibits antioxidant behavior and possesses excellent qualities as inks. The MX‐C‐printed MSC exhibits ultra‐high areal capacitance (68 mF cm−2 ( = 5)) and power density (170.6 µW cm−2) compared to the reported printed MSC system. Similarly, the MX‐C facilitates a high capacity for selectively adsorbing lead while also exhibiting excellent performance in terms of adsorption–desorption. The adsorption‐induced effectiveness of cysteine is additionally validated by density functional theory simulations. The versatile approach emphasizes the potential of MX‐C inks with antioxidation properties for the invention of MSCs and metal uptake for printable electronics and clean water applications, respectively. [ABSTRACT FROM AUTHOR]

As demand for micro‐power sources grows, micro‐supercapacitors (MSCs) have become critical for miniaturized devices, offering robust electrochemical energy storage. However, the challenge remains to develop a simple, scalable fabrication method that achieves both high energy and power densities. In this study, we present a refined approach to fabricating MSCs with 3D interconnected graphene/carbon nanotube (CNT) composite electrodes. Our method combines flash lamp annealing (FLA) and laser ablation, where FLA converts graphene oxide (GO) and CNT composite films into 3D‐structured graphene/CNT electrodes, and laser ablation precisely patterns them into interdigitated designs. This dual‐process technique produces MSCs with exceptional electrochemical performance, including an impressive areal capacitance of 26.11 mF/cm2 and a volumetric capacitance of 31.88 F/cm3. These devices also achieve energy densities of 3.72 μWh/cm2 and 4.43 mWh/cm3, maintaining 97 % of their initial capacitance under extreme bending, demonstrating outstanding mechanical flexibility and durability. Furthermore, the scalability of this method was validated by configuring MSCs in series and parallel, achieving enhanced voltage and current outputs without additional interconnections. Overall, the integration of FLA and laser ablation holds significant promise for advancing the performance and scalability of micro‐sized energy storage devices, addressing the growing need for efficient, flexible, and high‐capacity micro‐power sources. [ABSTRACT FROM AUTHOR]

Nanoporous graphene own high surface area and unique structural and physical properties due to nano-sized pores in graphene nanosheet. Nanoporous graphene has been modified by the introduction of surface functional groups, doping, or nanoparticle modification and applied for nanocomposites. The overview basically highlights design, properties, and potential of functionalized nanoporous graphene derived nanocomposites in advanced membranes (desalination/gas/oil separation), thermal management, electrocatalysts, and micro-supercapacitors. According to literature, pore size of neat nanoporous graphene is 3–11 Å and hydroxyl functional nanoporous graphene also had nanopore size of <10 Å. Functionalized nanoporous graphene revealed 100% salt rejection, while hydroxyl functional nanoporous graphene had 89% salt rejection due to altered surface properties. Both neat and functionalized nanoporous graphene has high gas permeance of ∼103–105 GPU towards separation CO2, CH4, N2, etc. Few attempts on micro-supercapacitor like molybdenum disulfide nanoporous graphene resulted in volumetric capacitance of 55 F cm−3 and capacitance retention of 82%. Forthcoming research on functionalized nanoporous graphene may overcome design/performance challenges leading to superior features and large-scale utilizations. [ABSTRACT FROM AUTHOR]

The micro‐scale energy storage devices (MESDs) have experienced significant revolutions driven by developments in micro‐supercapacitors (MSCs) and micro‐batteries (MBs). This review summarizes the advancements of MSC and MB architecture, highlighting the electrode–electrolyte designs and the emergence of alkali metal ions aqueous batteries. The performance and synthesis of carbon quantum dots (CQDs), graphene quantum dots (GQDs), and their synergistic effects for energy storage applications are investigated. The focus is on integrating CQDs/GQDs into the MESDs for enhanced performance. The development of compositing CQD/GQD with other materials, reveals their capacitive and pseudocapacitive performance, extending the MESDs’ possibilities. Moreover, this review systematically covers various fabrication techniques from photolithography to printing techniques. The merits and practicality of each technique for fabricating MSCs and MBs are assessed. Electrochemical performance evaluation, capacitance enhancement, charge–discharge kinetics, and stability assessments are presented to demonstrate the efficiency of MESDs with practical applications. Despite significant progress, challenges remain, particularly in the scalability of fabrication and understanding long‐term stability. Nevertheless, the prospects are promising, with avenues in synthesis, fabrication, and electrochemical performance evaluation, which lead to a paradigm shift in MESDs. This review offers a broad perspective, combining innovations across diverse domains and directing the frontline of microelectronics. [ABSTRACT FROM AUTHOR]

2D materials have garnered considerable interest in various applications from catalysis to energy storage. However, the self‐stacking and poor air stability of 2D materials (e.g., MXene) leads to serious performance degradation, in particular, of micro‐supercapacitors (MSCs) with narrow working voltage and low energy density. Here, a universal confined interfacial assembly strategy is demonstrated for controllably synthesizing a series of 2D mesoporous heterostructures for high‐voltage and high‐energy ionogel‐based MSCs. This assembly process reveals accurate controllability and extraordinary versatility, endowing the 2D mesoporous heterostructures with highly adjustable mesopore size (7–22 nm), tunable thickness (15–29 nm), variable carbon precursors (including oligochitosan, glucose, and sucrose), and replaceable 2D substrates (e.g., MXene, graphene, BN, and MoS2). As a proof of concept, the 2D mesoporous carbon@MXene based MSCs with ionic liquid ionogel electrolyte deliver ultrahigh voltage of 3.7 V, superior areal energy density of 181.3 µWh cm−2, excellent flexibility with 99% of capacitance retention at 180°, and excellent modular self‐integration for variable voltage/capacitance output, surpassing most reported MXene based MSCs. Therefore, this work will open a novel available paradigm for scalable fabrication of 2D mesoporous materials to target high‐performance and functional microscale power source. [ABSTRACT FROM AUTHOR]

Nanoporous graphene own high surface area and unique structural and physical properties due to nano-sized pores in graphene nanosheet. Nanoporous graphene has been modified by the introduction of surface functional groups, doping, or nanoparticle modification and applied for nanocomposites. The overview basically highlights design, properties, and potential of functionalized nanoporous graphene derived nanocomposites in advanced membranes (desalination/gas/oil separation), thermal management, electrocatalysts, and micro-supercapacitors. According to literature, pore size of neat nanoporous graphene is 3–11 Å and hydroxyl functional nanoporous graphene also had nanopore size of

Ultra‐thin 2D materials have great potential as electrodes for micro‐supercapacitors (MSCs) because of their facile ion transport channels. Here, a high‐precision controllable photonic‐synthesis strategy that provided 1 inch wafer‐scale ultra‐thin film arrays of alloyed WxMo2xSy with sulfur vacancies and expanded interlayer (13.2 Å, twice of 2H MoS2) is reported. This strategy regulates the nucleation and growth of transition metal dichalcogenides (TMDs) on the picosecond or even femtosecond scale, which induces Mo–W alloying, interlayer expansion, and sulfur loss. Therefore, the diffusion barrier of WxMo2xSy is reduced, with charge transfer and ion diffusion enhancing. The as‐prepared symmetric MSCs with the size of 100 × 100 µm2 achieve ultrahigh specific capacitance (242.57 mF cm−2 and 242567.83 F cm−3), and energy density (21.56 Wh cm−3 with power density of 485.13 W cm3). The established synthesis strategy fits numerous materials, which provides a universal method for the flexible synthesis of electrodes in microenergy devices. [ABSTRACT FROM AUTHOR]

Miniaturized energy storage devices, such as electrostatic nanocapacitors and electrochemical micro-supercapacitors (MSCs), are important components in on-chip energy supply systems, facilitating the development of autonomous microelectronic devices with enhanced performance and efficiency. The performance of the on-chip energy storage devices heavily relies on the electrode materials, necessitating continuous advancements in material design and synthesis. This review provides an overview of recent developments in electrode materials for on-chip MSCs and electrostatic (micro-/nano-) capacitors, focusing on enhancing energy density, power density, and device stability. The review begins by discussing the fundamental requirements for electrode materials in MSCs, including high specific surface area, good conductivity, and excellent electrochemical stability. Subsequently, various categories of electrode materials are evaluated in terms of their charge storage mechanisms, electrochemical performance, and compatibility with on-chip fabrication processes. Furthermore, recent strategies to enhance the performance of electrode materials are discussed, including nanostructuring, doping, heteroatom incorporation, hybridization with other capacitive materials, and electrode configurations. [ABSTRACT FROM AUTHOR]

The addition of two‐dimensional MXene materials gives micro‐supercapacitors (MSCs) the advantages of higher power density, faster charging and discharging speeds, and longer lifetimes. To date, various fabrication methods and strategies have been used to finely synthesize MXene electrodes. However, different technologies not only affect the electrode structure of MXene but also directly affect the performance of MSCs. Here, we provide a comprehensive and critical review of the design and microfabrication strategies for MXene's fork‐finger microelectrodes. First, we provide a systematic overview of micromachining techniques applied to MXene, including graphic cutting, screen‐printing, 3D printing, inkjet, and stamp methods. In addition, we discuss in detail the advantages and disadvantages of these machining techniques, summarizing the environment in which the technique is used and the results expected to be achieved. Finally, the challenges as well as the outlook for future applications are summarized to promote the further development of MXene materials in the field of MSCs. [ABSTRACT FROM AUTHOR]

Simple and scalable production of micro-supercapacitors (MSCs) is crucial to address the energy requirements of miniature electronics. Although significant advancements have been achieved in fabricating MSCs through solution-based printing techniques, the realization of high-performance MSCs remains a challenge. In this paper, graphene-based MSCs with a high power density were prepared through screen printing of aqueous conductive inks with appropriate rheological properties. High electrical conductivity (2.04 × 104 S∙m−1) and low equivalent series resistance (46.7 Ω) benefiting from the dense conductive network consisting of the mesoporous structure formed by graphene with carbon black dispersed as linkers, as well as the narrow finger width and interspace (200 µm) originating from the excellent printability, prompted the fully printed MSCs to deliver high capacitance (9.15 mF∙cm−2), energy density (1.30 µWh∙cm−2) and ultrahigh power density (89.9 mW∙cm−2). Notably, the resulting MSCs can effectively operate at scan rates up to 200 V∙s−1, which surpasses conventional supercapacitors by two orders of magnitude. In addition, the MSCs demonstrate excellent cycling stability (91.6% capacity retention and ~100% Coulombic efficiency after 10,000 cycles) and extraordinary mechanical properties (92.2% capacity retention after 5000 bending cycles), indicating their broad application prospects in flexible wearable/portable electronic systems. [ABSTRACT FROM AUTHOR]

The rapid advancement in the miniaturization, integration, and intelligence of electronic devices has escalated the demand for customizable micro‐supercapacitors (MSCs) with high energy density. However, efficient microfabrication of safe and high‐energy MXene MSCs for integrating microelectronics remains a significant challenge due to the low voltage window in aqueous electrolytes (typically ≤0.6 V) and limited areal mass loading of MXene microelectrodes. Here, we tackle these challenges by developing a high‐concentration (18 mol kg−1) "water‐in‐LiBr" (WiB) gel electrolyte for MXene symmetric MSCs (M‐SMSCs), demonstrating a record high voltage window of 1.8 V. Subsequently, additive‐free aqueous MXene ink with excellent rheological behavior is developed for three‐dimensional (3D) printing customizable all‐MXene microelectrodes on various substrates. Leveraging the synergy of a high‐voltage WiB gel electrolyte and 3D‐printed microelectrodes, quasi‐solid‐state M‐SMSCs operating stably at 1.8 V are constructed, and achieve an ultrahigh areal energy density of 1772 μWh cm−2 and excellent low‐temperature tolerance, with a long‐term operation at −40°C. Finally, by extending the 3D printing protocol, M‐SMSCs are integrated with humidity sensors on a single planar substrate, demonstrating their reliability in miniaturized integrated microsystems. [ABSTRACT FROM AUTHOR]

Printed micro‐supercapacitors (MSCs) have shown broad prospect in flexible and wearable electronics. Most of previous studies focused on printing the electrochemically active materials paying less attention to other key components like current collectors and electrolytes. This study presents an all‐printing strategy to fabricate in‐plane flexible and substrate‐free MSCs with hierarchical encapsulation. This new type of "all‐in‐one" MSC is constructed by encapsulating the in‐plane interdigital current collectors and electrodes within the polyvinyl‐alcohol‐based hydrogel electrolyte via sequential printing. The bottom electrolyte layer of this fully printed MSCs helps protect the device from the limitation of conventional substrate, showing excellent flexibility. The MSCs maintain a high capacitance retention of 96.84% even in a completely folded state. An optimal electrochemical performance can be achieved by providing ample and shorter transport paths for ions. The MSCs using commercial activated carbon as the active material are endowed with a high specific areal capacitance of 1892.90 mF cm−2 at a current density of 0.3 mA cm−2, and an outstanding volumetric energy density of 9.20 mWh cm−3 at a volumetric power density of 6.89 mW cm−3. For demonstration, a thermo‐hygrometer is stably powered by five MSCs which are connected in series and wrapped onto a glass rod. This low‐cost and versatile all‐printing strategy is believed to diversify the application fields of MSCs with high capacitance and excellent flexibility. [ABSTRACT FROM AUTHOR]

High‐concentration electrolyte effectively improves the energy density and anti‐freezing property of aqueous micro‐supercapacitors (MSCs), endowing them the opportunity serving as power sources for miniaturized electronics. However, the excessive usage of salt significantly increases the cost of the electrolyte. Herein, a cost‐effective moderate‐concentration hybrid electrolyte is designed by introducing CaCl2 and ethylene glycerol (EG) additives for low‐temperature and high‐voltage MSCs. The results manifest that the introduction of CaCl2 minimizes the number of water molecules with strong hydrogen bonds while the addition of EG can reduce the amount of H2O molecules in the primary solvation shell sheath of Ca2+ ion and strengthen the hydrogen bonds between EG and water molecules, thus endowing the optimal electrolyte with a wide electrochemical stability window of 3.5 V and a freezing point lower than −120 °C. Furthermore, the resulting hybrid MSCs offer a high voltage of 1.6 V, and realize 62% capacitance retention at −40 °C compared to that at room temperature. Moreover, The MSCs can endure 20000 cycles with 98.5% capacitance retention at −40 °C. This work provides a meaningful guidance for designing low‐cost moderate‐concentration hybrid electrolyte with wide electrochemical stability window and anti‐freezing property for intrinsically safe and environmentally adaptable devices. [ABSTRACT FROM AUTHOR]

An all-in-one self-sustained integrated system composed of a Si film solar cell, spray-printed a micro-supercapacitor and a gas sensor, exhibits excellent flexibility and durability. [Display omitted] Printable micro-supercapacitors (MSCs) with remarkable versatility, customizability, high power density and long cycling lifespan, are regarded as a promising class of miniaturized power source for wearable and portable microelectronics. Herein, we demonstrate a novel Fe-based zeolitic imidazolate framework (Fe-ZIF)/graphene (FZG) heterostructure with high specific surface area and outstanding electrical conductivity for planar MSCs (FZG-MSCs) worked in a high-voltage ionic liquid gel electrolyte via a spray-printed strategy. The fully printed FZG-MSCs deliver a high areal energy density of 9.5 μWh/cm2, extraordinary cyclability, and tailored voltage/capacitance output. Furthermore, using a fully printed FZG-MSC, we seamlessly integrate a monolithically planar all-flexible self-sustained sensor system with a mounted solar cell and a printable NH 3 gas sensor on the same side of single flexible substrate. The self-sustained sensor system exhibits high-sensitivity NH 3 detection with a good response of 18.3% at 20 ppm and linear sensibility exposed to 2–20 ppm. Such a fully integrated system can utilize the converted solar energy stored in the MSC, and offer efficient electricity to power microelectronics whenever needed. Therefore, this contribution of printable planar device and integrated system paves a new avenue for constructing flexible microelectronics. [ABSTRACT FROM AUTHOR]

Flexible electronic products, with their characteristics of flexibility and wearability, have attracted significant attention and have become an important direction in the research and development of the electronics industry. Planar micro-supercapacitors (MSCs) with flexible composite electrodes can provide reliable energy support for these products, propelling their further development. The research employed a quick, effective, and environmentally friendly method of laser scribing to create shape-controllable flexible composite electrodes on composite films of Poly(3,4-ethylenedioxythiophene) and graphene oxide (PEDOT/GO), which were subsequently assembled into MSCs. An analysis of the composite electrode morphology, structure, and elemental distribution was conducted through the utilization of SEM, TEM, and XPS techniques. Following this, a comprehensive evaluation of the electrochemical performance of the flexible MSCs was carried out, which included cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and assessment of cyclic stability. The analysis of the CV results indicated that the MSCs achieved the areal capacitance of 5.78 mF/cm2 at 5 mV/s. After 5000 cycles at a current density of 0.05 mA/cm2, the capacitance retention rate was 85.4%. The high areal capacitance and strong cycle stability of MSCs highlight the potential of PEDOT/reduced graphene oxide (PEDOT/rGO) electrodes in electrode applications. [ABSTRACT FROM AUTHOR]

Due to the rapid technological advancements of various sectors in recent decades, there has been a growing need for energy, necessitating the development of large-capacity, robust, adaptable, and economical energy storage systems. The most current energy-storage material known as “MXene” is a two-dimensional layered transition metal nitride or carbonitride and carbide. A covalently bonded layer is exfoliated from its parent MAX (Mn + 1AXn) phase by selective chemical etching. MXene commands the highest demand of all the two-dimensional families of materials due to its extraordinary characteristics, which include high conductivity, flexible surface functional groups, excellent mechanical properties, superior hydrophilicity, electrochemical nature, and the thickness of its atomic layers. MXene is used in solid-state supercapacitors, batteries, antimicrobial films, gas and biosensors, water splitting, electromagnetic interference shielding, and photo- and electrocatalysis. Because of MXene’s special qualities, researchers are concentrating on developing the material further, both theoretically and experimentally. Utilizing a variety of microfabrication processes, MXene microelectrodes of micro-sized energy storage devices (MESDs) have been previously created. Distinct methodologies influence not only the apparatus’s arrangement but also the composition of MXene microelectrodes and the electrochemical efficacy of MESDs. ,This review study addresses relevant topics and provides a topical summary of the state-of-the-art regarding MXene-based energy storage devices. The field’s challenges and prospects for the future are discussed in the final part.

Abstract The rapid advancement in the miniaturization, integration, and intelligence of electronic devices has escalated the demand for customizable micro‐supercapacitors (MSCs) with high energy density. However, efficient microfabrication of safe and high‐energy MXene MSCs for integrating microelectronics remains a significant challenge due to the low voltage window in aqueous electrolytes (typically ≤0.6 V) and limited areal mass loading of MXene microelectrodes. Here, we tackle these challenges by developing a high‐concentration (18 mol kg−1) “water‐in‐LiBr” (WiB) gel electrolyte for MXene symmetric MSCs (M‐SMSCs), demonstrating a record high voltage window of 1.8 V. Subsequently, additive‐free aqueous MXene ink with excellent rheological behavior is developed for three‐dimensional (3D) printing customizable all‐MXene microelectrodes on various substrates. Leveraging the synergy of a high‐voltage WiB gel electrolyte and 3D‐printed microelectrodes, quasi‐solid‐state M‐SMSCs operating stably at 1.8 V are constructed, and achieve an ultrahigh areal energy density of 1772 μWh cm−2 and excellent low‐temperature tolerance, with a long‐term operation at −40°C. Finally, by extending the 3D printing protocol, M‐SMSCs are integrated with humidity sensors on a single planar substrate, demonstrating their reliability in miniaturized integrated microsystems.

Micro‐supercapacitors, emerging as promising micro‐energy storage devices, have attracted significant attention due to their unique features. This comprehensive review focuses on two key aspects: the scalable fabrication of MSCs and their diverse applications. The review begins by elucidating the energy storage mechanisms and guiding principles for designing high‐performance devices. It subsequently explores recent advancements in scalable fabrication techniques for electrode materials and micro‐nano fabrication technologies for micro‐devices. The discussion encompasses critical application domains, including multifunctional MSCs, energy storage integration, integrated power generation, and integrated applications. Despite notable progress, there are still some challenges such as large‐scale production of electrode material, well‐controlled fabrication technology, and scalable integrated manufacture. The summary concludes by emphasizing the need for future research to enhance micro‐supercapacitor performance, reduce production costs, achieve large‐scale production, and explore synergies with other energy storage technologies. This collective effort aims to propel MSCs from laboratory innovation to market viability, providing robust energy storage solutions for MEMS and portable electronics. [ABSTRACT FROM AUTHOR]

The burgeoning demand for miniaturized energy storage devices compatible with the miniaturization trend of electronic technologies necessitates advancements in micro-supercapacitors (MSCs) that promise safety, cost efficiency, and high-speed charging capabilities. However, conventional aqueous MSCs face a significant limitation due to their inherently narrow electrochemical potential window, which restricts their operational voltage and energy density compared to their organic and ionic liquid counterparts. In this study, we introduce an innovative aqueous NaCl/H2O/EG hybrid gel electrolyte (comprising common salt (NaCl), H2O, ethylene glycol (EG), and SiO2) for Ti3C2Tx MXene MSCs that substantially widens the voltage window to 1.6 V, a notable improvement over traditional aqueous system. By integrating the hybrid electrolyte with 3D-printed MXene electrodes, we realized MSCs with remarkable areal capacitance (1.51 F cm−2) and energy density (675 µWh cm−2), significantly surpassing existing benchmarks for aqueous MSCs. The strategic formulation of the hybrid electrolyte—a low-concentration NaCl solution with EG—ensures both economic and environmental viability while enabling enhanced electrochemical performance. Furthermore, the MSCs fabricated via 3D printing technology exhibit exceptional flexibility and are suitable for modular device integration, offering a promising avenue for the development of high-performance, sustainable energy storage devices. This advancement not only provides a tangible solution to the challenge of limited voltage windows in aqueous MXene MSCs but also sets a new precedent for the design of next-generation MSCs that align with the needs of an increasingly microdevice-centric world. [ABSTRACT FROM AUTHOR]

Flexible and small-scale energy storage technologies are critical for future applications such as wearable electronics. In this context, paper has emerged as a lightweight, low-cost, and ecologically friendly flexible substrate for energy storage devices. This paper presents a simple method for fabricating a micro-supercapacitor (MSC) using a wax printing approach that can achieve high resolution without requiring complex processes. In addition, the developed MnO2–Au-paper (MAP) microelectrodes with high porosity exhibit enhanced charge and ion transfer while maintaining a stable flexibility. The solid-state micro-supercapacitor delivers a very large areal capacitance of 624.32 mF cm−2 at 0.2 mA cm−2 and is stable under external stress. The highest energy and power densities obtained for the present MSCs (55.5 μWh cm−2 and 1.59 mW cm−2, respectively), are much larger than those previously reported for pseudocapacitive MSCs, including flexible ones. [ABSTRACT FROM AUTHOR]

The escalating demand for micro/nano-sized devices, such as micro/nano-robots, intelligent portable/wearable microsystems, and implantable medical microdevices, necessitates the expeditious development of integrated microsystems incorporating energy conversion, storage, and consumption. Critical bottlenecks in microscale energy storage/sensors and their integrated systems are being addressed by exploring new technologies and new materials, e.g., MXene, holding great potential for developing lightweight and deformable integrated microdevices. This review summarizes the latest progress and milestones in the realization of MXene-based micro-supercapacitors (MSCs) and sensor arrays, and thus discusses the design fundamentals and key advancements of MXene-based energy conversion-storage-consumption integrated microsystems. Finally, we outline the key challenges in fabricating MXene-based MSCs/sensors and their self-powered integrated microsystems, which is crucial for their practical applications. Particularly, we illuminate viable solutions to such unsolved issues and highlight the exciting opportunities.

Miniaturized energy storage devices, such as electrostatic nanocapacitors and electrochemical micro-supercapacitors (MSCs), are important components in on-chip energy supply systems, facilitating the development of autonomous microelectronic devices with enhanced performance and efficiency. The performance of the on-chip energy storage devices heavily relies on the electrode materials, necessitating continuous advancements in material design and synthesis. This review provides an overview of recent developments in electrode materials for on-chip MSCs and electrostatic (micro-/nano-) capacitors, focusing on enhancing energy density, power density, and device stability. The review begins by discussing the fundamental requirements for electrode materials in MSCs, including high specific surface area, good conductivity, and excellent electrochemical stability. Subsequently, various categories of electrode materials are evaluated in terms of their charge storage mechanisms, electrochemical performance, and compatibility with on-chip fabrication processes. Furthermore, recent strategies to enhance the performance of electrode materials are discussed, including nanostructuring, doping, heteroatom incorporation, hybridization with other capacitive materials, and electrode configurations.

Incorporating 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. [ABSTRACT FROM AUTHOR]

Engineered 2D MXene-based materials for advanced supercapacitors and micro-supercapacitors. [Display omitted] The class of two-dimensional transition metal carbides/nitrides/oxycarbides (known as MXenes) has shown great potential in energy storage applications due to their intrinsic layered structure, outstanding electrical conductivity, tunable surface chemistry, and unique physicochemical properties. This review summarizes the latest progresses of MXene-based materials for supercapacitors and micro-supercapacitors. First, state-of-the-art structural engineering strategies for the construction of novel MXene-based electrodes are highlighted, as the electrochemical performance of MXenes is influenced by their structure, such as interlayer spacing and surface functional group density. Furthermore, the charge storage mechanisms of MXene-based electrodes in different electrolytes are discussed to stimulate further design and development of tailored materials for high-performance devices. Moreover, different device fabrication technologies are summarized and the achievements of specific device geometries (e.g. , fiber-shape, planar-type, and three-dimensional devices) containing MXene-based materials are critically reviewed. Finally, perspectives and outlook for the development of high-performance MXene-based electrodes in terms of material engineering, performance improvement and device innovation are provided, clearly indicating research directions for next-generation advanced energy storage devices. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 Co3O4‐quantum dots (Co3O4 QDs). The Co3O4 QDs are distributed in the pores of the electrode surface, and the insertion of Co3O4 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 0.108 mW 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. [ABSTRACT FROM AUTHOR]

The simple and eco‐friendly preparation of microsupercapacitor remains a great challenge. Here are presented the preparation and the characterizations of an all‐solid symmetric micro‐supercapacitor based on a new composite formed of highly ordered graphene sheets due to the presence of polydopamine between the layers, which present a d‐spacing of 0.356 nm. This graphene‐polydopamine composite is prepared by electroreduction of graphene oxide (GO) followed by the electrooxidation of dopamine added into the initial solution, i.e., after GO reduction. In Na2SO4 solution, this composite material shows excellent capacitance and stability even at a high scan rate (2 V s−1) and a very low relaxation time (τ0) of 62 ms. This value is in very good agreement with the high transfer kinetic and low transfer resistance values of the ions implied in the charge storage process (Na+·2H2O and Na+) determined by ac‐electrogravimetry. Finally, it is shown that the all‐solid micro‐supercapacitor (interdigitated electrodes obtained using a CO2 laser and Na2SO4/PVA hydrogel) prepared with this new composite delivers a remarkable energy density of 6.36 mWh cm−3 for a power density of 0.22 W cm−3 and exhibits excellent cycling stability (98% of retention after 10 000 cycles at 2 V s−1). [ABSTRACT FROM AUTHOR]

With the rapid development of flexible and portable microelectronics, the extreme demand for miniaturized, mechanically flexible, and integrated microsystems are strongly stimulated. Here, biomass‐derived carbons (BDCs) are prepared by KOH activation using Qamgur precursor, exhibiting three‐dimensional (3D) hierarchical porous structure. Benefiting from unobstructed 3D hierarchical porous structure, BDCs provide an excellent specific capacitance of 433 F g−1 and prominent cyclability without capacitance degradation after 50 000 cycles at 50 A g−1. Furthermore, BDC‐based planar micro‐supercapacitors (MSCs) without metal collector, prepared by mask‐assisted coating, exhibit outstanding areal‐specific capacitance of 84 mF cm−2 and areal energy density of 10.6 μWh cm−2, exceeding most of the previous carbon‐based MSCs. Impressively, the MSCs disclose extraordinary flexibility with capacitance retention of almost 100% under extreme bending state. More importantly, a flexible planar integrated system composed of the MSC and temperature sensor is assembled to efficiently monitor the temperature variation, providing a feasible route for flexible MSC‐based functional micro‐devices. [ABSTRACT FROM AUTHOR]

Miniaturization of supercapacitors offers an attractive route to the fabrication of portable and wearable electronic devices, but still suffers from limited areal capacity. Herein, we utilize a facile stamping approach to fabricate flexible paper-based micro-supercapacitors that are based on the ternary composite containing polyaniline (PANI) as patterned interdigital electrode materials. The ternary composites are composed of PANI, metal-organic frameworks derived from porous carbon (C800) and low-oxidized graphene (LGE). Benefiting from the synergy of C800 and LGE, the electrical conductivity and capacitance retention of PANI composites were enhanced, obviously. The resultant composites displayed high areal capacitance of 162 mF cm−2, remarkable energy density of 24.9 μWh·cm−2, 90 % capacitance over thousands of charge-discharge cycles and excellent stability against bending even at large angles.

Abstract The simple and eco‐friendly preparation of microsupercapacitor remains a great challenge. Here are presented the preparation and the characterizations of an all‐solid symmetric micro‐supercapacitor based on a new composite formed of highly ordered graphene sheets due to the presence of polydopamine between the layers, which present a d‐spacing of 0.356 nm. This graphene‐polydopamine composite is prepared by electroreduction of graphene oxide (GO) followed by the electrooxidation of dopamine added into the initial solution, i.e., after GO reduction. In Na2SO4 solution, this composite material shows excellent capacitance and stability even at a high scan rate (2 V s−1) and a very low relaxation time (τ0) of 62 ms. This value is in very good agreement with the high transfer kinetic and low transfer resistance values of the ions implied in the charge storage process (Na+·2H2O and Na+) determined by ac‐electrogravimetry. Finally, it is shown that the all‐solid micro‐supercapacitor (interdigitated electrodes obtained using a CO2 laser and Na2SO4/PVA hydrogel) prepared with this new composite delivers a remarkable energy density of 6.36 mWh cm−3 for a power density of 0.22 W cm−3 and exhibits excellent cycling stability (98% of retention after 10 000 cycles at 2 V s−1).

The development of scientific and technological foundations for the creation of high-performance energy storage devices is becoming increasingly important due to the rapid development of microelectronics, including flexible and wearable microelectronics. Supercapacitors are indispensable devices for the power supply of systems requiring high power, high charging-discharging rates, cyclic stability, and long service life and a wide range of operating temperatures (from −40 to 70 °C). The use of printing technologies gives an opportunity to move the production of such devices to a new level due to the possibility of the automated formation of micro-supercapacitors (including flexible, stretchable, wearable) with the required type of geometric implementation, to reduce time and labour costs for their creation, and to expand the prospects of their commercialization and widespread use. Within the framework of this review, we have focused on the consideration of the key commonly used supercapacitor electrode materials and highlighted examples of their successful printing in the process of assembling miniature energy storage devices. [ABSTRACT FROM AUTHOR]

The exceptional properties of 2D transition metal carbides and nitrides (MXene) have led to numerous promising applications. However, the performance of MXene is often dependent on the size of the flakes, and obtaining large‐sized, high‐quality MXene flakes remains challenging. Herein, a carbon nanotube (CNT)‐assisted exfoliation strategy is introduced, which significantly improves the yield of large‐flake MXene while entirely transforming the centrifugation residues into small‐flake MXene, resulting in waste‐free synthesis of MXene. The average size of the obtained MXene flakes can reach over 10 and 0.7 µm for the two populations, respectively. Additionally, the capacitive performance of MXene can be greatly enhanced with a small amount of CNTs. As a proof of concept, a planar interdigital micro‐supercapacitor with heterogeneous layers assembled by large‐ and small‐flake MXene simultaneously exhibits outstanding synergistic enhancement in volumetric capacitance (1072 F cm⁻3) and energy density (53.5 mWh cm⁻3). This CNT‐assisted method provides explicit directions for achieving the ideal utilization of MXene, improving the yield of large flakes while making judicious use of waste, to meet specific application needs. [ABSTRACT FROM AUTHOR]

Fabrication of miniature‐integrated devices combining energy harvester, energy storage, and various sensors via simple, fast, and efficient ways is strongly desired for the practical application of integrated smart systems. Herein, this work presents a simple one‐step laser scribing method to prepare an all MXene‐based seamlessly integrated system with integrated wireless charging coil, micro‐supercapacitor, and photodetector in a small area of only 1.78 cm2. All the three modules in the integrated system are composed entirely of Ti3C2Tx MXene and are connected with highly conductive MXene wires without additional welding or assembling operation. The energy is first received by the wireless charging coil and then stored in the Zn‐ion micro‐supercapacitor, which is subsequently used to drive the surface‐modified (dodecyl triethoxysilane) DCTES‐MXene‐based photodetector, thus realizing the complete energy cycles. This work conceptually illustrates a simple method for designing and preparing integrated multifunctional wearable devices. [ABSTRACT FROM AUTHOR]

Micro‐electrochemical energy storage devices (MEESDs) including micro‐supercapacitors (MSCs), micro‐batteries (MBs), and metal‐ion hybrid micro‐supercapacitors (MIHMSCs) are critical components of electronic systems, especially in the expanding field of the Internet of Things (IoT). In recent years, three‐dimensional (3D) printing techniques also known as additive manufacturing (AM) techniques have emerged as promising approaches to overcome the limitations of conventional fabrication procedures. Employing advanced manufacturing techniques to fabricate MEESDs offers potential benefits, including mass production and programmable prototyping. In this review, we provide a comprehensive overview of the recent advancements in the applications of 3D printing techniques for MEESDs such as MBs, MSCs, and MIHMSCs. First, this review discusses the fundamental of micro/nano energy storage devices by 3D printing technology. Further, we examine the critical properties of the printable inks used in these processes. We also highlighted the current developments in 3D printing‐based MEESDs including various types of MBs, pseudocapacitive and electrochemical double‐layer‐based MSCs, and a range of MIHMSCs. Additionally, this review addresses the challenges and future prospects of 3D printing based MEESDs, including material limitations, printing resolution, manufacturing scalability, mechanical properties, and cost. Overall, this review presents a unique and valuable contribution by providing a comprehensive overview of the recent advancements in 3D printing based MEESDs. [ABSTRACT FROM AUTHOR]

The rapid development of smart wearable microdevices has stimulated the urgent demand for micro‐supercapacitors (MSCs) with multiple form factors, however, several factors like conventional bulky stacked geometries, rigid substrates, and complex manufacturing processes have blocked their path toward practical application. Herein, a microfluidics‐assisted fabrication strategy is demonstrated which utilizes capillary action for precisely customising planar MSCs, showing substrate‐free configuration attributed to the use of polyvinyl alcohol hydrogel in both electrolytes and transfer template. Remarkably, the resulting MSCs with highly conductive polymer (PEDOT:PSS)‐based active materials as microelectrodes, exhibit excellent areal capacitance of 21.4 mF cm−2 and noticeable capacitance retention of 88% after 10000 cycles. Furthermore, the substrate‐free MSCs display extraordinary flexibility and remarkable stretchability of 640% strain. Significant serial and parallel integration is demonstrated for boosting voltage and capacitance output, demonstrative of impressive performance uniformity and applicability for different scenarios. Therefore, the exploration of microfluidics‐assisted fabrication is shown to be a reliable strategy for high performance standalone microelectronics with in‐plane configuration. [ABSTRACT FROM AUTHOR]

Two‐dimensional (2D) transition metal carbides, and/or nitrides, so‐called MXenes, have triggered intensive research interests in applications ranging from electrochemical energy storage to electronics devices. Producing these functional devices by printing necessitates to match the rheological properties of MXene dispersions to the requirements of various solution processing techniques. In particular, for additive manufacturing such as extrusion‐printing, MXene inks with high solid fraction are typically required, which is commonly achieved by tediously removing excessive free water (top‐down route). Here, the study reports on a bottom‐up route to reach a highly concentrated binary MXene‐water blend, so‐called MXene dough, by controlling the water admixture to freeze‐dried MXene flakes by exposure to water mist. The existence of a critical threshold of MXene solid content (≈60%), beyond which no dough is formed, or formed with compromised ductility is revealed. Such metallic MXene dough possesses high electrical conductivity, excellent oxidation stability, and can withstand a couple of months without apparent decay, providing that the MXene dough is properly stored at low‐temperature with suppressed dehydration environment. Solution processing of the MXene dough into a micro‐supercapacitor with gravimetric capacitance of 161.7 F g−1 is demonstrated. The impressive chemical and physical stability/redispersibility of MXene dough indicate its great promise in future commercialization. [ABSTRACT FROM AUTHOR]

The development of 3D ceramic pseudocapacitive micro-supercapacitors (pMSCs) with patterned design was greatly hindered by the existing fabrication techniques that requires expensive equipment, harsh manufacturing environments, expensive materials and complicated fabrication processes. Herein, for the first time, one step electric discharge direct writing (EDDW) technique has been developed to fabricate 3D pMSCs, which are composed of Mo-MoO x integrated electrodes with designable patterns. The developed 3D pMSCs exhibited a high capacitance of 49.1 mF cm−2 (Scanning Rate: 5 mV s−1) and achieved a good capacitance retention of 96% after 5000 cycles. Additionally, the 3D pMSCs without adding any conductive additives could be operated up to an extremely high scanning rate of 20 V s−1 and retained a high areal capacitance of 6.3 mF cm−2. This simple, safe, low-cost, binder-free, conductive additive free and environmentally friendly fabrication technique of EDDW opens a new strategy for efficient fabricating different kinds of energy storage devices with designable 3D patterns and improved electrochemical performance. [Display omitted] [ABSTRACT FROM AUTHOR]

In plane micro‐supercapacitors that are miniaturized energy storage components have attracted significant attention due to their high power densities for various ubiquitous and sustainable device systems as well as their facile integration on various flexible/wearable platform. To implement the micro‐supercapacitors in various practical applications that can accompany solid state or gel electrolyte and flexible substrates, ions must be readily transported to electrodes for achieving high power densities. Herein, we show large enhancement in electrochemical properties of flexible, in‐plane micro‐supercapacitor using sharp‐edged interdigitated electrode design, which was simply fabricated through direct laser scribing method. The sharp‐edged electrodes allowed strong electric field to be induced at the corners of the electrode fingers which led to the greater accumulation of ions near the surface of electrode, significantly enhancing the energy storage performance of micro‐supercapacitors. The electric field‐enhanced in‐plane micro‐supercapacitor showed the volumetric energy density of 1.52 Wh L−1 and the excellent cyclability with capacitive retention of 95.4% after 20 000 cycles. We further showed various practicability of our sharp‐edged design in micro‐supercapacitors by showing circuit applicability, mechanical stability, and air stability. These results present an important pathway for designing electrodes in various energy storage devices. [ABSTRACT FROM AUTHOR]

Although MnO2 has been intensively investigated for energy storage, further applications are limited by van der Waals force‐triggered self‐aggregation that always leads to poorly exposed active sites and compromised reaction dynamics, especially under high‐mass‐loading conditions. Herein, by synergistically coupling interfacial modulation with the Kirkendall effect, this work achieves in situ topological structure reorganization of MnOOH toward the high‐aspect‐ratio MnO2 heterostructure (Heter‐MnO2) with fully exposed active sites, which is ready to assemble into self‐supporting high‐mass‐loading film (30 mg cm−2) with restrained self‐aggregation. Theoretical calculation and dynamics analysis results demonstrate the generation of the built‐in field within the heterostructure, thus enhancing the electronic‐transfer and ionic‐adsorption/transport rates. As such, the 30 mg cm−2 Heter‐MnO2 electrode achieves a superior areal capacitance of 4762 mF cm−2 at 1 mA cm−2 and a sound rate performance (79% at 100 mA cm−2) comparable to those of low‐mass‐loading/thin‐film electrodes. As a proof of concept, the fabricated planar interdigital quasi‐solid‐state symmetric micro‐supercapacitor (MSC) based on the Heter‐MnO2 electrode can deliver a remarkable areal capacitance of 181 mF cm−2 and a considerable volumetric energy density of 10.3 mWh cm−3. This methodology highlights the promise of surface/interface chemistry modulation for the configuration of easy‐to‐integrate hierarchical nanostructures to better meet practical energy applications. [ABSTRACT FROM AUTHOR]

Despite the ever‐growing interest in micro‐supercapacitors (MSCs) as a promising power source for microelectronics, their low areal energy density has plagued practical applications. Herein, accordion foldable MSCs (af‐MSCs) are presented as a cell architectural strategy in contrast to traditional material‐driven approaches. The constituent unit cells of an in‐plane MSC array are compactly stacked in a confined device footprint via accordion folding. Decoupling the energy storage (MSC cells) and folding section (electrical interconnection between the cells) in the MSC array, in combination with neutral plane‐controlled flexible hydrophobic cellulose nanofiber (CNF) substrates, enables the realization of the af‐MSCs. The af‐MSCs achieve high areal integration density with a fill factor of 81.1% and on‐demand (in‐series/in‐parallel) cell configurations owing to the microscale direct‐ink–writing of rheology‐tuned MSC cell components on the CNF substrates. The af‐MSC with a miniaturized footprint (22.75 mm2) achieves exceptional areal electrochemical performances (areal energy density of 89.2 µWh cm−2), which exceed those of previously reported in‐plane MSCs. [ABSTRACT FROM AUTHOR]

This study reports a sustainable approach for developing electrodes for microsupercapacitors. This approach includes the synthesis of TiO2 nanoparticles via a green sol–gel method and the deposition of thin films of that electrochemically active material on three-dimensional (3D) Si substrates with a high area enlargement factor (AEF) via a simple, fast, and inexpensive spin-coating pathway. The thickness of the film was first optimized via its deposition over two-dimensional (2D) substrates to achieve high capacitances to provide high energy density but also to deliver a good rate capability to ensure the power density required for a supercapacitor device. A film thickness of ~120 nm realizes the best compromise between the electronic/ionic conductivity and capacitance in a supercapacitor device. Such layers of TiO2 were successfully coated onto 3D microstructured substrates with different architectures, such as trenches and pillars, and different aspect ratios. The spin-coating-based route developed here has been established to be superior as, on the one hand, a conformal deposition can be achieved over high AEF subtracts, and on the other hand, the 3D electrodes present higher surface capacitances than those obtained using other deposition techniques. The rate capability and appreciable cyclability ensure a reliable supercapacitor behavior. [ABSTRACT FROM AUTHOR]

Abstract Owing to high power density and long cycle life, micro‐supercapacitors (MSCs) are regarded as a prevalent energy storage unit for miniaturized electronics in modern life. A major bottleneck is achieving enhanced energy density without sacrificing both power density and cycle life. To this end, designing electrodes in a “smart” way has emerged as an effective strategy to achieve a trade‐off between the energy and power densities of MSCs. In the past few years, considerable research efforts have been devoted to exploring new electrode materials for high capacitance, but designing clever configurations for electrodes has rarely been investigated from a structural point of view, which is also important for MSCs within a limited footprint area, in particular. This review article categorizes and arranges these “smart” design strategies of electrodes into three design concepts: layer‐by‐layer, scaffold‐assisted and rolling origami. The corresponding strengths and challenges are comprehensively summarized, and the potential solutions to resolve these challenges are pointed out. Finally, the smart design principle of the electrodes of MSCs and key perspectives for future research in this field are outlined.

Recent researches in the development of in-plane micro-supercapacitor (MSC) have been dedicated to advancing its energy density in a finite storage area. However, the low ion-accessible surface area of plane electrode material has been the bottleneck limiting the energy output of MSC. Herein, we design a stable ionic liquid (IL)-MXene microemulsion system in virtue of tween-20 (TW20), gathering IL-TW20 microdroplets around MXene nanosheets. The microemulsion can adhere on the current collector and form the dense MXene-TW20-IL film. The IL as spacer and electrolyte is retained in the interlamination of MXene with the elimination of the TW20 during heat treatment, which enlarges the ion-accessible surface area of the MXene electrode. Thus, the MSC based on the flexible MXene-IL film exhibits a high areal capacitance (44.6 mF·cm−2), a high areal and volumetric energy density (50.7 µW·h·cm−2 and 39 mW·h·cm−3), surpassing most of the reported MXene-based MSCs. And the MSC unit can be arbitrarily integrated in terms of various energy and voltage requirements. For instance, the integrated array with thirty MSC units in series realizes a high voltage output of 90 V, widening the range of application in next-generation microelectronic devices. [ABSTRACT FROM AUTHOR]