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In this work, we demonstrate a facile, rational and novel strategy to assemble micro-supercapacitors (MSCs) via employing laser-induced graphene (LIG) microelectrodes and sodium alginate/polyacrylamide hydrogel electrolytes soaked in sulfuric acid solution (SA/PAAM-H 2 SO 4). The microelectrodes are conductive graphene materials with porous structure that use laser direct writing technology to carbonize insulating polyimide (PI) sheets. The importance of good wetting of the electrode material by the electrolyte on the performance of the device is explained. There is good compatibility and interfacial contact between electrode and electrolyte. Impressively, the SA/PAAM-H 2 SO 4 hydrogel electrolyte with high ionic conductivity (574.7 mS cm−1) also exhibit good water retention capability and performs normally even after 60 h of exposure to air. The capacitance of LIG-MSCs based on SA/PAAM-H 2 SO 4 hydrogel is comparable to that of PVA/H 2 SO 4 hydrogel. The LIG-MSCs exhibit high areal capacitance of 7.12 mF cm−2 and outstanding cycling stability. Moreover, our LIG-MSCs displays excellent mechanical flexibility and stable performance, the capacitance is almost unaffected even in highly bent states and during continuously hammering. Furthermore, the LIG-MSCs can be arbitrarily connected in series and in parallel without the requirement of metal-based interconnects for high-voltage and high-capacitance output. Our design strategy aims to provide new insights for the development of flexible MSCs. [Display omitted] • A facile, rational and novel method to assemble micro-supercapacitors is proposed. • Direct laser writing produces interdigitated microelectrodes with low-resistance. • The hydrogel has excellent water retention and good compatibility with electrode. • Flexible micro-supercapacitors with good electrochemical properties are obtained. [ABSTRACT FROM AUTHOR]

Abstract We demonstrate the successful fabrication of all-solid-state flexible micro-supercapacitors (μSCs) on commercial polyethylene terephthalate (PET) sheet using a commercial laser printer. The interdigitated in-planar electrodes of the μSC are fabricated by commercial toner cartridge and their self-aligned stacking configurations are made by depositing Pt thin films and hydrous ruthenium oxide (RuO·xH 2 O, hRuO 2) layers on the PET sheets using a post-low-temperature annealing process. The μSC cells can be combined in parallel or series by an arbitrary printing process operated on a personal computer, thereby avoiding unnecessary external connections and improving the capacitive behavior. The fabricated hRuO 2 -based μSCs exhibit excellent electrochemical-energy storage, along with ultrahigh volumetric power density (73460 mW cm−3) and energy density (24.9 mWh cm−3). This facile and simplified strategy constructs μSCs with tailored self-aligned electrodes of arbitrary design, excellent mechanical stability, and high flexibility. Therefore, it offers a high-productivity, low-cost, photolithography-free microfabrication of μSCs for microscale supercapacitor applications. Graphical abstract Image 1 Highlights • Laser printer patterned sacrificed layer to prepare the interdigitated in-planar pattern. • Hydrous ruthenium oxides synthesized on PET to fabricate the flexible micro SCs. • The all-solid-state micro SCs showed excellent volumetric power and energy densities. [ABSTRACT FROM AUTHOR]

Abstract Micro-supercapacitors are a kind of state-of-the-art energy storage devices and have great potential to be developed in portable and wearable electronics. Here, we report a novel strategy for scalable fabrication of all-printed solid-state micro-supercapacitors with multilayer structure via multi-material 3D printing technique. To obtain electrode materials, we synthesize polypyrrole/polyaniline coaxis nanotubes by utilizing the self-degraded template polymerization method and in situ electrochemical polymerization. The as-prepared aqueous composite electrode ink shows significant shear thinning behavior and excellent processability: a complex electrode patterning with 484 retractions was proved. In addition, the inks are well-adapted to various substrates (paper, texitle, plastic film etc), allowing the device to be printed onto different substrates, even directly on the desired surface. As a conceptual exhibition, we design two schemes of in situ fabricated energy storage devices to meet the ever-changing energy needs and expand the application range of micro-supercapacitors. The transferable tape-type micro-supercapacitors can be stuck to any surfaces where energy is needed immediately. The in situ fabricated wearable micro-supercapacitor on lab-gown shows promising performance and excellent flexibility. Graphical abstract Image 1 Highlights • Printed micro-supercapacitors were fabricated on different substrates. • Successful synthesis of new-type polypyrrole/polyaniline coaxis nanotubes. • A complex 3D printed energy storage device with 484 retractions was built. • Tape-type micro-supercapacitors were developed for easy transferable electronics. • An in situ fabricated micro-supercapacitor on lab-gown for wearable applications. [ABSTRACT FROM AUTHOR]

Currently, the exploration of energy conversion/storage devices for harsh environment applications with satisfying property is still a grand challenge. In the present work, the highly robust and flexible micro-supercapacitors (MSCs) based on (Ta, Ti, Nb)C nanowires (NWs) and activated carbon hybrid structures as the electrode materials are reported. Given to the inherent advantages of (Ta, Ti, Nb)C NWs, e.g. stable electrical conductivity and mechanical flexibility, and abundant porous structure stemed from cross-linked (Ta, Ti, Nb)C NWs and bamboo-based active carbon, the as-prepared (Ta, Ti, Nb)C/C-MSCs show high electrochemical performance, mechanical stability, and temperature tolerance over a wide temperature range. Remarkably, the as-constructed (Ta, Ti, Nb)C/C-MSCs can endure the sub-ambient temperature operation down to −50 °C with a capacitance retention of 82.7% and present capacitance retention up to 97.7% over one cycle of cooling and heating between −50 and 25 °C, compared with that at room temperature. Even under progressive variation in temperatures ranged between 25 and -50 °C, the capacitance retention keeps up to 92.6% over 9000 cycles, representing their promising to be serviced as highly robust MSCs against harsh low-temperature conditions for energy storage. • Medium-entropy carbide (Ta, Ti, Nb)C NWs are synthesized via carbothermal method. • (Ta, Ti, Nb)C/C-MSCs present excellent flexibility and superior cycling stability. • (Ta, Ti, Nb)C/C-MSCs show stable stored energy performance under low-temperature. [ABSTRACT FROM AUTHOR]

Fabric-based micro-supercapacitors have a great potential in the field of wearable flexible energy storage devices because of the controllable volume, changeable structure, intrinsic stretchability/bendability/foldability, easy integration and washability resistance. The design and construction of energy storage devices with complex structure and function of different dimensions have great influence on the flexible energy storage mechanism and electrochemical performance. One-dimensional MSCs with the advantage of good formability, small size, high flexiblity and easy capability of multi-device integration are useful to increase energy density. However, they cannot be used alone due to their limited loading of electroactive materials. In addition, their spinnability and mechanical strength need to be improved to achieve large-scale forming and manufacturing. Two-dimensional MSCs with short ion diffusion distances, improved in-plane charge transport kinetics and tunable surface/interlayer structures tend to enhance reactivity. However, the high aspect ratio of two-dimensional structure and excessive loading of pseudocapacitive materials weaken surface mass transfer and electron transport, reducing the material utilization and overall multiplicity of characteristics. Three-dimensional MSCs take into account the joint improvement of loading per unit area, conductivity and electrochemical activity of pseudo capacitive materials to combine energy/power enhancement and achieve rapid/high electrical energy storage. Also, the difficult conformal deposition of active substances and complex manufacturing process limit their wearable application. The energy storage mechanisms, construction methods, electrochemical properties and low-cost/scale-up preparation strategies for 1D/2D/3D micro-supercapacitors from the perspective of textiles aimed at their structural types and parameters are reviewed here and the key issues and promising research directions for the development of fabric-based micro-supercapacitors are proposed. • Construction methods of 1D/2D/3D fabric-based wearable MSCs. • Fabric-based MSCs are stretchable/foldable, highly integrated and wash/rub resistant. • 3D MSCs significantly increase the energy capacity per unit area of microelectrodes. • Fabric types and parameters directly affect electrochemical performance of MSCs. [ABSTRACT FROM AUTHOR]

Carbide derived carbons (CDCs) are promising materials for preparing integrated micro-supercapacitors, as on-chip CDC films are prepared via a process fully compatible with current silicon-based device technology. These films show good adherence on the substrate and high capacitance thanks to their unique nanoporous structure which can be fine-tuned by adjusting the synthesis parameters during chlorination of the metallic carbide precursor. The carbon porosity is mostly related to the synthesis temperature whereas the thickness of the films depends on the chlorination duration. Increasing the pore size allows the adsorption of large solvated ions from organic electrolytes and leads to higher energy densities. Here, we investigated the electrochemical behavior and performance of on-chip TiC-CDC in ionic liquid solvent mixtures of 1-ethyl-3-methylimidazolium tetrafluoroborate (EMIBF 4 ) diluted in either acetonitrile or propylene carbonate via cyclic voltammetry and electrochemical impedance spectroscopy. Thin CDC films exhibited typical capacitive signature and achieved 169 F cm −3 in both electrolytes; 65% of the capacitance was still delivered at 1 V s −1 . While increasing the thickness of the films, EMI + transport limitation was observed in more viscous PC-based electrolyte. Nevertheless, the energy density reached 90 μW h cm −2 in 2M EMIBF 4 /ACN, confirming the interest of these CDC films for micro-supercapacitors applications. [ABSTRACT FROM AUTHOR]

The development of portable electronics puts forward new challenges for miniaturization of energy storage devices to match them. Micro-supercapacitors (MSCs) with significant advantages have attracted increasing attention recently. MSCs are usually encapsulated in practical use to ensure a stable performance due to uncertainty of electrolyte in open system, even quasi-solid electrolyte such as hydrogels electrolyte which gradually dries once exposed to air for a few hours or freezes in cold environment. Herein, we demonstrate a high water-retaining and antifreeze micro-supercapacitor (AW-MSC) without encapsulation adaptable to all-weather for the first time. Ion conductive hydrogel through copolymerizing sulfobetaine methacrylate and sodium acrylate acts as electrolyte after soaking by lithium chloride aqueous solution. The resultant polyelectrolyte exhibits an outstanding water holding capacity even in simulated dry desert climate (lower than 20% relative humidity) and high freeze resistance in cold environment (under −20 °C). Consequently, the assembled AW-MSC without encapsulation exhibits the capacitance retention above 85.0% after 32 days in either severe cold, drought, or high heat environments, superior to those MSCs-based on hydrogels reported previously. In various harsh simulation scenarios, the AW-MSC connected in series can steadily power an electronic watch for a long time. • A micro-supercapacitor without encapsulation for all-weather is demonstrated. • The electrolyte exhibits an outstanding water-holding capacity and freeze resistance. • It shows capacitance retention above 85% after 32 days in harsh environment. [ABSTRACT FROM AUTHOR]

The re-stacking of graphene sheets leads to the far lower areal capacitance and energy density of the graphene-based micro-supercapacitors (MSC) than the expected. Herein, to solve this issue, a novel 0D/2D porous carbon integrated architecture (PC-IA) is ingeniously in-situ constructed by a two-step fabrication strategy, which is realized by the synthesis of 0D/2D TiC integrated architecture in a molten salt-containing Ti environment based on graphene nanosheets (GNS) as the template followed by high-temperature chlorination. Interestingly, the newly synthesized PC-IA shows huge advantages compared with the original GNS, such as higher specific surface area, more abundant porosity, better wettability to electrolyte and more effective ion channels in the c-axis direction, etc. As a result, when PC-IA is used as the electrode material, the fabricated MSC exhibits excellent electrochemical performances, such as ultrahigh areal capacitance of 70.12 mF cm−2 and high energy density of 9.48 μWh cm−2. Moreover, the fabricated MSC also behaves excellent mechanical flexibility and can be easily adjusted in the voltage and capacitance by connecting multiple MSC devices in series and parallel. Hence, this work opens up a new way for the reasonable design of carbon-based electrodes, which has broad application prospects in various flexible/wearable electronic devices. [Display omitted] • A unique 0D/2D porous carbon integrated architecture (PC-IA) is first synthesized. • The PC-IA behaves high specific surface area and effective ion channels. • The micro-supercapacitor (MSC) is fabricated by mask-assisted vacuum filtration. • The PC-IA-based MSC exhibits ultrahigh areal capacitance and energy density. [ABSTRACT FROM AUTHOR]

Silicon nanotrees (SiNTrs) have been grown by Chemical Vapor Deposition (CVD) via gold catalysis and a three steps process: trunks and branches growth are separated by a new gold catalyst deposition. The influence of growth conditions and the second gold catalyst deposition method on SiNTrs morphology are investigated. SiNTrs based electrodes show a capacitive behavior and better capacitance than the corresponding silicon nanowires (SiNWs) electrode. Electrode capacitance is increased up to 900 µF cm-2, i.e. 150 fold higher than for bulk silicon. Micro-supercapacitors with SiNTrs electrodes have a remarkable stability (only 1.2% loses of their initial capacitance after more than one million cycles). The use of an ionic liquid based electrolyte leads to a high maximum power density (around 225 mW cm-2) which is competitive with Onion Like Carbon based micro-supercapacitors. [ABSTRACT FROM AUTHOR]

Abstract: We have investigated the influence of the geometric configuration of planar interdigitated micro-supercapacitors on their specific energy and specific power. The theoretical values of the Equivalent Series Resistance (ESR) were deduced from an analytical expression of the cell constant К, and compared with experimental Electrochemical Impedance Spectroscopy (EIS) measurements performed on gold current collectors with different interdigitated patterns (varying the interspace, width, length and number of interdigitated fingers). It is shown that the configuration plays a key-role on the electrochemical performances of the device, and that the specific power is enhanced by a reduction of the interspace. Based on these results, we have realized hydrous RuO2-based thin films electrochemical capacitors integrated on silicon with an optimized configuration, using conventional photolithography techniques and electrodeposition from an aqueous chloride solution. The micro-supercapacitor is characterized by a cell capacitance of 0.2 mF cm−2 per footprint area, and was able to cycle at a scan rate of 100 V s−1. [Copyright &y& Elsevier]

Abstract: Interdigitated on-chip micro-supercapacitors based on Carbide Derived Carbon (CDC) films were fabricated and tested. A titanium carbide (TiC) film was patterned and treated with chlorine to obtain a TiC derived carbon (TiC–CDC) film, followed by the deposition of two types of current collectors (Ti/Au and Al) using standard micro-fabrication processes. CDC based micro-supercapacitors were electrochemically characterized by cyclic voltammetry and impedance spectroscopy using a 1 M tetraethylammonium tetrafluoroborate, NEt4BF4, in propylene carbonate (PC) electrolyte. A capacitance of 0.78 mF for the device and 1.5 mF cm−2 as the specific capacitance for the footprint of the device was measured for a 2 V potential range at 100 mV s−1. A specific energy of 3.0 mJ cm−2 and a specific power of 84 mW cm−2 were calculated for the devices. These devices provide a pathway for fabricating pure carbon-based micro-supercapacitors by micro-fabrication, and can be used for powering micro-electromechanical systems (MEMS) and electronic devices. [Copyright &y& Elsevier]

Abstract: Carbon-based micro-supercapacitors dedicated to energy storage in self-powered modules were fabricated with inkjet printing technology on silicon substrate. An ink was first prepared by mixing an activated carbon powder with a PTFE polymer binder in ethylene glycol stabilized with a surfactant then deposited by inkjet on patterned gold current collectors with the substrate heated at 140°C in order to assure a good homogeneity. Electrochemical micro-capacitors with electrodes in an interdigital configuration were fabricated, and characterized using electrochemical techniques in 1M Et4NBF4 propylene carbonate electrolyte. These micro-devices show an excellent capacitive behavior over a wide potential range of 2.5V for a cell capacitance of 2.1mFcm−2. The newly developed technology will allow the integration of the storage device as close as possible to the MEMS-based energy harvesting device, minimizing power losses through connections. [Copyright &y& Elsevier]

Functional electrodes with unique ion storage and rapid ion migration properties through microstructure and chemical-doping modulation are always crucial for rapid charging devices such as micro-supercapacitors (MSCs). In this work, proton exchange membrane named phosphoric acid (PA) doped polybenzimidazole membrane (PA-PBI) is studied as a unique precursor for assembling laser induced graphene (LIG) based electrodes (PA-PBI-LIG) in MSCs, toward the enhancement of energy storage performance via simultaneous heteroatoms doping, microporous structure improving and proton-conducting substrate introducing. By tuning PA concentration, the microporous structures perform adjustable specific surface area from 20.2 to 384.46 m2 g−1, thereby enhancing changeable capacitance from 2.44 mF cm−2 to 149 mF cm−2, with highest specific energy density of 20.7 μWh cm−2. To understand the mechanism, PA and the initiated free radicals are proposed to motivate microporous formation and heteroatoms doping during laser fabrication via unique laser absorption properties of PA. Additionally, PA-PBI substrates work synergistically on ions migration with microporous graphene, potentially promoting energy storage efficiency especially in the acid-based electrolyte. Overall, the raised PA-PBI-LIG electrodes simultaneously promote microporous, heteroatomic and multilayered graphene with proton conducting substrate, which show great potentials in micro energy storage devices. [Display omitted] • Phosphoric acid involved PBI-LIG improve micro pores, heteroatoms & ions transfer. • Phosphoric acid tunes the LIG specific surface area from 384.46 to 20.2 m2 g−1. • The optimized capacitance and energy density reach 149 mF cm−2 and 20.7 μWh cm−2. [ABSTRACT FROM AUTHOR]

Layered metal chalcogenide are emerging candidate materials for high-performance supercapacitor electrode materials. However, poor conductivity resulting from low carrier mobility limits the further improvement of supercapacitor performance based on layered transition metal chalcogenide. Here we prepare flexible interdigital all-solid-state micro-supercapacitors (MSCs) based on layered III-VI metal chalcogenides InSe with high carrier mobility. When the mass ratio of InSe nanosheets to graphene is 1:2, the best performing MSCs exhibit high areal and volumetric capacitances up to 0.72 F cm−2 and 1.79 F cm−3. Moreover, the MSCs show outstanding long-life cycling stability (retaining 93.6% of specific capacitances after 10000 cycles) and excellent mechanical flexibility (remaining capacitance at 98.2% after 2000 cycles under bending angle of 90°). The MSCs have an outstanding power density of 7.31 W cm−3 and a high energy density of 0.48 mWh cm−3. • InSe nanosheets are used as electrode materials with high performance of MSCs. • MSCs based on InSe-Graphene has a long-life cycling stability. • MSCs based on InSe-Graphene has mechanical flexibility. [ABSTRACT FROM AUTHOR]

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

The rapid growth of portable and wearable electronics have greatly stimulated simplified fabrication of energy storage devices, from which micro-supercapacitors (MSCs) are an ideal power source, due to high power density and long lifetime. However, the development of a simple and cost-effective procedure towards the fabrication of high-performance MSCs is still a challenge. To this end, here we report a self-patterned stamping process through pre-designed patterns (Fractal & Interdigital) on parafilm® coated polyethylene terephthalate (PET) substrate for the fabrication of a flexible and planar MSC. The imprinted patterns on parafilm® are filled by graphene oxide (GO)/carbon aerogel/MnO 2 hybrid paste as a binder and additive-free active material, followed by GO reduction through a safe, low cost, and effective procedure using nascent hydrogen. In contrast to the hydrazine based reduction method, nascent hydrogen affords the integrity and stability to the active material without any peeling off from the substrate, with low ohmic resistance. The prepared MSCs display large capacitance and energy density of 8.7 mF cm−2 (43.66 F cm−3) and 6 mWh cm−3 for Interdigital electrode and 14.2 mF cm−2 (71.34 F cm−3) and 9.9 mWh cm−3 for Fractal electrode, respectively. Furthermore, the MSC displays capacitance retention of 85% after 25,000 cycles. The presented procedure is a simple and cost-effective strategy towards the fabrication of flexible MSCs with state-of-the-art performance. Image 1 • Using Parafilm®-covered PET afforded good flexibility and electrode adherence. • Carbon aerogel added to graphene based active material enhanced the performance. • Good integrity and performance was realized by reduction with nascent hydrogen. [ABSTRACT FROM AUTHOR]

Developing patterning techniques with practicability, cost-effectiveness and safety are essential for shape-confirmable integrated energy storage devices. Herein we design a novel flash foam stamp-inspired technique for simple fabrication of flexible high energy in-plane micro-supercapacitors based on interdigital electrodes of self-depositing electrochemically exfoliated graphene on paper substrates. This technique is an attractive and novel bottom-up microfabrication technology due to its advantages of simplicity and low-cost. These novelly developed all-solid-state, paper-based in-plane graphene micro-supercapacitors exhibit excellent electrochemical performances, such as high area specific capacitance of ∼4.02 mF cm−2 and excellent cycling stability (95.6% retention at 0.08 mA cm−2 for 5000 cycles). And these solid-state flexible micro-supercapacitors are observed non-obvious structural change and loss of performance under bending state, suggesting remarkable flexibility and mechanical stability. Therefore, such all-solid-state, flexible paper-based graphene micro-supercapacitors can potentially be used for wearable and portable electronics. Image 1 • Flash foam stamp-inspired technique to realize paper-based graphene supercapacitors. • Electrochemical exfoliation of graphite foil to fabricate graphene nanosheets. • Graphene supercapacitors exhibit high area specific capacitance of ∼4.02 mF cm−2. • Paper-based supercapacitors have stable electrochemical properties under bending. [ABSTRACT FROM AUTHOR]