Architectural design and optimization of internal structures in 3D printed electrodes for superior supercapacitor performance.

The architecture of electrodes plays a pivotal role in the transfer and transportation of charges during electrochemical reactions. Selecting optimal electrode materials and devising well-conceived electrode structures can substantially enhance the electrochemical performance of devices. This manuscript leverages 3D printing technology to fabricate asymmetric supercapacitor devices featuring regular layered configurations. By investigating the impact of various materials on the internal architecture of printed electrodes, we establish a stratified electrode structure with an orderly arrangement, thereby significantly improving asymmetric charge transfer between electrodes. The application of 3D printing technology to construct electrode structures effectively mitigates the agglomeration of electrode materials. The 3D-printed VCG//MXene devices demonstrate exceptional areal capacitance (205.57 mF cm-2) and energy density (60.03 µWh cm-2), with a power density of 0.174 W cm-2. Consequently, selecting appropriate materials for fabricating printable electrode structures and achieving efficient 3D printing is anticipated to offer novel insights into the construction and enhancement of miniature asymmetric micro-supercapacitor (MSCs) devices.

3D Printing of Hierarchical Structures Made of Inorganic Silicon-Rich Glass Featuring Self-Forming Nanogratings.

Hierarchical structures are abundant in nature, such as in the superhydrophobic surfaces of lotus leaves and the structural coloration of butterfly wings. They consist of ordered features across multiple size scales, and their advantageous properties have attracted enormous interest in wide-ranging fields including energy storage, nanofluidics, and nanophotonics. Femtosecond lasers, which are capable of inducing various material modifications, have shown promise for manufacturing tailored hierarchical structures. However, existing methods, such as multiphoton lithography and three-dimensional (3D) printing using nanoparticle-filled inks, typically involve polymers and suffer from high process complexity. Here, we demonstrate the 3D printing of hierarchical structures in inorganic silicon-rich glass featuring self-forming nanogratings. This approach takes advantage of our finding that femtosecond laser pulses can induce simultaneous multiphoton cross-linking and self-formation of nanogratings in hydrogen silsesquioxane. The 3D printing process combines the 3D patterning capability of multiphoton lithography and the efficient generation of periodic structures by the self-formation of nanogratings. We 3D-printed micro-supercapacitors with large surface areas and a high areal capacitance of 1 mF/cm2 at an ultrahigh scan rate of 50 V/s, thereby demonstrating the utility of our 3D printing approach for device applications in emerging fields such as energy storage.

Wafer-level heterogeneous integration of electrochemical devices and semiconductors for a monolithic chip.

Micro-scale electrochemical devices, despite their wide applications and unique potential to achieve 'More than Moore's law', face significant limitations in constructing functional chips due to their inability to integrate with semiconductors. In this study, we propose an electrochemical gating effect and material work function matching criteria, and thus establish the first heterogeneous integration theory for electrochemical devices and semiconductors. Accordingly, we create a novel 3D integration architecture and CMOS-compatible fabrication methodology, including optimizing individual devices, electron/ionic isolation, interconnection, and encapsulation. As a demonstration, we integrate electrochemical micro supercapacitors with a P-N junction diode rectifier bridge circuit and successfully obtain the first monolithic rectifier-filter chip, which shows a revolutionary volume reduction of 98% compared to non-integrateable commercial products. The chip can provide a stable output with a tiny ripple factor of 0.23% in typical conditions, surpassing the requirements of most applications by more than one order of magnitude. More importantly, all the processes are suitable for mass production in standard foundries, allowing ubiquitous applications of electrochemistry in integrated electronics.

From Friction to Function: A High-Voltage Sliding Triboelectric Nanogenerator for Highly Efficient Energy Autonomous IoTs and Self-Powered Actuation.

An advanced energy autonomous system that simultaneously harnesses and stores energy on the same platform offers exciting opportunities for the near-future self-powered miniature electronics. However, achieving optimal synchronization between the power output of an energy harvester and the storage unit or integrating it seamlessly with real-time microelectronics to build a highly efficient energy autonomous system remains challenging. Herein, a unique bimetallic layered double hydroxide (LDH) based tribo-positive layer is introduced for a high-voltage sliding triboelectric nanogenerator (S-TENG) with an output voltage of ≈1485 V and power output of 250 µW, respectively. To demonstrate the potential of a self-charging power system, S-TENG is integrated with on-chip micro-supercapacitors (MSCs) as a storage unit. The MSC array effectively self-charged up to 4.8 V (within 220s), providing ample power to support micro-sensory systems. In addition, by utilizing the high-voltage output of the S-TENG, the efficient operation of electrostatic actuators and digital microfluidic (DMF) systems driven directly by simple mechanical motion is further demonstrated. Overall, this work can provide a solid foundation for the advancement of next-generation energy-autonomous systems.

Ballistic-aggregated Carbon Nanofoam in Target-side of Pulsed Laser Deposition for Energy Storage Applications.

In pulsed laser deposition, along the traditionally exploited deposition on the front-side of the plasma-plume, a coating forms on the surface of the target as well. For reproducibility, this residue is usually cleaned and discarded. Here we instead investigate the target-side coated materials and employ them as a binder-free supercapacitor electrode. The ballistic-aggregated, target-side nanofoam is compact and features a larger fraction of sp2-carbon, higher nitrogen content with higher graphitic-N and lower oxygen content with fewer COOH groups than that of diffusive-aggregated conventional nanofoams. They are highly hydrogenated graphite-like amorphous carbon and superhydrophilic. The resulting symmetric micro-supercapacitor delivers higher volumetric capacitance of 522 mF/cm3 at 100 mV/s and 104% retention after 10000 charge-discharge cycles over conventional nanofoam (215 mF/cm3 and 85% retention) with an areal capacitance of 134 µF/cm2 at 120 Hz and ultrafast frequency response. Utilizing the normally discarded target-side material can therefore enable high performing devices while reducing waste, cost and energy input per usable product. leading towards a greater sustainability on nanomaterials synthesis and deposition techniques.

Sputtered thin film deposited laser induced graphene based novel micro-supercapacitor device for energy storage application.

Pioneering flexible micro-supercapacitors, designed for exceptional energy and power density, transcend conventional storage limitations. Interdigitated electrodes (IDEs) based on laser-induced graphene (LIG), augmented with metal-oxide modifiers, harness synergies with layered graphene to achieve superior capacitance. This study presents a novel one-step process for sputtered plasma deposition of HfO2, resulting in enhanced supercapacitance performance. Introducing LIG-HfO2 micro-supercapacitor (MSC) devices with varied oxygen flow rates further boosts supercapacitance performance by introducing oxygen functional groups. FESEM investigations demonstrate uniform coating of HfO2 on LIG fibers through sputtering. Specific capacitance measurements reveal 6.4 mF/cm2 at 5 mV/s and 4.5 mF/cm2 at a current density of 0.04 mA/cm2. The LIG-HfO2 devices exhibit outstanding supercapacitor performance, boasting at least a fourfold increase over pristine LIG. Moreover, stability testing indicates a high retention rate of 97% over 5000 cycles, ensuring practical real-time applications.

Photon-beam-inducing synthesis of a tunable porous graphene/Ti3C2Txheterostructure for energy conversion-storage system.

Flexible electronic device requires a novel micro-supercapacitors (MSCs) energy conversion-storage system based on two-dimensional (2D) materials to solve the problems of stiffness and complexity. Herein, we report a novel catalytic introduction method of graphene with adjustable porosity by high-energy photon beam. The graphene/Ti3C2Txheterostructure was constructed by electrostatic self-assembly, has a high cycle life (98% after 8000 cycles), energy density (11.02 mWh cm-3), and demonstrate excellent flexible alternating current line-filtering performance. The phase angle of -79.8° at 120 Hz and a resistance-capacitance constant of 0.068 ms. Furthermore, the porous graphene/Ti3C2Txstructures produced by multiple catalytic inductions allowed ions to deeply penetrate the electrode, thereby increasing the stacking density. The special 'pore-layer nesting' graphene structure with adjustable pores effectively increased the specific surface area, and its superior matching with electrolyte solutions greatly improved surface-active site utilization. This work offers an alternative strategy for fabricating a 2D heterostructure for an MSC.

Development of Light-Scribing Process Using L-Ascorbic Acid for Graphene Micro-Supercapacitor.

The rapid development of smart technologies is accelerating the growing demand for microscale energy storage devices. This work reports a facile and practical approach to fabricating interdigitated graphene micro-patterns through the LSC process accompanied by the l-ascorbic acid (L-AA) and preheating treatment. Our work offered a higher degree of GO reduction than the conventional microfabrication. It significantly shortened the overall processing time to obtain the micro-patterns with improved electrical and electrochemical performances. The interdigitated MSC composed of 16 electrodes exhibited a high capacitance of 14.1 F/cm3, energy density of 1.78 mWh/cm3, and power density of 69.9 mW/cm3. Furthermore, the fabricated MSC device demonstrated excellent cycling stability of 88.2% after 10,000 GCD cycles and a high rate capability of 81.1% at a current density of 1.00 A/cm3. The fabrication process provides an effective means for producing high-performance MSCs for miniaturized electronic devices.

Direct Electrodeposition of Electrically Conducting Ni3(HITP)2 MOF Nanostructures for Micro-Supercapacitor Integration.

Micro-supercapacitors emerge as an important electrical energy storage technology expected to play a critical role in the large-scale deployment of autonomous microdevices for health, sensing, monitoring, and other IoT applications. Electrochemical double-layer capacitive storage requires a combination of high surface area and high electronic conductivity, with these being attained only in porous or nanostructured carbons, and recently found also in conducting metal-organic frameworks (MOFs). However, techniques for conformal deposition at micro- and nanoscale of these materials are complex, costly, and hard to upscale. Herein, the study reports direct, one step non-sacrificial anodic electrochemical deposition of Ni3(2,3,6,7,10,11-hexaiminotriphenylene)2 - Ni3(HITP)2, a porous and electrically conducting MOF. Employing this strategy enables the growth of Ni3(HITP)2 films on a variety of 2D substrates as well as on 3D nanostructured substrates to form Ni3(HITP)2 nanotubes and Pt@ Ni3(HITP)2 core-shell nanowires. Based on the optimal electrodeposition protocols, Ni3(HITP)2 films interdigitated micro-supercapacitors are fabricated and tested as a proof of concept.

Emerging Vanadium-Doped Cobalt Chloride Carbonate Hydroxide for Flexible Electrochromic Micro-Supercapacitor: Charged-State Prediction from RGB Input by ANN Model.

Multifunctional devices integrated with electrochromic and supercapacitance properties are fascinating because of their extensive usage in modern electronic applications. In this work, vanadium-doped cobalt chloride carbonate hydroxide hydrate nanostructures (V-C3H NSs) are successfully synthesized and show unique electrochromic and supercapacitor properties. The V-C3H NSs material exhibits a high specific capacitance of 1219.9 F g-1 at 1 mV s-1 with a capacitance retention of 100% over 30 000 CV cycles. The electrochromic performance of the V-C3H NSs material is confirmed through in situ spectroelectrochemical measurements, where the switching time, coloration efficiency (CE), and optical modulation (∆T) are found to be 15.7 and 18.8 s, 65.85 cm2 C-1 and 69%, respectively. A coupled multilayer artificial neural network (ANN) model is framed to predict potential and current from red (R), green (G), and blue (B) color values. The optimized V-C3H NSs are used as the active materials in the fabrication of flexible/wearable electrochromic micro-supercapacitor devices (FEMSDs) through a cost-effective mask-assisted vacuum filtration method. The fabricated FEMSD exhibits an areal capacitance of 47.15 mF cm-2 at 1 mV s-1 and offers a maximum areal energy and power density of 104.78 Wh cm-2 and 0.04 mW cm-2, respectively. This material's interesting energy storage and electrochromic properties are promising in multifunctional electrochromic energy storage applications.

On-Chip Micro-Supercapacitor with High Areal Energy Density Based on Dielectrophoretic Assembly of Nanoporous Metal Microwire Electrodes.

Advances in the Internet of Things (IoT) technology have driven the demand for miniaturized electronic devices, prompting research on small-scale energy-storage systems. Micro-supercapacitors (MSCs) stand out in this regard because of their compact size, high power density, high charge-discharge rate, and extended cycle life. However, their limited energy density impedes commercialization. To resolve this issue, a simple and innovative approach is reported herein for fabricating highly efficient on-chip MSCs integrated with nanoporous metal microwires formed by dielectrophoresis (DEP)-driven gold nanoparticle (AuNP) assembly. Placing a water-based AuNP suspension onto interdigitated electrodes and applying an alternating voltage induces in-plane porous microwire formation in the electrode gap. The DEP-induced AuNP assembly and the gold microwire (AuMW) growth rate can be adjusted by controlling the applied alternating voltage and frequency. The microwire-integrated MSC (AuMW-MSC) electrically outperforms its unmodified counterpart and exhibits a 30% larger electrode area, along with 72% and 78% higher specific and areal capacitances, respectively, than a microwire-free MSC. Additionally, AuMW-MSC achieves maximum energy and power densities of 3.33 µWh cm-2 and 2629 µW cm-2, respectively, with a gel electrolyte. These findings can help upgrade MSCs to function as potent energy-storage devices for small electronics.

Ultraconformable Integrated Wireless Charging Micro-Supercapacitor Skin.

Conformable and wireless charging energy storage devices play important roles in enabling the fast development of wearable, non-contact soft electronics. However, current wireless charging power sources are still restricted by limited flexural angles and fragile connection of components, resulting in the failure expression of performance and constraining their further applications in health monitoring wearables and moveable artificial limbs. Herein, we present an ultracompatible skin-like integrated wireless charging micro-supercapacitor, which building blocks (including electrolyte, electrode and substrate) are all evaporated by liquid precursor. Owing to the infiltration and permeation of the liquid, each part of the integrated device attached firmly with each other, forming a compact and all-in-one configuration. In addition, benefitting from the controllable volume of electrode solution precursor, the electrode thickness is easily regulated varying from 11.7 to 112.5 µm. This prepared thin IWC-MSC skin can fit well with curving human body, and could be wireless charged to store electricity into high capacitive micro-supercapacitors (11.39 F cm-3) of the integrated device. We believe this work will shed light on the construction of skin-attachable electronics and irregular sensing microrobots.

A Biodegradable High-Performance Microsupercapacitor for Environmentally Friendly and Biocompatible Energy Storage.

Biodegradable and biocompatible microscale energy storage devices are very crucial for environmentally friendly microelectronics and implantable medical applications. Herein, a biodegradable and biocompatible microsupercapacitor (BB-MSC) with satisfying overall performance is realized via the combination of three-dimensional (3D) printing technique and biodegradable materials. Due to the 3D-interconnected structure of electrodes and elaborated design of electrolyte, the as-prepared BB-MSC exhibits superior overall performance than most of biodegradable devices, including a wide operation voltage of 1.8 V, high areal specific capacitance of 251 mF/cm2, good cycle stability, and favorable low-temperature resistance (-20 °C), demonstrative of reliability and practicality of our devices even in frosty environments. Importantly, the smooth degradation has been realized for the BB-MSC after being buried in natural soil for ∼90 days, and its implantation does not affect the healthy status of SD rats. Therefore, this work explores avenues for the design and construction of environmentally friendly and biocompatible microscale energy storage devices.

Untethered Magnetic Soft Robot with Ultra-Flexible Wirelessly Rechargeable Micro-Supercapacitor as an Onboard Power Source.

Soft robotics has developed rapidly in recent years as an emergent research topic, offering new avenues for various industrial and biomedical settings. Despite these advancements, its applicability is limited to locomotion and actuation due to the lack of an adequate charge storage system that can support the robot's sensory system in challenging conditions. Herein, an ultra-flexible, lightweight (≈50 milligrams), and wirelessly rechargeable micro-supercapacitor as an onboard power source for miniaturized soft robots, capable of powering a range of sensory is proposed. The simple and scalable direct laser combustion technique is utilized to fabricate the robust graphene-like carbon micro-supercapacitor (GLC-MSC) electrode. The GLC-MSC demonstrates superior areal capacitance (8.76 mF cm-2 ), and maintains its original capacitance even under extreme actuation frequency (1-30 Hz). As proof of conceptthe authors fabricate a fully integrated magnetic-soft robot that shows outstanding locomotion aptitude and charged wirelessly (up to 2.4 V within 25s), making it an ideal onboard power source for soft robotics.

Facile Self-Assembly of Exfoliated Graphene/PANI Film for High-Energy Zn-Ion Micro-Supercapacitors.

The Zn-ion micro-supercapacitor (ZMSC) is a promising candidate for developing miniaturized and integrated energy storage devices. To achieve high-performance functional groups with simple processing to composite with rod-like active PANI fibers, we prepared exfoliated graphene (EG) with an appropriate amount of O-containing functional groups. The appropriate O content simultaneously facilitated self-assembly of the EG and PANI fibers and maintained the electric conductivity of the composite, producing a free-standing EG/PANI film without additional conductive additives or current collectors. As an interdigital electrode for the ZMSC, the EG/PANI film showed ultrahigh capacitance of 1.8 F cm-2 at 2.6 mA cm-2 (361.3 F g-1 at 0.5 A g-1) and landmark energy density of 755.8 µWh cm-2 at 2.3 mW cm-2 (148.2 Wh kg-1 at 451.7 W kg-1). The facile preparation of the high-performance EG/PANI electrode provides a potential path for practical applications with ZMSCs.

Flexible and alternately layered high electrochemical active electrode based on MXene, carboxymethylcellulose, and carbon nanotube for asymmetric micro-supercapacitors.

Recent studies have shown that Ti-based MXene has great potential for electrochemical energy storage applications, including Li-ion batteries and micro-supercapacitors. However, self-stacking and weak interlayer interactions lead to poor electrochemical properties. Herein, a simple one-step vacuum filtration method was used to prepare a MXene/carboxymethylcellulose/carbon nanotube (Ti3C2Tx/CMC/CNT) hybrid membrane. Due to the unique adhesion and flexibility of CMC, it can be interwoven with CNT to form an interconnected mesh structure, which on the one hand mitigates the self-aggregation of CNT, and on the other hand, the CNT entangled on the surface of CMC imparts its electrical conductivity. Moreover, the -OH of CMC can form hydrogen bonds with the reactive terminal groups (-O, -OH, -F) of Ti3C2Tx, resulting in the tight anchoring of CMC and CNT to Ti3C2Tx nanosheet layers and bridging adjacent Ti3C2Tx nanosheets to form a complete conductive pathway. As a result, the mechanical property test indicates that the Ti3C2Tx/CMC/CNT hybrid film could achieve a maximum tensile strength of 64.9 MPa. Furthermore, an asymmetric micro-supercapacitor (MSC) using Ti3C2Tx/CMC/CNT as the cathode and reduced graphene oxide/carboxymethylcellulose/polypyrrole (RGO/CMC/PPy) as the anode was fabricated, which exhibited a high energy density of 258.8 µWh cm-2 at a power density of 750 µW cm-2, and an ultra-long cycle life (93.2% capacitance retention after 15,000 GCD cycles). The simple and scalable preparation process makes this MSC device very promising for commercial electronics applications.

Editable 3D Micro-Supercapacitor with High Energy Density Based on Mortise-Tenon Joint Structures.

Three-dimensional micro-supercapacitors (3D MSCs) have accelerated the development of microenergy-storage modules for miniaturized and portable electronics. However, the low energy density, complex construction strategy, and low assembly accuracy of a 3D MSC restrict its practical application. Herein, we design a simple construction strategy for a 3D MSC with high energy density by mortise and tenon structures. Wood-derived carbon modified by nitrogen-doped carbon nanotube arrays (N-CNT-WDC) provides an ordered ion transport channel and a large active specific surface area, availing the improvement of the energy density of a 3D MSC. Its strong carbon skeleton structure supports the construction of 3D interdigital electrodes with a tenon structure by laser, realizing precise and regulable assembly of 3D MSCs through a mortise and tenon joint. The prepared 3D MSC based on N-CNT-WDC shows an excellent volumetric capacitance of 93.66 F cm-3, a high volumetric energy density of 12 mW h cm-3 at 600 mA cm-3, and an 85% retention rate of capacitance after 10,000 cycles of charge and discharge at 1000 mA cm-3. Furthermore, the mortise and tenon structure realizes diversified integration of 3D MSCs, making the integrated manufacturing of 3D microdevices more convenient and promoting their application in microelectronic devices.

Simultaneous detection of ultraviolet irradiation and vitamin C using an all-carbon-based integrated wearable system powering by a micro-supercapacitor.

Ultraviolet (UV) radiation is a harmful exogenous factor for human skin. Wearable UV photodetectors can monitor UV exposure in the surroundings, and wearable vitamin C (VC) sensors tracking the levels in the human body present the potential ability to defend the UV radiation. Herein, we reported on the fabrication of an all-in-one wearable system with a UV photodetector and VC sensor powered by a micro-supercapacitor. Based on direct laser writing carbonization of polyimide sheets, the patterned electrodes and interconnects of the circuit were fabricated by a facile one-step operation, obtaining an all-carbon-based integrated system. Such a system exhibited outstanding energy storage ability (56.2 µWh cm-2 at 4.17 mW cm-2), high areal capacitance (1.06 mF cm-2 at 5 mV s-1), satisfying capacitive stability, and good mechanical flexibility. The UV photodetector and the VC sensor were powered to obtain a linear range of UV intensity from 11 to 44 µW cm-2 (equivalent to Ultraviolet Index 4.4 to 17.6), and VC levels of 1.0-200 µM with a low limit of detection of 0.83 µM. Furthermore, the integrated system was successfully applied to the determination of VC in commercial beverage and human sweat samples. This work provided a simple and promising method to fabricate integrated wearable systems for on-site providing information on the UV intensity of the external environment and the VC level of the human body simultaneously.

Ethanol-Induced Ni2+ -Intercalated Cobalt Organic Frameworks on Vanadium Pentoxide for Synergistically Enhancing the Performance of 3D-Printed Micro-Supercapacitors.

The synthesis of metal-organic framework (MOF) nanocomposites with high energy density and excellent mechanical strength is limited by the degree of lattice matching and crystal surface structure. In this study, dodecahedral ZIF-67 is synthesized uniformly on vanadium pentoxide nanowires. The influence of the coordination mode on the surface of ZIF-67 in ethanol is also investigated. Benefitting from the different coordination abilities of Ni2+ , Co2+ , and N atoms, spatially separated surface-active sites are created through metal-ion exchange. Furthermore, the incompatibility between the d8 electronic configuration of Ni2+ and the three-dimensional (3D) structure of ZIF-67 afforded the synthesis of hollow structures by controlling the amount of Ni doping. The formation of NiCo-MOF@CoOOH@V2 O5 nanocomposites is confirmed using X-ray absorption fine structure analysis. The high performance of the obtained composite is illustrated by fabricating a 3D-printed micro-supercapacitor, exhibiting a high area specific capacitance of 585 mF cm-2 and energy density of 159.23 µWh cm-2 (at power density = 0.34 mW cm-2 ). The solvent/coordination tuning strategy demonstrated in this study provides a new direction for the synthesis of high-performance nanomaterials for electrochemical energy storage applications.

All-Solid-State Interdigitated Micro-Supercapacitors Based on Porous Gold Electrodes.

Recent developments in embedded electronics require the development of micro sources of energy. In this paper, the fabrication of an on-chip interdigitated all-solid-state supercapacitor, using porous gold electrodes and a PVA/KOH quasisolid electrolyte, is demonstrated. The fabrication of the interdigitated porous gold electrode is performed using an original bottom-up approach. A templating method is used for porosity, using a wet chemistry process followed by microfabrication techniques. This paper reports the first example of an all-gold electrode micro-supercapacitor. The supercapacitor exhibits a specific capacitance equal to 0.28 mF·cm-2 and a specific energy of 0.14 mJ·cm-2. The capacitance value remains stable up to more than 8000 cycles.