Re-stickable All-Solid-State Supercapacitor Supported by Cohesive Thermoplastic for Textile Electronics

Metal-Organic Frameworks and Their Derivatives-Based Nanostructure with Different Dimensionalities for Supercapacitors

With the urgent demand for the achievement of carbon neutrality, novel nanomaterials, and environmentally friendly nanotechnologies are constantly being explored and continue to drive the sustainable development of energy storage and conversion installations. Among various candidate materials, metal-organic frameworks (MOFs) and their derivatives with unique nanostructures have attracted increasing attention and intensive investigation for the construction of next generation electrode materials, benefitting from their unique intrinsic characteristics such as large specific surface area, high porosity, and chemical tunability as well as the interconnected channels. Nevertheless, the poor electrochemical conductivity severely limits their application prospects, hence a variety of nanocomposites with multifarious structures have been designed and proposed from different dimensionalities. In this review, recent advances based on MOFs and their derivatives in different dimensionalities ranging from 1D nanopowders to 2D nanofilms and 3D aerogels, as well as 4D self-supporting electrodes for supercapacitors are summarized and highlighted. Furthermore, the key challenges and perspectives of MOFs and their derivatives-based materials for the practical and sustainable electrochemical energy conversion and storage applications are also briefly discussed, which may be served as a guideline for the design of next-generation electrode materials from different dimensionalities.

Re-Stickable Yarn Supercapacitors with Vaper Phase Polymerized Multi-Layered Polypyrrole Electrodes for Smart Garments

Yarn supercapacitors have attracted significant attention for wearable energy storage due to their ability to be directly integrated with garments. Conducting polymer polypyrrole (PPy) based yarn supercapacitors show limited cycling stability because of the huge volume changes during the charge-discharge processes. In addition, laundering may cause damage to such yarn supercapacitors. Here, the fabrication of PPy-based re-stickable yarn supercapacitors is reported with good cycling stability by employing vapor phase polymerization (VPP) and water-soluble polyethylene oxide (PEO) film as the adhesive layer. VPP duration and cycle are controlled to achieve multi-layered PPy electrodes. The assembled yarn supercapacitors show a good cycling stability with capacitance retention of 79.1% after 5000 charge-discharge cycles. The energy stored in the yarn supercapacitor is sufficient to power a photodetector. After gluing the yarn supercapacitors onto a PEO film, the devices can be stunk on and peeled off the garment to avoid the mechanical stresses during the washing process. Three yarn supercapacitors connected in parallel on PEO film show negative changes in electrochemical performance after 5 sticking-peeling cycles. This work provides a facile way to fabricate PPy-based re-stickable energy storage devices with high cycling stability for smart garments.

High-Performance MnO2 Nanowire/MoS2 Nanosheet Composite for a Symmetrical Solid-State Supercapacitor

To improve the production rate of MoS₂ nanosheets as an excellent supercapacitor (SC) material and enhance the performance of the MoS₂-based solid-state SC, a liquid phase exfoliation method is used to prepare MoS₂ nanosheets on a large scale. Then, the MnO₂ nanowire sample is synthesized by a one-step hydrothermal method to make a composite with the as-synthesized MoS₂ nanosheets to achieve a better performance of the solid-state SC. The interaction between the MoS₂ nanosheets and MnO₂ nanowires produces a synergistic effect, resulting in a decent energy storage performance. For practical applications, all-solid-state SC devices are fabricated with different molar ratios of MoS₂ nanosheets and MnO₂ nanowires. From the experimental results, it can be seen that the synthesized nanocomposite with a 1:4 M ratio of MoS₂ nanosheets and MnO₂ nanowires exhibits a high Brunauer-Emmett-Teller surface area (∼118 m²/g), optimum pore size distribution, a specific capacitance value of 212 F/g at 0.8 A/g, an energy density of 29.5 W h/kg, and a power density of 1316 W/kg. Besides, cyclic charging-discharging and retention tests manifest significant cycling stability with 84.1% capacitive retention after completing 5000 rapid charge-discharge cycles. It is believed that this unique, symmetric, lightweight, solid-state SC device may help accomplish a scalable approach toward powering forthcoming portable energy storage applications.

Washable Patches with Gold Nanowires/Textiles in Wearable Sensors for Health Monitoring

Textile-based flexible electronic devices have attracted tremendous attention in wearable sensors due to their excellent skin affinity and conformability. However, the washing process of such devices may damage the electronic components. Here, a textile-based piezoresistive sensor with ultrahigh sensitivity was fabricated through the layered integration of gold nanowire (AuNW)-impregnated cotton fabric and silver ink screen-printed nylon fabric electrodes, sealing with Parafilm. The prepared piezoresistive sensing patch exhibits outstanding performance, including high sensitivity (914.970 kPa^-1, <100 Pa), a fast response time (load: 38 ms, recovery: 34 ms), and a low detection limit (0.49 Pa). More importantly, it can maintain a stable signal output even after 30 000 s of loading-unloading cycles. Furthermore, this sensing patch can efficiently detect breathing, pulse, heart rate, and joint movements during the activities. After five cycles of mechanical washing, the piezoresistive performance keeps 90.3%, demonstrating the high feasibility of this sensor in practical applications. This sensor has a simple fabrication, with good fatigue resistance and durability due to its all-fabric core element. It provides a strategy to address the machine-washing issues in textile electronics. This washable textile sensor is expected to show significant potential in future applications of health monitoring, human-machine interfaces, and artificial skin.

Dry Synthesis of Binder-Free Ruthenium Nitride-Coated Carbon Nanotubes as a Flexible Supercapacitor Electrode

Ruthenium nitride was successfully deposited on a multiwalled carbon nanotube (MWCNT) forest grown on a stainless-steel mesh substrate by radiofrequency plasma-assisted pulsed laser deposition. This novel dry fabrication method for flexible supercapacitor electrodes eliminates toxic byproducts and the need for any binder component. Experimental results show a successful thin film coating of the individual MWCNTs with RuN_x under various synthesis conditions. The electrochemical characterization demonstrates a significant improvement in capacitance of the synthesized RuN_x-MWCNT electrode compared to the bare MWCNT forest, with a large potential window of 1.2 V. Capacitance values as high as 818.2 F g^-1 (37.9 mF cm^-2) have been achieved.

A Weavable and Scalable Cotton-Yarn-Based Battery Activated by Human Sweat for Textile Electronics

Sweat-activated batteries (SABs) are lightweight, biocompatible energy generators that produce sufficient power for skin-interface electronic devices. However, the fabrication of 1D SABs that are compatible with conventional textile techniques for self-powered wearable electronics remains challenging. In this study, a cotton-yarn-based SAB (CYSAB) with a segmental structure is developed, in which carbon-black-modified, pristine yarn and Zn foil-wrapped segments are prepared to serve as the cathode, salt bridge, and anode, respectively. Upon electrolyte absorption, the CYSAB can be rapidly activated. Its performance is closely related to the ion concentration, infiltrated electrolyte volume, and evaporation rate. The CYSAB can tolerate repeated bending and washing without any significant influence on its power output. Moreover, the CYSABs can be woven into fabrics and connected in series and parallel configurations to produce an energy supplying headband, which can be activated by the sweat secreted from a volunteer during a cycling exercise to power light-emitting diode headlights. The developed CYSAB can also be integrated with yarn-based strain sensors to achieve a smart textile for the self-powered sensing of human motion and breathing. This weavable, washable, and scalable CYSAB is expected to contribute to the manufacturing of self-powered smart textiles for future applications in wearable healthcare monitoring.