Recent Advances in Fiber Supercapacitors: Materials, Device Configurations, and Applications

Enhanced Wire-Shaped Micro-Supercapacitor Treated with a Continuous Surface Atmospheric Pressure Plasma Jet Approach

Microscale, wire-shaped flexible supercapacitors are gaining significant attention due to the growing demand for wearable electronics and microrobotic technologies. Among various materials, copper sulfide stands out as an ideal candidate because of its superior electrochemical properties, which can be attributed to its nanostructured composition. This structure enhances the surface area, reduces ion transport distances, and improves charge-discharge kinetics. However, conventional electrode synthesis methods-such as annealing and hydrothermal processes-are limited by long production times and scalability issues, making them unsuitable for wire-shaped supercapacitor development. In this study, an innovative fabrication technique using an atmospheric pressure plasma jet (APPJ) for both surface treatment and material synthesis is proposed. By integrating the APPJ with a winding mechanism, roll-to-roll processing for continuous production is enabled, significantly enhancing the scalability of the manufacturing process. The fabricated wire-shaped microscale electrodes demonstrate high specific capacitance (153.39 mF cm-2), specific energy density (15.48 µWh cm-2), and excellent capacitance retention (91.32%) after 30 000 charge-discharge cycles. Furthermore, a wire-shaped solid-state flexible asymmetric supercapacitor is assembled using the fabricated electrodes in a coaxial configuration. The supercapacitor exhibits exceptional flexibility and energy storage performance, underscoring the practical applicability of the proposed method for advanced electronics.

Eco-friendly cellulose paper composites: A sustainable solution for EMI shielding and green engineering applications

Cellulose paper-based composites represent a promising and sustainable alternative for electromagnetic interference (EMI) shielding applications. Derived from renewable and biodegradable cellulose fibers, these composites are enhanced with conductive fillers namely carbon nanotubes, graphene, or metallic nanoparticles, achieving efficient EMI shielding while maintaining environmental friendliness. Their lightweight, flexible nature, and mechanical robustness make them ideal for diverse applications, including wearable electronics, flexible circuits, and green electronics. This paper explores the fabrication techniques, composite properties, with particular emphasis on ways to enhance the shielding properties, and performance metrics of cellulose-based composites, highlighting their potential to replace traditional metallic materials in various EMI shielding scenarios, thus contributing to the development of eco-friendly and high-performance electronic devices. Despite advancements, challenges such as achieving uniform filler dispersion and scalability of eco-friendly production methods persist, limiting industrial application.

Recent Advances in Next-Generation Textiles

Textiles have played a pivotal role in human development, evolving from basic fibers into sophisticated, multifunctional materials. Advances in material science, nanotechnology, and electronics have propelled next-generation textiles beyond traditional functionalities, unlocking innovative possibilities for diverse applications. Thermal management textiles incorporate ultralight, ultrathin insulating layers and adaptive cooling technologies, optimizing temperature regulation in dynamic and extreme environments. Moisture management textiles utilize advanced structures for unidirectional transport and breathable membranes, ensuring exceptional comfort in activewear and outdoor gear. Protective textiles exhibit enhanced features, including antimicrobial, antiviral, anti-toxic gas, heat-resistant, and radiation-shielding capabilities, providing high-performance solutions for healthcare, defense, and hazardous industries. Interactive textiles integrate sensors for monitoring physical, chemical, and electrophysiological parameters, enabling real-time data collection and responses to various environmental and user-generated stimuli. Energy textiles leverage triboelectric, piezoelectric, and hygroelectric effects to improve energy harvesting and storage in wearable devices. Luminous display textiles, including electroluminescent and fiber optic systems, enable dynamic visual applications in fashion and communication. These advancements position next-generation textiles at the forefront of materials science, significantly expanding their potential across a wide range of applications.

Self-Healing Flexible Fiber Optic Sensors for Safe Underwater Monitoring

The advancement of underwater monitoring technologies has been significantly hampered by the limitations of traditional electrical sensors, particularly in the presence of electromagnetic interference and safety concerns in aquatic environments. Fiber optic sensors are therefore nowadays widely applied to underwater monitoring devices. However, silicon- and polymer-based optical fibers often face challenges, such as rigidity, susceptibility to environmental stress, and limited operational flexibility. Here, we propose an ingenious flexible step-index fiber construction strategy for the preparation of core-cladding poly(polymerizable deep eutectic solvent (PDES)) optical fiber (CPOF) by in situ light curing of the functional PDES monomer in a commercial silicone tube. The liquid-free poly(PDES) fiber core not only possesses high transparency (>90%), excellent flexibility, and wide temperature range tolerance (from -27 to 156 °C), but the supramolecular network of it also provides self-adhesion and optical self-healing, which ensures the bonding stability of the core-cladding interface as well as the lifetime of the optical device. On the other hand, the hydrophobic fiber cladding allows CPOF to stably transmit optical signals under water, and the application potential of CPOF for underwater sensing devices was verified by underwater motion monitoring.

Scalable Production of Functional Fibers with Nanoscale Features for Smart Textiles

Functional fibers, retaining nanoscale characteristics or nanomaterial properties, represent a significant advance in nanotechnology. Notably, the combination of scalable manufacturing with cutting-edge nanotechnology further expands their utility across numerous disciplines. Manufacturing kilometer-scale functional fibers with nanoscale properties are critical to the evolution of smart textiles, wearable electronics, and beyond. This review discusses their design principles, manufacturing technologies, and key advancements in the mass production of such fibers. In addition, it summarizes the current applications and state of progress in scalable fiber technologies and provides guidance for future advances in multifunctional smart textiles, by highlighting the upcoming impending demands for evolving nanotechnology. Challenges and directions requiring sustained effort are also discussed, including material selection, device design, large-scale manufacturing, and multifunctional integration. With advances in functional fibers and nanotechnology in large-scale production, wearable electronics, and smart textiles could potentially enhance human-machine interaction and healthcare applications.

Multi-Interface Engineering of MXenes for Self-Powered Wearable Devices

Self-powered wearable devices with integrated energy supply module and sensitive sensors have significantly blossomed for continuous monitoring of human activity and the surrounding environment in healthcare sectors. The emerging of MXene-based materials has brought research upsurge in the fields of energy and electronics, owing to their excellent electrochemical performance, large surface area, superior mechanical performance, and tunable interfacial properties, where their performance can be further boosted via multi-interface engineering. Herein, a comprehensive review of recent progress in MXenes for self-powered wearable devices is discussed from the aspects of multi-interface engineering. The fundamental properties of MXenes including electronic, mechanical, optical, and thermal characteristics are discussed in detail. Different from previous review works on MXenes, multi-interface engineering of MXenes from termination regulation to surface modification and their impact on the performance of materials and energy storage/conversion devices are summarized. Based on the interfacial manipulation strategies, potential applications of MXene-based self-powered wearable devices are outlined. Finally, proposals and perspectives are provided on the current challenges and future directions in MXene-based self-powered wearable devices.

Direct Growth of Vertical Graphene on Fiber Electrodes and Its Application in Alternating Current Line-Filtering Capacitors

Fiber-shaped electrochemical capacitors (FSECs) have garnered substantial attention to emerging portable, flexible, and wearable electronic devices. However, achieving high electronic and ionic conductivity in fiber electrodes while maintaining a large specific surface area is still a challenge for enhancing the capacitance and rapid response of FSECs. Here, we present an electric-field-assisted cold-wall plasma-enhanced chemical vapor (EFCW-PECVD) method for direct growth of vertical graphene (VG) on fiber electrodes, which is incorporated in the FSECs. The customized reactor mainly consists of two radio frequency coils: one for plasma generation and the other for substrate heating. Precise temperature control can be achieved by adjusting the conductive plates and the applied power. With induction heating, only the substrate is heated to above 500 °C within just 5 min, maintaining a low temperature in the gas phase for the growth of VG with a high quality. Using this method, VG was easily grown on metallic fibers. The VG-coated titanium fibers for FSECs exhibit an ultrahigh rate performance and quick ion transport, enabling the conversion of an alternating current signal to a direct current signal and demonstrating outstanding filtering capabilities.

Cultivating High-Performance Flexible All-in-One Supercapacitors With 3D Network Through Continuous Biosynthesis

Flexible supercapacitors can potentially power next-generation flexible electronics. However, the mechanical and electrochemical stability of flexible supercapacitors under different flexible conditions is limited by the weak bonding between adjacent layers, posing a significant hindrance to their practical applicability. Herein, based on the uninterrupted 3D network during the growth of bacterial cellulose (BC), a flexible all-in-one supercapacitor is cultivated through a continuous biosynthesis process. This strategy ensures the continuity of the 3D network of BC throughout the material, thereby forming a continuous electrode-separator-electrode structure. Benefitting from this bioinspired structure, the all-in-one supercapacitor not only achieves a high areal capacitance (3.79 F cm-2) of electrodes but also demonstrates the integration of high tensile strength (2.15 MPa), high shear strength (more than 54.6 kPa), and high bending resistance, indicating a novel pathway toward high-performance flexible power sources.

Development and Application of an Advanced Biomedical Material-Silk Sericin

Sericin, a protein derived from silkworm cocoons, is considered a waste product derived from the silk industry for thousands of years due to a lack of understanding of its properties. However, in recent decades, a range of exciting properties of sericin are studied and uncovered, including cytocompatibility, low-immunogenicity, photo-luminescence, antioxidant properties, as well as cell-function regulating activities. These properties make sericin-based biomaterials promising candidates for biomedical applications. This review summarizes the properties and bioactivities of silk sericin and highlights the latest developments in sericin in tissue engineering and regenerative medicine. Furthermore, the extended application of sericin in developing flexible electronic devices and 3D bioprinting is also discussed. It is believed that sericin-based biomaterials have great potential of being developed into novel tissue engineering products and smart implantable devices for various medical applications toward improving clinical outcomes.

In-situ forming ultra-mechanically sensitive materials for high-sensitivity stretchable fiber strain sensors

Fiber electronics with flexible and weavable features can be easily integrated into textiles for wearable applications. However, due to small sizes and curved surfaces of fiber materials, it remains challenging to load robust active layers, thus hindering production of high-sensitivity fiber strain sensors. Herein, functional sensing materials are firmly anchored on the fiber surface in-situ through a hydrolytic condensation process. The anchoring sensing layer with robust interfacial adhesion is ultra-mechanically sensitive, which significantly improves the sensitivity of strain sensors due to the easy generation of microcracks during stretching. The resulting stretchable fiber sensors simultaneously possess an ultra-low strain detection limit of 0.05%, a high stretchability of 100%, and a high gauge factor of 433.6, giving 254-folds enhancement in sensitivity. Additionally, these fiber sensors are soft and lightweight, enabling them to be attached onto skin or woven into clothes for recording physiological signals, e.g. pulse wave velocity has been effectively obtained by them. As a demonstration, a fiber sensor-based wearable smart healthcare system is designed to monitor and transmit health status for timely intervention. This work presents an effective strategy for developing high-performance fiber strain sensors as well as other stretchable electronic devices.

Electrospun network based on polyacrylonitrile-polyphenyl/titanium oxide nanofibers for high-performance supercapacitor device

Nanofibers and mat-like polyacrylonitrile-polyphenyl/titanium oxide (PAN-Pph./TiO2) with proper electrochemical properties were fabricated via a single-step electrospinning technique for supercapacitor application. Scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM), thermogravimetry (TGA), fourier transform infrared (FTIR), X-ray diffraction (XRD) and energy dispersive X-ray (EDX) were conducted to characterize the morphological and chemical composition of all fabricated nanofibers. Furthermore, the electrochemical activity of the fabricated nanofibers for energy storage applications (supercapacitor) was probed by cyclic voltammetry (CV), charge-discharge (CD), and electrochemical impedance spectroscopy (EIS). The PAN-PPh./TiO2 nanofiber electrode revealed a proper specific capacitance of 484 F g-1 at a current density of 11.0 A g-1 compared with PAN (198 F g-1), and PAN-PPh. (352 F g-1) nanofibers using the charge-discharge technique. Furthermore, the PAN-PPh./TiO2 nanofiber electrode displayed a proper energy density of 16.8 Wh kg-1 at a power density (P) of 2749.1 Wkg-1. Moreover, the PAN-PPh./TiO2 nanofiber electrode has a low electrical resistance of 23.72 Ω, and outstanding cycling stability of 79.38% capacitance retention after 3000 cycles.

Rational electrolyte design and electrode regulation for boosting high-capacity Zn-iodine fiber-shaped batteries with four-electron redox reactions

Aqueous Zn ion-based fiber-shaped batteries (AZFBs) with the merits of high flexibility and safety have received much attention for powering wearable electronic devices. However, the relatively low specific capacity provided by cathode materials limits their practical application. Herein, we first propose a simple strategy for fabricating high-capacity Zn-iodine fiber-shaped batteries with a high concentration electrolyte and a reduced graphene oxide fiber (GF) cathode. It was found that oxygen functional groups in the graphene sheet demonstrate strong interaction with polyiodides but hinder electron conductivity; thus, the optimal balance between the specific capacity and coulombic efficiency of the GF electrode can be a function of the surface properties at different hydrothermal temperatures. Besides, the regulated high concentration electrolyte effectively suppresses the diffusion of polyiodides, which is attributed to the constrained freedom of water. More importantly, a four-electron redox mechanism was experimentally revealed through in situ Raman spectra. As a result, this fiber-shaped battery delivers a superior high reversible capacity of 390 mA h cm-3 at 1 A cm-3, an excellent rate performance of 125.7 mA h cm-3 at a high current density of 8 A cm-3 and outstanding cycling life with 82% capacitance retention after 2500 cycles.

MnO2 porous carbon composite from cellulose enabling high gravimetric/volumetric performance for supercapacitor

Preparing electrode material integrated with high gravimetric/volumetric capacitance and fast electron/ion transfer is crucial for the practical application. Owing to the structural contradiction, it is a big challenge to construct electrode material with high packing density, sufficient ion transport channels, and fast electronic transfer pathways. Herein, MnO2 porous carbon composite with abundant porous structure and 3D carbon skeleton was facilely fabricated from Linum usitatissimum. L stems via NaOH activation and MnO2 introduction. The in-situ introduced MnO2 not only increases the packing density and the electrical conductivity of the porous carbon but also provides more active sites for oxidation reactions. These unique characteristics endow the resultant MnO2 porous carbon composite with remarkable gravimetric capacitance of 549 F g-1, volumetric capacitance of 378 F cm-3, and capacitance retention of 54.9 %. Giving the simple process and low cost, this work might offer a new approach for structural design and the practical application of high-performance electrode materials.

Constructing Hierarchical CoGa2O4-S@NiCo-LDH Core-Shell Heterostructures with Crystalline/Amorphous/Crystalline Heterointerfaces for Flexible Asymmetric Supercapacitors

The rational design and construction of composite electrodes are crucial for overcoming the issues of poor working stability and slow ionic electron mobility of a single component. Nevertheless, it is a big challenge to construct core-shell heterostructures with crystalline/amorphous/crystalline heterointerfaces in straightforward and efficient methods. Here, we have successfully converted a portion of crystalline CoGa2O4 into the amorphous phase by employing a facile sulfidation process (denoted as CoGa2O4-S), followed by anchoring crystalline NiCo-layered double hydroxide (denoted as NiCo-LDH) nanoarrays onto hexagonal plates and nucleation points of CoGa2O4-S, synthesizing dual-type hexagonal and flower-like 3D CoGa2O4-S@NiCo-LDH core-shell heterostructures with crystalline/amorphous/crystalline heterointerfaces on carbon cloth. Furthermore, we further adjust the Ni/Co ratio in LDH, achieving precise and controllable core-shell heterostructures. Benefiting from the abundant crystalline/amorphous/crystalline heterointerfaces and synergistic effect among various components, the CoGa2O4-S@Ni2Co1-LDH electrode exhibits a specific capacity of 247.8 mAh·g-1 at 1 A·g-1 and good rate performance. A CoGa2O4-S@Ni2Co1-LDH//AC flexible asymmetric supercapacitor provides an energy density of 58.2 Wh·kg-1 at a power density of 850 W·kg-1 and exhibits an impressive capacitance retention of 105.7% after 10,000 cycles at 10 A·g-1. Our research provides profound insights into the design of other similar core-shell heterostructures.

Advancements in silicon carbide-based supercapacitors: materials, performance, and emerging applications

Silicon carbide (SiC) nanomaterials have emerged as promising candidates for supercapacitor electrodes due to their unique properties, which encompass a broad electrochemical stability range, exceptional mechanical strength, and resistance to extreme conditions. This review offers a comprehensive overview of the latest advancements in SiC nanomaterials for supercapacitors. It encompasses diverse synthesis methods for SiC nanomaterials, including solid-state, gas-phase, and liquid-phase synthesis techniques, while also discussing the advantages and challenges associated with each method. Furthermore, this review places a particular emphasis on the electrochemical performance of SiC-based supercapacitors, highlighting the pivotal role of SiC nanostructures and porous architectures in enhancing specific capacitance and cycling stability. A deep dive into SiC-based composite materials, such as SiC/carbon composites and SiC/metal oxide hybrids, is also included, showcasing their potential to elevate energy density and cycling stability. Finally, the paper outlines prospective research directions aimed at surmounting existing challenges and fully harnessing SiC's potential in the development of next-generation supercapacitors.

Oxygen defect enriched hematite nanorods @ reduced graphene oxide core-sheath fiber for superior flexible asymmetric supercapacitor

The development of flexible asymmetric supercapacitors with high operating potential, superior energy density, and exceptional rate performance holds significant implications for the advancement of flexible electronics. Herein, oxygen-deficient hematite nanorods @ reduced graphene oxide (Fe2O3-x@RGO) core-sheath fiber was rationally designed and fabricated. The introduction of oxygen defects can simultaneously enhance the conductivity, create a mesoporous crystalline structure, increase active surface area and sites. This leads to a significantly improved electrochemical performance, exhibiting a high specific capacitance of 525.2F cm-3 at 5 mV s-1 and remarkable rate capability (53.7 % retention from 5 to 100 mV s-1). Additionally, a flexible asymmetric supercapacitor was assembled employing Fe2O3-x@RGO fibers as anode and MnO2/RGO fibers as cathode. This design achieved a maximum operating voltage of 2.35 V, high energy density of 71.4 mWh cm-3, and outstanding cycling stability with 97.1 % retention after 5000 cycles. This study proposes a straightforward and efficient strategy to substantially enhance the electrochemical performances of transition metal oxide anodes, thereby promoting their practical application in asymmetric supercapacitors.

One-Dimensional Nickel Molybdate Nanostructures with Enhanced Supercapacitor Performance

One-dimensional NiMoO4 nanofibers were successfully prepared by electrospinning and high-temperature calcination. The supercapacitor performance tests were conducted on the prepared materials in a three-electrode system, and it was found that the calcination temperature during the preparation of the fibers seriously affects the final morphology and electrochemical performance of the obtained samples. The sample with a calcination temperature of 500 °C has better performance, its specific capacitance can reach 1947 F g-1, and the retention rate is 82.35% after 3000 cycles of constant current charging-discharging. The improvement of electrochemical performance is primarily on account of the unique one-dimensional nanostructure of the material, which can both enhance the charge transfer efficiency and effectively increase the speed of electrolyte ion diffusion.

Microfluidic-Assembled Covalent Organic Frameworks@Ti3 C2 Tx MXene Vertical Fibers for High-Performance Electrochemical Supercapacitors

The delicate design of innovative and sophisticated fibers with vertical porous skeleton and eminent electrochemical activity to generate directional ionic pathways and good faradic charge accessibility is pivotal but challenging for realizing high-performance fiber-shaped supercapacitors (FSCs). Here, hierarchically ordered hybrid fiber combined vertical-aligned and conductive Ti3 C2 Tx MXene (VA-Ti3 C2 Tx ) with interstratified electroactive covalent organic frameworks LZU1 (COF-LZU1) by one-step microfluidic synthesis is developed. Due to the incorporation of vertical channels, abundant redox active sites and large accessible surface area throughout the electrode, the VA-Ti3 C2 Tx @COF-LZU1 fibers express exceptional gravimetric capacitance of 787 F g-1 in a three-electrode system. Additionally, the solid-state asymmetric FSCs deliver a prominent energy density of 27 Wh kg-1 , capacitance of 398 F g-1 and cycling life of 20 000 cycles. The key to high energy storage ability originates from the decreased ions adsorption energy and ameliorative charge density distribution in vertically aligned and active hybrid fiber, accelerating ions transportation/accommodation and interfacial electrons transfer. Benefiting from excellent electrochemical performance, the FSCs offer sufficient energy supply to power watches, flags, and digital display tubes as well as be integrated with sensors to detect pulse signals, which opens a promising route for architecting advanced fiber toward the carbon neutrality market beyond energy-storage technology.

Rheology Engineering for Dry-Spinning Robust N-Doped MXene Sediment Fibers toward Efficient Charge Storage

MXene nanosheets are believed to be an ideal candidate for fabricating fiber supercapacitors (FSCs) due to their metallic conductivity and superior volumetric capacitance, while challenges remain in continuously collecting bare MXene fibers (MFs) via the commonly used wet-spinning technique due to the intercalation of water molecules and a weak interaction between Ti3 C2 TX nanosheets in aqueous coagulation bath that ultimately leads to a loosely packed structure. To address this issue, for the first time, a dry-spinning strategy is proposed by engineering the rheological behavior of Ti3 C2 TX sediment and extruding the highly viscose stock directly through a spinneret followed by a solvent evaperation induced solidification. The dry-spun Ti3 C2 TX fibers show an optimal conductivity of 2295 S cm-1 , a tensile strength of 64 MPa and a specific capacitance of 948 F cm-3 . Nitrogen (N) doping further improves the capacitance of MFs to 1302 F cm-3 without compromising their mechanical and electrical properties. Moreover, the FSC based on N-doped MFs exhibits a high volumetric capacitance of 293 F cm-3 , good stability over 10 000 cycles, excellent flexibility upon bending-unbending, superior energy/power densities and anti-self-discharging property. The excellent electrochemical and mechanical properties endow the dry-spun MFs great potential for future applications in wearable electronics.

Current trends in the detection and removal of heavy metal ions using functional materials

The shortage of freshwater resources caused by heavy metal pollution is an acute global issue, which has a great impact on environmental protection and human health. Therefore, the exploitation of new strategies for designing and synthesizing green, efficient, and economical materials for the detection and removal of heavy metal ions is crucial. Among the various methods for the detection and removal of heavy ions, advanced functional systems including nanomaterials, polymers, porous materials, and biomaterials have attracted considerable attention over the past several years due to their capabilities of real-time detection, excellent removal efficiency, anti-interference, quick response, high selectivity, and low limit of detection. In this tutorial review, we review the general design principles underlying the aforementioned functional materials, and in particular highlight the fundamental mechanisms and specific examples of detecting and removing heavy metal ions. Additionally, the methods which enhance water purification quality using these functional materials have been reviewed, also current challenges and opportunities in this exciting field have been highlighted, including the fabrication, subsequent treatment, and potential future applications of such functional materials. We envision that this tutorial review will provide invaluable guidance for the design of functional materials tailored towards the detection and removal of heavy metals, thereby expediting the development of high-performance materials and fostering the development of more efficient approaches to water pollution remediation.

Strategic Design and Synthesis of Ferrocene Linked Porous Organic Frameworks toward Tunable CO2 Capture and Energy Storage

This work focuses on porous organic polymers (POPs), which have gained significant global attention for their potential in energy storage and carbon dioxide (CO2) capture. The study introduces the development of two novel porous organic polymers, namely FEC-Mel and FEC-PBDT POPs, constructed using a simple method based on the ferrocene unit (FEC) combined with melamine (Mel) and 6,6'-(1,4-phenylene)bis(1,3,5-triazine-2,4-diamine) (PBDT). The synthesis involved the condensation reaction between ferrocenecarboxaldehyde monomer (FEC-CHO) and the respective aryl amines. Several analytical methods were employed to investigate the physical characteristics, chemical structure, morphology, and potential applications of these porous materials. Through thermogravimetric analysis (TGA), it was observed that both FEC-Mel and FEC-PBDT POPs exhibited exceptional thermal stability. FEC-Mel POP displayed a higher surface area and porosity, measuring 556 m2 g-1 and 1.26 cm3 g-1, respectively. These FEC-POPs possess large surface areas, making them promising materials for applications such as supercapacitor (SC) electrodes and gas adsorption. With 82 F g-1 of specific capacitance at 0.5 A g-1, the FEC-PBDT POP electrode has exceptional electrochemical characteristics. In addition, the FEC-Mel POP showed remarkable CO2 absorption capabilities, with 1.34 and 1.75 mmol g-1 (determined at 298 and 273 K; respectively). The potential of the FEC-POPs created in this work for CO2 capacity and electrical testing are highlighted by these results.

Hierarchical Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)/Reduced graphene oxide/Polypyrrole hybrid electrode with excellent rate capability and cycling stability for fiber-shaped supercapacitor

Fiber-shaped supercapacitor (FSSC) is considered as a promising energy storage device for wearable electronics due to its high power density and outstanding safety. However, it is still a great challenge to simultaneously achieve high specific capacitance especially at rapid charging/discharging rate and long-term cycling stability of fiber electrode in FSSC for practical application. Here, a ternary poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)/reduced graphene oxide/polypyrrole (PEDOT:PSS/rGO/PPy) fiber electrode was constructed by in situ chemical polymerization of pyrrole on hydrothermally-assembled and acid-treated PEDOT:PSS/rGO (PG) hybrid hydrogel fiber. In this case, the porous PG hybrid fiber framework possesses combined advantages of highly-conductive PEDOT and flexible two-dimensional (2D) small-sized rGO sheets, which provides large surface area for the deposition of high-pseudocapacitance PPy, multiscale electrons/ions transport channels for the efficient utilization of active sites, and buffering layers to accommodate the structure change during electrochemical process. Attributed to the synergy, as-obtained ternary fiber electrode presents ultrahigh volumetric/areal specific capacitance (389 F cm^-3 at 1 A cm^-3 or 983 mF cm^-2 at 2.5 mA cm^-2) and outstanding rate performance (56 %, 1-20 A cm^-3). In addition, 80 % preservation of initial capacitance after 8000 cycles for the corresponding FSSC also illustrates its greatly improved cycle stability compared with 64 % of binary PEDOT:PSS/PPy based counterpart. Accordingly, here proposed strategy promises a new opportunity to develop high-activity and durable electrode materials with potential applications in supercapacitor and beyond.

Carbonized Aminal-Linked Porous Organic Polymers Containing Pyrene and Triazine Units for Gas Uptake and Energy Storage

Porous organic polymers (POPs) have plenteous exciting features due to their attractive combination of microporosity with π-conjugation. Nevertheless, electrodes based on their pristine forms suffer from severe poverty of electrical conductivity, precluding their employment within electrochemical appliances. The electrical conductivity of POPs may be significantly improved and their porosity properties could be further customized by direct carbonization. In this study, we successfully prepared a microporous carbon material (Py-PDT POP-600) by the carbonization of Py-PDT POP, which was designed using a condensation reaction between 6,6'-(1,4-phenylene)bis(1,3,5-triazine-2,4-diamine) (PDA-4NH₂) and 4,4',4'',4'''-(pyrene-1,3,6,8-tetrayl)tetrabenzaldehyde (Py-Ph-4CHO) in the presence of dimethyl sulfoxide (DMSO) as a solvent. The obtained Py-PDT POP-600 with a high nitrogen content had a high surface area (up to 314 m² g^-1), high pore volume, and good thermal stability based on N₂ adsorption/desorption data and a thermogravimetric analysis (TGA). Owing to the good surface area, the as-prepared Py-PDT POP-600 showed excellent performance in CO₂ uptake (2.7 mmol g^-1 at 298 K) and a high specific capacitance of 550 F g^-1 at 0.5 A g^-1 compared with the pristine Py-PDT POP (0.24 mmol g^-1 and 28 F g^-1).

All-solid-state Ti3C2Tx neutral symmetric fiber supercapacitors with high energy density and wide temperature range

All-solid-state Ti₃C₂T_x neutral symmetric fiber supercapacitors (PVA EGHG Ti₃C₂T_x FSCs) with high energy density and wide temperature range are constructed by using polyvinyl alcohol (PVA)-ethylene glycol hydrogel (EGHG)-sodium perchlorate (NaClO₄) as electrolyte and separator, and Ti₃C₂T_x fiber as electrodes. Ti₃C₂T_x fiber is prepared using 130 mg mL^-1 Ti₃C₂T_x nanosheet ink as an assembly unit in a coagulation bath of isopropyl alcohol (IPA) and distilled water with 5 wt% CaCl₂ by a wet spinning method. The prepared Ti₃C₂T_x fiber exhibits a specific capacity of 385 F cm^-3 and a capacitance retention of 94 % after 10,000 cycles in 1 M NaClO₄ electrolyte. The assembled PVA EGHG Ti₃C₂T_x FSCs deliver a specific capacitance of 41 F cm^-3, a volumetric energy density of 5 mWh cm^-3, and a capacitance retention of 92 % after 500 times continuous bending. Furthermore, it shows good flexibility and excellent capacitance over a wide temperature range of -40 to 40 °C and maintains its electrochemical performance under varying degrees of bending. This study provides a viable strategy for designing and assembling all-solid-state neutral symmetric fiber supercapacitors with high energy density and wide temperature range.

Recent advances in polyaniline-based micro-supercapacitors

The rapid development of the Internet of Things (IoTs) and proliferation of wearable electronics have significantly stimulated the pursuit of distributed power supply systems that are small and light. Accordingly, micro-supercapacitors (MSCs) have recently attracted tremendous research interest due to their high power density, good energy density, long cycling life, and rapid charge/discharge rate delivered in a limited volume and area. As an emerging class of electrochemical energy storage devices, MSCs using polyaniline (PANI) electrodes are envisaged to bridge the gap between carbonaceous MSCs and micro-batteries, leading to a high power density together with improved energy density. However, despite the intensive development of PANI-based MSCs in the past few decades, a comprehensive review focusing on the chemical properties and synthesis of PANI, working mechanisms, design principles, and electrochemical performances of MSCs is lacking. Thus, herein, we summarize the recent advances in PANI-based MSCs using a wide range of electrode materials. Firstly, the fundamentals of MSCs are outlined including their working principle, device design, fabrication technology, and performance metrics. Then, the working principle and synthesis methods of PANI are discussed. Afterward, MSCs based on various PANI materials including pure PANI, PANI hydrogel, and PANI composites are discussed in detail. Lastly, concluding remarks and perspectives on their future development are presented. This review can present new ideas and give rise to new opportunities for the design of high-performance miniaturized PANI-based MSCs that underpin the sustainable prosperity of the approaching IoTs era.

Electrostatic Interfacial Cross-Linking and Structurally Oriented Fiber Constructed by Surface-Modified 2D MXene for High-Performance Flexible Pseudocapacitive Storage

Fiber supercapacitors are promising power supplies suitable for wearable electronics, but the internally insufficient cross-linking and random structure of fiber electrodes restrict their performance. This study describes how interfacial cross-linking and oriented structure can fabricate an MXene fiber with high flexibility and electrochemical performance. The continuous and highly oriented macroscopic fibers were constructed by 2D MXene sheets via a liquid-crystalline wet-spinning assembly. The oxyanion-enriched terminations of surface-modified MXene in situ could reinforce the interfacial cross-linking by electrostatic interactions while mediating the sheet-to-sheet lamellar structure within the fiber. The resultant MXene fiber exhibits high electrical conductivity (3545 S cm^-1) and mechanical strength (205.5 MPa) and high pseudocapacitance charge storage capability up to 1570.5 F cm^-3. Notably, the assembled fiber supercapacitor delivers an energy density of 77.6 mWh cm^-3 at 401.9 mW cm^-3, exceptional flexibility and stability exhibiting ∼99.5% capacitance retention under mechanical deformation, and can be integrated into commercial textiles to power microelectronic devices. This work provides insight into the fabrication of an advanced MXene fiber and the development of high-performance flexible fiber supercapacitors.

Soft Fiber Electronics Based on Semiconducting Polymer

Fibers, originating from nature and mastered by human, have woven their way throughout the entire history of human civilization. Recent developments in semiconducting polymer materials have further endowed fibers and textiles with various electronic functions, which are attractive in applications such as information interfacing, personalized medicine, and clean energy. Owing to their ability to be easily integrated into daily life, soft fiber electronics based on semiconducting polymers have gained popularity recently for wearable and implantable applications. Herein, we present a review of the previous and current progress in semiconducting polymer-based fiber electronics, particularly focusing on smart-wearable and implantable areas. First, we provide a brief overview of semiconducting polymers from the viewpoint of materials based on the basic concepts and functionality requirements of different devices. Then we analyze the existing applications and associated devices such as information interfaces, healthcare and medicine, and energy conversion and storage. The working principle and performance of semiconducting polymer-based fiber devices are summarized. Furthermore, we focus on the fabrication techniques of fiber devices. Based on the continuous fabrication of one-dimensional fiber and yarn, we introduce two- and three-dimensional fabric fabricating methods. Finally, we review challenges and relevant perspectives and potential solutions to address the related problems.

Controlling the electrochemical activity of dahlia-like β-NiS@rGO by interface polarization

Transition metal sulfides have become more and more important in the field of energy storage due to their superior chemical and physical properties. Herein, dahlia β-NiS with a rough surface and β-NiS@reduced graphene oxide (rGO) have been green synthesized by a one-step hydrothermal method. The interface characteristics of β-NiS@ rGO composites have been systematically studied by XPS, Raman, and first-principles calculations. It is found that the residual O atoms in the interface and the polarization charge generated by them play an important role in performance enhancement. The NiS@rGO composite material has the best electrochemical performance when the C/O ratio is 6.48. Furthermore, we designed a NiS@rGO//rGO asymmetric supercapacitor with a potential window of 1.7 V. Its excellent energy density and power density demonstrate the advantages of the optimized NiS@rGO electrode. When the power density is 850 W kg^-1, the energy density can reach 40.4 W h kg^-1. Even at a power density of up to 6800 W kg^-1, the energy density can be maintained at 17.6 W h kg^-1. These encouraging results provide a possible pathway for designing asymmetric supercapacitors with ultra-high performance and a feasible strategy for the precise control of electrochemical performance.

Functional Fiber Materials to Smart Fiber Devices

The development of fiber materials has accompanied the evolution of human civilization for centuries. Recent advances in materials science and chemistry offered fibers new applications with various functions, including energy harvesting, energy storing, displaying, health monitoring and treating, and computing. The unique one-dimensional shape of fiber devices endows them advantages to work as human-interfaced electronics due to the small size, lightweight, flexibility, and feasibility for integration into large-scale textile systems. In this review, we first present a discussion of the basics of fiber materials and the design principles of fiber devices, followed by a comprehensive analysis on recently developed fiber devices. Finally, we provide the current challenges facing this field and give an outlook on future research directions. With novel fiber devices and new applications continuing to be discovered after two decades of research, we envision that new fiber devices could have an important impact on our life in the near future.

Shape-Programmable Liquid Metal Fibers

Conductive and stretchable fibers are the cornerstone of intelligent textiles and imperceptible electronics. Among existing fiber conductors, gallium-based liquid metals (LMs) featuring high conductivity, fluidity, and self-healing are excellent candidates for highly stretchable fibers with sensing, actuation, power generation, and interconnection functionalities. However, current LM fibers fabricated by direct injection or surface coating have a limitation in shape programmability. This hinders their applications in functional fibers with tunable electromechanical response and miniaturization. Here, we reported a simple and efficient method to create shape-programmable LM fibers using the phase transition of gallium. Gallium metal wires in the solid state can be easily shaped into a 3D helical structure, and the structure can be preserved after coating the wire with polyurethane and liquifying the metal. The 3D helical LM fiber offered enhanced stretchability with a high breaking strain of 1273% and showed invariable conductance over 283% strain. Moreover, we can reduce the fiber diameter by stretching the fiber during the solidification of polyurethane. We also demonstrated applications of the programmed fibers in self-powered strain sensing, heart rate monitoring, airflow, and humidity sensing. This work provided simple and facile ways toward functional LM fibers, which may facilitate the broad applications of LM fibers in e-skins, wearable computation, soft robots, and smart fabrics.

Carbon-Yarn-Based Supercapacitors with In Situ Regenerated Cellulose Hydrogel for Sustainable Wearable Electronics

Developing sustainable options for energy storage in textiles is needed to power future wearable "Internet of Things" (IoT) electronics. This process must consider disruptive alternatives that address questions of sustainability, reuse, repair, or even a second life application. Herein, we pair stretch-broken carbon fiber yarns (SBCFYs), as current collectors, and an in situ regenerated cellulose-based ionic hydrogel (RCIH), as an electrolyte, to fabricate 1D fiber-shaped supercapacitors (FSCs). The areal specific capacitance reaches 433.02 μF·cm^-2 at 5 μA·cm^-2, while the specific energy density is 1.73 × 10^-2 μWh·cm^-2. The maximum achieved specific power density is 5.33 × 10^-1 mW·cm^-2 at 1 mA·cm^-2. The 1D FSCs possess a long-life cycle and 92% capacitance retention after 10 000 consecutive voltammetry cycles, higher than similar ones using the reference PVA/H₃PO₄ gel electrolyte. Additionally, the feasibility and reproducibility of the produced devices were demonstrated by connecting three devices in series and parallel, showing a small variation of the current density in flat and bent positions. An environmentally responsible approach was implemented by recovering the active materials from the 1D FSCs and reusing or recycling them without compromising the electrochemical performance, thus ensuring a circular economy path.

Arrayed Heterostructures of MoS2 Nanosheets Anchored TiN Nanowires as Efficient Pseudocapacitive Anodes for Fiber-Shaped Ammonium-Ion Asymmetric Supercapacitors

Nonmetallic ammonium ions that feature high safety, low molar mass, and small hydrated radius properties have shown great advantages in wearable aqueous supercapacitors. The construction of high-energy-density flexible ammonium-ion asymmetric supercapacitors (AASCs) is promising but still challenging due to the lack of high-capacitance pseudocapacitive anodes. Herein, freestanding core-shell heterostructures supported on carbon nanotube fibers were designed by anchoring MoS₂ nanosheets on nanowires (MoS₂@TiN/CNTF) as anodes for AASCs. With contributions of abundant active sites and conspicuous synergistic effects of multiple components for arrayed heterostructure engineering, the developed MoS₂@TiN/CNTF anodes exhibit a specific capacitance of 1102.5 mF cm^-2 at 2 mA cm^-2. Theoretical calculations confirm the dramatic enhancement of the binding strength of ammonium ions on the MoS₂ shell layer at the heterostructure, where a built-in electric field exists to accelerate the charge transfer. By utilizing a MnO₂/CNTF cathode and NH₄Cl/poly(vinyl alcohol) (PVA) as a gel electrolyte, quasi-solid-state fiber-shaped AASCs were successfully constructed, achieving a specific capacitance of 351.2 mF cm^-2 and an energy density of 195.1 μWh cm^-2, outperforming most recently reported fiber-shaped supercapacitors. This work provides a promising strategy to rationally design heterostructure engineering of MoS₂@TiN nanoarrays toward advanced anodes for application in next-generation AASCs.

A New Strategy for Fabricating Well-Distributed Polyaniline/Graphene Composite Fibers toward Flexible High-Performance Supercapacitors

Fiber-shaped supercapacitors are promising and attractive candidates as energy storage devices for flexible and wearable electric products. However, their low energy density (because their microstructure lacks homogeneity and they have few electroactive sites) restricts their development and application. In this study, well-distributed polyaniline/graphene composite fibers were successfully fabricated through a new strategy of self-assembly in solution combined with microfluidic techniques. The uniform assembly of polyaniline on graphene oxide sheets at the microscale in a water/N-methyl-2-pyrrolidone blended solvent was accompanied by the in situ reduction of graphene oxides to graphene nanosheets. The assembled fiber-shaped supercapacitors with gel-electrolyte exhibit excellent electrochemical performance, including a large specific areal capacitance of 541.2 mF cm^-2, along with a high energy density of 61.9 µW h cm^-2 at a power density of 294.1 µW cm^-2. Additionally, they can power an electronic device and blue LED lights for several minutes. The enhanced electrochemical performance obtained is mainly attributed to the homogeneous architecture designed, with an increased number of electroactive sites and a synergistic effect between polyaniline and graphene sheets. This research provides an avenue for the synthesis of fiber-shaped electrochemically active electrodes and may promote the development of future wearable electronics.

Polypyrrole/SnCl2 modified bacterial cellulose electrodes with high areal capacitance for flexible supercapacitors

Polypyrrole (PPy)/bacterial cellulose (BC) composite membranes are a promising kind of lightweight and flexible electrodes for supercapacitors. Herein, we explored a facile and efficient electrostatic self-assembly approach to uniformly depositing anion-doped PPy onto positively charged SnCl₂-modifed BC (SBC). The obtained PPy@SBC electrode exhibited a high areal capacitance of 5718 mF cm^-2 at a current density of 0.5 mA cm^-2, a desirable capacitance retention of 83.1% at 5.0 mA cm^-2 and excellent cycling stability (a capacitance retention of 86.8% after 10,000 cycles at 10 mA cm^-2). A symmetric flexible supercapacitor was further assembled with the PPy@SBC electrodes, which delivered outstanding mechanical flexibility with negligible capacitance decay under different bent states. This study shows impressive potential in fabricating high-performance electrodes for flexible supercapacitors.

Flexible and Conductive Polymer Threads for Efficient Fiber-Shaped Supercapacitors via Vapor Copolymerization

Flexible fiber electrodes are critical for high-performance fiber and wearable electronics. In this work, we presented a highly conductive all-polymer fiber electrode by vapor copolymerization of 2,5-dibromo-3,4-vinyldioxythiophene (DBEDOT) and 2,5-diiodo-3,4-vinyldioxythiophene (DIEDOT) monomers on commonly used polyester threads (PETs) at a temperature as low as 80 °C. The poly(3,4-ethylenedioxythiophene) (PEDOT)-coated PET threads maintain excellent flexibility and show conductivity of 7.93 S cm^-1, nearly four times higher than that reported previously via homopolymerization of DBEDOT monomer. A MnO₂ active layer was embedded into the PEDOT double layers, and the flexible fiber composite electrode showed a high linear specific capacitance of 157 mF cm^-1 and improved stability, retaining 86.5% capacitance after 5000 cycles. Fiber-shaped solid-state supercapacitors (FSSCs) based on the composite electrodes were assembled, and they displayed superior electrochemical performance. This work provides a new approach to realize high-performance and stable wearable electronics.

Preparation of high-value porous carbon by microwave treatment of chili straw pyrolysis residue

Microwave technology is utilized to prepare porous carbon from the chili straw pyrolysis residue in this study. As the pyrolysis temperature increases, the thermal stability of biochar is higher. The carbon speciation of the porous carbon PC500 is closest to that of graphite, and its inorganic-C reaches to 51.21%. Notably, the specific surface area of the activated porous carbon increases with increasing pyrolysis temperature, with a maximum value of 2768.52 m²/g for PC500. Further testing of the electrochemical properties of the porous carbon, PC500 possesses a high specific capacitance of 352F/g at 1 A/g while that of conventional heating is only 226.1F/g. The porous carbon prepared by microwave heating has better electrical properties compared to conventional heating, and the biochar obtained at higher pyrolysis temperature has a richer pore structure after activation.

Hardwood Kraft lignin-derived carbon microfibers with enhanced electrochemical performance

It is of great challenge to prepare lignin-derived carbon microfibers with suitable graphite crystallites due to the volatilization of incorporated polymers. In this work, we proposed a simple method for the construction of graphite crystallites based on the regulation of the hydrogen-bonding interaction between hardwood Kraft lignin (HKL) and poly(m-phenylene isophthalamide) (PMIA). The strong hydrogen-bonding interaction demonstrated by the results of TG, FTIR, XPS, Raman and XRD increased the graphite crystal size and perfected the crystal structure of HKL-based carbon microfibers, which further enhanced the electrochemical performance of HKL/PMIA-based carbon microfibers electrodes, especially for the increase of capacitance and cycle performance and the decrease of charge transfer resistance. The specific capacitance, energy density and power density of P2H2-based (HKL/PMIA = 1:1) carbon microfibers electrode were up to 190.8 F g^-1, 34.4 Wh kg^-1 and 540 W kg^-1 at a current density of 0.5 A g^-1, respectively, which were comparable to or even higher than those of lignin composites-based carbon fibers electrodes. This work reveals the relationship between hydrogen-bonding interaction and crystalline structure, which can be further considered in the preparation of lignin-based carbon fibers electrodes.

Bimetallic CoSe2/FeSe2 hollow nanocuboids assembled by nanoparticles as a positive electrode material for a high-performance hybrid supercapacitor

Design and fabrication of impressive and novel electrode materials for energy storage devices, especially supercapacitors, are of great importance. Herein, bimetallic CoSe₂/FeSe₂ hollow nanocuboid nanostructures derived from Co/Fe-Prussian Blue analogues (denoted as CoSe₂/FeSe₂ HNCs) are successfully designed and fabricated as a remarkable positive electrode material for high-performance supercapacitors. The bimetallic CoSe₂/FeSe₂ HNC nanostructures can have increased active sites and short electron-ion diffusion pathways. Bimetallic CoSe₂/FeSe₂ HNCs@NiF as a positive electrode showed efficient supercapacitive properties with a great specific capacity of 332.75 mA h g^-1 (1197.90 C g^-1) at 1 A g^-1, retaining 80.61% of its initial capacity at 20 A g^-1, considerable longevity (91.47% of its initial capacity after 10 000 cycles) and an excellent coulombic efficiency of 98.49%. Also, the designed and fabricated CoSe₂/FeSe₂ HNCs@NiF||AC@NiF hybrid supercapacitor device using bimetallic CoSe₂/FeSe₂ HNCs@NiF (positive electrode) and activated carbon@NiF (AC, negative electrode) exhibited an efficient energy density of 63.62 W h kg^-1 and a superior durability of 91.14% after 10 000 cycles.

The synthesis of CoS/MnCo2O4-MnO2 nanocomposites for supercapacitors and energy-saving H2 production

In this study, CoS/MnCo₂O₄-MnO₂ (CMM) nanocomposites were synthesized by hydrothermal and then electrochemical deposition. Their electrochemical properties were systematically investigated for supercapacitors and energy-saving H₂ production. As an electrode material for supercapacitor, CMM demonstrates a specific capacitance of 2320F g^-1 at 1 A/g, and maintains a specific capacitance of 1216F g^-1 at 10 A/g. It also shows 72.8 % capacitance retention after 8000 cycles. The aqueous asymmetric supercapacitor exhibited high energy storage capacity (887.86F g^-1 specific capacitance at a current density of 1 A/g), good rate performance and cycling stability. Besides, CMM shows outstanding urea oxidation reaction(UOR) and glycol oxidation reaction (MOR) performances for H₂ production. Compared to oxygen evolution reaction (OER) (1.635 V) at 20 mA cm^-2, the potentials were reduced by 213 mV for UOR and 233 mV for MOR, respectively. Therefore, this study shows the promising practical applications of CMM nanocomposites for energy storage and energy-saving H₂ production.

Two-Dimensional Hybrid Nanosheet-Based Supercapacitors: From Building Block Architecture, Fiber Assembly, and Fabric Construction to Wearable Applications

Fiber-based supercapacitors (F-SCs) have inspired widespread interest in the fields of wearable technology, energy, and carbon neutralization due to their highly deformable flexibility, fast charging/discharging capability, long-term stability, and energy conservation ability. In this review, we summarize the latest developments for fabricating fibrous electrodes of F-SCs where advanced micro two-dimensional (2D) building blocks (e.g., MXene and graphene) are chemically assembled and constructed into ordered mesofibers and multifunctional macrofabrics. Diverse fundamental principles of 2D hybrid nanosheets with respect to surface controls, pseudocapacitive modifications, and microstructural manipulations, promoting rapid electron transfer and charge conduction, are introduced. Additionally, various spinning methods for assembling and fabricating sophisticated fibers with advanced nano/microstructures, including hierarchical skeletons, anisotropic backbones, surface/entire porous frameworks, and vertical-aligned networks, for boosting ionic kinetic transport/storage are presented. Likewise, the structure-activity relationships between the porous structure and electrochemical performance are clarified. Moreover, multifunctional fabrics in terms of high flexibilities/strengths, superior electrical conductivities, and stabilized operations, which realize large energy density, deformable capability, and robust stability under harsh conditions, are emphasized. In particular, the potential power-supply applications, including flexible electronic devices, self-powered functions, and energy-sensor systems, are highlighted. Finally, a short conclusion and outlook, along with the current challenges and future opportunities of next-generation F-SCs, are proposed.

Laser Processing of Flexible In-Plane Micro-supercapacitors: Progresses in Advanced Manufacturing of Nanostructured Electrodes

Flexible in-plane architecture micro-supercapacitors (MSCs) are competitive candidates for on-chip miniature energy storage applications owing to their light weight, small size, high flexibility, as well as the advantages of short charging time, high power density, and long cycle life. However, tedious and time-consuming processes are required for the manufacturing of high-resolution interdigital electrodes using conventional approaches. In contrast, the laser processing technique enables high-efficiency high-precision patterning and advanced manufacturing of nanostructured electrodes. In this review, the recent advances in laser manufacturing and patterning of nanostructured electrodes for applications in flexible in-plane MSCs are comprehensively summarized. Various laser processing techniques for the synthesis, modification, and processing of interdigital electrode materials, including laser pyrolysis, reduction, oxidation, growth, activation, sintering, doping, and ablation, are discussed. In particular, some special features and merits of laser processing techniques are highlighted, including the impacts of laser types and parameters on manufacturing electrodes with desired morphologies/structures and their applications on the formation of high-quality nanoshaped graphene, the selective deposition of nanostructured materials, the controllable nanopore etching and heteroatom doping, and the efficient sintering of nanometal products. Finally, the current challenges and prospects associated with the laser processing of in-plane MSCs are also discussed. This review will provide a useful guidance for the advanced manufacturing of nanostructured electrodes in flexible in-plane energy storage devices and beyond.

Construction of hierarchical polypyrrole coated copper-catecholate grown on poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) fibers for high-performance supercapacitors

Fiber-shaped supercapacitors (FSCs) are considered as the optimal candidate for wearable energy devices, due to their high safety, excellent electrochemical stability, workability and body adaptability. However, the specific capacitances of today's FSCs such as carbon nanotube fibers and graphene fibers, are still not high enough for practical applications due to the limitation of their energy storage mode. So, we design a ternary composite fiber-shaped electrode: First, a kind of metal organic framework (MOF), copper-catecholate (Cu-CAT) nanorods, are in-situ grown on a wet-spun poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) fiber at the ambient temperature. Second, polypyrrole (PPy) is electrodeposited on the surface of the Cu-CAT/PEDOT:PSS fiber to obtain PPy@Cu-CAT@PEDOT:PSS fiber (PPy@Cu-CAT@PF). The growing Cu-CAT with high porosity anchored on the fiber surface provides electrochemical activate sites and the encapsulation of PPy effectively provides a continuous charge transfer path and improve its cycling stability. Notably, the PPy@Cu-CAT@PF electrode exhibits a satisfactory areal capacitance of 669.93 mF cm^-2 at 2 mA cm^-2, which remains 61.66% even at a high current density of 20 mA cm^-2. Furthermore, the assembled symmetric FSC displays excellent electrochemical properties and outstanding mechanical flexibility, demonstrating its feasibility as a wearable supercapacitor.

Stretchable sodium-ion capacitors based on coaxial CNT supported Na2Ti3O7 with high capacitance contribution

Stretchable sodium-ion capacitors (SSICs) are promising energy storage devices for wearable electronic devices, and the development bottleneck is the realization of stretchable battery-type electrodes with desirable electrochemical properties during dynamic deformation. Herein, we find that electrostatic modification of acidified carbon nanotubes with polyamines can introduce active sites and modulate the surface pH microenvironment, thereby developing a route to realize the in situ coaxial nanometerization of sodium titanate (nCNT@NTO). The nCNT@NTO anode material has a fast Na⁺ transport and the high capacitive contribution, which can deliver a high specific capacity (206.5 mA h g^-1 at 0.1 A g^-1) and high rate performance (maintain 51% capacity at 10 A g^-1), and the ideal cycle stability (∼93% capacity retention after 1000 cycles at 5 A g^-1). In addition, acrylate-rubber with high stickiness and stretchability are served as the elastic matrix both of the stretchable electrodes and quasi-solid-state electrolytes, which endows strong adhesion between electrodes and electrolytes. Thus, the accordingly assembled SSIC delivers high energy density of 8.8 mW h cm^-3 (at a power density of 0.024 W cm^-3), and excellent deformation stability (89% capacitance retention after 500 stretching cycles under 100% strain).

Hierarchical Co3O4@Ni3S2 electrode materials for energy storage and conversion

Transition metal oxides are considered to be one of the most potential electrode materials. However, poor conductivity and insufficient active sites limit their actual applications. Rationally designed electrode materials with unique structural features can be ascribed to the efficient route for enhancing electrochemical performance. Here, we report hybrid Co₃O₄@Ni₃S₂ nanostructures obtained via a hydrothermal strategy and subsequent electrodeposition process. The obtained products can be used as electrodes for a hybrid supercapacitor with a specific capacity of 1071 C g^-1 at 1 A g^-1 and excellent rate capability. The as-assembled device delivers an energy density of 77.92 W h kg^-1 at 2880 W kg^-1. As an electrocatalyst, the above electrode possesses an overpotential of 237.6 mV at 50 mA cm^-2 for oxygen evolution reaction.

Ultrastable Covalent Triazine Organic Framework Based on Anthracene Moiety as Platform for High-Performance Carbon Dioxide Adsorption and Supercapacitors

Conductive and porous nitrogen-rich materials have great potential as supercapacitor electrode materials. The exceptional efficiency of such compounds, however, is dependent on their larger surface area and the level of nitrogen doping. To address these issues, we synthesized a porous covalent triazine framework (An-CTFs) based on 9,10-dicyanoanthracene (An-CN) units through an ionothermal reaction in the presence of different molar ratios of molten zinc chloride (ZnCl₂) at 400 and 500 °C, yielding An-CTF-10-400, An-CTF-20-400, An-CTF-10-500, and An-CTF-20-500 microporous materials. According to N₂ adsorption–desorption analyses (BET), these An-CTFs produced exceptionally high specific surface areas ranging from 406–751 m²·g⁻¹. Furthermore, An-CTF-10-500 had a capacitance of 589 F·g⁻¹, remarkable cycle stability up to 5000 cycles, up to 95% capacity retention, and strong CO₂ adsorption capacity up to 5.65 mmol·g⁻¹ at 273 K. As a result, our An-CTFs are a good alternative for both electrochemical energy storage and CO₂ uptake.