Application of Electrospun Nanofibers for Fabrication of Versatile and Highly Efficient Electrochemical Devices: A Review

The Impact of Recovered Lignin on Solid-State PEO-Based Electrolyte Produced via Electrospinning: Manufacturing and Characterisation

Lithium batteries have gained significant attention due to their high energy density, specific capacity, operating voltage, slow self-discharge rate, good cycle stability, and rapid charging capabilities. However, the use of liquid electrolytes presents several safety hazards. Solid-state polymer electrolytes (SPEs) offer a promising alternative to mitigate these issues. This study focuses on the preparation of an ionically conductive electrospun membrane and its potential application as an SPE. To support a circular approach and reduce the environmental impact, the target polymeric formulation combines poly(ethylene oxide) (PEO) and lignin, sourced from paper industry waste. The formulation is optimised to ensure the dissolution of lithium salts and enhance the membrane integrity. The addition of lignin is crucial to contrast the dendrites' growth and prevent the consequent battery breakdown. The electrospinning process is adjusted to obtain stable, homogeneous nanofibrous membranes, which are characterised using electron scanning microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). The membranes' potential as an SPE is assessed by measuring their ionic conductivity (>10-5 S cm-1 above 50 °C) and anodic stability (≈4.6 V vs. Li/Li+), and by testing their compatibility with lithium metal by reversible cycling in a symmetric Li|Li cell at 55 °C.

Fabrication electro-spun Poly(vinyl alcohol)-Melamine nonwoven membrane composite separator for high-power lithium-ion batteries

Current commercial separators used in lithium-ion batteries have inherent flaws, especially poor thermal stability, which pose substantial safety risks. This study introduces a high-safety composite membrane made from electrospun poly(vinyl alcohol)-melamine (PVAM) and polyvinylidene fluoride (PVDF) polymer solutions via a dip coating method, designed for high-voltage battery systems. The poly(vinyl alcohol) and melamine components enhance battery safety, while the PVDF coating improves lithium-ion conductivity. The dip-coated PVDF/Esp-PVAM composite separators were evaluated for electrolyte uptake, contact angle, thermal stability, porosity, electrochemical stability and ionic conductivity. Notably, our Dip 1 % PVDF@Esp-PVAM composite separator exhibited excellent wettability and a lithium-ion conductivity of approximately 7.75 × 10⁻⁴ S cm⁻1 at room temperature. These separators outperformed conventional PE separators in half-cells with Ni-rich NCM811 cathodes, showing exceptional cycling stability with 93.4 % capacity retention after 100 cycles at 1C/1C, as compared to 84.8 % for PE separators. Our Dip 1 % PVDF@Esp-PVAM composite separator demonstrates significant potential for enhancing the long-term durability and high-rate performance of lithium-ion batteries, making it a promising option for long-term energy storage applications.

Overlooked Promising Green Features of Electrospun Cellulose-Based Fibers in Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are accounted as promising power tools, applicable in a wide range of energy-based equipment, from portable devices to electric vehicles. Meanwhile, approaching a cost-effective, environmentally friendly, and safe LIB array has remained sluggish yet. In this regard, cellulose, as a nontoxic natural renewable polymer, has provided a stable and cohesive electrode structure with excellent mechanical stability and reduced electrode cracking or delamination during cycling. Additionally, the porous configuration of the cellulose allows for efficient and faster ion transport as a separator component. Miniaturizing cellulose and its derivatives have revealed more fabulous characteristics for the anode, cathode, and separator resulting from the increased surface-to-volume ratio and superior porosity, as well as their thin and lightweight architectures. The focal point of this review outlines the challenges relating to the extraction and electrospinning of cellulose-based nanofibers. Additionally, the efforts to employ these membranes as the LIBs' components are elucidated. Correspondingly, despite the great performance of cellulose-based LIB structures, a research gap is sensed in this era, possibly due to the difficulties in processing the electrospun cellulose fibers. Hence, this review can provide a source of recent advancements and innovations in cellulose-based electrospun LIBs for researchers who aim to develop versatile battery structures using green materials, worthwhile, and eco-friendly processing techniques.

A Recent Review of Electrospun Porous Carbon Nanofiber Mats for Energy Storage and Generation Applications

Electrospun porous carbon nanofiber mats have excellent properties, such as a large surface area, tunable porosity, and excellent electrical conductivity, and have attracted great attention in energy storage and power generation applications. Moreover, due to their exceptional properties, they can be used in dye-sensitized solar cells (DSSCs), membrane electrodes for fuel cells, catalytic applications such as oxygen reduction reactions (ORRs), hydrogen evolution reactions (HERs), and oxygen evolution reactions (OERs), and sensing applications such as biosensors, electrochemical sensors, and chemical sensors, providing a comprehensive insight into energy storage development and applications. This study focuses on the role of electrospun porous carbon nanofiber mats in improving energy storage and generation and contributes to a better understanding of the fabrication process of electrospun porous carbon nanofiber mats. In addition, a comprehensive review of various alternative preparation methods covering a wide range from natural polymers to synthetic carbon-rich materials is provided, along with insights into the current literature.

Current advances of nanocellulose application in biomedical field

Nanocellulose (NC) is a natural fiber that can be extracted in fibrils or crystals form from different natural sources, including plants, bacteria, and algae. In recent years, nanocellulose has emerged as a sustainable biomaterial for various medicinal applications including drug delivery systems, wound healing, tissue engineering, and antimicrobial treatment due to its biocompatibility, low cytotoxicity, and exceptional water holding capacity for cell immobilization. Many antimicrobial products can be produced due to the chemical functionality of nanocellulose, such disposable antibacterial smart masks for healthcare use. This article discusses comprehensively three types of nanocellulose: cellulose nanocrystals (CNC), cellulose nanofibrils (CNF), and bacterial nanocellulose (BNC) in view of their structural and functional properties, extraction methods, and the distinctive biomedical applications based on the recently published work. On top of that, the biosafety profile and the future perspectives of nanocellulose-based biomaterials have been further discussed in this review.

Proton-conductive aromatic membranes reinforced with poly(vinylidene fluoride) nanofibers for high-performance durable fuel cells

Durability and ion conductivity are counteracting properties of proton-conductive membranes that are challenging to achieve simultaneously and determine the lifetime and performance of proton exchange membrane fuel cells. Here, we developed aromatic ionomers reinforced with nonwoven poly(vinylidene fluoride) (PVDF) nanofibers. Because of the right combination of an isotropic nonwoven PVDF with high porosity (78%) and partially fluorinated aromatic ionomers (SPP-TFP-4.0), the resulting composite membrane (SPP-TFP-4.0-PVDF) outperformed state-of-the-art chemically stabilized and physically reinforced perfluorinated Nafion XL membrane, in terms of fuel cell operation and in situ chemical stability at a high temperature (120°C) and low relative humidity (30%). The SPP-TFP-4.0-PVDF membrane exhibited excellent chemical stability and stable rupture energy at high and low RH levels, allowing it to be an alternative proton-conductive membrane to meet the U.S. Department of Energy target to be used in automobile fuel cells in 2025.

The Mechanical Properties of Blended Fibrinogen:Polycaprolactone (PCL) Nanofibers

Electrospinning is a process to produce versatile nanoscale fibers. In this process, synthetic and natural polymers can be combined to produce novel, blended materials with a range of physical, chemical, and biological properties. We electrospun biocompatible, blended fibrinogen:polycaprolactone (PCL) nanofibers with diameters ranging from 40 nm to 600 nm, at 25:75 and 75:25 blend ratios and determined their mechanical properties using a combined atomic force/optical microscopy technique. Fiber extensibility (breaking strain), elastic limit, and stress relaxation times depended on blend ratios but not fiber diameter. As the fibrinogen:PCL ratio increased from 25:75 to 75:25, extensibility decreased from 120% to 63% and elastic limit decreased from a range between 18% and 40% to a range between 12% and 27%. Stiffness-related properties, including the Young's modulus, rupture stress, and the total and relaxed, elastic moduli (Kelvin model), strongly depended on fiber diameter. For diameters less than 150 nm, these stiffness-related quantities varied approximately as D-2; above 300 nm the diameter dependence leveled off. 50 nm fibers were five-ten times stiffer than 300 nm fibers. These findings indicate that fiber diameter, in addition to fiber material, critically affects nanofiber properties. Drawing on previously published data, a summary of the mechanical properties for fibrinogen:PCL nanofibers with ratios of 100:0, 75:25, 50:50, 25:75 and 0:100 is provided.

Biopolymer-based electrospun fibers in electrochemical devices: versatile platform for energy, environment, and health monitoring

Electrochemical power tools are regarded as essential keys in a world that is becoming increasingly reliant on fossil fuels in order to meet the challenges of rapidly depleting fossil fuel supplies. Additionally, due to the industrialization of societies and the growth of diseases, the need for sensitive, reliable, inexpensive, and portable sensors and biosensors for noninvasive monitoring of human health and environmental pollution is felt more than ever before. In recent decades, electrospun fibers have emerged as promising candidates for the fabrication of highly efficient electrochemical devices, such as actuators, batteries, fuel cells, supercapacitors, and biosensors. Meanwhile, the use of synthetic polymers in the fabrication of versatile electrochemical devices has raised environmental concerns, leading to an increase in the quest for natural polymers. Natural polymers are primarily derived from microorganisms and plants. Despite the challenges of processing bio-based electrospun fibers, employing natural nanofibers in the fabrication of electrochemical devices has garnered tremendous attention in recent years. Here, various natural polymers and the strategies employed to fabricate various electrospun biopolymers are briefly covered. The recent advances and research strategies used to apply the bio-based electrospun membranes in different electrochemical devices are carefully summarized, along with the scopes in various advanced technologies. A comprehensive and critical discussion about the use of biopolymer-based electrospun fibers as the potential alternative to non-renewable ones in future technologies is briefly highlighted. This review will serve as a field opening platform for using different biopolymer-based electrospun fibers to advance the electrochemical device-based renewable and sustainable technologies, which will be of high interest to a large community. Accordingly, future studies should focus on feasible and cost-effective extraction of biopolymers from natural resources as well as fabrication of high-performance nanofibrous biopolymer-based components applicable in various electrochemical devices.

Effects of Incorporating Titanium Dioxide with Titanium Carbide on Hybrid Materials Reinforced with Polyaniline: Synthesis, Characterization, Electrochemical and Supercapacitive Properties

We report on the synthesis of titanium dioxide by titanium carbide for the preparation of hybrid material reinforced with polyaniline (PANI@TiO2–TiC) using the in situ polymerization technique. The effectiveness of the samples on the thermal, optical and electrochemical properties was investigated. The XRD, XPS, FTIR, SEM and TEM results confirm the successful synthesis of the PANI, PANI@TiC and PANI@TiO2–TiC samples. Through this, a good connection, an excellent relationship between the structures and the properties of the synthesized hybrid materials were obtained. Moreover, the electrical conductivity and optical bandgap were also tested. Remarkably good electrochemical characteristics were identified by cyclic voltammetry. Moreover, the galvanostatic charge–discharge (GCD) of the supercapacitor was remarkably high. Cyclic stability showed good retention after 1500 cycles at 1.5 A·g−1.

Influence of Filament Winding Tension on the Deformation of Composite Flywheel Rotors with H-Shaped Hubs

The residual stress plays an important role in composite flywheel rotors composed of filament windings. The fiber tension during high-prestressed winding is the main source of the rotor deformation and residual stress of composite layers. In this study, the effect of the winding tension gradient on deformation was monitored in real-time. Two types of in-plane winding tension fluctuation methods were developed to investigate the effect of tension on deformation. Online and offline measurements were performed for the strain acquisition. A wireless strain instrument was used for online deformation monitoring and a laser scanner was used for the offline surface reconstruction. Additionally, different filament winding strategies were carried out to improve the efficiency of the winding tension by finite element analysis. The results indicated that the deviation between numerical and experimental results was within 8%. Based on the proposed numerical method, the influence of the in-plane and out-of-plane winding tension gradient distributions on the rotation process of the H-shaped rotor was analyzed. An in-plane winding strategy with variable tension was developed, which increased the initial failure speed by 160%.

Carbon Nanofibers Based on Potassium Citrate/Polyacrylonitrile for Supercapacitors

Wearable supercapacitors based on carbon materials have been emerging as an advanced technology for next-generation portable electronic devices with high performance. However, the application of these devices cannot be realized unless suitable flexible power sources are developed. Here, an effective electrospinning method was used to prepare the one-dimensional (1D) and nano-scale carbon fiber membrane based on potassium citrate/polyacrylonitrile (PAN), which exhibited potential applications in supercapacitors. The chemical and physical properties of carbon nanofibers were characterized by X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, and the Brunnauer–Emmett–Teller method. The fabricated carbon nanofiber membrane illustrates a high specific capacitance of 404 F/g at a current density of 1 A/g. The good electrochemical properties could be attributed to the small diameter and large specific surface area, which promoted a high capacity.

Comparative Study of Metal Substrates for Improved Carbonization of Electrospun PAN Nanofibers

Carbon nanofibers are used for a broad range of applications, from nano-composites to energy storage devices. They are typically produced from electrospun poly(acrylonitrile) nanofibers by thermal stabilization and carbonization. The nanofiber mats are usually placed freely movable in an oven, which leads to relaxation of internal stress within the nanofibers, making them thicker and shorter. To preserve their pristine morphology they can be mechanically fixated, which may cause the nanofibers to break. In a previous study, we demonstrated that sandwiching the nanofiber mats between metal sheets retained their morphology during stabilization and incipient carbonization at 500 °C. Here, we present a comparative study of stainless steel, titanium, copper and silicon substrate sandwiches at carbonization temperatures of 500 °C, 800 °C and 1200 °C. Helium ion microscopy revealed that all metals mostly eliminated nanofiber deformation, whereas silicone achieved the best results in this regard. The highest temperatures for which the metals were shown to be applicable were 500 °C for silicon, 800 °C for stainless steel and copper, and 1200 °C for titanium. Fourier transform infrared and Raman spectroscopy revealed a higher degree of carbonization and increased crystallinity for higher temperatures, which was shown to depend on the substrate material.

Research on the Morphology Reconstruction of Deep Cryogenic Treatment on PtRu/nitrogen-Doped Graphene Composite Carbon Nanofibers

To improve the performance of PtRu/nitrogen-doped graphene composite carbon nanofibers, the composite carbon nanofibers were thermally compensated by deep cryogenic treatment (DCT), which realized the morphology reconstruction of composite carbon nanofibers. The effects of different DCT times were compared: 12 h, 18 h, and 24 h. The morphology reconstruction mechanism was explored by combining the change of inner chain structure and material group. The results showed that the fibers treated for 12 h had better physical and chemical properties, where the diameter is evenly distributed between 500 and 800 nm. Combined with Fourier infrared analysis, the longer the cryogenic time, the more easily the water vapor and nitrogen enter polymerization reaction, causing changes of chain structure and degradation performance. With great performance of carbonization and group transformation, the PtRu/nitrogen-doped graphene composite carbon nanofibers can be used as an efficient direct alcohol fuel cell catalyst and promote its commercialization.

Electrospinning of Chitosan for Antibacterial Applications—Current Trends

Chitosan is a natural biopolymer that can be suitable for a wide range of applications due to its biocompatibility, rigid structure, and biodegradability. Moreover, it has been proven to have an antibacterial effect against several bacteria strains by incorporating the advantages of the electrospinning technique, with which tailored nanofibrous scaffolds can be produced. A literature search is conducted in this review regarding the antibacterial effectiveness of chitosan-based nanofibers in the filtration, biomedicine, and food protection industries. The results are promising in terms of research into sustainable materials. This review focuses on the electrospinning of chitosan for antibacterial applications and shows current trends in this field. In addition, various aspects such as the parameters affecting the antibacterial properties of chitosan are presented, and the application areas of electrospun chitosan nanofibers in the fields of air and water filtration, food storage, wound treatment, and tissue engineering are discussed in more detail.

Recent developments in polysaccharide-based electrospun nanofibers for environmental applications

Electrospinning has become an inevitable approach to produce nanofibrous structures for diverse environmental applications. Polysaccharides, due to their variety of types, biobased origins, and eco-friendly, and renewable nature are wonderful materials for the said purpose. The present review discusses the electrospinning process, the parameters involved in the formation of electrospun nanofibers in general, and the polysaccharides in specific. The selection of materials to be electrospun depends on the processing conditions and properties deemed desirable for specific applications. Thereby, the conditions to electrospun polysaccharides-based nanofibers have been focused on for possible environmental applications including air filtration, water treatment, antimicrobial treatment, environmental sensing, and so forth. The polysaccharide-based electrospun membranes, for instance, due to their active adsorption sites could find significant potential for contaminants removal from the aqueous systems. The study also gives some recommendations to overcome any shortcomings faced during the electrospinning and environmental applications of polysaccharide-based matrices.

Opportunities, Challenges and Prospects for Electrodeposition of Thin-Film Functional Layers in Solid Oxide Fuel Cell Technology

Electrolytic deposition (ELD) and electrophoretic deposition (EPD) are relevant methods for creating functional layers of solid oxide fuel cells (SOFCs). This review discusses challenges, new findings and prospects for the implementation of these methods, with the main emphasis placed on the use of the ELD method. Topical issues concerning the formation of highly active SOFC electrodes using ELD, namely, the electrochemical introduction of metal cations into a porous electrode backbone, the formation of composite electrodes, and the electrochemical synthesis of perovskite-like electrode materials are considered. The review presents examples of the ELD formation of the composite electrodes based on porous platinum and silver, which retain high catalytic activity when used in the low-temperature range (400–650 °C). The features of the ELD/EPD co-deposition in the creation of nanostructured electrode layers comprising metal cations, ceramic nanoparticles, and carbon nanotubes, and the use of EPD to create oriented structures are also discussed. A separate subsection is devoted to the electrodeposition of CeO₂-based film structures for barrier, protective and catalytic layers using cathodic and anodic ELD, as well as to the main research directions associated with the deposition of the SOFC electrolyte layers using the EPD method.

Textile-Based Sensors for Biosignal Detection and Monitoring

Biosignals often have to be detected in sports or for medical reasons. Typical biosignals are pulse and ECG (electrocardiogram), breathing, blood pressure, skin temperature, oxygen saturation, bioimpedance, etc. Typically, scientists attempt to measure these biosignals noninvasively, i.e., with electrodes or other sensors, detecting electric signals, measuring optical or chemical information. While short-time measurements or monitoring of patients in a hospital can be performed by systems based on common rigid electrodes, usually containing a large amount of wiring, long-term measurements on mobile patients or athletes necessitate other equipment. Here, textile-based sensors and textile-integrated data connections are preferred to avoid skin irritations and other unnecessary limitations of the monitored person. In this review, we give an overview of recent progress in textile-based electrodes for electrical measurements and new developments in textile-based chemical and other sensors for detection and monitoring of biosignals.

Metallic Supports Accelerate Carbonization and Improve Morphological Stability of Polyacrylonitrile Nanofibers during Heat Treatment

Electrospun poly(acrylonitrile) (PAN) nanofibers are typical precursors of carbon nanofibers. During stabilization and carbonization, however, the morphology of pristine PAN nanofibers is not retained if the as-spun nanofiber mats are treated without an external mechanical force, since internal stress tends to relax, causing the whole mats to shrink significantly, while the individual fibers thicken and curl. Stretching the nanofiber mats during thermal treatment, in contrast, can result in fractures due to inhomogeneous stress. Previous studies have shown that stabilization and carbonization of PAN nanofibers electrospun on an aluminum substrate are efficient methods to retain the fiber mat dimensions without macroscopic cracks during heat treatment. In this work, we studied different procedures of mechanical fixation via metallic substrates during thermal treatment. The influence of the metallic substrate material as well as different methods of double-sided covering of the fibers, i.e., sandwiching, were investigated. The results revealed that sandwich configurations with double-sided metallic supports not only facilitate optimal preservation of the original fiber morphology but also significantly accelerate the carbonization process. It was found that unlike regularly carbonized nanofibers, the metal supports allow complete deoxygenation at low treatment temperature and that the obtained carbon nanofibers exhibit increased crystallinity.

The Production of Carbon Nanofiber on Rubber Fruit Shell-Derived Activated Carbon by Chemical Activation and Hydrothermal Process with Low Temperature

Recently, the conversion of biomass into carbon nanofibers has been extensively studied. In this study, carbon nanofibers (CNFs) were prepared from rubber fruit shell (RFS) by chemical activation with H₃PO₄, followed by a simple hydrothermal process at low temperature and without a vacuum and gas catalyst. XRD and Raman studies show that the structure formed is an amorphous graphite formation. From the thermal analysis, it is shown that CNFs have a high thermal stability. Furthermore, an SEM/TEM analysis showed that CNFs’ morphology varied in size and thickness. The obtained results reveal that by converting RFS into an amorphous carbon through chemical activation and hydrothermal processes, RFS is considered a potential biomass source material to produce carbon nanofibers.