Jiadeng Zhu

Use of a tin antimony alloy-filled porous carbon nanofiber composite as an anode in sodium-ion batteries

Lithium-ion battery is currently the dominant energy storage technology for electronic devices and electric vehicles. However, the predictable rising cost of lithium raw materials has attracted increasing interest in less expensive rivals, such as sodium-ion battery. In this work, a tin antimony (SnSb) alloy-filled porous carbon nanofiber composite was prepared as a sodium-ion battery anode material by a simple electrospinning method with subsequent thermal treatment. The spinning solution contained antimony tin oxide nanoparticles as the SnSb alloy precursor, polyacrylonitrile as the carbon precursor, and polymethyl methacrylate (PMMA) as the pore generator. The resultant SnSb@C nanofiber composite formed a continuous conductive network, which was favorable for enhancing its electrochemical performance. The presence of the SnSb alloy significantly increased the energy storage capacity of the composite due to its high theoretical capacity. The porous structure created by the decomposition of the PMMA polymer provided a free space to buffer the volume change of the SnSb alloy during the sodiation–desodiation process. The resultant SnSb@C nanofiber composite exhibited high capacity and a stable rate capability, and it was demonstrated to be a promising anode candidate for sodium-ion batteries.

A laser ultrasound transducer using carbon nanofibers-polydimethylsiloxane composite thin film

The photoacoustic effect has been broadly applied to generate high frequency and broadband acoustic waves using lasers. However, the efficient conversion from laser energy to acoustic power is required to generate acoustic waves with high intensity acoustic pressure (>10 MPa). In this study, we demonstrated laser generated high intensity acoustic waves using carbon nanofibers–polydimethylsiloxane (CNFs-PDMS) thin films. The average diameter of the CNFs is 132.7 ± 11.2 nm. The thickness of the CNFs film and the CNFs-PDMS composite film is 24.4 ± 1.43 μm and 57.9 ± 2.80 μm, respectively. The maximum acoustic pressure is 12.15 ± 1.35 MPa using a 4.2 mJ, 532 nm Nd:YAG pulsed laser. The maximum acoustic pressure using the CNFs-PDMS composite was found to be 7.6-fold (17.62 dB) higher than using carbon black PDMS films. Furthermore, the calculated optoacoustic energy conversion efficiency K of the prepared CNFs-PDMS composite thin films is 15.6 × 10−3 Pa/(W/m2), which is significantly higher than carbon black-P...

A novel bi-functional double-layer rGO–PVDF/PVDF composite nanofiber membrane separator with enhanced thermal stability and effective polysulfide inhibition for high-performance lithium–sulfur batteries

A novel, bi-functional double-layer reduced graphene oxide (rGO)–polyvinylidene fluoride (PVDF)/PVDF membrane was fabricated by a simple electrospinning technique and was used as a promising separator for lithium–sulfur batteries. This double-layer membrane separator delivers two different functionalities: (i) the porous PVDF nanofiber framework in both rGO–PVDF and PVDF layers provides good thermal stability and maintains the structural integrity of the separator; and (ii) the conductive rGO–PVDF layer serves as a polysulfide inhibitor and ensures the fast transfer of lithium ions. Compared to conventional polypropylene membrane separators, this new separator design can significantly enhance the cycling stability and rate capability of the incorporated lithium–sulfur batteries. Overall, it is demonstrated that this new double-layer rGO–PVDF/PVDF composite membrane separator opens an alternate avenue in the structural design of high-performance lithium–sulfur batteries in dealing with multiple challenges.

Poly(vinyl Alcohol) Borate Gel Polymer Electrolytes Prepared by Electrodeposition and Their Application in Electrochemical Supercapacitors

Gel polymer electrolytes (GPEs) have been studied for preparing flexible and compact electrochemical energy storage devices. However, the preparation and use of GPEs are complex, and most GPEs prepared through traditional methods do not have good wettability with the electrodes, which retard them from achieving their performance potential. In this study, these problems are addressed by conceiving and implementing a simple, but effective, method of electrodepositing poly(vinyl alcohol) potassium borate (PVAPB) GPEs directly onto the surfaces of active carbon electrodes for electrochemical supercapacitors. PVAPB GPEs serve as both the electrolyte and the separator in the assembled supercapacitors, and their scale and shape are determined solely by the geometry of the electrodes. PVAPB GPEs have good bonding to the active electrode materials, leading to excellent and stable electrochemical performance of the supercapacitors. The electrochemical performance of PVAPB GPEs and supercapacitors can be manipulated simply by adjusting the concentration of KCl salt used during the electrodeposition process. With a 0.9 M KCl concentration, the as-prepared supercapacitors deliver a specific capacitance of 65.9 F g(-1) at a current density of 0.1 A g(-1) and retain more than 95% capacitance after 2000 charge/discharge cycles at a current density of 1 A g(-1). These supercapacitors also exhibit intelligent high voltage self-protection function due to the electrolysis-induced cross-linking effect of PVAPB GPEs.

Hierarchical multi-component nanofiber separators for lithium polysulfide capture in lithium–sulfur batteries: an experimental and molecular modeling study

Sulfur (S) has been considered as a promising cathode candidate for lithium batteries due to its high theoretical specific capacity and energy density. However, the low active material utilization, severe capacity fading, and short lifespan of the resultant lithium–sulfur (Li–S) batteries have greatly hindered their practicality. In this work, a multi-functional polyacrylonitrile/silica nanofiber membrane with an integral ultralight and thin multi-walled carbon nanotube sheet is presented and it provides a new approach to significantly improve the overall electrochemical performance of Li–S batteries. The experimental results are in agreement with molecular modeling studies based on density functional theory and Monte Carlo simulations. Remarkably, this design is favorable for the fast diffusion of both lithium ions and electrons and the mitigation of the diffusion of polysulfides. As a consequence, a high reversible capacity of 741 mA h g−1 at 0.2C after 100 cycles with excellent cyclability and high-rate performance (627 mA h g−1 at 1C) are achieved even with a high sulfur loading of 70 wt% in the cathode, revealing its great potential for energy storage applications. Moreover, a capacity of 426 mA h g−1 is retained after 300 cycles at a high current density of 2C. These results represent a major step forward in the progress of Li–S battery technologies.

NiCu Alloy Nanoparticle-Loaded Carbon Nanofibers for Phenolic Biosensor Applications

NiCu alloy nanoparticle-loaded carbon nanofibers (NiCuCNFs) were fabricated by a combination of electrospinning and carbonization methods. A series of characterizations, including SEM, TEM and XRD, were employed to study the NiCuCNFs. The as-prepared NiCuCNFs were then mixed with laccase (Lac) and Nafion to form a novel biosensor. NiCuCNFs successfully achieved the direct electron transfer of Lac. Cyclic voltammetry and linear sweep voltammetry were used to study the electrochemical properties of the biosensor. The finally prepared biosensor showed favorable electrocatalytic effects toward hydroquinone. The detection limit was 90 nM (S/N = 3), the sensitivity was 1.5 µA µM−1, the detection linear range was 4 × 10−7–2.37 × 10−6 M. In addition, this biosensor exhibited satisfactory repeatability, reproducibility, anti-interference properties and stability. Besides, the sensor achieved the detection of hydroquinone in lake water.

Photosensitizer-Embedded Polyacrylonitrile Nanofibers as Antimicrobial Non-Woven Textile

Toward the objective of developing platform technologies for anti-infective materials based upon photodynamic inactivation, we employed electrospinning to prepare a non-woven textile comprised of polyacrylonitrile nanofibers embedded with a porphyrin-based cationic photosensitizer; termed PAN-Por(+). Photosensitizer loading was determined to be 34.8 nmol/mg material; with thermostability to 300 °C. Antibacterial efficacy was evaluated against four bacteria belonging to the ESKAPE family of pathogens (Staphylococcus aureus; vancomycin-resistant Enterococcus faecium; Acinetobacter baumannii; and Klebsiella pneumonia), as well as Escherichia coli. Our results demonstrated broad photodynamic inactivation of all bacterial strains studied upon illumination (30 min; 65 ± 5 mW/cm2; 400–700 nm) by a minimum of 99.9996+% (5.8 log units) regardless of taxonomic classification. PAN-Por(+) also inactivated human adenovirus-5 (~99.8% reduction in PFU/mL) and vesicular stomatitis virus (>7 log units reduction in PFU/mL). When compared to cellulose-based materials employing this same photosensitizer; the higher levels of photodynamic inactivation achieved here with PAN-Por(+) are likely due to the combined effects of higher photosensitizer loading and a greater surface area imparted by the use of nanofibers. These results demonstrate the potential of photosensitizer-embedded polyacrylonitrile nanofibers to serve as scalable scaffolds for anti-infective or self-sterilizing materials against both bacteria and viruses when employing a photodynamic inactivation mode of action.

Superior high-voltage aqueous carbon/carbon supercapacitors operating with in situ electrodeposited polyvinyl alcohol borate gel polymer electrolytes

Electrodeposited polyvinyl alcohol borate (PVAB) aqueous gel polymer electrolytes (GPEs) have been found to possess excellent high-voltage stability and high ionic conductivity which are promising in building aqueous supercapacitors with high operating voltage and good electrochemical performance. In this study, PVAB GPEs were formed directly on activated carbon electrodes by in situ electrodeposition to serve as both electrolytes and separators for high-voltage aqueous carbon/carbon supercapacitors. The morphology and structure of the prepared PVAB GPE layers were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. The electrochemical performance of supercapacitors using PVAB GPEs was tested and compared with those of supercapacitors using neutral salt aqueous electrolytes and organic electrolytes. The results show that the PVA molecules in PVAB GPEs are in the amorphous state and crosslinked by O → B− coordination bonds. The supercapacitors using PVAB GPEs can operate stably at 2 V, and no drastic electrolysis is observed in these supercapacitors even at 4 V. Among all the PVABs, PVA potassium borate (PVAPB) GPEs possess the best ionic conductivity. The high energy densities of 12.47 and 7.14 W h kg−1 can be achieved for the supercapacitor using the PVAPB GPE at the current densities of 0.2 and 2 A g−1, respectively, which are better than those of supercapacitors using 1 M Li2SO4 aqueous electrolyte and 1 M LiPF6 organic electrolyte especially at high current densities. The reversible ionization of water molecules cooperating with the reversible formation of O → B− coordination bonds is considered to play a critical role in the ionic transportation of PVAB GPEs.

High-strength, thermally stable nylon 6,6 composite nanofiber separators for lithium-ion batteries

Abstract Electrospun nylon 6,6 composite nanofiber membranes containing TiO2 or SiO2 nanoparticles were fabricated, and their physical and electrochemical properties were assessed for use as high-strength, thermally stable separators for lithium-ion batteries. Experimental results demonstrated that TiO2/nylon 6,6 and SiO2/nylon 6,6 nanofiber membranes not only displayed good mechanical strength and excellent thermal stability, but also showed improved electrochemical properties compared to commercial polypropylene membrane separator. Larger liquid electrolyte uptake, higher ionic conductivity, higher electrochemical oxidation limit, and lower interfacial resistance with lithium were obtained for TiO2/nylon 6,6 and SiO2/nylon 6,6 nanofiber membranes. Among all membranes studied, SiO2/nylon 6,6 nanofiber membranes showed the highest ionic conductivity and lowest interfacial resistance with lithium owing to their highest porosity and well-dispersed nanoparticles. In addition, Li/LiCoO2 and Li/LiFePO4 cells containing these composite nanofiber membranes demonstrated high cell capacities, good cycling performance, and superior C-rate performance at room temperature.

Li0.33La0.557TiO3 ceramic nanofiber-enhanced polyethylene oxide-based composite polymer electrolytes for all-solid-state lithium batteries

A polyethylene oxide (PEO)-based composite solid polymer electrolyte filled with one-dimensional (1D) ceramic Li0.33La0.557TiO3 (LLTO) nanofibers was designed and prepared. It exhibits a high ionic conductivity of 2.4 × 10−4 S cm−1 at room temperature and a large electrochemical stability window of up to 5.0 V vs. Li/Li+, and is a promising electrolyte candidate for all solid-state lithium batteries.