Wearable flexible zinc-ion batteries based on electrospinning technology

Flexible wearable batteries are widely used in smartwatches, foldable phones, and fitness trackers due to their thinness and small size. Zinc-based batteries have the advantages of low cost, high safety, and ecofriendliness, which are considered to be the best alternative to flexible lithium-ion batteries(LIBs).Therefore, wearable flexible zinc-ion batteries(FZIBs) have attracted considerable interest as a promising energy storage device. Electrospun nanofibers(ESNFs) have great potential for application in wearable FZIBs due to their low density, high porosity, large specific surface area, and flexibility. Moreover, electrospinning technology can achieve the versatility of nanofibers through structural design and incorporation of other multifunctional materials. This paper reviews a wide range of applications of electrospinning in FZIBs, mainly in terms of cathode, anode, separator, polymer electrolyte, and all-inone flexible batteries. Firstly, the electrospinning device, principles, and influencing parameters are briefly described, showing its positive impact on FZIBs. Subsequently, the energy storage principles and electrode configurations of FZIBs are described, and some of the common problems of the batteries are illustrated, including zinc anode dendrite growth, corrosion, cathode structure collapse, and poor electrical conductivity. This is followed by a comprehensive overview of research progress on the individual components of FZIBs(cathode, anode, separator, and polymer electrolyte) from the perspective of electrostatically spun fiber materials and an in-depth study of all-in-one flexible batteries. Finally, the challenges and future development of FZIBs are individually concluded and look forward. We hope that this work will provide new ideas and avenues for the development of advanced energy technologies and smart wearable systems.

Application of different fiber structures and arrangements by electrospinning in triboelectric nanogenerators

In recent years,nanogenerators(NGs)have attracted wide attention in the energy field,among which triboelectric nanogenerators(TENGs)have shown superior performance.Multiple reports of electrospinning(ES)-based TENGs have been reported,but there is a lack of deep analysis of the designing method from microstructure,limiting the creative of new ES-based TENGs.Most TENGs use polymer materials to achieve corresponding design,which requires structural design of polymer materials.The existing polymer molding design methods include macroscopic molding methods,such as injection,compression,extrusion,calendering,etc.,combined with liquid-solid changes such as soluting and melting;it also includes micro-nano molding technology,such as melt-blown method,coagulation bath method,ES method,and nanoimprint method.In fact,ES technology has good controllability of thickness dimension and rich means of nanoscale structure regulation.At present,these characteristics have not been reviewed.Therefore,in this paper,we combine recent reports with some microstructure regulation functions of ES to establish a more general TENGs design method.Based on the rich microstructure research results in the field of ES,much more new types of TENGs can be designed in the future.

Fabrication of High-Efficiency Polyvinyl Alcohol Nanofiber Membranes for Air Filtration Based on Principle of Stable Electrospinning

A mass flow matching model(MFMM)was established for studying the stable status of solution electrospinning.The study of the solution droplet status at the needle tip focused on various combinations of applied voltages and injection rates to figure out their influence on steadily fabricating polyvinyl alcohol(PVA)nanofibers prepared from PVA spinning solutions with two different mass fractions(10%and 16%).The results revealed that during the stable electrospinning,the influence resulted from the change of the injection rate approximately canceled out the impact brought by adjusting the applied voltage,leading to almost the same morphology as that of the PVA nanofibers.And the mass fraction of PVA in the spinning solution dominated the structure and the diameter distribution of the electrospun nanofibers.Under stable electrospinning conditions,the composite membrane was produced by depositing PVA nanofibers on the polyethylene terephthalate(PET)nonwoven substrate for an air filtration test.Furthermore,the prepared composite membrane exhibited a high air filtration efficiency(99.97%)and a low pressure drop(120 Pa)for 300-500 nm neutralized polystyrene latex(PSL)aerosol particles,demonstrating its potential as an alternative for a variety of commercial applications in air filtration.

Comparative structural and electrochemical properties of mixed P2/O′3-layered sodium nickel manganese oxide prepared by sol-gel and electrospinning methods:Effect of Na-excess content

The effect of Na-excess content in the precursor on the structural and electrochemical performances of sodium nickel manganese oxide(NNMO)prepared by sol-gel and electrospinning methods is investigated in this paper.X-ray diffraction results of the prepared NNMO without adding Na-excess content indicate sodium loss,while the mixed phase of P2/O′3-type layered NNMO presented after adding Na-excess content.Compared with the sol-gel method,the secondary phase of NiO is more suppressed by using the electrospinning method,which is further confirmed by field emission scanning electron microscope images.N_(2) adsorption-desorption isotherms show no remarkably difference in specific surface areas between different preparation methods and Na-excess contents.The analysis of X-ray absorption near edge structure indicates that the oxidation states of Ni and Mn are+2 and+4,respectively.For the electrochemical properties,superior electrochemical performance is observed in the NNMO electrode with a low Na-excess content of 5wt%.The highest specific capacitance is 36.07 F·g^(-1)at0.1 A·g^(-1)in the NNMO electrode prepared by using the sol-gel method.By contrast,the NNMO electrode prepared using the electrospinning method with decreased Na-excess content shows excellent cycling stability of 100%after charge-discharge measurements for 300 cycles.Therefore,controlling the Na excess in the precursor together with the preparation method is important for improving the electrochemical performance of Na-based electrode materials in supercapacitors.

An energetic nano-fiber composite based on polystyrene and 1,3,5-trinitro-1,3,5-triazinane fabricated via electrospinning technique

Electrospinning is a simple technique used to fabricate polymeric nano-fibrous membranes.These nano-fibers have found a wide range of valuable applications in the biomedical field.However,it has not been utilized with solid high explosives yet.Herein,the electrospinning technique has been used to fabricate polystyrene(PS)/1,3,5-trinitro-1,3,5-triazinane(RDX)composite nanofibers.The governed electrospinning parameters,voltage,distance from the collector,flow rate,mandrel rotating speed,time,and solution concentration,that greatly affect the morphology of the obtained nanofibers were optimized.The fabricated PS/RDX nano-fibers were characterized using scanning electron microscopy(SEM),X-ray diffractometer(XRD),and Fourier Transform Infrared(FTIR)spectroscopy.The impact and friction sensitivities of PS/RDX were also measured.The thermal behavior of the prepared composite and the pure materials were studied by the thermal gravimetric analysis technique(TGA).SEM results proved the fabrication of PS/RDX fibers in the nano-size via electrospinning.FTIR spectroscopy confirmed the existence of the characteristic functional groups of both PS and RDX in the composite nano-fibers.XRD sharp peaks showed the conversion of amorphous PS into crystalline shape via electrospinning and also confirmed the formation of PS/RDX composite.The PS fibers absorbed the heat and increased the onset decomposition of the pure RDX from 181.5 to 200.7℃in the case of PS/RDX fibers.Interestingly,PS/RDX nano-fibers showed the relatively low impact and friction sensitivities of 100 J and 360 N respectively.These results could introduce PS/RDX nanofibrous composite in the field of explosives detection with high levels of safety.

Composite bioabsorbable vascular stents via 3D bio-printing and electrospinning for treating stenotic vessels

A new type of vascular stent is designed for treating stenotic vessels. Aiming at overcoming the shortcomings of existing equipment and technology for preparing a bioabsorbable vascular stent （BVS）, a new method which combines 3D bio-printing and electrospinning to prepare the composite bioabsorbable vascular stent （CBVS） is proposed. The inner layer of the CBVS can be obtained through 3D bio- printing using poly-p-dioxanone （PPDO）. The thin nanofiber film that serves as the outer layer can be built through electrospinning using mixtures of chitosan-PVA （poly （vinyl alcohol））. Tests of mechanical properties show that the stent prepared through 3D bio-printing combined with electrospinning is better than that prepared through 3D bio- printing alone. Cells cultivated on the CBVS adhere and proliferate better due to the natural, biological chitosan in the outer layer. The proposed complex process and method can provide a good basis for preparing a controllable drug-carrying vascular stent. Overall, the CBVS can be a good candidate for treating stenotic vessels.

Polymer nanofibers prepared by low-voltage near-field electrospinning

Elcctrospiiming is a straightforward method to produce micro/nanoscale fibers from polymer solutions typically using an operating voltage of 10 kV 30 kV and spinning distance of 10 cm 20 cm. In this paper, polyvinyl pyrrolidone （PVP） non-woven nanofibers with diameters of 200 nm 900 nm were prepared by low-voltage near-field electrospinning with a working voltage of less than 2.8 kV and a spinning distance of less than 10 mm. Besides the uniform fibers, beaded-fibers were also fabricated and the formation mechanism was discussed. Particularly, a series of experiments were carried out to explore the influence of processing variables on the formation of near-field electrospun PVP nanofibers, including concentration, humidity, collecting position, and spinning distance.

Tunable 3D Nanofiber Architecture of Polycaprolactone by Divergence Electrospinning for Potential Tissue Engineering Applications

The creation of biomimetic cell environments with micro and nanoscale topographical features resembling native tissues is critical for tissue engineering. To address this challenge, this study focuses on an innovative electrospinning strategy that adopts a symmetrically divergent electric field to induce rapid self-assembly of aligned polycaprolactone(PCL) nanofibers into a centimeter-scale architecture between separately grounded bevels. The 3D microstructures of the nanofiber scaffolds were characterized through a series of sectioning in both vertical and horizontal directions. PCL/collagen(type I)nanofiber scaffolds with different density gradients were incorporated in sodium alginate hydrogels and subjected to elemental analysis. Human fibroblasts were seeded onto the scaffolds and cultured for 7 days. Our studies showed that the inclination angle of the collector had significant effects on nanofiber attributes, including the mean diameter, density gradient, and alignment gradient. The fiber density and alignment at the peripheral area of the 45°-collector decreased by 21% and 55%, respectively, along the z-axis,while those of the 60°-collector decreased by 71% and 60%, respectively. By altering the geometry of the conductive areas on the collecting bevels, polyhedral and cylindrical scaffolds composed of aligned fibers were directly fabricated. By using a four-bevel collector, the nanofibers formed a matrix of microgrids with a density of 11%. The gradient of nitrogen-to-carbon ratio in the scaffold-incorporated hydrogel was consistent with the nanofiber density gradient. The scaffolds provided biophysical stimuli to facilitate cell adhesion, proliferation, and morphogenesis in 3D.

Influence of Sorbitan Monooleate on Morphology and Drug Release Behavior of Emulsion Electrospinning Polycaprolactone Nanofibers

Ultrafine polycaprolactone(PCL)fibers containing watersoluble drug tetracycline hydrochloride(Tet)were prepared by emulsion electrospinning.Sorbitan monooleate(Span80)was added as an essential additive to form stable water/oil emulsions and fabricate fibers with core-sheath structure.Different concentrations of Span80(0-40 g/L)were used to investigate the stability of emulsion and size of dispersed droplets.The scanning electron microscope(SEM)images indicated that the morphology of the fibers with Span80 were beaded-free with diameters of 200-400 nm,and Span80 enhanced the spinnability of electrospinning solution.The laser scanning confocal microscope(LSCM)images indicated that Tet was well encapsulated into the core region of the PCL fibers.The transmission electron microscope(TEM)image showed the formation of core-sheath structure.The loading efficiency(LE)and entrapment efficiency(EE)of Tet were calculated and release profiles in artificial saliva buffer solution(pH=6.8)were also analyzed.The results revealed that LE and EE of fibers with Span80decreased with the increase of its concentration.Fibers with coresheath structure had a longer effective release lifetime than without Span80.The increase of Span80 resulted in higher hydrophilicity of fibers and faster release rate of Tet.

Fabrication and Magnetic Properties of Composite Ni_(0.5)Zn_(0.5)Fe_2O_4/Pb(Zr_(0.52)Ti_(0.48))O_3 Nanofibers by Electrospinning

One-dimensional and quasi-one-dimensional nanostructure materials are promising building blocks for electromagnetic devices and nanosystems.In this work,the composite Ni0.5Zn0.5Fe2O4（NZFO）/ Pb（Zr0.52Ti0.48）O3（PZT） nanofibers with average diameters about 65 nm are prepared by electrospinning from poly（vinyl pyrrolidone） （PVP） and metal salts.The precursor composite NZFO/PZT/PVP nanofibers and the subsequent calcined NZFO/PZT nanofibers are investigated by Fourier transform infrared spectroscopy （FT- IR） ,X-ray diffraction （XRD）,scanning electron microscopy （SEM）.The magnetic properties for nanofibers are measured by vibrating sample magnetometer（VSM）.The NZFO/PZT nanofibers obtained at calcination temperature of 900 °C for 2 h consist of the ferromagnetic spinel NZFO and ferroelectric perovskite PZT phases,which are constructed from about 37 nm NZFO and 17 nm PZT grains.The saturation magnetization of these NZFO/PZT nanofibers increases with increasing calcination temperature and contents of NZFO in the composite.

Microstructural Changes of Graphene/PLA/PBC Nanofibers by Electrospinning during Tensile Tests

This study focuses on the nanostructure and nanostructural changes of novel graphene/poly（lactic acid） （PLA）/ poly（butylene carbonate） （PBC） nanofibers via electrospinning, which are characterized by differential scanning calorimetry （DSC）, scanning electron microscopy （SEM）, tensile test and in situ small angle x-ray scattering. DSC indicates that the endothermic peak at 295℃ of pure PLA/PBC nanofibers shifted from 317℃ to lower 290℃ with the increasing graphene content. SEM observations reveal a fine dispersion of graphene in the nanofiber matrices. The graphene/PLA/PBC nanofiSers exhibit good improvements in mechanical property. The tensile strength of nanofibers increases with the addition of 0.01 g graphene but reduces with further addition of 0.04g graphene. The scattering intensities increase dramatically when the strain levels are higher than the yield point due to the nucleation and growth of nanovoids or crystals. However, the increasing content of graphene in the PLA/PBC matrix provokes a strong restriction to the deformation-induced crystals.

Effect of Electric Field Intensity on the Morphology of Magnetic-field-assisted Electrospinning PVP Nanofibers

Polyvinylpyrrolidone （PVP） nanofibers were processed by magnetic-field-assisted electrospinning （MFAES） technique. Since electric field intensity was one of the most important parameters influencing fiber morphology, the research aimed to study how electric field intensity affects fiber morphology in MFAES technique. The experimental results revealed that the distribution of diameter widened while the average diameter of PVP fibers decreased and the degree of the alignment reduced with the increase of electric field intensity. However, the fibers would be conglutinated together when the electric field intensity was too low. Also, the increase of working distance made the average diameter and the degree of the alignment increase slightly under the same electric field intensity, but the fibers could be partially curved instead of being fully straight if the working distance was too long. It was also indicated that maintaining the electric field intensity at 1 kV/cm With the voltage-distance combinations of 12 kV-12 cm （for 12wt% PVP） and 15 kV-15 cm （for 14wt% PVP） among all other combinations would result in the optimal alignment as well as a narrow size distribution of the fibers.

SnO_(2)/Co_(3)O_(4)nanofibers using double jets electrospinning as low operating temperature gas sensor

SnO_(2)/Co_(3)O_(4)nanofibers(NFs)are synthesized by using a homopolar electrospinning system with double jets of positive polarity electric fields.The morphology and structure of SnO_(2)/Co_(3)O_(4)hetero-nanofibers are characterized by using field emission scanning electron microscope(FE-SEM),transmission electron microscope(TEM),x-ray diffraction(XRD),and x-ray photoelectron spectrometer(XPS).The analyses of SnO_(2)/Co_(3)O_(4)NFs by EDS and HRTEM show that the cobalt and tin exist on one nanofiber,which is related to the homopolar electrospinning and the crystallization during sintering.As a typical n-type semiconductor,Sn O_(2)has the disadvantages of high optimal operating temperature and poor reproducibility.Comparing with Sn O_(2),the optimal operating temperature of SnO_(2)/Co_(3)O_(4)NFs is reduced from 350℃to 250℃,which may be related to the catalysis of Co_(2)O_(2).The response of SnO_(2)/Co_(3)O_(4)to 100-ppm ethanol at 250℃is 50.9,9 times higher than that of pure Sn O_(2),which may be attributed to the p–n heterojunction between the n-type Sn O_(2)crystalline grain and the p-type Co_(2)O_(2)crystalline grain.The nanoscale p–n heterojunction promotes the electron migration and forms an interface barrier.The synergy effects between Sn O_(2)and Co_(2)O_(2),the crystalline grain p–n heterojunction,the existence of nanofibers and the large specific surface area all jointly contribute to the improved gas sensing performance.

Synthesis of Ordered Ultra-long Manganite Nanowires via Electrospinning Method

We develop a new electrospinning method to prepare ultra-long ordered La1-xSrxMnO3 （LSMO） nanowires. The length is up to several centimeters and is only limited by the size of the collector. The well-ordered straight-line structure ensures the transport measurement, which is impossible to be carried out for the random nanowires fabricated by the traditional electrospinning method. Magnetic and transport measurements indicate that the physical properties of the LSMO nanowires depend sensitively on the doping concentration. At the optimum doping, the LSMO wires are ferromagnetic at room temperature with a metal-insulator transition temperature close to room temperature. Magnetic force microscopy studies are also performed to provide a microscopic view of these ultra-long nanowires.

Needleless Electrospinning:Reciprocation vs.Rotation

Needleless electrospinning is a versatile method to produce nanofibers.In particular,the rotary version of this technique has enjoyed widespread use because there is no need to clean the spinneret.The rotation speed is limited by the potential deviation of the jet due to the centrifugal force.Other limitations are due to the fast volatilization of the solvent from the opened spinning system.In order to overcome these drawbacks,here a novel reciprocating system based on a moving spinning-plate is proposed.The spinning process is implemented in a half-closed system with the spinning-plate immersed in the solution tank.When the immersed spinning-plate moves up from the solution tank,multiple jets are ejected from the droplets on the tips of the spinning-plate under the effect of an electric field force.The morphology of the obtained nanofibers has been analyzed by scanning electron microscopy.The results indicated that the obtained fibers are uniform in structures and small in diameters.Both issues of needle clogging and intense solvent evaporation can be mitigated using this alternate approach.

Macromolecule’s Orientation in a Nanofiber by Bubble Electrospinning

In the search for sustainable alternatives to harmful synthetic fibers,an increasing amount of research focuses on biomimicry and natural fibers.Sea silk is an exceptional textile material.It is a kind of natural silk produced using the long silky filaments secreted by a specific bivalve mollusk(Pinna nobilis);now at edge of extinction.This paper suggests a simple but effective way to prepare artificial sea silk from Mytilus edulis.A sea silk solution is prepared using a Mytilus edulis protein,and a polyvinyl alcohol(PVA)solution is mixed with the sea silk solution in order to produce artificial sea silk through a bubble electrospinning technique.The effects of the sea silk concentration on the nanofiber’s morphology and mechanical properties are studied experimentally.

Characterization of V_2O_5/MoO_3 composite photocatalysts prepared via electrospinning and their photodegradation activity for dimethyl phthalate

Vanadium pentoxide（V2O5）/molybdenum trioxide（MoO 3） composites with different molar ratios of vanadium（V） to molybdenum（Mo） were synthesized via a simple electrospinning technique. The photocatalytic activity of the composites were evaluated by their ability to photodegrade methylene blue and dimethyl phthalate（DMP） under visible-light irradiation. Compared with pure V2O5 and MoO 3,the V2O5/MoO 3 composites showed enhanced visible-light photocatalytic activity because of a V 3d impurity energy level and the formation of heterostructures at the interface between V2O5 and MoO 3. The optimal molar ratio of V to Mo in the V2O5/MoO 3 composites was found to be around 1/2. Furthermore,high-performance liquid chromatographic monitoring revealed that phthalic acid was the main intermediate in the photocatalytic degradation process of DMP.

Fabrication of LaNiO3 nanofibers by electrospinning

In order to acquire LaNiO3 nanofibers with particular morphology and structure, electrospinning technique, for the first time, was successfully applied to fabricate LaNiO3 nanofibers in the paper. Polyvinyl alcohol（PVA）/ [La（NO3）3＋Ni（CH3COO）2] composite nanofibers were fabricated by electrospinning, and polycrystalline LaNiO3 nanofibers were prepared by calcination of the PVA/[La（NO3）3＋Ni（CH3COO）2] composite nanofibers at 6000C for 10 h. The samples were characterized by using thermogravimetric-differential thermal analysis （TG-DTA）, X-ray diffraction spectrometry（XRD）, scanning electron microscopy （SEM） and Fourier transform infrared spectrometry （FTIR）. The results showed that PVA/[La（NO3）3＋ Ni（CH3COO）2] composite nanofibers were amorphous in structure, and pure phase LaNiO3 nanofibers were trigonal with space group R3m. The surface of as-prepared composite nanofibers was smooth, and the diameter was about 200 nm. The diameter of LaNiO3 nanofibers was smaller than that of the relevant composite fibers. The surface of the LaNiO3 nanofibers becomes coarse with the increase of calcination temperatures. The diameter of LaNiO3 nanofibers was ca. 80 nm, and the length was greater than 100μm. The mass of the sample remained constant when the temperature was above 463℃, and the total mass loss percentage was 90.9%. Possible formation mechanism of LaNiO3 nanofibers was preliminarily proposed.

Direct fabrication of cerium oxide hollow nanofibers by electrospinning

Electrospinning technique was used to fabricate PVP/Ce（NO3）3 composite microfibers. Different morphological CeO2 nanofibers were obtained by calcination of the PVP/Ce（NO3）3 composite microfibers and were characterized by scanning electron microscopy （SEM）, Transmission electron microscopy （TEM）, X-ray diffraction （XRD）, thermal gravimetric and differential thermal analysis （TG-DTA）, and （FTIR）. SEM micrographs indicated that the surface of the composite fibers was smooth and became coarse with the increase of calcination temperatures. The diameters of CeO2 hollow nanofibers （300 nm at 600 ℃ and 600 nm at 800 ℃ ） were smaller than those of PVP/Ce（NO3）3 composite fibers （1-2 um ）. CeO2 hollow nanofibers were obtained at 600 ℃ and CeO2 hollow and porous nanofibers formed by nanoparti- cles were obtained at 800 ℃. The length of the CeO2 hollow nanofibers was greater than 50 um. XRD analysis revealed that the composite microfibers were amorphous in structure and CeO2 nanofibers were cubic in structure with space group O^5H - FM3m when calcination tem- peratures were 600-800 ℃. TG-DTA and FTIR revealed that the formation of CeO2 nanofibers was largely influenced by the calcination temperatures. Possible formation mechanism of CeO2 hollow nanofibers was proposed.

Microporous carbon nanofibers prepared by combining electrospinning and phase separation methods for supercapacitor

Microporous carbon nanofibers (MCNFs) derived from polyacrylonitrile nanofibers were fabricated via electrospinning technology and phase separation in the presence of polyvinylpyrrolidone (PVP). PVP together with a mixed solvent of N, N-Dimethylformamide and dimethyl sulfoxide was used as pore forming agent. The influences of PVP content in casting solution on the structure and electrochemical performance of the MCNFs were also investigated. The highest capacitance of 200 F/g was obtained on a three-electrode system at a scan rate of 0.5 A/g. The good performance was owing to the high specific surface area and the large amount of micro-pores, which enhanced the absorption and the transportation efficiency of electrolyte ion during charge/discharge process. This research indicated that the combination of electrospinning and phase separation technology could be used to fabricate microporous carbon nanofibers as electrode materials for supercapacitors with high specific surface area and outstanding electrochemical performance. (C) 2016 Science Press and Dalian Institute of Chemical Physics, Chinese Academy of Sciences. Published by Elsevier B.V. and Science Press. All rights reserved.