Nanofibrous Electrolyte Research Articles

Mechanically robust and conductive zwitter ionic polymer coated electrospun nanofibrous electrolyte membranes for wireless human motion detection and capacitor applications

To address the limitations of poor ionic conductivity, low toughness, and high mass ratios in hydrogel-based electrolytes for flexible energy storage and wearable devices, here in a simple synthesis method of poly(ionic liquids) (PILs) based electrolyte membrane was developed. Briefly, PILs were utilized to coat electrospun PVDF-HFP nanofibrous membranes, resulting in ionically conducting composite electrolyte membranes (CPEMs) with enhanced physio-chemical properties. The obtained CPEMs exhibited an ionic conductivity of 0.056 S/m, along with a high tensile strength of 5.06 MPa and elongation to break of 156 %. Furthermore, we utilized these CPEMs as the electrolyte in symmetric capacitors by sandwiching them between carbon nanotube (CNT) coated Ni-foams. The resulting capacitors demonstrated a specific capacitance of 170F/g, an energy density of 53.41 Wh/kg, and a power density of 108.9 W/kg at an applied current of 1 mA. The suitability of these CPEMs as chemo-resistive sensors was investigated by attaching them to different body parts and monitoring changes in resistance during physical motion. The results demonstrated that the CPEMs exhibited effective gauge factors ranging from 1.85 to 6.44 and could detect movements up to 1 % strains.

A comparative analysis on the morphology and electrochemical performances of solution-casted and electrospun PEO-based electrolytes: The effect of fiber diameter and surface density

Solvent-free polymer electrolytes have been prepared through standard electrospinning and solution casting techniques, respectively. A series of nanofibrous electrolytes with various average fiber diameters and different surface densities were electrospun. In addition, polymeric films were casted with several thicknesses. It was shown that crystalline regions as well as fraction of free lithium ions were enhanced by fabrication of the finer fibers. The solution-casted electrolytes with the higher thicknesses displayed lower free ions and less amorphous phases. The nanofibrous mats illustrated the ionic conductivity from 0.062 to 0.172 mS.cm−1.While, the solution-casted ones presented lower ionic conductance in the range of 0.006 to 0.008 mS.cm−1. As surface density of the nanofibrous and solution-casted mats increased, the bulk resistance was improved. Moreover, it was identified that the prepared solvent-free electrolytes obeyed the Arrhenius behavior. The nanofibrous and solution-casted electrolytes with the highest ionic conductivities showed the highest values for the dielectric parameters. Furthermore, the optimum as-spun membrane illustrated higher specific capacity and Faradic current density compared with the solution-casted one. The results implied that the electrospun membranes are good candidates for solvent-free electrolyte application in the Li-ion batteries.

Novel electrospun polymer electrolytes incorporated with Keggin‐type hetero polyoxometalate fillers as solvent‐free electrolytes for lithium ion batteries

AbstractIn this study, solvent‐free nanofibrous electrolytes were fabricated through an electrospinning method. Polyethylene oxide (PEO), lithium perchlorate and ethylene carbonate were used as polymer matrix, salt and plasticizer respectively in the electrolyte structures. Keggin‐type hetero polyoxometalate (Cu‐POM@Ru‐rGO, Ni‐POM@Ru‐rGO and Co‐POM@Ru‐rGO (POM, polyoxometalate; rGO, reduced graphene oxide)) nanoparticles were synthesized and inserted into the PEO‐based nanofibrous electrolytes. TEM and SEM analyses were carried out for further evaluation of the synthesized filler structures and the electrospun nanofibre morphologies. The fractions of free ions and crystalline phases of the as‐spun electrolytes were estimated by obtaining Fourier transform infrared and XRD spectra, respectively. The results showed a significant improvement in the ionic conductivity of the nanofibrous electrolytes by increasing filler concentrations. The highest ionic conductivity of 0.28 mS cm−1 was obtained by the introduction of 0.49 wt% Co‐POM@Ru‐rGO into the electrospun electrolyte at ambient temperature. Compared with solution‐cast polymeric electrolytes, the electrospun electrolytes present superior ionic conductivity. Moreover, the cycle stability of the as‐spun electrolytes was clearly improved by the addition of fillers. Furthermore, the mechanical strength was enhanced with the insertion of 0.07 wt% fillers to the electrospun electrolytes. The results implied that the prepared nanofibres are good candidates as solvent‐free electrolytes for lithium ion batteries. © 2020 Society of Chemical Industry

The effect of concentration and ratio of ethylene carbonate and propylene carbonate plasticizers on characteristics of the electrospun PEO-based electrolytes applicable in lithium-ion batteries

In this study, plasticized electrospun fibers have been designed and fabricated as an electrolyte for lithium-ion batteries using electrospinning method. Polyethylene oxide (PEO) and lithium perchlorate were used as polymer matrix and lithium salt, respectively. Ethylene carbonate and propylene carbonate were applied to investigate the effects of the plasticizer concentration and various EC:PC ratios on the characteristics of the as-spun electrolytes. In addition, the influence of fiber orientation was examined on the ionic conductivity of the nanofibrous electrolytes. Results illustrated that compared with PC, EC can lead to a greater fraction of free ions, lower activation energy (Ea) and so more ionic conductivity. However, the highest room temperature ion conductivity of 0.171 mS·cm−1 was obtained for the as-spun electrolyte containing EC:PC (3:1) mixture. Moreover, with the increase of PC content, cycle stability of the electrospun electrolytes faded significantly. Furthermore, the ionic conductivity reduced from 0.212 to 0.020 mS·cm−1 with increasing of the fiber alignment. The results implied that the proposed nanostructured fibers can be a great candidate as free-solvent polymer electrolytes applicable in lithium-ion batteries.

Electrospun PEO nanofibrous membrane enable by LiCl, LiClO4, and LiTFSI salts: a versatile solvent-free electrolyte for lithium-ion battery application

In this study, the effect of type of lithium salts on the main properties of the nanostructure electrolytes was studied. Electrospinning process was applied to production of solvent-free PEO-based nanofibrous electrolytes containing various lithium salts, i.e., LiCl, LiClO4, and LiTFSI. Then, the characteristics of the electrospun nanofibers were evaluated by various techniques. The fraction of free ions was estimated by the FTIR spectrum. Also, to investigate the crystalline phases of the as-spun electrolytes, the samples were subjected to X-ray analysis. The highest room temperature ionic conductivity of the fabricated electrolytes was obtained as 0.33 mS cm−1 by the addition of 1.5 wt% LiClO4 into the nanofibers. Furthermore, the cycling stability of the as-spun structures was enhanced by increasing the amount of LiClO4 and LiCl salts in the produced nanofibers. The results implied that the prepared nanofibers are good candidates as solvent-free electrolytes for Li-ion batteries.

Nanofibrous poly(ethylene oxide)‐based structures incorporated with multi‐walled carbon nanotube and graphene oxide as all‐solid‐state electrolytes for lithium ion batteries

AbstractNanofibrous solid polymer electrolytes were prepared using the electrospinning method. These nanofibres were constructed from poly(ethylene oxide), lithium perchlorate and ethylene carbonate, which were incorporated with multi‐walled carbon nanotube (MWCNT) and graphene oxide (GO). The morphological properties of the as‐prepared electrolytes and the interaction between the components of the composites were characterized using scanning electron microscopy and Fourier transform infrared spectroscopy, respectively. X‐ray spectra and differential scanning calorimetry indicated an increase in amorphous regions of the nanofibrous electrolytes on addition of the fillers. However, the crystalline regions were increased on incorporation of fillers into polymeric film electrolytes. The conductivity values of the nanofibrous electrolytes reached 0.048 and 0.057 mS cm−1 when 0.35 wt% MWCNT and 0.21 wt % GO were introduced into the nanofibrous structures, respectively. The capacity and cycling stability of the nanofibrous electrolytes were improved by incorporation of MWCNT filler. Furthermore, stress and elongation modulus were improved at low MWCNT and GO filler contents. Results revealed that the nanofibrous structures could be promising candidates as solvent‐free electrolytes applicable in lithium ion batteries. © 2019 Society of Chemical Industry

Effect of titanium dioxide and zinc oxide fillers on morphology, electrochemical and mechanical properties of the PEO-based nanofibers, applicable as an electrolyte for lithium-ion batteries

In this study, preparation and characterization of filler-filled nanofibrous electrolytes based on polyethylene oxide (PEO) matrix are studied. The electrospun electrolytes are fabricated by an electrospinning method, using PEO, lithium perchlorate (LiClO4) as a salt, ethylene carbonate as a plasticizer and titanium dioxide (TiO2) and zinc oxide (ZnO) as fillers. Surface morphology, fraction of free ions and crystalline phases of the electrolytes are examined. The highest ion conductivities of 0.045 mS.cm−1 and 0.035 mS.cm−1 are obtained with incorporation of 0.21 wt% of the TiO2 and ZnO fillers into the electrospun nanofibers, respectively. However, film electrolytes embedded with the TiO2 and ZnO nano particles, synthesized by a film casting method, present ion conductivities of 0.0044 mS.cm−1 and 0.0147 mS.cm−1, respectively. In addition, it is identified that ion migration follows Arrhenius behavior in the as-spun electrolytes. The filler-filled nanofibrous electrolytes loss about 40% of their capacity after 45 cycles. Moreover, mechanical strength improves in filler-filled nanofibers up to an optimum ratio. The results imply that nanofibrous structures can be a great candidate as solid-state electrolytes for lithium ion batteries.

Morphology and electrochemical and mechanical properties of polyethylene‐oxide‐based nanofibrous electrolytes applicable in lithium ion batteries

AbstractWe report the synthesis of all‐solid‐state polymeric electrolytes based on electrospun nanofibers. These nanofibers are composed of polyethylene oxide (PEO) as the matrix, lithium perchlorate (LiClO4) as the lithium salt and propylene carbonate (PC) as the plasticizer. The effects of the PEO, LiClO4 and PC ratios on the morphological, mechanical and electrochemical characteristics were investigated using the response surface method (RSM) and analysis of variance test. The prepared nanofibrous electrolytes were characterized using SEM, Fourier transform infrared, XRD and DSC analyses. Conductivity measurements and tensile tests were conducted on the prepared electrolytes. The results show that the average diameter of the nanofibers decreased on reduction of the PEO concentration and addition of PC and LiClO4. Fourier transport infrared analysis confirmed the complexation between PEO and the additives. The highest conductivity was 0.05 mS cm−1 at room temperature for the nanofibrous electrolyte with the lowest PEO concentration and the highest ratio of LiClO4. The optimum nanofibrous electrolyte showed stable cycling over 30 cycles. The conductivity of a polymer film electrolyte was 29 times lower than that of the prepared nanofibrous electrolyte with similar chemical composition. Furthermore, significant fading in mechanical properties was observed on addition of the PC plasticizer. The results obtained imply that further optimization might lead to practical uses of nanofibrous electrolytes in lithium ion batteries. © 2019 Society of Chemical Industry

Evaluating the electrochemical properties of PEO‐based nanofibrous electrolytes incorporated with TiO2 nanofiller applicable in lithium‐ion batteries

In the present work, nanofibrous composite polymer electrolytes consist of polyethylene oxide (PEO), ethylene carbonate (EC), propylene carbonate (PC), lithium perchlorate (LiClO4), and titanium dioxide (TiO2) were designed using response surface method (RSM) and synthesized via an electrospinning process. Morphological properties of the as‐prepared electrolytes were studied using SEM. FTIR spectroscopy was conducted to investigate the interaction between the components of the composites. The highest room temperature ionic conductivity of 0.085 mS.cm−1 was obtained with incorporation of 0.175 wt. % TiO2 filler into the plasticized nanofibrous electrolyte by EC. Moreover, the optimum structure was compared with a film polymeric electrolyte prepared using a film casting method. Despite more amorphous structure of the film electrolyte, the nanofibrous electrolyte showed superior ion conductivity possibly due to the highly porous structure of the nanofibrous membranes. Furthermore, the mechanical properties illustrated slight deterioration with incorporation of the TiO2 nanoparticles into the electrospun electrolytes. This investigation indicated the great potential of the electrospun structures as all‐solid‐state polymeric electrolytes applicable in lithium ion batteries.

Nanofiber membrane based on ionic liquids as high-performance polymer electrolyte for sodium electrochemical device

Composite nanofibrous electrolyte membranes (CFEM) of poly(vinylidene fluoride-hexafluoropropylene) P(VdF-HFP)-1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) and its NaSCN are electrospun as nanofibrous membranes. Scanning electron microscope (SEM) images clearly inform that electrospun CFEM and CFEM–NaSCN with average fiber diameters of 50–200 nm have interconnected multifibrous layers with ultrafine porous structures. They exhibited a high uptake of the electrolyte solution (370–880 %). The polymer electrolytes have decreased crystalline, which is advantage to the increase in ionic conductivity. In addition, polymer electrolytes also are prepared by swelling nanofibre into blend of sodium salt and BMIMBF4. CFEM obtained 15 % BMIMBF4 exhibited higher ionic conductivity maximum of 5.6 × 10−5 S cm−1 at room temperature, and the conductive model of CFEM–NaSCN electrolyte answer for Arrhenius function. CFEM–NaSCN electrolyte showed a high electrochemical window of above 4.5 V, which is higher than electrospun pure P(VdF-HFP) without BMIMBF4 or BMIMBF4–NaSCN. With these improved performance characteristics, CFEM electrolyte and CFEM–NaSCN electrolyte will be found its suitability as polymer electrolyte for high-performance rechargeable batteries and super capacitor.