Polymer gel electrolytes containing sulfur-based ionic liquids in lithium battery applications at room temperature

Polymer gel electrolytes comprising a sulfur-based ionic liquid (IL), a lithium salt, and butyrolactone (GBL) as an additive hosted in PVdF-HFP matrix were prepared and characterized. The result shows that adding small amount of GBL to the polymer electrolytes can improve the cathodic stability of the electrolytes, which ensures the lithium plating/stripping in the redox process. Furthermore, cyclic voltammograms studies indicate that the polymer electrolytes have well reversible redox process. When the IL component reaches 75 wt%, the polymer electrolyte has higher ionic conductivity than the other samples and it is 6.32 × 10^?4 S cm^?1. The assembled batteries with the polymer electrolyte have better discharge capacity, and after 100 cycles, the discharge capacity of the battery still retains 148 mAh g^?1.     

Effective influences of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIMTFSI) ionic liquid on the ion transport properties of micro-porous zinc-ion conducting poly (vinyl chloride) /poly (ethyl methacrylate) blend-based polymer electrolytes

A series of new gel polymer electrolytes (GPEs) based on different concentrations of a hydrophobic ionic liquid (IL) 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide (EMIMTFSI) entrapped in an optimized typical composition of polymer blend-salt matrix [poly(vinyl chloride) (PVC) (30 wt%) / poly(ethyl methacrylate) (PEMA) (70 wt%) : 30 wt% zinc triflate Zn(CF₃SO₃)₂] has been prepared using facile solution casting technique. The AC impedance analysis has revealed the occurrence of the maximum ionic conductivity of 1.10 × 10^?4 Scm^?1 at room temperature (301 K) exhibited by the PVC/PEMA- Zn(OTf)₂ system containing 80 wt% ionic liquid. The addition of EMIMTFSI into the optimized PVC/PEMA- Zn(OTf)₂ system in different weight percentages enhances the number of free zinc ions thereby leading to enrichment of ionic conductivity. The structural and complexation behaviour of the as prepared polymer gel electrolytes was substantiated by subjecting these electrolyte films to X-ray diffraction (XRD) and Attenuated total reflectance - Fourier transformed infrared (ATR-FTIR) investigations. The wider electrochemical stability window ~ 3.23 V and a reasonable cationic transference number (t_Zn ²⁺) of 0.63 have been attained for the polymer gel electrolyte film containing higher loading of (80 wt%) ionic liquid. The development of the amorphous phase of these gel polymer electrolyte membranes with increasing ionic liquid content was observed from scanning electron microscopic (SEM) analysis. The results of the current work divulge the assurance of developing GPEs based on ionic liquids for prospective application in zinc battery systems.     

Poly(methyl methacrylate) based nanocomposite gel polymer electrolytes with enhanced safety and performance

The study presents preparation of poly methyl methacrylate (PMMA) based nanocomposite gel polymer electrolytes consisting of, salt lithium perchlorate (LiClO₄), plasticizer PC/DEC and different proportions of SiO₂ nanofiber by solution casting process. The effect of the composition of the electrolytes on their ionic, mechanical and thermal characteristics was investigated. Morphology of the nanocomposite electrolyte films has been observed by scanning and transmission electron microscopes. Interactions among the constituents of the composite and structural changes of the base polymer were investigated by Fourier Transform Infrared (FTIR) spectroscopy and X-ray diffraction (XRD) techniques. The maximum conductivity i.e. 10^?3 Scm^?1 at room temperature is obtained with the electrolyte composition of 0.6(PMMA)-0.15(PC + DEC)-0.1LiClO₄ (wt%) containing 10 wt% SiO₂ nanofiber and the temperature dependent conductivity data of the electrolyte follows Vogel-Tamman-Fulcher (VTF) behavior.     

A study on polymer blend electrolyte based on PVA/PVP with proton salt

Proton-conducting polymer blend electrolytes based on PVA–PVP–NH₄NO₃ were prepared for different compositions by solution cast technique. The prepared films are investigated by different techniques. The XRD study reveals the amorphous nature of the polymer electrolyte. The FTIR and laser Raman studies confirm the complex formation between the polymer and salt. DSC measurements show decrease in T _g with increasing salt concentration. The ionic conductivity of the prepared polymer electrolyte was found by ac impedance spectroscopy analysis. The maximum ionic conductivity was found to be 1.41 × 10^?3 S cm^?1 at ambient temperature for the composition of 50PVA:50PVP:30 wt% NH₄NO₃ with low-activation energy 0.29 eV. The conductivity temperature plots are found to follow an Arrhenius nature. The dielectric behavior was analyzed using dielectric permittivity (ε*) and the relaxation frequency (τ) was calculated from the loss tangent spectra (tan δ). Using this maximum ionic conducting polymer blend electrolyte, the primary proton battery with configuration Zn + ZnSO₄·7H₂O/50PVA:50PVP:30 wt% NH₄NO₃/PbO₂ + V₂O₅ was fabricated and their discharge characteristics studied.     

Dielectric and electrical characterization of (PEO–PMMA)–LiBF<Subscript>4</Subscript>–EC plasticized solid polymer electrolyte films

Plasticized solid polymer electrolytes (PSPEs) consisting of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend (50/50 wt%) based matrix with lithium tetrafluoroborate (LiBF₄) as dopant ionic salt (10 wt%) and varied concentrations (x = 0, 5, 10 and 15 wt%) of ethylene carbonate (EC) as plasticizer have been prepared. Classical solution-cast (SC) and the ultrasonic assisted followed by microwave irradiated (US–MW) solution-cast methods have been used for the preparation of (PEO–PMMA)–LiBF₄–x wt% EC films, and the same have been hot–pressed to get their smooth surfaces. Dielectric relaxation spectroscopy (DRS) and X–ray diffraction (XRD) techniques have been employed to characterize the dielectric and electrical dispersions and the structural properties of the PSPE films, respectively. It has been observed that the ionic conductivity of these semicrystalline ion-dipolar complexes is governed by their dielectric permittivity and polymers chain segmental dynamics. The increase in ionic conductivity values with the increase of plasticizer concentration in the PSPEs also varies with the films’ preparation methods. The US–MW method prepared PSPE film containing 15 wt% EC has a maximum ionic conductivity (1.86 × 10^?5 S cm^?1) at room temperature, whereas, the films having low concentrations of EC exhibit the conductivity of the order of 10^?6 S cm^?1.     

Lithium Ion-conducting Blend Polymer Electrolyte Based on PVA–PAN Doped with Lithium Nitrate

A new blend polymer electrolyte based on poly(vinyl alcohol) and polyacrylonitrile doped with lithium nitrate (LiNO₃) has been prepared and characterized. The complexation of blend polymer (92.5 PVA:7.5 PAN) with LiNO₃ has been studied using X-ray diffraction and Fourier transform infrared spectroscopy. Differential scanning calorimetry thermograms show a decrease in glass transition temperature with the addition of salt. The maximum ionic conductivity of the blend polymer electrolyte is 1.5 × 10^?3 Scm^?1 for 15 wt% LiNO₃ doped–92.5 PVA:7.5 PAN electrolyte. The conductivity values obey Arrhenius equation. Ionic transference number measurement reveals that the conducting species are predominantly ions.     

Electrical performance of lithium ion based polymer electrolyte with polyethylene glycol and polyvinyl alcohol network

A solid polymer electrolyte based on lithium hydroxide (LiOH) added with polyethylene glycol and polyvinyl alcohol polymers was synthesized by solution casting. The structural variation with respect to loading wt% of LiOH reveals the semicrystalline property of polymer electrolyte. The differential scanning calorimetry data shows the onset of crystalline to amorphous transition, which occurs nearly to the melting peak, for higher salt content. The structural properties and cross-linking between polymer and salt were demonstrated by polarized optical microscopy. The polymer electrolytes were subjected to AC impedance analysis spectra for obtaining the ionic conductivity at different temperature. The charge carriers relax much faster for higher lithium salt concentration based polymer electrolyte and produces higher conductivity. The highest room temperature conductivity 2.63 × 10^?5 S/cm is obtained for 8 wt% loading of lithium salt based polymer electrolyte, confirming their use in preparation of ion conducting devices.     

Investigations on Structural and Electrical Properties of KClO4 Complexed PVP Polymer Electrolyte Films

Potassium ion-conducting polymer electrolytes based on poly (vinyl pyrrolidone) (PVP) complexed with KClO₄ were prepared using a solution cast technique. These samples were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR), Differential Scanning Calorimetry (DSC), and impedance spectroscopy. The complexation of the salt with polymer was confirmed by FT-IR and XRD studies. The ionic conductivity was found to increase with increasing temperature and salt concentration. The highest ionic conductivity (0.91 × 10^?5 S/cm) and low activation energy (0.29 eV) was obtained for the polymer complexed with 15 wt% KClO₄ among all the compositions.     

Effect on properties of PVDF-HFP based composite polymer electrolyte doped with nano-SiO2

Various kinds of nano-SiO₂ using different catalysts were obtained and characterized by scanning electron microscope (SEM) technique. The results showed that the nano-SiO₂ using NH₃·H₂O as catalyst presented the best morphology. Poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) based composite polymer electrolyte (CPE) membranes doped with different contents of nano-SiO₂ were prepared by phase inversion method. The as-prepared CPE membranes were immersed into 1.0 M LiPF₆-EC/DMC/EMC electrolytes for 0.5 h to be activated. The physicochemical and electrochemical properties of the CPEs were characterized by SEM, X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and linear sweep voltammetry (LSV) techniques. The results indicate that the CPEs doped with 10 % nano-SiO₂ exhibit the best performance. SEM micrographs showed that the CPE membranes have uniform surface with abundant interconnected micro-pores, and the uptake ratio was up to 104.4 wt%. EIS and LSV analysis also showed that the ionic conductivity at room temperature and electrochemical stability window of the modified membrane can reach 3.372 mS cm^?1 and 4.7 V, respectively. The interfacial resistance R _i was 670 Ω cm^?2 in the first day, then increased to a stable value of about 850 Ω cm^?2 in 10 days storage at room temperature. The Li/As-fabricated CPEs/LiCoO₂ cell also showed good charge–discharge performance, which suggested that the prepared CPE membranes can be used as potential electrolytes for lithium ion batteries.     

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

In 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 Incorporation of Multi-Walled Carbon Nanotube into Poly(Ethylene Oxide) Gel Electrolyte on the Photovoltaic Performance of Dye-Sensitized Solar Cell

Gel polymer electrolytes (GPEs) consist of poly(ethylene oxide) (PEO), sodium iodide (NaI) and different amount of multi-walled carbon nanotubes (MWCNT) were prepared. The conductivity study revealed that the highest ionic conductivity of GPE was 7.02 × 10^?3 S cm^?1. The structural and complexation between the materials are authenticated via X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. Under the exposure of AM 1.5, the fabricated DSSCs exhibited the highest photoenergy conversion efficiency of 7.23% with a short circuit current density (J_SC) of 18.64 mA cm^?2, open circuit voltage (V_OC) of 0.590 mV and fill factor (FF) of 65.7%.     

Dynamic Mechanical,DSC, and Electrical Investigations on Nano Al2O3 Filled PVA:NH4SCN:DMSO Polymer Composite Dried Gel Electrolytes

This paper reports the dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and ionic conductivity studies on nanosized Al₂O₃(aluminium oxide) filled PVA:NH₄SCN:DMSO polymer composite dried gel electrolytes prepared by the wet chemistry route. Better mechanical stability and thermal behavior are noticed in the composite system. Multiple relaxation peaks seen in tangent loss measurements (in DMA studies) have been suitably correlated. Enhancement in ionic conductivity has been noticed with an optimum value of 4.02 × 10^?3 Scm^?1 for 4 wt% nano Al₂O₃ filled composite electrolytes. Temperature dependence of ionic conductivity shows a combination of Arrhenius and VTF (Vogel-Tamman-Fulcher) behavior.     

Efficiency enhancement of dye-sensitized solar cells with PAN:CsI:LiI quasi-solid state (gel) electrolytes

While many attempts have been made in the recent past to improve the power conversion efficiencies of dye-sensitized solar cells (DSSCs), only a few reports can be found on the study of these cells using binary iodides in the gel polymer electrolyte. This paper reports the effect of using a binary mixture of (large and small cation) alkaline salts, in particular CsI and LiI, on the efficiency enhancement in DSSCs with gel polymer electrolytes. The electrolyte with the binary mixture of CsI:LiI = 1:1 (by weight) shows the highest ionic conductivity 2.9 × 10^?3 S cm^?1 at 25 °C. DC polarization measurements showed predominantly ionic behavior of the electrolyte. The density of charge carriers and mobility of mobile ions were calculated using a newly developed method. The temperature dependent behavior of the conductivity can be understood as due to an increase of both the density and mobility of charge carriers. The solar cell with only CsI as the iodide salt gave an energy conversion efficiency of ~3.9 % while it was ~3.6 % for the cell with only LiI. However, the electrolyte containing LiI:CsI with mass ratio 1:1 showed the highest solar cell performance with an energy conversion efficiency of ~4.8 % under the irradiation of one Sun highlighting the influence of the mixed cation on the performance of the cell. This is an efficiency enhancement of 23 %.     

Semi-interpenetrating gel polymer electrolyte based on PVDF-HFP for lithium ion batteries

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolyte (GPE) is considered one of the promising candidate electrolytes in the polymer lithium ion battery (LIB) because of its free standing, shape versatility, security, flexibility, lightweight, reliability, and so on. However, the pristine PVDF-HFP GPE cannot still meet the requirement of large-scale LIBs and other electrochemical devices due to its relatively low ionic conductivity and deterioration of mechanical strength caused by the incorporation of organic liquid electrolyte into the polymer matrix as well as high cost. In order to overcome above deficiencies of PVDF-HFP based GPE, ultraviolet (UV)-curable semi-interpenetrating polymer network is designed and synthesized through UV-irradiation technique, and the as-prepared semi-interpenetrating matrix is constituted by pentaerythritol tetracrylate polymer network and PVDF-HFP. The ionic conductivity of the optimized GPE is as high as 5 × 10⁻⁴ S/cm and electrochemical window is up to 4.8 V at room temperature. Especially, the LIB prepared by GPE shows the high initial discharge specific capacity of 151 mAh/g at 0.5 C and good rate capability. Therefore, the semi-interpenetrating GPE based on PVDF-HFP exhibits a promising prospect for the application of rechargeable LIBs.     

Preparation of poly(vinylidene fluoride)/poly(methyl methacrylate) membranes by novel electrospinning system for lithium ion batteries

Fibrous membranes of poly(vinylidene fluoride)/poly(methyl methacrylate) (PVdF/PMMA) were fabricated by electrospinning method with different concentrations of polymer solution: 14, 16, and 18 wt %. The morphology of the electrospun membranes was observed by scanning electron microscopy. The images revealed that the nanofibers showed uniform diameter and no bead formation was observed with the concentration of 16 wt %. Also, the structure, crystallinity, ionic conduction, and electrochemical stability of the electrospun membranes were characterized. The results suggested that electrolyte uptake, ionic conduction, and electrochemical stability were improved by the addition of PMMA. Furthermore, with the 16 wt % concentration of the polymer solution, the membrane showed a high ionic conductivity of 3.5 mS cm^?1 at room temperature and electrochemical stability of up to 5.1 V. We predicted that this new method may be very promising for preparing microporous PVdF/PMMA polymer electrolytes. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Electrospun poly(vinylidene‐fluoride)/POSS nanofiber membrane‐based polymer electrolytes for lithium ion batteries

In this study, poly(vinylidene fluoride) (PVDF)/polyhedral oligomeric silsesquioxanes (POSS) nanofibrous membranes are prepared through electrospun process. Field emission scanning electron microscope images clearly show that PVDF/POSS membranes have interconnected multi fibrous layers with ultrafine porous structures. The average fiber diameter and crystallinity of PVDF/POSS membranes are lesser than that of pure PVDF membrane. Thermal stability and electrolyte uptake of blend membranes increase with increasing POSS content. Finally, PVDF/POSS membranes are soaked in a liquid electrolyte to form the polymer electrolytes and are assembled in coin cells to test their electrochemical properties such as ionic conductivity, interfacial characteristics, and electrochemical stability windows. The ionic conductivity improves with increasing POSS content and the highest ionic conductivity reaches 2.91 × 10⁻³ S/cm at room temperature. It is also worth mention that the composite polymer electrolytes show low interfacial resistance and high electrochemical stability window of 5.6 V (vs. Li⁺ /Li) with storage time. POLYM. COMPOS., 38:629–636, 2017. © 2015 Society of Plastics Engineers     

The effect of ionic liquid fragment on the performance of polymer electrolytes

An ionic liquid 1‐methyl‐3‐[2‐(methacryloyloxy)ethyl]imidazolium bis(trifluoromethane sulfonylimide) (MMEIm‐TFSI) was synthesized and polymerized. Composite polymer electrolytes based on polymeric MMEIm‐TFSI (PMMEIm‐TFSI) and poly[(methyl methacrylate)‐co‐(vinyl acetate)] (P(MMA‐VAc)) were prepared, with lithium bis(trifluoromethane sulfonylimide) (LiTFSI) as target ions (Li⁺). DSC/TGA analysis showed good flexibility and thermal stability of the composite electrolyte membranes. The AC impedance showed that the ionic conductivity of the electrolytes increased with PMMEIm‐TFSI up to a maximum value of 1.78 × 10^?4 S cm^?1 when the composition was 25 wt% P(MMA‐VAc)/75 wt% PMMEIm‐TFSI/30 wt% LiTFSI at 30 °C. The composite electrolyte membrane (transmittance ≥ 90%) can also be used as the ion‐conductive layer material for electrochromic devices, and revealed excellent colorization performance. Copyright © 2011 Society of Chemical Industry     

Evaluation of photovoltaic efficiency of dye‐sensitized solar cells fabricated with electrospun PVDF‐PAN‐Fe2O3 composite membrane

Poly(vinylidene fluoride)‐polyacrylonitrile‐based membranes containing Fe₂O₃ nanoparticles were prepared by electrospinning technique and characterized by HR‐SEM, FTIR, and XRD analysis. The effect of electrolyte in the electrospun nanofibers on electrolyte uptake, ionic conductivity and porosity were studied. The electrospun membranes containing Fe₂O₃ showed an enhanced ionic conductivity than that of without Fe₂O₃. Among the prepared membranes, the membrane with 7 wt % Fe₂O₃ has the highest liquid electrolyte uptake of 562% and ionic conductivity of 6.81 × 10^?2 S cm^?1. The photovoltaic performance for open circuit voltage (V_oc), Short‐circuit current density (J_sc), Fill factor (FF), and η of the DSSC fabricated with 7 wt % Fe₂O₃ are 0.77 V, 10.4 mA/cm², 0.62 and 4.9%, respectively. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41107.     

Environmental Friendly, Low Cost Quasi Solid State Dye Sensitized Solar Cell: Polymer Electrolyte Introduction

The most efficient DSSCs reported till date contains liquid electrolytes with I^?/I^3? redox couple. However, the disadvantages of liquid electrolytes lead to reduce the impact of DSSCs. In the present work, the I^?/I^3? liquid electrolyte was replaced by quasi-solid gel polymer electrolytes (GPEs) using polyethylene glycol (M_wt = 20,000), which are incorporated in small fractions (0, 1, 5, 10, 15 and 20 % w/v) into the liquid iodine/iodide electrolyte matrix. The roughness and homogeneity of the GPEs on the surface of the TiO₂ electrodes was monitored by atomic force microscope which indicates the physical cross linking of polymer chains in a gel network. The conductivity (σ) and the thermal stability (TGA) of the GPEs compared with the liquid electrolyte were studied in details. The photovoltaic characteristics [V_oc, I_sc, fill factor and efficiency (η)] of the DSSCs based GPEs were recorded, The results revealed the DSSCs assembled with the gel polymer electrolyte reports a higher short circuit density (J_SC) and lower or similar open circuit voltage (V_OC) than the cells with liquid electrolyte. The overall light-to-electrical-energy conversion efficiencies (η) of the cells based GPEs showed a relatively higher stability over a period of time compared with those based liquid electrolyte, indicating that the quasi-solid nature of the GPEs may impart flexibility to DSSCs so that some large-scale productions such as roll-to-roll process can be realized.     

Novel Proton-Conducting Polymer Electrolytes Based on Poly(Vinylidene fluoride-co-hexafluoropropylene)–Ammonium Thiocyanate

The polymer electrolytes composed of poly(vinylidene fluoride-co-hexafluoropropylene) with various concentration of ammonium thiocyanate salt have been prepared by solution casting technique. The complex formation between polymer and dissociated salt has been confirmed by X-ray diffraction analysis and Fourier transform infrared spectroscopy. The highest conductivity has been found to be 6.5?×?10^?3?S?cm^?1 at 343?K for 25?wt% ammonium thiocyanate. The temperature-dependent conductivity of polymer electrolyte follows Arrhenius hopping relation. Thermogravimetric analysis has been used to ascertain the thermal stability of the polymer electrolytes. Atomic force microscopy analysis predicts the roughness parameter of the sample with higher conductivity.