Preparation and properties of gel‐filled PVDF separators for lithium ion cells

Polyether gel‐filled poly(vinylidene fluoride) separators (GF‐PVDF separators) were prepared by means of thermal crosslinking of poly(ethylene glycol) methyl ether acrylate (PEGMEA) and poly(ethylene glycol) diacrylate (PEGDA) as gel constituents. The intrinsic properties of GF‐PVDF and their corresponding gel polymer electrolyte (GPE) were characterized by SEM, DSC, and electrochemical methods. It was found a relatively better GPE could be got when the filled polyether content no more than 60 wt % and its ion conductivity could reach 1.3 × 10^?3 S cm^?1. The GPE is compatible with anode and cathode of lithium ion battery at high voltage and its electrochemical window is 4.6 V (vs. Li/Li⁺). The coulombic efficiency could reach 94% after 100 cycles for the cells using such GPE. The results reveal that the composite polymer electrolyte qualifies as a potential application in lithium cells. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 44473.     

Gel Polymer Electrolyte with Anion‐Trapping Boron Moieties via One‐Step Synthesis for Symmetrical Supercapacitors

A novel gel polymer electrolyte (GPE) which is based on new synthesized boron‐containing monomer, benzyl methacrylate, 1 m LiClO₄/N,N‐dimethylformamidel liquid electrolyte solution is prepared through a one‐step synthesis method. The boron‐containing GPE (B‐GPE) not only displays excellent mechanical behavior, favorable thermal stability, but also exhibits an outstanding ionic conductivity of 2.33 mS cm^?1 at room temperature owing to the presence of anion‐trapping boron sites. The lithium ion transference in this gel polymer film at ambient temperature is 0.60. Furthermore, the symmetrical supercapacitor which is fabricated with B‐GPE as electrolyte and reduced graphene oxide as electrode demonstrates a broad potential window of 2.3 V. The specific capacitance of symmetrical B‐GPE supercapacitors retains 90% after 3000 charge–discharge cycles at current density of 1 A g^?1.     

Novel nanocomposite of poly(acrylonitrile‐co‐glycidyl methacrylate) crosslinked with Jeffamine‐functionalized multiwalled carbon nanotubes as gel polymer electrolytes

Multiwalled carbon nanotubes (MWCNTs) were functionalized with α,ω‐diamino poly(propylene oxide) (Jeffamine) of different molecular weights and crosslinked with poly(acrylonitrile‐co‐glycidyl methacrylate) [P(AN‐GMA)] to prepare a novel nanocomposite for applications in gel polymer electrolytes (GPEs). The synthesized copolymer was characterized by ¹H‐NMR, Fourier transform infrared, and thermal analysis. Scanning electron microscope observation revealed that the Jeffamine‐functionalized MWCNTs distributed uniformly in the nanocomposite membrane. The mechanical behaviors of the nanocomposite membranes were investigated. It was found that the crosslinked nanocomposite membranes of P(AN‐GMA) and Jeffamine‐functionalized MWCNTs exhibited much higher mechanical strength than the counterpart nanocomposite obtained by physical blending. Moreover, the weight content and molecular weights of Jeffamine had an effect on the mechanical properties of the nanocomposites. Differential scanning calorimeter measurements showed that the crosslinked nanocomposite membranes were amorphous. GPEs based on the nanocomposite were prepared and characterized by complex impedance measurements. The GPE based on the nanocomposite of P(AN‐GMA) crosslinked with 6 wt % of MWCNTs functionalized by Jeffamine D400 showed an ionic conductivity of about 3.39 × 10^?4 S cm^?1 at 25°C, which is much higher than the counterpart nanocomposite of physically blended P(AN‐GMA) and MWCNTs. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Performance of PVDF-HFP-based gel polymer electrolytes with different pore forming agents

Poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolytes (GPEs) with polyvinylpyrrolidone (PVP) and urea as a pore forming agent, respectively, were fabricated by phase inversion method. Physicochemical properties of the as-prepared polymer electrolytes were characterized by SEM, XRD, TG, electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). The results showed that the GPE membranes using urea as pore forming agent present a uniform surface with abundant interconnected micro-pores and possess upto 330?°C decomposition temperature; the XRD patterns indicate that adding urea into the polymer matrix can attain more amorphous areas than adding PVP; the reciprocal temperature dependence of ionic conductivity of as-prepared GPEs follows Vogel-Tamman-Fulcher relation and the ionic conductivity at room temperature is 2.212?mS cm^?1 for PVP pore forming GPEs and 2.823?mS cm^?1 for urea pore forming GPEs, respectively; the interfacial resistance of the Li/GPEs/Li cell using urea as pore forming agent can achieve a quick steady value of about 660??? cm^?1 lower than that of PVP of about 760??? cm^?1 during the same storage conditions; the electrochemical stability window of the GPEs with urea can be stable upto 5.0?V (vs. Li⁺/Li) at room temperature. The battery performance of the assembled Li/GPEs/LiCoO₂ coin cell also showed that the cell using urea as pore forming agent in GPEs demonstrated excellent first charge/discharge rate and cycle performances. These excellent physicochemical and battery properties indicated that urea can be used as a kind of excellent pore forming agent for polymer electrolytes in the lithium-ion polymer battery.     

Novel microporous poly(vinylidene fluoride)‐graft‐poly(tert‐butyl acrylate) electrolytes for secondary lithium batteries

BACKGROUND: Much interest has recently been shown in improving the performance of lithium‐ion polymer batteries with gel polymer electrolytes (GPEs) due to a rapid expansion in industrial demand. Novel GPEs based on poly(vinylidene fluoride)‐graft‐poly(tert‐butyl acrylate) (PVDF‐g‐tBA) microporous mats are suggested in this study. RESULTS: Microfibrous polymer electrolytes were prepared using electrospinning and characterized for extent of grafting, morphology, crystallinity, electrochemical stability, ionic conductivity, interfacial resistance and cell cycleability. The degree of crystallinity was lower for tBA‐grafted PVDF mats than that of neat PVDF. The PVDF‐g‐tBA showed an improvement in the ionic conductivity, electrochemical stability, interfacial resistance and cyclic performance. CONCLUSION: The tBA‐grafted PVDF microporous electrolytes are promising candidates for enhancing the performance of lithium‐ion polymer batteries. Copyright © 2008 Society of Chemical Industry     

Enhanced mechanical strength and conductivity of PVFM based membrane and its supporting polymer electrolytes

Polyvinyl formal based polymer electrolyte membranes are prepared via the optimized phase inversion method with poly(ethylene oxide) (PEO) blending. The physical properties of blend membranes and the electrochemical properties of corresponding gel polymer electrolytes (GPEs) are characterized by field emission scanning electron microscopy, X‐ray diffraction, differential scanning calorimetry, mechanical strength test, electrolyte uptake test, AC impedance spectroscopy, cyclic voltammetry, and galvanostatic charge–discharge test. The comparative study shows that the appearance of PEO obviously enhances the tensile strength of membranes and the ionic conductivity of corresponding GPEs. When the weight ratio of PEO is 30%, the tensile strength of membrane achieves 12.81 MPa, and its GPE shows high ionic conductivity of 2.20 × 10⁻³ S cm⁻¹, wide electrochemical stable window of 1.9–5.7 V (vs. Li/Li⁺), and good compatibility with LiFePO₄ electrode. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41839.     

Influence of a rigid polystyrene block on the free volume and ionic conductivity of a gel polymer electrolyte based on poly(methyl methacrylate)‐block‐polystyrene

Diblock copolymers poly(methyl methacrylate)‐block‐polystyrene with three different molar ratios [poly(methyl methacrylate)/polystyrene (PS) = 1:1, 1:1.5, and 1:1.8] were synthesized by atom transfer radical polymerization and used as a polymer matrix for gel polymer electrolytes (GPEs). The positron annihilation lifetime spectroscopy was applied to determine the free‐volume behaviors of different GPEs, respectively. We illustrated that a proper PS ratio may led to the formation of a high fraction of free volume, and the influence of the PS ratio on the free‐volume fraction was caused by the different morphologies of the GPEs because of the different packing densities of the PS rigid block. The ionic conductivity was correlated with the free volume in the GPE through the study of the ionic conductivity dependence on the temperature; this followed the Vogel–Tamman–Fulcher equation. Moreover, an ionic conductive model was proposed, in which variations of the free‐volume behavior provide different ionic‐conducting abilities. Thermogravimetric analysis indicated that GPEs based on different block copolymers exhibited high liquid‐electrolyte preservation properties. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43901.     

Polyacrylonitrile–poly(1-vinyl pyrrolidone-co-vinyl acetate) blend based gel polymer electrolytes incorporated with sodium iodide salt for dye-sensitized solar cell applications

New gel polymer electrolytes (GPEs) were prepared via the blending of a polyacrylonitrile polymer and a poly(1-vinyl pyrrolidone-co-vinyl acetate) copolymer. The sodium iodide (NaI) salt concentration was varied for each GPE sample. From ionic conductivity (σ) studies, we observed that the sample with a 40 wt % NaI salt content (N40) showed the highest σ of 3.54 × 10⁻³ ± 0.05 S/cm at room temperature, and all of the GPE samples obeyed Arrhenius behavior. The dielectric properties of the GPE samples were also analyzed to study the electrical polarization of the materials. The developed GPE samples were also characterized with X-ray diffraction and Fourier transform infrared spectroscopy. We also then used the developed GPE samples for the fabrication of dye-sensitized solar cells by sandwiching them between a photoanode and Pt counter electrode for photovoltaic studies. The highest photovoltaic performance was achieved by N40, with an efficiency of 3.04%. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47810.     

Exploration on polypropylene carbonate polymer for gel polymer electrolyte preparation and dye‐sensitized solar cell application

Gel polymer electrolytes (GPEs) with incorporation of polypropylene carbonate (PPC) polymer and different weight percentages of sodium iodide (NaI) salt are prepared. Ethylene carbonate and propylene carbonate are used as plasticizers. The maximum ionic conductivity of 2.01 mS cm^?1 is achieved at room temperature. Temperature‐dependent ionic conductivity study is performed. The GPEs are studied for structural properties using Fourier transform infrared (FTIR). The FTIR analysis confirms that complexation between PPC and NaI has occurred. By using GPEs, dye‐sensitized solar cells (DSSC) are fabricated under the one Sun light intensity. The highest energy conversion efficiency of 6.38% is achieved with incorporation of 60 wt % of NaI. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134 , 45091.     

Amelioration of electrochemical and photovoltaic performances on P(VP‐co‐VAc) based gel polymer electrolyte by incorporating double salt for dye‐sensitized solar cells

Dye‐sensitized solar cell (DSSC) is an alternative photovoltaic application used to replace the liquid electrolyte dependent conventional photovoltaic cell. In this research, gel polymer electrolyte (GPE) was used to replace the unstable liquid electrolyte. This GPE consists of poly[1‐vinylpyrrolidone‐co‐vinyl acetate] (P[VP‐co‐VAc]), tetrabutylammonium iodide (TBAI), sodium iodide (NaI), iodine (I₂), ethylene carbonate (EC), and propylene carbonate (PC). The GPE was tested for its ionic conductivity and an optimum level was reached at sample with 30% TBAI and 6% NaI at 1.17 × 10^?3 S cm^?1. The DSSC was then fabricated with all GPEs and a photovoltaic performance study was conducted. As a result, the highest photovoltaic conversion efficiency (PCE), η for a single salt was 3.04% for 40% TBAI. When a second salt is added, the system showed improvement in efficiency, η to 4.54% with short circuit current density, J_sc of 11.02 mA cm^?2 and open circuit voltage, V_oc of 0.67 V and FF of 61%. The other changes after the addition of TBAI and NaI salts have been observed through X‐ray diffraction, Fourier transformation and thermal analysis studies. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43805.     

All-solid secondary polyaniline-zinc battery

A solid state battery based on polyaniline (PANI), Zinc (Zn) and a gel polymer electrolyte (GPE) is reported for the first time. Poly (ethylene oxide)–zinc sulphate-nanoclay-H₂O based GPE was used as the separator. The GPEs with a varying composition of salt were evaluated for their electrochemical performance. The highest conductivity at ambient temperature for the GPEs was found to be 5.54 × 10⁻⁴ S cm⁻¹. Cyclic voltammetry and impedance studies, with the Zn/GPE/Zn cell, showed reversibility with respect to Zn/Zn²⁺ couple. The battery showed a capacity of 43.9 Ah kg⁻¹ of PANI and a coulombic efficiency higher than 100%. However, a decrease in capacity was observed for the system during the cycling.     

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.     

Preparation and characterization of proton exchange membrane based on polyphosphoric acid modified by PVDF‐HFP

A polyphosphoric acid functionalized proton exchange membrane (PEM) was prepared by a ring opening reaction using the epoxycyclohexylethyltrimethoxysilane (EHTMS) and amino trimethylene phosphonic acid (ATMP) as raw materials and was modified by poly(vinylidene fluoride)–hexafluoro propylene (PVDF‐HFP). The structure of the membranes was characterized by Fourier transform infrared and scanning electron microscopy. The X‐ray photoelectron spectroscopy explores the content of the elements in the membrane related to the ion exchange capacity value. The membranes’ properties including water uptake, swelling ratio, proton conductivity, and hydrolysis stability were studied. Performance tests show that when ATMP/EHTMS = 1/5, conductivity of the PVDF‐HFP modified PEMs increased from 0.83 × 10^?4 S cm^?1 at 20 °C to 9.53 × 10^?3 S cm^?1 at 160 °C, the swelling ratio of membranes decreased from 2.71% to 2.13%. The results indicate that the introduction of F atoms is beneficial to increase the proton conductivity and the dimensional stability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46737.     

Study on preparation and properties of gel polymer electrolytes based on comb-like copolymer matrix of poly(ethylene glycol) monomethylether grafted carboxylated butadiene-acrylonitrile rubber

A novel kind of gel polymer electrolytes (GPE) based on comb-like copolymers of poly(ethylene glycol) monomethylether (mPEG) grafted carboxylated butadiene-acrylonitrile rubber (XNBR) were prepared by introducing ionic liquids and LiClO₄ into polymer framework. FTIR spectra confirmed the grafting of mPEG to XNBR as side chains, and the content of grafted mPEG were calculated from the integral area of related peaks in ¹ H NMR spectra. Such grafted copolymer based GPE with ionic liquids as solvent showed higher ionic conductivity and reached a maximum ionic conductivity of 1.64?×?10^?3?S/cm (30?°C) in the experimental range, because the copolymers performed better polymer chain flexibility, which could be concluded from the decrease of T _g and crystallinity through DSC analysis. The generated GPE exhibited high electrochemical stability and the unit cell of LiFePO₄/GPE/Li could be cycled at room temperature.     

1H NMR,thermal, and conductivity studies on PVAc based gel polymer electrolytes

The lithium‐ion conducting gel polymer electrolytes (GPE), PVAc‐DMF‐LiClO₄ of various compositions have been prepared by solution casting technique. ¹H NMR results reveal the existence of DMF in the gel polymer electrolytes at ambient temperature. Structure and surface morphology characterization have been studied by X‐ray diffraction analysis (XRD) and scanning electron microscopy (SEM) measurements. Thermal and conductivity behavior of polymer‐ and plasticizer‐salt complexes have been studied by differential scanning calorimetry (DSC), TG/DTA, and impedance spectroscopy results. XRD and SEM analyses indicate the amorphous nature of the gel polymer‐salt complex. DSC measurements show a decrease in T_g with the increase in DMF concentrations. The thermal stability of the PVAc : DMF : LiClO₄ gel polymer electrolytes has been found to be in the range of (30–60°C). The dc conductivity of gel polymer electrolytes, obtained from impedance spectra, has been found to vary between 7.6 × 10^?7 and 4.1 × 10^?4 S cm^?1 at 303 K depending on the concentration of DMF (10–20 wt %) in the polymer electrolytes. The temperature dependence of conductivity of the polymer electrolyte complexes appears to obey the VTF behavior. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Chemical modification of calcium alginate gel beads for controlling the release of insect repellent N,N‐diethyl‐3‐methylbenzamide

Calcium alginate gel beads containing insect repellent N,N‐diethyl‐3‐methylbenzamide (CAGBDs) were modified via grafting copolymerization with a vinyl monomer. CAGBDs (5 g) were initiated with 8.5 × 10^?2 mol/L potassium persulfate and 7.0 × 10^?2 mol/L sodium bisulfite at the ambient temperature for 10 min, and then 6.22 mol/L acrylonitrile was added in droplets; the mixture was allowed to react at the same temperature for another 30 min. The effects of reaction conditions such as the stirring speed and monomer concentration on the modification of CAGBDs were investigated. Scanning electron microscopy analysis showed that the surface of modified CAGBDs was compact enough to keep N,N‐diethyl‐3‐methylbenzamide from touching. The release rate of N,N‐diethyl‐3‐methylbenzamide from modified CAGBDs was slower than that from unmodified CAGBDs. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 4850–4855, 2006     

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.     

Conductive poly(vinylidene fluoride)/polyethylene/graphene blend‐nanocomposites: Relationship between rheology,morphology, and electrical conductivity

Relationship between rheology, morphology, and electrical conductivity of the poly(vinylidene fluoride)/polyethylene/graphene nano‐platelets ternary system (PVDF/PE/GnP) were investigated. All the blend nanocomposites were prepared via a two‐step melt mixing method. GnP (0.75 and 1.5 wt %) was first compounded with PVDF and then the resulted premixtuers were melt mixed with PE to achieve the desired compositions. The corresponding reference nanocomposites and filler‐less blends were also prepared. Effect of an interfacial agent (PEMA; maleic anhydride grafted polyethylene) was also studied in this work. The results of rheological analysis in conjunction with the Raman spectroscopy experiments revealed that GnP had higher affinity to PVDF than PE, which in turn led to creation of conductive networks of GnP (1.5 wt %) in PVDF matrix exhibiting the electrical conductivity of about 10^?2 (S/cm). Double percolated micro‐structure was predicted for the PE/PVDF 40/60 (wt/wt) blend containing low GnP content (0.9 wt %) and confirmed via direct electron microscopy and conductivity analysis. Using 5 wt % of the PEMA reduced the conductivity to 10^?5 (S/cm) and further increase in PEMA content to 10 wt % led to non‐conductive characteristics. The latter was attributed to the migration of GnP from the PVDF phase to PE/PEMA phase and hence disturbance of double percolated micro‐structure. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46333.     

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%.     

Chemically Modified Polyvinyl Butyral Polymer Membrane as a Gel Electrolyte for Lithium Ion Battery Applications

A novel porous membrane of chemically modified polyvinyl butyral (mPVB), with improved thermal properties and chemical stability for lithium ion battery applications, is successfully synthesized by utilizing the chain extension reaction of the OH units from PVB. The porous mPVB membranes are obtained via the tape casting and phase inversion method. The corresponding gel polymer electrolyte (GPE) is achieved by immersing the as‐prepared membranes in the liquid electrolyte. The electrochemical performances of the GPE show that the mPVB membranes have the features of good uniformity, high porosity ( ≈ 90%), great thermal stability, and high mechanical strength. Moreover, the GPE exhibits good chemical stability, a wide electrochemical window, as well as high ionic conductivity ( ≈ 1.21 × 10^?3 S cm^?1). A test of a Li/GPE/LiFePO₄ battery cell shows a capacity of 147.7 mAh g^?1 and excellent cycling stability, demonstrating the great potential of the mPVB‐based GPE for lithium ion battery applications.