Investigations on the enhancement mechanism of inorganic filler on ionic conductivity of PEO-based composite polymer electrolyte: The case of molecular sieves

Polarized optical microscopy (POM) and differential scanning calorimeter (DSC) techniques are used to study the effect of ZSM-5 molecular sieves on the crystallization mechanism of poly(ethylene oxide) (PEO) in composite polymer electrolyte. POM results show that ZSM-5 has great influence on both the nucleation stage and the growth stage of PEO spherulites. ZSM-5 particles can act as the nucleus of PEO spherulites and thus increase the amount of PEO spherulites. POM and DSC results show that ZSM-5 can restrain the recrystallize tendency of PEO chains through Lewis acid-base interactions and hence decrease the growth speed of PEO spherulites. Room temperature ionic conductivity of PEO-LiClO₄-based polymer electrolyte can be enhanced by more than two magnitudes during long time storage with the addition of ZSM-5.     

Preparation and ionic conductivity of solid polymer electrolyte based on polyacrylonitrile‐polyethylene oxide

The transparent and flexible solid polymer electrolytes (SPEs) were fabricated from polyacrylonitrile‐polyethylene oxide (PAN‐PEO) copolymer which was synthesized by methacrylate‐headed PEO macromonomer and acrylonitrile. The formation of copolymer is confirmed by Fourier‐transform infrared spectroscopy (FTIR) measurements. The ionic conductivity was measured by alternating current (AC) impedance spectroscopy. Ionic conductivity of PAN‐PEO‐LiClO₄ complexes was investigated with various salt concentration, temperatures and molecular weight of PEO (Mn). And the maximum ionic conductivity at room temperature was measured to be 3.54 × 10^?4 S/cm with an [Li⁺]/[EO] mole ratio of about 0.1. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 461–464, 2006     

Nanocomposite polymer electrolytes for solid-state lithium-ion batteries with enhanced electrochemical properties

Solid-state polymer electrolytes (SPEs) have attracted significant attention owing to their improvement in high energy density and high safety performance. However, the low lithium-ion conductivity of SPEs at room temperature restricts their further application in lithium-ion batteries (LIBs). Herein, we propose a novel poly (ethylene oxide) (PEO)-based nanocomposite polymer electrolytes by blending boron-containing nanoparticles (BNs) in the PEO matrix (abbreviated as: PEO/BNs NPEs). The boron atom of BNs is sp²-hybridized and contains an empty p-orbital that can interact with the anion of lithium salt, promoting the dissociation of the lithium salts. In addition, the introduction of the BNs could reduce the crystallinity of PEO. And thus, the ionic conductivity of PEO/BNs NPEs could reach as high as 1.19 × 10⁻³ S cm⁻¹ at 60°C. Compared to the pure PEO solid polymer electrolyte (PEO SPEs), the PEO/BNs NPEs showed a wider electrochemical window (5.5 V) and larger lithium-ion migration number (0.43). In addition, the cells assembled with PEO/BNs NPEs exhibited good cycle performance with an initial discharge capacity of 142.5 mA h g⁻¹ and capacity retention of 87.7% after 200 cycles at 2 C (60°C).     

Optical microscopy and conductivity of poly(ethylene oxide) complexed with KI salt

The optical microscopy, crystallinity and ion conductivity of PEO complexed with potassium iodide (KI) salt are present. The spherulite structure derived from polarized optical microscopy (POM) suggested the ion induces different spherulite structures from that without salt. The size of the spherulites decreases with increasing salt concentration and is completely destroyed with KI salt content of 20 wt% (O-K ratio 15:1). This result concurs with the X-ray diffraction and DSC studies, that PEO crystallinity is reduced upon addition of KI salt. Upon elevating the temperature, the POM micrographs elucidate degradation of the spherulite structure when smaller crystallites begin to melt before the melting temperature of SPE, and become completely opaque above PEO melting temperature (T_m). The pseudo-activation energy derived from variable temperature conductivity measurements of about 0.24 eV is similar to that of PEO-lithium salt systems and suggested the identical PEO segmental motion governs the fundamental ion movement. Stable PEO-K complex (T_m from 135 to 155 °C) is formed after annealing at 120 °C for 12 h. However, the conductivity is about one order smaller compared to lithium salt due to the shorter hopping distance of the heavier potassium ion.     

Influence of molar mass on the thermal properties,conductivity and intermolecular interaction of poly(ethylene oxide) solid polymer electrolytes

The sample preparation pathway of solid polymer electrolytes (SPEs ) influences their thermal properties, which in turn governs the ionic conductivity of the materials especially for systems consisting of a crystallizable constituent. Majority of poly(ethylene oxide) (PEO)‐based SPEs with molar masses of PEO well above 10⁴ g mol^?1 (where PEO is crystallizable and should reach an asymptote in thermal behaviour) display molar mass dependence of the thermal properties and ionic conductivities in non‐equilibrium conditions, as reported in the literature. In this study, PEO of different viscosity‐molar masses (M _η = 3 × 10⁵, 6 × 10⁵, 1 × 10⁶, 4 × 10⁶ g mol^?1) and LiClO₄ salt (0 to 16.7 wt%) were used. The SPEs were thermally treated under inert atmosphere above the melting temperature of PEO and then cooled down for subsequent isothermal crystallization for sufficient experimental time to develop morphology close to equilibrium conditions. The thermal properties (e.g. glass transition temperature, melting temperature, crystallinity) according to differential scanning calorimetry and the ionic conductivity obtained from impedance spectroscopy at room temperature (σ _DC ～ 10^?6 S cm^?1) demonstrate insignificant variation with respect to the molar mass of PEO at constant salt concentration. These findings are in agreement with the PEO crystalline structures using X‐ray diffraction and ion ? dipole interaction by Fourier transform infrared results. © 2017 Society of Chemical Industry     

A novel PEO-based composite polymer electrolyte with absorptive glass mat for Li-ion batteries

A novel PEO (polyethylene oxide)-based composite polymer electrolyte (CPE) using absorptive glass mat (AGM) as filler was prepared and characterized. Scanning electronic micrograph (SEM) images showed that the addition of Li salt and modified AGM may improve the surface morphology of CPE. The results of Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and differential scanning calorimeters (DSC) indicated that the inclusion of LiClO₄ salt and the addition of AGM filler can reduce the crystallinity of PEO. It was concluded that the addition of AGM plays two roles in PEO-based CPEs, namely, interruption of the PEO recrystallization and reinforcement of CPEs, accordingly enhancing room temperature ionic conductivity of CPEs and improving its mechanical strength and electrochemical stability at high temperatures.     

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     

Effect of filler‐polymer interactions on the crystalline morphology of PEO‐based solid polymer electrolytes by Y2O3 nano‐fillers

A novel lithium solid polymer electrolyte (SPE) based on polyethylene oxide (PEO) matrix and yttrium oxide (Y₂O₃) as nano‐filler was prepared by solution casting technique. The Lewis acid‐based filler‐polymer coordination interactions between the surface of Y₂O₃ and the ether oxygen of PEO were proved by FTIR, which induced an obvious modification of crystalline morphology of the PEO‐based SPEs. Polarized optical microscope (POM) analysis shows that the induced nucleation and steric hindrance effects of Y₂O₃ nano‐filler result in the increased amount as well as decreased size of spherulites in the PEO matrix, respectively. Atomic force microscope (AFM) images indicate the surface morphology of PEO gets rougher as Y₂O₃ content increases. X‐ray diffractomer (XRD) and differential scanning calorimetry (DSC) results demonstrate the crystallinity of SPEs decreases from 51.1% to 32.5% with the Y₂O₃ weight ratio [m(Y₂O₃)/m(PEO+LiI)] increasing from 0 to 0.15. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

Morphological,infrared, and ionic conductivity studies of poly(ethylene oxide)–49% poly(methyl methacrylate) grafted natural rubber–lithium perchlorate salt based solid polymer electrolytes

The potential of poly(ethylene oxide) (PEO) and 49% poly(methyl methacrylate) grafted natural rubber (MG49) as a polymer host in solid polymer electrolytes (SPE) was explored for electrochemical applications. PEO–MG49 SPEs with various weight percentages of lithium perchlorate salt (LiClO₄) was prepared with the solution casting technique. Characterization by scanning electron microscopy, Fourier transform infrared spectroscopy, and impedance spectroscopy was done to investigate the effect of LiClO₄ on the morphological properties, chemical interaction, and ionic conductivity behavior of PEO–MG49. Scanning electron microscopy analysis showed that the surface morphology of the sample underwent a change from rough to smooth with the addition of lithium salts. Infrared analysis showed that the interaction occurred in the polymer host between the oxygen atom from the ether group (C? O? C) and the Li⁺ cation from doping salts. The ionic conductivity value increased with the addition of salts because of the increase in charge carrier up to the optimum value. The highest ionic conductivity obtained was 8.0 × 10^?6 S/cm at 15 wt % LiClO₄. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effect of blend composition on crystallization behavior of polyoxymethylene/poly(ethylene oxide) crystalline/crystalline blends

The influence of blend composition on crystallization behavior of a typical crystalline/crystalline blend, polyoxymethylene (POM)/poly(ethylene oxide) (PEO), during slow non-isothermal crystallization was investigated by polarized light microscope (PLM) connected with a THMS600 hot-stage, scanning electron microscope (SEM), differential scanning calorimetry (DSC) and X-ray diffraction (XRD). The experimental results indicated that with increasing PEO content in the blend, the crystallization temperature of POM of the blends reduced and the multiple crystalline morphologies or structures including two kinds of interfibrillar or interlamellar structures were produced. The melting point of each component decreased with raising the content of the other constituent due to the inclusion and entanglement between POM and PEO molecules. The shoulder melting peak of POM appeared in DSC heating traces of the PEO-rich blend because the stronger inclusion and entanglement induced the imperfect crystallization of POM.     

Optimization of PVC– PAN‐based polymer electrolytes

The hybrid plasticized polymer electrolyte composed of the blend of poly(vinyl chloride) (PVC) and poly(acrylonitrile) (PAN) as host polymer, propylene carbonate as plasticizer, and LiClO₄ as a salt was studied. An attempt was made to optimize the polymer blend ratio. XRD, Fourier transform infrared, and DSC studies confirm the formation of polymer–salt complex and miscibility of the PVC and PAN. The electrical conductivity and temperature dependence of ionic conductivity of polymer films are also studied and reported here. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Effects of ultrasonic assisted processing and clay nanofiller on dielectric properties and lithium ion transport mechanism of poly(methyl methacrylate) based plasticized polymer electrolytes

Lithium ion conducting solid polymer electrolyte (SPE) films consisted of poly(methyl methacrylate) (PMMA) matrix with lithium perchlorate as a dopant ionic salt, poly(ethylene glycol) as plasticizer and montmorillonite clay as inorganic nanofiller have been prepared by classical solution casting and high intensity ultrasonic assisted solution casting methods. The X‐ray diffraction study confirmed the amorphous structure of all these PMMA‐based solid electrolytes and the clay nanosheets existed in exfoliated form in their amorphous phase. Dielectric relaxation spectroscopy had been employed for the investigation of complex dielectric function, ac electrical conductivity, electric modulus, and impedance spectra of these electrolytes over the frequency range from 20 Hz to 1 MHz. It was observed that the dielectric properties and ionic conductivity of the electrolytes strongly depended on the sample preparation methods, and also had changes with addition of the clay nanofiller. Temperature‐dependent dielectric study of the electrolyte films confirmed that their dc ionic conductivity and conductivity relaxation time values obeyed the Arrhenius behavior. This study also revealed that the lithium ion transportation in the ion–dipolar complexes of these electrolytes occurred through hopping mechanism and it was correlated with the conductivity relaxation time. Preparation of these electrolyte films through ultrasonic assisted solution casting method increased the ionic conductivity by more than one order of magnitude in comparison to that of the classical solution casting method, which revealed that the former was a novel method for the preparation of these SPEs of relatively enhanced ionic conductivity. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42188.     

Ionic conductivity in polyethylene-b-poly(ethylene oxide)/lithium perchlorate solid polymer electrolytes

The ionic conductivity and phase arrangement of solid polymeric electrolytes based on the block copolymer polyethylene-b-poly(ethylene oxide) (PE-b-PEO) and LiClO₄ have been investigated. One set of electrolytes was prepared from copolymers with 75% of PEO units and another set was based on a blend of copolymer with 50% PEO units and homopolymers. The differential scanning calorimetry (DSC) results, for electrolytes based on the copolymer with 75% of PEO units, were dominated by the PEO phase. The PEO block crystallinity dropped and the glass transition increased with salt addition due to the coordination of the cation by PEO oxygen. The conductivity for copolymers 75% PEO-based electrolyte with 15 wt% of salt was higher than 10⁻⁵ S/cm at room temperature and reached to 10⁻³ S/cm at 100 °C on a heating measurement. The blend of PE-b-PEO (50% PEO)/PEO/PE showed a complex thermal behavior with decoupled melting of the blocks and the homopolymers. Upon salt addition the endotherms associated with PEO domains disappeared and the PE crystals remained untouched. The conductivity results were limited at 100 °C to values close to 10⁻⁴ S/cm and at room temperature values close to 3 × 10⁻⁶ S/cm were obtained for the 15 wt% salt electrolyte. Raman study showed that the ionic association of the highly concentrated blend electrolytes at room temperature is not significant. Therefore, the lower values of conductivity in the case of the blend with 50% PEO can be assigned to the higher content of PE domains leading to a morphology with lower connectivity for ionic conduction both in the crystalline and melted state of the PE domains.     

Synthesis, characterization and device application of hot-pressed solid polymer electrolytes:(1 − x) PEO:x NaHCO3

Synthesis and io n transport characterization of hot-pressed solid polymer electrolyte (SPE) membranes:(1 ? x) poly (ethylene oxide) (PEO):x NaHCO₃, where 0 < x < 50 wt.%, have been reported. SPE films have been synthesized using a hot-press technique in place of the traditional solution-cast method. A conductivity enhancement of the two orders of magnitude was achieved in SPE film:70PEO:30NaHCO₃ and this composition has been referred to as optimum conducting composition (OCC). Materials characterization was done with the help of XRD, SEM, FTIR, DSC and TGA techniques. The ion transport behavior in SPE membranes has been discussed on the basis of experimental measurements on their ionic conductivity (σ), ionic mobility (μ) and some other important parameters. A solid-state polymer battery was fabricated using SPE OCC at room temperature, as a device application.     

Preparation and electrochemical behaviors of polymeric composite electrolytes containing mesoporous silicate fillers

In the present study, poly(ethylene oxide) (PEO)-based polymeric composite electrolytes (PCEs) had been prepared by using a different content of mesoporous silicate MCM-41, in order to examine the filler addition effect on the microstructural and electrochemical properties. The interactions between MCM-41 and PEO matrix were studied by XRD, DSC, and SEM techniques. The electrochemical properties of the PCEs, such as ionic conductivity, its temperature dependence, and lithium transference number were investigated. MCM-41 could maintain the pore structure effectively, resulting in nanocomposites that were homogeneously complexed with the PEO chains. The PCEs with 8 wt.% MCM-41 showed the smallest crystallinity, 30.4%. Accordingly, those PCEs showed the highest ion conductivity, 1.2 × 10⁻⁴ S/cm, a two-order-of-magnitude higher value than that of the pristine PEO-LiClO₄. This might have reflected decreased crystallinity and improved ion transport. Furthermore, those PCEs showed an increased Li ion transference number of ∼0.5. In conclusion, the filler addition could enhance the ionic conductivity and increase the Li ion transference number at the same time.     

Decoupled ion conduction mechanism of poly(vinyl alcohol) based Mg-conducting solid polymer electrolyte

Investigation on solid state rechargeable magnesium batteries are considered important similar to lithium batteries. In view of negligible hazard and less reactivity of the magnesium, in comparison with lithium, studies on rechargeable magnesium batteries are expected to have a wide scope in future. In the present investigations, decoupled ion conduction of poly(vinyl alcohol) (PVA)-based Mg-conducting solid polymer electrolytes (SPEs) is essential component of the studies. In common SPEs, ion transport has mostly been associated with the segmental motion of the polymer, so significant conductivity is only observed above the glass transition temperature of the system. But the results of ac impedance spectroscopy, FT-IR, XRD and AFM indicated that prepared PVA-based Mg-conducting SPE shows ionic transport decoupled from polymer segmental motion and high ionic conductivity at room temperature.     

Effect of ethylene carbonate on properties of PVP-CsAlO2-LiClO4 solid polymer electrolytes

ABSTRACT

Solid polymer electrolytes (SPEs) have been widely studied due to its extensive applications in high energy rechargeable batteries, supercapacitors, fuel cells, photoelectrochemical and electrochromic displays. Herein, SPEs based on polyvinyl pyrrolidone (PVP) doped with cesium aluminate (CsAlO₂) nanoparticles (NPs), lithium perchlorate (LiClO₄) as an electrolyte and varying amounts viz., 2, 4, 6 and 8 wt.% of ethylene carbonate (EC) as plasticizer have been fabricated by solution intercalation technique. The structural features of PVP-CsAlO₂-LiClO₄-EC SPEs have been studied by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The morphology of PVP-CsAlO₂-LiClO₄-EC SPEs has been examined by scanning electron microscopy (SEM). The thermal properties of the SPEs were characterized by the thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC) techniques. The TGA and DSC results revealed that a significant reduction in thermal stability and glass transition temperature (T_g) of PVP with an increase in EC content in SPE films. The optoelectrical properties of PVP-CsAlO₂-LiClO₄-EC SPE films have been evaluated using UV–visible spectroscopy. The band gap energy (E_g) was found to decrease with an increase in EC content, exhibiting a minimum of 4.23 eV for PVP-8 wt.% CsAlO₂-15 wt.% LiClO₄-8 wt.% EC. This could be ascribed to the formation of localized states and increased degree of disorder in the PVP-CsAlO₂-LiClO₄ SPE films. The integrated plasticizers increase the values of refractive index (RI), optical conductivity, and dielectric constants of PVP-CsAlO₂-LiClO₄ SPE films. The AC conductivity of the SPEs has been evaluated at room temperature using digital LCR meter in the frequency range 100 Hz – 5 MHz. The conductivity strongly depends on CsAlO₂ NPs and EC plasticizer content in SPEs.     

Conductance investigation of p‐MIECs fabricated by poly(3,4‐ethylenedioxy thiophene), polyacrylic acid,polyethylene oxide,and lithium‐ion salt

Polymer blends and composite films were facilely prepared from their aqueous solutions with varying contents of poly(3,4‐ethylenedioxythiophene) (PEDOT), polyethylene oxide (PEO), and polyacrylic acid (PAA). The physicochemical and electric properties of the composite films were analyzed by Raman spectra, infrared spectra (FT‐IR), scanning electronic microscopy (SEM), thermogravimetric analysis (TGA), and four‐point probe method. PEDOT was successfully incorporated into each blend which was confirmed by spectra analysis. The crystallization of PAA or PEO and the structure of PEDOT should be taken into consideration for the electronic conductivity. According to Raman spectra, in the case of PEDOT–PAA–PEO, conformation of the PEDOT backbone changed from the quinoid to the benzoid structure partly. The ionic conductivities of lithium‐ion salt‐mixed PAA–PEO and ternary blend were characterized by AC impedance spectroscopy. The ternary blend with LiCoO₂ presents good electronic and ionic conductivity, and it appears to be a new candidate for polymeric mixed ionic electronic conductor. POLYM. COMPOS., 36:2076–2083, 2015. © 2014 Society of Plastics Engineer     

Conformational,thermal, and ionic conductivity behavior of PEO in PEO/PMMA miscible blend: Investigating the effect of lithium salt

In this research, influence of incorporating LiClO₄ salt on the crystallization, conformation, and ionic conductivity of poly(ethylene oxide) (PEO) in its miscible blend with poly(methyl methacrylate) (PMMA) is studied. Differential scanning calorimetry showed that the incorporation of salt ions into the blend suppresses the crystallinity of PEO. The X‐ray diffraction revealed that the unit‐cell parameters of the crystals are independent of the LiClO₄ concentration despite of the existence of ionic interactions between PEO and Li cations. In addition, the complexation of the Li⁺ ions by oxygen atoms of PEO is investigated via Fourier transform infrared spectroscopy. The conformational changes of PEO segments in the presence of salt ions are studied via Raman spectroscopy. It is found that PEO chains in the blend possess a crown‐ether like conformation because of their particular complexation with the Li⁺ ions. This coordination of PEO with lithium cations amorphize the PEO and is accounted for suppressed crystallinity of PEO in the presence of salt ions. Finally, electrochemical impedance spectroscopy is used to characterize the ionic conductivity of PEO in the PEO/PMMA/LiClO₄ ternary mixture at various temperatures. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Polypropylene/Organoclay Nanocomposites: Effects of Clay Content on Properties

The effects of clays as nanoscale fillers have been rarely addressed. Influence of the amount of organoclay (ranging between 1 and 10 wt.%) on the nanocomposites structure, i.e., intercalated or exfoliated, and on the enhancement of mechanical, rheological and morphological properties of polypropylene (PP) nanocomposites was studied in this work. The fundamental material characterization was conducted using XRD, SEM, TEM, DSC, POM, DMTA as well as RMS. Overall mechanical properties determined by tensile tests showed improvements. DSC and POM results demonstrated decrease of nanocomposites crystallinity. XRD and TEM Showed intercalate/exfoliate structures in the resultant nanocomposites.