Ionic conductance behaviour of plasticized polymer electrolytes containing different plasticizers

The effect of different plasticizers on the properties of PEO-NH₄F polymer electrolytes has been studied. Aprotic organic solvents like propylene carbonate (PC), ethylene carbonate (EC), γ-butyrolactone (γ-BL), dimethylacetamide (DMA), dimethylformamide (DMF), diethylcarbonate (DEC) and dimethylcarbonate (DMC) having different values of donor number, dielectric constant, viscosity etc. have been used as plasticizers in the present study. The addition of plasticizer has been found to modify the conductivity of polymer electrolytes by increasing the amorphous content as well as by dissociating the ion aggregates present in polymer electrolytes at higher salt concentrations. The conductivity enhancement with different plasticizers has been found to be closely related to the donor number of the plasticizer used rather than its dielectric constant. The increase in conductivity with the addition of plasticizer has further been found to be dependent upon the level of ion association present in the electrolytes. The variation of conductivity as a function of plasticizer concentration and temperature has also been studied and maximum conductivity of ∼ 10⁻³ S /cm at room temperature has been obtained. X-ray diffraction studies show an increase of amorphous content in polymer electrolytes with the addition of plasticizers.     

Role of polyvinyl alcohol in the conductivity behaviour of polyethylene glycol-based composite gel electrolytes

An attempt has been made in the present work to combine gel and composite polymer electrolyte routes together to form a composite polymeric gel electrolyte that is expected to possess high ionic conductivity with good mechanical integrity. Polyethylene glycol (PEG) based composite gel electrolytes using polyvinyl alcohol (PVA) as guest polymer have been synthesized with 1 molar solution of ammonium thiocyanate (NH₄SCN) in dimethyl sulphoxide (DMSO) and electrically characterized. The ionic conductivity measurements indicate that PEG:PVA:NH₄SCN-based composite gel electrolytes are superior (σ _max = 5.7 × 10⁻² S cm⁻¹) to pristine electrolytes (PEG:NH₄SCN system) and conductivity variation with filler concentration remains within an order of magnitude. The observed conductivity maxima have been correlated to PEG:PVA:NH₄SCN-and PVA:NH₄SCN-type complexes. Temperature dependence of conductivity profiles exhibits Arrhenius behaviour in low temperature regime followed by VTF character at higher temperature.      

Conductivity studies on PEO:NaClO3 electrolyte system with different plasticizers

A new ion conducting solid polymer electrolyte thin film based on Polyethylene oxide (PEO) with NaClO₃ salt is prepared by solution-casting method. The solvation of salt with PEO has been confirmed by X-ray diffraction and IR spectral studies. Plasticizer effects were studied in PEO:NaClO₃ system by using low molecular weight polyethylene glycol (PEG), dimethyl formamide (DMF) and propylene carbonate(PC). AC conductivity in the temperature range (308–378 K) was measured to evaluate the conductivity of the polymer electrolytes. From the conductivity data, it was found that the conductivity value of pure PEO increases 10²–10⁴ order of magnitude with the addition of salts as well as plasticizers. From the transference number experiments, it was confirmed that the charge transport in these electrolyte is mainly due to the ions (t_ion≈0.94). Finally, the conductivity value of all PEO: NaClO₃ systems were compared.     

Effect of plasticizer on ionic transport and dielectric properties of PVA-H3PO4 proton conducting polymeric electrolytes

Solid polymer electrolytes have attracted considerable attention due to their wide variety of electrochemical device applications. The present paper is focused on the effect of plasticizer to study the structural, electrical and dielectric properties of PVA-H₃PO₄ complex polymer electrolytes. XRD results show that the crystallinity decreases due to addition of plasticizer up to particular amount of polyethylene glycol (PEG) and thereafter it increases. Consequently, there is an enhancement in the amorphicity of the samples responsible for process of ion transport. This characteristic behavior can be verified by the analysis of the differential scanning calorimetry results. FTIR spectroscopy has been used to characterize the structure of polymer and confirms the complexation of plasticizer with host polymeric matrix. Electrical and dielectric properties have been studied for different wt% of plasticizer and their variations have been observed. The addition of PEG has significantly improved the ionic conductivity. The optimum ionic conductivity value of the plasticized polymer electrolyte film of 30 wt% PEG has been achieved to be of the order of 10⁻⁴ S cm⁻¹ at room temperature and corresponding ionic transference number is 0.98. The minimum activation energy is found to be 0.25 eV for optimum conductivity condition.     

Li ion conduction on plasticizer-added PVAc-based hybrid polymer electrolytes

Poly(vinyl acetate), poly(vinylidene fluoride–hexafluoropropylene), lithium perchlorate salt, and the different plasticizer-based gel polymer electrolytes were prepared by solvent-casting technique. The structural and the complex formation have been confirmed by X-ray diffraction spectroscopic analysis. Thermal stability of the different plasticizer-added electrolyte films has been analyzed by means of thermogravimetric analysis. Ionic conductivity of the electrolyte samples has been found as a function of temperature and the plasticizers. Among the various plasticizers, ethylene carbonate-based complexes exhibit maximum ionic conductivity value of the order of 10⁻⁴ Scm⁻¹. Finally, the microstructure of the maximum ionic conductivity sample has been depicted with the help of scanning electron microscope analysis.     

Ion transport mechanism in proton-conducting gel-type electrolytes: solvent and polymer effects

The development and characterization of proton-conducting gel-type electrolytes containing simple aliphatic dicarboxylic acids gelled with poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-HFP) has been investigated in the present work. The relation between the various properties and the composition of the electrolyte constituents with different electrical/physical properties has been investigated and established. Electrical properties for the developed gel-type electrolytes were found to depend upon the acidity and concentration of acid and the amount of polymer present. This dependence is explained due to the combined effect of change in ion concentration, viscosity, and physical interactions taking place between the constituents of electrolytes. Maximum conductivity of 1.59 × 10⁻³ S/cm is observed at room temperature for electrolytes containing 1 M oxalic acid. The interactions and behavior of the electrolytes are supported by Fourier transform infrared, nuclear magnetic resonance, viscosity, and pH studies.     

Evidence of ion pair breaking by dispersed polymer in polymer gel electrolytes

Non-aqueous polymer gel electrolytes containing trifluoromethanesulfonic acid (HCF₃SO₃) and polyethylene oxide (PEO) as the gelling polymer has been studied. The increase in conductivity observed with the addition of PEO to liquid electrolytes has been explained to be due to the breaking of ion aggregates present in electrolytes at higher acid concentrations. The increase in free H⁺ ion concentration upon breaking of ion aggregates has also been observed in pH measurements and viscosity of gel electrolytes has been found to increase with PEO addition. Polymer gel electrolytes containing dimethylacetamide (DMA) have σ ∼ 10⁻² S/cm at room temperature and are stable over −50 to 125 °C range of temperature. Gels based on propylene carbonate (PC) and ethylene carbonate (EC) are stable in the −50 to 40 °C temperature range and loose their gelling nature above 40 °C.     

Evidence of ion pair breaking by dispersed polymer in polymer gel electrolytes

Non-aqueous polymer gel electrolytes containing trifluoromethanesulfonic acid (HCF₃SO₃) and polyethylene oxide (PEO) as the gelling polymer has been studied. The increase in conductivity observed with the addition of PEO to liquid electrolytes has been explained to be due to the breaking of ion aggregates present in electrolytes at higher acid concentrations. The increase in free H⁺ ion concentration upon breaking of ion aggregates has also been observed in pH measurements and viscosity of gel electrolytes has been found to increase with PEO addition. Polymer gel electrolytes containing dimethylacetamide (DMA) have σ ∼ 10⁻² S/cm at room temperature and are stable over −50 to 125 °C range of temperature. Gels based on propylene carbonate (PC) and ethylene carbonate (EC) are stable in the −50 to 40 °C temperature range and loose their gelling nature above 40 °C.     

Synthesis and studies of new plasticized PVP: NaClO3 electrolyte system for battery applications

A new thin film sodium ion conducting plasticized polymer electrolyte based on poly(vinyl pyrrolidone) (PVP) complexed with NaClO₃ salt systems was prepared by the solution-cast method. The interaction of NaClO₃ salt with PVP was confirmed by Infrared (IR) study. Charge transport of these polymer electrolytes is due to ions, which was confirmed by Wagner’s polarization method. From the conductivity measurements, the highest conductivity value 6.71×10⁻⁵ S/cm was observed for the composition PVP:PEG:NaClO₃(30:60:10) at room temperature 35 °C. The redox behaviour and good reversibility of the plasiticized electrolytes are confirmed by electrochemical techniques. Electrochemical cell studies of these polymer electrolytes were analyzed from their discharge characteristics. The open-circuit voltage (OCV) and short-circuit current (SCC) were found to in the range of 2.52 V to 2.36 V and 760 μA to 1040 μA, respectively.     

Effects of MnO<Subscript>2</Subscript> nano-particles on the conductivity of PMMA-PEO-LiClO<Subscript>4</Subscript>-EC polymer electrolytes

Li-ion rechargeable batteries based on polymer electrolytes are of great interest for solid state electrochemical devices nowadays. Many studies have been carried out to improve the ionic conductivity of polymer electrolytes, which include polymer blending, incorporating plasticizers and filler additives in the electrolyte systems. This paper describes the effects of incorporating nano-sized MnO₂ filler on the ionic conductivity enhancement of a plasticized polymer blend PMMA–PEO–LiClO₄–EC electrolyte system. The maximum conductivity achieved is within the range of 10⁻³ S cm⁻¹ by optimizing the composition of the polymers, salts, plasticizer, and filler. The temperature dependence of the polymer conductivity obeys the VTF relationship. DSC and XRD studies are carried out to clarify the complex formation between the polymers, salts, and plasticizer.     

Structural and electrochemical characteristics of 49% PMMA grafted polyisoprene-LiCF3SO3-PC based polymer electrolytes

Gel polymer electrolytes consisting of 49% PMMA grafted polyisoprene-LiCF₃SO₃, were plasticized with propylene carbonate (PC) are reported. The effect of PC on the electrochemical properties of the polymer electrolyte has been investigated. Analysis of FTIR spectra shows the interaction of salt and plasticizers with the polymer chain. The ionic conductivity was measured and exhibited a maximum value of 10⁻⁴ S/cm. The temperature dependence of the electrical conductivity follows the Arrhenius law. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Effects of plasticizer and nanofiller on the dielectric dispersion and relaxation behaviour of polymer blend based solid polymer electrolytes

Solid polymer electrolytes consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) blend (50:50 wt/wt%) with lithium triflate (LiCF₃SO₃) as a dopant ionic salt at stoichiometric ratio [EO + (CO)]:Li⁺ = 9:1, poly(ethylene glycol) (PEG) as plasticizer (10 wt%) and montmorillonite (MMT) clay as nanofiller (3 wt%) have been prepared by solution cast followed by melt–pressing method. The X–ray diffraction study infers that the (PEO–PMMA)–LiCF₃SO₃ electrolyte is predominantly amorphous, but (PEO–PMMA)–LiCF₃SO₃–10 wt% PEG electrolyte has some PEO crystalline cluster, whereas (PEO–PMMA)–LiCF₃SO₃–10 wt% PEG–3 wt% MMT electrolyte is an amorphous with intercalated and exfoliated MMT structures. The complex dielectric function, ac electrical conductivity, electric modulus and impedance spectra of these electrolytes have been investigated over the frequency range 20 Hz to 1 MHz. These spectra have been analysed in terms of the contribution of electrode polarization phenomenon in the low frequency region and the dynamics of cations coordinated polymer chain segments in the high frequency region, and also their variation on the addition of PEG and MMT in the electrolytes. The temperature dependent dc ionic conductivity, dielectric relaxation time and dielectric strength of the plasticized nanocomposite electrolyte obey the Arrhenius behaviour. The mechanism of ions transportation and the dependence of ionic conductivity on the segmental motion of polymer chain, dielectric strength, and amorphicity of these electrolytes have been explored. The room temperature ionic conductivity values of the electrolytes are found ∼10⁻⁵ S cm⁻¹, confirming their use in preparation of all-solid-state ion conducting devices.     

Physicochemical studies of PVdF–HFP-based polymer–ionic liquid composite electrolytes

Polymer–ionic liquid composite electrolytes based on poly (vinylidenefluoride-co-hexafluoropropylene) (PVdF–HFP) and room temperature ionic liquid: 2,3-dimethyl-1-octylimidazolium hexafluorophosphate (DMOImPF₆) have been synthesized and studied. The addition of dimethylacetamide (DMA) and propylene carbonate (PC), both with high dielectric constant and low viscosity, to polymer electrolytes has been found to result in an enhancement of conductivity by one order of magnitude. Composite polymer electrolytes containing ionic liquid have been found to be thermally stable upto 300°C. Motional narrowing observed in the variation of line width of ¹H and ¹⁹F NMR peaks with temperature suggests that both cations and anions are mobile in these electrolytes.     

FTIR and conductivity studies of PVC based polymer electrolyte systems

Poly (vinylchloride) (PVC)-LiBF₄ polymer electrolytes plasticized with DBP in different mole ratios have been studied by FTIR and Impedance Spectroscopic techniques. The complexation has been confirmed from FTIR studies. The maximum room temperature conductivity (2.1·.10⁻⁷ S·.cm⁻¹) has been observed for PVC-LiBF₄-DBP (10-5-85 mole%) complex. The temperature dependence of the conductivity of the polymer films seems to obey the VTF relation. The conductivity values are presented and the results are discussed.     

Performance evaluation of PVdF gel polymer electrolytes

A series of gel polymer electrolytes containing PVdF as homo polymer, a mixture of 1:1 Ethylene Carbonate (EC) : Propylene Carbonate (PC) as plasticizer and lithium-bistrifluoromethane sulphone imide [imide — LiN (CF₃SO₂)₂] has been developed. Amounts of polymer (PVdF), plasticizer and the imide lithium salt have been varied as a function of their weight ratio composition in this regard. Dimensionally stable films possessing appreciable room temperature conductivity values have been obtained with respect to certain weight ratio compositions. However, conductivity data have been recorded at different possible temperatures, i.e., from 20 °C to 65 °C. XRD and DSC studies were carried out to characterize the polymer films for better amorphicity and reduced glass transition temperature, respectively. The electrochemical interface stability of the PVdF based gel polymer electrolytes over a range of storage period (24 h – 10 days) have been investigated using A.C. impedance studies. Test cells containing Li/gel polymer electrolyte (GPE)/Li have been subjected to undergo 50 charge-discharge cycles in order to understand the electrochemical performance behaviour of the dimensionally stable films of superior conductivity. The observed capacity fade of less than 20% even after 50 cycles is in favour of the electrochemical stability of the gel polymer electrolyte containing 27.5% PVdF −67.5 % EC+PC −5% imide salt. Cyclic voltammetry studies establish the possibility of a reversible intercalation — deintercalation process involving Li⁺ ions through the gel polymer electrolyte.     

Effects of gamma radiation treatment and plasticizer on alkaline solid polymer electrolytes

Alkaline solid polymer electrolyte films have been prepared by the solvent-casting method. Gamma radiation treatment and propylene carbonate plastisizer were used to improve the ionic conductivity of the electrolytes at ambient temperature. The structure of the irradiated electrolytes changes from semi-crystalline to amorphous, indicating that the crosslinking of the polymer has been achieved at a dose of 200 kGy. The ionic conductivity at room temperature of PVA/KOH blend increases from 10⁻⁷ to 10⁻³ Scm⁻¹ after the PVA crosslinking and when the plasticizer concentration was increased from 20 to 30%. Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6 – 8, 2005.     

Effect of radiation on conductivity of solid PVA–KOH–PC composite polymer electrolytes

The aim of this work is to enhance the room temperature conductivity of solid alkaline composite polymer electrolytes (ACPEs) based on polyvinyl alcohol/potassium hydroxide/propylene carbonate (PVA–KOH–PC) composites by cross-linking the PVA and bond scission of the PC by γ-radiation. The ACPEs were prepared by solvent-casting technique and irradiated with doses up to 200 kGy at room temperature. The microstructure of the ACPEs was measured using XRD spectrometer, and the results show the structural change from semicrystalline to amorphous, indicating that the cross-linking has been achieved at higher doses. It was found that the PKOH composite at 40 wt% KOH and PPC composite at 60 wt% PC show higher conductivities. The conductivity of the PKPC composites is dominated by dc conductivity at higher frequencies and that PC with 60 wt% has the highest conductivity at a dose of 200 kGy.Paper presented at the International Conference on Functional Materials and Devices 2005, Kuala Lumpur, Malaysia, June 6–8, 2005.     

Effect of storage time on the properties of PVA–KOH alkaline solid polymer electrolyte system

Polyvinyl alcohol (PVA) and potassium hydroxide (KOH) have been used to prepare alkaline solid polymer electrolytes (ASPE) films. The films were stored in a dry environment for 30 and 100 days. The highest room temperature conductivity for the PVA:KOH film with weight percentage ratio of 1:0.67 during storage for 30 and 100 days were (8.5±0.2)×10⁻⁴ and (1.3±0.1)×10⁻⁷ S cm⁻¹, respectively. The conductivity–temperature behaviour after 30 and 100 days of storage of the alkaline polymer electrolytes is Arrhenian and liquid-like. The structural, morphological and thermal studies of the ASPE films are also presented in this paper.     

PMMA based protonic polymer gel electrolytes

The paper reports the synthesis of protonic polymer gel electrolytes containing different hydroxy benzoic acids (ortho-, meta- and para-) and aliphatic dicarboxylic acids. Gel electrolytes were prepared by adding polymethylmethacrylate (PMMA) in different weight ratios to the 1M solution of above acids in a ternary solvent mixture of propylene carbonate (PC), ethylene carbonate (EC) and dimethylformamide (DMF) in equal volume ratio. The conductivity of these gel electrolytes has been found to depend upon the amount of PMMA added to the system. A “Breathing Polymeric Chain Model” has been proposed to explain the variation of conductivity with PMMA concentration in these gel electrolytes.     

Comparative study of the electrical and dielectric properties of PVA–PEG–Al2O3–MI (M=Na,K, Ag) complex polymer electrolytes

Plasticized nanocomposite polymer electrolytes (PNCPEs) based on poly(vinyl alcohol) (PVA)–MI (M=Na, K, Ag) dispersed with nanofillers Al₂O₃ and plasticized with poly(ethylene glycol) (PEG) have been prepared by solution cast technique. The structural properties of the samples have been characterized using various experimental techniques such as XRD, DSC, FTIR and B-G spectroscopy. The ionic conductivity and dielectric constant of the samples have been estimated using a LCZ meter in a wide temperature range, i.e. from 30 to 170 °C. It has been observed that the presence of water molecules in polymer electrolytes significantly affects the mobility of ionic species. The temperature dependent ionic conductivity shows the Arrhenius type behavior separated in three distinct regions. The ionic transference number for all PNCPE samples is found to be ≈1, which strongly suggests their ionic nature.