Magnesium ion conducting polyvinyl alcohol–polyvinyl pyrrolidone-based blend polymer electrolyte

Structural, thermal, electrical and electrochemical behaviour of polymer blend electrolytes comprising polyvinyl alcohol (PVA) and polyvinyl pyrrolidone (PVP) as host polymers and Mg(ClO₄)₂ as dopant salt have been investigated. The changes in the structural properties on the incorporation of dopant in the blends were investigated by XRD and FTIR analyses. Thermal properties of pure PVA–PVP blend and their complexes were examined by DSC to measure how the thermal transitions of the prepared films were affected by different concentration of Mg(ClO₄)₂. The ionic conductivity and dielectric behaviour were explored using A.C. impedance spectroscopy. The trend of ionic conductivity increases almost proportionally to the content of magnesium salt and can be related to an increase of amorphous phase at high level of dopant salt. The electrochemical stability of the optimum conducting blend polymer electrolyte is found to be ～3.5 V. The Mg²⁺ transference number for the sample with optimized conductivity was found to be 0.31.     

Structural, vibrational, thermal, and conductivity studies on proton-conducting polymer electrolyte based on poly (N-vinylpyrrolidone)

The proton-conducting polymer electrolytes based on poly (N-vinylpyrrolidone) (PVP), doped with ammonium chloride (NH₄Cl) in different molar ratios, have been prepared by solution-casting technique using distilled water as solvent. The increase in amorphous nature of the polymer electrolytes has been confirmed by XRD analysis. The FTIR analysis confirms the complex formation of the polymer with the salt. A shift in glass transition temperature (T _g) of the PVP/NH₄Cl electrolytes has been observed from the DSC thermograms which indicates the interaction between the polymer and the salt. From the AC impedance spectroscopic analysis, the ionic conductivity of 15?mol% NH₄Cl-doped PVP polymer complex has been found to be maximum of the order of 2.51?×?10^?5?Scm^?1 at room temperature. The dependence of T _g and conductivity upon salt concentration has been discussed. The linear variation of the proton conductivity of the polymer electrolytes with increasing temperature suggests the Arrhenius type thermally activated process. The activation energy calculated from the Arrhenius plot for all compositions of PVP doped with NH₄Cl has been found to vary from 0.49 to 0.92?eV. The dielectric loss curves for the sample 85?mol% PVP:15?mol% NH₄Cl reveal the low-frequency ?? relaxation peak pronounced at high temperature, and it may be caused by side group dipoles. The relaxation parameters of the electrolytes have been obtained by the study of Tan?? as a function of frequency.     

Proton-conducting biopolymer electrolytes based on pectin doped with NH4X (X=Cl,Br)

Research has been undertaken to develop polymer electrolytes based on biodegradable natural polymers such as cellulose acetate, starch, gelatin, and chitosan, which are being used as polymer hosts for obtaining new polymer electrolytes for their applications in various electrochemical devices such as batteries, sensors, and electrochromic windows. Pectin is a naturally available material which is extracted from the skin of citrus fruits. Pectins, also known as pectic polysaccharides, are rich in galacturonic acid. The present study focuses on the proton-conducting polymer electrolytes based on the biopolymer pectin doped with ammonium chloride (NH₄Cl) and ammonium bromide (NH₄Br) prepared by solution casting technique. The prepared membranes are characterized using XRD, FTIR, and AC impedance techniques to study their complexation behavior, amorphous nature, and electrical properties. The conductivity of pure pectin membrane has been found to be 9.41 × 10⁻⁷ S cm⁻¹. The polymer systems with 30 mol% NH₄Cl-doped pectin and 40 mol% NH₄Br-doped pectin have been found to have maximum ionic conductivity of 4.52 × 10⁻⁴ and 1.07 × 10⁻³ S cm⁻¹, respectively. The conductivity value has increased by three orders of magnitude compared to pure pectin membrane. The dielectric behavior of both the systems has been explained using dielectric permittivity and electric modulus spectra.

     

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.     

Synthesis and characterization of proton-conducting polymer electrolyte based on polyacrylonitrile (PAN)

Solid polymer electrolytes based on polyacrylonitrile (PAN) doped with ammonium iodide (NH₄I) have been prepared by solution casting method with different molar ratios of polymer and salt using DMF as solvent. The XRD pattern confirms the dissociation of salt. The FTIR analysis confirms the complex formation between the polymer and the salt. A shift in glass transition temperature (T _g ) of the PAN/NH₄I electrolytes has been observed from the DSC thermograms, which indicates the interaction between the polymer and the salt. The conductivity analysis shows that the polymer electrolyte with 20 mol% NH₄I has the highest conductivity equal to 1.106 × 10⁻³ S cm⁻¹ at room temperature. The activation energy (E _a ) has been found to be low for the highest conductivity sample. The dielectric permittivity (ε*) and modulus (M*) have been calculated from the alternating current (AC) impedance spectroscopy in the frequency range 42 Hz–1 MHz. The DC polarization measurement shows that the conductivity is mainly due to ions.

     

Structural,electrical conductivity,and transport analysis of PAN–NH<Subscript>4</Subscript>Cl polymer electrolyte system

Poly (acrylonitrile) (PAN) and ammonium chloride (NH₄Cl)-based proton conducting polymer electrolytes with different compositions have been prepared by solution casting technique. The amorphous nature of the polymer electrolytes has been confirmed by XRD analysis. The FTIR analysis confirms the complex formation of the host polymer (PAN) with the salt (NH₄Cl). DSC measurements show a decrease in T_g with the increase in salt concentration. The conductivity analysis shows that the 25 mol% ammonium chloride doped polymer electrolyte has a maximum ionic conductivity, and it has been found to be 6.4 × 10^?3 Scm^?1, at room temperature. The temperature dependence of conductivity of the polymer electrolyte complexes appears to obey the Arrhenius nature. The activation energy (E_a = 0.23 eV) has been found to be low for 25 mol% salt doped polymer electrolyte. The dielectric behavior has been analyzed using dielectric permittivity (ε*), and the relaxation frequency (τ) has been calculated from the loss tangent spectra (tan δ). Using this maximum ionic conducting polymer electrolyte, the primary proton conducting battery with configuration Zn + ZnSO₄·7H₂O/75 PAN:25 NH₄Cl/PbO₂ + V₂O₅ has been fabricated and their discharge characteristics have been studied.     

AC impedance studies on proton-conducting PAN : NH4SCN polymer electrolytes

Solid polymer electrolytes based on polyacrylonitrile (PAN) doped with ammonium thiocyanate (NH₄SCN) in different molar ratios of polymer and salt have been prepared by solution-casting method using DMF as solvent. The increase in amorphous nature of the polymer electrolytes has been confirmed by XRD analysis. A shift in glass transition temperature (T _g) of the PAN?:?NH₄SCN electrolytes has been observed from the DSC thermograms which indicates the interaction between the polymer and the salt. From the AC impedance spectroscopic analysis, the ionic conductivity has been found to increase with increasing salt concentration up to 30 mol% of NH₄SCN beyond which the conductivity decreases and the highest ambient temperature conductivity has been found to be 5.79?×?10^?3 S cm^?1. The temperature-dependent conductivity of the polymer electrolyte follows an Arrhenius relationship which shows hopping of ions in the polymer matrix. The dielectric loss curves for the sample 70 mol% PAN?:?30 mol% NH₄SCN reveal the low-frequency β-relaxation peak pronounced at high temperature, and it may be caused by side group dipoles. The ionic transference number of polymer electrolyte has been estimated by Wagner’s polarization method, and the results reveal that the conductivity species are predominantly ions.     

Effect of different anions of lithium salt and MMT nanofiller on ion conduction in melt-compounded PEO–LiX–MMT electrolytes

Polymer nanocomposite electrolyte (PNCE) films composed of poly(ethylene oxide) (PEO), lithium salt ( \textLiX;  \textX = ClO₄ ^- ,  BF₄ ^- ,  CF₃SO₃ ^- {\text{LiX}};\;{\text{X}} = ClO_4^{ - },\;BF_4^{ - },\;C{F_3}SO_3^{ - } ) and montmorillonite (MMT) clay as nanofiller were prepared by melt-compounded hot-pressed technique at 70 °C under 3 tons of pressure. The ionic conductivity and relaxation behaviour of the films were investigated by dielectric relaxation spectroscopy in the frequency range of 20 Hz to 1 MHz at ambient temperature. The results revealed that the ionic conductivity of the PNCE films having 20:1 stoichiometric ratio of ethylene oxide monomer units to the lithium cation are governed by the size of different anions and the dissociation constant of salt, and also MMT concentration. It was found that PEO–LiBF₄ film has comparative high dc ionic conductivity, whereas both the LiBF₄ and LiClO₄ containing PNCE films exhibit anomalous conductivity behaviour with varying MMT concentration. The PEO–LiCF₃SO₃ film has two orders of magnitude low value of dc ionic conductivity as compared to that of the other salts electrolyte films, but its conductivity enhances by one order of magnitude when 2 wt.% MMT is added as filler. A correlation between the values of ionic conductivity, conductivity relaxation time and the real part of permittivity at 1 MHz were found and the same was discussed in relation to the transient ion-dipolar type cross-linked structural behaviour of the polymeric nanocomposite electrolytes.     

Effect of dibutyl phthalate as plasticizer on high-molecular weight poly(vinyl chloride)–lithium tetraborate-based solid polymer electrolytes

A series of different composition of polymer electrolytes-based on poly(vinyl chloride) (PVC) as host polymer, lithium tetraborate (Li₂B₄O₇) as dopant salt, and dibutyl phthalate (DBP) as plasticizer were prepared by solution casting method. The interaction between the PVC, Li₂B₄O₇, and DBP were studied by Fourier transform infrared. The shifting, broadening, and splitting of transmission peaks were the evidences of complexation. The highest ionic conductivity polymer electrolyte of 2.83 × 10⁻⁶ S/cm was achieved at ambient temperature upon addition of 30 wt.% of DBP. In addition, the temperature-dependent conductivity, frequency-dependent conductivity, dielectric permittivity, and modulus studies were performed. The temperature-dependent conductivity of the polymer electrolytes was found to obey the Arrhenius behavior. The thermal stability of polymer electrolytes was verified by thermogravimetric analysis. The lower in glass transition temperature was proven in differential scanning calorimetry, whereas the higher amorphous region within the polymer matrix was demonstrated in X-ray diffraction.     

Thermal,vibrational, and dielectric studies on PVP/LiBF4+ionic liquid [EMIM][BF4]-based polymer electrolyte films

Free-standing polymer electrolyte membranes based on poly(vinyl) pyrrolidone (PVP)/salt(LiBF₄) having different amounts of ionic liquid (IL) [EMIM][BF₄] were prepared and characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), Fourier transform infrared (FT-IR) spectroscopy, and alternating current (AC) impedance spectroscopic techniques. The DSC results show a shift in T_m of PVP with salt/or IL content. TGA and DTGA (first derivative of TGA) results give evidence of the presence of uncomplexed PVP, PVP/salt, and PVP/IL complexes. Signatures of these entities are also present in the dielectric spectra. Complexation of PVP with salt and IL has been confirmed by FT-IR analysis. Electrical conductivity as a function of temperature has been studied for PVP/LiBF₄/IL [EMIM][BF₄]. Role of IL in changing phase transition, conductivity, and dielectric relaxation frequency has been discussed.     

Structural, vibrational and electrical characterization of PVA-NH4Br polymer electrolyte system

Polymer electrolyte based on PVA doped with different concentrations of NH₄Br has been prepared by solution casting technique. The complexation of the prepared polymer electrolytes has been studied using X-ray diffraction (XRD) and Fourier transform infra red (FTIR) spectroscopy. The maximum ionic conductivity (5.7×10⁻⁴ S cm⁻¹) has been obtained for 25 mol% NH₄Br-doped PVA polymer electrolyte. The temperature dependence of ionic conductivity of the prepared polymer electrolytes obeys Arrhenius law. The ionic transference number of mobile ions has been estimated by dc polarization method and the results reveal that the conducting species are predominantly ions. The dielectric behavior of the polymer electrolytes has been analyzed using dielectric permittivity and electric modulus spectra.     

Characterization of blend polymer PVA-PVP complexed with ammonium thiocyanate

Thin films of blend polymer electrolytes comprising poly(vinyl alcohol) (PVA) and poly(vinyl pyrrolidone) (PVP) complexed with ammonium thiocyanate (NH₄SCN) salt in different compositions have been prepared by solution casting technique using distilled water as solvent. The prepared films have been investigated by different experimental techniques. The complexation of these films has been studied by FTIR spectroscopy. The increase in amorphousness of the films with increase in NH₄SCN content has been confirmed by XRD analysis. The addition of ammonium thiocyanate salt to PVA-PVP polymer blend shows a shift in T_g of the blend. The effect of salt concentration and temperature on the ionic conductivity of the polymer blend films has been analyzed using AC impedance spectroscopy. The maximum conductivity of 6.85 × 10^?4 S cm^?1 at room temperature has been observed for the blend with 50 mol% PVA-50 mol% PVP complexed with 40 mol% NH₄SCN. The activation energy has been found to be minimum (0.24 eV) for this sample. Wagner’s polarization technique shows that the charge transport in these blend films is predominantly due to ions. Using the highest conductivity blend polymer electrolyte, a proton battery has been fabricated and its discharge characteristics have been studied.     

On dielectrics of polymer electrolytes studied by impedance spectroscopy

We present a phenomenological view on dielectric relaxation in polymer electrolytes in the frequency range where conductivity is independent of frequency. Polymer electrolytes are seen as molecular mixtures of an organic polymer and an inorganic salt. The discussion applies also to ionic liquids. The following is based on systems with poly(ethylene oxide) (PEO) comprising the lithium perchlorate salt (LiClO₄) and also pure low-molecular PEO. In those systems, dipole-dipole interactions form an association/dissociation equilibrium which rules properties of the system in the low-frequency region. It turns out that effective concentration, c _S, of relaxing species provides a suitable variable for discussing electrochemical behavior of the electrolytes. Quantity c _S is proportional to the ratio of DC conductivity and mobility. Polymer salt mixtures form weak electrolytes. However, diffusion coefficient and corresponding molar conductivity display the typical (c _S)^1/2 dependence as well known from strong electrolytes, due to the low effective concentration c _S.     

Performance of ferrite fillers on electrical behavior of polymer nanocomposite electrolyte

Dispersal of nanofillers in polymer electrolytes have shown to improve the ionic properties of Polyethylene oxide (PEO)-based polymer electrolytes in recent times. The effects of different nanoferrite fillers (i.e., Al–Zn ferrite, Mg–Zn ferrite, and Zn ferrite) on the electrical transport properties have been studied here on the composite polymer electrolyte system. The interaction of salt/filler with electrolyte has been investigated by XRD studies. SEM image and infrared spectral studies give an indication of nanocomposite formation. In conductivity studies, all electrolyte systems are seen to follow universal power law. Composition dependence (with ferrite filler) gives the maximum conductivity in [93PEO–7NH₄SCN]: X ferrite (where X?=?2% in Al–Zn ferrite, 1% Mg–Zn ferrite, and 1% Zn ferrite) system.     

Enhancement of the electrochemical properties with the effect of alkali metal systems on PEO/PVdF-HFP complex polymer electrolytes

Polymer blend electrolytes based on poly(ethylene oxide) (PEO) and poly(vinylidene fluoride-hexafluoropropylene) (PVdF-HFP) were prepared by using different lithium salts LiX (X = ClO₄, BF₄, CF₃SO₃, and N [CF₃SO₂]₂) using solution casting technique. To confirm the structure and complexation of the electrolyte films, the prepared electrolytes were subjected to X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) analysis. Alternating current (AC) impedance analysis was performed for all the electrolyte samples at various temperatures from 303 to 343 K. The result suggests that among the various lithium salts, LiN[CF₃SO₂]₂-based electrolytes exhibited the highest ionic conductivity at 8.20 × 10^?4 S/cm. The linear variation of the ionic conductivity of the polymer electrolytes with increasing temperature suggests the Arrhenius-type thermally activated process. Activation energies were found to decrease when doping with lithium imide salt. The dielectric behavior has been analyzed using dielectric permittivity (ε*), electric modulus (M*), and dissipation factor (tanδ) of the samples. Cyclic voltammetry has been performed for the electrolyte films to study their cyclability and reversibility. Thermogravimetric and differential thermal analysis (TG/DTA) was used to ascertain the thermal stability of the electrolytes, and the porous nature of the electrolytes was identified using scanning electron microscopy via ion hopping conduction. Surface morphology of the sample having maximum conductivity was studied by an atomic force microscope (AFM).     

Spectroscopic studies on ion dynamics of PVP–NH4SCN polymer electrolytes

Proton-conducting polymer electrolyte comprising of poly(N-vinyl pyrrolidone) (PVP) and ammonium thiocyanate (NH₄SCN) are prepared by solvent casting method with different polymer–salt concentrations. The changes in the Raman spectra with increasing NH₄SCN concentration state that the free ion concentration is maximum for 20 mol% NH₄SCN concentrated system. At higher salt concentrations (25 mol%), the effective number of charge carriers decreases due to the formation of ion aggregates as confirmed by the Raman analysis. Solid-state NMR and MAS NMR studies are performed to obtain the information about the ionic structure, mobility of the charge carriers, and also to gain insight into the polymer–salt interactions in the polymer electrolytes. The results of ionic transference number show that the charge transport in these polymer electrolytes is mainly due to ions.     

Poly-acrylonitrile-based gel-polymer electrolytes for sodium-ion batteries

Research and development activities on sodium-ion batteries are becoming prominent in the past few years. Compared to lithium-based batteries, the sodium-based batteries will be cheaper because of the abundancy of sodium raw materials in the earth’s crust and also in seawater. In the current study, we synthesized and characterized poly-acrylonitrile (PAN)-based gel-polymer electrolytes formed with NaClO₄ and dissolved in ethylene carbonate (EC) and propylene carbonate (PC). By systematically varying the weight ratios of polymer, salt, and the solvents, we obtained an optimum room temperature ionic conductivity of 4.5 mS cm⁻¹ for the composition 11PAN-12NaClO₄-40EC-37PC (wt.%), which is reasonably good for practical applications. This value of conductivity is comparable to a few other Na⁺ ion conducting gel-polymer electrolyte systems studied in the recent past. Variation of ionic conductivity with inverse temperature showed Arrhenius behavior. Activation energies estimated for all the samples showed only a slight variation suggesting that a single activation process which depends on the EC/PC co-solvent governs the ionic mobility in these gel-polymer electrolytes. Thermo-gravimetric analysis (TGA) revealed that there is no noticeable weight loss of these electrolytes up to 100 °C and hence the electrolytes are thermally stable for operating temperatures up to 100 °C.

     

Magnesium ion-conductive poly(ethylene carbonate) electrolytes

Magnesium (Mg) electrolytes are presently under investigation for their promising performance capabilities in the next generation of batteries. The present work studies Mg-ion transport in polymers using different types of Mg salts. Polymer electrolytes comprising poly(ethylene carbonate) (PEC) with Mg salts (MgX₂; X?=?TFSI, ClO₄) were prepared by solution casting. The structural, thermal, and electrochemical properties of flexible self-standing membranes were studied as potential Mg electrolytes. The impedance results at 90 °C found the highest conductivities of 6.0?×?10^?6 S cm^?1 for PEC-Mg(TFSI)₂, and 5.2?×?10^?5 S cm^?1 for PEC-Mg(ClO₄)₂, at 40 mol%. FT-IR measurements revealed changes in the peak fraction from the region of carbonyl group, which explain the interaction with Mg ions. The glass transition temperature of the TFSI system decreased with increasing salt concentration due to the plasticizing effect of TFSI anions. Thermal gravimetric analysis revealed that the highest values of the 5% weight-loss temperature at 40 mol% are 174 °C for PEC-Mg(TFSI)₂ and 160 °C for PEC-Mg(ClO₄)₂. The electrochemical stability of PEC-Mg(TFSI)₂ at 40 mol% was up to 2.2 V. To confirm the redox reaction of Mg ions in PEC, CV measurement was carried out using symmetrical cells with quasi Mg electrodes. Cathodic and anodic current peaks were clearly observed, and the presence of these peaks indicates Mg-ion conduction in PEC.     

Transport, structural and thermal studies on nanocomposite polymer blend electrolytes for Li-ion battery applications

Nanocomposite polymer electrolytes (NCPEs) composed of poly(vinylidenefluoride-co-hexafluoropropylene) (PVdF-co-HFP) as a host polymer, Poly(vinyl acetate) (PVAc) as an additive, Ethylene Carbonate (EC) as a plasticizer, Lithium Perchlorate as dopant salt and Barium Titanate (BaTiO₃) as a filler were prepared for various concentrations of BaTiO₃ using solvent casting technique. Thermal stability of the sample having maximum ionic conductivity was found using TG/DTA analysis. Nano composite polymer electrolytes were subjected to ac impedance analysis spectra for acquiring the ionic conductivity values at different temperature. Surface structure of the sample was analysed using scanning electron microscope and the complexations of samples were analysed using X-ray diffraction analysis. It was noted that the polymer electrolyte contains 8 wt. % of BaTiO₃ showed maximum ionic conductivity than the other ratios of BaTiO₃.     

Investigation on the effects of addition of SiO<Subscript>2</Subscript> nanoparticles on ionic conductivity,FTIR, and thermal properties of nanocomposite PMMA–LiCF<Subscript>3</Subscript>SO<Subscript>3</Subscript>–SiO<Subscript>2</Subscript>

Composite polymer electrolyte systems composed of poly(methyl methacrylate) (PMMA) as the host polymer, lithium trifluoromethanesulphonate (also known as lithium triflate; LiCF₃SO₃) as dopant salt, and a variety of different concentrations of nano-sized fumed silica (SiO₂) as inorganic filler were studied. The effect upon addition of SiO₂ on the ionic conductivity of the composite polymer electrolytes was investigated, and it was proven that the ionic conductivity had been enhanced. In addition, the interfacial stability also showed improvement. Maximum conductivity was obtained upon addition of 2 wt.% SiO₂. The complexation of PMMA and LiCF₃SO₃ was verified through Fourier transform infrared studies. The thermal stability of the polymer electrolytes was also found to improve after dispersion of inorganic filler. This was proven in the thermogravimetric studies.