Dc Ionic Conductivity Research Articles

Structural and electrical characteristics of PVA:NaTf based solid polymer electrolytes: role of lattice energy of salts on electrical DC conductivity

Solid polymer electrolytes (SPEs) based on polyvinyl alcohol (PVA) and sodium triflate (NaTf) have been prepared by solution cast technique. X-ray diffraction was performed for structural analysis. The decrease of intensity of crystalline peaks of PVA upon addition of NaTf salt reveals the increase of amorphous domain in SPEs. Impedance plots (Zi vs. Zr) shows that the electrolyte samples have a smaller bulk resistance. The highest achieved room temperature DC conductivity is 7.39 × 10−5 S/cm for the sample incorporated with 30 wt% of NaTf. The influence of lattice energy of sodium salts on DC conductivity is discussed. It was appeared that the lattice energy of salts significantly affects the conductivity behavior of polymer electrolytes. High DC conductivity can be achieved for polymer electrolytes incorporated with low lattice energy salts. The pattern of DC ionic conductivity against 1000/T is follows Arrhenius equation. The highest conducting composition has the lowest activation energy (0.109 eV). The DC conductivities calculated from the complex impedance plots are close to those obtained from the plateau region of AC conductivity spectra. Transport parameters such as density of mobile ions (Na+), mobility, and diffusion coefficient were determined for the samples using the Rice and Roth models. The dielectric analysis suggests non-Debye type of relaxation of ions in the present work.

Structural and electrical transport properties of La2Mo2O9 thin films prepared by pulsed laser deposition

We have studied the structure and electrical properties of La2Mo2O9 thin films of different thicknesses prepared by the laser deposition technique at different substrate temperatures. The structural properties of the thin films have been investigated using XRD, XPS, AFM, TEM, SEM, and Raman spectroscopy. The electrical transport properties of the thin films have been investigated in wide temperature and frequency ranges. The cubic nature of the thin films has been confirmed from structural analysis. An enhancement of the oxygen ion conductivity of the films up to five orders of magnitude is obtained compared to that of the bulk La2Mo2O9, suggesting usefulness of the thin films as electrolytes in micro-solid oxide fuel cells. The enhanced dc ionic conductivity of the thin films has been interpreted using the rule of the mixture model, while a power law model has been used to investigate the frequency and temperature dependences of the conductivity. The analysis of the results predicts the three-dimensional oxygen ion conduction in the thin films.

Improvement of Proton-ExchangeMembranes Based on(1x)(H3PO2/PVA)-xTiO2

Using impedance spectroscopy (IS), differential scanning calorimetry (DSC),thermogravimetric analysis (TGA), and infrared spectroscopy (IR) tech-niques to study the polymer electrolyte membranes based on poly(vinylalcohol) (PVA) and hypophosphorous acid (H3PO2) with different tita-nium oxide nanoparticles (TiO2) concentrations. The polymer systems(1−x)(H3PO2/ PVA) +xTiO2were prepared using the sol-casting methodand different weight percent of TiO2,x≤10.0œ. The DSC results showthat the glass transition for molar fraction P/OH = 0.3 appears around 75°Cand for the samples doped with TiO2around 35°C; the melting pointfor all membranes appear around 175°C. The FTIR spectra show changesin the profiles of the absorption bands with the addition of H3PO2andthe different concentrations of TiO2. The IS results show dielectric andconductivity relaxations as well as a change in DC ionic conductivity withthe TiO2content. The order of the ionic conductivity is about10−2S/cmfor 5.0œof TiO2. The TGA in the heating run shows water loss that is inagreement with DC conductivity measurements.

Structural, Morphological and Electrochemical Impedance Study of CS:LiTf based Solid Polymer Electrolyte: Reformulated Arrhenius Equation for Ion Transport Study

This paper discusses ion conduction mechanism in terms of reformulated Arrhenius equation. Understanding the fundamental concepts of Li ion transport is crucial for Li battery technology. Structural and morphological investigations are significant to understand the structure-properties relationships. The broadening of X-ray peaks of chitosan upon the addition of LiTf salt reveals that the crystalline domains are reduced. The SEM micrographs reveal that the samples have a smooth surface. Electrochemical impedance spectroscopy (EIS) was used to obtain the electrical and dielectric parameters. The dielectric constant and DC ionic conductivity follows the same trend with salt concentration. The behavior of Arrhenius and modified Arrhenius equations versus temperature are clarified. The influence of dielectric constant on DC conductivity experimentally achieved. The reformulated Arrhenius equation exhibited more linearity between the DC conductivity and 1000/(e'×T). The shortcoming of Arrhenius equation can be understood from the less linear behavior of DC conductivity versus 1000/T. The pre-exponential factor is almost constant at different temperature and independent on dielectric constant. The calculated activation energy from the reformulated Arrhenius equation is greater than that obtained from Arrhenius equation.

Study of D.C.Ionic Conductivity in BaCl2:SiO2 Composite Solid Electrolyte System

Study of d.c. ionic conductivity in pure BaCl2 and BaCl2 dispersed with the insulating material SiO2 is presented in this work.Variation of dc ionic conductivity with temperature has shown a gradual enhancement of conductivity with m/o of dispersoid reaching to a maximum of nearly two orders of magnitude at 6.6m/o. The fall of enhancement was observed with further increase in m/o of dispersoid. The enhancement of conductivity in this system is interpreted due to increased concentration of charge carriers in the space charge region formed at the interface between the host BaCl2 and insulating dispersoid particles SiO2. XRD and FTIR studies have ruled out the formation of new compound or solid solution, between the host and the dispersoid, as there are no new peaks observed in all these systems.

Electrical properties and thermal degradation of poly(vinyl chloride)/polyvinylidene fluoride/ZnO polymer nanocomposites

AbstractIn this work, polymer nanocomposites consisting of a poly(vinyl chloride) (PVC) and polyvinylidene fluoride (PVDF) polymer network with ZnO nanoparticles as a dopant were prepared by solution casting. An XRD study of the PVC/PVDF/ZnO polymer nanocomposites shows predominantly sharp and high intensity peaks. However, the intensity and sharpness of the XRD peaks decreases with further increment in loading of ZnO (wt%), which reveals a proper intercalation of ZnO nanoparticles within the PVC/PVDF polymer system. Fourier transform infrared spectroscopy has been used to verify the chemical compositional change as a function of ZnO nanoparticle loading. TGA analysis clearly describes the thermal degradation of the pure polymer and polymer nanocomposites. The complex dielectric function, AC electrical conductivity and impedance spectra of these nanocomposites were investigated over the frequency range from 10 Hz to 35 MHz. These spectra were studied with respect to the Wagner − Maxwell − Sillars phenomenon in the low frequency region. Nyquist plots of the PVC/PVDF/ZnO nanocomposites were established from impedance measurements. The temperature‐dependent DC ionic conductivity obtained from the Nyquist plots follows Arrhenius behaviour. © 2016 Society of Chemical Industry

Effect of ionic contaminants on dielectric dispersion and relaxation processes over static permittivity frequency region in neat liquid poly(ethylene glycol)

Complex dielectric permittivity, ac electrical conductivity, electric modulus and impedance spectra of poly(ethylene glycol) (PEG200) were investigated in the frequency range from 20Hz to 1MHz and temperatures from 5 to 55°C. Temperature dependent relaxation processes caused by charging and discharging of electric double layers (EDLs) in the 1kHz–10kHz range and by the ions dynamics above 100kHz were explored from the comparative analysis of the spectra of complex quantities. The values of static permittivity, Kirkwood correlation factor, dc ionic conductivity, EDLs and conductivity relaxation times, and the activation energies of PEG200 were determined. It has been observed that the ionic contaminants influence the electric conduction behaviour of neat PEG200 which is found exactly similar to that of the diluted ionic electrolyte solution of lithium perchlorate dissolved in PEG200. The temperature dependent conductivity and viscosity data related to the ions movement in viscous media were analyzed which revealed that the Stokes-Einstein-Nernst model was not fulfilled for PEG200.

Electronic and ionic conductivities in superionicLi4C60

The $10$ GHz microwave conductivity, $\sigma(T)$ and high field, $222$ GHz electron spin resonance (HF-ESR) of Li$_4$C$_{60}$ fulleride is measured in a wide temperature range. We suggest that the majority of ESR active sites and at least some of the charge carriers for $\sigma(T)$ are electrons bound to a small concentration of surplus or vacancy ions in the polymer phase. Both $\sigma(T)$ and the ESR line shape depend on ionic motion. A change of the activation energy of $\sigma(T)$ at $125$ K coincides with the onset of the ionic DC conductivity. The ESR line shape is determined mainly by Li ionic motion within octahedral voids below $150$ K. At higher temperatures, fluctuations due to ionic diffusion change the environment of defects from axial to effectively isotropic on the ESR time scale. $\sigma(T)$ data up to $700$ K through the depolymerization transition confirm that the monomeric phase of Li$_4$C$_{60}$ is a metal.

Influence of the crystallization on the molecular mobility and ionic DC conductivity behaviors of relaxor ferroelectric P(VDF‐TrFE‐CTFE) terpolymers

ABSTRACTThe dynamics of semicrystalline poly(vinylidene fluoride‐trifluoroethylene‐chlorotrifluoroethylene) (P(VDF‐TrFE‐CTFE)) terpolymers were fully investigated as a function of temperature and frequency, by means of broadband dielectric spectroscopy. Four types of relaxation regimes were observed over the full dielectric spectroscopy, namely (second) relaxation in the sub‐glass state, (segmental dynamics) in the rubbery state, the Curie transition and space charge carrier motion at high temperatures. Constrained segmental dynamics were observed in the terpolymer containing the highest crystalline fraction for which a narrow relaxation time distribution was found. These results indicate a decreasing average size of the cooperative rearranging region over the crystalline fraction. A decrease of the strength index values also implied a more fragile behavior for terpolymers with a higher degree of crystallinity. An exceptional increase in dielectric strength was found as the crystallinity increased. This behavior could be explained by an enhanced interphase (constrained amorphous phase). The Curie transition showed an accelerating relaxation rate for a more fragile terpolymer. Moreover, a motion of the space charge carrier ions was observed in the higher temperature range. Finally, there was evidence that the segmental dynamics in the amorphous phase was responsible for the motion of the space charge carrier ions. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 1645–1657

Superionic behavior in the xAgI–(1−x)CsAg2I3 polycrystalline system

A superionic phase behavior (with DC ionic conductivities higher than 0.01S/cm) has been observed in xAgI–(1−x)CsAg2I3 (x≈0.67) polycrystalline system grown by slow evaporation using AgI and CsI powders (molar ratio Cs/Ag=0.25) as starting salts and an aqueous solution of HI as solvent. The transition from the normal-to- the superionic state is first-order with a hysteretic behavior in temperature centered at about 116°C as reflected by thermal (DSC) and electrical conductivity measurements. This mixture is composed of CsAg2I3 and AgI crystalline phases and an additional amorphous AgI phase that explains the glassy-type behavior observed in the superionic phase transition.

Structural and electrical characterizations of 50:50 PVA:starch blend complexed with ammonium thiocyanate

The present work deals with the preparation and characterization of polymer blend electrolyte films. Glutaraldehyde is used as a cross-linker to cross-link polymers polyvinyl alcohol (PVA) and starch for the proper film formation. Structural characterizations such as X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR) have been performed. X-ray diffraction is done to investigate the amorphous nature of the sample. FTIR study confirms about the complexation of salt with the polymer and interaction of thiocyanate ion with the polymer matrix. Electrical characterizations were done using impedance spectroscopy. DC and AC ionic conductivity was obtained at varying salt concentration in the films which shows maximum ionic conductivity of the polymer electrolyte containing 30 wt% of salt content. The AC conductivity behaviour of the polymer electrolyte follows Jonscher’s power law. Dielectric parameters such as dielectric constant, dielectric loss and loss tangent have been determined. Relaxation time is obtained and decreases to lower value with the increase in the salt concentration in the polymer electrolyte.

Proton Conducting Micro-Solid Oxide Fuel Cells with Nanoscale Palladium Interlayers

We will consider solid oxide fuel cells with electrolyte membranes whose dimensions approach the tunneling limit. Suspended oxide membranes allow exploring ionic and electronic conduction in quasi-2D structures without interference from the substrate at temperatures below 600C. One can consider minority carrier transport mechanisms at such lengthscales to design solid electrolytes wherein dc ionic conductivity alone may not be the critical factor. The thermo-mechanical stabilty of such membranes are in turn closely related to the electroneutrality conditions under the operating environment. Cation valence change driven lattice distortions can profundly modify the strain states and dictate material selection. At the same time, oxide heterostructures can be fabricated in freestanding manner to explore the possibility of local energy storage in an electrode at such low temperatures. We will consider opportunities with Mott insulators for the same wherein the onset of correlated metallic state is closely linked to disorder. Representative examples of fuel cells operating directly in methane will be presented.

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

ABSTRACTLithium 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.

Electrical and Dielectrical Properties of 0.19Ba(NO3)2 - 0.81KNO3:CeO2 Solid Electrolyte System

The characterization, dc and ac ionic conductivity studies of 0.19Ba(NO3)2 - 0.81KNO3: CeO2 nano dispersed sysyem, σx, has been measured from room temperature to nearly their melting points. At any temperature the maximum enhancement in conductivity occurs at 10.8m/o 0.19Ba(NO3)2 - 0.81KNO3:CeO2. The activation energies are calculated in the extrinsic region of temperature. XRD and DSC indicate that no new structure is formed in the dispersoid material and the melting point is not affected. The gradual increase in conductivity (0.19Ba(NO3)2 - 0.81KNO3:CeO2) is due to the presence of nano CeO2, which interacts with cations, thereby reducing ion pairing and increases the number of charge carriers. The incorporation of nano dispersoid particles not only reduces the interfacial resistance but also provides better enhancement in conductivity.

Conductivity of aqueous HCl, NaOH and NaCl solutions: Is water just a substrate?

According to the Arrhenius theory, the ionic conductivity of aqueous electrolytes is realized by the electrolyte ions. Water is considered to be a chemically inactive environmental media. Here, we succeeded in modeling the ionic dc conductivity and dielectric constant of aqueous HCl, NaOH and NaCl solutions without considering Na+ and Cl− ions. Instead, we assumed that i) water has a high concentration of the intrinsic H3O+ and OH− ions (much larger than it is implied by ), masked in the dc conductivity by the electrophoretic effect, i.e. by a strong ion-ion attraction, and ii) the chemical interaction between the electrolyte molecules and the water ions happens to break down the electrophoretic effect, thus “activating” the water ions for the dc conductivity. The hypothesis about the active role of water in the conductivity of electrolytes may look controversial, but nevertheless it consistently accounts for a set of basic empirical data and is therefore worth examining.

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.

Role of preparation methods on the structural and dielectric properties of plasticized polymer blend electrolytes: Correlation between ionic conductivity and dielectric parameters

The polymer blend based electrolyte films consisted of poly(ethylene oxide) (PEO) and poly(methyl methacrylate) (PMMA) with lithium triflate (LiCF3SO3) as a dopant ionic salt and poly(ethylene glycol) (PEG) as plasticizer have been prepared by solution cast melt–pressed and ultrasonic assisted followed by microwave irradiated solution cast melt–pressed methods. The X–ray diffraction study infers that the amorphous phase of (PEO–PMMA)–LiCF3SO3–x wt% PEG electrolytes decreases with the increase of PEG concentration. The complex dielectric function, ac electrical conductivity, electric modulus and the impedance spectra of these electrolytes have been investigated over the frequency range from 20Hz to 1MHz. It is found that all the dielectric/electrical functions of these electrolytes vary anomalously with the increase of PEG concentration, and also with the change of samples preparation methods. The activation energies have been determined from the temperature dependent values of dc ionic conductivity, polymer segmental relaxation time and dielectric strength. Results reveal that besides the amorphicity, the ionic conductivity of these electrolytes is also governed by the relaxation time and the dielectric strength, and the transport of ions is due to hopping mechanism which is coupled with segmental motion of polymers chain. Room temperature ionic conductivity values of the PEO–PMMA blend based electrolytes are found about one to two orders of magnitude higher than that of the PEO and PMMA based electrolytes.

Dielectric properties and fluctuating relaxation processes of poly(methyl methacrylate) based polymeric nanocomposite electrolytes

Solid polymer nanocomposite electrolytes (SPNEs) consisted of poly(methyl methacrylate) (PMMA) and lithium perchlorate (LiClO4) of molar ratio C=O:Li+=4:1 with varying concentration of montmorillonite (MMT) clay as nanofiller have been prepared by classical solution casting and high intensity ultrasonic assisted solution casting methods. The dielectric/electrical dispersion behaviour of these electrolytes was studied by dielectric relaxation spectroscopy at ambient temperature. The dielectric loss tangent and electric modulus spectra have been analyzed for relaxation processes corresponding to the side groups rotation and the segmental motion of PMMA chain, which confirm their fluctuating behaviour with the sample preparation methods and also with change of MMT concentration. The feasibility of these relaxation fluctuations has been explained using a transient complex structural model based on Lewis acid–base interactions. The low permittivity and moderate dc ionic conductivity at ambient temperature suggest the suitability of these electrolytes in fabrication of ion conducting electrochromic devices and lithium ion batteries. The amorphous behaviour and the exfoliated/intercalated MMT structures of these nanocomposite electrolytes were confirmed by X-ray diffraction measurements.

Dielectric Dispersion and Electric Relaxation Processes Induced by Ionic Conduction in Formamide, 2-Aminoethanol and Their Binary Mixtures

The complex dielectric permittivity, ionic conductivity, electric modulus and impedance spectra of the dipolar molecules formamide (FA), 2-aminoethanol (AE) and their binary mixtures were investigated in the frequency range from 20 Hz to 1 MHz at 303.15 K. Debye-type distributions of the frequency dependent electric modulus and complex impedance were found, corresponding to an ionic conduction relaxation process in the upper frequency regime of the spectra, whereas a spike in the impedance spectra at low frequencies confirms the contribution of an electrode polarization (EP) relaxation process induced by ionic conduction. Due to the high static permittivity of FA, its ionic conductivity was found more than one order of magnitude higher than that of the AE, which is also shown by the comparative values of their EP and ionic conductivity relaxation times. The dependences of dc ionic conductivity values of the binary mixtures on their relaxation times and static permittivity were explored. The concentration dependent static permittivity and the relaxation times led us to infer the formation of a 1:1 H-bonded stable complex between FA and AE molecules with reduction in the number of effective parallel-aligned dipoles.

Structural and DC Ionic conductivity studies of carboxy methylcellulose doped with ammonium nitrate as solid polymer electrolytes

Solid polymer electrolytes have been prepared by solution casting technique. Carboxy methylcellulose (CMC)-ammonium nitrate (AN) films were studied with varied AN salt concentration from 5-50 wt.% at ambient temperature. X-ray diffraction (XRD) pattern shows the amorphous nature of polymer electrolyte samples. IR-spectra confirm the polymer-salt complexes in the range of 1633 - 829 cm-1. Impedance analysis reveals that polymer electrolyte film containing 45wt.% AN exhibits the highest ionic conductivity of (7.71 ± 0.04) x10-3 Scm-1, while pure CMC film gives the lowest ionic conductivity of (1.86 ± 0.03) x10-8 Scm-1. It was evident from this study that the increase of ionic conductivity depends on the AN salt concentration. The present polymer-salt system has potential application in electrochemical devices based on the results obtained. Key words: Carboxy methylcellulose, ammonium nitrate, solid polymer electrolytes, ionic conductivity.