Field enhanced Li ion conduction in nanoferroelectric modified polymer electrolyte systems

Nanocomposite polymer electrolyte (NCPE) films based on polyethylene oxide (PEO) complexed with lithium perchlorate (LiClO₄) and nanosized ferroelectric ceramic fillers such as BaTiO₃, SrTiO3 have been prepared using solution cast technique. The films showed very good mechanical stability when exposed to ambient atmospheres for prolonged periods. Lithium ion transport studies revealed that the conductivity is predominantly ionic. The effect of electric field on ionic conductivity of NCPE films was investigated. One order enhancement in conductivity due to the field was observed at 323 K. NCPE films exhibited conductivity of 3.46?×?10^?5 Scm^?1 at 323 K. NCPE films were characterized using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) technique. The DSC and XRD studies revealed reduced crystallinity which confirmed the higher amorphous phase and hence the improved ionic conductivity.     

Solid electrolytes with oxygen ion conduction

Oxygen ion conductors constitute an important class of solid electrolytes and have been extensively studied from scientific and technological standpoint. Most of the oxygen ion conductors (eg. those based on ZrO₂, ThO₂, CeO₂ and Bi₂O₃) have a perfect or distorted fluorite type structure. Some oxides with a perovskite type structure also exhibit oxygen ion conduction. All these materials show enhanced conductivity when doped with aliovalent impurities. The defect structure of these materials and the resulting transport properties (electrical conductivity, diffusion and transference number) are discussed as a function of temperature, oxygen partial pressure and composition. Some of the important measurement methods are briefly surveyed. Interface phenomena receive attention as they affect transport behaviour at the electrode - electrolyte combination. Defect interactions in these massively defective solids are presented through an analysis of theoretical models. Finally, some of the important applications of the oxygen ion conductors in fuel cells, oxygen probes and pumps and electrochemical decomposition of water are indicated.     

Mathematical modeling of field-assisted Li ion conduction in nanocomposite solid polymer electrolyte systems

Ionics - Nanocomposite solid polymer electrolyte films were prepared to study the effect of electric field on the ionic conductivity. The studies were carried out by varying the electric field from...     

Effect of ceramic oxide on PVC-PMMA hybrid polymer electrolytes

The preparation and characterization of PVC-PMMA-LiBF₄/LiAsF₆-DBP composite polymer electrolytes for different concentrations of ZrO₂ have been investigated. FTIR studies indicate complex formation between the polymers, salt and plasticizer. The electrical conductivity values measured by ac impedance spectroscopy were found to depend upon the ZrO₂ concentration. 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.     

Dielectric spectroscopy and confirmation of ion conduction mechanism in direct melt compounded hot-press polymer nanocomposite electrolytes

Solid-type polymer nanocomposite electrolyte (PNCE) comprising poly(ethylene oxide) (PEO), lithium perchlorate (LiClO₄) and montmorillonite (MMT) nano-platelets were synthesized by direct melt compounded hot-press technique at 70 °C under 3 tons of pressure. The spectra of complex dielectric function, electric modulus and alternating current (ac) electrical conductivity, and complex impedance plane plots of these materials were investigated in the frequency range 20 Hz to 1 MHz at ambient temperature. The variation of electrode polarization and ionic conduction relaxation times with MMT concentration up to 20 wt.% confirms their strong correlation with direct current ionic conductivity. The predominance of exfoliated MMT structures in PEO matrix and their effect on cation conduction mechanism and ion pairing were discussed by considering a supramolecular transient cross-linked structure. The normalized ac conductivity as a function of scaled frequency of these PNCE materials obey the universal time–concentration superposition behaviour alike the disordered solid ionic conductors.     

Blended lithium ion conducting polymer electrolytes based on boroxine polymers

A new series of blended polymer electrolytes based on a boroxine polymer (BP) with poly(ethylene oxide) (PEO), an ethylene oxide–propylene oxide copolymer or poly(methyl methacrylate) were prepared. Good room temperature mechanical properties were exhibited by electrolytes containing in excess of 30% PEO. Cationic transference number measurements indicated that a slight improvement in lithium ion conductivity could be achieved by using a mixture of LiCF₃SO₃ and LiN(CF₃SO₂)₂ as the electrolyte salt. Electrolytes incorporating significant proportions of BP exhibited reduced lithium–polymer electrolyte interfacial resistance.     

Ionic conduction in plasticized PVC/PAN blend polymer electrolytes

Blended polymer electrolytes with poly(vinyl chloride) (PVC)–poly(acrylonitrile) (PAN) were prepared with different plasticizer concentrations and constant lithium perchlorate (LiClO₄) ratio by the solution-casting technique. The structure and complexation of the prepared films were studied by X-ray diffraction and Fourier transform infrared spectroscopy. The effect of the plasticizer on the ionic conduction in these electrolytes was investigated using alternating current impedance measurement and discussed. The temperature-dependant ionic conductivity was carried out in the range 302–373 K. The prepared films were also examined by thermogravimetry/differential thermal analysis to determine their thermal stability.     

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.     

Electrical current pulsations through ion irradiated polymer foils in electrolytes

Funnel-type ion tracks were produced in thin polymer foils by swift heavy ion irradiation and subsequent treatment with both low concentration etchants and acids from two different sides. The funnel shapes consist of shallow etched cones and residual latent tracks and thus combine both their characteristic properties, rectification and current spike emission, in one track each. Arrays of spike-emitting tracks are known to exhibit phase-locked synchronous electrical pulsations in accordance with the neural network theory. These pulsations were studied here on arrays of funnel-type tracks for the first time. As expected, the results strongly depend on the track density. In foils with low track densities, synchronous oscillations are rare and rather unstable events, whereas foils with high track densities exhibit stable, strong and long-lasting pulsations. Insertion of 0.1 M KCl solution into tracks at low density improved the shape and regularity of the spuriously occurring spikes somewhat, as compared with water in these tracks.     

Lithium ion conduction in substituted Li5GaO4 phases

The electrical conductivity of substituted Li₅GaO₄ phases was investigated by complex impedance techniques. Substitution by divalent cations to increase the concentration of vacancies in Li_5–2xZn_xGaO₄ did not enhance the ionic conductivity in β-Li₅GaO₄ -type solid solutions. High Li⁺ conduction was observed in Li_5+xGa_1–xM_xO₄ with M=Mg and Zn in the β-Li₅GaO₄ structure. The maximum conductivity at 300°C is 4.1 × 10^–3 (ω-cm)^–1 for Li_5.4Ga_0.6Zn_0.4O₄ and 1.3 × 10^–3 (ω-cm)^–1 for Li_5.7Ga_0.7Mg _0.3O₄. These results are discussed in relation to the structural properties.     

Optimization of divalent magnesium ion conduction in phosphate based polycrystalline solid electrolytes

A highest Mg²⁺ ion conducting polycrystalline solid electrolyte was successfully realized by improving the characteristics of both grain bulks and grain boundaries simultaneously. The former improvement was achieved by making a solid solution to substitute cation site for higher valent one to create Mg²⁺ ion vacancies in grain bulks. The latter was realized by obtaining a composite in such a manner to microscopically deposit the insulating secondary phase in grain boundaries. By combining above mentioned two effects, the optimization of Mg²⁺ ion conductivity at around 800 °C was effectively achieved to reach the total Mg²⁺ ion conductivity of approximately 10⁻² S·cm⁻¹ which is applicable in a practical range.     

A quantum-chemical study on ion complexation in polymer electrolytes containing lithium aluminate salts

A quantum-chemical study on single-ion conducting electrolytes based on lithium aluminate salts is presented. Geometry optimizations for salts and corresponding anions have been performed. Stabilization energies for Li⁺ complexed at aluminate anions have been calculated. Information about Li⁺ coordination changes has been obtained from Born–Oppenheimer Molecular Dynamics simulations. Complexation energies for lithium cation have been shown to correlate with experimental conductivity values [T. Fujinami, Y. Buzoujima, J. Power Sources 119–121 (2003) 438].     

Investigations on Na+ ion conducting polyvinylidenefluoride-co-hexafluoropropylene/poly ethylmethacrylate blend polymer electrolytes

Sodium ion conducting composite polymer electrolytes (CPE) have been prepared by solution casting technique in the skeleton of polyvinylidenefluoride-co-hexafluoropropylene/poly ethylmethacrylate blend. The binary mixture of diethyl carbonate and ethylene carbonate were used as plasticizer, and nanosized Sb₂O₃ as filler. The sodium trifluoromethanesulfonate (NaCF₃SO₃) was used as an ionic conducting source. The a.c. impedance study shows that 10 wt% Sb₂O₃ containing CPE exhibits the maximum conductivity 0.569 mS cm⁻¹ at ambient temperature. Molecular interactions of the constituents were analyzed by Fourier transform infra red spectroscopy. X-ray diffractogram reveals the amorphous nature of the CPE. A surface morphological feature was studied through scanning electron microscope. The activation energy and coherence length calculated were in support of the ionic transport.     

The ion conduction mechanism of isovalent cation-doped Li2SO4

2 SO₄:(x)Me₂ SO₄ (where Me = Na, K, Rb, and Ag; x=0.0025to0.09) is systematically investigated by using complex impedance spectroscopy. The solid solubility limit up to 2 mole% of Me₂SO₄ in β-Li₂SO₄ is determined by X-ray powder diffraction, scanning electron microscopy, and differential scanning calorimetry techniques. The partial replacement of Li⁺ with Me⁺ of bigger ionic size increases the conductivity due to lattice opening. The maximum conductivity enhancement is achieved by Ag⁺ substitution. A simple model, based on change in entropy and Coulomb interaction, is applied to understand the increase in conductivity. A semi-quantitative treatment provides some useful conclusions such as the decrease in activation energy of ion conduction and increase in ion jump probability after doping. It is found that the normal expansion of the lattice by substituting larger isovalent ions alone is not sufficient, but requires a proper ionic size for conductivity enhancement in β-Li₂SO₄. Received: 6 January 1998/Accepted: 28 May 1998     

Characterization of polymer electrolytes based on high molecular weight PVC and Li2SO4

The polymer–salt complex with high molecular weight poly(vinyl chloride) (PVC) as the host polymer and lithium sulphate (Li₂SO₄) as the dopant salt are constructed in the form of thin film. Ionic conductivity studies in the temperature range of 303–373 K are performed for polymer complexes with 75% and 85% PVC. Arrhenius and Vogel–Tamman–Fulcher (VTF) behaviour was observed before and after the T_g of polymer, respectively. Dielectric constant and electrical modulus were analyzed and it was concluded that the films had ion conducting potential. Fourier transform infrared (FTIR) study confirmed that complexation occurred between PVC and Li₂SO₄.     

Li ion conduction in TiO2 filled polyvinylidenefluoride-co-hexafluoropropylene based novel nanocomposite polymer electrolyte membranes with LiDFOB

This paper describes, nanocomposite polymer electrolyte (NCPE) based on polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP), which comprises the novel lithium difluoro(oxalato)borate (LiDFOB). Ehtylene carbonate (EC) and diethyl carbonate (DEC) mixture was used as gelling agent and nanoparticulate TiO₂ used as filler. The NCPE membranes were subjected to a.c. impedance, tensile strength, Raman studies, TG/DTA and morphological studies. 5 wt% TiO₂ comprising membranes exhibited enhanced conductivity of 0.56 mS cm⁻¹and the Young’s modulus was increased from 1.32 to 2.74 MPa. The structural change of α to β phase was confirmed by Raman studies. The thermal stability of the NCPE membrane is found to be 130 °C. Calculation of activation energy and synthesis of LiDFOB has also been presented.     

Nanocomposite polymer electrolytes

The present effort reviews the state-of-the-art trends in respect of composite polymer electrolytes (CPEs) which are nowadays revolutionizing the modern approach towards energy storage and power supply gadgets. This evaluation mainly encompasses a series of systems based on polymer hosts such as poly(ethylene oxide) (PEO), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP), poly(vinylidene fluoride) (PVDF), poly(acrylonitrile) (PAN), poly(methyl methacrylate) (PMMA), and polyvinylchloride (PVC) developed and analyzed so far apart from certain nanofiller incorporated composite polymer electrolytes being used in conjunction with well-suited electrodes owing to their practical significance in several advanced types of power sources including hybrid electric vehicles. The emerging nanoscale techniques have by now led the market to appreciate the application potential of nanostructured inorganic and organic materials so as to realize enhanced efficiencies of batteries thereby providing one of the most promising energy storage devices as well.     

Investigation of ionic conduction and mechanical properties of PMMA–PVdF blend-based polymer electrolytes

Polymeric gel electrolytes, based on a blend of poly(methylmethacrylate)/poly(vinylidene fluoride) (PMMA/PVdF), ethylene carbonate/propylene carbonate (EC/PC) as plasticizer and lithium perchlorate as electrolyte, have been studied as a function of the different polymeric ratios to obtain the best compromise between ionic conduction and mechanical properties of the systems involved. Ionic conductivity and the lithium self-diffusion coefficient were measured by the PFG–NMR method, which revealed a maximum of lithium mobility for the composition PMMA 60%–PVdF 40%. The Raman spectroscopic study revealed a change of the interaction between that of the lithium cations and the plasticizer molecules for different PMMA / PVdF ratios. Oscillatory rheological tests have shown better mechanical properties for the intermediate compositions of the blend.