Tamarind seed polysaccharide (TSP)-based Li-ion conducting membranes

Polysaccharide-based biopolymers have gained much attention in electrochemical devices recently. Tamarind seed polysaccharide (TSP) is a biopolymer obtained from the extract of tamarind seed. It is used as thickening and gelling agent in food and textile industries. There are no works in polymer electrolytes based on TSP in lithium-ion conducting membranes. A pure TSP membrane has been prepared by dissolving 1 g of TSP in distilled water by using solution-casting technique. The prepared biopolymer membranes are subjected to Fourier transform infrared (FTIR), X-ray diffraction (XRD), and AC-impedance techniques. FTIR analysis has been conducted to observe the possible interaction between the polymer and lithium salt based upon the changes in wave numbers of the peaks. The nature of the membrane (crystalline or amorphous) has been revealed by XRD. The electrical properties of the membranes have been analyzed by AC-impedance spectroscopy. The maximum ionic conductivity for the salt-doped membrane 1 g TSP:0.4 g lithium bromide (LiBr) has been found to be 4.83 × 10^?4 S cm^?1. The primary lithium-ion battery has been constructed using the best conductivity membrane, and the open circuit voltage (OCV) has been observed as 1.63 V.     

Ionic conductivity studies on Sr stabilized zirconia by impedance spectroscopy

Sr stabilized zirconia has been prepared by the co-precipitation method and electrically characterized by using impedance spectroscopy in the frequency range from 42 Hz to 5 MHz. The charge carrier concentration of the material has been calculated from the conductance spectra and it is found to be of the order of 10²⁵ cm⁻³. The conductance spectra show a dc plateau and a dispersive region suggesting correlated hopping motion of the ions. The impedance analysis shows a depressed semicircle indicating non-Debye nature of the material as well as the broad nature of modulus peaks indicates non-Debye behaviour. The bulk resistance of the material has been extracted from the impedance spectra and it is found to be 3.5×10⁷ Ω·cm⁻¹ at 673 K. The low frequency dispersion of the dielectric constant implies the space charge effects arising from the electrodes. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28 – 30, 2003.     

Characterization of high ionic conducting PVAc–PMMA blend-based polymer electrolyte for electrochemical applications

A solid polymer blend electrolyte is prepared using poly(vinyl acetate) (PVAc) and poly(methyl methacrylate) (PMMA) polymers with different molecular weight percentage (wt%) of ammonium thiocyanate (NH₄SCN) by solution casting technique with tetrahydrofuran (THF) as a solvent. The structural, morphological, vibrational, thermal and electrical properties of the prepared polymer blend electrolytes have been studied. The incorporation of NH₄SCN into the polymeric matrix causes decrease in the degree of crystallinity of the samples. The complex formation between the polymer and salt has been confirmed by FTIR technique. The increase in T _g with increase in salt concentration has been investigated. The maximum conductivity of 3.684?×?10^?3 S cm^?1 has been observed for the composition of 70PVAc/30PMMA/30 wt% of NH₄SCN at 303 K. This value of ionic conductivity is five orders of magnitude greater than that of 70PVAc/30PMMA polymer membrane. Dielectric and transport studies have been done. The highest conducting polymer electrolyte is used to fabricate proton battery with the configuration Zn/ZnSO₄·7H₂O (anode) ||polymer electrolyte||PbO₂/V₂O₅ (cathode). The open circuit voltage of the fabricated battery is 1.83 V, and its performance has been studied.     

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.     

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.     

Thermoluminescence and photoluminescence studies on gamma irradiated CsI: Pb2+ crystals

Pure and Pb²⁺-doped CsI crystals have been grown by the Bridgemann technique. Optical absorption, thermoluminescence (TL) and photoluminescence (PL) measurements have been performed. In undoped and Pb²⁺-doped cesium iodide crystals, F-centers and V-centers have been produced at 770 nm and 350 nm, respectively. In Pb²⁺-doped crystals, additional centers at 373 nm, 290 nm and 258 nm bands have been produced. In undoped samples, only two glow peaks at 343 K and 373 K have been produced, and in Pb²⁺-doped samples additional glow peaks at 383 K and 423 K have been produced. For all the samples, TL emission, PL and excitation measurements have been performed.     

Characterization of nanocomposite polymer electrolyte based on P(ECH-EO)

ZrO₂ nanoparticles have been prepared by poly acrylamide gel route. The synthesized nanosized ZrO₂ have been incorporated into plasticized polymer electrolyte (PPE), P(ECH-EO): LiClO₄: γ-BL system to understand the effect of ZrO₂ on the ionic conductivity. The X-ray diffraction pattern of the synthesized ZrO₂ nanoparticles reveals the crystalline phase. The X-ray diffraction patterns of P(ECH-EO) based NCPEM confirm the polymer-salt-nanoparticle complexation. The scanning electron microscope image of NCPEM confirms that the ZrO₂ nanoparticles were distributed uniformly in the polymer matrix. The presence of nano filler has increased the ionic conductivity and the maximum dc conductivity value is found to be 6.24×10⁻⁶ S cm⁻¹ at 303 K for 96(PPE): 4ZrO₂ (mol%).     

Synthesis and characterization of Li<Subscript>1-x</Subscript>Tb<Subscript>x</Subscript>NiPO<Subscript>4</Subscript> solid solution as cathode materials for lithium ion battery application

Modified Pechini-type polymerizable precursor method has been used to prepare nanosized Li_1-xTb_xNiPO₄ (x = 0, 0.03, 0.05, and 0.07) solid solutions to obtain homogeneous with controlled stoichiometry and smaller particle size. The reaction temperature was determined by thermogravimetric (TG/DTA) analysis. X-ray diffraction analysis reveals the formation of orthorhombic structure and the calculated crystallite sizes are found to be in the range of 75–89 nm. Morphological, compositional, and vibrational properties were performed by SEM, EDAX, and FTIR, respectively. Conductivity measurements were carried out at room temperature by AC impedance analysis. The Li_0.97Tb_0.03Ni_0.99PO₄ sample shows one order of higher conductivity than pure LiNiPO₄. Higher concentration of terbium samples such as Li_0.95Tb_0.05Ni_0.99PO₄ and Li_0.93Tb_0.07Ni_0.99PO₄ lead to decrease of conductivity. The frequency dependency of dielectric permittivity, dielectric loss, and electric modulus of Li_1-x Tb_xNiPO₄ solid solutions are studied. The frequency-dependent plot of modulus reveals that the conductivity relaxation is of non-Debye type.     

Development of proton conducting biopolymer membrane based on agar–agar for fuel cell

A proton-conducting polymer electrolyte based on agar and ammonium nitrate (NH₄NO₃) has been prepared through solution casting technique. The prepared polymer electrolytes were characterized by impedance spectroscopy, X-ray diffraction, and Fourier transform infra-red spectroscopy. Impedance analysis shows that sample with 60 wt.% NH₄NO₃ has the highest ionic conductivity of 6.57 × 10⁻⁴ S cm⁻¹ at room temperature. As a function of temperature, the ionic conductivity exhibits an Arrhenius behaviour increasing from 6.57 × 10⁻⁴ S cm⁻¹ at room temperature to 1.09 × 10⁻³ S cm⁻¹ at 70 °C. Transport parameters of the samples were calculated using Wagner’s polarization method and thus shows that the increase in conductivity is due to the increase in the number of mobile ions. Fuel cell has been constructed with the highest proton conductivity polymer 40agar/60NH₄NO₃ and the open circuit voltage is found to be 558 mV.

     

Synthesis and characterization of dextrin-based polymer electrolytes for potential applications in energy storage devices

An attempt has been made to synthesise a new proton conducting polymer electrolyte using the biopolymer dextrin doped with ammonium thiocyanate salts using solution casting technique. The complexation has been studied using X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). The differential scanning calorimetry (DSC) thermograms of dextrin with NH₄SCN showed that T_g value increases with respect to the increase of NH₄SCN concentration. The electrical conductivity was measured using AC impedance analyser which showed that ionic conductivity increases with increase in salt concentration up to 40%. Transference number measurement was carried out to investigate the nature of the charge transport species in the polymer electrolyte. Surface morphology of the electrolytes was determined using scanning electron microscope (SEM) studies, and the chemical composition of the elements present was determined using EDAX. The proton battery was constructed with the highest conducting polymer electrolyte Dex-40%NH₄SCN and its open circuit voltage with load were carried out.