Showing papers in "Ionics in 2012"
TL;DR: In this paper, Li2SnO3 has been prepared by solution evaporation method and the precursor obtained is sintered at 800°C for 5, 6, and 7h, respectively.
Abstract: Lithium stannate (Li2SnO3) has been prepared by solution evaporation method. The precursor obtained is sintered at 800°C for 5, 6, and 7 h, respectively. X-ray diffractogram confirmed that the sample obtained after sintering is Li2SnO3. The pelletized Li2SnO3 after heating at 500 °C for 3 h is used for electrochemical impedance spectroscopy characterization. Impedance measurements have been carried out over frequency range from 50 Hz to 1 MHz and temperature range from 563 to 633 K. The conductivity–temperature relationship is Arrhenian. Several important parameters such as activation energy, ionic hopping frequency and its rate, carrier concentration term, mobile ion number density, ionic mobility, and diffusion coefficient have been determined. The characteristics of log conductivity and log ionic hopping rate against temperature for the system suggest that the conduction and ionic hopping processes are thermally activated. The values of activation energy for conduction and relaxation processes as well as activation enthalpy for ionic hopping are about the same.
80 citations
TL;DR: In this paper, the effect of varying amounts of LiBOB (lithium bis(oxalato) borate) as additive in mixed liquid electrolyte on the electrochemical performance of lithium-sulfur batteries was investigated at room temperature.
Abstract: The effect of varying amounts (in the range 1–10 wt.%) of LiBOB (lithium bis(oxalato) borate) as additive in mixed liquid electrolyte on the electrochemical performance of lithium–sulfur batteries is investigated at room temperature. The electrochemical impedance spectroscopy (EIS) of lithium anode with LiBOB has two semicircles, corresponding to charge transfer impedance and ion migration impedance, respectively. The lithium anode with LiBOB shows a higher ion migration impedance, which could reduce the ionic diffusion rate in the anode. Scanning electron microscopy (SEM) observations shows that lithium anode with LiBOB has a smoother and denser surface morphology than the anode without LiBOB. The lithium–sulfur batteries with LiBOB shows the improvement of both the discharge capacity and cycle performance, a maximum discharge capacity of 1,191 mA h g−1 is obtained with 4 wt.% LiBOB. The lithium–sulfur batteries with 4 wt.% LiBOB can maintain a reversible capacity of 756 mA h g−1 after 50 cycles.
71 citations
TL;DR: LiFePO4 is a cathode material for new-generation power lithium ion battery applications because of its abundance in raw materials, environmental friendliness, perfect cycling performance, and safety characteristics as mentioned in this paper.
Abstract: Lithium ion batteries have become attractive for portable devices due to their higher energy density compared to other systems. With a growing interest to develop rechargeable batteries for electric vehicles, lithium iron phosphate (LiFePO4) is considered to replace the currently used LiCoO2 cathodes in lithium ion cells. LiFePO4 is a technically important cathode material for new-generation power lithium ion battery applications because of its abundance in raw materials, environmental friendliness, perfect cycling performance, and safety characteristics. However, the commercial use of LiFePO4 cathode material has been hindered to date by their low electronic conductivity. This review highlights the recent progress in improving and understanding the electrochemical performance like the rate ability and cycling performance of LiFePO4 cathode. This review sums up some important researches related to LiFePO4 cathode material, including doping and coating on surface. Doping elements with coating conductive film is an effective way to improve its rate ability.
69 citations
TL;DR: In this article, a review classifies all the available methods of nanomaterials synthesis in liquid by glow discharge in to three and it is discussed in detail. But, only few results are available yet and most of them are on metal nanoparticle preparation, so that more studies are needed to understand the nature of growth of the nanoparticles under glow discharge.
Abstract: There are many methods available to synthesize nanomaterials and the glow discharge plasma electrolysis is a novel and a green method in this category. It is seen that most of the papers are published after 2005 and the interest in it is growing due to its applicability in the industry for preparing nanomaterials at large scale. But, only few results are available yet and most of them are on metal nanoparticle preparation, so that more studies are needed to understand the nature of growth of the nanoparticles under glow discharge in liquid and its applicability in preparing semi-conductor nanomaterials. Many have tried many methods to prepare nanoparticles by the glow discharge and a review like this is the need of the time to understand its present status that helps to modify the present situation to a better one. This review classifies all the available methods of nanomaterials synthesis in liquid by glow discharge in to three and it is discussed in detail.
66 citations
TL;DR: In this article, 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.
Abstract: 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 β 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 Tanδ as a function of frequency.
65 citations
TL;DR: In this paper, a carbon paste electrode modified with ferrocene and carbon nanotubes was used as a voltammetric sensor for determination of sulfite at pH 7.0.
Abstract: This paper introduces a carbon paste electrode modified with ferrocene and carbon nanotubes as a voltammetric sensor for determination of sulfite at pH 7.0. The results showed that under the optimum condition (pH 7.0) in cyclic voltammetry, the oxidation of sulfite occurred at a potential about 280 mV less positive than the unmodified carbon paste electrode. Kinetic parameters such as electron transfer coefficient (α) and heterogeneous rate constant (k) for sulfite were also determined using electrochemical approaches. Under the optimized conditions, the electrocatalytic oxidation peak current of sulfite showed two linear dynamic ranges with a detection limit of 0.1 μM for sulfite. The proposed method was examined as a selective, simple, and precise method for voltammetric determination of sulfite in some real samples such as weak liquor from wood and paper industry, boiler water, river water, industrial water, and tap water.
62 citations
TL;DR: LiNiPO4 powders have been prepared by solid-state reaction using various precursors as mentioned in this paper, and characterisation of the structure and morphology of powders was performed using XRD, SEM, HRTEM, Raman, and FTIR.
Abstract: Microcrystalline LiNiPO4 powders have been prepared by solid-state reaction using various precursors. Characterization of the structure and morphology of powders was performed using XRD, SEM, HRTEM, Raman, and FTIR. The electronic properties of materials were investigated by SQUID and ESR. The LiNiPO4 material adopts the olivine-like structure (Pnma S.G.). Analysis of the Raman and FTIR spectra figures out, with the aid of a molecular vibration model, the bonding between NiO6 octahedral and (PO4)3− tetrahedral groups. The electronic configuration and the local cationic arrangement are confirmed by magnetic susceptibility and electron spin resonance spectroscopy.
45 citations
TL;DR: In this article, the authors analyzed the dielectric properties of cellulose acetate (CA) and its complexes consisting of ammonium tetrafluoroborate (NH4BF4) and polyethylene glycol with a molecular weight of 600 g/mol (PEG600) using the solution casting method.
Abstract: The present work deals with the findings on the dielectric behaviour of cellulose acetate (CA) and its complexes consisting of ammonium tetrafluoroborate (NH4BF4) and polyethylene glycol with a molecular weight of 600 g/mol (PEG600) that were prepared using the solution casting method. The highest σ obtained for CA-NH4BF4 film was 2.18 × 10−7 S cm−1 and enhanced to 1.41 × 10−5 S cm−1 with the addition of 30 wt.% PEG600. The dielectric behaviours of the selected samples were analyzed using complex impedance Z*, complex admittance A*, complex permittivity ɛ*, and complex electric modulus M*-based frequency and temperature dependence in the range of 10 Hz–1 MHz and 303–363 K, respectively. The variation in dielectric permittivity (er and ei) as a function of frequency at different temperatures exhibits a dispersive behaviour at low frequencies and decays at higher frequencies. The variation in dielectric permittivity as a function of temperature at different frequencies is typical of polar dielectrics in which the orientation of dipoles is facilitated with the rising temperature, and thereby the permittivity is increased. Modulus analysis was also performed to understand the mechanism of electrical transport process, whereas relaxation time was determined from the variation in loss tangent with temperature at different frequencies.
43 citations
TL;DR: In this paper, the effect of electrolyte pH on Ni coatings was studied by using the cyclic voltammetry, the scanning electron microscopy (SEM), x-ray diffraction, and alternating gradient force magnetometer measurements.
Abstract: Ni thin films were electrodeposited on gold substrate from chloride solution with different pH at room temperature. The effect of electrolyte pH on Ni coatings was studied by using the cyclic voltammetry, the scanning electron microscopy (SEM), x-ray diffraction, and alternating gradient force magnetometer measurements. From electrochemical measurements, the onset potential for reduction of Ni was gradually shifted towards more cathodic scan with increase in pH; this is due to the protons in the case of low pH values and to the hydroxide ions in the case of higher pH values. The SEM study showed that a granular and compact structure of the electrodeposited Ni layers and the variation of film morphology with bath pH are established. The x-ray diffraction spectra revealed the formation of fcc structure Ni thin films with a preferential orientation along the Ni(111). The size of the deposited crystals in both the cases has been found to be in the range of 49–153 nm. Magnetic properties such as coercivity and saturation magnetization showed strong dependence on the electrolyte solution pH and consequently the crystallite size. Coercivity higher than 130–160 Oe was achieved for a pH value of 4 to 5. The differences observed in the magnetic properties were attributed to the structural changes caused by the electrolyte pH.
43 citations
TL;DR: In this paper, the ionic conductivity and relaxation behavior of polymeric nanocomposite electrolyte (PNCE) films were investigated by dielectric relaxation spectroscopy in the frequency range of 20 Hz to 1 MHz at ambient temperature.
Abstract: Polymer nanocomposite electrolyte (PNCE) films composed of poly(ethylene oxide) (PEO), lithium salt (\( {\text{LiX}};\;{\text{X}} = ClO_4^{ - },\;BF_4^{ - },\;C{F_3}SO_3^{ - } \)) 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.
40 citations
TL;DR: In this paper, the authors used tracer technique for characterization of two widely used nuclear grade ion exchange resins Tulsion A-33 and Duolite ARA 9366 under identical experimental conditions.
Abstract: The present paper deals with the study of iodide and bromide ion-isotopic exchange reactions by application of radioactive tracer technique. The specific reaction rate (per minute) of both the reactions decreases with rise in temperature and increases with concentration of ionic solution. It was observed that due to solvation effect, the iodide ion-isotopic exchange reaction take place at a faster rate than bromide ion-isotopic exchange reaction. Also for iodide ion-isotopic exchange reaction, the distribution coefficient (K
d
) values were higher than that for bromide ion-isotopic exchange reaction. The application of tracer technique was further extended for characterization of two widely used nuclear grade ion exchange resins Tulsion A-33 and Duolite ARA 9366. It was observed that the values of K
d, specific reaction rate (per minute), amount of ion exchanged (millimoles), and percentage of ions exchanged for Tulsion A-33 resins are higher than that for Duolite ARA 9366 resins under identical experimental conditions.
TL;DR: In this article, polyaniline-modified tin oxide and tin oxide nanoparticles were synthesized using a solution route technique using X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and optical absorption spectroscopy.
Abstract: Polyaniline-modified tin oxide and tin oxide nanoparticles were synthesized using a solution route technique. The obtained pristine products were characterized with X-ray diffraction, thermogravimetric analysis, scanning electron microscopy, and optical absorption spectroscopy. Thermogravimetric analysis results showed that the polyaniline-modified SnO2 nanoparticles exhibit higher thermal stability than the SnO2 nanoparticles. Scanning electron microscopy analysis on the as-synthesized powders showed spherical particle in the range of 50–100 nm.
TL;DR: PEO-based solid polymer electrolyte films with various concentrations of nanochitosan as filler and LiCF3SO3 as salt were prepared by membrane hot-press technique.
Abstract: PEO-based solid polymer electrolyte films with various concentrations of nanochitosan as filler and LiCF3SO3 as salt were prepared by membrane hot-press technique. Nanochitosan was prepared from chitosan by conventional chemical cure method. The prepared composite membranes were characterized by FT-IR, XRD, thermal, SEM, AFM analyses, electrochemical impedance spectroscopy, cyclic voltammetry and compatibility studies. The ionic conductivity and thermal stability of the polymer membranes were enhanced significantly by addition of nanofiller. The compatibility studies reveal that filler incorporated membrane is better compatible with lithium interface than filler free electrolyte.
TL;DR: In this paper, the physicochemical and electrochemical properties of ionic liquids based on fluorinated pyrrolidi-nium and piperidinium ammonium cations and imide anion were analyzed.
Abstract: Ionic liquids, ILs, based on fluorinated pyrrolidi- nium and piperidinium ammonium cations and imide anion were prepared and characterized. The physicochemical and electrochemical properties of these ILs including melting point, glass transition and degradation temperatures, viscosity, ionic conductivity, and electrochemical stability were deter- mined and compared to alkyl pyrrolidinium and piperidinium ILs.TheincorporationofaCF3group instead of a CH3induces an increase of the IL viscosity, thus a conductivity decrease. However, good ionic conductivity is obtained with fluorinated pyrrolidinium IL. Cyclic amine ILs with propyl alkyl chain or fluorinated ammonium exhibit very high electrochemical sta- bility toward oxidation. The effect of the addition of LiTFSI on the IL properties was studied with the same methodology.
TL;DR: In this article, the effect of single doping and co-doping on the enhancement of ionic conductivity in ceria (CeO2), CeO2 and a few compositions in the system Ce0.85Sm0.925 (x = 0.00, 0.06,0.09, and 0.15) were prepared using citrate-nitrate auto-combustion method.
Abstract: In order to investigate the effect of single doping and co-doping on the enhancement of ionic conductivity in ceria (CeO2), CeO2 and a few compositions in the system Ce0.85Sm0.15 − xGdxO1.925 (x = 0.00, 0.06, 0.09, and 0.15) were prepared using citrate–nitrate auto-combustion method. Gels were characterized by simultaneous differential thermal analysis and thermogravimetric analysis to confirm the formation of end product from the precursor. All the compositions were found to be single-phase solid solution from their X-ray diffraction pattern. Complex plane impedance analysis clearly revealed the contribution of grains, grain boundaries, and electrode specimen interface to the total value of the resistance. The value of activation energy, Ea, of conduction shows that the conduction process is mainly due to diffusion of O2− ions through oxygen vacancies. Effect of doping has been analyzed using the concept of radius mismatch and effective index reported earlier in the literature.
TL;DR: A carbon paste electrode modified with 5-amino-3′,4′-dimethoxy-biphenyl-2-ol and carbon nanotubes was used for the sensitive voltammetric determination of norepinephrine (NE).
Abstract: A carbon paste electrode modified with 5-amino-3′,4′-dimethoxy-biphenyl-2-ol and carbon nanotubes was used for the sensitive voltammetric determination of norepinephrine (NE). The electrochemical response characteristics of the modified electrode toward NE, acetaminophen (AC), and folic acid (FA) were investigated by cyclic and square wave voltammetry (SWV). The results show an efficient catalytic activity of the electrode for the electrooxidation of NE, which leads to lowering its overpotential more than 160 mV. The modified electrode exhibits an efficient electron-mediating behavior together with well-separated oxidation peaks for NE, AC, and FA. Under the optimum pH of 7.0 in 0.1 M phosphate buffer solution, the SWV anodic peak current showed a linear relation vs. NE concentration in the range of 15.0 to 1,000.0 μM with a detection limit of 8.0 μM.
TL;DR: In this article, a polymer electrolyte consisting of poly(acrylonitrile) (PAN) and poly(methyl methacrylate) (PMMA) as host polymers and lithium perchlorate as a salt were prepared by solution casting technique.
Abstract: Polymer blend electrolytes composed of poly(acrylonitrile) (PAN) and poly(methyl methacrylate) (PMMA) as host polymers and lithium perchlorate as a salt were prepared by solution casting technique. The electrolytes were prepared for different ratios of host polymers with standard weight ratio of the ionic salt (LiClO4). Among the different concentrations, the polymer electrolyte film containing PAN/PMMA (75:25 wt.%) was found to be a suitable candidate for the battery applications on the basis of ionic conductivity and thermal stability. Complexation, structural reorganizations and ionic conductivity as a function of temperature were studied using X-ray diffraction analysis, Fourier transform infrared, and ac impedance analysis, respectively. Thermal stability of the electrolyte film having maximum ionic conductivity was also studied using thermogravimetric analysis.
TL;DR: An effective potentiometric sensor had been fabricated for the rapid determination of Pb2+ based on carbon paste electrode consisting of room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6), multiwalled carbon nanotubes (MWCNTs), nanosilica, synthesized Schiff base, as an ionophore, and graphite powder as mentioned in this paper.
Abstract: An effective potentiometric sensor had been fabricated for the rapid determination of Pb2+ based on carbon paste electrode consisting of room temperature ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF6), multiwalled carbon nanotubes (MWCNTs), nanosilica, synthesized Schiff base, as an ionophore, and graphite powder. The constructed nanocomposite electrode showed better sensitivity, selectivity, response time, response stability, and lifetime in comparison with typical Pb2+ carbon paste electrode for the successfully determination of Pb2+ ions in water and in waste water samples. The best response for nanocomposite electrode was obtained with electrode composition of 18% ionophore, 20% BMIM-PF6, 49% graphite powder, 10% MWCNT, and 3% nanosilica. The new electrode exhibited a Nernstian response (29.76 ± 0.10 mV decade−1) toward Pb2+ ions in the range of 5 × 10−9–1.0 × 10−1 mol L−1 with a detection limit of 2.51 × 10−9 mol L−1. The potentiometric response of prepared sensor is independent of the pH of test solution in the pH range of 4.5–8.0. It has quick response with response time of about 6 s. The proposed electrode show fairly good selectivity over some alkali, alkaline earth, transition, and heavy metal ions.
TL;DR: In this article, composite nanofibrous membranes based on polyvinyl chloride (PVC) and polymethyl methacrylate (PMMA) were prepared by electrospinning and then they were soaked in liquid electrolyte to form polymer electrolytes (PEs).
Abstract: Composite nanofibrous membranes based on poly (vinyl chloride) (PVC)–poly (methyl methacrylate) (PMMA) were prepared by electrospinning and then they were soaked in liquid electrolyte to form polymer electrolytes (PEs) The introduction of PMMA into the PVC matrix enhanced the compatibility between the polymer matrix and the liquid electrolyte The composite nanofibrous membranes prepared by electrospinning involved a fully interconnected pore structure facilitating high electrolyte uptake and easy transport of ions The ion conductivity of the PEs increased with the increase in PMMA content in the blend and the ion conductivity of the polymer electrolyte based on PVC–PMMA (5:5, w/w) blend was 136 × 10−3 S cm−1 at 25 °C The polymer electrolyte based on PVC–PMMA (5:5, w/w) blend presented good electrochemical stability up to 50 V (vs Li/Li+) and good interfacial stability with the lithium electrode The promising results showed that nanofibrous PEs based on PVC–PMMA were of great potential application in polymer lithium-ion batteries
TL;DR: In this article, a novel Nafion-sulfonated diphenyldimethoxysilane (N-sDDS) composite membrane is prepared and employed in vanadium redox flow battery (VRB).
Abstract: A novel Nafion-sulfonated diphenyldimethoxysilane (N-sDDS) composite membrane is prepared and employed in vanadium redox flow battery (VRB). Ion exchange capacity, proton conductivity, water transport behavior, and the cell performances are characterized. Fourier transform-infrared and X-ray diffraction analysis indicate that the sulfonated diphenyldimethoxysilane (sDDS) particles are successfully introduced into the Nafion matrix. In VRB single cell test, the VRB with N-sDDS membrane exhibits nearly the same coulombic efficiency as the unmodified Nafion membrane, but higher voltage efficiency than that of the VRB with unmodified Nafion membrane. The VRB with N-sDDS composite membrane keeps a stable performance after 60 times charge–discharge test. In the self-discharge test, the VRB with the N-sDDS membrane presented a lower self-discharge rate than that of the VRB with Nafion membrane. All results show that the addition of s-DDS is a simple and efficient way to improve the conductivity of Nafion, and the composite membrane shows good potential use for VRB.
TL;DR: In this article, a kind of solid polymer electrolyte (SPE) based on poly(vinylidene difluoride-co-hexafluoropropylene)/poly(methyl methacrylate) blends was prepared by a casting method to solve the safety problem of lithium secondary batteries.
Abstract: In the present study, a kind of solid polymer electrolyte (SPE) based on poly(vinylidene difluoride-co-hexafluoropropylene)/poly(methyl methacrylate) blends was prepared by a casting method to solve the safety problem of lithium secondary batteries. Owing to being plasticized with a room temperature ionic liquid, N-butyl-N′-methyl-imidiazolium hexafluorophosphate, the obtained SPE shows a thermal decomposition temperature over 300°C and an ionic conductivity close to 10−3 S cm−1. The SPE-3 sample, in which the weight of two polymers is equivalent, possesses an ionic conductivity of 0.45 × 10−3 S cm−1 at 25°C and presents an electrochemical window of 4.43 V. The ionic conductivity of the SPE-3 is as high as 1.73 × 10−3 S cm−1 at 75°C approaching to that of liquid electrolyte. The electrochemical performances of the Li/LiFePO4 cells confirmed its feasibility in lithium secondary batteries.
TL;DR: In this paper, the authors studied the oxidation process of polysulfides to element sulfur in charge process by solution thermodynamic analysis and means of cyclic voltammetry (CV), X-ray diffraction (XRD), and charge-discharge test.
Abstract: The oxidation of polysulfides to element sulfur in charge process was studied by solution thermodynamic analysis and means of cyclic voltammetry (CV), X-ray diffraction (XRD), and charge–discharge test. Basing on the solution thermodynamic analysis, the oxidation process of polysulfides to element sulfur would arise only if the charge voltage exceeds 3.36 V in a lithium–sulfur cell employing 1.0 M LiN(CF3SO2)2 in 1,2-dimethoxy ethane. Furthermore, the minimum of charge voltage which can push the oxidation would fall down with the increasing solubility of elemental sulfur in electrolyte solution. These analyses were confirmed by practical measurements. One new anodic peak corresponding to the oxidation process of polysulfides to solid sulfur was observed by CV. Both XRD patterns and charge–discharge test showed that the element sulfur appeared in the cathode after the battery was charged over 3.4 V. Hence, the lithium–sulfur cell charged over 3.4 V exhibited an improved cycle life since the capacity degradation between the first cycle and the second was depressed. In order to improve the energy efficiency, carbon disulfide was added in the electrolyte solution of lithium–sulfur cell to increase the solubility of sulfur.
TL;DR: In this paper, the AMX membrane has been modified by adsorption of polyethyleneimine on its surface, and a factorial experimental design was used for determining the influent parameters on the AM X membrane modification.
Abstract: Previous works have been made on the improvement of selectivity of ion exchange membranes using adsorption of polyelectrolyte on the surface of the materials. The modification of the surface material in the case of an anion exchange membrane concerns the hydrophilic/hydrophobic balance properties and its relationship with the hydration state. Starting from this goal, the AMX membrane has been modified, in this work, by adsorption of polyethyleneimine on its surface. Many conditions of modification of the AMX membrane surface were studied. A factorial experimental design was used for determining the influent parameters on the AMX membrane modification. The results obtained have shown that the initial concentration of polyethyleneimine and the pH of solution were the main influent parameters on the adsorption of polyethyleneimine on the membrane surface. Competitive ion exchange reactions were studied for the modified and the unmodified membrane involving \( {\text{C}}{{\text{l}}^{ - }} \), \( {\text{NO}}_3^{ - } \) and \( {\text{SO}}_4^{{2 - }} \) ions. All experiments were carried out at constant concentration of 0.3 mol L−1 and at 25 °C. Ion exchange isotherms for the binary systems \( \left( {{\text{C}}{{\text{l}}^{ - }}/{\text{NO}}_3^{ - }} \right) \), \( \left( {{\text{C}}{{\text{l}}^{ - }}/{\text{SO}}_4^{{2 - }}} \right) \) and \( \left( {{\text{NO}}_3^{ - }/{\text{SO}}_4^{{2 - }}} \right) \) were studied. The obtained results show that chloride was the most sorbed and the selectivity order both for the modified membrane and the unmodified one is: \( {\text{Cl}} > {\text{NO}}_3^{ - } > {\text{SO}}_4^{{2 - }} \), under the experimental conditions. Selectivity coefficients \( {\text{K}}_{{{\text{C}}{{\text{l}}^{ - }}}}^{{{\text{NO}}_3^{ - }}} \), \( {\text{K}}_{{2{\text{C}}{{\text{l}}^{ - }}}}^{{{\text{SO}}_4^{{2 - }}}} \) and \( {\text{K}}_{{2{\text{NO}}_3^{ - }}}^{{{\text{SO}}_4^{{2 - }}}} \) for the three binary systems and for the two membranes were determined. It was also observed that for the modified membrane the selectivity towards sulfate ion decrease and the modified membrane became more selective towards monovalent anions.
TL;DR: In this article, the biopolymer of a Bacto agar-based gel polymer electrolyte (GPE) was prepared by adding NaI and I2 as redox couple, and the prepared GPE was characterized using impedance spectroscopy and X-ray diffraction (XRD) in order to determine its electrical and structural properties.
Abstract: The biopolymer of a Bacto agar-based gel polymer electrolyte (GPE) was prepared by addition of NaI and I2 as redox couple. The prepared GPE was characterized using impedance spectroscopy and X-ray diffraction (XRD) in order to determine its electrical and structural properties, respectively. An optimized ionic conductivity of 12.41 × 10−4 S cm−1 was achieved for the samples containing 1.6 M NaI and 50 μL I2. Meanwhile, XRD revealed that the addition of NaI and I2 altered agar properties and formed an amorphous structure. Linear sweep voltammetry showed that the electrochemical stability window of the sample had a working voltage of 2.0 V.
TL;DR: The effect of strontium doping on densification and ionic conductivity of gadolinium-doped ceria (GDC) was investigated in this article, where the results showed that co-doping is very effective in identifying new materials with remarkably high ionicity with substantial reduction in the cost for solid oxide fuel cell application.
Abstract: The effect of strontium doping on densification and ionic conductivity of gadolinium-doped ceria (GDC) was investigated Doped (Sr-GDC) and un-doped GDC green specimens were subjected to dilatometric measurements to evaluate their sintering behavior and to identify the sintering temperature regimes XRD spectra show the crystal structure of the sintered samples to be cubic Strontium doping has exhibited a relatively larger grain size as is evident by the microstructural characterization AC impedance analysis exhibited a threefold increase in ionic conductivity for Sr-GDC (0072 S/cm) in comparison to GDC (0028 S/cm) samples which can be attributed to improved density and increased grain size, resulting in enhancement of total conductivity Additionally, strontium doping to GDC lattice not only increases the oxygen vacancies but also decreases the lattice binding energy, leading to increase in oxygen ion mobility which is also confirmed by the lower activation energy exhibited by the Sr-GDC formulation Our experimental results established that co-doping is very effective in identifying new materials with remarkably high ionic conductivity with substantial reduction in the cost for solid oxide fuel cell application
TL;DR: In this paper, a polyethylene glycol (PEG)-assisted rheological phase method was used to synthesize a composite cathode material with high discharge capacity of 134.8 and 129.9 mAh g−1.
Abstract: 5LiFePO4⋅Li3V2(PO4)3/C composite cathode material is synthesized by a polyethylene glycol (PEG)-assisted rheological phase method. As a surfactant and dispersing agent, PEG can effectively inhabit the aggregation of colloidal particles during the formation of the gel. Meanwhile, PEG will coat on the particles to play the role of carbon source during the sintering. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy, and electrochemical methods. XRD results indicate that the 5LiFePO4⋅Li3V2(PO4)3/C composites are well crystallized and contain olivine-type LiFePO4 and monoclinic Li3V2(PO4)3 phases. The composite synthesized at 650 °C exhibits the initial discharge capacities of 134.8 and 129.9 mAh g−1 and the capacity retentions of 96.2 and 97.1 % after 50 cycles at 1C and 2C rates, respectively.
TL;DR: In this paper, a series of carbon-coated LiFe1 − xMnxPO4 compounds are prepared by a hydrothermal method at 170 °C for 12 h. The structure and morphology of the prepared composites are characterized to examine the effects of Mn2+ substitution.
Abstract: A series of carbon-coated LiFe1 − xMnxPO4 compounds are prepared by a hydrothermal method at 170 °C for 12 h. The structure and morphology of the prepared composites are characterized to examine the effects of Mn2+ substitution. All LiFe1 − xMnxPO4 compositions are found to have an ordered olivine-type structure with homogeneous Fe2+ and Mn2+ distributions. The substitution leads to grain refinement from ~500 to ~150 nm, as well as to increased initial capacity and improved electronic conductivity. The amount of carbon coating varies with increased doping amount. The discharge curves of the LiFe1 − xMnxPO4/C materials reveal a high discharge plateau corresponding to Fe2+/3+ and no obvious plateau assigned to Mn2+/3+, although a slight contribution of manganese is detected. However, the electrochemical performance, including the discharge capacity and cyclic performance, deteriorates with increased Mn content in the composite.
TL;DR: In this article, the optical and electrical properties of Pt nanoparticle-dispersed tungsten trioxide (Pt/WO3) thin films were investigated using the sol-gel process, and the optical transmittance and electrical conductivity were found to be dependent on the hydrogen and oxygen gas concentration in the atmosphere.
Abstract: A well-known gasochromic material is Pt particle-dispersed tungsten trioxide (Pt/WO3). Its optical properties could make it effective as a hydrogen gas sensor. In this study, Pt nanoparticle-dispersed WO3 thin films were prepared using the sol–gel process, and their optical and electrical properties dependent on the working environment (i.e., temperature, hydrogen gas concentration, oxygen partial pressure, etc.) were investigated. The Pt/WO3 thin films prepared at 400 °C showed the largest change in optical transmittance and electrical conductivity when exposed to hydrogen gas compared with the films prepared at other temperatures. The optical absorbance and electrical conductivity were found to be dependent on the hydrogen and oxygen gas concentration in the atmosphere because generation and disappearance of W5+ in the thin films depend on the equilibrium reaction between injection and rejection of H+ into and from the thin films. In addition, the equilibrium reaction depends on the hydrogen and oxygen gas concentrations.
TL;DR: In this paper, the microstructure and electrochemical properties of the resulting porous electrodes were investigated with respect to sintering temperature, and the results indicated that elevating sinting temperature was favorable to the charge transfer process whereas undesired for the oxygen surface exchange process due to an increase of the grain size.
Abstract: Superfine and uniform La2NiO4+δ powder was synthesized by a polyaminocarboxylate complex precursor method. La2NiO4+δ layers were screen-printed on dense Ce0.8Sm0.2O1.9 electrolyte substrates and sintered at 900–1,100 °C. The microstructure and electrochemical properties of the resulting porous electrodes were investigated with respect to sintering temperature. The results indicate a significant effect of sintering temperature on the microstructure and electrode polarization. It was found that elevating sintering temperature was favorable to the charge transfer process whereas undesired for the oxygen surface exchange process due to an increase of the grain size. Sintering at 900 °C was determined to be preferred in terms of the polarization resistance of the electrode. The porous electrode sintered at the temperature showed a fine-grained microstructure (about 200 nm) and a relatively low polarization resistance of 0.28 Ω cm2 at 800 °C. This work suggests that preparing the electrode from superfine starting powder is contributive to modifying the polarization properties.
TL;DR: In this article, carbon-coated LiFeBO3 has been successfully synthesized by solid state reaction method at 750 °C under Ar atmosphere, and X-ray diffraction pattern confirms the formation of phase with monoclinic structure.
Abstract: Carbon-coated LiFeBO3 has been successfully synthesized by solid state reaction method at 750 °C under Ar atmosphere. Adipic acid was chosen for the source material for carbon during synthesis process. X-ray diffraction pattern confirms the formation of phase with monoclinic structure. Scanning electron microscopic study vindicates the particulate nature of the synthesized LiFeBO3 with weak agglomeration. Electrochemical impedance spectroscopy parallels the enhanced conducting properties of carbon-coated LiFeBO3 rather pristine LiFeBO3. The Li/carbon-coated LiFeBO3 and LiFeBO3 cells presented the initial discharge capacities 93 and 47 mAh/g, respectively. After few cycles, the carbon-coated LiFeBO3 exhibited stable discharge behavior (~53 mAh/g), whereas bare LiFeBO3 is concerned because poor electrochemical performance has resulted.