Ionic Conductivity

To prepare miscible polyethylene glycol diacrylate/polyvinylidene fluoride ͑PEGDA/PVdF͒ blend gel polymer electrolytes, low molecular weight (M ϭ 742) liquid PEGDA oligomer was mixed with PVdF-HFP dissolved in ethylene carbonate/dimethyl carbonate/LiPF 6 liquid electrolytes, and then cured under ultraviolet irradiation. Room temperature conductivity of PEGDA/PVdF blend films was found to be comparable to that of PVdF-HFP gel polymer electrolytes, and they were electrochemically stable up to 4.6 V vs. Li/Li ϩ. Scanning electron micrographs revealed that PEGDA/PVdF blend electrolytes have pore size intermediate between dense PEGDA and highly porous PVdF-HFP. It was confirmed by weight change measurement that liquid electrolyte was likely to evaporate through large pores in PVdF-HFP at 80°C, while PEGDA/PVdF blend showed better liquid electrolyte retention ability. This result was in good agreement with more stable interfacial properties of PEGDA/PVdF blend at 80°C in ac impedance analysis. Consequently, both PVdF-HFP and PEGDA/PVdF gel polymer electrolytes delivered similar discharge capacity at room temperature, but PEGDA/PVdF blend gel polymer electrolyte showed much better cycle performance than pure PVdF-HFP at 80°C.

The polymer electrolytes comprising blend of poly(vinyl acetate) (PVAc) and poly(methylmethacrylate) (PMMA) as a host polymer and LiClO4 as a dopant are prepared by solution casting technique. The amorphous nature of the polymer–salt complex has been confirmed by XRD analysis. The DSC thermograms show two Tg's for PVAc–PMMA blend. A decrease in Tg with the LiClO4 content reveals the increase of segmental motion. Conductance spectra results are found to obey the Jonscher's power law and the maximum dc conductivity value is found to be 1.76 × 10− 3 S cm− 1 at 303 K for the blend polymer complex with 20 wt.% LiClO4, which is suitable for the Li rechargeable batteries. The conductivity–temperature plots are found to follow an Arrhenius nature. The dc conductivity is found to increase with increase of salt concentration in the blend polymer complexes.

A new approach for studying the effect of temperature on anodic oxide growth on aluminium is presented in this paper. Using an in-house developed electrode holder, anodizing is performed under conditions of applied and controlled electrode temperature. The influence of temperature on the process is evaluated by experiments in a broad temperature range for both the electrode and the electrolyte temperature. The electrochemical behaviour of the aluminium electrodes is demonstrated to be more susceptible to variations of the electrode temperature than to variations of the electrolyte temperature. Concerning the morphology of the anodic film it is shown that by cooling the electrode a normal oxide layer could be grown at high electrolyte temperatures, whereas anodizing in a cool electrolyte at high electrode temperature results in a collapsed porous structure at the oxide surface. Furthermore, the electrode temperature affects the formation ratio of the oxide to a larger extent than the electrolyte temperature, indicating its important influence even on the level of the ionic conductivity during anodic oxide growth. All observations indicate that merely considering the electrolyte temperature upon studying the influence of temperature on the process is not sufficient; the electrode temperature is much more determining.

The main objective of this study was to broaden the assortment of I À /I 3 À redox ionic liquids using polyhedral oligomeric silsesquioxanes (POSS) acting as nanobuilding blocks for the construction of functionalized 1,3-alkylimidazolium iodide solid (melting temperature 150-200 1C) and room temperature (RT) ionic liquids.

Different substitutions, i.e. Sr 2+ , Ba 2+ , K + , Nb 5+ and V 5+ , have been performed in the triclinic a-La 2 W 2 O 9 structure in order to stabilise the high temperature and better ionic conductor cubic b-phase. This approach has been used to try to obtain a new series of ionic conductors with LAMOX-type structure without molybdenum and presumably better redox stability compared to b-La 2 Mo 2 O 9 . Nanocrystalline materials obtained by a freeze-drying precursor method at 600 1C exhibit mainly the b-La 2 W 2 O 9 structure, however, the triclinic a-form is stabilised as the firing temperature increases and the crystallite size grows. Only high levels of Ba 2+ and V 5+ substitutions retained the cubic form at room temperature after firing above 1100 1C. However, these phases are metastable above 700 1C, exhibiting an irreversible transformation to the low temperature triclinic a-phase. The synthesis, structure, phase stability, kinetic of phase transformation and electrical conductivity of these materials have been studied in the present report. r

A new silver-cobalt arsenate, Ag 4 Co 7 (AsO 4) 6 , is synthesized by solid state reaction method and characterized by X-ray diffraction and impedance spectroscopy. The phase crystallizes in the monoclinic space group C2/m with a = 10.755(2) Å, b = 14.937(2) Å, c = 6.731(2) Å, and b = 106.17(3)°. The structure is described as a three-dimensional anionic framework having interconnecting tunnels running along [1 0 0] and [0 1 0]. The former contains the silver cations. Ball milling is used as mechanical means to reduce the particles sizes of the as synthesized powder. At the optimal sintering temperature of 1173 K, dense ceramics (96% of the relative density) are obtained. Their microstructure is characterized by scanning electron microscopy. The conductivity of the ceramics is studied at different relative densities over a temperature interval from 437 to 773 K. The high conductivity at 210°C (3.3 Â 10 À5 S cm À1) and the activation energy (Ea = 0.45 eV) show that Ag 4 Co 7 (AsO 4) 6 is a fast ionic conductor.

We present a parametric experimental study of convective electrokinetic instability (EKI) in an isotropically etched, cross-shaped microchannel using quantitative epifluorescence imaging. The base state is a three-inlet, one-outlet electrokinetic focusing flow configuration where the centre sample stream and sheath flows have mismatched ionic conductivities. Electrokinetic flows with conductivity gradients become unstable when the electroviscous stretching and folding of conductivity interfaces grows faster than the dissipative effect of molecular diffusion. Scalar images, critical applied fields required for instability, and temporal and spatial scalar energy are presented for flows with a wide range of applied d.c. electric field and centre-tosheath conductivity ratios. These parameters impose variations of the electric Rayleigh number across four orders of magnitude. We introduce a scaling for charge density in the bulk fluid as a function of local maximum conductivity gradients in the flow. This scaling shows that the flow becomes unstable at a critical electric Rayleigh number (Ra e, = 205) and applies to a wide range of applied field and centre-tosheath conductivity ratios. This work is relevant to on-chip electrokinetic flows with conductivity gradients such as field amplified sample stacking, flow at the intersections of multi-dimensional assays, electrokinetic control and separation of sample streams with poorly specified chemistry, and low-Reynolds number micromixing.

The synthesis of one-piece electronic conducting interpenetrating polymer networks is proposed as an alternative to multilayer architectures for the design of electroactive devices. The electronic conducting polymer poly(3,4-ethylenedioxythiophene) (PEDOT) as active component was symmetrically distributed in a solid polymer electrolyte (SPE) matrix based on poly(ethylene oxide) which was subsequently swollen with either LiClO 4 or an ionic liquid. Depending on the composition and the crosslinking density of the SPEs, the ionic conductivities vary between 0.9 × 10 −3 and 2.2 × 10 −3 S cm −1 at 30 • C. Controlling the PEDOT content from 0.3 to 12 wt% in the material, electrochromic, electroemissive or electromechanical properties are obtained. Typical transmissive and reflective contrast values reach 33 and 27% at 630 and 2500 nm, respectively, for free-standing films upon application of a 1.2 V bias voltage. Both bending and linear actuating devices were developed as beam-shaped or hollow fibres. The actuation occurs under low applied voltage up to 4 V and the output force ranges from 50 to 300 mN. In all cases the electroactive properties are stable over 10 000 (electroemissivity) to 3.5 × 10 6 (actuation) cycles in open air providing an ionic liquid is used as electrolyte.

LiPON films were deposited using radio-frequency magnetron sputtering in a pure N 2 gas atmosphere. The influence of rf power, N 2 pressure, target-substrate distance and target density on thin film composition and ionic conductivity has been studied. Impedance measurements performed between 25 and 80-C have indicated that ionic conductivity increases with nitrogen incorporation into the glass structure. An increase in the deposition rate with the target density has also been observed.

Chitosan membranes with various degrees of deacetylation and different molecular weights (MW) were prepared by film casting with aqueous solutions of chitosan and acetic acid. Ultraviolet (UV) spectrometry and infrared (IR) spectrometry were used to determine the degree of deacetylation (DDA) of chitosan. The viscosity -average MW of chitosan was measured in an aqueous solvent system of 0.25 M CH 3 COOH/0.25 M CH 3 COONa. The intrinsic ionic conductivities of the hydrated chitosan membranes were investigated using impedance spectroscopy. It was found that the intrinsic ionic conductivity was as high as 10 24 S cm 21 after hydration for 1 h. The tensile strength and breaking elongation of the membranes were evaluated according to standard ASTM methods. The crystallinity and swelling ratio of the membranes were examined. A tentative mechanism for the ionic conductivity of chitosan membranes is also suggested. q

Dielectric properties directly influence microwave drying characteristics of food products. A knowledge of dielectric properties of foods as a function of moisture content and temperature is essential in the design and control of microwave drying systems. Dielectric constant e4 and loss factor e, of Red Delicious apples (Malus domestica Borkh.) were measured over a moisture content range of 4% to 87.5% at 225 C and 605 C. At high moisture content (>70%), free water dispersion and ionic conduction accounted for the dielectric behavior. At medium moisture (23%), ionic conduction played a major role. At low moisture contents (4%), bound water accounted for the major dispersion mechanism. A decrease in moisture content resulted in a decrease in e4 and e,. Based on this study, we expect a strong moisture leveling effect when drying apples from 50% to 4% at elevated temperatures in 915 MHz or 2.45 GHz microwave drying systems.

The study of nanoparticles has become a target of major interest in science. Metallic silver nanoparticles (Ag 0) and ionic silver (Ag +) are the future of the post-antibiotic era, with the latter playing perhaps the central role in this fight. Traditional chemical synthesis methods for colloidal silver (CS) may lead to the presence of toxic chemical species or chemical residues, which may inhibit the effective authentication of CS as an antibacterial agent. To counter these problems a good alternative method-electric spark discharge system (ESDS) was used to fabricate a silver nanoparticles suspension in deionized water with no added chemical additives. Most related research in this field is confined to exploring the composition of nanoparticle, ignoring ions. However, we aim to identify and quantify the proportion of ionic silver in ESDS-CS. The results reveal that ESDS-CS contains both metallic silver nanoparticles and ionic silver. Furthermore, the antimicrobial affect of ESDS-CS on Staphylococcus aureus was also studied. The experimental data suggest that CS solutions with an ionic silver concentration of 30 ppm or higher are strong enough to eliminate S. aureus. In addition, it was found that a solution's antimicrobial potency is directly related to its level of silver ion concentration.

Ceramic solid solutions Bi4MnxV2–xO11–(x/2)–δ in the composition range 0.07 ≤ x ≤ 0.30 were obtained by solid state synthesis. Structural investigations were carried out by using a combination of FT-IR and powder X-ray diffraction technique. Polymorphic transitions (β↔γ and γ′↔γ) were detected by DTA and variation in the Arrhenius plots of conductivity. The solid solutions with composition 0.07 ≤ x ≤ 0.17 are isostructural with the orthorhombic β-phase, and those with x ≤ 0.30 represent tetragonal γ-phase. With increasing Mn concentration, the conductivity of solid solutions increases from 3.684×10-6 (x = 0.07) to 2.467×10-5 (x = 0.17). AC impedance plots show that the conductivity is mainly due to the grain contribution which is evident in the enhanced short range diffusion of oxide ion vacancy in the grains with increasing temperature.

The electrochemical, rheological, calorimetric, spectroscopic and morphological investigations have been used to examine poly(methyl methacrylate), PMMA based electrolytes dispersed with nano-sized fumed silica (SiO 2 ). The observed ionic conductivity was one of the highest and is of the order wmS/cm at ambient temperature which was studied as a function of concentration of fumed silica nano-particles. It was further found that the fumed silica acted as a passive filler and played a predominant role in controlling the rheological properties while ion transport properties were least effected. The differential calorimetry studies revealed single glass transition temperature pointing towards homogeneous nature of the composite polymeric electrolytes (CPEs). At an optimum concentration of fumed silica (2 wt%) the observed maximum conductivity and morphology was attributed to the presence of a strong network structure, while at a higher concentration the elastic behavior was more pronounced which impeded ion transport. This contention was supported by spectroscopic data. q .in (S.A. Agnihotry).

Gel Polymer Electrolytes (GPE) based on agar and containing LiClO4 have been prepared, characterized and applied to electrochromic devices. The ionic conductivity revealed the best result of 6.5 × 10−5 S/cm for the sample with 17 wt.% of LiClO4, which increased to 5.4 × 10−4 S/cm at 72°C. The GPE have been used in electrochromic devices (ECD) with K-glass/WO3/GPE/CeO2-TiO2/K-glass configuration. The ECD changed transmittance values up to 30% between the colored and transparent states. The charge density measurements revealed an increase of 5.5 to 7.5 mC/cm2 from the first to 500th cycles and then a decrease to 4.4 mC/cm2 during the next 4500 cycles. Coloration efficiency (η) of 25 cm2/C was obtained.

A great number of compounds with electronic and ionic conductivity and new synthesis routes are being explored for electrochemical applications. In this work, selected examples are described. (a) CaO-TiO -Fe O materials prepared by 2 2 3 combustion synthesis are low cost products with interesting mixed conduction, the electrical behavior of which indicates the existence of a transition, where the grain interior electrical contribution is the dominant effect from 7% mol iron content. (b) Mixed electronic-ionic conducting SmCoO perovskites with dispersed Pt particles were prepared by combustion synthesis. 3

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We have applied the concept of heterogeneous doping [1] to prepare and examine composite electrolytes, consisting of silica particles, low molecular weight polyethylene glycol solvents and lithium perchlorate salt. These "soggy sand" electrolytes combine high ionic conductivities (on the order of mS cm −1 ) and high Li transference numbers (typically 60-80%) with improved mechanical properties. They were characterized using differential scanning calorimetry, dc-polarization and ac-impedance spectroscopy, zeta potential measurements and viscosimetry. Oxide, size and concentration as well as solvent molecular weight were varied to better understand the influence of ceramic oxide fillers on the ion conduction in these systems. As regarding the filler content, we observe that both conductivity and transference number of Li + start increasing already at low volume fractions of oxide particles, reach a maximum and subsequently decrease to low values. The percolating network is -after initial partial coarsening -found to be stable within the time periods of the measurements.

A series of different composition of polymer electrolytes-based on poly(vinyl chloride) (PVC) as host polymer, lithium tetraborate (Li 2 B 4 O 7 ) as dopant salt, and dibutyl phthalate (DBP) as plasticizer were prepared by solution casting method. The interaction between the PVC, Li 2 B 4 O 7 , and DBP were studied by Fourier transform infrared. The shifting, broadening, and splitting of transmission peaks were the evidences of complexation. The highest ionic conductivity polymer electrolyte of 2.83× 10 −6 S/cm was achieved at ambient temperature upon addition of 30 wt.% of DBP. In addition, the temperaturedependent conductivity, frequency-dependent conductivity, dielectric permittivity, and modulus studies were performed. The temperature-dependent conductivity of the polymer electrolytes was found to obey the Arrhenius behavior. The thermal stability of polymer electrolytes was verified by thermogravimetric analysis. The lower in glass transition temperature was proven in differential scanning calorimetry, whereas the higher amorphous region within the polymer matrix was demonstrated in X-ray diffraction.

Gel electrolytes synthesized from poly(methylmethacrylate), ethylene carbonate, propylene carbonate and various lithium salts [LiClO,, LiAsF,, or LiN(CF,SO,),] have been investigated by differential scanning calorimetry, electrical conductivity, and Ll, ' 19F and 75As NMR spectroscopy. Although the ionic conductivities of the gels approach those of liquid electrolytes above room temperature, the NMR results indicate that the immediate environments of both the cations and anions differ significantly in the gel and in the liquid. Thus the presence of microscopic regions of pure liquid electrolyte in the gel can be ruled out.

A new approach to electrochromics, based on the reversible coating-dissolution of an oxide from an inorganic electrochromic electrolyte consisting of a silver-amine complex in a polymer electrolyte (PEO), has proven successful. The reversible electrodeposition of silver onto indium-tin oxide coated glass (ITO) was investigated and the influence of HClO 4 and KI was evaluated. Several characteristics of the electrolyte Ag-PEO make it suitable for use in electrochromic reversible silver electrodeposition devices, such as visible absorption spectrum with an absorbance variation of 60%, an electrochromic efficiency of 5.2 cm 2 C −1 and an ionic conductivity 4.4 × 10 −4 S cm −1. The addition of perchloric acid improved the transparency of Ag-PEO, and potassium iodide (KI) was fundamental in setting up the process of reversible silver electrodeposition in the PEO polymeric matrix. A description of the electrochemical processes implied is presented. A number of approaches focusing on the improvement of system performance are tested.

An identical set of thermal oxidation and nitridation experiments has been performed for four common dopants and self-diffusion in Si. Selectively perturbing the equilibrium point-defect concentrations by these surface reactions is a powerful tool for identifying the relative importance of the various atomic-scale diffusion mechanisms. We obtain bounds on the fractional contributions of the self-interstitial, vacancy, and concerted exchange mechanisms for arsenic, boron, phosphorus, antimony, and self-diffusion in Si at temperatures of 1100 and 1000°C. These bounds are found by simultaneously solving a system of equations making only very conservative assumptions. The validity of common approximations found in previous work and their effects on the results are also analyzed in detail. We find that B and P diffuse by a self-interstitial mechanism, whereas Sb diffusion is almost exclusively vacancy mediated. As and self-diffusion, on the other hand, exhibit evidence for a dual vacancy-interstitial mechanism with the possibility of some concerted exchange component.

The physical and electrochemical properties of a new class of lithium ion conducting polymer electrolytes formed by incorporating MgAl 2 O 4 as filler into poly(ethylene oxide) − LiClO 4 complex are reported and discussed. The MgAl 2 O 4 -incorporated polymer electrolytes exhibited higher ionic conductivity and mechanical strength than those with filler-free membranes. These unique properties are accompanied by a good compatibility with lithium electrodes. The membranes were also subjected to scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermal gravimetry (TG) and Fourier Transform-infrared (FT-IR) analyses. The lithium surface upon contact with polymeric membranes was analyzed by FT-IR by single internal reflection mode. Using the technique the formation of Li 3 MgAlO 4 on the lithium surface was identified.

The perspective of hydrogen utilization as a clean fuel, mainly produced from renewable energy sources, compels the refinement of the water electrolysis process, thus reducing hydrogen generation costs. This paper presents the research now in progress at the Laboratório de Hidrogênio ...

Simultaneous impedance measurements and optical observations of polymer electrolytes were conducted in an automated experimental setup, combining an impedance analyser, polarizing microscope with a heating stage and a digital camera. The polymer film was placed between glasses with indium tin oxide conductive layers, forming a transparent cell mounted in a custom-designed holder, which preserved an argon atmosphere. Results of in-situ studies for various compositions of poly(ethylene oxide) (PEO) with LiN(CF 3 SO 2 ) 2 salt (LiTFSI), as well as pure PEO, are presented. In the investigated systems, crystallization had a strong impact on ionic conductivity. It was found that the initial growth of crystalline structures caused only a small fraction of the total decrease of conductivity. A large decrease in conductivity was observed during the second stage of crystallization, when no significant changes in microscope picture were observed. In pure PEO and the PEO:LiTFSI 6:1 system, a dense crystalline structure developed, resulting in a decrease in conductivity of over two orders of magnitude. In dilute PEO:LiTFSI systems, a "loose" structure was formed, with amorphous areas preserved between crystallites, and conductivity decreased by only a factor of about 6.

Nanoparticles of rubidium-doped gadolinium titanates oxide were prepared by the sol-gel process from the titanium alcoxyde Ti(OBu) 4 and the two oxides Rb 2 CO 3 and Gd 2 O 3 . Thermal gravimetric (TG) and differential thermal analysis (DTA) results suggest that thermal decomposition of the xerogel takes place when the xerogel is heated at 400 1C. X-ray powder diffraction (XRD) measurements were carried out to study the structure evolution of the sample and to determine the crystalline phases present after heat treatment. A well-crystallized single-phased nanopowder was obtained after calcination at 1000 1C. X-ray diffraction combined to the Raman analysis confirmed the powder's single-phase nature at this temperature. The Rb + did not enter the pyrochlore crystal lattice to substitute Gd 3+ or Ti 4+ as shown by XRD and X-ray photoelectron spectroscopy (XPS). It is probably dispersed uniformly onto gadolinium titanate nanoparticles. Crystal structure of the non-stoichiometry pyrochlore Rb + -doped phase Gd 1.8 Ti 2 O 6.7 , was determined using the Rietveld method. Conductivity analysis shows that the presence of Rb + dopant in Gd 1.8 Ti 2 O 6.7 leads to an increase of the ionic conductivity compared to the non-doped Gd 1.8 Ti 2 O 6.7 .

New techniques for cleaning acrylic emulsion paint surfaces continue to emerge in the practice of contemporary conservation. The discipline is currently in the process of identifying problematic first-generation practices, pursuing improved and alternative treatments, and framing a dialogue to guide future innovations. This paper will present four case studies that illustrate a new aqueous cleaning system for acrylic paint films on paper supports. It will also address this system’s potential to treat discolored paper and board. Driving this evolution in practice is acrylic works’ sensitivity to aqueous cleaning methods. Paint film swelling and surfactant or pigment disruption are two primary risks conservators regularly face when cleaning acrylic works of art on paper. The aqueous cleaning system discussed in this paper mitigates these risks by using pH and conductivity meters to test acrylic paint surfaces and to create customized aqueous cleaning solutions—a technique demonstrated...

The structure and transport properties of lithium-containing lanthanum metaniobates with defect-perovskite structure, La 2/3-x Li 3x & 4/3-2x Nb 2 O 6 , have been studied. It has been shown that in the structure of La 2/3-x Li 3x & 4/3-2x Nb 2 O 6 , Li + cations occupy, preferably, positions 1a in the range x=0À%0.5, and occupy positions 1c (vacancies) at x> 0.5. It has been noted that the direction 1c$1c is energetically a more favorable pathway of lithium ion migration. It has been shown that the materials under investigation possess a high lithium ion-conductivity. #

A conductivity relaxation experiment has been conducted on an SrFeCo0.5Ox sample by abruptly changing the oxygen partial pressure in the atmosphere and monitoring the change of conductivity as a function of time. The re-equilibrium process obeys Fick's second law. By fitting the relaxation data to the solution of the diffusion equation with appropriate boundary conditions, we could determine the oxygen chemical diffusion coefficient and the activation energy. The oxygen diffusion coefficient is 8.9 × 10−7 cm2/s at 900 °C and it increases with increase in temperature. Measured activation energy is 0.92 eV, which is slightly lower than that of other oxides in the system SrFe1 − xCoxOy.

The electrical properties of solvent-free, PEO-LiTFSI solid polymer electrolytes (SPEs), incorporating different N-alkyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, PYR 1A TFSI, ionic liquids (ILs), are reported. For this purpose, PYR 1A TFSI materials containing side alkyl groups with different chain-length and branching, i.e., n-propyl, sec-propyl, n-butyl, iso-butyl, sec-butyl and n-pentyl, were properly synthesized and homogeneously incorporated into the SPE samples without phase separation. The addition of ILs to PEO-LiTFSI electrolytes results in a large increase of the conductivity and in a decrease of the interfacial resistance with the lithium metal anode. Most of the PEO-LiTFSI-PYR 1A TFSI samples showed similar ionic conductivities (>10 −4 S cm −1 at 20 • C) and stable interfacial resistance values (400 cm 2 at 40 • C and 3000 cm 2 at 20 • C) upon several months of storage. Preliminary battery tests have shown that Li/P(EO) 10 LiTFSI + 0.96 PYR 1A TFSI/LiFePO 4 solid-state cells are capable to deliver a capacity of 125 mAh g −1 and 100 mAh g −1 at 30 • C and 25 • C, respectively.

The single-layered microporous polyethylene
separator is prepared by dry process and has been
stretched in uni-axial direction to two different ratios
namely 180 and 300 % in order to create highperformance
and cost-effective separator for practical application
in lithium-ion batteries. In this study, the structures
of the microporous polyethylene separator prepared
by dry process and uni-axially stretched to two different
ratios of 180 and 300 % were characterized. The physical
structure of the stretched separator is characterized by key
factors such as thickness, mean pore size, porosity, Gurley
value, ionic resistivity, MacMullin number and tortuosity.
The thermal behavior of the stretched separator is
explained by using differential scanning calorimeter
(DSC). DSC explains the melting and shutdown behavior
of the separator. Electrochemical property is studied by
linear sweep voltammetry, electrochemical impedance
spectroscopy (EIS) and cyclic performance. EIS is performed
to explain, in elaborate, the resistance of separator
and the specific discharge capacity is observed using the
cyclic performance. Three hundred percent stretched separator is observed to have comparatively less resistance
and higher discharge capacity than the 180 % stretched
separator.

The solubility of potassium fluoride (KF) in dimethylformamide (DMF) and the dielectric constant of the solvent have been determined in the temperature range (25-125)°C by means of electrical conductivity and capacity measurements. The solubility of KF in this aprotic solvent seems to be almost temperature independent (mean value (0.33 ( 0.03) × 10 -3 mol‚dm -3 ). The speciation of KF in DMF is also discussed in relation to the concentration dependence of the molar conductance. It is concluded that ion pairs could account for around 50 to 70% of the species and that triple ions could be present in the concentration range studied.

Solid polymer electrolytes based on poly (vinyl alcohol) (PVA) complexed with sodium fluoride (NaF) at different weight percent ratios were prepared using solution cast technique. The structural properties of these electrolyte films were examined by XRD studies. The XRD data revealed that the amorphous domains of PVA polymer matrix increased with increase of NaF salt concentration. The complexation of the salt with the polymer was confirmed by FT-IR studies. Electrical conductivity was measured in the temperature range of 303-373 K and the conductivity was found to increase with the increase of dopant concentration as well as temperature. The dielectric constant (e 0 ) increased with the increase in temperature and decreased with the increase in frequency. A loss peak was identified at 365 K in the dielectric loss spectra and is attributed to the orientation of polar groups. Measurement of transference number was carried out to investigate the nature of charge transport in these polymer electrolyte films using Wagner's polarization technique and Watanabe technique. Transport number data showed that the charge transport in these polymer electrolyte systems was predominantly due to ions and in particular due to anions. Using these polymer electrolytes, solid state electrochemical cells were fabricated. Various cell parameters like open circuit voltage (OCV), short circuit current (SCC), power density and energy density were determined.

A number of iodide-based electrolytes (LiCl-LiI, LiI-KI, LiCl-LiBr-LiI, LiCl-LiI-KI and LiF-LiCl-LiI) were considered to be used in thermal batteries. Ionic conductivity of multi-cation and all-lithium electrolytes were evaluated. They were compared to the classical electrolytes (LiCl-KCl, LiF-LiBr-KBr and LiF-LiCl-LiBr) used in thermal battery applications. Measurements were realised by electrochemical impedance spectroscopy (E.I.S.). It was shown that some all-lithium iodide-based electrolytes exhibit interesting ionic conductivities and are suitable as electrolytes in thermal batteries. It was pointed out that activation energy E a was close to 11 kJ mol −1 for multi-cation electrolytes, whereas it was equal to 7 kJ mol −1 for all-lithium electrolytes.

A novel lithium salt, lithium (fluorosulfonyl)(nonafluorobutanesulfonyl)imide (LiFNFSI), is investigated as a conducting salt to improve the high-temperature resilience of lithium-ion cells. It shows better thermal stability than LiPF 6 . The electrolyte having 1.0 M LiFNFSI in a mixture of ethylene carbonate (EC)/ethyl methyl carbonate (EMC) (3:7, v/v) shows high conductivity comparable to LiClO 4 , good electrochemical stability, and does not corrode aluminum. At both room temperature (25°C) and elevated temperature (60°C), the graphite/LiCoO 2 cells with LiFNFSI exhibit better cycling performances than those with LiPF 6 . Particularly, at 60°C, the capacity fading rate of the LiFNFSI-based cell without any additive is 37% after 100 cycles, while the cell with LiPF 6 fails rapidly. These outstanding properties of LiFNFSI make it an attractive candidate to overcome the rapid capacity fading of lithium-ion batteries at elevated temperatures.

As a potential electrolyte for lithium-ion batteries, a porous polymer electrolyte membrane based on poly(vinylidenefluoride-hexafluoropropylene) (PVDF-HFP) was prepared by a phase inversion method. The casting solution, effects of the solvent and non-solvent and addition of micron scale TiO 2 particles were investigated. The membranes were characterized by SEM, XRD, AC impedance, and charge/discharge tests. By using acetone as the solvent and water as the non-solvent, the prepared membranes showed good ability to absorb and retain the lithium ion containing electrolyte. Addition of micron TiO 2 particles to the polymer electrolyte was found to enhance the tensile strength, electrolyte uptake, ion conductivity and the electrolyte/electrode interfacial stability of the membrane. , in the polymer electrolyte . Usually, these inorganic fillers are dispersed in the polymer electrolyte in the form of nanoparticles, however, nanoparticles tend to aggregate because of the high surface energy. For example, Kim et al. reported that TiO 2 nanoparticles cannot be well dispersed, even under conditions such as ultrasonication and the subsequent ball-milling. In this study, the (PVDF-HFP)-based PSPE was prepared by the phase inversion method. The preparation process of the casting solution and effects of solvent and non-solvent on the configuration and performance have been investigated. The influence of micron particles of TiO 2 incorporated in PSPE on the structure and properties of PSPE have been examined.

Solid polymer electrolyte PEO 9 Mg(ClO 4 ) 2 incorporating 10 wt.% nano-porous Al 2 O 3 filler grains has been prepared by the solvent casting technique using acetonitrile as the common solvent. Al 2 O 3 powder (activated acidic, Aldrich) with grain size 104 Am and pore size 5.8 nm were incorporated as an inert filler. Electrolyte films have been characterized by differential scanning calorimetry, complex impedance and dc polarization measurements. The nano-composite electrolyte as well as the filler-free electrolyte appear to be predominantly anionic conductors with ClO 4 À ions being the migrating species. The presence of the alumina filler has enhanced the ionic conductivity significantly. The conductivity enhancement has been attributed to Lewis acid -base type interactions between H groups at the filler grain surface and the ClO 4 À ions. Transient H-bonding through these interactions is expected to provide additional hopping sites and favourable conducting pathways for migrating ionic species. D

Nanocomposite polymer electrolytes (NCPE) composed of poly(vinylidenefluoride-co-hexafluoropropylene) (PVDF-HFP) and chitin for different concentrations of LiClO 4 have been prepared by a hot-press technique. The prepared NCPE films were subjected to XRD, SEM, FTIR and tensile analyses. The thermal stability of NCPE membrane was investigated by TG-DTA. Ionic conductivity studies have also been made as a function of lithium salt concentration for different temperatures ranging from 0 to 80°C. The polymeric membrane comprising PVDF-HFP/ chitin/LiClO 4 of ratio 75:20:5 (wt.%) offered maximum ionic conductivity. Thermal study reveals that these membranes are stable up to 260°C.

Sulfone-based electrolytes have been investigated as electrolytes for lithium-ion cells using high-voltage positive electrodes, such as LiMn 2 O 4 and LiNi 0.5 Mn 1.5 O 4 spinels, and Li 4 Ti 5 O 12 spinel as negative electrode. In the presence of imide salt (LiTFSI) and ethyl methyl sulfone or tetramethyl sulfone (TMS) electrolytes, the Li 4 Ti 5 O 12 /LiMn 2 O 4 cell exhibited a specific capacity of 80 mAh g À1 with an excellent capacity retention after 100 cycles. In a cell with high-voltage LiNi 0.5 Mn 1.5 O 4 positive electrode and 1 M LiPF 6 in TMS as electrolyte, the capacity reached 110 mAh g À1 at the C/12 rate. When TMS was blended with ethyl methyl carbonate, the Li 4 Ti 5 O 12 /LiNi 0.5 Mn 1.5 O 4 cell delivered an initial capacity of 80 mAh g À1 and cycled fairly well for 1000 cycles under 2C rate. The exceptional electrochemical stability of the sulfone electrolytes and their compatibility with the Li 4 Ti 5 O 12 safer and stable anode were the main reason behind the outstanding electrochemical performance observed with high-potential spinel cathode materials. These electrolytes could be promising alternative electrolytes for high-energy density battery applications such as plug-in hybrid and electric vehicles that require a long cycle life.

The correlation between ionic conductivity and viscosity in liquid electrolytes formed by the dissolution of lithium tritlate in N,N-dimethyl formamide and tetraethylene glycol dimethyl ether has been investigated. These liquid electrolytes may be incorporated in polymer gel electrolytes based on poly(vinylidene fluoride). The use of the Walden product to investigate ionic interactions is discussed.

We report here several synthesis routes and their respective drawbacks/advantages for the preparation of pure LiFePO 4 . We demonstrate the possibility of using LiFePO 4 for electrochemical applications, with respect that an effective carbon coating was realized onto the smallest particles. Actually, to bypass the weak ionic conductivity of lithium iron phosphate, the thinnest would be the particles; the highest would be the performance under severe electrochemical conditions.