Effect of Salt Concentration on Dielectric Properties of Li-Ion Conducting Blend Polymer Electrolytes

In the present article, we have studied the effect of the salt concentration (LiPF6) on transport properties and ion dynamics of blend solid polymer electrolyte (PEO PAN) prepared by solution cast technique. Fourier transform infrared (FTIR) spectroscopy confirms the presence of microscopic interactions such as polymer ion and ion ion interaction evidenced by a change in peak area of anion stretching mode. The fraction of free anions and ion pairs obtained from the analysis of FTIR implies that both influence the ionic conductivity with different salt concentration. The complex dielectric permittivity, dielectric loss, complex conductivity have been analyzed and fitted in the entire frequency range (1 Hz to 1 MHz) at room temperature. The addition of salt augments the dielectric constant and shift of relaxation peak in loss tangent plot toward high frequency indicates a decrease of relaxation time. We have implemented the Sigma representation sigma double prime vs sigma prime for solid lithium ion conducting films which provide better insight toward understating of the dispersion region in Cole Cole plot epsilon double prime vs epsilon prime in lower frequency window. The dielectric strength, relaxation time and hopping frequency are in correlation with the conductivity which reveals the authenticity of results. Finally, the ion transport mechanism was proposed for getting the better understanding of the ion migration in the polymer matrix.Comment: Journal of Materials Science: Materials in Electronics, 201

Structural, Electrical Properties and Dielectric Relaxation in Na+ Ion Conducting Solid Polymer Electrolyte

Present paper reports, the structural, microstructural, electrical, dielectric properties and ion dynamics of a sodium based solid polymer electrolyte films comprising of PEO8-NaPF6+ x wt. % SN. The structural and surface morphology properties have been investigated by XRD and FESEM. Different microscopic interaction among the polymer, salt and SN have been analyzed through FTIR. The dielectric permittivity and loss tangent enable us to estimate the dc conductivity, dielectric strength, double layer capacitance, and relaxation time. The loss tangent relaxation peak shifts towards high-frequency side which indicates the decrease of relaxation time and faster ion dynamics. Further, the relation among various relaxation times ...... has been developed systematically. The ionic conductivity has been estimated in whole frequency window including JPL and displays strong dependency on SN content. The sigma representation ........ has been introduced for exploring the ion dynamics by highlighting the dispersion region in Cole-Cole plot (........) at lower frequency window and increase in the radius of semicircle indicates a decrease of relaxation time. A well convincing/logical scheme has been proposed which justify the recorded experimental data

Insights into the use of polyethylene oxide in energy storage/conversion devices: A critical review

In this review, latest updates in the poly (ethylene oxide) based electrolytes are summarized. The ultimate goal of researchers globally is towards the development of free standing solid polymeric separator for energy storage devices. This single free standing solid polymeric separator may replace the liquid and separator (organic/Inorganic) used in existing efficient/smart energy technology. As an example polyethylene oxide (PEO) consist of an electron donor rich group which provides coordinating sites to the cation for migration. Owing to this exclusive structure PEO exhibits some remarkable properties such as; low glass transition temperature, excellent flexibility and ability to make complexation with various metal salts which are unattainable by another polymer host. Hence, the PEO is the most emerging candidate that have been examined or is currently under audition for application in energy storage devices. So, this review article first provides the detailed study of the PEO properties, characteristic of constituents of the polymer electrolyte and suitable approaches for the modification of polymer electrolytes. Then, the synthesization and characterizations techniques are outlined. The structures, characteristics, and performance during charge-discharge of four types of electrolyte/separators which are Liquid, Plasticized, and dispersed/intercalated electrolyte are highlighted. The suitable ion transport mechanism proposed by researchers in the different renowned group have been discussed for better understanding of the ion dynamics in such systems

Efficient Inference in Large Discrete Domains

In this paper we examine the problem of inference in Bayesian Networks with discrete random variables that have very large or even unbounded domains. For example, in a domain where we are trying to identify a person, we may have variables that have as domains, the set of all names, the set of all postal codes, or the set of all credit card numbers. We cannot just have big tables of the conditional probabilities, but need compact representations. We provide an inference algorithm, based on variable elimination, for belief networks containing both large domain and normal discrete random variables. We use intensional (i.e., in terms of procedures) and extensional (in terms of listing the elements) representations of conditional probabilities and of the intermediate factors.Comment: Appears in Proceedings of the Nineteenth Conference on Uncertainty in Artificial Intelligence (UAI2003

Optimization of salt concentration and Explanation of Two Peak Percolation in Blend Solid Polymer Nanocomposite Films

The present paper report is focused toward the preparation of the flexible and freestanding blend solid polymer electrolyte films based on PEO-PVP complexed with NaPF6 by solution cast technique. The structural/morphological features of the synthesized polymer nanocomposite films have been investigated in detail using X-ray diffraction, Fourier transform infra-red spectroscopy, field emission scanning electron microscope, and atomic force microscopy techniques. The film PEO-PVP+NaPF6 O/Na:8 exhibits highest ionic conductivity ~5.92x10-6 S cm-1 at 40 oC and ~2.46x10-4 S cm-1 at 100 oC. The temperature dependent conductivity shows Arrhenius type behavior and activation energy decreases with the addition of salt. The high temperature (100 oC) conductivity monitoring is done for the optimized PEO-PVP+NaPF6 O/Na:8 highly conductive system and the conductivity is still maintained stable up to 160 h (approx. 7 days). The thermal transitions parameters were measured by the differential scanning calorimetry (DSC) measurements. The prepared polymer electrolyte film displays the smoother surface in addition of salt and a thermal stability up to 300 oC...........

Structural, Microstructural and Electrochemical Properties of Dispersed Type Polymer Nanocomposite Films

The free standing solid polymer nanocomposite films has been prepared through standard solution cast technique. The improvement in structural, microstructural and electrochemical properties has been observed on the dispersion of nanofiller in polymer salt complex. X Ray diffraction studies clearly reflect the formation of complex formation as no corresponding salt peak appeared in the diffractograms. The FTIR analysis suggested a clear and convincing evidence of polymer ion, ion ion and polymer ion nanofiller interaction. The highest ionic conductivity of the prepared solid polymer electrolyte films is 5x10-5 S cm-1 for 7 wt. TiO2. The Linear Sweep Voltammetry provide the electrochemical stability window of the prepared solid polymer electrolyte films, which is of the order of 3.5 V. The ion transference number has been estimated, tion is 0.99 through dc polarization technique. Dielectric spectroscopic studies were performed to understand the ion transport process in polymer electrolytes. All solid polymer electrolyte possesses good thermal stability up to 300C. DSC analysis confirms the decrease of melting temperature and signal of glass transition temperature with addition of nanofiller which indicates the decrease of crystallinity of polymer matrix. An absolute correlation between diffusion coefficient, ion mobility, number density, double layer capacitance, glass transition temperature, melting temperature, free ion area and conductivity has been observed. A convincing model to study the role of nanofiller in polymer salt complex has been proposed which supports the experimental findings. The prepared polymer electrolyte system with significant ionic conductivity, high ionic transference number, good thermal, voltage stability could be suggested as a potential candidate as electrolyte cum separator for fabrication of rechargeable lithium-ion battery system.Comment: arXiv admin note: text overlap with arXiv:1807.0353

On maximal area integral problem for analytic functions in the starlike family

For an analytic function $f$ defined on the unit disk $|z|<1$, let $\Delta(r,f)$ denote the area of the image of the subdisk $|z|<r$ under $f$, where $0<r\le 1$. In 1990, Yamashita conjectured that $\Delta(r,z/f)\le \pi r^2$ for convex functions $f$ and it was finally settled in 2013 by Obradovi\'{c} and et. al.. In this paper, we consider a class of analytic functions in the unit disk satisfying the subordination relation $zf'(z)/f(z)\prec (1+(1-2\beta)\alpha z)/(1-\alpha z)$ for $0\le \beta<1$ and $0<\alpha\le 1$. We prove Yamashita's conjecture problem for functions in this class, which solves a partial solution to an open problem posed by Ponnusamy and Wirths.Comment: 12 pages, 8 figures, 2 tables, submitted to a journa

On a generalization of close-to-convex functions

A motivation comes from {\em M. Ismail and et al.: A generalization of starlike functions, Complex Variables Theory Appl., 14 (1990), 77--84} to study a generalization of close-to-convex functions by means of a $q$-analog of a difference operator acting on analytic functions in the unit disk $\mathbb{D}=\{z\in \mathbb{C}:\,|z|<1\}$. We use the terminology {\em $q$-close-to-convex functions} for the $q$-analog of close-to-convex functions. The $q$-theory has wide applications in special functions and quantum physics which makes the study interesting and pertinent in this field. In this paper, we obtain some interesting results concerning conditions on the coefficients of power series of functions analytic in the unit disk which ensure that they generate functions in the $q$-close-to-convex family. As a result we find certain dilogarithm functions that are contained in this family. Secondly, we also study the famous Bieberbach conjecture problem on coefficients of analytic $q$-close-to-convex functions. This produces several power series of analytic functions convergent to basic hypergeometric functions.Comment: 14 pages, to appear in a journal (this version of the paper may not be the final version

Revisiting the entropic force between fluctuating biological membranes

The complex interplay between the various attractive and repulsive forces that mediate between biological membranes governs an astounding array of biological functions: cell adhesion, membrane fusion, self-assembly, binding-unbinding transition among others. In this work, the entropic repulsive force between membranes---which originates due to thermally excited fluctuations---is critically reexamined both analytically and through systematic Monte Carlo simulations. A recent work by Freund \cite {Freund13} has questioned the validity of a well-accepted result derived by Helfrich \cite{Helfrich78}. We find that, in agreement with Freund, for small inter-membrane separations ($d$), the entropic pressure scales as $p\sim 1/d$, in contrast to Helfrich's result: $p\sim 1/d^3$. For intermediate separations, our calculations agree with that of Helfrich and finally, for large inter-membrane separations, we observe an exponentially decaying behavior.Comment: accepted to Journal of Mechanics and Physics of Solid

Development of Novel Cathode Materials based on MWCNT for Energy Storage/Conversion Devices

Novel compound comprising of Li2FexMn(1-x)SiO4/MWCNT were prepared by using Sol-Gel technique. In this study, improved electrochemical properties are observed by substituting Fe to replace Mn. and further multiwalled carbon nano tubes are used to prepare composite with prepared cathode material in Lithium ion battery and electrode materials in super capacitors. Various characterization techniques like: FESEM, EDX confirms the structure, morphology and texture of the material. Average particle size is found to be of order of 20-30 nm. As particles with smaller size reveal better electrical conductivity/electrochemical properties, which are confirmed by A.C Impedence spectroscopy and cyclic voltammetery results