A crosslinked “polymer–gel” rechargeable lithium-ion battery electrolyte from free radical polymerization using nonionic plastic crystalline electrolyte medium

A cross-linked polymer–gel soft matter electrolyte with superior electrochemical, thermal and mechanical properties obtained from free radical polymerization of vinyl monomers in a semi-solid organic nonionic plastic crystalline electrolyte for application in rechargeable lithium-ion batteries is discussed here

DIFFUSION ON A REARRANGING LATTICE

In this paper we present a computer simulation of a random walk (RW) for diffusion on a rearranging lattice. The lattice consists of two types of sites – one good conducting (type 1) and the other poor conducting (type 2), distributed at random. The two types of sites are assigned different waiting times (τ1 for type 1 and τ2 for type 2). We assume that at intervals of time τr, the site distribution changes. The effect of this rearrangement on the diffusion coefficient is studied with varying τr. We study this effect for different ratios of dwell times of the two types of sites (R) and also for different fractions (X) of the less conducting sites. An empirical relation for D(τ1,τ2,τr,X) is suggested. We have employed the well model and considered diffusion controlled by sites, rather than bonds. So our approach is different from the dynamic bond percolation model, which studies these aspects. Our results show that the diffusion coefficient D may change by a factor of upto 3 (approximately) for rapid rearrangement, and there is a considerable effect of varying X and R on the range of variation of D, where X is the fraction of low conducting sites, and R is the ratio of the dwell times for the two types of sites. Further for τr ¿ 250τ (τ is the time unit for the random walk) the effect of rearrangement becomes negligible. The results may be useful for studying diffusion and conduction of ion conducting polymers

A crosslinked ``polymer-gel'' rechargeable lithium-ion battery electrolyte from free radical polymerization using nonionic plastic crystalline electrolyte medium

A cross-linked polymer-gel soft matter electrolyte with superior electrochemical, thermal and mechanical properties obtained from free radical polymerization of vinyl monomers in a semi-solid organic nonionic plastic crystalline electrolyte for application in rechargeable lithium-ion batteries is discussed here

Study of morphology diversity in polymer salt complex films

245-247A morphology study in films of polyethylene oxide (PEO) complexed with ammonium perchlorate (NH4ClO4) is presented. Wide variety of structures were obtained by varying salt concentration from x = 0 - 0.35 (where x is the weight fraction of the salt, NH4ClO4). The transition in morphology is studied in detail by photography and optical microscopy. Variable temperature polarising microscopy was also done to identify the individual phases present in the films

Probing the “Universal” Amorphization of Crystalline Sulfur in its Mixture with Ultrahigh Surface Area Porous Carbon

We discuss here a fundamental observation regarding the time-dependent amorphization of sulfur in contact with ultrahigh surface area porous carbon. The simple sulfur–carbon mixture discussed here effectively resembles a sulfur-cathode in metal–sulfur batteries. Systematic time dependent powder X-ray diffraction and Raman spectroscopy clearly reveal a crystalline to amorphous phase transition, which has been recently referred as a liquid spillover effect. The occurrence of the structural phase transformation only above a certain carbon surface area (≥2000–3000 m2/g) in the binary sulfur–carbon mixture is equivalent to a “universal” phenomenon, having deep implications in metal–sulfur battery electrochemistry. As revealed by thermal and electron paramagnetic resonance measurements, the (nonpolar) interactions between sulfur and carbon induces a transformation from crystalline orthorhombic to a highly dispersed amorphous phase comprising of small chain sulfur radicals. Amorphization leads to higher degree of sulfur-mass utilization and effective polysulfide management resulting in superior specific capacity of the sulfur-cathode in a Li–S battery

Ionic conductivity of PEO-NH₄ClO₄ films by admittance spectroscopy: correlation with crystallinity and morphology

In this paper we present a study of ionic conductivity versus salt fraction for PEO-NH₄ClO₄ films. Films with salt concentration x in the range 0 – 0.35 (x is the weight fraction of the salt) were prepared for the study. X-ray diffraction and differential scanning calorimetry were done to detect the different species present and to estimate the crystallinity of the films. The films have a wide variety of structures and exhibit a transformation from fractal to nonfractal morphology as x is increased. We attempt a correlation of ionic conductivity with crystallinity and morphology of films with varying x and find that the fractal to compact crossover region has the highest ionic conductivity

A COMPUTER SIMULATION STUDY OF IONIC CONDUCTIVITY IN POLYMER ELECTROLYTES

simulation In this paper we present a computer simulation study of ionic conductivity in solid polymeric electrolytes. The multiphase nature of the material is taken into account. The polymer is represented by a regular lattice whose sites represent either crystalline or amorphous regions with the charge carrier performing a random walk. Different waiting times are assigned to sites corresponding to the different phases. A random walk (RW) is used to calculate the conductivity through the Nernst-Einstein relation. Our walk algorithm takes into account the reorganisation of the different phases over time scales comparable to time scales for the conduction process. This is a characteristic feature of the polymer network. The qualitative nature of the variation of conductivity with salt concentration agrees with the experimental values for PEO-NH4I and PEO-NH4SCN. The average jump distance estimated from our work is consistent with the reported bond lengths for such polymers.