Modeling Of Transport Properties Of Some Nanoionic Composite Electrolytes

Abstract

Solid state ionics is an interdisciplinary branch of science and technology. It shows several technological promises in various solid state electrochemical devices viz. solid state batteries, fuel cells, electro chromic displays, sensors, super capacitors etc. Solid state ionic materials are termed as Superionic Solids or Fast Ion Conductors or Solid Electrolytes or Hyperionic Solids. A large number of fast ion conductors with various mobile cations as well as anions have been investigated. newlineIn the composite electrolyte systems a better enhancement in the conductivity have been achieved by the dispersion of nano-size particles in the ionic host salt. Many experimental works have been done in this regards. To understand the mechanism responsible for the enhancement of ionic conductivity requires further research work. newlineFor the study of transport properties and electrets-type behavior of ionic/superionic systems, a polarization/self-depolarization method is considered and theoretical models are prepared in the present thesis. Modeled transport properties are: ionic mobility, ionic charge density, ionic diffusion, space charge dielectric constant, ionic current density. At last, a computational program SIESTA is used for the chemical nature analysis of polymer electrolyte systems. newlineAt the beginning of the thesis a description on solid state ionics, classification of super ionic solids, scope of the study and objectives of present research work are introduced. A historical background, characteristic properties of super ionic solids and various models of ionic conductors are reviewed later. newlineA theoretical analysis is made in which the fundamental transport properties, techniques used in the modeling and the computational program SIESTA are described. newlineThe theoretical modeling of ionic mobility is performed in which an open-circuit condition is considered in the space charge depolarization process. Therefore the sum of drift current density, trapped current density and displacement current density must be equal to zero. As