This volume presents a comprehensive collection of state-of-the-art advances in the field of solid state ionic materials and the design, fabrication and performance of devices that use them, such as lithium batteries, gas sensors, fuel cells, supercapacitors and electrochromic displays. These electrochemical devices are becoming pervasive in our technologically driven lifestyles. The book includes research activities being carried out in the new millennium, through special keynote addresses, as well as invited and contributed papers, related to experimental and theoretical modeling in solid state ionics. The excellent coverage of topics arranged in such a fashion helps students and beginners to understand the field with enthusiasm. It also encompasses various experimental techniques often employed in solid state ionics research, such as XRD, XPS, hole-burning spectroscopy, EDAX, EXAFS, SEM, thermal analysis techniques, ac-impedance spectroscopy and other electrochemical techniques such as cyclic voltammetry, galvanostatic and potentiostatic electrochemical techniques. Theoretical and applied aspects of mixed conduction for applications mainly in solid oxide fuel cells occupy a portion of the text. Finally, this volume demonstrates the amount of research activities being carried out in this application-oriented field. Solid State Ionics will be of interest to all in the solid state ionics community, including chemists, physicists, materials scientists and electrochemists, both in industry and in research.