Solid-state ionics is at the foundation for the development of environmentally friendly devices such as batteries and fuel cells for energy storage and conversion, and chemical sensors for pollution monitoring and control. The progress of such devices is crucial for sustainable development. Further insight into the study of fundamentals of ion transport and interfacial phenomena in advanced materials, including ceramics, glasses, polymers, composites and hybrids will allow better design, fabrication and performance of devices for their extensive use. This book is intended to help promote the fundamental understanding of ionic (including protonic) and electronic transport in solids, especially of interfacial transport, including the developing field of nanostructured materials. Contributions encompass fundamental materials R&D, characterization and materials for batteries, sensors, membranes, and fuel cells. Special emphasis is given to the development of high-temperature proton conductors and their application in solid-oxide fuel cells and hydrogen permeation membranes.