From fundamental concepts such as the nature of the superionic bond and its fluctuations, to phonons and electronic structure, this book offers comprehensive insight into the nature of the superionic solid state essentially attained through structural phase transitions with useable materials design synthesis and characterization technologies including nanoionics. An ideal reference for contemporary electrochemical energy conversion applications, the text combines principles and practice to provide a holistic treatment of ionic materials, presenting a healthy balance of phenomenology, theory, and applications while maintaining depth and focus.