All-solid-state batteries have gained much attention as the next-generation batteries. This book is about various Li ion ceramic electrolytes and their applications to all-solid-state battery. It contains a wide range of topics from history of ceramic electrolytes and ion conduction mechanisms to recent research achievements. Here oxide-type and sulfide-type ceramic electrolytes are described in detail. Additionally, their applications to all-solid-state batteries, including Li-air battery and Li-S battery, are reviewed. Consisting of fundamentals and advanced technology, this book would be suitable for beginners in the research of ceramic electrolytes; it can also be used by scientists and research engineers for more advanced development.