This book presents theoretical studies on ion diffusion in (Li?O)?(B?O?)??? compounds and at the interfaces of Li?O:B?O? nanocomposite. In recent years, ceramic oxides have attracted considerable attention due to their broad potential applications as advanced materials with controlled chemical, mechanical, electrical, magnetic, and optical properties. Many of these properties are attributed to the mobility of metal ions. Ion conductivity in ceramic oxides has been observed in single-phase systems as well as in composites of different components. Therefore, this book considers the study of defects and diffusion in single crystalline materials such as Li?O, Li?B?O? as well as nanocomposite materials of Li?O-B?O? mixtures. The structural, energetic and electronic properties are investigated in order to observe their relationship with defects and diffusion in ceramic oxide materials. The results show that ionic conductivity is enhanced at the interfaces of a conductor-insulator mixture which may have a potential application in battery technology.