This research text covers the fundamentals, working mechanisms, electrode materials, challenges, and opportunities for energy storage devices of Lithium-ion and Lithium-sulfur battery technology. The book presents the features, advantages, disadvantages,and efforts made to enhance the performance of each class of material used in Lithium-ion and Lithium-sulfur batteries. The content of the book focuses on energy storage technologies, namely lithium-ion and lithium-sulfur batteries. Chapter 1 begins with a highly readable and informative summary on lithium-ion batteries (LIB), providing essential fundamentals and perspectives. Chapter 2 is on the positive electrode (cathode) materials of a LIB. With a reference list of 334 items, it provides a very good scientific summary of different choices for cathode material. Chapter 3 is on fundamentals and perspectives of lithium-sulfur batteries, with a reference list of 53 articles. The author is optimistic about the future developments of lithium-sulfur battery chemistry. The final chapter of the book is on cathodes for lithium-sulfur batteries. Overall, this is a very fine piece of work on electrochemistry of lithium based batteries, with a strong practical orientation. This will be a very useful reference book for postgraduate students working on lithium batteries, and academics who work on electrochemistry research. Nihal Kularatna, IEEE Magazine, July/August 2023