Starting from physical and electrochemical foundations, this textbook explains working principles of energy storage devices. After a history of galvanic cells, different types of primary, secondary and flow cells as well as fuel cells and supercapacitors are covered. An emphasis lies on the general setup and mechanisms behind those devices to enable easy understanding for students from all technical and natural science disciplines. New: two current batteries types are added and explained to complete and update the content. New: two current batteries types are added and explained to complete and update the content.