Flexible batteries This book highlights the key advance of flexible batteries a booming new direction in energy storage field. The authors first introduce lithium ion batteries which are the most widely used batteries so far. Flexible aqueous batteries such as aqueous lithium ion sodium ion and zinc ion batteries are discussed subsequently due to the safety concerns of organic electrolytes. Since flexible metal air batteries are recognized as primary choices for the next generations the authors take lithium air and aluminum air batteries as examples to explore their applications in flexible constructions. They further summarize flexible batteries under the most challenging working conditions such as stretching and integrating flexible batteries with flexible energy harvesting devices sensors and supercapacitors. Covering both important fundamental and application development the book may effectively bridge the academy and industry. It will be helpful not only to scholars and students studying materials science and engineering chemical engineering physics energy science and biomedical science but also to scientists and engineers in the industry