The increasing global population and energy consumption have led to a rapid rise in the usage of fossil fuels in recent years. Consequently, there has been a significant increase in greenhouse gas emissions, which had detrimental effects on aquatic and animal life as well as the ecosystem. To address this problem, efficient energy storage and conversion devices with no greenhouse gas emissions, such as batteries, supercapacitors, and fuel cells, are becoming popular.The development of suitable materials is essential for making efficient energy storage and conversion devices. Thus, this book is organized to highlight significant breakthroughs in energy storage and conversion systems, focusing on material development.This book includes 12 researches. For energy storage devices, material research on lithium-ion batteries and supercapacitor is described. Studies on solar cells and solid oxide fuel cells for energy conversion devices are also revealed. Additionally, phase change materials are also introduced as a different type of energy storage devices.This book will make a substantial contribution in developing efficient energy storage and conversion devices.