The book offers detailed progress and challenges in energy storage technologies with respect to various electrolyte chemistries including energy storage devices such as batteries and supercapacitors. It introduces energy storage systems and explains the selection of electrolytes for energy storage systems, aqueous- and non-aqueous-based electrolytes, metal-air batteries, and multivalent chemistries. Key features:Provides a better understanding of electrolytes for electrochemical energy storage devicesFocuses on electrolytes and electrolytes valencePresents challenges and opportunities in energy storage systemsExplains supercapacitors with respect to electrolyte systemsSummarizes multivalent-based energy storage systemsThis book is written for graduate students and researchers in electrochemistry, physical chemistry, and renewable energy.