Electrolytes are indispensable components in electrochemistry and the fast-growing electrochemical energy storage markets. Research in electrolytes has witnessed exponential growth in recent years, accompanied by their applications in the most popular electrochemical cell ever invented, lithium-ion batteries LIBs. In myriads of LIBs, electrolytes and their interphases determine how high the voltage of a battery is, how many times it can be chargeddischarged, or how rapid the energy stored therein could be released. The conquest of further technical challenges around safety, life and cost-effectiveness of lithium-based or beyond-lithium batteries requires in-depth understanding of electrolytes and interphases. This will be the authoritative textbook for those entering the field. Chapters will establish the fundamental principles for the field, before moving onto important knowledge acquired in recent years. There will be special emphasis on linking these fundamentals to real-world probl