This book reports the results that the author has achieved on the study of electrochemistry fundamentals of Se/Te in molten salts and ionic liquids. The book mainly introduces the new low-temperature molten-salt electrochemistry method, reaction mechanism, and product regulation strategy for green extraction of Se/Te metal, as well as the electrochemical behaviors and energy storage applications of related Se/Te products. By analyzing the mechanisms and performance in thermodynamics, kinetics, and multi-scale characterizations, the breakthroughs in product recovery and energy storage value-added applications are achieved, and new insights for the sustainable development of scattered metal Se/Te are provided. The book is likely to be of interest to university teachers, graduate students, researchers and engineers in electrochemical metallurgy and energy storage who wish to exploring innovative methods and technologies that lead to more energy efficient and environmentally sustainable solutions in the area.