Fundamental Chemistry and Functional Mechanisms of Nitrile‐Based Electrolyte in Advanced Battery Systems

Nitriles have gained attention as promising candidates for secondary battery electrolytes due to the high polarity of cyano groups, excellent cathode compatibility, remarkable oxidation resistance, and broad thermal stability. As additives, nitriles effectively stabilize cathode surfaces and inhibit the dissolution of transition metals. Besides, as the electrolyte solvent, the characteristics of a wide liquidus range, excellent high‐voltage tolerance, and superior conductivity endow it with outstanding performance. Moreover, nitriles are also beneficially applied in solid‐state electrolytes, offering advantages such as strong cation coordination, excellent thermal and electrochemical stability, and enhanced ionic conductivity. However, obstacles such as side reactions with anodes, the formation of non‐robust SEI layers, and inherent toxicity hinder their broader application. Herein, the mechanism of nitriles as additives, and the application progress of nitriles in liquid electrolytes and solid‐state electrolytes are introduced in detail. Furthermore, the current challenges faced by nitriles are in depth analyzed, and the advanced modification strategies of nitriles as secondary battery electrolytes are thoroughly summarized and discussed. Additionally, the future development of nitriles in the field of secondary batteries is prospected. This review provides important references for the future development of nitrile‐based electrolytes, with guiding significance for other electrolyte solvents and additives.