Rational Design of High Concentration Gel Electrolytes for Advanced Rechargeable Batteries

ABSTRACT High‐concentration electrolytes (HCEs) reshape cation solvation by reducing free solvent and increasing anion participation, thereby broadening the electrochemical stability window and favoring inorganic‐rich interphases. By coupling salt‐rich solvation chemistry with polymer‐network confinement, high‐concentration gel electrolytes (HC‐GEs) inherit the favorable anion‐rich solvation environment of HCEs while gaining self‐supporting and leakage‐free characteristics from the polymeric matrix, making them a promising electrolyte system. In this review, HC‐GEs are discussed through a structure‐property‐performance framework that connects solvation structure, ion aggregation, gelation behavior, polymer‐chain dynamics, interphase chemistry, and device‐level validation. We summarize how gel networks form and how polymer‐ion, polymer‐solvent, and ion‐ion interactions regulate transport and interfacial reactions. Advanced design and screening methods, including phase diagrams, theoretical calculations, and high‐throughput strategies, are discussed. Representative systems, including water‐in‐salt electrolytes, localized high concentration electrolytes, molecular crowding electrolytes, and polymer‐in‐salt systems, are systematically compared to clarify their regulation mechanisms and limitations. Finally, application‐oriented structure‐performance regulation strategies and practical implementation challenges are summarized, including salt‐tolerant network design, interfacial regulation, electrochemical performance, wide‐temperature adaptability, and the challenges associated with translating laboratory‐scale HC‐GE demonstrations toward scalable manufacturing and realistic battery systems. This review provides a structure‐guided reference for developing HC‐GEs with improved electrochemical performance, mechanical reliability, and practical applicability.