Low‐Concentration Electrolyte Engineering for Rechargeable Batteries

Low-concentration electrolytes (LCEs) present significant potential for actual applications because of their cost-effectiveness, low viscosity, reduced side reactions, and wide-temperature electrochemical stability. However, current electrolyte research predominantly focuses on regulation strategies for conventional 1 m electrolytes, high-concentration electrolytes, and localized high-concentration electrolytes, leaving design principles, optimization methods, and prospects of LCEs inadequately summarized. LCEs face unique challenges that cannot be addressed by the existing theories and approaches applicable to the three common electrolytes mentioned above; thus, tailored strategies to provide development guidance are urgently needed. Herein, a systematic overview of recent progress in LCEs is provided and subsequent development directions are suggested. This review proposes the core challenge of the high solvent ratio in LCEs, which triggers unstable organic-enriched electrolyte/electrode interface formation and anion depletion near the anode. On the basis of these issues, modification strategies for LCEs, including passivation interface construction and solvent‒anion interaction optimization, are used in various rechargeable battery systems. Finally, the role of advanced simulations and cutting-edge characterization techniques in revealing LCE failure mechanisms is further highlighted, offering new perspectives for their future development and practical application in next-generation rechargeable batteries.