Electrolyte Engineering for Rejuvenating Inactive Lithium and Constructing High‐Performance Lithium Metal Batteries

Abstract Lithium metal batteries with gel polymer electrolytes have garnered significant interest due to their high energy‐density and enhanced safety. However, the persistent challenges of inactive lithium accumulation and the unstable solid‐electrolyte interphase (SEI) remain significant obstacles to their practical application. To mitigate these issues, a tiny amount of iodobenzene is employed as a source of triiodine/iodine ion (I ₃ ^‐ /I ^‐ ) redox couple, exhibiting dual functionality in rejuvenating inactive lithium and simultaneously optimizing the SEI composition. Combined by experimental characterization and theoretical analysis, it is demonstrated that the I ₃ ⁻ /I ⁻ redox couple can actively participate in lithium regeneration chemistry to compensate for irreversible lithium loss, while promoting the formation of a robust LiI‐endorsed and LiF‐rich SEI layer. Consequently, symmetrical Li batteries with the engineered electrolyte achieve an improved cycling performance of 4000 h at a current density of 0.2 mA cm ⁻² . Moreover, the assembled NCM811||Li batteries perform an impressive capacity retention of 70.31% after cycling for 720 cycles at 3C, and even at 4C, an equally remarkable capacity retention rate of 75.94% is maintained after 650 cycles.