High‐Concentration Additive and Triiodide/Iodide Redox Couple Stabilize Lithium Metal Anode and Rejuvenate the Inactive Lithium in Carbonate‐Based Electrolyte

Abstract Carbonate‐based electrolytes are incompatible with lithium (Li) metal anode because the generated solid electrolyte interphase (SEI) undergoes repeated breakage‐repair, resulting in the accumulation of inactive Li including Li + compounds and electrically isolated dead Li 0 in the SEI. Therefore, exploiting a suitable strategy to construct a stable SEI while efficiently rejuvenating the inactive Li capacity is urgent and more thoughtful than just building a stereotyped SEI layer. Herein, an innovative strategy is proposed of high‐concentration additive (HCA) of LiNO 3 inspired by (localized) high‐concentration electrolyte and inactive Li restoration methodology via triiodide/iodide (I 3 − /I − ) redox couple to improve the compatibility of carbonate‐based electrolytes. The HCA of LiNO 3 can maintain the cation–anion aggregates solvation structures in the carbonate‐based bulk electrolyte and induce the in situ formation of superior‐ionic‐conductivity NO 3 − ‐derived SEI. Moreover, the reversible I 3 − /I − redox couple can further optimize the SEI and constantly rejuvenate the inactive Li including solvent/LiNO 3 ‐derived Li 2 O, a derivative has almost been acquiescent in LiNO 3 ‐additive electrolytes, and dead Li 0 into delithiated cathode. Consequently, epitaxy‐like planar Li deposition, better reversibility, and higher capacity retention can be realized and are systematically verified by Li||Cu half cells, full cells with excess/limited Li (N/P ratio = 1.5) and anode‐free lithium metal batteries.