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

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 Li0 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 LiNO3 inspired by (localized) high‐concentration electrolyte and inactive Li restoration methodology via triiodide/iodide (I3−/I−) redox couple to improve the compatibility of carbonate‐based electrolytes. The HCA of LiNO3 can maintain the cation–anion aggregates solvation structures in the carbonate‐based bulk electrolyte and induce the in situ formation of superior‐ionic‐conductivity NO3−‐derived SEI. Moreover, the reversible I3−/I− redox couple can further optimize the SEI and constantly rejuvenate the inactive Li including solvent/LiNO3‐derived Li2O, a derivative has almost been acquiescent in LiNO3‐additive electrolytes, and dead Li0 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. The high‐concentration additive (HCA) of LiNO3 and triiodide/iodide (I3−/I−) redox couple are synergistically introduced into carbonate‐based electrolyte. The HCA of LiNO3 can maintain the cation–anion aggregate structure in carbonate‐based bulk electrolyte, leading to the NO3−‐derived solid electrolyte interphase (SEI). The I3−/I− redox couple can further optimize the SEI and constantly rejuvenate the inactive Li capacity contained in solvent/LiNO3‐derived Li2O and dead Li0 into delithiated cathode.