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 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. (© 2022 Wiley‐VCH GmbH)