Highly Stable Lithium Metal Batteries by Regulating the Lithium Nitrate Chemistry with a Modified Eutectic Electrolyte

Abstract Lithium nitrate is widely used as an additive in electrolytes to regulate the solid electrolyte interphase (SEI). However, the application of LiNO 3 in lithium metal batteries (LMBs) is limited by its extremely low solubility in conventional carbonate‐based electrolytes. In this study, a non‐flammable deep eutectic solvent (DES) with lithium bis(trifluoromethanesulfonyl)imide and N‐methylacetamide (NMAC) as the main components is chosen as the LMB electrolyte. Using theoretical calculations and experiments, the strong interaction between NMAC and LiNO 3 is proved to be effective in increasing the solubility of LiNO 3 (up to 4 wt%) and realizing stable anion‐rich SEI layers. DES synergizes with LiNO 3 to produce LiF, Li x N, and LiN x O y enriched SEI layer, which improves the uniformity of lithium deposition. In particular, the NCM622||DES‐2||Li full cells achieve 84% capacity retention after 600 cycles at 0.5 C, far exceeding that of conventional carbonate electrolytes (56%). Consequently, this study provides a new strategy for employing LiNO 3 in LMBs, in addition to its potential application in other alkali metal batteries and anode‐free batteries.