High Ion‐Conductive Interphase Enabled by Nitrate‐Ionic Liquid Additive for Low‐Temperature Lithium Metal Batteries

Abstract The development of high‐performance low‐temperature lithium metal batteries (LMBs) is hindered by severe lithium dendrite growth and sluggish charge transfer, both of which can be effectively addressed by constructing a robust solid electrolyte interphase (SEI) with improved Li + transport kinetics. Compared to the soft organic SEI layers, LiF‐rich SEI shows sufficient mechanical strength to impede lithium dendrite growth, however, its extremely low ionic conductivity (≈10 −13 S cm −1 ) hinders Li + transport kinetics at low temperatures. Herein, a quasi‐ionic liquid (QIL, [Li(15‐crown‐5)]NO 3 ) additive with rich NO 3 − is developed by introducing 15‐crown‐5 into LiNO 3 , which induces the in situ formation of SEI with abundant Li 3 N. Impressively, this Li 3 N SEI exhibits superior lithium affinity and lower ionic diffusion barriers as learned from empirical and computational studies, suggesting that it may be powerful to conquer the sluggish Li + kinetics at low temperature. With the assistance of QIL additive, Li/LiCoO 2 cells with a high mass loading of 11.5 mg cm −2 demonstrate stable cycling for 250 cycles without any capacity decay at ‐20 °C. This work opens an emerging avenue to construct high‐performance low‐temperature LMBs by manipulating SEI composition.