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

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)]NO₃) additive with rich NO₃⁻ is developed by introducing 15-crown-5 into LiNO₃, which induces the in situ formation of SEI with abundant Li₃N. Impressively, this Li₃N 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/LiCoO₂ 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.