Multifunctional Additives to Realize Dendrite-Free Lithium Deposition in Carbonate Electrolytes toward Low-Temperature Li Metal Batteries

Li metal is recognized as one of the most promising anode candidates for next-generation high specific energy batteries. However, the fragile solid electrolyte interface (SEI) and heterogeneous Li plating/stripping in carbonate electrolyte severely encumber its practical application. Here, the heptafluorobutyramide (HFT) and lithium nitrate (LiNO3) are proposed to synergistically construct a robust SEI layer with excellent Li+ transport kinetics. The HFT can promote the dissolution of LiNO3 in carbonate electrolyte due to the strong cooperation. The results of theoretical calculations, in situ Raman and X-ray photoelectron spectroscopy with deep Ar-ion etching demonstrate that HFT and NO3- will be preferentially reduced to a Li3N/LiF-rich composite structure on the surface of Li metal. Particularly, after the addition of additives, the first solvent shell is converted from solvent-dominated to anion-dominated structure, and thus a significantly lower Li-ion desolvation barrier is presented. Consequently, the Coulombic efficiency (CE) of Li||Cu half cells using the designed carbonate electrolyte can reach 97.1%. The full cells matched with LiFePO4 and LiNi0.8Co0.1Mn0.1O2 (NCM 811) can deliver high-capacity retention over 100% at -20 degrees C. This work provides an effective strategy for the regulation of solvation structure and the construction of high-performance Li metal batteries. In this work, heptafluorobutyramide (HFT) and LiNO3 additives are introduced in Li metal batteries with carbonate-based electrolyte. The HFT can promote dissolution of LiNO3 and inhibit generation of destructive HF. The additives will be preferentially reduced to LiF and Li3N on Li metal, prompting the full cell matched with LiFePO4 to maintain high capacity retention for 500 cycles at low temperature of -20 degrees C. image