Homogeneous Li Flux and Mechanical Stable Solid-Electrolyte Interphase Enabled by Different Solvation Chemistry for Lithium Metal Batteries

Abstract

The solid-electrolyte interphase (SEI) in lithium metal batteries (LMBs) is significantly heterogenous, comprising a diverse array of chemical species and suffering from poor mechanical stability. SEI undergoes continuous fracture, leading to exhausted active lithium and electrolyte, which hinders the application of LMBs. Here, the Sn@LixSn@Rich inorganic Li inner layer is formed through Li metal reaction with Sn2+ in FSI-/NO3(-)-coordinated SnI2 aggregates, accompanied by LiNO3 and FSI- deposition, enhancing Li-ion conductivity homogeneity. Meanwhile, the mechanically stabilizing Sn@LixSn@Poly-DME(1,2-dimethoxyethane) outer layer resulted from Li metal reaction with Sn2+ in NO3(-)-coordinated SnI2 aggregates, followed by DME polymerization mediated by Sn@LixSn and DME(-H) <middle dot> radicals. In ether-based electrolytes, Li || LiFePO4 metal (with Sn@LixSn@Rich inorganic Li) coin cells maintained 80% capacity retention after 1200 cycles at 0.5C/1C due to the ring-open polymerization of 1,3-Dioxolane (DOL). Furthermore, the artificial inter/outer layers exhibited stable cycling performance over 350 cycles at 1C/1C in carbonate-based electrolytes. The Li with the Bilayer SEI assembled with a mass-loading lithium nickel cobalt manganese oxide (NCM622 cathode, 3.0 mA h cm-2) coin cells maintain a capacity of 72 mAh g-1 while the cells with pure Li metal own 32 mAh g-1 at 0.5C/1C in carbonate electrolytes after 200 cycles.