Stable Anion-Derived Solid Electrolyte Interphase in Lithium Metal Batteries

High-energy-density lithium (Li) metal batteries are severely hindered by the dendritic Li deposition dictated by non-uniform solid electrolyte interphase (SEI). Despite its unique advantages in improving the uniformity of Li deposition, the current anion-derived SEI is unsatisfactory under practical conditions. Herein regulating the electrolyte structure of anions by anion receptors was proposed to construct stable anion-derived SEI. Tris(pentafluorophenyl)borane (TPFPB) anion acceptors with electron-deficient boron atoms interact with bis(fluorosulfonyl)imide anions (FSI⁻) and decrease the reduction stability of FSI⁻. Furthermore, the type of aggregate cluster of FSI⁻ in electrolyte changes, FSI⁻ interacting with more Li ions in the presence of TPFPB. Therefore, the decomposition of FSI⁻ to form Li₂S is promoted, improving the stability of anion-derived SEI. In working Li | LiNi_0.5Co_0.2Mn_0.3O₂ batteries under practical conditions, the anion-derived SEI with TPFPB undergoes 194 cycles compared with 98 cycles of routine anion-derived SEI. This work inspires a fresh ground to construct stable anion-derived SEI by manipulating the electrolyte structure of anions.