xLi6PS5Cl/(1 – x)(Perfluoropolyethers-ethoxy-diol/Lithium Bis(trifluoromethanesulfonyl)imide) Electrolyte for Superior Stability against a Metallic Lithium Anode

Lithium-metal batteries with solid-state electrolytes are the focus of extensive research because of their high theoretical specific capacity. However, their practical applications are hindered by the narrow electrochemical stability window of lithium-sulfide-based electrolytes and the high reactivity of lithium, as evidenced by undesirable lithium dendrite growth and electrochemical reduction of the electrolyte. In this study, we developed a facile, one-step approach for creating an artificial lithium-metal/solid-state electrolyte interphase by introducing a Li 6 PS 5 Cl/(perfluoropolyethers-ethoxy-diol/lithium bis(trifluoromethanesulfonyl)imide) composite electrolyte, which forms an interfacial layer containing lithium fluoride. This interface was characterized both experimentally and theoretically to examine the interactions between Li 6 PS 5 Cl and PFPE-ethoxy-diol. This artificial solid electrolyte interphase performs several roles; specifically, it suppresses the reduction of the solid-state electrolyte and ensures fast lithium-ion diffusion. Interestingly, it also introduces the synergistic effects of a compliant lithium-metal/solid-state electrolyte contact and enables homogeneous lithium plating. Lithium symmetrical cells with this interphase exhibit superior plating/stripping cycles compared with cells with bare Li 6 PS 5 Cl.