Elucidating the Impact of Functional Additives on the Structure and Ion Dynamics of Hybrid Solid Electrolytes

Abstract One of the major challenges in advancing polymer‐inorganic hybrid solid electrolytes (HSEs) lies in comprehending and controlling their internal structure. In addition, the intricate interplay between multiple phases further complicates efforts to establish the structure‐property relationships. In this study, by introducing a multifunctional LiI additive to an HSE compromising of polyethylene oxide (PEO) polymeric electrolyte and the fast lithium‐ion conductor Li 6 PS 5 Cl, the relationship between the bulk and interface structure and ascertaining their impact on lithium‐ion dynamics within the HSE is disentangled. Using multidimensional solid‐state nuclear magnetic resonance, we find that the addition of LiI stabilizes the internal interfaces and enhances lithium‐ion mobility. A kinetically stable solid‐electrolyte interphase is formed at the lithium‐metal anode, increasing the critical current density to 1.3 mA cm −2 , and enabling long‐term stable cycling of lithium symmetric cells (>1200 h). This work sheds light on tailoring the structure of HSEs to improve their conductivity and stability for enabling all‐solid‐state lithium‐metal batteries.