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

Using multinuclear and multiscale solid-state NMR, the bulk and interfacial structures of a LiI-integrated PEO-LiTFSI-Li₆PS₅Cl hybrid solid electrolytes are elucidated, revealing LiI's dual role in enhancing bulk Li-ion mobility and facilitating Li-ion diffusion across the organic/inorganic interfaces.

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 Li₆PS₅Cl, 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.