New Amorphous Oxy-Sulfide Solid Electrolyte Material: Anion Exchange, Electrochemical Properties, and Lithium Dendrite Suppression via <i>In Situ</i> Interfacial Modification

Abstract

Glassy sulfide materials have been considered as promising candidates for solid-state electrolytes (SSEs) in lithium and sodium metal (LM and SM) batteries. While much of the current research on lithium glassy SSEs (GSSEs) has focused on the pure sulfide binary Li₂S + P₂S₅ system, we have expanded these efforts by examining mixed-glass-former (MGF) compositions which have mixtures of glass formers, such as P and Si, which allow melt-quenching synthesis under ambient pressure and therefore the use of grain-boundary-free SSEs. We have doped these MGF compositions with oxygen to improve the chemical, electrochemical, and thermal properties of these glasses. In this work, we report on the short-range order (SRO), namely atomic-level, structures of Li₂S + SiS₂ + P₂O₅ MGF mixed oxy-sulfide glasses and, for the first time, study the critical current density (CCD) of these Si-doped oxy-sulfide GSSEs in LM symmetric cells. The samples were synthesized by planetary ball milling (PBM), and it was observed that a certain minimum milling time was necessary to achieve a final SRO structure. To address the short-circuiting lithium dendrite (LD) problems that were observed in these GSSEs, we demonstrate a simple and novel strategy for these Si-doped oxy-sulfide GSSEs to engineer the LM-GSSE interface by forming an <i>in situ</i> interlayer via heat treatment. Stable cycling to ∼1200 h at a capacity of 2 mAh·cm^-2 per discharge/charge cycle under a current density of 1 mA·cm^-2 is achieved. These results indicate that these MGF oxy-sulfide GSSEs combined with an optimized interfacial modification may find use in LM, and by extrapolation, SM, batteries.