Excellent Deformable Oxide Glass Electrolytes and Oxide-Type All-Solid-State Li₂S–Si Batteries Employing These Electrolytes

Oxide-type all-solid-state lithium-ion batteries have attracted great attention as a candidate for a next-generation battery with high safety performance. However, batteries based on oxide systems exhibit much lower energy densities and rate performances than liquid-type lithium-ion batteries, owing to the difficulty in preparing the ion- and electron-transfer path between particles. In this study, Li₂SO₄–Li₂CO₃–LiX (X = Cl, Br, and I) glass systems are investigated as highly deformable and high-ionic-conductive oxide electrolytes. These electrolytes show excellent deformable properties and better ionic conductivity. The LiI oxide glass system is a suitable electrolyte for the negative electrode because it shows a higher ionic conductivity and is stable up to 2.8 V. The LiCl or LiBr oxide glass systems are suitable electrolytes for the positive electrode and separation layer because they show high ionic conductivity and kinetic stability up to 3.2 V. The Li₂S positive and Si negative composite electrodes employing LiBr and LiI oxide glass electrolytes, respectively, show high battery performances because of increased reaction points between active materials and the solid electrolyte and carbon via a mechanical milling process and are capable of forming good interparticle contact. Therefore, it suggests that the excellent deformable electrolytes are suitable for solid electrolytes in composite electrodes because their ionic conductivity does not change by the mechanical milling process. Furthermore, an oxide-type all-solid-state Li₂S–Si full-battery cell employing these positive and negative composite electrodes and a LiBr oxide glass electrolyte separation layer is demonstrated. The full-battery cell indicates a relatively high discharge capacity of 740 mA h g^–1(Li₂S) and an area capacity of 2.8 mA h cm^–2 at 0.064 mA cm^–2 and 45 °C despite using only safe oxide electrolytes.