The β-Li 3 PS 4 is known as a metastable phase, observed only as a precipitate in the glassy phase or as nanocrystals within nanopores. This metastable β-Li 3 PS 4 phase exhibits high ionic conductivity at room temperature of around 1 × 10 -4 S/cm, suggesting that the interface between the crystal and the surface or glassy phase is key to stabilizing the β-Li 3 PS 4 structure and achieving high conductivity. Therefore, it is essential to understand the interfaces in glass-ceramics that have these special properties to accelerate materials development.