Sulfide glass solid-state electrolyte separators for Li metal batteries: using an interlayer to increase rate performance and reduce stack pressure

Abstract

We report on the solubility of (Li₂S)₆₀(SiS₂)_x(P₂S₅)_40−x, (0 ≤ x ≤ 40) sulfide glass solid-state electrolytes in the 1 : 1 (v/v) DME : DOL solvent mixture, a popular choice for lithium metal battery liquid electrolytes. SiS₂-rich glasses within the compositional range of (Li₂S)₆₀(SiS₂)_x(P₂S₅)_40−x (28 ≤ x ≤ 40) were found to be functionally insoluble in DME : DOL. Hybrid symmetric test cells with a thin liquid electrolyte layer (0.6 M LiTFSI + 0.4 M LiNO₃ in 1 : 1 (v/v) DME : DOL) at the interface between lithium metal electrodes and an insoluble (Li₂S)₆₀(SiS₂)₂₈(P₂S₅)₁₂ glass wafer were tested. Hybrid test cells delivered a critical current density of 3.0 mA cm⁻² at 25 °C and 0.1 MPa, which is nearly double the CCD of comparable dry symmetric test cells cycled at 10× higher stack pressure.