Compatibility\nof Halide Bilayer Separators for All-Solid-State\nBatteries

Considering the lack of solid electrolytes that are electrochemically\nstable when in contact with a high-voltage cathode and a low-voltage\nmetallic anode, bilayer separators in all-solid-state batteries are\ngaining increasing attention. However, previous studies have shown\nthat the chemical reactivity between materials comprising the electrolyte\nbilayer is one of the contributing factors to the deterioration of\nbattery performance during cycling. Here, we computationally screen\nthe chemical compatibility of an extensive range of materials forming\na bilayer separator using first-principles calculations. Notably,\nseveral bilayer separators are found to be thermodynamically stable;\namong them, the stability of the Li<sub>3</sub>PO<sub>4</sub>/Li<sub>3</sub>InCl<sub>6</sub> pairing is further verified experimentally\nusing a combination of X-ray diffraction, solid-state nuclear magnetic\nresonance, and X-ray photoelectron spectroscopy. This study underscores\nthe importance of understanding the chemical compatibility of bilayer\nseparators when engineering high-energy-density all-solid-state batteries.