High pressure-high temperature synthesis of lithium-rich Li3O(Cl, Br) and Li3 − xCax/2OCl anti-perovskite halides

• Report two new lithium hydrate halides of Li3Cl(OH)2 and Li5Br(OH)4
• Propose a general formula, Li2x + 1A(OH)2y, that predicts several new halide hydrates
• Unveil a new reaction path for the synthesis of lithium-rich anti-perovskite halides

In this work, we investigated the systems of (Li, Ca)–O–(Cl, Br) under high pressure and temperature for the synthesis of lithium-rich anti-perovskite (LiRAP) halides. We successfully synthesized Li3 − xCax/2OCl anti-perovskite with x = 0.0, 0.1, 0.2 near 0.5 GPa and temperatures of 400–425 K and Li3OBr anti-perovskite at 3.0 GPa and 450 K. Different from the synthetic route previously reported at ambient pressure, LiA + 2LiOH → Li3OA + H2O, the LiRAP halides under high P–T conditions are formed by dehydration of end-member and Ca-doped halide hydrates with a general formula of Li2x + 1A(OH)2y, where A can be Cl or Br and x must be equal to y. This proposed formula predicts several new halide hydrates including Li3Cl(OH)2, Li5Cl(OH)4, Li3Br(OH)2, and Li5Br(OH)4, indicating that halide hydrates are structurally flexible to accommodate a range of lithium and hydroxide occupancies in the puckered layers of [Li2x + 1(OH)2y+].

Synthesis of lithium-rich anti-perovskite halides through dehydration of new halide hydrates of Li3Cl(OH)2 and Li5Br(OH)4 under high-pressure/high-temperature conditions.Figure optionsDownload as PowerPoint slide