Synthesis-Controlled Polymorphism and Anion Solubility in the Sodium-Ion Conductor Na3InCl6-x Br x (0 ≤ x ≤ 2)

Motivated by thesignificant transport property improvementofthe anion-substituted lithium metal halides, a series of anion mixedsolid solutions of Na3InCl6-x Br x (0 & LE; x & LE; 2) are successfully synthesized by ball milling and subsequentannealing. By milling, the Na3InCl6-x Br x solid solution seriescrystallizes in a monoclinic P2(1)/n phase, while the subsequently annealed Na3InCl6-x Br x seriestransforms into a trigonal P3 1c phase. Through annealing and changes of the structure type, greateranion solubility can be achieved. The halide substitution slightlyimproves the ionic conductivity in the Na3InCl6-x Br x series, indicatingthat mixed halide compositions and their structural changes affectthe ionic transport albeit less strongly than in the lithium analoguessuch as Li3YCl6-x Br x and Li3InCl6-x Br x . A series of halide mixed solid solutions of Na3InCl6-x Br x (0 & LE; x & LE; 2) are successfullysynthesized. By mechanical milling, the Na3InCl6-x Br x solid solution seriesadopts a monoclinic P2(1)/n phase, while the subsequent annealing transforms it into a trigonal P3 1c phase.

Automated summary

A series of halide mixed solid solutions of Na3InCl6-xBrx (0≤x≤2) were successfully synthesized by ball milling and subsequent annealing, inspired by the significant improvement in transport property of anion-substituted lithium metal halides. The Na3InCl6-xBrx solid solution series crystallizes in a monoclinic P2(1)/n phase through milling, while the subsequent annealing transforms it into a trigonal P3 1c phase. The ionic conductivity in the Na3InCl6-xBrx series is slightly improved by halide substitution, indicating that mixed halide compositions and structural changes have an impact on ionic transport, although less strongly than in lithium analogues such as Li3YCl6-xBrx and Li3InCl6-xBrx.