Critical Role of Framework Flexibility and Disorder in Driving High Ionic Conductivity in LiNbOCl₄

4 V Na Solid State Batteries Enabled by a Scalable Sodium Metal Oxyhalide Solid Electrolyte

“…Nonetheless, the distances of Ta–Cl (2.38 Å), Ta–O (1.88 Å) and Ta–Ta (3.77 Å) agree well with those of crystalline TaOCl 3 , and also mirror those of LiNbOCl 4 (Nb–Cl; avg. 2.41 Å), Nb–O (1.76 Å/2.25 Å) and Nb–Nb (3.75 Å) . This supports our local structural model.…”

“…This suggests that TaCl 5 /NbCl 5 reacts with NaOH to form chains of oxygen corner-sharing (Ta/Nb)O 2 Cl 4 octahedral moieties (Figure b inset), similar to TaOCl 3 , but with Na + randomly distributed within the matrix . We note that we determined such building blocks - consisting of 1-D [NbOCl 4 ] − anionic chains linked by Nb–O–Nb bonds and separated by multiple, disordered Li + sites - exist in semicrystalline LiNbOCl 4 on the basis of fitting its X-ray and neutron pair distribution function (PDF) . However, the fully amorphous nature of NaTaOCl 4 precludes generating a definitive model.…”