Lithium superionic conductors Li3InBr6 and LiInBr4 studied by 7Li, 115In NMR

Li3InBr6 undergoes a phase transition to a superionic phase at 314 K associated with a steep increase of the conductivity (σ = 4 × 10− 3 Scm− 1 at 330 K). This superionic phase is isomorphous with Li3InCl6 in which a positional disorder at the In3+ site is introduced. A pseudo cubic-close-packing of the bromide ions is formed in this phase. On the other hand, a new superionic phase of LiInBr4 was found above ca 315 K and its structure was confirmed to be a defect spinel. The dynamic properties of the cations in these two superionic phases were investigated by 7Li and 115In NMR spectroscopy.