Li ion conductivity of solid electrolyte, Li3−2xMxInBr6 (M=Mg, Ca, Sr, Ba)

Li3−2xMxInBr6 (M=Mg, Ca, Sr, Ba; x=0–1.0) was synthesized and the cation substitution effect was investigated by means of X-ray diffraction, 7Li and 115In nuclear magnetic resonance (NMR), and AC conductivity measurements. In Li3−2xMgxInBr6, the lattice constants a and c increased with an increase of x, but b and β did not show significant changes. In the high-temperature phase for Li3−2xMxInBr6 (M=Mg, Ca, Ba), the conductivity decreased with x, accompanied by a broadening of the 115In NMR spectra. In Li3−2xSrxInBr6 (x≤0.7), the conductivity of the high-temperature phase also decreased with an increase of x, but LiSrInBr6 showed almost the same conductivity to Li3InBr6. On the other hand, the conductivity of the low-temperature phase in Li3−2xMgxInBr6 (x≤0.4) increased with x, associated with a narrowing of the 7Li NMR spectra.