EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Solid-state electrolytes potentially offer an increased energy density and safety for Li-ion batteries as required for the large-scale production of electrical vehicles. Recently, halide solid electrolytes with formula Li3M(III)X6 (M=In,Sc, lanthanides, X=Cl,Br,I) have come to the attention of many researchers, due to their stability against high potential cathodes and high ionic conductivity. Li3InCl6 is a promising candidate, reaching room temperature ionic conductivities in the order of 10^-3 S/cm. It crystallizes in the monoclinic space group C2/m, with a quasi-cubic close packed framework of the Cl atoms and In/Li in (mostly) partially occupied octahedral sites. Nazar and coworkes found for Li3M(III)Cl6 with M(III)= Er,Y that aliovalent doping with Zr leads to a phase transition from trigonal P-3m1 to orthorhombic Pnma, accompanied with an increase in ionic conductivity.
In this study we doped the Li3InCl6 with varying amounts of Zr(IV) to obtain series of solid electrolytes with composition of Li3-1In1-xZrxCl6 where 0>=x>=0.5. The structural body of that material is not affected by this substitution, probably due to their similarity in Shannon radius. We found an almost twofold increase in ionic conductivity measured by impedance spectrometry of 2.2 mS/cm for the Li2.7In0.7Zr0.3Cl6 doped variant. With a combined X-ray and neutron diffraction analysis, the structures of the different compositions was solved, shedding light into the complex cation arrangements in these materials and their correlation to the enhanced conductivity observed. The effect of these arrangements on the Li-ion diffusivity is further investigated with solid-state NMR relaxometry.