Aliovalent Substitution in Li3InCl6: A Combined Experimental and Computational Investigation of Structure and Ion Diffusion in Lithium-Halide Solid State Electrolytes

Metal-halide superionic conductors are promising electrolytes for solid state Li-ion batteries. Their transport properties may be effectively influenced by doping and a synthetic approach. In this study, a combination of experimental (neutron and X-ray diffraction, total scattering techniques, solid state NMR, impedance spectroscopy) and computational techniques is used to investigate the Li3InCl6 system and, in particular, the effect of Nb substitution on the In site. A maximum conductivity (0.46 mS cm-1 at room temperature) is found for 10% atomic substitution of Nb for In. The increase in conductivity due to doping is primarily associated with an increase in charge carrier concentration (i.e., Li vacancies). Computational modeling highlights the role of point and extended defects on the transport properties of this class of materials and corroborates the experimental finding of 3D diffusion in this layered structure, clearly supporting the choice of a highly disordered structural model to describe the average and the local structure of Li3InCl6