Lithium Ion Conductivity in Double Antiperovskite Li6.5OS1.5I1.5: Alloying and Boundary Effects

Solid electrolytes based on theoretically identified double antiperovskite phases Li6OSI2 were successfully synthesized. Experimental characterization supported the theoretical prediction that S substitution of O leads to stabilization of the double antiperovskite structure and lattice softening to significantly enhance ionic conductivity, so that the total Li+ conductivity in Li6.5OS1.5I1.5 was two to three orders better than that of the best stoichiometric antiperovskite phase Li3OCl. However, both antiperovskite and double antiperovskite materials are fundamentally susceptible to surface reconstruction, which is behind significant boundary resistances typically known for materials based on antiperovskite hali-chalcogenides. Such a surface related problem was then effectively reduced through amorphous phase formation, thus offering a feasible route to exploit the full potential of this class of new materials as competitive candidates for solid Li-ion batteries.