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

Solid electrolytes based on theoretically identified double antiperovskite phases Li 6 OSI 2 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 Li 6.5 OS 1.5 I 1.5 was two to three orders better than that of the best stoichiometric antiperovskite phase Li 3 OCl. 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.