Structural environment of chloride ion‐conducting solids based on lanthanum oxychloride

The effect of the structural environment on the Cl − ion conductivity was demonstrated in LaOCl‐based solid electrolytes. By replacing the La 3+ site with lower‐valent Mg 2+ or Ca 2+ ions, the conductivity was enhanced owing to the formation of a Cl − ion vacancy. Despite the same dopant content, the conductivity of La 0.8 Ca 0.2 OCl 0.8 was considerably greater than La 0.8 Mg 0.2 OCl 0.8 . This enhancement of the conductivity was influenced by the high ionicity of the Cl − ions, which facilitated the weakening of the La‐Cl bond cleavage to conduct inside the lattice. The elongation of the La‐La distance, associated with the Cl − ion conduction, could also cause an increase of the conductivity.