A commonly employed strategy to increase the ionic conductivity of a material is through aliovalent substitution. For the chloride Li3M(III)Cl6, this was successfully achieved by Zr(IV) substitution for M(III) = Y (ref. ), Er (ref ), Yb (ref. ), In (ref. ) and Sc (ref. ). The Zr(IV) replaces the M(III), and the excess charge is compensated by a lithium vacancy. In all cases, the ionic conductivity measured by impedance spectroscopy has been shown to increase up to a certain substituent concentration .