A halospinel-based solid electrolyte for an all-solid-state battery has the following composition: LiM1M2ScX, wherein X is one or more halogen; M1 is a divalent cation selected from the group consisting of Mg, Ca, Sr and Zn; M2 is one of a divalent, trivalent or tetravalent cation; 1.75≤a≤2.75; 0≤y≤0.375; 0.125≤b≤0.5; and 0.125≤c≤0.5.
