A solidelectrolyte material can include an ammonium-containing complex metalhalide. In an embodiment, the ammonium-containing complex metalhalide can be represented by (NH4)nM3−z(Mek+)fXn+3−z+k*f, wherein 0<n, 0≤z<3, 2≤k<6, 0≤f≤1; M comprises at least an alkali metal element, X comprises a halogen, and Me comprises a divalentmetal element, a trivalent metal element, a tetravalent metal element, a pentavalent metal element, a hexavalent metal element or any combination thereof.