Electrification of the automotive industry has increased demand for batteries to be safer, have a higher energy density, higher energy capacity, and improved lifespans. Lithium-ion batteries with liquid electrolytes have met most of these requirements. In contrast, solid-state lithium-ion batteries have higher safety due to the presence of non-flammable, non-volatile electrolytes. Solid electrolytes are considered to be effective at inhibiting lithium dendrite formation and growth, which will allow the use of metallic lithium as the anode thereby increasing the energy density. However, due to the increased demand for lithium across multiple industries and limited recycling methods, lithium reserves will likely become strained. Na-ion batteries have garnered much interest to support and offer an alternative energy storage option to Li-ion batteries. This work will compare the electrical conductivities, ionic conductivities, interfacial attributes, and performance of lithium and sodium oxychlorides (Li₃OCl and Na₃OCl) electrolytes for use in solid-state half-cells. The sodium-ion and lithium-ion half-cells contained an alkaline metal iron phosphate cathode, the appropriate alkaline metal oxychloride solid electrolyte, and the corresponding metallic anode. Each half cell was evaluated based on the performance at different current loads (C-rate), and charge-transfer resistances by electrochemical impedance spectroscopy. The authors acknowledge financial support from the NSF IUCRC program “Center for solid-state electric power storage” (#2052631) and the South Dakota “Governor’s Research Center for electrochemical energy storage”.