A solid electrolyte switch turns on or off when a metallic bridge is formed or dissolved respectively in the solid electrolyte (here we use Cu2-αS). For logic applications, the switching voltage (<0.3 V) should be larger than the operating voltage of the logic circuit (about 1 V). We reveal that the switching voltage is mainly affected by Cu+ ionic transport in Cu2-αS and that a solid electrolyte with an ion diffusion coefficient smaller than that of Cu2-αS by several tens of orders of magnitude makes it possible to increase the switching voltage to 1 V.