The electrochemical behavior of molten K2S2O7 and its mixtures with V2O5 [2–20 mole percent (m/o) V2O5] was studiedat 440°C in argon, by using cyclic voltammetry on a gold electrode. The effect of the addition of sulfate and lithium ions onthe electrochemical processes in the molten potassium pyrosulfate was also investigated. The potential window for pureK2S2O7 was estimated as 2.1 V, being limited by the S2O72- oxidation and reduction. The oxidation of SO4-2 to oxygen isreversible in the basic melt. It is found that V(V) electroreduction proceeds in two steps. The first reduction stage [V(V) V(IV)], starting at 0.7–0.8 V vs. Ag+/Ag, is reversible for V2O5 concentrations lower than 5 m/o and at potential scan ratesless than 200 mV/s. For all studied compositions, the first reduction stage is a one-electron reaction. The second reductionstage [V(IV) --> V(III)], starting at 0.1–0.2 V, is irreversible and under ohmic control at all studied V2O5 concentrations. Thepresence of Li2SO4 causes a noticeable depolarization effect on the V(V) reduction and the V(IV) oxidation.