The electrical conductivity of LiAsF6 solutions in a propylene carbonate–N,N-dimethylformamide mixed solvent is measured at temperatures of 253.15, 273.15, 293.15, 313.15, and 333.15 K, the ionophore concentration being 0.2 to 1.8 mol/kg. The N,N-dimethylformamide mole fraction in the mixed solvent varied over the 0.2–1.0 range. Concentration dependences of the system’s conductivity can be described by the Casteel–Amis equation; the ionophore solution in N,N-dimethylformamide has the highest conductivity value. The analysis of the charge transfer process in the studied system is carried out in terms of the transition state theory, by using the conductivity data obtained for LiClO4 solutions in N,N-dimethylformamide and propylene carbonate. The electrochemical window width for 0.5 m LiAsF6 solutions in the propylene carbonate–N,N-dimethylformamide mixed solvent is determined. It is restricted by the decomposition potentials: the lithium reduction from the cathodic side; the solvent oxidation, from the anodic side.