Abstract: In a high-temperature cell using, for example, the system Li(Al)/LiCl, KCl/MeS (wherein Me is a heavy metal) the operating temperatures and the composition of the molten electrolyte are so selected that a solid phase is created through partial precipitation of at least one of the components of the salt mixture, which provides the separator function between the electrode plates. For example, a non-eutectically composed molten electrolyte of 80% by volume LiCl and 20% by volume KCl, at a given temperature corresponding to the operating point in the phase diagram, contains a solid LiCl frame whose pore volume of about 50% is filled with ion-conducting residual molten LiCl and KCl. Through combination with non-electron conducting inert material in grid or powder form, the permeability of the precipitated solid separator can be further controlled.