Electrochemical cell

A high temperature rechargeable electrochemical cell having a housing containing an anode and a cathode, the housing having an interior divided by a solid electrolyte separator into a pair of electrode compartments, namely an anode compartment and a cathode compartment, containing respectively active anode material and active cathode material, the active anode material being sodium and the cell having an operating temperature at which the sodium is molten, the separator being a conductor of sodium ions, the separator being tubular or cup-shaped, having a closed end and an open end, and having a plurality of circumferentially spaced radially outwardly projecting ribs or lobes, the housing being in the form of a tubular canister which is polygonal in cross-section, so that it has a plurality of circumferentially spaced corners corresponding in number to the number of lobes of the separator, the separator being concentrically located in the housing, each lobe of the separator being circumferentially aligned with, and projecting radially from the separator towards, one of said corners.