Electrochemical cell stack

The present invention provides for an electrochemical cell stack formed of a plurality of electrochemical cell units each comprising a sheet separator; a pair of cathodic and anodic sheet electrodes impregnated with an electrolytic solution and disposed facing each other either side of the separator; a pair of cathodic and anodic current collectors disposed adjacent the pair of the cathodic and the anodic electrodes respectively; and a gasket surrounding the electrodes for the sealing thereof; the stack including a sheet conductor located between the units thereof; wherein the sheet conductor is arranged such that the outer dimension of its face contacting with a unit is disposed to almost overlap with the inner dimension of the gasket in the unit and which can advantageously provide a more reliable electrochemical cell stack.