Abstract: The present invention relates to an electrochemical cell comprising a solid electrolyte which conducts O.sup.2- anions in contact with an anode and a cathode of identical or different composition, the solid electrolyte being comprised of a composition derived from Bi.sub.4 V.sub.2 O.sub.11 of which at least one of the constituent cationic elements is substituted by at least one substituting element such that the gamma phase structural type of Bi.sub.4 V.sub.2 O.sub.11 is maintained as well as the equilibrium of charges, at least one of the anode or of the cathode is a material containing at least one element of substitution of said composition derived from Bi.sub.4 V.sub.2 O.sub.11, that element being in a metallic or cationic state. The invention equally relates to the use of the electrochemical cell with a view towards the separation or extraction of oxygen.