The invention relates to an electricity generating electrochemical device of the solid-oxide fuel-cell stack type. The device includes a planar assembly having at least one electrochemical cell comprised between first and second gas diffusing plates made of ceramic of expansion coefficient between 8×10−6 K−1 and 10×10−6 K−1 and drilled with equidistant holes. First and second current conductive metal grids each are connected to a conductive wire allowing current to flow out of the device. The grilles are placed on either side of the at least one electrochemical cell between this cell and each of the first and second gas diffusing plates. A clamping device mechanically holds the planar assembly together.