A fuel cell comprises at least two current collectors, an electrically insulating separator element and solid electrolyte. Each current collector comprises at least one transverse passage passing through it from a first surface to a second surface and the separator element comprising opposite first and second faces is arranged between the current collectors. A plurality of transverse channels pass through the separator element from the first face to the second face and the ionically conducting solid electrolyte occupies the volume bounded by the channels of the separator element and by the passages of the current collectors. The separator element is formed by a thermoplastic polymer material and hard particles are arranged in the transverse channels.