A fuel cell for production of electrical energy, such as a fuel cell, comprising a fuel chamber (1), an anode (2a), a cathode (2b), an electrolyte (3) disposed between said anode and said cathode, an oxidant chamber (4), wherein said chambers (1 and 4) enclose said anode, cathode and electrolyte, wherein a fuel flowing from the fuel chamber is oxidized at the anode, thereby producing electrical energy, wherein said electrolyte (3) is a ceramic composite electrolyte comprising at least one salt and at least one oxide in mixture.