Provided is a magnesium-air fuel cell in which a conductive state is achieved when a lid is fastened, and a nonconductive state is achieved when the lid is loosened, so that the power supply can be turned ON and OFF based on a fastening state of the lid. A lid includes a lower end portion that comes into contact with a main body at a time of fastening, an anode body inserted in the main body, and an electrode plate made of metal coupled to an end of the anode body. The electrode plate includes a first terminal at least positioned at the lower end portion. The main body includes a second terminal positioned on a surface that comes into contact with the lower end portion of the lid at the time of fastening the lid. Electrical conduction is achieved when the first terminal and the second terminal come into contact with each other.

A metal-carbon dioxide battery and a hydrogen generation and carbon dioxide storage system including the same are disclosed. The metal-carbon dioxide battery includes: a first plate with a designated area; a second plate with a designated area and spaced apart from the first plate by a distance in an X-axis direction; a separator between the first and second plates; a frame-shaped spacer disposed between the first plate and the separator with a space between the first plate and the separator; a plurality of anode sheets in the space; a pressing unit in the space between the first plate and the anode sheets and biasing the anode sheets toward the separator; and a cathode between the second plate and the separator.