It consists of a negative electrode (cathode) and a positive electrode (anode), with a vacuum between them.

ECONOMIST: Medical technology

The spheres are then dissolved to leave a 3D-metal scaffold onto which a nickel-tin alloy is added to form the anode, and a mineral called manganese oxyhydroxide to form the cathode.

BBC: Super-powered battery breakthrough claimed by US team

There are several sorts of fuel cell, but all consist of two electrodes (an anode and a cathode) separated by a material called an electrolyte.

ECONOMIST: The dawn of micropower