In
materials science,
fast ion conductors are solids in which ions are highly mobile. These materials are important in the area of
solid-state ionics, and are also known as
solid electrolytes and
superionic conductors. These materials are useful in batteries and various sensors. Fast ion conductors are used primarily in
solid oxide fuel cells. As solid electrolytes they allow the movement of ions without the need for a liquid or soft membrane separating the electrodes. The phenomenon relies on the hopping of ions through an otherwise rigid
crystal structure.