An electrochemical cell employs an ionic semiconductor material as a separator between an anolyte and a catholyte. Ionic semiconductor material includes 10 to approximately 50 percent by weight of a hydrogel which is dispersed within an inert nonporous matrix material to form a composite wherein the quantity of water that can be absorbed by the composite does not substantially exceed the weight of the composite.

An electrode comprising: metallic electrode material; and a nonporous solid composite material encapsulating the electrode material, the composite material comprising an inert matrix material having hydrogel substantially uniformly dispersed therein, the hydrogel comprising 10% to approximately 50% by weight of the dry composite material, there being sufficient bonding between molecules of the hydrogel and the matrix material to prevent substantial leach-out of hydrogel molecules from the composite.