1. A method for producing a stack of layers as a part of a lithium ion switching device comprising the steps of: providing an electro conductive substrate; coating a lithium activatable electrode onto said substrate, said electrode comprising a metal oxide which is super-stoichiometric in oxygen; and sputter coating a solid state electrolyte layer from a compound comprising lithium onto said electrode, whereby lithium atoms intercalate into said electrode to provide a source of lithium to said electrode eliminating the need for a separate lithiation step and wherein the intercalation of at least part of the lithium is reversible.