High energy density solid state cell

A solid state lithium electrochemical cell having a lithium anode, a solid state electrolyte capable of lithium-ion transport, having a high electronic resistivity and selected from the group of lithium nitride, lithium sulfide, lithium metaborate and lithium iodide in contact with said lithium anode and a cathode, separated from said lithium anode by said electrolyte, comprising at least one high energy denisty compound reactive with said electrolyte and separated from said electrolyte by a stable, in-situ formed, self-healing layer of electrolytically conductive reaction product of said electrolyte and said cathode material, said anode and said cathode being in electrolytically conductive contact through said electrolyte and said in-situ formed, self-healing layer.