The present invention relates to apparatus, compositions and methods of fabricating high performance thin-film batteries on metallic substrates, polymeric substrates, or doped or undoped silicon substrates by fabricating an appropriate barrier layer composed, for example, of barrier sublayers between the substrate and the battery part of the present invention thereby separating these two parts chemically during the entire battery fabrication process as well as during any operation and storage of the electrochemical apparatus during its entire lifetime. In a preferred embodiment of the present invention thin-film batteries fabricated onto a thin, flexible stainless steel foil substrate using an appropriate barrier layer that is composed of barrier sublayers have uncompromised electrochemical performance compared to thin-film batteries fabricated onto ceramic substrates when using a 700° C. post-deposition anneal process for a LiCoO2 positive cathode.