Methods for forming three-layer thin-film battery (TFB) structures by sequential electrophoretic deposition (EPD) on a single conductive substrate. The TFBs may be two-dimensional or three-dimensional. The sequential EPD includes EPD of a first battery electrode followed by EPD of a porous separator on the first electrode and by EPD of a second battery electrode on the porous separator. In some embodiments of a Li or Li-ion TFB, the separator includes a Li ion conducting solid. In some embodiments of a Li or Li-ion TFB, the separator includes an inorganic porous solid rendered ionically conductive by impregnation with a liquid or polymer. In some embodiments, the TFBs are coated and sealed with an EPDd PEEK layer.