NOVELTY - The packaging unit (20) has a corrugation structure pattern formed on a surface of a sheet-type thin-metal layer (1) along longitudinal direction. A first polymer resin layer (2) is formed in a side of the sheet-type thin-metal layer that is coated on a packaging sheet. A mechanical support layer (3) is laminated in another side of the sheet-type thin-metal layer. The thin-metal layer is made of iron, carbon, chrome, manganese, nickel, copper or aluminum material. The first polymer resin layer is made of polyolefin resin, polyester resin, polyamide-based resin or fluoro resin.    USE - Hollow packaging unit for a cable-type secondary battery (claimed) utilized in a vehicle i.e. car, e.g. electric vehicle and hybrid electric vehicle.    ADVANTAGE - The corrugation structure pattern is formed on the surface of the sheet-type thin-metal layer along the longitudinal direction, and the first polymer resin layer is formed in the side of the sheet-type thin-metal layer that is coated on the packaging sheet so as to effectively prevent contamination of electrolyte, so that deterioration of battery capacity can be prevented, thus improving mechanical intensity and mechanical flexibility of the cable-type secondary battery.    DETAILED DESCRIPTION - The first polymer resin layer comprises hydrophobic inorganic particle that is silicon oxide, aluminum oxide, magnesium oxide, barium titanium oxide, zirconium oxide or zinc oxide. The mechanical support layer is made of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultrahigh molecular weight polyethylene, polypropylene, polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, polyamide, polycarbonate, polyimide, polyether ether ketone, polyethersulfone, polyphenyleneoxide, polyphenylenesulfide or polyethylene naphthalate. An INDEPENDENT CLAIM is also included for a cable-type secondary battery.    DESCRIPTION OF DRAWING(S) - The drawing shows a perspective view of a hollow packaging unit.    Sheet-type thin-metal layer (1)    First polymer resin layer (2)    Mechanical support layer (3)    Packaging unit (20)