NOVELTY - Device comprises: first conductive sheet (110); second conductive sheet (130) being substantially parallel to first conductive sheet, and a layer (120) of substance placed between the first and second conductive sheet, the substance allowing migration of free ions, where at least one of the first and second conductive sheet comprises a metal foil layer and a carbon nanotube layer, which is adjacent to the layer of the substance, and where the carbon nanotube layer is grown on the metal foil layer.    USE - The device is useful: as energy conversion and storage devices e.g. batteries and supercapacitors, having charge collectors made with the carbon nanotubes grown on the flexible substrate.    ADVANTAGE - The device has highly packed and vertically aligned carbon nanotube structure, which can be directly used in making electrodes for batteries and supercapacitors and provides mass productions of the nanostructured carbon material and mass production of the energy storage units comprising the nanostructured carbon material.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for:    (1) forming a layer of carbon nanotubes on a flexible metal foil, comprising: coating a catalyst on a surface of the metal foil by low temperature evaporation of the catalyst, annealing the catalyst coated metal foil in ammonia gas at a first temperature, and growing the carbon nanotubes directly on the catalyst coated surface of the metal foil in a hydrocarbon gas atmosphere at a second temperature, where the first temperature is lower than the second temperature and the second temperature is no higher than 550 degrees C; and    (2) a device comprising: a first energy storage unit, an energy converting unit, configured to convert light energy to electrical energy, a first circuit, configured to transfer at least part of the electrical energy generated by the energy converting unit to the first energy storage unit, a second energy storage unit, configured to provide electrical energy to at least one external circuit, and a second circuit, configured to transfer at least part of the electrical energy stored in the first energy storage unit to the second energy storage unit, where at least one of the first and second energy storage units comprises the first conductive sheet, the second conductive sheet as above per se.    DESCRIPTION OF DRAWING(S) - The figure shows a schematic illustration of a layer of aligned carbon nanotubes grown on a flexible metal foil.    Multilayered energy storage device (100)    First sheet of a conductive material (110)    Layer of a free ion conductive electrolyte/separator (120)    Second sheet conductive material (130)    First insulator sheet (140)