NOVELTY - The method involves forming a heat transcription film (200) in a side of a battery cell (302). The heat transcription film is separated from a thermal transfer roller (110). An adhesion layer (220) is laminated in an upper part of a release paper (210). The release paper is reeled in an outer side of the heat transcription film through a release paper roller (120). The heat transcription film is heated and pressurized. The thermal transfer roller is connected with a side of a thermo transfer printing machine (100). The battery cell is transferred through a battery cell transport unit.    USE - Method for printing product information e.g. type of secondary battery, voltage value and capacity value, on a surface of a battery cell e.g. secondary lithium battery cell, prismatic-type battery cell, lithium-ion secondary battery cell, lithium polymer secondary battery cell, nickel hydrogen secondary battery cell and pouch-type battery cell, of a power source of an electronic device e.g. handheld computer, smart phone, smart pad and netbook, a vehicle e.g. electric vehicle (EV), light EV (LEV), hybrid EV and plug-in hybrid EV, and a power storage system through a thermo transfer printing machine (all claimed).    ADVANTAGE - The method enables forming the heat transcription film in the side of the battery cell, and laminating the adhesion layer in the upper part of the release paper so as to effectively prevent inflow of foreign substance and moisture content into the battery cell, so that deformation of the battery cell can be avoided, thus improving durability of the battery cell.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for a power source.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a thermo transfer printing machine.    Thermo transfer printing machine (100)    Thermal transfer roller (110)    Release paper roller (120)    Heat transcription film (200)    Release paper (210)    Adhesion layer (220)    Battery cell (302)