Electrolytic copper foil for secondary battery, having enhanced physical properties at low temperature, and method for producing same
The present invention relates to an electrolytic copper foil for a secondary battery, having excellent physical properties at a low temperature, and a method for producing the electrolytic copper foil. The electrolytic copper foil for a secondary battery shows little change in the physical properties, such as tensile strength and elongation, of a copper foil even at a low temperature and thereby exhibits excellent cycle properties at the low temperature. The electrolytic copper foil for a secondary battery is produced from a plating solution, containing total organic carbon (TOC), cobalt, iron and zinc, by using a drum and coated with a cathode active material, wherein the ratio between the TOC, cobalt, iron and zinc contained in the electrolytic copper foil follows the following formula 1: TOC/(cobalt+iron+zinc)=1.0-1.2. [Formula 1]
1. A method for producing an electrolytic copper foil for a secondary battery, the method comprising:
(1) preparing a plating solution containing copper, total organic carbon (TOC), cobalt, iron and zinc; and
(2) performing electrolytic-plating of the plating solution using a drum at a temperature of 30° C. to 70° C. by applying a current at a current density 30 ASD to 150 ASD to the drum, thereby to form the electrolytic copper foil,
wherein a content of TOC and contents of cobalt, iron and zinc contained in the electrolytic copper foil satisfy a following Equation 1:
TOC content/(cobalt content+iron content+zinc content)=1.0 to 1.2. [Equation 1]
2. The method of claim 1 , wherein each of a tensile strength and an elongation at −30° C. of the electrolytic copper foil is maintained to be greater than or equal to 80% of each of a tensile strength and an elongation at room temperature of the electrolytic copper foil.
3. The method of claim 1 , wherein a concentration of the TOC contained in the plating solution is 100 ppm or greater.
4. The method of claim 1 , wherein the electrolytic copper foil formed by the electrolytic-plating in (2) has one face in direct contact with the drum and the other face opposite to said one face,
wherein a cross-sectional average of a grain size in said one face is smaller than or equal to 80% of a cross-sectional average of a grain size of the other face.
5. The method of claim 1 , wherein a tensile strength of the electrolytic copper foil is in a range of 40 kgf/mm 2 to 51 kgf/mm 2 .
6. The method of claim 1 , wherein an elongation of the electrolytic copper foil is in a range of 2% to 12%.
7. The method of claim 1 , wherein a thickness of the electrolytic copper foil is in a range of 4 μm to 10 μm.