Electrolytic copper foil for secondary battery and method for producing the same
The present invention relates to an electrolytic copper foil for a secondary battery and a method of producing the same. The electrolytic copper foil for a secondary battery, in which a burr and curl of a negative electrode plate are inhibited from being formed after an electrolytic copper foil is coated with a negative electrode active material, thereby increasing the loading volume of a negative electrode and increasing a capacity. The electrolytic copper foil for a secondary battery is produced from a plating solution containing Total Organic Carbon (TOC) by using a drum, in which the electrolytic copper foil is formed of one surface that is in direct contact with the drum and the other surface that is an opposite surface of the one surface, and an average cross-sectional grain size of the one surface is 80% or less of an average cross-sectional grain size of the other surface.
1. A method of producing an electrolytic copper foil for a secondary battery, the method comprising:
(1) preparing a plating solution containing copper ions and Total Organic Carbon (TOC);
(2) applying a current density that is higher than 70 Ampere per Square Deci-metre (ASD) and equal to or lower than 150 ASD under a temperature condition of 30° C. to 70° C. and performing electroplating by using a drum; and
(3) coating an electrolytic copper foil formed by the electroplating with a negative electrode active material and pressing the electrolytic copper foil,
wherein the electrolytic copper foil formed by the electroplating in operation (2) is formed of one surface that is in contact with the drum and the other surface that is an opposite surface of the one surface, and
an average grain size of the one surface is 80% or less of an average grain size of the other surface,
wherein a concentration of the TOC contained in the plating solution is equal to or higher than 450 ppm, and
wherein an average cross-sectional grain size of the electrolytic copper foil before the step of pressing is 0.5 μm to 1 μm or less, and the average cross-sectional grain size of the electrolytic copper foil after the step of pressing is 90% or more of the average cross-sectional grain size of the electrolytic copper foil before the step of pressing.
2. The method of claim 1 , wherein tensile strength of the electrolytic copper foil is 30 kgf/mm 2 to 50 kgf/mm 2 .
3. The method of claim 1 , wherein an elongation percentage of the electrolytic copper foil is 2% to 15%.
4. The method of claim 1 , wherein a thickness of the electrolytic copper foil is 2 μm to 10 μm.
5. The method of claim 1 , wherein a concentration of the copper ions contained in the plating solution is higher than 110 g/L and equal to or lower than 140 g/L.