Electrolytic copper foil capable of improving capacity retention rate of secondary battery, electrode including the same, secondary battery including the same, and method of manufacturing the same

1. A method of manufacturing a secondary battery electrolytic copper foil, the method comprising:

forming a copper layer by applying electricity between a positive electrode plate and a rotating negative electrode drum which are disposed in an electrolytic solution containing 70 to 90 g/L of copper ions and 50 to 150 g/L of sulfuric acid to be spaced apart from each other; and

forming a protective layer on the copper layer,

wherein the forming of the copper layer includes:

performing a heat treatment on a copper wire;

pickling the heat-treated copper wire;

preparing the electrolytic solution by introducing the pickled copper wire into sulfuric acid;

performing electroplating by applying electricity between the positive electrode plate and the rotating negative electrode drum at a current density of 40 to 80 A/dm 2 ; and

performing continuous filtration at a flow rate of 31 to 45 m 3 /hr to remove solid impurities from the electrolytic solution while the electroplating is performed,

wherein, while the electroplating is performed, total carbon (TC) in the electrolytic solution is maintained at a range of 0.04 to 0.24 g/L, a concentration of silver (Ag) therein is maintained at a range of 0.03 to 0.19 g/L, and a concentration of iron (Fe) therein is maintained at a range of 0.05 to 0.51 g/L.

2. The method of claim 1 , further comprising:

monitoring the concentration of iron (Fe) in the electrolytic solution while the electroplating is performed; and

replacing all or some of the electrolytic solution when the concentration of iron (Fe) is more than 0.54 g/L.

3. The method of claim 1 , wherein the copper wire is heat-treated at a temperature of 600 to 900° C. for 30 to 60 minutes.

4. The method of claim 1 , wherein the electrolytic solution further includes chloride ion capable of precipitating silver (Ag) in the form of AgCl in order to prevent the concentration of silver (Ag) from exceeding 0.2 g/L by silver (Ag) being introduced into the electrolytic solution while the electroplating is performed.

5. The method of claim 1 , wherein the forming of the copper layer further includes introducing hydrogen peroxide and air into the electrolytic solution while the electroplating is performed.

6. The method of claim 1 , wherein the electrolytic solution further includes an organic additive selected from a group consisting of hydroxyethyl cellulose (HEC), organic sulfides, organic nitrides, and thiourea-based compounds.

7. The method of claim 1 , wherein the electrolytic solution further includes 1 to 10 ppm of ethylene thiourea.

8. The method of claim 1 , wherein the forming of the copper layer includes polishing a surface of the rotating negative electrode drum with an abrasive brush having #800 to #1500 of a particle-size (Grit).

9. The method of claim 1 , wherein:

the forming of the protective layer includes immersing the copper layer in an antirust solution containing 0.5 to 1.5 g/L of Cr; and

a concentration of copper (Cu) in the antirust solution is maintained at 0.1 g/L or less.

10. A secondary battery electrolytic copper foil, which is manufactured by the method of claim 1 , and includes a first surface and a second surface opposite the first surface, the electrolytic copper foil comprising:

a copper layer including a matte surface facing the first surface and a shiny surface facing the second surface; and

a first protective layer on the matte surface of the copper layer,

wherein the first surface has a peak density (PD) of 3 to 110, a texture coefficient [TC(220)] of a (220) plane of 1.32 or less, and a surface roughness (R z )) of 0.5 to 2.7 μm.

11. The electrolytic copper foil of claim 10 , further comprising a second protective layer on the shiny surface of the copper layer,

wherein the second surface has a PD of 3 to 110, a texture coefficient [TC(220)] of a (220) plane of 1.32 or less, and a surface roughness (R z )) of 0.5 to 2.7 μm.

12. The electrolytic copper foil of claim 11 , wherein:

a difference between the PDs of the first and second surfaces is 95 or less;

a difference between the texture coefficients [TC(220)] of the (220) planes of the first and second surfaces is 0.53 or less; and,

a difference between the surface roughnesses (R z ) of the first and second surfaces is 0.8 μm or less.

13. The electrolytic copper foil of claim 12 , wherein each of the first and second protective layers includes chromium (Cr).

14. The electrolytic copper foil of claim 10 , wherein the electrolytic copper foil has a yield strength of 21 to 63 kgf/mm 2 and an elongation of 3% or more at room temperature.

15. A secondary battery electrode comprising:

an electrolytic copper foil being manufactured by the method of claim 1 , and including a first surface and a second surface opposite the first surface; and

a first active material layer on the first surface of the electrolytic copper foil,

wherein the electrolytic copper foil includes:

a copper layer including a matte surface facing the first surface and a shiny surface facing the second surface; and

a first protective layer on the matte surface of the copper layer, and

wherein the first surface has a PD of 3 to 110, a texture coefficient [TC(220)] of a (220) plane of 1.32 or less, and a surface roughness (R z ) of 0.5 to 2.7 μm.

16. The secondary battery electrode of claim 15 , wherein:

the electrolytic copper foil further includes a second protective layer on the shiny surface of the copper layer;

the secondary battery electrode further includes a second active material layer on the second protective layer; and

the second surface has a PD of 3 to 110, a texture coefficient [TC(220)] of a (220) plane of 1.32 or less, and a surface roughness (R z ) of 0.5 to 2.7 μm.

17. The secondary battery electrode of claim 16 , wherein:

a difference between the PDs of the first and second surfaces is 95 or less;

a difference between the texture coefficients [TC(220)] of the (220) planes of the first and second surfaces is 0.53 or less; and

a difference between the surface roughnesses (R z ) of the first and second surfaces is 0.8 μm or less.

18. The secondary battery electrode of claim 16 , wherein each of the first and second active material layers comprises at least one active material selected from a group consisting of carbon, a metal such as Si, Ge, Sn, Li, Zn, Mg, Cd, Ce, Ni, or Fe, an alloy containing the metal, an oxide of the metal, and a composite of the metal and carbon.

19. The secondary battery electrode of claim 18 , wherein each of the first and second active material layers comprises Si.

20. A secondary battery comprising:

a cathode;

an anode opposite to the cathode and including a secondary battery electrode;

an electrolyte configured to provide an environment in which lithium ions may move between the cathode and the anode; and

a separator configured to electrically insulate the cathode from the anode,

wherein the secondary battery electrode is manufactured by the method of claim 1 , and comprises:

an electrolytic copper foil including a first surface and a second surface opposite the first surface; and

a first active material layer on the first surface of the electrolytic copper foil,

wherein the electrolytic copper foil includes:

a copper layer including a matte surface facing the first surface and a shiny surface facing the second surface; and

a first protective layer on the matte surface of the copper layer, and

wherein the first surface has a PD of 3 to 110, a texture coefficient [TC(220)] of a (220) plane of 1.32 or less, and a surface roughness (R z ) of 0.5 to 2.7 μm.