Electrodeposited copper foil, current collector, electrode, and lithium ion secondary battery comprising the same

Abstract

Provided are an electrodeposited copper foil, a current collector, an electrode, and a lithium-ion secondary battery comprising the same. The electrodeposited copper foil has a deposited side and a drum side opposite the deposited side. In a first aspect, ΔRS between the deposited side and the drum side is at most about 95 MPa, and the deposited side exhibits a Vv in a range from about 0.15 μm.sup.3/μm.sup.2 to about 1.35 μm.sup.3/μm.sup.2. In a second aspect, the deposited side has a Sku of about 1.5 to about 6.5 and the deposited side exhibits a Vv in a range from about 0.15 μm.sup.3/μm.sup.2 to about 1.35 μm.sup.3/μm.sup.2. The characteristics are beneficial to improve the quality of the electrodeposited copper foil, thereby extending the charge-discharge cycle life of a lithium-ion secondary battery comprising the same.

Claims

1. An electrodeposited copper foil comprising a deposited side and a drum side opposite the deposited side, wherein the deposited side and the drum side each possess a residual stress, an absolute value of a difference in the residual stress between the deposited side and the drum side is at most 95 MPa, and the deposited side exhibits a void_volume (Vv) in a range from 0.15 μm.sup.3/μm.sup.2 to 1.35 μm.sup.3/μm.sup.2, and the deposited side of the electrodeposited copper foil has a Kurtosis (Sku) in a range from 1.5 to 6.5.

2. The electrodeposited copper foil as claimed in claim 1, wherein the deposited side of the electrodeposited copper foil has the Sku in the range from 1.6 to 6.2.

3. The electrodeposited copper foil as claimed in claim 2, wherein the deposited side of the electrodeposited copper foil has the Sku in the range from 1.7 to 5.8.

4. The electrodeposited copper foil as claimed in claim 1, wherein the drum side of the electrodeposited copper foil has a Sku in a range from 1.5 to 6.5.

5. The electrodeposited copper foil as claimed in claim 1, wherein the deposited side of the electrodeposited copper foil exhibits the Vv in the range from 0.15 μm.sup.3/μm.sup.2 to 1.30 μm.sup.3/μm.sup.2.

6. The electrodeposited copper foil as claimed in claim 5, wherein the deposited side of the electrodeposited copper foil exhibits the Vv in the range from 0.16 μm.sup.3/μm.sup.2 to 1.18 μm.sup.3/μm.sup.2.

7. The electrodeposited copper foil as claimed in claim 6, wherein the deposited side of the electrodeposited copper foil exhibits the Vv in the range from 0.17 μm.sup.3/μm.sup.2 to 1.11 μm.sup.3/μm.sup.2.

8. The electrodeposited copper foil as claimed in claim 1, wherein the absolute value of the difference in the residual stress between the deposited side and the drum side of the electrodeposited copper foil is at most 85 MPa.

9. The electrodeposited copper foil as claimed in claim 1, wherein the absolute value of the difference in the residual stress between the deposited side and the drum side of the electrodeposited copper foil is in a range from 5 MPa to 95 MPa.

10. The electrodeposited copper foil as claimed in claim 9, wherein the absolute value of the difference in the residual stress between the deposited side and the drum side of the electrodeposited copper foil is in the range from 5 MPa to 60 MPa.

11. The electrodeposited copper foil as claimed in claim 1, wherein the deposited side of the electrodeposited copper foil exhibits a core void volume (Vvc) in a range from 0.14 μm.sup.3/μm.sup.2 to 1.15 μm.sup.3/μm.sup.2.

12. The electrodeposited copper foil as claimed in claim 1, wherein the deposited side of the electrodeposited copper foil exhibits a dale void volume (Vvv) of at most 0.15 μm.sup.3/μm.sup.2.

13. The electrodeposited copper foil as claimed in claim 1, wherein the drum side of the electrodeposited copper foil exhibits a Vv in a range from 0.15 μm.sup.3/μm.sup.2 to 1.30 μm.sup.3/μm.sup.2.

14. The electrodeposited copper foil as claimed in claim 1, wherein the electrodeposited copper foil comprises a bare copper foil and a surface-treated layer disposed on the bare copper foil, and the drum side and the deposited side are located at outermost sides of the electrodeposited copper foil.

15. A current collector for a lithium-ion secondary battery, comprising the electrodeposited copper foil as claimed in claim 1.

16. An electrode for a lithium-ion secondary battery, comprising the current collector as claimed in claim 15 and an active substance coated on the current collector.

17. A lithium-ion secondary battery, comprising the electrode as claimed in claim 16.

18. An electrodeposited copper foil comprising a deposited side and a drum side opposite the deposited side, wherein the deposited side has a Sku in a range from 1.5 to 6.5, and the deposited side exhibits a Vv in a range from 0.15 μm.sup.3/μm.sup.2 to 1.35 μm.sup.3/μm.sup.2.

19. The electrodeposited copper foil as claimed in claim 18, wherein the deposited side of the electrodeposited copper foil has the Sku in the range from 1.6 to 6.2.

20. The electrodeposited copper foil as claimed in claim 19, wherein the deposited side of the electrodeposited copper foil has the Sku in the range from 1.7 to 5.8.

21. The electrodeposited copper foil as claimed in claim 18, wherein the drum side of the electrodeposited copper foil has a Sku in a range from 1.5 to 6.5.

22. The electrodeposited copper foil as claimed in claim 18, wherein the deposited side of the electrodeposited copper foil exhibits the Vv in the range from 0.15 μm.sup.3/μm.sup.2 to 1.30 μm.sup.3/μm.sup.2.

23. The electrodeposited copper foil as claimed in claim 22, wherein the deposited side of the electrodeposited copper foil exhibits the Vv in the range from 0.17 μm.sup.3/μm.sup.2 to 1.11 μm.sup.3/μm.sup.2.

24. The electrodeposited copper foil as claimed in claim 22, wherein the deposited side of the electrodeposited copper foil exhibits a Vvc in a range from 0.14 μm.sup.3/μm.sup.2 to 1.15 μm.sup.3/μm.sup.2.

25. The electrodeposited copper foil as claimed in claim 22, wherein the deposited side of the electrodeposited copper foil exhibits a Vvv of at most 0.15 μm.sup.3/μm.sup.2.

26. The electrodeposited copper foil as claimed in claim 22, wherein the drum side of the electrodeposited copper foil exhibits a Vv in a range from 0.15 μm.sup.3/μm.sup.2 to 1.30 μm.sup.3/μm.sup.2.

27. The electrodeposited copper foil as claimed in claim 18, wherein the electrodeposited copper foil comprises a bare copper foil and a surface-treated layer disposed on the bare copper foil, and the drum side and the deposited side are located at outermost sides of the electrodeposited copper foil.

28. A current collector for a lithium-ion secondary battery, comprising the electrodeposited copper foil as claimed in claim 18.

29. An electrode for a lithium-ion secondary battery, comprising the current collector as claimed in claim 28 and an active substance coated on the current collector.

30. A lithium-ion secondary battery, comprising the electrode as claimed in claim 29.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 illustrates an areal material ratio plot drawn corresponding to the 3D structure of a surface.

(2) FIG. 2 is an areal material ratio plot illustrating the relationship of Vv, Vvc, and Vvv.

DETAILED DESCRIPTION OF THE DISCLOSURE

(3) Hereinafter, several examples are described to illustrate the embodiments of an electrodeposited copper foil, a current collector, an electrode, and a lithium-ion secondary battery of the instant disclosure, and several comparative examples are provided for comparison. From comparison of the following examples and comparative examples, one person skilled in the art can easily realize that the electrodeposited copper foil of each example used as a current collector can exhibit good performance because it has small difference value in residual stress between the deposited side and the drum side as well as properly controlled Vv or has properly controlled Sku and Vv. The good performance is that, for example, the active substance can adhere to the electrodeposited copper foil of each of the examples well and is used to prepare a negative electrode of the lithium-ion secondary battery to provide a good charge-discharge cycle life performance.

(4) It should be understood that the descriptions proposed herein are just for the purpose of illustrations only, not intended to limit the scope of the disclosure. Various modifications and variations could be made in order to practice or apply the instant disclosure without departing from the spirit and scope of the instant disclosure.

(5) Electrodeposited Copper Foil

Examples 1 to 5 (E1 to E5) and Comparative Examples 1 to 5 (C1 to C5): Electrodeposited Copper Foils

(6) The system for preparing electrodeposited copper foils comprises a metal cathode drum and an insoluble metal anode. The metal cathode drum is rotatable and has a polished surface. In this system, the insoluble metal anode approximately surrounds the lower half of the metal cathode drum. The cathode drum and the anode plate are spaced apart from each other and allow the copper electrolyte solution to be introduced through the feed pipe. The surface treatment device comprises an anti-tarnish treatment tank and electrode plates disposed therein. In addition, the system further comprises multiple guide rollers for transporting a bare copper foil, an anti-tarnish treated copper foil, and an end product, and finally the electrodeposited copper foil is wound on the guide roller. During the process that the electrodeposited copper foil is manufactured by using continuous electrodeposition, a copper electrolyte solution was fed between a titanium plate coated by iridium-containing components or iridium oxides as insoluble anode and titanium cathode drum and a direct current was applied between these two electrodes to allow the copper ions in the copper electrolyte solution continuously to be electrodeposited on the titanium cathode drum, and then the bare copper foil was detached and wound from the guide roller when a predetermined thickness was obtained. After the bare copper foil of the predetermined thickness was obtained, the bare copper foil was transported and immersed in the anti-tarnish treatment tank filled with an anti-tarnish solution by the guide roller to undergo an anti-tarnish treatment, and continuous electroplating was applied to the two sides of the bare copper foil by using the electrode plates, so as to form two surface-treated layers (i.e., anti-tarnish layers) respectively adhered onto the two sides of the bare copper foil.

(7) The conditions for manufacturing the electrodeposited copper foil are described as follows:

(8) (1) Composition of the Copper Electrolyte Solution:

(9) Copper sulfate (CuSO.sub.4.5H.sub.2O): about 280 grams per liter (g/L);

(10) Sulfuric acid with a concentration of 50 wt. %: about 80 g/L;

(11) Chloride ion (derived from HCl, purchased from RCI Labscan Ltd.): about 30 mg/L;

(12) Polyethylenimine (abbreviated as PEI, linear, which has a number average molecular weight (Mn)=5000, purchased from Sigma-Aldrich Company): about 4.0 mg/L to 17 mg/L; and

(13) Saccharin (1,1-dioxo-1,2-benzothiazol-3-one, purchased from Sigma-Aldrich Company): about 2.3 mg/L to 8.3 mg/L.

(14) (2) Parameters of Manufacturing the Bare Copper Foil:

(15) Temperature of the copper electrolyte solution: about 45° C.; and

(16) Current density: about 40 amperes per square decimeter (A/dm.sup.2).

(17) (3) Composition of the Anti-Tarnish Solution:

(18) Chromic acid (CrO.sub.3, purchased from Sigma-Aldrich Company): about 1.5 g/L.

(19) (4) Parameters for Anti-Tarnish Treatment:

(20) Temperature of the anti-tarnish solution: about 25° C.;

(21) Current density: about 0.5 A/dm.sup.2; and

(22) Processing time: about 2 seconds.

(23) Finally, the anti-tarnish treated copper foil was passed through an air knife to remove excess anti-tarnish layer and dry, and the electrodeposited copper foil having a thickness of about 6 micrometers (μm) was then wound on the guide roller.

(24) The differences among the manufacturing processes of the electrodeposited copper foils of Examples 1 to 5 and Comparative Examples 1 to 5 were the amounts of PEI and saccharin in the copper electrolyte solution, and the parameters were listed in Table 1 below.

(25) It should be noted that the aforesaid method for manufacturing the electrodeposited copper foil is illustrative only for the manner of obtaining the electrodeposited copper foil in the instant disclosure, but the electrodeposited copper foil in the instant disclosure, such as Examples 1 to 5, is not limited to that the electrodeposited copper foil needs to be manufactured by the aforesaid method.

(26) It should be noted that regardless of whether the bare copper foil is processed with surface treatment after the electrodeposition step, two outermost opposite sides of the electrodeposited copper foil used herein are defined by the relative positions between the bare copper foil and the titanium cathode drum and between the bare copper foil and the copper electrolyte solution during the electrodeposition step. In one of the embodiments, for the manufacturing process in which no surface treatment is performed after the electrodeposition step, the electrodeposited copper foil is the bare copper foil wound after the electrodeposition step, a side of the bare copper foil near the copper electrolyte solution is called “deposited side”, the other side of the bare copper foil near the titanium cathode drum is called “drum side”, and the drum side and the deposited side are located at the outermost sides of the electrodeposited copper foil. In another embodiment, for the manufacturing process in which a surface treatment is performed on a single side of the bare copper foil after the electrodeposition step, the electrodeposited copper foil comprises a bare copper foil and a surface-treated layer on the bare copper foil. Taking the surface treatment processed on a single side of the bare copper foil near the titanium cathode drum as an example for illustration, “drum side” is the outer side of the surface-treated layer which is opposite a side of the bare copper foil, and “deposited side” is the side of the bare copper foil near the copper electrolyte solution during the electrodeposition, and the deposited side and the drum side are located at the outermost sides of the electrodeposited copper foil. In further another embodiment, for the manufacturing process in which a surface treatment is performed on double sides of the bare copper foil after the electrodeposition step, the electrodeposited copper foil comprises a bare copper foil and two surface-treated layers on the bare copper foil. In this case, “deposited side” is the outer side of one of the surface-treated layers, and it is opposite to a side of the bare copper foil near the copper electrolyte solution during electrodeposition, and “drum side” is the outer side of another surface-treated layer, and it is opposite to the other side of the bare copper foil near the titanium cathode drum during electrodeposition. Herein, the deposited side and the drum side are both located at the outermost sides of the electrodeposited copper foil.

(27) TABLE-US-00001 TABLE 1 amounts of PEI and saccharin in the copper electrolyte solution of Examples 1 to 5 and Comparative Examples 1 to 5. Amount Amount of of PEI Saccharin (mg/L) (mg/L) Example 1 (E1) 13 5.3 Example 2 (E2) 9.5 5.3 Example 3 (E3) 9.5 6.8 Example 4 (E4) 9.5 3.8 Example 5 (E5) 6 5.3 Comparative Example 1 (C1) 14.5 5.3 Comparative Example 2 (C2) 9.5 8.3 Comparative Example 3 (C3) 9.5 2.3 Comparative Example 4 (C4) 4 5.3 Comparative Example 5 (C5) 17 3

Test Example 1: Surface Texture Analysis

(28) Surface texture of each of the electrodeposited copper foils of Examples 1 to 5 and Comparative Examples 1 to 5 was observed by a laser microscope, and the respective resulting image was captured. Moreover, the respective Vv, Vvc, Vvv, and Sku of the deposited side and the drum side of the electrodeposited copper foil of each of Examples 1 to 5 and Comparative Examples 1 to 5 were analyzed in accordance with the Standard Method of ISO 25178-2: 2012, and the results were listed in Tables 2 and 3.

(29) Herein, the instruments and condition of the surface texture analysis were described as follows:

(30) (1) Instruments:

(31) Laser microscope: LEXT OLS5000-SAF, manufactured by Olympus; and

(32) Objective lenses: MPLAPON-100×LEXT.

(33) (2) Analysis Conditions:

(34) Wavelength of light source: 405 nm;

(35) Objective lens magnification: 100× magnification;

(36) Optical zoom: 1.0×;

(37) Resolution: 1024 pixels×1024 pixels;

(38) Image area: 129 μm×129 μm;

(39) Condition: auto tilt removal;

(40) Filter: no filter;

(41) Temperature: 24±3° C.; and

(42) Relative humidity: 63±3%.

(43) Vv was the sum of the Vvc and Vvv, and its unit is μm.sup.3/μm.sup.2. The Vv was the void volume calculated with a material ratio of 10%, Vvv was the void volume calculated with a material ratio of 80%, and Vvc was a difference in the void volume between the material ratios of 10% and 80%.

(44) TABLE-US-00002 TABLE 2 Vvc, Vvv, and Vv of the electrodeposited copper foils of E1 to E5 and C1 to C5. Electrodeposited Copper Foil Vvc (μm.sup.3/μm.sup.2) Vvv (μm.sup.3/μm.sup.2) Vv (μm.sup.3/μm.sup.2) Characteristics Deposited Drum Deposited Drum Deposited Drum Target Side Side Side Side Side Side E1 0.16 0.59 0.01 0.03 0.17 0.62 E2 0.68 0.60 0.10 0.02 0.78 0.62 E3 0.21 0.59 0.10 0.03 0.31 0.62 E4 0.98 0.58 0.05 0.04 1.03 0.62 E5 1.07 0.59 0.04 0.03 1.11 0.62 C1 0.06 0.60 0.01 0.03 0.07 0.63 C2 0.08 0.60 0.01 0.02 0.09 0.62 C3 1.31 0.58 0.34 0.04 1.65 0.62 C4 1.27 0.59 0.21 0.04 1.48 0.63 C5 0.82 0.60 0.09 0.02 0.91 0.62

Test Example 2: Residual Stress

(45) In the instant test example, the residual stress of the deposited sides and the drum sides of the electrodeposited copper foils of Examples 1 to 5 and Comparative Examples 1 to 5 was measured by using an X-ray apparatus, and the results were listed in Table 3.

(46) Herein, the instruments and conditions of the residual stress analysis were described as follows:

(47) (1) Instruments:

(48) X-ray apparatus: Empyrean, manufactured by PANalytical;

(49) X-ray tube: copper target (λ=1.54184 Å);

(50) Mirror in the incident beam: X-ray hybrid mirror;

(51) Collimator in the diffracted beam: 0.27 parallel plate collimator; and

(52) Detector: proportional counter.

(53) (2) Conditions:

(54) Tube voltage: 45 kV;

(55) Tube current: 20 mA; and

(56) Grazing incidence angle: 1°.

(57) In Table 3 below, the difference value of the residual stress is directed to the absolute value of the difference in residual stress between the deposited side and the drum side (ΔRS). Because the residual stress of the deposited side of the electrodeposited copper foil is larger than that of the drum side, the difference value between both sides is just the same with the difference calculated by subtracting the residual stress of the drum side from the residual stress of the deposited side.

(58) Electrode

Examples 1A to 5A and Comparative Examples 1A to 5A: Negative Electrodes

(59) The foresaid electrodeposited copper foil of Examples 1 to 5 and Comparative Examples 1 to 5 could be used as current collectors. The two outermost opposite sides of each electrodeposited copper foil (i.e., the foresaid drum side and deposited side) could be further coated with a negative electrode slurry containing negative electrode active substances to prepare a negative electrode for a lithium-ion secondary battery.

(60) Specifically, the negative electrode could be substantially prepared by the following steps.

(61) Firstly, at a solid-liquid ratio of 100:60, 100 g of negative electrode active material was mixed with 60 g of a solvent (N-methylpyrrolidone (NMP)) to prepare the negative electrode slurry. Herein, the composition of the negative electrode active material (the content of each component was based on the entire negative electrode active material as 100 wt. %) was described as follows: 93.9 wt. % of negative electrode active substances (mesophase graphite powders, MGP);

(62) 1 wt. % of conductive additive (conductive carbon black powders, Super P®);

(63) 5 wt. % of a solvent binder (polyvinylidene fluoride, PVDF 6020); and

(64) 0.1 wt. % of oxalic acid.

(65) Next, the negative electrode slurry was coated on the deposited side and the drum side of the electrodeposited copper foil, then pressed and cut into a suitable size after the solvent evaporation, and a negative electrode was obtained. Accordingly, the negative electrodes of Examples 1A to 5A and Comparative Examples 1A to 5A could be respectively prepared by using the electrodeposited copper foils of Examples 1 to 5 and Comparative Examples 1 to 5 through the foresaid method.

(66) Lithium-ion Secondary Battery

Examples 1B to 5B and Comparative Examples 1B to 5B: Lithium-Ion Secondary Batteries

(67) The aforesaid negative electrodes of Examples 1A to 5A and Comparative Examples 1A to 5A could be further associated with the positive electrodes to respectively prepare the lithium-ion secondary batteries of Examples 1B to 5B and Comparative Examples 1B to 5B.

(68) Specifically, the positive electrode for the lithium-ion secondary battery could be substantially prepared by the following steps.

(69) First, at a solid-liquid ratio of 100:195, 100 g of the positive electrode active material was mixed with 195 g of NMP to prepare a positive electrode slurry. Herein, the composition of the positive electrode active material (the content of each component was based on the entire positive electrode active material as 100 wt. %) was described as follows:

(70) 89 wt. % of positive electrode active substance (LiCoO.sub.2);

(71) 5 wt. % of conductive additive (flaked graphite, KS 6);

(72) 1 wt. % of conductive additive (conductive carbon black powders, Super P®); and

(73) 5 wt. % of polyvinylidene fluoride (PVDF 1300).

(74) Next, the positive electrode slurry was coated on an aluminum foil, and after the solvent was evaporated, the positive electrodes and the negative electrodes were cut into a specific size, and then the positive electrodes and the negative electrodes were alternately stacked with a microporous separator (manufactured by Celgard Co., Ltd.) sandwiched there between, and then placed in a pressing mold filled with the electrolyte solution, and sealed to form a lithium-ion secondary battery. The lithium-ion secondary battery was in a size of 41 mm×34 mm×53 mm.

Test Example 3: Charge-Discharge Cycle Life Performance

(75) In the instant test example, the lithium-ion secondary batteries of the Examples 1B to 5B and Comparative Examples 1B to 5B, as the test samples, were subjected to charge-discharge cycling tests. The analysis conditions of the charge-discharge cycling test were as follows:

(76) Charging mode: constant current-constant voltage (CCCV);

(77) Discharging mode: constant current (CC);

(78) Charging voltage: 4.2 Volts (V);

(79) Charging current: 5 C;

(80) Discharging voltage: 2.8 V;

(81) Discharging current: 5 C;

(82) Test temperature: about 55° C.

(83) The charge-discharge cycle life of the lithium-ion secondary battery was defined as the number of charge and discharge cycles a lithium-ion secondary battery performed when the capacity dropped to 80% of its initial capacity after a series of cycles of charging and discharging. The results of the charge-discharge cycle life performance test of the lithium-ion secondary batteries of Examples 1B to 5B, which respectively comprise the electrodeposited copper foils of Examples 1 to 5 and Comparative Examples 1B to 5B, which respectively comprise the electrodeposited copper foils of Comparative Examples 1 to 5, were also shown in Table 3 below.

(84) According to the aforesaid manufacturing method, the differences between the lithium-ion secondary batteries of Examples 1B to 5B and those of Comparative Examples 1B to 5B only came from the use of the electrodeposited copper foils used in the negative electrodes, so the charge-discharge cycle life performance of the lithium-ion secondary battery was mainly attributed to the characteristics of each electrodeposited copper foil.

(85) TABLE-US-00003 TABLE 3 characteristics of the electrodeposited copper foils of E1 to E5 and C1 to C5 and their charge-discharge cycle lives when applied to the lithium-ion secondary batteries. Battery Charge- Discharge Electrodeposited Copper Foil Cycle Vv (μm.sup.3/μm.sup.2) Residual Stress (MPa) Sku Life Deposited Drum Deposited Drum Difference Deposited Drum (cycles) Target Side Side Side Side Value Side Side Overall E1 0.17 0.62 98.8 6 92.8 5.8 5.5  926 E2 0.78 0.62 54.4 −5.2 59.6 3.7 3.4  997 E3 0.31 0.62 82.5 41.8 40.7 4.2 4.2 1114 E4 1.03 0.62 80.5 −10.2 90.7 3.8 3.4  902 E5 1.11 0.62 −39.4 −46.8 7.4 1.7 1.8 1224 C1 0.07 0.63 102.5 −3.2 105.7 6.9 6.6  815 C2 0.09 0.62 86.2 38 48.2 3.8 3.8  803 C3 1.65 0.62 66.8 −36.1 102.9 3.5 3.6  658 C4 1.48 0.63 1.8 −10.6 12.4 0.9 0.9  681 C5 0.91 0.62 107.5 −2.4 109.9 8.2 7.8  788

(86) Discussion of Experimental Results

(87) As shown in Table 3, the electrodeposited copper foils of Examples 1 to 5 at least had two characteristics of the ΔRS at most 95 MPa and the Vv of the deposited side in the range from 0.15 μm.sup.3/μm.sup.2 to 1.35 μm.sup.3/μm.sup.2; in contrast, the electrodeposited copper foils of Comparative Examples 1 to 5 failed to have both of these two characteristics. Comparing the performance of the electrodeposited copper foils of Examples 1 to 5 and Comparative Examples 1 to 5 applied to the lithium-ion secondary batteries, the charge-discharge cycle lives of the lithium-ion secondary batteries of Examples 1B to 5B could all reach 900 times or more, while the charge-discharge cycle lives of the lithium-ion secondary batteries of Comparative Examples 1B to 5B were at most 815 times. These experimental results demonstrated that controlling the ΔRS and the Vv of the deposited side of the electrodeposited copper foil is actually beneficial to extend the useful lifetime and improve the performance of the lithium-ion secondary battery comprising the same.

(88) It is clear from the experimental results that both of the ΔRS and the Vv of the deposited side of the electrodeposited copper foil have significant influence on the charge-discharge cycle life of a lithium-ion secondary battery, and both are indispensable. That is, controlling the ΔRS and the Vv of the deposited side of the electrodeposited copper foil is actually beneficial to improve the performance of the lithium-ion secondary battery. In contrast, taking the electrodeposited copper foils of Comparative Examples 2 to 4 as examples, these electrodeposited copper foils had controlled the ΔRS but failed to suitably control the Vv of the deposited side, such that the performance of charge-discharge cycle lives of the lithium-ion secondary batteries of Comparative Examples 2B to 4B was unsatisfactory. Further, taking the electrodeposited copper foil of Comparative Example 5 as an example, the Vv of the deposited side was properly controlled but the ΔRS was not, such that the charge-discharge cycle life of the lithium-ion secondary battery of Comparative Example 5B could not reach 800 times.

(89) Further analyzing the experimental results of the above Table 3 from another way, the electrodeposited copper foils of Examples 1 to 5 at least had two characteristics of the Sku of the deposited side in the range from 1.5 to 6.5 as well as the Vv of the deposited side in the range from 0.15 μm.sup.3/μm.sup.2 to 1.35 μm.sup.3/μm.sup.2; in contrast, the electrodeposited copper foils of Comparative Examples 1 to 5 failed to have both of these two characteristics. From the comparison of the performance of the electrodeposited copper foils of Examples 1 to 5 and Comparative Examples 1 to 5 applied to the lithium-ion secondary batteries, the charge-discharge cycle lives of the lithium-ion secondary batteries of Examples 1B to 5B could all reach 900 times or more, while the charge-discharge cycle lives of the lithium-ion secondary batteries of Comparative Examples 1B to 5B were at most 815 times. It could be seen that controlling the Sku as well as the Vv of the deposited side of the electrodeposited copper foil is actually beneficial to extend the useful lifetime and improve the performance of the lithium-ion secondary battery comprising the same.

(90) Both of the Sku and the Vv of the deposited side of the electrodeposited copper foil have significant influence on the charge-discharge cycle life of a lithium-ion secondary battery, and both are indispensable. That is, controlling the Sku as well as the Vv of the deposited side of the electrodeposited copper foil in suitable ranges is actually beneficial to improve the performance of the lithium-ion secondary battery. For example, the electrodeposited copper foils of Comparative Examples 2 and 3 had controlled the Sku of the deposited side but failed to suitably control the Vv of the deposited side, and thus the performance of charge-discharge cycle lives of the lithium-ion secondary batteries of Comparative Examples 2B and 3B were unsatisfactory. Further, taking the electrodeposited copper foil of Comparative Example 5 as an example, the Vv of the deposited side was properly controlled but the Sku of the deposited side was not, such that the charge-discharge cycle life of the lithium-ion secondary battery of Comparative Example 5B could not reach 800 times.

(91) In addition to the foresaid two technical means for improving the electrodeposited copper foil (i.e., controlling both of the ΔRS and the Vv of the deposited side of the electrodeposited copper foil or controlling both of the Sku and the Vv of the deposited side of the electrodeposited copper foil), one person skilled in the art can control three characteristics of ΔRS, the Sku of the deposited side, and the Vv of the deposited side depending on conditions, so as to extend the charge-discharge cycle life of the lithium-ion secondary battery.

(92) Moreover, analyzing the ΔRS of the electrodeposited copper foils of Examples 1 to 5 and charge-discharge cycle lives of the lithium-ion secondary batteries comprising the same, the charge-discharge cycle life of the lithium-ion secondary battery could be further prolonged when the ΔRS was reduced as much as possible to 60 MPa or less, making the charge-discharge cycle lives of the lithium-ion secondary batteries of Examples 2B, 3B, and 5B reached 950 times or more. Likely, reducing the ΔRS as much as possible to 45 MPa or less allowed the lithium-ion secondary batteries of Examples 3B and 5B to have the charge-discharge cycle lives reaching 1100 times or more. Further, reducing the ΔRS of the electrodeposited copper foil as much as possible to 20 MPa or less allowed the lithium-ion secondary battery of Example 5B to have the charge-discharge cycle life reaching 1200 times or more.

(93) In summary, multiple technical means of controlling the characteristics of the electrodeposited copper foil are provided in the instant disclosure. For example, the technical means of controlling two characteristics of the ΔRS as well as the Vv of the deposited side of the electrodeposited copper foil, controlling two characteristics of the Sku of the deposited side as well as the Vv of the deposited side of the electrodeposited copper foil, and controlling three characteristics of the ΔRS as well as Sku of the deposited side and the Vv of the deposited side of the electrodeposited copper foil indeed significantly improve the quality of the electrodeposited copper foil, exerting the beneficial effects of extension of the charge-discharge cycle life when it is applied to the lithium-ion secondary battery as well as improving the useful lifetime and performance of the lithium-ion secondary battery, and all foresaid beneficial effects have been proved by the experimental results.