TW201602418A - Electrolytic copper foil and method for producing the same, and current collector for lithium secondary battery and secondary battery comprising the electrolytic copper foil - Google Patents

Abstract

An electrolytic copper foil according to an exemplary embodiment of the present disclosure corresponds to an electrolytic copper foil which is applied as a current collector for a lithium secondary battery, and the electrolytic copper foil has a modulus of rupture characteristics (f) in a range between 5.0 and 18.0 when annealed at 190 DEG C for 1 hour, in which the modulus of rupture characteristics (f) is defined as f={(C-B)/A}*1000, where A denotes the stress in the electrolytic copper foil at a point in time when the rupture of the electrolytic copper foil starts in a tensile test of the electrolytic copper foil, B denotes an elongation at the point in time when the rupture of the electrolytic copper foil starts, C denotes an elongation at a point in time when the rupture of the electrolytic copper foil ends, the point in time when the rupture of the electrolytic copper foil starts corresponds to a point in time when the stress increasing with the increasing elongation starts to reduce in the tensile test, and the point in time when the rupture of the electrolytic copper foil ends corresponds to a point in time when the electrolytic copper foil ruptures and is split into two or more pieces.

Description

Electrolytic copper foil and method for producing electrolytic copper foil, and current collector for lithium secondary battery, and secondary battery containing the same

The present invention relates to an electrolytic copper foil, a method for producing the electrolytic copper foil, a current collector for a lithium secondary battery, and a secondary battery including the electrolytic copper foil; more specifically, the related one is limited by the schedule An electrolytic copper foil characterized by a rupture modulus characteristic of the range to improve secondary battery characteristics; a method for producing an electrolytic copper foil; and a current collector for a lithium secondary battery and a lithium secondary battery containing the electrolytic copper foil.

The present application claims priority to Korean Patent Application No. 10-2014-0086970, filed on Jan. 10, 2014, the entire disclosure of which is hereby incorporated by reference.

Compared with other secondary batteries, lithium secondary batteries are widely used in various types of electronic devices, including personal computers and hand-held cameras, due to advantages such as higher energy density, higher operating voltage, and better preservation and life characteristics. , mobile phone, portable CD player, and personal digital assistant (PDA, Personal Digital Assistant).

Generally, a lithium secondary battery includes a positive electrode and a negative electrode with an electrolyte therebetween, a positive electrode active material of the positive electrode is bonded to a positive electrode current collector, and a negative electrode active material of the negative electrode is bonded to a negative electrode set. fluid.

In a lithium secondary battery, the negative electrode current collector is mainly made of an electrolytic copper foil, and the electrolytic copper foil needs to have good characteristics, so that when the secondary battery is charged and discharged, the repetition in the secondary battery is severe. Maintain secondary battery performance under conditions.

The characteristics required for the electrolytic copper foil may, for example, include the following characteristics: avoiding cracking generation under repeated severe conditions during charging and discharging; and suppressing accelerated decay rate of discharge capacity retention rate when charging and discharging are continued; Eliminates secondary battery performance degradation due to internal overheating and/or risk of accidents.

Electrolytic copper foil can have good characteristics by controlling various factors, but it is very difficult to find out which factors should be controlled to obtain the desired characteristics and the range to be controlled.

technical problem

The present invention has been devised in order to solve the aforementioned problems. Therefore, the present invention provides an electrolytic copper foil having appropriate characteristics for a lithium secondary battery having good performance by discovering and controlling an important factor for ensuring good performance of a lithium secondary battery.

Other objects and advantages of the present invention will become apparent from the following description and exemplary embodiments. In the meantime, it is to be understood that the objects and advantages of the present invention can be realized by the elements and combinations described in the appended claims. Technical solution

In order to achieve the foregoing objectives, the inventors have repeated research and experiments. Therefore, they have found that when an electrolytic copper foil having a suitably controlled modulus of rupture is used as a current collector of a lithium secondary battery, lithium is repeatedly charged and discharged despite repeated charging and discharging. The secondary battery can preferably maintain its characteristics.

Similarly, an electrolytic copper foil which can preferably maintain the characteristics of a lithium secondary battery according to an exemplary embodiment of the present invention conforms to an electrolytic copper foil used as a current collector of a lithium secondary battery, and when at 190 ^o C was annealed for 1 hour and the electrolytic copper foil had a modulus of rupture characteristic (f) ranging between 5.0 and 18.0.

In the present specification, the modulus of rupture (f) is defined as f = {(CB) / A} × 1000, where A represents the time when the fracture of the electrolytic copper foil is at the beginning of the tensile test of the electrolytic copper foil. The stress of the electrolytic copper foil at the point; B represents the elongation at the time when the fracture of the electrolytic copper foil starts; C represents the elongation at the time when the fracture of the electrolytic copper foil is finished, when the electrolytic copper foil The point in time at which the fracture starts is a point in time when the stress which increases as the elongation increases gradually starts to decrease in the tensile test, and the time point when the fracture of the electrolytic copper foil ends Corresponding to a point in time when the electrolytic copper foil is broken and divided into two or more segments.

The electrolytic copper foil has a protective layer formed on the surface, and the protective layer can be made of at least one selected from chromate, benzotriazole (BTA), and a decane coupling agent.

The electrolytic copper foil may have a thickness of less than 20 mm (micrometers).

The electrolytic copper foil may have a surface roughness (Rz) of more than 0 and less than or equal to 2 mm (micrometers).

The electrodeposited copper foil can be used to produce by a method in accordance with one exemplary embodiment of the present invention, particularly an electrolytic copper foil of the embodiment is generated, and when annealed at 190 ^o C for 1 hour, one for producing the present invention in accordance with an exemplary The method of electrolytic copper foil of a specific embodiment is in accordance with a method of producing an electrolytic copper foil having a modulus of rupture (f) ranging between 5.0 and 18.0, and comprising (a) an aqueous solution of copper sulfate prepared having a Copper concentration between 70 g/L (g/L) and 80 g/L (g/L), and sulfuric acid concentration between 80 g/L (g/L) and 110 g/L (g/L) And (b) between 40 ^o C and 45 ^o C and between 40 A/m ² (amps per square meter) and 70 A/m ² (amps per square meter) The current density is used as an electrolyte solution of copper sulfate, and copper (Cu) is electrodeposited on the drum surface of the electrolysis machine.

The method may comprise (c) forming a protective layer on the surface of the electrodeposited copper layer, the protective layer being at least one selected from the group consisting of chromate, benzotriazole (BTA), and a decane coupling agent. to make.

Meanwhile, the foregoing object can be attained by an electrode current collector for a lithium secondary battery made of the electrolytic copper foil, and a lithium secondary battery including an electrode current collector for a lithium secondary battery. Favorable effect

According to the present invention, under the severe severe conditions in the lithium secondary battery caused by the charging and discharging of the secondary battery, it is possible to reduce the capacity retention rate of the lithium secondary battery and/or to avoid a fire caused by internal overheating, This improves the performance of the secondary battery and/or ensures the safety when the secondary battery is used.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the scope of the patent application should not be construed as being limited to the general and dictionary sense, but based on the principle that the inventor is allowed to appropriately define the best interpretation term, based on the technical aspect consistent with the present invention. The meaning and concept of the explanation. Therefore, the descriptions of the present invention are intended to be illustrative only and not to limit the scope of the present invention; therefore, it is understood that other equivalents and modifications are possible without departing from the spirit and scope of the invention.

An electrolytic copper foil (10) according to an exemplary embodiment of the present invention will be described with reference to FIG.

1 is a cross-sectional view schematically illustrating an electrolytic copper foil in accordance with an exemplary embodiment of the present invention.

Referring to FIG. 1, an electrolytic copper foil (10) according to an exemplary embodiment of the present invention includes a copper layer (11); and a protective layer (12) selectively formed on the copper layer (11). s surface.

The electrolytic copper foil (10) is preferably used as a negative electrode current collector of a lithium secondary battery. That is, in the lithium secondary battery, it is preferable to use the electrolytic copper foil (10) as a negative electrode current collector for bonding the active material of the negative electrode. A foil made of aluminum (Al) is generally used as a positive electrode current collector for bonding the active material of the positive electrode.

Accordingly, the present invention is described by way of an example in which a current collecting system using a secondary battery of an electrolytic copper foil (10) according to an exemplary embodiment of the present invention corresponds to a negative electrode current collector.

When used as a current collector of a lithium secondary battery, the electrolytic copper foil (10) is subjected to force due to expansion of the electrode volume due to repeated charging and discharging, and in this case, even if the applied tensile strength is greater than that of the electrolytic copper foil (10) The breaking strength does break immediately.

That is, referring to Fig. 2, the electrolytic copper foil (10) is completely broken on the surface by a necking step, a void generating step, a gap growing and joining step, and a shear generating step.

The form of this fracture is called ductile fracture, and referring to FIG. 3, in the stress and elongation diagram representing the ductile fracture, the electrolytic copper foil (10) appears after the stress of the electrolytic copper foil reaches the breaking strength, with The tendency to gradually increase and gradually reduce the stress is gradually increased, and finally, the electrolytic copper foil (10) reaches a complete fracture.

After the change from the point at which the stress reaches the breaking strength to the point at which the electrolytic copper foil (10) reaches the complete fracture is divided by the value of the stress at the beginning of the fracture, it is a value of the breaking strength, The result obtained by multiplying the result by 1000 is called a modulus of rupture (f).

Referring to Figure 3, the modulus of rupture (f) can be expressed by the following equation: F = {(C-B) / A} × 1000

Wherein, in the tensile test of the electrolytic copper foil, A represents the stress of the electrolytic copper foil at the time point when the fracture of the electrolytic copper foil starts; and B represents the elongation at the time point when the fracture of the electrolytic copper foil starts; And C represents the elongation at the time point when the fracture of the electrolytic copper foil ends.

In the pressure and extension diagram of Fig. 3, the time point when the fracture of the electrolytic copper foil starts is a time at which the point P1 corresponding to the stress which gradually increases as the gradually increasing extension starts to decrease.

Meanwhile, in the pressure and extension relationship diagram of FIG. 3, the time point when the fracture of the electrolytic copper foil ends is a time corresponding to a point P2 at which the stress gradually decreased as the gradually increasing extension becomes zero, and is here. At the time point, the electrolytic copper foil is broken and divided into two or more segments.

In the case where the rupture modulus characteristic (f) has a too small value, when the electrolytic copper foil (10) is cracked by an external force, the electrolytic copper foil (10) is cracked in a short time, and therefore, when the electrolytic copper foil ( 10) When used as a current collector of a lithium secondary battery, the secondary battery does not easily maintain its efficiency under the severe internal conditions of the secondary battery caused by repeated charging and discharging.

In contrast, in the case where the modulus of rupture (f) has a large value, the unstable state in which the electrolytic copper foil (10) is subjected to an external force and cracked may last for a long time, and overheating may occur, so there may be The problem of deterioration of battery performance and the safety of the secondary battery cannot be ensured.

Therefore, the modulus of rupture (f) needs to be maintained in an appropriate range, preferably in the range between 5.0 and 18.0.

Characterized in modulus of rupture (f) in the electrolytic copper foil (10) for 1 hour in this state is measured 190 ^o C annealing, and annealing is performed at a high temperature is applied in the manufacture of a lithium secondary battery, which The electrolytic copper foil (10) is used as a current collector.

The modulus of rupture (f) can be controlled by changing the concentration of copper and sulfuric acid in the plating solution (electrolyte) for power supply plating in the manufacture of the electrolytic copper foil (10), and changing the selectivity to the plating. The concentration of various types of additives (inorganic additives, homogenizers, brighteners) of the liquid, changes in current density during plating, and changes in the temperature of the plating solution.

In this illustration, an electrolytic copper foil (10) made by using an electric ferrite includes a glossy surface (11a) having a low surface roughness (Rz) and a delustering surface (11b) having a surface opposite to The glossy surface (11a) has a high surface roughness (Rz) exhibiting a so-called mountain contour structure.

The surface roughness (Rz) of the glossy surface (11a) is determined based on the degree of surface treatment of the cylindrical drum (negative electrode) which precipitates copper, and the surface roughness (Rz) of the gloss-removing surface (11b) can be in the electrolytic copper foil. In the production of (10), it is controlled by changing the constituent material composition and current density of the plating solution during the electrolysis reaction.

When the surface roughness (Rz) of the de-glazed surface (11b) of the electrolytic copper foil (10) is too high, uniform contact between an active material and the electrolytic copper foil (10) is unsatisfactory, and lithium may be reduced. The discharge capacity retention rate of the secondary battery. Therefore, it is necessary to control the roughness (Rz) of the surface to an appropriate degree, and it is preferable to limit the surface roughness (Rz) of the delustered surface (11b) of the electrolytic copper foil (10) to about 2 mm (micrometer). ) or less.

The protective layer (12) is selectively formed on the surface of the copper layer (11) as a rustproof treatment of the electrolytic copper foil (10), and can be utilized from chromate, benzotriazole (BTA), and decane At least one of the selected agents is made. The protective layer (12) provides the rust-proof and heat-resistant characteristics of the electrolytic copper foil (10), and/or the adhesion-enhancing enhancement feature of the active material. Electrolytic copper foil production

An electrolytic copper foil according to an exemplary embodiment of the present invention is supplied with a plating solution (electrolyte) between a cylindrical negative electrode (rotated at a predetermined rate) and a positive electrode (disposed on the opposite side). Produced so that copper is electrodeposited and reduced precipitated on the surface of the rotating cylindrical negative electrode, wherein the aqueous solution of copper sulfate is used as a plating solution, and the electrolytic copper foil is about 20 mm (micrometer) or thinner (when electrolytic copper foil When the thickness is reduced, a large amount of current collector having an active material bonded thereto may be included in the secondary battery, which is advantageous for achieving high capacity, but in contrast, application of a thicker electrolytic copper foil to the secondary battery is not suitable for achieving high capacity, Preferably, the thickness of the electrolytic copper foil does not exceed 20 mm (micrometers). Each of the cases applied to the instance and the comparative instance is as follows:

Electrolytic copper foils produced by electroplating typically have opposite faces. That is, the electrolytic copper foil has a gloss side (S surface) which contacts a negative electrode drum; and a deluster side (M surface) which is disposed in a direction in which crystal grains are grown by precipitation. The surface roughness (Rz) of the S face and the M face of the electrolytic copper foil is in the range of less than or equal to about 2 mm (micrometer). (example)

As shown in Table 1, the electrolytic copper foil is made of a plating solution at a current density of between about 40 ASD and 70 ASD and a temperature range of about 40 ^o C and 45 ^o C. Copper concentration between 70 g/L (g/L) and 80 g/L (g/L) and sulfuric acid concentration between 80g/L (g/L) and 110g/L (g/L), and addition Various types of additives (inorganic metals, homogenizers, and brighteners) (however, the present invention is not necessarily limited to this range, and appropriate control can be employed within the scope of achieving the object of the present invention).

In the present specification, inorganic additives include Fe (iron), W (tungsten), Zn (zinc), and Mo (molybdenum), and the homogenizer includes gel, collagen, and polyethylene glycol (PEG, Polyethylene Glycol), and Brighteners include bis(3-sulfopropyl)disulfide (SPS), mercapto-propanesulfonic acid (MPS), 3-N, N-dimethylthiohydroformylpropane sulfonic acid (DPS).

For the purpose of protection (for example, rust prevention), the electrolytic copper foil produced by the above process conditions is chromed on the surface. (Comparative example)

As shown in Table 1, at a temperature of about 45 ^o C, under interposed between current density and between about 50 ASD 70 ASD, containing an electrolytic copper foil can be used to add various types of additives (additives are the same as in the example) of Plating of 70 g/L (g/L) and 80 g/L (g/L), and sulfuric acid concentration between 95 g/L (g/L) and 105 g/L (g/L) Made of liquid. Measurement of fracture modulus characteristics

The electrolytic copper foil according to the example of the present invention produced under the foregoing process conditions, and the electrolytic copper foil according to the comparative example, are measured to determine the modulus of rupture (f).

The modulus of rupture (f) of the electrolytic copper foil is measured using a Universal Testing Machine (UTM) according to a standard measurement method, and in this example, as in the case of UTM application, the calculated length is 50 mm ( The width is 12.7 mm (mm) and the test speed is 2 mm/min (mm/min).

First, annealing at 190 ^o C for 1 hour and then measuring the modulus of rupture of an electrolytic copper foil characterized in (F), such that under the circumstances, in the case of the electrodeposited copper foil produced according to Example / Comparative Example equivalent to complete a lithium secondary The condition inside the battery. That is, the lithium secondary battery can be maintained in a high temperature state in the process of the lithium secondary battery for a predetermined period of time, and in order to establish a similar situation, annealing is performed for the electrolytic copper foil.

The results of measuring the modulus of rupture (f) of the electrolytic copper foil subjected to the annealing process are shown in Table 2 below.

Referring to the results of Table 2, the electrolytic copper foils of Examples 1 to 6 exhibited a modulus of rupture characteristic ranging between 5.0 and 18.0. However, the electrolytic copper foils of Comparative Examples 1 to 3 exhibited a modulus of fracture characteristic of less than 5.0, and were compared. The electrolytic copper foil of Example 4 exhibited a modulus of rupture characteristic exceeding 18.0. Fabrication of a lithium secondary battery Manufacture of a positive electrode plate and a negative electrode plate (components mixed with a positive electrode material) Positive electrode material (LiCoO2): 85 wt% Conductive material (acetylene black): 8 wt% binder ( Polyvinyl fluoride): 7 wt% (ingredients mixed with a negative electrode material) Negative electrode material (graphite or carbon material): 95 wt% to 98 wt% Adhesive (polyvinyl fluoride): 2wt %~5 wt%

N-methylpyrrolidone is added to the above ingredients to prepare a slurry, which is then applied to a positive electrode current collector (made of aluminum foil) and a negative electrode after the solvent is evaporated, rolled, and cut into a predetermined size. Each surface of the current collector (made of electrolytic copper foil) is used to manufacture a positive electrode plate and a negative electrode tip. Lithium secondary component

a positive electrode plate, a separator plate (a hydrophilic porous polyethylene film), and a negative electrode plate are sequentially stacked and entangled, and after the electrolyte is poured/sealed, then placed in a container to complete a cylinder Type battery. The battery is a generally round cylindrical 18650 format.

In the present specification, the electrolytic solution is a solution in which 1 M LiPF ₆ is dissolved in a mixed solvent of ethylene carbonate (EC) and dimethyl carbonate (DMC) in a 1:1 volume ratio. Charging/discharging test

Among the lithium secondary batteries fabricated under the foregoing circumstances, lithium secondary batteries fabricated using a negative electrode current collector based on the electrolytic copper foils of Examples 1 to 6 as shown in Table 1 (secondary batteries according to examples of the present invention) ) Lithium secondary batteries according to Examples 1 to 6 are respectively referred to.

Also, based on the electrolytic copper foils according to Comparative Examples 1 to 4 as shown in Table 1, lithium secondary batteries fabricated using the negative electrode current collectors were respectively referred to as lithium secondary batteries according to Comparative Examples 1 to 4.

A charge/discharge test of 500 cycles was performed for the lithium secondary battery fabricated as described above. In this example, charging is performed at a charging voltage of 4.3 V (volts) and a charging current of 0.2 C (where the battery is fully charged after 5 hours), using constant current and constant voltage (CCCV, Constant Current & Constant Voltage). The mode is performed, and the discharge is performed in a constant current (CC) mode with a discharge voltage of 3.0 V (volts) and a discharge current of 0.5 C (where the battery is completely discharged within 2 hours).

After the repeated charging and discharging were completed, the lithium secondary battery was measured to determine the capacity retention ratio, which is the degree of heat generation, and whether or not cracking occurred in the electrolytic copper foil constituting the current collector, and the results thereof are shown in Table 3 below. (1~6: an example of the present invention; 1*~4*: comparative example)

Referring to Table 3 above, in the case where the modulus of rupture (f) of the electrolytic copper foil is in the range of 5.0 and 18.0, the lithium secondary battery (Examples 1 to 6) according to the example of the present invention is in 500 cycles. After the charging and discharging, there is no cracking in the current collector, and the high capacity maintenance ratio from about 84% to 93% based on the initial capacity is maintained (the secondary battery usually exhibits about 80 when performing 500 cycles of charging and discharging). The capacity retention ratio between % and 90%, and if the defect occurs in the secondary battery, the capacity retention rate is significantly lowered, which is significantly different from the normal value).

At the same time, the heat generation was measured by a charging/discharging test in a constant temperature chamber, and the lithium secondary batteries of Examples 1 to 6 exhibited a surface temperature ranging between 25 ^o C and 28 ^o C, which was in compliance with the normal temperature range (less than A temperature equal to or greater than about 30 ^o C is considered to be within the normal range, and even if a temporary temperature increase occurs, the surface temperature does not exceed 40 ^o C unless there is a particular abnormality.

In contrast, in the case where the piezoelectric modulus of the electrolytic copper foil (f) is less than 5.0 due to repeated charging and discharging, the lithium secondary battery according to the comparative example (Comparative Examples 1 to 3) undergoes cracking at the current collector, and Based on the initial capacity, a capacity retention ratio from about 24% to 42% is presented, resulting in a significant loss of secondary battery function. The splitting of the current generated by the current collector causes the electrode active material to peel off, and the cracking occurs directly affects the decrease in the capacity retention rate.

In spite of repeated charging and discharging, in the case where the modulus of rupture (f) of the electrolytic copper foil exceeds 18.0, the lithium secondary battery according to the comparative example (Comparative Example 4) can avoid cracking and maintain a relatively high capacity retention rate, but In the heat generated measurement, a temperature of about 41 ^o C is exhibited, which is generally considered to deviate from the normal range by 30 ^o C. An abnormal heat generation phenomenon may deteriorate the performance of the lithium secondary battery and increase the risk of an accident.

From the experimental results, it is clear that when the modulus of rupture (f) of the electrolytic copper foil (10) is maintained within a predetermined range (between 5.0 and 18.0), even in the case of severe charging due to repeated charging and discharging The performance of the secondary battery is maintained, and therefore, the safety of the secondary battery can be ensured.

The present invention is not limited to the specific embodiments and drawings described above, but the present invention is not limited thereto, and it should be understood that various changes and modifications may be made without departing from the invention. The scope of the patent application and its related spirit and scope.

10‧‧‧electrolytic copper foil
11‧‧‧ copper layer
11a‧‧‧Glossy face
11b‧‧‧Glossy face
12‧‧‧Protective layer

BRIEF DESCRIPTION OF THE DRAWINGS The present invention, together with a preferred embodiment of the present invention, is provided to provide a further understanding of the technical spirit of the present invention, and thus the present invention is not limited by the accompanying drawings.

1 is a cross-sectional view schematically illustrating an electrolytic copper foil in accordance with an exemplary embodiment of the present invention.

Fig. 2 is a view schematically showing a process for breaking an electrolytic copper foil during an electrolytic copper foil tensile test.

Figure 3 is a graph showing stress and elongation relationships illustrating the modulus of rupture.

10‧‧‧electrolytic copper foil

11‧‧‧ copper layer

11a‧‧‧Glossy face

11b‧‧‧Glossy face

12‧‧‧Protective layer

Claims (8)

An electrolytic copper foil as a lithium secondary battery using the current collector, wherein when annealed up to 190 ^o C in one hour, the electrolytic copper foil having a modulus of rupture characteristic (f) the range between 5.0 and 18.0, which The modulus of rupture characteristic (f) is defined as f = {(C - B) / A} × 1000, where A represents the time when the fracture of the electrolytic copper foil is at the beginning of the tensile test of the electrolytic copper foil The stress of the electrolytic copper foil; B represents an extension at a time point when the fracture of the electrolytic copper foil starts; C represents an extension at a time point when the fracture of the electrolytic copper foil ends; when the electrolytic copper foil is broken The point in time at the beginning corresponds to a point in time when the stress which increases as the gradually increasing extension starts to decrease in the tensile test; and the point in time when the fracture of the electrolytic copper foil ends is corresponding to A point in time when the electrolytic copper foil is broken and divided into two or more segments. The electrolytic copper foil according to claim 1, wherein the electrolytic copper foil has a protective layer formed on the surface, and the protective layer can utilize a chromate, a benzotriazole (BTA), and a decane coupling agent. At least one of the selected ones are made. The electrolytic copper foil according to claim 1, wherein the electrolytic copper foil has a thickness of less than 20 mm (micrometers). The electrolytic copper foil according to claim 1, wherein the electrolytic copper foil has a surface roughness (Rz) of more than 0 and less than or equal to 2 mm (micrometer). When one kind of annealed 190 ^o C for 1 hour, the method of the electrodeposited copper foil produced is between 5.0 and 18.0 scope modulus of rupture of the feature (f) is used, the method comprising: (a) preparing an aqueous solution of copper sulfate, which Has a copper concentration between 70 g/L (g/L) and 80 g/L (g/L) and between 80 g/L (g/L) and 110 g/L (g/L) Sulfuric acid concentration; and (b) at temperatures between 40 ^o C and 45 ^o C and between 40 A/m ² (amps per square meter) and 70 A/m ² (ampere per square meter) The current density between the two uses an aqueous solution of copper sulfate as an electrolyte to electrodeposite copper (Cu) on the drum surface of the electrolyzer. A method for producing an electrolytic copper foil according to claim 5, wherein the method comprises (c) forming a protective layer on a surface of the electrodeposited copper layer, the protective layer being usable from chromate, benzotriazine At least one of azole (BTA), and a decane coupling agent is selected. The electrode current collector for a lithium secondary battery made of an electrolytic copper foil according to any one of claims 1 to 4. A lithium secondary battery containing an electrode current collector for one of lithium secondary batteries as described in claim 7.