CN104805478A - Electrolytic copper foil for negative electrode current collector and manufacturing method thereof - Google Patents

Abstract

The invention discloses an electrolytic copper foil for a negative electrode collector and a manufacturing method thereof, wherein the manufacturing method comprises the following steps: firstly, an electrolytic copper foil is formed on the surface of a cathode by an electrolytic method of a copper sulfate electrolyte, and then the electrolytic copper foil is stripped from the surface of the cathode, particularly, the copper sulfate electrolyte comprises a polyether compound, a sulfonate of an active organic sulfide and chlorine. The copper foil manufactured by the method can be applied to the field of secondary batteries, and is not easy to deform or break in the charging and discharging processes. The copper foil produced by the method has good elastic properties and toughness, and is not easy to deform or break even if the battery is repeatedly charged and discharged, so that the charge and discharge cycle characteristics can be remarkably improved.

Description

Electrolytic copper foil for negative electrode current collector and manufacturing method thereof

technical field

The invention relates to an electrolytic copper foil, in particular to an electrolytic copper foil for a negative electrode collector with high elastic performance and high toughness applied to a lithium secondary battery and a manufacturing method thereof.

Background technique

By the way, lithium secondary batteries are mostly used in portable electronic products such as smart phones, tablet computers, music players, digital cameras, etc. as their power sources. The characteristics of lithium secondary batteries are also relatively required to be improved, and among the many characteristics of lithium secondary batteries, electric capacity, charging speed and cycle times of charging and discharging are particularly important.

For the purpose of high capacity, the industry is currently actively developing negative electrode materials with a charge-discharge capacity that greatly exceeds the theoretical capacity of carbon materials, as negative electrode active materials for lithium secondary batteries, which contain silicon (Si) and tin ( Metal materials such as Sn) that can be alloyed with lithium (Li) have attracted more attention.

However, in the electrodes of such lithium-ion secondary batteries, the active material (such as silicon) expands about 4 times in volume due to absorbing and storing lithium ions during charging, and shrinks when releasing lithium ions during discharging. Repeated charging and discharging in this way will cause the volume of the electroactive material layer to expand and shrink accordingly, causing the active material to be micronized and peeled off from the current collector. In addition, since the electroactive material layer is closely attached to the current collector, the volume expansion and contraction of the electroactive material layer will cause great stress on the current collector and cause the current collector to wrinkle. The copper foil of the electric body is deformed, broken and other problems.

In addition, when the traditional lithium secondary battery achieves the goal of fast charging, it often encounters problems such as a decrease in capacity, an early decrease in capacity during charge and discharge cycles, and a decrease in battery performance. The reasons for the degradation of battery performance, on the one hand, are considered to be related to the adhesion between the copper foil and the negative electrode material or surface impurities; on the other hand, lithium ions are acquired to the negative electrode material when the lithium secondary battery is charged. Lithium ions are released during discharge. However, the negative electrode material will expand when it acquires lithium ions and will return to its original shape when it is released. The load of repeated charge and discharge of the battery may cause deformation on the copper foil, and in severe cases, it may even break; in this way, If the copper foil is deformed, it will be peeled off from the negative electrode material, which will reduce the cycle charge and discharge efficiency of the battery, and if the copper foil is broken, the battery performance will not be able to maintain long-term stability.

Therefore, in view of the fact that the copper foil for the negative electrode current collector of the traditional lithium secondary battery has its necessity of improvement, the present inventor has been engaged in creative design and professional manufacturing experience in related fields for many years, and actively aims at negative electrode current collection. The present invention was finally developed under the careful consideration of various conditions after carrying out improvement research on the characteristics of copper foil for body use.

Contents of the invention

The main purpose of the present invention is to provide an electrolytic copper foil for negative electrode current collector with high elastic properties and high toughness and its manufacturing method, the copper foil obtained by this method has good elastic properties and toughness It is not easy to deform or break during charging and discharging of the battery, so the cycle characteristics of charging and discharging can be significantly improved.

In order to achieve the above object, the present invention adopts the following technical solutions: a method for manufacturing an electrolytic copper foil for negative electrode current collectors with high elastic performance and high toughness, comprising the following steps: The surface of the cathode is precipitated to form an electrolytic copper foil, wherein the copper sulfate electrolyte contains polyether compound, sulfonate of active organic sulfide and chlorine; then, the electrolytic copper foil is peeled off from the cathode.

In an embodiment of the present invention, the concentration of sulfuric acid in the copper sulfate electrolyte is 70g/L-100g/L, and the concentration of copper is 80g/L-100g/L.

In one embodiment of the present invention, the polyether compound concentration in the copper sulfate electrolyte is 50 ppm-250 ppm, the sulfonate concentration of active organic sulfide is 0.3 ppm-10 ppm, and the chlorine concentration is 10 ppm-50 ppm.

In an embodiment of the present invention, the electrolysis of the copper sulfate electrolyte is carried out at an electrolyte temperature of 58°C-62°C and a current density of 50A/dm ² -80A/dm ² .

In an embodiment of the present invention, after the step of stripping the electrolytic copper foil from the cathode, it further includes the step of forming a chromium resist on at least one surface of the electrolytic copper foil by dipping or electrolysis. oxide layer.

According to the above manufacturing method, the present invention further proposes an electrolytic copper foil for negative electrode current collector with high elastic energy and high toughness, which is characterized in that the elastic energy is 60-100KJ/M ² , and the toughness is at least greater than 1500KJ/M ² .

From the viewpoint of mechanical properties, the tensile strength of the electrodeposited copper foil for negative electrode current collector with high elastic performance and high toughness of the present invention is at least greater than 300N/mm ² under normal conditions, and the elongation is at least greater than 10%.

Furthermore, in the electrolytic copper foil for negative electrode current collector having high elastic performance and high toughness of the present invention, the thickness is preferably 8 μm to 35 μm and has at least one surface, and the roughness Rz of the surface is 1.0 μm to 2.5 μm .

In addition, in the electrolytic copper foil for negative electrode current collector with high elastic performance and high toughness of the present invention, a chromium anti-oxidation layer is further formed on the surface.

Moreover, in the electrolytic copper foil for negative electrode current collector with high elastic performance and high toughness of the present invention, the chromium anti-oxidation layer is a chromate film.

The present invention has at least the following beneficial effects:

The manufacturing method of the present invention uses a copper sulfate electrolyte solution containing special additives (including polyether compounds, sulfonates of active organic sulfides, and chlorine) for electrolytic plating, and the electrolytic copper foil formed by precipitation can have high elastic properties and high toughness , wherein the characteristics of high elastic properties can improve the defect that copper foil is prone to deformation, and the characteristics of high toughness can improve another defect that copper foil is prone to fracture. Therefore, the present invention is applied to the negative electrode collector of lithium secondary battery In this way, the excellent effect of maintaining the charge-discharge cycle characteristics of the lithium secondary battery can be achieved.

The above descriptions about the content of the present invention and the following descriptions of the embodiments are used to illustrate and explain the principles of the present invention, and provide further explanations of the patent scope of the present invention.

Description of drawings

FIG. 1 is a scanning electron micrograph of the deposition surface of the electrodeposited copper foil of Comparative Example 2. FIG.

2 is a scanning electron micrograph of the deposition surface of the electrodeposited copper foil for negative electrode current collector having high elastic performance and high toughness of Example 1. FIG.

FIG. 3 is a stress-strain curve diagram obtained through a tensile test of the electrolytic copper foil for negative electrode current collector with high elastic performance and high toughness in Example 1. FIG.

FIG. 4 is a stress-strain curve diagram obtained through a tensile test of the electrolytic copper foil for negative electrode current collector with high elastic performance and high toughness in Example 2. FIG.

FIG. 5 is a stress-strain curve diagram obtained through a tensile test of the electrolytic copper foil for negative electrode current collector with high elastic performance and high toughness in Example 3. FIG.

FIG. 6 is a stress-strain curve diagram obtained through a tensile test of the electrolytic copper foil for negative electrode current collector with high elastic performance and high toughness in Example 4. FIG.

FIG. 7 is a stress-strain curve diagram obtained through a tensile test of the electrolytic copper foil for negative electrode current collector with high elastic performance and high toughness in Example 5. FIG.

FIG. 8 is a stress-strain curve diagram of the electrolytic copper foil of Comparative Example 1 obtained through a tensile test.

FIG. 9 is a stress-strain curve diagram of the electrolytic copper foil of Comparative Example 2 obtained through a tensile test.

Detailed ways

The present invention proposes a kind of electrolytic copper foil that can be used as the conductor that collects electrons and its manufacturing method when battery discharging chemical reaction takes place for lithium-ion secondary battery, and the present invention finds that if electrolytic plating is carried out with the copper sulfate electrolyte solution containing special additive, The formed electrolytic copper foil can have good elasticity and toughness, and the application of the electrolytic copper foil to the negative electrode collector of the lithium secondary battery can prevent deformation or fracture due to repeated charging and discharging, so that the lithium secondary battery can be charged Discharge cycle characteristics can be significantly improved.

The characteristics of the present invention and the technical means adopted in the present invention will be described in detail below. Those of ordinary skill in the art can easily understand the advantages and effects of the present invention from the contents of this description, and perform various tasks without departing from the spirit of the present invention. Modifications and alterations to practice or apply the methods of the invention.

The present invention proposes a method for manufacturing an electrolytic copper foil for negative electrode current collectors with high elastic performance and high toughness, which includes first performing the first step: depositing an electrolytic copper on the surface of a cathode by electrolysis of copper sulfate electrolyte foil, wherein the copper sulfate electrolyte contains polyether compounds, sulfonates of active organic sulfides, and chlorine; and then performs a second step of peeling off the electrolytic copper foil from the cathode.

In the first step, the manufacture of electrolytic copper foil adopts a continuous production method. Specifically, copper sulfate electrolyte is pumped between the rotating cathode and the opposite anode (such as lead anode or ruthenium oxide anode), and then used The electrolytic reaction precipitates copper on the surface of the cathode, and the deposited electrolytic copper foil is continuously stripped from the rotating cathode and coiled.

In this embodiment, the manufacture of electrolytic copper foil includes three procedures of copper wire dissolution, manufacture of electrolyte solution and electrolytic copper foil. First, put the copper wire into the dissolving tank with sulfuric acid and blow in air to dissolve it to form a copper sulfate solution; then, the copper sulfate solution is passed through a transfer pump through a filter and then poured into an adjustment tank, and at the same time, special additives are added The concentration is analyzed and adjusted to form an electrolyte; finally, the electrolyte is put into the foil machine after the temperature is adjusted through a heat exchanger to carry out the electrolysis process, and the electrolyte is circulated and pumped back to the dissolution tank after the electrolysis is completed.

It is worth noting that the special additives selected in the present invention include polyether compounds, sulfonates of active organic sulfides, and chlorine; in order to impart excellent elastic properties and toughness to electrolytic copper foil, the copper sulfate electrolyte The concentration of sulfuric acid is preferably between 70g/L and 100g/L, the concentration of copper is preferably between 80g/L and 100g/L, the concentration of polyether compounds is preferably between 50ppm and 250ppm, and the sulfur of active organic sulfide The salt concentration is preferably between 0.3 ppm and 10 ppm, and the chlorine concentration is preferably between 10 ppm and 50 ppm. In practical applications, the polyether compound can be but not limited to polyethylene glycol (PEG), polypropylene glycol (PPG), etc., and the sulfonate of active organic sulfide can be but not limited to 3-mercapto-1-propanesulfonic acid Sodium salt, bis(3-sulfopropyl) disulfide, etc.

Furthermore, when using the above-mentioned copper sulfate electrolyte for electrolytic plating, the preferred liquid temperature is set between 58°C and 62°C, and the preferred current density is set between 50A/dm ² and 80A/dm ² , and this EXAMPLES Electrolysis is performed using a cathode with a surface roughness adjusted in a desired range and an insoluble anode. Thus, the elastic property of the formed electrolytic copper foil is 60-100KJ/M ² , and the toughness is at least greater than 1500KJ/M ² .

It is worth noting that if the elastic energy is lower than 60KJ/M ² , the current collector cannot maintain elastic deformation during rapid charging and discharging, resulting in permanent deformation and wrinkles, which will cause the negative electrode material to peel off or the performance of the battery will decrease; if the elastic energy is high If it is less than 100KJ/M ² , the material is too rigid, which is not conducive to processing. It is further worth noting that the characteristics of high elastic properties can improve the defect that the copper foil is prone to deformation, and the characteristics of high toughness can improve the defect that the copper foil is prone to fracture.

Furthermore, the electrolytic copper foil is an ultra-thin copper foil, the thickness of which is between 8 μm and 35 μm, and has a glossy surface in contact with the surface of the rotating cathode and another surface opposite to the glossy surface, Among them, the surface is smooth (precipitation surface) because its roughness (Surface Roughness; refers to the ten-point average roughness value Rz) is between 1.0 μm and 2.5 μm; The difference of the foil is that the other surface of the glossy surface usually has many uneven mountain-shaped structures due to the difference in the crystallization and growth rate of the electrolytic copper. This surface is also called a rough surface.

In addition, by optimizing the electrolytic conditions, the electrolytic copper foil can have excellent mechanical properties such as the tensile strength at least greater than 300N/mm ² and the elongation at least greater than 10% under normal conditions. This mechanical property is not only sufficient It is used for bending of flexible printed wiring boards and is also sufficiently suitable for constituting negative electrode current collectors of lithium secondary batteries subject to expansion and compression behavior.

In the second step, the electrolytic copper foil is peeled from the surface of the rotating cathode and rolled into a raw foil roll, and then inspected and cut into final finished products for packaging and storage and transportation. In this embodiment, the wavy pattern of the cut edge is less than 2 per centimeter, and the amplitude does not exceed 0.5 cm, and the cut ear material is further recycled to the dissolution tank for reuse.

Preferably, in order to improve the heat resistance and weather resistance (oxidation resistance) of the electrolytic copper foil, the present invention can further use impregnation or electroplating to form an alloy plating layer and a chromate layer on the precipitation surface or both sides of the electrolytic copper foil. And/or silane coupling layer.

[Example]

Please refer to Table 1 and Table 2 to show the embodiments of the present invention, but it is not intended to limit the present invention to the following embodiments. The following will be accompanied by experimental data such as elastic properties, toughness and others such as tensile strength, elongation, 0.2% offset yield strength, elastic modulus, etc., to prove the characteristics and effects of the present invention. As shown in Table 1, Examples 1-5 used experimental samples of copper sulfate electrolytes containing additives in different proportions, while Comparative Examples 1-2 used control samples of copper sulfate electrolytes containing additives in different formulations.

(Example 1)

In the electrolytic cell, introduce copper concentration: 88g/L, sulfuric acid concentration: 95g/L, polyethylene glycol concentration: 60mg/L, bis(3-sulfopropyl) disulfide concentration: 2mg/L, chloride ion concentration : 40mg/L to make copper sulfate electrolyte. And, adjust to electrolyte temperature: 60°C, current density: 60A/dm ² , copper is deposited on the surface of the rotating cathode, and then the copper deposited on the surface of the rotating cathode is stripped to continuously produce electrolytic copper with a thickness of 18 μm foil.

The SEM photograph of the deposited surface of the electrodeposited copper foil of Example 1 is shown in FIG. 2 , and it can be seen that the electrodeposited copper foil for negative electrode current collector having high elastic properties and high toughness of the present invention has a smooth and uniform surface. Furthermore, the tensile strength test was carried out based on IPC-TM-650, and the elastic properties, toughness, tensile strength, and elongation were evaluated. The results are shown in Table 2, and the stress-strain curve was prepared, as shown in Figure 3.

(Example 2)

In the electrolytic cell, introduce copper concentration: 88g/L, sulfuric acid concentration: 95g/L, polyethylene glycol concentration: 80mg/L, bis(3-sulfopropyl) disulfide concentration: 3mg/L, chloride ion concentration : 35mg/L to make copper sulfate electrolyte. And, adjust to electrolyte temperature: 60°C, current density: 60A/dm ² , copper is deposited on the surface of the rotating cathode, and then the copper deposited on the surface of the rotating cathode is stripped to continuously produce electrolytic copper with a thickness of 12 μm foil.

For the electrolytic copper foil of Example 2, perform a tensile strength test based on IPC-TM-650, and evaluate the elastic properties, toughness, tensile strength, and elongation. The results are shown in Table 2, and a stress-strain curve is made, as shown in Figure 4 Show.

(Example 3)

In the electrolytic cell, introduce copper concentration: 88g/L, sulfuric acid concentration: 95g/L, polyethylene glycol concentration: 200mg/L, bis(3-sulfopropyl) disulfide concentration: 6mg/L, chloride ion concentration : 40mg/L to make copper sulfate electrolyte. And, adjust to electrolyte temperature: 60°C, current density: 58A/dm ² , copper is deposited on the surface of the rotating cathode, and then the copper deposited on the surface of the rotating cathode is stripped to continuously produce electrolytic copper with a thickness of 18 μm foil.

For the electrolytic copper foil of Example 3, perform a tensile strength test based on IPC-TM-650, and evaluate the elastic properties, toughness, tensile strength, and elongation. The results are shown in Table 2, and a stress-strain curve is made, as shown in Figure 5 Show.

(Example 4)

In the electrolytic cell, introduce copper concentration: 88g/L, sulfuric acid concentration: 95g/L, polyethylene glycol concentration: 250mg/L, bis(3-sulfopropyl) disulfide concentration: 5mg/L, chloride ion concentration : 35mg/L to make copper sulfate electrolyte. And, adjust to electrolyte temperature: 60°C, current density: 58A/dm ² , copper is deposited on the surface of the rotating cathode, and then the copper deposited on the surface of the rotating cathode is stripped to continuously produce electrolytic copper with a thickness of 18 μm foil.

For the electrolytic copper foil of Example 4, perform a tensile strength test based on IPC-TM-650, and evaluate the elastic properties, toughness, tensile strength, and elongation. The results are shown in Table 2, and a stress-strain curve is made, as shown in Figure 6 Show.

(Example 5)

In the electrolytic cell, introduce copper concentration: 88g/L, sulfuric acid concentration: 95g/L, polyethylene glycol concentration: 150mg/L, bis(3-sulfopropyl) disulfide concentration: 3.5mg/L, chloride ion Concentration: 40mg/L to make copper sulfate electrolyte. And, adjust to electrolyte temperature: 60°C, current density: 60A/dm ² , copper is deposited on the surface of the rotating cathode, and then the copper deposited on the surface of the rotating cathode is stripped to continuously produce electrolytic copper with a thickness of 12 μm foil.

For the electrolytic copper foil of Example 4, perform a tensile strength test based on IPC-TM-650, and evaluate the elastic properties, toughness, tensile strength, and elongation. The results are shown in Table 2, and a stress-strain curve is made, as shown in Figure 7 Show.

(comparative example 1)

In the electrolytic cell, introduce copper concentration: 88g/L, sulfuric acid concentration: 95g/L, polyethylene glycol concentration: 150mg/L, 3-mercapto-1-propanesulfonic acid sodium salt concentration: 7mg/L, polyethylene sub Amine concentration: 0.5mg/L, chloride ion concentration: 40mg/L to make copper sulfate electrolyte. And, adjust to electrolyte temperature: 60°C, current density: 58A/dm ² , copper is deposited on the surface of the rotating cathode, and then the copper deposited on the surface of the rotating cathode is stripped to continuously produce electrolytic copper with a thickness of 12 μm foil.

For the electrolytic copper foil of Comparative Example 1, the tensile strength test was carried out based on IPC-TM-650, and the elastic properties, toughness, tensile strength, and elongation were evaluated. The results are shown in Table 2, and the stress-strain curve was prepared, as shown in Figure 8 Show.

(comparative example 2)

In the electrolytic cell, introduce copper concentration: 88g/L, sulfuric acid concentration: 95g/L, hydroxyethyl cellulose concentration: 5mg/L, gelatin concentration: 0.5mg/L, chloride ion concentration: 35mg/L to make sulfuric acid copper electrolyte. And, adjust to electrolyte temperature: 70°C, current density: 60A/dm ² , copper is deposited on the surface of the rotating cathode, and then the copper deposited on the surface of the rotating cathode is stripped to continuously produce electrolytic copper with a thickness of 12 μm foil.

For the electrodeposited copper foil of Comparative Example 2, the SEM photo of the deposition surface is shown in Figure 1. It can be seen that the deposition surface of the copper foil of Comparative Example 1 has uneven textures, and the light scattered in the concave and convex parts will make the glossiness [ Gs(60°)] becomes smaller, so that the surface roughness (Rzjis) becomes larger. Conduct tensile strength test based on IPC-TM-650, evaluate elastic properties, toughness, tensile strength, and elongation, the results are shown in Table 2, and a stress-strain curve is made, as shown in Figure 9.

Table I

Table II

In Table 2, the so-called tensile strength represents the value of the case where the tensile strength test based on IPC-TM-650 is carried out, and the so-called elongation represents the deformation amount when the test piece is broken in the above test. In addition, the so-called stress-strain curve represents a graph of strain and corresponding stress, which can be obtained using data obtained in a material test in which a certain load is applied to a material and the stress and strain are simultaneously and continuously measured at a certain speed. make.

It can be found from Table 2 that the present invention uses the copper sulfate electrolyte solution containing special additives for electrolytic plating (Examples 1-5), compared with the electrolytic copper foil obtained by using different compositions of electrolyte solutions (Comparative Examples 1-2), It can have more appropriate elastic properties and higher toughness; with the appropriate ratio of each component in the selected additives, the electrolytic copper foil also has other excellent properties, such as high elongation (High Temperature Elongation), extremely low roughness (Very Low Profile), very excellent tensile strength and good processing characteristics, etc., suitable for anode materials used in secondary batteries.

In summary, compared with traditional electrolysis technology and copper foil for negative electrode collectors of lithium secondary batteries, the manufacturing method of the present invention utilizes sulfonic acid containing special proportioning additives (comprising polyether compounds, active organic sulfides) Salt and chlorine) copper sulfate electrolyte for electrolytic plating, the obtained electrolytic copper foil can have high elasticity and high toughness, so the negative electrode collector used in lithium secondary batteries can prevent repeated charge and discharge due to volume The deformation or fracture caused by repeated expansion and contraction can achieve the excellent effect of maintaining the charge-discharge cycle characteristics of the lithium secondary battery.

Furthermore, the electrolytic copper foil also has excellent mechanical properties such as a tensile strength of at least greater than 300N/ ^m2 and an elongation rate of at least greater than 10% under normal conditions, which are not only sufficient for flexible printed circuit boards Bending is also sufficiently suitable for a negative electrode current collector constituting a lithium secondary battery subjected to expansion and compression behavior.

Although the embodiments of the present invention are disclosed above, they are not intended to limit the present invention. Those skilled in the art of the present invention may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be defined by the scope of the appended patent application.

Claims (10)

1. An electrolytic copper foil for negative electrode current collector, characterized in that the elastic energy of the electrolytic copper foil is at least greater than 60KJ/m ² , and the toughness of the electrolytic copper foil is at least greater than 1500KJ/m ² . 2 . The electrolytic copper foil for negative electrode current collector according to claim 1 , wherein the tensile strength of the electrolytic copper foil under normal conditions is at least greater than 300 N/mm ² , and the elongation is at least greater than 10%. 3. The electrolytic copper foil for negative electrode current collector according to claim 2, wherein the thickness of the electrolytic copper foil is 8 μm to 35 μm and has at least one surface, and the roughness Rz of the surface is 1.0 μm to 1.0 μm. 2.5 μm. 4 . The electrolytic copper foil for negative electrode current collector according to claim 3 , wherein the electrolytic copper foil further comprises a chromium anti-oxidation layer, and the chromium anti-oxidation layer is formed on the surface. 5 . The electrolytic copper foil for negative electrode current collector according to claim 4 , wherein the chromium anti-oxidation layer is a chromate film. 6. A manufacturing method of electrolytic copper foil for negative electrode current collector, characterized in that, said manufacturing method comprises the following steps: An electrolytic copper foil is deposited on the surface of a cathode by electrolysis of copper sulfate electrolyte, wherein the copper sulfate electrolyte contains polyether compound, sulfonate of active organic sulfide, and chlorine; and The electrolytic copper foil was peeled off from the cathode. 7. The manufacturing method of electrolytic copper foil for negative electrode current collector according to claim 6, characterized in that, the sulfuric acid concentration in the copper sulfate electrolyte is 70g/L～100g/L, and the copper concentration is 80g/L ~100g/L. 8. The manufacturing method of electrolytic copper foil for negative electrode current collector according to claim 7, characterized in that, the concentration of the polyether compound in the copper sulfate electrolyte is 50ppm～250ppm, and the sulfonic acid of active organic sulfide The concentration of salt is 0.3 ppm to 10 ppm, and the concentration of chlorine is 10 ppm to 50 ppm. 9. The manufacturing method of electrolytic copper foil for negative electrode current collector according to claim 6, characterized in that, the electrolysis method of the copper sulfate electrolyte is at an electrolyte temperature of 58°C to 62°C, using 50A/dm ² ~ 80A/dm ² of the current density for electrolysis. 10. The manufacturing method of electrolytic copper foil for negative electrode current collector according to claim 6, characterized in that, after the step of peeling off the electrolytic copper foil from the cathode, further comprising: dipping or electrolytic method A step of forming a chromium anti-oxidation layer on at least one surface of the electrolytic copper foil.