Electrolytic copper foil for improving wrinkles, manufacturing method thereof, electrode comprising electrolytic copper foil, and battery

Abstract

The invention discloses an electrolytic copper foil for improving wrinkles and a preparation method thereof, and an electrode and a battery comprising the electrolytic copper foil, and the preparation method comprises the following steps: (1) preparing an additive: mixing sodium dimethyl dithiocarbamate, sodium 3-mercaptopropane sulfonate, thiourea and polyethylene glycol, adding water, and uniformly stirring for 1-3 minutes, the molecular weight of the polyethylene glycol being 1000-4000; (2) adding an additive into the electrolyte: adding the additive into the electrolyte at a certain speed; and (3) copper foil electrolysis: electrolyzing the electrolyte to form a raw foil. The additive has the beneficial effects that the additive can reduce the tensile strength difference between the initial state and the stable state of the copper foil, so that the phenomenon of seersucker is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytic copper foil for lithium ion batteries, and in particular to an electrolytic copper foil capable of improving wrinkles and a preparation method thereof, and an electrode and a battery comprising the electrolytic copper foil. Background Art

[0002] Lithium battery copper foil is one of the key materials used in lithium-ion batteries, and it plays an important role in battery manufacturing. Due to its excellent properties such as high conductivity, good mechanical properties and stability, lithium battery copper foil has become an ideal choice for manufacturing high-performance and high-safety lithium-ion batteries. With the substantial increase in the demand for lithium battery copper foil, the production capacity of copper foil companies has also expanded. However, the lithium battery copper foil produced will have a self-annealing effect, and it will take a long time to reach a stable state. In the process of microscopic grain changes, it is easy to produce uneven size changes, resulting in macroscopic copper foil wrinkles. This wrinkle is wavy after unfolding, with a width ranging from a few millimeters to a few centimeters and running through the entire roll length. In severe cases, the tension on the belt is still visible. In the industry, this defect is commonly known as "seersucker" or "water ripples". This defect will cause the copper foil itself to fold and roll unevenly, resulting in uneven coating and folding of the negative electrode slurry of the lithium battery, making the pole scrapped, causing customer complaints and claims.

[0003] For example, Chinese invention patent publication number CN117702113A discloses a copper foil current collector production device and process that can reduce current collector wrinkles, wherein the lower end of the operating box is provided with an electroplating box, the electroplating box is connected to the operating box by argon arc welding, the lower end of the electroplating box is provided with an evaporation box, the evaporation box is connected to the electroplating box by argon arc welding, the evaporation machine is provided inside the evaporation box, the evaporation machine is connected to the evaporation box by bolts, the electroplating tank is provided inside the electroplating box, the electroplating tank and the electroplating box are set to be fixedly connected, a magnetron sputtering device is provided on the operating box, the magnetron sputtering device is provided with multiple devices, the magnetron sputtering device is connected to the operating box by bolts, and a rotating disk is provided inside the operating box. This process solves the problem of wrinkles or reduced pass rate caused by low film thickness by setting a magnetron sputtering device and an evaporation machine, but does not solve the copper foil wrinkles caused by the self-annealing effect.

[0004] For another example, Chinese invention patent publication number CN113661587A discloses an electrolytic copper foil capable of preventing tearing or wrinkling, a method for making the same, an electrode comprising the electrolytic copper foil, and a secondary battery comprising the electrode, wherein the electrolyte comprises: 70 to 90 g / L of copper ions; 50 to 150 g / L of sulfuric acid; 5 to 45 mg / L of arsenic As; 5 to 25 mg / L of acetamide; and 5 to 20 mg / L of polypropylene glycol PPG. This patent addresses the problem that as the electrolytic copper foil becomes thinner, it curls, resulting in tearing or wrinkling of the electrolytic copper foil due to the curling of the edge when the electrolytic copper foil is rolled up, but does not address the wrinkling of the copper foil caused by the self-annealing effect. Summary of the invention

[0005] The problem to be solved by the present invention is that the existing lithium battery copper foil generates wrinkles due to the self-annealing effect. To this end, an electrolytic copper foil capable of improving wrinkles and a method for preparing the same, as well as an electrode and a battery comprising the electrolytic copper foil are provided.

[0006] A large number of experiments have shown that reducing the difference in tensile strength between the initial state and the stable state of copper foil can effectively reduce the decay caused by self-annealing, thereby alleviating the "bucker" phenomenon. Therefore, based on this mechanism, the technical problem to be solved by the present invention is to reduce or even eliminate the appearance defect of "bucker", and for this purpose, a set of electrolytic copper foil low self-annealing effect additives is developed.

[0007] Prior to this, people only sought improvement methods at the nodes of the lithium battery copper foil annealing process, such as adjusting the annealing temperature and annealing time. Multiple adjustments were required to achieve the desired effect, which took a long time and had high costs. Therefore, it was urgently needed in this field to find a new method that could solve the appearance defects of seersucker at one time.

[0008] The applicant accidentally discovered that adding a certain amount of low self-annealing effect additives to the electrolyte can reduce the difference in tensile strength between the initial state and the stable state of copper foil, and obtained a clear additive formula through multiple experiments. As long as this additive formula is added to the electrolyte, the appearance defects of seersucker can be greatly improved.

[0009] The technical solution of the present invention is: a method for preparing an electrolytic copper foil with improved wrinkles, comprising the following steps: (1) preparing an additive: mixing sodium dimethyldithiocarbamate, sodium 3-mercaptopropane sulfonate, thiourea and polyethylene glycol, and then adding water and stirring evenly for 1 min to 3 min, wherein the molecular weight of the polyethylene glycol is 1000 to 4000; (2) adding the additive to the electrolyte: adding the additive to the electrolyte at a certain speed; (3) electrolytic copper foil: electrolyzing the electrolyte to form a raw foil.

[0010] In the above scheme, the amount of sodium dimethyldithiocarbamate is 5 mg / L ~ 80 mg / L, the amount of thiourea is 10 mg / L ~ 60 mg / L, the amount of sodium 3-mercaptopropane sulfonate is 6 mg / L ~ 80 mg / L, and the amount of polyethylene glycol is 5 mg / L ~ 80 mg / L.

[0011] The Cu in the electrolyte described in the above scheme 2+ 60g / L±2g / L, H2SO490g / L±5g / L, Cl - 45mg / L -50mg / L, the electrolyte current density is 75A / dm 2 , the temperature is 45℃±2℃.

[0012] The addition rate of the additive in the above scheme is 100 ml / min.

[0013] The electrolytic copper foil is made by the method for preparing the electrolytic copper foil with improved wrinkles.

[0014] The negative electrode of a lithium-ion battery comprises: a current collector, which is made of the electrolytic copper foil; and an active material, which is carried on the current collector.

[0015] A lithium-ion battery comprises: a positive electrode; a negative electrode of the lithium-ion battery as described above; an electrolyte; and a separator.

[0016] The beneficial effect of the present invention is that the additive can reduce the difference in tensile strength between the initial state and the stable state of the copper foil, thereby alleviating the "buccleaning" phenomenon. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a tensile strength diagram of Example 1 of the present invention and Comparative Example 1 after being placed for different time periods; Figure 2 This is a photo of the appearance of lithium battery copper foil before improvement; Figure 3 This is a photo of the improved appearance of lithium battery copper foil. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention and the accompanying drawings to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the examples described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field belong to the scope of protection of the present invention.

[0019] A method for improving the appearance defects of electrolytic copper foil seersucker for lithium-ion batteries comprises the following steps: (1) preparing additives: mixing sodium dimethyldithiocarbamate, sodium 3-mercaptopropane sulfonate, thiourea and polyethylene glycol, and then adding water and stirring evenly for 1 to 3 minutes, wherein the molecular weight of collagen is 1000 to 4000; (2) adding additives to an electrolyte: adding the additives to the electrolyte at a certain speed.

[0020] In Cu 2+ 60±2g / L, H2SO490±5g / L, Cl - 45-50mg / L, electrolysis current density 75A / dm 2 , add the additive to a solution having a temperature of 45±2°C.

[0021] The additives of Examples 1-15 and Comparative Examples 1-10 were selected according to different additive parameters, as shown in Table 1.

[0022]

[0023] The electrolytic copper foil was prepared and the data was tested, as shown in Table 2.

[0024]

[0025] As shown in Table 1 and Table 2, Examples 1-15 are preferred examples of the present invention, and Comparative Examples 1-10 are general examples of the present invention. It can be seen that when the amount of sodium dimethyldithiocarbamate is 5 mg / L to 15 mg / L, the amount of thiourea is 10 mg / L to 20 mg / L, the amount of sodium 3-mercaptopropane sulfonate is 6 mg / L to 10 mg / L, and the amount of polyethylene glycol is 5 mg / L to 10 mg / L, the maximum difference before and after tensile strength is 30.6 kgf / mm 2 The difference between the tensile strength of general electrolytic copper foil before and after tensile strength exceeds 40 kgf / mm 2 ,like Figure 2 and Figure 3 As shown, by comparison, it can be seen that the difference before and after tensile strength of the electrolytic copper foil after using the additive of the above formula of the present invention is significantly reduced, the electrolytic copper foil prepared without using the additive of the present invention has obvious surface wrinkles, and the surface of the electrolytic copper foil after using the additive of the above formula of the present invention is smooth. When the amount of sodium dimethyldithiocarbamate, thiourea, sodium 3-mercaptopropane sulfonate, and polyethylene glycol exceeds the above range, even if some component falls within the above range (such as Comparative Examples 5, 7, and 8), a more ideal difference before and after tensile strength cannot be obtained.

[0026] like Figure 1As shown, the electrolytic copper foils prepared in Example 1 and Comparative Example 1 were placed separately, and the changes in tensile strength were compared. It can be seen that the tensile strength of the electrolytic copper foil of Example 1 did not change much over time, indicating that the difference before and after tensile strength changed little, and the tensile strength of the electrolytic copper foil of Comparative Example 1 decreased linearly over time.

[0027] As described above, the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents, and these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an electrolytic copper foil with improved wrinkles, characterized in that: The following steps are involved: (1) preparing additives: mixing sodium dimethyldithiocarbamate, sodium 3-mercaptopropane sulfonate, thiourea and polyethylene glycol, and then adding water and stirring evenly for 1 min to 3 min, wherein the molecular weight of the polyethylene glycol is 1000 to 4000; (2) adding additives to the electrolyte: adding the additives to the electrolyte at a certain speed; (3) Electrolytic copper foil: The electrolyte is electrolyzed to form raw foil.

2. The method for preparing the wrinkle-reduced electrolytic copper foil according to claim 1, wherein: The dosage of the sodium dimethyldithiocarbamate is 5 mg / L to 15 mg / L, the dosage of the thiourea is 10 mg / L to 20 mg / L, the dosage of the sodium 3-mercaptopropane sulfonate is 6 mg / L to 10 mg / L, and the dosage of the polyethylene glycol is 5 mg / L to 10 mg / L.

3. The method for preparing the wrinkle-reduced electrolytic copper foil according to claim 1, wherein: The electrolyte contains Cu 2+ 60g / L±2g / L, H2SO490g / L±5g / L, Cl - 45mg / L -50mg / L, the electrolyte current density is 75A / dm 2 , the temperature is 45℃±2℃.

4. The method for preparing the wrinkle-reduced electrolytic copper foil according to claim 1, wherein: The addition rate of the additive is 100 ml / min.

5. Electrolytic copper foil, characterized by: The invention is made by the method for preparing the electrolytic copper foil with improved wrinkles as described in any one of claims 1 to 4.

6. A lithium-ion battery negative electrode, characterized by: The invention comprises: a current collector, which is made of the electrolytic copper foil according to claim 5; and an active substance, which is carried on the current collector.

7. Lithium-ion battery, characterized by: include: Positive electrode; A negative electrode of a lithium-ion battery as claimed in claim 6; Electrolyte; separator.

Images