Composite copper foil having copper-carbon-copper structure, and preparation method therefor and use thereof

Abstract

A composite copper foil having a copper-carbon-copper structure, and a preparation method therefor and a use thereof. The method comprises the following preparation steps: (1) depositing copper foils (1) on a metal foil to obtain double-sided smooth copper foils having carriers; (2) respectively uniformly coating a graphite binder on rough surfaces of the two double-sided smooth copper foils having the carriers, and respectively recording the double-sided smooth copper foils as a first copper foil and a second copper foil; (3) uniformly coating a graphite (3) slurry on the surface of the first copper foil coated with the binder to obtain an intermediate; (4) laminating a graphite layer of the intermediate and the surface of the second copper foil coated with the binder, and stripping the metal foil to obtain a composite copper foil having a copper-carbon-copper structure; and (5) carrying out passivation treatment on the composite copper foil. The composite copper foil is wound and folded to obtain a final composite current collector, and has the outstanding advantages of light weight and excellent conductivity. By means of continuous preparation, the production cost is reduced, the energy loss is reduced, and the problem of fracture caused by slitting, rewinding and the like of the copper foils (1) is alleviated.

Description

Copper-carbon-copper structure composite copper foil and its preparation method and application Technical Field

[0001] The present invention relates to the technical field of composite copper foils, and in particular to a copper-carbon-copper structure composite copper foil and a preparation method and application thereof. Background Art

[0002] Traditional copper foil is composed of metal and has low internal resistance, making it advantageous for electron collection and current transmission. Composite copper foil, on the other hand, uses polymer materials to replace some of the copper, resulting in an extremely thin and lightweight structure that can increase battery energy density. Composite copper foil, a sandwich structure of "copper-polymer-copper," is soft, ductile, and compressive. Its use as a negative electrode in lithium batteries effectively inhibits the formation of lithium dendrites, reduces the risk of internal short circuits, reduces battery weight, and improves battery energy density and safety.

[0003] Although composite copper foil has a low material cost, it remains expensive due to the complex processing steps. This leads to complex production processes, high costs, and poor electrical properties. Therefore, to address the problems of the existing technology, there is an urgent need to provide a composite copper foil with a simple production process.

[0004] Summary of the Invention

[0005] In view of the deficiencies in the prior art, the present invention aims to provide a copper-carbon-copper structure composite copper foil and its preparation method and application.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0007] A first aspect of the present invention provides a method for preparing a copper-carbon-copper structure composite copper foil, comprising the following preparation steps:

[0008] (1) placing the surface-treated metal foil into a raw foil tank and depositing copper foil on both sides to obtain a double-sided smooth copper foil with a peelable carrier;

[0009] (2) A graphite adhesive is uniformly coated on the matte sides of two sheets of double-sided smooth copper foil with a peelable carrier, and the copper foils with peelable carriers coated with the graphite adhesive are respectively designated as the first copper foil and the second copper foil;

[0010] (3) evenly coating a graphite slurry on the surface of the first copper foil coated with the graphite binder to obtain a carrier-copper foil-graphite intermediate;

[0011] (4) pressing the exposed surface of the graphite layer of the carrier-copper foil-graphite intermediate to the surface of the second copper foil coated with a graphite binder, and peeling off the metal foil after pressing and leveling to obtain a copper-carbon-copper structure composite copper foil;

[0012] (5) The obtained copper-carbon-copper structure composite copper foil is subjected to an anti-oxidation passivation treatment.

[0013] In some embodiments, in step (1), the metal foil is selected from any one of titanium foil, aluminum foil, and stainless steel foil.

[0014] In some embodiments, in step (1), the composition of the green foil tank solution is 60-120 g / L of copper sulfate, 80-150 g / L of sulfuric acid, 10-20 ppm of chloride ions, and 10-500 mg / L of organic additives.

[0015] In some embodiments, the organic additive is an additive containing a thiol group or an amine group, selected from at least one of sodium 3-mercapto-1-propane sulfonate, sodium disulfide propane sulfonate, sodium N,N-dimethyldithiocarboxamide propane sulfonate, quaternary ammonium salt, and diamino urea polymer, and is used to improve copper ion deposition and refine grains.

[0016] It should be noted that the metal foil needs to be surface treated before use, including the following steps:

[0017] A 0.1-0.3mm thick metal foil is mechanically polished to a surface roughness Ra of 0.2-0.4μm. Anodization is then performed using the foil as the anode and a metal plate of equal width as the cathode. The oxidizing solution consists of 10g / L oxalic acid, 200g / L 98wt% sulfuric acid, 30g / L nitrilotriacetic acid, and the remainder water. Anodization is performed at a constant voltage of 20-50V for 2-3 minutes.

[0018] The oxidized metal foil is placed in a foil bath to deposit an extremely thin copper foil. In some embodiments, the bath solution comprises 60-120 g / L copper sulfate, 80-150 g / L sulfuric acid, 10-20 ppm chloride ions, and 10-500 mg / L organic additives. The current density is 20-60 ASD to prepare a double-sided smooth copper foil with metal foil.

[0019] It should be noted that the present invention uses pre-oxidation treatment of metal foil to plate an extremely thin metal-copper layer, which can obtain a copper foil with zero pinholes. Compared with vacuum sputtering, evaporation, ion plating and other methods on a polymer substrate in PET / PP composite copper foil, oxidation pretreatment of the metal foil can improve the warping that occurs when peeling off due to excessive bonding between the metal foil and the copper foil, and has the advantages of high efficiency, low cost and recyclable metal foil.

[0020] In some embodiments, in step (1), the thickness of the double-sided smooth copper foil is 1.0-2.5 μm.

[0021] In some embodiments, in step (2), the graphite binder is selected from at least one of polyvinylidene fluoride modified binder (PVDF), sodium carboxymethyl cellulose cross-linked modified binder (CMC), polyacrylic acid modified binder, and sodium alginate binder.

[0022] In some embodiments, in step (3), the coating thickness of the graphite slurry is 1.0-2.0 μm.

[0023] It should be noted that the anti-oxidation passivation treatment is electro-deposition of chromium trioxide CrO3 or electro-deposition of Ni-Mo, and the roughness of the anti-oxidation passivation treated coating is Ra≤0.3 μm.

[0024] Electrodeposition CrO3 process parameters: current density is 1.0-10.0A / dm 2 The plating solution is selected from at least one of chromium trioxide, glucose, BTA, EDTA, triethanolamine, and deionized water. The plating solution temperature is 30-35°C, the plating solution concentration is 1.0-40.0g / L, and the electrodeposition time is 2-10s.

[0025] Electrodeposition Ni-Mo process parameters: The plating solution includes Ni with a concentration of 7.0-13.0g / L 2+ , Mo concentration is 0.1-7.0g / L 6+ , concentration of 48-70g / L P2O7 4- , with a concentration of 5-10 g / L NH 4+ , use 25% ammonia water to adjust the pH of the plating solution to 8-12, the additive concentration range is 0-0.6g / L, the additives include 1,4-butynediol, saccharin sodium, sodium lauryl sulfate, 2,5-dimethylhexynediol, benzenesulfonamide, the current density is 0.2-5.0A / dm 2 , the electrodeposition time is 2-60s.

[0026] In some embodiments, the copper-carbon-copper structure composite copper foil has a thickness of 3.0-6.0 μm.

[0027] A second aspect of the present invention is to provide a copper-carbon-copper structure composite copper foil.

[0028] The third aspect of the present invention is to provide an application of a copper-carbon-copper structure composite copper foil in the preparation of a current collector or a composite current collector.

[0029] The steps of preparing the current collector or composite current collector are as follows: partially coating the copper-carbon-copper structure composite copper foil with graphite, winding and folding the structure to obtain the composite current collector, and the graphite coating thickness is 0.5-1.0 μm.

[0030] It should be noted that when preparing a current collector or a composite current collector, graphite coating is performed on part of the area of ​​the copper foil-graphite-copper foil structure composite copper foil, and the coated area and the uncoated area are staggered and distributed at intervals, and the area of ​​the two areas is the same. The uncoated area serves as the outer surface after winding. The graphite coating thickness here is half the thickness of the graphite slurry coated in step S3 to ensure that the thickness of the graphite layer after winding is consistent. After completing the interval coating, the structure is wound and folded to obtain a current collector or a composite current collector.

[0031] The present invention includes the following beneficial effects:

[0032] (1) The copper-carbon-copper structure composite copper foil provided by the present invention has a mass that is at least half that of the traditional electrolytic copper foil, and therefore has the outstanding advantage of being light in weight. Compared with the existing PET / PP / PI composite copper foil, it has the advantage of better conductivity.

[0033] (2) The copper-carbon-copper structure composite copper foil provided by the present invention has the same structure as the current collector used in the final battery cell. The final composite current collector can be obtained by coating graphite, winding, and folding, which has the obvious advantage of simple process.

[0034] (3) Compared with the traditional process of separate copper foil preparation and graphite coating, the preparation method provided by the present invention has the advantages of continuous preparation, reduced production costs, lower energy loss, and reduced copper foil breakage caused by slitting, rewinding and other processes, which greatly reduces the difficulty of coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] FIG1 is a schematic diagram of the preparation process of a copper-graphite-copper structure composite copper foil. In FIG1 , 1 is copper foil, 2 is titanium foil, 3 is graphite, and there is a binder between 1 and 2;

[0036] FIG2 is a schematic diagram of a composite current collector formed by rolling a copper-graphite-copper structure composite copper foil. In FIG2 , 1 is copper foil, 2 is graphite, and 3 is binder.

[0037] Figure 3 shows the specific production steps of copper-graphite-copper structure composite copper foil and current collector. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the accompanying drawings. The embodiments described with reference to the accompanying drawings are exemplary and intended to explain the present invention, but should not be understood as limiting the present invention.

[0039] Example 1

[0040] A method for preparing a copper-carbon-copper structure composite copper foil comprises the following steps:

[0041] S1: Titanium foil and surface treatment

[0042] Two pieces of 0.1mm thick titanium foil were mechanically polished to a surface roughness Ra of 0.2μm. After removing the surface oxide layer, an oxidation pretreatment was performed, using the titanium foil as the anode and a titanium plate of equal width as the anode. The oxidizing solution consisted of 10g / L oxalic acid, 200g / L 98wt% sulfuric acid, 30g / L nitrilotriacetic acid, and the remainder water. Anodization was performed at a constant voltage of 30V for 2 minutes, resulting in a uniform blue oxide film. These are titanium foils A and B.

[0043] S2: Ultra-thin copper foil deposition

[0044] Titanium foil A and titanium foil B were placed in a green foil tank to deposit copper foil. The thickness of the deposited copper foil was 1.5 μm. The green foil tank liquid consisted of 90 g / L copper sulfate, 120 g / L sulfuric acid, 10 ppm chloride ions, 15 mg / L sodium disulfide dipropane sulfonate, and the remainder water. The current density of the green foil tank was 60 ASD, and the glossiness of the copper foil rough surface was 100-200 GU to obtain titanium foil-copper foil A and titanium foil-copper foil B.

[0045] S3: Graphite coating

[0046] After washing, anti-oxidation, and drying, titanium foil-copper foil A and titanium foil-copper foil B were coated with a PVDF-modified binder on the copper foil surface of titanium foil-copper foil A and titanium foil-copper foil B, respectively. A 1.0 μm thick graphite slurry was then coated on the copper foil surface of titanium foil-copper foil A to obtain a titanium foil-copper foil-graphite intermediate with a thickness of 4.0 μm.

[0047] S4: Titanium foil peeling

[0048] After the copper foil surface of the titanium foil-copper foil B was bonded to the exposed surface of the graphite layer of the intermediate, the titanium foil layer was peeled off to obtain a copper foil-graphite-copper foil structure.

[0049] S5: Antioxidant treatment

[0050] The copper foil-graphite-copper foil structure is passed through an anti-oxidation tank to deposit chromium trioxide on the surface. The roughness of the chromium plating layer is Ra≤0.3μm. The electrodeposition parameters are: current density 2.0A / dm 2 The plating solution is a chromium trioxide solution, the plating temperature is 30°C, the plating concentration is 4.0g / L, and the electrodeposition time is 5s to obtain a copper foil-graphite-copper foil structure composite copper foil.

[0051] A copper-carbon-copper structure composite copper foil is used in the preparation of a current collector or a composite current collector. Graphite is coated on part of the copper foil-graphite-copper foil structure composite copper foil. The graphite coating thickness is 0.5 μm. Combined with Figure 2, it can be seen that the graphite is evenly coated on the folded area. The coated area and the uncoated area are alternately distributed, and the areas of the two areas are the same. The uncoated area serves as the outer surface after winding. After coating is completed, the structure is wound and folded to obtain a composite current collector.

[0052] Example 2

[0053] The preparation steps are the same as those in Example 1, except that in step S2, the thickness of the deposited copper foil is 1.25 μm, and in step S3, the thickness of the graphite coating is 1.5 μm.

[0054] Comparative Example 1

[0055] The preparation steps are the same as steps S1 and S2 in Example 1, except that in step S2, the thickness of the deposited copper foil is 4.5 μm.

[0056] Comparative Example 2

[0057] The preparation steps are the same as those in Example 1, except that in step S3, the graphite slurry is replaced by a PET resin film with a thickness of 3 μm.

[0058] Test case test tensile properties

[0059] The copper foil was cut into pieces with a width of 0.5 inches using a double-edged cutting knife (JDC, THWING-ALBERT), and then the tensile properties of the copper foil were tested using a single tensile testing machine (Dynamics, LD22.502).

[0060] Example 1 shows the mechanical properties of a copper (1.5μm) + graphite (1.0μm) + copper (1.5μm) composite structure, and Example 2 shows the mechanical properties of a copper (1.25μm) + graphite (1.5μm) + copper (1.25μm) composite structure. Comparative Example 1 shows an extremely thin 4.5μm electrolytic copper foil, and Comparative Example 2 shows a 6μm PET composite copper foil. The test results are shown in Table 1. The results show that the examples provided in this application are thinner than the comparative examples, and the tensile strength and yield strength of the composite copper foil provided in the examples are superior to those of the comparative examples.

[0061] Table 1

[0062] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the inventive concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. A method for preparing a copper-carbon-copper structure composite copper foil, characterized in that, it comprises the following steps: (1) Put the surface-treated metal foil into the raw foil tank to deposit a copper foil, and a double-sided polished copper foil with a peelable carrier is obtained; (2) Uniformly coat the rough surfaces of two double-sided polished copper foils with a peelable carrier with a graphite binder, and the double-sided polished copper foils coated with the graphite binder are respectively denoted as the first copper foil and the second copper foil; (3) Uniformly coat the surface of the first copper foil coated with the graphite binder with a graphite slurry to obtain a carrier-copper foil-graphite intermediate; (4) Press the exposed graphite layer surface of the carrier-copper foil-graphite intermediate against the surface of the second copper foil coated with the graphite binder. After pressing flat, peel off the metal foil to obtain a copper-carbon-copper structure composite copper foil; (5) Perform an antioxidant passivation treatment on the obtained copper-carbon-copper structure composite copper foil, and that's it.

2. The method for preparing a copper-carbon-copper structure composite copper foil according to claim 1, characterized in that, in the step (1), the metal foil is selected from any one of titanium foil, aluminum foil, and stainless steel foil.

3. The method for preparing a copper-carbon-copper structure composite copper foil according to claim 1, characterized in that, in the step (1), the raw foil tank solution comprises 60-120 g / L of copper sulfate, 80-150 g / L of sulfuric acid, 10-20 ppm of chloride ions, and 10-500 mg / L of an organic additive.

4. The method for preparing a copper-carbon-copper structure composite copper foil according to claim 3, characterized in that, the organic additive is selected from at least one of sodium 3-mercapto-1-propanesulfonate, sodium disulfide dipropanesulfonate, sodium N,N-dimethyldithiocarbamoylpropane sulfonate, quaternary ammonium salt, and diaminourea polymer.

5. The method for preparing a copper-carbon-copper structure composite copper foil according to claim 1, characterized in that, in the step (1), the thickness of the double-sided polished copper foil is 1.0-2.5 μm.

6. The method for preparing a copper-carbon-copper structure composite copper foil according to claim 1, characterized in that, in the step (2), the graphite binder is selected from at least one of polyvinylidene fluoride modified binder, sodium carboxymethyl cellulose cross-linked modified binder, polyacrylic acid modified binder, and sodium alginate binder.

7. The method for preparing a copper-carbon-copper structure composite copper foil according to claim 1, characterized in that, in the step (3), the coating thickness of the graphite slurry is 1.0-2.0 μm.

8. The method for preparing a copper-carbon-copper structure composite copper foil according to claim 1, characterized in that, in the step (4), the thickness of the copper-carbon-copper structure composite copper foil is 3.0-6.0 μm.

9. A copper-carbon-copper structure composite copper foil prepared by the preparation method according to any one of claims 1-8.

10. The application of the copper-carbon-copper structure composite copper foil according to claim 9 in preparing a current collector or a composite current collector, characterized in that, graphite coating is performed on the copper-carbon-copper structure composite copper foil, and the graphite coating thickness is 0.5-1.0 μm.

Images