Composite copper foil with spherical structure on surface and preparation method thereof

Abstract

The invention discloses a composite copper foil with a spherical structure on its surface and a preparation method thereof. The composite copper foil comprises: an upper granular copper layer, an upper thickened copper layer, an upper copper seed layer, a polymer film, a lower copper seed layer, a lower thickened copper layer and a lower granular copper layer from top to bottom; the upper surface of the upper granular copper layer and the lower surface of the lower granular copper layer both have spherical structures, and the spherical structures are used to increase the surface areas of the upper granular copper layer and the lower granular copper layer, thereby improving the bonding force between the composite copper foil and the negative electrode material; the invention adopts 3.5-6.0μm PP, PET and other polymer films as raw materials, greatly reducing the cost of copper raw materials compared with electrolytic copper foil, and obtaining a composite copper foil with a tensile strength of ≥250MPa and an elongation of ≥10%. Compared with double-light lithium battery copper foil, the spherical structure on the surface of the prepared composite copper foil is small, uniform and dense, with a surface roughness Rz of 0.7-1.0μm, thereby reducing the problem of low cycle life of silicon negative electrode batteries caused by drastic volume changes during charging and discharging, and meeting the life requirement of high-capacity batteries for silicon negative electrodes.

Description

Technical Field

[0001] The present invention belongs to the field of electronic materials, and in particular relates to a composite copper foil with a spherical structure on the surface and a preparation method thereof. Background Art

[0002] Lithium-ion batteries are widely used in new energy vehicles, electronic devices, and other applications. Further increasing battery capacity and suppressing the decline in charge and discharge efficiency have become research hotspots. Currently, the negative electrode of commonly used lithium-ion batteries often uses smooth copper foil coated with activated graphite as the negative electrode current collector. However, the theoretical lithium storage capacity of graphite-based negative electrode materials is approximately 372 mA·h / g, which seriously restricts the increase in lithium battery capacity. Silicon negative electrode materials have a theoretical lithium storage capacity of up to 4200 mAh / g, more than 10 times higher than graphite-based negative electrode materials, and are expected to become the preferred negative electrode material for high-energy-density lithium batteries.

[0003] Compared to graphite anodes, silicon anodes present significant challenges. For example, silicon undergoes drastic volume changes during charge and discharge, which can easily lead to battery failure and, consequently, the expected cycle life of silicon anodes. Recent research has shown that depositing an active thin-film silicon layer on a copper foil surface using CVD or sputtering methods can significantly improve the charge-discharge cycle characteristics of silicon anode batteries. Furthermore, anode current collectors prepared by coating copper foil with a slurry of active materials such as silicon powder using an organic solvent also offer significant advantages over graphite anodes. Furthermore, the slurry coating process is similar to existing graphite anode production processes, making it more readily applicable and attracting increasing attention. However, the particle size of the powdered silicon in the slurry prepared by the coating method is typically 0.1-3 μm, making it difficult to apply a uniform thickness and excellent adhesion to the copper foil surface, presenting coating process challenges. Furthermore, volume expansion and contraction during charge and discharge can cause active silicon anodes produced by coating processes to peel off the copper foil surface, leading to battery failure.

[0004] Therefore, how to change the surface structure of the copper foil used for the negative electrode current collector so that it still has excellent adhesion after undergoing the drastic volume changes caused by the charging and discharging of the silicon negative electrode has become a difficult problem that needs to be solved in the development of lithium battery copper foil. Summary of the Invention

[0005] The purpose of the present invention is to provide a composite copper foil with a spherical structure on the surface and a preparation method thereof, so as to solve the problem of low cycle life of silicon negative electrode batteries caused by drastic volume changes during the charge and discharge process.

[0006] The present invention adopts the following technical solution: a composite copper foil having a spherical structure on its surface, comprising:

[0007] From top to bottom: upper granular copper layer, upper thickened copper layer, upper copper seed layer, polymer film, lower copper seed layer, lower thickened copper layer and lower granular copper layer;

[0008] The upper surface of the upper granular copper layer and the lower surface of the lower granular copper layer both have spherical structures, which are used to increase the surface area of ​​the upper granular copper layer and the lower granular copper layer and improve the bonding force between the composite copper foil and the negative electrode material.

[0009] Furthermore, the thickness of the polymer film is 3.5-6.0 μm, the thickness of the upper thickened copper layer and the lower thickened copper layer are both 0.95-2.4 μm, the thickness of the upper copper seed layer and the lower copper seed layer are 40-100 nm, and the tensile strength of the composite copper foil is ≥250 MPa and the elongation is ≥10%.

[0010] Furthermore, the surface roughness Rz of the upper granular copper layer and the lower granular copper layer is 0.7-1.0 μm, and the particle size of the spherical structure is 0.5-0.8 μm.

[0011] A method for preparing a composite copper foil having a spherical structure on its surface comprises:

[0012] Step 1: attaching an upper copper seed layer and a lower copper seed layer to both sides of the polymer film;

[0013] Step 2: Attach a thickened copper layer to the upper side of the upper copper seed layer, and attach a lower thickened copper layer to the lower side of the lower copper seed layer.

[0014] Step 3: Attach an upper granular copper layer to the upper side of the upper thickened copper layer, and attach a lower granular copper layer to the lower side of the lower thickened copper layer.

[0015] Furthermore, step 1 adopts physical vapor deposition method, specifically:

[0016] The surface of a polymer film with a thickness of 3.5-6.0 μm is activated by an ion source, and then 4 to 8 sets of magnetron sputtering arc-shaped cathode copper targets with a size of 300 mm × 600 to 1500 mm and a copper target purity of 99.99% are used at the cathode. The cathode power supply is a 1-10 kW DC power supply. The moving speed of the polymer film is controlled at 5 to 15 m / min. The upper and lower copper seed layers with a thickness of 40 to 100 nm are deposited under the conditions of a coating roller temperature of -30 to 10°C and an argon pressure of 0.1 to 0.5 Pa.

[0017] Furthermore, step 1 adopts chemical plating deposition method, specifically:

[0018] After roughening, activation, sensitization and chemical copper deposition, an upper copper seed layer and a lower copper seed layer with a thickness of 40 to 100 nm are finally deposited on the surface of the polymer film, wherein the moving speed of the polymer film is 5 to 25 M / min.

[0019] Furthermore, when roughening the surface of the polymer film by chemical plating deposition, the roughening agent is H2O2-H2SO4 solution (φH2O2:φH2SO4=1:4), the roughening time is 10-120s, and the roughening treatment temperature is 30-50°C;

[0020] When the polymer film is activated by chemical plating deposition, the activation temperature is 21 to 32°C and the activation time is 10 to 120 seconds.

[0021] When chemical copper is deposited on the surface of a polymer film by chemical plating deposition, the copper deposition reagent is CuSO4.5H2O 10-20g / L, EDTA (2Na) 15-25g / L, potassium sodium tartrate 10-20g / L, and formaldehyde 10-20ml / L. The copper deposition temperature is 35-45°C, the pH is 12.0-13.0, and the copper deposition time is 10-120s.

[0022] Furthermore, step 2 adopts an electroplating thickening method, specifically: after acid washing, multiple electroplating, water washing and drying, the polymer film moves at a speed of 5 to 25 m / min, and finally deposits an upper thickened copper layer and a lower thickened copper layer of 1.0 to 2.4 μm;

[0023] When pickling is performed using the electroplating thickening method, the acid temperature is 25-40°C and the acid is sulfuric acid;

[0024] When electroplating is carried out by electroplating thickening method, the bath temperature is 35-55℃ and the current density is 10-50A / dm 2 The plating solution is: sulfuric acid: 80-140 g / L, copper: 70-130 g / L, sodium 3-mercapto-1-propanesulfonate: 10-40 ppm, high molecular weight polysaccharide: 5-30 ppm, molecular weight 2000-5000 collagen: 15-50 ppm, chloride ion: 10-40 ppm.

[0025] Furthermore, step 3 specifically comprises: sequentially performing pickling, first roughening, first curing, second roughening, second curing and chromium passivation, thereby depositing an upper granular copper layer and a lower granular copper layer with a surface roughness Rz of 0.7 to 1.0 μm;

[0026] When pickling is performed during the deposition of the upper granular copper layer and the lower granular copper layer, the acid temperature is 25 to 40°C and the solution is sulfuric acid;

[0027] During the first and second roughening processes of the upper and lower granular copper layers, the bath temperature is 25-40°C and the current density is 20-40A / dm 2The plating solution is: sulfuric acid: 50-150g / L, copper: 20-40g / L, sodium tungstate: 20-50ppm, PEG: 20-40ppm, SH110: 20-60ppm;

[0028] During the first and second curing processes of depositing the upper and lower granular copper layers: the curing temperature is 35-45°C, and the current density is 20-40A / dm 2 ;The plating solution is: sulfuric acid: 100~150g / L, copper: 30~60g / L.

[0029] The beneficial effects of the present invention are:

[0030] The present invention uses 3.5-6.0μm PP, PET and other polymer films as raw materials, greatly reducing the cost of copper raw materials compared to electrolytic copper foil, and obtaining a composite copper foil with a tensile strength of ≥250MPa and an elongation of ≥10%. Compared with double-light lithium battery copper foil, the prepared composite copper foil has a fine, uniform and dense spherical structure on the surface, with a surface roughness Rz of 0.7-1.0μm. This reduces the problem of low cycle life of silicon negative electrode batteries caused by drastic volume changes during the charge and discharge process, and meets the life requirements of high-capacity batteries for silicon negative electrodes.

[0031] The present invention has a spherical structure, and the spherical structure on the surface can improve the long-term stable adhesion between the silicon negative electrode with SiO as the main active material and the spherical structure composite copper foil;

[0032] The spherical structure composite copper foil of the present invention reduces the amount of copper used, improves the energy density of power batteries using electrolytic copper foil of the same thickness as the negative electrode current collector, solves the problem of low cycle life of silicon negative electrode batteries caused by drastic volume changes during the charge and discharge process, and improves the cycle life of silicon negative electrode batteries.

[0033] The preparation method of the present invention realizes the preparation of high-strength and high-elongation composite copper foil and the surface modification treatment of the spherical structure by combining multiple technologies. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a microstructure diagram of the composite copper foil with a spherical structure in Example 1 of the present invention;

[0035] Figure 1 a is a surface morphology of the thickened copper layer on the composite copper foil prepared in step 2 of Example 1 of the present invention; Figure 1 b is a cross-sectional microstructure layer and component analysis diagram of the composite copper foil prepared in step 2 of Example 1; Figure 1 c is the surface morphology of the spherical structure composite copper foil prepared in step 3 of Example 1. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] It should be noted that the structures, proportions, sizes, etc. depicted in the drawings of this specification are only used to match the contents disclosed in the specification so that people familiar with this technology can understand and read them. They are not used to limit the conditions under which the present invention can be implemented. Therefore, they have no substantive technical significance. Any structural modification, change in proportional relationship or adjustment of size should still fall within the scope of the technical content disclosed in the present invention without affecting the efficacy and purpose that can be achieved by the present invention.

[0038] The present invention discloses a composite copper foil with a spherical structure on its surface, comprising: from top to bottom: an upper granular copper layer, an upper thickened copper layer, an upper copper seed layer, a polymer film, a lower copper seed layer, a lower thickened copper layer and a lower granular copper layer; the upper surface of the upper granular copper layer and the lower surface of the lower granular copper layer both have a spherical structure, and the spherical structure is used to increase the surface area of ​​the upper granular copper layer and the lower granular copper layer, thereby improving the bonding force between the composite copper foil and the negative electrode material.

[0039] The polymer film has a thickness of 3.5-6.0 μm, the upper and lower thickened copper layers have thicknesses of 0.95-2.4 μm, and the upper and lower copper seed layers have thicknesses of 40-100 nm. The composite copper foil has a tensile strength of ≥250 MPa and an elongation of ≥10%. The surface roughness Rz of the upper and lower granular copper layers is 0.7-1.0 μm, and the particle size of the spherical structure is 0.5-0.8 μm.

[0040] The present invention also discloses a method for preparing a composite copper foil having a spherical structure on its surface, comprising:

[0041] Step 1: attaching an upper copper seed layer and a lower copper seed layer to both sides of the polymer film;

[0042] Step 2: Attach a thickened copper layer to the upper side of the upper copper seed layer, and attach a lower thickened copper layer to the lower side of the lower copper seed layer.

[0043] Step 3: Attach an upper granular copper layer to the upper side of the upper thickened copper layer, and attach a lower granular copper layer to the lower side of the lower thickened copper layer.

[0044] Step 1 adopts physical vapor deposition method, specifically:

[0045] The surface of a polymer film with a thickness of 3.5-6.0 μm is activated by an ion source, and then 4 to 8 sets of magnetron sputtering arc-shaped cathode copper targets with a size of 300 mm × 600 to 1500 mm and a copper target purity of 99.99% are used at the cathode. The cathode power supply is a 1-10 kW DC power supply. The moving speed of the polymer film is controlled at 5 to 15 m / min. The upper and lower copper seed layers with a thickness of 40 to 100 nm are deposited under the conditions of a coating roller temperature of -30 to 10°C and an argon pressure of 0.1 to 0.5 Pa.

[0046] Step 1 adopts chemical plating deposition method, specifically:

[0047] After roughening, activation, sensitization and chemical copper deposition, an upper copper seed layer and a lower copper seed layer with a thickness of 40 to 100 nm are finally deposited on the surface of the polymer film, wherein the moving speed of the polymer film is 5 to 25 M / min.

[0048] When the surface of the polymer film is roughened by chemical plating deposition, the roughening agent is H2O2-H2SO4 solution (φH2O2:φH2SO4=1:4), the roughening time is 10~120s, and the roughening treatment temperature is 30~50℃;

[0049] When the polymer film is activated by chemical plating deposition, the activation temperature is 21 to 32°C and the activation time is 10 to 120 seconds.

[0050] When chemical copper is deposited on the surface of a polymer film by chemical plating deposition, the copper deposition reagent is CuSO4.5H2O 10-20g / L, EDTA (2Na) 15-25g / L, potassium sodium tartrate 10-20g / L, and formaldehyde 10-20ml / L. The copper deposition temperature is 35-45°C, the pH is 12.0-13.0, and the copper deposition time is 10-120s.

[0051] Step 2 uses an electroplating thickening method, specifically: after pickling, multiple electroplating, water washing and drying, the polymer film moves at a speed of 5 to 25 m / min, and finally deposits a 1.0-2.4 μm upper thickened copper layer and a lower thickened copper layer;

[0052] When pickling is performed using the electroplating thickening method, the acid temperature is 25-40°C and the acid is sulfuric acid;

[0053] When electroplating is carried out by electroplating thickening method, the bath temperature is 35-55℃ and the current density is 10-50A / dm 2The plating solution is: sulfuric acid: 80-140 g / L, copper: 70-130 g / L, sodium 3-mercapto-1-propanesulfonate: 10-40 ppm, high molecular weight polysaccharide: 5-30 ppm, molecular weight 2000-5000 collagen: 15-50 ppm, chloride ion: 10-40 ppm.

[0054] Step 3 specifically comprises: sequentially performing pickling, first roughening, first curing, second roughening, second curing and chromium passivation, thereby depositing an upper granular copper layer and a lower granular copper layer with a surface roughness Rz of 0.7 to 1.0 μm;

[0055] When pickling is performed during the deposition of the upper granular copper layer and the lower granular copper layer, the acid temperature is 25 to 40°C and the solution is sulfuric acid;

[0056] During the first and second roughening processes of the upper and lower granular copper layers, the bath temperature is 25-40°C and the current density is 20-40A / dm 2 The plating solution is: sulfuric acid: 50-150g / L, copper: 20-40g / L, sodium tungstate: 20-50ppm, PEG: 20-40ppm, SH110: 20-60ppm;

[0057] During the first and second curing processes of depositing the upper and lower granular copper layers: the curing temperature is 35-45°C, and the current density is 20-40A / dm 2 ;The plating solution is: sulfuric acid: 100~150g / L, copper: 30~60g / L.

[0058] PEG, sodium tungstate and SH110 were used in the first and second roughening processes during the deposition of the upper and lower granular copper layers. This transformed the surface roughening morphology of the copper foil from a dendritic structure to a spherical structure, which not only changed the growth state of the copper particles but also significantly reduced the roughness of the surface roughening morphology.

[0059] During the coarsening process, copper ions and tungstates form metal complexes, which affect ion diffusion in the solution. When the tungstate content is low, copper ions and tungstates easily condense to form metal complexes, inhibiting copper deposition, thereby transforming the copper coarsening morphology from a dendritic structure to a spherical / cellular structure. As the sodium tungstate content increases, the excess tungstate can directly occupy the cathode surface reduction sites, promoting cathode polarization and copper deposition. However, the action of sodium tungstate alone is insufficient to achieve a fine spherical structure. The wetting agent PEG and SH110, which acts as a leveler and brightener, are required to promote the nucleation of new grains, ultimately achieving a fine and dense spherical structure layer.

[0060] During chromium passivation, chromate passivation treatment is performed to form an anti-rust layer. The specific method is as follows: the plating solution uses a potassium dichromate aqueous solution with a chromium concentration of 6 to 12 g / L, and the process tank temperature is 25 to 35°C.

[0061] The spherical structure is composed of a plurality of spherical protrusions, the distance between the upper ends of two adjacent spherical protrusions is greater than the diameter of the graphite particles, and the distance between the upper ends of two adjacent spherical protrusions is less than or equal to the diameter of the SiO particles.

[0062] Example 1

[0063] The polymer film of this embodiment is a 4.5 μm PET film, the thickness of the upper copper seed layer and the lower copper seed layer are both 100 nm, the thickness of the upper thickened copper layer and the lower thickened copper layer are both 2.4 μm, and the spherical structure of the upper granular copper layer and the lower granular copper layer has a particle size of about 0.5 μm and a surface roughness Rz of 0.70 μm. The specific operation is as follows:

[0064] Step 1: Attach the upper copper seed layer and the lower copper seed layer to the two sides of the polymer

[0065] The physical vapor deposition method is adopted: the film surface is treated using an ion source, the cathode is 4 sets of magnetron sputtering arc cathode copper targets, the size is 300mm×600, the copper target purity is 99.99%, and the cathode power supply is a 5KW DC power supply; the process speed is controlled at 5M / min; the coating roller temperature is selected to be -15℃, the argon pressure is: 0.2Pa, and the upper copper seed layer and the lower copper seed layer are deposited on the PET film through vacuum coating.

[0066] Step 2: Attach a thickened copper layer to the upper side of the upper copper seed layer, and attach a lower thickened copper layer to the lower side of the lower copper seed layer

[0067] The electroplating thickening method is adopted, specifically: after pickling, three electroplatings, water washing and drying, the process speed is controlled at 5M / min, and finally the upper thickening copper layer and the lower thickening copper layer are deposited.

[0068] During pickling, the acid solution temperature is 30°C, the acid solution is sulfuric acid, and the concentration is 30g / L.

[0069] Among them, during electroplating: the plating solution composition is: sulfuric acid 100g / L, copper 80g / L, MPS 20ppm, high molecular weight polysaccharide HEC 10 ppm, collagen with a molecular weight of 3000 20ppm, chloride ion 20ppm, the plating solution temperature is 45℃, and the current density of the three electroplatings is 10, 20 and 25A / dm respectively. 2 .

[0070] Step 3: Attach an upper granular copper layer to the upper side of the upper thickened copper layer, and attach a lower granular copper layer to the lower side of the lower thickened copper layer. Step 3 specifically involves: pickling, first roughening, first curing, second roughening, second curing, and chromium passivation in sequence, with the process speed controlled at 10M / min, and finally depositing the upper and lower granular copper layers with a roughness of 10M / min.

[0071] Among them, during the first and second roughening, the plating solution composition was 80g / L sulfuric acid, 30g / L copper, 50ppm sodium tungstate, 20ppm PEG, 30ppm sodium thiazoline disulfide propane sulfonate SH110, the plating solution temperature was 35℃, and the current density of the first roughening was 30A / dm 2 The current density of the second coarsening is 25A / dm 2 .

[0072] Among them, during the first and second curing, the plating solution composition is: sulfuric acid 120g / L, copper 40g / L, the plating solution temperature is 40℃, and the current density of the first curing is 30A / dm 2 The current density of the second curing is 35A / dm 2 .

[0073] Among them, during chromium passivation: the plating solution is 8g / L potassium dichromate aqueous solution, and the process tank temperature is 30°C.

[0074] Figure 1 a is a surface morphology image of the thickened copper layer on the composite copper foil prepared in step 2 of Example 1 of the present invention; it can be seen that a dense and smooth copper layer is attached to the polymer surface.

[0075] Figure 1 b is the cross-sectional microstructure layer and component analysis diagram of the composite copper foil prepared in step 2 of Example 1; it can be seen that an upper thickened copper layer, an upper copper seed layer, a lower copper seed layer, and a lower thickened copper layer are formed on the upper and lower surfaces of the 4.5 μm PET; and the prepared copper layer is flat and uniform.

[0076] Figure 1 c is the surface morphology of the spherical structure composite copper foil prepared in step 3 of Example 1; it can be seen that uniform and fine spherical particles are generated on the surface of the composite copper foil after roughening and curing treatment, indicating that this example can obtain a spherical particle composite copper foil.

[0077] Example 2

[0078] The operation steps of this embodiment are the same as those of embodiment 1, except that:

[0079] The polymer film of this embodiment is a 4.5 μm PET film, the thickness of the upper copper seed layer and the lower copper seed layer are both 50 nm, the thickness of the upper thickened copper layer and the lower thickened copper layer are both 0.95 μm; the spherical structure of the upper granular copper layer and the lower granular copper layer is a composite copper foil with a particle size of about 0.8 μm and a surface roughness Rz of 1.0 μm. The specific operation is as follows:

[0080] In step 1, the chemical plating deposition method is adopted, and the process is carried out in sequence through roughening, activation, sensitization, and chemical copper deposition, and finally an upper copper seed layer and a lower copper seed layer are deposited on the surface of the polymer film. The equipment width is 600 mm; the process speed is set to 5 M / min.

[0081] During roughening: the roughening agent is H2O2-H2SO4 solution (φH2O2:φH2SO4=1:4), the roughening time is 120s, and the roughening treatment temperature is 50℃;

[0082] During activation, the activation reagent was colloidal palladium, the activation temperature was 28°C, and the activation time was selected as 15s;

[0083] During chemical copper deposition: the copper deposition solution is CuSO4.5H2O 15g / L, EDTA (2Na) 20g / L, potassium sodium tartrate 15g / L, formaldehyde 15ml / L, the copper deposition temperature is 40°C, the pH is selected to be 12.5, and the copper deposition time is 50s.

[0084] In step 2, an upper thickened copper layer and a lower thickened copper layer are deposited. During electroplating, the plating solution composition is: sulfuric acid 100g / L, copper 80g / L, MPS 30ppm, high molecular weight polysaccharide HEC 30ppm, collagen with a molecular weight of 3000 20ppm, chloride ion 30ppm, the plating solution temperature is 40°C, and the current density of the three electroplatings is 5, 10 and 25A / dm respectively. 2 .

[0085] Step 3: Attach an upper granular copper layer to the upper side of the upper thickened copper layer, and attach a lower granular copper layer to the lower side of the lower thickened copper layer. Step 3 specifically involves: acid pickling, first roughening, first curing, second roughening, second curing, and chromium passivation, with the process speed controlled at 8M / min, and finally depositing the upper and lower granular copper layers.

[0086] Among them, during the first and second roughening, the plating solution composition was 80g / L sulfuric acid, 30g / L copper, 50ppm sodium tungstate, 40ppm PEG, and 60ppm sodium thiazolyl disulfide propane sulfonate SH110. The plating solution temperature was 35°C, and the current density of the first roughening was 35A / dm 2 The current density of the second coarsening is 30A / dm 2 .

[0087] Among them, during the first and second curing, the plating solution composition is: sulfuric acid 120g / L, copper 40g / L, the plating solution temperature is 40℃, and the current density of the first curing is 35A / dm 2 The current density of the second curing is 38A / dm 2 .

[0088] Example 3

[0089] The operation steps of this embodiment are the same as those of embodiment 1, except that:

[0090] The polymer film of this embodiment is a 4.5 μm PET film, the thickness of the upper copper seed layer and the lower copper seed layer are both 40 nm, the thickness of the upper thickened copper layer and the lower thickened copper layer are both 1.0 μm; the spherical structure of the upper granular copper layer and the lower granular copper layer is a composite copper foil with a particle size of about 0.5 μm and a surface roughness Rz of 0.70 μm. The specific operation is as follows:

[0091] In step 1: the cathode power supply is a 4KW DC power supply, and the process speed is controlled at 8M / min; an upper copper seed layer and a lower copper seed layer are deposited on the PET film.

[0092] In step 2: the process speed is controlled at 10M / min, and the current density of the three electroplating times is 5, 15 and 20A / dm respectively. 2 .

[0093] In step 3: During the first and second roughening, the plating solution composition is 80g / L sulfuric acid, 30g / L copper, 20ppm sodium tungstate, 30ppm PEG, 20ppm sodium thiazolinyl dithiopropane sulfonate SH110. The current density of the first roughening is 25A / dm 2 The current density of the second coarsening is 20A / dm 2 .

[0094] Comparative Example 1

[0095] The polymer film of this embodiment is a 4.5 μm PET film, the thickness of the upper copper seed layer and the lower copper seed layer are both 100 nm, and the thickness of the upper thickened copper layer and the lower thickened copper layer are both 2.4 μm. The specific operation is as follows:

[0096] Step 1: Attach the upper copper seed layer and the lower copper seed layer to the two sides of the polymer film

[0097] The physical vapor deposition method is adopted: the film surface is treated using an ion source, the cathode is 4 sets of magnetron sputtering arc cathode copper targets, the size is 300mm×600, the copper target purity is 99.99%, and the cathode power supply is a 5KW DC power supply; the process speed is controlled at 5M / min; the coating roller temperature is selected to be -15℃, the argon pressure is: 0.2Pa, and the upper copper seed layer and the lower copper seed layer are deposited on the PET film through vacuum coating.

[0098] Step 2: Attach a thickened copper layer to the upper side of the upper copper seed layer, and attach a lower thickened copper layer to the lower side of the lower copper seed layer

[0099] The electroplating thickening method is adopted, specifically: after pickling, three electroplatings, water washing and drying, the process speed is controlled at 5M / min, and finally the upper thickening copper layer and the lower thickening copper layer are deposited.

[0100] During pickling, the acid solution temperature is 30°C, the acid solution is sulfuric acid, and the concentration is 30g / L.

[0101] Among them, during electroplating: the plating solution composition is: sulfuric acid 100g / L, copper 80g / L, MPS 20ppm, high molecular weight polysaccharide HEC 10 ppm, collagen with a molecular weight of 3000 20ppm, chloride ion 20ppm, the plating solution temperature is 45℃, and the current density of the three electroplatings is 10, 20 and 25A / dm respectively. 2 .

[0102] Comparative Example 2

[0103] In this embodiment, an electrolytic copper foil for lithium batteries was prepared using a sulfuric acid copper sulfate solution and additives as a copper plating solution. The plating solution composition was: 120 g / L sulfuric acid, 80 g / L copper, 20 ppm SPS, 10 ppm high molecular weight polysaccharide HEC, 20 ppm collagen with a molecular weight of 3000, and 20 ppm chloride ions. A titanium drum electrode with a diameter of 2.7 μm was used as the cathode, and a dimensionally stable anode was used as the anode for electrodepositing copper. The plating solution temperature was 55° C., and the selected current density of the titanium cathode roller was 50 A / dm 2 .

[0104] The composite copper foil obtained in Example 1, the composite copper foil obtained in Comparative Example 1, and the electrolytic copper foil obtained in Comparative Example 2 were prepared into button batteries and subjected to a 100-cycle charge-discharge stability test.

[0105] The results show that the initial discharge specific capacity of the composite copper foil of Example 1 reaches 311.05 mAh / g, and the final discharge capacity is 195.56 mAh / g; the initial discharge specific capacity of the composite copper foil of Comparative Example 1 reaches 285.10 mAh / g, and the final discharge capacity is 167.67 mAh / g; the initial discharge specific capacity of the composite copper foil of Comparative Example 2 reaches 210.40 mAh / g, and the final discharge capacity is 132.67 mAh / g; therefore, the composite copper foil prepared in Example 1 has better performance.

[0106] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A composite copper foil having a spherical structure on its surface, characterized in that: include: From top to bottom: upper granular copper layer, upper thickened copper layer, upper copper seed layer, polymer film, lower copper seed layer, lower thickened copper layer and lower granular copper layer; The upper surface of the upper granular copper layer and the lower surface of the lower granular copper layer both have spherical structures, and the spherical structures are used to increase the surface area of ​​the upper granular copper layer and the lower granular copper layer, thereby improving the bonding strength between the composite copper foil and the negative electrode material; The method for preparing the composite copper foil is characterized by comprising: Step 1: attaching an upper copper seed layer and a lower copper seed layer to both sides of the polymer film; Step 2: attaching an upper thickened copper layer to the upper side of the upper copper seed layer, and attaching a lower thickened copper layer to the lower side of the lower copper seed layer, Step 3: attaching an upper granular copper layer to the upper side of the upper thickened copper layer, and attaching a lower granular copper layer to the lower side of the lower thickened copper layer; Step 3 specifically comprises: sequentially performing pickling, first roughening, first curing, second roughening, second curing and chromium passivation, thereby depositing an upper grain copper layer and a lower grain copper layer with a surface roughness Rz of 0.7 to 1.0 μm; When pickling is performed during the deposition of the upper granular copper layer and the lower granular copper layer, the acid temperature is 25 to 40°C and the solution is sulfuric acid; During the first and second roughening processes of the upper and lower granular copper layers, the bath temperature is 25-40°C and the current density is 20-40A / dm 2 The plating solution is as follows: sulfuric acid: 50-150 g / L, copper: 20-40 g / L, sodium tungstate: 20-50 ppm, PEG: 20-40 ppm, SH110: 20-60 ppm; During the first and second curing processes of depositing the upper and lower granular copper layers: the curing temperature is 35-45°C, and the current density is 20-40A / dm 2 ;The plating solution is: sulfuric acid: 100-150g / L, copper: 30-60g / L; The spherical structure is obtained by transforming the dendritic structure; The particle size of the spherical structure is 0.5-0.8 μm; The spherical structure is composed of a plurality of spherical protrusions, and the diameter of the graphite particle is less than the distance between the upper ends of two adjacent spherical protrusions and is less than or equal to the diameter of the SiO particle.

2. The composite copper foil having a spherical structure on the surface according to claim 1, characterized in that: The thickness of the polymer film is 3.5-6.0 μm, the thickness of the upper thickened copper layer and the lower thickened copper layer are both 0.95-2.4 μm, the thickness of the upper copper seed layer and the lower copper seed layer are 40-100 nm, and the tensile strength of the composite copper foil is ≥250 MPa and the elongation is ≥10%.

3. The composite copper foil having a spherical structure on the surface according to claim 2, characterized in that: The surface roughness Rz of the upper granular copper layer and the lower granular copper layer is 0.7-1.0 μm.

4. The composite copper foil having a spherical structure on the surface according to claim 1, characterized in that: The step 1 adopts a physical vapor deposition method, specifically: The surface of a polymer film with a thickness of 3.5-6.0 μm is activated using an ion source, and then 4 to 8 sets of magnetron sputtering arc cathode copper targets with a size of 300 mm × 600 to 1500 mm and a copper target purity of 99.99% are used at the cathode. The cathode power supply is a 1-10 kW DC power supply. The moving speed of the polymer film is controlled at 5 to 15 M / min. The upper and lower copper seed layers with a thickness of 40 to 100 nm are deposited at a coating roller temperature of -30 to 10°C and an argon pressure of 0.1 to 0.5 Pa.

5. The composite copper foil having a spherical structure on the surface according to claim 4, characterized in that: The step 1 adopts chemical plating deposition method, specifically: After roughening, activation, sensitization and chemical copper deposition, an upper copper seed layer and a lower copper seed layer with a thickness of 40 to 100 nm are finally deposited on the surface of the polymer film, wherein the moving speed of the polymer film is 5 to 25 M / min.

6. The composite copper foil having a spherical structure on the surface according to claim 1, characterized in that: When roughening the surface of the polymer film by chemical plating deposition, the roughening agent is H2O2-H2SO4 solution (φ H2O2:φ H2SO4=1:4), the roughening time is 10~120s, and the roughening treatment temperature is 30~50℃; When the polymer film is activated by chemical plating deposition, the activation temperature is 21 to 32°C and the activation time is 10 to 120 seconds. When chemical copper is deposited on the surface of a polymer film by chemical plating deposition, the copper deposition reagent is CuSO4.5H2O 10-20g / L, EDTA (2Na) 15-25g / L, potassium sodium tartrate 10-20g / L, and formaldehyde 10-20ml / L. The copper deposition temperature is 35-45°C, the pH is 12.0-13.0, and the copper deposition time is 10-120s.

7. The composite copper foil having a spherical structure on the surface according to claim 1, characterized in that: Step 2 uses an electroplating thickening method, specifically: after pickling, multiple electroplating, water washing and drying, the polymer film moves at a speed of 5 to 25 m / min, and finally deposits a 1.0-2.4 μm upper thickened copper layer and a lower thickened copper layer; When pickling is performed using the electroplating thickening method, the acid temperature is 25-40°C and the acid is sulfuric acid; When electroplating is carried out by electroplating thickening method, the bath temperature is 35-55℃ and the current density is 10-50A / dm 2 The plating solution is: sulfuric acid: 80-140 g / L, copper: 70-130 g / L, sodium 3-mercapto-1-propanesulfonate: 10-40 ppm, high molecular weight polysaccharide: 5-30 ppm, molecular weight 2000-5000 collagen: 15-50 ppm, chloride ion: 10-40 ppm.

Images