Microporous copper foil and method for manufacturing the same and use thereof

Abstract

The application provides a microporous copper foil and a preparation method and application thereof, and comprises the following steps: (1) pretreating a copper foil surface; (2) plating a catalytic layer on the copper foil surface pretreated in step (1); (3) placing the copper foil obtained in step (2) in a chemical plating solution to deposit a nickel alloy layer; (4) chemically oxidizing the nickel alloy layer and then performing alkaline etching; and (5) selectively etching off the nickel alloy layer on the surface of the copper foil, cleaning, and obtaining a microporous copper foil. The method does not need to perform destructive treatment on a cathode roller or super-high-temperature treatment, only needs to construct a soluble nickel alloy layer on the surface of a copper foil substrate to serve as a template of the microporous copper foil, and the method is simple, and the microporous copper foil obtained has increased micropore distribution density and high yield strength.

Description

Technical Field

[0001] This invention belongs to the field of microporous copper foil technology, and particularly relates to a microporous copper foil, its preparation method and application. Background Technology

[0002] Currently, the preparation of microporous copper foil mainly involves two methods: the stencil method and the dealloying method. The stencil method involves creating shielding sites on the cathode, which have electrical insulating properties. The cathode with these shielding sites is then immersed in an electroplating solution for electroplating to obtain microporous copper foil. The dealloying method utilizes the reactivity of different elements. A suitable leaching solution is selected for leaching or high-temperature heat treatment, and highly reactive elements are selectively precipitated, leaving micropores on the copper foil, thus obtaining microporous copper foil.

[0003] In the template method, prolonged immersion of the shielding sites in the electroplating solution can cause the solution to seep into the gaps, resulting in tearing and breakage during copper foil peeling. The dealloying method typically involves ultra-high temperature processing, which is energy-intensive; leaching requires the use of a suitable leaching solution and pre-activation of the copper foil substrate. The distribution depth of alloying elements in the copper foil is very limited, resulting in the dealloying method only being able to process a thin surface layer of the copper foil, and the depth of the micropores processed is limited. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a microporous copper foil, its preparation method and application. The method does not require destructive treatment of the cathode roller or ultra-high temperature treatment. It only requires constructing a soluble porous template on the surface of the copper foil substrate.

[0005] This invention provides a method for preparing microporous copper foil, comprising the following steps:

[0006] (1) Pre-treat the surface of the copper foil;

[0007] (2) Apply a catalytic layer to the copper foil surface that has been pretreated in step (1);

[0008] (3) Place the copper foil obtained in step (2) in a chemical plating solution to deposit a nickel alloy layer;

[0009] (4) The nickel alloy layer is chemically oxidized and then etched in an etching solution;

[0010] (5) Selectively etch away the nickel alloy layer on the surface of the copper foil, clean it, and obtain microporous copper foil.

[0011] Preferably, the pretreatment method is micro-etching;

[0012] The micro-etching solution used includes 80-120 g / L concentrated sulfuric acid, 10-60 g / L hydrogen peroxide, 0.5-3 g / L corrosion inhibitor, 20-100 mg / L chloride ions, 0.02-0.1 g / L stabilizer, 3-20 g / L solubilizer, and the remainder is water.

[0013] The corrosion inhibitor is selected from one or more of 2-mercaptobenzimidazole, benzotriazole, 4-methylbenzotriazole, sodium 2-mercaptobenzimidazole-5-sulfonate, and 1-phenyl-5-mercapto-tetrazazole;

[0014] The stabilizer is selected from one or more of polymethacrylamide propyltrimethylammonium chloride, polydimethyldiallylammonium chloride, and dimethylaminoethyl methacrylate copolymer with quaternized ammonium methacrylate.

[0015] The solubilizer is selected from anhydrous ethanol and / or polyethylene glycol;

[0016] The micro-etching temperature is 25–40℃, and the time is 40–90s; the surface roughness of the copper foil after micro-etching is 0.5–3.0μm.

[0017] Preferably, the pretreatment method is roughening, and the roughening solution used includes 8-15 g / L of copper ions, 90-110 g / L of sulfuric acid, 5-40 mg / L of additives, and the remainder is pure water;

[0018] The additive is selected from one or more of urea, choline chloride, sodium tungstate, sodium metasilicate, potassium sodium tartrate, sodium molybdate, and vanadium pentoxide.

[0019] The current density used for roughening is 8–20 A / dm. 2 The roughening time is 5 to 20 seconds, and the roughening temperature is 30 to 40 degrees Celsius.

[0020] Preferably, the electroless plating solution includes a nickel source, a phosphorus source, a complexing agent, a buffer, and a stabilizer;

[0021] The nickel source is selected from nickel sulfate hexahydrate or nickel chloride hexahydrate;

[0022] The phosphorus source is selected from sodium hypophosphite monohydrate;

[0023] The complexing agent is selected from trisodium citrate dihydrate and / or potassium pyrophosphate;

[0024] The buffer is selected from boric acid;

[0025] The stabilizer is selected from bismuth nitrate and / or bismuth sulfate;

[0026] The concentration of nickel sulfate hexahydrate is 50–100 g / L, the concentration of nickel chloride hexahydrate is 30–100 g / L, the concentration of sodium hypophosphite monohydrate is 20–60 g / L, the concentration of sodium citrate dihydrate is 100–200 g / L, the concentration of potassium pyrophosphate is 100–300 g / L, the concentration of boric acid is 30–60 g / L, and the stabilizer is 1–10 mg / L based on the bismuth ion concentration.

[0027] The pH value of the electroless plating solution is 7-9;

[0028] The deposition temperature of nickel alloy is 55–75°C.

[0029] Preferably, the chemical oxidation method is photocatalytic oxidation;

[0030] The photocatalytic oxidation uses Degussa P25 titanium dioxide photocatalyst, with an irradiation wavelength of 280–460 nm and an irradiation intensity of 300–900 mW / cm². 2 .

[0031] Preferably, alkaline etching includes first performing the etching in alkaline etching solution A, and then performing it in alkaline etching solution B;

[0032] The alkaline etching solution A comprises 30-100 g / L hydrogen peroxide, 10-50 g / L bipyridine, 30-60 g / L boric acid, and 15-40 g / L borax. The pH is adjusted to 7.8-9.0 using sodium hydroxide, and the remainder is water. The etching temperature of alkaline etching solution A is 25-40°C, and the etching time is 5-15 seconds.

[0033] The alkaline etching solution B comprises 50-100 g / L copper chloride dihydrate, 80-120 g / L ammonium chloride, 200-400 g / L ammonia, and the remainder is water; the etching temperature of the alkaline etching solution B is 35-50℃, and the etching time is 15-60 s.

[0034] Preferably, the etching solution used in step (5) is an acidic copper sulfate etching solution;

[0035] The acidic copper sulfate etching solution comprises 200-300 g / L copper sulfate pentahydrate, 3-15 g / L concentrated sulfuric acid, and the remainder is water;

[0036] The etching temperature is 80–95°C.

[0037] This invention provides a microporous copper foil, prepared by the method described in the above technical solution;

[0038] The microporous copper foil includes a copper foil body and micropores distributed on both sides of the copper foil body;

[0039] The depth of the micropores in the direction perpendicular to the copper foil surface is 1.0–2.5 μm, and the inner diameter of the micropores is 13–25 μm;

[0040] The total areal density of the microporous copper foil is 0.32–1.56 g / dm³. 2 .

[0041] Preferably, the distribution density of micropores on the surface of the microporous copper foil is 100–350 per mm. 2 The arithmetic mean waviness Wa on the surface of the microporous copper foil is less than or equal to 2.0 μm.

[0042] The present invention provides a negative electrode current collector, comprising a microporous copper foil prepared by the preparation method described above.

[0043] This invention provides a method for preparing microporous copper foil, comprising the following steps: (1) pretreating the surface of copper foil; (2) depositing a catalytic layer on the surface of the copper foil pretreated in step (1); (3) placing the copper foil obtained in step (2) in a chemical plating solution to deposit a nickel alloy layer; (4) chemically oxidizing the nickel alloy layer and then etching it in an etching solution; (5) selectively etching away the nickel alloy layer on the surface of the copper foil, cleaning it, and obtaining microporous copper foil. This method does not require destructive treatment of the cathode roller or ultra-high temperature treatment. It only requires constructing a soluble nickel alloy layer on the surface of the copper foil substrate to serve as a template for the microporous copper foil. The method is simple, and the resulting microporous copper foil has increased micropore distribution density and higher yield strength. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the structure of the catalytic layer deposited on the surface of the copper foil of the present invention;

[0045] Figure 2 This is a schematic diagram of the nickel alloy layer deposited on the surface of the catalyst layer in this invention;

[0046] Figure 3 This is an enlarged schematic diagram of the nickel alloy layer in this invention;

[0047] Figure 4 This is a schematic diagram of the structure of the catalyst layer etched using alkaline etching solution A in this invention;

[0048] Figure 5 This is a schematic diagram of the structure of copper foil etched using alkaline etching solution B according to the present invention;

[0049] Figure 6 This is a schematic diagram of the structure of the present invention, which uses an acidic etching solution to etch away the nickel alloy layer. Detailed Implementation

[0050] This invention provides a method for preparing microporous copper foil, comprising the following steps:

[0051] (1) Pre-treat the surface of the copper foil;

[0052] (2) Apply a catalytic layer to the copper foil surface that has been pretreated in step (1);

[0053] (3) Place the copper foil obtained in step (2) in a chemical plating solution to deposit a nickel alloy layer;

[0054] (4) Chemically oxidize the nickel alloy layer and then perform alkaline etching;

[0055] (5) Selectively etch away the nickel alloy layer on the surface of the copper foil, clean it, and obtain microporous copper foil.

[0056] This invention pre-treats the surface of copper foil. The pre-treatment method is micro-etching; the micro-etching solution used includes 80-120 g / L concentrated sulfuric acid, 10-60 g / L hydrogen peroxide, 0.5-3 g / L corrosion inhibitor, 20-100 mg / L chloride ions, 0.02-0.1 g / L stabilizer, 3-20 g / L solubilizer, and the remainder is water; the corrosion inhibitor is selected from one or more of 2-mercaptobenzimidazole, benzotriazole, 4-methylbenzotriazole, sodium 2-mercaptobenzimidazole-5-sulfonate, and 1-phenyl-5-mercapto-tetrazazole; the stabilizer is selected from one or more of polymethacrylamide propyltrimethylammonium chloride, polydimethyldiallylammonium chloride, and dimethylaminoethyl methacrylate copolymer; the solubilizer is selected from anhydrous ethanol and / or polyethylene glycol. The chloride ions are provided by sodium chloride or potassium chloride.

[0057] The micro-etching solution contains concentrated sulfuric acid at concentrations of 80 g / L, 90 g / L, 100 g / L, 110 g / L, or 120 g / L; hydrogen peroxide at concentrations of 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, or 60 g / L; corrosion inhibitor at concentrations of 0.5 g / L, 1.0 g / L, 1.5 g / L, 2.0 g / L, 2.5 g / L, or 3.0 g / L; and chloride ion at concentrations of 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, 80 mg / L, or 90 g / L. 0 mg / L or 100 mg / L; the stabilizer content is specifically 0.02 g / L, 0.03 g / L, 0.04 g / L, 0.05 g / L, 0.06 g / L, 0.07 g / L, 0.08 g / L, 0.09 g / L or 0.1 g / L; the solubilizer content is specifically 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, 15 g / L, 16 g / L, 17 g / L, 18 g / L, 19 g / L or 20 g / L.

[0058] The micro-etching temperature described in this invention is 25–40°C, specifically 25°C, 26°C, 28°C, 30°C, 32°C, 34°C, 36°C, 38°C, or 40°C; the time is 40–90 s, specifically 40 s, 45 s, 50 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, 85 s, or 90 s; the surface roughness Rz of the copper foil after micro-etching is 0.5–3.0 μm, specifically 0.5 μm, 0.6 μm, 0.8 μm, 1.0 μm, 1.2 μm, 1.4 μm, 1.6 μm, 1.8 μm, 2.0 μm, 2.2 μm, 2.4 μm, 2.6 μm, 2.8 μm, or 3.0 μm.

[0059] The pretreatment method in this invention can also be roughening. The roughening solution includes 8-15 g / L copper ions, 90-110 g / L sulfuric acid, 5-40 mg / L additives, and the remainder is pure water; the current density used for roughening is 8-20 A / dm³. 2 Specifically, it can be 8A / dm 2 10A / dm 2 12A / dm 2 14A / dm 2 16A / dm 2 18A / dm 2 Or 20A / dm 2 The roughening time is 5–20 s, specifically 5 s, 6 s, 8 s, 10 s, 12 s, 14 s, 16 s, 18 s, or 20 s; the roughening temperature is 30–40 ℃, specifically 30 ℃, 35 ℃, or 40 ℃. The roughened copper foil interface expansion area ratio (Sdr) is 15%–45%, specifically 15%, 20%, 25%, 30%, 35%, 40%, or 45%; Rz is 1.0–3.0 μm, specifically 1.0 μm, 1.5 μm, 2.0 μm, 2.5 μm, or 3.0 μm.

[0060] The purpose of micro-etching or roughening in this invention is, firstly, to enhance the adhesion of the catalyst layer and prevent it from peeling off in the electroless plating solution; and secondly, to provide a larger reaction area for subsequent etching, which is beneficial to improving the porosity of the microporous copper foil.

[0061] The present invention applies a catalytic layer to the surface of the copper foil pretreated in step (1), as shown in the schematic diagram below. Figure 1 As shown. In this invention, the catalyst is deposited by sputtering, vapor deposition, or electroplating; or any combination of two of the above; a catalyst layer is deposited on both sides of the copper foil.

[0062] The catalyst layer described in this invention comprises any two or more elements selected from nickel, iron, titanium, and zinc; the thickness of the catalyst layer, calculated based on the amount of elemental adhesion, is 3–15 mg / dm². 2Specifically, it can be 3mg / dm 2 4mg / dm 2 5mg / dm 2 6mg / dm 2 7mg / dm 2 8mg / dm 2 9mg / dm 2 10mg / dm 2 11mg / dm 2 12mg / dm 2 13mg / dm 2 14mg / dm 2 Or 15mg / dm 2 The method for testing the amount of elemental adhesion is inductively coupled plasma spectroscopy (ICP).

[0063] In this invention, the copper foil obtained in step (2) is placed in a chemical plating solution to deposit a nickel alloy layer, as shown in the schematic diagram below. Figure 2 As shown. Before depositing the nickel alloy, the present invention preferably places the copper foil obtained in step (2) into an airflow drying oven and heats it at a temperature of 50-100°C for 20-60 minutes under a reducing atmosphere; the reducing atmosphere is a mixture of hydrogen and argon, with a volume ratio of hydrogen to argon of 1:4; the specific temperature is 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C; the specific heating time is 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, or 60 minutes. The present invention treats the copper foil under a reducing atmosphere to: firstly, maintain the chemical activity of the catalyst layer; secondly, because the atomic radii of different elements in the catalyst layer are different, their diffusion rates in the copper foil are different, and the content of the catalyst layer remaining on the surface of the copper foil substrate is not completely uniform. Heating under a reducing atmosphere can promote the diffusion of elements in the catalyst layer into the copper foil substrate, making their distribution uneven.

[0064] This invention involves immersing copper foil in a chemical plating solution, ensuring complete contact between the catalyst layer and the solution. The chemical plating solution comprises a nickel source, a phosphorus source, a complexing agent, a buffer, and a stabilizer. The nickel source is selected from nickel sulfate hexahydrate or nickel chloride hexahydrate; the phosphorus source is selected from sodium hypophosphite monohydrate; the complexing agent is selected from trisodium citrate dihydrate and / or potassium pyrophosphate; the buffer is selected from boric acid; and the stabilizer is selected from bismuth nitrate and / or bismuth sulfate. The concentration of nickel sulfate hexahydrate is 50–100 g / L, specifically 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 75 g / L, 80 g / L, 85 g / L, 90 g / L, 95 g / L, or 100 g / L; the concentration of nickel chloride hexahydrate is 30–10 g / L. 0 g / L, specifically 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, 60 g / L, 65 g / L, 70 g / L, 75 g / L, 80 g / L, 85 g / L, 90 g / L, 95 g / L, or 100 g / L; sodium hypophosphite monohydrate concentration is 20–60 g / L, specifically 20 g / L, 25 g / L, 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, or 60 g / L; sodium citrate dihydrate concentration is 100–200 g / L, specifically 100 g / L, 105 g / L, 110 g / L, or 100 g / L. / L, 115g / L, 120g / L, 125g / L, 130g / L, 135g / L, 140g / L, 145g / L, 150g / L, 155g / L, 160g / L, 165g / L, 170g / L, 175g / L, 180g / L, 185g / L, 190g / L, 195g / L or 200g / L; the concentration of potassium pyrophosphate is 100-300g / L, specifically 100g / L, 110g / L, 120g / L, 130g / L, 140g / L, 150g / L, 160g / L, 170g / L, 180g / L, 190g / L, 2 The concentrations are 00 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, 260 g / L, 270 g / L, 280 g / L, 290 g / L, or 300 g / L; the concentration of boric acid is 30–60 g / L, specifically 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, or 60 g / L; the concentration of the stabilizer, calculated as bismuth ion concentration, is 1–10 mg / L, specifically 1 mg / L, 2 mg / L, 3 mg / L, 4 mg / L, 5 mg / L, 6 mg / L, 7 mg / L, 8 mg / L, 9 mg / L, or 10 mg / L.The pH value of the chemical plating solution described in this invention is 7 to 9, specifically 7, 8 or 9; the temperature for depositing nickel alloy is 55 to 75°C, specifically 55°C, 60°C, 65°C, 70°C or 75°C.

[0065] The nickel alloy layer deposited in this invention has a porous structure with a thickness of 1–5 μm. It contains channels that penetrate the nickel alloy layer, allowing the etching solution to seep into these channels and etch the copper foil substrate. A schematic diagram of the structure is shown below. Figure 3 The image shown is an enlarged view of the nickel alloy layer, with pores distributed on its surface. The porosity of the nickel alloy layer ranges from 10% to 40%, and the porosity is calculated as follows:

[0066]

[0067] Where ε represents porosity, ρ i ρ0 represents the actual density of the nickel alloy layer, while ρ0 represents the theoretical density of the nickel alloy layer. The actual density can be calculated from the weight and volume of the nickel alloy layer.

[0068] This invention involves chemically oxidizing the nickel alloy layer followed by alkaline etching. The chemical oxidation is performed via photocatalytic oxidation, using Degussa P25 titanium dioxide photocatalyst. The selected light wavelength is 280–460 nm, and the light intensity is 300–900 mW / cm². 2 The specific wavelengths of the illumination are 280nm, 290nm, 300nm, 310nm, 320nm, 330nm, 340nm, 350nm, 360nm, 370nm, 380nm, 390nm, 400nm, 410nm, 420nm, 430nm, 440nm, 450nm, or 460nm; the specific illumination intensity is 300mW / cm². 2 400mW / cm 2 500mW / cm 2 600mW / cm 2 700mW / cm 2 800mW / cm 2 Or 900mW / cm 2 The photocatalytic oxidation is carried out in water, with the catalyst added to the water. After the photocatalytic oxidation treatment, the nickel alloy layer is immersed and spray-cleaned. The purpose of the chemical oxidation in this invention is to dope oxygen atoms to enhance the corrosion resistance of the nickel alloy layer and improve its corrosion resistance in alkaline etching solutions.

[0069] In this invention, alkaline etching includes first being carried out in alkaline etching solution A, and then in alkaline etching solution B; alkaline etching solution A etches away the catalyst layer on the surface of the copper foil, and alkaline etching solution B etches the surface of the copper foil.

[0070] The alkaline etching solution A described in this invention comprises 30-100 g / L hydrogen peroxide, 10-50 g / L bipyridine, 30-60 g / L boric acid, and 15-40 g / L borax. The pH is adjusted to 7.8-9.0 using sodium hydroxide, with the remainder being water. The etching temperature using alkaline etching solution A is 25-40°C, and the etching time is 5-15 seconds. This invention uses a nickel alloy layer as a porous template and alkaline etching solution A to etch the catalyst layer. A schematic diagram of the structure is shown below. Figure 4 .

[0071] Specifically, the hydrogen peroxide content in alkaline etching solution A is 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, or 100 g / L; the bipyridine content is 10 g / L, 20 g / L, 30 g / L, 40 g / L, or 50 g / L; the boric acid content is 30 g / L, 35 g / L, 40 g / L, 45 g / L, 50 g / L, 55 g / L, or 60 g / L; the borax content is 15 g / L, 20 g / L, 25 g / L, 30 g / L, 35 g / L, or 40 g / L; and the pH value of alkaline etching solution A is adjusted to 7.8, 8, 8.2, 8.4, 8.6, 8.8, or 9.0 using sodium hydroxide. The etching temperature of the alkaline etching solution A is specifically 25℃, 30℃, 35℃ or 40℃; the etching time is specifically 5s, 10s or 15s.

[0072] The alkaline etching solution B comprises 50-100 g / L copper chloride dihydrate, 80-120 g / L ammonium chloride, 200-400 g / L ammonia, and the remainder is water. Specifically, the content of copper chloride dihydrate is 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L, or 100 g / L; the content of ammonium chloride is 80 g / L, 90 g / L, 100 g / L, 110 g / L, or 120 g / L; and the content of ammonia is 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, 260 g / L, 270 g / L, 280 g / L, 290 g / L, or 300 g / L. / L, 310g / L, 320g / L, 330g / L, 340g / L, 350g / L, 360g / L, 370g / L, 380g / L, 390g / L, or 400g / L; the etching temperature of the alkaline etching solution B is 35-50℃, specifically 35℃, 40℃, 45℃, or 50℃; the etching time is 15-60s, specifically 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, or 60s; this invention controls the alkaline etching time to prevent the nickel alloy layer from being completely etched away, thus allowing the nickel alloy layer to act as a template for the microporous copper foil within a specific etching time. The etching in this invention uses a porous nickel alloy layer as a template and alkaline etching solution B to etch the copper foil to obtain micropores. A schematic diagram of the structure is shown below. Figure 5 The alkaline etching solution B used in this invention has an etching effect on both copper and nickel alloys. Therefore, by photocatalytically oxidizing the nickel alloy layer, an oxygen-containing protective layer is obtained on the surface of the alloy layer.

[0073] This invention selectively etches away the nickel alloy layer on the surface of a copper foil, followed by cleaning to obtain a microporous copper foil. The selective etching solution used is an acidic copper sulfate etching solution; for example... Figure 6As shown, the nickel alloy layer is etched away using an acidic etching solution to obtain a microporous copper foil. The catalytic layer can be retained as an auxiliary antioxidant layer. The acidic copper sulfate etching solution described in this invention comprises 200–300 g / L copper sulfate pentahydrate, 3–15 g / L concentrated sulfuric acid, and the remainder being water; the specific content of the copper sulfate pentahydrate is 200 g / L, 210 g / L, 220 g / L, 230 g / L, 240 g / L, 250 g / L, 260 g / L, 270 g / L, 280 g / L, 290 g / L, or 300 g / L; the content of the concentrated sulfuric acid is 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L, 12 g / L, 13 g / L, 14 g / L, or 15 g / L. The etching temperature is 80–95°C, specifically 80°C, 85°C, 90°C, or 95°C. The acidic copper sulfate etching solution used in this invention has an etching effect on nickel alloys but not on copper, thus exhibiting a selective etching effect.

[0074] The present invention preferably performs an anti-oxidation treatment on both sides of the cleaned copper foil, and the anti-oxidation solution used contains chromium.

[0075] In step (5), after the nickel alloy layer is etched away, the catalyst layer on the surface of the copper foil is exposed. Since the catalyst layer is very thin, it can be retained on the surface of the copper foil as an auxiliary antioxidant layer.

[0076] The present invention obtains microporous copper foil by selective etching followed by rinsing.

[0077] This invention provides a microporous copper foil, prepared by the method described above. The microporous copper foil includes a copper foil body and micropores distributed on both sides of the copper foil body. The depth of the micropores in the direction perpendicular to the copper foil surface is 1.0–2.5 μm, and the inner diameter of the micropores is 13–25 μm. The inner diameter is measured by ion polishing of the cross-section of the copper foil, observing and measuring the cross-section of the micropores under a scanning electron microscope, measuring four points for each micropore, and finally calculating the average value. The total areal density of the microporous copper foil is 0.32–1.56 g / dm³. 2 .

[0078] The micropore density on the surface of the microporous copper foil described in this invention is 100–350 pores / mm. 2 The surface of the copper foil was observed using a scanning electron microscope at magnifications of 100–500, and the number of micropore regions caused by etching was counted. The arithmetic mean waviness Wa of the microporous copper foil surface was less than or equal to 2.0 μm; preferably, based on the full strain method at a strain of 0.5%, the microporous copper foil had a waviness of 12 kg / mm². 2 Up to 20kg / mm 2 Yield strength within the range.

[0079] The microporous copper foil provided by the present invention has an antioxidant layer on its surface, the antioxidant layer containing chromium.

[0080] This invention differs from traditional template methods and dealloying methods: the method provided by this invention does not require destructive treatment of the cathode roller, nor does it require ultra-high temperature treatment. It only requires constructing a soluble porous template on the surface of the copper foil substrate.

[0081] The catalyst layer in the microporous copper foil provided by this invention contains catalytically active elements that are uniformly distributed on the surface of the copper foil substrate before heating. During low-temperature heat treatment, the elements in the catalyst layer diffuse into the copper foil substrate. Due to the different diffusion rates of different elements in the catalyst layer within the copper foil, the element content remaining on the surface of the copper foil substrate is not completely uniform. The resulting nickel alloy layer obtained through electroless plating has a porous structure. This porous structure acts as a channel for the etching solution, which etches the surface of the copper foil through these channels. By controlling the element content of the catalyst layer and the heat treatment temperature, this invention can obtain nickel alloy layers with different porosities. The microporous copper foil of this invention has micropores on both surfaces that do not penetrate the copper foil body, thus maintaining excellent tensile strength and ensuring that the copper foil does not break during downstream processing.

[0082] The etching solution and selective etching solution formulation used in this invention are simple and readily available, have excellent etching efficiency, and are inexpensive.

[0083] The present invention provides a negative electrode current collector, comprising a microporous copper foil prepared by the preparation method described above.

[0084] This invention uses microporous copper foil as the negative electrode current collector for lithium-ion batteries, which can improve the coating adhesion of the negative electrode slurry while maintaining good tensile strength, thereby improving the energy density and cycle life of the battery.

[0085] The method for preparing the negative electrode in this invention is as follows:

[0086] A slurry is prepared by mixing silicon carbide alloy active material, conductive carbon black, CMC and PVDF in high-purity water; preferably, the amount of each raw material in the slurry by weight is: 95 parts of KELOD silicon carbide alloy active material, 2 parts of conductive carbon black, 2 parts of CMC and 1 part of PVDF.

[0087] Mix in solvent for 2 hours until a uniform slurry is formed. Apply the slurry uniformly to copper foil using a coating applicator, with a single-sided loading of 7 ± 0.5 mg / cm². 2 The electrode sheet coated with the negative electrode material was placed in a vacuum oven and dried at 60°C to achieve an electrode density of 1.75 ± 0.05 g / cm³. 3The coated copper foil is then die-cut into negative electrode sheets measuring 60mm x 80mm.

[0088] The obtained negative electrode sheet was assembled with a commercially available separator, electrolyte, and positive electrode sheet to manufacture a pouch battery. The battery was then subjected to charge-discharge cycles at a rate of 0.5C. Constant current charge-discharge testing was performed: maintaining a voltage window of 0.01V-1.5V, the rate performance was tested by cycling at 0.5C to obtain the initial coulombic efficiency and cycle life (the number of cycles when the capacity retention first falls below 80%).

[0089] The yield strength test method is as follows: According to test method GB / T 29847-2013, the yield strength of electrolytic copper foil is tested using an Instron 6800 universal testing machine at a strain rate of 50 mm / min and room temperature (approximately 25°C). The yield strength is calculated on the stress-strain curve using the stress value corresponding to 0.5% of the total strain (including elastic and plastic deformation). The tensile test specimen is a strip specimen with a total length of 100 mm and a width of 15 mm. The sample is measured three times, and the average value is taken as the final yield strength of the sample.

[0090] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a microporous copper foil, its preparation method, and its applications, but these descriptions should not be construed as limiting the scope of protection of the present invention.

[0091] Example 1

[0092] Step (1):

[0093] An 8μm copper foil was selected as the substrate, and micro-etching was performed on both surfaces of the copper foil. The micro-etching solution formula and process are as follows: concentrated sulfuric acid 90g / L, hydrogen peroxide 20g / L, chloride ion 30mg / L, 2-mercaptobenzimidazole 1g / L, polydimethyldiallylammonium chloride 0.04g / L, polyethylene glycol 10g / L, and the remainder being pure water; the micro-etching temperature was 30℃, the etching time was 50s, and the surface roughness Rz of the copper foil after micro-etching was 1.81μm.

[0094] Step (2):

[0095] A titanium-nickel alloy layer was vacuum magnetron sputtered onto a copper foil substrate as a catalyst layer, with an elemental deposition rate of 5 mg / dm³. 2 The mass fraction of titanium is 70%.

[0096] Step (3):

[0097] ① Place the copper foil obtained in step (2) into an airflow drying oven and keep it at 80°C for 40 minutes. While keeping it at 80°C, introduce a mixed gas with a volume ratio of hydrogen to argon of 1:4.

[0098] ② The copper foil was placed in a chemical plating solution with the following formula: nickel sulfate hexahydrate 60 g / L, sodium hypophosphite monohydrate 25 g / L, trisodium citrate dihydrate 100 g / L, boric acid 35 g / L, bismuth ions 2 mg / L, and the remainder being pure water; the pH of the plating solution was 7.5, and the temperature of the plating solution was 65℃; the thickness of the obtained nickel alloy layer was 1.5 μm, and the porosity was 22%;

[0099] Step (4):

[0100] ① Disperse the photocatalyst in water and stir to ensure full dispersion; place the copper foil obtained in step (3) vertically into the reaction tank and irradiate the nickel alloy layer with ultraviolet light of wavelength 320nm at an intensity of 800mW / cm. 2 Continue for 25 minutes. After completion, soak and spray the nickel alloy layer with pure water.

[0101] ②Prepare an alkaline etching solution:

[0102] Alkaline etching solution A: 50g / L hydrogen peroxide, 30g / L bipyridine, 45g / L boric acid, 30g / L borax, the remainder is pure water, pH=8.5. Put the copper foil into the etching solution and etch for 7s at 25℃. After etching, clean the copper foil with pure water.

[0103] Alkaline etching solution B: 80 g / L copper chloride dihydrate, 100 g / L ammonium chloride, 250 g / L ammonia, and the remainder is pure water; continue to immerse the copper foil in the etching solution and etch for 40 seconds at 45°C. After etching, rinse the copper foil with pure water.

[0104] Step (5):

[0105] Prepare an acidic etching solution: 250 g / L copper sulfate pentahydrate, 8 g / L concentrated sulfuric acid, and the remainder pure water. Immerse the copper foil in the etching solution and etch at 90°C until the nickel alloy layer is completely dissolved. After etching, rinse the copper foil thoroughly with pure water. Finally, perform an anti-oxidation treatment on both sides of the microporous copper foil using an anti-oxidation solution containing chromium.

[0106] Next, the electrolytic copper foil was assembled into a pouch cell and subjected to charge-discharge cycle tests to obtain the corresponding electrochemical performance parameters.

[0107] Example 2

[0108] Step (1):

[0109] A 6μm copper foil was selected as the substrate, and both surfaces of the copper foil were roughened. The roughening solution formula and process are as follows: concentrated sulfuric acid 100g / L, copper ions 12g / L, sodium molybdate dihydrate 10mg / L (calculated as molybdenum ions), and the remainder being pure water; the roughening current density was 15A / dm³. 2 The roughening time was 15s, the roughening solution temperature was 35℃, and the roughening time was 8s. The roughened copper foil interface expansion area ratio Sdr was 19%, and Rz was 1.63μm.

[0110] Step (2):

[0111] A titanium-zinc alloy layer was vacuum magnetron sputtered onto a copper foil substrate as a catalyst layer, with an elemental deposition rate of 5 mg / dm³. 2 The mass fraction of titanium is 70%.

[0112] Step (3):

[0113] ① Place the copper foil obtained in step (2) into an airflow drying oven and keep it at 60°C for 40 minutes. While keeping it at 60°C, introduce a mixed gas with a volume ratio of hydrogen to argon of 1:4.

[0114] ② The copper foil was placed in a chemical plating solution with the following formula: nickel sulfate hexahydrate 80 g / L, sodium hypophosphite monohydrate 25 g / L, trisodium citrate dihydrate 120 g / L, boric acid 40 g / L, bismuth ions 2 mg / L, and the remainder being pure water; the pH of the plating solution was 7.5, and the temperature of the plating solution was 60℃; the thickness of the obtained nickel alloy layer was 1.5 μm, and the porosity was 32%.

[0115] Step (4):

[0116] ① Disperse the photocatalyst in water and stir to ensure full dispersion; place the copper foil obtained in step (3) vertically into the reaction tank and irradiate the nickel alloy layer with ultraviolet light of wavelength 320nm at an intensity of 800mW / cm. 2 Continue for 25 minutes. After completion, soak and spray the nickel alloy layer with pure water.

[0117] ②Prepare an alkaline etching solution:

[0118] Alkaline etching solution A: 50g / L hydrogen peroxide, 30g / L bipyridine, 45g / L boric acid, 30g / L borax, the remainder is pure water, pH=8.5. Put the copper foil into the etching solution and etch for 5s at 30℃. After etching, clean the copper foil with pure water.

[0119] Alkaline etching solution B: 80 g / L copper chloride dihydrate, 100 g / L ammonium chloride, 250 g / L ammonia, and the remainder is pure water; continue to immerse the copper foil in the etching solution and etch for 40 seconds at 45°C. After etching, rinse the copper foil with pure water.

[0120] Step (5):

[0121] Prepare an acidic etching solution: 250 g / L copper sulfate pentahydrate, 8 g / L concentrated sulfuric acid, and the remainder pure water. Immerse the copper foil in the etching solution and etch at 90°C until the nickel alloy layer is completely dissolved. After etching, rinse the copper foil thoroughly with pure water.

[0122] Next, the electrolytic copper foil was assembled into a pouch cell and subjected to charge-discharge cycle tests to obtain the corresponding electrochemical performance parameters.

[0123] Example 3

[0124] Step (1):

[0125] An 8μm copper foil was selected as the substrate, and micro-etching was performed on both surfaces of the copper foil. The micro-etching solution formula and process are as follows: concentrated sulfuric acid 90g / L, hydrogen peroxide 20g / L, chloride ion 30mg / L, benzotriazole 0.5g / L, polymethacrylamide propyltrimethylammonium chloride 0.02g / L, polyethylene glycol 10g / L, and the remainder being pure water; the micro-etching temperature was 30℃, the etching time was 50s, and the surface roughness Rz of the copper foil after micro-etching was 1.75μm.

[0126] Step (2):

[0127] A titanium-nickel alloy layer was vacuum magnetron sputtered onto a copper foil substrate as a catalyst layer, with an elemental deposition rate of 5 mg / dm³. 2 The mass fraction of titanium is 70%.

[0128] Step (3):

[0129] ① Place the copper foil obtained in step (2) into an airflow drying oven and keep it at 80°C for 40 minutes. While keeping it at 80°C, introduce a mixed gas with a volume ratio of hydrogen to argon of 1:4.

[0130] ② The copper foil was placed in a chemical plating solution with the following formula: nickel sulfate hexahydrate 60 g / L, sodium hypophosphite monohydrate 25 g / L, trisodium citrate dihydrate 100 g / L, boric acid 35 g / L, bismuth ions 2 mg / L, and the remainder being pure water; the pH of the plating solution was 7.5, and the temperature of the plating solution was 65℃; the thickness of the obtained nickel alloy layer was 1.5 μm, and the porosity was 23%.

[0131] Step (4):

[0132] ① Disperse the photocatalyst in water and stir to ensure full dispersion; place the copper foil obtained in step (3) vertically into the reaction tank and irradiate the nickel alloy layer with ultraviolet light of wavelength 320nm at an intensity of 800mW / cm. 2 Continue for 25 minutes. After completion, soak and spray the nickel alloy layer with pure water.

[0133] ②Prepare an alkaline etching solution:

[0134] Alkaline etching solution A: 30g / L hydrogen peroxide, 45g / L bipyridine, 45g / L boric acid, 30g / L borax, the remainder is pure water, pH=8.0. Put the copper foil into etching solution A and etch for 10s at 30℃. After etching, clean the copper foil with pure water.

[0135] Alkaline etching solution B: 100g / L copper chloride dihydrate, 120g / L ammonium chloride, 300g / L ammonia, and the remainder is pure water; the copper foil is then immersed in etching solution B and etched at 45°C for 40s. After etching, the copper foil is rinsed clean with pure water.

[0136] Step (5):

[0137] Prepare an acidic etching solution: 250 g / L copper sulfate pentahydrate, 8 g / L concentrated sulfuric acid, and the remainder pure water. Immerse the copper foil in the etching solution and etch at 90°C until the nickel alloy layer is completely dissolved. After etching, rinse the copper foil thoroughly with pure water. Finally, perform an anti-oxidation treatment on both sides of the microporous copper foil using an anti-oxidation solution containing chromium.

[0138] Next, the electrolytic copper foil was assembled into a pouch cell and subjected to charge-discharge cycle tests to obtain the corresponding electrochemical performance parameters.

[0139] Example 4

[0140] Step (1):

[0141] An 8μm copper foil was selected as the substrate, and micro-etching was performed on both surfaces of the copper foil. The micro-etching solution formula and process are as follows: concentrated sulfuric acid 90g / L, hydrogen peroxide 20g / L, chloride ion 30mg / L, 2-mercaptobenzimidazole 1g / L, polydimethyldiallylammonium chloride 0.04g / L, polyethylene glycol 10g / L, and the remainder being pure water; the micro-etching temperature was 30℃, the etching time was 50s, and the surface roughness Rz of the copper foil after micro-etching was 1.96μm.

[0142] Step (2):

[0143] A titanium-nickel alloy layer was vacuum magnetron sputtered onto a copper foil substrate as a catalyst layer, with an elemental deposition rate of 5 mg / dm³. 2 The mass fraction of titanium is 60%.

[0144] Step (3):

[0145] ① Place the copper foil obtained in step (2) into an airflow drying oven and keep it at 100℃ for 60 minutes. While keeping it at 100℃, introduce a mixed gas with a volume ratio of hydrogen to argon of 1:4.

[0146] ② The copper foil was placed in a chemical plating solution with the following formula: nickel sulfate hexahydrate 60 g / L, sodium hypophosphite monohydrate 25 g / L, trisodium citrate dihydrate 100 g / L, boric acid 35 g / L, bismuth ions 2 mg / L, and the remainder being pure water; the pH of the plating solution was 7.5, and the temperature of the plating solution was 65℃; the thickness of the obtained nickel alloy layer was 1.5 μm, and the porosity was 40%.

[0147] Step (4):

[0148] ① Disperse the photocatalyst in water and stir to ensure full dispersion; place the copper foil obtained in step (3) vertically into the reaction tank and irradiate the nickel alloy layer with ultraviolet light of wavelength 320nm at an intensity of 800mW / cm. 2 Continue for 25 minutes. After completion, soak and spray the nickel alloy layer with pure water.

[0149] ②Prepare an alkaline etching solution:

[0150] Alkaline etching solution A: 30g / L hydrogen peroxide, 45g / L bipyridine, 45g / L boric acid, 30g / L borax, the remainder is pure water, pH=8.0. Put the copper foil into the etching solution and etch for 10s at 30℃. After etching, clean the copper foil with pure water.

[0151] Alkaline etching solution B: 80 g / L copper chloride dihydrate, 100 g / L ammonium chloride, 250 g / L ammonia, and the remainder is pure water; continue to immerse the copper foil in the etching solution and etch for 40 seconds at 45°C. After etching, rinse the copper foil with pure water.

[0152] Step (5):

[0153] Prepare an acidic etching solution: 250 g / L copper sulfate pentahydrate, 8 g / L concentrated sulfuric acid, and the remainder pure water. Immerse the copper foil in the etching solution and etch at 90°C until the nickel alloy layer is completely dissolved. After etching, rinse the copper foil thoroughly with pure water. Finally, perform an anti-oxidation treatment on both sides of the microporous copper foil using an anti-oxidation solution containing chromium.

[0154] Next, the electrolytic copper foil was assembled into a pouch cell and subjected to charge-discharge cycle tests to obtain the corresponding electrochemical performance parameters.

[0155] Example 5

[0156] Step (1):

[0157] An 8μm copper foil was selected as the substrate, and micro-etching was performed on both surfaces of the copper foil. The micro-etching solution formula and process are as follows: concentrated sulfuric acid 90g / L, hydrogen peroxide 20g / L, chloride ion 30mg / L, 2-mercaptobenzimidazole 1g / L, polydimethyldiallylammonium chloride 0.04g / L, polyethylene glycol 10g / L, and the remainder being pure water; the micro-etching temperature was 30℃, the etching time was 50s, and the surface roughness Rz of the copper foil after micro-etching was 1.82μm.

[0158] Step (2):

[0159] A titanium-nickel alloy layer was vacuum magnetron sputtered onto a copper foil substrate as a catalyst layer, with an elemental deposition rate of 5 mg / dm³. 2 The mass fraction of titanium is 70%.

[0160] Step (3):

[0161] ① Place the copper foil obtained in step (2) into an airflow drying oven and keep it at 80°C for 40 minutes. While keeping it at 80°C, introduce a mixed gas with a volume ratio of hydrogen to argon of 1:4.

[0162] ② The copper foil was placed in a chemical plating solution with the following formula: nickel sulfate hexahydrate 60 g / L, sodium hypophosphite monohydrate 25 g / L, trisodium citrate dihydrate 100 g / L, boric acid 35 g / L, bismuth ions 2 mg / L, and the remainder being pure water; the pH of the plating solution was 7.5, and the temperature of the plating solution was 65℃; the thickness of the obtained nickel alloy layer was 1.5 μm, and the porosity was 21%.

[0163] Step (4):

[0164] ① Disperse the photocatalyst in water and stir to ensure full dispersion; place the copper foil obtained in step (3) vertically into the reaction tank and irradiate the nickel alloy layer with ultraviolet light of wavelength 320nm at an intensity of 800mW / cm. 2 Continue for 25 minutes. After completion, soak and spray the nickel alloy layer with pure water.

[0165] ②Prepare an alkaline etching solution:

[0166] Alkaline etching solution A: 50g / L hydrogen peroxide, 30g / L bipyridine, 45g / L boric acid, 30g / L borax, the remainder is pure water, pH=8.5. Put the copper foil into the etching solution and etch for 7s at 25℃. After etching, clean the copper foil with pure water.

[0167] Alkaline etching solution B: 100g / L copper chloride dihydrate, 120g / L ammonium chloride, 300g / L ammonia, and the remainder is pure water; continue to immerse the copper foil in the etching solution and etch for 60s at 50℃. After etching, rinse the copper foil with pure water.

[0168] Step (5):

[0169] Prepare an acidic etching solution: 250 g / L copper sulfate pentahydrate, 8 g / L concentrated sulfuric acid, and the remainder pure water. Immerse the copper foil in the etching solution and etch at 90°C until the nickel alloy layer is completely dissolved. After etching, rinse the copper foil thoroughly with pure water. Finally, perform an anti-oxidation treatment on both sides of the microporous copper foil using an anti-oxidation solution containing chromium.

[0170] Next, the electrolytic copper foil was assembled into a pouch cell and subjected to charge-discharge cycle tests to obtain the corresponding electrochemical performance parameters.

[0171] Comparative Example 1

[0172] Compared with Example 1, in step (4), the nickel alloy layer is not chemically oxidized, and the other conditions are the same as in Example 1.

[0173] Comparative Example 2

[0174] Compared with Example 1, the porosity of the nickel alloy layer deposited by sputtering pure titanium on the surface of the copper foil in step (2) is different.

[0175] Comparative Example 3

[0176] Compared with Example 1, in step (3), the catalyst layer is not subjected to a reducing atmosphere treatment before depositing the nickel alloy layer, and other conditions are the same as in Example 1.

[0177] Comparative Example 4

[0178] Compared with Example 1, the etching time of alkaline etching solution B in step (4) is 80s, and other conditions are the same as in Example 1.

[0179] Table 1

[0180]

[0181] In Table 1, ○ represents yes; × represents no; / indicates that it cannot be tested or implemented.

[0182] As can be seen from Example 1, according to the method of the present invention, a copper foil with micropores on its surface can be obtained, with an average inner diameter of 19.1 μm and a distribution density of 212 micropores / mm on the surface of the copper foil. 2 The yield strength at 0.5% total strain is 18.2 kg / mm². 2The initial coulombic efficiency was 90.38%. The porous structure can alleviate the stress generated by the expansion of silicon-carbon anode materials and improve the adhesion of anode materials. The cycle life reached 212 cycles.

[0183] In Example 2, the catalyst layer composition was a titanium-zinc alloy. Compared with nickel, zinc diffuses more easily in copper. After heating, the active components of the catalyst layer decreased, resulting in an increase in the porosity of the nickel alloy layer obtained by electroless plating to 32%. Ultimately, the micropore distribution density on the copper foil surface increased, the yield strength decreased, and the cycle life was improved compared to Example 1.

[0184] In Example 3, compared to Example 1, increasing the concentration of the alkaline etching solution helps to expand the inner diameter of the micropores. Since the porosity of the nickel alloy layer does not change significantly, the micropore distribution density does not change significantly either, and the yield strength decreases slightly to 17.5 kg / mm². 2 The cycle life is not much different from that of Example 1.

[0185] Example 4, compared to Example 1, increased the mass fraction of nickel in the catalyst layer and increased the temperature and time of the heat treatment of the catalyst layer, which facilitated the diffusion of nickel into copper, resulting in an increase in the porosity of the electroless plated nickel alloy layer to 40%, and ultimately achieving a micropore distribution density of 342 pores / mm on the copper foil surface. 2 The yield strength is 13.1 kg / mm². 2 The reduced yield strength makes it impossible for copper foil to remain stable for extended periods during battery applications, thus reducing its cycle life to 174 cycles.

[0186] In Example 5, compared to Example 1, slightly increasing the time and temperature of the alkaline etching solution B increased the inner diameter of the micropores and decreased the yield strength. Because the change in micropore density was small, the cycle life decay was not significant.

[0187] In Comparative Example 1, without chemical oxidation treatment of the nickel alloy layer, the corrosion resistance of the nickel alloy layer decreased. During the etching process, the porosity of the nickel alloy layer dynamically increased, leading to a significant increase in the micropore inner diameter and micropore distribution density, and a decrease in yield strength to 10.3 kg / mm². 2 During repeated charging and discharging, fine cracks will form on the copper foil, resulting in a cycle life of only 119 cycles.

[0188] In Comparative Example 2, the catalyst layer consisted only of titanium, which prevented the nickel alloy layer from forming effective pores. As a result, the micropore diameter and distribution density of the copper foil were too small, and the initial coulombic efficiency was less than 84%.

[0189] In Comparative Example 3, the catalyst layer was not subjected to a reducing atmosphere protection heat treatment before the nickel alloy layer was deposited. As a result, the catalyst layer lost its catalytic activity, making it impossible to carry out subsequent chemical plating and thus impossible to obtain a nickel alloy layer as a porous template.

[0190] Comparative Example 4: Extending the etching time of alkaline etching solution B in step (4) increases the micropore inner diameter to 29.3 μm, and significantly reduces the yield strength of the micropore copper foil and the cycle life of the battery.

[0191] As can be seen from the above embodiments, the present invention provides a method for preparing microporous copper foil, comprising the following steps: (1) pretreating the surface of copper foil; (2) depositing a catalytic layer on the surface of the copper foil pretreated in step (1); (3) placing the copper foil obtained in step (2) in a chemical plating solution to deposit a nickel alloy layer; (4) chemically oxidizing the nickel alloy layer and then performing alkaline etching; (5) selectively etching away the nickel alloy layer on the surface of the copper foil, cleaning, and obtaining microporous copper foil. This method does not require destructive treatment of the cathode roller or ultra-high temperature treatment. It only requires constructing a soluble nickel alloy layer on the surface of the copper foil substrate to serve as a template for the microporous copper foil. The method is simple, and the resulting microporous copper foil has increased micropore distribution density and higher yield strength.

[0192] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing microporous copper foil, comprising the following steps: (1) Pre-treat the surface of the copper foil; (2) A catalyst layer is deposited on the copper foil surface that has been pretreated in step (1); the catalyst layer includes any two or more of the following elements: nickel, iron, titanium, and zinc. The copper foil obtained in step (2) is heated at a temperature of 50~100℃ for 20~60 min under a reducing atmosphere; (3) Place the copper foil obtained in step (2) in a chemical plating solution to deposit a nickel alloy layer; (4) The nickel alloy layer is chemically oxidized and then alkaline etched; the chemical oxidation is carried out by photocatalytic oxidation; the photocatalytic oxidation uses Degussa P25 titanium dioxide photocatalyst, with a light wavelength of 280~460nm and a light intensity of 300~900mW / cm. 2 ; Alkaline etching involves first performing the etching in alkaline etching solution A, and then performing it in alkaline etching solution B. The alkaline etching solution A comprises 30-100 g / L hydrogen peroxide, 10-50 g / L bipyridine, 30-60 g / L boric acid, and 15-40 g / L borax. The pH is adjusted to 7.8-9.0 using sodium hydroxide, and the remainder is water. The etching temperature of alkaline etching solution A is 25-40°C, and the etching time is 5-15 seconds. The alkaline etching solution B comprises 50-100 g / L copper chloride dihydrate, 80-120 g / L ammonium chloride, 200-400 g / L ammonia, and the remainder is water; the etching temperature of the alkaline etching solution B is 35-50℃, and the etching time is 15-60 s. (5) Selectively etch away the nickel alloy layer on the surface of the copper foil, clean it, and obtain microporous copper foil.

2. The preparation method according to claim 1, characterized in that, The pretreatment method is micro-etching; The micro-etching solution used includes 80-120 g / L concentrated sulfuric acid, 10-60 g / L hydrogen peroxide, 0.5-3 g / L corrosion inhibitor, 20-100 mg / L chloride ions, 0.02-0.1 g / L stabilizer, 3-20 g / L solubilizer, and the remainder is water. The corrosion inhibitor is selected from one or more of 2-mercaptobenzimidazole, benzotriazole, 4-methylbenzotriazole, sodium 2-mercaptobenzimidazole-5-sulfonate, and 1-phenyl-5-mercapto-tetrazazole; The stabilizer is selected from one or more of polymethacrylamide propyltrimethylammonium chloride, polydimethyldiallylammonium chloride, and dimethylaminoethyl methacrylate copolymer with quaternized ammonium methacrylate. The solubilizer is selected from anhydrous ethanol and / or polyethylene glycol; The micro-etching temperature is 25~40℃, and the time is 40~90s; the surface roughness Rz of the copper foil after micro-etching is 0.5~3.0μm.

3. The preparation method according to claim 1, characterized in that, The pretreatment method is roughening, and the roughening solution used includes 8~15g / L of copper ions, 90~110g / L of sulfuric acid, 5~40mg / L of additives, and the remainder is pure water; The additive is selected from one or more of urea, choline chloride, sodium tungstate, sodium metasilicate, potassium sodium tartrate, sodium molybdate, and vanadium pentoxide. The current density used for roughening is 8~20 A / dm. 2 The roughening time is 5~20s, and the roughening temperature is 30~40℃.

4. The preparation method according to claim 1, characterized in that, The electroless plating solution includes a nickel source, a phosphorus source, a complexing agent, a buffer, and a stabilizer; The nickel source is selected from nickel sulfate hexahydrate or nickel chloride hexahydrate; The phosphorus source is selected from sodium hypophosphite monohydrate; The complexing agent is selected from trisodium citrate dihydrate and / or potassium pyrophosphate; The buffer is selected from boric acid; The stabilizer is selected from bismuth nitrate and / or bismuth sulfate; The concentration of nickel sulfate hexahydrate is 50-100 g / L, the concentration of nickel chloride hexahydrate is 30-100 g / L, the concentration of sodium hypophosphite monohydrate is 20-60 g / L, the concentration of sodium citrate dihydrate is 100-200 g / L, the concentration of potassium pyrophosphate is 100-300 g / L, the concentration of boric acid is 30-60 g / L, and the stabilizer is 1-10 mg / L based on the bismuth ion concentration. The pH value of the chemical plating solution is 7~9; The deposition temperature of nickel alloy is 55~75℃.

5. The preparation method according to claim 1, characterized in that, The etching solution used in step (5) is an acidic copper sulfate etching solution; The acidic copper sulfate etching solution comprises 200-300 g / L copper sulfate pentahydrate, 3-15 g / L concentrated sulfuric acid, and the remainder is water; The etching temperature is 80~95℃.

6. A microporous copper foil, characterized in that, Prepared by the preparation method according to any one of claims 1 to 5; The microporous copper foil includes a copper foil body and micropores distributed on both sides of the copper foil body; The depth of the micropores in the direction perpendicular to the copper foil surface is 1.0~2.5μm, and the inner diameter of the micropores is 13~25μm; The total areal density of the microporous copper foil is 0.32~1.56 g / dm³. 2 .

7. The microporous copper foil according to claim 6, characterized in that, The distribution density of micropores on the surface of the microporous copper foil is 100~350 per mm. 2 Arithmetic mean waviness W on the surface of microporous copper foil a Less than or equal to 2.0 μm.

8. A negative electrode current collector, comprising a microporous copper foil prepared by the preparation method according to any one of claims 1 to 5.

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