A method for preparing electrolyte of microporous copper foil

Abstract

The present invention discloses a method for preparing an electrolyte for microporous copper foil, comprising the following steps: adding copper raw material, sulfuric acid, and deionized water according to a process ratio into a copper dissolving tank for mixing; introducing steam to cause the copper to oxidize and react with the sulfuric acid to form a copper sulfate solution; filtering the copper sulfate solution to obtain a copper sulfate electrolyte; and adding the copper sulfate electrolyte to the electrolyte tank. The present invention prepares the copper sulfate electrolyte and adds the required copper foil additives to the copper sulfate electrolyte to obtain a microporous copper foil with uniform micropore size, uniform micropore distribution, and a bright foil surface. The microporous region has dense and smooth crystals and high tensile strength, making it suitable for use in various fields such as all-solid-state secondary batteries, polymer secondary batteries, and lithium-ion supercapacitors.

Description

Technical Field

[0001] The present invention relates to the technical field of electrolytic copper foil preparation, and in particular to an electrolyte method for preparing microporous copper foil. Background Art

[0002] Lithium-ion batteries, due to their high energy density, long cycle life, and low self-discharge, are widely used in new energy vehicle power batteries, consumer electronics, and energy storage systems. Lithium-ion batteries are the preferred power source for new energy vehicles, so producing lithium-ion batteries with enhanced safety, high energy density, and low cost is crucial to the development of the new energy vehicle industry.

[0003] Improving the safety and energy density of lithium-ion batteries has always been a goal for battery companies. Lithium-ion batteries are composed of anode, cathode, separator, and electrolyte. To reduce the weight of the copper foil used as the cathode current collector, in addition to producing thinner copper foil, microporous copper foil is also an important development direction.

[0004] Microporous copper foil is a foil with micron-sized pores, making it lighter than foils of the same thickness. At the same time, microporous copper foil can increase the contact area between the positive and negative electrode materials and the foil, enhancing the adhesion of the material, thereby better preventing powder shedding and material dropout, and reducing the electrode contact internal resistance, thereby increasing power density. Micropores can enhance the bonding strength between the copper foil and the electrode material, improving battery safety, and reduce the amount of binder used, increasing surface density and thus increasing specific energy. At the same time, micropores can improve the electrolyte infiltration efficiency in the battery, so microporous copper foil can be widely used in various fields such as all-solid-state secondary batteries, polymer secondary batteries, and lithium-ion capacitors.

[0005] Current methods for producing microporous copper foil include copper foil punching, oxidation etching, and electroplating. The punching method involves mechanically punching or laser-drilling holes in the original copper foil substrate. The oxidation etching method is performed on certain alloy carriers. The alloy cathode is first oxidized to form a certain oxide film. A copper layer is then electrolytically deposited on the oxide film. The uneven conductivity of the oxide film is exploited to cause copper particles to precipitate, forming the microporous copper foil. The punching method has high production costs and may produce burrs at the edges of the holes. In the oxidation etching method, the oxide film changes over time, making it difficult to control the pore size and porosity. The electroplating method pre-treats and shields the cathode substrate, then deposits microporous copper foil onto the cathode substrate through an electric current to form the finished product. This method allows for continuous production and effectively guarantees the pore size and porosity.

[0006] However, when producing microporous copper foil using electroplating, because the substrate surface is pre-treated and shielded, poor control of the cuprate ions in the electrolyte, temperature exceeding the specified range, or suboptimal additive performance during electroplating can lead to copper buildup on the pore walls, deformation of the pores, de-pore formation, and color variations. Furthermore, due to the presence of pores in microporous copper foil, loose copper ion deposition at the edges of the pores can result in insufficient tensile strength. Furthermore, if copper buildup on the pore walls reaches a certain level, it can adhere to the titanium roller surface, making it difficult to peel, leading to foil tearing and impacting production.

[0007] There is currently no effective solution to the above problems. Summary of the Invention

[0008] In response to the above-mentioned technical problems in the related art, the present invention proposes a method for preparing an electrolyte for microporous copper foil. By preparing a copper sulfate electrolyte and adding the required copper foil additives to the copper sulfate electrolyte, a microporous copper foil with uniform micropore size, uniform micropore distribution, and bright foil surface color is obtained; and the microporous area is densely crystallized and smooth, with high tensile strength, which can meet the needs of use in various fields such as all-solid-state secondary batteries, polymer secondary batteries, lithium-ion supercapacitors, etc., and can overcome the above-mentioned shortcomings of the prior art.

[0009] To achieve the above technical objectives, the technical solution of the present invention is implemented as follows:

[0010] A method for preparing an electrolyte for microporous copper foil comprises the following steps:

[0011] S1: copper raw materials are added to a copper dissolving tank together with sulfuric acid and deionized water according to the process ratio. When steam is introduced, copper is oxidized and reacts with sulfuric acid to form a copper sulfate solution. The copper sulfate solution is filtered to obtain a copper sulfate electrolyte, which is added to an electrolyte tank. The copper sulfate electrolyte has a copper ion concentration of 70-90 g / L and a sulfuric acid content of 100-120 g / L. When the copper sulfate electrolyte flow rate is 30-50 m 3 / hour, the temperature of the electrolyte is 50-60°C when entering the foil machine;

[0012] S2 adds a copper foil additive specifically for microporous copper foil into the electrolyte tank, wherein the copper foil additive includes chloride ions, brightener, leveling agent and wetting agent;

[0013] S3 performs local shielding treatment on the cathode roller of the electrolytic foil;

[0014] S4 transports the copper sulfate in the electrolyte tank to the foil machine for electrolytic foil production;

[0015] After S5 electrolytic foil is produced, it is treated with chromic acid aqueous solution for anti-oxidation, and a double-sided bright copper foil with uniform micropores can be produced.

[0016] 2. The method for preparing an electrolyte for microporous copper foil according to claim 1, wherein the specific steps of S1 are as follows:

[0017] S11: adding cathode copper plates with a purity of ≥99.9% and copper wires with a purity of ≥99.8% into a copper dissolving tank containing sulfuric acid in a ratio of 1:1 or 1:2, wherein the diameter of the copper wires is 3-8 mm;

[0018] S12 uses a screw fan to blow high-temperature air to dissolve the copper and prepare a copper sulfate solution;

[0019] S13 is coarsely filtered through a diatomaceous earth filter and then finely filtered through a precision filter to finally obtain a pure electrolyte.

[0020] Furthermore, the copper foil additive is added by preparing chloride ions, brightener, leveling agent and wetting agent at specific concentrations through different additive barrels or adding units, and adding them into the copper sulfate electrolyte at a specific flow rate before electrolyzing the copper foil.

[0021] Furthermore, the chloride ion preparation method is to add a hydrogen chloride solution with a content of 36-38% into deionized water to prepare a hydrogen chloride aqueous solution with a concentration of 0.25-0.5%, wherein the chloride ion concentration in the hydrogen chloride aqueous solution is 15-25 mg / L.

[0022] Furthermore, the brightener is DPS (sodium N,N-dimethyldithiocarboxamide propane sulfonate) containing S and N, and the concentration range of DPS after being added to the electrolyte is 10-20 mg / L.

[0023] Furthermore, the wetting agent is PEG with a molecular weight of 4000-6000, and the concentration of the PEG after being added into the electrolyte is 5-10 mg / L.

[0024] Furthermore, the leveling agent is a mixture of collagen and iodine, which improves the leveling performance of microporous copper foil through the interaction between iodine ions and collagen; the concentration of the collagen after being added to the electrolyte is 8-15 mg / L, and the concentration of the iodine after being added to the electrolyte is 2-4 mg / L.

[0025] Furthermore, after the copper foil additive is added to the electrolyte tank, the concentration of different additive components in the electrolyte is measured by cyclic voltammetry stripping method, and then the amount of additive added is adjusted according to the concentration value at the measuring point.

[0026] Furthermore, the method of locally shielding the cathode roller of the electrolytic foil includes etching the cathode roller base surface and then making shielding points with shielding material, or pre-coating the cathode roller base surface with a material having good insulation properties to make shielding points.

[0027] Furthermore, the shielding point diameter is 100-1000 μm, the copper foil prepared by electrolysis has a thickness of 6-12 μm, the micropore diameter of the copper foil is 100-1000 μm, and the porosity of the copper foil is between 10% and 30%.

[0028] Beneficial effects of the present invention:

[0029] The present invention prepares a copper sulfate electrolyte and adds a required copper foil additive to the copper sulfate electrolyte to obtain a microporous copper foil with uniform micropore size, uniform micropore distribution and bright foil surface color. The microporous copper foil can be prepared with a pore size range of 100-1000 μm, the micropore diameter deviation can be controlled within ±50 μm, and the pore size can be adjusted according to process requirements. The porosity of the prepared microporous copper foil can be distributed between 10% and 30%, the micropore size is uniformly distributed, the pore wall is smooth without copper nodules, and the copper foil surface has good uniformity without obvious color difference.

[0030] Secondly, the prepared microporous copper foil has good performance. The tensile strength of the prepared microporous copper foil can reach more than 300MPa, which is more than 50% higher than the tensile strength of 200MPa microporous copper foil produced by ordinary processes. It can better meet the use requirements of all-solid-state lithium-ion secondary batteries, polymer lithium-ion batteries, and supercapacitors.

[0031] Thirdly, compared with ordinary electrolyte processes, the copper ion demand is lower and the electrolyte flow demand is lower, which can improve the copper accumulation phenomenon in the electrolyte system and pipelines, and reduce manufacturing costs.

[0032] In addition, the use of special additives for microporous copper foil has a stronger leveling effect and a stronger ability to suppress defects. While improving the quality of the foil surface, it can reduce the use of additives and reduce costs. In long-term production, the process method is simple to operate and has high production stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0034] Figure 1 is a flow chart of an electrolyte method for preparing microporous copper foil according to an embodiment of the present invention;

[0035] Figure 2 Schematic diagram of the structure of an apparatus for preparing an electrolyte solution for microporous copper foil according to an embodiment of the present invention;

[0036] Figure 3 3. The SEM morphology comparison of microporous copper foils prepared using the electrolyte method for preparing microporous copper foils according to an embodiment of the present invention. The images shown are morphologies of the micropores at 100X magnification. The left, middle, and right images represent the first, second, and third levels of the microporous copper foil morphology, respectively.

[0037] In the figure: 1. Copper dissolving tank; 2. Electrolyte tank; 3. Foil raw machine; 4. Anti-oxidation treatment tank; 5. Additive A barrel; 6. Additive B barrel; 7. Additive C barrel; 8. Additive D barrel. DETAILED DESCRIPTION

[0038] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention are within the scope of protection of the present invention.

[0039] like Figure 1-2 As shown, an electrolyte process for preparing microporous copper foil according to an embodiment of the present invention includes the following steps:

[0040] 1) First, copper raw materials such as copper plates and copper wires are put into a copper dissolving tank together with sulfuric acid and deionized water according to the process ratio. When steam is introduced, the copper is oxidized and reacts with sulfuric acid to produce a copper sulfate solution;

[0041] 2) Add a copper foil additive specifically for microporous copper foil into the electrolyte tank. This additive is added into the electrolyte system by combining multiple components.

[0042] 3) Partially shield the cathode roller of the electrolytic foil;

[0043] 4) transporting the copper sulfate in the electrolyte tank to the foil production machine for electrolytic foil production;

[0044] 5) After electrolytic production, the foil is treated with chromic acid aqueous solution for anti-oxidation to produce a copper foil with bright double sides and uniform micropores.

[0045] In step 1), a cathode copper plate with a purity of 99.9% or more and a copper wire with a purity of 99.8% or more are added to a copper dissolving tank containing sulfuric acid in a ratio of 1:1 or 1:2, and high-temperature air is blown into the tank using a screw blower to dissolve the copper to prepare a copper sulfate solution. The solution is coarsely filtered through a diatomaceous earth filter and then finely filtered through a security precision filter to obtain a pure electrolyte.

[0046] In step 1), the copper sulfate electrolyte has a copper ion concentration of 70-90 g / L, a sulfuric acid content of 100-120 g / L, and a flow rate of 30-50 m 3 / hour, the temperature of the electrolyte is 50-60°C when entering the foil production machine.

[0047] The step 2) is to add the core component additive of the electrolytic copper foil into the filtered electrolyte, and the additive is added into the electrolyte system by combining multiple components.

[0048] The method for adding additives in step 2) is to prepare chloride ions, brighteners, leveling agents, wetting agents, etc. according to specific concentrations through different additive barrels, and add them into the copper sulfate electrolyte at a specific flow rate.

[0049] The chloride ion is prepared by adding a hydrogen chloride solution with a content of 36-38% into deionized water to prepare a hydrogen chloride aqueous solution with a concentration of 0.25-0.5%.

[0050] The aqueous hydrogen chloride solution is added to the copper sulfate electrolyte to provide chloride ions as a copper foil additive, which plays a role in cathode depolarization and promotes copper deposition during the electrodeposition process, improves the morphology of the copper foil micropore edges, and makes the pore wall structure denser.

[0051] The additives of the microporous copper foil in step 2) also include brightener, wetting agent and leveling agent.

[0052] The brightener is DPS (sodium N,N-dimethyldithiocarboxamide propane sulfonate) containing S and N, which replaces the common additive SPS (sodium polydisulfide propane sulfonate) because the former has the properties of both brightener and leveler and can preform defects on the holes of microporous copper foil. After DPS is added to the electrolyte, its concentration range is 10-20 mg / L.

[0053] The wetting agent is a macromolecular PEG, which can block the diffusion of copper ions near the cathode and thus inhibit the reduction of copper ions, ultimately making the microporous copper foil more dispersed and flat. Its molecular weight is 4000-6000, and its concentration after adding into the electrolyte is 5-10 mg / L.

[0054] The leveling agent uses collagen and iodine as additives, and the interaction between iodine ions and collagen improves the leveling performance of the microporous copper foil and can reduce the amount of collagen used.

[0055] The collagen iodine additive has a concentration of 8-15 mg / L after the collagen is added to the electrolyte, and a concentration of 2-4 mg / L after the iodine is added to the electrolyte.

[0056] The additives include chloride ions, brighteners, leveling agents, and wetting agents. After being added to the electrolyte tank, the concentration of different additive components in the electrolyte is determined by cyclic voltammetry stripping method, and the amount of additive added is adjusted according to the concentration value at the measuring point.

[0057] The step 3) is to perform local shielding on the cathode roller of the electrolytic foil. The shielding method includes etching shielding points on the surface of the cathode roller substrate, or pre-coating the cathode roller substrate with a material having good insulation properties to form shielding points.

[0058] The diameter of the shielding points on the surface of the substrate is 100-1000 μm, the diameter of the micropores of the copper foil prepared by electrolysis is 100-1000 μm, and the porosity of the copper foil is between 10% and 30%.

[0059] The step 4) is to transport the copper sulfate electrolyte to the foil machine for electrolysis of the foil, and the current density of the foil machine for electrolysis of the foil is 40-60A / dm 2 After electrolytic foil production, chromium anhydride aqueous solution or silane coupling agent is used for anti-oxidation treatment to produce microporous copper foil with uniform pores and bright double sides. The thickness of the microporous copper foil is 6-12μm.

[0060] In order to facilitate understanding of the above technical solutions of the present invention, the above technical solutions of the present invention are described in detail below through specific usage methods.

[0061] In specific use, according to the electrolyte process for preparing microporous copper foil described in the present invention, Example 1: A cathode copper plate with a purity of ≥99.9% and a copper wire with a purity of ≥99.8% are added to a copper dissolving tank 1 containing sulfuric acid in a ratio of 1:2, and high-temperature air is blown into the copper using a screw blower to dissolve the copper to prepare a copper sulfate solution. The copper sulfate solution is filtered through multiple stages and enters the electrolyte tank 2 for storage. Additives are added to the electrolyte tank 2. The copper ion concentration in the electrolyte tank 2 is 90g / L, the sulfuric acid content is 110g / L, and the flow rate is 50m 3 / hour, the electrolyte with a temperature of 55℃ is transported to the foil machine 3 to produce 8μm microporous copper foil. The foil current density is 55A / dm 2 After the raw foil is processed through an anti-oxidation liquid treatment tank 4, a microporous copper foil is finally obtained.

[0062] The additives added to the electrolyte storage tank 2 include: barrel A 5 containing a 0.5% aqueous solution of hydrogen chloride, with a chloride ion concentration of 20 mg / L in the electrolyte tank 2; barrel B 6 containing a brightener DPS, with a brightener concentration of 15 mg / L in the electrolyte tank 2; barrel C 7 containing a wetting agent PEG, with a concentration of 7.5 mg / L in the electrolyte tank 2; and barrel D 8 containing a leveling agent collagen, with a concentration of 8 mg / L in the electrolyte tank 2.

[0063] Four rolls of 1,000-meter microporous copper foil were produced in batches and samples were taken for testing. The average diameter of the micropores in the copper foil was 145 μm, the porosity was 16%, the copper foil was rough, and there was slight copper accumulation on the pore walls. After baking at 150°C for 10 minutes, the average tensile strength was measured to be 267 MPa and the average elongation was 1.8%.

[0064] Example 2: A cathode copper plate with a purity of ≥99.9% and a copper wire with a purity of ≥99.8% are added to a copper dissolving tank 1 containing sulfuric acid in a ratio of 1:2, and high-temperature air is blown into the tank by a screw blower to dissolve the copper into a copper sulfate solution. The copper sulfate solution is filtered through multiple stages and then stored in an electrolyte tank 2. Additives are added to the electrolyte tank. The copper ion concentration in the electrolyte tank is 80 g / L, the sulfuric acid content is 110 g / L, and the flow rate is 40 m 3 / hour, the electrolyte with a temperature of 55℃ is transported to the foil machine 3 to produce 8μm microporous copper foil. The foil current density is 55A / dm 2 After the raw foil is processed through an anti-oxidation liquid treatment tank 4, a microporous copper foil is finally obtained.

[0065] The additives added to the electrolyte storage tank 2 include: barrel A 5 containing a 0.5% hydrogen chloride aqueous solution, and the chloride ion concentration in the electrolyte tank 2 is 20 mg / L; barrel B 6 containing a brightener DPS, and the brightener concentration in the electrolyte tank 2 is 15 mg / L; barrel C 7 containing a wetting agent PEG, and the concentration in the electrolyte tank 2 is 5 mg / L; barrel D 8 containing a leveling agent collagen, and the concentration in the electrolyte tank 2 is 8 mg / L.

[0066] Four rolls of 1000-meter microporous copper foil were produced in batches and samples were taken for testing. The average diameter of the micropores in the copper foil was 151μm, the porosity was 17%, the micropores were rough, and there was slight copper accumulation on the pore walls. After baking at 150°C for 10 minutes, the average tensile strength was measured to be 272MPa and the average elongation was 1.7%.

[0067] Example 3: A cathode copper plate with a purity of ≥99.9% and a copper wire with a purity of ≥99.8% are added to a copper dissolving tank 1 containing sulfuric acid in a ratio of 1:2, and a screw blower is used to blow high-temperature air to dissolve the copper to prepare a copper sulfate solution. The copper sulfate solution is filtered through multiple stages and then stored in an electrolyte tank 2. Additives are added to the electrolyte tank. The copper ion concentration in the electrolyte tank is 80 g / L, the sulfuric acid content is 110 g / L, and the flow rate is 40 m 3 / hour, the electrolyte with a temperature of 55℃ is transported to the foil machine 3 to produce 8μm microporous copper foil. The foil current density is 55A / dm 2 After the raw foil is processed through an anti-oxidation liquid treatment tank 4, a microporous copper foil is finally obtained.

[0068] The additives added to the electrolyte storage tank 2 include: barrel A 5 containing a 0.5% aqueous hydrogen chloride solution, with a chloride ion concentration of 22 mg / L in the electrolyte tank 2; barrel B 6 containing a brightener DPS, with a brightener concentration of 17 mg / L in the electrolyte tank 2; barrel C 7 containing a wetting agent PEG, with a concentration of 5 mg / L in the electrolyte tank 2; and barrel D 8 containing a leveling agent collagen, with a concentration of 8 mg / L in the electrolyte tank 2.

[0069] Four rolls of 1000-meter microporous copper foil were produced in batches and samples were taken for testing. The average diameter of the micropores in the copper foil was 166μm, the porosity was 19%, the micropores were slightly rough, and the pore walls were slightly copper-deposited. After baking at 150°C for 10 minutes, the average tensile strength was measured to be 285MPa and the average elongation was 1.7%.

[0070] Example 4: A cathode copper plate with a purity of ≥99.9% and a copper wire with a purity of ≥99.8% are added to a copper dissolving tank 1 containing sulfuric acid in a ratio of 1:2, and high-temperature air is blown into the tank by a screw blower to dissolve the copper into a copper sulfate solution. The copper sulfate solution is filtered through multiple stages and then stored in an electrolyte tank 2. Additives are added to the electrolyte tank. The copper ion concentration in the electrolyte tank is 80 g / L, the sulfuric acid content is 110 g / L, and the flow rate is 40 m 3 / hour, the electrolyte with a temperature of 55℃ is transported to the foil machine 3 to produce 8μm microporous copper foil. The foil current density is 55A / dm 2 After the raw foil is processed through an anti-oxidation liquid treatment tank 4, a microporous copper foil is finally obtained.

[0071] The additives added to the electrolyte storage tank 2 include: barrel A 5 containing a 0.5% hydrogen chloride aqueous solution, and the chloride ion concentration in the electrolyte tank 2 is 22 mg / L; barrel B 6 containing a brightener DPS, and the brightener concentration in the electrolyte tank 2 is 17 mg / L; barrel C 7 containing a wetting agent PEG, and the concentration in the electrolyte tank 2 is 5 mg / L; barrel D 8 containing a leveling agent collagen, and the concentration in the electrolyte tank 2 is 11.5 mg / L; barrel F 9 containing a leveling agent iodine, and the concentration in the electrolyte tank 2 is 2 mg / L.

[0072] Four rolls of 1,000-meter microporous copper foil were produced in batches and samples were taken for testing. The average diameter of the micropores in the copper foil was 203 μm, the porosity was 24%, the micropore morphology was uniform, and the pore walls were smooth. After baking at 150°C for 10 minutes, the average tensile strength was measured to be 326 MPa and the average elongation was 1.9%.

[0073] Example 5: A cathode copper plate with a purity of ≥99.9% and a copper wire with a purity of ≥99.8% are added to a copper dissolving tank 1 containing sulfuric acid in a ratio of 1:2, and high-temperature air is blown into the tank by a screw blower to dissolve the copper into a copper sulfate solution. The copper sulfate solution is filtered through multiple stages and then stored in an electrolyte tank 2. Additives are added to the electrolyte tank. The copper ion concentration in the electrolyte tank is 80 g / L, the sulfuric acid content is 110 g / L, and the flow rate is 40 m 3 / hour, the electrolyte with a temperature of 55℃ is transported to the foil machine 3 to produce 8μm microporous copper foil. The foil current density is 55A / dm 2 After the raw foil is processed through an anti-oxidation liquid treatment tank 4, a microporous copper foil is finally obtained.

[0074] The additives added to the electrolyte storage tank 2 include: barrel A 5 containing a 0.5% aqueous hydrogen chloride solution, and the chloride ion concentration in the electrolyte tank 2 is 22 mg / L; barrel B 6 containing a brightener DPS, and the brightener concentration in the electrolyte tank 2 is 17 mg / L; barrel C 7 containing a wetting agent PEG, and the concentration in the electrolyte tank 2 is 5 mg / L; barrel D 8 containing a leveling agent collagen, and the concentration in the electrolyte tank 2 is 15 mg / L; barrel F 9 containing a leveling agent iodine, and the concentration in the electrolyte tank 2 is 4 mg / L.

[0075] Four rolls of 1,000-meter microporous copper foil were produced in batches and samples were taken for testing. The average diameter of the micropores in the copper foil was 180 μm, and the porosity was 21%. The microporous copper foil was slightly rough and the smoothness of the pore wall was reduced. After baking at 150°C for 10 minutes, the average tensile strength was measured to be 319 MPa and the average elongation was 1.7%.

[0076] Comparative Example 1: A cathode copper plate with a purity of ≥99.9% and a copper wire with a purity of ≥99.8% are added to a copper dissolving tank 1 containing sulfuric acid in a ratio of 1:2, and a screw blower is used to blow high-temperature air to dissolve the copper to prepare a copper sulfate solution. The copper sulfate solution is filtered through multiple stages and then stored in an electrolyte tank 2. Additives are added to the electrolyte tank. The copper ion concentration in the electrolyte tank is 90g / L, the sulfuric acid content is 110g / L, and the flow rate is 45m 3 / hour, the electrolyte with a temperature of 55℃ is transported to the foil machine 3 to produce 8μm microporous copper foil. The foil current density is 55A / dm 2 After the raw foil is processed through an anti-oxidation liquid treatment tank 4, a microporous copper foil is finally obtained.

[0077] The additives added to the electrolyte storage tank 2 include: barrel A 5 containing a 0.5% hydrogen chloride aqueous solution, with a chloride ion concentration of 20 mg / L in the electrolyte tank 2; barrel B 6 containing a brightener SPS, with a concentration of 15 mg / L in the electrolyte tank 2; barrel C 7 containing a wetting agent PEG, with a concentration of 5 mg / L in the electrolyte tank 2; and barrel D 8 containing a leveling agent collagen, with a concentration of 10 mg / L in the electrolyte tank 2.

[0078] Four rolls of 1,000-meter microporous copper foil were produced in batches, and samples were taken for testing. The average diameter of the micropores in the copper foil was 89μm, the porosity was 13%, and there was serious copper accumulation on the micropore walls. After baking at 150°C for 10 minutes, the average tensile strength was measured to be 213MPa and the average elongation was 1.4%.

[0079] Comparative Example 2: A cathode copper plate with a purity of ≥99.9% and a copper wire with a purity of ≥99.8% are added to a copper dissolving tank 1 containing sulfuric acid in a ratio of 1:2, and a screw blower is used to blow high-temperature air to dissolve the copper to prepare a copper sulfate solution. The copper sulfate solution is filtered through multiple stages and then stored in an electrolyte tank 2. Additives are added to the electrolyte tank. The copper ion concentration in the electrolyte tank is 90g / L, the sulfuric acid content is 110g / L, and the flow rate is 45m 3 / hour, the electrolyte with a temperature of 55℃ is transported to the foil machine 3 to produce 8μm microporous copper foil. The foil current density is 55A / dm 2 After the raw foil is processed through an anti-oxidation liquid treatment tank 4, a microporous copper foil is finally obtained.

[0080] The additives added to the electrolyte storage tank 2 include: barrel A 5 containing a 0.5% aqueous hydrogen chloride solution, with a chloride ion concentration of 22 mg / L in the electrolyte tank 2; barrel B 6 containing a brightener SPS, with a concentration of 20 mg / L in the electrolyte tank 2; barrel C 7 containing a wetting agent PEG, with a concentration of 5 mg / L in the electrolyte tank 2; and barrel D 8 containing a leveling agent collagen, with a concentration of 15 mg / L in the electrolyte tank 2.

[0081] Four rolls of 1000-meter microporous copper foil were produced in batches, and samples were taken for testing. The average diameter of the micropores in the copper foil was 93μm, the porosity was 14%, and there was serious copper accumulation on the micropore walls. After baking at 150°C for 10 minutes, the average tensile strength was measured to be 218MPa and the average elongation was 1.5%.

[0082] The performance and appearance tests of the microporous copper foils prepared in each embodiment and comparative example are shown in Table 1. SEM comparison of microporous copper foils of different grades is shown in Figure 3 .

[0083] Table 1: Summary of implementation results

[0084]

[0085] In summary, by adopting the above-mentioned electrolyte process, a microporous copper foil with uniform micropore size distribution, smooth pore walls and no copper nodules can be obtained. The copper foil prepared in this way has high tensile strength and relatively ideal porosity.

[0086] In summary, with the aid of the above technical solution of the present invention, by preparing a copper sulfate electrolyte and adding the required copper foil additives to the copper sulfate electrolyte, a microporous copper foil with uniform micropore size, uniform micropore distribution, and bright foil surface color is obtained; a microporous copper foil with a pore size range of 100-1000μm can be prepared, the micropore diameter deviation can be controlled between ±50μm, and the pore size can be adjusted according to process requirements; the porosity of the prepared microporous copper foil can be distributed between 10% and 30%, the micropore size is uniformly distributed, the pore wall is smooth without copper nodules, and the copper foil surface has good uniformity without obvious color difference. Secondly, the prepared microporous copper foil has good performance, and the tensile strength of the prepared microporous copper foil can reach more than 300MPa, which is more than 50% higher than the tensile strength of 200MPa microporous copper foil produced by conventional processes, and can better meet the use requirements of all-solid-state lithium-ion secondary batteries, polymer lithium-ion batteries, and supercapacitors. Thirdly, compared to conventional electrolyte processes, the copper ion requirement and electrolyte flow rate requirements are lower, which can improve copper buildup in the electrolyte system and pipelines, and reduce manufacturing costs. Furthermore, the use of additives specifically formulated for microporous copper foil provides a stronger leveling effect and greater defect suppression, improving foil surface quality while reducing additive usage and costs. The process is simple to operate and offers high production stability over long-term production.

[0087] 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 method for preparing a microporous copper foil electrolyte, characterized in that: The steps include: S1: copper raw materials are added to a copper dissolving tank along with sulfuric acid and deionized water according to a process ratio. When steam is introduced, the copper is oxidized and reacts with sulfuric acid to form a copper sulfate solution. The copper sulfate solution is filtered to obtain a copper sulfate electrolyte, which is added to an electrolyte tank. The copper sulfate electrolyte has a copper ion concentration of 70-90 g / L and a sulfuric acid content of 100-120 g / L. When the flow rate of the copper sulfate electrolyte is 30-50 m³ / h, the temperature of the electrolyte is 50-60°C when it enters the foil production machine. S2 adds a copper foil additive specifically for microporous copper foil to the electrolyte tank, wherein the copper foil additive includes chloride ions, a brightener, a leveling agent, and a wetting agent; the leveling agent is a mixture of collagen and iodine, and the interaction between iodine ions and collagen improves the leveling performance of the microporous copper foil; the concentration of the collagen after being added to the electrolyte is 8-15 mg / L, and the concentration of the iodine after being added to the electrolyte is 2-4 mg / L; S3 performs local shielding treatment on the cathode roller of the electrolytic foil; S4 transports the copper sulfate in the electrolyte tank to the foil machine for electrolytic foil production; After S5 electrolytic foil is produced, it is treated with chromic acid aqueous solution for anti-oxidation, and a double-sided bright copper foil with uniform micropores can be produced.

2. The method for preparing a microporous copper foil electrolyte according to claim 1, characterized in that: The specific steps of S1 are as follows: S11 Add cathode copper plates with a purity of ≥99.9% and copper wires with a purity of ≥99.8% into a copper dissolving tank containing sulfuric acid at a ratio of 1:1 or 1:

2. The diameter of the copper wires should be 3-8mm. S12 uses a screw blower to blow high-temperature air to dissolve the copper and prepare a copper sulfate solution; S13 is coarsely filtered through a diatomaceous earth filter and then finely filtered through a precision filter to finally obtain a pure electrolyte.

3. The method for preparing a microporous copper foil electrolyte according to claim 1, characterized in that: The copper foil additive is added by preparing chloride ions, brightener, leveling agent and wetting agent in specific concentrations through different additive barrels or adding units, and adding them into the copper sulfate electrolyte at a specific flow rate before electrolyzing the copper foil.

4. The method for preparing a microporous copper foil electrolyte according to claim 3, characterized in that: The preparation method of the chloride ion is to add a hydrogen chloride solution with a content of 36-38% into deionized water to prepare a hydrogen chloride aqueous solution with a concentration of 0.25-0.5%, wherein the chloride ion concentration in the hydrogen chloride aqueous solution is 15-25 mg / L.

5. The method for preparing a microporous copper foil electrolyte according to claim 3, characterized in that: The brightener is DPS (sodium N,N-dimethyldithiocarboxamide propane sulfonate) containing S and N. The concentration range of DPS after being added to the electrolyte is 10-20 mg / L.

6. The method for preparing a microporous copper foil electrolyte according to claim 3, characterized in that: The wetting agent is PEG with a molecular weight of 4000-6000, and the concentration of the PEG after being added into the electrolyte is 5-10 mg / L.

7. The method for preparing a microporous copper foil electrolyte according to any one of claims 1 to 6, characterized in that: After the copper foil additive is added to the electrolyte tank, the concentration of different additive components in the electrolyte is measured by cyclic voltammetry stripping method, and then the amount of additive added is adjusted according to the concentration value at the measuring point.

8. The method for preparing a microporous copper foil electrolyte according to claim 1, characterized in that: The method for locally shielding the cathode roller of electrolytic foil includes etching the cathode roller base surface and then making shielding points with shielding material, or pre-coating the cathode roller base surface with a material having good insulation properties to make shielding points.

9. The method for preparing a microporous copper foil electrolyte according to claim 8, characterized in that: The shielding point has a diameter of 100-1000 μm, the copper foil prepared by electrolysis has a thickness of 6-12 μm, the micropore diameter of the copper foil is 100-1000 μm, and the porosity of the copper foil is between 10% and 30%.

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