Ultrathin copper foil, preparation method thereof and battery

Abstract

The invention relates to the technical field of batteries, in particular to an ultra-thin copper foil, a preparation method thereof and a battery. The preparation method comprises the following steps: providing an initial copper foil, fixing the initial copper foil on an anode plate, placing the initial copper foil and a cathode plate in an electrolyte together, electrifying and carrying out electrochemical etching, so that the thickness of the initial copper foil fixed on the anode plate is reduced, and the ultra-thin copper foil is obtained. According to the method, the thick initial copper foil is used as the anode, the electrochemical etching method is used for preparing the ultra-thin copper foil, the problems that when the ultra-thin copper foil is produced in the prior art, the copper foil with the specific thickness is selected as a carrier, and stripping is needed again, so that the process is tedious, and the cost is high are solved, and a new thought is provided for development of the ultra-thin copper foil. Meanwhile, no specific requirement on the copper foil of the anode exists, that is, the copper foil at the anode is easy to obtain, and the preparation cost of the ultrathin copper foil is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and more specifically, to an ultrathin copper foil, its preparation method, and a battery. Background Technology

[0002] Electrolytic copper foil is a foil material with a thickness in the micrometer range, prepared from copper using an electrolytic reaction. It can be categorized into lithium-ion battery copper foil and electronic circuit copper foil based on its application. Lithium-ion battery copper foil is primarily used in lithium-ion batteries and is one of the six main components of a lithium-ion battery. As lithium batteries trend towards higher energy density, higher safety, and lower cost, this has driven the trend towards thinner and lighter lithium-ion battery copper foil. Thinner copper foil results in a lighter lithium-ion battery and a higher overall energy density. For lithium-ion battery copper foil manufacturers, it also allows for a reduction in the amount of copper used. Furthermore, less copper foil naturally leads to lower costs. However, the preparation of ultra-thin copper foil with a thickness below 6μm faces challenges due to high technical difficulty and cost.

[0003] Currently, there are two main methods for producing ultra-thin copper foil. One is the electrolytic method, which prepares copper foil by depositing copper ions at the cathode. However, ultra-thin copper foil produced by the electrolytic method often suffers from defects such as edge tearing and pinholes, and the low yield leads to a significant increase in cost. Furthermore, this method requires the addition of more additives during the production of ultra-thin copper foil, further increasing production costs. The other method uses a carrier. First, a copper foil of a certain thickness (usually 18-35 μm) is selected as the carrier. Then, a release layer is prepared on its surface, followed by the deposition of ultra-thin copper foil on the release layer. Finally, a laminate is used to peel off the ultra-thin copper foil. This method uses the copper foil containing the release layer as the cathode, allowing copper ions to deposit on the release layer through electrolysis. This can produce even thinner copper foil, but the production process is complex and the cost is relatively high.

[0004] Therefore, it is necessary to find a new method for preparing ultrathin copper foil to solve the above-mentioned problems in the preparation of ultrathin copper foil. Summary of the Invention

[0005] In view of this, the present invention aims to at least partially solve one of the technical problems in the related art. To this end, the present invention provides an ultra-thin copper foil, a method for preparing the same, and a battery, which can solve the problems of complex production processes and high costs in the existing technology for preparing ultra-thin copper foil.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows: According to one aspect of this application, an embodiment of this application provides a method for preparing an ultrathin copper foil, comprising the following steps: An initial copper foil is provided, which is then fixed around an anode plate and placed in an electrolyte along with a cathode plate. Electrochemical etching is performed by applying an electric current to reduce the thickness of the initial copper foil fixed on the anode plate, resulting in an extremely thin copper foil.

[0007] In some of these embodiments, the initial copper foil thickness is 6-14 μm.

[0008] In some of these embodiments, the initial copper foil roughness Rz is less than 3 μm.

[0009] In some embodiments, the anode plate comprises a titanium plate or an acrylic plate.

[0010] In some of these embodiments, the roughness Ra of the anode plate is less than 0.3 μm.

[0011] In some embodiments, the electrolyte comprises Cu 2+ Complexing agents, additives, halogen anions, and solvents.

[0012] In some of these embodiments, the Cu 2+ The concentration is 0.2~0.5mol / L.

[0013] In some embodiments, the concentration of the complexing agent is 0.45 to 1 mol / L; the complexing agent includes at least one of sodium citrate, triethanolamine, or tetrahydroxypropylethylenediamine.

[0014] In some embodiments, the concentration of the additive is 25-100 mg / L; the additive includes at least one of polyethylene glycol, cellulose, or gelatin.

[0015] In some embodiments, the concentration of the halide anion is 5-25 mg / L; the halide anion includes F... - Cl - I - At least one of the following; preferably, the halide anion is Cl. - .

[0016] In some of these embodiments, the solvent includes water.

[0017] In some embodiments, the complexing agent is a mixture of sodium citrate, triethanolamine, and tetrahydroxypropylethylenediamine, wherein the concentration ratio of sodium citrate, triethanolamine, and tetrahydroxypropylethylenediamine is 1:(1~3):(0.25~1).

[0018] In some embodiments, the additive is a mixture of polyethylene glycol, cellulose and gelatin, wherein the mass ratio of polyethylene glycol, cellulose and gelatin is (10~50):(5~20):(15~30).

[0019] In some of these embodiments, a regulated DC power supply is used when the power is applied.

[0020] In some of these embodiments, the current density is 200~1000 mA / cm². 2 .

[0021] In some of these embodiments, the energizing time is 100 to 500 seconds.

[0022] In some of these embodiments, the temperature of the electrolyte is 20~60°C when energized.

[0023] According to another aspect of this application, an embodiment of this application provides an ultrathin copper foil prepared by the above-described preparation method.

[0024] In some embodiments, the ultrathin copper foil has a thickness of 3.5~4.2μm, a light brightness of 91~107GU at an incident angle of 60°, and a surface roughness Rz of 2~2.6μm.

[0025] According to another aspect of this application, an embodiment of this application provides a battery including an ultrathin copper foil, the ultrathin copper foil including the ultrathin copper foil prepared by the aforementioned preparation method, or the aforementioned ultrathin copper foil.

[0026] The technical solution of this application has at least the following beneficial effects: This application provides an ultra-thin copper foil and its preparation method. The method uses a relatively thick initial copper foil as the anode, and electrochemically etches the initial copper foil at the anode to reduce its thickness, thereby obtaining the target product – the ultra-thin copper foil. The specific mechanism is as follows: under the action of an external power source, the copper on the surface of the initial copper foil at the anode undergoes an oxidation reaction, becoming copper ions that enter the electrolyte. These ions then flow to the cathode plate and are deposited on its surface. By precisely controlling the current density and electrolysis time, the thickness of the initial copper foil at the anode can be precisely reduced, thus obtaining the desired ultra-thin copper foil. Simultaneously, by adjusting the composition of the electrolyte, the brightness and surface roughness of the copper foil are ensured.

[0027] This application solves the problem of cumbersome processes and high costs associated with the previous production of ultra-thin copper foil, which required selecting copper foil of a specific thickness as a carrier and then peeling it off again after cathode deposition. Most importantly, this application does not have specific requirements for the initial copper foil at the anode; that is, copper foil at the anode is readily available. When the thickness of the copper foil generated at the cathode is ≥4.5μm, it can also be peeled off and used as copper foil. This further improves the utilization efficiency of raw materials and effectively reduces the preparation cost of ultra-thin copper foil.

[0028] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0029] Figure 1 The image shown is a scanning electron microscope image of the ultrathin copper foil prepared in Example 5 of the present invention.

[0030] Figure 2 The image shown is a scanning electron microscope (SEM) image of the ultrathin copper foil prepared in Comparative Example 1 of this invention.

[0031] Figure 3 The image shown is a scanning electron microscope image of the ultrathin copper foil prepared in Comparative Example 2 of this invention. Detailed Implementation

[0032] The present application will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the present application.

[0033] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges or individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0034] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0035] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0036] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0038] In the existing technology, the preparation of ultra-thin copper foil with a thickness of less than 6μm faces the problems of high technical difficulty and high cost.

[0039] In view of this, embodiments of this application provide a method for preparing an ultrathin copper foil, comprising the following steps: An initial copper foil is provided, which is then fixed onto an anode plate and placed in an electrolyte along with a cathode plate. Electrochemical etching is performed by applying an electric current, which reduces the thickness of the initial copper foil fixed on the anode plate to obtain an extremely thin copper foil.

[0040] In this application, an initial copper foil is used as the anode. The initial copper foil and the cathode plate are connected by an external power source. After the initial copper foil and the cathode plate are placed in the electrolyte and energized, the initial copper foil at the anode is electrochemically etched to thin it. The copper on the surface of the initial copper foil undergoes an oxidation reaction and becomes copper ions that enter the electrolyte. These ions then flow to the cathode plate and are deposited on the surface of the cathode plate. After the initial copper foil is etched to thin it, an extremely thin copper foil is obtained.

[0041] This application uses a relatively thick initial copper foil as the anode and employs electrochemical etching to etch the initial copper foil at the anode, thereby reducing the thickness of the initial copper foil and producing an ultra-thin copper foil. This solves the problems of cumbersome processes and high costs associated with the previous production of ultra-thin copper foil, which required selecting copper foil of a specific thickness as a carrier and then peeling it off again. Furthermore, this application does not have specific requirements for the copper foil at the anode; that is, the copper foil at the anode can be readily sourced. When the thickness of the copper foil generated at the cathode is ≥4.5μm, it can also be peeled off and used as copper foil, effectively reducing the production cost of ultra-thin copper foil.

[0042] In some embodiments, the initial copper foil thickness used as the anode is 6-14 μm. As an example, the copper foil thickness of the anode can be 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, etc., or other values ​​within the above range, and is not limited here. The copper foil of the anode in this application can be any of the above-mentioned thicknesses for chemical etching, and can be commercially available copper foil, offering advantages such as easy material sourcing and a wide range of selectable thicknesses.

[0043] In some embodiments, the initial copper foil roughness Rz, which serves as the anode, is less than 3 μm. If the initial copper foil roughness is too high, the resulting ultra-thin copper foil will have too high a roughness and will be unusable.

[0044] In some embodiments, the anode plate includes a titanium plate or an acrylic plate. As an example, the anode plate can act as a carrier for the anode copper foil, providing support and fixation. Specifically, the anode copper foil can be fixed to the surface of the anode plate using clamps or double-sided tape. The anode plate is selected based on the principles of acid resistance, resistance to electrolysis, and support function. As an example, its material can be a titanium plate, an acrylic plate, or other acid-resistant and electrolysis-resistant materials.

[0045] In some embodiments, the roughness Ra of the anode plate is less than 0.3 μm. For example, the roughness Ra of the anode plate can be 0.29 μm, 0.25 μm, 0.2 μm, etc. Accordingly, before use, the anode plate can be polished to reduce its roughness Ra to less than 0.3 μm. A roughness Ra within this range ensures that the surface of the anode plate will not scratch the copper foil surface and guarantees the flatness of the copper foil.

[0046] In some embodiments, the electrolyte includes Cu-containing solutions. 2+ Complexing agents, additives, halogen anions, and solvents.

[0047] In some embodiments, Cu 2+ The concentration is 0.2~0.5 mol / L, preferably 0.2~0.4 mol / L. As an example, Cu... 2+ The concentration can be 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, 0.5 mol / L, etc., or other values ​​within the above range; no limitation is made here. Cu in the electrolyte 2+ With a concentration within this range, the Cu in the electrolyte can be ensured. 2+ The content is stable, avoiding hydrogen evolution at the cathode. For example, Cu is provided. 2+ It can be copper sulfate.

[0048] In some embodiments, the concentration of the complexing agent is 0.45~1 mol / L, preferably 0.6~1 mol / L. As an example, the concentration of the complexing agent can be 0.45 mol / L, 0.6 mol / L, 0.75 mol / L, 0.8 mol / L, 1 mol / L, etc., or other values ​​within the above range, which are not limited here.

[0049] In some embodiments, the complexing agent includes at least one of sodium citrate, triethanolamine, or tetrahydroxypropylethylenediamine. A preferred complexing agent is a mixture of sodium citrate, triethanolamine, and tetrahydroxypropylethylenediamine, with a concentration ratio of 1:(1-3):(0.25-1), more preferably 1:(1-2):(0.3-1). As an example, the concentration ratio of sodium citrate, triethanolamine, and tetrahydroxypropylethylenediamine can be 1:1:0.25, 1:2:0.5, 1:2.5:0.9, 1:3:1, etc., and other values ​​within the above range are also possible and are not limited herein. When the concentration ratio of sodium citrate, triethanolamine, and tetrahydroxypropylethylenediamine is lower than the above range, it will affect the reaction rate, resulting in some copper ions not being complexed and forming Cu. + When the concentration ratio of sodium citrate, triethanolamine, and tetrahydroxypropylethylenediamine exceeds the above range, some of the complexing agent cannot dissolve due to exceeding the upper limit of solubility, resulting in waste and adversely affecting the reaction.

[0050] In this application, a combination of complexing agents is preferably used, which can react with Cu 2+ A stable complex is formed, which can be directly reduced to elemental copper deposition without the formation of Cu. + This effectively improves the stability of the electrolyte. Simultaneously, the addition of the complexing agent can alter the reaction potential of copper at the cathode, thereby increasing the deposition rate.

[0051] In some embodiments, the concentration of the additive is 25-100 mg / L, preferably 35-60 mg / L. As an example, the concentration of the additive can be 25 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, 80 mg / L, 90 mg / L, 100 mg / L, etc., or other values ​​within the above range, which are not limited here.

[0052] In some embodiments, the additive includes at least one of polyethylene glycol, cellulose, or gelatin. Preferably, the additive is a mixture of polyethylene glycol, cellulose, and gelatin, with a mass ratio of polyethylene glycol, cellulose, and gelatin of (10~50):(5~20):(15~30), more preferably (10~20):(10~20):(15~20). As an example, the mass ratio of polyethylene glycol, cellulose, and gelatin can be 10:5:15, 20:8:20, 30:12:22, 40:15:25, 50:20:30, etc., and of course, other values ​​within the above range are also possible and are not limited herein. When the mass ratio of polyethylene glycol, cellulose, and gelatin is lower than the above range, phenomena such as insignificant grain refinement and leveling effects will occur, which will affect the electrode spacing. When the mass ratio of polyethylene glycol, cellulose, and gelatin exceeds the above range, abnormalities such as scorching of the cathode copper foil surface will occur, leading to changes in the electrode spacing during electrochemical etching, thereby affecting the uniformity of anode copper foil etching.

[0053] In this application, the hydrophilicity of the additive itself allows for more thorough contact between the electrolyte and the surface of the anode copper foil, thereby ensuring the uniformity of the electrochemical etching process. In addition, the additive also has the effect of refining grains and leveling, making the coating on the surface of the cathode copper foil denser and smoother, avoiding uneven coating thickness that could affect the electrode spacing and ultimately affect the uniformity of the electrochemical etching process. Furthermore, when the additive is a mixture of polyethylene glycol, cellulose, and gelatin, or a combination of any two of them, it can achieve better results than adding a single additive. For example, polyethylene glycol, as a surfactant, enhances the wetting effect of the electrolyte on the electrode surface, while cellulose, as a grain refiner, can effectively reduce the grain size of the copper foil, making the copper foil surface smoother. Gelatin, as a leveling agent, can effectively improve the roughness of the electrolytic copper foil surface. The three work together to achieve a combined effect of wetting, grain refinement, and leveling. By controlling the proportion of the three, a synergistic effect can be achieved, optimizing the above-mentioned wetting, grain refinement, and leveling effects, resulting in better flatness of the cathode copper foil, avoiding uneven electrode spacing, and thus ensuring the uniformity of anode copper foil etching by precisely controlling the electrode spacing.

[0054] In some embodiments, the concentration of halide anions is 5~25 mg / L. For example, the concentration of halide anions can be 5 mg / L, 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, etc., or other values ​​within the above range, which are not limited here. If the concentration of halide anions is too low, the cathode surface cannot be made smooth and bright. The smoothness of the cathode copper foil surface will affect the electrode spacing, indirectly affecting the uniformity of the etching process, adversely affecting the preparation of the ultra-thin anode copper foil, and consequently, the etching effect of the anode copper foil by affecting the electrode spacing. If the concentration of halide anions is too high, the cathode surface will be too rough or even have burrs, which will also affect the electrode spacing and adversely affect the etching effect of the anode copper foil.

[0055] In this application, additives and halogen anions can work together. For example, when polyethylene glycol and chloride ions are used in combination, the "chlorine bridge" effect of chloride ions can be effectively utilized to reduce the adsorption energy of polyethylene glycol at the cathode, making it easier for polyethylene glycol to be adsorbed at the cathode and enhancing the wetting effect of polyethylene glycol.

[0056] In some embodiments, the halide anion includes F - Cl - I - At least one of the following. The halide anion is preferably Cl. - .

[0057] In some embodiments, the solvent includes water.

[0058] In some embodiments, a regulated DC power supply is used when powered on.

[0059] In some embodiments, the current density is 200~1000 mA / cm². 2 Preferably, it is 200~500 mA / cm 2 As an example, the current density could be 200 mA / cm². 2 400mA / cm 2 600mA / cm 2 800mA / cm 2 1000mA / cm 2 "etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0060] In some embodiments, the energizing time is 100~500s, preferably 100~300s. As an example, the electrolysis treatment time can be 100s, 200s, 300s, 400s, 500s, etc., or other values ​​within the above range, which are not limited here.

[0061] In some embodiments, the temperature of the electrolyte during energization is 20~60°C, preferably 30~50°C. As an example, the electrolysis temperature can be 20°C, 30°C, 40°C, 50°C, 60°C, etc., or other values ​​within the above range, which are not limited here.

[0062] In some embodiments, the electrolysis process, in order to eliminate the concentration difference of the electrolyte, also includes steps of stirring or aerating the electrolyte. This application does not limit the specific operating method, as long as the purpose of eliminating the concentration difference of the electrolyte is achieved.

[0063] In some embodiments, the process further includes pickling, washing, and drying of the ultra-thin copper foil. Pickling removes the oxide layer on the surface of the ultra-thin copper foil, and washing removes residual pickling solution from the surface of the ultra-thin copper foil. Pickling solution formulation: Cu 2+ The concentration is 15~20g / L, the H2SO4 concentration is 120~130g / L, and the solvent is water.

[0064] Therefore, based on the above scheme, a method for preparing ultra-thin copper foil is provided. The provided ultra-thin copper foil and its preparation method use initial copper foil as the anode. After electrolysis (electro-etching), ultra-thin copper foil is obtained. The mechanism of obtaining ultra-thin copper foil from the initial copper foil at the anode through electrolysis is as follows: under the action of an external power source, the copper on the surface of the initial copper foil at the anode undergoes an oxidation reaction, becoming copper ions that enter the electrolyte. These ions then flow to the cathode plate and are deposited on the cathode plate surface. The thickness of the initial copper foil can be controlled by controlling the current density and electrolysis time. By adjusting the composition of the electrolyte, the brightness and surface roughness of the copper foil can be ensured. This application solves the problem of cumbersome processes and high costs associated with using copper foil of a specific thickness as a carrier and then peeling it off again after obtaining ultra-thin copper foil at the cathode. Furthermore, this application does not have specific requirements for the copper foil at the anode; that is, the copper foil at the anode is readily available, and the copper foil generated at the cathode can also be peeled off and utilized, effectively reducing the preparation cost of ultra-thin copper foil.

[0065] Based on the same inventive concept, this application provides an ultrathin copper foil prepared by the above-described preparation method.

[0066] It should be understood that all the features and advantages described above regarding the "method for preparing ultra-thin copper foil" also apply to this "ultra-thin copper foil," and will not be repeated here.

[0067] In some embodiments, the thickness of the ultrathin copper foil is 3.5~4.2μm, the gloss level is 91~107GU at an incident angle of 60°, and the surface roughness Rz is 2~2.6μm. In this application, the thickness of the ultrathin copper foil was measured using a Mitutoyo micrometer; the gloss level was measured using a KOSGA gloss meter; and the roughness was measured using a Mitutoyo roughness tester.

[0068] In this application, the ultrathin copper foil has an extremely thin thickness and a surface roughness Rz and brightness comparable to conventional ultrathin copper foil. When used in lithium-ion batteries, it can effectively reduce the weight of lithium-ion batteries and thus increase energy density.

[0069] According to another aspect of this application, an embodiment of this application provides a battery including an ultrathin copper foil, the ultrathin copper foil including the ultrathin copper foil prepared by the aforementioned preparation method, or the aforementioned ultrathin copper foil.

[0070] The following describes the implementation methods of this application. The implementation methods described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the implementation methods, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents, materials, or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0071] Example 1 The initial copper foil thickness at the anode is 6.8 ± 0.2 μm; Electrolyte: Cu 2+ The concentration was 0.2 mol / L, the complexing agent (sodium citrate concentration 0.3 mol / L, triethanolamine to sodium citrate concentration ratio 1:2), the additives (polyethylene glycol concentration 12 mg / L, gelatin concentration 16 mg / L), Cl - The concentration is 15 mg / L.

[0072] Electrolysis conditions: Temperature 35℃, Current density 330mA / cm³ 2 The etching time was 150 seconds. The resulting sample was then acid-washed, water-washed, and dried to obtain the prepared ultra-thin copper foil product.

[0073] Pickling solution formula: Cu 2+ The concentration is 15 g / L, the H2SO4 concentration is 120 g / L, and the solvent is water.

[0074] Example 2 The initial copper foil thickness at the anode is 8.7 ± 0.2 μm; Electrolyte: Cu 2+ The concentration was 0.2 mol / L, the complexing agent (sodium citrate concentration 0.3 mol / L, the concentration ratio of tetrahydroxypropylethylenediamine to sodium citrate was 1:1), the additives (polyethylene glycol concentration 12 mg / L, gelatin concentration 16 mg / L), Cl - The concentration is 15 mg / L.

[0075] Electrolysis conditions: Temperature 35℃, Current density 330mA / cm³ 2The etching time was 150 seconds. The resulting sample was then acid-washed, water-washed, and dried to obtain the prepared ultra-thin copper foil product.

[0076] Pickling solution formula: Cu 2+ The concentration is 20 g / L, the H2SO4 concentration is 130 g / L, and the solvent is water.

[0077] Example 3 The initial copper foil thickness at the anode was 11.4 ± 0.2 μm; Electrolyte: Cu 2+ The concentration was 0.2 mol / L, the complexing agent (triethanolamine concentration 0.3 mol / L, tetrahydroxypropylethylenediamine to triethanolamine concentration ratio 1:1.5), the additives (gelatin concentration 20 mg / L, cellulose concentration 18 mg / L), Cl - The concentration is 16 mg / L.

[0078] Electrolysis conditions: Temperature 40℃, Current density 250mA / cm³ 2 The etching time was 300 seconds. The resulting sample was then acid-washed, water-washed, and dried to obtain the prepared ultra-thin copper foil product.

[0079] Pickling solution formula: Cu 2+ The concentration is 20 g / L, the H2SO4 concentration is 130 g / L, and the solvent is water.

[0080] Example 4 The initial copper foil thickness at the anode was 13.8 ± 0.2 μm; Electrolyte: Cu 2+ The concentration was 0.2 mol / L, the complexing agent (tetrahydroxypropyl ethylenediamine concentration 0.2 mol / L, the concentration ratio of tetrahydroxypropyl ethylenediamine to triethanolamine was 1:2), the additives (gelatin concentration 15 mg / L, cellulose concentration 12 mg / L), Cl - The concentration is 18 mg / L.

[0081] Electrolysis conditions: Temperature 45℃, Current density 500mA / cm³ 2 The etching time was 150 seconds. The resulting sample was then acid-washed, water-washed, and dried to obtain the prepared ultra-thin copper foil product.

[0082] Pickling solution formula: Cu 2+ The concentration is 20 g / L, the H2SO4 concentration is 120 g / L, and the solvent is water.

[0083] Example 5 The initial copper foil thickness at the anode was 9.6 ± 0.2 μm; Electrolyte: Cu 2+The concentration was 0.2 mol / L, the complexing agent (sodium citrate concentration 0.2 mol / L, the concentration ratio of tetrahydroxypropylethylenediamine, sodium citrate, and triethanolamine was 1:1:3), the additives (polyethylene glycol concentration 12 mg / L, gelatin concentration 16 mg / L, cellulose concentration 18 mg / L), Cl - The concentration is 15 mg / L.

[0084] Electrolysis conditions: Temperature 35℃, Current density 330mA / cm³ 2 The etching time was 150 seconds. The resulting sample was then acid-washed, water-washed, and dried to obtain the prepared ultra-thin copper foil product.

[0085] Pickling solution formula: Cu 2+ The concentration is 20 g / L, the H2SO4 concentration is 130 g / L, and the solvent is water.

[0086] Comparative Example 1 The difference between Comparative Example 1 and Example 5 is that the etching was performed without the use of a complexing agent, while the other conditions were the same.

[0087] Comparative Example 2 The difference between Comparative Example 2 and Example 5 is that the etching was performed without the use of additives and chloride ions, while the other conditions were the same.

[0088] Performance testing Thickness test of the ultrathin copper foil prepared at the anode: After locking the micrometer chuck and zeroing it, place the copper foil between the micrometer chucks along the thickness direction, gently rotate the screw to lock the copper foil in place, and then read the copper foil thickness reading in μm. The maximum resolution is 0.1 μm. The test is performed 3 times (at different positions), and the average of the 3 results is taken.

[0089] Brightness test of ultra-thin copper foil prepared at the anode with an incident angle of 60°: The copper foil was placed on a flat surface, and then a gloss meter was placed on the rough surface of the copper foil. The reading was then taken, and the unit was Gu. The test was performed 3 times (at different positions), and the average of the 3 results was taken.

[0090] Rz test of the surface roughness of the ultrathin copper foil prepared at the anode: Place the copper foil on a plane, then place the probe of the roughness tester on the surface of the copper foil, select the Rz test mode, click start, and read the reading after the test is completed. The unit is μm. The test is performed 3 times (at different positions), and the average of the 3 results is taken.

[0091] The test results of the ultrathin copper foils prepared at the anode in each embodiment and comparative example are shown in Table 1.

[0092] Table 1 As shown in Table 1, under the complexing agent + additive system, the ultra-thin copper foils prepared in each example have similar gloss and roughness properties to commercially available 3.5μm copper foils. In Comparative Example 1, no complexing agent was added, resulting in a poorer etching effect, less and uneven reduction in copper foil thickness, leading to poorer gloss and roughness. Comparative Example 2 lacked additives and chloride ions, resulting in poor surface smoothness of the cathode copper foil, affecting the electrode distance between the anode and cathode, and consequently affecting the etching effect, ultimately leading to poor gloss and roughness of the prepared ultra-thin copper foil. Figure 1 SEM image of the ultrathin copper foil prepared for implementation of Case 5. Figure 2 SEM image of the copper foil prepared for Comparative Example 1. Figure 3 This is a SEM image of the copper foil prepared in Comparative Example 2. Figure 1 compared to, Figure 2 and Figure 3 The flatness of the copper foil is significantly lower than that of the others. Figure 1 The copper foil shown.

[0093] The copper foil obtained from the cathode was tested using the same method as that for ultrathin copper foil. The test results of the copper foil obtained from the cathodes of each embodiment and comparative example are shown in Table 2.

[0094] Table 2 Note: The test methods for gloss and surface roughness Rz in Table 2 are the same as above.

[0095] As shown in Table 2, the copper foils obtained at the cathode in each implementation case generally exhibit good physical properties, except for some that were not peeled off. The copper foil obtained at the cathode in Comparative Example 1 was too thin due to poor etching, making it impossible to peel off. While the copper foil obtained at the cathode in Comparative Example 2 could be peeled off, the lack of additives resulted in poor flatness and brightness, meaning poor gloss and roughness, failing to meet the application requirements.

[0096] The parts of this invention not described in detail are techniques known to those skilled in the art.

[0097] The basic principles of the present invention have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in the present invention are merely examples and not limitations, and should not be considered as essential features of each embodiment of the present invention. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the present invention to the necessity of employing the aforementioned specific details.

[0098] It should be noted that the terms "and / or" or " / " used herein are merely descriptions of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The singular forms "a," "described," and "the" used in the embodiments of the invention and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0099] In the detailed description and claims, a list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, then the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, then the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single element or multiple elements. Item B may contain a single element or multiple elements. Item C may contain a single element or multiple elements.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing an ultrathin copper foil, characterized in that, Includes the following steps: An initial copper foil is provided, which is fixed on an anode plate and placed together with a cathode plate in an electrolyte. Electrochemical etching is performed by applying an electric current to reduce the thickness of the initial copper foil fixed on the anode plate, thereby obtaining an extremely thin copper foil.

2. The method for preparing ultrathin copper foil according to claim 1, characterized in that, The initial copper foil thickness is 6~14μm; And / or, the initial copper foil surface roughness Rz is less than 3.0 μm.

3. The method for preparing ultrathin copper foil according to claim 1, characterized in that, The anode plate includes a titanium plate or an acrylic plate; And / or, the roughness Ra of the anode plate is less than 0.3 μm.

4. The method for preparing ultrathin copper foil according to claim 1, characterized in that, The electrolyte includes Cu 2+ Complexing agents, additives, halogen anions, and solvents; Wherein, Cu 2+ The concentration is 0.2~0.5 mol / L; And / or, the concentration of the complexing agent is 0.45~1 mol / L; the complexing agent includes at least one of sodium citrate, triethanolamine or tetrahydroxypropylethylenediamine; And / or, the concentration of the additive is 25~100 mg / L; the additive includes at least one of polyethylene glycol, cellulose or gelatin; And / or, the concentration of the halide anion is 5~25 mg / L; the halide anion includes F - Cl - I - At least one of them; And / or, the solvent includes water.

5. The method for preparing ultrathin copper foil according to claim 4, characterized in that, The complexing agent is a mixture of sodium citrate, triethanolamine and tetrahydroxypropyl ethylenediamine, wherein the concentration ratio of sodium citrate, triethanolamine and tetrahydroxypropyl ethylenediamine is 1:(1~3):(0.25~1).

6. The method for preparing ultrathin copper foil according to claim 4, characterized in that, The additive is a mixture of polyethylene glycol, cellulose and gelatin, and the mass ratio of polyethylene glycol, cellulose and gelatin is (10~50):(5~20):(15~30).

7. The method for preparing ultrathin copper foil according to claim 1, characterized in that, The electrochemical etching performed by applying current satisfies at least one of the following characteristics (1) to (4): (1) A regulated DC power supply is used when the power is applied; (2) The current density of the energized circuit is 200~1000mA / cm 2 ; (3) The energizing time is 100~500s; (4) The temperature of the electrolyte when the current is applied is 20~60℃.

8. An ultra-thin copper foil, characterized in that, The ultrathin copper foil is prepared by the preparation method according to any one of claims 1 to 7.

9. The ultra-thin copper foil according to claim 8, characterized in that, The ultrathin copper foil has a thickness of 3.5~4.2μm, a light brightness of 91~107GU at an incident angle of 60°, and a surface roughness Rz of 2~2.6μm.

10. A battery comprising an extremely thin copper foil, characterized in that, The ultrathin copper foil is the ultrathin copper foil prepared by the preparation method according to any one of claims 1 to 7, or the ultrathin copper foil according to any one of claims 8 to 9.

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