Electrolytic copper foil and preparation method and application thereof

Abstract

The invention relates to an electrolytic copper foil and a preparation method and application thereof. The preparation method of the electrolytic copper foil is carried out by adopting a crude foil engine, the crude foil engine comprises an electrolytic bath, an anode piece and a cathode piece, the anode piece comprises n anode sub-pieces which are arranged at intervals in the circumferential direction of the cathode piece, the interval between every two adjacent anode sub-pieces is marked as an interval point, and at least one interval point is a liquid inlet; the preparation method comprises the following steps: introducing an electrolyte into an electrolytic bath, and electrifying an anode piece and a cathode piece; the cathode piece rotates around the axis of the cathode piece, and electrolytic copper foil is deposited on the area, opposite to the anode piece, of the surface of the cathode piece; in the electrolysis process, at least one anode sub-piece is not electrified and / or the width of at least one liquid inlet is larger than or equal to 5 mm, and the anode sub-piece which is not electrified is located between the first anode sub-piece and the last anode sub-piece. The preparation method of the electrolytic copper foil is simple in process, the tensile strength of the electrolytic copper foil can be improved, and the roughness can be reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of copper foil, in particular to an electrolytic copper foil and a preparation method and application thereof. BACKGROUND

[0002] The electrolytic copper foil plays a vital role in many fields such as electronics and new energy due to its excellent electrical conductivity, flexibility and reasonable cost-effectiveness. For example, the electrolytic copper foil can be used as a conductor material for printed circuit boards and as an indispensable negative current collector in lithium-ion batteries.

[0003] The tensile strength and surface roughness of the conventional electrolytic copper foil need to be improved. SUMMARY

[0004] Therefore, some embodiments of the present application provide a preparation method of an electrolytic copper foil, which is simple in process and can improve the tensile strength and reduce the roughness of the electrolytic copper foil.

[0005] In addition, some other embodiments of the present application also provide an electrolytic copper foil and an application thereof.

[0006] A preparation method of an electrolytic copper foil is performed by a green foil machine, the green foil machine comprises an electrolytic cell, an anode member and a cathode member, the anode member is arranged in the electrolytic cell, at least part of the cathode member is located in the electrolytic cell and is arranged in a spaced manner with the anode member, the anode member comprises n anode sub-members arranged in a spaced manner along the circumferential direction of the cathode member, the interval between two adjacent anode sub-members is denoted as an interval point, at least one interval point is a liquid inlet, and the liquid inlet is used to pass in electrolyte;

[0007] The preparation method comprises the following steps:

[0008] Passing electrolyte into the electrolytic cell and electrifying the anode member and the cathode member;

[0009] Rotating the cathode member around its axis to deposit electrolytic copper foil on the region opposite to the anode member on the surface of the cathode member;

[0010] In the electrolysis process, at least one anode sub-member is not electrified and / or the width of at least one liquid inlet is greater than or equal to 5 mm, and the anode sub-member not electrified is located between the first anode sub-member and the last anode sub-member.

[0011] In some embodiments, the number of anode sub-members not electrified in the electrolysis process is m, and the percentage of m to n is less than or equal to 50%;

[0012] Optionally, the percentage of m to n is less than or equal to 25%.

[0013] In some embodiments, n is 10-22, and / or, m is 1-11.

[0014] In some embodiments, the width of at least one of the liquid inlets is 5-50 mm; optionally, the width of at least one of the liquid inlets is 10-25 mm; and / or,

[0015] In some embodiments, the width of each of the spacing points other than the liquid inlets with a width ≥ 5 mm is independently ≤ 3 mm.

[0016] In some embodiments, the percentage of the number of the liquid inlets with a width ≥ 5 mm to the total number of the spacing points is ≤ 50%.

[0017] Optionally, the number of the liquid inlets with a width ≥ 5 mm is 1-11.

[0018] In some embodiments, the total number of the liquid inlets with a width ≥ 5 mm and the anode subpieces without electricity is 1-11.

[0019] Optionally, the total number of the liquid inlets with a width ≥ 5 mm and the anode subpieces without electricity is 1-5.

[0020] In some embodiments, the liquid inlets with a width ≥ 5 mm are arranged between two of the anode subpieces with electricity; and / or,

[0021] In some embodiments, the width of each of the anode subpieces is independently 10-50 cm; and / or,

[0022] In some embodiments, the concentration of copper ions in the electrolyte is 50-120 g / L, and the concentration of acid is 90-150 g / L; and / or,

[0023] In some embodiments, the current density during the electrolysis is 40-80 A / dm 2 .

[0024] An electrolytic copper foil, which has a layered structure in the thickness direction in the microstructure, and an interface between adjacent two layers, the interface does not have grains; or, the electrolytic copper foil is prepared by the above preparation method.

[0025] In some embodiments, the electrolytic copper foil satisfies one or more of the following conditions:

[0026] (1) the thickness of the electrolytic copper foil is 3-420 μm, optionally, the thickness of the electrolytic copper foil is 18-105 μm;

[0027] (2) the number of layers of the layered structure is 2-12, optionally, the number of layers of the layered structure is 2-6;

[0028] (3) Along the thickness direction, the grains formed on both sides of the interface are discontinuous;

[0029] (4) The thickness of the interface is 5nm~5000nm, and optionally, the thickness of the interface is 5nm~1000nm.

[0030] A battery comprising the aforementioned electrolytic copper foil.

[0031] A copper-clad laminate comprising the aforementioned electrolytic copper foil.

[0032] A printed circuit board comprising the aforementioned electrolytic copper foil.

[0033] This application research found that in traditional methods for preparing electrolytic copper foil, copper foil is continuously deposited on the cathode surface corresponding to the anode region, resulting in continuous grain growth and a layer structure with large grain size. This leads to low tensile strength and high surface roughness in the copper foil. Based on this, some embodiments of this application provide a novel method for preparing electrolytic copper foil. During electrolysis, at least one anode component is not energized and / or at least one liquid inlet has a width ≥ 5 mm. This ensures that when the corresponding region on the cathode surface rotates past the unenergized anode component and / or the wider liquid inlet, electrolysis does not occur, and grain growth stops. Electrolysis resumes when the rotation passes through other locations, allowing grains to nucleate and grow again, resulting in a new layer structure with smaller grain size in each layer. Smaller grain size is beneficial for improving tensile strength and reducing surface roughness. Therefore, the electrolytic copper foil preparation method of some embodiments of this application, by improving the electrolysis process, can obtain a multi-layer structure, reducing grain size and thus improving tensile strength and reducing surface roughness. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of a process flow for preparing electrolytic copper foil according to some embodiments of this application;

[0036] Figure 2 This is a schematic diagram of the structure of a foil-making machine according to some embodiments of this application;

[0037] Figure 3 This is a microstructure image of the cross-section of the electrolytic copper foil prepared in Example 1 under a scanning electron microscope;

[0038] Figure 4 forFigure 3 The enlarged view shown below;

[0039] Figure 5 The image shows the microstructure of the cross-section of the electrolytic copper foil prepared in Example 2 under a scanning electron microscope.

[0040] Figure 6 The image shows the microstructure of the cross-section of the electrolytic copper foil prepared in Example 3 under a scanning electron microscope.

[0041] Figure 7 The image shows the microstructure of the cross-section of the electrolytic copper foil prepared in Example 4 under a scanning electron microscope.

[0042] Figure 8 The image shows the microstructure of the cross-section of the electrolytic copper foil prepared in Comparative Example 1 under a scanning electron microscope.

[0043] Figure 9 The image shows the microstructure of the cross-section of the electrolytic copper foil prepared in Comparative Example 2 under a scanning electron microscope.

[0044] Explanation of reference numerals in the attached drawings: foil production machine 200, electrolytic cell 210, anode component 220, cathode component 230, anode sub-component 222, spacer point 2221, liquid inlet 2223. Detailed Implementation

[0045] To facilitate understanding of this application, a more comprehensive description of the application will be provided below in conjunction with specific embodiments. Preferred embodiments of the application are given in the specific embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0046] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0047] Unless otherwise stated or in case of conflict, the terms or phrases used in this application shall have the following meanings:

[0048] In this application, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include at least one of those features.

[0049] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise expressly and specifically limited.

[0050] In this application, "one or more" refers to any one, two, or more of the listed items. "Multiple" refers to any two or more of the listed items.

[0051] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0052] In this application, terms such as "further," "even more," "particularly," "for example," "like," "example," and "exemplary" are used for descriptive purposes to indicate a connection in the coverage of different technical solutions presented earlier and later, but should not be construed as limiting the preceding technical solution or restricting the scope of protection herein. Unless otherwise specified herein, A (e.g., B) indicates that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0053] In this application, "optionally," "optionally," and "optional" mean that something is optional, that is, it is selected from either "present" or "absent." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "option" is independent. In this application, descriptions such as "optionally contains" and "optionally includes" indicate "contains or does not contain." "Optional component X" indicates whether component X exists or does not exist, or whether component X is contained or not.

[0054] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.

[0055] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0056] The terms "comprising" and "having," and any variations thereof, used in the embodiments of this application, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or device that includes a series of steps or units is not limited to the steps or units listed, but may optionally include steps or units not listed, or may optionally include other steps or components inherent to such processes, methods, products, or devices.

[0057] In this application, the reference to "embodiment" means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this application can be combined with other embodiments.

[0058] In the flowchart of this application, although the steps are shown sequentially according to the arrows, these steps are not necessarily performed in the order indicated by the arrows. Unless otherwise specified herein, there is no strict order restriction on the execution of these steps. They can be executed in other orders. Moreover, at least some of the steps in the diagram may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily completed at the same time, but can be executed at different times. Their execution order is not necessarily sequential, but can be performed alternately or in turn with at least some of other steps or other sub-steps or stages.

[0059] As described in the background section, traditional electrolytic copper foil still suffers from issues with unimproved tensile strength and surface roughness. Researchers have attempted to address these problems by developing additives with complex formulations; however, the development of these additives is challenging, costly, and prone to runaway issues. Therefore, some embodiments of this application provide a method for effectively controlling the physical properties of copper foil without the need for complex additives, including enhancing the tensile strength and reducing the surface roughness of electrolytic copper foil.

[0060] Specifically, the first aspect of this application provides a method for preparing electrolytic copper foil, which is carried out using a foil-making machine. The foil-making machine includes an electrolytic cell, an anode, and a cathode. The anode is disposed within the electrolytic cell, and at least a portion of the cathode is located within the electrolytic cell and spaced apart from the anode. The anode includes n anode sub-components arranged circumferentially around the cathode. The interval between two adjacent anode sub-components is denoted as an interval point. At least one interval point is a liquid inlet for introducing electrolyte. Please refer to [link to relevant documentation]. Figure 1 It includes the following steps:

[0061] Step S110: Pass electrolyte into the electrolytic cell and energize the anode and cathode components.

[0062] Step S120: Rotate the cathode element about its axis and deposit electrolytic copper foil on its surface in the area opposite to the anode element.

[0063] During electrolysis, at least one anode component is not energized and / or at least one liquid inlet has a width ≥ 5 mm, and the non-energized anode component is located between the first anode component and the last anode component.

[0064] This application research found that in traditional methods for preparing electrolytic copper foil, copper foil is continuously deposited on the cathode surface corresponding to the anode region, resulting in continuous grain growth and a layer structure with large grain size. This leads to low tensile strength and high surface roughness in the copper foil. Based on this, some embodiments of this application provide a novel method for preparing electrolytic copper foil. During electrolysis, at least one anode component is not energized and / or at least one liquid inlet has a width ≥ 5 mm. This ensures that when the corresponding region on the cathode surface rotates past the unenergized anode component and / or the wider liquid inlet, electrolysis does not occur, and grain growth stops. Electrolysis resumes when the rotation passes through other locations, allowing grains to nucleate and grow again, resulting in a new layer structure with smaller grain size in each layer. Smaller grain size is beneficial for improving tensile strength and reducing surface roughness. Therefore, the electrolytic copper foil preparation method of some embodiments of this application, by improving the electrolysis process, can obtain a multi-layer structure, reducing grain size and thus improving tensile strength and reducing surface roughness.

[0065] It is understood that in this application, "at least one anode component is not energized" and / or "at least one inlet has a width ≥ 5 mm" means that at least one anode component can be not energized, in which case n ≥ 3; or, at least one inlet has a width ≥ 5 mm, in which case n ≥ 2; or, at least one anode component is not energized while at least one inlet has a width ≥ 5 mm, in which case n ≥ 3. That is to say, in this application, anode components can be set to be not energized individually, or the inlet width can be wider, or both can be set simultaneously. The number of anode components not energized and the number of inlets with a width ≥ 5 mm are independent of each other.

[0066] An unenergized anode sub-component located between the first and last anode sub-components refers to any anode sub-component other than the first and last two anode sub-components. If the unenergized anode sub-component is one of the first or last anode sub-components, it is impossible to separate the layers and reduce the grain size. For example, if n is 3, the three anode sub-components are designated as anode sub-component 1, anode sub-component 2, and anode sub-component 3, and the unenergized anode sub-component is anode sub-component 2. Alternatively, if n is 4, the four anode sub-components are designated as anode sub-component 1, anode sub-component 2, anode sub-component 3, and anode sub-component 4, and the unenergized anode sub-component can be either anode sub-component 2 or anode sub-component 3.

[0067] In some embodiments, the total number of anode sub-components in the anode assembly is n, and the number of unenergized anode sub-components is m, where m represents ≤50% of n. For example, the percentage of m to n can be, but is not limited to, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any combination of these values. Optionally, the percentage of m to n is ≤25%. It can be understood that m can be 0, meaning m represents 0% of n, i.e., all anode sub-components are energized, in which case at least one inlet has a width ≥5mm.

[0068] In some embodiments, n is 10 to 22. For example, n may be, but is not limited to, 10, 11, 12, 13, 14, 15, 16, 18, 20, 22 or any combination of these values.

[0069] In some embodiments, m is 1 to 11. For example, m may be, but is not limited to, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or a range of any two of these values.

[0070] In some embodiments, when there are multiple unenergized anode pieces, these unenergized anode pieces are not adjacent to each other. If the unenergized anode pieces are adjacent, electrolysis will be delayed for a longer period, reducing production efficiency. Therefore, in the actual electrolysis process, when there are multiple unenergized anode pieces, the fact that they are not adjacent to each other is beneficial for improving tensile strength, reducing roughness, and simultaneously increasing production efficiency.

[0071] In some embodiments, the width of each anode sub-component is independently between 10cm and 50cm. For example, the width of each anode sub-component may be, but is not limited to, 10cm, 15cm, 20cm, 25cm, 30cm, 35cm, 40cm, 45cm, 50cm, or any combination of these values.

[0072] In some embodiments, the anode element can be one commonly used in the art, such as a titanium substrate that has undergone surface treatment and high-temperature oxidation to form a noble metal coating. In one example, the anode element is a ruthenium-titanium anode or a ruthenium-iridium-titanium anode.

[0073] In some embodiments, the anode element is a plate-like structure. Specifically, the anode element is an anode plate.

[0074] Setting the anode component as multiple anode sub-components reduces edge effects, resulting in a more uniform electric field distribution and preventing the copper foil from being too thick at the edges or too thin in the center. Furthermore, bubbles generated during electrolysis can quickly escape through the gaps, preventing bubble adhesion and abnormal local current density. Additionally, if an anode sub-component fails during production, it can be replaced individually, reducing maintenance costs.

[0075] In some embodiments, in the step of rotating the cathode element about its axis to deposit electrolytic copper foil in the area on its surface opposite the anode element, after rotating the cathode element about its axis by 180°, the deposited electrolytic copper foil is peeled off, and the next copper foil deposition continues.

[0076] In some embodiments, during electrolysis, the rotational speed of the cathode element is 0.1 m / min to 10 m / min, and the current density is 20 A / dm³. 2 ~80 A / dm 2 The thickness of the electrolytic copper foil can be adjusted by controlling the rotational speed and current density of the cathode.

[0077] In some embodiments, the cathode element is a cathode roller.

[0078] In some embodiments, the anode element includes n arc-shaped anode sub-elements arranged circumferentially along the cathode element, wherein the concave curved surface of the anode sub-elements is coaxially disposed with the outer cylindrical surface of the cathode element. This arrangement is beneficial for improving the thickness uniformity of the deposited electrolytic copper foil.

[0079] In some embodiments, the cathode element is made of titanium or stainless steel.

[0080] In some embodiments, at least one inlet has a width ≥ 5 mm. Specifically, the width of at least one inlet is 5 mm to 50 mm. For example, the width of at least one inlet may be, but is not limited to, 5 mm, 6 mm, 7 mm, 8 mm, 10 mm, 15 mm, 20 mm, 25 mm, 30 mm, 35 mm, 40 mm, 50 mm, or any range of two of these values. Optionally, the width of at least one inlet is 10 mm to 25 mm.

[0081] In this application, "at least one liquid inlet with a width ≥ 5 mm" means that there are x liquid inlets, x ≥ 1, of which at least one liquid inlet has a width ≥ 5 mm, and the widths of the other liquid inlets are less than 5 mm, or all liquid inlets have a width ≥ 5 mm.

[0082] In some embodiments, among the multiple spacer points, the width of each spacer point, excluding the inlet with a width ≥ 5 mm, is independently ≤ 3 mm. This arrangement ensures that the cathode element undergoes continuous electrolysis as it passes through the spacer point without stratification. It is understood that the spacer points, excluding the inlet with a width ≥ 5 mm, can be either spacer points without electrolyte flow or inlets with electrolyte flow, but their width must be ≤ 3 mm.

[0083] Optionally, among the multiple interval points, the width of each interval point, excluding the inlet with a width ≥ 5 mm, is independently 0.1 mm to 3 mm.

[0084] In some embodiments, the percentage of inlets with a width ≥ 5 mm to the total number of interval points is ≤ 50%. For example, the percentage of inlets with a width ≥ 5 mm to the total number of interval points can be, but is not limited to, 5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or any combination of these values. An excessively high percentage of inlets with a width ≥ 5 mm to the total number of interval points is detrimental to improving electrolysis efficiency. It can be understood that the percentage of inlets with a width ≥ 5 mm to the total number of interval points can be 0, i.e., there are no inlets with a width ≥ 5 mm, in which case at least one anode component is not energized.

[0085] In some embodiments, the number of inlets with a width ≥ 5 mm is 1 to 11. For example, the number of inlets with a width ≥ 5 mm may be, but is not limited to, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or any combination of these values.

[0086] In some embodiments, the total number of inlets with a width ≥ 5 mm and unenergized anode components is 1 to 11. Optionally, the total number of inlets with a width ≥ 5 mm and unenergized anode components is 1 to 5. This configuration helps to further improve tensile strength, reduce surface roughness, and obtain an electrolytic copper foil with a suitable layered microstructure.

[0087] In some embodiments, an inlet with a width of ≥5mm is positioned between two energized anode components. This arrangement is beneficial for improving tensile strength, reducing surface roughness, and increasing efficiency. If an inlet with a width of ≥5mm is positioned between unenergized anode components, the cathode component will not be electrolyzed for a longer period, reducing production efficiency.

[0088] In some embodiments, there is one inlet with a width of ≥5mm, located at the bottom of the electrolytic cell. This arrangement helps to improve the uniformity of the electrolyte.

[0089] In some embodiments, please refer to Figure 2 The foil production machine 200 includes an electrolytic cell 210, an anode 220, and a cathode 230. The anode 220 is disposed in the electrolytic cell 210. At least a portion of the cathode 230 is located in the electrolytic cell 210 and is spaced apart from the anode 220. The anode 220 includes a plurality of anode sub-components 222 arranged at intervals along the cathode 230. The interval between two adjacent anode sub-components 222 is denoted as an interval point 2221. At least one interval point 2221 is a liquid inlet 2223. The liquid inlet 2223 is used to introduce electrolyte. In the figure, W represents the width of the liquid inlet 2223.

[0090] exist Figure 2The relationships between the structures are shown here only as examples. Figure 2 In this embodiment, there are 12 anode components and 1 liquid inlet. It is understood that in other embodiments, the number of anode components is not limited to 12, and the number of liquid inlets is not limited to 1; other numbers are also possible.

[0091] In some embodiments, the electrolytic power source is a DC power source.

[0092] In some embodiments, the concentration of copper ions in the electrolyte is 50 g / L to 120 g / L, and the acid concentration is 90 g / L to 150 g / L. Optionally, the concentration of copper ions in the electrolyte is 80 g / L to 95 g / L, and the acid concentration is 100 g / L to 120 g / L.

[0093] In some embodiments, the electrolyte also contains additives. These additives can be those commonly used in the art. Specifically, the additives include one or more of chloride ions, wetting agents, leveling agents, and brighteners.

[0094] Specifically, the wetting agent includes one or more of hydroxyethyl cellulose, polyethanol ether (EO), polypropylene ether (PO), block copolymers of ethylene oxide and propylene oxide (EO-PO), and polypyrrolidone. The leveling agent includes one or more of collagen and nitrogen-containing organic compounds. The glossing agent includes one or more of sodium mercaptopropane sulfonate, sodium polydithiomercaptopropane sulfonate, sodium thiazolinyl dithiopropane sulfonate, and sodium N,N-dimethyldithioformamide propane sulfonate.

[0095] In some embodiments, the electrolysis temperature is 25°C to 55°C. Optionally, the electrolysis temperature is 45°C to 50°C.

[0096] In some embodiments, the current density during electrolysis is 20 A / dm³. 2 ~80A / dm 2 .

[0097] In some embodiments, compared with electrolytic copper foil prepared by a process in which all anode components are energized and the width of all spacing points is less than or equal to 3 mm during electrolysis, the electrolytic copper foil prepared by the preparation method of some embodiments of this application has a tensile strength increased by 5 MPa to 50 MPa and a roughness Rz decreased by 0.1 μm to 5 μm.

[0098] The second aspect of this application provides an electrolytic copper foil, which has a multilayer structure along the thickness direction at the microscopic level, with an interface between adjacent layers, and no grains at the interface.

[0099] Specifically, after polishing and micro-etching, the electrolytic copper foil exhibits a layered structure along its thickness direction under a scanning electron microscope. The micro-etching solution is a mixture of ammonia and hydrogen peroxide. In one example, the micro-etching solution comprises 15 mL of ammonia, 20 mL of water, and 150 μL of hydrogen peroxide.

[0100] In some embodiments, the number of layers in the multi-layer structure is 2 to 12. For example, the number of layers in the multi-layer structure may be, but is not limited to, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12 layers, or any range of these values. Optionally, the number of layers in the multi-layer structure is 2 to 6.

[0101] In some embodiments, the multiple interfaces are distributed uniformly or non-uniformly along the thickness direction. Specifically, uniform distribution means that the multiple interfaces are distributed at equal intervals, while non-uniform distribution means that the interfaces are distributed at arbitrary locations and at unequal intervals, for example, the interfaces are distributed in a certain part.

[0102] In some embodiments, the grains formed on both sides of the interface are discontinuous along the thickness direction. Specifically, discontinuity means that the grains observed after micro-etching are separated by the interface, or the interface blocks the continuous growth or physical connection of the grains.

[0103] In some embodiments, the interface thickness is 5 nm to 5000 nm. For example, the interface thickness may be, but is not limited to, 5 nm, 10 nm, 20 nm, 50 nm, 80 nm, 100 nm, 200 nm, 500 nm, 800 nm, 1000 nm, 2000 nm, 5000 nm, or any combination of these values. Optionally, the interface thickness is 5 nm to 1000 nm.

[0104] In some embodiments, the thickness of the electrolytic copper foil is 3 μm to 420 μm. For example, the thickness of the electrolytic copper foil may be, but is not limited to, 3 μm, 4.5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 105 μm, 120 μm, 140 μm, 160 μm, 180 μm, 200 μm, 420 μm, or any range of two of these values. Optionally, the thickness of the electrolytic copper foil is 4.5 μm to 210 μm. Optionally, the thickness of the electrolytic copper foil is 18 μm to 105 μm.

[0105] In some embodiments, the electrolytic copper foil is prepared by the preparation method described in the first aspect above.

[0106] A third aspect of this application provides a battery comprising the aforementioned electrolytic copper foil.

[0107] Specifically, the battery includes a positive electrode, a negative electrode, and a separator disposed between the positive and negative electrode. The negative electrode includes a negative current collector and a layer of negative active material disposed on at least one surface of the negative current collector, the negative current collector including the aforementioned electrolytic copper foil.

[0108] In some embodiments, when electrolytic copper foil is used in a battery, the thickness of the electrolytic copper foil is 4.5 μm to 8 μm. Specifically, the number of layers in the multilayer structure of the electrolytic copper foil is 2 to 6.

[0109] It is understandable that the positive electrode, separator, and other components in the battery can be commonly used in this field, and will not be elaborated here.

[0110] A fourth aspect of this application provides a copper-clad laminate, including the electrolytic copper foil described above.

[0111] Copper clad laminate (CCL) is a core substrate used in the electronics industry to manufacture printed circuit boards (PCBs). Its basic structure includes a substrate, copper foil, and an adhesive layer disposed between the substrate and the copper foil. The copper foil in CCL includes the electrolytic copper foil described above.

[0112] In some embodiments, when electrolytic copper foil is used in copper-clad laminates, the thickness of the electrolytic copper foil is 9 μm to 210 μm. Specifically, the number of layers in the multilayer structure of the electrolytic copper foil is 2 to 12.

[0113] A fifth aspect of this application provides a printed circuit board comprising the aforementioned electrolytic copper foil.

[0114] In some embodiments, the printed circuit board includes a copper-clad laminate, which includes the electrolytic copper foil described above.

[0115] To make the objectives and advantages of this application clearer, the electrolytic copper foil, its preparation method, and its effects are further described in detail below with reference to specific embodiments. It should be understood that the specific embodiments described herein are only for explaining this application and should not be used to limit this application. Unless otherwise specified, the following embodiments do not include components other than unavoidable impurities. Unless otherwise specified, the drugs and instruments used in the embodiments are conventional choices in the art. Experimental methods in the embodiments that do not specify specific conditions were implemented according to conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0116] The structural schematic diagrams of the foil-making machines used in the following embodiments and comparative examples are shown below. Figure 2 As shown. The anode assembly consists of 12 sub-plates. There is one liquid inlet.

[0117] Example 1

[0118] This embodiment provides an electrolytic copper foil, the preparation method of which includes the following steps:

[0119] (1) Add metallic copper wire or copper plate to a copper dissolving tank containing sulfuric acid, and use a screw blower to blow in high-temperature air to dissolve it and prepare a copper sulfate solution. Add an additive solution to the copper sulfate solution in the copper dissolving tank, and mix to obtain an electrolyte. The electrolyte is filtered through multiple stages and then enters the electrolyte tank. The composition of the electrolyte is as follows: copper ion concentration of 55 g / L, acid concentration of 120 g / L, chloride ion concentration of 20 mg / L, and hydroxyethyl cellulose concentration of 10 mg / L.

[0120] (2) The electrolyte is heated to a set temperature of 50°C via a heat exchanger and then transported to, for example, Figure 2 The foil-making machine shown has an anode plate installed in its electrolytic cell. The anode plate consists of 12 spaced-apart anode sub-plates, each 30 cm wide. The liquid inlet is located at... Figure 2 The width between the sixth and seventh anode sub-plates from left to right is 30mm, and the width of other intervals is 0.5mm. All anode sub-plates are connected to the positive terminal of the power supply, and the cathode roller is connected to the negative terminal. The cathode roller is rotated 180° around its axis at a speed of 6m / min and a current density of 50A / dm³. 2 An electrolytic copper foil with a theoretical thickness of 35 μm is deposited in the area where the cathode roller and the anode are opposite.

[0121] Example 2

[0122] This embodiment provides an electrolytic copper foil, the preparation method of which is similar to that of Embodiment 1, the difference being that the liquid inlet of the foil-making machine is located at... Figure 2 The width between the sixth and seventh anode sub-plates from left to right is 3mm. Simultaneously, two of the sub-plates within the anode plate are not energized. Specifically... Figure 2 The fourth and ninth sub-boards from left to right are not powered. The other steps are the same as in Example 1, and will not be repeated here.

[0123] Example 3

[0124] This embodiment provides an electrolytic copper foil, the preparation method of which is similar to that of Embodiment 2, the difference being that the liquid inlet of the foil-making machine is located at... Figure 2 Between the sixth and seventh anode sub-plates from left to right, the width is 15mm. Simultaneously, the two sub-plates within the anode plate are not energized. Specifically... Figure 2 The fourth and ninth sub-boards from left to right are not powered. The other steps are the same as in Example 2, and will not be repeated here.

[0125] Example 4

[0126] This embodiment provides an electrolytic copper foil, prepared using a method similar to that of Embodiment 1, except that: the raw foil is an electrolytic copper foil with a thickness of 105 μm, the cathode roller speed is 2 m / min, and the foil-forming machine has 5 liquid inlets, respectively located at... Figure 2 The width between the second, third, fourth, fifth, sixth, seventh, eighth, ninth, tenth, and eleventh anode sub-plates from left to right is 10mm. All anode sub-plates are energized. Other steps are the same as in Example 1 and will not be repeated.

[0127] Comparative Example 1

[0128] Comparative Example 1 provides an electrolytic copper foil, the preparation method of which is similar to that of Example 1, except that the liquid inlet of the foil-making machine is located at... Figure 2 Between the sixth and seventh anode sub-plates from left to right, the inlet width is 3mm, and all anode sub-plates are energized. The other steps are the same as in Example 1, and will not be repeated here.

[0129] Comparative Example 2

[0130] Comparative Example 2 provides an electrolytic copper foil, the preparation method of which is similar to that of Example 4, except that the liquid inlet of the foil-making machine is located at... Figure 3 Between the sixth and seventh anode sub-plates from left to right, the inlet width is 3mm, and all anode sub-plates are energized. The other steps are the same as in Example 4, and will not be repeated here.

[0131] The obtained electrolytic copper foil was subjected to surface roughness Rz, tensile strength TS, and cross-section tests. The performance test results, surface roughness Rz, the decrease in surface roughness Rz ΔRz, tensile strength TS, and the increase in tensile strength TS ΔTS, are shown in Table 1. Here, the "surface roughness" of the electrolytic copper foil refers to the surface from which the electrolytic copper foil is deposited during manufacturing, i.e., the surface that does not contact the cathode roller. The decrease in surface roughness Rz ΔRz represents the decrease in surface roughness Rz of the electrolytic copper foil in the examples relative to the electrolytic copper foil in the comparative examples. For Examples 1 to 3, ΔRz = surface roughness Rz of the electrolytic copper foil in Comparative Example 1 - surface roughness Rz of the electrolytic copper foil in the examples; for Example 4, ΔRz = surface roughness Rz of the electrolytic copper foil in Comparative Example 2 - surface roughness Rz of the electrolytic copper foil in Example 4. The increase in tensile strength TS, ΔTS, represents the increase in tensile strength TS of the electrolytic copper foil in the embodiment relative to that of the electrolytic copper foil in the comparative example. Specifically, for Embodiments 1 to 3, ΔTS = tensile strength TS of the electrolytic copper foil in the embodiment - tensile strength TS of the electrolytic copper foil in Comparative Example 1; for Embodiment 4, ΔTS = tensile strength TS of the electrolytic copper foil in Embodiment 4 - tensile strength TS of the electrolytic copper foil in Comparative Example 2.

[0132] The tensile strength test was conducted according to test method IPC-TM-650. The test was performed using an AGS-X tensile testing machine manufactured by SHIMADZU. Electrolytic copper foil was cut into specimens with a length of 100 mm and a width of 12.7 mm at room temperature (approximately 25°C) and the test analysis was carried out with a clamping distance of 50 mm.

[0133] Roughness (Rz) was tested according to test method IPC-TM-650 using a Mitutoyo SJ-210 portable roughness tester from Japan to measure the roughness Rz value of the copper foil surface.

[0134] Section testing method: After cleaning and drying the polished section with ethanol, micro-etching can be performed to distinguish the metal layer from its crystal structure. The micro-etching solution formula is as follows: 15mL ammonia, 20mL water, and 150μL hydrogen peroxide. After mixing evenly, use a cotton swab to apply the micro-etching solution to the section surface and gently wipe it for about 10s~30s. Immediately clean with ethanol and dry. Gold plating is then performed on the section surface. The images were taken using a TESCAN scanning electron microscope.

[0135] Table 1. Test results of physical properties of electrolytic copper foil

[0136]

[0137] The slice tests of Examples 1, 2, 3, 4, Comparative Example 1, and Comparative Example 2 are as follows: Figure 5 , Figure 6 , Figure 7 , Figure 8 , Figure 9 and Figure 3 As shown. Figure 3 In Example 1, the electrolytic copper foil prepared has a two-layer structure along the thickness direction at the microscopic level, with an interface between the two layers. Figure 4 A magnified view of the part is as follows Figure 4 As shown, from Figure 5 As can be seen, there are no grains at the interface, and the grains on both sides of the interface are discontinuous. Figure 6 In Example 2, the electrolytic copper foil prepared has a three-layer structure along the thickness direction at the microscopic level, with an interface between two adjacent sublayers. Figure 7 In Example 3, the electrolytic copper foil prepared has a four-layer structure along the thickness direction at the microscopic level, with three interfaces between the four layers. Figure 8 In Example 4, the electrolytic copper foil prepared has a six-layer structure along the thickness direction at the microscopic level, with five interfaces between the six layers. Figure 9 and ​ In the comparison, the electrolytic copper foils prepared in Comparative Example 1 and Comparative Example 2 do not have a layered structure along the thickness direction at the microscopic level.

[0138] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0139] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification and drawings can be used to interpret the content of the claims.

Claims

1. A method for preparing electrolytic copper foil, characterized in that, The foil forming process is carried out using a foil forming machine, which includes an electrolytic cell, an anode component, and a cathode component. The anode component is disposed in the electrolytic cell, and at least a portion of the cathode component is located in the electrolytic cell and is spaced apart from the anode component. The anode component includes n anode sub-components arranged circumferentially along the cathode component. The interval between two adjacent anode sub-components is denoted as an interval point. At least one interval point is a liquid inlet, which is used to introduce electrolyte. The preparation method includes the following steps: Electrolyte is introduced into the electrolytic cell, and electricity is applied to the anode and cathode. The cathode is rotated about its axis, and an electrolytic copper foil is deposited on its surface in the region opposite to the anode. During electrolysis, at least one of the anode components is not energized and / or at least one of the liquid inlets has a width ≥ 5 mm, and the anode component that is not energized is located between the first anode component and the last anode component.

2. The method for preparing electrolytic copper foil according to claim 1, characterized in that, During electrolysis, the number of anode components that are not energized is m, and the percentage of m to n is ≤50%; Optionally, m represents ≤25% of n.

3. The method for preparing electrolytic copper foil according to claim 2, characterized in that, n is 10~22, and / or m is 1~11.

4. The method for preparing electrolytic copper foil according to claim 1, characterized in that, At least one of the liquid inlets has a width of 5mm to 50mm; optionally, at least one of the liquid inlets has a width of 5mm to 25mm; and / or, Of the multiple interval points, the width of each interval point, except for the inlet with a width ≥ 5 mm, is independently ≤ 3 mm.

5. The method for preparing electrolytic copper foil according to any one of claims 1 to 4, characterized in that, The percentage of the number of liquid inlets with a width ≥ 5 mm to the total number of the interval points is ≤ 50%; Optionally, the number of liquid inlets with a width of ≥5mm is 1 to 11.

6. The method for preparing electrolytic copper foil according to any one of claims 1 to 4, characterized in that, The total number of the liquid inlet with a width ≥ 5 mm and the anode sub-component that is not energized is 1 to 11; Optionally, the total number of the liquid inlet with a width ≥ 5 mm and the anode sub-component that is not energized is 1 to 5.

7. The method for preparing electrolytic copper foil according to any one of claims 1 to 4, characterized in that, The liquid inlet, with a width ≥ 5 mm, is positioned between the two energized anode components; and / or, The width of each of the aforementioned anode sub-components is independently 10cm to 50cm; and / or, The concentration of copper ions in the electrolyte is 50 g / L to 120 g / L, and the acid concentration is 90 g / L to 150 g / L; and / or, During electrolysis, the current density is 20 A / dm³. 2 ~80A / dm 2 .

8. An electrolytic copper foil, characterized in that, The electrolytic copper foil has a multi-layer structure along the thickness direction at the microscopic level, with an interface between adjacent layers, and the interface is free of grains; or, the electrolytic copper foil is prepared by the preparation method according to any one of claims 1 to 7.

9. The electrolytic copper foil according to claim 8, characterized in that, The electrolytic copper foil satisfies one or more of the following conditions: (1) The thickness of the electrolytic copper foil is 3μm~420μm, and optionally, the thickness of the electrolytic copper foil is 18μm~105μm; (2) The number of layers in the multi-layer structure is 2 to 12, and optionally, the number of layers in the multi-layer structure is 2 to 6. (3) Along the thickness direction, the grains formed on both sides of the interface are discontinuous; (4) The thickness of the interface is 5nm~5000nm, and optionally, the thickness of the interface is 5nm~1000nm.

10. A battery, characterized in that, Includes the electrolytic copper foil as described in claim 8 or 9.

11. A copper-clad laminate, characterized in that, Includes the electrolytic copper foil as described in claim 8 or 9.

12. A printed circuit board, characterized in that, Includes the electrolytic copper foil as described in claim 8 or 9.

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