Negative electrode current collector, copper plating composite additive, copper plating solution, battery cell, battery device, and electric device

Abstract

The application relates to the technical field of batteries, and discloses a negative electrode current collector, a copper plating composite additive, a copper plating solution, a battery monomer, a battery device and a power utilization device. The negative electrode current collector comprises a base material and a copper plating layer, wherein the base material comprises a polymer material layer and a copper seed layer, the copper seed layer is arranged on the surface of at least one side of the polymer material layer; the copper plating layer is arranged on the surface of the copper seed layer; the surface roughness Ra of the copper plating layer satisfies 0.1 mu m <= Ra <= 0.3 mu m; and the thickness deviation of the copper plating layer is not greater than + / - 0.2 mu m. The negative electrode current collector provided in the application can significantly reduce the overall weight of the battery and improve the energy density of the battery because the polymer material layer is lighter than a pure metal copper foil. The surface roughness of the copper plating layer is low, and the thickness is uniform, which indicates that the copper plating layer has high leveling property, which is helpful to the uniform distribution of the current on the current collector, avoids local overheating and uneven electrochemical reaction.

Description

Technical Field

[0001] This application relates to the field of battery technology, specifically to a negative electrode current collector, a copper plating composite additive, a copper plating solution, a battery cell, a battery device, and an electrical device. Background Technology

[0002] Copper foil has become the preferred current collector for lithium-ion batteries due to its excellent conductivity, oxidation resistance, good mechanical properties, and cost-effectiveness. It serves as both the carrier of the negative electrode material and the collector of current, accounting for approximately 11% of the total battery cost.

[0003] Currently, lithium-ion batteries primarily use electrolytic copper foil, and the quality of the copper foil is crucial to battery performance. As lithium-ion batteries develop towards higher energy density and higher safety, copper foil is trending towards thinner and lighter designs. Reducing the thickness of the copper foil can decrease battery weight and internal resistance, increase the content of active materials, and thus improve battery capacity.

[0004] Most composite copper foil production processes use an organic polymer film as a support layer, depositing a copper seed layer on both sides before electroplating to thicken the copper layer. During electroplating, the distribution of current density is a key factor affecting the leveling of the copper foil. Due to the resistance and potential difference on the film, the current density distribution becomes uneven. This unevenness causes differences in the copper foil deposition rate during electroplating, leading to leveling problems and failing to meet the performance requirements of composite copper foil for lithium-ion batteries. Summary of the Invention

[0005] In view of the above problems, this application provides a negative electrode current collector, a copper plating composite additive, a copper plating solution, a battery cell, a battery device, and an electrical device, aiming to solve the problem of poor leveling of the negative electrode current collector.

[0006] In a first aspect, embodiments of this application provide a negative electrode current collector, comprising:

[0007] The substrate includes a polymer material layer and a copper seed layer, wherein the copper seed layer is disposed on at least one surface of the polymer material layer;

[0008] A copper plating layer is disposed on the surface of the copper seed layer; the surface roughness Ra of the copper plating layer satisfies: 0.1μm≤Ra≤0.3μm; and the thickness deviation of the copper plating layer is not greater than ±0.2μm.

[0009] Polymer material layers are generally lighter than pure copper foil, significantly reducing the overall weight of the battery and increasing its energy density. The copper seed layer, acting as a connector between the polymer material layer and the copper plating layer, enhances the bonding between them and imparts conductivity to the substrate, thus facilitating the electroplating deposition of the copper plating layer. The copper plating layer provides conductivity to the current collector. Furthermore, the copper plating layer exhibits low and moderate surface roughness. Surface roughness primarily reflects the microscopic unevenness of the surface; surface roughness within the aforementioned range indicates high microscopic leveling of the copper plating layer surface. This contributes to the uniform distribution of current in the current collector, preventing localized overheating and uneven electrochemical reactions. Simultaneously, this roughness also enhances the adhesion between the copper plating layer and the active material, reducing active material detachment and improving electrode stability. Thickness deviation refers to the difference in thickness of the copper plating layer at different locations, i.e., thickness uniformity. The small thickness deviation of the copper plating layer in the embodiments of this application indicates uniform copper plating layer thickness, further demonstrating high leveling of the copper plating layer.

[0010] In some embodiments, the negative electrode current collector satisfies at least one of the following:

[0011] (1) The thickness of the copper plating layer ranges from 0.7 μm to 1.5 μm;

[0012] (2) The thickness of the copper seed layer ranges from 0.4 μm to 0.8 μm;

[0013] (3) The thickness of the polymer material layer ranges from 1.5 μm to 2.5 μm;

[0014] (4) The polymer material layer includes at least one of polyethylene terephthalate, polypropylene, and polyetherimide.

[0015] This can further improve the uniform deposition of the copper plating layer and enhance its conductivity.

[0016] Secondly, embodiments of this application provide a copper plating composite additive, comprising the following components in parts by weight:

[0017]

[0018] The first inhibitor includes isooctanol polyoxyethylene ether;

[0019] The second inhibitor includes at least one of polyethylene glycol, carboxymethyl cellulose, alkoxynaphthol, polyethylene glycol esters, and poly(ethylene glycol-propylene glycol) copolymers;

[0020] The leveling agent comprises a quaternary ammonium salt copolymerized with alkyl dimethyl ammonium chloride and sulfur dioxide.

[0021] In the copper electroplating process, the role of copper plating additives is to optimize the formation process of the coating by adjusting the deposition behavior of copper ions in the electroplating solution, so as to achieve a uniform and smooth coating effect. For flexible substrates with a large width, the components in the copper plating composite additive of this application embodiment work synergistically through specific chemical and physical mechanisms to improve the smoothness of the coating.

[0022] First, the primary inhibitor, isooctanol polyoxyethylene ether, functions mainly to slow down the reduction rate of copper ions, thereby forming a more uniform copper deposition layer during electroplating. As a nonionic surfactant, isooctanol polyoxyethylene ether adsorbs onto the substrate surface, forming an inhibitory film that prevents copper ions from directly contacting the substrate surface, thus slowing down the copper deposition rate. The secondary inhibitor further refines the microstructure of the coating, improving its density and uniformity. These compounds, through different mechanisms such as steric hindrance and charge repulsion, inhibit the excessively rapid deposition of copper ions in certain areas, promoting a uniform distribution of copper ions across the entire substrate surface. The combined action of the primary and secondary inhibitors slows down the overall deposition rate of copper ions and promotes a uniform distribution of copper ions in the copper plating solution through steric hindrance, avoiding uneven coating thickness caused by excessively rapid local deposition.

[0023] The leveling agent, a quaternary ammonium salt copolymerized with sulfur dioxide, can be uniformly distributed on the electroplating surface, making it particularly suitable for wide flexible substrates. It reduces the deposition rate in the high-current zone (HCD) and increases the deposition rate in the low-current zone (LCD), improving the uniformity and brightness of the copper plating. The combination of the leveling effect of the first inhibitor and the leveling agent's even plating capability results in a more uniform coating on wide flexible substrates, avoiding problems such as uneven local deposition or inconsistent coating thickness. The leveling agent further enhances the wettability of the plating solution on the substrate, enabling the plating solution to uniformly cover the entire substrate, especially the edge areas, reducing coating defects caused by poor wetting. The use of brighteners further improves the gloss and smoothness of the coating.

[0024] The copper plating additives of this application are applicable to copper plating on various substrate surfaces and have wide applicability, especially to flexible substrates with large widths, such as copper plating on conductive polymer films. For substrates with large widths, the copper plating additives can be evenly distributed across the entire surface, avoiding problems such as uneven local deposition or inconsistent plating thickness. At the same time, they improve the dispersion and wettability of the plating solution, enabling the plating layer to be more uniform on flexible substrates with large widths and improving leveling.

[0025] In some embodiments, the leveling agent comprises at least one of polyethylene oxide-polypropylene oxide monobutyl ether, polypropylene glycol, gelatin, sodium dodecyl sulfonate, polyvinyl diallyl ammonium chloride, and a copolymer of vinyl diallyl ammonium chloride and sulfur dioxide. This further improves the coverage of the copper plating solution on the substrate surface, particularly at edges and corners, and further enhances the uniformity of the plating layer.

[0026] In some embodiments, the brightener comprises at least one selected from sodium polydithiopropane sulfonate, sodium thiopropane sulfonate, sodium N,N-dimethyldithiocarbamate, sodium methyl thiopropane sulfonate, sodium 2-mercapto-1-benzothiazole sulfonate, and sodium N,N-dipropyldithiocarbamate. This further reduces porosity and defects in the coating, resulting in a smoother coating surface.

[0027] In some embodiments, the brightener further includes at least one of (O-ethyl dithiocarbonate)-S-(3-sulfonylpropyl) ester potassium salt, sodium phenyl polydithiopropane sulfonate, 2-tetrahydrothiazothione, and sodium thiazolinyl dithiopropane sulfonate. This improves the adsorption characteristics in low current density regions and further enhances the overall coating thickness uniformity by flattening the coating in both high and low current density regions.

[0028] In some embodiments, the second inhibitor is polyethylene glycol, wherein the number-average molecular weight of the polyethylene glycol is 5000 g / mol to 10000 g / mol. This further enhances the synergistic effect among the components in the copper plating additive.

[0029] Thirdly, embodiments of this application provide a copper plating solution, including the copper plating composite additive described in the second aspect.

[0030] In some embodiments, the copper plating solution comprises the following components:

[0031]

[0032] In some embodiments, the copper plating solution comprises the following components:

[0033]

[0034] In some embodiments, the copper plating solution further includes copper sulfate, sulfuric acid, and hydrochloric acid.

[0035] In some embodiments, the copper plating solution comprises the following components:

[0036] Copper sulfate 50g / L~150g / L;

[0037] Sulfuric acid concentration: 100 g / L to 250 g / L;

[0038] Hydrochloric acid 1 mg / L~500 mg / L.

[0039] During the electroplating process, the aforementioned copper plating solution can uniformly and stably deposit metal ions onto the substrate surface, forming a high-quality coating. The coating exhibits good thickness uniformity and excellent flow properties. These characteristics enable the copper plating solution to provide a uniform current distribution during electroplating, thereby improving the uniformity and consistency of the coating. For wide and flexible substrates, this copper plating solution can achieve excellent electroplating results across the entire substrate surface.

[0040] Fourthly, embodiments of this application provide a method for preparing a negative electrode current collector, comprising the following steps: providing a substrate, the substrate comprising a polymer material layer and a copper seed layer; and the copper plating solution described in the third aspect; placing the substrate in the copper plating solution and performing electroplating treatment. The negative electrode current collector prepared using the above method exhibits high flatness and uniform plating thickness. Thanks to the additives in the copper plating solution, the uniform deposition of metal ions on the substrate surface is improved, which helps to improve the quality of subsequent battery cells.

[0041] In some embodiments, the steps of preparing the copper plating solution include: adding the first inhibitor to water, then adding the leveling agent and the second inhibitor, then adding the brightener and the leveling agent to obtain the copper plating composite additive; adding the copper sulfate, the sulfuric acid and the hydrochloric acid to water to prepare the initial copper plating solution; and adding the copper plating composite additive to the initial copper plating solution to obtain the copper plating solution.

[0042] In some embodiments, the electroplating process conditions include: an operating current density of 10 mA / cm². 2 ~200mA / cm 2 .

[0043] In the electroplating process, current density (current per unit area) is a key parameter that directly affects the plating speed and coating quality. The current operating range refers to the range of current densities that can be used during electroplating while ensuring coating quality. Copper plating solutions using the aforementioned copper plating additives allow for electroplating within a wider current density range, up to 10 mA / cm². 2 ~200mA / cm 2 This not only improved the coating quality but also significantly increased production speed.

[0044] Fifthly, embodiments of this application provide a battery cell including a negative electrode sheet, wherein the negative electrode sheet includes the negative current collector described in the first aspect, or the negative current collector described in the fourth aspect.

[0045] Sixthly, embodiments of this application provide a battery device including the battery cell described in the fifth aspect.

[0046] In a seventh aspect, embodiments of this application provide an electrical device, including a battery cell as described in the first aspect or a battery device as described in the sixth aspect, wherein the battery cell or the battery device is used to store or provide electrical energy.

[0047] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0048] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings:

[0049] Figure 1 This is a schematic diagram of the structure of the electrode sheet in some embodiments of this application;

[0050] Figure 2 This is a schematic diagram of the structure of the electrode assembly in some embodiments of this application;

[0051] Figure 3 This is a schematic diagram of the vehicle structure according to some embodiments of this application;

[0052] Figure 4 The figures show the CVS test results of Example 1 and Comparative Example 1 of this application;

[0053] The reference numerals in the detailed embodiments are as follows:

[0054] 10-Electrode; 1-Current collector; 2-Active material layer;

[0055] 20 - Electrode assembly; 101 - Negative electrode; 102 - Positive electrode; 103 - Separator; 104 - Negative electrode tab; 105 - Positive electrode tab;

[0056] 40 - Battery device;

[0057] 50 - Electrical appliance; 501 - Controller; 502 - Motor; Detailed Implementation

[0058] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0059] In this application, the term "and / or" describes 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. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0060] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0061] It should be understood that in the various embodiments of this application, the sequence number of each process does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0062] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0063] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0064] During the production of composite copper foil used as a current collector, uneven current distribution and poor plating solution flow can easily lead to a decrease in plating levelness. Uneven copper plating thickness in the current collector will increase the battery impedance, thereby reducing the overall battery performance.

[0065] Based on this, this application proposes a negative electrode current collector, including a substrate and a copper plating layer; wherein, the substrate includes a polymer material layer and a copper seed layer, the copper seed layer is disposed on at least one side of the surface of the polymer material layer; the copper plating layer is disposed on the surface of the copper seed layer; the surface roughness Ra of the copper plating layer satisfies: 0.1μm≤Ra≤0.3μm; and the thickness deviation of the copper plating layer is not greater than ±0.2μm.

[0066] In this embodiment, the negative electrode current collector includes a polymer material layer, a copper seed layer, and a copper plating layer. The polymer material layer refers to a thin film or coating made of polymer materials. Due to the light weight of polymer materials, the overall weight of the negative electrode current collector can be reduced, thereby increasing the energy density of the battery. The "copper seed layer" refers to a very thin copper layer deposited first on both sides of the polymer material film (such as PET). The main function of this copper seed layer is to provide a good conductive substrate for the subsequent electroplating process, allowing the electroplated copper to be deposited uniformly and continuously on the polymer film substrate, ultimately forming a composite copper foil with the required thickness and performance. The copper seed layer can be formed on both surfaces of the polymer material layer in the thickness direction, or it can be formed only on one side of the polymer material layer. The copper plating layer refers to a copper layer deposited on the surface of the substrate through an electroplating process, which provides conductivity for the negative electrode current collector. By scanning electron microscopy (SEM) or focused ion beam (FIB) technology, we can clearly observe the difference between the copper seed layer and the copper plating layer, mainly due to the differences in microstructure caused by their unique crystallization modes.

[0067] Surface roughness Ra is the arithmetic mean of the absolute values ​​of profile offsets within a sampling length. It is an important indicator for evaluating the micro-geometric errors of an object's surface. The smaller the Ra value, the smoother the surface. "0.1μm≤Ra≤0.3μm" indicates that the arithmetic mean of the micro-geometric errors of the copper plating layer cannot be less than 0.1 μm or greater than 0.3 μm. This range indicates that the surface roughness of the copper plating layer is controlled at a low level, thereby reducing contact resistance, which is the resistance when current passes through a contact surface, making the current flow smoother. At the same time, this roughness will not be too smooth, making it difficult for the negative electrode active material to adhere to the current collector when fabricating the negative electrode sheet.

[0068] Thickness deviation refers to the difference in thickness of the copper plating layer at different locations, reflecting the non-uniformity of the copper plating layer. This parameter is crucial for evaluating the leveling performance of the copper plating layer. Specifically, "thickness deviation" refers to the difference between the actual thickness of the copper plating layer and the expected or specified standard thickness. The "±" in "not greater than ±0.2μm" indicates that the deviation can be positive or negative, but whether it is higher or lower than the standard thickness, the absolute value of this deviation cannot exceed 0.2 micrometers (μm). For example, if the standard thickness of the copper plating layer is X μm, then its actual thickness is between X-0.2μm and X+0.2μm.

[0069] In some embodiments, the thickness of the copper plating layer ranges from 0.7 μm to 1.5 μm. As examples, typical but not limiting values ​​for the copper plating layer include 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, and 1.5 μm. The thickness of the copper plating layer affects the conductivity of the negative electrode current collector. Within the aforementioned thickness range, the negative electrode current collector exhibits good conductivity, uniform current distribution, and good adhesion. Depositing a copper layer of this thickness on a substrate containing a polymer layer presents significant challenges; if not properly controlled, localized areas may exhibit insufficient or excessive thickness. Therefore, it is necessary to select a suitable electroplating solution to control the overall quality of the plating layer.

[0070] In some embodiments, the thickness of the copper seed layer ranges from 0.4 μm to 0.8 μm. As examples, the thickness of the copper seed layer can be typical but not limiting values ​​such as 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, and 0.8 μm. This can further improve the uniform deposition of the copper plating layer and enhance its conductivity.

[0071] In some embodiments, the thickness of the polymer material layer ranges from 1.5 μm to 2.5 μm. As an example, the thickness of the polymer material layer can be typical but not limiting values ​​such as 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, and 2.5 μm.

[0072] In some embodiments, the polymer material layer comprises at least one of polyethylene terephthalate (PET), polypropylene (PP), and polyetherimide (PI). These polymer materials all possess excellent mechanical properties and good chemical stability.

[0073] Secondly, embodiments of this application provide a copper plating composite additive, comprising the following components in parts by weight:

[0074]

[0075] The first inhibitor includes isooctanol polyoxyethylene ether;

[0076] The second inhibitor includes at least one of polyethylene glycol, carboxymethyl cellulose, alkoxynaphthol, polyethylene glycol esters, and poly(ethylene glycol-propylene glycol) copolymers;

[0077] Leveling agents include quaternary ammonium salts copolymerized from alkyl dimethyl ammonium chloride and sulfur dioxide.

[0078] The term "inhibitor" refers to chemical additives used to control the reduction rate and deposition behavior of metal ions during the electroplating process.

[0079] The term "dispersion agent" refers to a class of additives used to improve the dispersion and deep plating capabilities of electroplating solutions.

[0080] The term "brightener" refers to a class of additives used to improve the appearance and performance of coatings. They can promote the refinement of metal crystals and increase the gloss and smoothness of the coating.

[0081] The term "leveling agent" refers to a class of additives used to improve the smoothness and uniformity of the coating surface.

[0082] The first inhibitor, isooctanol polyoxyethylene ether (CAS No. 26468-86-0), is a nonionic surfactant. Its molecular structure gives it both hydrophilic and hydrophobic parts, enabling it to form a dynamic equilibrium at the interface between the plating bath and the substrate. By adjusting its concentration in the plating bath, the growth rate and uniformity of the coating can be precisely controlled. It also exhibits good surface activity, helping to reduce the surface tension of the copper plating bath, making it easier for the copper plating bath to wet and cover the flexible substrate surface. Isooctanol polyoxyethylene ether also contributes to the uniform distribution of other additives (e.g., inhibitors, poly(ethylene oxide)-poly(propylene oxide) monobutyl ether, sodium dithiodipropane sulfonate, etc.) on the copper foil surface, thereby enhancing the synergistic effect between the components.

[0083] The second inhibitor primarily inhibits the reduction and deposition of copper ions by forming a protective film, adsorption film, or steric hindrance effect on the copper surface, thereby reducing the copper deposition rate and controlling it. The inhibitors selected in this application mostly have high molecular weights, enabling them to form a certain steric hindrance effect in the electroplating solution, slowing down the deposition rate of copper ions, or they can adsorb onto the cathode surface to form a barrier film, inhibiting the rapid deposition of copper ions. These inhibitor molecules can form complex network structures in the plating solution, affecting the migration path and deposition rate of copper ions. Especially for substrates with large widths, they can effectively reduce edge effects, resulting in a more uniform coating thickness.

[0084] PAS-A-5, a quaternary ammonium salt copolymerized with alkyl dimethyl ammonium chloride and sulfur dioxide (CAS No. 26470-16-6), is commonly used as a wetting agent and leveling agent to improve the fluidity of electroplating solutions. PAS-A-5 has a unique chemical structure that allows it to preferentially adsorb onto protruding areas of the plating surface during coating growth, slowing down the deposition rate in these areas while promoting copper ion deposition in recessed areas, thus achieving overall plating smoothness. Through interaction with the plating surface, the leveling agent molecules utilize their charge properties and spatial structure to dynamically adjust the deposition rate differences on the plating surface. Particularly on flexible substrates with large widths, it can reduce uneven plating thickness caused by uneven surface tension.

[0085] Positioning agents are typically used to improve the wettability and flowability of the plating solution on the substrate surface, enabling the plating solution to evenly cover the entire substrate surface, especially the edges and corners, thus helping to reduce coating unevenness.

[0086] Brighteners enhance the gloss and smoothness of the coating by optimizing the copper ion deposition process, reducing porosity and defects in the coating, and making the coating surface smoother and brighter.

[0087] These additives can exert various synergistic effects in the electroplating solution, significantly improving the electroplating effect of copper foil, especially for flexible substrates. They improve the wettability, dispersibility, stability, and conductivity of the electroplating solution, enabling it to be evenly distributed on copper foil with a large width, forming a uniform and smooth coating. Simultaneously, the content of each additive affects the stability, fluidity, and electroplating efficiency of the electroplating solution, thus influencing the smoothness of the coating.

[0088] In some embodiments, the leveling agent includes at least one selected from polyethylene oxide-propylene oxide monobutyl ether, polypropylene glycol, gelatin, sodium dodecyl sulfonate, polyvinyl diallyl ammonium chloride, and a copolymer of vinyl diallyl ammonium chloride and sulfur dioxide. In some optional embodiments, polyethylene oxide-propylene oxide monobutyl ether (CAS No. 9038-95-3, hereinafter referred to as 50HB-400) is selected as the leveling agent. 50HB-400 can improve the distribution of metal ions on the copper foil surface and reduce localized over-thickness or under-thinness. The synergistic effect of 50HB-400 with the first inhibitor, isooctyl alcohol polyoxyethylene ether, can further improve the wettability of the electrolyte, reduce the formation of bubbles and voids, and promote a more uniform electrolyte coverage on the copper foil substrate surface.

[0089] In some embodiments, the brightener includes at least one selected from sodium polydithiopropane sulfonate, sodium thiopropane sulfonate, sodium N,N-dimethyldithiocarbamate, sodium methyl thiopropane sulfonate, sodium 2-mercapto-1-benzothiazole sulfonate, and sodium N,N-dipropyldithiocarbamate. In some optional embodiments, sodium polydithiopropane sulfonate (CAS No. 27206-35-5, hereinafter referred to as SPS) is selected as the brightener. Sodium polydithiopropane sulfonate (CAS No. 27206-35-5, hereinafter referred to as SPS) can form an adsorption film on the coating surface, changing the microstructure of the coating surface and increasing the gloss and smoothness of the coating surface. SPS has anionic properties and can form stable complexes with cations in the electrolyte (such as PAS-A-5), promoting the uniform distribution of metal ions and improving the stability and uniformity of the electrolyte. SPS can also work synergistically with the first inhibitor, isooctyl polyoxyethylene ether, and the second inhibitor to change the polarization sites on the electrode surface, improve the stability and conductivity of the electroplating solution, and promote the reduction reaction of copper ions.

[0090] In some embodiments, the brightener further includes at least one of (O-ethyl dithiocarbonate)-S-(3-sulfonylpropyl) ester potassium salt, sodium phenyl polydithiopropane sulfonate, 2-tetrahydrothiazothione, and sodium thiazolinyl dithiopropane sulfonate. The above-mentioned brightener is a low-current-density brightener, which is an additive used to improve the gloss of the coating in low-current-density areas. During electroplating, the current density is higher in areas near the electrode or the edge of the electrolytic cell, resulting in a faster deposition rate of metal ions, while the current density is lower in areas located in the center of the electrolytic cell or far from the electrode, resulting in a slower deposition rate of metal ions. This may lead to localized areas of excessive thickness or thinness on the entire substrate surface. In the embodiments of this application, the gloss and smoothness of the coating in low-current-density areas are improved by further using the above-mentioned brightener. In some optional embodiments, the brightener is selected from (O-ethyl dithiocarbonate)-S-(3-sulfonylpropyl) ester potassium salt (CAS No. 93841-14-6, hereinafter referred to as OPX). OPX exhibits adsorption properties in low current density regions. At low current densities, OPX preferentially adsorbs onto the coating surface, forming a protective film that improves the coating's microstructure and enhances gloss and smoothness. By smoothing the coating in both high and low current density regions, the overall coating thickness uniformity can be improved.

[0091] Furthermore, OPX can also synergize with other additives such as sodium polydipropane sulfonate (SPS) and inhibitors. This synergistic effect helps to further improve the overall quality of the coating, enhancing its uniformity, gloss, and adhesion.

[0092] In some embodiments, the second inhibitor is polyethylene glycol (hereinafter referred to as PEG), with a number-average molecular weight of 5000 g / mol to 10000 g / mol. Compared with other inhibitors, PEG is relatively inexpensive, readily available and easy to use, has good stability, and exhibits synergistic effects with various additive components. The molecular weight of PEG affects its adsorption capacity on the electrode surface, thereby affecting its inhibitory effect. PEG with higher molecular weights generally has better inhibitory effects due to its greater steric hindrance effect. As examples, the molecular weight of PEG can be typical but not limiting values ​​such as 5000 g / mol, 6000 g / mol, 7000 g / mol, 8000 g / mol, 9000 g / mol, and 10000 g / mol.

[0093] Thirdly, embodiments of this application provide a copper plating solution including the aforementioned copper plating composite additive. The copper plating solution using the aforementioned copper plating composite additive has the following advantages: the optimized additive composition can significantly improve the dispersion and wettability of the copper plating solution, enabling the plating layer to be uniformly deposited on the substrate surface. It is particularly suitable for substrates with large widths, improving the levelness of the plating layer across the entire surface and avoiding the problem of uneven local deposition.

[0094] In some embodiments, the copper plating solution comprises the following components:

[0095]

[0096] Because the isooctanol polyoxyethylene ether (IOE) has a long molecular chain, excessive addition may lead to excessively high viscosity of the copper plating solution. Therefore, in the copper plating of this application embodiment, the content of IOE is controlled within the range of 10 mg / L to 500 mg / L. This allows it to fully exert its effect while maintaining a suitable viscosity in the copper plating solution, thereby achieving better electroplating results. As an example, the concentration of IOE can be typical but not limiting values ​​such as 10 mg / L, 20 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, and 500 mg / L.

[0097] Increasing the concentration of the second inhibitor suppresses the deposition rate of copper ions, resulting in a finer and denser coating. However, excessive amounts of the second inhibitor can also affect the density and mechanical properties of the copper foil. Therefore, in the copper plating solution of this application embodiment, controlling the content of the second inhibitor within the range of 10 mg / L to 400 mg / L allows for better control of the fineness of the coating crystals. As an example, the concentration of the second inhibitor can be typical but not limiting values ​​such as 10 mg / L, 20 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 300 mg / L, and 400 mg / L.

[0098] The amount of leveling agent added may affect the fluidity and wettability of the plating solution. Therefore, in the copper plating solution of this application embodiment, controlling the content of the leveling agent within the range of 10 mg / L to 500 mg / L can better control the smoothness and quality of the plating layer. As an example, the concentration of the leveling agent can be typical but not limiting values ​​such as 10 mg / L, 20 mg / L, 50 mg / L, 100 mg / L, 150 mg / L, 200 mg / L, 300 mg / L, 400 mg / L, and 500 mg / L.

[0099] The amount of brightener added has a significant impact on the gloss and roughness of the copper foil surface. Therefore, in the copper plating solution of this application embodiment, controlling the content of brightener in it within the range of 10 mg / L to 40 mg / L can better refine the grains and improve the flatness of the copper foil. As an example, the concentration of brightener can be typical but not limiting values ​​such as 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 35 mg / L, and 40 mg / L.

[0100] The amount of leveling agent (PAS-A-5) added affects the stability of the electroplating solution and the uniformity of the plating layer. Therefore, in the copper plating solution of this application embodiment, controlling the content of PAS-A-5 within the range of 10 mg / L to 50 mg / L can better improve the leveling of the electroplating layer by changing the charge state and interfacial properties of the electroplating solution. As an example, the concentration of PAS-A-5 can be typical but not limiting values ​​such as 10 mg / L, 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 35 mg / L, 40 mg / L, 45 mg / L, and 50 mg / L.

[0101] By optimizing the concentration of each additive within the above range, a coating with good flatness can be obtained on copper foil with a large width.

[0102] In some embodiments, the copper plating solution comprises the following components:

[0103]

[0104] The embodiments of this application further optimize the content of each component in the copper plating solution. Through the above optimization, the copper plating composite additive can further enhance the stability of the electroplating solution and improve the smoothness of the electroplated copper layer.

[0105] In some embodiments, the copper plating solution further includes copper sulfate, sulfuric acid, and hydrochloric acid. Copper sulfate is the main source of copper ions in the plating solution. Sulfuric acid provides an acidic environment, maintaining the pH value of the plating solution within a suitable range and simultaneously improving conductivity. The chloride ions in the hydrochloric acid can refine the grains, contributing to a smooth and dense coating. The synergistic effect of copper sulfate, sulfuric acid, hydrochloric acid, and the aforementioned copper plating additives can form a uniform copper coating on a flexible substrate with a large width.

[0106] In some embodiments, the copper plating solution comprises the following components:

[0107] Copper sulfate 50g / L~150g / L;

[0108] Sulfuric acid concentration: 100 g / L to 250 g / L;

[0109] Hydrochloric acid 1 mg / L~500 mg / L.

[0110] In the embodiments of this application, the copper sulfate content ranges from low copper concentration (typically 50 g / L to 180 g / L) to medium copper concentration (typically 180 g / L to 240 g / L). The sulfuric acid content ranges from high acid (typically pH between 1 and 2) to medium acid concentration. Such a copper plating solution system helps improve the solubility and stability of copper ions, reduces the roughness of the coating, and is suitable for copper plating on wide, flexible substrates. It allows the plating solution to be evenly distributed on large-area substrates, reducing the problem of uneven local deposition. By optimizing the type and content of copper plating additives, the smoothness of the copper plating layer is significantly improved. Moreover, by adjusting the content of the copper plating agent, the brightness of the coating can be flexibly adjusted, achieving effects from high gloss to matte, meeting different application requirements.

[0111] Fourthly, embodiments of this application provide a method for preparing a negative electrode current collector, comprising the following steps: providing a substrate; and the aforementioned copper plating solution; the substrate comprising a polymer material layer and a copper seed layer, and placing the substrate in the aforementioned copper plating solution for electroplating treatment.

[0112] Here, "substrate" refers to the carrier used for copper electroplating. In the embodiments of this application, the substrate includes a polymer material layer, which can be a single polymer material layer or a polymer material layer laminated to the surface of other substrate materials in the form of a coating. The copper seed layer can be formed on the polymer material surface using physical vapor deposition (PVD) technology. Before electroplating, the substrate surface can be cleaned using ultrasonic cleaning or chemical cleaning methods, and the substrate surface can also be activated by chemical or electrochemical treatment.

[0113] Providing copper plating solution, in this context, refers to preparing a solution containing the aforementioned components such as copper sulfate, sulfuric acid, chloride ions, and copper plating composite additives.

[0114] Electroplating involves placing the substrate in contact with a copper plating solution. This means immersing the substrate in the solution and allowing copper ions to deposit on its surface through electrolysis, forming a uniform, dense, high-quality copper plating layer. The electrolytic apparatus used can be an electrolytic cell, with the substrate as the cathode and the anode being a copper plate, phosphor bronze anode, or titanium anode with iridium dioxide on its surface. During the electroplating process, appropriate current density, plating time, and temperature must be controlled.

[0115] Regarding the substrate, polymer films, due to their low density and good flexibility, help to improve the energy density of batteries and are suitable for complex battery designs, thus making them suitable as the support layer for composite copper foil. The following describes the preparation method of composite copper foil using organic polymer films as the support layer:

[0116] (1) Select a suitable organic polymer film (such as polyethylene terephthalate (PET) film, polypropylene (PP) film, polyetherimide (PI) film, etc.) as the support layer and clean the surface of the support layer;

[0117] (2) A copper seed layer is deposited on both sides of the polymer film using physical vapor deposition (PVD) technology;

[0118] (3) The polymer film with the copper seed layer deposited is used as the substrate and immersed in the copper plating solution. An electrolytic cell is set up, with the substrate as the cathode and the copper plate as the anode. The current density and electroplating time are controlled to electroplat the substrate. The electroplating solution can be stirred appropriately to make the metal ions in the plating solution evenly distributed.

[0119] In some embodiments, the preparation steps of the copper plating solution include: adding a first inhibitor to water, then adding a leveling agent and a second inhibitor, then adding a brightener and a leveling agent to obtain a copper plating composite additive; adding copper sulfate, sulfuric acid and hydrochloric acid to water to prepare an initial copper plating solution; and adding the copper plating composite additive to the initial copper plating solution to obtain a copper plating solution.

[0120] By preparing the copper plating solution in the above order, the components can be fully dissolved and mixed evenly, and they can exert the best synergistic effect, thus obtaining a copper plating solution with excellent performance.

[0121] When preparing copper plating composite additives, the first inhibitor, isooctanol polyoxyethylene ether, is added to water first because it has excellent wetting and penetrating properties, which helps in the dispersion and adsorption of subsequent additives. Then, the leveling agent and the second inhibitor are added, which further provides good dispersibility and stability, creating favorable conditions for the addition of subsequent components. The brightener and leveling agent need to be thoroughly mixed with other components to improve their conductivity and adhesion. The first few components already provide good dispersibility and stability, which helps in the uniform distribution and full effect of the latter two components.

[0122] In preparing the copper plating solution, copper sulfate and sulfuric acid are added first. These components are the basic ingredients of the copper plating solution; adding them to water first improves the acidity and stability of the solution. Adding copper plating additives on this basis prevents unnecessary chemical reactions, thus promoting optimal performance. Hydrochloric acid is then added to adjust the chloride ion concentration.

[0123] In some embodiments, the electroplating process conditions include: an operating current density of 10 mA / cm². 2 ~200mA / cm 2 As an example: the current density can be 10 mA / cm². 2 20mA / cm 2 50mA / cm 2 80mA / cm 2 100mA / cm 2 120mA / cm 2 150mA / cm 2 180mA / cm 2 200mA / cm 2 Typical but not limiting values.

[0124] The "operating current density" here refers to the operating current density range of 10 mA / cm² during the electroplating process. 2 ~200mA / cm 2 This current operating range is relatively wide. In the embodiments of this application, by using the aforementioned copper plating additive, the current operating range can be significantly expanded, thereby improving the plating quality while using a larger current, and thus improving the production efficiency of electroplating.

[0125] Normally, in electroplating solutions with copper ion concentrations of 50 g / L to 150 g / L, using excessively high current densities can lead to scorching of the plating layer. This is because excessively high current densities cause localized areas to experience excessive current, preventing copper ions in the plating solution from replenishing the plating layer in time, thus causing plating quality problems. However, by using the electroplating solution of the embodiments of this application, even at higher currents, problems such as plating scorching do not occur, thereby significantly improving production speed.

[0126] Electrolytic copper foil is prepared using the method described above, resulting in a highly uniform plating thickness. This is attributed to the copper plating additives in the plating solution, which significantly improve the uniform deposition of metal ions on the substrate surface. The high flatness of the electrolytic copper foil contributes to improving the quality of the negative electrode current collector in subsequent processing.

[0127] Fifthly, embodiments of this application provide a battery cell including a negative electrode sheet, which includes the aforementioned negative electrode current collector or a negative electrode current collector prepared by the aforementioned method. The aforementioned negative electrode current collector has a uniform plating thickness, improving the consistency and performance stability of the negative electrode sheet. The aforementioned copper plating additive exhibits good leveling performance on electrolytic copper foil with a particularly large width, which helps to improve the surface quality of the negative electrode sheet and the accuracy of subsequent processing.

[0128] Sixthly, embodiments of this application provide a battery device including the aforementioned battery cell. The coating thickness of the negative electrode sheet of the battery cell is uniform, improving the consistency and performance stability of the battery cell. The surface of the negative electrode sheet is smooth, which helps to improve the overall quality and performance of the battery device.

[0129] The components of a single battery cell are described in detail below.

[0130] Please refer to Figure 1 , Figure 1 This is a schematic diagram of the structure of the electrode 10 in some embodiments of this application. The electrode 10 includes a current collector 1 and an active material layer 2, the active material layer 2 being disposed on at least one side of the current collector 1.

[0131] Current collector 1 refers to the component used to collect current. Depending on the application, current collector 1 can be either a negative electrode current collector or a positive electrode current collector. When current collector 1 is a negative electrode current collector, the corresponding active material layer 2 coated on the negative electrode current collector is a negative electrode active material layer, and the resulting electrode 10 is a negative electrode electrode. When current collector 1 is a positive electrode current collector, the corresponding active material layer 2 coated on the positive electrode current collector is a positive electrode active material layer, and the resulting electrode 10 is a positive electrode electrode. Taking a lithium-ion battery as an example, the material of the negative electrode current collector can be copper, and the material of the positive electrode current collector can be aluminum. Furthermore, current collector 1 can have various shapes, such as strips or squares, and is not limited here.

[0132] The active material layer 2 includes active materials, conductive agents, and binders. Active materials refer to materials that participate in electrochemical oxidation / reduction reactions. Optionally, the active material is a powder. When active material layer 2 is a negative electrode material layer, the active material is a negative electrode active material. When active material layer 2 is a positive electrode material layer, the active material is a positive electrode active material. Taking a lithium-ion battery as an example, the negative electrode active material can be silicon-based materials, etc.; the positive electrode active material can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The conductive agent refers to the material that collects microcurrents between active materials and between the active material and current collector 1. The conductive agent can be, but is not limited to, conductive graphite, carbon nanotubes, acetylene black, etc. The binder is the material that binds the active materials together to enhance the electronic contact between the active material and the conductive agent, and between the active material and current collector 1. The binder can be, but is not limited to, styrene-butadiene rubber (SBR), acrylonitrile, acrylate, polyvinylidene fluoride (PVDF), carboxymethyl cellulose (CMC), etc.

[0133] The current collector 1 has a first surface and a second surface opposite to each other along the thickness direction of the current collector 1. At least one side of the current collector 1 includes the first surface and / or the second surface of the current collector 1. It is understood that the active material layer 2 may be disposed on the first surface, or on the second surface, or the active material layer 2 may be disposed on both the first surface and the second surface.

[0134] Please refer to Figure 2 , Figure 2 This is a schematic diagram of the structure of the electrode assembly 20 in some embodiments of this application. The electrode assembly 20 is the component in the battery where the electrochemical reaction occurs. The electrode assembly 20 is mainly formed by winding or stacking an electrode structure in which the negative electrode 101 and the positive electrode 102 are integrated. Typically, a separator 103 is provided between adjacent negative electrode 101 and positive electrode 102. The negative electrode current collector is connected to a negative electrode tab 104, and the positive electrode current collector is connected to a positive electrode tab 105.

[0135] [Negative electrode plate]

[0136] The negative electrode 101 includes a negative current collector and a negative active material layer, with the negative active material layer coated on the surface of the negative current collector.

[0137] In some embodiments, the negative electrode active material may further include at least one of artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, and tin-based materials.

[0138] In some embodiments, the negative electrode active material may also include a binder. Examples of binders include styrene-butadiene rubber, polyacrylic acid, sodium polyacrylate, polyacrylamide, polyvinyl alcohol, sodium alginate, polymethacrylic acid, carboxymethyl chitosan, etc.

[0139] In some embodiments, the negative electrode active material further includes a conductive agent. Examples of conductive agents include superconducting carbon, acetylene black, carbon black, Ketjen black, carbon nanotubes, graphene, etc.

[0140]

Positive Electrode

[0141] The positive electrode 102 includes a positive current collector and a positive active material layer, with the positive active material layer coated on the surface of the positive current collector. Taking a lithium-ion battery as an example, the material of the positive current collector can be aluminum, and the positive material layer includes a positive active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc.

[0142]

Isolation Film

[0143] The separator 103 is a porous plastic film that allows alkali metal ions in the electrolyte to pass through freely, but isolates the negative electrode 101 and the positive electrode 102, preventing electrons inside the battery from passing through freely. The separator 103 can be made of PP (polypropylene) or PE (polyethylene), etc. Organic or inorganic composite coatings can also be applied to the separator 103, including but not limited to ceramic particle coatings, metal oxide coatings, polymer adhesive layers, etc.

[0144] In a seventh aspect, embodiments of this application provide an electrical device, including the aforementioned battery cell or battery device, wherein the battery cell or battery device is used to store or provide electrical energy.

[0145] Because the electrical device uses the aforementioned battery device, its operational stability is improved.

[0146] The battery devices disclosed in some embodiments of this application can be used, but are not limited to, in electrical devices such as vehicles, ships, or aircraft. A power system incorporating the battery devices disclosed in this application can be used to construct such electrical devices.

[0147] For ease of explanation, the following embodiments will be described using a vehicle 50 as an example of an electrical device according to an embodiment of this application.

[0148] Please refer to Figure 3 , Figure 3 This is a schematic diagram of the structure of a vehicle 50 provided in some embodiments of this application. A battery device 40 is disposed inside the vehicle 50, and the battery device 40 may be located at the bottom, front, or rear of the vehicle 50. The battery device 40 can be used to power the vehicle 50; for example, the battery device 40 can serve as the operating power source for the vehicle 50. The vehicle 50 may also include a controller 501 and a motor 502. The controller 501 is used to control the battery device 40 to supply power to the motor 502, for example, to meet the power needs of the vehicle 50 during starting, navigation, and driving.

[0149] In some embodiments of this application, the battery device 40 can not only serve as the operating power source for the vehicle 50, but also as the driving power source for the vehicle 50, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 50.

[0150] In some embodiments of this application, the battery device 40 is a secondary battery. Secondary batteries can take many different forms, including but not limited to battery cells, battery modules, and battery packs. Here, a secondary battery refers to a battery that can be recharged after discharge to activate its active materials and continue to be used.

[0151] The following description is based on specific embodiments.

[0152] Example 1

[0153] (1) Copper plating composite additives

[0154] This application provides a copper plating composite additive comprising the following components in parts by weight: 200 parts of isooctanol polyoxyethylene ether, 300 parts of polyethylene glycol (number average molecular weight 8000 g / mol), 200 parts of polyethylene oxide polyoxypropylene monobutyl ether, 15 parts of sodium polydisulfide dipropane sulfonate, and 30 parts of a quaternary ammonium salt copolymerized with alkyl dimethyl ammonium chloride and sulfur dioxide.

[0155] (2) Copper plating solution

[0156] Copper plating additives include water and the following components:

[0157]

[0158] The preparation method of copper plating solution includes the following steps:

[0159] S1: Heat isooctyl alcohol polyoxyethylene ether to 50°C, then add it to 100mL of distilled water while stirring. After it dissolves, add polyethylene oxide polyoxypropylene monobutyl ether (50HB-400) and polyethylene glycol, and continue stirring until dissolved.

[0160] S2: Add sodium polydisulfide dipropane sulfonate (SPS), quaternary ammonium salt (PAS-A-5) copolymerized with alkyl dimethyl ammonium chloride and sulfur dioxide to the solution and stir until dissolved to obtain copper plating composite additive.

[0161] S3: Prepare an initial copper plating solution containing copper sulfate and sulfuric acid, add copper plating composite additives, add hydrochloric acid to adjust the chloride ion concentration, and stir to obtain the copper plating solution.

[0162] (3) Preparation of negative electrode current collector

[0163] Substrate: A copper seed layer is deposited on both sides of the PET film using physical vapor deposition technology. The size of the PET film is 10cm × 6.5cm.

[0164] The copper plating solution was added to a 267 mL electrolytic cell (Hull cell), and the substrate was placed into the electrolytic cell. The electroplating test was carried out at a constant current of 2A for 5 minutes at 25°C. The anode used was a phosphor bronze anode.

[0165] Example 2

[0166] The difference between Example 4 and Example 1 is that the copper plating composite additive also includes 0.5 parts of potassium salt of (O-ethyl dithiocarbonate)-S-(3-sulfonylpropyl) ester, and the concentration of potassium salt of (O-ethyl dithiocarbonate)-S-(3-sulfonylpropyl) ester in the copper plating solution is 0.5 mg / L.

[0167] Example 3

[0168] The difference between Example 5 and Example 1 is that carboxymethyl cellulose is used instead of polyethylene glycol.

[0169] Comparative Example 1

[0170] The difference between Comparative Example 1 and Example 1 is that the copper plating additive used is Okuno JRM COPPER, a copper plating additive manufactured by Okuno Corporation of Japan.

[0171] Comparative Example 2

[0172] The difference between Comparative Example 2 and Example 1 is that the copper plating additive does not include the first inhibitor, isooctyl alcohol polyoxyethylene ether.

[0173] Battery fabrication:

[0174] Lithium iron phosphate (LFP) as the positive electrode active material, carbon black (Super P) as the conductive agent, and polyvinylidene fluoride (PVDF) as the binder are thoroughly mixed in an appropriate amount of NMP solvent at a weight ratio of 90:5:5 to form a uniform positive electrode slurry. The positive electrode slurry is then coated onto the surface of the positive electrode current collector aluminum foil, with a coating weight ≤25mg / cm². 2 After drying and cold pressing, a positive electrode sheet is obtained;

[0175] Artificial graphite, styrene-butadiene rubber (SBR), sodium carboxymethyl cellulose (CMC), and a conductive agent were thoroughly mixed in an appropriate amount of deionized water at a weight ratio of 80:5:5:10 to form a negative electrode slurry. The negative electrode slurry was then coated onto the surface of the negative electrode current collector provided in Example 1 and Comparative Example 1 to a thickness of 5 μm, thus obtaining a negative electrode sheet.

[0176] A polyethylene film with a thickness of 9 μm was used as the separator.

[0177] The electrolyte is a ethylene carbonate (EC) solution with a composition of 1M LiPF6.

[0178] The positive electrode, negative electrode, separator, and electrolyte are assembled into a stacked cell, and the encapsulation material is aluminum-plastic film, thus obtaining a battery.

[0179] Performance testing

[0180] To verify the progressiveness of the embodiments of this application, the samples of the embodiments and comparative examples were subjected to the following tests:

[0181] 1. XRF Testing

[0182] That is, X-ray fluorescence spectrometry, using XRF to test the copper plating thickness at different current densities of the electrolytic copper foils of Examples 1 to 5 and Comparative Examples 1 to 4.

[0183] 2. Leveling ability of copper plating solution

[0184] The leveling capability of the copper plating solutions in each embodiment and comparative example was evaluated by cyclic voltammetry (CVS). A Cu-RDE (copper-based rotating disk electrode) was used as the working electrode, a platinum sheet as the auxiliary electrode, and a calomel electrode as the reference electrode. Cyclic voltammetry (CV) tests were performed on the copper plating solutions of each embodiment and comparative example at room temperature. The test conditions were 0 rpm and 2500 rpm, with a measurement voltage range of 0.2–0.5 V and a scan rate of 1 mV / s. The leveling capability of each copper plating solution was calculated.

[0185] CVS (Continuous Voltage Suppression) is an electrochemical-based analytical method that records the current response in a solution by applying a change in voltage. In copper plating, the plating solution typically contains metal ions (such as Cu2+), electrolytes, and various additives. The main function of these additives is to adjust the structure, gloss, stress, and plating rate of the coating. CVS analysis monitors the effect of these additives based on the following principles:

[0186] Brighteners: These additives typically affect the current response by accelerating the copper deposition rate. In the CVS curve, this is represented by an increase in current.

[0187] Suppressor: Suppressors reduce the current response by slowing down the deposition process. The current in the CVS curve decreases or diminishes.

[0188] CVS (Cyclic VS) indirectly characterizes the concentration and effect of additives in the plating solution by observing changes in the current-voltage curve. During copper plating, a typical CVS curve usually exhibits multiple peaks. These peaks are related to the electrochemical behavior of the additives, and the peak current is directly proportional to the additive concentration. Therefore, the peak height reflects the relative concentration of the additive in the solution. Higher peaks indicate stronger accelerating effects, while lower peaks indicate stronger inhibiting effects.

[0189] Leveling capacity (LP%) is determined by the following formula:

[0190]

[0191] Here, Ar represents the peak area after adding the copper plating additive in cyclic voltammetric stripping (CVS) electrochemical measurements. This peak area Ar is used to evaluate the effect of the leveling agent in controlling the deposition rate and uniformity on the electrode surface.

[0192] As represents the peak area without copper plating additives.

[0193] 3. Surface roughness

[0194] Surface roughness was tested in accordance with the standards GB / T 1031-2009 "Surface texture profile method for surface roughness parameters and their numerical values" and GB / T131-2006 (ISO1302:2002) "Representation of surface texture".

[0195] 4. Test method for thickness deviation

[0196] The cross-section of the negative electrode current collector slice was observed using a scanning electron microscope (SEM). The copper plating thickness was measured at 10 locations, the thickness value at each location was recorded, and the thickness deviation was calculated.

[0197] Battery performance test

[0198] The electrolytic copper foils from Example 1 and Comparative Example 1 were used as negative electrode current collectors to assemble batteries. The cycle performance test process of the batteries was as follows: 1) rest for 12 hours; 2) charge at a constant current rate of 0.1C to a voltage of 3.65V; 3) rest for 5 minutes; 4) discharge at a constant current rate of 0.2C to a voltage of 2.5V; 5) rest for 5 minutes; 6) charge at a constant current rate of 0.2C to a voltage of 3.65V, and then charge at a constant voltage of 3.65V to... 0.1C; 7) Let stand for 5 min; 8) Discharge at a constant current rate of 1C until the voltage reaches 2.5V; 9) Let stand for 5 min; 10) Cycle steps 6-9 for 10 cycles; 11) Charge at a constant current rate of 0.1C until the voltage reaches 3.65V; 12) Let stand for 5 min; 13) Discharge at a constant current rate of 0.2C until the voltage reaches 2.5V; 14) Let stand for 5 min; 15) Cycle steps 6-14 for 200 cycles. The cycle performance data are shown in Table 3.

[0199] The test results are shown in Tables 1 to 3 below. Figure 1 and Figure 2 .

[0200] Table 1 shows the film thickness of each embodiment and comparative example under different current densities. This table reflects the coating performance of different additives under different current density conditions. Table 1 allows observation of the film thickness variation trend with current density.

[0201] Table 1

[0202]

[0203] As shown in Table 1, the copper plating thickness of Examples 1 to 3 exhibits a steady decreasing trend with decreasing current density, indicating that these examples have good copper plating growth characteristics under different current densities. In contrast, Comparative Examples 1 and 2 show more drastic changes in film thickness at certain test locations, especially with the copper plating thickness at low current densities being significantly lower than that of the Examples. This indicates that Examples 1 to 3 show smaller fluctuations in copper plating thickness under different current densities, demonstrating better control and stability. Compared to the Comparative Examples, the increase in copper plating thickness is more significant at high current densities. At low current densities, the copper plating growth characteristics are better.

[0204] Table 2

[0205]

[0206] Table 3

[0207]

[0208] Test results show that the leveling ability of the copper plating additive in this embodiment is better than that of the copper plating additive in Comparative Example 1, and through... Figure 4The CVS curves show that at higher current densities, the copper plating additive of Example 1 exhibits a smoother current change, a wider current operating range, and a leveling capability of 90.16%, which is superior to the copper plating additive of Comparative Example 1.

[0209] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application 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 or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A negative electrode current collector, characterized in that, include: The substrate includes a polymer material layer and a copper seed layer, wherein the copper seed layer is disposed on at least one surface of the polymer material layer; A copper plating layer is disposed on the surface of the copper seed layer; the surface roughness Ra of the copper plating layer satisfies: 0.1μm≤Ra≤0.3μm; and the thickness deviation of the copper plating layer is not greater than ±0.2μm.

2. The negative electrode current collector according to claim 1, characterized in that, The negative electrode current collector satisfies at least one of the following: (1) The thickness of the copper plating layer ranges from 0.7 μm to 1.5 μm; (2) The thickness of the copper seed layer ranges from 0.4 μm to 0.8 μm; (3) The thickness of the polymer material layer ranges from 1.5 μm to 2.5 μm; (4) The material of the polymer material layer includes at least one of polyethylene terephthalate, polypropylene, and polyetherimide.

3. A copper plating composite additive, characterized in that, The components include the following parts by weight: The first inhibitor includes isooctanol polyoxyethylene ether; The second inhibitor includes at least one of polyethylene glycol, carboxymethyl cellulose, alkoxynaphthol, polyethylene glycol esters, and poly(ethylene glycol-propylene glycol) copolymers; The leveling agent comprises a quaternary ammonium salt copolymerized with alkyl dimethyl ammonium chloride and sulfur dioxide.

4. The copper plating composite additive according to claim 3, characterized in that, The positioning agent comprises at least one of polyethylene oxide-polypropylene oxide monobutyl ether, polypropylene glycol, gelatin, sodium dodecyl sulfonate, polyvinyl diallyl ammonium chloride, and a copolymer of vinyl diallyl ammonium chloride and sulfur dioxide; and / or, The brightener includes at least one of sodium polydithiopropane sulfonate, sodium thiopropane sulfonate, sodium N,N-dimethyldithiocarbamate, sodium methyl thiopropane sulfonate, sodium 2-mercapto-1-benzothiazole sulfonate, and sodium N,N-dipropyldithiocarbamate.

5. The copper plating composite additive according to claim 3 or 4, characterized in that, The brightener also includes at least one of (O-ethyl dithiocarbonate)-S-(3-sulfonylpropyl) ester potassium salt, sodium phenyl polydithiopropane sulfonate, 2-tetrahydrothiazothione, and sodium thiazolinyl dithiopropane sulfonate.

6. The copper plating composite additive according to any one of claims 3 to 5, characterized in that, The second inhibitor is polyethylene glycol, wherein the number average molecular weight of the polyethylene glycol is 5000-10000 g / mol.

7. A copper plating solution, characterized in that, The copper plating composite additive includes any one of claims 3 to 6.

8. The copper plating solution according to claim 7, characterized in that, Includes the following components:

9. The copper plating solution according to claim 7 or 8, characterized in that, Includes the following components:

10. The copper plating solution according to any one of claims 7 to 9, characterized in that, The copper plating solution also includes copper sulfate, sulfuric acid, and hydrochloric acid.

11. The copper plating solution according to claim 10, characterized in that, The copper plating solution comprises the following components: Copper sulfate 50g / L~150g / L; Sulfuric acid concentration: 100 g / L to 250 g / L; Hydrochloric acid 1 mg / L~500 mg / L.

12. A method for preparing a negative electrode current collector as described in claim 1 or 2, characterized in that, Includes the following steps: A substrate is provided, and a copper plating solution according to any one of claims 7 to 11; the substrate comprises a polymer material layer and a copper seed layer; The substrate is placed in the copper plating solution for electroplating.

13. The method for preparing the negative electrode current collector according to claim 12, characterized in that, The preparation steps of the copper plating solution include: The first inhibitor is added to water, then the positioning agent and the second inhibitor are added, then the brightener and the leveling agent are added to obtain the copper plating composite additive; The initial copper plating solution is prepared by adding the copper sulfate, the sulfuric acid, and the hydrochloric acid to water; The copper plating composite additive is added to the initial copper plating solution to obtain the copper plating solution.

14. The method for preparing the negative electrode current collector according to claim 12 or 13, characterized in that, The electroplating process conditions include: a working current density of 10 mA / cm². 2 ~200mA / cm 2 .

15. A single battery cell, characterized in that, Includes a negative electrode sheet, wherein the negative electrode sheet includes the negative current collector as described in claim 1 or 2, or the negative current collector prepared by any one of claims 12 to 14.

16. A battery device, characterized in that, Includes the battery cell as described in claim 15.

17. An electrical appliance, characterized in that, Includes the battery cell of claim 15 or the battery device of claim 16, wherein the battery cell or the battery device is used to store or provide electrical energy.

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