A copper plating solution and negative electrode composite current collector prepared therefrom

Abstract

This application provides a copper plating solution for composite current collectors, comprising a leveling agent of general formula (1) wherein the anion X is F. ‑ Cl ‑ or Br ‑ R1, R2 and R3 are each independently selected from O or S; R4, R5 and R6 are each independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted aryl and substituted or unsubstituted heteroaryl.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a copper plating solution and a negative electrode composite current collector, a secondary battery, a battery module, a battery pack and an electrical device prepared therefrom. Background Technology

[0002] In recent years, with the increasingly widespread application of lithium-ion batteries, they have been widely used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric vehicles, military equipment, aerospace, and many other fields. Due to the significant advancements in lithium-ion battery technology, higher demands have been placed on its energy density, cycle performance, and safety performance. Especially when using composite current collectors, the safety and cycle performance of lithium-ion batteries urgently need further improvement. Summary of the Invention

[0003] This application is made in view of the above-mentioned problems, and its purpose is to provide a copper plating solution that enables the negative electrode composite current collector prepared therefrom to have excellent coating adhesion as well as high tensile strength and elongation.

[0004] To achieve the above objectives, this application provides a copper plating solution and a negative electrode composite current collector, a secondary battery, a battery module, a battery pack, and an electrical device prepared therefrom.

[0005] The first aspect of this application provides a copper plating solution for composite current collectors, comprising a leveling agent represented by general formula (1).

[0006]

[0007] Where the anion X is F - Cl - or Br - ;

[0008] R1, R2, and R3 are each independently selected from O or S;

[0009] R4, R5, and R6 are each independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl.

[0010] The copper plating solution of this application contains a leveling agent with a specific structure. The leveling agent has a low energy level difference and a high dipole moment. During the electroplating process, it can be adsorbed on the surface of copper, resulting in an increase in both cathode potential and charge transfer resistance. This inhibits copper surface deposition, making the electroplated copper layer more uniform. Consequently, the composite current collector prepared from it has excellent coating adhesion, as well as high tensile strength and elongation, thereby improving the cycle performance of lithium-ion batteries.

[0011] In any embodiment, R4, R5 and R6 are each independently selected from hydrogen, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, substituted or unsubstituted alkenyl groups having 2 to 6 carbon atoms, and substituted or unsubstituted pyrimidinyl groups.

[0012] In any embodiment, the leveling agent is

[0013]

[0014] In any embodiment, the copper plating solution further comprises copper sulfate, sulfuric acid, hydrochloric acid, brightener, wetting agent, and deionized water.

[0015] In any embodiment, the brightener is a compound containing a disulfide bond, a sulfonic acid group, or a thiol group.

[0016] In any embodiment, the brightener is one or both of sodium dithiopropane sulfonate and sodium 3-mercaptopropane sulfonate.

[0017] In any embodiment, the wetting agent is at least one of polyethylene glycol and polypropylene glycol.

[0018] In any embodiment, the number-average molecular weight of the polyethylene glycol is 4000-15000, and the number-average molecular weight of the polypropylene glycol is 5000-20000. When the molecular weight of the wetting agent is controlled within the given range, a dense barrier layer can be formed on the cathode surface, thereby inhibiting the rapid deposition of copper.

[0019] In any embodiment, the copper plating solution further comprises a grain refiner. When the copper plating solution further comprises a grain refiner, it can further refine the copper grains.

[0020] In any embodiment, the grain refiner is at least one of acetaldehyde and ethylenediaminetetraacetic acid (EDTA).

[0021] In any embodiment, each liter of copper plating solution contains: 60-120 g / L copper sulfate, 80-110 mL / L 98% sulfuric acid, 40-90 ppm hydrochloric acid (based on chloride ions), 2-12 mL / L brightener, 1-4 mL / L leveling agent, 0.5-2 mL / L wetting agent, 0.01-0.2 mL / L grain refiner, and the remainder is deionized water. When the specific content of each component is controlled within the given range, the uniformity of the coating can be further improved.

[0022] In any embodiment, the applicable temperature range for the copper plating solution is 20-50℃, optionally 20-45℃, and further optionally 20-35℃. When the temperature is controlled within the given range, the activity of the organic additives can be more effectively utilized.

[0023] In any embodiment, the applicable cathode current density for the copper plating solution is 1-20 A / dm². 2 Available in 1-15A / dm 2 Further options include 1-10 A / dm 2 When the cathode current density is controlled within the given range, a dense coating can be obtained.

[0024] In any embodiment, the applicable anodic current density for the copper plating solution is 0.5-3 A / dm³. 2 When the anodic current density is controlled within the given range, the brightness and smoothness of the resulting coating can be further improved.

[0025] In any embodiment, the pH value of the copper plating solution is 0.5-4. When the pH is controlled within the given range, the plating uniformity and anodic dissolution performance of the plating solution can be improved.

[0026] A second aspect of this application also provides a negative electrode composite current collector, which includes a polymer material substrate and a copper layer formed on two surfaces of the polymer material substrate, wherein the copper layer is obtained by electroplating using the copper plating solution of the first aspect of this application.

[0027] A third aspect of this application provides a secondary battery, including the negative electrode composite current collector of the second aspect of this application.

[0028] A fourth aspect of this application provides a battery module including the secondary battery of the third aspect of this application.

[0029] A fifth aspect of this application provides a battery pack that includes the battery module of the fourth aspect of this application.

[0030] A sixth aspect of this application provides an electrical device comprising at least one selected from the third aspect of this application, the fourth aspect of this application, or the fifth aspect of this application. Attached Figure Description

[0031] Figure 1 This is a scanning electron microscope (SEM) image of a copper layer prepared using a traditional PCB plating solution.

[0032] Figure 2 This is a SEM image of the copper layer prepared in Example 1-1 of this application.

[0033] Figure 3 This is a SEM image of the copper layer prepared in Example 3-1 of this application.

[0034] Figure 4 This is a schematic diagram of a secondary battery according to one embodiment of this application.

[0035] Figure 5 yes Figure 4 An exploded view of a secondary battery according to one embodiment of this application is shown.

[0036] Figure 6 This is a schematic diagram of a battery module according to one embodiment of this application.

[0037] Figure 7 This is a schematic diagram of a battery pack according to one embodiment of this application.

[0038] Figure 8 yes Figure 7 An exploded view of a battery pack according to one embodiment of this application is shown.

[0039] Figure 9 This is a schematic diagram of an electrical device that uses a secondary battery as a power source according to one embodiment of this application.

[0040] Explanation of reference numerals in the attached figures:

[0041] 1 Battery pack; 2 Upper housing; 3 Lower housing; 4 Battery module; 5 Secondary battery; 51 Casing; 52 Electrode assembly; 53 Top cover assembly Detailed Implementation

[0042] The following detailed description, with appropriate reference to the accompanying drawings, discloses embodiments of the copper plating solution and the negative electrode composite current collector, secondary battery, battery module, battery pack, and electrical device prepared therefrom. However, unnecessary details may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of practically identical structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided for a thorough understanding of this application by those skilled in the art and are not intended to limit the subject matter of the claims.

[0043] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of a particular range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, it is expected that ranges of 60-110 and 80-120 are also included. Furthermore, if minimum range values ​​of 1 and 2 are listed, and if maximum range values ​​of 3, 4, and 5 are listed, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed in this article; "0-5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is stated as an integer ≥2, it is equivalent to disclosing that the parameter is, for example, an integer such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0044] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0045] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0046] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order; for example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0047] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0048] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0049] The plating solution formulations used in the PCB industry have traditionally been suitable for addressing through-hole filling issues, resulting in plating thicknesses typically in the tens of micrometers. While electroplating is also necessary for composite current collectors, it differs from traditional electroplating in that it's not performed on a metal surface, but rather on a polymer layer with a metal underlayer, resulting in a plating thickness of approximately 1 micrometer. The electroplating process for composite current collectors does not prioritize high aspect ratios, but rather excellent adhesion and sufficient tensile strength and elongation. Therefore, traditional plating solution formulations are unsuitable for the production of composite current collectors.

[0050] Through extensive experiments, the inventors of this application discovered that when a specific leveling agent is present in the copper plating solution, it can improve the uniformity of the surface of the negative electrode composite current collector coating, thereby improving the coating adhesion, tensile strength, and elongation of the negative electrode composite current collector, and thus improving the cycle performance of the lithium-ion battery.

[0051] Copper plating solution

[0052] In one embodiment of this application, a copper plating solution for composite current collectors is provided, comprising a leveling agent represented by general formula (1).

[0053]

[0054] Where the anion X is F - Cl - or Br - ;

[0055] R1, R2, and R3 are each independently selected from O or S;

[0056] R4, R5, and R6 are each independently selected from hydrogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted aryl, and substituted or unsubstituted heteroaryl.

[0057] This application adds a leveling agent with a specific structure to the copper plating solution. The leveling agent has a low energy level difference and a high dipole moment. During the electroplating process, it can be adsorbed on the surface of copper, resulting in an increase in both the cathode potential and charge transfer resistance. This inhibits copper surface deposition, making the electroplated copper layer more uniform. Consequently, the composite current collector prepared from it has excellent coating adhesion, as well as high tensile strength and elongation.

[0058] The molecular structure of the leveling agent mainly consists of two parts: a pyrimidine ring structure on the left and an N-type ring on the right. + Ionic structure. During electroplating, the pyrimidine ring structure is adsorbed parallel to the copper surface, reducing the effective area for electrochemical reactions and slowing down the copper surface deposition rate, thus resulting in a more uniform deposition layer; N + The ionic structure carries a strong positive charge in strong acid solutions and readily adsorbs in regions of high current density under the influence of an electric field, thereby reducing the Cu content in these high current density regions. 2+ The deposition rate further improves the uniformity of the deposited copper layer.

[0059] In some embodiments, R4, R5 and R6 are each independently selected from hydrogen, substituted or unsubstituted alkyl groups having 1 to 6 carbon atoms, substituted or unsubstituted alkenyl groups having 2 to 6 carbon atoms, and substituted or unsubstituted pyrimidinyl groups.

[0060] In some embodiments, R4, R5 and R6 are each independently selected from hydrogen, substituted or unsubstituted alkyl groups having 1 to 4 carbon atoms, or substituted or unsubstituted alkenyl groups having 2 to 4 carbon atoms.

[0061] In some embodiments, R4, R5 and R6 are each independently selected from hydrogen, methyl, ethyl, propyl, isopropyl, butyl, sec-butyl, tert-butyl, vinyl, propenyl, butenyl, phenyl and pyrimidinyl.

[0062] In some embodiments, R4, R5 and R6 are each independently selected from hydrogen, methyl, ethyl, propyl, vinyl, phenyl and pyrimidinyl.

[0063] In some embodiments, the leveling agent is

[0064]

[0065] In some embodiments, the leveling agent is present in a concentration of 1-4 mL / L in the copper plating solution.

[0066] In some embodiments, the copper plating solution further comprises copper sulfate, sulfuric acid, hydrochloric acid, brightener, wetting agent, and deionized water.

[0067] The main functions of sulfuric acid are to reduce the resistance of the plating solution, improve its conductivity, prevent the hydrolysis of copper salts, and improve the plating uniformity and anodic dissolution performance of the plating solution. The main functions of copper sulfate are to conduct electricity and provide copper ions. The main functions of chloride ions are to help the anodic dissolution and assist the cathode crystallization. Brighteners mainly act to increase nucleation in the recessed areas. Wetting agents are adsorbed on the surface of the coating, increasing surface resistance and inhibiting rapid copper growth.

[0068] In some embodiments, the brightener is a compound containing a disulfide bond, a sulfonic acid group, or a thiol group.

[0069] In some embodiments, the brightener is one or both of sodium dithiopropane sulfonate and sodium 3-mercaptopropane sulfonate.

[0070] In some embodiments, the wetting agent is at least one of polyethylene glycol and polypropylene glycol.

[0071] In some embodiments, the number-average molecular weight of the polyethylene glycol is 4,000-15,000, and the number-average molecular weight of the polypropylene glycol is 5,000-20,000.

[0072] When the molecular weight of the wetting agent is controlled within the given range, a dense barrier layer can be formed on the cathode surface, thereby inhibiting the rapid deposition of copper. If the molecular weight of the wetting agent is too small, it cannot form a dense barrier layer on the cathode surface and cannot inhibit copper deposition; if the molecular weight is too large, its solubility decreases, and micelles will form in the plating solution, reducing its wettability.

[0073] In some embodiments, the copper plating solution further includes a grain refiner.

[0074] The main function of grain refiners is to increase the deposition of copper ions under low current, prevent them from being etched by sulfuric acid, and at the same time make the deposited copper grains more refined.

[0075] In some embodiments, the grain refiner is at least one of acetaldehyde and ethylenediaminetetraacetic acid (EDTA).

[0076] In some embodiments, each liter of copper plating solution contains: 60-120 g / L copper sulfate, 80-110 mL / L 98% sulfuric acid, 40-90 ppm hydrochloric acid (based on chloride ions), 2-12 mL / L brightener, 1-4 mL / L leveling agent, 0.5-2 mL / L wetting agent, 0.01-0.2 mL / L grain refiner, and the remainder is deionized water.

[0077] When the specific content of each component is controlled within the given range, the uniformity of the coating can be further improved. If the concentration of sulfuric acid is too high, it will reduce the Cu content. 2+The migration rate of the copper sulfate solution decreases the elongation of the coating. If the concentration is too low, the conductivity of the solution is poor, and the dispersion ability of the plating solution is poor. If the concentration of copper sulfate is too high, the leveling ability of the plating solution decreases, the deposition rate is too fast, and the generated particles are large, affecting the uniformity of the coating. If the concentration is too low, although the coverage and dispersion ability of the plating solution are improved, the brightness and levelness of the copper coating decrease, the deposition rate is slow, and scorching may occur during high current density electroplating. When the concentration of chloride ions is too high, it will cause anode passivation, resulting in a white film on the cathode and the release of a large number of bubbles, reducing electrode efficiency. When the concentration is too low, the coating is dull and has a stepped rough coating, which is prone to pinholes and scorching.

[0078] In some embodiments, the grain refiner is acetaldehyde.

[0079] In some embodiments, each liter of copper plating solution contains: 60-120 g / L copper sulfate, 80-110 mL / L 98% sulfuric acid, 40-90 ppm hydrochloric acid (based on chloride ions), 2-12 mL / L brightener, 1-4 mL / L leveling agent, 0.5-2 mL / L wetting agent, 0.01-0.05 mL / L acetaldehyde, and the remainder is deionized water.

[0080] In some embodiments, the grain refiner is ethylenediaminetetraacetic acid (EDTA).

[0081] In some embodiments, each liter of copper plating solution contains: 60-120 g / L copper sulfate, 80-110 mL / L 98% sulfuric acid, 40-90 ppm hydrochloric acid (based on chloride ions), 2-10 mL / L brightener, 1-4 mL / L leveling agent, 0.5-2 mL / L wetting agent, 0.05-0.2 mL / L ethylenediaminetetraacetic acid, and the remainder is deionized water.

[0082] In some embodiments, the grain refiner is acetaldehyde and ethylenediaminetetraacetic acid.

[0083] In some embodiments, each liter of copper plating solution contains: 60-120 g / L copper sulfate, 80-110 mL / L 98% sulfuric acid, 40-90 ppm hydrochloric acid (based on chloride ions), 2-12 mL / L brightener, 1-4 mL / L leveling agent, 0.5-2 mL / L wetting agent, 0.01-0.1 mL / L acetaldehyde and ethylenediaminetetraacetic acid, with the remainder being deionized water.

[0084] In some embodiments, the volume ratio of acetaldehyde to ethylenediaminetetraacetic acid is 2:1.

[0085] In some embodiments, the applicable temperature range for the copper plating solution is 20-50°C, optionally 20-45°C, and further optionally 20-35°C.

[0086] If the operating temperature of the copper plating solution is too low, it will affect the reactivity of the organic additives, resulting in a decrease in the migration and deposition rate of copper ions; if the temperature is too high, the organic matter will decompose more easily, leading to its failure or reduced effectiveness.

[0087] In some embodiments, the applicable cathode current density for the copper plating solution is 1-20 A / dm². 2 Available in 1-15A / dm 2 Further options include 1-10 A / dm 2 .

[0088] When the cathode current density is controlled within the given range, a dense coating can be obtained. If the cathode current density is too high, the coating will be burned or charred; if the cathode current density is too low, the grains of the coating will coarsen, or the coating may not even be deposited.

[0089] In some embodiments, the applicable anodic current density for the copper plating solution is 0.5-3 A / dm³. 2 .

[0090] When the anode current density is controlled within the given range, the brightness and smoothness of the resulting coating can be further improved. If the anode current density is too high, the copper ions generated by electrolysis are greater than the copper ions deposited, the copper content in the bath increases continuously, the additives are consumed more quickly, the copper powder and anode mud in the bath increase, the anode utilization efficiency decreases, and the coating is prone to burrs and roughness defects. If the current density is too low, the copper content will decrease continuously, affecting the brightness and smoothness of the coating.

[0091] In some embodiments, the pH value of the copper plating solution is 0.5-4.

[0092] When the pH is controlled within the given range, it can improve the plating uniformity and anodic dissolution performance of the plating solution.

[0093] In some embodiments, the method for preparing the copper plating solution includes the following steps:

[0094] 1. Add deionized water to the container, the amount of which should be 2 / 3 of the required volume of deionized water;

[0095] 2. Add concentrated sulfuric acid according to the ratio while stirring. Keep the liquid temperature below 50°C during stirring. Let stand for 1 hour until the liquid temperature cools down to below 30°C.

[0096] 3. Add copper sulfate according to the ratio and stir until it is completely dissolved;

[0097] 4. While stirring, add hydrochloric acid, brightener, leveling agent, wetting agent, and grain refiner according to the formula ratio;

[0098] 5. Add the remaining 1 / 3 volume of deionized water, stir well, and obtain the copper plating solution.

[0099] In one embodiment of this application, a negative electrode composite current collector is provided, which includes a polymer material substrate and a copper layer formed on two surfaces of the polymer material substrate. The copper layer is obtained by electroplating with the copper plating solution of the first aspect of this application.

[0100] In some embodiments, the polymer material substrate is selected from polyamide, polyterephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly(p-phenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenolic resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, and polycarbonate.

[0101] In some embodiments, the thickness of the copper layer is 2-12 μm.

[0102] In some embodiments, the method for preparing the coating includes: using a PVD polymer substrate as the cathode and phosphor bronze as the anode, and performing direct current electroplating in an electroplating bath containing the copper plating solution of the first aspect of this application.

[0103] In some embodiments, the method for preparing the PVD substrate includes: depositing a copper layer on the surface of a polymer substrate using a physical vapor deposition (PVD) method.

[0104] In some embodiments, the PVD method is preferably at least one of evaporation and sputtering.

[0105] In some embodiments, the temperature during the electroplating process is 20-50°C, optionally 20-45°C, and further optionally 20-35°C.

[0106] In some embodiments, the cathode current density is 1-20 A / dm during the electroplating process. 2 Available in 1-15A / dm 2 Further options include 1-10 A / dm 2 .

[0107] In some implementations, the anolyte current density is 0.5-3 A / dm³ during the electroplating process. 2 .

[0108] In some implementations, the electroplating time is 1-5 minutes.

[0109] In addition, the secondary battery, battery module, battery pack and power device of this application will be described below with appropriate reference to the accompanying drawings.

[0110] In one embodiment of this application, a secondary battery is provided.

[0111] Typically, a secondary battery consists of a positive electrode, a negative electrode, an electrolyte, and a separator. During charging and discharging, active ions move back and forth between the positive and negative electrodes, inserting and releasing. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits while allowing ions to pass through.

[0112] [Positive electrode plate]

[0113] The positive electrode includes a positive current collector and a positive electrode film layer disposed on at least one surface of the positive current collector, the positive electrode film layer including a positive electrode active material.

[0114] As an example, the positive current collector has two surfaces opposite each other in its own thickness direction, and the positive electrode film layer is disposed on either or both of the two opposite surfaces of the positive current collector.

[0115] In some embodiments, the positive current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. The composite current collector may include a polymer substrate and a metal layer formed on at least one surface of the polymer substrate. The composite current collector may be formed by forming a metal material (aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy, etc.) on a polymer substrate (such as a substrate of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.).

[0116] In some embodiments, the positive electrode active material may be a known battery positive electrode active material. As an example, the positive electrode active material may include at least one of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, this application is not limited to these materials, and other conventional materials that can be used as battery positive electrode active materials may also be used. These positive electrode active materials may be used alone or in combination of two or more. Examples of lithium transition metal oxides include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNi). 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.85 Co 0.15 Al 0.05 At least one of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also referred to as LFP)), lithium iron phosphate and carbon composites, lithium manganese phosphate (such as LiMnPO4), lithium manganese phosphate and carbon composites, lithium manganese iron phosphate, and lithium manganese iron phosphate and carbon composites.

[0117] In some embodiments, the positive electrode film layer may optionally include a binder. As an example, the binder may include at least one selected from polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), PVDF-tetrafluoroethylene-propylene terpolymer, PVDF-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorinated acrylate resin.

[0118] In some embodiments, the positive electrode film may optionally include a conductive agent. As an example, the conductive agent may include at least one selected from superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0119] In some embodiments, the positive electrode sheet can be prepared by dispersing the above-mentioned components for preparing the positive electrode sheet, such as positive active material, conductive agent, binder and any other components, in a solvent (e.g., N-methylpyrrolidone) to form a positive electrode slurry; coating the positive electrode slurry onto the positive electrode current collector, and then obtaining the positive electrode sheet after drying, cold pressing and other processes.

[0120] [Negative electrode plate]

[0121] The negative electrode sheet includes a negative current collector and a negative electrode film layer disposed on at least one surface of the negative current collector. The negative current collector is a negative electrode composite current collector according to the second aspect of this application, and the negative electrode film layer includes a negative electrode active material.

[0122] As an example, the negative electrode current collector has two surfaces opposite each other in its own thickness direction, and the negative electrode film layer is disposed on either or both of the two opposite surfaces of the negative electrode current collector.

[0123] In some embodiments, the negative electrode active material may be a negative electrode active material known in the art for use in batteries. As an example, the negative electrode active material may include at least one of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, and lithium titanate, etc. The silicon-based material may be selected from at least one of elemental silicon, silicon oxide compounds, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. The tin-based material may be selected from at least one of elemental tin, tin oxide compounds, and tin alloys. However, this application is not limited to these materials, and other conventional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone or in combination of two or more.

[0124] In some embodiments, the negative electrode film layer may optionally include a binder. The binder may be selected from at least one of styrene-butadiene rubber (SBR), polyacrylic acid (PAA), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS).

[0125] In some embodiments, the negative electrode film may optionally include a conductive agent. The conductive agent may be selected from at least one of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers.

[0126] In some embodiments, the negative electrode film may optionally include other additives, such as thickeners (e.g., sodium carboxymethyl cellulose (CMC-Na)).

[0127] In some embodiments, the negative electrode sheet can be prepared by dispersing the components used to prepare the negative electrode sheet, such as the negative electrode active material, conductive agent, binder and any other components, in a solvent (e.g., deionized water) to form a negative electrode slurry; coating the negative electrode slurry onto the negative electrode current collector, and then obtaining the negative electrode sheet after drying, cold pressing and other processes.

[0128] [Electrolytes]

[0129] The electrolyte acts as a conductor of ions between the positive and negative electrodes. This application does not impose specific restrictions on the type of electrolyte; it can be selected according to requirements. For example, the electrolyte can be liquid, gel, or entirely solid.

[0130] In some embodiments, the electrolyte is an electrolyte solution. The electrolyte solution includes an electrolyte salt and a solvent.

[0131] In some embodiments, the electrolyte salt may be selected from at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, lithium hexafluoroarsenate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium trifluoromethanesulfonate, lithium difluorophosphate, lithium difluorooxalate borate, lithium dioxalate borate, lithium difluorodioxalate phosphate, and lithium tetrafluorooxalate phosphate.

[0132] In some embodiments, the solvent may be selected from at least one of ethylene carbonate, propylene carbonate, methyl ethyl carbonate, diethyl carbonate, dimethyl carbonate, dipropyl carbonate, methyl propyl carbonate, ethyl propyl carbonate, butyl carbonate, fluoroethylene carbonate, methyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, methyl butyrate, ethyl butyrate, 1,4-butyrolactone, sulfolane, dimethyl sulfone, methyl ethyl sulfone, and diethyl sulfone.

[0133] In some embodiments, the electrolyte may optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0134] [Isolation membrane]

[0135] In some embodiments, the secondary battery also includes a separator. This application does not impose any particular limitation on the type of separator; any known porous separator with good chemical and mechanical stability can be selected.

[0136] In some embodiments, the material of the separator can be selected from at least one of glass fiber, nonwoven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator can be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer can be the same or different, without particular limitation.

[0137] In some implementations, the positive electrode, negative electrode, and separator can be fabricated into an electrode assembly using a winding or stacking process.

[0138] In some embodiments, the secondary battery may include an outer packaging. This outer packaging may be used to encapsulate the electrode assembly and electrolyte described above.

[0139] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, or a steel shell. The outer packaging of the secondary battery can also be a soft pack, such as a pouch. The material of the soft pack can be plastic; examples of plastics include polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0140] This application does not impose any particular limitation on the shape of the secondary battery; it can be cylindrical, square, or any other arbitrary shape. For example, Figure 4 This is an example of a square-structured secondary battery 5.

[0141] In some implementations, refer to Figure 5 The outer packaging may include a housing 51 and a cover plate 53. The housing 51 may include a bottom plate and side plates connected to the bottom plate, the bottom plate and side plates forming a receiving cavity. The housing 51 has an opening communicating with the receiving cavity, and the cover plate 53 can be placed over the opening to close the receiving cavity. The positive electrode, negative electrode, and separator can be formed into an electrode assembly 52 by a winding process or a stacking process. The electrode assembly 52 is encapsulated within the receiving cavity. Electrolyte is immersed in the electrode assembly 52. ​​The secondary battery 5 may contain one or more electrode assemblies 52, which can be selected by those skilled in the art according to specific practical needs.

[0142] In some implementations, the secondary batteries can be assembled into a battery module, and the number of secondary batteries contained in the battery module can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery module.

[0143] Figure 6 This is battery module 4, used as an example. (See reference...) Figure 6 In battery module 4, multiple secondary batteries 5 can be arranged sequentially along the length of battery module 4. Of course, they can also be arranged in any other manner. Furthermore, these multiple secondary batteries 5 can be fixed in place using fasteners.

[0144] Optionally, the battery module 4 may also include a housing with a receiving space in which a plurality of secondary batteries 5 are received.

[0145] In some embodiments, the battery modules described above can also be assembled into a battery pack, and the number of battery modules contained in the battery pack can be one or more, the specific number of which can be selected by those skilled in the art according to the application and capacity of the battery pack.

[0146] Figure 7 and Figure 8 This is battery pack 1 as an example. (See reference...) Figure 7 and Figure 8 The battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box includes an upper body 2 and a lower body 3, with the upper body 2 covering the lower body 3 to form a closed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0147] In addition, this application also provides an electrical device, which includes at least one of the secondary battery, battery module, or battery pack provided in this application. The secondary battery, battery module, or battery pack can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0148] As the electrical device, a secondary battery, battery module, or battery pack can be selected according to its usage requirements.

[0149] Figure 9 This is an example of an electrical device. The device could be a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the high power and high energy density requirements of the secondary battery for this device, a battery pack or battery module can be used.

[0150] Another example device could be a mobile phone, tablet, or laptop. These devices typically require a slim and lightweight design and can use a rechargeable battery as their power source.

[0151] Example

[0152] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0153] Example 1-1

[0154] [Preparation of copper plating solution]

[0155] 1. Add deionized water to the container, the amount of which should be 2 / 3 of the required volume of deionized water;

[0156] 2. Add 98% concentrated sulfuric acid according to the ratio while stirring. Keep the liquid temperature below 50°C during stirring. Let stand for 1 hour until the liquid temperature cools down to below 30°C.

[0157] 3. Add copper sulfate according to the ratio and stir until it is completely dissolved;

[0158] 4. While stirring, add hydrochloric acid, sodium polydithiopropane sulfonate as a brightener, the compound shown in Formula I as a leveling agent, and polyethylene glycol (with a number average molecular weight of 10,000) as a wetting agent according to the specified ratio.

[0159]

[0160] 5. Add the remaining 1 / 3 volume of deionized water, stir well, and obtain the copper plating solution, which consists of 90 g / L copper sulfate, 95 mL / L 98% sulfuric acid, 65 ppm hydrochloric acid (calculated as chloride ions), 7 mL / L brightener, 2.5 mL / L leveling agent, 1.3 mL / L wetting agent, and the remainder is deionized water; the pH is 1.

[0161] [Preparation of Negative Electrode Composite Current Collector]

[0162] A copper layer is deposited on the surface of a polyimide polymer substrate using physical vapor deposition (PVD) to obtain a polyimide PVD substrate. The polyimide PVD substrate is then used as the cathode and phosphor bronze as the anode, and is placed in an electroplating bath containing the copper plating solution for direct current electroplating.

[0163] The electroplating parameters are set as follows:

[0164] Electroplating temperature: 25℃;

[0165] Cathode current density: 2A / dm 2 ;

[0166] Anode current density: 0.5 A / dm 2 ;

[0167] Electroplating time: 2 minutes.

[0168] Examples 1-2

[0169] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the leveling agent is replaced with the compound shown in Formula II.

[0170]

[0171] Examples 1-3

[0172] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the leveling agent is replaced with the compound shown in Formula III.

[0173]

[0174] Examples 1-4

[0175] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the leveling agent is replaced with the compound shown in Formula IV.

[0176]

[0177] Examples 1-5

[0178] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the leveling agent is replaced with the compound shown in Formula V.

[0179]

[0180] Comparative Example 1-1

[0181] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the leveling agent is replaced with the compound shown in Formula VI.

[0182]

[0183] Comparative Examples 1-2

[0184] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the leveling agent is replaced with the compound shown in Formula VII.

[0185]

[0186] Comparative Examples 1-3

[0187] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that no leveling agent is added.

[0188] Example 2-1

[0189] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the amount of leveling agent in the copper plating solution is 1 mL / L.

[0190] Example 2-2

[0191] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the amount of leveling agent in the copper plating solution is 4 mL / L.

[0192] Example 2-3

[0193] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the amount of leveling agent in the copper plating solution is 0.5 mL / L.

[0194] Examples 2-4

[0195] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the amount of leveling agent in the copper plating solution is 6 mL / L.

[0196] Examples 2-5

[0197] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the brightener is replaced with sodium 3-mercaptopropanesulfonate.

[0198] Examples 2-6

[0199] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that the wetting agent is replaced with polypropylene glycol, which has a number average molecular weight of 10,000.

[0200] Example 3-1

[0201] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that acetaldehyde and ethylenediaminetetraacetic acid in a volume ratio of 2:1 are added as grain refiners, and the amount of grain refiners in the copper plating solution is 0.08 mL / L.

[0202] Example 3-2

[0203] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that acetaldehyde and ethylenediaminetetraacetic acid in a volume ratio of 2:1 are added as grain refiners, and the amount of grain refiners in the copper plating solution is 0.01 mL / L.

[0204] Example 3-3

[0205] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that acetaldehyde and ethylenediaminetetraacetic acid with a volume ratio of 2:1 are added as grain refiners, and the amount of grain refiners in the copper plating solution is 0.1 mL / L.

[0206] Examples 3-4

[0207] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that acetaldehyde is added as a grain refiner, and the amount of acetaldehyde in the copper plating solution is 0.01 mL / L.

[0208] Examples 3-5

[0209] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that acetaldehyde is added as a grain refiner, and the amount of acetaldehyde in the copper plating solution is 0.03 mL / L.

[0210] Examples 3-6

[0211] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that acetaldehyde is added as a grain refiner, and the amount of acetaldehyde in the copper plating solution is 0.05 mL / L.

[0212] Examples 3-7

[0213] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that ethylenediaminetetraacetic acid (EDTA) is added as a grain refiner, and the amount of EDTA in the copper plating solution is 0.05 mL / L.

[0214] Examples 3-8

[0215] The preparation of the copper plating solution and the negative electrode composite current collector are generally the same as in Example 1-1, except that ethylenediaminetetraacetic acid (EDTA) is added as a grain refiner, and the amount of EDTA in the copper plating solution is 0.12 mL / L.

[0216] Performance testing of negative electrode composite current collector:

[0217] 1. Coating adhesion

[0218] Metal layer adhesion test method: Apply double-sided tape to a smooth steel plate. Cut the composite current collector to the same width as the double-sided tape and then apply it flat to the surface of the double-sided tape. Cut the surface tape to the same width as the composite current collector and attach it to the surface of the composite current collector. Attach an A4 paper strip longer than the length of the steel plate to the end of the tape. Roll the tape back and forth on the surface with a 2.5kg roller until the tape is flat. Fix one end of the steel plate to a tensile testing machine, and fix the A4 paper strip connected to the surface tape to the other end of the tensile testing machine. Peel the tape at a speed of 500mm / min to obtain the peel force curve and calculate the average peel force.

[0219] 2. Tensile strength

[0220] The current collector is punched into strips of 15mm×150mm using a strip sampler. The punched strip samples are then tested using a tensile testing machine with an initial spacing of 50mm. The sample is stretched at a constant speed of 50mm / min until it breaks. The tensile strength is read directly from the tensile testing machine.

[0221] 3. Elongation

[0222] The current collector is punched into strips of 15mm × 150mm using a strip sampler. The punched strip samples are then tested using a tensile testing machine with an initial spacing of 50mm. The sample is stretched at a constant speed of 50mm / min until it breaks. The elongation at break = stretching distance / initial spacing × 100% is the elongation.

[0223] Performance testing of secondary batteries

[0224] The negative electrode composite current collectors obtained in the above embodiments and comparative examples were used to prepare secondary batteries as shown below, and their performance was tested.

[0225] 1. Preparation of secondary batteries

[0226] Using conventional battery manufacturing processes, the positive electrode sheet (compacted density: 3.4 g / cm3), PP / PE / PP separator, and negative electrode sheet (compacted density: 1.6 g / cm3) are wound together to form a bare cell, which is then placed into a battery casing. Electrolyte (EC:EMC volume ratio of 3:7, LiPF6 of 1 mol / L) is injected, followed by sealing, formation, and other processes to finally obtain a lithium-ion battery.

[0227] 2. Cyclic testing of secondary batteries

[0228] The cycle life test for lithium-ion batteries is conducted using the following specific methods:

[0229] The lithium-ion battery was charged and discharged at 25°C. First, it was charged at 1C to 4.2V, and then discharged at 1C to 2.8V. The discharge capacity of the first cycle was recorded. Then, the battery was subjected to 1C / 1C charge-discharge cycles for 1000 cycles. The discharge capacity of the battery in the 1000th cycle was recorded. The discharge capacity of the 1000th cycle was divided by the discharge capacity of the first cycle to obtain the capacity retention rate in the 1000th cycle. The number of cycles when the battery had 80% capacity remaining was also recorded.

[0230]

[0231]

[0232]

[0233] As shown in Tables 1-3, the coating adhesion, tensile strength, and elongation of the negative electrode composite current collectors in all the above embodiments are significantly higher than those in the comparative examples. Correspondingly, the cycle performance of the lithium-ion batteries corresponding to all embodiments is also better than that of the comparative examples. Furthermore, in comparison... Figure 1 and Figure 2 It is evident that the uniformity of the copper layer obtained from the copper plating solution containing the structural leveling agent described in this application is significantly better than that of the copper layer prepared from the conventional PCB plating solution.

[0234] Comparing Examples 1-1 to 1-5, when the copper plating solution contains the leveling agent of the aforementioned structure, the coating adhesion of the resulting negative electrode composite current collector is higher than 2.3 N, the tensile strength is higher than 186 MPa, the elongation is higher than 4.4%, and the lithium-ion battery containing the negative electrode composite current collector has a battery cycle count of 80% capacity higher than 2221, and a capacity retention rate of higher than 90.3% after 1000 cycles.

[0235] Comparative studies of Examples 1-1 and 2-1 to 2-6 show that when the leveling agent content in the copper plating solution is 1-4 mL / L, the coating adhesion, tensile strength, and elongation of the negative electrode composite current collector prepared by it are further improved.

[0236] Comparing Examples 1-1 and 3-1 to 3-8, when the copper plating solution further contains a grain refiner, the adhesion, tensile strength, and elongation of the coating of the negative electrode composite current collector prepared therefrom are further improved, thereby further improving the cycle performance of the lithium-ion battery. Furthermore, from... Figure 2 and Figure 3 It can be seen that grain refiners can further improve the uniformity of the obtained copper layer.

[0237] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A copper plating solution for composite current collectors, characterized in that, Leveling agent containing the general formula (1) (1) Where the anion X is F - Cl - or Br - ; R1, R2, and R3 are each independently selected from O or S; R4, R5, and R6 are each independently selected from hydrogen, alkyl groups having 1-6 carbon atoms, alkenyl groups having 2-6 carbon atoms, and pyrimidinyl groups.

2. The copper plating solution according to claim 1, characterized in that, The leveling agent is （2）。 3. The copper plating solution according to claim 1, characterized in that, It also contains copper sulfate, sulfuric acid, hydrochloric acid, brightener, wetting agent, and deionized water.

4. The copper plating solution according to claim 3, characterized in that, The brightener is a compound containing disulfide bonds, sulfonic acid groups, or thiol groups.

5. The copper plating solution according to claim 4, characterized in that, The brightener is one or both of sodium polydisulfide dipropane sulfonate and sodium 3-mercaptopropane sulfonate.

6. The copper plating solution according to any one of claims 3-5, characterized in that, The wetting agent is at least one of polyethylene glycol and polypropylene glycol.

7. The copper plating solution according to claim 6, characterized in that, The number average molecular weight of the polyethylene glycol is 4,000-15,000, and the number average molecular weight of the polypropylene glycol is 5,000-20,000.

8. The copper plating solution according to claim 1, characterized in that, It also contains grain refiners.

9. The copper plating solution according to claim 8, characterized in that, The grain refiner is at least one of acetaldehyde and ethylenediaminetetraacetic acid.

10. The copper plating solution according to claim 1, characterized in that, Each liter of copper plating solution contains: 60-120 g / L copper sulfate, 80-110 mL / L 98% sulfuric acid, 40-90 ppm hydrochloric acid (chloride ion concentration), 2-12 mL / L brightener, 1-4 mL / L leveling agent, 0.5-2 mL / L wetting agent, 0.01-0.2 mL / L grain refiner, and the remainder is deionized water.

11. The copper plating solution according to claim 1, characterized in that, The applicable temperature range for the copper plating solution is 20-50℃.

12. The copper plating solution according to claim 11, characterized in that, The applicable temperature range for the copper plating solution is 20-45℃.

13. The copper plating solution according to claim 12, characterized in that, The applicable temperature range for the copper plating solution is 20-35℃.

14. The copper plating solution according to claim 1, characterized in that, The applicable cathode current density for the copper plating solution is 1-20 A / dm. 2 .

15. The copper plating solution according to claim 14, characterized in that, The applicable cathode current density for the copper plating solution is 1-15 A / dm. 2 .

16. The copper plating solution according to claim 15, characterized in that, The applicable cathode current density for the copper plating solution is 1-10 A / dm³. 2 .

17. The copper plating solution according to claim 1, characterized in that, The applicable anodic current density for the copper plating solution is 0.5-3 A / dm³. 2 .

18. The copper plating solution according to claim 1, characterized in that, The pH value of the copper plating solution is 0.5-4.

19. A negative electrode composite current collector, comprising a polymer material substrate and copper layers formed on both surfaces of the polymer material substrate, characterized in that, The copper layer is obtained by electroplating using the copper plating solution described in any one of claims 1 to 18.

20. A secondary battery, characterized in that, Includes the negative electrode composite current collector as described in claim 19.

21. A battery module, characterized in that, Includes the secondary battery as described in claim 20.

22. A battery pack, characterized in that, Includes the battery module as described in claim 21.

23. An electrical appliance, characterized in that, It includes at least one selected from the secondary battery of claim 20, the battery module of claim 21, or the battery pack of claim 22.

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