Preparation method of functional current collector containing tin-cadmium alloy, functional current collector containing tin-cadmium alloy, and secondary battery

Abstract

The invention provides a preparation method of a functional current collector containing tin-cadmium alloy, the preparation method comprises a conducting layer forming process of forming a conducting layer on the surface of a base film, the base film comprises a polymer base material and a first metal layer which are laminated, and the first metal layer comprises at least one of copper, copper alloy, aluminum and aluminum alloy; the conducting layer forming procedure comprises the following steps that S1, the base film serves as a machining object, the surface of the first metal layer is plated with a tin-cadmium alloy layer, and metal contained in the tin-cadmium alloy layer comprises tin-cadmium alloy; and S2, plating a second metal layer on the surface of the tin-cadmium alloy layer, wherein metals contained in the second metal layer comprise copper, a copper alloy, aluminum and an aluminum alloy. According to the method, the second metal layer is formed by thickening the conductive layer so as to enable the functional current collector to have enough conductivity, and the method is characterized in that the tin-cadmium alloy layer is formed on the surface of the base film before the second metal layer is formed, so that the processing efficiency and the qualified rate of finished products of the functional current collector are improved, and the production cost is reduced. And the compactness of the conducting layer of the functional current collector is also improved, and the ductility of the functional current collector is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of functional current collectors, and specifically relates to a preparation method of a functional current collector containing a tin-cadmium alloy, a functional current collector containing a tin-cadmium alloy, and a secondary battery. Background Art

[0002] The current collector is an important component in a lithium-ion battery. It can collect and output the current generated by the active material and input the electrode current to the active material. With the development of lithium battery technology, the thickness, weight, and safety of traditional current collectors can no longer meet the requirements of high energy density and high safety. Under such circumstances, the functional current collector with a "sandwich" structure (metal - polymer substrate - metal) has emerged. Compared with traditional aluminum foil or copper foil, the functional current collector has a thinner thickness and can effectively reduce the thermal runaway of the battery in case of short circuit. Based on the advantages of high energy density, low cost, and high safety, the functional current collector is expected to be widely used in the production and manufacturing of lithium-ion batteries in the future.

[0003] Currently, for industrial mass production of functional current collectors, generally, a thin metal conductive layer is magnetron sputtered and deposited on a polymer substrate first to make the thin film substrate conductive, and then the metal conductive layer is thickened by electroplating. The functional current collectors prepared by this process usually have the problem of loose surface structure of the metal conductive layer, and it is easy to have the situation of unqualified density. In addition, during the processes of magnetron sputtering and electroplating thickening of the thin film substrate, the change of environmental temperature, the impact of magnetron sputtering, and the corrosion of the electroplating solution will all lead to a decrease in the elongation rate of the thin film substrate, and thus the functional current collector has the problem of insufficient elongation rate. Summary of the Invention

[0004] In order to improve the density of the conductive layer of the functional current collector and the elongation rate of the functional current collector, the present invention provides a preparation method of a functional current collector containing a tin-cadmium alloy, a functional current collector containing a tin-cadmium alloy, and a secondary battery.

[0005] According to the first aspect of the present invention, a method for preparing a functional current collector containing a tin-cadmium alloy is provided. The preparation method includes a conductive layer forming process for forming a conductive layer on the surface of a base film. The base film includes a polymer substrate and a first metal layer stacked thereon. The first metal layer includes at least one of copper, copper alloy, aluminum, and aluminum alloy. The following operations are performed in the conductive layer forming process: S1. Using the base film as the processing object, a tin-cadmium alloy layer is plated on the surface of the first metal layer. The metals contained in the tin-cadmium alloy layer include tin-cadmium alloy. S2. A second metal layer is plated on the surface of the tin-cadmium alloy layer. The metals contained in the second metal layer include copper, copper alloy, aluminum, and aluminum alloy. In the above method, the formation of the second metal layer is to thicken the conductive layer so that the functional current collector has sufficient electrical conductivity. The feature of the present invention is that a tin-cadmium alloy layer is first formed on the surface of the base film before forming the second metal layer. During the processing of the functional current collector, the setting of the tin-cadmium alloy layer has the following beneficial effects: The tin-cadmium alloy layer can provide protection for the base film and reduce the probability of the base film being corroded during the formation of the second metal layer. Using the film composed of the base film and the tin-cadmium alloy layer as the formation carrier of the second metal layer, the setting of the tin-cadmium alloy layer can improve the surface defects of the first metal layer and reduce the sheet resistance of the formation carrier of the second metal layer, thereby achieving the beneficial effect of improving the formation quality of the second metal layer. Because the setting of the tin-cadmium alloy layer is beneficial to improving the formation quality of the second metal layer, it is not necessary to strictly control the thickness and sheet resistance of the base film within a very low numerical range to ensure the finished product quality of the second metal layer, which is beneficial to reducing the production difficulty of the base film and also beneficial to reducing the probability of the base film perforation caused by too thin thickness. Thus, the production efficiency of the base film is improved, and the production energy consumption and cost of the base film are reduced.

[0006] Preferably, in S1 of the conductive layer forming process, the plating solution for plating the tin-cadmium alloy is a first plating solution. The first plating solution includes a main salt component and a complexing agent component. The main salt component includes cadmium salt and tin salt. The complexing agent component includes nitrilotriacetic acid, disodium ethylenediaminetetraacetate, and ammonium salt. The ammonium salt includes at least one of ammonium chloride and ammonium fluoride. Based on the types of main salts, a specific complexing agent component is matched to comprehensively control the component composition, coating brightness, and coating uniformity of the tin-cadmium alloy layer.

[0007] Preferably, the cadmium salt includes cadmium sulfate, and the tin salt includes stannous chloride; when the ammonium salt includes ammonium chloride, calculated by mass ratio, the component composition of the first plating solution satisfies that cadmium sulfate: stannous chloride: nitrilotriacetic acid: disodium ethylenediaminetetraacetate: ammonium chloride = 30-50: 8-15: 30-60: 30-60: 200-300; when the ammonium salt includes ammonium fluoride, calculated by mass ratio, the component composition of the first plating solution satisfies that cadmium sulfate: stannous chloride: nitrilotriacetic acid: disodium ethylenediaminetetraacetate: ammonium fluoride = 30-50: 8-15: 30-60: 30-60: 80-100. Further limiting the component ratio of the main salt component and the complexing agent component to the above range can control the tin content of the tin-cadmium alloy formed by electroplating based on the plating solution within 20wt.% - 40wt.%, which is beneficial to maintaining a high-efficiency level of the cathode current during the subsequent plating of the second metal layer and can improve the flatness and compactness of the second metal layer. The ammonium salt in the first plating solution mainly plays a role in complexing tin ions. If the dosage of the ammonium salt contained in the first plating solution is higher than the above range, the tin content of the tin-cadmium alloy is lower than the preferred range. If the ammonium salt contained in the first plating solution is lower than the above range, the tin content of the tin-cadmium alloy is higher than the preferred range, which will lead to poor uniformity of the tin-cadmium alloy layer. And disodium ethylenediaminetetraacetate acts as a complexing agent in the first plating solution. Making the dosage of disodium ethylenediaminetetraacetate in the electroplating solution conform to the above preferred ratio range is beneficial to improving the electroplating efficiency of the formed tin-cadmium alloy layer. When the dosage of disodium ethylenediaminetetraacetate is lower than the above ratio range, the crystallization fineness of the tin-cadmium alloy decreases, and the brightness of the tin-cadmium alloy layer decreases. When the dosage of disodium ethylenediaminetetraacetate is higher than the above ratio range, white precipitates are likely to appear in the first plating solution.

[0008] Preferably, the first plating solution further includes a leveling agent component and / or a brightening agent component. The leveling agent component includes at least one of peregal and polyethylene glycol, and the brightening agent component includes at least one of piperonal, gum arabic, and dextrin. Among the leveling agent components, both peregal and polyethylene glycol can prevent burrs from forming on the tin-cadmium alloy layer. In addition, polyethylene glycol can also eliminate pinholes during the process of forming the tin-cadmium alloy layer. The combination of peregal and polyethylene glycol can further promote the fine crystallization of the tin-cadmium alloy. And in the brightening agent component, the combination of piperonal and gum arabic can effectively improve the gloss of the tin-cadmium alloy layer.

[0009] Preferably, the weight-average molecular weight of polyethylene glycol is 6000 - 12000.

[0010] Preferably, the first plating solution comprises cadmium sulfate, stannous chloride, disodium ethylenediaminetetraacetate, nitrilotriacetic acid, ammonium chloride, polyethylene glycol, heliotropin, and gum arabic. The component composition of the first plating solution satisfies: cadmium sulfate 30 g / L to 50 g / L, stannous chloride 8 g / L to 15 g / L, disodium ethylenediaminetetraacetate 30 g / L to 60 g / L, nitrilotriacetic acid 30 g / L to 60 g / L, ammonium chloride 200 g / L to 300 g / L, polyethylene glycol 2 g / L to 5 g / L, heliotropin 1 g / L to 2 g / L, and gum arabic 2 g / L to 5 g / L; or ammonium fluoride replaces ammonium chloride in the above formula, and the content of ammonium fluoride in the first electroplating solution reaches 80 g / L to 100 g / L; or dextrin replaces gum arabic in the above formula, and the content of dextrin in the first electroplating solution reaches 2 g / L to 3 g / L.

[0011] Preferably, the first electroplating solution further comprises peregal, and the content of peregal in the first electroplating solution reaches 3 g / L to 5 g / L.

[0012] Preferably, the pH value of the first electroplating solution is 4 to 6. By controlling the pH value of the first electroplating solution within the above range, it is beneficial to the co-deposition of the two metals, tin and cadmium, and thus the coating quality of the tin-cadmium alloy layer can be further improved.

[0013] Preferably, the pH value of the first electroplating solution is 4.5 to 5.

[0014] Preferably, the preparation of the first electroplating solution includes the following operations: Step A. Dissolve disodium ethylenediaminetetraacetate and cadmium salt with water respectively to obtain an aqueous solution of disodium ethylenediaminetetraacetate and an aqueous solution of cadmium salt, and mix the aqueous solution of disodium ethylenediaminetetraacetate and the aqueous solution of cadmium salt to obtain a first raw material solution; Step B. Dissolve the ammonium salt in water to obtain an aqueous solution of ammonium salt, dissolve nitrilotriacetic acid in water to obtain a solution of nitrilotriacetic acid, then add stannous salt to obtain an acidified stannous salt solution, and mix the aqueous solution of ammonium salt and the acidified stannous salt solution to obtain a second raw material solution; Step C. Mix the first raw material solution and the second raw material solution. It should be noted that during the preparation process of the first electroplating solution, there is no need to strictly follow a specific order between the preparation of the first raw material solution (the above Step A) and the preparation of the second raw material solution (the above Step B). The first raw material solution can be prepared first and then the second raw material solution, or the second raw material solution can be prepared first and then the first raw material solution, or the first raw material solution and the second raw material solution can be prepared synchronously. By preparing the first electroplating solution in the above manner, the corrosion effect of the first electroplating solution on the magnetron film as the base film can be reduced, and further, the co-deposition state of the two metals, tin and cadmium, can be optimized, achieving the effect of improving the coating quality of the tin-cadmium alloy layer.

[0015] Preferably, when the first electroplating solution further includes a leveling agent component and a brightening agent component, during the preparation of the first electroplating solution, after step C above, there is further a step D, and step D includes: dissolving the leveling agent component in water to prepare a leveling agent solution, dissolving the brightening agent component in an alcohol solvent to prepare a brightening agent solution, and then adding the leveling agent solution and the brightening agent solution to the mixed solution obtained in step C.

[0016] Preferably, during the preparation of the first electroplating solution, a pH adjustment operation is further included to make the pH of the first electroplating solution reach 4 to 6 before it is used for electroplating.

[0017] Preferably, in S1 of the conductive layer forming process: using the first electroplating solution, forming a tin-cadmium alloy layer by electroplating, with a cathode current density of 0.5A*dm -2 ~1A*dm -2 , and the electroplating temperature is 10°C to 30°C.

[0018] Optionally, in S1 of the conductive layer forming process, the anode used for electroplating and forming the tin-cadmium alloy layer is selected from a tin-cadmium alloy anode, a tin metal anode, and a cadmium metal anode.

[0019] According to the second aspect of the present invention, there is provided a functional current collector containing a tin-cadmium alloy, and the functional current collector includes a base film and a conductive layer; the base film includes a polymer substrate and a first metal layer arranged in a stacked manner, and the first metal layer includes at least one of copper, copper alloy, aluminum, and aluminum alloy; the conductive layer includes a tin-cadmium alloy layer and a second metal layer arranged in a stacked manner, the metal contained in the tin-cadmium alloy layer includes a tin-cadmium alloy, and the metal contained in the second metal layer includes at least one of copper, copper alloy, aluminum, and aluminum alloy; in the thickness direction of the functional current collector, the first metal layer, the tin-cadmium alloy layer, and the second metal layer are arranged in a stacked manner in sequence. In the functional current collector provided by the present invention, the setting of the tin-cadmium alloy layer effectively improves the adhesion between the base film and the conductive layer, improves the denseness of the second metal layer, thereby improving the structural stability and electrical conductivity of the functional current collector. In addition, the elongation rate of the functional current collector is also improved, which is beneficial to improving the mechanical strength of the functional current collector.

[0020] Preferably, in the tin-cadmium alloy, the tin content is 20wt.% to 40wt.%, and the cadmium content is 60wt.% to 80wt.%.

[0021] Preferably, in the tin-cadmium alloy, the tin content is 30wt.%, and the cadmium content is 70wt.%.

[0022] Preferably, the thickness of the tin-cadmium alloy layer is 100nm to 500nm. Making the thickness of the tin-cadmium alloy layer reach the above range is beneficial to reducing the forming difficulty of the subsequent second metal layer.

[0023] Preferably, the thickness of the first metal layer is 20 nm to 100 nm.

[0024] Preferably, the thickness of the second metal layer is 100 nm to 500 nm.

[0025] Preferably, the sheet resistance of the functional current collector is ≤ 23 mΩ.

[0026] According to the third aspect of the present invention, a secondary battery is provided, which includes the functional current collector containing a tin-cadmium alloy as described above. Detailed Description of the Invention

[0027] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0028] Example 1

[0029] In this example, a magnetron film with a sheet resistance of 1.5 Ω is used as the base film for preparing the functional current collector. The magnetron film used in this example is composed of a polymer substrate and copper metal layers provided on both sides of the polymer substrate. The material of the polymer substrate is polypropylene (PP) with a thickness of 4.5 μm. The copper metal layer directly compounded with the surface of the polymer substrate is marked as the first metal layer, and the thickness of each first metal layer is 40 nm.

[0030] In the process of preparing the functional current collector in this example, two electroplating treatments are involved. The electroplating solutions used include a first electroplating solution and a second electroplating solution. The component compositions and preparation methods of the first electroplating solution and the second electroplating solution are specifically described below.

[0031] The component composition of the first electroplating solution used in this example is specifically as follows: cadmium sulfate 40 g / L, stannous chloride 12 g / L, disodium ethylenediaminetetraacetate 50 g / L, nitrilotriacetic acid 40 g / L, ammonium chloride 250 g / L, polyethylene glycol (weight average molecular weight of 8000) 5 g / L, peregal 5 g / L, heliotropin 2 g / L, gum arabic 5 g / L. Prepare materials according to the above component composition, and complete the preparation of the first electroplating solution according to the following steps:

[0032] Step A. Dissolve disodium ethylenediaminetetraacetate in pure water at 70 °C until it is completely dissolved to obtain a disodium ethylenediaminetetraacetate aqueous solution; dissolve cadmium sulfate in a small amount of pure water to obtain a cadmium sulfate aqueous solution; add the cadmium sulfate aqueous solution to the disodium ethylenediaminetetraacetate aqueous solution and stir evenly to obtain the first raw material solution.

[0033] Step B. Add a small amount of warm pure water to ammonium chloride until ammonium chloride is dissolved to obtain an ammonium chloride aqueous solution; dissolve nitrilotriacetic acid in a small amount of warm pure water to obtain a nitrilotriacetic acid solution, then add stannous chloride to the nitrilotriacetic acid solution, and fully dissolve it to obtain an acidified stannous chloride solution; then add the acidified stannous chloride solution to the ammonium chloride aqueous solution and stir evenly to obtain a second raw material solution.

[0034] Step C. Mix the first raw material solution and the second raw material solution to obtain a mother solution of the electroplating solution.

[0035] Step D. Dissolve heliotropin and gum arabic in an ethanol solution to obtain a brightener solution; dissolve polyethylene glycol and Peregal O in a small amount of hot pure water to obtain a leveling agent solution, then add the leveling agent solution to the mother solution of the electroplating solution, and then add the brightener solution to it and stir well to obtain a first semi-finished electroplating solution.

[0036] Step E. Dilute the first semi-finished electroplating solution to a preset total volume according to the component composition of the first electroplating solution, stir evenly, and adjust the pH value of the solution with ammonia water until the solution pH = 5, thereby obtaining the first electroplating solution.

[0037] The component composition of the second electroplating solution used in this example is specifically as follows: 1,4-cyclohexanedione monoethylene ketal 0.1 g / L, potassium phthalimide 0.2 g / L, 3-amino-1,2-propanediol 0.3 g / L, copper sulfate 120 g / L, sulfuric acid 70 g / L, chloride ion 70 mg / L, ethylene thiourea 0.0005 mg / L, sodium dodecyl sulfonate 0.08 mg / L, polyethylene glycol 0.07 g / L. Prepare materials according to the above component composition, and complete the preparation of the second electroplating solution according to the following steps:

[0038] Step A. Add 200 mL of pure water to 10 g of 1,4-cyclohexanedione monoethylene ketal and stir until 1,4-cyclohexanedione monoethylene ketal is completely dissolved to obtain a clear solution, complete the preparation of the 1,4-cyclohexanedione monoethylene ketal solution, and set aside.

[0039] Step B. Add 500 mL of pure water to 30 g of 3-amino-1,2-propanediol and stir until 3-amino-1,2-propanediol is completely dissolved to obtain a clear solution, complete the preparation of the 3-amino-1,2-propanediol solution, and set aside.

[0040] Step C. Slowly add potassium phthalimide to the 1,4-cyclohexanedione monoethylene ketal solution, stir and dissolve it fully, then slowly add the 3-amino-1,2-propanediol solution to the resulting mixture, and then add pure water to make the volume up to 1 L, and continue to stir to make it evenly mixed, thereby obtaining a copper plating additive.

[0041] Step D. Mix copper sulfate, sulfuric acid, chloride ions (the chloride ions are provided by commercially available hydrochloric acid with a concentration of 10 ml / L and an analytical purity grade), ethylene thiourea, sodium dodecyl sulfonate, and polyethylene glycol in pure water, and then add 10 mL of copper plating additive thereto, and mix well to obtain the second electroplating solution.

[0042] Load the base film into the electroplating equipment loaded with the first electroplating solution and the second electroplating solution prepared in this embodiment, and complete the conductive layer forming process according to the following operations:

[0043] S1. Use the electroplating equipment to unwind the base film, wash it with water, and the full-line film pulling speed is 3 m / min. Let the base film enter the electroplating bath filled with the first electroplating solution, control the temperature of the plating solution at 20 °C, use a tin-cadmium alloy plate (mass ratio Cd / Sn = 6:4) as the anode, and set the cathode current density at 1 A*dm -2 , thereby plating a tin-cadmium alloy layer on the surface of the first metal layer of the base film.

[0044] S2. Let the base film covered with the tin-cadmium alloy layer enter the brush plating bath filled with the second electroplating solution, control the temperature of the plating solution at 40 °C, set the brush plating voltage at 2 V, and perform brush plating copper treatment on the surface of the tin-cadmium alloy layer, thereby plating a copper metal layer on the surface of the tin-cadmium alloy layer as the second metal layer to obtain a semi-finished film.

[0045] S3. Perform double-link countercurrent water washing treatment, antioxidant treatment, drying treatment, and winding treatment on the semi-finished film in sequence. Among them, the winding treatment includes slitting. Thus, the functional current collector of this embodiment is prepared.

[0046] In the functional current collector prepared in this embodiment, the surface of the base film is successively covered with a tin-cadmium alloy layer and a second metal layer. On any surface of the base film, the thickness of the tin-cadmium alloy layer is 500 nm, and the thickness of the second metal layer is 460 nm. The tin-cadmium alloy layer and the second metal layer together serve as the conductive layer of the functional current collector.

[0047] Example 2

[0048] The base film used in this embodiment to prepare the functional current collector is the same as the base film used in Example 1.

[0049] In the process of preparing the functional current collector in this embodiment, two electroplating treatments are involved. The electroplating solutions used include the first electroplating solution and the second electroplating solution. Among them, the component composition and preparation method of the second electroplating solution are the same as those of the second electroplating solution used in Example 1. The component composition and preparation method of the first electroplating solution are specifically described below.

[0050] The component composition of the first electroplating solution used in this embodiment is specifically as follows: cadmium sulfate 40 g / L, stannous chloride 12 g / L, disodium ethylenediaminetetraacetate 50 g / L, nitrilotriacetic acid 40 g / L, ammonium chloride 250 g / L, polyethylene glycol (weight average molecular weight of 8000) 5 g / L, piperonal 2 g / L, gum arabic 5 g / L. Prepare materials according to the above component composition, and complete the preparation of the first electroplating solution according to the following steps:

[0051] Step A. Dissolve disodium ethylenediaminetetraacetate in pure water at 70 °C until it is completely dissolved to obtain an aqueous solution of disodium ethylenediaminetetraacetate; dissolve cadmium sulfate in a small amount of pure water to obtain an aqueous solution of cadmium sulfate; add the aqueous solution of cadmium sulfate to the aqueous solution of disodium ethylenediaminetetraacetate and stir evenly to obtain the first raw material solution.

[0052] Step B. Add a small amount of warm pure water to ammonium chloride until it is dissolved to obtain an aqueous solution of ammonium chloride; dissolve nitrilotriacetic acid in a small amount of warm pure water to obtain a solution of nitrilotriacetic acid, and then add stannous chloride to the solution of nitrilotriacetic acid and dissolve it fully to obtain an acidified stannous chloride solution; then add the acidified stannous chloride solution to the aqueous solution of ammonium chloride and stir evenly to obtain the second raw material solution.

[0053] Step C. Mix the first raw material solution and the second raw material solution to obtain the mother liquor of the electroplating solution.

[0054] Step D. Dissolve piperonal and dextrin in an ethanol solution to obtain a brightener solution; dissolve polyethylene glycol with a small amount of hot pure water to obtain a leveling agent solution, then add the leveling agent solution to the mother liquor of the electroplating solution, and then add the brightener solution thereto and stir fully to obtain a semi-finished product of the first electroplating solution.

[0055] Step E. Dilute the semi-finished product of the first electroplating solution to the preset total volume according to the component composition of the first electroplating solution, stir evenly, and adjust the pH value of the solution with ammonia water until the solution pH = 5, thereby obtaining the first electroplating solution.

[0056] Load the base film into the electroplating equipment loaded with the first electroplating solution and the second electroplating solution prepared in this embodiment to complete the conductive layer forming process. During the conductive layer forming process of this embodiment, the full-line film pulling line speed is 5 m / min. Except for the film pulling line speed and the first electroplating solution used being different from those in Example 1, other materials and corresponding operations involved in the conductive layer forming process of this embodiment are the same as those in the conductive layer forming process of Example 1.

[0057] In the functional integrated fluid prepared in this embodiment, a tin-cadmium alloy layer and a second metal layer are sequentially covered on the surface of the base film. On any surface of the base film, the thickness of the tin-cadmium alloy layer is 500 nm, and the thickness of the second metal layer is 460 nm. The tin-cadmium alloy layer and the second metal layer together serve as the conductive layer of the functional integrated fluid.

[0058] Example 3

[0059] The base film used to prepare the functional integrated fluid in this embodiment is the same as the base film used in Example 1.

[0060] In the process of preparing the functional integrated fluid in this embodiment, two electroplating treatments are involved. The electroplating solutions used include a first electroplating solution and a second electroplating solution. Among them, the component composition and preparation method of the second electroplating solution are the same as those of the second electroplating solution used in Example 1. The component composition and preparation method of the first electroplating solution are specifically described below.

[0061] The component composition of the first electroplating solution used in this embodiment is specifically as follows: cadmium sulfate 40 g / L, stannous chloride 12 g / L, disodium ethylenediaminetetraacetate 50 g / L, nitrilotriacetic acid 40 g / L, ammonium fluoride 90 g / L, polyethylene glycol (weight average molecular weight 8000) 5 g / L, peregal 5 g / L, heliotropin 2 g / L, dextrin 4 g / L. Prepare materials according to the above component composition, and complete the preparation of the first electroplating solution according to the following steps:

[0062] Step A. Dissolve disodium ethylenediaminetetraacetate in pure water at 70 °C until disodium ethylenediaminetetraacetate is completely dissolved to obtain an aqueous solution of disodium ethylenediaminetetraacetate; dissolve cadmium sulfate in a small amount of pure water to obtain an aqueous solution of cadmium sulfate; add the aqueous solution of cadmium sulfate to the aqueous solution of disodium ethylenediaminetetraacetate and stir evenly to obtain the first raw material solution.

[0063] Step B. Add a small amount of warm pure water to ammonium fluoride until ammonium fluoride is dissolved to obtain an aqueous solution of ammonium fluoride; dissolve nitrilotriacetic acid in a small amount of warm pure water to obtain a solution of nitrilotriacetic acid, and then add stannous chloride to the solution of nitrilotriacetic acid and dissolve it fully to obtain an acidified stannous chloride solution; then add the acidified stannous chloride solution to the aqueous solution of ammonium fluoride and stir evenly to obtain the second raw material solution.

[0064] Step C. Mix the first raw material solution and the second raw material solution to obtain the mother liquor of the electroplating solution.

[0065] Step D. Dissolve heliotropin and dextrin in an ethanol solution to obtain a brightener solution; dissolve polyethylene glycol and peregal in a small amount of hot pure water to obtain a leveling agent solution, then add the leveling agent solution to the mother liquor of the electroplating solution, and then add the brightener solution to it and stir fully to obtain a semi-finished product of the first electroplating solution.

[0066] Step E. Dilute the semi-finished first electroplating solution to a preset total volume according to the component composition of the first electroplating solution, stir evenly, and adjust the pH value of the solution with ammonia water until the pH of the solution is 5, thereby obtaining the first electroplating solution.

[0067] Load the base film into the electroplating equipment loaded with the first electroplating solution and the second electroplating solution prepared in this embodiment to complete the conductive layer forming process. During the conductive layer forming process of this embodiment, the full-line film pulling line speed is 7 m / min. Except for the difference in the film pulling line speed and the first electroplating solution used, other materials and corresponding operations involved in the conductive layer forming process of this embodiment are the same as those in the conductive layer forming process of Embodiment 1.

[0068] In the functional current collector prepared in this embodiment, the surface of the base film is sequentially covered with a tin-cadmium alloy layer and a second metal layer. On any surface of the base film, the thickness of the tin-cadmium alloy layer is 500 nm, and the thickness of the second metal layer is 460 nm. The tin-cadmium alloy layer and the second metal layer together serve as the conductive layer of the functional current collector.

[0069] Comparative Example 1

[0070] The base film used in this comparative example to prepare the functional current collector is the same as the base film used in Embodiment 1.

[0071] During the process of preparing the functional current collector in this comparative example, the electroplating solution used in the electroplating treatment is the second electroplating solution prepared in Embodiment 1.

[0072] Load the base film into the electroplating equipment loaded with the second electroplating solution prepared in Embodiment 1, and complete the conductive layer forming process according to the following operations:

[0073] S1. Use the electroplating equipment to unwind the base film, wash it with water, the full-line film pulling line speed is 3 m / min, let the base film enter the brush plating tank filled with the second electroplating solution, control the temperature of the plating solution at 40 °C, and set the brush plating voltage at 2 V, so as to electroplate a copper metal layer on the surface of the first metal layer of the base film as the second metal layer to obtain a semi-finished thin film.

[0074] S2. Perform double-link countercurrent water washing treatment, antioxidant treatment, drying treatment and winding treatment on the semi-finished thin film in sequence. The relevant operations involved in this step are the same as those in S3 of the conductive layer forming process of Embodiment 1. Thus, the functional current collector of this comparative example is prepared.

[0075] In the functional current collector prepared in this comparative example, the surface of the base film is covered with a second metal layer. On any surface of the base film, the thickness of the second metal layer is 960 nm, and the second metal layer serves as the conductive layer of the functional current collector.

[0076] Comparative Example 2

[0077] The base film used in this comparative example for preparing the functional current collector is the same as the base film used in Example 2.

[0078] In the process of preparing the functional current collector in this comparative example, the electroplating solution used in the electroplating treatment involved is the second electroplating solution used in Example 2, that is, the same as the second electroplating solution prepared in Example 1.

[0079] Load the base film into the electroplating equipment loaded with the above-mentioned second electroplating solution, and complete the conductive layer forming process according to the following operations:

[0080] S1. Use the electroplating equipment to unwind the base film, wash it with water, the full-line film pulling speed is 5 m / min, let the base film enter the brush plating tank filled with the second electroplating solution, control the plating solution temperature at 40 °C, set the brush plating voltage at 2 V, so as to electroplate a copper metal layer on the surface of the first metal layer of the base film as the second metal layer, and obtain a semi-finished thin film.

[0081] S2. Perform double-link reverse water washing treatment, antioxidant treatment, drying treatment and winding treatment on the semi-finished thin film in sequence. The relevant operations involved in this step are the same as S3 in the conductive layer forming process of Example 2. Thus, the functional current collector of this comparative example is prepared.

[0082] In the functional current collector prepared in this comparative example, the surface of the base film is covered with a second metal layer. On any surface of the base film, the thickness of the second metal layer is 960 nm, and the second metal layer is used as the conductive layer of the functional current collector.

[0083] Comparative Example 3

[0084] The base film used in this comparative example for preparing the functional current collector is the same as the base film used in Example 3.

[0085] In the process of preparing the functional current collector in this comparative example, the electroplating solution used in the electroplating treatment involved is the second electroplating solution used in Example 3, that is, the same as the second electroplating solution prepared in Example 1.

[0086] Load the base film into the electroplating equipment loaded with the above-mentioned second electroplating solution, and complete the conductive layer forming process according to the following operations:

[0087] S1. Use the electroplating equipment to unwind the base film, wash it with water, the full-line film pulling speed is 7 m / min, let the base film enter the brush plating tank filled with the second electroplating solution, control the plating solution temperature at 40 °C, set the brush plating voltage at 2 V, so as to electroplate a copper metal layer on the surface of the first metal layer of the base film as the second metal layer, and obtain a semi-finished thin film.

[0088] S2. The semi-finished film is successively subjected to double-link reverse water washing treatment, antioxidant treatment, drying treatment, and winding treatment. The relevant operations involved in this step are the same as those in S3 of the conductive layer forming process in Example 3. Thus, the functional current collector of this comparative example is obtained.

[0089] In the functional current collector obtained in this comparative example, the surface of the base film is covered with a second metal layer. On any surface of the base film, the thickness of the second metal layer is 960 nm, and the second metal layer is used as the conductive layer of the functional current collector.

[0090] Comparative Example 4

[0091] The base film used in this comparative example to prepare the functional current collector is the same as the base film used in Example 1.

[0092] In the process of preparing the functional current collector in this comparative example, two electroplating treatments are involved. The electroplating solutions used include a first electroplating solution and a second electroplating solution. Among them, the component composition and preparation method of the second electroplating solution are the same as those of the second electroplating solution used in Example 1. The component composition and preparation method of the first electroplating solution are specifically described as follows.

[0093] The difference between the first electroplating solution used in this comparative example and the first electroplating solution used in Example 1 is that the first electroplating solution used in this comparative example does not contain cadmium sulfate. Specifically, the component composition of the first electroplating solution used in this comparative example is as follows: stannous chloride 12 g / L, disodium ethylenediaminetetraacetate 50 g / L, nitrilotriacetic acid 40 g / L, ammonium chloride 250 g / L, polyethylene glycol (weight average molecular weight of 8000) 5 g / L, peregal 5 g / L, heliotropin 2 g / L, gum arabic 5 g / L.

[0094] Based on the difference in the component composition between the first electroplating solution used in this comparative example and the first electroplating solution used in Example 1, the raw materials used in this comparative example to prepare the first electroplating solution do not include cadmium sulfate. Correspondingly, this comparative example refers to the steps for preparing the first electroplating solution in Example 1 to complete the preparation of the first electroplating solution in this comparative example. The difference from Example 1 is that in the process of preparing the first electroplating solution in this comparative example, the operation involving cadmium sulfate is omitted. Except for this, other operations for preparing the first electroplating solution in this comparative example are the same as those for preparing the first electroplating solution in Example 1.

[0095] The base film is loaded into the electroplating equipment loaded with the first electroplating solution and the second electroplating solution prepared in this comparative example to complete the conductive layer forming process. In the process of the conductive layer forming process in this comparative example, the full-line film pulling line speed is 3 m / min. Except for the difference in the first electroplating solution used from Example 1, other materials and corresponding operations involved in the conductive layer forming process in this comparative example are the same as those in the conductive layer forming process in Example 1.

[0096] In the functional integrated fluid prepared in this comparative example, a tin metal layer and a second metal layer are successively covered on the surface of the base film. On any surface of the base film, the thickness of the tin metal layer is 500 nm, and the thickness of the second metal layer is 460 nm. The tin metal layer and the second metal layer together serve as the conductive layer of the functional integrated fluid.

[0097] Comparative Example 5

[0098] The base film used in this comparative example to prepare the functional integrated fluid is the same as the base film used in Example 1.

[0099] In the process of preparing the functional integrated fluid in this comparative example, two electroplating treatments are involved. The electroplating solutions used include a first electroplating solution and a second electroplating solution. Among them, the component composition and preparation method of the second electroplating solution are the same as those of the second electroplating solution used in Example 1. The component composition and preparation method of the first electroplating solution are specifically described below.

[0100] The difference between the first electroplating solution used in this comparative example and the first electroplating solution used in Example 1 is that the first electroplating solution used in this comparative example does not contain stannous chloride. Specifically, the component composition of the first electroplating solution used in this comparative example is as follows: cadmium sulfate 40 g / L, disodium ethylenediaminetetraacetate 50 g / L, nitrilotriacetic acid 40 g / L, ammonium chloride 250 g / L, polyethylene glycol (weight average molecular weight of 8000) 5 g / L, peregal 5 g / L, heliotropin 2 g / L, gum arabic 5 g / L.

[0101] Based on the difference in the component composition between the first electroplating solution used in this comparative example and the first electroplating solution used in Example 1, the raw materials for preparing the first electroplating solution in this comparative example do not include stannous chloride. Correspondingly, this comparative example refers to the steps for preparing the first electroplating solution in Example 1 to complete the preparation of the first electroplating solution in this comparative example. The difference from Example 1 is that the operation involving stannous chloride is omitted in the process of preparing the first electroplating solution in this comparative example. Except for this, other operations for preparing the first electroplating solution in this comparative example are the same as those for preparing the first electroplating solution in Example 1.

[0102] The base film is loaded into the electroplating equipment loaded with the first electroplating solution and the second electroplating solution prepared in this comparative example to complete the conductive layer forming process. In the process of the conductive layer forming process in this comparative example, the full-line film pulling line speed is 3 m / min. Except for the difference in the first electroplating solution used from Example 1, other materials and corresponding operations involved in the conductive layer forming process in this comparative example are the same as those in the conductive layer forming process in Example 1.

[0103] In the functional current collector prepared in this comparative example, a cadmium metal layer and a second metal layer are successively covered on the surface of the base film. On any surface of the base film, the thickness of the cadmium metal layer is 500 nm, and the thickness of the second metal layer is 460 nm. The cadmium metal layer and the second metal layer together serve as the conductive layer of the functional current collector.

[0104] Test Example 1

[0105] 1. Test Object

[0106] In this test example, the functional current collectors prepared in Examples 1 to 3 and Comparative Examples 1 to 5 are used as test objects. 50 repetitions are set for each test object, and each sample is 1 repetition.

[0107] 2. Test Items and Their Test Methods

[0108] (1) Densification Test: The densification test is completed in a dark room. The test object is closely attached to and completely covers the backlight panel (light-emitting surface) of the planar backlight. The planar backlight is turned on, and a camera is used to photograph the projection of the light-emitting surface along the light propagation direction at an angle perpendicular to the backlight panel of the planar backlight. The non-dense area of the test object is represented by the light spot area (light-transmitting area) in the photo, and the dense area of the test object is represented by the dark area in the photo. The densification of the test object is characterized as follows:

[0109] Densification = Dense Area / Backlight Panel Area.

[0110] Taking densification ≥ 90% as the passing standard.

[0111] (2) Elongation Test: The test object is baked at 150 °C for 3 minutes, and then the test object is cut into strip samples 15 mm wide along the MD (longitudinal direction) and TD (transverse direction) respectively. The strip samples are inspected to ensure that there are no notches or burrs at the edge cuts of the strip samples, and there are no hard or soft damages on the film surface of the strip samples. The qualified strip samples are used for testing. The strip samples are placed in the upper and lower chucks of a tensile machine, and the strip samples are clamped by the chucks and tightened. The running speed of the tensile machine is set to 50 mm / min and the stretching distance is set to 50 mm for tensile testing. Taking elongation ≥ 3% as the passing standard.

[0112] (3) Adhesion Test: The functional current collector is baked at a temperature of 150 °C for 3 minutes, and then cooled to room temperature. Then, a 3M tape is adhered to the surface of the functional current collector, and then a 2 kg standard pressure roller is used to roll back and forth once on the surface of the 3M tape (the side facing away from the functional current collector). Then, the 3M tape is peeled off from the surface of the functional current collector at an angle of 180° and a speed of 100 mm / min. After the 3M tape is completely peeled off, calculate the proportion of the area of the second metal layer adhered and peeled off by the 3M tape to the total area of the second metal layer.

[0113] 3. Test Results

[0114] Among the test objects, the functional set fluids provided by Example 1 and Comparative Example 1 were used as controls for each other, the functional set fluids provided by Example 2 and Comparative Example 2 were used as controls for each other, and the functional set fluids provided by Example 3 and Comparative Example 3 were used as controls for each other. In the above-mentioned groups that were used as controls for each other, the difference was whether the electroplating treatment process using the first electroplating solution containing cadmium salt and tin salt was included in the process of preparing the functional set fluid. Based on the above difference, the functional set fluids of Examples 1 to 3 all had a tin-cadmium alloy layer, while the functional set fluids of Comparative Examples 1 to 3 did not have a tin-cadmium alloy layer. From the test data, it can be seen that among the above-mentioned groups that were used as controls for each other, the functional set fluids with a tin-cadmium alloy layer achieved higher densification of the conductive layer and higher ductility. Moreover, in the adhesion test, the functional set fluids with a tin-cadmium alloy layer did not show any peeling of the second metal layer, while about 2% to 5% of the second metal layers of the functional set fluids without a tin-cadmium alloy layer peeled off to varying degrees. In the process of preparing the functional set fluids of Examples 1 to 3, a tin-cadmium alloy layer was made on the surface of the first metal layer before forming the second metal layer. After the tin-cadmium alloy layer was formed, the film composed of the base film and the tin-cadmium alloy layer was used as the forming carrier of the second metal layer. The setting of the tin-cadmium alloy layer could improve the surface defects of the first metal layer and reduce the sheet resistance of the forming carrier of the second metal layer, thereby improving the forming quality of the second metal layer. Just as in the process of preparing the functional set fluids of Examples 1 to 3, the second metal layer formed on the surface of the tin-cadmium alloy layer basically did not peel off in the adhesion test, which indicated that the second metal layers of these functional set fluids had higher cohesive force. In summary, based on the setting of the tin-cadmium alloy layer, the functional set fluids separately prepared in Examples 1 to 3 all achieved high densification, high elongation rate, and excellent structural stability. The sheet resistance of the functional set fluids prepared in these 3 examples did not exceed 23 mΩ.

[0115] In Comparative Example 4 and Comparative Example 5 during the preparation of the functional current collector, the film-drawing linear speed of electroplating was the same as that in Example 1. The difference in the arrangement of the conductive layer of the functional current collectors prepared by the three was that a tin-cadmium alloy layer was arranged between the first metal layer and the second metal layer of the functional current collector in Example 1, a tin metal layer was arranged between the first metal layer and the second metal layer of the functional current collector in Comparative Example 4, and a cadmium metal layer was arranged between the first metal layer and the second metal layer of the functional current collector in Comparative Example 5. Taking the functional current collector prepared in Example 1 as the comparison object, the elongation rates of the functional current collectors separately prepared in Comparative Example 4 and Comparative Example 5 were also on the low side. This shows that, compared with tin metal and cadmium metal, the tin-cadmium alloy is more conducive to improving the elongation rate of the functional current collector. In addition, in the adhesion test of the functional current collector with a tin metal layer (Comparative Example 4), the second metal layer peeled off, which proves that the quality of the second metal layer in this functional current collector is poor. Although the functional current collector with a cadmium metal layer (Comparative Example 5) can remain non-peeling in the adhesion test, compared with the arrangement of the tin-cadmium alloy layer, the arrangement of the cadmium metal layer will greatly increase the cost of the functional current collector.

[0116] Table 1. Statistical situation of test results in Test Example 1

[0117]

[0118] Example 4

[0119] This example prepared the functional current collector with reference to Example 1. During the preparation of the functional current collector in this example, two electroplating treatments were also involved. The electroplating solutions used included the first electroplating solution and the second electroplating solution. Among them, the component composition and preparation method of the second electroplating solution were the same as those of the second electroplating solution used in Example 1. This example completed the preparation of the first electroplating solution in this example with reference to the process of preparing the first electroplating solution in Example 1. During the preparation of the first electroplating solution in this example, the specific operations, types of materials, and dosages in Steps A, B, C, and D were the same as those in Example 1. However, in Step E of preparing the first electroplating solution in this example, the pH value of the first electroplating solution semi-finished product was adjusted to 4, and thus the first electroplating solution in this example was obtained. As a result, the only difference between the first electroplating solutions prepared in this example and Example 1 lies in the pH value. The pH value of the first electroplating solution prepared in this example is 4, while the pH value of the first electroplating solution prepared in Example 1 is 5.

[0120] Load the base film into the electroplating equipment loaded with the first electroplating solution and the second electroplating solution prepared in this embodiment to complete the conductive layer forming process. During the conductive layer forming process of this embodiment, the full-line film pulling line speed is 3 m / min. Except for the difference in the first electroplating solution used, other materials and corresponding operations involved in the conductive layer forming process of this embodiment are the same as those in the conductive layer forming process of Embodiment 1.

[0121] In the functional current collector obtained in this embodiment, the surface of the base film is successively covered with a tin-cadmium alloy layer and a second metal layer. On any surface of the base film, the thickness of the tin-cadmium alloy layer is 500 nm, and the thickness of the second metal layer is 460 nm. The tin-cadmium alloy layer and the second metal layer together serve as the conductive layer of the functional current collector.

[0122] Embodiment 5

[0123] This embodiment prepares a functional current collector with reference to Embodiment 1. During the process of preparing the functional current collector in this embodiment, two electroplating treatments are also involved. The electroplating solutions used include a first electroplating solution and a second electroplating solution. Among them, the component composition and preparation method of the second electroplating solution are the same as those of the second electroplating solution used in Embodiment 1. This embodiment prepares the first electroplating solution of this embodiment with reference to the process of preparing the first electroplating solution in Embodiment 1. During the process of preparing the first electroplating solution in this embodiment, the specific operations, material types, and dosages in Steps A, B, C, and D involved are the same as those in Embodiment 1. However, in Step E of preparing the first electroplating solution in this embodiment, the pH value of the first electroplating solution semi-finished product is adjusted to 6, thereby obtaining the first electroplating solution of this embodiment. As a result, the only difference between the first electroplating solutions prepared in this embodiment and Embodiment 1 lies in the pH value. The pH value of the first electroplating solution prepared in this embodiment is 6, while the pH value of the first electroplating solution prepared in Embodiment 1 is 5.

[0124] Load the base film into the electroplating equipment loaded with the first electroplating solution and the second electroplating solution prepared in this embodiment to complete the conductive layer forming process. During the conductive layer forming process of this embodiment, the full-line film pulling line speed is 3 m / min. Except for the difference in the first electroplating solution used, other materials and corresponding operations involved in the conductive layer forming process of this embodiment are the same as those in the conductive layer forming process of Embodiment 1.

[0125] In the functional current collector obtained in this embodiment, the surface of the base film is successively covered with a tin-cadmium alloy layer and a second metal layer. On any surface of the base film, the thickness of the tin-cadmium alloy layer is 500 nm, and the thickness of the second metal layer is 460 nm. The tin-cadmium alloy layer and the second metal layer together serve as the conductive layer of the functional current collector.

[0126] Embodiment 6

[0127] In this embodiment, the functional current collector is prepared with reference to Embodiment 1. During the preparation of the functional current collector in this embodiment, two electroplating treatments are also involved. The electroplating solutions used include a first electroplating solution and a second electroplating solution. Among them, the component composition and preparation method of the second electroplating solution are the same as those of the second electroplating solution used in Embodiment 1. This embodiment prepares the first electroplating solution of this embodiment according to the process of preparing the first electroplating solution in Embodiment 1. During the process of preparing the first electroplating solution in this embodiment, the specific operations, types of materials, and dosages in Step A, Step B, Step C, and Step D are the same as those in Embodiment 1. However, in Step E of preparing the first electroplating solution in this embodiment, the pH value of the first electroplating solution semi-finished product is adjusted to 3.8, thereby obtaining the first electroplating solution of this embodiment. As a result, the only difference between the first electroplating solutions prepared in this embodiment and Embodiment 1 lies in the pH value. The pH value of the first electroplating solution prepared in this embodiment is 3.8, while the pH value of the first electroplating solution prepared in Embodiment 1 is 5.

[0128] Load the base film into the electroplating equipment loaded with the first electroplating solution and the second electroplating solution prepared in this embodiment to complete the conductive layer forming process. During the conductive layer forming process of this embodiment, the full-line film pulling line speed is 3 m / min. Except for the difference in the first electroplating solution used compared with Embodiment 1, other materials and corresponding operations involved in the conductive layer forming process of this embodiment are the same as those in the conductive layer forming process of Embodiment 1.

[0129] In the functional current collector prepared in this embodiment, a tin-cadmium alloy layer and a second metal layer are sequentially covered on the surface of the base film. On any surface of the base film, the thickness of the tin-cadmium alloy layer is 500 nm, and the thickness of the second metal layer is 460 nm. The tin-cadmium alloy layer and the second metal layer together serve as the conductive layer of the functional current collector.

[0130] Embodiment 7

[0131] In this embodiment, the functional current collector is prepared with reference to Embodiment 1. During the preparation of the functional current collector in this embodiment, two electroplating treatments are also involved. The electroplating solutions used include a first electroplating solution and a second electroplating solution. Among them, the component composition and preparation method of the second electroplating solution are the same as those of the second electroplating solution used in Embodiment 1. In this embodiment, the first electroplating solution of this embodiment is prepared by referring to the process of preparing the first electroplating solution in Embodiment 1. During the process of preparing the first electroplating solution in this embodiment, the specific operations, types of materials, and dosages in Step A, Step B, Step C, and Step D are the same as those in Embodiment 1. However, in Step E of preparing the first electroplating solution in this embodiment, the pH value of the first electroplating solution semi-finished product is adjusted to 6.2, thereby obtaining the first electroplating solution of this embodiment. As a result, the only difference between the first electroplating solutions prepared in this embodiment and Embodiment 1 lies in the pH value. The pH value of the first electroplating solution prepared in this embodiment is 6.2, while the pH value of the first electroplating solution prepared in Embodiment 1 is 5.

[0132] The base film is loaded into the electroplating equipment filled with the first electroplating solution and the second electroplating solution prepared in this embodiment to complete the conductive layer forming process. During the conductive layer forming process of this embodiment, the full-line film pulling line speed is 3 m / min. Except for the difference in the first electroplating solution used compared with Embodiment 1, other materials and corresponding operations involved in the conductive layer forming process of this embodiment are the same as those in the conductive layer forming process of Embodiment 1.

[0133] In the functional current collector prepared in this embodiment, a tin-cadmium alloy layer and a second metal layer are sequentially covered on the surface of the base film. On any surface of the base film, the thickness of the tin-cadmium alloy layer is 500 nm, and the thickness of the second metal layer is 460 nm. The tin-cadmium alloy layer and the second metal layer together serve as the conductive layer of the functional current collector.

[0134] Test Example 2

[0135] 1. Test Object

[0136] In this test example, the functional current collectors prepared in Embodiments 4 to 7 are used as test objects. 50 repetitions are set for each test object, and each sample is 1 repetition.

[0137] 2. Test Items and Their Test Methods

[0138] (1) Densification Test: The relevant test method is the same as that in Test Example 1.

[0139] (2) Elongation Rate Test: The relevant test method is the same as that in Test Example 1.

[0140] (3) Adhesion Test: The relevant test method is the same as that in Test Example 1.

[0141] 3. Test Results

[0142] The test results are shown in Table 2. The test results of the functional current collector tightness test, elongation rate test, and adhesion test provided in Example 1 shown in Table 2 are the same as those in Test Example 1. The test results of this test example show that the pH of the first electroplating solution will affect the product performance of the functional current collector. When the pH of the first electroplating solution is 4-6, the comprehensive performance of the prepared functional current collector is better. When the pH of the first electroplating solution used for forming the tin-cadmium alloy layer reaches 4-6, it is beneficial to the co-deposition of the two metals, tin and cadmium, improve the coating quality of the tin-cadmium alloy layer, and further improve the coating quality of the second metal layer.

[0143] Table 2. Statistical situation of the test results of Test Example 2

[0144]

[0145]

[0146] The above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced, but these modifications or replacements are all within the protection scope of the present invention.

Claims

1. A method for preparing a functional current collector containing a tin-cadmium alloy, characterized in that: The preparation method comprises a conductive layer forming step of forming a conductive layer on a surface of a base film, wherein the base film comprises a polymer substrate and a first metal layer stacked in layers, wherein the first metal layer comprises at least one of copper, copper alloy, aluminum, and aluminum alloy; The conductive layer forming process is as follows: S1. Using the base film as a processing object, a tin-cadmium alloy layer is plated on the surface of the first metal layer, wherein the metal contained in the tin-cadmium alloy layer includes a tin-cadmium alloy; S2. A second metal layer is plated on the surface of the tin-cadmium alloy layer, wherein the second metal layer contains metals including copper, copper alloy, aluminum, and aluminum alloy.

2. The preparation method according to claim 1, characterized in that: In S1 of the conductive layer forming process, the plating solution used for plating the tin-cadmium alloy is a first plating solution, which includes a main salt component and a complexing agent component, the main salt component includes a cadmium salt and a tin salt, the complexing agent component includes nitrilotriacetic acid, disodium ethylenediaminetetraacetic acid, and an ammonium salt, and the ammonium salt includes at least one of ammonium chloride and ammonium fluoride.

3. The preparation method according to claim 2, characterized in that: The cadmium salt includes cadmium sulfate, and the tin salt includes stannous chloride; When the ammonium salt includes ammonium chloride, the composition of the first plating solution satisfies the following ratio, calculated by mass ratio: cadmium sulfate: stannous chloride: nitrilotriacetic acid: disodium ethylenediaminetetraacetate: ammonium chloride = 30-50:8-15:30-60:30-60:200-300; When the ammonium salt includes ammonium fluoride, the composition of the first plating solution satisfies the following ratio, calculated by mass ratio: cadmium sulfate: stannous chloride: nitrilotriacetic acid: disodium ethylenediaminetetraacetate: ammonium fluoride = 30-50:8-15:30-60:30-60:80-100.

4. The preparation method according to claim 2, characterized in that: The first plating solution further comprises a leveler component and / or a brightener component, wherein the leveler component comprises at least one of peregrin and polyethylene glycol, and the brightener component comprises at least one of heliotropin, gum arabic and dextrin.

5. The preparation method according to claim 2, characterized in that: The pH value of the first electroplating solution is 4-6.

6. The preparation method according to claim 2, characterized in that: The preparation of the first electroplating solution comprises the following operations: Step A. dissolving disodium ethylenediaminetetraacetate and cadmium salt in water respectively to obtain a disodium ethylenediaminetetraacetate aqueous solution and a cadmium salt aqueous solution, and mixing the disodium ethylenediaminetetraacetate aqueous solution and the cadmium salt aqueous solution to obtain a first raw material solution; Step B. dissolving the ammonium salt in water to obtain an ammonium salt aqueous solution, dissolving nitrilotriacetic acid in water to obtain a nitrilotriacetic acid solution, then adding a tin salt thereto to obtain an acidified tin salt solution, and mixing the ammonium salt aqueous solution and the acidified tin salt solution to obtain a second raw material solution; Step C: mixing the first raw material liquid and the second raw material liquid.

7. A functional current collector containing tin-cadmium alloy, characterized in that: The functional current collector includes a base film and a conductive layer; The base film comprises a polymer substrate and a first metal layer stacked in layers, wherein the first metal layer comprises at least one of copper, copper alloy, aluminum, and aluminum alloy; The conductive layer includes a tin-cadmium alloy layer and a second metal layer stacked together, the metal contained in the tin-cadmium alloy layer includes a tin-cadmium alloy, and the metal contained in the second metal layer includes at least one of copper, a copper alloy, aluminum, and an aluminum alloy; In the thickness direction of the functional current collector, the first metal layer, the tin-cadmium alloy layer, and the second metal layer are stacked in sequence.

8. The functional current collector containing tin-cadmium alloy as claimed in claim 7, characterized in that: In the tin-cadmium alloy, the tin content is 20wt.% to 40wt.%, and the cadmium content is 60wt.% to 80wt.%.

9. The functional current collector containing tin-cadmium alloy as claimed in claim 7, characterized in that: The thickness of the tin-cadmium alloy layer is 100nm-500nm.

10. A secondary battery, characterized in that: The secondary battery comprises the functional current collector containing the tin-cadmium alloy according to any one of claims 7 to 9.

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