A method for low temperature electroplating copper on a functional current collector based on a bimetallic seed layer

Abstract

The application discloses a kind of functional current collector low-temperature copper electroplating methods based on bimetallic seed layer, comprising the following steps: S1: using magnetron sputtering to deposit nickel layer as seed layer on the surface of polymer base film, then using formaldehyde reduction system chemical copper layer as transition layer on the nickel layer, to obtain the base film with bimetallic seed layer;S2: the base film with bimetallic seed layer is placed in electrolyte, and copper is electroplated using periodic commutation current;During electroplating, ultrasonic vibration is applied by ultrasonic generator arranged at the bottom of electroplating tank.The application solves the problems of poor adhesion between base film and copper layer in functional current collector copper electroplating, deformation of base film caused by high-temperature process, and many plating defects, and realizes the preparation of copper plating layer with high adhesion, no defects, size stability and high efficiency.

Description

Technical Field

[0001] This invention relates to the field of functional current collector technology, and specifically to a method for low-temperature copper electroplating of functional current collectors based on a bimetallic seed layer. Background Technology

[0002] Functional current collectors (such as polymer-based film composite metal-coated current collectors) have become a core research hotspot and key development direction in the battery field due to their outstanding energy density advantages. However, there are still three major technical problems in the copper electroplating process, which seriously restrict the industrial application and comprehensive performance improvement of this type of current collector: First, the surface energy of polymer base films such as PP and PET is extremely low and chemically inert, making it difficult for metallic copper to form a strong bond with them. The copper coating deposited directly has weak adhesion and is prone to peeling and detachment during subsequent use, which seriously affects the structural stability of the current collector. Second, the traditional copper electroplating process requires maintaining a high-temperature environment of 50~60℃ to ensure the deposition rate. This not only significantly increases production energy consumption, but also easily causes thermal deformation and dimensional displacement of the polymer base film, destroying the dimensional stability of the current collector and thus reducing the assembly accuracy of the subsequent battery. Finally, the copper coating prepared by conventional processes has the problem of coarse grains and dense defects such as pinholes and pores inside the coating. This not only damages the structural integrity of the current collector, but also significantly reduces its conductivity uniformity, failing to meet the stringent application requirements of high-performance batteries. Summary of the Invention

[0003] This invention aims to solve the problems of poor adhesion between the base film and the copper layer, base film deformation caused by high-temperature process, and many coating defects in the electroplating of copper with functional current collectors. It provides a method for low-temperature electroplating of copper with functional current collectors based on a bimetallic seed layer, which achieves high adhesion, defect-free, dimensionally stable and efficient copper coating preparation.

[0004] To achieve the above objectives, the technical solution provided by the present invention is as follows: The first aspect of this application provides a method for low-temperature copper electroplating using a functional current collector based on a bimetallic seed layer, comprising the following steps: S1: A nickel layer is deposited on the surface of a polymer base film by magnetron sputtering as a seed layer, and then a copper layer is electroless plated on the nickel layer using a formaldehyde reduction system as a transition layer to obtain a base film with a bimetallic seed layer. S2: The base film with a bimetallic seed layer is placed in the electrolyte and copper is electroplated using a periodic commutation current; during the electroplating process, ultrasonic vibration is applied by an ultrasonic generator set at the bottom of the electroplating tank.

[0005] To optimize the above technical solution, the specific limitations also include: In step S1, the thickness of the deposited nickel layer is 5~10 nm; the thickness of the electroless copper plating layer is 50~100 nm.

[0006] Furthermore, during the electroless plating process, the pH is controlled at 11-12 and the temperature is controlled at 38-42℃.

[0007] Preferably, the electroless plating solution consists of the following components: 4-6 g / L copper sulfate, 13-17 g / L disodium EDTA, and 9-11 mL / L formaldehyde.

[0008] Furthermore, during electroplating, the electroplating temperature is controlled at 25~35℃, and the total electroplating time is 20~40min, so that the total thickness of the copper layer reaches 1~3μm.

[0009] Preferably, the electrolyte for electroplating consists of the following components: 150-180 g / L copper sulfate, 30-40 g / L sulfuric acid, 0.02-0.08 g / L 2-mercaptobenzimidazole, and 0.5-1.0 g / L gelatin.

[0010] Preferably, the ultrasonic frequency of the ultrasonic vibration is 20~40kHz and the power is 50~100W.

[0011] A second aspect of this application provides a functional current collector prepared using the method described above.

[0012] A third aspect of this application provides an electrode comprising the aforementioned functional current collector.

[0013] A fourth aspect of this application provides a battery comprising the aforementioned electrode.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention effectively solves the core problems existing in the current process of electroplating copper in functional current collectors, such as poor adhesion, thermal deformation of the base film, numerous coating defects, and low low-temperature deposition rate, by constructing a bimetallic seed layer through magnetron sputtering of a nickel layer and electroless copper plating, optimizing the low-temperature electroplating process, and introducing an ultrasonic-assisted system.

[0015] Compared to existing technologies, the process of this invention can achieve high-quality copper plating at low temperatures. Specifically, the electroplating temperature is controlled within a low-temperature range. This low-temperature setting effectively avoids thermal deformation of the polymer base film caused by high temperatures, significantly improving the dimensional stability of the base film. Simultaneously, the bimetallic seed layer adopts a structure of a magnetron sputtered nickel layer + a chemically plated copper transition layer. The chemically plated copper layer on the nickel layer serves as a transition layer, forming a continuous and uniform conductive layer. This effectively avoids tip discharge during subsequent electroplating. Furthermore, combined with the chemical coordination and lattice matching characteristics of the nickel layer and the base film, the adhesion between the metal layer and the base film is significantly improved. In addition, with the synergistic effect of relevant additives and an ultrasonic-assisted system, the diffusion layer during electroplating is broken by ultrasonic vibration, accelerating copper ion transport. This effectively solves the problem of low mass transfer rate at low temperatures and significantly refines the copper plating grains, reducing pinhole defects. Ultimately, a high-quality plating layer with no pinholes and low wrinkles is achieved, while simultaneously improving the plating elongation and conductivity. Moreover, the ultrasonic-assisted technology allows the deposition rate at low temperatures to be comparable to traditional high-temperature processes, without sacrificing production efficiency.

[0016] The technical advantages of the synergistic approach of bimetallic seed layer preparation, low-temperature electroplating solution formulation, and ultrasonic assistance in this invention can effectively improve the overall performance of functional current collectors, providing a reliable solution for the efficient and high-quality preparation of functional current collectors in the battery field. Detailed Implementation

[0017] The present invention will be further described in detail below through specific embodiments, but it should not be construed as limiting the scope of the subject matter of the present invention to the following embodiments. All technologies implemented based on the above content of the present invention fall within the scope of the present invention.

[0018] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the reagents, methods and equipment used are conventional reagents, methods and equipment in this technical field.

[0019] This invention provides a method for low-temperature copper electroplating using a functional current collector based on a bimetallic seed layer, comprising the following steps: S1: A nickel layer is deposited on the surface of a polymer base film by magnetron sputtering as a seed layer, and then a copper layer is electroless plated on the nickel layer using a formaldehyde reduction system as a transition layer to obtain a base film with a bimetallic seed layer. S2: The base film with a bimetallic seed layer is placed in the electrolyte and copper is electroplated using a periodic commutation current; during the electroplating process, ultrasonic vibration is applied by an ultrasonic generator set at the bottom of the electroplating tank.

[0020] This invention achieves a synergistic effect by defining the core combination of the bimetallic seed layer preparation step and the low-temperature electroplating step, fundamentally solving the core defects of existing technologies for electroplating copper in functional current collectors, such as poor adhesion, large thermal deformation of the base film, numerous pinholes in the plating layer, and coarse grains. Specifically, the bimetallic seed layer, through the chemical coordination and lattice matching between the nickel seed layer and the polymer base film, combined with a chemically plated copper transition layer, thoroughly improves the problem of insufficient adhesion of a single seed layer. The bimetallic seed layer adopts a structure of a magnetron sputtered nickel layer + a chemically plated copper transition layer. The chemically plated copper layer on the nickel layer serves as a transition layer, forming a continuous and uniform conductive layer, effectively preventing tip discharge during subsequent electroplating. Furthermore, the chemical coordination and lattice matching characteristics between the nickel layer and the base film significantly enhance the adhesion between the metal layer and the base film. Low-temperature electroplating combined with periodic commutation current effectively avoids the risk of thermal deformation of the base film and improves dimensional stability; ultrasonic assistance at the bottom of the electroplating tank can break the electrolyte diffusion layer, solving the problem of low mass transfer rate at low temperatures; multi-process coupling and synergistic optimization of coating defects improve the overall performance and conductivity stability of the coating.

[0021] In some embodiments, in step S1, the thickness of the deposited nickel layer is 5-10 nm; the thickness of the electroless copper plating layer is 50-100 nm. A reasonable nickel seed layer thickness ensures lattice matching and chemical coordination effects, avoiding increased costs and stress concentration in the plating layer; a suitable electroless copper plating transition layer thickness forms a continuous conductive layer, avoiding subsequent electroplating defects and achieving seamless connection with the subsequent electroplated copper layer, thereby improving the overall elongation performance of the plating layer.

[0022] In some embodiments, during the electroless plating process, the pH is controlled at 11-12 and the temperature at 38-42°C. The preferred alkaline pH range ensures uniform and impurity-free electroless copper plating, reducing subsequent electroplating defects. This temperature range balances reaction rate and substrate film tolerance, ensuring the deposition rate while preventing substrate film softening and deformation. The synergistic effect of these two factors refines the grains of the electroless copper plating, enhances its bonding with the nickel seed layer, and further improves the adhesion between the metal layer and the substrate film.

[0023] In some embodiments, the electroless plating bath consists of the following components: copper sulfate 4-6 g / L, disodium EDTA 13-17 g / L, and formaldehyde 9-11 mL / L. A proper ratio of the main salt to the complexing agent ensures the stable presence of copper ions in the plating bath, avoiding particle defects in the plating layer caused by hydrolysis and precipitation. An appropriate reducing agent concentration balances the reduction reaction rate and the plating layer density, avoiding problems caused by excessively slow or vigorous reactions. This component range ensures a uniform thickness of the electroless copper plating layer, providing a smooth substrate for subsequent low-temperature electroplating.

[0024] In some embodiments, during electroplating, the electroplating temperature is controlled at 25~35℃, and the total electroplating time is 20~40 minutes, so that the total thickness of the copper layer reaches 1~3μm. The preferred electroplating temperature range can completely avoid thermal deformation of the base film caused by high temperature, and at the same time, the addition of electrolyte additives can achieve grain refinement; the electroplating time is precisely matched with the total thickness of the copper layer to ensure a stable deposition rate and avoid performance defects caused by insufficient thickness or stress concentration.

[0025] In some embodiments, the electroplating electrolyte consists of the following components: 150-180 g / L copper sulfate, 30-40 g / L sulfuric acid, 0.02-0.08 g / L 2-mercaptobenzimidazole, and 0.5-1.0 g / L gelatin. The appropriate ratio of the main salt to the conductive medium provides sufficient copper ions and ensures the conductivity of the electrolyte, guaranteeing the deposition rate meets standards at low temperatures. The synergistic effect of the two additives precisely refines copper grains, ensures uniform distribution of copper ions, effectively reduces pinholes in the plating layer, and improves the plating elongation.

[0026] In some embodiments, the ultrasonic frequency of the ultrasonic vibration is 20~40kHz, and the power is 50~100W. This frequency range can effectively break the electrolyte diffusion layer, accelerate copper ion transport, and ensure the deposition rate at low temperatures; at the same time, it avoids damage to the base film and seed layer and reduces coating defects. When these ultrasonic parameters are combined with low-temperature electroplating and periodic commutation current, the coating uniformity and the adhesion between the metal layer and the base film can be improved, achieving optimal performance.

[0027] The present invention also provides a functional current collector, which is prepared by the above method.

[0028] The present invention also provides an electrode comprising the above-described functional current collector.

[0029] The present invention also provides a battery comprising the above-described electrode.

[0030] The functional current collector of this invention has significantly better core performance indicators than existing products. It can maintain good conductivity even under the condition of rising temperature during fast charging, and is suitable for the high-rate charging and discharging requirements of new energy batteries. Its composite structure has excellent structural reliability and can withstand multiple bending cycles without coating peeling, which significantly improves its service life.

[0031] With the help of this functional current collector, the production yield, electrochemical performance and energy density of the electrode can be improved, which is in line with the industry development trend. On this basis, the cycle life, fast charging performance and dimensional stability of the battery are significantly optimized. The core performance meets the industry standards, the manufacturing process is compatible with existing production lines, no large-scale equipment modification is required, and it has the prospect of industrial promotion.

[0032] The technical solution of the present invention will be further described in detail below with reference to specific embodiments: Example 1: 1. Base film pretreatment A PP (polypropylene) membrane with a thickness of 4.5 μm was selected as the polymer base membrane and subjected to oxygen plasma cleaning treatment. The cleaning parameters were set as follows: power 200W and cleaning time 30s. This pretreatment increased the hydroxyl content on the surface of the base membrane and enhanced the bonding performance between the subsequent seed layer and the base membrane.

[0033] 2. Preparation of bimetallic seed layers 2.1 Magnetron sputtering deposition of nickel seed layer The pretreated PP base film was placed in a magnetron sputtering apparatus under a vacuum of 5×10⁻⁶. -3 Under conditions of Pa, argon flow rate of 30 sccm, and sputtering power of 150 W, a nickel layer is deposited on the surface of the base film as a seed layer. The thickness of the nickel layer is controlled to be 8 nm, which can effectively play a seed induction role and provide a good adhesion substrate for the subsequent electroless copper plating layer.

[0034] 2.2 Electroless Copper Plating Transition Layer On the surface of the aforementioned nickel seed layer, a formaldehyde reduction system is used for chemical copper plating to prepare a transition layer, forming a bimetallic seed layer. The specific operation is as follows: A chemical copper plating solution was prepared with the following components and concentrations: copper sulfate 5 g / L, disodium EDTA 15 g / L, and formaldehyde 10 mL / L. The pH of the plating solution was adjusted to 11.5 using sodium hydroxide, the chemical plating temperature was controlled at 40℃, and the reaction time was 10 min. Finally, a chemical copper plating transition layer with a thickness of 80 nm was formed on the surface of the nickel seed layer, resulting in a PP base film with a bimetallic seed layer.

[0035] 3. Low-temperature copper electroplating The base film with the bimetallic seed layer was placed in the electrolyte of the electroplating tank, and copper was electroplated at low temperature using a periodic commutation current while ultrasonic vibration was applied. The specific parameters are as follows: 3.1 Electrolyte preparation: The electrolyte components and concentrations are copper sulfate 160g / L, sulfuric acid 35g / L, 2-mercaptobenzimidazole 0.05g / L, and gelatin 0.8g / L.

[0036] 3.2 Electroplating parameters: The electroplating temperature was controlled at 30℃, and the total electroplating time was 30 min; the periodic commutation current parameter was set as follows: forward current density 2 A / dm³. 2 Forward current conduction time: 80ms; reverse current density: 0.3A / dm³ 2 The reverse power-on time is 8ms.

[0037] 3.3 Ultrasonic Assistance: During the electroplating process, the ultrasonic generator set at the bottom of the electroplating tank is turned on to apply ultrasonic vibration. The ultrasonic frequency is 30kHz and the power is 80W. Ultrasonic vibration reduces pinhole defects in the electroplated copper layer and improves the density of the copper layer.

[0038] After electroplating, a functional current collector with a 1μm thick copper plating layer on both the front and back sides is obtained.

[0039] Example 2: The difference between this embodiment and Embodiment 1 is that the thickness of the bimetallic seed layer and the chemical plating and electroplating parameters are changed. All other processes are completely consistent with Embodiment 1, as detailed below: 1. Base film pretreatment: Same as in Example 1, a 4.5μm thick PP film was selected and cleaned with oxygen plasma (power 200W, time 30s).

[0040] 2. Preparation of bimetallic seed layers 2.1 Magnetron sputtering deposition of nickel seed layer: The parameters are the same as in Example 1, and the nickel layer thickness is controlled to be 5 nm.

[0041] 2.2 Electroless Copper Plating Transition Layer: The electroless copper plating solution consists of: 4 g / L copper sulfate, 13 g / L disodium EDTA, and 9 mL / L formaldehyde; the pH value is adjusted to 11, the electroless plating temperature is 38℃, and the reaction time is 8 min, forming an electroless copper plating transition layer with a thickness of 50 nm.

[0042] 3. Low-temperature copper electroplating 3.1 Electrolyte preparation: The electrolyte components are: copper sulfate 150g / L, sulfuric acid 30g / L, 2-mercaptobenzimidazole 0.02g / L, and gelatin 0.5g / L.

[0043] 3.2 Electroplating parameters: Electroplating temperature 25℃, total electroplating time 20min; periodic commutation current parameters are the same as in Example 1, and a functional current collector with a total copper layer thickness of 1μm is finally obtained.

[0044] 3.3 Ultrasonic assistance: Ultrasonic frequency 20kHz, power 50W, the rest is the same as in Example 1.

[0045] Example 3: The difference between this embodiment and Embodiment 1 is that the thickness of the bimetallic seed layer and the chemical plating and electroplating parameters are changed. All other processes are completely consistent with Embodiment 1, as detailed below: 1. Base film pretreatment: Same as in Example 1, a 4.5μm thick PP film was selected and cleaned with oxygen plasma (power 200W, time 30s).

[0046] 2. Preparation of bimetallic seed layers 2.1 Magnetron sputtering deposition of nickel seed layer: The parameters are the same as in Example 1, and the nickel layer thickness is controlled to be 10 nm.

[0047] 2.2 Electroless copper plating transition layer: The components of the electroless copper plating solution are: copper sulfate 6g / L, disodium EDTA 17g / L, formaldehyde 11mL / L; the pH value is adjusted to 12, the electroless plating temperature is 42℃, and the reaction time is 12min, forming an electroless copper plating transition layer with a thickness of 100nm.

[0048] 3. Low-temperature copper electroplating 3.1 Electrolyte preparation: The electrolyte components are: copper sulfate 180g / L, sulfuric acid 40g / L, 2-mercaptobenzimidazole 0.08g / L, and gelatin 1.0g / L.

[0049] 3.2 Electroplating parameters: Electroplating temperature 35℃, total electroplating time 40min; periodic commutation current parameters are the same as in Example 1, and a functional current collector with a total copper layer thickness of 3μm is finally obtained.

[0050] 3.3 Ultrasonic assistance: Ultrasonic frequency 40kHz, power 100W, the rest is the same as in Example 1.

[0051] Comparative Example 1: This comparative example uses a conventional electroplating method from the existing technology. The specific process steps are as follows: 1. Base film pretreatment: The same 4.5μm thick PP film as in Example 1 was selected. Only conventional alcohol wiping and cleaning were performed. Oxygen plasma cleaning was not performed. The base film surface had low hydroxyl content and poor surface energy.

[0052] 2. Seed layer preparation: A bimetallic seed layer structure was not used. Instead, a nickel layer was directly magnetron sputtered onto the pretreated PP substrate as a single seed layer. The sputtering parameters were the same as in Example 1 (vacuum degree 5 × 10⁻⁶). -3 Pa, argon flow rate 30 sccm, sputtering power 150 W), nickel layer thickness 8 nm, no subsequent transition layer.

[0053] 3. Conventional High-Temperature Copper Electroplating: A conventional high-temperature electroplating process was used, with the electrolyte composition identical to that in Example 1 (copper sulfate 160 g / L, sulfuric acid 35 g / L, 2-mercaptobenzimidazole 0.05 g / L, gelatin 0.8 g / L); the electroplating temperature was controlled at 55°C, using ordinary direct current without periodic commutation, and a current density of 2 A / dm³. 2 Without applying ultrasonic vibration, the electroplating time is 30 minutes, and a functional current collector with a copper plating thickness of 1μm on both the front and back sides is finally obtained.

[0054] Comparative Example 2: This comparative example provides a method for electroplating copper onto a functional current collector. The only difference between this method and Example 1 is that the transition layer of the bimetallic seed layer uses magnetron sputtered copper instead of electroless copper plating. All other process parameters (base film pretreatment, magnetron sputtering of nickel seed layer, ultrasonic vibration, low-temperature electroplating parameters, etc.) are completely consistent with Example 1. The specific process is as follows: 1. Base film pretreatment: Same as in Example 1, a 4.5μm thick PP film was selected and cleaned by oxygen plasma (power 200W, time 30s).

[0055] 2. Seed layer preparation: A nickel seed layer was deposited by magnetron sputtering (parameters were the same as in Example 1: vacuum degree 5 × 10⁻⁶). - 3 (At Pa, argon flow rate 30 sccm, sputtering power 150 W, 8 nm nickel layer was deposited); then, a copper layer was deposited as a transition layer on the surface of the nickel seed layer by magnetron sputtering, with sputtering parameters consistent with those of the nickel seed layer, and the thickness of the copper layer was controlled to be 80 nm, thus obtaining a PP base film with a nickel + copper dual sputtering seed layer.

[0056] 3. Low-temperature copper electroplating: Completely consistent with Example 1, with unchanged electrolyte composition, electroplating temperature, periodic commutation current parameters, ultrasonic vibration parameters (30kHz, 80W), and electroplating time, ultimately obtaining a functional current collector with a 1μm thick copper plating on both the front and back sides.

[0057] Comparative Example 3: This comparative example provides a method for electroplating copper with a functional current collector. The only difference between this method and Example 1 is that ultrasonic vibration is not applied during the low-temperature electroplating process. All other process parameters (base film pretreatment, bimetallic seed layer preparation, electrolyte preparation, electroplating temperature, and periodic commutation current parameters, etc.) are completely consistent with Example 1. The specific process is as follows: 1. Base film pretreatment: Same as in Example 1, a 4.5μm thick PP film was selected and cleaned by oxygen plasma (power 200W, time 30s).

[0058] 2. Preparation of bimetallic seed layer: exactly the same as in Example 1, 8nm nickel seed layer was sputtered by magnetron sputtering, and then 80nm copper transition layer was chemically plated through a formaldehyde reduction system (the composition of the plating solution, pH value, temperature and reaction time were all unchanged).

[0059] 3. Low-temperature copper electroplating: The electrolyte composition, electroplating temperature (30℃), periodic commutation current parameters and electroplating time (30min) are the same as in Example 1. Only the ultrasonic generator is turned off and no ultrasonic vibration is applied. Finally, a functional current collector with a copper plating thickness of 1μm on both the front and back sides is obtained.

[0060] Comparative Example 4: This comparative example provides a method for electroplating copper onto a functional current collector. The only difference between this method and Example 1 is that the electroplating process uses the same conventional high temperature (controlled at 55°C in this comparative example) instead of the low temperature used in Example 1. All other process parameters (base film pretreatment, bimetallic seed layer preparation, electrolyte preparation, ultrasonic vibration parameters, and periodic commutation current parameters, etc.) are completely consistent with Example 1. The specific process is as follows: 1. Base film pretreatment: Same as in Example 1, a 4.5μm thick PP film was selected and cleaned by oxygen plasma (power 200W, time 30s).

[0061] 2. Preparation of bimetallic seed layer: exactly the same as in Example 1, 8nm nickel seed layer was sputtered by magnetron sputtering, and then 80nm copper transition layer was chemically plated through a formaldehyde reduction system (the composition of the plating solution, pH value, temperature and reaction time were all unchanged).

[0062] 3. Conventional high-temperature copper electroplating: The electrolyte composition, periodic commutation current parameters, ultrasonic vibration parameters (30kHz, 80W), and electroplating time (30min) were all the same as in Example 1. Only the electroplating temperature was adjusted to the same conventional high temperature of 55℃ as in Comparative Example 1. Finally, a functional current collector with a copper plating thickness of 1μm on both the front and back sides was obtained.

[0063] Comparative Example 5: This comparative example provides a method for electroplating copper onto a functional current collector. The only difference between this method and Example 1 is that the electroplating process uses ordinary direct current without periodic commutation. All other process parameters are completely consistent with Example 1. The specific process is as follows: 1. Base film pretreatment: Same as in Example 1, a 4.5μm thick PP film was selected and cleaned by oxygen plasma (power 200W, time 30s).

[0064] 2. Preparation of bimetallic seed layer: exactly the same as in Example 1, 8nm nickel seed layer was sputtered by magnetron sputtering, and then 80nm copper transition layer was chemically plated by formaldehyde reduction system.

[0065] 3. Low-temperature copper electroplating: The electrolyte composition, electroplating temperature (30℃), ultrasonic vibration parameters (30kHz, 80W), and electroplating time (30min) were all the same as in Example 1; only the periodic commutation current was replaced with ordinary DC current at a current density of 2A / dm³. 2 Without switching between forward and reverse power supply, a functional current collector with a 1μm thick copper plating on both the front and back sides is finally obtained.

[0066] Comparative Example 6: This comparative example provides a method for electroplating copper onto a functional current collector. The only difference between this method and Example 1 is that a nickel seed layer is not prepared; instead, copper is directly electroplated onto the pretreated base film surface as a seed layer. There is no bimetallic seed layer structure. All other process parameters are completely consistent with Example 1. The specific process is as follows: 1. Base film pretreatment: Same as in Example 1, a 4.5μm thick PP film was selected and cleaned by oxygen plasma (power 200W, time 30s).

[0067] 2. Seed layer preparation: Without magnetron sputtering of nickel seed crystal layer, copper is directly electroplated on the surface of pretreated PP base film using formaldehyde reduction system consistent with Example 1 to prepare a copper seed layer with a thickness of 88nm (consistent with the total thickness of nickel + copper in Example 1), without bimetallic structure.

[0068] 3. Low-temperature copper electroplating: exactly the same as in Example 1, with no change in electrolyte composition, electroplating temperature, periodic commutation current parameters, ultrasonic vibration parameters and electroplating time, finally obtaining a functional current collector with a 1μm thick copper plating on both the front and back sides.

[0069] All samples underwent uniform performance testing, and the overall performance comparison results are shown in Table 1: Table 1

[0070] Note: 1. The same testing standard is used for pinhole detection. In Example 1, "no pinhole defects" corresponds to a detection result of 0.2 pinholes / m. 2 1. The conductivity is far lower than that of the comparison processes and can be ignored; 2. The increase in conductivity when the fast charging temperature rises in each example is calculated based on Comparative Example 1.

[0071] Experimental Analysis: Examples 1-3, employing the scheme of this invention, exhibit superior overall performance compared to all comparative examples, demonstrating the best performance in dimensional stability, coating density, toughness, adhesion, conductivity compatibility, and resistance to thermal deformation. The combination of the bimetallic seed layer, electroless plating, low-temperature electroplating, and ultrasonic-assisted parameters in this invention creates a synergistic effect, maximizing the overall performance of the functional current collector.

[0072] The performance of existing conventional processes (Comparative Example 1) is far inferior to that of this invention, with core defects concentrated in poor adhesion, large thermal deformation of the base film, and numerous pinholes in the coating. This invention fundamentally solves the above defects by coupling multiple processes including a bimetallic seed layer, low-temperature electroplating, periodic commutation current, and ultrasonic assistance, achieving a qualitative improvement in overall performance.

[0073] Comparative analysis with other examples using different combinations of conditions shows that the bimetallic seed layer structure of nickel seed layer + electroless copper transition layer is crucial: replacing the electroless copper transition layer with a magnetron sputtered copper transition layer, eliminating the nickel seed layer and using only a single copper seed layer, and using conventional high temperature instead of the low-temperature electroplating of this invention all lead to significant performance degradation. The electroless copper transition layer can form a dense bond structure with the nickel seed layer, and the nickel seed layer can improve the adhesion between the metal layer and the base film and induce seed growth. In addition, this invention further improves the coating quality through low-temperature electroplating, periodic commutation current, and ultrasonic assistance: low-temperature electroplating can avoid softening and deformation of the base film and ensure bonding stability; periodic commutation current can reduce coating defects and improve density and conductivity stability; ultrasonic assistance can solve the problem of low mass transfer rate at low temperatures, reduce pinholes and improve coating uniformity. The combination of the three forms a good synergistic effect.

[0074] In summary, by limiting the preparation parameters of the bimetallic seed layer and combining it with a synergistic process of low-temperature electroplating, periodic commutation current, and ultrasonic assistance, the present invention can prepare a functional current collector that meets the fast charging requirements of new energy batteries, is compatible with existing production lines, does not require large-scale equipment modification, has the potential for industrial-scale promotion, can further optimize the overall performance of batteries, and aligns with industry development trends.

[0075] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent substitutions, and improvements made by those skilled in the art to the above embodiments without departing from the scope of the technical solution of the present invention, based on the technical essence of the present invention, shall still fall within the protection scope of the technical solution of the present invention.

Claims

1. A method for low-temperature copper electroplating using a functional current collector based on a bimetallic seed layer, characterized in that, Includes the following steps: S1: A nickel layer is deposited on the surface of a polymer base film by magnetron sputtering as a seed layer, and then a copper layer is electroless plated on the nickel layer using a formaldehyde reduction system as a transition layer to obtain a base film with a bimetallic seed layer. S2: The base film with a bimetallic seed layer is placed in the electrolyte and copper is electroplated using a periodic commutation current; during the electroplating process, ultrasonic vibration is applied by an ultrasonic generator set at the bottom of the electroplating tank.

2. The method for low-temperature copper electroplating based on a bimetallic seed layer functional current collector according to claim 1, characterized in that: In step S1, the thickness of the deposited nickel layer is 5~10 nm; the thickness of the electroless copper plating layer is 50~100 nm.

3. The method for low-temperature copper electroplating based on a bimetallic seed layer functional current collector according to claim 1, characterized in that: During the electroless plating process, the pH is controlled at 11-12 and the temperature is controlled at 38-42℃.

4. The method for low-temperature copper electroplating based on a bimetallic seed layer functional current collector according to claim 1, characterized in that: The electroless plating solution consists of the following components: copper sulfate 4~6g / L, disodium EDTA 13~17g / L, and formaldehyde 9~11mL / L.

5. The method for low-temperature copper electroplating based on a bimetallic seed layer functional current collector according to claim 1, characterized in that: During electroplating, the electroplating temperature is controlled at 25~35℃, and the total electroplating time is 20~40min, so that the total thickness of the copper layer reaches 1~3μm.

6. The method for low-temperature copper electroplating based on a bimetallic seed layer functional current collector according to claim 1, characterized in that: The electrolyte for electroplating consists of the following components: 150-180 g / L copper sulfate, 30-40 g / L sulfuric acid, 0.02-0.08 g / L 2-mercaptobenzimidazole, and 0.5-1.0 g / L gelatin.

7. The method for low-temperature copper electroplating based on a bimetallic seed layer functional current collector according to claim 1, characterized in that: The ultrasonic frequency of ultrasonic vibration is 20~40kHz, and the power is 50~100W.

8. A functional current collector, characterized in that: Prepared using the method described in any one of claims 1 to 7.

9. An electrode sheet, characterized in that: It includes the functional current collector as described in claim 8.

10. A battery, characterized in that: It includes the electrode sheet as described in claim 9.

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