Preparation method of composite current collector

Abstract

The invention discloses a preparation method of a composite current collector, and belongs to the technical field of lithium battery current collector manufacturing. Comprising the following steps: S1, carrying out plasma treatment on the surface of a polymer matrix film twice in sequence to obtain an activated film; wherein air is used as a gas source in the first plasma treatment, and mixed gas of nitrogen and argon is used as a gas source in the second plasma treatment; s2, depositing metal on two sides of the activated thin film to obtain a thin film deposited with a metal seed layer; and S3, thickening the two surfaces of the thin film deposited with the metal seed layer to a certain thickness by adopting a water electroplating mode to obtain the composite current collector. According to the invention, plasma treatment is successively carried out twice, active groups can be introduced to the surface of the film, heat balance of the surface of the film is considered, damage to the structural performance of the film caused by excessive heat is avoided, metals in the metal seed layer can be better combined with the active groups, the adhesive force of the metal seed layer is improved, and the service life of the film is prolonged. And the comprehensive mechanical property of the composite copper foil is obviously improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium battery current collector manufacturing, in particular to a preparation method of a composite current collector. BACKGROUND

[0002] The composite current collector is a research hotspot in the field of lithium batteries at present. Compared with the traditional copper foil current collector, the composite current collector adds a polymer material to form a composite foil, commonly in a sandwich structure of "metal-polymer material-metal". Among them, the metal layer is usually copper or aluminum, and the middle layer can use PET (polyethylene terephthalate), PP (polypropylene), PI (polyimide) and other polymer materials, which has the advantages of high safety, long cycle life and large energy density.

[0003] The composite current collector is mainly prepared by a two-step method, that is, the magnetron sputtering and electroplating processes are sequentially performed. Taking the PP material as an example, first, a copper film with a thickness of several tens to hundreds of nanometers is formed on the surface of the material by magnetron sputtering technology, which gives the material preliminary conductivity; then the copper layer is thickened to the micron level by electroplating process, and finally the sandwich structure current collector is prepared.

[0004] However, there are many problems in the preparation process of the composite current collector. Due to the significant difference in crystal structure between copper metal and polymer material, the adhesion of the copper seed layer formed by magnetron sputtering is poor, and the nanometer-thick seed layer is prone to fall off. In addition, the copper seed layer will also affect the bonding effect of the copper layer in the subsequent electroplating process, thereby interfering with the morphology quality and yield of the final current collector.

[0005] Therefore, optimizing the preparation process is crucial to improving the comprehensive performance of the composite current collector. SUMMARY

[0006] The purpose of the present application is to provide a preparation method of a composite current collector, which modifies the surface of the base film to generate certain active functional groups on the surface of the base film, thereby improving the adhesion between the base film and the copper layer, and further reducing or even avoiding the occurrence of the falling phenomenon, so as to solve the problem of poor performance of the final product caused by the poor adhesion of the metal seed layer in the existing composite current collector.

[0007] The purpose of the present application is achieved by the following technical scheme:

[0008] A preparation method of a composite current collector, comprising the following steps:

[0009] S1. The surface of the polymer substrate film is treated by plasma twice in succession to obtain an activated film; wherein the first plasma treatment uses air as the gas source, and the second plasma treatment uses a mixed gas of nitrogen and argon as the gas source;

[0010] S2. Deposit metal on both sides of the activated thin film to obtain a thin film with a metal seed layer deposited on it;

[0011] S3. Using electroplating, the film with the deposited metal seed layer is thickened to a certain thickness on both sides to obtain the composite current collector.

[0012] This invention first uses air as a gas source, and uses gas ions generated by a gas ion source to bombard the surface of a polymer matrix film to activate it, generating active functional groups such as carboxyl (-COOH) and amino (-NH2). Then, a mixture of nitrogen and argon is used as an ion source to treat the film with a plasma beam to introduce more active groups, ensure the activity of the functional groups formed after the first plasma treatment, and take into account the cleanliness of the film surface and avoid impurity contamination, thereby ensuring better bonding of the film with metals in the future.

[0013] As one embodiment of this application, the polymer matrix film is a polypropylene film or polyethylene terephthalate.

[0014] As one embodiment of this application, the thickness of the polymer matrix film is 4-8 μm.

[0015] As one embodiment of this application, in step S1, the relevant parameters during plasma treatment are:

[0016] The beam current voltage is 400–700 V, the beam current velocity is 100–600 sccm, the processing time is 0.5–10 min, the ion source power is 10–1000 W, and the ion source working pressure is 20–40 kPa. In actual implementation, the power of the two ion beam treatments should not be too high, otherwise it will cause wrinkles on the film surface, thus compromising the flatness of the film surface. This invention, by limiting the power, enables the two plasma beam treatments to introduce more active groups while protecting the flatness and integrity of the film surface, greatly improving the adhesion strength between the copper seed layer and the polymer surface, significantly enhancing the bonding force of the product, and ultimately resulting in a significant improvement in the overall mechanical properties of the composite copper foil.

[0017] As one embodiment of this application, in step S2, the deposited metal element is one or more of Cu, Ni, and Al.

[0018] As one embodiment of this application, in step S2, the deposited metal element is Cu;

[0019] The deposition method used was magnetron sputtering. The copper target diameter of the deposition system was 100 mm, the magnetron temperature was -30 to 10 °C, the sputtering power was 5 to 7 kW, the target bias voltage was 350 to 500 V, and the vacuum degree was 10. -2 ~10 -1Pa, nitrogen flow rate 50-200 ml / min, argon flow rate 400-2000 ml / min.

[0020] As one embodiment of this application, in step S3, the electroplating solution used for water electroplating includes 100-200 g / L Cu. 2+ and 100-200 g / L sulfuric acid;

[0021] The relevant parameters for water electroplating are: temperature 15~30℃, pH 5~6.5, and current density 0.5~5A / dm.

[0022] In addition, to achieve the above objectives, the present invention also provides a composite current collector prepared by the above method.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention utilizes high-energy non-metallic ions to bombard polymer films, causing the hydrocarbon groups in the polymer chains to break. The broken groups react with oxygen, nitrogen, or other reactive gases in the air to form new chemical bonds, thereby effectively activating the polymer film surface and generating active groups such as carboxyl groups (-COOH) and amino groups (-NH2). Among these, the negatively charged carboxylate group (-COOH)... - ) through electrostatic attraction with metal ions (such as Cu) in the metal seed layer 2+ This process forms strong coordinate bonds. The oxygen atom in the carboxylate group provides two lone pairs of electrons, forming bidentate coordination with the metal ion, further enhancing bond stability. Similarly, the amino group can combine with the metal ion to form stable coordinate bonds. Subsequent nitrogen plasma treatment introduces more amino groups that form stable coordinate bonds with the metal ion. Through multiple connections between the surface groups of the film and the metal ions in the metal seed layer, the bonding strength between the polymer base film and the metal seed layer, as well as the adhesion strength between the copper seed layer and the polymer surface, is significantly improved. This enhances the adhesion between the base film and the copper layer, reducing or even eliminating detachment, ultimately improving the bonding strength and overall mechanical properties of the composite copper foil. Attached Figure Description

[0025] Figure 1 Infrared spectrum of untreated PP film;

[0026] Figure 2 Infrared spectrum of PP film after first ion beam treatment (the red circle indicates the characteristic peak position of amino-NH2);

[0027] Figure 3 Infrared spectrum of PP film after second ion beam treatment (the red circle indicates the characteristic peak position of amino-NH2);

[0028] Figure 4Images of the composite copper foil tape in Example 1 after testing;

[0029] Figure 5 Images of the composite copper foil tape after testing in Example 2;

[0030] Figure 6 Images of the composite copper foil tape after testing in Example 3;

[0031] Figure 7 Image of the composite copper foil tape in Comparative Example 1 after testing. Detailed Implementation

[0032] Example 1

[0033] A method for preparing composite copper foil, the method comprising the following steps:

[0034] S1. A 4.5μm thick polypropylene film is used (infrared spectrum as shown). Figure 1 (As shown), the preparation method can be referred to the published relevant patents CN118789857A and CN118683093A.

[0035] S2. Air was used as the gas source to supply gas for the ion source, and gas ions generated by the gas ion source bombarded the surface of the polymer matrix film. Ion source parameters: the beam current voltage of the gas ion source was set to 500V, the beam current velocity to 500sccm, the treatment time to 1min, the ion source power to 1000W, and the ion beam working pressure to 38kPa. Nitrogen and argon treatment times were 0.5min, the nitrogen flow rate was 100ml / min, and other parameters were consistent with the air gas source settings. A small number of film samples treated twice with plasma beams were taken for infrared spectroscopy testing. The infrared spectra are as follows: Figure 2 and Figure 3 As shown.

[0036] S3. Copper is deposited on both sides of the activated substrate film after ion beam treatment using magnetron sputtering to obtain a metal seed layer. Magnetron sputtering parameters: the copper target diameter of the deposition system is 100 mm, the magnetron temperature is maintained at -20℃, the sputtering power is 6 kW, the target bias voltage is 400 V, and the vacuum degree is 10. -1 Pa, argon flow rate 500 ml / min. Each metal seed layer is 100 nm thick.

[0037] S4. Using electroplating, the metal seed layer obtained in step S3 is thickened to 1 μm to obtain a composite current collector with a metal-polymer-metal structure. The electroplating solution contains: Cu 2+ The concentration of the plating agent was 120 g / L, the concentration of sulfuric acid was 120 g / L, the electroplating temperature was 25℃, the pH was 6, and the current density was 2.5 A / dm.

[0038] Example 2

[0039] A method for preparing composite copper foil includes the following steps:

[0040] S1. A 4.5μm thick polypropylene film is used.

[0041] S2. Air is used as the gas source to supply gas for the ion source. Gas ions generated by the gas ion source bombard the surface of the polymer matrix film. Ion source parameters: beam voltage of the gas ion source is set to 500V, beam velocity to 500sccm, processing time to 1min, ion source power to 1000W, and ion beam working pressure to 38kPa. The mixed gas of nitrogen and argon is processed for 1min at a nitrogen flow rate of 100ml / min; other parameters are the same as those for the air gas source.

[0042] S3. Copper is deposited on both sides of the activated substrate film after ion beam treatment using magnetron sputtering to obtain a metal seed layer. Magnetron sputtering parameters: the copper target diameter of the deposition system is 100 mm, the magnetron temperature is maintained at -20℃, the sputtering power is 6 kW, the target bias voltage is 400 V, and the vacuum degree is 10. -1 Pa, argon flow rate 500 ml / min. Each metal seed layer is 100 nm thick.

[0043] S4. Using electroplating, the metal seed layer obtained in step S3 is thickened to 1 μm to obtain a composite current collector with a metal-polymer-metal structure. The electroplating solution contains: Cu 2+ The concentration of the plating agent was 120 g / L, the concentration of sulfuric acid was 120 g / L, the electroplating temperature was 25℃, the pH was 6, and the current density was 2.5 A / dm.

[0044] Example 3

[0045] A method for preparing composite copper foil, the method comprising the following steps:

[0046] S1. A 4.5μm thick polypropylene film is used.

[0047] S2. Air is used as the gas source to supply gas for the ion source. Gas ions generated by the gas ion source bombard the surface of the polymer matrix film. Ion source parameters: beam voltage of the gas ion source is set to 500V, beam velocity to 500sccm, processing time to 1min, ion source power to 1000W, and ion beam working pressure to 38kPa. The mixed gas of nitrogen and argon is processed for 1.5min at a nitrogen flow rate of 100ml / min, with other parameters consistent with the air gas source settings.

[0048] S3. Copper is deposited on both sides of the activated substrate film after ion beam treatment using magnetron sputtering to obtain a metal seed layer. -1 Pa, argon flow rate 500 ml / min. Each metal seed layer is 100 nm thick.

[0049] S4. Using electroplating, the metal seed layer obtained in step S3 is thickened to 1 μm to obtain a composite current collector with a metal-polymer-metal structure. The electroplating solution contains: Cu 2+ The concentration of the plating agent was 120 g / L, the concentration of sulfuric acid was 120 g / L, the electroplating temperature was 25℃, the pH was 6, and the current density was 2.5 A / dm.

[0050] Comparative Example 1:

[0051] A method for preparing composite copper foil includes the following steps:

[0052] S1. A 4.5μm thick polypropylene film is used.

[0053] S2. This experiment does not use plasma beam treatment; instead, it directly deposits metallic copper on both sides of the base film using magnetron sputtering to obtain a metal seed layer. Magnetron sputtering parameters: the copper target diameter of the deposition system is 100 mm, the magnetron temperature is maintained at -20℃, the sputtering power is 6 kW, the target bias voltage is 400 V, and the vacuum degree is 10... -1 Pa, argon flow rate 500 ml / min. Each metal seed layer is 100 nm thick.

[0054] S3. Using electroplating, the metal seed layer obtained in step S2 is thickened to 1 μm to obtain a composite current collector with a metal-polymer-metal structure. The electroplating solution contains: Cu 2+ The concentration of the plating agent was 120 g / L, the concentration of sulfuric acid was 120 g / L, the electroplating temperature was 25℃, the pH was 6, and the current density was 2.5 A / dm.

[0055] Comparative Example 2:

[0056] A method for preparing composite copper foil, the method comprising the following steps:

[0057] S1. A 4.5μm thick polypropylene film is used.

[0058] S2. Air is used as the gas source to supply gas for the ion source, and the gas ions generated by the gas ion source bombard the surface of the polymer matrix film. Nitrogen and argon are used as gas sources to supply gas for the ion source. Ion source parameters: the beam voltage of the gas ion source is set to 500V, the beam flow rate is set to 500sccm, the processing time is set to 1min, the ion source power is set to 1150W, and the ion beam working pressure is 38kPa. The nitrogen and argon processing time is 0.5min, the nitrogen flow rate is 100ml / min, and other parameters are the same as those for the air gas source.

[0059] S3. Other parameters are set in the same way as in Example 1.

[0060] Comparative Example 3:

[0061] A method for preparing composite copper foil, the method comprising the following steps:

[0062] S1. A 4.5μm thick polypropylene film is used.

[0063] S2. Using only air as the gas source to supply gas to the ion source, the gas ions generated by the gas ion source bombard the surface of the polymer matrix film. Ion source parameters: the beam voltage of the gas ion source is set to 500V, the beam velocity is set to 500sccm, the processing time is set to 1min, the ion source power is set to 1000w, and the ion beam working pressure is 38kPa.

[0064] S3. Other parameter settings are the same as in Example 1.

[0065] Comparative Example 4:

[0066] A method for preparing composite copper foil, the method comprising the following steps:

[0067] S1. A 4.5μm thick polypropylene film is used.

[0068] S2. Using only a mixture of nitrogen and argon as the gas source for the ion source, the gas ions generated by the ion source bombard the surface of the polymer matrix film. Ion source parameters: beam voltage of the gas ion source is set to 500V, beam flow rate is set to 500sccm, processing time is set to 1min, ion source power is set to 1000W, and ion beam working pressure is 38kPa. Nitrogen and argon processing time is 0.5min, and nitrogen flow rate is 100ml / min.

[0069] S3. Other parameter settings are the same as in Example 1.

[0070] Experimental Example

[0071] 1. The composite copper foils obtained in Examples 1-3 and Comparative Examples 1-4 were subjected to mechanical property tests. The test results are shown in Tables 1 and 2.

[0072] Table 1:

[0073]

[0074]

[0075] Table 2:

[0076]

[0077] Tables 1 and 2 show that data analysis from Examples 1, 2, and 3 preliminarily indicates that the uniformity of heat on the film surface can be maintained relatively well within a certain time range, thus ensuring the stability of its mechanical properties. Furthermore, Comparative Example 1 shows that compared to the film without any plasma treatment, the two plasma treatments significantly improved the mechanical properties of the composite copper foil. However, the heat cannot be too high; otherwise, as in Comparative Example 2, excessive power will cause heat to accumulate on the film surface, preventing timely heat dissipation and dissipation, which will damage the internal and surface structure of the film, leading to impaired mechanical properties and ultimately affecting the mechanical properties of the composite copper foil. Subsequent single plasma treatments, such as Comparative Examples 3 and 4, also improved the mechanical properties of the composite copper foil to some extent.

[0078] 2. Adhesion strength tape test (as shown in Table 3).

[0079] Table 3:

[0080]

[0081]

[0082] Table 3 shows that the bonding strength test of the composite copper foil adhesive tape prepared above was conducted on samples prepared in Examples 1, 2, 3, and Comparative Example 1 using the same tape. The same sample was subjected to three tensile tests, and the test results are as follows: Figure 4 , Figure 5 , Figure 6 , Figure 7As shown, it is evident that the two plasma beam treatments do indeed help improve the adhesion between the copper layer and the surface substrate film. Compared to the untreated film, the treated composite copper foil showed significantly less copper foil detachment in the three test areas. Furthermore, the amount of detached copper foil decreased significantly with the extension of the second treatment time. This indicates that the plasma beam treatment of the second treatment increases the number of polar functional groups such as amino and carboxyl groups generated on the film surface, resulting in more stable structures that subsequently bond with copper, thereby improving the adhesion of the macroscopic composite copper foil.

[0083] In summary, compared with Comparative Example 1, Embodiments 1, 2, and 3 of the present invention have the following inventive effects:

[0084] The three embodiments of the present invention provide a scheme for producing composite copper foil by including two plasma beam treatments, magnetron sputtering and electroplating. The scheme can obtain composite copper foil with uniform film thickness and excellent mechanical properties, which is extremely suitable for manufacturing battery negative electrodes, and is especially suitable for applications such as new energy vehicles that require lithium battery current collectors.

Claims

1. A method of making a composite current collector, characterized by, The method comprises the following steps: S1. treating the surface of the polymer matrix film twice by plasma to obtain an activated film; wherein the first plasma treatment uses air as the gas source, and the second plasma treatment uses a mixed gas of nitrogen and argon as the gas source; S2. depositing metal on both sides of the activated film to obtain a film with a metal seed layer deposited thereon; S3. thickening the film with the metal seed layer deposited thereon to a certain thickness by water electroplating to obtain the composite current collector.

2. The method of claim 1, wherein the composite current collector is prepared by the steps of: The polymer matrix film is a polypropylene film or a polyethylene terephthalate film.

3. The method of claim 1, wherein the copper foil is prepared on a polymer film. The thickness of the polymer matrix film is 4-8 μm.

4. The method of claim 1, wherein the composite current collector is prepared by the steps of: In step S1, the relevant parameters during plasma treatment are as follows: The beam voltage is 400-700 V, the beam flow rate is 100-600 sccm, the treatment time is 0.5-10 min, the ion source power is 10-1200 W, and the ion source working pressure is 20-40 kPa.

5. The method of claim 1, wherein the composite current collector is prepared by the steps of: In step S2, the deposited metal element is one or more of Cu, Ni and Al.

6. The method of claim 1, wherein the composite current collector is prepared by the steps of: In step S2, the deposited metal element is Cu. The method of deposition is magnetron sputtering, the magnetron temperature is -30-10℃, the sputtering power is 5-7kW, the target material bias is 350-500v, the vacuum degree is 10 -2 -10 -1 Pa, the nitrogen flow is 50-200ml / min, the argon flow is 400-2000ml / min.

7. The method of claim 6, wherein the composite current collector is prepared by the steps of: In step S3, the electroplating solution used for water electroplating includes 100-200 g / L Cu 2+ and 100-200 g / L sulfuric acid. The relevant parameters of water electroplating are as follows: the temperature is 15-30 ℃, the pH is 5-6.5, and the current density is 0.5-5 A / dm.

8. A composite current collector, characterized by, Prepared by the method of any one of claims 1-7.

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