A method of adjusting the fracture elongation of a composite current collector

Abstract

The application discloses a method for adjusting the breaking elongation of a composite current collector, comprising the following steps: providing a polymer film substrate; placing the polymer film substrate in a vacuum winding and plating equipment; performing plasma bombardment treatment on the polymer film substrate in a vacuum environment to regulate the surface recrystallization degree of the polymer film substrate; and depositing a metal conductive layer on at least one surface of the polymer film substrate after the plasma bombardment treatment to form a composite current collector. The application uses a plasma treatment system integrated in the vacuum winding and plating equipment to bombard the polymer substrate, regulates the surface recrystallization degree of the polymer material, and does not affect the overall crystallinity of the substrate, that is, the breaking elongation of the composite current collector is adjusted without sacrificing the mechanical strength of the substrate and without adding additional production steps.

Description

Technical Field

[0001] This invention relates to the field of composite current collector preparation, specifically a method for adjusting the elongation at break of composite current collectors. Background Technology

[0002] Composite current collectors are a new type of battery current collector material formed by depositing a metal conductive layer on the surface of a polymer film as a substrate. Compared with traditional metal current collectors, they have significant advantages in improving battery energy density and safety. However, the introduction of polymer materials also brings new challenges: the elongation at break of composite current collectors differs greatly from that of traditional metal materials, making it difficult to match the process windows of existing battery production processes such as coating and rolling. This often requires modification of the production line or adjustment of process parameters, leading to increased production costs and reduced production efficiency.

[0003] Currently, to adjust the mechanical properties of composite current collectors, the industry typically employs methods such as adjusting the thickness or number of metal layers, or replacing different types or batches of polymer substrates. These methods are not only complex in process and inefficient in control, but also difficult to achieve continuous and precise control of the elongation at break. They often come at the cost of sacrificing other properties (such as tensile strength and interfacial bonding strength), thus limiting the widespread application and rapid iteration of composite current collectors.

[0004] Therefore, how to maintain tensile strength without reducing elongation at break, and achieve efficient, flexible, and low-cost performance control, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a method for adjusting the elongation at break of a composite current collector. The method utilizes a plasma treatment system integrated in a vacuum winding coating equipment to bombard a polymer substrate, thereby controlling the degree of recrystallization on the surface of the polymer material without affecting the overall crystallinity of the substrate. In other words, the elongation at break of the composite current collector is adjusted without sacrificing its mechanical strength or adding additional production steps.

[0006] To achieve the above objectives, the present invention provides the following technical solution: In a first aspect, the present invention discloses a method for adjusting the elongation at break of a composite current collector, comprising the following steps: Provide polymer film substrates; The polymer film substrate is placed in a vacuum roll-to-roll coating equipment; under vacuum conditions, the polymer film substrate is subjected to plasma bombardment treatment to regulate the degree of surface recrystallization. After plasma bombardment treatment, a metal conductive layer is deposited on at least one surface of the polymer film substrate to form a composite current collector.

[0007] As a further aspect of the present invention: the power of plasma bombardment is 1000W-3000W, and the plasma bombardment time per unit area of ​​polymer film substrate is 0.75-3s.

[0008] As a further aspect of the present invention: the polymer film substrate is at least one of PET, PP, PI, and PPS.

[0009] As a further aspect of the present invention, the thickness of the polymer film substrate does not exceed 15 μm.

[0010] As a further aspect of the present invention: the gas type of the plasma bombardment is at least one of Ar, O2, and N2, and the gas pressure is 0.1~1 Pa.

[0011] As a further aspect of the present invention: the plasma bombardment uses a radio frequency plasma source, a microwave plasma source, or a DC plasma source.

[0012] Secondly, the present invention provides a composite current collector obtained by the method described above, wherein the elongation at break of the composite current collector is reduced by 10% to 30% compared with that of the untreated composite current collector; and the tensile strength of the composite current collector fluctuates by ≤±10% compared with that of the untreated composite current collector. It should be noted that the untreated composite current collector refers to a composite current collector prepared using the same preparation method, the same polymer film substrate, and the same metal conductive layer deposition process as the composite current collector described above, but without the plasma bombardment treatment step.

[0013] As a further aspect of the present invention: the thickness of the metal conductive layer is 0.5 μm. 1.5μm.

[0014] Compared with the prior art, the beneficial effects of the present invention are: This invention achieves precise control over the elongation at break of composite current collectors through an online plasma treatment system integrated into a vacuum roll-to-roll coating equipment. Its core mechanism lies in the fact that plasma bombardment of the polymer film substrate surface induces controlled dissociation of the polymer chains, thereby forming a nanoscale recrystallized layer on the substrate surface. This recrystallized layer alters the microstructure orientation and crystallinity of the substrate surface, while the crystallinity and mechanical strength of the substrate itself are fully preserved.

[0015] Based on this mechanism, this invention allows for continuous adjustment of the elongation at break of the composite current collector within a wide range, without adding extra production steps or damaging the strength of the substrate, simply by adjusting the power of plasma bombardment and processing time. Simultaneously, the formation of the surface recrystallization layer improves the interfacial compatibility between the polymer substrate and the metal conductive layer, significantly enhancing the bonding force of the composite current collector. This method achieves a synergistic effect of elongation at break control and enhanced interfacial bonding force, and seamlessly integrates with subsequent vacuum coating processes, exhibiting excellent process integration and scalability.

[0016] This method effectively solves the production line adaptation problem caused by the mismatch between the ductility of composite current collectors and traditional battery manufacturing processes. By parametrically controlling the degree of surface recrystallization, it can quickly match the different requirements of various battery systems for the flexibility of current collectors, significantly improve the production first-pass yield, and reduce the cost and time losses caused by changing substrates or modifying equipment. It provides a reliable technical path for the high-performance and customized production of composite current collectors. Attached Figure Description

[0017] Figure 1 The images show DSC diagrams of polymer substrates subjected to plasma bombardment with different parameters in the examples and comparative examples. Detailed Implementation

[0018] To facilitate understanding of the present invention, a more comprehensive description will be given below with reference to specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of the present invention.

[0019] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the description of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0020] Example 1 (1) Take a 6μm thick PET film as the polymer substrate, install it on the unwinding roller of the vacuum winding coating equipment, and complete the tape path so that it passes through the subsequent plasma treatment zone and coating zone in sequence.

[0021] (2) After closing the equipment chamber, start the vacuum system to evacuate. When the background vacuum level in the chamber reaches 5.0 × 10⁻⁶, -3 After Pa, we prepare to enter the process operation stage.

[0022] (3) Start the winding system to drive the substrate to run at a constant speed. At the same time, start the integrated radio frequency Ar plasma treatment system and set its power to 1000 W and pressure to 0.1 Pa. Under these parameters, by controlling the winding speed, the plasma bombardment time per unit area of ​​PET substrate surface is ensured to be about 3 seconds.

[0023] (4) After plasma treatment, the substrate is then placed in the evaporation coating zone, where aluminum metal layers are deposited on both surfaces of the PET substrate. By controlling the evaporation rate, the thickness of the aluminum layer on each side is precisely controlled at 1.0 μm, and the composite current collector is finally obtained.

[0024] Example 2 (1) Take a PET film with a thickness of 4.5 μm as a polymer substrate, install it on the unwinding roller of the vacuum winding coating equipment, and complete the tape threading path so that it passes through the subsequent plasma treatment zone and coating zone in sequence.

[0025] (2) After closing the equipment chamber, start the vacuum system to evacuate. When the background vacuum in the chamber reaches 5.0×10-3Pa, prepare to enter the process operation stage.

[0026] (3) Start the winding system to drive the substrate to run at a constant speed. At the same time, start the integrated DC N2 plasma treatment system and set its power to 3000 W and pressure to 1.0 Pa. Under these parameters, by controlling the winding speed, the plasma bombardment time per unit area of ​​PET substrate surface is ensured to be approximately 0.75 seconds.

[0027] (4) After plasma treatment, the substrate is then placed in the evaporation coating zone, where aluminum metal layers are deposited on both surfaces of the PET substrate. By controlling the evaporation rate, the thickness of the aluminum layer on each side is precisely controlled at 1.5 μm, and the composite current collector is finally obtained.

[0028] Example 3 (1) Take a PP film with a thickness of 4.5 μm as a polymer substrate, install it on the unwinding roller of the vacuum winding coating equipment, and complete the tape threading path so that it passes through the subsequent plasma treatment zone and coating zone in sequence.

[0029] (2) After closing the equipment chamber, start the vacuum system to evacuate. When the background vacuum level in the chamber reaches 5.0 × 10⁻⁶, -3 After Pa, we prepare to enter the process operation stage.

[0030] (3) The winding system is activated to drive the substrate at a constant speed. At the same time, the integrated radio frequency Ar / O2 (90:10 at.%) plasma treatment system is activated, and its power is set to 1800 W and the pressure to 0.5 Pa. Under these parameters, the plasma bombardment time per unit area of ​​the substrate surface is ensured to be approximately 2 seconds by controlling the winding speed.

[0031] (4) After plasma treatment, the substrate is then placed in the evaporation coating zone, where aluminum layers are deposited on both surfaces of the PP substrate. By controlling the evaporation rate, the thickness of the aluminum layer on each side is precisely controlled at 0.5 μm, and the composite current collector is finally obtained.

[0032] Comparative Example 1 (1) Take a 6μm thick PET film as the polymer substrate, install it on the unwinding roller of the vacuum winding coating equipment, and complete the tape path so that it passes through the subsequent plasma treatment zone and coating zone in sequence.

[0033] (2) After closing the equipment chamber, start the vacuum system to evacuate. When the background vacuum level in the chamber reaches 5.0 × 10⁻⁶, -3 After Pa, we prepare to enter the process operation stage.

[0034] (3) The winding system is turned on to drive the substrate to run at a constant speed. In this comparative example, no plasma treatment is performed on the polymer film substrate; the substrate directly enters the coating area.

[0035] (4) The substrate enters the evaporation coating area, and aluminum metal layers are deposited on both surfaces of the PET substrate. By controlling the evaporation rate, the thickness of the aluminum layer on one side is precisely controlled at 1.0 μm, and the composite current collector is finally obtained.

[0036] Comparative Example 2 (1) Take a 6μm thick PET film as the polymer substrate, install it on the unwinding roller of the vacuum winding coating equipment, and complete the tape path so that it passes through the subsequent plasma treatment zone and coating zone in sequence.

[0037] (2) After closing the equipment chamber, start the vacuum system to evacuate. When the background vacuum level in the chamber reaches 5.0 × 10⁻⁶, - After reaching ³Pa, we prepare to enter the process operation phase.

[0038] (3) Start the winding system to drive the substrate to run at a constant speed. At the same time, start the integrated radio frequency Ar plasma treatment system and set its power to 600 W and pressure to 0.1 Pa. Under these parameters, by controlling the winding speed, the plasma bombardment time per unit area of ​​PET substrate surface is ensured to be about 3 seconds.

[0039] (4) After plasma treatment, the substrate is then placed in the evaporation coating zone, where aluminum metal layers are deposited on both surfaces of the PET substrate. By controlling the evaporation rate, the thickness of the aluminum layer on each side is precisely controlled at 1.0 μm, and the composite current collector is finally obtained.

[0040] Comparative Example 3 (1) Take a 6μm thick PET film as the polymer substrate, install it on the unwinding roller of the vacuum winding coating equipment, and complete the tape path so that it passes through the subsequent plasma treatment zone and coating zone in sequence.

[0041] (2) After closing the equipment chamber, start the vacuum system to evacuate. When the background vacuum level in the chamber reaches 5.0 × 10⁻⁶, -3 After Pa, we prepare to enter the process operation stage.

[0042] (3) Start the winding system to drive the substrate to run at a constant speed. At the same time, start the integrated radio frequency Ar plasma treatment system and set its power to 3500 W and pressure to 0.1 Pa. Under these parameters, by controlling the winding speed, the plasma bombardment time per unit area of ​​PET substrate surface is ensured to be about 3 seconds.

[0043] (4) After plasma treatment, the substrate was damaged before entering the evaporation coating zone, making it impossible to deposit the subsequent aluminum layer and thus failing to produce the composite current collector. In this comparative example, the substrate was broken down due to excessive plasma power, so there is no test data in Tables 1 and 2.

[0044] Comparative Example 4 (1) Take a 6μm thick PET film as the polymer substrate, install it on the unwinding roller of the vacuum winding coating equipment, and complete the tape path so that it passes through the subsequent plasma treatment zone and coating zone in sequence.

[0045] (2) After closing the equipment chamber, start the vacuum system to evacuate. When the background vacuum level in the chamber reaches 5.0 × 10⁻⁶, -3 After Pa, we prepare to enter the process operation stage.

[0046] (3) Start the winding system to drive the substrate to run at a constant speed. At the same time, start the integrated radio frequency Ar plasma treatment system and set its power to 1000 W and pressure to 0.1 Pa. Under these parameters, by controlling the winding speed, the plasma bombardment time per unit area of ​​PET substrate surface is ensured to be about 0.5 seconds.

[0047] (4) After plasma treatment, the substrate is then placed in the evaporation coating zone, where aluminum metal layers are deposited on both surfaces of the PET substrate. By controlling the evaporation rate, the thickness of the aluminum layer on each side is precisely controlled at 1.0 μm, and the composite current collector is finally obtained.

[0048] Comparative Example 5 (1) Take a 6μm thick PET film as the polymer substrate, install it on the unwinding roller of the vacuum winding coating equipment, and complete the tape path so that it passes through the subsequent plasma treatment zone and coating zone in sequence.

[0049] (2) After closing the equipment chamber, start the vacuum system to evacuate. When the background vacuum level in the chamber reaches 5.0 × 10⁻⁶, -3 After Pa, we prepare to enter the process operation stage.

[0050] (3) Start the winding system to drive the substrate to run at a constant speed. At the same time, start the integrated radio frequency Ar plasma treatment system and set its power to 1000 W and pressure to 0.1 Pa. Under these parameters, the plasma bombardment time per unit area of ​​PET substrate surface is ensured to be about 5 seconds by controlling the winding speed.

[0051] (4) After plasma treatment, the substrate was torn before entering the evaporation coating zone, making it impossible to deposit the subsequent aluminum layer and thus failing to produce the composite current collector. In this comparative example, the substrate was broken down due to excessively long plasma treatment time, so there is no test data in Tables 1 and 2.

[0052] Comparative Example 6 (1) Take a PET film with a thickness of 4.5μm as a polymer substrate, install it on the unwinding roller of the vacuum winding coating equipment, and complete the tape path so that it passes through the subsequent plasma treatment zone and coating zone in sequence.

[0053] (2) After closing the equipment chamber, start the vacuum system to evacuate. When the background vacuum level in the chamber reaches 5.0 × 10⁻⁶, -3 After Pa, we prepare to enter the process operation stage.

[0054] (3) The winding system is turned on to drive the substrate to run at a constant speed. In this comparative example, no plasma treatment is performed on the polymer film substrate; the substrate directly enters the coating area.

[0055] (4) The substrate enters the evaporation coating area, and aluminum metal layers are deposited on both surfaces of the PET substrate. By controlling the evaporation rate, the thickness of the aluminum layer on one side is precisely controlled at 1.5 μm, and the composite current collector is finally obtained.

[0056] Comparative Example 7 (1) Take a PP film with a thickness of 4.5μm as a polymer substrate, install it on the unwinding roller of the vacuum winding coating equipment, and complete the tape path so that it passes through the subsequent plasma treatment zone and coating zone in sequence.

[0057] (2) After closing the equipment chamber, start the vacuum system to evacuate. When the background vacuum level in the chamber reaches 5.0 × 10⁻⁶, -3 After Pa, we prepare to enter the process operation stage.

[0058] (3) The winding system is turned on to drive the substrate to run at a constant speed. In this comparative example, no plasma treatment is performed on the polymer film substrate; the substrate directly enters the coating area.

[0059] (4) The substrate enters the evaporation coating area, and metallic aluminum layers are deposited on both surfaces of the PP substrate. By controlling the evaporation rate, the thickness of the aluminum layer on one side is precisely controlled at 0.5 μm, and the composite current collector is finally obtained.

[0060] Test case To characterize the effect of plasma treatment on the surface crystallization structure of polymer substrates, differential scanning calorimetry (DSC) tests were performed on the base film samples (sampled before coating) in the examples and comparative examples. Circular samples weighing 5.0 ± 0.5 mg were cut from the plasma-treated PET base film rolls using a cutting machine to ensure representative sampling locations and clean, uncontaminated sample surfaces. The tests were conducted using a Netzsch DSC 214 Polyma differential scanning calorimeter. Tests were performed under a high-purity nitrogen protective atmosphere (flow rate 50 mL / min) to eliminate oxidation effects. The temperature program was as follows: heating from 30°C to 300°C at a heating rate of 10°C / min. The obtained heat flow-temperature curves were analyzed using the instrument's software. The peak temperature (Tm) and enthalpy of fusion (ΔHm) of the melting peak were automatically calculated by the software. The enthalpy of fusion can be used to compare the relative changes in crystallinity between samples. Figure 1 The figures show the DSC curves of the substrates in Examples 1, 1, and 2 after plasma treatment with different powers. The results show that the PET substrate film of Example 1 exhibits a melting peak at approximately 255°C, and an additional melting peak at approximately 250°C. This peak is formed by chain dissociation of the PET surface due to plasma bombardment, resulting in surface recrystallization of shorter molecular chains. The PET substrate films of Comparative Examples 1 and 2 only show a single peak, indicating that no plasma treatment was performed or the plasma treatment energy was too low to induce surface recrystallization of the PET. Similarly, the PET substrate film of Comparative Example 4 also suffers from insufficient plasma treatment time, preventing chain dissociation on the surface.

[0061] Mechanical property testing: Standard tensile testing was conducted with a specimen width of 15 mm, an initial clamp spacing of 50 mm, and a tensile rate of 100 mm / min. The tests were performed automatically using a universal testing machine, and the tensile strength and elongation at break were recorded. Five samples were tested for each example and comparative example, and the average value was taken as the final result. The results are shown in Table 1.

[0062] Table 1

[0063] As shown in Table 1, comparing Examples 1, 2, and 4, it can be seen that by reasonably adjusting the plasma treatment power and the plasma treatment time per unit area of ​​the base film, the elongation at break can be significantly reduced while maintaining the tensile strength of the composite current collector. Comparing Examples 2, 6, 3, and 7, it can be seen that for composite current collectors of different specifications and using different substrates, the elongation at break can be controlled by reasonably adjusting the plasma treatment power and the plasma treatment time per unit area of ​​the base film. It should be noted that in Examples 3 and 5, the base film was damaged or torn after plasma treatment due to excessive plasma power or excessively long plasma bombardment time per unit area of ​​the substrate, making it impossible to effectively prepare the composite current collector product.

[0064] Adhesion test: Standard square samples with a side length of 100 mm were cut using a cutting machine and completely immersed in a 1 mol / L LiPF6 electrolyte in a self-sealing bag at 60℃. Samples were removed at 6h, 24h, 72h, 168h, and 360h, and a 180° peel test was performed on the surface coating using 3M brand 681 tape. The adhesion was determined based on the peel area, including: no peel, small peel area (peel area less than half the test area), large peel area (peel area not less than half the test area), and complete separation of the coating from the substrate. The test results are listed in Table 2.

[0065] Table 2

[0066] As shown in Table 2, the composite current collector samples of each embodiment exhibit better bonding strength compared to the comparative examples. This indicates that reasonable control of the plasma treatment power and time can not only adjust the elongation at break of the composite current collector but also further improve its bonding strength. Comparing Example 1, Comparative Example 1, and Example 2 with Comparative Example 1, it can be seen that whether or not plasma treatment is performed has a significant impact on the bonding strength of the composite current collector. Comparing Example 1, Comparative Example 2, and Comparative Example 4, it can be seen that reasonable control of the intensity and time of plasma treatment can further improve the bonding strength of the composite current collector. Comparing Example 3 and Comparative Example 7, reasonable control of the intensity and time of plasma treatment can also improve the bonding strength between the PP substrate and the coating.

[0067] Although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

[0068] Therefore, the above description is only a preferred embodiment of this application and is not intended to limit the scope of this application; that is, all equivalent modifications made in accordance with the scope of the claims of this application shall be within the protection scope of the claims of this application.

Claims

1. A method for adjusting the elongation at break of a composite current collector, characterized in that, Includes the following steps: Provide polymer film substrates; The polymer film substrate is placed in a vacuum roll-to-roll coating equipment; under vacuum conditions, the polymer film substrate is subjected to plasma bombardment treatment to regulate the degree of surface recrystallization. After plasma bombardment treatment, a metal conductive layer is deposited on at least one surface of the polymer film substrate to form a composite current collector.

2. The method according to claim 1, characterized in that, in, The plasma bombardment power is 1000W-3000W, and the plasma bombardment time per unit area of ​​polymer film substrate is 0.75-3s.

3. The method according to claim 1, characterized in that, The polymer film substrate is at least one of PET, PP, PI, and PPS.

4. The method according to claim 1, characterized in that, The thickness of the polymer film substrate does not exceed 15 μm.

5. The method according to claim 1, characterized in that, The plasma bombardment gas is at least one of Ar, O2, and N2, and the gas pressure is 0.1~1 Pa.

6. The method according to claim 1, characterized in that, The plasma bombardment uses a radio frequency plasma source, a microwave plasma source, or a DC plasma source.

7. A composite current collector obtained by the method according to any one of claims 1-6, characterized in that, The elongation at break of the composite current collector is reduced by 10% to 30% compared to the untreated composite current collector; the tensile strength of the composite current collector fluctuates by ≤±10% compared to the untreated composite current collector.

8. The composite current collector according to claim 7, characterized in that, The thickness of the metallic conductive layer is 0.5 μm. 1.5μm.

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