Composite current collector and vacuum full-dry preparation method thereof

Abstract

The invention relates to the technical field of lithium battery materials, and particularly discloses a composite current collector and a vacuum full-dry preparation method thereof, and the preparation method comprises the following steps: S1, pretreating a base material; s2, a metal base layer is deposited through magnetron sputtering; s3, plasma enhanced chemical vapor deposition of a metal thickening layer; and S4, a post-processing step. According to the method, magnetron sputtering and PECVD are continuously carried out in the same vacuum system, so that full-dry production is realized, and pollution caused by a water electroplating process is thoroughly abandoned. In the prepared composite current collector, the metal thickening layer deposited by PECVD is compact and uniform, the porosity is lower than 0.2%, and the composite current collector has excellent adhesive force, conductivity and corrosion resistance, is suitable for a lithium battery and other new energy battery current collectors, and can significantly improve the safety and prolong the cycle life of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium battery materials technology, specifically to a composite current collector and its vacuum dry preparation method. Background Technology

[0002] Current collectors are an important component of lithium batteries, serving to collect current and carry active materials. Traditional current collectors are mostly single metal foils, such as copper or aluminum foil. However, these current collectors are heavy and, under conditions of battery abuse (such as puncture or crushing), are prone to internal short circuits, thermal runaway, and even fire and explosion.

[0003] To address these issues, composite current collectors have emerged. Composite current collectors typically employ a "metal-polymer-metal" sandwich structure, with the middle layer being a polymer insulating material (such as polyethylene terephthalate (PET) or polypropylene (PP), and the top and bottom layers being conductive metal layers (such as copper or aluminum). This structure offers advantages such as light weight, high energy density, and good flexibility. In particular, when the battery suffers localized damage, its polymer substrate can rapidly melt and break, effectively preventing the spread of thermal runaway and significantly improving safety.

[0004] Currently, the metal coating process for composite current collectors mainly employs magnetron sputtering (as the underlayer) combined with electroplating (as the thickening layer). However, electroplating has the following inherent drawbacks: 1. Serious environmental pollution: Electroplating solutions contain a large number of heavy metal ions, complexing agents and organic additives, resulting in high wastewater treatment costs and significant environmental pressure.

[0005] 2. Complex process: It requires multiple processes such as pretreatment, activation, and multiple water washing, which is long and energy-intensive.

[0006] 3. Difficulty in controlling coating uniformity: On complex structures or large-sized substrates, it is difficult to ensure a high degree of uniformity in coating thickness, which affects product consistency and yield.

[0007] 4. Substrate limitations: Electroplating requires high chemical corrosion resistance of polymer substrates, and some high-performance polymers may not be suitable.

[0008] Therefore, developing a new composite current collector coating process that is green, efficient, produces high-quality coatings, and is applicable to a variety of substrates has become an urgent technical problem to be solved in this field. Summary of the Invention

[0009] The purpose of this invention is to overcome the shortcomings of existing electroplating processes and provide a new composite current collector coating process that is all-dry, environmentally friendly, efficient, and produces coatings with excellent performance.

[0010] To achieve the above objectives, the present invention adopts the following technical solution: A vacuum dry method for preparing a composite current collector includes the following steps: S1. Substrate pretreatment: Cleaning and activating the polymer film substrate; S2. Magnetron sputtering deposition of metal underlayer: In a vacuum environment, a dense metal underlayer is deposited on at least one side of the substrate using a magnetron sputtering process. S3. Plasma-enhanced chemical vapor deposition process for depositing a thick metal layer: After depositing the metal underlayer, while maintaining the vacuum environment, a metal-organic precursor and a reducing gas are introduced. The precursor is decomposed and reduced by plasma excitation, and a thick metal layer is deposited on the metal underlayer to form a thick metal layer. S4. Post-treatment: Anneal the deposited composite current collector.

[0011] Preferably, the magnetron sputtering process and the plasma-enhanced chemical vapor deposition process are carried out continuously in the same vacuum chamber or in series of vacuum chambers, without disrupting the vacuum in between.

[0012] More preferably, the magnetron sputtering process and the plasma-enhanced chemical vapor deposition process are performed continuously in the same vacuum chamber.

[0013] Preferably, in step S1, the substrate surface is subjected to plasma cleaning to remove surface contaminants and activate functional groups, thereby improving adhesion. Subsequently, the cleaned substrate is loaded into a vacuum coating apparatus.

[0014] Preferably, the polymer substrate comprises polyethylene terephthalate, polypropylene, polyimide, or polyethylene naphthalate.

[0015] Preferably, in step S2, an inert gas, preferably argon, is introduced.

[0016] Preferably, in step S2, the material of the metal underlayer is copper or aluminum, and the thickness is 50nm to 500nm; the working pressure of the magnetron sputtering process is 0.1 Pa to 2.0 Pa.

[0017] Preferably, in step S3, the organometallic precursor is a copper organometallic compound or an aluminum organometallic compound; wherein, copper trifluoroacetylacetonate or copper hexafluoroacetylacetonate is used when depositing the copper layer, and trimethylaluminum is used when depositing the aluminum layer.

[0018] Preferably, in step S3, the organometallic precursor is a volatile organometallic compound.

[0019] Preferably, in step S3, the reducing gas is hydrogen or an inert gas.

[0020] Preferably, in step S3, the inert gas is Ar.

[0021] Preferably, in step S3, the reducing gas is hydrogen, and the flow ratio of hydrogen to the organometallic precursor is 5:1-15:1.

[0022] Preferably, in step S3, plasma is generated by excitation with radio frequency (RF) or microwave power supply, causing the metal precursor gas to decompose in the plasma environment. The metal atoms are reduced and deposited on the underlayer to form a thickened layer with high purity and high density.

[0023] Preferably, in step S3, the plasma is excited by a radio frequency power supply with a power of 200W-1500W; the working pressure of the plasma-enhanced chemical vapor deposition process is 1 Pa-50 Pa.

[0024] Preferably, in step S3, the thickness of the metal thickening layer is 1μm-5μm.

[0025] Preferably, in step S4, the annealing temperature is 100°C to 300°C, the treatment time is 10 minutes to 120 minutes, and the treatment atmosphere is nitrogen or an inert gas atmosphere. The purpose of annealing is to eliminate internal stress and improve the crystallinity and conductivity of the coating.

[0026] The present invention also provides a composite current collector prepared according to the vacuum dry method, comprising: Polymer film substrate; A metal underlayer formed on at least one side of the substrate; A thickened metal layer formed on the metal underlayer; The metal thickening layer is formed by plasma-enhanced chemical vapor deposition; the porosity of the metal thickening layer in the composite current collector is less than 0.2%.

[0027] The present invention also provides a lithium battery, which uses the aforementioned composite current collector as the positive electrode current collector and / or negative electrode current collector.

[0028] A vacuum dry method for preparing a composite current collector is characterized in that a metal underlayer is deposited on at least one surface of a polymer substrate by magnetron sputtering; and a metal thickening layer is deposited on the metal underlayer by plasma-enhanced chemical vapor deposition.

[0029] Compared with the prior art, the beneficial technical effects of this invention are reflected in: 1. All-dry process, green and environmentally friendly: It completely abandons the traditional water electroplating process. The entire process is completed in a vacuum environment, with no wastewater or waste liquid discharge, which is in line with the development trend of green manufacturing.

[0030] 2. Excellent coating quality: Strong adhesion: The magnetron sputtering underlayer has good adhesion to the polymer substrate, providing a solid foundation for the PECVD thickening layer.

[0031] High density: The PECVD process can form a dense, pinhole-free film at a lower temperature, avoiding the porosity and impurity problems common in electroplating, and has better conductivity and corrosion resistance.

[0032] Good uniformity: Plasma has excellent spatial uniformity, making it particularly suitable for uniform coating on ultra-thin, flexible or three-dimensional substrates, resulting in high product consistency and yield.

[0033] 3. High process integration and high efficiency: MS and PECVD can be carried out continuously in the same vacuum chamber or in series chambers, reducing intermediate links such as air breaking and transmission, improving production efficiency, and making it easy to realize large-scale continuous roll-to-roll production.

[0034] 4. Wide applicability of substrates: As it is a low-temperature process and there is no chemical liquid corrosion, this method can be applied to various new polymer substrates that are sensitive to wet processing and high temperature, such as PI (polyimide) and PEN, thus expanding the range of materials to be selected for composite current collectors.

[0035] 5. Enhanced safety: The dense and uniform metal layer deposited by PECVD is firmly bonded to the substrate, further improving the structural stability and safety of the composite current collector during battery use. Attached Figure Description

[0036] Figure 1 This is a schematic diagram of the composite current collector structure prepared in Example 1.

[0037] Figure reference numerals: 1. Base film layer; 2. Underlayment layer; 3. Thickening layer. Detailed Implementation

[0038] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0039] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0040] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0041] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0042] The raw materials used in the examples and comparative examples are commercially available conventional materials.

[0043] Example 1: like Figure 1 As shown, in this embodiment, a PET film with a thickness of 4μm is used as the base film layer 1.

[0044] 1: The PET film is cleaned by Ar plasma and then transferred to the vacuum coating system.

[0045] 2: Under an argon atmosphere of 0.5 Pa, a 100 nm thick underlayer was deposited on one side of the PET using a copper target and DC magnetron sputtering. The sputtering power was 5 kW.

[0046] 3. In the same chamber, maintain a vacuum and adjust the chamber pressure to 10 Pa. Introduce vaporized copper trifluoroacetylacetone precursor and hydrogen gas, with an H2 to precursor flow rate ratio of 10:1. Turn on a 13.56 MHz RF power supply at 800 W and perform PECVD deposition. The deposition time is 30 minutes, resulting in a thickened layer with a thickness of 2 μm.

[0047] 4: Flip the film over and repeat steps 2 and 3 to deposit the same underlayer 2 and thickening layer 3 on the other side.

[0048] 5: Finally, the sample was annealed at 150°C under a nitrogen atmosphere for 30 minutes.

[0049] Example 2: A PET film with a thickness of 4μm was used as the substrate.

[0050] 1: The PET film is cleaned by Ar plasma and then transferred to the vacuum coating system.

[0051] 2: Under an argon atmosphere of 0.5 Pa, a copper underlayer with a thickness of approximately 100 nm was deposited on the PET side by DC magnetron sputtering using a copper target. The sputtering power was 5 kW.

[0052] 3. In the same chamber, maintain a vacuum and adjust the chamber pressure to 10 Pa. Introduce vaporized copper trifluoroacetylacetone precursor and hydrogen gas, with an H2 / precursor flow ratio of approximately 8:1. Turn on a 13.56 MHz RF power supply at 1000 W and perform PECVD deposition. The deposition time is 20 minutes, resulting in a copper thickened layer with a thickness of approximately 2 μm.

[0053] 4: Flip the film over and repeat steps 2 and 3 to deposit a copper layer with the same structure on the other side.

[0054] 5: Finally, the sample was annealed at 150°C under a nitrogen atmosphere for 30 minutes.

[0055] Example 3: A PET film with a thickness of 4μm was used as the substrate.

[0056] 1: The PET film is cleaned by Ar plasma and then transferred to the vacuum coating system.

[0057] 2: Under an argon atmosphere of 0.2 Pa, a copper underlayer with a thickness of approximately 150 nm was deposited on the PET side by DC magnetron sputtering using a copper target. The sputtering power was 3 kW.

[0058] 3. In the same chamber, maintain a vacuum and adjust the chamber pressure to 10 Pa. Introduce vaporized copper trifluoroacetylacetone precursor and hydrogen gas, with an H2 / precursor flow ratio of approximately 8:1. Turn on a 13.56 MHz RF power supply at 600 W and perform PECVD deposition. The deposition time is 40 minutes, resulting in a copper thickened layer with a thickness of approximately 2 μm.

[0059] 4: Flip the film over and repeat steps 2 and 3 to deposit a copper layer with the same structure on the other side.

[0060] 5: Finally, the sample was annealed at 150°C under a nitrogen atmosphere for 30 minutes.

[0061] Comparative Example: Magnetron sputtering combined with electroplating process 1: A PET film with a thickness of 4 μm, identical to that in Example 1, was used as the substrate. After plasma cleaning, a copper underlayer with a thickness of approximately 100 nm was deposited on one side of the film under the same magnetron sputtering equipment and process parameters (DC power 5kW, argon pressure 0.5 Pa).

[0062] 2: Thickening through electroplating. The substrate that has been primed undergoes a series of pretreatments, including water washing, acid pickling, and activation.

[0063] 3. Place the treated substrate into a standard acidic copper sulfate electroplating solution with a current density of 3A / m. 2At a temperature of 25°C, by controlling the electroplating time, a copper thickening layer with a target thickness of 2µm is deposited.

[0064] 4. After electroplating, perform multiple water washing and drying processes.

[0065] 5: Repeat steps 1, 2, and 3 to deposit a copper layer with the same structure on the other side of the substrate.

[0066] 6: To ensure a fair comparison, the comparative sample was also annealed at 150°C in a nitrogen atmosphere for 30 minutes.

[0067] Performance comparison test and data analysis The performance of the composite current collectors prepared in Examples 1-2 and the comparative example was tested, and the test results are shown in Table 1.

[0068] The test method for porosity is GB / T6462-2005; The test method for adhesion is GB / T9286-2021; The test method for sheet resistance is SJ / T11480-2015; The test method for corrosion resistance is GB / T10125-2021.

[0069] Table 1

[0070] The data above show that the copper layers prepared in Examples 1-3 have extremely low porosity (all less than 0.2%, with Example 3 even below 0.05%), far lower than the 0.5%-1.5% of the comparative electroplating process. This directly results in excellent corrosion resistance. In the CuSO4 spray test, the samples of this invention (Examples 1-3) remained corrosion-free for 48-72 hours, while the comparative samples showed oxidation dark spots after 36 hours, proving that the coating formed by the PECVD process is denser and can effectively isolate corrosive media.

[0071] The adhesion test results of all embodiments of the present invention were the highest level 5B (no peeling), while the comparative example was only 4B (slight peeling at the edges). This indicates that the bonding between the magnetron sputtering underlayer and the PECVD thickened layer, as well as between the overall coating and the PET substrate, is stronger and the structure is more stable under the process of the present invention.

[0072] Although the average sheet resistance of the embodiments of the present invention is similar to that of the comparative examples, the sheet resistance fluctuation range of the embodiments of the present invention is significantly smaller than that of the comparative examples. This demonstrates that the PECVD process has excellent spatial uniformity, enabling the production of products with higher electrical performance consistency, which is beneficial for improving the consistency of battery packs.

[0073] The comparative example uses the commonly used "magnetron sputtering + electroplating" process in the industry as a reference. Experimental data fully demonstrates that the all-dry alternative route adopted in this invention not only has an absolute advantage in environmental protection, but also fully meets or surpasses the traditional wet process in key coating quality indicators (density, adhesion, uniformity), achieving a unity of "green" and "high performance".

[0074] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. All equivalent implementations or modifications that do not depart from the present invention should be included within the scope of the technical solution of the present invention.

[0075] It should be particularly noted that the various embodiments listed in this specification and accompanying drawings are intended to illustrate the technical solutions and advantages of the present invention, and not to limit the scope of protection of the present invention. Without departing from the core ideas and technical effects of the present invention, those skilled in the art can make any form of improvement, substitution, combination, or modification to the structural arrangement, process parameters, material selection, control logic, etc., of the described embodiments; any obvious changes based on the same concept should be considered equivalent solutions of the present invention and should be included within the scope of protection defined by the claims of the present invention. The actual scope of protection of the present invention is determined by the appended claims and should be correctly understood in conjunction with the specification and accompanying drawings.

Claims

1. A vacuum dry method for preparing a composite current collector, characterized in that, Includes the following steps: S1. Substrate pretreatment: Cleaning and activating the polymer film substrate; S2. Magnetron sputtering deposition of metal underlayer: In a vacuum environment, a dense metal underlayer is deposited on at least one side of the substrate using a magnetron sputtering process. S3. Plasma-enhanced chemical vapor deposition process for depositing a thick metal layer: After depositing the metal underlayer, while maintaining the vacuum environment, a metal-organic precursor and a reducing gas are introduced. The precursor is decomposed and reduced by plasma excitation, and a thick metal layer is deposited on the metal underlayer to form a thick metal layer. S4. Post-treatment: Anneal the deposited composite current collector.

2. The preparation method according to claim 1, characterized in that, The magnetron sputtering process and the plasma-enhanced chemical vapor deposition process are performed continuously in the same vacuum chamber or in series of vacuum chambers.

3. The preparation method according to claim 1, characterized in that, In step S2, the material of the metal substrate is copper or aluminum, and the thickness is 50nm to 500nm; the working pressure of the magnetron sputtering process is 0.1 Pa to 2.0 Pa.

4. The preparation method according to claim 1, characterized in that, In step S3, the organometallic precursor is a copper organometallic compound or an aluminum organometallic compound; wherein, copper trifluoroacetylacetonate or copper hexafluoroacetylacetonate is used when depositing the copper layer, and trimethylaluminum is used when depositing the aluminum layer.

5. The preparation method according to claim 1, characterized in that, In step S3, the reducing gas is hydrogen, and the flow ratio of hydrogen to the organometallic precursor is 5:1-15:

1.

6. The preparation method according to claim 1, characterized in that, In step S3, a radio frequency power supply is used to excite the plasma, with a radio frequency power of 200W-1500W; the working pressure of the plasma-enhanced chemical vapor deposition process is 1 Pa-50 Pa.

7. The preparation method according to claim 1, characterized in that, In step S3, the thickness of the metal thickening layer is 1μm-5μm.

8. The preparation method according to claim 1, characterized in that, In step S4, the annealing temperature is 100°C to 300°C, the treatment time is 10 minutes to 120 minutes, and the treatment atmosphere is nitrogen or an inert gas atmosphere.

9. A composite current collector prepared by the vacuum dry method according to any one of claims 1 to 8, characterized in that, include: Polymer film substrate; A metal underlayer formed on at least one side of the substrate; A thickened metal layer formed on the metal underlayer; The metal thickening layer is formed by plasma-enhanced chemical vapor deposition; the porosity of the metal thickening layer in the composite current collector is less than 0.2%.

10. A lithium battery, characterized in that, The composite current collector as described in claim 9 is used as the positive current collector and / or negative current collector.

Images