Method for preparing composite current collector, composite current collector and lithium ion battery

Abstract

This application discloses a method for preparing a composite current collector, the composite current collector itself, and a lithium-ion battery. The method for preparing the composite current collector includes: forming a first current collector layer on a first surface of a polymer base film using magnetron sputtering and vacuum evaporation processes; creating vias on a second surface of the polymer base film opposite to the first surface using a non-thermal plasma etching method, forming through-holes that penetrate only the polymer base film, wherein the maximum etching temperature during the via-forming process is lower than the melting temperature of the polymer base film; and forming a second current collector layer on the second surface of the polymer base film and within the through-holes using vacuum evaporation and electroplating processes, thereby obtaining the composite current collector. This application at least solves the problems of thermal damage during via-forming, incompatibility with low-melting-point heat-sensitive substrates such as PP, and limited control over pore size and shape in existing composite current collectors.

Description

Technical Field

[0001] This application relates to the field of battery technology, and more specifically, to a method for preparing a composite current collector, the composite current collector, and a lithium-ion battery. Background Technology

[0002] In related technologies, porous composite current collectors have emerged to further improve the conductivity of composite current collectors. The preparation of through holes in existing porous composite current collectors mostly adopts laser technology. However, when using laser technology to create holes, the following problems exist: (1) Thermal damage problem: The laser ablation process generates a heat-affected zone at the edge of the hole, which leads to local melting, carbonization or microcracks of the polymer base film, affecting the adhesion strength and interface reliability of the subsequent metal coating on the inner wall of the through hole. (2) Poor material versatility: The thermal stability of polypropylene (PP) base film is poor, with a melting point of only about 170°C. Under the thermal influence of laser drilling, it is very easy to undergo thermal shrinkage and melting deformation, resulting in loss of control of hole morphology. (3) Limited control of hole diameter and hole shape: Laser drilling is difficult to achieve through holes with a depth-to-width ratio greater than 5:1, and the hole wall roughness is high, which is not conducive to uniform metal coating deposition. Summary of the Invention

[0003] The main objective of this application is to provide a method for preparing a composite current collector, the composite current collector, and a lithium-ion battery, so as to solve the problems of thermal damage during pore formation, inability to adapt to low-melting-point heat-sensitive substrates such as PP, and limited control of pore size and shape in the existing composite current collector.

[0004] According to one aspect of this application, a method for preparing a composite current collector is provided, comprising: Based on magnetron sputtering and vacuum evaporation processes, a first current collection layer is formed on the first surface of the polymer base film; Based on a non-thermal plasma etching method, a hole is formed from the second surface of the polymer base film opposite to the first surface, forming a through hole that penetrates only the polymer base film. During the hole formation process, the highest etching temperature is lower than the melting temperature of the polymer base film. A second current collector layer is formed on the second surface of the polymer base film and within the through-hole based on vacuum evaporation and chemical electroplating processes to prepare a composite current collector.

[0005] Furthermore, prior to the pore-forming step of the polymer-based film, the method for preparing the composite current collector further includes: The second surface of the polymer-based film is activated and modified using the non-thermal plasma etching method described above.

[0006] Furthermore, the non-thermal plasma etching method includes atmospheric pressure micro-plasma jet etching technology or low-temperature low-pressure plasma etching technology; Wherein, when the non-thermal plasma etching method is atmospheric pressure micro-plasma jet etching technology, the process gas is air or an oxygen-enriched mixed gas, and the volume concentration of oxygen in the oxygen-enriched mixed gas is 40% to 100%; When the non-thermal plasma etching method is a low-temperature, low-pressure plasma etching technique, the process gas includes oxygen and fluorine-containing gas, and the molar ratio of oxygen to fluorine-containing gas is 2:1 to 10:1.

[0007] Furthermore, the step of creating pores in the polymer-based film is performed on a roll-to-roll continuous production line, including: The polymer-based film is controlled to pass through the plasma etching cavity at a speed of 0.1 m / min to 20 m / min; Atmospheric pressure plasma is generated by applying a high-frequency electric field using multiple nozzle electrode arrays, or low-pressure plasma is generated by applying a high-frequency electric field using a single mask chamber, thereby forming a regular array of through holes on the polymer base film; The gas composition and radio frequency bias of the plasma source in the plasma etching cavity are adjusted to control the shape and anisotropy ratio of the via.

[0008] Furthermore, the roll-to-roll continuous production line includes: The membrane is equipped with an air flotation guide device and a tension control device to control the tension of the polymer-based membrane to be 0.2 N / cm to 1.0 N / cm; and / or, An online optical inspection module is configured to detect in real time at least one of the following: the etching depth of the hole, the hole diameter, the hole spacing, and the running speed of the polymer base film.

[0009] Furthermore, in the pore-forming step of the polymer-based film: The diameter of the through hole is 2μm to 100μm; The spacing between the through holes is 10μm to 2000μm; The aspect ratio of the through hole is 1:1 to 10:1; The projection of the through-hole onto the polymer base film is circular, elliptical, rectangular, or polygonal.

[0010] Furthermore, the polymer-based film includes at least one of polyethylene phthalate-based film, polypropylene-based film, and polyimide-based film.

[0011] Furthermore, after forming the second current collection layer, the method for preparing the composite current collector further includes: By setting an etching protective layer or a masking film, based on wet chemical etching or low-temperature plasma micro-etching, a portion of the metal in the via and the metal on the second current collector layer on the side of the via away from the first current collector layer are selectively removed, forming a partitioned metal retention area and a metal removal area on the second surface of the polymer base film, thus forming a composite current collector with a partitioned wiring pattern.

[0012] Secondly, this application provides a composite current collector, which is prepared using the above-described method for preparing composite current collectors.

[0013] Thirdly, this application provides a lithium-ion battery in which the aforementioned composite current collector is used as the negative electrode current collector.

[0014] In this application, a first current collector layer is formed on a polymer substrate film using magnetron sputtering and vacuum evaporation processes. Then, vias are created on the polymer substrate film using a non-thermal plasma etching method. During via creation, the maximum etching temperature is lower than the melting temperature of the polymer substrate film, eliminating the heat-affected zone (HAZ). This fundamentally solves the thermal damage problems of melting, carbonization, and microcracks in the polymer substrate film caused by laser via creation, effectively improving the adhesion strength and interface reliability of the metal coating on the inner wall of the via. Simultaneously, the non-thermal plasma etching method is suitable for low-melting-point heat-sensitive substrates such as polypropylene (PP), avoiding thermal shrinkage and melting deformation of the substrate, significantly broadening the applicability of polymer substrates. Furthermore, non-thermal plasma chemical etching allows for precise control of the aperture and shape, facilitating the fabrication of high aspect ratio vias with a depth-to-width ratio greater than 5:1. Moreover, in this application, by forming vias that penetrate only the polymer substrate film, the first current collector layer physically blocks the vias, preventing leakage during subsequent active material coating. Attached Figure Description

[0015] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, are illustrative and descriptive, serving to explain this application and do not constitute an undue limitation thereof. In the drawings: Figure 1 This is a schematic flowchart of a method for preparing a composite current collector disclosed in an embodiment of this application; Figure 2 This is a cross-sectional view of a composite current collector disclosed in an embodiment of this application; Figure 3 This is a side view of a composite current collector disclosed in an embodiment of this application.

[0016] The above figures include the following reference numerals: 10. Polymer base film; 11. Through-hole; 20. First current collector layer; 30. Second current collector layer. Detailed Implementation

[0017] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0018] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0019] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following figures denote similar items; therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0020] As described in the background section, in related technologies, the fabrication of vias on polymer-based films often employs laser technology. This technology suffers from thermal damage to the polymer-based film, poor material versatility, and limited control over pore diameter and shape during the via formation process, which is detrimental to uniform metal coating deposition. Therefore, this application provides a novel method for preparing a composite current collector. This method uses a non-thermal plasma etching method instead of laser drilling, with the maximum etching temperature lower than the melting temperature of the polymer-based film, thus avoiding the aforementioned adverse effects on the polymer-based film. The preparation method of the composite current collector of this application will be described below with reference to the accompanying drawings.

[0021] See Figures 1 to 3 As shown, this application provides a method for preparing a composite current collector.

[0022] Specifically, in this application, the composite current collector is a copper composite current collector, and the preparation method of the composite current collector includes: Step 1: Based on magnetron sputtering and vacuum evaporation processes, a first current collector layer 20 is formed on the first surface of the polymer base film 10.

[0023] Specifically, in this step, a clean polymer base film 10 is first unwound and placed in a magnetron sputtering cavity. A copper layer is deposited on the first surface of the polymer base film 10 as a seed layer by magnetron sputtering. For example, the thickness of the seed layer can be 20 nm to 30 nm. In this application, copper metal is sputtered onto the polymer base film 10, and the embedding effect formed by its high-energy particles ensures that the metal layer and the polymer base film 10 are firmly bonded, forming a basic conductive layer with high adhesion. Although the film layer generated by magnetron sputtering is dense and has strong adhesion, the deposition rate is slow. Vacuum evaporation can quickly thicken the copper layer, and the copper layer is uniform. It is simple to operate and has low cost. Therefore, the copper layer on the seed layer is then thickened to a predetermined thickness by vacuum evaporation, for example, the thickness can be 0.5 μm to 1.0 μm, forming a continuous conductive metal layer, which is the first current collector layer 20.

[0024] In other words, in the first step, the first current collector layer 20 is prepared by using a low-temperature physical vapor deposition process of magnetron sputtering and vacuum evaporation to form a composite coating. The coating adheres firmly and has a uniform and dense thickness, which can ensure the stability of subsequent steps. At the same time, by using magnetron sputtering and vacuum evaporation processes, the temperature rise of the polymer base film 10 is controllable, and it will not cause thermal deformation or thermal shrinkage to the low-melting-point polymer base film 10, thus ensuring compatibility with subsequent steps.

[0025] Furthermore, in this application, the polymer base film 10 includes at least one of polyethylene phthalate (PET) base film, polypropylene (PP) base film, and polyimide (PI) base film. Of course, in other embodiments of this application, the polymer base film 10 can also be a polyethylene base film, polystyrene film, polyvinyl chloride film, or polycarbonate film, etc. No specific limitation is made in this application; in actual production, an adaptive selection can be made according to requirements.

[0026] After the first current collector layer 20 is prepared on the first surface of the polymer base film 10 by magnetron sputtering and vacuum evaporation, the second step is then performed, specifically: Step 2: Based on the non-thermal plasma etching method, holes are formed on the second surface of the polymer base film 10 that is opposite to the first surface, forming through holes 11 that penetrate only the polymer base film 10. During the hole formation process, the highest etching temperature is lower than the melting temperature of the polymer base film 10.

[0027] It is understood that in this application, non-thermal plasma etching, also known as non-equilibrium low-temperature plasma dry etching (i.e., cold chemical etching), is a cold processing technology that relies on active free radical chemical etching in non-equilibrium plasma and low-energy ion-assisted bombardment to remove polymer materials. Its electron temperature ranges from several thousand to tens of thousands of degrees Celsius, but the temperature of ions, gas molecules, and the overall temperature of the processed substrate film is lower than the polymer melting temperature. There is no macroscopic high-temperature heat source throughout the process, distinguishing it from the thermal processing method of laser melting and ablation. Its etching mechanism includes: chemical primary etching and ion-assisted morphology control. Among these, chemical primary etching involves the ionization of process gas by a high-frequency electric field to generate a large amount of O. F Active free radicals attack the C-C and CH chemical bonds of the polymer, decomposing the polymer into gaseous small molecules that are then removed by gas flow / vacuum, thus achieving material removal. Ion-assisted morphology control involves an electric field accelerating low-energy ions to vertically impact the polymer substrate film 10 surface, breaking the passivation layer of byproducts on the pore walls, inhibiting lateral corrosion, and controlling the anisotropy and aspect ratio of the vias 11. The entire etching process does not rely on high-temperature melting of the substrate, eliminating thermal damage issues such as melting and carbonization.

[0028] Specifically, in this application, the non-thermal plasma etching method includes atmospheric pressure micro-plasma jet etching technology or low-temperature low-pressure plasma etching technology.

[0029] Atmospheric pressure micro-plasma jet etching technology refers to high-frequency discharge under normal pressure, using air / high-concentration oxygen-rich gas as the process gas. Plasma is ejected from a nozzle to form a jet, which is used for targeted and localized etching of openings. No vacuum chamber is required, making it suitable for selective hole creation in zones and arrays. The etching medium in atmospheric pressure micro-plasma jet etching technology uses only oxygen-containing systems, without corrosive fluorine-containing gases, resulting in low production costs, low equipment corrosion requirements, and simple exhaust gas treatment. Furthermore, the high-concentration oxygen ionization generates a large number of oxygen free radicals, achieving chemical cold etching of polymer base films through oxidation bond breaking. The entire process temperature is below the substrate melting temperature, preventing low-melting-point substrates such as PP base films from melting, shrinking, or deforming due to heat, thus fundamentally avoiding laser thermal carbonization and thermal cracking defects.

[0030] Furthermore, in this application, the volume concentration of oxygen in the oxygen-enriched mixed gas is 40% to 100%. When the oxygen content is within this range, it ensures sufficient free radical concentration, stable etching rate, uniform etching of the inner wall of the through-hole 11, and no local over-etching or under-etching. In this way, excessive gas source waste can also be avoided, there is no carbonized deterioration layer on the hole wall, and the adhesion of the metal coating is greatly improved when the second current collector layer 30 is subsequently plated on the inner wall of the through-hole 11.

[0031] Low-temperature, low-pressure plasma etching technology involves evacuating a sealed chamber to a low-pressure vacuum and using an oxygen-fluorine mixed gas as the process gas. This allows for uniform plasma etching across the entire surface, precisely fabricating high aspect ratio straight-walled vias 11, suitable for large-area mass production. Furthermore, the low-pressure environment enables directional and accelerated ion bombardment, allowing for controllable anisotropy of the etching. The vias 11 have steep sidewalls and high diameter consistency, which facilitates uniform film formation of the second current collector layer 30 on the inner wall of the via, ensuring the conductivity stability of the upper and lower current collector layers.

[0032] Furthermore, in the low-temperature, low-pressure plasma etching technology, the molar ratio of oxygen to fluorine-containing gas in the process gas is 2:1 to 10:1. For example, the fluorine-containing gas can be CF4, SF6, etc. It is understood that in this etching technology, O2 oxidizes the polymeric hydrocarbon framework, while the fluorine-containing gas breaks the CC and CN chemical bonds. The two gases work together to achieve controllable etching. Limiting the O2:fluorine-containing gas ratio to 2:1 to 10:1, a higher oxygen content can suppress excessive fluorination of the hole walls, forming a dense passivation film, ensuring continuous longitudinal etching, and easily preparing high aspect ratio straight-walled vias with an aspect ratio greater than 5:1, overcoming the shortcomings of lasers in preparing high aspect ratio micropores and excessively large hole taper. Simultaneously, limiting the molar ratio of oxygen to fluorine-containing gas within the above range can avoid excessive fluorine-containing gas, which could lead to excessive sidewall passivation causing etching stagnation and insufficient via depth; it can also avoid an excessively high oxygen content, which could exacerbate lateral free radical corrosion, resulting in hole enlargement and deterioration of anisotropy.

[0033] In actual production, by controlling the gas composition and bias settings, the high aspect ratio etching morphology is significantly improved, avoiding rough hole walls and sidewall deposition. For example, precise control of the O2 / CF4 mixing ratio can suppress polymer byproduct deposition on the hole sidewalls while etching the polymer, keeping the hole walls clean to facilitate metal coating deposition. Furthermore, this low-temperature, low-pressure plasma etching technology can simultaneously fabricate hundreds of through-holes

[11] without micro-nozzle clogging issues, making it suitable for large-scale production.

[0034] In actual production, customers can configure two etching gas source systems simultaneously: atmospheric pressure jet and low-pressure cavity. The choice can be made flexibly according to production needs: atmospheric pressure jet is used for small-scale, fixed-point through-hole processing, while low-pressure plasma is used for mass production of through-holes with high aspect ratios on a whole polymer base film. Both processes are non-thermal low-temperature etching, with processing temperatures below the melting point of the polymer. They are uniformly compatible with heat-sensitive substrates such as PP and PI, and comprehensively solve the technical pain points of existing laser drilling, such as thermal damage, narrow substrate applicability, and difficulty in controlling hole shape and aspect ratio.

[0035] Furthermore, since the melting point of the PP base film is approximately 170°C, it is extremely prone to melting and deformation under laser drilling conditions. In this application, the highest etching temperature is lower than the melting temperature of the polymer base film 10. Non-thermal plasma etching can efficiently complete the etching at low temperatures, fully adapting to various polymer base films 10 such as PP, PET, and PI, including low-melting-point / heat-sensitive substrates. Moreover, based on the non-thermal plasma etching method, this application achieves reliable through-hole fabrication 11 on the PP base film, breaking the mandatory requirement of laser drilling on the thermal stability of the substrate, expanding the range of material selection, and reducing the fabrication cost of the composite current collector.

[0036] In other words, in the second step, the polymer base film 10 is etched using a non-thermal plasma etching method. During the etch, the highest etching temperature is lower than the melting temperature of the polymer base film 10, resulting in no heat-affected zone. This fundamentally solves the thermal damage problems of melting, carbonization, and microcracks in the polymer base film 10 caused by laser etch, effectively improving the adhesion strength and interface reliability of the metal coating on the inner wall of the through-hole 11. Simultaneously, this design also reduces the fabrication cost of the composite current collector.

[0037] Furthermore, in this application, the first current collector layer 20 is formed before via formation, and this first current collector layer 20 covers the entire first surface of the polymer base film 10. In the second step, vias are formed from the second surface of the polymer base film 10 opposite to the first surface using a non-thermal plasma etching method, forming through holes 11 that only penetrate the polymer base film 10. The first current collector layer 20 will not be etched away (because the anisotropic etching direction is perpendicular to the first surface of the polymer base film 10, and the plasma etching rate of metal is much lower than that of the polymer base film 10). Thus, the first current collector layer 20 acts as a physical seal during the coating of active materials, effectively preventing slurry leakage from the through holes 11.

[0038] In this application, after creating vias using a non-thermal plasma etching method, a micro / nano structure can be formed on the surface of the via 11, and the inner wall of the via 11 is simultaneously micro-roughened, with good consistency and no slag residue. In contrast, after laser drilling, the hole wall is in a molten and then solidified state, resulting in a relatively smooth hole wall with obvious slag at the hole edge, which may affect the continuity of subsequent metal deposition. Furthermore, the non-thermal plasma etching method is a low-temperature process with a very small heat-affected zone, and the polymer base film 10 does not experience thermal deformation. Laser drilling, on the other hand, creates a heat-affected zone, and thin PET base films (e.g., 4μm–6μm) are prone to deformation or perforation.

[0039] It is worth noting that, in this application, before the pore-forming step of the polymer base film 10, the preparation method of the composite current collector further includes: activating and modifying the second surface of the polymer base film 10 based on a non-thermal plasma etching method. It is understood that the bombardment of high-energy particles in the plasma can simultaneously introduce polar functional groups such as –OH, –COOH, and –NH2 onto the polymer surface, significantly enhancing the chemical adsorption and adhesion of the polymer base film 10 to the subsequent metal coating.

[0040] It is understood that in this application, the surface activation of the polymer base film 10 and the etching of the through-hole 11 are completed continuously within the same set of non-thermal plasma processes, and the two processes rely on the same plasma environment to form a synergistic effect. Conventional single-sided plasma surface activation treatment can only build a surface interface bonding structure on the planar surface of the polymer base film 10; in this application, the activation modification of the inner wall of the through-hole 11 is completed simultaneously with the formation of the polymer base film 10, forming a modified interface on the planar surface of the polymer base film 10 and simultaneously generating an activated modified interface on the inner wall of the through-hole 11. The planar interface and the modified interface on the inner wall of the through-hole cooperate with each other, so that the subsequent deposition of metal coating can simultaneously form a composite bonding interface on both the second surface of the polymer base film 10 and the inner wall of the micropore. Compared with a single planar activation structure, it can increase the number of interface bonding sites between the coating and the polymer base film 10 from multiple dimensions and optimize the interface bonding structure between the coating and the polymer base film 10. The second surface of the polymer base film 10 and the through-hole 11 form a tight chemical bond, thereby improving the peel strength of the composite current collector.

[0041] Furthermore, the pore-forming step of the polymer base film 10 is performed on a roll-to-roll continuous production line (not shown in the figure). On the roll-to-roll continuous production line, "surface activation → selective pore-forming → electroplating thickening" can be achieved sequentially, enabling unattended mass production throughout the entire process, significantly improving production line utilization and yield. Specifically, the roll-to-roll continuous production line includes an unwinding and rewinding system, a plasma etching chamber, an air flotation guide device, and a real-time etching depth detection system. This roll-to-roll continuous production line is suitable for PET base films, PP base films, and PI base films with base film thicknesses ranging from 4.5μm to 9.0μm.

[0042] The unwinding and rewinding system includes an unwinding roller, a rewinding roller, and a tension control device. The unwinding roller loads a rolled polymer base film 10, which has a pre-formed first current collector, and releases the polymer base film 10 at a uniform speed. The rewinding roller rewinds the finished composite current collector, after all processing is complete. The tension control device maintains the tension of the polymer base film 10 at 0.2 N / cm to 1.0 N / cm (where tension refers to the tension across the width of the polymer base film 10), thus preventing wrinkles, stretching deformation, or breakage of the polymer base film 10 (e.g., 4.5 μm to 9.0 μm) during transit.

[0043] In the plasma etching chamber, Nx×Ny micro-nozzles (typically Nx = 8–32 columns, Ny = 1–4 rows) are arranged perpendicularly to the conveying direction of the polymer base film 10, and are staggered or parallel along the conveying direction. The etching direction starts from the second surface of the polymer base film 10 (i.e., the side opposite to the first surface of the polymer base film 10), forming through holes 11 that penetrate only through the polymer base film 10. Compared to laser drilling, where a single laser beam needs to scan each hole individually or where the galvanometer is limited to parallel operation, the processing efficiency decreases with higher hole density due to limitations in scanning speed. In this application, multiple nozzles are used for parallel etching, which improves the efficiency of creating holes in the polymer base film 10. At the same time, the Nx nozzles are arranged perpendicularly along the width direction of the polymer base film 10, and the position of each nozzle relative to the polymer base film 10 remains fixed. The lateral hole spacing is determined by the mechanical precision of the nozzle spacing and is not affected by fluctuations in the conveying speed of the polymer base film 10. Meanwhile, the staggered distribution reduces the airflow overlap area between adjacent nozzles in the belt conveyor direction, avoiding electromagnetic coupling between plasma jets that could lead to unstable discharge. It also prevents airflow interference from causing distortion of the etched via 11 shape or inconsistent etching rates, and avoids heat accumulation that could lead to excessive temperature rise in the localized polymer film 10. Furthermore, the Nx nozzles are uniformly distributed along the width of the polymer film 10, covering the entire effective area (e.g., for a 300mm wide film, 32 nozzles can cover the entire width). In other embodiments of this application, when the width of the polymer film 10 increases, only the number of transverse nozzles needs to be increased; there is no need to change the belt conveyor speed or the number of longitudinal nozzle rows, allowing for flexible production line upgrades.

[0044] Furthermore, an air-floating guide device is provided in the plasma etching chamber to spray clean gas to form an air cushion on the first surface of the polymer base film 10, allowing the polymer base film 10 to levitate and move without contact. This protects the first current-collecting layer 20 on the first surface of the polymer base film 10 from scratches or indentations caused by mechanical rollers.

[0045] During unwinding, the polymer base film 10 is controlled to pass through the plasma etching chamber at a speed of 0.1 m / min to 20 m / min. In actual production, the appropriate travel speed can be selected according to the selected polymer base film 10. Inside the plasma etching chamber, a high-frequency electric field is applied using a multiple nozzle electrode array to generate atmospheric pressure plasma, or a low-pressure plasma is generated by applying a high-frequency electric field using a single mask chamber, forming a regular array of through holes 11 on the polymer base film 10.

[0046] This method employs atmospheric pressure air micro-plasma jets, using air as the gas source, and constrains the discharge channel through quartz glass micro-nozzles to create masksless, selective, and high-precision pores in the polymer substrate film 10. The main process parameters are: the nozzle inner diameter ranges from 50μm to 500μm; for example, the nozzle inner diameter can be 50μm, 100μm, 250μm, or 500μm, etc., and the nozzle inner diameter determines the diameter accuracy of the etched holes. The operating voltage (i.e., RF power) ranges from 0.8kV to 3kV; for example, the operating voltage can be 0.8kV, 1.2kV, 2.0kV, 3.0kV, etc. In this application, the discharge current ranges from 0.5mA to 10mA to control the concentration of active species and etching efficiency. The distance between the polymer base film 10 and the nozzle ranges from 0.5 mm to 10 mm. Exemplarily, the distance can be 0.5 mm, 1.0 mm, 2.0 mm, 5 mm, and 10 mm, etc., and this distance affects the etching spot radius and etching rate. The etching time ranges from 10 s / hole to 120 s / hole. Exemplarily, the etching time can be 10 s / hole, 50 s / hole, and 120 s / hole, etc.

[0047] Furthermore, the high-frequency electric field applied to the single mask chamber generates low-pressure plasma, which is achieved by forming the entire polymer base film 10 through holes 11 in one go using the entire mask. The through hole 11 array has excellent size consistency, making it suitable for mass production of large batches of uniformly opened through holes with high aspect ratios 11.

[0048] In practical applications, multi-nozzle electrode arrays operate at atmospheric pressure, eliminating the need for a vacuum chamber. Their etching mechanism is purely chemical etching, exhibiting weak anisotropy (the ratio of vertical etching rate to horizontal etching rate). They offer high production efficiency and low cost, making them suitable for mass production lines with less stringent requirements on hole shape. In contrast, single-mask chambers operate at low pressure, requiring a vacuum system to maintain the pressure between 1.3 Pa and 6.7 Pa. Their etching mechanism is ion bombardment-assisted chemical etching, exhibiting strong anisotropy. The taper of the via 11 can be less than or equal to 5°, and the aspect ratio can be greater than 10:1. Due to the need for vacuuming, their production efficiency is moderate, and their production cost is high. They are suitable for scenarios with strict requirements on high aspect ratios and vertical hole shape. Both methods can achieve a regular via 11 array, meeting the basic requirement of double-sided conductivity for composite current collectors. In actual production, customers can flexibly choose according to their specific needs; this application does not impose specific limitations.

[0049] During the etching process, the gas composition and radio frequency bias of the plasma source in the plasma etching chamber need to be adjusted to control the shape and anisotropy ratio of the via 11. Specifically, when using atmospheric pressure micro-plasma jet etching technology, the etching rate and via morphology can be adjusted by regulating the gas composition. For example, adjusting the oxygen volume concentration within the range of 40% to 100% can regulate the etching rate (5 μm / min to 20 μm / min). Oxygen-rich conditions improve etching efficiency and are suitable for high-speed production of thin substrate films; lower oxygen concentrations (40%) reduce the rate. When using low-temperature, low-pressure plasma etching technology, the molar ratio of oxygen to fluorine-containing gas is 2:1 to 10:1. Fluorine-containing gases (such as CF4, SF6, etc.) provide F radicals, which can remove non-volatile byproducts (hydrocarbon fragments) generated during the etching process and prevent via wall deposition; at the same time, F radicals form a fluorocarbon passivation layer on the sidewall, which is key to anisotropic etching. The higher the proportion (the more CF4), the stronger the anisotropy, but too much will lead to a decrease in the etching rate; the lower the proportion (the less CF4), the more isotropic the etching becomes, and the smoother the hole walls.

[0050] In low-pressure plasma, after applying a radio frequency bias (e.g., 13.56 MHz, 100 W–300 W) to the polymer-based film 10, the positive ions (e.g., O2) in the plasma... + CF3 + The polymer substrate film 10 is accelerated and vertically bombarded. The anisotropy ratio refers to the ratio of the vertical etching rate to the horizontal etching rate. The higher the RF bias voltage, the greater the vertical bombardment energy of the ions, the more the sidewall passivation layer is continuously broken down, the vertical etching rate is much greater than the horizontal rate, the higher the anisotropy ratio, and the steeper the sidewall of the via 11. For example, a high bias voltage (200W~300W) can obtain a vertical via 11 with a high aspect ratio (greater than 10:1) and a taper of less than 5°, which is suitable for high-precision current collectors required for high-energy-density batteries. A low bias voltage (100W~200W) results in isotropic etching, and the sidewall of the via 11 has a certain taper (e.g., 10°~20°), with the orifice opening slightly larger than the bottom, which is beneficial for the subsequent flow of the electroless plating solution and metal deposition in the orifice.

[0051] Optionally, during the via fabrication process, an online optical inspection module is configured to detect in real time at least one of the following: the etching depth, aperture, spacing between vias, and the operating speed of the polymer base film 10. For example, the online optical inspection module may be an optical coherence tomography (OCT) system or a laser displacement sensor, providing real-time feedback on the etching time or base film speed of each nozzle, thereby enabling real-time online monitoring of at least one of the following: the etching depth, aperture, spacing between vias 11, and the operating speed of the polymer base film 10.

[0052] Furthermore, in the pore-forming step of the polymer base film 10, the diameter of the through-hole 11 is 2μm to 100μm. For example, the diameter of the through-hole 11 can be 2μm, 50μm, or 100μm. When the diameter of the through-hole 11 is greater than or equal to 2μm, it can ensure that there is sufficient coverage space on the inner wall of the hole, and the metal of the second current collector layer 30 can be continuously deposited, reliably connecting the upper and lower current collector layers and reducing the overall internal resistance of the current collector. If the pore diameter is too small, it is easy to cause pore blockage and interlayer disconnection. Moreover, if the diameter of the through-hole 11 is less than or equal to 100μm, it can avoid the precipitous drop in the mechanical strength of the base film caused by excessively large openings, and prevent the electrode from breaking during coating and rolling processes; at the same time, it can control the opening ratio, taking into account both electrolyte conductivity and the structural stability of the polymer base film 10.

[0053] Furthermore, the hole spacing of the via 11 is 10μm to 2000μm. For example, the hole spacing of the via 11 can be 10μm, 200μm, 1500μm, 2000μm, etc. When the hole spacing of the via 11 is within the above range, the hole spacing is not too dense, preventing short circuits in the interconnection of metal plating layers of adjacent vias 11, and ensuring the formation of the insulating isolation area when subsequent partition etching is used to prepare tab patterns with different resistivity. At the same time, the reserved area of ​​the non-porous polymer base film 10 is used as a tab welding position, which facilitates the subsequent selective removal of metal to construct conductive wiring; it also allows for flexible adjustment of the overall porosity, balancing conductivity and mechanical strength of the polymer base film 10.

[0054] Furthermore, the aspect ratio of the via 11 is 1:1 to 10:1. When the aspect ratio of the via 11 is greater than or equal to 1:1, it ensures that the via 11 has sufficient height to effectively penetrate the polymer base film 10, and that the metal of the hole wall achieves cross-layer conductivity. Simultaneously, the non-thermal plasma etching method used in this application allows for controlled etching to achieve a high aspect ratio via 11. Compared to existing laser drilling methods, which struggle to overcome the limitation of an aspect ratio of 5:1, this application demonstrates significant advantages. When the aspect ratio of the via 11 is within the above range, it avoids the problems of excessively narrow holes causing difficulties in coating and electrolyte blockage.

[0055] Optionally, the projection of the through-hole 11 onto the polymer base film 10 can be circular, elliptical, rectangular, or polygonal. This arrangement allows for flexible matching of different tab wiring layouts. Circular through-holes 11 are easy to process and control, with isotropic inner walls, resulting in uniform metal layer thickness distribution and consistent conductivity during electroless plating. Elliptical through-holes 11 can optimize conductivity or mechanical properties. When the major axis of the ellipse is aligned along a certain direction (e.g., the substrate film's travel direction), the current conduction cross-sectional area in that direction can be increased without increasing the aperture ratio, suitable for practical applications where current mainly flows along the tab direction in the electrode sheet. Simultaneously, the stress concentration factor of an ellipse is between that of a circle and a rectangle, and the aperture ratio can be improved while maintaining good mechanical strength by optimizing the major-to-minor axis ratio (e.g., 2:1). Furthermore, when the major axis of the ellipse is along the travel direction, the etching process can utilize the relative movement of the polymer base film 10 and the fixed position of the nozzle to naturally form elongated etching spots, eliminating the need to adjust the nozzle shape. Rectangular / polygonal through-holes 11 maximize the aperture ratio. Specifically, with the same hole spacing, the opening area of ​​rectangular or polygonal through-holes 11 is larger than that of circles, which can achieve lower current collector internal resistance at the same through-hole density. The array of rectangular through-holes 11 can form a grid-like structure, and the metal layers on the first and second surfaces of the polymer base film 10 are connected by the sidewalls of multiple parallel slits to form regular low-resistance channels.

[0056] After the via 11 is fabricated using a non-thermal plasma etching method, it is transported via a polymer base film 10 to the vacuum evaporation and chemical electroplating station for the third step operation.

[0057] Step 3: Based on vacuum evaporation and electroplating processes, a second current collector layer 30 is formed on the second surface of the polymer base film 10 and inside the through-hole 11 to prepare a composite current collector. Specifically, a continuous copper seed layer is uniformly deposited on the inner wall of the through-hole 11 and the second surface of the polymer base film 10 with an aspect ratio of 1:1 to 10:1 using vacuum evaporation. Since the polymer base film 10 itself is non-conductive, electroplating cannot deposit metal inside the through-hole 11 without evaporation as a base. The seed layer constructs a globally conductive substrate, and the subsequent electroplated metal grows uniformly along the seed layer. The plating layer on the inner wall of the through-hole 11 is complete and without breaks, stably achieving the connection between the first current collector layer 20 and the second current collector layer 30 through the metal inside the hole.

[0058] Understandably, vacuum evaporation is a low-temperature deposition process, which avoids the thermal melting and shrinkage of low-melting-point base films such as PP and PI films. Furthermore, the evaporated seed layer serves as a highly adhesive base layer, preventing the subsequent electroplated copper layer from peeling off. Simultaneously, the evaporated copper layer can cover contaminants on the inner wall of the through-hole 11, improving the stability of the composite current collector. Vacuum evaporation only prepares an ultra-thin seed layer, facilitating copper deposition during subsequent chemical electroplating. The subsequent chemical electroplating process allows for rapid thickening of the copper metal plating layer on top of the seed layer, increasing the overall metal thickness at low cost and effectively reducing the internal resistance of the current collector. This design avoids the high cost of pure evaporation and the limitation of pure electroplating being unable to deposit through holes.

[0059] Furthermore, for through-holes 11 with an aspect ratio greater than 5:1, the chemical plating solution is unable to completely wet the deep inner walls of the hole due to surface tension, easily resulting in uncoated blind areas at the bottom or middle of the sidewalls, leading to poor conductivity between the first current collector layer 20 and the second current collector layer 30. During vacuum evaporation, the long mean free path of copper vapor molecules (under low pressure) allows for deposition in a straight line, forming a continuous thin film even deep within the hole. First, an extremely thin layer of copper (e.g., 10nm–30nm) is deposited to ensure that the entire inner wall of the through-hole 11 is covered with copper. Subsequent chemical plating is then performed on this fully metallized surface; the plating solution only needs to wet the existing copper layer (no direct contact with the polymer is required), thus completely solving the problem of metallization of deep micro-holes.

[0060] Furthermore, the dense copper layer deposited first acts as a base layer, effectively preventing electrolyte from penetrating into the substrate / plating interface. Even if the subsequent chemical plating layer has micropores, the deposited layer can still function as a barrier layer, significantly improving the corrosion resistance and cycle life of the composite current collector.

[0061] Furthermore, after forming the second current collector layer 30, the method for preparing the composite current collector also includes: by setting an etching protective layer or a masking film, selectively removing part of the metal in the through hole 11 and the metal on the second current collector layer 30 on the side of the through hole 11 away from the first current collector layer 20 based on a wet chemical etching process or a low-temperature plasma micro-etching process, forming a metal retention area and a metal removal area arranged in a partition on the second surface of the polymer base film 10, thereby forming a composite current collector with a partition wiring pattern.

[0062] It is understandable that conventional composite current collectors have uniform conductivity across their entire surface. However, during battery operation, the current is mainly concentrated in the tab welding area (i.e., the metal retention area, which must withstand current densities several times higher than other areas), leading to localized heating and uneven current distribution, affecting the battery's rate performance and cycle life. This application addresses this by selectively removing metal from a portion of the through-holes 11 and the metal on the second current collector layer 30 in the non-tab area (i.e., the metal removal area). In the area where metal is removed, the first and second surfaces of the polymer base film 10 are disconnected and separated via the metal pathway of the through-holes 11, forming a metal retention area and a metal removal area on the surface of the same composite current collector. The area where the metal is completely retained is the high-conductivity tab welding area, while the metal removal area forms a low-conductivity / insulating isolation area. This eliminates the need for subsequent cutting and applying insulating adhesive, simplifying the tab processing steps. By creating in-situ partitioning of the composite current collector surface to form high and low conductivity zones and an integrally formed tab wiring structure, the current distribution of the battery is optimized, thereby improving the performance of the lithium battery.

[0063] The specific process steps are as follows: (1) Zoned protection: deploying masks or etching protective layers On the surface of the second current collector layer 30, a masking film or an etch-resistant protective layer is applied to the locations where metal needs to be retained and where it is used as a high-conductivity area for the electrode tabs; areas requiring insulation are exposed without protection. The protective layer can be photoresist, peelable adhesive, etc., and the mask can be a metal mask with a specific pattern, with the cutout areas corresponding to the areas where metal needs to be removed, or a polymer mask (such as laser-cut polyimide film).

[0064] (2) Selective etching to remove metal Wet chemical etching or low-temperature plasma micro-etching is used to etch the exposed areas: ① The surface metal of the second current collector layer 30 at the exposed location is etched away; ②The metal inside the corresponding through hole 11 is simultaneously etched and stripped away, and the first current collector layer 20 and the second current collector layer 30 at this location lose their conductive connection channel; ③In the area shielded by the protective layer, the surface metal and the inner wall metal of the through hole 11 are fully protected and completely preserved.

[0065] (3) Remove the protective layer / mask and form the partitioned pattern. After removing the protective layer / mask, the metal in the area covered by the protective layer is intact, and the first current collector layer 20 and the second current collector layer 30 are conductive, forming a high-conductivity electrode tab connection area. In the exposed etched area, the metal in the second current collector layer 30 and the via 11 is missing, and the first current collector layer 20 and the second current collector layer 30 are disconnected, forming an insulating isolation area. The high and low conductivity areas are arranged alternately to obtain the differential conductivity electrode tab connection pattern required by the design.

[0066] Of course, the above-mentioned method for preparing composite current collectors can be used not only to prepare copper composite current collectors, but also to prepare aluminum composite current collectors as battery positive electrodes, and silver composite current collectors for special applications. It is worth noting that during the preparation process, it is sufficient to select a metal and plating solution that are compatible with the current collector to be prepared.

[0067] To verify the technical effects of this application, the following specific embodiments are provided: Example 1 1. Materials The polymer base film 10 is a PET base film with a thickness of 6.0 μm and a width of 300 mm.

[0068] First current collector layer 20: magnetron sputtered Cu, with a thickness of 20nm to 50nm; vacuum evaporation deposited Cu film, with a thickness of 1.0μm.

[0069] Plasma gas source: atmospheric pressure air.

[0070] Second current collector layer 30: vacuum evaporation + chemical Cu plating, with a thickness of 1.0 μm.

[0071] 2. Preparation method The first step involves unwinding the PET base film and placing it in a magnetron sputtering chamber. A Cu seed layer with a thickness of 20 nm to 30 nm is deposited on the first surface of the PET base film. On the deposited 20 nm to 30 nm Cu seed layer, a copper layer is thickened to 0.5 μm to 1.0 μm using a vacuum evaporation process to form a continuous conductive metal (i.e., the first current collector layer 20).

[0072] The second step involves transporting the PET substrate film, with the first current collector layer 20 already deposited, to an atmospheric pressure air micro-plasma jet etching station. The etching parameters are set as follows: nozzle inner diameter 100 μm, process gas air, discharge voltage 1.5 kV, and discharge current 3 mA. The distance between the PET substrate film and the nozzle is 2 mm, and the etching time is 38 s (calculated considering an etching rate of 5.1 μm / min, assuming the via 11 completely penetrates the 6.0 μm PET substrate film). It is noteworthy that the second surface of the PET substrate film is activated and modified before the via 11 is fabricated.

[0073] The third step involves transferring the PET substrate film with etched through-hole 11 to the vacuum evaporation and electroplating station. A copper layer with a thickness of 0.5 μm to 1.0 μm is deposited on the second surface of the PET substrate film and inside the through-hole 11. The electroplating solution consists of: CuSO4·5H2O 15 g / L, EDTA·2Na 30 g / L, HCHO 8 mL / L, NaOH 8 g / L, and appropriate additives; pH=12.5; temperature: 45℃.

[0074] The fourth step is to wind up a copper-PET base film-copper composite current collector with a total thickness of approximately 8μm to 10μm (including 1μm to 2.0μm of copper on both sides + 6.0μm of PET). The diameter of the through-hole 11 is approximately 100μm, and the spacing between the holes is 500μm.

[0075] The fifth step involves testing the performance of the prepared copper-PET base film-copper composite current collector. The double-sided internal resistance is tested using the dual-disc controlled voltage four-electrode DC method; the copper peel strength is tested using the 180° peel test method according to GB / T2790-1995; and the tensile strength is tested using the thin film tensile test method according to GB / T1040.1-2018.

[0076] Performance test results: (1) Internal resistance on both sides: less than 0.4 mΩ / cm 2 ; (2) Copper layer peel strength: greater than 8 N / cm (meets the requirements for power battery assembly); (3) Tensile test: greater than 250MPa.

[0077] In summary, the composite current collector prepared by the method described in this application has the characteristics of low internal resistance, high peel strength, and high mechanical strength, which meets the requirements of power batteries for the conductivity, adhesion, and processing performance of the current collector.

[0078] Comparative Example 1 Comparative Example 1 is basically the same as Example 1, except that laser drilling is used in this application. The relevant parameters for laser drilling are: laser wavelength of 355nm, pulse frequency of 50kHz, scanning speed of 500mm / s, and laser thermal ablation to form holes.

[0079] Performance test results: (1) Internal resistance of both sides: 0.5mΩ / cm 2 ~0.7mΩ / cm 2 ; (2) Copper layer peel strength: 5.5 N / cm~6.5 N / cm; (3) Tensile test: greater than 250MPa.

[0080] By comparing Example 1 and Comparative Example 1, it can be seen that the internal resistance in Example 1 is less than 0.4 mΩ / cm. 2 The value in Comparative Example 1 is 0.5 mΩ / cm. 2 ~0.7mΩ / cm 2In other words, the internal resistance of the composite current collector is higher after laser drilling. This may be because laser drilling is a thermal process, which generates a carbonized layer and microcracks on the inner wall and edges of the through-hole 11, disrupting the continuity of the copper plating and the interfacial contact, thus increasing the internal resistance. However, using atmospheric pressure air micro-plasma as a low-temperature cold etching process, and further activating and modifying the surface of the PET base film before etching the through-hole 11, results in no carbonized layer on the inner wall of the through-hole 11, a complete and continuous copper plating, and excellent metal conductivity between the current collector layers on the first and second surfaces of the PET base film through the hole, leading to a lower internal resistance.

[0081] Meanwhile, the peel strength in Example 1 was greater than 8 N / cm, while the peel strength in Comparative Example 1 was 5.5 N / cm to 6.5 N / cm, indicating a significant improvement in the adhesion of the copper layer. This may be because the high temperature of the laser causes localized melting and thermal aging of the PET base film at the aperture, disrupting the physical anchoring interface between the copper plating and the polymer base film, making the plating prone to peeling. In contrast, the processing temperature using atmospheric pressure air micro-plasma technology is lower than the melting temperature of the PET base film, resulting in no thermal damage. Furthermore, the surface activation modification by plasma further enhances the interfacial adhesion, significantly improving the bonding strength between the copper layer and the PET base film and aperture walls.

[0082] In summary, this embodiment uses atmospheric pressure air micro-plasma jet etching to prepare the through hole 11. Compared with traditional laser thermal ablation drilling, it can effectively eliminate thermal damage to the polymer base film 10 and carbonization defects on the hole wall. While ensuring that the overall mechanical strength of the polymer base film 10 remains unchanged, it can significantly reduce the internal resistance of the composite current collector and improve the peel strength of the copper layer. The product has better conductivity and structural reliability, and is more suitable for the preparation of composite current collectors for power batteries.

[0083] Example 2 1. Materials The polymer base film 10 is a PP base film with a thickness of 4.5μm and a width of 300mm.

[0084] First current collector layer 20: magnetron sputtered Cu, with a thickness of 20nm to 50nm; vacuum evaporation deposited Cu film, with a thickness of 1.0μm.

[0085] Plasma gas source: low-pressure oxygen and fluorine-containing gas.

[0086] Second current collector layer 30: vacuum evaporation + chemical electroplating, with a thickness of 1.0 μm.

[0087] 2. Preparation method The first step involves unwinding the PP base film and placing it in a magnetron sputtering cavity. A Cu seed layer with a thickness of 20 nm to 30 nm is deposited on the first surface of the PP base film. After the 20 nm to 30 nm Cu seed layer has been deposited, the copper layer is thickened to 0.5 μm to 1.0 μm using a vacuum evaporation process to form a continuous conductive metal (i.e., the first current collector layer 20).

[0088] The second step involves transporting the PP base film, on which the first current collector layer 20 has been deposited, to a low-temperature, low-pressure plasma etching station. First, Ar / O2 plasma is used to activate the second surface of the PP base film for 30 seconds at a bias power of 200W and a working pressure of 30Pa, forming a hydrophilic surface (e.g., reducing the water contact angle from 103° to 32°). Then, anisotropic vias 11 are etched using an O2 / CF4 mixed gas plasma (flow rate O2:CF4 = 6:1, diluted with 50 sccm of Ar) at a radio frequency bias of 150W for 45 seconds. The vias 11 penetrate the PP base film, with steep sidewalls (taper < 5°).

[0089] The third step involves transferring the PP base film with etched through-hole 11 to the vacuum evaporation and electroplating station. A copper layer with a thickness of 0.5 μm to 1.0 μm is deposited on the second surface of the PP base film and inside the through-hole 11. The electroplating solution consists of: CuSO4·5H2O 15 g / L, EDTA·2Na 30 g / L, HCHO 8 mL / L, NaOH 8 g / L, appropriate amount of additives, pH=12.5, and temperature 45℃.

[0090] The fourth step is to wind up a copper-PP base film-copper composite current collector with a total thickness of approximately 5.5μm to 6.5μm (including 1μm to 2.0μm of copper on both sides + 4.5μm of PP base film), and through-hole 11 with a diameter of approximately 100μm and a hole spacing of 500μm.

[0091] The fifth step involves testing the copper-PP base film-copper composite current collector using the 180° peel strength test method according to GB / T2790-1995.

[0092] 3. Performance test results: (1) Copper layer interface peel strength: 7.2 N / cm; (2) Through-hole yield: greater than 96%.

[0093] The results show that the through-hole composite copper current collector was successfully prepared on PP substrate film using the preparation method of Example 2 (low-pressure plasma anisotropic etching + activation followed by hole formation). The peel strength meets the basic requirements of power battery (≥6N / cm), and the yield of through hole 11 is high (>96%), which verifies the applicability of this method to low melting point and difficult-to-bond PP substrate.

[0094] Example 3 1. Materials The polymer base film 10 is a PET base film with a thickness of 6.0 μm and a width of 300 mm.

[0095] Nozzle array: 4×1 nozzle array (i.e., 4 nozzles are evenly arranged in a row along the width of the PET base film), with a spacing of 2mm between two adjacent nozzles and a pressure difference of 400Pa.

[0096] The cooling baffle is in close contact with the first surface of the PET base film (assisted by an air flotation guide device). 2. Production process Unwinding → Pre-activated plasma (15s) → Multi-nozzle parallel through-hole etching (continuous mode, 10mm distance between adjacent holes) → Online CCD inspection of hole diameter / spacing quality → Missing hole rate ≤1.0%, cumulative non-conforming rate → Transfer to chemical copper plating section.

[0097] 3. Results (1) The array pattern of through holes 11 is uniform and consistent, and the hole spacing deviation is less than 0.1 mm; (2) The rate of missing holes is less than 0.5%, and the rate of misaligned holes is less than 0.3%.

[0098] In other words, in this embodiment, a narrow 4×1 nozzle array is used to achieve roll-to-roll continuous atmospheric pressure plasma array hole formation, which has high hole size accuracy and extremely low hole position error rate, is suitable for large-scale high-speed mass production, and facilitates subsequent selective mask etching to process the zoned electrode conductive pattern.

[0099] Comparative Example 2 Comparative Example 2 is basically the same as Example 3, except that laser drilling is used. The relevant parameters for laser drilling are: laser power, laser wavelength of 355nm, pulse frequency of 50kHz, scanning speed of 500mm / s, and laser thermal ablation to form holes.

[0100] result: (1) The hole spacing deviation is greater than 0.15 mm; (2) The rate of missing holes is 1% to 3%, and the rate of misaligned holes is 0.5% to 1%.

[0101] By comparing Example 3 and Comparative Example 2, it can be seen that Example 3 uses a fixed nozzle array with a fixed nozzle position, resulting in no significant vibration during the conveyor belt operation. Therefore, the fluctuation in the aperture spacing is small, and the array consistency is high. In contrast, laser scanning is a high-speed dynamic single-point scanning method. The reciprocating motion of the scanning mechanism is prone to mechanical vibration and trajectory deviation. Furthermore, the high-temperature thermal effect of the laser causes local micro-deformation of the PET base film. These two factors lead to a significant increase in aperture spacing deviation and insufficient dimensional accuracy.

[0102] Meanwhile, in Example 3, the stabilizing gas path ensures stable gas output and etching energy for each nozzle, with only momentary airflow disturbances, resulting in a significantly lower defect rate than the production line's internal control standard. In contrast, during laser drilling, the laser equipment, due to long-term continuous operation, is prone to issues such as optical path contamination, laser power fluctuations, and abnormal pulse signals, frequently resulting in missed holes (11), thus leading to a significantly higher defect rate. Furthermore, in Example 3, the use of fixed nozzles and a stable roll-to-roll system minimizes the risk of hole misalignment, making the misalignment rate controllable. However, during laser drilling, the laser scanning system accumulates positioning errors during high-speed movement, compounded by the micro-displacement difference in the PET base film caused by laser thermal shock, leading to frequent hole misalignment and a higher misalignment rate.

[0103] In other words, in this embodiment, compared with traditional laser ablation drilling, the use of a 4×1 nozzle array combined with atmospheric pressure plasma parallel etching, and combined with a roll-to-roll continuous production line, can not only control the hole spacing deviation within 0.1mm, but also significantly reduce the missing hole rate and misaligned hole rate.

[0104] In summary, in this application, a non-thermal plasma etching method is used to create pores in the polymer base film 10 during the preparation of the copper composite current collector. Compared with existing laser drilling, the copper layer and the polymer base film 10 exhibit stronger interfacial bonding in the prepared copper composite current collector. Furthermore, the non-thermal plasma etching method can create pores in PP base films that cannot be achieved with laser drilling. Simultaneously, the through-holes 11 prepared using the non-thermal plasma etching method and a roll-to-roll continuous production line exhibit superior hole spacing, missing hole rate, and misaligned hole rate compared to laser drilling.

[0105] In other words, this application uses a non-thermal plasma etching method to replace laser drilling technology, achieving breakthroughs in eliminating thermal damage, expanding the range of substrates, improving processing accuracy, reducing defect rate, and enhancing bonding strength. It also provides a practical and feasible technical path for the high-performance, low-cost, and large-scale manufacturing of composite current collectors.

[0106] Secondly, this application also provides a composite current collector, which is a copper composite current collector. This composite current collector is prepared using the aforementioned method for preparing composite current collectors. Therefore, all the technical effects of the composite current collector provided in this embodiment will not be repeated here, as the technical effects of the preparation method for the composite current collector have already been described in detail above.

[0107] Thirdly, this application also provides a lithium-ion battery that uses the aforementioned composite current collector as the negative electrode current collector. Therefore, all the technical effects of the lithium-ion battery provided in this embodiment will not be repeated here, as the technical effects of the composite current collector have already been described in detail above.

[0108] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects: (1) This application uses a non-thermal plasma etching method to create pores in polymer base films (such as PP base films, PET base films and PI base films, etc.), which will not produce thermal melting or heat-affected zones, and the edges of the through holes are smooth and sharp, without carbonization or microcracks. At the same time, this pore-forming method can be adapted to low-melting-point heat-sensitive substrates such as PP base films, avoiding thermal shrinkage and melting deformation of the substrate, and greatly expanding the application range of polymer substrates.

[0109] (2) In this application, a first current collector layer is first formed on the first surface of the polymer base film, and then a hole is formed from the second surface of the polymer base film based on a non-thermal plasma etching method. The first current collector layer physically blocks the through hole, which can avoid the leakage problem during subsequent active material coating. At the same time, plasma dry etching will not leave slag and recast layer on the inner wall of the hole, ensuring the high reliability of the metal coating on the inner wall of the hole and realizing low resistance two-sided conduction.

[0110] (3) This application combines roll-to-roll continuous production line with non-thermal plasma etching method. At the same time, before the hole-making step, non-thermal plasma etching method is used to activate and modify the second surface of the polymer base film, which not only improves the production efficiency of through holes, but also improves the chemical adsorption and adhesion of the subsequent metal coating of the polymer base film.

[0111] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0112] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0113] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a composite current collector, characterized in that, include: Based on magnetron sputtering and vacuum evaporation processes, a first current collector layer (20) is formed on the first surface of the polymer base film (10). Based on the non-thermal plasma etching method, a hole is formed from the second surface of the polymer base film (10) opposite to the first surface, forming a through hole (11) that only penetrates the polymer base film (10). During the hole formation process, the highest etching temperature is lower than the melting temperature of the polymer base film (10). Based on vacuum evaporation and chemical electroplating processes, a second current collector layer (30) is formed on the second surface of the polymer base film (10) and in the through hole (11) to prepare a composite current collector.

2. The method for preparing the composite current collector according to claim 1, characterized in that, Before performing the pore-forming step on the polymer-based film (10), the method for preparing the composite current collector further includes: The second surface of the polymer base film (10) is activated and modified based on the non-thermal plasma etching method.

3. The method for preparing the composite current collector according to claim 1, characterized in that, The non-thermal plasma etching method includes atmospheric pressure micro-plasma jet etching technology or low temperature and low pressure plasma etching technology. Wherein, when the non-thermal plasma etching method is atmospheric pressure micro-plasma jet etching technology, the process gas is air or an oxygen-enriched mixed gas, and the volume concentration of oxygen in the oxygen-enriched mixed gas is 40% to 100%; When the non-thermal plasma etching method is a low-temperature, low-pressure plasma etching technique, the process gas includes oxygen and fluorine-containing gas, and the molar ratio of oxygen to fluorine-containing gas is 2:1 to 10:

1.

4. The method for preparing the composite current collector according to claim 1, characterized in that, The step of creating pores in the polymer-based film (10) is performed on a roll-to-roll continuous production line, including: The polymer-based film (10) is controlled to pass through the plasma etching cavity at a speed of 0.1 m / min to 20 m / min; Atmospheric pressure plasma is generated by applying a high-frequency electric field using multiple nozzle electrode arrays, or low-pressure plasma is generated by applying a high-frequency electric field using a single mask chamber, forming a regular array of through holes (11) on the polymer base film (10); The gas composition and radio frequency bias of the plasma source of the plasma etching cavity are adjusted to control the shape and anisotropy ratio of the via (11).

5. The method for preparing the composite current collector according to claim 4, characterized in that, The roll-to-roll continuous production line includes: The air flotation guide device and tension control device are configured to control the tension of the polymer base film (10) to be 0.2 N / cm to 1.0 N / cm; and / or, An online optical inspection module is configured to detect in real time at least one of the following: the etching depth of the hole, the hole diameter, the hole spacing, and the operating speed of the polymer base film (10).

6. The method for preparing the composite current collector according to any one of claims 1 to 5, characterized in that, In the pore-forming step of the polymer-based film (10): The diameter of the through hole (11) is 2μm to 100μm; The hole spacing of the through hole (11) is 10μm to 2000μm; The depth-to-width ratio of the through hole (11) is 1:1 to 10:1; The projection of the through hole (11) onto the polymer base film (10) is circular, elliptical, rectangular or polygonal.

7. The method for preparing the composite current collector according to any one of claims 1 to 5, characterized in that, The polymer-based film (10) includes at least one of polyethylene phthalate-based film, polypropylene-based film, and polyimide-based film.

8. The method for preparing the composite current collector according to any one of claims 1 to 5, characterized in that, After forming the second current collection layer (30), the method for preparing the composite current collector further includes: By setting an etching protective layer or a masking film, based on wet chemical etching process or low-temperature plasma micro-etching process, some of the metal in the through hole (11) and the metal on the second current collector layer (30) on the side of the through hole (11) away from the first current collector layer (20) are selectively removed, forming a metal retention area and a metal removal area arranged in a partitioned manner on the second surface of the polymer base film (10), forming a composite current collector with a partitioned wiring pattern.

9. A composite current collector, characterized in that, The composite current collector is prepared by the method described in any one of claims 1 to 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery uses the composite current collector described in claim 9 as the negative electrode current collector.

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