A busbar coated with a coating layer and a coating method thereof

Abstract

A busbar covered with a cladding layer and a cladding method thereof. The busbar comprises a metal conductor base and a composite insulating layer formed on the surface of the metal conductor base by a reactive co-extrusion process; the composite insulating layer comprises a polyethylene-based adhesive inner layer in direct contact with the metal conductor base; the raw materials for preparing the polyethylene-based adhesive inner layer comprise, by weight fraction, PA12 75%-85%, antioxidant 0.1%-1%, anti-UV additive 0.1%-2%, color powder 0.5%-5%, and special additive 5%-20%. Through the synergy of material end group design and reactive co-extrusion process, a stable chemical bonding network is constructed in situ at the interface while continuously producing rapidly, which greatly improves the interlayer bonding force, heat aging resistance and long-term reliability of the cladding layer, and is particularly suitable for high-voltage battery systems of new energy vehicles with extremely high requirements for insulation and durability.

Description

Technical Field

[0001] This invention belongs to the field of high-voltage electrical connection technology for new energy vehicles, specifically relating to a high-voltage busbar for high-current connection between battery modules, and more particularly to a busbar structure and covering method with a high-strength, high-temperature resistant, and anti-delamination composite insulating coating layer. Background Technology

[0002] With the rapid development of the new energy vehicle industry, power battery systems have placed extremely high demands on the electrical safety, long-term reliability, and environmental tolerance of high-voltage connection components. As a key component for transmitting large currents between battery modules, the performance of the insulating coating layer of the busbar is crucial.

[0003] Traditional busbar insulation layers often use a single material or a simple double-layer extrusion coating. Single materials are silicone rubber or epoxy resin, which are difficult to balance insulation, mechanical strength, and high-temperature resistance. Simple double-layer structures, on the other hand, have poor material compatibility and weak interlayer bonding, making them prone to delamination and cracking under long-term thermal cycling, mechanical vibration, and humid and hot environments, leading to insulation failure and posing risks of short circuits and fires.

[0004] In the prior art, CN121097092A discloses a multilayer polymer film for lithium battery current collectors. This film uses a blend of ultra-high molecular weight polyethylene / high-density polyethylene and a nylon layer, co-extruded and cast together, and undergoes complex post-treatments such as plasma activation and dopamine coating to enhance adhesion to the metal coating. This technology targets ultra-thin current collector base films, primarily achieving lightweighting through plastic-based metal coatings. In contrast, this application targets a busbar coating layer providing insulation protection for existing metal conductors, with a thickness on the order of millimeters, representing a fundamental difference. Another point is that the existing multilayer polymer film serves as the main structure, with only a surface coating on the metal, while this application uses a metal conductor as the main body and a polymer layer as the external coating, resulting in a completely different interface and stress state. Furthermore, the existing technology relies on multi-step surface treatment processes after film formation to enhance adhesion. These processes are lengthy, energy-intensive, and may introduce contamination, making them unsuitable for the high-efficiency, continuous extrusion coating production line required for the busbar in this application.

[0005] To this end, the applicant has been committed to developing a high-voltage busbar insulation coating solution that can bond firmly to the metal conductor substrate, has extremely high interlayer bonding strength, can adapt to harsh automotive-grade environments, and is efficient and suitable for continuous production. Summary of the Invention

[0006] The technical problem to be solved by this invention is to overcome the shortcomings of the prior art and provide a busbar covered with a coating layer and a coating method thereof. By introducing functional groups capable of in-situ chemical reactions into the coating layer material system and optimizing the co-extrusion coating process, a chemically bonded transition layer is generated in-situ at the interface, thereby solving the problem of strong and tough bonding between the coating layer and the metal substrate, as well as between different material layers within the coating layer, significantly improving the product's heat resistance, resistance to damp heat aging, and long-term reliability.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] The first aspect of this application provides a busbar covered with a coating layer, including a metal conductor substrate, the surface of which is coated with a composite insulation layer formed in one step by a reactive co-extrusion process;

[0009] The composite insulation layer includes a polyethylene-based adhesive inner layer that is in direct contact with the metal conductor substrate;

[0010] The raw materials for preparing the polyethylene-based adhesive inner layer include, by weight: PA12 75%-85%, antioxidant 0.1%-1%, UV resistant additive 0.1%-2%, colorant 0.5%-5%, and special additives 5%-20%.

[0011] Furthermore, the special additives are long-term heat stabilizers.

[0012] The composite insulating layer provided in the second aspect of this application also includes

[0013] A polyamide-based weather-resistant outer layer located outside the polyethylene-based adhesive inner layer;

[0014] And a reactive co-extruded interlayer formed at the interface between the adhesive inner layer and the weather-resistant outer layer;

[0015] The polyethylene-based adhesive inner layer comprises maleic anhydride-grafted polyethylene, the polyamide-based weather-resistant outer layer further comprises amino-terminated polyamide, and the reactive co-extruded interlayer is a chemically bonded transition region formed by the in-situ acylation reaction between the anhydride groups in the maleic anhydride-grafted polyethylene and the terminal amino groups in the amino-terminated polyamide during the co-extrusion process.

[0016] Furthermore, the grafting rate of maleic anhydride-grafted polyethylene is 0.8 wt% to 1.5 wt%, the melt index is 2-5 g / 10 min, and the yield is 190℃ / 2.16 kg; the terminal amino concentration of amino-terminated polyamide is 35-50 mmol / kg.

[0017] Furthermore, the thickness of the reactive co-extruded interlayer is 10-200 μm; the thickness of the polyethylene-based adhesive inner layer is 0.3-0.6 mm; and the thickness of the polyamide-based weather-resistant outer layer is 0.5-0.8 mm.

[0018] A third aspect of this application provides a method for preparing a busbar covered with a coating layer as described in the first aspect, comprising the following steps:

[0019] A. Select the metal conductor substrate to be processed and preheat the metal conductor substrate to 200℃-250℃;

[0020] B melts and plasticizes the raw materials for preparing the polyethylene-based adhesive inner layer to form the first melt;

[0021] C introduces the first melt into the co-extrusion die;

[0022] D continuously draws the metal conductor matrix through the core of the co-extrusion die;

[0023] E, at the exit of the co-extrusion die, causes the first melt to coat the surface of the passing metal conductor substrate, forming a tightly adhered composite insulation layer.

[0024] F involves cooling and shaping the coated busbar and subsequent processing.

[0025] The fourth aspect of this application provides a method for preparing a busbar covered with a coating layer as described in the first aspect, comprising the following steps:

[0026] A. Select the metal conductor substrate to be processed and preheat the metal conductor substrate to 200℃-250℃;

[0027] B melts and plasticizes the raw materials for preparing the polyethylene-based adhesive inner layer and the raw materials for preparing the polyamide-based weather-resistant outer layer to form the first melt and the second melt.

[0028] C introduces the first melt and the second melt together into the co-extrusion die, so that the first melt is located inside the co-extrusion die and the second melt is located outside the co-extrusion die;

[0029] D continuously draws the metal conductor matrix through the core of the co-extrusion die;

[0030] E. At the exit of the co-extrusion die, the first melt and the second melt together coat the surface of the passing metal conductor substrate, and at the contact interface between the first melt and the second melt, an in-situ acylation reaction occurs under set process conditions to form a composite insulation layer.

[0031] F involves cooling and shaping the coated busbar and subsequent processing.

[0032] Furthermore, the co-extrusion die head is provided with an interactive flow channel for the first melt and the second melt to flow together after they merge. The length of the interactive flow channel is 150mm-250mm, which allows the first melt and the second melt to stay in it for 15 seconds-40 seconds after they interact.

[0033] Furthermore, the process conditions for the in-situ acylation reaction include:

[0034] The temperature inside the interactive flow channel is 230℃-260℃; the melt pressure is 8MPa-15MPa; a vacuum of -0.05MPa to -0.08MPa is applied in the subsequent section to remove the water generated in the reaction.

[0035] Furthermore, the cooling and shaping process adopts a gradient cooling process, which includes a first stage of cooling at 70℃-80℃, a second stage of cooling at 40℃-50℃, and a third stage of cooling at 20℃-25℃.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0037] This application utilizes an in-situ acylation reaction between maleic anhydride-grafted polyethylene and amino-terminated polyamide at the co-extrusion interface to form a "reactive co-extrusion interlayer" dominated by amide bonds between the inner PE layer and the outer PA layer. This interlayer fundamentally solves the weak interface problem caused by material incompatibility in traditional physical co-extrusion, resulting in an order-of-magnitude increase in interlayer peel strength. It effectively resists long-term thermal cycling, mechanical vibration, and hygrothermal stress, greatly reducing the risk of delamination.

[0038] This application seamlessly integrates interface-enhancing chemical reactions into a single co-extrusion coating process, utilizing the melt's own thermal energy to drive the reaction. By optimizing the die flow channel design and introducing online vacuum degassing and gradient cooling processes, the chemical reaction is made highly efficient and controllable. This results in a simpler, more continuous, and energy-efficient process, making it more suitable for large-scale industrial production.

[0039] In this application, the chemically bonded interlayer in the chemical reaction acts as an ideal stress buffer and transfer layer, enabling the composite insulation layer to exhibit excellent resistance to heat aging, damp heat, dimensional stability, and resistance to thermal shock. Simultaneously, the inner PE layer provides good insulation and initial tack, while the outer PA layer provides excellent mechanical strength, wear resistance, and chemical corrosion resistance. The synergistic effect of these two layers fully meets the stringent requirements of automotive-grade high-voltage busbars.

[0040] Overall, this application is precisely positioned to address the long-term reliability issues of insulation coating for high-voltage busbars in new energy vehicles, and the material system and process parameters are tailored and optimized for this specific application scenario. Attached Figure Description

[0041] Figure 1This is a schematic diagram of the structure of Embodiment 1.

[0042] Figure 2 This is a schematic diagram of the structure of Example 2.

[0043] In the figure: 1-Metal conductor substrate; 2-Composite insulation layer; 21-Polyethylene-based adhesive inner layer; 22-Polyamide-based weather-resistant outer layer; 23-Reactive co-extruded interlayer. Detailed Implementation

[0044] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0045] like Figure 1 The first embodiment shown includes a busbar covered with a coating layer, comprising a metal conductor substrate 1, the surface of which is coated with a composite insulation layer 2 formed in one step by a reactive co-extrusion process;

[0046] The composite insulation layer 2 includes a polyethylene-based adhesive inner layer 21 that is in direct contact with the metal conductor substrate 1;

[0047] The raw materials for preparing the polyethylene-based adhesive inner layer 21 include, by weight: PA12 75%-85%, antioxidant 0.1%-1%, UV resistant additive 0.1%-2%, colorant 0.5%-5%, and special additives 5%-20%.

[0048] The special additives are long-term heat stabilizers.

[0049] like Figure 2 The illustrated embodiment two describes a busbar covered with a coating layer, comprising a copper metal conductor substrate 1. A composite insulation layer 2 is coated onto the surface of the metal conductor substrate 1 using a reactive co-extrusion process. The composite insulation layer 2, from the inside out, consists of: a 0.5 mm thick polyethylene-based adhesive inner layer 21, a reactive co-extruded interlayer 23 with a thickness of approximately 50 μm, and a 0.7 mm thick polyamide-based weather-resistant outer layer 22.

[0050] Example 3: A method for coating a busbar with a coating layer, the preparation method of which is as follows:

[0051] A. Select the metal conductor substrate to be processed and preheat the metal conductor substrate to 200℃-250℃;

[0052] B melts and plasticizes the raw materials for preparing the polyethylene-based adhesive inner layer to form the first melt;

[0053] C introduces the first melt into the co-extrusion die;

[0054] D continuously draws the metal conductor matrix through the core of the co-extrusion die;

[0055] E, at the exit of the co-extrusion die, causes the first melt to coat the surface of the passing metal conductor substrate, forming a tightly adhered composite insulation layer.

[0056] F involves cooling and shaping the coated busbar and subsequent processing.

[0057] Example 4: A method for coating a busbar with a coating layer, the preparation method of which is as follows:

[0058] A. Select the metal conductor substrate 1 to be processed; take the coiled copper busbar as the metal conductor substrate 1, clean it and preheat it to 120°C through a preheating device.

[0059] B melts and plasticizes the raw material containing maleic anhydride-grafted polyethylene and the raw material containing amino-terminated polyamide respectively to form a first melt and a second melt.

[0060] The inner polyethylene adhesive layer 21 is made of maleic anhydride-grafted polyethylene (PE-g-MAH) with a grafting rate of 1.2 wt% and a melt index of 3.5 g / 10 min. The outer polyamide weather-resistant layer 22 is made of amino-terminated polyamide 66 (PA66-NH2) with a terminal amino concentration of 42 mmol / kg. PA66-NH2 differs significantly from general-purpose PA66 in that its chain ends with highly reactive primary amino groups (-NH2) rather than inert acetyl groups.

[0061] PE-g-MAH granules are fed into the first extruder, with the temperature set at 180 / 195 / 205 / 215℃ from the feed section to the die head. The first melt flows out from the die head. PA66-NH2 granules are fed into the second extruder, with the temperature set at 255 / 270 / 280 / 275℃ from the feed section to the die head. The second melt flows out from the die head.

[0062] C introduces both the first and second melts into the co-extrusion die, positioning the first melt inside the die and the second melt outside. The die contains an interactive flow channel, 150mm-250mm in length, allowing the first and second melts to remain within it for 15-40 seconds after interaction. This interactive flow channel ensures the first and second melts remain separate until they reach the channel's outlet. Near the outlet, the two melts merge according to a pre-defined layered structure.

[0063] In this embodiment, the length of the interactive flow channel is L = 200 mm. The residence time of the melt within it is approximately 28 seconds. The temperature in the interactive flow channel region needs to be controlled at 235°C, and the melt pressure at approximately 12 MPa. A vacuum valve is opened at the downstream end of the interactive flow channel to maintain a vacuum of -0.06 MPa to remove moisture generated during the reaction online.

[0064] The in-situ reaction within the interaction channel is as follows:

[0065] PE-g-MAH (containing anhydride group) + PA66-NH2 (containing terminal amino group) → PE-g-amide-PA66 (forming amide bond) + H2O↑.

[0066] D continuously pulls the metal conductor matrix through the core of the co-extrusion die; at the exit of the inter-flow channel, the already combined multi-layer melt is extruded around the passing metal conductor and instantly wraps around the conductor.

[0067] E, at the exit of the co-extrusion die, causes the first melt and the second melt to jointly coat the surface of the passing metal conductor substrate, and at the contact interface between the first melt and the second melt, an in-situ acylation reaction occurs under set process conditions to form a composite insulating layer.

[0068] F involves cooling, shaping, and subsequent processing of the coated busbar. The coated busbar immediately enters a cooling water tank; the first section is pre-cooled by 75°C warm water spray; the second section is immersed in a 45°C water bath for primary cooling; and the third section is immersed in 25°C room temperature water for final cooling. Finally, after inspection, traction, and winding, the finished product is obtained.

[0069] In this embodiment, PE and PA are thermodynamically incompatible polymers. Simply stacking them together results in weak interfacial bonding, making them prone to delamination under stress or thermal shock. In the co-extrusion process, PE and PA are melted separately in different extruders, becoming viscous melts. When these two high-temperature, high-pressure polymer melts are jointly introduced into a co-extrusion die and converge therein, a reactive co-extrusion interlayer is formed between them under high temperature, high pressure, and high shear force. The microscopic mechanism of this reactive co-extrusion interlayer is as follows: despite their incompatibility, in the extremely thin interfacial region, some molecular chain segments, especially the amide end groups of PA or the polar groups of modified PE, overcome the energy barrier and undergo short-range diffusion into the other phase. These diffused segments physically entangle with the molecular chains of the other phase, forming an interlocking network structure. Moreover, when the PE or PA material has undergone special modification, under the high temperature of co-extrusion, the anhydride groups on the modified PE may undergo in-situ chemical reactions with the amino (-NH2) groups at the PA ends, forming strong chemical bonds. This reactive co-extrusion can greatly enhance the interlayer bonding force. Moreover, the aforementioned diffusion and possible reactions make the interface no longer sharp and abruptly changing, but a region with a gradual transition in composition and properties from 100% PE to 100% PA. This region is the reactive co-extrusion interaction layer.

[0070] Therefore, this embodiment does not simply use commercially available PE-g-MAH and general PA66, but instead end-capsulates the PA66 with amino groups and designs a matching ratio with the MAH grafting rate to form a reaction specifically optimized for busbar co-extrusion coating.

[0071] The main properties of the composite insulating layer 2 formed in Examples 1 and 3 are good adhesion to copper and aluminum, high temperature and UV stability, low moisture absorption, high abrasion resistance, high dielectric strength, and constant specific volume resistivity at high temperatures. The properties of the composite insulating layer 2 formed in Examples 2 and 4 are similar to those of the composite insulating layer 2 in Examples 1 and 3.

[0072] The specific parameters are shown in Table 1:

[0073] Test conditions standard unit Test results of Example 1 and Example 3 Test results of Examples 2 and 4 Moisture absorption rate 23℃ / 50% r.h ISO 62 % 1.00 1.00 Water absorption rate 23℃ / sat ISO 62 % 2.50 2.50 Flame retardant properties (UL 94) 0.8MM ISO 1210 Rating HB HB Glass transition temperature DSC ISO 11357 ℃ 155 156 Heat distortion temperature, 1.8 MPa HDT Dry ISO 75 ℃ 115 115 Heat distortion temperature, 0.45 MPa HDT Dry ISO 75 ℃ 135 136 specific volume resistivity Cond IEC 60093 Ω m <![CDATA[10 10 ]]> <![CDATA[10 10 ]]> Dielectric strength IEC 60243-1 kV / mm 45 45

[0074] Table 1

[0075] Comparative Example

[0076] Comparative Example 1 was formed by replacing the raw material of the polyethylene-based adhesive inner layer 21 in Examples 1 and 3 with ordinary low-density polyethylene. Furthermore, Comparative Example 2 was formed by replacing the raw material of the polyethylene-based adhesive inner layer 21 in Examples 2 and 4 with ordinary low-density polyethylene, and replacing the raw material of the polyamide-based weather-resistant outer layer 22 with commercially available ordinary acetyl-terminated PA66. The composite insulation layer was formed using a co-extrusion process, shortening the interactive channels to 50 mm according to its characteristics, without applying a vacuum, and employing a rapid cooling method involving direct immersion in a 25°C water bath.

[0077] The performance of the busbar samples from Examples 1, 3, 2, 4, Comparative Examples 1 and 2 was tested, and the results are shown in Table 2 below:

[0078] Test Project Test standards / conditions Examples 1 and 3 Examples 2 and 4 Comparative Example 1 Comparative Example 2 interlayer peel strength Homemade clamp, 180° peeling, speed 100mm / min 45N / 10mm 45N / 10mm 8N / 10mm 8N / 10mm Strength retention rate after heat aging at 150℃ Peel strength was measured after placing the food in a 150℃ oven for 1000 hours. 88% 88% 42% 42% Moist heat resistance After 500 hours at 85℃ / 85%RH, observe the interface. No layering, no bubbles No layering, no bubbles Clear layering is visible at the edges Clear layering is visible at the edges Insulation resistance 1000V DC, normal operation >10 GΩ·m >10 GΩ·m >10 GΩ·m >10 GΩ·m Insulation resistance (after damp heat) 85℃ / 85% RH, 500h, 1000V DC 8.5 GΩ·m 8.5 GΩ·m 1.2 GΩ·m 1.2 GΩ·m

[0079] Table 2

[0080] As shown in Table 2 above, the busbars provided in Examples 1 and 2 exhibit significantly higher interlayer peel strength of the composite insulation layer 2 compared to Comparative Examples 1 and 2, exceeding 460%. After rigorous thermal aging and damp heat testing, Example 1 demonstrates significantly higher performance retention and no appearance defects. Furthermore, the reactive co-extruded interlayer 23 in Example 2 offers a fundamental advantage through chemical bonding: it not only provides extremely high initial bonding strength, but the chemical bonds exhibit far greater stability against heat and moisture than physical forces, thus ensuring the product's extreme reliability under long-term harsh environments. The significant decrease in insulation resistance after damp heat in Comparative Examples 1 and 2 is also related to the increased moisture absorption pathways caused by interfacial delamination.

[0081] In summary, through meticulous material design and process control, this invention successfully constructs a stable chemical bonding interface within the insulating coating layer of high-voltage busbars, solving the long-standing problem of delamination reliability in the industry and possessing extremely high industrial application value.

[0082] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A busbar covered with a cladding layer, comprising a metal conductor substrate (1), characterized in that, The surface of the metal conductor substrate (1) is covered with a composite insulating layer (2) formed in one step by a reactive co-extrusion process. The composite insulation layer (2) includes a polyethylene-based adhesive inner layer (21) that is in direct contact with the metal conductor substrate (1). The raw materials for preparing the polyethylene adhesive inner layer (21) include, by weight: PA12 75%-85%, antioxidant 0.1%-1%, anti-UV additive 0.1%-2%, colorant 0.5%-5%, and special additives 5%-20%.

2. The busbar covered with a coating layer according to claim 1, characterized in that, The special additive is a long-term heat stabilizer.

3. The busbar covered with a coating layer according to claim 1, characterized in that, The composite insulating layer (2) also includes A polyamide-based weather-resistant outer layer (22) located outside the polyethylene-based adhesive inner layer (21); And a reactive co-extruded interlayer (23) formed at the interface between the adhesive inner layer (21) and the weather-resistant outer layer (22); The polyethylene-based adhesive inner layer (21) comprises maleic anhydride-grafted polyethylene, the polyamide-based weather-resistant outer layer (22) comprises amino-terminated polyamide, and the reactive co-extrusion interlayer (23) is a chemically bonded transition region formed by the in-situ acylation reaction between the anhydride groups in the maleic anhydride-grafted polyethylene and the terminal amino groups in the amino-terminated polyamide during co-extrusion.

4. The busbar covered with a coating layer according to claim 3, characterized in that, The maleic anhydride-grafted polyethylene has a grafting rate of 0.8 wt% to 1.5 wt%, a melt index of 2-5 g / 10 min, and a yield of 2.16 kg at 190 °C; the amino-terminated polyamide has a terminal amino concentration of 35-50 mmol / kg.

5. The busbar covered with a coating layer according to claim 3 or 4, characterized in that, The thickness of the reactive co-extruded interlayer (23) is 10-200 μm; the thickness of the polyethylene-based adhesive inner layer (21) is 0.3-0.6 mm; and the thickness of the polyamide-based weather-resistant outer layer (22) is 0.5-0.8 mm.

6. A method for preparing a busbar covered with a coating layer as described in any one of claims 1-2, characterized in that, Includes the following steps: A selects the metal conductor substrate (1) to be processed and preheats the metal conductor substrate (1) to 200℃-250℃; B melts and plasticizes the raw materials for preparing the polyethylene-based adhesive inner layer (21) to form the first melt; C introduces the first melt into the co-extrusion die; D continuously draws the metal conductor matrix through the core of the co-extrusion die; E, at the outlet of the co-extrusion die, causes the first melt to coat the surface of the passing metal conductor substrate (1), forming a tightly fitted composite insulation layer (2). F involves cooling and shaping the coated busbar and subsequent processing.

7. A method for preparing a busbar covered with a coating layer as described in any one of claims 1-5, characterized in that, Includes the following steps: A selects the metal conductor substrate (1) to be processed and preheats the metal conductor substrate (1) to 200℃-250℃; B melts and plasticizes the raw materials for preparing the polyethylene-based adhesive inner layer (21) and the raw materials for preparing the polyamide-based weather-resistant outer layer (22) to form the first melt and the second melt. C introduces the first melt and the second melt into the co-extrusion die, such that the first melt is located inside the co-extrusion die and the second melt is located outside the co-extrusion die; D continuously draws the metal conductor matrix through the core of the co-extrusion die; E, at the outlet of the co-extrusion die, causes the first melt and the second melt to jointly coat the surface of the passing metal conductor substrate (1), and at the contact interface between the first melt and the second melt, an in-situ acylation reaction occurs under set process conditions to form a composite insulating layer (2). F involves cooling and shaping the coated busbar and subsequent processing.

8. The method for covering a busbar with a covering layer according to claim 7, characterized in that, The co-extrusion die head is provided with an interactive flow channel for the first melt and the second melt to flow together after they merge. The length of the interactive flow channel is 150mm-250mm, which allows the first melt and the second melt to stay in it for 15 seconds-40 seconds after they interact.

9. The method for covering a busbar with a covering layer according to claim 7, characterized in that, The process conditions for the in-situ acylation reaction include: The temperature inside the interactive flow channel is 230℃-260℃; the melt pressure is 8MPa-15MPa; and a vacuum of -0.05MPa to -0.08MPa is applied in the subsequent section to remove the water generated in the reaction.

10. The method for covering a busbar with a covering layer according to claim 7, characterized in that, The cooling and shaping process adopts a gradient cooling process, which includes a first stage of cooling at 70℃-80℃, a second stage of cooling at 40℃-50℃, and a third stage of cooling at 20℃-25℃.

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