Lithium battery aluminum plastic film packaging method

Abstract

The invention relates to a lithium battery aluminum-plastic film packaging method which comprises the following steps: S1, surface cleaning and surface modification treatment are performed on an aluminum-plastic film, and the aluminum-plastic film comprises a middle Al layer and CPP layers located on the two sides of the middle Al layer; s2, performing the pretreated aluminum-plastic film, including bending two ends of the aluminum-plastic film to overlap to form an intermediate with a cavity, the cavity being matched with the outline of the battery cell; s3, placing the battery cell in the cavity, and performing hot melting packaging on the overlapping area of the aluminum plastic film; and S4, performing sealing treatment on the edge of the aluminum plastic film after hot melting packaging. The two ends of the aluminum-plastic film are bent to be overlapped to form the intermediate body with the cavity, and the cavity is matched with the outline of the battery cell, so that the aluminum-plastic film can tightly wrap the battery cell, and air residues are reduced; the CPP layers are arranged on the two sides of the aluminum-plastic film, any surface of the aluminum-plastic film can be packaged, and therefore heat sealing can be directly carried out on the overlapping area of the aluminum-plastic film.

Description

Technical Field

[0001] This application relates to the field of lithium battery manufacturing technology, specifically to a lithium battery aluminum-plastic film encapsulation method. Background Technology

[0002] Aluminum-plastic film, as a core packaging material for pouch lithium batteries, is widely used in the lithium battery packaging field due to its light weight, low internal resistance, and ease of cell design. However, the traditional aluminum-plastic film packaging process for lithium batteries currently faces several technical bottlenecks. Traditional packaging often employs ordinary hot-pressing processes, which can easily leave tiny gaps between the aluminum-plastic film and the battery cell. During battery charging and discharging, the expansion or contraction of internal gases allows moisture and oxygen to seep into the battery, accelerating cell aging and affecting battery performance and lifespan. Furthermore, during the aluminum-plastic film molding process, insufficient precision in temperature and pressure control makes it difficult for the film to adhere tightly to the battery cell, easily leading to defects such as wrinkles and bubbles, affecting the battery's appearance and mechanical properties.

[0003] The electrolyte inside lithium batteries is corrosive. Under traditional packaging processes, the inner polymer layer of the aluminum-plastic film is prone to swelling and corrosion after prolonged contact with the electrolyte, leading to a decrease in the barrier properties of the aluminum-plastic film and an increased risk of electrolyte leakage. Furthermore, the existing packaging processes suffer from inefficient workflows, low automation, and significant manual intervention, resulting in low production efficiency and difficulty in meeting the demands of large-scale industrial production. Traditional aluminum-plastic film packaging methods suffer from low packaging efficiency and poor packaging quality. The single-sided CPP layer structure requires additional bending steps to achieve effective sealing, increasing process complexity and production time. Simultaneously, air residue is easily generated during packaging, affecting battery performance and lifespan. Moreover, the low compatibility between the aluminum-plastic film and the battery cell in traditional methods leads to uneven stress distribution, increasing the risk of packaging defects. These problems limit the improvement of lithium battery production efficiency and product quality.

[0004] Therefore, it is of great significance to develop a new lithium battery aluminum-plastic film encapsulation process that can improve sealing performance, molding accuracy and corrosion resistance, while also increasing production efficiency. Summary of the Invention

[0005] To address the aforementioned issues, this application provides a lithium battery aluminum-plastic film encapsulation method.

[0006] This application provides a lithium battery aluminum-plastic film encapsulation method, including the following steps: S1: The aluminum-plastic film is subjected to surface cleaning and surface modification treatment, wherein the aluminum-plastic film comprises an intermediate Al layer and CPP layers located on both sides of the intermediate layer; S2: The pre-treated aluminum-plastic film is pre-formed, the pre-forming process including bending the two ends of the aluminum-plastic film to overlap and form an intermediate body with a cavity, the cavity matching the outline of the battery cell; S3: Place the battery cell in the cavity and perform heat fusion encapsulation on the overlapping area of ​​the aluminum-plastic film; S4: Seal the edges of the aluminum-plastic film after hot-melt sealing.

[0007] This solution improves encapsulation efficiency and quality through the synergistic effect of a pre-forming step and a novel aluminum-plastic film structure. First, by bending both ends of the aluminum-plastic film to form a cavity-like intermediate body, and ensuring the cavity matches the battery cell contour, the aluminum-plastic film can tightly wrap the battery cell, reducing air residue. Both sides of the aluminum-plastic film are CPP layers, allowing encapsulation on either surface. This allows for direct heat sealing of the overlapping area. In contrast, traditional face-to-face side-sealing processes use a single-layer CPP aluminum-plastic film, requiring bending at the edges before heat sealing. This can easily lead to stress concentration at the bending points, resulting in micro-gaps that become channels for moisture and oxygen penetration. This solution changes the direction and method of encapsulation stress, significantly improving sealing performance. In addition, in the CPP+Al+CPP three-layer structure, the outer CPP layer provides good heat sealing performance and mechanical strength, the middle Al layer forms a dense physical barrier to effectively block the penetration of moisture and oxygen, and the inner CPP layer not only provides good resistance to electrolyte corrosion, but also forms a double heat sealing structure with the outer CPP layer to further enhance the sealing performance.

[0008] The CPP layer can be selected from materials such as cast polypropylene and modified polypropylene, while the intermediate Al layer can be selected from materials such as pure aluminum and aluminum alloy.

[0009] Furthermore, the process includes sealing tests on the packaged lithium batteries. This step effectively filters out products that fail to meet sealing performance standards, ensuring stable product quality and improving product reliability.

[0010] Furthermore, the surface cleaning is performed using ultrasonic cleaning, and the surface modification is performed using plasma treatment. Ultrasonic cleaning effectively removes oil, dust, and other impurities from the aluminum-plastic film surface, providing a clean surface for subsequent processing. Plasma treatment enhances the activity of the aluminum-plastic film surface, strengthens its surface adhesion, and facilitates subsequent packaging processes. Specifically, the ultrasonic cleaning temperature is 40-50℃, the ultrasonic frequency is 40kHz, and the cleaning time is 10-15 minutes. During plasma treatment, the vacuum degree is 10-20Pa, the volume ratio of argon to oxygen mixture is 3:1, the processing power is 100-150W, and the processing time is 3-5 minutes. These parameter ranges ensure optimal surface cleaning and modification results.

[0011] Furthermore, the thickness of the CPP layer is 30-40 μm, and the thickness of the intermediate Al layer is 35-45 μm. This range ensures both sufficient barrier properties and good heat-sealing performance and mechanical strength.

[0012] Furthermore, the aluminum-plastic film is pre-formed using molds and vacuum hot pressing equipment. Using molds and vacuum hot pressing equipment ensures the precision of the aluminum-plastic film pre-forming. Specifically, the mold surface is coated with a polytetrafluoroethylene (PTFE) coating, which provides high-temperature resistance and low surface energy, facilitating demolding of the aluminum-plastic film and improving molding quality. Specifically, the mold can be a high-precision metal mold, and the PTFE coating thickness can be 1-10 μm to ensure its durability and demolding effect.

[0013] Furthermore, the aluminum-plastic film preforming is carried out in an environment with a vacuum degree ≤1Pa, with a heating rate of 5-8℃ / min, the temperature rising to 120-130℃, a pressure of 1.5-2.0MPa applied, and a holding time of 15-20 minutes, followed by a cooling rate of 3-5℃ / min to room temperature. These process parameters ensure the quality of the aluminum-plastic film preforming, making it precisely match the battery cell contour, laying the foundation for subsequent packaging processes.

[0014] Furthermore, the overlapping hot-melt sealing is performed in an environment with a vacuum degree ≤1Pa, with a heating rate of 5-8℃ / min, reaching a temperature of 180-190℃, applying a pressure of 0.3-0.5MPa, holding the pressure for 2-6 seconds, and then cooling down to room temperature at a cooling rate of 3-5℃ / min. By directly overlapping the CPP layers of the upper and lower aluminum-plastic films and then hot-melting them, the main seal is completed in one step, changing the force direction of traditional face-to-face side sealing and improving the sealing performance.

[0015] Furthermore, the sealing process includes two steps: laser welding and sealant coating and curing. Laser welding provides a high-precision edge seal, while sealant coating and curing further enhance the sealing performance. The combination of these two steps forms a dual sealing mechanism, effectively preventing the infiltration of moisture and oxygen. Specifically, the laser wavelength for laser welding is 1064nm, the laser power is 80-120W, and the welding speed is 3-5mm / s. The sealant is an epoxy resin sealant with a curing temperature of 80-90℃ and a curing time of 2-3 hours. The epoxy resin sealant can be selected from two-component epoxy resins, one-component thermosetting epoxy resins, etc., and has good resistance to electrolyte corrosion and sealing performance. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the cross-sectional structure of aluminum-plastic film in the prior art.

[0017] Figure 2This is a schematic cross-sectional view of the intermediate body of the aluminum-plastic film according to the first embodiment of this application.

[0018] Figure 3 This is a schematic cross-sectional view of the intermediate body of the aluminum-plastic film according to the second embodiment of this application.

[0019] Figure 4 for Figure 3 The diagram shows a planar structure of the intermediate component of the aluminum-plastic film.

[0020] Figure 5 This is a schematic diagram of the cross-sectional structure of a square pouch cell.

[0021] Figure 6 for Figure 5 The diagram shows a planar structure of a square pouch cell.

[0022] Figure 7 This is a schematic diagram of the cross-sectional structure of the battery pack.

[0023] Figure 8 This is a schematic diagram of the planar structure of the battery pack.

[0024] Figure 9 This is a schematic diagram of the side sealing process for the intermediate component of the aluminum-plastic film.

[0025] Figure 10 This is a schematic diagram of the end-sealing process for the intermediate component of the aluminum-plastic film. Detailed Implementation

[0026] To facilitate understanding of this application, a more complete description will be provided below. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0027] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of the application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The terminology used herein includes any and all combinations of one or more of the associated listed items.

[0029] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0030] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0031] Unless otherwise specified, the percentage content mentioned in this application refers to mass percentage for solid-liquid mixtures and solid-phase-solid mixtures, and volume percentage for liquid-phase-liquid mixtures.

[0032] Unless otherwise specified, all percentage concentrations mentioned in this application refer to the final concentration. The final concentration refers to the proportion of the added component in the system after the addition of that component.

[0033] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0034] The particles mentioned in this application, or substances with defined particle size distributions, are not necessarily spherical in shape; they may be irregular in shape and can be primary or secondary particles. The particle size of irregular particles is calculated as the average of their maximum and minimum diameters.

[0035] Terminology Explanation Face-to-face side sealing is a traditional method for encapsulating lithium-ion batteries using aluminum-plastic film. The main steps include: first, bending the edges of two aluminum-plastic films so that their CPP layers are in face-to-face contact, and then heat-sealing the sides. The disadvantages of this process are that stress concentration easily occurs at the bending points of the aluminum-plastic film, forming tiny gaps that become channels for moisture and oxygen to permeate, resulting in poor sealing. Furthermore, face-to-face side sealing requires heat sealing on the sides of the battery, which is complex, has low production efficiency, and makes it difficult to guarantee the consistency and reliability of the encapsulation.

[0036] Vacuum hot pressing is a hot pressing process performed in a vacuum environment, playing a crucial role in the aluminum-plastic film encapsulation of lithium batteries. Vacuum hot pressing equipment mainly consists of a vacuum system, a heating system, a pressure system, and a control system. During the forming process, the material to be processed is first placed in a vacuum chamber. A vacuum pump reduces the pressure inside the chamber to a predetermined value (e.g., ≤1 Pa). Then, the heating system heats the material, while the pressure system applies pressure, causing the material to deform or bond under high temperature and high pressure. The vacuum environment effectively removes gases and impurities from the material surface, prevents oxidation reactions, and improves the forming quality.

[0037] Laser welding is a technique that uses a high-energy-density laser beam to join materials, playing an important role in the edge sealing of aluminum-plastic films for lithium batteries. The basic principle of laser welding is: a laser beam is focused onto the surface of the material through an optical system, rapidly heating a localized area of ​​the material to its melting or vaporization temperature, and then cooling and solidifying to form a weld joint.

[0038] Helium mass spectrometry (HMS) leak detection technology is a high-precision leak detection method that plays an important role in the sealing test of lithium batteries. The working principle of a HMS leak detector is as follows: the object to be tested is placed in a vacuum chamber, and helium gas is introduced into it. If a leak exists, helium gas will enter the vacuum chamber through the leak point and be detected by the mass spectrometer.

[0039] Gas leakage rate is an important indicator of sealing performance, representing the amount of gas passing through a leak point per unit time. In the International System of Units (SI), the unit for gas leakage rate is Pa·m. 3 / s indicates that, under a pressure difference of 1 Pascal, the gas volume passing through the leak point per second is 1 cubic meter. In the field of lithium battery packaging, the gas leakage rate is directly related to the safety and lifespan of the battery. If the gas leakage rate is too high, it means that the packaging seal is poor, and harmful substances such as moisture and oxygen from the outside can easily seep into the battery, accelerating cell aging, affecting battery performance, and even causing safety hazards.

[0040] Please see Figure 1 A schematic diagram of a conventional aluminum-plastic film encapsulation structure, including PA layer, Al layer and CPP layer. Using side sealing process, the edge of aluminum-plastic film needs to be bent on the side of the cell so that the CPP layers can contact each other, thereby achieving heat sealing.

[0041] Please see Figure 2This is a schematic diagram of the intermediate body 100 of the aluminum-plastic film according to the first embodiment of this application. This embodiment is used for the encapsulation of cylindrical soft-pack battery cells. The intermediate body 100 includes an intermediate Al layer 11, CPP layers 12 located on both sides of the intermediate Al layer, a lamination region 20, and a cavity 30. The intermediate body 100 is obtained by pre-forming the aluminum-plastic film, that is, bending the two ends of the aluminum-plastic film to form the intermediate body 100 by lamination. The cavity 30 matches the contour of the cylindrical soft-pack battery cell, and the cylindrical soft-pack battery cell can be placed in the cavity 30. The two CPP layers in the lamination region can contact each other without bending the edges of the aluminum-plastic film.

[0042] Please see Figure 3 and 4 This is a schematic diagram of the intermediate 100 of the aluminum-plastic film according to the second embodiment of this application. This embodiment is used for... Figure 5 and 6 The diagram shows the packaging of a square soft-pack battery cell. The intermediate body 100 includes an intermediate Al layer 11, CPP layers 12 located on both sides of the intermediate Al layer, a stacking region 20, and a cavity 30. The intermediate body 100 is pre-formed from an aluminum-plastic film, i.e., the two ends of the aluminum-plastic film are bent to stack and form the intermediate body 100. The cavity 30 matches the contour of the square soft-pack battery cell, and the square soft-pack battery cell can be placed inside the cavity 30. The edges of the aluminum-plastic film do not need to be bent to allow the two CPP layers in the stacking region to contact.

[0043] Please see Figure 7 and 8 Here is a schematic diagram of the battery pack structure, and its manufacturing process is as follows: Will Figure 5 and 6 The square soft-pack battery cell shown is placed in Figure 3 and 4 The intermediate 100 of the aluminum-plastic film shown; like Figure 8 As shown, the overlapping area 20 is heated and pressurized by the heating head 401, causing the CPP layers 12 located on both sides of the middle Al layer to melt and fuse. like Figure 9 As shown, the tail end of the intermediate body 100 is heated and pressurized by the heating head 402, so that the aluminum-plastic film intermediate body 100 completely wraps the square soft-pack battery cell to form a battery pack (as shown in the figure). The fourth embodiment of this application provides a lithium battery aluminum-plastic film encapsulation method, as follows: Aluminum-plastic film pretreatment: The aluminum-plastic film is placed in an ultrasonic cleaning device, using 45℃ deionized water as the cleaning solution, and cleaned at a 40kHz ultrasonic frequency for 12 minutes. After cleaning, it is dried with high-purity nitrogen gas. Then, the aluminum-plastic film is sent to a plasma treatment device, where an argon-oxygen mixed gas (volume ratio 3:1) is introduced under a vacuum of 15Pa and treated at a power of 120W for 4 minutes. The aluminum-plastic film consists of a 35μm thick intermediate Al layer and 30μm thick CPP layers on both sides of the Al layer.

[0044] Aluminum-plastic film forming process: The pre-treated aluminum-plastic film is laid flat in a mold coated with polytetrafluoroethylene. The aluminum-plastic film is placed in the center and its position is adjusted using a mechanical positioning device to control the positional deviation within 0.08mm. The vacuum degree of the mold is evacuated to 8Pa using a vacuum adsorption device. Then, the joint is sealed using an aluminum-plastic film hot pressing forming tool to initially form the aluminum-plastic film. The aluminum-plastic film is then bent to obtain an intermediate body, which has a cavity that matches the square battery cell.

[0045] Pre-assembly of battery cell and aluminum-plastic film: The pre-formed aluminum-plastic film is placed in a special assembly mold, and then the battery cell is placed in the center of the aluminum-plastic film. The position of the battery cell is precisely adjusted by a mechanical positioning device so that the relative position of the battery cell and the aluminum-plastic film is controlled at 0.08mm. Then, the mold is vacuumed using a vacuum adsorption device to a vacuum degree of 6Pa, so that the aluminum-plastic film initially adheres to the surface of the battery cell.

[0046] Vacuum hot pressing: The pre-assembled battery cell and aluminum-plastic film are transferred to a vacuum hot pressing device. Under a vacuum of 0.8 Pa, the temperature is raised to 190°C at a heating rate of 6°C / min, and a pressure of 0.5 MPa is applied and held for 5 seconds. During the hot pressing process, the surface temperature uniformity of the aluminum-plastic film is monitored by an infrared thermometer to ensure that the deviation is within 1.5°C. After the hot pressing is completed, the temperature is lowered to room temperature at a cooling rate of 4°C / min while maintaining the pressure.

[0047] Edge sealing treatment: Laser welding technology is used to weld the edges of the aluminum-plastic film. The laser wavelength is 1064nm, the power is 100W, and the welding speed is 4mm / s. During the welding process, the visual inspection system monitors in real time and automatically repairs any defective parts. After welding, liquid epoxy resin sealant is applied to the edges and cured at 85℃ for 2.5 hours.

[0048] Online detection and post-processing: The gas leakage rate was determined to be 3×10⁻⁶ using a helium mass spectrometer leak detector. -9 Pa·m 3 / s; No appearance defects were found during machine vision inspection, and the dimensional deviation was within ±0.15mm; After 100 charge-discharge cycles at 0.5C, the battery capacity, internal resistance and other performance indicators were normal; After aging in an environment of 55℃ and 90% humidity for 72 hours, the battery performance was stable.

[0049] The fifth embodiment of this application provides a lithium battery aluminum-plastic film encapsulation method, as detailed below: Aluminum-plastic film pretreatment: Place the aluminum-plastic film into an ultrasonic cleaning device, use 40℃ deionized water as the cleaning solution, and clean it for 10 minutes at an ultrasonic frequency of 40kHz. After cleaning, dry it with high-purity nitrogen. Then send the aluminum-plastic film into a plasma treatment device, and in a vacuum environment of 10Pa, introduce an argon-oxygen mixed gas (volume ratio 3:1) and treat it with 100W power for 3 minutes.

[0050] Aluminum-plastic film forming process: The pre-treated aluminum-plastic film is laid flat in a mold coated with polytetrafluoroethylene. The aluminum-plastic film is placed in the center and its position is adjusted using a mechanical positioning device to control the positional deviation within 0.08mm. The vacuum degree of the mold is evacuated to 8Pa using a vacuum adsorption device. Then, the joint is sealed using an aluminum-plastic film hot pressing forming tool to initially form the aluminum-plastic film. The aluminum-plastic film is then bent to obtain an intermediate body, which has a cavity that matches the cylindrical soft-pack battery cell.

[0051] The remaining steps are the same as the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application, and the final product gas leakage rate is 4×10⁻⁶. -9 Pa·m 3 / s, no appearance defects, dimensional deviation within ±0.18mm, and performance test results are normal.

[0052] The sixth embodiment of this application provides a lithium battery aluminum-plastic film encapsulation method, as detailed below: The aluminum-plastic film consists of a 45μm thick intermediate Al layer and 40μm thick CPP layers on both sides of the Al layer.

[0053] Aluminum-plastic film pretreatment: Place the aluminum-plastic film into an ultrasonic cleaning device, use 50℃ deionized water as the cleaning solution, and clean it for 15 minutes at an ultrasonic frequency of 40kHz. After cleaning, dry it with high-purity nitrogen. Then send the aluminum-plastic film into a plasma treatment device, and in a vacuum environment of 20Pa, introduce an argon-oxygen mixed gas (volume ratio 3:1) and treat it with a power of 150W for 5 minutes.

[0054] The remaining steps are the same as the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application, and the final product gas leakage rate is 3.5 × 10⁻⁶. -9 Pa·m 3 / s, no appearance defects, dimensional deviation within ±0.17mm, and performance test results are normal.

[0055] The seventh embodiment of this application provides a lithium battery aluminum-plastic film encapsulation method, as detailed below: Vacuum hot pressing: The pre-assembled battery cell and aluminum-plastic film are transferred to a vacuum hot pressing device. Under a vacuum of 0.5 Pa, the temperature is raised to 180°C at a heating rate of 5°C / min, and a pressure of 0.3 MPa is applied and held for 2 seconds. During the hot pressing process, the surface temperature uniformity of the aluminum-plastic film is monitored by an infrared thermometer to ensure that the deviation is within 2°C. After the hot pressing is completed, the temperature is lowered to room temperature at a cooling rate of 3°C / min while maintaining the pressure.

[0056] The remaining steps are the same as the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application, and the final product gas leakage rate is 4.2 × 10⁻⁶. -9 Pa·m 3 / s, no appearance defects, dimensional deviation within ±0.18mm, and performance test results are normal.

[0057] The eighth embodiment of this application provides a lithium battery aluminum-plastic film encapsulation method, as detailed below: Vacuum hot pressing: The pre-assembled battery cell and aluminum-plastic film are transferred to a vacuum hot pressing device. Under a vacuum of 1 Pa, the temperature is raised to 190°C at a heating rate of 8°C / min, and a pressure of 0.5 MPa is applied and held for 6 seconds. During the hot pressing process, the surface temperature uniformity of the aluminum-plastic film is monitored by an infrared thermometer to ensure that the deviation is within 1°C. After the hot pressing is completed, the temperature is lowered to room temperature at a cooling rate of 5°C / min while maintaining the pressure.

[0058] The remaining steps are the same as the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application, and the final product gas leakage rate is 3.8 × 10⁻⁶. -9 Pa·m 3 / s, no appearance defects, dimensional deviation within ±0.16mm, and performance test results are normal.

[0059] The ninth embodiment of this application provides a lithium battery aluminum-plastic film encapsulation method, as detailed below: Edge sealing treatment: Laser welding technology is used to weld the edges of the aluminum-plastic film. The laser wavelength is 1064nm, the power is 80W, and the welding speed is 3mm / s. During the welding process, the visual inspection system monitors in real time and automatically repairs any defective parts. After welding, liquid epoxy resin sealant is applied to the edges and cured at 80℃ for 2 hours.

[0060] The remaining steps are the same as the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application, and the final product gas leakage rate is 4.5 × 10⁻⁶. -9 Pa·m 3 / s, no appearance defects, dimensional deviation within ±0.19mm, and performance test results are normal.

[0061] The tenth embodiment of this application provides a lithium battery aluminum-plastic film encapsulation method, as detailed below: Edge sealing treatment: Laser welding technology is used to weld the edges of the aluminum-plastic film. The laser wavelength is 1064nm, the power is 120W, and the welding speed is 5mm / s. During the welding process, the visual inspection system monitors in real time and automatically repairs any defective parts. After welding, liquid epoxy resin sealant is applied to the edges and cured at 90℃ for 3 hours.

[0062] The remaining steps are the same as the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application, and the final product gas leakage rate is 3.9 × 10⁻⁶. -9 Pa·m 3 / s, no appearance defects, dimensional deviation within ±0.17mm, and performance test results are normal.

[0063] The eleventh embodiment of this application provides a lithium battery aluminum-plastic film encapsulation method, as detailed below: Aluminum-plastic film forming process: The pre-treated aluminum-plastic film is laid flat in a mold coated with polytetrafluoroethylene (PTFE). The aluminum-plastic film is placed in the center, and its position is adjusted using a mechanical positioning device to control the positional deviation within 0.05mm. The vacuum degree of the mold is evacuated to 5Pa using a vacuum adsorption device. Then, in an environment with a vacuum degree ≤1Pa, the temperature is raised to 120℃ at a heating rate of 5℃ / min, and a pressure of 1.5MPa is applied and held for 15 minutes. During the hot pressing process, the surface temperature of the aluminum-plastic film is monitored in real time using an infrared thermometer to ensure that the temperature uniformity deviation is ≤2℃. After the hot pressing is completed, the temperature is lowered to room temperature at a cooling rate of 3℃ / min while maintaining the pressure, so that the aluminum-plastic film edges are tightly sealed and the forming process is completed.

[0064] The remaining steps are the same as the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application, and the final product gas leakage rate is 4.0 × 10⁻⁶. -9 Pa·m 3 / s, no appearance defects, dimensional deviation within ±0.16mm, and performance test results are normal.

[0065] The twelfth embodiment of this application provides a lithium battery aluminum-plastic film encapsulation method, as detailed below: Aluminum-plastic film forming process: The pre-treated aluminum-plastic film is laid flat in a mold coated with polytetrafluoroethylene (PTFE). The aluminum-plastic film is placed in the center, and its position is adjusted using a mechanical positioning device to control the positional deviation within 0.1mm. The mold is then evacuated to a vacuum level of 10Pa using a vacuum adsorption device. Under a vacuum level of ≤1Pa, the temperature is raised to 130℃ at a heating rate of 8℃ / min, and a pressure of 2.0MPa is applied and held for 20 minutes. During the hot pressing process, the surface temperature of the aluminum-plastic film is monitored in real time using an infrared thermometer to ensure that the temperature uniformity deviation is ≤2℃. After the hot pressing is completed, the film is cooled to room temperature at a cooling rate of 5℃ / min while maintaining the pressure, so that the aluminum-plastic film edges are tightly sealed, completing the forming process.

[0066] The remaining steps are the same as the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application, and the final product gas leakage rate is 3.7 × 10⁻⁶. -9 Pa·m 3 / s, no appearance defects, dimensional deviation within ±0.18mm, and performance test results are normal.

[0067] Comparative Example 1: This comparative example uses an aluminum-plastic film with a PA+Al+CPP structure, instead of the CPP+Al+CPP structure of the present invention. The other steps are the same as the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application.

[0068] Aluminum-plastic film pretreatment: The aluminum-plastic film with PA+Al+CPP structure is placed in an ultrasonic cleaning device, using 45℃ deionized water as the cleaning solution, and cleaned at a 40kHz ultrasonic frequency for 12 minutes. After cleaning, it is dried with high-purity nitrogen. Then, the aluminum-plastic film is sent to a plasma treatment device, and under a vacuum of 15Pa, an argon-oxygen mixed gas (volume ratio 3:1) is introduced and treated at a power of 120W for 4 minutes.

[0069] The remaining steps are the same as the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application, and the final product gas leakage rate is 1.2 × 10⁻⁶. -8 Pa·m 3 / s, with a small number of wrinkle defects, and dimensional deviations within ±0.25mm. Performance tests show that the capacity retention rate is lower than that of the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application.

[0070] Comparative Example 2: This comparative example uses a traditional face-to-face side sealing process, rather than the process of this invention.

[0071] Aluminum-plastic film pretreatment: Place the aluminum-plastic film into an ultrasonic cleaning device, use 45℃ deionized water as the cleaning solution, and clean it for 12 minutes at an ultrasonic frequency of 40kHz. After cleaning, dry it with high-purity nitrogen. Then send the aluminum-plastic film into a plasma treatment device, and in a vacuum environment of 15Pa, introduce an argon-oxygen mixed gas (volume ratio 3:1) and treat it with a power of 120W for 4 minutes.

[0072] Aluminum-plastic film side sealing molding: The pre-treated aluminum-plastic film is laid flat in the molding mold, and the edges of the aluminum-plastic film are bent using a mechanical fixing device so that the CPP layers of the upper and lower aluminum-plastic films are in face-to-face contact; then the bent aluminum-plastic film is transferred to a hot press equipment, and under normal pressure, the temperature is raised to 180°C at a heating rate of 6°C / min, a pressure of 0.5MPa is applied, and the pressure is held for 5 seconds for side heat sealing; after the hot pressing is completed, the temperature is lowered to room temperature at a cooling rate of 4°C / min.

[0073] Battery cell and aluminum-plastic film assembly: Unfold the side-sealed aluminum-plastic film, place the battery cell in the center of the aluminum-plastic film, adjust the position of the battery cell through a mechanical positioning device, and then close the aluminum-plastic film to wrap the battery cell inside.

[0074] Vacuum hot pressing: The assembled battery cell and aluminum-plastic film are transferred to a vacuum hot pressing device. Under a vacuum of 0.8 Pa, the temperature is raised to 180°C at a rate of 6°C / min, and a pressure of 0.3 MPa is applied and held for 5 seconds. During the hot pressing process, an infrared thermometer is used to monitor and ensure that the temperature uniformity deviation of the aluminum-plastic film surface is within 1.5°C. After the hot pressing is completed, the temperature is lowered to room temperature at a rate of 4°C / min while maintaining the pressure.

[0075] Edge sealing treatment: Laser welding technology is used to weld the edges of the aluminum-plastic film. The laser wavelength is 1064nm, the power is 100W, and the welding speed is 4mm / s. During the welding process, the visual inspection system monitors in real time and automatically repairs any defective parts. After welding, liquid epoxy resin sealant is applied to the edges of the aluminum-plastic film and cured at 85℃ for 2.5 hours.

[0076] Online detection and post-processing: The gas leakage rate was determined to be 8.5 × 10⁻⁹ Pa·m⁻¹ using a helium mass spectrometer leak detector. 3 / s; Machine vision inspection revealed edge wrinkles and bubble defects, with dimensional deviations within ±0.30mm; After 100 charge-discharge cycles at 0.5C, the battery capacity retention rate was lower than that of the lithium battery aluminum-plastic film encapsulation method of the fourth embodiment of this application.

[0077] As can be seen from the test results of various embodiments and comparative examples, the lithium battery aluminum-plastic film encapsulation method-9 of the fourth embodiment of this application exhibits excellent sealing performance, appearance quality, and dimensional accuracy, with the gas leakage rate controlled within 5×10⁻⁶. -9 Pa·m 3 With a speed of less than 1 / s, the dimensional deviation is controlled within ±0.2mm, and the capacity retention rate reaches more than 97.8%.

[0078] Comparative Example 1 used an aluminum-plastic membrane with a PA+Al+CPP structure, instead of the CPP+Al+CPP structure of this invention, which resulted in a significantly increased gas leakage rate, reaching 1.2 × 10⁻⁶. -8 Pa·m 3 The temperature was / s, exceeding the standard requirements, and there were also wrinkles and significant dimensional deviations. This indicates that the CPP+Al+CPP three-layer structure plays a crucial role in improving sealing performance and molding accuracy. The heat-sealing performance of PA material is inferior to that of CPP, resulting in a decrease in encapsulation effectiveness.

[0079] Comparative Example 2 uses a traditional face-to-face side-sealing process, rather than the pre-forming followed by head-sealing process of this invention, resulting in an increased gas leakage rate of 8.5 × 10⁻⁶. -9 Pa·m3 The battery exhibits both wrinkles and bubbles, resulting in the largest dimensional deviation. This is because in traditional processes, the edges of the aluminum-plastic film need to be bent before heat sealing, which easily leads to stress concentration at the bending points, causing tiny gaps to form and becoming channels for moisture and oxygen to permeate. The face-to-face top and bottom sealing process of this invention uses pre-forming to precisely match the aluminum-plastic film to the battery cell contour, and then directly overlaps the CPP layers of the two aluminum-plastic films before heat sealing, avoiding the bending process and fundamentally eliminating stress concentration points, resulting in a smoother and tighter sealing interface.

[0080] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0081] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for encapsulating lithium batteries with aluminum-plastic film, characterized in that, Includes the following steps: S1: The aluminum-plastic film is subjected to surface cleaning and surface modification treatment, wherein the aluminum-plastic film comprises an intermediate Al layer and CPP layers located on both sides of the intermediate layer; S2: The pre-treated aluminum-plastic film is pre-formed, the pre-forming process including bending the two ends of the aluminum-plastic film to overlap and form an intermediate body with a cavity, the cavity matching the outline of the battery cell; S3: Place the battery cell in the cavity and perform heat fusion encapsulation on the overlapping area of ​​the aluminum-plastic film; S4: Seal the edges of the aluminum-plastic film after hot-melt sealing.

2. The lithium battery aluminum-plastic film encapsulation method according to claim 1, characterized in that, It also includes testing the sealing performance of the packaged lithium batteries.

3. The lithium battery aluminum-plastic film encapsulation method according to claim 1, characterized in that, The surface cleaning is ultrasonic cleaning, and the surface modification is plasma treatment.

4. The lithium battery aluminum-plastic film encapsulation method according to claim 3, characterized in that, The thickness of the CPP layer is 30-40 μm, and the thickness of the intermediate Al layer is 35-45 μm.

5. The lithium battery aluminum-plastic film encapsulation method according to claim 1, characterized in that, The aluminum-plastic film is pre-formed using molds and vacuum hot pressing equipment.

6. The lithium battery aluminum-plastic film encapsulation method according to claim 5, characterized in that, The aluminum-plastic film preforming is carried out in an environment with a vacuum degree ≤1Pa, with a heating rate of 5-8℃ / min, the temperature is raised to 120-130℃, a pressure of 1.5-2.0MPa is applied, the pressure is held for 15-20s, and then the temperature is lowered to room temperature at a cooling rate of 3-5℃ / min.

7. The lithium battery aluminum-plastic film encapsulation method according to claim 1, characterized in that, The overlapping hot-melt sealing is carried out in an environment with a vacuum degree ≤1Pa, with a heating rate of 5-8℃ / min, the temperature is raised to 180-190℃, a pressure of 0.3-0.5MPa is applied, the pressure is held for 2-6 seconds, and then the temperature is reduced to room temperature at a cooling rate of 3-5℃ / min.

8. The lithium battery aluminum-plastic film encapsulation method according to claim 1, characterized in that, The sealing process includes laser welding and curing of the applied sealant.

9. The lithium battery aluminum-plastic film encapsulation method according to claim 8, characterized in that, The laser wavelength for laser welding is 1064nm, the laser power is 80-120W, and the welding speed is 3-5mm / s.

10. The lithium battery aluminum-plastic film encapsulation method according to claim 8, characterized in that, The sealant is an epoxy resin sealant with a curing temperature of 80-90℃ and a curing time of 2-3 hours.

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