Packaging film and battery

Abstract

The utility model discloses a packaging film and a battery. The packaging film comprises a first organic matter film layer and a second organic matter film layer which are laminated, the first organic matter film layer comprises a barrier layer, and the thickness of the barrier layer is A; the second organic matter film layer comprises a hot melting layer, and the thickness of the hot melting layer is B; wherein A and B meet the condition that A / B is greater than 1 and less than or equal to 1.8. According to the packaging film disclosed by the utility model, by limiting the thickness ratio of the barrier layer to the hot melting layer of the packaging film, on the basis of ensuring the packaging performance of the packaging film, the overall thickness of the packaging film is limited, and meanwhile, the overall elongation at break of the packaging film is improved, so that the bending resistance of the packaging film is improved; and the situation that the packaging film is damaged during packaging can be reduced.

Description

Technical Field

[0001] This utility model relates to the field of batteries, and in particular to a packaging film and a battery. Background Technology

[0002] Traditional soft-pack lithium-ion batteries typically use aluminum-plastic film for their outer packaging. This film mainly consists of three layers: an organic anti-friction layer, a metal aluminum foil layer, and an organic heat-sealing layer. The packaging sequence for the battery cell is as follows: the packaging film wraps the battery cell, and then the film is heat-pressed to seal it.

[0003] In order to reduce the overall area of ​​lithium-ion batteries and increase the volumetric energy density of pouch batteries, manufacturers will seal the edges of the aluminum-plastic film during hot pressing to ensure that the packaging film seals fit the side of the battery cell.

[0004] In existing technologies, by eliminating the aluminum layer in traditional aluminum-plastic films, a multi-layer structure with only organic film layers is formed, which can effectively reduce the thickness of the packaging film and thus the overall thickness of the battery. However, due to the lack of the aluminum layer to support tensile strength, the overall breaking elongation of the packaging film decreases, which makes the packaging film prone to damage during the process of folding and sealing the battery cell. Utility Model Content

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. Therefore, one objective of this invention is to propose a packaging film and battery that, by limiting the thickness ratio of the barrier layer and the heat-fused layer of the packaging film, improves the overall elongation at break of the packaging film while ensuring its sealing performance and limiting its overall thickness, thereby improving the bending resistance of the packaging film and reducing the likelihood of damage during sealing.

[0006] In a first aspect, the present invention provides a packaging film, comprising: a first organic film layer and a second organic film layer stacked together; the first organic film layer includes a barrier layer with a thickness of A; the second organic film layer includes a hot-melt layer with a thickness of B; wherein A and B satisfy: 1 ​​< A / B ≤ 1.8.

[0007] The packaging film of this invention ensures sufficient thickness of the hot-melt layer by limiting the thickness ratio of the barrier layer and the hot-melt layer within the aforementioned range. This guarantees adequate sealing performance of the packaging film during the hot-pressing encapsulation of the battery cell. Simultaneously, it avoids excessive thickness of the hot-melt layer, which could lead to adhesive overflow during hot pressing.

[0008] Furthermore, the thickness ratio of the barrier layer to the heat-sealing layer of the packaging film is within the aforementioned range, effectively balancing the overall thickness and elongation at break of the packaging film. While maintaining the thinness of the packaging film, it ensures sufficient tensile and tear resistance, making it less prone to breakage during the folding and sealing of the battery cells, thus improving the battery's durability and reliability. The increased bending resistance and elongation at break of the packaging film also enhance its pressure resistance during battery use, reducing cell damage and improving battery safety.

[0009] Because the aluminum foil layer has been removed from the packaging film of this application, and the thickness ratio of the barrier layer and the hot-melt layer has been optimized, it is beneficial to control the overall thickness of the packaging film. Thus, the capacity of the battery cell can be increased within the same volume, thereby improving the battery's energy density and range.

[0010] In some embodiments, A and B satisfy: 1.35 ≤ A / B ≤ 1.55.

[0011] In some embodiments, the thickness B of the hot melt layer satisfies: 20μm≤B≤40μm.

[0012] In some embodiments, the packaging film further includes an adhesive layer, the adhesive layer being located at least between the first organic film layer and the second organic film layer, and the thickness C of the adhesive layer satisfying: 2μm≤C≤6μm.

[0013] According to some embodiments of the present invention, the barrier layer includes at least one of amide polymers, polyvinyl fluoride polymers, polyvinyl chloride polymers, enol polymers, saturated polyester polymers, and fluorinated ethylene propylene copolymer polymers, and / or the hot melt layer includes at least one of polypropylene homopolymer, polypropylene copolymer, and polypropylene copolymer containing toughening agent, and / or the adhesive layer includes at least one of acrylate adhesives, polyurethane adhesives, vinyl alcohol adhesives, and polyolefin adhesives.

[0014] Secondly, this utility model embodiment also provides a battery, including: a battery cell, including a first electrode, a separator, and a second electrode stacked together, wherein the first electrode and the second electrode have opposite polarities; and the aforementioned packaging film, wherein the second organic film layer is located on the side of the first organic film layer facing the battery cell, the packaging film covers the battery cell and forms a sealing structure on both sides of the battery cell along its width direction, the packaging film including arc segments on both sides of the battery cell along its width direction and straight segments on both sides of the battery cell along its width direction, the arc segments being located on both sides of the straight segments.

[0015] The battery of this invention, due to the use of the aforementioned packaging film, has improved bending resistance and elongation at break, making the battery packaging more reliable. This helps improve the product quality of the battery, prevents battery damage, and extends the battery's lifespan.

[0016] Because the thickness of the aforementioned packaging film is smaller than that of traditional aluminum-plastic film, the capacity of the battery cells within the same volume is larger, which is beneficial for improving the energy density of the battery.

[0017] In some embodiments, the edge sealing structure is fitted to the arc segment and there is a gap between it and the arc segment, the gap being no greater than 450 μm; preferably, the gap is no greater than 350 μm.

[0018] In some embodiments, the edge sealing structure includes a bent portion and a bent segment formed by bending towards the arc segment, the bent portion being connected to the bent segment, and the radius of curvature R1 of the bent portion satisfying: 20μm≤R1≤35μm; preferably, 22μm≤R1≤30μm.

[0019] In some embodiments, the sealing structure has a free end extending along the thickness direction of the cell, and the battery further includes an adhesive element, wherein the free end is attached to the sidewall of the packaging film along the width direction of the cell via the adhesive element.

[0020] According to some embodiments of the present invention, the adhesive component is adhesive paper, one end of which covers the free end, and the other end is located in the arc segment.

[0021] Additional aspects and advantages of this invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0022] The above and / or additional aspects and advantages of this utility model will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0023] Figure 1 This is a schematic cross-sectional view of the packaging film according to an embodiment of the present invention;

[0024] Figure 2 This is a schematic diagram of the battery structure according to an embodiment of the present invention;

[0025] Figure 3 This is a schematic diagram of the sealing structure of the packaging film according to an embodiment of the present invention;

[0026] Figure 4 This is a schematic diagram of the sealing structure of the packaging film according to another embodiment of the present invention.

[0027] Figure label:

[0028] 10-Packaging film; 11-First packaging section; 12-Second packaging section; 13-Arc segment; 14-Straight segment;

[0029] 1-First organic film layer; 2-Adhesive layer; 3-Second organic film layer;

[0030] 20-battery;

[0031] 21-Battery cell; 22-Edge sealing structure; 221-Bending part; 222-Bending section; 223-Free end; 23-Gap. Detailed Implementation

[0032] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0033] Traditional soft-pack lithium-ion batteries typically use aluminum-plastic film for their outer packaging. This film mainly consists of three layers: an organic anti-friction layer, a metal aluminum foil layer, and an organic heat-sealing layer. The packaging sequence for the battery cell is as follows: the packaging film wraps the battery cell, and then the film is heat-pressed to seal it.

[0034] In order to reduce the overall area of ​​lithium-ion batteries and increase the volumetric energy density of pouch batteries, manufacturers will seal the edges of the aluminum-plastic film during hot pressing to ensure that the packaging film seals fit the side of the battery cell.

[0035] In existing technologies, by eliminating the aluminum layer in traditional aluminum-plastic films, a multi-layer structure with only organic film layers is formed, which can effectively reduce the thickness of the packaging film and thus the overall thickness of the battery. However, due to the lack of the aluminum layer to support tensile strength, the overall breaking elongation of the packaging film decreases, which makes the packaging film prone to damage during the process of folding and sealing the battery cell.

[0036] In view of this, the present invention provides a packaging film and a battery. By limiting the thickness ratio of the barrier layer and the hot melt layer of the packaging film, the overall breaking elongation of the packaging film is increased while limiting the overall thickness of the packaging film, thereby improving the bending resistance of the packaging film and helping to reduce the occurrence of damage to the packaging film during packaging.

[0037] refer to Figure 1 The packaging film 10 of the first aspect of the present invention is described below.

[0038] The packaging film 10 of this embodiment can be used for encapsulating the cell 21 of a lithium-ion battery 20, a sodium-ion battery 20, or other types of batteries 20.

[0039] After the packaging film 10 covers and encapsulates the battery cell 21, it provides a physical barrier for the internal components of the battery 20, such as the battery cell 21 and the electrolyte, to prevent external impact, wear and damage; at the same time, it provides a good sealing effect for the battery 20, ensuring that the internal environment of the battery 20 is isolated from the outside world, preventing harmful substances such as moisture and oxygen from entering the battery 20, which would lead to a decrease in the performance of the battery 20 or failure.

[0040] The packaging film 10 may include a first organic film layer 1 and a second organic film layer 3 stacked together. The first organic film layer 1 may include a barrier layer with a thickness of A, and the second organic film layer 3 may include a hot-melt layer with a thickness of B, wherein A and B satisfy: 1 ​​< A / B ≤ 1.8. For example, A / B can be 1.01, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, or 1.8. Of course, the value of A / B can also be other values, and designers can choose according to their needs. This embodiment does not limit this.

[0041] Understandably, the first organic film layer 1 may also include a reinforcing layer and a corrosion-resistant layer. The reinforcing layer may contain reinforcing fibers or particles, such as organic fibers or carbon fibers, to improve the tensile and tear resistance of the packaging film 10. The corrosion-resistant layer may include polytetrafluoroethylene (PTFE), fluorinated ethylene propylene copolymer (FEP), etc. These materials have good chemical stability and can resist the erosion of chemicals such as acids, alkalis, and organic solvents.

[0042] The second organic film layer 3 may also include a thermally stable layer and an oxide layer. The thermally stable layer may include thermal stabilizers or antioxidants. These additives can improve the thermal stability of the hot-melt layer and reduce decomposition and volatilization during the hot-pressing process. The conductive layer may include conductive materials, such as conductive polymers, carbon nanotubes, etc. These conductive materials can impart certain conductivity to the packaging film 10, thereby enabling the monitoring of the internal state of the battery 20 or wireless charging functions.

[0043] The packaging film 10 of this invention ensures that the hot-melt layer has sufficient thickness by limiting the thickness ratio of the barrier layer and the hot-melt layer within the aforementioned range, thereby guaranteeing sufficient sealing performance of the packaging film 10 during the hot-pressing encapsulation of the battery cell 21. Simultaneously, it avoids excessive thickness of the hot-melt layer, which could lead to adhesive overflow during hot pressing.

[0044] Furthermore, the thickness ratio of the barrier layer and the hot-melt layer of the packaging film 10 is within the aforementioned range, effectively balancing the overall thickness and elongation at break of the packaging film 10. While maintaining the thinness and lightness of the packaging film 10, it ensures sufficient tensile and tear resistance, making it less prone to damage during the folding and sealing of the battery cell 21, thus improving the durability and reliability of the battery 20. Due to the increased bending resistance and elongation at break of the packaging film 10, the battery 20 also has stronger pressure resistance during use, which helps reduce damage to the battery cell 21 and improves the safety of the battery 20.

[0045] Because the aluminum foil layer has been removed from the packaging film 10 of this application, and the thickness ratio of the barrier layer and the hot-melt layer has been optimized, it is beneficial to control the overall thickness of the packaging film 10. Thus, the capacity of the battery cell 21 can be increased within the same volume, thereby improving the energy density and range of the battery 20.

[0046] Furthermore, A and B can satisfy: 1.35 ≤ A / B ≤ 1.55. For example, A / B can be 1.35, 1.40, 1.45, 1.50 or 1.55. Of course, A / B can also be other values, and designers can choose according to their needs. This embodiment does not limit this.

[0047] Thus, further limiting the A / B ratio range allows for a more precise balance between the mechanical strength and flexibility of the packaging film 10. A thicker barrier layer provides better tensile and tear resistance, while the heat-sealing layer ensures a tight bond with the cell 21 surface during hot pressing. This ratio range ensures that the packaging film 10 is not easily damaged when folding and sealing the cell 21, while also maintaining good processability. Since the thickness and performance of the packaging film 10 directly affect the overall performance of the battery 20, an A / B ratio between 1.35 and 1.55 allows the packaging film 10 to maintain its thinness while possessing sufficient mechanical strength and heat-sealing performance, thereby improving the volumetric energy density, safety, and cycle life of the battery 20.

[0048] In some embodiments, the thickness B of the hot-melt layer satisfies: 20μm≤B≤40μm. For example, the thickness B of the hot-melt layer can be 20μm, 25μm, 30μm, 35μm, or 40μm. Of course, the thickness of the hot-melt layer can also be other values, and designers can choose them according to their needs. This embodiment does not limit this. Having a suitable thickness of the hot-melt layer improves its mechanical strength, thereby enhancing its tear resistance, i.e., improving its ductility, and preventing the hot-melt layer from cracking when the packaging film 10 forms the sealing structure 22. Furthermore, after the packaging film 10 covers the battery cell 21, the connection stability is high when the two inner film layers on both sides of the battery cell 21 are hot-melted together, and glue overflow at the connection point is also avoided, thereby improving the packaging quality and ultimately improving the safety of the battery 20.

[0049] It is understood that the design dimensions of the hot melt layer are given in this embodiment. Combined with the A / B ratio mentioned above, the thickness dimension B of the hot melt layer can be deduced accordingly.

[0050] Thus, by limiting the thickness range of the hot-melt layer and the barrier layer, the size of the packaging film 10 is determined, facilitating production. On the one hand, this avoids the packaging film 10 being too thin, which would easily deform under external force and provide poor protection for the battery cell 21 of the battery 20. On the other hand, it avoids the packaging film 10 being too thick, which would lead to excessively high production costs and hinder large-scale production. Furthermore, if the packaging film 10 is too thick, there will be significant stress concentration at the bending point when bending to form the sealing structure 22, which could also cause damage to the sealing structure 22 formed by the packaging film 10.

[0051] In some embodiments, there may be at least one hot-melt layer; in other words, there may be one hot-melt layer or two or more hot-melt layers. When there is only one hot-melt layer, it can provide good sealing performance for the inside of the battery 20; or, when there are more than one hot-melt layers, it further improves the sealing performance of the packaging film 10, while also improving the structural strength of the packaging film 10, providing additional mechanical support for the battery 20, improving the battery 20's resistance to pressure and impact, and thus improving the strength of the battery 20 sealing edge structure 22 formed by the packaging film 10.

[0052] In some embodiments, the packaging film 10 may further include an adhesive layer 2, which is located at least between the first organic film layer 1 and the second organic film layer 3. The addition of the adhesive layer 2 significantly enhances the adhesive force between the first organic film layer 1 and the second organic film layer 3. This helps ensure that the first organic film layer 1 and the second organic film layer 3 do not separate or delaminate during processing and use, thereby improving the overall structural stability and durability of the packaging film 10.

[0053] Understandably, the adhesive layer 2 can be disposed not only between the first organic film layer 1 and the second organic film layer 3, but also between adjacent film layers when the first organic film layer 1 and the second organic film layer 3 are multi-layer structures, thereby improving the overall structural stability of the packaging film 10 and the sealing performance of the battery 20.

[0054] The thickness C of the adhesive layer 2 satisfies: 2μm ≤ C ≤ 6μm. The thickness of the adhesive layer 2 can be 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 4.5μm, 5μm, 5.5μm, or 6μm. Of course, the thickness of the adhesive layer 2 can also be other values, and designers can choose according to their needs; this embodiment does not impose any restrictions. Having a suitable thickness for the adhesive layer 2 facilitates the large-scale production of the packaging film 10. On the one hand, it avoids the adhesive layer 2 being too thin (e.g., less than 2μm), resulting in weak adhesion between the first organic film layer 1 and the second organic film layer 3, which is detrimental to the long-term use of the battery 20. On the other hand, it also avoids the adhesive layer 2 being too thick (e.g., exceeding 6μm), resulting in an excessively thick packaging film 10, causing a significant increase in cost and hindering production.

[0055] According to some embodiments of the present invention, the barrier layer may include at least one of amide polymers, polyvinyl fluoride polymers, polyvinyl chloride polymers, enol polymers, saturated polyester polymers, and fluorinated ethylene propylene copolymer polymers. That is, the barrier layer may include one of the above polymers, or a combination of any two, three, four, five, or six polymers. Of course, the barrier layer may also be a combination of the above seven polymers.

[0056] Among them, amide polymers, polyvinyl fluoride polymers, polyvinyl chloride polymers, enol polymers, and saturated polyester polymers all have good barrier properties: amide polymers (such as nylon) have good gas barrier properties, especially for oxygen and carbon dioxide, which can prevent oxygen and carbon dioxide from entering the battery 20 and reacting with the electrolyte, thus reducing the battery's range; polyvinyl fluoride polymers (such as polytetrafluoroethylene) and fluorinated ethylene propylene copolymers have excellent chemical barrier properties, effectively preventing chemical penetration and avoiding electrolyte leakage through the packaging film 10. The following materials are used to improve the sealing performance of the battery 20: Polyvinyl chloride polymers (such as polyvinyl chloride) have good water and gas barrier properties, preventing moisture and oxygen from entering the battery 20 and causing corrosion and failure; enol polymers (such as ethylene-vinyl alcohol copolymers) have extremely high gas barrier properties, especially excellent oxygen barrier properties, effectively preventing oxygen from entering the battery 20 and participating in the electrochemical reaction process of the electrolyte; saturated polyester polymers (such as polyethylene terephthalate) have good water vapor and gas barrier properties, effectively preventing internal corrosion of the battery 20. Amide polymers, polyvinyl fluoride polymers, saturated polyester polymers, and fluorinated ethylene propylene copolymers all have good heat resistance properties, allowing the battery 20 to be used under high-temperature conditions. Furthermore, amide polymers have high strength and good wear resistance, while saturated polyester polymers have good toughness and impact resistance, all of which can effectively improve the overall performance of the packaging film 10, making the sealing structure 22 formed by the packaging film 10 less prone to damage. Furthermore, all of the above materials have good processing properties and are easy to process into shapes through extrusion, injection molding, or blow molding processes.

[0057] The barrier layer comprises one or more of the above polymers, which improves the barrier properties, chemical resistance, heat resistance, mechanical properties and processing properties of the packaging film 10.

[0058] The hot-melt layer may include at least one of polypropylene homopolymer, polypropylene copolymer, and polypropylene copolymer containing a toughening agent. For example, the hot-melt layer may include polypropylene homopolymer, polypropylene copolymer, or polypropylene copolymer containing a toughening agent; alternatively, the hot-melt layer may include polypropylene homopolymer and polypropylene copolymer, polypropylene homopolymer and polypropylene copolymer containing a toughening agent, or polypropylene copolymer and polypropylene copolymer containing a toughening agent; or the hot-melt layer may simultaneously include polypropylene homopolymer, polypropylene copolymer, and polypropylene copolymer containing a toughening agent. The polypropylene homopolymer provides excellent rigidity and strength to the packaging film 10, the polypropylene copolymer enhances the toughness and impact resistance of the packaging film 10, and the polypropylene copolymer containing a toughening agent further improves the material's impact resistance and flexibility. By combining different types of materials, the packaging film 10 can possess the aforementioned properties, thereby improving the overall performance of the packaging film 10 and preventing damage to the sealing structure 22 when the packaging film 10 forms the sealing structure 22 to encapsulate the battery cell 21.

[0059] The adhesive layer 2 may include at least one of acrylate adhesives, polyurethane adhesives, vinyl alcohol adhesives, and polyolefin adhesives. In other words, the adhesive layer 2 may include one of the above materials, or a combination of any two or three of them. Of course, the adhesive layer 2 may also be a combination of the above four adhesives.

[0060] Among these adhesives, all possess excellent bonding properties: acrylic adhesives exhibit good bonding strength and durability, forming a strong bond between various substrates to extend the service life of the packaging film 10; polyurethane adhesives offer excellent bonding performance and elasticity, enhancing the mechanical strength and toughness of the packaging film 10; alkenyl alcohol adhesives possess good bonding performance and water resistance, suitable for bonding the outermost two layers and the innermost two layers of the packaging film 10, thus providing good waterproof and moisture-proof effects; polyolefin adhesives possess good bonding performance and chemical resistance, suitable for bonding the layers of the packaging film 10. This results in the packaging film 10 exhibiting excellent stability, durability, tensile strength, tear strength, and impact resistance, improving the structural strength of the sealing structure 22 formed by the packaging film 10 and preventing bending and damage to the sealing structure 22.

[0061] Understandably, the preparation of the packaging film 10 of this invention may include the following steps:

[0062] S1: Hot melt layers and barrier layers of different thicknesses and materials are prepared by compression molding, injection molding or co-extrusion molding processes;

[0063] S2: The surfaces of each organic film layer in the contact adhesive layer 2 are treated with a corona discharge process;

[0064] S3: Apply adhesive layer 2 between the obtained film layers, and after baking at 60-70℃, adhesive layer 2 fixes the adjacent film layers to obtain packaging film 10.

[0065] The following are specific embodiments and comparative examples of the packaging film 10 of the first aspect of this utility model:

[0066] Example 1

[0067] The packaging film 10 has a total thickness of 66 μm. From the outside to the inside, it consists of a barrier layer and a hot-melt layer. Adjacent film layers are fixed together by an adhesive layer 2 (modified polyurethane), which has a thickness of 3 μm. The barrier layer comprises organic nylon (amide polymer) and polyethylene terephthalate (saturated polyester polymer), with a thickness A of 33 μm. The hot-melt layer is a polypropylene layer with a thickness B of 30 μm. During the hot-press encapsulation of the battery 20 cells using the packaging film 10, the hot-pressing temperature is 180℃, the hot-pressing pressure is 0.3 MPa, and the hot-pressing time is 3 s. The thickness of the sealing structure 22 at the hot-press encapsulation point is 0.155 mm. The sealing structure 22 of the battery 20 is close to the packaging film 10, and the sealing structure 22 and the portion of the battery cell 21 covered by the packaging film 10 are fixed together using an adhesive dispensing process.

[0068] Example 2

[0069] Unlike Example 1, the thickness A of the barrier layer is set to 35 μm, and the thickness B of the hot melt layer is set to 28 μm.

[0070] Example 3

[0071] Unlike Example 1, the thickness A of the barrier layer is set to 37 μm, and the thickness B of the hot melt layer is set to 26 μm.

[0072] Comparative Example 1

[0073] Unlike Example 1, the thickness A of the barrier layer is set to 23 μm, and the thickness B of the hot melt layer is set to 40 μm.

[0074] Comparative Example 2

[0075] Unlike Example 1, the thickness A of the barrier layer is set to 31.5 μm, and the thickness B of the hot melt layer is set to 31.5 μm.

[0076] Comparative Example 3

[0077] Unlike Example 1, the thickness A of the barrier layer is set to 41 μm, and the thickness B of the hot melt layer is set to 22 μm.

[0078] The inventors of this application tested the bending resistance of the packaging film 10 in Embodiments 1 to 3 and Comparative Examples 1 to 3 during the heat-sealing process, and the results are shown in the table below: Table 1 Test Results of Bending Resistance of Packaging Film 10 in Each Embodiment and Comparative Example during Heat-Sealing

[0079]

[0080] Based on the analysis of Examples 1 to 3 and Comparative Examples 1 to 3, it can be concluded that when the thickness of the packaging film 10 is constant, the physical properties of the packaging film 10 can be changed by altering the thickness ratio A / B of the barrier layer and the hot-melt layer. When the thickness ratio A / B of the barrier layer and the hot-melt layer of the packaging film 10 satisfies 1 < A / B ≤ 1.8, the packaging film 10 exhibits good ductility and bending resistance, resulting in a low risk of edge breakage during the encapsulation of the battery cell 21. When the thickness ratio A / B of the barrier layer and the hot-melt layer of the packaging film 10 does not satisfy 1 < A / B ≤ 1.8, the packaging film 10 exhibits poor ductility and bending resistance, resulting in a high risk of edge breakage during the encapsulation of the battery cell 21.

[0081] The cross-bending resistance test method is as follows: First, fold the packaging film 10 sample 180° towards the opposite direction of the heat-fused layer, and repeatedly roll and press it three times with a 2kg roller. Then, fold the packaging film 10 a second time 180°, ensuring that the crease is perpendicular to the previous crease, forming a cross structure, and roll and press it three times again with a 2kg roller. Repeat the above operation. After each pressing, observe the packaging film 10 sample against a light source to check for damage or cracks, mainly observing the intersection of the two folds. When a light-transmitting point appears on the packaging film 10 sample, the number of folds at this point is the number of times the packaging film 10 breaks due to cross bending. The breaking elongation test method for packaging film 10 is as follows: Cut long strip samples from the packaging film 10, with a sample width of 15mm and a total sample length of not less than 150mm, and the number of samples is not less than 5. Ensure that the sample edges are smooth and free of damage or gaps. Clamp the two ends of the specimen onto the upper and lower grips of the tensile testing machine, respectively, ensuring that the centerline of the specimen coincides with the centerline of the upper and lower grips. Set the pulling speed to 230 mm / min, start the tensile testing machine to stretch the specimen, and when the specimen breaks, the ratio of the increase in distance between two spaced lines along the length of the specimen to the original distance between the two lines is the breaking elongation of the packaging film 10.

[0082] refer to Figures 2 to 4 Secondly, embodiments of this utility model also provide a battery 20, which can be a lithium-ion battery 20, a sodium-ion battery 20, or other types of batteries 20. The battery 20 may include a cell 21 and the aforementioned packaging film 10.

[0083] The battery cell 21 may include a first electrode, a separator, and a second electrode arranged in a stacked manner, with the polarities of the first electrode and the second electrode being opposite. The battery cell 21 may be a wound-core battery cell or a stacked-core battery cell.

[0084] The second organic film layer 3 is located on the side of the first organic film layer 1 facing the battery cell 21. The packaging film 10 covers the battery cell 21 and forms sealing structures 22 on both sides of the battery cell 21 along the width direction. The packaging film 10 may include arc segments 13 on both sides along the width direction of the battery cell and straight segments 14 on both sides along the width direction of the battery cell, with the arc segments 13 located on both sides of the straight segments 14.

[0085] Understandably, when the packaging film 10 encapsulates the battery cell 21, arc segments 13 are formed on both sides of the packaging film 10 along the width direction of the battery cell 21. When the battery cell 21 is a stacked battery cell, the arc segments 13 can be formed by the extension of the packaging film 10 itself. When the battery cell 21 is a stacked battery cell, the arc segments 13 can also be formed by the extension of the packaging film 10 itself. Alternatively, the arc segments 13 can also be formed by bonding the packaging film 10 with the roll-type battery cell.

[0086] The preparation process of the battery 20 of this utility model may include the following steps:

[0087] S1: The positive electrode active material, conductive agent, binder and solvent are stirred evenly and then coated on the surface of the positive electrode substrate to obtain the positive electrode sheet; the positive electrode substrate is selected as 9μm aluminum foil; the obtained electrode sheet is dried and rolled to obtain the positive electrode sheet; the negative electrode active material graphite, conductive agent, binder and solvent are stirred evenly and then coated on the surface of the negative electrode substrate to obtain the negative electrode sheet; the negative electrode substrate is selected as 6μm copper foil; the obtained electrode sheet is dried and rolled to obtain the negative electrode sheet;

[0088] S2: The positive electrode tab is welded to the empty foil of the aluminum foil, and the negative electrode tab is welded to the empty foil of the copper foil. The electrode is then laminated or wound with the separator to obtain the battery cell 21.

[0089] S3: The battery cell 21 is placed inside the packaging film 10 of the battery 20, and then the battery 20 is obtained through liquid injection, sealing, aging, formation, resealing, and OCV processes.

[0090] S4: After the packaging film 10 covers the battery cell 21, it extends and stacks along both sides of the width of the battery 20 and is heat-pressed to form an edge sealing structure 22. The edge sealing structure 22 is fixed to the packaging film 10 by dispensing or adhesive bonding.

[0091] The battery 20 of this utility model, due to the use of the above-mentioned packaging film 10, has improved bending resistance and elongation at break, making the packaging of the battery 20 more reliable, which is conducive to improving the product quality of the battery 20, avoiding damage to the battery 20, and extending the service life of the battery 20.

[0092] Since the thickness of the packaging film 10 is smaller than that of traditional aluminum-plastic film, the capacity of the battery cell 21 inside the battery 20 is larger for the same volume, which is beneficial to improving the energy density of the battery 20.

[0093] In some embodiments, the edge sealing structure 22 is fitted to the arc segment 13, and there is a gap 23 between the edge sealing structure 22 and the arc segment 13.

[0094] Understandably, the packaging film 10 may also include a first packaging portion 11 and a second packaging portion 12 opposite to each other along the thickness direction of the battery cell 21, wherein the inner film layers of the first packaging portion 11 and the second packaging portion 12 are heat-fused together at the sealing structure 22.

[0095] The first packaging section 11 and the second packaging section 12 are both part of the packaging film 10. The first packaging section 11 covers the top end of the battery cell 21 in the thickness direction and both sides in the width direction, and the second packaging section 12 covers the bottom end of the battery cell 21 in the thickness direction. After the first packaging section 11 and the second packaging section 12 cover the battery cell 21, they are stacked on both sides of the battery cell 21 in the width direction, and the inner film layers of the first packaging section 11 and the second packaging section 12 are heat-fused together at the stacking point. The stacked structure extends away from the battery cell 21. This part of the structure is bent and heat-sealed to form a sealing structure 22, which encapsulates the battery cell 21 of the battery 20. It has good ductility, and the sealing structure 22 will not be damaged, which helps to improve the safety of the battery 20. The arc segment 13 mentioned above can be located on the first packaging section 11.

[0096] While making the sealing structure 22 fit the arc segment 13, a certain gap 23 is left between the sealing structure 22 and the arc segment 13. In this way, the sealing structure 22 and the arc segment 13 can be fixed by filling with adhesive, thereby improving the sealing effect of the packaging film 10.

[0097] Since the packaging film 10 in this embodiment has a higher elongation at break, when bending to form the sealing structure 22 and fixing the battery cell 21, the bending range of the sealing structure 22 can be greater while ensuring sufficient structural strength. In other words, the sealing structure 22 can be closer to the arc segment 13. Thus, with the same battery volume 20, the capacity of the battery cell 21 in this embodiment can be designed to be larger, thereby improving the energy density of the battery 20.

[0098] The gap 23 does not exceed 450 μm. For example, the gap 23 can be 200 μm, 250 μm, 300 μm, 350 μm, 400 μm, or 450 μm. Of course, the gap 23 can also be other values, and designers can choose according to their needs. This embodiment does not limit this. When fixing the sealing structure 22, glue is applied into the gap 23 to fix the sealing structure 22, resulting in a good sealing effect. Preferably, the gap 23 can not exceed 350 μm. Under the premise of ensuring sufficient structural strength, this allows the sealing structure 22 to be closer to the arc segment 13, thereby improving the energy density of the battery 20.

[0099] In some embodiments, the edge sealing structure 22 includes a bent portion 221 and a bent segment 222 formed by bending toward the arc segment 13, wherein the bent portion 221 is connected to the bent segment 222.

[0100] In other words, the bend in the stacked structure of the first packaging section 11 and the second packaging section 12 constitutes a bend 221, the extension of the stacked structure constitutes a bend segment 222, and a gap 23 is defined between the bend segment 222 and the arc segment 13.

[0101] The radius of curvature R1 of the bending portion 221 satisfies: 20μm ≤ R1 ≤ 35μm. For example, R1 can be 20μm, 21μm, 22μm, 23μm, 24μm, 25μm, 26μm, 27μm, 28μm, 29μm, 30μm, 31μm, 32μm, 33μm, 34μm, or 35μm. Preferably, the range of R1 is 22μm ≤ R1 ≤ 30μm. Of course, R1 can also be other values, and designers can choose according to their needs; this embodiment does not impose any limitations on this.

[0102] Traditional aluminum-plastic film is used to bend and form the sealing structure. To avoid damage to the aluminum-plastic film and subsequent air leakage, the radius of curvature of the bend is usually above 40μm. In this embodiment, due to the use of the aforementioned packaging film 10, the radius of curvature R1 of the bent portion 221 can be below 40μm. While ensuring sufficient structural strength, the bending range of the sealing structure 22 can be greater, allowing the sealing structure 22 to be closer to the arc segment 13. Thus, with the same battery volume 20, the capacity of the cell 21 in this embodiment can be designed to be larger, thereby further improving the energy density of the battery 20.

[0103] Understandably, the bent portion can be a bent structure formed by bending the portion of the stacked structure of the first packaging portion 11 and the second packaging portion 12 along the width direction towards the arc segment 13. Therefore, the radius of curvature R1 of the bent portion can be the radius of the fitted circle at the bend of the aforementioned bent structure. R1 can be measured using the following image processing method:

[0104] Capture clear images of the curved area; use software such as MATLAB or ImageJ to perform edge detection and curve fitting on the curved area images, and then obtain the radius of curvature R1 based on the fitting results.

[0105] Optionally, in some embodiments, the edge sealing structure 22 may include a bent segment 222 formed by at least one bend. For example, the edge sealing structure 22 may include a bent segment 222 (see reference). Figure 3 Alternatively, the edge sealing structure 22 may also include two bent sections 222 (see reference). Figure 4 The bent sections 222 are connected by a bend 221. In this way, the sealing structure 22 provides a sealing and protective effect for the battery cell 21 inside the packaging film 10.

[0106] It should be noted that the sealing structure 22 of the battery 20 can be selected according to the thickness of the specific cell 21. When the thickness of the cell 21 is large (e.g., not less than 6mm), the sealing structure can include two bending sections 222, so that the sealing effect of the sealing structure 22 is better. When the thickness of the cell 21 is small (e.g., less than 6mm), the sealing structure 22 can include only one bending section 222, so that the sealing structure 22 is more compatible with the cell 21 and will not exceed the thickness of the cell 21.

[0107] refer to Figure 3 In some embodiments, the sealing structure 22 has a free end 223 extending along the thickness direction of the cell 21. The battery 20 may also include an adhesive component, with the free end 223 adhered to the sidewall of the packaging film 10 along the width direction of the cell 21, i.e., the sidewall of the first packaging section 11 along the width direction of the cell 21, via the adhesive component. Compared to fixing the sealing structure 22 and the packaging film 10 using an adhesive dispensing process, this embodiment uses an adhesive component to bond and fix the sealing structure 22 and the packaging film 10, reducing the adhesive layer between the sealing structure 22 and the packaging film 10, which can also improve the energy density of the battery 20. Furthermore, since the sealing structure 22 is formed by bending, the radius of curvature at the bend in the first packaging section 11 is the smallest, making it most prone to breakage. Sealing with an adhesive component can effectively block leakage paths and improve the sealing performance of the battery 20.

[0108] In some embodiments, the adhesive can be adhesive tape, with one end covering the free end 223 of the sealing structure 22 and the other end located on the arc segment 13. In other words, when the sealing structure 22 is fixed by adhesive tape, the adhesive tape is not pasted onto the straight segment 14. This helps to ensure the flatness of the side of the battery 20 along the thickness direction, making the force on the battery 20 more uniform, avoiding affecting the structural strength of the battery 20, and thus extending the service life of the battery 20.

[0109] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0110] In the description of this utility model, "first feature" and "second feature" may include one or more of the features.

[0111] In the description of this utility model, "multiple" means two or more.

[0112] In the description of this utility model, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or it may include the first and second features not being in direct contact but being in contact through another feature between them.

[0113] In the description of this utility model, the terms "above", "over" and "on top" for the first feature and the second feature include the first feature being directly above or diagonally above the second feature, or simply indicate that the first feature is at a higher horizontal level than the second feature.

[0114] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0115] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A packaging film, characterized in that, include: A first organic membrane layer and a second organic membrane layer are stacked together; The first organic film layer includes a barrier layer, the thickness of which is A; The second organic film layer includes a hot-melt layer, the thickness of which is B; Among them, A and B satisfy: 1 ​​< A / B ≤ 1.

8.

2. The packaging film according to claim 1, characterized in that, The condition A and the condition B satisfy: 1.35 ≤ A / B ≤ 1.

55.

3. The packaging film according to claim 1, characterized in that, The thickness B of the hot melt layer satisfies: 20μm≤B≤40μm.

4. The packaging film according to claim 1, characterized in that, Also includes: An adhesive layer is located at least between the first organic film layer and the second organic film layer, and the thickness C of the adhesive layer satisfies: 2μm≤C≤6μm.

5. The packaging film according to claim 4, characterized in that, The barrier layer comprises at least one of amide polymers, polyvinyl fluoride polymers, polyvinyl chloride polymers, enol polymers, saturated polyester polymers, and fluorinated ethylene propylene copolymer polymers, and / or, The hot melt layer comprises at least one of polypropylene homopolymer, polypropylene copolymer, and polypropylene copolymer containing a toughening agent, and / or, The adhesive layer includes at least one of acrylate adhesives, polyurethane adhesives, vinyl alcohol adhesives, and polyolefin adhesives.

6. A battery, characterized in that, include: A battery cell includes a first electrode, a separator, and a second electrode stacked together, wherein the first electrode and the second electrode have opposite polarities; The packaging film according to any one of claims 1-5, wherein the second organic film layer is located on the side of the first organic film layer facing the battery cell, the packaging film covers the battery cell and forms a sealing structure on both sides of the battery cell along the width direction, the packaging film includes arc segments on both sides of the battery cell along the width direction and straight segments on both sides of the battery cell along the width direction, the arc segments being located on both sides of the straight segments.

7. The battery according to claim 6, characterized in that, The edge sealing structure is fitted to the arc segment and there is a gap between it and the arc segment, the gap being no greater than 450μm.

8. The battery according to claim 7, characterized in that, The gap is no greater than 350 μm.

9. The battery according to claim 6, characterized in that, The edge sealing structure includes a bent portion and a bent segment formed by bending towards the arc segment. The bent portion is connected to the bent segment, and the radius of curvature R1 of the bent portion satisfies: 20μm≤R1≤35μm.

10. The battery according to claim 9, characterized in that, 22μm≤R1≤30μm.

11. The battery according to claim 6, characterized in that, The sealing structure has a free end extending along the thickness direction of the battery cell. The battery further includes an adhesive component, wherein the free end is attached to the sidewall of the packaging film along the width direction of the cell via the adhesive component.

12. The battery according to claim 11, characterized in that, The adhesive component is adhesive tape, with one end of the adhesive tape covering the free end and the other end located on the arc segment.

Images