Battery module and battery pack comprising same

Abstract

The application provides an electric core and a battery module comprising the same. The electric core comprises: a shell, the surface of the shell has a dynamic value of 36 dyn / cm or more; and an insulating film attached to the surface of the shell through a surface adhesive layer, the glass transition temperature of the surface adhesive layer being -50 DEG C to -20 DEG C. In the electric core, the polarity of the surface of the shell is matched with the flexibility and stress release capacity of the surface adhesive layer of the insulating film on the surface of the shell, so that a stable and firm interface adhesion is established between the insulating film and the shell, and the reliability of the long-term adhesion of the insulating film to the surface of the shell under small-area adhesion is improved.

Description

Technical Field

[0001] This invention belongs to the field of new energy battery technology, specifically, it relates to a battery cell and a battery module including the same. Background Technology

[0002] In the field of new energy battery technology, insulating films are typically attached to the outer surface of the cell casing (such as an aluminum casing) to achieve insulation between the casing and the module structural components. Currently, commonly used insulating films are applied by roll forming on the casing surface. The design of the surface adhesive layer mainly focuses on the initial tack at the moment of application, assuming that a stable contact is achieved between the surface adhesive layer and the casing interface after application. However, the casing surface has microscopic irregularities after stretching and forming, and the surface adhesive layer deforms during the roll forming process. After application, it needs to undergo stress relaxation and molecular chain springback to stabilize. During this process, residual stress can easily be generated within the surface adhesive layer, leading to localized lifting or bubble formation of the insulating film. Summary of the Invention

[0003] In order to ensure that the insulating film of the battery cell adheres smoothly and firmly to the surface of the battery cell casing during long-term use, the present invention provides a battery cell and a battery module including the same.

[0004] According to a first aspect of the present invention, a battery cell is provided, comprising: a housing having a dyn value ≥ 36 dyn / cm on the outer surface of the housing; and an insulating film including a surface adhesive layer and attached to the outer surface of the housing through the surface adhesive layer, the surface adhesive layer having a glass transition temperature of -50°C to -20°C.

[0005] Furthermore, the static contact angle between the surface adhesive layer and ultrapure water is ≥90°.

[0006] Furthermore, the static contact angle between the surface adhesive layer and ultrapure water is ≥95°.

[0007] Furthermore, the glass transition temperature of the surface adhesive layer is -40℃ to -25℃.

[0008] Furthermore, the surface adhesive layer includes an acrylic copolymer, which is obtained by polymerization of at least a comonomer; the comonomer includes a soft monomer and a hard monomer, and the mass ratio of the soft monomer to the hard monomer is 45~80:8~48; the soft monomer includes at least one of 2-ethylhexyl acrylate and n-butyl acrylate, and the hard monomer includes at least one of acrylic acid, methyl methacrylate, and vinyl acetate.

[0009] Furthermore, the comonomer also includes functional monomers, including at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, acrylic acid, and methacrylic acid.

[0010] Furthermore, the comonomer includes at least one of acrylic acid and methacrylic acid.

[0011] Furthermore, the surface adhesive layer also contains a crosslinking agent, which includes at least one of polyisocyanate and metal chelate.

[0012] Furthermore, the comonomer also includes a silane coupling monomer, which is γ-methacryloyloxypropyltrimethoxysilane.

[0013] Furthermore, the comonomer also includes auxiliary soft monomers, which include one or more of isooctyl acrylate, ethyl acrylate, and lauryl acrylate.

[0014] Furthermore, the surface adhesive layer also includes additives, including at least one of liquid acrylate oligomers, polyethylene glycol, polypropylene glycol, or derivatives of the above materials.

[0015] Furthermore, the dyn value of the shell is 38 dyn / cm to 50 dyn / cm.

[0016] Furthermore, the shell includes large side surfaces arranged opposite each other and small side surfaces connecting the two large side surfaces. The large side surfaces and small side surfaces are connected by a transition angle (R-angle), where the R-angle is the curved part of the shell surface transitioning from a planar area to a curved arc area, and the outer radius of the R-angle is ≥1.5 mm. The insulating film includes a starting end and a ending end. The insulating film is continuously attached to the large side surface, the R-angle, and the small side surface starting from the starting end. The ending end of the insulating film is stacked above the starting end in the thickness direction to form an overlapping area. The distance d mm between the cutting end of the starting end and the cutting end of the ending end of the insulating film, and the distance D mm between the cutting end of the ending end and the adjacent end of the R-angle, where the adjacent end refers to the position where the surface curvature of the shell increases from zero. The value of d is 1~15, and D≥d+5.

[0017] Furthermore, the outer fillet radius R of the R-angle satisfies 1.5 mm ≤ R ≤ 5 mm.

[0018] Furthermore, the shell is made of aluminum. Under the conditions of temperature 23℃±5℃ and relative humidity 65%±5% RH, the surface adhesive layer is attached to the outer surface of the shell. The peel strength between the two is measured after 1 day of continuous attachment, which is T1, T1>7 N / 25mm; the peel strength between the two is measured after 7 days of continuous attachment, which is T7, T7-T1≥0 N / 25mm.

[0019] Furthermore, T7-T1≥4 N / 25mm.

[0020] Furthermore, T7-T1≥6 N / 25mm.

[0021] Furthermore, under the conditions of a temperature of 23℃±5℃ and a relative humidity of 65%±5% RH, the surface adhesive layer was attached to the outer surface of the shell and the peel strength between the two was measured after 3 days; T3>10 N / 25mm, T7>13 N / 25mm.

[0022] Furthermore, T1 > 9 N / 25mm, T3 > 11 N / 25mm, and T7 > 15 N / 25mm.

[0023] According to a second aspect of the invention, a battery module is provided, which includes at least one battery cell as described above.

[0024] Implementing the technical solution of the present invention has at least the following beneficial effects: In the battery cell provided by this invention, the dyn value of the shell surface is not less than 36 dyn / cm, ensuring that the shell provides suitable polar surface conditions for the surface adhesive layer, which helps the surface adhesive layer to form a tight initial contact with the shell during adhesion. Meanwhile, in the aforementioned insulating film, the glass transition temperature of the surface adhesive layer is -50℃ to -20℃, which allows the polymer contained in the surface adhesive layer to possess suitable flexibility and chain segment mobility at room temperature. This enables the surface adhesive layer to conform to the microscopic undulations of the shell surface during adhesion, and to release internal residual stress through the slow adjustment of molecular chain segments after adhesion. Therefore, at the location where the insulating film is attached to the shell, especially on the small side and near the cut end of the insulating film, localized lifting or blistering of the film surface caused by stress concentration can be reduced. Thus, by matching the polarity of the shell's outer surface with the flexibility and stress release capability of the insulating film's surface adhesive layer on the shell's outer surface, a stable and firm interfacial adhesion is established between the insulating film and the shell, improving the reliability of long-term adhesion between the insulating film and the shell surface in small-area applications. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the insulating film covering the battery cell housing in Application Example 1; Figure 2 This is a cross-sectional schematic diagram of the insulating film covering the battery cell housing in Application Example 1; Figure 3 This is a partially enlarged cross-sectional view of the insulating film covering the battery cell casing in Application Example 1. Detailed Implementation

[0026] To enable those skilled in the art to better understand the technical solutions of this invention, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this invention.

[0027] The relevant parameter testing methods mentioned below include: 1. Test method for glass transition temperature of adhesive layer on insulating film surface The glass transition temperature of the surface adhesive layer was determined using differential scanning calorimetry (DSC). The testing equipment used was a Netzsch DSC 214 Polyma.

[0028] (1) Sample preparation: The adhesive on the surface to be tested was dried at 150°C for 1 hour to remove the solvent and obtain a dry adhesive film. About 2 g of the dry adhesive film was placed in an aluminum crucible and pressed tightly to seal it.

[0029] (2) Test atmosphere conditions: The test was conducted in a nitrogen atmosphere with a nitrogen flow rate of 50 mL / min.

[0030] (3) The temperature program is set as follows: First, the temperature is raised rapidly to 100℃ and held for 5 minutes; then the temperature is lowered to -60℃ at a rate of 10℃ / min; then the temperature is raised again to 100℃ at a rate of 10℃ / min.

[0031] (4) Data Analysis: Record the heat flow curve during the second heating process. The glass transition temperature is shown as a step-like baseline shift on the DSC curve, and the midpoint temperature is taken as the glass transition temperature. The glass transition temperatures of the adhesive layer on the surface of the insulating film in this invention are all measured according to the above method.

[0032] 2. Test method for static contact angle between surface adhesive layer and ultrapure water The static contact angle between the surface adhesive layer and ultrapure water was determined using a KZS-20 contact angle measuring instrument from Dongguan Kezhong Company.

[0033] (1) Sample preparation: Place the surface adhesive layer of the insulating film to be tested on the instrument test platform with the surface of the adhesive layer facing up, and ensure that the insulating film sample to be tested is free of wrinkles, curling and contamination.

[0034] (2) Liquid used for static contact angle test: ultrapure water. The ultrapure water used in this test should conform to the general industry specifications and have a resistivity ≥18.2MΩ·cm.

[0035] (3) Test Procedure: Under constant temperature and humidity conditions (temperature 23℃±5℃, relative humidity ≤60%RH), use a microsyringe to draw ultrapure water and drop approximately 5 μL of ultrapure water onto the surface of the adhesive layer. After the droplet is placed, let it stand for 60 seconds, then use the instrument's built-in camera to photograph the droplet morphology and calculate the static contact angle using the accompanying software. At least three different locations should be selected for measurement on each sample, and the arithmetic mean should be taken as the static contact angle test result between the surface adhesive layer and ultrapure water for that sample. The static contact angle between the insulating film surface adhesive layer and ultrapure water in this invention refers to the measurement performed using the above method.

[0036] 3. Test method for peel strength between adhesive layer on insulating film surface and outer surface of housing The peel strength between the adhesive layer on the surface of the insulating film and the outer surface of the shell was determined using a Meters E43.104 electronic universal testing machine.

[0037] (1) Sample preparation: Cut the insulating film to be tested into strips with a width of 25 mm and a length of 120 mm.

[0038] (2) Test method: Under the conditions of temperature of 23℃±5℃ and relative humidity of 65%±5% RH, the strip sample to be tested was attached to the surface of the battery cell shell through its surface adhesive layer. The shell used was an aluminum shell. After attachment, the samples were left to stand for 1 day, 3 days and 7 days respectively. The peel strength between the adhesive layer on the surface of the insulating film and the outer surface of the shell was measured using a Meters E43.104 electronic universal testing machine. The peel speed for the peel strength test was 300 mm / min and the peel angle was 180°. Five parallel samples were set for each type of insulating film at each standing time point, and the average value of the measured peel strength was taken as the reading.

[0039] According to a first aspect of the present invention, a battery cell is provided, comprising: a housing, the dyn value of the outer surface of the housing being ≥ 36 dyn / cm; and an insulating film, including a surface adhesive layer and attached to the outer surface of the housing via the surface adhesive layer, the glass transition temperature of the surface adhesive layer being -50°C to -20°C. In the battery cell provided by the present invention, the dyn value of the housing surface is not less than 36 dyn / cm, ensuring that the housing provides suitable polar surface conditions for the surface adhesive layer, which helps the surface adhesive layer to form a tight initial contact with the housing during attachment. Simultaneously, the glass transition temperature of the surface adhesive layer in the aforementioned insulating film is -50°C to -20°C, which allows the polymer contained in the surface adhesive layer to possess suitable flexibility and chain segment mobility at room temperature. This enables the surface adhesive layer to conform to the microscopic undulations of the housing surface during attachment, and to release internal residual stress through the slow adjustment of molecular chain segments after attachment. Therefore, at the location where the insulating film is attached to the housing, especially at the small side surface and near the cut end of the insulating film, localized warping or blistering of the film surface caused by stress concentration can be reduced. Therefore, by matching the polarity of the outer surface of the shell with the flexibility and stress release capability of the adhesive layer on the outer surface of the insulating film, a stable and firm interface adhesion is established between the insulating film and the shell, which improves the reliability of the long-term adhesion between the insulating film and the shell surface under small-area adhesion.

[0040] Furthermore, the static contact angle between the surface adhesive layer and ultrapure water is ≥90°. This hydrophobic property helps inhibit the penetration of moisture from the environment into the interface between the surface adhesive layer and the shell, thus maintaining stable interfacial adhesion. Based on the surface adhesive layer's combined glass transition temperature and static contact angle, it possesses suitable segment mobility to ensure continued wetting of the shell surface and sufficient contact after attachment. Furthermore, the interfacial interaction of moderate hydrophobicity and polar groups ensures stable and durable interfacial adhesion. Therefore, the insulating film maintains a firm and smooth adhesion to the shell during long-term use, and its adhesion performance is less prone to degradation over time, significantly reducing the possibility of delamination, end lifting, wrinkling, or bubble formation.

[0041] Furthermore, the static contact angle between the surface adhesive layer and ultrapure water is ≥95°.

[0042] Furthermore, the glass transition temperature of the surface adhesive layer is -40℃ to -25℃. The polymer molecular chains contained in this surface adhesive layer have higher mobility at room temperature, which helps to more effectively alleviate the stress on the tape through the adjustment of the polymer molecular chains in the surface adhesive layer, further reducing the possibility of the insulating film lifting.

[0043] Furthermore, the surface adhesive layer includes an acrylic copolymer, which is obtained by polymerization of at least one comonomer. The comonomer includes soft monomers and hard monomers, and the mass ratio of soft monomers to hard monomers is 45-80:8-48. The soft monomers include at least one of 2-ethylhexyl acrylate and n-butyl acrylate, and the hard monomers include at least one of acrylic acid, methyl methacrylate, and vinyl acetate. Using at least one of 2-ethylhexyl acrylate and n-butyl acrylate as the soft monomer for preparing the surface adhesive layer can impart a lower glass transition temperature to the surface adhesive layer, allowing it to maintain good flexibility and chain segment mobility at room temperature. Using at least one of acrylic acid, methyl methacrylate, and vinyl acetate as the hard monomer for preparing the surface adhesive layer helps to regulate the cohesive force of the surface adhesive layer, preventing it from losing structural stability due to excessive softness. By selecting and optimizing the types and ratios of the aforementioned soft and hard monomers, the glass transition temperature of the surface adhesive layer can be controlled within the range of -50℃ to -20℃, achieving a balance between the initial wettability of the shell and the long-term cohesive force of the surface adhesive layer. Based on this, the surface adhesive layer can conform to the microstructure of the shell surface during adhesion. After adhesion, internal stress can be released through the slow rearrangement of molecular chain segments, thereby reducing localized lifting or unevenness of the film surface caused by stress concentration. This is beneficial for the insulating film to form a long-term smooth and firm adhesion.

[0044] Furthermore, the comonomer also includes functionalized monomers, including at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, acrylic acid, and methacrylic acid. These functionalized monomers introduce hydroxyl and / or carboxyl groups into the surface adhesive layer, providing active sites for the surface adhesive layer to participate in subsequent cross-linking reactions. Based on the presence of these active sites, the cohesive force of the surface adhesive layer can be gradually established or strengthened during long-term use. At the same time, the hydroxyl and / or carboxyl groups can also form stable interfacial interactions with the shell surface, helping to maintain the firm adhesion of the surface adhesive layer to the shell surface. As a result, the insulating film can maintain a flat and stable adhesion state during long-term use, and is not prone to degradation of adhesion or interfacial separation due to prolonged use, thereby reducing the risk of the insulating film peeling, wrinkling, or bubbling.

[0045] Furthermore, the comonomer includes at least one of acrylic acid and methacrylic acid.

[0046] Furthermore, the surface adhesive layer also includes a crosslinking agent, which includes at least one of polyisocyanate and metal chelate. This crosslinking agent can undergo a crosslinking reaction with the hydroxyl or carboxyl groups provided by the functional monomer, achieving controllable late-stage curing of the surface adhesive layer after application. Due to the introduction of the crosslinking agent, the surface adhesive layer maintains a low modulus and good wettability in the initial stage of application, which is beneficial for fully wetting the shell surface and releasing residual stress. After application, as the crosslinking reaction proceeds, the cohesive force of the surface adhesive layer gradually increases, thereby maintaining a firm adhesion to the shell surface during long-term use and preventing degradation of adhesion performance or interface separation.

[0047] Furthermore, the comonomer also includes a silane coupling monomer, namely γ-methacryloxypropyltrimethoxysilane. γ-methacryloxypropyltrimethoxysilane contains hydrophobic carbon chains, the introduction of which helps to enhance the hydrophobic properties of the surface adhesive layer, making it easier for the static contact angle between the surface adhesive layer and ultrapure water to reach over 90°. This inhibits the penetration of moisture from the environment into the interface between the surface adhesive layer and the shell, maintaining the stability of the interfacial bonding. Simultaneously, the methoxy groups in γ-methacryloxypropyltrimethoxysilane can hydrolyze upon contact with ambient moisture, reacting with the active groups on the shell surface to form stable siloxane-type covalent bonds. If the shell is aluminum, the siloxane-type covalent bond formed between γ-methacryloxypropyltrimethoxysilane and the shell is a Si-O-Al covalent bond. This siloxane-type covalent bond directly anchors the surface adhesive layer molecular chains to the shell surface, equivalent to establishing a durable chemical connection between the surface adhesive layer and the shell. Based on the combined effect of the above-mentioned hydrophobic properties and covalent bonding, the surface adhesive layer can maintain a firm and flat fit to the aluminum shell during long-term use. It is not easy for the adhesion performance to decline, interface separation or lifting to occur due to the long time or water erosion, thereby reducing the possibility of the insulating film detaching, lifting at the end, wrinkling or forming bubbles.

[0048] Furthermore, the comonomer also includes auxiliary soft monomers, which include one or more of isooctyl acrylate, ethyl acrylate, and lauryl acrylate. The introduction of auxiliary soft monomers can be used to fine-tune the viscoelasticity and cohesive properties of the surface adhesive layer, optimizing the balance between the adhesive properties and cohesive forces of the surface adhesive layer while maintaining a low glass transition temperature.

[0049] Furthermore, the surface adhesive layer also includes additives, including at least one of liquid acrylate oligomers, polyethylene glycol, polypropylene glycol, or derivatives thereof. The liquid acrylate oligomers or their derivatives can act as plasticizers, exhibiting good compatibility with the acrylic-based main polymer and providing a long-lasting plasticizing effect, significantly reducing the glass transition temperature and modulus of the surface adhesive layer without migration. Softeners, including polyethylene glycol, polypropylene glycol, or derivatives thereof, can act as softeners, providing flexibility and a certain degree of polarity, which helps to adjust the polarity and hydrophobicity balance of the surface adhesive layer.

[0050] Furthermore, the dyn value of the shell is 38 dyn / cm to 50 dyn / cm.

[0051] Furthermore, the shell includes large side surfaces arranged opposite each other and small side surfaces connected between the two large side surfaces. The large side surfaces and the small side surfaces are connected by a transition angle R. The R angle is the curved part of the shell surface that transitions from the planar area to the curved arc area. The outer radius of the R angle is ≥1.5 mm. The insulating film includes a starting end and a ending end. The insulating film is continuously attached to the large side, the rounded corner, and the small side starting from the starting end. The ending end of the insulating film is stacked above the starting end in the thickness direction to form an overlapping area. The distance d mm between the cutting ends of the starting end and the cutting ends of the ending end of the insulating film is defined as the distance D mm between the cutting ends of the ending end and the adjacent end of the rounded corner. The adjacent end refers to the position where the surface curvature of the shell increases from zero. The value of d is 1~15, and D≥d+5.

[0052] The presence of the overlapping area constrains the starting cut end by covering the terminating membrane, reducing its risk of becoming a source of warping. Controlling the width d of the overlapping area within the range of 1 mm to 15 mm ensures effective coverage of the starting cut end while avoiding excessive material accumulation and stress concentration due to an overly wide overlapping area. The distance D between the terminating cut end and the adjacent end of the R-corner, in conjunction with the overlapping area width d, determines the length of the membrane extending from the terminating end, directly attached to the shell surface, and uncovered in the thickness direction (i.e., Dd). By reasonably controlling the difference between D and d, the range of this high-risk area can be effectively limited, mitigating localized warping caused by stress concentration at the cut end. Simultaneously, allowing the overlapping area and terminating end of the insulating film to be relatively close to the R-corner improves the space utilization of the shell surface and achieves a reasonable balance between stress control and volumetric energy density. Furthermore, the outer radius R of the R-corner satisfies 1.5 mm ≤ R ≤ 5 mm. Setting the radius of the R-corner within this range allows the insulating film to achieve a sufficiently smooth bending transition when it passes around the R-corner, effectively reducing stress concentration caused by geometric abrupt changes and reducing the risk of warping or wrinkling near the cut end. On the other hand, it avoids excessive occupation of the internal space of the housing by an excessively large R-corner radius, which is conducive to maintaining a high volumetric energy density while ensuring bonding reliability.

[0053] Furthermore, the shell is made of aluminum. Under the conditions of temperature 23℃±5℃ and relative humidity 65%±5% RH, the surface adhesive layer is attached to the outer surface of the shell. The peel strength between the two is measured after 1 day of continuous attachment, which is T1, T1>7 N / 25mm; the peel strength between the two is measured after 7 days of continuous attachment, which is T7, T7-T1≥0 N / 25mm.

[0054] Furthermore, T7-T1≥4 N / 25mm.

[0055] Furthermore, T7-T1≥6 N / 25mm.

[0056] Furthermore, under the conditions of a temperature of 23℃±5℃ and a relative humidity of 65%±5% RH, the surface adhesive layer was attached to the outer surface of the shell and the peel strength between the two was measured after 3 days; T3>10 N / 25mm, T7>13 N / 25mm.

[0057] Furthermore, T1 > 9 N / 25mm, T3 > 11 N / 25mm, and T7 > 15 N / 25mm.

[0058] According to a second aspect of the invention, a battery module is provided, which includes at least one battery cell as described above.

[0059] Example 1 This embodiment provides an insulating film, which is a blue film, comprising a surface adhesive layer and a substrate layer stacked sequentially along the thickness direction. The substrate layer is made of polyethylene terephthalate (PET) film, and the surface adhesive layer is an acrylic pressure-sensitive surface adhesive layer.

[0060] The adhesive formulation for preparing the above surface adhesive layer (the following parts refer to parts by weight) is as follows: Soft monomer: 80 parts of 2-ethylhexyl acrylate; Hard monomer: 10 parts methyl methacrylate; Functional monomer: 9 parts hydroxyethyl acrylate; Silane coupling monomer: 0.6 parts of γ-methacryloyloxypropyltrimethoxysilane; Initiator: 0.4 parts of azobisisobutyronitrile; Plasticizer: 5 parts liquid acrylate oligomer; Solvent: Ethyl acetate, the amount of which is sufficient to ensure that the solid content of the adhesive formulation reaches 28%.

[0061] Mix the materials according to the above-mentioned weight proportions to obtain the adhesive surface layer.

[0062] The specific process for preparing the insulating film used in this embodiment is as follows: The aforementioned adhesive is applied to one side of a 25 μm thick PET substrate layer. After coating, it is dried to obtain an inner adhesive layer. Using the aforementioned PET substrate layer as the first substrate layer, another 25 μm thick PET substrate layer is applied to the surface of the first substrate layer with adhesive. Then, a 35 μm thick layer of adhesive is applied to the surface of the second PET substrate layer and dried. The adhesive layer between the first and second substrate layers is used as the intermediate adhesive layer. The dry film thickness of both the surface adhesive layer and the intermediate adhesive layer is 30 μm, thus forming a composite structure consisting of a surface adhesive layer, a first substrate layer, an intermediate adhesive layer, and a second substrate layer stacked sequentially. The structure is then cured at 40°C for 2 hours to obtain an insulating film. The surface adhesive layer of the insulating film is used to attach to the outer surface of the battery cell casing.

[0063] The surface adhesive layer of the insulating film in this embodiment has the following performance parameters after testing: glass transition temperature is -50℃, and static contact angle with ultrapure water is 107°.

[0064] Example 2 This embodiment refers to the preparation of the insulating film in Example 1, except that the formulation for preparing the surface adhesive layer in Example 2 is adjusted based on the adhesive formulation used in Example 1. Specifically, it uses 66 parts of soft monomer and 24 parts of hard monomer. Apart from the above differences, the other materials and amounts used to prepare the insulating film in Example 2, as well as the corresponding operations, are consistent with those in Example 1.

[0065] Tests showed that the glass transition temperature of the surface adhesive layer in the insulating film of this embodiment is -40°C, and the static contact angle between the surface adhesive layer and ultrapure water is 106°.

[0066] Example 3 This embodiment refers to the preparation of the insulating film in Example 1. The difference between Example 3 and Example 1 is that the formulation for preparing the surface adhesive layer in Example 3 is adjusted based on the adhesive formulation used in Example 1. Specifically, 56 parts of soft monomer and 34 parts of hard monomer are used. Apart from the above differences, the other materials and amounts used to prepare the insulating film in Example 3, as well as the corresponding operations, are consistent with those in Example 1.

[0067] Tests showed that the glass transition temperature of the surface adhesive layer in the insulating film of this embodiment is -32°C, and the static contact angle between the surface adhesive layer and ultrapure water is 104°.

[0068] Example 4 This embodiment refers to the preparation of the insulating film in Example 1. The difference between Example 4 and Example 1 is that the formulation for preparing the surface adhesive layer in Example 4 is adjusted based on the adhesive formulation used in Example 1. Specifically, 48 parts of soft monomer and 42 parts of hard monomer are used. Apart from the above differences, the other materials and amounts used to prepare the insulating film in Example 4, as well as the corresponding operations, are consistent with those in Example 1.

[0069] Tests showed that the glass transition temperature of the surface adhesive layer in the insulating film of this embodiment is -25°C, and the static contact angle between the surface adhesive layer and ultrapure water is 102°.

[0070] Example 5 This embodiment refers to the preparation of the insulating film in Example 1. The difference between Example 5 and Example 1 is that the formulation for preparing the surface adhesive layer in Example 5 is adjusted based on the adhesive formulation used in Example 1. Specifically, 42 parts of soft monomer and 48 parts of hard monomer are used. Apart from the above differences, the other materials and amounts used to prepare the insulating film in Example 5, as well as the corresponding operations, are consistent with those in Example 1.

[0071] Tests showed that the glass transition temperature of the surface adhesive layer in the insulating film of this embodiment is -20°C, and the static contact angle between the surface adhesive layer and ultrapure water is 99°.

[0072] Comparative Example 1 This comparative example prepares an insulating film according to Example 1. The difference between Comparative Example 1 and Example 1 is that the formulation for preparing the surface adhesive layer in Comparative Example 1 was adjusted based on the adhesive formulation used in Example 1. Specifically, 35 parts of soft monomer and 55 parts of hard monomer were used. Apart from the above differences, the other materials and amounts used to prepare the insulating film in Comparative Example 1, as well as the corresponding operations, are consistent with those in Example 1.

[0073] Tests showed that the glass transition temperature of the surface adhesive layer in the comparative example insulating film was -15℃, and the static contact angle between the surface adhesive layer and ultrapure water was 97°.

[0074] Comparative Example 2 The insulating film prepared in Comparative Example 2 was prepared according to Example 1. The difference between Comparative Example 2 and Example 1 is that the formulation for preparing the surface adhesive layer was adjusted based on the adhesive formulation used in Example 1. Specifically, 88 parts of soft monomer and 2 parts of hard monomer were used. Apart from the above differences, the other materials and amounts used to prepare the insulating film in Comparative Example 2, as well as the corresponding operations, were consistent with those in Example 1.

[0075] Tests showed that the glass transition temperature of the surface adhesive layer in the comparative example insulating film was -55°C, and the static contact angle between the surface adhesive layer and ultrapure water was 109°.

[0076] Application Example 1 In this application example, an insulating film is applied to the square battery casing. The casing of the square battery includes large side surfaces 11 arranged opposite each other and small side surfaces 12 connecting the two large side surfaces 11. The large side surfaces 11 and small side surfaces 12 are connected by a radius (R) 13, which is the curved surface portion of the casing surface that transitions from a planar area to a curved arc area. The dimensions of the casing are as follows: the length of the large side surface 11 is 291.94 mm and the width is 91.37 mm; the length of the small side surface 12 is 291.94 mm and the width is 20.48 mm; the outer radius of the radius (R) 13 is 2 mm.

[0077] Experimental Group 1: The insulating films provided in Examples 1-5 and Comparative Examples 1 and 2 were respectively used to attach the insulating films to the casing of the aforementioned square-shell battery. The attachment process is as follows: Using a coating machine at a rolling speed of 100 mm / min (the difference between the roller spacing and the cell width ≤ 0.3 mm), the insulating film was continuously applied to the small side 12, R-corner 13, and large side 11 of the cell to obtain the square-shell cell of this application example. Specifically, the insulating film was extended along one of the small side 12 of the casing, passing through R-corner 13, large side 11, and R-corner 13 to the opposite small side 12, so that both ends of the insulating film were located on the two opposite small side 12 of the casing. At the interface between the two ends of the insulating film, along its thickness direction, one end fell above the other end, thus forming an overlapping area. The lower cutting end of the insulating film in the overlapping area was used as the starting cutting end 22, and the upper cutting end was used as the ending cutting end 21. Figure 1 , 2 As shown. Figure 3As shown, the width of the overlapping area is defined as the distance d (in mm) between the starting end cut end 22 and the ending end cut end 21 of the insulating film, and the distance D (in mm) is defined as the distance between the ending end cut end 21 of the insulating film and the adjacent end 131 of the shell R angle 13 (the adjacent end 131 refers to the position where the surface curvature of the shell increases from zero). In this application example, the positions where the insulating film is attached to the shell all satisfy D=11.34 and d=3. The dyn value of the outer surface of the prismatic battery used in this experimental group is 36 dyn / cm. The cell numbers corresponding to the insulating films applied according to the above operations using the insulating films provided in Examples 1, 2, 3, 4, 5, Comparative Example 1, and Comparative Example 2 are cell 1-1, cell 1-2, cell 1-3, cell 1-4, cell 1-5, cell D1-1, and cell D1-2.

[0078] Experimental group 2: The prismatic batteries used in Experimental Group 1 were subjected to corona treatment to achieve a dyn value of 38 dyn / cm on the outer surface of the battery casing. Then, following the film-applying operation and position of Experimental Group 1 in this application example, the insulating film prepared in Example 3 was applied to the side of the casing using a wrapping machine by rolling. The cells that underwent insulating film application according to the above operation were numbered cells 1-6.

[0079] Experimental group 3: The prismatic batteries used in Experimental Group 1 were subjected to corona treatment to achieve a dyn value of 50 dyn / cm on the outer surface of the battery casing. Then, following the film-applying operation and position of Experimental Group 1 in this application example, the insulating film prepared in Example 3 was applied to the side of the casing using a wrapping machine by rolling. The battery cells that underwent insulating film application according to the above operation are designated as cells 1-7.

[0080] Experimental group 4: The prismatic batteries used in Experimental Group 1 were subjected to corona treatment to achieve a dyn value of 56 dyn / cm on the outer surface of the battery casing. Then, following the film-applying operation and position of Experimental Group 1 in this application example, the insulating film prepared in Example 3 was applied to the side of the casing using a wrapping machine by rolling. The cells that underwent insulating film application according to the above operation are designated as cells 1-8.

[0081] Experimental group 5: The prismatic batteries used in Experimental Group 1 underwent plasma treatment to achieve a dyn value of 32 dyn / cm on the outer surface of the battery casing. Then, following the film-applying operation and position of Experimental Group 1 in this application example, the insulating film prepared in Example 3 was applied to the side of the casing using a coating machine via rolling. The cells whose insulating film was applied according to the above operation are designated as cells D1-3.

[0082] Test Example 1 1. Test Object The battery cell that has completed the insulation film attachment in Application Example 1 will immediately enter the test of this test example and serve as the test object of this test example.

[0083] 2. Testing Methods The battery cell prepared in Application Example 1 was stored at room temperature (23℃±5℃) and relative humidity (65%±5% RH) for a period of time. Visual inspections were conducted on days 1, 7, 21, and 70 after storage. The adhesion between the insulating film and the casing surface was observed visually, with a focus on checking for defects such as bubbles, warping, and localized peeling. "Warping" was defined as a localized bulge on the casing surface with a base width exceeding 4 mm and a height exceeding 15 mm. The occurrence of each type of defect was recorded at each observation time. If the sample showed no of the above defects at all observation time points and maintained good adhesion, it was deemed to have passed the adhesion stability test; otherwise, it was deemed to have failed.

[0084] 3. Test Results The test results for this test case are shown in Table 1.

[0085] Comparative Example 1 provides an insulating film with a surface adhesive layer glass transition temperature of -15°C. Compared to the insulating films prepared in other embodiments, the former has a higher surface adhesive layer glass transition temperature, resulting in severely insufficient chain mobility of the surface adhesive layer at room temperature. Consequently, residual internal stress cannot be effectively released after attachment, and stress continues to accumulate near the cut end, eventually leading to interface separation. This causes cell D1-1 using this insulating film to develop a warping defect after being left to stand for one day. The glass transition temperature of the surface adhesive layer of the insulating film provided in Comparative Example 2 is -55°C. Compared with the insulating films prepared in other embodiments, the glass transition temperature of the surface adhesive layer of the former is relatively low, making the surface adhesive layer too soft at room temperature. Its cohesive strength is insufficient to resist the stress generated during attachment and use, resulting in early damage to the interfacial bond. Consequently, the battery cell D1-2 using this insulating film developed a warping defect after being left to stand for one day. Cell D1-3 also developed a warping defect after being left to stand for one day. Compared to other test subjects, the dyne value of the casing surface of cell D1-3 was lower, resulting in insufficient polarity of the casing surface. The surface adhesive layer could not form a tight initial contact with the casing, and a sufficiently strong adhesion could not be established at the interface. Therefore, even though the insulating film used in cell D1-3 was exactly the same as that used in cell 1-3, it could not achieve long-term stable adhesion.

[0086] In this test case, except for cells D1-1, D1-2, and D1-3, all other cells maintained a smooth insulating film appearance after a long period of rest. Specifically, cells 1-1, 1-2, 1-3, 1-4, 1-6, 1-7, and 1-8 did not exhibit any defects such as warping after 70 days of resting.

[0087] The glass transition temperature of the surface adhesive layer of the insulating film provided in Example 5 is -20°C, which is higher than the glass transition temperature of the surface adhesive layer of the insulating films prepared in Examples 1 to 4. Based on this difference, the interfacial stress release capability of the surface adhesive layer of the insulating film in Example 5 is relatively weaker than that of the surface adhesive layers of the other insulating films mentioned above, resulting in warping defects appearing in cells 1-5 under extreme storage conditions of up to 70 days.

[0088] The surface dyn values ​​of cells 1-6, 1-7, and 1-8 were 38 dyn / cm, 50 dyn / cm, and 56 dyn / cm, respectively, and all three passed the tests at all time points. Combined with the fact that cell 1-3 (dyn / cm) also passed all tests, it can be concluded that when the surface dyn / cm value reaches 36 dyn / cm or higher, it is sufficient to provide adequate interfacial polarity and wetting driving force for the surface adhesive layer. Further increasing the dyn / cm value has no significant effect on improving adhesion stability. However, when the surface dyn / cm value is below 36 dyn / cm, the adhesion strength of the surface adhesive layer to the surface is insufficient to maintain long-term stability, as demonstrated by cell D1-3 in this test example.

[0089] Table 1. Statistics on the appearance defects of the test objects in Test Example 1

[0090] Application Example 2 In this application example, an insulating film is applied to the casing of the square battery, referring to Application Example 1.

[0091] Experimental group 1: The battery cell casing used in this experimental group is consistent with that in Experiment 1 of Application Example 1. The insulating films provided in Examples 1-5 and Comparative Examples 1 and 2 were respectively attached to the battery cell casing used for testing. The attachment process is as follows: Using a coating machine at a rolling speed of 100 mm / min (the difference between the roller spacing and the battery cell width ≤ 0.3 mm), the insulating film was continuously attached to the small side 12, R-corner 13, and large side 11 of the battery cell, resulting in the square-shell battery cell of this application example. Specifically, the insulating film was extended along one small side 12 of the casing, passing through R-corner 13, large side 11, and R-corner 13 to the opposite small side 12, so that both ends of the first insulating film were located on the two opposite small side 12s of the casing. At the interface between the two ends of the insulating film, along its thickness direction, one end fell above the other end, thus forming an overlapping area. The lower cutting end of the insulating film in the overlapping area was designated as the starting cutting end 22, and the upper cutting end was designated as the ending cutting end 21. The width of the overlapping area is defined as the distance d (in mm) between the starting end cut end 22 and the ending end cut end 21 of the insulating film, and the distance D (in mm) is defined as the distance between the ending end cut end 21 of the insulating film and the adjacent end 131 of the shell R angle 13 (the adjacent end 131 refers to the position where the surface curvature of the shell increases from zero). In this application example, the positions where the insulating film is attached to the shell all satisfy D=8 and d=3. The cell numbers of the cells that have completed the insulating film application according to the above operation using the insulating films provided in Examples 1, 2, 3, 4, 5, Comparative Example 1, and Comparative Example 2 are cell 2-1, cell 2-2, cell 2-3, cell 2-4, cell 2-5, cell D2-1, and cell D2-2, respectively.

[0092] Experimental group 2 The cell casing used in this experimental group is consistent with that in Experimental Group 2 of Application Example 1. Then, following the film-applying operation and position of Experimental Group 1 of this application example, the insulating film prepared in Example 3 is applied to the side of the casing by rolling using a film-applying machine. The cells that have completed the insulating film application according to the above operation are numbered as cells 2-6.

[0093] Experimental group 3 The cell casing used in this experimental group is consistent with that in Experiment 3 of Application Example 1. Then, following the film-applying operation and position of Experiment 1 of this application example, the insulating film prepared in Example 3 was applied to the side of the casing by rolling using a wrapping machine. The cells that completed the insulating film application according to the above operation are numbered as cells 2-7.

[0094] Experimental group 4 The cell casing used in this experimental group is consistent with that in experimental group 4 of application example 1. Then, following the film-applying operation and position of experimental group 1 of this application example, the insulating film prepared in example 3 was applied to the side of the casing by rolling using a wrapping machine. The cells that completed the insulating film application according to the above operation are numbered as cells 2-8.

[0095] Experimental group 5 The cell casing used in this experimental group is consistent with that in experimental group 5 of application example 1. Then, following the film-applying operation and position of experimental group 1 of this application example, the insulating film prepared in example 3 is applied to the side of the casing by rolling using a film-applying machine. The cell that has completed the insulating film application according to the above operation is numbered cell D2-3.

[0096] Test Example 2 1. Test Object The battery cell that has completed the insulation film attachment in Application Example 2 will immediately be tested in this test example and will be used as the test object in this test example.

[0097] 2. Testing Methods The battery cell prepared in Application Example 2 was stored at room temperature (23℃±5℃) and relative humidity (65%±5% RH) for a period of time. Visual inspections were conducted on days 1, 7, 21, and 70 after storage. The adhesion between the insulating film and the casing surface was observed visually, with a focus on checking for defects such as bubbles, warping, and localized peeling. "Warping" was defined as a localized bulge on the casing surface with a base width exceeding 4 mm and a height exceeding 15 mm. The occurrence of each type of defect was recorded at each observation time. If the sample showed no defects at any of the above observation time points and maintained good adhesion, it was deemed to have passed the adhesion stability test; otherwise, it was deemed unqualified. The test results for this example are shown in Table 2.

[0098] 3. Test Results The test results for this test example are shown in Table 2. The results show that, compared to Application Example 1, in Application Example 2, the initial position of the first insulating film directly attached to the cell casing is closer to the radius (R), meaning the difference in diameter (Dd) is reduced. This shortens the length of the film that is directly attached to the casing surface and not covered in the thickness direction, correspondingly increasing the stress concentration near the cut end. Under these conditions, the attachment stability of each test object exhibits a similar but more stringent trend to that of Test Example 1.

[0099] Cells D2-1, D2-2, and D2-3, which applied the insulating films provided in Comparative Examples 1, 2, and 3 respectively, all exhibited warping defects after being left to stand for one day. Their behavior was consistent with that of the cells in Test Example 1 that used the corresponding insulating film or the same casing. This indicates that when the glass transition temperature of the surface adhesive layer of the insulating film deviates significantly from the suitable range or the dyne value of the casing is insufficient, adjusting the attachment position of the insulating film (i.e., changing the difference between D and d) cannot overcome the inherent defect of insufficient adhesion stability between the insulating film and the casing.

[0100] Cell 2-1, the test subject in this test example, uses the same insulating film and cell housing as cell 1-1, the test subject in Test Example 1. However, cell 2-1 (with a glass transition temperature of -50°C for the surface adhesive layer) developed a surface defect of insulating film peeling after 70 days of resting, while cell 1-1, at the same time point, still passed the appearance defect test and met the "qualified" standard. This difference indicates that as the difference between D and d decreases, the length of the film extending from the termination end and directly attached to the surface of the housing, without being covered in the thickness direction, shortens. The stress that could have been dispersed and released through a longer attachment area near the cut end is forced to accumulate in a shorter area, making the requirements for stress release capability more stringent, thus making peeling defects more likely to occur.

[0101] Similarly, cells 2-2 (with a glass transition temperature of -40°C for the surface adhesive layer of the insulating film) and 2-3 (with a glass transition temperature of -32°C for the surface adhesive layer of the insulating film) both passed the tests at all time points in this test example, indicating that the glass transition temperature of the surface adhesive layer of the insulating film used in the above test objects can provide sufficient chain segment mobility for the adhesive layer under more stringent stress conditions. However, cell 2-4 showed insulating film warping after 70 days of rest, and cell 2-5 showed insulating film warping after 21 days of rest. These test results differ from those of cells 1-4 and 1-5 in Test Example 1, respectively. The above comparison further confirms that as the difference between D and d decreases, the difficulty of interfacial stress release increases, and the adhesive layer needs to possess stronger chain segment mobility to complete sufficient stress release within the same time range.

[0102] Table 2. Statistics on the appearance defects of the test objects in Test Example 2

[0103] Application Example 3 In this application example, an insulating film is applied to the casing of the square battery, referring to Application Example 1.

[0104] Experimental group 1: The battery cell casing used in this experimental group is consistent with that in Experiment 1 of Application Example 1. The insulating films provided in Examples 1-5 and Comparative Examples 1 and 2 were respectively attached to the battery cell casing used for testing. The attachment process is as follows: Using a coating machine at a rolling speed of 100 mm / min (the difference between the roller spacing and the battery cell width ≤ 0.3 mm), the insulating film was continuously attached to the small side 12, R-corner 13, and large side 11 of the battery cell, resulting in the square-shell battery cell of this application example. Specifically, the insulating film was extended along one small side 12 of the casing, passing through R-corner 13, large side 11, and R-corner 13 to the opposite small side 12, so that both ends of the first insulating film were located on the two opposite small side 12s of the casing. At the interface between the two ends of the insulating film, along its thickness direction, one end fell above the other end, thus forming an overlapping area. The lower cutting end of the insulating film in the overlapping area was designated as the starting cutting end 22, and the upper cutting end was designated as the ending cutting end 21. The width of the overlapping area is defined as the distance d (in mm) between the starting end cut end 22 and the ending end cut end 21 of the insulating film, and the distance D (in mm) is defined as the distance between the ending end cut end 21 of the insulating film and the adjacent end 131 of the shell R angle 13 (the adjacent end 131 refers to the position where the surface curvature of the shell increases from zero). In this application example, the positions where the insulating film is attached to the shell all satisfy D=5 and d=3. The cell numbers of the cells that have been covered with the insulating film according to the above operation using the insulating films provided in Examples 1, 2, 3, 4, 5, Comparative Example 1, and Comparative Example 2 are cell 3-1, cell 3-2, cell 3-3, cell 3-4, cell 3-5, cell D3-1, and cell D3-2, respectively.

[0105] Experimental group 2 The cell casing used in this experimental group is consistent with that in Experimental Group 2 of Application Example 1. Then, following the film-applying operation and position of Experimental Group 1 of this application example, the insulating film prepared in Example 3 is applied to the side of the casing by rolling using a wrapping machine. The cells that have completed the insulating film application according to the above operation are numbered as cells 3-6.

[0106] Experimental group 3 The cell casing used in this experimental group is consistent with that in Experimental Group 3 of Application Example 1. Then, following the film-applying operation and position of Experimental Group 1 of this application example, the insulating film prepared in Example 3 is applied to the side of the casing by rolling using a film-applying machine. The cells that have completed the insulating film application according to the above operation are numbered as cells 3-7.

[0107] Experimental group 4 The cell casing used in this experimental group is consistent with that in experimental group 4 of application example 1. Then, following the film-applying operation and position of experimental group 1 of this application example, the insulating film prepared in example 3 is applied to the side of the casing by rolling using a film-applying machine. The cells that have completed the insulating film application according to the above operation are numbered as cells 3-8.

[0108] Experimental group 5 The cell casing used in this experimental group is consistent with that in experimental group 5 of application example 1. Then, following the film application operation and position of experimental group 1 of this application example, the insulating film prepared in example 3 is applied to the side of the casing by rolling using a film wrapping machine. The cell with insulating film applied according to the above operation is numbered cell D3-3.

[0109] Test Example 3 1. Test Object The battery cell that has completed the insulation film attachment in Application Example 3 will immediately be tested in this test example and will be used as the test object in this test example.

[0110] 2. Testing Methods The battery cell prepared in Application Example 2 was stored at room temperature (23℃±5℃) and relative humidity (65%±5% RH) for a period of time. Visual inspections were conducted on days 1, 7, 21, and 70 after storage. The adhesion between the insulating film and the casing surface was observed visually, with a focus on checking for defects such as bubbles, warping, and localized peeling. "Warping" was defined as a localized bulge on the casing surface with a base width exceeding 4 mm and a height exceeding 15 mm. The occurrence of each type of defect was recorded at each observation time. If the sample showed no defects at any of the above observation time points and maintained good adhesion, it was deemed to have passed the adhesion stability test; otherwise, it was deemed unqualified. The test results for this example are shown in Table 3.

[0111] 3. Test Results The test results for this test example are shown in Table 3. Compared to Application Examples 1 and 2, in Application Example 3, the initial position of the first insulating film directly attached to the cell casing is further closer to the R-angle, meaning the difference between D and d is further shortened to 2 mm. This further shortens the length of the film that is not covered in the thickness direction and is directly attached to the casing surface, resulting in the highest stress concentration near the cut end among the three. Under these conditions, the adhesion stability of each test object exhibits a more stringent trend than in Test Example 2.

[0112] The cells D3-1, D3-2 and D3-3 respectively using the insulating films provided by Comparative Example 1, Comparative Example 2 and Comparative Example 3 all developed warping defects after 1 day of standing, and the manifestations were consistent with the corresponding cells in Test Example 1 and Test Example 2. This indicates that when the glass transition temperature of the surface adhesive layer of the insulating film seriously deviates from the suitable range or the dyne value of the housing is insufficient, even if the attaching position of the insulating film is further adjusted, the defect of insufficient interface adhesion cannot be remedied.

[0113] Cell 3-1, cell 1-1 and cell 2-1 all use the insulating film provided in Example 1 and the same cell housing. Cell 1-1 remained qualified after standing for 70 days, cell 2-1 developed a warping defect after standing for 70 days, while cell 3-1 developed a warping defect after standing for 21 days. As the difference of D-d is shortened from 8.34 mm in Application Example 1 to 5 mm in Application Example 2, and then to 2 mm in Application Example 3, the length of the film body extending from the terminal end, directly attached to the housing surface and not covered in the thickness direction is gradually shortened. The stress that could have been dispersed and released along a longer attachment area is compressed into a shorter area, the degree of stress concentration is gradually increased, and the time point at which the warping defect occurs is also advanced accordingly.

[0114] The glass transition temperature of the surface adhesive layer of the insulating film used in cell 1-2, cell 2-2 and cell 3-2 is -40°C. Among them, cell 3-2 developed a warping defect after standing for 70 days, while cell 1-2 remained qualified at 70 days, and cell 2-2 also remained qualified at 70 days. The glass transition temperature of the surface adhesive layer of the insulating film used in cell 1-3, cell 2-3 and cell 3-3 is all -32°C. Cell 3-3 passed the tests at all time points, which is consistent with the performance of cell 1-3 and cell 2-3, indicating that the chain mobility of the adhesive layer corresponding to this temperature value is sufficient to cope with the gradually increasing stress concentration. Cell 3-4 developed a warping defect after standing for 70 days, and cell 3-5 developed a warping defect after standing for 21 days, which are respectively stricter than the performance of the corresponding cells in Test Example 1 and Test Example 2. The above comparison further confirms that as the difference between D and d decreases, the difficulty of interface stress release increases, and the adhesive layer needs to have stronger chain mobility to complete sufficient stress release within the same time range.

[0115] Table 3. Statistics of appearance defects of test objects in Test Example 3

[0116] The above embodiments are only used to illustrate the technical solution of the present invention, not to limit the protection scope of the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solution of the present invention can be modified or equivalently replaced without departing from the essence and scope of the technical solution of the present invention.

Claims

1. A battery cell, characterized in that, include: The housing, wherein the dyn value of the outer surface of the housing is ≥ 36 dyn / cm; An insulating film, including a surface adhesive layer and attached to the outer surface of the housing via the surface adhesive layer, wherein the glass transition temperature of the surface adhesive layer is -50℃ to -20℃.

2. The battery cell according to claim 1, characterized in that: The static contact angle between the surface adhesive layer and ultrapure water is ≥90°.

3. The battery cell according to claim 1, characterized in that: The glass transition temperature of the surface adhesive layer is -40℃ to -25℃.

4. The battery cell according to claim 1, characterized in that: The surface adhesive layer includes an acrylic copolymer, which is obtained by polymerization of at least a comonomer; The comonomer includes soft monomers and hard monomers, and the mass ratio of the soft monomers to the hard monomers is 45~80:8~48; The soft monomer includes at least one of 2-ethylhexyl acrylate and n-butyl acrylate, and the hard monomer includes at least one of acrylic acid, methyl methacrylate, and vinyl acetate.

5. The battery cell according to claim 4, characterized in that: The comonomer also includes at least one of functional group monomers and silane coupling monomers; The functional group monomer includes at least one of hydroxyethyl acrylate, hydroxypropyl acrylate, acrylic acid, and methacrylic acid; The comonomer also includes a silane coupling monomer, wherein the silane coupling monomer is γ-methacryloyloxypropyltrimethoxysilane.

6. The battery cell according to claim 4, characterized in that: The surface adhesive layer also includes additives, which include at least one of liquid acrylate oligomers, polyethylene glycol, polypropylene glycol, or derivatives of the above materials.

7. The battery cell according to claim 1, characterized in that: The dyn value of the shell is 38 dyn / cm to 50 dyn / cm.

8. The battery cell according to claim 1, characterized in that: The housing includes large side surfaces arranged opposite each other and small side surfaces connected between the two large side surfaces. The large side surfaces and the small side surfaces are connected by a transition angle R. The R angle is the curved part of the housing surface that transitions from a planar area to a curved arc area. The outer radius of the R angle is ≥1.5 mm. The insulating film includes a starting end and a ending end. The insulating film is continuously attached to the large side surface (11), the R-corner (13) and the small side surface (12) starting from the starting end. The ending end of the insulating film is stacked above the starting end in the thickness direction to form an overlapping area. The distance d mm between the starting end cut end (22) and the ending end cut end (21) of the insulating film, and the distance D mm between the ending end cut end (21) and the adjacent end (131) of the R-corner (13), the adjacent end (131) refers to the position where the surface curvature of the shell increases from zero. The value of d is 1~15, and D≥d+5.

9. The battery cell according to any one of claims 1 to 8, characterized in that, The housing is made of aluminum, and the adhesive layer is attached to the outer surface of the housing under the conditions of a temperature of 23℃±5℃ and a relative humidity of 65%±5% RH. The peel strength between the two was measured after 1 day of continuous adhesion, and T1 was greater than 7 N / 25 mm. The peel strength between the two was measured after 7 days of continuous adhesion, which was T7, and T7-T1≥0 N / 25mm.

10. A battery module, characterized in that, It includes at least one battery cell as described in any one of claims 1 to 9.

Images