A membrane and battery pack

Abstract

The application discloses a film piece and a battery pack comprising the same. The film piece comprises a first piece, a second piece and a third piece connected in sequence along a first direction and provided with corresponding side wings on both sides. At least two positioning holes are arranged on the corresponding four side wings of the first piece and the third piece. After being folded, the at least two positioning holes are arranged on the opposite sides of a second direction of a pole group. In addition, a crease line and other structures are arranged. The structure enables the film piece to cooperate with a positioning needle of a film wrapping workbench, accurately wraps the pole group and avoids deviation and poor insulation. By reasonably designing parameters such as the diameter, spacing and overlapping area width of the positioning holes, the structural strength, insulation performance and film wrapping quality of the film piece are guaranteed. The battery pack adopting the film piece is significantly improved in safety, consistency and production efficiency, reduces the size deviation of the battery cell assembly, reduces the risk of internal short circuit, prolongs the cycle life, is suitable for various scenes and enhances the market competitiveness.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a diaphragm and battery pack. Background Technology

[0002] Currently, the electrode insulation film of square battery cells is mainly covered on the surface of the electrode group. However, the existing insulation film is thin and large in size, making it prone to warping and deformation. The worktable of the electrode group coating equipment cannot properly position the insulation film. During the coating process, it is easy to cause skew and misalignment, resulting in poor coating of the insulation film. It cannot be heat-fused with the cover plate, and finally, it causes poor internal insulation problems when installed inside the battery cell.

[0003] Therefore, in order to overcome the above problems, this application provides a diaphragm and a battery pack. Summary of the Invention

[0004] Therefore, it is necessary to address the technical problem that the insulating film of the electrode assembly in existing square cells is prone to warping and deformation during the coating process, leading to film misalignment and misalignment with the cover plate, which in turn causes poor insulation. A diaphragm and battery pack should be provided so that the diaphragm can accurately coat the electrode assembly, effectively solve the problem of poor insulation protection, and improve the safety and stability of the battery pack.

[0005] A first aspect of the present invention provides a diaphragm for covering an electrode assembly. Before the diaphragm is folded, it includes a first sheet, a second sheet, and a third sheet connected sequentially along a first direction. The first sheet, the second sheet, and the third sheet each have corresponding side wings on both sides of a second direction, and the four side wings of the first sheet and the third sheet each have two positioning holes. After the diaphragm is folded, the two positioning holes are located on opposite sides of the electrode assembly in the second direction. By providing positioning holes, they can cooperate with positioning pins on the coating worktable to solve the problem of diaphragm misalignment when wrapping the electrode assembly, avoid misalignment between the diaphragm and the cover plate after coating, ensure accurate coating, effectively improve insulation protection, and reduce battery safety problems caused by poor insulation.

[0006] In other embodiments, the first and second directions are perpendicular and on the same plane. After the diaphragm is folded, the positioning holes are distributed on opposite sides near the top of the electrode assembly. The axes of the two positioning holes are on the same straight line and parallel to the end face of the electrode assembly in the first direction. This design helps to maintain the symmetry and stability of the diaphragm during the coating process, so that the diaphragm can be evenly stressed when wrapping the electrode assembly, avoiding the risk of local stress concentration or insulation failure caused by tilting, and further improving the coating accuracy and insulation effect.

[0007] In other embodiments, along the second direction, the two positioning holes are distributed on opposite sides of the first or third sheet, which facilitates the flexible selection of the positioning hole positions according to actual production needs and electrode assembly structure, meets the requirements of different coating processes, and improves the versatility and adaptability of the diaphragm.

[0008] In other embodiments, the two positioning holes are respectively distributed on the side wings of the first and third pieces, and before the diaphragm is folded, at least two positioning holes are distributed along the diagonal direction of the diaphragm. The diagonal double hole layout forms a spatial cross positioning, which is particularly suitable for asymmetric pole group structures. It can effectively improve the accuracy and stability of positioning, ensure that the diaphragm can be accurately aligned when wrapping the asymmetric pole group, and ensure the insulation protection effect.

[0009] In other embodiments, the diameter d of the positioning hole satisfies: 2mm≤d≤5mm. This diameter range is determined by the material tear strength test, which can ensure the matching accuracy between the positioning hole and the positioning pin, and avoid the membrane material being easily torn during the coating process due to the hole diameter being too small, or the insulation performance and structural strength of the membrane being too large.

[0010] In other embodiments, before the diaphragm is folded, crease lines distributed along a first direction are provided between the first, second, and third sheets and their corresponding side wings. In a second direction, the end of the positioning hole near the edge line of the diaphragm is the outer edge, and the end of the positioning hole near the crease line is the inner edge. The crease lines provide a clear path for the folding of the diaphragm, enabling the diaphragm to be folded in a predetermined direction and angle during the folding process, ensuring the accuracy and consistency of the wrapping, and also helping to improve the wrapping efficiency.

[0011] In other embodiments, the distance L from the outer edge of the positioning hole to the edge line of the diaphragm in the second direction satisfies: 2mm≤L≤10mm. The distance L2 from the inner edge of the positioning hole to the crease line of the diaphragm in the second direction is reasonably set. Setting the value of L can avoid the problem of insufficient edge strength of the diaphragm and easy breakage, while ensuring the effective folding width of the side wings and ensuring the side coverage. The setting of L2 ensures that there is no hole interference near the crease line, avoids the hole edge cracking due to bending stress during folding, and ensures the structural integrity and insulation performance of the diaphragm.

[0012] In other embodiments, the distance H from the positioning hole to the edge line of the diaphragm in the first direction satisfies: 5mm≤H≤12mm. The H value is set based on the dual considerations of hot melt process window and particle contamination control. A suitable H value can ensure that there is enough space between the top of the diaphragm and the lower plastic of the cover plate for hot melt, ensuring the hot melt strength, and can also prevent the positioning hole from being too low below the top of the electrode group, avoiding the electrode powder particles from overflowing into the housing and causing corrosion and other problems, thus ensuring the overall insulation effect of the diaphragm.

[0013] In other embodiments, the two side wings on the same side are folded to form an overlapping area. The width 'a' of the overlapping area satisfies: 6mm ≤ a ≤ 20mm, and the ratio of the overlapping width 'a' to the electrode assembly thickness satisfies: 0.3 ≤ a / W ≤ 0.7. The distance L1 from the inner edge of the positioning hole of the overlapping area to the edge line of the other diaphragm satisfies: 2mm ≤ L1 ≤ L2. By reasonably setting the width of the overlapping area and the a / W ratio, the side protection effect can be guaranteed, while avoiding material waste and affecting the heat dissipation of the electrode assembly. The setting of L1 takes into account both insulation safety and assembly process, ensuring that the overlapping area has sufficient insulation layer thickness, while avoiding stress concentration at the folding corner, ensuring smooth insertion of the electrode assembly into the casing, and improving the overall performance and reliability of the battery.

[0014] A second aspect of the present invention provides a battery pack comprising the aforementioned diaphragm. Battery packs using this diaphragm exhibit significant improvements in safety, consistency, and production efficiency. Precise positioning design reduces dimensional deviations after cell assembly, improving module integration; optimized insulation performance reduces the risk of internal short circuits; and the coordinated design of overlapping areas and positioning holes extends battery cycle life, enhancing the overall performance and market competitiveness of the battery pack. This makes it suitable for various scenarios, including high-energy-density power batteries and energy storage systems. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of the membrane in Embodiment 1 of this application.

[0016] Figure 2 This is a schematic diagram of the structure of another membrane in Embodiment 1 of this application.

[0017] Figure 3 for Figure 1 A magnified view of part A in the middle.

[0018] Figure 4 This is a schematic diagram of the structure after the diaphragm and electrode assembly are combined in this application.

[0019] Figure label:

[0020] 10. Diaphragm; 20. Electrode assembly;

[0021] 100. First piece; 101. First piece side wing one; 102. First piece side wing two; 200. Second piece; 201. Second piece side wing one; 202. Second piece side wing two; 300. Third piece; 301. Third piece side wing one; 302. Third piece side wing two; 400. Crease line; 500. Edge line; 600. Positioning hole; 700. Overlapping area. Detailed Implementation

[0022] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0023] In the description of this application, it should be understood that if terms such as "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not 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 application.

[0024] Furthermore, where the terms "first" and "second" appear, these terms are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this application, where the term "multiple" appears, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0025] In this application, unless otherwise expressly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0026] In this application, unless otherwise expressly specified and limited, the use of descriptions such as "above" or "below" the second feature indicates that the first and second features are in direct contact or indirect contact via an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. Similarly, "below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0027] It should be noted that if an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. If so, the terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the only possible implementation.

[0028] like Figures 1-4 As shown, this embodiment discloses a diaphragm 10 for covering the electrode assembly 20. Before the diaphragm 10 is folded, the diaphragm 10 includes a first piece 100, a second piece 200, and a third piece 300 connected sequentially along a first direction. The first piece 100, the second piece 200, and the third piece 300 are provided with corresponding side wings (first side wing 101, first side wing 202, second side wing 201, second side wing 202, third side wing 301, and third side wing 202) on both sides of the second direction. The four side wings (first side wing 101, first side wing 202, third side wing 301, and third side wing 202) of the first piece 100 and the third piece 300 are provided with two positioning holes 600.

[0029] After the diaphragm 10 is folded, the two positioning holes 600 are located on opposite sides of the electrode group 20 in the second direction.

[0030] The first direction and the second direction are perpendicular and lie on the same plane. The introduction of the first direction and the second direction facilitates a detailed analysis of the structure of the diaphragm 10.

[0031] Specifically, such as Figure 1 and Figure 2As shown, this embodiment proposes a diaphragm 10, which is a single sheet of insulating film with insulating properties, divided into 9 parts: a first sheet 100, two first side wings (first side wing one 101, first side wing two 102), a second sheet 200, two second side wings (second side wing one 201, second side wing two 202), a third sheet 300, and two third side wings (third side wing one 301, third side wing two 302), covering nine zones. The first piece 100 and the third piece 300 are used to wrap the two large surfaces of the pole group 20. The first side wing (first side wing one 101, first side wing two 102) and the third side wing (third side wing one 301, third side wing two 302) are used to wrap the sides of the pole group 20. The second piece 200 is used to wrap the bottom surface of the pole group 20. The second side wing (second side wing one 201, second side wing two 202) is used to protect the protective edge at the connection between the sides and bottom of the pole group 20.

[0032] Before the diaphragm 10 is folded, the first piece 100, the second piece 200 and the third piece 300 are all provided with crease lines 400 distributed along the first direction between them and the corresponding side wings (first side wing 101, first side wing 202, second side wing 201, second side wing 202, third side wing 101 and third side wing 202), that is, the corresponding connecting pieces and side wings are divided by the crease lines 400.

[0033] In this embodiment, for ease of description, in the second direction, the end of the positioning hole 600 near the edge line 500 of the diaphragm 10 is defined as the outer edge, and the end of the positioning hole 600 near the crease line 400 is defined as the inner edge.

[0034] By dividing the entire insulating film into nine functional zones, protection is achieved for five sides of the cell electrode assembly 20. The first piece 100 and the third piece 300 serve as the main wrapping surfaces, and their area design must cover the two largest surfaces of the electrode assembly 20 on both sides. The side wing design adopts a contoured structure, and the ratio between the width of the side wing and the thickness of the electrode assembly 20 is determined through experiments to ensure that the sides are completely covered without redundancy after folding. The second piece 200 serves as the bottom wrapping layer, and its dimensions must take into account the bottom boss structure of the electrode assembly 20, with a 0.5-1.0mm assembly tolerance. The second side wing (Second side wing one 201 and second side wing two 202) forms a rounded corner transition after folding, effectively dispersing the edge stress when the electrode assembly 20 is inserted into the shell.

[0035] In this embodiment, two positioning holes 600 are provided on the four side wings (first side wing 101, first side wing 2 102, third side wing 1 301, and third side wing 2 302) corresponding to the first piece 100 and the third piece 300. After the diaphragm 10 is folded, the two positioning holes 600 are located on opposite sides of the electrode group 20 in the second direction, which are used to fix the position on the worktable for wrapping the diaphragm 10 of the electrode group 20. At the same time, positioning pins are provided on the wrapping worktable. The positioning holes 600 cooperate with the positioning pins to solve the problem of the diaphragm 10 shifting when wrapping the electrode group 20, and to avoid misalignment between the diaphragm 10 and the cover plate after the electrode group 20 is wrapped. This effectively solves the problem that the overlapping area 700 of the plastic under the diaphragm 10 and the cover plate is too small to be heat-melted.

[0036] The positioning hole 600 features a symmetrical dual-hole layout. The positioning hole 600 and the worktable positioning pin are fitted with a clearance fit. This design solves the problem of offset caused by inertia in traditional single-positioning-point production at high speeds, improving the coating accuracy from ±0.5mm to ±0.15mm. The positioning hole 600 is located on the side wing near the top of the electrode assembly 20, ensuring a safe overlap of 3-5mm between the diaphragm 10 and the plastic under the cover plate during hot-melt operation. Even if a single positioning hole 600 is accidentally damaged, the spare hole can still maintain normal production.

[0037] In this embodiment, the positioning hole 600 is circular to facilitate centering. The two positioning holes 600 are on the same axis and are parallel to the plane of the cover plate of the pole group 20.

[0038] The geometric characteristics of the circular positioning hole 600 enable it to self-center during rotational positioning. The coaxial design ensures that the diaphragm 10 maintains symmetry during folding, further ensuring that the diaphragm 10 is geometrically aligned with the electrode assembly 20 during wrapping, avoiding the risk of localized stress concentration or insulation failure due to tilting.

[0039] The design of the positioning hole 600 includes three cases:

[0040] Same film settings:

[0041] The first type: The two side wings of the first piece 100 (first side wing one 101, first side wing two 102) are each provided with at least one positioning hole 600;

[0042] The second type: The two side wings of the third piece 300 (third side wing one 301, third side wing two 302) are each provided with at least one positioning hole 600;

[0043] The dual-hole design on the same sheet is suitable for symmetrical coating processes. By setting positioning holes 600 on opposite sides of a single film 10, single-station double-sided positioning is achieved. This solution reduces the number of positioning pins on the worktable, lowers equipment complexity, and provides optimal coating stability.

[0044] Diagonal settings:

[0045] The third type: The first piece 100 and the third piece 300 are located on two diagonally opposite side wings (first side wing one 101, third side wing two 302) and each is provided with at least one positioning hole 600; the diagonal double hole layout forms a spatial cross positioning, which is particularly suitable for the asymmetric pole group 20 structure. The diagonal holes are staggered to avoid interference of the positioning pins.

[0046] The number of positioning holes 600 should be at least two, with the most preferred number being two. The two positioning holes 600 need to be distributed separately, arranged on the two sides of the pole group 20 and closer to the top of the pole group 20, i.e., the position of the cover plate of the pole group 20.

[0047] The minimum spacing design of the dual holes is based on the stiffness analysis of the pole group 20. When the hole spacing is greater than 1 / 3 of the width of the pole group 20, an effective positioning constraint can be formed. The top centralized arrangement strategy shortens the positioning lever arm and reduces torque fluctuations during the coating process.

[0048] Since the commonly used method of wrapping the diaphragm 10 of the square battery cell electrode group 20 is usually to overlap two layers of the first side wing (first side wing one 101, first side wing two 102) to form complete insulation protection for the side of the electrode group 20, that is, after the diaphragm 10 wraps the electrode group 20, the first side wing one 101 and the third side wing one 301 overlap on the same side, and the first side wing two 102 and the third side wing two 302 overlap on the same side, the principle of hole arrangement is that after wrapping the electrode group 20, the two positioning holes 600 are not on the same side of the electrode group 20, which can effectively avoid the situation where the two positioning holes 600 overlap and cause local loss of insulation protection.

[0049] This design uses staggered positioning holes 600 to ensure that there are no overlapping holes in the overlapping area 700, thereby maintaining the continuous insulation protection of the diaphragm 10. In addition, this design also avoids the problem of localized strength reduction of the diaphragm 10 caused by overlapping positioning holes 600, significantly improving the reliability of the battery under conditions such as vibration and impact.

[0050] Based on this, it is necessary to further standardize the size of the holes and the distances to various points on the diaphragm 10, and to standardize the diameter d of the positioning hole 600, satisfying: 2mm≤d≤5mm. The diameter range of the positioning hole 600 is determined through material tear strength testing.

[0051] Meanwhile, the distance L from the outer edge of the positioning hole 600 to the second-direction edge line 500 of the diaphragm 10 satisfies: 2mm ≤ L ≤ 10mm. If L is too small, the edge strength of the diaphragm 10 will be insufficient and it will be prone to breakage. If L is too large, the distance from the outer edge of the positioning hole 600 to the edge line of the other side wing will be too small. The L value is set based on edge stress analysis. When L < 2mm, the edge stress concentration factor exceeds 2.5, and the elongation at break decreases. When L > 10mm, the effective folding width of the side wing is insufficient, resulting in a decrease in side coverage. When L = 6mm, the edge stress concentration factor is controlled within a certain range, while ensuring that the overlap width of the side wing after folding meets the requirements. This parameter also affects the insertion guidance performance of the pole group 20 into the shell. The L value is matched with the shell chamfer radius to improve the smoothness of insertion into the shell.

[0052] The distance L2 from the inner edge of the positioning hole 600 to the second direction crease line 400 of the diaphragm 10, where L + the diameter d of the positioning hole 600 + L2 is the dimension of the side wing in the second direction, and since the dimensions of L and the diameter d of the positioning hole 600 are already defined, the dimension of L2 is also defined.

[0053] The setting of L2 must ensure that there are no holes interfering near the crease line 400 to avoid cracking of the hole edges due to bending stress during folding. For example, when L = 5mm and d = 3mm, L2 must be at least 2mm to ensure that the total width of the side wings is ≥10mm (5mm + 3mm + 2mm), thereby meeting the full coverage requirement of the side of the pole group 20.

[0054] Therefore, it is also necessary to standardize the distance L1 from the inner edge of the positioning hole 600 in the overlapping area 700 to the edge line 500 of the diaphragm 10 located within the overlapping area 700 after the two side wings overlap. That is, the distance L1 from the inner edge of the positioning hole 600 to the edge line 500 of the other diaphragm 10 must satisfy: 2mm≤L1≤L2. If L1 is too small, the overlapping area 700 of the two diaphragms 10 will be insufficient, and there is a risk of local insulation failure of the positioning hole 600. L1 cannot be too large either, to prevent it from being too close to the crease line 400, which would cause the diaphragm 10 at the rear folding corner to wrinkle and affect the insertion of the electrode assembly 20 into the housing. The setting of the L1 value takes into account both insulation safety and assembly process. When L1 < 2mm, the insulation layer thickness of the overlapping area 700 drops to below 0.05mm, which poses a risk of breakdown. When L1 > L2, stress concentration occurs at the folding corner, which increases the resistance of the electrode assembly 20 into the housing by more than 50%. This parameter also affects the hot-melt process. The L1 value is matched with the width of the hot-melt head to ensure that the hot-melt area completely covers the overlapping area 700.

[0055] L is the edge distance of the positioning hole 600 of the diaphragm 10 itself, which ensures the strength of the positioning hole 600 position to prevent tearing due to insufficient strength; L1 is the distance from the positioning hole 600 to the other side after the diaphragm 10 wraps the electrode group 20, which ensures that the overlapping area of ​​the two layers covers the positioning hole 600 to prevent powder leakage from affecting the insulation.

[0056] The distance H between the positioning hole 600 and the first direction edge line 500 of the diaphragm 10 should satisfy: 5mm≤H≤12mm. If H is too small, there will not be enough space between the top of the diaphragm 10 and the lower plastic of the cover plate for heat fusion, and the heat fusion point may even melt onto the positioning hole 600, affecting the heat fusion strength. This will make the diaphragm 10 prone to breakage and tearing after the electrode assembly 20 is inserted into the shell. If H is too large, the positioning hole 600 will be too low below the top of the electrode assembly 20, and there will be risk of electrode powder particles overflowing into the shell, causing corrosion and affecting the overall insulation effect of the diaphragm 10.

[0057] The H value setting is based on both the hot-melt process window and particulate contamination control. When H < 5 mm, the hot-melt energy will be conducted to the edge of the positioning hole 600, the melting temperature of the film material will drop, resulting in insufficient bonding strength. When H > 12 mm, the risk of electrode powder overflow increases.

[0058] Therefore, further restrictions are needed. When two flaps on the same side are folded, they will form an overlapping area 700. The relationship between the width a of the overlapping area 700 and the thickness W of the electrode group 20 should satisfy: 0.3≤a / W≤0.7. The width a of the overlapping area 700 should satisfy: 6mm≤a≤20mm. At the same time, to ensure the protective effect and prevent local adhesive application due to the folding width being too small, the width of the side folding area should also be at least more than half the thickness of the electrode group 20.

[0059] The overlap width 'a' is dynamically calculated based on the thickness W of the electrode group 20. When a / W < 0.3, the equivalent thickness of the side protection is insufficient, increasing the risk of insulation failure. When a / W > 0.7, the material utilization rate decreases. In addition, the overlap width also affects the heat dissipation performance of the electrode group 20.

[0060] Example 1

[0061] In this embodiment, the width 'a' of the overlapping area 700 of the diaphragm is 6 mm, the thickness 'W' of the electrode group 20 is 20.0 mm, the a / W ratio is 0.3, and L1 is 3 mm. Under these parameter settings, the side insulation film of the electrode group 20 is well-covered, the positioning holes 600 are functioning correctly, the resistance of the exposed cells is acceptable, and the insulation effect is excellent. Specifically, the overlap width just meets the basic requirements for side protection, and the spacing parameters of the positioning holes 600 are reasonable, ensuring accurate alignment of the diaphragm during the wrapping process. Furthermore, there is no misalignment between the diaphragm and the cover plate after wrapping, guaranteeing the reliability of the insulation and effectively avoiding insulation failure caused by insufficient overlap area 700 or positioning deviation.

[0062] Example 2

[0063] In this embodiment, a is 7mm, W is 21.2mm, the a / W ratio is 0.33, and L1 is 4mm. Testing showed that the insulating film covering the side of the electrode assembly 20 was good, the positioning holes 600 were accurately positioned, the resistance of the exposed cells was qualified, and the insulation effect was good. Under this parameter combination, the width of the overlapping area 700 is increased compared to Embodiment 1, providing more sufficient protection for the sides. At the same time, the spacing of the positioning holes 600 is reasonably set, ensuring precise positioning during the film coating process. This allows the film to tightly and accurately cover the electrode assembly 20, effectively preventing problems such as electrode powder leakage and ensuring the overall performance of the cell.

[0064] Example 3

[0065] In this embodiment, a is 8.5mm, W is 23.6mm, the a / W ratio is 0.36, and L1 is 5mm. The results show that the insulating film covering the side of electrode group 20 is good, the positioning hole 600 has excellent positioning effect, the exposed cell resistance is qualified, and the insulation performance is excellent. With the further increase in the width of the overlapping area 700, the side protection is more reliable. At the same time, the reasonable layout of the positioning hole 600 ensures the accuracy of the film covering, allowing the film to be evenly stressed when wrapping electrode group 20, avoiding localized stress concentration, thereby ensuring the integrity and insulation effect of the insulating film and meeting the cell's usage requirements.

[0066] Example 4

[0067] In this embodiment, a is 10mm, W is 25.0mm, the a / W ratio is 0.4, and L1 is 6mm. Tests show that the insulating film covering the side of the electrode assembly 20 is good, the positioning holes 600 are accurately positioned, the exposed cell resistance is qualified, and the insulation effect is good. Under these parameters, the width of the overlapping area 700 is moderate, ensuring the protection requirements of the side without wasting material. The spacing of the positioning holes 600 ensures a stable film covering process, and the film adheres tightly to the electrode assembly 20, effectively preventing external factors from interfering with the electrode assembly 20 and ensuring the safety and stability of the cell.

[0068] Example 5

[0069] In this example, a is 11.5mm, W is 25.6mm, the a / W ratio is 0.45, and L1 is 7mm. Inspection revealed that the insulating film covering the side of electrode group 20 is good, the positioning hole 600 is correctly positioned, the exposed cell resistance is acceptable, and the insulation performance is good. As the a / W ratio increases, the overlapping area 700 provides more comprehensive protection to the side. Simultaneously, the reasonable design of the positioning hole 600 ensures the accuracy of the film covering, allowing the diaphragm to fully exert its insulating and protective functions when wrapping electrode group 20, effectively avoiding insulation problems caused by incomplete covering or positioning deviations.

[0070] Example 6

[0071] In this embodiment, a is 13mm, W is 26.0mm, the a / W ratio is 0.5, and L1 is 8mm. The results show that the insulating film covering the side of the electrode assembly 20 is good, the positioning holes 600 have good positioning effect, the exposed cell resistance is qualified, and the insulation effect meets the requirements. Under these parameters, the width of the overlapping area 700 is further increased, providing stronger protection for the side. At the same time, the spacing of the positioning holes 600 is reasonably set, ensuring the smooth progress of the film coating process, allowing the film to tightly adhere to the electrode assembly 20, effectively preventing electrode powder leakage and the influence of external factors on the electrode assembly 20.

[0072] Example 7

[0073] In this embodiment, a is 15.5mm, W is 28.2mm, the a / W ratio is 0.55, and L1 is 9mm. Tests show that the insulating film on the side of electrode group 20 is well-covered, the positioning holes 600 are accurately positioned, the resistance of the exposed cell is acceptable, and the insulation effect is good. With changes in parameters, the reasonable combination of the overlap area 700 width and the spacing of the positioning holes 600 allows the diaphragm to achieve good insulation and protection when wrapping electrode group 20, ensuring stable operation of the cell under various operating conditions.

[0074] Example 8

[0075] In this embodiment, a is 17mm, W is 28.3mm, the a / W ratio is 0.6, and L1 is 10mm. Testing showed that the insulating film covering the side of electrode group 20 was good, the positioning holes 600 had excellent positioning effect, the exposed cell resistance was qualified, and the insulation performance was excellent. Under these parameters, the width of the overlapping area 700 and the spacing of the positioning holes 600 allow the diaphragm to better adapt to the shape and size of electrode group 20, ensuring the accuracy of the coating and the insulation effect, effectively improving the overall performance of the cell.

[0076] Example 9

[0077] In this example, a is 18.5 mm, W is 28.5 mm, the a / W ratio is 0.65, and L1 is 11 mm. The results show that the insulating film on the side of electrode group 20 is well-covered, the positioning holes 600 are accurately positioned, the resistance of the exposed cell is qualified, and the insulation effect is good. With the adjustment of parameters, the reasonable configuration of the overlap area 700 width and the spacing of the positioning holes 600 allows the diaphragm to fit tightly when wrapping electrode group 20, effectively preventing insulation failure and electrode powder leakage, thus ensuring the safety and reliability of the cell.

[0078] Example 10

[0079] In this embodiment, a is 20mm, W is 28.6mm, the a / W ratio is 0.7, and L1 is 12mm. Tests show that the insulating film covering the side of electrode group 20 is good, the positioning hole 600 is correctly positioned, the resistance of the exposed cell is qualified, and the insulation effect meets the requirements. Under these parameters, the overlap area 700 reaches a large width, providing sufficient protection for the side. At the same time, the reasonable design of the positioning hole 600 ensures the accuracy of the film covering, allowing the film to fully exert its insulating and protective functions, meeting the cell's usage requirements.

[0080] Comparative Example 1

[0081] In this comparative example, a is 5.5mm, W is 20.0mm, the a / W ratio is 0.275, and L1 is 3mm. The results show that the side overlap area 700 is too small, resulting in insufficient coverage and leakage of electrode powder into the casing, leading to substandard resistance. Because the overlap area 700 is too narrow, it cannot provide sufficient protection for the sides of electrode group 20, making electrode powder prone to leakage. Furthermore, parameters such as the spacing of the positioning holes 600 fail to effectively compensate for this defect, resulting in serious safety hazards in the coated cell, rendering it unusable.

[0082] Comparative Example 2

[0083] In this comparative example, a is 5mm, W is 21.2mm, the a / W ratio is 0.236, and L1 is 4mm. Inspection revealed that the side overlap area 700 is even smaller, indicating severely insufficient coverage. A large amount of electrode powder leaked into the casing, resulting in substandard resistance and failure to meet usage requirements. The excessively small overlap area 700 width rendered the side protection almost ineffective, and the positioning function of the positioning holes 600 was also difficult to perform, leading to extremely poor insulation performance of the coated cell and compromising its safe operation.

[0084] Comparative Example 3

[0085] In this comparative example, a is 22.3mm, W is 28.5mm, the a / W ratio is 0.782, and L1 is 11mm. The results show that the 700mm overlap area on the side is large, the resistance is acceptable, but the side coating bulges, making it difficult to assemble electrode group 20 into the casing. Because the 700mm overlap area is too wide, although it ensures side protection, it affects the flatness of the coating, causing bulging and making it difficult to assemble electrode group 20 into the casing, thus affecting production efficiency and cell quality.

[0086] Comparative Example 4

[0087] In this example, a is 25.5mm, W is 28.6mm, the a / W ratio is 0.892, and L1 is 12mm. Testing revealed that the side overlap area 700 was too large, causing severe bulging of the side coating, making the assembly of electrode group 20 extremely difficult and failing to meet production requirements. The excessively large overlap area 700 not only resulted in material waste but also severely affected the quality of the coating and the assembly of electrode group 20, hindering the smooth production of the battery cell and preventing it from achieving the expected performance.

[0088]

[0089] Example 11

[0090] This embodiment discloses a battery pack, which includes the diaphragm 10 from Embodiment 1. By adopting the diaphragm 10 from Embodiment 1, the battery pack exhibits significant improvements in safety, consistency, and production efficiency. Specifically, the precise positioning design of the diaphragm 10 reduces dimensional deviations after cell assembly, improving module integration; optimized insulation performance reduces the risk of internal short circuits; and the collaborative design of the overlapping area 700 and the positioning hole 600 extends battery cycle life, making it particularly suitable for high-energy-density power batteries and energy storage systems.

[0091] This battery pack is adaptable to various cell configurations, including square and pouch cells, and exhibits excellent membrane stability under extreme temperature and vibration conditions. Furthermore, the high degree of standardization of the membrane 10 significantly reduces battery production costs and facilitates subsequent reuse and recycling. The specific effects have been described in Example 1 and will not be elaborated upon here.

[0092] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0093] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A diaphragm for coating an electrode assembly, characterized in that: Before the diaphragm is folded, it includes a first sheet, a second sheet, and a third sheet connected sequentially along a first direction. The first sheet, the second sheet, and the third sheet are provided with corresponding side wings on both sides of the second direction. The four side wings of the first sheet and the third sheet are provided with two positioning holes. The positioning holes are circular and the diameter d of the positioning holes satisfies: 2mm≤d≤5mm. The distance L from the outer edge of the positioning hole to the edge line of the diaphragm in the second direction satisfies: 2mm≤L≤10mm; After the diaphragm is folded, the two positioning holes are located on opposite sides of the second direction of the electrode group; The first direction and the second direction are perpendicular and on the same plane. After the diaphragm is folded, the positioning holes are distributed on opposite sides near the top of the electrode group. The axes of the two positioning holes are on the same straight line and parallel to the end face of the electrode group in the first direction. The two side wings on the same side fold over to form an overlapping area, and the ratio of the width a of the overlapping area to the thickness W of the pole group satisfies: 0.3≤a / W≤0.7; Before the diaphragm is folded, the first, second and third pieces are provided with crease lines distributed along the first direction between them and the corresponding side wings. In the second direction, the end of the positioning hole near the edge line of the diaphragm is the outer edge, and the end of the positioning hole near the crease line is the inner edge. The distance L2 from the inner edge of the positioning hole to the second direction crease line of the diaphragm, and the distance L1 from the inner edge of the positioning hole in the overlapping area to the edge line of another diaphragm, satisfy: 2mm≤L1≤L2.

2. The diaphragm according to claim 1, characterized in that: Along the second direction, the two positioning holes are distributed on opposite sides of the first piece or the third piece.

3. The diaphragm according to claim 1, characterized in that: The two positioning holes are respectively distributed on the side wings of the first and third pieces, and before the diaphragm is folded, the two positioning holes are distributed along the diagonal direction of the diaphragm.

4. The diaphragm according to any one of claims 1-3, characterized in that: The distance H from the positioning hole to the edge line of the diaphragm near the top of the electrode group in the first direction satisfies: 5mm≤H≤12mm.

5. The diaphragm according to claim 4, characterized in that: The width 'a' of the overlapping region satisfies: 6mm ≤ a ≤ 20mm.

6. A battery pack, characterized in that: It includes the membrane according to any one of claims 1-5.

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