Insulating film and secondary battery

Abstract

The utility model provides a kind of insulating film and secondary battery, insulating film includes bottom surface cladding sheet, side surface cladding sheet and thickening layer, the wall thickness of thickening layer is greater than the wall thickness of side surface cladding sheet;Side surface cladding sheet is connected to bottom surface cladding sheet, and side surface cladding sheet includes first side surface cladding area and second side surface cladding area;Thickening layer is located at one end of side surface cladding sheet away from bottom surface cladding sheet;The first thickening layer unit of thickening layer is connected first side surface cladding area, and first thickening layer unit extends towards second side surface cladding area to form second thickening layer unit, and second thickening layer unit is connected second side surface cladding area.The utility model is provided with thickening layer in the edge folding area of side surface cladding sheet easy to tear, increases the overall wall thickness of insulating film at this place, to effectively enhance the structural strength and tear resistance of this area, improve the reliability of insulating film and the safety of battery.

Description

Technical Field

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

[0002] Square batteries are a commonly used structure for lithium-ion power batteries. They consist of wound or stacked battery cells made of positive and negative electrodes and a separator, which are then assembled into a square casing before encapsulation. During the casing assembly process, because the casing is typically made of hard materials like aluminum or steel, its sharp edges and burrs pose a risk of scratching and damaging the battery cells. Therefore, before installing the battery cells into the casing, a soft and flexible insulating film (also called Mylar film) is used to cover the battery cells. This prevents direct contact between the battery cells and the outer aluminum casing, avoiding short circuits, aluminum corrosion, and damage to the battery cells caused by scratches from the aluminum casing.

[0003] Currently, with increasing demands for battery capacity and lower costs for structural components, engineers have considered increasing the space reserved for battery cell assemblies inside the casing by thinning the insulating film. However, as the insulating film is thinned, stress concentration easily occurs in the folded areas near the opening, leading to film tearing. This damages the insulation barrier between the casing and the battery cell assembly, reduces electrical clearance and creepage distance, and poses safety risks. Utility Model Content

[0004] The technical problem to be solved by this utility model is to overcome the defect in the prior art that the thinning of the insulating film wall thickness leads to easy tearing of the insulating film edge area, resulting in a reduction of the insulating effect of the insulating film and affecting the safety of the battery, and to provide an insulating film and a secondary battery.

[0005] The present invention solves the above-mentioned technical problems through the following technical solution:

[0006] An insulating film for covering a battery cell assembly of a secondary battery, the insulating film comprising a bottom covering sheet, a side covering sheet, and a thickening layer, wherein the wall thickness of the thickening layer is greater than the wall thickness of the side covering sheet;

[0007] The side covering sheet is connected to one end of the bottom covering sheet in its wall thickness direction. The side covering sheet includes two first side covering areas respectively located at both ends in the length direction of the bottom covering sheet, and two second side covering areas respectively located at both ends in the width direction of the bottom covering sheet.

[0008] The thickening layer is disposed on the end face of the side covering sheet on the side away from the bottom covering sheet in the wall thickness direction, and

[0009] The thickening layer includes a first thickening layer unit and a second thickening layer unit. The first thickening layer unit is connected to the first side covering area. The first thickening layer unit extends toward the second side covering area to form the second thickening layer unit. The second thickening layer unit is connected to the second side covering area.

[0010] In this solution, the junction of the first side covering area and the second side covering area forms the folded edge area of ​​the side covering sheet. By setting a thickening layer in the easily torn folded edge area, the overall wall thickness of the insulating film at this location is increased, thereby effectively enhancing the structural strength and tear resistance of this area. This solves the stress concentration and tearing problems caused by the thinning of the wall thickness of the side covering sheet, thereby improving the reliability of the insulating film and the safety of the battery.

[0011] Preferably, the wall thickness of the thickened layer is greater than or equal to 0.1 mm.

[0012] In this solution, by limiting the wall thickness range of the thickening layer, it is ensured that the thickening layer has sufficient mechanical strength to withstand the stress during bending and assembly, avoiding the inability to effectively reinforce due to excessively thin walls, thereby further improving the tear resistance of the insulating film.

[0013] Preferably, the wall thickness of the side covering sheet is 0.08~0.2mm, and the wall thickness of the thickened layer is less than or equal to 0.3mm.

[0014] In this solution, by reasonably setting the wall thickness range of the side covering sheet and the thickening layer, sufficient structural support can still be provided in key areas while ensuring that the overall wall thickness of the insulating film is reduced. This balances space utilization and structural strength, and avoids excessive occupation of the storage space of the battery cell assembly due to excessive thickening, thereby ensuring the power of the secondary battery.

[0015] Preferably, the insulating film satisfies one or more of the following conditions:

[0016] a1. The length of the thickening layer in the wall thickness direction of the bottom covering sheet is defined as a, where 1.6mm≤a≤10mm;

[0017] b2. Define the length of the first thickening layer unit in the width direction of the bottom covering sheet as b, where 5mm≤b≤20mm;

[0018] c3. Define the length of the second thickening layer unit in the length direction of the bottom covering sheet as c, where 5mm≤c≤20mm.

[0019] In this solution, by limiting the size of the thickened layer, it is ensured that the area covered by the thickened layer is sufficient to disperse stress and prevent tearing, while saving the total amount of insulating film and reducing costs.

[0020] Preferably, the side covering sheet and the thickening layer are integrally formed.

[0021] In this solution, the thickened layer and the side covering sheet are integrally molded, which simplifies the manufacturing process, avoids the risk of interface peeling caused by multi-layer structure splicing, improves the stability and consistency of the overall structure, and reduces production costs.

[0022] Preferably, the side covering sheet has a body region and a thickened region. The body region extends outward from the end of the bottom covering sheet away from the wall thickness direction to form the thickened region. The thickened region is folded towards the body region to form the thickened layer.

[0023] This solution provides a method for forming a thickened layer, in which the thickened area is folded over and superimposed on a portion of the corresponding body area to form the thickened layer. The forming method is simple, facilitates the positioning of the thickened layer, and improves assembly efficiency.

[0024] Preferably, the thickened layer includes a first portion and a second portion, the first portion being integrally formed with the side covering sheet, the second portion being independent of the side covering sheet, and the second portion covering the first portion.

[0025] In this design, the second part is set independently from the side covering sheet, which makes it easy to flexibly adjust the material and thickness of the thickening layer according to actual needs. It is suitable for different battery structures and assembly processes, improving the flexibility and adaptability of the design.

[0026] Preferably, the second part has an adhesive layer at one end facing the first part, and the second part is bonded to the first part through the adhesive layer.

[0027] In this solution, by setting an adhesive layer, a firm connection between the first and second parts of the thickened layer is ensured, preventing peeling or displacement during bending or assembly, and further enhancing structural stability and insulation reliability.

[0028] Preferably, the insulating film satisfies one or more of the following conditions:

[0029] a2. The thickening layer further includes an auxiliary bending portion disposed between the first thickening layer unit and the second thickening layer unit and extending along the wall thickness direction of the bottom covering sheet;

[0030] The wall thickness of the auxiliary bending portion is less than the wall thickness of the first thickening layer unit or the second thickening layer unit; or, the connecting portion of the first thickening layer unit and the second thickening layer unit is partially cut to form the auxiliary bending portion;

[0031] b2. The end of the thickened layer away from the bottom covering sheet in the wall thickness direction is flush with the end of the side covering sheet away from the bottom covering sheet in the wall thickness direction.

[0032] Alternatively, the thickened layer extends beyond the end of the side cover sheet in the wall thickness direction of the bottom cover sheet, away from the bottom cover sheet.

[0033] In this design, the first and second side covering areas are generally formed by bending a large sheet of insulating film, and the auxiliary bending part facilitates bending of the insulating film.

[0034] A secondary battery includes a casing, a cell assembly, and an insulating film as described above. The insulating film covers the outer surface of the cell assembly, and both the cell assembly and the insulating film are disposed inside the casing.

[0035] In this solution, the insulating film is used to cover the battery cell assembly before it is installed into the housing, preventing the housing from scratching or damaging the battery cell assembly during the installation process and avoiding damage to the battery cell assembly during assembly.

[0036] The positive and progressive effects of this utility model are as follows: By setting a thickened layer in the easily torn folded edge area of ​​the side cover sheet, the overall wall thickness of the insulating film in that area is increased, thereby effectively enhancing the structural strength and tear resistance of that area. This solves the stress concentration and tearing problems caused by the thinning of the side cover sheet wall thickness, thereby improving the reliability of the insulating film and the safety of the battery. Attached Figure Description

[0037] Figure 1 This is a three-dimensional structural diagram of the secondary battery according to Embodiment 1 of this utility model.

[0038] Figure 2 This is a cross-sectional view of the assembly of the insulating film, battery cell assembly and cover plate in Embodiment 1 of this utility model.

[0039] Figure 3 This is a three-dimensional structural diagram of the assembly of the insulating film and cover plate in Embodiment 1 of this utility model.

[0040] Figure 4 This is a three-dimensional structural diagram of the side covering sheet of Embodiment 1 of this utility model.

[0041] Figure 5 This is a schematic diagram of the unfolded structure of the insulating film in Embodiment 1 of this utility model.

[0042] Figure 6This is a partial structural schematic diagram of the secondary battery of Embodiment 1 of this utility model.

[0043] Figure 7 This is a schematic diagram of the unfolded structure of the insulating film in Embodiment 2 of this utility model.

[0044] Explanation of reference numerals in the attached figures:

[0045] Casing 1

[0046] Cover plate 2

[0047] Lower plastic 21

[0048] pole 3

[0049] Battery cell assembly 4

[0050] Insulating film 5

[0051] Bottom coating sheet 51

[0052] Side wrapping 52

[0053] First side coverage area 521

[0054] First side coverage area unit 5211

[0055] Second side covering area 522

[0056] Thickened area 523

[0057] Folded edge area 524

[0058] Body area 525

[0059] Thickened layer 53

[0060] First thickening layer unit 531

[0061] Second thickening layer unit 532

[0062] Capacity 54

[0063] First side bread slice unit 55

[0064] Second side bread slice unit 56

[0065] First auxiliary bending section 61

[0066] Second auxiliary bending section 62 Detailed Implementation

[0067] The present invention will be described more clearly and completely below with reference to the accompanying drawings, using a preferred embodiment.

[0068] Example 1

[0069] This embodiment provides a secondary battery for powering electric vehicles and other electrical equipment. Figure 1 and Figure 2 As shown, the secondary battery includes a casing 1, a cover plate 2, terminals 3, a cell assembly 4, and an insulating film 5 covering the cell assembly 4. This embodiment uses a top-terminal type secondary battery as an example; however, in other alternative embodiments, the secondary battery can also be of other forms, such as a two-terminal type.

[0070] Specifically, such as Figure 1 and Figure 2 As shown, the housing 1 is a hollow structure with an open top. The interior of the housing 1 has a cavity (not shown) for accommodating the battery cell assembly 4. A cover plate 2 covers the opening at the top of the housing 1 and completely seals it, ensuring that the cavity inside the housing 1 remains closed after the battery cell assembly 4 is inserted. A terminal post 3 is mounted on the cover plate 2 and is electrically connected to the battery cell assembly 4 to facilitate current transmission. A lower plastic insert 21, made of insulating material, is located on the lower part of the cover plate 2 (towards the cavity) to insulate the battery cell assembly 4. The insulating film 5 is used to cover the outer surface of the battery cell assembly 4 before it is installed into the housing 1. After the covering is completed, the battery cell assembly 4 and the insulating film 5 are installed together into the receiving cavity inside the housing 1. The insulating film 5 plays a protective role for the battery cell assembly 4, preventing the housing 1 from causing scratches or other damage to the battery cell assembly 4 during the process of the battery cell assembly 4 being installed into the housing, avoiding damage to the battery cell assembly 4 during the assembly process, achieving insulation isolation between the battery cell assembly 4 and the housing 1, and preventing short circuits, corrosion and mechanical damage.

[0071] Figure 3 and Figure 4 The diagram illustrates the structural state of the insulating film after it has been folded five times. Figure 5 This illustrates the structural state of the insulating film 5 when it is unfolded (unfolded). For example... Figures 3-5 As shown, the insulating film 5 includes a bottom covering sheet 51 and a side covering sheet 52. When the insulating film 5 is in a folded state, the side covering sheet 52 is connected to the bottom covering sheet 51 in its wall thickness direction. Figure 3 The bottom cover plate 51 and the side cover plate 52 form a receiving space 54 for accommodating the battery cell assembly 4 at one end facing the cover plate 2 in the Z direction. The receiving space 54 is open at one end facing the cover plate 2 to facilitate the electrical connection between the battery cell assembly 4 and the terminal post 3.

[0072] like Figure 3 and Figure 4As shown, the secondary battery in this embodiment is a square battery. When the insulating film 5 is in a folded state, the side covering sheet 52 includes two opposing first side covering areas 521 and two opposing second side covering areas 522. The two first side covering areas 521 are respectively located on the bottom covering sheet 51 along its length direction. Figure 3 At both ends of the bottom covering sheet 51 in the X direction, two second side covering areas 522 are respectively provided in the width direction of the bottom covering sheet 51. Figure 3 At both ends of the Y direction in the bottom cover sheet 51, the two first side cover areas 521 are connected to the corresponding second side cover areas 522 at both ends of the width direction of the bottom cover sheet 51, and the junction of the first side cover area 521 and the second side cover area 522 forms the folded edge area 524 of the side cover sheet 52.

[0073] like Figure 5 As shown, the side covering sheet 52 includes a first side covering sheet unit 55 and a second side covering sheet unit 56. When the insulating film 5 is in the unfolded state, the first side covering sheet unit 55 and the second side covering sheet unit 56 are respectively disposed at both ends of the bottom covering sheet 51 in the width direction. The first side covering sheet unit 55 and the second side covering sheet unit 56 each include a partial structure of a second side covering area 522 and two first side covering areas 521.

[0074] Specifically, in Figure 5 In the first side cover unit 55, the second side cover area 522 extends outward along the width direction of the bottom cover 51 at both ends to form two second side cover areas 522. Similarly, the second side cover area 522 in the second side cover unit 56 extends outward along the length direction of the bottom cover 51 at both ends to form two first side cover area units 5211. Figure 4 As shown, after the insulating film 5 is folded, the first side covering area unit 5211 in the first side covering sheet unit 55 and the first side covering area unit 5211 on the same side in the second side covering sheet unit 56 overlap and fix to form the first side covering area 521.

[0075] like Figure 3 and Figure 5 As shown, the insulating film 5 also includes a thickening layer 53. When the insulating film 5 is in a folded state, the thickening layer 53 is disposed on the end face of the side cover sheet 52 away from the bottom cover sheet 51 in the wall thickness direction. The wall thickness of the thickening layer 53 is greater than the wall thickness of the side cover sheet 52.

[0076] like Figure 3 As shown, in this embodiment, when the insulating film 5 is in a folded state, the end of the thickened layer 53 away from the bottom cover sheet 51 in the wall thickness direction is flush with the end of the side cover sheet 52 away from the bottom cover sheet 51 in the wall thickness direction.

[0077] Specifically, such as Figure 5 As shown, the first side bread slice unit 55 and the second side bread slice unit 56 have notches at their ends away from the bottom bread slice 51. The notches penetrate the side bread slice 52 at their upper ends in the wall thickness direction of the first side bread slice unit 55 and the second side bread slice unit 56, and at their ends away from the bottom bread slice 51 in the width direction. A thickening layer 53 is partially disposed within the notch, and the outer contour of the thickening layer 53 matches the shape of the notch. The peripheral side surface of the thickening layer 53 is tightly fitted to the inner wall surface of the notch. The thickening layer 53 extends to the outer edge of the first side bread slice unit 55 and the second side bread slice unit 56 at its end away from the bottom bread slice 51 in the width direction.

[0078] In this embodiment, the thickening layer 53 is only provided at the location of the folded edge area 524. In other alternative embodiments, a thickening layer 53 can be provided around one end of the opening of the receiving space 54.

[0079] In other alternative embodiments, the thickening layer 53 and the side covering sheet 52 may be flush with the end of the bottom covering sheet 51 away from the wall thickness direction, and the end of the thickening layer 53 away from the bottom covering sheet 51 in the wall thickness direction may extend beyond the end of the side covering sheet 52 away from the bottom covering sheet 51 in the wall thickness direction.

[0080] In this embodiment, the entire insulating film 5 is integrally formed, namely, the bottom covering sheet 51, the side covering sheet 52, and the thickening layer 53 are integrally formed. During the manufacturing process of the insulating film 5, the thickness of the insulating material is directly increased in the area of ​​the thickening layer 53. The integral forming process is simple, avoids the risk of interface peeling caused by multi-layer structure splicing, improves the stability and consistency of the overall structure, and reduces production costs.

[0081] In other alternative embodiments, the side covering sheet 52 and the thickening layer 53 may also be formed by splicing two independently molded structures.

[0082] Furthermore, such as Figures 3-5As shown, the thickening layer 53 includes a first thickening layer unit 531 and a second thickening layer unit 532. The first thickening layer unit 531 is connected to the first side covering area 521, and the first thickening layer unit 531 extends toward the second side covering area 522 to form the second thickening layer unit 532. The second thickening layer unit 532 is connected to the second side covering area 522. That is, in this embodiment, the first thickening layer unit 531 and the second thickening layer unit 532 in a single thickening layer 53 are continuous to completely cover the folded edge area 524 of the side covering sheet 52.

[0083] In this embodiment, by providing a thickening layer 53 in the easily torn folded edge area 524 of the side cover sheet 52, the overall wall thickness of the insulating film 5 in that area is increased, thereby effectively enhancing the structural strength and tear resistance of that area. This solves the stress concentration and tearing problems caused by the thinning of the wall thickness of the side cover sheet 52, thereby improving the reliability of the insulating film 5 and the safety of the battery.

[0084] Furthermore, such as Figure 3 and Figure 5 As shown, in this embodiment, the side covering sheet 52 has four folded edge areas 524, and each folded edge area 524 is provided with a thickening layer 53 to ensure that all four folded edge areas 524 can be effectively protected.

[0085] Furthermore, the shape of the thickened layer 53 is not specifically limited and can be rectangular, semi-circular, etc.

[0086] In this embodiment, the wall thickness of the side covering sheet 52 is the same everywhere, at 0.1 mm, and the wall thickness of the thickening layer 53 is the same everywhere, at 0.2 mm. By reasonably setting the wall thickness range of the side covering sheet 52 and the thickening layer 53, this embodiment can still provide sufficient structural support in key areas while ensuring that the overall wall thickness of the insulating film 5 is reduced. This balances space utilization and structural strength, and avoids excessive occupation of the storage space of the cell assembly 4 due to excessive thickening, thereby ensuring the power of the secondary battery.

[0087] In other alternative embodiments, the wall thickness of the thickening layer 53 should be greater than or equal to 0.1 mm to ensure that the thickening layer 53 has sufficient mechanical strength to withstand the stress during bending and assembly, avoiding the inability to provide effective reinforcement due to excessively thin walls, thereby further improving the tear resistance of the insulating film 5. Preferably, the wall thickness of the side covering sheet 52 is 0.08~0.2 mm, and the wall thickness of the thickening layer 53 is 0.1~0.3 mm.

[0088] like Figures 3-5As shown, when the insulating film 5 is in a folded state, the length of the thickening layer 53 in the wall thickness direction of the bottom covering sheet 51 is defined as 'a', the length of the first thickening layer unit 531 in the width direction of the bottom covering sheet 51 is defined as 'b', and the length of the second thickening layer unit 532 in the length direction of the bottom covering sheet 51 is defined as 'c', where 1.6mm ≤ a ≤ 10mm, 5mm ≤ b ≤ 20mm, and 5mm ≤ c ≤ 20mm. This embodiment, by limiting the size of the thickening layer 53, ensures that the area covered by the thickening layer 53 is sufficient to disperse stress and prevent tearing, while also saving the total amount of insulating film 5 and reducing costs.

[0089] In other alternative implementations, the dimensions of the thickened layer 53 can be designed to other values ​​according to actual needs.

[0090] like Figure 3 , Figure 5 and Figure 6 As shown, the side covering sheet 52 is bent to form a first side covering area 521 and a second side covering area 522. To facilitate bending of the side covering sheet 52, a first auxiliary bending portion 61 extending along the wall thickness direction of the bottom covering sheet 51 is provided between the first side covering area 521 and the second side covering area 522. Furthermore, since a single thickening layer 53 also covers the folded edge area 524, the thickening layer 53 also needs to be bent. Therefore, to facilitate bending of the thickening layer 53, a second auxiliary bending portion 62 extending along the wall thickness direction of the bottom covering sheet 51 is provided between the first thickening layer unit 531 and the second thickening layer unit 532 of a single thickening layer 53. The second auxiliary bending portion 62 corresponds to the first auxiliary bending portion 61, that is, the two correspond in the length and width directions of the bottom covering sheet 51.

[0091] Specifically, in this embodiment, the first auxiliary bending portion 61 and the second auxiliary bending portion 62 are both sawtooth structures extending along the wall thickness direction of the bottom covering sheet 51. The sawtooth structure can be formed by rolling a structure such as gears on the insulating film 5. During the rolling process, the structure such as gears cuts the connecting part of the first thickening layer unit 531 and the second thickening layer unit 532 as well as the thickening layer 53 to form the first auxiliary bending portion 61 and the second auxiliary bending portion 62 respectively.

[0092] In other alternative embodiments, the first auxiliary bending portion 61 and the second auxiliary bending portion 62 may also adopt other structures that can play an auxiliary bending role, such as a groove extending along the wall thickness direction of the bottom covering sheet 51. In this state, the wall thickness of the first auxiliary bending portion 61 is less than the wall thickness of the first thickening layer unit 531 or the second thickening layer unit 532, and the wall thickness of the second auxiliary bending portion 62 is less than the wall thickness of the thickening layer 53.

[0093] Example 2

[0094] The insulating film in this embodiment is basically the same as that in Embodiment 1, except that:

[0095] like Figure 7 As shown, in this embodiment, the side covering sheet 52 and the thickening layer 53 are integrally formed. The integral forming process is simple, avoids the risk of interface peeling caused by the splicing of multi-layer structures, improves the stability and consistency of the overall structure, and reduces production costs.

[0096] like Figure 7 As shown, the side covering sheet 52 has a body region 525 and a thickened region 523. When the insulating film 5 is in the unfolded state, the body region 525 extends outward from the end away from the bottom covering sheet 51 in the width direction to form the thickened region 523 (when the insulating film 5 is in the folded state, the body region 525 extends outward from the end away from the bottom covering sheet 51 in the wall thickness direction to form the thickened region 523). The thickened region 523 is bendable relative to the body region 525, and folds over the body region 525 in the direction towards the body region 525 to cover the body region 525, thereby forming the thickened layer 53. This molding method does not require changing the thickness of a portion of the insulating film, and the molding method is simple. The folding and covering method facilitates the positioning between the body region 525 and the thickened region 523, improving assembly efficiency.

[0097] Furthermore, when the insulating film 5 is in a folded state, the thickened region 523 is located between the body region 525 and the housing 1, that is, the thickened region 523 is folded outward toward the receiving space to prevent interference with the cell assembly 4. In other alternative embodiments, the thickened region 523 may also be folded inward toward the receiving space.

[0098] Furthermore, after the insulating film 5 is folded, an adhesive layer is provided at the end of the thickened area 523 facing the body area 525. The body area 525 and the thickened area 523 are bonded together by the adhesive layer to fix their positions. In this embodiment, by providing an adhesive layer, a firm connection between the body area 525 and the thickened area 523 is ensured, preventing peeling or displacement during bending or assembly, thereby further enhancing structural stability and insulation reliability.

[0099] In this embodiment, the adhesive layer is fixed on the thickened area 523. In other alternative embodiments, the adhesive layer can also be fixed on the body area 525, ensuring that the adhesive layer is positioned between the body area 525 and the thickened area 523. This embodiment fixes the adhesive layer on the thickened area 523 to omit the positioning process of the adhesive layer on the body area 525, thereby improving assembly efficiency.

[0100] In other alternative implementations, the body region 525 and the thickened region 523 can also be fixed in other ways, such as local heat fusion.

[0101] In this embodiment, after the positions of the body region 525 and the thickened region 523 are fixed, the first auxiliary bending portion 61 and the second auxiliary bending portion 62 are uniformly processed on the insulating film 5, so that the second auxiliary bending portion 62 with corresponding positions is formed on both the body region 525 and the thickened region 523.

[0102] In other alternative embodiments, the first auxiliary bending portion 61 and the second auxiliary bending portion 62 may be processed first, and then the thickened area 523 may be folded over to fix the positions of the main body area 525 and the thickened area 523.

[0103] Example 3

[0104] The insulating film in this embodiment is basically the same as that in Embodiment 1, except that:

[0105] In this embodiment, the thickening layer includes a first part and a second part. The first part is integrally formed with the side covering sheet, while the second part is independent of the side covering sheet and covers the first part. That is, the first part and the second part are independently formed components, which allows for flexible adjustment of the material and thickness of the thickening layer according to actual needs. This makes it suitable for different battery structures and assembly processes, improving the flexibility and adaptability of the design.

[0106] After the insulating film is folded, an adhesive layer is provided at the end of the second part facing the first part, and the first part and the second part are bonded together by the adhesive layer. In this embodiment, by providing an adhesive layer, a firm connection between the first part and the second part is ensured, preventing peeling or displacement during bending or assembly, and further enhancing structural stability and insulation reliability.

[0107] In this embodiment, the adhesive layer is fixed to the second part. In other alternative embodiments, the adhesive layer can also be fixed to the first part, ensuring that the adhesive layer is positioned between the first and second parts. This embodiment fixes the adhesive layer to the second part to omit the positioning process of the adhesive layer on the first part, thereby improving assembly efficiency.

[0108] In other alternative implementations, the thickened area and the thickened layer can also be connected in other ways, such as localized heat fusion.

[0109] In this embodiment, after the positions of the first part and the second part are fixed, the first auxiliary bending part and the second auxiliary bending part are uniformly processed on the insulating film to form the second auxiliary bending part with corresponding positions on both the first part and the second part.

[0110] In other alternative implementations, the first auxiliary bending portion and the second auxiliary bending portion can be processed first, and then the second portion can be bonded together to fix the positions of the first portion and the second portion.

[0111] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship of the device or component shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or component referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0112] While specific embodiments of this utility model have been described above, those skilled in the art should understand that these are merely illustrative examples, and the scope of protection of this utility model is defined by the appended claims. Those skilled in the art can make various changes or modifications to these embodiments without departing from the principles and essence of this utility model, but all such changes and modifications fall within the scope of protection of this utility model.

Claims

1. An insulating film for covering a cell assembly (4) of a secondary battery, characterized in that, The insulating film (5) includes a bottom cover sheet (51), a side cover sheet (52) and a thickening layer (53), wherein the wall thickness of the thickening layer (53) is greater than the wall thickness of the side cover sheet (52); The side covering sheet (52) is connected to one end of the bottom covering sheet (51) in the wall thickness direction. The side covering sheet (52) includes two first side covering areas (521) respectively located at both ends of the length direction of the bottom covering sheet (51), and two second side covering areas (522) respectively located at both ends of the width direction of the bottom covering sheet (51). The thickening layer (53) is disposed on the end face of the side covering sheet (52) on the side away from the bottom covering sheet (51) in the wall thickness direction, and The thickening layer (53) includes a first thickening layer unit (531) and a second thickening layer unit (532). The first thickening layer unit (531) is connected to the first side covering area (521). The first thickening layer unit (531) extends toward the second side covering area (522) to form the second thickening layer unit (532). The second thickening layer unit (532) is connected to the second side covering area (522).

2. The insulating film as described in claim 1, characterized in that, The wall thickness of the thickened layer (53) is greater than or equal to 0.1 mm.

3. The insulating film as described in claim 2, characterized in that, The wall thickness of the side covering sheet (52) is 0.08~0.2mm, and the wall thickness of the thickening layer (53) is less than or equal to 0.3mm.

4. The insulating film as described in claim 2, characterized in that, The insulating film (5) satisfies one or more of the following conditions: a1. Define the length of the thickened layer (53) in the wall thickness direction of the bottom covering sheet (51) as a, where 1.6mm≤a≤10mm; b2. Define the length of the first thickening layer unit (531) in the width direction of the bottom covering sheet (51) as b, where 5mm≤b≤20mm; c3. Define the length of the second thickening layer unit (532) in the length direction of the bottom covering sheet (51) as c, where 5mm≤c≤20mm.

5. The insulating film as described in claim 1, characterized in that, The side covering sheet (52) and the thickening layer (53) are integrally formed.

6. The insulating film as described in claim 5, characterized in that, The side cover sheet (52) has a body region (525) and a thickened region (523). The body region (525) extends outward from the bottom cover sheet (51) in the wall thickness direction to form the thickened region (523). The thickened region (523) is folded towards the body region (525) to form the thickened layer (53).

7. The insulating film as described in claim 1, characterized in that, The thickened layer (53) includes a first part and a second part. The first part is integrally formed with the side cover sheet (52), and the second part is independent of the side cover sheet (52) and covers the first part.

8. The insulating film as described in claim 7, characterized in that, The second part has an adhesive layer at one end facing the first part, and the second part is bonded to the first part through the adhesive layer.

9. The insulating film as described in claim 1, characterized in that, The insulating film (5) satisfies one or more of the following conditions: a2. The thickening layer (53) further includes an auxiliary bending portion disposed between the first thickening layer unit (531) and the second thickening layer unit (532) and extending along the wall thickness direction of the bottom covering sheet (51); The wall thickness of the auxiliary bending portion is less than the wall thickness of the first thickening layer unit (531) or the second thickening layer unit (532); or, the connecting portion of the first thickening layer unit (531) and the second thickening layer unit (532) is partially cut to form the auxiliary bending portion; b2. The thickened layer (53) is flush with the end of the bottom cover sheet (51) away from the bottom cover sheet (51) in the wall thickness direction, and the side cover sheet (52) is flush with the end of the side cover sheet (52) away from the bottom cover sheet (51) in the wall thickness direction. Alternatively, the thickened layer (53) extends beyond the side cover (52) at one end of the bottom cover (51) away from the bottom cover (51) in the wall thickness direction.

10. A secondary battery, characterized in that, The secondary battery includes a housing (1), a cell assembly (4), and an insulating film (5) as described in any one of claims 1-9. The insulating film (5) covers the outer surface of the cell assembly (4), and both the cell assembly (4) and the insulating film (5) are disposed inside the housing (1).

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