Cover plate assembly and battery cell

Abstract

The application discloses a cover plate assembly and a battery monomer, and belongs to the technical field of batteries, and aims to solve the technical problem that the ventilation part of the cover plate is blocked, the internal pressure of the battery cannot be effectively released and continuously accumulated, and the battery shell is easily broken, the structure is disintegrated, and even secondary explosion is caused. The cover plate assembly provided by the application comprises a cover plate, the cover plate has a thickness direction, a pressure relief structure is arranged on the cover plate, a lower plastic comprises a lower plastic body, a ventilation part and a weakened part arranged on the lower plastic body, the lower plastic body is stacked along the thickness direction with the cover plate, the pressure relief structure at least partially covers the ventilation part, and the weakened part is located outside the orthographic projection area of the pressure relief structure on the lower plastic body.

Description

Technical Field

[0001] This application relates to the field of battery technology, and in particular to a cover plate assembly and a battery cell. Background Technology

[0002] In related technologies, the structural component located at the bottom of a battery cell is usually referred to as the lower plastic layer. The main function of this lower plastic layer is to provide structural support and spatial constraints for the battery cells, electrode assemblies, and related components inside the battery.

[0003] However, in the event of thermal runaway in a single battery cell, the internal temperature rises rapidly within a short period due to a violent exothermic reaction. The lower plastic layer softens, melts, and may even thermally decompose. Simultaneously, the thermal runaway process generates a large amount of high-temperature gas and reaction byproducts, creating airflow within the battery. Under the influence of this airflow, the softened or melted polymer material in the lower plastic layer is easily driven and migrates to the venting areas and surrounding regions inside the battery, where it accumulates and blocks the venting. This blockage prevents effective release of internal pressure, leading to its continuous accumulation and potentially causing battery casing rupture, structural disintegration, or even a secondary explosion. Utility Model Content

[0004] This application provides a cover plate assembly and a battery cell to at least partially solve the above-mentioned technical problems.

[0005] To achieve the above objectives, according to a first aspect of this application, a cover plate assembly is provided, the cover plate assembly comprising: Cover plate, having thickness direction; A pressure relief structure is installed on the cover plate; The lower plastic includes a lower plastic body, and a venting part and a weakening part disposed on the lower plastic body. The lower plastic body and the cover plate are stacked along the thickness direction. The pressure relief structure at least partially covers the venting part, and the weakening part is located outside the orthogonal projection area of ​​the pressure relief structure on the lower plastic body.

[0006] In some embodiments of this application, there are two weakening portions, which are respectively disposed on opposite sides of the venting portion, or the weakening portions are disposed around the venting portion.

[0007] In some embodiments of this application, the weakened portion includes a plurality of hollow holes that penetrate the lower plastic body along the thickness direction.

[0008] In some embodiments of this application, the diameter of the inscribed circle of the perforated hole is greater than or equal to 0.5 mm and less than or equal to 1 mm; and / or, 5 to 10 perforated holes are distributed per centimeter along the surface of the lower plastic body.

[0009] In some embodiments of this application, the weakening portion includes a weakening groove recessed along the thickness direction in the lower plastic body.

[0010] In some embodiments of this application, the thickness of the lower plastic body in the thickness direction is H, and the depth of the weakening groove in the thickness direction is H1, wherein 0.6×H≤H1≤0.8×H.

[0011] In some embodiments of this application, the lower plastic body includes a separate first part and a second part, a venting part is disposed in the first part, a weakening part connects the first part and the second part, and the glass transition temperature of the material of the weakening part is lower than the glass transition temperature of the material of the lower plastic body.

[0012] In some embodiments of this application, at least one of the first part and the second part is connected to the weakened part by a hot melt solder joint or a snap-fit ​​structure.

[0013] In some embodiments of this application, the cover plate has a length direction and a width direction, and there are two weakened portions, which are symmetrically arranged on opposite sides of the vent in the length direction, and each weakened portion covers the lower plastic body in the width direction.

[0014] According to a second aspect of this application, a battery cell is provided, the battery cell comprising: The cover plate assembly as described in any of the above technical solutions.

[0015] In the cover assembly of this application embodiment, through the above technical solution, a pressure relief structure is disposed on the cover and at least partially covers the vent, for timely release of high-pressure gas when the internal pressure of the battery exceeds a safety threshold. Correspondingly, it is arranged outside the orthogonal projection area of ​​the pressure relief structure on the lower plastic body, i.e., not directly below the pressure relief structure or on the pressure relief path opposite to the vent. Therefore, when the battery experiences thermal runaway and generates high-pressure gas, the gas will preferentially impact and act on the pressure relief structure through the vent, enabling the pressure relief structure to serve as the main pressure relief path for efficient and controllable gas release. The weakened section, serving as an auxiliary pressure relief path or backup fracture zone, is not located on the main pressure relief path for gas release. Therefore, it is not easily impacted by high-pressure airflow during normal pressure relief, nor is it easily blocked by molten material, migration material, or structural deformation in the venting section. This weakened section can function as an alternative auxiliary pressure relief channel when the main pressure relief path where the venting section is located becomes blocked, fails, or the internal pressure further increases. This provides an additional gas release path for the battery, ensuring continuous pressure release. This helps reduce the risk of the battery's internal pressure exceeding the bearing limit of the casing or pressure relief structure, thereby effectively preventing problems such as casing rupture, structural disintegration, or even secondary explosion.

[0016] Other features and advantages of this application will be described in detail in the following detailed description section. Attached Figure Description To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] To gain a more complete understanding of this application and its beneficial effects, the following description will be provided in conjunction with the accompanying drawings, wherein the same reference numerals in the following description denote the same parts.

[0018] Figure 1 This is an exploded view of the cover plate assembly provided in the embodiments of this disclosure; Figure 2 This is a schematic diagram of the structure of the first type of lower plastic in the cover plate assembly provided in this embodiment of the present disclosure; Figure 3 This is a schematic diagram of the structure of the second type of lower plastic in the cover plate assembly provided in this embodiment of the present disclosure; Figure 4 This is a schematic diagram of the third type of lower plastic in the cover plate assembly provided in this embodiment of the present disclosure; Figure 5 This is a schematic diagram of the fourth type of lower plastic in the cover plate assembly provided in this embodiment of the present disclosure; Figure 6 This is a schematic diagram of the structure of the fifth type of lower plastic in the cover plate assembly provided in this embodiment of the present disclosure; Figure 7 This is a schematic diagram of the sixth type of lower plastic in the cover plate assembly provided in this embodiment of the present disclosure; Figure 8 yes Figure 3 Cross-sectional view of section AA.

[0019] Explanation of reference numerals in the attached figures: 1-Cover plate; 2-Pressure relief structure; 3-Lower plastic; 31-Lower plastic body; 311-First part; 312-Second part; 3121-Hook hole; 32-Ventilation part; 321-Ventilation hole; 33-Weakening part; 331-Hollow hole; 332-Weakening groove; 333-Snap fastener; Z-Thickness direction; Y-Width direction; X-Length direction. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In the description of this application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They 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. Therefore, they should not be construed as limitations on this application.

[0022] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0023] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection, a direct connection, or an indirect connection through an intermediate medium; or they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0024] This application provides a cover plate assembly and a battery cell, which are described in detail below. It should be noted that the order of description of the following embodiments is not intended to limit the preferred order of the embodiments of this application. Furthermore, the descriptions of each embodiment have their own emphasis; parts not described in detail in a certain embodiment can be referred to in the relevant descriptions of other embodiments.

[0025] In related technologies, the structural component located at the bottom of a battery cell is usually referred to as the lower plastic layer. The main function of this lower plastic layer is to provide structural support and spatial constraints for the battery cells, electrode assemblies, and related components inside the battery.

[0026] However, in the event of thermal runaway in a single battery cell, the internal temperature rises rapidly within a short period due to a violent exothermic reaction. The lower plastic layer softens, melts, and may even thermally decompose. Simultaneously, the thermal runaway process generates a large amount of high-temperature gas and reaction byproducts, creating airflow within the battery. Under the influence of this airflow, the softened or melted polymer material in the lower plastic layer is easily driven and migrates to the venting areas and surrounding regions inside the battery, accumulating and blocking these areas. This blockage prevents effective release of internal pressure, leading to its continuous accumulation. When the internal pressure exceeds the bearing capacity of safety components such as the battery casing or explosion-proof structure, it can easily cause problems such as battery casing rupture, structural disintegration, or even secondary explosions.

[0027] Therefore, this application provides a cover assembly that can ensure the continuous release of internal battery pressure when the vent is blocked, so as to avoid problems such as battery casing rupture, structural disintegration, or even secondary explosion caused by the internal pressure of the battery exceeding the bearing limit of safety components such as battery casing or explosion-proof structure.

[0028] Please refer to Figure 1 The cover assembly provided in this application includes a cover plate 1, a pressure relief structure 2, and a lower plastic 3. The cover plate 1 has a thickness direction Z, and the pressure relief structure 2 is disposed on the cover plate 1. The lower plastic 3 includes a lower plastic body 31, and a venting portion 32 and a weakening portion 33 disposed on the lower plastic body 31. The lower plastic body 31 and the cover plate 1 are stacked along the thickness direction Z. The pressure relief structure 2 at least partially covers the venting portion 32, and the weakening portion 33 is located outside the orthogonal projection area of ​​the pressure relief structure 2 on the lower plastic body 31. As an example, the pressure relief structure 2 may completely cover the venting portion 32 or partially cover the venting portion 32.

[0029] In this technical solution, the pressure relief structure 2 is disposed on the cover plate 1 and at least partially covers the venting section 32, for timely release of high-pressure gas when the internal pressure of the battery exceeds a safety threshold. Correspondingly, it is positioned outside the orthogonal projection area of ​​the pressure relief structure 2 on the lower plastic body 31, i.e., not directly below the pressure relief structure 2 or on the pressure relief path opposite to the venting section 32. Therefore, when the battery experiences thermal runaway and generates high-pressure gas, the gas will preferentially impact and act on the pressure relief structure 2 through the venting section 32, enabling the pressure relief structure 2 to serve as the main pressure relief path for efficient and controllable gas release. The weakened section 33 serves as an auxiliary pressure relief path or a backup fracture zone. It is not located on the main pressure relief path for gas release. Therefore, it is not easily impacted by high-pressure airflow during normal pressure relief, nor is it easily blocked by molten material, migration material, or structural deformation in the venting section 32. The weakened section 33 can function as an alternative auxiliary pressure relief channel when the main pressure relief path where the venting section 32 is located is blocked, fails, or the internal pressure further increases, thereby providing an additional gas release path for the battery and ensuring that the pressure is continuously released.

[0030] Through the aforementioned functional zoning and risk-avoidance structural layout, this application effectively avoids problems such as multi-point failure, structural disorder, or loss of overall pressure relief function caused by the disorderly impact of high-pressure gas on the entire lower plastic 3 structure. Simultaneously, even when the venting section 32 is blocked, the weakened section 33 can still maintain a certain pressure relief capacity, thereby reducing the risk of the battery's internal pressure exceeding the bearing limit of the casing or pressure relief structure 2. This effectively prevents problems such as casing rupture, structural disintegration, or even secondary explosion, improving the battery's safety and reliability under thermal runaway conditions.

[0031] In some embodiments, the pressure relief structure 2 can be an explosion-proof valve, explosion-proof grooves, weak areas, etc. The lower plastic 3, located below the cover plate 1 (stacked with the cover plate 1 along the thickness direction Z), is an important structural support and limiting component inside the battery, typically made of thermoplastic polymer material. The lower plastic body 31 is the main part of the lower plastic 3, serving a supporting and fixing function. A vent 32 is provided on the lower plastic body 31, providing a path for gas flow and functionally cooperating with the pressure relief structure 2, allowing gas to flow from the vent 32 of the lower plastic 3 to the pressure relief structure 2.

[0032] The ventilation section 32 includes a plurality of spaced-apart ventilation holes 321. For example... Figure 1 As shown, the venting section 32 includes a plurality of vent holes 321 arranged in an array. The weakening section 33 is a structural area on the lower plastic body 31 designed to preferentially deform, break, or guide tearing under extreme conditions such as high temperature and high pressure. It can function as an auxiliary pressure relief path or a fracture guiding area when the main pressure relief path (such as the venting section 32 and the pressure relief structure 2) fails or the pressure further increases.

[0033] like Figure 2 , Figure 3 and Figure 4 As shown, in this embodiment, there are two weakening sections 33, which are respectively disposed on opposite sides of the venting section 32. Therefore, by distributing the two weakening sections 33 on opposite sides of the venting section 32, auxiliary gas release channels or interruption guidance functions can be provided from both sides when the main pressure relief path (i.e., the area where the venting section 32 and the pressure relief structure 2 are located) is blocked, thereby creating multi-directional and multi-path gas escape possibilities and enhancing the responsiveness and reliability of the pressure relief system. For example, the two weakening sections 33 are symmetrically distributed on both sides of the venting section 32, which helps to guide and divert the high-pressure airflow during gas release, preventing gas from concentrating and impacting a local area, thus avoiding excessive pressure concentration, damage to the lower plastic body 31 structure, or poor pressure relief.

[0034] like Figure 5 , Figure 6 and Figure 7 As shown, in this embodiment, the weakening part 33 is arranged around the venting part 32. This is equivalent to forming a ring-shaped auxiliary pressure relief path around the main pressure relief path. If the main pressure relief path (such as the venting part 32 or the pressure relief structure 2) fails due to melting, blockage, or high pressure overload, the weakening part 33 can respond in time (such as breaking or cracking) to form a new gas release channel, thereby providing an additional pressure relief path and preventing high pressure gas from disorderly impacting the entire lower plastic body 31, thus avoiding disorderly structural damage or overall failure of the lower plastic body 31.

[0035] The weakening part 33 is arranged around the ventilating part 32, which means that the weakening part 33 surrounds the ventilating part 32 in a ring, elliptical, frame or near-ring shape.

[0036] like Figure 2 and Figure 5 As shown, the weakened portion 33 includes multiple perforated holes 331 extending through the lower plastic body 31 along the thickness direction Z, thereby reducing the material continuity of the lower plastic body 31 in this region and weakening its overall structural strength and rigidity. When the battery experiences thermal runaway and the main pressure relief path (such as the venting portion 32 and the pressure relief structure 2) fails due to melting, blockage, or high-pressure overload, the weakened portion 33 forms an auxiliary pressure relief path through local cracking, hole expansion, or structural tearing, thereby guiding gas to preferentially pass through this region for release, achieving a more controllable opening of the pressure relief path.

[0037] Specifically, such as Figure 2 As shown, in this embodiment, there are two weakened portions 33, which are respectively disposed on opposite sides of the venting portion 32. Each weakened portion 33 includes a plurality of spaced-apart perforations 331. Figure 5As shown, the weakened portion 33 includes a plurality of perforated holes 331 arranged around the vent portion 32. Exemplarily, the perforated holes 331 can be square holes; of course, in other embodiments not shown in the accompanying drawings, the perforated holes 331 can also be circular holes, U-shaped holes, elliptical holes, waist-shaped holes or other irregularly shaped holes.

[0038] The diameter of the inscribed circle of the perforated hole 331 is greater than or equal to 0.5 mm and less than or equal to 1 mm. When the diameter of the inscribed circle of the perforated hole 331 is in the range of 0.5 mm to 1 mm, the perforated hole 331 is sufficient to form a local structural weak zone in the material, enabling it to respond preferentially and guide pressure relief or fracture when subjected to high-pressure gas impact or high temperature, without causing premature instability or unnecessary premature failure of the overall structure due to the excessive size of the perforated hole 331. For example, the diameter of the inscribed circle of the perforated hole 331 can be 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, or 1 mm.

[0039] Furthermore, 5 to 10 perforated holes 331 are distributed per centimeter along the surface of the lower plastic body 31 to form a structurally weakened zone in this area, reducing material continuity and decreasing local stiffness and load-bearing capacity. In the event of thermal runaway, internal high-pressure gas generation, or high temperature, this weakened area will preferentially deform, crack, or fracture, thereby guiding the gas to be released preferentially through the weakened portion 33.

[0040] like Figure 3 and Figure 6 As shown, the weakened portion 33 includes a weakening groove 332 recessed along the thickness direction Z in the lower plastic body 31. The weakening groove 332, by forming a recess inside the lower plastic body 31, reduces the effective load-bearing area and moment of inertia of the material in that region, thereby reducing the local structural strength and stiffness of that portion. Therefore, when the battery experiences thermal runaway and the internal gas pressure rises sharply, the area where the weakening groove 332 is located will preferentially deform, buckle, or partially fracture due to factors such as reduced material strength and stress concentration, thereby guiding gas to preferentially release through that region.

[0041] Specifically, the weakening groove 332 refers to a recessed groove or channel structure on a surface (usually the upper or lower surface) of the lower plastic body 31 in the thickness direction Z. It can be linear, annular, frame-shaped, arc-shaped, or other specific shapes. The weakening groove 332 is recessed inward along the thickness direction Z of the lower plastic body 31, but does not penetrate the entire lower plastic body 31, that is, it does not penetrate to the other side of the lower plastic body 31.

[0042] Based on the above embodiments, combined with Figure 3 and Figure 8The thickness of the lower plastic body 31 in the thickness direction Z is H, and the depth of the weakening groove 332 in the thickness direction Z is H1, wherein 0.6×H≤H1≤0.8×H. When 0.6×H≤H1, the depth of the weakening groove 332 is large enough to reduce the effective thickness of the material in this area, enabling it to preferentially deform, buckle, crack, or locally tear when subjected to high-pressure gas impact or high temperature. When H1≤0.8×H, a certain material load-bearing capacity and structural integrity can be maintained while achieving a good weakening effect, avoiding unexpected deformation, cracking, or failure under normal working conditions (such as assembly stress, slight vibration, and temperature changes).

[0043] like Figure 4 and Figure 7 As shown, in this embodiment, the lower plastic body 31 includes a separate first part 311 and a second part 312. A venting section 32 is disposed in the first part 311, and a weakening section 33 connects the first part 311 and the second part 312. The glass transition temperature (Tg) of the material in the weakening section 33 is lower than that of the material in the lower plastic body 31. The glass transition temperature (Tg) is the critical temperature point at which a thermoplastic material transitions from a hard and brittle glassy state to a soft and tough (or flowable) state. The fact that the glass transition temperature of the weakening section 33 is lower than that of the lower plastic body 31 means that when the battery experiences thermal runaway and the internal temperature rises, the weakening section 33 will soften and melt before the lower plastic body 31. This area will preferentially deform and fracture, forming a new auxiliary pressure relief path to guide gas through for release.

[0044] For example, at least one of the first part 311 and the second part 312 is connected to the weakened part 33 via a thermoplastic weld or a snap-fit ​​structure. By employing a relatively weakened connection method such as a thermoplastic weld or a snap-fit ​​structure, this application makes it easier for the weakened part 33 to fracture, deform, or separate as designed under thermal runaway conditions, thereby guiding the gas release path to open and entering the next stage of pressure relief, thus improving the controllability of the pressure relief function. Specifically, the thermoplastic weld melts when the temperature rises, and the snap-fit ​​structure loosens or detaches when the material softens or deforms under stress. In the event of thermal runaway or a rise in temperature, the thermoplastic weld or snap-fit ​​structure can preferentially disconnect.

[0045] For example, Figure 4The illustration shows an embodiment in which a buckle 333 is provided on the weakened portion 33 and a locking hole 3121 is provided on the second portion 312, with the buckle 333 engaging with the locking hole 3121. Of course, in some embodiments not shown in the accompanying drawings, a locking hole may be provided on the weakened portion 33 and a buckle on the second portion 312. Alternatively, in other embodiments not shown in the accompanying drawings, a buckle is provided on the weakened portion 33, and locking holes are provided on both the first portion 311 and the second portion 312; some buckles engage with the locking holes on the first portion 311, and other buckles engage with the locking holes on the second portion 312.

[0046] Please refer to Figure 2 or Figure 3 or Figure 4 The cover plate 1 has a length direction X and a width direction Y. Two weakening portions 33 are symmetrically arranged on opposite sides of the venting portion 32 in the length direction X. Each weakening portion 33 covers the lower plastic body 31 in the width direction Y. Thus, on the one hand, the symmetrical arrangement of the two weakening portions 33 on opposite sides of the venting portion 32 in the length direction X helps guide gas to diffuse evenly from the venting portion 32 to both sides, optimizing gas flow organization. When the venting portion 32 is blocked, the weakening portions 33 on both sides can respond synergistically or separately, providing a more stable and reliable auxiliary pressure relief capability. On the other hand, the extension or distribution of each weakening portion 33 along the width direction Y and its covering of the lower plastic body 31 expands the spatial range of the weakening effect of the weakening portion 33, thereby more effectively guiding gas release or forming an auxiliary pressure relief path.

[0047] Specifically, in embodiments where the weakening portion 33 includes multiple perforations 331 extending through the lower plastic body 31 along the thickness direction Z, the multiple perforations 331 in each weakening portion 33 are arranged along the width direction Y, and the distance (which can be 0) between the outermost perforation 331 in the width direction Y and the outer edge of the adjacent lower plastic body 31 is smaller than the distance between two adjacent perforations 331. In embodiments where the weakening portion 33 includes a weakening groove 332 recessed in the lower plastic body 31 along the thickness direction Z, the weakening groove 332 extends along the width direction Y and penetrates the two sidewalls of the lower plastic body 31 in the width direction Y.

[0048] In some embodiments of this application, the battery cell provided in this application includes the cover plate assembly described in any of the above-mentioned technical solutions. Since the cover plate assembly in this battery cell has the same technical features as the aforementioned cover plate assembly, the two can solve the same technical problems and achieve the same technical effects, and will not be described again here.

[0049] In the description of this specification, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0050] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of protection of the claims. Furthermore, specific examples have been used in the specification to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the method and core ideas of this application, and the content of this specification should not be construed as a limitation of this application.

Claims

1. A cover plate assembly, characterized in that, The cover plate assembly includes: Cover plate, having thickness direction; A pressure relief structure is provided on the cover plate; The lower plastic includes a lower plastic body, and a venting portion and a weakening portion disposed on the lower plastic body. The lower plastic body and the cover plate are stacked along the thickness direction. The pressure relief structure at least partially covers the venting portion, and the weakening portion is located outside the orthogonal projection area of ​​the pressure relief structure on the lower plastic body.

2. The cover plate assembly according to claim 1, characterized in that, The weakening part has two parts, which are respectively disposed on opposite sides of the venting part, or the weakening part is disposed around the venting part.

3. The cover plate assembly according to claim 2, characterized in that, The weakened portion includes multiple hollow holes that penetrate the lower plastic body along the thickness direction.

4. The cover plate assembly according to claim 3, characterized in that, The diameter of the inscribed circle of the hollow hole is greater than or equal to 0.5 mm and less than or equal to 1 mm; and / or, 5 to 10 hollow holes are distributed per centimeter along the surface of the lower plastic body.

5. The cover plate assembly according to claim 2, characterized in that, The weakening portion includes a weakening groove recessed along the thickness direction in the lower plastic body.

6. The cover plate assembly according to claim 5, characterized in that, The thickness of the lower plastic body in the thickness direction is H, and the depth of the weakening groove in the thickness direction is H1, wherein 0.6×H≤H1≤0.8×H.

7. The cover plate assembly according to claim 2, characterized in that, The lower plastic body includes a separate first part and a second part. The venting part is disposed in the first part. The weakening part connects the first part and the second part. The glass transition temperature of the material of the weakening part is lower than that of the material of the lower plastic body.

8. The cover plate assembly according to claim 7, characterized in that, At least one of the first part and the second part is connected to the weakened part by a hot melt solder joint or a snap-fit ​​structure.

9. The cover plate assembly according to claim 1, 3, 5, or 7, characterized in that, The cover plate has a length direction and a width direction, and there are two weakened portions, which are symmetrically arranged on opposite sides of the venting portion in the length direction. Each weakened portion covers the lower plastic body in the width direction.

10. A single battery cell, characterized in that, include: The cover plate assembly as described in any one of claims 1 to 9.

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