Liquid injection assembly for secondary battery and cover plate assembly of secondary battery

Abstract

The utility model relates to a liquid injection assembly for a secondary battery and a cover plate assembly of the secondary battery. The liquid injection assembly comprises a liquid injection hole, a stress guide part and a flexible part, and the liquid injection hole is a through hole penetrating through the cover plate sheet; the stress guide part is arranged on the cover plate sheet and located on the periphery of the liquid injection hole, and the stress guide part is provided with a containing space; and the flexible part is arranged in the accommodating space. According to the liquid injection assembly, the stress in the cover plate piece can be effectively guided to the stress guiding part in a concentrated mode, and then the stress is conducted to the flexible piece located in the containing space, so that the stress is released or offset through the flexible piece. By adopting the liquid injection assembly, metal fatigue caused by nowhere release of internal stress of the whole cover plate assembly can be prevented, and the service life of the cover plate assembly and the service life of the secondary battery can be prolonged.

Description

Technical Field

[0001] This application relates to the field of secondary batteries, and more specifically to a liquid injection assembly and a cover plate assembly for a secondary battery. Background Technology

[0002] In the manufacturing process of secondary batteries, electrolyte injection is an indispensable step. During injection, electrolyte is typically injected into the secondary battery through the injection port of the cover assembly. Since the finished battery requires complete isolation between the internal and external parts, the design of the injection port and its sealing are key aspects of the cover design. One commonly used design is the steel ball seal. Due to the properties of steel, it is not prone to aging and deformation, thus ensuring both a long service life for the steel ball and a strong seal. However, because steel balls are relatively hard and stronger than the cover plate, the injection port is prone to deformation during the sealing process, creating a circular stress concentration area centered on the injection port. This stress remains concentrated inside the cover assembly and cannot be released, leading to metal fatigue in the cover assembly, affecting its service life, and ultimately impacting the safety and lifespan of the secondary battery. Utility Model Content

[0003] Based on the above-mentioned technical problems, this application proposes a liquid injection assembly that can reduce stress and improve the life of the cover plate and the secondary battery, as well as a cover plate assembly containing the liquid injection assembly.

[0004] The technical solution adopted in this application to solve the above-mentioned technical problems is a liquid injection assembly for a secondary battery. The secondary battery includes a cover plate, characterized in that it includes: a liquid injection hole, a stress guiding part, and a flexible member, wherein the liquid injection hole is a through hole penetrating the cover plate; the stress guiding part is disposed on the cover plate and located around the liquid injection hole, and the stress guiding part has a receiving space; the flexible member is disposed within the receiving space.

[0005] In one embodiment of this application, the stress guiding portion includes a groove located on the upper and / or lower surface of the cover plate, and the flexible member is located within the groove.

[0006] In one embodiment of this application, the injection hole has a hole wall, the stress guiding portion includes a groove located on the hole wall, and the flexible member is located within the groove.

[0007] In one embodiment of this application, a sealing element is further included, the sealing element being interference-fitted with the injection hole, and the flexible element being in contact with the sealing element.

[0008] In one embodiment of this application, the groove is arranged around the injection hole.

[0009] In one embodiment of this application, the stress guiding portion includes a groove located on the upper surface of the cover plate, and also includes a first protrusion, at least a portion of which is located in the groove for retaining the flexible member in the groove.

[0010] In one embodiment of this application, a seal and a third protrusion are further included. The seal is interference-fitted with the injection hole, which has a first end and a second end opposite to each other. The first end is located on the upper surface of the cover plate, and at least a portion of the third protrusion is located in the first end of the injection hole for retaining the seal in the injection hole.

[0011] In one embodiment of this application, the first protrusion and the third protrusion are integrally formed parts.

[0012] In one embodiment of this application, a second protrusion is further included, which is disposed on the lower insulating member of the secondary battery. The lower insulating member is located on one side of the lower surface of the cover plate. The stress guiding portion includes a groove located on the lower surface of the cover plate. At least a portion of the second protrusion is located in the groove for retaining the flexible member in the groove.

[0013] To address the aforementioned technical problems, this application also proposes a cover plate assembly for a secondary battery, comprising: a cover plate sheet, a lower insulating member, and an injection assembly as described above.

[0014] The liquid injection assembly of this application has a stress guiding section around the injection hole. Because this stress guiding section has a receiving space, it can effectively concentrate and guide the stress inside the cover plate to the stress guiding section, and then transmit the stress to the flexible component located within the receiving space, allowing the stress to be released or offset through the flexible component. This arrangement prevents the internal stress of the cover plate assembly from having nowhere to be released, thus preventing metal fatigue and improving the lifespan of both the cover plate assembly and the secondary battery. Attached Figure Description

[0015] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the specific embodiments of this application will be described in detail below with reference to the accompanying drawings, wherein:

[0016] Figure 1 This is an exploded view of the cover plate assembly of a secondary battery according to an embodiment of this application;

[0017] Figure 2 This is a partial structural cross-sectional view of the cover plate assembly, including the liquid injection assembly of Embodiment 1 of this application.

[0018] Figure 3 yes Figure 2 The isometric view of the protective cover shown;

[0019] Figure 4 yes Figure 2 Axonometric view of the flexible component shown;

[0020] Figure 5 This is a partial structural cross-sectional view of the cover plate assembly, including the liquid injection assembly of Embodiment 2 of this application;

[0021] Figure 6 This is a partial structural cross-sectional view of the cover plate assembly, including the liquid injection assembly of Embodiment 3 of this application. 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 will be described in detail below with reference to the accompanying drawings.

[0023] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein, and therefore this application is not limited to the specific embodiments disclosed below.

[0024] As indicated in this application and claims, unless the context clearly indicates otherwise, the words "a," "an," "an," and / or "the" are not specifically singular and may include plural forms. Generally speaking, the terms "comprising" and "including" only indicate the inclusion of explicitly identified steps and elements, which do not constitute an exclusive list, and the method or apparatus may also include other steps or elements.

[0025] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms 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 on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0026] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, these terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application. In addition, although the terminology used in this application is selected from commonly known and used terms, some terms mentioned in this application's specification may have been chosen by the applicant according to his or her judgment, and their detailed meanings are explained in the relevant sections of this description. Moreover, this application should be understood not only through the actual terms used, but also through the meaning implied by each term.

[0027] Hereinafter, embodiments of this application will be described based on the accompanying drawings. However, the embodiments shown below are examples of liquid injection components and cover plate components for secondary batteries used to embody the technical concept of this application, and the liquid injection components and cover plate components for secondary batteries of this application are not specifically defined as follows. Furthermore, in order to facilitate understanding of the scope of the claims, the components shown in the "Claims" and "Utility Model Content" columns are assigned numbers corresponding to the components shown in the embodiments. However, the components shown in the claims are not intended to be specific to the components of the embodiments. In particular, the dimensions, materials, shapes, and relative arrangements of the constituent components described in the embodiments are not intended to limit the scope of this application unless specifically stated otherwise, but are merely illustrative examples.

[0028] However, the dimensions or positional relationships of the components shown in the accompanying drawings are sometimes exaggerated for clarity. Therefore, in the following description, detailed descriptions of the same names and symbols representing the same or homogeneous components are appropriately omitted. Furthermore, the elements constituting this application may be multiple elements composed of the same components, thus allowing one component to function as multiple elements; conversely, multiple components may share the function of one component. Additionally, the content described in some embodiments and implementations can be applied to other embodiments and implementations. Furthermore, in this specification, "upper" is not limited to the case of being formed in contact with an upper surface, but also includes the case of being formed separately on top, and also includes the meaning of an intermediate layer between layers.

[0029] The secondary batteries described in this application include, but are not limited to, nickel-metal hydride batteries, nickel-cadmium batteries, lead-acid (or lead-acid) batteries, lithium-ion batteries, and polymer lithium-ion batteries. The shapes of the secondary batteries include square and round. This application specification uses a square battery as an example for illustration.

[0030] Figure 1 This is an exploded view of the cover plate assembly of a secondary battery according to an embodiment of this application. (Reference) Figure 1As shown, the cover plate assembly includes a cover plate 110 and a lower insulating member 120. The cover plate 110 has an upper surface 111 and a lower surface 112. The lower insulating member 120 is located on one side of the lower surface 112. A positive electrode assembly and a negative electrode assembly can be disposed on the cover plate 110. The positive electrode assembly includes a positive electrode block 131, a positive electrode plastic part 132, and a positive electrode post 133; the negative electrode assembly includes a negative electrode block, a negative electrode plastic part 142, and a negative electrode post 143. Figure 1 In the illustrated embodiment, the negative electrode block includes a first negative electrode block 141a and a second negative electrode block 141b stacked vertically. The lower surface 112 of the cover plate 110 refers to the side of the cover plate 110 facing the interior of the secondary battery when applied in the secondary battery, while the upper surface 111 is the side facing away from the interior of the secondary battery.

[0031] In some embodiments, the positive electrode block 131 and the first negative electrode block 141a are both aluminum blocks, and the second negative electrode block 141b is a copper block.

[0032] like Figure 1 As shown, both the cover plate 110 and the lower insulating member 120 are provided with electrode through holes. The positive electrode 133 and the negative electrode 143 can pass through the corresponding electrode through holes and be electrically connected to the positive electrode block 131 and the second negative electrode block 141b, respectively.

[0033] exist Figure 1 In the illustrated embodiment, the cover plate assembly further includes an upper positive electrode sealing ring 134, a lower positive electrode sealing ring 135, an upper negative electrode sealing ring 144, and a lower negative electrode sealing ring 145, which are used to seal the positive electrode assembly and the negative electrode assembly, respectively. The cover plate 110 may also be provided with an explosion-proof sheet 101 and an explosion-proof sheet protective patch 102.

[0034] It should be noted that Figure 1 The illustration is merely an example and does not limit the specific structure of the cover plate assembly of this application. The cover plate assembly of this application includes at least a cover plate 110 and a lower insulating member 120, as well as a liquid injection assembly to be described later. Other structures and components may be added or reduced depending on the specific embodiment.

[0035] like Figure 1 As shown, the cover plate assembly is also provided with a liquid injection assembly. The liquid injection assembly includes an injection hole 210, a stress guiding part 220, and a flexible member 230.

[0036] Figure 2 This is a partial structural cross-sectional view of the cover plate assembly, including the liquid injection assembly of Embodiment 1 of this application. Figure 2 It can be Figure 1 The sectional view of the cover plate assembly shown may not be the only one. For ease of understanding, this specification uses... Figure 1 and Figure 2 Using the same label to label the same structure name does not imply that they must be exactly the same structure. (See reference) Figure 2 As shown, the injection assembly includes an injection hole 210, a stress guiding part 220, and a flexible member 230. The injection hole 210 is a through hole penetrating the cover plate 110. The stress guiding part 220 is disposed on the cover plate 110 and located around the injection hole 210, and has a receiving space; the flexible member 230 is disposed within the receiving space.

[0037] In Embodiment 1, the stress guiding portion 220 includes a groove located on the upper surface 111 of the cover plate 110. This groove has an accommodating space, corresponding to the accommodating space of the stress guiding portion 220. For the cover plate 110, the thickness of the cover plate 110 corresponding to the groove is reduced due to the groove. Figure 1 and Figure 2 In the illustrated embodiment, the stress guiding portion 220 includes a continuous annular groove surrounding the injection hole 210, meaning there is a certain distance between the groove and the injection hole 210, forming a circular structure between the groove and the injection hole 210. In other embodiments, the groove of the stress guiding portion 220 may not be a continuous annular groove, but rather multiple independent grooves. These independent grooves may be spaced apart along a circumference, for example, equally or unequally spaced. The flexible element may be specifically implemented as an elastic sealing ring made of flexible material, which may be disposed within the annular groove of the stress guiding portion 220.

[0038] The liquid injection assembly of this application has a stress guiding portion 220 provided around the injection hole 210. Because the stress guiding portion 220 has a receiving space, it can effectively concentrate and guide the stress inside the cover plate 110 to the stress guiding portion 220, and then transmit the stress to the flexible member 230 located within the receiving space, allowing the stress to be released or offset through the flexible member 230. This arrangement prevents the internal stress of the cover plate assembly from having nowhere to be released, thereby preventing metal fatigue and the problems mentioned in the background art.

[0039] In some embodiments, such as Figure 2 As shown, the injection assembly also includes a seal 240, which is interference-fitted with the injection port 210. In some embodiments, the seal 240 is a steel ball.

[0040] By providing a seal 240 in the injection hole 210, the injection hole 210 can be sealed after injection is completed. The seal 240 can be mechanically pressed into the injection hole 210. By designing the dimensions of the seal 240 and the diameter of the injection hole 210, an interference fit can be achieved between the two.

[0041] According to the injection assembly of this application, in such a way... Figure 2In the illustrated embodiment, because the cover plate 110 at the location of the stress guiding part 220 is thinned, deformation may occur at the thinned area during the process of pressing the seal 240 into the injection hole 210, causing the seal 240 to lose its sealing function. However, the presence of a flexible element in the receiving space can prevent such deformation from occurring.

[0042] In some embodiments, the flexible element 230 fills the receiving space of the stress guiding portion 220. According to these embodiments, the flexible element 230 can either exactly fill the receiving space or have a larger volume, i.e., partially fill the receiving space, both of which can serve to absorb stress.

[0043] In other embodiments, such as Figure 2 As shown, the flexible component 230 does not fill the entire accommodating space, but only occupies part of the space.

[0044] In some embodiments, the injection assembly further includes a first protrusion 250, at least a portion of which is located in a groove of the stress guide portion 220 for retaining the flexible member 230 in the groove.

[0045] refer to Figure 1 and Figure 2 As shown, in Embodiment 1, the injection assembly further includes a protective cap 260. The first protrusion 250 may be part of the protective cap 260, for example, a structural member protruding outward from the body structure of the protective cap 260. The first protrusion 250 protrudes toward the bottom of the groove of the stress guiding portion 220, which can close the opening of the groove, thereby keeping the flexible member 230 in the receiving space and preventing the flexible member 230 from falling out of the groove.

[0046] like Figure 2 As shown, the first protrusion 250 can be in contact with or in a sealed contact with the flexible member 230. In other embodiments, the first protrusion 250 may not be in contact with the flexible member 230, and there may be a certain gap between the two.

[0047] like Figure 2 As shown, the cross-section of the groove in the stress guiding part 220 is a trapezoidal structure with a smaller opening at the top and a larger opening at the bottom, also known as a dovetail groove structure. That is, the opening of the groove is smaller, and the bottom is larger. Therefore, the cross-sectional sizes of the flexible member 230 and the first protrusion 250 can be adapted to the cross-sectional size of the groove. By providing such a groove, it is beneficial to prevent the first protrusion 250 from falling out of the groove, allowing the protective cover 260 to be firmly mounted on the upper surface 111 of the cover plate 110.

[0048] In some embodiments, the injection hole 210 has a first end 211 and a second end 212 opposite to each other, the first end 211 being located on the upper surface 111 of the cover plate 110, and the second end 212 being located on the lower surface 112 of the cover plate 110. In this embodiment, the first end 211 and / or the second end 212 are tapered openings, and the cross-sectional area of ​​the tapered openings gradually decreases from the upper surface 111 or the lower surface 112 of the cover plate 110 toward the interior of the cover plate 110.

[0049] like Figure 2 As shown, in Embodiment 1, the first end 211 of the injection hole 210 is a tapered opening. According to... Figure 2 As shown, the conical opening is wider at the top and narrower at the bottom, and the diameter of the injection hole 210 remains constant from the bottom of the conical opening to the second end 212. With this configuration, when installing the seal 240, it can be pressed into the injection hole 210 through the conical opening from one side of the upper surface 111 of the cover plate 110, achieving an interference fit between the seal 240 and the injection hole 210.

[0050] In some embodiments, the injection assembly further includes a third protrusion 270, at least a portion of which is located in the tapered opening for retaining the seal 240 in the injection hole 210.

[0051] In Embodiment 1, the third protrusion 270 may also be part of the protective cover 260. The third protrusion 270 is a structural member that protrudes outward from the main body structure of the protective cover 260. The third protrusion 270 protrudes towards the conical opening and the interior of the injection hole 210, which can close the conical opening, thereby keeping the seal 240 in the injection hole 210 and preventing the seal 240 from falling off from the upper surface 111 side.

[0052] like Figure 2 As shown, the third protrusion 270 is in contact with the seal 240. In other embodiments, the third protrusion 270 may not be in contact with the seal 240, but it can still prevent the seal 240 from falling off.

[0053] In Embodiment 1, the first protrusion 250 and the third protrusion 270 are integrally formed, and can also be integrally formed with the protective cover 260. After the liquid injection is completed, by placing the protective cover 260 on the upper surface 111, both the flexible member 230 and the sealing member 240 can be protected simultaneously. Furthermore, since the first protrusion 250 can fix the protective cover 260 to the upper surface 111 of the cover plate 110, the third protrusion 270 will not easily separate from the upper surface 111.

[0054] Figure 3 yes Figure 2 Axonometric view of the protective cover 260 shown. (Reference) Figure 3As shown, the protective cover 260 is circular to match the circular injection hole 210, with a third protrusion 270 at its center and an annular first protrusion 250 in the middle.

[0055] Figure 4 yes Figure 2 The isometric view of the flexible element 230 shown. (Refer to...) Figure 4 As shown, the flexible component 230 is generally a circular sealing ring. The upper part 231 of the flexible component 230 has a relatively small ring width, while the lower part 232 has a relatively large ring width, thus adapting to the accommodating space of the stress guiding part 220, which is smaller at the top and larger at the bottom.

[0056] Figure 5 This is a partial structural cross-sectional view of the cover plate assembly, including the liquid injection assembly of Embodiment 2 of this application. (Reference) Figure 5 As shown, the injection assembly in Embodiment 2 includes an injection hole 210, a stress guiding part 220, and a flexible member 230. The injection hole 210 is a through hole penetrating the cover plate 110. The stress guiding part 220 is disposed on the cover plate 110 and located around the injection hole 210, and has a receiving space; the flexible member 230 is disposed within the receiving space.

[0057] The difference between Embodiment 2 and Embodiment 1 is that the stress guiding part 220 includes a groove located on the lower surface 112 of the cover plate 110, and the flexible member 230 is located in the groove.

[0058] In some embodiments, the liquid injection assembly further includes a second protrusion 280 disposed on the lower insulating member 120 of the secondary battery. The lower insulating member 120 is located on one side of the lower surface 112 of the cover plate 110. At least a portion of the second protrusion 280 is located in a groove of the stress guiding portion 220 located on the lower surface 112 of the cover plate 110, for retaining the flexible member 230 in the groove. According to these embodiments, the second protrusion 280 can be integrally formed with the lower insulating member 120 or can be a separate design.

[0059] Apart from the differences mentioned above, all or part of the description of the stress guiding part 220 and the flexible part 230 in Embodiment 1 can be used to describe Embodiment 2, and will not be repeated here.

[0060] It should be noted that the first protrusion 250, the second protrusion 280, and the third protrusion 270 in this application are all independent structural components. (Reference) Figure 5 In some embodiments, the injection assembly of Embodiment 2 may further include a third protrusion ( Figure 5 (Not shown in the drawing) is used to seal the conical opening of the injection hole 210 to prevent the seal 240 from falling off.

[0061] Figure 6This is a partial structural cross-sectional view of the cover assembly, including the liquid injection assembly of Embodiment 3 of this application. (Reference) Figure 6 As shown, the injection assembly in Embodiment 3 includes an injection hole 210, a stress guiding part 220, and a flexible member 230. The injection hole 210 is a through hole penetrating the cover plate 110. The stress guiding part 220 is disposed on the cover plate 110 and located around the injection hole 210, and has a receiving space; the flexible member 230 is disposed within the receiving space.

[0062] The difference between Embodiment 3 and Embodiments 1 and 2 is that the stress guiding part 220 is disposed at the hole wall 213 of the injection hole 210. In Embodiment 3, the injection hole 210 has a hole wall 213, and the stress guiding part...

[0063] 220 includes a groove located on the hole wall 213, and a flexible member 230 is located within the groove. The groove is arranged around the periphery of the injection hole 210. In Embodiment 3, the receiving space of the stress guiding part 220 is in communication with the injection hole 210.

[0064] Apart from the differences mentioned above, all or part of the descriptions of the stress guiding part 220 and the flexible part 230 in Embodiments 1 and 2 can be used to describe Embodiment 3, and will not be repeated here.

[0065] In Embodiment 3, the flexible element 230 is in contact with the sealing element 240.

[0066] In some embodiments, the seal 240 is a steel ball. In order to make the flexible member 230 contact the seal 240, a groove as a stress guiding part 220 can be provided at the contact position between the steel ball and the hole wall 213. This allows the flexible member 230 provided in the groove to contact the steel ball, thereby guiding stress and strengthening the sealing effect of the seal 240.

[0067] In Embodiment 3, the flexible member 230 can fill the stress guiding portion 220 and has a portion extending out of the stress guiding portion 220, so that the flexible member 230 is in close contact with the sealing member 240.

[0068] refer to Figure 6 In some embodiments, the injection assembly of Embodiment 3 may further include a third protrusion ( Figure 6 (Not shown in the drawing) is used to seal the conical opening of the injection hole 210 to prevent the seal 240 from falling off.

[0069] It should be noted that in embodiments not shown in the figures, grooves serving as stress guiding portions 220 are provided on both the upper surface 111 and the lower surface 112 of the cover plate 110. That is, all or part of the above embodiments one, two, and three can be combined, and the resulting liquid injection assemblies are all within the scope of protection of this application.

[0070] According to the liquid injection assembly of this application, by providing the stress guiding part 220, the stress of the cover plate assembly is concentrated at the stress guiding part 220, and the transmitted stress is absorbed by the flexible member 230, thereby improving the fatigue resistance of other parts of the cover plate assembly and increasing the life of the secondary battery. The stress guiding part 220 and the flexible member 230 also overcome the large deformation caused by the hard contact between the two metals of the liquid injection hole 210 and the sealing member 240 (which is a steel ball), improving the sealing performance of the liquid injection hole 210 and further increasing the life of the secondary battery.

[0071] While the foregoing disclosure has discussed various embodiments that are currently considered useful, it should be understood that such details are for illustrative purposes only, and the appended claims are not limited to the disclosed embodiments. Rather, the claims are intended to cover all modifications and equivalent combinations that conform to the spirit and scope of the embodiments of this application. For example, although the system components described above can be implemented by hardware devices, they can also be implemented solely by software solutions, such as installing the described system on existing servers or mobile devices.

[0072] Similarly, it should be noted that, in order to simplify the description of the present application and thus aid in the understanding of one or more embodiments, the foregoing description of the embodiments of the present application sometimes combines multiple features into a single embodiment, drawing, or description thereof. However, this disclosure method does not imply that the subject matter of the present application requires more features than those mentioned in the claims. In fact, the embodiments contain fewer features than all the features of the single embodiments disclosed above.

[0073] In some embodiments, numbers describing the quantity of components and attributes are used. It should be understood that such numbers used in the description of embodiments are modified in some examples with the terms "approximately," "approximately," or "generally." Unless otherwise stated, "approximately," "approximately," or "generally" indicates that the numbers are allowed to vary by ±20%. Accordingly, in some embodiments, the numerical parameters used in the specification and claims are approximate values, which may be changed depending on the characteristics required by individual embodiments. In some embodiments, numerical parameters should take into account specified significant digits and employ a general method of digit reservation. Although the numerical ranges and parameters used to confirm their breadth of scope in some embodiments of this application are approximate values, in specific embodiments, such values ​​are set as precisely as feasible.

Claims

1. A liquid injection assembly for a secondary battery, the secondary battery including a cover sheet, characterized by, The injection port assembly includes: an injection port, a stress guide, and a flexible member, wherein the injection port is a through-hole passing through the cover sheet; the stress guide is provided on the cover sheet and located at the periphery of the injection port, the stress guide having an accommodation space; the flexible member is provided in the accommodation space.

2. The liquid injection assembly of claim 1, wherein, The stress guide includes a groove on the upper surface and / or the lower surface of the cover sheet, and the flexible member is located in the groove.

3. The liquid injection assembly of claim 1, wherein, The injection port has a hole wall, the stress guide includes a groove on the hole wall, and the flexible member is located in the groove.

4. The liquid injection assembly of claim 3, wherein, Further comprising a sealing member, the sealing member is in interference fit with the injection port, and the flexible member is in contact with the sealing member.

5. The liquid injection assembly of claim 2 or 3, wherein, The groove is annularly arranged at the periphery of the injection port.

6. The liquid injection assembly of claim 2, wherein, The stress guide includes a groove on the upper surface of the cover sheet, and further includes a first protruding member, at least a part of the first protruding member is located in the groove, for retaining the flexible member in the groove.

7. The liquid injection assembly of claim 6, wherein, Further comprising a sealing member and a third protruding member, the sealing member is in interference fit with the injection port, the injection port has opposite first and second ends, the first end is located on the upper surface of the cover sheet, and at least a part of the third protruding member is located in the first end of the injection port, for retaining the sealing member in the injection port.

8. The liquid injection assembly of claim 7, wherein, The first protruding member and the third protruding member are integrally formed.

9. The liquid injection assembly of claim 2, wherein, Further comprising a second protruding member, the second protruding member is provided on the lower insulating member of the secondary battery, the lower insulating member is located on the lower surface side of the cover sheet, the stress guide includes a groove on the lower surface of the cover sheet, and at least a part of the second protruding member is located in the groove, for retaining the flexible member in the groove.

10. A cover plate assembly for a secondary battery, characterized by The injection port assembly includes: a cover sheet, a lower insulating member, and the injection port assembly according to any one of claims 1 to 9.

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