Double-layer explosion-proof valve cover plate structure

Abstract

This invention provides a double-layer explosion-proof valve cover structure, belonging to the field of lithium battery technology. It includes a light aluminum sheet with a mounting hole at its center. A downwardly extending protrusion is formed around the bottom of the aluminum sheet around the mounting hole. A top explosion-proof valve is disposed at the bottom of the aluminum sheet, facing the mounting hole, and a bottom explosion-proof valve is disposed at the bottom of the protrusion, facing the mounting hole. The opening pressure threshold of the top explosion-proof valve is greater than that of the bottom explosion-proof valve. The bottom explosion-proof valve is used to withstand the reciprocating stress generated by internal air pressure fluctuations during normal use of the battery cell, thus isolating the impact of air pressure fluctuations on the top explosion-proof valve. The top explosion-proof valve is used to open and release air when the internal air pressure of the battery cell rises to a set threshold. This invention solves the technical problem of existing single-layer explosion-proof valves experiencing mechanical fatigue due to long-term cyclic use, leading to explosion threshold drift or premature valve opening.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, and in particular to a double-layer explosion-proof valve cover structure. Background Technology

[0002] With the rapid development of the new energy industry, the demand for lithium battery cells both domestically and internationally continues to expand, and cell production is also constantly increasing. Given this massive shipment volume, the safety control of battery cells is particularly important. Square lithium batteries are currently one of the mainstream battery types on the market. Their top cover structure is typically equipped with an explosion-proof valve, which is used to release pressure when the internal pressure of the cell abnormally increases, thus preventing serious safety accidents such as cell explosions.

[0003] Currently, most square batteries on the market use a single-layer explosion-proof valve structure, meaning that only one explosion-proof valve is installed on the top cover of the battery. When the internal gas pressure of the cell rises to a preset threshold, this single-layer explosion-proof valve opens to release gas and relieve pressure. However, during long-term cyclic use of the battery cell, the single-layer explosion-proof valve structure has significant technical defects.

[0004] Specifically, during the cyclic charging and discharging of the battery cell, gas is generated and consumed inside the cell, causing periodic changes in internal gas pressure. As a vulnerable structure directly subjected to this internal pressure, the explosion-proof valve is repeatedly subjected to these pressure changes, resulting in two adverse phenomena: First, the explosion-proof valve experiences a "breathing effect," where it repeatedly bulges and dents under pressure fluctuations. Second, the explosion-proof valve is subjected to a continuous, unidirectional pressure. Both phenomena cause mechanical fatigue in the explosion-proof valve material, leading to fluctuations in its actual burst threshold and even causing it to open prematurely before the designed threshold, severely impacting the safety and reliability of the battery cell during use.

[0005] Therefore, there is an urgent need for a technical solution that can effectively prevent explosion-proof valves from mechanical fatigue caused by long-term cyclic use, thereby improving the safety and reliability of the battery cell throughout its entire life cycle. Summary of the Invention

[0006] This invention provides a double-layer explosion-proof valve cover structure, aiming to solve the technical problem of existing single-layer explosion-proof valves experiencing burst threshold drift or premature valve opening due to mechanical fatigue during long-term cyclic use of battery cells. The technical solution is as follows: This invention provides a double-layer explosion-proof valve cover structure, comprising: a light aluminum sheet, A mounting hole is provided at the center of the aluminum sheet, and a downwardly extending protrusion is formed around the bottom of the aluminum sheet around the outer periphery of the mounting hole. The bottom of the aluminum sheet is provided with a top explosion-proof valve facing the mounting hole, and the bottom of the protrusion is provided with a bottom explosion-proof valve facing the mounting hole. The opening pressure threshold of the top explosion-proof valve is greater than that of the bottom explosion-proof valve. The opening pressure threshold of the bottom explosion-proof valve is greater than the reciprocating stress caused by the internal air pressure fluctuations during normal battery use. It is used to withstand the reciprocating stress caused by internal air pressure fluctuations during normal use of the battery cell, so as to isolate the influence of air pressure fluctuations on the top explosion-proof valve. The top explosion-proof valve is used to open for venting when the internal air pressure of the battery cell rises to a set threshold.

[0007] Optionally, the lower limit of the opening pressure of the top explosion-proof valve is a, and the lower limit of the opening pressure of the bottom explosion-proof valve is b, satisfying a > b.

[0008] Optionally, the upper limit of the opening pressure of the bottom explosion-proof valve is d, which satisfies a > d > b.

[0009] Optionally, the design preset pressure value of the bottom explosion-proof valve is c, which corresponds to the upper limit of the internal pressure of the battery cell at the preset end of its lifespan, satisfying b > c.

[0010] Optionally, the mounting hole has an elliptical shape.

[0011] Optionally, the protrusion has an annular structure and is disposed around the periphery of the mounting hole.

[0012] Optionally, the top of the aluminum sheet is provided with an explosion-proof valve patch covering the mounting hole, the explosion-proof valve patch being used to protect the top explosion-proof valve from external mechanical damage.

[0013] Optionally, the top explosion-proof valve is located in the inner space of the protrusion.

[0014] Optionally, a lower plastic layer is provided at the bottom of the aluminum sheet, and the lower plastic layer covers the bottom surface of the aluminum sheet.

[0015] Optionally, the bottom of the lower plastic sheet is provided with a negative electrode assembly and a positive electrode assembly that penetrate the lower plastic sheet and the aluminum sheet.

[0016] The beneficial effects of the technical solutions provided in the embodiments of the present invention include at least the following: By setting a double-layer structure of top and bottom explosion-proof valves on the aluminum sheet, the bottom explosion-proof valve can withstand the reciprocating stress generated by internal air pressure fluctuations during the normal circulation of the battery cell. This effectively distributes the mechanical fatigue load that was originally applied to the top explosion-proof valve, thereby avoiding the problem of the top explosion-proof valve drifting or opening prematurely due to long-term breathing effect or continuous high pressure.

[0017] By rationally setting the opening pressure relationship between the top and bottom explosion-proof valves, it is ensured that in the event of abnormal conditions such as thermal runaway in the battery cell, the internal pressure can sequentially break through the bottom and top explosion-proof valves, achieving effective venting and pressure relief, ensuring the safety of the battery cell, and significantly improving the safety and reliability of the battery cell throughout its entire life cycle. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a three-dimensional exploded view of the overall structure provided in the embodiment of the present invention; Figure 2 This is a schematic diagram of the overall structure provided in an embodiment of the present invention; Figure 3 This is a cross-sectional view of the aluminum sheet provided in an embodiment of the present invention; Figure 4 This is provided by the embodiments of the present invention. Figure 3 Enlarged view of a portion of point A in the middle.

[0020] In the diagram: 1-Negative electrode assembly; 2-Explosion-proof valve patch; 3-Positive electrode assembly; 4-Top explosion-proof valve; 5-Bright aluminum sheet; 6-Bottom explosion-proof valve; 7-Lower plastic; 8-Protrusion. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be described in further detail below with reference to the accompanying drawings.

[0022] Figure 1 This is a three-dimensional exploded view of the overall structure provided in the embodiment of the present invention; Figure 2 This is a schematic diagram of the overall structure provided in an embodiment of the present invention; Figure 3 This is a cross-sectional view of the aluminum sheet provided in an embodiment of the present invention; Figure 4 This is provided by the embodiments of the present invention. Figure 3 A magnified view of a portion of point A in the middle. (See image below.) Figures 1 to 4 As shown, this embodiment of the invention provides a double-layer explosion-proof valve cover structure, which aims to solve the technical problem that existing single-layer explosion-proof valves suffer from mechanical fatigue due to long-term cyclic use, resulting in explosion threshold drift or premature valve opening.

[0023] The double-layer explosion-proof valve cover structure includes an aluminum sheet 5, a top explosion-proof valve 4, a bottom explosion-proof valve 6, an explosion-proof valve patch 2, and a lower plastic sheet 7.

[0024] The aluminum sheet 5, serving as the main load-bearing component of the cover structure, is made of aluminum material through a stamping process. A mounting hole, which is elliptical in this embodiment, is provided at the center of the aluminum sheet 5 to facilitate gas exhaust. A downwardly extending protrusion 8 is formed around the outer periphery of the mounting hole at the bottom of the aluminum sheet 5. The protrusion 8 has a ring-shaped structure and is integrally formed with the aluminum sheet 5 through a stamping process. The protrusion 8 creates a stepped structure with a height difference at the bottom of the aluminum sheet 5, providing installation space for the layered arrangement of the top explosion-proof valve 4 and the bottom explosion-proof valve 6.

[0025] The top explosion-proof valve 4 is located at the bottom of the aluminum sheet 5, directly opposite the mounting hole. The top explosion-proof valve 4 is situated within the inner space of the protrusion 8 and is fixedly connected to the aluminum sheet 5 via laser welding. The top explosion-proof valve 4 is the main safety pressure relief component in the cover plate structure. Its opening pressure threshold is set to a relatively high value, used to open and release pressure when the internal pressure rises sharply to the set threshold due to abnormal conditions such as thermal runaway of the battery cell. The top explosion-proof valve 4 is manufactured using a stamping process, and its groove depth and shape are precisely designed to ensure reliable opening under the preset pressure.

[0026] The bottom explosion-proof valve 6 is located at the bottom of the protrusion 8, directly opposite the mounting hole, and is fixedly connected to the protrusion 8 by laser welding. The bottom explosion-proof valve 6 is also manufactured using a stamping process. The opening pressure threshold of the bottom explosion-proof valve 6 is lower than that of the top explosion-proof valve 4, and the opening pressure threshold of the bottom explosion-proof valve 6 is greater than the reciprocating stress caused by the internal air pressure fluctuations during normal battery use. It is used to withstand the reciprocating stress generated by internal air pressure fluctuations during normal use of the battery cell, so as to isolate the influence of air pressure fluctuations on the top explosion-proof valve. Its main function is: during the normal charge and discharge cycle of the battery cell, gas will be continuously generated inside the battery cell, and the internal air pressure will fluctuate periodically. The bottom explosion-proof valve 6 withstands the reciprocating stress generated by these air pressure fluctuations and responds to air pressure changes through its own micro-deformation, thereby isolating the influence of air pressure fluctuations at the bottom explosion-proof valve 6 level. This effectively distributes the mechanical fatigue load that originally acted on the top explosion-proof valve 4, and prevents the top explosion-proof valve 4 from drifting due to long-term fatigue.

[0027] The lower limit of the opening pressure of the top explosion-proof valve 4 is a, the lower limit of the opening pressure of the bottom explosion-proof valve 6 is b, and a>b is satisfied. The upper limit of the opening pressure of the bottom explosion-proof valve 6 is d, and a>d>b is satisfied. The design preset pressure value of the bottom explosion-proof valve 6 is c, which corresponds to the upper limit of the internal pressure of the battery cell at the preset end of its lifespan, and b>c is satisfied.

[0028] Specifically, the lower limit of the opening pressure of the top explosion-proof valve 4 is 'a', the lower limit of the opening pressure of the bottom explosion-proof valve 6 is 'b', the upper limit of the opening pressure of the bottom explosion-proof valve 6 is 'd', and the upper limit of the internal gas generation pressure at the end of the cell's lifespan is 'c'. Each pressure parameter must satisfy the following relationship: a > d > b > c. It should be further noted that in this embodiment, the lower limit of the opening pressure 'a' of the top explosion-proof valve 4 is 0.7 MPa, the lower limit of the opening pressure 'b' of the bottom explosion-proof valve 6 is 0.4 MPa, the upper limit of the internal gas generation pressure at the end of the cell's lifespan is 0.2 MPa, and the upper limit of the opening pressure 'd' of the bottom explosion-proof valve 6 is 0.6 MPa.

[0029] The design principle of this pressure relationship is as follows: b>c ensures that during the normal use of the battery cell throughout its entire life cycle, the bottom explosion-proof valve 6 will not be broken by the normal gas circulation. The bottom explosion-proof valve 6 will only breathe within its elastic deformation range to maintain structural integrity. a>d ensures that the top explosion-proof valve 4 will not be triggered to open within the entire working pressure range of the bottom explosion-proof valve 6. The top explosion-proof valve 4 will only open when the battery cell experiences an abnormal situation (such as thermal runaway) that causes a sharp increase in internal pressure.

[0030] When thermal runaway occurs in the battery cell, the internal pressure continues to rise, first exceeding the opening pressure threshold of the bottom explosion-proof valve 6, and then breaking through the bottom explosion-proof valve 6; subsequently, the internal pressure continues to rise, exceeding the opening pressure threshold of the top explosion-proof valve 4, and breaking through the top explosion-proof valve 4. The gas is discharged through the mounting hole, achieving effective pressure relief protection.

[0031] An explosion-proof valve patch 2 is positioned on top of the aluminum sheet 5, covering the mounting hole. The explosion-proof valve patch 2 is fixedly connected to the upper surface of the aluminum sheet 5 by adhesive bonding, protecting the top explosion-proof valve 4 from external mechanical damage such as impacts and scratches during battery transport, assembly, and handling. The material and adhesive strength of the explosion-proof valve patch 2 are designed to ensure that it firmly covers the mounting hole under normal operating conditions, while not obstructing the normal discharge of gas when the top explosion-proof valve 4 is open.

[0032] The lower plastic 7 is disposed at the bottom of the aluminum sheet 5, covering the bottom surface of the aluminum sheet 5. The lower plastic 7 serves as insulation and protection, isolating the aluminum sheet 5 from the electrode assembly inside the battery cell. The lower plastic 7 is provided with through holes for the negative electrode assembly 1 and the positive electrode assembly 3 to pass through. The negative electrode assembly 1 and the positive electrode assembly 3 pass through the lower plastic 7 and the aluminum sheet 5 respectively, realizing the electrical connection between the internal electrodes of the battery cell and the external terminals.

[0033] The negative electrode post assembly 1 includes a negative electrode post body, an upper plastic, a sealing ring, and a riveting block. The upper plastic and the riveting block are stacked sequentially on top of the aluminum sheet 5 at the position corresponding to the negative electrode post body. The negative electrode post body passes through the aluminum sheet 5, the upper plastic, and the riveting block sequentially from bottom to top. The negative electrode post body is fixed to the riveting block. The sealing ring is fitted around the outer periphery of the negative electrode post body and is squeezed by the upper plastic and the negative electrode post body.

[0034] The positive electrode post assembly 3 includes a positive electrode post body, an upper plastic, a sealing ring, and a riveting block. The upper plastic and the riveting block are stacked sequentially on top of the aluminum sheet 5 at the position corresponding to the positive electrode post body. The positive electrode post body passes through the aluminum sheet 5, the upper plastic, and the riveting block sequentially from bottom to top. The positive electrode post body is fixed to the riveting block. The sealing ring is fitted around the outer periphery of the positive electrode post body and is squeezed by the upper plastic and the negative electrode post body.

[0035] In general, the positive terminal assembly 1 and the negative terminal assembly 2 have the same structure; the difference between them lies in their different locations.

[0036] The shape of the explosion-proof valve patch 2 is the same as that of the mounting hole, and it is slightly larger than the mounting hole as a whole, so as to ensure that the explosion-proof valve patch 2 can cover the mounting hole when it is attached to the aluminum sheet 5. In this embodiment, the mounting hole is elliptical and the explosion-proof valve patch 2 is an elliptical thin sheet.

[0037] The top explosion-proof valve 4 and the bottom explosion-proof valve 6 have the same shape as the mounting hole. The top explosion-proof valve 4 is slightly larger than the mounting hole, and the bottom explosion-proof valve 6 is slightly larger than the top explosion-proof valve 4. Both the top explosion-proof valve 4 and the bottom explosion-proof valve are elliptical. This ensures that the bottom explosion-proof valve 6, together with the protrusion 8, covers the top explosion-proof valve 4, and the top explosion-proof valve 4 covers the mounting hole.

[0038] The aluminum sheet 5 is a rectangular sheet structure with rounded corners at all four corners. Specifically, the aluminum sheet is an aluminum or aluminum alloy sheet used for battery cover plates. More specifically, at the finished part level, it can be called a cover plate. The aluminum sheet 5 has liquid injection holes.

[0039] The shape of the lower plastic 7 is basically the same as that of the light aluminum sheet 5. The lower plastic 7 is a rectangular sheet structure with rounded corners at the four corners. The bottom of the lower plastic has downward protrusions in the middle and on both the left and right sides. Auxiliary holes are opened on the lower plastic 7 corresponding to the injection hole.

[0040] The protrusion 8 is located at the bottom of the aluminum sheet 5. Its overall shape is the same as the mounting hole. The protrusion 8 is located outside the mounting hole. The protrusion 8 is elliptical in shape. Alternatively, the protrusion 8 can be other shapes as long as it can completely cover the top explosion-proof valve 4 with the bottom explosion-proof valve 6.

[0041] It should be noted that the shape of the explosion-proof valve in the embodiments of the present invention is not limited to the shape shown in the above embodiments. Explosion-proof valves with elliptical, circular, rectangular or other geometric shapes, as long as they adopt the above-mentioned double-layer explosion-proof valve structural design and functional division, are all within the protection scope of the present invention.

[0042] The double-layer explosion-proof valve cover structure provided in this embodiment of the invention, through the coordinated design of the top explosion-proof valve and the bottom explosion-proof valve, enables the bottom explosion-proof valve to assume the breathing function during the normal cycle of the battery cell, effectively isolating the influence of air pressure fluctuations on the top explosion-proof valve, avoiding mechanical fatigue of the top explosion-proof valve, and significantly improving the safety and reliability of the battery cell throughout its entire life cycle.

[0043] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms “an” or “a” and similar terms do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms “comprising” or “including” and similar terms mean that the elements or objects preceding “comprising” or “including” encompass the elements or objects listed following “comprising” or “including” and their equivalents, and do not exclude other elements or objects. The terms “connected” or “linked” and similar terms are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0044] The above description is merely an optional embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A double-layer explosion-proof valve cover structure, characterized in that, include: Light aluminum sheet (5) The light aluminum sheet (5) has a mounting hole at its center, and the bottom of the light aluminum sheet (5) has a downwardly extending protrusion (8) around the outer periphery of the mounting hole. The bottom of the aluminum sheet (5) is provided with a top explosion-proof valve (4) facing the mounting hole, and the bottom of the protrusion (8) is provided with a bottom explosion-proof valve (6) facing the mounting hole. The opening pressure threshold of the top explosion-proof valve (4) is greater than the opening pressure threshold of the bottom explosion-proof valve (6). The opening pressure threshold of the bottom explosion-proof valve (6) is greater than the reciprocating stress caused by the internal air pressure fluctuation during normal use of the battery. It is used to withstand the reciprocating stress caused by the internal air pressure fluctuation during normal use of the battery cell, so as to isolate the influence of air pressure fluctuation on the top explosion-proof valve (4). The top explosion-proof valve (4) is used to open for venting when the internal air pressure of the battery cell rises to a set threshold.

2. The double-layer explosion-proof valve cover structure according to claim 1, characterized in that, The lower limit of the opening pressure of the top explosion-proof valve (4) is a, and the lower limit of the opening pressure of the bottom explosion-proof valve (6) is b, satisfying a > b.

3. The double-layer explosion-proof valve cover structure according to claim 2, characterized in that, The upper limit of the opening pressure of the bottom explosion-proof valve (6) is d, which satisfies a>d>b.

4. The double-layer explosion-proof valve cover structure according to claim 3, characterized in that, The design preset pressure value of the bottom explosion-proof valve (6) is c. The design preset pressure value c corresponds to the upper limit of the internal pressure of the battery cell at the preset end of its life, satisfying b>c.

5. The double-layer explosion-proof valve cover structure according to claim 1, characterized in that, The mounting hole has an elliptical shape.

6. The double-layer explosion-proof valve cover structure according to claim 5, characterized in that, The protrusion (8) has a ring-shaped structure and is arranged around the periphery of the mounting hole.

7. The double-layer explosion-proof valve cover structure according to claim 1, characterized in that, The top of the aluminum sheet (5) is provided with an explosion-proof valve patch (2) covering the mounting hole. The explosion-proof valve patch (2) is used to protect the top explosion-proof valve (4) from external mechanical damage.

8. The double-layer explosion-proof valve cover structure according to claim 1, characterized in that, The top explosion-proof valve (4) is located in the inner space of the protrusion (8).

9. The double-layer explosion-proof valve cover structure according to claim 1, characterized in that, The bottom of the light aluminum sheet (5) is provided with a lower plastic (7), which covers the bottom surface of the light aluminum sheet (5).

10. A double-layer explosion-proof valve cover structure according to claim 9, characterized in that, The bottom of the lower plastic (7) is provided with a negative electrode assembly (1) and a positive electrode assembly (3) that penetrate the lower plastic (7) and the light aluminum sheet (5).

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