Secondary battery

Abstract

Secondary battery (10) comprising a housing, a bare cell and an upper cover assembly (300), characterized in that: the housing (100) has an opening (110) at one end and; the bare cell (200) is arranged in the housing (100); The upper cover assembly (300) comprises an end cover (310) and a lower plastic element (320) arranged on the end cover (310), the end cover (310) being sealed to the opening (110), the end cover (310) being provided with an explosion-proof valve, a side of the lower plastic element (320) facing away from the end cover (310) being opposite the bare cell (200), the lower plastic element (320) being provided with a gas vent opening (321) connected to the explosion-proof valve, the lower plastic element (320) being provided with a receiving recess (322) arranged on a side of it opposite the end cover (310), the receiving recess (322) being provided with a return opening (323) in a base thereof,and a first area of ​​an orthographic projection of the gas vent opening (321) and the return opening (323) in the end cover (310) occupies 2% to 10% of an area of ​​the end cover (310), and the area of ​​the end cover (310) is in the range of 4200 mm, 2 up to 75000 mm 2 lies.

Description

TECHNICAL AREA

[0001] This application relates to the field of energy storage technology, in particular to a secondary battery. BACKGROUND

[0002] Lithium batteries have advantages such as small size, high energy density, long service life and environmental friendliness, and are used in many industries, such as the automotive industry, electronic products and energy storage systems.

[0003] During the use of lithium batteries, situations such as overcharging, over-discharging, short circuits, or harsh environments currently cause the generation of a large amount of gas inside the lithium battery and also lead to a significant increase in the battery's temperature, thereby increasing the internal pressure, which poses certain dangers to users. Furthermore, shaking the lithium battery causes electrolyte to splash onto a surface of a lower plastic element opposite an end cover, creating electrolyte that accumulates on the surface of the lower plastic element or in grooves, resulting in electrolyte waste. SUMMARY

[0004] A secondary battery is provided, the secondary battery comprising a housing, a bare cell and a top cover assembly, wherein: the case has an opening at one end, and the bare cell is arranged in the casing; The upper cover assembly comprises an end cover and a lower plastic element arranged on the end cover. The end cover is sealed to the opening and is provided with an explosion-proof valve. One side of the lower plastic element facing away from the end cover is opposite the bare cell. The lower plastic element is provided with a gas vent opening connected to the explosion-proof valve. The lower plastic element is provided with a receiving recess located on one side opposite the end cover. The receiving recess has a return opening in its base. A first surface of an orthographic projection of the gas vent opening and the return opening on the end cover occupies 2% to 10% of the area of ​​the end cover. The area of ​​the end cover is in the range of 4200 mm². 2 up to 75000 mm2 lies.

[0005] In one embodiment, the lower plastic element is provided with several gas vent openings, wherein the several gas vent openings are arranged at intervals and a second surface of an orthographic projection of all gas vent openings on the end cover occupies 1% to 5% of the surface of the end cover and the second surface is in the range of 42 mm 2 up to 3750 mm 2 lies.

[0006] In one embodiment, the receiving recess is provided with several return openings, the several return openings are divided into two groups, the two groups of return openings are each arranged at two ends of the lower plastic element, and a third area of ​​an orthographic projection of all return openings on the end cover occupies 0.5% to 3% of the area of ​​the end cover, and the third area extends from 21 mm 2 up to 2250 mm 2 .

[0007] In one embodiment, the secondary battery further comprises a connecting piece, wherein the lower plastic element comprises a main body and projecting buttons arranged at two ends of the main body, wherein:

[0008] the main body is connected to the end cover, a side of the projecting knob facing away from the main body is opposite the blank cell, a side of the main body facing away from the end cover has a fixed height relative to the side of the projecting knob facing away from the main body;

[0009] the connecting piece is arranged on the main body and spaced apart from the protruding knob, the connecting piece is connected to the bare cell with a curved tab, and the set height is a sum of a thickness of the connecting piece and a reserved height of the curved tab.

[0010] In one embodiment, the set height ranges from 1.76 mm to 5.82 mm.

[0011] In one embodiment, the curved tab comprises several sequentially connected single electrode plates, wherein the reserved height is a product of the thickness of a single electrode plate, the number of single electrode plates and a specified coefficient, and the specified coefficient is in the range of 3 to 6.

[0012] In one embodiment, the thickness of the connecting piece is between 0.5 mm and 1.5 mm.

[0013] In one embodiment, a fourth area, enclosed by an orthographic projection of an outer contour of the lower plastic element onto the end cover, occupies 85% to 95% of the area of ​​the end cover, and the fourth area extends from 3570 mm 2 up to 71250 mm 2 .

[0014] In one embodiment, the distance between an edge of the lower plastic element and an edge of the end cover along the longitudinal direction of the lower plastic element is a first distance value, and the first distance value is in the range of 1 mm to 1.5 mm.

[0015] A distance between an edge of the lower plastic element and an edge of the end cover along a width direction of the lower plastic element is a second distance value, and the second distance value is in the range of 1 mm to 5 mm.

[0016] In one embodiment, a first corner of the lower plastic element is a rounded shape, a second corner of the end cover is a chamfer, a straight-line distance between a center point of the first corner and a center point of the second corner is a third distance, and the third distance is greater than the first distance and the second distance.

[0017] In the secondary battery, by providing the gas vent opening in the lower plastic element connected to the explosion-proof valve, the gas flows through the gas vent hole to the explosion-proof valve for pressure relief when the internal pressure of the secondary battery increases, thus preventing an explosion of the secondary battery;Furthermore, the electrolyte flows through the provision of the receiving recess, which is located on the side of the lower plastic element opposite the end cover and is designed for the temporary receipt of electrolyte, and through the provision of the return orifice at the bottom of the receiving recess when the secondary battery is shaken, causing electrolyte to splash onto the surface of the lower plastic element opposite the end cover, into the receiving recess, and then flow through the return orifice at the bottom of the receiving recess to the bare cell, thus preventing electrolyte waste; and by setting the first surface of the orthographic projection of the gas vent and the return orifice on the end cover to 2% to 10% of the area of ​​the end cover in the range of 4200 mm; 2 up to 75000 mm 2A reduction in the weight of the lower plastic element is achieved without affecting the strength of the lower plastic element. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic exploded view of a secondary battery as provided for in this application. Fig. Figure 2 is a schematic structural view of a lower plastic element provided for in this application. Fig. Figure 3 is a structural cross-sectional view of the lower plastic element in Fig. 2. Fig. Figure 4 is a structural top view of the lower plastic element in Fig. 2. Fig. Figure 5 is a schematic structural contour view of the lower plastic element and an end cover as provided for in this application.

[0018] 10, secondary battery; 100, casing; 110, opening; 120, receiving cavity; 200, bare cell; 300, upper cover assembly; 310, end cover; 320, lower plastic element; 321, gas vent opening; 322, receiving recess; 323, return opening; 324, main body; 325, protruding knob; 400, curved tab. DETAILED DESCRIPTION

[0019] To clarify and make the aforementioned objectives, elements, and advantages of this application more readily understandable, the specific embodiments of this application are described in detail below with reference to the accompanying drawings. Numerous specific details are set forth in the following description to facilitate a comprehensive understanding of this application. However, this application can be implemented in many other ways that differ from those described herein, and those skilled in the art can make similar improvements without departing from the spirit of this application. Therefore, this application is not limited by the specific embodiments disclosed below.

[0020] When terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "top", "bottom", "front", "back", "left", "right", "vertical", "horizontal", "above", "below", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are used in the description of this application, these terms serve only for the purpose of simplified description. These terms denote orientations or positional relationships based on those shown in the drawings, serve only to simplify the description of this application, and do not imply that the device or element in question must have a specific orientation or be designed and operated in a specific orientation, and therefore cannot be construed as a limitation of this application.

[0021] When terms such as "first" or "second" appear, these terms are used for descriptive purposes only and cannot be understood as indicating a relative significance or as an implicit indication of the number of technical elements specified. Thus, elements defined as "first" or "second" may explicitly or implicitly include at least one of the elements. When the term "several" appears in the description of this application, it means at least two, e.g., two, three, etc., unless expressly defined otherwise.

[0022] When terms such as "install", "connect", "attach", "fasten", etc., appear in this application, they are to be understood in the broadest sense unless expressly stated and defined otherwise. For example, they may refer to a permanent connection, a detachable connection, or an integral connection; they may refer to a mechanical connection, an electrical connection, a direct connection, an indirect connection through an intermediate medium, an internal connection between two elements, or an interaction relationship between two elements, unless specifically defined otherwise. Those skilled in the field will be able to understand the specific meanings of the aforementioned terms in this application depending on the specific situations.

[0023] When descriptions such as "a first element is located on" or "under" a second element appear in this application, this may mean that the first and second elements are in direct contact or that they are in indirect contact through an intermediary, unless expressly specified and defined otherwise. The first element being "on," "above," or "over" the second element may also mean that the first element is located directly above or diagonally above the second element, or it may simply mean that the horizontal height of the first element is greater than that of the second element. The first element being "below," "under," or "below" the second element may mean that the first element is located directly below or diagonally below the second element, or it may simply mean that the horizontal height of the first element is less than that of the second element.

[0024] It should be noted that an element described as being "arranged" or "on" another element may be located directly on top of that element or it may be an intervening element. Similarly, when an element is considered "connected" to another element, it may be directly connected to that element or it may be an intervening element. Where applicable, the terms "vertical," "horizontal," "above," "below," "left," "right," and similar expressions used in this application are for illustrative purposes only and do not represent the sole implementation.

[0025] Referring to Fig. 1, Fig. 2 and Fig. 3, is Fig. 1 a structural schematic exploded view of a secondary battery 10 provided in an embodiment of this application, Fig. Figure 2 is a structural schematic view of a lower plastic element 320 provided in an embodiment of this application, and Fig. Figure 3 is a structural cross-sectional view of the lower plastic element 320 in Fig. 2. The secondary battery 10 provided in an embodiment of this application comprises a housing 100, a bare cell 200 and an upper cover assembly 300.

[0026] The housing 100 has an opening 110 at one end, and a receiving cavity 120 is formed inside the housing 100, the bare cell 200 is arranged in the receiving cavity 120, and the bare cell 200 is arranged to be electrically connected to an external conductive element.

[0027] The upper cover assembly 300 comprises an end cover 310 and a lower plastic element 320, which is arranged on the end cover 310. The end cover 310 is sealed to the opening 110. The end cover 310 is provided with an explosion-proof valve. A side of the lower plastic element 320 facing away from the end cover 310 faces the bare cell 200. The lower plastic element 320 is provided with a gas vent 321, which is connected to the explosion-proof valve. In the specific application, if the secondary battery 10 thermally fails, the explosion-proof valve opens, and the interior of the secondary battery 10 is connected to the outside world through the gas vent 321 for pressure relief.

[0028] One side of the lower plastic element 320, opposite the end cover 310, is provided with a receiving recess 322 for the temporary storage of electrolyte; the bottom of the receiving recess 322 is provided with a return opening 323; the first surface of an orthographic projection of the gas vent opening 321 and the return opening 323 on the end cover 310 occupies 2% to 10% of the area of ​​the end cover 310; and the area of ​​the end cover 310 is 4200 mm². 2 up to 75000 mm 2 This is sufficient. In specific situations, the area of ​​the end cover can be between 310 and 5500 mm². 2 and 60000 mm 2 or 65000 mm 2 and 75000 mm 2 The area of ​​the end cover 310, which lies in other area intervals within the range of 4200 mm. 2 up to 75000 mm 2 A drop is also permissible. According to the aforementioned proportional ratio of 2% to 10%, the first area of ​​84 mm is sufficient.2 up to 7500 mm 2 In a specific situation, the first area can be between 550 mm 2 and 6000 mm 2 or 6500 mm 2 and 7500 mm 2 lie, and the first area that lies within other range intervals within the range of 84 mm 2 up to 7500 mm 2 Falling is also permissible.

[0029] For example, the area of ​​the end cover can be 310 mm² from 4200 mm². 2 , 5586 mm 2 , 6600 mm 2 , 7791 mm 2 , 8859 mm 2 , 9986 mm 2 , 10204 mm 2 , 11400 mm 2 , 12040 mm 2 , 13056 mm 2 , 22500 mm 2 , 33800 mm 2 , 43589 mm 2 , 55500 mm 2 , 62500 mm 2 , 70400 mm 2 , 75000 mm 2 , are selected so that the specific value of the first surface is 84 mm 2 , 279 mm 2 , 660 mm 2 , 779 mm 2 , 885 mm 2, 998 mm 2 , 1020 mm 2 , 1140 mm 2 , 1305 mm 2 , 2250 mm 2 , 3380 mm 2 , 4358 mm 2 , 5550 mm 2 , 6250 mm 2 , 7040 mm 2 , 7500 mm 2 can be selected. It should be noted that the area of ​​the end cover 310 and the first area are not limited to the specific values ​​provided above. For example, the area of ​​the end cover 310 can have other values ​​within the range of 4200 mm. 2 up to 75000 mm 2 and the first area other values ​​within the range of 84 mm 2 up to 7500 mm 2 assume.

[0030] According to the above secondary battery 10, by providing the gas vent opening 321 in the lower plastic element 320, which is connected to the explosion-proof valve, the gas flows through the gas vent hole 321 to the explosion-proof valve for pressure relief when the internal pressure of the secondary battery 10 increases, thereby preventing an explosion of the secondary battery;Furthermore, the electrolyte flows through the receiving recess 322, which is located on the side of the lower plastic element 320 opposite the end cover and is designed to temporarily receive electrolyte 310, and through the return opening 323 at the bottom of the receiving recess 322 when the secondary battery is shaken, causing electrolyte to splash onto the surface of the lower plastic element 320 opposite the end cover 310, to the receiving recess 322 and then flows through the return opening 323 at the bottom of the receiving recess 322 to the bare cell 200, thus avoiding waste of electrolyte; and by adjusting the first surface of the orthographic projection of the gas vent opening 321 and the return opening 323 on the end cover 310 to 2% to 10% of the surface of the end cover 310 in the range of 4200 mm; 2 up to 75000 mm 2A reduction in the weight of the lower plastic element 320 is achieved without affecting the strength of the lower plastic element 320.

[0031] If the explosion-proof valve is required to increase the efficiency of gas venting inside the secondary battery 10 while simultaneously ensuring the strength of the lower plastic element 320, in one embodiment the number of gas vent openings 321 is multiple, with several gas vent openings 321 arranged at intervals, and a second area of ​​an orthographic projection of all gas vent openings 321 onto the end cover 310 occupies 1% to 5% of the area of ​​the end cover 310, and the second area is in the range of 42 mm 2 up to 3750 mm 2 The second area can be, for example, between 55 mm. 2 and 600 mm 2 or 3250 mm 2 and 3750 mm 2lie, and the first area that lies within other range intervals within the range of 42 mm 2 up to 3750 mm 2 Falling is also permissible.

[0032] In a specific situation, the number of gas vent openings 321 can be 4, 8, 12 or more, and the shape of the gas vent opening 321 can be any geometric figure, which is not excessively restricted here.

[0033] For example, the specific value of the second surface can be calculated from 42 mm. 2 , 56 mm 2 , 66 mm 2 , 78 mm 2 , 442 mm 2 , 499 mm 2 , 512 mm 2 , 570 mm 2 , 652 mm 2 , 1125 mm 2 , 1690 mm 2 , 2179 mm 2 , 2775 mm 2 , 3125 mm 2 , 3520 mm 2 , 3750 mm 2The second area can be selected. It should be noted that the second area is not limited to the specific values ​​provided above. For example, the second area can also have other values ​​within the range of 4200 mm. 2 up to 75000 mm 2 have.

[0034] To increase the path for the return of the electrolyte to the bare cell 200 without compromising the structural strength of the lower plastic element 320, in one embodiment several return openings 323 are divided into two groups, with the two groups of return openings 323 each being arranged at opposite ends of the lower plastic element 320. In this specific situation, the two groups of return openings 323 are distributed on opposite sides of the gas vent opening 321, the number of return openings 323 in each group can be 4, 8, 12 or more, and the shape of the return opening 323 can be any geometric figure, which is not unduly restricted here. A third area of ​​an orthographic projection of all return openings 323 onto the end cover 310 occupies 0.5% to 3% of the area of ​​the end cover 310, and this third area ranges from 21 mm². 2 up to 2250 mm 2The third surface can, for example, be between 165 mm 2 and 1800 mm 2 or 1950 mm 2 and 2250 mm 2 The third surface can also be placed in other intervals within the range of 21 mm. 2 up to 2250 mm 2 In the above situation, when the battery is shaken and electrolyte splashes onto the surface of the lower plastic element 320, which is opposite the end cover 310, the electrolyte flows to the receiving recesses 322 at both ends of the lower plastic element 320 and then flows through the return openings 323 at the bottom of the receiving recesses 322 to the bare cell 200, thus largely preventing electrolyte waste.

[0035] In this specific situation, the specific value of the third surface can be 21 mm. 2 , 33 mm 2 , 49 mm 2 , 198 mm 2 , 299 mm 2 , 306 mm 2 , 342 mm 2to be selected, 361 mm 2 , 391 mm 2 , 675 mm 2 , 1014 mm 2 , 1307 mm 2 , 1665 mm 2 , 1875 mm 2 , 2112 mm 2 , 2250 mm 2 can be selected. It should be noted that the third area is not limited to the specific values ​​provided above. For example, the third area can also have other values ​​within the range of 21 mm. 2 up to 2250 mm 2 exhibit.

[0036] To make the lower plastic element 320 more practical, in one embodiment the lower plastic element 320 comprises a main body 324 and projecting knobs 325 arranged at two ends of the main body 324. The main body 324 is connected to the end cover 310, and one side of the projecting knob 325 facing away from the main body 324 faces the bare cell 200. In a specific situation, a section of the surface of the main body 324 opposite the end cover 310, which is opposite the projecting knob 325, is provided with the receiving recess 322. The depth of the receiving recess 322 extends along the vertical direction of the projecting knob 325 and does not pass through the protruding knob 325, thus facilitating the containment of any splashed electrolyte by the receiving recess 322.

[0037] In the specific installation, the lower plastic element 320 is received in the receiving cavity 120. To improve the stability of the secondary battery 10, the side of the projecting knob 325 facing away from the main body 324 abuts the bare cell 200, which is placed in the receiving cavity 120. It should be noted that the secondary battery 10 also includes a connecting piece. The connecting piece is arranged on the main body 324 and is spaced apart from the projecting knob 325. The connecting piece is also connected to the bare cell 200 by a curved tab 400. It is understood that the connecting piece and the curved tab 400 are placed between the main body 324 and the blank cell 200, wherein a side of the main body 324 facing away from the end cover 310 has a certain height in relation to the side of the projecting knob 325 facing away from the main body 324.The installation space for the connector and the curved tab 400 is influenced by the height of the main body 324 and the set height.

[0038] Specifically to design the height of the main body 324 in a sensible way, the height of the main body 324 is optionally 1 mm to ensure the connection strength between the main body 324 and the end cover 310 without affecting the installation space for the connector and the curved tab 400.

[0039] To ensure a suitable target height, it is specifically defined as the sum of the connector thickness and a reserved height for the bent tab 400. More precisely, the connector thickness ranges from 0.5 mm to 1.5 mm. For example, the connector thickness could be between 0.85 mm and 1 mm or between 1.1 mm and 1.5 mm, although it could also fall within other intervals of 0.5 mm to 1.5 mm. It should be noted that the specific thickness of the connector can be selected from 0.6 mm, 0.75 mm, 0.8 mm, 0.85 mm, 0.9 mm, 0.95 mm, 1.0 mm, 1.05 mm, 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, and 1.5 mm. The thickness of the connector is not limited to the specific values ​​provided above. For example, the thickness of the connector can also have other values ​​in the range of 0.5 mm to 1.5 mm.

[0040] The curved tab 400 comprises several sequentially connected single electrode plates, wherein the reserved height is a product of the thickness of a single electrode plate, the number of single electrode plates, and a specified coefficient, the specified coefficient being in the range of 3 to 6. In a specific situation, the thickness of a single electrode plate is preferably 0.012 mm, and the number of single electrode plates is preferably between 35 and 60. It should be noted that the number of single electrode plates can be selected from 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 55, 56, 58, and 60. The number of single electrode plates is not limited to the specific values ​​provided above. For example, the number of single electrode plates can be any integer in the range of 35 to 60.

[0041] Due to the above situation, the target height ranges from 1.76 mm to 5.82 mm. For example, the set height can range from 1.8 mm to 3.85 mm or 3.9 mm to 5.8 mm, and set heights falling within other intervals of 1.76 mm to 5.82 mm are also acceptable. Specific set height values ​​can be selected from 1.86 mm, 2.01 mm, 2.06 mm, 2.11 mm, 2.16 mm, 2.21 mm, 2.26 mm, 2.31 mm, 2.36 mm, 2.76 mm, 4.92 mm, 5.07 mm, 5.42 mm, 5.47 mm, 5.52 mm, 5.57 mm, 5.62 mm, or any value between 1.76 mm and 5.82 mm.It should be noted that if the set height is less than 1.76 mm, this results in the installation space for the connector and the bent tab 400 being too small, increasing the likelihood of the tab breaking and the insertion of the tab causing a short circuit; if the set height is greater than 5.82 mm, this affects the height setting of the bare cell 200 in the receiving cavity 120, thereby impairing the capacity of the secondary battery 10.

[0042] With reference to Fig. 4 and Fig. 5 is Fig. 4 a structural top view of the lower plastic element 320 in Fig. 2 and Fig. Figure 5 is a schematic structural contour view of the lower plastic element 320 and the end cover 310 provided in an embodiment of this application. To ensure excellent insulating performance of the lower plastic element 320 while simultaneously reducing its weight, in a preferred embodiment a fourth area, enclosed by an orthographic projection of an outer contour of the lower plastic element 320 onto the end cover 310, occupies 85% to 95% of the area of ​​the end cover 310, and the fourth area extends from 3570 mm². 2 up to 71250 mm 2 In a specific situation, the area of ​​the fourth surface can be 4950 mm. 2 up to 54000 mm 2 or 58500 mm 2 up to 67500 mm 2 and the fourth area, which is divided into other intervals within the range of 3570 mm 2 up to 71250 mm 2If it happens, all are permissible.

[0043] For example, the specific value of the fourth area can be calculated from 4748 mm². 2 , 5610 mm 2 , 6622 mm 2 , 7530 mm 2 , 8488 mm 2 , 8673 mm 2 , 9690 mm 2 , 10234 mm 2 , 11097 mm 2 , 19125 mm 2 , 28730 mm 2 , 41409 mm 2 , 52725 mm 2 , 59375 mm 2 , 66880 mm 2 , 71250 mm 2 can be selected. It should be noted that the fourth area is not limited to the specific values ​​provided above. For example, the fourth area can also have other values ​​within the range of 3570 mm. 2 up to 71250 mm 2 have.

[0044] Again with reference to Fig. In this specific situation, the end cover 310 is a rectangular plate. The length of the long side of the end cover 310 is L, and the length of the short side of the end cover 310 is H. During the specific installation, the lower plastic element 320 enters the receiving cavity 120 from the opening 110, and then the end cover 310 is welded to the housing 100.

[0045] To prevent the laser from bypassing the lower plastic element 320 and irradiating other components inside the housing 100 during laser welding between the end cover 310 and the housing 100, a first distance value, i.e., L1, is defined in a preferred embodiment as the distance between an edge of the lower plastic element 320 and an edge of the end cover 310 along a longitudinal direction of the lower plastic element 320. L1 ranges from 1 mm to 1.5 mm. In a specific situation, L1 may be between 1.1 mm and 1.35 mm or between 1.4 mm and 1.5 mm, and L1 may also fall into other intervals within the range of 1 mm to 1.5 mm. For example, the specific value of L1 can be 1.1 mm, 1.15 mm, 1.2 mm, 1.25 mm, 1.3 mm, 1.35 mm, 1.4 mm, 1.45 mm, 1.48 mm or any value between 1 mm and 1.5 mm.A distance between an edge of the lower plastic element 320 and an edge of the end cover 310 along the width direction of the lower plastic element 320 is a second distance value, i.e., H1. H1 ranges from 1 mm to 5 mm. In specific situations, H1 may be between 1.5 mm and 3.5 mm or between 4.0 mm and 4.9 mm, and H1 may also fall within other intervals within the range of 1 mm to 5 mm. The specific value of H1 may be, for example, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.3 mm, 4.5 mm, 4.8 mm, or any value between 1 mm and 5 mm.

[0046] The above situation creates a gap between the edge of the lower plastic element 320 and the edge of the end cover 310, so that the lower plastic element 320 does not interfere with the housing 100 when entering it, thus facilitating the encapsulation between the end cover 310 and the housing 100. Furthermore, by setting the first distance value between the lower plastic element 320 and the end cover 310 in the range of 1 mm to 1.5 mm and the second distance value in the range of 1 mm to 5 mm when the end cover 310 and the housing 100 are encapsulated, it is less likely that the laser, during laser welding between the end cover 310 and the housing 100, will bypass the lower plastic element 320 and irradiate other components of the housing 100, thereby improving safety during the installation of the secondary battery 10.

[0047] It should be emphasized that a first corner of the lower plastic element 320 is a rounding, a second corner of the end cover 310 is a chamfer, a straight-line distance between a center point of the first corner and a center point of the second corner is a third distance, i.e. D, and the third distance is greater than the first and the second distance. Examples of technical effects

[0048] To strongly substantiate the beneficial effects of this application, further test data are provided as shown in Table 1 below. Table 1 No. A B C S1 S2 H L H1 L1 1 126 42 84 4200 3822 30 140 1 1 2 196 56 140 5586 5027 38 147 1.5 1 3 224 78 146 7791 7020 49 159 2 1.5 4 303 120 183 12040 10985 70 172 2.5 1.5 5 3750 1500 2250 75000 69000 150 500 3.5 1.5

[0049] As shown in Table 1, five types of lower plastic elements 320 were designed according to the solution of this application. The table shows the area in mm². 2The length dimension is given in mm. A is the first surface, B is the second surface, C is the third surface, S1 is the surface of the end cover 310, S2 is the surface enclosed by the outer contour of the lower plastic element 320, H is the short side of the end cover 310, L is the long side of the end cover 310, L1 is the first distance value, and H1 is the second distance value. The above configuration meets the requirements for improved gas venting efficiency, backflow efficiency, and safety during welding of the end cover 310 and the housing 100 without compromising the strength of the lower plastic element 320.

[0050] Specific comparative examples are shown in Table 2. Table 2 No. A B C S1 S2 H L H1 L1 6 42 21 16.8 4200 3822 30 140 1 1 7 55 27 22 5586 5027 38 147 1.5 1 8 77 39 31 7791 7020 49 159 2 1.5 9 1806 963 602 12040 10985 70 172 2.5 1.5 10 11250 4500 3750 75000 69000 150 500 3.5 1.5

[0051] As shown in Table 2, five types of bottom plastic support structures were designed for comparison. The table shows the area in mm². 2, the length dimension is given in mm. A is the first surface, B is the second surface, C is the third surface, S1 is the surface of the end cover 310, S2 is the surface enclosed by the outer contour of the lower plastic element 320, H is the short side of the end cover 310, L is the long side of the end cover 310, L1 is the first distance value and H1 is the second distance value.

[0052] For the lower plastic components numbered 6 to 8, the first area of ​​the orthographic projection of the gas vent and return port on the end cover occupies less than 2% of the end cover's area, the second area of ​​the orthographic projection of the gas vent alone on the end cover occupies less than 1% of the end cover's area, and the third area of ​​the orthographic projection of the return port alone on the end cover occupies less than 0.5% of the end cover's area. If the battery required venting for pressure relief, the gas flow efficiency was low and the venting rate slow, which could easily lead to a secondary battery explosion; conversely, if the electrolyte had to flow back into the bare cell through the return port, the flow rate was reduced, impairing efficiency.

[0053] It should be noted that in the lower plastic element structures numbered 9 to 10, the first surface occupies more than 10% of the end cover's surface area, the second surface more than 5%, and the third surface more than 3%. This situation resulted in an excessive number of through-holes in the lower plastic element's structure, and after strength tests such as elongation and compression, the lower plastic element exhibited significant deformation, making it difficult for the lower plastic element to meet the requirements.

[0054] In summary, the example shown in Table 1 demonstrates that the structure of the lower plastic element designed according to the solution of this application is rational.

[0055] The various technical elements of the embodiments described above can be combined in any way desired. For the sake of brevity, not all possible combinations of the various technical elements in the embodiments described above are presented here. However, as long as the combination of these technical elements is not contradictory, it should be considered to fall within the scope of this application.

[0056] The embodiments described above express only some embodiments of this application, and while the descriptions are specific and detailed, they should not be interpreted as limiting the scope of the patent. It should be noted that, for those skilled in the field, various modifications and improvements could be made without departing from the concept of this application, all of which would fall within the scope of protection of this application. The scope of protection of the present patent application is therefore determined by the attached claims.

[0057] This application relates to a secondary battery. The secondary battery comprises a housing, a bare cell, and an upper cover assembly. The housing has an opening at one end and defines a receiving cavity; the bare cell is arranged in the receiving cavity; the upper cover assembly comprises an end cover and a lower plastic element arranged on the end cover, the end cover being sealed to the opening and being provided with an explosion-proof valve, a side of the lower plastic element facing away from the end cover being opposite the bare cell, the lower plastic element being provided with a gas vent in conjunction with the explosion-proof valve, and the lower plastic element being provided with a receiving recess arranged on a side of the same that faces the end cover.and which is designed for the temporary storage of electrolyte, has a bottom of the storage depression with a return opening, a first surface of an orthographic projection of the gas vent opening and the return opening on the end cover occupies 2% to 10% of an area of ​​the end cover, and the area of ​​the end cover is in the range of 4200 mm, 2 up to 75000 mm 2 lies.

Claims

[1] Secondary battery (10) comprising a housing, a bare cell and an upper cover assembly (300), characterized by , that: the housing (100) has an opening (110) at one end and; the bare cell (200) is arranged in the housing (100); The upper cover assembly (300) comprises an end cover (310) and a lower plastic element (320) arranged on the end cover (310), the end cover (310) being sealed to the opening (110), the end cover (310) being provided with an explosion-proof valve, a side of the lower plastic element (320) facing away from the end cover (310) being opposite the bare cell (200), the lower plastic element (320) being provided with a gas vent opening (321) connected to the explosion-proof valve, the lower plastic element (320) being provided with a receiving recess (322) arranged on a side of it opposite the end cover (310), the receiving recess (322) being provided with a return opening (323) in a base thereof,and a first area of ​​an orthographic projection of the gas vent opening (321) and the return opening (323) in the end cover (310) occupies 2% to 10% of an area of ​​the end cover (310), and the area of ​​the end cover (310) is in the range of 4200 mm, 2 up to 75000 mm 2 lies. [2] Secondary battery (10) according to claim 1, wherein the lower plastic element (320) is provided with several gas vent openings (321) which are arranged at intervals and a second surface of an orthographic projection of all gas vent openings (321) in the end cover (310) occupies 1% to 5% of the surface of the end cover (310) and the second surface is in the range of 42 mm 2 up to 3750 mm 2 lies. [3] Secondary battery (10) according to claim 1 or 2, wherein the receiving recess (322) is provided with several return openings (323), the return openings (323) being divided into two groups, the two groups of return openings (323) being arranged at two ends of the lower plastic element (320), and a third surface of an orthographic projection of all return openings (323) in the end cover (310) occupying 0.5% to 3% of the surface of the end cover (310), and the third surface being 21 mm 2 up to 2250 mm 2 suffices. [4] Secondary battery (10) according to one of claims 1 to 3, wherein the secondary battery (10) further comprises a connecting piece, wherein the lower plastic element (320) comprises a main body (324) and projecting buttons (325) arranged at two ends of the main body (324), wherein: the main body (324) is connected to the end cover (310), a side of the projecting knob (325) facing away from the main body (324) is opposite the blank cell, a side of the main body (324) facing away from the end cover (310) has a defined height relative to the side of the projecting knob (325) facing away from the main body (324); the connecting piece is arranged on the main body (324) and is spaced apart from the projecting knob (325), the connecting piece is connected to the bare cell with a curved tab (400) and the set height is a sum of a thickness of the connecting piece and a reserved height of the curved tab (400). [5] Secondary battery (10) according to claim 4, wherein the set height is in the range of 1.76 mm to 5.82 mm. [6] Secondary battery (10) according to claim 4, wherein the curved tab (400) comprises several sequentially connected single electrode plates, the reserved height is a product of a single electrode plate thickness, a number of single electrode plates and a set coefficient, and the set coefficient is in the range of 3 to 6. [7] Secondary battery (10) according to claim 4, wherein the thickness of the connecting piece is between 0.5 mm and 1.5 mm. [8] Secondary battery (10) according to any one of claims 1 to 7, wherein a fourth area enclosed by an orthographic projection of an outer contour of the lower plastic element (320) on the end cover (310) occupies 85% to 95% of the area of ​​the end cover (310) and the fourth area is in the range of 3570 mm 2 up to 71250 mm 2 lies. [9] Secondary battery (10) according to any one of claims 1 to 8, wherein a distance between an edge of the lower plastic element (320) and an edge of the end cover (310) along a longitudinal direction of the lower plastic element (320) is a first distance value, and the first distance value is in the range of 1 mm to 1.5 mm; a distance between an edge of the lower plastic element (320) and an edge of the end cover (310) along a transverse direction of the lower plastic element (320) is a second distance value, and the second distance value is in the range of 1 mm to 5 mm. [10] Secondary battery (10) according to claim 9, wherein a first corner of the lower plastic element (320) is a rounded shape, a second corner of the end cover (310) is a chamfer, a straight-line distance between a center point of the first corner and a center point of the second corner is a third distance and the third distance is greater than the first distance and the second distance.

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