Secondary battery

Abstract

The present application relates to a secondary battery. The secondary battery comprises a shell, a naked battery cell and a top cover assembly, one end of the shell is provided with an opening, and an accommodating space is formed in the shell; the naked battery cell is arranged in the accommodating space; the top cover assembly comprises an end cover and lower plastic arranged on the end cover, the end cover is connected to the opening in a sealed mode, an anti-explosion valve is arranged on the end cover, the side, away from the end cover, of the lower plastic faces the naked battery cell, the lower plastic is provided with an exhaust through hole communicated with the anti-explosion valve, and the side, close to the end cover, of the lower plastic is provided with a containing groove used for temporarily storing electrolyte. A backflow through hole is formed in the groove bottom of the containing groove, the first area of the orthographic projection of the exhaust through hole and the backflow through hole on the end cover accounts for 2%-10% of the area of the end cover, and the area of the end cover ranges from 4200 mm < 2 > to 75000 mm < 2 >.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of energy storage, in particular to a secondary battery. BACKGROUND

[0002] Lithium batteries have the advantages of small size, high energy density, long service life, green environmental protection, etc., and are widely used in the automobile, electronic product and energy storage system industries.

[0003] At present, in the use process of lithium batteries, on the one hand, due to overcharging, overdischarging, short circuit or harsh environment, etc., a large amount of gas will be generated in the lithium battery, and the temperature of the lithium battery will also rise sharply, thereby causing the internal pressure of the lithium battery to increase, which will cause certain danger to the user; on the other hand, the shaking of the lithium battery will cause part of the electrolyte to splash to the surface of the lower plastic facing the end cover, thereby causing liquid accumulation on the surface or groove of the lower plastic, resulting in waste of electrolyte. CONTENT OF THE UTILITY MODEL

[0004] Therefore, it is necessary to provide a secondary battery in view of the problems of explosion risk and electrolyte waste in the use process of the lithium battery.

[0005] A secondary battery, comprising a shell, a bare battery core and a top cover assembly, wherein:

[0006] One end of the shell has an opening, and an accommodation space is formed in the interior of the shell;

[0007] The bare battery core is arranged in the accommodation space;

[0008] The top cover assembly comprises an end cover and a lower plastic arranged on the end cover, the end cover is sealingly connected to the opening, and a pressure relief valve is arranged on the end cover, the side of the lower plastic away from the end cover faces the bare battery core, the lower plastic is provided with exhaust through holes in communication with the pressure relief valve, the side of the lower plastic close to the end cover is provided with an accommodation groove for temporarily storing electrolyte, the groove bottom of the accommodation groove is provided with a backflow through hole, the first area of the normal projection of the end cover occupied by the exhaust through hole and the backflow through hole accounts for 2%-10% of the area of the end cover, and the area of the end cover ranges from 4200mm 2 to 75000mm 2 .

[0009] In one of the embodiments, the number of exhaust through holes is multiple, the multiple exhaust through holes are arranged at intervals, and the second area of the normal projection of the end cover occupied by all the exhaust through holes accounts for 1%-5% of the area of the end cover, and the second area ranges from 42mm 2 to 3750mm 2 .

[0010] In one of the embodiments, the number of the reflow through holes is multiple, the multiple reflow through holes are divided into two groups, the two groups of the reflow through holes are arranged at two ends of the lower plastic respectively, all the reflow through holes occupy 0.5%-3% of the area of the end cover in a third area of the orthographic projection of the end cover, the third area ranges from 21mm 2 -2250mm 2 .

[0011] In one of the embodiments, the secondary battery further comprises a connecting sheet, the lower plastic comprises a body and bosses arranged at two ends of the body, wherein:

[0012] The body is connected with the end cover, the side of the boss away from the body faces the bare battery cell, the side of the body away from the end cover and the side of the boss away from the body have a set height;

[0013] The connecting sheet is arranged on the body and spaced apart from the boss, the connecting sheet is further connected with the bent tab on the bare battery cell, the set height is the sum of the thickness of the connecting sheet and the reserved height of the bent tab.

[0014] In one of the embodiments, the range of the set height is 1.76mm-5.82mm.

[0015] In one of the embodiments, the bent tab comprises multiple single tabs connected in sequence, the reserved height is the product of the thickness of the single tab, the number of the single tabs and a set coefficient, the range of the set coefficient is 3-6.

[0016] In one of the embodiments, the thickness of the connecting sheet ranges from 0.5mm to 1.5mm.

[0017] In one of the embodiments, a fourth area surrounded by the outer contour of the lower plastic on the orthographic projection of the end cover occupies 85%-95% of the area of the end cover, the range of the fourth area is 3570mm 2 -71250mm 2 .

[0018] In one of the embodiments, along the length direction of the lower plastic, the distance between the edge of the lower plastic and the edge of the end cover is a first distance value, the range of the first distance value is 1mm-1.5mm.

[0019] Along the width direction of the lower plastic, the distance between the edge of the lower plastic and the edge of the end cover is a second distance value, the range of the second distance value is 1mm-5mm.

[0020] In one embodiment, the first corner of the lower plastic is rounded, the second corner of the end cap is chamfered, and the straight-line distance between the center point of the first corner and the center point of the second corner is a third distance, which is greater than the first distance and the second distance.

[0021] The aforementioned secondary battery features a vent hole in the lower plastic section that connects to an explosion-proof valve. When the internal pressure of the battery increases, the pressure is released through the vent hole to the explosion-proof valve, preventing the secondary battery from exploding. Furthermore, a reservoir for temporarily storing electrolyte is located on the side of the lower plastic section near the end cap. A return flow hole is located at the bottom of the reservoir. When the battery shakes and some electrolyte splashes onto the surface of the lower plastic section facing the end cap, the electrolyte flows back to the reservoir and then through the return flow hole at the bottom of the reservoir to the bare battery cell, avoiding electrolyte waste. The vent hole and the return flow hole, when projected onto the end cap, occupy 2%-10% of the end cap area, which is approximately 4200 mm². 2 -75000mm 2 This allows for a reduction in the weight of the lower plastic without compromising its strength. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the exploded structure of the secondary battery provided in this application.

[0023] Figure 2 This is a schematic diagram of the structure of the lower plastic provided in this application.

[0024] Figure 3 for Figure 2 Cross-sectional view of the lower plastic structure.

[0025] Figure 4 for Figure 2 Top view of the lower plastic structure.

[0026] Figure 5 This is a schematic diagram of the outline structure of the lower plastic and end cap provided in this application.

[0027] in:

[0028] 10. Secondary battery; 100. Casing; 110. Opening; 120. Accommodation space; 200. Bare cell; 300. Top cover assembly; 310. End cap; 320. Lower plastic; 321. Vent hole; 322. Accommodation groove; 323. Return flow hole; 324. Body; 325. Boss; 400. Bending tab. Detailed Implementation

[0029] In order to make the above objectives, features and advantages of the present application more clear and comprehensible, the specific embodiments of the present application will be described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in a number of different ways beyond the specific embodiments described herein and by one of ordinary skill in the art without departing from the spirit and scope of the present application, and it is therefore intended that all such variations be considered as falling within the scope of the present application. It should be understood that the use of the terms "include", "comprise" or "contain" herein should not be understood as limiting the present application to the features or steps described herein, but rather the use of these terms is intended to cover the presence of the features or steps described herein as well as the presence of other features or steps not described herein.

[0030] In the description of the present application, it should be understood that, if these terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like appear, these terms indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0031] In addition, if these terms "first", "second" appear, these terms are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features referred to. Therefore, the features defined with "first", "second" can include at least one of the features explicitly or implicitly. In the description of the present application, if the term "a plurality of" appears, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise explicitly specified.

[0032] In the present application, unless otherwise explicitly specified and limited, if the terms "mount", "connect", "connect", "fix" and the like appear, these terms should be interpreted broadly. For example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements, unless otherwise explicitly limited. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0033] In the present application, unless specifically defined and limited otherwise, if there is a description of a first feature "on" or "under" a second feature, it can mean that the first and second features are in direct contact, or the first and second features are indirectly in contact through an intermediate medium. Moreover, the first feature "over", "above" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or only means that the horizontal height of the first feature is higher than that of the second feature. The first feature "under", "below" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or only means that the horizontal height of the first feature is less than that of the second feature.

[0034] It should be noted that if an element is referred to as "fixed to" or "disposed on" another element, it can be directly on the other element or there can be an intermediate element. If an element is considered to be "connected" to another element, it can be directly connected to the other element or there can be an intermediate element. If present, the terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used in the present application are only for illustrative purposes and do not represent the only implementation.

[0035] Referring to Figure 1 , Figure 2 and Figure 3 , Figure 1 is an exploded structural schematic view of a secondary battery 10 provided by an embodiment of the present application, Figure 2 is a structural schematic view of a lower plastic 320 provided by an embodiment of the present application, Figure 3 is Figure 2 a cross-sectional view of the lower plastic 320 structure. The secondary battery 10 provided by an embodiment of the present application includes a housing 100, a bare battery cell 200 and a top cover assembly 300.

[0036] The housing 100 has an opening 110 at one end, and an accommodation space 120 is formed inside the housing 100, and the bare battery cell 200 is disposed in the accommodation space 120, and the bare battery cell 200 is used for electrical connection with an external conductive member.

[0037] The top cover assembly 300 includes an end cover 310 and a lower plastic 320 disposed on the end cover 310, the end cover 310 is sealingly connected to the opening 110, and the end cover 310 is provided with a pressure relief valve, the side of the lower plastic 320 away from the end cover 310 faces the bare battery cell 200, and the lower plastic 320 is provided with an exhaust through hole 321 in communication with the pressure relief valve. In specific use, when the secondary battery 10 has a thermal runaway, the pressure relief valve is opened, and the inside of the secondary battery 10 is communicated with the outside through the exhaust through hole 321 to release pressure.

[0038] The lower plastic 320 is provided with a containing groove 322 for temporarily storing electrolyte on the side close to the end cover 310. The groove bottom of the containing groove 322 is provided with a backflow through hole 323. The first area of the projection of the exhaust through hole 321 and the backflow through hole 323 on the end cover 310 accounts for 2%-10% of the area of the end cover 310. The area of the end cover 310 ranges from 4200mm 2 -75000mm 2 In a specific arrangement, the area of the end cover 310 can range from 5500mm 2 -60000mm 2 , 65000mm 2 -75000mm 2 The area of the end cover 310 ranges from 4200mm 2 -75000mm 2 Other range intervals within this range are also possible. According to the above-mentioned proportion of 2%-10%, the first area ranges from 84mm 2 -7500mm 2 In a specific arrangement, the first area can range from 550mm 2 -6000mm 2 , 6500mm 2 -7500mm 2 The first area ranges from 84mm 2 -7500mm 2 Other range intervals within this range are also possible.

[0039] Exemplarily, the area of the end cover 310 can be any one of 4200mm 2 , 5586mm 2 , 6600mm 2 , 7791mm 2 , 8859mm 2 , 9986mm 2 , 10204mm 2 , 11400mm 2 , 12040mm 2 , 13056mm 2 , 22500mm 2 , 33800mm 2 , 43589mm 2 , 55500mm 2 , 62500mm 2 , 70400mm 2 , 75000mm 2 , thereby the specific value of the first area can be 84mm 2 , 279mm 2 , 660mm2 , 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 . 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, such as the area of the end cover 310 can be 4200 mm 2 -75000 mm 2 , the first area can be 84 mm 2 -7500 mm 2 , and other values within this range.

[0040] The above secondary battery 10, by setting the lower plastic 320 to open the exhaust hole 321 communicated with the explosion-proof valve, when the pressure inside the battery increases, through the exhaust hole 321 to the explosion-proof valve for pressure relief, to prevent the secondary battery 10 explosion; again by setting the lower plastic 320 close to the end cover 310 side is provided with a storage tank 322 for temporary storage of electrolyte, the tank bottom of the storage tank 322 is provided with a backflow hole 323, when the battery is shaken to cause part of the electrolyte splashing to the lower plastic 320 towards the end cover 310 surface, the electrolyte will flow to the storage tank 322 again from the backflow hole 323 of the tank bottom of the storage tank 322 to the bare cell 200, to avoid the waste of electrolyte, and by setting the exhaust hole 321 and the backflow hole 323 in the end cover 310 of the first area of the orthographic projection occupies 2%-10% of the area of the end cover 310, the area of the end cover 310 ranges from 4200 mm 2 -75000 mm 2 , to achieve the premise of reducing the weight of the lower plastic 320 without affecting the strength of the lower plastic 320.

[0041] When the explosion-proof valve is needed, in order to increase the exhaust efficiency inside the secondary battery 10 while ensuring the strength of the lower plastic 320, a preferred embodiment, the number of exhaust holes 321 is multiple, multiple exhaust holes 321 are arranged at intervals, and all the exhaust holes 321 occupy 1%-5% of the area of the end cover 310 in the second area of the orthographic projection of the end cover 310, the second area ranges from 42 mm 2 -3750 mm2 For example, the second area can range from 55mm 2 -600mm 2 , 3250mm 2 -3750mm 2 For example, the second area can range from 42mm 2 -3750mm 2 Other ranges within this range are also possible.

[0042] In a specific arrangement, the number of exhaust through holes 321 can be 4, 8, 12, and more, and the shape of the exhaust through hole 321 can be any geometric shape, which is not limited here.

[0043] For example, the second area can be any one of 42mm 2 , 56mm 2 , 66mm 2 , 78mm 2 , 442mm 2 , 499mm 2 , 512mm 2 , 570mm 2 , 652mm 2 , 1125mm 2 , 1690mm 2 , 2179mm 2 , 2775mm 2 , 3125mm 2 , 3520mm 2 , 3750mm 2 . It should be noted that the second area is not limited to the specific values provided above, such as the second area can also be 4200mm 2 -75000mm 2 Other values within this range are also possible.

[0044] In order to increase the electrolyte backflow to the bare cell 200 path without affecting the structural strength of the lower plastic 320, in a preferred embodiment, the number of backflow through holes 323 is multiple, and the multiple backflow through holes 323 are divided into two groups, and the two groups of backflow through holes 323 are arranged at both ends of the lower plastic 320, in a specific arrangement, the two groups of backflow through holes 323 are distributed on both sides of the exhaust through hole 321, and the number of backflow through holes 323 in each group can be 4, 8, 12, and more, and the shape of the backflow through hole 323 can be any geometric shape, which is not limited here. The third area of the orthographic projection of all backflow through holes 323 occupies 0.5%-3% of the area of the end cover 310, and the range of the third area is 21mm 2 -2250mm 2, the third area range can be 165mm 2 -1800mm 2 , 1950mm 2 -2250mm 2 , the third area range is 21mm 2 -2250mm 2 Other range intervals within this range are also available. Through the above setting, when the battery shakes and causes some electrolyte to splash onto the surface of the lower plastic 320 towards the end cover 310, the electrolyte will flow to the accommodation groove 322 at both ends of the lower plastic 320, and then flow to the bare battery cell 200 from the backflow through hole 323 at the bottom of the accommodation groove 322, greatly avoiding the waste of electrolyte.

[0045] In a specific setting, the specific value of the third area can be any one of 21mm 2 , 33mm 2 , 49mm 2 , 198mm 2 , 299mm 2 , 306mm 2 , 342mm 2 , 361mm 2 , 391mm 2 , 675mm 2 , 1014mm 2 , 1307mm 2 , 1665mm 2 , 1875mm 2 , 2112mm 2 , 2250mm 2 . It should be noted that the third area is not limited to the specific values provided above, such as the third area can also be 21mm 2 -2250mm 2 Other values within this range.

[0046] In order to more conveniently design the lower plastic 320, a preferred embodiment, the lower plastic 320 includes a body 324 and a boss 325 arranged at both ends of the body 324, the body 324 is connected with the end cover 310, the boss 325 away from the body 324 side towards the bare battery cell 200, in a specific setting, the surface of the body 324 towards the end cover 310 is provided with an accommodation groove 322 opposite the boss 325, the depth of the accommodation groove 322 extends along the height direction of the boss 325 and does not penetrate the boss 325, facilitating the accommodation groove 322 to accommodate the splashed electrolyte.

[0047] In the specific installation, the lower plastic 320 is accommodated in the accommodating space 120. In order to improve the stability of the secondary battery 10, the side of the boss 325 away from the body 324 is in abutment with the bare cell 200 located in the accommodating space 120. It should be noted that the secondary battery 10 also includes a connecting piece, which is arranged on the body 324 and is spaced apart from the boss 325, and is connected with the bent tab 400 on the bare cell 200. It is not difficult to understand that the connecting piece and the bent tab 400 are located between the body 324 and the bare cell 200, and the side of the body 324 away from the end cover 310 and the side of the boss 325 away from the body 324 have a set height, and the installation space of the connecting piece and the bent tab 400 is affected by the height of the body 324 and the set height.

[0048] In order to reasonably design the height of the body 324, specifically, the height of the body 324 is preferably 1mm, so as to ensure the connection strength of the body 324 and the end cover 310 while not affecting the installation space of the connecting piece and the bent tab 400.

[0049] In order to reasonably design the set height, specifically, the set height is set as the sum of the thickness of the connecting piece and the reserved height of the bent tab 400. More specifically, the thickness of the connecting piece ranges between 0.5mm-1.5mm, and exemplarily, the thickness of the connecting piece can range between 0.85mm-1mm, 1.1mm-1.5mm, and the thickness of the connecting piece can belong to any other range interval within the range of 0.5mm-1.5mm. It should be noted that the thickness of the connecting piece can be any one of 0.6mm, 0.75mm, 0.8mm, 0.85mm, 0.9mm, 0.95mm, 1.0mm, 1.05mm, 1.1mm, 1.15mm, 1.2mm, 1.25mm, 1.3mm, 1.35mm, 1.4mm, 1.45mm, 1.5mm, but the thickness of the connecting piece is not limited to the specific values provided above, such as the thickness of the connecting piece can also be any other value within the range of 0.5mm-1.5mm.

[0050] The bent tab 400 includes a plurality of single tabs connected in sequence, and the reserved height is the product of the thickness of the single tab, the number of the single tab and the set coefficient, and the set coefficient ranges between 3-6. In the specific setting, the thickness of the single tab is preferably 0.012mm, and the number of the single tab is preferably in the range of 35-60. It should be noted that the number of the single tab can be any one of 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 55, 56, 58, 60, but the number of the single tab is not limited to the specific values provided above, such as the number of the single tab can be any other integer within the range of 35-60.

[0051] With the above settings, the height can be set to a range of 1.76mm-5.82mm. For example, the height range can be 1.8mm-3.85mm, 3.9mm-5.8mm, or any other range falling within the 1.76mm-5.82mm range. Specific height values ​​can be any of the following: 1.86mm, 2.01mm, 2.06mm, 2.11mm, 2.16mm, 2.21mm, 2.26mm, 2.31mm, 2.36mm, 2.76mm, 4.92mm, 5.07mm, 5.42mm, 5.47mm, 5.52mm, 5.57mm, 5.62mm, and 1.76mm-5.82mm. It should be noted that when the set height is less than 1.76mm, the installation space between the connecting piece and the bent tab 400 will be too small, thereby increasing the probability of tab tearing and short circuit caused by tab insertion; when the set height is less than 5.82mm, it will affect the height setting of the bare cell 200 in the accommodating space 120, affecting the power of the secondary battery 10.

[0052] Combination Figure 4 and Figure 5 As shown, Figure 4 for Figure 2 Top view of the middle and lower plastic 320 structure. Figure 5 This is a schematic diagram showing the outline structure of the lower plastic 320 and the end cap 310 according to an embodiment of this application. To ensure excellent insulation performance of the lower plastic 320 while reducing its weight, in a preferred embodiment, the fourth area enclosed by the outer contour of the lower plastic 320 on the orthographic projection of the end cap 310 occupies 85%-95% of the area of ​​the end cap 310, and the range of the fourth area is 3570 mm². 2 -71250mm 2 In specific settings, the fourth area can be in the range of 4950 mm². 2 -54000mm 2 58500mm 2 -67500mm 2 The fourth area range is 3570mm. 2 -71250mm 2 Any other range within this scope is acceptable.

[0053] For example, the specific value of the fourth area could be 4748 mm². 2 5610mm 2 6622mm 2 7530mm 2 8488mm 2 8673mm 2 9690mm 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 . It is to be noted that the fourth area is not limited to the specific values provided above, such as the fourth area can also be 3570 mm 2 - 71250 mm 2 other values within this range.

[0054] Referring back to Figure 5 , in a specific arrangement, the end cover 310 is a rectangular plate body, 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. In a specific installation, the lower plastic 320 enters the accommodation space 120 from the opening 110, and the end cover 310 is then welded with the shell 100.

[0055] In order to avoid the laser from hitting other components inside the shell 100 during the laser welding of the end cover 310 and the shell 100, and to avoid the laser from hitting the lower plastic 320, in an exemplary embodiment, the distance between the edge of the lower plastic 320 and the edge of the end cover 310 along the length direction of the lower plastic 320 is a first distance value L1, and the range of L1 is 1 mm-1.5 mm. In a specific arrangement, the range of L1 can be 1.1 mm-1.35 mm, 1.4 mm-1.5 mm, and the range of L1 can also belong to other range intervals within the range of 1 mm-1.5 mm. Exemplarily, 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, and any value within the range of 1 mm-1.5 mm. The distance between the edge of the lower plastic 320 and the edge of the end cover 310 along the width direction of the lower plastic 320 is a second distance value H1, and the range of H1 is 1 mm-5 mm. In a specific arrangement, the range of H1 can be 1.5 mm-3.5 mm, 4.0 mm-4.9 mm, and the range of H1 can also belong to other range intervals within the range of 1 mm-5 mm. Exemplarily, the specific value of H1 can be 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.3 mm, 4.5 mm, 4.8 mm, and any value within the range of 1 mm-5 mm.

[0056] Through the above setting, the edge of the lower plastic 320 and the edge of the end cover 310 have a gap, so that the lower plastic 320 does not interfere with the shell 100 during entering the shell 100, thereby facilitating the packaging between the end cover 310 and the shell 100. On the other hand, by setting the first distance value of the lower plastic 320 and the end cover 310 in the range of 1mm-1.5mm, and the second distance value in the range of 1mm-5mm, when the end cover 310 and the shell 100 are packaged, during the laser welding process between the end cover 310 and the shell 100, the laser is not easy to avoid the lower plastic 320 to hit other components on the shell 100, thereby improving the safety of the secondary battery 10 during installation.

[0057] It should be emphasized that the first corner of the lower plastic 320 is set to be a circular arc type, and the second corner of the end cover 310 is set to be chamfered, and the straight line distance between the center point of the first corner and the center point of the second corner is a third distance, that is, D, which is greater than the first distance and the second distance.

[0058] Technical effect embodiment

[0059] To effectively support the beneficial effects of the present application, further test data is provided as follows in Table 1.

[0060] Table 1

[0061]

[0062] As shown in Table 1, according to the scheme of the present application, five kinds of lower plastics 320 are designed. In the table, the area unit is mm 2 , the length dimension unit is mm, A is the first area, B is the second area, C is the third area, S1 is the area of the end cover 310, S2 is the area surrounded by the outer contour of the lower plastic 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. Through the above setting, the strength of the lower plastic 320 can be improved without affecting the exhaust efficiency, the backflow efficiency, and the safety during welding of the end cover 310 and the shell 100. Specific comparative examples are shown in Table 2

[0063] Table 2

[0064]

[0065] As shown in Table 2, Table 2 designs five kinds of lower plastic structures for comparison. In the table, the area unit is mm 2 , the length dimension unit is mm, A is the first area, B is the second area, C is the third area, S1 is the area of the end cover 310, S2 is the area surrounded by the outer contour of the lower plastic 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.

[0066] The first area of the exhaust vent hole and the backflow vent hole in the lower plastic structure numbered 6-8 in the end cover orthographic projection accounts for less than 2% of the end cover area, the second area of the exhaust vent hole in the end cover orthographic projection accounts for less than 1% of the end cover area, and the third area of the backflow vent hole in the end cover orthographic projection accounts for less than 0.5% of the end cover area. Through the above setting, when the battery needs to exhaust to relieve pressure, the gas flow efficiency is low, the exhaust speed is slow, and it is easy to cause secondary explosion of the battery. On the other hand, when the electrolyte needs to flow from the backflow vent hole to the bare battery cell, the flow rate is reduced, affecting the efficiency.

[0067] It should be noted that the first area of the lower plastic structure numbered 9-10 accounts for more than 10% of the end cover area, the second area accounts for more than 5% of the end cover area, and the third area accounts for more than 3% of the end cover area. Through the above setting, the lower plastic structure is provided with too many vent holes, and the lower plastic structure has a large amount of deformation after strength tests such as stretching and compression, so that the lower plastic structure is difficult to meet the requirements.

[0068] In summary, taking Table 1 as an example, the rationality of the lower plastic structure designed according to the scheme of the present application can be obtained.

[0069] The technical features of the above-mentioned embodiments can be combined in any way. In order to make the description simple, all possible combinations of the technical features in the above-mentioned embodiments are not described, but as long as the combination of the technical features does not exist contradictory, it should be considered as the scope of the present application.

[0070] The above-mentioned embodiments only express several embodiments of the present application, and the description is more specific and detailed, but it should not be understood as a limitation on the scope of the patent application. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, a number of variations and improvements can be made, which are within the scope of the present application. Therefore, the scope of the patent application of the present application should be subject to the appended claims.

Claims

1. A secondary battery, characterized in that, The secondary battery includes a casing, bare cells, and a top cover assembly, wherein: One end of the housing has an opening, and the interior of the housing forms an accommodating space; The bare battery cell is disposed within the accommodating space; The top cover assembly includes an end cover and a lower plastic part disposed on the end cover. The end cover is sealed to the opening and is provided with an explosion-proof valve. The side of the lower plastic part facing away from the end cover faces the bare battery cell. The lower plastic part has a vent hole communicating with the explosion-proof valve. The side of the lower plastic part near the end cover has a receiving tank for temporarily storing electrolyte. The bottom of the receiving tank has a return flow hole. The first area of ​​the vent hole and the return flow hole projected onto the end cover occupies 2%-10% of the area of ​​the end cover. The area of ​​the end cover is 4200 mm². 2 -75000mm 2 .

2. The secondary battery according to claim 1, characterized in that, The number of exhaust vents is multiple, and the multiple exhaust vents are spaced apart. The second area of ​​the orthographic projection of all the exhaust vents on the end cap occupies 1%-5% of the area of ​​the end cap, and the range of the second area is 42mm. 2 -3750mm 2 .

3. The secondary battery according to claim 1, characterized in that, The number of return flow holes is multiple, and the multiple return flow holes are divided into two groups. The two groups of return flow holes are respectively located at both ends of the lower plastic. The third area of ​​the orthographic projection of all the return flow holes on the end cap occupies 0.5%-3% of the area of ​​the end cap, and the range of the third area is 21mm. 2 -2250mm 2 .

4. The secondary battery according to claim 1, characterized in that, The secondary battery further includes a connecting piece, and the lower plastic includes a body and bosses disposed at both ends of the body, wherein: The body is connected to the end cap, the side of the protrusion away from the body faces the bare cell, and the side of the body away from the end cap and the side of the protrusion away from the body have a set height. The connecting piece is disposed on the body and spaced apart from the boss. The connecting piece is also connected to the bent tab on the bare battery cell. The set height is the sum of the thickness of the connecting piece and the reserved height of the bent tab.

5. The secondary battery according to claim 4, characterized in that, The set height range is 1.76mm-5.82mm.

6. The secondary battery according to claim 4, characterized in that, The bent tab includes multiple single-electrode plates connected in sequence. The reserved height is the product of the thickness of the single-electrode plate, the number of single-electrode plates, and a set coefficient, wherein the set coefficient ranges from 3 to 6.

7. The secondary battery according to claim 4, characterized in that, The thickness of the connecting piece ranges from 0.5mm to 1.5mm.

8. The secondary battery according to claim 1, characterized in that, The fourth area enclosed by the outer contour of the lower plastic on the orthographic projection of the end cap occupies 85%-95% of the area of ​​the end cap, and the range of the fourth area is 3570 mm. 2 -71250mm 2 .

9. The secondary battery according to claim 1, characterized in that, Along the length of the lower plastic, the distance between the edge of the lower plastic and the edge of the end cap is a first distance value, and the first distance value is in the range of 1mm-1.5mm; Along the width direction of the lower plastic, the distance between the edge of the lower plastic and the edge of the end cap is a second distance value, and the second distance value ranges from 1mm to 5mm.

10. The secondary battery according to claim 9, characterized in that, The first corner of the lower plastic is rounded, and the second corner of the end cap is chamfered. The straight-line distance between the center point of the first corner and the center point of the second corner is a third distance, which is greater than the first distance and the second distance.

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