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 through hole provided with an anti-explosion valve is formed in the end cover, the side, away from the end cover, of the lower plastic faces the naked battery cell, an exhaust through hole communicated with the anti-explosion valve is formed in the lower plastic, and the area of the anti-explosion valve through hole accounts for 1.5%-8% of the area of the end cover. The second area of the orthographic projection of all the exhaust through holes on the end cover accounts for 1%-5% 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 field of energy storage technology, and in particular to a secondary battery. Background Art

[0002] Lithium batteries have the advantages of small size, high energy density, long service life, and green environmental protection. They are widely used in industries such as automobiles, electronic products, and energy storage systems.

[0003] At present, during the use of lithium batteries, on the one hand, due to overcharging, over-discharging, short circuit or harsh environment, a large amount of gas will be generated inside the lithium battery, and the temperature of the lithium battery will also rise sharply, thereby increasing the internal pressure of the lithium battery, posing a certain danger to the user; on the other hand, the shaking of the lithium battery will cause part of the electrolyte to splash onto the surface of the lower plastic facing the end cover, thereby accumulating liquid on the surface of the lower plastic or in the groove, causing waste of electrolyte. Summary of the invention

[0004] Based on this, it is necessary to provide a secondary battery to address the problems of explosion risk and electrolyte waste during the use of current lithium batteries.

[0005] A secondary battery, the secondary battery comprising a shell, a bare cell and a top cover assembly, wherein: one end of the shell has an opening, and an accommodating space is formed inside the shell; the bare cell is arranged in the accommodating space; the top cover assembly comprises an end cover and a lower plastic arranged on the end cover, the end cover is sealed and connected to the opening, and an explosion-proof valve through hole with an explosion-proof valve installed is arranged on the end cover, the side of the lower plastic away from the end cover faces the bare cell, the lower plastic is provided with an exhaust through hole connected to the explosion-proof valve, and the area of ​​the explosion-proof valve through hole occupies 1.5% to 8% of the area of ​​the end cover; the number of the exhaust through holes is multiple, the multiple exhaust through holes are arranged at intervals, and the second area of ​​the orthographic projection of all the exhaust through holes on the end cover occupies 1% to 5% of the area of ​​the end cover, and the range of the second area is 42mm 2 -3750mm 2 , the end cover area range is 4200mm 2 -75000mm 2 .

[0006] In one embodiment, a storage tank for temporarily storing electrolyte is provided on one side of the lower plastic near the end cap, and the first area of ​​the orthographic projection of the exhaust through hole and the reflux through hole on the end cap occupies 2%-10% of the area of ​​the end cap, and the range of the end cap area is 4200mm 2 -75000mm 2 .

[0007] In one embodiment, a storage tank for temporarily storing electrolyte is provided on one side of the lower plastic near the end cap, the number of the reflux holes is multiple, the multiple reflux holes are divided into two groups, the two groups of reflux holes are respectively arranged at the two ends of the lower plastic, and the third area of ​​the orthographic projection of all the reflux 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 .

[0008] In one embodiment, the secondary battery also includes a connecting piece, the lower plastic includes a main body and bosses arranged at both ends of the main body, wherein: the main body is connected to the end cover, the side of the boss away from the main body faces the bare battery cell, and the side of the body away from the end cover and the side of the boss away from the main body have a set height; the connecting piece is arranged on the main body and spaced apart from the boss, and the connecting piece is also connected to the bent pole ear on the bare battery cell, and the set height is the sum of the thickness of the connecting piece and the reserved height of the bent pole ear.

[0009] In one embodiment, the set height ranges from 1.76mm to 5.82mm; the bent pole ear includes a plurality of monopole sheets connected in sequence, and the reserved height is the product of the thickness of the monopole sheet, the number of the monopole sheets and the set coefficient, and the set coefficient ranges from 3 to 6; the thickness of the connecting sheet ranges from 0.5mm to 1.5mm.

[0010] In one embodiment, the fourth area enclosed 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, and the range of the fourth area is 3570mm 2 -71250mm 2 ; Along the length direction 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 range of the first distance value is 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 range of the second distance value is 1mm-5mm; the first corner of the lower plastic is set to an arc shape, and a chamfer is set at the second corner of the end cap, 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, and the third distance is greater than the first distance and the second distance.

[0011] In one of the embodiments, the end cover is further provided with two pole through holes penetrating along the thickness direction of the end cover, and along a plane perpendicular to the thickness direction of the end cover, the ratio of the area of ​​each pole through hole to the area of ​​the end cover is 0.5% to 5%.

[0012] In one embodiment, the end cover is a rectangular plate, and the end cover includes two long sides and two short sides, the length of the long side is L, and the length of the short side is H; the minimum distance between the pole through hole and the short side is L3, the ratio of L3 to L is 5% to 25%, the value range of L is 140 mm to 500 mm, and the value range of L3 is 7 mm to 125 mm; the shortest distance between the pole through hole and the long side is H3, the ratio of H3 to H is 12% to 50%, the value range of H is 30 mm to 150 mm, and the value range of H3 is 3.6 mm to 75 mm.

[0013] In one embodiment, the end cover is a rectangular plate, and the end cover includes two long sides and two short sides, the length of the long side is L, and the length of the short side is H; in the length direction of the end cover, the minimum distance between the explosion-proof valve through hole and the short side is L2, the ratio of L2 to L is 30% to 50%, the value range of L is 140mm to 500mm, and the value range of L2 is 42mm to 250mm; in the width direction of the end cover, the shortest distance between the explosion-proof valve through hole and the long side is H2, the ratio of H2 to H is 15% to 50%, the value range of H is 30mm to 150mm, and the value range of H2 is 4.5mm to 75mm.

[0014] In one embodiment, the end cover is a rectangular plate, the end cover includes two long sides and two short sides, the length of the long side is L, and the length of the short side is H; the explosion-proof valve through hole includes two straight sides and two arc-shaped sides, the L:H<3:1, the two straight sides are spaced apart in the length direction of the end cover, the extension direction of the straight sides is the length direction of the explosion-proof valve through hole, and the straight sides are parallel to the short sides of the end cover; or, the explosion-proof valve through hole includes two straight sides and two arc-shaped sides, wherein the L:H≥3:1, the two straight sides are spaced apart in the width direction of the end cover, the extension direction of the straight sides is the length direction of the explosion-proof valve through hole, and the straight sides are parallel to the long sides of the end cover.

[0015] The above-mentioned secondary battery, based on the external dimensions of the end cover, selects the area of ​​the explosion-proof valve through hole and the area of ​​the exhaust through hole that are suitable for the value range, while ensuring that the secondary battery has the ability to quickly release pressure, and ensures the structural strength of the end cover and the lower plastic, thereby being able to take into account both the performance parameter requirements and the safety performance requirements of the secondary battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of the explosion structure of the secondary battery provided in this application.

[0017] Figure 2 This is a schematic diagram of the assembly of the secondary battery provided in this application.

[0018] Figure 3 A schematic diagram of the top view of the end cover of an embodiment provided in the present application.

[0019] Figure 4 This is a schematic diagram of the structure of the lower plastic provided in this application.

[0020] Figure 5 for Figure 4 Cross-sectional view of the lower and middle plastic structure.

[0021] Figure 6 for Figure 4 Top view of the lower and middle plastic structure.

[0022] Figure 7 This is a schematic diagram of the outline structure of the lower plastic and end cover provided in this application.

[0023] Figure 8 It is a schematic structural diagram of an end cover according to another embodiment provided in the present application.

[0024] Fig. 9 It is a schematic structural diagram of an end cover according to another embodiment provided in the present application.

[0025] Fig.10 It is a schematic structural diagram of an end cover according to yet another embodiment provided in the present application.

[0026] Fig.11 Schematic diagram of the connection between the top cover assembly and the bar according to one embodiment of the present application.

[0027] Fig.12 for Fig.11 A side view of the assembly shown.

[0028] Fig.13 It is a schematic diagram of the structure of a bar piece according to an embodiment of the present application.

[0029] Fig.14 for Fig.13 A schematic diagram of the structure of the bar piece at another angle is shown.

[0030] Fig.15 for Fig.13 A top view of the blade shown.

[0031] Fig.16 for Fig.13 Side view of the blade shown.

[0032] in:

[0033] 10. Secondary battery; 100. Shell; 110. Opening; 120. Accommodation space; 200. Bare battery cell; 210. Positive pole; 220. Negative pole; 300. Top cover assembly; 310. End cover; 311. Pole through hole; 312. Explosion-proof valve through hole; 3121. Straight edge; 3122. Arc edge; 313. Long edge; 314. Short edge; 320. Lower plastic; 321. Exhaust through hole; 322. Accommodation groove; 323. Reflux hole; 324. Body; 325. Boss; 400. Bent ear; 500. Explosion-proof valve; 600. Tab; 610. First surface; 620. Second surface; 630. First groove; 640. First connection hole; 650. Second connection hole; 660. Second groove. DETAILED DESCRIPTION

[0034] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0035] In the description of the present application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0036] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0037] In this application, unless otherwise clearly specified and limited, if the terms "installed", "connected", "connected", "fixed" and the like appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0038] In the present application, unless otherwise clearly specified and limited, if there is a description that a first feature is "above" or "below" a second feature, etc., or similar descriptions appear, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0039] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only implementation method.

[0040] See also Figures 1 to 5 As shown, Figure 1 This is a schematic diagram of an exploded structure of a secondary battery 10 provided in an embodiment of the present application. Figure 2 This is a schematic diagram of the assembly of the secondary battery provided in this application. Figure 3 A schematic diagram of the top view of the end cover of an embodiment provided in the present application. Figure 4 This is a schematic diagram of the structure of the lower plastic 320 provided in an embodiment of the present application. Figure 5 for Figure 4 A cross-sectional view of the structure of the middle and lower plastic 320. A secondary battery 10 provided in an embodiment of the present application includes a housing 100, a bare cell 200 and a top cover assembly 300.

[0041] One end of the shell 100 has an opening 110 , and a receiving space 120 is formed inside the shell 100 . The bare battery cell 200 is disposed in the receiving space 120 , and the bare battery cell 200 is used to be electrically connected to an external conductive member.

[0042] The bare cell 200 is filled with an electrolyte, which contains electrolytes and is a carrier for ion transmission in the battery. It is generally composed of lithium salts and organic solvents. During the charging and discharging process of the lithium battery, lithium ions move back and forth between the positive and negative electrodes. The electrolyte is the medium for the back and forth migration and transmission of lithium ions, which creates a potential difference between the positive and negative electrodes of the battery, thereby generating current, and thus enabling the battery to work normally. The positive and negative ears in the bent tabs 400 of the bare cell 200 are connected to the positive column 210 and the negative column 220, respectively.

[0043] 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 sealed and connected to the opening 110, and an explosion-proof valve 500 is disposed on the end cover 310. 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 that is connected to the explosion-proof valve. The lower plastic 320 is also provided with a storage tank 322 for temporarily storing electrolyte on the side close to the end cover 310, and a reflux hole 323 is provided at the bottom of the storage tank 322. In specific use, when the secondary battery 10 has thermal runaway, the explosion-proof valve is opened, and the interior of the secondary battery 10 is connected to the outside through the exhaust through hole 321 for pressure relief.

[0044] refer to Figure 3 The end cover 310 is provided with two pole through holes 311 and explosion-proof valve through holes 312 along its thickness direction. The two pole through holes 311 are used to respectively set the positive pole 210 and the negative pole 220. The two pole through holes 311 are respectively used for the positive pole 210 and the negative pole 220 to pass through and extend to the outside of the shell 100. The explosion-proof valve through hole 313 is used to install the explosion-proof valve 50. When the secondary battery 10 has thermal runaway, the explosion-proof valve 500 can connect the inside of the battery with the outside to relieve pressure. The number of explosion-proof valve through holes 312 is at least 1. The number of explosion-proof valves 500 is at least one.

[0045] For the battery, the size of the electrode through hole 311 determines the size of the cross-sectional area of ​​the positive electrode 210 and the negative electrode 220, and then determines the overcurrent capacity when the battery is electrically connected to an external conductive component. The larger the cross-sectional area of ​​the positive electrode 210 and the negative electrode 220, the stronger the overcurrent capacity.

[0046] The area of ​​the explosion-proof valve through hole 312 limits the pressure relief speed of the explosion-proof valve 500. Specifically, the pressure relief speed of the explosion-proof valve 500 is related to the caliber of the pressure relief channel of the explosion-proof valve 500, that is, the exhaust through hole 321, and the caliber of the pressure relief channel affects the overall size of the explosion-proof valve 500. Therefore, the overall size of the explosion-proof valve 500 is affected by the size of the explosion-proof valve through hole 312. The larger the size of the explosion-proof valve through hole 312, the larger the exhaust through hole 321 may be, which can increase the gas flow rate when the explosion-proof valve 500 is relieved, so that the gas in the battery is discharged faster.

[0047] However, the structural strength of the battery is also extremely important for the safe operation of the secondary battery 10. When the battery is squeezed, it is necessary to ensure that the shell 100 will not collapse, and it is also necessary to ensure that the top cover assembly 300 will not deform. Among them, the size of the pole through hole 311 and the size of the explosion-proof valve through hole 312 cannot be set arbitrarily because they affect the strength of the end cover 310. At the same time, the size of the exhaust through hole 321 directly affects the strength of the lower plastic 320 and the gas release capacity of the secondary battery 10, and it cannot be set arbitrarily. Therefore, how to take into account the performance parameter requirements and safety performance requirements of the battery cell is an issue that cannot be avoided when designing the end cover 310 and the lower plastic 320.

[0048] In view of the above problems, the present application firstly makes the following improvements to the end cover 310 and the lower plastic 320 , so as to ensure the strength of the end cover 310 and the lower plastic while ensuring the pressure relief capability of the secondary battery 10 .

[0049] Specifically, in the present application, the area of ​​the explosion-proof valve through hole 312 occupies 1.5% to 8% of the area of ​​the end cover 310; the number of exhaust through holes 321 is multiple, and the multiple exhaust through holes 321 are arranged at intervals, and the second area of ​​the orthographic projection of all exhaust through holes 321 on the end cover 310 occupies 1% to 5% of the area of ​​the end cover, and the range of the end cover area is 4200mm 2 -75000mm 2 .

[0050] The end cap 310 may be a thin plate structure. Optionally, the end cap 310 is made of aluminum. The end cap 310 is assembled to the housing 100 along the thickness direction. Figure 3 In the figure, the thickness direction of the end cover 310 is perpendicular to the drawing. In the thickness direction of the end cover 310, the end cover 310 includes an inner side and an outer side, wherein the inner side faces the inside of the housing 100 and the outer side faces the outside of the housing 100. The pole through hole 311 and the explosion-proof valve through hole 312 both extend through the inner side and the outer side in the thickness direction. The areas of the inner side and the outer side can be roughly equal.

[0051] In this embodiment, the plane perpendicular to the thickness direction of the end cover 10 is the projection plane. The projection plane can be the plane where the inner side or the outer side is located. The area of ​​the pole through hole 311 can be the area of ​​the positive projection of the pole through hole 311 on the projection plane. The area of ​​the explosion-proof valve through hole 312 can be the area of ​​the positive projection of the explosion-proof valve through hole 312 on the projection plane. The area of ​​the end cover 310 can be the smallest of the areas of the positive projection of the inner side and the outer side on the projection plane.

[0052] In specific configuration, the number of the exhaust holes 321 can be 4, 8, 12 or more, and the shape of the exhaust holes 321 can be any geometric figure, and there is no excessive restriction here. Multiple exhaust holes 321 can increase the exhaust efficiency inside the secondary battery 10 while ensuring the strength of the lower plastic 320.

[0053] For example, in a specific configuration, the area of ​​the end cover 310 ranges from 4200 mm 2 ~15000mm 2, , 15000mm 2 ~45000mm 2, , 5500mm 2 -60000mm 2 , 45000mm 2 ~75000mm 2, ; 65000mm 2 -75000mm 2 The area of ​​the explosion-proof valve through hole 312 can range from 63 mm 2 ~225 mm 2 , 1200mm 2 ~1600 mm 2 , 675mm 2 ~6000mm 2 .

[0054] The second area range is 42mm 2 -3750mm 2 For example, the second area may be in the range of 55 mm 2 -600mm 2 、3250mm 2 -3750mm 2 , the second area range belongs to 42mm 2 -3750mm 2 Other range intervals within this range are also acceptable.

[0055] For example, the area of ​​the end cover 310 may be 4200 mm 2 、5586mm 2 、6600mm2 、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 The area of ​​the explosion-proof valve through hole 312 can be 63mm 2 , 327mm 2 , 393mm 2 , 6000mm 2 The specific value of the second area can be 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 Any one of .

[0056] It should be noted that the area of ​​the end cover 310 , the area of ​​the explosion-proof valve through hole 312 , and the second area are not limited to the specific values ​​provided above.

[0057] In the present application, based on the external dimensions of the end cover 310, by selecting the area of ​​the explosion-proof valve through hole 312 and the area of ​​the exhaust through hole 321 that are suitable for the value range, the structural strength of the end cover 310 and the lower plastic 320 is guaranteed while ensuring that the secondary battery has the ability to quickly release pressure, thereby being able to take into account both the performance parameter requirements and the safety performance requirements of the secondary battery.

[0058] Considering that the opening of the reflux hole 323 also has a certain influence on the strength of the lower plastic 320, in some embodiments, the first area of ​​the orthographic projection of the exhaust hole 321 and the reflux hole 323 on the end cover 310 occupies 2%-10% of the area of ​​the end cover 310. The area of ​​the end cover 310 is 4200mm 2 -75000mm 2 According to the above 2%-10% ratio, the first area is 84mm 2 -7500mm 2 In specific settings, the first area can be 550mm 2 -6000mm 2 、6500mm 2 -7500mm 2 , the first area range belongs to 84mm 2 -7500mm 2 Other range intervals within this range are also acceptable.

[0059] The specific value of the first area may be 84 mm 2 、279mm 2 、660mm 2 、779mm 2 、885mm 2 、998mm 2 、1020mm 2 、1140mm 2 、1305mm 2 、2250mm 2 、3380mm 2 、4358mm 2 、5550mm 2 、6250mm 2 、7040mm 2 、7500mm 2 Any one of .

[0060] 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 may be 4200 mm 2 -75000mm 2 For other values ​​within this range, the first area can be 84mm 2 -7500mm 2 Other values ​​within this range.

[0061] The secondary battery 10 is provided with an exhaust hole 321 connected to the explosion-proof valve by setting the lower plastic 320. When the pressure inside the battery increases, the exhaust hole 321 flows to the explosion-proof valve for pressure relief to prevent the secondary battery 10 from exploding. A storage tank 322 for temporarily storing electrolyte is provided on one side of the lower plastic 320 close to the end cover 310, and a reflux hole 323 is provided at the bottom of the storage tank 322. When the battery shakes and causes part of the electrolyte to splash onto the surface of the lower plastic 320 facing the end cover 310, the electrolyte will flow to the storage tank 322 and then flow from the reflux hole 323 at the bottom of the storage tank 322 to the bare battery cell 200, thereby avoiding the waste of electrolyte. In addition, the exhaust hole 321 and the reflux hole 323 are provided on the first area of ​​the positive projection of the end cover 310, which occupies 2%-10% of the area of ​​the end cover 310. The area range of the end cover 310 is 4200mm. 2 -75000mm 2 , achieving the goal of not affecting the strength of the lower plastic 320 while reducing the weight of the lower plastic 320 .

[0062] In order to increase the path of electrolyte reflux to the bare cell 200 without affecting the structural strength of the lower plastic 320, a preferred embodiment is that the number of reflux holes 323 is multiple, and the multiple reflux holes 323 are divided into two groups. The two groups of reflux holes 323 are respectively arranged at the two ends of the lower plastic 320. In the specific setting, the two groups of reflux holes 323 are distributed on both sides of the exhaust through hole 321. The number of reflux holes 323 in each group can be 4, 8, 12 or more. The shape of the reflux holes 323 can be any geometric figure, and there are no excessive restrictions here. The third area of ​​the positive projection of all reflux holes 323 on the end cover 310 occupies 0.5%-3% of the area of ​​the end cover 310, and the range of the third area is 21mm 2 -2250mm 2 , for example, the third area may range from 165 mm 2 -1800mm 2 、1950mm 2 -2250mm 2 , the third area range belongs to 21mm 2 -2250mm 2 Through the above arrangement, when the battery shakes and part of the electrolyte splashes onto the surface of the lower plastic 320 facing the end cover 310, the electrolyte will flow to the receiving grooves 322 at both ends of the lower plastic 320, and then flow from the return flow holes 323 at the bottom of the receiving grooves 322 to the bare battery 200, thereby greatly avoiding the waste of electrolyte.

[0063] In specific settings, the specific value of the third area can be 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. For example, the third area can also be 21mm 2 -2250mm 2 Other values ​​within this range.

[0064] In order to design the lower plastic 320 more conveniently, a preferred embodiment is that the lower plastic 320 includes a main body 324 and bosses 325 arranged at both ends of the main body 324, the main body 324 is connected to the end cover 310, and the side of the boss 325 away from the main body 324 faces the bare battery cell 200. In the specific setting, a portion of the surface of the main body 324 facing the end cover 310 that is opposite to the boss 325 is provided with a receiving groove 322, and the depth of the receiving groove 322 extends along the height direction of the boss 325 and does not penetrate the boss 325, so that the receiving groove 322 can accommodate the splashed electrolyte.

[0065] During 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 abuts against the bare battery 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 the connecting piece is also connected to the bent pole ear 400 on the bare battery cell 200. It is not difficult to understand that the connecting piece and the bent pole ear 400 are located between the body 324 and the bare battery 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 pole ear 400 is affected by the height of the body 324 and the set height.

[0066] In order to reasonably design the height of the body 324 , specifically, the height of the body 324 is preferably 1 mm, so as to ensure the connection strength between the body 324 and the end cover 310 while not affecting the installation space of the connecting piece and the bent tab 400 .

[0067] In order to reasonably design the set height, specifically, the set height is set to the sum of the thickness of the connecting piece and the reserved height of the bent tab 400. More specifically, the thickness range of the connecting piece is between 0.5mm-1.5mm. For example, the thickness range of the connecting piece can be 0.85mm-1mm, 1.1mm-1.5mm, and the thickness range of the connecting piece can be 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, and 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 other values ​​within the range of 0.5mm-1.5mm.

[0068] The bent tab 400 includes a plurality of monopolar sheets connected in sequence, and the reserved height is the product of the thickness of the monopolar sheet, the number of the monopolar sheets, and the set coefficient, and the set coefficient range is 3-6. In specific settings, the thickness of the monopolar sheet is preferably 0.012 mm, and the number of the monopolar sheets is preferably in the range of 35-60. It should be noted that the number of monopolar sheets can be any one of 36, 38, 40, 42, 44, 46, 48, 50, 52, 54, 55, 56, 58, and 60, but the number of monopolar sheets is not limited to the specific values ​​provided above, such as the number of monopolar sheets can be any other integer in the range of 35-60.

[0069] Through the above settings, the range of the set height is 1.76mm-5.82mm. Exemplarily, the range of the set height can be 1.8mm-3.85mm, 3.9mm-5.8mm, and the range of the set height belongs to other range intervals within the range of 1.76mm-5.82mm. The specific value of the set height can be 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 any one of 1.76mm-5.82mm. It should be noted that when the set height is lower than 1.76 mm, the installation space between the connecting plate and the bent pole ear 400 will be too small, thereby increasing the probability of short circuit caused by pole ear tearing and pole ear insertion; when the set height is lower than 5.82 mm, it will affect the height setting of the bare battery cell 200 in the accommodating space 120 and affect the power of the secondary battery 10.

[0070] 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 The following is a schematic diagram of the outline structure of the lower plastic 320 and the end cap 310 provided in an embodiment of the present application. In order to ensure that the lower plastic 320 has excellent insulation performance while reducing the weight of the lower plastic 320, 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 3570mm 2 -71250mm 2 In specific settings, the fourth area can be 4950mm 2 -54000mm 2 、58500mm 2 -67500mm 2 , the fourth area range belongs to 3570mm 2 -71250mm 2 Other range intervals within this range are also acceptable.

[0071] For example, the specific value of the fourth area may be 4748 mm 2 、5610mm 2 、6622mm 2 、7530mm 2 、8488mm 2 、8673mm 2 、9690mm 2 、10234mm 2 、11097mm 2 、19125mm 2 、28730mm 2 、41409mm 2 、52725mm 2 、59375mm 2 、66880mm 2 、71250mm 2 It should be noted that the fourth area is not limited to the specific values ​​provided above, such as the fourth area can also be 3570mm 2 -71250mm 2 Other values ​​within this range.

[0072] See again Figure 5In a specific configuration, 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. In a specific installation, the lower plastic 320 enters the accommodating space 120 from the opening 110, and the end cover 310 is welded to the housing 100.

[0073] In order to prevent the laser from avoiding the lower plastic 320 and hitting other components in the shell 100 during the laser welding of the end cover 310 and the shell 100, in a preferred embodiment, along the length direction of the lower plastic 320, the distance between the edge of the lower plastic 320 and the edge of the end cover 310 is a first distance value, i.e., L1, and the range of L1 is 1mm-1.5mm. In specific settings, the range of L1 can be 1.1mm-1.35mm, 1.4mm-1.5mm, and the range of L1 within the range of 1mm-1.5mm is also acceptable. Exemplarily, the specific value of L1 can be any value among 1.1mm, 1.15mm, 1.2mm, 1.25mm, 1.3mm, 1.35mm, 1.4mm, 1.45mm, 1.48mm and 1mm-1.5mm; along the width direction of the lower plastic 320, the distance between the edge of the lower plastic 320 and the edge of the end cap 310 is the second distance value, i.e., H1, and the range of H1 is 1mm-5mm. In specific settings, the range of H1 can be 1.5mm-3.5mm, 4.0mm-4.9mm, and any other range intervals within the range of 1mm-5mm are acceptable. Exemplarily, the specific value of H1 can be any value among 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.3mm, 4.5mm, 4.8mm and 1mm-5mm.

[0074] Through the above configuration, there is a gap between the edge of the lower plastic 320 and the edge of the end cap 310, so that the lower plastic 320 will not interfere with the shell 100 during the process of entering the shell 100, thereby facilitating the packaging between the end cap 310 and the shell 100. On the other hand, by setting the first distance value between the lower plastic 320 and the end cap 310 to be in the range of 1mm-1.5mm and the second distance value to be in the range of 1mm-5mm, when the end cap 310 and the shell 100 are packaged, during the laser welding process between the end cap 310 and the shell 100, the laser will not easily avoid the lower plastic 320 and hit other components of the shell 100, thereby improving the safety of the secondary battery 10 during installation.

[0075] It should be emphasized that the first corner of the lower plastic 320 is set to be an arc shape, and the second corner of the end cover 310 is chamfered. The straight-line distance between the center point of the first corner and the center point of the second corner is the third distance D, which is greater than the first distance and the second distance.

[0076] In order to strongly support the beneficial effects of this application, further experimental data are provided as shown in Table 1 below.

[0077] Table 1

[0078]

[0079] As shown in Table 1, according to the solution of this application, five types of lower plastics 320 are designed. The area unit in the table 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 settings, it is possible to improve the exhaust efficiency, the reflux efficiency, and the safety of the end cover 310 and the housing 100 when welding without affecting the strength of the lower plastic 320.

[0080] The specific comparative example is shown in Table 2

[0081] Table 2

[0082]

[0083] As shown in Table 2, five lower plastic structures are designed for comparison. The area unit in the table 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 enclosed 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.

[0084] Among the lower plastic structures numbered 6-8, the first area of ​​the exhaust through hole and the reflux through hole in the orthographic projection of the end cap accounts for less than 2% of the end cap area, the second area of ​​the orthographic projection of the single exhaust through hole in the end cap accounts for less than 1% of the end cap area, and the third area of ​​the orthographic projection of the single reflux through hole in the end cap accounts for less than 0.5% of the end cap area. Through the above arrangement, when the battery needs to be vented for pressure relief, the gas flow efficiency is low and the exhaust speed is slow, which can easily lead to secondary explosion of the battery. On the other hand, when the electrolyte needs to flow from the reflux through hole to the bare battery cell, the flow rate is reduced, affecting the efficiency.

[0085] It should be noted that, for the lower plastic structure No. 9-10, the first area occupies more than 10% of the end cap area, the second area occupies more than 5% of the end cap area, and the third area occupies more than 3% of the end cap area. Through the above arrangement, too many through holes are opened on the lower plastic structure, and the lower plastic is greatly deformed after tensile and compression strength tests, so that the lower plastic is difficult to meet the requirements.

[0086] In summary, it can be concluded that, taking Table 1 as an example, the rationality of the lower plastic structure designed according to the solution of the present application is reasonable.

[0087] Furthermore, in order to take into account both the current carrying capacity and the safety performance of the secondary battery, the present application improves the design of the pole through hole 311 of the end cover 310 in the following manner.

[0088] Specifically, refer to Figure 2 , along the plane perpendicular to the thickness direction of the end cover 310, define the area of ​​each pole through hole 311 as E, the area of ​​the explosion-proof valve through hole 312 as F, and the area of ​​the end cover 310 as S1, where the ratio of E to S1 is 0.5% to 5%, and the ratio of F to S1 is 1.5% to 8%; where the value range of E is 21mm 2 ~3750mm 2 ; F value range 63mm 2 ~6000mm 2 ; S1 value range 4200 mm 2 ~75000 mm 2 .

[0089] In specific settings, the value range of S1 is 4200mm 2 ~15000mm 2, , 15000mm 2 ~45000mm 2, , 45000mm 2 ~75000mm 2, The value range of E can be 21mm 2 ~450 mm 2 , 750mm 2 ~1350mm 2 , 2250mm 2 ~3750mm 2 The F value range can be 63mm 2 ~225 mm 2 , 1200mm 2 ~1600 mm 2 , 675mm 2 ~6000mm 2 . Optionally, the value of E can be 21mm2 , 28.26mm 2 , 283mm 2 , 3750mm 2 The value of F can be 63mm 2 , 327mm 2 , 393mm 2 , 6000mm 2 The value of S1 can be 4200mm 2 , 5586mm 2 ,7791mm 2 or 12040 mm 2 ;75000mm 2 .

[0090] It should be noted that the end cover 310 can be in any shape and is not limited here.

[0091] In some embodiments, the end cover 310 is a rectangular plate, and the end cover 310 includes two long sides 313 and two short sides 314 . The length of the long side 313 is L, and the length of the short side 314 is H.

[0092] Specifically, the inner side and the outer side of the end cover 310 may be substantially rectangular. The four vertex angles of the end cover 310 may be right angles or rounded angles, which are not limited here.

[0093] The two long sides 313 are arranged opposite to each other, and the two short sides 314 are arranged opposite to each other. The length direction of the end cover 310 is the extension direction of the long sides 313, and the width direction of the end cover 310 is the extension direction of the short sides 314. In this embodiment, the rectangular plate can be suitable for square batteries.

[0094] In some embodiments, in the length direction of the end cover 310, the minimum distance between the explosion-proof valve through hole 312 and the short side 314 is L2, the ratio of L2 to L is 30% to 50%, the value range of L is 140 mm to 500 mm, and the value range of L2 is 42 mm to 250 mm. For example, the value range of L is 140 mm to 200 mm, or 200 mm to 500 mm. The value range of L2 is 42 mm to 100 mm, or 100 mm to 150 mm, or 150 mm to 250 mm.

[0095] Optionally, the value of L can be 140mm, 159mm, 220mm, 400mm, 500mm. The value of L2 can be 42mm; 71.5mm; 95mm; 195mm, 250mm.

[0096] In some embodiments, in the width direction of the end cover 310, the shortest distance between the explosion-proof valve through hole 312 and the long side 313 is H2, the ratio of H2 to H is 15% to 50%, the value range of H is 30 mm to 150 mm, and the value range of H2 is 4.5 mm to 75 mm. Exemplarily, the value range of H is 30 mm to 50 mm, or 50 mm to 80 mm, or 80 mm to 150 mm. The value range of H2 is 4.5 mm to 18 mm, or 20 mm to 50 mm, or 50 mm to 75 mm.

[0097] Optionally, the value of H can be: 30mm, 40mm, 70mm, 109mm, 120mm, 150mm. The corresponding values ​​of H2 can be: 4.5mm; 10.5mm; 21mm, 52mm, 56mm, 75mm. Whether the explosion-proof valve 500 is too close to the long side 313 or too close to the short side 314, it is not conducive to the installation of the explosion-proof valve 500, and may also affect the strength of the edge area of ​​the end cover 310 and the structural strength of the end cover 310.

[0098] To this end, the ratio of the minimum distance L2 between the explosion-proof valve through hole 312 and the short side 314 to the length L of the long side 313 is 30% to 50%. In this way, there is enough distance between the explosion-proof valve through hole 312 and the short side 314, and the space can also be used to set the pole through hole 311. The ratio of the minimum distance H2 between the explosion-proof valve through hole 312 and the long side 313 to the length H of the short side 314 is 15% to 50%. When the short side 314 is relatively small, it is ensured that the explosion-proof valve through hole 312 is not too close to the long side 313.

[0099] In some embodiments, the minimum distance between the pole through hole 311 and the short side 314 is L3, the ratio of L3 to L is 5% to 25%, the value range of L is 140 mm to 500 mm, and the value range of L3 is 7 mm to 125 mm. Exemplarily, the value range of L is 140 mm to 200 mm, or 200 mm to 500 mm. The value range of L3 is 7 mm to 30 mm, or 40 mm to 75 mm, or 80 mm to 125 mm.

[0100] Optionally, the value of L can be 140mm, 159mm, 220mm, 400mm, 500mm. The value of L3 can be 7mm, 21.5mm, 35mm, 89mm, or 125mm.

[0101] In some embodiments, the shortest distance between the pole through hole 311 and the long side 313 is H3, the ratio of H3 to H is 12% to 50%, the value range of H is 30 mm to 150 mm, and the value range of H3 is 3.6 mm to 75 mm. For example, the value range of H is 30 mm to 50 mm, or 50 mm to 80 mm, or 80 mm to 150 mm. The value range of H3 is 3.6 mm to 20 mm, or 30 mm to 45 mm, or 45 mm to 75 mm.

[0102] Optionally, the value of H can be: 30mm, 40mm, 70mm, 109mm, 120mm, 150mm. The corresponding value of H3 can be: 3.6mm; 11mm; 15mm, 48.5mm, 55mm; 75mm. The minimum distance between the pole through hole 311 and the long side 313 and the short side 314 is set within the above range, ensuring that the pole through hole 311 is not too close to the long side 313 or too close to the short side 314.

[0103] In some embodiments, such as Figure 2 As shown, the explosion-proof valve through hole 312 includes two straight edges 3121 and two arcuate edges 3122, L:H<3:1, the two straight edges 3121 are spaced apart in the length direction of the end cover 310, and the extension direction of the straight edges 3121 is the length direction of the explosion-proof valve through hole 312. When the explosion-proof valve through hole 312 includes two straight edges 3121 and two arcuate edges 3122, the explosion-proof valve through hole 312 is roughly a waist-shaped hole. The extension direction of the straight edge 3121 is the length direction of the explosion-proof valve through hole 312.

[0104] When the two straight sides 3121 are spaced apart in the width direction of the end cover 310 , the straight side 3121 of the explosion-proof valve through hole 312 is parallel to the short side 314 of the end cover 310 .

[0105] L:H<3:1, the difference between the length dimension of the end cover 310 and the width dimension of the end cover 310 is relatively small. For this reason, the straight side 3121 of the explosion-proof valve through hole 312 is set to be parallel to the short side 314 of the end cover 310. In this way, the explosion-proof valve through hole 312 makes more use of the space in the width direction of the end cover 310, freeing up more space for setting the pole through hole 311 in the length direction.

[0106] The available L:H values ​​are 2.45, 2.5, 2.68, and 2.83.

[0107] In some embodiments, such as Figure 8 As shown, the explosion-proof valve through hole 312 includes two straight edges 3121 and two arcuate edges 3122 , wherein L:H≥3:1, the two straight edges 3121 are spaced apart in the width direction of the end cover 310 , and the extension direction of the straight edges 3121 is the length direction of the explosion-proof valve through hole 312 .

[0108] When the two straight sides 3121 are spaced apart in the width direction of the end cover 310 , the straight side 3121 of the explosion-proof valve through hole 312 is parallel to the long side 313 of the end cover 310 .

[0109] When L:H≥3:1, the dimension of the end cover 310 in the length direction is much larger than the dimension of the end cover 310 in the width direction, and the end cover 310 has a large space in the length direction. For this reason, the straight side 3121 of the explosion-proof valve through hole 312 is set to be parallel to the long side 313 of the end cover 310. In this way, the longitudinal direction of the explosion-proof valve through hole 312 is along the length direction of the end cover 310, so that the explosion-proof valve through hole 312 can make full use of the space on the length of the end cover 310, which has little effect on the structural strength of the end cover 310 and also makes the position arrangement of each through hole on the end cover 310 coordinated.

[0110] Optionally, the L:H values ​​are 3.19, 3.61, 3.77, and 3.86.

[0111] In some embodiments, such as Fig. 9 As shown, in the length direction of the end cover 310 , the explosion-proof valve through hole 312 is located between the two pole through holes 311 , and the two pole through holes 311 are asymmetrically arranged with respect to the explosion-proof valve through hole 312 .

[0112] In the prior art, the two pole through holes 311 are usually symmetrically arranged with respect to the explosion-proof valve through hole 312 , so that the positions of the two pole through holes 311 and the explosion-proof valve through hole 312 are relatively limited, and the design flexibility is insufficient.

[0113] In the present application, under the condition of satisfying the aforementioned dimensional relationship, the two pole through holes 311 do not need to be symmetrically arranged with respect to the explosion-proof valve through hole 312 , and the structural strength of the end cover 310 can still be ensured, thereby providing more options for the design of the end cover 310 .

[0114] Specifically, in this embodiment, Figure 8 As shown, in the length direction of the end cover 310, the explosion-proof valve through hole 312 is centrally arranged. Fig. 9 The distance between the pole through hole 311 on the middle left side and the explosion-proof valve through hole 312 is slightly closer; Figure 4 The distance between the pole through hole 311 on the middle right side and the explosion-proof valve through hole 312 is slightly far.

[0115] In some embodiments, such as Fig.10 As shown, in the length direction of the end cover 310, the explosion-proof valve through hole 312 is not arranged in the center. Specifically, Fig.10 In the embodiment, in the length direction of the end cover 310 , the explosion-proof valve through hole 312 is relatively close to the left end of the end cover, and relatively far away from the right end of the end cover 310 .

[0116] Further, on the basis that the explosion-proof valve through hole 312 is not arranged in the center, the two pole through holes 311 can be arranged symmetrically with respect to the explosion-proof valve through hole 312 ; or can be arranged asymmetrically with respect to the explosion-proof valve through hole 312 .

[0117] In the present application, under the condition of satisfying the aforementioned dimensional relationship, the explosion-proof valve through hole 312 can be arranged in a non-central position, and the structural strength of the end cover 310 can still be ensured, thereby providing more options for the design of the end cover 310 .

[0118] In order to strongly support the beneficial effects of this application, further experimental data are provided as shown in Table 3 below.

[0119] Table 3

[0120]

[0121] As shown in Table 3, according to the scheme of this application, 12 end caps are designed, Examples 11-22. The area unit in the table is mm 2 , length dimension unit is mm. Among the 12 types of end caps 310, the ratio of E to S1 is within 0.5% to 5%, the ratio of F to S1 is within 1.5% to 8%; and the range of E is 21mm 2 ~3750mm 2 ; F value range 63mm 2 ~6000mm 2 ; S1 value range 4200mm 2 ~75000mm 2 .

[0122] In addition, in the preparation of the end caps of Comparative Examples 1 and 2, the ratio of E to S1 is not within the range of 0.5% to 5%; the ratio of F to S1 is not within the range of 1.5% to 8%.

[0123] Strength tests were performed on the 12 end caps of this embodiment and the two end caps of embodiments 23 and 24, and performance tests were performed on the 12 batteries using the 12 end caps and the batteries using the end caps of embodiments 23 and 24. The test results showed that:

[0124] (1) When the end caps 310 were subjected to an extrusion test at 1 MPE pressure, the deformation was less than 1 mm, and the extrusion test passed. When the end caps of Examples 23 and 24 were subjected to an extrusion test, the deformation was 1.5 mm and 1.6 mm, respectively, and the deformation was greater than 1 mm.

[0125] (2) Test the overcurrent capacity of the positive pole 210 and the negative pole 40. Taking copper as an example, the overcurrent is ≤8E / mm 2 , that is, the maximum overcurrent can be 8E / mm 2, which meets the design requirements. In Examples 23 and 24, the overcurrent capacity of the adaptable positive and negative poles is greater than 8E / mm 2 .

[0126] (3) The thermal runaway test was performed on each battery, and all the batteries passed the thermal runaway test, indicating that the size of the explosion-proof valve through hole 312 is reasonable. In Examples 23 and 24, the thermal runaway test was not passed, and the battery shells of Examples 23 and 24 all had different degrees of cracking and deformation.

[0127] From the above comparative analysis, it can be seen that although the comparative example can achieve better current carrying capacity of the pole, it cannot take into account the safety requirements of the battery. However, the structural design of the end cover of the embodiment of the present application can take into account the performance parameter requirements of the battery cell while also taking into account the safety issues of the battery.

[0128] When the secondary battery is used, a plurality of batteries are generally connected in series and in parallel through a bar 600, and the bar can connect the poles of two adjacent batteries. Alternatively, the battery is connected to a signal acquisition circuit through a bar. Fig.11 and Fig.12 As shown, the connection state between the bar piece 600 and the positive electrode column 210 assembled in the top cover assembly 300 is illustrated.

[0129] The existing long bar is closely attached to the surface of the battery cell pole, but the battery cell pole is getting shorter and shorter, and the battery cell pole will heat up seriously under high power or high current conditions, and there is a lack of corresponding heat dissipation channels or methods. At the same time, the bar needs to be connected to the charging and discharging equipment wires during the performance test of large battery cells. Since the battery cells are getting bigger and bigger, and their working conditions are getting closer to high power or high current, the charging and discharging equipment wires are particularly thick. For the bar made of pure aluminum, the weight of the wires can easily crush the bar, especially when the charging and discharging reaches certain conditions, the temperature of the bar itself increases due to the high current, which further reduces its strength. Therefore, it is easy to deform and bend after the test. At the same time, when conducting safety tests, before the battery cell fails, the bar sometimes causes its strength to decrease due to the high temperature, so that the battery cell test is not completed, and the bar breaks.

[0130] In view of the above problems, the present application also improves the bar 600. Figures 13 to 16As shown, in one embodiment of the present application, the bar sheet 600 includes a first surface 610 and a second surface 620 opposite to each other in the thickness direction. A first groove 630 is provided on the first surface 610, and the outer wall of the bottom of the first groove protrudes from the second surface by a height H4, wherein the range of H4 is 0.5-2 mm. The bar sheet is also provided with a first connection hole 640 and a second connection hole 650 penetrating the bar sheet along its thickness direction, and the first connection hole 640 and the second connection hole 650 are arranged at intervals along the length direction of the bar sheet 600. The first connection hole 640 is opened on the inner wall of the bottom of the first groove 630 and penetrates the bottom of the first groove 630.

[0131] Specific to Fig.15 In the embodiment, the length direction of the tab 600 is along the left-right direction, and the width direction of the tab 600 is along the up-down direction. The length dimension of the tab is L5, and the width dimension is H5. The first connection hole 640 is used to connect with the positive pole 210 of the battery, and the two can be connected by welding. The second connection hole 650 can be used to connect with the pole of another battery.

[0132] The first groove 630 is provided on the first surface 610 and the bottom of the groove protrudes from the second surface 620. Thus, when viewed from the second surface 620 of the tab 600, the tab 600 forms a boss near the first connection hole 640. The top surface of the boss, i.e., the outer wall of the bottom of the first groove 630, is welded to the positive electrode column 210. The shape of the boss is not limited and may be round or square.

[0133] Exemplarily, the range of H4 is 0.5-0.8mm, 0.8-1.2mm, 1.2-2mm. H4 can specifically be 0.5mm, 1mm, 1.2mm, 1.5mm, 2mm.

[0134] In the above-mentioned bar sheet 600, reference Fig.12 , Fig.13 The first connection hole 640 is disposed on the inner wall of the bottom of the first groove 630, and the outer wall of the bottom of the first groove 630 is welded to the positive electrode column 210. There is a gap between the area of ​​the bar sheet 600 other than the first groove 630 and the positive electrode column 210, and between the bar sheet 600 and the end cover 310. In this way, there is enough space between the area of ​​the bar sheet 600 other than the first groove 630 and the positive electrode column 210 for heat dissipation of the positive electrode column 630.

[0135] In some embodiments, between the first connection hole 640 and the second connection hole 650, a plurality of second grooves 660 are provided on the first surface 610 along the width direction of the bar sheet, and the outer wall of the bottom of the second groove 660 protrudes from the second surface 620, with a protruding height H6, wherein the range of H6 is 0.2-01mm, and the area S3 of the outer wall of the bottom of all the second grooves 660 is 20%-40% of the area S4 of the bar sheet.

[0136] Exemplarily, the range of H6 may be 0.2-0.5 mm, 0.3-0.6 mm, 0.7-1 mm. H6 may specifically be 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 1 mm.

[0137] Exemplarily, the ratio of the area S3 of the outer wall of the bottom of all the second grooves 660 to the area S4 of the bar 600 is 20%-25%, 23%-30%, 25%-40%. The ratio S4 of the area S3 of the outer wall of the bottom of all the second grooves 660 to the area S4 of the bar 600 can be 20%, 23%, 25%, 30%, 40%.

[0138] In the present application, the first groove 630 and the second groove 660 increase the heat dissipation space, which can enhance the overall heat dissipation capacity of the bar. The first groove 630 and the second groove 660 can be cooled and hardened by extrusion to enhance their mechanical properties. At the same time, the aluminum crystals are elongated by cold hardening to reduce their resistivity and improve their conductivity. Cooling hardening is the process of causing the metal to undergo plastic deformation based on extrusion or stretching at low or normal temperatures. Usually, after cold hardening, the area where the plastic deformation occurs and the vicinity of the area will have bright lines extending to the unprocessed area that are similar to the shape of the deformed area or the shape of the processed workpiece. The range of the lines increases with the degree of processing.

[0139] In some embodiments, the length L5 of the bar piece 600, the distance L6 from the first connecting hole 640 to the edge of the bar piece 600 and the distance L7 from the second connecting hole 650 to the edge of the bar piece 600 in the length direction of the bar piece 600, the ratio of the sum of L6 and L7 to the length L5 of the bar piece 600 is in the range of 15%-20%.

[0140] Exemplarily, the ratio of the sum of L6 and L7 to the length of the bar L5 is in the range of 15%-17%, 16%-18% and 17%-20%. Optionally, the ratio of the sum of L6 and L7 to the length of the bar L5 is 15%, 18%, 20% or 25%.

[0141] Along the length direction, the first connection hole 640 points to the second connection hole 650, which is the current flow direction. In the present application, by setting a bar of suitable length in the opposite direction of the current, the heat dissipation area of ​​the bar itself can be increased, thereby reducing its temperature rise under large current, thereby reducing its resistance, and at the same time, the temperature rise reduction can also effectively prevent the bar from breaking.

[0142] In some embodiments, the thickness H7 of the tab 600 is 3-4 mm; the ratio of the thickness H8 of the bottom of the first groove 630 to the thickness H7 of the tab 600 is in the range of 60%-80%.

[0143] Conventional blade thickness is 1.5mm or 2mm, and the blade thickness of the present invention 600 is increased to 3-4mm, so that the blade current capacity is improved, while reducing its heat generation power, that is, reducing the temperature rise of the blade. At the same time, the increase in thickness can also improve its force bearing capacity. The current capacity of the maximum current path cross section of the blade is ≤4A / mm².

[0144] At the same time, in order to avoid the difficulty of welding with the pole due to the increase of the overall thickness, the bottom of the first groove 630 is also thinned. The ratio of the bottom thickness H8 of the first groove 630 to the thickness H7 of the bar 600 is within the range of 60%-80%, which can ensure both convenient welding and strength.

[0145] Exemplarily, the ratio of the groove bottom thickness H8 of the first groove 630 to the bar thickness H7 ranges from 60% to 65%, 65% to 70%, and 7% to 80%. The ratio of the groove bottom thickness H8 of the first groove 63 to the bar thickness H7 can specifically be 60%, 65%, 70%, 75%, and 80%.

[0146] In order to strongly support the beneficial effects of this application, further experimental data are provided as shown in Table 4 below.

[0147] Table 4

[0148]

[0149] As shown in Table 4, according to the solution of the present application, five types of bar sheets 600 (Examples 25-29) were designed and compared with the bar sheet of the existing design (Example 30). The area unit in the table is mm 2 The length dimension unit is mm. The distance between the two connecting holes of the bar piece of the present application and the bar piece of the prior design is 65 mm.

[0150] Compared with the existing design, the five types of bars in this application can improve the heat dissipation capacity of the bars without affecting the strength of the bars, so that the energy efficiency of the same battery cell is improved by an average of about 2%, and the temperature rise of the pole in normal cycle is reduced by about 5°C.

[0151] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0152] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A secondary battery, characterized in that: The secondary battery comprises a shell, a bare cell and a top cover assembly, wherein: One end of the shell has an opening, and an accommodating space is formed inside the shell; The bare battery cell is arranged in the accommodating space; The top cover assembly includes an end cover and a lower plastic disposed on the end cover, the end cover is sealed and connected to the opening, and an explosion-proof valve through hole with an explosion-proof valve installed is disposed on the end cover, the side of the lower plastic away from the end cover faces the bare battery cell, and the lower plastic is provided with an exhaust through hole connected to the explosion-proof valve, and the area of ​​the explosion-proof valve through hole occupies 1.5% to 8% of the area of ​​the end cover; the number of the exhaust through holes is multiple, and the multiple exhaust through holes are arranged at intervals, and the second area of ​​all the exhaust through holes on the orthographic projection of the end cover occupies 1% to 5% of the area of ​​the end cover, and the range of the second area is 42mm 2 -3750mm 2 , the end cover area range is 4200mm 2 -75000mm 2 .

2. The secondary battery according to claim 1, characterized in that: A storage tank for temporarily storing electrolyte is provided on one side of the lower plastic near the end cover. The first area of ​​the orthographic projection of the exhaust through hole and the reflux through hole on the end cover occupies 2%-10% of the area of ​​the end cover. The area of ​​the end cover is 4200mm 2 -75000mm 2 .

3. The secondary battery according to claim 1, characterized in that: A storage tank for temporarily storing electrolyte is provided on one side of the lower plastic near the end cap. The number of the reflux holes is multiple, and the multiple reflux holes are divided into two groups. The two groups of reflux holes are respectively arranged at the two ends of the lower plastic. The third area of ​​the orthographic projection of all the reflux holes on the end cap occupies 0.5%-3% of the area of ​​the end cap. 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 also includes a connecting piece, and the lower plastic includes a main body and bosses arranged at both ends of the main body, wherein: the main body is connected to the end cover, the side of the boss away from the main body faces the bare battery cell, and the side of the body away from the end cover and the side of the boss away from the main body have a set height; the connecting piece is arranged on the main body and spaced apart from the boss, and the connecting piece is also connected to the bent pole ear on the bare battery cell, and the set height is the sum of the thickness of the connecting piece and the reserved height of the bent pole ear.

5. The secondary battery according to claim 4, characterized in that: The set height ranges from 1.76mm to 5.82mm; the bent pole ear includes a plurality of monopole sheets connected in sequence, and the reserved height is the product of the thickness of the monopole sheet, the number of the monopole sheets and the set coefficient, and the set coefficient ranges from 3 to 6; the thickness of the connecting sheet ranges from 0.5mm to 1.5mm.

6. 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 cover occupies 85%-95% of the area of ​​the end cover, and the range of the fourth area is 3570mm 2 -71250mm 2 ; Along the length direction 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 ranges from 1 mm to 1.5 mm; 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, and the second distance value ranges from 1 mm to 5 mm; The first corner of the lower plastic is set to an arc shape, the second corner of the end cover 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, and the third distance is greater than the first distance and the second distance.

7. The secondary battery according to claim 1, characterized in that: The end cover is also provided with two pole through holes penetrating along the thickness direction of the end cover. Along a plane perpendicular to the thickness direction of the end cover, the ratio of the area of ​​each pole through hole to the area of ​​the end cover is 0.5% to 5%.

8. The secondary battery according to claim 7, characterized in that: The end cover is a rectangular plate, and the end cover includes two long sides and two short sides, the length of the long side is L, and the length of the short side is H; the minimum distance between the pole through hole and the short side is L3, the ratio of L3 to L is 5% to 25%, the value range of L is 140mm to 500mm, and the value range of L3 is 7mm to 125mm; the shortest distance between the pole through hole and the long side is H3, the ratio of H3 to H is 12% to 50%, the value range of H is 30mm to 150mm, and the value range of H3 is 3.6mm to 75mm.

9. The secondary battery according to claim 1, characterized in that: The end cover is a rectangular plate, and the end cover includes two long sides and two short sides, the length of the long side is L, and the length of the short side is H; in the length direction of the end cover, the minimum distance between the explosion-proof valve through hole and the short side is L2, the ratio of L2 to L is 30% to 50%, the value range of L is 140mm to 500mm, and the value range of L2 is 42mm to 250mm; in the width direction of the end cover, the shortest distance between the explosion-proof valve through hole and the long side is H2, the ratio of H2 to H is 15% to 50%, the value range of H is 30mm to 150mm, and the value range of H2 is 4.5mm to 75mm.

10. The secondary battery according to claim 1, characterized in that: The end cover is a rectangular plate, and the end cover includes two long sides and two short sides, the length of the long side is L, and the length of the short side is H; the explosion-proof valve through hole includes two straight sides and two arc-shaped sides, and the L:H is less than 3:1, and the two straight sides are spaced apart in the length direction of the end cover, and the extension direction of the straight sides is the length direction of the explosion-proof valve through hole, and the straight sides are parallel to the short sides of the end cover; or, the explosion-proof valve through hole includes two straight sides and two arc-shaped sides, wherein the L:H is greater than or equal to 3:1, and the two straight sides are spaced apart in the width direction of the end cover, and the extension direction of the straight sides is the length direction of the explosion-proof valve through hole, and the straight sides are parallel to the long sides of the end cover.

Images