Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery comprises a shell and an electrode assembly, the shell comprises a first end wall and a side wall surrounding the first end wall; the electrode assembly is accommodated in the shell and comprises a first tab facing the first end wall; the first end wall comprises a tab connecting part and a side wall connecting part surrounding the tab connecting part, the tab connecting part is in welded connection with the first tab, the side wall connecting part is connected with the end face of the side wall, the wall thickness of the tab connecting part is smaller than that of the side wall connecting part, and the technical problem that welding between the end wall and the tab is prone to failure can be solved.

Description

TECHNICAL FIELD

[0001] The utility model relates to a battery technical field, concretely relates to a secondary battery, battery pack and electronic device. BACKGROUND

[0002] At present, large cylinders are more and more favored by major car enterprises due to their high safety, long service life, excellent fast charging performance, excellent battery consistency and low production cost.

[0003] The periphery of the end wall of the cylindrical battery is sealingly connected with the side wall of the shell, and the middle part of the end wall is weldingly connected with the tab, and the thickness of each position of the end wall is usually consistent. However, when the thick end wall is weldingly connected with the tab, it is difficult to control the accurate welding power, and the power that is too high will scald the diaphragm, and the power that is too low will also appear virtual welding, thereby causing the problem of welding failure. SUMMARY

[0004] The utility model provides a kind of secondary battery, battery pack and electronic device to improve the technical problem that welding between end wall and tab is easy to appear welding failure.

[0005] To achieve the above object and other related purposes, the utility model provides a kind of secondary battery, battery pack and electronic device, the secondary battery includes shell and electrode assembly;The shell includes first end wall and the side wall around first end wall;Electrode assembly is contained in shell, and electrode assembly includes the first tab towards first end wall;First end wall includes tab connecting portion and the side wall connecting portion around tab connecting portion, tab connecting portion is weldingly connected with first tab, side wall connecting portion is connected with the end surface of side wall, and the wall thickness of tab connecting portion is less than the wall thickness of side wall connecting portion.

[0006] In the above technical solution, the wall thickness of the tab connecting portion weldingly connected with the first tab is less than the wall thickness of the side wall connecting portion connected with the side wall, and the wall thickness of the side wall connecting portion is thickly arranged, which is beneficial to the maintenance of the strength of the first end wall on the one hand, and is beneficial to the reliability of the welding quality between the side wall connecting portion and the side wall in the case of welding connection between the side wall connecting portion and the side wall on the other hand. In addition, the thin wall thickness of the tab connecting portion can first reduce the consumption of welding energy, secondly, it is beneficial to control the welding power, thereby reducing the difficulty of welding, and can prevent the problem of diaphragm scalding caused by excessive melting during high-power welding. Thirdly, it can also reduce the possibility of virtual welding. In summary, the technical solution improves the technical problem that welding between end wall and tab is easy to appear welding failure.

[0007] In the secondary battery of the utility model, the inner side of the side wall connecting portion is connected with a recess recessed towards the direction of the electrode assembly, the recess is formed with a protrusion on the side of the first end wall facing the electrode assembly, and the tab connecting portion is located on the bottom wall of the recess.

[0008] In the above technical solution, the recess can be arranged to enable only the relatively flat, thick and circumferential side wall connecting portion at the outermost circle to be in contact with the external plane when the first end wall is placed with one side downward, thereby avoiding the contact between the tab connecting portion with the weld mark on the surface and the external plane, and improving the stability of the secondary battery when the first end wall is placed with one side downward, and protecting the relatively thin tab connecting portion.

[0009] In the secondary battery example of the present application, the side wall connecting portion is welded to the end face of the side wall, and the recess is sunken into the shell.

[0010] In the above technical solution, the recess sunken into the shell can block the laser when the side wall connecting portion is welded to the end face of the side wall.

[0011] In the secondary battery example of the present application, the thickness of the side wall is t1, the thickness of the side wall connecting portion is t2, and 0.8t1≤t2≤1.2t1.

[0012] In the above technical solution, the side wall connecting portion is limited to the range of 0.8t1≤t2≤1.2t1, so that the side wall connecting portion has sufficient thickness to form good welding quality with the side wall, and the structural strength of the first end wall is improved.

[0013] In the secondary battery example of the present application, the thickness of the bottom wall is less than the thickness of the side wall connecting portion, the bottom wall is welded to the side of the side wall connecting portion facing the electrode assembly, and the outer periphery of the bottom wall and the inner periphery of the side wall connecting portion have an overlapping portion.

[0014] In the above technical solution, the recess and the side wall connecting portion of the first end wall are formed by separate welding, which reduces the processing difficulty of forming two different thickness structures on the first end wall; the side of the bottom wall welded to the side wall connecting face facing the electrode assembly can form a recess, which can protect the relatively thin bottom wall.

[0015] In the secondary battery example of the present application, the side of the overlapping portion facing the electrode assembly is provided with a first weld mark.

[0016] In the above technical solution, the first weld mark is formed by welding from the relatively thin bottom wall to the relatively thick side wall connecting portion, which can reduce energy consumption, improve welding precision and welding quality; in addition, the first weld mark is inside the shell, which can also reduce the problem of rusting of the first weld mark exposed outside the shell.

[0017] In the secondary battery example of the present application, a weak portion is provided on the bottom wall, and the weak portion is configured to break when the internal pressure of the secondary battery exceeds a threshold value.

[0018] In the technical scheme, the weak part is arranged on the bottom wall and located in the recess, which is beneficial to better protect the weak part and reduce the possibility of the weak part being damaged in advance due to collision during transportation and use. Since the tab connecting part welded to the first tab is also located on the bottom wall, when the internal pressure of the secondary battery exceeds the threshold value, the weak part is broken, the bottom wall directly explodes to form a pressure relief channel without other obstructions, and the explosion discharge in the shell can be discharged more smoothly from the pressure relief channel. The arrangement improves the pressure relief efficiency and is beneficial to improve the safety performance of the battery.

[0019] In an example of the secondary battery of the utility model, the inner diameter of the side wall is d, the first end wall has an annular area with an inner diameter of 0.6d and an outer diameter of 0.7d, and the weak part is located in the annular area.

[0020] In the technical scheme, the weak part is located in the annular area with an inner diameter of 0.6d and an outer diameter of 0.7d, which is beneficial to form a larger pressure relief area on the first end wall. In addition, the larger the pressure relief area, the thicker the required wall thickness of the corresponding weak part, and the thicker the weak part wall thickness, the more beneficial to the structural strength of the first end wall, and the less likely the weak part is damaged in advance due to collision during transportation and use.

[0021] In an example of the secondary battery of the utility model, the wall thickness of the weak part is e, and 0.1mm≤e≤0.15mm.

[0022] In the technical scheme, the weak part with a wall thickness of 0.1mm≤e≤0.15mm cooperates with the pressure relief area surrounded by weak parts of different sizes to achieve the rupture and pressure relief when the secondary battery exceeds the threshold value, and to meet the requirement of the structural strength of the first end wall.

[0023] In an example of the secondary battery of the utility model, the secondary battery further comprises a protective sheet, the protective sheet is arranged on the side of the first end wall away from the electrode assembly, and the projection of the protective sheet on the first end wall in the height direction of the secondary battery covers the bottom wall.

[0024] In the technical scheme, the bottom wall is provided with a tab connecting part with a welding mark on the surface and a weak part with a relatively thin wall thickness, and the protective sheet is arranged to prevent rust on the welding mark of the tab connecting part and to protect the weak part from being damaged in advance during transportation and assembly.

[0025] In an example of the secondary battery of the utility model, the wall thickness of the side wall connecting part is t2, the wall thickness of the tab connecting part is t3, and 0.5t2≤t3≤0.7t2.

[0026] In the technical scheme, the wall thickness of the tab connecting part is within the range, which reduces the energy consumption of welding, is beneficial to control the welding power, thereby reduces the difficulty of welding, and is also beneficial to improve the precision and quality of welding.

[0027] In the secondary battery example of the utility model, a plurality of groups of welding mark units are formed on the tab connecting part, each group of welding mark units is arranged at intervals around the center of the first end wall, and each group of welding mark units comprises a plurality of second welding marks.

[0028] In the above technical solution, the arrangement mode of the plurality of groups of welding mark units arranged at intervals around the center of the first end wall can facilitate uniform distribution of the current passing through the first tab, thereby enhancing the performance of the secondary battery, and can also improve the welding strength. Each group of welding mark units comprises a plurality of second welding marks, so that the welding mark unit and the first tab have a larger welding area, so as to realize better resistance stability of the secondary battery and facilitate enhancement of the overcurrent capacity.

[0029] In the secondary battery example of the utility model, the shape of the second welding mark is a curve, and the radius of curvature of any point on the curve is greater than or equal to 1 mm.

[0030] In the above technical solution, the radius of curvature of any point on the curve is greater than or equal to 1 mm, so that the welding time at any point during the welding process is uniform, which can improve the uniformity of the size of the molten pool at any point on the second welding mark, and can also make the transition at the corner of the welding track smooth, reducing the risk of burning the diaphragm due to the concentration of welding heat at a certain point.

[0031] The utility model also provides a battery pack, the battery pack includes the secondary battery of any one of the above.

[0032] The utility model also provides an electronic device, the electronic device includes the battery pack.

[0033] The secondary battery of the utility model, the wall thickness of the tab connecting part welded and connected with the first tab is smaller than the wall thickness of the side wall connecting part connected with the side wall, and the wall thickness of the side wall connecting part is relatively thick, which is beneficial to the maintenance of the strength of the first end wall on the one hand, and is beneficial to the reliability of the welding quality between the side wall connecting part and the side wall in the case of welding connection between the side wall connecting part and the side wall on the other hand.In addition, the wall thickness of the tab connecting part is relatively thin, firstly, the consumption of welding energy can be reduced, secondly, the welding power can be controlled, thereby reducing the difficulty of welding, and the problem of diaphragm burn caused by excessive melting during high-power welding can be prevented, and thirdly, the possibility of false welding can also be reduced.In summary, the technical scheme improves the technical problem of welding failure between the end wall and the tab. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application or the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and for those skilled in the art, other embodiments can also be obtained from these drawings without creative labor.

[0035] Figure 1 The whole structure schematic diagram of a secondary battery example of the present application;

[0036] Figure 2 The electrode assembly structure schematic diagram of a secondary battery example of the present application;

[0037] Figure 3 The assembly drawing of the first end wall, the side wall and the electrode assembly of a secondary battery example of the present application;

[0038] Figure 4 The assembly drawing of the first end wall, the side wall, the electrode assembly and the protective sheet of a secondary battery example of the present application;

[0039] Figure 5 The assembly drawing of the first end wall, the side wall and the electrode assembly of a secondary battery example of the present application;

[0040] Figure 6 The assembly drawing of the first end wall, the side wall, the electrode assembly and the protective sheet of a secondary battery example of the present application;

[0041] Figure 7 The schematic diagram of a battery pack example of the present application;

[0042] Figure 8 The schematic diagram of an electronic device example of the present application.

[0043] Element number explanation

[0044] 1. Electronic device; 10. Battery pack; 11. Working part; 101. Box body; 102. Box cover; 100. Secondary battery; 110. Housing; 111. Second end wall; 112. Side wall; 113. Opening; 114. First end wall; 1141. Tab connecting portion; 1142. Side wall connecting portion; 1143. Concave portion; 11431. Bottom wall; 1144. Overlapping portion; 1145. First weld; 1146. Weak portion; 1147. Weld unit; 11471. Second weld; 120. Electrode assembly; 121. Second tab; 1211. Positive current collector; 1212. Second coated area; 1213. Second uncoated area; 122. Separator; 123. First tab; 1231. Negative current collector; 1232. First coated area; 1233. First uncoated area; 124. First tab; 125. Second tab; 130. Pole; 140. Protective sheet. DETAILED DESCRIPTION

[0045] The above and other advantages and effects of the present application will become readily apparent to those of ordinary skill in the art from the following description thereof, taken in conjunction with the accompanying drawings. The present application can also be embodied in many different forms, all of which are not described herein. The various aspects of the present application are not limited to the specific embodiments described herein, but are applicable to any embodiment that falls within the scope of the present application. It should be understood that the embodiments described herein are merely illustrative of the present application and should not be construed to limit the scope of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains. Any methods and materials similar or equivalent to those described herein can be used in the practice of the present application.

[0046] When the embodiments give numerical ranges, it should be understood that, unless the present application indicates otherwise, each numerical range has two endpoints and any number between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the present application pertains and the present application, and any method, equipment and material similar or equivalent to those described in the embodiments of the present application can be used to implement the present application.

[0047] It should be understood that the terms such as "upper", "lower", "left", "right", "middle" and "one" used in the specification are only for the convenience of clear description, and are not intended to limit the scope of the present application. The change or adjustment of the relative relationship without substantial change of the technical content is also regarded as the scope of the present application.

[0048] The secondary battery includes an electrode assembly, which is a component in which electrochemical reactions occur in the secondary battery, and can include one or more electrode assemblies.

[0049] The secondary battery further includes a case including first and second end walls disposed opposite each other and a side wall surrounding the first and second end walls, one end of the side wall having an opening through which the electrode assembly can be fitted into the case, the first end wall being welded to the opening or being connected to the other end of the side wall distal from the opening.

[0050] However, the inventors have found that when the first end wall is welded to the electrode assembly at a conventional wall thickness, it is difficult to control the welding power accurately, and too high a power can scald the separator, and too low a power can result in a false weld, thereby causing welding failure.

[0051] In view of this, the present application provides a technical solution in which the wall thickness of the tab connecting portion welded to the first tab is less than the wall thickness of the side wall connecting portion connected to the side wall, which facilitates control of the welding power and thereby reduces the difficulty of welding, prevents the problem of scalding of the separator caused by excessive melting when high-power welding is performed, and reduces the possibility of a false weld, thereby improving the technical problem of welding failure between the end wall and the tab.

[0052] Please refer to Figures 1 to 8 The present application provides a secondary battery 100, a battery pack 10, and an electronic device 1, the secondary battery 100 including a case 110, an electrode assembly 120, and a pole 130.

[0053] Please refer to Figure 1 and Figures 3 to 6The shell 110 includes a first end wall 114 and a side wall 112 surrounding the first end wall 114, and a second end wall 111 opposite to the first end wall 114 is arranged at the other end of the side wall 112 away from the first end wall 114. The first end wall 114, the second end wall 111 and the side wall 112 can form a stable sealing and electrical connection relationship. The connection between the first end wall 114 and the side wall 112 and the connection between the second end wall 111 and the side wall 112 can be achieved in various ways, such as one-piece stamping, one-piece casting or separate welding. The surrounding of the side wall 112 is not limited, and can be cylindrical or prismatic, or any other closed loop profile that can be matched with the first end wall 114 and the second end wall 111. In the embodiment, the outer edges of the first end wall 114 and the second end wall 111 are circular, the side wall 112 is cylindrical and surrounds the outer edges of the first end wall 114 and the second end wall 111, and one of the second end wall 111 or the first end wall 114 is integrally formed with the side wall 112 and forms a circular opening 113 at the other end of the side wall 112. The second end wall 111 and the side wall 112 form a receiving cavity in the shell 110 for accommodating the electrode assembly 120, electrolyte and other necessary components of the battery. Specifically, the diameter of the shell 110 can be determined according to the specific size of the electrode assembly 120, such as 18mm, 21mm, 46mm, etc. The material of the shell 110 can be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. In order to prevent rusting of the shell 110 during long-term use, a layer of anti-rust material such as metal nickel can be plated on the surface of the shell 110.

[0054] Referring to Figures 1 to 2 The electrode assembly 120 is accommodated in the shell 110 and includes a first tab 124 facing the first end wall 114. Specifically, the electrode assembly 120 is a component that undergoes electrochemical reaction in the secondary battery 100. The shell 110 can contain one or more electrode assemblies 120. The electrode assembly 120 includes a first electrode sheet 123, a second electrode sheet 121 and a separator 122 stacked and wound to form a wound structure. The first electrode sheet 123 and the second electrode sheet 121 have opposite polarities. In some embodiments, the first electrode sheet 123 is a positive electrode sheet and the second electrode sheet 121 is a negative electrode sheet. In other embodiments, the first electrode sheet 123 is a negative electrode sheet and the second electrode sheet 121 is a positive electrode sheet.

[0055] Referring to Figures 1 to 2In this embodiment, the negative electrode tab includes a negative current collector 1231 and a negative active material, and the negative active material is coated on the surface of the negative current collector 1231; the negative current collector 1231 includes a first coated area 1232 coated with the active material and a first uncoated area 1233 not coated with the active material, and the first uncoated area 1233 is located at the end of the first electrode tab 123, and the first uncoated area 1233 extends out of the separator 122 along the winding axis direction of the electrode assembly 120 and is bent towards the winding axis to form a negative electrode tab.

[0056] Referring to Figures 1 to 2 , the positive electrode tab includes a positive current collector 1211 and a positive active material, and the positive active material is coated on the surface of the positive current collector 1211; the positive current collector 1211 includes a second coated area 1212 coated with the active material and a second uncoated area 1213 not coated with the active material, and the second uncoated area 1213 is located at the end of the second electrode tab 121, and the second uncoated area 1213 extends out of the separator 122 along the winding axis direction of the electrode assembly 120 and is bent towards the winding axis to form a positive electrode tab.

[0057] Referring to Figures 1 to 2 , the separator 122 is arranged between the positive electrode tab and the negative electrode tab to separate the positive active material layer and the negative active material layer. Taking the lithium ion secondary battery 100 as an example, the material of the positive current collector 1211 can be aluminum, the positive active material layer includes a positive active material, and the positive active material can be lithium cobaltate, lithium iron phosphate, ternary lithium, or lithium manganate, etc. The material of the negative current collector 1231 can be copper, the negative active material layer includes a negative active material, and the negative active material can be carbon or silicon, etc. The base material of the separator 122 can be polypropylene (PP) or polyethylene (PE), etc. In order to protect and insulate the battery cell, an insulating film can also be wrapped outside the battery cell, and the insulating film can be synthesized by PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other high molecular polymer materials.

[0058] Referring to Figure 1 and Figure 2Further, if the first tab 124 facing the first end wall 114 is a positive or negative tab, then the second tab 125 facing the second end wall 111 is a negative or positive tab. In the present embodiment, the second tab 125 is a positive tab, and the second end wall 111 is electrically connected to the post 130 to make the post 130 positive. The first tab 124 is a negative tab, and the housing 110 is electrically connected to the first tab 124 to make the housing 110 negative. However, in other embodiments, the first tab 124 can be a negative tab and electrically connected to the post 130, and the second tab 125 can be a positive tab and electrically connected to the housing 110.

[0059] Referring to Figure 1 and Figure 2 The post 130 passes through the second end wall 111 and is insulated from the second end wall 111. The post 130 can have any suitable form that allows it to pass through the second end wall 111 and be electrically connected to the first tab 124 or the second tab 125, such as a circular, square, prismatic, or any other suitable cross-section that allows for stable electrical conduction. One end of the post 130 facing the electrode assembly 120 can be directly or indirectly electrically connected to the first tab 124 or the second tab 125. For example, the post 130 can be indirectly electrically connected to the first tab 124 via a current collecting member. The other end of the post 130 can be exposed outside the housing 110 to form a corresponding electrode. The post 130 can be positive or negative. For example, in one embodiment, the post 130 is electrically connected to the first tab 124, and the first tab 124 is a positive tab. In this case, the post 130 is positive, and the housing 110 forms a corresponding negative electrode. In another embodiment, the first tab 124 is a negative tab, and the post 130 is negative. In this case, the housing 110 forms a corresponding positive electrode. In the present embodiment, the second end wall 111 has a post 130 mounting hole, and the post 130 is sealingly and insulatingly mounted in the post 130 mounting hole. The post 130 is indirectly electrically connected to the second tab 125 via a current collecting member. The second tab 125 is a positive tab, and the other end of the post 130 is exposed outside the housing 110 to make the post 130 positive. A second current collecting member is electrically connected to the positive tab. The second current collecting member is preferably made of aluminum.

[0060] The pole 130 is made of a metal material with electrical conductivity. The material of the pole 130 can be aluminum. If the material of the pole 130 is aluminum, the riveting process can be easily performed. In the embodiment, the material of the pole 130 is aluminum, and the pole 130 is a positive electrode. Correspondingly, the shell 110 is made of low-carbon steel and forms a negative electrode. The pole 130 is electrically insulated from the shell 110. The electrical insulation between the pole 130 and the second end wall 111 of the shell 110 can be achieved in various ways. For example, the insulation can be achieved by placing an insulating washer between the pole 130 and the second end wall 111. Alternatively, the insulation can be achieved by forming an insulating coating layer on a portion of the pole 130. Alternatively, some of the above methods can be combined.

[0061] Further, referring to Figures 3 to 6 The first end wall 114 includes a tab connecting portion 1141 and a side wall connecting portion 1142 surrounding the tab connecting portion 1141. The tab connecting portion 1141 and the side wall connecting portion 1142 can be integrally formed or connected in a split structure, which is not limited. The tab connecting portion 1141 is welded to the first tab 124. The welding method can be ultrasonic welding, resistance welding, laser welding, etc., which is not limited. In the embodiment, laser welding is adopted. The side wall connecting portion 1142 is connected to the end face of the side wall 112. The connection can be achieved in various ways, such as integrally stamping, integrally casting, or split welding.

[0062] Referring to Figures 3 to 6 When the tab connecting portion 1141 is welded to the first tab 124, the welding is usually performed from the tab connecting portion 1141 to the first tab 124. If the thickness of the tab connecting portion 1141 is too thick, a higher power is required for welding, and it is difficult to control the appropriate power. If the power is too high, the separator 122 can be burned, causing a short circuit. If the power is too low, the welding can be incomplete. Preferably, the thickness of the tab connecting portion 1141 is less than the thickness of the side wall connecting portion 1142. The thicker thickness of the side wall connecting portion 1142 is beneficial to the strength of the first end wall 114. In the case of welding connection between the side wall connecting portion 1142 and the side wall 112, it is beneficial to ensure the reliability of the welding quality between the side wall connecting portion 1142 and the side wall 112. In addition, the thinner thickness of the tab connecting portion 1141 can reduce the consumption of welding energy. It is beneficial to control the welding power, thereby reducing the difficulty of welding and preventing the problem of burning the separator 122 caused by excessive melting during high-power welding. In addition, it can also reduce the possibility of incomplete welding. In summary, the technical solution improves the technical problem of welding failure between the end wall and the first tab 124.

[0063] It should be noted that, referring toFigures 3 to 6 In some embodiments, the wall thickness of the first end wall 114 is thinner only at the tab connecting portion 1141, and the wall thickness of the side wall connecting portion 1142 and other portions is thicker, which can make the first end wall 114 have better structural strength; in the present embodiment, the wall thickness of the side wall connecting portion 1142 is thicker, and the wall thickness of the tab connecting portion 1141 and other portions is thicker, that is, the thickness of the middle region of the first end wall 114 surrounded by the side wall connecting portion 1142 is uniform and thinner, which can reduce the processing difficulty of the first end wall 114.

[0064] Please refer to Figures 3 to 6 In an example of the secondary battery 100 of the present application, the inner side of the side wall connecting portion 1142 is connected with a recessed portion 1143 recessed towards the direction of the electrode assembly 120, and the recessed portion 1143 is formed with a protrusion on the side of the first end wall 114 facing the electrode assembly 120, which can make only the side wall connecting portion 1142 with a relatively flat surface, thicker thickness and surrounding the outermost circle be in contact with the external plane when the side of the first end wall 114 is placed downward, avoiding the contact between the tab connecting portion 1141 with the welding mark on the surface and the external plane, and can improve the stability of the secondary battery 100 when the side of the first end wall 114 is placed downward. The recessed portion 1143 and the side wall connecting portion 1142 can be integrally stamped or integrally cast, as shown in Figures 3 to 4 The recessed portion 1143 and the side wall connecting portion 1142 can also be in the form of separate welding, as shown in Figures 5 to 6 which is not limited. Further, the tab connecting portion 1141 is located on the bottom wall 11431 of the recessed portion 1143, and the recessed portion 1143 can also play a protective role for the thinner tab connecting portion 1141. It should be noted that the thickness of the bottom wall 11431 of the recessed portion 1143 can be consistent with the wall thickness of the position where the tab connecting portion 1141 is located and be thinner, or the bottom wall 11431 can be provided with a region where the wall thickness of the tab connecting portion 1141 is thinner, which is not limited.

[0065] Please refer to Figures 3 to 6In the secondary battery 100 example of the utility model, the side wall connecting part 1142 and the end surface of the side wall 112 are welded, the welding mode of the side wall connecting part 1142 and the end surface of the side wall 112 can be some welding mode that can realize sealing at the welding position, for example, in the embodiment, the welding head is welded in the mode of seam welding along the direction perpendicular to the side wall 112, and the secondary battery 100 is relatively moved along the circumferential direction in the welding process, so that the annular welding mark is formed on the side wall 112; in some other embodiments, the welding head is welded along the height direction of the secondary battery 100, that is, from the opening 113 to the end wall, and the secondary battery 100 is relatively rotated along the circumferential direction of the first end wall 114 in the welding process, so that the closed loop welding mark is formed at the position where the outer edge of the side wall connecting part 1142 contacts the end surface of the side wall 112. It should be noted that the welding mark in the figure is only used as an example of an embodiment, and is not limited to the welding mode. Preferably, the recess 1143 is sunken into the shell 110. When the side wall connecting part 1142 and the end surface of the side wall 112 are welded by seam welding, the setting can block the laser.

[0066] Further, please refer to Figure 3 In the secondary battery 100 example of the utility model, the side wall 112 wall thickness is t1, the side wall connecting part 1142 wall thickness is t2, 0.8t1≤t2≤1.2t1. Limiting the side wall connecting part 1142 in the above range can make the side wall connecting part 1142 have sufficient thickness and form good welding quality with the side wall 112, and also facilitate to improve the structural strength of the first end wall 114.

[0067] Please refer to Figures 5 to 6In the secondary battery 100 example of the utility model, the wall thickness of the bottom wall 11431 is less than the wall thickness of the side wall connecting portion 1142, and the overall thin setting of the bottom wall 11431 has the advantage of facilitating processing. Further, the bottom wall 11431 is welded to the side of the side wall connecting portion 1142 facing the electrode assembly 120, i.e., the first end wall 114, and the recess 1143 and the side wall connecting portion 1142 are separately welded to form a further reduction in the processing difficulty of forming two different thicknesses of structure on the first end wall 114, and in addition, the setting can also achieve the setting of the bottom wall 11431 and the side wall connecting portion 1142 as different materials, for example, the side wall connecting portion 1142 can select a steel or alloy material with high hardness, and the bottom wall 11431 can select an aluminum alloy, copper, copper alloy or carbon steel with good welding performance, and the like, which are not limited. The bottom wall 11431 is welded to the side of the side wall 112 connecting surface facing the electrode assembly 120, which can form a recess 1143, which can protect the thin bottom wall 11431. Considering that the bottom wall 11431 and the side wall connecting portion 1142 are to be sealed and welded, the outer periphery of the bottom wall 11431 and the inner periphery of the side wall connecting portion 1142 have an overlapping portion 1144, which can meet the requirements of firmness and sealing of the welding between the bottom wall 11431 and the side wall connecting portion 1142. It should be noted that there are many welding methods between the bottom wall 11431 and the side wall connecting portion 1142, which can be ultrasonic welding, resistance welding, laser welding, etc., which are not limited, as long as the sealing welding between the bottom wall 11431 and the side wall connecting portion 1142 can be achieved. The present embodiment uses laser welding, and the specific construction method of laser welding is not limited, which can be penetrated from the outside of the side wall connecting portion 1142 to the direction of the bottom wall 11431, or it can be penetrated from the inside of the bottom wall 11431 to the direction of the side wall connecting portion 1142, or it can be seam welded at the joint surface of the bottom wall 11431 and the side wall connecting portion 1142, which is not limited.

[0068] Preferably, in the secondary battery 100 example of the utility model, please refer to Figures 5 to 6 , the overlapping portion 1144 is formed with a first weld mark 1145 on the side facing the electrode assembly 120. The first weld mark 1145 is formed by welding from the thinner bottom wall 11431 to the thicker side wall connecting portion 1142, which can reduce energy consumption, improve welding precision and welding quality; in addition, the first weld mark 1145 is inside the shell 110, which can also reduce the problem of easy rusting of the first weld mark 1145 due to exposure outside the shell 110.

[0069] Please refer to Figures 3 to 6In the secondary battery 100 example of the utility model, bottom wall 11431 is provided with weak part 1146, weak part 1146 is configured to fracture when the internal pressure of secondary battery 100 exceeds threshold value, specifically, the shape of weak part 1146 can be closed or not closed curve, polygon or irregular figure etc., weak part 1146 can be for example the notch or thin set on the surface of bottom wall 11431, it should be understood that in some other embodiments, weak part 1146 can also be replaced by other brittle structure, for example, change the material of weak part 1146, so that its structural strength is lower than the structural strength of other areas of end cover. The weak part 1146 in the embodiment is a closed annular notch, the thickness changes suddenly at the notch position, so when the end cover is stressed, the end cover will first crack at the notch due to stress concentration, the pressure relief area falls off to form a discharge port, guiding the internal material to discharge from the discharge port, avoiding the explosion of secondary battery 100.

[0070] It can be understood that, referring to Figures 3 to 6 , weak part 1146 is arranged on bottom wall 11431 and located in recess 1143, which is beneficial to better protect weak part 1146 and reduce the possibility of early damage of weak part 1146 caused by bumping during transportation and use. Since the tab connecting part 1141 welded and connected with the first tab 124 is also located on the bottom wall 11431, when the internal pressure of the secondary battery 100 exceeds the threshold value, the weak part 1146 breaks, and the bottom wall 11431 directly explodes to form a pressure relief channel without other obstructions, so that the explosion discharge in the shell 110 can be more smoothly discharged from the pressure relief channel. This setting improves the pressure relief efficiency and is beneficial to improve the safety performance of the battery.

[0071] Referring to Figure 4 , in the secondary battery 100 example of the utility model, the inner diameter of the side wall 112 is d, the first end wall 114 has an annular area with an inner diameter of 0.6d and an outer diameter of 0.7d, and the weak part 1146 is located in the annular area. The weak part 1146 is located in the above-mentioned annular area, which is beneficial to form a larger pressure relief area on the first end wall 114. In addition, the larger the pressure relief area is, the thicker the required wall thickness of the weak part 1146 is, and the thicker the wall thickness of the weak part 1146 is, the more beneficial to the structural strength of the first end wall 114, reducing the possibility of early damage of the weak part 1146 caused by bumping during transportation and use.

[0072] Referring to Figure 5In the secondary battery 100 example of the utility model, the wall thickness of the weak part 1146 is e, satisfying the range of 0.1mm<=e<=0.15mm, for example, can be 0.1mm, 0.11mm, 0.12mm, 0.13mm, 0.14mm or 0.15mm, etc.. The form of the weak part 1146 can be a notch or a thin spot, which is not limited. The weak part 1146 in the wall thickness range, in cooperation with the size of the pressure relief area surrounded by the weak part 1146 of different sizes, can not only realize the rupture and complete pressure relief when the secondary battery 100 exceeds the threshold, but also meet the requirement of the structural strength of the first end wall 114.

[0073] Please refer to Figure 4 And Figure 6 In the secondary battery 100 example of the utility model, the secondary battery 100 further comprises a protective sheet 140, the material of the protective sheet 140 can be carbon steel, alloy steel or stainless steel, etc., which is not limited. Since the bottom wall 11431 is provided with the tab connecting part 1141 with welding marks on the surface and the thin weak part 1146, the protective sheet 140 is arranged on the side of the first end wall 114 away from the electrode assembly 120, and the projection of the protective sheet 140 along the height direction of the secondary battery 100 towards the first end wall 114 covers the bottom wall 11431. This arrangement can not only prevent rust on the welding marks of the tab connecting part 1141, but also protect the weak part 1146 from premature rupture during transportation and assembly.

[0074] Please refer to Figure 3 In the secondary battery 100 example of the utility model, the wall thickness of the side wall connecting part 1142 is t2, the wall thickness of the tab connecting part 1141 is t3, and 0.5t2<=t3<=0.7t2. The wall thickness of the tab connecting part 1141 is in this range, which reduces the energy consumption of welding, is conducive to controlling the welding power, thereby reducing the difficulty of welding, and is also conducive to improving the precision and quality of welding.

[0075] Please refer to Figures 3 to 6In the secondary battery 100 example of the utility model, the plurality of sets of welding mark units 1147 are formed on the tab connecting portion 1141, for example, can be 2 sets, 3 sets, 4 sets, 5 sets, 6 sets or more, the shape and size of the welding mark unit 1147 are not limited, as long as the reliable electrical connection between the tab connecting portion 1141 and the first tab 124 can be realized, each set of welding mark units 1147 is arranged around the center of the first end wall 114, preferably, each set of welding mark units 1147 is evenly arranged around the center of the first end wall 114, which is beneficial to evenly distribute the current through the first tab 124, thereby enhancing the performance of the secondary battery 100, and the welding strength can also be improved. Each set of welding mark units 1147 includes a plurality of second welds 11471, which can be 2, 3, 4, 5, 6 or more, which are not limited. The plurality of second welds 11471 are arranged so that the welding mark unit 1147 and the first tab 124 have a large welding area to achieve good resistance stability of the secondary battery 100, and also facilitate the enhancement of the overcurrent capacity. In the embodiment, the welding mark unit 1147 has 4 sets, and each set of welding mark units 1147 includes 3 welds.

[0076] Preferably, referring to Figure 3 and Figure 5 In the secondary battery 100 example of the utility model, the shape of the second weld 11471 is a curve, and the radius of curvature of any point on the curve is greater than or equal to 1mm. The welding time at any point during the welding process can be uniform, which can improve the uniformity of the molten pool size at any point on the second weld 11471, and also make the transition at the corner of the welding trajectory smooth, reducing the risk of burning the diaphragm 122 due to the concentration of welding heat at a certain point.

[0077] Preferably, referring to Figure 7 The application also provides a battery pack 10, which includes the secondary battery 100 of any one of the above, in an embodiment of the battery pack 10 of the application, the battery pack 10 includes a box body 101, a box cover 102 and a plurality of secondary batteries 100, the plurality of secondary batteries 100 are placed in the box body 101 and are connected in series or parallel with each other, or a combination of series and parallel connection, the box cover 102 is capped on the box body 101 to protect the plurality of secondary batteries 100. It should be noted that the battery pack 10 can also include a battery pack 10 thermal management system, a circuit board and other parts in addition to the secondary battery 100 of the application, the battery pack 10 can be a battery module or a battery pack, and a power storage cabinet; hereinafter will not be described one by one.

[0078] Preferably, referring to Figure 8The application further provides an electronic device 1 comprising the battery pack 10. The working part 11 is electrically connected with the battery pack 10 to obtain power support. As an example, the electronic device 1 is a vehicle, which can be a fuel automobile, a gas automobile or a new energy automobile, and the new energy automobile can be a pure electric vehicle, a hybrid vehicle or a range extended vehicle, but is not limited thereto. The working part 11 is a vehicle body, and the battery pack 10 is arranged at the bottom of the vehicle body and provides power support for driving of the vehicle or operation of electrical elements in the vehicle. However, in some other embodiments, the electronic device 1 can also be a mobile phone, a portable device, a notebook computer, a ship, a spacecraft, an electric toy and an electric tool, etc. The spacecraft includes an airplane, a rocket, a space shuttle and a spacecraft, etc. The working part 11 can be a unit component capable of obtaining power of the battery pack 10 and making corresponding work, such as a fan blade rotating unit of a fan or a dust suction working unit of a dust collector. The electric toy includes a fixed or mobile electric toy, such as a game console, an electric car toy, an electric ship toy and an electric airplane toy, etc. The electric tool includes a metal cutting electric tool, a grinding electric tool, an assembling electric tool and a railway electric tool, such as an electric drill, an electric grinder, an electric wrench, an electric screwdriver, an electric hammer, an impact electric drill, a concrete vibrator and an electric planer, etc. The embodiments of the application do not specially limit the above-mentioned electronic device 1.

[0079] The wall thickness of the tab connecting part connected with the first tab by welding is smaller than the wall thickness of the side wall connecting part connected with the side wall, which is beneficial to control the welding power and further reduces the difficulty of welding, and can prevent the problem of membrane scalding caused by excessive melting during high-power welding; and can also reduce the possibility of false welding; and further improves the technical problem that welding failure is prone to occur between the end wall and the tab. Therefore, the utility model effectively overcomes some practical problems in the prior art, thereby having high utilization value and use significance. The above embodiments only exemplarily illustrate the principle and effect of the utility model, and are not used to limit the utility model. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the utility model. Therefore, all equivalent modifications or changes made by those skilled in the art without departing from the spirit and technical thought disclosed by the utility model should be covered by the claims of the utility model.

Claims

1. A secondary battery, characterized in that, include: The housing includes a first end wall and a side wall surrounding the first end wall; An electrode assembly, housed within the housing, the electrode assembly including a first tab facing the first end wall; The first end wall includes a tab connection portion and a side wall connection portion surrounding the tab connection portion. The tab connection portion is welded to the first tab, and the side wall connection portion is connected to the end face of the side wall. The wall thickness of the tab connection portion is less than the wall thickness of the side wall connection portion.

2. The secondary battery according to claim 1, characterized in that, The inner side of the sidewall connection portion is connected to a recessed portion that is recessed toward the electrode assembly. The recessed portion has a protrusion formed on the side of the first end wall facing the electrode assembly. The tab connection portion is located on the bottom wall of the recessed portion.

3. The secondary battery according to claim 2, characterized in that, The sidewall connecting part is welded to the end face of the sidewall, and the recess is sunk into the housing.

4. The secondary battery according to claim 3, characterized in that, The sidewall thickness is t1, and the sidewall connection thickness is t2, wherein 0.8t1≤t2≤1.2t1.

5. The secondary battery according to claim 2, characterized in that, The thickness of the bottom wall is less than the thickness of the side wall connection. The bottom wall is welded to the side of the side wall connection facing the electrode assembly. The outer peripheral side of the bottom wall and the inner peripheral side of the side wall connection have overlapping portions.

6. The secondary battery according to claim 5, characterized in that, A first solder mark is formed on the side of the overlapping portion facing the electrode assembly.

7. The secondary battery according to any one of claims 2 to 6, characterized in that, The bottom wall is provided with a weak part, which is configured to break when the internal pressure of the secondary battery exceeds a threshold.

8. The secondary battery according to claim 7, characterized in that, The inner diameter of the sidewall is d, and the first endwall has an annular region with an inner diameter of 0.6d and an outer diameter of 0.7d, and the weak part is located in the annular region.

9. The secondary battery according to claim 8, characterized in that, The wall thickness of the weak part is e, where 0.1mm ≤ e ≤ 0.15mm.

10. The secondary battery according to claim 7, characterized in that, The secondary battery also includes a protective sheet, which is disposed on the side of the first end wall away from the electrode assembly and projects onto the first end wall along the height direction of the secondary battery. The projection of the protective sheet covers the bottom wall.

11. The secondary battery according to claim 1, characterized in that, The wall thickness of the sidewall connecting part is t2, and the wall thickness of the electrode connecting part is t3, wherein 0.5t2≤t3≤0.7t2.

12. The secondary battery according to claim 11, characterized in that, Multiple sets of soldering units are formed on the electrode connection portion. Each set of soldering units is arranged at intervals around the center of the first end wall, and each set of soldering units includes multiple second soldering lines.

13. The secondary battery according to claim 12, characterized in that, The shape of the second solder mark is a curve, and the radius of curvature of any point on the curve is greater than or equal to 1 mm.

14. A battery pack, characterized in that, The secondary battery includes any one of claims 1 to 13.

15. An electronic device, characterized in that, Includes the battery pack as described in claim 14.

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