Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a kind of secondary battery, battery pack and electronic device, the secondary battery includes shell, electrode assembly and current collecting member;Shell includes end wall, and end wall includes explosion-proof valve;Electrode assembly is housed in shell, including the first tab of stack setting in close to electrode assembly one end;Current collecting member is between electrode assembly and end wall, current collecting member is welded with first tab, and it is formed on current collecting member corresponding tab welding portion several weld mark area, each weld mark area includes several first weld mark and several second weld mark, several second weld mark is connected or interval arrangement with corresponding first weld mark, first weld mark is at least partially located in the projection of explosion-proof valve opening valve area, second weld mark is at least partially located in the projection outside opening valve area;Along the axial direction of electrode assembly, the layer number of the first tab connected to first weld mark is less than the layer number of the first tab connected to second weld mark, can improve the technical problem that current collecting member folding effect is not good when explosion-proof valve opens.

Description

Technical Field

[0001] This utility model relates to the field of battery technology, specifically to a secondary battery, battery pack, and electronic device. Background Technology

[0002] Due to their high energy density and cost-effectiveness, rechargeable batteries have been widely used in the automotive industry. Currently, mature rechargeable batteries are generally equipped with explosion-proof valves. These valves open to release internal gases and substances when the internal pressure rises to a threshold, thus depressurizing the battery and preventing it from exploding due to excessive pressure.

[0003] In existing secondary batteries, explosion-proof valves are typically located on the end wall of the casing. A current collector is usually installed on the end face of the electrode assembly on the corresponding side of the end wall, and a corresponding explosion-proof zone for the explosion-proof valve is provided. The current collector is usually connected to the electrode lugs of the electrode assembly via laser welding. When the explosion-proof valve opens to release pressure, the explosion-proof zone of the current collector needs to fold over to achieve rapid release of internal pressure. However, with current current collector structures, the folding effect is often poor due to the constraint force of the welding on the current collector when the explosion-proof valve opens, thus affecting the pressure relief effect of the secondary battery and reducing its safety performance. Utility Model Content

[0004] This invention provides a secondary battery, a battery pack, and an electronic device to improve the technical problem of poor folding effect of the current collector when the explosion-proof valve is opened.

[0005] To achieve the above and other related objectives, this utility model provides a secondary battery, a battery pack, and an electronic device. The secondary battery includes a casing, an electrode assembly, and a current collector. The casing includes an end wall, which includes an explosion-proof valve. The electrode assembly is housed within the casing and includes a first tab stacked at one end of the electrode assembly. The current collector is located between the electrode assembly and the end wall, and is welded to the first tab to form a plurality of mutually spaced tab weld portions between the current collector and the first tab. A plurality of solder marks corresponding to the tab weld portions are formed on the current collector. Each solder mark includes a plurality of first solder marks and a plurality of second solder marks. The second solder marks are connected to or spaced apart from the corresponding first solder marks and projected onto the current collector along the axial direction of the electrode assembly. The first solder marks are at least partially located within the projection of the opening area of ​​the explosion-proof valve, and the second solder marks are at least partially located outside the projection of the opening area. Along the axial direction of the electrode assembly, the number of layers of the first tab to which the tab weld portion corresponding to the first solder mark is connected is less than the number of layers of the first tab to which the tab weld portion corresponding to the second solder mark is connected.

[0006] In one example of the secondary battery of this utility model, the electrode assembly includes a first electrode, a second electrode, and a separator layered and wound together to form a wound structure. The end of the first electrode facing the end wall includes a plurality of empty foils extending out of the separator along the axial direction of the electrode assembly. The plurality of empty foils are stacked to form a first tab. The height of at least a portion of the first tab located within the projection of the opening area of ​​the explosion-proof valve is less than the height of at least a portion of the first tab located outside the projection of the opening area.

[0007] In one example of the secondary battery of this utility model, the height of at least a portion of the first tab within the projection of the opening area of ​​the explosion-proof valve gradually increases from the radially inner side to the radially outer side of the electrode assembly.

[0008] In one example of the secondary battery of this utility model, each first solder mark and the corresponding second solder mark are connected by a continuous welding path to form an integral solder mark structure; there is a gap between the first solder mark and the second solder mark, and the first solder mark and the second solder mark are set as independent solder marks relative to each other.

[0009] In one example of the secondary battery of this utility model, the coverage area of ​​a plurality of first solder marks in each solder area is greater than the coverage area of ​​a plurality of second solder marks; the plurality of first solder marks extend linearly and are arranged at intervals to form the coverage area of ​​the first solder marks, and the plurality of second solder marks extend linearly and are arranged at intervals to form the coverage area of ​​the second solder marks, the second solder marks being located radially outside the first solder marks; the number of the plurality of first solder marks is greater than the number of the plurality of second solder marks; the length of the linear extension direction of the first solder marks is less than the length of the linear extension direction of the second solder marks.

[0010] In one example of the secondary battery of this utility model, a plurality of first solder marks are respectively connected to corresponding second solder marks, and at least a portion of each first solder mark is located within the projection of the opening area of ​​the explosion-proof valve. The interconnected first solder marks and corresponding second solder marks form an integral solder mark group extending linearly in the radial direction. The plurality of solder mark groups are arranged at intervals between each other, or the plurality of second solder marks are located on the radial outer side of the plurality of first solder marks and are arranged at intervals between each other.

[0011] In one example of the secondary battery of this utility model, the first solder marks are interconnected and / or the second solder marks are interconnected.

[0012] In one example of the secondary battery of this utility model, along the circumferential direction of the current collector, a weak part is provided between adjacent solder areas of the current collector, and the weak part is configured to break when the internal pressure of the secondary battery exceeds a threshold.

[0013] In one example of the secondary battery of this utility model, the area of ​​the valve opening region is S. The current collector is projected along the axial direction of the electrode assembly toward the current collector. The area of ​​the current collector falling into the projection of the valve opening region is S1, and 0.4S≤S1<S.

[0014] In one example of the secondary battery of this utility model, the weak part is projected along the axial direction of the electrode assembly toward the current collector, and at least part of the weak part is located within the projection of the valve opening region.

[0015] In one example of the secondary battery of this utility model, a tear is provided in the central region of the current collector, one end of the weak part is located close to the center of the current collector, adjacent weak parts are connected by the tear, and the tear is torn when the explosion-proof valve is opened.

[0016] This utility model also provides a battery pack, which includes any of the above-mentioned secondary batteries.

[0017] This invention also provides an electronic device that includes the aforementioned battery pack.

[0018] This novel secondary battery design features a first weld mark located at least part within the projection of the explosion-proof valve's opening area, and a second weld mark located at least part outside the projection of the opening area. This ensures that the weld mark within the projection of the explosion-proof valve's opening area includes at least a portion of the first weld mark, while simultaneously reducing the number of layers connecting the first electrode tab to the first weld mark. This effectively reduces the folding resistance of the first electrode tab to the current collector when the explosion-proof valve is opened, ensuring rapid pressure relief. Furthermore, the second weld mark, connecting more layers of the first electrode tab, is located outside the opening area, guaranteeing a stable connection between the first electrode tab and the current collector and excellent conductivity. This differentiated welding design cleverly balances explosion-proof safety requirements with current collection and transmission performance requirements, solving the pressure relief failure problem caused by poor folding of the current collector while maintaining the low internal resistance characteristics of the secondary battery. In addition, this structural design simplifies welding process requirements, improves production efficiency, and enhances the safety and reliability of the secondary battery under extreme conditions such as thermal runaway. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other embodiments can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a cross-sectional view of the overall structure of an example of a secondary battery of this utility model;

[0021] Figure 2 for Figure 1 A partial sectional view of region A in the middle;

[0022] Figure 3 This is a schematic diagram of the electrode assembly structure of an example of the secondary battery of this utility model;

[0023] Figure 4 This is a top view of the current collector and electrode assembly in an example of the secondary battery of this utility model after assembly;

[0024] Figure 5 This is a top view of the current collector and electrode assembly in an example of the secondary battery of this utility model after assembly;

[0025] Figure 6 for Figure 5 A magnified view of a section at point B in the middle;

[0026] Figure 7 This is a top view of the current collector and electrode assembly in an example of the secondary battery of this utility model after assembly;

[0027] Figure 8 This is a partial schematic diagram of the first tab of the electrode assembly in an example of the secondary battery of this utility model;

[0028] Figure 9 This is a schematic diagram of an example of the battery pack of this utility model;

[0029] Figure 10 This is a schematic diagram of an example of the electronic device of this utility model.

[0030] Component designation explanation:

[0031] 1. Electronic device; 10. Battery pack; 11. Working part; 101. Housing; 102. Housing cover; 100. Secondary battery; 110. Housing; 111. End wall; 1111. First end wall; 1112. Second end wall; 112. Explosion-proof valve; 1121. Explosion-proof groove; 1122. Valve opening area; 113. Side wall; 120. Electrode assembly; 121. First electrode; 1211. Negative current collector; 1212. First coated area; 1213. First uncoated area; 122. Separator; 123. Second electrode; 1231. Positive electrode Current collector; 1232, second coated area; 1233, second uncoated area; 124, first tab; 125, second tab; 126, empty foil; 127, winding shaft; 130, current collector component; 131, body; 132, solder area; 1321, first solder mark; 1322, second solder mark; 133, housing connection; 134, through hole; 135, tab connection; 140, projection of valve opening area; 150, weak part; 160, tear; 1601, tear opening; 1602, tear unit; 170, pole post. Detailed Implementation

[0032] The following specific examples illustrate the implementation of this utility model. Those skilled in the art can easily understand other advantages and effects of this utility model from the content disclosed in this specification. This utility model can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this utility model. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. It should also be understood that the terminology used in the embodiments of this utility model is for describing specific implementation schemes and not for limiting the scope of protection of this utility model. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or according to the conditions recommended by the respective manufacturers.

[0033] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise specified in this invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used in this invention, as well as the prior art known to those skilled in the art and the description of this invention, may be implemented using any prior art methods, equipment, and materials similar to or equivalent to those in the embodiments of this invention.

[0034] It should be noted that the terms such as "upper", "lower", "left", "right", "middle" and "one" used in this specification are only for clarity of description and are not intended to limit the scope of implementation of this utility model. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered as within the scope of implementation of this utility model.

[0035] Please see Figures 1 to 10 This utility model provides a secondary battery 100, a battery pack 10, and an electronic device 1. In the secondary battery 100, the end wall 111 of the casing 110 includes an explosion-proof valve 112. A current collector 130 is welded to a first tab 124, forming mutually spaced solder areas 132. Each solder area 132 has a plurality of first solder marks 1321 and a plurality of second solder marks 1322. By setting at least a portion of the first solder marks 1321 to be located within the projection 140 of the opening area of ​​the explosion-proof valve 112, and at least a portion of the second solder marks 1322 to be located outside the projection 140 of the opening area, the solder marks within the projection 140 of the opening area of ​​the explosion-proof valve 112 include at least a portion of the first solder marks 1321. At the same time, the number of layers of the tab welding part corresponding to the first solder mark 1321 connected to the first tab 124 is reduced, effectively reducing the constraint effect of the first tab 124 on the current collector 130 when the explosion-proof valve 112 is opened, ensuring smooth pressure relief.

[0036] Please see Figures 1 to 3The secondary battery 100 includes a housing 110, an electrode assembly 120, and a current collector 130. The housing 110 has a cavity for accommodating the electrode assembly 120, electrolyte (not shown), and other components. The housing 110 can be open at one end or both ends. Specifically, the dimensions of the housing 110 can be determined based on the specific dimensions of the electrode assembly 120, for example, a diameter of 46 mm and heights of 80 mm, 95 mm, or 120 mm. The housing 110 can be made of various materials, such as copper, iron, aluminum, steel, or aluminum alloy. To prevent rusting during long-term use, a rust-preventive material, such as nickel, can be plated onto the surface of the housing 110.

[0037] like Figure 1 and Figure 2 As shown, the housing 110 includes a cylindrical sidewall 113 and an end wall 111, with the end wall 111 including an explosion-proof valve 112. The end wall 111 can be a first end wall 1111 that closes one open end of the side wall 113, or a second end wall 1112 that closes the other open end of the side wall 113. The first end wall 1111 and one end of the side wall 113 can be fixed and sealed together by welding, mechanical pressing, or riveting, or they can be integrally formed. The second end wall 1112 and the other end of the side wall 113 can be integrally stamped or welded together. The explosion-proof valve 112 can be disposed on either the first end wall 1111 or the second end wall 1112; there is no limitation on this. In this embodiment, the explosion-proof valve 112 is disposed on the first end wall 1111.

[0038] The explosion-proof valve 112 can be at least partially opened when the internal pressure of the secondary battery 100 exceeds a threshold, in order to release the pressure inside the housing 110 and complete the directional pressure relief of the secondary battery 100. The type of explosion-proof valve 112 is not limited; for example, it can be an explosion-proof valve 112 assembly mounted on the first end wall 1111. See also... Figure 1 and Figure 3In one embodiment of the secondary battery 100 of this utility model, the explosion-proof valve 112 includes an explosion-proof groove 1121 disposed on the first end wall 1111, and the explosion-proof groove 1121 has an annular structure. It should be noted that the annular structure is not limited to the groove being circular or elliptical. In this utility model, the explosion-proof groove 1121 can be considered an annular structure as long as the ends are connected. In other embodiments, the explosion-proof groove 1121 may not be connected end to end, for example, it may be a C-shaped, cross-shaped or other non-annular contour, as long as it can open when the pressure is greater than a set threshold. The explosion-proof groove 1121 may be coaxial with the first end wall 1111 or not coaxial. Preferably, in order to facilitate the positioning and processing of the explosion-proof groove 1121 on the first end wall 1111, the explosion-proof groove 1121 is coaxial with the first end wall 1111. The explosion-proof notch 1121 is equivalent to an explosion-proof valve 112, and is located in a weaker area of ​​the first end wall 1111. When the internal pressure of the housing 110 exceeds a certain threshold (which can be calculated by measuring the strength at the explosion-proof notch 1121 to ensure at least partial opening when the pressure exceeds a certain threshold), the explosion-proof notch 1121 on the first end wall 1111 ruptures, and a portion of it folds outward under internal pressure. This folded area is defined as the valve opening area 1122. At this time, the internal pressure of the housing 110 is released from the valve opening area 1122, thereby preventing the secondary battery 100 from exploding at the housing 110 and causing module-level thermal runaway.

[0039] Considering that the scoring will damage the nickel plating layer on the surface of the first end wall 1111, and thus make it easy for corrosion to occur at the scoring location, it is preferable to set the scoring opening on the side of the first end wall 1111 facing the electrode assembly 120. This makes the scoring located in the enclosed space inside the housing 110, reducing the contact between the scoring and the air, which can slow down the corrosion of the scoring and improve the service life of the scoring.

[0040] Please see Figure 1 and Figure 3 In this embodiment, the electrode assembly 120 includes a first electrode 121, a second electrode 123, and a diaphragm 122. The three are stacked and wound around a winding shaft 127 to form a winding structure. The first electrode 121 is a negative electrode. The first electrode 121 includes a negative current collector 1211 and a negative active material. The negative active material is coated on the surface of the negative current collector 1211. The negative current collector 1211 includes a first coated area 1212 coated with active material and a first uncoated area 1213 uncoated with active material. The first uncoated area 1213 is located at the end of the first electrode 121. The first uncoated area 1213 includes a plurality of empty foils 126 extending from the diaphragm 122 along the axial direction of the electrode assembly 120. The plurality of empty foils 126 are bent toward the winding shaft 127 of the electrode assembly 120 and stacked to form a first tab 124. The first tab 124 is the corresponding negative tab.

[0041] Please see Figure 1 and Figure 3 The second electrode 123 is a positive electrode. Specifically, the second electrode 123 includes a positive current collector 1231 and a positive active material. The positive active material is coated on the surface of the positive current collector 1231. The positive current collector 1231 includes a second coated area 1232 coated with active material and a second uncoated area 1233 uncoated with active material. The second uncoated area 1233 is located at the end of the second electrode 123. The second uncoated area 1233 extends out of the diaphragm 122 along the axial direction of the electrode assembly 120 and is bent toward the winding shaft 127 to form a second tab 125. The second tab 125 is the corresponding positive tab.

[0042] Please see Figure 1 and Figure 3 A separator 122 is disposed between the first electrode 121 and the second electrode 123 to isolate the positive electrode active material layer and the negative electrode active material layer. Taking a lithium-ion secondary battery 100 as an example, the positive electrode current collector 1231 can be made of aluminum, and the positive electrode active material layer includes positive electrode active material, which can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc. The negative electrode current collector 1211 can be made of copper, and the negative electrode active material layer includes negative electrode active material, which can be carbon or silicon, etc. The substrate material of the separator 122 can be polypropylene (PP) or polyethylene (PE), etc. To protect and insulate the electrode assembly 120, an insulating film can also be wrapped around the electrode assembly 120. The insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET), polyvinyl chloride (PVC), or other polymer materials.

[0043] Please see Figure 1 and Figure 3 Furthermore, if the first tab 124 faces the first end wall 1111 or the second end wall 1112 of the housing 110, then the second tab 125 faces the other end of the housing 110. In this embodiment, the second tab 125 faces the second end wall 1112 and is electrically connected to the post 170, making the post 170 positively charged. The first tab 124 faces the first end wall 1111, and the housing 110 is electrically connected to the first tab 124, thus becoming negatively charged. However, in another embodiment, the first tab 124 can be connected to the post 170, and the second tab 125 can be connected to the housing 110.

[0044] Please see Figure 1The electrode post 170 is fixed to the second end wall 1112 and electrically connected to the electrode assembly 120. Specifically, the second end wall 1112 is provided with a hole for the electrode post 170, and the electrode post 170 is installed through the hole and insulated from the second end wall 1112. The end of the electrode post 170 facing the electrode assembly 120 passes through the second end wall 1112 and is directly electrically connected to the second tab 125 or indirectly connected via a transfer connection. The structure of the electrode post 170 can be any suitable form that can pass through the second end wall 1112 and be electrically connected to the second tab 125 of the electrode assembly 120. For example, the cross-section can be circular, square, prismatic, or an irregular contour that can achieve stable conductivity. The shape of the hole in the electrode post 170 corresponds to the shape of the electrode post 170. In this embodiment, the cross-section of the electrode post 170 is circular.

[0045] The current collecting member 130 is disposed within the housing 110, located between the electrode assembly 120 and the end wall 111. It should be noted that when an explosion-proof valve 112 is provided on the first end wall 1111, the current collecting member 130 is disposed between the electrode assembly 120 and the first end wall 1111, as shown below. Figure 2 As shown. When an explosion-proof valve 112 is provided on the second end wall 1112, the current collector 130 is disposed between the electrode assembly 120 and the second end wall 1112. For ease of description, in this embodiment, the explosion-proof valve 112 is provided on the first end wall 1111 as an example, and the current collector 130 is disposed on the side of the electrode assembly 120 facing the first end wall 1111. The current collector 130 is welded to the first electrode tab 124 to form an electrode tab welding part. The welding method can be ultrasonic welding, resistance welding, laser welding, etc., and is not limited thereto. In this embodiment, laser welding is used, and during the welding process, spaced weld marks 132 are formed on the current collector 130. Several weld marks are formed in the weld marks 132. The weld marks are formed by heating and subsequent cooling processes, which can characterize the welding path of the current collector 130 and the first electrode tab 124. The electrode tab welding part is formed within a fixed number of layers of the first electrode tab 124.

[0046] Please see Figures 4 to 7 In this embodiment, each solder area 132 includes a plurality of first solder marks 1321 and a plurality of second solder marks 1322. The number of first solder marks 1321 and second solder marks 1322 is not limited; there can be one or more of each. The shapes of the first solder marks 1321 and second solder marks 1322 are not limited; they can be straight lines, curves (wavy lines, arcs, sine curves, etc.), broken lines, or other irregular shapes. The first solder marks 1321 form a first solder mark 1321 coverage area, and the second solder marks 1322 form a second solder mark 1322 coverage area. The first solder mark 1321 coverage area is at least partially located within the projection 140 of the opening area of ​​the explosion-proof valve 112 along the axial direction of the electrode assembly 120. The second solder mark 1322 coverage area is at least partially located outside the projection 140.

[0047] The relative positions of the first solder mark 1321 and the second solder mark 1322 can vary. They can be connected to each corresponding second solder mark 1322 to form an integral solder mark structure, or they can be independent solder marks; there is no limitation in this regard. When the first solder mark 1321 and the second solder mark 1322 are an integral solder mark structure, the areas covered by the first solder mark 1321 and the areas covered by the second solder mark 1322 are formed in a continuous shape. When the first solder mark 1321 and the second solder mark 1322 are independent solder marks, the areas covered by the first solder mark 1321 and the areas covered by the second solder mark 1322 are generally spaced apart.

[0048] The above embodiments are only some embodiments of the application. In other embodiments, as long as the first solder mark 1321 is at least partially located within the projection 140 of the opening region of the explosion-proof valve 112, and the second solder mark 1322 is at least partially located outside the projection 140 of the opening region, it is sufficient that the electrode assembly 120 is projected onto the current collector 130 along its axial direction. It should be noted that... Figures 4 to 7 The area enclosed by the dashed line represents the projection 140 of the valve opening area. The first solder mark 1321 can fall entirely within the projection 140 of the valve opening area, or it can fall partially within the projection 140 of the valve opening area. There is no limitation on this, as long as at least a portion of the first solder mark 1321 is located within the projection 140 of the valve opening area.

[0049] Considering that the welded portions of the first weld mark 1321 and the second weld mark 1322 formed by welding the current collector 130 to the first electrode lug 124 exert a strong restraining force on the current collector 130, it may cause difficulty in folding the current collector 130 when the explosion-proof valve 112 is opened. Please refer to... Figures 4 to 7 In this embodiment, for distinction, the tab welding portion corresponding to the first solder mark 1321 is defined as the first tab welding portion, and the tab welding portion corresponding to the second solder mark 1322 is defined as the second tab welding portion. Along the axial direction of the electrode assembly 120, the number of layers of the first welding connection portion connected to the first tab 124 is less than the number of layers of the second welding connection portion connected to the first tab 124. In actual operation, the number of layers of the tab welding portion connected to the first tab 124 can be adjusted by adjusting the welding power. Specifically, the higher the welding power, the more layers of the first tab welding portion connected to the first tab 124. The number of layers of the first tab welding portion or the second tab welding portion connected to the first tab 124 can be measured by first performing a CT scan on the electrode assembly 120 or making a cross-section along the axial direction of the electrode assembly 120, and then observing to determine the number of layers of the first tab welding portion or the second tab welding portion connected to the first tab 124.

[0050] It should be noted that during welding, the laser power at the beginning of the welding process gradually increases, and the number of layers of the electrode welding part connected to the first electrode 124 also gradually increases. Similarly, at the end of the welding process, the laser power gradually decreases, and the number of layers of the weld connected to the first electrode 124 also gradually decreases. Therefore, the above-mentioned welding start and welding end parts cannot be used to compare the number of layers of the electrode welding part formed on the first electrode 124. Instead, the comparison is made by comparing the number of layers of the first electrode welding part connected to the first electrode 124 at the middle of the first electrode welding part and the middle of the second electrode welding part.

[0051] By placing the first weld mark 1321 within the opening region 1122 of the explosion-proof valve 112 and reducing the number of layers connecting it to the first tab 124, the resistance of the current collector 130 within the projection 140 is effectively reduced when the explosion-proof valve 112 is opened, ensuring smooth pressure relief. Simultaneously, a second tab weld section connecting more layers of the first tab 124 is provided outside the opening region 1122, ensuring better connection stability and excellent conductivity between the first tab 124 and the current collector 130. Therefore, this zoned differentiated welding design cleverly balances explosion-proof safety requirements with current collection and transmission performance requirements, solving the pressure relief failure problem caused by poor clearance of the current collector 130 while maintaining the low internal resistance characteristics of the secondary battery 100. Furthermore, this structural design simplifies welding process requirements, improves production efficiency, and enhances the safety and reliability of the secondary battery 100 under extreme conditions such as thermal runaway.

[0052] To better control the DC internal resistance and constraint force within the projection area 140, the number of layers of the first tab 124 can be adjusted to meet the welding depth requirements of the tab welding portion, thereby further ensuring the internal resistance requirements of the secondary battery 100. Please refer to... Figure 8 In one example of the secondary battery 100 of this utility model, the height of at least a portion of the first tab 124 within the projection of the opening region of the explosion-proof valve 112 is less than the height of at least a portion of the first tab 124 outside the projection of the opening region. This arrangement results in fewer folded layers in the first tab 124 located in the inner ring of the electrode assembly 120, meaning a shorter current transmission path in the first tab 124. This makes the current in the inner ring more concentrated and the transmission more direct, reducing the dispersion and detours of the current in the first tab 124, which is beneficial for reducing internal resistance.

[0053] Please see Figure 8In one example of the secondary battery 100 of this utility model, the height of at least a portion of the first tab 124 within the projection 140 of the opening region of the explosion-proof valve 112 gradually increases from the radially inner side to the radially outer side of the electrode assembly 120. That is, the length of the empty foil 126 extending out of the separator 122 gradually decreases from the radially outer side to the radially inner side of the electrode assembly 120. This arrangement enables the number of layers of the empty foil 126 after bending to form the first tab 124 to gradually decrease from the radially outer side to the radially inner side of the electrode assembly 120. This results in the number of layers of the first tab 124 located within the opening region 1122 being less than the number of layers of the second tab 125 located outside the opening region 1122. This setting matches the welding requirement that the number of layers of the first tab weld to the first tab 124 is less than the number of layers of the second tab weld to the first tab 124. This ensures that even if the number of layers of the first tab weld to the first tab 124 is reduced, the number of turns of the first tab weld to the first tab 124 will not decrease, thus guaranteeing current collection and transmission performance and reducing internal resistance. It also reduces the probability of incomplete soldering and bursting, thereby improving the production yield of the secondary battery 100.

[0054] Please see Figures 4 to 5 In one example of the secondary battery 100 of this utility model, each first solder mark 1321 and its corresponding second solder mark 1322 are connected through a continuous welding path to form an integral solder mark structure. In actual operation, this can be achieved by reducing the welding power of the first solder mark 1321 located within the valve opening region 1122 and increasing the welding power of the second solder mark 1322 located outside the valve opening region 1122. The welding process of the first solder mark 1321 and the second solder mark 1322 is completed continuously in one step without interruption, improving processing efficiency. The continuous transmission path of the first solder mark 1321 and the second solder mark 1322 also makes current transmission smoother, reduces resistance, strengthens the weld, and makes the battery performance more stable.

[0055] It should be noted that the number of first solder marks 1321 and second solder marks 1322 included in each tab connection 132 is not limited; for example, there can be one, two, three, four, or more. Please refer to [link / reference]. Figure 4 In one embodiment, there are four of each of the first solder mark 1321 and the second solder mark 1322. Please refer to [link / reference]. Figure 5 In another embodiment, there is one first solder mark 1321 and two second solder marks 1322. The shapes of the first solder mark 1321 and the second solder mark 1322 are not limited; please refer to [reference needed]. Figure 4 In one embodiment, the integral solder joint structure formed by the first solder joint 1321 and the second solder joint 1322 is shaped like a wavy curve. Please refer to [link / reference]. Figure 5In another embodiment, the integral solder mark structure formed by the first solder mark 1321 and the second solder mark 1322 is a U-shaped curve that opens radially outward toward the current collector 130.

[0056] Please see Figure 7 In one example of the secondary battery 100 of this utility model, the first solder mark 1321 and the second solder mark 1322 are spaced apart and have no physical connection. The first solder mark 1321 and the second solder mark 1322 are set as independent solder marks. This setting allows the first solder mark 1321 and the second solder mark 1322 to form a natural weak point at the opening position of the explosion-proof valve 112, making it easier for the current collector 130 to bend outward. In addition, the first solder mark 1321 and the second solder mark 1322 are processed separately, which facilitates the adjustment of welding power when welding the first solder mark 1321 and the second solder mark 1322, and reduces the processing difficulty. It should be noted that the number of the first solder mark 1321 and the second solder mark 1322 is not limited. For example, there can be one, two, three, four or more, and there is no limitation in this regard.

[0057] Considering that within the projection area 140, the reduced number of first electrode layers (124) at the welding point of the first electrode will cause increased internal resistance, the secondary battery 100 of this utility model addresses this issue. Figures 4 to 6 In the three embodiments shown, the coverage area of ​​a plurality of first solder marks 1321 in each solder area 132 is greater than the coverage area of ​​a plurality of second solder marks 1322. By adjusting the welding area of ​​the first tab welding portion (that is, the area of ​​the first solder mark 1321 region of the first solder mark 1321), the constraint force between the first tab 124 and the current collector 130 in the solder area 132 and the DC internal resistance in the solder area 132 are balanced, so as to ensure the current collection and transmission performance requirements while avoiding the problem of pressure relief failure caused by excessive constraint force.

[0058] Please see Figure 7 In one example of the secondary battery 100 of this utility model, a plurality of first solder marks 1321 extend linearly and are arranged at intervals to form the coverage area of ​​the first solder marks 1321, and a plurality of second solder marks 1322 extend linearly and are arranged at intervals to form the coverage area of ​​the second solder marks 1322, and the second solder marks 1322 are located radially outside the first solder marks 1321.

[0059] Please see Figure 7In one example of the secondary battery 100 of this utility model, there are intervals between the plurality of first solder marks 1321 and the plurality of second solder marks 1322, and the number of the plurality of first solder marks 1321 is greater than the number of the plurality of second solder marks 1322. For example, there are two first solder marks 1321 and one second solder mark 1322. In this embodiment, the coverage area of ​​the two first solder marks 1321 in each solder region 132 is greater than the coverage area of ​​the one second solder mark 1322, so as to balance the constraint force between the first electrode tab 124 and the current collector 130 in the solder region 132 and the DC internal resistance in the solder region 132. The shapes of the first solder marks 1321 and the second solder marks 1322 are not limited; please refer to [reference needed]. Figure 7 In one embodiment, the first solder mark 1321 and the second solder mark 1322 are both wavy curves.

[0060] Please continue reading. Figure 7 In one example of the secondary battery 100 of this utility model, the length of the linear extension direction of the first solder mark 1321 is less than the length of the linear extension direction of the second solder mark 1322. When the first solder mark 1321 is closer to the center of the current collector 130 than the second solder mark 1322, this arrangement is beneficial to make more reasonable use of the limited space while ensuring the coverage area of ​​the first solder mark 1321.

[0061] Please see Figure 4 In one example of the secondary battery 100 of this utility model, a plurality of first solder marks 1321 are respectively connected to corresponding second solder marks 1322, and at least a portion of each first solder mark 1321 is located within the projection 140 of the opening area of ​​the explosion-proof valve 112. The interconnected first solder marks 1321 and corresponding second solder marks 1322 form an integral solder mark group extending linearly in the radial direction, and a plurality of solder mark groups are arranged at intervals between each other. Please continue reading Figure 4 In one embodiment, the first solder mark 1321 and the second solder mark 1322 form an integral solder mark assembly extending linearly in the radial direction, and the shape of the integral solder mark structure is a wavy curve. Preferably, the radius of curvature at any point on the curve is greater than or equal to 1 mm. This structure can ensure that the welding time is uniform at any point during the welding process, which can improve the uniformity of the number of layers connected to the first tab 124 at any point on the first solder mark 1321 and the second solder mark 1322, and also make the transition at the corners of the welding trajectory smooth, reducing the risk of the first tab 124 being burned by the diaphragm 122 due to the heat concentration at a certain point. Please refer to [link to relevant documentation]. Figure 7In one embodiment, a plurality of second solder marks 1322 are located radially outside a plurality of first solder marks 1321 and are spaced apart from each other. This arrangement allows the first solder marks 1321 and the second solder marks 1322 to form a natural weak point at the opening position of the explosion-proof valve 112, making it easier for the flow manifold 130 to fold outward.

[0062] Please see Figures 4 to 5 In one example of the secondary battery 100 of this utility model, the first solder marks 1321 are interconnected and / or the second solder marks 1322 are interconnected. In one embodiment, please refer to... Figure 4 The first solder mark 1321 and the second solder mark 1322 are interconnected. Please refer to [link / reference]. Figure 5 The two first solder marks 1321 are connected to each other.

[0063] In one example of the secondary battery 100 of this utility model, the welding power for forming the first solder mark 1321 is less than the welding power for forming the second solder mark 1322. This arrangement ensures that the number of layers of the first electrode tab weld portion corresponding to the first solder mark 1321 connected to the first electrode tab 124 is less than the number of layers of the second electrode tab weld portion corresponding to the second solder mark 1322 connected to the first electrode tab 124.

[0064] In one example of the secondary battery 100 of this utility model, the number of layers S of the first tab 124 is 10≤S≤20. It should be noted that the number of layers of the first tab 124 can be measured by first performing a CT scan on the electrode assembly 120 or by making a cross-section along the axial direction of the electrode assembly 120 and then observing the result.

[0065] Please see Figures 4 to 7 In one example of the secondary battery 100 of this utility model, the current collector 130 includes a plurality of tab connection portions 135 connected to the first tab 124. In this embodiment, the current collector 130 also includes a body portion 131 and a plurality of housing connection portions 133. The plurality of tab connection portions 135 are arranged around the center of the current collector 130 and are connected to the body portion 131. The plurality of housing connection portions 133 are connected to the outer periphery of the body portion 131 and are electrically connected to the housing 110. There are various electrical connection methods. For example, the housing connection portion 133 can be welded to the first end wall 1111, and the first end wall 1111 can be welded to the side wall 113, thereby realizing the electrical connection between the current collector 130 and the housing 110. Alternatively, the tab connection portion 135 can be directly welded to the side wall 113 to realize the electrical connection between the current collector 130 and the housing 110. Optionally, in this embodiment, the tab connection 135 is welded to the side wall 113, thereby realizing the electrical connection between the current collector 130 and the housing 110.

[0066] Please see Figures 4 to 7Each tab connection 135 is welded to the first tab 124 to achieve electrical connection between the current collector 130 and the electrode assembly 120. Each tab connection 135 has a solder area 132, each solder area 132 including a first solder mark 1321 and a second solder mark 1322. When the explosion-proof valve 112 is opened, the tab connection 135 folds away from the electrode assembly 120, thus exposing the end face of the first tab 124. Along the circumferential direction of the current collector 130, a weak portion 150 is provided between adjacent tab connections 135. The weak portion 150 is configured to break when the internal pressure of the secondary battery 100 exceeds a threshold, causing the tab connection 135 to fold away from the electrode assembly 120. The weak part 150 can be any structure that is easy to fold when the adjacent tab connection part 135 is opened, such as the thinning area formed by the block seal, the thinning area formed by the scoring process, or the hollow structure.

[0067] Preferably, please refer to Figures 4 to 7 In this embodiment, the weak portion 150 is a hollow structure. Since the hollow structure is a through-hole, the forming method is simple, reducing the processing difficulty of the weak portion 150. The weak portion 150 can be a straight segment, a curved segment, or a combination of straight and curved segments. The weak portion 150 can extend along the radial direction of the current collecting member 130 or extend away from the radial direction of the current collecting member 130. To facilitate the positioning and processing of the weak portion 150 on the current collecting member 130, preferably, in this embodiment, the weak portion 150 is a straight segment extending along the radial direction of the current collecting member 130, and the weak portions 150 between adjacent tab connections 135 are distributed in an array along the center of the current collecting member 130.

[0068] The area of ​​the valve opening region 1122 is S. Projecting this area along the axial direction of the electrode assembly 120 towards the current collector 130, then... Figures 4 to 7The area of ​​the projected valve opening region 140 shown is S, and the area of ​​the current collector 130 falling within the projected valve opening region 140 is S1, where 0.4S ≤ S1 < S. This configuration limits the obstruction area of ​​the current collector 130 on the pressure relief path of the explosion-proof valve 112. Under this obstruction area, when the explosion-proof valve 112 opens to relieve pressure, the current collector 130 can be subjected to a sufficiently large airflow impact pressure, thus facilitating the tearing of the current collector 130. This improves the tearing effect of the current collector 130, ensures the folding area of ​​the electrode connection 135, and reduces the obstruction of the pressure relief path of the explosion-proof valve 112 by the current collector 130 during pressure relief. This improves the pressure relief effect of the secondary battery 100 and reduces the risk of the secondary battery 100 exploding due to excessive pressure. Meanwhile, since the current collector 130 has a weak part 150 between adjacent tab connections 135, the weak part 150 can make the adjacent tab connections 135 easy to fold when the explosion-proof valve 112 is opened, which can further improve the tearing effect of the current collector 130, thereby further improving the pressure relief speed and pressure relief effect of the secondary battery 100.

[0069] Please see Figures 4 to 7 In one example of the secondary battery 100 of this utility model, the weak portion 150 is projected along the axial direction of the electrode assembly 120 toward the current collector 130, and is at least partially located within the projection 140 of the opening region of the explosion-proof valve 112. It should be noted that the weak portion 150 may fall entirely within the projection 140 of the opening region, or it may fall only partially within the projection 140 of the opening region; this is not limited, as long as the weak portion 150 is located within the projection 140 of the opening region. Through the spatial matching design between the weak portion 150 and the opening region 1122 of the explosion-proof valve 112, it is ensured that the weak portion 150 can break immediately when the explosion-proof valve 112 is opened, allowing the internal high-pressure gas to be released along the optimal path. This improves the safety performance of the secondary battery 100.

[0070] Please see Figures 4 to 7 In one example of the secondary battery 100 of this utility model, a tear 160 is provided in the central region of the current collector 130, and one end of the weak portion 150 is located near the center of the current collector 130. Adjacent weak portions 150 are connected by the tear 160, and the tear 160 tears when the explosion-proof valve 112 is opened. The tear 160 can be multiple solid portions distributed between adjacent solder areas 132, or it can be a single solid portion located in the central region of the current collector 130. Optionally, in this embodiment, the tear 160 is a single solid portion located in the central region of the current collector 130. Please refer to [link to relevant documentation]. Figure 6It should be noted that the tear portion 160 is the location where the explosion-proof valve 112 is prone to tearing when it is opened. The so-called solid portion refers to the solid structure of the tear portion 160 before tearing. The above arrangement allows multiple electrode connecting portions 135 to be interconnected in the central region of the current collector 130 through the tear portion 160, thereby reducing the probability of warping deformation in the central region of the current collector 130 and facilitating the installation and positioning of the current collector 130 within the housing 110.

[0071] Please see Figures 4 to 7 In this embodiment, a tear 160 is provided in the central region of the current collector 130, connecting adjacent weak points 150 through the tear 160. The tear 160 tears when the explosion-proof valve 112 is opened. This arrangement ensures the uniformity of the tear area among the multiple electrode tab connections 135 when the explosion-proof valve 112 is open, thus improving the tearing effect of the current collector 130. Simultaneously, since the tear 160 is far from the electrode tab connections 135, the transmission of compressive stress generated during the sealing of the housing 110 to the tear 160 is reduced. This reduces the probability of tearing when the explosion-proof valve 112 is not open, thereby improving the stability of the electrical connection between the current collector 130 and the electrode assembly 120.

[0072] Please see Figures 4 to 7 In one example of the secondary battery 100 of this utility model, a through hole 134 is provided in the central region of the current collector 130. The through hole 134 can be a circular hole, a rectangular hole, or a polygonal hole, etc. Optionally, in this embodiment, the through hole 134 is a circular hole. A tear portion 160 is disposed between the through hole 134 and the weak portion 150, and the through hole 134 is connected to the weak portion 150 through the tear portion 160. Specifically, the tear portion 160 includes a plurality of tearing units 1602, which are disposed around the outer periphery of the through hole 134. Each tearing unit 1602 corresponds to a weak portion 150, and each weak portion 150 is connected to the through hole 134 through a tearing unit 1602. By providing a through hole 134 in the center of the current collector 130, when the explosion-proof valve 112 is opened, the high-pressure gas will first be rapidly discharged outward from the through hole 134, which will then generate a large impact force on the tearing unit 1602 at the edge of the through hole 134, thereby facilitating the rapid tearing of the tearing part 160, improving the folding speed of the electrode connection part 135, and ensuring the pressure relief effect of the secondary battery 100.

[0073] To further improve the tearing speed of the tear section 160, please refer to an example of the secondary battery 100 of this utility model. Figures 4 to 7The tear section 160 includes a tear opening 1601, which communicates with the through hole 134 and is located on the extension line of the weak section 150. The tear opening 1601 can be U-shaped, rectangular, or arc-shaped, etc. Specifically, the number of tear openings 1601 corresponds to the number of tearing units 1602, that is, one tear opening 1601 corresponds to one tearing unit 1602. With this configuration, when the explosion-proof valve 112 is opened, when high-pressure gas passes through the through hole 134, the tear section 160 will first begin to tear at the tear opening 1601, thereby achieving rapid tearing of the tearing unit 1602, which increases the tearing speed of the tear section 160, thereby increasing the folding speed of the tab connection 135 and the depressurization speed of the secondary battery 100.

[0074] Please see Figure 9 This utility model also provides a battery pack 10, which includes the secondary battery 100 described above. In one embodiment of the battery pack 10, the battery pack 10 includes a housing 101, a cover 102, and multiple secondary batteries 100. The multiple secondary batteries 100 are placed in the housing 101 and are connected in series or parallel, or a combination of series and parallel connections. The cover 102 covers the housing 101 to protect the multiple secondary batteries 100. It should be noted that, in addition to the secondary battery 100 of this utility model, the battery pack 10 may also include a battery pack thermal management system, circuit board, etc. The battery pack 10 can be a battery module, a battery pack, an energy storage cabinet, etc.; these will not be described in detail here.

[0075] Please see Figure 10This utility model also provides an electronic device 1, which includes the aforementioned battery pack 10. A working part 11 is electrically connected to the battery pack 10 to obtain electrical power. As an example, the electronic device 1 is a vehicle, which can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, but are not limited thereto. The working part 11 is the vehicle body, and the battery pack 10 is located at the bottom of the vehicle body, providing electrical power for the vehicle's operation or the operation of its internal electrical components. However, in other embodiments, the electronic device 1 can also be a mobile phone, portable device, laptop computer, ship, spacecraft, electric toy, and power tool, etc. Spacecraft include airplanes, rockets, space shuttles, and spacecraft, etc.; the working part 11 can be a unit component capable of obtaining electrical power from the battery pack 10 and performing corresponding work, such as a fan blade rotation unit or a vacuum cleaner suction unit. Electric toys include stationary or mobile electric toys, such as game consoles, electric car toys, electric boat toys, and electric airplane toys, etc.; power tools include metal cutting power tools, grinding power tools, assembly power tools, and railway power tools, such as electric drills, electric grinders, electric wrenches, electric screwdrivers, electric hammers, impact drills, concrete vibrators, and electric planers, etc. This application does not impose any special limitations on the aforementioned electronic device 1.

[0076] This utility model also provides a welding method for a current collector 130, used for welding the current collector 130 and the electrode assembly 120 in the secondary battery 100 of any of the above claims, characterized in that the welding method includes:

[0077] An electrode assembly 120 is provided with a first tab 124, the first tab 124 being stacked near one end of the electrode assembly 120;

[0078] Provide a manifold component 130;

[0079] The first electrode 124 is laser welded to the current collector 130, and a plurality of mutually spaced electrode welding portions are formed between the current collector 130 and the first electrode 124. A plurality of solder marks 132 corresponding to the electrode welding portions are formed on the current collector 130. Each solder mark 132 includes a plurality of first solder marks 1321 and a plurality of second solder marks 1322 connected to or spaced from the corresponding first solder marks 1321. The first solder marks 1321 are projected toward the current collector 130 along the axial direction of the electrode assembly 120. The first solder marks 1321 are at least partially located within the projection of the valve opening area 1122 of the explosion-proof valve 112, and the second solder marks 1322 are located outside the projection of the valve opening area 1122.

[0080] The welding power for forming the first weld mark 1321 by laser welding is set to P1, 800w≤P1≤1200w, and the welding power for forming the second weld mark 1322 by laser welding is set to P2, 1200w<P2≤1600w.

[0081] The number of layers of the electrode lug welded to the first electrode lug 124 can be adjusted by regulating the welding power; the higher the welding power, the more layers of the first electrode lug welded to the first electrode lug 124. This welding method ensures that the number of layers of the first electrode lug welded to the first electrode lug 124 is less than the number of layers of the second electrode lug welded to the first electrode lug 125. This effectively reduces the constraint effect of the first electrode lug 124 on the manifold 130 when the explosion-proof valve 112 is opened, ensuring smooth pressure relief.

[0082] In one example of the welding method of this utility model, laser welding of the first electrode tab 124 and the current collector 130 includes: intermittently welding the first weld mark 1321 and the second weld mark 1322; first setting the welding power to P1 to weld the first weld mark 1321, and then setting the welding power to P2 to weld the second weld mark 1322; or, first setting the welding power to P2 to weld the second weld mark 1322, and then setting the welding power to P1 to weld the first weld mark 1321. This welding method allows the first weld mark 1321 and the second weld mark 1322 to form a natural weak point at the opening position of the explosion-proof valve 112, making it easier for the current collector 130 to bend outward. In addition, processing the first weld mark 1321 and the second weld mark 1322 separately facilitates the adjustment of the welding power when welding the first weld mark 1321 and the second weld mark 1322, reducing the processing difficulty.

[0083] In one example of the welding method of this utility model, laser welding of the first electrode 124 and the current collector 130 includes: laser welding of the first electrode 124 and the current collector 130 includes: continuously welding a first weld mark 1321 and a second weld mark 1322; firstly, the welding power is set to P1 to weld the first weld mark 1321, and then during the welding process, the welding power is set to P2 to weld the second weld mark 1322; or, firstly, the welding power is set to P2 to weld the second weld mark 1322, and then during the welding process, the welding power is set to P1 to weld the first weld mark 1321. In this technical solution, the process of welding the first weld mark 1321 and the second weld mark 1322 is completed continuously in one step without interruption, which improves processing efficiency. The continuous transmission path of the first weld mark 1321 and the second weld mark 1322 also makes the current transmission smoother, the resistance lower, the welding stronger, and the battery performance more stable.

[0084] This novel secondary battery design features a first weld mark located at least part within the projection of the explosion-proof valve's opening area, and a second weld mark located at least part outside the projection of the opening area. This ensures that the weld mark within the projection of the explosion-proof valve's opening area includes at least part of the first weld mark. Simultaneously, it reduces the number of layers connecting the first electrode to the corresponding tab weld, effectively lowering the resistance of the first electrode to the current collector when the explosion-proof valve opens, ensuring rapid pressure relief. Furthermore, by providing a second weld mark outside the opening area, connecting more layers of the first electrode, it guarantees a stable connection between the first electrode and the current collector, maintaining excellent conductivity. This differentiated welding design cleverly balances explosion-proof safety requirements with current collection and transmission performance requirements, solving the pressure relief failure problem caused by poor current collector folding while maintaining the low internal resistance characteristics of the secondary battery. Moreover, this structural design simplifies welding process requirements, improves production efficiency, and enhances the safety and reliability of the secondary battery under extreme conditions such as thermal runaway.

[0085] Therefore, this utility model effectively overcomes some practical problems in the prior art, thus possessing high utilization value and significance. The above embodiments are merely illustrative of the principles and effects of this utility model and are not intended to limit it. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in this utility model should still be covered by the claims of this utility model.

Claims

1. A secondary battery, characterized in that, include: The housing includes an end wall, the end wall including an explosion-proof valve; An electrode assembly is housed within the housing, the electrode assembly including a first tab stacked at one end of the electrode assembly; A current collector is located between the electrode assembly and the end wall. The current collector is welded to the first electrode tab to form a plurality of mutually spaced electrode tab weld portions between the current collector and the first electrode tab. A plurality of solder marks corresponding to the electrode tab weld portions are formed on the current collector. Each solder mark includes a plurality of first solder marks and a plurality of second solder marks. The second solder marks are connected to or spaced apart from the corresponding first solder marks and projected toward the current collector along the axial direction of the electrode assembly. The first solder marks are at least partially located within the projection of the valve opening area of ​​the explosion-proof valve, and the second solder marks are at least partially located outside the projection of the valve opening area. Wherein, along the axial direction of the electrode assembly, the number of layers to which the electrode tab welding portion corresponding to the first solder mark is connected is less than the number of layers to which the electrode tab welding portion corresponding to the second solder mark is connected.

2. The secondary battery according to claim 1, characterized in that, The electrode assembly includes a wound structure formed by stacking and winding a first electrode, a second electrode, and a diaphragm. The end of the first electrode facing the end wall includes a plurality of empty foils extending from the diaphragm along the axial direction of the electrode assembly. The plurality of empty foils are stacked to form a first electrode tab. The height of at least a portion of the first electrode tab located within the projection of the valve opening area of ​​the explosion-proof valve is less than the height of at least a portion of the first electrode tab located outside the projection of the valve opening area.

3. The secondary battery according to claim 2, characterized in that, The height of at least a portion of the first tab located within the projection of the valve opening area of ​​the explosion-proof valve gradually increases from the radially inner side to the radially outer side of the electrode assembly.

4. The secondary battery according to claim 1, characterized in that, Each of the first solder marks and the corresponding second solder mark is connected by a continuous welding path to form an integral solder mark structure; or, there is a gap between the first solder mark and the second solder mark, and the first solder mark and the second solder mark are set as independent solder marks relative to each other.

5. The secondary battery according to claim 1, characterized in that, The coverage area of ​​a plurality of first solder marks in each solder mark region is greater than the coverage area of ​​a plurality of second solder marks. A plurality of first solder marks extend linearly and are spaced apart from each other to form a coverage area of ​​the first solder marks, and a plurality of second solder marks extend linearly and are spaced apart from each other to form a coverage area of ​​the second solder marks, wherein the second solder marks are located radially outside the first solder marks. The number of some of the first solder marks is greater than the number of some of the second solder marks; The length of the first solder mark in the linear extension direction is less than the length of the second solder mark in the linear extension direction.

6. The secondary battery according to claim 5, characterized in that, A plurality of first solder marks are respectively connected to corresponding second solder marks, and at least a portion of each first solder mark is located within the projection of the opening area of ​​the explosion-proof valve. The interconnected first solder marks and corresponding second solder marks form an integral solder mark group extending linearly in the radial direction. The plurality of solder mark groups are arranged at intervals between each other, or the plurality of second solder marks are located radially outside the plurality of first solder marks and are arranged at intervals between each other.

7. The secondary battery according to claim 1, characterized in that, The first solder marks are interconnected and / or the second solder marks are interconnected.

8. The secondary battery according to claim 1, characterized in that, Along the circumferential direction of the current collector, the current collector is provided with a weak portion between adjacent solder areas, the weak portion being configured to break when the internal pressure of the secondary battery exceeds a threshold. Projecting along the axial direction of the electrode assembly toward the current collector, the weak portion is at least partially located within the projection of the valve opening region; The central region of the current collecting component is provided with a tear, one end of the weak part is located near the center of the current collecting component, adjacent weak parts are connected by the tear, and the tear is torn when the explosion-proof valve is opened.

9. A battery pack, characterized in that, The secondary battery includes any one of claims 1 to 8.

10. An electronic device, characterized in that, Includes the battery pack as described in claim 9.

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