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, an electrode assembly and a current collecting component, the shell comprises an end wall; the electrode assembly is accommodated in the shell, and the electrode assembly comprises a tab facing the end wall; the current collecting component is arranged between the electrode assembly and the end wall, and is welded with the tab to form a plurality of groups of first welding marks; wherein the multiple groups of first welding marks are uniformly distributed in the circumferential direction of the current collecting component, a central angle alpha is formed by a point, closest to the center of the current collecting component, of every two adjacent groups of first welding marks and a center connecting line of the current collecting component, and alpha is smaller than or equal to 120 degrees, so that the technical problem that the performance and the service life of the battery are affected due to high direct-current resistance is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of batteries, in particular to a secondary battery, a battery pack and an electronic device. Background Art

[0002] DC resistance is an important parameter of battery performance, which refers to the internal resistance value of the battery when direct current passes through. Heat is generated during the charging and discharging process of the battery. If the DC resistance is high, more energy will be dissipated in the form of heat, which may cause the battery temperature to rise, affecting the performance and life of the battery. Continuous high temperature will accelerate battery aging, reduce its cycle life, and increase the risk of thermal runaway. In addition, a high DC resistance will also reduce the charging and discharging rate of the battery.

[0003] Therefore, the DC resistance has an important impact on the efficiency, life, safety and cost-effectiveness of the battery. Therefore, in the process of battery design and manufacturing, how to control and optimize the DC resistance to a lower value is a technical problem that needs to be overcome in this field. Summary of the Utility Model

[0004] The utility model provides a secondary battery, a battery pack and an electronic device to improve the technical problem that the performance and life of the battery are affected due to high DC resistance.

[0005] To achieve the above and other related purposes, the utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery includes: a housing, an electrode assembly, and a current collector member; the housing includes an end wall; the electrode assembly is accommodated in the housing, and the electrode assembly includes a tab facing the end wall; the current collector member is disposed between the electrode assembly and the end wall and is welded to the tab to form multiple groups of first weld marks; wherein, the multiple groups of first weld marks are evenly distributed along the circumferential direction of the current collector member, and the central angles formed by connecting the center of the current collector member with the points closest to the center of the current collector member for each adjacent two groups of first weld marks are α, where α ≤ 120°.

[0006] In the above technical solution, the multiple groups of first weld marks are evenly distributed along the circumferential direction of the current collector member, which is beneficial to the uniform distribution of current between the current collector member and the tab, so as to reduce the overheating problem caused by too high local current density, and at the same time helps to maintain the consistency of the secondary battery to improve production efficiency. Limiting the central angle α to α ≤ 120° can ensure that there are at least 3 groups of first weld marks along the circumferential direction of the current collector member. This setting enables more tabs to be connected, which is beneficial to reducing the DC resistance of the battery, improving the current-carrying capacity, reducing heat generation, and improving the comprehensive performance and life of the secondary battery.

[0007] In an example of the secondary battery of the present utility model, along the circumferential direction of the current collector member, the central angles formed by connecting the outermost points on the adjacent sides of every two adjacent groups of first welding marks to the center of the current collector member are β, where β ≤ 90°.

[0008] In the above technical solution, the central angle β is defined and further limited to β ≤ 90°. This setting can enable the first welding marks to have a relatively large span in the circumferential direction of the current collector member, further increase the number of tabs welded to the first welding marks, be beneficial to reducing the internal resistance of the battery, improving the over-current capacity of the current, reducing heat generation, and further improving the comprehensive performance of the secondary battery.

[0009] In an example of the secondary battery of the present utility model, a circle passing through the first welding marks is made with the center of the current collector member as the center. The circle intersects with both sides of each group of first welding marks along the circumferential direction of the current collector member to form a first intersection point and a second intersection point. The center of the circle is respectively connected to the first intersection point and the second intersection point to form a central angle γ. The circle intersects with the adjacent sides of every two adjacent groups of first welding marks to form a third intersection point and a fourth intersection point. The center of the circle is respectively connected to the third intersection point and the fourth intersection point to form a central angle δ. Wherein, when the circle has the maximum radius, -10° ≤ γ - δ ≤ 10°.

[0010] In the above technical solution, there are first welding marks within the area covered by each γ central angle, and the area corresponding to the coverage area of each δ central angle is the area where there are no first welding marks between two adjacent first welding marks. The circle in this technical solution is the circle that can simultaneously intersect with both sides of the first welding marks. Then the two intersection points of the circle and the first welding marks, namely the first intersection point and the second intersection point, are the outermost points of the first welding marks in the radial direction of the current collector member, and the boundary points of the maximum span of the first welding marks in the circumferential direction of the current collector member. Similarly, the third intersection point and the fourth intersection point are the outermost points of the blank area without the first welding marks in the radial direction of the current collector member, and the boundary points of the maximum span in the circumferential direction of the current collector member. Limiting -10° ≤ γ - δ ≤ 10° can make the span difference between the two boundary points of the first welding marks and the span between adjacent first welding marks less than or equal to 10°. This setting makes the distribution of the welding points on the tabs located on the same above-mentioned circle of multiple first welding marks in the circumferential direction of the current collector member tend to be uniform, can achieve the effect that the resistance between the tabs and the current collector member tends to be uniform, and the over-current of the current tends to be uniform, and further reduces the overheating problem caused by too high local current density, and can play the role of reducing the internal resistance and improving the comprehensive performance of the secondary battery. In addition, when limiting that the circle has the maximum radius, a more significant effect of reducing the internal resistance can be obtained.

[0011] In an example of the secondary battery of the present utility model, when the circle is of any radius, -10° ≤ γ - δ ≤ 10°.

[0012] In the above technical solution, further, it is defined that the γ central angle and the δ central angle on a circle with any radius both satisfy -10° ≤ γ - δ ≤ 10°, which can make the distribution of the welding points between the tab and the current collector member on a circle with any radius tend to be uniform. This setting can further improve the uniformity of the resistance between the tab and the current collector member, achieve the effect that the current overcurrent also tends to be uniform, and further reduce the overheating problem caused by too high local current density, thereby further improving the comprehensive performance of the secondary battery.

[0013] In an example of the secondary battery of the present utility model, the current collector member is welded to the housing and at least one group of second welding marks are formed. Along the radial direction of the current collector member, the maximum distance from the first welding mark to the center of the current collector member is R1, and the maximum distance from the second welding mark to the center of the current collector member is R2. The electrode assembly includes a winding structure formed by laminating and winding a first electrode tab, a second electrode tab, and a separator. The radius of the winding structure is R5, wherein R2 - R1 ≤ 0.5R5.

[0014] In the above technical solution, it is defined that R2 - R1 ≤ 0.5R5, that is, the maximum distance between the first welding mark and the second welding mark is less than 0.5 times of R5. This setting makes the distance between the first welding mark and the second welding mark smaller, which can reduce the resistance between the first welding mark and the second welding mark, improve the current overcurrent capacity, reduce heat generation, and further improve the comprehensive performance of the secondary battery. This limitation can also keep a safe distance between the second welding mark and the tab cutting area at the outer edge of the first tab, prevent scalding the separator during the welding of the second welding mark, and reduce the risk of short circuit inside the secondary battery.

[0015] In an example of the secondary battery of the present utility model, along the radial direction of the current collector member, the maximum distance from the first welding mark to the center of the current collector member is R1, the minimum distance from the first welding mark to the center of the current collector member is R3, and the radius of the outer peripheral edge of the current collector member is R4, wherein 0.2R4 ≤ R3 < R1 ≤ 0.9R4.

[0016] In the above technical solution, the area of the tab corresponding to the 0.2R4 - 0.9R4 region is the region where the number of tab layers is relatively stable. The number of tab layers in this region is the largest and relatively uniform. The first welding mark is distributed in the stable region of the stacked number of tabs, which can realize connecting with more layers of tabs and is not easily welded through, so as to play the role of reducing internal resistance, improving conductivity, safety, and energy density, etc., and improving the battery performance.

[0017] In an example of the secondary battery of the present utility model, the electrode assembly includes a winding structure formed by laminating and winding a first electrode tab, a second electrode tab, and a separator. The winding structure includes a winding hole. Along the radial direction of the current collector member, the radius of the winding structure is R5, and the radius of the winding hole is R6, wherein R3 - R6 ≤ 0.5R5.

[0018] In the above technical solution, the setting of R3 - R6 ≤ 0.5R5 can be understood as the distance from the position where the first weld mark is closest to the center of the current collector member to the inner periphery of the winding structure being less than or equal to 0.5 times of R5. This setting enables the first weld mark to have a relatively close distance to the inner periphery of the winding structure, which can achieve the effect of increasing the number of turns connected to the tab, thereby reducing the internal resistance and improving the conductivity, safety, and energy density, etc., to improve the battery performance.

[0019] In an example of the secondary battery of the present utility model, the electrode assembly includes a winding structure formed by laminating and winding a first electrode tab, a second electrode tab, and a separator. Along the radial direction of the current collector member, the radius of the winding structure is R5, where R5 - R1 ≤ 0.5R5.

[0020] In the above technical solution, the setting of R5 - R1 ≤ 0.5R5 can be understood as the distance from the position where the first weld mark is farthest from the center of the current collector member to the outer periphery of the winding structure being less than or equal to 0.5 times of R5. This setting enables the first weld mark to have a relatively close distance to the outer periphery of the winding structure. On the one hand, it can achieve the effect of increasing the number of turns connected to the tab. On the other hand, since the single - turn length of the winding structure is larger closer to the outer periphery, the effect of reducing the internal resistance and improving the battery performance when the first weld mark increases the number of connection turns at the position close to the outer periphery is more prominent.

[0021] In an example of the secondary battery of the present utility model, along the axial direction of the current collector member, the current collector member at least covers part of the tab located on the outermost side of the electrode assembly.

[0022] In the above technical solution, at least part of the tab located on the outermost side can be covered and pressed by the current collector member, which can effectively prevent the tab from warping, so as to reduce the risk of the tab breaking and falling into the interior of the housing under the action of external force, causing a short - circuit.

[0023] The present utility model also provides a battery pack, which includes the secondary battery of any one of the above.

[0024] The present utility model also provides an electronic device, which includes the above - mentioned battery pack.

[0025] In the secondary battery of the present utility model, multiple groups of first weld marks are evenly distributed along the circumferential direction of the current collector member, which is beneficial to the uniform distribution of current between the current collector member and the tab, so as to reduce the overheating problem caused by too high local current density. At the same time, it helps to maintain the consistency of the secondary battery to improve the production efficiency. By limiting the central angle α to α ≤ 120°, at least 3 groups of first weld marks can be achieved along the circumferential direction of the current collector member. This setting enables more tabs to be connected, which is beneficial to reducing the DC resistance of the battery, improving the current - carrying capacity, reducing heat generation, and improving the comprehensive performance and service life of the secondary battery. Description of the Drawings

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other embodiments can be obtained based on these drawings.

[0027] Figure 1 Schematic diagram of the overall structure of an example of the secondary battery of the present invention;

[0028] Figure 2 Schematic diagram of the electrode assembly structure of an example of the secondary battery of the present invention;

[0029] Figure 3 Schematic diagram of the welding of the first current collector member and the electrode assembly of an example of the secondary battery of the present invention;

[0030] Figure 4 Schematic diagram of the welding of the first current collector member and the electrode assembly of an example of the secondary battery of the present invention;

[0031] Figure 5 Schematic diagram of the welding of the first current collector member and the electrode assembly of another example of the secondary battery of the present invention;

[0032] Figure 6 Schematic diagram of the welding of the first current collector member and the electrode assembly of another example of the secondary battery of the present invention;

[0033] Figure 7 Schematic diagram of the welding of the first current collector member and the electrode assembly of yet another example of the secondary battery of the present invention;

[0034] Figure 8 Schematic diagram of an example of the battery pack of the present invention;

[0035] Figure 9 Schematic diagram of an example of the electronic device of the present invention.

[0036] Element reference numeral description

[0037] 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; 120. Electrode assembly; 121. Second electrode plate; 1211. Positive current collector; 1212. Second coating area; 1213. Second uncoated area; 122. Separator; 123. First electrode plate; 1231. Negative current collector; 1232. First coating area; 1233. First uncoated area; 124. First pole tab; 125. Second pole tab; 126. Winding structure; 127. Winding hole; 130. Terminal; 140. First current collecting member; 141. First welding mark; 142. Second welding mark; 143. Circle; 150. Second current collecting member. Detailed implementation manners

[0038] The following describes the implementation manners of the present utility model through specific examples. Those skilled in the art can easily understand other advantages and effects of the present utility model from the content disclosed in this specification. The present utility model can also be implemented or applied through other different specific implementation manners. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present utility model. It should be noted that, without conflict, the following embodiments and the features in the embodiments can be combined with each other. It should also be understood that the terms used in the embodiments of the present utility model are for describing specific implementation manners, rather than limiting the protection scope of the present utility model. The test methods without specific conditions noted in the following embodiments are usually in accordance with conventional conditions or in accordance with the conditions recommended by each manufacturer.

[0039] When the embodiments give a numerical range, it should be understood that unless otherwise stated in the present utility model, any value between the two endpoints of each numerical range and any value between the two endpoints can be selected. Unless otherwise defined, all technical and scientific terms used in the present utility model, based on the understanding of those skilled in the art of the prior art and the description of the present utility model, can also use any methods, devices, and materials similar or equivalent to the methods, devices, and materials in the embodiments of the present utility model to implement the present utility model.

[0040] It should be noted that the terms such as "upper", "lower", "left", "right", "middle", and "one" cited in this specification are only for the convenience of clear narration, rather than to limit the scope of implementation of the present utility model. The change or adjustment of their relative relationships, without substantial change in the technical content, should also be regarded as the scope of implementation of the present utility model.

[0041] The secondary battery includes a housing and an electrode assembly. The electrode assembly is accommodated in the housing and is the component in the secondary battery where the electrochemical reaction occurs. One or more electrode assemblies may be included in the housing.

[0042] The electrode assembly is mainly formed by winding or laminating a positive electrode tab and a negative electrode tab, and a separator is usually provided between the positive electrode tab and the negative electrode tab. The positive electrode tab includes a positive current collector and a positive active material, and the positive active material is coated on the surface of the positive current collector; the positive current collector includes a coated area coated with the active material and an uncoated area not coated with the active material, and the uncoated area forms the positive electrode ear of the electrode assembly after winding. The negative electrode tab includes a negative current collector and a negative active material, and the negative active material is coated on the surface of the negative current collector; the negative current collector includes a coated area coated with the active material and an uncoated area not coated with the active material, and the uncoated area forms the negative electrode ear of the electrode assembly after winding. Taking a lithium-ion secondary battery as an example, the material of the positive current collector 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, lithium manganate, etc. The material of the negative current collector 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 material of the separator can be PP (polypropylene) or PE (polyethylene), etc. To protect and insulate the battery cell, an insulating film can also be coated on the outside of the battery cell, and the insulating film can be synthesized from PP, PE, PET, PVC or other polymer materials.

[0043] However, the inventors found that the DC resistance has an important impact on the efficiency, life, safety and cost-effectiveness of the secondary battery. Therefore, in the design and manufacturing process of the secondary battery, how to control and optimize the DC resistance to a lower value is a technical problem that needs to be overcome in this field.

[0044] In view of this, the present utility model provides a technical solution. Along the radial direction of the secondary battery, multiple groups of first welding marks are evenly distributed along the circumferential direction of the current collector member. The central angles formed by connecting the centers of the current collector member with the points closest to the center of the current collector member for each adjacent two groups of first welding marks are α, where α ≤ 120°. This setting enables more electrode ears to be connected, which is beneficial to reducing the DC resistance of the battery, improving the overcurrent capacity of the current, reducing heat generation, and improving the comprehensive performance and life of the secondary battery.

[0045] Please refer to Figures 1 to 9 , the present utility model provides a secondary battery 100, which includes: a housing 110, an electrode assembly 120, a pole column 130 and a current collector member.

[0046] Please refer to Figure 1, the housing 110 includes end walls. Specifically, in this embodiment, the housing 110 includes a first end wall 114 and a second end wall 111 disposed opposite to each other, and a side wall 112 surrounding the first end wall 114 and the second end wall 111. As long as a stable sealing and electrical connection relationship can be formed, 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 integral stamping, integral casting, or split welding. The surrounding of the side wall 112 is not limited. It can be surrounded in a cylindrical or prismatic shape, or can be surrounded along any other closed-loop contour that can match the first end wall 114 and the second end wall 111. As an embodiment, in this embodiment, the outer edges of the first end wall 114 and the second end wall 111 are circular, and the side wall 112 is surrounded in a cylindrical shape around the outer edges of the first end wall 114 and the second end wall 111. The second end wall 111 and the side wall 112 are integrally formed, and a circular opening 113 is formed at one end of the side wall 112 close to the first end wall 114. An accommodation cavity is formed inside the housing 110 surrounded by the second end wall 111 and the side wall 112 for accommodating the electrode assembly 120, the electrolyte, and other necessary battery components. Specifically, the diameter size of the housing 110 can be determined according to the specific size of the electrode assembly 120, such as 18 mm, 21 mm, 46 mm, etc. The material of the housing 110 can be various, such as copper, iron, aluminum, steel, aluminum alloy, etc. In order to prevent the housing 110 from rusting during long-term use, an anti-rust material such as metal nickel can also be plated on the surface of the housing 110.

[0047] Please refer to Figures 1 to 2 , the electrode assembly 120 is accommodated in the housing 110 and includes tab ears facing the end walls. Specifically, the electrode assembly 120 is a component that undergoes an electrochemical reaction in the secondary battery 100. One or more electrode assemblies 120 can be included in the housing 110. The electrode assembly 120 includes a winding structure 126 formed by laminating and winding a first electrode plate 123, a second electrode plate 121, and a separator 122. The polarities of the first electrode plate 123 and the second electrode plate 121 are opposite. In some embodiments, the first electrode plate 123 is a positive electrode plate, and the second electrode plate 121 is a negative electrode plate. In other embodiments, the first electrode plate 123 is a negative electrode plate, and the second electrode plate 121 is a positive electrode plate.

[0048] Please refer to Figures 1 to 2, in this embodiment, the first electrode tab 123 is a negative electrode tab. The first electrode tab 123 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. The first uncoated area 1233 is located at the end of the first electrode tab 123. The first uncoated area 1233 extends out of the separator 122 along the winding axis direction of the electrode assembly 120 and is bent toward the winding axis to form a first tab 124, and the first tab 124 is the corresponding negative electrode tab.

[0049] Please refer to Figures 1 to 2 , the second electrode tab 121 is a positive electrode tab. Specifically, the second electrode tab 121 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. The second uncoated area 1213 is located at the end of the second electrode tab 121. The second uncoated area 1213 extends out of the separator 122 at the other end along the winding axis direction of the electrode assembly 120 and is bent toward the winding axis to form a second tab 125, and the second tab 125 is the corresponding positive electrode tab.

[0050] Please refer to Figures 1 to 2 , the separator 122 is disposed between the first electrode tab 121 and the second electrode tab 123 to isolate 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, and the positive active material layer includes a positive active material, and the positive active material can be lithium cobaltate, lithium iron phosphate, ternary lithium, lithium manganate, etc. The material of the negative current collector 1231 can be copper, and 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 for short) or polyethylene (PE for short), etc. To protect and insulate the battery cell, an insulating film can also be coated on the outside of the battery cell, and the insulating film can be synthesized from PP, PE, polyethylene terephthalate (PET for short), polyvinyl chloride (PVC for short), or other high molecular polymer materials.

[0051] Please refer to Figure 1 and Figure 2, Further, if the first tab 124 faces the first end wall 114 or the second end wall 111, 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 111 and is electrically connected to the terminal 130 to make the terminal 130 positively charged, and the first tab 124 faces the first end wall 114, and the housing 110 is electrically connected to the first tab 124, thus being negatively charged. However, in other embodiments, the first tab 124 may also be connected to the terminal 130, and the second tab 125 may be connected to the housing 110.

[0052] Please refer to Figure 1 and Figure 2 , the terminal 130 passes through the second end wall 111 and is insulated from the second end wall 111. The structural form of the terminal 130 can be any suitable form that can pass through the second end wall 111 and be electrically connected to the first electrode plate 123 or the second electrode plate 121. For example, the cross-section can be circular, square, prismatic, or a special-shaped profile that can achieve stable electrical conduction. One end of the terminal 130 facing the electrode assembly 120 passes through the second end wall 111 and is directly or indirectly electrically connected to the first tab 124 or the second tab 125. For example, the terminal 130 can be indirectly electrically connected to the first electrode plate 123 through a current collector member. One end of the terminal 130 facing away from the electrode assembly 120 is exposed to the outside of the housing 110 to form a corresponding electrode. The electrical property of the terminal 130 can be positive or negative. For example, in one embodiment, the terminal 130 is electrically connected to the first electrode plate 123, and the first electrode plate 123 has a positive polarity, then the terminal 130 is positive, and the housing 110 forms a corresponding negative electrode. In another embodiment, the first electrode plate 123 has a negative polarity, then the terminal 130 is negative, and the housing 110 forms a corresponding positive electrode. In this embodiment, a terminal 130 mounting hole is provided on the second end wall 111, and the terminal 130 is hermetically and insulatingly mounted in the terminal 130 mounting hole. The terminal 130 is indirectly electrically connected to the second tab 125 through a current collector member. For the convenience of distinction and understanding, the current collector member electrically connected to the second tab 125 is named the second current collector member 150. One end of the terminal 130 facing away from the electrode assembly 120 is exposed to the outside of the housing 110 and is positively charged. The second current collector member 150 is connected to the positive tab, and it is preferably made of aluminum metal.

[0053] The terminal post 130 is made of a conductive metal material. The material of the terminal post 130 can be aluminum. If the material of the terminal post 130 is aluminum, the riveting process can be easily performed. In this embodiment, the material of the terminal post 130 is aluminum and the polarity is positive. Correspondingly, the material of the housing 110 is low-carbon steel and forms the negative pole correspondingly. The terminal post 130 and the housing 110 are electrically insulated. The electrical insulation between the terminal post 130 and the second end wall 111 of the housing 110 can be achieved in various ways. For example, the insulation can be achieved by placing an insulating washer between the terminal post 130 and the second end wall 111. Alternatively, the insulation can be achieved by forming an insulating coating layer on a part of the terminal post 130. Alternatively, some of the above methods can be combined and applied.

[0054] Further, please refer to Figure 1 , the electrode assembly 120 is electrically connected to the housing 110 through a current collecting member. Specifically, the current collecting member is welded to the first pole ear 124. For the convenience of distinction and understanding, the current collecting member electrically connected to the first pole ear 124 is named the first current collecting member 140. The welding method can be ultrasonic welding, resistance welding, laser welding, etc., which is not limited herein. Laser welding is used in this embodiment. The first current collecting member 140 is connected to the negative pole ear, and it is preferable to select copper metal as the material. It should be noted that the shapes of the first current collecting member 140 and the second current collecting member 150 can be any rotationally symmetric shape, such as circular, square, regular polygon, petal-shaped or other shapes with a symmetry center and can coincide with the original figure after rotating a certain angle around the symmetry center. This is not limited herein, and it is suitable to be able to achieve a stable and reliable electrical connection relationship. The centers of the first current collecting member 140 and the second current collecting member 150 are their own symmetry centers. In order to improve the positioning, processing convenience, interchangeability and unity of the current collecting member during installation, the first current collecting member 140 and the second current collecting member 150 in this embodiment both adopt circular structures.

[0055] Please refer to Figures 1 to 7, at least one set of first welding imprints 141 are formed between the current collector member and the tab during the welding process. The first welding imprints 141 can be formed by welding between the first tab 124 and the first current collector member 140, or can be formed by welding between the second tab 125 and the second current collector member 150. The number of the first welding imprints 141 can be one set, two sets, three sets, four sets, five sets or more sets. It should be noted that there is a large interval between different sets of the first welding imprints 141, and the welding tracks within the same set of the first welding imprints 141 are close to each other; each set of the first welding imprints 141 includes one or more welding points or welding lines. The shape of the first welding imprints 141 can be various, for example, it can be a straight line, a curve (such as a wavy line, an arc line, a sine curve, etc.), a broken line, other irregular figures or a combination of the above. The shapes of each set of the first welding imprints 141 can be the same or different, and no limitation is made thereto, as long as the stable electrical connection between the first tab 124 and the first current collector member 140, and between the second tab 125 and the second current collector member 150 can be achieved.

[0056] Please refer to Figure 3 , Figure 5 and Figure 7 , further, taking the first tab 124 and the first current collector member 140 as an example for illustration, multiple sets of the first welding imprints 141 are evenly distributed along the circumferential direction of the first current collector member 140. The evenly distributed setting is beneficial to the even distribution of current between the first current collector member 140 and the first tab 124, so as to reduce the overheating problem caused by too high local current density, and at the same time helps to maintain the consistency of the secondary battery 100 to improve the production efficiency. Further, the central angle formed by connecting the centers of the first current collector member 140 with the points on the first current collector member 140 that are closest to the center of the first current collector member 140 respectively for each adjacent two sets of the first welding imprints 141 is α, and the central angle α is limited to α ≤ 120°, so that at least 3 sets of the first welding imprints 141 can be achieved along the circumferential direction of the current collector member. This setting enables more tabs to be connected, which is beneficial to reducing the DC resistance of the battery, improving the current over-current capacity, reducing heat generation, and improving the comprehensive performance and service life of the secondary battery 100.

[0057] Please refer to Figure 3 , Figure 5 and Figure 7 , in an example of the secondary battery 100 of the present utility model, along the circumferential direction of the first current collector member 140, the central angle formed by connecting the centers of the first current collector member 140 with the outermost points on the adjacent sides of each adjacent two sets of the first welding imprints 141 is β, and further limited to β ≤ 90°. This setting can achieve a larger span of the first welding imprints 141 in the circumferential direction of the first current collector member 140, further increasing the number of the first tabs 124 welded to the first welding imprints 141, which is beneficial to reducing the internal resistance of the battery, improving the current over-current capacity, reducing heat generation, and further improving the comprehensive performance of the secondary battery 100.

[0058] See also Figure 4 and Figure 6 In an example of the secondary battery 100 of the present invention, a circle 143 with the center of the first current collecting member 140 as the center is formed by the first weld mark 141. The circle 143 intersects with each group of first weld marks 141 along both sides of the circumference of the first current collecting member 140 to form a first intersection and a second intersection. The first intersection and the second intersection are boundary points of the maximum span of the first weld mark 141 on the circumference of the first current collecting member 140 on the circle 143. The center of the circle 143 is connected to the first intersection and the second intersection to form a central angle γ, which means that there is a first weld mark 141 in the area covered by each central angle γ. The circle 143 intersects with one side of each adjacent two groups of first weld marks 141 to form a third intersection and a fourth intersection. The third intersection and the fourth intersection are the boundary points of the maximum span of the blank area without the first weld marks 141 in the circumferential direction of the first current collecting member 140. The center of the circle 143 is connected to the third intersection and the fourth intersection to form a central angle δ. The area covered by each central angle δ corresponds to the blank area without the first weld marks 141 between the two adjacent first weld marks 141.

[0059] See also Figure 4 , further, when the circle 143 has a maximum radius, the first intersection and the second intersection are the radially outermost sides of the first weld mark 141 in the first current collecting member 140, and the third intersection and the fourth intersection are the radially outermost sides of the blank area without the first weld mark 141 in the first current collecting member 140, and -10°≤γ-δ≤10° is further defined, so that the difference between the span of the two boundary points of the first weld mark 141 and the span between the adjacent first weld marks 141 is less than or equal to 10°, and this setting makes the distribution of the welding points of the plurality of groups of first weld marks 141 on the first pole tab 124 located on the same circle 143 in the circumferential direction of the first current collecting member 140 tend to be uniform, so that the resistance between the first pole tab 124 and the first current collecting member 140 tends to be uniform, and the length of the current flow path tends to be uniform, thereby reducing the overheating problem caused by excessive local current density, so as to improve the comprehensive performance of the secondary battery 100, and in addition, when the circle 143 is defined to have a maximum radius, a more significant effect of reducing the internal resistance can be obtained.

[0060] See also Figure 4, in an example of the secondary battery 100 of the present utility model, when the above-mentioned circle 143 has an arbitrary radius, both the γ central angle and the δ central angle satisfy -10° ≤ γ - δ ≤ 10°, which can make the distribution of the welding points between the first tab 124 and the first current collector member 140 on the circle 143 with an arbitrary radius tend to be uniform. This setting can further improve the uniformity of the resistance between the first tab 124 and the first current collector member 140, achieve the effect that the current overcurrent also tends to be uniform, and further reduce the overheating problem caused by too high local current density, thereby further improving the comprehensive performance of the secondary battery 100.

[0061] It should be noted that the above technical solution is equally applicable to the welded connection between the second current collector member 150 and the second tab 125. The specific structure will not be elaborated here. This technical solution is only applicable to the first current collector member 140 and the first tab 124, only to the second current collector member 150 and the second tab 125, and when both are used simultaneously, it can achieve the effect of reducing the DC resistance and improving the performance of the secondary battery 100.

[0062] Please refer to Figure 3 、 Figure 5 and Figure 7 , in an example of the secondary battery 100 of the present utility model, the first current collector member 140 is welded to the housing 110. The first current collector member 140 can be directly welded to the side wall 112 or welded to the first end wall 114, and this is not limited. The welding method can be ultrasonic welding, resistance welding, laser welding, etc., and this is not limited. In this embodiment, laser welding is used, and at least one group of second weld marks 142 are formed during the welding process; the number of the second weld marks 142 can be one group, two groups, three groups, four groups, five groups or more groups. It should be noted that there is a large gap between different groups of second weld marks 142, and the welding tracks within the same group of second weld marks 142 are close to each other. Each group of second weld marks 142 includes one or more welding points or weld lines. The shape of the second weld marks 142 can be various, for example, it can be a straight line, a curve (such as a wavy line, an arc line, a sine curve, etc.), a broken line, other irregular figures, or a combination of the above, and the shape of each group of second weld marks 142 can be the same or different, and this is not limited, as long as the stable electrical connection between the housing 110 and the first current collector member 140 can be achieved. Preferably, the shape of the second weld marks 142 is an arc centered on the center of the first current collector member 140.

[0063] It should be noted that the structure and shape of the first current collecting member 140 are not limited. In some embodiments, the first current collecting member 140 includes a current collecting body and a housing 110 connecting portion connected to the outer peripheral edge of the current collecting body. The current collecting body is welded to the first tab 124, and the housing 110 connecting portion is welded to the side wall 112. The specific assembly process of this structure is that the housing 110 connecting portion is first welded to the side wall 112, and then a rolling groove is rolled on the side wall 112. At the same time, the housing 110 connecting portion welded to the side wall 112 continues to bend towards the axis of the housing 110. Then, the first end wall 114 is placed on the side of the rolling groove away from the first current collecting member 140 and connected to the side wall 112 to seal the opening 113. The installation method of the first end wall 114 seals and plugs the opening 113 by means of mechanical seal. In some other embodiments, please refer to Figure 1 that the first end wall 114 seals and plugs the opening 113, the outer edge shape of the first end wall 114 corresponds to the shape of the opening 113, the outer edge of the first end wall 114 is welded to the side wall 112 to seal the opening 113, and the first current collecting member 140 is welded to the first end wall 114.

[0064] Please refer to Figure 3 、 Figure 5 and Figure 7 . Further, along the radial direction of the first current collecting member 140, the maximum distance from the first welding mark 141 to the center of the first current collecting member 140 is R1, the maximum distance from the second welding mark 142 to the center of the first current collecting member 140 is R2, and the radius of the winding structure 126 is R5. Among them, R2 - R1 ≤ 0.5R5, for example, it can be 0.1R5, 0.2R5, 0.3R5, 0.4R5 or 0.5R5, etc. Defining R2 - R1 ≤ 0.5R5 means defining that the maximum distance between the first welding mark 141 and the second welding mark 142 is less than 0.5 times of R5. This setting makes the distance between the first welding mark 141 and the second welding mark 142 smaller, which can reduce the resistance between the first welding mark 141 and the second welding mark 142, improve the current over-current capacity, reduce heat generation, and further improve the comprehensive performance of the secondary battery 100. This limitation can also keep a safe distance between the second welding mark 142 and the tab cutting area at the outer edge of the first tab 124, prevent the diaphragm 122 from being scalded when the second welding mark 142 is welded, and reduce the risk of short circuit inside the secondary battery 100.

[0065] Please refer to Figure 3 、 Figure 5 and Figure 7, in an example of the secondary battery 100 of the present utility model, along the radial direction of the first current collector member 140, the minimum distance from the first welding mark 141 to the center of the first current collector member 140 is R3, and the radius of the outer peripheral edge of the first current collector member 140 is R4. Preferably, the relationship between the difference between R1 and R3 and R4 is defined as 0.2R4 ≤ R3 < R1 ≤ 0.9R4. For example, it can be 0.2R4, 0.3R4, 0.4R4, 0.5R4, 0.6R4, 0.7R4, 0.8R4 or 0.9R4, etc. The area of the first tab 124 corresponding to the 0.2R4 - 0.9R4 region is the region where the number of layers of the first tab 124 is relatively stable. The number of layers of the first tab 124 in this region is the largest and relatively uniform. Distributing the first welding mark 141 in the stable region of the stacked number of layers of the first tab 124 can achieve connecting a larger number of layers with the first tab 124 and is not easily welded through, so as to achieve the effects of reducing internal resistance, improving conductivity, safety and energy density, etc., and improving battery performance. This technical solution is also applicable to the second current collector member 150 and the second tab 125, which will not be elaborated here.

[0066] Please refer to Figure 3 , Figure 5 and Figure 7 , in an example of the secondary battery 100 of the present utility model, the electrode assembly 120 includes a winding structure 126 formed by laminating and winding a first electrode plate 123, a second electrode plate 121 and a separator 122. The winding structure 126 includes a winding hole 127. Along the radial direction of the first current collector member 140, the radius of the winding hole 127 is R6. Preferably, the difference between R6 and R3 is defined as R3 - R6 ≤ 0.5R5. For example, it can be 0.1R5, 0.2R5, 0.3R5, 0.4R5 or 0.5R5, etc. This setting can be understood as the distance from the position where the first welding mark 141 is closest to the center of the first current collector member 140 to the inner peripheral edge of the winding structure 126 is less than or equal to 0.5 times of R5. This setting makes the first welding mark 141 have a relatively close distance to the inner peripheral edge of the winding structure 126, which can achieve the effect of increasing the number of turns connected with the first tab 124, and further achieve the effects of reducing internal resistance, improving conductivity, safety and energy density, etc., and improving battery performance. This technical solution is also applicable to the second current collector member 150 and the second tab 125, which will not be elaborated here.

[0067] Please refer to Figure 2 , Figure 3 , Figure 5 and Figure 7, in an example of the secondary battery 100 of the present utility model, the electrode assembly 120 includes a winding structure 126 formed by laminating and winding a first electrode tab 123, a second electrode tab 121, and a separator 122. Along the radial direction of the first current collector member 140, the radius of the winding structure 126 is R5. Preferably, the difference between R5 and R1 is defined as R5 - R1 ≤ 10 mm. For example, it can be 0.1R5, 0.2R5, 0.3R5, 0.4R5, or 0.5R5, etc. The setting of R5 - R1 ≤ 0.5R5 can be understood as the distance from the position where the first welding mark 141 is farthest from the center of the first current collector member 140 to the outer peripheral edge of the winding structure 126 is less than or equal to 0.5 times of R5. This setting makes the first welding mark 141 have a relatively close distance from the outer peripheral edge of the winding structure 126. On the one hand, it can achieve the effect of increasing the number of turns connected to the first electrode tab 124. On the other hand, since the single-turn length of the winding structure 126 is larger when it is closer to the outer peripheral edge, the effect of reducing the internal resistance and improving the battery performance when the first welding mark 141 increases the number of turns connected to the first electrode tab 124 at the position close to the outer peripheral edge is more prominent. This technical solution is also applicable to the second current collector member 150 and the second electrode tab 125, which will not be elaborated here.

[0068] Considering that the outermost first electrode tab 124 is in a free state and has a risk of breaking off, in an example of the secondary battery 100 of the present utility model, along the axial direction of the first current collector member 140, the first current collector member 140 at least covers a part of the outermost first electrode tab 124 located in the electrode assembly 120. At least a part of the outermost first electrode tab 124 can be covered and pressed by the first current collector member 140, which can effectively prevent the first electrode tab 124 from warping, so as to reduce the risk of the first electrode tab 124 breaking and falling into the interior of the housing 110 under external force, causing a short circuit.

[0069] In an example of the secondary battery 100 of the present utility model, please refer to Figure 3 and Figure 4 , there are 4 groups of the first welding marks 141. The shape of each group of the first welding marks 141 is the same, and it is a Y-shaped structure formed by three straight lines opening towards the outer peripheral edge of the first current collector member 140, and they are evenly arranged along the circumferential direction of the first current collector member 140. There are 3 groups of the second welding marks 142. The shapes of the second welding marks 142 are all arcs with the center of the first current collector member 140 as the center of the circle, and they are evenly arranged along the circumferential direction of the first current collector member 140. α = 90°, β = 40°, γ = 45°, δ = 45°. R1 = 15 mm, R2 = 20.5 mm, R3 = 4.7 mm, R4 = 23 mm, R5 = 22 mm, R6 = 2.6 mm.

[0070] In another example of the secondary battery 100 of the present utility model, please refer to Figure 5 and Figure 6, there are 3 groups of the first welding marks 141, and the shapes of each group of the first welding marks 141 are the same, all being a V-shaped structure opening towards the outer peripheral edge of the first current collector member 140, and they are evenly arranged circumferentially along the first current collector member 140. The m value of the second welding marks 142 is 3, and the shapes of the second welding marks 142 are all arcs centered on the center of the first current collector member 140, and they are evenly arranged circumferentially along the first current collector member 140. α = 120°, β = 60°, γ = 45°, δ = 75°. R1 = 15 mm, R2 = 21 mm, R3 = 7.5 mm, R4 = 23 mm, R5 = 22 mm, R6 = 2.6 mm.

[0071] In another example of the secondary battery 100 of the present utility model, please refer to Figure 7 , there are 4 groups of the first welding marks 141, and the shapes of each group of the first welding marks 141 are the same, all composed of three parallel wavy lines arranged, and they are evenly arranged circumferentially along the first current collector member 140. There are 3 groups of the second welding marks 142, and the shapes of the second welding marks 142 are all arcs centered on the center of the first current collector member 140, and they are evenly arranged circumferentially along the first current collector member 140. α = 90°, β = 57.5°. R1 = 16 mm, R2 = 21.5 mm, R3 = 6.5 mm, R4 = 23 mm, R5 = 22 mm, R6 = 2.6 mm.

[0072] Please refer to Figure 8 , the present utility model also provides a battery pack 10. The battery pack 10 includes the secondary battery 100 of any one of the above. In an embodiment of the battery pack 10 of the present utility model, 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 in parallel with each other, or in a mixed manner of series and parallel. The box cover 102 covers the box body 101 to protect the plurality of secondary batteries 100. It should be noted that in addition to the secondary battery 100 of the present utility model, the battery pack 10 may also include parts such as a battery pack thermal management system, a circuit board, etc. The battery pack 10 may be a battery module or a battery pack, an energy storage electric cabinet, etc.; details are not elaborated here one by one.

[0073] Please refer to Figure 9, the present utility model further provides an electronic device 1, and the electronic device 1 includes the above-mentioned battery pack 10. The working part 11 is electrically connected to the battery pack 10 to obtain electrical energy support. As an example, the electronic device 1 is a vehicle, and the vehicle can be a fuel vehicle, a gas vehicle or a new energy vehicle. The new energy vehicle can be a pure electric vehicle, a hybrid vehicle or an extended-range vehicle, etc., but is not limited thereto. The working part 11 is the vehicle body, and the battery pack 10 is arranged at the bottom of the vehicle body and provides electrical energy support for the running of the vehicle or the operation of the electrical components in the vehicle. However, in some other embodiments, the electronic device 1 can also be a mobile phone, a portable device, a laptop 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 spaceship, etc.; the working part 11 can be a unit component that can obtain the electrical energy of the battery pack 10 and perform corresponding work, such as the fan blade rotation unit of a fan, the dust suction working unit of a vacuum cleaner, etc. The electric toy includes a fixed or mobile electric toy, for example, a game console, an electric vehicle 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 assembly electric tool and a railway electric tool, for example, an electric drill, an electric grinding wheel, an electric wrench, an electric screwdriver, a hammer drill, an impact electric drill, a concrete vibrator and a planer, etc. The embodiments of the present application do not impose special restrictions on the above-mentioned electronic device 1.

[0074] For the secondary battery of the present utility model, multiple groups of first welding marks are evenly distributed along the circumference of the current collector member, which is beneficial to the uniform distribution of current between the current collector member and the tab, so as to reduce the overheating problem caused by too high local current density. At the same time, it helps to maintain the consistency of the secondary battery to improve production efficiency. By limiting the central angle α to α≤120°, at least 3 groups of first welding marks can be realized along the circumference of the current collector member. This setting enables more tabs to be connected, which is beneficial to reducing the DC resistance of the battery, improving the overcurrent capacity of the current, reducing heat generation, and improving the comprehensive performance and lifespan of the secondary battery. Therefore, the present utility model effectively overcomes some practical problems in the prior art and thus has high utilization value and practical significance. The above embodiments are only illustrative of the principles and effects of the present utility model and are not used to limit the present utility model. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present utility model. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present utility model should still be covered by the claims of the present utility model.

Claims

1. A secondary battery, characterized in that, Comprising: A housing including an end wall; An electrode assembly accommodated in the housing, the electrode assembly including a tab facing the end wall; A current collecting member disposed between the electrode assembly and the end wall and welded to the tab to form multiple groups of first welding imprints; Wherein, multiple groups of the first welding imprints are evenly distributed circumferentially along the current collecting member, and the central angles formed by connecting the centers of the current collecting member to the points closest to the center of the current collecting member for each adjacent two groups of first welding imprints are α, wherein, α ≤ 120°.

2. The secondary battery according to claim 1, wherein Circumferentially along the current collecting member, the central angles formed by connecting the centers of the current collecting member to the outermost points on the adjacent sides of each adjacent two groups of first welding imprints are β, wherein, β ≤ 90°.

3. The secondary battery according to claim 1, characterized in that, Taking the center of the current collecting member as the center of a circle and making a circle passing through the first welding imprint, the circle intersects the two circumferential sides of each group of the first welding imprints to form a first intersection point and a second intersection point, connecting the center of the circle to the first intersection point and the second intersection point respectively to form a central angle γ, the circle intersects the adjacent sides of each adjacent two groups of the first welding imprints to form a third intersection point and a fourth intersection point, connecting the center of the circle to the third intersection point and the fourth intersection point respectively to form a central angle δ, wherein, when the circle has the maximum radius, -10° ≤ γ - δ ≤ 10°.

4. The secondary battery according to claim 3, characterized in that, When the circle is of any radius, -10° ≤ γ - δ ≤ 10°.

5. The secondary battery according to claim 1, wherein The current collecting member is welded to the housing and forms at least one group of second welding imprints. Radially along the current collecting member, the maximum distance from the first welding imprint to the center of the current collecting member is R1, the maximum distance from the second welding imprint to the center of the current collecting member is R2, the electrode assembly includes a winding structure formed by laminating and winding a first pole piece, a second pole piece and a separator, and the radius of the winding structure is R5, wherein, R2 - R1 ≤ 0.5R5.

6. The secondary battery according to claim 1, characterized in that, Radially along the current collecting member, the maximum distance from the first welding imprint to the center of the current collecting member is R1, the minimum distance from the first welding imprint to the center of the current collecting member is R3, and the radius of the outer periphery of the current collecting member is R4, wherein, 0.2R4 ≤ R3 < R1 ≤ 0.9R4.

7. The secondary battery according to claim 6, wherein The electrode assembly includes a winding structure formed by laminating and winding a first pole piece, a second pole piece and a separator. The winding structure includes a winding hole. Radially along the current collecting member, the radius of the winding structure is R5, and the radius of the winding hole is R6, wherein, R3 - R6 ≤ 0.5R5.

8. The secondary battery according to claim 6, characterized in that, The electrode assembly includes a winding structure formed by laminating and winding a first pole piece, a second pole piece and a separator. Radially along the current collecting member, the radius of the winding structure is R5, wherein, R5 - R1 ≤ 0.5R5.

9. The secondary battery according to claim 1, wherein Axially along the current collecting member, the current collecting member at least covers part of the tabs located on the outermost side of the electrode assembly.

10. A battery pack, characterized in that, Including the secondary battery according to any one of claims 1 to 9.

11. An electronic device, characterized in that, Including the battery pack according to claim 10.

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