Secondary battery, battery pack, and electronic device

Abstract

The utility model provides a secondary battery, battery pack and electronic device, the secondary battery includes shell, electrode subassembly and current collecting member, shell includes end wall, electrode subassembly is provided in the shell, electrode subassembly includes the tab facing the end wall. The current collecting component is arranged between the electrode assembly and the end wall and comprises a tab welding area, and the tab welding area is in welded connection with the tab. The thickness of the tab welding area is T, the ten-point average roughness of the surface, deviating from the tab direction, of the tab welding area is Rz, and Rz / T is smaller than 25%. The technical problem that the laser welding reject ratio of the current collecting component is high can be solved.

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] In some large cylindrical batteries, the current collector and the tab are usually fixedly connected by laser welding. Since the substrate material of the current collector is copper, and copper has a high reflectivity to lasers, the welding quality between the current collector and the tab is difficult to control, resulting in a relatively high product defect rate. Utility Model Content

[0003] This invention provides a secondary battery, a battery pack, and an electronic device to improve the technical problem of high defect rate in laser welding of current collector components.

[0004] 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, and the electrode assembly is disposed within the casing, including tabs facing the end wall. The current collector is disposed between the electrode assembly and the end wall, and includes a tab welding area, which is welded to the tab. The thickness of the tab welding area is T, and the ten-point average roughness of the surface of the tab welding area facing away from the tab is Rz, where Rz / T < 25%.

[0005] In the above technical solution, by limiting the surface roughness of the electrode welding area away from the electrode, the electrode welding area can have a higher laser capture capability, reducing the direct reflection of the laser by the current collector during laser welding and increasing the scattering direction and frequency. This improves the stability of the current collector's laser absorption, thereby improving the welding effect between the electrode and the current collector, reducing welding bursts, and increasing the welding yield. This addresses the technical problems of high nickel plating cost and difficulty in controlling process stability on the current collector surface.

[0006] In one example of the secondary battery of this utility model, the arithmetic mean roughness of the surface of the electrode welding area away from the electrode direction is Ra; wherein, Ra>0.2μm, 1.2μm<Rz<3μm.

[0007] In the above technical solution, by controlling the arithmetic mean roughness Ra and the ten-point mean roughness Rz of the surface of the electrode welding area away from the electrode, the contact area between the laser beam and the surface of the electrode welding area is increased, the radial reflection during laser welding is reduced, the absorption of laser energy is increased, defects such as burst points or pores during welding are reduced, the welding effect is improved and the welding yield is increased.

[0008] In one example of the secondary battery of this utility model, the oxygen content of the metal in the electrode welding area is n, where n < 0.04%.

[0009] In the above technical solution, the oxygen content of the metal n < 0.04%, which reduces welding defects such as poor weld formation, easy deformation, hot cracking, spatter, and porosity during the welding process, improves the strength and sealing performance of the weld, enhances the stability and reliability of the welding, and thus enhances the overall performance and reliability of the battery.

[0010] In one example of the secondary battery of this utility model, the surface of the electrode welding area away from the electrode is an embossed area, and the surface of the electrode welding area facing the electrode is a flat area.

[0011] In the above technical solution, an embossing process is performed on the surface of the electrode welding area away from the electrode tab direction to form an embossed area. This changes the surface roughness of the current collector component. The embossed structure of the embossed area enhances the ability to capture laser energy, reduces the direct reflection of the laser by the current collector component during laser welding, increases the scattering direction and frequency, and further enhances the surface's ability to capture laser energy. The design of the embossed area optimizes the absorption and distribution of laser energy, avoiding uneven distribution of welding heat, which could lead to excessive local welding heat in the electrode welding area and damage to the diaphragm below the electrode tab.

[0012] In one example of the secondary battery of this utility model, the cross-section of the embossed area includes multiple spaced embossed patterns. The bottom of adjacent embossed patterns is arc-shaped, and the top of some embossed patterns extends beyond the reference plane. The distance from the top of the embossed pattern extending beyond the reference plane to the reference plane is H, where H < 1 / 2Rz. The reference plane is flush with the surface of the current collector located outside the embossed area.

[0013] In the above technical solution, the bottom of the embossed area is designed with an arc shape, which allows for diffuse reflection of the laser when it contacts the bottom surface of the embossed area. This further reduces the laser's radial reflectivity, improves welding uniformity and quality, and avoids welding defects such as incomplete welds or over-welds. Simultaneously, the arc shape at the bottom of the embossed area reduces metal debris during the stamping process, minimizing contamination of the battery interior and reducing the likelihood of short circuits and other malfunctions. Controlling the distance H from the top of the embossed pattern to the reference plane to be less than 1 / 2Rz further optimizes beam reflection and heat distribution during laser welding, preventing excessively high peaks in the embossed pattern that could cause excessive reflection during laser welding, thereby improving welding quality and avoiding welding defects.

[0014] In one example of the secondary battery of this utility model, the surface area of ​​the embossed area is S, the embossed area includes multiple flat portions, the multiple flat portions are located at the top and / or bottom of the embossed area, and the total area of ​​the multiple flat portions is S1, wherein S1 < 0.2S.

[0015] In the above technical solution, controlling the total area S1 of the flat part in the embossed area reduces the reflectivity of the laser's direct reflection, thereby reducing welding defects such as porosity and spatter that may occur during laser welding, ensuring that more laser energy can be absorbed by the embossed area, and improving the uniformity of welding.

[0016] In one example of the secondary battery of this utility model, the surface oil stain value of the electrode welding area is RFU, and RFU < 8.

[0017] In the above technical solution, the welding surface of the electrode welding area is cleaned, and the surface oil stain value is controlled to be <8. This reduces the reflection of laser by oil stains or other contaminants, increases the absorption rate of laser by the electrode welding area, and increases the penetration depth. This improves the problem of the presence of oil stains or other contaminants affecting the welding quality and enhances the stability and reliability of the welding.

[0018] In one example of the secondary battery of this utility model, the current collector is made of copper, and the Vickers hardness value of the current collector ranges from 45 to 75 Hv.

[0019] In the above technical solution, using copper as the current collector ensures efficient current transmission within the battery, reduces internal resistance, and improves charge and discharge efficiency. Copper current collectors with a Vickers hardness of 45-75 HV possess moderate hardness, ensuring mechanical stability during welding, reducing damage caused by mechanical stress, and achieving good intermetallic bonding through plastic deformation during welding, thus increasing the stability and safety of the structural connection. Furthermore, using copper as the current collector offers good chemical stability and can reduce battery production costs.

[0020] This utility model also provides a battery pack, which includes any of the above-mentioned secondary batteries.

[0021] This invention also provides an electronic device that includes the aforementioned battery pack.

[0022] This novel secondary battery, by limiting the surface roughness of the electrode welding area away from the electrode tab, enables the electrode welding area to have a higher laser capture capability. This reduces the direct reflection of laser light from the current collector component during laser welding, increasing the direction and frequency of scattering. It improves the stability of laser absorption by the current collector component, thereby improving the welding effect between the electrode tab and the current collector component, reducing welding bursts, incomplete welds, and over-welding, and increasing the welding yield. This addresses the technical problem of high defect rates in laser welding of current collector components. Attached Figure Description

[0023] 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.

[0024] Figure 1 This is a schematic diagram of the overall structure of an example of a secondary battery of this utility model;

[0025] Figure 2 This is a schematic diagram of the electrode assembly structure of an example of the secondary battery of this utility model;

[0026] Figure 3 This is a schematic diagram of the current collector structure of an example of the secondary battery of this utility model;

[0027] Figure 4 This is a schematic diagram of the cross-sectional structure of the embossed area of ​​an example of a secondary battery of this utility model;

[0028] Figure 5 This is a schematic diagram of the cross-sectional structure of the embossed area of ​​another example of the secondary battery of this utility model;

[0029] Figure 6 for Figure 5 A magnified structural diagram of region A;

[0030] Figure 7 This is a schematic diagram of the embossed area receiving laser light in an example of a secondary battery of this utility model;

[0031] Figure 8 This is a schematic diagram of an example of the battery pack of this utility model;

[0032] Figure 9 This is a schematic diagram of an example of the electronic device of this utility model.

[0033] Component designation explanation:

[0034] 1. Electronic device; 10. Battery pack; 101. Housing; 102. Cover; 11. Working part; 100. Secondary battery; 110. Housing; 111. First end wall; 112. Side wall; 113. Opening; 114. Second end 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 current collector; 1232. Second coated area; 1233. Second uncoated area; 124. First tab; 125. Second tab; 130. First current collector component; 131. Tab welding area; 132. Embossed area; 1321. Embossed pattern; 1322. Flat part; 133. Flat area; 140. Terminal post; 150. Second current collector component. Detailed Implementation

[0035] 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.

[0036] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated 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, devices, and materials similar to or equivalent to those described, used, or made of materials in the embodiments of this invention.

[0037] 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.

[0038] To address the high defect rate in existing laser welding of current collector components, this invention provides a secondary battery, a battery pack, and an electronic device. This secondary battery improves the welding effect, reduces welding bursts, and enhances the stability of laser absorption and welding yield by altering the surface roughness of the current collector component.

[0039] Please see Figures 1 to 9 This utility model provides a secondary battery, a battery pack and an electronic device. The secondary battery 100 includes: a housing 110, an electrode assembly 120, a current collector and a terminal post 140.

[0040] Please see Figure 1 The housing 110 includes end walls. Specifically, in this embodiment, the housing 110 includes a first end wall 111 and a second end wall 114 disposed opposite to each other, and a side wall 112 surrounding the first end wall 111 and the second end wall 114. As long as a stable sealing and electrical connection relationship can be formed, the connection between the first end wall 111 and the side wall 112, and between the second end wall 114 and the side wall 112, can be achieved in various ways, such as integral stamping, integral casting, or separate welding. The circumference of the side wall 112 is not limited; it can be cylindrical or prismatic, or it can be along any other closed-loop contour that can match the end wall. In this embodiment, the outer edges of the first end wall 111 and the second end wall 114 are circular, and the side wall 112 is cylindrical and surrounds the outer edges of the first end wall 111 and the second end wall 114. The first end wall 111 and the side wall 112 are integrally formed, and a circular opening 113 is formed at the end of the side wall 112 opposite to the first end wall 111. The second end wall 114 seals the opening 113. A receiving cavity is formed within the housing 110, enclosed by the first end wall 111 and the side wall 112, for accommodating the electrode assembly 120, electrolyte, and other necessary battery components. Specifically, the diameter of the housing 110 can be determined according to the specific dimensions of the electrode assembly 120, such as 18mm, 21mm, 46mm, etc. The housing 110 can be made of various materials, such as copper, iron, aluminum, steel, aluminum alloy, etc. To prevent the housing 110 from rusting during long-term use, a rust-preventive material such as metallic nickel can be plated on the surface of the housing 110.

[0041] Please see Figures 1 to 2The electrode assembly 120 is housed within the casing 110 and is a component in the secondary battery 100 where electrochemical reactions occur. The casing 110 may contain one or more electrode assemblies 120. The electrode assembly 120 includes a wound structure formed by stacking and winding a first electrode 121, a second electrode 123, and a separator 122. The first electrode 121 and the second electrode 123 have opposite polarities. In some embodiments, the first electrode 121 is a positive electrode and the second electrode 123 is a negative electrode; in other embodiments, the first electrode 121 is a negative electrode and the second electrode 123 is a positive electrode.

[0042] Please see Figures 1 to 2 In this embodiment, 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 extends out of the diaphragm 122 along the winding axis direction of the electrode assembly 120 and bends towards the winding axis to form a first tab 124. The first tab 124 is the corresponding negative tab.

[0043] Please see Figures 1 to 2 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 other end of the second uncoated area 1233 extends out of the diaphragm 122 along the winding axis of the electrode assembly 120 and is bent toward the winding axis to form a second tab 125. The second tab 125 is the corresponding positive tab.

[0044] Please see Figures 1 to 2A 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.

[0045] Please see Figure 1 and Figure 2 Furthermore, if the first tab 124 faces either the first end wall 111 or the second end wall 114, then the second tab 125 faces the other end of the housing 110. In this embodiment, the second tab 125 faces the first end wall 111 and is electrically connected to the terminal post 140, making the terminal post 140 positively charged. The tab facing the second end wall 114 is the first tab 124, 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 terminal post 140, and the second tab 125 can be connected to the housing 110.

[0046] Please see Figure 1The electrode post 140 passes through the first end wall 111 and is insulated from it. The electrode post 140 can be any suitable form that can pass through the first end wall 111 and be electrically connected to the first electrode 123 or the second electrode 121. For example, the cross-section can be circular, square, prismatic, or an irregular shape that can achieve stable conductivity. The end of the electrode post 140 facing the electrode assembly 120 passes through the first end wall 111 and is directly electrically connected to the first tab 124 or the second tab 125 or indirectly connected. For example, the electrode post 140 can be electrically connected to the first electrode 121 through a current collector. The end of the electrode post 140 facing away from the electrode assembly 120 is exposed to the outside of the housing 110 to form a corresponding electrode. The electrical polarity of the electrode post 140 can be positive or negative. For example, in one embodiment, the electrode post 140 is electrically connected to the first electrode 121. If the first electrode 121 is positive, then the electrode post 140 is positive, and the housing 110 forms the corresponding negative electrode. In another embodiment, the first electrode 121 is negative, so the electrode post 140 is negative, and the housing 110 forms the corresponding positive electrode. In this embodiment, the first end wall 111 is provided with an electrode post 140 mounting hole. The electrode post 140 is sealed and insulatedly installed in the electrode post 140 mounting hole. The electrode post 140 is electrically connected to the second electrode tab 125 through a current collector. For ease of distinction and understanding, the current collector connected to the second electrode tab 125 is named the second current collector 150. The end of the electrode post 140 facing away from the electrode assembly 120 is exposed to the outside of the housing 110 and is positively charged. The second current collector 150 is connected to the positive electrode tab. Aluminum is a preferred material.

[0047] The electrode post 140 is made of a conductive metallic material. The material of the electrode post 140 can be aluminum. If the material of the electrode post 140 is aluminum, a riveting process can be easily performed. In this embodiment, the electrode post 140 is made of aluminum and is positively polarized. Corresponding to the electrode post 140, the housing 110 is made of low-carbon steel and forms the negative electrode. The electrode post 140 and the housing 110 are electrically insulated. Electrical insulation between the electrode post 140 and the first end wall 111 of the housing 110 can be achieved in various ways. For example, insulation can be achieved by placing an insulating washer between the electrode post 140 and the first end wall 111. Alternatively, insulation can be achieved by forming an insulating coating layer on a portion of the electrode post 140. Alternatively, some of the above methods can be combined.

[0048] For further details, please refer to Figure 1The electrode assembly 120 is electrically connected to the housing 110 via a current collector, specifically, the current collector is welded to the first tab 124. For ease of distinction and understanding, the current collector electrically connected to the first tab 124 is named the first current collector 130. In this embodiment, the first current collector 130 and the first tab 124 are laser-welded, and the first tab 124 is the negative electrode tab. It should be noted that the shapes of the first current collector 130 and the second current collector 150 can be any rotationally symmetrical shape, such as a circle, square, regular polygon, petal shape, or other shape with a center of symmetry that can coincide with the original shape after rotating around the center of symmetry by a certain angle. There is no limitation on this, as long as a stable and reliable electrical connection can be achieved. The center of the first current collector 130 and the second current collector 150 is their own center of symmetry. To improve the positioning, processing convenience, interchangeability, and uniformity of the current collectors during installation, both the first current collector 130 and the second current collector 150 in this embodiment adopt a circular structure.

[0049] Please see Figures 1 to 5 The current collector includes a tab welding area 131. The tab welding area 131 can be the area where the first current collector 130 is welded to the first tab 124 to achieve electrical connection between the first current collector 130 and the first tab 124; or it can be the area where the second current collector 150 is welded to the second tab 125 to achieve electrical connection between the second current collector 150 and the second tab 125.

[0050] Please see Figures 3 to 7 Taking the first current collector 130 and the first electrode 124 as an example, the first current collector 130 includes an electrode welding area 131, which is welded to the first electrode 124. The thickness of the electrode welding area 131 is T, which is the thickness of the substrate in the electrode welding area 131 before the surface roughness is changed. The surface roughness of the electrode welding area 131 in the direction away from the first electrode 124 is changed; that is, the surface of the electrode welding area 131 that receives the welding laser is the surface where the surface roughness is changed. The ten-point average roughness of the surface of the electrode welding area 131 in the direction away from the first electrode 124 is Rz, where Rz / T < 25%, and the ten-point average roughness Rz is the maximum distance between the peaks and troughs within the area. The process of changing the surface roughness state of the electrode welding area 131 in the direction away from the first electrode 124 is not limited. For example, it can be embossing, laser cleaning or acid etching of the electrode welding area 131, but is not limited to these.

[0051] By roughening the surface of the electrode welding area 131 in the direction away from the first electrode 124, the surface roughness of the welding area of ​​the first current collector 130 is changed, increasing the laser energy capture capability of the surface of the first current collector 130 and reducing the direct reflection of the laser by the surface of the first current collector 130 during laser welding with the first electrode 124, thus increasing the direction and frequency of laser scattering. This improves the stability of laser absorption by the first current collector 130, thereby improving the welding effect between the first electrode 124 and the first current collector 130, reducing welding bursts, incomplete welds, over-welding, etc., and improving the welding yield. At the same time, changing the surface roughness of the electrode welding area 131 can optimize the laser energy distribution and avoid uneven welding heat distribution, which could cause excessive local welding heat in the electrode welding area 131 and damage the diaphragm 122 below the first electrode 124. It should be noted that this technical solution is also applicable to the second current collector 150 and the second electrode 125, which will not be described in detail here.

[0052] It should be noted that the number of electrode welding areas 131 is not limited; there can be two, four, six, or more. The arrangement of the multiple electrode welding areas 131 is also not limited; they can be arranged circumferentially along the first current collector 130, or horizontally and vertically. The shape of the electrode welding areas 131 is also not limited; they can be circular, square, elliptical, polygonal, or other irregular shapes. In this embodiment, please refer to... Figure 3 Four electrode welding areas 131 are provided. Each electrode welding area 131 is rectangular and is evenly distributed circumferentially around the axis of the first current collector 130. Please refer to... Figure 4 and Figure 5 In one example of the secondary battery of this utility model, the arithmetic mean roughness of the surface of the electrode welding area 131 facing away from the first electrode 124 is Ra, where Ra > 0.2 μm. The control range of the ten-point average roughness Rz of the surface of the electrode welding area 131 facing away from the first electrode 124 is 1.2 μm < Rz < 3 μm. For example, Rz can be 1.3 μm, 1.5 μm, 2.2 μm, etc., but is not limited thereto. By controlling the arithmetic mean roughness Ra and the ten-point average roughness Rz of the surface of the electrode welding area 131 facing away from the first electrode 124, the contact area between the laser beam and the surface of the electrode welding area 131 is increased, the direct reflection during laser welding is reduced, the absorption of laser energy is increased, defects such as bursts or pores during welding are reduced, the welding effect is improved, and the welding yield is increased. It should be noted that the arithmetic mean roughness Ra involved in this embodiment refers to the value calculated by arithmetically averaging the absolute values ​​of the surface height deviations within the area. In this embodiment, the ten-point average roughness Rz refers to the maximum height difference between the peaks and troughs within the region. It should be noted that this technical solution also applies to the second current collector 150 and the second tab 125, and will not be elaborated further here.

[0053] In one example of the secondary battery of this utility model, the oxygen content of the metal in the tab welding area 131 is n, where n < 0.04%. Specifically, in this embodiment, the first current collector 130 is made of copper, and the oxygen content of the copper in the tab welding area 131 is n < 0.04%. This reduces welding defects such as poor weld formation, easy deformation, hot cracking, spatter, and porosity during the welding process, improves the strength and sealing performance of the weld, enhances the stability and reliability of the welding, and thus improves the overall performance and reliability of the battery. It should be noted that this technical solution is also applicable to the second current collector 150 and the second tab 125, which will not be described in detail here.

[0054] Please see Figure 4 and Figure 5 Compared to the uncertainty and low efficiency of laser cleaning or acid etching in changing the surface roughness of the tab welding area 131, in this example of a secondary battery, an embossing process is used to change the surface roughness of the tab welding area 131. The embossing process uses a mold, which can be reused, resulting in higher processing speed and efficiency. Furthermore, mold embossing allows for more precise control of the surface roughness value, leading to greater consistency and predictability in the surface roughness of the embossed tab welding area 131. Specifically, in this embodiment, the surface of the tab welding area 131 facing away from the first tab 124 is the embossed area 132, i.e., the surface of the tab welding area 131 on the laser-receiving side is the embossed area 132. The shape of the embossed pattern in the embossed area 132 is not limited; it can be any suitable shape that satisfies the surface roughness state of the tab welding area 131 and increases the laser energy capture capability of the tab welding area 131 surface. Examples include regular indentations, flat teeth, grids, dots, lines, stripes, or wavy patterns, but these are not limited to these. Specifically, in this embodiment, the embossing pattern of the embossed area 132 consists of dotted raised areas distributed throughout the embossed area 132. This alters the surface roughness of the tab welding area 131, increasing its ability to capture laser energy and reducing direct reflection of the laser beam during laser welding, thus increasing the direction and frequency of scattering. This improves the welding yield between the first tab 124 and the first current collector 130 and reduces welding bursts. Simultaneously, the design of the embossed area 132 optimizes laser energy absorption and distribution, preventing uneven heat distribution during welding. This avoids excessive localized welding heat in the tab welding area 131 during welding, which could cause heat to penetrate the first tab 124 and damage the diaphragm 122 beneath it. It should be noted that this technical solution also applies to the second current collector 150 and the second tab 125, and will not be elaborated further here.

[0055] Please see Figure 1 , Figure 2 and Figure 4The surface of the electrode welding area 131 facing the first electrode 124 is a flat area 133. The flat area 133 is located on the surface of the first current collector 130 facing the first electrode 124, and is on the side where the first electrode 124 is welded to the first current collector 130. The surface of the flat area 133 maintains the surface morphology of the original substrate of the first current collector 130. Maintaining the surface morphology of the original substrate ensures the welding area between the first current collector 130 and the first electrode 124, ensuring the welding quality between the first current collector 130 and the first electrode 124, thereby maintaining a stable electrical connection between the electrode assembly 120 and the first current collector 130. It should be noted that this technical solution also applies to the second current collector 150 and the second electrode 125, which will not be elaborated further here.

[0056] Please see Figure 4 and Figure 7 In one example of the secondary battery of this utility model, the cross-section of the embossed area 132 includes multiple spaced embossed patterns 1321. These patterns are distributed in a dotted pattern within the embossed area 132, with each individual pattern exhibiting a peak-valley structure. The bottoms of adjacent embossed patterns 1321 are arc-shaped; that is, the valley bottoms and peak tops of the peak-valley structure embossed patterns 1321 are arc-shaped or smooth surfaces. The arc-shaped bottom design of the embossed area 132 allows for diffuse reflection of the laser when it contacts the bottom surface, further reducing direct reflection and thus lowering the laser's radial reflectivity, improving welding uniformity and quality. Simultaneously, the arc-shaped bottom design of the embossed area 132 reduces metal debris during the stamping process, minimizing contamination of the battery interior and reducing the likelihood of short circuits and other malfunctions.

[0057] Please see Figure 4 and Figure 7 Provided that the ten-point average roughness of the embossed area 132 is Rz and Rz / T < 25%, the heights of the peaks and valleys of the multiple embossed patterns 1321 can be the same or different. In this embodiment, the tops of some embossed patterns 1321 extend beyond the reference plane, and the distance from the top of the embossed pattern 1321 extending beyond the reference plane to the reference plane is H, where H < 1 / 2Rz. This reference plane is flush with the surface of the first current collector 130 located outside the embossed area 132; that is, the reference plane is the horizontal position of the electrode welding area 131 when it is not embossed. By limiting the height of the peaks of the embossed patterns 1321, the beam reflection and heat distribution during the laser welding process are further optimized, avoiding excessive reflection caused by excessively high peaks of the embossed patterns 1321 during laser welding, thereby improving welding quality and avoiding welding defects. It should be noted that this technical solution also applies to the second current collector 150 and the second electrode 125, which will not be elaborated further here.

[0058] Please see Figure 5 and Figure 6 To reduce the difficulty of mold design and further precisely control the surface roughness of the embossed area 132 after stamping, in one example of the secondary battery of this utility model, the surface area of ​​the embossed area 132 is S. The embossed area 132 includes multiple flat portions 1322, which are relatively evenly distributed at the top and bottom of the embossed area 132. Specifically, the flat portions 1322 are located at the peaks or valleys of the embossed pattern 1321. The surface appearance of the flat portions 1322 is flush with the surface appearance when unembossed, that is, when laser light irradiates the flat portions 1322, the radial reflectivity of the flat portions 1322 to the laser is close to the radial reflectivity of the substrate in the unembossed state. Let the total area of ​​the multiple flat portions 1322 be S1, such that S1 < 0.2S. By controlling the proportion of the total area S1 of the flat portion 1322 in the surface area S of the embossed area 132, the influence of direct laser reflection is reduced, thereby reducing welding defects such as porosity and spatter that may occur during laser welding, ensuring that more laser energy can be absorbed by the embossed area, and improving the uniformity of welding.

[0059] It should be noted that the method for measuring the total area S1 of multiple flat portions 1322 is not limited. For example, a three-dimensional scanning method can be used to measure the total area S1. A charge-coupled device (CCD) camera is used to scan the surface contour of the embossed area 132, and computer software is used to automatically identify the flat portions 1322 and calculate the total area S1 and the surface area S of the embossed area. Alternatively, the total area S1 can be measured using a liquid covering method. One or more embossed current collectors and an unembossed current collector are immersed in a liquid with a known surface. The overflow of the liquid is observed, and the volume change difference of the electrode welding area 131 before and after embossing is calculated, i.e., the recess volume. Assuming that the recess depth of the embossing is relatively consistent or approximately consistent, the surface area of ​​the recess can be obtained by multiplying the recess depth by the recess surface area, which equals the recess volume. The total area S1 of the multiple flat portions 1322 can then be calculated. Alternatively, the total area S1 can be measured by a grid division method. The surface contour of the embossed area 132 is scanned by an area array CCD camera and divided into multiple grid units of unit area. Then, the area of ​​the flat part 1322 in a single grid unit is calculated. Finally, the areas of all grid units are added together to obtain the total volume S1.

[0060] In one example of the secondary battery of this utility model, the surface oil stain value RFU of the tab welding area 131 is controlled, and RFU < 8. Here, RFU is a relative fluorescence unit, representing the cleanliness of the surface of the tab welding area 131. The surface of the tab welding area 131 for which the oil stain value needs to be controlled can be only the surface facing away from the first tab 124, i.e., the surface of the first current collector 130 or the tab welding area 131 receiving the laser, or it can be the entire surface of the first current collector 130. Specifically, in this embodiment, the surface for controlling the oil stain value is the surface of the tab welding area 131 receiving the laser, to reduce oil stain control in unnecessary areas, improve efficiency, and save production costs. By cleaning the welding surface of the tab welding area 131 and controlling the surface oil stain value RFU < 8, the reflection of laser light by oil or other contaminants is reduced, the absorption rate of laser light by the tab welding area 131 is increased, and the penetration depth is increased, thereby improving the problem of the presence of oil or other contaminants affecting the welding quality and improving the stability and reliability of the welding. It should be noted that this technical solution is also applicable to the second current collector 150 and the second tab 125, and will not be described in detail here.

[0061] In one example of the secondary battery of this utility model, the first current collector 130 is made of copper. Using copper as the first current collector 130 can ensure efficient current transmission within the battery, reduce internal resistance, and improve charge and discharge efficiency. Secondly, the copper-based first current collector 130 has good chemical stability and can reduce battery production costs. The Vickers hardness value of the copper-based first current collector 130 is not limited, for example, it can be 45-75 HV or 50-70 HV. Specifically, in this embodiment, the first current collector 130 is made of T2 copper with a copper content >99.9% and a hardness range of 45-75 HV. The copper first current collector 130, with a Vickers hardness value of 45-75 HV, possesses moderate hardness. This ensures the mechanical stability of the first current collector 130 and the first tab 124 during the welding process, reducing damage caused by mechanical stress. Simultaneously, it allows for good intermetallic bonding through plastic deformation during welding, increasing the stability of the structural connection between the tab welding area 131 and the first tab 124. It should be noted that this technical solution is also applicable to the second current collector 150 and the second tab 125, which will not be elaborated upon here.

[0062] Please see Figure 9 This utility model also provides an electronic device 1, which includes a battery pack 10. Please refer to [link / reference]. Figure 8The battery pack 10 includes any of the aforementioned secondary batteries 100. In one embodiment of the battery pack 10 of this utility model, 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 in parallel, or a combination of series and parallel connections. The cover 102 seals the housing 101 to protect the multiple secondary batteries 100. It should be noted that, in addition to the secondary batteries 100 of this utility model, the battery pack 10 may also include a battery pack thermal management system, circuit boards, 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.

[0063] Further, please refer to Figure 9 The 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, 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 tasks, 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.

[0064] This utility model of a secondary battery, by limiting the surface roughness of the electrode welding area away from the electrode tab, enables the electrode welding area to have a higher laser capture capability, reduces the direct reflection of laser light by the current collector during laser welding, and increases the scattering direction and frequency. This improves the stability of laser absorption by the current collector, thereby improving the welding effect between the electrode tab and the current collector, reducing welding bursts, and increasing welding yield. Therefore, this utility model effectively overcomes some practical problems in the prior art and has 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 change the above embodiments without departing from the spirit and scope of this utility model. Therefore, all equivalent modifications or changes 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, including the end walls; An electrode assembly is disposed within the housing, the electrode assembly including tabs facing the end wall; A current collector is disposed between the electrode assembly and the end wall; the current collector includes a tab welding area, which is welded to the tab. Wherein, the thickness of the electrode welding area is T, the ten-point average roughness of the surface of the electrode welding area away from the electrode direction is Rz, and Rz / T < 25%.

2. The secondary battery according to claim 1, characterized in that, The arithmetic mean roughness of the surface of the electrode welding area away from the electrode direction is Ra; where Ra > 0.2 μm, 1.2 μm < Rz < 3 μm.

3. The secondary battery according to claim 1, characterized in that, The oxygen content of the metal in the electrode welding area is n, where n < 0.04%.

4. The secondary battery according to claim 1, characterized in that, The surface of the electrode welding area facing away from the electrode is an embossed area, while the surface of the electrode welding area facing the electrode is a flat area.

5. The secondary battery according to claim 4, characterized in that, The cross-section of the embossed area includes multiple embossed patterns arranged at intervals. The bottom of adjacent embossed patterns is arc-shaped, and the top of some embossed patterns extends beyond the reference plane. The distance from the top of the embossed pattern extending beyond the reference plane to the reference plane is H, where H < 1 / 2Rz. The reference plane coincides with the surface of the flow collection component located outside the embossed area.

6. The secondary battery according to claim 4, characterized in that, The surface area of ​​the embossed area is S, and the embossed area includes a plurality of flat portions, which are located at the top and / or bottom of the embossed area. The total area of ​​the plurality of flat portions is S1, wherein S1 < 0.2S.

7. The secondary battery according to claim 1, characterized in that, The surface oil stain value of the electrode welding area is RFU, and RFU < 8.

8. The secondary battery according to claim 1, characterized in that, The current collector is made of copper, and its Vickers hardness ranges from 45 to 75 Hv.

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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