Cathode collector plate and cylindrical lithium ion battery

Abstract

The utility model provides a cathode current collector plate and a cylindrical lithium ion battery, the cathode current collector plate comprises a plate body and a plurality of flanges, the plate body comprises a main body part and a plurality of connecting parts, and the edges of the connecting parts and the edges of the flanges are jointly recessed inwards in a junction area to form first stress release grooves; the first stress releasing groove is used for enabling the flange to be bent relative to the disc body along the first stress releasing groove, the first stress releasing groove is a V-shaped groove, and an included angle alpha ranging from 30 degrees to 50 degrees is formed by the V-shaped groove. In the groove rolling process, when the turned-over edge is bent relative to the disc body, due to the action of the first stress release groove, bending occurs near the junction area of the connecting part and the turned-over edge, the first stress release groove can provide space for material deformation at the bent position, material extrusion or deformation transmitted to the disc body or the turned-over edge is relieved, and therefore the machining quality of the disc body or the turned-over edge is improved. Therefore, the problems that the welding point position is broken due to pulling and the middle of the disc surface is bulged due to deformation of the disc body and the turned-over edge can be avoided.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a negative electrode current collector and a cylindrical lithium-ion battery. Background Technology

[0002] Currently, in 46-series cylindrical lithium-ion batteries, the negative electrode current collector typically includes a disk body and a flange around the perimeter of the disk body. During the assembly of the cylindrical lithium-ion battery, the disk body is welded to the negative terminal of the core, while the outer surface of the flange is attached to the inner surface of the casing and connected by through-welding, thereby enabling the casing and the core to be electrically connected. For example, in Chinese patent document CN221407360U, the disclosed cylindrical battery negative electrode current collector includes a welded perimeter 2 that basically covers its outer perimeter. This welded perimeter 2 is used to attach to the casing of the cylindrical battery and is connected by laser welding. However, if this type of negative electrode current collector is sealed using a grooving process on the negative electrode side, the material of the shell will deform towards the center of the shell after grooving. This will pull the flange of the negative electrode current collector together and bend it. As a result, the disc body connected to the flange will also deform in a wavy shape. This will cause the welding point between the disc body of the negative electrode current collector and the negative end of the core to be pulled or even broken, which will directly affect the flow of the overall current of the battery. Excessive local heat generation at the welding point will cause safety problems.

[0003] In addition, during the grooving process, the welded flanges are also grooved, causing the center of the negative electrode current collector to bulge, forming an arch shape. As shown, this can tear the weld between the disc surface and the negative terminal of the core, potentially causing problems such as tearing of the tab foil or poor soldering, which can affect the cell performance. Summary of the Invention

[0004] This application provides a negative electrode current collector and a cylindrical lithium-ion battery to at least solve the technical problems of deformation of the negative electrode current collector and tensile breakage at the welding point between the negative electrode current collector and the core during the grooving process of existing cylindrical lithium-ion batteries.

[0005] The first aspect of this application provides a negative electrode current collector, including a disk body and a plurality of flanges protruding to one side along the outer periphery of the disk body. The plurality of flanges are used to fit and connect with the shell wall of a cylindrical lithium-ion battery casing. The disk body includes a main body and a plurality of connecting portions extending radially outward from the main body. The plurality of flanges are connected to the plurality of connecting portions one by one. The negative electrode current collector is also provided with a first stress relief groove on its edge. The first stress relief groove is formed by the edge of the connecting portion and the edge of each flange concave inward at the junction area. The first stress relief groove is used to allow the flange to bend relative to the disk body along the first stress relief groove. The first stress relief groove is a V-shaped groove, and the V-shaped groove forms an included angle α, the range of which is 30° to 50°.

[0006] The negative current collector according to the embodiments of this application has at least the following beneficial effects:

[0007] By forming a V-shaped groove by the inward indentation of the edge of the disc and the edge of each flange, and by designing a reasonable angle for the V-shaped groove, when the flange bends relative to the disc during the grooving process, the bending occurs near the junction area between the disc and the flange due to the action of the first stress relief groove. Furthermore, the first stress relief groove provides space for material deformation at the bending position, reducing the material compression or deformation transmission to the disc or flange. This avoids problems such as breakage of the welding point due to deformation of the disc and flange, and bulging in the middle of the disc surface.

[0008] In one possible implementation, the negative electrode current collector is further provided with a second stress relief groove on its edge. The second stress relief groove is formed by the inward indentation of the edge of the main body, and the edge of the second stress relief groove is connected to the edge of the connecting part.

[0009] By setting a second stress relief groove as a further supplement, the stress caused by the bending of the flange during the grooving process is further relieved, which greatly reduces the stress on the main body and avoids deformation of the main body structure.

[0010] In one possible implementation, the connecting portion is provided with a thinned portion extending in the radial direction, the thickness of which is less than the thickness of other portions of the connecting portion.

[0011] By setting up a connecting part and a thinning part, the thinning part has the function of bearing stress. Based on the first stress relief groove, the thinning part can further disperse the stress and prevent the disc from deforming.

[0012] In one possible implementation, the thinning portion is formed by the two opposing surfaces of the connecting portion being recessed inward along the thickness direction of the connecting portion. The thinning portion includes, in a radial direction from the inside out, a first transition region with gradually decreasing thickness, a thickness holding region with constant thickness, and a second transition region with gradually increasing thickness. The thickness of the thickness holding region is L3, and the thickness of the main body portion is L4. The range of L3 / L4 is 30% to 60%.

[0013] By reasonably setting the range of L3 / L4, both the structural strength of the connection and the stress dispersion effect can be taken into account.

[0014] In one possible implementation, the length of the thickness retention area in the radial direction is L5, the radius of the main body is L6, and the range of L5 / L6 is 1% to 5%.

[0015] By reasonably setting the range of L5 / L6, both the structural strength and stress dispersion effect of the connection can be taken into account.

[0016] In one possible implementation, the arc length of the flange along the circumferential direction is L1, the length of the first stress relief groove recessed inward along the circumferential direction is L2, and the range of L2 / L1 is 3% to 10%.

[0017] By reasonably setting the range of L2 / L1, it is possible to balance the structural strength of the negative electrode current collector and control the degree of bending deformation of the flange.

[0018] In one possible implementation, the bottom of the first stress relief groove is located at the junction of the flange and the connecting portion.

[0019] By setting the bottom of the first stress relief groove at the junction of the flange and the connecting part, the bending position of the flange relative to the disc body is located exactly at the junction of the two, thereby minimizing the adverse effects of the bending position on the disc body and the flange.

[0020] In one possible implementation, the total arc length of the main body portion corresponding to the second stress relief groove is L7, and the length of the main body portion after deducting the total arc length corresponding to the connecting portion is L8, with L7 / L8 ranging from 5% to 20%.

[0021] By reasonably setting the range of L7 / L8, both the structural strength and stress dispersion effect of the negative electrode current collector can be taken into account.

[0022] In one possible implementation, the second stress relief groove is recessed inward in the radial direction by a length of L9, the radius of the main body is L6, and the range of L9 / L6 is 2% to 5%.

[0023] By setting the L9 / L6 range appropriately, both electrolyte injection efficiency and stress dispersion effect can be taken into account.

[0024] A second aspect of this application provides a cylindrical lithium-ion battery, including a housing, a winding core, and a negative electrode current collector as described in any of the above embodiments. The housing is provided with an inwardly recessed groove extending circumferentially along the housing. The disk body of the negative electrode current collector is connected to the negative end of the winding core, and the flange of the negative electrode current collector is fitted and connected to the shell wall of the groove portion of the housing.

[0025] The cylindrical lithium-ion battery according to the embodiments of this application has at least the following beneficial effects:

[0026] Because of the negative electrode current collector of the first aspect embodiment described above, the cylindrical lithium-ion battery does not deform or bulge during the grooving process, thus possessing the characteristics of high quality, low cost, and safety and reliability. Attached Figure Description

[0027] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a cross-sectional schematic diagram of a cylindrical lithium-ion battery after grooving, provided in an embodiment of this application;

[0029] Figure 2 This is a cross-sectional schematic diagram of a cylindrical lithium-ion battery without grooves provided in an embodiment of this application;

[0030] Figure 3 This is a schematic diagram of the structure of a negative electrode current collector provided in an embodiment of this application;

[0031] Figure 4 yes Figure 3 A partial schematic diagram of point A in the middle;

[0032] Figure 5 yes Figure 4 A partial schematic diagram at point E in the middle; Figure 6 This is a view of a negative electrode current collector provided in an embodiment of this application, from the side without a flange to the side with a flange;

[0033] Figure 7 yes Figure 6 A partial schematic diagram at point B in the middle;

[0034] Figure 8 yes Figure 6 A partial schematic diagram at point C in the middle;

[0035] Figure 9 This is a cross-sectional view of a negative current collector provided in an embodiment of this application;

[0036] Figure 10 yes Figure 9 A partial schematic diagram at point D in the middle.

[0037] Figure label:

[0038] 100-Negative electrode current collector, 110-Disc body, 111-Main body, 1111-Second stress relief groove, 1112-Central hole, 1113-Auxiliary hole, 112-Connecting part, 1121-Thinning part, 1121a-First transition zone, 1121b-Thickness holding zone, 1121c-Second transition zone, 1122-Fifth side, 1123-Sixth side, 120-Flanged edge, 121-First side, 122-Second side, 123-Notch, 130-First stress relief groove, 131-Third side, 1311-First straight edge, 1312-First chamfer, 132-Fourth side, 1321-Second straight edge, 1322-Second chamfer;

[0039] 200 - Housing, 210 - Groove section;

[0040] 300-core. Detailed Implementation

[0041] The embodiments of this implementation are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this implementation, and should not be construed as limiting this implementation.

[0042] In the description of this embodiment, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this embodiment.

[0043] In the description of this embodiment, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0044] In the description of this embodiment, unless otherwise explicitly limited, terms such as setting, installing, and connecting should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this embodiment in conjunction with the specific content of the technical solution.

[0045] Figure 1 This is a schematic diagram of a cylindrical lithium-ion battery provided in an embodiment of this application. Figure 1In a cylindrical lithium-ion battery, the negative electrode side is on top and the positive electrode side is on the bottom. Figure 1 The cylindrical lithium-ion batteries in this process have already undergone the grooving process. Figure 2 These are cylindrical lithium-ion batteries that have not yet undergone the grooving process. For example... Figure 1 As shown, the cylindrical lithium-ion battery includes a negative electrode current collector 100, a core 300, and a casing 200. The negative terminal of the core 300 is connected to the casing 200 via the negative electrode current collector 100. The casing 200 serves as the negative electrode of the cylindrical lithium-ion battery, used for electrical connection to external electrical devices. The casing 200 has an inwardly recessed groove 210 extending circumferentially. The disc body 110 of the negative electrode current collector 100 is connected to the negative terminal of the core 300, and the flange 120 of the negative electrode current collector 100 is fitted and connected to the shell wall of the groove 210 in the casing 200.

[0046] Figure 3 This is a schematic diagram of the structure of the negative electrode current collector 100 provided in the embodiment of this application. The negative electrode current collector 100 includes a disk body 110 and a plurality of flanges 120 protruding along one side of the outer periphery of the disk body 110. It can be understood that the flanges 120 are used to fit and connect with the shell wall of the cylindrical lithium battery casing 200. The shell wall of the cylindrical lithium battery refers to the inner side wall of the cylindrical lithium battery casing 200, so that the core 300 forms a passage between the negative electrode current collector 100 and the casing 200, thereby the casing 200 itself serves as the negative electrode of the cylindrical lithium-ion battery.

[0047] Specifically, the disc body 110 is the main structural part of the negative electrode current collector 100. It is a thin sheet and includes two opposing disc surfaces. One disc surface is used to connect to the negative terminal of the core 300, specifically by welding. The other disc surface is open before sealing, and in the subsequent electrolyte injection process, the electrolyte will enter the core 300 through this side disc surface. There are multiple flanges 120, that is, the flanges 120 are not complete circular structures. Multiple flanges 120 protrude along the outer periphery of the disc body 110 towards the negative electrode side away from the disc surface, for example, at an angle approximately perpendicular to the disc surface, and are spaced apart from each other. Multiple flanges 120 increase the welding area between the negative electrode current collector 100 and the housing 200, thereby improving the connection strength between the negative electrode current collector 100 and the housing 200. At the same time, due to the increased welding area, the conduction resistance is reduced and the conduction current of the battery is increased.

[0048] It is understandable that the connection between the disc body 110 and the flange 120 can be any fixed connection method. To ensure a stable connection, structural strength, and economical processing, the disc body 110 and the flange 120 can be integrally connected, for example, by stamping. It can be further understood that forming the disc body 110 and the flange 120 integrally through stamping will create a crease at the connection point between the disc body 100 and the flange 120.

[0049] In this embodiment, the negative electrode current collector 100 is further provided with a first stress relief groove 130 on its edge. The first stress relief groove 130 is formed by the inward indentation of the edge of the disk body 110 and the edges of each flange 120 at the junction area. The first stress relief groove 130 allows the flange 120 to bend relative to the disk body 110 along the first stress relief groove 130. It can be understood that the negative electrode current collector 100 has an edge formed on the disk body 110 and an edge formed on the flange 120. These edges together constitute the edge of the negative electrode current collector 100. Thus, on both sides of the connection between each flange 120 and the disk body 110, such as on both sides of the aforementioned crease, a first stress relief groove 130 is formed. Therefore, for each flange 120, two symmetrically arranged first stress relief grooves 130 are formed at its bottom.

[0050] It is understandable that the first stress relief groove 130 is a structure formed by the indentation of the edge constituting the negative electrode current collector 100 from the outside to the inside. This structure causes the material length of the flange 120 and the disk body 100 at the corresponding first stress relief groove 130 to be shortened. When the flange 120 bends relative to the disk body 110, the first stress relief groove 130 can release stress, so that the material in the area between the two first stress relief grooves 130 bends preferentially, so that the bending occurs at the junction area of ​​the flange 120 and the disk body 110, such as the crease, thus avoiding a series of problems caused by the deformation of the disk body 110 and the flange 120 themselves. Therefore, by forming a first stress relief groove 130 by recessing the edge of the disc body 110 and the edges of each of the flanges 120 together, when the flange 120 bends relative to the disc body 110 during the grooving process, the bending occurs near the junction area between the disc body 110 and the flange 120 due to the action of the first stress relief groove 130. Furthermore, the first stress relief groove 130 provides space for material deformation at the bending position, reducing the material compression or deformation transmission to the disc body 110 or the flange 120, thereby avoiding problems such as breakage of the welding point due to deformation of the disc body 110 and the flange 120, and bulging of the middle of the disc surface.

[0051] As mentioned earlier, the first stress relief groove 130 is formed by the inward indentation of the edge of the disc body 110 and the edges of each flange 120 at their junction. Therefore, it can be understood that part of the first stress relief groove 130 is located at the flange 120, and part is located on the disc body 110. Specifically, refer to... Figure 4 , Figure 4 yes Figure 3 A partial schematic diagram at point A shows that, specifically, the flange 120 includes a first side 121 and a second side 122 connected to the edge of the disc body 110. The edge of the disc body 110 includes a fifth side 1122 and a sixth side 1123 located at the connecting portion 112. The fifth side 1122 is connected to the first side 121, and the sixth side 1123 is connected to the second side 122. Thus, a portion of the first stress relief groove 130 is formed by the inward indentation of the first side 121 and the second side 122 toward the disc body 110, while the other portion is formed by the inward indentation of the fifth side 1122 and the sixth side 1123 at the end connected to the flange 120.

[0052] To ensure that the bending point of the flange 120 relative to the disk body 110 is precisely at their junction, in some embodiments, the bottom of the first stress relief groove 130 is located at the junction of the flange 120 and the disk body 110. For example, in a negative electrode current collector 100 formed by stamping, the flange 120 is formed by bending at the edge of the disk body 110, with a crease between them; this crease is the junction of the flange 120 and the disk body 110. Here, the location of the bottom of the first stress relief groove 130 refers to the deepest part of the first stress relief groove 130. It can be understood that the bottom of the first stress relief groove 130 is located at the junction of the flange 120 and the disk body 110, thus ensuring that the bending point of the flange 120 relative to the disk body 110 is precisely at their junction. This minimizes the adverse effects of the bending point of the flange 120 relative to the disk body 110 on both the disk body 110 and the flange 120.

[0053] Of course, it is not limited to this. It is understood that the bottom of the first stress relief groove 130 can be set on either side of the disc body 110 or the flange 120, so that the flange 120 bends along the line connecting the bottoms of the two first stress relief grooves 130, so as to more accurately locate the position and direction of the bend, so that the bend occurs at the required position as much as possible, and control the direction of the bend.

[0054] Further, please refer to Figure 6 and Figure 7 , Figure 6 This is a view of the negative electrode current collector 100 from the side without the flange to the side with the flange 120. Figure 7 yes Figure 6A partial schematic diagram at point B shows that the arc length of the flange 120 along the circumferential direction of the disk body 110 is L1, and the length of the first stress relief groove 130 recessed inward along the circumferential direction of the disk body 110 is L2. The ratio of L2 / L1 ranges from 3% to 10%. For example, the range of L2 / L1 can be 3%, 3.8%, 6%, 8%, and 10%, etc. In some embodiments, the length of L2 is 0.38 mm, and the length of L1 is 10 mm. If the range of L2 / L1 is greater than 10%, then L2 / L1 is too large, the V-groove depth is too deep, and the straight-line distance between the two V-grooves corresponding to the flange 120 is too short, making this area more prone to deformation. The degree of deformation cannot be controlled, and the strength of the flange 120 at this bending point is weak, increasing the difficulty of control during production, transportation, and material loading during the manufacturing process. The flange 120 is more prone to deformation and bending, making it difficult to position the tooling for welding to the shell wall, and easily causing the problem of incomplete welding. If the range of L2 / L1 is less than 3%, then L2 / L1 is too small, the depth of the V-groove is too shallow, and the guiding effect of the V-groove is greatly reduced.

[0055] Further, please refer to Figure 4 and Figure 5The first stress relief groove 130 is a V-shaped groove, which includes a third side 131 and a fourth side 132 forming the V-shape. The third side 131 and the fourth side 132 form an included angle α, which is in the range of 30° to 50°. Specifically, the third side 131 includes a first straight side portion 1311 and a first chamfered portion 1312, and the fourth side 132 includes a second straight side portion 1321 and a second chamfered portion 1322. The first chamfered portion 1312 is connected to the second chamfered portion 1322, wherein the first straight side portion 1311 and the second straight side portion 1321 form the included angle α. It is understood that the third side 131, from the outside in, consists of a first straight edge 1311 and a first chamfered portion 1312, which are straight segments. The fourth side 132, from the outside in, consists of a second straight edge 1321 and a second chamfered portion 1322, which are straight segments. The first chamfered portion 1312 and the second chamfered portion are connected 1322 to form a V-shaped groove. For example, α can be 30°, 35°, 40°, 45°, and 50°, etc., and is not specifically limited. If α is less than 30°, the angle is too small and cannot provide good guidance. After the flange 120 is welded to the housing 200, stress concentration is severe when it is grooved together with the housing 200. If the angle of the V-groove is too small, the positioning and bending guidance effect is not obvious, and some stress cannot be released. This causes the center of the disk surface 110 of the negative electrode current collector 100 to arch during grooving. When α is greater than 50°, the angle is too large, and the opening angle of the V-groove is too large. Since the weld marks of the negative electrode current collector 100 and the housing 200 are usually welded in the lower middle part, close to the disk surface, if α is too large, it will occupy part of the welding area at both ends, resulting in a smaller welding area, poorer current carrying capacity, increased temperature in the welding area, increased internal resistance of the battery, and affected battery performance. It can be understood that the included angle α refers to the angle after the negative electrode current collector 100 forms the flange 120 and before the grooving process. It is understandable that by setting the first chamfer 1312 and the second chamfer 1322, stress concentration in the bottom area of ​​the V-groove can be reduced.

[0056] In some embodiments, the shape of the first stress relief groove 130 is not limited to a V-shaped groove, but may be a rectangular groove, a U-shaped groove, etc.

[0057] Furthermore, the first stress relief groove 130 is located at the junction of the flange 120 and the disk 110. The first stress relief groove 130 is a V-shaped groove, which includes a third side 131 and a fourth side 132 forming the V-shaped groove. The third side 131 is located on the flange 120, and the fourth side 132 is located on the disk 110. It can be understood that the grooving process causes the flange 120 to bend, thereby reducing the overall height of the cylindrical lithium-ion battery. The lower the bending height, the lower the height of the cylindrical lithium-ion battery after grooving, which helps to improve the unit energy density of the cylindrical lithium-ion battery. By setting the position of the first stress relief groove 130 at the junction of the flange 120 and the disk 110, the bending occurs on the same plane as the disk 110, which is equivalent to lowering the bending position, thereby reducing the height of the cylindrical lithium-ion battery and improving the unit energy density. It is understandable that since the flange 120 protrudes from the edge of the disc body 110 away from the disc surface, there is a crease between the disc body 110 and the flange 120. At this time, the bottom of the first stress relief groove 130 is located at the crease, that is, the bottom is located at both the connecting part 112 and the flange 120.

[0058] Further, please refer to Figure 9 and Figure 10 , Figure 10 yes Figure 9A partial schematic diagram at point D shows that the disc body 110 includes a main body 111 and a connecting part 112 extending radially outward from the main body 111. The number of connecting parts 112 corresponds to the number of flanges 120, that is, the flanges 120 are connected to the connecting parts 112 one by one. The connecting part 112 is provided with a thinning part 1121. The thickness of the thinning part 1121 is less than the thickness of the other parts of the connecting part 112. The connecting part 112 includes a fifth side 1122 and a sixth side 1123 connected to the edge of the main body 111. The thinning part 1121 extends from the fifth side 1122 to the sixth side 1123. The aforementioned fourth side 132 is provided on the connecting part 112. By setting the thinning section 1121, the problem of excessively deep grooving during the grooving process after welding the flange 120 of the negative current collector 100 to the housing 200 can be effectively avoided. This would increase the pulling force on the flange 120, potentially causing it and even the edge of the plate to deform towards the axis. When the V-shaped groove at the junction of the flange 120 and the plate has already deformed, and the deformation force is insufficient, the thinning section 1121 provides secondary stress relief. The thinning section 1121 continues to deform until the required deformation is achieved. Since the stress is decomposed by the first stress relief groove 130 and the thinning section 1121, stress concentration does not occur at the center of the plate. Therefore, the welding of the plate to the negative electrode side tab of the core 300 is not affected, and the middle part of the plate does not deform or bulge. The reliability of the negative current collector 100 welding is ensured, and the safety performance of the battery cell is improved. Meanwhile, by providing a connecting portion 112 that extends radially outward from the main body 111, a gap is left between the shell wall of the housing 200 and the main body 111 after the negative electrode current collector 100 enters the housing 200, thereby accelerating the injection of electrolyte.

[0059] Furthermore, the thinning portion 1121 extends from the fifth side 1122 along the circumferential direction of the main body portion 111 to the sixth side 1123. The circumferential extension is provided so that the force transmitted by the bending of the flange 120 during the grooving process can be evenly absorbed by the thinning portion 1121.

[0060] Furthermore, the thinning portion 1121 is formed by the two opposing surfaces of the connecting portion 112 being recessed inward along the thickness direction of the connecting portion 112. The thinning portion 1121 includes a first transition region 1121a with gradually decreasing thickness, a thickness-retaining region 1121b with constant thickness, and a second transition region 1121c with gradually increasing thickness in the radial outward direction along the main body portion 111, such as... Figure 10As shown, the thickness of the thickness holding region 1121b is L3, and the thickness of the main body 111 is L4, with the L3 / L4 ratio ranging from 30% to 60%. For example, the L3 / L4 ratio can be 30%, 35%, 40%, 45%, 50%, 55%, and 60%, without specific limitation. In some embodiments, the thickness L3 of the thickness holding region 1121b is 0.1 mm, and the thickness L4 of the main body 111 is 0.2 mm, in which case the L3 / L4 ratio is 50%. When L3 / L4 < 30%, the thickness of the thinning part 1121 is too thick. During the grooving process of the negative electrode current collector 100, when the groove depth pulls on the flange 120, the thinning part 1121 cannot play a good role in relieving stress. Moreover, most of the stress is concentrated at the junction of the flange 120 and the connecting part 112 and cannot be released and decomposed. As a result, the middle of the plate surface is prone to arching, causing the foil at the laser welding point of the plate surface and the negative electrode side of the core 300 to tear, resulting in problems such as poor welding and poor contact. The current carrying capacity at the welding point is insufficient, causing the temperature to rise rapidly during overcurrent, affecting the performance of the cell, reducing the safety factor of the cell, and making it easy to have risks such as thermal runaway. When L3 / L4 > 60%, the thickness of the thinned portion 1121 is too thin. During the grooving process of the negative electrode current collector 100, the flange 120 is stretched, causing severe deformation of the thinned portion 1121. This results in insufficient strength, making it unsuitable for processing and increasing the risk of breakage of the thinned portion 1121, leading to cell failure. This increases the difficulty of cell manufacturing and raises the manufacturing cost. By setting a first transition region 1121a and a second transition region 1121c, the thinned portion 1121 is thinned gradually, reducing stress concentration between the connecting portion 112 and the thickness holding region 1121b. Furthermore, the gradual thinning increases the overall structural strength of the thinned portion 1121, preventing breakage of the thinned portion 1121 during transportation and processing of the negative electrode current collector 100.

[0061] Furthermore, the thickness change slopes of the first transition region 1121a and the second transition region 1121c are the same, which facilitates the manufacturing of the thinning section 1121.

[0062] In some embodiments, the first transition region 1121a and the second transition region 1121c may not be provided, or only one transition region may be provided in the first transition region 1121a and the second transition region 1121c, thus saving the manufacturing process of the thinning part 1121.

[0063] In some embodiments, the thickness retention area 1121b of the thinning portion 1121 has a length of L5 along the radial direction of the main body portion 111, and the radius of the main body portion 111 is L6. The ratio of L5 / L6 ranges from 1% to 5%. For example, the ratio of L5 / L6 can be 1%, 1.2%, 2%, 3%, 4%, and 5%, etc., and is not specifically limited. For example, if the length of L5 is 0.23 mm and the radius of the main body portion 111 is 19.7 mm, then L5 / L6 is 1.2%. When L5 / L6 is less than 1%, the width of the thinned portion 1121 is too narrow. During grooving, the groove depth is relatively deep, and the thinned portion 1121, which plays a secondary protective role, begins to deform and bend. However, bending requires a certain bending radius to achieve the bending function. At this time, the width of the thinned portion 1121 is too narrow, so the bending deformation cannot be completed directly within the thinned portion 1121 during the secondary bending. It is necessary to deform the surrounding normal thickness disk surface of the thinned portion 1121 as well. This will cause uneven thickness in the deformation area, resulting in uneven stress distribution, increased bending difficulty, process difficulties, reduced battery output, and a corresponding increase in battery manufacturing costs. When L5 / L6 is greater than 5%, the width of the thinned portion 1121 is too wide, the structural strength decreases, the flatness of the entire disk surface is difficult to control, the manufacturing difficulty increases, and a later step of shaping the flatness is required. The added steps increase the input costs of manpower and equipment, thus increasing the manufacturing cost.

[0064] Furthermore, such as Figure 6 , Figure 7 and Figure 8 As shown, the negative electrode current collector 100 is further provided with a second stress relief groove 1111 on its edge. The second stress relief groove 1111 is formed by the recess of the main body 111 on both sides of the connecting part 112, and the edge of the second stress relief groove 1111 is connected to the edge of the connecting part 112. By providing the second stress relief groove 1111, the stress is transferred from the flange 120 through the connecting part 112 to the thinning part 1121, and then to the second stress relief groove 1111. At this time, the second stress relief groove 1111 acts as a third stress-reducing structure, further relieving the stress caused by the bending of the flange 120 during the grooving process, thereby greatly reducing the stress on the main body 111 and preventing structural deformation of the main body 111.

[0065] It is understood that, for a single connection portion 112, there is a pair of second stress relief grooves 1111. These two second stress relief grooves 1111 are respectively disposed on the main body portion 111 in the area connected to the connection portion 112, which helps to disperse stress and further ensures that the structure of the main body portion 111 does not deform. Furthermore, the shape of the second stress relief grooves 1111 is arc-shaped, which helps to avoid stress concentration.

[0066] Furthermore, such as Figure 8 As shown, Figure 8 yes Figure 6 A partial schematic diagram at point C shows that the main body 111 is provided with multiple second stress relief grooves 1111 and multiple connecting parts 112. The total arc length of the main body 111 corresponding to the second stress relief grooves 1111 is L7. The length of the main body 111 after deducting the total arc length corresponding to the connecting parts 112 from its total arc length is L8. The ratio of L7 / L8 ranges from 5% to 20%, for example, the ratio of L7 / L8 can be 5%, 7%, 10%, 12%, 15%, 17%, and 20%, etc. The arc length L7 corresponding to the second stress relief grooves 1111 of the main body 111 is the total arc length of all the second stress relief grooves 1111, and L8 is the length of the main body 111 after deducting the arc length corresponding to the multiple connecting parts 112 from its total arc length. Figure 6 and Figure 8 Only the arc length L7 of the second stress relief groove 1111 is marked, and only a section of L8 is marked. When L7 / L8 is less than 5%, the arc length is too small, and the second stress relief groove 1111 structure, which is meant to alleviate stress concentration, cannot effectively decompose the stress. As a result, some stress will still be concentrated on the disk surface of the main body 111. This causes a certain height of arching and deformation in the middle of the disk surface after grooving. When the electrolyte flows into the cell through the through holes on the disk surface, the flow rate of the electrolyte is slowed down because the arc of the second stress relief groove 1111 is too small, thus reducing the electrolyte injection efficiency, increasing the injection time, and increasing the manufacturing cost. If L7 / L8 > 20%, the arc length is too long, and the structural strength of the second stress relief groove 1111 will be lower. The second stress relief groove 1111 is prone to deformation, which increases the difficulty of process control during manufacturing and transportation. During transportation, it is easy to cause deformation due to bumps and knocks. When welding the flange 120 to the shell 200, the problem of incomplete welding is likely to occur. In some embodiments, L7 is 8.4 mm, L8 is 69.84 mm, and the ratio of L7 to L8 is 12%.

[0067] Furthermore, the second stress relief groove 1111 is recessed inward along the radial direction of the main body 111 for a length of L9, the radius of the main body 111 is L6, and the range of L9 / L6 is 2% to 5%, for example, the ratio of L9 / L6 can be 2%, 3%, 4% and 5%. When L9 / L6 is less than 2%, the depth of the second stress relief groove 1111 is too shallow. As the third stress concentration mitigation protection structure, the second stress relief groove 1111 cannot effectively decompose the stress, resulting in some stress still concentrating on the disk surface. After grooving, there will be a certain height of arching and deformation in the middle of the disk surface. When the electrolyte flows into the cell through the through holes of the disk surface, the shallow depth of the second stress relief groove 1111 on the disk surface slows down the electrolyte diversion speed, thereby reducing the injection efficiency, increasing the injection time, and increasing the manufacturing cost. When L9 / L6 is greater than 5%, the depth of the second stress relief groove 1111 is too deep, which will occupy the welding area on the disk surface and the negative electrode side of the core 300, resulting in a smaller welding area, poorer current carrying capacity at the welding point, and higher welding temperature, affecting battery performance. In some embodiments, L9 is 0.68mm and L6 is 19.7mm, then the ratio of L9 / L6 is 3%.

[0068] Furthermore, the main body 111 also has a central hole 1112 located at its center and a plurality of auxiliary holes 1113 located around the central hole 1112. The central hole 1112 and the plurality of auxiliary holes 1113 are used to inject electrolyte into the battery. It is understood that the core 300 is manufactured using a winding process, and after winding, a circular core 300 hole is formed at the center of the core 300. To match the shape of the core 300 hole, the shape of the central hole 1112 is preferably circular. In this case, the central hole 1112 and the main body 111 are concentric. It is understood that the diameter of the central hole 1112 can be specifically selected based on a balance between achieving electrolyte injection efficiency and weldable area. The size of the auxiliary holes 1113 can be specifically selected based on a balance between achieving electrolyte injection efficiency and weldable area. Furthermore, the auxiliary holes 1113 are waist-shaped holes, and there are 4 of them. The combined shape of the 4 auxiliary holes 1113 is a centrally symmetrical shape, with the center of symmetry being the center of the central hole 1112, so as to ensure the uniformity of electrolyte injection.

[0069] The effects of this application will be further described below with specific embodiments and comparative examples.

[0070] Example 1:

[0071] Example 1 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 100. The negative electrode current collector 100 includes a disk body 110, a main body 111, and a plurality of connecting portions 112 disposed on the outer periphery of the main body 111. The negative electrode current collector 100 also includes flanges 120 in number corresponding to the connecting portions 112. The flanges 120 are integrally bent from the edge of the connecting portions 112, thereby protruding along one side of the outer periphery of the disk body 110. The negative electrode current collector 100 has V-shaped grooves at both ends of the connecting portions 112 and the fold of the flanges 120, which serve as first stress relief grooves 130. The included angle α of the V-shaped grooves is 40°. The arc length L1 of the flanges 120 along the circumferential direction of the disk body 110 is 10 mm, and the length L2 of the V-shaped grooves recessed inward along the circumferential direction of the disk body 110 is 0.38 mm. The connecting portion 112 is provided with a thinning portion 1121, which is formed by the two opposing surfaces of the connecting portion 112 being recessed inward along the thickness direction of the connecting portion 112. The thinning portion 1121 includes a first transition region 1121a with gradually decreasing thickness, a thickness holding region 1121b with constant thickness, and a second transition region 1121c with gradually increasing thickness in the radial direction. The main body portion 111 is also provided with a second stress relief groove 1111 formed by the indentation of the edge of the main body portion 111. The second stress relief groove 1111 is provided on both sides of the connecting portion 112, and the edge of the second stress relief groove 1111 is connected to the edge of the connecting portion 112.

[0072] Comparative Example 1:

[0073] Comparative Example 1 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 100, and differs from Example 1 in that α is 25°.

[0074] Comparative Example 2:

[0075] Comparative Example 2 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 100, and differs from Example 1 in that α is 65°.

[0076] Comparative Example 3:

[0077] Comparative Example 3 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 100. The difference between this battery and Example 1 is that the first stress relief groove 130 is not provided.

[0078] Comparative Example 4:

[0079] Comparative Example 4 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 100. The difference between it and Example 1 is that the thinning portion 1121 is not provided.

[0080] Comparative Example 5:

[0081] Comparative Example 5 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 100. The difference between it and Example 1 is that a second stress relief groove 1111 is not provided.

[0082] Table 1 below shows the tests conducted on the negative electrode current collector 100 fabricated in the above embodiments and comparative examples, including the height difference of the arched part of the main body (ΔH), the maximum temperature of the flanged solder mark (Tmax), and the electrolyte injection time (t). Wherein:

[0083] The specific test method for the arch height difference (△H) of the main body is as follows: The battery is prepared according to the normal process until the negative electrode current collector 100 is welded to the shell wall and the grooving process is carried out. Before the grooving process, the height of the surface of the negative electrode current collector 100 is measured with a height gauge. Taking the center of the disk surface of the main body 111 of the negative electrode current collector 100 as the center and the radius as 1mm, three points are randomly selected for height measurement and the average value H is taken. The battery grooving tool is fed towards the center of the battery at a speed of 1800r / min until the grooving depth is 3.0mm. The battery is then taken out. According to the same test method, three points are randomly selected at the middle of the disk surface of the main body 111 of the negative electrode current collector 100 to measure the height H. The arch height difference △H is calculated as H - H. Under stress concentration, △H = 0.9~1.0mm.

[0084] The specific testing method for the maximum temperature (Tmax) of the flanged solder mark is as follows: The negative electrode current collector 100 is made into a battery. During the manufacturing process, a 3mm diameter through hole is drilled in the negative electrode cover plate of the battery. The temperature control wire is passed through the through hole and attached to the solder mark on the flange 120 of the negative electrode current collector 100 and the shell wall, as well as the solder mark on the disc surface of the main body 111 and the core 300. After filling with electrolyte according to the normal battery manufacturing process, the cover plate is sealed and the battery is subjected to formation and capacity testing to produce a qualified battery. The battery is then charged and discharged for 10 cycles at a 3C high rate. After 10 cycles of charge and discharge, the temperature data of the welding area collected by the temperature control wire is obtained. The maximum value Tmax within the temperature fluctuation range of the 10 cycles is taken. Tmax represents the maximum temperature of the flanged solder mark 120 (unit: degrees Celsius).

[0085] The specific test method for the time (t) required to inject electrolyte into the battery is as follows: The negative electrode current collector 100 is installed inside the battery. Following the normal battery manufacturing process, after the grooving process, proceed to the electrolyte injection stage. 75g of electrolyte is injected into the holding cup, which is then pressed into the groove opening. The sealing ring below the holding cup is completely flush against the groove depth end face. Then, the electrolyte is injected. First, a negative pressure is drawn into the holding cup for 15 seconds, reaching -90KPa. The electrolyte height can be observed to decrease from the holding cup, indicating that the electrolyte is flowing into the battery. After maintaining this pressure for 40 seconds, positive pressure electrolyte injection is initiated, and nitrogen gas is injected into the battery. The internal pressure gradually becomes positive (0.8 MPa), and electrolyte continuously flows into the battery from the holding cup, causing the electrolyte level in the holding cup to gradually decrease. Then, the pressure is adjusted to negative pressure and maintained. This process is repeated until the electrolyte in the holding cup has completely flowed into the battery, and the electrolyte level in the holding cup is 0. The time t (in seconds) at which the electrolyte has completely flowed into the battery is recorded.

[0086]

[0087] Table 1 shows that with the included angle α of the V-groove being 40°, the arc length L1 of the flange 120 along the circumferential direction of the disk 110 being 10 mm, the inward concavity length L2 of the V-groove along the circumferential direction of the disk 110 being 0.38 mm, the height difference ΔH of the arched main body 111 being 0.01 mm, the maximum welding temperature Tmax of the flange 120 being 103℃, and the electrolyte injection time t being 684 seconds, it can be seen that within the above numerical range, the structural strength, electrolyte injection rate, and welding temperature rise of the negative electrode current collector 100 can be well balanced, thereby effectively improving the battery's safety and charge / discharge performance, as well as reducing the battery's production cost.

[0088] As shown in Table 1, if the included angle α is too small, the main body 111 of the disk body 110 will have a high arch height; if the included angle α is too large, the maximum temperature of the solder joint on the flange 120 will increase. Therefore, setting the included angle α within a reasonable range can balance the arch height of the main body 111 of the negative electrode current collector 100 and the maximum temperature of the solder joint on the flange 120.

[0089] As shown in Table 1, without the first stress relief groove 130, the main body 111 of the disk body 110 will have a high arch height. Therefore, providing the first stress relief groove 130 helps to control the arch height of the main body 111 of the disk body 110.

[0090] As shown in Table 1, without the thinning section 1121, the main body 111 of the disk body 110 would have a high bulge height. Therefore, providing the thinning section 1121 helps control the bulge height of the main body 111 of the disk body 110.

[0091] As shown in Table 1, without the second stress relief groove 1111, the main body 111 of the disc 110 will have a high arch height and low electrolyte injection efficiency. Therefore, providing the first stress relief groove 130 is beneficial for controlling the arch height of the main body 111 of the disc 110 and improving the electrolyte injection efficiency.

[0092] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this implementation. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0093] Although embodiments of this implementation have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this implementation, the scope of which is defined by the claims and their equivalents.

Claims

1. A negative electrode current collector, characterized in that, The device includes a disk body (110) and multiple flanges (120) protruding to one side along the outer periphery of the disk body (110). The multiple flanges (120) are used to fit and connect with the shell wall of the cylindrical lithium-ion battery casing (200). The disk body (110) includes a main body (111) and multiple connecting portions (112) extending radially outward from the main body (111). The multiple flanges (120) are connected one-to-one with the multiple connecting portions (112). The negative electrode current collector is also provided with a... The first stress relief groove (130) is formed by the edge of the connecting part (112) and the edge of each flange (120) being recessed inward at the junction area. The first stress relief groove (130) is used so that the flange (120) can be bent relative to the disc body (110) along the first stress relief groove (130). The first stress relief groove (130) is a V-shaped groove, and the V-shaped groove includes forming an included angle α, the range of which is 30° to 50°.

2. The negative electrode current collector according to claim 1, characterized in that, The negative electrode current collector is also provided with a second stress relief groove (1111) on the edge. The second stress relief groove (1111) is formed by the inward indentation of the edge of the main body (111), and the edge of the second stress relief groove (1111) is connected to the edge of the connecting part (112).

3. The negative electrode current collector according to claim 1, characterized in that, The connecting portion (112) is provided with a thinning portion (1121) extending in the radial direction, the thickness of the thinning portion (1121) being less than the thickness of the other parts of the connecting portion (112).

4. The negative electrode current collector according to claim 3, characterized in that, The thinning portion (1121) is formed by the two opposing surfaces of the connecting portion (112) being recessed inward along the thickness direction of the connecting portion (112). The thinning portion (1121) includes, in the radial direction from the inside to the outside, a first transition region (1121a) with gradually decreasing thickness, a thickness holding region (1121b) with constant thickness, and a second transition region (1121c) with gradually increasing thickness. The thickness of the thickness holding region (1121b) is L3, and the thickness of the main body portion (111) is L4. The range of L3 / L4 is 30% to 60%.

5. The negative electrode current collector according to claim 4, characterized in that, The thickness retention area (1121b) has a radial length of L5, and the main body (111) has a radius of L6, with L5 / L6 ranging from 1% to 5%.

6. The negative electrode current collector according to any one of claims 1 to 5, characterized in that, The arc length of the flange (120) along the circumferential direction is L1, and the length of the first stress relief groove (130) that is recessed inward along the circumferential direction is L2. The range of L2 / L1 is 3% to 10%.

7. The negative electrode current collector according to any one of claims 1 to 5, characterized in that, The bottom of the first stress relief groove (130) is located at the junction of the flange (120) and the connecting part (112).

8. The negative electrode current collector according to claim 2, characterized in that, The total arc length of the main body (111) at the second stress relief groove (1111) is L7, and the length of the main body (111) after deducting the total arc length of the connecting part (112) is L8. The range of L7 / L8 is 5% to 20%.

9. The negative electrode current collector according to claim 2, characterized in that, The second stress relief groove (1111) is recessed inward in the radial direction for a length of L9, and the radius of the main body (111) is L6, with L9 / L6 ranging from 2% to 5%.

10. A cylindrical lithium-ion battery, characterized in that, The device includes a negative electrode current collector (100), a housing (200), and a core (300) as described in any one of claims 1 to 9. The housing (200) is provided with an inwardly recessed groove portion (210) extending circumferentially along the housing (200). The disc body (110) of the negative electrode current collector is connected to the negative end of the core (300), and the flange (120) of the negative electrode current collector is fitted and connected to the shell wall of the groove portion (210) of the housing (200).

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