A cylindrical lithium-ion battery

Abstract

This application discloses a cylindrical lithium-ion battery, including a positive electrode current collector and a negative electrode current collector. The positive electrode current collector includes a first disk body and a second disk body. The first disk body has a first central hole, and the second disk body includes a connecting portion with a fusible groove. The negative electrode current collector includes a third disk body and a flange. The third disk body includes a main body and a plurality of radially outwardly extending extensions from the main body. The edges of the extensions and the edges of the flange are recessed inward at the junction area to form a first stress relief groove. The flange can be bent relative to the third disk body along the first stress relief groove. The extensions are provided with radially extending thinning portions. This cylindrical lithium-ion battery allows for liquid injection on either the positive or negative electrode side during assembly and also features low manufacturing cost, high reliability, and high safety.

Description

Technical Field

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

[0002] Currently, large cylindrical lithium-ion batteries like the 46 series typically include positive and negative current collectors. The positive current collector connects the positive terminal of the battery to the positive electrode of the core, while the negative current collector connects the metal casing of the battery to the negative electrode of the core. Current designs for the positive and negative current collectors in large cylindrical lithium-ion batteries only consider these aspects. However, the structure of the positive and negative current collectors has a significant impact on battery performance, reliability, and manufacturing costs. For example:

[0003] In the assembly of cylindrical lithium-ion batteries, a common approach is to inject electrolyte onto the negative electrode side. In this case, the negative electrode current collector undergoes a specific structural design to meet the requirement of electrolyte injection on the negative electrode side. Conversely, since there is no need for electrolyte injection on the positive electrode side, its current collector uses a simple sheet-like structure to reduce design and manufacturing costs. Understandably, due to the limitations of the positive electrode current collector structure, it is not easy to adjust the electrolyte injection scheme during manufacturing to achieve electrolyte injection on the positive electrode side. If manufacturers need to adjust the electrolyte injection scheme, they must modify and verify the structure of the positive electrode current collector to meet the requirement of electrolyte injection on the positive electrode side. Therefore, current cylindrical lithium-ion batteries cannot easily meet the requirement of electrolyte injection on the positive electrode side.

[0004] Cylindrical lithium-ion batteries typically have a flanged edge on their negative electrode current collector. During battery assembly, the outer surface of this flanged edge is bonded to the casing wall and connected via through-welding, thus establishing a conductive connection between the casing and the negative electrode of the core. However, if a grooving process is used to seal the negative electrode side, the casing material deforms towards the center after grooving, pulling the flanged edge of the negative electrode current collector together and causing it to bend. This results in a wavy deformation of the current collector plate connected to the flange, leading to the welding point between the current collector plate and the negative electrode of the core being pulled or even broken. This directly affects the overall current flow of the battery, causing excessive localized heat generation at the welding point and posing a safety hazard.

[0005] 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

[0006] This application provides a cylindrical lithium-ion battery to at least solve the technical problems of high manufacturing cost, insufficient safety and reliability caused by unreasonable design of the positive and negative current collectors in existing cylindrical lithium-ion batteries.

[0007] This application provides a cylindrical lithium-ion battery, including a casing and a positive electrode current collector, a winding core, and a negative electrode current collector disposed within the casing. The casing has an electrode post on the positive electrode side, and the electrode post has a through-hole for liquid injection.

[0008] The positive electrode current collector includes a first disk body located at the center and a second disk body connected to the edge of the first disk body and extending radially outward. The first disk body is welded to the electrode post, and the center of the first disk body is provided with a through first central hole, which communicates with the liquid injection hole. The second disk body includes a connecting part and a welding part connected to each other. The welding part is connected to the edge of the first disk body by the connecting part, and the connecting part has a fusion groove on its edge along its length direction.

[0009] The negative electrode current collector includes a third disk body and multiple flanges that protrude to one side along the outer periphery of the third disk body. The multiple flanges are fitted and welded to the shell wall of the housing. The third disk body includes a main body and multiple extensions that extend radially outward from the main body. The multiple flanges are connected to the multiple extensions one by one. The negative electrode current collector is also provided with a first stress relief groove at its edge. The first stress relief groove is formed by the edge of the extension and the edge of each flange concave inward at the junction area. The first stress relief groove is used to allow the flanges to bend relative to the third disk body along the first stress relief groove. The extension is provided with a thinning part that extends radially. The thickness of the thinning part is less than the thickness of other parts of the extension.

[0010] The cylindrical lithium-ion battery according to the embodiments of this application has at least the following beneficial effects:

[0011] Firstly, by creating a central hole in the positive current collector that connects to the electrolyte injection hole located on the electrode post, the cylindrical lithium-ion battery can be assembled by injecting electrolyte on either the positive or negative side, allowing for convenient adjustment of the electrolyte injection scheme according to actual process requirements. Furthermore, a fuse groove is provided in the positive current collector. This fuse groove reduces the width of the connection portion. When the current passing through this groove is too high, the heat increases and reaches the melting point, causing the connection portion to melt at that location, thus cutting off the current. This provides the positive current collector with a fuse protection function, improving the safety of the cylindrical lithium battery.

[0012] Secondly, by providing a first stress relief groove along the edge of the negative electrode current collector and a thinning portion in the extended portion, during the grooving process, when the flange bends relative to the disk body, the first stress relief groove ensures that the bending occurs near the junction area between the disk body and the flange. Furthermore, the first stress relief groove provides space for material deformation at the bending location, reducing material compression or deformation transmission to the disk body or flange. This avoids problems such as weld point breakage and bulging in the center of the disk caused by deformation of the third disk body and flange. The thinning portion serves to absorb stress; based on the first stress relief groove, it further disperses stress, preventing disk deformation. Therefore, the cylindrical lithium-ion battery of the proposed embodiment has high reliability and good safety, and also boasts a good yield rate during manufacturing, resulting in lower manufacturing costs.

[0013] In one possible implementation, the area of ​​the first disc is S2a, the area of ​​the first central hole is S2b, and the ratio of S2b to S2a is in the range of 4.2% to 8.6%; the first stress relief groove is a V-shaped groove, the V-shaped groove including forming an included angle α, the range of α being 30° to 50°.

[0014] In one possible implementation, along the thickness direction of the positive current collector, the first disk body is higher than the second disk body, and the height difference between the surface of the first disk body on the side that is higher than the second disk body and the surface of the second disk body on the same side is H2a, where H2a ranges from 0.6 to 1.4 mm; the thinning portion is formed by the two opposing surfaces of the extension portion being recessed inward along the thickness direction, and the thinning portion includes, in a radial direction from the inside to the outside, a first transition region with gradually decreasing thickness, a thickness holding region with constant thickness, and a second transition region with gradually increasing thickness, where the thickness holding region has a thickness of L4c, the thickness of the main body portion has a thickness of L4d, and the ratio of L4c to L4d ranges from 30% to 60%.

[0015] In one possible implementation, the edge of the second disc body is provided with a plurality of first notches; the length of the thickness holding area in the radial direction is L4e, the radius of the main body is L4f, and the range of L4e / L4f is 1% to 5%.

[0016] In one possible implementation, the connecting portion has a first edge extending along the length direction for forming the fusible groove, the length of the first edge being L2a, and L2a ranging from 2 to 4 mm; the arc length of the flange along the circumferential direction is L4a; the length of the first stress relief groove recessed inward along the circumferential direction is L4b, and the ratio of L4b to L4a ranging from 3% to 10%.

[0017] In one possible implementation, the connecting portion includes:

[0018] Multiple first connecting portions are arranged circumferentially along the first disc body and extend radially outward from its edge, and the fusible groove is disposed in the first connecting portion;

[0019] A second connecting portion is formed by extending circumferentially to both sides from the outer ends of each of the first connecting portions;

[0020] The welding part has multiple parts, and each welding part is disposed in a corresponding manner in the area defined by two adjacent first connecting parts and second connecting parts, and is formed by extending radially inward from the inner edge of the second connecting part;

[0021] The negative electrode current collector is also 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 extension portion.

[0022] In one possible implementation, the edges on both sides of the welded portion and the inner edge of the second connecting portion define a circumferentially extending slit, the perimeter of the outer edge of the second connecting portion is L2b, the total arc length of the slit is L2c, and the range of L2c / L2b is 43% to 58%; the total arc length of the main body portion corresponding to the second stress relief groove is L4g, the length of the total arc length of the main body portion after deducting the total arc length corresponding to the extension portion is L4h, and the range of L4g / L4h is 5% to 20%.

[0023] In one possible implementation, the second disc body is provided with a plurality of first notches, each of the first notches being disposed on the outer edge of the second connecting portion at the position corresponding to the welding portion. The perimeter of the outer edge of the second connecting portion is L2b, the total arc length of the first notches is L2d, and the range of L2d / L2b is 4% to 9%. The length of the second stress relief groove recessed inward in the radial direction is L4i, the radius of the main body is L4f, and the range of L4i / L4f is 2% to 5%.

[0024] In one possible implementation, the maximum depth of the first notch is L2f, which ranges from 0.9 to 2.1 mm; the bottom of the first stress relief groove is located at the junction of the flange and the extension.

[0025] In one possible implementation, the slit has a radial width of L2e, which ranges from 0.4 to 1.5 mm; the second connecting portion has a radial width W2c in the region corresponding to the slit, which ranges from 1 to 3 mm. Attached Figure Description

[0026] 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.

[0027] Figure 1 This is a cross-sectional schematic diagram of a cylindrical lithium-ion battery provided in an embodiment of this application;

[0028] Figure 2 This is a schematic diagram of the structure of a positive current collector provided in an embodiment of this application;

[0029] Figure 3 yes Figure 2 A schematic diagram of the area S2a in the positive current collector of the circuit;

[0030] Figure 4 yes Figure 2 A schematic diagram of the area S2b in the positive current collector of the circuit;

[0031] Figure 5 yes Figure 3 Schematic sectional view along the middle AA direction;

[0032] Figure 6 yes Figure 5 A partial schematic diagram at point B in the middle;

[0033] Figure 7 yes Figure 1 A top view of the positive current collector in the circuit;

[0034] Figure 8 yes Figure 7 A partial schematic diagram at point C in the middle;

[0035] Figure 9 yes Figure 7 A partial schematic diagram at point D in the middle;

[0036] Figure 10 This is a schematic diagram of the structure of a negative electrode current collector provided in an embodiment of this application;

[0037] Figure 11 yes Figure 10 A cross-sectional view of the negative electrode current collector connected to the housing without being grooved;

[0038] Figure 12 yes Figure 11 A cross-sectional view of the structure behind the groove;

[0039] Figure 13 yes Figure 10 A partial schematic diagram at point G in the middle;

[0040] Figure 14 yes Figure 13 A partial schematic diagram at point H in the middle;

[0041] Figure 15 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;

[0042] Figure 16 yes Figure 15 A partial schematic diagram at point I in the middle;

[0043] Figure 17 yes Figure 15 A partial schematic diagram at point J in the middle;

[0044] Figure 18 This is a cross-sectional view of a negative current collector provided in an embodiment of this application;

[0045] Figure 19 yes Figure 18 A partial schematic diagram at point K. Detailed Implementation

[0046] Figure 1 This is a schematic diagram of a cylindrical lithium-ion battery provided in an embodiment of this application. The cylindrical lithium-ion battery in this embodiment includes various large cylindrical lithium-ion batteries, such as the 46 series (outer diameter 46mm), and is not limited thereto. Figure 1 As shown, the cylindrical lithium-ion battery includes a casing 100, a positive electrode current collector 200, a core 300, a negative electrode current collector 400, an electrode post 500, and a cap 600, etc.

[0047] The housing 100 is cylindrical in shape, with opposing positive and negative electrode sides. The electrode post 500, as part of the positive electrode cover assembly, is installed on the positive electrode side of the housing 100. The cap 600 is sealed on the negative electrode side of the housing 100 using a rolling and sealing process. The housing 100 defines an inner cavity in which the positive electrode current collector 200, the core 300, and the negative electrode current collector 400 are enclosed, thus isolating the core 300 and the electrolyte from the external environment, forming a closed electrochemical system within the housing 100. The positive electrode of the core 300 is connected to the electrode post 500 via the positive electrode current collector 200, while the negative electrode of the core 300 is connected to the housing 100 via the negative electrode current collector 400. It can be understood that the electrode post 500 serves as the positive electrode of the cylindrical lithium-ion battery, and the housing 100 serves as the negative electrode, both used for electrical connection to external electrical devices.

[0048] Understandably, the core 300 is formed by winding together positive electrode sheets, negative electrode sheets, and a separator, as shown below. Figure 1As shown, the core 300 is cylindrical in shape and has a positive terminal 310 as the positive electrode and a negative terminal 320 as the negative electrode. The positive terminal 310 is used to weld to the positive current collector 200, and the negative terminal 320 is used to weld to the negative current collector 400. The core 300 is manufactured by a winding process, and a circular core hole 330 is formed at the center of the core 300 after winding.

[0049] The following is a detailed introduction to the positive current collector 200.

[0050] Figure 2 This is a schematic diagram of the structure of a positive current collector provided in an embodiment of this application, as shown below. Figure 2 As shown, the positive current collector 200 includes two parts: a first disk body 210 and a second disk body 220. The first disk body 210 is used to connect to the electrode post 500, and the second disk body 220 is used to connect to the winding core 300, so that a passage is formed between the winding core 300 and the electrode post 500. It can be understood that, as... Figure 2 As shown, in a cylindrical lithium-ion battery, the electrode post 500 and the core 300 are located in the thickness direction of the positive electrode current collector 200. Figure 1 The two sides of the first disc 210 (in the height direction) are connected to the bottom of the pole post 500, and the lower surface of the second disc 220 is connected to the positive end 310 of the core 300.

[0051] Understandably, to accommodate the circular cross-sectional shape of the core 300 and the housing 100, and to improve space utilization, the positive electrode current collector 200 is a thin, circular disk shape, and is typically made of materials such as aluminum. Furthermore, to correspond to the position of the terminal post 500 in a cylindrical lithium-ion battery, the first disk 210 is located in the central region of the positive electrode current collector 200, while the second disk 220 is located in the peripheral region of the positive electrode current collector 200; that is, viewed radially, the second disk 220 extends radially from the edge of the first disk 210. Thus, the lower surface of the second disk 220 precisely corresponds to the positive terminal 310 on the periphery of the core hole 330.

[0052] Furthermore, the terminal 500 of a cylindrical lithium-ion battery is typically a cylindrical structure with a circular bottom surface. To match the circular bottom surface shape of the terminal 500, in some embodiments, such as... Figure 2 As shown, the first disc 210 can be circular, and the second disc 220 can be circular to match the annular end face shape of the positive terminal 310. Thus, the required welding areas can be formed between the first disc 210 and the pole post 500, and between the second disc 220 and the positive terminal 310, so as to form a good welding connection between the two.

[0053] Continue to refer to Figure 2In this embodiment of the application, a first central hole 211 is provided at the center of the first disc 210, which is used for liquid injection on the positive electrode side. Combined with... Figure 1 On the positive electrode side of the cylindrical lithium-ion battery, an injection hole 510 is provided on the electrode post 500, so that the injection hole 510 is aligned and connected with the first central hole 211. This allows electrolyte to be injected externally through the channel formed by the injection hole 510 and the first central hole 211, thus enabling electrolyte injection on the positive electrode side. Furthermore, to match the shape of the circular core hole 330, the first central hole 211 is preferably a circular hole.

[0054] It is understood that the positive current collector 200 provided in this application embodiment, by providing a first central hole 211 on the first plate body 210, can be compatible with either negative electrode side liquid injection or positive electrode side liquid injection for cylindrical lithium-ion batteries, in conjunction with the negative electrode current collector 400 which can be used for liquid injection on the negative electrode side. Therefore, in the liquid injection process, liquid injection can be freely selected on the positive electrode side or the negative electrode side without making any structural changes to the positive current collector 200. Manufacturers can manufacture or purchase it as a general structural component, which can effectively reduce design and manufacturing costs and facilitate internal material management in the factory.

[0055] refer to Figure 3 and Figure 4 In this embodiment, the area of ​​the first disc is S2a, the area of ​​the first central hole 211 is S2b, and the ratio of S2b to S2a ranges from 4.2% to 8.6%. For example, S2b / S2a can be 4.2%, 5%, 6.8%, 8.6%, etc. In some embodiments, the area S2a of the first disc 210 is 107.51 mm². 2 The area S2b of the first central hole 211 is 7.51 mm. 2 If S2b / S2a is greater than 8.6%, the effective welding area of ​​the welding region of the first plate 210 will be reduced, thereby decreasing the current carrying capacity at the weld and causing an increase in the overcurrent temperature rise of the solder area, which in turn increases the internal resistance of the battery and reduces the overall performance of the battery. Conversely, if S2b / S2a is less than 4.2%, the electrolyte inflow time will be too long during electrolyte injection, resulting in reduced injection efficiency, which in turn reduces production efficiency and increases the manufacturing cost of the battery. By setting S2b / S2a in the range of 4.2% to 8.6%, both the welding effect of the positive electrode current collector 200 and the electrode post 500 and the injection efficiency can be balanced.

[0056] In some embodiments, the diameter of the first central hole 211 ranges from 2 to 4 mm. For example, the diameter of the first central hole 211 is 2 mm, 3 mm, or 4 mm. If the diameter of the first central hole 211 is greater than 4 mm, the effective welding area of ​​the welding region of the first plate 210 will be reduced, thereby reducing the current carrying capacity at the welding point and causing the overcurrent temperature rise in the solder area to increase, which in turn increases the internal resistance of the battery and reduces the overall performance of the battery. Conversely, if the diameter of the first central hole 211 is less than 2 mm, the electrolyte inflow time will be too long during electrolyte injection, thereby reducing the electrolyte injection efficiency, which in turn reduces the production efficiency and increases the manufacturing cost of the battery. By setting the diameter of the first central hole 211 to 2 to 4 mm, both the welding effect of the positive electrode current collector 200 and the electrode post 500 and the electrolyte injection efficiency can be balanced.

[0057] In some embodiments, such as Figure 3 and Figure 4 As shown, and in combination Figure 1 Along the thickness direction of the positive electrode current collector 200, the first disk body 210 and the second disk body 220 are staggered, meaning the first disk body 210 is higher than the second disk body 220. This creates a recess 260 at the bottom of the positive electrode current collector 200 corresponding to the area of ​​the first disk body 210. Thus, after the positive electrode current collector 200 is assembled into the cylindrical lithium-ion battery, the bottom of the first disk body 210 can define a chamber between itself and the positive terminal 310 of the core 300. During electrolyte injection, this chamber can temporarily store the electrolyte injected through the first central hole 211. Furthermore, since the surface of the first disk body 210 used for welding to the electrode post 500 is not coplanar with the upper surface of the second disk body 220 and has a smaller surface area, the flatness of the first disk body 210 can be better guaranteed, allowing it to fit well with the bottom surface of the electrode post 500, thereby improving the welding effect.

[0058] Furthermore, an outlet 270 is provided on the positive current collector 200, connecting the recess 260 to the upper surface of the second disc 220. It is understood that during electrolyte injection, the electrolyte entering the chamber can spread through the outlet 270 to the upper surface of the second disc 220, and be injected into the core 300 through through-hole structures constructed on the second disc 220, such as the slit 240 and the first notch 250 described below, thereby effectively improving the injection efficiency.

[0059] Furthermore, in some embodiments, the height difference between the surface of the second disc 220 near the first disc 210 and the surface of the first disc 210 is H2a, where H2a ranges from 0.6 to 1.4 mm. For example, H2a can be 0.6 mm, 0.8 mm, 1.1 mm, or 1.4 mm. It should be noted that the surface of the first disc 210 described herein refers to the surface used for welding to the electrode post 500, i.e. Figure 3 and Figure 4 The upper surface of the second disk 220, and the side of the second disk 220 closest to the first disk 210, refers to the surface located on the same side as the surface used for welding to the pole post 500, i.e. Figure 3 and Figure 4 The upper surface of the battery. If H2a is greater than 1.4 mm, the positive current collector 200 will occupy the assembly space of the internal core 300, resulting in a decrease in battery capacity and performance. Conversely, if H2a is less than 0.6 mm, the height of the first disc 210 relative to the second disc 220 will be too low, resulting in a small cavity space between the bottom of the first disc 210 and the positive terminal 310 of the core 300. During electrolyte injection, the electrolyte will flow from the cavity to the surface of the second disc 220 and be injected into the core 300 through the through-hole structure on the second disc 220 for too long, thus reducing the injection efficiency, leading to reduced production efficiency, increased battery manufacturing costs, and a higher risk of electrolyte overflow during injection. By setting H2a in the range of 0.6–1.4 mm, battery performance and injection efficiency can be balanced.

[0060] In some embodiments, such as Figure 2 , Figure 3 , Figure 4 as well as Figure 7As shown, the second disc body 220 includes a connecting portion 221 and a welding portion 222 connected together, and the welding portion 222 is connected to the edge of the first disc body 210 by the connecting portion 221. It is understood that in the connecting portion 221 and the welding portion 222 constituting the second disc body 220, the welding portion 222 is used to weld to the positive terminal 310 of the core 300, while the connecting portion 221 is used to connect the welding portion 222 to the first disc body 210. In this embodiment, a fusing groove 230 is provided on the edge of the connecting portion 221 along its length direction. Specifically, the fusing groove 230 is a structure formed by an inward indentation along the width direction of the edge of the connecting portion 221 along its length direction. This fusing groove 230 can reduce the width of the connecting portion 221. In the event of an abnormally high current, when the current passes through this location, the heat increases and reaches the melting point, causing the connecting portion 221 to melt at that location, achieving the effect of cutting off the current, thereby reducing the risk of thermal runaway of the battery cell. It is understandable that when the second plate body 220 is provided with multiple sets of connecting parts 221 and welding parts 222, each connecting part 221 is provided with a fusible groove 230 so as to completely cut off the current flowing through the positive current collector 200 in the event of an abnormal current exceeding the limit.

[0061] Specifically, the connecting portion 221 is elongated and extends radially, with a certain width extending circumferentially. Two fuse grooves 230 are provided on each connecting portion 121, and these two fuse grooves 230 are symmetrically arranged on both sides of the width direction of the connecting portion 221. Since the positive current collector 200 itself is thin, the connecting portion 221 is also thin in the thickness direction. Therefore, by providing fuse grooves 230 on both sides of its width direction, the cross-sectional area at this position can be significantly reduced, so that the connecting portion 221 can quickly fuse under abnormal conditions of excessive current.

[0062] Further, refer to Figure 8 In some embodiments, the connecting portion 221 has a first width W2a, and the connecting portion 221 has a second width W2b in the area where the fuse groove 230 is formed, with W2b / W2a ranging from 42% to 63%. For example, W2b / W2a can be 42%, 48%, 56%, 63%, etc. In some embodiments, the first width W2a is 4 mm, and the second width W2b is 2 mm. In the embodiments of this application, the second width W2b refers to the change in the width of the connecting portion 221 relative to the first width W2a due to the design of the fuse groove 230. Based on the definition of the second width W2b in the embodiments of this application, the first width W2a in this application refers to the width of the connecting portion 221 at the location other than the fuse groove 230. Further, the first width W2a and the second width W2b are of equal width.

[0063] If W2b / W2a is greater than 63%, the second width W2b of the connecting part 221 at the corresponding fuse groove 230 is too wide, preventing it from quickly melting under abnormal conditions of excessive current, thus increasing safety risks. Conversely, if W2b / W2a is less than 42%, the second width W2b of the connecting part 221 at the corresponding fuse groove 230 is too small. This would result in excessively high fuse sensitivity, easily causing battery open-circuit failure, and would also increase internal resistance, affecting normal battery use. By setting W2b / W2a within the range of 42% to 63%, the melting effect of the connecting part 221 can be guaranteed, thereby ensuring the safety performance of the battery.

[0064] In some embodiments, the connecting portion 221 has a first edge 231 extending along its length for forming the fuse groove 230. The length of the first edge 231 is L2a, which ranges from 2 to 4 mm. For example, L2a is 2 mm, 3 mm, or 4 mm. As mentioned earlier, the positive electrode current collector 200 is usually made of aluminum, which is relatively soft and has low strength. Therefore, if L2a is greater than 4 mm, the connecting portion 221 is more likely to deform or even break at the location of the fuse groove 230. The positive electrode current collector 200 itself is easily scrapped, resulting in waste and increased management difficulty. In addition, if the resulting metal shavings fall into the battery, there is a risk of battery short circuit. Furthermore, burrs and sharp corners at the cross-section may puncture the separator and cause battery short circuit, thereby increasing the battery safety risk. Conversely, if L2a is less than 2mm, heat is easily transferred to the first plate 210 and the welding part 222, which will reduce the fusing sensitivity of the fusing groove 230 and prolong the fusing time, thereby increasing the safety risk of the battery. By setting L2a in the range of 2-4mm, it is possible to improve the yield rate and reduce costs while ensuring battery safety.

[0065] It is understood that in this embodiment, both sides of the connecting portion 221 in the width direction are provided with fuse grooves 230. Therefore, the aforementioned second width W2b is the vertical distance between the first edges 231 of the two fuse grooves 230. Furthermore, as... Figure 8 As shown, in addition to the first edge 231, the bottom of the fuse groove 230 also has a second edge 232 and a third edge 233 that are respectively connected to the two ends of the first edge 231. The first edge 231, the second edge 232 and the third edge 233 together form a fuse groove 230 with a generally trapezoidal shape.

[0066] Continue to refer to Figure 2 , Figure 3 , Figure 4 as well as Figure 7In some embodiments, the second disc 220 includes a connecting portion 221 and a welding portion 222. Further, the connecting portion 221 includes a first connecting portion 2211 and a second connecting portion 2212. Multiple first connecting portions 2211 are arranged circumferentially around the first disc 210 and extend radially outward from their edges; that is, these first connecting portions 2211 are radially distributed with the center of the first disc 210 as the center. The second connecting portions 2212 are formed by extending circumferentially to both sides from the outer ends of each first connecting portion 2211. Furthermore, multiple welding portions 222 are correspondingly disposed within the area defined by two adjacent first connecting portions 2211 and second connecting portions 2212, and are formed by extending radially inward from the inner edge of the second connecting portion 2212. It is understood that the second connecting portion 2212, formed by extending circumferentially from the outer ends of each first connecting portion 2211, constitutes an annular structure surrounding the periphery of the first disk body 210, and the outer edge of this annular structure is used to define the boundary of the entire positive current collector disk 200.

[0067] It is understandable that, in order to simplify the structure, the aforementioned fuse groove 230 can be provided on the first connecting part 2211.

[0068] It is understood that in the above structure, there are multiple welding parts 222 for welding to the positive terminal 310, and their number corresponds to the number of the first connecting parts 2211. For example, if there are 3 first connecting parts 2211, there are also 3 welding parts 222. These welding parts 222 are arranged in multiple areas separated by the first connecting parts 2211 along the circumferential direction. Thus, when viewed from the top view of the positive current collector 200, it is divided into multiple welding areas, and the boundaries of these welding areas are clear. Therefore, during welding, it is easy to position the welding area using tooling and to weld it using welding equipment. After welding, it is easy to judge whether the welding position is reasonable by visual observation or visual inspection equipment, which can reduce the difficulty of identification and workload.

[0069] It can be further understood that the weld portion 222 extends inward from the inner edge of the second connecting portion 2212. In some embodiments, in order to increase the welding area of ​​each weld portion 222 (see reference...), Figure 7In the shaded area E), the edge of the welded portion 222 extends close to the edge of the first disc 210 and the edge of the first connecting portion 2211. Thus, a circumferentially extending gap exists between the welded portion 222 and the first disc 210. This gap serves as the aforementioned outlet 270, allowing the electrolyte entering the chamber to spread to the upper surface of the second disc 220 during injection. Furthermore, a radially extending gap exists between the welded portion 222 and the first connecting portions 2211 located on both sides thereon, and this gap serves as a through-hole structure for injecting electrolyte into the core 300. It is understood that in the above configuration, the gaps formed between the welded portion 222 and the first disc 210 and the first connecting portion 2211 are connected; therefore, the electrolyte can flow along the two gaps, improving injection efficiency.

[0070] Furthermore, in some embodiments, such as Figure 7 As shown, circumferentially extending slits 240 are defined on both sides of the welding portion 222 and on the inner side of the second connecting portion 2212. By defining circumferentially extending slits 240 on both sides of the welding portion 222 and on the inner side of the second connecting portion 2212, during electrolyte injection, electrolyte can be injected into the interior of the core 300 through the slits 240 at the far end away from the first disc 210, thus improving the electrolyte injection efficiency.

[0071] In some embodiments, the perimeter of the outer edge of the second connecting portion 2212 is L2b, the total arc length of the slits 240 is L2c, and the ratio of L2c / L2b ranges from 43% to 58%. For example, L2c / L2b can be 43%, 50%, 58%, etc. For example, in some embodiments, L2b is 233.52 mm, the number of welded portions 222 is 3, the number of slits 240 is 6, and the total arc length L2c of the 6 slits 240 is 66.78 mm. It should be noted that the perimeter L2b referred to in the embodiments of this application refers to the circumference of the entire circle containing the outer edge of the annular structure formed by the second connecting portions 2212 extending circumferentially from the outer ends of each first connecting portion 2211. Figure 7 The circumference of the circle containing the baseline F at the first gap (250) is given for ease of understanding. Figure 7 The outer edge of the second connecting portion 2212 is indicated by a dashed line. Furthermore, Figure 9Only a portion of L2c, specifically the arc length of one section of the slit 240, is indicated. Furthermore, L2c here also includes the arc length of the gap formed between the welded portion 222 and the first connecting portion 2211, which communicates with the slit 240. If L2c / L2b is greater than 58%, the structural strength of the connection between the welded portion 222 and the second connecting portion 2212 is low, making it prone to deformation and affecting the welding effect. A lower yield also leads to increased costs. Conversely, if L2c / L2b is less than 43%, the time required for the electrolyte to be injected into the core through the slit 240 during electrolyte injection remains relatively long, and the slit 240's effect on improving injection efficiency is not significant. By setting the L2c / L2b range to 43%–58%, it is possible to improve injection efficiency while ensuring the welding effect of the positive current collector 200, and also to increase the yield and reduce costs.

[0072] Furthermore, in some embodiments, the radial width of the slit 240 is L2e, which ranges from 0.4 to 1.5 mm. For example, L2e can be 0.4 mm, 0.8 mm, 1.2 mm, or 1.5 mm. If L2e is greater than 1.6 mm, the opening area of ​​the slit 240 will occupy the welding area between the welded part 222 and the core 300, resulting in a reduction in the effective welding area and a decrease in the current-carrying capacity at the weld, which in turn leads to an increase in the temperature rise at the weld. Conversely, if L2e is less than 0.4 mm, the electrolyte flows into the core 300 through the slit 240 at a slower rate during electrolyte injection, and the slit 240 has little effect on improving the injection efficiency. By setting L2e in the range of 0.4 to 1.5 mm, both the welding effect between the positive current collector 200 and the core 300 and the injection efficiency can be balanced.

[0073] Furthermore, in some embodiments, the second connecting portion 2212 has a radial width W2c in the corresponding slit 240 region, where W2c ranges from 1 to 3 mm. For example, W2c can be 1 mm, 3 mm, etc. If W2c is greater than 3 mm, the second connecting portion will excessively intrude into the central region of the positive current collector 200, reducing the effective welding area between the welding portion 222 and the core 300, resulting in reduced current carrying capacity at the weld and consequently increased temperature rise at the weld. Conversely, if W2c is less than 1 mm, the structural strength of the second connecting portion 2212 at this location is insufficient, making it prone to breakage. If the resulting metal shavings fall into the battery, there is a risk of a short circuit. Furthermore, burrs and sharp corners at the fracture surface may puncture the separator, causing a short circuit and increasing the battery's safety risk. By setting the range of W2c to 1 to 3 mm, both the welding effect between the positive current collector 200 and the core 300 and the battery's safety can be balanced.

[0074] In some embodiments, such as Figure 7 As shown, the second connecting portion 2212 has a plurality of evenly distributed first notches 250 on its outer edge. Specifically, for example, the first notches 250 can be formed by the radial inward recess of the outer edge of the second connecting portion 2212, thereby defining the first notches 250 by the recessed edge of the second connecting portion 2212 and its reference line, wherein the reference line F can be referenced to... Figure 9 The dashed line at the first notch 250 is for illustrative purposes only. This line represents the shape of the second connecting portion 2212 before the notch 113 is formed on its outer edge; that is, the dashed line extends naturally along the outer edge of the second connecting portion 2212. By providing the first notch 250, during electrolyte injection, the electrolyte spreading along the upper surface of the second disc 220 to its edge can flow into the core 300 through the first notch 250, thereby further improving the injection efficiency.

[0075] Further, in some embodiments, the first notch 250 is positioned circumferentially opposite to the welded portion 222 in the second connecting portion 2212, that is, in the radial direction, the center of the first notch 250 is collinear with the center of the welded portion 222, and the total arc length of the first notch 250 is L2d, with L2d / L2b ranging from 4% to 9%. For example, L2d / L2b can be 4%, 6%, 9%, etc. For example, in some embodiments, the number of first notches 250 is three, and the total arc length L2d of the three first notches 250 is 9 mm. It should be noted that the arc length of the first notch 250 referred to in the embodiments of this application refers to the arc length defining the reference line F forming the first notch 250. Figure 9 Only a portion of L2d is shown. If L2d / L2b is greater than 9%, the connection area between the second connecting part 2212 and the welding part 222 is too small, making it difficult to guarantee the flatness of the welding part 222, and consequently, the welding effect. Conversely, if L2d / L2b is less than 4%, during electrolyte injection, the electrolyte flows into the core 300 through the first notch 250 at a slower rate, and the first notch 250 has little effect on improving the injection efficiency. By setting the L2d / L2b range to 4%–9%, ​​both the welding effect and injection efficiency of the positive electrode current collector 200 can be balanced.

[0076] Furthermore, in some embodiments, such as Figure 9As shown, the maximum depth of the first notch 250 is L2f, which ranges from 0.9 to 2.1 mm. For example, L2f can be 0.9 mm, 1.5 mm, or 2.1 mm. If L2f is greater than 2.1 mm, the first notch 250 will occupy the welding area between the welding part 222 and the core 300, resulting in a reduction in the effective welding area and a decrease in the current carrying capacity at the weld, which in turn leads to an increase in the temperature rise at the weld. Conversely, if L2f is less than 0.9 mm, the electrolyte flows into the core 300 through the first notch 250 at a slower rate during electrolyte injection, and the first notch 250 has little effect on improving the electrolyte injection efficiency. By setting the range of L2f to 0.9–2.1 mm, both the welding effect of the positive current collector 200 and the electrolyte injection efficiency can be balanced.

[0077] The effects of this application will be further described below with specific embodiments and comparative examples.

[0078] It should be noted that the following embodiments and comparative examples of this application are all based on the design and fabrication of the 4680 cylindrical lithium-ion battery commonly used in the art. Therefore, except for fabricating the negative electrode current collector 400 according to the aforementioned structure, other components and materials can be obtained by referring to the 4680 cylindrical lithium-ion battery. For example, after the positive electrode sheet and negative electrode sheet are rolled, slit, and die-cut respectively, they are wound together with the separator. The positive electrode sheet, negative electrode sheet and separator are wound together by a winding machine to form a core 300. The two ends of the core 300 are cut and stacked to form positive electrode tabs and negative electrode tabs. Then, the negative electrode current collector 400 and the positive electrode current collector are welded to the core 300 respectively. Then, the negative electrode current collector 400 is welded to the shell 100. The negative electrode cover plate 600 is welded to the shell 100. After liquid injection, sealing and formation processes are completed, an experimental cylindrical lithium-ion battery is obtained.

[0079] Example 1:

[0080] Example 1 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200. The positive electrode current collector 200 includes a first disk body 210 and a second disk body 220 that are offset from each other in the thickness direction. The surface of the first disk body 210 that is higher than the surface of the second disk body 220 has a height difference H2a from the surface of the second disk body 220 that is on the same side. A circular first central hole 211 is provided at the center of the first disk body 210. The second disk body 220 includes three first connecting portions 2211 that extend radially outward from the edge of the first disk body 210. The two sides of the outer ends of the three first connecting portions 2211 extend circumferentially to form There are second connecting portions 2212, which together form an annular structure. In each region formed by the three first connecting portions 2211 in pairs in the circumferential direction, the inner edge of the second connecting portion 2212 extends inward to form a welding portion 222. A circumferentially extending slit 240 is defined between the edges on both sides of the welding portion 222 and the inner edge of the second connecting portion 2212. A pair of trapezoidal welding grooves 230 are provided on the edge of each first connecting portion 2211 in the length direction. A first notch 250 is provided on the outer edge of the second connecting portion 2212 corresponding to the position of the welding portion 222.

[0081] In addition, the positive current collector 200 also meets the following parameters:

[0082] The area S2a of the first disk 210 is 107.51 mm². 2 The area S2b of the first central hole 211 is 7.07 mm. 2 H2a = 1mm, first width W2a = 4mm, second width W2b = 2mm at the location where the fuse groove 230 is provided, length L2a = 3mm at the bottom edge 231 of the fuse groove 230, perimeter L2b = 233.52mm at the outer edge of the second connection 2212, total arc length L2c = 66.78mm at the six slits 240, width L2e = 0.8mm at the slits 240, width W2c = 2mm at the area corresponding to the slits 240 at the second connection 2212, total arc length L2d = 9mm at the three first notches 250, maximum depth L2f = 1.5mm at the first notches 250.

[0083] As can be seen from the above, in the positive current collector 200, S2b / S2a = 6.6%, W2b / W2a = 50%, L2c / L2b = 50%, and L2d / L2b = 6.74%.

[0084] Comparative Example 1: Comparative Example 1 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200. The difference between Comparative Example 1 and Example 1 is that S2b / S2a = 3%.

[0085] Comparative Example 2:

[0086] Comparative Example 2 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that S2b / S2a = 10%.

[0087] Comparative Example 3:

[0088] Comparative Example 3 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that H2a = 0.3 mm.

[0089] Comparative Example 4:

[0090] Comparative Example 4 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that H2a = 1.7 mm.

[0091] Comparative Example 5:

[0092] Comparative Example 5 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that W2b / W2a = 36%.

[0093] Comparative Example 6:

[0094] Comparative Example 6 provides a cylindrical lithium-ion battery, which includes a positive current collector 200, and differs from Example 1 in that W2b / W2a = 68%.

[0095] Comparative Example 7:

[0096] Comparative Example 7 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that L2a = 1.5 mm.

[0097] Comparative Example 8:

[0098] Comparative Example 8 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that L2a = 4.5 mm.

[0099] Comparative Example 9:

[0100] Comparative Example 9 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that: L2c / L2b = 36%.

[0101] Comparative Example 10:

[0102] Comparative Example 10 provides a cylindrical lithium-ion battery including a positive current collector 200, which differs from Example 1 in that L2c / L2b = 68%.

[0103] Comparative Example 11:

[0104] Comparative Example 11 provides a cylindrical lithium-ion battery including a positive current collector 200, which differs from Example 1 in that L2d / L2b = 2%.

[0105] Comparative Example 12:

[0106] Comparative Example 12 provides a cylindrical lithium-ion battery including a positive electrode current collector 200, which differs from Example 1 in that L2d / L2b = 14%.

[0107] Comparative Example 13:

[0108] Comparative Example 13 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that L2e = 0.3 mm.

[0109] Comparative Example 14:

[0110] Comparative Example 14 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that L2e = 1.8 mm.

[0111] Comparative Example 15:

[0112] Comparative Example 15 provides a cylindrical lithium-ion battery including a positive electrode current collector 200, which differs from Example 1 in that W2c = 0.7 mm.

[0113] Comparative Example 16:

[0114] Comparative Example 16 provides a cylindrical lithium-ion battery including a positive electrode current collector 200, which differs from Example 1 in that W2c = 3.5 mm.

[0115] Comparative Example 17:

[0116] Comparative Example 17 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that L2f = 0.6 mm.

[0117] Comparative Example 18:

[0118] Comparative Example 18 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that L2f = 2.6 mm.

[0119] Comparative Example 19:

[0120] Comparative Example 19 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that it does not have a fuse groove 230.

[0121] Comparative Example 20:

[0122] Comparative Example 20 provides a cylindrical lithium-ion battery, which includes a positive electrode current collector 200, and differs from Example 1 in that it does not have a first notch 250.

[0123] Table 1 below shows the electrolyte injection time (t) required for the positive electrode current collector 200 fabricated in the above embodiments and comparative examples, the highest soldering temperature of the first plate 210 (T1max), the highest soldering temperature of the second plate 220 (T2max), the highest temperature at the fuse groove 230 (T3max), the number of folds (C1) at which the first connecting part 2211 breaks after being folded at the fuse groove 230, the number of folds (C2) at which the second connecting part 2212 breaks after being folded, and the battery short circuit rate test, wherein:

[0124] The test method for the time (t) required for electrolyte injection into the battery is as follows: Assemble the positive electrode current collector 200 into a cylindrical lithium-ion battery. During the electrolyte injection stage, inject 77g of electrolyte into the holding cup. Align the nozzle of the holding cup with the injection hole 510 on the electrode post 500 and press it tightly. First, draw negative pressure in the holding cup for 15s, drawing it to -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 for 40s, positive pressure injection is performed, and nitrogen gas is injected into the battery. The battery gradually becomes positive pressure 0.8MPa. The electrolyte in the holding cup continues to flow into the battery, and the electrolyte height in the holding cup gradually decreases. Then, adjust to negative pressure injection and maintain this. Then, adjust to positive pressure injection and maintain this. Repeat the positive and negative pressure injection cycle multiple times until the electrolyte in the holding cup has completely flowed into the battery and the electrolyte height in the holding cup is 0. Record the time t at which the electrolyte has completely flowed into the battery.

[0125] The testing method for the highest temperature (T1max) of the first plate 210 solder mark, the highest temperature (T2max) of the second plate 220 solder mark, and the highest temperature (T3max) at the fuse groove 230 is as follows: During the assembly of the cylindrical lithium-ion battery, the temperature acquisition wire is inserted into the battery through the liquid injection hole 510 of the terminal 500. One wire is attached to the welding point between the first plate 210 and the terminal 500, one wire is attached to the welding point between the second plate 220 and the positive terminal 310 of the core 300, and the other wire is attached to the position where the fuse groove 230 is set in the first connecting part 2211. Then, the battery is manufactured according to the normal process and finally the finished battery is obtained. Then, it is charged and discharged for 10 cycles at a rate of 2C, and the highest temperatures T1max, T2max and T3max at the three positions obtained by the temperature acquisition wire are recorded.

[0126] The test method for determining the number of folds (C1) at which the first connecting part 2211 breaks after being folded at the fuse groove 230 is as follows: Use scissors to cut along the radial direction from two adjacent first notches 250 to obtain a 1 / 3 piece of positive current collector 200 containing a first connecting part 2211. Fold this part of the disk along the center line of the fuse groove 230. After the two sides are completely glued together, unfold it to 180° and count it as one fold. Continue until the fold breaks, then stop folding and record the number of folds.

[0127] The test method for determining the number of folds (C2) at which the second connecting part 2212 breaks after folding is as follows: Use scissors to cut radially from a first notch 250 to the first center hole 211, then cut radially along the edge of the first connecting part 2211 to the second connecting part 2212. Fold the obtained fan-shaped positive current collector 200 in two fan shapes. When the two disks are completely closed and then unfolded to 180°, it is counted as one fold. Continue until the first connecting part 2212 breaks, then stop folding and record the number of folds.

[0128] The battery short circuit rate test method is as follows: Battery samples are made according to the same positive and negative electrode ratio, process method and parameters, and 200pcs are produced continuously. The 200pcs of semi-finished batteries are short-circuited using a Hipot device. The battery is judged as defective if the Hipot value is ≤300MΩ, and the battery short circuit failure rate is calculated.

[0129] Table 1

[0130]

[0131]

[0132]

[0133] As shown in Table 1, when S2b / S2a is set to 6.6%, W2b / W2a to 50%, L2 / L2b to 50%, L2d / L2b to 6.74%, H2a to 1mm, L2a to 3mm, L2e to 0.8mm, W2c to 2mm, and L2f to 1.5mm, the electrolyte injection time t is 693 seconds, the maximum temperature T1max at the welding point between the first disc 210 and the electrode post 500 is 56.4℃, the maximum temperature T2max at the welding point between the second disc 220 and the core 300 is 68.9℃, the maximum temperature T3max at the fuse groove 230 is 73.6℃, ​​the number of folds C1 for the first connecting part 2211 to break after being folded at the fuse groove 230 is 5, the number of folds C2 for the second connecting part 2212 to break after being folded is 5, and the battery short circuit rate is only 1%. It can be seen that within the above numerical range, the liquid injection rate, welding temperature rise, structural strength and connection reliability of the positive electrode current collector 200 can be well balanced, thereby effectively improving the safety and charge / discharge performance of the battery, as well as reducing the production cost of the battery.

[0134] As shown in Table 1, if S2b / S2a is too small, H2a is too small, W2b / W2a is too large, L2 / L2b is too small, L2d / L2b is too small, L2e is too small, L2f is too small, and the fusible groove 230 or the first notch 250 is not set, the electrolyte injection time t will increase to a certain extent.

[0135] As shown in Table 1, an excessively large S2b / S2a ratio will cause a significant increase in the maximum temperature T1max at the welding point between the first disk 210 and the pole post 500.

[0136] As shown in Table 1, excessively large L2 / L2b, L2d / L2b, L2e, W2c, and L2f will all lead to an increase in the maximum temperature T2max at the welding point between the second disc 220 and the core 300.

[0137] As shown in Table 1, if W2b / W2a is too small, the maximum temperature T3max at the fuse groove 230 will increase significantly. Conversely, if W2b / W2a is too large, or L2a is too short, the maximum temperature T3max at the fuse groove 230 will be lower. It is understandable that, for the location of the fuse groove 230, if the temperature cannot rise to the fusing threshold, the first connection 2211 cannot fuse in time, thus failing to provide safety protection.

[0138] As shown in Table 1, if W2b / W2a is too small or L2a is too large, the number of folds C1 that the first connecting part 2211 will break after being folded at the fusion groove 230 will decrease.

[0139] As shown in Table 1, if W2c is too small, the number of folds C2 that cause the second connecting part 2212 to break after folding will be significantly reduced, and the second connecting part 2212 will be more prone to breakage.

[0140] As shown in Table 1, an excessively high H2a will significantly increase the probability of a short circuit in the battery.

[0141] The following is a detailed introduction to the negative electrode collector 400.

[0142] Figure 10 This is a schematic diagram of the structure of the negative electrode current collector 400 provided in the embodiment of this application. The negative electrode current collector 400 includes a third disk body 410 and a plurality of flanges 420 protruding along one side of the outer periphery of the third disk body 410. Figure 11 yes Figure 10 A cross-sectional view of the negative electrode current collector connected to the housing without grooves, as shown in the figure. Figure 11 As shown, it can be understood that on the negative electrode side of the cylindrical lithium-ion battery, the third disk 410 of the negative electrode current collector 400 is connected to the negative electrode of the core 300, and the flange 420 is attached to and welded to the shell wall of the cylindrical lithium battery casing 100. Here, the shell wall of the cylindrical lithium battery refers to the inner wall of the casing 100, so that the core 300 forms a passage between the negative electrode current collector 400 and the casing 100, thereby making the casing 100 itself the negative electrode of the cylindrical lithium-ion battery. (Refer to...) Figure 12 , Figure 12 yes Figure 11 The diagram shows a cross-sectional view of the structure after the groove. After the groove, the shell 100 forms an inwardly recessed groove portion 110 extending circumferentially. The flange 420 is connected to the shell wall of the groove portion 110 in the shell 100 and is bent and deformed relative to the third disc 410.

[0143] Specifically, the third disc 410 is the main structural part of the negative electrode current collector 400. It is a thin sheet and includes two opposing disc surfaces. One disc surface is used to connect to the negative terminal 320 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 420, meaning that the flanges 420 are not complete annular structures. Multiple flanges 420 protrude along the outer periphery of the third disc 410 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 420 increase the welding area between the negative electrode current collector 400 and the housing 100, thereby improving the connection strength between the negative electrode current collector 400 and the housing 100. At the same time, due to the increased welding area, the conduction resistance is reduced, and the conduction current of the battery is increased.

[0144] It is understandable that the connection between the third disc 410 and the flange 420 can be any fixed connection method. To ensure a stable connection, structural strength, and processing economy, the third disc 410 and the flange 420 can be integrally connected, for example, by stamping. It can be further understood that forming the third disc 410 and the flange 420 integrally through stamping will create a crease at the connection point between the disc 100 and the flange 420.

[0145] In this embodiment, the negative electrode current collector 400 is further provided with a first stress relief groove 430 on its edge. The first stress relief groove 430 is formed by the inward indentation of the edge of the third plate 410 and the edges of each flange 420 at the junction area. The first stress relief groove 430 allows the flange 420 to bend relative to the third plate 410 along the first stress relief groove 430. It can be understood that the negative electrode current collector 400 has an edge formed on the third plate 410 and an edge formed on the flange 420. These edges together constitute the edge of the negative electrode current collector 400. Thus, on both sides of the connection between each flange 420 and the third plate 410, such as on both sides of the aforementioned crease, a first stress relief groove 430 is formed. Therefore, for each flange 420, two symmetrically arranged first stress relief grooves 430 are formed at its bottom.

[0146] It is understandable that the first stress relief groove 430 is a structure formed by the indentation of the edge constituting the negative electrode current collector 400 from the outside to the inside. This structure causes the material length of the flange 420 and the disk body 100 at the corresponding first stress relief groove 430 to be shortened. When the flange 420 bends relative to the third disk body 410, the first stress relief groove 430 can release stress, so that the material in the area between the two first stress relief grooves 430 bends preferentially, so that the bending occurs at the junction area of ​​the flange 420 and the third disk body 410, such as at the crease, thus avoiding a series of problems caused by the deformation of the third disk body 410 and the flange 420 themselves. Therefore, by forming a first stress relief groove 430 by recessing the edge of the third disc 410 and the edges of each of the flanges 420 together, when the flange 420 bends relative to the third disc 410 during the grooving process, the bending occurs near the junction area between the third disc 410 and the flange 420 due to the action of the first stress relief groove 430. Furthermore, the first stress relief groove 430 provides space for material deformation at the bending position, reducing the material compression or deformation transmission to the third disc 410 or the flange 420, thereby avoiding problems such as breakage of the welding point due to deformation of the third disc 410 and the flange 420, and bulging of the middle of the disc surface.

[0147] As previously mentioned, the first stress relief groove 430 is formed by the inward indentation of the edge of the third disc 410 and the edges of each flange 420 at their junction. Therefore, it can be understood that part of the first stress relief groove 430 is located at the flange 420, and part is located on the third disc 410. Specifically, refer to... Figure 13 , Figure 13 yes Figure 10 A partial schematic diagram at point G shows that, specifically, the flange 420 includes a first side 421 and a second side 422 connected to the edge of the third disc 410. The edge of the third disc 410 includes a fifth side 4122 and a sixth side 4123 located in the extension portion 412. The fifth side 4122 is connected to the first side 421, and the sixth side 4123 is connected to the second side 422. Thus, a portion of the first stress relief groove 430 is formed by the inward indentation of the first side 421 and the second side 422 toward the third disc 410, while the other portion is formed by the inward indentation of the fifth side 4122 and the sixth side 4123 at the end connected to the flange 420.

[0148] In order to ensure that the bending position of the flange 420 relative to the third disk 410 is exactly at the junction of the two, in some embodiments, the bottom of the first stress relief groove 430 is located at the junction of the flange 420 and the third disk 410. For example, in a negative electrode current collector 400 formed by stamping, the flange 420 is formed by bending at the edge of the third disk 410, and there is a crease between the two, which is the junction of the flange 420 and the third disk 410. Here, the location of the bottom of the first stress relief groove 430 refers to the part of the first stress relief groove 430 with the deepest indentation. It can be understood that the bottom of the first stress relief groove 430 is located at the junction of the flange 420 and the third disc 410, so that the bending position of the flange 420 relative to the third disc 410 is exactly located at the junction of the two, thereby minimizing the adverse effects of the bending position of the flange 420 relative to the third disc 410 on the third disc 410 and the flange 420.

[0149] Of course, it is not limited to this. It is understood that the bottom of the first stress relief groove 430 can be set on either side of the third disc 410 or the flange 420, so that the flange 420 bends along the line connecting the bottoms of the two first stress relief grooves 430, 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.

[0150] Further, please refer to Figure 15 and Figure 16 , Figure 15 This is a view of the negative electrode current collector 400 from the side without the flange to the side with the flange 420. Figure 16 yes Figure 15 The partial schematic diagram at point I shows that the arc length of the flange 420 along the circumferential direction of the third disc 410 is L4a, and the length of the inward indentation of the first stress relief groove 430 along the circumferential direction of the third disc 410 is L4b. The ratio of L4b / L4a is between 3% and 10%. For example, the range of L4b / L4a can be 3%, 3.8%, 6%, 8%, and 10%, etc. In some embodiments, the length of L4b is 0.38mm, and the length of L4a is 10mm. If the range of L4b / L4a is greater than 10%, then L4b / L4a is too large, the depth of the V-groove is too deep, and the straight-line distance between the two V-grooves corresponding to the flange 420 is too short, making this area more prone to deformation. The degree of deformation cannot be controlled, and the strength of the flange 420 at the bend is weak, increasing the difficulty of control during production, transportation, and material loading. The flange 420 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 L4b / L4a is less than 3%, then L4b / L4a is too small, the depth of the V-groove is too shallow, and the guiding effect of the V-groove is greatly reduced.

[0151] Further, please refer to Figure 13 and Figure 14The first stress relief groove 430 is a V-shaped groove, which includes a third side 431 and a fourth side 432 forming the V-shape. The third side 431 and the fourth side 432 form an included angle α, which is in the range of 30° to 50°. Specifically, the third side 431 includes a first straight edge portion 4311 and a first chamfered portion 4312, and the fourth side 432 includes a second straight edge portion 4321 and a second chamfered portion 4322. The first chamfered portion 4312 is connected to the second chamfered portion 4322, wherein the first straight edge portion 4311 and the second straight edge portion 4321 form the included angle α. It is understood that the third side 431, from the outside in, includes a first straight edge 4311 and a first chamfered edge 4312, which are straight segments. The fourth side 432, from the outside in, includes a second straight edge 4321 and a second chamfered edge 4322, which are straight segments. The first chamfered edge 4312 and the second chamfered edge 4322 are connected 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 420 is welded to the housing 100, stress concentration is severe when it is grooved together with the housing 100. 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 middle of the disk surface of the third disk 410 of the negative electrode current collector 400 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 400 and the housing 100 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 400 forms the flange 420 and before the grooving process. It is understandable that by setting the first chamfer 4312 and the second chamfer 4322, stress concentration in the bottom area of ​​the V-groove can be reduced.

[0152] In some embodiments, the shape of the first stress relief groove 430 is not limited to a V-shaped groove, but may be a rectangular groove, a U-shaped groove, etc.

[0153] Furthermore, the first stress relief groove 430 is located at the junction of the flange 420 and the third disk 410. The first stress relief groove 430 is a V-shaped groove, which includes a third side 431 and a fourth side 432 forming the V-shaped groove. The third side 431 is located on the flange 420, and the fourth side 432 is located on the third disk 410. It can be understood that the grooving process causes the flange 420 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 placing the first stress relief groove 430 at the junction of the flange 420 and the third disk 410, the bending occurs on the same plane as the third disk 410, which is equivalent to lowering the bending location, thereby reducing the height of the cylindrical lithium-ion battery and improving the unit energy density. It is understandable that since the flange 420 protrudes from the edge of the third disc 410 away from the disc surface, there is a crease between the third disc 410 and the flange 420. At this time, the bottom of the first stress relief groove 430 is located at the crease, that is, the bottom is located at both the extension 412 and the flange 420.

[0154] Further, please refer to Figure 18 and Figure 19 , Figure 19 yes Figure 18A partial schematic diagram at point K shows that the third disc 410 includes a main body 411 and an extension portion 412 extending radially outward from the main body 411. The number of extension portions 412 corresponds to the number of flanges 420, that is, the flanges 420 and the extension portions 412 are connected in a one-to-one correspondence. The extension portion 412 is provided with a thinning portion 4121. The thickness of the thinning portion 4121 is less than the thickness of other parts of the extension portion 412. The extension portion 412 includes a fifth side 4122 and a sixth side 4123 connected to the edge of the main body 411. The thinning portion 4121 extends from the fifth side 4122 to the sixth side 4123. The aforementioned fourth side 432 is provided on the extension portion 412. By setting the thinning section 4121, the problem of excessive grooving depth after welding the flange 420 of the negative current collector 400 to the housing 100 can be effectively avoided. This would increase the pulling force on the flange 420, causing it and even the edge of the plate to be pulled and deformed towards the axis. When the V-shaped groove at the junction of the flange 420 and the plate has already deformed, and the deformation force is insufficient, the thinning section 4121 provides a secondary stress relief effect. The thinning section 4121 continues to deform until the required deformation is achieved. Because the stress is decomposed by the first stress relief groove 430 and the thinning section 4121, the stress does not concentrate in the center of the plate, thus not affecting the welding of the plate to the negative electrode side tab of the core 300, and preventing deformation and bulging of the middle part of the plate. The reliability of the welding of the negative current collector 400 is guaranteed, and the safety performance of the battery cell is improved. Meanwhile, by providing an extension portion 412 that extends radially outward from the main body portion 411, a gap is left between the shell wall of the housing 100 and the main body portion 411 after the negative electrode current collector 400 enters the housing 100, thereby accelerating the injection of electrolyte.

[0155] Furthermore, the thinning portion 4121 extends from the fifth side 4122 along the circumferential direction of the main body portion 411 to the sixth side 4123. That is, the thinning portion 4121 is formed on the extension portion 412 in a radial direction. Thus, during the grooving process, the force transmitted by the bending of the flange 420 can be evenly absorbed by the thinning portion 4121.

[0156] Furthermore, the thinning portion 4121 is formed by recessing the two opposing surfaces of the extension portion 412 inward along the thickness direction of the extension portion 412. The thinning portion 4121 includes a first transition region 4121a with gradually decreasing thickness, a thickness holding region 4121b with constant thickness, and a second transition region 4121c with gradually increasing thickness in the radial outward direction along the main body portion 411, such as... Figure 19As shown, the thickness of the thickness holding region 4121b is L4c, and the thickness of the main body 411 is L4d, with the L4c / L4d ratio ranging from 30% to 60%. For example, the L4c / L4d ratio can be 30%, 35%, 40%, 45%, 50%, 55%, and 60%, and is not specifically limited. In some embodiments, the thickness L4c of the thickness holding region 4121b is 0.1 mm, and the thickness L4d of the main body 411 is 0.2 mm, in which case the L4c / L4d ratio is 50%. When L4c / L4d < 30%, the thickness of the thinning part 4121 is too thick. During the grooving process of the negative electrode current collector 400, when the groove depth pulls on the flange 420, the thinning part 4121 cannot play a good role in relieving stress. Moreover, most of the stress is concentrated at the junction of the flange 420 and the extension part 412 and cannot be released and decomposed. As a result, the middle of the disk surface is prone to arching, causing the foil at the laser welding point of the disk 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 L4c / L4d > 60%, the thickness of the thinned portion 4121 is too thin. During the grooving process of the negative electrode current collector 400, the flange 420 is stretched, causing severe deformation of the thinned portion 4121. This results in insufficient strength, making it unsuitable for processing and increasing the risk of breakage of the thinned portion 4121, leading to cell failure. This increases the difficulty of cell manufacturing and raises the manufacturing cost. By setting a first transition region 4121a and a second transition region 4121c, the thinned portion 4121 is thinned gradually, reducing stress concentration between the epitaxial portion 412 and the thickness holding region 4121b. Furthermore, the gradual thinning increases the overall structural strength of the thinned portion 4121, preventing breakage of the thinned portion 4121 during transportation and processing of the negative electrode current collector 400.

[0157] Furthermore, the thickness change slopes of the first transition region 4121a and the second transition region 4121c are the same, which facilitates the manufacturing of the thinning section 4121.

[0158] In some embodiments, the first transition region 4121a and the second transition region 4121c may not be provided, or only one transition region may be provided in the first transition region 4121a and the second transition region 4121c, thus saving the manufacturing process of the thinning part 4121.

[0159] In some embodiments, the thickness holding region 4121b of the thinning portion 4121 has a length L4e along the radial direction of the disk body portion 411, and the radius of the body portion 411 is L4f. The ratio of L4e / L4f ranges from 1% to 5%. For example, the ratio of L4e / L4f can be 1%, 1.2%, 2%, 3%, 4%, and 5%, etc., and is not specifically limited. For example, if the length of L4e is 0.23 mm and the radius of the body portion 411 is 19.7 mm, then L4e / L4f is 1.2%. When L4e / L4f is less than 1%, the width of the thinned portion 4121 is too narrow. During grooving, the groove depth is relatively deep, and the thinned portion 4121, 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 4121 is too narrow, so the bending deformation cannot be completed directly within the thinned portion 4121 during the secondary bending. It is necessary to deform the surrounding normal thickness disk surface of the thinned portion 4121 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 L4e / L4f is greater than 5%, the width of the thinned portion 4121 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.

[0160] Furthermore, such as Figure 15 , Figure 16 and Figure 17 As shown, the negative electrode current collector 400 is further provided with a second stress relief groove 4111 on its edge. The second stress relief groove 4111 is formed by the recess of the edge of the main body 411 on both sides of the extension portion 412, and the edge of the second stress relief groove 4111 is connected to the edge of the extension portion 412. By providing the second stress relief groove 4111, the stress is transferred from the flange 420 from the extension portion 412 to the thinning portion 4121, and then to the second stress relief groove 4111. At this time, the second stress relief groove 4111 acts as a third stress-reducing structure, further relieving the stress caused by the bending of the flange 420 during the grooving process, thereby greatly reducing the stress on the main body 411 and preventing structural deformation of the main body 411.

[0161] Understandably, for a single location of the extension portion 412, there is a pair of second stress relief grooves 4111. These two second stress relief grooves 4111 are respectively disposed on the main body portion 411 in the area connected to the extension portion 412, which helps to disperse stress and further ensures that the structure of the main body portion 411 does not deform. Furthermore, the shape of the second stress relief grooves 4111 is arc-shaped, which helps to avoid stress concentration.

[0162] Furthermore, such as Figure 17 As shown, Figure 17 yes Figure 15 A partial schematic diagram at point J shows that the main body 411 is provided with multiple second stress relief grooves 4111 and multiple extension portions 412. The total arc length of the main body 411 corresponding to the second stress relief grooves 4111 is L4g. The length of the main body 411 after deducting the total arc length corresponding to the extension portions 412 from the total arc length of the main body 411 is L4h. The ratio of L4g / L4h ranges from 5% to 20%, for example, the ratio of L4g / L4h can be 5%, 7%, 10%, 12%, 15%, 17%, and 20%, etc. The arc length L4g corresponding to the second stress relief grooves 4111 of the main body 411 is the total arc length of all the second stress relief grooves 4111, and L4h is the length of the main body 411 after deducting the arc length corresponding to the multiple extension portions 412 from the total arc length of the main body 411. Figure 15 and Figure 17 Only the arc length L4g of the second stress relief groove 4111 and only a section of L4h are marked. When L4g / L4h is less than 5%, the arc length is too small, and the second stress relief groove 4111 structure, which is meant to alleviate stress concentration, cannot effectively decompose the stress. As a result, some stress will still be concentrated on the disc surface of the main body 411. This causes a certain height of arching and deformation in the middle of the disc surface after grooving. When the electrolyte flows into the cell through the through holes on the disc surface, the flow rate of the electrolyte is slowed down because the arc of the second stress relief groove 4111 is too small, thus reducing the injection efficiency, increasing the injection time, and increasing the manufacturing cost. If L4g / L4h > 20%, the arc length is too long, and the structural strength of the second stress relief groove 4111 will be lower. The second stress relief groove 4111 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 420 to the shell 100, the problem of incomplete welding is likely to occur. In some embodiments, L4g is 8.4 mm, L4h is 69.84 mm, and the ratio of L4g / L4h is 12%.

[0163] Furthermore, the second stress relief groove 4111 is recessed inward along the radial direction of the main body 411 by a length of L4i, the radius of the main body 411 is L4f, and the range of L4i / L4f is 2% to 5%, for example, the ratio of L4i / L4f can be 2%, 3%, 4% and 5%. When L4i / L4f is less than 2%, the second stress relief groove 4111 is too shallow. As the third stress concentration mitigation protection structure, the second stress relief groove 4111 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 4111 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 L4i / L4f is greater than 5%, the second stress relief groove 4111 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 increased welding temperature, affecting battery performance. In some embodiments, L4i is 0.68mm and L4f is 19.7mm, then the ratio of L4i / L4f is 3%.

[0164] Furthermore, the main body 411 also has a second central hole 4112 located at its center and a plurality of auxiliary holes 4113 located around the second central hole 4112. The second central hole 4112 and the plurality of auxiliary holes 4113 are used to inject electrolyte into the battery. To match the shape of the hole in the core 300, the shape of the second central hole 4112 is preferably circular. In this case, the second central hole 4112 shares a common center with the main body 411. It is understood that the diameter of the second central hole 4112 can be specifically selected according to the balance between achieving liquid injection efficiency and weldable area. The size of the auxiliary holes 4113 can be specifically selected according to the balance between achieving liquid injection efficiency and weldable area. Furthermore, the auxiliary holes 4113 are oblong holes, and there are four of them. The combined shape of the four auxiliary holes 4113 is a centrally symmetrical shape, with the center of symmetry being the center of the second central hole 4112, thereby ensuring uniformity during electrolyte injection.

[0165] The effects of this application will be further described below with specific embodiments and comparative examples.

[0166] Example 1:

[0167] Example 1 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400. The negative electrode current collector 400 includes a third disk body 410, which includes a main body 411 and a plurality of extension portions 412 disposed on the outer periphery of the main body 411. The negative electrode current collector 400 also includes flanges 420 in number corresponding to the number of extension portions 412. The flanges 420 are integrally bent from the edge of the extension portions 412, thereby protruding along one side of the outer periphery of the third disk body 410. The negative electrode current collector 400 has V-shaped grooves at both ends of the fold lines of the extension portions 412 and the flanges 420, which serve as first stress relief grooves 430. The epitaxial portion 412 is provided with a thinning portion 4121, which is formed by the two opposing surfaces of the epitaxial portion 412 being recessed inward along the thickness direction of the epitaxial portion 412. The thinning portion 4121 includes a first transition region 4121a with gradually decreasing thickness, a thickness holding region 4121b with constant thickness, and a second transition region 4121c with gradually increasing thickness in the radial direction. The main body portion 411 is also provided with a second stress relief groove 4111 formed by the indentation of the edge of the main body portion 411. The second stress relief groove 4111 is provided on both sides of the epitaxial portion 412, and the edge of the second stress relief groove 4111 is connected to the edge of the epitaxial portion 412.

[0168] In addition, the negative current collector 400 also meets the following parameters:

[0169] The arc length L4a of the flange 420 along the circumferential direction of the third disc 410 is 10 mm; the length L4b of the V-groove recessed inward along the circumferential direction of the third disc 410 is 0.38 mm; the included angle α of the V-groove is 40°; the thickness of the thickness holding area 4121b is L4c, which is 0.1 mm; the thickness of the main body 411 is L4d, which is 0.2 mm; the length L4e of the thinning part 4121 along the radial direction of the main body 411 is 0.23 mm. The radius L4f of the main body 411 is 19.7 mm; the arc length L4g of the main body 411 at the second stress relief groove 4111 is 8.4 mm; the length L4h of the main body 411 after deducting the arc length corresponding to the extension 412 and the arc length corresponding to the second stress relief groove 4111 is 69.84 mm; the length L4i of the second stress relief groove 4111 recessed inward along the radial direction of the main body 411 is 0.68 mm.

[0170] As can be seen from the above, in the negative current collector 400, L4b / L4a = 3.8%, L4c / L4d = 50%, L4e / L4f = 1.2%, L4g / L4h = 12%, and L4i / L4f = 3%.

[0171] Example 2:

[0172] Example 2 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400. The difference between Example 1 and Example 2 is that: L4b / L4a = 6%, α is 35°, L4c / L4d = 40%, L4e / L4f = 1%, L4g / L4h = 8%, and L4i / L4f = 2%.

[0173] Example 3:

[0174] Example 3 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400. The difference between Example 3 and Example 1 is that: L4b / L4a = 8%, α is 45°, L4c / L4d = 60%, L4e / L4f = 4%, L4g / L4h = 16%, and L4i / L4f = 5%.

[0175] Comparative Example 1:

[0176] Comparative Example 1 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that L4b / L4a = 2%.

[0177] Comparative Example 2:

[0178] Comparative Example 2 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400, and differs from Example 1 in that L4b / L4a = 12%.

[0179] Comparative Example 3:

[0180] Comparative Example 3 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400, and differs from Example 1 in that α is 25°.

[0181] Comparative Example 4:

[0182] Comparative Example 4 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400, and differs from Example 1 in that α is 65°.

[0183] Comparative Example 5:

[0184] Comparative Example 5 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400, and differs from Example 1 in that: L4c / L4d = 25%.

[0185] Comparative Example 6:

[0186] Comparative Example 6 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that L4c / L4d = 65%.

[0187] Comparative Example 7:

[0188] Comparative Example 7 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that L4e / L4f = 0.05%.

[0189] Comparative Example 8:

[0190] Comparative Example 8 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that L4e / L4f = 8%.

[0191] Comparative Example 9:

[0192] Comparative Example 9 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that: L4g / L4h = 2%.

[0193] Comparative Example 10:

[0194] Comparative Example 10 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that: L4g / L4h = 25%.

[0195] Comparative Example 11:

[0196] Comparative Example 11 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that L4i / L4f = 1%.

[0197] Comparative Example 12:

[0198] Comparative Example 12 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that L4i / L4f = 8%.

[0199] Comparative Example 13:

[0200] Comparative Example 13 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400, and differs from Example 1 in that it does not have a first stress relief groove 430.

[0201] Comparative Example 14:

[0202] Comparative Example 14 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400, and differs from Example 1 in that it does not have a thinning section 4121.

[0203] Comparative Example 15:

[0204] Comparative Example 15 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400, and differs from Example 1 in that it does not have a second stress relief groove 4111.

[0205] Comparative Example 16:

[0206] Comparative Example 16 provides a cylindrical lithium-ion battery, which includes a negative electrode current collector 400. The difference between it and Example 1 is that the first stress relief groove 430, the thinning portion 4121 and the second stress relief groove 4111 are not provided.

[0207] Table 1 below shows the following tests for the negative electrode current collector 400 fabricated in the above embodiments and comparative examples: the height difference of the arch of the main body 411 (ΔH), the maximum temperature of the weld on the flange 420 (T1max), the maximum temperature of the weld on the main body 411 (T2max), the number of folds (C) at which the main body 411 breaks after being folded, and the time (t) required for electrolyte injection into the battery. Wherein:

[0208] The specific test method for the height difference △H (mm) of the arched part 411 is as follows: The battery is prepared according to the normal process until the negative electrode current collector 400 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 400 is measured with a height gauge. Taking the center of the disk surface of the main body 411 of the negative electrode current collector 400 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 continuously 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 411 of the negative electrode current collector 400 to measure the height H. The height difference △H of the arched part is calculated as H-H. Under stress concentration, △H = 0.9~1.0mm.

[0209] The specific testing method for the maximum temperature (T1max) of the flange 420 solder mark and the maximum temperature (T2max) of the main body 411 solder mark is as follows: The negative electrode current collector 400 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 of the flange 420 of the negative electrode current collector 400 and the shell wall, and the solder mark of the disc surface of the main body 411 and the core 300, respectively. 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 make a qualified battery. The battery is 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 10 cycles is taken. T1max represents the maximum temperature of the flange 420 solder mark, and T2max represents the maximum temperature of the main body 411 solder mark.

[0210] The specific test method for the number of folds (C) at which the main body 411 breaks after folding is as follows: The flange 420 of the negative electrode current collector 400 is completely cut off, leaving a complete plate surface. Then, the negative electrode current collector 400 is folded along the central axis formed by the line connecting the midpoint of the flange 420 and the center of the circle. One half is completely folded over and attached to the other half. The folded negative electrode current collector 400 is then opened to 180°, which is counted as one fold. The same method is then used to fold the plate. Each fold requires the two halves to be completely attached. After folding, the plate is opened to 180°. This process is repeated multiple times until a break appears on the plate surface. The number of folds (C) is recorded.

[0211] The specific test method for the time (t) required to inject electrolyte into the battery is as follows: The negative electrode current collector 400 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 within the holding cup, indicating that the electrolyte is flowing into the battery. Inside the cell, after maintaining the pressure for 40 seconds, positive pressure electrolyte injection is initiated by flushing nitrogen into the battery. The internal pressure gradually becomes positive at 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, and then adjusted to positive pressure and maintained. This positive and negative pressure injection cycle continues 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 at which the electrolyte has completely flowed into the battery is recorded.

[0212] Table 2

[0213]

[0214]

[0215] As shown in Table 2, when the range of L4b / L4a is set to 3%–10%, the range of included angle α is set to 30°–50°, the range of L4c / L4d is set to 30%–60%, the range of L4e / L4f is set to 1%–5%, the range of L4g / L4h is set to 5%–20%, and the range of L4i / L4f is set to 2%–5%, the height difference ΔH of the arch of the main body 411 is usually 0.01mm–0.02mm, the maximum temperature T1max of the flange 420 soldering is usually 102–104℃, the maximum temperature T2max of the main body 411 disk soldering is usually 112–115℃, the number of folds C that cause the main body 411 disk to break after folding is usually around 9 times, and the time t required for electrolyte injection into the battery is usually 683–686. It can be seen that within the above numerical range, the structural strength, liquid injection rate, and welding temperature rise of the negative electrode current collector 400 can be well balanced, thereby effectively improving the safety and charge / discharge performance of the battery, as well as reducing the production cost of the battery.

[0216] As shown in Table 2, if L4b / L4a is too small (the first stress relief groove 430 is not sufficiently recessed inward), the arch height of the main body 411 of the third disk 410 will be too high; if L4b / L4a is too large, the maximum temperature of the flange 420 solder mark will increase. Therefore, setting L4b / L4a within a reasonable range can balance the arch height of the main body 411 of the third disk 410 of the negative electrode current collector 400 and the maximum temperature of the flange 420 solder mark.

[0217] As shown in Table 2, if the included angle α is too small, the main body 411 of the third disk 410 will have a high arch height; if the included angle α is too large, the maximum temperature of the flange 420 solder mark will increase. Therefore, setting the included angle α within a reasonable range can balance the arch height of the main body 411 of the third disk 410 of the negative electrode current collector 400 and the maximum temperature of the flange 420 solder mark.

[0218] As shown in Table 2, if L4c / L4d is too small (the thinned portion 4121 is too thin), the main body 411 of the third disk 410 of the negative current collector 400 will be easily broken; if L4c / L4d is too large, the surface of the main body 411 of the third disk 410 will have a high arch height. Therefore, setting L4c / L4d within a reasonable range can balance the arch height of the surface of the main body 411 of the third disk 410 of the negative current collector 400 and the structural strength of the third disk 410.

[0219] As shown in Table 2, if L4e / L4f is too small (the thinned portion 4121 is too narrow), the main body 411 of the third disk 410 will have a high arch height; if L4e / L4f is too large, the main body 411 of the third disk 410 of the negative electrode current collector 400 will be easily broken. Therefore, setting L4e / L4f within a reasonable range can balance the arch height of the main body 411 of the third disk 410 of the negative electrode current collector 400 and the structural strength of the third disk 410.

[0220] As shown in Table 2, if L4g / L4h is too small (the opening of the second stress relief groove 4111 is too small), it will cause the main body 411 of the third disk 410 to have a high arch height and a decrease in the electrolyte injection rate; if L4g / L4h is too large, it will cause the maximum temperature of the flange 420 solder mark to increase. Therefore, setting L4g / L4h within a reasonable range can balance the arch height of the main body 411 of the third disk 410 of the negative electrode current collector 400, the electrolyte injection rate, and the maximum temperature of the flange 420 solder mark.

[0221] As shown in Table 2, if L4i / L4f is too small (the second stress relief groove 4111 is not sufficiently recessed inward), it will result in a high arch height on the surface of the main body 411 of the third disk 410 and a decrease in the electrolyte injection rate; if L4i / L4f is too large, it will result in a high maximum temperature of the solder joint on the surface of the main body 411 of the third disk 410. Therefore, setting L4i / L4f within a reasonable range can balance the arch height on the surface of the main body 411 of the third disk 410, the electrolyte injection rate, and the maximum temperature of the solder joint on the surface of the main body 411 of the third disk 410 of the negative electrode current collector 400.

[0222] As shown in Table 2, without the first stress relief groove 430, the surface of the main body 411 of the third disc 410 will have a high arch height. Therefore, providing the first stress relief groove 430 is beneficial for controlling the arch height of the surface of the main body 411 of the third disc 410.

[0223] As shown in Table 2, without the thinning section 4121, the surface arch of the main body 411 of the third disk 410 would be too high. Therefore, providing the thinning section 4121 helps to control the surface arch of the main body 411 of the third disk 410.

[0224] As shown in Table 2, without the second stress relief groove 4111, the main body 411 of the third disc 410 will have a high arch height and low electrolyte injection efficiency. Therefore, setting the first stress relief groove 430 is beneficial for controlling the arch height of the main body 411 of the third disc 410 and improving the electrolyte injection efficiency.

[0225] As shown in Table 2, if the first stress relief groove 430, the thinning part 4121 and the second stress relief groove 4111 are not provided, the arch height of the main body part 411 of the third disk 410 will be higher than when all three are provided.

Claims

1. A cylindrical lithium-ion battery, characterized in that, The device includes a housing (100) and a positive electrode current collector (200), a core (300), and a negative electrode current collector (400) disposed within the housing (100). The housing (100) has an electrode post (500) on the positive electrode side, and the electrode post (500) has a through-hole (510) for liquid injection. The positive current collector (200) includes a first disk body (210) located at the center and a second disk body (220) connected to the edge of the first disk body (210) and extending radially outward. The first disk body (210) is welded to the electrode post (500), and the center of the first disk body (210) is provided with a through first central hole (211), which communicates with the liquid injection hole (510). The second disk body (220) includes a connecting part (221) and a welding part (222) connected to each other. The welding part (222) is connected to the edge of the first disk body (210) by the connecting part (221), and the connecting part (221) has a fusion groove (230) on its edge along its length direction. The negative electrode current collector (400) includes a third disk body (410) and a plurality of flanges (420) protruding to one side along the outer periphery of the third disk body (410). The plurality of flanges (420) are fitted and welded to the shell wall of the housing (100). The third disk body (410) includes a main body (411) and a plurality of extensions (412) extending radially outward from the main body (411). The plurality of flanges (420) and the plurality of extensions (412) are connected one-to-one. The negative electrode current collector (400) is also provided with a first edge. The first stress relief groove (430) is formed by the edge of the extension portion (412) and the edge of each flange (420) being recessed inward in the junction area. The first stress relief groove (430) is used so that the flange (420) can be bent relative to the third disk body (410) along the first stress relief groove (430). The extension portion (412) is provided with a thinning portion (4121) extending in the radial direction. The thickness of the thinning portion (4121) is less than the thickness of other parts of the extension portion (412).

2. The cylindrical lithium-ion battery according to claim 1, characterized in that, The area of ​​the first disc (210) is S2a, the area of ​​the first central hole (211) is S2b, and the ratio of S2b to S2a is in the range of 4.2% to 8.6%; the first stress relief groove (430) is a V-shaped groove, the V-shaped groove includes forming an included angle α, the range of α is 30° to 50°.

3. The cylindrical lithium-ion battery according to claim 1, characterized in that, Along the thickness direction of the positive current collector, the first disk body (210) is higher than the second disk body (220). The height difference between the surface of the first disk body (210) that is higher than the second disk body (220) and the surface of the second disk body (220) that is on the same side is H2a, and H2a ranges from 0.6 to 1.4 mm. The thinning portion (4121) is formed by the two opposing surfaces of the extension portion (412) being recessed inward along the thickness direction. The thinning portion (4121) includes, in the radial direction from the inside to the outside, a first transition region (4121a) with gradually decreasing thickness, a thickness holding region (4121b) with unchanged thickness, and a second transition region (4121c) with gradually increasing thickness. The thickness of the thickness holding region (4121b) is L4c, and the thickness of the main body portion (411) is L4d. The range of L4c / L4d is 30% to 60%.

4. The cylindrical lithium-ion battery according to claim 3, characterized in that, The second disc body (220) has multiple first notches (250) along its edge; the thickness holding area (4121b) has a radial length of L4e, the main body (411) has a radius of L4f, and the range of L4e / L4f is 1% to 5%.

5. The cylindrical lithium-ion battery according to claim 1, characterized in that, The connecting portion (221) has a first edge (231) extending along the length direction for forming the fusion groove (230), the length of the first edge (231) is L2a, and the range of L2a is 2 to 4 mm; the arc length of the flange (420) along the circumferential direction is L4a, and the length of the first stress relief groove (430) recessed inward along the circumferential direction is L4b, and the range of L4b / L4a is 3% to 10%.

6. The cylindrical lithium-ion battery according to any one of claims 1 to 5, characterized in that, The connecting part (221) includes: Multiple first connecting portions (2211) are arranged circumferentially along the first disc body (210) and extend radially outward from its edge, and the fuse groove (230) is provided on the first connecting portion (2211); A second connecting portion (2212) is formed by extending circumferentially to both sides from the outer ends of each of the first connecting portions (2211); The welding part (222) has a plurality of parts, and each welding part (222) is disposed in a corresponding manner in the area defined by two adjacent first connecting parts (2211) and second connecting parts (2212), and is formed by extending radially inward from the inner edge of the second connecting part (2212); The negative electrode current collector (400) is further provided with a second stress relief groove (4111) on its edge. The second stress relief groove (4111) is formed by the inward indentation of the edge of the main body (411), and the edge of the second stress relief groove (4111) is connected to the edge of the extension (412).

7. The cylindrical lithium-ion battery according to claim 6, characterized in that, The edges on both sides of the welded portion (222) and the inner edge of the second connecting portion (2212) define a circumferentially extending slit (240). The perimeter of the outer edge of the second connecting portion (2212) is L2b, and the total arc length of the slit (240) is L2c. The range of L2c / L2b is 43% to 58%. The total arc length of the main body portion (411) at the second stress relief groove (4111) is L4g. The length of the total arc length of the main body portion (411) after deducting the total arc length corresponding to the extension portion (412) is L4h. The range of L4g / L4h is 5% to 20%.

8. The cylindrical lithium-ion battery according to claim 6, characterized in that, The second disc (220) is provided with a plurality of first notches (250), each of the first notches (250) being provided on the outer edge of the second connecting part (2212) at the position corresponding to the welding part (222). The circumference of the outer edge of the second connecting part (2212) is L2b, the total arc length of the first notches (250) is L2d, and the range of L2d / L2b is 4% to 9%. The length of the second stress relief groove (4111) recessed inward in the radial direction is L4i, the radius of the main body (411) is L4f, and the range of L4i / L4f is 2% to 5%.

9. The cylindrical lithium-ion battery according to claim 8, characterized in that, The maximum depth of the first notch (250) is L2f, and L2f ranges from 0.9 to 2.1 mm; the bottom of the first stress relief groove (430) is located at the junction of the flange (420) and the extension (412).

10. The cylindrical lithium-ion battery according to claim 7, characterized in that, The slit (240) has a radial width of L2e, which ranges from 0.4 to 1.5 mm; the second connecting part (2212) has a radial width of W2c in the region corresponding to the slit (240), which ranges from 1 to 3 mm.

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