A cylindrical lithium-ion battery

Abstract

The application provides a cylindrical lithium ion battery, which comprises a positive electrode current collector and a negative electrode current collector, the positive electrode current collector comprises a first disc body and a second disc body, the first disc body is provided with a first center hole, the second disc body comprises a connecting part, the connecting part is provided with a fuse slot, and a plurality of first notches are formed in the edge of the second disc body; the negative electrode current collector comprises a third disc body and a flange protruding from one side of the outer periphery of the third disc body, the third disc body has a shape of a closed figure formed by a plurality of arc edges and a plurality of concave edges which are alternately connected in sequence, the flange is arranged on the arc edge, the second notch is formed in the concave edge of the third disc body, the third disc body is provided with a second center hole, and the following conditions are met: the range of S4b / S4a is 2% to 10%, and the range of H4b / H4a is 42% to 58%. The cylindrical lithium ion battery can be injected on the positive electrode side or the negative electrode side during assembly, the injection scheme can be conveniently adjusted according to actual process requirements, and the cylindrical lithium ion battery has the characteristics of good safety, high welding reliability and good battery performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of lithium ion batteries, in particular to a cylindrical lithium ion battery. BACKGROUND

[0002] At present, in the 46 series large cylindrical lithium ion battery, the positive and negative current collecting plates are usually included, wherein the positive current collecting plate is used for the conduction of the positive pole of the battery and the positive pole of the winding core, and the negative current collecting plate is used for the conduction of the metal shell of the battery and the negative pole of the winding core. In the current large cylindrical lithium ion battery, the positive and negative current collecting plates are designed only from the above-mentioned angle, however, the structure of the positive and negative current collecting plates has a significant influence on the performance, reliability and manufacturing cost of the battery, for example:

[0003] When the cylindrical lithium ion battery is assembled, the battery is usually injected on the negative side, in this case, in order to meet the requirement of injecting on the negative side, the negative current collecting plate is designed accordingly, and correspondingly, since there is no injection requirement on the positive side of the battery, the positive current collecting plate adopts a simple sheet structure design to reduce the design and manufacturing cost. It can be understood that due to the limitation of the structure of the positive current collecting plate, the injection scheme cannot be easily adjusted to realize injection on the positive side in the manufacturing link, if the manufacturer needs to adjust the injection scheme, the structure of the positive current collecting plate needs to be changed and verified to meet the requirement of injecting on the positive side of the battery. Therefore, the current structure of the positive current collecting plate is difficult to meet the requirement of injecting on the positive side of the battery, further speaking, it is also difficult to meet the requirement of flexible production of the 46 series cylindrical lithium battery.

[0004] In addition, the negative current collecting plate usually has a ring-shaped flange, when the cylindrical lithium ion battery is assembled, the outer surface of the flange is attached to the shell wall and connected by penetration welding, so that the shell and the negative pole of the winding core are connected in conduction, however, if the injection scheme on the negative side is adopted, the flange of the negative current collecting plate is tightly connected with the inner wall of the shell, the electrolyte can only enter the inside of the battery through the injection hole in the middle of the negative current collecting plate, the injection efficiency is low, and the overflow problem is prone to occur; for the cylindrical lithium ion battery adopting the above-mentioned pressure relief scheme, if short circuit or other thermal runaway occurs during use, a large amount of gas will be generated in the shell, the disc body and the flange of the negative current collecting plate will hinder the gas from being discharged from the negative side, thereby increasing the safety risk of the battery.

[0005] In addition, for the above-mentioned structure of the flange, when welding with the shell, the welding line formed is relatively long, and the longer the welding, the higher the risk of welding quality problems, for example, liquid leakage, false welding, and missing welding may occur at the welding line, thereby increasing the internal resistance of the battery. SUMMARY

[0006] The embodiment of the present application provides a cylindrical lithium ion battery to at least solve the technical problems of high manufacturing cost, limited performance, poor reliability and insufficient safety of the existing cylindrical lithium ion battery caused by unreasonable design of the positive current collector and the negative current collector.

[0007] The embodiment of the present application provides a cylindrical lithium ion battery, which comprises a shell, a positive current collector, a winding core and a negative current collector arranged in the shell, and a pole is arranged on the positive side of the shell, wherein the pole has a liquid injection hole penetrating through.

[0008] The positive current collector comprises a first disc body at the center and a second disc body connected with the edge of the first disc body and extending radially outward, the first disc body is welded with the pole, and the center of the first disc body is provided with a first center hole penetrating through, the first center hole is in communication with the liquid injection hole, the second disc body comprises a connecting part and a welding part connected with each other, the welding part is connected to the edge of the first disc body from the connecting part, the connecting part is provided with a fuse slot at the edge in the length direction, the welding part is welded with the positive electrode of the winding core, and the edge of the second disc body is provided with a plurality of first notches.

[0009] The negative current collector comprises a third disc body and a flange protruding from one side of the outer periphery of the third disc body, the third disc body is welded with the negative electrode of the winding core, the shape of the third disc body is a closed figure composed of a plurality of circular arc edges and a plurality of inner concave edges connected in turn, the flange is arranged on the circular arc edge, the third disc body is provided with a second center hole penetrating through at the inner concave edge, the area of the third disc body is S4a, the total area of the second notches is S4b, the range of S4b / S4a is 2% to 10%, the circumference of the third disc body is H4a, the total arc length of the flange is H4b, and the range of H4b / H4a is 42% to 58%.

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

[0011] Firstly, by arranging the first center hole, the first notch, the second center hole and the second notch on the positive current collector and the negative current collector, the cylindrical lithium ion battery can be injected on the positive side or the negative side during assembly, and the injection scheme can be conveniently adjusted according to the actual process requirements. Moreover, the first notch or the second notch also helps to improve the injection efficiency and assist in exhaust when the internal pressure of the battery rises.

[0012] Secondly, a melting groove is arranged on the positive current collector plate, which can reduce the width of the connecting part, and in the case of abnormal current overload, the heat will rise to the melting point when the current passes through the melting groove, so that the connecting part melts at this position to cut off the current, thereby improving the safety of the cylindrical lithium battery.

[0013] Furthermore, by arranging the flange only at the edge of the circular arc along the edge and setting the range of H4b / H4a to 42% to 58%, the length of the welding line when welding the negative current collector plate with the shell can be effectively reduced, thereby reducing the risk of liquid leakage, false welding and incomplete welding at the welding position, improving the welding reliability, and reducing the internal resistance of the battery. In addition, the weight of the negative current collector plate can also be effectively reduced to improve the energy density of the battery.

[0014] In a possible implementation, the area of the first disc body is S2a, the area of the first center hole is S2b, and the range of S2b / S2a is 4.2% to 8.6%; the area of the second center hole is S4c, and the range of S4c / S4a is 1% to 3%.

[0015] In a possible implementation, along the thickness direction of the positive current collector plate, the first disc body is higher than the second disc body, and the height difference between the surface of the side of the first disc body higher than the second disc body and the surface of the same side of the second disc body is H2a, and the range of H2a is 0.6 to 1.4 mm; the third disc body is further provided with a plurality of auxiliary holes located at the outer periphery of the second center hole, and the total area of the plurality of auxiliary holes is S4d, and the range of S4d / S4a is 9% to 21%.

[0016] In a possible implementation, the connecting part has a first width W2a, and the connecting part has a second width W2b in the area where the melting groove is arranged, and the range of W2b / W2a is 42% to 63%; the connecting part has a first edge extending in the length direction for forming the melting groove, and the length of the first edge is L2a, and the range of L2a is 2 to 4 mm.

[0017] In a possible implementation, the connecting part includes:

[0018] A plurality of first connecting parts are arranged along the circumference of the first disc body and extend radially outward from the edge thereof, and the melting groove is arranged on the first connecting part;

[0019] A second connecting part is formed by extending the outer end of each first connecting part to both sides in the circumferential direction;

[0020] The welding portions are provided in the areas defined by the two adjacent first connecting portions and the second connecting portion, and are formed by extending the edge inside the second connecting portion radially inwardly.

[0021] The circumference of the third disc is H4a, the total arc length of the second notch is H4c, and H4c / H4a is in the range of 25% to 38%.

[0022] In a possible implementation, the edges on both sides of the welding portion and the edge inside the second connecting portion define a slit extending in the circumferential direction, the circumference of the edge outside the second connecting portion is L2b, the total arc length of the slit is L2c, and L2c / L2b is in the range of 43% to 58%; the shape of the concave edge is arc-shaped, the maximum depth of the second notch is H4d, and H4d is in the range of 2 to 5 mm.

[0023] In a possible implementation, the first notch is provided on the edge outside the second connecting portion at the position corresponding to the welding portion, the circumference of the edge outside the second connecting portion is L2b, the total arc length of the first notch is L2d, and L2d / L2b is in the range of 4% to 9%; the radius of the third disc is L4a, the third disc is further provided with a plurality of auxiliary holes located outside the second central hole, the distance from the inner edge of the auxiliary hole to the center of the second central hole is L4b, and L4b / L4a is in the range of 18% to 36%.

[0024] In a possible implementation, the maximum depth of the first notch is L2f, and L2f is in the range of 0.9 to 2.1 mm; the auxiliary hole is a waist-shaped hole, and the long axis direction of the auxiliary hole is consistent with the radial direction of the third disc.

[0025] In a possible implementation, the width of the slit in the radial direction is L2e, and L2e is in the range of 0.4 to 1.5 mm; the third disc and the turned edge are integrally connected.

[0026] In a possible implementation, the second connecting portion has a width W2c in the radial direction at the position corresponding to the slit, and W2c is in the range of 1 to 3 mm; the third disc is further provided with auxiliary holes located outside the second central hole, the number of the arc-shaped edges, the concave edges, and the auxiliary holes is four, the arc-shaped edges and the auxiliary holes are one-to-one corresponding, and the midpoints of the corresponding arc-shaped edges, the centers of the auxiliary holes, and the center of the second central hole are collinear. BRIEF DESCRIPTION OF DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the description of the embodiments of the present application will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor under the premise of the drawings.

[0028] Figure 1 is a cross-sectional view of a cylindrical lithium ion battery provided by the embodiments of the present application;

[0029] Figure 2 is a structural schematic view of a positive current collector disc provided by the embodiments of the present application;

[0030] Figure 3 is Figure 2 a schematic view of an area S2a in the positive current collector disc in

[0031] Figure 4 is Figure 2 a schematic view of an area S2b in the positive current collector disc in

[0032] Figure 5 is Figure 3 a cross-sectional view of A-A in

[0033] Figure 6 is Figure 5 a partial view at B in

[0034] Figure 7 is Figure 1 a top view of the positive current collector disc in

[0035] Figure 8 is Figure 7 a partial view at C in

[0036] Figure 9 is Figure 7 a partial view at D in

[0037] Figure 10 is a structural schematic view of a negative current collector disc provided by the embodiments of the present application;

[0038] Figure 11 is Figure 10 a schematic view of the assembly of the negative current collector disc, the winding core and the shell in

[0039] Figure 12 is Figure 10 a front view of the negative current collector disc in

[0040] Figure 13 is Figure 10 a schematic view of an area S4a of the negative current collector disc in

[0041] Figure 14 is Figure 10 a schematic view of the area S4b of the negative current collector plate;

[0042] Figure 15 is Figure 10 a schematic view of the area S4c of the negative current collector plate;

[0043] Figure 16 is Figure 10 a schematic view of the area S4d of the negative current collector plate;

[0044] Figure 17 is Figure 10 a front view schematic view of the negative current collector plate. DETAILED DESCRIPTION

[0045] Figure 1 is a schematic view of a cylindrical lithium ion battery provided by the embodiments of the present application, the cylindrical lithium ion battery of the embodiments of the present application includes various large cylindrical lithium ion batteries, for example, 46 series (with an outer diameter of 46 mm), which are not limited herein. As shown in the figure, the cylindrical lithium ion battery includes a shell 100, a positive current collector plate 200, a roll core 300, a negative current collector plate 400, a pole 500, a negative cover plate 600, a sealing nail 700, and the like. Figure 1

[0046] The shell 100 is in a cylindrical shape as a whole, has opposite positive and negative sides, the pole 500 is part of the positive cover plate assembly, is installed on the positive side of the shell 100, and the negative cover plate 600 is installed on the negative side of the shell 100. The shell 100 defines an inner cavity, and the positive current collector plate 200, the roll core 300, the negative current collector plate 400, and the like are all enclosed in the inner cavity. The positive electrode of the roll core 300 is connected with the pole 500 through the positive current collector plate 200, and the negative electrode of the roll core 300 is connected with the shell 100 through the negative current collector plate 400. It can be understood that the pole 500 is the positive electrode of the cylindrical lithium ion battery, and the shell 100 is the negative electrode of the cylindrical lithium ion battery, and is respectively used for electrical connection with an external electrical equipment.

[0047] It can be understood that the negative cover plate 600 of the cylindrical lithium ion battery is provided with a liquid injection hole sealed by the sealing nail 700, through which electrolyte can be injected into the inside of the cylindrical lithium ion battery through one side of the negative cover plate 600. At the same time, a structure such as an explosion-proof notch groove can be constructed on the negative cover plate 600 to be opened in time for pressure relief when the pressure in the cylindrical lithium ion battery abnormally rises. Similarly, the pole 500 is also provided with a liquid injection hole 510, through which electrolyte can be injected into the inside of the cylindrical lithium ion battery through one side of the positive side.

[0048] ​Understandably, the core 300 is formed by winding together positive electrode sheets, negative electrode sheets, and a separator, as shown below. Figure 1 As 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] With reference to the foregoing Figure 2 In the embodiments of the present application, the first center hole 211 is arranged at the center of the first disc body 210, and is used for liquid injection at the positive electrode side. In combination with Figure 1 At the positive electrode side of the cylindrical lithium ion battery, the liquid injection hole 510 is arranged on the pole 500, so that the liquid injection hole 510 is aligned with and communicated with the first center hole 211. Thus, the electrolyte can be injected from outside through the channel formed by the liquid injection hole 510 and the first center hole 211, so as to realize liquid injection at the positive electrode side. Further, the first center hole 211 is preferably a circular hole, so as to match the shape of the circular winding core hole 330.

[0054] It can be understood that the positive electrode current collecting disc 200 provided by the embodiments of the present application, by arranging the first center hole 211 on the first disc body 210, can be compatible with liquid injection at the negative electrode side or liquid injection at the positive electrode side, in combination with the negative electrode current collecting disc 400 capable of liquid injection at the negative electrode side. Thus, in the liquid injection process, liquid injection at the positive electrode side or liquid injection at the negative electrode side can be freely selected, without any structural change of the positive electrode current collecting disc 200. The manufacturer can manufacture or purchase the positive electrode current collecting disc 200 as a universal structure, which can effectively reduce the design and manufacturing cost, and is convenient for internal material management of the factory.

[0055] With reference to the foregoing Figure 3 And Figure 4 In the embodiments of the present application, the area of the first disc body 210 is S2a, the area of the first center hole 211 is S2b, and the range of S2b / S2a is 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 body 210 is 107.51mm 2 , and the area S2b of the first center hole 211 is 7.51mm 2 If S2b / S2a is greater than 8.6%, the effective welding area of the welding area of the first disc body 210 will be reduced, so that the overcurrent capacity of the welding position is reduced, and the overcurrent temperature rise of the welding position is increased, which further leads to an increase in the internal resistance of the battery and a decrease in the overall performance of the battery. Conversely, if S2b / S2a is less than 4.2%, the electrolyte takes too long to flow in during liquid injection, which reduces the liquid injection efficiency, and further leads to a decrease in production efficiency and an increase in the manufacturing cost of the battery. By setting the range of S2b / S2a to 4.2% to 8.6%, the welding effect of the positive electrode current collecting disc 200 and the pole 500 and the liquid injection efficiency can be considered.

[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] Further, in some embodiments, the second disc 220 is arranged to have a height difference H2a from the surface of the first disc 210 at the side surface of the first disc 210, and the height difference H2a is in a range of 0.6-1.4 mm. For example, the height difference 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 referred to herein is the surface used for welding with the pole 500, i.e., the upper surface in Figure 3 and Figure 4 , and the side surface of the second disc 220 referred to herein is the surface on the same side as the surface used for welding with the pole 500, i.e., the upper surface in Figure 3 and Figure 4 . If the height difference H2a is greater than 1.4 mm, the positive current collector disc 200 will occupy the assembly space of the battery internal winding 300, thereby causing the capacity and performance of the battery to decrease. Conversely, if the height difference H2a is less than 0.6 mm, the height of the first disc 210 relative to the second disc 220 is too low, thereby causing the cavity space formed between the bottom of the first disc 210 and the positive electrode end 310 of the winding 300 to be too small. During liquid injection, the electrolyte flows out of the cavity to the surface of the second disc 220 and then flows into the internal winding 300 through the through-hole structure on the second disc 220 for a long time, thereby causing the liquid injection efficiency to decrease, which in turn causes the production efficiency to decrease, the manufacturing cost of the battery to increase, and the risk of electrolyte overflow during liquid injection to be high. By setting the height difference H2a in a range of 0.6-1.4 mm, the battery performance and liquid injection efficiency can be balanced.

[0060] In some embodiments, as shown in Figure 2 , Figure 3 , Figure 4 and Figure 7As shown, the second disc body 220 includes a connecting portion 221 and a welding portion 222, and the welding portion 222 is connected to the edge of the first disc body 210 by the connecting portion 221. It can be understood that, among the connecting portion 221 and the welding portion 222 constituting the second disc body 220, the welding portion 222 is used for welding with the positive electrode end 310 of the core 300, and the connecting portion 221 is used for connecting the welding portion 222 to the first disc body 210. In the embodiment, the connecting portion 221 is provided with a fuse groove 230 at the edge along the length direction thereof. Specifically, the fuse groove 230 is a structure in which the edge of the connecting portion 221 along the length direction is concave in the width direction, which can reduce the width of the connecting portion 221, and in the case of an abnormal situation of excessive current, when the current passes through this position, the heat rises and reaches the melting point, so that the connecting portion 221 is fused at this position, achieving the effect of cutting off the current, thereby reducing the risk of thermal runaway of the battery cell. It can be understood that, when the second disc body 220 is provided with multiple sets of connecting portions 221 and welding portions 222, each connecting portion 221 is provided with a fuse groove 230, so as to completely cut off the current passing through the positive electrode current collecting disc 200 in the case of an abnormal situation of excessive current.

[0061] Specifically, the connecting portion 221 is in a strip shape and is provided along the radial direction, has a certain width extending along the circumferential direction, and the two fuse grooves 230 on each connecting portion 121 are symmetrically arranged on both sides of the width direction of the connecting portion 221, and since the positive electrode current collecting disc 200 itself is in a sheet shape, the connecting portion 221 is also in a sheet shape from the thickness direction, so that by arranging the fuse grooves 230 on both sides of the width direction, the cross-sectional area of this position can be significantly reduced, so that the connecting portion 221 can be quickly fused in the case of an abnormal situation of excessive current.

[0062] Further, with reference 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 region where the fuse groove 230 is opened, and the range of W2b / W2a is 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. The second width W2b in the embodiment of the application refers to the change of the width of the connecting portion 221 at this position 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 embodiment of the application, the first width W2a in the application refers to the width of the connecting portion 221 at the position other than the fuse groove 230 on the connecting portion 221. Further, the first width W2a and the second width W2b are equal in width.

[0063] If W2b / W2a is greater than 63%, the second width W2b of the connection portion 221 at the corresponding fusing groove 230 is too wide, which cannot be quickly fused in the abnormal situation of excessive current, increasing the safety risk. Conversely, if W2b / W2a is less than 42%, the second width W2b of the connection portion 221 at the corresponding fusing groove 230 is too small, which on the one hand makes the fusing sensitivity too high, easily causing the battery to be open-circuit failure, and on the other hand also increases the internal resistance, affecting the normal use of the battery. By setting the range of W2b / W2a to 42%-63%, the fusing effect of the connection portion 221 can be guaranteed, thereby ensuring the safety performance of the battery.

[0064] In some embodiments, the connection portion 221 has a first edge 231 extending in the length direction for forming the fusing groove 230, and the length of the first edge 231 is L2a, which is in the range of 2-4 mm. For example, L2a is 2 mm, 3 mm or 4 mm. As mentioned earlier, the positive current collector 200 is usually made of aluminum material, which is relatively soft and low in strength. Therefore, if L2a is greater than 4 mm, the connection portion 221 at the position of the fusing groove 230 is prone to deformation and even breakage, and the positive current collector 200 itself is prone to scrap, causing waste and increasing management difficulty. In addition, the metal chips generated thereby may fall into the battery, which may cause the risk of battery short circuit, and the burrs and sharp corners at the broken section may also cause the risk of piercing the diaphragm and causing battery short circuit, thereby increasing the safety risk of the battery. Conversely, if L2a is less than 2 mm, heat is easily transferred to the first disc body 210 and the welding portion 222, which may cause the fusing sensitivity of the fusing groove 230 to decrease, the fusing time to become longer, and the safety risk of the battery to increase. By setting the range of L2a to 2-4 mm, the yield can be improved while ensuring the safety of the battery, thereby reducing the cost.

[0065] It can be understood that in the present embodiment, the fusing groove 230 is provided on both sides of the connection portion 221 in the width direction, and therefore the aforementioned second width W2b is the vertical distance between the first edges 231 of the two fusing grooves 230. In addition, as shown in Figure 8 , in addition to the first edge 231, the bottom of the fusing groove 230 also has a second edge 232 and a third edge 233 connected to the two ends of the first edge 231, respectively, and the first edge 231, the second edge 232 and the third edge 233 together constitute the fusing groove 230 which has a generally trapezoidal shape.

[0066] Continuing to refer to Figure 2 , Figure 3 , Figure 4 and Figure 7In some embodiments, the second disc body 220 comprises a connecting portion 221 and a welding portion 222, and the connecting portion 221 comprises a first connecting portion 2211 and a second connecting portion 2212. The first connecting portion 2211 has a plurality of first connecting portions 2211 arranged along the circumference of the first disc body 210 and extending radially outward from the edge of the first disc body 210, i.e., the first connecting portions 2211 are distributed in a radial pattern with the center of the first disc body 210 as the center. The second connecting portion 2212 extends from the outer end of each first connecting portion 2211 to both sides along the circumference. In addition, the welding portion 222 has a plurality of welding portions 222, each of which is arranged in the area defined by the adjacent two first connecting portions 2211 and the second connecting portion 2212, and extends radially inward from the inner edge of the second connecting portion 2212. It can be understood that the second connecting portion 2212 extending from the outer end of each first connecting portion 2211 along the circumference forms a circular ring structure around the periphery of the first disc body 210, and the outer edge of the circular ring structure is used to define the boundary of the entire positive current collector disc 200.

[0067] It can be understood that, in order to simplify the structure, the aforementioned fuse groove 230 can be arranged on the first connecting portion 2211.

[0068] It can be understood that, in the above structure, the welding portion 222 for welding with the positive electrode terminal 310 is provided with a plurality of welding portions 222, the number of which corresponds to the number of first connecting portions 2211, for example, the number of first connecting portions 2211 is 3, and the number of welding portions 222 is also 3, and these welding portions 222 are arranged in a plurality of areas separated by the first connecting portions 2211 along the circumferential direction, so that when viewed from the top of the positive current collector disc 200, a plurality of welding areas are divided, and the boundaries of these welding areas are clear, so that during welding, it is easy to position by tooling and weld by welding equipment, and after welding, it is easy to judge whether the welding position is reasonable by visual observation or visual detection equipment, so as to reduce the difficulty and workload of identification.

[0069] It can be further understood that the welding portion 222 extends inward from the inner edge of the second connecting portion 2212, and in some embodiments, in order to increase the area of the welding area of each welding portion 222 (refer to the area enclosed by the dashed line in the figure), the welding portion 222 is arranged to extend radially inward from the inner edge of the second connecting portion 2212 to the outer edge of the first connecting portion 2211. Figure 7The edge of the welding portion 222 extends close to the edge of the first disc body 210 and the edge of the first connecting portion 2211, so that there is a gap extending in the circumferential direction between the welding portion 222 and the first disc body 210, which can serve as the aforementioned liquid outlet 270, so that the electrolyte entering the chamber can spread to the upper surface of the second disc body 220 through the liquid outlet 270 when liquid injection is performed. Further, the welding portion 222 and the first connecting portion 2211 on both sides thereof have a gap extending in the radial direction, and the gap can serve as a through-hole structure for liquid injection into the interior of the winding core 300. It can be understood that in the above configuration, the gaps formed between the welding portion 222, the first disc body 210 and the first connecting portion 2211 are communicated, so that the electrolyte can flow along the two gaps, and the liquid injection efficiency can be improved.

[0070] Further, in some embodiments, as shown in FIG. 2B, the edges of the welding portion 222 on both sides and the edges of the inner side of the second connecting portion 2212 define a slit 240 extending in the circumferential direction. By defining the slit 240 extending in the circumferential direction by the edges of the welding portion 222 on both sides and the edges of the inner side of the second connecting portion 2212, when liquid injection is performed, the electrolyte can be injected into the interior of the winding core 300 through the slit 240 at the distal end away from the first disc body 210, and thus the liquid injection efficiency can be improved. Figure 7

[0071] In some embodiments, the circumference of the outer edge of the second connecting portion 2212 is L2b, the total arc length of the slit 240 is L2c, and the ratio of L2c / L2b is in the range of 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 welding portions 222 is 3, and 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 circumference L2b referred to in the embodiments of the present application refers to the circumference of the whole circle in which the outer edge of the circular ring structure formed by the outer side end of each first connecting portion 2211 extends in the circumferential direction, that is, the circumference of the circle in which the outer edge of the circular ring structure formed by the outer side end of each first connecting portion 2211 extends in the circumferential direction. Figure 7 Figure 7 In FIG. 2B, the outer edge of the second connecting portion 2212 is represented by a dashed line. In addition, Figure 9 ​​Only a part of L2c, i.e. the arc length of one segment of the slit 240, is identified, and L2c here also includes the arc length of the gap formed between the welding 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 connecting portion between the welding portion 222 and the second connecting portion 2212 is low, deformation is prone to occur, the welding effect is difficult to guarantee, and a lower yield rate also leads to cost increase. Conversely, if L2c / L2b is less than 43%, the time spent by the electrolyte in flowing through the slit 240 to flow into the inside of the winding core during the liquid injection is still long, and the slit 240 has no obvious effect on the improvement of the liquid injection efficiency. By setting the range of L2c / L2b to 43% to 58%, the liquid injection efficiency can be improved while the welding effect of the positive current collector plate 200 is guaranteed, and the yield rate can also be improved to reduce the cost.

[0072] Further, in some embodiments, the width of the slit 240 along the radial direction is L2e, and the range of L2e is 0.4 to 1.5 mm. For example, L2e can be 0.4 mm, 0.8 mm, 1.2 mm or 1.5 mm, etc. If L2e is greater than 1.6 mm, the opening area of the slit 240 will occupy the welding area between the welding portion 222 and the winding core 300, resulting in a decrease in the effective welding area and a decrease in the overcurrent capacity of the welding portion, which in turn leads to an increase in the temperature rise of the welding portion. Conversely, if L2e is less than 0.4 mm, the speed of the electrolyte flowing into the winding core 300 through the slit 240 during the liquid injection is slow, and the slit 240 has no obvious effect on the improvement of the liquid injection efficiency. By setting the range of L2e to 0.4 to 1.5 mm, the welding effect and the liquid injection efficiency of the positive current collector plate 200 and the winding core 300 can be considered.

[0073] Further, in some embodiments, the second connecting portion 2212 has a width W2c along the radial direction in the region corresponding to the slit 240, and the range of W2c is 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 plate 200, resulting in a decrease in the effective welding area of the welding portion 222 and the winding core 300, a decrease in the overcurrent capacity of the welding portion, and an increase in the temperature rise of the welding portion. Conversely, if W2c is less than 1 mm, the structural strength of the second connecting portion 2212 at this part is insufficient, and fracture is prone to occur. The metal chips generated thereby may, if falling into the battery, cause a risk of short circuit of the battery, and the burrs and sharp corners at the fracture section may also cause a risk of puncturing the separator and causing a short circuit of the battery, which in turn leads to an increase in the safety risk of the battery. By setting the range of W2c to 1 to 3 mm, the welding effect of the positive current collector plate 200 and the winding core 300 and the safety of the battery can be considered.

[0074] In some embodiments, asFigure 7 As shown, the second connecting portion 2212 is provided with a plurality of first notches 250 evenly distributed on the outer side edge. Specifically, for example, the first notches 250 can be formed by the outer side edge of the second connecting portion 2212 being concave inward in the radial direction, and the first notches 250 are formed by the concave edge of the second connecting portion 2212 and the reference line F. The reference line F can refer to the dashed line at the first notches 250 in FIG. 13, which is only used for illustration, and the dashed line represents the shape of the outer side edge of the second connecting portion 2212 when no notches 113 are formed, that is, the dashed line is obtained by extending the outer side edge of the second connecting portion 2212 in its natural direction. By providing the first notches 250, when the electrolyte spreads along the upper surface of the second current collector 220 to the edge thereof during liquid injection, the electrolyte can flow into the core 300 along the first notches 250, thereby further improving the liquid injection efficiency. Figure 9

[0075] Further, in some embodiments, the position of the first notches 250 in the circumferential direction of the second connecting portion 2212 corresponds to the welding portion 222, that is, the center of the first notches 250 is arranged in line with the center of the welding portion 222 in the radial direction, and the total arc length of the first notches 250 is L2d, and the range of L2d / L2b is 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 3, and the total arc length L2d of the 3 first notches 250 is 9mm. It should be noted that the arc length of the first notches 250 referred to in the embodiments of the present application refers to the arc length of the reference line F defining the formation of the first notches 250, and therefore, Figure 9 only a part of L2d is identified. If L2d / L2b is greater than 9%, the connection area of the second connecting portion 2212 and the welding portion 222 is too small, which makes it difficult to ensure the flatness of the welding portion 222, and further makes it difficult to ensure the welding effect. Conversely, if L2d / L2b is less than 4%, the speed of the electrolyte flowing into the core 300 through the first notches 250 during liquid injection is slow, and the first notches 250 have little effect on improving the liquid injection efficiency. By setting the range of L2d / L2b to 4% to 9%, the welding effect and the liquid injection efficiency of the positive current collector 200 can be considered.

[0076] Further, in some embodiments, as Figure 9 ​As shown, the maximum depth of the first gap 250 is L2f, and L2f ranges from 0.9 to 2.1 mm. For example, L2f is 0.9 mm, 1.5 mm, or 2.1 mm. If L2f is greater than 2.1 mm, the first gap 250 will occupy the welding area between the welding portion 222 and the winding core 300, resulting in a decrease in the effective welding area, causing the overcurrent capacity of the welding portion to decrease, and further causing the temperature rise of the welding portion to increase. Conversely, if L2f is less than 0.9 mm, the speed of the electrolyte flowing into the winding core 300 through the first gap 250 is slow during the liquid injection, and the first gap 250 has no obvious effect on the liquid injection efficiency. By setting the range of L2f to 0.9-2.1 mm, the welding effect of the positive current collector 200 and the liquid injection efficiency can be considered.

[0077] The effects of the present application are further described below with specific examples and comparative examples.

[0078] It should be noted that the following examples and comparative examples of the present application are based on the common 4680 cylindrical lithium ion battery design and manufacturing in the art, and therefore, in addition to the negative current collector 400 being manufactured according to the foregoing 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 the negative electrode sheet are respectively rolled, cut, and die-cut, the positive electrode sheet, the negative electrode sheet, and the separator are simultaneously wound to form the winding core 300, the positive and negative electrode tabs are formed by cutting and folding the winding core 300 at both ends, then the negative current collector 400 and the positive current collector are respectively welded to the winding core 300, the negative current collector 400 is welded to the shell 100, the negative cover plate 600 is welded to the shell 100, and the liquid injection, sealing, and formation processes are completed to obtain the experimental cylindrical lithium ion battery.

[0079] Example 1:

[0080] Embodiment 1 provides a cylindrical lithium ion battery, which comprises a positive electrode current collector 200, the positive electrode current collector 200 comprises a first disc body 210 and a second disc body 220 staggered in the thickness direction, the first disc body 210 is higher than the surface of one side of the second disc body 220 by a height difference H2a, the center of the first disc body 210 is provided with a circular first center hole 211, the second disc body 220 comprises three first connecting parts 2211 extending radially outward from the edge of the first disc body 210, two sides of the outer end of the three first connecting parts 2211 are formed with second connecting parts 2212 extending in the circumferential direction, the second connecting parts 2212 together form an annular structure, and in each region formed by two of the three first connecting parts 2211 in the circumferential direction, the inner side edge of the second connecting part 2212 extends inward to form a welding part 222, and a slit 240 extending in the circumferential direction is defined between the edge on both sides of the welding part 222 and the inner side edge of the second connecting part 2212, and a pair of trapezoidal-shaped fuse grooves 230 are arranged on the lengthwise edge of each first connecting part 2211, and a first notch 250 is arranged on the outer side edge of the second connecting part 2212 corresponding to the position of the welding part 222.

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

[0082] The area S2a of the first disc body 210 is 107.51 mm 2 The area S2b of the first center hole 211 is 7.07 mm 2 H2a=1 mm, the first width W2a of the first connecting part 2211 is 4 mm, the second width W2b of the first connecting part 2211 at the position where the fuse groove 230 is arranged is 2 mm, the length L2a of the first edge 231 at the bottom of the fuse groove 230 is 3 mm, the circumference L2b of the outer side edge of the second connecting part 2212 is 233.52 mm, the total arc length L2c of the six slits 240 is 66.78 mm, the width L2e of the slit 240 is 0.8 mm, the width W2c of the second connecting part 2212 in the region corresponding to the slit 240 is 2 mm, the total arc length L2d of the three first notches 250 is 9 mm, and the maximum depth L2f of the first notch 250 is 1.5 mm.

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

[0084] Comparative Example 1 provides a cylindrical lithium ion battery, which comprises a positive electrode current collector 200, which is different from Embodiment 1 in that S2b / S2a=3%.

[0085] Comparative Example 2:

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

[0087] Comparative Example 3:

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

[0089] Comparative Example 4:

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

[0091] Comparative Example 5:

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

[0093] Comparative Example 6:

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

[0095] Comparative Example 7:

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

[0097] Comparative Example 8:

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

[0099] Comparative Example 9:

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

[0101] Comparative Example 10:

[0102] Comparative Example 10 provides a cylindrical lithium-ion battery including the positive current collector tab 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 the positive current collector tab 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 the positive current collector tab 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 including the positive current collector tab 200, which differs from Example 1 in that L2e = 0.3 mm.

[0109] Comparative Example 14:

[0110] Comparative Example 14 provides a cylindrical lithium-ion battery including the positive current collector tab 200, which 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 the positive current collector tab 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 the positive current collector tab 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 including the positive current collector tab 200, which differs from Example 1 in that L2f = 0.6 mm.

[0117] Comparative Example 18:

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

[0119] Comparative Example 19:

[0120] Comparative Example 19 provides a cylindrical lithium-ion battery including the positive current collector tab 200, which differs from Example 1 in that the fuse groove 230 is not provided.

[0121] Comparative Example 20:

[0122] Comparative Example 20 provides a cylindrical lithium ion battery including the positive current collector 200, which is different from Example 1 in that the first notch 250 is not provided.

[0123] The following Table 1 shows the time (t) required for electrolyte to be injected into the battery, the maximum temperature (T1max) of the welding mark of the first disc body 210, the maximum temperature (T2max) of the welding mark of the second disc body 220, the maximum temperature (T3max) at the fuse groove 230, the folding number (C1) of the first connecting part 2211 at which the first connecting part 2211 breaks after being folded at the fuse groove 230, the folding number (C2) of the second connecting part 2212 at which the second connecting part 2212 breaks after being folded, and the battery short circuit rate test for the positive current collector 200 manufactured in the above examples and comparative examples.

[0124] The test method for the time (t) required for electrolyte to be injected into the battery is as follows: the positive current collector 200 is assembled into a cylindrical lithium ion battery, and during the liquid injection stage, 77 g of electrolyte is injected into a liquid holding cup, the nozzle of the liquid holding cup is aligned with the liquid injection hole 510 on the pole 500 and is pressed tightly, negative pressure is first extracted in the liquid holding cup for 15 s, and the extraction is stopped at -90 KPa. The electrolyte height can be observed to decrease in the liquid holding cup, and the electrolyte flows into the battery interior. After being maintained for 40 s, positive pressure injection is performed, nitrogen gas is injected into the battery interior, the battery interior gradually becomes a positive pressure of 0.8 MPa, the electrolyte in the liquid holding cup continuously flows into the battery interior, and the electrolyte height in the liquid holding cup gradually decreases. Then, negative pressure injection is adjusted again, maintained, and positive pressure injection is adjusted again, maintained. The positive and negative pressure injection is cycled multiple times until the electrolyte in the liquid holding cup completely flows into the battery interior, the electrolyte height in the liquid holding cup is 0, and the time t at which the electrolyte completely flows into the battery interior is recorded.

[0125] The test method for the maximum temperature (T1max) of the welding mark of the first disc body 210, the maximum temperature (T2max) of the welding mark of the second disc body 220, and the maximum temperature (T3max) at the fuse groove 230 is as follows: during the assembly of the cylindrical lithium ion battery, temperature collection lines are inserted into the battery interior through the liquid injection hole 510 of the pole 500, one is attached to the welding position between the first disc body 210 and the pole 500, one is attached to the welding position between the second disc body 220 and the positive electrode end 310 of the winding core 300, and the other is attached to the position at which the fuse groove 230 is provided on the first connecting part 2211. Then, the battery is manufactured according to the normal process flow and finally obtained as a finished product. After that, 10 cycles of charge and discharge are performed at a rate of 2C, and the maximum temperatures T1max, T2max, and T3max at the three positions obtained by the temperature collection lines are recorded.

[0126] The test method for the number of folds (C1) at which the first connecting portion 2211 breaks after folding at the fusing groove 230 is as follows: a 1 / 3 piece of the positive current collector plate 200 containing one first connecting portion 2211 is obtained by cutting along the radial direction from two adjacent first notches 250 using scissors, the piece is folded along the center line of the fusing groove 230, and the two surfaces are completely attached after being unfolded to 180°, which is counted as one fold, until the fold breaks, the folding is stopped, and the number of folds is recorded.

[0127] The test method for the number of folds (C2) at which the second connecting portion 2212 breaks after folding is as follows: a fan-shaped piece of the positive current collector plate 200 is obtained by cutting along the radial direction from one first notch 250 using scissors, and the cutting is stopped at the first center hole 211, then the cutting is continued along the radial direction to the second connecting portion 2212 along the edge of one first connecting portion 2211, the two fan-shaped pieces of the positive current collector plate 200 are folded, the two surfaces are completely attached after being unfolded to 180°, which is counted as one fold, until the first connecting portion 2212 breaks, the folding is stopped, and the number of folds is recorded.

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

[0129] Table 1

[0130]

[0131]

[0132] As shown in Table 1, when S2b / S2a is 6.6%, W2b / W2a is 50%, L2 / L2b is 50%, L2d / L2b is 6.74%, H2a is 1 mm, L2a is 3 mm, L2e is 0.8 mm, W2c is 2 mm, and L2f is 1.5 mm, the injection time t of the electrolyte is 693 seconds, the maximum temperature T1max at the welding position of the first disc body 210 and the pole 500 is 56.4°C, the maximum temperature T2max at the welding position of the second disc body 220 and the winding core 300 is 68.9°C, the maximum temperature T3max at the melting slot 230 is 73.6°C, the folding number C1 of the first connecting part 2211 after folding at the melting slot 230 is 5, the folding number C2 of the second connecting part 2212 after folding is 5, and the short-circuit rate of the battery is only 1%. It can be seen that, within the above numerical range, the injection rate, the welding temperature rise, the structural strength, and the connection reliability of the positive current collecting disc 200 can be well balanced, thereby effectively improving the safety and the charge-discharge performance of the battery and reducing the production cost of the battery.

[0133] As shown in Table 1, too small S2b / S2a, too small H2a, too large W2b / W2a, too small L2 / L2b, too small L2d / L2b, too small L2e, too small L2f, and no melting slot 230 or first notch 250 will all cause the injection time t of the electrolyte to increase to some extent.

[0134] As shown in Table 1, too large S2b / S2a will cause the maximum temperature T1max at the welding position of the first disc body 210 and the pole 500 to rise significantly.

[0135] As shown in Table 1, too large L2 / L2b, too large L2d / L2b, too large L2e, too large W2c, and too large L2f will all cause the maximum temperature T2max at the welding position of the second disc body 220 and the winding core 300 to rise.

[0136] As shown in Table 1, too small W2b / W2a will cause the maximum temperature T3max at the melting slot 230 to rise significantly. Too large W2b / W2a or too short L2a will both cause the maximum temperature T3max at the melting slot 230 to be relatively low. It can be understood that, for the position of the melting slot 230, if the temperature cannot rise to the melting critical value, the first connecting part 2211 cannot be melted in time, thereby failing to produce the safety protection effect.

[0137] As shown in Table 1, too small W2b / W2a or too large L2a will reduce the folding number C1 of the first connecting part 2211 after folding at the melting slot 230.

[0138] As shown in Table 1, if W2c is too small, the folding number C2 of the second connecting portion 2212 after folding will be significantly reduced, and the second connecting portion 2212 will be more likely to be broken.

[0139] As shown in Table 1, if H2a is too large, the probability of short circuit of the battery will be significantly increased.

[0140] The negative current collector 400 will be described in detail below.

[0141] Figure 10 is a structural schematic diagram of the negative current collector 400 provided by the embodiment of the present application, Figure 11 is Figure 10 is a combined structural schematic diagram of the negative current collector 400 and the winding core and the shell, as shown in Figure 10 Figure 11 The negative current collector 400 includes a third disc body 410 and a flange 420 protruding from one side of the outer periphery of the third disc body 410, wherein the third disc body 410 is used to be connected with the negative terminal 220 of the winding core 300, and the flange 420 is used to be connected with the shell 100, so that a passage is formed between the winding core 300 and the shell 100, and thus the shell 100 itself serves as the negative electrode of the cylindrical lithium ion battery.

[0142] It can be understood that the third disc body 410 and the flange 420 can be connected in any fixed connection manner, and in order to ensure stable connection, structural strength and processing economy, the third disc body 410 and the flange 420 can be integrally connected, for example, integrally formed by stamping forming.

[0143] As shown in Figure 10 and Figure 11 , the third disc body 410 is the main structural part of the negative current collector 400, and the whole third disc body 410 is in the shape of a sheet, and a second center hole 411 and a plurality of auxiliary holes 412 are formed through the third disc body 410, and in addition, a plurality of second notches 413 are formed at the outer periphery of the third disc body 410. It can be understood that the third disc body 410 has two disc surfaces away from each other. As shown in Figure 10 , the flange 420 protrudes from the edge of the third disc body 410 at an angle approximately perpendicular to the disc surface, as shown in Figure 11 , the disc surface away from the protruding direction of the flange 420 can be used to be welded with the negative terminal 220 of the winding core 300, and in this case, the disc surface on the side where the flange 420 is located faces the opening direction of the shell 100, and in the subsequent liquid injection process, the electrolyte will enter the inside of the battery through the disc surface.

[0144] It can be understood that the cross-sectional shape of the cylindrical lithium ion battery roll core 300 and the shell 100 is circular, so that the third disc body 410 of the negative electrode current collector 400 is generally circular in shape to facilitate welding between the third disc body 410 and the roll core 300, and to facilitate welding between the flange 420 and the shell 100. In the present embodiment, due to the presence of the second notch 413, the outer contour shape of the third disc body 410 is not a complete circular shape, and the outer contour shape of the third disc body 410 is not a complete circular shape. Figure 12 As can be seen, the shape of the third disc body 410 is a closed figure composed of a plurality of circular arc edges 414 and a plurality of concave edges 415 connected in order.

[0145] As described above, the third disc body 410 is not a complete circular shape, but the two sides of each circular arc edge 414 can be connected to form a complete circle by extending the end portions, so the third disc body 410 can be considered as a circular member.

[0146] As shown in Figure 10 and Figure 11 In the present embodiment, the flange 420 is not a complete circular ring structure, specifically, the flange 420 is only provided at the edge of the circular arc edge 414, that is, the plurality of second notches 413 divide the flange 420 into multiple segments. In this way, each segment of the flange 420 is well fitted with the shell wall surface of the shell 100 and is connected by penetration welding. At the same time, by providing the second notch 413, on the one hand, during the electrolyte injection process, when the electrolyte flows into the disc surface of the third disc body 410, part of the electrolyte will flow directly into the battery through the second center hole 411 and the auxiliary hole 412, and part of the electrolyte will flow along the disc surface of the third disc body 410 to the outer periphery of the third disc body 410. Due to the presence of the second notch 413, this part of the electrolyte will flow into the battery along the second notch 413, improving the electrolyte injection efficiency, reducing the injection time, improving the production efficiency, and reducing the manufacturing cost of the battery; on the other hand, in the case of short circuit or thermal runaway gas production in the battery, part of the gas can be shunted through the second notch 413, improving the exhaust efficiency and improving the safety of the battery.

[0147] It can be understood that by providing the flange 420 only at the position of the circular arc edge 414, the weight of the negative electrode current collector 400 can be reduced to the first degree, thereby improving the energy density of the battery. In addition, since the flange 420 is not a complete circle, the length of the welding line between the flange 420 and the shell 100 can be effectively reduced, thereby reducing the risk of liquid leakage, virtual welding, and missed welding at the welding position, and further reducing the internal resistance of the battery.

[0148] It can also be understood that for the negative current collector plate 400, the art generally adopts the method of opening a hole in the inside of the third disc body 410 to improve the liquid injection efficiency, and in the design process, the weldable area of the third disc body 410 itself and the structure of the flange 420 at the edge of the third disc body 410 need to be balanced in order to be welded with the winding core 300 and the shell 100 and to design the welding tool clamp. The application assists in liquid injection and exhaust by separating the flange 420 into multiple segments and opening the second notch 413 at the outer periphery of the third disc body 410, which minimizes the adverse effects on the third disc body 410 and the flange 420. For example, by reasonably designing the size and shape of the second notch 413, the effect on the welding of the third disc body 410 can be effectively avoided.

[0149] Further, from the Figure 12 , the second notch 413 is a structure formed by recessing inwardly from the outer periphery of the third disc body 410 to the center of the third disc body 410, for example, the second notch 413 can be formed by various methods such as mechanical cutting, laser cutting, etc. at the outer periphery of the third disc body 410 in a material-removing manner.

[0150] It can be further understood that various shapes of the second notch 413 can be formed at the outer periphery of the third disc body 410, for example, as shown in Figure 12 , a circular arc shape, in which case the second notch 413 is formed by the inner recessed edge 415 and the reference line of the outer periphery of the third disc body 410, wherein the reference line can refer to the dashed line at the second notch 413 in Figures 13 to 17 , which is used for illustration, and the dashed line represents the shape of the third disc body 410 when the third disc body 410 is not cut with the second notch 413, and the dashed line is obtained by extending the outer periphery of the third disc body 410 along the original outer periphery. Of course, it is not limited to this, for example, the second notch 413 can be rectangular, sector-shaped, waist-shaped, etc.

[0151] It can be understood that at least one second notch 413 needs to be provided in order to facilitate auxiliary exhaust and auxiliary liquid injection at the outer periphery of the third disc body 410. Of course, in order to further improve the exhaust efficiency and the liquid injection efficiency, multiple second notches 413 can be provided, in which case the circular arc edges 414 between the multiple second notches 413 also have multiple segments, and accordingly, the flanges 420 can be respectively provided on these circular arc edges 414. Of course, it is not limited to this, and under the premise of meeting the requirements, the number of second notches 413 and flanges 420 need not be one-to-one corresponding, for example, no flange 420 can be provided on the circular arc edge 414 at some positions.

[0152] As shown in Figure 13As shown, in some embodiments, the number of the arc-shaped edges 414, the concave edges 415 and the auxiliary holes 412 are all 4, the 4 arc-shaped edges 414 and the 4 auxiliary holes 412 are arranged one by one in correspondence, and the midpoints of the corresponding arc-shaped edges 414, the centers of the auxiliary holes 412 and the center of the second central hole 411 are collinear. It can be understood that in this way, the auxiliary holes 412 and the second notch 413 are staggered with each other in the radial direction of the third disc body 410. By corresponding the number of the arc-shaped edges 414, the concave edges 415 and the auxiliary holes 412, and all setting them to 4, it is beneficial to balance the liquid injection and exhaust effect of the third disc body 410 and the welding effect of the flange 420 and the shell 100, and at the same time, the second central hole 411, the auxiliary hole 412 and the arc-shaped edge 414 are arranged to be collinear, thereby avoiding the weakening of the structure strength of the third disc body 410 caused by the collinearity of the auxiliary hole 412, the second notch 413 and the second central hole 411, and effectively ensuring the structure strength of the third disc body 410, while ensuring the weldable area between the third disc body 410 and the winding core 300.

[0153] Further, as shown in Figure 12 , the auxiliary hole 412 is in the shape of a waist, that is, the auxiliary hole 412 is a waist-shaped hole, and the long axis direction of the auxiliary hole 412 is consistent with the radial direction of the third disc body 410. It can be understood that for a large cylindrical battery, the disc surface of the negative electrode current collector 400 is also large, and the auxiliary hole 412 adopts a waist-shaped hole and the long axis direction is arranged to extend along the radial direction of the third disc body 410, which can effectively increase the opening area of the auxiliary hole 412 without affecting the welding area, thereby improving the auxiliary liquid injection effect.

[0154] As shown in Figure 13 and Figure 14 , in some embodiments, the area of the third disc body 410 is S4a, the total area of the second notch 413 is S4b, and the range of S4b / S4a is 2%~10%, that is, 2%≤S4b / S4a≤10%. For example, S4a is 1604.6mm 2 , S4b is 95.56mm 2 , and S4b / S4a is 5.96%. As shown in Figure 13 , the area S4a of the third disc body 410 refers to the disc surface area of the third disc body 410, that is, the area of the third disc body 410 without structures such as the second central hole 411, the auxiliary hole 412 and the second notch 413, as shown in Figure 14As shown, the total area S4b of the second notch 413 is the sum of the areas of the closed figures formed by the inner recess edge 415 and the baseline (dashed line in the figure) of the outer periphery of the third disc body 410. It should be further understood that, in terms of a single second notch 413, the area thereof refers to the area of the region defined by the baseline of the outer periphery of the third disc body 410 and the inner recess edge 415 of the second notch 413.

[0155] It should be understood that, if the total area S4b of the second notch 413 is too small, on the one hand, the second notch 413 does not significantly improve the injection efficiency during the injection process, and there is also a risk of electrolyte overflow, which can cause the outer surface of the shell 100 to be contaminated and rusted by the electrolyte, and even cause the battery to be scrapped, and the problem of electrolyte overflow also needs to be handled by manpower, which can increase the manufacturing cost; on the other hand, when the battery short-circuits or other thermal runaway occurs during use, the gas generated inside the battery cannot be timely discharged through the second notch 413, and the effect on improving the safety of the battery is limited. Conversely, if the total area S4b of the second notch 413 is too large, the second notch 413 will occupy the welding area on the disc surface of the third disc body 410, resulting in a decrease in the actual effective welding area between the third disc body 410 and the negative electrode terminal 220, and the overcurrent capacity of the welding position cannot meet the demand, thereby causing the overcurrent temperature to be too high, triggering subsequent thermal control and other safety problems, and the safety performance of the battery is reduced. By setting the range of S4b / S4a to be 2% to 10%, the injection efficiency and the exhaust efficiency of the third disc body 410 can be considered, and at the same time, good welding effect between the third disc body 410 and the jelly roll 300 can be ensured, and the increase in the internal resistance of the battery can also be effectively avoided.

[0156] As mentioned above, in the present embodiment, the third disc body 410 is provided with a second center hole 411 that penetrates the third disc body 410 and is arranged at the center of the third disc body 410, and is used for injecting electrolyte into the battery. It should be noted that the center of the third disc body 410 can be the center of the third disc body 410. In combination with the above description of the first embodiment, the second center hole 411 is arranged at the center of the third disc body 410, and the third disc body 410 is provided with a plurality of second notches 413 arranged around the second center hole 411. Figure 1 It should be understood that the jelly roll 300 is made by winding process, and the center of the jelly roll 300 forms a circular jelly roll hole 330 after winding. In order to match the shape of the jelly roll hole 330, the shape of the second center hole 411 is preferably circular, and in this case, the second center hole 411 and the third disc body 410 share the same center. It should be understood that the diameter of the second center hole 411 can be specifically selected according to the balance between the injection efficiency and the weldable area.

[0157] Further, as mentioned above, the third disc body 410 is provided with a plurality of second notches 413 arranged around the second center hole 411. Figure 13 and Figure 15As shown, in some embodiments, the area of ​​the second central hole 411 is S4c, and the ratio of S4c to S4a ranges from 1% to 3%, i.e., 1% ≤ S4c / S4a ≤ 3%. For example, the area of ​​the second central hole 411 is 28.27 mm. 2 S4a is 1604.6mm. 2 S4c / S4a is 1.76%. Among them, the second central hole 411 is located at the center of the third disk 410, and there is only one of them. Therefore, the area S4c of the second central hole 411 here refers only to the area of ​​the second central hole 411 itself.

[0158] Understandably, if the area S4c of the second central hole 411 is too small, on the one hand, during the electrolyte injection process, the narrow injection channel makes it difficult for the electrolyte to be injected into the battery, increasing the injection time and reducing injection efficiency; on the other hand, if a short circuit or other thermal runaway occurs during battery use, the gas generated inside the battery cannot be discharged in time through the second central hole 411, reducing battery safety. Conversely, if the area S4c of the second central hole 411 is too large, the second central hole 411 will occupy the welding area on the surface of the third disk 410, reducing the actual effective welding area between the third disk 410 and the negative terminal 220. The current-carrying capacity at the welding position will not meet the requirements, resulting in excessive overcurrent temperature rise and subsequent thermal control and other safety issues, thus reducing battery safety performance. Furthermore, the reduced welding area will increase the battery's internal resistance. By setting the range of S4c / S4a to 1% to 3%, it is possible to ensure good welding effect between the third plate 410 and the core 300 while taking into account the liquid injection efficiency and venting efficiency of the negative electrode current collector 400. In addition, it is also possible to effectively avoid increasing the internal resistance of the battery.

[0159] As mentioned earlier, in this embodiment, a through auxiliary hole 412 is provided on the third disc 410. This auxiliary hole 412 is located around the second central hole 411 and is used to assist in electrolyte injection. It can be understood that the size of the auxiliary hole 412 can be specifically selected according to the balance between achieving injection efficiency and weldable area.

[0160] Furthermore, such as Figure 13 and Figure 16 As shown, in some embodiments, the total area of ​​the auxiliary hole 412 is S4d, and the ratio of S4d to S4a ranges from 9% to 21%, i.e., 9% ≤ S4d / S4a ≤ 21%. For example, the total area of ​​the auxiliary hole 412 is 226.27 mm. 2 S4a is 1604.6mm. 2 S4d / S4a is 14.1%. Among them, the total area S4d of the auxiliary holes 412 refers to the sum of the areas of all the auxiliary holes 412 on the third disk 410.

[0161] Understandably, if the total area S4d of the auxiliary hole 412 is too small, on the one hand, the increased injection time during the electrolyte injection process will lead to a decrease in injection efficiency and a risk of electrolyte overflow. This could result in electrolyte contamination, rusting, or even battery failure on the outer surface of the casing 100. Furthermore, increased manpower is required to handle the overflow, increasing manufacturing costs. On the other hand, if a short circuit or other thermal runaway occurs during battery use, the gas generated inside the battery cannot be discharged in time through the auxiliary hole 412, limiting its effectiveness in improving battery safety. Conversely, if the total area S4d of the auxiliary hole 412 is too large, the auxiliary hole 412 will occupy the welding area on the surface of the third disk 410, reducing the welding area between the third disk 410 and the negative terminal 220. The current-carrying capacity at the welding position will not meet the requirements, resulting in excessive overcurrent temperature rise and subsequent thermal control safety issues. The battery's safety performance will decrease, and the reduced welding area will increase the battery's internal resistance. By setting the S4d / S4a range to 9% to 21%, it is possible to ensure good welding between the third plate 410 and the core 300 while taking into account the liquid injection efficiency and venting efficiency of the negative electrode current collector 400. In addition, it is also possible to effectively avoid increasing the internal resistance of the battery.

[0162] As mentioned earlier, the third disc 410 is a closed shape composed of multiple alternating arc edges 414 and multiple concave edges 415 connected end to end. Thus, the outer periphery of the third disc 410 includes multiple arc edges 414 that are disconnected from each other. As mentioned earlier, the two ends of each arc edge 414 can be extended to connect and form a complete circle. Therefore, the third disc 410 can be considered a circular component. It can be understood that these arc edges 414 themselves are partial arc segments of a complete circle, and multiple flanges 420 are correspondingly arranged on these arc edges 414, with each flange 420 extending along the edge of the arc edge 414, thus each flange 420 is also arc-shaped. It should be noted that the arc length of the flange 420 can be less than the arc length of the arc edge 414. In this case, the second notch 413 and the flange 420 are not directly connected.

[0163] In some embodiments, such as Figure 17 As shown, with the perimeter of the third disc 410 as H4a and the total arc length of the flange 420 as H4b, the ratio of H4b / H4a ranges from 42% to 58%, i.e., 42% ≤ H4b / H4a ≤ 58%. For example, if the perimeter H4a of the third disc 410 is 142 mm and the total arc length H4b of the flange 420 is 70.68 mm, then H4b / H4a is 49.77%. Here, the perimeter H4a of the third disc 410 refers to the perimeter of the complete circular shape along the edge 414, i.e. Figure 13The perimeter of the outer contour of the shaded area, while the total arc length of the flange 420, H4b, refers to the sum of the arc lengths of multiple flange segments 420. Figure 17 (Only the arc length of one flange 420 is marked in the text). For example, the third disc body 410 has a total of 4 flanges 420, each with an arc length of 17.67mm, so the total arc length H4b of the flanges 420 is 70.68mm.

[0164] Understandably, when welding the flange 420 to the housing 100, the clamping fixture occupies part of the flange 420. If the total arc length H4b of the flange 420 is too small, positioning becomes difficult, affecting the actual welding area and reducing the effective welding area. This leads to a decrease in the current-carrying capacity at the weld, resulting in excessive temperature rise during subsequent use and increased internal resistance, thus affecting battery performance. Conversely, if the total arc length H4b of the flange 420 is too large, it increases the weight of the negative electrode current collector 400, reducing the battery's energy density. It also results in excessively long weld lines, which not only fail to reduce battery resistance but also decrease welding reliability, such as increasing the risk of leakage, incomplete welds, and missed welds, potentially increasing the battery's internal resistance. By setting the H4b / H4a range to 42%–58%, it is possible to achieve a good welding effect between the flange 420 and the housing 100, while ensuring that the negative electrode current collector 400 is relatively light, thereby improving the energy density of the battery and effectively avoiding increasing the internal resistance of the battery.

[0165] In some embodiments, such as Figure 17 As shown, the perimeter of the third disc 410 is H4a, and the total arc length of the second notch 413 is H4c. The ratio of H4c / H4a is between 25% and 38%, i.e., 25% ≤ H4c / H4a ≤ 38%. For example, the perimeter of the third disc 410, H4a, is 142 mm, and the total arc length of the second notch 413, H4c, is 45.32 mm, so H4c / H4a is 31.92%. Here, the perimeter of the third disc 410, H4a, refers to the perimeter of the complete circular shape along the edge 414 of the arc. Figure 13 The perimeter of the outer contour of the shaded area, and the total arc length H4c of the second notch 413 refers to the arc length of the aforementioned third disk 410 after deducting the arc length of all the arcs along the edge 414, that is... Figure 17 The sum of the arc lengths of the dashed segments in the middle ( Figure 17 (Only the arc length of a dashed line is marked in the text). For example, the third disc 410 has a total of 4 second notches 413, and the arc length of each individual second notch 413 is 11.33mm. Then the total arc length H4c of the second notches 413 is 45.32mm.

[0166] Understandably, if the total arc length H4c of the second notch 413 is too short, on the one hand, the increased injection time during the electrolyte injection process will lead to a decrease in injection efficiency and a risk of electrolyte overflow. This could result in electrolyte contamination, rusting, or even battery failure on the outer surface of the casing 100. Furthermore, increased manpower is required to handle the overflow, increasing manufacturing costs. On the other hand, if a short circuit or other thermal runaway occurs during battery use, the gas generated inside the battery cannot be discharged in time through the second notch 413, limiting its effectiveness in improving battery safety. Conversely, if the total arc length H4c of the second notch 413 is too long, the second notch 413 will occupy the welding area on the surface of the third disk 410, reducing the actual effective welding area between the third disk 410 and the negative terminal 220. The current-carrying capacity at the welding position will not meet the requirements, resulting in excessive overcurrent temperature rise and subsequent thermal control safety issues. The battery's safety performance will decrease, and the reduced welding area will increase the battery's internal resistance. By setting the H4c / H4a range to 25%–38%, it is possible to ensure good welding between the third plate 410 and the core 300 while taking into account the liquid injection efficiency and venting efficiency of the negative electrode current collector 400. Furthermore, it is also possible to effectively avoid increasing the internal resistance of the battery.

[0167] In some embodiments, such as Figure 17 As shown, the maximum depth H4d of the second notch 413 ranges from 2 to 5 mm, i.e., 2 mm ≤ H4d ≤ 5 mm. It should be noted that the maximum depth H4d of the second notch 413 refers to the distance from the highest point of the baseline at the outer periphery of the third disc 410 to the deepest point of the second notch 413. For example, Figure 17 The concave edge 415 shown is arc-shaped, and its deepest point is located at the midpoint of the arc-shaped concave edge 415. The highest point of the baseline of the outer periphery of the third disc 410 is located at the midpoint of the dashed line. Therefore, in this case, the maximum depth H4d is the distance between the midpoint of the concave edge 415 and the midpoint of the dashed line.

[0168] It can be understood that if the maximum depth H4d of the second notch 413 is too small, i.e., the depth of the second notch 413 is too shallow, the area of the second notch 413 will be smaller, and the channel formed by the shell 100 will be narrow. On the one hand, in the process of liquid injection, the second notch 413 is not obvious in improving the liquid injection efficiency, and there is a risk of electrolyte overflow, which causes the outer surface of the shell 100 to be contaminated by electrolyte, rust, and even battery scrap, etc. And, it also needs to increase the manpower to handle the overflow problem, which will increase the manufacturing cost. On the other hand, when the battery short-circuits or other thermal runaway occurs during use, the gas generated inside the battery cannot be discharged in time through the second notch 413, and the effect on improving the safety of the battery is limited. Conversely, if the maximum depth H4d of the second notch 413 is too large, i.e., the depth of the second notch 413 is too deep, the second notch 413 will occupy the welding area on the disc surface of the third disc body 410, resulting in a decrease in the actual effective welding area between the third disc body 410 and the negative electrode terminal 220, and the overcurrent capacity of the welding position does not meet the demand, thereby causing the overcurrent temperature to rise too much, triggering subsequent thermal control and other safety problems, and the safety performance of the battery decreases. And, the decrease in the welding area will increase the internal resistance value of the battery. By setting the range of the maximum depth H4d of the second notch 413 to 2-5 mm, the liquid injection efficiency and the exhaust efficiency of the third disc body 410 can be considered, and at the same time, the welding effect between the third disc body 410 and the winding core 300 is ensured, and the increase in the internal resistance of the battery can also be effectively avoided.

[0169] As shown in Figure 17 some embodiments, the second center hole 411 is arranged with the circular arc along the edge 414 as a common center, the radius of the third disc body 410 is L4a, the distance from the inner side edge of the auxiliary hole 412 to the center of the second center hole 411 is L4b, and the range of L4b / L4a is 18%-36%, i.e., 18%≤L4b / L4a≤36%. For example, L4a is 22.6 mm, L4b is 6 mm, and L4b / L4a is 26.55%.

[0170] It is understandable that the dimensions of a cylindrical lithium-ion battery are basically fixed, that is, the diameter of the cylindrical lithium-ion battery casing is determined. Therefore, the diameter of the third disk 410 of the negative electrode current collector 400 assembled into the casing is basically determined. Since the second central hole 411 is located at the center of the third disk 410, if L4b / L4a is too small, the auxiliary hole 412 will be too close to the second central hole 411. In this case, the structural strength of the connection between the auxiliary hole 412 and the second central hole 411 may be insufficient, and there is a risk of breakage. Moreover, once this part breaks, metal shavings will be generated, and the burrs generated at the fracture point can easily deform inward and puncture the separator. Both metal shavings and burrs may cause short circuit failure of the battery, which poses a safety risk. Conversely, if L4b / L4a is too large, the auxiliary hole 412 will be too far from the second central hole 411. During the electrolyte injection process through the second central hole 411, if the second central hole 411 cannot meet the injection speed requirements, the time it takes for the electrolyte to spread from the surface of the third disc 410 to the auxiliary hole 412 will increase. Furthermore, during this spread, the electrolyte will continuously inject into the battery, easily causing overflow. This can lead to problems such as electrolyte contamination, rusting, and even battery failure on the outer surface of the casing 100. Additionally, it requires additional manpower to handle the overflow, increasing manufacturing costs. By setting the L4b / L4a range to 18%–36%, the structural strength of the connection between the second central hole 411 and the auxiliary hole 412 can be ensured while maintaining the auxiliary injection effect of the auxiliary hole 412.

[0171] The effects of this application will be further described below with specific embodiments and comparative examples.

[0172] Example 1:

[0173] 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 and four flanges 420 protruding from the outer periphery of the third disk body 410. One side of the third disk body 410 of the negative electrode current collector 400 is laser-welded to the core 300, and the flanges 420 are attached to the shell wall of the housing 100 in the direction away from the core 300, and the two are connected by laser through welding. The third disk body 410 has a second central hole 411 located at its center and four auxiliary holes 412 located around the second central hole 411. Four arc-shaped second notches 413 are also provided on the outer periphery of the third disk body 410. The midpoint of each arc edge 414, the center of the auxiliary holes 412, and the center of the second central hole 411 are collinear. Furthermore, the negative electrode current collector 400 also satisfies the following parameters:

[0174] The area S4a of the third disk 410 is 1604.6 mm². 2 The total area S4b of the second gap 413 is 95.56 mm. 2; the area S4c of the second center hole 411 is 28.27 mm 2 ; the total area S4d of the auxiliary hole 412 is 226.27 mm 2 ; the circumference H4a of the third disc body 410 is 142 mm; the total arc length H4b of the flange 420 is 70.68 mm; the total arc length H4c of the second notch 413 is 45.32 mm; the depth H4d of the second notch 413 is 3 mm; the radius L4a of the circular arc edge 414 (third disc body 410) is 22.6 mm; the distance L4b from the innermost side of the auxiliary hole 412 to the center position of the second center hole 411 is 6 mm.

[0175] From the above, in the negative current collector disc 400, S4b / S4a = 6%, S4c / S4a = 2%, S4d / S4a = 14%, H4b / H4a = 50%, H4c / H4a = 32%, L4b / L4a = 27%.

[0176] Example 2:

[0177] Comparative Example 1 provides a cylindrical lithium ion battery including a negative current collector disc 400, which is different from Example 1 in that S4b / S4a = 4%, S4d / S4a = 16%, H4b / H4a = 54%, H4c / H4a = 29%, H4d = 2 mm, L4b / L4a = 24%.

[0178] Example 3:

[0179] Comparative Example 1 provides a cylindrical lithium ion battery including a negative current collector disc 400, which is different from Example 1 in that S4b / S4a = 8%, S4d / S4a = 12%, H4b / H4a = 46%, H4c / H4a = 33%, H4d = 4 mm, L4b / L4a = 30%.

[0180] Comparative Example 1:

[0181] Comparative Example 1 provides a cylindrical lithium ion battery including a negative current collector disc 400, which is different from Example 1 in that S4b / S4a = 1%, H4c / H4a = 14.8%, H4d = 0.9 mm.

[0182] Comparative Example 2:

[0183] Comparative Example 2 provides a cylindrical lithium ion battery including a negative current collector disc 400, which is different from Example 1 in that S4b / S4a = 15%, H4c / H4a = 41%, H4d = 5.83 mm.

[0184] Comparative Example 3:

[0185] Comparative Example 3 provides a cylindrical lithium-ion battery including a negative current collector 400 that differs from Example 1 in that S4d / S4a = 5%.

[0186] Comparative Example 4:

[0187] Comparative Example 4 provides a cylindrical lithium-ion battery including a negative current collector 400 that differs from Example 1 in that S4d / S4a = 25%.

[0188] Comparative Example 5:

[0189] Comparative Example 5 provides a cylindrical lithium-ion battery including a negative current collector 400 that differs from Example 1 in that S4c / S4a = 0.5%.

[0190] Comparative Example 6:

[0191] Comparative Example 6 provides a cylindrical lithium-ion battery including a negative current collector 400 that differs from Example 1 in that S4c / S4a = 8%.

[0192] Comparative Example 7:

[0193] Comparative Example 7 provides a cylindrical lithium-ion battery including a negative current collector 400 that differs from Example 1 in that L4b / L4a = 12%.

[0194] Comparative Example 8:

[0195] Comparative Example 8 provides a cylindrical lithium-ion battery including a negative current collector 400 that differs from Example 1 in that L4b / L4a = 46%.

[0196] Comparative Example 9:

[0197] Comparative Example 9 provides a cylindrical lithium-ion battery including a negative current collector 400 that differs from Example 1 in that H4b / H4a = 35%.

[0198] Comparative Example 10:

[0199] Comparative Example 10 provides a cylindrical lithium-ion battery including a negative current collector 400 that differs from Example 1 in that H4b / H4a = 68%.

[0200] Comparative Example 11:

[0201] Comparative Example 11 provides a cylindrical lithium-ion battery including a negative current collector 400 that differs from Example 1 in that S4b / S4a = 4.1%, H4c / H4a = 20%.

[0202] Comparative Example 12:

[0203] Comparative Example 12 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that: S4b / S4a = 8.3% and H4c / H4a = 45%.

[0204] Comparative Example 13:

[0205] Comparative Example 13 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that: S4b / S4a = 2.6% and H4d = 1.25mm.

[0206] Comparative Example 14:

[0207] Comparative Example 14 provides a cylindrical lithium-ion battery including a negative electrode current collector 400, which differs from Example 1 in that: S4b / S4a = 14.8% and H4d = 6.5mm.

[0208] Table 2 below evaluates the following parameters for the negative electrode current collector 400 fabricated in the above embodiments and comparative examples: the number of folds (C) at which the third disk body breaks after being folded, the time required for electrolyte injection into the battery (t), the maximum temperature of the solder joint between the third disk body and the core (TMax), and the battery internal resistance (R). Wherein:

[0209] The specific test method for determining the number of folds (C) required for the third disc to break after folding is as follows: Take the negative electrode current collector 400, cut the connection between the third disc 410 and the flange 420 with scissors, remove the flange 420, and fold and unfold along the line connecting the auxiliary hole 412 and the second central hole 411 of the third disc 410 as one fold. Repeat this process multiple times until the connection between the second notch 413 and the second central hole 411 is completely broken. Record the number of folds. For each fold, both halves must be completely joined together, and then the folded disc must be opened to 180°.

[0210] The specific test method for the time (t) required to inject electrolyte into the battery is as follows: The negative electrode current collector 400 fabricated in the above embodiments and comparative examples is installed inside the battery. Following the normal cell 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 of the grooving. The sealing ring below the holding cup is completely flush with the groove depth end face. Then, electrolyte injection is performed. First, a negative pressure is drawn to -90KPa inside the holding cup. Electrolyte can be observed inside the holding cup. As the electrolyte level decreases, the electrolyte flows into the battery. After maintaining this position for 40 seconds, positive pressure injection is applied, and nitrogen gas is introduced into the battery to gradually create a positive pressure of 0.8 MPa. The electrolyte in the holding cup continues to flow into the battery, and the electrolyte level in the holding cup gradually decreases. Then, the system is adjusted to negative pressure injection, and this cycle of positive and negative pressure injection is repeated until all the electrolyte in the holding cup has flowed into the battery. The time taken for the electrolyte level in the holding cup to drop to 0 is recorded.

[0211] The specific test method for the maximum temperature (TMax) of the third disc body and the welding mark of the core is as follows: the negative electrode current collecting disc 400 prepared in the above examples and comparative examples is assembled into an experimental cylindrical lithium ion battery, a through hole with a diameter of 3 mm is drilled on the negative electrode cover plate 600 of the experimental cylindrical lithium ion battery, the temperature control wire is passed through the through hole and attached to the welding mark of the welding between the negative electrode current collecting disc 400 and the negative electrode end 220 of the core 300, the negative electrode cover plate 600 is sealed after liquid injection according to the normal sample preparation process, and formation and capacity distribution are performed to prepare a qualified cylindrical lithium ion battery, 10 cycles of charge and discharge at a large rate of 3C are performed, and the temperature data of the welding area collected by the temperature control wire is obtained after 10 cycles of charge and discharge. The maximum value Tmax in the fluctuation range of the temperature in 10 cycles is taken and recorded.

[0212] The specific test method for the battery internal resistance (R) is as follows: the negative electrode current collecting disc 400 and the core 300 prepared in the above examples and comparative examples are welded and then placed in the shell 100, welding is performed according to the normal process, the battery is of a ternary high-nickel system, the ratio, electrolyte, positive and negative electrode formula, and material selection are consistent, the shell wall of the shell 100 is penetrated and welded with the flange 420 of the negative electrode current collecting disc 400, the welding parameters are as follows: the welding focal length is 0, the welding speed is 160 mm / s, and the welding power is 330 W. After the welding mark with a width of 0.6 mm is welded along the arc length of the flange 420, the subsequent liquid injection, sealing, and formation and capacity distribution are performed, and the qualified cylindrical lithium ion battery is prepared for offline testing of the internal resistance.

[0213] Table 2

[0214]

[0215]

[0216] As can be seen from Table 2, the range of S4b / S4a is set to 2% to 10%, the range of S4c / S4a is set to 1% to 3%, the range of S4d / S4a is set to 9% to 21%, the range of H4b / H4a is set to 42% to 58%, the range of H4c / H4a is set to 25% to 38%, the range of H4d is set to 2 to 5 mm, the range of L4b / L4a is set to 18% to 36%, the liquid injection time is usually 705 to 708 seconds, the folding number is usually 11, the maximum temperature rise of the welding position is 117° to 118°, and the internal resistance of the battery is 2.7 mΩ. It can be seen that in the above numerical range, the structural strength, the liquid injection rate, the welding temperature rise, and the welding internal resistance of the negative electrode current collecting disc can be well balanced, thereby effectively improving the safety and charge-discharge performance of the battery and reducing the production cost of the battery.

[0217] As shown in Table 2, if S4b / S4a is too large (the depth of the second notch 413 is increased and the arc length of the second notch 413 is increased), although the liquid injection rate can be increased, the welding temperature of the third disc body 410 and the winding core 300 will be significantly increased, and the battery internal resistance will be increased; on the contrary, if S4b / S4a is too small, the liquid injection rate will be reduced. Therefore, by setting S4b / S4a in a reasonable range, the liquid injection rate of the negative current collector 400, the welding temperature, and the battery internal resistance can be balanced.

[0218] As shown in Table 2, if S4c / S4a is too large, although the liquid injection rate can be increased, the structural strength of the negative current collector 400 will be reduced to some extent, the welding temperature of the third disc body 410 and the winding core 300 will be increased, and the battery internal resistance will be increased; on the contrary, if S4c / S4a is too small, although the structural strength of the negative current collector 400 can be improved and the battery internal resistance and the welding temperature can be ensured to be within a reasonable range, the liquid injection rate will be reduced. Therefore, by setting S4c / S4a in a reasonable range, the structural strength of the negative current collector 400, the liquid injection rate, the welding temperature, and the battery internal resistance can be balanced.

[0219] As shown in Table 2, if S4d / S4a is too large, although the liquid injection rate can be increased, the structural strength of the negative current collector 400 will be significantly reduced, the welding temperature of the third disc body 410 and the winding core 300 will be increased, and the battery internal resistance will be increased; on the contrary, if S4d / S4a is too small, although the structural strength of the negative current collector 400 can be improved and the battery internal resistance and the welding temperature can be ensured to be within a reasonable range, the liquid injection rate will be reduced. Therefore, by setting S4d / S4a in a reasonable range, the structural strength of the negative current collector 400, the liquid injection rate, the welding temperature, and the battery internal resistance can be balanced.

[0220] As shown in Table 2, if H4b / H4a is too large or too small, the battery internal resistance and the welding temperature of the third disc body 410 and the winding core 300 will be increased to some extent. Therefore, by setting H4b / H4a in a reasonable range, the welding temperature of the negative current collector 400 and the battery internal resistance can be balanced.

[0221] As shown in Table 2, under the condition that the maximum depth H4d of the second notch 413 is unchanged, if H4c / H4a is too large, the opening area of the second notch 413 will be increased, so that although the liquid injection rate can be increased, the welding temperature of the third disc body 410 and the winding core 300 will be increased to some extent, and the battery internal resistance will be increased; on the contrary, if H4c / H4a is too small, the opening area of the second notch 413 will be reduced, so that although the welding temperature of the third disc body 410 and the winding core 300 and the battery internal resistance can be ensured to be within a reasonable range, the liquid injection rate will be reduced to some extent.

[0222] As shown in Table 2, if H4d is too large when the arc length of the second notch 413 remains constant, the opening area of ​​the second notch 413 will increase. This will increase the liquid injection rate, but the temperature rise at the welding point between the third disc 410 and the core 300 will increase to some extent, and the internal resistance of the battery will also increase. Conversely, if H4d is too small, the opening area of ​​the second notch 413 will decrease. This will ensure that the temperature rise at the welding point between the third disc 410 and the core 300 and the internal resistance of the battery are within a reasonable range, but it will reduce the liquid injection rate to some extent.

[0223] As shown in Table 2, both excessively large and small L4b / L4a ratios will significantly reduce the structural strength of the negative electrode manifold 400. Furthermore, if L4b / L4a is too large, it will increase the injection time to some extent, thus affecting the injection rate. Therefore, setting L4b / L4a within a reasonable range can ensure that the structural strength of the negative electrode manifold 400 meets the requirements while balancing the injection rate.

Claims

1. A cylindrical lithium-ion battery, characterized by, The application relates to a battery shell, which comprises a shell (100), a positive electrode current collector (200), a winding core (300) and a negative electrode current collector (400) arranged in the shell (100), the shell (100) is provided with a pole (500) on the positive electrode side, the pole (500) is provided with a liquid injection hole (510) penetrating through, wherein: The positive electrode current collector (200) comprises a first disc body (210) located at the center and a second disc body (220) connected with the edge of the first disc body (210) and extending radially outward, the first disc body (210) is welded with the pole (500), the center of the first disc body (210) is provided with a first center hole (211) penetrating through, the first center hole (211) is communicated with the liquid injection hole (510), the second disc body (220) comprises a connecting part (221) and a welding part (222) connected with each other, the welding part (222) is connected to the edge of the first disc body (210) from the connecting part (221), the connecting part (221) is provided with a fuse slot (230) at the edge in the length direction, the welding part (222) is welded with the positive electrode of the winding core (300), the edge of the second disc body (220) is provided with a plurality of first notches (250); The negative electrode current collector (400) comprises a third disc body (410) and a flange (420) protruding from one side of the outer periphery of the third disc body (410), the third disc body (410) is welded with the negative electrode of the winding core (300), the shape of the third disc body (410) is a closed figure composed of a plurality of circular arc edges (414) and a plurality of concave edges (415) connected in sequence, the flange (420) is arranged on the circular arc edge (414), the third disc body (410) forms a second notch (413) at the concave edge (415), the center of the third disc body (410) is provided with a second center hole (411) penetrating through, the area of the third disc body (410) is S4a, the total area of the second notch (413) is S4b, the range of S4b / S4a is 2% to 10%, the circumference of the third disc body (410) is H4a, the total arc length of the flange (420) is H4b, and the range of H4b / H4a is 42% to 58%.

2. The cylindrical lithium-ion battery of claim 1, wherein, The area of the first disc body (210) is S2a, the area of the first center hole (211) is S2b, and the range of S2b / S2a is 4.2% to 8.6%; the area of the second center hole (411) is S4c, and the range of S4c / S4a is 1% to 3%.

3. The cylindrical lithium-ion battery of claim 1, wherein, The first disc body (210) is higher than the second disc body (220) along the thickness direction of the positive electrode current collector disc, the surface of the side of the first disc body (210) higher than the second disc body (220) has a height difference of H2a from the surface of the same side of the second disc body (110), and H2a ranges from 0.6 mm to 1.4 mm; the third disc body (410) is further provided with a plurality of auxiliary holes (412) located at the outer periphery of the second center hole (411), the total area of the plurality of auxiliary holes (412) is S4d, and S4d / S4a ranges from 9% to 21%.

4. The cylindrical lithium-ion battery of claim 1, wherein, The connecting part (221) has a first width W2a, and has a second width W2b in the area where the fuse groove (230) is opened, and W2b / W2a ranges from 42% to 63%; the connecting part (221) has a first side (231) extending along the length direction for forming the fuse groove (230), and the length of the first side (231) is L2a, and L2a ranges from 2 mm to 4 mm.

5. The cylindrical lithium-ion battery according to any one of claims 1 to 4, characterized in that, The connecting part (221) comprises: a plurality of first connecting parts (2211) arranged at intervals along the circumference of the first disc body (210) and extending radially outward from the edge thereof, and the fuse groove (230) is arranged in the first connecting part (2211); a second connecting part (2212) formed by extending the outer end of each first connecting part (2211) to both sides in the circumferential direction; wherein the welding part (222) has a plurality of welding parts (222) arranged one by one in the area defined by the two adjacent first connecting parts (2211) and the second connecting part (2212), and extending radially inward from the inner edge of the second connecting part (2212); The circumference of the third disc body (410) is H4a, the total arc length of the second notch (413) is H4c, and H4c / H4a ranges from 25% to 38%.

6. The cylindrical lithium-ion battery of claim 5, wherein, The edges on both sides of the welding part (222) and the inner edge of the second connecting part (2212) define a slit (240) extending in the circumferential direction, the circumference of the outer edge of the second connecting part (2212) is L2b, the total arc length of the slit (240) is L2c, and L2c / L2b ranges from 43% to 58%; the shape of the inner recessed edge (415) is arc-shaped, the maximum depth of the second notch (413) is H4d, and H4d ranges from 2 mm to 5 mm.

7. The cylindrical lithium-ion battery of claim 5, wherein, The first notch (250) is arranged at the outer edge of the second connecting part (2212) corresponding to the position of 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 notch (250) is L2d, and the range of L2d / L2b is 4%-9%; the radius of the third disc body (410) is L4a, and the third disc body (410) is further provided with a plurality of auxiliary holes (412) located at the outer periphery of the second central hole (411), the distance from the inner edge of the auxiliary hole (412) to the center of the second central hole (411) is L4b, and the range of L4b / L4a is 18%-36%.

8. The cylindrical lithium-ion battery of claim 7, wherein, The maximum depth of the first notch (250) is L2f, and the range of L2f is 0.9-2.1 mm; the auxiliary hole (412) is a waist-shaped hole, and the long axis direction of the auxiliary hole (412) is consistent with the radial direction of the third disc body (410).

9. The cylindrical lithium-ion battery of claim 6, wherein, The width of the slit (240) in the radial direction is L2e, and the range of L2e is 0.4-1.5 mm; the third disc body (410) and the flange (420) are integrally connected.

10. The cylindrical lithium-ion battery of claim 6, wherein, The second connecting part (2212) has a width W2c in the radial direction corresponding to the area of the slit (240), and the range of W2c is 1-3 mm; the third disc body (410) is further provided with an auxiliary hole (412) located at the outer periphery of the second central hole (411), the number of the arcuate edges (414), the concave edges (415) and the auxiliary holes (412) is 4, the four arcuate edges (414) and the four auxiliary holes (412) are arranged one by one, and the midpoint of the corresponding arcuate edge (414), the center of the auxiliary hole (412) and the center of the second central hole (411) are collinear.

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