Cylindrical lithium battery

Abstract

A cylindrical lithium battery. A necking groove (1123) is formed on a casing (110) of the cylindrical lithium battery, the height H2 of the necking groove (1123) is 0.1%-1% of the height H1 of the casing (110), and the depth H3 of the necking groove (1123) in the radial direction is 5%-10% of the outer diameter D1 of the casing (110). The sum of the areas of all second holes (1316) of a positive electrode current collector (130) in the cylindrical lithium battery is 0.9-1.5 times the area of a first hole (1315), a fuse groove (1321) is formed on a tail body portion (132) of the positive electrode current collector (130), the distance between the center of the fuse groove (1321) and the end of the tail body portion (132) distant from a disc body portion (131) is 68%-78% of the length of the tail body portion (132), and the minimum cross-sectional area S2 of the tail body portion (132) at the position of the fuse groove (1321) is 45%-65% of the overall cross-sectional area S1 of the tail body portion (132). A negative electrode current collector (150) in the cylindrical lithium battery is provided with a raised platform (1521) having a flat surface, and the flatness of the surface of the raised platform (1521) ranges from 0.01 mm to 0.05 mm. By reasonably designing the necking groove (1123), the positive electrode current collector (130), and the negative electrode current collector (150), the cylindrical lithium battery achieves a balance among electrolyte injection performance, safety, weldability and other aspects.

Description

A cylindrical lithium battery Technical Field

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

[0002] In related technologies, cylindrical batteries are typically packaged in a cylindrical steel casing. The bare cell is manufactured using a winding process to form a cylindrical core. The cap is located at the top of the battery and is connected to the positive electrode in the core through a positive current collector. The steel casing is connected to the negative electrode in the core through a negative current collector. The positive and negative current collectors allow electrons to be transferred longitudinally from the current collector to the current collector. By increasing the current conduction area and shortening the current conduction distance, the charge and discharge performance of cylindrical lithium batteries can be effectively improved.

[0003] As mentioned earlier, cylindrical lithium batteries involve various structural components such as steel casings, cores, positive current collectors, and negative current collectors, as well as electrical connectors. The assembly process also involves multiple steps such as welding and electrolyte injection. In order to achieve a better assembly effect and to make the final battery performance reach its best state, many factors need to be considered in the design of the above components. For example, taking the positive current collector as an example, its electrical transmission performance, electrolyte injection, safety protection when the battery is overheated, and welding processability are all factors to consider. Therefore, how to reasonably design cylindrical lithium batteries to achieve a balance in terms of electrolyte injection performance, safety, and weldability is an urgent problem to be solved. Summary of the Invention

[0004] This application provides a cylindrical lithium battery to at least address the technical problems of imbalances in the assemblability, safety, and battery performance of existing cylindrical lithium batteries.

[0005] The first aspect of this application provides a cylindrical lithium battery, including a casing, a cap, a positive electrode current collector, a winding core, and a negative electrode current collector, wherein:

[0006] The core has a positive electrode flattening structure and a negative electrode flattening structure. Both the positive electrode flattening structure and the negative electrode flattening structure are formed by flattening a full-electrode tab stacking structure. The positive electrode flattening structure is connected to the cap through the positive electrode current collector, and the negative electrode flattening structure is connected to the outer shell through the negative electrode current collector.

[0007] The outer shell includes a bottom and a sidewall. The top of the sidewall has an opening. The sidewall is circumferentially concave near the opening to form a neck. The outer surface of the sidewall forms a necking groove at the neck. The core is located within the area defined by the neck and the bottom of the outer shell. The height H2 of the necking groove is 0.1%-1% of the height H1 of the outer shell. The radial depth H3 of the necking groove is 5%-10% of the outer diameter D1 of the outer shell.

[0008] The positive electrode current collector includes a disk body and a tail body connected to each other. The disk body is connected to the positive electrode flattening structure, and the tail body is connected to the cap. The disk body has a circular first hole at its center, and at least one circular second hole is provided around the first hole. The sum of the areas of all the second holes is 0.9-1.5 times the area of ​​the first hole. The tail body has at least one fuse groove. The tail body has an overall cross-sectional area S1 at the position other than the fuse groove. The tail body has a minimum cross-sectional area S2 at the position of the fuse groove. The minimum cross-sectional area S2 is 45%-65% of the overall cross-sectional area S1.

[0009] The negative electrode current collector has a first side and a second side. The first side is connected to the negative electrode. The center of the second side is provided with a flat raised platform. The raised platform is connected to the inner surface of the bottom of the shell. The flatness of the raised platform surface is 0.01-0.05mm.

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

[0011] First, by rationally designing the height and depth of the necking groove on the outer casing, the internal space utilization of the casing can be effectively improved to increase the energy density of the battery. In addition, the structural strength of the necking groove and the sealing process can also be improved.

[0012] Secondly, by rationally designing the dimensions of the first and second holes on the positive electrode current collector through which the electrolyte permeates, a balance can be achieved between electrolyte injection efficiency and weldable area, while ensuring welding safety. Furthermore, the rationally designed size of the fuse groove located in the tail section ensures current cutoff in the event of battery thermal runaway, thus achieving a balance between battery safety and low internal resistance in the tail section.

[0013] Furthermore, by setting a flat raised platform on the side where the negative current collector connects to the inner surface of the shell bottom, the small area of ​​the raised platform ensures good surface flatness. The surface of the raised platform can fit well with the inner surface of the shell bottom, effectively avoiding welding quality problems such as incomplete welding.

[0014] In summary, by rationally designing the necking, positive current collector, and negative current collector, the cylindrical lithium battery of this application achieves a balance in multiple aspects such as liquid injection performance, safety, and solderability, and can provide battery performance.

[0015] In one possible implementation, the core has a through core hole, the diameter of the first hole D4 being 1.4-1.8 times the diameter of the core hole D7; the raised platform is circular and located at the center of the second side, the diameter of the raised platform D9 being 28%-38% of the diameter of the negative electrode current collector D8.

[0016] By rationally designing the diameter range of the first hole, a balance can be achieved between injection efficiency and weldable area, while ensuring welding safety. Furthermore, by rationally designing the size of the raised platform, the welding effect and weldability to the shell bottom can be improved.

[0017] In one possible implementation, the diameter D3 of the disk body is 80%-95% of the core diameter D6; the diameter D8 of the negative electrode current collector is 90%-98% of the core diameter D6.

[0018] By rationally designing the size of the positive and negative current collectors, the welding area between the two and the core can be effectively increased, thereby improving the welding effect and facilitating the design of welding tools.

[0019] In one possible implementation, the diameter D5 of the second hole is 50%-70% of the diameter D4 of the first hole; the height difference H8 between the surface of the raised platform and the surface of the first side is 18%-30% of the thickness T5 of the negative electrode collector.

[0020] By rationally designing the size of the first and second holes of the positive electrode current collector, the liquid injection efficiency and the welding effect with the positive electrode can be balanced. At the same time, by rationally designing the height of the raised platform, the machinability and usage requirements of the negative electrode current collector are met, while the negative electrode current collector does not occupy too much of the internal longitudinal space of the housing, thereby improving the space utilization rate of the housing.

[0021] In one possible implementation, the disk portion is a closed axisymmetric shape formed by connecting the first side, an arc, a second side, and a third side end to end. The tail portion is a closed axisymmetric shape formed by connecting the third side, a fifth side extending along the length of the tail, a fourth side away from the disk portion, and a sixth side extending along the length of the tail end. The two ends of the fifth side are connected to the fourth side and the first side, respectively, and the two ends of the sixth side are connected to the fourth side and the second side, respectively. The raised platform is integrally formed by stamping the negative electrode current collector. A recess is formed on the first side at a position corresponding to the raised platform. A welding area is formed on the first side around the recess. The surface of the welding area abuts against the negative electrode flattening structure.

[0022] By rationally designing the shapes of the disk body and tail section, the manufacturing and assembly of the positive current collector are facilitated. Meanwhile, the negative current collector and the raised platform are formed through appropriate stamping, resulting in high dimensional accuracy and good surface quality, which facilitates welding with the core and outer shell.

[0023] In one possible implementation, the length L4 of the tail portion is 85%-95% of the diameter D3 of the disc portion; the distance L5 between the center of the fuse groove and the end of the tail portion away from the disc portion is 68%-78% of the length L4 of the tail portion.

[0024] By rationally designing the length of the tail section, a balance is achieved between welding processability and battery safety. At the same time, the tail section's fusion groove is positioned so that the tail section and the cap can be welded smoothly.

[0025] In one possible implementation, the disc portion has a central angle A, and 40°≤∠A≤60°, wherein the central angle A has the center of the circle corresponding to the arc as its vertex, and the two sides pass through the endpoints of the first side away from the arc and the second side away from the arc, respectively; the first width W2 of the tail portion is D3*sin(∠B / 2), and 20°≤∠B≤40°, wherein ∠B has the center of the circle corresponding to the arc as its vertex, and the two sides pass through the intersections of the fifth side and the sixth side with the complete circle containing the arc, respectively.

[0026] By designing a reasonable center angle A, a large solderable area can be ensured even after the hole is opened in the disk section. Simultaneously, a well-designed tail section width helps retain the largest possible solderable area while ensuring sufficient mechanical strength to prevent breakage during production. Furthermore, it facilitates rapid electron passage and reduces battery internal resistance.

[0027] In one possible implementation, the second width W3 of the tail portion at the fuse groove is 3 / 8 to 3 / 4 of the first width W2; the dimension L6 of the fuse groove along the length direction of the tail portion is 0 < L6 ≤ W2.

[0028] When the second width W2 is too small, the tail section lacks sufficient strength at the fuse groove, making it prone to breakage during bending. Conversely, when the second width W2 is too large, the tail section cannot fuse quickly, posing a safety hazard. By rationally designing the width of the tail section at the fuse groove, the mechanical performance of the tail section and the safety performance of the battery can be balanced. Furthermore, if L5 is too large, the fuse location of the tail section becomes difficult to determine, increasing the battery's safety risk. Conversely, if L5 is too small, the fuse sensitivity of the tail section increases, potentially leading to fuse failure even at a safe current. Rationally designing the dimensions of the fuse groove helps improve battery safety.

[0029] In one possible implementation, the angle θ1 between the fifth side and the first side is 45-90°, and the angle θ2 between the sixth side and the second side is 45-90°.

[0030] By rationally designing the angle θ1 between the fifth side and the first side, and the angle θ2 between the sixth side and the second side, the mechanical performance of the positive current collector and the size of the weldable area of ​​the plate body can be balanced.

[0031] In one possible implementation, the neck includes a first wall portion and a second wall portion extending toward the center of the outer shell. The neck also includes a connecting portion for connecting the first wall portion and the second wall portion. The outer surfaces of the first wall portion, the second wall portion, and the connecting portion together define a necking groove. The first wall portion and the second wall portion are both inclined at a certain angle to the bottom of the shell. The cap includes an explosion-proof valve plate and a terminal plate stacked together. The tail portion is connected to the bottom of the terminal plate. The explosion-proof valve plate is provided with a first groove and a second groove. The first groove is a closed circle with its ends connected. The second groove is a line segment. The first groove and the second groove intersect.

[0032] By setting the first and second walls constituting the neck to be inclined towards the bottom of the casing, the neck has a certain amount of sag allowance. Therefore, it is convenient to design the grooving process in the preceding grooving process, which facilitates the formation of the required neck structure in the sealing process. Simultaneously, by setting the first and second notches on the explosion-proof valve plate, when the internal pressure of the battery rises sharply due to abnormal conditions such as overheating or short circuits, either the pressure value in the edge region or the central region will reach the preset value first, and one of the first and second notches will break first. This allows the battery to release pressure in a timely manner. Furthermore, since the first and second notches intersect, the breaking of either the first or second notch will also cause the other to break, thereby expanding the opening area of ​​the explosion-proof valve plate and improving the pressure relief effect. Thus, when the gas pressure inside the battery exceeds the preset value, the explosion-proof valve plate can open quickly and effectively to release the pressure, thereby improving battery safety.

[0033] In one possible implementation, the larger of the angle between the first wall portion and the bottom of the shell and the angle between the second wall portion and the bottom of the shell is α, and the range of α is α < 10°; the explosion-proof valve plate is provided with a thinning portion extending in the radial direction, the first groove is provided within the radial range of the thinning portion, the thickness of the thinning portion is T3, the depth of the first groove is H4, and the range of H4 / T3 is 30%-60%.

[0034] By rationally designing the included angle α, the design difficulty of the groove is reduced, while also minimizing the impact of the necking on the lower cavity space and ensuring the sealing effect of the cap. Simultaneously, by rationally setting the thickness of the thinned portion and the depth of the first notch, the first notch can be effectively made to break when the opening conditions are met, allowing the battery to depressurize. This also ensures that the explosion-proof valve plate has sufficient strength and rigidity, facilitating processing and assembly.

[0035] In one possible implementation, the range of α is 1-5°; the width of the thinned portion is W1, and the range of W1 is 3-8 mm.

[0036] By rationally designing the included angle α, the design difficulty of the groove is reduced, while also minimizing the impact of the necking on the lower cavity space and ensuring the sealing effect of the cap. Simultaneously, by rationally designing the width of the thinned section, the first notch can be effectively made to break when the opening conditions are met, allowing the battery to release pressure. This also ensures that the explosion-proof valve plate has sufficient strength and rigidity, facilitating processing and assembly.

[0037] In one possible implementation, the minimum wall thickness of the neck is T2, the wall thickness of the sidewall is T1, and the range of T2 / T1 is 80% or more; the diameter D2 of the first notch is equal to the length L2 of the second notch.

[0038] By rationally designing the wall thickness at the thinnest point of the neck, the pressure resistance of the casing can be ensured to meet the requirements. Simultaneously, by setting the diameter of the first notch to be equal to the length of the second notch, the second notch divides the first notch into two symmetrical parts, facilitating processing. Furthermore, after the explosion-proof valve plate is assembled into the cylindrical lithium battery, the second notch is located in the central region of the cylindrical lithium battery, allowing the explosion-proof valve plate to open smoothly to release pressure.

[0039] In one possible implementation, the range of T2 is 0.1-0.2 mm; the bottom of the first notch and the second notch are provided with chamfered portions, and the radii of the chamfered portions are the same, the radius of the chamfered portions is R, and the range of R is 0.05-0.15 mm.

[0040] By rationally designing the wall thickness at the thinnest point of the neck, the pressure resistance of the outer casing can be ensured to meet the requirements. At the same time, by rationally setting the radius of the chamfer, stress concentration at the bottom of the first and second notches can be effectively reduced, while also reducing processing difficulty and manufacturing costs.

[0041] In one possible implementation, the distance L1 from the lowest point of the constricted neck to the upper surface of the shell bottom is 90%-98% of the height H1 of the shell; the depth H4 of the first notch is less than the depth H5 of the second notch, and the depth of the middle part of the second notch is greater than the depth of both ends.

[0042] By rationally designing the distance between the bottom of the neck and the bottom of the casing, the utilization rate of the internal space of the casing can be effectively improved, thereby increasing the energy density of the battery. At the same time, it can also ensure the structural strength of the neck and the sealing process. Furthermore, by increasing the depth of the second notch, the impact of the increased thickness of the explosion-proof valve plate in the middle region on the second notch can be reduced, ensuring that the explosion-proof valve plate opens smoothly at the second notch. Additionally, by setting the depth of the second notch to be greater in the middle than at both ends (i.e., deeper in the middle and shallower at both ends), the impact of the stepped thickness change of the explosion-proof valve plate in the middle region can be reduced, ensuring that the explosion-proof valve plate opens smoothly at the second notch.

[0043] In one possible implementation, the full-tab stack structure includes a current collector substrate, which is divided along its width into a material area for coating a polar material and an anode area. Both the material area and the anode area extend along the length of the current collector substrate. The current collector substrate has a plurality of anodes spaced apart along its length in the anode area. The width of the side of the anode facing the material area is W4, and the distance between the sides of two adjacent anodes facing the material area is W5. The range of W5 / W4 is 20%-30%, and the shape of the anode is a parallelogram. The angle β between the side of the anode connected to the side facing the material area and the width direction of the current collector substrate is 14-18°.

[0044] By optimizing the width W2 and spacing W3 of the die-cut tabs, and controlling the ratio of W3 / W2 within the range of 20%-30%, the tension of the tabs is improved. This allows the tabs to withstand the pressure of subsequent flattening operations, reducing debris generation and the possibility of debris falling into the battery, thus lowering the probability of short circuits. Furthermore, the appropriate tab width W2 and spacing W3 design ensures that the density of the flattened tabs is not too high, maintaining effective gaps between them, which facilitates electrolyte wetting and improves battery cycle performance. Additionally, by selecting an angle β between the beveled edge of the tab and the width direction of the current collector substrate at 14-18°, the tabs can still fit together as closely as possible after flattening, resulting in a suitable density. This ensures sufficient electrolyte wetting while also considering welding performance and reducing debris generation, thereby improving battery safety and cycle performance.

[0045] In one possible implementation, a connecting area is further provided between the material area and the tab area. The distance between the side of the tab connected to the connecting area and the material area is H7, and the distance between the side of the tab away from the material area and the material area is H6. The range of H7 / H6 is 10%-20%.

[0046] By setting up a connection area and rationally designing the dimensions of the connection area and the tab, the flattened positive electrode flattening structure and negative electrode flattening structure formed by the flattening have good welding performance, current carrying performance and reliability.

[0047] In one possible implementation, the range of H7 is 0.4-0.6 mm, and the range of W4 is 1.5-2.2 mm.

[0048] By rationally designing the distance between the edge connecting the electrode tab and the connecting area and the material area, the problem of the material area protruding outwards and the welding effect and current overcurrent effect are balanced. At the same time, by rationally setting the electrode tab width, sufficient tension can be ensured for the electrode tab, reducing chipping during the flattening process, preventing scattering and chipping, and improving the flattening effect to ensure welding performance.

[0049] In one possible implementation, the length of the plurality of tabs in the tab region along the length direction of the current collector substrate is less than the length L7 of the material region. One end of the tab region has a first cut-off area, and the other end has a second cut-off area. The length of the first cut-off area along the length direction of the current collector substrate is L8, and the range of L8 / L7 is 5%-15%. The length of the second cut-off area along the length direction of the current collector substrate is L9, and the range of L9 / L7 is 10%-20%.

[0050] By setting a first or second cut-off area, it is beneficial to reduce the blockage of the core center hole and prevent the tabs from protruding outwards during subsequent winding and flattening, thereby facilitating liquid injection and core insertion into the shell.

[0051] In one possible implementation, the range of L8 is 105-130 mm, and the range of L9 is 175-205 mm.

[0052] By rationally designing the lengths of the first and second cutting zones, it is beneficial to reduce the blockage of the core center hole and prevent the tabs from protruding outwards during subsequent winding and flattening, thereby facilitating liquid injection and core insertion into the shell. Attached Figure Description

[0053] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0054] Figure 1 is an exploded view of a cylindrical lithium battery according to an embodiment of this application;

[0055] Figure 2 is a schematic diagram of the state of the outer casing of a cylindrical lithium battery after sealing according to an embodiment of this application;

[0056] Figure 3 is a partial schematic diagram of point A in Figure 2;

[0057] Figure 4 is a cross-sectional schematic diagram of the cap in a cylindrical lithium battery according to an embodiment of this application;

[0058] Figure 5 is a top view of an explosion-proof valve plate in a cylindrical lithium battery according to an embodiment of this application;

[0059] Figure 6 is a cross-sectional view of the explosion-proof valve plate in Figure 5;

[0060] Figure 7 is a partial schematic diagram of point B in Figure 6;

[0061] Figure 8 is a partial schematic diagram of point C in Figure 6;

[0062] Figure 9 is a top view of the positive electrode current collector in a cylindrical lithium battery according to an embodiment of this application, wherein the tail portion is in an unfolded state.

[0063] Figure 10 is a schematic diagram of the connection between the positive current collector and the winding core in Figure 9;

[0064] Figure 11 is a schematic diagram of the tail section of the positive current collector in Figure 9;

[0065] Figure 12 is a schematic diagram of the cross section along direction AA in Figure 11;

[0066] Figure 13 is a schematic diagram of the tail section of the positive current collector in Figure 9;

[0067] Figure 14 is a schematic diagram of the connection between the core and the positive current collector and the negative current collector in a cylindrical lithium battery according to an embodiment of this application.

[0068] Figure 15 is a schematic diagram of the core in a cylindrical lithium battery before winding, according to an embodiment of this application.

[0069] Figure 16 is a schematic diagram of the full tab stacking structure of the core in a cylindrical lithium battery according to an embodiment of this application;

[0070] Figure 17 is a partial schematic diagram of point D in Figure 16;

[0071] Figure 18 is a schematic diagram of the flattened full-teg stacked structure in Figure 16;

[0072] Figure 19 is a partial schematic diagram of point E in Figure 18;

[0073] Figure 20 is a schematic diagram of the structure in which the negative electrode current collector is connected to the core and the bottom of the casing in a cylindrical lithium battery according to an embodiment of this application;

[0074] Figure 21 is a cross-sectional schematic diagram of the negative electrode current collector in Figure 20;

[0075] Figure 22 is a partial schematic diagram of point F in Figure 21.

[0076] Reference numerals: 110-Outer shell, 111-Shell bottom, 112-Side wall, 1121-Neck, 1121a-First wall portion, 1121b-Second wall portion, 1121c-Connecting portion, 1122-Rolled edge, 1123-Necked groove, 113-Inner cavity, 1131-Upper cavity, 1132-Lower cavity, 114-Opening; 120-Cap, 121-Top cover, 122-Explosion-proof valve plate, 1221a-First notch, 1221b-Second notch, 1222-Thinning portion, 1223-Groove, 1224-Welding platform, 123-Insulating plate, 124-Terminal plate, 125-Insulating ring; 130-Positive current collector, 131-Disc body portion, 1311-First side, 1312-Arch, 1313-Second side, 1314- Third side, 1315-First hole, 1316-Second hole, 132-Tail body, 1321-Fuse groove, 1322-Fifth side, 1323-Sixth side, 1324-Fourth side; 140-Core, 141-Positive electrode flattening structure, 142-Negative electrode flattening structure, 143a-First diaphragm, 143b-Second diaphragm, 144-Current collector substrate, 144a-Positive electrode sheet, 144b-Negative electrode sheet, 1441-Material area, 1442-Electrode tab area, 1443-Electrode tab, 14431-Side connecting electrode tab and connecting area, 14432-Side connecting electrode tab towards material area, 14433-Side of electrode tab away from material area, 1444-Connecting area, 1445-First cut-out area, 1446-Second cut-out area, 145-Core hole; 150 - Negative current collector, 151 - First side, 1511 - Recessed part, 1512 - Welding area, 152 - Second side, 1521 - Elevated platform. Detailed Implementation

[0077] The embodiments of this implementation are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this implementation, and should not be construed as limiting this implementation.

[0078] In the description of this embodiment, it should be understood that the orientation descriptions, such as up, down, front, back, left, right, etc., are based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this embodiment.

[0079] In the description of this embodiment, "several" means one or more, "multiple" means two or more, "greater than," "less than," and "exceeding" are understood to exclude the stated number, while "above," "below," and "within" are understood to include the stated number. The use of "first" and "second" in the description is merely for distinguishing technical features and should not be construed as indicating or implying relative importance, or implicitly indicating the number of indicated technical features, or implicitly indicating the order of the indicated technical features.

[0080] In the description of this embodiment, unless otherwise explicitly limited, terms such as setting, installing, and connecting should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this embodiment in conjunction with the specific content of the technical solution.

[0081] The cylindrical lithium battery provided in this application includes various size series, such as the 21 series (cylindrical lithium battery with an outer diameter of 21mm) and the 46 series (cylindrical lithium battery with an outer diameter of 46mm), and is not limited herein. Specifically, as shown in FIG1, the cylindrical lithium battery includes a casing 110, a cap 120, a positive current collector 130, a core 140, and a negative current collector 150. The positive terminal of the core 140 is connected to the cap 120 through the positive current collector 130, and the negative terminal of the core 140 is connected to the casing 110 through the negative current collector 150. Thus, the cap 120 serves as the positive terminal of the cylindrical lithium battery, and the casing 110 serves as the negative terminal of the cylindrical lithium battery for electrical connection with external electrical equipment.

[0082] The following is a detailed description of the casing 110.

[0083] As shown in Figures 1 and 2, the outer shell 110 is cylindrical in shape and is closed on the negative electrode side (lower part of the figure) and open on the positive electrode side (upper part of the figure). Specifically, the outer shell 110 includes a bottom 111 and a sidewall 112. The bottom 111 is circular, and the sidewall 112 extends upward along the edge of the bottom 111. The bottom 111 and the sidewall 112 together define an inner cavity 113. The top of the sidewall 112 has an opening 114 that communicates with the inner cavity 113.

[0084] Understandably, the inner cavity 113, defined by the bottom 111 and the sidewall 112, is also cylindrical, used to accommodate the cap 120 (whose top is exposed), the positive current collector 130, the core 140, and the negative current collector 150, which will be described below. Furthermore, by setting the outer casing 110 to be open at the top, i.e., by providing an opening 114 at the top of the outer casing 110, it is also convenient for the aforementioned components to enter the outer casing 110 through the opening 114.

[0085] It is understandable that the bottom of the shell 111 is in the shape of a thin circular plate, and the bottom surface of the negative electrode current collector 150 is in contact with the inner surface of the bottom of the shell 111, thereby forming a conductive connection between the two, thus connecting the outer shell 110 and the negative electrode of the core 140.

[0086] It is understandable that the outer casing 110 can be made of nickel-plated steel, which has advantages such as high pressure resistance. Of course, it is not limited to this; for example, it can also be made of aluminum. The following explanation takes the use of nickel-plated steel for the outer casing 110 as an example. It can be stamped from steel strip, which is simple to process and manufacture, easy to mass-produce, and can effectively reduce costs.

[0087] As shown in Figures 2 and 3, the sidewall 112 is circumferentially concave near the opening 114 to form a constricted neck 1121 for sealing the cap 120. This constricted neck 1121 divides the inner cavity 113 into an upper cavity 1131 and a lower cavity 1132. It can be formed by grooving and sealing processes. Furthermore, in the sealing process, in addition to the concave neck 1121, the sidewall 112 also forms a rolled edge 1122 at its top. This rolled edge 1122... The constricted neck 1121 and the side wall 112 together achieve a sealed connection to the cap 120. Specifically, the top surface of the constricted neck 1121 on one side of the upper cavity 1131 is used to receive the cap 120 and is in contact with the bottom of the cap 120. The inner wall surface of the part of the side wall 112 located between the constricted neck 1121 and the rolled edge 1122 is in contact with the outer peripheral surface of the cap 120, and the inner wall surface of the rolled edge 1122 is in contact with the top surface of the cap 120. Thus, the cap 120 completely closes the opening 114 and seals the negative electrode current collector 150, the rolled core 140, and the positive electrode current collector 130 in the lower cavity 1132, thereby forming a closed electrochemical system within the outer casing 110.

[0088] Specifically, the neck 1121 includes a first wall portion 1121a and a second wall portion 1121b, which are flat and parallel to each other and extend toward the center of the inner cavity 113, and a connecting portion 1121c for connecting the first wall portion 1121a and the second wall portion 1121b. In the direction shown in FIG2, the first wall portion 1121a is located above the second wall portion 1121b. The ends of the first wall portion 1121a and the second wall portion 1121b near the center of the inner cavity 113 are connected by the connecting portion 1121c. The outer surfaces of the first wall portion 1121a, the second wall portion 1121b, and the connecting portion 1121c together define a necking groove 1123. It can be understood that the inner surface, i.e., the top surface, of the first wall portion 1121a is used to receive the cap 120 and is in contact with the bottom of the cap 120.

[0089] Although the first wall portion 1121a, the second wall portion 1121b, and the connecting portion 1121c are described above as interconnected, it is understood that the first wall portion 1121a, the second wall portion 1121b, and the connecting portion 1121c are themselves part of the wall portion of the side wall 112. During the sealing process, the side wall 112 undergoes inward plastic deformation at the position corresponding to the neck 1121 to form the first wall portion 1121a, the second wall portion 1121b, and the connecting portion 1121c, that is, the first wall portion 1121a, the second wall portion 1121b, and the connecting portion 1121c are integral. Of course, in the preceding process before the sealing process, a groove can be cut at this position to form a groove, for example, by the feed motion of a cutting roller and the rotational motion of the outer shell 110, so that during sealing, the groove undergoes plastic deformation to form the required neck 1121.

[0090] In this embodiment, both the first wall portion 1121a and the second wall portion 1121b are flat, and they are inclined towards the bottom of the shell 111 along their concave direction. Specifically, when the first wall portion 1121a and the second wall portion 1121b are parallel to each other, the angle between the first wall portion 1121a or the second wall portion 1121b and the bottom of the shell 111 is α, satisfying α < 10°. It can be understood that in this case, since the first wall portion 1121a and the second wall portion 1121b are both flat and parallel to each other, that is, the central plane of the necking groove 1123 defined by the first wall portion 1121a, the second wall portion 1121b and the connecting portion 1121c is inclined to the surface of the bottom of the shell 111, and the inclination angle is not greater than 10°.

[0091] When the first wall portion 1121a and the second wall portion 1121b are not perfectly parallel, the larger of the angles between the first wall portion 1121a or the second wall portion 1121b and the shell bottom 111 is α, satisfying α < 10°. It is understandable that in this case, since the first wall portion 1121a and the second wall portion 1121b are not perfectly parallel, the angles α between the first wall portion 1121a and the shell bottom 111, and between the second wall portion 1121b and the shell bottom 111, are both less than 10°.

[0092] Therefore, firstly, by setting the first wall portion 1121a and the second wall portion 1121b constituting the neck 1121 to be inclined towards the bottom of the shell 111, the neck 1121 has a certain amount of sag allowance. Therefore, it is convenient to design the grooving in the preceding grooving process, and it is convenient to form the required neck structure in the sealing process. Secondly, the inclination angle of the first wall portion 1121a and the second wall portion 1121b does not exceed 10°, and the height of the neck 1121 entering the lower cavity 1132 is small, which ensures the effective space of the lower cavity 1132 and also avoids damage to the core electrode assembly. Furthermore, since the tilt angle of the first wall portion 1121a and the second wall portion 1121b does not exceed 10°, the top surface of the constricted neck 1121 in the inner cavity 113, which is also the top surface of the first wall portion 1121a, is basically horizontal. Its contact area with the bottom surface of the cap 120 is large, and there is sufficient compression between the two, resulting in a good sealing effect and improving the safety of the lithium battery.

[0093] Furthermore, in some embodiments, the included angle α satisfies: 1° < α < 5°. It is understood that the included angle α affects the design difficulty of the groove, the utilization rate of the internal space of the outer shell 110, and the sealing effect on the cap 120. If α is too large, although the design difficulty of the groove is lower, the utilization rate of the internal space of the outer shell 110 will decrease, and the sealing effect on the cap 120 will worsen. Conversely, if α is too small, the groove is difficult to design, and the necking 1121 is difficult to form. By reasonably designing the size of the included angle α, the design difficulty of the groove is reduced, while also minimizing the impact of the necking 1121 on the lower cavity 1132 space and ensuring the sealing effect on the cap 120.

[0094] In some embodiments, the distance L1 is the distance from the lowest point of the constricted neck 1121 in the inner cavity 113 to the upper surface of the bottom shell 111, and the height H1 is the outer shell 110. The range of L1 / H1 is 90%-98%, that is, 90%≤L1 / H1≤98%. It can be understood that if the distance L1 from the lowest point of the constricted neck 1121 to the upper surface of the bottom shell 111 is too large, that is, if L1 / H1 is too large, it will affect the height of the upper cavity 1131, resulting in a poorer sealing effect; conversely, if the distance L1 from the lowest point of the constricted neck 1121 to the upper surface of the bottom shell 111 is too small, that is, if L1 / H1 is too small, it will affect the height of the lower cavity 1132, which will waste the height of the outer shell 110 and result in a lower energy density of the battery. By rationally designing the distance L1 between the lowest point of the neck 1121 in the inner cavity 113 and the upper surface of the bottom of the shell 111, the sealing effect at the opening can be ensured, while also improving the utilization rate of the internal space of the shell 110 and increasing the energy density of the battery.

[0095] Furthermore, in some embodiments, the height of the necking groove 1123 is defined as H2, and the height of the outer casing 110 is defined as H1. The range of H2 / H1 is 0.1%-1%, i.e., 0.1% ≤ H2 / H1 ≤ 1%. It is understandable that if the height H2 of the necking groove 1123 is too large, it will waste the height of the outer casing 110, resulting in a lower energy density of the lithium battery. Conversely, if the height H2 of the necking groove 1123 is too small, stress will easily concentrate at the connection 1121c, and the necking 1121 will be at risk of breakage at this location. Furthermore, the sealing process will be more difficult, leading to a decrease in yield. By rationally designing the height H2 of the necking groove 1123, while ensuring that the structural strength of the necking 1121 meets the requirements, the utilization rate of the internal space of the outer casing 110 and the manufacturability of the sealing process can also be effectively improved. It is also understood that, as shown in Figure 3, the height H2 described here refers to the height at the opening of the necking groove 1123. Of course, if the first wall portion 1121a and the second wall portion 1121b are set to be parallel, then the height inside the necking groove 1123 will be consistent with this height H2. More preferably, 0.2% ≤ H2 / H1 ≤ 0.5%.

[0096] In some embodiments, the depth of the necking groove 1123 in the radial direction is H3, and the outer diameter of the housing 110 is D1. The range of H3 / D1 is 5%-10%, that is, it satisfies: 5%≤H3 / D1≤10%. Understandably, if the depth H3 of the constriction groove 1123 is too large, i.e., H3 / D1 is too large, the constriction groove 1121 will over-intrude into the inner cavity 113 in the radial direction, resulting in a smaller inner diameter of the inner cavity 113 at the constriction groove 1121, causing wasted space. It will also weaken the structural rigidity of the constriction groove 1121 itself, increase stress, and pose a risk of cracking, thus making it impossible to guarantee the sealing performance. Conversely, if the depth H3 of the constriction groove 1123 is too small, i.e., H3 / D1 is too small, the cap 120 cannot be stably supported by the first wall portion 1121a. The dimensional chain matching between the two is poor. When sealing, the cap 120 may directly pass through the groove defined by the constriction groove 1121 and enter the lower cavity 1132. By rationally designing the depth H3 of the necking groove 1123, while ensuring that the cap 120 can be stably supported by the first wall portion 1121a to facilitate smooth sealing, the utilization rate of the internal space of the outer casing 110 can also be improved, further increasing the energy density of the lithium battery.

[0097] It is understandable that during the sealing process, the wall thicknesses of the first wall portion 1121a, the second wall portion 1121b, and the connecting portion 1121c will change due to plastic deformation of the material. To ensure the pressure resistance of the outer shell 110, in some embodiments, the minimum wall thickness of the neck 1121 is defined as T2, and the wall thickness of the outer shell 110 is defined as T1, wherein T2 / T1 ≥ 80%, more preferably, T2 / T1 ≥ 85%. It is understandable that this minimum wall thickness T2 may occur at any one of the first wall portion 1121a, the second wall portion 1121b, and the connecting portion 1121c. It is also understandable that if T2 / T1 is less than 80%, the safety margin of the mechanical strength of the outer shell 110 is insufficient. For example, when the internal air pressure of the outer shell 110 increases, it may cause the outer shell 110 to tear at that point. By reasonably designing the wall thickness T2 at the thinnest point of the neck 1121, it can be ensured that the pressure resistance of the outer shell 110 meets the requirements.

[0098] In some embodiments, to ensure the pressure resistance of the housing 110, the minimum wall thickness of the neck 1121 is set as T2, where T2 ranges from 0.1 to 0.2 mm, i.e., 0.1 mm ≤ T2 ≤ 0.2 mm. It is understood that setting the minimum wall thickness T2 of the neck 1121 to between 0.1 and 0.2 mm allows the neck 1121 to meet the pressure resistance requirements of housings 110 with common wall thicknesses. For example, for a housing 110 with a wall thickness of 0.2 mm, the minimum wall thickness T2 of the neck 1121 can be 0.17 mm.

[0099] The following is a detailed introduction to the 120-point block.

[0100] It is understandable that the cap 120 and the outer casing 110 together act as a physical barrier to isolate the active material of the cylindrical lithium battery from the outside world. Furthermore, when the gas pressure inside the battery exceeds a preset value, the explosion-proof valve 122 of the cap 120 opens to release the pressure, so as to prevent the battery from deforming, bulging, or even burning or exploding.

[0101] As shown in Figure 4, the cap 120 includes a top cover 121, an explosion-proof valve plate 122, an insulating plate 123, a terminal plate 124, and an insulating ring 125 located on the outer edge. The top cover 121, the explosion-proof valve plate 122, and the terminal plate 124 are stacked sequentially from top to bottom and electrically connected to each other. After the cap 120 is sealed to the outer casing 110, the top cover 121 protrudes outside the outer casing 110, serving as the positive terminal for electrical connection with the positive terminal of external electrical equipment. The bottom surface of the terminal plate 124 is connected to the positive current collector 130, for example, by welding the positive current collector 130 to the terminal plate 124, thereby forming a conductive connection and connecting the top cover 121 to the positive terminal of the core 140. The explosion-proof valve plate 122, which constitutes the cap 120, is described in detail below.

[0102] Referring to Figures 5 and 6, the explosion-proof valve plate 122 is a single component made of aluminum, with an overall circular thin disc or thin plate structure. Along the thickness direction, it has a top surface and a bottom surface that are opposite to each other. After being assembled into a cylindrical lithium battery, the bottom surface (lower part in Figure 6) faces the core 140, and the top surface (upper part in Figure 6) faces the top cover 121. The explosion-proof valve plate 122 has a scoring assembly 1221 on one side of the top surface. The scoring assembly 1221 includes a first annular scoring 1221a and a second scoring 1221b extending in a line segment shape. The second scoring 1221b is located within the area defined by the first scoring 1221a, and both ends of the second scoring 1221b are connected to the first scoring 1221a. That is, the first scoring 1221a presents a closed shape with the ends connected. The first scoring 1221a is preferably a closed circle, and the second scoring 1221b is in the shape of a line segment. In this process, at least one of the first notch 1221a and the second notch 1221b breaks when the internal pressure of the cylindrical lithium battery exceeds a preset value, thereby opening the explosion-proof valve plate 122. Furthermore, the first notch 1221a and the second notch 1221b that breaks first can cause the other notch to break as well.

[0103] It is understood that, since the explosion-proof valve plate 122 of this application embodiment has an annular first notch 1221a and a line segment second notch 1221b, and the two ends of the second notch 1221b are connected to the first notch 1221a, when an abnormal state such as overheating or short circuit occurs inside the battery, causing a sharp rise in internal gas pressure, when the gas pressure value in the edge area reaches the preset value first, the first notch 1221a will break first, and the gas inside the battery will rush out from the gap created by the breakage of the first notch 1221a to release pressure in time. Furthermore, the first notch 1221a will also drive the second notch 1221b during the breakage process. The second notch 1221b also breaks, thereby expanding the opening area of ​​the explosion-proof valve plate 122 and improving the pressure relief effect. When the gas pressure in the middle region reaches the preset value first, the second notch 1221b breaks first, and the gas inside the battery rushes out from the gap created by the breakage of the second notch 1221b to relieve pressure in time. In addition, the second notch 1221b will also cause the first notch 1221a to break during the breaking and opening process, thereby expanding the opening area of ​​the explosion-proof valve plate 122 and improving the pressure relief effect. Thus, when the gas pressure inside the battery exceeds the preset value, the explosion-proof valve plate 122 can open quickly and effectively to release the pressure, thereby improving the safety of the battery.

[0104] It should be noted that if the first notch 1221a and the second notch 1221b are not connected, they can only break individually and form a gap for pressure relief, resulting in poor pressure relief and failing to achieve the purpose of rapid and effective pressure relief of the battery proposed in this application. Therefore, in this embodiment, the first notch 1221a and the second notch 1221b constituting the notch assembly 1221 are configured to be connected, that is, they intersect. Therefore, if either one breaks, it can extend to the other, causing the other to also break. Thus, the opening area of ​​the explosion-proof valve plate 122 can be increased, thereby rapidly relieving pressure on the battery.

[0105] It is understandable that although more complex internal grooves, such as cross-shaped grooves, could be used to replace the second groove 1221b in order to achieve the purpose of timely explosion when the pressure in the middle region of the battery increases, this would significantly increase the processing difficulty of the explosion-proof valve plate 122, thereby reducing the yield and increasing the cost. The embodiment of this application only sets a straight second groove 1221b inside the explosion-proof valve plate 122, which can effectively achieve rapid and effective pressure relief of the battery, while being easy to process and having a lower cost, thus having better economic benefits.

[0106] It is understandable that the first notch 1221a and the second notch 1221b are structures formed on the explosion-proof valve plate 122 by removing material. Therefore, the explosion-proof valve plate 122 is thinner at the location of the first notch 1221a and the second notch 1221b compared to other locations. When the internal pressure of the battery increases and exceeds the preset value, one or both of the first notch 1221a and the second notch 1221b will deform according to the specific pressure distribution. When the deformation accumulates to a certain extent, the first notch 1221a and the second notch 1221b will break. The material after the breakage will be flipped under the influence of pressure, thereby creating a gap at the breakage point. The high-pressure gas inside the battery will be released through the gap.

[0107] In some embodiments, as shown in FIG5, the first notch 1221a is circular, and the second notch 1221b is set to pass through the center of the first notch 1221a, that is, the second notch 1221b is exactly the diameter of the annular pattern shown by the first notch 1221a. Thus, with the diameter of the first notch 1221a as D2 and the length of the second notch 1221b as L2, L2 = D2 is satisfied. Therefore, the second notch 1221b divides the first notch 1221a into two symmetrical parts, which facilitates the processing and construction of the first notch 1221a and the second notch 1221b. Furthermore, after the explosion-proof valve plate 122 is assembled into the cylindrical lithium battery, the second notch 1221b is located in the central region of the cylindrical lithium battery, so that the explosion-proof valve plate 122 can open smoothly to release pressure. Furthermore, it can be understood that, in order to facilitate the construction of the annular first notch 1221a and the segment-shaped second notch 1221b, the first notch 1221a can be set to be concentric with the explosion-proof valve plate 122.

[0108] As shown in Figure 6, in some embodiments, the explosion-proof valve plate 122 is provided with a thinning portion 1222 extending in the radial direction. The first notch 1221a is provided within the radial range where the thinning portion 1222 is located. Specifically, the thinning portion 1222 can be implemented by forming a groove 1223 on one side of the explosion-proof valve plate 122. The thinning portion 1222 can effectively cause the notch assembly 1221 to break when the opening conditions are met, thereby releasing the battery pressure. At the same time, it also ensures that the explosion-proof valve plate 122 has sufficient strength and rigidity, making it easy to process and assemble.

[0109] As shown in Figures 7 and 8, relative to the surface of the explosion-proof valve plate 122, the first notch 1221a has a depth H4, and the second notch 1221b has a depth H5. It is understood that if H4 and H5 are large, meaning the first notch 1221a and the second notch 1221b are deep, then the first notch 1221a and the second notch 1221b are prone to breakage, resulting in insufficient opening pressure. Conversely, if H4 and H5 are large, meaning the first notch 1221a and the second notch 1221b are shallow, then the first notch 1221a and the second notch 1221b are not easily broken, resulting in excessive opening pressure, preventing timely release of gas from the battery, and increasing safety risks. Therefore, in some embodiments, the ratio of the depth H4 of the first notch 1221a to the thickness T3 of the thinned portion 1222 is between 30% and 60%, satisfying: 30% ≤ H1 / T1 ≤ 60%, and more preferably, 40% ≤ H1 / T1 ≤ 55%. The specific values ​​of H4 and H5 can be determined based on the opening pressure and the thickness of the thinned part 1222 (or the explosion-proof valve plate 122).

[0110] It is understandable that the first notch 1221a and the second notch 1221b are positioned differently on the explosion-proof valve plate 122. Specifically, the first notch 1221a is arranged in a ring around the center of the explosion-proof valve plate 122 on the end face of the explosion-proof valve plate 122, while the second notch 1221b is radially constructed on the end face of the explosion-proof valve plate 122 through the center of the explosion-proof valve plate 122. Due to requirements such as strength and installation, the thickness of the explosion-proof valve plate 122 is usually different in different areas along the radial direction. For example, the wall thickness of the inner part of the explosion-proof valve plate 122 adjacent to the thinned part 1222 is thicker than that of the thinned part 1222, and the wall thickness changes in a step and forms a thicker welding platform 1224 in the middle. The explosion-proof valve plate 122 is welded to the terminal plate 124 through this welding platform 1224. Therefore, in order to ensure that the first notch 1221a and the second notch 1221b located in different areas of the explosion-proof valve plate 122 can be opened smoothly when the pressure reaches the preset value, in some embodiments, the depth of the first notch 1221a is different from the depth of the second notch 1221b.

[0111] Furthermore, in some embodiments, the depth H4 of the first notch 1221a is less than the depth H5 of the second notch 1221b. By increasing the depth of the second notch 1221b, the impact of the increased thickness of the explosion-proof valve plate 122 in the central region on the second notch 1221b can be reduced, thereby ensuring that the explosion-proof valve plate 122 opens smoothly at the second notch 1221b.

[0112] Furthermore, the depth of the second notch 1221b is set to be deeper in the middle and shallower at both ends. By setting the depth of the second notch 1221b to be deeper in the middle and shallower at both ends, the influence of the stepped change in thickness of the explosion-proof valve plate 122 in the radial direction can be reduced, so as to ensure that the explosion-proof valve plate 122 opens smoothly at the second notch 1221b.

[0113] Furthermore, to reduce stress concentration and the risk of accidental breakage of the first notch 1221a and the second notch 1221b, referring again to Figures 7 and 8, chamfered portions are provided at the bottom of both the first notch 1221a and the second notch 1221b. By providing chamfered portions at the bottom of the first notch 1221a and the second notch 1221b, stress concentration at the bottom of the first notch 1221a and the second notch 1221b can be reduced, thereby lowering the risk of accidental opening of the explosion-proof valve plate 122 when the pressure value has not reached the preset value.

[0114] Furthermore, the radii of the chamfered portions at the bottom of the first notch 1221a and the second notch 1221b are the same. By setting the radii of the chamfered portions of the first notch 1221a and the second notch 1221b to be the same, design and manufacturing costs can be reduced. For example, if the radius of the chamfered portion at the bottom of the first notch 1221a and the second notch 1221b is R, and R is in the range of 0.05-0.15mm, that is, satisfying: 0.05mm≤R≤0.15mm, more preferably, 0.05mm≤R≤0.1mm. With the radius of the chamfered portion within this range, stress concentration at the bottom of the first notch 1221a and the second notch 1221b can be effectively reduced, and it is also easier to process by molds, thus reducing costs.

[0115] The following is a detailed introduction to the positive current collector 130.

[0116] As shown in Figures 9 and 10, the positive current collector 130 includes a disc body portion 131 and a tail portion 132 connected to each other. The disc body portion 131 is used to connect to the positive end of the winding core 140, and the tail portion 132 is used to connect to the cap 120, so that a passage is formed between the winding core 140 and the cap 120. In this application, the connection between the disc body portion 131 and the winding core 140, and the connection between the tail portion 132 and the cap 120, can adopt any connection method known to those skilled in the art, such as welding; the connection between the tail portion 132 and the disc body portion 131 can be any fixed connection method, but to ensure the stability of the connection and structural strength, an integral connection is preferred.

[0117] As shown in Figure 9, in order to match the circular cross-section of the core 140 and facilitate the welding between the disc body 131 and the core 140, the disc body 131 is a closed axisymmetric figure composed of a first side 1311, an arc 1312, a second side 1313, and a third side 1314 connected end to end. The tail body 132 includes a fifth side 1322 and a sixth side 1323 along its length direction, as well as a fourth side 1324 away from the disc body 131. The two ends of the fifth side 1322 are connected to the fourth side 1324 and the first side 1311, respectively. The two ends of the sixth side 1323 are connected to the fourth side 1324 and the second side 1313, respectively. Thus, as can be seen from Figure 9, the tail body 132 is also a closed axisymmetric figure extending from one end of the disc body 131. It should be noted that the third side 1314 is a virtual edge line proposed for the convenience of describing the disk portion 131. This side does not exist in the actual product, so it is marked with a dashed line in Figure 9 to distinguish it. In addition, referring to Figures 1 and 10, it can also be understood that when the positive electrode current collector 130 is assembled into the cylindrical lithium battery, the tail portion 132 bends, and its distal end will be located above the closed axisymmetric shape formed by the disk portion 131.

[0118] To improve the efficiency of electrolyte injection during battery production, the disc portion 131 typically has holes through which the electrolyte passes. To ensure that the solid area of ​​the disc portion 131 still accounts for more than 75% of its total area after drilling, facilitating welding to the core 140, the disc portion 131 has a central angle A, with 40°≤∠A≤60°, and more preferably 45°≤∠A≤55°. Specifically, the total area of ​​the disc portion 131 is the sum of the solid area of ​​the disc portion 131 and the area of ​​the hole; the included angle A of the circles takes the center of the circle corresponding to the arc 1312 as the vertex, and the two sides pass through the endpoints of the first side 1311 away from the arc 1312 and the second side 1313 away from the arc 1312, respectively. It can be understood that the endpoints of the first side 1311 away from the arc 1312 and the endpoints of the second side 1313 away from the arc 12 are also the connection points of the first side 1311, the second side 1313 and the tail portion 132.

[0119] In some embodiments, the diameter D3 of the disc portion 131 is 80%-95% of the diameter D6 of the core 140, where the diameter D3 of the disc portion 131 refers to the longest line segment between two points on the arc 1312, and the diameter D6 of the core 140 refers to the diameter of the circular cross-section of the core 140. Depending on actual needs, the diameter D3 of the disc portion 131 is, for example, 15-23 mm. Within the preferred diameter range, the disc portion 131 ensures a large contact area between itself and the core 140, increasing the weldable area and expanding the adaptability of the weld wire length and shape. It is also understood that when the contact area of ​​the negative electrode current collector 150 is large, within the aforementioned diameter range, the positive electrode current collector 130 will not become a bottleneck limiting the charge and discharge performance of the cylindrical lithium battery.

[0120] In some embodiments, a first hole 1315 is provided at the center of the disc portion 131 for injecting electrolyte into the battery. The center of the disc portion 131 may be the center of a circle corresponding to the arc 1312. The core 140 is manufactured by a winding process, and a circular core hole 145 is formed at the center of the core 140 after winding. To match the shape of the core hole 145, the shape of the first hole 1315 is preferably circular.

[0121] In some embodiments, the diameter D4 of the first hole 1315 is 1.4-1.8 times the diameter D7 of the core hole 145 of the core 140. Depending on actual needs, the diameter D4 of the first hole 1315 is, for example, 4-8 mm. Within this diameter range, the first hole 1315 achieves a balance between liquid injection efficiency and weldable area, while ensuring welding safety. If the diameter D4 of the first hole 1315 is too small, it is not conducive to liquid wetting, and when using resistance welding at the bottom of the battery, the electrode tip extending into the core hole 145 of the core 140 may make undesirable contact with the current collector, posing an interference risk. If the diameter D4 of the first hole 1315 is too large, the weldable area is correspondingly reduced, limiting the welding processability between the disc body 131 and the core 140.

[0122] In some embodiments, the diameter D4 of the first hole 1315 is 25%-35% of the diameter D3 of the disc portion 131. Depending on actual needs, the diameter D4 of the first hole 1315 is, for example, 4-8 mm. Within this diameter range, the first hole 1315 achieves a balance between liquid injection efficiency and weldable area, while ensuring welding safety. If the diameter D4 of the first hole 1315 is too small, it is not conducive to liquid wetting, and when using resistance welding at the bottom of the battery, the electrode tip extending into the core hole 145 of the core 140 may make undesirable contact with the current collector, posing an interference risk. If the diameter D4 of the first hole 1315 is too large, the weldable area is correspondingly reduced, limiting the welding process between the disc portion 131 and the core 140.

[0123] In some embodiments, at least one second hole 1316 is provided around the periphery of the first hole 1315 to assist electrolyte wetting. Preferably, the second hole 1316 is a circular hole. More preferably, the area of ​​a single second hole 1316 is 0.3-0.5 times the area of ​​the first hole 1315, and the sum of the areas of all second holes 1316 is 0.9-1.5 times the area of ​​the first hole 1315. If the area of ​​the second hole 1316 is too small compared to the area of ​​the first hole 1315, the auxiliary wetting effect will be insignificant; if the area of ​​the second hole 1316 is too large, the solderable area of ​​the disc portion 131 will be significantly reduced, affecting the connection between the disc portion 131 and the core 140.

[0124] In some embodiments, the distance L3 between the center of the second hole 1316 and the center of the first hole 1315 is 25%-35% of the diameter D3 of the disk portion 131. Depending on actual needs, L3 is, for example, 4.5-7 mm. By rationally designing the distance L2 between the second hole 1316 and the first hole 1315, it is helpful to improve the wetting effect of the electrolyte while ensuring the area of ​​the solderable region. If the distance L3 between the second hole 1316 and the first hole 1315 is too small, the wetting effect of the electrolyte cannot be significantly improved; if the distance L3 between the second hole 1316 and the first hole 1315 is too large, the second hole 1316 will be too close to the edge of the disk portion 131, thereby restricting the battery encapsulation. If the encapsulation blocks the second hole 1316, the electrolyte cannot be injected through the second hole 1316.

[0125] For ease of processing and improved yield, in a preferred embodiment, the diameter D5 of the second hole 1316 is 50%-70% of the diameter D4 of the first hole 1315, for example, 2-4.8 mm. If the diameter D5 of the second hole 1316 is smaller than the preferred diameter range, it is difficult to achieve the auxiliary wetting effect; if the diameter D5 of the second hole 1316 is larger than the preferred diameter range, the weldable area of ​​the disc body 131 is reduced. It is understood that the number of second holes 1316 can be determined according to the actual welding process, where the number of welding areas is n, and the number of second holes 1316 is n-1, where n≥2.

[0126] The disk portion 131 will be further described below with reference to the embodiments and comparative examples. The embodiments and comparative examples in this application are designed with reference to a common 21 series cylindrical lithium battery.

[0127] Example 1:

[0128] Example 1 provides a cylindrical lithium battery, comprising a casing 110, a cap 120, a positive current collector 130, a core 140, and a negative current collector 150. The positive current collector 130 includes an interconnected disk body portion 131 and a tail portion 132. The disk body portion 131 is connected to the positive end of the core 140, and the tail portion 132 is connected to the cap 120. The disk body portion 131 has a circular first hole 1315 at its center, and multiple similarly circular second holes 1316 are provided around the periphery of the first hole 1315. Furthermore, the shape of the disk body portion 131 is a closed axisymmetric figure formed by sequentially connecting a first side 1311, an arc 1312, a second side 1313, and a third side 1314, with a central angle B.

[0129] Wherein, the diameter D6 of the core 140 is 20mm; the diameter D3 of the disc body 131 is 85% of the diameter D6 of the core 140; the diameter D4 of the first hole 1315 is 30% of the diameter D3 of the disc body 131; the diameter D5 of the second hole 1316 is 60% of the diameter D4 of the first hole 1315; the sum of the areas of all the second holes 1316 is 1.2 times the area of ​​the first hole 1315; the distance L3 between the center of the second hole 1316 and the center of the first hole 1315 is 30% of the diameter D3 of the disc body 131; and the included angle B of the center of the disc body 131 is 35°.

[0130] Comparative Example 1:

[0131] Comparative Example 1 provides a cylindrical lithium battery that differs from Example 1 in that the sum of the areas of all the second holes 1316 is 0.4 times the area of ​​the first hole 1315.

[0132] Comparative Example 2:

[0133] Comparative Example 2 provides a cylindrical lithium battery, which differs from Example 1 in that the diameter D4 of the first hole 1315 is 10% of the diameter D3 of the disk portion 131.

[0134] Table 1 below evaluates the electrolyte wetting effect of the sealed cylindrical lithium batteries produced in the above embodiments and comparative examples. The specific electrolyte wetting test method is as follows: Samples of the casing 110, cap 120, positive electrode current collector 130, core 140, negative electrode current collector 150, and electrolyte were taken. The positive electrode current collector 130 and negative electrode current collector 150 were welded to the core 140. After placing the assembly into the casing 100, the cap 120 was welded again, resulting in an unsealed cylindrical lithium battery. Next, the cylindrical lithium battery was placed in an electrolyte injection device for injection, with an injection volume of 6.8g. After positive and negative pressure cycling of the device, the cylindrical lithium battery was mechanically sealed. After standing for 1 hour, the cylindrical lithium battery was disassembled, the core 140 was removed and unfolded, and placed on a CCD detection device for photographing. The wetting area was depicted, and the device program was started to calculate the wetting area S0. With the total electrode area set as S, the wetting rate was S0 / S.

[0135] Table 1

[0136] As shown in Table 1, when the sum of the areas of all the second holes 1316 is 1.2 times the area of ​​the first hole 1315, and the diameter D4 of the first hole 1315 is 30% of the diameter D3 of the disc body 131, the electrolyte wetting effect of the core 140 is better. However, if the sum of the areas of all the second holes 1316 is too low or the area of ​​the first hole 1315 is too small, the electrolyte wetting effect of the core 140 will be worse.

[0137] Referring again to Figure 9, in some embodiments, at least one fuse groove 1321 is formed on the tail section 132. By designing the fuse groove, the width of the tail section 132 at the fuse groove 1321 is reduced. During battery thermal runaway, current converges at this location, heat rises and reaches the melting point, causing the tail section 132 to melt and achieve the current interruption effect. Specifically, the shape of the fuse groove 1321 can be any shape, such as trapezoidal, rectangular, U-shaped, V-shaped, or semi-circular. This application does not limit the number of fuse grooves 1321; the accompanying drawings exemplarily show two symmetrically arranged fuse grooves 1321. When there are multiple fuse grooves 1321, all fuse grooves 1321 can be of the same shape or different shapes. In principle, the arrangement of the fuse grooves 1321 must simultaneously ensure the melting effect and mechanical strength of the tail section 132.

[0138] In some embodiments, as shown in FIG11, the distance L5 between the center of the fuse groove 1321 and the end of the tail portion 132 away from the disc portion 131 is 68%-78% of the length L4 of the tail portion 132. Depending on actual needs, the distance between the center of the fuse groove 1321 and the end of the tail portion 132 away from the disc portion 131 is, for example, 8-18 mm. If the shape of the fuse groove 1321 is a simple graphic, the center of the fuse groove 1321 can be a location recognized by those skilled in the art. For example, for a trapezoidal or rectangular fuse groove 1321, the center can be the intersection of two diagonals; for a semi-circular fuse groove 1321, the center can be the center of the circle. If the shape of the fuse groove 1321 is more complex or irregular, the center of the fuse groove 1321 is the geometric center of its shape, that is, the average position of all points in the shape. This can be determined by any method mastered by those skilled in the art, such as integration, discrete point method, graphic segmentation method, or directly calculated using software tools. The length L4 of the tail section 132 is the distance from the connection point between the tail section 132 and the disk section 131 to the end of the tail section 132 away from the disk section 131. The fuse groove 1321 is positioned appropriately to ensure smooth welding between the tail section 132 and the cap 120, while also ensuring current cutoff in the event of battery thermal runaway. If the distance between the fuse groove 1321 and the end of the tail section 132 away from the disk section 131 is too small, the fuse groove 1321 will be too close to the welding position, and the welding between the tail section 132 and the cap 120 will be interfered with; conversely, if the distance between the fuse groove 1321 and the disk section 131 is greater, the current path at the fuse groove 1321 will be larger, and if there is overcurrent, it will not be able to melt in time, increasing the safety risk of the battery.

[0139] In some embodiments, to improve battery safety, the length L4 of the tail portion 132 is 85%-95% of the diameter D3 of the disc portion 131. Depending on actual needs, the length of the tail portion 132 is, for example, 12-20 mm. Within the preferred length range, the tail portion 132 ensures both smooth welding with the cap 120 and battery safety. If the tail portion 132 is too short, it will not extend sufficiently beyond the outer casing 110 after a single bend, making welding with the cap 120 impossible. If the tail portion 132 is too long, the end of the tail portion 132 furthest from the disc portion 131 will contact the outer casing 110 during a second bend of the cap 120, causing a short circuit in the battery and occupying internal battery space, affecting the installation and normal operation of other components.

[0140] For ease of bending and welding, the tail portion 132 is typically elongated. In some embodiments, as previously described, the tail portion 132 has a first width W2, satisfying: W2 = D3 * sin(∠B / 2), where D3 is the diameter of the disc portion 131, which is the longest line segment between two points on the arc 1312. Depending on actual needs, the diameter of the disc portion 131 is, for example, 15-23 mm. Furthermore, the included angle B is with the center of the circle corresponding to the arc 1312 as its vertex, and the two sides pass through the intersection points of the fifth side 1322 and the sixth side 1323 of the tail portion 132 with the entire circle containing the arc 1312 (refer to Figure 9), for example, and 20° ≤ ∠B ≤ 40°. The larger the first width W2 of the tail portion 132, the smaller the weldable area of ​​the disc portion 131 will be. A reasonable width design helps to retain the largest weldable area, while ensuring that the tail portion 132 has sufficient mechanical strength to prevent it from being broken during production. At the same time, it is conducive to the rapid passage of electrons and reduces the internal resistance of the battery.

[0141] In some embodiments, the tail portion 132 has a second width W3 at the fuse groove 1321, and 3W2 / 8 ≤ W3 < 3W2 / 4, that is, the second width W3 is 3 / 8 to 3 / 4 of the first width W2. In this application, the second width W3 refers to the change in width of the tail portion 132 relative to the first width W2 at this location due to the design of the fuse groove 1321. Based on the definition of the second width W3 in this application, the first width W2 in this application refers to the width of the tail portion 132 at locations other than the fuse groove 1321. A second width W2 at the fuse groove 1321 within a reasonable range can balance the mechanical properties of the tail portion 132 and the safety performance of the battery. When the second width W3 is too small, the tail portion 132 lacks sufficient strength at the fuse groove 1321 and is easily broken when bent.

[0142] In some embodiments, the dimension L6 of the fuse groove 1321 along the length of the tail portion 132 satisfies: 0 < L6 ≤ W2, that is, the length of the fuse groove 1321 in the vertical direction does not exceed the first width W2 of the tail portion 132. Preferably, W2 / 4 < L6 ≤ 3W2 / 4, that is, the dimension L6 is 1 / 4 to 3 / 4 of the first width W2. In this application, the dimension of the fuse groove 1321 along the length of the tail portion 132 refers to the length between the end of the fuse groove 1321 closest to the disc portion 131 and the end farthest from the disc portion 131. A reasonable dimension of the fuse groove 1321 along the length of the tail portion 132 helps to improve battery safety. If the dimension is too large, the melting position of the tail portion 132 is difficult to determine, thereby increasing the safety risk of the battery; conversely, if the dimension is too small, the melting sensitivity of the tail portion 132 increases, and there is a possibility of melting even at a safe current.

[0143] In some embodiments, as shown in FIG12, the minimum cross-sectional area S2 of the tail portion 132 at the fuse groove 1321 is 45%-65% of the overall cross-sectional area S1 of the tail portion 132. Specifically, the minimum cross-sectional area S2 of the tail portion 132 at the fuse groove 1321 is the cross-sectional area at the narrowest position of the fuse groove 1321. For example, as shown in FIG12, when the cross-section at this position is square, its cross-sectional area S2 = W3 * T4; the overall cross-sectional area S1 of the tail portion 132 is the cross-sectional area of ​​the tail portion 132 at positions other than the fuse groove 1321, S1 = W2 * T4, where T4 is the thickness of the tail portion 132, which is usually a uniform thickness. Depending on actual needs, T4 is, for example, 0.15-0.35 mm. Within a reasonable minimum cross-sectional area S2 range, the tail portion 132 can achieve a balance between battery safety and low internal resistance. When the minimum cross-sectional area S1 is too large, the tail portion 132 cannot quickly melt and break in the event of thermal runaway, increasing the safety risk. Conversely, when the minimum cross-sectional area S2 is too small, on the one hand, the melting sensitivity will be too high, and on the other hand, the internal resistance will increase, seriously affecting the normal use of the battery. Of course, it is understood that when calculating S1 and S2 above, the thickness of the tail portion 132 at the melting groove 1321 is the same as the thickness of the rest of the portion, that is, the tail portion 132 is of equal thickness. However, it is not limited to this, and the thicknesses of the two portions can also be set to be different.

[0144] As shown in Figure 13, the tail portion 132 includes a fifth side 1322 and a sixth side 1323 along its length, and a fourth side 1324 away from the disc portion 131. The two ends of the fifth side 1322 are connected to the fourth side 1324 and the first side 1311, respectively. The two ends of the sixth side 1323 are connected to the fourth side 1324 and the second side 1313, respectively. The angle θ1 between the fifth side 1322 and the first side 1311 is 45-90°, and the angle θ2 between the sixth side 1323 and the second side 1313 is 45-90°. It is understandable that if the angles θ1 and θ2 are too small, the bending of the tail portion 132 will cause the stress to be too concentrated at the angles θ1 and θ2, causing the disc portion 131 to deform or even crack. If the angles θ1 and θ2 are too large, it cannot be guaranteed that the disc portion 131 has sufficient weldable area. In addition, the reasonable angle design of the included angles θ1 and θ2 also helps the electrolyte to penetrate into the battery through the included angles θ1 and θ2.

[0145] The tail portion 132 will be further described below with reference to the embodiments and comparative examples. The embodiments and comparative examples described below are designed with reference to a common 21 series cylindrical lithium battery.

[0146] Example 1:

[0147] Example 1 provides a cylindrical lithium battery, comprising a casing 110, a cap 120, a positive current collector 130, a core 140, and a negative current collector 150. The positive current collector 130 includes an interconnected disk body portion 131 and a tail portion 132. The disk body portion 131 is connected to the positive end of the core 140, and the tail portion 132 is connected to the cap 120. The tail portion 132 has a constant thickness along its length, and at least one pair of fuse grooves 1321 are formed on it. The distance L5 between the center of the fuse groove 1321 and the end of the tail portion 132 away from the disk body portion 131 is 72% of the length L4 of the tail portion 132. The minimum cross-sectional area S2 of the tail portion 132 at the fuse groove 1321 is 50% of the overall cross-sectional area S1 of the tail portion 132.

[0148] Comparative Example 1:

[0149] Comparative Example 1 provides a cylindrical lithium battery, which differs from Example 1 in that the minimum cross-sectional area S2 of the tail portion 132 at the fuse groove 1321 is 20% of the overall cross-sectional area S1 of the tail portion 132.

[0150] Comparative Example 2:

[0151] Comparative Example 2 provides a cylindrical lithium battery, which differs from Example 1 in that the minimum cross-sectional area S2 of the tail portion 132 at the fuse groove 1321 is 85% of the overall cross-sectional area S1 of the tail portion 132.

[0152] Comparative Example 3:

[0153] Comparative Example 3 provides a cylindrical lithium battery, which differs from Example 1 in that the distance L5 between the center of the fuse groove 1321 and the end of the tail portion 132 away from the disc portion 131 is 90% of the length L4 of the tail portion 132.

[0154] Table 2 below evaluates the safety protection effect of the positive current collector 130 fabricated in the above embodiments and comparative examples. The specific test method is as follows: The sampled positive current collector 130 is fixed on the fixture of a high-power programmable DC power supply device. The test conditions are set as follows: voltage 20V, current 170A, power 150W, delay time 10s. The temperature sensor is turned on and aimed at the positive current collector 130. The recording function is clicked, and the test is started on the instrument. The experiment ends when the fuse slot 1321 of the positive current collector 130 is observed to be melted. The time and current correlation curves obtained by the device and the melting temperature read by the temperature sensor are recorded.

[0155] Table 2

[0156] As shown in Table 2, when the distance L5 between the center of the fuse groove 1321 and the end of the tail section 132 away from the disc section 131 is 72% of the length L4 of the tail section 132, and the minimum cross-sectional area S2 of the tail section 132 at the fuse groove 1321 is 50% of the total cross-sectional area S1 of the tail section 132, the breaking temperature and melting time of the fuse groove 1321 are relatively reasonable. When the ratio of the minimum cross-sectional area S2 of the tail section 132 at the fuse groove 1321 to the total cross-sectional area S1 of the tail section 132 is too low, or when the ratio of the distance L5 between the center of the fuse groove 1321 and the end of the tail section 132 away from the disc section 131 to the length L4 of the tail section 132 is too high, the fuse groove 1321 is relatively sensitive to temperature and will melt quickly. When the ratio of the minimum cross-sectional area S2 at the fuse groove 1321 to the overall cross-sectional area S1 of the tail body 132 is too high, the fuse groove 1321 becomes less sensitive to temperature and cannot fuse quickly.

[0157] In some embodiments, the positive current collector 130 is made of aluminum. On the one hand, aluminum has the characteristics of low internal resistance and good conductivity. On the other hand, aluminum has a relatively low melting point, so that the fuse groove 1312 can be melted to cut off the current in the event of battery thermal runaway.

[0158] The following is a detailed introduction to core 140.

[0159] As shown in Figures 1, 14, and 18, the core 140 is cylindrical in shape. A positive electrode flattening structure 141 and a negative electrode flattening structure 142 are provided on opposite sides along the axial direction of the core 140. To facilitate its entry into the inner cavity 113 of the outer shell 110 through the opening 114, its diameter is slightly smaller than the inner diameter of the outer shell 110. It can be understood that after the core 140 is inserted into the shell, it is located within the area defined by the neck 1121 and the bottom 111 of the outer shell 110, i.e., in the lower cavity 1132. Furthermore, the positive electrode flattening structure 141 is connected to the cap 120 via the positive electrode current collector 130, and the negative electrode flattening structure 142 is connected to the outer shell 110 via the negative electrode current collector 150.

[0160] As shown in Figure 15, it can be understood that the core 140 is formed by sequentially stacking and winding a first separator 143a, a positive electrode 144a, a second separator 143b, and a negative electrode 144b. After winding, a core hole 145 is formed along the axial direction of the core 140 for injecting electrolyte. It can be understood that before forming the core 140, the positive electrode 144a and the negative electrode 142b need to be fabricated. Both the positive electrode 144a and the negative electrode 144b include a single sheet of current collector substrate, such as aluminum foil or copper foil. Generally, the current collector substrate is rectangular, with a length much greater than its width. The current collector substrate is divided into two regions along the width direction. One region is used for subsequent coating of electrode material, and the other region is used for subsequent die-cutting of tabs. First, the region where the electrode material is to be coated is coated with electrode material, and then multiple tabs spaced apart are die-cut in the tab region. The die-cutting method can be mechanical die-cutting or laser die-cutting, etc. It is understandable that the positive electrode 144a and the negative electrode 144b have basically the same structure. The difference lies in the material of the current collector substrate and the electrode material coated in the material area.

[0161] It is understandable that after the stacked structure of the first separator 143a, the positive electrode 144a, the second separator 143b, and the negative electrode 144b is completed, the full-electrode tab stacked structure located on the positive electrode 144a and the negative electrode 144b needs to be flattened to form a positive electrode flattening structure 141 and a negative electrode flattening structure 142 on opposite sides in the axial direction of the core 140. Furthermore, the positive electrode flattening structure 141 and the negative electrode flattening structure 142 have flat cross-sections, which are suitable for connection with the positive electrode current collector 130 and the negative electrode current collector 150.

[0162] Understandably, during the flattening process of the stacked tab structure, each tab is subjected to flattening force, causing it to bend. During this process, debris may be generated from the tabs. Since the tabs themselves are made of conductive material, this debris falling into the battery may connect the positive and negative electrodes, causing an internal short circuit. Furthermore, if the positive electrode 144a and negative electrode 144b are poorly designed, the flattened positive electrode structure 141 and negative electrode structure 142, due to their high density, lack effective gaps between them, which is detrimental to electrolyte wetting and thus affects the battery's cycle performance.

[0163] This application embodiment, through the rational design of the full-tab stacked structure in the positive electrode 144a and negative electrode 144b, effectively avoids the problem of electrode debris generation caused by the flattening process during the formation of the positive electrode flattening structure 141 and the negative electrode flattening structure 142, and can improve the electrolyte wetting effect to a certain extent, thereby improving the cycle performance of the battery. It should be noted that since the structures of the positive electrode 144a and the negative electrode 144b are basically the same, the following description of the full-tab stacked structure does not specifically distinguish between the positive electrode flattening structure 141 and the negative electrode flattening structure 142. That is, the full-tab stacked structure described below applies to both the positive electrode flattening structure 141 and the negative electrode flattening structure 142.

[0164] Referring to Figures 16 and 17, the full tab stack structure includes a current collector substrate 144, which includes a material area 1441 for coating a polar material and a tab area 1442. Both the material area 1441 and the tab area 1442 extend along the length of the current collector substrate 144. At the location of the tab area 1442, the current collector substrate 144 has a plurality of tabs 1443 spaced apart along the length of the current collector substrate 144. The width of the edge (14431) of the tab 1443 facing the material area is W4, and the distance between the edges 14431 of two adjacent tabs 1443 facing the material area 1441 is W5.

[0165] Experimental testing showed that setting the tab W5 / W4 within the range of 20%-30% helps improve the tension of tab 1443 and avoids debris generation due to the force applied during the flattening process. However, if the width W4 of the tab facing the material area is too wide, it will cause wrinkles during the winding process. These wrinkles on tab 1443 will result in unevenness after the subsequent flattening process, which is detrimental to the subsequent welding process. Specifically, after flattening, tab 1443 needs to be welded to the collector plate. If the flattened tab 1443 is uneven, the thickness will be thinner in the concave areas, easily leading to through-welds. Unevenness also results in poor flatness of the flattened tab 1443, making it prone to weld breakage in the concave areas. Experimental tests showed that setting the W5 / W4 ratio of the tabs within the range of 20%-30% can reduce wrinkles on the tabs during electrode winding, reduce debris generation during tab flattening, and also promote electrolyte wetting. Furthermore, experimental tests also showed that controlling the W5 / W4 ratio within the range of 20%-30% can improve the self-discharge rate K. A smaller K value generally indicates better battery performance. The applicant tested the K values ​​for different W5 / W4 ratios, as shown in Table 3 below.

[0166] Table 3

[0167] As can be seen from the table, controlling the W5 / W4 ratio within the range of 20%-30% can significantly improve its self-discharge rate K, effectively keeping the average self-discharge rate K value below 0.040, resulting in relatively better battery performance.

[0168] In some embodiments, the width W4 of the edge of the tab facing the material area is 0.5-3.0 mm, preferably 1.0-2.5 mm, and more preferably 1.5-2.2 mm. The applicant found through testing that a width W4 of 1.5-2.2 mm for the edge of the tab facing the material area can balance the debris generated during flattening, reduce wrinkles, and decrease self-discharge rate. Specifically, the width W4 of the edge of the tab facing the material area can be 1.7 mm, 1.8 mm, or 1.9 mm, and is not specifically limited.

[0169] In some embodiments, the distance W5 between the edges 14431 of two adjacent tabs 1443 facing the material area is 0.2-0.6 mm. During flattening, the tabs 1443 are bent sequentially from the starting end c to the ending end d of the winding, so that the later bent tab overlaps the previous tab, as shown in Figure 19. An overlap area f and a gap area g are formed between two adjacent tabs 1443. If the gap area g is too large, it will increase the internal resistance of the tab and reduce the current carrying effect. If the gap area g is minimized, the distance W5 between the edges of two adjacent tabs facing the material area should be as small as possible, but this will increase the difficulty of die-cutting and reduce the yield. After testing, controlling the distance W5 between the edges of two adjacent tabs facing the material area to 0.2-0.6 mm can balance the die-cutting difficulty and the current carrying effect. In some embodiments, W5 is preferably 0.3-0.5 mm. In some embodiments, the distance W5 between the edges of two adjacent tabs facing the material area is further preferably 0.3 mm, 0.4 mm, 0.5 mm, etc.

[0170] In some embodiments, the current collector substrate 144 further includes a connecting region 1444, which is located between a plurality of tabs 1443 and a material area 1441. That is, on the current collector substrate 144, a plurality of tabs 1443, a connecting region 1444, and a material area 1441 are sequentially arranged at intervals along the width direction of the current collector substrate 144. In Figure 17, the area between the dashed lines a and b is the connecting region 1444, the area above the dashed line a is the plurality of tabs 1443, and the area below the dashed line is the material area 1441. In the flattening process, if the tabs 1443 are directly connected to the material area 1441, when the tabs 1443 are subjected to the flattening force, the material area 1441 connected to the tabs 1443 is easily subjected to force. In this case, the wound material area 1441 may protrude outward, which will affect the subsequent assembly of the core 140 into the battery casing. Therefore, the purpose of setting the connecting area 1444 is to achieve a certain buffer. When flattening, the connecting area 1444 bends inward, thereby avoiding the problem of the material area 1441 protruding outward.

[0171] In some embodiments, the distance between the edge 14431 connecting the tab 1443 and the connecting area 1444 and the material area 1441 is H7. The tab 1443 is parallelogram in shape, and the length of the edge 14433 of the tab 1443 away from the material area 1441 is H6. The range of H7 / H6 is 10%-20%. The H7 area is the pre-bending area before battery winding. Bending at the connection between the tab and the material area will damage the material area and affect the coating. Therefore, a certain spacing is provided to facilitate bending. If the H7 / H6 ratio is too small, for example, if the H7 spacing is too small, the electrode material area will be bent, affecting the battery coating effect and easily causing a short circuit. For example, if the H6 spacing is too large, the tab will be too high, and the tab will be inserted during the stacking process. Tab insertion refers to the overlapping phenomenon after two adjacent tabs are flattened, which affects the performance of the battery. If the H7 / H6 ratio is too large, for example, if the H7 spacing is too high, the effective height of the tabs will be short, affecting welding and current flow. Conversely, if the H6 spacing is too small, the H6 height will be too low, resulting in a lower number of stacked layers and affecting welding performance. In some embodiments, H7 / H6 is 13%, 15%, 17%, 19%, etc., and the specific ratio is not limited.

[0172] As shown in Figures 16 and 17, 14433 and 14431 are two parallel sides of the parallelogram, and 14432 is the side connecting 14433 and 14431. As those skilled in the art know, the dashed line 14431 is for illustration only and does not exist in the actual product. As mentioned above, the tab 1443 is die-cut from the current collector substrate 144. The tab 1443 includes a side 14431 connected to the current collector substrate, two sides 14432 connected to the first and last ends of the first side, which are generated by die-cutting off part of the electrode material of the current collector substrate, and a side 14433 opposite to the side 14431 connected to the current collector substrate 144. The four sides are connected to form a parallelogram.

[0173] In some embodiments, the distance H7 between the edge 14431 connecting the tab 1443 and the connecting area 1444 and the material area 1441 is 0.4-0.6 mm. If the distance H7 between the edge connecting the tab and the connecting area and the material area is too high, it will reduce the height of the tab 1443, thereby affecting the subsequent welding effect and current flow effect. During battery manufacturing, the height and diameter of the battery are generally fixed according to industry standards. Therefore, the length, width, and thickness of the current collector substrate 144 are also basically fixed. A connection area 1443 is reserved in the tab area 1442 of the current collector substrate 144 for bending. At this time, in order to maximize the battery capacity, the width of the material area 1441 remains unchanged, and the width of the tab 1443 can only be reduced. If the width of the connection area 1444 is too wide, the width of the tab 1443 will be too narrow. If the tab 1443 is too narrow, it will affect the welding effect. After flattening, the outer tab 1443 will overlap the inner tab 1443. If the tab 1443 is too narrow, some areas will appear very thin due to the small number of overlapping tabs 1443, which will easily cause through welding during subsequent welding. Secondly, it will affect the current carrying effect. If the tab 1443 is too short, the entire tab area becomes thinner, the internal resistance increases, and the overcurrent decreases. After testing, the distance H7 between the edge connecting the electrode tab and the connection area and the material area is 0.4-0.6mm, which easily balances the problem of the material area protruding outward and the welding effect and the current overcurrent effect.

[0174] In some embodiments, the angle β between the edge 14432 of the electrode tab connected to the edge facing the material area and the width direction of the current collector substrate 144 is 14-18°.

[0175] The purpose of the beveling is to tilt the tabs to one side after flattening. Although there is a gap after the tabs are cut, they can still fit together as closely as possible after flattening, increasing the density of the flattened tabs. After flattening, two adjacent tabs 1443 will form an overlap area f and a gap area g. If the included angle is too small, such as in the case of a rectangular structure, it will result in an excessively large gap area g between the tabs, making the overall density of the tabs too low, which will make them prone to soldering through and thus affecting the welding performance. In addition, if the included angle is too small, the stress on the tabs will be too high, which will still easily generate particles and debris during the subsequent flattening process, posing a short circuit risk and affecting the battery safety performance. If the included angle is too large, it will also result in an excessively large gap area g between the tabs, which will reduce the overall density of the tabs and affect the subsequent welding performance. In addition, an excessively large included angle will result in insufficient stress between the tabs, which will easily cause wrinkles and cracks in the wound electrode sheets, ultimately affecting the overall safety and cycle performance of the battery. Therefore, this invention sets the included angle β in the range of 14-18°, which ensures sufficient electrolyte wetting of the electrode while maintaining appropriate density after the electrode tab is flattened, and also takes into account the welding performance of the electrode tab, thus providing sufficient safety and cycle performance. The applicant tested the area values ​​of the gap region g at different included angles β, as shown in Table 4 below. In some embodiments, the included angle β is set to 14°, 16°, 18°, etc.

[0176] Table 4

[0177] In some embodiments, as shown in FIG15, the core 140 is formed by sequentially stacking and winding a first separator 143a, a positive electrode 144a, a second separator 143b, and a negative electrode 144b. The starting end of winding is called the beginning end c, and the end at the outermost layer after winding is called the end end d. After winding, the first separator 143a is located at the innermost side of the core 140.

[0178] As shown in Figure 15, in some embodiments, the length of the plurality of tabs 1443 of the tab region 1442 along the length direction of the current collector substrate 144 is less than the length L7 of the material region 1441. The end of the material region 1441 facing the tab region 1442 along the length direction of the current collector substrate 144 is not connected to the connection region 1444. The end not connected to the connection region 1444 is called the first cut-off region 1445. The end not connected to the connection region 1444 can be located at either the beginning c or the end d.

[0179] In some embodiments, the first cut-out area 1445 of the current collector substrate 144 is located at the first end c, that is, the first end c of the current collector substrate 144 is die-cut during die cutting so that the first end c does not have tabs. If the first end c has tabs, after winding and flattening, the tabs located at the first end c are prone to clogging the core hole 145, which is not conducive to subsequent electrolyte injection.

[0180] In some embodiments, the length of the first cut-out region 1445 is L8, and the ratio of L8 to L7 is 5%-15%. If L8 / L7 is too small, it can easily cause blockage of the core hole 145; if L8 / L7 is too large, it can easily expose the diaphragm, allowing metal debris to enter the electrolyte and potentially causing a short circuit. Controlling the value of L8 / L7 between 5% and 15% reduces both the blockage of the core hole 145 and the probability of a short circuit. In some embodiments, L8 / L7 is 7%, 9%, 11%, 13%, etc., and there is no specific limitation.

[0181] In some embodiments, the length L8 of the first excision region 1445 is 105-130 mm. Further, L8 is preferably 144 mm, 115 mm, 120 mm, 125 mm, etc., and there is no specific limitation.

[0182] In some embodiments, one end of the material area 1441 facing the tab area 1442 along the length of the current collector substrate 144 is not connected to the connecting area 1444. This end is referred to as the second cutting area 1446, which can be located at either the beginning end c or the end end d. In some embodiments, the second cutting area 1446 is located at the end d. If the end d has a tab, the tab will protrude outward during the flattening process, affecting the subsequent assembly of the core 140 into the shell.

[0183] In some embodiments, the length of the second cut-out area 1446 is L9, and the ratio of L9 to L7 is 10%-20%. If L9 / L7 is too small, the core 140 is prone to folding, causing it to protrude from the diaphragm and affecting its insertion into the casing. If L9 / L7 is too long, the diaphragm is easily exposed, allowing metal debris to enter the electrolyte and potentially causing a short circuit. Controlling L9 / L7 to 10%-20% facilitates the insertion of the core 140 into the casing while reducing the probability of a short circuit. In some embodiments, L9 / L7 is 13%, 15%, 18%, etc., and there is no specific limitation.

[0184] In some embodiments, the length L9 of the second excision region 1446 is 175-205 mm. Further, L9 is preferably 185 mm, 195 mm, etc., and there is no specific limitation.

[0185] In some embodiments, one end of the tab region 1442 has a first cut-off region 1445, and the other end has a second cut-off region 1446. The length of the first cut-off region 1445 along the length direction of the current collector substrate 144 is L8, and the ratio of L8 / L7 is in the range of 5%-15%. The length of the second cut-off region 1446 along the length direction of the current collector substrate 144 is L9, and the ratio of L9 / L7 is in the range of 10%-20%. In some embodiments, the heights of the first cut-off region 1445 and the second cut-off region 1446 are flush along the width direction.

[0186] The following is a detailed introduction to the negative electrode current collector 150.

[0187] As shown in Figures 1 and 20, the negative electrode current collector 150 is generally circular. Along the thickness direction, the negative electrode current collector 150 has a first side 151 and a second side 152 that are opposite to each other. Since the second side 152 is provided with the raised platform 1521 described below, it is necessary to distinguish the direction when welding the negative electrode current collector 150 to the outer shell 110 and the core 140. Specifically, the second side 152 is welded to the bottom of the shell 111 through the raised platform 1521, and the first side 151 is welded to the negative end of the core 140. Thus, the welding connection between the core 140, the negative electrode current collector 150 and the outer shell 110 is realized, and a passage is formed between the three. That is, the negative electrode current collector 150 indirectly connects the core 140 and the outer shell 110.

[0188] To ensure good contact between the raised platform 1521 and the surface of the housing 110, in this embodiment, the negative electrode current collector 150 is provided with a raised platform 1521 with a flat surface on the second side 152. The surface of the raised platform 1521 is higher than the surface of the second side 152, and the surface area of ​​the raised platform 1521 is smaller than the surface area of ​​the second side 152. The surface of the raised platform 1521 is suitable for contacting the inner surface of the bottom of the housing 111, and the flatness of the surface of the raised platform 1521 is 0.01-0.05mm. Understandably, since the surface of the raised platform 1521 is higher than the surface of the second side 152, meaning the surface of the raised platform 1521 is the top surface of the second side 152, after the negative current collector 150 is assembled into the housing 110, the surface of the raised platform 1521 will abut against the inner surface of the housing bottom 111. That is, the surface of the raised platform 1521 and the inner surface of the housing bottom 111 are tightly fitted together, forming a surface-to-surface contact connection. Then, laser welding can be performed through the outer surface 1112 of the base plate to the area where the raised platform 1521 overlaps with the housing bottom 111, thus welding the raised platform 1521 to the housing 110. It is also understandable that if the flatness of the raised platform 1521 is too large, its fit with the inner surface of the housing bottom 111 will be poor, thus affecting the welding quality; conversely, if the flatness of the raised platform 1521 is too small, it will be difficult to process and the cost will be too high.

[0189] In this embodiment, since the ratio of the diameter D8 of the negative electrode current collector 150 to the diameter D6 of the core 140 is set at 90%-98%, the weldable area between the negative electrode current collector 150 and the core 140 can be effectively increased, resulting in good welding processability. At the same time, a smaller raised platform 1521 is provided on the second side 152 of the negative electrode current collector 150. Due to its smaller area, the raised platform 1521 can maintain good surface flatness during processing, thereby improving the fit between the surface of the raised platform 1521 and the inner surface of the shell bottom 111. This effectively avoids welding quality problems such as incomplete welding. The battery using this negative electrode current collector 150 has better performance and yield.

[0190] For ease of processing and cost reduction, in some embodiments, the raised platform 1521 is formed from the negative electrode current collector 150 by a stamping process; that is, the raised platform 1521 and the negative electrode current collector 150 are integrally formed. Therefore, with a reasonable stamping die design, the negative electrode current collector 150 of this embodiment can be processed efficiently, and both the negative electrode current collector 150 and the raised platform 1521 have high dimensional accuracy and good surface quality, facilitating welding with the core 140 and the outer shell 110. Of course, this is not the only possibility; the raised platform 1521 can also be formed in other ways. For example, the raised platform 1521 can be a sheet metal component with excellent weldability and conductivity, which can be bonded to the surface of the second side 152 of the negative electrode current collector 150 by pressing, thereby forming the raised platform 1521.

[0191] In some embodiments, the raised platform 1521 is formed in the central region of the second side 152, so that after the negative current collector 150 is assembled into the housing 110, the raised platform 1521 can be aligned with the central region of the bottom of the housing 111, which facilitates welding of the housing 110 and the raised platform 1521 by welding equipment.

[0192] Furthermore, the raised platform 1521 is circular in shape, so that it can be set with the negative electrode current collector 150 at the same center, which facilitates stamping and forming by a stamping die. Of course, the shape of the raised platform 1521 is not limited to circular; for example, the raised platform 1521 can also be square, triangular, or other shapes.

[0193] As shown in Figures 20 and 21, it can be understood that a raised platform 1521 is punched out on the second side 152 of the negative electrode current collector 150 through a stamping process. Correspondingly, a recess 1511 is formed on the first side 151 at the position corresponding to the raised platform 1521. For the purpose of facilitating the welding of the negative electrode current collector 150 and the core 140, in some embodiments, the first side 151 has an annular welding area 1512 around the recess 1511. The surface of the welding area 1512 is adapted to abut against the negative end of the core 140. For example, the welding area 1512 is also configured to have a flat surface so that the surfaces of the two can fit tightly against each other to improve the welding quality.

[0194] As shown in Figure 21, in some embodiments, the diameter D9 of the raised platform 1521 is 28%-38% of the diameter D8 of the negative electrode current collector 150, i.e., D9 / D8 = 28%-38%. As mentioned earlier, the diameter D8 of the negative electrode current collector 150 is roughly the same as the diameter of the core 140. If the diameter of the raised platform 1521 is too large, its surface flatness will be poor, and its fit with the inner surface of the shell bottom 111 will be poor, thus affecting the welding quality. Conversely, if the diameter of the raised platform 1521 is too small, the weldable area of ​​the raised platform 1521 will be small, and it will be easy to detach during welding, which will increase the difficulty of subsequent welding processes and lead to increased costs.

[0195] Further, as shown in Figure 22, in some embodiments, the height difference H8 between the surface of the raised platform 1521 and the surface of the second side 152 is 18%-30% of the thickness T5 of the negative electrode current collector 150, that is, H8 / T5 = 18%-30%. It is understood that if the raised platform 1521 is set too high, that is, H8 / T5 is too large, the core 140 will squeeze and deform the periphery of the negative electrode current collector 150 during the assembly process, and will also occupy additional longitudinal space of the battery; conversely, if the raised platform 1521 is set too low, that is, H8 / T5 is too small, the raised platform 1521 will be difficult to process, for example, it will be difficult to form the raised platform 1521 by stamping process.

[0196] In some embodiments, the negative current collector 150 is made of copper, and its surface is plated with a nickel layer. Compared to a negative current collector 150 made of copper-nickel alloy, using copper as the substrate has the characteristic of extremely low internal resistance. At the same time, by plating a nickel layer on the surface of the negative current collector 150, the corrosion resistance of the negative current collector 150 can be effectively improved.

[0197] Furthermore, the thickness of the nickel layer is set to 0.08-1.5 μm, more preferably 0.9-1.1 μm. It is understandable that if the nickel layer thickness is too small, it cannot provide oxidation protection; conversely, if the nickel layer thickness is too large, it increases the difficulty and cost of the nickel plating process, and also increases the hardness of the negative electrode current collector 150, leading to reduced plasticity and increased internal resistance, resulting in decreased battery performance.

[0198] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this implementation. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0199] Although embodiments of this implementation have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of this implementation, the scope of which is defined by the claims and their equivalents.

Claims

1. A cylindrical lithium battery, characterized by, Includes a housing (110), a cap (120), a positive current collector (130), a core (140), and a negative current collector (150), wherein: The outer shell (110) includes a bottom (111) and a side wall (112). The top end of the side wall (112) has an opening (114). The side wall (112) is circumferentially concave to form a neck (1121) near the opening (114). The outer surface of the side wall (112) forms a necking groove (1123) at the necking groove (1121). The core (140) is located in the area defined by the necking groove (1121) and the bottom (111) within the outer shell (110). The height H2 of the necking groove (1123) is 0.1%-1% of the height H1 of the outer shell (110). The depth H3 of the necking groove (1123) in the radial direction is 5%-10% of the outer diameter D1 of the outer shell (110). The positive current collector (130) includes a disk body (131) and a tail body (132) connected to each other. The disk body (131) is connected to the positive end of the winding core (140), and the tail body (132) is connected to the cap (120). The center of the disk body (131) is provided with a circular first hole (1315), and at least one circular second hole (1316) is provided around the first hole (1315). All the second holes (1316) are... The sum of the areas is 0.9-1.5 times the area of ​​the first hole (1315); at least one fusion groove (1321) is provided on the tail body (132), and the tail body (132) has an overall cross-sectional area S1 at the position other than the fusion groove (1321), and the tail body (132) has a minimum cross-sectional area S2 at the position of the fusion groove (1321), and the minimum cross-sectional area S2 is 45%-65% of the overall cross-sectional area S1.

2. The cylindrical lithium battery of claim 1, wherein, The core (140) has a through core hole (145), the diameter D4 of the first hole (1315) is 1.4-1.8 times the diameter D7 of the core hole (145); the negative electrode current collector (150) has a first side (151) and a second side (152) opposite to each other, the first side (151) is connected to the negative end of the core (140), and the center of the second side (152) is provided with a flat raised platform (1521), the raised platform (1521) is connected to the inner surface of the shell bottom (111), and the flatness of the surface of the raised platform (1521) is 0.01-0.05mm.

3. The cylindrical lithium battery of claim 2, wherein, The diameter D3 of the disk body (131) is 80%-95% of the diameter D6 of the core (140); the diameter D8 of the negative electrode current collector (150) is 90%-98% of the diameter D6 of the core (140); the raised platform (1521) is circular and located at the center of the second side (152); the diameter D9 of the raised platform (1521) is 28%-38% of the diameter D8 of the negative electrode current collector (150).

4. The cylindrical lithium battery of claim 2, wherein, The diameter D5 of the second hole (1316) is 50%-70% of the diameter D4 of the first hole (1315); the height difference H8 between the surface of the raised platform (1521) and the surface of the first side (151) is 18%-30% of the thickness T5 of the negative electrode collector (150).

5. The cylindrical lithium battery according to any one of claims 2 to 4, characterized in that, The disc body (131) is a closed axisymmetric figure formed by connecting the first side (1311), the arc (1312), the second side (1313), and the third side (1314) end to end. The tail body (132) is a closed axisymmetric figure formed by connecting the third side (1314), the fifth side (1322) extending along the length of the tail, the fourth side (1324) away from the disc body, and the sixth side (1323) extending along the length of the tail end to end. The two ends of the fifth side (1322) are respectively connected to the fourth side (1324). The sixth side (1323) is connected to the first side (1311), and the two ends of the sixth side (1323) are connected to the fourth side (1324) and the second side (1313) respectively. The raised platform (1521) is integrally formed by stamping the negative electrode current collector (150). The first side (151) forms a recess (1511) at a position corresponding to the raised platform (1521). Around the recess (1511), the first side (151) forms a welding area (1512). The surface of the welding area (1512) abuts against the negative end of the core (140).

6. The cylindrical lithium battery of claim 5, wherein, The length L4 of the tail section (132) is 85%-95% of the diameter D3 of the disc section (131); the distance L5 between the center of the fuse groove (1321) and the end of the tail section (132) away from the disc section (131) is 68%-78% of the length L4 of the tail section (132).

7. The cylindrical lithium battery of claim 5, wherein, The disc body (131) has a central angle A, and 40°≤∠A≤60°, wherein the central angle A has the center of the circle corresponding to the arc (1312) as its vertex, and the two sides pass through the endpoints of the first side (1311) away from the arc (1312) and the second side (1313) away from the arc (1312), respectively; the first width W2 of the tail body (132) is D3*sin(∠B / 2), and 20°≤∠B≤40°, wherein ∠B has the center of the circle corresponding to the arc (1312) as its vertex, and the two sides pass through the intersection points of the fifth side (1322) and the sixth side (1323) with the whole circle containing the arc (1312), respectively.

8. The cylindrical lithium battery of claim 7, wherein, The second width W3 of the tail section (132) at the fuse groove (1321) is 3 / 8 to 3 / 4 of the first width W2; the dimension L6 of the fuse groove (1321) along the length direction of the tail section (132) is 0 < L6 ≤ W2.

9. The cylindrical lithium battery of claim 5, wherein, The angle θ1 between the fifth side (1322) and the first side (1311) is 45-90°, and the angle θ2 between the sixth side (1323) and the second side (1313) is 45-90°.

10. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that, The neck (1121) includes a first wall portion (1121a) and a second wall portion (1121b) extending toward the center of the outer casing (110). The neck (1121) also includes a connecting portion (1121c) for connecting the first wall portion (1121a) and the second wall portion (1121b). The outer surfaces of the first wall portion (1121a), the second wall portion (1121b), and the connecting portion (1121c) together define a necking groove (1123). 1b) All are inclined at a certain angle to the bottom of the shell (111); the cap (120) includes a stacked explosion-proof valve plate (122) and a terminal plate (124), the tail part (132) is connected to the bottom of the terminal plate (124), the explosion-proof valve plate (122) is provided with a first groove (1221a) and a second groove (1221b), the first groove (1221a) is a closed circle with the ends connected, the second groove (1221b) is a line segment, and the first groove (1221a) and the second groove (1221b) intersect.

11. The cylindrical lithium battery of claim 10, wherein, The larger of the angles between the first wall portion (1121a) and the shell bottom (111) and the second wall portion (1121b) and the shell bottom (111) is α, and the range of α is α < 10°; the explosion-proof valve plate (122) is provided with a thinning portion (1222) extending in the radial direction, the first notch (1221a) is provided within the radial range of the thinning portion (1222), the thickness of the thinning portion (1222) is T3, the depth of the first notch (1221a) is H4, and the range of H4 / T3 is 30%-60%.

12. The cylindrical lithium battery of claim 11, wherein, The range of α is 1-5°; the width of the thinned portion (1222) is W1, and the range of W1 is 3-8 mm.

13. The cylindrical lithium battery of claim 10, wherein, The minimum wall thickness of the neck (1121) is T2, the wall thickness of the sidewall (112) is T1, and the range of T2 / T1 is more than 80%; the diameter D2 of the first notch (1221a) is equal to the length L2 of the second notch (1221b).

14. The cylindrical lithium battery of claim 13, wherein, The range of T2 is 0.1-0.2mm; the bottom of the first notch (1221a) and the second notch (1221b) are provided with chamfered portions, and the radii of the chamfered portions are the same, the radius of the chamfered portions is R, and the range of R is 0.05-0.15mm.

15. The cylindrical lithium battery of claim 10, wherein, The distance L1 from the lowest point of the constricted neck (1121) to the upper surface of the shell bottom (111) is 90%-98% of the height H1 of the outer shell (110); the depth H4 of the first notch (1221a) is less than the depth H5 of the second notch (1221b), and the depth of the middle part of the second notch (1221b) is greater than the depth of both ends.

16. The cylindrical lithium battery according to any one of claims 1 to 4, characterized by, The core (140) has opposing positive electrode flattening structures (141) and negative electrode flattening structures (142). Both the positive electrode flattening structure (141) and the negative electrode flattening structure (142) are formed by flattening a full-tab stacked structure. The full-tab stacked structure includes a current collector substrate (144). The current collector substrate (144) is divided along its width into a material area (1441) for coating polar materials and an electrode area (1442). Both the material area (1441) and the electrode area (1442) extend along the length direction of the current collector substrate (144). The current collector substrate (144) has a [specific feature] at the electrode area (1442). There are multiple tabs (1443) spaced apart along the length direction. The width of the side (14431) of the tab (1443) facing the material area (1441) is W4. The distance between the sides (14431) of two adjacent tabs (1443) facing the material area (1441) is W5. The range of W5 / W4 is 20%-30%. The shape of the tab (1443) is a parallelogram. The angle β between the side (14432) connected to the side (14431) of the tab (1443) facing the material area (1441) and the width direction of the current collector substrate (144) is 14-18°.

17. The cylindrical lithium battery of claim 16, wherein, A connecting area (1444) is also provided between the material area (1441) and the electrode area (1442). The distance between the edge (14431) connecting the electrode (1443) and the connecting area (1444) and the material area (1441) is H7. The length of the edge (14433) of the electrode (1443) away from the material area (1441) is H6. The range of H7 / H6 is 10%-20%.

18. The cylindrical lithium battery of claim 17, wherein, The range of H7 is 0.4-0.6 mm, and the range of W4 is 1.5-2.2 mm.

19. The cylindrical lithium battery of claim 16, wherein, The length of the plurality of tabs (1443) of the tab region (1442) along the length direction of the current collector substrate (144) is less than the length L7 of the material region (1441). One end of the tab region (1442) has a first cut-off area (1445) and the other end has a second cut-off area (1446). The length of the first cut-off area (1445) along the length direction of the current collector substrate (144) is L8, and the range of L8 / L7 is 5%-15%. The length of the second cut-off area (1446) along the length direction of the current collector substrate (144) is L9, and the range of L9 / L7 is 10%-20%.

20. The cylindrical lithium battery of claim 19, wherein, The range of L8 is 105-130mm, and the range of L9 is 175-205mm.

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