Cylindrical lithium battery

Abstract

Provided in the present application is a cylindrical lithium battery. A jelly roll of the cylindrical lithium battery has a flattened positive electrode structure and a flattened negative electrode structure, which are formed by flattening full-tab cut-and-stack structures, wherein each full-tab cut-and-stack structure comprises a current collector substrate, the current collector substrate being divided into a material region for applying a polar material and a tab region, and having a plurality of tabs arranged at intervals in the direction of length; the width of the edge of each tab facing the material region is W2, and the distance between the edges of two adjacent tabs facing the material region is W3, with W3 / W2 ranging from 20% to 30%; and the included angle β between the edge connected to the edge of each tab facing the material region and the direction of width of each current collector substrate is 14-18°. By means of optimally selecting the width W2 of a die-cut tab and the tab spacing W3, and setting the included angle β between the obliquely cut edge of each tab and the direction of width of each current collector substrate to be 14-18°, the cycle performance and safety performance of the battery can be improved.

Description

A cylindrical lithium battery TECHNICAL FIELD

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

[0002] The cylindrical battery is usually packaged with a cylindrical steel shell, and the bare cell is made by winding the positive and negative electrode sheets into a cylindrical core. The cap is located at the top of the battery and is connected to the positive electrode of the core through the positive current collector plate, and the bottom of the steel shell is connected to the negative electrode of the core.

[0003] In the related art, in order to facilitate connection with the positive and negative current collector plates, corresponding positive and negative end structures need to be provided at both ends of the core. At present, due to the advantages of full tab in reducing battery internal resistance, improving battery capacity and rate discharge capacity, etc., the positive and negative electrode sheets adopting full tab and the positive and negative end structures formed by full tab have gradually become the mainstream. However, if the full tab design is unreasonable, various process defects and structural defects will be generated in the process of forming the positive and negative end structures, thereby affecting the cycle performance and safety of the battery. Therefore, reasonable design and implementation of the positive and negative end structures are urgent technical problems to be solved. SUMMARY

[0004] The present application provides a cylindrical lithium battery to at least solve the technical problem of unsatisfactory cycle performance and safety performance caused by unreasonable positive and negative structures of the core in the existing cylindrical lithium battery.

[0005] The first aspect of the present application provides a cylindrical lithium battery, comprising a shell, a cap, a positive current collector plate, a core and a negative current collector plate, the core having opposite positive and negative tabbing structures, the positive and negative tabbing structures are both formed by full tab tabbing, the positive tabbing structure is connected to the cap through the positive current collector plate, and the negative tabbing structure is connected to the shell through the negative current collector plate.

[0006] The full tab tabbing structure comprises a current collector substrate, the current collector substrate is divided into a material area for applying a polar material and a tab area along the width direction, the material area and the tab area both extend along the length direction of the current collector substrate, the current collector substrate has a plurality of tabs spaced apart along the length direction at the tab area, the width of the edge of the tab facing the material area is W2, the distance between the edges of two adjacent tabs facing the material area is W3, the range of W3 / W2 is 20%-30%, and the shape of the tab is a parallelogram, the angle β between the edge of the tab facing the material area and the width direction of the current collector substrate is 14-18°.

[0007] The cylindrical lithium battery according to the embodiments of this application has at least the following beneficial effects:

[0008] 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 likelihood of debris falling into the battery, thus lowering the probability of a short circuit. 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 the battery's cycle performance.

[0009] Furthermore, 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 tab can still fit as closely as possible after being flattened, thus ensuring that the tab has a suitable density after being flattened. This ensures that the tab has sufficient electrolyte wetting effect while also taking into account the welding performance of the tab and reducing the generation of debris particles, thereby improving the safety and cycle performance of the battery.

[0010] In one possible implementation, the outer casing includes a bottom and a sidewall. The top of the sidewall has an opening, and 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 casing. The cap is received by the neck and closes the opening. The cap includes an explosion-proof valve plate. The explosion-proof valve plate has a first notch and a second notch. The first notch is a closed circle with its ends connected, and the second notch is a line segment. The first notch and the second notch intersect.

[0011] By incorporating a necked-off section on the side wall, sealing is facilitated to enclose the core and other components within the casing. Simultaneously, the explosion-proof valve plate features a first and second notch. When an abnormal condition such as overheating or a short circuit occurs inside the battery, causing a rapid increase in internal pressure, either the edge or central pressure zone will reach the preset value first, and one of the first and second notches will break. This allows for timely pressure relief. Furthermore, since the first and second notches intersect, the breakage of either notch will also cause the other to break, thus expanding the opening area of ​​the explosion-proof valve plate and improving the pressure relief effect. Consequently, when the internal gas pressure exceeds the preset value, the explosion-proof valve plate can quickly and effectively open to release pressure, thereby enhancing battery safety.

[0012] In one possible implementation, the distance L1 from the lowest point of the neck to the upper surface of the shell bottom is equal to the height H of the shell, the height of the neck groove is H1, and the range of L1 / H is 90%-98%; a connecting area is also 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 H6, the distance between the side of the tab away from the material area and the material area is H5, and the range of H6 / H5 is 10%-20%.

[0013] 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. In addition, by setting up the connection area and rationally designing the dimensions of the connection area and the tab, the flattened positive and negative electrode structures have good welding performance, current carrying capacity and reliability.

[0014] In one possible implementation, the height of the necking groove is H1, and the range of H1 / H is 0.1%-1%; the range of H6 is 0.4-0.6 mm.

[0015] By rationally designing the height of the necking groove, the internal space utilization 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 necking groove and the sealing process. In addition, by rationally designing the distance between the edge connecting the tab and the connection area and the material area, the problem of the material area protruding outward and the welding effect and current flow effect are balanced.

[0016] In one possible implementation, the depth of the necking groove in the radial direction is H2, the outer diameter of the outer shell is D1, the range of H2 / D1 is 5%-10%, and the range of W2 is 1.5-2.2 mm.

[0017] By rationally designing the depth of the necking groove, the cap can be stably supported by the first wall for easy sealing, while also improving the utilization rate of the internal space of the casing, further increasing the energy density of the lithium battery. Simultaneously, by rationally setting the tab width, sufficient tension can be ensured on the tabs, reducing chipping during the flattening process and preventing scattering and chipping, while also improving the flattening effect to guarantee welding performance.

[0018] 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 the 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 explosion-proof valve plate has a thinning portion extending in the radial direction. The first groove is provided within the radial range where the thinning portion is located.

[0019] By setting the first and second wall portions constituting the neck to be inclined towards the bottom of the shell, a certain amount of sag allowance is reserved in the neck. Therefore, it is convenient to design the grooving in the preceding grooving process, which facilitates the formation of the required neck structure in the sealing process. At the same time, by setting the thinning part, the first notch can be effectively broken when the opening conditions are met to release the battery pressure, while also ensuring that the explosion-proof valve plate has sufficient strength and rigidity, which is convenient for processing and assembly.

[0020] 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 thickness of the thinned portion is T2, the depth of the first notch is H3, and the range of H3 / T2 is 30%-60%.

[0021] 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.

[0022] In one possible implementation, the range of α is 1° < α < 5°; the width of the thinned portion is W1, and the range of W1 is 3-8 mm.

[0023] 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.

[0024] In one possible implementation, the minimum wall thickness of the neck is T1, the wall thickness of the sidewall is T, and the range of T1 / T is 80% or more; the diameter D2 of the first notch is equal to the length L2 of the second notch.

[0025] 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.

[0026] In one possible implementation, the minimum wall thickness of the neck is T1, the wall thickness of the sidewall is T, and the range of T1 / T is 85% or more; the bottom of the first notch and the second notch are provided with chamfered portions.

[0027] By rationally designing the wall thickness at the thinnest point of the neck, the pressure resistance of the outer shell can be ensured to meet the requirements. Simultaneously, by providing chamfered portions at the bottom of the first and second notches, stress concentration at the bottom of the first and second notches can be reduced, lowering the risk of the explosion-proof disc accidentally opening when the pressure value does not reach the preset value.

[0028] In one possible implementation, T1 ranges from 0.1 to 0.2 mm; the radius of the chamfered portion is the same, and the radius of the chamfered portion is R, which ranges from 0.05 to 0.15 mm.

[0029] 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.

[0030] In one possible implementation, the neck is formed by a groove formed on the sidewall through a sealing process; the depth H3 of the first notch is less than the depth H4 of the second notch, and the depth of the middle part of the second notch is greater than the depth of both ends.

[0031] The sealing process allows for plastic deformation of the sidewall at the groove, achieving the desired necking. This process is simple and produces consistent quality. Simultaneously, increasing the depth of the second notch reduces the impact of the increased thickness of the explosion-proof valve disc in the central region, ensuring smooth opening at the second notch. Furthermore, setting the depth of the second notch to be greater in the middle than at the ends (i.e., deeper in the middle and shallower at the ends) mitigates the impact of the stepped thickness variation in the central region, further ensuring smooth opening at the second notch.

[0032] 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 L3 of the material region. One end of the tab region has a first cut-off area or a second cut-off area. The length of the first cut-off area along the length direction of the current collector substrate is L4, and the range of L4 / L3 is 5%-15%. The length of the second cut-off area along the length direction of the current collector substrate is L5, and the range of L5 / L3 is 10%-20%.

[0033] 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 L3 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 L4, and the range of L4 / L3 is 5%-15%. The length of the second cut-off area along the length direction of the current collector substrate is L5, and the range of L5 / L3 is 10%-20%.

[0034] 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.

[0035] In one possible implementation, the range of L4 is 105-130 mm, and the range of L5 is 175-205 mm.

[0036] 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

[0037] 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.

[0038] Figure 1 is an exploded view of a cylindrical lithium battery according to an embodiment of this application;

[0039] 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;

[0040] Figure 3 is a partial schematic diagram of point A in Figure 2;

[0041] Figure 4 is a cross-sectional schematic diagram of the cap in a cylindrical lithium battery according to an embodiment of this application;

[0042] Figure 5 is a top view of an explosion-proof valve plate in a cylindrical lithium battery according to an embodiment of this application;

[0043] Figure 6 is a cross-sectional view of the explosion-proof valve plate in Figure 5;

[0044] Figure 7 is a partial schematic diagram of point B in Figure 6;

[0045] Figure 8 is a partial schematic diagram of point C in Figure 6;

[0046] Figure 9 is a schematic diagram of the structure of a cylindrical lithium battery according to an embodiment of this application, showing the welding of the core to the positive electrode current collector and the negative electrode current collector.

[0047] Figure 10 is a schematic diagram of the core in a cylindrical lithium battery before winding, according to an embodiment of this application.

[0048] Figure 11 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;

[0049] Figure 12 is a partial schematic diagram of point D in Figure 11;

[0050] Figure 13 is a schematic diagram of the flattened full-teg stacked structure in Figure 11;

[0051] Figure 14 is a partial schematic diagram of point E in Figure 13.

[0052] 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-thinned portion, 1223-groove, 1224-welding platform, 123-insulating plate, 124-terminal plate, 125-insulating ring; 130-positive current collector, 131-disc body portion, 132-tail body portion; 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-Taper area, 1443-Taper, 14431-Side connecting the tab and the connecting area, 14432-Side connecting the tab towards the material area, 14433-Side of the tab away from the material area, 1444-Connecting area, 1445-First cut-out area, 1446-Second cut-out area; 150-Negative electrode current collector. Detailed Implementation

[0053] 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.

[0054] 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.

[0055] 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.

[0056] 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.

[0057] The cylindrical lithium batteries provided in this application include various size series, such as the 21 series (cylindrical lithium batteries with an outer diameter of 21 mm) and the 46 series (cylindrical lithium batteries with an outer diameter of 46 mm), and are not limited herein. Specifically, as shown in Figure 1, 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 electrode of the core 140 is connected to the cap 120 through the positive current collector 130, and the negative electrode of the core 140 is connected to the casing 110 through the negative current collector 150. Thus, the cap 120 serves as the positive electrode of the cylindrical lithium battery, and the casing 110 serves as the negative electrode of the cylindrical lithium battery for electrical connection with external electrical equipment.

[0058] The following is a detailed description of the casing 110.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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°.

[0067] 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°.

[0068] 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.

[0069] 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.

[0070] In some embodiments, the distance L1 between the lowest point of the neck 1121 in the inner cavity 113 and the upper surface of the bottom shell 111 is taken as L1, and the height H of the outer shell 110 is taken as H, satisfying the condition: 90% ≤ L1 / H ≤ 98%. It is understood that if the distance L1 between the lowest point of the neck 1121 and the upper surface of the bottom shell 111 is too large, i.e., L1 / H is too large, it will affect the height of the upper cavity 1131, resulting in a poorer sealing effect; conversely, if the distance L1 between the lowest point of the neck 1121 and the upper surface of the bottom shell 111 is too small, i.e., L1 / H is too small, it will affect the height of the lower cavity 1132, wasting the height of the outer shell 110 and resulting in a lower battery energy density. 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 shell 111, the sealing effect at the seal can be ensured while also improving the utilization rate of the internal space of the outer shell 110 and increasing the battery energy density.

[0071] Furthermore, in some embodiments, the height of the necking groove 1123 is defined as H1, and the height of the outer casing 110 is defined as H, where 0.1% ≤ H1 / H ≤ 1%. It is understood that if the height H1 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 H1 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, and the sealing process will also be more difficult, leading to a decrease in yield. By rationally designing the height H1 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 H1 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 H1. More preferably, 0.2% ≤ H1 / H ≤ 0.5%.

[0072] In some embodiments, the depth of the constriction groove 1123 in the radial direction is H2, and the outer diameter of the outer shell 110 is D1, wherein 5% ≤ H2 / D1 ≤ 10%. It is understood that if the depth H2 of the constriction groove 1123 is too large, i.e., H2 / D1 is too large, the constriction neck 1121 will excessively intrude into the inner cavity 113 in the radial direction, resulting in a smaller inner diameter of the inner cavity 113 at the constriction neck 1121, causing wasted space, and also weakening the structural rigidity of the constriction neck 1121 itself, increasing stress, and posing a risk of cracking, thereby failing to guarantee the sealing performance; conversely, if the depth H2 of the constriction groove 1123 is too small, i.e., H2 / D1 is too small, the cap 120 cannot be stably supported by the first wall portion 1121a, and the dimensional chain matching between the two is poor. During sealing, the cap 120 may directly pass through the groove defined by the constriction neck 1121 and enter the lower cavity 1132. By rationally designing the depth H2 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.

[0073] 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 T1, and the wall thickness of the outer shell 110 is defined as T, wherein T1 / T ≥ 80%, more preferably, T1 / T ≥ 85%. It is understandable that this minimum wall thickness T1 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 T1 / T 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 location. By reasonably designing the wall thickness T1 at the thinnest point of the neck 1121, it can be ensured that the pressure resistance of the outer shell 110 meets the requirements.

[0074] In some embodiments, to ensure the pressure resistance of the housing 110, the minimum wall thickness of the neck 1121 is set as T1, where 0.1mm ≤ T1 ≤ 0.2mm. It is understood that setting the minimum wall thickness T1 of the neck 1121 between 0.1mm and 0.2mm 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 0.2mm, the minimum wall thickness T1 of the neck 1121 can be 0.17mm.

[0075] The following is a detailed introduction to the 120-point block.

[0076] 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.

[0077] 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 to 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.

[0078] 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 first annular groove 1221a and a second groove 1221b extending in a line segment shape on one side of the top surface. The second groove 1221b is located in the area defined by the first groove 1221a, and the two ends of the second groove 1221b are connected to the first groove 1221a. That is, the first groove 1221a presents a closed shape with the ends connected. The first groove 1221a is preferably a closed circle, and the second groove 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.

[0079] 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.

[0080] 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 are connected, that is, they intersect. Thus, if either one breaks, it can extend to the other, causing the other to break as well. Therefore, the opening area of ​​the explosion-proof valve plate 122 can be increased, thereby rapidly relieving pressure on the battery.

[0081] 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.

[0082] 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.

[0083] 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.

[0084] As shown in Figure 6, in some embodiments, the explosion-proof valve plate 122 is provided with a thinning portion 1222 extending radially. The first notch 1221a is located within the radial range of the thinning portion 1222. 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 effectively enables the first notch 1221a to break when the opening condition is met, thereby releasing the battery pressure. It also ensures that the explosion-proof valve plate 1222 has sufficient strength and rigidity, facilitating processing and assembly. Further, the thinning portion 1222 is an annular body with a certain width, where the width W1 satisfies: 3mm ≤ W1 ≤ 8mm. The thickness and width of the thinning portion 1222 are reasonably designed, effectively enabling the first notch 1221a to break when the opening condition is met, thereby releasing the battery pressure. It also ensures that the explosion-proof valve plate 1222 has sufficient strength and rigidity, facilitating processing and assembly. Meanwhile, when the internal pressure of the battery is high, the thinned portion 1222 itself may break at the bottom of the groove 1223, which in turn helps the battery to depressurize quickly.

[0085] 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 H3, and the second notch 1221b has a depth H4. It is understood that if H3 and H4 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 H3 and H4 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 H3 of the first notch 1221a to the thickness T2 of the thinned portion 1222 is between 30% and 60%, i.e., satisfying: 30% ≤ H3 / T2 ≤ 60%, more preferably, 40% ≤ H3 / T2 ≤ 55%. The specific values ​​of H3 and H4 can be determined based on the opening pressure and the thickness of the thinned part 1222 (or the explosion-proof valve plate 122).

[0086] 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.

[0087] Furthermore, in some embodiments, the depth H3 of the first notch 1221a is less than the depth H4 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.

[0088] 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.

[0089] 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.

[0090] 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, with the radius R of the chamfered portions at the bottom of the first notch 1221a and the second notch 1221b, the following condition is met: 0.05mm ≤ R ≤ 0.15mm, more preferably, 0.05mm ≤ R ≤ 0.1mm. With the chamfered portion radius 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 using molds, thus reducing costs.

[0091] The following is a detailed introduction to the positive current collector 130.

[0092] As shown in Figures 1 and 9, the positive current collector 130 includes a body portion 131 and a tail portion 132, with the tail portion 132 connected to the body portion 131. The body portion 131 is connected to the positive electrode side of the core 140, while the tail portion 132 is connected to the terminal plate 124 in the aforementioned cap 120. For example, the body portion 131 and the core 140, as well as the tail portion 132 and the terminal plate 124, can be connected by laser welding. Thus, positive electrode conduction between the cap 120 and the core 140 can be achieved through the positive current collector 130.

[0093] The following is a detailed introduction to core 140.

[0094] As shown in Figures 1, 9, and 13, 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.

[0095] As shown in Figure 10, 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 central hole 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. Typically, the current collector substrate is rectangular, with a length much greater than its width. The current collector substrate is divided into two regions along its width: one region is used for subsequent electrode material coating, and the other region is used for subsequent electrode tab cutting. First, the region where the electrode material is applied is coated with the electrode material, and then multiple spaced electrodes are die-cut in the electrode 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] Referring to Figures 11 and 12, 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 W2, and the distance between the edges 14431 of two adjacent tabs 1443 facing the material area 1441 is W3.

[0100] Experimental testing showed that setting the ratio of tab W3 / W2 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 W2 of the tab facing the material area is too wide, it can 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 recessed 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 recessed areas. Experimental tests showed that setting the W3 / W2 ratio of the electrode 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 W3 / W2 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 W3 / W2 ratios, as shown in Table 1 below.

[0101] Table 1

[0102] As can be seen from the table, controlling the W3 / W2 ratio within the range of 20%-30% can significantly improve the self-discharge rate K, effectively keeping the average self-discharge rate K value below 0.040, resulting in relatively better battery performance.

[0103] In some embodiments, the width W2 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 W2 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 W2 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.

[0104] In some embodiments, the distance W3 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. Each bent tab overlaps the previous one, as shown in Figure 14. An overlap area f and a gap area g are formed between two adjacent tabs 1443. An excessively large gap area g increases the internal resistance of the tab and reduces the current carrying capacity. To minimize the gap area g, the distance W3 between the edges of two adjacent tabs facing the material area must be as small as possible, but this increases the difficulty of die-cutting and reduces the yield. Testing has shown that controlling the distance W3 between the edges of two adjacent tabs facing the material area to 0.2-0.6 mm balances the die-cutting difficulty and the current carrying capacity. In some embodiments, W3 is preferably 0.3-0.5 mm. In some embodiments, the distance W3 between the edges of two adjacent tabs facing the material area is further preferably 0.3 mm, 0.4 mm, 0.5 mm, etc.

[0105] 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 12, 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.

[0106] In some embodiments, the distance between the edge 14431 connecting the tab 1443 and the connecting area 1444 and the material area 1441 is H6. 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 H5. The range of H6 / H5 is 10%-20%. The H6 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 H6 / H5 ratio is too small, for example, if the H6 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 H5 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 adjacent tabs are flattened, which affects the performance of the battery. If the H6 / H5 ratio is too large, for example, if the H6 spacing is too high, the effective height of the tabs will be short, affecting welding and current flow. Conversely, if the H5 spacing is too small, the H5 height will be too low, resulting in a lower number of stacked layers and affecting welding performance. In some embodiments, H6 / H5 is 13%, 15%, 17%, 19%, etc., and the specific ratio is not limited.

[0107] As shown in Figures 11 and 12, 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.

[0108] In some embodiments, the distance H6 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 H6 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 1444 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 ring tab 1443 will overlap the inner ring 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 H6 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 current overcurrent effect.

[0109] 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°.

[0110] 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 achieving 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 2 below. In some embodiments, the included angle β is set to 14°, 16°, 18°, etc.

[0111] Table 2

[0112] In some embodiments, as shown in FIG10, 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.

[0113] As shown in Figure 11, 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 L3 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.

[0114] 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 likely to cause blockage of the center hole of the core 140, which is not conducive to subsequent electrolyte injection.

[0115] In some embodiments, the length of the first cut-out region 1445 is L4, and the ratio of L4 / L3 is 5%-15%. If L4 / L3 is too small, it can easily cause blockage of the center hole of the core 140; if L4 / L3 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 L4 / L3 between 5% and 15% reduces both the blockage of the center hole of the core 140 and the probability of a short circuit. In some embodiments, L4 / L3 is 7%, 9%, 11%, 13%, etc., and there is no specific limitation.

[0116] In some embodiments, the length L4 of the first excision region 1445 is 105-130 mm. Further, L4 is preferably 144 mm, 115 mm, 120 mm, 125 mm, etc., and there is no specific limitation.

[0117] 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.

[0118] In some embodiments, the length of the second cut-out area 1446 is L5, and the ratio of L5 to L3 is 10%-20%. If L5 / L3 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 L5 / L3 is too long, the diaphragm is easily exposed, allowing metal debris to enter the electrolyte and potentially causing a short circuit. Controlling L5 / L3 to 10%-20% facilitates the insertion of the core 140 into the casing while reducing the probability of a short circuit. In some embodiments, L5 / L3 is 13%, 15%, 18%, etc., and there is no specific limitation.

[0119] In some embodiments, the length L5 of the second excision region 1446 is 175-205 mm. Further, L5 is preferably 185 mm, 195 mm, etc., and there is no specific limitation.

[0120] 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 L4, and the ratio of L4 / L3 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 L5, and the ratio of L5 / L3 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.

[0121] The following is a detailed introduction to the negative electrode current collector 150.

[0122] As shown in Figures 1 and 9, the negative electrode current collector 150 is circular in shape. Along the thickness direction, the negative electrode current collector 150 has a first end and a second end that are opposite to each other. One end is welded to the negative electrode flattening structure 142 in the aforementioned core 140, and the other end is welded to the outer shell 110. Thus, the core 140, the negative electrode current collector 150 and the outer shell 110 are welded together, 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.

[0123] 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.

[0124] 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, The battery includes a shell (110), a cap (120), a positive current collector (130), a roll core (140) and a negative current collector (150), wherein: The roll core (140) has opposite positive and negative flat structures (141) and (142), both of which are formed by full tab cut-and-fold structure flat, the positive flat structure (141) is connected with the cap (120) through the positive current collector (130), and the negative flat structure (142) is connected with the shell (110) through the negative current collector (150); The full tab cut-and-fold structure includes a current collector substrate (144), which is divided into a material area (1441) for applying a polar material and a tab area (1442) along the width direction, both of which extend along the length direction of the current collector substrate (144), the current collector substrate (144) has a plurality of tabs (1443) arranged at intervals along the length direction at the tab area (1442), the width of the edge (14431) of the tab (1443) facing the material area (1441) is W2, the distance between the edges (14431) of two adjacent tabs (1443) facing the material area (1441) is W3, W3 / W2 ranges from 20% to 30%, and the shape of the tab (1443) is a parallelogram, the angle β between the edge (14432) of the tab (1443) facing the material area (1441) and the width direction of the current collector substrate (144) is 14-18°.

2. The cylindrical lithium battery of claim 1, wherein, The shell (110) includes a shell bottom (111) and a side wall (112), the top end of the side wall (112) has an opening (114), the side wall (112) is recessed inward along the circumferential direction at a position close to the opening (114) to form a necking portion (1121), the outer surface of the side wall (112) forms a necking groove (1123) at the necking portion (1121), the roll core (140) is located in the area defined by the necking portion (1121) and the shell bottom (111) in the shell (110); the cap (120) is received by the necking portion (1121) and closes the opening (114), the cap includes an explosion-proof valve piece (122), the explosion-proof valve piece (122) is provided with a first notch (1221a) and a second notch (1221b), the first notch (1221a) is a closed circle with the first and last ends connected, the second notch (1221b) is a line segment, and the first notch (1221a) intersects with the second notch (1221b).

3. The cylindrical lithium battery of claim 2, wherein, The lowest point of the neck part (1121) is at a distance L1 from the upper surface of the shell bottom (111), the height of the shell (110) is H, the height of the neck groove (1123) is H1, and the range of L1 / H is 90%-98%; a connecting area (1444) is further arranged between the material area (1441) and the tab area (1442), the edge (14431) of the tab (1443) connected with the connecting area (1444) is at a distance H6 from the material area (1441), and the length of the edge (14433) of the tab (1443) away from the material area (1441) is H5, and the range of H6 / H5 is 10%-20%.

4. The cylindrical lithium battery of claim 3, wherein, The height of the neck groove (1123) is H1, and the range of H1 / H is 0.1%-1%; the range of H6 is 0.4-0.6 mm.

5. The cylindrical lithium battery of claim 2, wherein, The depth of the neck groove (1123) in the radial direction is H2, the outer diameter of the shell (110) is D1, and the range of H2 / D1 is 5%-10%; the range of W2 is 1.5-2.2 mm.

6. The cylindrical lithium battery of claim 2, wherein, The neck part (1121) comprises a first wall part (1121a) and a second wall part (1121b) extending towards the center of the shell (110), and a connecting part (1121c) for connecting the first wall part (1121a) and the second wall part (1121b), the outer surfaces of the first wall part (1121a), the second wall part (1121b) and the connecting part (1121c) jointly define the neck groove (1123), and the first wall part (1121a) and the second wall part (1121b) are both arranged at a certain inclination angle with the shell bottom (111); the explosion-proof valve sheet (122) is provided with a thinning part (1222) extending in the radial direction, and the first score (1221a) is arranged within the radial range of the thinning part (1222).

7. The cylindrical lithium battery of claim 6, wherein, The angle between the first wall part (1121a) and the shell bottom (111) and the angle between the second wall part (1121b) and the shell bottom (111) are relatively larger, and the range of the angle is α<10°; the thickness of the thinning part (1222) is T2, the depth of the first score (1221a) is H3, and the range of H3 / T2 is 30%-60%.

8. The cylindrical lithium battery of claim 7, wherein, The range of the angle is 1-5°; the width of the thinning part (1222) is W1, and the range of W1 is 3-8 mm.

9. The cylindrical lithium battery of claim 2, wherein, The minimum wall thickness of the neck part (1121) is T1, the wall thickness of the side wall (112) is T, and the range of T1 / T is 80% or more; the diameter D2 of the first score (1221a) is equal to the length L2 of the second score (1221b).

10. The cylindrical lithium battery of claim 9, wherein, The minimum wall thickness of the necked portion (1121) is T1, the wall thickness of the side wall (112) is T, and T1 / T is greater than or equal to 85%; the bottom of the first score (1221a) and the second score (1221b) is provided with a chamfer portion.

11. The cylindrical lithium battery of claim 10, wherein, The T1 is in the range of 0.1-0.2mm; the chamfer portions have the same radius, the radius of the chamfer portion is R, and the R is in the range of 0.05-.15mm.

12. The cylindrical lithium battery of claim 2, wherein, The necked portion (1121) is formed by a plug formed in the rolling groove of the side wall (112); the depth H3 of the first score (1221a) is less than the depth H4 of the second score (1221b), and the middle of the second score (1221b) is deeper than the two ends.

13. The cylindrical lithium battery according to any one of claims 1 to 12, characterized in that, The length of the plurality of tabs (1443) of the tab area (1442) in the length direction of the current collector substrate (144) is less than the length L3 of the material area (1441), one end of the two ends of the tab area (1442) has a first cut-off area (1445) or a second cut-off area (1446), the length of the first cut-off area (1445) in the length direction of the current collector substrate (144) is L4, and L4 / L3 is in the range of 5%-15%; the length of the second cut-off area (1446) in the length direction of the current collector substrate (144) is L5, and L5 / L3 is in the range of 10%-20%.

14. The cylindrical lithium battery according to any one of claims 1 to 12, characterized in that, The length of the plurality of tabs (1443) of the tab area (1442) in the length direction of the current collector substrate (144) is less than the length L3 of the material area (1441), one end of the two ends of the tab area (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) in the length direction of the current collector substrate (144) is L4, and L4 / L3 is in the range of 5%-15%; the length of the second cut-off area (1446) in the length direction of the current collector substrate (144) is L5, and L5 / L3 is in the range of 10%-20%.

15. The cylindrical lithium battery of claim 14, wherein, The L4 is in the range of 105-130mm, and the L5 is in the range of 175-205mm.

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