Cylindrical lithium battery

Abstract

The invention provides a cylindrical lithium battery. The sum of the areas of all second holes of a positive collector plate in the cylindrical lithium battery is 0.9-1.5 times of the area of a first hole, a fusing groove is formed in a tail body part of the positive collector plate, and the minimum sectional area S2 of the tail body part at the position of the fusing groove is 45%-65% of the overall sectional area S1 of the tail body part; a negative collector plate in the cylindrical lithium battery is provided with a heightening platform with a flat surface, the diameter D8 of the heightening platform is 28%-38% of the diameter D7 of the negative collector plate, and the height difference H4 between the surface of the heightening platform and the surface of the first side is 18%-30% of the thickness T4 of the negative collector plate. By reasonably designing the necking part, the positive collector plate and the negative collector plate, the cylindrical lithium battery disclosed by the invention is balanced in multiple aspects of liquid injection performance, safety, weldability and the like, and the battery performance can be improved.

Description

Technical Field

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

[0002] In the related technology, cylindrical batteries are usually packaged in a cylindrical steel shell, and the bare cell is made by a winding process to form a cylindrical core. The cap is located on the top of the battery and is connected to the positive electrode in the core through the positive current collector disk. The steel shell is connected to the negative electrode in the core through the negative current collector disk. The positive current collector disk and the negative current collector disk enable electrons to be transmitted from the current collector to the current collector disk in the longitudinal direction, which can effectively improve the charging and discharging performance of the cylindrical lithium battery by increasing the current conduction area and shortening the current conduction distance.

[0003] As mentioned above, in cylindrical lithium batteries, the positive electrode collector plate and the negative electrode collector plate are important electrical connectors. Many factors need to be considered when designing the positive electrode collector plate. For example, taking the positive electrode collector plate as an example, its electrical transmission performance, electrolyte injection, safety protection when the battery is overheated, and welding processability, etc. Therefore, how to reasonably design the positive electrode collector plate and the negative electrode collector plate to achieve a balance among the above-mentioned aspects is a problem that needs to be solved urgently. Summary of the invention

[0004] The embodiment of the present application provides a cylindrical lithium battery to at least solve the technical problem of imbalance in battery filling, weldability and safety caused by unreasonable design of positive electrode collector plates and negative electrode collector plates in existing cylindrical lithium batteries.

[0005] The first aspect of the present application provides a cylindrical lithium battery, comprising a housing, a cap, a positive electrode current collecting disk, a winding core and a negative electrode current collecting disk, wherein the positive terminal of the winding core is connected to the cap through the positive electrode current collecting disk, and the negative terminal of the winding core is connected to the housing through the negative electrode current collecting disk;

[0006] The positive electrode current collector comprises a disc body and a tail body connected to each other, the disc body is connected to the positive terminal, the tail body is connected to the cap, a circular first hole is arranged at the center of the disc body, at least one circular second hole is arranged at the periphery of the first hole, and the sum of the areas of all the second holes is 0.9-1.5 times the area of ​​the first hole; at least one fuse slot is arranged on the tail body, and the tail body has an overall cross-sectional area S1 at a position other than the fuse slot on the tail body, and the tail body has a minimum cross-sectional area S2 at the position of the fuse slot, and the minimum cross-sectional area S2 is 45%-65% of the overall cross-sectional area S1;

[0007] The negative electrode current collector has a first side and a second side opposite to each other, the first side is connected to the negative terminal, and a circular raised platform with a flat surface is provided at the center of the second side, the raised platform is connected to the outer shell, the diameter D8 of the raised platform is 28%-38% of the diameter D7 of the negative electrode current collector, and the height difference H4 between the surface of the raised platform and the surface of the first side is 18%-30% of the thickness T4 of the negative electrode current collector.

[0008] The cylindrical lithium battery according to the embodiment of the present application has at least the following beneficial effects:

[0009] First, by reasonably designing the size of the first hole and the second hole on the positive electrode current collector through which the electrolyte penetrates, it is possible to achieve a balance between the injection efficiency and the weldable area, while ensuring the safety of welding. In addition, the size of the fuse slot set in the tail body is reasonably designed to ensure that the current is cut off when the battery is thermally runaway, so that the tail body can achieve a balance between battery safety and low internal resistance.

[0010] Secondly, by providing a flat raised platform on the side where the negative electrode current collector is connected to the inner surface of the shell bottom, the raised platform has a small area, so it can ensure that it has good surface flatness. The surface of the raised platform can fit well with the inner surface of the shell bottom, which can effectively avoid welding quality problems such as cold welding between the two. By reasonably designing the height of the raised platform, while meeting the machinability and use requirements of the negative electrode current collector, the negative electrode current collector will not occupy too much of the internal longitudinal space of the shell, so as to improve the space utilization of the shell, thereby further improving the performance of the battery.

[0011] In summary, by rationally designing the positive electrode current collector and the negative electrode current collector, the cylindrical lithium battery of the present application achieves a balance in terms of safety, liquid injection performance, weldability, etc., and can improve battery performance.

[0012] In a possible implementation, the winding core has a through winding core hole, the first hole diameter D3 is 1.4-1.8 times the winding core hole diameter D6, the second hole diameter D3 is 50%-70% of the first hole diameter D2; the flatness of the raised platform surface is 0.01-0.05mm.

[0013] By properly designing the diameter range of the first hole, it is possible to achieve a balance between the injection efficiency and the weldable area, while ensuring the safety of welding. At the same time, by properly designing the flatness of the raised platform, the surface of the raised platform can be well fitted with the inner surface of the shell bottom, which can effectively avoid welding quality problems such as cold welding between the two.

[0014] In a possible implementation, the positive terminal and the negative terminal are both formed by flattening the entire tab, and the side of the disk body facing the positive terminal abuts against the positive terminal formed by flattening the entire tab; the first side of the negative current collector disk abuts against the flattened negative terminal.

[0015] By setting the positive and negative ends of the winding core to be formed by flattening the full pole ear, the positive end is stacked densely and has a flat cross section, avoiding wasting space in the longitudinal direction, and the internal space of the shell is highly utilized, which can further improve the energy density of the battery. At the same time, the positive end has a good bonding effect after abutting against the positive collector plate and the negative collector plate, which is conducive to laser welding and can effectively reduce process defects such as cold welding.

[0016] In a possible implementation manner, the diameter D2 of the disk body is 80%-95% of the diameter D5 of the winding core; and the diameter D7 of the negative electrode current collecting disk is 90%-98% of the diameter D5 of the winding core.

[0017] By rationally designing the size of the positive electrode collector disc and the negative electrode collector disc, the welding area between the two and the winding core can be effectively increased, thereby improving the welding effect and facilitating the design of welding tools.

[0018] In a possible embodiment, the shape of the disk body is a closed axially symmetrical figure composed of a first side, an arc, a second side and a third side connected end to end in sequence, and the shape of the tail body is a closed axially symmetrical figure composed of the third side, a fifth side extending along the length direction of the tail body, a fourth side away from the disk body and a sixth side extending along the length direction of the tail body connected end to end in sequence, wherein the two ends of the fifth side are respectively connected to the fourth side and the first side, and the two ends of the sixth side are respectively connected to the fourth side and the second side; the raised platform is formed by integral stamping of the negative electrode current collector disk, a recessed portion is formed at a position corresponding to the raised platform on the first side, and a welding area is formed on the first side around the recessed portion, and the surface of the welding area abuts the negative terminal formed by flattening.

[0019] The shape of the disc body and the tail body is reasonably designed to facilitate the manufacture and assembly of the positive collector disc. At the same time, the negative collector disc and the padding platform are formed by reasonable stamping, with high dimensional accuracy and good surface quality, which is convenient for welding with the winding core and the shell.

[0020] In a possible implementation, the positive electrode current collecting disc is made of aluminum, the negative electrode current collecting disc is made of copper, and the surface of the negative electrode current collecting disc is plated with a nickel layer.

[0021] The positive electrode current collector made of aluminum and the negative electrode current collector made of copper have the characteristics of low internal resistance and good conductivity. In the event of thermal runaway, the positive electrode current collector is easy to fuse to cut off the current, and the nickel plating layer on the surface of the negative electrode current collector can effectively improve the corrosion resistance of the negative electrode current collector.

[0022] In a possible implementation manner, the length L3 of the tail body is 85%-95% of the diameter D2 of the disc body; and the thickness of the nickel layer is 0.08-1.5 μm.

[0023] By properly designing the length of the tail body, a balance can be achieved between welding processability and battery safety. At the same time, by properly designing the thickness of the nickel layer, the corrosion resistance of the negative electrode collector can be effectively improved.

[0024] In a possible embodiment, the outer shell includes a shell bottom and a side wall, the top end of the side wall has an opening, and the side wall is circumferentially concave near the opening to form a neck portion, the neck portion includes a first wall portion and a second wall portion extending toward the center of the outer shell, the neck portion 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 jointly define a necking groove, and the first wall portion and the second wall portion are both set at a certain inclination angle to the shell bottom, and the raised platform is connected to the inner surface of the shell bottom.

[0025] By setting the first wall portion and the second wall portion constituting the necking portion to be inclined toward the shell bottom, the necking portion has reserved a certain amount of collapse margin. Therefore, it is convenient to design the groove in the previous groove rolling process, and it is convenient to form the required necking portion structure in the sealing process.

[0026] In a possible implementation, the first width of the tail body W1 = D2*sin(∠B / 2), and 20°≤∠B≤40°, wherein ∠B has the center point corresponding to the arc as its vertex, and its two sides respectively pass through the intersection of the fifth side and the sixth side with the full circle where the arc is located; the larger of the angles between the first wall portion and the shell bottom and the angles between the second wall portion and the shell bottom is α, satisfying: α<10°.

[0027] By properly designing the width of the tail body, it is helpful to retain the largest weldable area, while ensuring that the tail body has sufficient mechanical strength to prevent it from being broken during the production process. In addition, it is also conducive to the rapid passage of electrons and reduces the internal resistance of the battery. At the same time, by properly designing the size of the angle α, while reducing the difficulty of rolling groove design, it can also reduce the impact of the neck shrinkage on the lower cavity space and ensure the sealing effect of the cap.

[0028] In a possible implementation manner, the second width W2 of the tail body at the fuse slot is 3 / 8-3 / 4 of the first width W1; and the angle α satisfies: 1°<α<5°.

[0029] When the second width W2 is too small, the tail body is not strong enough at the fuse slot and is easily broken when bent; on the contrary, when the second width W2 is too large, the tail body cannot be quickly fused, which poses a safety hazard. By reasonably designing the width of the tail body at the fuse slot, the mechanical properties of the tail body and the safety performance of the battery can be balanced. At the same time, by reasonably designing the size of the angle α, while reducing the difficulty of rolling groove design, it can also reduce the impact of the necking on the lower cavity space and ensure the sealing effect of the cap.

[0030] In a possible implementation, the disk body has a center angle A, and 40°≤∠A≤60°; wherein the center angle A takes the center of the arc as its vertex, and the two edges pass through the first edge away from the end point of the arc and the second edge away from the end point of the arc respectively.

[0031] By reasonably designing the center angle A, it can be ensured that the disc body still has a large weldable area after the hole is opened.

[0032] In a possible implementation manner, a dimension L5 of the fuse groove along the length direction of the tail body is 0<L5≤W1; a depth H3 of the necking groove in the radial direction is 5%-10% of the outer diameter D1 of the shell.

[0033] If L5 is too large, the fuse position of the tail body is difficult to determine, thereby increasing the safety risk of the battery; on the contrary, if L5 is too small, the fuse sensitivity of the tail body increases, and there is a possibility of melting under safe current. By reasonably designing the size of the fuse slot, it helps to improve the safety of the battery. At the same time, by reasonably designing the depth of the necking groove on the shell, the internal space utilization rate of the shell can be effectively improved to increase the energy density of the battery, and the structural strength of the necking neck and the sealing processability can also be improved.

[0034] In a possible implementation, the dimension L5 of the fuse slot along the length direction of the tail body is 1 / 4 to 3 / 4 of the first width W1; the minimum wall thickness T2 of the neck portion is 0.1-0.2 mm, and it is more than 80% of the wall thickness T1 of the side wall.

[0035] By properly designing the size of the fuse slot, it helps to improve the safety of the battery. At the same time, by properly designing the wall thickness at the thinnest part of the neck, it can be ensured that the compressive strength of the shell meets the requirements.

[0036] In a 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°; the distance L1 from the lowest point of the neck portion to the upper surface of the shell bottom is 90%-98% of the height of the shell H1, and the height of the necking groove is H2, which is 0.1%-1% of the height of the shell H1.

[0037] By properly 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 properties of the positive electrode current collector and the size of the weldable area of ​​the disc body can be balanced. At the same time, by properly designing the depth of the necking groove on the shell, the internal space utilization of the shell can be effectively improved to improve the energy density of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0039] Figure 1 is an exploded schematic diagram of a cylindrical lithium battery according to an embodiment of the present application;

[0040] Figure 2 It is a cross-sectional schematic diagram of the connection between the outer shell and the cap in a cylindrical lithium battery of an embodiment of the present application;

[0041] Figure 3 yes Figure 2 The local schematic diagram of the A in the middle;

[0042] Figure 4 is a cross-sectional schematic diagram of a cap in a cylindrical lithium battery in one embodiment of the present application;

[0043] Figure 5 1 is a schematic top view of a positive electrode current collector in a cylindrical lithium battery according to an embodiment of the present application, wherein the tail body is in an unfolded state;

[0044] Figure 6 yes Figure 5 A schematic diagram of the structure in which the positive electrode current collecting disk is connected to the winding core;

[0045] Figure 7 yes Figure 5 A schematic diagram of the structure of the tail portion of the middle positive electrode current collector;

[0046] Figure 8 yes Figure 7 Schematic diagram of the cross section along the AA direction;

[0047] Fig. 9 yes Figure 5 A schematic diagram of the structure of the tail portion of the middle positive electrode current collector;

[0048] Fig.10 It is a structural schematic diagram of a cylindrical lithium battery in an embodiment of the present application in which a negative electrode current collecting disk is connected to a winding core and a shell bottom;

[0049] Fig.11 yes Fig.10 A schematic cross-sectional view of the middle negative electrode current collector;

[0050] Fig.12 yes Fig.11 Partial schematic diagram of point B in the middle.

[0051] Reference numerals:

[0052] 110-shell, 111-shell bottom, 112-side wall, 1121-neck portion, 1121a-first wall portion, 1121b-second wall portion, 1121c-connecting portion, 1122-curling edge, 1123-neck groove, 113-inner cavity, 1131-upper cavity, 1132-lower cavity, 114-opening;

[0053] 120-cap, 121-top cover, 122-explosion-proof valve plate, 123-insulating plate, 124-terminal plate, 125-insulating ring;

[0054] 130-positive electrode current collecting disk, 131-disk body, 1311-first side, 1312-arc, 1313-second side, 1314-third side, 1315-first hole, 1316-second hole, 132-tail body, 1321-fuse slot, 1322-fifth side, 1323-sixth side, 1324-fourth side;

[0055] 140-winding core, 141-positive terminal, 142-negative terminal, 143-winding core hole;

[0056] 150 - negative electrode current collecting plate, 151 - first side, 1511 - recessed portion, 1512 - welding area, 152 - second side, 1521 - raised platform. DETAILED DESCRIPTION

[0057] Embodiments of the present embodiment are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present embodiment, and should not be construed as limiting the present embodiment.

[0058] In the description of this embodiment, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and 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, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this embodiment.

[0059] In the description of this embodiment, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0060] In the description of this embodiment, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this embodiment based on the specific content of the technical solution.

[0061] The cylindrical lithium battery provided in the embodiment of the present application includes various size series, such as 21 series (cylindrical lithium battery with an outer diameter of 21 mm) and 46 series (cylindrical lithium battery with an outer diameter of 46 mm), which are not limited here. Figure 1 As shown, the cylindrical lithium battery includes a shell 110, a cap 120, a positive electrode current collecting disk 130, a winding core 140, and a negative electrode current collecting disk 150, wherein the positive terminal 141 of the winding core 140 is connected to the cap 120 through the positive electrode current collecting disk 130, and the negative terminal 142 of the winding core 140 is connected to the shell 110 through the negative electrode current collecting disk 150, so that the cap 120 serves as the positive electrode of the cylindrical lithium battery, and the shell 110 serves as the negative electrode of the cylindrical lithium battery, which is used to be electrically connected to an external electrical device.

[0062] The housing 110 is described in detail below.

[0063] like Figure 1 and Figure 2 As shown, the shell 110 is cylindrical in shape as a whole, and is configured to be closed on the negative electrode side (the lower side in the figure) and open on the positive electrode side (the upper side in the figure). Specifically, the shell 110 includes a shell bottom 111 and a side wall 112, wherein the shell bottom 111 is circular, and the side wall 112 is extended upward along the edge of the shell bottom 111, and the shell bottom 111 and the side wall 112 jointly define an inner cavity 113, and the top of the side wall 112 has an opening 114, and the opening 114 is connected to the inner cavity 113.

[0064] It is understandable that the inner cavity 113 defined by the shell bottom 111 and the side wall 112 is also cylindrical, and is used to accommodate the cap 120 (with its top exposed), the positive electrode collector 130, the winding core 140, and the negative electrode collector 150 to be introduced below. In addition, by setting the shell 110 to be open at the top, that is, the top of the shell 110 is provided with an opening 114, it is also convenient for the above components to enter the shell 110 through the opening 114.

[0065] It can be understood that the shell bottom 111 is in the shape of a thin circular plate, and the bottom surface of the negative electrode current collecting disk 150 is in contact with the inner surface of the shell bottom 111 , thereby forming a conductive connection between the two, thereby conducting the negative electrode of the outer shell 110 and the winding core 140 .

[0066] It is understandable that the housing 110 can be made of nickel-plated steel, which has advantages such as high compressive strength, but is not limited thereto. For example, an aluminum housing can also be used. The following description takes the housing 110 as an example of a nickel-plated steel, which can be punched out of a steel strip, is simple to manufacture, and is easy to mass produce, which can effectively reduce costs.

[0067] like Figure 2 and Figure 3 As shown, the side wall 112 is concave inwardly at a position close to the opening 114 to form a constricted portion 1121 for sealing the cap 120. The constricted portion 1121 divides the inner cavity 113 into an upper cavity 1131 and a lower cavity 1132. The constricted portion 1121 can be formed by rolling grooves and sealing processes. In addition, in the sealing process, the side wall 112 is concave to form the constricted portion 1121, and a curling edge 1122 is formed at the top. The curling edge 1122 and the constricted portion are 1121 and the side wall 112 together realize the sealing connection of the cap 120. Specifically, the top surface of the neck portion 1121 located on one side of the upper cavity 1131 is used to receive the cap 120, and it 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 neck portion 1121 and the curling edge 1122 is in contact with the outer peripheral surface of the cap 120, and the inner wall surface of the curling 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 collecting disc 150, the winding core 140, and the positive electrode current collecting disc 130 in the lower cavity 1132, thereby forming a closed electrochemical system in the housing 110.

[0068] Specifically, the neck portion 1121 includes a first wall portion 1121a and a second wall portion 1121b extending toward the center of the inner cavity 113 and parallel to each other, and a connecting portion 1121c for connecting the first wall portion 1121a and the second wall portion 1121b. Figure 2In the middle direction, the first wall portion 1121a is located above the second wall portion 1121b, and the first wall portion 1121a and the second wall portion 1121b are connected at one end close to the center of the inner cavity 113 by a connecting portion 1121c, and the outer surfaces of the first wall portion 1121a, the second wall portion 1121b and the connecting portion 1121c jointly define a necking groove 1123. It can be understood that the inner surface of the first wall portion 1121a, i.e., the top surface, is used to receive the cap 120 and is in contact and connection with the bottom of the cap 120.

[0069] Although the first wall portion 1121a, the second wall portion 1121b and the connecting portion 1121c are described as being connected to each other, it is understandable that the first wall portion 1121a, the second wall portion 1121b and the connecting portion 1121c themselves are part of the wall portion of the side wall 112. In the sealing process, the side wall 112 undergoes an inward concave plastic deformation at the position corresponding to the neck portion 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 integrated. Of course, in the preceding process before the sealing process, a rolling groove can be cut at this position, for example, by the feeding motion of the rolling cutter and the rotation motion of the housing 110, so that when sealing, the rolling groove undergoes plastic deformation to form the desired neck portion 1121.

[0070] In this embodiment, the first wall portion 1121a and the second wall portion 1121b are both in the shape of a flat plate, and the first wall portion 1121a and the second wall portion 1121b are arranged along their concave direction to be inclined toward the side of the shell bottom 111. 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 shell bottom 111 is α, and satisfies: α<10°. It can be understood that in this case, since the first wall portion 1121a and the second wall portion 1121b are both in the shape of a flat plate and are 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 shell bottom 111, and the inclination angle is not greater than 10°.

[0071] When the first wall portion 1121a and the second wall portion 1121b are not completely parallel, the angle between the first wall portion 1121a or the second wall portion 1121b and the shell bottom 111, whichever is relatively larger, 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 not completely parallel to each other, the angle between the first wall portion 1121a and the shell bottom 111 and the angle between the second wall portion 1121b and the shell bottom 111 are both less than 10°.

[0072] Therefore, firstly, by setting the first wall portion 1121a and the second wall portion 1121b constituting the necking portion 1121 to be inclined toward the shell bottom 111, the necking portion 1121 has reserved a certain amount of collapse margin, so it is convenient to design the groove in the previous groove rolling process, and to form the required necking portion 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 necking portion 1121 intruding into the lower cavity 1132 is small, which ensures the effective space of the lower cavity 1132, and can also avoid damage to the winding core pole group. Furthermore, since the inclination angle of the first wall portion 1121a and the second wall portion 1121b does not exceed 10°, the top surface of the neck portion 1121 in the inner cavity 113, that is, the top surface of the first wall portion 1121a, is basically horizontal, and its contact area with the bottom surface of the cap 120 is large. There is sufficient compression between the two, and the sealing effect is good, which can improve the safety of the lithium battery.

[0073] Furthermore, in some embodiments, the angle α satisfies: 1°<α<5°. It is understandable that the angle α will affect the difficulty of designing the rolling groove, the utilization rate of the internal space of the housing 110, and the sealing effect of the cap 120. If α is too large, although the difficulty of designing the rolling groove is relatively small, the utilization rate of the internal space of the housing 110 will be reduced, and the sealing effect of the cap 120 will be worse; on the contrary, if α is too small, the rolling groove is difficult to design, and the neck portion 1121 is difficult to form. By reasonably designing the size of the angle α, while reducing the difficulty of designing the rolling groove, it is also possible to reduce the impact of the neck portion 1121 on the space of the lower cavity 1132 and ensure the sealing effect of the cap 120.

[0074] In some embodiments, the distance between the lowest point of the neck 1121 in the inner cavity 113 and the upper surface of the shell bottom 111 is L1, and the height of the outer shell 110 is H1, which satisfies: 90%≤L1 / H1≤98%. It can be understood that if the distance L1 between the lowest point of the neck 1121 and the upper surface of the shell bottom 111 is too large, that is, L1 / H1 is too large, it will affect the height of the upper cavity 1131, resulting in a poor sealing effect; conversely, if the distance L1 between the lowest point of the neck 1121 and the upper surface of the shell bottom 111 is too small, that is, L1 / H1 is too small, it will affect the height of the lower cavity 1132, and the height of the outer shell 110 will be wasted, resulting in a decrease in the energy density of the battery. By reasonably designing the distance L1 between the lowest point of the neck 1121 in the inner cavity 113 and the upper surface of the shell bottom 111, while ensuring the sealing effect at the seal, the utilization rate of the internal space of the outer shell 110 can also be improved, thereby improving the energy density of the battery.

[0075] Furthermore, in some embodiments, the height of the necking groove 1123 is H2, and the height of the outer shell 110 is H1, wherein 0.1%≤H2 / H1≤1%. It is understandable that if the height H2 of the necking groove 1123 is too large, the height of the outer shell 110 will be wasted, resulting in a decrease in the energy density of the lithium battery; conversely, if the height H2 of the necking groove 1123 is too small, the stress at the connecting portion 1121c will easily concentrate, and the necking portion 1121 will be at risk of breaking at this position, and the sealing process will also be more difficult, resulting in a decrease in the yield rate. By reasonably designing the height H2 of the necking groove 1123, while ensuring that the structural strength of the necking portion 1121 meets the requirements, the utilization rate of the internal space of the outer shell 110 and the processability of the sealing process can also be effectively improved. It is also understandable that if Figure 3 As shown, the height H2 described here refers to the height of 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, the height inside the necking groove 1123 is consistent with the height H2. More preferably, 0.2%≤H2 / H1≤0.5%.

[0076] 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, wherein 5%≤H3 / D1≤10%. It is understandable that if the depth H3 of the necking groove 1123 is too large, that is, H3 / D1 is too large, the necking portion 1121 will excessively intrude into the inner cavity 113 in the radial direction, causing the inner diameter of the inner cavity 113 at the necking portion 1121 to become smaller, resulting in space waste, and also causing the structural rigidity of the necking portion 1121 itself to be weakened, stress to be increased, and there is a risk of cutting, which leads to the inability to ensure sealing; on the contrary, if the depth H3 of the necking groove 1123 is too small, that is, H3 / D1 is too small, the cap 120 cannot be stably carried by the first wall portion 1121a, and the size chain matching of the two is poor. When sealing, the cap 120 may directly pass through the notch defined by the necking portion 1121 and enter the lower cavity 1132. By properly designing the depth H3 of the necking groove 1123 , while ensuring that the cap 120 can be stably supported by the first wall portion 1121 a for smooth sealing, the utilization rate of the internal space of the housing 110 can be improved, further improving the energy density of the lithium battery.

[0077] It is understood that in the sealing process, the wall thickness of the first wall portion 1121a, the second wall portion 1121b and the connecting portion 1121c will change as the material undergoes plastic deformation. In order to ensure the compressive strength of the shell 110, in some embodiments, the minimum wall thickness of the neck portion 1121 is T2, and the wall thickness of the shell 110 is T1, wherein T2 / T1≥80%, and more preferably, T2 / T1≥85%. It is understood that the minimum wall thickness T2 may appear on any one of the first wall portion 1121a, the second wall portion 1121b and the connecting portion 1121c. It is also understood that if T2 / T1 is less than 80%, the safety margin of the mechanical strength of the shell 110 is insufficient. For example, when the air pressure inside the shell 110 increases, the shell 110 may be torn at this location. By reasonably designing the wall thickness T2 at the thinnest part of the neck portion 1121, it can be ensured that the compressive strength of the shell 110 meets the requirements.

[0078] In some embodiments, in order to ensure the compressive strength of the housing 110, in some embodiments, the minimum wall thickness of the neck portion 1121 is T2, wherein 0.1 mm ≤ T2 ≤ 0.2 mm. It is understandable that the minimum wall thickness T2 of the neck portion 1121 is set between 0.1 and 0.2 mm, so that the neck portion 1121 can meet the compressive strength requirements of the housing 110 with a common wall thickness. For example, for the housing 110 with a wall thickness of 0.2 mm, the minimum wall thickness T2 of the neck portion 1121 can be 0.17 mm.

[0079] The cap 120 is described in detail below.

[0080] It can be understood that the cap 120 and the outer shell 110 together serve as a physical barrier to isolate the active materials of the cylindrical lithium battery from the outside world, and when the gas pressure inside the battery exceeds a preset value, the explosion-proof valve plate 122 of the cap 120 opens to release the pressure to prevent the battery from deforming, bulging, or even burning or exploding.

[0081] like Figure 4 As shown, the cap 120 includes a top cover 121, an explosion-proof valve sheet 122, an insulating plate 123, a terminal plate 124, and an insulating ring 125 located at the outer edge, wherein the top cover 121, the explosion-proof valve sheet 122, and the terminal plate 124 are stacked in sequence from top to bottom, and are conductively connected to each other. After the cap 120 is sealed and connected to the outer shell 110, the top cover 121 is exposed outside the outer shell 110, and it is used as a positive terminal for electrical connection with the positive electrode of the external electrical equipment. The bottom surface of the terminal plate 124 is connected to the positive current collector 130, for example, the positive current collector 130 and the terminal plate 124 are welded, thereby forming a conductive connection between the two, thereby connecting the top cover 121 to the positive terminal 141 of the winding core 140.

[0082] The positive electrode current collecting disk 130 is described in detail below.

[0083] like Figure 7 and Figure 8 As shown, the positive electrode current collecting disc 130 includes a disc body 131 and a tail body 132 connected to each other, wherein the disc body 131 is used to connect to the positive terminal 141 of the winding core 140, and the tail body 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 the present application, the connection between the disc body 131 and the winding core 140, and the connection between the tail body 132 and the cap 120 can adopt any connection method well known to those skilled in the art, such as welding; the connection between the tail body 132 and the disc body 131 can be any fixed connection method, and in order to ensure the stability of the connection and the structural strength, it is preferably an integral connection.

[0084] like Figure 7 As shown, in order to match the circular cross-section of the winding core 140 and facilitate welding between the disk body 131 and the winding core 140, the shape of the disk 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 in sequence, and the tail body 132 includes a fifth side 1322 and a sixth side 1323 along its length direction, and a fourth side 1324 away from the disk body 131, the two ends of the fifth side 1322 are respectively connected to the fourth side 1324 and the first side 1311, and the two ends of the sixth side 1323 are respectively connected to the fourth side 1324 and the second side 1313, thereby, Figure 7 From the perspective of the tail body 132, 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 side line proposed for the convenience of describing the disc body 131. There is no such side in the actual product. Figure 7 Dotted lines are used to mark the difference. Figure 1 and Figure 8 It can also be understood that when the positive electrode current collecting disk 130 is assembled to the cylindrical lithium battery, the tail body portion 132 is bent, and its distal end portion is located above the closed axially symmetrical figure formed by the disk body portion 131.

[0085] In order to improve the efficiency of injecting electrolyte during the battery production process, the disc body 131 is usually provided with holes for the electrolyte to pass through, and to ensure that the solid area of ​​the disc body 131 after the holes are punched still accounts for more than 75% of the total area of ​​the disc body 131, so as to facilitate welding with the winding core 140. The disc body 131 has a central angle A, and 40°≤∠A≤60°, and more preferably 45°≤∠A≤55°. Specifically, the total area of ​​the above-mentioned disk body 131 is the sum of the solid area of ​​the disk body 131 and the hole area; the center angle A takes the center of the circle corresponding to the arc 1312 as the vertex, and the two edges pass through the end point of the first edge 1311 away from the arc 1312 and the end point of the second edge 1313 away from the arc 1312 respectively. It can be understood that the end point of the first edge 1311 away from the arc 1312 and the end point of the second edge 1313 away from the arc 12 are also the connection points of the first edge 1311, the second edge 1313 and the tail body 132.

[0086] In some embodiments, the diameter D2 of the disk body 131 is 80%-95% of the diameter D5 of the winding core 140, wherein the diameter D2 of the disk body 131 refers to the longest line segment between two points on the arc 1312, and the diameter D5 of the winding core 140 refers to the diameter of the circular cross section of the winding core 140. According to actual needs, the size of the diameter D2 of the disk body 131 is, for example, 15-23 mm. The disk body 131 ensures a large contact area between the disk body 131 and the winding core 140 within the preferred diameter range, increases the weldable area, and expands the adaptability range of the welding wire length and shape. It can also be understood that when the contact area of ​​the negative electrode current collector 150 is large, within the above diameter range, the positive electrode current collector 130 will not become a bottleneck limiting the charging and discharging performance of the cylindrical lithium battery.

[0087] In some embodiments, a first hole 1315 is provided at the center of the disk body 131 for injecting electrolyte into the battery. The center of the disk body 131 may be the center of the circle corresponding to the arc 1312. The winding core 140 is made by a winding process, and a circular winding core hole 143 is formed at the center of the winding core 140 after winding. To match the shape of the winding core hole 143, the shape of the first hole 1315 is preferably circular.

[0088] In some embodiments, the diameter D3 of the first hole 1315 is 1.4-1.8 times the diameter D6 of the core hole 143 of the core 140. According to actual needs, the diameter D3 of the first hole 1315 is, for example, 4-8 mm. The first hole 1315 can achieve a balance between injection efficiency and weldable area within this diameter range while ensuring the safety of welding. If the diameter D3 of the first hole 1315 is too small, it is not conducive to the infiltration of the injection, and when the resistance welding process is used at the bottom of the battery, the electrode head extending into the core hole 143 of the core 140 may produce undesirable contact with the collecting disk, and there is a risk of interference; if the diameter D3 of the first hole 1315 is too large, the weldable area is correspondingly reduced, which limits the welding processability between the disk body 131 and the core 140.

[0089] In some embodiments, the diameter D3 of the first hole 1315 is 25%-35% of the diameter D2 of the disk body 131. According to actual needs, the diameter D3 of the first hole 1315 is, for example, 4-8 mm. The first hole 1315 can achieve a balance between the injection efficiency and the weldable area within this diameter range while ensuring the safety of welding. If the diameter D3 of the first hole 1315 is too small, it is not conducive to the infiltration of the injection, and when the resistance welding process is used at the bottom of the battery, the electrode head extending into the core hole 143 of the core 140 may produce undesirable contact with the collector plate, and there is a risk of interference; if the diameter D3 of the first hole 1315 is too large, the weldable area is correspondingly reduced, which limits the welding process between the disk body 131 and the core 140.

[0090] In some embodiments, at least one second hole 1316 is provided on the periphery of the first hole 1315 to assist the infiltration of the electrolyte. Preferably, the second hole 1316 is a circular hole. Further 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 infiltration effect will not be obvious; if the area of ​​the second hole 1316 is too large, the weldable area of ​​the disc body 131 will be greatly reduced, affecting the connection between the disc body 131 and the winding core 140.

[0091] In some embodiments, the distance L2 between the center of the second hole 1316 and the center of the first hole 1315 is 25%-35% of the diameter D2 of the disk body 131. According to actual needs, L2 is, for example, 4.5-7 mm. By reasonably 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 weldable area. If the spacing L2 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 spacing L2 between the second hole 1316 and the first hole 1315 is too large, the second hole 1316 is too close to the edge of the disk body 131, thereby limiting the battery pack. If the pack blocks the second hole 1316, the electrolyte cannot be injected through the second hole 1316.

[0092] In order to facilitate processing and improve yield, in a preferred embodiment, the diameter D4 of the second hole 1316 is 50%-70% of the diameter D3 of the first hole 1315, and the diameter D4 of the second hole 1316 is, for example, 2-4.8 mm. If the diameter D4 of the second hole 1316 is smaller than the preferred diameter range, it is difficult to achieve the auxiliary infiltration effect; if the diameter D4 of the second hole 1316 is larger than the preferred diameter range, the weldable area of ​​the disk body 131 is reduced. It can be understood that the number of the second holes 1316 can be determined according to the actual welding process, the number of welding areas is n, and the number of the second holes 1316 is n-1, where n≥2.

[0093] The disk body 131 is further described below with reference to examples and comparative examples. The following examples and comparative examples of the present application are designed with reference to ordinary 21 series cylindrical lithium batteries.

[0094] Embodiment 1:

[0095] Embodiment 1 provides a cylindrical lithium battery, which includes a housing 110, a cap 120, a positive electrode current collector 130, a winding core 140, and a negative electrode current collector 150. Among them, the positive electrode current collector includes a positive electrode current collector 130 that is connected to each other, and a disc body 131 and a tail body 132 that are connected to each other, wherein the disc body 131 is connected to the positive terminal 141 of the winding core 140, and the tail body 132 is connected to the cap 120. A first circular hole 1315 is provided at the center of the disc body 131, and a plurality of second circular holes 1316 are provided on the periphery of the first hole 1315. In addition, the shape of the disc body 131 is a closed axially symmetrical figure composed of a first side 1311, an arc 1312, a second side 1313, and a third side 1314 connected end to end, and has a center angle B.

[0096] Among them, the diameter D5 of the winding core 140 is 20 mm; the diameter D2 of the disk body 131 is 85% of the diameter D5 of the winding core 140; the diameter D3 of the first hole 1315 is 30% of the diameter D2 of the disk body 131; the diameter D4 of the second hole 1316 is 60% of the diameter D3 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 L2 between the center position of the second hole 1316 and the center of the first hole 1315 is 30% of the diameter D1 of the disk body 131; the center angle B of the disk body 131 is 35°.

[0097] Comparative Example 1:

[0098] Comparative Example 1 provides a cylindrical lithium battery, which differs from Example 1 in that the sum of the areas of all second holes 1316 is 0.4 times the area of ​​the first hole 1315 .

[0099] Comparative Example 2:

[0100] Comparative Example 2 provides a cylindrical lithium battery, which differs from Example 1 in that the diameter D3 of the first hole 1315 is 10% of the diameter D2 of the disk body 131 .

[0101] The following Table 1 evaluates the electrolyte infiltration effect of the cylindrical lithium batteries in the sealed state made by the above-mentioned embodiments and comparative examples. The specific electrolyte infiltration test method is: sampling the outer shell 110, the cap 120, the positive electrode current collector 130, the winding core 140, the negative electrode current collector 150 and the electrolyte, welding the positive electrode current collector 130, the negative electrode current collector 150 and the winding core 140, and after placing the assembly into the outer shell 100, welding the cap 120, thereby obtaining an unsealed cylindrical lithium battery. Next, the cylindrical lithium battery is placed in the liquid injection equipment for liquid injection, and the liquid injection volume is 6.8g. After the positive and negative pressure cycles of the equipment, the cylindrical lithium battery is mechanically sealed. After the battery is left to stand for 1h, the cylindrical lithium battery is disassembled, the winding core 140 is taken out and unfolded, and placed on the CCD detection equipment for photographing, the infiltration area is depicted, and the equipment program is started to calculate the infiltration area area S0, and the total area of ​​the pole piece is set to S, then the infiltration rate is S0 / S.

[0102] Table 1

[0103] Example 1 Comparative Example 1 Comparative Example 2 Infiltration rate (%) 90.574％ 82.367％ 71.546％

[0104] It can be seen from Table 1 that when the ratio of the sum of the areas of all the second holes 1316 to the area of ​​the first holes 1315 is 1.2 times, and the diameter D3 of the first hole 1315 is 30% of the diameter D2 of the disk body 131, the electrolyte infiltration effect of the core 140 is better, and if the ratio of the sum of the areas of all the second holes 1316 to the area of ​​the first holes 1315 is too low, or the first holes 1315 are too small, the electrolyte infiltration effect of the core 140 will deteriorate.

[0105] Continue to refer Figure 7 In some embodiments, at least one fuse slot 1321 is provided on the tail body 132. The width of the tail body 132 at the fuse slot 1321 is reduced by designing the fuse slot. When the battery is in thermal runaway, the current converges there, the heat rises and reaches the melting point, causing the tail body 132 to melt, thereby achieving the current cutting effect. Specifically, the shape of the fuse slot 1321 can be any shape such as a trapezoid, a rectangle, a U-shape, a V-shape, a semicircle, etc. The present application does not limit the number of fuse slots 1321, and the accompanying drawings exemplarily show two symmetrically arranged fuse slots 1321. When there are multiple fuse slots 1321, all fuse slots 1321 can be of the same shape or of different shapes. In principle, the setting of the fuse slot 1321 must simultaneously ensure the fusing effect and mechanical strength of the tail body 132.

[0106] In some embodiments, Fig. 9 As shown, the distance L4 between the center position of the fuse slot 1321 and the end of the tail body 132 away from the disk body 131 is 68%-78% of the length L3 of the tail body 132. According to actual needs, the distance between the center position of the fuse slot 1321 and the end of the tail body 132 away from the disk body 131 is, for example, 8-18 mm. If the shape of the fuse slot 1321 is a simple figure, the center position of the fuse slot 1321 can be a position recognized by those skilled in the art. For example, the center position of the fuse slot 1321 of a trapezoidal or rectangular shape can be the intersection of two diagonal lines; for another example, the center position of the semicircular fuse slot 1321 can be the center of the circle. If the shape of the fuse slot 1321 is more complex or irregular, the center position of the fuse slot 1321 is the geometric center of its shape, that is, the average position of all points in the shape, which can be determined by any method known to those skilled in the art, such as integral method, discrete point method, graphic segmentation method, etc., or directly calculated using software tools. The length L3 of the tail body 132 is the distance between the connection between the tail body 132 and the disk body 131 and the end of the tail body 132 away from the disk body 131. The fuse slot 1321 is set at a reasonable position so that the tail body 132 and the cap 120 can be welded smoothly, while ensuring that the current is cut off when the battery is thermally runaway. If the distance between the fuse slot 1321 and the end of the tail body 132 away from the disk body 131 is too small, the fuse slot 1321 will be too close to the welding position, and the welding of the tail body 132 and the cap 120 will be interfered; on the contrary, the fuse slot 1321 is closer to the disk body 131, and the current path at the fuse slot 1321 is larger. If there is an overcurrent, it cannot be fused in time, which increases the safety risk of the battery.

[0107] In some embodiments, in order to improve the safety of the battery, the length L3 of the tail body 132 is 85%-95% of the diameter of the disk body 131. According to actual needs, the length of the tail body 132 is, for example, 12-20 mm. The tail body 132 can ensure smooth welding with the cap 120 and ensure the safety of the battery within the preferred length range. If the length of the tail body 132 is too short, the tail body 132 will not extend out of the shell 110 enough after the first bend, and the welding with the cap 120 cannot be completed; if the length of the tail body 132 is too long, the end of the tail body 132 away from the disk body 131 will contact the shell 110 when the cap 120 is closed and bent for the second time, causing the battery to short-circuit, and it will also occupy the internal space of the battery, affecting the arrangement of other components and normal operation.

[0108] In order to facilitate bending and welding, the tail body 132 is usually in the shape of a long strip. In some embodiments, as mentioned above, the tail body 132 has a first width W1, which satisfies: W1 = D2*sin(∠B / 2), where D2 is the diameter of the disc body 131, which refers to the longest line segment between two points on the arc 1312. According to actual needs, the diameter of the disc body 131 is, for example, 15-23 mm; in addition, the center angle B is the vertex of the circle center corresponding to the arc 1312, and the two sides pass through the intersection of the fifth side 1322 and the sixth side 1323 of the tail body 132 and the full circle where the arc 1312 is located (reference Figure 7 ), for example, and 20°≤∠B≤40°. The larger the first width W1 of the tail body 132, the smaller the weldable area of ​​the disc body 131. Reasonable width design helps to retain the maximum weldable area, while ensuring that the tail body 132 has sufficient mechanical strength to prevent it from being broken during the production process, and at the same time facilitates the rapid passage of electrons and reduces the internal resistance of the battery.

[0109] In some embodiments, the tail body 132 has a second width W2 at the fuse slot 1321, and 3W1 / 8≤W2<3W1 / 4, that is, the second width W2 is 3 / 8 to 3 / 4 of the first width W1. The second width W2 in the present application refers to the change in the width of the tail body 132 relative to the first width W1 due to the design of the fuse slot 1321. Based on the definition of the second width W2 in the present application, the first width W1 in the present application also refers to the width of the tail body at a position other than the fuse slot 1321 on the tail body 132. The second width W2 of the tail body 132 at the fuse slot 1321 can balance the mechanical properties of the tail body 132 and the safety performance of the battery within a reasonable range. When the second width W2 is too small, the strength of the tail body 132 at the fuse slot 1321 is insufficient and it is easy to be broken when bent.

[0110] In some embodiments, the dimension L5 of the fuse slot 1321 along the length direction of the tail body 132 satisfies: 0<L5≤W1, that is, the length of the fuse slot 1321 in the vertical direction does not exceed the first width W1 of the tail body 132. Preferably, W1 / 4<L5≤3W1 / 4, that is, the dimension L5 is 1 / 4 to 3 / 4 of the first width W1. In the present application, the dimension of the fuse slot 1321 along the length direction of the tail body 132 refers to the length between the end of the fuse slot 1321 closest to the disc body 131 and the end farthest from the disc body 131. The dimension of the fuse slot 1321 along the length direction of the tail body 132 within a reasonable range helps to improve the safety of the battery. If the dimension is too large, the fuse position of the tail body 132 is difficult to determine, thereby increasing the safety risk of the battery; on the contrary, if the dimension is too small, the fuse sensitivity of the tail body 132 increases, and there is a possibility of fuse under safe current.

[0111] In some embodiments, Figure 8 As shown, the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 is 45%-65% of the overall cross-sectional area S1 of the tail body 132. Specifically, the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 is the cross-sectional area at the narrowest position of the fuse slot 1321, for example, Fig.10 As shown, when the cross section at this location is square, its cross-sectional area S2 = W2*T3; the overall cross-sectional area S1 of the tail body 132 is the cross-sectional area of ​​the position on the tail body 132 except the fuse slot 1321, S1 = W1*T3, wherein T3 is the thickness of the tail body 132, which is usually a uniform thickness. According to actual needs, T3 is, for example, 0.15-0.35mm. Within a reasonable minimum cross-sectional area S2 range, the tail body 132 can achieve a balance between battery safety and low internal resistance. When the minimum cross-sectional area S1 is too large, the tail body 132 cannot be quickly fused in the event of thermal runaway, increasing safety risks; on the contrary, when the minimum cross-sectional area S2 is too small, on the one hand, the fuse sensitivity will be too high, and on the other hand, the internal resistance will be increased, seriously affecting the normal use of the battery. Of course, it is understandable that when calculating S1 and S2 above, the thickness of the tail body 132 at the fuse slot 1321 is the same as the thickness of the rest of the tail body 132, that is, the tail body 132 is of equal thickness, but it is not limited to this, and the thicknesses of the two can also be set to be different.

[0112] like Fig. 9As shown, the tail body 132 includes a fifth side 1322 and a sixth side 1323 along its length direction, and a fourth side 1324 away from the disc body 131, the two ends of the fifth side 1322 are respectively connected to the fourth side 1324 and the first side 1311, and the two ends of the sixth side 1323 are respectively connected to the fourth side 1324 and the second side 1313, 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°. It can be understood that if the angles θ1 and θ2 are too small, the bending of the tail body 132 will cause the stress to be too concentrated at the angles θ1 and θ2, causing the disc body 131 to deform or even break; if the angles θ1 and θ2 are too large, it is impossible to ensure that the disc body 131 has a sufficient weldable area. In addition, a reasonable angle design of the angles θ1 and θ2 also helps the electrolyte to penetrate into the battery through the angles θ1 and θ2.

[0113] The tail body 132 is further described below with reference to embodiments and comparative examples. The following embodiments and comparative examples of the present application are designed with reference to ordinary 21 series cylindrical lithium batteries.

[0114] Embodiment 1:

[0115] Embodiment 1 provides a cylindrical lithium battery, which includes a housing 110, a cap 120, a positive current collector 130, a winding core 140, and a negative current collector 150. The positive current collector 130 includes a disk body 131 and a tail body 132 connected to each other, wherein the disk body 131 is connected to the positive terminal 141 of the winding core 140, and the tail body 132 is connected to the cap 120. The thickness of the tail body 132 along the length direction is constant, and at least one pair of fuse grooves 1321 are provided on the tail body 132, and the distance L4 between the center position of the fuse groove 1321 and the end of the tail body 132 away from the disk body 131 is 72% of the length L3 of the tail body 132, and the minimum cross-sectional area S2 of the tail body 132 at the fuse groove 1321 is 50% of the overall cross-sectional area S1 of the tail body 132.

[0116] Comparative Example 1:

[0117] Comparative Example 1 provides a cylindrical lithium battery, which differs from Example 1 in that the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 is 20% of the overall cross-sectional area S1 of the tail body 132 .

[0118] Comparative Example 2:

[0119] Comparative Example 2 provides a cylindrical lithium battery, which differs from Example 1 in that the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 is 85% of the overall cross-sectional area S1 of the tail body 132 .

[0120] Comparative Example 3:

[0121] Comparative Example 3 provides a cylindrical lithium battery, which differs from Example 1 in that a distance L4 between the center of the fuse slot 1321 and the end of the tail body 132 away from the disc body 131 is 90% of the length L3 of the tail body 132 .

[0122] The safety protection effect of the positive current collector 130 produced in the above embodiment and comparative example is evaluated in the following Table 2. The specific test method is: fix the sampled positive current collector 130 on the tooling of a high-power (rated power 15150W) programmable DC power supply device, set the measurement conditions as follows: voltage 20V, current 170A, delay time 10s, turn on the temperature sensing instrument and aim it at the positive current collector 130, click the recording function, and click to start the test on the instrument, and end the experiment when the fuse slot 1321 of the positive current collector 130 is observed to be blown, and record the time and current related curves obtained by the device, as well as the blown temperature read by the temperature sensing instrument.

[0123] Table 2

[0124] Disconnection temperature Fuse time; Example 1 90.3℃ 2.383s Comparative Example 1 85.9℃ 0.273s Comparative Example 2 100.2℃ 68.563s Comparative Example 3 88.6℃ 21.8s

[0125] It can be seen from Table 2 that when the distance L4 between the center position of the fuse slot 1321 and the end of the tail body 132 away from the disc body 131 is 72% of the length L3 of the tail body 132, and the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 is 50% of the overall cross-sectional area S1 of the tail body 132, the disconnection temperature and the fusing time of the fuse slot 1321 are relatively reasonable. When the ratio of the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 to the overall cross-sectional area S1 of the tail body 132 is too low, the fuse slot 1321 is relatively sensitive to temperature and will be quickly fused; on the contrary, when the ratio of the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 to the overall cross-sectional area S1 of the tail body 132 is too high, the sensitivity of the fuse slot 1321 to temperature becomes poor and cannot be quickly fused. When the ratio of the distance L4 between the center of the fuse slot 1321 and the end of the tail portion 132 away from the disk portion 131 to the length L3 of the tail portion 132 is too high, the fuse slot 1321 cannot be quickly fused.

[0126] In some embodiments, the material of the positive electrode current collecting disk 130 is aluminum. On the one hand, aluminum has the characteristics of low internal resistance and good conductivity. On the other hand, the melting point of aluminum is relatively low. When the battery thermally runs away, the fuse slot 1312 can be melted to cut off the current.

[0127] The winding core 140 is described in detail below.

[0128] It can be understood that the winding core 140 is formed by winding the positive electrode sheet, the negative electrode sheet and the separator after stacking. Figure 1 As shown, the winding core 140 is cylindrical in shape as a whole, and in order to smoothly pass through the opening 114 and enter the inner cavity 113 of the housing 110, its diameter D5 is slightly smaller than the inner diameter of the housing 110. Figure 1 and Fig.12 As shown, it can be understood that after the winding core 140 is put into the shell, it is located in the area defined by the neck portion 1121 and the shell bottom 111 in the outer shell 110, that is, in the lower cavity 1132.

[0129] In this embodiment, the winding core 140 is provided with a positive terminal 141 and a negative terminal 142 opposite to each other. The positive terminal 141 is connected to the cap 120 via the positive current collecting disk 130 , and the negative terminal 142 is connected to the housing 110 via the negative current collecting disk 150 .

[0130] It is understandable that in order to improve the energy density of the battery and the welding effect with the positive electrode collector plate 130 and the negative electrode collector plate 150, the positive terminal 141 and the negative terminal 142 can be formed by flattening the full-pole ear. For example, the full-pole ear foil of the positive and negative electrode collectors is rotated and pressed as a whole for a certain stroke by a mechanical conical roller. Thus, on the one hand, the positive terminal 141 and the negative terminal 142 formed by the flattening process are stacked densely, without wasting space in the longitudinal direction. Thus, the utilization rate of the internal space of the housing 110 is high, which can further improve the energy density of the battery. On the other hand, the positive electrode flattening structure 141 and the negative electrode flattening structure 142 formed by the flattening process have a flat cross-section, and the two can be respectively abutted with the positive electrode collector plate 130 and the negative electrode collector plate 150, and the bonding effect is good, which is conducive to laser welding and can effectively reduce process defects such as cold welding.

[0131] In addition, during the winding process, a through winding core hole 143 is formed in the middle of the winding core 140 along the axial direction. The diameter D6 of the winding core hole 143 needs to consider the balance between the injection efficiency and the weldable area while ensuring the safety of welding.

[0132] The negative electrode current collecting disk 150 is described in detail below.

[0133] like Figure 1 and Fig.11As shown, the negative electrode current collecting disc 150 is circular as a whole. Along the thickness direction, the negative electrode current collecting disc 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 a raised platform 1521 described below, when welding the negative electrode current collecting disc 150 to the outer shell 110 and the winding core 140, it is necessary to distinguish the direction. Specifically, the second side 152 is welded to the shell bottom 111 through the raised platform 1521, and the first side 151 is welded to the negative end 142 of the winding core 140. Thus, the welding connection between the winding core 140, the negative electrode current collecting disc 150 and the outer shell 110 is realized, and a passage is formed between the three. That is, the negative electrode current collecting disc 150 indirectly connects the winding core 140 to the outer shell 110.

[0134] To ensure that the raised platform 1521 fits well with the surface of the outer shell 110, in the present embodiment, the negative electrode current collecting plate 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 abutting against the inner surface of the shell bottom 111, and the surface flatness of the raised platform 1521 is 0.01-0.05mm. It is understandable that, since the surface of the raised platform 1521 is higher than the surface of the second side 152, that is, the surface of the raised platform 1521 is the top surface of the second side 152, after the negative electrode current collecting plate 150 is assembled into the outer shell 110, the surface of the raised platform 1521 will abut against the inner surface of the shell bottom 111, that is, the surface of the raised platform 1521 and the inner surface of the shell bottom 111 are closely fitted to each other, and a surface-to-surface contact connection is formed between the two, and then the area where the raised platform 1521 overlaps with the shell bottom 111 can be laser-welded through the outer surface 1112 of the bottom plate, so that the raised platform 1521 is welded to the outer shell 110. It is also understandable that if the flatness of the raised platform 1521 is too large, the fitting effect between it and the inner surface of the shell bottom 111 is not good, thereby affecting the welding quality; on the contrary, if the flatness of the raised platform 1521 is too small, it is difficult to process and the cost is too high.

[0135] In this embodiment, since the ratio of the diameter D7 of the negative electrode current collecting disk 150 to the diameter D5 of the winding core 140 is set at 90%-98%, the weldable area between the negative electrode current collecting disk 150 and the winding core 140 can be effectively increased, and the welding processability is good. At the same time, a smaller raised platform 1521 is set on the second side 152 of the negative electrode current collecting disk 150. Since the raised platform 1521 has a small area, it can ensure that it has good surface flatness during the processing process, so that the surface of the raised platform 1521 can be better fitted with the inner surface of the shell bottom 111, and the welding quality problems such as cold welding between the two can be effectively avoided. The battery using the negative electrode current collecting disk 150 has better performance and yield rate.

[0136] For the purpose of facilitating processing and reducing costs, in some embodiments, the raised platform 1521 is formed by the negative electrode current collector 150 through a stamping process, that is, the raised platform 1521 is formed integrally with the negative electrode current collector 150. Therefore, through a reasonable stamping die design, the negative electrode current collector 150 of this embodiment can be efficiently processed, and the negative electrode current collector 150 and the raised platform 1521 have high dimensional accuracy and good surface quality, which is convenient for welding with the winding core 140 and the housing 110. Of course, it is not limited to this, and 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 welding performance and conductive performance, and the metal component can be combined with the surface of the second side 152 of the negative electrode current collector 150 by pressing, thereby forming the raised platform 1521.

[0137] In some embodiments, the raised platform 1521 is formed in the central area of ​​the second side 152, so that after the negative electrode current collecting plate 150 is assembled into the outer shell 110, the raised platform 1521 can be aligned with the central area of ​​the shell bottom 111, making it convenient to weld the outer shell 110 and the raised platform 1521 using welding equipment.

[0138] Furthermore, the shape of the raised platform 1521 is circular, so that the raised platform 1521 can be co-centered with the negative electrode current collecting plate 150, which is convenient for stamping by a stamping die. Of course, the shape of the raised platform 1521 is not limited to a circle, for example, the raised platform 1521 can also be a square, a triangle, etc.

[0139] like Fig.10 and Fig.11 As shown, it can be understood that the raised platform 1521 is punched out on the second side 152 of the negative electrode current collector 150 through the stamping process, and accordingly, a recessed portion 1511 is formed at a position corresponding to the raised platform 1521 on the first side 151. For the purpose of conveniently welding the negative electrode current collector 150 and the winding core 140, in some embodiments, the first side 151 has an annular welding area 1512 around the recessed portion 1511, and the surface of the welding area 1512 is suitable for abutting against the negative terminal 142 of the winding 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 closely to each other to improve the welding quality.

[0140] like Fig.11As shown, in some embodiments, the diameter of the raised platform 1521 is D8, satisfying D8 / D7=28%-38%. As mentioned above, the diameter D7 of the negative electrode current collecting disk 150 is substantially consistent with the diameter of the winding core 140. If the diameter of the raised platform 1521 is too large, its surface flatness will deteriorate, and its bonding effect with the inner surface of the shell bottom 111 will be poor, thereby affecting the welding quality; on the contrary, if the diameter of the raised platform 1521 is too small, the weldable area of ​​the raised platform 1521 is small, and it is easy to desolder during welding, which will increase the difficulty of subsequent welding process and increase the cost.

[0141] Furthermore, if Fig.12 As shown, in some embodiments, the height difference between the surface of the raised platform 1521 and the surface of the second side 152 is H4, and the thickness of the negative electrode collector 150 is T4, which satisfies: H4 / T4=18%-30%. It can be understood that if the raised platform 1521 is set too high, that is, H4 / T4 is too large, then during the assembly process, the winding core 140 will squeeze and deform the periphery of the negative electrode collector 150, and will also occupy additional longitudinal space of the battery; on the contrary, if the raised platform 1521 is set too low, that is, H4 / T4 is too small, then the raised platform 1521 is difficult to process, for example, it is difficult to form the raised platform 1521 through a stamping process.

[0142] The negative electrode current collecting plate 150 is further described below with reference to embodiments and comparative examples. The following embodiments and comparative examples of the present application are designed with reference to ordinary 21 series cylindrical lithium batteries.

[0143] Embodiment 1:

[0144] Embodiment 1 provides a cylindrical lithium battery, which includes a housing 110, a cap 120, a positive electrode current collector 130, a winding core 140, and a negative electrode current collector 150. The negative electrode current collector 150 has a diameter of 18 mm, and a raised platform 1521 is punched out on the second side 152 thereof. Accordingly, a recessed portion 1511 is formed at a position corresponding to the raised platform 1521 on the first side 151. Surrounding the recessed portion 1511, the first side 151 has an annular welding area 1512, and the surface of the welding area 1512 is connected to the negative terminal 142 of the winding core 140 by laser penetration welding, wherein the diameter D8 of the raised platform 1521 is 35% of the diameter D7 of the negative electrode current collector 150, and the height difference between the surface of the raised platform 1521 and the surface of the second side 152 is H4, which is 25% of the thickness T4 of the negative electrode current collector 150.

[0145] Comparative Example 1:

[0146] Comparative Example 1 provides a cylindrical lithium battery, which differs from Example 1 in that the diameter D8 of the elevated platform 1521 is 35% of the diameter D7 of the negative electrode current collecting disk 150, the height difference H4 between the surface of the elevated platform 1521 and the surface of the second side 152 is 60% of the thickness T4 of the negative electrode current collecting disk 150.

[0147] Comparative Example 2:

[0148] Comparative Example 2 provides a cylindrical lithium battery, which differs from Example 1 in that the diameter D8 of the elevated platform 1521 is 60% of the diameter D7 of the negative electrode current collecting disk 150, the height difference H4 between the surface of the elevated platform 1521 and the surface of the second side 152 is 25% of the thickness T4 of the negative electrode current collecting disk 150.

[0149] Comparative Example 3:

[0150] Comparative Example 3 provides a cylindrical lithium battery, which differs from Example 1 in that the diameter D8 of the elevated platform 1521 is 10% of the diameter D7 of the negative electrode current collecting disk 150, the height difference H4 between the surface of the elevated platform 1521 and the surface of the second side 152 is 25% of the thickness T4 of the negative electrode current collecting disk 150.

[0151] The following Table 3 evaluates the welding and assembly effects of the negative electrode current collector 150 produced by the above-mentioned embodiments and comparative examples. The specific test method is: the sampled negative electrode current collector 150 is welded to the winding core 140, and loaded into the outer shell 110, so that the shell 111 fits the raised platform 1521, and the shell bottom 111 and the negative electrode current collector 150 are welded by laser penetration welding at the bottom of the shell bottom 111. Use a cutter to cut along the diameter direction at 3mm from the bottom of the outer shell 110, visually observe the shape of the negative electrode current collector 150, then use diagonal pliers to clamp out 4 small edges of the negative electrode current collector 150, use a tensile machine tool to clamp the 4 edges for pulling, read and record the maximum tensile force that pulls the negative electrode current collector 150 and the outer shell 110 to separation, and use a microscope to draw the edge line of the part of the negative electrode current collector 150 remaining on the shell bottom 111, measure and record the residual area, and visually observe the weld mark state of the residual part.

[0152] Table 3

[0153]

[0154] It can be seen from Table 3 that when the diameter D8 of the raised platform 1521 is 35% of the diameter D7 of the negative electrode current collecting disc 150, and the height difference H4 between the surface of the raised platform 1521 and the surface of the second side 152 is 25% of the thickness T4 of the negative electrode current collecting disc 150, the overall rigidity of the negative electrode current collecting disc 150 is good and can resist deformation during assembly. In addition, the raised platform 1521 can also fit well with the inner surface of the shell bottom 111, and the welding quality between the two is good, and no welding defects such as cold welding and welding penetration are found, and the connection strength between the two is also relatively ideal. When the height difference H4 between the surface of the raised platform 1521 and the surface of the second side 152 is large, the negative electrode current collecting disc 150 is deformed after assembly, and there is a welding defect of cold welding between it and the shell bottom 111, and the connection strength between the two is not high. When the diameter of the raised platform 1521 is too large, the negative electrode current collector 150 is deformed after assembly. Although the connection strength between the negative electrode current collector 150 and the shell bottom 111 is relatively large, there is a welding defect of welding through between the two. When the area of ​​the raised platform 1521 is too small, the negative electrode current collector 150 is deformed after assembly, and there is a welding defect of cold welding between the negative electrode current collector 150 and the shell bottom 111, and the connection strength between the two is relatively poor.

[0155] In some embodiments, the negative electrode current collecting disc 150 is made of copper, and a nickel layer is plated on the surface of the negative electrode current collecting disc 150. Compared with the negative electrode current collecting disc 150 made of copper-nickel alloy, the copper material as the base material has the characteristic of extremely low internal resistance. At the same time, by plating the nickel layer on the surface of the negative electrode current collecting disc 150, the corrosion resistance of the negative electrode current collecting disc 150 can be effectively improved.

[0156] 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 thickness of the nickel layer is too small, it cannot play an anti-oxidation role; on the contrary, if the thickness of the nickel layer is too thick, on the one hand, the difficulty of the nickel plating process is increased, and the cost is increased, and on the other hand, the hardness of the negative electrode collector 150 is increased, resulting in a decrease in the plasticity of the negative electrode collector 150, and at the same time, the internal resistance is increased, resulting in a decrease in battery performance.

[0157] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present implementation. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0158] Although examples of the present embodiment have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present embodiment, and the scope of the present embodiment is defined by the claims and their equivalents.

Claims

1. A cylindrical lithium battery, characterized in that: The invention comprises a housing (110), a cap (120), a positive electrode current collecting disk (130), a winding core (140) and a negative electrode current collecting disk (150), wherein the positive terminal (141) of the winding core (140) is connected to the housing (110) through the cap (120), and the negative terminal (142) of the winding core (140) is connected to the housing (110) through the negative electrode current collecting disk (150); The positive electrode current collecting disk (130) comprises a disk body (131) and a tail body (132) connected to each other, the disk body (131) is connected to the positive terminal (141), the tail body (132) is connected to the cap (120), a circular first hole (1315) is provided at the center of the disk body (131), at least one circular second hole (1316) is provided around the periphery of the first hole (1315), and the surfaces of all the second holes (1316) are The sum of the products is 0.9-1.5 times the area of ​​the first hole (1315); at least one fuse slot (1321) is provided on the tail body (132); at positions other than the fuse slot (1321) on the tail body (132), the tail body (132) has an overall cross-sectional area S1; the tail body (132) has a minimum cross-sectional area S2 at the position of the fuse slot (1321); the minimum cross-sectional area S2 is 45%-65% of the overall cross-sectional area S1; The negative electrode current collector (150) has a first side (151) and a second side (152) opposite to each other, the first side (151) being connected to the negative terminal (142), a circular raised platform (1521) with a flat surface being provided at the center of the second side (152), the raised platform (1521) being connected to the outer shell (110), a diameter D8 of the raised platform (1521) being 28%-38% of a diameter D7 of the negative electrode current collector (150), and a height difference H4 between a surface of the raised platform (1521) and a surface of the first side (151) being 18%-30% of a thickness T4 of the negative electrode current collector (150).

2. The cylindrical lithium battery according to claim 1, characterized in that: The winding core (140) has a winding core hole (143) extending therethrough; the diameter D3 of the first hole (1315) is 1.4-1.8 times the diameter D6 of the winding core hole (143); the diameter D3 of the second hole (1316) is 50%-70% of the diameter D2 of the first hole (1315); and the flatness of the surface of the raised platform (1521) is 0.01-0.05 mm.

3. The cylindrical lithium battery according to claim 1, characterized in that: The positive terminal (141) and the negative terminal (142) are both formed by flattening the entire electrode tab; the side of the disk body (131) facing the positive terminal (141) abuts against the positive terminal (141) formed by flattening the entire electrode tab; the first side (151) of the negative electrode current collecting disk (150) abuts against the flattened negative terminal (142).

4. The cylindrical lithium battery according to claim 3, characterized in that: The diameter D2 of the disk body (131) is 80%-95% of the diameter D5 of the winding core (140); and the diameter D7 of the negative electrode current collecting disk (150) is 90%-98% of the diameter D5 of the winding core (140).

5. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that: The shape of the disk 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 in sequence, and the shape of the tail body (132) is a closed axisymmetric figure composed of a third side (1314), a fifth side (1322) extending along the length direction of the tail body (132), a fourth side (1324) away from the disk body and a sixth side (1323) extending along the length direction of the tail body (132) connected end to end in sequence, wherein the two ends of the fifth side are respectively connected to the fourth side (1314). 24) is connected to the first side (1311), and the two ends of the sixth side (1323) are respectively connected to the fourth side (1324) and the second side (1313); the raised platform (1521) is formed by the negative electrode current collecting plate (150) through integral stamping, and the first side (151) forms a recessed portion (1511) at a position corresponding to the raised platform (1521), and a welding area (1512) is formed around the recessed portion (1511), and the surface of the welding area (1512) abuts against the negative terminal (142) formed by flattening.

6. The cylindrical lithium battery according to claim 5, characterized in that: The material of the positive electrode current collecting disc (130) is aluminum, the material of the negative electrode current collecting disc (150) is copper, and the surface of the negative electrode current collecting disc (150) is plated with a nickel layer.

7. The cylindrical lithium battery according to claim 6, characterized in that: The length L3 of the tail body (132) is 85%-95% of the diameter D2 of the disc body (131); and the thickness of the nickel layer is 0.08-1.5 μm.

8. The cylindrical lithium battery according to claim 5, characterized in that: The housing (110) comprises a housing bottom (111) and a side wall (112); the top end of the side wall (112) comprises an opening (114); the side wall (112) is concave inwardly along the circumferential direction at a position close to the opening (114) to form a constricted portion (1121); the constricted portion (1121) comprises a first wall portion (1121a) and a second wall portion (1121b) extending toward the center of the housing (110); the constricted portion (121) further comprises a first wall portion (1121a) and a second wall portion (1121b) for connecting the first wall portion (1121a) and the second wall portion (1121b). The first wall portion (1121a), the second wall portion (1121b) and the connecting portion (1121c) of the shell bottom (111), the outer surfaces of the first wall portion (1121a), the second wall portion (1121b) and the connecting portion (1121c) jointly define a necking groove (1123), and the first wall portion (1121a) and the second wall portion (1121b) are both arranged at a certain inclination angle with the shell bottom (111); the raised platform (1521) is connected to the inner surface of the shell bottom (111).

9. The cylindrical lithium battery according to claim 8, characterized in that: The first width W1 of the tail body (132) is equal to D2*sin(∠B / 2), and 20°≤∠B≤40°, wherein ∠B has the center point corresponding to the arc (1312) as its vertex, and its two sides respectively pass through the intersection of the fifth side (1322) and the sixth side (1323) with the full circle where the arc (1312) is located; the larger of the angles between the first wall portion (1121a) and the shell bottom (111) and the angles between the second wall portion (1121b) and the shell bottom (111) is α, and the following is satisfied: α<10°.

10. The cylindrical lithium battery according to claim 9, characterized in that: The second width W2 of the tail body (132) at the fuse slot (1321) is 3 / 8-3 / 4 of the first width W1; and the angle α satisfies: 1°<α<5°.

11. The cylindrical lithium battery according to claim 8, characterized in that: The disc body (131) has a center angle A, and 40°≤∠A≤60°; wherein the center angle A takes the center of the circle corresponding to the arc (1312) as a vertex, and the two sides respectively pass through the end point of the first side (1311) away from the arc (1312) and the end point of the second side (1313) away from the arc (1312).

12. The cylindrical lithium battery according to claim 8, characterized in that: The dimension L5 of the fuse groove (1321) along the length direction of the tail body (132) is 0<L5≤W1; the depth H3 of the necking groove (1123) in the radial direction is 5%-10% of the outer diameter D1 of the housing (110).

13. The cylindrical lithium battery according to claim 12, characterized in that: The dimension L5 of the fuse slot (1321) along the length direction of the tail body (132) is 1 / 4 to 3 / 4 of the first width W1; the minimum wall thickness T2 of the neck portion (1121) is 0.1-0.2 mm, and it is more than 80% of the wall thickness T1 of the side wall (112).

14. The cylindrical lithium battery according to claim 8, characterized in that: 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°; the distance L1 between the lowest point of the neck portion (1121) and the upper surface of the shell bottom (111) is 90%-98% of the height H1 of the shell (110); the height H2 of the necking groove (1123) is 0.1%-1% of the height H1 of the shell (110).

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