Cylindrical lithium battery

Abstract

The invention provides a cylindrical lithium battery. A necking groove is formed in a shell in the cylindrical lithium battery, the height H2 of the necking groove is 0.1%-1% of the height H1 of the shell, and the depth H3 of the necking groove in the radial direction is 5%-10% of the outer diameter D1 of the shell; 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 distance between the center position of the fusing groove and the end, away from a plate body part, of the tail body part is 68-78% of the length of the tail body part; 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; the negative collector plate in the cylindrical lithium battery is provided with a heightening platform with a flat surface, and the flatness of the surface of the heightening platform is 0.01-0.05 mm. 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, cylindrical lithium batteries involve a variety of structural parts such as steel shells, winding cores, positive electrode collector plates and negative electrode collector plates, as well as electrical connectors. During the assembly process, there are also a variety of processes such as welding and injection. In order to achieve a better assembly effect and make the final battery performance reach a better state, many factors need to be considered in the design process of the above components. 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 a cylindrical lithium battery so that it can achieve a balance in injection performance, safety, and weldability 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 problems of the existing cylindrical lithium batteries being unbalanced in terms of assemblability, safety, and battery performance.

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

[0006] The winding core has a positive electrode flattening structure and a negative electrode flattening structure relative to each other, the positive electrode flattening structure and the negative electrode flattening structure are both formed by flattening a full-electrode ear cut-and-stacked structure, the positive electrode flattening structure is connected to the cap through the positive electrode collector plate, and the negative electrode flattening structure is connected to the housing through the negative electrode collector plate;

[0007] The shell comprises a shell bottom and a side wall, the top end of the side wall has an opening, the side wall is concave inwardly along the circumferential direction near the opening to form a necking portion, the outer surface of the side wall forms a necking groove at the necking portion, the winding core is located in the area defined by the necking portion and the shell bottom in the shell, the height H2 of the necking groove is 0.1%-1% of the height H1 of the shell, and the depth H3 of the necking groove in the radial direction is 5%-10% of the outer diameter D1 of the shell;

[0008] 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 electrode flattening structure, 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;

[0009] 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 flat elevated platform is provided at the center of the second side, the elevated platform is connected to the inner surface of the shell bottom, and the flatness of the elevated platform surface is 0.01-0.05mm.

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

[0011] Firstly, by rationally designing the height and depth of the necking groove on the shell, the internal space utilization of the shell can be effectively improved to increase the energy density of the battery, and the structural strength and sealing processability of the necking portion can also be improved.

[0012] Secondly, 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.

[0013] Furthermore, by providing a flat raised platform on the side where the negative electrode current collecting disk is connected to the inner surface of the shell bottom, the raised platform has a small area and can ensure 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.

[0014] In summary, by reasonably designing the neck portion, the positive electrode current collector and the negative electrode current collector, the cylindrical lithium battery of the present application achieves a balance in multiple aspects such as liquid injection performance, safety and weldability, and can provide battery performance.

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

[0016] 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. In addition, by properly designing the size of the raised platform, the welding effect and welding processability between the platform and the shell bottom can be improved.

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

[0018] 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.

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

[0020] By properly designing the size of the first hole and the second hole of the positive electrode collector, the injection efficiency and the welding effect with the positive terminal can be balanced. At the same time, by properly designing the height of the padding platform, while meeting the machinability and use requirements of the negative electrode collector, the negative electrode collector will not occupy too much longitudinal space inside the shell, thereby improving the space utilization of the shell.

[0021] 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 in sequence end to end, 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, a fourth side away from the disk body and a sixth side extending along the length direction of the tail connected in sequence end to end, 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 electrode flattening structure.

[0022] 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.

[0023] In a possible implementation, the length L4 of the tail body is 85%-95% of the diameter D3 of the disk body; the distance L5 between the center position of the fuse slot and the end of the tail body away from the disk body is 68%-78% of the length L4 of the tail body.

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

[0025] In a possible embodiment, the disc body has a center angle A, and 40°≤∠A≤60°, wherein the center angle A has the center of the circle corresponding to the arc as the vertex, and two sides pass through the first side away from the endpoint of the arc and the second side away from the endpoint of the arc respectively; the first width W2 of the tail body is W2=D3*sin(∠B / 2), and 20°≤∠B≤40°, wherein ∠B has the center of the circle corresponding to the arc as the vertex, and two sides pass through the intersection of the fifth side and the sixth side with the whole circle where the arc is located.

[0026] By properly designing the center angle A, it is possible to ensure that the disc body still has a large weldable area after the hole is opened. At the same time, 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.

[0027] In a possible implementation manner, the second width W3 of the tail body at the fuse slot is 3 / 8-3 / 4 of the first width W2; and the dimension L6 of the fuse slot along the length direction of the tail body is in the range of 0<L6≤W2.

[0028] 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, 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 a safe current. By reasonably designing the size of the fuse slot, it is helpful to improve the safety of the battery.

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

[0030] By reasonably 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 collecting disk and the size of the weldable region of the disk body can be balanced.

[0031] In a possible embodiment, the neck portion includes a first wall portion and a second wall portion extending toward the center of the shell, and 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 with the bottom of the shell; the cap includes a stacked explosion-proof valve plate and a terminal plate, the tail body portion is connected to the bottom of the terminal plate, the explosion-proof valve plate is provided with a first notch and a second notch, the first notch is a closed circle connected at the head and tail ends, and the second notch is a line segment shape, and the first notch intersects with the second notch.

[0032] By setting the first wall and the second wall constituting the necking portion to be inclined toward the shell bottom, the necking portion has reserved a certain amount of collapse margin, so 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. At the same time, by setting the first notch and the second notch on the explosion-proof valve sheet, when the battery is in an abnormal state such as overheating or short circuit, which causes the internal air pressure to rise sharply, whether the air pressure value of the edge area or the middle area reaches the preset value first, one of the first notch and the second notch will break first, so that the battery can release pressure in time, and because the first notch intersects with the second notch, the first notch or the second notch will also drive the other to break during the process of breaking, so that the opening area of ​​the explosion-proof valve sheet can be expanded and the pressure relief effect can be improved. Therefore, when the gas pressure inside the battery exceeds the preset value, the explosion-proof valve sheet can be opened quickly and effectively to release the pressure, thereby improving the safety of the battery.

[0033] In a possible implementation, 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, and the range of α is α<10°; the explosion-proof valve plate is provided with a thinning portion extending in a radial direction, the first notch is arranged within the radial range where the thinning portion is located, the thickness of the thinning portion is T3, the depth of the first notch is H4, and the range of H4 / T3 is 30%-60%.

[0034] By reasonably designing the size of the angle α, the difficulty of rolling groove design is reduced, the influence of the neck portion on the lower cavity space can be reduced, and the sealing effect of the cap can be ensured. At the same time, by reasonably setting the thickness of the thinned portion and the depth of the first notch, the first notch can be effectively broken when the opening condition is met to release the battery pressure, while also ensuring that the explosion-proof valve sheet has sufficient strength and rigidity for easy processing and assembly.

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

[0036] By properly designing the angle α, the difficulty of rolling groove design is reduced, the impact of the neck portion on the lower cavity space is reduced, and the sealing effect of the cap is ensured. At the same time, by properly designing the width of the thinned portion, the first notch can be effectively broken when the opening condition is met to release the pressure of the battery, while also ensuring that the explosion-proof valve sheet has sufficient strength and rigidity for easy processing and assembly.

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

[0038] By rationally designing the wall thickness at the thinnest part of the neck, it is possible to ensure that the pressure resistance of the shell meets the requirements. At the same time, by setting the diameter of the first notch to be equal to the length of the second notch, the second notch divides the first notch into two symmetrical parts, which is convenient for processing. After the explosion-proof valve is assembled to the cylindrical lithium battery, the second notch is located in the middle area of ​​the cylindrical lithium battery, so that the explosion-proof valve can be opened smoothly to release pressure.

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

[0040] By properly designing the wall thickness at the thinnest part of the neck portion, it is possible to ensure that the compressive strength of the shell meets the requirements. At the same time, by properly setting the radius of the chamfered portion, the stress concentration at the bottom of the first notch and the second notch can be effectively reduced, while reducing the processing difficulty and manufacturing cost.

[0041] In a possible embodiment, the distance L1 between the lowest point of the neck portion and the upper surface of the shell bottom is 90%-98% of the height H1 of the shell; the depth H4 of the first notch is less than the depth H5 of the second notch, and the depth in the middle of the second notch is greater than the depth at both ends.

[0042] By reasonably designing the distance between the bottom of the neck and the bottom of the shell, the internal space utilization of the shell can be effectively improved, thereby improving the energy density of the battery, and at the same time, the structural strength of the neck and the sealing processability can be ensured. At the same time, by increasing the depth of the second notch, the effect of the increase in the thickness of the explosion-proof valve sheet in the middle area on the second notch can be reduced, so as to ensure that the explosion-proof valve sheet opens smoothly at the second notch, and by setting the depth of the second notch so that the depth in the middle is greater than the depth at both ends, that is, the depth of the second notch is deeper in the middle and shallower at both ends, the effect of the step-wise change in the thickness of the explosion-proof valve sheet in the middle area can be reduced, so as to ensure that the explosion-proof valve sheet opens smoothly at the second notch.

[0043] In one possible embodiment, the full-ear stacking structure includes a current collector substrate, which is divided into a material area and a ear area for coating polar materials along the width direction, and the material area and the ear area both extend along the length direction of the current collector substrate. The current collector substrate has a plurality of ears arranged at intervals along the length direction at the ear area, and the width of the edge of the ear facing the material area is W4, and the distance between the edges of two adjacent ears facing the material area is W5. The range of W5 / W4 is 20%-30%, and the shape of the ear is a parallelogram, and the angle β between the edge connected to the edge of the ear facing the material area and the width direction of the current collector substrate is 14-18°.

[0044] By optimizing the die-cutting tab width W2 and tab spacing W3, and controlling W3 / W2 to be within the range of 20%-30%, it is beneficial to increase the tension of the tab, so that the tab can withstand the pressure of flattening when subjected to the subsequent flattening operation, reduce the generation of debris, reduce the possibility of debris falling into the battery, and reduce the probability of battery short circuit. In addition, the appropriate tab width W2 and tab spacing W3 structural design can ensure that the density of the full tab after flattening is not too high to a certain extent, and there is a certain effective gap between each other, which is conducive to the infiltration of the electrolyte, thereby improving the cycle performance of the battery. In addition, by selecting the angle β between the beveled edge of the tab and the width direction of the current collector substrate to be 14-18°, the tab can still fit as closely as possible after flattening, and then the tab has a suitable density after flattening, so that while ensuring that the tab has sufficient electrolyte infiltration effect, it can take into account the welding performance of the tab and reduce the generation of debris particles, thereby improving the safety performance and cycle performance of the battery.

[0045] In a possible embodiment, a connecting area is further provided between the material area and the lug area, the distance between the edge where the lug is connected to the connecting area and the material area is H7, the length between the edge of the lug away from the material area and the material area is H6, and the range of H7 / H6 is 10%-20%.

[0046] By setting the connection area and reasonably designing the size of the connection area and the pole ear, the positive electrode leveling structure and the negative electrode leveling structure formed by leveling have good welding performance, current flow performance and reliability.

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

[0048] By rationally designing the distance between the edge where the tab and the connection area are connected and the material area, the problem of the material area protruding outwards and the welding effect and the current flow effect are balanced. At the same time, by rationally setting the tab width, it is possible to ensure that the tab has sufficient tension, reduce chipping during the flattening process, and is less likely to cause scattering and chipping, and improve the flattening effect to ensure welding performance.

[0049] In one possible embodiment, the length of the multiple pole ears in the pole ear area along the length direction of the current collector substrate is less than the length L7 of the material area, one of the two ends of the pole ear area has a first cut-off area, and the other end has a second cut-off area, the length of the first cut-off area along the length direction of the current collector substrate is L8, and the range of L8 / L7 is 5%-15%, and the length of the second cut-off area along the length direction of the current collector substrate is L9, and the range of L9 / L7 is 10%-20%.

[0050] The first cut-away area or the second cut-away area is provided to reduce the blockage of the center hole of the winding core and avoid the tabs from protruding outward during subsequent winding and flattening, thereby facilitating liquid injection and the winding core into the shell.

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

[0052] By rationally designing the length of the first cut-off area and the second cut-off area, it is beneficial to reduce the blockage of the center hole of the core and avoid the tabs protruding outward during subsequent winding and flattening, thereby facilitating liquid injection and core shelling. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] 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.

[0054] Figure 1 is an exploded schematic diagram of a cylindrical lithium battery according to an embodiment of the present application;

[0055] Figure 2This is a schematic diagram of the state of the outer shell of a cylindrical lithium battery after being sealed in one embodiment of the present application;

[0056] Figure 3 yes Figure 2 The local schematic diagram of the A in the middle;

[0057] Figure 4 is a cross-sectional schematic diagram of a cap in a cylindrical lithium battery in one embodiment of the present application;

[0058] Figure 5 It is a top view schematic diagram of an explosion-proof valve sheet in a cylindrical lithium battery according to an embodiment of the present application;

[0059] Figure 6 yes Figure 5 A schematic cross-sectional view of the middle explosion-proof valve plate;

[0060] Figure 7 yes Figure 6 The local schematic diagram of point B in the middle;

[0061] Figure 8 yes Figure 6 The local schematic diagram of the C in the middle;

[0062] Fig. 9 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;

[0063] Fig.10 yes Fig. 9 A schematic diagram of the structure in which the positive electrode current collecting disk is connected to the winding core;

[0064] Fig.11 yes Fig. 9 A schematic diagram of the structure of the tail portion of the middle positive electrode current collector;

[0065] Fig.12 yes Fig.11 Schematic diagram of the cross section along the AA direction;

[0066] Fig.13 yes Fig. 9 A schematic diagram of the structure of the tail portion of the middle positive electrode current collector;

[0067] Fig.14 This is a schematic diagram of the structure of the connection between the winding core and the positive electrode current collecting disk and the negative electrode current collecting disk in a cylindrical lithium battery of an embodiment of the present application;

[0068] Fig.15 This is a schematic diagram of a cylindrical lithium battery in an embodiment of the present application before winding;

[0069] Fig.16 Schematic diagram of a full-ear cut-and-stack structure of a roll core in a cylindrical lithium battery according to an embodiment of the present application;

[0070] Fig.17 yes Fig.16 The local schematic diagram of point D in the middle;

[0071] Fig.18 yes Fig.16 Schematic diagram of the flattened structure of the full-ear cut;

[0072] Fig.19 yes Fig.18 The local schematic diagram at E in the middle;

[0073] Fig. 20 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;

[0074] Fig.21 yes Fig. 20 A schematic cross-sectional view of the middle negative electrode current collector;

[0075] Fig. 22 yes Fig.21 Partial schematic diagram of point F in the middle.

[0076] Reference numerals:

[0077] 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;

[0078] 120-cap, 121-top cover, 122-explosion-proof valve plate, 1221a-first notch, 1221b-second notch, 1222-thinning portion, 1223-groove, 1224-welding platform, 123-insulating plate, 124-terminal plate, 125-insulating ring;

[0079] 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;

[0080] 140-winding core, 141-positive electrode flattening structure, 142-negative electrode flattening structure, 143a-first separator, 143b-second separator, 144-current collector substrate, 144a-positive electrode sheet, 144b-negative electrode sheet, 1441-material area, 1442-ear area, 1443-ear, 14431-edge connected to the ear and the connection area, 14432-edge connected to the edge of the ear facing the material area, 14433-edge away from the ear, 1444-connecting area, 1445-first cut-off area, 1446-second cut-off area, 145-winding core hole;

[0081] 150 - negative electrode current collecting plate, 151 - first side, 1511 - recessed portion, 1512 - welding area, 152 - second side, 1521 - raised platform. DETAILED DESCRIPTION

[0082] 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.

[0083] 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.

[0084] 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.

[0085] 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.

[0086] 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 1As 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.

[0087] The housing 110 is described in detail below.

[0088] 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.

[0089] 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.

[0090] 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 .

[0091] 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.

[0092] like Figure 2 and Figure 3As 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.

[0093] 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 2 In 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.

[0094] 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.

[0095] 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°.

[0096] 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°.

[0097] 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.

[0098] 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.

[0099] 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 shell 110 is H1, and the range of L1 / H1 is 90%-98%, that is, it 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 shell 110 will be wasted, resulting in a lower energy density of the battery. By properly designing the distance L1 between the lowest point of the neck portion 1121 in the inner cavity 113 and the upper surface of the shell bottom 111, the sealing effect of the seal can be ensured while improving the utilization of the internal space of the shell 110 and the battery energy density.

[0100] Furthermore, in some embodiments, the height of the necking groove 1123 is H2, the height of the outer shell 110 is H1, and the range of H2 / H1 is 0.1%-1%, that is, it satisfies: 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 3As 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%.

[0101] In some embodiments, the depth of the necking groove 1123 in the radial direction is H3, the outer diameter of the housing 110 is D1, and the range of H3 / D1 is 5%-10%, that is, 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 invade 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 weaken, stress to increase, and there is a risk of cutting, which in turn makes the sealing unable to be guaranteed; conversely, 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 supported by the first wall portion 1121a, and the dimensional chains of the two are poorly matched. 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.

[0102] 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.

[0103] 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, and the range of T2 is between 0.1-0.2 mm, that is, it satisfies: 0.1 mm ≤ T2 ≤ 0.2 mm. It can be understood that the minimum wall thickness T2 of the neck portion 1121 is set between 0.1-0.2 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.

[0104] The cap 120 is described in detail below.

[0105] 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.

[0106] 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 housing 110, the top cover 121 is exposed outside the housing 110, and it is used as a positive terminal for electrical connection with the positive electrode of an external electrical device. 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. The explosion-proof valve sheet 122 constituting the cap 120 is described in detail below.

[0107] refer to Figures 5 and 6 The explosion-proof valve plate 122 is a single member made of aluminum material, and is in the shape of a circular thin disk or a thin plate. In the thickness direction, it has a top surface and a bottom surface that are separated from each other. After being assembled into a cylindrical lithium battery, the bottom surface ( Figure 6 The lower middle surface) faces the side of the winding core 140, and the top surface ( Figure 6The explosion-proof valve sheet 122 is provided with a notch assembly 1221 on one side of the top surface. The notch assembly 1221 includes a first notch 1221a in an annular shape and a second notch 1221b extending in a line segment shape. The second notch 1221b is located in the area defined by the first notch 1221a, and the two ends of the second notch 1221b are connected to the first notch 1221a, that is, the first notch 1221a presents a closed figure connected end to end. The first notch 1221a is preferably a closed circle, and the second notch 1221b is in a line segment shape. At least one of the first notch 1221a and the second notch 1221b breaks when the internal pressure of the cylindrical lithium battery exceeds a preset value, so that the explosion-proof valve sheet 122 opens, and the first notch 1221a and the second notch 1221b that breaks first can drive the other to break as well.

[0108] It can be understood that, since the explosion-proof valve sheet 122 of the embodiment of the present application is provided with an annular first notch 1221a and a line-segment-shaped second notch 1221b, and both ends of the second notch 1221b are connected to the first notch 1221a, therefore, when an abnormal state such as overheating or short circuit occurs inside the battery and causes the internal air pressure to rise sharply, when the air pressure value in the edge area reaches the preset value first, the first notch 1221a will break first, and the gas inside the battery will rush out from the gap created by the break of the first notch 1221a to release the pressure in time, and the first notch 1221a will also drive the second notch 1221b in the process of breaking. The second notch 1221b also breaks, thereby expanding the opening area of ​​the explosion-proof valve sheet 122 and improving the pressure relief effect. When the air pressure in the middle area reaches the preset value first, the second notch 1221b breaks first, and the internal gas of the battery rushes out from the gap caused by the break of the second notch 1221b to release the pressure in time. Moreover, the second notch 1221b will also drive the first notch 1221a to break during the process of breaking and opening, thereby expanding the opening area of ​​the explosion-proof valve sheet 122 and improving the pressure relief effect. Therefore, when the gas pressure inside the battery exceeds the preset value, the explosion-proof valve sheet 122 can be opened quickly and effectively to release the pressure, thereby improving the safety of the battery.

[0109] It should be noted that if the first notch 1221a and the second notch 1221b are not connected, the two may only break separately and form a gap to release pressure, which has a poor pressure release effect and cannot achieve the purpose of quickly and effectively releasing pressure on the battery proposed in this application. Therefore, in the embodiment of the present application, the first notch 1221a and the second notch 1221b constituting the notch assembly 1221 are arranged to be connected, that is, the two intersect, so that after any one of them breaks, it can extend to the other, so that the other also breaks, so that the opening area of ​​the explosion-proof valve sheet 122 can be expanded, thereby quickly releasing pressure on the battery.

[0110] It is understandable that although a more complex internal notch, such as a cross-shaped notch, can be used to replace the second notch 1221b to achieve the purpose of timely explosion when the pressure in the middle area of ​​the battery increases, this will significantly increase the difficulty of processing the explosion-proof valve plate 122, thereby resulting in a decrease in the yield rate and an increase in cost. The embodiment of the present application only provides a straight second notch 1221b inside the explosion-proof valve plate 122, which can effectively achieve rapid and effective pressure relief for the battery while being easy to process and low in cost, thereby having better economic benefits.

[0111] It can be understood that the first notch 1221a and the second notch 1221b are structures formed by removing material on the explosion-proof valve sheet 122. Therefore, the explosion-proof valve sheet 122 is thinner at the position where the first notch 1221a and the second notch 1221b are located relative to the other positions. When the internal pressure of the battery increases and exceeds the preset value, according to the specific pressure position distribution, one or both of the first notch 1221a and the second notch 1221b are deformed as a whole. When the deformation accumulates to a certain extent, the first notch 1221a and the second notch 1221b will break, and the broken material will flip over due to the pressure to form a gap at the break, and the high-pressure gas inside the battery will be released through the gap.

[0112] In some embodiments, Figure 5 As shown, the first notch 1221a is circular, and the second notch 1221b is set to pass through the center of the first notch 1221a, that is, the second notch 1221b is just the diameter of the annular figure displayed by the first notch 1221a. In this way, if the diameter of the first notch 1221a is D2 and the length of the second notch 1221b is L2, then L2=D2 is satisfied. Therefore, the second notch 1221b divides the first notch 1221a into two symmetrical parts, which is convenient for processing and constructing the first notch 1221a and the second notch 1221b, and after the explosion-proof valve sheet 122 is assembled to the cylindrical lithium battery, the second notch 1221b is located in the middle area of ​​the cylindrical lithium battery, so that the explosion-proof valve sheet 122 can be smoothly opened to release pressure. Furthermore, it can be understood that in order to facilitate the construction of the annular first notch 1221a and the segment-shaped second notch 1221b, the first notch 1221a can be set to be co-centered with the explosion-proof valve plate 122.

[0113] like Figure 6As shown, in some embodiments, the explosion-proof valve sheet 122 is provided with a thinning portion 1222 extending in the radial direction, and the first notch 1221a is provided within the radial range where the thinning portion 1222 is located. Specifically, the thinning portion 1222 can be realized by providing a groove 1223 on one side of the explosion-proof valve sheet 122. The thinning portion 1222 can effectively cause the notch assembly 1221 to break when the opening condition is met to release the pressure of the battery, while also ensuring that the explosion-proof valve sheet 122 has sufficient strength and rigidity for easy processing and assembly.

[0114] like Figure 7 and Figure 8 As shown, relative to the surface of the explosion-proof valve sheet 122, the first notch 1221a has a depth H4, and the second notch 1221b has a depth H5. It can be understood that if H4 and H5 are large, that is, the first notch 1221a and the second notch 1221b are deep, the first notch 1221a and the second notch 1221b are easy to break, and the opening pressure will be too small. If H4 and H5 are large, that is, the first notch 1221a and the second notch 1221b are shallow, the first notch 1221a and the second notch 1221b are not easy to break, and the opening pressure will be too large, and the gas inside the battery cannot be released in time, increasing the safety risk. Therefore, in some embodiments, the ratio of the depth H4 of the first notch 1221a to the thickness T3 of the thinned portion 1222 is between 30% and 60%, that is, it satisfies: 30%≤H1 / T1≤60%, and more preferably, 40%≤H1 / T1≤55%. The specific values ​​of H4 and H5 can be determined according to the opening pressure and the thickness of the thinned portion 1222 (or the explosion-proof valve plate 122).

[0115] It can be understood that the first notch 1221a and the second notch 1221b are arranged at different positions on the explosion-proof valve plate 122. Specifically, the first notch 1221a is arranged in a ring shape around the center of the explosion-proof valve plate 122 on the end surface of the explosion-proof valve plate 122, while the second notch 1221b is radially constructed on the end surface of the explosion-proof valve plate 122 through the center of the explosion-proof valve plate 122. Due to strength, installation and other requirements, the thickness of the explosion-proof valve plate 122 in different radial areas is usually different. For example, the wall thickness of the inner part of the explosion-proof valve plate 122 adjacent to the thinning portion 1222 is thicker than that of the thinning portion 1222, and the wall thickness changes in a step-by-step manner and forms a thicker welding platform 1224 in the middle, and the explosion-proof valve plate 122 is welded to the terminal plate 124 through the welding platform 1224. Therefore, in order to ensure that the first notch 1221a and the second notch 1221b located in different areas of the explosion-proof valve plate 122 can both open smoothly when the pressure reaches a preset value, in some embodiments, the depth of the first notch 1221a is different from the depth of the second notch 1221b.

[0116] Furthermore, in some embodiments, the depth H4 of the first notch 1221a is less than the depth H5 of the second notch 1221b. By increasing the depth of the second notch 1221b, the effect of the increased thickness of the explosion-proof valve plate 122 in the middle region on the second notch 1221b can be reduced, so as to ensure that the explosion-proof valve plate 122 opens smoothly at the second notch 1221b.

[0117] Furthermore, the depth of the second notch 1221b is set to be deeper in the middle and shallower at both ends. By setting the depth of the second notch 1221b to be deeper in the middle and shallower at both ends, the influence of the step-wise change in the thickness of the explosion-proof valve plate 122 in the radial direction can be reduced, so as to ensure that the explosion-proof valve plate 122 opens smoothly at the second notch 1221b.

[0118] Further, in order to reduce stress concentration and reduce the risk of accidental breakage of the first notch 1221a and the second notch 1221b, continue to refer to Figure 7 and Figure 8 The first notch 1221a and the second notch 1221b are both provided with chamfered portions at their bottoms. By providing the chamfered portions at the bottoms of the first notch 1221a and the second notch 1221b, stress concentration at the bottoms of the first notch 1221a and the second notch 1221b can be reduced, thereby reducing the risk of accidental opening of the explosion-proof valve disc 122 when the pressure value does not reach the preset value.

[0119] Furthermore, the radii of the chamfered portions at the bottom of the first notch 1221a and the second notch 1221b are the same. By setting the radii of the chamfered portions of the first notch 1221a and the second notch 1221b to be the same, the design and manufacturing costs can be reduced. For example, the radius of the chamfered portions at the bottom of the first notch 1221a and the second notch 1221b is R, and the range of R is between 0.05-0.15mm, that is, it satisfies: 0.05mm≤R≤0.15mm, and more preferably, 0.05mm≤R≤0.1mm. The radius of the chamfered portion is within this range, which can firstly effectively reduce the stress concentration at the bottom of the first notch 1221a and the second notch 1221b, and secondly, it is also easy to process through a mold, which can reduce costs.

[0120] The positive electrode current collecting disk 130 is described in detail below.

[0121] like Fig. 9 and Fig.10As 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.

[0122] like Fig. 9 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, Fig. 9 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. Fig. 9 Dotted lines are used to mark the difference. Figure 1 and Fig.10 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.

[0123] 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.

[0124] In some embodiments, the diameter D3 of the disk body 131 is 80%-95% of the diameter D6 of the winding core 140, wherein the diameter D3 of the disk body 131 refers to the longest line segment between two points on the arc 1312, and the diameter D6 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 D3 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.

[0125] 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 145 is formed at the center of the winding core 140 after winding. To match the shape of the winding core hole 145, the shape of the first hole 1315 is preferably circular.

[0126] In some embodiments, the diameter D4 of the first hole 1315 is 1.4-1.8 times the diameter D7 of the core hole 145 of the core 140. According to actual needs, the diameter D4 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 D4 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 145 of the core 140 may produce undesirable contact with the collecting disk, and there is a risk of interference; if the diameter D4 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.

[0127] In some embodiments, the diameter D4 of the first hole 1315 is 25%-35% of the diameter D3 of the disk body 131. According to actual needs, the diameter D4 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 D4 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 145 of the core 140 may produce undesirable contact with the collector plate, and there is a risk of interference; if the diameter D4 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.

[0128] 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.

[0129] In some embodiments, the distance L3 between the center of the second hole 1316 and the center of the first hole 1315 is 25%-35% of the diameter D3 of the disk body 131. According to actual needs, L3 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 L3 between the second hole 1316 and the first hole 1315 is too small, the wetting effect of the electrolyte cannot be significantly improved; if the spacing L3 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.

[0130] In order to facilitate processing and improve yield, in a preferred embodiment, the diameter D5 of the second hole 1316 is 50%-70% of the diameter D4 of the first hole 1315, and the diameter D5 of the second hole 1316 is, for example, 2-4.8 mm. If the diameter D5 of the second hole 1316 is smaller than the preferred diameter range, it is difficult to achieve the auxiliary infiltration effect; if the diameter D5 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.

[0131] 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.

[0132] Embodiment 1:

[0133] 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.

[0134] Among them, the diameter D6 of the winding core 140 is 20 mm; the diameter D3 of the disk body 131 is 85% of the diameter D6 of the winding core 140; the diameter D4 of the first hole 1315 is 30% of the diameter D3 of the disk body 131; the diameter D5 of the second hole 1316 is 60% of the diameter D4 of the first hole 1315; the sum of the areas of all the second holes 1316 is 1.2 times the area of ​​the first hole 1315; the distance L3 between the center position of the second hole 1316 and the center of the first hole 1315 is 30% of the diameter D3 of the disk body 131; the center angle B of the disk body 131 is 35°.

[0135] Comparative Example 1:

[0136] 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 .

[0137] Comparative Example 2:

[0138] Comparative Example 2 provides a cylindrical lithium battery, which differs from Example 1 in that the diameter D4 of the first hole 1315 is 10% of the diameter D3 of the disk body 131 .

[0139] 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.

[0140] Table 1

[0141] Example 1 Comparative Example 1 Comparative Example 2 Infiltration rate (%) 90.574％ 82.367％ 71.546％

[0142] 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 hole 1315 is 1.2 times, and the diameter D4 of the first hole 1315 is 30% of the diameter D3 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 hole 1315 is too low, or the first hole 1315 is too small, the electrolyte infiltration effect of the core 140 will deteriorate.

[0143] Continue to refer Fig. 9 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.

[0144] In some embodiments, Fig.11 As shown, the distance L5 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 L4 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 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 L4 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.

[0145] In some embodiments, in order to improve the safety of the battery, the length L4 of the tail body 132 is 85%-95% of the diameter D3 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.

[0146] 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 W2, which satisfies: W2 = D3*sin(∠B / 2), where D3 is the diameter of the disk body 131, which refers to the longest line segment between two points on the arc 1312. According to actual needs, the diameter of the disk 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 Fig. 9 ), for example, and 20°≤∠B≤40°. The larger the first width W2 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.

[0147] In some embodiments, the tail body 132 has a second width W3 at the fuse slot 1321, and 3W2 / 8≤W3<3W2 / 4, that is, the second width W3 is 3 / 8 to 3 / 4 of the first width W2. The second width W3 in the present application refers to the change in the width of the tail body 132 relative to the first width W2 due to the design of the fuse slot 1321. Based on the definition of the second width W3 in the present application, the first width W2 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 W3 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.

[0148] In some embodiments, the dimension L6 of the fuse slot 1321 along the length direction of the tail body 132 satisfies: 0<L6≤W2, that is, the length of the fuse slot 1321 in the vertical direction does not exceed the first width W2 of the tail body 132. Preferably, W2 / 4<L6≤3W2 / 4, that is, the dimension L6 is 1 / 4 to 3 / 4 of the first width W2. 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 a safe current.

[0149] In some embodiments, Fig.12 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.12 As shown, when the cross section at this location is square, its cross-sectional area S2 = W3*T4; 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 = W2*T4, wherein T4 is the thickness of the tail body 132, which is usually a uniform thickness. According to actual needs, T4 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 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.

[0150] like Fig.13As 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.

[0151] 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.

[0152] Embodiment 1:

[0153] 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 L5 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 L4 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.

[0154] Comparative Example 1:

[0155] 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 .

[0156] Comparative Example 2:

[0157] 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 .

[0158] Comparative Example 3:

[0159] Comparative Example 3 provides a cylindrical lithium battery, which differs from Example 1 in that a distance L5 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 L4 of the tail body 132 .

[0160] The safety protection effect of the positive current collecting disc 130 produced by the above-mentioned embodiment and comparative example is evaluated in the following Table 2. The specific test method is: fix the sampled positive current collecting disc 130 on the tooling of the high-power programmable DC power supply device, set the measurement conditions as follows: voltage 20V, current 170A, power 150w, delay time 10s, turn on the temperature sensing instrument and aim it at the positive current collecting disc 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 collecting disc 130 is observed to be fused, and record the time and current related curves obtained by the device, as well as the fuse temperature read by the temperature sensing instrument.

[0161] Table 2

[0162] 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

[0163] It can be seen from Table 2 that when the distance L5 between the center position of the fuse slot 1321 and the end of the tail body 132 away from the disk body 131 is 72% of the length L4 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, or when the ratio of the distance L5 between the center position of the fuse slot 1321 and the end of the tail body 132 away from the disk body 131 to the length L4 of the tail body 132 is too high, the fuse slot 1321 is relatively sensitive to temperature and will be quickly fused. When the ratio of the minimum cross-sectional area S2 of the fuse slot 1321 to the overall cross-sectional area S1 of the tail portion 132 is too high, the fuse slot 1321 becomes less sensitive to temperature and cannot be quickly fused.

[0164] 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.

[0165] The winding core 140 is described in detail below.

[0166] like Figure 1 , Fig.14 and Fig.18As shown, the winding core 140 is cylindrical as a whole, and a positive electrode flattening structure 141 and a negative electrode flattening structure 142 are provided on opposite sides along the axial direction of the winding core 140, and in order to smoothly enter the inner cavity 113 of the shell 110 through the opening 114, its diameter is slightly smaller than the inner diameter of the shell 110. 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 1121 and the shell bottom 111 in the shell 110, that is, in the lower cavity 1132, and the positive electrode flattening structure 141 is connected to the cap 120 through the positive current collecting plate 130, and the negative electrode flattening structure 142 is connected to the shell 110 through the negative current collecting plate 150.

[0167] like Fig.15 As shown, it can be understood that the core 140 is formed by stacking the first diaphragm 143a, the positive electrode sheet 144a, the second diaphragm 143b and the negative electrode sheet 144b in sequence and then winding them. After winding, a core hole 145 will be formed along the axial direction of the core 140 for injecting electrolyte. It can be understood that before forming the core 140, it is necessary to make the positive electrode sheet 144a and the negative electrode sheet 142b. The positive electrode sheet 144a and the negative electrode sheet 144b both include a whole current collector substrate, such as aluminum foil or copper foil, and generally speaking, the current collector substrate is rectangular, and the length is much greater than the width. The current collector substrate is divided into two areas along the width direction, one area is used for subsequent coating of electrode materials, and the other area is used for subsequent die-cutting of pole ears. The electrode material is first coated on the area where the electrode sheet is coated with the electrode material, and then a plurality of pole ears spaced apart are die-cut in the pole ear area. The die-cutting method can be mechanical die-cutting or laser die-cutting. It can be understood that the structures of the positive electrode sheet 144a and the negative electrode sheet 144b are basically the same, except that the materials of the current collector substrate used are different, and the electrode materials coated in the material area are different.

[0168] It can be understood that after the stacking structure of the first separator 143a, the positive electrode sheet 144a, the second separator 143b and the negative electrode sheet 144b is wound, the full-ear cut stacking structure located on the positive electrode sheet 144a and the negative electrode sheet 144b needs to be flattened to form a positive electrode flattening structure 141 and a negative electrode flattening structure 142 on opposite sides of the axial direction of the winding core 140, and the positive electrode flattening structure 141 and the negative electrode flattening structure 142 have flat cross-sections and are suitable for connection with the positive electrode collector 130 and the negative electrode collector 150.

[0169] It is understandable that in the process of flattening the full-tab stacking structure, each tab is subjected to the flattening force and thus bends. In this process, the tab may produce debris. Since the tab itself is made of conductive material, the debris falling into the battery may connect the positive and negative plates, causing a short circuit inside the battery. In addition, if the positive and negative plates 144a and 144b are not designed properly, the positive and negative flattening structures 141 and 142 after flattening lack effective spaces between each other due to their high density, which is not conducive to the infiltration of the electrolyte, thereby affecting the cycle performance of the battery.

[0170] The embodiment of the present application can effectively avoid the problem of debris generated by the tabs due to the flattening process in the process of forming the positive electrode flattening structure 141 and the negative electrode flattening structure 142 by reasonably designing the full tab stacking structure in the positive electrode sheet 144a and the negative electrode sheet 144b, and can improve the electrolyte infiltration effect to a certain extent, thereby improving the cycle performance of the battery. It should be noted that since the structures of the positive electrode sheet 144a and the negative electrode sheet 144b are basically the same, when describing the full tab stacking structure below, the positive electrode flattening structure 141 and the negative electrode flattening structure 142 are not specifically distinguished, that is, the full tab stacking structure described below is applicable to both the positive electrode flattening structure 141 and the negative electrode flattening structure 142.

[0171] refer to Fig.16 and Fig.17 The full-ear stacking structure includes a current collector substrate 144, which includes a material area 1441 for coating polar materials and an ear area 1442. The material area 1441 and the ear area 1442 both extend along the length direction of the current collector substrate 144. At the location of the ear area 1442, the current collector substrate 144 has a plurality of ears 1443 spaced apart along the length direction of the current collector substrate 144. The width of the edge (14431) of the ear 1443 facing the material area is W4, and the distance between the edges 14431 of two adjacent ears 1443 facing the material area 1441 is W5.

[0172] Through experimental tests, setting the pole tab W5 / W4 in the range of 20%-30% is conducive to increasing the tension of the pole tab 1443 and avoiding the generation of debris due to the force applied by the flattening process. At the same time, if the width W4 of the edge of the pole tab facing the material area is too wide, wrinkles will be generated during the winding process. The wrinkles on the pole tab 1443 will cause the pole tab 1443 to be uneven after the subsequent flattening process, which is not conducive to the subsequent welding process. That is, the pole tab 1443 needs to be welded to the collector plate after flattening. If the pole tab 1443 is uneven after flattening, the thickness of the concave part is thin, which is easy to cause penetration welding; the unevenness also causes the flatness of the pole tab 1443 after flattening to be poor, and the concave part is easy to break the welding. Through experimental tests, setting the W5 / W4 ratio of the pole ear within the range of 20%-30% can reduce the wrinkles of the pole ear during the winding process of the pole sheet, reduce the debris generated during the flattening process of the pole ear, and achieve the effect of facilitating the infiltration of the electrolyte. At the same time, through experimental tests, controlling the W5 / W4 ratio within the range of 20%-30% can also improve its self-discharge rate K. The smaller the K value is, the better the battery performance is reflected to a certain extent. The applicant tested the K value under different W5 / W4 ratios, as shown in Table 3 below.

[0173] Table 3

[0174] Number of cells tested Tab W5 / W4 ratio K value mean 20 10％ 0.042 20 20％ 0.038 20 28％ 0.032 20 30％ 0.036 20 40％ 0.041 20 50％ 0.052 20 60％ 0.067

[0175] It can be seen from the table that controlling the W5 / W4 ratio within the range of 20%-30% can greatly improve the self-discharge rate K, and can effectively control the mean value of the self-discharge rate K to be within 0.040, which has relatively better battery performance.

[0176] In some embodiments, the width W4 of the edge of the pole ear toward the material area is 0.5-3.0 mm, preferably W4 is 1.0-2.5 mm, and further preferably W4 is 1.5-2.2 mm. The applicant has found through testing that the width W4 of the edge of the pole ear toward the material area of ​​1.5-2.2 mm can balance the generation of debris during flattening, reduce wrinkles and self-discharge rate. Specifically, the width W4 of the edge of the pole ear toward the material area can be 1.7 mm, 1.8 mm, 1.9 mm, and is not specifically limited.

[0177] In some embodiments, the distance W5 between the edges 14431 of two adjacent tabs 1443 facing the material area is 0.2-0.6 mm. When flattening, the tabs 1443 are bent in sequence from the beginning c of the winding to the end d, so that the latter bent tab overlaps the previous tab. Fig.19As shown, an overlapping area f and a gap area g will be formed between two adjacent pole ears 1443. If the gap area g is too large, the internal resistance of the pole ear will increase and the current overcurrent effect will be reduced. If the gap area g is reduced as much as possible, the distance W5 between the edges of the two adjacent pole ears facing the material area must be as small as possible, but this will increase the difficulty of die cutting and cause the yield rate to decrease. After testing, the distance W5 between the edges of the two adjacent pole ears facing the material area is controlled to 0.2-0.6mm, which can balance the difficulty of die cutting and the overcurrent effect. In some embodiments, W5 is preferably 0.3-0.5mm. In some embodiments, the distance W5 between the edges of the two adjacent pole ears facing the material area is further preferably 0.3mm, 0.4mm, 0.5mm, etc.

[0178] In some embodiments, the current collector substrate 144 further includes a connection region 1444, which is located between a plurality of tabs 1443 and a material region 1441, that is, on the current collector substrate 144, there are a plurality of tabs 1443, a connection region 1444, and a material region 1441 arranged in sequence along the width direction of the current collector substrate 144. Fig.17 In the figure, the area between the dotted lines ab is the connection area 1444, the area above the dotted line a is a plurality of pole ears 1443, and the area below the dotted line is the material area 1441. In the flattening process, if the pole ear 1443 is directly connected to the material area 1441, when the pole ear 1443 is subjected to the flattening force, the material area 1441 connected to the pole ear 1443 is easily subjected to force, so that the wound material area 1441 may protrude outward, which will affect the subsequent assembly of the winding core 140 into the battery housing. Therefore, the purpose of setting the connection area 1444 is to achieve a certain buffer, and the connection area 1444 bends inward when flattening, thereby avoiding the problem of the material area 1441 protruding outward.

[0179] In some embodiments, the distance between the edge 14431 where the pole ear 1443 is connected to the connection area 1444 and the material area 1441 is H7, the shape of the pole ear 1443 is a parallelogram, the length of the edge 14433 of the pole ear 1443 away from the material area 1441 is H6, and the range of H7 / H6 is 10%-20%. The H7 area is the pre-bending area before the battery is wound. If the bending is done at the connection between the pole ear and the material area, the material area will be damaged and the coating will be affected, so a certain spacing is given to facilitate bending; if the H7 / H6 ratio is too small, for example, if the H7 spacing is too small, the pole sheet material area will be bent, affecting the battery coating effect and easily causing a short circuit. For example, if the H6 spacing is too large, the pole ear is too high, and the cutting and stacking process causes the pole ear to be interpolated. The pole ear interpolation refers to the overlapping phenomenon after the adjacent pole ears are flattened, which affects the battery performance. If the ratio of H7 / H6 is too large, for example, if the H7 spacing is too high, the effective height of the tab is short, affecting the welding and current flow effect; for example, if the H6 spacing is too small, the H6 height is too low, and the corresponding number of stacked layers is low, affecting the welding performance. In some embodiments, H7 / H6 is 13%, 15%, 17%, 19%, etc., without specific limitation.

[0180] like Fig.16 and Fig.17 As shown, 14433 and 14431 are two parallel sides of the parallelogram, and 14432 is the side connecting 14433 and 14431. It is well known to those skilled in the art that the dotted line 14431 is for illustration and there is no such dotted line in the actual product. As mentioned above, the pole ear 1443 is die-cut on the current collector substrate 144, wherein the pole ear 1443 includes an edge 14431 connected to the current collector substrate, two edges 14432 connected to the beginning and the end of the edge respectively, the two edges are generated by die-cutting part of the pole sheet material of the current collector substrate, and an edge 14433 opposite to the edge 14431 connected to the current collector substrate 144, wherein the four edges are connected to form a parallelogram.

[0181] In some embodiments, the distance H7 between the edge 14431 where the tab 1443 and the connection area 1444 are connected and the material area 1441 is 0.4-0.6 mm. If the distance H7 between the edge 14431 where the tab 1443 and the connection area are connected and the material area is too high, the height of the tab 1443 will be reduced, thereby affecting the subsequent welding effect and the flow effect. During the battery manufacturing process, the height and diameter of the battery are generally fixed according to industry standards, so the length, width and thickness of the current collector substrate 144 are basically fixed. A connection area 1443 is reserved for bending in the ear area 1442 of the current collector substrate 144. At this time, in order to maximize the capacity of the battery, the width of the material area 1441 remains unchanged, and only the width of the ear 1443 can be reduced. If the width of the connection area 1444 is too wide, the width of the ear 1443 will be too narrow. If the ear 1443 is too narrow, it will affect the welding effect. After flattening, the outer ear 1443 will overlap on the inner ear 1443. If the ear 1443 is too narrow, some areas will appear very thin due to the small number of overlapping ears 1443, which is easy to cause penetration in subsequent welding; secondly, it will affect the overcurrent effect of the current. If the ear 1443 is too short, the entire ear area will become thinner, the internal resistance will increase, and the overcurrent current will be reduced. After testing, the distance H7 between the edge where the tab is connected to the connection area and the material area is 0.4-0.6mm, which can easily balance the problem of the material area protruding outward and the welding effect and current overcurrent effect.

[0182] In some embodiments, the angle β between the edge 14432 of the electrode tab connected to the edge facing the material region and the width direction of the current collector substrate 144 is 14-18°.

[0183] The purpose of beveling is to make the tabs lean to one side after flattening. Although there is a gap between the tabs after cutting, the tabs can still fit as closely as possible after flattening, increasing the density of the tabs after flattening. After flattening, two adjacent tabs 1443 will form an overlapping area f and a gap area g. If the angle is too small, such as a rectangular structure, there will be too large a gap area g between the tabs, which will make the overall density of the tabs too small, and it is easy to weld through in the subsequent process, thus affecting the welding performance. In addition, if the angle is too small, due to the excessive stress of the tabs, it is still easy to generate particle debris in the subsequent flattening process, which will cause a short circuit risk and affect the safety performance of the battery. If the angle is too large, it will also cause the area of ​​the tab gap area g to be too large, thereby reducing the overall density of the tabs, thereby affecting the subsequent welding performance. In addition, if the angle is too large, the stress between the tabs is too small, which will easily cause the wound pole sheet to have wrinkles and ruptures, ultimately affecting the overall safety performance and cycle performance of the battery. Therefore, the present invention sets the angle β in the range of 14-18°, which can ensure that the tab has sufficient electrolyte infiltration effect while maintaining a suitable density after the tab is flattened, and can take into account the welding performance of the tab, thereby having sufficient safety performance and cycle performance. The applicant tested the area values ​​of the gap region g at different angles β, as shown in Table 4 below. In some embodiments, the angle β is set to 14°, 16°, 18°, etc.

[0184] Table 4

[0185]

[0186] In some embodiments, Fig.15 As shown, the core 140 is formed by stacking the first separator 143a, the positive electrode sheet 144a, the second separator 143b and the negative electrode sheet 144b in sequence and then winding them. The starting end of the winding is called the head end c, and the end at the outermost layer after winding is the end d. After the winding is completed, the first separator 143a is located at the innermost side of the core 140.

[0187] like Fig.15 As shown, in some embodiments, the length of the multiple pole tabs 1443 in the pole tab region 1442 along the length direction of the current collector substrate 144 is less than the length L7 of the material region 1441, and one end of the material region 1441 along the length direction of the current collector substrate 144 facing the pole tab region 1442 is not connected to the connection region 1444, and the end not connected to the connection region 1444 is called the first cut-off region 1445, wherein the end not connected to the connection region 1444 can be located at either the head end c or the end end d.

[0188] In some embodiments, the first cut-off area 1445 of the current collector substrate 144 is located at the head end c, that is, the head end c of the current collector substrate 144 is die-cut during die-cutting so that the head end c does not have a tab. If the head end c has a tab, after winding and flattening, the tab at the head end c is likely to cause the winding core hole 145 to be blocked, which is not conducive to the subsequent injection of electrolyte.

[0189] In some embodiments, the length of the first cut-away area 1445 is L8, and L8 / L7 is 5%-15%. If L8 / L7 is too small, the core hole 145 is easily blocked; if L8 / L7 is too large, the diaphragm is easily exposed, and metal debris enters the electrolyte, which is easy to cause a short circuit. Controlling the value of L8 / L7 between 5%-15% can reduce the blockage of the core hole 145 and the probability of a short circuit. In some embodiments, L8 / L7 is 7%, 9%, 11%, 13%, etc., without specific limitation.

[0190] In some embodiments, the length L8 of the first cut-away area 1445 is 105-130 mm. Further, L8 is preferably 144 mm, 115 mm, 120 mm, 125 mm, etc., without limitation.

[0191] In some embodiments, one end of the material area 1441 along the length direction of the current collector substrate 144 that faces the pole ear area 1442 is not connected to the connection area 1444, and the end that is not connected to the connection area 1444 is called the second cut-out area 1446, wherein the second cut-out area 1446 can be located at the head end c or at the end d. In some embodiments, the second cut-out area 1446 is located at the end d. If the end d has a pole ear, the pole ear will protrude outward during the flattening process, affecting the subsequent assembly of the winding core 140 into the shell.

[0192] In some embodiments, the length of the second cut-away area 1446 is L9, and L9 / L7 is 10%-20%. If L9 / L7 is too small, it is easy to cause the core 140 to be flanging, causing the core 140 to protrude from the diaphragm, affecting the shell entry; if L9 / L7 is too long, the diaphragm is easily exposed, and metal debris enters the electrolyte, which is easy to cause a short circuit. Controlling L9 / L7 to 10%-20% not only facilitates the shell entry of the core 140, but also reduces the probability of short circuits. In some embodiments, L9 / L7 is 13%, 15%, 18%, etc., without specific limitation.

[0193] In some embodiments, the length L9 of the second cut-away area 1446 is 175-205 mm. Further, L9 is preferably 185 mm, 195 mm, etc., without specific limitation.

[0194] In some embodiments, one of the two ends of the tab region 1442 has a first cut-out region 1445, and the other end has a second cut-out region 1446. The length of the first cut-out region 1445 along the length direction of the current collector substrate 144 is L8, and the range of L8 / L7 is 5%-15%. The length of the second cut-out region 1446 along the length direction of the current collector substrate 144 is L9, and the range of L9 / L7 is 10%-20%. In some embodiments, the heights of the first cut-out region 1445 and the second cut-out region 1446 along the width direction are flush.

[0195] The negative electrode current collecting disk 150 is described in detail below.

[0196] like Figure 1 and Fig. 20 As 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.

[0197] 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 flatness of the surface 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 fit 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.

[0198] In this embodiment, since the ratio of the diameter D8 of the negative electrode current collecting disk 150 to the diameter D6 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.

[0199] 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.

[0200] 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.

[0201] 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.

[0202] like Fig. 20 and Fig.21 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.

[0203] like Fig.21As shown, in some embodiments, the diameter D9 of the raised platform 1521 is 28%-38% of the diameter D8 of the negative electrode current collecting disk 150, that is, D9 / D8=28%-38%. As mentioned above, the diameter D8 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 fit 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.

[0204] Furthermore, if Fig. 22 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 H8, which is 18%-30% of the thickness T5 of the negative electrode collector 150, that is, H8 / T5=18%-30%. It can be understood that if the raised platform 1521 is set too high, that is, H8 / T5 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, H8 / T5 is too small, then the raised platform 1521 is difficult to process, for example, it is difficult to form the raised platform 1521 by a stamping process.

[0205] 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.

[0206] 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.

[0207] 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.

[0208] 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 disc (130), a winding core (140) and a negative electrode current collecting disc (150), wherein: The winding core (140) has a positive electrode flattening structure (141) and a negative electrode flattening structure (142) that are opposite to each other. The positive electrode flattening structure (141) and the negative electrode flattening structure (142) are both formed by flattening a full-ear cut-and-stacked structure. The positive electrode flattening structure (141) is connected to the cap (120) via the positive electrode current collector (130), and the negative electrode flattening structure (142) is connected to the housing (110) via the negative electrode current collector (150). The outer shell (110) comprises an outer shell bottom (111) and a side wall (112); the top end of the side wall (112) has an opening (114); the side wall (112) is concave inwardly along the circumferential direction at a position close to the opening (114) to form a necking portion (1121); the outer surface of the side wall (112) forms a necking groove (1123) at the necking portion (1121); the winding core (140) is located in an area defined by the necking portion (1121) and the outer shell bottom (111) in the outer shell (110); the height H2 of the necking groove (1123) is 0.1%-1% of the height H1 of the outer shell (110); and the depth H3 of the necking groove (1123) in the radial direction is 5%-10% of the outer diameter D1 of the outer shell (110); The positive 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 electrode flattening structure (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 all the second holes (1316) are The sum of the areas is 0.9-1.5 times the area of ​​the first hole (1315); at least one 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 collecting plate (150) has a first side (151) and a second side (152) opposite to each other, the first side (151) is connected to the negative terminal (142), and a raised platform (1521) with a flat surface is provided at the center of the second side (152), the raised platform (1521) is connected to the inner surface of the shell bottom (111), and the flatness of the surface of the raised platform (1521) is 0.01-0.05 mm.

2. The cylindrical lithium battery according to claim 1, characterized in that: The winding core (140) has a winding core hole (145) extending therethrough, and a diameter D4 of the first hole (1315) is 1.4-1.8 times a diameter D7 of the winding core hole (145); the raised platform (1521) is circular and located at the center of the second side (152), and a diameter D9 of the raised platform (1521) is 28%-38% of a diameter D8 of the negative electrode current collecting disk (150).

3. The cylindrical lithium battery according to claim 1, characterized in that: The diameter D3 of the disk body (131) is 80%-95% of the diameter D6 of the winding core (140); and the diameter D8 of the negative electrode current collecting disk (150) is 90%-98% of the diameter D6 of the winding core (140).

4. The cylindrical lithium battery according to claim 1, characterized in that: The diameter D5 of the second hole (1316) is 50%-70% of the diameter D4 of the first hole (1315); the height difference H8 between the surface of the raised platform (1521) and the surface of the first side (151) is 18%-30% of the thickness T5 of the negative electrode collector (150).

5. The cylindrical lithium battery according to any one of claims 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, a fourth side (1324) away from the disk body and a sixth side (1323) extending along the length direction of the tail connected end to end in sequence, wherein the two ends of the fifth side (1322) are respectively connected to the fourth side (1324) and the sixth side (1323) extending along the length direction of the tail. ) 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 electrode flattening structure (142).

6. The cylindrical lithium battery according to claim 5, characterized in that: The length L4 of the tail body (132) is 85%-95% of the diameter D3 of the disk body (131); the distance L5 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 L4 of the tail body (132).

7. The cylindrical lithium battery according to claim 5, characterized in that: The disc body portion (131) has a center angle A, and 40°≤∠A≤60°, wherein the center angle A has a vertex at the center of the circle corresponding to the arc (1312), and 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); the first width W2 of the tail body portion (132) is W2=D3*sin(∠B / 2), and 20°≤∠B≤40°, wherein ∠B has a vertex at the center of the circle corresponding to the arc (1312), and 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.

8. The cylindrical lithium battery according to claim 6, characterized in that: The second width W3 of the tail body (132) at the fuse slot (1321) is 3 / 8-3 / 4 of the first width W2; the dimension L6 of the fuse slot (1321) along the length direction of the tail body (132) is in the range of 0<L6≤W2.

9. The cylindrical lithium battery according to claim 5, characterized in that: The included angle θ1 between the fifth side (1322) and the first side (1311) is 45-90°, and the included angle θ2 between the sixth side (1323) and the second side (1313) is 45-90°.

10. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that: The neck portion (1121) includes a first wall portion (1121a) and a second wall portion (1121b) extending toward the center of the housing (110), and the neck portion (1121) also includes a connecting portion (1121c) for connecting the first wall portion (1121a) and the second wall portion (1121b), 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), and the first wall portion (1121a) and the second wall portion (1121b) are connected to each other. 1b) are arranged at a certain inclination angle with the shell bottom (111); the cover cap (120) comprises a stacked explosion-proof valve plate (122) and a terminal plate (124); the tail body (132) is connected to the bottom of the terminal plate (124); the explosion-proof valve plate (122) is provided with a first notch (1221a) and a second notch (1221b); the first notch (1221a) is a closed circle connected at the head and tail ends; the second notch (1221b) is a line segment; the first notch (1221a) and the second notch (1221b) intersect.

11. The cylindrical lithium battery according to claim 10, characterized in that: 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 range of α is α<10°; the explosion-proof valve plate (122) is provided with a thinning portion (1222) extending in the radial direction, the first notch (1221a) is arranged within the radial range where the thinning portion (1222) is located, the thickness of the thinning portion (1222) is T3, the depth of the first notch (1221a) is H4, and the range of H4 / T3 is 30%-60%.

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

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

14. The cylindrical lithium battery according to claim 13, characterized in that: The range of T2 is 0.1-0.2mm; the bottom of the first notch (1221a) and the second notch (1221b) is provided with a chamfered portion, and the radius of the chamfered portion is the same, the radius of the chamfered portion is R, and the range of R is 0.05-.15mm.

15. The cylindrical lithium battery according to claim 10, characterized in that: 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 depth H4 of the first notch (1221a) is less than the depth H5 of the second notch (1221b), and the depth of the middle part of the second notch (1221b) is greater than the depth at both ends.

16. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that: The full-ear stacking structure comprises a current collector substrate (144), wherein the current collector substrate (144) is divided into a material area (1441) for coating polar materials and an ear area (1442) along a width direction, wherein both the material area (1441) and the ear area (1442) extend along a length direction of the current collector substrate (144), and the current collector substrate (144) has a plurality of ear areas (1443) spaced apart along a length direction at the ear area (1442), wherein the ear areas (1443) face the material area (1441) and the ear areas (1442). The width of the edge (14431) of the electrode (1441) is W4, the distance between the edges (14431) of two adjacent electrode ears (1443) facing the material area (1441) is W5, the range of W5 / W4 is 20%-30%, and the shape of the electrode ear (1443) is a parallelogram, and the angle β between the edge (14432) connected to the edge (14431) of the electrode ear (1443) facing the material area (1441) and the width direction of the current collector substrate (144) is 14-18°.

17. The cylindrical lithium battery according to claim 16, characterized in that: A connecting area (1444) is also provided between the material area (1441) and the pole lug area (1442); the distance between the edge (14431) where the pole lug (1443) is connected to the connecting area (1444) and the material area (1441) is H7; the length between the edge (14433) of the pole lug (1443) away from the material area (1441) and the material area (1441) is H6; and the range of H7 / H6 is 10%-20%.

18. The cylindrical lithium battery according to claim 17, characterized in that: The range of H7 is 0.4-0.6 mm, and the range of W4 is 1.5-2.2 mm.

19. The cylindrical lithium battery according to claim 16, characterized in that: The length of the multiple pole ears (1443) of the pole ear region (1442) along the length direction of the current collector substrate (144) is less than the length L7 of the material region (1441), and one of the two ends of the pole ear region (1442) has a first cut-off region (1445), and the other end has a second cut-off region (1446). The length of the first cut-off region (1445) along the length direction of the current collector substrate (144) is L8, and the range of L8 / L7 is 5%-15%. The length of the second cut-off region (1446) along the length direction of the current collector substrate (144) is L9, and the range of L9 / L7 is 10%-20%.

20. The cylindrical lithium battery according to claim 19, characterized in that: The range of L8 is 105-130mm, and the range of L9 is 175-205mm.

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