Cylindrical lithium battery

Abstract

The invention provides a cylindrical lithium battery. A roll core of the cylindrical lithium battery is provided with a positive electrode flattening structure and a negative electrode flattening structure which are formed by flattening a full-tab cutting and stacking structure, the full-tab cutting and stacking structure comprises a current collector base material, the current collector base material is divided into a material area and a tab area, the material area is used for coating a polar material, the current collector base material is provided with a plurality of tabs which are arranged at intervals in the length direction, and the tabs are arranged in the material area. The width of the edge, facing the material area, of each tab is W2, the distance between the edges, facing the material area, of every two adjacent tabs is W3, the range of W3 / W2 is 20-30%, and the included angle beta between the edge connected with the edge, facing the material area, of each tab and the width direction of the current collector base material is 14-18 degrees. By optimizing and selecting the die-cutting tab width W2 and the tab distance W3 and selecting the included angle beta between the beveled edge of the tab and the width direction of the current collector base material to be 14-18 degrees, the cycle performance and the safety performance of the battery 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] Cylindrical batteries are usually packaged in a cylindrical steel shell. The bare cell is made by winding the positive and negative electrodes into a cylindrical core. The cap is located on the top of the battery and connected to the positive electrode of the core through the positive electrode collector, while the bottom of the steel shell is connected to the negative electrode of the core.

[0003] In the related art, in order to facilitate the connection with the positive collector plate and the negative collector plate, the corresponding positive terminal structure and negative terminal structure need to be set at both ends of the winding core. At present, due to the advantages of full-pole ears in reducing battery internal resistance, improving battery capacity and rate discharge capability, the positive and negative terminal structures formed by full-pole ears for positive and negative plates have gradually become the mainstream. However, if the full-pole ear design is unreasonable, various process defects and structural defects will occur in the process of forming the positive terminal structure and the negative terminal structure, thereby affecting the cycle performance and safety of the battery. Therefore, the reasonable design and implementation of the positive terminal structure and the negative terminal structure are technical problems that need to be solved urgently. Summary of the invention

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

[0005] The first aspect of the present application provides a cylindrical lithium battery, including a shell, a cap, a positive electrode collector, a winding core and a negative electrode collector, wherein the winding core has a positive electrode flattening structure and a negative electrode flattening structure relative to each other, wherein the positive electrode flattening structure and the negative electrode flattening structure are both formed by flattening a full-ear cut-and-stacked structure, wherein the positive electrode flattening structure is connected to the cap through the positive electrode collector, and the negative electrode flattening structure is connected to the shell through the negative electrode collector;

[0006] Among them, the full-ear stacking structure includes a current collector substrate, which is divided into a material area and a pole ear area for coating polar materials along the width direction, and the material area and the pole ear area both extend along the length direction of the current collector substrate. The current collector substrate has a plurality of pole ears arranged at intervals along the length direction at the pole ear area, and the width of the edge of the pole ear facing the material area is W2, and the distance between the edges of two adjacent pole ears facing the material area is W3, and the range of W3 / W2 is 20%-30%, and the shape of the pole ear is a parallelogram, and the angle β between the edge connected to the edge of the pole ear facing the material area and the width direction of the current collector substrate is 14-18°.

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

[0008] By optimizing the die-cutting tab width W2 and tab spacing W3, and controlling W3 / W2 within the range of 20%-30%, it is helpful to increase the tab tension, so that the tab can withstand the pressure of flattening during 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.

[0009] In addition, by selecting the angle β between the chamfered 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 being flattened, so that the tab has a suitable density after being flattened. While ensuring that the tab has sufficient electrolyte infiltration effect, it can also take into account the welding performance of the tab and reduce the generation of debris particles, thereby improving the safety and cycle performance of the battery.

[0010] In a possible embodiment, the outer shell includes a shell bottom and a side wall, the top end of the side wall has an opening, the side wall is circumferentially concave near the opening to form a necking portion, the outer surface of the side wall forms a necking groove at the necking portion, and the winding core is located in the area defined by the necking portion and the shell bottom in the outer shell; the cover cap is supported by the necking portion and closes the opening, the cover cap includes an explosion-proof valve 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 both ends, and the second notch is a line segment, and the first notch intersects with the second notch.

[0011] By setting a necking neck on the side wall, sealing is facilitated to seal the winding core and the like in the outer shell. At the same time, by setting the first notch and the second notch on the explosion-proof valve sheet, when the internal pressure rises sharply due to abnormal conditions such as overheating and short circuit inside the battery, the pressure value of the edge area or the middle area reaches the preset value first, and one of the first notch and the second notch breaks first, so that the battery can release pressure in time. Moreover, since 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, thereby expanding the opening area of ​​the explosion-proof valve sheet and improving the pressure relief effect. 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.

[0012] In a possible embodiment, the distance L1 between the lowest point of the necking portion and the upper surface of the shell bottom is H, the height of the shell is H, the height of the necking groove is H1, and the range of L1 / H is 90%-98%; a connecting area is also provided between the material area and the lug area, and the distance between the edge of the lug connected to the connecting area and the material area is H6, and the length of the edge of the lug away from the material area is H5, and the range of H6 / H5 is 10%-20%.

[0013] By rationally designing the distance between the bottom of the neck and the bottom of the shell, the internal space utilization of the shell can be effectively improved, thereby improving the energy density of the battery, while also ensuring the structural strength of the neck and the sealing processability. At the same time, by setting the connection area and rationally designing the size of the connection area and the pole ear, the positive electrode flattening structure and the negative electrode flattening structure formed by flattening have good welding performance, current flow performance and reliability.

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

[0015] By properly designing the height of the necking groove, the internal space utilization of the shell can be effectively improved, thereby increasing the energy density of the battery, while also ensuring the structural strength of the necking neck and the sealing processability. At the same time, by properly 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 current flow effect are balanced.

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

[0017] By properly designing the depth of the necking groove, the cap can be stably supported by the first wall portion to facilitate smooth sealing, while the utilization rate of the internal space of the shell can be improved, further improving the energy density of the lithium battery. At the same time, by properly setting the width of the tab, it can be ensured that the tab has sufficient tension, reducing chip drop during the flattening process, and it is not easy to produce scattered and chip drop, and the flattening effect can be improved to ensure welding performance.

[0018] 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 the necking groove, and the first wall portion and the second wall portion are both set at a certain inclination angle to the shell bottom; the explosion-proof valve plate is provided with a thinning portion extending in a radial direction, and the first notch is set within the radial range where the thinning portion is located.

[0019] 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 to form the required necking portion structure in the sealing process. At the same time, by setting the thinning portion, the first notch can be effectively broken when the opening condition is met to release the battery pressure, and at the same time, it is ensured that the explosion-proof valve sheet has sufficient strength and rigidity, which is convenient for processing and assembly.

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

[0021] By 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.

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

[0023] By 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.

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

[0025] By rationally designing the wall thickness at the thinnest 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.

[0026] In a possible implementation manner, the minimum wall thickness of the neck portion is T1, the wall thickness of the side wall is T, and the range of T1 / T is greater than 85%; and chamfered portions are provided at the bottoms of the first notch and the second notch.

[0027] By rationally designing the wall thickness at the thinnest part of the neck portion, it is possible to ensure that the pressure resistance of the shell meets the requirements. At the same time, by providing chamfered portions at the bottom of the first notch and the second notch, it is possible to reduce stress concentration at the bottom of the first notch and the second notch, thereby reducing the risk of accidental opening of the burst disk when the pressure value does not reach the preset value.

[0028] In a possible implementation manner, the range of T1 is 0.1-0.2 mm; the radius of the chamfered portions is the same, the radius of the chamfered portions is R, and the range of R is 0.05-0.15 mm.

[0029] 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.

[0030] In a possible implementation, the neck portion is formed by sealing a rolling groove formed on the side wall; the depth H3 of the first notch is smaller than the depth H4 of the second notch, and the depth of the middle portion of the second notch is greater than the depths at both ends.

[0031] Through the sealing process, the side wall can be plastically deformed at the rolling groove to obtain the required necking part, which is simple in process and stable in quality. At the same time, by increasing the depth of the second notch, the influence of the increase in the thickness of the explosion-proof valve sheet in the middle area on the second notch can be reduced to ensure that the explosion-proof valve sheet opens smoothly at the second notch, and by setting the depth of the second notch to be 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 influence of the step-wise change in the thickness of the explosion-proof valve sheet in the middle area can be reduced to ensure that the explosion-proof valve sheet opens smoothly at the second notch.

[0032] 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 L3 of the material area, and one of the two ends of the pole ear area has a first cut-off area or a second cut-off area, and the length of the first cut-off area along the length direction of the current collector substrate is L4, and the range of L4 / L3 is 5%-15%, and the length of the second cut-off area along the length direction of the current collector substrate is L5, and the range of L5 / L3 is 10%-20%.

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

[0034] 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.

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

[0036] 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

[0037] 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.

[0038] Figure 1 is an exploded schematic diagram of a cylindrical lithium battery according to an embodiment of the present application;

[0039] Figure 2 This 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;

[0040] Figure 3 yes Figure 2 The local schematic diagram of the A in the middle;

[0041] Figure 4is a cross-sectional schematic diagram of a cap in a cylindrical lithium battery in one embodiment of the present application;

[0042] 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;

[0043] Figure 6 yes Figure 5 A schematic cross-sectional view of the middle explosion-proof valve plate;

[0044] Figure 7 yes Figure 6 The local schematic diagram of point B in the middle;

[0045] Figure 8 yes Figure 6 The local schematic diagram of the C in the middle;

[0046] Fig. 9 This is a schematic structural diagram of welding the winding core, the positive electrode current collector, and the negative electrode current collector in a cylindrical lithium battery in one embodiment of the present application;

[0047] Fig.10 This is a schematic diagram of a cylindrical lithium battery in an embodiment of the present application before winding;

[0048] Fig.11 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;

[0049] Fig.12 yes Fig.11 The local schematic diagram of point D in the middle;

[0050] Fig.13 yes Fig.11 Schematic diagram of the flattened structure of the full-ear cut;

[0051] Fig.14 yes Fig.13 Partial schematic diagram at point E in the middle.

[0052] Reference numerals:

[0053] 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;

[0054] 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;

[0055] 130-positive electrode current collecting disk, 131-disk body, 132-tail body;

[0056] 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-connection area, 1445-first cut-off area, 1446-second cut-off area;

[0057] 150-Negative electrode collector plate. DETAILED DESCRIPTION

[0058] 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.

[0059] 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.

[0060] 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.

[0061] 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.

[0062] The cylindrical lithium battery provided in the embodiment of the present application includes various size series, such as 21 series (cylindrical lithium battery with an outer diameter of 21 mm) and 46 series (cylindrical lithium battery with an outer diameter of 46 mm), which are not limited here. Figure 1 As shown, the cylindrical lithium battery includes a shell 110, a cap 120, a positive electrode current collecting disk 130, a core 140, and a negative electrode current collecting disk 150, wherein the positive electrode of the core 140 is connected to the cap 120 through the positive electrode current collecting disk 130, and the negative electrode of the 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.

[0063] The housing 110 is described in detail below.

[0064] 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.

[0065] 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.

[0066] 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 .

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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.

[0071] 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°.

[0072] 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°.

[0073] 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.

[0074] 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.

[0075] In some embodiments, the distance between the lowest point of the neck 1121 in the inner cavity 113 and the upper surface of the shell bottom 111 is L1, and the height of the outer shell 110 is H, which satisfies: 90%≤L1 / H≤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 / H 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 / H is too small, it will affect the height of the lower cavity 1132, and the height of the outer shell 110 will be wasted, resulting in a decrease in the energy density of the battery. By reasonably designing the distance L1 between the lowest point of the neck 1121 in the inner cavity 113 and the upper surface of the shell bottom 111, while ensuring the sealing effect at the seal, the utilization rate of the internal space of the outer shell 110 can also be improved, thereby improving the energy density of the battery.

[0076] Furthermore, in some embodiments, the height of the necking groove 1123 is H1, and the height of the outer shell 110 is H, wherein 0.1%≤H1 / H≤1%. It is understandable that if the height H1 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 H1 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 H1 of the necking groove 1123, while ensuring that the structural strength of the necking portion 1121 meets the requirements, the utilization rate of the internal space of the outer shell 110 and the processability of the sealing process can also be effectively improved. It is also understandable that if Figure 3 As shown, the height H1 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 H1. More preferably, 0.2%≤H1 / H≤0.5%.

[0077] In some embodiments, the depth of the necking groove 1123 in the radial direction is H2, and the outer diameter of the housing 110 is D1, wherein 5%≤H2 / D1≤10%. It is understandable that if the depth H2 of the necking groove 1123 is too large, that is, H2 / D1 is too large, the necking portion 1121 will excessively intrude into the inner cavity 113 in the radial direction, causing the inner diameter of the inner cavity 113 at the necking portion 1121 to become smaller, resulting in space waste, and also causing the structural rigidity of the necking portion 1121 itself to be weakened, stress to be increased, and there is a risk of cutting, which leads to the inability to ensure sealing; on the contrary, if the depth H2 of the necking groove 1123 is too small, that is, H2 / D1 is too small, the cap 120 cannot be stably carried by the first wall portion 1121a, and the size chain matching of the two is poor. When sealing, the cap 120 may directly pass through the notch defined by the necking portion 1121 and enter the lower cavity 1132. By properly designing the depth H2 of the necking groove 1123, while ensuring that the cap 120 can be stably supported by the first wall portion 1121a for smooth sealing, the utilization rate of the internal space of the shell 110 can be improved, further improving the energy density of the lithium battery.

[0078] 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 T1, and the wall thickness of the shell 110 is T, wherein T1 / T≥80%, and more preferably, T1 / T≥85%. It is understood that the minimum wall thickness T1 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 T1 / T 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 T1 at the thinnest part of the neck portion 1121, it can be ensured that the compressive strength of the shell 110 meets the requirements.

[0079] 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 T1, wherein 0.1 mm ≤ T1 ≤ 0.2 mm. It is understandable that the minimum wall thickness T1 of the neck portion 1121 is set between 0.1 mm and 0.2 mm, so that the neck portion 1121 can meet the compressive strength requirements of the housing 110 with a common wall thickness. For example, for the housing 110 with a wall thickness of 0.2 mm, the minimum wall thickness T1 of the neck portion 1121 can be 0.17 mm.

[0080] The cap 120 is described in detail below.

[0081] 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.

[0082] like Figure 4 As shown, the cap 120 includes a top cover 121, an explosion-proof valve sheet 122, an insulating plate 123, a terminal plate 124, and an insulating ring 125 located at the outer edge, wherein the top cover 121, the explosion-proof valve sheet 122, and the terminal plate 124 are stacked in sequence from top to bottom, and are conductively connected to each other. After the cap 120 is sealed and connected to the outer shell 110, the top cover 121 is exposed outside the outer shell 110, and it is used as a positive terminal for electrical connection with the positive electrode of the external electrical equipment. The bottom surface of the terminal plate 124 is connected to the positive electrode collector 130, for example, the positive electrode 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 electrode of the winding core 140. The explosion-proof valve sheet 122 constituting the cap 120 is described in detail below.

[0083] 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 6 The explosion-proof valve sheet 122 is provided with a first notch 1221a in the shape of an annular ring and a second notch 1221b extending in the shape of a line segment on one side of the top surface. 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 the shape of a line segment. 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.

[0084] 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.

[0085] 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 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.

[0086] 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.

[0087] 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.

[0088] 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.

[0089] 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 arranged 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 first notch 1221a to break when the opening condition is met so as to release the pressure of the battery, and at the same time, it also ensures that the explosion-proof valve sheet 122 has sufficient strength and rigidity for easy processing and assembly. Further, the thinning portion 1222 is a torus with a certain width, and the width of the thinning portion 1222 is W1, which satisfies: 3mm≤W1≤8mm. The thickness and width of the thinning portion 1222 are reasonably designed, which can effectively cause the first notch 1221a to break when the opening condition is met so as to release the pressure of the battery, and at the same time, it also ensures that the explosion-proof valve sheet 122 has sufficient strength and rigidity for easy processing and assembly. At the same time, when the internal pressure of the battery is relatively high, the thinned portion 1222 itself may also be broken at the bottom of the groove 1223, thereby helping the battery to release pressure quickly.

[0090] 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 H3, and the second notch 1221b has a depth H4. It can be understood that if H3 and H4 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 H3 and H4 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 H3 of the first notch 1221a to the thickness T2 of the thinned portion 1222 is between 30% and 60%, that is, it satisfies: 30%≤H3 / T2≤60%, and more preferably, 40%≤H3 / T2≤55%. The specific values ​​of H3 and H4 can be determined according to the opening pressure and the thickness of the thinned portion 1222 (or the explosion-proof valve plate 122).

[0091] 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.

[0092] Furthermore, in some embodiments, the depth H3 of the first notch 1221a is less than the depth H4 of the second notch 1221b. By increasing the depth of the second notch 1221b, the 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.

[0093] 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.

[0094] 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.

[0095] 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, which 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.

[0096] The positive electrode current collecting disk 130 is described in detail below.

[0097] like Figure 1 and Fig. 9 As shown, the positive current collector 130 includes a disc body 131 and a tail body 132, and the tail body 132 is connected to the disc body 131, wherein the disc body 131 is connected to the positive side of the winding core 140, and the tail body 132 is connected to the terminal plate 124 in the cap 120. For example, the disc body 131 and the winding core 140, and the tail body 132 and the terminal plate 124 can be connected by laser welding. Thus, the positive electrode conduction between the cap 120 and the winding core 140 can be achieved through the positive current collector 130.

[0098] The winding core 140 is described in detail below.

[0099] like Figure 1 , Fig. 9 and Fig.13 As 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.

[0100] like Fig.10As 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 central hole 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.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] refer to Fig.11 and Fig.12 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 W2, and the distance between the edges 14431 of two adjacent ears 1443 facing the material area 1441 is W3.

[0105] Through experimental tests, setting the pole tab W3 / W2 within 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 W2 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 W3 / W2 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 can also achieve the effect of facilitating the infiltration of the electrolyte. At the same time, through experimental tests, controlling the W3 / W2 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 W3 / W2 ratios, as shown in Table 1 below.

[0106] Table 1

[0107] Number of cells tested Tab W3 / W2 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

[0108] It can be seen from the table that controlling the W3 / W2 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 within 0.040, which has relatively better battery performance.

[0109] In some embodiments, the width W2 of the edge of the pole ear toward the material area is 0.5-3.0 mm, preferably W2 is 1.0-2.5 mm, and further preferably W2 is 1.5-2.2 mm. The applicant has found through testing that the width W2 of the edge of the pole ear toward the material area is 1.5-2.2 mm, which can balance the generation of debris during flattening, reduce wrinkles and self-discharge rate. Specifically, the width W2 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.

[0110] In some embodiments, the distance W3 between the edges 14431 of two adjacent tabs 1443 facing the material area is 0.2-0.6 mm. When flattening, the tabs 1443 are first bent in sequence from the beginning c of the winding to the end d, so that the latter bent tab overlaps the previous tab, such as Fig.14 As 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 be increased and the current overcurrent effect will be reduced. If the gap area g is reduced as much as possible, the distance W3 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 W3 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, W3 is preferably 0.3-0.5mm. In some embodiments, the distance W3 between the edges of the two adjacent pole ears facing the material area is further preferably 0.3mm, 0.4mm, 0.5mm, etc.

[0111] 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.12In 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.

[0112] 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 H6, 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 H5, and the range of H6 / H5 is 10%-20%. The H6 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 H6 / H5 ratio is too small, for example, if the H6 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 H5 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 H6 / H5 is too large, for example, if the H6 spacing is too high, the effective height of the tab is short, affecting the welding and current flow effect; for example, if the H5 spacing is too small, the H5 height is too low, and the corresponding number of stacked layers is low, affecting the welding performance. In some embodiments, H6 / H5 is 13%, 15%, 17%, 19%, etc., without specific limitation.

[0113] like Fig.11 and Fig.12 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.

[0114] In some embodiments, the distance H6 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 H6 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 H6 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.

[0115] 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°.

[0116] 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 2 below. In some embodiments, the angle β is set to 14°, 16°, 18°, etc.

[0117] Table 2

[0118]

[0119] In some embodiments, Fig.10 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.

[0120] like Fig.11 As shown, in some embodiments, the length of multiple pole ears 1443 in the pole ear region 1442 along the length direction of the current collector substrate 144 is less than the length L3 of the material region 1441, and one end of the material region 1441 facing the pole ear region 1442 along the length direction of the current collector substrate 144 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.

[0121] 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 central hole of the winding core 140 to be blocked, which is not conducive to the subsequent injection of electrolyte.

[0122] In some embodiments, the length of the first cut-away area 1445 is L4, and L4 / L3 is 5%-15%. If L4 / L3 is too small, the center hole of the core 140 is easily blocked; if L4 / L3 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 L4 / L3 between 5% and 15% can reduce the blockage of the center hole of the core 140 and reduce the probability of a short circuit. In some embodiments, L4 / L3 is 7%, 9%, 11%, 13%, etc., without specific limitation.

[0123] In some embodiments, the length L4 of the first cut-away area 1445 is 105-130 mm. Further, L4 is preferably 144 mm, 115 mm, 120 mm, 125 mm, etc., without limitation.

[0124] 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.

[0125] In some embodiments, the length of the second cut-away area 1446 is L5, and L5 / L3 is 10%-20%. If L5 / L3 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 insertion; if L5 / L3 is too long, the diaphragm is easily exposed, and metal debris enters the electrolyte, which is easy to cause a short circuit. Controlling L5 / L3 to 10%-20% can facilitate the shell insertion of the core 140 and reduce the probability of short circuit. In some embodiments, L5 / L3 is 13%, 15%, 18%, etc., without specific limitation.

[0126] In some embodiments, the length L5 of the second cut-away area 1446 is 175-205 mm. Further, L5 is preferably 185 mm, 195 mm, etc., without specific limitation.

[0127] 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 L4, and the range of L4 / L3 is 5%-15%. The length of the second cut-out region 1446 along the length direction of the current collector substrate 144 is L5, and the range of L5 / L3 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.

[0128] The negative electrode current collecting disk 150 is described in detail below.

[0129] like Figure 1 and Fig. 9 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 end and a second end that are separated from each other, one end of which is welded to the negative electrode flattening structure 142 in the aforementioned winding core 140, and the other end is welded to the outer shell 110. 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 among the three, that is, the negative electrode current collecting disc 150 indirectly connects the winding core 140 and the outer shell 110.

[0130] 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.

[0131] 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 full-ear stacking structure includes 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 the width direction, wherein the material area (1441) and the ear area (1442) both extend along the length direction of the current collector substrate (144), and the current collector substrate (144) has a plurality of ear tabs (1443) spaced apart along the length direction at the ear area (1442), and the ear tabs (1443) face the material area. The width of the edge (14431) of (1441) is W2, the distance between the edges (14431) of two adjacent pole ears (1443) facing the material area (1441) is W3, the range of W3 / W2 is 20%-30%, and the shape of the pole ear (1443) is a parallelogram, and the angle β between the edge (14432) connected to the edge (14431) of the pole ear (1443) facing the material area (1441) and the width direction of the current collector substrate (144) is 14-18°.

2. The cylindrical lithium battery according to claim 1, characterized in that: The outer shell (110) comprises a shell bottom (111) and a side wall (112); the top end of the side wall (112) has an opening (114); the side wall (112) is concave inwardly along the circumferential direction at a position close to the opening (114) to form a constricted portion (1121); the outer surface of the side wall (112) forms a constricted groove (1123) at the constricted portion (1121); the winding core (140) is located in the outer shell (110) and is connected to the shell bottom (111) by the constricted portion (1121). ) within the area defined by the cover cap (120); the cover cap (120) is received by the neck portion (1121) and closes the opening (114); the cover cap comprises an explosion-proof valve plate (122); 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 both ends; the second notch (1221b) is a line segment; the first notch (1221a) and the second notch (1221b) intersect.

3. The cylindrical lithium battery according to claim 2, 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 H, the height of the shell (110) is H, the height of the necking groove (1123) is H1, and the range of L1 / H is 90%-98%; a connecting area (1444) is also provided between the material area (1441) and the pole lug area (1442), and the distance between the edge (14431) connecting the pole lug (1443) and the connecting area (1444) and the material area (1441) is H6, and the length of the edge (14433) of the pole lug (1443) away from the material area (1441) is H5 from the material area (1441), and the range of H6 / H5 is 10%-20%.

4. The cylindrical lithium battery according to claim 3, characterized in that: The height of the necking groove (1123) is H1, and the range of H1 / H is 0.1%-1%; the range of H6 is 0.4-0.6 mm.

5. The cylindrical lithium battery according to claim 2, characterized in that: The depth of the necking groove (1123) in the radial direction is H2, the outer diameter of the housing (110) is D1, the range of H2 / D1 is 5%-10%, and the range of W2 is 1.5-2.2 mm.

6. The cylindrical lithium battery according to claim 2, characterized in that: The neck portion (1121) comprises a first wall portion (1121a) and a second wall portion (1121b) extending toward the center of the shell (110); the neck portion (1121) further comprises a connecting portion (1121c) for connecting the first wall portion (1121a) and the second wall portion (1121b); the outer surfaces of the first wall portion (1121a), the second wall portion (1121b) and the connecting portion (1121c) jointly define the necking groove (1123); and the first wall portion (1121a) and the second wall portion (1121b) are both arranged at a certain inclination angle with the shell bottom (111); the explosion-proof valve plate (122) is provided with a thinning portion (1222) extending in a radial direction, and the first notch (1221a) is arranged within the radial range where the thinning portion (1222) is located.

7. The cylindrical lithium battery according to claim 6, 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 thickness of the thinned portion (1222) is T2, the depth of the first notch (1221a) is H3, and the range of H3 / T2 is 30%-60%.

8. The cylindrical lithium battery according to claim 7, 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.

9. The cylindrical lithium battery according to claim 2, characterized in that: The minimum wall thickness of the neck portion (1121) is T1, the wall thickness of the side wall (112) is T, and the range of T1 / T is above 80%; the diameter D2 of the first notch (1221a) is equal to the length L2 of the second notch (1221b).

10. The cylindrical lithium battery according to claim 9, characterized in that: The minimum wall thickness of the neck portion (1121) is T1, the wall thickness of the side wall (112) is T, and the range of T1 / T is above 85%; the bottoms of the first notch (1221a) and the second notch (1221b) are provided with chamfered portions.

11. The cylindrical lithium battery according to claim 10, characterized in that: The range of T1 is 0.1-0.2 mm; 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-.15 mm.

12. The cylindrical lithium battery according to claim 2, characterized in that: The neck portion (1121) is formed by sealing a rolling groove formed on the side wall (112); the depth H3 of the first notch (1221a) is smaller than the depth H4 of the second notch (1221b), and the depth of the middle portion of the second notch (1221b) is greater than the depth at both ends.

13. The cylindrical lithium battery according to any one of claims 1 to 12, 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 L3 of the material region (1441), and one of the two ends of the pole ear region (1442) has a first cut-off region (1445) or a second cut-off region (1446), and the length of the first cut-off region (1445) along the length direction of the current collector substrate (144) is L4, and the range of L4 / L3 is 5%-15%, and the length of the second cut-off region (1446) along the length direction of the current collector substrate (144) is L5, and the range of L5 / L3 is 10%-20%.

14. The cylindrical lithium battery according to any one of claims 1 to 12, 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 L3 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 L4, and the range of L4 / L3 is 5%-15%. The length of the second cut-off region (1446) along the length direction of the current collector substrate (144) is L5, and the range of L5 / L3 is 10%-20%.

15. The cylindrical lithium battery according to claim 14, characterized in that: The range of L4 is 105-130 mm, and the range of L5 is 175-205 mm.

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