Cylindrical lithium battery

Abstract

The utility model provides a cylindrical lithium battery. The position, close to an opening, of the side wall of a shell in the cylindrical lithium battery is concaved inwards in the circumferential direction to form a necking part, a necking groove is formed in the outer surface, the ratio of the distance L1 from the lowest point of the necking part to the upper surface of the shell bottom to the height H of the shell is 90%-98%, and the ratio of the height H1 of the necking groove to the height H of the shell is 0.1%-1%. An anti-explosion valve plate in the cylindrical lithium battery is provided with a first nick and a second nick which are intersected, the first nick is a closed circle with the head end and the tail end connected, the second nick is in a line segment shape, and a roll core is provided with a positive electrode rubbing structure and a negative electrode rubbing structure which are formed by rubbing all tabs. The cylindrical lithium battery disclosed by the utility model has the characteristic of relatively high utilization rate of the internal space of the shell, so that the energy density of the battery is relatively high, in addition, when the gas pressure in the battery exceeds a preset value, the anti-explosion valve plate can be quickly and effectively opened to release the pressure, and the safety of the battery is relatively high.

Description

Technical Field

[0001] This application relates to the technical field of lithium-ion batteries, and particularly to a cylindrical lithium battery. Background Art

[0002] Cylindrical batteries are usually encapsulated with a cylindrical steel shell. The bare battery core is made by a winding process to form a cylindrical wound core electrode group. The cap is located at the top of the battery and is connected to the positive electrode in the wound core electrode group through a positive current collector plate. In related technologies, a cylindrical lithium battery with a full tab structure includes components such as a metal shell, a wound core electrode group, and a cap.

[0003] In related technologies, before and after the wound core is inserted into the shell, a series of plastic processing is also required for the cylindrical battery shell, including necking, grooving, and sealing, etc., so that after the cylindrical battery shell is finally sealed, a necking part is compressed and formed at the sealing position. However, due to the unreasonable size design of the necking part, and at the same time, the tabs at both ends of the wound core further occupy a certain longitudinal space, resulting in limited energy density of the cylindrical lithium battery itself.

[0004] In addition, an explosion-proof valve sheet is provided in the cap. The explosion-proof valve sheet is usually provided with an explosion-proof notch at the edge position. Its function is to tear when the internal gas pressure of the battery reaches a limited value, so that the battery can relieve pressure, to avoid the battery from deforming and bulging or even catching fire or exploding. However, for cylindrical lithium batteries, the causes and positions of the internal gas generation are relatively complex. Therefore, the internal pressure distribution of the battery usually has no pattern. In some cases, the explosion-proof notch cannot respond and break immediately. Therefore, this kind of explosion-proof sheet structure has certain safety hazards. Summary of the Utility Model

[0005] The embodiments of this application provide a cylindrical lithium battery to at least solve the technical problems of limited energy density and insufficient safety of existing cylindrical lithium batteries.

[0006] The embodiments of the first aspect of this application provide a cylindrical lithium battery, including a shell, a cap, a positive current collector plate, a wound core, and a negative current collector plate, wherein:

[0007] The shell includes a bottom and a side wall. The top end of the side wall has an opening. The side wall is concaved inward along the circumferential direction near the opening to form a necking part. A necking groove is formed on the outer surface of the side wall at the necking part. Taking the distance from the lowest point of the necking part to the upper surface of the bottom as L1, the height of the shell as H, and the height of the necking groove as H1, it satisfies: 90% ≤ L1 / H ≤ 98%, 0.1% ≤ H1 / H ≤ 1%;

[0008] The cap is received by the necking portion and closes the opening. The cap includes an explosion-proof valve sheet, and the explosion-proof valve sheet is provided with a first notch and a second notch. The first notch is a closed circle with its head and tail ends connected, the second notch is in a line shape, and the first notch intersects with the second notch.

[0009] The winding core is located within the housing in the area defined by the necking portion and the bottom of the housing. The winding core has opposite positive electrode flattening structures and negative electrode flattening structures. The positive electrode flattening structures and negative electrode flattening structures are both formed by flattening the full tab. The positive electrode flattening structure is connected to the cap through the positive current collector plate, and the negative electrode flattening structure is connected to the housing through the negative current collector plate.

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

[0011] By reasonably designing the distance from the bottom of the necking portion to the bottom of the housing and the height of the necking groove, the internal space utilization rate of the housing can be effectively improved, thereby improving the energy density of the battery. At the same time, the structural strength of the necking portion and the sealing processability can be ensured. In addition, the positive electrode flattening structure and negative electrode flattening structure formed by the flattening process are stacked densely, without space waste in the longitudinal direction, and the internal space utilization rate of the housing is relatively high, which can further improve the energy density of the battery.

[0012] Furthermore, by providing the first notch and the second notch on the explosion-proof valve sheet, when abnormal conditions such as overheating and short circuit occur inside the battery, resulting in a sharp rise in the internal air pressure, whether the air pressure value in the edge area or the middle area reaches the preset value first, one of the first notch and the second notch breaks first, so that the battery can relieve pressure in time. And because the first notch intersects with the second notch, the first notch or the second notch will drive the other to break during the breaking process, thereby expanding the opening area of the explosion-proof valve sheet and improving the pressure relief effect. Thus, when the gas pressure inside the battery exceeds the preset value, the explosion-proof valve sheet can be quickly and effectively opened to release the pressure, thereby enhancing the safety of the battery.

[0013] In a possible implementation manner, the necking portion includes a first wall portion and a second wall portion extending towards the center of the housing. The necking portion further 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 both the first wall portion and the second wall portion are provided with a certain inclination angle with respect to the bottom of the housing; the explosion-proof valve sheet is provided with a thinning portion extending in the radial direction, and the first notch is provided within the radial range where the thinning portion is located.

[0014] By setting the first wall portion and the second wall portion constituting the necking portion to be inclined toward the bottom of the shell, a certain amount of collapse margin has been reserved in the necking portion. Therefore, it is convenient to design the rolling groove in the previous rolling groove process and facilitate the formation of the required necking portion structure in the sealing process. At the same time, by setting the thinning portion, it can effectively cause the first notch to break when the opening condition is met to relieve the pressure of the battery, and at the same time ensure that the explosion-proof valve piece has sufficient strength and rigidity, which is convenient for processing and assembly.

[0015] In a possible implementation manner, taking the larger of the angle between the first wall portion and the bottom of the shell and the angle between the second wall portion and the bottom of the shell as α, it satisfies: α < 10°; the thickness of the thinning portion is T2, and the depth of the first notch is H3, which satisfies: 30% ≤ H3 / T2 ≤ 60%.

[0016] By reasonably designing the size of the angle α, while reducing the difficulty of rolling groove design, it can also reduce the influence of the necking portion on the lower cavity space and ensure the sealing effect on the cap. At the same time, by reasonably setting the thickness of the thinning portion and the depth of the first notch, it can effectively cause the first notch to break when the opening condition is met to relieve the pressure of the battery, and at the same time ensure that the explosion-proof valve piece has sufficient strength and rigidity, which is convenient for processing and assembly.

[0017] In a possible implementation manner, α satisfies: 1° < α < 5°; the width of the thinning portion is W1, which satisfies: 3 mm ≤ W1 ≤ 8 mm.

[0018] By reasonably designing the size of the angle α, while reducing the difficulty of rolling groove design, it can also reduce the influence of the necking portion on the lower cavity space and ensure the sealing effect on the cap. At the same time, by reasonably designing the width of the thinning portion, it can effectively cause the first notch to break when the opening condition is met to relieve the pressure of the battery, and at the same time ensure that the explosion-proof valve piece has sufficient strength and rigidity, which is convenient for processing and assembly.

[0019] In a possible implementation manner, taking the depth of the necking groove in the radial direction as H2 and the outer diameter of the outer shell as D1, it satisfies: 5% ≤ H2 / D1 ≤ 10%; the diameter D2 of the first notch is equal to the length L2 of the second notch.

[0020] By reasonably designing the depth H2 of the necking groove, while ensuring that the cap can be stably supported by the first wall portion for smooth sealing, it can also improve the utilization rate of the internal space of the outer shell and further improve the energy density of the lithium battery. 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 symmetric parts, which is convenient for processing. And after the explosion-proof valve piece is assembled to the cylindrical lithium battery, the second notch is located in the central region of the cylindrical lithium battery so that the explosion-proof valve piece can be smoothly opened to relieve pressure.

[0021] In a possible implementation, taking the minimum wall thickness of the necking part as T1 and the wall thickness of the side wall as T, it satisfies: T1 / T≥80%; chamfered parts are provided at the bottoms of the first notch and the second notch.

[0022] By reasonably designing the wall thickness of the thinnest part of the necking part, the pressure resistance of the outer shell can be ensured to meet the requirements. At the same time, by providing chamfered parts at the bottoms of the first notch and the second notch, the stress concentration at the bottoms of the first notch and the second notch can be reduced, and the risk of accidental opening of the explosion-proof piece when the pressure value has not reached the preset value can be reduced.

[0023] In a possible implementation, 0.1mm≤T1≤0.2mm; the chamfered parts have the same radius.

[0024] By reasonably designing the wall thickness of the thinnest part of the necking part, the pressure resistance of the outer shell can be ensured to meet the requirements. At the same time, by setting the radii of the rounded corners of the first notch and the second notch to be the same, the design and manufacturing costs can be reduced.

[0025] In a possible implementation, it satisfies: T1 / T≥85%; the radius R of the chamfered part satisfies: 0.05mm≤R≤0.15mm.

[0026] By reasonably designing the wall thickness of the thinnest part of the necking part, the pressure resistance of the outer shell can be ensured to meet the requirements. At the same time, by reasonably setting the radius of the chamfered part, while effectively reducing the stress concentration at the bottoms of the first notch and the second notch, the processing difficulty and manufacturing cost can be reduced.

[0027] In a possible implementation, the necking part is formed by sealing a rolling groove formed in the side wall; the depth H3 of the first notch is less than the depth H4 of the second notch.

[0028] Through the sealing process, plastic deformation can occur at the rolling groove of the side wall to obtain the required necking part. The process is simple and the quality is stable. At the same time, by increasing the depth of the second notch, the influence of the increased thickness of the explosion-proof valve piece in the middle area on the second notch can be reduced to ensure the smooth opening of the explosion-proof valve piece at the second notch.

[0029] In a possible implementation, the depth of the middle part of the second notch is greater than the depths of both ends.

[0030] By setting the depth of the second notch such that the depth of the middle part is greater than the depths of both ends, that is, the depth of the second notch is deeper in the middle and shallower at both ends, the influence of the stepped change in the thickness of the explosion-proof valve piece in the middle area can be reduced to ensure the smooth opening of the explosion-proof valve piece at the second notch. Description of the Drawings

[0031] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required for the description of the embodiments of the present application. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0032] Figure 1 is an exploded view of a cylindrical lithium battery according to an embodiment of the present application;

[0033] Figure 2 is a schematic diagram of the state of the outer shell of a cylindrical lithium battery after sealing according to an embodiment of the present application;

[0034] Figure 3 is Figure 2 a partial schematic diagram at position A in

[0035] Figure 4 is a sectional view of the cap of a cylindrical lithium battery according to an embodiment of the present application;

[0036] Figure 5 is a top view of the explosion-proof valve sheet of a cylindrical lithium battery according to an embodiment of the present application;

[0037] Figure 6 is Figure 5 a sectional view of the explosion-proof valve sheet in

[0038] Figure 7 is Figure 6 a partial schematic diagram at position B in

[0039] Figure 8 is Figure 6 a partial schematic diagram at position C in

[0040] Figure 9 is a schematic diagram of the structure of the wound core welded to the positive current collector plate and the negative current collector plate of a cylindrical lithium battery according to an embodiment of the present application.

[0041] Reference numerals:

[0042] 110 - outer shell, 111 - bottom of the shell, 112 - side wall, 1121 - necking part, 1121a - first wall part, 1121b - second wall part, 1121c - connecting part, 1122 - crimp, 1123 - necking groove, 113 - inner cavity, 1131 - upper cavity, 1132 - lower cavity, 114 - opening;

[0043] 120 - cap, 121 - top cover, 122 - explosion-proof valve sheet, 1221a - first notch, 1221b - second notch, 1222 - thinning part, 1223 - groove, 1224 - welding platform, 123 - insulating plate, 124 - terminal plate, 125 - insulating ring;

[0044] 130 - Positive current collector plate, 131 - Plate body part, 132 - Tail body part;

[0045] 140 - Core, 141 - Positive flattening structure, 142 - Negative flattening structure;

[0046] 150 - Negative current collector plate. Detailed implementation manners

[0047] The embodiments of the present implementation manner will be described in detail below. The examples of the embodiments are shown in the drawings, where the same or similar reference numerals represent the same or similar elements or elements with the same or similar functions from beginning to end. The embodiments described below by referring to the drawings are exemplary and are only used to explain the present implementation manner, and should not be construed as a limitation to the present implementation manner.

[0048] In the description of the present implementation manner, it should be understood that for the orientation description, such as the upper, lower, front, rear, left, right, etc., the orientation or positional relationship indicated is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present implementation manner and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present implementation manner.

[0049] In the description of the present implementation manner, the meaning of "several" is one or more, the meaning of "multiple" is more than two, and understandings such as "greater than", "less than", "exceeding", etc. do not include the present number, and understandings such as "above", "below", "within", etc. include the present number. If there is a description of "first" and "second", it is only for the purpose of distinguishing technical features and should not be construed as indicating or implying relative importance or implicitly indicating the quantity of the indicated technical features or implicitly indicating the sequence relationship of the indicated technical features.

[0050] In the description of the present implementation manner, unless otherwise clearly defined, words such as "set", "installed", "connected", etc. should be understood in a broad sense, and those skilled in the art can reasonably determine the specific meanings of the above words in the present implementation manner in combination with the specific content of the technical solution.

[0051] The cylindrical lithium batteries provided by the embodiments of the present application include various size series, such as the 21 series (cylindrical lithium batteries with an outer diameter of 21 mm), the 46 series (cylindrical lithium batteries with an outer diameter of 46 mm), which are not limited herein. Specifically, as Figure 1As shown in the figure, the cylindrical lithium battery includes a housing 110, a cap 120, a positive current collector plate 130, a wound core 140, and a negative current collector plate 150. Among them, the positive electrode of the wound core 140 is connected to the cap 120 through the positive current collector plate 130, and the negative electrode of the wound core 140 is connected to the housing 110 through the negative current collector plate 150. Thus, the cap 120 serves as the positive electrode of the cylindrical lithium battery, and the housing 110 serves as the negative electrode of the cylindrical lithium battery, which is used for electrical connection with external electrical devices.

[0052] The housing 110 will be introduced in detail below.

[0053] As Figure 1 and Figure 2 shown in the figure, the housing 110 is generally cylindrical in shape and is arranged to be closed on the negative electrode side (the lower part in the figure) and open on the positive electrode side (the upper part in the figure). Specifically, the housing 110 includes a bottom shell 111 and a side wall 112. Among them, the bottom shell 111 is circular, the side wall 112 extends upward along the edge of the bottom shell 111, and the bottom shell 111 and the side wall 112 jointly define an inner cavity 113. The top end of the side wall 112 has an opening 114, and the opening 114 communicates with the inner cavity 113.

[0054] It can be understood that the inner cavity 113 defined by the bottom shell 111 and the side wall 112 is also cylindrical in shape, and is used to accommodate the cap 120 (the top of which is exposed), the positive current collector plate 130, the wound core 140, and the negative current collector plate 150 to be introduced below. And by setting the housing 110 to be open at the top, that is, there is an opening 114 at the top of the housing 110, it is also convenient for the above components to enter the housing 110 through the opening 114.

[0055] It can be understood that the bottom shell 111 is in the shape of a thin circular plate, and the bottom surface of the negative current collector plate 150 is in contact connection with the inner surface of the bottom shell 111. Thus, a conductive connection is formed between the two, thereby conducting the housing 110 and the negative electrode of the wound core 140.

[0056] It can be understood that the housing 110 can be made of a nickel-plated steel shell, which has the advantages of high pressure resistance, etc. Of course, it is not limited to this. For example, it can also be an aluminum shell. The following takes the housing 110 being made of a nickel-plated steel shell as an example for description. It can be formed by stamping a steel strip, and the processing and manufacturing are simple, easy to mass-produce, and can effectively reduce costs.

[0057] As Figure 2 and Figure 3As shown, at a position close to the opening 114, the side wall 112 is recessed inwardly in the circumferential direction to form a necking portion 1121 for sealing the cap 120. The necking portion 1121 divides the inner cavity 113 into an upper cavity 1131 and a lower cavity 1132. It can be formed by a rolling groove and a sealing process. And, in the sealing process, in addition to being recessed to form the necking portion 1121, the side wall 112 also forms a curled edge 1122 at the top. The curled edge 1122, together with the necking portion 1121 and the side wall 112, realizes the sealed connection to the cap 120. Specifically, the top surface of the necking portion 1121 on one side of the upper cavity 1131 is used to receive the cap 120, which is in contact connection with the bottom of the cap 120. The inner wall surface of the part of the side wall 112 between the necking portion 1121 and the curled edge 1122 is in contact connection with the outer peripheral surface of the cap 120. The inner wall surface of the curled edge 1122 is in contact connection with the top surface of the cap 120. Thus, the cap 120 completely closes the opening 114, sealing the negative current collector disk 150, the winding core 140, the positive current collector disk 130, etc. in the lower cavity 1132, thereby forming a sealed electrochemical system within the outer shell 110.

[0058] Specifically, the necking portion 1121 includes a first wall portion 1121a and a second wall portion 1121b that extend toward the center of the inner cavity 113 and are parallel to each other and are in a flat plate shape, and a connecting portion 1121c for connecting the first wall portion 1121a and the second wall portion 1121b, Figure 2 In terms of the middle direction, the first wall portion 1121a is located above the second wall portion 1121b. One end of the first wall portion 1121a and the second wall portion 1121b close to the center of the inner cavity 113 is connected by the connecting portion 1121c. The outer surfaces of the first wall portion 1121a, the second wall portion 1121b, and the connecting portion 1121c together define a necking groove 1123. It can be understood that the inner surface of the first wall portion 1121a, that is, the top surface, is used to receive the cap 120 and is in contact connection with the bottom of the cap 120.

[0059] Although the above describes the connection of the first wall portion 1121a, the second wall portion 1121b, and the connecting portion 1121c to each other, it can be understood that the first wall portion 1121a, the second wall portion 1121b, and the connecting portion 1121c are themselves part of the wall portion of the side wall 112. In the sealing process, the side wall 112 undergoes a plastic deformation of inward concavity at the position corresponding to the necking 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 integral. Of course, in the previous process before the sealing process, a rolling groove can be cut at this position, for example, by the feeding movement of a rolling cutter and the rotational movement of the outer shell 110, so that when sealing, the rolling groove undergoes plastic deformation to form the required necking portion 1121.

[0060] In this embodiment, both the first wall portion 1121a and the second wall portion 1121b are flat plates, and the first wall portion 1121a and the second wall portion 1121b are inclined toward the side of the bottom shell 111 along their concave directions. Specifically, when the first wall portion 1121a and the second wall portion 1121b are parallel to each other, taking the angle between the first wall portion 1121a or the second wall portion 1121b and the bottom shell 111 as α, it satisfies: α < 10°. It can be understood that in this case, since both the first wall portion 1121a and the second wall portion 1121b are flat plates and parallel to each other, that is to say, 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 with respect to the surface of the bottom shell 111, and the inclination angle is not greater than 10°.

[0061] When the first wall portion 1121a and the second wall portion 1121b are not completely parallel to each other, then the relatively larger one of the angles between the first wall portion 1121a or the second wall portion 1121b and the bottom shell 111 is α, which satisfies: α < 10°. It can be understood that in this case, since the first wall portion 1121a and the second wall portion 1121b are not in a completely parallel state, at this time, both the angle between the first wall portion 1121a and the bottom shell 111 and the angle α between the second wall portion 1121b and the bottom shell 111 are less than 10°.

[0062] Thus, first of all, by arranging the first wall portion 1121a and the second wall portion 1121b that constitute the necking portion 1121 to be inclined toward the bottom shell 111, a certain amount of collapse margin has been reserved in the necking portion 1121. Therefore, it is convenient to design the rolling groove in the previous rolling groove process and facilitate the formation of the required necking structure in the sealing process. Secondly, the inclination angles of the first wall portion 1121a and the second wall portion 1121b do not exceed 10°, and the height of the necking portion 1121 invading into the lower cavity 1132 is small, ensuring the effective space of the lower cavity 1132, and also being able to avoid damaging the wound core electrode group. Moreover, since the inclination angles of the first wall portion 1121a and the second wall portion 1121b do not exceed 10°, the top surface of the necking portion 1121 located in the inner cavity 113, that is, the top surface of the first wall portion 1121a, is basically horizontal, its contact area with the bottom surface of the cap 120 is large, and there is sufficient compression amount between the two, with good sealing effect, which can improve the safety of the lithium battery.

[0063] Furthermore, in some embodiments, the included angle α satisfies: 1° < α < 5°. It can be understood that the included angle α affects the design difficulty of the rolling groove, the utilization rate of the internal space of the housing 110, and the sealing effect on the cap 120. If α is too large, although the design difficulty of the rolling groove is small, the utilization rate of the internal space of the housing 110 will decrease, and the sealing effect on the cap 120 will deteriorate; conversely, if α is too small, it is difficult to design the rolling groove, and the forming difficulty of the necking portion 1121 is large. By reasonably designing the size of the included angle α, while reducing the design difficulty of the rolling groove, it is also possible to reduce the influence of the necking portion 1121 on the space of the lower cavity 1132 and ensure the sealing effect on the cap 120.

[0064] In some embodiments, the distance from the lowest point of the necking portion 1121 located in the inner cavity 113 to the upper surface of the housing bottom 111 is L1, and the height of the housing 110 is H, satisfying: 90% ≤ L1 / H ≤ 98%. It can be understood that if the distance L1 from the lowest point of the necking portion 1121 to the upper surface of the housing 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 from the lowest point of the necking portion 1121 to the upper surface of the housing 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 housing 110 will be wasted, resulting in a smaller energy density of the battery. By reasonably designing the distance L1 from the lowest point of the necking portion 1121 located in the inner cavity 113 to the upper surface of the housing bottom 111, while ensuring the sealing effect at the sealing position, it is also possible to improve the utilization rate of the internal space of the housing 110 and the energy density of the battery.

[0065] Furthermore, in some embodiments, the height of the necking groove 1123 is H1, and the height of the housing 110 is H, where 0.1% ≤ H1 / H ≤ 1%. It can be understood that if the height H1 of the necking groove 1123 is too large, the height of the housing 110 will be wasted, resulting in a smaller 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 is likely to concentrate, and there is a risk of breakage at the necking portion 1121 at this position, and the sealing process is also 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, it is also possible to effectively improve the utilization rate of the internal space of the housing 110 and the processability of the sealing process. It can also be understood that as Figure 3 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 the same as this height H1. Further preferably, 0.2% ≤ H1 / H ≤ 0.5%.

[0066] In some embodiments, the depth of the necking groove 1123 in the radial direction is H2, and the outer diameter of the outer shell 110 is D1, where 5% ≤ H2 / D1 ≤ 10%. It can be understood that if the depth H2 of the necking groove 1123 is too large, that is, H2 / D1 is too large, the necking part 1121 will excessively invade the inner cavity 113 in the radial direction, resulting in a decrease in the inner diameter of the inner cavity 113 at the necking part 1121, causing waste of space, and also weakening the structural rigidity of the necking part 1121 itself, increasing stress, and there is a risk of cutting, which further leads to the inability to ensure the sealing performance; conversely, 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 part 1121a, and the dimensional chain matching between the two is poor. When sealing, the cap 120 may directly pass through the notch defined by the necking part 1121 and enter the lower cavity 1132. By reasonably designing the depth H2 of the necking groove 1123, while ensuring that the cap 120 can be stably carried by the first wall part 1121a for smooth sealing, the utilization rate of the internal space of the outer shell 110 can be improved, and the energy density of the lithium battery can be further increased.

[0067] It can be understood that in the sealing process, the wall thicknesses of the first wall part 1121a, the second wall part 1121b, and the connecting part 1121c will change as the material undergoes plastic deformation. In order to ensure the pressure resistance of the outer shell 110, in some embodiments, the minimum wall thickness of the necking part 1121 is T1, and the wall thickness of the outer shell 110 is T, where T1 / T ≥ 80%, and more preferably, T1 / T ≥ 85%. It can be understood that the minimum wall thickness T1 may appear on any one of the first wall part 1121a, the second wall part 1121b, and the connecting part 1121c. It can also be understood that if T1 / T is less than 80%, the safety margin of the mechanical strength of the outer shell 110 is insufficient. For example, when the internal air pressure in the outer shell 110 increases, the outer shell 110 may be torn at this place. By reasonably designing the wall thickness T1 at the thinnest part of the necking part 1121, the pressure resistance of the outer shell 110 can be ensured to meet the requirements.

[0068] In some embodiments, in order to ensure the pressure resistance of the outer shell 110, in some embodiments, the minimum wall thickness of the necking part 1121 is T1, where 0.1 mm ≤ T1 ≤ 0.2 mm. It can be understood that setting the minimum wall thickness T1 of the necking part 1121 between 0.1 mm and 0.2 mm enables the necking part 1121 to meet the pressure resistance requirements of the outer shell 110 with a common wall thickness. For example, for the outer shell 110 with a wall thickness of 0.2 mm, the minimum wall thickness T1 of the necking part 1121 can be 0.17 mm.

[0069] The cap 120 is introduced in detail below.

[0070] It can be understood that the cap 120 and the outer shell 110 together serve as a physical barrier to isolate the active material of the cylindrical lithium battery from the outside. Moreover, 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, so as to prevent the battery from deforming and bulging or even catching fire or exploding.

[0071] As Figure 4 shown, the cap 120 includes a top cover 121, an explosion-proof valve plate 122, an insulating plate 123, a terminal plate 124, and an insulating ring 125 located at the outer edge. Among them, the top cover 121, the explosion-proof valve plate 122, and the terminal plate 124 are stacked in sequence from top to bottom and are conductively connected to each other pairwise. After the cap 120 is hermetically connected to the outer shell 110, the top cover 121 is exposed outside the outer shell 110 and serves as the positive terminal for electrically connecting to the positive electrode of an external electrical device. The bottom surface of the terminal plate 124 is connected to the positive current collector plate 130. For example, the positive current collector plate 130 and the terminal plate 124 are welded together. Thus, a conductive connection is formed between the two, thereby conducting the top cover 121 and the positive electrode of the wound core 140. The following details the explosion-proof valve plate 122 that makes up the cap 120.

[0072] Refer to Figures 5 to 6 , the explosion-proof valve plate 122 is a single-component member processed from aluminum, and as a whole, it has a circular thin disk-shaped or thin plate-shaped structure. Along the thickness direction, it has a top surface and a bottom surface facing away from each other. Among them, after being assembled into the cylindrical lithium battery, this bottom surface ( Figure 6 lower middle) faces the side of the wound core 140, and the top surface ( Figure 6 upper middle) faces the side of the top cover 121. Among them, the explosion-proof valve plate 122 is provided with an annular first notch 1221a and a second notch 1221b extending in a line shape on the top surface side. The second notch 1221b is located within the area defined by the first notch 1221a, and both ends of the second notch 1221b are connected to the first notch 1221a. That is, the first notch 1221a presents a closed figure with its head and tail connected. The first notch 1221a is preferably a closed circle, and the second notch 1221b is in a line shape. Among them, 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 plate 122 opens. Moreover, the first one to break among the first notch 1221a and the second notch 1221b can drive the other one to break as well.

[0073] It can be understood that, since the explosion-proof valve piece 122 of the embodiment of the present application is provided with an annular first notch 1221a and a linear second notch 1221b on the explosion-proof valve piece 122, and both ends of the second notch 1221b are connected to the first notch 1221a. Therefore, when abnormal conditions such as overheating and short circuit occur inside the battery, resulting in a sharp rise in the internal air pressure, when the air pressure value in the edge area reaches the preset value first, the first notch 1221a breaks first, and the gas inside the battery rushes out from the gap generated by the break of the first notch 1221a to relieve the pressure in time. Moreover, during the break of the first notch 1221a, it will also drive the second notch 1221b to break, so as to expand the opening area of the explosion-proof valve piece 122 and improve the pressure relief effect. When the air pressure value in the middle area reaches the preset value first, the second notch 1221b breaks first, and the gas inside the battery rushes out from the gap generated by the break of the second notch 1221b to relieve the pressure in time. Moreover, during the break and opening of the second notch 1221b, it will also drive the first notch 1221a to break, so as to expand the opening area of the explosion-proof valve piece 122 and improve the pressure relief effect. Thus, when the gas pressure inside the battery exceeds the preset value, the explosion-proof valve piece 122 can be quickly and effectively opened to release the pressure, thereby enhancing the safety of the battery.

[0074] It should be noted that if the first notch 1221a and the second notch 1221b are not connected, they may only break separately to form gaps for pressure relief, and the pressure relief effect is not good, and the purpose of quickly and effectively relieving the pressure of the battery proposed in the present application cannot be achieved. Therefore, in the embodiment of the present application, the first notch 1221a and the second notch 1221b are set to be connected, that is, they intersect. Therefore, after any one of them breaks, it can extend to the other, causing the other to break as well. Therefore, the opening area of the explosion-proof valve piece 122 can be expanded, so as to quickly relieve the pressure of the battery.

[0075] It can be understood 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 rises, this will significantly increase the processing difficulty of the explosion-proof valve piece 122, resulting in a reduction in the qualified rate and an increase in cost. In the embodiment of the present application, only a straight second notch 1221b is provided inside the explosion-proof valve piece 122, which can effectively achieve quick and effective pressure relief for the battery while being easy to process and having a lower cost, and has better economic benefits.

[0076] It can be understood that the first notch 1221a and the second notch 1221b are structures formed on the explosion-proof valve sheet 122 by removing materials. Therefore, the explosion-proof valve sheet 122 is thinner at the positions where the first notch 1221a and the second notch 1221b are located than at the remaining positions. When the internal pressure of the battery rises 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. When the deformation accumulates to a certain extent, the first notch 1221a and the second notch 1221b will break. The broken material is flipped under the influence of pressure to generate a gap at the break, and the high-pressure gas inside the battery is released through the gap.

[0077] In some embodiments, as Figure 5 shown, the first notch 1221a is circular, and the second notch 1221b is set to pass through the center of the circle of the first notch 1221a. That is, the second notch 1221b exactly serves as the diameter of the circular pattern shown by the first notch 1221a. Thus, taking the diameter of the first notch 1221a as D2 and the length of the second notch 1221b as 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. Moreover, after the explosion-proof valve sheet 122 is assembled to the cylindrical lithium battery, the second notch 1221b is located in the central region of the cylindrical lithium battery, so that the explosion-proof valve sheet 122 can be smoothly opened to relieve pressure. Further, it can be understood that in order to facilitate the construction of the circular first notch 1221a and the linear second notch 1221b, the first notch 1221a can be set to be concentric with the explosion-proof valve sheet 122.

[0078] As Figure 6As shown, in some embodiments, the explosion-proof valve sheet 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. Specifically, the thinning portion 1222 can be realized by opening 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 that the battery can relieve pressure. At the same time, it also ensures that the explosion-proof valve sheet 122 has sufficient strength and rigidity, which is convenient for processing and assembly. Further, the thinning portion 1222 is an annular body with a certain width. Taking the width of the thinning portion 1222 as W1, it 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 that the battery can relieve pressure. At the same time, it also ensures that the explosion-proof valve sheet 122 has sufficient strength and rigidity, which is convenient for processing and assembly. At the same time, in the case of a relatively large internal pressure in the battery, the thinning portion 1222 itself may also break due to the bottom of the groove 1223, which further helps the battery to relieve pressure quickly.

[0079] As 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 relatively large, that is, the first notch 1221a and the second notch 1221b are relatively deep, then 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 relatively large, that is, the first notch 1221a and the second notch 1221b are relatively shallow, then the first notch 1221a and the second notch 1221b are not easy to break, and the opening pressure will be too large, and the internal gas of 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 thinning portion 1222 is between 30% and 60%, that is, it satisfies: 30% ≤ H3 / T2 ≤ 60%. 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 thinning portion 1222 (or the explosion-proof valve sheet 122).

[0080] 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 around the center of the explosion-proof valve plate 122 on the end face of the explosion-proof valve plate 122, while the second notch 1221b is radially constructed through the center of the explosion-proof valve plate 122 on the end face of the explosion-proof valve plate 122. Due to requirements such as strength and installation, the thickness of the explosion-proof valve plate 122 is usually different in different regions along the radial direction. For example, the wall thickness of the inner part of the explosion-proof valve plate 122 adjacent to the thinning part 1222 is thicker than that of the thinning part 1222, and the wall thickness changes in a stepped manner and forms a thicker welding platform 1224 in the middle. The explosion-proof valve plate 122 is welded to the terminal plate 124 through this welding platform 1224. Therefore, in order to ensure that the first notch 1221a and the second notch 1221b located in different regions of the explosion-proof valve plate 122 can both be smoothly opened when the pressure reaches the preset value, in some embodiments, the depth of the first notch 1221a is different from the depth of the second notch 1221b.

[0081] 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 influence of the increased thickness of the explosion-proof valve plate 122 in the middle region on the second notch 1221b can be reduced to ensure that the explosion-proof valve plate 122 is smoothly opened at the second notch 1221b.

[0082] Even further, the depth of the second notch 1221b is set to be deeper in the middle and shallower at both ends. By setting the depth of the second notch 1221b to be deeper in the middle and shallower at both ends, the influence of the stepped change in the thickness of the explosion-proof valve plate 122 along the radial direction can be reduced to ensure that the explosion-proof valve plate 122 is smoothly opened at the second notch 1221b.

[0083] Furthermore, in order to reduce stress concentration and the risk of accidental fracture of the first notch 1221a and the second notch 1221b, continue to refer to Figure 7 and Figure 8 , chamfered portions are provided at the bottoms of both the first notch 1221a and the second notch 1221b. By providing chamfered portions at the bottoms of the first notch 1221a and the second notch 1221b, the stress concentration at the bottoms of the first notch 1221a and the second notch 1221b can be reduced, and the risk of accidental opening of the explosion-proof valve plate 122 when the pressure value does not reach the preset value can be lowered.

[0084] Furthermore, the radii of the chamfered portions provided at the bottoms 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, taking the radius of the chamfered portion at the bottom of the first notch 1221a and the second notch 1221b as R, it satisfies: 0.05 mm ≤ R ≤ 0.15 mm, and more preferably, 0.05 mm ≤ R ≤ 0.1 mm. When the radius of the chamfered portion is within this range, firstly, the stress concentration at the bottoms of the first notch 1221a and the second notch 1221b can be effectively reduced, and secondly, it is also easy to process through a mold, which can reduce costs.

[0085] The positive current collector plate 130 will be introduced in detail below.

[0086] As Figure 1 and Figure 9 shown, the positive current collector plate 130 includes a plate body portion 131 and a tail body portion 132. The tail body portion 132 is connected to the plate body portion 131. Among them, the plate body portion 131 is connected to the positive electrode side of the wound core 140, and the tail body portion 132 is connected to the terminal plate 124 in the aforementioned cap 120. For example, the plate body portion 131 and the wound core 140, as well as the tail body portion 132 and the terminal plate 124, can all be connected by laser welding. Thus, through the positive current collector plate 130, the electrical connection between the cap 120 and the positive electrode of the wound core 140 can be achieved.

[0087] The wound core 140 will be introduced in detail below.

[0088] It can be understood that the wound core 140 is formed by laminating and winding positive electrode sheets, negative electrode sheets, and separator membranes. As Figure 1 and Figure 9 shown, the wound core 140 is generally cylindrical in shape, and in order to smoothly pass through the opening 114 into the inner cavity 113 of the outer shell 110, its diameter is slightly smaller than the inner diameter of the outer shell 110. It can be understood that after the wound core 140 is inserted into the shell, it is located within the region defined by the necking portion 1121 and the bottom 111 of the outer shell 110, that is, in the lower cavity 1132.

[0089] In this embodiment, the wound core 140 is provided with opposite positive electrode flattening structures 141 and negative electrode flattening structures 142. Both the positive electrode flattening structures 141 and the negative electrode flattening structures 142 are formed by flattening the full tab. Among them, the positive electrode flattening structures 141 are connected to the cap 120 through the positive current collector plate 130, and the negative electrode flattening structures 142 are connected to the outer shell 110 through the negative current collector plate 150. It can be understood that the full tabs located on the positive electrode side of the wound core and the full tabs located on the negative electrode side are both foil materials. The positive electrode flattening structures 141 and the negative electrode flattening structures 142 can be formed by a flattening process. For example, the foil material is rotated and pressed as a whole for a certain stroke by a mechanical conical roller.

[0090] It can be understood that, on the one hand, the positive electrode flattening structure 141 and the negative electrode flattening structure 142 formed by the flattening process are stacked densely, without wasting the space in the longitudinal direction. Thus, the utilization rate of the internal space of the housing 110 is relatively high, and the energy density of the battery can be further improved. On the other hand, the cross-sections of the positive electrode flattening structure 141 and the negative electrode flattening structure 142 formed by the flattening process are flat, and they can respectively fit well with the positive electrode current collector plate 130 and the negative electrode current collector plate 150, which is beneficial for laser welding and can effectively reduce process defects such as virtual soldering.

[0091] The negative electrode current collector plate 150 will be introduced in detail below.

[0092] As Figure 1 and Figure 9 shown, the negative electrode current collector plate 150 is generally circular as a whole. In the thickness direction, the negative electrode current collector plate 150 has a first end and a second end facing away from each other. One end is welded and connected to the negative electrode flattening structure 142 in the aforementioned core 140, and the other end is welded and connected to the housing 110. Thus, the welding connection among the core 140, the negative electrode current collector plate 150, and the housing 110 is realized, and a path is formed among the three. That is to say, the negative electrode current collector plate 150 indirectly connects the core 140 and the housing 110.

[0093] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this implementation. In this specification, the schematic expressions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0094] Although the embodiments of this implementation have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and purposes of this implementation. The scope of this implementation is defined by the claims and their equivalents.

Claims

1. A cylindrical lithium battery, characterized in that, It includes a housing (110), a cap (120), a positive current collector plate (130), a wound core (140) and a negative current collector plate (150), where: The housing (110) includes a bottom shell (111) and a side wall (112). The top end of the side wall (112) has an opening (114). A necking portion (1121) is formed by inward concavity along the circumferential direction near the opening (114). A necking groove (1123) is formed on the outer surface of the side wall (112) at the necking portion (1121). Taking the distance from the lowest point of the necking portion (1121) to the upper surface of the bottom shell (111) as L1, the height of the housing (110) as H, and the height of the necking groove (1123) as H1, it satisfies: 90% ≤ L1 / H ≤ 98%, 0.1% ≤ H1 / H ≤ 1%; The cap (120) is received by the necking portion (1121) and closes the opening (114). The cap includes an explosion-proof valve sheet (122). The explosion-proof valve sheet (122) is provided with a first notch (1221a) and a second notch (1221b). The first notch (1221a) is a closed circle with its head and tail connected. The second notch (1221b) is in the shape of a line segment. The first notch (1221a) intersects with the second notch (1221b); The wound core (140) is located within the area defined by the necking portion (1121) and the bottom shell (111) inside the housing (110). The wound core (140) has opposite positive electrode flattening structures (141) and negative electrode flattening structures (142). Both the positive electrode flattening structure (141) and the negative electrode flattening structure (142) are formed by flattening the full pole ears. The positive electrode flattening structure (141) is connected to the cap (120) through the positive current collector plate (130). The negative electrode flattening structure (142) is connected to the housing (110) through the negative current collector plate (150).

2. The cylindrical lithium battery according to claim 1, characterized in that, The necking portion (1121) includes a first wall portion (1121a) and a second wall portion (1121b) extending towards the center of the housing (110). The necking portion (1121) further includes a connecting portion (1121c) for connecting the first wall portion (1121a) and the second wall portion (1121b). The outer surfaces of the first wall portion (1121a), the second wall portion (1121b) and the connecting portion (1121c) jointly define the necking groove (1123). And both the first wall portion (1121a) and the second wall portion (1121b) are set at a certain inclination angle with the bottom shell (111); The explosion-proof valve sheet (122) is provided with a thinning portion (1222) extending in the radial direction. The first notch (1221a) is set within the radial range where the thinning portion (1222) is located.

3. The cylindrical lithium battery according to claim 2, wherein Let the larger of the angles between the first wall portion (1121a) and the bottom of the shell (111), and between the second wall portion (1121b) and the bottom of the shell (111) be α, and it satisfies: α < 10°; the thickness of the thinning portion (1222) is T2, and the depth of the first notch (1221a) is H3, and it satisfies: 30% ≤ H3 / T2 ≤ 60%.

4. The cylindrical lithium battery according to claim 3, wherein, α satisfies: 1° < α < 5°; the width of the thinning portion (1222) is W1, and it satisfies: 3 mm ≤ W1 ≤ 8 mm.

5. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that, Let the depth of the necking groove (1123) in the radial direction be H2, and the outer diameter of the outer shell (110) be D1, and it satisfies: 5% ≤ H2 / D1 ≤ 10%; the diameter D2 of the first notch (1221a) is equal to the length L2 of the second notch (1221b).

6. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that, Let the minimum wall thickness of the necking portion (1121) be T1, and the wall thickness of the side wall (112) be T, and it satisfies: T1 / T ≥ 80%; chamfered portions are provided at the bottoms of the first notch (1221a) and the second notch (1221b).

7. The cylindrical lithium battery according to claim 6, wherein, 0.1 mm ≤ T1 ≤ 0.2 mm; the radii of the chamfered portions are the same.

8. The cylindrical lithium battery according to claim 7, wherein It satisfies: T1 / T ≥ 85%; the radius R of the chamfered portion satisfies: 0.05 mm ≤ R ≤ 0.15 mm.

9. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that, The necking portion (1121) is formed by sealing a rolling groove formed in the side wall (112); the depth H3 of the first notch (1221a) is less than the depth H4 of the second notch (1221b).

10. The cylindrical lithium battery according to claim 9, wherein The depth in the middle of the second notch (1221b) is greater than the depths at both ends.

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