Cylindrical lithium battery

Abstract

The cylindrical lithium battery comprises a shell, a roll core, a cap, a positive current collecting plate and a negative current collecting plate, the positive current collecting plate comprises a first main body part and a connecting part which are connected with each other, and the connecting part is provided with at least one safety section; the connecting part has an overall sectional area S at the position, except the safety section, of the connecting part; at the position of the safety section, the connecting part has a minimum cross section Sn, and the minimum cross section Sn is 45%-65% of the overall sectional area S; the negative collector plate comprises a second main body part, the second main body part is provided with a first end face and a second end face which are deviated from each other, the second main body part is provided with a cylindrical welding table with the diameter d2 on the first end face, the area of the table top of the welding table is smaller than that of the first end face, and the diameter d2 of the welding table is 28%-38% of the diameter d1 of the second main body part. By improving the structures of the positive collector plate and the negative collector plate, an electron circulation path in the battery is optimized, efficient diversion is realized, and meanwhile, the structural stability and the use safety of the cylindrical lithium battery are enhanced.

Description

Technical Field

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

[0002] In related technologies of cylindrical batteries, the winding core of a cylindrical lithium battery with a full tab structure is cylindrical. After the tabs of the positive and negative electrodes are flattened, end faces that are circular and have a flat cross-section are formed at both ends. Therefore, a positive current collector disk and a negative current collector disk can be added to the positive and negative end faces respectively. The full tab structure and the addition of the positive and negative current collector disks enable electrons to be transmitted longitudinally from the current collector to the current collector disk, effectively improving the charge and discharge performance of the cylindrical lithium battery by increasing the current conduction area and shortening the current conduction distance.

[0003] The positive and negative current collector disks need to be welded to the winding core respectively to achieve electrical connection. To increase the welding area between the positive and negative current collector disks and the winding core and thus increase the current conduction area, it can be considered to increase the diameter of the positive and negative current collector disks. However, when the diameter of the negative current collector disk is relatively large, the flatness of its surface will deteriorate. Therefore, it is difficult to ensure good fitting between the negative current collector disk and the metal shell. In the case of poor fitting between the two, risks such as false soldering are likely to occur after welding, further resulting in defects such as open circuit of the lithium battery and inability to work properly.

[0004] Furthermore, while the positive current collector disk should have high-efficiency current guiding performance, it should also have short-circuit protection performance. Therefore, a fusing area can be set on the positive current collector disk. However, if the size of the fusing area is not designed reasonably, on the one hand, it will reduce the mechanical strength of the connection part of the current collector disk, increasing the risk of breakage of the connection part during the production process; on the other hand, there may also be adverse effects such as uncontrollable fusing current and uncontrollable fusing position in the fusing area, which is not conducive to the rapid passage of electrons, increasing the internal resistance of the battery and affecting the normal use of the battery.

[0005] Therefore, for cylindrical lithium batteries, how to ensure efficient current conduction through reasonable structural design of the positive and negative current collector disks, and how to ensure the reliability and controllability of the short-circuit protection performance of the positive current collector disk; are problems that need to be solved urgently at present. Summary of the Utility Model

[0006] To solve the above problems and improve the high-efficiency current conduction performance of the negative current collector disk and balance the short-circuit protection performance and mechanical strength of the positive current collector disk, this application provides a cylindrical lithium battery, including a shell, a winding core, a cap, a positive current collector disk electrically connecting the winding core and the cap, and a negative current collector disk electrically connecting the winding core and the shell, wherein,

[0007] The positive current collector plate includes a first main body portion and a connecting portion connected to each other. The positive current collector plate is electrically connected with the first main body portion attached to the positive end face of the core, and is also electrically connected with the cap by the connecting portion. An insurance section is provided on the connecting portion. The position of the connecting portion other than the insurance section has an overall cross-sectional area S, while the insurance section has a minimum cross-section Sn, and the minimum cross-section Sn is 45%-65% of the overall cross-sectional area S.

[0008] The negative current collector plate includes a second main body portion with a diameter of d1. The second main body portion has a predetermined thickness T and has a first end face and a second end face facing away from each other in the thickness direction. The second end face (513) is attached to the negative end face of the core for electrical connection. A cylindrical welding platform with a diameter of d2 protrudes from the first end face in a direction away from the second end face. The table surface of the welding platform has a predetermined flatness and an area smaller than the first end face. The table surface of the welding platform is attached to the bottom wall of the housing for electrical connection. The diameter d2 of the welding platform is 28%-38% of the diameter d1 of the second main body portion.

[0009] Through the improvement of the structures of the positive and negative current collector plates, not only is the good fitting of the negative current collector plate ensured to guarantee the efficient conduction of current, but also while maintaining the low internal resistance characteristic of the positive current collector plate, the mechanical strength of the connecting portion is enhanced to ensure the smooth conduction of current and the safe and controllable short-circuit protection performance of the insurance section.

[0010] In some alternative embodiments, the distance L2 between the center position of the insurance section and the end of the connecting portion away from the first main body portion is 60%-80% of the total length L1 of the connecting portion.

[0011] The height difference between the table surface of the welding platform and the first end face is H, and the height difference H is 18%-30% of the thickness T of the second main body portion.

[0012] Defining the position of the insurance section on the connecting portion enables the prediction of the fusing position, ensures the current cut-off during the thermal runaway of the battery, improves the battery safety, and the insurance section is set at a reasonable position, enabling the smooth welding of the connecting portion and the battery cap. On the other hand, restricting the height of the welding platform reduces the longitudinal space occupation within the reasonable processing accuracy requirements and reduces the stress load within each component of the battery.

[0013] In some alternative embodiments, a circular liquid injection hole is provided at the center of the first main body portion, and at least one circular auxiliary hole is provided around the periphery of the liquid injection hole. The diameter D2 of the liquid injection hole is 1.4-1.8 times the diameter D0 of the inner hole of the core, and the diameter D3 of the auxiliary hole is 50%-70% of the diameter D2 of the liquid injection hole.

[0014] The welding table is located in the central area of the first end face, and a concave pit is formed at the position corresponding to the welding table on the second end face, and the concave pit is arranged opposite to the liquid injection hole.

[0015] By providing the liquid injection hole and the auxiliary hole, when filling the electrolyte in the housing, it is convenient for the electrolyte to be quickly injected into the housing; a concave pit is formed on the second end face opposite to the liquid injection hole, and the electrolyte is injected into the housing from the liquid injection hole, and is preferentially accumulated in the concave space of the concave pit, and then gradually spreads upward, reducing the bubbles generated by the splashing of the electrolyte during the liquid injection operation, assisting the electrolyte to completely immerse the bottom of the winding core, and ensuring the wetting effect on the winding core; in addition, the welding table is arranged in the central area of the second main body, which is convenient for the forming of the welding table.

[0016] In some alternative embodiments, the area of a single auxiliary hole is 0.3-0.5 times the area of the liquid injection hole, the sum of the areas of all the auxiliary holes is 0.9-1.5 times the area of the liquid injection hole, and the part of the surface of the first main body except the liquid injection hole and the auxiliary holes is in contact with and electrically connected to the positive end face of the winding core;

[0017] A welding area is formed around the concave pit on the second end face, and the surface of the welding area is in contact with and electrically connected to the negative end face of the winding core.

[0018] By further defining the area relationship between the liquid injection hole and the auxiliary hole, it is ensured that both the liquid injection hole and the auxiliary hole can play the corresponding penetration improvement effect, while retaining a larger weldable area; the second main body is in contact with the negative end face of the winding core through the welding area formed by the second end face around the concave pit, which is convenient for welding the negative current collector plate and the winding core.

[0019] In some alternative embodiments, the center distance L3 between the auxiliary hole and the liquid injection hole is 25%-35% of the diameter D1 of the first main body;

[0020] The flatness of the tabletop of the welding table is 0.01 mm - 0.05 mm.

[0021] According to the center distance L3 between the auxiliary hole and the liquid injection hole, the positional relationship between the auxiliary hole and the liquid injection hole can be determined, improving the auxiliary wetting effect of the auxiliary hole and avoiding the auxiliary hole being blocked by the encapsulation; the flatness of the tabletop of the welding table is 0.01 mm - 0.05 mm, which is easy to process and has a good fit with the bottom wall of the housing.

[0022] In some alternative embodiments, at a position on the connecting portion other than the insurance section, the connecting portion has a first width L4, the dimension L5 of the insurance section along the length direction of the connecting portion is 0 < L5 ≤ L4, and the material of the connecting portion is aluminum.

[0023] The material of the second main body is copper material.

[0024] The first width L4 of the connecting part first ensures that the connecting part has sufficient mechanical strength to prevent breakage during the production process, and at the same time is conducive to the rapid passage of electrons, reducing the internal resistance of the battery; the dimension L5 of the fuse section along the length direction of the connecting part not exceeding the first width L4 of the connecting part helps to improve the safety of the battery. The connecting part is made of aluminum material, which has a relatively low melting point and good thermal conductivity, and can be melted at a specific position in a timely and controllable manner when the battery is thermally out of control, ensuring safety and controllability; the second main body is made of copper material to enhance the heat dissipation performance of the battery under safe current and reduce the internal resistance of the battery.

[0025] In some alternative embodiments, the diameter D2 of the liquid injection hole is 25%-35% of the diameter D1 of the first main body; the length L1 of the connecting part is 85%-95% of the diameter D1 of the first main body, and the connecting part has a second width L6 at the position of the fuse section, and the second width L6 is 37.5%-75% of the first width L4;

[0026] The surface of the second main body is plated with a nickel layer, and the thickness of the nickel layer is 0.08μm - 1.5μm.

[0027] By reasonably designing the diameter parameters of the auxiliary holes, the area of the weldable region is retained, and the infiltration effect of the electrolyte is improved; reasonably designing the length of the connecting part and the width of the fuse section helps to balance the production efficiency and safety performance of the battery, as well as balance the mechanical performance of the connecting part and the safety performance of the battery, reducing the risk of breakage at the fuse section and increasing the yield rate; on the other hand, nickel plating is performed on the second main body. By plating a nickel layer on the surface of the second main body, the corrosion resistance of the negative current collector can be effectively improved.

[0028] In some alternative embodiments, the diameter D1 of the first main body is 80%-95% of the diameter D of the core;

[0029] The diameter d1 of the second main body is 90%-98% of the diameter D of the core.

[0030] The diameter D1 of the first main body is 80%-95% of the diameter D of the core, and the diameter d1 of the second main body is 90%-98% of the diameter D of the core. Within this diameter range, a large contact area between the first main body and the core is ensured, the weldable region increases, the adaptation range of the wire bonding length and shape is expanded, which is beneficial to reducing the internal resistance of the battery contact surface.

[0031] In some alternative embodiments, the outer contour of the first main body portion includes a major arc segment and two straight line segments connected to both ends of the major arc segment. The two vertical sides of the connecting portion are correspondingly connected to the free ends of the two straight line segments to enclose the complete outer contour of the positive current collector plate with the first main body portion. Moreover, the two vertical sides respectively form two symmetrically left and right avoiding angles with the straight line segments. The size of the avoiding angle is 45° - 90°. The connecting portion is bent from the connection with the first main body portion towards the direction of the cap to abut against the cap and be electrically connected.

[0032] The welding table is integrally stamped and formed at the center of the second main body portion by the second main body portion.

[0033] The shape of the first main body portion is an axisymmetric figure composed of a major arc segment and straight line segments connected to both ends of the major arc segment. The two vertical sides of the connecting portion are respectively connected to the free ends of the two straight line segments to form avoiding angles. The avoiding angles reserve corresponding deformation spaces for the bending of the connecting portion at the connection with the first main body portion, making it more convenient to perform the bending operation of the connecting portion. The second main body portion forms the welding table by using an integral stamping and forming process, which is easy to process, has low cost, and has high dimensional accuracy and good surface quality.

[0034] In some alternative embodiments, the first main body portion has a central angle B, and 40° ≤ ∠B ≤ 60°; wherein, the central angle B takes the center of the circle corresponding to the major arc segment as the vertex, and the two sides respectively pass through the two endpoints where the two straight line segments connect the connecting portion.

[0035] The first width L4 of the connecting portion = D1 * sin(∠A / 2), and 20° ≤ ∠A ≤ 40°; the ∠A takes the center of the circle corresponding to the major arc segment as the vertex, and the two sides respectively pass through the intersection points of the straight lines where the two vertical sides are located and the entire circle where the major arc segment is located.

[0036] The design of the central angle B ensures that the first main body portion still has a weldable area of more than 75% after the opening. The first width L4 of the connecting portion first ensures that the connecting portion has sufficient mechanical strength to prevent being broken during the production process, is conducive to the rapid passage of electrons, reduces the internal resistance of the battery, and can retain the weldable area on the first main body portion to the greatest extent. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order 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, other drawings can be obtained based on these drawings without creative efforts.

[0038] Figure 1 It is a three - dimensional structural schematic diagram of the exploded state of the cap and the housing of a cylindrical lithium battery according to an embodiment of the present application;

[0039] Figure 2 It is a three - dimensional structural schematic diagram of the exploded state of the positive and negative current collectors, the wound core, and the cell of the housing of a cylindrical lithium battery according to an embodiment of the present application;

[0040] Figure 3 It is a schematic cross - sectional view through the central axis plane after the cylindrical lithium battery is assembled according to an embodiment of the present application;

[0041] Figure 4 It is the front view of the positive current collector of a cylindrical lithium battery according to an embodiment of the present application;

[0042] Figure 5 It is the front view of the positive current collector of a cylindrical lithium battery with corresponding dimensions marked according to an embodiment of the present application;

[0043] Figure 6 It is a schematic cross - sectional view of the positive current collector of a cylindrical lithium battery taken horizontally at the insurance section of the connecting part according to an embodiment of the present application;

[0044] Figure 7 is Figure 3 an enlarged schematic diagram of part C in;

[0045] Figure 8 It is a three - dimensional structural schematic diagram of the negative current collector of a cylindrical lithium battery according to an embodiment of the present application.

[0046] Reference numerals: housing - 1, wound core - 2, cap - 3, positive current collector - 4, negative current collector - 5, first main body part - 41, connecting part - 43, insurance section - 430, second main body part - 51, first end face - 511, second end face - 513, welding table - 52, table top - 521, liquid injection hole - 410, auxiliary hole - 412, inner hole - 21, pit - 54, welding area - 56, straight line segment - 414, superior arc segment - 416, avoidance angle - 419, vertical side - 432. Detailed implementation manners

[0047] The embodiments of the present implementation manner are 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 with reference 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 this embodiment, it should be understood that with regard to the orientation description, such as the orientation or positional relationship indicated by up, down, front, back, left, right, etc., it is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing this embodiment 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 this embodiment.

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

[0050] In the description of this embodiment, 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 this embodiment in combination with the specific content of the technical solution.

[0051] Please refer to Figures 1-3 , Figure 1 , which shows a schematic diagram of the split structure of the cap and the housing of a cylindrical lithium battery according to an embodiment of the present application. Figure 2 , which shows a schematic diagram of the split structure of the housing, the winding core and the positive and negative current collectors of a cylindrical lithium battery according to an embodiment of the present application. Figure 3The figure shows a schematic cross-sectional structure of a cylindrical lithium battery according to an embodiment of the present application. The cylindrical lithium battery includes a housing 1, a wound core 2, and a cap 3. The positive electrode of the wound core 2 is connected to the cap 3 through a positive current collector plate 4, and the negative electrode of the wound core 2 is connected to the housing 1 through a negative current collector plate 5. The positive current collector plate 4 includes a first main body portion 41 and a connecting portion 43 that are connected to each other. The first main body portion 41 is used to connect to the wound core 2, and the connecting portion 43 is used to connect to the cap 3 so as to form a path between the wound core 2 and the battery cap 3. The negative current collector plate 5 includes a second main body portion 51. A welding table 52 is provided on a first end face 511 of the second main body portion 51 facing the bottom wall of the housing 1. A second end face 513 of the second main body portion 51 facing the wound core 2 is attached to the negative end face of the wound core 2, and a table top 521 of the welding table 52 is attached to the bottom wall of the housing 1 so as to form a path between the wound core 2 and the housing 1. In the present application, the connection between the first main body portion 41 and the wound core 2, the connection between the connecting portion 43 and the cap 3, the connection between the welding table 52 and the housing 1, and the connection between the second end face 513 and the wound core 2 can all adopt any connection method well-known to those skilled in the art, such as welding; the connection between the connecting portion 43 and the first main body portion 41 can be any fixed connection method. To ensure the connection firmness and the overall structural strength of the positive current collector plate 4, it is preferably an integral connection.

[0052] Please refer to Figure 2 and Figure 4 , Figure 4 The figure shows a front view of the positive current collector plate 4 according to an embodiment of the present application. To match the circular cross-section of the wound core 2 and facilitate the welding between the first main body portion 41 and the wound core 2, it is preferred that the outer contour of the first main body portion 41 includes a superior arc segment 416 and straight line segments 414 connected to both ends of the superior arc segment 416. Its shape can also be considered as the remaining shape after two angles symmetric about a diameter are cut off from the whole circle (shown by a long dashed - dotted line) where the superior arc segment 416 is located, and can also be considered as a shape similar to a bow. It should be noted that since the first main body portion 41 and the connecting portion 43 are connected, there is no connection relationship between the two straight line segments 414 and there are two free ends.

[0053] Refer to Figure 2 , Figure 3 and Figure 8 , Figure 2 , Figure 3 and Figure 8 The figure shows a structural schematic diagram of the negative current collector plate 5 according to an embodiment of the present application. The negative current collector plate 5 includes a circular second main body portion 51 with a diameter of d1.

[0054] In order to increase the current density of the positive and negative current collector plates and improve the charge and discharge rate of the battery, on the one hand, it can be achieved by increasing the contact area between the positive current collector plate 4 and the negative current collector plate 5 and the winding core 2 respectively. Among them, for the positive current collector plate 4, it is achieved by controlling the shape and diameter of the first main body 41, as well as the areas of the liquid injection hole 410 and the auxiliary hole 412.

[0055] Specifically, the diameter D1 of the first main body 41 is 80%-95% of the diameter D of the winding core 2. The diameter D1 of the first main body 41 refers to the diameter of the entire circle corresponding to the major arc segment 416, and the diameter D of the winding core 2 refers to the diameter of the circular cross-section of the winding core 2. According to actual needs, the size of the diameter D1 of the first main body 41 is, for example, 15-23 mm. The first main body 41 within the preferred diameter range ensures a large contact area between the first main body 41 and the winding core 2, and the weldable area increases.

[0056] For the convenience of processing and improving the yield rate, in a preferred embodiment, the diameter D3 of the auxiliary hole 412 is 50%-70% of the diameter D2 of the liquid injection hole 410. The diameter D3 of the auxiliary hole 412 is, for example, 2-4.8 mm. If the diameter D3 of the auxiliary hole 412 is less than the preferred diameter range, it is difficult to achieve the function of auxiliary infiltration; if the diameter D3 of the auxiliary hole 412 is greater than the preferred diameter range, the weldable area of the first main body 41 decreases. It can be understood that the number of the auxiliary holes 412 can be determined according to the actual welding process. The number of the welding areas is n, and the number of the auxiliary holes 412 is n-1, where n≥2.

[0057] For the negative current collector plate 5, the effective flow area is maximized by designing the diameter of the second main body 51, reasonably designing the diameter of the welding platform 52, and simultaneously restricting the flatness of the surface 521 of the welding platform 52. The diameter d1 of the second main body 51 and the diameter D of the core 2 satisfy d1 / D = 90% - 98%, such that the diameter d1 of the second main body 51 is as close as possible to the diameter D of the core 2. Thus, the welding area between it and the core 2 can be greatly increased, thereby adapting to various welding shapes and sizes, facilitating the design of welding jigs, and reducing manufacturing costs. At the same time, the diameter of the welding platform 52 is d2, satisfying d2 / d1 = 28% - 38%. In actual application, the diameter d1 of the second main body 51 of the 21 series battery can be set to 19 - 21 mm, and at this time, the diameter d2 of the welding platform 52 is set to 5.32 mm - 7.98 mm. It can be understood that if the diameter of the welding platform 52 is too large, the flatness of its surface 521 will deteriorate, and its fitting effect with the bottom wall of the housing 1 will be poor, thus affecting the area of the effective flow surface after the negative current collector plate 5 is welded to the housing 1. On the contrary, if the diameter of the welding platform 52 is too small, the weldable area of the welding platform 52 is small, and it is easy to have a solder joint break during welding, which will increase the process difficulty of subsequent welding and lead to an increase in cost.

[0058] Specifically, in order to ensure a good fitting effect between the welding platform 52 and the surface of the housing 1, in some embodiments, the flatness of the surface of the welding platform 52 is 0.01 mm - 0.05 mm. It can be understood that if the flatness of the welding platform 52 is too large, its fitting effect with the bottom wall of the housing 1 will be poor, thus affecting the welding quality. On the contrary, if the flatness of the welding platform 52 is too small, it is not easy to process and the cost is too high.

[0059] In some embodiments, to enable the electrolyte to smoothly pass through the positive current collector plate 4 to effectively infiltrate the core 2, see Figure 3 , the liquid injection hole 410 is also set as a circular hole to match the shape of the inner hole 21 of the core 2, and the diameter D2 of the liquid injection hole 410 is 1.4 - 1.8 times the diameter D0 of the inner hole 21 of the core 2. Further, the diameter D2 of the liquid injection hole 410 is 25% - 35% of the diameter D1 of the first main body 41. According to actual needs, the size of the diameter D2 of the liquid injection hole 410 is, for example, 4 - 8 mm. The liquid injection hole 410 within this diameter range can achieve a balance between the liquid injection efficiency and the weldable area, while ensuring the safety of welding: if the diameter D2 of the liquid injection hole 410 is too small, it is not conducive to the infiltration of liquid injection, and when using the resistance welding process at the bottom of the battery, the electrode head extending into the inner hole 21 of the core 2 may have an undesired contact with the first main body 41, presenting an interference risk; if the diameter D2 of the liquid injection hole 410 is too large, the weldable area will be correspondingly reduced, restricting the welding process between the first main body 41 and the core 2.

[0060] In addition, the distance L3 between the center of the auxiliary hole 412 and the center of the liquid injection hole 410 is 25%-35% of the diameter D1 of the first main body 41. According to actual needs, L3 is, for example, 4.5-7 mm. By reasonably designing the distance L3 between the auxiliary hole 412 and the liquid injection hole 410, it helps to improve the infiltration effect of the electrolyte while ensuring the area of the weldable region. If L3 is too small, the infiltration effect of the electrolyte cannot be significantly improved; if L3 is too large, the auxiliary hole 412 is too close to the edge of the first main body 41, thus restricting the battery encapsulation. If the encapsulation blocks the auxiliary hole 412, the electrolyte cannot be injected through the auxiliary hole 412. Preferably, the area of a single auxiliary hole 412 is 0.3-0.5 times the area of the liquid injection hole 410, and the sum of the areas of all the auxiliary holes 412 is 0.9-1.5 times the area of the liquid injection hole 410. If the area of the auxiliary hole 412 is too small compared to the area of the liquid injection hole 410, the effect of auxiliary infiltration will not be obvious; if the area of the auxiliary hole 412 is too large, the weldable area of the first main body 41 will be significantly reduced, affecting the connection between the first main body 41 and the winding core 2. It can be understood that according to the above area limitation, the number of auxiliary holes 412 can be calculated to be 2-5.

[0061] On the other hand, referring to Figure 2 , Figure 3 and Figure 8 , the negative current collector plate 5 forms a welding table 52 in the central region of the first end face 511. Thus, after the second main body 51 is assembled into the housing 1, the welding table 52 can be aligned with the central region of the housing 1, facilitating the welding of the housing 1 and the welding table 52 through welding equipment. At the same time, the pit 54 formed corresponding to the welding table 52 on the second end face 513 can also be aligned with the liquid injection hole 410 of the first main body 41. The electrolyte is injected into the housing 1 from the liquid injection hole 410 and preferentially accumulates in the recessed space of the pit 54, and then gradually spreads upward, reducing the bubbles generated by the splashing of the electrolyte during the liquid injection operation, assisting the electrolyte to completely submerge the bottom of the winding core 2, and ensuring the infiltration effect on the winding core 2.

[0062] To ensure that the solid area of the first main body 41 after punching can still account for more than 75% of the total area of the first main body 41 to facilitate welding with the winding core 2, referring to Figure 4 and Figure 5, preferably, the first main body portion 41 has a central angle ∠B, and 40° ≤ ∠B ≤ 60°, more preferably 45° ≤ ∠B ≤ 55°. The central angle ∠B has the center of the circle corresponding to the major arc segment 416 as the vertex, and the two sides respectively pass through the endpoints where the two straight line segments 414 are connected to the connecting portion 43. Preferably, two relief angles 419 are formed at the connection between the first main body portion 41 and the connecting portion 43, reserving sufficient operating space to bend the connecting portion 43, so that the bent connecting portion 43 is closer to the center of the circle of the first main body portion 41, increasing the distance between the connecting portion 43 and the inner wall of the housing 1, and preventing the connecting portion 43 from contacting the inner wall of the housing 1 to cause battery short circuit. Preferably, the size of the relief angle 419 is 45° - 90°; more preferably, the size of the relief angle 419 is 60° - 80°. If the relief angle 419 is too small, the bending of the connecting portion 43 will cause the stress to be too concentrated at the relief angle 419, resulting in deformation or even fracture of the first main body portion 41; if the relief angle 419 is too large, it cannot be ensured that the first main body portion 41 has sufficient weldable area. In addition, the reasonable angle design of the relief angle 419 also helps the electrolyte to penetrate into the inner part of the core 2 through the relief angle 419.

[0063] For the convenience of bending and welding, refer to Figures 1-4 , the connecting portion 43 is usually strip-shaped. Refer to Figure 4 , in some embodiments, the connecting portion 43 has a first width L4 = D1 * sin(∠A2), and 20° ≤ ∠A ≤ 40°, preferably 25° ≤ ∠A ≤ 35°, where ∠A has the center of the circle corresponding to the major arc segment 416 as the vertex, and the two sides respectively pass through the intersection points of the straight lines where the two vertical sides 432 of the connecting portion 43 are located and the entire circle where the major arc segment 416 is located (refer to Figure 5 ). The larger the first width L4 of the connecting portion 43, the smaller the weldable area of the first main body portion 41. The reasonable width design helps to retain the largest weldable area, while ensuring that the connecting portion 43 has sufficient mechanical strength to prevent breakage during the production process. In addition, it is also beneficial for electrons to pass quickly and reduce the internal resistance of the battery.

[0064] In actual assembly, the connecting portion 43 needs to be bent twice to connect with the battery cap 3. The first bending is that the connecting portion 43 is bent in the direction away from the core 2, that is Figure 1 and Figure 2In the state shown, the connecting portion 43 faces upward, and one end away from the first main body portion 41 is exposed from the upper edge of the housing 1; the second bending is that the connecting portion 43 bends away from the housing 1 and then is connected to the cap 3. Sufficient longitudinal space needs to be reserved for the assembly and welding of the connecting portion 43; in some embodiments, the thickness T of the second main body portion 51 of the negative current collector plate 5 should be 0.1 mm - 0.5 mm. If the thickness T is too small, the mechanical strength of the second main body portion 51 is insufficient and it is prone to deformation; on the contrary, it will occupy more longitudinal space and affect the bending design and structural stability of the connecting portion 43. In addition, setting the thickness T of the second main body portion 51 to 0.1 mm - 0.5 mm can also effectively improve the processing manufacturability, for example, it is convenient to perform stamping to form the second main body portion 51 and the welding table 52.

[0065] Furthermore, as Figure 7 shown, in some embodiments, taking the height difference between the surface of the welding table 52 and the surface of the first end face 511 as H, it satisfies: H / T = 18% - 30%. It can be understood that if the welding table 52 is set too high, that is, H / T is too large, during the assembly process, the pole group of the core 2 will squeeze and deform the periphery of the second main body portion 51, and it will also additionally occupy the longitudinal space of the battery; on the contrary, if the welding table 52 is set too low, that is, H / T is too small, it is difficult to process the welding table 52, for example, the welding table 52 cannot be formed by stamping process.

[0066] In order to ensure that the connecting portion 43 has sufficient welding length, in some embodiments, the length L1 of the connecting portion 43 is 85% - 95% of the diameter D1 of the first main body portion 41, and the dimension L5 of the insurance section 430 along the length direction of the connecting portion 43 is 0 < L5 ≤ L4, that is, the length of the insurance section 430 in the vertical direction does not exceed the first width L4 of the connecting portion 43. Preferably, 1 / 4L4 < L5 ≤ 3 / 4L4. The length L1 of the connecting portion 43 is the distance between the end where the connecting portion 43 is connected to the first main body portion 41 and the end of the connecting portion 43 away from the first main body portion 41. According to actual needs, the length L1 of the connecting portion 43 is, for example, 12 - 20 mm. Within the preferred length range of the connecting portion 43, it can not only ensure the smooth welding with the cap 3, but also ensure the safety of the battery. The dimension L5 of the insurance section 430 along the length direction of the connecting portion 43 within a reasonable range helps to improve the safety of the battery. If L5 is too large, it is difficult to determine the fusing position of the connecting portion 43, thereby increasing the safety risk of the battery; on the contrary, if L5 is too small, the fusing sensitivity of the connecting portion 43 increases, and there is a possibility of fusing under the safety current.

[0067] In some embodiments, referring to Figure 5, the distance L2 between the central position of the fuse section 430 and the end of the connecting portion 43 away from the first main body portion 41 is 60%-80% of the length L1 of the connecting portion 43; preferably, the distance L2 between the central position of the fuse section 430 and the end of the connecting portion 43 away from the first main body portion 41 is 68%-78% of the length L1 of the connecting portion 431. According to actual needs, the distance L2 between the central position of the fuse section 430 and the end of the connecting portion 43 away from the first main body portion 41 is, for example, 8-18 mm. The fuse section 430 is arranged at a reasonable position so that the connecting portion 43 can be smoothly welded to the cap 3, and at the same time, current interruption can be achieved when the battery is thermally out of control. If the distance L2 is too small, the fuse section 430 will be too close to the welding position, and the welding of the connecting portion 43 to the cap 3 will be interfered; on the contrary, the fuse section 430 is closer to the first main body portion 41, and the current path at the fuse section 430 is larger. If there is an overcurrent, it cannot be melted in time, increasing the safety risk of the battery.

[0068] In some embodiments, the connecting portion 43 has a second width L6 at the fuse section 430, and the second width L6 is 37.5%-75% of the first width L4. The second width L6 in the present application means that due to the design of the fuse section 430, the width of the connecting portion 43 changes relative to the first width L4 at this position. Based on the definition of the second width L6 in the present application, the first width L4 in the present application further means the width of the connecting portion 43 at positions other than the fuse section 430 on the connecting portion 43. The second width L6 of the connecting portion 43 at the fuse section 430 can balance the mechanical properties of the connecting portion 43 and the safety performance of the battery within a reasonable range. When the second width L6 is too small, the strength of the connecting portion 43 at the fuse section 430 is insufficient, and it is easily broken when bent. In addition, in order to enable the connecting portion 43 to reach the melting point and achieve melting at the fuse section 430 when the battery is thermally out of control, the material of the connecting portion is preferably aluminum.

[0069] Please refer to Figure 6 , Figure 6Fig. 0 shows a schematic cross-sectional view of the positive current collector plate 4 cut across at the fuse section 430. In some embodiments, the minimum cross-sectional area Sn of the connecting portion 43 at the fuse section 430 is 45%-65% of the overall cross-sectional area S of the connecting portion 43. The connecting portion 43 has a consistent overall thickness L7. Specifically, the minimum cross-sectional area Sn of the connecting portion 43 at the fuse section 430 is the cross-sectional area at the narrowest position of the fuse section 430, Sn = L6 * L7; the overall cross-sectional area S of the connecting portion 43 is the cross-sectional area at positions on the connecting portion 43 other than the fuse section 430, S = L4 * L7. Within a reasonable range of the minimum cross-sectional area Sn, the connecting portion 43 can achieve a balance between battery safety and low internal resistance. When the minimum cross-sectional area Sn is too large, the connecting portion 43 cannot quickly fuse during thermal runaway, increasing the safety risk; conversely, when the minimum cross-sectional area Sn is too small, on the one hand, the fusing sensitivity will be too high, and on the other hand, the internal resistance will increase, seriously affecting the normal use of the battery.

[0070] For the purpose of facilitating processing and reducing costs, in some embodiments, the welding table 52 is formed by the second main body portion 51 through a stamping process, that is, the welding table 52 and the second main body portion 51 are integrally formed. Thus, through reasonable stamping die design, the negative current collector plate 5 of this embodiment can be efficiently processed, and the dimensional accuracy of the second main body portion 51 and the welding table 52 is high, and the surface quality is good, which is convenient for welding with the core 2 and the housing 1. Of course, it is not limited to this, and the welding table 52 can also be formed in other ways. For example, the welding table 52 can be a sheet metal member with excellent welding performance and electrical conductivity, and the metal member can be combined with the surface of the first end face 511 of the second main body portion 51 by a pressing method to form the welding table 52.

[0071] As Figure 2 shown, for the purpose of facilitating the welding of the second main body portion 51 and the core 2, in some embodiments, around the concave pit 54, the second end face 513 has an annular welding area 56 (see the annular area shown by the dotted line in Figure 2 ), and the surface of the welding area 56 is adapted to abut against the negative end face of the core 2. For example, the welding area 56 is also set to have a flat surface so that the surfaces of the two can be closely attached to each other to improve the welding quality.

[0072] Furthermore, the shape of the welding table 52 is circular. In this way, the welding table 52 can be concentric with the second main body portion 51, which is convenient for stamping and forming through a stamping die. Of course, the shape of the welding table 52 is not limited to circular. For example, the welding table 52 can also be square, triangular, etc.

[0073] In some embodiments, the material of the second main body portion 51 is copper, and the surface of the second main body portion 51 is plated with a nickel layer. Compared with the negative current collector plate 5 made of copper-nickel alloy, using copper as the base material has the characteristic of extremely low internal resistance. At the same time, by plating a nickel layer on the surface of the second main body portion 51, the corrosion resistance of the negative current collector plate 5 can be effectively improved.

[0074] Furthermore, the thickness of the nickel layer is set to be 0.08 μm - 1.5 μm, and more preferably 0.9 μm - 1.1 μm. It can be understood that if the thickness of the nickel layer is too small, it cannot play the role of anti-oxidation; on the contrary, if the thickness of the nickel layer is too thick, on the one hand, it increases the difficulty of the nickel plating process and the cost, and on the other hand, it will increase the hardness of the second main body portion 51, resulting in a decrease in the plasticity of the second main body portion 51. At the same time, it will also increase the internal resistance and lead to a decrease in battery performance.

[0075] It can be understood that by improving the structures and dimensions of the positive current collector plate 4 and the negative current collector plate 5, the balance problem of the low internal resistance performance, structural strength, and short-circuit protection performance of the connecting portion 43 can be solved. Furthermore, the performance of the first main body portion 41 in assisting the electrolyte to infiltrate the core 2 is improved. Considering the simplicity and yield rate of the bending process of the connecting portion 43, the welding stability of the negative current collector plate 5 is enhanced, and the low internal resistance and corrosion resistance of the negative current collector plate 5 are optimized. Ultimately, the structural stability and use safety of the cylindrical lithium battery are enhanced. And through the structural improvement, the yield rates of the production processes of the positive and negative current collector plates, the welding steps of the positive current collector plate 4 to the core 2 and the cap 3 respectively, the welding steps of the negative current collector plate 5 to the core 2 and the housing 1 respectively, and the electrolyte injection and infiltration steps during the manufacturing process of the cylindrical lithium battery can be correspondingly improved, greatly improving the production efficiency.

[0076] In the description of this specification, reference terms such as "some embodiments" or "an embodiment" or similar descriptions mean that the specific features, structures, materials, or characteristics described in connection with the embodiment are included in at least one embodiment or example. In this specification, the schematic representations 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.

[0077] Although the embodiments of this embodiment 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 embodiment. The scope of this embodiment is defined by the claims and their equivalents.

Claims

1. A cylindrical lithium battery, characterized in that, It includes a housing (1), a bobbin (2), a cap (3), a positive current collector plate (4) connecting the bobbin (2) and the cap (3), and a negative current collector plate (5) connecting the bobbin (2) and the housing (1), wherein, The positive current collector plate (4) includes a first main body portion (41) and a connecting portion (43). The first main body portion (41) is connected to the positive end face of the bobbin (2), and the connecting portion (43) is connected to the cap (3). An insurance section (430) is provided on the connecting portion (43); at a position other than the insurance section (430) on the connecting portion (43), it has an overall cross-sectional area S, while at the insurance section (430), it has a minimum cross-section Sn, and the minimum cross-section Sn is 45%-65% of the overall cross-sectional area S; The negative current collector plate (5) includes a second main body portion (51) with a diameter of d1. The second main body portion (51) has a predetermined thickness T and has a first end face (511) and a second end face (513) facing away from each other in the thickness direction. The second end face (513) is attached to the negative end face of the bobbin (2), and a cylindrical welding platform (52) with a diameter of d2 protrudes from the first end face (511) in a direction away from the second end face (513). The tabletop (521) of the welding platform (52) is attached to the bottom wall of the housing (1). The area of the tabletop (521) of the welding platform (52) is smaller than the first end face (511), and the diameter d2 of the welding platform (52) is 28%-38% of the diameter d1 of the second main body portion (51).

2. The cylindrical lithium battery according to claim 1, wherein, The distance L2 between the central position of the insurance section (430) and the end of the connecting portion (43) away from the first main body portion (41) is 60%-80% of the total length L1 of the connecting portion (43); The height difference between the tabletop (521) of the welding platform (52) and the first end face (511) is H, and the height difference H is 18%-30% of the thickness T of the second main body portion (51).

3. The cylindrical lithium battery according to claim 1, wherein A circular liquid injection hole (410) is provided at the center of the first main body portion (41), and at least one circular auxiliary hole (412) is provided around the periphery of the liquid injection hole (410). The diameter D2 of the liquid injection hole (410) is 1.4-1.8 times the diameter D0 of the inner hole (21) of the bobbin 2, and the diameter D3 of the auxiliary hole (412) is 50%-70% of the diameter D2 of the liquid injection hole (410); The welding platform (52) is located in the central area of the first end face (511), and a concave pit (54) is formed at the position corresponding to the welding platform (52) on the second end face (513). The concave pit (54) is arranged directly opposite to the liquid injection hole (410).

4. The cylindrical lithium battery according to claim 3, wherein The area of a single one of the auxiliary holes (412) is 0.3 - 0.5 times the area of the liquid injection hole (410), and the sum of the areas of all the auxiliary holes (412) is 0.9 - 1.5 times the area of the liquid injection hole (410). The portion of the surface of the first main body (41) excluding the liquid injection hole (410) and the auxiliary holes (412) is connected to the positive end face of the core (2). A welding area (56) is formed on the surface of the second end face (513) around the pit (54), and the surface of the welding area (56) is connected to the negative end face of the core (2).

5. The cylindrical lithium battery according to any one of claims 3-4, characterized in that, The center distance L3 between the auxiliary hole (412) and the liquid injection hole (410) is 25% - 35% of the diameter D1 of the first main body (41). The flatness of the tabletop (521) of the welding table (52) is 0.01 mm - 0.05 mm.

6. The cylindrical lithium battery according to any one of claims 1 to 3, characterized in that, The connection part (43) has a first width L4 at positions other than the insurance section (430). The dimension L5 of the insurance section (430) along the length direction of the connection part (43) satisfies 0 < L5 ≤ L4. The connection part (43) is made of aluminum. The second main body (51) is made of copper.

7. The cylindrical lithium battery according to claim 3, wherein The diameter D2 of the liquid injection hole (410) is 25% - 35% of the diameter D1 of the first main body (41). The length L1 of the connection part (43) is 85% - 95% of the diameter D1 of the first main body (41). The connection part (43) has a first width L4 at positions other than the insurance section (430), and the connection part (43) has a second width L6 at the position of the insurance section (430). The second width L6 is 37.5% - 75% of the first width L4. The surface of the second main body (51) is plated with a nickel layer, and the thickness of the nickel layer is 0.08 μm - 1.5 μm.

8. The cylindrical lithium battery according to any one of claims 1-3, characterized in that, The diameter D1 of the first main body (41) is 80% - 95% of the diameter D of the core (2). The diameter d1 of the second main body (51) is 90% - 98% of the diameter D of the core (2).

9. The cylindrical lithium battery according to claim 1, wherein The outer contour of the first main body (41) includes a major arc section (416) and two straight line sections (414) connected to both ends of the major arc section (416). The two vertical sides (432) of the connection part (43) are correspondingly connected to the free ends of the two straight line sections (414) to enclose the complete outer contour of the positive current collector plate (4) with the first main body (41). And the two vertical sides (432) and the straight line sections (414) respectively form two symmetrically located avoidance angles (419) on the left and right. The size of the avoidance angle (419) is 45° - 90°. The connection part (43) is bent from the connection with the first main body (41) towards the direction of the cap (3) to abut against the cap. The welding table (52) is integrally formed by stamping on the second main body (51) at the center of the second main body (51).

10. The cylindrical lithium battery according to claim 9, characterized in that, The first main body part (41) has a central angle B, and 40° ≤ ∠B ≤ 60°; wherein, the central angle B takes the center of the circle corresponding to the major arc segment (416) as the vertex, and the two sides respectively pass through the two endpoints of the two straight line segments (414) connecting the connecting part (43). The first width L4 of the connecting part (43) = D1 * sin(∠A / 2), and 20° ≤ ∠A ≤ 40°; the ∠A takes the center of the circle corresponding to the major arc segment (416) as the vertex, and the two sides respectively pass through the intersections of the straight lines where the two vertical sides (432) are located and the entire circle where the major arc segment (416) is located.

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