Cylindrical lithium battery

Abstract

The cylindrical lithium battery comprises a shell, a cap, a positive collector plate, a roll core and a negative collector plate, the cap comprises an anti-explosion valve plate, the anti-explosion valve plate is provided with a nick assembly, the nick assembly comprises a first nick and a second nick, 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, the first nick intersects with the second nick, and the first nick and the second nick intersect with each other. The negative collector plate is provided with a first end face and a second end face which are deviated from each other, the first end face is connected with the roll core, the second end face is convexly provided with a heightening part, the surface area of the heightening part is smaller than that of the second end face, the surface of the heightening part is propped against the inner surface of the shell bottom of the shell, and the diameter of the negative collector plate accounts for 90-98% of the diameter of the roll core. The explosion-proof valve of the cylindrical lithium battery can be timely and effectively opened for pressure relief, the pressure relief direction is controllable, so that the safety is relatively high, and the heightening part of the negative collector plate is well attached to the inner surface of the bottom plate of the shell, so that the electrical connection effect of the cylindrical lithium battery is good.

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] In the related art, a cylindrical lithium battery with a full-tab structure includes components such as a metal shell, a wound core, and a cap. Among them, the wound core is cylindrical. After the tabs of its positive and negative electrodes are flattened, circular end faces with a flat cross-section are formed at both ends. Therefore, a positive current collector disk and a negative current collector disk can also be added to the positive and negative electrodes respectively. The full-tab structure and the addition of the positive current collector disk and the negative current collector disk 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] However, for the negative current collector disk among them, it needs to be welded to the wound core and the metal shell respectively. Therefore, in order to increase the welding area between the negative current collector disk and the metal shell and the wound core, and at the same time increase the current conduction area, the diameter of the negative current collector disk can be considered to be increased. However, when the diameter of the negative current collector disk is large, the flatness of its surface will become poor. Therefore, it is very difficult to ensure good fitting between the negative current collector disk and the metal shell. In the case of poor fitting between the two, there is a risk of poor welding such as virtual welding after welding, which will further cause defects such as the lithium battery being open-circuited and unable to work normally.

[0004] In addition, an explosion-proof sheet is provided in the cap. The explosion-proof valve sheet usually has an explosion-proof groove provided at the edge position. Its function is to tear and release the pressure of the battery when the gas pressure inside the battery reaches a limit value, so as to avoid the battery deforming and bulging or even catching fire or exploding. However, for a cylindrical battery, the reasons and positions for the generation of gas inside it are relatively complex. Therefore, the pressure distribution inside the battery usually has no pattern. For example, in some cases, the gas pressure in the middle area of the battery rises rapidly and reaches the limit value, while in other cases, the gas pressure in the edge area inside the battery rises rapidly and reaches the limit value. Although the existing explosion-proof sheet can meet the requirement of bursting when the gas pressure in the edge area inside the battery rises and reaches the limit value, for the situation where the gas pressure in the middle area inside the battery rises and reaches the limit value, the explosion-proof groove cannot respond and break immediately. As the gas continues to be generated inside the battery and the gas pressure in the edge area also reaches the limit value, the explosion-proof groove will break and the battery will release pressure. Therefore, such an explosion-proof sheet structure has certain potential safety hazards.

[0005] Furthermore, for a cylindrical lithium battery, when the internal pressure of the battery increases, it is desired that the explosion-proof groove of the explosion-proof sheet can be torn in time to relieve pressure on the cap side. However, due to the small wall thickness of the metal shell, during the plastic processing of the metal shell, the bottom of the metal shell may also have insufficient pressure resistance due to material tensile deformation, resulting in the defect of uncontrollable pressure relief direction. Summary of the Invention

[0006] The embodiments of the present application provide a cylindrical lithium battery and a cylindrical lithium battery, so as to at least to some extent solve the technical problems that the explosion-proof valve sheet in the existing cylindrical lithium battery cannot be opened in time, the negative current collector plate is prone to false soldering, and the pressure relief direction is uncontrollable.

[0007] The cylindrical lithium battery provided by the embodiments of the present application includes a housing, a cap, a positive current collector plate, a wound core, and a negative current collector plate. The positive electrode of the wound core is connected to the cap through the positive current collector plate, and the negative electrode of the wound core is connected to the housing through the negative current collector plate, wherein:

[0008] The cap includes an explosion-proof valve sheet, the explosion-proof valve sheet is provided with a scoring assembly, the scoring assembly includes a first score and a second score, the first score is a closed circle with the head and tail connected, the second score is a line segment, and the first score intersects with the second score;

[0009] The negative current collector plate has a first end face and a second end face facing away from each other. The first end face is connected to the wound core, and a raised portion with a flat surface protrudes from the second end face. The surface area of the raised portion is smaller than the surface area of the second end face. The surface of the raised portion abuts against the inner surface of the bottom of the housing. Taking the diameter of the negative current collector plate as D1 and the diameter of the wound core as D2, it satisfies: D1 / D2 = 90% - 98%.

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

[0011] First, the explosion-proof valve sheet is provided with a scoring assembly composed of a first score and a second score. When the internal pressure of the battery rises sharply due to abnormal states such as overheating and short circuit inside the battery, whether the air pressure value in the edge area or the middle area reaches the preset value first, one of the first score and the second score breaks first, so that the battery can relieve pressure in time. And because the first score intersects with the second score, when the first score or the second score breaks, it will also drive the other one to break, so as to expand the opening area of the explosion-proof valve sheet and improve 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 improving the safety of the battery.

[0012] Secondly, since the diameter of the negative current collector plate is set to be adapted to the diameter of the core electrode group, on the one hand, the weldable area between the negative current collector plate and the core can be effectively increased, the welding processability is good, and the current conduction area is large. At the same time, a raised portion with a smaller area and a flat surface is provided on the negative current collector plate to fit well with the inner surface of the bottom plate of the outer shell, and a reliable surface-to-surface contact connection can be formed between the two, and the electrical connection effect is good.

[0013] Furthermore, the negative current collector plate can be pressed by the core onto the inner surface of the bottom plate, so that the negative current collector plate and the bottom plate form a stacked structure at the bottom of the outer shell. The thickness of this stacked structure is thicker than that of the bottom plate. Therefore, the pressure resistance of the bottom of the outer shell can be increased to a certain extent, thereby reducing the risk of insufficient pressure resistance caused by the wall thickness change during the stamping process of the outer shell. In this way, when the pressure inside the battery rises to the limit value, the battery will only release pressure at the cap, so that the pressure release direction of the battery is more controllable.

[0014] In a possible implementation manner, the explosion-proof valve plate is provided with a thinning portion extending in the radial direction, the first notch is disposed within the radial range where the thinning portion is located, the thickness of the thinning portion is T1, and the depth of the first notch is H1, satisfying: 30% ≤ H1 / T1 ≤ 60%. First, by providing the thinning portion, it can effectively cause the first notch to break when the opening condition is met to allow the battery to release pressure, and at the same time ensure that the explosion-proof valve plate has sufficient strength and rigidity, which is convenient for processing and assembly. Second, if H1 / T1 is too small, that is, the first notch is set too shallow, the first notch is not easy to break, resulting in too high an opening pressure and the gas inside the battery cannot be released in time, increasing the safety risk; conversely, if H1 / T1 is too large, that is, the first notch is deeper, the first notch is easy to break and the opening pressure will be too small.

[0015] In a possible implementation manner, taking the height difference between the surface of the raised portion and the surface of the second end face as H2, and the thickness of the negative current collector plate as T2, satisfying: H2 / T2 = 18% - 30%. If the raised portion is set too high, that is, H2 / T2 is too large, during the assembly process, the core will squeeze and deform the periphery of the negative current collector plate, and it will also additionally occupy the longitudinal space of the battery; conversely, if the raised portion is set too low, that is, H2 / T2 is too small, the raised portion is difficult to process.

[0016] In a possible implementation manner, the surface of the negative current collector plate is plated with a nickel layer, and the thickness of the nickel layer is 0.08 - 1.5 μm. By providing a nickel plating layer on the surface of the negative current collector plate, the nickel content in the negative current collector plate can be reduced. While ensuring oxidation resistance, the resistance of the negative current collector plate can be effectively reduced, which is beneficial to improving the battery performance.

[0017] In a possible implementation manner, the elevation part is circular. Taking the diameter of the elevation part as d, it satisfies d / D1 = 28% - 38%; chamfered parts are provided at the bottoms of the first notch and the second notch. By setting the elevation part to be circular, it is convenient to position and weld the metal shell and the negative current collector plate through a welding device. At the same time, if the diameter d of the elevation part is too small, that is, d / D1 is too small, it is easy to have poor welding during welding; conversely, if the diameter d of the elevation part is too large, that is, d / D1 is too large, the surface flatness will become poor, and its fitting effect with the inner surface of the bottom plate will be bad. Moreover, 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 the explosion-proof film accidentally opening when the pressure value does not reach the preset value can be lowered.

[0018] In a possible implementation manner, the flatness of the surface of the elevation part is 0.01 - 0.05 mm; the radii of the chamfered parts are the same. If the flatness of the surface of the elevation part is too large, the fitting effect between the elevation part and the inner surface of the bottom plate will become poor; conversely, if the flatness of the surface of the elevation part is too small, it is not easy to process and the cost is too high. Moreover, 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.

[0019] In a possible implementation manner, the elevation part is located in the central area of the second end face, and the elevation part is integrally formed by stamping the negative current collector plate; the radius of the chamfered part is R, satisfying: 0.05 mm ≤ R ≤ 0.15 mm. By setting the elevation part in the central area of the second end face, it is convenient to weld the housing and the elevation part through a welding device. Moreover, the elevation part is integrally formed by stamping the negative current collector plate, which is easy to process, has a low cost, high dimensional accuracy, and good surface quality. And if the radius of the chamfered part is too small, the stress concentration at the bottoms of the first notch and the second notch cannot be effectively reduced; conversely, if the radius of the chamfered part is too large, the processing difficulty of the mold will be too great, increasing the cost.

[0020] In a possible implementation manner, a recessed part is formed at the position of the first end face corresponding to the elevation part. Around the recessed part, a welding area is formed on the first end face, and the surface of the welding area abuts against the negative extreme face of the core. The elevation part is formed in the central area of the second end face through a stamping process. Therefore, the negative current collector plate is not affected at the position corresponding to the negative extreme face of the core on the first end face, which is convenient for connecting the negative current collector plate and the core on the first end face.

[0021] In a possible implementation, the diameter D3 of the first notch is equal to the length L of the second notch; the material of the negative current collector plate is copper. By setting the second notch to pass through the center of the first notch, the second notch divides the first notch into two symmetrical parts, which is convenient for processing. Moreover, the second notch can be located in the central region of the cylindrical lithium battery, so that the explosion-proof valve plate can be smoothly opened to relieve pressure. And by using copper as the base material, the internal resistance of the negative current collector plate can be made lower to improve the performance of the battery.

[0022] In a possible implementation, the depth H1 of the first notch is less than the depth H3 of the second notch, and the depth in the middle of the second notch is greater than the depths at both ends. By increasing the depth of the second notch, the influence of the increased thickness of the explosion-proof valve plate in the middle region on the second notch can be reduced to ensure that the explosion-proof valve plate is smoothly opened at the second notch. And by setting the depth of the second notch to be greater in the middle than at both ends, that is, the depth of the second notch is deeper in the middle and shallower at both ends, the influence of the stepped change in the thickness of the explosion-proof valve plate in the middle region can be reduced to ensure that the explosion-proof valve plate is smoothly opened at the second notch. Brief Description of the Drawings

[0023] To more clearly illustrate the technical solutions of the embodiments of the present application, the following will briefly introduce the drawings required to be used in 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 also be obtained based on these drawings.

[0024] Figure 1 is an exploded schematic view of a cylindrical lithium battery according to an embodiment of the present application;

[0025] Figure 2 is Figure 1 a cross-sectional schematic view of the cylindrical lithium battery shown in ;

[0026] Figure 3 is Figure 2 a partial schematic view of part A in ;

[0027] Figure 4 is a cross-sectional schematic view of the cap in a cylindrical lithium battery according to an embodiment of the present application;

[0028] Figure 5 is a top view schematic view of the explosion-proof valve plate in a cylindrical lithium battery according to an embodiment of the present application;

[0029] Figure 6 is Figure 5 a cross-sectional schematic view of the explosion-proof valve plate in ;

[0030] Figure 7 isFigure 6 Partial schematic view at position B in [the figure];

[0031] Figure 8 is Figure 6 Partial schematic view at position C in [the figure];

[0032] Figure 9 is a cross-sectional schematic view of the negative current collector plate in a cylindrical lithium battery according to an embodiment of the present application;

[0033] Figure 10 is Figure 9 Partial schematic view at position D in [the figure].

[0034] Reference numerals:

[0035] 110 - Outer shell, 111 - Bottom plate, 1111 - Inner surface of the bottom plate, 1112 - Outer surface of the bottom plate, 112 - Outer peripheral wall, 1121 - Necking part, 113 - Inner cavity, 114 - Opening;

[0036] 120 - Cap, 121 - Top cover, 122 - Explosion-proof valve plate, 1221 - Notch assembly, 1221a - First notch, 1221b - Second notch, 1222 - Thinning part, 1223 - Groove, 1224 - Welding platform, 123 - Insulating plate, 124 - Terminal plate, 125 - Insulating ring;

[0037] 130 - Positive current collector plate, 131 - Plate body part, 132 - Tail;

[0038] 140 - Winding core, 141 - Positive electrode end face, 142 - Negative electrode end face;

[0039] 150 - Negative current collector plate, 151 - First end face, 1511 - Concave part, 1512 - Welding area, 152 - Second end face, 1521 - Raised part. Detailed implementation manners

[0040] The embodiments of the present implementation manner will be described in detail below. The examples of the embodiments are shown in the accompanying drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present implementation manner and should not be construed as a limitation of the present implementation manner.

[0041] In the description of the present implementation manner, it should be understood that the orientation or positional relationship indicated by terms such as up, down, front, back, left, right, etc. is based on the orientation or positional relationship shown in the accompanying 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, and thus should not be construed as a limitation of the present implementation manner.

[0042] In the description of this embodiment, "several" means one or more, "multiple" means two or more, and understandings such as "greater than", "less than", "exceeding", etc. do not include the base number, while understandings such as "above", "below", "within", etc. include the base 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 implicitly specifying the sequence relationship of the indicated technical features.

[0043] 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.

[0044] The cylindrical lithium batteries provided in 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 1 and Figure 2 shown, 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 for electrically connecting to an external electrical device.

[0045] The housing 110 is introduced in detail below.

[0046] As Figure 1 and Figure 2 shown, the housing 110 is generally cylindrical and is set to be closed on the negative electrode side (the lower side in the figure) and open on the positive electrode side (the upper side in the figure). Specifically, the housing 110 includes a bottom plate 111 and an outer peripheral wall 112. Among them, the bottom plate 111 is circular, the outer peripheral wall 112 extends upward along the edge of the bottom plate 111, the bottom plate 111 and the outer peripheral wall 112 jointly define an inner cavity 113, and the top end of the outer peripheral wall 112 has an opening 114, and the opening 114 communicates with the inner cavity 113.

[0047] It can be understood that the inner cavity 113 defined by the bottom plate 111 and the outer peripheral wall 112 is also generally cylindrical and is used to accommodate the cap 120 (with its top 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.

[0048] It can be understood that the bottom plate 111 is in the shape of a thin circular plate, having a bottom plate inner surface 1111 and a bottom plate outer surface 1112 that face away from each other. Among them, the bottom plate inner surface 1111 is located on the side facing the inner cavity 113. The bottom surface of the negative current collector plate 150 is in contact connection with the bottom plate inner surface 1111. Thus, a conductive connection is formed between the two, thereby conducting the outer shell 110 and the negative electrode of the core 140.

[0049] It can be understood that the outer shell 110 can be a nickel-plated steel shell, which has advantages such as high pressure resistance. Of course, it is not limited to this. For example, it can also be an aluminum shell. The following takes the cylindrical battery case using a nickel-plated steel shell as an example for illustration. It can be formed by punching a steel strip, with simple processing and manufacturing, easy to scale production, and can effectively reduce costs.

[0050] As Figure 1 shown, it can also be understood that the outer peripheral wall 112 forms an inwardly concave necking portion 1121 along the circumferential direction at a position close to the opening 114. The necking portion 1121 is used to seal the cap 120. The necking portion 1121 can be formed by a rolling groove and a sealing process. And, in the sealing process, in addition to forming the inwardly concave necking portion 1121, the outer peripheral wall 112 will also form a curled edge 1122 at the top. The curled edge 1122, together with the necking portion 1121 and the outer peripheral wall 112, realizes the sealed connection to the cap 120. At the same time, the cap 120 completely closes the opening 114, sealing the negative current collector plate 150, the core 140, the positive current collector plate 130, etc. in the inner cavity 113, thereby forming a closed electrochemical system inside the outer shell 110.

[0051] The following details the cap 120.

[0052] It can be understood that the cap 120 and the outer shell 110 together serve as a physical barrier to isolate the active substances of the cylindrical lithium battery from the outside. And, when the gas pressure inside the battery exceeds the preset value, the explosion-proof valve plate 122 of the cap 120 opens to release the pressure, so as to avoid the battery deforming and bulging or even catching fire or exploding.

[0053] As Figure 4As 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 electrically connected to each other pairwise. After the cap 120 is hermetically connected to the housing 110, the top cover 121 is exposed outside the housing 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, an electrical 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.

[0054] Reference Figures 5 to 6 , the explosion-proof valve plate 122 is a single-piece component processed from aluminum material, and the whole is in a circular thin plate shape or a thin plate shape. Along the thickness direction, it has a top surface and a bottom surface facing away from each other. Among them, after being assembled into a 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 a scoring assembly 1221 on the top surface side. The scoring assembly 1221 includes a circular first score 1221a and a linearly extending second score 1221b. The second score 1221b is located within the area defined by the first score 1221a, and both ends of the second score 1221b are connected to the first score 1221a. That is, the first score 1221a presents a closed figure with its head and tail connected. The first score 1221a is preferably a closed circle, and the second score 1221b is in a linear shape. Among them, at least one of the first score 1221a and the second score 1221b breaks when the internal pressure of the cylindrical lithium battery exceeds a preset value, so that the explosion-proof valve plate 122 opens, and the first broken one of the first score 1221a and the second score 1221b can drive the other one to break as well.

[0055] 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 communicated with 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 will break first, and the gas inside the battery will rush out from the gap generated by the break of the first notch 1221a to relieve the pressure in time. Moreover, during the breaking process 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 will break first, and the gas inside the battery will rush out from the gap generated by the break of the second notch 1221b to relieve the pressure in time. Moreover, during the breaking and opening process 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 improving the safety of the battery.

[0056] It should be noted that if the first notch 1221a and the second notch 1221b are not communicated, they may only break separately to form a gap 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 constituting the notch assembly 1221 are set to be communicated, 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.

[0057] 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 decrease in the yield 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 of the battery, is easy to process and has a low cost, and has better economic benefits.

[0058] It can be understood that the first notch 1221a and the second notch 1221b are structures formed on the explosion-proof valve piece 122 by removing materials. Therefore, the explosion-proof valve piece 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 materials are 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.

[0059] In some embodiments, as Figure 5 shown, the first notch 1221a is circular, and the second notch 1221b is arranged 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 D3 and the length of the second notch 1221b as L, then L = D3 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 piece 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 piece 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 piece 122.

[0060] As Figure 6 shown, in some embodiments, the explosion-proof valve piece 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 piece 122. The thinning portion 1222 can effectively cause the notch assembly 1221 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 122 has sufficient strength and rigidity, which is convenient for processing and assembly.

[0061] As Figure 7 and Figure 8As shown, relative to the surface of the explosion-proof valve piece 122, the first notch 1221a has a depth H1, and the second notch 1221b has a depth H3. It can be understood that if H1 and H3 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 prone to breakage, and the opening pressure will be too small. If H1 and H3 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 easily broken, and the opening pressure will be too large, and the gas inside the battery cannot be released in time, increasing the safety risk. Therefore, in some embodiments, the ratio of the depth H1 of the first notch 1221a to the thickness T1 of the thinning portion 1222 is between 30% and 60%, that is, it satisfies: 30% ≤ H1 / T1 ≤ 60%. More preferably, 40% ≤ H1 / T1 ≤ 55%. The specific values of H1 and H3 can be determined according to the opening pressure and the thickness of the thinning portion 1222 (or the explosion-proof valve piece 122).

[0062] It can be understood that the setting areas of the first notch 1221a and the second notch 1221b on the explosion-proof valve piece 122 are different. Specifically, the first notch 1221a is arranged in a ring around the center of the explosion-proof valve piece 122 on the end face of the explosion-proof valve piece 122, while the second notch 1221b is radially constructed through the center of the explosion-proof valve piece 122 on the end face of the explosion-proof valve piece 122. Due to requirements such as strength and installation, the thickness of the explosion-proof valve piece 122 in different regions along the radial direction is usually different. For example, the wall thickness of the inner part of the explosion-proof valve piece 122 adjacent to the thinning portion 1222 is thicker than that of the thinning portion 1222, and the wall thickness changes in a stepwise manner and forms a thicker welding platform 1224 in the middle. The explosion-proof valve piece 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 piece 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.

[0063] Furthermore, in some embodiments, the depth H1 of the first notch 1221a is less than the depth H3 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 piece 122 in the middle region on the second notch 1221b can be reduced to ensure that the explosion-proof valve piece 122 is smoothly opened at the second notch 1221b.

[0064] 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 sheet 122 in the radial direction can be reduced to ensure the smooth opening of the explosion-proof valve sheet 122 at the second notch 1221b.

[0065] Further, in order to reduce stress concentration and the risk of accidental fracture of the notch assembly 1221, continue to refer to Figure 7 and Figure 8 , chamfered portions are provided at the bottoms of 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 sheet 122 when the pressure value does not reach the preset value can be lowered.

[0066] Further, 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 portions at the bottoms 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 be processed by a mold, which can reduce costs.

[0067] The positive current collector plate 130 is introduced in detail below.

[0068] As Figure 1 shown, the positive current collector plate 130 includes a plate body portion 131 and a tail portion 132. The tail 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 core 140, while the tail portion 132 is connected to the terminal plate 124 in the aforementioned cap 120. For example, both the plate body portion 131 and the core 140, and the tail portion 132 and the terminal plate 124 can be connected by laser welding. Thus, through the positive current collector plate 130, the conduction between the cap 120 and the positive electrode of the core 140 can be achieved.

[0069] The core 140 is introduced in detail below.

[0070] It can be understood that the core 140 is formed by winding positive electrode sheets, negative electrode sheets and separator membranes in a stacked manner, as Figure 1 , Figure 2 and Figure 3As shown, the core 140 is generally cylindrical in shape, and in order to smoothly pass through the opening 114 into the inner cavity 113 of the housing 110, its diameter is slightly smaller than the inner diameter of the housing 110. After the tabs of the positive and negative electrodes of the core 140 are flattened, a flat and circular positive electrode end face 141 and a negative electrode end face 142 are formed at both ends. The upper positive electrode end face 141 is connected to the positive current collector plate 130, and the lower negative electrode end face 142 is connected to the negative current collector plate 150. For example, the positive electrode end face 141 can be connected to the positive current collector plate 130, and the negative electrode end face 142 can be connected to the negative current collector plate 150 by laser welding. Thus, by connecting to the positive current collector plate 130 and the negative current collector plate 150, the core 140 is electrically connected to the cap 120 and the housing 110 respectively.

[0071] The negative current collector plate 150 will be introduced in detail below.

[0072] As Figure 1 , Figure 2 and Figure 3 shown, the negative current collector plate 150 is generally circular in shape. Taking the diameter of the negative current collector plate 150 as D1 and the diameter of the core 140 as D2, it satisfies D1 / D2 = 90% - 98%. It can be understood that setting the ratio of the diameter D1 of the negative current collector plate 150 to the diameter D2 of the core 140 within 90% - 98%, on the one hand, makes the diameter D1 of the negative current collector plate 150 as close as possible to the diameter D2 of the core 140. Thus, the welding area between it and the core 140 can be greatly increased, which can adapt to various welding shapes and sizes, facilitate the design of welding jigs, and reduce manufacturing costs. On the other hand, the negative current collector plate 150 can be pressed by the core 140 against the inner surface 1111 of the bottom plate. Therefore, the negative current collector plate 150 and the bottom plate 111 form a laminated structure at the bottom of the housing 110. The thickness of this laminated structure is thicker than that of the bottom plate 111. Therefore, this laminated structure can increase the pressure resistance of the bottom of the housing 110 to a certain extent, thereby reducing the risk of insufficient pressure resistance caused by wall thickness changes during the stamping process of the housing 110. In this way, when the pressure inside the battery rises to the limit value, the battery will only release pressure at the cap 120, so the pressure release direction of the battery is more controllable.

[0073] Referring to Figure 9 and Figure 10 , it can be understood that along the thickness direction, the negative current collector plate 150 has a first end face 151 and a second end face 152 facing away from each other. Since the second end face 152 is provided with a heightening portion 1521 introduced below, there is a strict direction distinction when the second end face 152 and the first end face 151 are welded to the housing 110 and the core 140. As Figure 2 and Figure 3As shown, specifically, the second end face 152 is welded to the outer shell 110 through the elevation portion 1521, and the first end face 151 is welded to the core 140. Thus, the welding connection among the core 140, the negative current collector plate 150, and the outer shell 110 is realized, and a path is formed among the three. That is to say, the negative current collector plate 150 indirectly connects the core 140 and the outer shell 110.

[0074] As Figure 2 and Figure 3 shown, in this embodiment, the negative current collector plate 150 is provided with an elevation portion 1521 with a flat surface on the second end face 152. The surface of the elevation portion 1521 is higher than the surface of the second end face 152, and the surface area of the elevation portion 1521 is smaller than the surface area of the second end face 152. The surface of the elevation portion 1521 is adapted to abut against the inner surface 1111 of the bottom plate of the outer shell 110. It can be understood that since the surface of the elevation portion 1521 is higher than the surface of the second end face 152, that is, the surface of the elevation portion 1521 is the top surface of the second end face 152. After the negative current collector plate 150 is assembled into the outer shell 110, the surface of the elevation portion 1521 will abut against the inner surface 1111 of the bottom plate of the outer shell 110. That is to say, the surface of the elevation portion 1521 and the inner surface 1111 of the bottom plate of the outer shell 110 are closely attached to each other, and a surface-to-surface contact connection is formed between the two. Then, the area where the elevation portion 1521 overlaps with the bottom plate 111 can be laser penetration welded through the outer surface 1112 of the bottom plate, so that the elevation portion 1521 is welded to the outer shell 110.

[0075] In this embodiment, since the ratio of the diameter D1 of the negative current collector plate 150 to the diameter D2 of the core 140 is set between 90% and 98%, the weldable area between the negative current collector plate 150 and the core 140 can be effectively increased, and the welding processability is good. At the same time, an elevation portion 1521 with a smaller area is provided on the second end face 152 of the negative current collector plate 150. Due to the smaller area of the elevation portion 1521, during the processing, it can be ensured that it has good surface flatness, so that the fitting effect between the surface of the elevation portion 1521 and the inner surface 1111 of the bottom plate of the outer shell 110 is better, and welding quality problems such as virtual welding between the two can be effectively avoided. The battery using the negative current collector plate 150 has better performance and yield.

[0076] For the purpose of facilitating processing and reducing costs, in some embodiments, the raised portion 1521 is formed by stamping the negative current collector plate 150, that is, the raised portion 1521 and the negative current collector plate 150 are integrally formed. Thus, through reasonable stamping die design, the negative current collector plate 150 of this embodiment can be efficiently processed, and the dimensional accuracy of the negative current collector plate 150 and the raised portion 1521 is high, and the surface quality is good, which is convenient for realizing the welding with the core 140 and the housing 110. Of course, it is not limited to this, and the raised portion 1521 can also be formed in other ways. For example, the raised portion 1521 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 second end face 152 of the negative current collector plate 150 by pressing to form the raised portion 1521.

[0077] As Figure 2 and Figure 3 shown, and in combination with Figure 9 , in some embodiments, the raised portion 1521 is formed in the central region of the second end face 152. Thus, after the negative current collector plate 150 is assembled into the housing 110, the raised portion 1521 can align with the central region of the bottom plate 111, which is convenient for welding the housing 110 and the raised portion 1521 through a welding device.

[0078] Furthermore, the shape of the raised portion 1521 is circular. In this way, the raised portion 1521 can be concentrically arranged with the negative current collector plate 150, which is convenient for stamping and forming through a stamping die. Of course, the shape of the raised portion 1521 is not limited to circular. For example, the raised portion 1521 can also be square, triangular, etc.

[0079] As Figure 9 shown, it can be understood that by stamping the raised portion 1521 on the second end face 152 of the negative current collector plate 150 through a stamping process, correspondingly, a recessed portion 1511 is formed at the position corresponding to the raised portion 1521 on the first end face 151. For the purpose of facilitating the welding of the negative current collector plate 150 and the core 140, in some embodiments, around the recessed portion 1511, the first end face 151 has an annular welding area 1512, and the surface of the welding area 1512 is adapted to abut against the negative end face 142 of the core 140. For example, the welding area 1512 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.

[0080] As Figure 9As shown, in some embodiments, the diameter of the negative current collector plate 150 is D1, and the diameter of the elevation portion 1521 is d, satisfying d / D1 = 28% - 38%. As described above, the diameter D1 of the negative current collector plate 150 is substantially the same as the diameter of the core 140. For example, for 21-series batteries, the diameter D1 of the negative current collector plate 150 can be set to 19 - 21 mm; for 46-series batteries, the diameter D1 of the negative current collector plate 150 can be set to 42 - 44 mm. Thus, continuing with the example of 21-series cylindrical lithium batteries, the diameter of the elevation portion 1521 is set to 5.32 - 7.98 mm. It can be understood that if the diameter of the elevation portion 1521 is too large, the surface flatness will deteriorate, and its fitting effect with the inner surface 1111 of the bottom plate of the outer shell 110 will be poor, thus affecting the welding quality; conversely, if the diameter of the elevation portion 1521 is too small, the weldable area of the elevation portion 1521 will be small, and it is easy to have a weld break during welding, which will increase the process difficulty of subsequent welding and lead to an increase in cost.

[0081] As Figure 10 As shown, in some embodiments, the thickness T2 of the negative current collector plate 150 is 0.1 - 0.5 mm. It can be understood that if the thickness T2 of the negative current collector plate 150 is too small, the mechanical strength of the negative current collector plate 150 will be insufficient and it is easy to deform; conversely, if the thickness T2 of the negative current collector plate 150 is too large, it will increase the internal resistance of the battery and also occupy more longitudinal space, thus increasing the height of the battery. In addition, setting the thickness T2 of the negative current collector plate 150 to 0.1 - 0.5 mm can also effectively improve the processing manufacturability, for example, it is convenient for stamping to form the negative current collector plate 150 and the elevation portion 1521.

[0082] Further, in some embodiments, taking the height difference between the surface of the elevation portion 1521 and the surface of the second end face 152 as H2, it satisfies: H2 / T2 = 18% - 30%. It can be understood that if the elevation portion 1521 is set too high, that is, H2 / T2 is too large, during the assembly process, the core 140 will squeeze and deform the periphery of the negative current collector plate 150, and it will also additionally occupy the longitudinal space of the battery; conversely, if the elevation portion 1521 is set too low, that is, H2 / T2 is too small, it is difficult to process the elevation portion 1521, for example, it is impossible to form the elevation portion 1521 through stamping process.

[0083] To ensure good fitting between the elevation portion 1521 and the surface of the outer shell 110, in some embodiments, the flatness of the surface of the elevation portion 1521 is 0.01 - 0.05 mm. It can be understood that if the flatness of the elevation portion 1521 is too large, its fitting effect with the inner surface 1111 of the bottom plate of the outer shell 110 will be poor, thus affecting the welding quality; conversely, if the flatness of the elevation portion 1521 is too small, it is not easy to process and the cost is too high.

[0084] In some embodiments, the negative current collector plate 150 is made of copper, and the surface of the negative current collector plate 150 is plated with a nickel layer. Compared with the negative current collector plate 150 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 negative current collector plate 150, the corrosion resistance of the negative current collector plate 150 can be effectively improved.

[0085] Furthermore, the thickness of the nickel layer is set to be 0.08 - 1.5 μm, and more preferably 0.9 - 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 negative current collector plate 150, resulting in a decrease in the plasticity of the negative current collector plate 150. At the same time, it will also increase the internal resistance and lead to a decrease in battery performance.

[0086] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. mean 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.

[0087] Although the embodiments of this implementation have been shown and described, those of ordinary skill in the art can understand that: without departing from the principles and purposes of this implementation, these embodiments can be subject to various changes, modifications, substitutions, and variations. The scope of this implementation is defined by the claims and their equivalents.

Claims

1. A cylindrical lithium battery, characterized in that: The invention comprises a housing (110), a cap (120), a positive electrode current collecting disk (130), a winding core (140), and a negative electrode current collecting disk (150), wherein the positive electrode of the winding core (140) is connected to the housing (110) through the positive electrode current collecting disk (130), and the negative electrode of the winding core (140) is connected to the housing (110) through the negative electrode current collecting disk (150), wherein: The cover cap (120) comprises an explosion-proof valve plate (122), the explosion-proof valve plate (122) is provided with a notch assembly (1221), the notch assembly (1221) comprises a first notch (1221a) and a second notch (1221b), the first notch (1221a) is a closed circle connected at both ends, the second notch (1221b) is a line segment, and the first notch (1221a) and the second notch (1221b) intersect; The negative electrode current collector (150) has a first end face (151) and a second end face (152) which are opposite to each other, the first end face (151) is connected to the winding core (140), the second end face (152) is provided with a raised portion (1521) with a flat surface, the surface area of ​​the raised portion (1521) is smaller than the surface area of ​​the second end face (152), the surface of the raised portion (1521) is in contact with the inner surface of the shell bottom of the shell (110), the diameter of the negative electrode current collector (150) is D1, and the diameter of the winding core (140) is D2, and the following condition is satisfied: D1 / D2=90% to 98%.

2. The cylindrical lithium battery according to claim 1, characterized in that: The explosion-proof valve plate (122) is provided with a thinning portion (1222) extending in the radial direction, the first notch (1221a) is arranged within the radial range where the thinning portion (1222) is located, the thickness of the thinning portion (1222) is T1, and the depth of the first notch (1221a) is H1, satisfying: 30%≤H1 / T1≤60%.

3. The cylindrical lithium battery according to claim 1, characterized in that: The height difference between the surface of the raised portion (1521) and the surface of the second end surface (152) is H2, and the thickness of the negative electrode current collecting disk (150) is T2, which satisfies: H2 / T2=18% to 30%.

4. The cylindrical lithium battery according to claim 1, characterized in that: The surface of the negative electrode current collecting disk (150) is plated with a nickel layer, and the thickness of the nickel layer is 0.08 to 1.5 μm.

5. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that: The raised portion (1521) is circular, and the diameter of the raised portion (1521) is d, satisfying d / D1=28% to 38%; the bottoms of the first notch (1221a) and the second notch (1221b) are provided with chamfered portions.

6. The cylindrical lithium battery according to claim 5, characterized in that: The flatness of the surface of the raised portion (1521) is 0.01-0.05 mm; the radii of the chamfered portions are the same.

7. The cylindrical lithium battery according to claim 6, characterized in that: The raised portion (1521) is located in the central area of ​​the second end surface (152), and the raised portion (1521) is formed by integral stamping of the negative electrode current collecting disc (150); the radius of the chamfered portion is R, satisfying: 0.05 mm ≤ R ≤ 0.15 mm.

8. The cylindrical lithium battery according to claim 7, characterized in that: The first end surface (151) forms a recessed portion (1511) at a position corresponding to the raised portion (1521), and the first end surface (151) forms a welding area (1512) around the recessed portion (1511), and the surface of the welding area (1512) abuts against the negative end surface (142) of the winding core (140).

9. The cylindrical lithium battery according to any one of claims 1 to 4, characterized in that: The diameter D3 of the first notch (1221a) is equal to the length L of the second notch (1221b); and the negative electrode current collecting plate (150) is made of copper.

10. The cylindrical lithium battery according to claim 9, characterized in that: The depth H1 of the first notch (1221a) is smaller than the depth H3 of the second notch (1221b), and the depth of the middle portion of the second notch (1221b) is greater than the depths at both ends.

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