Cylindrical lithium battery

Abstract

The invention provides a cylindrical lithium battery. A first hole and second holes are formed in a plate body part of a positive collector plate in the cylindrical lithium battery, the diameter of each second hole is 25%-35% of the diameter of the plate body part, the sum of the areas of all the second holes is 0.9-1.5 times of the area of the first hole, and a fusing groove is formed in a tail body part of the positive collector plate. The distance between the center position of the fusing groove and the end, away from the disc body part, of the tail body part is 68%-78% of the length of the tail body part, and the minimum sectional area S2 of the tail body part in the fusing groove is 45%-65% of the overall sectional area S1 of the tail body part. According to the cylindrical lithium battery, the disc body part and the tail body part of the positive collector disc are reasonably designed, so that the cylindrical lithium battery is balanced in the aspects of safety, liquid injection performance, weldability and the like.

Description

Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, and in particular to a cylindrical lithium battery. Background Art

[0002] In the related technology, cylindrical batteries are usually packaged in a cylindrical steel shell, and the bare cell is made by a winding process to form a cylindrical core. The cap is located on the top of the battery and is connected to the positive electrode in the core through the positive current collector disk. The steel shell is connected to the negative electrode in the core through the negative current collector disk. The positive current collector disk and the negative current collector disk enable electrons to be transmitted from the current collector to the current collector disk in the longitudinal direction, which can effectively improve the charging and discharging performance of the cylindrical lithium battery by increasing the current conduction area and shortening the current conduction distance.

[0003] As mentioned above, in cylindrical lithium batteries, the positive electrode collector plate is an important electrical connector, which is usually composed of a collector plate body and a tail, wherein the collector plate body is used to connect to the winding core, and the tail is bent and connected to the cap. At present, many factors need to be considered when designing the positive electrode collector plate, such as electrical transmission performance, electrolyte injection, safety protection when the battery is overheated, and welding processability. Therefore, how to reasonably design the positive electrode collector plate to achieve a balance among the above multiple aspects is a problem that needs to be solved urgently. Summary of the invention

[0004] The embodiment of the present application provides a cylindrical lithium battery to at least solve the technical problem of unreasonable design of positive electrode collector plates in existing cylindrical lithium batteries.

[0005] The first aspect of the present application provides a cylindrical lithium battery, comprising a housing, a cap, a positive electrode current collecting disk, a winding core and a negative electrode current collecting disk, wherein the positive terminal of the winding core is connected to the cap through the positive electrode current collecting disk, and the negative terminal of the winding core is connected to the housing through the negative electrode current collecting disk;

[0006] The positive electrode current collector disk comprises a disk body portion and a tail body portion connected to each other, the disk body portion is connected to the positive terminal, and the tail body portion is connected to the cap, wherein:

[0007] A circular first hole is provided at the center of the disk body, and at least one circular second hole is provided around the first hole, wherein the diameter D3 of the second hole is 25%-35% of the diameter D2 of the disk body, and the sum of the areas of all the second holes is 0.9-1.5 times the area of ​​the first hole;

[0008] At least one fuse groove is provided on the tail body, and a distance L4 between a center position of the fuse groove and an end of the tail body away from the disc body is 68%-78% of a length L3 of the tail body, and at a position on the tail body other than the fuse groove, the tail body has an overall cross-sectional area S1, and the tail body has a minimum cross-sectional area S2 at the position of the fuse groove, and the minimum cross-sectional area S2 is 45%-65% of the overall cross-sectional area S1.

[0009] The cylindrical lithium battery according to the embodiment of the present application has at least the following beneficial effects:

[0010] By reasonably designing the size of the first hole and the second hole on the positive electrode current collector through which the electrolyte penetrates, it is possible to achieve a balance between the injection efficiency and the weldable area, while ensuring the safety of welding. In addition, the fuse slot provided in the tail body is reasonably positioned so that the tail body and the cap can be welded smoothly, while ensuring that the current is cut off when the battery is thermally runaway. At the same time, the size of the fuse slot is reasonably designed, so that the tail body can achieve a balance between battery safety and low internal resistance.

[0011] In summary, by rationally designing the disk body and tail body of the positive electrode current collector disk, the cylindrical lithium battery of the present application achieves a balance in terms of safety, liquid injection performance, weldability, and the like.

[0012] In a possible embodiment, the shape of the disk body is a closed axially symmetrical figure composed of a first side, an arc, a second side and a third side connected end to end in sequence; the shape of the tail body is a closed axially symmetrical figure composed of the third side, a fifth side extending along the length direction of the tail body, a fourth side away from the disk body and a sixth side extending along the length direction of the tail body connected end to end in sequence, wherein the two ends of the fifth side are respectively connected to the fourth side and the first side, and the two ends of the sixth side are respectively connected to the fourth side and the second side.

[0013] The manufacture and assembly of the positive electrode current collecting disc are facilitated by rationally designing the shapes of the disc body and the tail body.

[0014] In a possible embodiment, the outer shell includes a shell bottom, the negative electrode current collector has a first side and a second side opposite to each other, the first side is connected to the negative terminal, and the second side is provided with a raised platform with a flat surface, and the raised platform is connected to the inner surface of the shell bottom.

[0015] By providing a flat raised platform on the side where the negative electrode current collecting disk is connected to the inner surface of the shell bottom, the raised platform has a small area and can ensure good surface flatness. The surface of the raised platform can fit well with the inner surface of the shell bottom, which can reduce the risk of welding quality problems such as cold welding between the two.

[0016] In a possible embodiment, the positive terminal and the negative terminal are both formed by flattening the entire electrode tab, and the side of the disk body facing the positive terminal abuts against the positive terminal formed by flattening the entire electrode tab; the raised platform is formed by the negative electrode collector disk through integral stamping, and a recessed portion is formed on the first side at a position corresponding to the raised platform, and a welding area is formed on the first side around the recessed portion, and the surface of the welding area abuts against the negative terminal formed by flattening.

[0017] By setting the positive and negative ends of the winding core to be formed by flattening the full pole ear, the positive end is stacked densely and has a flat cross section, avoiding wasting space in the longitudinal direction, and the internal space of the shell is highly utilized, which can further improve the energy density of the battery. At the same time, the positive end has a good bonding effect after abutting against the positive collector plate and the negative collector plate, which is conducive to laser welding and can effectively reduce process defects such as cold welding.

[0018] In a possible implementation manner, the diameter D2 of the disk body is 80%-95% of the diameter D5 of the winding core; and the diameter D7 of the negative electrode current collecting disk is 90%-98% of the diameter D5 of the winding core.

[0019] By rationally designing the size of the positive electrode collector disc and the negative electrode collector disc, the welding area between the two and the winding core can be effectively increased, thereby improving the welding effect and facilitating the design of welding tools.

[0020] In a possible implementation manner, the diameter D3 of the second hole is 50%-70% of the diameter D2 of the first hole; and the flatness of the surface of the raised platform is 0.01-0.05 mm.

[0021] By reasonably designing the sizes of the first hole and the second hole of the positive electrode collector, the injection efficiency and the welding effect with the positive terminal can be further balanced; and by reasonably designing the surface flatness of the raised platform, the negative electrode collector can have good contact with the shell bottom.

[0022] In a possible embodiment, the winding core has a through winding core hole, and the first hole diameter D3 is 1.4-1.8 times the winding core hole diameter D6; the raised platform is circular and located at the center of the second side, and the diameter of the raised platform is D8 which is 28%-38% of the diameter D7 of the negative electrode collector.

[0023] By properly designing the diameter range of the first hole, it is possible to achieve a balance between the injection efficiency and the weldable area while ensuring the safety of welding. In addition, by properly designing the size of the raised platform, the welding effect and welding processability between the platform and the shell bottom can be improved.

[0024] In a possible implementation manner, the length L3 of the tail body is 85%-95% of the diameter D2 of the disc body; the height difference H3 between the surface of the raised platform and the surface of the first side is 18%-30% of the thickness T3 of the negative electrode collector disc.

[0025] By rationally designing the length of the tail body, a balance can be achieved between welding processability and battery safety; and by rationally designing the size of the raised platform, a balance can be achieved in terms of machinability and assembly processability, while also improving the utilization rate of the battery's internal space.

[0026] In a possible implementation manner, the thickness of the tail body is 0.15-0.35 mm.

[0027] By rationally designing the thickness of the tail body, the battery has better assembly processability and can also improve the utilization rate of the internal space of the battery.

[0028] In a possible implementation, the positive electrode current collecting disc is made of aluminum, the negative electrode current collecting disc is made of copper, and the surface of the negative electrode current collecting disc is plated with a nickel layer, and the thickness of the nickel layer is 0.08-1.5 μm.

[0029] The positive electrode current collector made of aluminum and the negative electrode current collector made of copper have the characteristics of low internal resistance and good conductivity. In the event of thermal runaway, the positive electrode current collector is easy to fuse to cut off the current, and the nickel plating layer on the surface of the negative electrode current collector can effectively improve the corrosion resistance of the negative electrode current collector.

[0030] In a possible embodiment, the cap includes a stacked explosion-proof valve plate and a terminal plate, the tail body is connected to the bottom of the terminal plate, the explosion-proof valve plate is provided with a first notch and a second notch, the first notch is a closed circle connected at the head and tail ends, the second notch is a line segment shape, and the first notch intersects with the second notch.

[0031] By providing the first notch and the second notch on the explosion-proof valve sheet, when the internal gas pressure rises sharply due to abnormal conditions such as overheating or short circuit inside the battery, the gas pressure value in either the edge area or the middle area reaches the preset value first, and one of the first notch and the second notch breaks first, so that the battery can release pressure in time. Moreover, since the first notch intersects with the second notch, the first notch or the second notch will also drive the other to break during the breaking process, thereby expanding the opening area of ​​the explosion-proof valve sheet and improving the pressure relief effect. Therefore, when the gas pressure inside the battery exceeds the preset value, the explosion-proof valve sheet can be opened quickly and effectively to release the pressure, thereby improving the safety of the battery.

[0032] In a possible implementation, the first width of the tail body W1 = D2*sin(∠B / 2), and 20°≤∠B≤40°, wherein ∠B has the center point corresponding to the arc as its vertex, and its two sides respectively pass through the intersection of the fifth side and the sixth side with the full circle where the arc is located.

[0033] By properly designing the width of the tail body, it helps to retain the largest weldable area, while ensuring that the tail body has sufficient mechanical strength to prevent it from being broken during the production process. It also facilitates the rapid passage of electrons and reduces the internal resistance of the battery.

[0034] In a possible embodiment, the second width W2 of the tail body at the fuse groove is 3 / 8-3 / 4 of the first width W1; the explosion-proof valve plate is provided with a thinning portion extending in the radial direction, the first notch is arranged within the radial range where the thinning portion is located, and the depth H1 of the first notch is 30%-60% of the thickness T1 of the thinning portion.

[0035] By reasonably designing the width of the tail body at the fuse groove, the mechanical properties of the tail body and the safety performance of the battery can be balanced. When the second width W2 is too small, the strength of the tail body at the fuse groove is insufficient and it is easy to be broken when bending. When the second width W2 is too large, the tail body cannot be quickly fused, which poses a safety hazard. In addition, by reasonably setting the thickness of the thinning portion and the depth of the first notch, the notch component can be effectively broken when the opening condition is met to release the battery pressure, while also ensuring that the explosion-proof valve sheet has sufficient strength and rigidity for easy processing and assembly.

[0036] In a possible implementation manner, a dimension L5 of the fuse slot along the length direction of the tail body portion is 0<L5≤W1; and a diameter D1 of the first notch is equal to a length L1 of the second notch.

[0037] By rationally designing the size of the fuse slot, it helps to improve the safety of the battery. If L5 is too large, the fuse position of the tail body is difficult to determine, thereby increasing the safety risk of the battery; on the contrary, if L5 is too small, the fuse sensitivity of the tail body increases, and there is a possibility of fuse under safe current. And by setting the diameter of the first notch to be equal to the length of the second notch, the second notch divides the first notch into two symmetrical parts, which is easy to process, and after the explosion-proof valve sheet is assembled to the cylindrical lithium battery, the second notch is located in the middle area of ​​the cylindrical lithium battery, so that the explosion-proof valve sheet can be opened smoothly to release pressure.

[0038] In a possible implementation, a dimension L5 of the fuse groove along the length direction of the tail body is 1 / 4 to 3 / 4 of the first width W1; a depth H1 of the first notch is less than a depth H2 of the second notch, and a depth in the middle of the second notch is greater than a depth at both ends.

[0039] By properly designing the size of the fuse slot, the safety of the battery can be improved. By increasing the depth of the second notch, the effect of the increased thickness of the explosion-proof valve sheet in the middle area on the second notch can be reduced, so as to ensure that the explosion-proof valve sheet opens smoothly at the second notch.

[0040] In a possible implementation, the angle θ1 between the fifth side and the first side is 45-90°, and the angle θ2 between the sixth side and the second side is 45-90°; chamfered portions are provided at the bottom of the first notch and the second notch, and the radius R of the chamfered portion is 0.05-0.15 mm.

[0041] By reasonably designing the angle θ1 between the fifth side and the first side, and the angle θ2 between the sixth side and the second side, the mechanical properties of the positive electrode current collector and the size of the weldable area of ​​the disc body can be balanced. And by designing chamfers at the bottom of the first notch and the second notch and reasonably designing the size of the chamfers, the stress concentration at the bottom of the first notch and the second notch can be effectively reduced, and at the same time, a balance can be achieved in terms of machinability. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the description of the embodiments of the present application will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0043] Figure 1 is an exploded schematic diagram of a cylindrical lithium battery according to an embodiment of the present application;

[0044] Figure 2 is a cross-sectional schematic diagram of a cap in a cylindrical lithium battery in one embodiment of the present application;

[0045] Figure 3 It is a top view schematic diagram of an explosion-proof valve sheet in a cylindrical lithium battery according to an embodiment of the present application;

[0046] Figure 4 yes Figure 3 A schematic cross-sectional view of the middle explosion-proof valve plate;

[0047] Figure 5 yes Figure 4 The local schematic diagram of the A in the middle;

[0048] Figure 6 yes Figure 4 The local schematic diagram of point B in the middle;

[0049] Figure 71 is a schematic top view of a positive electrode current collector in a cylindrical lithium battery according to an embodiment of the present application, wherein the tail body is in an unfolded state;

[0050] Figure 8 yes Figure 7 A schematic diagram of the structure in which the positive electrode current collecting disk is connected to the winding core;

[0051] Fig. 9 yes Figure 7 A schematic diagram of the structure of the tail portion of the middle positive electrode current collector;

[0052] Fig.10 yes Fig. 9 Schematic diagram of the cross section along the AA direction;

[0053] Fig.11 yes Figure 7 A schematic diagram of the structure of the tail portion of the middle positive electrode current collector;

[0054] Fig.12 It is a structural schematic diagram of a cylindrical lithium battery in an embodiment of the present application in which a negative electrode current collecting disk is connected to a winding core and a shell bottom;

[0055] Fig.13 yes Fig.12 A schematic cross-sectional view of the middle negative electrode current collector;

[0056] Fig.14 yes Fig.12 Partial schematic diagram of point C in the middle.

[0057] Reference numerals:

[0058] 110-shell, 111-shell bottom, 112-side wall, 1121-neck, 113-inner cavity, 114-opening;

[0059] 120-cap, 121-top cover, 122-explosion-proof valve plate, 1221-notch assembly, 1221a-first notch, 1221b-second notch, 1222-thinning portion, 1223-groove, 1224-welding platform, 123-insulating plate, 124-terminal plate, 125-insulating ring;

[0060] 130-positive electrode current collecting disk, 131-disk body, 1311-first side, 1312-arc, 1313-second side, 1314-third side, 1315-first hole, 1316-second hole, 132-tail body, 1321-fuse slot, 1322-fifth side, 1323-sixth side, 1324-fourth side;

[0061] 140-winding core, 141-positive terminal, 142-negative terminal, 143-winding core hole;

[0062] 150 - negative electrode current collecting plate, 151 - first side, 1511 - recessed portion, 1512 - welding area, 152 - second side, 1521 - raised platform. DETAILED DESCRIPTION

[0063] Embodiments of the present embodiment are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present embodiment, and should not be construed as limiting the present embodiment.

[0064] In the description of this embodiment, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing this embodiment and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on this embodiment.

[0065] In the description of this embodiment, "several" means one or more, "more" means more than two, "greater than", "less than", "exceed", etc. are understood to exclude the number itself, and "above", "below", "within", etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0066] In the description of this embodiment, unless otherwise clearly defined, terms such as setting, installing, connecting, etc. should be understood in a broad sense, and technicians in the relevant technical field can reasonably determine the specific meanings of the above terms in this embodiment based on the specific content of the technical solution.

[0067] The cylindrical lithium battery provided in the embodiment of the present application includes various size series, such as 21 series (cylindrical lithium battery with an outer diameter of 21 mm) and 46 series (cylindrical lithium battery with an outer diameter of 46 mm), which are not limited here. Figure 1 As shown, the cylindrical lithium battery includes a shell 110, a cap 120, a positive electrode current collecting disk 130, a winding core 140, and a negative electrode current collecting disk 150, wherein the positive terminal 141 of the winding core 140 is connected to the cap 120 through the positive electrode current collecting disk 130, and the negative terminal 142 of the winding core 140 is connected to the shell 110 through the negative electrode current collecting disk 150, so that the cap 120 serves as the positive electrode of the cylindrical lithium battery, and the shell 110 serves as the negative electrode of the cylindrical lithium battery, which is used to be electrically connected to an external electrical device.

[0068] The housing 110 is described in detail below.

[0069] like Figure 1 As shown, combined with Fig.12 The shell 110 is cylindrical in shape as a whole, and is closed on the negative electrode side (the lower side in the figure) and open on the positive electrode side (the upper side in the figure). Specifically, the shell 110 includes a shell bottom 111 and a side wall 112, wherein the shell bottom 111 is circular, and the side wall 112 extends upward along the edge of the shell bottom 111, and the shell bottom 111 and the side wall 112 jointly define an inner cavity 113, and the top of the side wall 112 has an opening 114, and the opening 114 is connected to the inner cavity 113.

[0070] like Figure 1 As shown, the side wall 112 is circumferentially concave near the opening 114 to form a necking portion 1121, and the necking portion 1121 is used to seal the cap 120. The necking portion 1121 can be formed by rolling grooves and sealing processes, and in the sealing process, the cap 120 completely closes the opening 114, and seals the negative electrode current collecting disc 150, the winding core 140 and the positive electrode current collecting disc 130 in the inner cavity 113, thereby forming a closed electrochemical system in the outer shell 110.

[0071] The cap 120 is described in detail below.

[0072] It can be understood that the cap 120 and the outer shell 110 together serve as a physical barrier to isolate the active materials of the cylindrical lithium battery from the outside world, and when the gas pressure inside the battery exceeds a preset value, the explosion-proof valve plate 122 of the cap 120 opens to release the pressure to prevent the battery from deforming, bulging, or even burning or exploding.

[0073] like Figure 2 As shown, the cap 120 includes a top cover 121, an explosion-proof valve sheet 122, an insulating plate 123, a terminal plate 124, and an insulating ring 125 located at the outer edge, wherein the top cover 121, the explosion-proof valve sheet 122, and the terminal plate 124 are stacked in sequence from top to bottom, and are conductively connected to each other. After the cap 120 is sealed and connected to the housing 110, the top cover 121 is exposed outside the housing 110, and it is used as a positive terminal for electrical connection with the positive electrode of an external electrical device. The bottom surface of the terminal plate 124 is connected to the positive current collector 130, for example, the positive current collector 130 and the terminal plate 124 are welded, thereby forming a conductive connection between the two, thereby connecting the top cover 121 to the positive terminal 141 of the winding core 140. The explosion-proof valve sheet 122 constituting the cap 120 is described in detail below.

[0074] refer to Figure 3 to Figure 4 The explosion-proof valve plate 122 is a single member made of aluminum material, and is in the shape of a circular thin disk or a thin plate. In the thickness direction, it has a top surface and a bottom surface that are separated from each other. After being assembled into a cylindrical lithium battery, the bottom surface ( Figure 4The lower middle surface) faces the side of the winding core 140, and the top surface ( Figure 4 The explosion-proof valve sheet 122 is provided with a notch assembly 1221 on one side of the top surface. The notch assembly 1221 includes a first notch 1221a in an annular shape and a second notch 1221b extending in a line segment shape. The second notch 1221b is located in the area defined by the first notch 1221a, and the two ends of the second notch 1221b are connected to the first notch 1221a, that is, the first notch 1221a presents a closed figure connected end to end. The first notch 1221a is preferably a closed circle, and the second notch 1221b is in a line segment shape. At least one of the first notch 1221a and the second notch 1221b breaks when the internal pressure of the cylindrical lithium battery exceeds a preset value, so that the explosion-proof valve sheet 122 opens, and the first notch 1221a and the second notch 1221b that breaks first can drive the other to break as well.

[0075] It can be understood that, since the explosion-proof valve sheet 122 of the embodiment of the present application is provided with an annular first notch 1221a and a line-segment-shaped second notch 1221b, and both ends of the second notch 1221b are connected to the first notch 1221a, therefore, when an abnormal state such as overheating or short circuit occurs inside the battery and causes the internal air pressure to rise sharply, when the air pressure value in the edge area reaches the preset value first, the first notch 1221a will break first, and the gas inside the battery will rush out from the gap created by the break of the first notch 1221a to release the pressure in time, and the first notch 1221a will also drive the second notch 1221b in the process of breaking. The second notch 1221b also breaks, thereby expanding the opening area of ​​the explosion-proof valve sheet 122 and improving the pressure relief effect. When the air pressure in the middle area reaches the preset value first, the second notch 1221b breaks first, and the internal gas of the battery rushes out from the gap caused by the break of the second notch 1221b to release the pressure in time. Moreover, the second notch 1221b will also drive the first notch 1221a to break during the process of breaking and opening, thereby expanding the opening area of ​​the explosion-proof valve sheet 122 and improving the pressure relief effect. Therefore, when the gas pressure inside the battery exceeds the preset value, the explosion-proof valve sheet 122 can be opened quickly and effectively to release the pressure, thereby improving the safety of the battery.

[0076] It should be noted that if the first notch 1221a and the second notch 1221b are not connected, the two may only break separately and form a gap to release pressure, which has a poor pressure release effect and cannot achieve the purpose of quickly and effectively releasing pressure on the battery proposed in this application. Therefore, in the embodiment of the present application, the first notch 1221a and the second notch 1221b constituting the notch assembly 1221 are arranged to be connected, that is, the two intersect, so that after any one of them breaks, it can extend to the other, so that the other also breaks, so that the opening area of ​​the explosion-proof valve sheet 122 can be expanded, thereby quickly releasing pressure on the battery.

[0077] It is understandable that although a more complex internal notch, such as a cross-shaped notch, can be used to replace the second notch 1221b to achieve the purpose of timely explosion when the pressure in the middle area of ​​the battery increases, this will significantly increase the difficulty of processing the explosion-proof valve plate 122, thereby resulting in a decrease in the yield rate and an increase in cost. The embodiment of the present application only provides a straight second notch 1221b inside the explosion-proof valve plate 122, which can effectively achieve rapid and effective pressure relief for the battery while being easy to process and low in cost, thereby having better economic benefits.

[0078] It can be understood that the first notch 1221a and the second notch 1221b are structures formed by removing material on the explosion-proof valve sheet 122. Therefore, the explosion-proof valve sheet 122 is thinner at the position where the first notch 1221a and the second notch 1221b are located relative to the other positions. When the internal pressure of the battery increases and exceeds the preset value, according to the specific pressure position distribution, one or both of the first notch 1221a and the second notch 1221b are deformed as a whole. When the deformation accumulates to a certain extent, the first notch 1221a and the second notch 1221b will break, and the broken material will flip over due to the pressure to form a gap at the break, and the high-pressure gas inside the battery will be released through the gap.

[0079] In some embodiments, Figure 3As shown, the first notch 1221a is circular, and the second notch 1221b is set to pass through the center of the first notch 1221a, that is, the second notch 1221b is just the diameter of the annular figure displayed by the first notch 1221a. In this way, if the diameter of the first notch 1221a is D1 and the length of the second notch 1221b is L1, then L1=D1 is satisfied. Therefore, the second notch 1221b divides the first notch 1221a into two symmetrical parts, which is convenient for processing and constructing the first notch 1221a and the second notch 1221b, and after the explosion-proof valve sheet 122 is assembled to the cylindrical lithium battery, the second notch 1221b is located in the middle area of ​​the cylindrical lithium battery, so that the explosion-proof valve sheet 122 can be opened smoothly to release pressure. Furthermore, it can be understood that in order to facilitate the construction of the annular first notch 1221a and the segment-shaped second notch 1221b, the first notch 1221a can be set to be co-centered with the explosion-proof valve plate 122.

[0080] like Figure 4 As shown, in some embodiments, the explosion-proof valve sheet 122 is provided with a thinning portion 1222 extending in the radial direction, and the first notch 1221a is provided within the radial range where the thinning portion 1222 is located. Specifically, the thinning portion 1222 can be realized by providing a groove 1223 on one side of the explosion-proof valve sheet 122. The thinning portion 1222 can effectively cause the notch assembly 1221 to break when the opening condition is met to release the pressure of the battery, while also ensuring that the explosion-proof valve sheet 122 has sufficient strength and rigidity for easy processing and assembly.

[0081] like Figure 5 and Figure 6 As shown, relative to the surface of the explosion-proof valve sheet 122, the first notch 1221a has a depth H1, and the second notch 1221b has a depth H2. It can be understood that if H1 and H2 are large, that is, the first notch 1221a and the second notch 1221b are deep, the first notch 1221a and the second notch 1221b are easy to break, and the opening pressure will be too small. If H1 and H2 are large, that is, the first notch 1221a and the second notch 1221b are shallow, the first notch 1221a and the second notch 1221b are not easy to break, and the opening pressure will be too large, and the gas inside the battery cannot be released in time, increasing the safety risk. Therefore, in some embodiments, the ratio of the depth H1 of the first notch 1221a to the thickness T1 of the thinned portion 1222 is between 30% and 60%, that is, it satisfies: 30%≤H1 / T1≤60%, and more preferably, 40%≤H1 / T1≤55%. The specific values ​​of H1 and H2 can be determined according to the opening pressure and the thickness of the thinned portion 1222 (or the explosion-proof valve plate 122).

[0082] It can be understood that the first notch 1221a and the second notch 1221b are arranged at different positions on the explosion-proof valve plate 122. Specifically, the first notch 1221a is arranged in a ring shape around the center of the explosion-proof valve plate 122 on the end surface of the explosion-proof valve plate 122, while the second notch 1221b is radially constructed on the end surface of the explosion-proof valve plate 122 through the center of the explosion-proof valve plate 122. Due to strength, installation and other requirements, the thickness of the explosion-proof valve plate 122 in different radial areas is usually different. For example, the wall thickness of the inner part of the explosion-proof valve plate 122 adjacent to the thinning portion 1222 is thicker than that of the thinning portion 1222, and the wall thickness changes in a step-by-step manner and forms a thicker welding platform 1224 in the middle, and the explosion-proof valve plate 122 is welded to the terminal plate 124 through the welding platform 1224. Therefore, in order to ensure that the first notch 1221a and the second notch 1221b located in different areas of the explosion-proof valve plate 122 can both open smoothly when the pressure reaches a preset value, in some embodiments, the depth of the first notch 1221a is different from the depth of the second notch 1221b.

[0083] Furthermore, in some embodiments, the depth H1 of the first notch 1221a is less than the depth H2 of the second notch 1221b. By increasing the depth of the second notch 1221b, the effect of the increased thickness of the explosion-proof valve plate 122 in the middle region on the second notch 1221b can be reduced, so as to ensure that the explosion-proof valve plate 122 opens smoothly at the second notch 1221b.

[0084] Furthermore, the depth of the second notch 1221b is set to be deeper in the middle and shallower at both ends. By setting the depth of the second notch 1221b to be deeper in the middle and shallower at both ends, the influence of the step-wise change in the thickness of the explosion-proof valve plate 122 in the radial direction can be reduced, so as to ensure that the explosion-proof valve plate 122 opens smoothly at the second notch 1221b.

[0085] Further, in order to reduce stress concentration and reduce the risk of accidental breakage of the first notch 1221a and the second notch 1221b, continue to refer to Figure 5 and Figure 6 The first notch 1221a and the second notch 1221b are both provided with chamfered portions at their bottoms. By providing the chamfered portions at the bottoms of the first notch 1221a and the second notch 1221b, stress concentration at the bottoms of the first notch 1221a and the second notch 1221b can be reduced, thereby reducing the risk of accidental opening of the explosion-proof valve disc 122 when the pressure value does not reach the preset value.

[0086] Furthermore, the radii of the chamfered portions at the bottom of the first notch 1221a and the second notch 1221b are the same. By setting the radii of the chamfered portions of the first notch 1221a and the second notch 1221b to be the same, the design and manufacturing costs can be reduced. For example, the radius of the chamfered portions at the bottom of the first notch 1221a and the second notch 1221b is R, which satisfies: 0.05mm≤R≤0.15mm, and more preferably, 0.05mm≤R≤0.1mm. The radius of the chamfered portion is within this range, which can firstly effectively reduce the stress concentration at the bottom of the first notch 1221a and the second notch 1221b, and secondly, it is also easy to process through a mold, which can reduce costs.

[0087] The positive electrode current collecting disk 130 is described in detail below.

[0088] like Figure 7 and Figure 8 As shown, the positive electrode current collecting disc 130 includes a disc body 131 and a tail body 132 connected to each other, wherein the disc body 131 is used to connect to the positive terminal 141 of the winding core 140, and the tail body 132 is used to connect to the cap 120, so that a passage is formed between the winding core 140 and the cap 120. In the present application, the connection between the disc body 131 and the winding core 140, and the connection between the tail body 132 and the cap 120 can adopt any connection method well known to those skilled in the art, such as welding; the connection between the tail body 132 and the disc body 131 can be any fixed connection method, and in order to ensure the stability of the connection and the structural strength, it is preferably an integral connection.

[0089] like Figure 7 As shown, in order to match the circular cross-section of the winding core 140 and facilitate welding between the disk body 131 and the winding core 140, the shape of the disk body 131 is a closed axisymmetric figure composed of a first side 1311, an arc 1312, a second side 1313 and a third side 1314 connected end to end in sequence, and the tail body 132 includes a fifth side 1322 and a sixth side 1323 along its length direction, and a fourth side 1324 away from the disk body 131, the two ends of the fifth side 1322 are respectively connected to the fourth side 1324 and the first side 1311, and the two ends of the sixth side 1323 are respectively connected to the fourth side 1324 and the second side 1313, thereby, Figure 7 From the perspective of the tail body 132, the tail body 132 is also a closed axisymmetric figure extending from one end of the disc body 131. It should be noted that the third side 1314 is a virtual side line proposed for the convenience of describing the disc body 131. There is no such side in the actual product. Figure 7 Dotted lines are used to mark the difference. Figure 1 and Figure 8It can also be understood that when the positive electrode current collecting disk 130 is assembled to the cylindrical lithium battery, the tail body portion 132 is bent, and its distal end portion is located above the closed axially symmetrical figure formed by the disk body portion 131.

[0090] In order to improve the efficiency of injecting electrolyte during the battery production process, the disc body 131 is usually provided with holes for the electrolyte to pass through, and to ensure that the solid area of ​​the disc body 131 after the holes are punched still accounts for more than 75% of the total area of ​​the disc body 131, so as to facilitate welding with the winding core 140. The disc body 131 has a central angle A, and 40°≤∠A≤60°, and more preferably 45°≤∠A≤55°. Specifically, the total area of ​​the above-mentioned disk body 131 is the sum of the solid area of ​​the disk body 131 and the hole area; the center angle A takes the center of the circle corresponding to the arc 1312 as the vertex, and the two edges pass through the end point of the first edge 1311 away from the arc 1312 and the end point of the second edge 1313 away from the arc 1312 respectively. It can be understood that the end point of the first edge 1311 away from the arc 1312 and the end point of the second edge 1313 away from the arc 12 are also the connection points of the first edge 1311, the second edge 1313 and the tail body 132.

[0091] In some embodiments, the diameter D2 of the disk body 131 is 80%-95% of the diameter D5 of the winding core 140, wherein the diameter D2 of the disk body 131 refers to the longest line segment between two points on the arc 1312, and the diameter D5 of the winding core 140 refers to the diameter of the circular cross section of the winding core 140. According to actual needs, the size of the diameter D2 of the disk body 131 is, for example, 15-23 mm. The disk body 131 ensures a large contact area between the disk body 131 and the winding core 140 within the preferred diameter range, increases the weldable area, and expands the adaptability range of the welding wire length and shape. It can also be understood that when the contact area of ​​the negative electrode current collector 150 is large, within the above diameter range, the positive electrode current collector 130 will not become a bottleneck limiting the charging and discharging performance of the cylindrical lithium battery.

[0092] In some embodiments, a first hole 1315 is provided at the center of the disk body 131 for injecting electrolyte into the battery. The center of the disk body 131 may be the center of the circle corresponding to the arc 1312. The winding core 140 is made by a winding process, and a circular winding core hole 143 is formed at the center of the winding core 140 after winding. To match the shape of the winding core hole 143, the shape of the first hole 1315 is preferably circular.

[0093] In some embodiments, the diameter D3 of the first hole 1315 is 1.4-1.8 times the diameter D6 of the core hole 143 of the core 140. According to actual needs, the diameter D3 of the first hole 1315 is, for example, 4-8 mm. The first hole 1315 can achieve a balance between injection efficiency and weldable area within this diameter range while ensuring the safety of welding. If the diameter D3 of the first hole 1315 is too small, it is not conducive to the infiltration of the injection, and when the resistance welding process is used at the bottom of the battery, the electrode head extending into the core hole 143 of the core 140 may produce undesirable contact with the collecting disk, and there is a risk of interference; if the diameter D3 of the first hole 1315 is too large, the weldable area is correspondingly reduced, which limits the welding processability between the disk body 131 and the core 140.

[0094] In some embodiments, the diameter D3 of the first hole 1315 is 25%-35% of the diameter D2 of the disk body 131. According to actual needs, the diameter D3 of the first hole 1315 is, for example, 4-8 mm. The first hole 1315 can achieve a balance between the injection efficiency and the weldable area within this diameter range while ensuring the safety of welding. If the diameter D3 of the first hole 1315 is too small, it is not conducive to the infiltration of the injection, and when the resistance welding process is used at the bottom of the battery, the electrode head extending into the core hole 143 of the core 140 may produce undesirable contact with the collector plate, and there is a risk of interference; if the diameter D3 of the first hole 1315 is too large, the weldable area is correspondingly reduced, which limits the welding process between the disk body 131 and the core 140.

[0095] In some embodiments, at least one second hole 1316 is provided on the periphery of the first hole 1315 to assist the infiltration of the electrolyte. Preferably, the second hole 1316 is a circular hole. Further preferably, the area of ​​a single second hole 1316 is 0.3-0.5 times the area of ​​the first hole 1315, and the sum of the areas of all second holes 1316 is 0.9-1.5 times the area of ​​the first hole 1315. If the area of ​​the second hole 1316 is too small compared to the area of ​​the first hole 1315, the auxiliary infiltration effect will not be obvious; if the area of ​​the second hole 1316 is too large, the weldable area of ​​the disc body 131 will be greatly reduced, affecting the connection between the disc body 131 and the winding core 140.

[0096] In some embodiments, the distance L2 between the center of the second hole 1316 and the center of the first hole 1315 is 25%-35% of the diameter D2 of the disk body 131. According to actual needs, L2 is, for example, 4.5-7 mm. By reasonably designing the distance L2 between the second hole 1316 and the first hole 1315, it is helpful to improve the wetting effect of the electrolyte while ensuring the area of ​​the weldable area. If the spacing L2 between the second hole 1316 and the first hole 1315 is too small, the wetting effect of the electrolyte cannot be significantly improved; if the spacing L2 between the second hole 1316 and the first hole 1315 is too large, the second hole 1316 is too close to the edge of the disk body 131, thereby limiting the battery pack. If the pack blocks the second hole 1316, the electrolyte cannot be injected through the second hole 1316.

[0097] In order to facilitate processing and improve yield, in a preferred embodiment, the diameter D4 of the second hole 1316 is 50%-70% of the diameter D3 of the first hole 1315, and the diameter D4 of the second hole 1316 is, for example, 2-4.8 mm. If the diameter D4 of the second hole 1316 is smaller than the preferred diameter range, it is difficult to achieve the auxiliary infiltration effect; if the diameter D4 of the second hole 1316 is larger than the preferred diameter range, the weldable area of ​​the disk body 131 is reduced. It can be understood that the number of the second holes 1316 can be determined according to the actual welding process, the number of welding areas is n, and the number of the second holes 1316 is n-1, where n≥2.

[0098] The disk body 131 is further described below with reference to examples and comparative examples. The following examples and comparative examples of the present application are designed with reference to ordinary 21 series cylindrical lithium batteries.

[0099] Embodiment 1:

[0100] Embodiment 1 provides a cylindrical lithium battery, which includes a housing 110, a cap 120, a positive electrode current collector 130, a winding core 140, and a negative electrode current collector 150. Among them, the positive electrode current collector includes a positive electrode current collector 130 that is connected to each other, and a disc body 131 and a tail body 132 that are connected to each other, wherein the disc body 131 is connected to the positive terminal 141 of the winding core 140, and the tail body 132 is connected to the cap 120. A first circular hole 1315 is provided at the center of the disc body 131, and a plurality of second circular holes 1316 are provided on the periphery of the first hole 1315. In addition, the shape of the disc body 131 is a closed axially symmetrical figure composed of a first side 1311, an arc 1312, a second side 1313, and a third side 1314 connected end to end, and has a center angle B.

[0101] Among them, the diameter D5 of the winding core 140 is 20 mm; the diameter D2 of the disk body 131 is 85% of the diameter D5 of the winding core 140; the diameter D3 of the first hole 1315 is 30% of the diameter D2 of the disk body 131; the diameter D4 of the second hole 1316 is 60% of the diameter D3 of the first hole 1315; the sum of the areas of all the second holes 1316 is 1.2 times the area of ​​the first hole 1315; the distance L2 between the center position of the second hole 1316 and the center of the first hole 1315 is 30% of the diameter D1 of the disk body 131; the center angle B of the disk body 131 is 35°.

[0102] Comparative Example 1:

[0103] Comparative Example 1 provides a cylindrical lithium battery, which differs from Example 1 in that the sum of the areas of all second holes 1316 is 0.4 times the area of ​​the first hole 1315 .

[0104] Comparative Example 2:

[0105] Comparative Example 2 provides a cylindrical lithium battery, which differs from Example 1 in that the diameter D3 of the first hole 1315 is 10% of the diameter D2 of the disk body 131 .

[0106] The following Table 1 evaluates the electrolyte infiltration effect of the cylindrical lithium batteries in the sealed state made by the above-mentioned embodiments and comparative examples. The specific electrolyte infiltration test method is: sampling the outer shell 110, the cap 120, the positive electrode current collector 130, the winding core 140, the negative electrode current collector 150 and the electrolyte, welding the positive electrode current collector 130, the negative electrode current collector 150 and the winding core 140, and after placing the assembly into the outer shell 100, welding the cap 120, thereby obtaining an unsealed cylindrical lithium battery. Next, the cylindrical lithium battery is placed in the liquid injection equipment for liquid injection, and the liquid injection volume is 6.8g. After the positive and negative pressure cycles of the equipment, the cylindrical lithium battery is mechanically sealed. After the battery is left to stand for 1h, the cylindrical lithium battery is disassembled, the winding core 140 is taken out and unfolded, and placed on the CCD detection equipment for photographing, the infiltration area is depicted, and the equipment program is started to calculate the infiltration area area S0, and the total area of ​​the pole piece is set to S, then the infiltration rate is S0 / S.

[0107] Table 1

[0108] Example 1 Comparative Example 1 Comparative Example 2 Infiltration rate (%) 90.574％ 82.367％ 71.546％

[0109] It can be seen from Table 1 that when the ratio of the sum of the areas of all the second holes 1316 to the area of ​​the first holes 1315 is 1.2 times, and the diameter D3 of the first hole 1315 is 30% of the diameter D2 of the disk body 131, the electrolyte infiltration effect of the core 140 is better, and if the ratio of the sum of the areas of all the second holes 1316 to the area of ​​the first holes 1315 is too low, or the first holes 1315 are too small, the electrolyte infiltration effect of the core 140 will deteriorate.

[0110] Continue to refer Figure 7 In some embodiments, at least one fuse slot 1321 is provided on the tail body 132. The width of the tail body 132 at the fuse slot 1321 is reduced by designing the fuse slot. When the battery is in thermal runaway, the current converges there, the heat rises and reaches the melting point, causing the tail body 132 to melt, thereby achieving the current cutting effect. Specifically, the shape of the fuse slot 1321 can be any shape such as a trapezoid, a rectangle, a U-shape, a V-shape, a semicircle, etc. The present application does not limit the number of fuse slots 1321, and the accompanying drawings exemplarily show two symmetrically arranged fuse slots 1321. When there are multiple fuse slots 1321, all fuse slots 1321 can be of the same shape or of different shapes. In principle, the setting of the fuse slot 1321 must simultaneously ensure the fusing effect and mechanical strength of the tail body 132.

[0111] In some embodiments, Fig. 9 As shown, the distance L4 between the center position of the fuse slot 1321 and the end of the tail body 132 away from the disk body 131 is 68%-78% of the length L3 of the tail body 132. According to actual needs, the distance between the center position of the fuse slot 1321 and the end of the tail body 132 away from the disk body 131 is, for example, 8-18 mm. If the shape of the fuse slot 1321 is a simple figure, the center position of the fuse slot 1321 can be a position recognized by those skilled in the art. For example, the center position of the fuse slot 1321 of a trapezoidal or rectangular shape can be the intersection of two diagonal lines; for another example, the center position of the semicircular fuse slot 1321 can be the center of the circle. If the shape of the fuse slot 1321 is more complex or irregular, the center position of the fuse slot 1321 is the geometric center of its shape, that is, the average position of all points in the shape, which can be determined by any method known to those skilled in the art, such as integral method, discrete point method, graphic segmentation method, etc., or directly calculated using software tools. The length L3 of the tail body 132 is the distance between the connection between the tail body 132 and the disk body 131 and the end of the tail body 132 away from the disk body 131. The fuse slot 1321 is set at a reasonable position so that the tail body 132 and the cap 120 can be welded smoothly, while ensuring that the current is cut off when the battery is thermally runaway. If the distance between the fuse slot 1321 and the end of the tail body 132 away from the disk body 131 is too small, the fuse slot 1321 will be too close to the welding position, and the welding of the tail body 132 and the cap 120 will be interfered; on the contrary, the fuse slot 1321 is closer to the disk body 131, and the current path at the fuse slot 1321 is larger. If there is an overcurrent, it cannot be fused in time, which increases the safety risk of the battery.

[0112] In some embodiments, in order to improve the safety of the battery, the length L3 of the tail body 132 is 85%-95% of the diameter of the disk body 131. According to actual needs, the length of the tail body 132 is, for example, 12-20 mm. The tail body 132 can ensure smooth welding with the cap 120 and ensure the safety of the battery within the preferred length range. If the length of the tail body 132 is too short, the tail body 132 will not extend out of the shell 110 enough after the first bend, and the welding with the cap 120 cannot be completed; if the length of the tail body 132 is too long, the end of the tail body 132 away from the disk body 131 will contact the shell 110 when the cap 120 is closed and bent for the second time, causing the battery to short-circuit, and it will also occupy the internal space of the battery, affecting the arrangement of other components and normal operation.

[0113] In order to facilitate bending and welding, the tail body 132 is usually in the shape of a long strip. In some embodiments, as mentioned above, the tail body 132 has a first width W1, which satisfies: W1 = D2*sin(∠B / 2), where D2 is the diameter of the disc body 131, which refers to the longest line segment between two points on the arc 1312. According to actual needs, the diameter of the disc body 131 is, for example, 15-23 mm; ∠B takes the center of the arc 1312 as the vertex, and the two sides pass through the intersection of the fifth side 1322 and the sixth side 1323 of the tail body 132 with the full circle of the arc 1312 (reference Figure 7 ), for example, and 20°≤∠B≤40°. The larger the first width W1 of the tail body 132, the smaller the weldable area of ​​the disc body 131. Reasonable width design helps to retain the maximum weldable area, while ensuring that the tail body 132 has sufficient mechanical strength to prevent it from being broken during the production process, and at the same time facilitates the rapid passage of electrons and reduces the internal resistance of the battery.

[0114] In some embodiments, the tail body 132 has a second width W2 at the fuse slot 1321, and 3W1 / 8≤W2<3W1 / 4, that is, the second width W2 is 3 / 8 to 3 / 4 of the first width W1. The second width W2 in the present application refers to the change in the width of the tail body 132 relative to the first width W1 due to the design of the fuse slot 1321. Based on the definition of the second width W2 in the present application, the first width W1 in the present application also refers to the width of the tail body at a position other than the fuse slot 1321 on the tail body 132. The second width W2 of the tail body 132 at the fuse slot 1321 can balance the mechanical properties of the tail body 132 and the safety performance of the battery within a reasonable range. When the second width W2 is too small, the strength of the tail body 132 at the fuse slot 1321 is insufficient and it is easy to be broken when bent.

[0115] In some embodiments, the dimension L5 of the fuse slot 1321 along the length direction of the tail body 132 satisfies: 0<L5≤W1, that is, the length of the fuse slot 1321 in the vertical direction does not exceed the first width W1 of the tail body 132. Preferably, W1 / 4<L5≤3W1 / 4, that is, the dimension L5 is 1 / 4 to 3 / 4 of the first width W1. In the present application, the dimension of the fuse slot 1321 along the length direction of the tail body 132 refers to the length between the end of the fuse slot 1321 closest to the disc body 131 and the end farthest from the disc body 131. The dimension of the fuse slot 1321 along the length direction of the tail body 132 within a reasonable range helps to improve the safety of the battery. If the dimension is too large, the fuse position of the tail body 132 is difficult to determine, thereby increasing the safety risk of the battery; on the contrary, if the dimension is too small, the fuse sensitivity of the tail body 132 increases, and there is a possibility of fuse under safe current.

[0116] In some embodiments, Fig.10 As shown, the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 is 45%-65% of the overall cross-sectional area S1 of the tail body 132. Specifically, the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 is the cross-sectional area at the narrowest position of the fuse slot 1321, for example, Fig.10 As shown, when the cross section at this location is square, its cross-sectional area S2 = W2*T2; the overall cross-sectional area S1 of the tail body 132 is the cross-sectional area of ​​the position on the tail body 132 except the fuse slot 1321, S1 = W1*T2, wherein T2 is the thickness of the tail body 132, which is usually a uniform thickness. According to actual needs, T2 is, for example, 0.15-0.35mm. Within a reasonable minimum cross-sectional area S2 range, the tail body 132 can achieve a balance between battery safety and low internal resistance. When the minimum cross-sectional area S1 is too large, the tail body 132 cannot be quickly fused in thermal runaway, increasing safety risks; on the contrary, when the minimum cross-sectional area S2 is too small, on the one hand, the fuse sensitivity will be too high, and on the other hand, the internal resistance will be increased, seriously affecting the normal use of the battery. Of course, it is understandable that when calculating S1 and S2 above, the thickness of the tail body 132 at the fuse slot 1321 is the same as the thickness of the rest of the tail body 132, that is, the tail body 132 is of equal thickness, but it is not limited to this, and the thicknesses of the two can also be set to be different.

[0117] like Fig.11As shown, the tail body 132 includes a fifth side 1322 and a sixth side 1323 along its length direction, and a fourth side 1324 away from the disc body 131, the two ends of the fifth side 1322 are respectively connected to the fourth side 1324 and the first side 1311, and the two ends of the sixth side 1323 are respectively connected to the fourth side 1324 and the second side 1313, wherein the angle θ1 between the fifth side 1322 and the first side 1311 is 45-90°, and the angle θ2 between the sixth side 1323 and the second side 1313 is 45-90°. It can be understood that if the angles θ1 and θ2 are too small, the bending of the tail body 132 will cause the stress to be too concentrated at the angles θ1 and θ2, causing the disc body 131 to deform or even break; if the angles θ1 and θ2 are too large, it is impossible to ensure that the disc body 131 has a sufficient weldable area. In addition, a reasonable angle design of the angles θ1 and θ2 also helps the electrolyte to penetrate into the battery through the angles θ1 and θ2.

[0118] The tail body 132 is further described below with reference to embodiments and comparative examples. The following embodiments and comparative examples of the present application are designed with reference to ordinary 21 series cylindrical lithium batteries.

[0119] Embodiment 1:

[0120] Embodiment 1 provides a cylindrical lithium battery, which includes a housing 110, a cap 120, a positive current collector 130, a winding core 140, and a negative current collector 150. The positive current collector 130 includes a disk body 131 and a tail body 132 connected to each other, wherein the disk body 131 is connected to the positive terminal 141 of the winding core 140, and the tail body 132 is connected to the cap 120. The thickness of the tail body 132 along the length direction is constant, and at least one pair of fuse grooves 1321 are provided on the tail body 132, and the distance L4 between the center position of the fuse groove 1321 and the end of the tail body 132 away from the disk body 131 is 72% of the length L3 of the tail body 132, and the minimum cross-sectional area S2 of the tail body 132 at the fuse groove 1321 is 50% of the overall cross-sectional area S1 of the tail body 132.

[0121] Comparative Example 1:

[0122] Comparative Example 1 provides a cylindrical lithium battery, which differs from Example 1 in that the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 is 20% of the overall cross-sectional area S1 of the tail body 132 .

[0123] Comparative Example 2:

[0124] Comparative Example 2 provides a cylindrical lithium battery, which differs from Example 1 in that the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 is 85% of the overall cross-sectional area S1 of the tail body 132 .

[0125] Comparative Example 3:

[0126] Comparative Example 3 provides a cylindrical lithium battery, which differs from Example 1 in that a distance L4 between the center of the fuse slot 1321 and the end of the tail body 132 away from the disc body 131 is 90% of the length L3 of the tail body 132 .

[0127] The safety protection effect of the positive current collector 130 produced in the above embodiment and comparative example is evaluated in the following Table 2. The specific test method is: fix the sampled positive current collector 130 on the tooling of a high-power (rated power 15150W) programmable DC power supply device, set the measurement conditions as follows: voltage 20V, current 170A, delay time 10s, turn on the temperature sensing instrument and aim it at the positive current collector 130, click the recording function, and click to start the test on the instrument, and end the experiment when the fuse slot 1321 of the positive current collector 130 is observed to be blown, and record the time and current related curves obtained by the device, as well as the blown temperature read by the temperature sensing instrument.

[0128] Table 2

[0129] Disconnection temperature Fuse time; Example 1 90.3℃ 2.383s Comparative Example 1 85.9℃ 0.273s Comparative Example 2 100.2℃ 68.563s Comparative Example 3 88.6℃ 21.8s

[0130] It can be seen from Table 2 that when the distance L4 between the center position of the fuse slot 1321 and the end of the tail body 132 away from the disc body 131 is 72% of the length L3 of the tail body 132, and the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 is 50% of the overall cross-sectional area S1 of the tail body 132, the disconnection temperature and the fusing time of the fuse slot 1321 are relatively reasonable. When the ratio of the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 to the overall cross-sectional area S1 of the tail body 132 is too low, the fuse slot 1321 is relatively sensitive to temperature and will be quickly fused; on the contrary, when the ratio of the minimum cross-sectional area S2 of the tail body 132 at the fuse slot 1321 to the overall cross-sectional area S1 of the tail body 132 is too high, the sensitivity of the fuse slot 1321 to temperature becomes poor and cannot be quickly fused. When the ratio of the distance L4 between the center of the fuse slot 1321 and the end of the tail portion 132 away from the disk portion 131 to the length L3 of the tail portion 132 is too high, the fuse slot 1321 cannot be quickly fused.

[0131] In some embodiments, the material of the positive electrode current collecting disk 130 is aluminum. On the one hand, aluminum has the characteristics of low internal resistance and good conductivity. On the other hand, the melting point of aluminum is relatively low. When the battery thermally runs away, the fuse slot 1312 can be melted to cut off the current.

[0132] The winding core 140 is described in detail below.

[0133] It can be understood that the winding core 140 is formed by winding the positive electrode sheet, the negative electrode sheet and the separator after stacking. Figure 1 As shown, the winding core 140 is cylindrical as a whole, and in order to smoothly pass through the opening 114 and enter the inner cavity 113 of the housing 110, its diameter D5 is slightly smaller than the inner diameter of the housing 110. Figure 1 and Fig.12 As shown, it can be understood that after the winding core 140 is put into the shell, it is located in the area defined by the neck portion 1121 and the shell bottom 111 in the outer shell 110, that is, in the lower cavity 1132.

[0134] In this embodiment, the winding core 140 is provided with a positive terminal 141 and a negative terminal 142 opposite to each other. The positive terminal 141 is connected to the cap 120 via the positive current collecting disk 130 , and the negative terminal 142 is connected to the housing 110 via the negative current collecting disk 150 .

[0135] It is understandable that in order to improve the energy density of the battery and the welding effect with the positive electrode collector plate 130 and the negative electrode collector plate 150, the positive terminal 141 and the negative terminal 142 can be formed by flattening the full-pole ear. For example, the full-pole ear foil of the positive and negative electrode collectors is rotated and pressed as a whole for a certain stroke by a mechanical conical roller. Thus, on the one hand, the positive terminal 141 and the negative terminal 142 formed by the flattening process are stacked densely, without wasting space in the longitudinal direction. Thus, the utilization rate of the internal space of the housing 110 is high, which can further improve the energy density of the battery. On the other hand, the positive electrode flattening structure 141 and the negative electrode flattening structure 142 formed by the flattening process have a flat cross-section, and the two can be respectively abutted with the positive electrode collector plate 130 and the negative electrode collector plate 150, and the bonding effect is good, which is conducive to laser welding and can effectively reduce process defects such as cold welding.

[0136] In addition, during the winding process, a through winding core hole 143 is formed in the middle of the winding core 140 along the axial direction. The diameter D6 of the winding core hole 143 needs to consider the balance between the injection efficiency and the weldable area while ensuring the safety of welding.

[0137] The negative electrode current collecting disk 150 is described in detail below.

[0138] like Fig.12 and Fig.13As shown, the negative electrode current collecting disc 150 is circular as a whole. Along the thickness direction, the negative electrode current collecting disc 150 has a first side 151 and a second side 152 that are opposite to each other. Since the second side 152 is provided with a raised platform 1521 described below, when welding the negative electrode current collecting disc 150 to the outer shell 110 and the winding core 140, it is necessary to distinguish the direction. Specifically, the second side 152 is welded to the shell bottom 111 through the raised platform 1521, and the first side 151 is welded to the negative end 142 of the winding core 140. Thus, the welding connection between the winding core 140, the negative electrode current collecting disc 150 and the outer shell 110 is realized, and a passage is formed between the three. That is, the negative electrode current collecting disc 150 indirectly connects the winding core 140 to the outer shell 110.

[0139] To ensure that the raised platform 1521 fits well with the surface of the outer shell 110, in the present embodiment, the negative electrode current collecting plate 150 is provided with a raised platform 1521 with a flat surface on the second side 152, the surface of the raised platform 1521 is higher than the surface of the second side 152, and the surface area of ​​the raised platform 1521 is smaller than the surface area of ​​the second side 152, the surface of the raised platform 1521 is suitable for abutting against the inner surface of the shell bottom 111, and the surface flatness of the raised platform 1521 is 0.01-0.05mm. It is understandable that, since the surface of the raised platform 1521 is higher than the surface of the second side 152, that is, the surface of the raised platform 1521 is the top surface of the second side 152, after the negative electrode current collecting plate 150 is assembled into the outer shell 110, the surface of the raised platform 1521 will abut against the inner surface of the shell bottom 111, that is, the surface of the raised platform 1521 and the inner surface of the shell bottom 111 are closely fitted to each other, and a surface-to-surface contact connection is formed between the two, and then the area where the raised platform 1521 overlaps with the shell bottom 111 can be laser-welded through the outer surface 1112 of the bottom plate, so that the raised platform 1521 is welded to the outer shell 110. It is also understandable that if the flatness of the raised platform 1521 is too large, the fitting effect between it and the inner surface of the shell bottom 111 is not good, thereby affecting the welding quality; on the contrary, if the flatness of the raised platform 1521 is too small, it is difficult to process and the cost is too high.

[0140] In this embodiment, since the ratio of the diameter D7 of the negative electrode current collecting disk 150 to the diameter D5 of the winding core 140 is set at 90%-98%, the weldable area between the negative electrode current collecting disk 150 and the winding core 140 can be effectively increased, and the welding processability is good. At the same time, a smaller raised platform 1521 is set on the second side 152 of the negative electrode current collecting disk 150. Since the raised platform 1521 has a small area, it can ensure that it has good surface flatness during the processing process, so that the surface of the raised platform 1521 can be better fitted with the inner surface of the shell bottom 111, and the welding quality problems such as cold welding between the two can be effectively avoided. The battery using the negative electrode current collecting disk 150 has better performance and yield rate.

[0141] For the purpose of facilitating processing and reducing costs, in some embodiments, the raised platform 1521 is formed by the negative electrode current collector 150 through a stamping process, that is, the raised platform 1521 is formed integrally with the negative electrode current collector 150. Therefore, through a reasonable stamping die design, the negative electrode current collector 150 of this embodiment can be efficiently processed, and the negative electrode current collector 150 and the raised platform 1521 have high dimensional accuracy and good surface quality, which is convenient for welding with the winding core 140 and the housing 110. Of course, it is not limited to this, and the raised platform 1521 can also be formed in other ways. For example, the raised platform 1521 can be a sheet metal component with excellent welding performance and conductive performance, and the metal component can be combined with the surface of the second side 152 of the negative electrode current collector 150 by pressing, thereby forming the raised platform 1521.

[0142] In some embodiments, the raised platform 1521 is formed in the central area of ​​the second side 152, so that after the negative electrode current collecting plate 150 is assembled into the outer shell 110, the raised platform 1521 can be aligned with the central area of ​​the shell bottom 111, making it convenient to weld the outer shell 110 and the raised platform 1521 using welding equipment.

[0143] Furthermore, the shape of the raised platform 1521 is circular, so that the raised platform 1521 can be co-centered with the negative electrode current collecting plate 150, which is convenient for stamping by a stamping die. Of course, the shape of the raised platform 1521 is not limited to a circle, for example, the raised platform 1521 can also be a square, a triangle, etc.

[0144] like Fig.12 and Fig.13 As shown, it can be understood that the raised platform 1521 is punched out on the second side 152 of the negative electrode current collector 150 through the stamping process, and accordingly, a recessed portion 1511 is formed at a position corresponding to the raised platform 1521 on the first side 151. For the purpose of conveniently welding the negative electrode current collector 150 and the winding core 140, in some embodiments, the first side 151 has an annular welding area 1512 around the recessed portion 1511, and the surface of the welding area 1512 is suitable for abutting against the negative terminal 142 of the winding core 140. For example, the welding area 1512 is also configured to have a flat surface so that the surfaces of the two can fit closely to each other to improve the welding quality.

[0145] like Fig.13As shown, in some embodiments, the diameter of the raised platform 1521 is D8, satisfying D8 / D7=28%-38%. As mentioned above, the diameter D7 of the negative electrode current collecting disk 150 is substantially consistent with the diameter of the winding core 140. If the diameter of the raised platform 1521 is too large, its surface flatness will deteriorate, and its bonding effect with the inner surface of the shell bottom 111 will be poor, thereby affecting the welding quality; on the contrary, if the diameter of the raised platform 1521 is too small, the weldable area of ​​the raised platform 1521 is small, and it is easy to desolder during welding, which will increase the difficulty of subsequent welding process and increase the cost.

[0146] Furthermore, if Fig.14 As shown, in some embodiments, the height difference between the surface of the raised platform 1521 and the surface of the second side 152 is H3, and the thickness of the negative electrode collector 150 is T3, which satisfies: H3 / T3=18%-30%. It can be understood that if the raised platform 1521 is set too high, that is, H3 / T3 is too large, then during the assembly process, the winding core 140 will squeeze and deform the periphery of the negative electrode collector 150, and will also occupy additional longitudinal space of the battery; on the contrary, if the raised platform 1521 is set too low, that is, H3 / T3 is too small, then the raised platform 1521 is difficult to process, for example, it is difficult to form the raised platform 1521 through a stamping process.

[0147] In some embodiments, the negative electrode current collecting disc 150 is made of copper, and a nickel layer is plated on the surface of the negative electrode current collecting disc 150. Compared with the negative electrode current collecting disc 150 made of copper-nickel alloy, the copper material as the base material has the characteristic of extremely low internal resistance. At the same time, by plating the nickel layer on the surface of the negative electrode current collecting disc 150, the corrosion resistance of the negative electrode current collecting disc 150 can be effectively improved.

[0148] Furthermore, the thickness of the nickel layer is set to 0.08-1.5 μm, more preferably 0.9-1.1 μm. It is understandable that if the thickness of the nickel layer is too small, it cannot play an anti-oxidation role; on the contrary, if the thickness of the nickel layer is too thick, on the one hand, the difficulty of the nickel plating process is increased, and the cost is increased, and on the other hand, the hardness of the negative electrode collector 150 is increased, resulting in a decrease in the plasticity of the negative electrode collector 150, and at the same time, the internal resistance is increased, resulting in a decrease in battery performance.

[0149] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present implementation. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0150] Although examples of the present embodiment have been shown and described, those skilled in the art will appreciate that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present embodiment, and the scope of the present embodiment is defined by the claims and their equivalents.

Claims

1. A cylindrical lithium battery, characterized in that: The invention comprises a housing (110), a cap (120), a positive electrode current collecting disk (130), a winding core (140) and a negative electrode current collecting disk (150), wherein the positive terminal (141) of the winding core (140) is connected to the housing (110) through the cap (120), and the negative terminal (142) of the winding core (140) is connected to the housing (110) through the negative electrode current collecting disk (150); The positive electrode current collecting disc (130) comprises a disc body (131) and a tail body (132) connected to each other, the disc body (131) is connected to the positive terminal (141), and the tail body (132) is connected to the cap (120), wherein: A circular first hole (1315) is provided at the center of the disk body (131), and at least one circular second hole (1316) is provided on the periphery of the first hole (1315), a diameter D3 of the first hole (1315) is 25%-35% of a diameter D2 of the disk body (131), and a sum of areas of all the second holes (1316) is 0.9-1.5 times the area of ​​the first hole (1315); At least one fuse slot (1321) is provided on the tail body (132), and a distance L4 between a center position of the fuse slot (1321) and an end of the tail body (132) away from the disc body (131) is 68%-78% of a length L3 of the tail body (132), and at positions on the tail body (132) other than the fuse slot (1321), the tail body (132) has an overall cross-sectional area S1, and the tail body (132) has a minimum cross-sectional area S2 at the position of the fuse slot (1321), and the minimum cross-sectional area S2 is 45%-65% of the overall cross-sectional area S1.

2. The cylindrical lithium battery according to claim 1, characterized in that: The shape of the disk body (131) is a closed axially symmetrical figure consisting of a first side (1311), an arc (1312), a second side (1313) and a third side (1314) connected end to end in sequence; the shape of the tail body (132) is a closed axially symmetrical figure consisting of a third side (1314), a fifth side (1322) extending along the length direction of the tail body (132), a fourth side (1324) away from the disk body and a sixth side (1323) extending along the length direction of the tail body (132) connected end to end in sequence, wherein two ends of the fifth side are respectively connected to the fourth side (1324) and the first side (1311), and two ends of the sixth side (1323) are respectively connected to the fourth side (1324) and the second side (1313).

3. The cylindrical lithium battery according to claim 2, characterized in that: The outer shell (110) comprises a shell bottom (111); the negative electrode current collecting plate (150) has a first side (151) and a second side (152) opposite to each other; the first side (151) is connected to the negative terminal (142); the second side (152) is provided with a flat raised platform (1521); the raised platform (1521) is connected to the inner surface of the shell bottom (111).

4. The cylindrical lithium battery according to claim 3, characterized in that: The positive terminal (141) and the negative terminal (142) are both formed by flattening the entire electrode tab, and the side of the disk body (131) facing the positive terminal (141) abuts against the positive terminal (141) formed by flattening the entire electrode tab; the raised platform (1521) is formed by integral stamping of the negative electrode current collecting disk (150), and a recessed portion (1511) is formed on the first side (151) at a position corresponding to the raised platform (1521), and a welding area (1512) is formed on the first side (151) around the recessed portion (1511), and the surface of the welding area (1512) abuts against the negative terminal (142) formed by flattening.

5. The cylindrical lithium battery according to claim 3, characterized in that: The diameter D2 of the disk body (131) is 80%-95% of the diameter D5 of the winding core (140); and the diameter D7 of the negative electrode current collecting disk (150) is 90%-98% of the diameter D5 of the winding core (140).

6. The cylindrical lithium battery according to claim 2, characterized in that: The diameter D3 of the second hole (1316) is 50%-70% of the diameter D2 of the first hole (1315); the flatness of the surface of the raised platform (1521) is 0.01-0.05 mm.

7. The cylindrical lithium battery according to claim 2, characterized in that: The winding core (140) has a winding core hole (143) extending therethrough, and a diameter D3 of the first hole (1315) is 1.4-1.8 times a diameter D6 of the winding core hole (143); the raised platform (1521) is circular and located at the center of the second side (152), and a diameter D8 of the raised platform (1521) is 28%-38% of a diameter D7 of the negative electrode current collecting disk (150).

8. The cylindrical lithium battery according to claim 2, characterized in that: The length L3 of the tail body (132) is 85%-95% of the diameter D2 of the disc body (131); the height difference H3 between the surface of the raised platform (1521) and the surface of the first side (151) is 18%-30% of the thickness T3 of the negative electrode current collecting disc (150).

9. The cylindrical lithium battery according to claim 8, characterized in that: The thickness of the tail body (132) is 0.15-0.35 mm.

10. The cylindrical lithium battery according to claim 2, characterized in that: The material of the positive electrode current collecting disc (130) is aluminum, the material of the negative electrode current collecting disc (150) is copper, and the surface of the negative electrode current collecting disc (150) is plated with a nickel layer, and the thickness of the nickel layer is 0.08-1.5 μm.

11. The cylindrical lithium battery according to any one of claims 2 to 10, characterized in that: The cover cap (120) comprises an explosion-proof valve plate (122) and a terminal plate (124) which are stacked, the tail body (132) being connected to the bottom of the terminal plate (124), the explosion-proof valve plate (122) being provided with a first notch (1221a) and a second notch (1221b), the first notch (1221a) being a closed circle connected at the head and tail ends, the second notch (1221b) being a line segment, and the first notch (1221a) and the second notch (1221b) intersecting.

12. The cylindrical lithium battery according to claim 11, characterized in that: The first width W1 of the tail body (132) is equal to D2*sin(∠B / 2), and 20°≤∠B≤40°, wherein ∠B has the center point corresponding to the arc (1312) as its vertex, and its two sides respectively pass through the intersection of the fifth side (1322) and the sixth side (1323) with the full circle where the arc (1312) is located.

13. The cylindrical lithium battery according to claim 12, characterized in that: The second width W2 of the tail body (132) at the fuse groove (1321) is 3 / 8-3 / 4 of the first width W1; 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, and the depth H1 of the first notch (1221a) is 30%-60% of the thickness T1 of the thinning portion (1222).

14. The cylindrical lithium battery according to claim 12, characterized in that: The dimension L5 of the fuse groove (1321) along the length direction of the tail body (132) is 0<L5≤W1; the diameter D1 of the first notch (1221a) is equal to the length L1 of the second notch (1221b).

15. The cylindrical lithium battery according to claim 14, characterized in that: The dimension L5 of the fuse groove (1321) along the length direction of the tail body (132) is 1 / 4 to 3 / 4 of the first width W1; the depth H1 of the first notch (1221a) is less than the depth H2 of the second notch (1221b), and the depth of the middle part of the second notch (1221b) is greater than the depth at both ends.

16. The cylindrical lithium battery according to claim 11, characterized in that: The angle θ1 between the fifth side (1322) and the first side (1311) is 45-90°, and the angle θ2 between the sixth side (1323) and the second side (1313) is 45-90°; the bottoms of the first notch (1221a) and the second notch (1221b) are provided with chamfered portions, and the radius R of the chamfered portions is 0.05-0.15 mm.

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