All-tab cylindrical battery

Abstract

The utility model belongs to the technical field of battery processing, and discloses a full-tab cylindrical battery. The full-tab cylindrical battery comprises a battery shell, a roll core and two current collecting pieces, the roll core and the two current collecting pieces are contained in the battery shell, the roll core is formed by winding a positive plate, a diaphragm, a negative plate and a diaphragm which are sequentially stacked, a positive electrode foil of the positive plate is provided with a positive electrode active material layer and a blank foil located at the axial end of the roll core, and a negative electrode foil of the negative plate is provided with a negative electrode active material layer. A negative electrode foil of the negative electrode sheet has a negative electrode active material layer and a blank foil located at the axial end of the winding core, one or both of the blank foil of the positive electrode sheet and the blank foil of the negative electrode sheet have a flat surface formed by being bent toward the central axis of the winding core and overlapping, a groove is formed in the flat surface, and the flat surface is joined to the corresponding collector sheet. And a welding wire for spiral welding faces the central axis of the roll core along the periphery of the roll core. An existing direct welding mode is changed into spiral welding, so that molten liquid metal has enough time to fill a welding wire, the stability of the welding wire is improved, and welding defects are reduced.

Description

TECHNICAL FIELD

[0001] The utility model relates to battery processing technical field especially relates to a full tab cylindrical battery. BACKGROUND

[0002] In order to greatly promote the battery overcurrent capacity, reduce the battery heat output, break through the bottleneck of cylindrical battery, lithium battery adopts the technology of full tab. Among them, the winding core and two current collectors of full tab cylindrical battery are connected by welding, and the winding core and two current collectors are welded in the prior art, the melting width is relatively narrow, and the typical beam waist shape is presented, complete penetration under the same total energy input, and the welding base material collapses, that is, the surface tension of excessive molten liquid metal cannot bear its gravity and collapses along the back.

[0003] Therefore, it is urgent to design a full tab cylindrical battery to solve the above problems. INVENTION CONTENTS

[0004] The utility model discloses a full tab cylindrical battery, avoids the collapse phenomenon after winding core and current collector welding, improves the stability of welding, and reduces the welding defect.

[0005] To achieve this purpose, the utility model adopts the following technical scheme:

[0006] Full tab cylindrical battery, including battery shell, winding core and two current collectors, the winding core and the two current collectors are accommodated in the battery shell, the winding core is wound by the positive plate, the diaphragm, the negative plate and the diaphragm in turn, the positive foil of the positive plate has a positive active material layer and a blank foil located at the axial end of the winding core, the negative foil of the negative plate has a negative active material layer and a blank foil located at the axial end of the winding core, either one or both of the blank foils of the positive plate and the blank foils of the negative plate have a flat surface formed by bending towards the center axis of the winding core and overlapping, and a groove is formed on the flat surface, the flat surface is engaged with the corresponding current collector, the flat surface is divided into several independent fan-shaped welding areas by the groove, and the welding mode of at least one welding area is spiral welding, the welding line of the spiral welding is along the outer periphery of the winding core towards the center axis of the winding core, and the welding line presents a straight line with a certain width.

[0007] As an optional scheme, the current collector and the corresponding flat surface are connected by a plurality of straight welding lines, the welding line is formed by spiral welding, and a plurality of welding lines are evenly distributed in the center of the winding core in a radial manner.

[0008] As an optional solution, the length of the welding wire is A, the thickness of the winding core is X, 25%≤A / X≤80%, wherein the winding core center forms a through hole, the outer radius of the winding core is R1, the radius of the through hole is R2, and X=R1-R2.

[0009] As an optional solution, the spiral diameter of the welding wire is D, 0.2mm≤D≤1mm, the pitch of the welding wire is Y, 0.2mm≤Y≤0.7mm, and D>Y.

[0010] As an optional solution, the width of the welding wire is W, 0.5mm≤W≤0.7mm.

[0011] As an optional solution, the length of the welding wire is A, 2.1mm≤A≤6.78mm.

[0012] As an optional solution, one welding wire is formed in each of the welding areas.

[0013] As an optional solution, the flat surface is divided into a positive electrode flat surface and a negative electrode flat surface located at both ends of the winding core, wherein,

[0014] The tensile force F between the negative electrode flat surface and the corresponding current collector plate is ≥15N; and / or

[0015] The tensile force F between the positive electrode flat surface and the current collector plate is ≥5N.

[0016] As an optional solution, the positive electrode sheet comprises a first blank foil from top to bottom and the positive electrode active material layer, the upper part of the plurality of the first blank foils is bent inward to form the positive electrode flat surface, the lower part of the first blank foil forms a vertical area L, and the top of the negative electrode sheet is located in the vertical area L.

[0017] As an optional solution, the top of the negative electrode sheet divides the vertical area L from top to bottom into an outer vertical area L1 and an inner vertical area L2, the height of the outer vertical area L1 is L1, the height of the inner vertical area L2 is L2, and 0.2≤L1 / L2≤2.

[0018] The beneficial effects of the utility model lie in:

[0019] The utility model provides a kind of full tab cylindrical battery, by the form of existing linear welding or point-shaped welding is changed into spiral welding, the track of laser is no longer linearly arranged, laser swing welding can make the heat of laser gather is dispersed, significantly widen the fusion width of welding line, reduce welding line melting depth, effectively improve the problem of collapse;Laser swing and the energy distribution of conventional laser welding exist great difference, the heat transfer behavior of molten pool and welding line appearance change, spiral welding mainly is to affect laser energy distribution on welding position and molten pool spoon hole dynamic behavior (speed, frequency stirring molten pool), with laser beam moves along spiral line path, molten pool upper surface is approximately circular, and boundary is smooth, with welding process proceeds, molten pool as a whole moves forward, due to spiral line track laser movement track is long, line energy is low, laser average scanning speed improves, the concentration of energy drops, molten pool surface energy distribution is more uniform, molten pool shape fluctuation is minimal and expand heat action area and molten pool, reduce temperature gradient, so that molten liquid metal has enough time to fill welding line, to improve welding line stability and reduce welding defects. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more obviously and easily explain the embodiments of the present application or the technical solutions in the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced as follows. The drawings described below are some embodiments of the present application. Those skilled in the art can also obtain other drawings based on these drawings without creative labor.

[0021] Figure 1 is the explosion view of the winding core, the positive current collector tab and the negative current collector tab provided by the embodiment of the present application.

[0022] Figure 2 is the layered diagram of the winding core provided by the embodiment of the present application.

[0023] Figure 3 is the partitioned schematic diagram of the positive flat surface of the winding core provided by the embodiment of the present application.

[0024] In the drawings:

[0025] 10, winding core;

[0026] 11, flat surface; 111, welding area; 1111, welding line; 112, groove; 113, intersection point;

[0027] 13, positive tab; 131, positive active material layer; 132, first blank foil; 14, negative tab; 15, separator;

[0028] 16, positive flat surface; 17, negative flat surface; 18, through hole;

[0029] 20, current collector tab. DETAILED DESCRIPTION

[0030] The utility model will be described in further detail below in combination with the drawings and embodiments. It can be understood that the specific embodiments described herein are merely used to explain the utility model and not limit the utility model. In addition, it should be noted that only the parts related to the utility model are shown in the drawings for the convenience of description, not all the structures.

[0031] In the description of the utility model, unless otherwise explicitly specified and limited, the terms "connected", "connected", "fixed" should be understood broadly, for example, it can be fixedly connected, or it can be detachably connected, or it can be integrated; it can be mechanically connected, or it can be electrically connected; it can be directly connected, or it can be indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship of two elements. For ordinary skilled in the art, the specific meaning of the above terms in the utility model can be understood according to the specific circumstances.

[0032] In the utility model, unless otherwise explicitly specified and limited, the "upper" or "lower" of the first feature to the second feature can include that the first and second features are in direct contact, or the first and second features are not in direct contact but are in contact through another feature between them. Moreover, the "upper", "upper" and "upper" of the first feature to the second feature include that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than that of the second feature. The "below", "below" and "below" of the first feature to the second feature include that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than that of the second feature.

[0033] In the description of the embodiment, the terms "upper", "lower", "left", "right" and other orientation or position relationship are based on the orientation or position relationship shown in the drawings, only for the convenience of description and simplification of operation, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, therefore cannot be understood as a limitation of the utility model. In addition, the terms "first" and "second" are only used to distinguish in description and have no special meaning.

[0034] As Figure 1 The structure of the full-tab cylindrical battery of an embodiment of the present application (only the winding core 10 and two current collectors 20 are shown), see Figure 2 The winding core 10 is wound by the positive plate 13, the separator 15, the negative plate 14 and the separator 15 in turn, and the whole is cylindrical. As Figure 2As shown, in an optional embodiment, the positive active material layer 131 covers most of the positive sheet 13, and the negative active material layer covers most of the negative sheet 14. In the unwound state, both ends of the positive sheet 13 and the negative sheet 14 in the width direction (i.e. the positions not coated with active material) form blank foils. As shown, Figure 2 As shown, taking the positive sheet 13 as an example, the position on the positive foil not coated with the positive active material layer 131 forms a first blank foil 132. Of course, the part on the negative foil not coated with the negative active material forms a second blank foil (not marked, Figure 2 As shown, in the center of the winding core 10, one end of the winding core 10 away from the first blank foil 132). As shown, Figure 2 As shown, in the winding process of the winding core 10, in the axial direction, the positive active material layer 131 and the negative active material layer (not shown in the figure) are arranged staggered, so that the blank foils of the positive sheet 13 and the negative sheet 14 are wound in opposite directions to form the winding core 10, and the upper and lower end faces (the lower end face is not shown) are pressed flat by the flattening device to form the flat face 11, and the groove 112 (see Figure 3 ) is formed on the flat face 11. The groove 112 can absorb the wrinkles formed by the inward bending of the blank foils of the multiple layers of the positive sheet 13 and the blank foils of the negative sheet 14, reduce the wrinkling of the flat face 11, and improve the flatness of the flat face.

[0035] The flattening method in the present application can be understood as follows: first, the tab area is pre-pressed by the pre-pressing device to form several grooves, and the whole tab is formed to be inwardly inclined, and then the device is transferred to the flattening mechanism for flattening operation to form the flat face. The above-mentioned flattening method does not involve cutting and rubbing of the tab, and the groove 112 and the flat face 11 are continuous and integrated in physics, and can also avoid the damage of the tab and the generation of metal debris caused by the rubbing method.

[0036] As shown, Figure 2 The winding core 10 is accommodated in the battery shell in the state of electrolyte impregnation. The positive foil can be a metal foil made of aluminum or aluminum alloy, and the material of the negative foil can be a metal foil made of copper or copper alloy.

[0037] As shown, Figure 2 As shown, in an optional embodiment, there is a through hole 18 in the center axis of the winding core 10, and a positioning pin (not shown in the figure) is inserted into the through hole 18 for welding the current collector tab 20 and the bottom of the battery shell. As shown, Figure 3 As shown, the positive blank foil and the negative blank foil are bent to form the flat face 11, and the bending direction is from the outer periphery of the winding core 10 towards the through hole 18, and the adjacent blank foils of the positive sheet 13 or the negative sheet 14 are bent to overlap each other.

[0038] As shown, Figure 1 and Figure 2As shown, in an optional embodiment, the current collector tab 20 is divided into a positive electrode current collector tab 30 and a negative electrode current collector tab 40, the positive electrode current collector tab 30 is welded with the flat surface 11 formed by the positive electrode blank foil, the positive electrode current collector tab 30 can be a metal plate or a metal sheet made of a single or composite material of aluminum or aluminum alloy, the negative electrode current collector tab 40 is welded with the flat surface 11 formed by the negative electrode blank foil, the negative electrode current collector tab 40 can be a metal plate or a metal sheet made of a single or composite material of nickel, nickel alloy, copper or copper alloy. The positive electrode current collector tab 30 has a hole near the center, the position of the hole is the position corresponding to the through hole 18, the negative electrode current collector tab 40 can be a circular current collector tab or a circular current collector tab with a circular protruding portion at the center. The center of the current collector tab 20 at one end of the negative electrode is further welded with the bottom of the battery shell through an externally inserted positioning pin.

[0039] It can be understood that the Figures 1 to 3 are only schematic, for example, the actual number of layers of the winding core 10 is subject to the embodiment. In an optional embodiment, the positive electrode active material layer 131 contains any one or more than two of the positive electrode materials capable of embedding and de-embedding lithium. The positive electrode active material layer 131 can further contain any one or more than two of the other materials such as positive electrode binder and positive electrode conductive agent. The positive electrode material can be lithium iron phosphate or nickel-cobalt-manganese ternary material, nickel-cobalt-aluminum ternary material and other existing lithium ion battery positive electrode materials.

[0040] In an optional embodiment, the negative electrode material can be a carbon material, such as artificial graphite and natural graphite, and other existing lithium ion battery negative electrode materials.

[0041] In an optional embodiment, the separator 15 can be a PE film, a PP film or a composite film, wherein the composite film includes at least two of a PP film, a PE film and a PP film. Of course, in an optional embodiment, the separator 15 can also be other similar ceramic-coated porous membranes.

[0042] In an optional embodiment, the electrolyte contains a solvent and an electrolyte salt. In addition, the electrolyte can further contain any one or more than two of the other materials such as additives.

[0043] In an optional embodiment, the aforementioned solvent contains any one or more than two of the non-aqueous solvents such as organic solvents. The non-aqueous electrolyte is so-called non-aqueous electrolyte, and the non-aqueous solvent can be, for example, a cyclic carbonate, a chain carbonate, a lactone, a chain carboxylate, a nitrile (mononitrile) and the like.

[0044] In an alternative embodiment, the aforementioned electrolyte salt may, for example, include any one or two or more of lithium salts and the like. In addition to this, the electrolyte salt may, for example, also include a salt other than a lithium salt. The salt other than a lithium salt may, for example, be a light metal salt other than lithium and the like.

[0045] In one embodiment, the battery case is a metal case, which may, for example, be a steel case, an aluminum case, and further preferably a steel case.

[0046] In an alternative embodiment, the aforementioned lithium salt may, for example, be lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium tetraphenylborate (LiB(C6H5)4), lithium methanesulfonate (LiCH3SO3), lithium trifluoromethanesulfonate (LiCF3SO3), lithium tetrachloroaluminate (LiAlCl4), lithium disilicon hexafluoride (Li2SF6), lithium chloride (LiCl), and lithium bromide (LiBr), and the like. Among these, the aforementioned lithium salt may, for example, be any one or two or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium perchlorate, and lithium hexafluoroarsenate, and further preferably lithium hexafluorophosphate. The content of the electrolyte salt is not particularly limited, and is preferably 0.3 mol / kg to 3 mol / kg with respect to the solvent.

[0047] In the prior art, after the winding core and the two current collectors are welded, the molten width is narrow and presents a typical waist shape, complete penetration occurs under the same total energy input, and the welding base material collapses, that is, the surface tension of the excess molten liquid metal cannot support its gravity and collapses along the back.

[0048] The present embodiment provides a full-tab cylindrical battery, as shown in Figures 1 to 3 Either one or both of the blank foils of the positive electrode tab 13 and the blank foils of the negative electrode tab 14 have a flat surface 11 formed by bending toward the center axis of the winding core 10 and overlapping, and a groove 112 is formed in the flat surface 11, the flat surface 11 is engaged with the corresponding current collector 20, the flat surface 11 is divided into a plurality of independent fan-shaped welding areas 111 by the groove 112, the welding method of at least one welding area 111 is spiral welding, the welding line 1111 of the spiral welding is along the outer periphery of the winding core 10 toward the center axis of the winding core 10, and the welding line 1111 presents a straight line with a certain width.

[0049] It can be understood that, by changing the existing direct welding form to spiral welding, the laser track is no longer arranged in a straight line or point welding, and the laser swing welding can disperse the heat of the laser, significantly widen the fusion width of the welding line 1111, reduce the welding line 1111 penetration, and effectively improve the collapse problem; the laser swing and the energy distribution of the conventional laser welding are greatly different, the heat transfer behavior of the molten pool and the welding line 1111 appearance change, and the spiral welding mainly affects the energy distribution of the laser on the welding position and the dynamic behavior (speed, frequency stirring molten pool) of the molten pool keyhole, with the movement of the laser beam along the spiral line path, the upper surface of the molten pool is approximately circular, and the boundary is smooth, with the welding process, the molten pool moves forward as a whole, due to the long spiral line track laser movement track, low line energy, the average scanning speed of the laser is improved, the energy concentration decreases, the energy distribution of the molten pool surface is more uniform, the molten pool shape fluctuation is small, and the heat action area and the molten pool are expanded, the temperature gradient is reduced, the molten liquid metal has enough time to fill the welding line 1111, thereby improving the stability of the welding line 1111 and reducing the welding defects.

[0050] The spiral welding in the application refers to spiral direction movement, forming a spiral welding line 1111, and the spiral welding line 1111 is preferably a straight line type or a welding line 1111 close to a straight line.

[0051] Optionally, as shown in Figure 3 The current collector tab 20 and the corresponding flat surface 11 are connected through a plurality of straight welding lines 1111, and the welding line 1111 is formed by spiral welding. The welding line 1111 is straight, simple in shape, and convenient for welding. Since the welding is spiral welding, it is not necessary to further change the welding track to increase the welding strength, and the straight spiral welding meets the technical requirements of the high-power full-tab cylindrical battery of the application.

[0052] Optionally, as shown in Figure 3 A plurality of welding lines 1111 are distributed radially with the center of the winding core 10. Through the above arrangement, the uniformity of the welding of the flat surface 11 and the corresponding current collector tab 20 is improved. In the embodiment, as shown in Figure 3 The number of welding lines 1111 is eight, and in other embodiments, the number of welding lines 1111 can also be three, four, five, etc., which is not limited here.

[0053] Optionally, as shown in Figure 3As shown, the length of the bonding wire 1111 is defined as A, the thickness of the core 10 is X, a through hole 18 is formed in the center of the core 10, the outer radius of the core 10 is R1, the radius of the through hole 18 is R2, X = R1 - R2, 25% ≤ A / X ≤ 80%, the preferred range is 45-70%, for example, a 21 series core 10 is selected. In a specific embodiment, the diameter of the core 10 is 20.45 mm, the diameter of the through hole 18 on the inner circumference is 3.5 mm, and the thickness X (inner and outer diameters) of the core 10 is 8.4 mm. If the length of the solder wire 1111111 is A, then the length of the solder wire 1111 is 2.1mm ≤ A ≤ 6.78mm. Preferably, the length of the solder wire 1111 is 3.8mm ≤ A ≤ 6mm. Optionally, the length A of the solder wire 1111 can be 2mm, 2.5mm, 2.8mm, 3mm, 3.3mm, 3.5mm, 4mm, 4.2mm, 4.5mm, 4.8mm, 5mm, 5.5, 5.7, 5.9, 6, 6.4, 6.7, etc., and is not limited here.

[0054] Optionally, regarding another parameter of the welding wire 1111, the spiral diameter D and pitch Y of the welding wire 1111, as the size of the core 10 changes, the diameter D of the welding wire 1111 can be adjusted according to the product requirements, with a range of 0.2mm ≤ D ≤ 1mm. The pitch can be selected as 0.2mm ≤ Y ≤ 0.7mm. However, to ensure that the spiral welds intersect, D > Y. These parameter settings ensure that the laser's trajectory overlaps between the previous and next spirals, guaranteeing the adequacy of the spiral welding.

[0055] Optionally, the width of the bonding wire 1111 is W, 0.5mm≤W≤0.7mm. For example, W can be 0.5mm, 0.55mm, 0.6mm, 0.65mm, 0.7mm, etc., which are not limited here. That is, a certain width refers to the width W of the bonding wire 1111.

[0056] Optionally, such as Figure 3 As shown, a weld line 1111 is formed within each welding area 111. This further improves the uniformity of the welding position, thereby improving the uniformity of the welding connection force when the current collector 20 is welded to the flat surface 11.

[0057] Optionally, such as Figure 1As shown, the two flat surfaces 11 of the core 10 are the positive electrode flat surface 16 and the negative electrode flat surface 17 located at both ends of the core 10, respectively. The overall flatness of the positive electrode flat surface 16 (i.e., the positive electrode tab) of the core 10 is less than or equal to 0.25 mm. The positive electrode flat surface 16 of the core 10 is divided into several welding areas 111, and the flatness of each welding area 111 is less than or equal to 0.2 mm. It is understandable that technicians have found that the positive electrode flat surface 11 of the prior art has many wrinkles, and the flatness of the positive electrode flat surface 11 before welding is generally above 0.75 mm. Due to the large flatness of the positive electrode flat surface 11, it is easy to have a poor weld when welding with the current collector 20. In this embodiment, by controlling the overall flatness of the positive electrode flat surface 11 to less than or equal to 0.25 mm and the flatness within each welding area 111 to within 0.2 mm, the welding area 111 and the current collector 20 have better fit when welded together. The gap within 0.2 mm allows the positive electrode flat surface 11 and the current collector 20 to completely melt under the high temperature of the welding gun during welding, reducing the occurrence of incomplete welding. This ensures that the internal resistance of the battery is reduced after the core 10 is assembled, thus ensuring excellent battery performance.

[0058] Optionally, such as Figure 1 As shown, the overall flatness of the negative electrode flat surface 17 (i.e., the negative electrode lug) of the core 10 is less than or equal to 0.22 mm. The negative electrode flat surface 17 of the core 10 is divided into several welding areas 111 (not shown in the figure, the negative electrode flat surface 17 and the welding areas 111 can be referenced). Figure 2 The positive electrode flat surface 16 and welding area 111 are designed with a flatness of less than or equal to 0.2 mm for each welding area 111. Similarly, the overall flatness of the negative electrode flat surface 17 is controlled to be less than or equal to 0.22 mm, and the flatness of each welding area 111 is controlled to be within 0.2 mm. When welding with the current collector 20, the welding area 111 and the current collector 20 have a better fit. The gap within 0.2 mm allows the negative electrode flat surface 17 and the current collector 20 to completely melt under the high temperature of the welding gun during welding, reducing the occurrence of cold solder joints. In other words, the flatness of the two flat surfaces 11 of the core 10 is lower than that of the prior art, the welding is more complete, cold solder joints are avoided, and the overall performance of the battery is improved.

[0059] Taking the positive electrode flat surface 16 of the core 10 as an example, before pressing, the blank foil of the positive electrode foil extends along the axial direction of the core 10. The pressing fixture flattens the top of the blank foil of the positive electrode foil (that is, the first blank foil 132) (part of the first blank foil 132) to form the positive electrode flat surface 16. The flattened part is the bending part, and the length of the bending part bent inward is W.

[0060] Among them, such as Figure 2As shown, the blank foil of the positive electrode 13 (i.e., the first blank foil 132) and the blank foil of the negative electrode 14 are discussed separately for positive and negative electrodes due to the different flattening structures. The blank foil of the positive electrode 13 can be divided into the form of L+W, where L is the vertical region L and W is the bending region W. Due to the design of the electrode structure, the negative electrode 14 will be larger than the positive electrode 13 in the width direction, and the entire negative electrode 14 will cover the positive electrode 13. Therefore, in the width direction of the electrode (i.e. the length direction of the core 10), the vertical region L can be further divided into the outer vertical region L1 and the inner vertical region L2, L=L1+L2, and the blank foil of the entire positive electrode 13 is L+W. Generally, since the physical stiffness requirements of L1 and L2 are much greater than those of the W section, in actual winding design, L2 is coated with ceramic slurry or insulating adhesive to increase its stiffness and resist bending. Simultaneously, its insulating coating effectively alleviates the internal shortness of the positive electrode 13 and the negative electrode 14. For the L1 section, depending on the needs, most or all of L1 is also coated with ceramic slurry or insulating adhesive to increase its stiffness and resist bending. The coatings on L1 and L2 are continuous coatings, and both can be made of the same material and coated simultaneously. This can be understood as the vertical region L having stronger physical stiffness than the bending region W, ensuring that the vertical region L maintains a generally vertical orientation during flattening and preventing excessive interference with the negative electrode 14.

[0061] Optionally, the tension F between the negative electrode flat surface 11 and the corresponding current collector 20 is ≥15N; the tension F between the positive electrode flat surface 16 and the current collector 20 is ≥5N, preferably between 6N and 10N. The connection between the core 10 and the two current collectors 20 is also more secure. When the battery is subjected to external impact or when it is subjected to a roller test, the core 10 and the two current collectors 20 are less likely to separate, and the strength of the battery, i.e., its anti-collision performance, is also improved.

[0062] In the structure of this invention, particularly with regard to the positive and negative electrode flat surfaces 16 being divided into several independent fan-shaped welding areas 111 by eight corresponding slots 112, this invention finds that the welding of the flat surfaces 11 and the current collector 20, using a practical spiral welding technique, is far superior to linear welding and spot welding.

[0063] Table 1 compares spiral welding, wire welding, and spot welding.

[0064] Table 1

[0065]

[0066] Each type of welding wire 1111 welds 100 coil cores 10. The spiral welding wire 1111 is the structure of this invention. Straight welding and spot welding are simply replaced in their original positions with straight welding and discrete spot welding for comparison. Finally, the positive / negative electrode pull force, internal resistance, and defect rate were compared. The spiral welding has the highest pull force and the smallest fluctuation. When assembled into a battery, the internal resistance of the spiral welding wire 1111 is the lowest and the tolerance is smaller, meeting the internal resistance requirements. After welding, the short circuit rate of the coil cores 10 was tested. The spiral welding has a stable penetration depth, and there are no short circuits in 500 coil cores 10. In the straight welding wire 1111, 5 out of 500 coil cores 10 short circuit, with a short circuit rate of 1%. In the spot welding, 15 out of 500 coil cores 10 short circuit, with a short circuit rate of 3%.

[0067] The flattened core 10 is used for welding the current collector 20. The weldable area 111 has a relatively thin dense region, and the thickness of the dense region inevitably varies throughout the welding area 111. Spot welding or straight welding results in unstable penetration depth, easily causing the dense region to be welded through. The hot melting of the diaphragm 15 can lead to a short circuit in the core 10. Spiral welding provides stable penetration depth, avoiding weld-through problems. The flat surface 11 is formed by multiple layers of tabs. For example, in this invention, the tabs are all tilted inwards (see Appendix). Figure 1 ), attached Figure 1 This is just an illustration. In actual operation, the stacking thickness of the multi-layer tabs perpendicular to the flat surface 11 (the length direction of the core 10) is more than 5 layers. The actual welding needs to take into account the actual number of tab layers that can be welded, which is actually a matter of welding penetration depth.

[0068] The welding path for spiral welding, such as Figure 3 As shown, a welding intersection 113 is formed where two adjacent pitches intersect. The welding intersection 113 has actually undergone two laser welding scans, and its weld depth is slightly higher than that of the non-intersection point 113 spiral welding area 111. (Refer to...) Figure 3 For the welding of multi-layer tab stacks, intersection point 113 serves as a preheating agent during the first laser scan, resulting in more stable weld penetration and superior weld quality during the second laser scan. In actual welding, to examine the welding effect, we typically irradiate the weld between the two perpendicular intersection points 113. We found that welding at intersection point 113 yields better results and more stable weld penetration. Spiral welding significantly improves the weld quality rate on the flat surface 11 formed by the multi-layer tabs.

[0069] Conventional straight-line welding produces a narrow weld line (1111) with a typical waisted shape. Even with the same total energy input, complete penetration occurs, but the base metal collapses. This occurs because the surface tension of the excess molten metal cannot support its weight, causing it to collapse along the back. Laser oscillating welding, however, can significantly widen the weld line (1111) and reduce its penetration depth, effectively mitigating the collapse problem. The energy distribution of laser oscillation welding differs greatly from conventional laser welding, altering the heat transfer behavior of the molten pool and the morphology of the weld line (1111). The core difference in laser oscillation welding lies primarily in its influence on the energy distribution of the laser on the weld line (1111). The quantity distribution (trajectory) and dynamic behavior of the molten pool keyhole (speed, frequency stirring of the molten pool) are as the laser beam moves along the spiral path. The upper surface of the molten pool is approximately circular with smooth boundaries. As the welding process proceeds, the molten pool moves forward as a whole. Due to the long laser trajectory of the spiral path and low linear energy, the average laser scanning speed is increased, the energy concentration decreases, the energy distribution on the surface of the molten pool is more uniform, the shape fluctuation of the molten pool is minimal, and the heat treatment area and molten pool are expanded. The temperature gradient is reduced, allowing the molten liquid metal sufficient time to fill the weld line 1111, thereby improving the stability of the weld line 1111 and reducing welding defects.

[0070] Obviously, the above embodiments of this utility model are merely examples for clearly illustrating the present utility model, and are not intended to limit the implementation of the present utility model. Those skilled in the art can make various obvious changes, readjustments, and substitutions without departing from the protection scope of this utility model. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this utility model should be included within the protection scope of the claims of this utility model.

Claims

1. A cylindrical battery with multiple tabs, characterized in that, The battery includes a battery casing, a winding core (10), and two current collectors (20). The winding core (10) and the two current collectors (20) are housed in the battery casing. The winding core (10) is formed by winding a positive electrode sheet (13), a separator (15), a negative electrode sheet (14), and a separator (15) stacked sequentially. The positive electrode sheet (13) has a positive electrode active material layer (131) and a blank foil located at the axial end of the winding core (10). The negative electrode sheet (14) has a negative electrode active material layer and a blank foil located at the axial end of the winding core (10). The blank foil of the positive electrode sheet (13) and the blank foil of the negative electrode sheet (14) are connected. One or both sides of the white foil have a flat surface (11) formed by bending and overlapping towards the central axis of the core (10), and a groove (112) is formed on the flat surface (11). The flat surface (11) is engaged with the corresponding current collector (20). The flat surface (11) is divided by the groove (112) into several independent fan-shaped welding areas (111). At least one of the welding areas (111) is welded by spiral welding. The weld line (1111) of the spiral welding is along the outer periphery of the core (10) towards the central axis of the core (10). The weld line (1111) is a straight line with a certain width.

2. The all-tab cylindrical battery according to claim 1, characterized in that, The current collector (20) and the corresponding flat surface (11) are connected by a number of straight welding lines (1111), which are formed by spiral welding, and the welding lines (1111) are evenly distributed radially around the center of the core (10).

3. The all-tab cylindrical battery according to claim 2, characterized in that, The length of the welding wire (1111) is A, the thickness of the core (10) is X, 25%≤A / X≤80%, wherein a through hole (18) is formed in the center of the core (10), the outer radius of the core (10) is R1, the radius of the through hole (18) is R2, and X=R1-R2.

4. The all-tab cylindrical battery according to claim 2, characterized in that, The spiral diameter of the welding wire (1111) is D, 0.2mm≤D≤1mm, and the pitch of the welding wire (1111) is Y, 0.2mm≤Y≤0.7mm, and D>Y.

5. The all-tab cylindrical battery according to claim 2, characterized in that, The width of the bonding wire (1111) is W, 0.5mm≤W≤0.7mm.

6. The all-tab cylindrical battery according to claim 2, characterized in that, The length of the welding wire (1111) is A, where 2.1mm ≤ A ≤ 6.78mm.

7. The all-tab cylindrical battery according to claim 1, characterized in that, Each of the welding areas (111) forms one welding line (1111).

8. The all-tab cylindrical battery according to any one of claims 1-7, characterized in that, The flat surface (11) is divided into a positive electrode flat surface (16) and a negative electrode flat surface (17) located at both ends of the core (10), wherein, The tension F between the negative electrode flat surface (17) and the corresponding current collector (20) is ≥15N; and / or The tension F between the positive electrode flat surface (16) and the current collector (20) is greater than or equal to 5 N.

9. The all-tab cylindrical battery according to claim 8, characterized in that, The positive electrode (13) includes a first blank foil (132) from top to bottom and the positive electrode active material layer (131). The upper part of the multiple layers of the first blank foil (132) is bent inward to form the positive electrode flat surface (16). The lower part of the first blank foil (132) forms a vertical region L. The top of the negative electrode (14) is located in the vertical region L.

10. The all-tab cylindrical battery according to claim 9, characterized in that, The top of the negative electrode (14) divides the vertical region L into an outer vertical region L1 and an inner vertical region L2 from top to bottom. The height of the outer vertical region L1 is L1, and the height of the inner vertical region L2 is L2, with 0.2 ≤ L1 / L2 ≤ 2.

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