Cylindrical lithium battery and preparation method thereof

Abstract

The invention discloses a cylindrical lithium battery, which comprises a shell, a roll core accommodated in the shell, a positive pole lug and a negative pole lug distributed at the two ends of the roll core, a positive pole collector plate welded with the positive pole lug, a negative pole collector plate welded with the negative pole lug, a positive pole cover plate and a negative pole cover plate, the shell is connected with the negative plate cover plate in a welded mode. The positive electrode cover plate is circular, a positive electrode post is integrally arranged in the middle of the positive electrode cover plate, an insulating sealing ring is arranged at the joint of the positive electrode cover plate and the shell, a hole is formed in the middle of the positive electrode post, and the bottom of the hole is of a sealing structure; and the positive electrode cover plate and the positive electrode collector plate are subjected to penetration welding by using laser through the hole in the positive electrode post. Through the integrated design of the positive electrode cover plate and the shell, the product structure is optimized, welding of the periphery of the positive electrode end is reduced, and the welding airtightness liquid leakage risk is effectively reduced. The invention also discloses a preparation method of the cylindrical lithium battery.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion battery manufacturing, and more specifically relates to a cylindrical lithium battery and a preparation method thereof. Background Art

[0002] Lithium batteries have the advantages of high voltage, high specific capacity, long charge and discharge life, and no memory effect, and are generally welcomed by consumers. In particular, cylindrical lithium batteries are becoming the mainstream choice in the market because of their advantages such as high space utilization, not easy to deform, and flexible grouping. As people's demand for lithium batteries is increasing, the safety of lithium batteries is also receiving more and more attention. At present, one of the main risks of cylindrical lithium batteries is that there are too many welding points, which is prone to poor welding airtightness leading to leakage and welding cold welding leading to high internal resistance of the battery and other adverse consequences.

[0003] After searching, it was found that the Chinese invention patent document (application number 2022100172708) discloses a cylindrical lithium battery structure and its manufacturing method, including a battery case, a positive cover assembly, a negative cover assembly and a wound battery cell. The positive cover assembly includes a positive pole, an insulating bracket, a sealing gasket and a positive connecting piece, and the negative cover assembly includes a negative pole, an insulating bracket, a sealing gasket, a negative connecting piece and an explosion-proof valve. Mechanical pressing is used to achieve sealing between the battery case and the positive cover assembly and the negative cover assembly. This solution solves the problem of improving the efficiency of the connection between the battery cover and the case, ensuring the consistency and efficiency of product production.

[0004] In the above scheme, although the mechanical pressing method can reduce the number of welding points and avoid the problems of cold welding of lithium battery and desoldering inside the battery cell, the mechanical pressing requires precise parameter control. Improper operation may lead to the decline of product quality or damage to equipment, and there are certain difficulties in popularization and application. It is urgent to find a new way to solve the problem of too many welding points of cylindrical lithium battery, which affects the air tightness of welding and cold welding. Summary of the invention

[0005] 1. Technical problem to be solved by the invention

[0006] The object of the present invention is to provide a cylindrical lithium battery, which optimizes the product structure through the integrated design of the positive electrode cover plate and the shell, reduces one welding around the positive terminal, and effectively reduces the risk of welding airtightness leakage.

[0007] 2. Technical solution

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A cylindrical lithium battery of the present invention comprises a shell, a winding core accommodated in the shell, a positive electrode tab and a negative electrode tab distributed at both ends of the winding core, a positive electrode collector plate welded to the positive electrode tab and a negative electrode collector plate welded to the negative electrode tab, a positive electrode cover plate and a negative electrode cover plate, wherein the shell and the positive electrode cover plate are integrally formed, and the shell and the negative electrode cover plate are welded to each other.

[0010] Furthermore, the positive electrode cover plate is circular, with a positive electrode column integrated in the middle, an insulating sealing ring is provided at the connection position between the positive electrode cover plate and the shell, a hole is provided in the middle of the positive electrode column, the bottom of the hole is a sealing structure, and the positive electrode cover plate is penetrated and welded to the positive current collecting plate using laser through the hole on the positive electrode column.

[0011] Furthermore, the positive electrode tab includes a first positive electrode tab and a second positive electrode tab, the first positive electrode tab is in a long strip shape and is directly connected to the positive electrode material area, and the second positive electrode tab is in a discontinuous equidistant sawtooth shape and is connected to the first positive electrode tab as a whole;

[0012] The negative electrode tabs include a first negative electrode tab and a second negative electrode tab. The first negative electrode tab is in an elongated strip shape and is directly connected to the negative electrode material area. The second negative electrode tab is in a discontinuous equidistant sawtooth shape and is connected to the first negative electrode tab as a whole.

[0013] Furthermore, a positive first pole ear is provided from the beginning to the end of the roll, and a positive second pole ear is provided between the beginning and the end of the roll, with both ends having a predetermined distance from the beginning and the end of the roll; a negative first pole ear is provided from the beginning to the end of the roll, and a negative second pole ear is provided between the beginning and the end of the roll, with both ends having a predetermined distance from the beginning and the end of the roll.

[0014] Furthermore, the positive electrode current collecting disk has a raised island structure in the middle, and three raised fork arm structures are evenly distributed around the island structure. Each fork arm structure is provided with a heat dissipation hole, and the area between adjacent fork arm structures is used for welding with the positive electrode ear.

[0015] Furthermore, the welding track between the positive electrode current collecting plate and the positive electrode tab is S-shaped.

[0016] Furthermore, the center of the negative electrode current collector is a circular hollow structure, and a vertical curling edge is arranged along the circumferential direction. A plurality of rectangular air permeable grooves are arranged along the radial direction on the negative electrode current collector, and the angles between adjacent rectangular air permeable grooves are equal. Partition holes are arranged at the vertical curling edges corresponding to the rectangular air permeable grooves to separate the vertical curling edges. One end of the rectangular air permeable groove facing the center of the circle is separated from the circular hollow structure, and the other end is separated from the partition hole.

[0017] The present invention also relates to a method for preparing a cylindrical lithium battery, comprising the following steps:

[0018] Rolling and slitting: Roll the pole piece, cut it into two pieces from the center of the middle foil material area, and then cut it from the center of the effective dressing area to form a pole piece;

[0019] Tab forming: Take a pole piece and laser cut the foil areas on both sides to form several discontinuous foil areas and foil areas connected at the beginning and the end, that is, to form a tab;

[0020] Making and winding: Laser cutting or die cutting is performed on the effective area of ​​the electrode dressing, the slicing direction is consistent with the electrode tape running direction, and the electrode is cut into fixed widths according to a predetermined width size to form a continuous cut electrode roll; the electrode is wound to form a winding core, and the positive electrode tabs are distributed on one side of the winding core, and the negative electrode tabs are distributed on the other side of the winding core;

[0021] Flattening and welding: Flatten the tabs on both sides of the winding core with the winding core; weld the positive tab to the positive current collector; weld the positive current collector to the positive pole column by penetrating welding through holes; weld the negative current collector to the inner wall of the shell; weld the negative tab to the negative current collector; weld the negative cover to the shell by peripheral welding;

[0022] Battery forming: Liquid is injected through the battery filling port on the negative electrode cover, and then the air tightness is tested to form a lithium battery.

[0023] Furthermore, the positive electrode tab and the positive electrode current collecting plate are welded in the following manner: the flattened positive electrode second tab and the positive electrode current collecting plate are laser welded, the welding position is an area equally divided by the fork arm structure, the welding track is S-shaped, with two rows of weld marks, and the overall welding track is continuous welding.

[0024] Furthermore, the negative electrode current collector is welded to the inner wall of the shell by laser lap welding, with a portion of the laser weld mark on the vertical curling edge of the negative electrode current collector and another portion of the laser weld mark on the inner wall of the shell.

[0025] 3. Beneficial effects

[0026] Compared with the prior art, the technical solution provided by the present invention has the following beneficial effects:

[0027] (1) A cylindrical lithium battery of the present invention comprises a shell, a winding core contained in the shell, positive and negative pole ears distributed at both ends of the winding core, a positive current collector plate welded to the positive pole ear and a negative current collector plate welded to the negative pole ear, a positive cover plate and a negative cover plate, wherein the shell and the positive cover plate are integrally formed, and the shell and the negative cover plate are welded and connected. The positive cover plate is circular, with a positive pole column integrated in the middle, an insulating sealing ring is provided at the connection position between the positive cover plate and the shell, a hole is provided in the middle of the positive pole column, and the bottom of the hole is a sealing structure, and the positive cover plate is penetrated and welded with the positive current collector plate through the hole on the positive pole column using a laser. Through the integrated design of the positive cover plate and the shell, the product structure is optimized, one welding around the positive end is reduced, and the risk of welding airtightness leakage is effectively reduced.

[0028] (2) A cylindrical lithium battery of the present invention, wherein the positive electrode tab comprises a first positive electrode tab and a second positive electrode tab, wherein the first positive electrode tab is in the shape of an elongated strip and is directly connected to the positive electrode material area, and the second positive electrode tab is in the shape of a discontinuous equidistant sawtooth and is connected to the first positive electrode tab as a whole; the negative electrode tab comprises a first negative electrode tab and a second negative electrode tab, wherein the first negative electrode tab is in the shape of an elongated strip and is directly connected to the negative electrode material area, and the second negative electrode tab is in the shape of a discontinuous equidistant sawtooth and is connected to the first negative electrode tab as a whole. The positive electrode tab is not provided with a second positive electrode tab within a predetermined distance between the beginning and the end of the roll, and the negative electrode tab is not provided with a second negative electrode tab within a predetermined distance between the beginning and the end of the roll. By optimizing the design of the pole ear shape and improving the pole ear leveling effect, the yield of mechanical leveling is increased, and the problem of uneven leveling caused by the toughness of the pole ear is eliminated. It is feasible to directly weld the pole ear to the collector plate after leveling. The pole ear and the collector plate are directly welded by laser welding, which reduces the risk of welding cold welds, reduces the design of connecting pieces required for traditional collector plates, and reduces poor welding caused by the pulling action of bending.

[0029] (3) A cylindrical lithium battery of the present invention, wherein the positive electrode current collector has a raised island structure in the middle, and three raised fork arm structures are evenly distributed around the island structure, each fork arm structure is provided with a heat dissipation hole, and the area between the adjacent fork arm structures is used for welding with the positive electrode tab, and the welding track between the positive electrode current collector and the positive electrode tab is S-shaped. The S-shaped welding method can improve the peel strength of the connection, making the connection between the positive electrode current collector and the positive electrode tab more secure.

[0030] (4) A cylindrical lithium battery of the present invention, wherein the center of the negative electrode current collector is a circular hollow structure, a vertical curling is arranged along the circumference, and a plurality of rectangular air-permeable grooves are arranged along the radial direction on the negative electrode current collector, the angles between adjacent rectangular air-permeable grooves are equal, and a partition hole is arranged at the vertical curling corresponding to the rectangular air-permeable groove to separate the vertical curling, and the end of the rectangular air-permeable groove facing the center is separated from the circular hollow structure, and the other end is separated from the partition hole. The negative electrode current collector adopts a vertical curling design, and the curling position is convenient for laser lap welding with the inner wall of the shell, which solidifies the welding position of the current collector, and solves the problem that the current collector of the conventional negative terminal is not fixed in position during welding due to the copper foil tab being too soft, resulting in the risk of gap cold welding during welding.

[0031] (5) The present invention also relates to a method for preparing a cylindrical lithium battery. By integrating the positive electrode cover plate and the shell, the positive electrode column and the positive electrode collector are connected by laser penetration welding. Compared with traditional cylindrical lithium batteries, one peripheral weld is reduced between the positive electrode cover plate and the shell, thereby reducing the risk of airtight leakage in the lithium battery welding. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A top view of the positive electrode sheet of the present invention;

[0033] Figure 2 A top view of the polarization sheet in the present invention;

[0034] Figure 3 It is a top view of the positive polarizer after laser cutting in the present invention;

[0035] Figure 4 It is a front view of the winding core in the present invention;

[0036] Figure 5 This is a disassembled and wrapped diagram of the winding core in the present invention;

[0037] Figure 6 It is a front view of the winding core tab after being flattened in the present invention;

[0038] Figure 7 A top view of the positive electrode current collecting disk of the present invention;

[0039] Figure 8 It is a stereoscopic diagram of the assembly of the positive electrode current collecting plate and the pole ear in the present invention;

[0040] Fig. 9 A top view of the welding between the positive electrode current collector and the electrode ear in the present invention;

[0041] Fig.10 It is a front view of the housing in the present invention;

[0042] Fig.11A top view of a positive electrode cover plate integrally connected to a housing in the present invention;

[0043] Fig.12 A top view of the negative electrode current collecting disk of the present invention;

[0044] Fig.13 It is a stereoscopic diagram of the assembly of the negative electrode current collector and the pole ear in the present invention;

[0045] Fig.14 A top view of the negative electrode cover plate of the present invention;

[0046] Fig.15 It is a top view of the assembly of the negative electrode cover plate and the shell in the present invention.

[0047] Explanation of the numbers in the schematic diagram: 1, pole ear, 11, positive pole ear, 111, first positive pole ear, 112, second positive pole ear, 12, negative pole ear, 121, first negative pole ear, 122, second negative pole ear;

[0048] 2. winding core, 21. positive electrode sheet, 22. negative electrode sheet;

[0049] 3. positive electrode current collecting plate, 31. island structure, 32. fork arm structure, 321. heat dissipation hole;

[0050] 4. shell, 41. positive electrode column, 42. insulating sealing ring, 43. hole, 44. positive electrode cover plate;

[0051] 5. Negative electrode current collector plate, 51. Circular hollow structure, 52. Rectangular air permeable groove, 53. Vertical curling; 54. Partition hole;

[0052] 6. negative electrode cover plate, 61. liquid injection port;

[0053] 7. Middle foil area, 8. Dressing effective area, 9. Edge foil areas on both sides, 10. Cutting line. DETAILED DESCRIPTION

[0054] In order to enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention is clearly and completely described below in conjunction with the accompanying drawings and embodiments.

[0055] The structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no substantial technical significance. Any modification of the structure, change in the proportion relationship, or adjustment of the size, without affecting the effects and purposes that can be achieved by the present invention, should still fall within the scope of the technical contents disclosed by the present invention. At the same time, the terms such as "upper", "lower", "first", "second", "left", "right" and so on quoted in this specification are only for the convenience of description, and are not used to limit the scope of implementation. The change or adjustment of their relative relationship should also be regarded as the scope of implementation of the present invention without substantially changing the technical contents.

[0056] In the prior art, the positive electrode cover and the shell of the cylindrical lithium battery are separated from each other and need to be connected by welding, which inevitably increases the risk of welding airtightness leakage and the risk of welding cold joints. One of the basic concepts of the present invention is to integrate the positive electrode cover and the shell into an integrated design, reducing the peripheral welding of the positive terminal, which naturally reduces the risk of welding airtightness leakage and the risk of welding cold joints.

[0057] Example 1

[0058] like Figures 4 to 15 As shown, a cylindrical lithium battery of this embodiment includes a shell 4, a winding core 2 accommodated in the shell 4, a positive electrode tab 11 and a negative electrode tab 12 distributed at both ends of the winding core, a positive electrode collector 3 welded to the positive electrode tab 11 and a negative electrode collector 5 welded to the negative electrode tab 12, a positive electrode cover plate 44 and a negative electrode cover plate 6, the shell 4 and the positive electrode cover plate 44 are integrally formed, and the shell and the negative plate cover plate 6 are welded together.

[0059] The positive electrode cover plate 44 is circular, with a positive electrode column 41 integrated in the middle. An insulating sealing ring 42 is provided at the connection position between the positive electrode cover plate 44 and the shell 4. A hole 43 is provided in the middle of the positive electrode column 41. The bottom of the hole 43 is a sealing structure. The positive electrode cover plate 44 is penetrated and welded to the positive current collecting plate 3 using laser through the hole 43 on the positive electrode column 41.

[0060] The shell 4 , the positive electrode cover 44 and the positive electrode column 41 are designed as an integrated whole and are made of a steel shell. A hole 43 is provided in the middle of the positive electrode column 41 . The bottom of the hole 43 is sealed and has a non-penetrating structure. The hole 43 is not directly connected to the interior of the shell 4 .

[0061] Preferably, the hole 43 is cylindrical and has a depth of 1-2 mm, so that the laser welding equipment can perform penetrating laser welding through the sealing structure. The sealing structure at the bottom of the hole 43 is made of 3 series aluminum, which has medium strength and good corrosion resistance, weldability and processability.

[0062] The penetration welding method is that the laser penetrates the 3 series aluminum material, melts it and welds it to the internal positive electrode collector plate 3, and the welding trajectory is a spiral line.

[0063] By integrating the positive electrode cover plate with the shell, the product structure is optimized, one weld around the positive terminal is reduced, and the risk of welding airtightness leakage is effectively reduced. Of course, the negative electrode cover plate and the shell can also be integrated to further reduce one weld at the negative terminal, which can further reduce the risk of welding airtightness leakage, but the manufacturing process will be relatively complicated.

[0064] Example 2

[0065] like Figure 5 As shown, in a cylindrical lithium battery of this embodiment, the positive electrode tab 11 includes a positive first tab 111 and a positive second tab 112. The positive first tab 111 is in the shape of an elongated strip, located at the root of the entire tab, and directly connected to the positive electrode material area. The positive second tab 112 is in a non-continuous equidistant sawtooth shape, and is connected to the positive first tab 111 as a whole. The positive second tab 112 is located on the outside of the positive first tab 111, and the positive first tab 111 and the positive second tab 112 are formed by laser cutting. The positive second tab 112 is offset to one side at a predetermined angle, preferably 70° to 72°, and the distance between adjacent positive second tabs 112 is less than 0.5 mm, which is conducive to the uniform flattening of the positive tab and the winding core.

[0066] The negative electrode tab 12 includes a first negative electrode tab 121 and a second negative electrode tab 122. The first negative electrode tab 121 is in the shape of an elongated strip, located at the root of the entire tab, and directly connected to the negative electrode material area. The second negative electrode tab 122 is in a non-continuous equidistant sawtooth shape, and is connected to the first negative electrode tab 121 as a whole. The second negative electrode tab 122 is located outside the first negative electrode tab 121, and the first negative electrode tab 121 and the second negative electrode tab 122 are formed by laser cutting. The second negative electrode tab 122 is offset to one side at a predetermined angle, preferably 74° to 76°, and the distance between the adjacent second positive electrode tabs 112 is less than 0.5 mm, which is conducive to the uniform flattening of the negative electrode tab and the winding core.

[0067] A positive first pole lug 111 is provided from the beginning to the end of the roll, and a positive second pole lug 112 is provided between the beginning and the end of the roll, with a predetermined distance between the two ends of the roll and the beginning and the end of the roll; a negative first pole lug 121 is provided from the beginning to the end of the roll, and a negative second pole lug 122 is provided between the beginning and the end of the roll, with a predetermined distance between the two ends of the roll and the beginning and the end of the roll. That is, the positive pole lug 11 is not provided with a positive second pole lug 112 within the predetermined distance between the beginning and the end of the roll, the length range of not providing a positive second pole lug at the beginning of the positive roll is 500mm to 600mm, and the length range of not providing a positive second pole lug at the end of the positive roll is 200mm to 300mm. The negative pole lug 12 is not provided with a negative second pole lug 122 within the predetermined distance between the beginning and the end of the roll, the length range of not providing a negative second pole lug 122 at the beginning of the negative roll is 500mm to 600mm, and the length range of not providing a negative second pole lug at the end of the negative roll is 300mm to 350mm.

[0068] The optimized lug shape design can improve the lug flattening effect. The lug and collector plate are directly welded by laser welding, which reduces the risk of cold welds, reduces the need for connecting pieces in the traditional collector plate design, and reduces poor welding caused by the pulling action of the bending.

[0069] Example 3

[0070] like Figures 7 to 15 As shown, in a cylindrical lithium battery of this embodiment, the positive current collector 3 is a circular island-type trident design, with a raised island structure 31 in the middle, and three raised fork arm structures 32 are evenly distributed around the island structure 31, each of which is provided with a heat dissipation hole 321, and the area between adjacent fork arm structures 32 is used for welding with the positive electrode tab 11. A circular weld print area is provided in the middle of the island structure 31, and the adjacent angles of the fork arm structures 32 are 120°. The height of the raised fork arm structure 32 is consistent with the height of the raised center island, and the height range is less than 0.1 mm. The material of the positive current collector is aluminum.

[0071] The welding track between the positive current collector 3 and the positive electrode tab 11 is S-shaped or multi-strip, with two rows of weld marks, and the overall welding track is continuous welding. The S-shaped welding method can improve the peel strength of the connection, making the connection between the positive current collector and the positive electrode tab more secure.

[0072] The negative electrode current collector disk 5 has a circular hollow structure 51 at the center, and a vertical curling edge 53 is arranged along the circumferential direction. A plurality of rectangular air permeable grooves 52 are arranged on the negative electrode current collector disk 5 along the radial direction, and the angles between adjacent rectangular air permeable grooves 52 are equal. Partition holes 54 are arranged at the vertical curling edges 53 corresponding to the rectangular air permeable grooves 52 to separate the vertical curling edges 53. One end of the rectangular air permeable groove 52 facing the center of the circle is separated from the circular hollow structure 51, and the other end is separated from the partition hole 54.

[0073] Preferably, there are six equally spaced rectangular ventilation grooves 52 , the height of the vertical curling edge is less than 1 mm, and the distance between the rectangular ventilation grooves 52 and the middle circular hollow area 51 ranges from 1 to 2 mm.

[0074] The negative electrode current collector adopts a vertical curling design, and the curling position is convenient for laser lap welding with the inner wall of the shell, which solidifies the welding position of the current collector. This solves the problem that the current collector of the conventional negative terminal is not fixed in position during welding due to the copper foil ear being too soft, resulting in the risk of gap cold welding during welding.

[0075] The lap welding method is direct laser welding, the welding track is single-point swing, the welding track is located on the inner wall of the shell and has a predetermined distance from the edge of the shell opening.

[0076] The positive electrode second pole tab 112 and the positive electrode current collecting disk 3 are in contact with each other, and the negative electrode second pole tab 122 and the negative electrode current collecting disk 5 are in contact with each other.

[0077] The negative electrode cover plate 6 is circular in shape and has a spiral ring structure. A circular liquid injection port 61 is provided in the middle of the negative electrode cover plate 6. The liquid injection port is a stepped ring design and is welded with subsequent glue nails and sealing nails.

[0078] Example 4

[0079] This embodiment also relates to a method for preparing a cylindrical lithium battery, comprising the following steps:

[0080] Rolling and slitting: The pole piece includes the middle foil area 7, the edge foil areas 9 on both sides and the dressing effective area 8. The middle foil area 7 has the main dressing effective areas 8 on both sides. The length of the middle foil area 7 is twice the length of the edge foil areas 9 on both sides. The pole piece is rolled, cut into two along the cutting line 10 of the middle foil area 7, and then cut from the center of the dressing effective area 8 to form four pole pieces.

[0081] Tab forming: Take a positive pole piece and cut the foil area at the edge of the pole piece to form a continuous and several discontinuous foil areas. The foil area is the positive pole tab. The spacing between two adjacent positive second pole tabs 112 is equal, the upper and lower widths of the positive second pole tabs are equal, and the inclination angles are the same; the negative pole tab is formed in the same way.

[0082] Specifically, a blank area is left on the positive electrode sheet 21, and a first positive electrode ear 111 and a second positive electrode ear 112 are cut out by laser. The first positive electrode ear 111 is relatively connected below the second positive electrode ear 112, and the second positive electrode ear 112 is not set at a predetermined distance between the beginning and the end of the roll. The length range of the positive electrode ear not set at the beginning of the roll is 500mm to 600mm, and the length range of the positive electrode ear not set at the end of the roll is 200mm to 300mm.

[0083] Leave a blank area on the negative electrode sheet 22, and use laser to cut out the negative first pole ear 121 and the negative second pole ear 122. The negative first pole ear 121 is relatively positioned and connected above the negative second pole ear 122. The negative second pole ear 122 is not set at a predetermined distance between the beginning and the end of the roll. The length range of the negative electrode head without a pole ear is 500mm to 600mm, and the length range of the negative electrode without a pole ear is 300mm to 350mm.

[0084] Preparation and winding: The effective dressing area 8 of the electrode sheet is laser cut or die-cut, and the slicing direction is consistent with the electrode sheet running direction. The electrode sheet is cut into fixed widths according to a predetermined width size to form a continuous cut electrode sheet; the electrode sheet is wound to form a winding core 2, and the positive electrode tabs 11 are distributed on one side of the winding core 2, and the negative electrode tabs 12 are distributed on the other side of the winding core. The positive electrode tabs 11 and the negative electrode tabs 12 are arranged in an orderly manner. The number of winding layers: the positive electrode is greater than 50 layers, and the negative electrode is greater than 51 layers.

[0085] Specifically, the positive electrode sheet 21, the negative electrode sheet 22 and the separator are rolled into a cylindrical winding core 2 by a winding machine, and the positive and negative electrode tabs at both ends of the winding core 2 are both hollowed out in the middle, and the positive and negative second tabs at the rest of the positions stand vertically.

[0086] Flattening and welding: The positive pole ear on one side of the winding core is tightly fixed together by flattening, and the negative pole ear on the other side of the winding core is tightly fixed together by flattening; the positive pole ear 11 is welded to the positive current collector 3; the positive current collector 3 is welded to the positive cover 44 by penetration welding through the hole 43, and the welding trajectory is a spiral line; the negative current collector 5 is welded to the inner wall of the shell 4; the negative pole ear 12 is welded to the negative current collector 5; the negative cover 6 is welded to the shell 4 by peripheral welding.

[0087] Specifically, after being flattened, the positive and negative pole tabs at both ends of the winding core are in a state of circular hollowing in the middle, and the second pole tabs in the remaining positions are laid horizontally, and protective tapes are attached to the roots of the positive and negative pole tabs at both ends.

[0088] The method of welding the positive electrode ear 11 to the positive electrode current collecting plate 3 is: laser welding the flattened positive second electrode ear 112 to the positive electrode current collecting plate 3, the welding position is the area equally divided by the fork arm structure 32, the welding track is S-shaped, with two rows of weld marks, and the overall welding track is continuous welding.

[0089] The welded positive electrode current collecting disc 3 is rolled into the shell, with the positive end being the direction of entry.

[0090] The negative electrode current collector 5 is welded to the inner wall of the shell 4 in the following manner: the negative electrode current collector 5 is overlapped with the inner wall of the shell 4 by laser, a part of the laser weld mark is on the vertical curling edge 53 of the negative electrode current collector 5, and another part of the laser weld mark is on the inner wall of the shell 4. After the overlap welding, the welding of the negative electrode current collector 5 and the negative electrode second pole ear 122 is relatively independent and does not overlap.

[0091] In practice, the negative electrode current collector plate 5 is docked with the negative electrode second pole ear 122 after the negative terminal is flattened, and a mechanical push rod is used to tightly fit the negative electrode current collector plate 5 with the negative electrode second pole ear. The height difference between the upper edge of the vertical curling edge 53 of the negative electrode current collector plate 5 and the negative terminal edge of the shell is measured, and then the upper edge of the vertical curling edge 53 and the inner wall of the shell are overlapped. The number of weld marks is 6, the weld mark length ranges from 20mm to 30mm, and the width ranges from 1mm to 2mm.

[0092] Laser welding is performed on the equally divided areas on the negative electrode current collecting plate 5 and the negative electrode second pole ear 122. The welding track is a serpentine S or multiple long strips. The S-shaped welding generally welds adjacent rows of weld marks. The overall welding track is continuous welding.

[0093] The negative electrode cover plate 6 is assembled with the shell, and the periphery is welded by means of annular laser welding.

[0094] Battery forming: Liquid is injected through the battery injection port on the negative electrode cover, and then the air tightness is tested to form a lithium battery. The diameter of the cylindrical lithium battery is greater than 40 mm.

[0095] The present invention and its embodiments are described schematically above, which is not restrictive. The drawings show only one embodiment of the present invention, and the actual structure is not limited thereto. If a person skilled in the art is inspired by the above, and does not deviate from the purpose of the present invention, and does not creatively design a structure similar to the present technical solution, it shall fall within the protection scope of the present invention.

Claims

1. A cylindrical lithium battery, comprising a housing (4), a winding core (2) contained in the housing (4), a positive electrode tab (11) and a negative electrode tab (12) distributed at both ends of the winding core, a positive electrode current collector (3) welded to the positive electrode tab (11) and a negative electrode current collector (5) welded to the negative electrode tab (12), a positive electrode cover plate (44) and a negative electrode cover plate (6), characterized in that: The shell (4) and the positive electrode cover plate (44) are integrally formed, and the shell and the negative electrode cover plate (6) are welded and connected.

2. The cylindrical lithium battery according to claim 1, characterized in that: The positive electrode cover plate (44) is circular, with a positive electrode column (41) integrally arranged in the middle; an insulating sealing ring (42) is arranged at the position where the positive electrode cover plate (44) and the shell (4) are connected; a hole (43) is arranged in the middle of the positive electrode column (41); the bottom of the hole (43) is a sealing structure; the positive electrode cover plate (44) is penetrated and welded to the positive current collecting plate (3) through the hole (43) on the positive electrode column (41) using laser.

3. The cylindrical lithium battery according to claim 1 or 2, characterized in that: The positive electrode tab (11) comprises a first positive electrode tab (111) and a second positive electrode tab (112); the first positive electrode tab (111) is in a long strip shape and is directly connected to the positive electrode material area; the second positive electrode tab (112) is in a discontinuous equidistant sawtooth shape and is connected to the first positive electrode tab (111) as a whole; The negative electrode tab (12) comprises a first negative electrode tab (121) and a second negative electrode tab (122); the first negative electrode tab (121) is in the shape of an elongated strip and is directly connected to the negative electrode material region; the second negative electrode tab (122) is in the shape of a discontinuous equidistant sawtooth and is integrally connected to the first negative electrode tab (121).

4. The cylindrical lithium battery according to claim 3, characterized in that: A positive first pole lug (111) is provided from the beginning to the end of the roll, and a positive second pole lug (112) is provided between the beginning and the end of the roll, with both ends having a predetermined distance from the beginning and the end of the roll; a negative first pole lug (121) is provided from the beginning to the end of the roll, and a negative second pole lug (122) is provided between the beginning and the end of the roll, with both ends having a predetermined distance from the beginning and the end of the roll.

5. The cylindrical lithium battery according to claim 1 or 2, characterized in that: The positive electrode current collecting disk (3) has a raised island structure (31) in the middle, and three raised fork arm structures (32) are evenly distributed around the island structure (31), each fork arm structure (32) is provided with a heat dissipation hole (321), and the area between adjacent fork arm structures (32) is used for welding with the positive electrode tab (11).

6. The cylindrical lithium battery according to claim 5, characterized in that: The welding track between the positive electrode current collecting plate (3) and the positive electrode tab (11) is S-shaped.

7. The cylindrical lithium battery according to claim 5, characterized in that: The center of the negative electrode current collector (5) is a circular hollow structure (51), and a vertical curling edge 53 is arranged along the circumferential direction. A plurality of rectangular air-permeable grooves (52) are arranged on the negative electrode current collector (5) along the radial direction, and the angles between adjacent rectangular air-permeable grooves (52) are equal. A partition hole (54) is arranged at the vertical curling edge (53) corresponding to the rectangular air-permeable groove (52) to separate the vertical curling edge (53). One end of the rectangular air-permeable groove (52) facing the center of the circle is separated from the circular hollow structure (51), and the other end is separated from the partition hole (54).

8. A method for preparing a cylindrical lithium battery, characterized in that: The steps include: Rolling and slitting: rolling the electrode sheet, cutting it into two pieces from the center of the middle foil area (7), and then cutting it from the center of the dressing effective area (8) to form a split electrode sheet; Tab forming: take the divided pole piece, and laser cut the foil area (9) on both sides to form a plurality of discontinuous foil areas and foil areas connected at the head and tail, thus forming the tab; Sheet making and winding: laser cutting or die cutting is performed on the effective dressing area (8) of the electrode sheet, the slicing direction is consistent with the electrode sheet tape running direction, and the electrode sheet is cut into fixed widths according to a predetermined width size to form a continuous cut electrode roll; the electrode sheet is wound to form a winding core (2), the positive electrode tab (11) is distributed on one side of the winding core (2), and the negative electrode tab (12) is distributed on the other side of the winding core; Flattening and welding: flattening the pole ears (1) and the winding core (2) on both sides of the winding core together; welding the positive pole ears (11) and the positive current collecting plate (3) together; welding the positive current collecting plate (3) and the positive cover plate (44) together by penetrating welding through the hole (43); welding the negative current collecting plate (5) and the inner wall of the shell (4); welding the negative pole ears (12) and the negative current collecting plate (5); and peripherally welding the negative cover plate (6) and the shell (4); Battery forming: Liquid is injected through the battery liquid injection port 61 on the negative electrode cover plate 6, and then the air tightness is tested to form a lithium battery.

9. The method for preparing a cylindrical lithium battery according to claim 8, characterized in that: The positive electrode tab (11) and the positive electrode current collecting plate (3) are welded in the following manner: the flattened positive electrode second tab (112) and the positive electrode current collecting plate (3) are laser welded, the welding position is an area equally divided by the fork arm structure (32), the welding track is S-shaped, with two rows of weld marks, and the overall welding track is continuous welding.

10. The method for preparing a cylindrical lithium battery according to claim 9, characterized in that: The negative electrode current collector (5) is welded to the inner wall of the shell (4) in the following manner: the negative electrode current collector (5) and the inner wall of the shell (4) are overlap-welded by laser, a portion of the laser weld mark is on the vertical curling edge (53) of the negative electrode current collector (5), and another portion of the laser weld mark is on the inner wall of the shell (4).

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