A cylindrical lithium battery with a full-tab structure and a full-tab structure winding process

Abstract

The application discloses a cylindrical lithium battery with full tab structure without tab and a winding process thereof. The lithium battery comprises a cylindrical shell, a wound cell, and positive and negative current collectors. The wound cell is formed by winding positive and negative sheets and a separator and has a center through hole. One end of the positive and negative current collectors is respectively formed into an annular full tab located at the axial two ends of the cell. The end face of the full tab is a step-shaped dense structure with an inner high and outer low structure. The current collector is directly welded with the full tab and is provided with an electrolyte through hole. An insulating isolation ring is arranged between the current collector and the inner wall of the shell. The winding process comprises sheet preparation, winding forming, segmented pressure end face treatment, laser welding, and shell packaging, and limits key process parameters. The application improves the welding yield and current conduction efficiency, accelerates electrolyte infiltration, enhances the safety and structural stability of the battery, simplifies the process, reduces the cost, is suitable for industrial mass production, and can be applied to the fields of electronic equipment, energy storage, and vehicle-mounted devices.

Description

Technical Field

[0001] This invention relates to the field of lithium battery technology, specifically to a tabless-free cylindrical lithium battery with a full tab structure and its winding process. Background Technology

[0002] Cylindrical lithium batteries are widely used in various electronic devices, energy storage, and automotive applications due to their compact structure and high energy density. All-tab technology, as a key means to improve battery performance, effectively reduces battery impedance and temperature rise by achieving "surface contact" current transmission, and has become an industry trend. However, existing all-tab cylindrical lithium batteries still have many technical challenges.

[0003] Existing tabless-type lithium batteries with fully tabbed electrode structures typically have planar end faces. After winding, the multiple layers of metal foil are loosely stacked, making them prone to defects such as burn-through and incomplete soldering during welding, affecting current conduction stability. Dead zones exist in electrolyte wetting, reducing battery electrochemical performance. Insufficient insulation between the current collector and the inner wall of the casing easily leads to short-circuit hazards. Furthermore, existing molding processes struggle to precisely control the tab structure, resulting in poor product consistency and low production yield, failing to meet the demands of industrial mass production and high-rate applications. Therefore, developing a tabless-free cylindrical lithium battery with a reasonable structure and stable performance that addresses these pain points has become an urgent need in this field. Summary of the Invention

[0004] To overcome the shortcomings of existing technical solutions, this invention provides a cylindrical lithium battery with a tabless-free, fully tabular structure and its winding process, which can effectively solve the problems raised in the background art.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A tabless cylindrical lithium battery includes a cylindrical shell, a wound cell disposed inside the cylindrical shell, a positive current collector and a negative current collector. The wound cell is formed by stacking a positive electrode sheet, a separator and a negative electrode sheet in sequence and spirally winding them along the winding direction. The wound cell has a central through hole.

[0007] The positive electrode sheet includes a positive current collector and a positive active material layer coated thereon, wherein one end of the positive current collector along the length direction forms a positive full electrode tab extending axially.

[0008] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated thereon, and the other end of the negative electrode current collector along the length direction forms a negative electrode tab that extends axially.

[0009] The positive and negative electrode tabs are located at the two ends of the axial direction of the wound battery cell, and each of them has an overall annular end face structure distributed radially.

[0010] The annular end faces of the positive electrode lug and the negative electrode lug each have a stepped structure that increases radially from the inside to the outside, and the stepped surfaces of the stepped structures all face the axial outer side of the wound cell. The positive electrode current collector is directly welded to the annular end face of the positive electrode lug, and the negative electrode current collector is directly welded to the annular end face of the negative electrode lug. Both the positive electrode current collector and the negative electrode current collector have multiple electrolyte through holes arranged circumferentially.

[0011] As a further description of the above technical solution, the stepped structure includes an inner ring stepped surface, at least one middle ring stepped surface, and an outer ring stepped surface distributed radially in sequence. The inner ring stepped surface has a first extension height relative to the axial end face of the wound cell, the middle ring stepped surface has a second extension height, and the outer ring stepped surface has a third extension height. The first extension height is greater than the second extension height, and the second extension height is greater than the third extension height.

[0012] As a further description of the above technical solution, an insulating isolation ring is provided between the radial outer edge of the positive current collector and the negative current collector and the inner wall of the cylindrical shell, and the inner diameter of the insulating isolation ring is adapted to the radial outer edge of the positive current collector or the negative current collector.

[0013] As a further description of the above technical solution, the annular end faces of the positive electrode lug and the negative electrode lug are integrally flattened before welding, and the stepped structure is a dense metal end face naturally formed after flattening.

[0014] A winding process for a tabless-free, fully tabbed cylindrical lithium battery, used to manufacture cylindrical lithium batteries, includes the following steps:

[0015] Step S1: Electrode preparation, coating the positive electrode current collector and the negative electrode current collector with a positive electrode active material layer and a negative electrode active material layer respectively, wherein one end of the positive electrode current collector is reserved as a blank area of ​​the positive electrode tab without active material coating, and one end of the negative electrode current collector is reserved as a blank area of ​​the negative electrode tab without active material coating.

[0016] Step S2: Winding and forming, the positive electrode sheet, separator and negative electrode sheet are stacked in sequence, and spirally wound along the winding direction with the winding needle as the core axis to form a cylindrical wound cell, and the blank area of ​​the positive electrode tab is located at one end of the axial direction of the wound cell, and the blank area of ​​the negative electrode tab is located at the other end of the axial direction of the wound cell.

[0017] Step S3: End face treatment. Axial pressure is applied to the positive electrode tab blank area and the negative electrode tab blank area on both ends of the axial direction of the wound battery cell, so that they form a stepped structure from the inside to the outside in the radial direction. At the same time, the metal foils in the tab blank area are fused together under pressure to form a dense annular end face.

[0018] Step S4: Current collector welding. The positive current collector and the negative current collector are laser welded to the annular end face of the positive electrode lug and the annular end face of the negative electrode lug, respectively. The laser welding is performed continuously or intermittently along the circumference of the annular end face.

[0019] Step S5: Encapsulation: The wound cell with the positive current collector and negative current collector welded on it is installed into the cylindrical shell. The positive current collector is electrically connected to the positive end cap of the cylindrical shell, and the negative current collector is electrically connected to the negative end cap of the cylindrical shell. After injecting electrolyte, it is sealed.

[0020] As a further description of the above technical solution, in step S3, the axial pressure is applied in a segmented pressurization manner: first, a first pressure is applied to the inner ring region, then a second pressure is applied to the middle ring region, and finally a third pressure is applied to the outer ring region, wherein the first pressure is greater than the second pressure, and the second pressure is greater than the third pressure.

[0021] As a further description of the above technical solution, in step S3, the stepped structure includes an inner ring stepped surface, at least one middle ring stepped surface, and an outer ring stepped surface. The extension height of the inner ring stepped surface relative to the axial end face of the wound cell is 1.0mm-1.5mm, the extension height of the middle ring stepped surface is 0.5mm-1.0mm, the extension height of the outer ring stepped surface is 0.1mm-0.5mm, and the height difference between adjacent stepped surfaces is 0.3mm-0.6mm.

[0022] As a further description of the above technical solution, in step S4, the power of the laser welding is 300W-800W, the welding speed is 50mm / s-200mm / s, and the spot diameter is 0.2mm-0.5mm.

[0023] As a further description of the above technical solution, in step S2, the diameter of the winding needle is 2mm-6mm, and the winding tension is controlled between 0.5N-3N.

[0024] As a further description of the above technical solution, after step S4 and before step S5, an insulating isolation ring is respectively assembled between the radial outer edge of the positive current collector and the negative current collector and the inner wall of the cylindrical shell.

[0025] Compared with the prior art, the beneficial effects of the present invention are:

[0026] The present invention discloses a cylindrical lithium battery with a tabless-free, fully tabbed structure and its winding process, which has at least one of the following beneficial effects during use:

[0027] Its stepped all-tab structure and integrated flattening treatment eliminate gaps between multiple foil layers, reduce contact resistance, and avoid problems such as burn-through and incomplete welding during soldering, thereby improving welding yield and current conduction stability. The electrolyte penetration holes in the current collector synergize with the stepped gaps to accelerate electrolyte wetting, eliminate wetting dead zones, and improve battery electrochemical performance. The insulating isolation ring eliminates short-circuit hazards, fixes the current collector position, and improves battery safety and structural stability. The segmented pressurization and parameter limiting design of the winding process ensures a regular stepped structure, high product consistency, and suitability for industrial mass production. It also simplifies the production process, reduces costs, and optimizes winding and welding parameters to further guarantee cell quality, comprehensively improving battery charge / discharge efficiency, cycle life, and deformation resistance, making it suitable for various electronic devices, energy storage, and automotive applications. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the overall cross-sectional structure of a cylindrical lithium battery with a tabless-free, full-tab structure according to the present invention.

[0029] Figure 2 This is a schematic axial cross-sectional view of the wound cell portion of a cylindrical lithium battery with a tabless-free, all-tab structure according to the present invention.

[0030] Figure 3 This is a schematic diagram of the electrode stacking and unfolding structure of a cylindrical lithium battery with a tabless-free, full-tab structure according to the present invention.

[0031] Figure 4 This is a top view of the current collector structure of a cylindrical lithium battery with a tabless-free, all-tab structure according to the present invention.

[0032] Figure 5 This is a flowchart illustrating the winding process of a cylindrical lithium battery with a tabless-free, full-tab structure according to the present invention.

[0033] Numbering on the map:

[0034] 1. Cylindrical casing; 2. Winded cell; 3. Positive current collector; 4. Negative current collector; 5. Central through hole; 6. Positive all-pole tab; 7. Negative all-pole tab; 8. Inner ring stepped surface; 9. Middle ring stepped surface; 10. Outer ring stepped surface; 11. Electrolyte through hole; 12. Insulating ring; 13. Positive end cap; 14. Negative end cap; 15. Positive electrode plate; 16. Negative electrode plate; 17. Separator; 18. Positive active material layer; 19. Negative active material layer; 20. Reservation area for positive all-pole tab; 21. Reservation area for negative all-pole tab. Detailed Implementation

[0035] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] like Figure 1-5 As shown, the present invention provides a cylindrical lithium battery with a tabless structure, including a cylindrical shell 1, a wound cell 2 disposed inside the cylindrical shell 1, a positive current collector 3 and a negative current collector 4. The wound cell 2 is formed by stacking a positive electrode sheet 15, a separator 17 and a negative electrode sheet 16 in sequence and spirally winding them along the winding direction. The wound cell 2 has a central through hole 5.

[0037] In this embodiment, the wound battery cell 2 is formed by stacking a positive electrode 15, a separator 17, and a negative electrode 16 in sequence, and then spirally winding them with a winding needle as the core axis to form a cylindrical structure with a central through hole 5. The positive electrode 15 is composed of a positive current collector (such as aluminum foil) and a positive active material layer 18 (such as ternary material or lithium iron phosphate) coated on it. The negative electrode 16 is composed of a negative current collector (such as copper foil) and a negative active material layer 19 (such as graphite) coated on it. The separator 17 (such as a polypropylene or polyethylene composite film) is located between the positive and negative electrode 16, which plays the role of isolating the positive and negative electrodes, preventing short circuits, and allowing lithium ions to pass through.

[0038] The positive electrode 15 includes a positive current collector and a positive active material layer 18 coated thereon, and one end of the positive current collector along the length direction forms a positive full electrode tab 6 extending axially.

[0039] The negative electrode sheet 16 includes a negative electrode current collector and a negative electrode active material layer 19 coated thereon, and the other end of the negative electrode current collector along the length direction forms a negative electrode full electrode ear 7 extending axially.

[0040] The positive electrode lug 6 and the negative electrode lug 7 are located at the two ends of the axial direction of the wound cell 2, and each of them has an overall annular end face structure distributed radially.

[0041] During the charging and discharging process of the battery, lithium ions are inserted or extracted between the positive electrode active material layer 18 and the negative electrode active material layer 19, and ion migration is achieved through the electrolyte. The current is conducted through the positive electrode current collector, the positive electrode tab 6, the positive electrode current collector disk 3, the positive electrode end cap 13, and the negative electrode current collector, the negative electrode tab 7, the negative electrode current collector disk 4, the negative electrode end cap 14, to complete the closure of the entire circuit. The design of the central through hole 5 provides a channel for electrolyte flow and heat dissipation.

[0042] The annular end faces of the positive electrode lug 6 and the negative electrode lug 7 each have a stepped structure that increases radially from the inside to the outside, and the stepped surfaces of the stepped structures all face the axial outer side of the wound cell 2. The positive electrode current collector 3 is directly welded to the annular end face of the positive electrode lug 6, and the negative electrode current collector 4 is directly welded to the annular end face of the negative electrode lug 7. Both the positive electrode current collector 3 and the negative electrode current collector 4 are provided with a plurality of electrolyte through holes 11 arranged circumferentially.

[0043] The positive electrode tab 6 is formed by winding the area at one end of the positive current collector that is not coated with active material, and the negative electrode tab 7 is formed by winding the area at the other end of the negative current collector that is not coated with active material. The two are located at the two ends of the axial direction of the wound cell 2, and the whole structure is a radially distributed annular end face structure. After winding, the tab area is a stack of multiple layers of metal foil. After integrated flattening, the metal foils are fused together under pressure to form a dense annular end face (to avoid gaps between the multiple layers of foil that could lead to poor contact).

[0044] The stepped design, with its higher inner surface and lower outer surface, allows the contact area to gradually transition from the inside to the outside when welding the end face of the tab to the current collector. This avoids problems such as burn-through and incomplete welding caused by uneven stress and differences in foil thickness when welding on a single plane. At the same time, the gaps between the steps can serve as channels for electrolyte flow, improving wetting efficiency.

[0045] An insulating isolation ring 12 is disposed between the radial outer edge of the current collector and the inner wall of the cylindrical housing 1. Its inner diameter is adapted to the radial outer edge of the current collector. Its function is to achieve insulation isolation between the current collector and the housing, prevent short circuit of the battery caused by contact between the current collector and the housing, and fix the position of the current collector to avoid welding failure and circuit abnormality caused by the current collector shifting during the transportation and use of the battery.

[0046] The positive current collector 3 is directly welded to the stepped annular end face of the positive electrode lug 6, and the negative current collector 4 is directly welded to the stepped annular end face of the negative electrode lug 7. The function of the current collector is to collect the current conducted by the lug and stably transmit it to the battery end cap, achieving uniform current output and avoiding heat generation and increased internal resistance caused by local current concentration. The circumferentially spaced electrolyte penetration holes 11 on the current collector allow the electrolyte to pass through the current collector and fully contact the lug end face and the inside of the cell, solving the problem of dead zones in electrolyte wetting caused by the obstruction of traditional current collectors.

[0047] Furthermore, the stepped structure includes an inner ring stepped surface 8, at least one middle ring stepped surface 9, and an outer ring stepped surface 10 distributed radially in sequence. The inner ring stepped surface 8 has a first protrusion height relative to the axial end face of the wound cell 2, the middle ring stepped surface 9 has a second protrusion height, and the outer ring stepped surface 10 has a third protrusion height. The first protrusion height is greater than the second protrusion height, and the second protrusion height is greater than the third protrusion height.

[0048] Adaptive to progressive welding of the current collector, avoiding burn-through and incomplete welds, improving welding yield and strength, and ensuring stable current conduction. The stepped gaps create multi-channel electrolyte flow paths, accelerating wetting speed, avoiding wetting dead zones, and improving battery electrochemical stability. The regular layered structure enhances the deformation resistance of the tabs, preventing wrinkles and damage during production and use. Clear structural standards adapt to segmented pressurization processes, improving product consistency and facilitating industrial mass production.

[0049] Furthermore, an insulating isolation ring 12 is provided between the radial outer edge of the positive current collector 3 and the negative current collector 4 and the inner wall of the cylindrical shell 1. The inner diameter of the insulating isolation ring 12 is adapted to the radial outer edge of the positive current collector 3 or the negative current collector 4.

[0050] The electrical connection between the current collector and the metal casing is isolated, completely eliminating the risk of short circuits and improving battery safety. Radial restraint is provided for the current collector, fixing its position and preventing displacement or desoldering caused by vibration or impact, ensuring structural stability. The inner diameter fitting design simplifies the assembly process, avoids assembly deviations, protects the current collector and casing from friction damage, and improves assembly yield.

[0051] Furthermore, the annular end faces of the positive electrode full electrode ear 6 and the negative electrode full electrode ear 7 are integrally flattened before welding, and the stepped structure is a dense metal end face naturally formed after flattening.

[0052] This process creates a dense metal end face for the tabs, eliminating gaps between multiple foil layers, reducing contact resistance, and improving current conduction efficiency. The dense end face reduces the risk of electrolyte leakage and improves weldability with the current collector, further reducing welding defects. After flattening, a stepped structure is naturally formed, eliminating the need for additional molding processes, simplifying the production process, and reducing production costs.

[0053] A winding process for a tabless-free, fully tabbed cylindrical lithium battery, used in cylindrical lithium batteries, includes the following steps:

[0054] Step S1: Electrode preparation, coating the positive electrode current collector and the negative electrode current collector with a positive electrode active material layer 18 and a negative electrode active material layer 19 respectively, wherein a blank area 20 of the positive electrode current collector without active material coating is reserved at one end, and a blank area 21 of the negative electrode current collector without active material coating is reserved at one end.

[0055] Positive and negative active material layers 19 are coated on the surfaces of the positive and negative current collectors, respectively. Simultaneously, a blank area 20 for the positive electrode tab without active material coating is reserved at one end of the positive current collector, and a blank area 21 for the negative electrode tab without active material coating is reserved at one end of the negative current collector. The core principle of this step is that the blank areas serve as the forming areas for the subsequent tabs, avoiding decreased conductivity and poor welding caused by active material coverage. Furthermore, the reserved positions ensure that the positive and negative tabs are located at opposite ends of the cell after winding, preventing short circuits between the positive and negative electrodes.

[0056] Step S2: Winding and forming, the positive electrode 15, the separator 17 and the negative electrode 16 are stacked in sequence, and spirally wound along the winding direction with the winding needle as the core axis to form a cylindrical wound cell, and the positive electrode tab blank area 20 is located at one end of the axial direction of the wound cell 2, and the negative electrode tab blank area 21 is located at the other end of the axial direction of the wound cell 2;

[0057] The positive electrode 15, separator 17, and negative electrode 16 are stacked sequentially. Using a winding needle of a specific diameter (2mm-6mm) as a mandrel, and controlling a specific tension (0.5N-3N), the electrode is spirally wound along the winding direction to form a cylindrical wound cell. The positive electrode tab clearance area 20 is located at one end of the cell's axial direction, and the negative electrode tab clearance area 21 is located at the other end. The working principle is as follows: the diameter of the winding needle determines the size of the central through-hole 5 of the cell, directly affecting electrolyte flow and heat dissipation efficiency; the winding tension control avoids loose winding leading to internal cell loosening and electrode displacement, or tight winding leading to separator 17 damage and electrode wrinkling, ensuring the consistency and stability of the cell structure.

[0058] Step S3: End face treatment. Axial pressure is applied to the positive electrode tab blank area 20 and the negative electrode tab blank area 21 on the two axial end faces of the wound battery cell 2, so that they form a stepped structure from the inside to the outside in the radial direction. At the same time, the metal foils of the tab blank areas are fused together under pressure to form a dense annular end face.

[0059] Axial pressure is applied to the blank areas of the tabs at both ends of the battery cell using a "segmented pressurization" method (first applying the first pressure to the inner ring area, then the second pressure to the middle ring, and finally the third pressure to the outer ring, with the first pressure > the second pressure > the third pressure). This creates a stepped surface 10 in the blank areas radially from the inside out, consisting of inner, middle, and outer rings (the inner ring has the highest extension height, and the outer ring has the lowest). Simultaneously, the multiple layers of metal foil are fused together under pressure, forming a dense annular end face. The principle is as follows: segmented pressurization allows for precise control over the density and extension height of the inner, middle, and outer ring foils of the tabs. The inner ring has the highest pressure, ensuring sufficient fusion and extension height for stable contact with the current collector. The outer ring has the lowest pressure, preventing foil damage due to excessive pressure. The gaps in the stepped structure also provide channels for electrolyte wetting and heat dissipation. The integrated flattening process eliminates gaps between the multiple layers of foil, improving the conductivity and structural strength of the tabs.

[0060] Step S4: Current collector welding. The positive current collector 3 and the negative current collector 4 are laser welded to the annular end face of the positive all-pole lug 6 and the annular end face of the negative all-pole lug 7, respectively. The laser welding is performed continuously or intermittently along the circumference of the annular end face.

[0061] The positive and negative current collectors 4 are laser-welded to the corresponding stepped annular end faces of the full-tab, with welding parameters controlled at power 300W-800W, speed 50mm / s-200mm / s, and spot diameter 0.2mm-0.5mm. Welding is performed continuously or intermittently along the circumference of the annular end face. The working principle is as follows: laser welding features high welding speed, small heat-affected zone, and high welding strength, making it suitable for welding the dense end faces of the full-tab. Specific welding parameters can prevent welding through the full-tab foil (preventing short circuits) or incomplete welding (preventing poor contact). Continuous / intermittent circumferential welding ensures full contact between the current collector and the full-tab end face, achieving uniform current conduction and reducing contact resistance.

[0062] Step S5: Encapsulation: The wound cell 2, with the positive current collector 3 and the negative current collector 4 welded on, is installed into the cylindrical housing 1. The positive current collector 3 is electrically connected to the positive end cap 13 of the cylindrical housing 1, and the negative current collector 4 is electrically connected to the negative end cap 14 of the cylindrical housing 1. After injecting electrolyte, the housing is sealed.

[0063] The wound battery cell with welded current collectors is installed into a cylindrical housing 1. The positive and negative current collectors 4 are electrically connected to the positive and negative end caps 14 of the housing, respectively. After injecting electrolyte, the housing is sealed. Simultaneously, an insulating isolation ring 12 is installed between the current collectors and the inner wall of the housing (this can be done separately after S4 and before S5). Its working principle is as follows: the housing protects the battery cell and prevents electrolyte leakage; the electrical connection between the end caps and the current collectors enables the battery current to be output; the injection of electrolyte provides a medium for lithium-ion migration; and the insulating isolation ring 12 insulates the current collectors from the housing, preventing short circuits, ultimately forming a complete and normally functioning cylindrical lithium battery.

[0064] To further explain, in step S3, the axial pressure is applied in a segmented pressurization manner: first, a first pressure is applied to the inner ring area, then a second pressure is applied to the middle ring area, and finally a third pressure is applied to the outer ring area, wherein the first pressure is greater than the second pressure, and the second pressure is greater than the third pressure.

[0065] Precise control of the step protrusion height ensures a regular formation of the stepped structure with an inner higher and outer lower profile; avoids foil damage or insufficient density caused by single pressure application, and improves the density of the end face of the full electrode tab; adapts to the layered step design to ensure subsequent welding compatibility and improve product consistency.

[0066] Furthermore, in step S3, the stepped structure includes an inner ring stepped surface 8, at least one middle ring stepped surface 9, and an outer ring stepped surface 10. The extension height of the inner ring stepped surface 8 relative to the axial end face of the wound cell 2 is 1.0mm-1.5mm, the extension height of the middle ring stepped surface 9 is 0.5mm-1.0mm, the extension height of the outer ring stepped surface 10 is 0.1mm-0.5mm, and the height difference between adjacent stepped surfaces is 0.3mm-0.6mm.

[0067] To ensure structural uniformity during mass production and improve product consistency; reasonable height and height difference take into account both welding contact area and electrolyte flow space, which not only avoids weld burn-through but also accelerates electrolyte wetting and enhances the deformation resistance of the tabs.

[0068] Furthermore, in step S4, the laser welding power is 300W-800W, the welding speed is 50mm / s-200mm / s, and the spot diameter is 0.2mm-0.5mm.

[0069] It is suitable for welding dense full-tab end faces, avoiding weld penetration or incomplete welding, and improving welding strength and yield; it controls the welding heat-affected zone to protect the diaphragm 17 and active material layer from damage; it ensures a balance between welding efficiency and welding quality, and is suitable for industrial mass production.

[0070] Furthermore, in step S2, the diameter of the winding needle is 2mm-6mm, and the winding tension is controlled between 0.5N and 3N.

[0071] To ensure a regular cell structure after winding and forming, avoid electrode wrinkles and separator 17 damage; control the size of the central through hole 5 to ensure smooth electrolyte flow and heat dissipation; stable winding tension to prevent cell loosening or excessive tightness, and improve winding yield and cell structure stability.

[0072] Furthermore, after step S4 and before step S5, there is also a step of assembling insulating isolation rings 12 between the radial outer edges of the positive current collector 3 and the negative current collector 4 and the inner wall of the cylindrical housing 1, respectively.

[0073] To prevent the insulating isolation ring 12 from being damaged by high temperature during the welding process and to ensure stable insulation performance; welding before assembly facilitates precise positioning of the isolation ring and avoids assembly deviation; to ensure reliable insulation between the current collector and the housing, eliminate the risk of short circuit, and improve assembly efficiency.

[0074] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A cylindrical lithium battery with a tabless-free, multi-tab structure, characterized in that, The device includes a cylindrical shell, a wound cell disposed inside the cylindrical shell, a positive current collector and a negative current collector. The wound cell is formed by stacking a positive electrode sheet, a separator and a negative electrode sheet in sequence and spirally winding them along the winding direction. The wound cell has a central through hole. The positive electrode sheet includes a positive current collector and a positive active material layer coated thereon, wherein one end of the positive current collector along the length direction forms a positive full electrode tab extending axially. The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated thereon, and the other end of the negative electrode current collector along the length direction forms a negative electrode tab that extends axially. The positive and negative electrode tabs are located at the two ends of the axial direction of the wound battery cell, and each of them has an overall annular end face structure distributed radially. The annular end faces of the positive electrode lug and the negative electrode lug each have a stepped structure that increases radially from the inside to the outside, and the stepped surfaces of the stepped structures all face the axial outer side of the wound cell. The positive electrode current collector is directly welded to the annular end face of the positive electrode lug, and the negative electrode current collector is directly welded to the annular end face of the negative electrode lug. Both the positive electrode current collector and the negative electrode current collector have multiple electrolyte through holes arranged circumferentially.

2. The cylindrical lithium battery with a tabless structure according to claim 1, characterized in that, The stepped structure includes an inner ring stepped surface, at least one middle ring stepped surface, and an outer ring stepped surface distributed radially in sequence. The inner ring stepped surface has a first protrusion height relative to the axial end face of the wound cell, the middle ring stepped surface has a second protrusion height, and the outer ring stepped surface has a third protrusion height. The first protrusion height is greater than the second protrusion height, and the second protrusion height is greater than the third protrusion height.

3. The cylindrical lithium battery with a tabless structure according to claim 1, characterized in that, An insulating isolation ring is provided between the radial outer edge of the positive current collector and the negative current collector and the inner wall of the cylindrical shell. The inner diameter of the insulating isolation ring is adapted to the radial outer edge of the positive current collector or the negative current collector.

4. The cylindrical lithium battery with a tabless structure according to claim 1, characterized in that, The annular end faces of the positive and negative electrode lugs are flattened in one piece before welding, and the stepped structure is a dense metal end face that is naturally formed after flattening.

5. A winding process for a tabless-free cylindrical lithium battery with a full-tab structure, used to manufacture the cylindrical lithium battery according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step S1: Electrode preparation, coating the positive electrode current collector and the negative electrode current collector with a positive electrode active material layer and a negative electrode active material layer respectively, wherein one end of the positive electrode current collector is reserved as a blank area of ​​the positive electrode tab without active material coating, and one end of the negative electrode current collector is reserved as a blank area of ​​the negative electrode tab without active material coating. Step S2: Winding and forming, the positive electrode sheet, separator and negative electrode sheet are stacked in sequence, and spirally wound along the winding direction with the winding needle as the core axis to form a cylindrical wound cell, and the blank area of ​​the positive electrode tab is located at one end of the axial direction of the wound cell, and the blank area of ​​the negative electrode tab is located at the other end of the axial direction of the wound cell. Step S3: End face treatment. Axial pressure is applied to the positive electrode tab blank area and the negative electrode tab blank area on both ends of the axial direction of the wound battery cell, so that they form a stepped structure from the inside to the outside in the radial direction. At the same time, the metal foils in the tab blank area are fused together under pressure to form a dense annular end face. Step S4: Current collector welding. The positive current collector and the negative current collector are laser welded to the annular end face of the positive electrode lug and the annular end face of the negative electrode lug, respectively. The laser welding is performed continuously or intermittently along the circumference of the annular end face. Step S5: Encapsulation: The wound cell with the positive current collector and negative current collector welded on it is installed into the cylindrical shell. The positive current collector is electrically connected to the positive end cap of the cylindrical shell, and the negative current collector is electrically connected to the negative end cap of the cylindrical shell. After injecting electrolyte, it is sealed.

6. The winding process of the cylindrical lithium battery with tabless-free and tab-free structure according to claim 5, characterized in that, In step S3, the axial pressure is applied in a segmented pressurization manner: first, a first pressure is applied to the inner ring region, then a second pressure is applied to the middle ring region, and finally a third pressure is applied to the outer ring region, wherein the first pressure is greater than the second pressure, and the second pressure is greater than the third pressure.

7. The winding process of the cylindrical lithium battery with tabless-free and tab-free structure according to claim 5, characterized in that, In step S3, the stepped structure includes an inner ring stepped surface, at least one middle ring stepped surface, and an outer ring stepped surface. The extension height of the inner ring stepped surface relative to the axial end face of the wound cell is 1.0mm-1.5mm, the extension height of the middle ring stepped surface is 0.5mm-1.0mm, the extension height of the outer ring stepped surface is 0.1mm-0.5mm, and the height difference between adjacent stepped surfaces is 0.3mm-0.6mm.

8. The winding process of the cylindrical lithium battery with tabless-free and tab-free structure according to claim 5, characterized in that, In step S4, the laser welding power is 300W-800W, the welding speed is 50mm / s-200mm / s, and the spot diameter is 0.2mm-0.5mm.

9. The winding process of the cylindrical lithium battery with tabless-free and tab-free structure according to claim 5, characterized in that, In step S2, the diameter of the winding needle is 2mm-6mm, and the winding tension is controlled between 0.5N and 3N.

10. The winding process of the cylindrical lithium battery with tabless-free and tab-free structure according to claim 5, characterized in that, After step S4 and before step S5, the process also includes assembling insulating isolation rings between the radial outer edges of the positive current collector and the negative current collector and the inner wall of the cylindrical shell, respectively.

Images