Steel shell cylindrical battery roll core structure and connection method

Abstract

The invention relates to the technical field of steel shell cylindrical battery manufacturing, in particular to a steel shell cylindrical battery roll core structure and a connection method, and the connection method comprises the following steps: S1, a positive plate, a negative plate and a diaphragm form a roll core in a winding mode, the positive plate and the negative plate both adopt a full-tab structure, and tab blank areas are reserved in corresponding tab areas, after winding is completed, the end face of the winding core is kneaded to be flat and shaped, and exposed platforms with certain flatness and mechanical strength are formed on the positive end face and the negative end face respectively; according to the invention, a full-tab roll core structure is adopted in the steel shell cylindrical battery, and the positive and negative end surfaces are kneaded and shaped, so that the end surfaces of the roll core form a compact and flat exposed platform with certain mechanical strength; and reliable connection between the positive electrode and the negative electrode and the collector plate is realized by adopting a continuous laser welding mode, so that the effective over-current area is obviously enlarged, the conductive path is shortened and the internal resistance of the battery is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of steel-cased cylindrical battery manufacturing technology, specifically to a steel-cased cylindrical battery core structure and connection method. Background Technology

[0002] Currently, steel-cased cylindrical batteries use single or multiple tabs for the positive and negative terminals. This structure has high internal resistance and low overcurrent capacity, which does not meet the requirements of many high-rate charging and discharging conditions.

[0003] Currently, the positive and negative current collectors of steel-cased cylindrical batteries are mostly connected by laser pulse welding. However, laser pulse welding is slow and has low cycle efficiency. Furthermore, pulse welding requires more clearance for the positive and negative tabs, increasing raw material costs and the difficulty of the smoothing process.

[0004] Current steel-cased cylindrical batteries suffer from poor weld uniformity in the positive and negative current collector designs, resulting in uneven conductive paths and insufficient current carrying capacity. Furthermore, the current current collector design of steel-cased cylindrical batteries has a small effective current carrying area, high internal resistance, and significant heat generation under high-rate charge / discharge, leading to reduced battery cycle life. Finally, current steel-cased cylindrical batteries are difficult to wet with electrolyte, time-consuming, and exhibit poor consistency.

[0005] In summary, existing steel cylindrical batteries suffer from problems such as slow cycle time, high cost, poor product performance (insufficient overcurrent capacity, high internal resistance), and difficulty in electrolyte filling. Summary of the Invention

[0006] The purpose of this invention is to solve the problems of slow cycle time, high cost, poor product performance, insufficient current carrying capacity, high internal resistance, and difficulty in electrolyte injection in existing steel cylindrical batteries.

[0007] To achieve the above objectives, the present invention provides the following technical solution: This invention provides a method for connecting the core of a steel-cased cylindrical battery, comprising the following steps: S1, forming a core by winding a positive electrode sheet, a negative electrode sheet, and a separator, wherein both the positive and negative electrode sheets adopt a full tab structure, and a tab blank area is reserved in the corresponding tab area; after winding, the end face of the core is flattened and shaped to form an exposed platform with a certain flatness and mechanical strength on the positive and negative end faces respectively; S2, attaching the negative current collector to the flattened end face of the negative electrode formed in step S1, and achieving electrical connection between the negative current collector and the flattened end face of the negative electrode using continuous laser welding; S3, connecting the positive current collector to the end face of the negative electrode formed in step S1. The positive electrode flattened end face is formed and bonded together. The positive electrode current collector and the positive electrode flattened end face are electrically connected by continuous laser welding. The positive electrode current collector is provided with a conductive extension handle. S4. After the conductive extension handle is insulated and wrapped, it is bent in a predetermined direction so that the bent conductive extension handle is electrically connected to the battery cap. S5. An insulating pad is placed on the positive electrode current collector, and the conductive extension handle and the insulating pad are glued and fixed to achieve electrical insulation and structural fixation between the positive electrode end face and the steel shell.

[0008] Furthermore, in step S1, the blank length of the positive electrode tab is X mm, the blank length of the negative electrode tab is X mm, and the blank area without tabs is set for three consecutive turns at the core entry head. The flattening and shaping process adopts a combination of axial compression and radial restriction to form a dense and continuous metal contact platform on the flattened positive and negative electrode surfaces.

[0009] Furthermore, in step S1, the exposed height of the positive end face after flattening is X mm, and the exposed height of the negative end face is X mm, in order to balance welding stability and core structure strength.

[0010] Furthermore, in step S2, the negative electrode current collector is provided with multiple circumferentially equidistant recessed areas, so that the negative electrode current collector is in close contact with the negative electrode flattened end face during the welding process. The welding of the negative electrode current collector and the negative electrode flattened end face adopts a single-mode ring continuous laser welding method. The outer ring is used for preheating the molten pool, and the inner ring is used to form a penetration weld. The negative electrode weld trajectory is a U-shaped curve trajectory to reduce heat concentration during the welding process and reduce the thermal impact on the internal diaphragm of the core.

[0011] Furthermore, in step S3, the positive current collector is provided with multiple circumferentially equidistant recessed areas and conductive extension handles. The conductive extension handle of the positive current collector is provided with a chamfer structure and a reinforcing rib structure to facilitate directional bending of the conductive extension handle. The positive current collector and the positive flattened end face are welded by a single-mode annular continuous laser welding method, with a total weld length greater than 140 mm and a weld width greater than 0.2 mm.

[0012] Furthermore, in step S4, the conductive extension handle is wrapped with high-temperature insulating tape before bending, and the conductive extension handle is bent once or multiple times in a predetermined direction to form a reliable electrical connection path with the battery cap.

[0013] Furthermore, in step S5, the insulating pad is disposed between the positive current collector and the steel shell to prevent short circuit between the positive electrode and the steel shell. The insulating pad is fixed to the positive current collector by high-temperature tape or encapsulation process and forms an integrated insulating structure with the conductive extension shank.

[0014] On the other hand, a steel-cased cylindrical battery core structure includes: a core, a positive current collector, a negative current collector, and an insulating component; wherein, the core is formed by winding a positive electrode sheet, a negative electrode sheet, and a separator, both the positive and negative electrode sheets adopting a full tab structure, with tab blank areas set in the corresponding tab regions; the positive and negative end faces of the core are both flattened and shaped to form a positive flattened exposed platform and a negative flattened exposed platform for welding, respectively; the negative current collector is disposed on the negative flattened exposed platform, and the negative current collector has equidistantly distributed circumferential... The battery has multiple recessed areas, with the negative current collector connected to the negative electrode flattened exposed platform via continuous laser welding. The positive current collector is located on the positive electrode flattened exposed platform and has multiple recessed areas and conductive extension handles evenly distributed circumferentially. The positive current collector is electrically connected to the positive electrode flattened exposed platform via continuous laser welding. The conductive extension handle is bent in a predetermined direction after being insulated and forms an electrical connection with the battery cap. An insulating component is located between the positive current collector and the steel shell to achieve electrical insulation between the positive current collector and the steel shell. Beneficial effects

[0015] Compared with known public technologies, the technical solution provided by this invention has the following beneficial effects: This invention employs a full-tab core structure in a steel-cased cylindrical battery, flattening and shaping the positive and negative end faces to create a dense, flat, and mechanically strong exposed platform at the core end faces. This, combined with circumferentially spaced recessed platforms on the current collector, and continuous laser welding, achieves a reliable connection between the positive and negative electrodes and the current collector. This significantly expands the effective current-carrying area, shortens the conductive path, and effectively reduces the battery's internal resistance. Under high-rate charge-discharge conditions, Joule heating is significantly reduced, temperature rise is significantly decreased, and battery safety and cycle life are improved. Simultaneously, continuous laser welding improves welding stability and consistency, reduces the risk of incomplete welds and explosions, and enhances the long-term reliability of electrical connections. Furthermore, the structure of this invention facilitates rapid and uniform electrolyte wetting of the core, improving cell consistency. The high-efficiency welding process can significantly increase production cycle time, reduce equipment quantity and maintenance costs, resulting in a comprehensive technical effect of low internal resistance, high-rate performance, high manufacturing efficiency, and high safety. Attached Figure Description

[0016] Figure 1 This is a flowchart of the method of the present invention; Figure 2 This is a schematic diagram and appearance view of the kneading process of the present invention; Figure 3 This is a schematic diagram and effect image of the welding of the negative electrode current collector of the present invention; Figure 4 This is a schematic diagram and effect diagram of the positive electrode current collector welding of the present invention; Figure 5 This is a schematic diagram of the negative electrode current collector of the present invention; Figure 6 This is a schematic diagram of the wire bonding dimensions of the present invention. Detailed Implementation

[0017] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. 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 should fall within the scope of protection of the present invention.

[0018] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but includes other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0019] The present invention will now be described in further detail with reference to the accompanying drawings: Example

[0020] Electrode assembly consists of: a flattened core, a positive current collector, a negative current collector, and an insulating pad. 1. Core: Utilizes a full tab pre-installation and flattening process; 2. Negative current collector; electrical connection is achieved using continuous laser welding; 3. Positive current collector: Electrically connected using continuous laser welding; 4. Conductive handle bending and coating: After coating the conductive handle with adhesive, it is bent in a specific direction. 5. Insulating pad coating: The insulating pad is fed into the conductive handle and attached to the positive current collector using high-temperature tape; Core Structure: The core is made by winding positive and negative electrode sheets, with pre-reserved tabs on all sides. The positive electrode tab has a blank space of Xmm, and the negative electrode tab has a blank space of Xmm. End face shaping is performed using a "flattening" method. After flattening, the core has exposed platforms for both positive and negative electrodes. The exposed platform end faces balance flatness and a certain degree of hardness, facilitating the welding of the positive and negative current collectors. See... Figure 2 Negative electrode end face connection: The negative electrode current collector is laser-welded to the aforementioned flattened negative electrode end face. The current collector is designed with six equidistant recessed areas, ensuring a tight fit between the current collector and the core during welding. See Figure 3 Positive terminal face connection: The positive current collector is laser-welded to the aforementioned flattened positive terminal face. The current collector is designed with five equidistant recessed areas and a conductive extension shank. The recessed area design ensures a tight fit between the current collector and the core during welding. The chamfered and reinforcing rib designs allow for directional bending of the extension shank. After directional bending, the extension shank forms an electrical connection with the cap. See Figure 4 Leave blank space on all tabs of the core, with Xmm blank space for the positive electrode and Xmm blank space for the negative electrode. Leave Xmm blank space in the first three loops before winding, with a total blank space length of approximately Xmm. After the positive electrode is flattened, the exposed height is Xmm. After the negative electrode is flattened, the exposed height is Xmm. The positive current collector is equipped with a D-shaped anti-fool hole, a countersunk area, reinforcement, and a bend chamfer; The conductive handle is insulated with high-temperature tape. The positive current collector is covered with an insulating pad; (1) Flattening the core: Leave Xmm blank for the positive electrode, Xmm blank for the negative electrode, and Xmm blank for the first three turns of the core, with a blank length of approximately Xmm; the exposed height of the positive electrode after flattening is Xmm, and the exposed height of the negative electrode after flattening is Xmm. The three turns of the core without tabs at the head prevent the central hole area from collapsing after flattening; the Xmm reserved high tabs make the flattened surface dense and flat, with uniform conductivity and good welding stability; (2) Welding of the negative electrode current collector; The negative electrode current collector is welded using a single-mode ring laser. The ring laser can preheat the molten pool, reduce the number of explosions during welding, and improve stability. The inner ring provides penetration, enabling the current collector and the core to form an effective connection. The weld trajectory adopts a "U-shaped" curve, which makes the curvature transition at the arc smooth, the laser scanning speed basically stable, less heat accumulation, and better protection of the diaphragm under the flattened end face. This greatly improves welding stability and cell safety. The dimensions of the negative electrode weld are as follows: amplitude X mm, period X mm. The total weld length is 105.48 mm, and the weld width is 0.15 mm. Based on a 32140 cylindrical 15AH, (105.48*0.15*8*80%) / 15=6.75C, which meets the 6C charge and discharge requirement. After small-batch trial production and verification, the weld tensile strength is stable >30N, the process performance index PPK >1.67, and the welding reliability is strong.

[0021] (3) Positive current collector welding: The positive current collector is welded using a single-mode ring laser. The ring laser can preheat the molten pool, reduce the number of explosions during welding, and improve stability. The inner ring provides penetration, enabling the current collector and the core to form an effective connection. The weld trajectory adopts a "U-shaped" curve, which makes the curvature transition at the arc smooth, the laser scanning speed basically stable, and the heat accumulation less, which can better protect the diaphragm under the flattened end face. This greatly improves the welding stability and cell safety. The positive current collector weld dimensions are as follows: total weld length 140.1mm, weld width 0.2mm. Amplitude Xmm, period Xmm, calculated according to 32140 cylindrical 15AH, (140.1*0.2*5*80%) / 15=7.47C, which meets the 6C charge and discharge requirement. After small-batch trial production verification, the weld tensile strength is stable >15N, and the process performance index PPK >1.67. The welding reliability is strong. See the weld trajectory size design. Figure 6 ; (4) Welding Equipment Cost and Efficiency: This welding design, equipped with a turret-based flying welding system, achieves a welding speed > 500 mm / s and an overall equipment efficiency > 120 ppm. A single device and a single laser are sufficient (one positive and one negative collector). In contrast, traditional pulsed laser welding requires 4 stations and 4 lasers per device, with an efficiency of only 20 ppm. It requires 6 parallel devices and 24 pulsed lasers. The equipment footprint increases by 6 times. Equipment investment: This solution requires 2 single-mode ring lasers, while the traditional solution requires 24 pulsed lasers. Investment costs increase by approximately 2.5 times. Maintenance Costs: This solution requires only 12 sets of tooling and fixtures, while the traditional solution requires 24 sets. The single-mode ring laser in this solution is essentially maintenance-free, whereas pulsed lasers require pump source replacement. The maintenance time and material costs are significantly different.

[0022] (5) Battery performance: The battery with this structure has an internal resistance as low as 1.2mΩ, compared with the internal resistance of 2.0mΩ of the traditional single-tab and multi-tab structure, the internal resistance is reduced by about 40%. This has a significant effect on improving the rate performance of the battery.

[0023] For example, the heat generated by the battery cell in 1 second at 1C: According to Joule's law Q=I²Rt, where Q is the heat generated, I is the current, R is the internal resistance of the battery, and t is the energizing time, Q(1.2 mΩ)= I²Rt=(15A)² *1.2 mΩ*1s=0.27J; Q(2 mΩ)= I²Rt=(15A)² *2 mΩ*1s=0.45J; the heat generation increases by 66.7%, and the difference in heat generation is even more obvious at a high rate of 6C.

[0024] Comparing the heat generation during charging and discharging at 6C for 30s: Q(1.2 mΩ) = I²Rt = (15*6A)² * 1.2 mΩ * 30s = 291.6J, Q(2 mΩ) = 484J, with a heat generation increase of 66.7%. For the rate-dependent temperature rise performance, which is of greater concern in battery usage scenarios, we compared the temperature rise accumulation during actual charging and discharging processes (without considering heat dissipation).

[0025] The typical temperature rise range for a lithium-ion battery at 6C charge / discharge for 1 minute is 800-1100 J / (kg·℃). Here, we take a commonly used estimated midpoint of 1000 J / (kg·℃). ΔT (1.2 mΩ) = Q / (m × c) = (291.6*2) J / 0.3Kg*1000 J / (kg·℃) = 1.944℃. In comparison, ΔT (2 mΩ) = Q / (m × c) = (484*2) J / 0.3Kg*1000 J / (kg·℃) = 3.24℃. The temperature rise difference is 3.24 - 1.944 = 1.296℃. For a single cell, a difference of 1.3℃ in rate-dependent temperature rise over a short period is already significant; after being assembled into a battery pack module, the difference in rate-dependent temperature rise will be even greater.

[0026] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions will not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for connecting the core of a steel-cased cylindrical battery, characterized in that, Includes the following steps: S1. The positive electrode sheet, negative electrode sheet and separator are wound to form a core. Both the positive electrode sheet and the negative electrode sheet adopt a full tab structure and a tab blank area is reserved in the corresponding tab area. After the winding is completed, the end face of the core is flattened and shaped so that the positive end face and the negative end face form an exposed platform with a certain flatness and mechanical strength. S2. The negative current collector is attached to the negative flattened end face formed in step S1, and the electrical connection between the negative current collector and the negative flattened end face is achieved by continuous laser welding. S3. The positive current collector is attached to the positive flattened end face formed in step S1, and the positive current collector and the positive flattened end face are electrically connected by continuous laser welding. The positive current collector is provided with a conductive extension handle. S4. After insulating the conductive extension handle, bend it in a predetermined direction so that the bent conductive extension handle forms an electrical connection with the battery cap. S5. An insulating pad is placed on the positive current collector, and the conductive extension shank is glued and fixed to the insulating pad to achieve electrical insulation and structural fixation between the positive terminal face and the steel shell.

2. The method for connecting steel-cased cylindrical battery cores according to claim 1, characterized in that, In step S1, the blank length of the positive electrode tab is X mm, the blank length of the negative electrode tab is X mm, and the blank area without tabs is set for three consecutive turns at the core entry head. The flattening and shaping process adopts a combination of axial compression and radial restriction to form a dense and continuous metal contact platform on the flattened positive and negative electrode surfaces.

3. The method for connecting steel-cased cylindrical battery cores according to claim 2, characterized in that, In step S1, the exposed height of the positive end face after flattening is X mm, and the exposed height of the negative end face is X mm, in order to balance welding stability and core structure strength.

4. The method for connecting steel-cased cylindrical battery cores according to claim 3, characterized in that, In step S2, the negative electrode current collector is provided with multiple circumferentially equidistant recessed areas, so that the negative electrode current collector is in close contact with the negative electrode flattened end face during the welding process. The welding of the negative electrode current collector and the negative electrode flattened end face adopts a single-mode ring continuous laser welding method. The outer ring is used for preheating the molten pool, and the inner ring is used to form a penetration weld. The negative electrode weld trajectory is a U-shaped curve trajectory to reduce heat concentration during the welding process and reduce the thermal impact on the internal diaphragm of the core.

5. The method for connecting a steel-cased cylindrical battery core according to claim 4, characterized in that, In step S3, the positive current collector is provided with multiple circumferentially equidistant recessed areas and conductive extension handles. The conductive extension handle of the positive current collector is provided with a chamfer structure and a reinforcing rib structure to facilitate directional bending of the conductive extension handle. The positive current collector and the positive flattened end face are welded by a single-mode annular continuous laser welding method. The total length of the weld is greater than 140 mm and the weld width is greater than 0.2 mm.

6. The method for connecting steel-cased cylindrical battery cores according to claim 5, characterized in that, In step S4, the conductive extension handle is wrapped with high-temperature insulating tape before bending. The conductive extension handle is bent once or multiple times in a predetermined direction to form a reliable electrical connection path with the battery cap.

7. The method for connecting steel-cased cylindrical battery cores according to claim 6, characterized in that, In step S5, the insulating pad is placed between the positive current collector and the steel shell to prevent short circuit between the positive electrode and the steel shell. The insulating pad is fixed to the positive current collector by high-temperature tape or encapsulation process and forms an integrated insulating structure with the conductive extension shank.

8. A steel-cased cylindrical battery core structure, comprising a steel-cased cylindrical battery core connection method according to any one of claims 1-7, characterized in that, include: Core, positive current collector, negative current collector, and insulation components; The core is formed by winding a positive electrode sheet, a negative electrode sheet, and a separator. Both the positive and negative electrode sheets adopt a full tab structure, and a tab blanking area is set in the corresponding tab area. The positive and negative end faces of the core are flattened and shaped to form a positive flattened exposed platform and a negative flattened exposed platform for welding, respectively. The negative electrode current collector is disposed on the negative electrode flattened exposed platform. The negative electrode current collector has multiple recessed areas evenly distributed along the circumference. The negative electrode current collector is electrically connected to the negative electrode flattened exposed platform by continuous laser welding. The positive electrode current collector is disposed on the positive electrode flattened exposed platform. The positive electrode current collector has multiple recessed areas and conductive extension handles that are equidistantly distributed along the circumference. The positive electrode current collector is electrically connected to the positive electrode flattened exposed platform by continuous laser welding. The conductive extension shank is bent in a predetermined direction after being insulated and forms an electrical connection with the battery cap. The insulating component is disposed between the positive current collector and the steel shell to achieve electrical insulation between the positive current collector and the steel shell.

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