A positive electrode tab flow guide assembly

Abstract

The present application relates to lithium battery manufacturing technology field, especially to a kind of positive tab flow guide combination.It includes positive cap and cell positive, the positive cap is welded with positive upper bus bar, the cell positive is welded with positive lower bus bar, and the conductive spring is crimped between positive upper bus bar and positive lower bus bar.Positive upper bus bar, conductive spring and positive lower bus bar are crimped, and spring is in compression state, which ensures that the crimping force between upper and lower bus bar and conductive spring remains constant, and cell positive is connected with positive cap through positive lower bus bar, conductive spring and positive upper bus bar.The combination structure of positive upper and lower bus bar and conductive spring improves the conduction cross section of positive tab, and improves the current conduction capacity of positive tab.The lithium battery positive tab flow guide structure obtained by the present application is highly stable and reliable, and the lithium battery discharge rate is high.

Description

Technical Field

[0001] This invention relates to the field of lithium battery manufacturing technology, and in particular to a positive electrode tab current-conducting assembly. Background Technology

[0002] Lithium-ion batteries have high energy density, long cycle life, and good safety performance. They are currently widely used in portable devices, electric vehicles, energy storage, and other industries.

[0003] In the manufacturing process of lithium batteries, the positive electrode tab is generally connected to the positive electrode plate, and the negative electrode tab is connected to the negative electrode plate. Then, the positive and negative electrode plates, connected with the positive and negative electrode tabs, are wound with a separator to form a cell. The cell is then placed in the battery casing, with the negative electrode tab connected to the bottom of the casing and the positive electrode tab connected to the positive cap. Currently, the direct pressing method (i.e., tight contact method) is used to connect the positive electrode tab and the positive cap, but this method has drawbacks. Gaps can easily form between the positive electrode tab and the cap, and external vibrations or drops can reduce the tightness of the contact between the positive electrode tab and the positive cap, leading to increased contact resistance. Some methods also employ direct welding to connect the positive electrode tab and the positive electrode cap. Patent application number 201110030497.8 discloses an explosion-proof assembly of the positive electrode tab and positive electrode cap using inert gas shielded welding. The width of the positive electrode tab and the explosion-proof assembly is 2-3.5mm, the thickness is 0.05-0.3mm, and the total flow-conducting cross-section is 1mm. 2 The process ensures the reliability of the welding points, but the current-carrying cross-section is relatively small. For long-term discharge of high currents of tens to hundreds of amps at high rates, there is a problem of insufficient current-carrying cross-section. Due to the limitations of the internal space of the battery and the flexibility of the tabs, it is difficult to significantly increase the current-carrying cross-section of the positive electrode tab. Summary of the Invention

[0004] To address the aforementioned technical deficiencies, this invention solves the technical problem of small positive electrode tab flow-conducting cross-section and provides a positive electrode tab flow-conducting assembly with large positive electrode tab flow-conducting cross-section and high reliability.

[0005] To solve the above-mentioned technical problems, the technical solution of the present invention is: a positive electrode tab current-conducting assembly, comprising a positive electrode cap and a positive electrode cell, wherein an upper positive electrode busbar is welded to the positive electrode cap, and a lower positive electrode busbar is welded to the positive electrode cell, and a conductive spring is pressed between the upper and lower positive electrode busbars. After the upper positive electrode busbar, the conductive spring, and the lower positive electrode busbar are pressed together, the spring is in a compressed state, ensuring that the pressing force between the upper and lower busbars and the conductive spring remains constant. The positive electrode cell is connected to the positive electrode cap through the lower positive electrode busbar, the conductive spring, and the upper positive electrode busbar.

[0006] Further: In the above-mentioned positive electrode tab current-conducting assembly, the positive electrode cap, the upper positive electrode busbar, and the lower positive electrode busbar are all disc-shaped. The conductive spring is a horizontal closed circular spring with an elliptical longitudinal section. The elliptical cross-section of each coil ensures consistent tilt direction, preventing inconsistent tilt directions when the spring is subjected to force, thus guaranteeing consistent spring compression force across the entire ring. There are two concentric circular springs with a spacing >0.2mm. The spring wire diameter is 0.15-0.5mm, with 50-60 coils in the inner ring and 80-100 coils in the outer ring to improve conductivity. Both the upper and lower positive electrode busbars have grooves to accommodate the circular springs. The inner side of each groove is plated with a silver layer, 5-10µm thick. The contact surfaces of the upper and lower positive busbars with the circular spring are arched. These arched surfaces cover the outer perimeter of the circular spring, increasing the contact area and reducing contact resistance. The gap between the upper and lower positive busbars is 0.3-1.3 mm. The current-conducting cross-section of the upper and lower positive busbars is greater than 10 mm². 2 The above significantly improves the current-carrying capacity of the positive electrode.

[0007] A positioning ring is provided in the hollow space of the inner ring spring. The upper end of the positioning ring is aligned with the center of the upper positive busbar, and the lower end of the positioning ring is aligned with the center of the lower positive busbar. Insulating rings are provided on the outer sides of the upper and lower positive busbars. The positioning rings ensure the concentricity of the upper and lower busbars and prevent eccentricity during installation. The insulating rings on the outer sides of the upper and lower positive busbars prevent the positive terminal of the battery cell from short-circuiting with the battery cell casing (negative terminal) through the upper and lower busbars during installation.

[0008] Alternatively: In the above-mentioned positive electrode tab current-conducting assembly, the conductive spring is a vertical spring with a wire diameter of 0.15-0.5mm and 4-7 coils.

[0009] The lower positive electrode busbar has elongated holes evenly distributed in the radial direction to facilitate the injection of electrolyte into the battery cell casing. The conductive spring is made of chromium zirconium copper or brass to improve the fatigue strength of the spring and ensure that the contact force between the spring and the upper and lower contact surfaces of the upper and lower positive electrode busbars is constant.

[0010] Compared with existing technologies, the above-mentioned positive electrode tab current-conducting assembly includes a positive electrode cap and a positive cell electrode. An upper positive electrode busbar is welded to the positive electrode cap, and a lower positive electrode busbar is welded to the positive cell electrode. A conductive spring is pressed between the upper and lower positive electrode busbars. After the upper and lower positive electrode busbars are pressed together, the spring is in a compressed state, ensuring that the pressing force between the upper and lower busbars and the conductive spring remains constant. The positive cell electrode is connected to the positive electrode cap through the lower positive electrode busbar, the conductive spring, and the upper positive electrode busbar. The combination structure of the upper and lower positive electrode busbars and the conductive spring increases the conduction cross-section of the positive electrode tab, improving its current conduction capacity. From the perspective of reducing the internal resistance of the battery tab, this increases the discharge rate of the lithium battery. Compared with existing technologies, the discharge rate of the lithium battery obtained using this technology is increased by 3-6 times. Therefore, the beneficial technical effect of this invention is that the positive electrode tab current-conducting structure is highly stable and reliable, and the discharge rate is high. Attached Figure Description

[0011] Figure 1 This is an enlarged longitudinal section view of the positive electrode tab current-conducting assembly in Embodiment 1;

[0012] Figure 2 This is a schematic diagram of the positive electrode busbar structure in Embodiment 1;

[0013] Figure 3 This is a schematic diagram of the positive electrode lower busbar structure in Embodiment 1;

[0014] Figure 4 This is a schematic diagram of the double-ring spring structure in Embodiment 1;

[0015] Figure 5 This is an enlarged longitudinal section view of the positive electrode tab current-conducting assembly in Embodiment 2;

[0016] Figure 6 yes Figure 5 A top view of the structure after removing the busbar on the positive electrode;

[0017] Figure 7 This is an enlarged longitudinal section view of the positive electrode tab current-conducting assembly in embodiment six;

[0018] Figure 8 This is an enlarged longitudinal section view of the positive electrode tab current-conducting assembly in embodiment seven;

[0019] Among them, 1 is the positive cap, 2 is the positive electrode of the battery cell, 3 is the upper positive busbar, 4 is the lower positive busbar, 5 is the conductive spring, 6 is the groove, 7 is the positioning ring, 8 is the insulating ring, 9 is the elongated hole, 10 is the inner ring spring, and 11 is the outer ring spring. Detailed Implementation

[0020] The main purpose of this invention is to improve the conductivity cross-section of the positive electrode tab by combining the upper and lower busbars with a conductive spring, thereby increasing the current conduction capacity of the positive electrode tab and improving the discharge rate of the lithium battery by reducing the internal resistance of the battery tab. By using the conductive spring as an intermediate current carrier, it maintains a certain elasticity between the upper and lower busbars and the spring contact surface, effectively solving the problem of loose connection of the battery positive electrode tab caused by various reasons.

[0021] Implementation method one: such as Figure 1-4 A positive electrode tab current-conducting assembly includes a positive electrode cap 1 and a battery cell positive electrode 2. An upper positive electrode busbar 3 is welded to the positive electrode cap, and a lower positive electrode busbar 4 is welded to the battery cell positive electrode 2. A conductive spring 5 is pressed between the upper positive electrode busbar 3 and the lower positive electrode busbar 4. The positive electrode cap 1, the upper positive electrode busbar 3, and the lower positive electrode busbar 4 are all disc-shaped. The conductive spring is a horizontal closed circular spring. There are two concentric circular springs with a spacing >0.2mm. The spring wire diameter is 0.15-0.5mm, with the inner circular spring having 50-60 turns (10 coils) and the outer circular spring having 80-100 turns (11 coils). Both the upper positive electrode busbar 3 and the lower positive electrode busbar 4 have grooves 6 for accommodating the circular springs. The groove has a silver plating layer with a thickness of 5-10 μm. The gap between the upper and lower positive electrode busbars is 0.3-1.3 mm. The lower positive electrode busbar has elongated holes 9 evenly distributed in the radial direction to facilitate the injection of electrolyte into the cell casing. The conductive spring is made of chromium zirconium copper or brass. In all embodiments of the present invention, the positive electrode cap includes a top cap and a bottom piece. For ease of understanding, the positive electrode cap 1 of the present invention is identified by the piece pointing to the bottom surface of the positive electrode cap.

[0022] Implementation Method Two: The positive electrode tab current-conducting assembly from Implementation Method One is applied to a lithium iron phosphate battery. The upper and lower positive electrode busbars are made of 0.25mm thick chromium-zirconium copper. The inner ring spring (10) has 68 inner turns, and the outer ring spring (11) has 97 turns. The wire diameter is 0.25mm, and the wire surface is plated with 8µm of silver. The calculated conductive cross-section is 16.2mm². 2The cross-sectional area of ​​the positive electrode tab is much larger than that of a normal lithium iron battery, effectively reducing the tab resistance and thus improving the discharge rate of the lithium iron battery. Utilizing the elasticity of the circular spring assembly structure, a moderate pressing force is maintained between the upper and lower positive electrode tabs and the spring, effectively solving the problem of loosening of the tab pressing surface caused by cell vibration, drops, etc. Taking the 26550 lithium iron battery as an example, the conventional positive electrode tab connection piece is 3-5mm wide, 0.2-0.4mm thick, with a current-conducting cross-section of less than 2mm², and a discharge rate of no more than 1C (the battery capacity in this embodiment is simply referred to as 1C). Using the horizontal double-circular spring of this embodiment, the current-conducting cross-section is 16.2mm², which is much larger than that of the conventional current-conducting tab connection method, effectively reducing the tab resistance and achieving a discharge rate of up to 5C.

[0023] In practice, to increase the current-conducting cross-section of the positive electrode tab, the present invention can also be implemented in the following manner, according to the actual application of the battery, resulting in a lithium battery with a discharge rate of 3C-6C, as detailed below:

[0024] Implementation Method 3: Unlike Implementation Methods 1 and 2, the circular springs are 1, 3, or 4 springs with the same center, which is determined by the area of ​​the positive electrode cap 1, the upper positive electrode busbar 3, and the lower positive electrode busbar 4.

[0025] Implementation Method Four: (e.g.) Figure 5 , 6 Unlike embodiment one, the conductive spring is a vertical spring with a wire diameter of 0.15-0.5 mm and 4-7 coils. This increases the current-conducting cross-section of the positive electrode tab, resulting in a lithium battery with a discharge rate of 3C.

[0026] Implementation Method 5: Unlike Implementation Methods 1 and 2, the longitudinal cross-section of the circular spring is elliptical. With an elliptical longitudinal cross-section, each coil of the spring has the same inclination direction, preventing inconsistent inclination directions when the spring is subjected to force from above and below, thus ensuring consistent spring compression force across the entire ring.

[0027] Implementation method six: such as Figure 7 Unlike embodiment five, the inner ring spring 10 has a positioning ring 7 in the hollow space of the ring. The upper end of the positioning ring is directly opposite the center of the upper positive busbar 3, and the lower end of the positioning ring is directly opposite the center of the lower positive busbar 4. The positioning ring 7 ensures the concentricity of the upper and lower busbars and prevents eccentricity during installation of the upper and lower busbars.

[0028] Implementation method seven: such as Figure 8Unlike embodiment six, insulating rings 8 are provided on the outer sides of the upper positive busbar 3 and the lower positive busbar 4. This prevents the positive terminal of the battery cell from short-circuiting with the battery cell casing (negative terminal) through the busbars during installation.

[0029] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A positive electrode tab current-conducting assembly, comprising a positive electrode cap (1) and a battery cell positive electrode (2), characterized in that: A positive upper busbar (3) is welded onto the positive cap, and a positive lower busbar (4) is welded onto the positive electrode (2) of the battery cell. A conductive spring (5) is pressed between the positive upper busbar (3) and the positive lower busbar (4). The conductive spring is a horizontal closed circular spring, and the longitudinal section of the circular spring is elliptical. Both the upper positive electrode busbar (3) and the lower positive electrode busbar (4) are provided with grooves (6) for accommodating a circular spring.

2. The positive electrode tab current-conducting assembly according to claim 1, characterized in that: The positive electrode cap (1), the upper positive electrode busbar (3), and the lower positive electrode busbar (4) are all disc-shaped.

3. The positive electrode tab current-conducting assembly according to claim 2, characterized in that: The circular springs are two concentric rings with a spacing of >0.2mm. The spring wire diameter of the circular springs is 0.15-0.5mm, the inner ring spring has 50-60 coils, and the outer ring spring has 80-100 coils.

4. The positive electrode tab current-conducting assembly according to claim 3, characterized in that: The groove has a silver plating layer with a thickness of 5-10 μm; the gap between the upper positive electrode busbar and the lower positive electrode busbar is 0.3-1.3 mm.

5. The positive electrode tab current-conducting assembly according to claim 3, characterized in that: A positioning ring (7) is provided in the hollow space of the inner ring spring. The upper end of the positioning ring is directly opposite the center of the upper positive terminal block (3), and the lower end of the positioning ring is directly opposite the center of the lower positive terminal block (4). An insulating ring (8) is provided on the outside of the upper positive terminal block (3) and the lower positive terminal block (4).

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