Busbar plate and battery

Abstract

A busbar plate and a battery, which are used in the technical field of battery production and processing. The battery comprises the busbar plate. A plurality of welding traces (2) is formed on one side of the busbar plate so as to be combined with a winding core (3). The welding traces (2) are distributed in an array around the circumference of the busbar plate, and each welding trace (2) presents a smooth wavy curve.

Description

Busbar and battery

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on December 18, 2023, with application number 202323461294.1. The entire contents of the above application are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of battery production and processing, and in particular to a busbar and a battery. Background Art

[0003] Cylindrical batteries are generally welded together by laser welding the battery busbar and the winding core to ensure the strength of the connection and the flow area on the pole and the connecting piece. In related technologies, the laser welding trajectory between the battery busbar and the winding core can adopt a zigzag welding trajectory. The zigzag welding trajectory requires the speed of the laser beam near the inflection point to first decrease to zero and then increase from zero to accelerate. Alternatively, the laser welding trajectory between the battery busbar and the winding core can also adopt a spiral curve welding trajectory (see Figure 1). SUMMARY OF THE INVENTION

[0004] In a broken-line welding trajectory, laser energy accumulates significantly at the inflection points, resulting in deeper welds and the risk of weld penetration. In a spiral welding trajectory, multiple overlapping weld points can easily cause over-welding, leading to weld penetration. These issues contribute to the poor quality of battery welding in related technologies.

[0005] The present application provides a busbar, comprising a busbar having a welding side and a back side arranged opposite to each other, wherein the welding side is configured to be welded to a coil core, and the back side is provided with a welding track, and the welding track presents a smooth wavy curve.

[0006] The present application also provides a battery, comprising a winding core and a busbar as described above, wherein the welding side of the busbar is welded to the tab of the winding core, and the welding track on the busbar overlaps with the tab at the orthographic projection of the welding side. Beneficial effects

[0007] The busbar provided in the present application can make it difficult for the welding trajectory to have inflection points by setting the welding trajectory as a smooth wavy curve without cross-overlap, thereby reducing the welding energy at the inflection point and avoiding breakdown of the busbar. It can also avoid the use of spiral welding in related technologies, which causes multiple overlapping points on the busbar, thereby avoiding excessive welding energy at the overlapping points on the busbar. Multiple welding trajectories are then evenly arranged in an array on the busbar, which can make the connection between the busbar and the winding core more firm and the flow area larger, while improving the over-welding situation and improving the welding quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG1 is a schematic structural diagram of a busbar in the related art;

[0009] FIG2 is a schematic structural diagram of a negative electrode busbar provided in an embodiment of the present application;

[0010] FIG3 is a schematic structural diagram of a positive busbar provided in an embodiment of the present application;

[0011] FIG4 is a schematic diagram of another structure of the negative electrode busbar provided in an embodiment of the present application;

[0012] FIG5 is another structural schematic diagram of the positive busbar provided in an embodiment of the present application;

[0013] FIG6 is a schematic diagram of a third structure of a negative electrode busbar provided in an embodiment of the present application;

[0014] Figure 7 is a cross-sectional structural diagram of a battery provided in an embodiment of the present application;

[0015] FIG8 is a schematic diagram of the structure of the tab provided in an embodiment of the present application.

[0016] The accompanying drawings are as follows:

[0017] 11. Busbar body; 12. Lead tab; 2. Welding track; 21. Semicircular portion; 22. Straight portion; 3. Winding core; 31. Section; A. First part; B. Second part; C. Third part. Modes for Carrying Out the Invention

[0018] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more features. In the description of this application, "plurality" means two or more, unless otherwise specifically specified.

[0019] In related technologies, the battery busbar includes a positive busbar and a negative busbar. The positive busbar needs to be welded to the winding core, and the negative battery needs to be welded to the winding core. This allows the cells to be combined to form a battery pack for powering the device being powered. The more uniform the welding between the battery busbar and the winding core, and the better the welding strength and current capacity of the multiple welding points between the battery busbar and the winding core, the better the welding effect.

[0020] The welding track used in the connection structure between the battery busbar and the winding core in the related art is usually a broken line and a spiral, so it is easy to have inflection points and overlapping points, resulting in over-welding between the battery busbar and the winding core.

[0021] Please refer to Figures 2 and 3. Figure 2 is a structural schematic diagram of the negative busbar provided in an embodiment of the present application, and Figure 3 is a structural schematic diagram of the positive busbar provided in an embodiment of the present application. The present application provides a busbar having a welding side and a back side relatively arranged, the welding side being configured to be welded to the winding core 3, and the back side being provided with a welding track 2, and the welding track 2 presents a smooth wavy curve.

[0022] It is understandable that the smooth wavy curve can be any curve without inflection points and overlap points (no intersection), for example, it can be a sine curve, or a curve without inflection points composed of straight lines and curves, or even a random curve.

[0023] Because in the related art, some welding trajectories are bent straight lines with multiple inflection points. Therefore, during the welding process, the laser beam needs to accelerate on the straight line and then maintain a uniform speed. It needs to decelerate when it is about to reach the inflection point until the speed of the laser beam drops to 0 at the inflection point, and then the speed of the laser beam increases from 0. Therefore, the energy of the laser beam accumulates greatly at the inflection point, which easily causes a large welding depth and the risk of welding through. The welding trajectory is set to a spiral pattern. Although there are no inflection points in the welding trajectory, there are multiple overlapping points. The existence of overlapping points in the welding trajectory means that the welding energy at that location is too high, and over-welding is likely to occur at that location. Both situations have over-welding to varying degrees, thus affecting the welding effect.

[0024] The beneficial effects of the present application are as follows: by setting the welding track 2 as a smooth wavy curve without cross-overlap (the wavy curve can be a smooth curve or a non-smooth curve, and the non-smooth wavy curve may also have inflection points), it is possible to make it difficult for the welding track 2 to have inflection points, thereby reducing the welding energy at the inflection points, avoiding the breakdown of the busbar, and also avoiding the use of spiral welding in related technologies to cause multiple overlapping points on the busbar, thereby avoiding excessive welding energy at the overlapping points on the busbar; and then arranging multiple welding tracks 2 in a uniform array on the busbar, which can make the connection between the busbar and the winding core 3 more firm and the flow area larger, while improving the over-welding situation and improving the welding quality.

[0025] The busbar in this embodiment is suitable for steel-shell cylindrical battery cells, and can of course also be used for batteries of other shapes (such as square).

[0026] In some embodiments of the present application, referring to Figures 4 and 5, Figure 4 is another structural schematic diagram of the negative busbar provided in the embodiment of the present application, and Figure 5 is another structural schematic diagram of the positive busbar provided in the embodiment of the present application. The welding track 2 includes a plurality of semicircular portions 21 and a plurality of straight portions 22, and the plurality of semicircular portions 21 and the plurality of straight portions 22 are alternately arranged and connected in sequence.

[0027] The alternating arrangement means that the straight portion 22 and the semicircular portion 21 are connected end to end, one end of a straight portion 22 is connected to one end of a semicircular portion 21 , and the other end of the straight portion 22 is connected to one end of another semicircular portion 21 .

[0028] It should be understood that the semicircular portion 21 is not limited to a semicircular curve, but can also be a part of an elliptical curve. The straight portion 22 can be a straight line or a curve with a certain curvature. The semicircular portion 21 and the straight portion 22 need to be tangent to each other so that the overall welding trajectory is a smooth curve (without inflection point). This curve is generally regarded as a wavy curve, but the wavy curve is not limited to the curve composed of the straight portion 22 and the semicircular portion 21.

[0029] It can be understood that the multiple semicircular portions 21 and the multiple straight portions 22 are alternately arranged and connected in sequence to form a wavy curve trajectory. There are no overlapping points and inflection points on the trajectory, which is an optimized structure of a common wavy arc.

[0030] By converting the wavy curve into semicircular portions 21 and straight portions 22, and alternating and connecting the semicircular portions 21 and straight portions 22, the embodiment of the present application can make the width of the welding track 2 (i.e., the length of the straight portion 22 in the wavy curve, and further, the length along the circumferential direction of the busbar) wider, thereby allowing the welding track 2 to cover a larger surface area of ​​the busbar, thereby making the welding contact surface larger and more uniform. This increases the connection strength between the busbar and the winding core 3, while also increasing the flow area between the busbar and the winding core 3, thereby increasing the overall effective flow area of ​​the battery, thereby eliminating the need for additional filler welding in the blank areas.

[0031] In some embodiments of the present application, referring to FIG. 4 and FIG. 5 , a plurality of straight portions 22 are sequentially arranged in parallel and at intervals.

[0032] It is understandable that the fact that the plurality of straight portions 22 are arranged in parallel and spaced apart in sequence does not necessarily mean that the lengths of the plurality of straight portions 22 are the same. The lengths of the plurality of straight portions 22 in each welding track 2 may be different.

[0033] Furthermore, the straight portion 22 can also be a part of the circle around the center of the busbar (i.e., one end arc). As long as multiple arcs (i.e., straight portions 22) are parallel to each other, the diameter of each semicircular portion 21 in the welding trajectory can also be kept consistent.

[0034] By arranging the straight portions 22 parallel to each other, the diameter of the semicircular portion 21 in the welding track 2 on the surface of the busbar can be maximized, so that during the welding process, the laser beam can more easily turn without deceleration or with the lowest deceleration amplitude, that is, turn smoothly, so that the variance of the welding energy value at each point of the welding track 2 is minimized, and the distribution of the welding energy at various points of the welding track 2 is more uniform, thereby effectively preventing over-welding at the bends of the welding track 2.

[0035] In some embodiments of the present application, the welding track 2 extends along the radial direction of the busbar.

[0036] It can be understood that the welding track 2 can be extended radially along the bus plate and connected along the diameter direction of the bus plate, or it can be offset at a certain angle relative to the diameter direction of the bus plate, so that one end of the welding track 2 is toward the center of the bus plate, and the other end of the welding track 2 is toward the edge of the bus plate.

[0037] By extending multiple welding tracks 2 along the radial direction of the busbar, the number of connection layers between the busbar and the pole ears on the winding core 3 can be increased, so that the connection strength between the busbar and the winding core 3 after welding and the flow area between the busbar and the winding core 3 are larger, thereby making the overall flow effect of the battery better.

[0038] In some embodiments of the present application, there are multiple welding tracks 2, and each of the welding tracks 2 is sequentially arranged around the center of the busbar.

[0039] The number of welding tracks 2 distributed in the annular array around the busbar can be set to eight as long as it can meet the welding strength and flow area between the busbar and the core 3. More than eight will reduce the welding efficiency, and less than eight will easily lead to reduced welding strength. The reason for setting multiple welding tracks 2 is to reduce the welding time between the busbar and the core 3 in the battery.

[0040] It should be understood that the annular array distribution of the welding tracks 2 around the busbar requires that the distance between adjacent welding tracks 2 remain consistent to ensure that the busbar and the winding core 3 have a higher overall welding strength and a larger overall flow area.

[0041] By distributing the welding tracks 2 in a circumferential array around the busbar, the welding time between the busbar and the winding core 3 can be greatly reduced while ensuring sufficiently strong welding strength and a sufficiently large flow area between the winding core and the busbar, thereby improving the efficiency of the entire welding process and thus improving the efficiency of the entire battery preparation process.

[0042] In some embodiments of the present application, the busbar can be a positive busbar or a negative busbar, which is not limited in the present application. In some embodiments, the busbar can be a positive busbar, which includes a circular busbar body 11 and a lead-out tab 12 extending from the busbar body 11.

[0043] It should be noted that the shapes of the positive busbar and the negative busbar may be different. The positive busbar includes a body 11 and a tab 12. However, the welding tracks on the positive busbar and the negative busbar need to meet the requirements of no inflection points and overlap points.

[0044] In some embodiments of the present application, referring to FIG6 , FIG6 is a schematic diagram of the third structure of the negative busbar provided in the embodiment of the present application, and the welding track 2 presents a circular closed wave curve arranged around the center of the busbar.

[0045] The welding track 2 can also be a closed annular welding track 2 surrounding the center of the busbar. This can also prevent the welding track 2 from generating inflection points and overlapping points. This prevents the welding energy at the inflection points and overlapping points on the welding track 2 from being too high, thereby causing over-welding, thereby avoiding damage to the weld strength between the winding core 3 and the busbar and reducing the flow area between the winding core 3 and the busbar. It should be noted that this is limited to an example of another embodiment in which the curve has no inflection points and no overlapping points.

[0046] In some embodiments, the busbar is a copper sheet, and the material of the busbar can also be a copper sheet with a plating layer, wherein the plating layer can be a chemical plating layer.

[0047] Some embodiments of the present application can relatively reduce the internal resistance of the busbar by setting the material of the busbar to copper sheet, reduce the heat generation during the operation of the busbar, thereby reducing the overcurrent loss of the busbar and the winding core, and improving the overall conductivity of the battery.

[0048] The thickness of the busbar can be determined according to actual needs and is not limited in the embodiments of the present application. In some embodiments of the present application, the thickness of the busbar is 0.1-0.5 mm, and further, it can be 0.15-0.25 mm, for example, 0.15 mm, 0.20 mm, 0.25 mm, etc.

[0049] Some embodiments of the present application can avoid welding through the busbar or the winding core 3 during the welding process by setting the thickness of the busbar to 0.1-0.5 mm.

[0050] In some embodiments of the present application, the welding track 2 is a laser welding track, so that the laser beam can perform laser welding on the busbar and the winding core 3 along the welding track 2 .

[0051] The embodiment of the present application uses laser welding for the welding track, which can improve the welding quality.

[0052] On the second aspect, the present application provides a battery, as shown in Figure 7, which is a cross-sectional structural diagram of the battery provided in an embodiment of the present application, the battery includes a winding core 3 and a busbar, the welding side of the busbar is welded to the pole ear of the winding core 3, and the welding track 2 on the busbar overlaps with the pole ear in the positive projection on the welding side. Because the battery is provided with a busbar, it has all the beneficial effects of the busbar, that is, the welding track between the busbar and the winding core 3 in the battery has no overlapping points and no inflection points, thereby reducing the welding energy at the inflection point and avoiding the breakdown of the busbar. It can also avoid the use of spiral welding in related technologies, which makes the existence of multiple overlapping points on the busbar, thereby making the welding energy at the overlapping points on the busbar too large. Then, multiple welding tracks 2 are evenly arranged in an array on the busbar, which can make the connection between the busbar and the winding core 3 more firm while improving the over-welding situation and improving the welding quality.

[0053] In some embodiments, referring to FIG8 , FIG8 is a schematic diagram of the structure of the tab provided in an embodiment of the present application. The winding core 3 is formed by winding the first electrode, the second electrode, and the separation membrane sandwiched therebetween around a winding axis. The winding core 3 has a core portion and an outer peripheral surface.

[0054] Along the winding axis, the first electrode includes an active material-coated portion and an uncoated portion. At least a portion of the uncoated portion serves as a tab. The uncoated portion includes a first portion A adjacent to the core of the winding core 3, a second portion B adjacent to the outer peripheral surface of the winding core 3, and a third portion C located between the first portion A and the second portion B. Along the winding axis, the height of the first portion A and / or the second portion B is lower than the height of the third portion C.

[0055] The third portion C is divided into a plurality of individually bendable segments 31. When the segments 31 are bent along the radius of the winding core 3, a bending surface region is formed. The bending surface region serves as the tab of the winding core 3. It is understood that the first portion A and the second portion B may also be divided.

[0056] Along the direction from the core side to the peripheral side, the bending surface area includes a uniform stacking number interval and a stacking number reduced interval. The stacking number of the slice 31 in the uniform stacking number interval is uniform, and the stacking number reduced interval is located outside the uniform stacking number interval. The stacking number of the slice 31 in the stacking number reduced interval decreases as it approaches the peripheral side.

[0057] It can be understood that, along the winding axis, the second electrode also includes an active material-coated portion and an uncoated portion, at least a portion of the uncoated portion serves as a tab, and the uncoated portion includes a first portion A adjacent to the core of the winding core 3, a second portion B adjacent to the outer peripheral surface of the winding core 3, and a third portion C located between the first portion A and the second portion B. Along the winding axis, the height of the first portion A and / or the second portion B is lower than the height of the third portion C.

[0058] The third portion C is divided into a plurality of individually bendable segments 31. When the segments 31 are bent along the radius of the winding core 3, a bending surface region is formed. The bending surface region serves as the tab of the winding core 3. It is understood that the first portion A and the second portion B may also be divided.

[0059] Along the direction from the core side to the peripheral side, the bending surface area includes a uniform stacking number interval and a stacking number reduced interval. The stacking number of the slice 31 in the uniform stacking number interval is uniform, and the stacking number reduced interval is located outside the uniform stacking number interval. The stacking number of the slice 31 in the stacking number reduced interval decreases as it approaches the peripheral side.

[0060] In some embodiments, the stacking number of the sections 31 in the uniform stacking number range is 10 or more.

[0061] It is understood that the region where the stacking number of the segments 31 reaches 10 or more can be set as the welding target region.

[0062] In some embodiments, the projected area of ​​the welding track 2 on the bending surface region is completely located within the uniform interval of the stacking number.

[0063] It can be understood that the uniform stacking number interval is the area with the largest number of stacking numbers on the bending surface area, so that when the collecting disk is welded to the tabs of the winding core 3, welding through the tab layer formed by the stacking of multiple tabs of the winding core 3 can be avoided.

[0064] In some embodiments, the width of the welding track 2 is greater than the width of the segment 31 .

[0065] In this way, it can be ensured that the welding track 2 can be successfully welded to two adjacent tabs in the same coil layer.

[0066] In some embodiments, along the radial direction of the winding core, the welding track 2 is at least partially welded to two adjacent segments 31 in the same coil.

[0067] In this way, it can be ensured that the welding track 2 can be successfully welded to two adjacent tabs in the same coil layer.

[0068] As shown in FIG7 , the welding side of the busbar is welded to the tabs of the winding core 3 , wherein the positive tab of the winding core 3 is made of aluminum foil, and the negative tab is made of copper foil.

Claims

1. A busbar having a welding side and a back side arranged opposite to each other, the welding side being configured to be welded to a winding core (3), the back side being provided with a welding track (2), the welding track (2) presenting a smooth wavy curve.

2. The busbar according to claim 1, wherein: The welding track (2) comprises a plurality of semicircular portions (21) and a plurality of straight portions (22), wherein the plurality of semicircular portions (21) and the plurality of straight portions (22) are alternately arranged and connected in sequence.

3. The busbar according to claim 2, wherein: The plurality of straight line portions (22) are arranged in parallel and at intervals in sequence.

4. The busbar according to claim 1, wherein: The welding track (2) extends along the radial direction of the busbar.

5. The busbar according to claim 4, wherein: There are a plurality of welding tracks (2), and each of the welding tracks (2) is arranged in sequence around the center of the busbar.

6. The busbar according to any one of claims 1 to 5, wherein: The busbar is a positive busbar, and comprises a busbar body (11) and a lead-out tab (12) extending from the busbar body (11).

7. The busbar according to any one of claims 1 to 6, wherein: The welding track (2) presents a circular closed wave curve arranged around the center of the busbar.

8. The busbar according to any one of claims 1 to 7, wherein: The thickness of the busbar is 0.1-0.5 mm.

9. A battery, comprising a winding core (3) and a busbar according to any one of claims 1 to 8, wherein a welding side of the busbar is welded to a tab of the winding core (3), and a welding track (2) on the busbar overlaps the tab on the orthographic projection of the welding side.

10. The battery according to claim 9, wherein The winding core (3) is formed by winding the first electrode, the second electrode and the separation membrane sandwiched therebetween around a winding axis, and the winding core (3) has a core portion and an outer peripheral surface; Along the winding axis, the first electrode comprises an active material coated portion and an uncoated portion, at least a portion of the uncoated portion serves as a pole lug, the uncoated portion comprises a first portion (A) adjacent to the core of the winding core (3), a second portion (B) adjacent to the outer peripheral surface of the winding core (3), and a third portion (C) located between the first portion (A) and the second portion (B), and along the winding axis, the height of the first portion (A) and / or the second portion (B) is lower than the height of the third portion (C); The third portion (C) is divided into a plurality of segments (31) that can be bent individually, and the plurality of segments (31) form a bending surface area when bent along the radial direction of the winding core (3); the bending surface area is the pole ear of the winding core (3); Along the direction from the core side to the peripheral side, the bending surface area includes a uniform stacking number interval and a stacking number reduction interval, the stacking number of the section (31) in the uniform stacking number interval is uniform, the stacking number of the section (31) is located on the peripheral side of the uniform stacking number interval, and the stacking number of the section (31) in the stacking number reduction interval decreases as it approaches the peripheral side.

11. The battery according to claim 10, wherein The stacking number of the slices (31) in the uniform stacking number interval is more than 10 layers.

12. The battery according to claim 10 or 11, wherein: The projection area of ​​the welding track (2) on the bending surface area is completely located within the uniform interval of the stacking number.

13. The battery according to any one of claims 10 to 12, wherein: The width of the welding track (2) is greater than the width of the section (31).

14. The battery according to any one of claims 10 to 12, wherein: Along the radial direction of the winding core, the welding track (2) is at least partially welded to two adjacent sections (31) in the same circle.

Images