WO2019174374A1

WO2019174374A1 - Bus bar and battery module

Info

Publication number: WO2019174374A1
Application number: PCT/CN2019/070438
Authority: WO
Inventors: 吴岸为; 徐冶
Original assignee: 宁德时代新能源科技股份有限公司
Priority date: 2018-03-15
Filing date: 2019-01-04
Publication date: 2019-09-19
Also published as: CN208127292U

Abstract

The present application provides a bus bar for connecting with an electrode pole of a single battery; the surface of the bus bar is provided with a welding groove for welding laser incidence; the welding groove is used to connect with the electrode pole of the single battery; and the welding groove is wide on top and narrow on bottom in a thickness direction of the bus bar. Since the welding groove which is wide on top and narrow on bottom is disposed on the surface of the bus bar of the single battery, when shooting into the welding groove, a laser beam can be repeatedly reflected in the welding groove, thus, the absorption area of the bus bar for the laser beam is greatly increased, and the laser absorptivity of the bus bar is improved, thereby improving the power utilization rate of the laser, and reducing the welding power. The present application further provides a battery module.

Description

Bus bar and battery module

The present application claims priority to Chinese Patent Application No. 2018203575945, filed on Jan.

Technical field

The present application relates to the field of battery technologies, and in particular, to a bus bar and a battery module.

Background technique

Currently, secondary batteries are widely used in various fields. The existing secondary battery and the bus bar are usually connected by welding, and the welded connection can ensure a relatively good overcurrent capability. The solder connection between the secondary battery and the bus bar is mostly laser penetration welding, that is, the bus bar is placed on the pole of the secondary battery, and the laser is used as a heat source, and the laser melts and penetrates the bus bar and reaches the pole. And partially melt the poles, and finally the pool cools to form a permanent joint. The soldered connection is not easy to loosen, and an interatomic connection can be formed between the bus bar and the pole, so that the overcurrent capability is good. And because of the penetration welding, the precision of the assembly welding is not high, and the tolerance tolerance is good.

However, solder joints using laser penetration have their drawbacks. As the requirements for the charge and discharge rate of the battery are getting higher and higher, the current overcurrent requirement is also getting larger and larger, and the bus bar is getting thicker and thicker. In the busbar welding process, since the busbar has a low laser absorption rate, laser welding requires a large power if it needs to penetrate the busbar, resulting in higher laser power requirements and increased production equipment costs. In addition, the large laser welding power will also lead to relatively unstable weld penetration, which will increase the risk and probability of burn-through and solder joint due to penetration fluctuations, and reduce the production efficiency. Moreover, if the welding power is too large, the temperature rise of the weld seam is large, the heat resistance of the insulating plastic of the battery is increased, and the airtightness requirement is also stricter, which increases the manufacturing cost. The unstable weld penetration will also cause the pole to become thicker, increasing battery cost and weight.

Application content

The present application provides a bus bar which can effectively reduce the laser welding power, thereby solving a series of the above problems caused by the high laser welding power during the welding connection of the battery cell group.

The present application provides a bus bar for connecting to an electrode post of a battery cell, the surface of the bus bar having a soldering groove for laser welding, the soldering groove for the battery The electrode poles of the cells are connected, and the soldering grooves are wide and narrow in the thickness direction of the bus bar.

Preferably, the weld groove presents a linear or circular or sinusoidal shape on the surface of the bus bar.

Preferably, the welding groove extends through the bus bar.

Preferably, the depth of the weld groove is smaller than the thickness of the bus bar.

Preferably, the bus bar has a thickness of 0.4 mm to 0.6 mm at a lower edge of the weld groove.

Preferably, the upper edge of the weld groove has a width of no more than 1 mm and a width of the lower edge of no more than 0.8 mm.

Preferably, the upper edge of the weld groove has a width of between 0.7 mm and 0.9 mm and a lower edge of between 0.3 mm and 0.5 mm.

Preferably, the upper edge of the weld groove has rounded corners.

Preferably, the groove wall of the welding groove comprises a first plane and a second plane, the first plane being connected to one side of the second plane and the other side being relatively far apart to form a V-shaped groove wall, Alternatively, the groove wall of the weld groove includes a tapered outer ring portion and a tapered inner ring portion, the tapered inner ring portion being located inside the tapered outer ring portion, the groove wall of the weld groove The cross section is a V-shaped cross section.

Preferably, the groove wall of the welding groove has a slope of between 60° and 86°.

The present application also provides a battery module comprising: a plurality of battery cells, each battery cell including an electrode post; and a bus bar as described above, the bus bar and the electrode of the battery cell The columns are connected by the weld grooves.

The technical solution provided by the present application can achieve the following beneficial effects:

A wide and narrow welding groove is arranged on the surface of the bus bar of the battery cell group, and when the laser beam is injected into the welding groove, repeated reflections can be performed in the welding groove, thereby greatly increasing the bus bar to the laser beam. The absorption area increases the absorption rate of the laser by the busbar, thereby increasing the power utilization of the laser and reducing the welding power.

The above general description and the following detailed description are merely exemplary and are not intended to limit the application.

DRAWINGS

1 is a schematic view showing a welding reflection of a laser beam on a surface of a bus bar in the prior art;

2 is a schematic diagram showing the welding reflection of a laser beam on a bus bar when the bus bar provided by the embodiment of the present application is used;

3 and FIG. 4 are schematic diagrams showing the structure of a bus bar and a battery cell according to an embodiment of the present application;

FIG. 5 is a schematic structural view of a bus bar of a first embodiment of the present application; FIG.

Figure 6 is a partial cross-sectional view of the bus bar shown in Figure 5 in the A-A direction;

FIG. 7 is a schematic structural view of a bus bar of a second embodiment of the present application; FIG.

Figure 8 is a partial cross-sectional view of the bus bar shown in Figure 7 in the B-B direction;

FIG. 9 is a schematic structural view of a bus bar of a third embodiment of the present application; FIG.

Figure 10 is a partial cross-sectional view of the bus bar shown in Figure 9 in the C-C direction.

Reference mark:

1-bus bar;

1’-busbar;

2-battery monomer;

21-electrode pole;

11-welding groove;

111-first plane;

112-second plane;

113-conical outer ring portion;

114-conical inner ring portion;

20-laser beam.

The drawings herein are incorporated in and constitute a part of the specification,

detailed description

The present application will be further described in detail below through specific embodiments and with reference to the accompanying drawings.

Fig. 1 is a schematic view showing a prior art welding reflection of a laser beam on a surface of a bus bar. As shown in Fig. 1, at the time of welding, the laser beam 20 indicated by the arrow is directly struck on the flat surface of the bus bar 1', and then reflected. Therefore, only one solder joint is formed on the flat surface, which results in a small absorption area of the laser light on the bus bar, which reduces the absorption rate of the laser light by the bus bar, thereby lowering the power utilization rate of the laser, forcing the laser welding process. The welding power must be greatly increased.

FIG. 2 is a schematic diagram showing the welding reflection of the laser beam on the bus bar when the bus bar (hereinafter referred to as the bus bar) provided by the embodiment of the present application is used. FIG. 3 and FIG. 4 are schematic diagrams showing the structure of a bus bar and a battery according to an embodiment of the present application. 3 clearly shows the interconnection relationship between the bus bar 1 and the battery cell 2, and the bus bar 1 is used for connection with the electrode post 21 of each battery cell 2. Specifically, a single bus bar 1 can be adjacent to two adjacent cells. The electrode posts 21 of the battery cells 2 are connected.

As shown in FIG. 2, in the embodiment of the present application, a soldering groove 11 is provided on the surface of the bus bar 1 for connecting with the electrode post 21 of the battery cell, and the welding groove 11 is used for soldering. The laser beam 20 is incident, and one, two or even more welding grooves 11 may be provided on a single bus bar 1. The welding groove 11 provided on the bus bar 1 is clearly visible in FIG. The welding groove 11 can be formed by stamping, rolling, planing, thinning or the like. Along the thickness direction of the bus bar 1, the cross section of the soldering groove 11 is in the form of an upper width and a lower width, wherein the side of the bus bar 1 facing away from the battery cell is defined as "upper", and the bus bar 1 is facing the battery. One side of the monomer is defined as "lower", and in addition, the cross section of the welded groove 11 refers to a section perpendicular to the extending direction of the welded groove 11. Specifically, in the foregoing thickness direction, the width of the cross section of the weld groove 11 (the width is the dimension in the X direction in Fig. 2) gradually decreases from the top to the bottom.

After the laser (e.g., charge coupled laser) accurately captures the soldering groove 11 on the surface of the bus bar 1, as seen in Fig. 2, after the laser beam 20 indicated by the arrow is incident on the soldering groove 11, the laser beam 20 will be soldered. A plurality of repeated reflections are formed on the inner wall of the groove 11, thereby greatly increasing the absorption area of the laser beam 20 by the bus bar 1, thereby increasing the absorption rate of the laser light by the bus bar 1, thereby improving the power utilization of the laser. The welding power is reduced, thereby reducing the cost of the production equipment, improving the production efficiency, and at the same time reducing the temperature rise of the weld seam, thereby reducing the heat resistance requirements and airtightness requirements of the insulating plastic of the battery, reducing the manufacturing cost, and This makes the weld penetration more stable, which in turn reduces battery cost and weight, and increases the power density of the battery cell group.

In a specific embodiment, the width of the soldering groove 11 in the direction in which the bus bar extends (specifically, the direction in which the battery cells 2 are connected to the bus bar 1) can be set according to factors such as current overcurrent requirements. Preferably, the width of the upper edge of the weld groove 11 may be set to not more than 1 mm, and the width of the lower edge may be set to not more than 0.8 mm. This width selection scheme can ensure that there are enough laser beams 20 to enter the welding groove 11, and can also increase the number of reflections of the laser beam 20 in the welding groove 11, and can also alleviate the welding groove 11 to the bus bar 1 The adverse effects of own strength.

In order to enhance the above technical effects, further, the width of the upper edge of the welding groove 11 is between 0.7 mm and 0.9 mm, and the width of the lower edge is between 0.3 mm and 0.5 mm.

Further, based on the same considerations as the foregoing, the ratio between the depth of the weld groove 11 and the width of the upper edge thereof may be set to 1.4 to 2.5.

Fig. 5 is a view showing the structure of a bus bar of the first embodiment of the present application. Figure 6 is a partial cross-sectional view of the bus bar shown in Figure 5 in the A-A direction.

As shown in FIG. 5, the welding groove 11 has a linear shape on the surface of the bus bar 1, that is, the welding groove 11 extends in the straight line direction. It should be noted that the shape of the welding groove 11 on the surface of the bus bar 1 can be changed according to different applications. For example, when the battery cell pole is a copper-aluminum composite pole, it is suitable to adopt a straight shape. Generally, the busbar 1 is aluminum, and copper-aluminum laser welding is difficult. The linear groove connection avoids welding of the bus bar and the pole copper material.

The laser emitting the laser beam 20 can accurately capture the linear welding groove 11 on the surface of the bus bar, thereby injecting the laser beam 20 into the linear welding groove 11, thereby causing the laser beam to be in the welding groove Repeated reflection on the inner wall of 11. As described above, the repeated reflection of the laser beam 20 inside the welding groove 11 can greatly increase the absorption area of the bus bar to the laser beam 20, thereby increasing the absorption rate of the laser light by the bus bar 1, thereby increasing the power of the laser light. Utilization, reducing welding power.

Specifically, the groove wall of the welding groove 11 described above may include two portions facing each other, and both of the portions may be provided as curved surfaces. In another configuration, the groove wall of the weld groove 11 may include a first plane 111 and a second plane 112, the first plane 111 being connected to one side of the second plane 112 and the other side being relatively distant to form a V Groove wall. The structure and processing technology of the welding groove 11 are relatively simple.

Since the degree of inclination of the first plane 111 and the second plane 112 with respect to the face where the entire bus bar 1 is located will directly determine the degree of opening of the welding groove 11, thereby affecting the amount of the laser beam 20 entering the welding groove 11 and the laser beam. The number of reflections in the welding groove 11 , so in the embodiment of the present application, the slope of the first plane 111 and the second plane 112 may be set between 60° and 86° to optimize the entry into the welding groove 11 . The amount of laser beam 20 and the number of reflections of laser beam 20 within weld groove 11 further reduce the welding power. Wherein, the slope can refer to P in FIG. 6.

In one embodiment, as shown in FIG. 6, the bottom of the welding groove 11 does not penetrate the bus bar 1, that is, the depth of the welding groove 11 is smaller than the thickness of the bus bar 1. On the one hand, this structure can ensure the structural strength of the bus bar 1, and on the other hand, it can ensure that the bus bar 1 has a large overcurrent area to ensure the overcurrent capability of the bus bar 1. Preferably, at the lower edge of the welding groove 11, the thickness D of the bus bar 1 may be between 0.4 mm and 0.6 mm, thereby reinforcing the aforementioned technical effects.

Fig. 7 is a view showing the structure of a bus bar of a second embodiment of the present application. Figure 8 is a partial cross-sectional view of the bus bar shown in Figure 7 in the B-B direction.

Compared with the first embodiment shown in Figs. 5 and 6, the difference in this embodiment is mainly that the welding groove 11 is a through groove which penetrates the bus bar 1, as clearly shown in Fig. 8. When the welding groove 11 penetrates the bus bar 1, the requirement for welding power is lower because in this case, it is not necessary to melt the metal at the bottom of the groove.

In this embodiment, under one configuration, the groove wall of the welding groove 11 may include two portions facing each other, and both portions may be provided as curved surfaces; in another structure, the groove wall of the welding groove 11 may also be The aforementioned first plane 111 and second plane 112 are included. When the groove wall of the welding groove 11 includes the first plane 111 and the second plane 112, the two portions may also have a slope P as described above, which will not be described herein.

In FIGS. 7 and 8, the welding groove 11 also has an upper width and a lower narrow structure. After the laser beam 20 is injected into the welding groove 11, it can still be repeatedly reflected on the inner wall of the welding groove 11, thereby greatly increasing the bus bar 1 The absorption area of the laser beam 20 increases the absorption rate of the laser light by the bus bar 1, thereby improving the power utilization of the laser and reducing the welding power.

It is to be noted that the shape of the welding groove 11 on the surface of the bus bar 1 is also not limited to the linear shape shown in Figs. 2-8. The shape of the welding groove 11 on the surface of the bus bar 1 can be set to a ring shape, a sinusoidal shape or other curved shape according to factors such as current overcurrent requirements, processing process requirements and the like. As mentioned above, the shape of the weld groove 11 on the surface of the bus bar 1 can be varied depending on the application. For example, in the case of applying a circular pole, the shape is more suitable for a ring shape.

Fig. 9 is a view showing the structure of a bus bar of a third embodiment of the present application. Figure 10 is a partial cross-sectional view of the bus bar shown in Figure 9 in the C-C direction.

The most critical difference of this embodiment compared to the first and second embodiments is that the welding groove 11 assumes an annular shape on the surface of the bus bar 1. When soldering, the laser accurately captures the soldering groove 11 on the bus bar 1, thereby accurately positioning the soldering position.

Similar to the first and second embodiments, the weld groove 11 still assumes an upper width and a lower narrow form. Therefore, after the laser light is injected into the welding groove 11, the reflection can be repeatedly performed on the inner wall of the welding groove 11, thereby greatly increasing the absorption area of the laser beam 20 by the bus bar 1, thereby increasing the absorption rate of the laser light by the bus bar 1. This increases the power utilization of the laser and reduces the welding power.

In this embodiment, the welding groove 11 may penetrate the bus bar 1 or may not penetrate the bus bar 1. When the welding groove 11 does not penetrate the bus bar 1, at the lower edge thereof, the thickness D of the bus bar 1 may be Between 0.4 mm and 0.6 mm. The welding groove 11 is in the form of an upper width and a lower width, and the upper edge width may be between 0.7 mm and 0.9 mm, and the lower edge width may be between 0.3 mm and 0.5 mm.

The welding groove 11 may be further provided as a circular groove. At this time, the groove wall of the welding groove 11 may include a tapered outer ring portion 113 and a tapered inner ring portion 114, and the tapered inner ring portion 114 is located The inside of the tapered outer ring portion 113 has a V-shaped cross section of the groove wall of the welded groove 11. Such a welded groove 11 is more convenient to process.

Preferably, as shown in FIGS. 6, 8, and 10, rounded corners may be poured on the upper edge of the weld groove 11 to facilitate the forming of the weld groove 11. In addition, when the welding groove 11 does not penetrate the bus bar 1, a rounded corner may be provided at the lower edge thereof to prevent stress concentration at the position. It should be noted that when the groove wall of the welding groove 11 includes the first plane 111 and the second plane 112, it indicates that the groove wall of the welding groove 11 includes two portions which are substantially planar, and the first plane 111 and the second at this time The upper and lower edges of the plane 112 can still be rounded.

In summary, in the present application, a wide and narrow welding groove is provided on the surface of the bus bar of the battery cell group, and when the laser beam is injected into the welding groove, repeated reflection in the welding groove can be performed. Therefore, the absorption area of the laser beam by the bus bar is greatly increased, thereby increasing the absorption rate of the laser light by the bus bar, thereby improving the power utilization rate of the laser and reducing the welding power.

Based on the above structure, as shown in FIG. 3 and FIG. 4 , the embodiment of the present application further provides a battery cell group including a plurality of battery cells 2 and a plurality of battery cells 2 for electrically connecting. The bus bar 1 is the bus bar described in any of the above embodiments.

The above description is only the preferred embodiment of the present application, and is not intended to limit the present application, and various changes and modifications may be made to the present application. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of this application are intended to be included within the scope of the present application.

Claims

a bus bar for connecting to an electrode post of a battery cell, characterized in that

a surface of the bus bar having a soldering groove for laser welding, the soldering groove for connecting to an electrode post of the battery cell, and in a thickness direction of the bus bar, The welding groove is wide and narrow.
The busbar according to claim 1, wherein said weld groove has a linear or circular or sinusoidal shape on a surface of said bus bar.
The bus bar according to claim 1, wherein the welding groove extends through the bus bar.
The busbar according to claim 1, wherein the depth of the weld groove is smaller than the thickness of the bus bar.
The bus bar according to claim 4, wherein said bus bar has a thickness of 0.4 mm to 0.6 mm at a lower edge of said welding groove.
The bus bar according to claim 1, wherein the upper edge of the weld groove has a width of not more than 1 mm and a width of the lower edge of not more than 0.8 mm.
The busbar according to claim 1, wherein the upper edge of the weld groove has rounded corners.
The bus bar according to claim 1, wherein the groove wall of the welding groove comprises a first plane and a second plane, the first plane being connected to one side of the second plane, and the other The sides are relatively far apart to form a V-shaped groove wall, or,

The groove wall of the welding groove includes a tapered outer ring portion and a tapered inner ring portion, the tapered inner ring portion is located inside the tapered outer ring portion, and a cross section of the groove wall of the welding groove is V-shaped section.
The busbar according to claim 1, wherein the groove wall of the weld groove has a slope of between 60[deg.] and 86[deg.].
A battery module, comprising:

a plurality of battery cells, each of which includes an electrode post;

The bus bar according to any one of claims 1 to 9, wherein the bus bar and the electrode post of the battery cell are connected by the soldering groove.