阅读说明：本技术 一种电池极耳与汇流排的焊接方法 (Method for welding battery tab and bus bar ) 是由 刘昊 冯伟贤 廖飞龙 向小群 胡勇 雷鹏飞 王培为 徐作斌 高云峰 于 2018-06-12 设计创作，主要内容包括：本发明公开了一种电池极耳与汇流排的焊接方法,属于激光焊接技术领域,包括以下步骤：将所述电池极耳贴在所述汇流排上,并保持相对固定；选择激光焊接装置,其中：所述激光焊接装置的传输光纤芯直径小于等于30μm,激光束的光学放大比为1：(1-3),激光器输出功率为500-2000W；将激光束光斑沿所述电池极耳与所述汇流排的待焊接区进行曲线轨迹焊接,其中：焊接速度大于等于50mm/s。采用偏小的激光束光斑点以及偏快的焊接速度,被焊接工件融化时间短,生成的金属间化合物少,工件间的焊接强度高,电导性能好。采用曲线条纹的焊接轨迹进行激光焊接,增长焊接轨迹,增大焊缝的连结面积。该焊接方法降低了电池模组的焊接成本。(The invention discloses a method for welding a battery tab and a bus bar, which belongs to the technical field of laser welding and comprises the following steps: attaching the battery tabs to the busbar and keeping the battery tabs fixed relatively; selecting a laser welding device, wherein: the diameter of a transmission optical fiber core of the laser welding device is less than or equal to 30 mu m, and the optical amplification ratio of a laser beam is 1: (1-3), the output power of the laser is 500-2000W; carrying out curve track welding on laser beam spots along to-be-welded areas of the battery tab and the bus bar, wherein: the welding speed is more than or equal to 50 mm/s. By adopting smaller laser beam spot and faster welding speed, the welding time of the welded workpiece is short, the generated intermetallic compounds are less, the welding strength between the workpieces is high, and the electric conductivity is good. And the welding track of the curve stripes is adopted for laser welding, so that the welding track is increased, and the connecting area of welding seams is increased. The welding method reduces the welding cost of the battery module.)

1. A method for welding a battery tab and a bus bar is characterized by comprising the following steps:

attaching the battery tabs to the busbar and keeping the battery tabs fixed relatively;

selecting a laser welding device, wherein: the diameter of a transmission optical fiber core of the laser welding device is less than or equal to 30 mu m, and the optical amplification ratio of a laser beam is 1: (1-3), the output power of the laser is 500-2000W;

carrying out curve track welding on laser beam spots along to-be-welded areas of the battery tab and the bus bar, wherein: the welding speed is more than or equal to 50 mm/s.

2. The method of claim 1, wherein the diameter of the core of the transmission fiber is 10-30 μm, and the optical amplification ratio of the laser beam is 1: 2, the output power of the laser is 1500W, and the welding speed is 120 mm/s.

3. The method as claimed in claim 1 or 2, wherein after the battery tab is attached to the busbar and kept relatively fixed, a positioning step is included; the positioning step is used for placing a to-be-welded area between the battery tab and the bus bar at an initial welding position.

4. The method as claimed in claim 3, wherein the battery tab and the bus bar are fixed on a welding platform, and the laser beam spot of the laser welding device moves along a wavy path of the to-be-welded area of the battery tab and the bus bar.

5. The method as claimed in claim 3, wherein the battery tab and the bus bar move together in the direction in which the regions to be welded extend, the laser beam spot of the laser welding device reciprocates in a straight line, and the straight line reciprocating direction has an angle with the direction in which the battery tab and the bus bar move together.

6. The method of claim 5, wherein the angle is 90 degrees.

7. The method of claim 3, wherein the positioning step comprises position acquisition, position comparison and position movement compensation;

the position acquisition is to acquire images of the positions of the battery tabs and the to-be-welded regions of the busbar;

the position comparison is to compare the image acquired by the position with a predefined image and generate an offset;

the position movement compensation is to offset the positions of the battery tabs and the bus bars according to the offset, so that the positions of to-be-welded areas between the battery tabs and the bus bars are at initial welding positions.

8. The method of claim 7, wherein the positional comparison comprises image preprocessing and comparison operations;

the image preprocessing is to perform feature recognition on the image acquired at the position and generate a recognition result;

the comparison operation is to compare the recognition result of the image preprocessing with a predefined image and generate an offset.

9. The method of welding a battery tab to a busbar according to any one of claims 1 or 2, wherein the battery tab and the busbar are held in relative fixation by an outer frame bracket.

10. The method as claimed in claim 9, wherein the battery tab is made of aluminum or copper, the bus bar is made of aluminum or copper, and the thickness of the battery tab is less than or equal to 1 mm.

Technical Field

The embodiment of the invention relates to a welding method, in particular to a laser welding method for a battery tab and a bus bar, and belongs to the technical field of laser welding.

Background

The soft package battery is a battery packaged by taking an aluminum plastic film as a shell, has the characteristics of flexible size design, high energy density, light weight and the like, is widely applied to the industries of 3C electronics and new energy automobiles, and is characterized in that positive and negative electrode lugs are usually made of copper and aluminum respectively and have the thickness of 0.2-0.6 mm. The positive and negative electrode lugs of the soft package batteries are connected in series and/or in parallel to form a battery module, so that the battery module becomes a basic power unit of electric facilities such as an electric automobile and the like.

When the tabs of a plurality of cells are connected in series and/or parallel, it is common to weld the cell tabs to the thicker bus bars, respectively. By adopting the traditional laser welding mode, the bus bar material needs to be the same as or close to the material of the battery tab, otherwise, the welding strength is poor, and the use requirement cannot be met, so the bus bar material needs to be made of copper-aluminum composite material. However, the composite material has high processing cost and heavy weight, which is not favorable for light weight of the battery module.

Disclosure of Invention

The embodiment of the invention provides a method for welding a battery tab and a bus bar, which can improve the welding strength among dissimilar materials, meet the use requirement, increase the combination area of welding seams among workpieces and meet the overcurrent capacity of a battery.

The embodiment of the invention adopts the technical scheme that:

a method for welding a battery tab and a bus bar comprises the following steps:

attaching the battery tabs to the busbar and keeping the battery tabs fixed relatively;

selecting a laser welding device, wherein: the diameter of a transmission optical fiber core of the laser welding device is less than or equal to 30 mu m, and the optical amplification ratio of a laser beam is 1: (1-3), the output power of the laser is 500-2000W;

carrying out curve track welding on laser beam spots along to-be-welded areas of the battery tab and the bus bar, wherein: the welding speed is more than or equal to 50 mm/s.

Further, in another embodiment, the transmission fiber core has a diameter of 10 to 30 μm, and the laser beam has an optical magnification ratio of 1: 2, the output power of the laser is 1500W, and the welding speed is 120 mm/s.

Further, in another embodiment, after the battery tabs are attached to the bus bars and held in relative fixation, a positioning step is included; the positioning step is used for placing a to-be-welded area between the battery tab and the bus bar at an initial welding position.

Further, in another embodiment, the battery tab and the bus bar are fixed on a welding platform, and a laser beam spot of the laser welding device moves along a wave-shaped track of an area to be welded of the battery tab and the bus bar.

Further, in another embodiment, the battery tab and the bus bar move together in a straight line along the region to be welded, the laser beam spot of the laser welding apparatus reciprocates in a straight line, and the direction of the straight line reciprocation has an angle with the direction in which the battery tab and the bus bar move together.

Further, in another embodiment, the angle is 90 degrees.

Further, in another embodiment, the positioning step comprises position acquisition, position comparison and position movement compensation; the position collection is to collect images of the positions of the battery tab and the to-be-welded area of the bus bar, the position comparison is to compare the collected images with predefined images and generate an offset, and the position motion compensation is to offset the positions of the battery tab and the bus bar according to the offset so that the positions of the battery tab and the to-be-welded area of the bus bar are at an initial welding position.

Further, in another embodiment, the positional comparison includes image pre-processing and comparison operations; the image preprocessing is to perform feature recognition on the image acquired at the position and generate a recognition result; the comparison operation is to compare the recognition result of the image preprocessing with a predefined image and generate an offset.

Further, in another embodiment, the battery tabs and the bus bars are held in relative fixation by an outer frame bracket.

Further, in another embodiment, the battery tab is made of aluminum or copper, the bus bar is made of aluminum or copper, and the thickness of the battery tab is less than or equal to 1 mm.

The embodiment of the invention adopts smaller laser beam spot and faster welding speed, the welded battery tab and the bus bar have small heating energy, short melting time and less generated intermetallic compounds, so that the welding strength between the battery tab and the bus bar is high and the conductivity is good. Meanwhile, the welding track of the curve stripes is adopted for laser welding, so that the welding track is increased, the welding strength between the battery tab and the bus bar is enhanced, and the connecting area of a welding seam is increased, so that the electrical connection between the battery tab and the bus bar is met.

When the battery tab in the embodiment of the invention is welded among different materials, a single material with simple structure and low cost can be selected as the bus bar material under the condition that the welding strength meets the use requirement, so that the welding cost of the battery module is reduced.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

Fig. 1 is a schematic view of a curved welding track involved in a method for welding a battery tab to a busbar according to an embodiment of the present invention;

fig. 2 is a schematic view of another curved welding track involved in the method for welding the battery tab and the bus bar according to the embodiment of the invention.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present invention are shown in the drawings. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

The plurality of single batteries can be combined into a battery module in series and/or parallel connection to have various special functions so as to meet the requirement of power equipment on electric energy, for example, the plurality of single batteries can be combined into the battery module in parallel connection to obtain a battery module with large electric capacity. The embodiment of the invention provides a method for welding a battery tab and a bus bar, which is used for combining a plurality of single batteries in series connection and/or parallel connection and belongs to the technical field of laser welding.

A method for welding a battery tab and a bus bar comprises the following steps:

attaching the battery tabs to the busbar and keeping the battery tabs fixed relatively;

selecting a laser welding device, wherein: the diameter of a transmission optical fiber core of the laser welding device is less than or equal to 30 mu m, and the optical amplification ratio of a laser beam is 1: (1-3), the output power of the laser is 500-2000W;

and carrying out curve stripe welding on the laser beam spots along the to-be-welded areas of the battery tab and the bus bar, wherein: the welding speed is more than or equal to 50 mm/s.

The welding method of the battery tab and the bus bar adopts a laser welding technology, the high-energy laser beam is used for heating and melting the to-be-welded part between the battery tab and the bus bar, and the two materials are fused with each other and then are solidified and formed, so that the battery tab and the bus bar are welded and fixed.

In the embodiment of the invention, by adopting smaller laser beam spot and faster welding speed, the welded battery tab and the bus bar have small heating energy, short melting time and less generated intermetallic compounds, so that the welding strength between the battery tab and the bus bar is high and the conductivity is good. Meanwhile, the welding track of the curve stripes is adopted for laser welding, so that the welding track is increased, the welding strength between the battery tab and the bus bars is enhanced, and the connection area is increased, so that the large-current electric connection between the battery tab and the bus bars is met.

Referring to fig. 1, in the embodiment of the present invention, a welding method of a battery tab 10 and a bus bar 20, which uses a laser welding technique, includes:

the battery tabs 10 are attached to the bus bars 20 and held in a relatively fixed position. Specifically, the battery tab 10 can be bent and then pasted on the bus bar 20, the battery tab 10 and the bus bar 20 can be held and fixed by an outer frame support, optionally, the battery tab 10 and the bus bar 20 are pasted by a small amount of viscous materials for pre-fixing treatment, and the viscous materials can be heated and evaporated or washed, so that the viscous materials are easy to remove, and the battery tab 10 and the bus bar 20 are not polluted.

The region where the edge of the battery tab 10 contacts the bus bar 20 is a region to be welded 30, and is in the shape of a line. When the battery tab 10 is attached to the bus bar 20, the height between a surface of the battery tab 10 away from the bus bar 20 and the surface of the bus bar 20 is the thickness of the battery tab 10. If the thickness of the battery tab 10 is excessively thick, more thermal energy may be required to melt the welding. It is necessary to select more proper laser beam energy according to the thickness of the battery tab 10 during welding. If the thickness of the battery tab 10 is too thick, a laser beam spot with too large power is selected for welding, and if the thickness of the battery tab 10 is too thin, a laser beam spot with too small power is selected for welding. In particular, if the thickness of the battery tab 10 is excessively thick, the extension of the line between the battery tab 10 and the bus bar 20 to both sides serves as a region to be welded 30.

The battery tab 10 is used to electrically connect with an external circuit part, so the thickness of the battery tab 10 is not large. In particular, the pouch battery tab 10 used to couple the battery modules formed therefrom will typically have a thickness of 1mm or less, and optionally the pouch battery tab 10 may have a thickness of 0.2 to 0.6 mm. Of course, the thickness of the battery tab 10 may be set as occasion demands according to the production design.

And selecting a laser welding device. The embodiment of the invention adopts the transmission optical fiber with smaller core diameter, and the diameter of the core of the transmission optical fiber is less than or equal to 30 mu m. The laser beam is transmitted in the transmission fiber and further processed by the optical assembly, and finally the laser beam spot is applied to the area to be welded 30. The magnification ratio of the optical assembly to the laser beam in the embodiment of the present invention is 1: (1-3). Wherein, the output power of the laser is 500-2000W.

On the basis that the battery tab 10 and the bus bar 20 are kept relatively fixed, the laser beam spot of the laser welding device performs curved track welding along the to-be-welded area 30 of the battery tab 10 and the bus bar 20. In the present embodiment, in order to obtain a stronger welding strength and to make the connection surface of the battery tab 10 to the bus bar 20 larger, the laser welding apparatus employs a curved trajectory welding in which the welding speed of the laser welding is 50mm/s or more.

In the welding process, the welding speed is high, otherwise, the welded material is too long in melting time, intermetallic compounds are easily generated, and the welding quality is affected.

The following is a detailed description of a curved trace welding process, optionally with two curved trace welding methods, with reference to the accompanying drawings:

the method comprises the following steps:

fixing the battery tab 10 and the bus bar 20 on a welding platform, wherein a laser beam spot of the laser welding device moves along an S-shaped wavy track of the to-be-welded area 30 of the battery tab 10 and the bus bar 20, so that an S-shaped welding track 31 (shown in FIG. 1) is formed on the to-be-welded area 30.

The curved-line welding method adopts the curved-line welding track 31 formed by the curved movement of the laser beam facula, has few moving parts, stable structure and simple process, and can accurately carry out the welding process. However, the curvilinear movement of the laser beam spot is not easy to achieve, and requires special chip control, especially for curvilinear operation in a small range, which further increases the difficulty of welding.

The second method comprises the following steps:

the battery tab 10 and the bus bar 20 move together along the extending direction of the region 30 to be welded, the laser beam spot of the laser welding device moves in a linear reciprocating manner, and the linear reciprocating direction has an angle with the direction in which the battery tab and the bus bar move together, optionally, the angle is 90 degrees. In particular, if the laser beam spot can linearly reciprocate in a periodic manner along the moving direction of the battery tab 10 and the bus bar 20, the welding locus 31 of the laser beam spot is a linear welding locus 31 along the region 30 to be welded.

The curve track welding method adopts the effect of achieving the curve-shaped welding track 31 through the synthesis of motion, and converts complex curve motion into simple linear motion and linear reciprocating motion, so that the curve track welding process is easier to realize, and meanwhile, the curve track welding of various types becomes possible. It is particularly noted that the complex curvilinear motion is broken down into simple forms of motion, which results in an increase in moving parts and less stability of the overall structure than in the first approach. Those skilled in the art can select the appropriate welding method according to the technical capability of the enterprise to achieve the maximum benefit.

Of course, those skilled in the art can make further technical improvements to make the advantages of the two curved-track welding methods more prominent in light of the above technical idea.

If the reciprocating periodic motion direction of the laser beam spot has an angle with the unidirectional motion direction of the battery tab 10 and the busbar 20, the welding locus 31 of the laser beam spot is curved. Under the condition that the movement speed of the laser beam spot is not changed, when the movement speed of the battery tab 10 and the bus bar 20 is larger, the curved welding track 31 of the region to be welded 30 is denser; when the moving speed of the battery tab 10 and the bus bar 20 is small, the curved welding locus 31 of the region 30 to be welded is relatively sparse. In an actual welding operation, an operator can select a suitable moving speed of the battery tab 10 and the bus bar 20 according to actual process requirements to obtain a proper curved welding track 31.

Optionally, the movement direction of the battery tab 10 and the bus bar 20 is perpendicular to the movement direction of the laser beam spot of the laser welding device. The moving direction of the laser beam light spots is perpendicular to the moving direction of the battery tab 10 and the bus bar 20, so that the instrument installation and the instrument operation process are convenient and visual, and the welding effect is easy to control.

Of course, in order to increase the length of the welding track 31, there are various ways of moving the laser beam spot, for example, the battery tab 10 and the busbar 20 are fixed, and the laser beam spot goes along the area to be welded 30 and moves forward in a partially circuitous curve, so that a partially overlapping curve welding track 31 (see fig. 2) is formed. It should be understood by those skilled in the art that there are many ways to achieve the curved weld without departing from the spirit of the present invention.

Further, in one or more embodiments, a positioning step is included after the battery tabs 10 are attached to the buss bars 20 and held in relative position. The positioning step is to place the region 30 to be welded between the battery tab 10 and the bus bar 20 at an initial welding position such that one end of the region 30 to be welded corresponds to a laser beam spot position of the laser welding apparatus to perform welding accurately.

For mass production in a production line, the battery tab 10 is bound to the bus bar 20 and placed at a fixing position such that the position of the area to be welded 30 is placed at an initial welding position, and accordingly, the laser welding apparatus is also placed at the fixed initial welding position. Accordingly, the battery tab 10 and the bus bar 20 are placed at the correct position, and the region 30 to be welded between the battery tab 10 and the bus bar 20 is placed at the initial welding position to enable accurate welding by the laser welding apparatus, thereby reducing the preparation time before welding and improving the welding efficiency and welding quality. This said positioning step is particularly important.

In this embodiment, the positioning step includes position acquisition, position comparison and position motion compensation. The position acquisition is to acquire images of the positions of the battery tabs 10 and the to-be-welded areas 30 of the busbar 20.

The position comparison is to compare the image acquired at the position with a predefined image and generate an offset. Specifically, the position comparison includes image preprocessing and comparison operation. And the image preprocessing is to perform feature recognition on the image acquired at the position and generate a recognition result. The comparison operation is to compare the recognition result of the image preprocessing with a predefined image and generate an offset.

The position shift compensation is to shift the positions of the battery tab 10 and the bus bar 20 according to the shift amount of the position comparison, so that the to-be-welded region 30 of the battery tab 10 and the bus bar 20 is located at an initial welding position.

Subdividing the positioning step into the position acquisition, the position comparison, and the position movement compensation, such that the positioning step is programmable for precise control by a control circuit. In the fine range of movement positioning, it is particularly important to use a logic control circuit means, so that precise fine movement positioning becomes possible.

In this embodiment, the position acquisition is to take a picture of the battery tab 10 and the bus bar 20 by using a camera to obtain image information.

The position comparison adopts an image preprocessing circuit and a comparison operation circuit. Firstly, the image preprocessing circuit performs binarization (black and white) processing on the image information acquired by the camera, identifies the features in the image, generates an identification result, and transmits the identification result to the comparison operation circuit. And secondly, the comparison operation circuit compares the identification result with a predefined image and calculates and generates an offset.

In the position comparison step, the image preprocessing is adopted to carry out binarization preprocessing on the image information, so that the features in the image are highlighted, and the identification result is more accurate. Further, the image preprocessing step may also include other image processing procedures, such as a step of intercepting a partial image in the image information. In the image preprocessing process, partial image information is firstly intercepted, and the feature recognition processing is carried out on the partial image information, so that the burden of feature recognition is reduced, the accuracy of feature recognition is increased, and the feature recognition process is completed quickly.

The position movement compensation is to adopt a transmission mechanism to move the battery tab 10 and the bus bar 20 so that the region 30 to be welded is at an initial welding position, and at this time, the offset between the battery tab 10 and the bus bar 20 is zero.

In one or more embodiments, the transmission may be a gear transmission, a pulley transmission, or a lead screw transmission. Optionally, the transmission mechanism is a screw transmission mechanism. One end of the screw rod is driven by a servo motor, and a moving nut on the screw rod is used for moving the battery tab 10 and the bus bar 20. After receiving the moving instruction, the servo motor drives the moving nut on the lead screw to drive the battery tab 10 and the bus bar 20 to move along the direction of the lead screw according to the moving instruction, so that the region 30 to be welded between the battery tab 10 and the bus bar 20 is placed at the correct initial welding position.

Further, in one or more embodiments, in order to conveniently combine a plurality of single cells into a battery module, the plurality of single cells and the bus bar 20 are fixedly disposed, and the battery tab 10 and the bus bar 20 are relatively fixed. Specifically, the plurality of unit cells and the bus bar 20 are bound together by the outer frame bracket. The outer frame bracket is used for binding a plurality of single batteries and the bus bar 20 into a whole, on one hand, the welding operation is convenient, and the whole welding process of the battery module is completed; on the other hand, the outer frame support can indirectly connect the plurality of single cells and the bus bars 20 which are bound and combined into a whole to the welding platform, and the single cells and the bus bars can be placed in any direction through the outer frame support, so that the placing position is more flexible, and convenience is brought to welding operation.

The battery module in which the plurality of unit cells and the bus bars 20 are bound and integrated is highly advantageous in terms of both welding operation and packaging and transportation.

The battery tab 10 is generally made of a metal material with excellent conductivity, and the positive and negative electrode tabs of the battery are made of a copper material and an aluminum material, preferably, the positive and negative electrode tabs of the battery are made of pure copper and pure aluminum, respectively. Pure copper and pure aluminum are two kinds of materials with better conductivity, and when the positive electrode lug and the negative electrode lug of the battery are respectively made of pure copper and pure aluminum, the bus bar 20 can be made of pure copper or pure aluminum, on one hand, because of having excellent conductivity, and on the other hand, because of single material, the processing is convenient. Adopt pure aluminium material the weight of busbar 20 is lighter, does benefit to battery module lightweight.

It should be noted that in fig. 1-2, the welding trace 31 in the embodiment of the present invention is a clearly recognizable curved line, however, in the actual welding workpiece, the welding trace 31 on the region 30 to be welded is not a clearly recognizable curved trace line due to the conduction of heat. During welding, the welding track 31 heats the periphery of the track and melts the periphery of the track into a piece, so that the welding track 31 is not a clearly identifiable curve track line, and on the contrary, the zones to be welded 30 are fused to form an integral welding and combining structure.

The technical solution of the present invention is further illustrated by the following specific examples: