As the core component of the new energy vehicle, the quality of the power battery directly determines the performance of the whole vehicle. Lithium battery manufacturing equipment is generally divided into three types: front-end equipment, mid-end equipment, and back-end equipment. The equipment precision and automation level will directly affect the production efficiency and consistency of products. As an alternative to traditional welding technology, laser processing technology has been widely used in lithium battery manufacturing equipment.

From the manufacture of lithium battery cells to battery pack grouping, welding is a very important manufacturing process. The conductivity, strength, air tightness, metal fatigue and corrosion resistance of lithium batteries are typical evaluation criteria for battery welding quality. . The selection of welding method and welding process will directly affect the cost, quality, safety and consistency of the battery.

1. Battery explosion-proof valve welding

The explosion-proof valve of the battery is a thin-walled valve body on the battery sealing plate. When the internal pressure of the battery exceeds the specified value, the explosion-proof valve body ruptures to prevent the battery from bursting. The safety valve has an ingenious structure, and this process has extremely strict requirements on the laser welding process.

Before continuous laser welding was used, the welding of battery explosion-proof valves was carried out by pulsed laser welding, and continuous sealing welding was realized by overlapping and covering the welding spot and the welding spot, but the welding efficiency was low and the sealing performance was relatively poor. Continuous laser welding can achieve high-speed and high-quality welding, and welding stability, welding efficiency and yield can be guaranteed.

2. Battery tab welding

The tabs are usually divided into three materials. The positive electrode of the battery uses aluminum material, and the negative electrode uses nickel material or copper nickel-plated material. In the manufacturing process of power batteries, one of the links is to weld the battery tabs and poles together. In the manufacture of the secondary battery, it needs to be welded with another aluminum safety valve. Welding not only needs to ensure the reliable connection between the tab and the pole, but also requires the welding seam to be smooth and beautiful.

3. Spot welding of battery poles

The materials used for battery pole strips include pure aluminum strips, nickel strips, aluminum-nickel composite strips, and a small amount of copper strips. The welding of battery strips generally uses pulse welding machines. With the emergence of IPG's QCW quasi-continuous laser, it has also been widely used in the welding of battery strips. At the same time, due to its good beam quality, the welding spot can be small. , which has unique advantages in the welding of aluminum strips, copper strips and narrow-band battery poles with high reflectivity.

4. Seal welding of power battery shell and cover plate

The shell materials of power batteries are aluminum alloy and stainless steel, among which aluminum alloy is the most used, generally 3003 aluminum alloy, and a few use pure aluminum. Stainless steel is the most laser weldable material, and both pulsed and continuous lasers can produce welds that look and perform well. Using continuous lasers to weld thin-shell lithium batteries, the efficiency can be increased by 5 to 10 times, and the appearance and sealing performance are better. Therefore, there is a trend to gradually replace pulsed lasers in this application field.

5. Power battery module and pack welding

The series-parallel connection between power batteries is generally completed by welding the connecting piece and the single battery. The positive and negative electrodes are made of different materials. Generally, there are two materials, copper and aluminum. Since copper and aluminum are laser welded to form brittle compounds, it is impossible to To meet the requirements of use, in addition to ultrasonic welding, copper and copper, aluminum and aluminum are generally laser welded.

At the same time, due to the fast heat transfer of copper and aluminum, and the high reflectivity to the laser, the thickness of the connecting piece is relatively large, so it is necessary to use a higher power laser to achieve welding.

It can be seen that laser welding has stood out among many welding methods. First of all, laser welding has high energy density, small welding deformation and small heat-affected zone, which can effectively improve the accuracy of parts, and the welds are smooth without impurities, uniform and dense, and no additional grinding work is required; secondly, laser welding can be precisely controlled, focusing light Small point, high-precision positioning, easy to achieve automation with robotic arms, improve welding efficiency, reduce man-hours, and reduce costs; in addition, when laser welding thin plates or thin-diameter wires, it is not as easy to be troubled by melting back as arc welding. And it can weld a wide range of materials, and can realize welding between different materials.