In the process of manufacturing and assembling square aluminum-shell lithium batteries, a large number of laser welding processes are required.

For example: the soft connection of the cell and the cover plate welding, the cover plate sealing welding, the sealing nail welding and so on. Laser welding is the main welding method for square power batteries. It is due to laser welding that it has many advantages such as high energy density, good power stability, high welding accuracy, and easy system integration. In the production process of square aluminum shell lithium batteries, there are irreplaceable effect.

Principle knowledge of laser welding technology

The laser welding machine uses high-energy laser pulses to locally heat the material in a small area. The energy of the laser radiation diffuses into the interior of the material through heat conduction, and the material is melted to form a specific molten pool.

It is a new type of welding method, mainly for the welding of thin-walled materials and fine parts, which can realize spot welding, butt welding, stitch welding, sealing welding, etc., with high aspect ratio, small weld width, small heat affected zone, Small deformation, fast welding speed, smooth and beautiful welding seam, no need or simple treatment after welding, high welding seam quality, no pores, accurate control, small focusing spot, high positioning accuracy, easy to realize automation.

Laser welding can be realized by pulsed or continuous laser beam; the principle of laser welding can be divided into heat conduction welding and laser deep penetration welding.

Thermal welding:

Laser radiation heats the surface to be processed, and the surface heat diffuses to the interior through thermal conduction. By controlling the laser parameters such as the width, energy, peak power and repetition frequency of the laser pulse, the workpiece is melted to form a specific molten pool.

Deep penetration welding:

Generally, continuous laser beams are used to complete the connection of materials, that is, the energy conversion mechanism is completed through a "key-hole" structure. When the laser is irradiated, the material evaporates and forms a small hole, which absorbs all the energy of the incident beam, and the temperature reaches about 25000 ℃, so that the metal surrounding the hole is melted.

The development prospect of laser welding of square aluminum shell:

The occupancy rate of lithium battery aluminum shell is higher than that of steel shell, which is determined by the advantages of high hardness, light weight, and high safety of aluminum shell. The square lithium battery can be customized according to the product size, so there are many models and specifications on the market, which makes it difficult to unify the process of the square battery. Standardization of prismatic batteries is a trend, which is of great significance for component production and post-maintenance.

The welding of the cover plate of the square battery shell is mainly divided into top welding and side welding. There is a rectangular cover plate on the top, with a positive terminal on the plate, insert the cover plate into the casing and flush with the upper opening, and then use a laser to weld the rectangular gap between the cover plate and the casing by repeating continuous laser welding. , This welding process is called top welding. During top welding, the laser beam can not move, and the battery can be fixed on the worktable. After the laser beam is aligned with the welding seam, the worktable is started to make the battery go out in turn along the X and Y coordinates of the worktable. The same rectangular shape of the weld. When the cover plate of the square battery adopts the top welding sealing structure process, the cover plate is placed without positioning steps, and the length and dimension tolerance requirements are stricter, and the welding assembly accuracy is required.