Electric vehicle lithium-ion battery important parts laser machine

Electric vehicle lithium-ion battery important parts laser machine

The main welding links are as follows:

1) Welding of battery explosion-proof valve: 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 will rupture 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) Welding of battery poles: The poles on the battery cover are divided into internal and external connections of the battery. The internal connection of the battery is the welding of the electrode lugs of the battery cell and the poles of the cover plate; the external connection of the battery is the welding of the battery poles through the connecting piece to form a series and parallel circuit to form a battery module. The poles of the battery are the positive and negative electrodes of the battery. Generally, the positive electrode is made of aluminum, and the negative electrode is made of copper. The commonly used structure is the riveting structure, which is fully welded after the riveting is completed, and its size is generally a circle with a diameter of 8. When welding, in the case of satisfying the tensile force and electrical conductivity required by the design, the fiber laser or compound welding laser with good beam quality and uniform energy distribution is preferred. Aluminum structure welding, copper-copper structure welding stability, reduce spatter, and improve welding yield.

3) Welding of the adapter sheet: The adapter sheet and the soft connection are the key components to connect the battery cover and the cell. It must also take into account the requirements of overcurrent, strength and low spatter of the battery, so during the welding process with the cover plate, there needs to be enough welding seam width, and it is necessary to ensure that no particles fall on the cell to avoid short circuit of the battery. . Copper, which is used as a negative electrode material, is a highly reflective material with low absorption rate, and requires higher energy density to weld during welding.

4) Shell sealing and welding: The shell materials of power batteries include aluminum alloy and stainless steel, among which aluminum alloy is used most, and pure aluminum is also used in a few. 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 can increase the efficiency by 5 to 10 times, and have better appearance and sealing. Now in pursuit of faster welding speed and more uniform appearance, most companies have begun to use composite welding and annular spot to replace the previous low-speed single-fiber welding.

5) Welding of sealing nails (electrolyte injection ports): There are also many forms of sealing nails (caps for injection holes), and their shape is usually a circular cap with a diameter of 8mm and a thickness of about 0.9mm. The basic requirement for welding is resistance. The pressure value reaches 1.1MPa, and it is sealed and free of pinholes, cracks and explosion points. As the last process of cell welding, the yield of sealing nail welding is particularly important. Due to the presence of residual electrolyte during welding of the sealing stud, defects such as explosion points and pinholes are caused, and the key way to suppress these defects is to reduce the heat input.

6) Power battery module and PACK welding: The battery module can be understood as a combination of lithium-ion cells in series and parallel, and a single battery monitoring and management device is installed. The structural design of the battery module can often determine the performance and safety of a battery pack. Its structure must support, fix and protect the cell. Because the brittle compound is easily formed after laser welding between copper and aluminum, which cannot meet the requirements of use, ultrasonic welding is usually used; 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 is particularly worth noting that in the power battery industry, compared with cutting and marking, laser welding has the characteristics of customization and strong customer stickiness, and has higher barriers to entry.

1) Laser welding equipment presents the characteristics of non-standard customization. The technical indicators of the products are determined by the customers according to their own products, and the technical indicators of the Ningde era are the most advanced in the industry. The laser welding equipment in the power battery industry mainly includes: sealing nail welding system, top cover welding system, soft connection welding system, pole welding system, explosion-proof valve welding system, PACK and module welding system, etc.; according to the site restrictions of downstream customers, The level of automation, technical requirements, etc., need to be re-customized design.

2) Stability control of laser output. In order to output a uniform and stable welding laser beam to the weldment, the laser output power needs to have good consistency and be able to precisely control the laser output power. If the power is too low, it will lead to insufficient welding melting and affect the welding quality. The power is too high or fluctuates up and down It will cause adverse effects such as splashes and blowholes. At the same time, some important industrial materials such as aluminum, copper and other materials are highly reflective and difficult to weld by laser welding, which is easy to form spatters, cracks and pores, which affect the welding quality and effect. Therefore, it is necessary to develop and design targeted lasers. especially important.

3) Set laser welding process parameters for different welding materials. Including laser beam properties, beam focusing and focus characteristics, auxiliary gas characteristics, processing material properties, suitable fixtures and mechanical parts and other process parameters to achieve optimal welding results.

4) The technical parameters and requirements of the welding process will affect the selection of lasers, the design and development of automatic transmission devices, fixtures, and control software. In the process of R&D and design, it is necessary to have a deep understanding and research on the laser light source, such as the wavelength range of the laser, the energy density of the laser, the speed of the welding of the laser, the positional relationship between the laser focus and the material, etc., and to understand the characteristics of the material.