SHINHOP laser

Square power batteries are an important part of integrated battery PACKs. These square battery cells are connected in series and parallel, fixed with adhesive for insulation, reinforced with outer frames, arranged with wire bundles, and finally undergo quality testing to form the power battery PACK. If any cell has a problem, it may cause the entire battery pack, or even the entire PACK, to be scrapped. Therefore, to control the quality of the batteries, we need to put significant effort into the internal cell manufacturing process. Among them, laser welding of cells is a significant technical task, and a small mistake can lead to quality issues with the cells.
Before laser welding the cells, let's first understand the structural issues of square battery cells and what needs to be welded.
Square cells are composed of several major parts, and we will focus on one part that requires laser welding.
1. Sealing welding of the square battery cover.
The material of the square battery cover is generally aluminum plate, which needs to be welded and sealed with the battery itself to form a cell body. The thickness is generally 3MM, and continuous welding can be achieved using a 1000W laser for sealing.
2. Welding of battery terminals.
The positive and negative electrode materials of the cell are aluminum and copper/nickel, respectively. The positive terminal requires aluminum posts, while the negative terminal uses copper-aluminum composite materials, both in an inverted T-shape, with the bottom being purple copper (T2). The T-shape is necessary because a conductive block, also made of aluminum, needs to be added on top of the post. The aluminum block/sheet has a small hole, and the terminal passes through the cover plate to the top. At this point, the hole on the aluminum sheet needs to be fitted tightly, as this seam is where we need to perform laser welding. Due to aluminum's relatively good conductivity, light weight, and suitable hardness, it meets the needs of power battery usage. Therefore, during laser welding, the surface of the aluminum material needs to be cleaned to ensure better welding of the terminals.
3. Laser welding of the battery explosion-proof valve and the welding of the explosion-proof valve safety groove bracket.
This function does not need much explanation; it ensures the safety of the battery and prevents explosions due to excessive pressure or temperature. Therefore, we need to understand its structure, which generally consists of an explosion-proof sheet and a groove bracket underneath, both made of aluminum sheets with different thicknesses. The aluminum sheet inside the explosion-proof valve needs to be continuously welded, while the groove bracket only requires pulse spot welding, with two spots generally welded at each of the four corners.
4. Laser welding of the SSD flip sheet. This function is similar to the above explosion-proof valve, mainly to prevent safety issues caused by high-pressure gas generated by the electrolyte. Its position is on the negative side, and the welding quality is also very important. It needs to be welded with a strength greater than the tensile strength of the flip sheet itself. Otherwise, if the tensile force at the weld seam is lower than the pressure resistance of the flip sheet, the flip sheet will not flip, but rather the entire flip sheet will crack at the weld seam and spray out, affecting the safety quality standards of the battery itself.
5. Sealing welding of the liquid injection hole.
After the cell is welded, we need to inject liquid, which requires extra caution because we need to ensure that the liquid does not leak. The area around the injection hole needs to be cleaned, and this area requires laser welding. If not done properly, it can easily cause a fire. Therefore, during welding, it is essential to ensure the power, pulse width, and current settings of the laser welding equipment are correct. Before normal use, the shell needs to undergo welding tests to find suitable parameters before proceeding with formal operations.

6. Welding of the cell connection piece.
Welding of the connection piece is a necessary process for the formation of the battery module. The materials for the connections vary, including pure nickel, copper-nickel alloys, nickel-plated stainless steel strips, and nickel-plated aluminum materials. Due to the high cost of nickel materials, nickel-plated aluminum alloy strips are often used. The methods of welding connection pieces for square batteries and cylindrical batteries (18650 batteries) and soft-pack batteries are different. Square batteries are relatively easier, while welding for 18650 and soft polymer batteries is more complex.
The formation of power battery PACKs requires multiple modules to be connected to ultimately form a marketable product. Therefore, the quality of power batteries needs to be strictly controlled, and laser welding is just one of the equipment processes. Other technical issues involved can only be solved by specialized battery manufacturers. Currently, battery manufacturers have detailed divisions of labor; some only provide battery components, some are responsible for cell production, some only conduct PACK research and assembly, and some, like SHINHOP battery laser equipment manufacturers, are responsible for the research and supply of welding technology equipment for the components and finished products used in power batteries. It is a bit excessive to expect a single company to provide all supporting production and supply. In today's specialized environment, we need to engage in global multilateral cooperation for better technological advancement. In short, laser welding of square power battery cells needs to play a guiding role in market development, and competition also requires cooperation.
【This article is original by "SHINHOP Laser Equipment", for reference and learning only, reproduction/copying is not allowed to avoid unnecessary legal liability issues】