Analysis of packaging process of soft pack battery

In the aluminum-plastic film forming process, the soft-packed batteries can be designed into different sizes according to the needs of customers. When the external dimensions are designed, the corresponding mold must be opened to form the aluminum-plastic film. The forming process is also called punching. As the name suggests, it uses a forming mold to punch a pit that can hold a core in the aluminum-plastic film under heating. After the aluminum-plastic film is punched and cut into shape, it is generally called a Pocket bag. Generally, when the battery core is thin, you choose to punch a single pit, and when the battery core is thick, you choose to punch a double pit, because too much deformation on one side will break the deformation limit of the aluminum-plastic film and cause breakage. Sometimes according to the design requirements, a small hole is punched in the position of the air bag to expand the volume of the air bag. The top-side sealing process, the top-side sealing process is the first packaging process of the soft-packed lithium-ion battery. The top side seal actually contains two processes, the top seal and the side seal. First put the wound core into the punched pit, and then fold the packaging film in half along the dotted line. The following picture shows several positions to be packaged after the aluminum-plastic film is loaded into the core, including the top sealing area, side sealing area, one sealing area and second sealing area. The following coating is analyzed separately online. After the core is placed in the pit, the entire aluminum plastic film can be placed in the fixture, and the top and side sealing are performed in the top side sealing machine. The top-side sealing machine is like this: the top-side sealing machine of this model in the picture is equipped with four clamps, the left station is the top seal, and the right station is the side seal. The two pieces of yellow metal are the upper head, and there is a lower head underneath. The two heads have a certain temperature (usually around 180°C) when they are packaged. They are pressed on the aluminum plastic film when they are closed. The PP layer of the film is melted and then bonded together, and the package is OK. It is important to talk about the top seal, the schematic diagram of the top seal area is shown in the figure below. The top seal is to seal the tabs. The tabs are made of metal (aluminum anode and nickel cathode). How can they be packaged with PP? This is done by a small part of the lug on the lug. The package at the tab position is shown in the circled part in the figure below. During packaging, the PP in the tab glue and the PP layer of the aluminum-plastic film melt and bond to form an effective packaging structure. In the process of liquid injection and pre-sealing, after the soft-packed cell is sealed on the top side, X-ray should be performed to check the parallelism of the core, and then go into the drying room to remove moisture. After a certain period of time in the drying room, it enters the liquid injection and pre-sealing process. Through the above analysis, we know that after the cell is sealed on the top side, there is only one opening on the air bag side, which is used for liquid injection. After the liquid injection is completed, the pre-sealing of the side of the air bag should be performed immediately, which is also called one. After a package is completed, the core is theoretically completely isolated from the external environment. The packaging principle of a letter is the same as that of the top side seal, so I won't repeat it here. In the process of standing, forming, and jig shaping, after the liquid injection and one seal are completed, the battery cell should be placed first. Depending on the process, it will be divided into high temperature standing and normal temperature standing. The purpose of standing is to make the injection The electrolyte is sufficient to soak the pole piece. Then the batteries can be used to make them. The picture above is the conversion cabinet of the soft-packed batteries, which is actually a charging and discharging device. I have not found a picture of the charged core for a long time. Think about the picture of the battery sandwiched on it. The chemical result is the first charging of the battery, but it will not be charged to the highest voltage used, and the charging current is also very small. The purpose of chemical conversion is to form a stable SEI film on the electrode surface, which is equivalent to a process of activating the cell. In this process, a certain amount of gas will appear, which is why the aluminum plastic film needs to reserve an air bag. In some factories, the process will use fixture formation, that is, the cell is clamped in the fixture (sometimes the picture is simple and the glass plate is used, and then the steel clamp is installed) and then the cabinet is formed, so that the gas that appears will be sufficiently squeezed to the side of the gas The electrode interface after chemical formation is also better. After formation, some cells, especially thick cells, may be deformed due to large internal stress. Therefore, some factories will set up a fixture shaping process after the formation, which is also called fixture baking. In the second sealing process, I just said that there will be gas during the formation process, so we have to extract the gas and then perform the second packaging. Some companies here have two processes: exhaust and second sealing, and the next process of cutting the air bag. Here, the coating line is collectively called the second sealing. In the second seal, the air bag is first pierced by a guillotine, and a vacuum is drawn at the same time, so that the gas and a small amount of electrolyte in the air bag will be drawn out. Then immediately the second sealing head is encapsulated in the second sealing area to ensure the air tightness of the cell. Finally, cut off the air bag of the encapsulated cell, and a soft-package cell is basically formed. The second seal is the last packaging process of the lithium battery, and its principle is the same as the previous thermal packaging, so I won't repeat it. Disclaimer: Some pictures and content of articles published on this site are from the Internet. If there is any infringement, please contact to delete. Previous: How to charge the lithium battery of electric vehicle correctly