6F22 carbon battery

Briefly describe the general production process of 6F22 carbon battery

Since the outer shell is an aluminum-plastic film, its production process is different from the other two types of commercial batteries in some aspects. For example, the packaging process of the aluminum-plastic film, such as the shaping process during the formation process, etc.

Soft-pack battery packaging process Aluminum-plastic film molding process, 6F22 carbon battery can be designed into different sizes according to customer needs. When the outer dimensions are designed, it is necessary to open the corresponding mold to form the aluminum-plastic film. The molding process is also called punching. As the name suggests, it is to use the molding mold to punch a pit on the aluminum-plastic film under heating to hold the core. See the figure below for details.

After the aluminum-plastic film is punched and cut into shape, it is generally called a pocket bag, as shown in the figure below. Generally, when the battery cell is thin, a single pit is selected (left in the figure below), and when the battery cell is thick, a double pit is selected (right in the figure below), because the deformation of one side is too large, which will break through the deformation limit of the aluminum-plastic film and cause rupture.

Sometimes, according to the design needs, a small pit will be punched at the position of the air bag to expand the volume of the air bag. The top and side sealing process is the first packaging process of soft-pack lithium-ion batteries. The top and side sealing actually includes two processes, top sealing and side sealing. First, put the wound core into the punched pit, and then fold the packaging film in half along the dotted line, as shown in the figure below.

The following figure shows several locations that need 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 two sealing areas. The following will introduce them separately.

After putting the core into the pit, the entire aluminum-plastic film can be placed in the fixture, and the top and side sealing are performed in the top and side sealing machine. The top and side sealing machine looks like this:

The top and side sealing machine of this model in the figure has four fixtures, the left station is the top sealing, and the right station is the side sealing. The two yellow metals are the upper heads, and there is a lower head below. When encapsulating, the two heads have a certain temperature (usually around 180℃). When they are closed, they are pressed on the aluminum-plastic film, and the PP layer of the aluminum-plastic film melts and then bonds together, so that the encapsulation is OK. Let's mainly 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 pole ear. The pole ear is metal (positive aluminum, negative nickel). How to encapsulate it with PP? This depends on a small component on the pole ear - the pole ear glue. I am not very clear about the specific structure of the pole ear glue, and I hope someone who knows the business can supplement it. I only know that it also has the cost of PP, that is, it can melt and bond when heated. The encapsulation at the pole ear position is shown in the circle part in the figure below. During encapsulation, the PP in the pole ear glue melts and bonds with the PP layer of the aluminum-plastic film to form an effective encapsulation structure.

In the process of liquid injection and pre-sealing, after the top and side sealing of the soft-pack battery cell, an X-ray is needed to check the parallelism of its winding core, and then it goes into the drying room to remove moisture. After being left in the drying room for a while, the process of liquid injection and pre-sealing begins.

From the above introduction, we know that after the top and side seals of the battery cell are completed, only an opening on the air bag side is left, and this opening is used for liquid injection. After the liquid injection is completed, the air bag side needs to be pre-sealed immediately, also called a seal. After the seal is completed, the battery cell is theoretically completely isolated from the external environment. The principle of a seal is the same as that of the top and side seals, so I won't go into details here. The process of static, formation, and fixture shaping. After the liquid injection and sealing are completed, the battery cell needs to be static first. According to the different processes, it can be divided into high-temperature static and normal-temperature static. The purpose of static is to allow the injected electrolyte to fully infiltrate the electrode. Then the battery cell can be taken for formation.

The picture above is the formation cabinet of the soft-pack battery cell, which is actually a charging and discharging device. I have been looking for a picture with a battery cell for a long time and I haven't found it. Just think about the picture of the battery cell clamped on it. The formation is the first charge 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 the formation is to form a stable SEI film on the electrode surface, which is equivalent to a process of "activating" the battery. In this process, a certain amount of gas will be generated, which is why an air bag should be reserved for the aluminum-plastic film. Some factories use fixture formation, that is, the battery is clamped in the fixture (sometimes a glass plate is used for simplicity, and then a steel clamp is put on) and then put on the cabinet for formation, so that the gas generated will be fully squeezed into the air bag next to it, and the electrode interface after formation will be better. After formation, some batteries, especially thick batteries, may be deformed due to the large internal stress. Therefore, some factories will set up a fixture shaping process after formation, also called fixture baking.

Second sealing process, I just said that gas will be generated 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 there is a process of cutting the air bag at the end. Here I will generally call them all second sealing. During the second sealing, the guillotine will first puncture the air bag and draw a vacuum at the same time, so that the gas in the air bag and a small part of the electrolyte will be extracted. Then the second sealing head will be immediately packaged in the second sealing area to ensure the airtightness of the battery cell. Finally, the air bag is cut off from the packaged battery cell, and a soft-pack battery cell is basically formed. The second sealing is the last packaging process of lithium-ion batteries. Its principle is the same as the previous thermal packaging, so I will not go into details.

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