What are the main assembly methods for soft-pack CR1225 battery?

Aluminum-plastic film forming process

Soft-pack CR1225 battery can be designed into different sizes according to customer needs. When the external dimensions are designed, the corresponding molds must be opened to form the aluminum-plastic film. Sometimes, according to the design requirements, a small pit will be punched at the position of the air bag to expand the volume of the air bag.

Top and side sealing process

The top and side sealing process is the first packaging process of soft-pack lithium 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. 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.

Liquid injection and pre-sealing process

After the top and side sealing of the soft-pack battery, an X-ray is used to check the parallelism of the core, and then it goes into the drying room to remove moisture. After standing in the drying room for a period of time, it enters the liquid injection and pre-sealing process. After the top and side seals of the battery cell are completed, only an opening at the air bag is left, which is used for liquid injection. After the liquid injection is completed, the air bag side must be pre-sealed immediately, also called a seal. After the seal is completed, the battery cell is theoretically completely isolated from the outside environment.

Station, formation, and fixture shaping process

After the liquid injection and sealing are completed, the battery cell must first be stationed. According to the difference in process, it can be divided into high-temperature stationary and room-temperature stationary. The purpose of the stationary is to allow the injected electrolyte to fully infiltrate the electrode. Then the battery cell can be taken for formation.

The formation is the first charge of the battery cell, 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 surface of the electrode, which is equivalent to a process of activating the battery cell. In this process, a certain amount of gas will appear, which is why an air bag should be reserved for the aluminum-plastic film.

After the formation, some batteries, especially thick batteries, may be deformed to a certain extent due to the large internal stress. Therefore, some factories will configure a fixture shaping process after formation, also known as fixture baking.

Secondary sealing process

Just now, we said that gas will appear during the formation process, so we need to extract the gas and then perform the second packaging. Some companies here have two processes: Degassing and secondary sealing, and there is also a process of cutting the air bag at the end. Here I will generally call them all secondary sealing. During the secondary sealing, the air bag is first punctured by the guillotine and vacuumed at the same time, so that the gas in the air bag and a small part of the electrolyte will be extracted. Then the secondary sealing head is immediately packaged in the secondary 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. Secondary sealing is the last packaging process of CR1225 battery. Its principle is the same as the previous thermal packaging, so I will not repeat it.

Subsequent process

After the airbags are cut, the edges need to be trimmed and folded. That is, the first and second edges are cut to the appropriate width, and then folded to ensure that the width of the battery cell does not exceed the standard. After the edges are folded, the battery cell can be put into the capacity cabinet for capacity division, which is actually a capacity test to see whether the capacity of the battery cell reaches the specified minimum value. In principle, all battery cells must be tested for capacity division before leaving the factory to ensure that batteries with unqualified capacity will not be delivered to customers. However, when the production volume of battery cells is large, some companies will do partial capacity division to determine the qualified rate of the capacity of the battery cells in this batch by statistical probability.

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