In previous article, we have introduced the first five steps in producing lipo batteries,
Dry li-Po battery’s pole sheet wet coating
Rolling the Pole Sheet
Cut Pole Sheet into strips to Make Pole Pieces
Pile Up Electrode Sheet
In this post, we will continue to show you how to make a lipo battery.
STEP 6–Insulation Test
The positive and negative electrodes are wound and separated by diaphragm paper; they are composed of batteries to test their insulation properties.
Li-Po battery insulation testing is the process of testing the insulation properties of polymer batteries. Li-Po battery is a new type of battery technology, which has the advantages of high energy density, high safety and long life, but its insulation properties are also very important, because once the insulation properties of the Li-Po battery are damaged, it may cause safety issues such as short circuit and fire inside the battery. Therefore, the insulation testing of Li-Po batteries is an important part of ensuring the safety performance of batteries. Testing methods include electrical testing, thermal testing, etc.
STEP 7–Seal LiPo Battery
Load the bare battery cell into the washed aluminum-plastic composite film and seal the opening at the top of the battery cell.Finally, seal the left side of the sealed battery.
Li-Po batteries are currently the most widely used lithium batteries. Because of their simple packaging method, easy to customize the dimensions, and good safety, they are widely used in various portable devices such as mobile phones, power tools, and portable medical equipment.
Types of Aluminum Plastic Compoosite Film
The aluminum-plastic composite film can be roughly divided into three layers-the inner layer and the adhesive layer. And Li-Po battery materials are mostly used to seal and bond; the middle layer is aluminum foil, which can prevent the infiltration of water vapor from the outside of the battery, while preventing the internal electrolyte from seeping out. The outer layer is a protective layer, mostly made of high melting point polyester or nylon materials, which have strong mechanical properties and prevent damage to the battery by external forces and protect the battery.
The development of high-quality aluminum-plastic composite film is the key to the successful development of high-tech products such as liquid flexible packaging lithium-ion batteries.As the shell of a liquid flexible packaging lithium-ion battery, the aluminum-plastic composite film is no longer just a simple outer packaging of the battery, but also an indispensable and important part of the liquid flexible packaging lithium-ion battery.
If the importance of this flexible packaging material is not understood enough, it will be very detrimental to the design and development of flexible packaging batteries. It has such an important position in the development of liquid flexible packaging lithium-ion batteries, which shows that the product has a high technical content and has qualitative differences in performance from ordinary composite packaging materials in design, manufacturing and application.
Soft-packed batteries can be designed into different sizes according to customer needs. When the dimensions are designed, corresponding molds need to be issued to make the aluminum-plastic film stamping and forming. The molding process is also called punching, which is the use of a molded mold to punch out a pit on the aluminum-plastic film that can roll the core.Soft-packed batteries can be designed into different sizes according to customer needs. When the dimensions are designed, corresponding molds need to be issued to make the aluminum-plastic film stamping and forming. The molding process is also called punching, which is the use of a molded mold to punch out a pit on the aluminum-plastic film that can roll the core.After the aluminum-plastic film is washed, it is cut and formed. It is generally called a pocket bag. Generally, when the battery cell is thinner, it is selected to punch a single pit, and when the battery cell is thicker, it is selected to punch a double pit. When punching a double pit, the deformation on one side will break through the deformation limit of the aluminum-plastic film and cause rupture.Sometimes according to the design requirements, a small pit will be selected on the side of the punching pit to expand the volume of the air bag.
Process of Packaging
The packaging process includes two processes: top sealing and side sealing. First, the wound core must be placed in the flushed pit, and then the un-flushed side is folded in half along the side of the flushed pit.The packaging process includes two processes: top sealing and side sealing. First, the wound core must be placed in the flushed pit, and then the un-flushed side is folded in half along the side of the flushed pit.After the core is placed in the aluminum-plastic film, the aluminum-plastic film can be placed in the fixture and encapsulated in the top sealing and side sealing machine. The top seal is to seal the pole ear. The pole ear is metal (positive aluminum, negative nickel). How can it be encapsulated with PP?This is done by a small part on the polar ear—polar ear glue.During packaging, the PP in the polar ear glue melts and binds to the PP layer of the aluminum-plastic film, forming an effective packaging structure.
STEP 8–Liquid Injection & Sealing
After the soft-packed battery cell is sealed on the top side, an x-ray needs to be done to check the parallelism of the core, and then it enters the drying room to remove water and gas.After standing in the drying room for a certain period of time, it enters the liquid injection and pre-sealing process.After the top side sealing of the battery cell is completed, there is only one opening on the other side of the air bag, which is used for liquid injection.After the injection is completed, the side of the air bag needs to be pre-sealed immediately, also known as a seal.After one letter is completed, the inside of the battery is completely isolated from the external environment.
STEP 9–Standing, forming, fixture shaping
After the injection and one seal are completed, the battery cell needs to be allowed to stand. According to the different production processes, it is divided into high temperature standing and room temperature standing. The purpose of standing is to allow the injected electrolyte to fully infiltrate the machine sheet, and then it can be used to make it into it.This is the first time the battery is charged, but it will not be charged to the highest voltage, and the charging current is very small.The purpose of chemical formation is to form a stable SEI film on the surface of the electrode, which is also equivalent to a process of activating the battery. A certain amount of gas will be produced in this process, which is why an air bag is reserved.Some factories will use fixture formation, put the battery cell in the fixture and then put it into the cabinet.The gas generated in this way will be fully squeezed into the air bag, and at the same time, the electrode interface after the formation is better.After the formation is completed, some batteries, especially thick batteries, will produce certain deformation due to the large internal stress.Therefore, some factories will set up a shaping process after the formation, also known as “baking”.
STEP 10–Twice-seal Process
During the second seal, the air bag is first pierced by a guillotine and vacuumed at the same time, so that the gas in the air bag and part of the electrolyte will be drawn out.Then two seals are immediately carried out to ensure the air tightness of the battery.Finally, the air bag was cut off, and a soft-packed battery cell was basically formed.
STEP 11–Follow-up Process
After the second seal is cut, the air bag needs to be trimmed and hemmed to ensure that the width of the battery does not exceed the standard.After the hemming, the battery cells will enter the sub-capacity cabinet for sub-capacity, which is actually a capacity test.
After the capacity separation is completed, the batteries with qualified capacity will enter the follow-up process, including appearance inspection, yellow glue, side voltage detection, pole ear adapter welding, etc., several processes can be increased or decreased according to customer needs, and finally OQC inspection, and then packaging and shipping.
Above are all about how to produce a lipo battery. Hope they can be useful to you!