Lithium-ion batteries are divided into two categories, hard case soft pack, according to the different s of the cells. The materials of the hard are mainly steel aluminum s, while the soft pack uses aluminum-plastic composite film material. Among them, the hard case is further divided into cylindrical square according to the arrangement of positive negative pole pieces inside.

Soft pack lithium batteries are just liquid lithium batteries packaged in a polymer . Structure type ion of aluminum-plastic film packaging, in the case of safety security hazards arising from the soft pack battery at most will be bulging cracking.

Hard pack lithium batteries are subdivided into two types: cylindrical square. The structure of the package has different advantages disadvantages, mainly for different market dem places. Hard pack lithium battery consistency is relatively difficult to ensure that more more models, the processing process is difficult to be completely consistent, suitable for customized production manufacturing, is not convenient for lithium battery pack automated production.

Flexible pack cells, in fact, are cells that use aluminum-plastic packaging film as a packaging material. The size change is flexible, the cost is low, the energy density of a single cell is higher than that of both cylindrical/square cells. Soft pack cells are thermally encapsulated due to their use of aluminum-plastic packaging film as a material.

Aluminum-plastic packaging film (referred to as Aluminum-plastic film), its cross-section of three layers: nylon layer, A layer PP layer.

Each of the three layers has its own role, first of all, the nylon layer is to ensure the shape of the aluminum-plastic film, to ensure that the film will not be deformed before the manufacture of lithium-ion batteries.

The AI layer is a layer of metal AI composition, its role is to prevent water infiltration. Hammer ion batteries are very afraid of water, generally require that the water content of the pole piece are at the PPM level, so the packaging film must be able to block the penetration of moisture. Nylon is not waterproof cannot provide protection. Instead, metal AI reacts with oxygen in the air at room temperature to generate a dense oxide film, resulting in moisture not being able to penetrate protecting the inside of the cell. the AI layer also provides the plasticity of the punching pits when the aluminum-plastic film is formed.

PP sts for polypropylene, a material characterized by melting at temperatures of more than one hundred degrees Celsius viscosity. So the thermal encapsulation of the battery relies mainly on the PP layer melting bonding together under the heat of the header, then the header is withdrawn the bond is cured by cooling down.

FPCs can be designed in different sizes according to customers' needs. When the dimensions are designed, it is necessary to open the corresponding molds to make the aluminum-plastic film forming. The molding process is also called punching. As the name suggests, it is to use the forming mold to punch out a pit on the aluminum-plastic film under the condition of heating to be able to load the core.

Sometimes, depending on the design, another small pit is punched where the air bag is to exp the volume of the air bag.

The top-side sealing process is the first encapsulation process of soft pack lithium-ion battery cell. Top side sealing actually contains two processes, top sealing side sealing. Firstly, the coiled core is put into the punched pit, then the packaging film is folded along the dotted line.

After the top side sealing of the soft package electric core, it needs to do X-ray to check the parallelism of the core, then it goes into the drying room to get rid of the water gas. In the drying room, it will enter into the liquid injection pre-sealing process after a certain period of time.

After the top side sealing of the core is completed, there is only one opening left on the side of the air pocket, this opening is used for liquid injection. After the liquid injection is completed, it is necessary to immediately carry out the pre-sealing of the air bag side, also known as an encapsulation. After the completion of one seal, the core is theoretically completely isolated from the external environment. The encapsulation principle of one seal is the same as that of the top side seal, will not be explained again.

After the liquid injection a letter is completed, the first need to be static core, according to the different processes will be divided into high-temperature static room temperature static, the purpose of static is to let the injected electrolyte fully infiltrate the pole piece. Then the core can be taken to do the chemical formation.

The picture above is the formation cabinet of the soft pack battery cell, which is actually a charging discharging device. Formation is the first charging of the battery cell, but it will not be charged to the highest voltage for use, the charging current is also very small. The purpose of formation is to let the electrode surface form a stable SEI film, which is equivalent to a process of "activation" of the battery cell.

During this process, a certain amount of gas is generated, which is why an air pocket is reserved for the aluminum-plastic film. Some factories will use the process of fixture formation, that is, the core clamped in the fixture (sometimes figure easy to use a glass plate, then on the steel clamps) then on the cabinet formation, so that the gas will be sufficiently squeezed to the side of the gas bag to go, at the same time after the formation of the electrode interface is also better.

After forming, some cells, especially thick cells, may be deformed due to high internal stress. Therefore, some factories will set up a fixture shaping process, also called fixture baking (baking), after the formation.

Gas will be generated during the formation process, so the gas has to be extracted then encapsulated for the second time. Here some companies become two processes: Degassing (exhaust) second sealing, there is also a later process of cutting the gas bag, here are generally referred to as second sealing.

When second sealing, the gas bag is first pierced by the guillotine vacuumed at the same time, so that the gas in the gas bag with a small part of the electrolyte will be pumped out.

Then immediately the second sealing head ° in the second sealing area for encapsulation, to ensure the gas tightness of the electric core. Finally, the encapsulated core cut off the gas bag, a soft pack battery cell is basically molded. The second seal is the last encapsulation process of the hammer ion battery, its principle is still the same as the previous thermal encapsulation, will not be described.

This article mainly explains the encapsulation, the back of the encapsulation has little to do, so the process after the second seal is briefly summarized:

After sealing cutting the air bag needs to be cut folded, that is, one edge two edges cut to the appropriate width, then folded up to ensure that the width of the core does not exceed the stard. After the folding of the core can be on the sub-capacity cabinet for sub-capacity, in fact, is the capacity test to see whether the capacity of the core has not reached the minimum value of the regulations. In principle, all batteries need to be tested before leaving the factory to ensure that unqualified batteries will not be sent to customers. However, when the production volume of battery cells is large, some companies will do part of the split capacity to determine the capacity of the batch of battery cells to pass the rate of statistical probability.

After dividing the capacity, the qualified cells will enter the post-process, including checking the appearance, pasting the yellow glue, side voltage testing, pole lug welding, etc., which can be increased or decreased according to the customer's needs. Finally, it will be checked by OQC then packaged for shipment.

Cylindrical Winding

Square Cascade

The square wound type combines the appearance characteristics of the square laminated type (but tends to be thicker) with the pole plate fabrication method of the cylindrical wound type, has the advantages of high space utilization high production efficiency. However, the design of this type of battery is also the most complex, with a large number of design variables to consider, as well as the fit between the the cell.