Lithium Battery Production Process

Lithium Battery Production Process

Lithium ion battery is a complex system, including positive electrode, anode electrode, diaphragm, electrolyte, fluid collector and binder, conductive agent, etc. The reactions involved include electrochemical reaction of positive electrode and negative electrode, lithium ion conduction, electron conduction, and heat diffusion, etc. The production process of lithium battery is long, involving more than 50 processes.

Lithium battery can be divided into cylindrical battery, square battery and soft package battery according to the form, and its production process has some differences, but overall, the lithium manufacturing process can be divided into the first step (pole manufacturing), the middle step (cell synthesis), the last step (forming and packaging). Because the safety performance of lithium ion battery is very high, the accuracy, stability and automation level of lithium battery equipment are highly required in the battery manufacturing process.

Lithium electric equipment is the anode and cathode materials, diaphragm materials, electrolyte and other raw materials through orderly process, manufacturing process equipment, lithium electric equipment has a significant impact on the performance and cost of lithium battery, is one of the determinants. According to different technological processes, lithium electric equipment can be divided into front section equipment, middle section equipment and rear section equipment. In the lithium production line, the value of front section, middle section and rear section equipment accounts for about 4:3:3.

The production objective of the first step is to complete the fabrication of (positive and negative) polar plates. The main process of the preceding process is: mixing, coating, roller pressing, cutting, production, die cutting, the equipment involved mainly includes: mixer, coating machine, roller press, slicing machine, production machine, die cutting machine and so on.

Slurry mixing (equipment: vacuum mixer) is to mix positive and negative solid battery materials evenly and then add solvent to stir into slurry. Slurry mixing is the beginning of the previous process, is to complete the subsequent coating, roller and other processes prior to the foundation.

Coating (equipment: coating machine) is to stir the slurry evenly coated on the metal foil and dried into positive and negative pieces. As the core part of the previous process, the execution quality of the coating process profoundly affects the consistency, safety and life cycle of the finished battery, so the coating machine is the highest value of the equipment in the previous process.

Roller pressing (equipment: roller press) is to further compress the coated electrode sheet to improve the energy density of the battery. The smoothness of the roller - pressed rear electrode directly affects the processing effect of the post - sequence cutting process, and the uniformity of the active material of the electrode indirectly affects the performance of the cell.

Slitting (equipment : slitting machine) is to continuously slice the wider coil of pole into a number of narrow pieces of required width. In the process of cutting, the pole slice encounters shearing fracture failure, and the level of edge after cutting (no burr, no buckling) is the key to evaluate the performance of the slicing machine.

Film-making (equipment: film-making machine) includes welding pole lugs after cutting, pasting protective tape, wrapping pole lugs or using laser cutting to shape pole lugs, etc., for subsequent winding process. Die cutting (used equipment: die cutting machine) is the coating after the pole piece punching molding, for the subsequent process.

The production goal of the mid-course process is to complete the manufacturing of the cell. There are differences in the technical route and production line equipment of the mid-course process for different types of lithium batteries. The essence of the middle process is the assembly process. Specifically, it is the orderly assembly of the (positive and negative) pole pieces made from the previous process with the diaphragm and electrolyte. Due to the different energy storage structures of square (roll), cylindrical (roll) and soft pack (layer) batteries, there are obvious differences in the technical route and production line equipment of different types of lithium batteries in the middle process. Specifically, the middle process of square and cylindrical battery mainly includes winding, liquid injection and packaging. The equipment involved mainly includes: winding machine, liquid injection machine, packaging equipment (shell feeding machine, groove rolling machine, sealing machine, welding machine), etc. The main process of the middle process of the soft pack battery is laminating, liquid injection and packaging. The equipment involved mainly includes laminating machine, liquid injection machine and packaging equipment.

Winding (equipment: winding machine) is used to wind the pole sheet made by the making process or winding die cutting mechanism into the battery cell of lithium ion battery, mainly used in the production of square and round lithium battery. Winding machine can be subdivided into square winding machine, cylindrical winding machine two categories, respectively for square, cylindrical lithium battery production. Compared with cylindrical winding, square winding process requires higher tension control, so square winding machine is more difficult.

Lamination (equipment: laminator) is the lamination of single pole pieces made in the die cutting process into lithium-ion battery cells, mainly used in the production of flexible battery. Compared with square and cylindrical cells, soft-clad cells have obvious advantages in energy density, safety and discharge performance. However, when the laminator completes a single stacking task, it involves the coordination of multiple sub-processes and complex mechanisms, so it needs to deal with complex dynamics control to improve the stacking efficiency. The speed of winding machine is directly related to the winding efficiency, and the method of efficiency enhancement is relatively simple. At present, the production efficiency and yield of laminated cell are not as good as those of wound cell.

Liquid injection machine (equipment: liquid injection machine) is the quantitative injection of battery electrolyte into the cell.
Core packaging (used equipment: shell machine, groove rolling machine, sealing machine, welding machine) is to put the coiling core into the shell of the core.

The production goal of the latter process is to complete formation and encapsulation. By the middle process, the functional structure of lithium battery cell has been formed, the significance of the latter process is to activate it, through detection, sorting, assembly, the use of safety, stable performance of lithium battery products. The main process of the latter part of the process includes: formation, volume separation, detection, sorting, etc. The equipment involved mainly includes: charging and discharging machine, detection equipment, etc.

Formation (equipment : charge-discharge machine) is to activate the cell through the first charge, during which effective passivation film (SEI film) is generated on the negative electrode surface to achieve the "initialization" of the lithium battery.

Capacity division (equipment: charging and discharging machine), namely, "analysis capacity", is to charge and discharge the cell in accordance with the design standard, in order to measure the electric capacity of the cell. Charge and discharge of the cell through the formation, capacitive process, so the charge and discharge machine is the most commonly used after the core equipment. The minimum working unit of charge-discharge machine is "channel". A "unit" (BOX) is composed of a number of "channels", and a number of "units" are combined together to form a charge-discharge machine.

Testing (equipment: testing equipment) should be carried out before and after charging, discharging and standing; Sorting is to classify and select the batteries after formation and volume separation according to certain standards according to test results. The significance of detection and sorting process is not only to eliminate unqualified products, because in the practical application of lithium ion battery, the cell is often combined in parallel and series, so the selection of the cell with similar performance is conducive to the overall performance of the battery to achieve the optimal.