Complete manual of lithium battery production process

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

Lithium battery equipment is a kind of process equipment that makes positive and negative materials, separator materials, electrolyte and other raw materials through orderly process. Lithium battery equipment has a significant impact on the performance and cost of lithium battery, which is one of the decisive factors. According to different technological processes, lithium battery equipment can be divided into front section equipment, middle section equipment and back section equipment. In the lithium battery production line, the value of front section equipment, middle section equipment and back section equipment accounts for about 4:3:3.

1、 Previous process

The production goal of the previous process is to complete the manufacturing of (positive and negative) pole pieces. The main processes of the previous process are: mixing, coating, rolling, slitting, film making, die-cutting, and the equipment involved mainly includes: mixer, coater, roller press, Slitter, film making machine, die-cutting machine, etc.

1. Slurry mixing (equipment used: vacuum mixer) is to mix the positive and negative solid battery materials evenly and then add solvent to stir them into slurry. Slurry mixing is the starting point of the previous process, which is the basis of the subsequent coating, rolling and other processes.

2. Coating (equipment used: coater) is to evenly coat the stirred slurry on the foil and dry it to make positive and negative plates. As the core link of the previous process, the execution quality of the coating process has a profound impact on the consistency, safety and life cycle of the finished battery, so the coating machine is the most valuable equipment in the previous process.

3. Roller pressing (equipment used: Roller Press) is to further compact the coated electrode piece, so as to improve the energy density of the battery. After rolling, the flatness of the electrode plate will directly affect the processing effect of the subsequent cutting process, and the uniformity of the active material of the electrode plate will indirectly affect the performance of the cell.

4. Slitting (equipment used: Slitter) is to cut the whole wide polar sheet into several narrow sheets of required width. In the process of slitting, the pole piece will be fractured due to shear action. The flatness of the slitting edge (no burr, no buckling) is the key to evaluate the performance of slitter.

5. Film making (equipment used: film making machine) includes welding the electrode lug, sticking protective adhesive tape, wrapping the electrode lug with glue or forming the electrode lug by laser cutting, so as to be used in the subsequent winding process. Die cutting (used equipment: die-cutting machine) is the coating after the pole piece punching forming, for the follow-up process.

2、 Intermediate process

The production goal of the middle process is to complete the cell manufacturing. The technical route and production line equipment of different types of lithium batteries are different. The essence of the middle process is the assembly process. Specifically, the (positive and negative) electrode pieces made in the previous process are orderly assembled with the diaphragm and electrolyte. Specifically, the main processes of the middle process of square and cylindrical batteries are: winding, liquid injection, packaging, and the equipment involved mainly includes: winding machine, liquid injection machine, packaging equipment (shell machine, grooving machine, sealing machine, welding machine), etc.; the main processes of the middle process of soft pack batteries are: laminating, liquid injection, packaging, and the equipment involved mainly includes: laminating machine, liquid injection machine Packaging equipment, etc.

1. Winding (equipment used: winding machine) is to wind the pole pieces made by the film making process or the rolling die-cutting machine into lithium-ion battery cells, which are mainly used for the production of square and round lithium-ion batteries. The winding machine can be divided into square winding machine and cylindrical winding machine, which are respectively used for the production of square and cylindrical lithium batteries. Compared with cylindrical winding, square winding process requires higher tension control, so square winding machine is more difficult.

2. Lamination (equipment used: laminating machine) is a kind of cell which is used to stack the single pole pieces made in the die-cutting process into lithium-ion batteries. It is mainly used for the production of soft pack batteries. Compared with square and cylindrical cells, soft core has obvious advantages in energy density, safety and discharge performance. However, to complete a single stacking task, the laminating machine involves multiple sub processes parallel and complex mechanism cooperation, so to improve the laminating efficiency, it needs to deal with complex dynamic control problems; and the speed of the winding machine is directly related to the winding efficiency, so the means of increasing efficiency is relatively simple. At present, there is a gap between the production efficiency and yield of laminated core and wound core.

3. Filling machine (equipment used: filling machine) is to inject the electrolyte of the battery into the cell quantitatively.

4. Core packaging (equipment used: shell machine, grooving machine, sealing machine, welding machine) is to put the core into the core shell.

3、 Later process

The production goal of the latter process is to complete the chemical packaging. Up to the middle stage process, the functional structure of lithium battery cell has been formed. The significance of the latter stage process is to activate it and form a safe and stable lithium battery product through detection, sorting and assembly. The main processes of the latter process include: formation, separation, detection, separation, etc., and the equipment involved mainly includes: charging and discharging motor, detection equipment, etc.

1. Formation (equipment used: charging and discharging motor) is to activate the cell through the first charge. In this process, an effective passive film (SEI film) is formed on the negative electrode surface to realize the "initialization" of lithium battery. Capacity sharing (equipment used: charging and discharging motor), namely "analytical capacity", is to charge and discharge the formed cell according to the design standard, so as to measure the capacitance of the cell. The charge and discharge of the cell runs through the formation and capacity separation process, so the charge and discharge motor is the most commonly used core equipment in the later stage. The minimum working unit of charging and discharging motor is "channel". A "unit" (box) is composed of several "channels", and multiple "units" are combined to form a charging and discharging motor.

2. Testing (equipment used: testing equipment) should be carried out before and after charging, discharging and standing; sorting is to classify and select the formed and divided capacity batteries according to a certain standard according to the testing results. The significance of the detection and sorting process is not only to eliminate the unqualified products, because in the practical application of lithium-ion battery, the cells are often combined in parallel or series, so the selection of cells with similar performance is helpful to optimize the overall performance of the battery.

The production of lithium battery is inseparable from the production equipment of lithium battery. In addition to the materials used in the battery itself, the manufacturing process and production equipment are important factors that determine the performance of the battery. In the early days, China's lithium battery equipment mainly depended on imports. After several years of rapid development, China's lithium battery equipment enterprises have gradually overtaken Japan and South Korea's equipment enterprises in technology, efficiency, stability and other aspects, and have the advantages of cost performance, after-sales maintenance and so on. At present, the domestic lithium battery equipment enterprise cluster has been formed, and has become China's high-end equipment business card to enter the international market. With the vertical alliance of lithium battery leaders and the expansion of production at sea, the downstream expansion of lithium battery equipment benefits and ushers in a new opportunity period of rapid growth.