Complete Manual of Lithium Battery Production Process
Lithium-ion battery is a complex system, including positive electrode, negative electrode, separator, electrolyte, current collector and binder, conductive agent, etc. The reactions involved include electrochemical reaction of positive and negative electrodes, lithium ion conduction and electron conduction, and heat dissipation. The production process of lithium batteries is long, and there are more than 50 processes involved in the production process.
Lithium batteries can be divided into cylindrical batteries, square batteries and soft pack batteries according to their shape, and their production processes are different to some extent, but the overall lithium battery manufacturing process can be divided into the front process (pole piece manufacturing), the middle process (cell synthesis) , The back-end process (chemical packaging).
Due to the high safety performance requirements of lithium-ion batteries, there are extremely high requirements for the precision, stability and automation level of lithium-ion batteries in the battery manufacturing process.
Lithium battery equipment is a process equipment for manufacturing and producing raw materials such as positive and negative electrode materials, diaphragm materials, and electrolytes through an orderly process. Lithium battery equipment has a significant impact on the performance and cost of lithium batteries and is one of the determining factors. According to different technological processes, lithium battery equipment can be divided into front-end equipment, middle-end equipment, and back-end equipment. In the lithium battery production line, the value ratio of front-end, middle-end, and back-end equipment is about 4:3:3.
The production goal of the previous process is to complete the manufacture of (positive and negative) pole pieces. The main processes of the front-end process are: stirring, coating, rolling, slitting, filming, and die-cutting. The equipment involved mainly includes: mixer, coating machine, rolling machine, slitting machine, tableting machine, die-cutting machine etc.
Slurry stirring (equipment used: vacuum mixer)
It is to mix the positive and negative solid-state battery materials evenly and then add the solvent and stir into a slurry. Slurry stirring is the starting point of the previous process, and it is the pre-process basis for the completion of subsequent coating, rolling and other processes.
Coating (equipment used: coating machine)
It is to uniformly coat the stirred slurry on the metal foil and dry it to make positive and negative electrodes. 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.
Rolling (equipment used: rolling machine)
It is to further compact the coated pole piece, thereby increasing the energy density of the battery. The flatness of the pole piece after rolling will directly affect the processing effect of the subsequent slitting process, and the uniformity of the active material of the pole piece will also indirectly affect the performance of the cell.
Slitting (equipment used: slitting machine)
It is to continuously slit the wider whole roll of pole pieces into several narrow pieces of required width. The pole piece encounters shearing failure during slitting, and the smoothness of the edge after slitting (no burr, no buckling) is the key to examining the performance of the slitting machine.
Filming (equipment used: filming machine)
Including welding the pole tabs after the slitting, sticking protective tape, wrapping the tabs or using laser cutting to form the tabs, etc., so as to be used for the subsequent winding process. Die-cutting (equipment used: die-cutting machine) is to die-cut the coated pole piece for subsequent processes.
The production goal of the mid-stage process is to complete the manufacture of cells. There are differences in the technical route and production line equipment of the mid-stage process of different types of lithium batteries. The essence of the middle process is the assembly process, specifically, the (positive and negative) pole pieces made in the previous process are assembled in an orderly manner with the separator and electrolyte. Due to the different energy storage structures of square (rolled), cylindrical (rolled) and soft pack (layered) batteries, there are obvious differences in the technical routes and production line equipment of different types of lithium batteries in the middle process. Specifically, the main processes of the middle process of square and cylindrical batteries are: winding, liquid injection, and packaging. The equipment involved mainly includes: winding machine, liquid injection machine, packaging equipment (shell machine, rolling groove machine, sealing machine) The main processes of the middle process of the soft pack battery are: lamination, liquid injection, packaging, and the equipment involved mainly includes: lamination machine, liquid injection machine, packaging equipment, etc.
Winding (equipment used: winder)
It is a battery cell that winds the pole piece made by the production process or the winding die-cutting machine into a lithium ion battery, which is mainly used for the production of square and round lithium batteries. Winding machines can be subdivided into square winding machines and cylindrical winding machines, which are used for the production of square and cylindrical lithium batteries respectively. Compared with cylindrical winding, the square winding process has higher requirements for tension control, so the technology of the square winding machine is more difficult.
Lamination (equipment used: lamination machine)
It is a cell that stacks the single pole pieces made in the die-cutting process into a lithium-ion battery, which is mainly used for the production of soft pack batteries. Compared with square and cylindrical cells, pouch cells have obvious advantages in terms of energy density, safety, and discharge performance. However, the stacking machine completes a single stacking task, which involves multiple sub-processes in parallel and complex mechanism coordination. To improve the stacking efficiency, complex dynamic control problems need to be dealt with; while the winding speed is directly related to the winding efficiency, and the means of increasing efficiency are relatively simple. . At present, there is a gap between the production efficiency and yield of laminated cells and that of wound cells.
Cell packaging (equipment used: shell machine, rolling groove machine, sealing machine, welding machine)
Is to put the core into the battery shell
The production goal of the back-end process is to complete the chemical packaging. As of the mid-stage process, the functional structure of the lithium battery cell has been formed. The significance of the latter stage process is to activate it. After testing, sorting, and assembly, a lithium battery product that is safe to use and has stable performance is formed. The main processes of the latter process are: formation, volume separation, testing, sorting, etc. The equipment involved mainly includes: charging and discharging machines, testing equipment, etc.
Formation (equipment used: charging and discharging machine)
It activates the cell through the first charging, and during this process, an effective passivation film (SEI film) is formed on the surface of the negative electrode to realize the "initialization" of the lithium battery. Dividing capacity (equipment used: charging and discharging machine) is "analyzed capacity", which is to charge and discharge the formed cells according to the design standards to measure the capacity of the cells. The charging and discharging of the cells is carried out through the formation and capacity separation process, so the charging and discharging machine is the most commonly used back-end core equipment. The minimum working unit of a charge and discharge machine is a "channel", a "unit" (BOX) is composed of several "channels", and a plurality of "units" are combined to form a charge and discharge machine.
Testing (equipment used: testing equipment)
It should be carried out before and after charging, discharging and standing; sorting is to classify and select the batteries after formation and capacity division according to certain standards according to the test results. The significance of the detection and sorting process is not only to exclude unqualified products, but also because the cells are often combined in parallel or in series in the practical application of lithium-ion batteries, so selecting cells with similar performance will help to optimize the overall performance of the battery. .
The production of lithium batteries is inseparable from lithium battery production equipment. 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 relied on imports. After several years of rapid development, Chinese lithium battery equipment companies have gradually caught up with Japanese and Korean equipment companies in terms of technology, efficiency, stability, etc., and have cost-effective, after-sales maintenance and other aspects. The advantages. At present, the domestic lithium battery equipment enterprise cluster has been formed, and it has become China's high-end equipment business card to enter the international market. With the vertical alliance and overseas expansion of lithium battery leaders, lithium battery equipment benefits from downstream expansion and ushered in a new period of opportunity for rapid growth.