Lithium-ion battery production is located in the middle reaches of the lithium power industry chain. In recent years, the production capacity of lithium-ion batteries has expanded vigorously. However, due to the rapid development of downstream new energy vehicles, it is expected that the power lithium power production capacity gap will still be about 850 GWh in 2025.

Lithium-ion batteries are a complex system, including positive, negative electrodes, diaphragms, electrolytes, collectors and binders, conductors, etc. The reactions involved include electrochemical reactions of positive and negative electrodes, lithium ion conduction conduction and electron conduction, and heat diffusion. The production process of lithium batteries is long, involving more than 50 processes in the production process.

The production process of power lithium-ion batteries can be divided into three parts, as shown in the figure below. The corresponding equipment is divided into electrode production (front section), cell assembly (middle section), cell activation detection and battery packaging (back section). In these three stages of the process, each process can be divided into several key processes, each of which will have a great impact on the final performance of the battery.

The lithium power equipment corresponding to the front process of lithium power production mainly includes vacuum mixers, coating machines, roller presses, etc.; the middle process mainly includes die-cutting machines, winding machines, laminates, liquid injection machines, etc.; the later process includes chemical machines, capacity separation testing equipment, process warehousing and logistics automation, etc. In addition, Pack automation equipment is also needed for the production of battery packs.

Production process of the first stage

Front part of the cell: It mainly involves electrode production, with four links: stirring, coating, roller pressure and cutting. The core performance of the battery is related to the electrode manufacturing.

The result of the front-end process of lithium batteries is the preparation of positive and negative electrodes of lithium batteries. The first process is stirring. That is, the positive and negative solid battery materials are evenly mixed, and the solvent is added, and stirred into a slurry through a vacuum mixer. The stirring of ingredients is the basis of the lithium electric follow-up process, and high-quality stirring is the basis for the high-quality completion of the subsequent coating and roller pressing process.

The coating and roller pressing process are followed by slitting, that is, the coating is slitting process. Coating, that is, use a coating machine to evenly coat the stirred slurry on the metal foil (usually copper foil or aluminum foil) and dry it to make positive and negative electrodes, and then bake it with a dryer to remove moisture and keep the poles dry. After drying, the energy density can be increased by compacting the poles of the roller press and the roller machine, which can be pressed to a minimum of 0.1-0.5mm. Finally, the cutting mainly refers to the polar cutting and diaphragm cutting, mainly to cut them into a single single pool. The required equipment includes a slitting machine and a diaphragm splitter.

If burrs occur during the cutting process, there will be potential safety hazards in subsequent assembly, electrolyte injection and other procedures, and even battery use. Therefore, the front-end equipment in the lithium power production process, such as mixers, coating machines, roller presses, slitting machines, etc., are the core machines of battery manufacturing, which is related to the quality of the whole production line. Therefore, the value (amount) of front-end equipment accounts for the highest proportion of the whole lithium power automation production line, about 35%.

Mid-section process assembly process

After the poles in the front section are finished, we also need a production machine/mold cutting machine to make or die-cutting, and the process differentiation will begin here. It mainly refers to the different treatment of the poles in the front. One is the winding process and the other is the stacking process.

At present, the cell manufacturing process of power lithium batteries is mainly winding and laminated. The corresponding battery structure forms are mainly cylindrical, square and soft package. Cylindrical and square batteries are mainly produced by winding process, and soft package batteries are mainly produced by laminated process. The cylinder is mainly represented by 18650 and 26650 (Tesla has developed 21700 batteries separately). The difference between squares and soft packages is that the shell is made of hard aluminum shells and aluminum plastic film respectively. Among them, the soft package is mainly based on the lamination process, and the aluminum shell is mainly winding process.

After the completion of these two processes, the process links begin to converge. They need to be packaged, injected and other links. Let's talk about packaging first. The operation here is relatively simple. First, put the bare cells into the cell shell and weld the battery cover. After welding, dry the uninjected cells and prepare for liquid injection. When it comes to the injection process, it should be more rigorous. Before the electrolyte is injected into the cell, the amount of injection should be weighed to determine. After the injection, it is also necessary to carry out liquid opening welding, sealing, cell overall plastic sealing and other finishing work.

Back-stage process test process

As of the assembly process, the cell functional structure of the lithium battery has been formed. The significance of the test section process is to activate it. After testing, sorting and assembly, it forms a finished product of lithium batteries with safe use and stable performance. The process route is roughly divided into: chemical composition capacity system → laser cleaning → sealing nail welding → cleaning → size measurement, accounting for about 35% of the value of the production line.

As the most important link in the later process, the molded battery is activated and tested. Due to the long charging and discharge test cycle of the battery, the value of the equipment is the highest. The main function of the transformation process is to activate the charging of the injected and packaged cells, and the capacity separation process is to test and grade the battery capacity and other electrical performance parameters after the battery is activated. Separation and capacity separation are usually completed by automatic separation into systems.

After this is the assembly, that is, the PACK link and logistics automation link.

In recent years, the localization process of lithium battery equipment has accelerated, and the localization rate has steadily increased. In 2008, the localization rate (proportion of output value) of lithium battery equipment in China was only 20%, but by 2016 it had reached 80%. Lithium battery equipment is a model of high-end automation equipment localization in China. By 2019, the localization rate of lithium battery equipment in China will reach as high as 90%. At present, China's lithium battery equipment import substitution is nearing completion, and some products have even been exported overseas. The lithium battery equipment industry chain as a whole is already at a world-class level. It is believed that the future development of the lithium battery industry will not be without the continuous progress of lithium battery production technology.