What are the principles and advantages of spray drying technology in the preparation of lithium-ion battery materials?

　　The spray drying technology can prepare spherical powders with uniform quality and good repeatability, shorten the preparation process of powders, and is also conducive to automation and continuous production. It is an effective method for large-scale preparation of fine powders and has become a variety of products. One of the best methods for ultra-micronization and drying.

　　Spray drying is a process that has both granulation and drying processes at the same time. Through continuous operation, the characteristics of the powder can be controlled to remain stable. Spray drying technology has a history of more than 100 years, and its industrial application has a history of nearly a hundred years. It was initially limited to the production of a few products such as egg powder, milk powder, and detergent. With the continuous deepening of research, it has now been used in many industries. It is widely used in the production of ultrafine powder and nano powder. The spray drying technology can prepare spherical powders with uniform quality and good repeatability, shorten the preparation process of powders, and is also conducive to automation and continuous production. It is an effective method for large-scale preparation of fine powders and has become a variety of products. One of the best methods for ultra-micronization and drying.

　　1. Basic principles and characteristics of spray drying

　　There are 3 types of commonly used sprayers: pressure sprayers, airflow sprayers, and centrifugal sprayers. There are many applications of pressure sprayers, so this article will explain the pressure spray drying technology in detail. Spray drying technology is a better way to obtain ultra-fine dry powder from the material liquid. The form of the material liquid can be a liquid that can be transported by a pump such as a solution, a suspension, and an emulsion. The basic principle is to use an atomizer to spray a certain concentration of material liquid into mist-like droplets, which fall into a certain flow rate of hot air to quickly dry and obtain a powdery product. The basic principle diagram is shown in Figure 1.

　　The specific process of the spray drying method is (shown in Figure 2): the hot air (hot drying medium) generated by the heater enters the tower from the top of the drying tower through the hot air pipe. The chemical nozzle sprays into extremely fine spherical droplets, which fall in a certain flow rate of hot air for heat exchange. Because the droplets are fine and the specific surface area is large, the solvent evaporates quickly, and the drying and granulation process is completed in an instant. The dried finished material enters the cyclone separator from the cone discharge port under the tower body, and is separated from the drying medium and collected in the product receiver. The hot exhaust gas is discharged from the exhaust port through the induced draft fan.

　　General spray drying includes 4 stages: ①Atomization of the material liquid; ②Contact and mixing of the mist group with the thermal drying medium; ③Evaporation and drying of the droplets; ④The separation of the dried product and the drying medium. The dried product can be in powder, granular or granular agglomerates.

　　Compared with other powder preparation methods, the spray drying method has the following advantages:

　　(1) Spray drying can complete granulation and drying in one step, simple production process, convenient operation and control, suitable for continuous industrial production, and easy to realize automation.

　　(2) The drying rate is high, the time is short, and it has little effect on heat-sensitive components, so it is especially suitable for drying heat-sensitive materials.

　　(3) During spray drying, the material liquid is sprayed into an atomized dispersion under constant stirring, and the drying is completed instantly, so the uniformity is better.

　　(4) In spray drying, because the solvent vaporizes rapidly, the finished product is loose and fine particles. When in contact with the solvent, the solvent easily enters the inside of the particles, and good dispersion and solubility can be obtained without further processing.

　　(5) Because spray drying is a continuous closed production, the product purity is high, which eliminates the chance of exposure and contact with operators in the production environment, and reduces environmental pollution.