clean room in laboratory

clean room in laboratory

Moisture clean room in laboratory has a significant impact on battery performance and must be strictly controlled during the manufacturing process. Moisture in the battery can cause the electrolyte to deteriorate or react with the electrolyte to produce harmful gases, leading to an increase in internal pressure and deformation of the battery. Excessive moisture in batteries can also cause high internal resistance, high self discharge, low capacity, poor cycling, and even leakage, greatly deteriorating battery performance. Therefore, the drying process is essential in the production of lithium batteries.
01 Introduction to Drying
clean room in laboratory Drying is a chemical unit operation that obtains dry materials by providing energy to wet materials, causing the moisture contained in them to vaporize and escape, and taking away the moisture. At present, there are a large number of drying equipment in the industry, and there are also different classification methods, as shown in Figure 1. According to the operation mode, it can be classified into continuous drying equipment and intermittent (batch) drying equipment; According to the operating pressure, it can be divided into atmospheric pressure drying equipment and vacuum drying equipment; According to the heat conduction mode, it can be divided into types such as conduction drying equipment, convection drying equipment, radiation drying equipment, and dielectric drying equipment.
The moisture in batteries mainly comes from the moisture in the raw materials of the battery (including positive and negative electrode plates, separators, electrolytes, and other metal components) as well as the moisture in the factory environment. For moisture in the environment, a drying workshop can be established to generate dry air using a dryer, which is continuously fed into the drying workshop to replace the humid air inside and eliminate environmental moisture. For the moisture inside the battery, due to the very high drying standard, the moisture content is usually required to be between (100~300) × 10-6. Therefore, vacuum drying equipment is generally needed to remove the water. After drying, test whether the battery is baked properly. In the production and manufacturing process of batteries, multiple processes require vacuum drying, such as battery positive and negative electrode powder, battery positive and negative electrode rolls, and battery cells before injection. Therefore, vacuum drying equipment is crucial for battery production and manufacturing.
At atmospheric pressure, the boiling point of water is 100 ℃, but as the pressure decreases, the boiling point of water also decreases continuously. Under a vacuum environment of around 100Pa, the boiling point of water has decreased to around -20 ℃. This is the basic principle that a vacuum environment can promote the drying process.
Therefore, vacuum drying is the process of removing moisture from materials under environmental conditions below one standard atmospheric pressure. The basic dynamic principle of vacuum drying is the theory of heat and mass transfer. During the process of vacuum drying, the vacuum system continuously heats the dried material while vacuuming, causing the internal moisture of the material to diffuse to the surface through pressure or concentration differences. Water molecules gain sufficient kinetic energy on the surface of the material, overcome intermolecular attraction, fly into the low-pressure space of the vacuum chamber, and are then pumped away by the vacuum pump.
The rate of water loss during vacuum drying and the mass of water evaporated and discharged from the dried material per unit drying area per unit time are referred to as the drying rate clean room in laboratory

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