The moisture content in lithium battery materials is one of the main sources of moisture in the battery cells, and the higher the environmental humidity, the easier it is for the battery materials to absorb moisture from the air. On the contrary, the better the humidity control of the environment, the more limited the ability of battery materials to absorb moisture from the air. At present, there is a recommended humidity control ladder for lithium battery production workshops (for reference only, humidity control is operated according to the actual situation of each battery enterprise):

　　 Workshop with relative humidity ≤ 30% (such as mixing, coating machine head, tail, etc.)

Workshop with relative humidity ≤ 20% (such as rolling, slicing, baking, etc.)

Workshop with relative humidity ≤ 10% (such as lamination, winding, assembly, etc.)

Dew point temperature ≤ -45 ℃ Workshop (such as cell baking, liquid injection, sealing, etc.)

Even if controlled according to the above humidity gradient, it is necessary to control the residence time of the process.

The lithium battery drying room is designed to control the humidity in the environment of the lithium battery production line.

Dehumidification process and working principle of drying room
1、 Dehumidification methods and classification

2、 Advantages of rotary dehumidifier;

1. Large dehumidification capacity and high efficiency. The rotary dehumidifier can easily achieve a low-temperature dew point of -10~-60 º C in the treated air,

For the production workshop of lithium batteries, the temperature requirements for the positive and negative electrode coating workshop, batching, film making, laser welding room, assembly room, etc. are 25 ℃± 2, and the relative humidity RH is ≤ 10% -30%; Lithium battery baking, negative electrode coating workshop, etc. require a temperature of 23 ± 2 and a relative humidity of ≤ 1% or 2%. The injection workshop (or glove box) has very high requirements for the manufacturing environment and requires a low humidity environment. The dew point Td is usually required to be ≤ -40 ℃ (25 ℃, relative humidity RH ≤ 0.6%). The rotary dehumidifier has excellent performance and can achieve a dew point of -65 ℃ at the outlet, fully meeting the dew point requirements of lithium battery production workshops. Moreover, due to the quadruple safety protection measures of the imported rotary wheels by Jierui, users can avoid the risk of sudden power outages in the factory.

3、 Working principle of drying wheel;

The main structure is a continuously rotating honeycomb shaped drying wheel, composed of a corrugated medium made of special composite heat-resistant materials, which contains a moisture absorbing agent.

2. Moisture absorbing agents include lithium chloride, high-efficiency silica gel, and molecular sieve, which are made by adding hydrophilic polymer additives with high adsorption cross-linking network structure in the modification and synthesis process of lithium chloride. They solve the problem of performance degradation of moisture absorbing media after long-term operation. The maximum dehumidification capacity during conventional dehumidification can reach 8g/kg, and deep dehumidification can handle ultra-low temperature dew points up to -70 º C. The absolute humidity is below 0.01g/Kg, and the relative humidity is below 2%.

On both sides of the dehumidification wheel, partitions made of materials with high sealing performance are divided into two fan-shaped areas, one is the 270 º fan-shaped area for processing humid air, and the other is the 90 º fan-shaped area for regenerating air. The regeneration air is automatically controlled between 110 º C and 130 º C, as shown in the following figure:

rotating wheel

4Lithium battery drying room, new energy drying roomWorking principle of drying room;

The drying room consists of three parts: insulation, anti-static room, IDS (Integrated Dehumidification System), and condenser. The room and IDS are placed on the second floor, and the condenser is placed on the rooftop, achieving linkage automatic control. As shown in the figure; The condenser consists of a 1 # 30 horsepower and a 2 # 10 horsepower refrigeration compressor, which sends liquid R22 to the evaporator of IDS for evaporation and refrigeration, and then returns to the compressor in a loop.

IDS uses a Make up air evaporator to cool 2100CFM of fresh air to 45 º F, condensing most of the water. It then mixes with 900CFM of return air and enters the Return air evaporator, where it is cooled to 55 º F before entering the drying wheel. 1000CFM of air is heated by a heater to 110-130 º C and then carried away by a 90 º fan-shaped living area to be discharged outdoors,

The working principle of lithium battery dehumidification process and drying room: In addition, 2000CFM of air is dehumidified in the 270 º dehumidification zone, and then cooled by the Supply air evaporator to control the temperature at 15-21 º C before being sent into the drying room. After a certain period of continuous cooling, drying, and dehumidification, the humidity in the drying room can be reduced to below 2%.

The entire system is affected by the following factors:;

1. The influence of external environmental temperature and humidity. In summer, the external fresh air is high temperature and high humidity air, requiring the Make up air evaporator to provide a large cooling capacity. The 1 # compressor will operate at full load, and the high temperature of the external environment also affects the air-cooled refrigeration machine to quickly cool the high temperature and high pressure gaseous fluorine into liquid state, which can easily cause the system's high pressure protection to trip. Daytime and nighttime, rainy and sunny days, and seasonal changes all have a significant impact.

2. Balance of air in the drying room

3. Control of personnel in the drying room and control of heating equipment
4. Temperature control of regenerated air
The use of chemicals in the drying room may affect the efficiency of the drying wheel.

5、 The test data is shown in the figure;

6、 Improve operational plan

The current operation control of the drying room is:;

Full load operation during production, shutdown during holidays. The purpose of shutdown is to save energy. According to the test results, the relative humidity of the drying room will exceed 2% within ten minutes after shutdown, which cannot guarantee the requirements of the process. Moreover, the drying time of the material is much longer than the moisture absorption time. After the holiday, the material cannot be completely dried in a short time by re drying at high temperature or vacuum drying, resulting in quality problems with the products every Monday.

The improved operational plan is:;

During holidays, the drying room does not shut down. The air inlet and exhaust fan are turned off, and 70% of the energy consumed by the drying room is used to process the moisture brought by the fresh air. By changing the control method, 1 # 30 horsepower compressors can be turned off. If the temperature of the drying room can be controlled at around 45 degrees during holidays, 2 # 10 horsepower compressors can be turned off, leaving only the fan, drying wheel, and regeneration heater to work, reducing the return air volume. This not only reduces energy consumption, but also ensures sustainable dehumidification and relative humidity in the drying room.

Clean drying room project: This part includes the panel room part, air duct part, steel frame ceiling part, ground treatment part, lighting part, and power cable laying part (supplied by cable A) in the factory area.

The panel room includes: color steel plate ceiling or optional handmade rock wool glass magnesium board (Class A fireproof, load-bearing); Color steel plate vertical wall or optional mechanism rock wool board (Class A fireproof), the door adopts a steel integrated door (with observation window), and the window adopts double-layer insulated glass.

Ground section: Stainless steel floor/PVC floor/epoxy self leveling floor.

Lighting section: The humidity control area is designed with an illuminance of 400LX and uses LED purification lighting; Circular ceiling mining lights are used in areas without suspended ceilings;

Steel frame ceiling section: In this steel structure factory building, steel frames are designed as load-bearing structures for ceiling panels, air ducts, process pipelines, cables, etc; Made of H-shaped steel and square steel.

The drying room can accommodate 2-3 people working simultaneously and provide 2100CFM of fresh air. Currently, there are usually only 1 or 2 people, which can reduce the amount of fresh air and extraction to save energy while ensuring the necessary amount of fresh air.