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Dry rooms for humidity control in Lithium-Ion Battery processing areas

Category: Blog
Date: May 23, 2021

With the massive rise of hybrid and electric vehicles, the demand for new and better power sources is also increasing. Lithium-Ion Batteries (LIB) are currently the most efficient and powerful solution for this. The production of lithium-ion batteries takes place in ultra-low humidity dry rooms and requires a great deal of technical knowledge and skills.

Lithium-ion battery dry rooms for optimal product quality

In order to maximise product quality, critical production points are provided with microclimates where the room humidity must be as close to 0 as possible. If slight deviations in the humidity levels occur during the production process, this not only negatively affects the life cycle of the lithium cells, but also their maximum storage capacity over time. In order to be able to produce optimally, cleanliness classifications ISO7/ISO6 in accordance with ISO14644 must be achieved. The area of LIB rooms can range from small R&D lab environments to large scale mass production facilities. As already mentioned, lithium-ion batteries are very sensitive to humidity (Li + H2O > LiOH + H2). When lithium gets in contact with water, lithium hydroxide is formed, which is a highly flammable hydrogen.

The most important aspect of a dry room is the dew point, which is currently allowed to range from -40°C to -65°C. At 20°C dry bulb temperature, a dew point of -60°C corresponds to a relative humidity of 0.05%. By combining these low humidity levels with high cleanliness ratings, we can define an area as a dry cleanroom.

In practice, the conditions and requirements for a dry cleanroom for applications such as lithium-ion battery production are following:

  • Room temperature: 25°C (+/- 2°C)
  • Absolute moisture content: 0,1 gr/kg (0,5% RH or dew point minus 40°C)
  • Cleanliness classification: ISO6 in operation
  • Air change rate: >55

Humidity loads

In order to ensure zero leakages of moisture through the envelope, a vapor tight construction is a necessary condition for this type of cleanroom. A certain amount of outside air is needed to create overpressure within the dry room and to supply the people with fresh air. It goes without saying that a thorough and correct calculation of the amount of fresh air will benefit the life cycle cost of the entire installation. Additionally, the number of people present in the cleanroom are a burden due to respiratory moisture content. Therefore, when installing the airlock for persons, attention must be paid to the airtightness of these doors.

In order to save energy, it is important that as little moisture migration as possible can occur from external factors. In the figure on the right, we can see the factors which have the highest impact on this.

Active desiccant dehumidification

Given the low dew points, there is only one appropriate technology to recover moisture from the air: active desiccant dehumidification. By using materials that dry naturally, such as silica gel or lithium chloride, an area of low vapour pressure is created on the surface of the drying agent. The desiccant wheel rotates slowly between the process and reactivation of the airstreams. To limit the energy consumption, ABN Cleanroom Technology proposes integrative solutions such as heat recovery systems that are capable of recovering up to 65% of the heat generated by the machine to re-enter the cycle of operation, generating considerable savings.

Points of attention to set up a dry cleanroom

  • High airtight level for walls and ceiling construction to prevent any moisture entering the cleanroom. Make sure there is no moisture infiltration after it comes off the desiccant wheel.
  • Anti-static design for walls, floors and materials (ESD).
  • Use of materials that do not hold moisture.
  • Sealed panel junctions to insure zero vapor transmission with zero crack.
  • FM approved modular wall systems to achieve the highest fire safety classification.
  • Solid redundant design in combination with a design for maintainability is essential for a high uptime of the dry cleanroom.
  • Recovery requirements are necessary after an event.
  • Modular design for changed specifications (design for upgradability).
  • People load and shift timing is important.
  • Maintenance must be achieved without compromising the envelope seal.
  • Separate the drying function from the cleanroom function to increase reliability.
  • Maximise energy efficiency by using heat recovery systems.

It is clear that a lot of knowledge and expertise is required not only during the design and construction phase, but throughout the entire life cycle of a dry cleanroom. Our cleanroom engineers can provide you not only with theoretical calculations, but also with thorough project management that pays attention to every detail during the construction of the cleanroom. We believe that maintainability always starts with a design for maintainability. It is clear that life cycle engineering in combination with modularity is a sine qua non in the field of dry cleanrooms.

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