How to choose the right dry room dehumidification solution for lithium-ion battery production

Sponsored by Munters

In the past year, electric mobility and the demand for lithium-ion batteries has surged beyond expectations and this trend is set to continue. This is leading to a boom in lithium-ion cell production facilities all over the world.

As countries look to reduce or ban vehicle-related emissions, some as early as 2030, battery manufacturers need to increase capacity and capability when it comes to producing lithium-ion batteries for electric vehicles.

Why you need a dry room

Lithium and other materials are highly reactive to moisture, so when using them as the basis for battery production, it is essential to operate in specially designed humidity controlled dry rooms.  This will ensure the highest possible quality and production yield and provide a safe working space for employees.  Issues with moisture can reduce production uptime leading to lost product, significant costs and negative impacts on the environment and brand reputation.  

As these rooms are so essential to the process, and so influential on the quality of the end product, manufacturers need to know what to look for in a dry room, and how to ensure they have the best humidity control solution to fit requirements. 

More important than anything else, a dry room’s integrated dehumidification system must be able to meet the right dew point—the temperature at which water vapour in ambient air starts to condense. The lower the dew point, the lower the water vapour content in the air.  Even small amounts of moisture in the air can compromise the quality of the finished battery. 

The generally accepted dew point for lithium battery production is -40°C (< 1% relative humidity), although this may drop further due to new battery chemistries which may be more moisture sensitive. Glove boxes can be used for small R&D labs but for high-volume production, the only alternative is to use efficient dehumidification technology designed to create this environment for the dry room. 

How it works

A typical specification for a dry room may call for the room dew point to be at -40°C. This equates to about 0.08 g/kg (grams of moisture per kilogram of dry air), 0.55 gr/lb (grains per pound air) or 79 PPMw. 

The internal moisture load comes mainly from people working in the dry room and infiltration from air lock openings.  Extremely dry supply air is provided into the dry room while room air is exhausted back to the dehumidifier as return air.  By supplying air at a lower dew point than the room/return air, we create a differential that is equal to the moisture load in the room.  

When outside air is used to make up for battery tool exhaust, mechanical cooling should be used to pre-cool the mixed air and condense out excess moisture before the dehumidifier. This improves conditions for creating the -40°C dew points required for the dry room.   

The optimal way to achieve the best dry room is through desiccant rotor dehumidification.  Desiccant rotors use heated reactivation air to continuously regenerate the rotor after moisture is adsorbed from the process air. A typical dehumidifier uses about three-quarters of the rotor for the process air and one-quarter of the rotor for the regeneration step.  Once regenerated, the desiccant wheel rotates back to the process area for further moisture adsorption.  

But, to achieve low dew points, the system should add a purge section to capture any residual moisture in the wheel and to recover heat to improve the systems’ energy efficiency. 

Munters’ patented Green PowerPurge technology reduces the required reactivation energy by up to 45%.  With Green PowerPurge, a slip stream of air is recirculated with a small fan to cool and heat the rotor media, improving reactivation efficiency.  The purge air reduces energy needs and improves desiccant performance.  

Figure 1: Munters Green PowerPurge Solution

Green PowerPurge technology:

Process air (return air from dry room plus fresh outside air) passes through the drying wheel and leaves as low dew point supply airHeated reactivation air collects the moisture from the drying wheel and is exhausted as “wet” airGreen PowerPurge loop provides additional energy recovery by recovering the heat left over in the wheel after reactivation, which is then used to preheat the wheel media before reactivation

The Industry standard energy purge incorporates some energy recovery but it is not as effective as Green PowerPurge.  Here we have 3 zones for process, regeneration and purge.  A slip stream of air is stolen from the process air and is sent through the purge section to recover heat from the wheel.  The purge air is then heated and used as reactivation air.  

Figure 2: Industry standard energy purge

 Industry standard energy purge:

Process air (return air from dry room plus fresh outside air) passes through the drying wheel and leaves as low dew point supply airHeated reactivation air collects the moisture from the drying wheel and is exhausted as “wet” airPurge air provides nominal energy recovery by recovering heat from the wheel as it exits the reactivation section and supplements reactivation air

Reduce energy consumption 

The case below compares energy usage for dehumidification systems using the Munters Green PowerPurge and Industry standard energy purge technologies. Reactivation gas consumption and cooling energy consumption is shown for an example dry room requiring 16,320 m3/h (9,600 cfm) of supply air.  As you can see, reactivation energy is reduced considerably and total energy consumption is reduced by more than 30% with Munters Green PowerPurge system.

Figure 3: Energy comparison of Munters Green PowerPurgeTM and Industry standard energy purge

Note: Reactivation energy is based on natural gas. However, electricity and steam are also available as reactivation options.

Optimizing dry room designs for the future

If you are designing a dry room, it is important to consider that over the life of the dry room, the operation expenditure (OPEX) is likely to be many times that of the original capital expenditure (CAPEX). 

Total annual energy savings of 30% can make a real difference to your bottom line, offering a quick return on investment alongside a lower total cost of ownership (TCO).

With proper service, your equipment will receive the maintenance needed to reach its maximum life expectancy. The expertise of Munters global service network will ensure optimal operation, minimum energy consumption, and extension of the life of your investment. This means you can focus on providing the best and most efficient power of the future.

Finding the right solution requires the right expert partner with the best technology. Munters can offer the most advanced, efficient dry room dehumidification solutions. We know that the design process and partnership is important, and we are there to offer advice and answers at every step of the way.

High-volume battery manufacturing is now coming on-line with factory energy costs significantly impacting the ultimate battery cost and thus the electric vehicle cost to the consumer. 

Choosing the most energy-efficient dry room solution incorporating Munters Green PowerPurge dehumidification technology will reduce factory OPEX, allowing more competitive battery prices that fuel market growth. We invite you to the advent of a more sustainable energy future.

Sponsored by Munters