Manufacturing modern battery cells places stringent demands on the environment in which they are produced. Controlling moisture, particulate matter, and potential emissions is especially critical. While dry rooms have long been established in conventional lithium-ion production, new battery types and specialized applications are introducing additional challenges. We spoke with Bahattin Celik, dry room expert at Weiss Technik, about how dry room requirements are currently evolving — and why these specialized production environments are becoming a priority once again.
Dry rooms have been a central component of battery cell production for years. What role do they play today in practice — and why is moisture control so critical for many battery types?
Dry rooms are no longer a ‘nice to have’ — they are an absolute prerequisite for many battery manufacturing processes. Depending on the cell chemistry, moisture directly interferes with the electrochemical properties and can significantly impact both performance and lifetime. Particularly in early process steps, such as electrode manufacturing or cell assembly, even trace amounts of water are enough to cause problems that only manifest weeks or months later in the field. That is why maintaining a stable, reproducible dry room atmosphere is critical.
Does this apply equally to all battery types — or do requirements differ significantly depending on the application?
The differences can be substantial. Conventional NMC or LFP battery cells — for example, those used in automotive applications — are already sensitive to moisture, but many specialty batteries are considerably more critical. For certain types, even minimal deviations from the target dew point can irreversibly damage materials. Add to this the fact that in specialty applications we frequently work not with high production volumes, but with very precisely defined processes. There is little margin for error, and the requirements for stability and process control are correspondingly higher.
Where do you see the most significant differences between dry rooms for conventional automotive cells and those for specialty batteries — for example, in defense or aerospace applications?
Automotive battery dry rooms are strongly oriented toward throughput and standardization — which makes perfect sense. Specialty batteries are exactly the opposite: smaller material quantities, unique cell chemistries, and often elevated safety requirements. Production processes must be more flexible, since reconfigurations inside the dry room are more frequent, and there are often additional requirements stemming from explosion protection or hazardous materials regulations. All of this has a major influence on dry room design — from airflow management to sensor systems, filtration, and controls.
You also work with battery types such as thermal batteries and thionyl chloride cells. What makes these applications particularly demanding from a dry room engineering perspective?
Thermal batteries involve highly reactive, extremely moisture-sensitive materials — sometimes in powder or pellet form. Other systems use aggressive or unstable media that must also be handled safely. From a dry room perspective, this means very stable dew points, controlled particulate levels, and at the same time a high degree of process safety. The fact that only very small quantities of materials are processed makes control and monitoring even more challenging.
Why do conventional gas detection systems and sensors struggle with very small quantities of substances?
Many gas detection systems and sensors are designed for standard industrial applications. In extremely dry air and with very low emission levels, these systems quickly reach their physical detection limits. Measurement signals become unstable or fall near the detection threshold. In an emergency, this can be problematic, because trends or gradual changes are recognized too late — posing a risk to both personnel and product. In the specialty battery environment, simply monitoring threshold values is usually not sufficient.
What solutions are available? Do sensor systems and safety concepts need to be specifically adapted for such environments?
Absolutely. In these applications, sensor systems, gas detection concepts, and filtration must be developed in an integrated system. This can mean incorporating additional filtration stages or repositioning measurement points — for example, closer to the hazard source, or through the use of redundant sensors. The suitability of sensors for extremely dry ambient conditions must also be factored into the technical selection process. The control strategy plays a central role as well: it is not simply a matter of ‘alarm yes or no,’ but rather how the overall system responds to even the smallest deviations.
For instance, when detecting hazardous substances, a pre-alarm level can be used to initiate technical countermeasures in the system at an early stage, preventing harm to personnel or product. In most cases, this is not purely a hardware issue, but rather a combination of well-thought-out design, intelligent programming, and the experience required for accurate hazard assessment.
You mention specialized adaptations in sensor systems and filters. Another concept that plays a role here is that of mini environments. What is behind this term?
Mini environments are essentially locally enclosed battery production units within a dry room that provide even stricter or more specialized conditions. Rather than bringing the entire dry room to an extremely low dew point, the focus is placed selectively on the truly critical process steps and production equipment along the battery manufacturing line. This increases process reliability while also being economically sensible — particularly for smaller production runs or changing production layouts.
Comparing these concepts — the conventional dry room, the mini environment, and taking it one step further: micro environments, i.e., the complete encapsulation of the process itself — what are the respective strengths of each, and which approach is right for which use case?
The conventional dry room is robust and easily accessible — ideal for many standard processes. Mini environments offer an excellent balance of control, flexibility, and cost. Micro environments — fully enclosed sections within the production equipment — enable maximum control, but also come with significant demands in terms of maintenance, service, and emergency procedures. The right solution depends heavily on the process, the cell chemistry, and the operational requirements. There is no blanket ‘better or worse’ answer.
Micro environments sound attractive at first — less space, more control. At the same time, maintenance and incident response become more complex. How do you evaluate this in practice?
That is exactly the point. In theory, micro environments are highly efficient; in practice, however, you have to consider the entire lifecycle. Maintenance, servicing, and troubleshooting of the more complex machinery become considerably more demanding — and this is reflected not only in capital expenditure, but also in ongoing operating costs. We therefore recommend these concepts only where the process benefits genuinely justify the additional effort.
Weiss Technik operates its own demo dry room for battery applications. How do you use this infrastructure in concrete terms?
The demo dry room is extremely important to us — first and foremost as a development and validation tool. We use it to test new sensor systems, filters, and control concepts under realistic conditions. Especially for specialty cell chemistries or safety-critical applications, many questions cannot be resolved at a desk — they can only be answered in actual operation.
Another key focus for us is clearly energy efficiency. Providing extremely dry environments is energy-intensive, and this is precisely where we see significant optimization potential. In the demo dry room, we investigate, for example, how adsorption-based dehumidification processes can be made more efficient, or how heat pumps can be effectively integrated into the overall system. In parallel, we work with a digital twin of the facility to simulate different operating strategies without having to intervene directly in the real process.
The goal is to operate dry rooms not only safely and reliably, but also significantly more energy-efficiently. This has a noticeable impact on operating costs — particularly for facilities that run around the clock. The insights gained from these trials feed directly into customer projects.
Can you give a concrete example — perhaps from thermal battery or igniter battery production — where such preliminary tests proved decisive?
Without going into specifics: in projects involving highly sensitive materials, we tested in advance how different airflow configurations or filtration stages affect measurement behavior and process stability. The interaction between gas detection technology and controls was also part of the investigation. These tests helped to optimize what had originally been planned as conventional facility layouts — allowing us to avoid later modifications during ongoing operations. For customers, this was a clear advantage.
To close: you are talking about thermal batteries, thionyl chloride cells, high-performance applications in defense and aerospace. These topics are being discussed with renewed intensity across Europe. What has changed that makes these specialized production environments a priority again?
The geopolitical situation plays a major role here. Critical production in areas such as energy, defense, and infrastructure should not be entirely dependent on global supply chains. At the same time, there is a growing recognition that it is not just about unit costs, but about availability, security, and technological sovereignty. Europe needs appropriate production capacities and the corresponding manufacturing environments for this — starting with the dry room.
