Leybold cooperates with manufacturers to develop battery technologies

Strategic role of vacuum technology in the development of electromobility.

In the production of lithium-ion batteries, vacuum technology is relevant to quality and safety for various process sections. The vacuum specialist Leybold has therefore been supporting manufacturers of lithium-ion batteries in their process technology challenges for many years and is therefore significantly involved in the development of electromobility.

Help shape developments
Electromobility is currently a hot topic in a very dynamic market environment. “We have been closely involved in this area from the perspective of vacuum technology for many years,” says Dr. Sina Forster, Business Development Manager at Leybold GmbH. “Being able to help shape current developments and research is therefore incredibly exciting,” adds Dr. Ranger.

According to her, one of the core tasks is to derive potential vacuum applications and markets from new technologies and developments as early as possible. The strategic role of vacuum technology is therefore to enable and promote certain developments. For example, the design of the vacuum environment is a factor that can positively influence the processes. For example, a vacuum is usually essential when filling the electrolyte, in order to ensure that the cell is evenly wetted with the electrolyte, but also to ensure a clean filling atmosphere.

Lithium-ion batteries as a vacuum application
Leybold focused on developments in this area in good time and identified the manufacturing process of lithium-ion batteries as a vacuum application. Because there was initially little information on the manufacturing process of the lithium-ion components, the company and the Verband Deutscher Maschinen- und Anlagenbau e. V. (VDMA) and the Chair for Production Engineering of E-Mobility Components PEM at the RWTH Aachen University in establishing an ideal-typical manufacturing process. In addition to lithium-ion batteries, Leybold is also focusing on fuel cell developments in this context. Relevant vacuum processes are already emerging here, for example in the coating of the bipolar plates under vacuum. Here it applies to accompany about cooperations.

Vacuum technology is used in various process steps in the manufacture of electrodes, but also in research and development. To this end, Leybold works closely with machine and system manufacturers who supply battery manufacturers with production systems. In addition, Leybold cooperates with battery manufacturers and institutions that research the further development of battery technologies.

Development increasingly in Europe
The majority of series production is currently still taking place in Asia. However, many
efforts in research and development are shifting to Europe, which means that the EU and Germany in particular are becoming increasingly important as a research and production location.

Vacuum technology is used in battery cell production but also in processes such as the application of active materials to the electrodes. “In general, the air is a disruptive factor in many production environments, because the millions of particles and gas molecules have a negative effect on this production step or even make it impossible. Particles and air bubbles should be avoided when mixing the slurry in order to achieve a high-quality slurry. “Most mixers therefore work under vacuum,” explains Dr. Sina Forster.

Vacuum secures processes
Vacuum is also essential during drying in order to remove even the smallest residues
remove solvents and moisture. Without a vacuum, the drying process would have to be carried out at significantly higher temperatures and would take much longer, which would have a negative impact on the electrode quality. As soon as electrolyte is used in the further process steps, the vacuum takes on a safety aspect, because many of the electrolytes used are very reactive and flammable. A good vacuum is essential here: On the one hand, for the cleanliness of the process, so that no particles or moisture enter the cell during electrolyte filling and any degassing. On the other hand, to provide a low-reaction environment without, for example, oxygen or moisture with which the electrolyte could react.

“The biggest challenge is always the gas mixture to be pumped – because in principle everything that is pumped and processed in the process is also transported by the vacuum pump. In cell production, this affects the solvents and the electrolytes, which tend to be toxic and can attack the pumps and the pump oil,” says Dr. Sina Forster out. “But also very warm ambient conditions or high humidity are generally circumstances that pose challenges for us,” she adds. This is where the battery manufacturers come into play, by ensuring the correct cooling of the pump or by using capacitors.

Good drying result under vacuum
Optimization possibilities exist in many areas because there are not yet any established processes that are proven to be efficient. For example, vacuum drying is a customer-specific sequence of pressure, temperature and process gas such as nitrogen. In order to achieve a good drying result with the help of vacuum drying, industry-related research projects are already underway under the leadership of the VDMA.

Leak detection also plays a central role in production from a safety perspective. For a long battery life, the cell must be absolutely leak-proof. A valid leak test can only be carried out using a vacuum leak detection. The smallest leaks can be detected with the help of a helium leak detector or mass spectrometer. On the other hand, undetected leaks would greatly reduce the life of the battery or result in the highly reactive electrolyte escaping. Some lithium-ion battery components that are handled in a vacuum are toxic. In order to protect the environment and the vacuum technology from pollutants, the vacuum pump must be able to withstand these gases. On the other hand, the toxic media should be kept in the process and safely discharged accordingly.

Dry pumps save money and time 
Dry-running vacuum pumps are used for these toxic gases. Oil-sealed vacuum pumps are rather unsuitable for these applications, as the pump oil could be attacked or contaminated by the gases. By using dry-compression pumps, battery manufacturers save time and money, since they would otherwise have to change the pump oil frequently. “Especially in the process step of electrolyte filling and degassing, oil-sealed vacuum pumps have been increasingly used, which we are now replacing with dry-running vacuum pumps at numerous customers,” summarizes Dr. Sina Forster.

In order to ensure sufficient process reliability when handling toxic gases, hermetically sealed pumps are used, from which not even the smallest amounts of the gas can escape. This is a decisive factor, especially with toxic electrolytes, because occupational safety is also a priority there.

Faster and more reliable with vacuum technology Vacuum technology 
plays an important role in drying, electrolyte filling and degassing. “A vacuum is essential in all three process steps,” emphasizes Dr. Sina Forster. However, upstream process steps such as mixing in vacuum mixers, stacking with vacuum grippers or downstream packaging are also processed faster and more reliably with vacuum technology.

In the future, the influence of a pure vacuum environment and the specification can be determined even better. With the development of individually labeled electrode sheets, which can be tracked through the entire production process using lasered QR codes, the influence of individual process parameters on battery quality can be traced back precisely.

Vacuum ensures handling of toxic electrolytes 
Vacuum technology also plays an important role in terms of safety during cell production and use. In the future, safe handling of toxic electrolytes will only be possible under vacuum conditions. During use in an e-car, we rely on the tightness of the battery, which can best be tested and guaranteed under a vacuum.

However, it must be said that processes under vacuum always require more energy than under atmospheric pressure. In recent years, however, enormous progress has been made towards energy-efficient pumps, so that today we use very economical vacuum pumps in battery production. “So today we can devote ourselves to the core questions: How can we achieve more throughput, safety and quality in cell production through the efficient design of the vacuum systems? And here, too, we will make a lot of important progress in the field of vacuum technology in the next few years,” says Dr. Sina Forster a positive balance.