As a result of the increasing demand for lithium-ion batteries (LIB), production capaci-ties in Germany and around the world will be greatly expanded over the next few years. In order to reduce the CO2 emissions of a lithium-ion battery over its entire life cycle, the current high energy requirements of battery cell production must be re-duced.

For this reason, there is an approach to use mini-environments in the future, which will enable the systems to be encapsulated close to the process, meaning that a small-er volume of treated air is required. This approach should help to reduce CO2 emis-sions over the entire life cycle of a lithium-ion-battery. In order to validate this ap-proach, a prototype concept was designed and evaluated. This consists of an inter-linked system in which the processes of cell housing welding and electrolyte filling are conducted.

Due to the new development of a prototype concept concerning the background of the critical and complex process conditions, a process failure mode and effect analysis (FMEA) was performed, in order to detect potential faults at the development stage. This allows optimization to be taken at an early stage, which should lead to lower development costs and a more stable process ramp-up.

By applying this methodology, many faults could be identified, analysed and rectified.
The faults also differ in terms of their probability of occurrence or how easy they are to rectify.

For example, if a cell tolerance that is too high is not detected, the cell can be pro-cessed incorrectly and damaged by the resulting welding process. As the probability of occurrence was estimated to be high here, quality control is now to be implemented immediately prior to the assembly of the product carrier with the aid of a precisely fitting setting box, which is easy to implement.

An example of a fault with a higher priority in the cell housing welding process step is that the cell is incorrectly positioned by the tensioning process. Due to deviations or excessive tolerances, the tensioning process, which should fix the cell in the correct position, could lead to incorrect positioning. The resulting incorrect welding process leads to a breach of safety requirements due to damage to the system. As a solution to this, vertical clamping plates are inserted to enable the cell to be fixed in place. The plates also serve to prevent plastic deformation of the cell in the event of thermal energy input or pressurization. This minimizes the complexity of the product carrier, as no moving parts or actuators need to be integrated.

A highly critical fault for the electrolyte filling, is a short circuit caused by open electri-cal components in conjunction with outgassing electrolyte. This fault can be prevented by using components that are designed for use in areas with flammable vapors in combination with corresponding sensors for vapor detection. Furthermore, the elec-trolyte vapors in the vicinity of the cell should be continuously extracted so that no flammable atmosphere is created in the Environment in the first place. The probability of occurrence can therefore be rated as low. However, the probability of detection is very low, as it is very difficult to recognize the exact cause of the fault. Due to the complex system structure, gradual wear of an electrical component in conjunction with outgassing electrolyte may be very difficult to detect.

In conclusion, it can be said that by carrying out the FMEA, significant failures were already discovered during the conceptualization phase. These could be optimized or at least considered at an early stage. For a few faults, it was not yet possible to take precise measures to avoid or detect them. However, these failures are taken into ac-count in the preliminary tests of the work sequences and solution concepts are de-fined in the further course. The FMEA enabled many technically necessary adjustments to be identified and implemented at an early stage, which ensured that the project could continue to run efficiently. With the successful validation of this system, the concept of Mini Environments can be extended to other processes in battery cell pro-duction in the future, which is why the successful implementation can be seen as a significant step towards saving energy and costs in LIB production.