Copyright: © PEM RWTH Aachen

Motivation and procedure

The electrolyte liquid and the separator are among the core elements of a LIB cell and have a significant influence on cell production, cell performance and cell safety. For example, the separator must electrically separate the anode and cathode and thus prevent direct electron exchange between the electrodes, but at the same time the separator and the electrolyte must have a high ionic conductivity for lithium ions. Filling a lithium-ion battery (LIB) with electrolyte fluid and subsequent wetting represent the interface between cell assembly and formation. Despite the high potential for throughput increase, cost reduction and the unclear influence on quality characteristics of the LIB, the investigation of separators and electrolyte filling has so far received little scientific attention. The wettability as a material property has been investigated in various publications, but without drawing any conclusions about the production process. Although various separator investigations and best-practice solutions for filling and wetting exist, which processes are decisive in the LIB and how they can be accelerated are still largely unknown. With regard to national cell production, this methodically prepared process knowledge is the prerequisite for cost reduction and more stable processes.

Research objectives

The aim of the project is to gain in-depth knowledge of the processability of the separator and the electrolyte, their influence on the process, the cell properties and the life cycle costs. On the one hand, the focus is on shortening filling and wetting times, setting stable product quality and selecting separators that are suitable for the application. This requires an extended and methodically described understanding of the process. Partial goals are therefore the development and validation of models, the simulations of the wetting processes in LIB and the investigation of different separators in the production process. In addition, a decision tool for the application-specific selection of separators is generated and guidelines for the cell design suitable for filling are derived. The combined consideration of separators and electrolytes offers great potential both to reduce costs (minimise service life, minimise use of electrolyte additives, minimise purchase price) and to increase quality (service life, safety, performance) and thus makes a significant contribution to economic battery production.

Research and project partners

• Technical University Braunschweig – Institute for Machine Tools and Production Engineering (IWF)
• Technical University Munich – Institute for Machine Tools and Industrial Management (IWB)
• Westfälische Wilhelms-Universität Münster – Institute of Physical Chemistry / MEET Battery Research Centre (MEET)