Battery research at IEK-3 focuses on future high-energy lithium-ion batteries and the components contained within them, as well as on characterizing and testing cells and integrating batteries to hybridize fuel cell systems.
In order to understand the degradation mechanisms of materials for high-voltage cathodes, basic electrochemical investigations are performed in combination with physical characterizations as a function of several parameters on materials such as Li Ni0.5 Mn1.5 O4. In parallel, new methods are being developed to characterize commercially available cells. Measuring the surrounding magnetic field by means of magnetic imaging makes it possible to infer the state of charge of cells from mechanical defects and the qualitative flow density distribution.
Hybridization with a suitable battery allows fuel cell systems to start spontaneously, peak loads to be covered, and detrimental operating situations and high load fluctuations to be avoided. Direct methanol fuel cells (DMFCs) can be used to replace supply batteries in applications in the light traction sector in the range of 0.5–5 kWel. To date, only lithium-ion batteries have been recommended for hybridization in small vehicles powered by DMFCs because of their good stability during charging and discharging processes and their capacity behavior, which is stable in the long term. However, current challenges include improving the safety engineering of the battery, developing new concepts and control strategies for heat management, and creating a new compact module design.
Auxiliary power units in vehicles powered by diesel or kerosene are based on high-temperature polymer electrolyte fuel cells (HT-PEFCs), which are supplied with fuel gas by a reformer. Hybridization of the system with a battery prevents critical operating situations. An optimized system architecture can only be ensured if the various conversion and storage processes (fuel processing, fuel cells, and battery) are matched to the system requirements and mode of operation.