Batteries are the pulse generators of electromobility

The battery is the key component in the manufacture of an electric car. It serves as the energy provider and is the part that determines both the range and the costs of an electric vehicle. Current electric cars are based on lithium-ion technology – according to experts, it is also not replaceable in the foreseeable future. 60 to 80 percent of the value creation in the battery system is determined by the battery cells. The lifespan, safety, costs, and performance of lithium-ion batteries are therefore the focus of research around electromobility.

The TU Berlin is a partner of the nationwide competence network for lithium-ion batteries (KLIB, http://www.klib-org.de/home/), and several departments are intensively engaged with various aspects of batteries. For example, the Handling and Assembly Technology department is part of the large competence cluster for battery cell production funded by the BMBF, called "ProZell" (https://www.prozell-cluster.de/). The opening event of the second funding phase of this research consortium was held at TU Berlin on November 13/14, 2019. The cluster involves 26 research institutions and universities across Germany at 14 locations. Over 100 scientists are researching battery cell manufacturing in twelve funded projects. The goal of the cluster, within the framework of the BMBF umbrella concept "Research Factory Battery," is to improve the process steps of battery cell production regarding cell performance, costs, environmental impact, as well as digitalization and recycling to enable intelligent closing of value and material cycles.

Faster Production Processes

"In the TU Berlin project 'HoLiB – High-Throughput Processes in Lithium-Ion Battery Manufacturing,' we are developing a novel high-speed process. It investigates a multitude of coupled influences to understand cause-and-effect relationships and optimize process limits," explains the department head Prof. Dr. Franz Dietrich and emphasizes the potential of faster and more cost-effective production processes for the economic and societal penetration of high-performance batteries in the global market.

Battery Lifespan Testing

Prof. Dr. Julia Kowal is engaged in the electrical, thermal, and lifespan modeling of batteries as well as their characterization regarding performance, thermal behavior, and aging. "In the future, lighter and smaller batteries will be needed, which have higher capacity, longer lifespan, and lower cost. Characterizing a battery cell, regarding its voltage, current, and temperature limits, as well as system design, model development, simulation, cell diagnostics, and cell monitoring, are crucial to increasing the range and lifespan of electric vehicles," says Julia Kowal, head of the Electrical Energy Storage Technology department at TU Berlin. In the collaborative project SiCWell with Daimler AG, Solfas GmbH, and two other TU Berlin departments, the scientist is investigating, for example, the influence of high-frequency switching operations, such as those generated by converters, on battery lifespan. "Converters are circuits made up of semiconductor switches that are operated at high frequencies. With the switch to silicon carbide (SiC) semiconductors, these circuits become more compact and efficient, but at a higher switching frequency. The impact on battery lifespan is still unclear, and that is exactly what we are investigating in this project."

Detecting Defects in Electrodes

The Ceramic Materials department, led by Prof. Dr. Aleksander Gurlo, deals with techniques and processes for synthesizing electrodes. Special methods such as tape casting and freeze casting are used. The department's specific expertise lies in preparing and drying battery materials as well as vacuum drying electrode materials. "In a current research project, we are developing a special analysis method to characterize defects in lithium-ion battery electrodes," explains Aleksander Gurlo. His team is also researching entirely new electrode materials. "For example, nanostructured tungsten disulfide is considered a promising electrode material for the post-lithium-ion era. Compared to other conventional materials, it shows high electrochemical stability," says the materials scientist.

Platform Provides Overview of Raw Materials

Prof. Dr. Vera Rotter, Professor of Circular Economy and Recycling Technology at TU Berlin, approaches the topic of electromobility from a different angle: As part of the Horizon 2020 project ProSUM, the Urban Mine platform was created: "This interactive, publicly accessible online platform inventories all major raw materials used within Europe, for example, in car batteries, mobile phones, or other products. It accounts for approximately 450 million tons of material overall. This overview enables manufacturers, recycling companies, associations, or policymakers to recognize which raw materials are currently or will be in demand within Europe. This allows recycling companies to better plan for future waste streams, and entrepreneurs to know where within Europe certain recycled raw materials can be sourced to avoid environmentally damaging primary production," explains the professor.

Further information gladly provided by:

Prof. Dr.-Ing. Franz Dietrich
TU Berlin
Handling and Assembly Technology Department
Phone: 030/314-22014
Email: f.dietrich@tu-berlin.de

Prof. Dr.-Ing. Julia Kowal
TU Berlin
Electrical Energy Storage Technology Department
Phone: 030/314-25394
Email: julia.kowal@tu-berlin.de

Prof. Dr. Aleksander Gurlo
TU Berlin
Ceramic Materials Department
Phone: 030/314-23425
Email: gurlo@ceramics.tu-berlin.de

Prof. Dr.-Ing Vera Rotter
TU Berlin
Circular Economy and Recycling Technology Department
Phone: 030/314-28512
Email: vera.rotter@tu-berlin.de