Fraunhofer ISE increases energy density of battery cells

Fraunhofer ISE has developed a new architecture for battery cells that aims to achieve 10 to 15 percent higher energy density while maintaining the same weight. This approach relies on significantly thicker electrodes, allowing for fewer current conductors. This could potentially be useful for electric vehicles in the future as well.

Semi-automatic production of battery cells at Fraunhofer ISE

Image: Fraunhofer ISE

If it is possible to develop battery cells with a higher energy density while maintaining the same weight, more energy can be stored in the same space. This could be advantageous for stationary battery storage systems, which were central to three research projects funded by the federal government at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg. However, the physical insights gained from this can also be applied to traction batteries in electric vehicles. There, a higher energy density could also lead to greater driving ranges for these vehicles.

But as for the projects of Franhofer ISE: It has worked with various partners to develop a new architecture for battery cells that enables higher energy density. The scientists focused on the electrodes of the battery cells and increased their coating thickness by more than three times—replacing the usual 100 to 200 micrometers with coatings up to 800 micrometers thick.

Battery cells with 10 to 15 percent higher energy density

According to the research institution, the energy density of the cells has increased by 10 to 15 percent depending on the battery type and design. The idea behind this is that in a battery cell, electrode coatings and conductors alternate in many thin layers. The coating contains the active material that stores energy, while the conductors carry electrical current. If the electrodes are thicker, fewer of these layers—and thus fewer conductors—are needed. This allows more space for active material at the same cell weight.

"Normally, the anode and cathode—the two electrodes of a battery cell—are made up of many thin layers alternating between electrode coatings and current conductors," explains Dr. Oliver Fitz, team leader for battery cell technology at Fraunhofer ISE. "We have managed to increase the thickness of the electrode coatings from the usual 100 to 200 micrometers to up to 800 micrometers, thereby significantly reducing the number of current conductors needed. As a result, we have much more space for active material, which increases the energy density by 10 to 15 percent depending on the battery type and design."

Focus on applications in battery storage systems

The concept is not yet ready for mass production. According to Fraunhofer ISE, the project results represent rather a “promising approach for the future industrialization of this novel electrode and cell architecture.” These new battery cells are interesting for use in battery storage systems (BESS) as well as in electric vehicles.

The research team developed this new electrode or cell structure as part of the projects “VORAN– Innovative Sodium-Ion Battery Storage for Stationary and Mobile Applications” (running until June 2027), “INFAB– Zinc-Ion Batteries for Stationary Energy Storage – Manufacturing and Assembly” (completed), and “WinZIB2– An Innovative Zinc-Ion Battery System Suitable for Global Use,” all of which were funded by the federal government.