Developing battery cells with higher energy density while maintaining the same weight enables more energy to be stored in the same space. This offers advantages for stationary battery storage systems, which were the focus of three research projects funded by the German Federal Government at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg. The physical insights gained can also be applied to traction batteries for electric vehicles, where higher energy density could extend vehicle range.
In the projects at Fraunhofer ISE, the institute collaborated with various partners to develop a new architecture for battery cells that achieves higher energy density. The researchers focused on the electrodes, increasing their coating thickness by more than threefold: instead of the previously typical 100 to 200 micrometres, they applied coatings of up to 800 micrometres.
Battery cells with 10 to 15 per cent higher energy density
According to the research institution, this has increased the energy density of the cells by 10 to 15 percent, depending on the battery type and design. The reasoning is that, in a battery cell, electrode coatings and current collectors alternate in many thin layers. The coating contains the active material that stores energy, while the current collectors conduct the electrical current. By making the electrodes thicker, fewer of these layers – and thus fewer current collectors – are needed. This leaves more space for active material at the same cell weight.
