Between Thermal Limits and Battery Degradation—Cell-Specific Optimization of Fast Charging Strategies

The latest study of the EVBox Mobility Monitor shows once again fast charging is one of the key features of an electric car that needs to be improved for more customer acceptance [1]. Over the last couple of years battery cells reached higher and higher energy densities. This leads to higher driving ranges. But there is a natural conflict between optimizing for energy or power density. High power charging capability suffers significantly when high-energy cells are used. This means longer charging times or battery systems that suffer extremely during fast charging and age prematurely.

APL sheds light on the bottlenecks during fast charging. Charging infrastructure, cables and plugs, and the battery itself all play a role. In the battery, the cell is the limiting factor. Temperature, kinetics and prevention of aging must be taken care of. With new analysis methods, optimized fast charging profiles are determined at cell level, tailored to the individual cell chemistry. For this purpose, APL builds special laboratory cells under an argon atmosphere and records anode potential-controlled charging curves. This prevents lithium-plating and takes the issue of aging into account. Another issue is the dissipation of the released thermal energy. For this reason, the right cooling strategy is an essential building block for successfully combining fast charging with high-energy cells. Through APL’s use of new test and development methods, the subject of immersed battery cooling is gaining momentum.