A team from the “Production Engineering of E-Mobility Components” (PEM) chair at RWTH Aachen University disassembled current drive batteries from Tesla and China’s leading electric vehicle manufacturer, BYD, and compared the two batteries. The results, published on March 6 in the journal “Cell Reports Physical Science,” show, among other things, that Tesla’s 4680 cells prioritize high energy density, while BYD’s Blade cell emphasizes volume efficiency and more cost-effective materials. According to the study, BYD’s battery is more efficient because it allows for easier thermal management.
“Both players have always disclosed very little data on their batteries, so the mechanical structure and most of the cell properties have remained hidden until now,” says PEM Director Professor Achim Kampker. In general, there is little detailed data and analysis on modern electric vehicle batteries. The RWTH researchers therefore investigated the mechanical construction, dimensions, and electrical and thermal properties of the cells, as well as the precise material composition of the electrodes. They also determined the costs of the cell materials and the processes used for assembly. “We were surprised that the anodes of both batteries do not contain silicon – especially in Tesla’s cell, since silicon is widely considered a key material for increasing energy density in research,” says PEM board member Professor Heiner Heimes.
The researchers also discovered that the two “highly innovative” and “fundamentally differently designed” battery types exhibit significant differences in the speed at which they can be charged or discharged relative to their maximum capacity. According to the study, BYD’s Blade cell is based on a special method in which the anodes and cathodes in the electrode stack are ideally positioned relative to one another by lamination of the separator edges. The Tesla battery, meanwhile, uses a novel binder that holds the active materials in the electrodes together. However, the batteries also exhibited unexpected similarities: For example, their thin electrode foils were joined together using the still-unusual laser welding process instead of the standard ultrasonic welding process. And: “Although BYD’s cell is much larger than Tesla’s, the proportion of passive cell components such as current collectors, housings, and busbars is similar,” says Kampker. “The results already provide the industry with a benchmark for large-scale cell designs and serve as a robust basis for further optimization.” According to PEM expert and lead author Jonas Gorsch, further studies for other parameters are needed, “but the current results already provide both research and industry with a benchmark for large-scale cell designs and serve as a robust basis for further analysis and optimization.” The study was conducted with the support of Münster Electrochemical Energy Technology (MEET) and the Fraunhofer Institute for Ceramic Technologies and Systems (IKTS) as part of the FoFeBat2 research project and is available as a free download.
This article appeared in the June issue of eMove360° Magazine. Download the free PDF or order the print version from sabine.metzger@emove360.com.
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