Engineers disassemble the battery from Tesla and China’s leading electric car manufacturer to see what’s inside

Two major manufacturers dominate the electric vehicle (EV) market: Tesla, Tesla’s most popular in Europe and North America, and Byd, which leads the Chinese electric vehicle market. However, both manufacturers have released limited data on batteries, so the mechanical structure and characteristics of these batteries remain mysterious. To compare the batteries used by each manufacturer and to better understand the overall functionality of electric vehicle batteries, a team of researchers separated each battery.

The results reported a physical science report on March 6 at the Cell Press Journal Cell and show that Tesla’s batteries prioritize high energy density and performance, while Byd’s batteries prioritize quantity efficiency and low-cost materials. Overall, the study shows that BYD’s battery is more effective because it allows for easier thermal management.

“The in-depth data and analysis of state-of-the-art batteries for automotive applications is very limited,” said Jonas Gorsch, a production engineering researcher at RWTH AACHEN University in Germany.

To solve this problem, the researchers looked under the hood of the Tesla battery (Tesla 4680 cell) and Byd’s battery (Byd Blade Cell) and focused on the specific design and performance characteristics of each battery. They evaluated the mechanical design and size of the cells, the exact material composition of the electrodes, and the electrical and thermal properties of the cells. They also derived the process used to assemble cells and the cost of the materials used to make them.

“We were surprised to find that there is no silicon content in the anode of any cell, especially in Tesla cells, as it is widely considered a key material for increasing energy density in the study,” Gorsch said.

The team found that the two types of batteries differ significantly in the speed at which the battery charge (or discharge) relative to its maximum capacity. The researchers also found that Byd Blade adopted a method of keeping the electrode paper at the appropriate level, which uses an electrode stack with novel processing steps to superimpose the edges of the separator located between the anode and the cathode. Tesla batteries also use a novel adhesive, a substance used by most manufacturers in the industry, to fuse the active material in the electrodes.

The battery also shows unexpected similarities: both use an unusual way to connect their thin electrode foils: laser welding instead of ultrasonic welding, which is used by many others in the industry. Similarly, although BYD cells are much larger than Tesla cells, the proportion of passive cell components (such as current collectors, housing and busbars) is similar.

The results of this study shed light on how Tesla’s batteries (Tesla 4,680 batteries) and Byd’s (Byd Blade Cell) achieve two “highly innovative” but “substantially different” design approaches, Gorchi said. He added that further studies are needed to determine the effect of mechanical cell design choice on electrode performance in electric battery cells and the lifetime of Tesla and bit cells.

“These findings provide a benchmark for research and industry for large-scale cell designs and are benchmarks for further cell analysis and optimization,” Gorsch said. The data can help battery cell developers make informed choices when determining formats, sizes and active materials, Gorsch added.