Engineers Took Apart Tesla and BYD Batteries – The Results Are Surprising

A recent study analyzed the internal structures of Tesla’s 4680 battery and BYD’s Blade battery to compare their engineering and performance.

Two major manufacturers dominate the electric vehicle (EV) market: Tesla, which leads in Europe and North America, and BYD, the top EV producer in China. Despite their prominence, both companies have disclosed limited information about the internal design and properties of their battery cells, leaving many technical details unknown.

To gain insight into how these batteries work and to compare the technologies used by each manufacturer, a team of researchers disassembled battery packs from both Tesla and BYD.

The findings, published on March 6 in Cell Reports Physical Science, reveal key differences in design priorities. Tesla’s batteries are engineered for high energy density and performance, while BYD’s focus on space efficiency and the use of more cost-effective materials. Notably, the study found that BYD’s battery design offers greater overall efficiency due to improved thermal management.

“There is very limited in-depth data and analysis available on state-of-the-art batteries for automotive applications,” said Jonas Gorsch, a researcher at Production Engineering of E-Mobility Components at RWTH Aachen University in Germany and lead author of the study.

A Closer Look at the 4680 and Blade Cells

To address this, the researchers looked under the hood of Tesla’s battery—the Tesla 4680 cell—and BYD’s battery—the BYD Blade cell—and focused on the specific design and performance features of each. They assessed the mechanical designs and dimensions of the cells, the exact material compositions of their electrodes, and the cells’ electrical and thermal performances. They also deduced the processes used to assemble the cells and the costs of the materials used to make them.

“We were surprised to find no silicon content in the anodes of either cell, especially in Tesla’s cell, as silicon is widely regarded in research as a key material for increasing energy density,” said Gorsch.

The team found that the two types of batteries had significant differences in the speed at which a battery charges (or discharges) relative to its maximum capacity. The researchers also discovered that the BYD Blade employs a different method of keeping the electrode sheets in place—by using an electrode stack featuring a novel processing step to laminate the edges of the separator that sits between the anode and the cathode. The Tesla battery also uses a novel binder—a substance that holds together the active materials in the electrodes—in comparison to those used by most manufacturers in the industry.

Two Innovative but Divergent Approaches

The batteries also showed unexpected similarities: both use an unusual way of connecting their thin electrode foils: with laser welding instead of ultrasonic welding, used by many others in the industry. Also, although the BYD cell is much larger than the Tesla cell, the fraction of passive cell components—such as current collectors, housing, and busbars—is similar.

The results of this study illuminate how Tesla’s battery—the Tesla 4680 cell—and BYD’s battery—the BYD Blade cell—achieve two “highly innovative” but “fundamentally different” design approaches, says Gorsch. Further studies are needed to determine the impact of mechanical cell-design choices on electrode performances in EV batteries, as well as the lifespans of the Tesla and BYD cells, he added.

“The findings provide both research and industry with a benchmark for large-format cell designs, serving as a baseline for further cell analysis and optimization,” said Gorsch, adding that the data can help battery-cell developers make informed choices when deciding on format, size, and active materials.

Reference: “Contrasting a BYD Blade prismatic cell and Tesla 4680 cylindrical cell with a teardown analysis of design and performance” by Jonas Gorsch, Julius Schneiders, Moritz Frieges, Niklas Kisseler, Domenic Klohs, Heiner Heimes, Achim Kampker, Marina Muñoz Castro and Eleonore Siebecke, 6 March 2025, Cell Reports Physical Science.
DOI: 10.1016/j.xcrp.2025.102453

This work was supported by financial support from the German Federal Ministry of Education and Research.

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