Tesla of the United States and BYD of China are leading the global electric vehicle market. Tesla has gained overwhelming popularity in the European and North American markets, while BYD is at the forefront of the Chinese market. So, what differences do the batteries, which are the core of electric vehicles, have? Until now, both companies have not disclosed detailed information about their batteries, leaving their internal structures and performance characteristics shrouded in mystery.
German scientists dissected the batteries to resolve curiosity. Achim Kampker, head of the Electric Vehicle Components Production Engineering Research Institute at RWTH Aachen University, noted on the 7th, "As a result of directly dissecting and comparing the batteries of both companies, we confirmed that Tesla focuses on performance, while BYD emphasizes cost-effectiveness." The research results were published in the international journal 'Cell Reports Physical Science' on the same day.
Electric vehicles include lithium-ion batteries, which are secondary batteries capable of charging and discharging. A lithium-ion battery mainly consists of a positive electrode and a negative electrode, separated by a separator. Lithium ions from the negative electrode move to the positive electrode through a liquid electrolyte, causing electrons to move in the opposite direction, thereby generating electric current.
Generally, battery manufacturers disclose data sheets that include basic performance and specifications of the batteries. However, detailed mechanical structures or characteristics related to charging and discharging, as well as heat generation, are often not disclosed. The German research team dissected Tesla's 4680 battery and BYD's Blade battery to evaluate from mechanical design to size, composition of electrode materials, electric and thermal performance, and also analyzed the battery assembly process and raw materials expense.
Tesla's 4680 battery is a cylindrical battery with a diameter of 46 mm and a length of 80 mm, while BYD's Blade battery is in the shape of a long and thin blade. The analysis revealed that the design philosophy of both batteries is fundamentally different. While Tesla's battery prioritizes high energy density and performance, BYD's battery focuses on maximizing space utilization and reducing manufacturing expense.
BYD's Blade battery features a lithium iron phosphate (LFP) positive electrode, while Tesla's 4680 battery has a positive electrode based on lithium combined with nickel, manganese, and cobalt (NMC811). Although NMC811 offers higher energy density, LFP is more stable and has lower material prices.
The analysis showed that Tesla's 4680 battery has an energy density 1.5 times higher per weight compared to BYD's Blade battery, and an energy density 1.8 times higher per volume. On the other hand, Tesla's 4680 battery was found to generate twice as much heat as BYD's Blade battery under the same load. While Tesla's 4680 cell can store a lot of energy, which is advantageous for securing long driving ranges, it means that additional cooling systems are necessary. BYD's Blade battery generates relatively less heat and has high charging and discharging efficiency, demonstrating superior long-term stability.
Significant differences were also found in the assembly methods of the batteries. BYD's Blade battery uses a 'stacked electrode' method, where electrodes are layered. In this process, the edges of the separator are laminated to increase the battery's lifespan and enhance safety. In contrast, Tesla used a different new binder from those commonly used by existing battery manufacturers. The binder serves as an adhesive that holds the electrode materials together within the battery.
Additionally, Tesla's 4680 battery employs laser welding technology to connect the electrodes, while BYD's Blade battery combines both laser welding and ultrasonic welding to join the electrodes. Laser welding uses a high-temperature laser to quickly and precisely connect thin electrodes, whereas ultrasonic welding is a more affordable and stable method that uses ultrasonic vibrations to bond two metals.
There was also a common element between the two batteries. Silicon, known as a key material for enhancing battery performance, was not used in either battery. Typically, adding silicon to the negative electrode can increase the battery's energy density, but it can also lead to expansion issues that shorten lifespan.
In response, the research team explained that it was an "unexpected result" and noted, "It is likely a design considering battery lifespan and stability." Furthermore, while BYD's battery was significantly larger than Tesla's battery, the proportion of components responsible for current transmission was found to be similar.
Jonas Gorsch, a researcher who led this analysis, stated, "This study shows that the two innovative battery design approaches are fundamentally different," adding, "Future research needs to analyze how these mechanical design differences affect electrode performance and battery lifespan."
The two companies plan to enhance their competitiveness by adopting each other's strengths in the future. Tesla is focusing on diversifying the types of its 4680 batteries. At the same time, they plan to introduce a dry process that coats the electrodes with solid materials, reducing expenses by 30% and decreasing greenhouse gas emissions. BYD plans to unveil its second-generation Blade battery this year, which has increased energy density.
Currently, Tesla's 4680 battery is being mass-produced at its own factories as well as at Panasonic and LG Energy Solution, while BYD's Blade battery is entirely produced by BYD's subsidiary, Fin Dreams Battery.
References
Cell Reports Physical Science (2025), DOI: https://doi.org/10.1016/j.xcrp.2025.102453