In past years, electric vehicle (EV) batteries have undergone a revolution. We’re at a stage where electric cars have autonomy comparable to petrol cars or are even better. But, as the industry moves forward, several competing visions for the future of batteries have emerged. Tesla and BYD are currently the two leading companies when it comes to electric vehicles and they have different approaches.

Tesla champions high-energy, cylindrical cells like its 4680 battery, designed for maximum power and range. Meanwhile, BYD takes a different path with its Blade battery, a prismatic lithium iron phosphate (LFP) cell that prioritizes safety, longevity, and affordability. Both represent cutting-edge innovation — but how do they differ, exactly?

To get to the bottom of things, a team of researchers tore them apart and analyzed their components.

The “Coca Cola” formula

Unsurprisingly, producers aren’t keen to share details about their batteries. After all, this is a very competitive area. Every bit of information and research can make a difference. So, the researchers had to tear down the batteries to properly analyze them.

“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.  

Gorsch and colleagues tested the two batteries, analyzing their mechanical structure, materials, and electrical performance. They tested energy density, thermal efficiency, internal resistance, and manufacturing processes, using tools like scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and direct current resistance measurements.

The Tesla 4680 cell follows a cylindrical format, is 46 mm in diameter and 80 mm long. BYD’s Blade battery, on the other hand, is a long and thin prismatic cell. It measures 90 mm in height, 965 mm in length, and just 14 mm in thickness. This geometry already shows the different angles the two companies take.

When it comes to raw energy storage, Tesla’s 4680 cell has a clear advantage in both gravimetric and volumetric energy density. The Tesla cell achieves 241 Wh/kg and 643 Wh/l, significantly outperforming the BYD Blade at 160 Wh/kg and 355 Wh/l. This means Tesla’s battery packs can be lighter and more compact for the same energy output.

However, high energy density comes with a cost — literally. The nickel-rich cathode material in the Tesla 4680 cell is more expensive than the LFP cathode in BYD’s Blade. Moreover, LFP cells like the Blade have superior thermal stability, making them less prone to overheating or thermal runaway. This is one reason why LFP batteries are becoming increasingly popular for budget-friendly and mass-market EVs.

Expectations and surprises

The geometric differences of the two batteries are more than just aesthetic. The Tesla 4680 cell adopts a “jelly roll” configuration, where electrode layers are wound tightly inside the can. Meanwhile, the BYD Blade uses what is called a Z-folded electrode stack, which contributes to its superior mechanical stability.

These design differences also influence how the batteries are manufactured. Tesla employs a streamlined process that eliminates traditional tabs, using laser welding to connect electrode sheets directly. BYD, on the other hand, relies on a combination of ultrasonic and laser welding, ensuring strong electrode connections while maintaining an efficient manufacturing flow.

There were also some surprises.

“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.

Two different visions

Cost remains a major factor in the widespread adoption of EVs. The study calculates that the Tesla 4680 cell, with its high-nickel cathode, has a cost disadvantage of about $10/kWh compared to BYD’s Blade. The reason is that nickel and cobalt prices have remained high, while LFP materials — mainly iron and phosphate — are more abundant and stable in cost.

Futhermore, the two batteries have different thermal efficiencies. The teardown analysis shows that the Tesla 4680 cell’s higher internal resistance leads to greater heat buildup, particularly at high charge levels. This could pose challenges for fast-charging and long-term durability.

BYD’s Blade, on the other hand, benefits from its LFP chemistry, which naturally generates less heat and is more resistant to thermal runaway. Additionally, its prismatic format allows for more straightforward thermal management strategies, a key reason why BYD batteries have been praised for safety.

Ultimately, the Tesla battery seems better suited for high-performance and luxury vehicles. Meanwhile, mass-market and commercial vehicles that value durability and reliability could make better use of the BYD’s approach

The question isn’t which battery is better, but which is better suited for a particular vehicle. Luxury EVs and high-performance models may favor Tesla’s energy-dense 4680, while mass-market and commercial vehicles could thrive on the stability of BYD’s Blade.

Ultimately, this battle may decide how the future of electric cars looks.

The study was published in Cell Reports Physical Science.