Partly uncovered battery pack showing cylindrical cells.
Credit: Getty Images
A Tesla battery pack contains hundreds of cylindrical nickel-manganese-cobalt cells
Today’s electric vehicles (EVs) mainly use batteries with cathodes made of lithium nickel manganese cobalt oxide (NMC) or lithium iron phosphate (LFP). Tesla and BYD, the world’s largest EV companies, have each adopted one of these chemistries. Chinese carmaker BYD uses LFP batteries, and Tesla chose NMC.
To determine how the two rivals’ batteries stack up against each other, a team of engineers and materials scientists in Germany took apart one cell from each company’s battery pack, which contain dozens of cells (Cell Rep. Phys. Sci. 2025, DOI: 10.1016/j.xcrp.2025.102453). The cells’ materials and designs held some surprises.
EV makers guard battery technology tightly. But engineering firms regularly disassemble batteries to peek at their innards. Battery engineers Jonas Gorsch and Moritz Frieges of RWTH Aachen University and their colleagues took a scientific sledgehammer to Tesla and BYD battery cells and did a detailed side-by-side analysis of materials composition, thermal and electrical performance, and mechanical design. “Most teardowns focus on some specific aspect,” Gorsch says. “We wanted a holistic comparison.”
This is the type of research that “helps researchers keep abreast of what’s happening commercially so they can target their early-stage R&D decisions appropriately,” says Micah S. Ziegler, who studies energy technology innovation at the Georgia Institute of Technology and was not involved in the work.
Gorsch, Frieges, and colleagues disassembled a 2022 Tesla 4680 cell and a 2023 BYD blade cell. Both cell designs entered the market in 2020. Tesla’s is a 46 mm wide, 80 mm long cylindrical cell that looks like a bulked-up AA battery. BYD’s cell, in contrast, looks like a roughly 1 m long flat blade. BYD claims that the space-efficient design boosts safety—the flat design dissipates heat better—and energy density.
The researchers found that anodes in both batteries were based on graphite. Neither used silicon. There is speculation that Tesla and other top-tier EV makers will add silicon to anodes to increase energy density, but that’s not the case for these relatively new cells, Gorsch says. Tesla has replaced the typical polyvinylidene fluoride binder that glues the graphite to a conductive copper foil with polyacrylic acid and polyethylene oxide.
Blade-shaped battery cells are arranged in a pack.
Credit: BYD Europe
Chinese electric vehicle company BYD packs a few dozen blade-shaped lithium iron phosphate cells into its battery.
At both electrodes, particles in the BYD cell were smaller than those in Tesla’s. "Smaller particles are not ideal for energy density, as they can decrease packing density,” he says. That aligns with BYD batteries’ lower energy density of 160 W·h /kg compared with Tesla’s 241 W·h /kg.
But there’s an upside to the smaller particles. Their higher surface-to-volume ratio means lithium ions flow through them easily, leading to better charging capabilities and lower resistance. Indeed, when the researchers charged the cells at various charging rates, the Tesla NMC cell got significantly hotter than BYD’s LFP cell. Gorsch says that the LFP cell’s improved electrical performance could pave the way for faster charging, and in addition to lower cost could be why carmakers are turning to LFP chemistry after chasing NMC for years.
Another surprise was that both companies used lasers to weld the coated copper foils to their cell’s external contact. State-of-the-art large batteries typically use ultrasonic welding, which uses heat produced by high-frequency sound waves to melt and fuse metals, he says. Copper’s high light reflectivity makes it difficult to laser-weld. It requires special high-power green or blue lasers operated very precisely, he says. “For large-volume production, those small differences can make huge impacts on production costs.”
Materials scientist Guihua Yu at the University of Texas at Austin says although the analysis is limited to only two types of cells from two manufacturers, it provides a deep understanding and quantitative insights into design trade-offs to balance performance, safety, and cost. “Researchers can leverage these insights to guide the design of future lithium-ion batteries. The detailed comparisons could help optimize heat management systems, refine electrode architectures, and improve material choices.”
Chemical & Engineering News
ISSN 0009-2347
Copyright © 2025 American Chemical Society
You might also like...