Dissecting Tesla Model 3’s 2170 lithium ion battery cell, what’s inside?

A teardown video featuring Tesla Model 3’s 2170 lithium-ion battery cell was recently uploaded on YouTube, showing the components of the cylindrical cell and how it stacks up against the Model S and Model X’s 18650 battery cell.

Aries RC, a channel dedicated to battery improvements in the remote control aircraft market, indicated that they acquired a 2170 lithium-ion cell from Tesla’s Gigafactory in Nevada.  The host noted that the first thing he did was to connect the battery to a resistor, in order to completely drain the cell. Next, he made a cut at the positive terminal of the battery unit to expose a plastic dielectric barrier on the cell. This barrier is utilized by Tesla as a means to prevent the jelly roll inside from physically touching the top of the battery, which would cause a short circuit. As noted by the YouTube channel’s host, the negative terminal of the 2170 lithium-ion cell also features a similar dielectric barrier.

The Model 3’s 2170 cell features a thin layer of insulation on its interior, which, according to the RC enthusiast, is an outer layer of material that protects the cell wall’s integrity during a thermal runaway. In instances when the lithium-ion cell does heat up, however, Tesla has implemented a safety system in the form of three small cooling holes at the top of the battery. These small holes are about 0.5 mm wide, and are designed to vent out gases when the cell reaches high temperatures.

The jelly roll of the 2170 battery is wrapped in a copper sheet, which acts as a ground for the battery. A grounding strip is also attached to the copper strip using tap welding, which, according to the YouTube channel’s host, is particularly impressive, since tap welding is notoriously difficult to accomplish on thin pieces of metal.

The jelly roll of the Model 3’s battery cell features a lithium-nickel-cobalt-aluminum oxide that’s responsible for storing energy in the battery. Fully unrolled, the strip fitted with the compound measured roughly 32 inches long, roughly a third longer than the strip in Tesla’s 18650 battery, which is roughly 24 inches long.

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As could be seen in a side-by-side comparison of the jelly rolls of the 2170 and 18650 cells, Tesla’s newest form factor 2170 cell features a roll that is significantly longer and thicker than the latter. Overall, the YouTube host suggested that Tesla seems to be accurate in its estimates that the 2170 cell carries roughly 30 percent more charge than the 18650 lithium-ion cell in the Model S and X.

Tesla uses thousands of 2170 cells to enable its mass market Long Range Model 3 to travel up to 310 miles on a single charge. Produced in partnership with Panasonic at the Nevada Gigafactory, Tesla’s 2170 lithium-ion battery modules proved to be one of the sources of the Model 3’s production bottlenecks last year. As revealed by recent building permits, however, Tesla is currently conducting large-scale improvements to the Gigafactory, aimed at automating its battery module production line.

Apart from the Model 3, Tesla also uses its 2170 lithium-ion cell for its Powerpack and Powerwall battery solutions. As confirmed by Tesla CEO Elon Musk through Twitter, however, the 2170 cells will not be making their way to the Model S and X, at least as of writing. 

Dissecting Tesla Model 3’s 2170 lithium ion battery cell, what’s inside?
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