YouTuber Aries RC posted a video recently in which he dissects what he claims to be a Tesla 2170 lithium ion battery cell — the cell that goes into the battery pack of the Model 3. He says the cell came from the Tesla Gigafactory. Check out the comments to the video and you will discover some skepticism about whether this is in fact a Model 3 cell made by Panasonic or one used in Tesla’s energy storage products made by Samsung. But let’s put such quibbles aside and focus on what the video shows instead.
First, Aries RC places the 2170 cell alongside an 18650 cell used in the Model S/Model X cars. Keep in mind that the volume of a cylinder increases geometrically with diameter. Even though the new cell is only a little bit larger, it is capable of storing about 30% more power than its smaller sibling.
After discharging the cell, Aries RC carefully removes the top to reveal a blue plastic insulator that keeps the internal components of the cell — popularly known as the “jelly roll” — from contacting the top and shorting out. A similar insulator is used at the bottom of the cell. After carefully removing the jelly roll, Aries RC sliced the exterior aluminum open to reveal a thin layer of plastic on the inside that acts as an insulator to help control internal temperatures. The top of the cell also has three tiny vent holes to allow gases to escape if the cell overheats.
The jelly roll itself is a tightly rolled piece of copper nearly 32″ long. In between the layers of coiled copper is the lithium nickel cobalt aluminum oxide mixture that actually stores the electrical charge. Aries RC notes that the ground wire connected to the copper coil is tap welded. He says this is significant because tap welding is extremely difficult to do on metal as thin as the copper used inside the 2170 cell.
Put thousands of these cells together into modules and then completed battery packs, figure out how to keep everything cool during driving and charging, and you have the makings of an electric car. In Tesla’s case, make that a groundbreaking, class-leading, industry-disrupting electric car.