Image: A cylindrical 18650 lithium-ion cell without the casing on, showing the "jelly roll" inside.

Cylindrical lithium-ion cell

A cylindrical lithium-ion cell is a cylindrical cell made from a single long "sandwich" of the positive electrode, separator, negative electrode, and insulating sheet which is then rolled and inserted into a hollow cylinder casing. This cell design is often called a "jelly roll" or "swiss roll" because the cross section looks like a swiss roll.