Lithium battery cells and cylinders

Cylindrical lithium battery cells are generally used in power batteries, such as the typical 21700 battery cells carried in the Tesla Model 3, which once made 21700 popular in the battery cell market. However, cylindrical cells are not the only advantages; their shortcomings are also obvious.

This paper investigates 19 Li-ion cylindrical battery cells from four cell manufacturers in four formats (18650, 20700, 21700, and 4680). We aim to systematically capture the design features, such as tab design and quality parameters, such as manufacturing tolerances and generically describe cylindrical cells.

In the last 3 years, cylindrical cells have gained strong relevance and popularity among automotive manufacturers, mainly driven by innovative cell designs, such as the Tesla tabless design. This paper investigates 19 Li-ion cylindrical battery cells from four cell manufacturers in four formats (18650, 20700, 21700, and 4680).

For instance, “65” represents a height of 65mm. Fifth Digit: The fifth digit indicates the cylindrical shape of the cell. Typically, it's “0” for cylindrical cells. By following this naming convention, we can easily identify the size and shape of cylindrical lithium-ion battery cells.

A generic overview of designing cylindrical Li-ion battery cells. Function 1: Two types of jelly roll designs can be distinguished: With tabs and tabless. Jelly rolls with tabs can be realized with a single tab (Design A) or several tabs in a multi-tab design (Design B).

Cylindrical Li-ion battery cells consist of (i) a jelly roll, a wound composite consisting of a cathode, an anode, and two separators, and (ii) a cell housing consisting of a can and a cap . Current and heat transport between the jelly roll and the cell housing is traditionally conducted by contacting elements called tabs .