Experimental Investigation of the Lithium Calendering Process for Direct Contact Prelithiation of Lithium‐Ion Batteries

Lithium‐ion batteries suffer from high initial capacity losses during formation. One possible approach to compensate for these initial capacity losses is prelithiation, which is the addition of lithium into the battery cell before formation. A promising method is direct contact prelithiation using lithium foil, which requires lithium foil thicknesses below 10 μm to ensure the safe and accurate performance of the prelithiation process. However, free‐standing lithium foils are only commercially available down to a thickness of 20 μm; hence, in this present work, the calendering process of lithium is investigated in detail. An already developed process model will be adapted to provide detailed information on the deformation properties and thickness reduction of different lithium foil thicknesses. A design of experiments is used to investigate the influences of lithium foil geometry, line load, web speed, and roller temperature on the deformation behavior of lithium during calendering. Lithium foil is applied onto anodes by calendering, which are electrochemically investigated using pouch cells. The cells prelithiated by calendering show improved electrochemical performance compared to the manually prelithiated cells, increasing cycle life by 19%.