Cell manufacturing/Formation

{{Semantic Element
|label=Cell manufacturing/Formation
|description===Production process==

*The formation describes the first charging and discharging processes of the battery cell.
*For formation, the cells are put in special good carriers in formation racks and contacted by spring-loaded contact pins.
*The cells are then charged or discharged according to precisely defined current and voltage curves.
*During formation, lithium ions are embedded in the crystal  structure of the graphite on the anode side. Here the Solid Electrolyte Interface (SEI) is formed, which creates a interface layer between the electrolyte and the electrode.
*The parameters during formation vary depending on the cell manufacturer and have a high impact on cell performance. They depend on the cell concept and chemistry and represent the core knowledge of a cell manufacturer.
*In some cases, pouch cells in particular are pressurised during formation by special good carriers.

==Process parameters & requirements==

*First charge: approx. 0.1 C - 0.5 C; State of Charge (SOC) approx. 20 % - 80 %
*Successive increase in C-rates with each charging and discharging cycle
*Duration of formation process: up to 24 h
*Low contact resistances at the spring-loaded contact pins

==Technology alternatives==

*There are different procedures for the formation depending on the cell manufacturer and cell chemistry.

==Quality influences==

*Orientation of the cells
*Contact method
*Process temperature
*Pressurisation, especially of pouch cells

==Quality features==

*Formation of the SEI layer
*Stability of the SEI layer
*Internal resistance of the cell

==Source==
Heimes, H.H.; Kampker, A.; Lienemann, C.; Locke, M.; Offermanns, C.; Michaelis, S.; Rahimzei, E. (2018) ''Lithium-Ion Battery Cell Production Process''; PEM of RWTH Aachen and VDMA, 3rd Edition, ISBN:978-3-947920-03-7
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