[sikeston34m]

VERY good read! Thank you Redshift.

Solid Electrolyte Interface/Interphase (SEI)
The SEI layer is essential for the stability of Lithium secondary cells using carbon anodes


The electrolyte reacts vigorously with the carbon anode during the initial formation charge and a thin passivating SEI layer builds up moderating the charge rate and restricting current




The deposition of the SEI layer is an essential part of the formation process when the cells take their first charge.

BUT the SEI layer increases the cell internal impedance and reduces the possible charge rates as well as the high and low temperature performance.

Excessive heat can cause the protective SEI barrier layer to beak down allowing the anode reaction to restart releasing more heat leading to thermal runaway.

The thickness of the SEI layer is not homogeneous and increases with age, increasing the cell internal impedance, reducing its capacity and hence its cycle life.