Battery knowledge · Aging and degradation
Passivation
The formation of a surface film that slows further reaction. In lithium-ion cells, the SEI passivates the graphite negative electrode. [1]
Example
Diffusion-limited film growth
At four reference time units, thickness is 2× the reference thickness.
Normalized analytical relation, not a capacity-loss or SOH prediction.
Explore the graph
Four times the elapsed time gives twice the film thickness in this model.
At four reference time units, thickness is 2× the reference thickness.
δ / δ_ref = √[(t / t_ref) A]
Illustrative model. Normalized analytical relation, not a capacity-loss or SOH prediction.
Use in Lemonergy
Lemonergy Core equation
Explore film growth
Lemonergy Core evaluates this relation.
Equation or tool to use
- parabolic_film_thickness
Core equation
Inputs & settings
- Reference thickness
- Elapsed and reference time
- Acceleration factor
This overview identifies the components to use. Follow the example in Lemonergy for their connections and settings.
- Open the lesson and inspect the equation.
- Change one input while holding the others fixed.
Example. At a factor of one, 10 nm at 1 h becomes 20 nm at 4 h and 30 nm at 9 h.
Observe. Compare the result with the equation and units.
This does not identify SEI chemistry or fit state of health.
Open the worked lesson →References & further reading
Technical references
- Lithium ion battery degradation: what you need to know
Physical Chemistry Chemical Physics · 2021
Technical reference · Degradation mechanisms, modes, operational effects and their interactions.