Battery knowledge · Aging and degradation
Knee point
The point in a capacity-versus-cycles curve where slow, roughly linear fade turns into rapid loss. It usually marks the onset of lithium plating or electrolyte dry-out, and a cell past its knee is unpredictable and should be retired. [1]
- Also called
- rollover, sudden death
Example
A knee changes the rate of capacity loss
The chosen knee is at 0.6 relative exposure. Beyond it, the illustrated loss rate accelerates.
A chosen teaching curve, not a prediction of cycles, years or a physical failure mechanism.
Explore the graph
A slow early decline can turn into much faster degradation.
The chosen knee is at 0.6 relative exposure. Beyond it, the illustrated loss rate accelerates.
Illustrative trend: retention = 100 − 10x − 120 max(0, x − knee)²
Illustrative model. A chosen teaching curve, not a prediction of cycles, years or a physical failure mechanism.
Use in Lemonergy
Separate mechanisms, observations and fitted models.
This is a reference concept. No executable Lemonergy block has been verified for this term.
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.