Meaning
Electrochemical evaluation metrics quantify the proportion of usable discharge capacity a secondary cell preserves after undergoing specified charge cycles or environmental exposure. A capacity retention factor defines the remaining health of an energy storage device relative to its nominal rated capacity under baseline test conditions. The measurement governs warranty validation thresholds and end of life criteria, ceasing to apply once a cell suffers catastrophic mechanical structural failure or internal short circuits.
Measurement Basis
Discharge capacity is recorded at standard ambient temperature using standardized constant current and constant voltage profiles. Calculating the capacity retention factor requires dividing the current discharge capacity by the initial measured baseline capacity. Test protocols fix the discharge rate to isolate chemical degradation from thermal polarization effects.
Degradation Pathway
Active material loss and solid electrolyte interphase growth continuously reduce available lithium ions during operation. Higher ambient storage temperatures accelerate these side reactions and cause rapid capacity decline over time. Tracking retention values across sequential cycles establishes predictable degradation curves for pack modeling.
Procurement Value
System integrators enforce strict retention minimums in commercial purchasing contracts to guarantee field service life. A cell model that drops below target thresholds during qualification is rejected prior to mass pack assembly. Guaranteeing retained capacity protects downstream operations from premature battery replacement expenses.
