Determination of lithium-ion battery state-of-health based on constant-voltage charge phase

Lithium battery performances degrade even at rest time that means when electric/hybrid electric vehicles are in the parking. This phenomenon is well known as calendar aging. In this paper, the kinetic of the CC-CV charge at 1 C and mainly kinetic of the voltage regulation, CV step, is investigated as an indicator of battery state-of-health through calendar aging. In fact, CV step is responsible in a major part of lithium intercalation into negative electrode and revealed to give signification on cyclable lithium loss which is the major cause of calendar aging according to literature and post mortem analysis. Comparison from the aging of four battery technologies is presented. Through aging, results show a difference in battery behavior even if the time for CC charge is decreasing for all the battery. According to battery technology, the current during CV charge phase has been useful for lithium-nickel-manganese-cobalt-oxide, lithium-nickel-cobalt-aluminum-oxide and lithium-ion-manganese battery state-of-health determination. However, in the case of the lithium-iron-phosphate battery, simple calculation of the duration of the CV step revealed to be very accurate compared to the classic discharged capacity measurement.