An exploration of Li-ion cell relaxation using EIS

This paper describes a systematic study of the effect of cell relaxation after a charge or discharge event. The EIS technique was used to investigate how the properties of the cells changed with time after charge or discharge up to a maximum of 15 hours. It was found that different chemistries show different relaxation rates and frequency dependence of R _o and R _d . The cells still showed a relaxation at 15 hours after a charge/discharge event. A suggested compromise of measurement accuracy and test length is to measure the properties of cells 4 hours after a charge/discharge event.