Impedance spectroscopy characterization of lithium batteries with different ages in second life application

The aging behavior of lithium cell has a profound impact on its performance in terms of energy, power efficiency and capacity fade, especially when it is considered in End of Life (EOL) in automotive field. Lithium battery is considered in EOL if at 85-80% of nominal capacity. Today, the reusing of Electric and Hybrid Vehicles EOL batteries on less-demanding grid connected energy storage applications, giving them a second use/life, is an interesting solution to reduce high potential cost of lithium batteries. Currently, there is a lack of investigation of the performances of these second life batteries. In this paper, authors show the results of the impedance spectroscopy of 20 Ah lithium NMC batteries after EOL, exactly at 100, 85, 80, 60 and 50% of rated capacity, in a wide range of frequency: 450 mHz to 3.5 kHz. By results, there are many way to correlate battery state of health and battery impedance spectroscopy, especially when the battery is in second life.