Impact of Lithium-Ion Cell Condition on Its Second Life Viability

Second life of lithium-ion batteries is under investigation, because it could be economically and environmentally profitable. The longevity of a second life of cells coming from electric vehicles mostly depends on what they experienced onboard. In this study, we target either lithium plating or loss of active material with two types (energyorpower) of 18650 cells, during first life. We find that theenergycells initially aged at +25 degrees C demonstrate a second life at least twice as long as other cells. Yet,post-mortemanalyses show that a thick lithium plating layer affects these cells, as observed after ageing at 0 degrees C. We quantify lithium plating, taking into account the heterogeneity of the degradation, using segmentation of negative electrode pictures, and local weight and thickness measurements. We demonstrate that the density of the deposit affects the resistance of the cell and thus its second life longevity. Prognosis rely thus on resistance, measured either with electrochemical impedance spectroscopy or current pulses, whereas the amount of lithium plating is diagnosed using differential voltage analysis. Thermal management of these aged cells is crucial, as 60 to 70 degrees C onset temperatures are measured using accelerated rate calorimetry.