Internal Impedance in Determining Usability of Used Lithium-Ion Batteries in Second-Life Applications

Li-ion batteries have become key energy storage devices in powering various industrial processes and consumer products. Increased demand for Li-ion batteries has raised environmental issues because most of the batteries are landfilled upon reaching end of life. However, studies have suggested that most of the used Li-ion batteries can be reused in second-life applications. Battery state parameters such as the state-of-health (SOH) and state-of-charge (SOC) are typically used for assessing the performance. The SOH is particularly useful in predicting the remaining life cycle of the battery and selecting suitable second-life applications for reuse. However, measuring the SOH can be difficult using existing technology. Recent studies have shown that a battery's internal impedance can be used to determine the SOH of the battery. This paper demonstrates the applicability of the internal impedance in evaluating the SOH and suitability of used Li-ion batteries in second-life applications. Experimental measurements from several commercial Li-ion batteries are shown and analyzed.