Evaluation of Retired Lithium-ion Batteries for Second-life Applications through Electrochemical Impedance Spectroscopy

The rapid growth of electric transportation will generate a substantial number of retired batteries. Recycling the retired LIBs is being looked at worldwide to recover the expensive raw materials from used batteries. Alternatively, the retired electric vehicle (EV) batteries can be reused directly or refurbished for second-life applications. Nevertheless, Lithium-ion batteries (LIBs) degrade during their first-life usage, hence ensuring safety, efficiency, and reliability in second-life applications is crucial. This study investigates LIB degradation using electrochemical impedance spectroscopy (EIS) to assess the battery condition at the end of its primary use. A Samsung 21700 nickel cobalt aluminium (NCA) battery is cycled to 80% of its initial capacity and equivalent circuit model (ECM) parameters obtained through electrochemical impedance spectroscopy (EIS) are analyzed. Individual ECM parameters are evaluated to acquire the health indicators. Although the battery capacity decreased by 20%, resistive components such as bulk resistance, charge transfer resistance and Warburg resistance increased by 140%, 150% and 132% respectively. Given the relative capacity and resistance, the battery is well-suited for second-life applications such as grid frequency regulation, uninterruptible power supply, electric forklifts, and material handling equipment. Other health indicators such as Loss of lithium inventory (LLI) and loss of active materials (LAM) are also captured.