• Evaluated 765 new and 765 used EV battery cells from Indonesia’s online motorcycle taxi fleet using cell-level grading based on SOH, resistance, and voltage. • Showed that resistance and voltage do not exhibit a reliable linear correlation with SOH in aged cells, confirming the need for cell-level assessment rather than pack-level assumptions. • Revealed through SEM-EDS that used cells undergo agglomeration, granule deformation, and compositional changes, linking cathode degradation to electrical performance loss. • Demonstrated that morphological degradation plays a significant role in the structure-performance relationship of used EV batteries under second-life operation. • Confirmed by cycle testing and EIS that a C-rate of 0.5C or below is the preferable operating condition for second-life battery applications, with better capacity retention and lower impedance than at 1C. The increasing number of resistance lithium-ion batteries from electric vehicles (EVs) has driven interest in second-life applications. In contrast to previous studies that relied on laboratory-tested batteries, this study utilizes used EV batteries obtained from electric motorcycles in Indonesia to analyze their performance and potential for future use. A total of 756 new and used battery cells were evaluated for their performance through capacity testing and ranking based on resistance, voltage, and state of health (SOH). The cells were classified into six grades (A–F), where Grade A indicates the highest SOH and suitability for reuse, while lower grades reflect significant capacity degradation. The used battery cells were measured for their voltage and resistance values, which showed low correlation with the SOH value, which were then further analyzed using Scanning Electron Microscopy – Energy Dispersive X-ray Spectroscopy (SEM-EDS) and Electrochemical Impedance Spectroscopy (EIS) to observe the morphology and elemental composition of the battery cathode to analyze the fundamental correlation between electrical and material properties. The morphology of the used batteries indicated agglomeration and the presence of new compounds, which may contribute to increased resistance, decreased voltage, and reduced battery capacity. Therefore, cell-level testing is necessary to evaluate the reuse of used batteries further.
Suroso et al. (Wed,) studied this question.