Voltage Relaxation Characterization Methods in Lithium-Ion Batteries

This study evaluated three approaches for characterizing voltage relaxation in lithium-ion batteries: voltage vs. time, the derivative of voltage vs. time, and the second derivative of voltage vs. time. The first two are well-established approaches, whereas the third was never investigated, to our knowledge. To assess the potential of each approach, characterizations were performed on data with various depth-of-discharges, regimes, SOHs, temperatures, and chemistries. Findings indicate that the established approaches do not comprehensively characterize voltage relaxation whereas the novel approach demonstrated promise in providing a quantitative feature to compare relaxation behaviors. However, limitations persisted in its application due to its reliance on heavy filtering and inability to identify trends in capacity loss, preventing widespread application.