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, state of healths, 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, it was found to have severe limitations in its application due to its lack of consistency between chemistry, rates, and temperatures, reliance on heavy filtering, and inability to identify trends in capacity loss, all preventing any potential for widespread application.