Study of aging mechanisms in LiFePO₄ batteries with various SOC levels using the zero-sum pulse method

Investigating the correlation between aging mechanisms and state of charge (SOC) can optimize cycling conditions and prolong the life cycle of lithium-ion batteries (LIBs). A long-term cycle between a certain SOC range is usually employed to study this correlation. However, this method necessitates a lengthy period, running from months to years, prolonging the research duration significantly. The aging mechanisms obtained through this method are a result of the coupling of various SOC levels; the aging mechanisms at a specific SOC level are not accurately decoupled and analyzable. The proposed Zero-sum pulse method, using symmetrical pulses with small SOC amplitude variations on SOC, can explore aging mechanisms of LIBs at a specific SOC level and reduce the time to less than a week, which significantly expedite the research process. The aging mechanisms at 30%, 50%, 70%, and 90% SOC levels are explored to verify the accuracy and timeliness of this method.