Quantitative analysis and modeling of calendar aging influence factors of Li-ion batteries based on impedance

To study the influencing factors of calendar aging of lithium-ion batteries, the evolution process of impedance at different temperatures and state-of-charge(SOC) was analyzed using the impedance test data of CALCE dataset. Moreover, an ohmic impedance increment model was established based on the variance analysis of the influence of storage conditions on the battery, considering the temperature and SOC. The results show that the influence of temperature on the calendar aging of lithium-ion batteries is significantly greater than that of SOC. At high temperatures, the ohmic impedance increases exponentially with time; at room temperatures, the ohmic impedance increases linearly, and at low temperatures, the ohmic impedance shows nonlinear changes. Therefore, high-temperature environments are the main factor affecting the performance degradation of lithium-ion batteries. The aging model constructed in this paper can be used to describe the influence of calendar aging on impedance changes within a wide temperature range.