Understanding the aging behavior of Li-ion batteries is critical to improving their lifetime, performance, safety, and sustainability. Temperature, among other factors, is one of the most impacting factors on the cyclic aging behavior of Li-ion batteries [1–3]. However, a battery’s operating temperature, and therefore the dominant aging mechanism, typically changes during its lifetime, for example when an EV is sold in a different region or the batteries are repurposed for a second use. The impact of a changing aging temperature and temperature-dependent aging pathways on battery lifetime is further discussed here. Therefore, 36 temperature variations during cyclic aging of commercial pouch and cylindrical cells between 0 °C and 45 °C were investigated [3].
Arrhenius plots of the cyclic aging rate are used to distinguish between Li plating and Solid-Electrolyte-Interphase (SEI) growth as the dominant aging mechanisms at low and high temperatures respectively. The V-shaped Arrhenius plot shows a minimum, which corresponds to the longest cycle life, at the transition between the two aging mechanisms. The minimum aging rate is observed at 25 °C for constant temperature cycling.
Changing the aging temperature during the life of a battery can result in significant changes in the aging rate. Previous low temperature cycling (< 25 °C), where Li plating dominates, exacerbates further Li plating due to loss of anode active material. In contrast, previous high temperature cycling (≥ 25 °C) with loss of Li inventory reduces the Li plating rate and shifts the onset of Li plating to lower temperatures during subsequent aging as the high lithiation states are no longer reached. Thus, a new optimum temperature of 20 °C is observed, which is associated with a superior cycle life. Similar to calendar aging [4], where SEI growth dominates aging across all temperatures [5], cyclic aging shows a path independent aging when the temperature paths exclusively involve high temperatures. Compared to aging paths with a low second aging temperature, aging at high second temperatures is only slightly influenced by previous aging processes. In conclusion, an evaluation of the temperature path dependence in Li-ion battery aging can be carried out using four principal temperature paths spanning two temperature ranges. The selection of appropriate temperature path has the potential to yield significant improvements in cycle life, even beyond constant temperature cycling. These are a valuable information for selecting suitable cells for a second-use application or for modelling of realistic battery usage scenarios. References [1] T. Waldmann, M. Wilka, M. Kasper, M. Fleischhammer, M. Wohlfahrt-Mehrens, Journal of Power Sources 262 (2014) 129–135. https://doi.org/10.1016/j.jpowsour.2014.03.112. [2] G. Kucinskis, M. Bozorgchenani, M. Feinauer, M. Kasper, M. Wohlfahrt-Mehrens, T. Waldmann, Journal of Power Sources 549 (2022) 232129. https://doi.org/10.1016/j.jpowsour.2022.232129. [3] M. Feinauer, M. Wohlfahrt-Mehrens, M. Hölzle, T. Waldmann, Journal of Power Sources 594 (2024) 233948. https://doi.org/10.1016/j.jpowsour.2023.233948. [4] L. Su, J. Zhang, J. Huang, H. Ge, Z. Li, F. Xie, B.Y. Liaw, Journal of Power Sources 315 (2016) 35–46. https://doi.org/10.1016/j.jpowsour.2016.03.043. [5] T. Waldmann, M. Kasper, M. Wohlfahrt-Mehrens, Electrochimica Acta 178 (2015) 525–532. https://doi.org/10.1016/j.electacta.2015.08.056.