Understanding the Interplay between Temperature, State of Health, Rate of Ageing, and Overvoltage in Li-Ion Battery Cells

Abstract

Li-ion batteries are currently the most popular battery technology. However, their service life remains limited and is typically in a range of 2-10 years of active use. The ageing is influenced by the materials used, temperature, charge/discharge rate and architecture of the battery cells. The governing ageing mechanisms are generally related to material stability, with the formation of solid-electrode interphase (SEI), decomposition of active materials or electrolyte and loss of contact being the main contributors. Externally, this can be observed as loss of capacity, increase in internal resistance (overvoltage or polarization) and heating of the cell while in use.In this work, we demonstrate how Arrhenius plots are a valuable tool to understand the rate of battery cell ageing over its operational temperature range [1,2]. The V-shaped Arrhenius plots correspond to two ageing mechanisms, lithium plating and growth of SEI, with the intersection (crossover) denoting the optimum temperature for the highest service life. The crossover temperature shifts towards higher values with increasing C-rate and anode thickness and depends on the state of health of the battery. The study shows that using Arrhenius-type dependences of the ageing rate can provide valuable insights for quality control and battery management systems, extending the service life of battery cells.Overvoltage of the battery cell typically grows as the battery cell ages. This increased internal resistance leads to a decrease in the battery's ability to deliver current, and thus reduces its power or what is in some cases called ‘rate capability’. We have studied this phenomenon for lab-assembled half-cells with LiFePO4 and NCM 811 cathode as well as for commercial cells, showing the overvoltage as a function of battery cell’s state of health, C-rate and temperature. While ultimately the overvoltage is undesirable, we show how it correlates with battery’s state of health and can be used as an effective predictor of the remaining service life of the battery cell from the operational data without performing a full charge and discharge measurement in a controlled environment. This reduces the failure risk and improves the safety and reliability of the battery. Acknowledgements Authors acknowledge Latvian Council of Science project “Cycle life prediction of lithium-ion battery electrodes and cells, utilizing current-voltage response measurements”, project No. LZP-2020/1-0425. Institute of Solid-State Physics, University of Latvia as the Centre of Excellence has received funding from the European Union's Horizon 2020 Framework Program H2020-WIDESPREAD-01-2016-2017-TeamingPhase2 under grant agreement No. 739508, project CAMART2. References Bozorgchenani, M., Kucinskis, G., Wohlfahrt-Mehrens, M. & Waldmann, T. Experimental Confirmation of C-Rate Dependent Minima Shifts in Arrhenius Plots of Li-Ion Battery Aging. J. Electrochem. Soc. 169, 030509 (2022).Kucinskis, G. et al. Arrhenius plots for Li-ion battery ageing as a function of temperature, C-rate, and ageing state – An experimental study. J. Power Sources 549, 232129 (2022).