Abstract
The capacity fading of lithium-ion batteries (LIBs) is reported by a linear dependency followed by a nonlinear ageing process, where the former is dominated by solid electrolyte interphase formation and reformation (SEI and SEI-re), while the latter is by lithium plating. In this work, a two-stage model is developed to quantitatively predict the turning point during the capacity fading of LIBs, which couples the electrochemical and thermal models accounting for SEI, SEI-re and lithium plating. Accordingly, a quantitative evaluation method of the turning point is proposed by attributing the transition of the capacity fading to the balance of consumption of active lithium for SEI growth and lithium plating per cycle in the two stages. The characteristics of capacity fading of LIBs are quantitatively analyzed under various operation conditions and design parameters. An NCM111/graphite battery is used to validate the proposed model. The results shows the validity of the proposed model. The turning points of the capacity fading processes are influenced by operation and design parameters of LIBs, where lithium plating or SEI growth reign. According to the effect on the turning point, the order of significance of the factors are charging current, charging cut-off voltage, temperature and N/P ratio, respectively.
Quantitative Estimation of Turning Point of Ageing Based on a Two-Stage Model for Lithium-Ion Batteries
