Electrochemical model boosting accurate prediction of calendar life for commercial LiFePO4|graphite cells by combining solid electrolyte interface side reactions

The lithium-ion battery (LIB) is considered an ideal next-generation energy storage device owing to its high safety, high energy density, and low cost. Calendar loss of LIBs is the most important element in the long-term degradation of batteries. However, the calendar life is difficult to measure precisely because of the uncertain and overlong storage years. Consequently, accurately predicting the calendar life of LIBs is a key but challenging issue. In this work, a calendar life prediction model is developed for commercial large-capacity LiFePO4|graphite LIBs based on the pseudo-two-dimensional (P2D) electrochemical model integrated with solid electrolyte interface (SEI) growth side reactions and an empirical degradation rate model for reliability research. The excellent agreement between the model and the experimental storage data over a wide range of temperatures (−40 °C ∼ 70 °C) and SOCs demonstrates the high-fidelity of the model. The established model is sufficiently generic to predict the storage aging of LIBs over a long period of years. On the basis of the verified model, the impact of graphite particle radius distribution on the calendar loss of Li-ion batteries throughout a broad temperature range is investigated. This modeling work contributes to an improved understanding of the calendar loss behavior of LIBs and provides valuable guidance for future battery design optimization. [Display omitted] •An electrochemical model combining SEI film growth side reactions is presented.•The model is able to predict the calendar aging of Li-ion batteries accurately.•Storage at high temperatures and at high SOCs can accelerate SEI film growth.•Increasing the graphite particle radius helps mitigate the calendar loss.