The Voltage-Based Implementation of the Tunneling Mechanism in Aging Models for Lithium-Ion Batteries

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Lithium-ion batteries (LIBs) have become one of the most crucial power sources for electronics and electric vehicles due to high energy density, long cycle life, environmental friendliness, etc. Precise explanation and prediction of the aging behavior of LIBs is quickly becoming a hotspot. A solid electrolyte interface (SEI) growth is regarded as the dominant factor of capacity losses in LIBs. However, the previous SEI growth and aging models were based on energy levels. That means the energy barrier related to the Fermi level of SEI and electrode was used as the input parameter. It is not straightforward to implement, especially for industrial applications. Furthermore, the state-of-charge (SoC) and the energy barrier were usually assumed to be constant during (dis)charging, contradicting common sense and affecting the calculations' accuracy.The present work proposes and experimentally validates an advanced voltage-based aging model. The voltage of the anode electrode is adopted as an input parameter in this model. It is easier to introduce dependence of aging on the voltage/SoC of the electrode with this model. It is found that deep delithiation of the anodes and lower SoC of LIBs will mitigate electron tunneling, lower SEI growth, and reduce calendar aging. Commonly used anode materials, such as graphite, Li4Ti5O12, and blended Si/C, are presented as interesting cases to investigate the effects of different electrode materials on the tunneling current profiles during (dis)charging for the first time. The model is instructive and can predict aging in LIBs with various electrode materials. This model and related analyses are beneficial for further optimizing LIB's electronic and electrode properties and as interesting limiting cases for testing battery modeling software.