Role of Charging Rate on Internal Short-Circuit Characteristics of Lithium-Ion Battery

Lithium-ion batteries used in electric vehicles (EVs) are facing issues owing to internal short-circuit (ISC), leading to thermal runaway. In this study, a pseudo-two-dimensional (P2D) model is employed to numerically investigate the effects of charging rate (C-rate) and separator electrical conductivity on the ISC behavior of a lithium-ion cell. The results reveal that as C-rate increases, both the voltage and capacity decrease more rapidly marked by higher solid potential gradient indicating increased internal resistance. These effects further intensified at higher separator conductivity, which facilitates greater ISC current and accelerates cell degradation. Also, the variations in current density and solid-phase lithium concentration become more pronounced at higher C-rates, particularly near the anode–separator interface, indicating increased non-uniformity during ISC conditions. Furthermore, the electrolyte voltage drop intensifies with rising C-rate, contributing to additional polarization. Further, it is observed that the separator conductivity has a significant influence on ISC current, although it shows a minimal effect on the terminal voltage. The value of the ISC current is found to increase with the increase in the value of the conductivity of the separator. Finally, it can be inferred that the lower electrical conductivity of the separator is desirable to prevent ISC of the Li-ion cell. The study highlights that a lower separator conductivity is beneficial in mitigating the severity of ISC events. These findings provide valuable insights for the design of safer lithium-ion cells considering the separator conductivity and operational C-rates.