Predicting adhesive sealing life of Li-ion pouch cell using a fusion method considering time-varying dependence

Abstract

ABSTRACT The adhesive sealing structure plays an important role in high-reliability long-life service of Li-ion pouch cells. The inner gas pressure increases inevitably owing to a diversity of chemical and thermal reactions during charging/discharging cycles of Li-ion pouch cells. It accelerates the degradation of adhesion properties, leading to the sealing failure and batteries’ being scrapped in advance. Therefore, an accurate sealing life prediction method is crucial for durable Li-ion batteries. Since existing physics-based methods cannot describe the time-varying dependence between the gas pressure and adhesion property variable (i.e. maximum peeling force) well, whereas pure data-driven methods have difficulties in determining failure thresholds, this paper proposes a fusion method for predicting the sealing life. Considering the irreversibility of the sealing degradation, the Gamma stochastic processes are used to describe the dispersivity and monotonous variation of gas pressure and maximum peeling force, and the time-varying dependence between them is modelled by time-varying copula functions. Then, two empirical physical equations are employed to determine the relationship between the gas pressure and the sealing stress, as well as the relationship between the peeling force and the adhesive strength. Finally, the sealing life prediction is obtained based on the stress-strength interference theory.