Life Cycle Prediction Model of Safety Vent Based on Two-Phase Degradation Process

The safety vent, the most important failsafe device of lithium ion batteries, is made of a high-ductility and a corrosion-resistant aluminum alloy. Safety vents are designed to release the gas pressure in the battery shell before a catastrophic explosion happens. This vent is required to keep a balance between the long service life and high operational safety. It is of great significance to understand the failure mechanisms and predict the life of the safety vent. This paper proposes a life cycle prediction method based on a two-phase physical degradation process. First, a piecewise creep equation is established to describe the degradation process of the vent under the slowly increasing inner pressure. Based on this equation, the total life cycle is divided into two parts: one is the time before gas pressure reaches the critical point at which the vent starts to creep and the other is the duration of time from that critical point to the failure threshold, which is calculated through accelerated degradation testing and the creep equation. Finally, life cycle prediction and uncertainty analysis are performed. It is believed that the proposed method can provide a reasonable and effective reference for the life cycle evaluation of the safety vent.