The Influence of Cycling, Temperature, and Electrode Gapping on the Safety of Prismatic Lithium-Ion Batteries

Lithium-ion batteries are prevalent in every aspect of modern life (cell phones, laptops, electric vehicles, and energy storage systems for the electric grid). For all applications, the battery safety is an important consideration. Compared to numerous studies on the safety behavior of 18650-type cells, limited research has been conducted to characterize prismatic cells with their unique challenges including how electrode gapping, cycling history, electrolyte degradation, or lithium plating affect the safety. In this paper, a systematic study is reported on prismatic cells cycled at 0 °C, 23 °C, and 45 °C. The safety aspect of the cells with electrode gapping is evaluated using accelerating rate calorimetry (ARC). The evolution of gaps was monitored using X-ray computed tomography. Our study demonstrates that gaps are intrinsic even in fresh cells. The gaps can evolve during cycling and are closely related to the localized lithium plating and electrolyte degradation, which can be more severe for cells cycled at 45 °C. However, the safety behavior is not simply correlated to cell internal structure (e.g. gapping), or the amount of degradation products after cycling; the aging mechanism at different temperatures also plays an important role. Understanding the thermal stability of prismatic cells during their lifecycle is necessary for risk mitigation in numerous applications.