(Invited) Quantitative Measurement of the Safety Performance of Li-Ion Batteries

Abstract

Safety is one of the essential requirements that should be taken into account and prioritized in the course of the development phases of lithium secondary batteries for any commercial applications. Even though different safety test standards exist to simulate the electric, mechanical, and thermal abuse conditions, there are only limited methods that can be used to quantify the safety performance of the cell. This study aims to compare the quantitative measurement techniques of safety evaluation and identify the methods to define the design parameters influencing the eventual safety performance of the full cells. The nail penetration, hot box, ARC (Accelerated Rate Calorimeter) and overcharging test are performed using the pouch cells (1-3 Ah) with different cell designs and aging conditions. It is found that hot box and nail penetration results are well correlated with the OCV (open circuit voltage) of the cells, suggesting that the OCV threshold can be used as a new quantitative indicator of the safety performance. Using this indicator, the cells having different P/E (power-to-energy ratio) designs and different electrolyte formulations are compared to identify the conditions to promote the safety performance of the cells. Figure 1