Effect of preload forces on multidimensional signal dynamic behaviours for battery early safety warning

Providing early safety warning for batteries in real-world applications is challenging. In this study, comprehensive thermal abuse experiments are conducted to clarify the multidimensional signal evolution of battery failure under various preload forces. The time-sequence relationship among expansion force, voltage, and temperature during thermal abuse under five categorised stages is revealed. Three characteristic peaks are identified for the expansion force, which correspond to venting, internal short-circuiting, and thermal runaway. In particular, an abnormal expansion force signal can be detected at temperatures as low as 42.4 °C, followed by battery thermal runaway in approximately 6.5 min. Moreover, reducing the preload force can improve the effectiveness of the early-warning method via the expansion force. Specifically, reducing the preload force from 6000 to 1000 N prolongs the warning time (i.e. 227 to 398 s) before thermal runaway is triggered. Based on the results, a notable expansion force early-warning method is proposed that can successfully enable early safety warning approximately 375 s ahead of battery thermal runaway and effectively prevent failure propagation with module validation. This study provides a practical reference for the development of timely and accurate early-warning strategies as well as guidance for the design of safer battery systems.