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.

Experimental Study on the Effect of State of Charge on Failure Propagation Characteristics within Battery Modules

To investigate the effect of different states of charge(SOC)on the thermal runaway(TR)propagation behaviors within lithium-ion-batteries based energy storage modules,an experimental setup was developed to conduct failure propagation tests on battery modules at an SOC of 97%,85%,and 50%.The result indicates that an increase in the SOC of batteries can decrease the TR trigger temperature,making batteries trigger TR earlier and reducing the average failure propagation time between two adjacent cells.In addition,the failure propagation tests reveal that at higher SOCs,the TR reaction becomes more violent,the maximal reaction temperature is also much higher,and the damage to the battery module is severe.Compared to the battery module with 97%SOC,the TR trigger time of the battery module with 50%SOC was postponed by approximately 57.8%.Meanwhile,the average failure propagation time got prolonged by approximately 36.0%.Thus,this study can provide references for the thermal safety design of energy-storage battery modules.