Comparative Study on Thermal Runaway and Gas Generation Behavior Between Sodium Ion Battery and Lithium Iron Phosphate/Ternary Lithium Ion Battery

ABSTRACT Sodium‐ion batteries (SIB) exhibit enormous application potential in energy storage applications due to their abundant sodium resources, low cost, and superior low‐temperature rate performance. However, public reports on the study of thermal runaway (TR) coupled with gas generation characteristics in SIB remain relatively limited. This study conducts a comparative investigation into the TR and gas generation characteristics of SIB, lithium iron phosphate (LFP)/graphite batteries, and nickel‐cobalt‐manganese/graphite batteries (NCM). The study quantifies the gas volume and composition generated during TR of the three battery types and employs the Analytic Hierarchy Process (AHP) to compare the disaster risks of TR in SIB, LFP, and NCM. The results show that at the same state of charge (SOC), SIB and NCM exhibit lower TR onset temperatures but significantly higher instantaneous pressures than LFP. Their gas production is approximately 2.84 and 2.72 that of LFP, respectively, posing greater challenges for gas‐induced disaster prevention at the system level. The gas compositions during TR are similar across the three systems, with LFP showing higher H 2 content and lower CO/CO 2 content. SIB and NCM have higher lower explosive limits (LEL), lower upper explosive limits (UEL), and narrower explosive ranges, indicating lower explosion risks. Comprehensive evaluation suggests that SIB and NCM present lower overall hazard levels than LFP under the same SOC, though risks in certain characteristic parameters cannot be ignored. These findings are expected to provide references for the safety design of large‐capacity multisystem batteries, thereby enhancing their safety in commercial applications.