Study on Thermal Behavior and Safety Properties of Na4Fe3(PO4)2(P2O7) and NaNi1/3Fe1/3Mn1/3O2 Cathode-Based Sodium Ion Battery

Sodium-ion batteries (SIBs) share similar working principles with lithium-ion batteries while demonstrating cost advantages. However, the current understanding of their safety characteristics remains insufficient, and the thermal runaway mechanisms of different SIB systems have not been fully elucidated. This study investigated the following two mainstream sodium-ion battery systems: polyanion-type compound (PAC) and layered transition metal oxide (TMO) cathodes. Differential scanning calorimetry (DSC) was employed to evaluate the thermal stability of cathodes and anodes, examining the effects of state of charge (SOC), cycling, and overcharging on electrode thermal stability. The thermal stability of electrolytes with different compositions was also characterized and analyzed. Additionally, adiabatic thermal runaway tests were conducted using an accelerating rate calorimeter (ARC) to explore temperature–voltage evolution patterns and temperature rise rates. The study systematically investigated heat-generating reactions during various thermal runaway stages and conducted a comparative analysis of the thermal runaway characteristics between these two battery systems.