Study on the Safety Characteristics of Flat Plate Compression of Sodium-Ion Batteries

Sodium-ion batteries (SIBs) have become one of the mainstream research objects of electric vehicle energy storage system due to their advantages of high safety performance and low cost. In the use of electric vehicles, thermal runaway may occur when the battery pack is subjected to compression loading, so it is crucial to study the collision safety characteristics and thermal runaway behaviors of SIBs for their development. In order to reveal the flat plate compression safety characteristics of SIBs, this work focused on 18650-type SIB with a positive electrode of NaNi_1/3Fe_1/3Mn_1/3O₂ and a negative electrode of hard carbon. A test platform for the flat plate compression safety characteristics of the batteries was established to investigate the force-electric-thermal response during the battery compression, the state of charge (SOC) range and the critical speed range for thermal runaway of SIBs were explored, the internal short-circuit process was analyzed, and the secondary usage limit of damaged batteries was determined. The results indicate that thermal runaway occurs at charge states of 80% and 90% for cylindrical SIBs, a critical speed for thermal runaway is between 14 mm/min and 15 mm/min, and the battery compression process conforms to a standard “4-stage” process. The damaged cylindrical SIBs under compression have a secondary usage safety limit.