Abstract:

In recent years, sodium-ion batteries (SIBs) have emerged as promising alternatives to lithium-ion batteries, owing to their low material cost, absence of resource constraints, and broad operational temperature range. However, research on the fire safety and thermal characteristics of SIBs lags behind their commercialization. In this study, a 180 Ah square aluminum-shell SIB was selected as the research subject. Using an adiabatic accelerating calorimeter and a closed pressure vessel, thermal runaway experiments under adiabatic, overheating, and 0.5C overcharge conditions were conducted to investigate temperature, voltage, and gas generation behaviors under electro-thermal abuse. The results show that (1) under adiabatic conditions, the self-heating onset temperature (T_onset) was 115.9 ℃, the thermal runaway trigger temperature (T_tr) was 201.3 ℃, and the maximum temperature (T_max) reached 444.8 ℃. The maximum temperature rise rate during thermal runaway was 2353 ℃/min, and the mass loss was 22.8%. (2) under overheating conditions, thermal runaway started at approximately 171.8 ℃, with a T_max of 484.5 ℃. The total volume of mixed gas released after thermal runaway was 123.3 L, mainly consisting of hydrogen (35.4%), carbon dioxide (31.0%), carbon monoxide (19.2%), and ethylene (4.3%), with a mass loss of 25.0%. (3) under 0.5C overcharge conditions, thermal runaway occurred when the state of charge reached approximately 190.8%. The T_max was 573.6 ℃, and the total gas released was 200.3 L, primarily containing carbon dioxide (29.1%), hydrogen (28.1%), carbon monoxide (20.8%), and ethylene (14.4%), with a mass loss of 48.0%. These findings provide a reference for the safety design and risk assessment of high-capacity SIBs.

Key words: sodium-ion battery, thermal runaway, adiabatic environment, electro-thermal abuse, gas-generating properties