Comparing thermal runaway behavior of sodium-ion, lithium-ion batteries

Researchers from Germany’s Otto von Guericke University Magdeburg have analyzed and compared the thermal runaway characteristics in sodium-ion batteries (SIBs) and lithium-ion batteries (LIBs) with layered oxide cathodes.

Thermal runaway is a chain reaction that can occur in batteries when they overheat, potentially resulting in fire and explosion.“During thermal runaway, the components of the cell decompose, releasing combustible and toxic gases in addition to electrolyte vapors, particulate matter and heat,” explained the researchers.

They compared the thermal runaway behavior and gas release from SIBs and LIBs of layered oxide cathode. “Herein, 18650-type cylindrical SIBs of NFM cathode (layered oxide cathode) and 18650-type cylindrical LIBs of NMC cathode (layered oxide cathode) were forced into thermal runaway,” they added.

A total of 30 commercial batteries were tested, with 15 of them featuring 3.6 Wh (1.2 Ah) SIB cells with NaNi1/3Fe1/ 3Mn1/3O2 (NFM) cathode and another 15 featuring 10.4 Wh (2.9 Ah) LIB cells of Li(NixMnyCo1-x-y)O2 (NMC) cathode. Three batteries of any type were tested under different states of charge (SOC), namely 0%, 25%, 50%, 75%, and 100%. The tests were conducted using a gas-tight 10-L reaction vessel with a pressure rating of 20 bar.

“The reaction vessel contains a cell holder with four 320 W heating cartridges. Each cell was forced into thermal runaway by local overheating,” the group said. “The heating cartridges were limited to a maximum power output of 100 W in each test, ensuring that the maximum temperature reached approximately 300 C with a heating rate of 12 K/min.”

Through this experiment, the research team found that in both SIBs and LIBs, thermal runaway was detected at SOC equal to or above 50%. In the SIBs, the rate of temperature rise was more than 2 K per second, and in the LIBs, it was more than 10 K per second. The onset temperature for the thermal runaway was measured as 135-165 C in the case of SIBs and 140-172 C in the case of LIBs.

“The normalized volume of gas produced suggests similar gas production characteristics for the SIBs and LIBs,” the results also showed. “Four gas components out of the seven considered in the present study – namely carbon monoxide (CO), methane (CH4), hydrogen cyanide (HCN), and ethylene (C2H4) – exhibited similar production patterns in the two cell types. The lower explosion limit (LEL) of 4.8 vol% and 5.5 vol% was measured from the explosible gaseous mixture of the SIBs and LIBs respectively. Such values present an explosive risk.”

Their findings were presented in “Comparing the thermal runaway characteristics in sodium-ion batteries and Li-ion batteries with layered oxide cathode materials: Influence of state of charge level,” published in the Journal of Power Sources.