Quantification of venting behavior of cylindrical lithium-ion and sodium-ion batteries during thermal runaway

Understanding the thermal runaway behavior of batteries is essential for designing safe battery systems. This study investigates thermal runaway behavior of cylindrical nickel-rich lithium-ion batteries (NMC811/SiC with EC/EMC/DMC electrolyte) in 21700 and 18650 formats, alongside commercial sodium-ion batteries in the 18650 format with the NaMn_1/3Fe_1/3Ni_1/3O₂ cathode, hard carbon anode and DMC/EMC/EC/EP/PC electrolyte. Additionally, a thermal runaway test bench equipped with shear force sensors and a high-speed camera for venting gas velocity and mass flow rate estimation was presented. Results indicate that the lithium-ion batteries reach venting gas temperatures exceeding 1370 °C, with surface temperatures surpassing 400 °C and venting gas velocities exceeding 150 m s⁻¹. Conversely, the investigated sodium-ion batteries exhibit lower temperatures due to the absence of gas ignition, precluding the estimation of venting gas velocity. Peak mass flow rates for lithium-ion batteries reach 2000 g s⁻¹, with average rates between 30 g s⁻¹ and 300 g s⁻¹. Total mass loss ranges from 55 % in 18650 sodium-ion batteries to 77 % in 18650 lithium-ion batteries. These findings provide valuable insights into the venting dynamics during thermal runaway, contributing to the development of safer battery systems and simplifying the process of venting simulations for cylindrical batteries.