Numerical Study on the Fire Characteristics and the Water Mist Suppression Performance for Lithium-Ion Battery Boxes on Storage Shelves

Lithium-ion batteries (LIBs) have been widely used in electric vehicles and energy storage systems. Due to their high energy density and complex structural components, thermal runaway of LIBs can lead to severe fire and explosion hazards. Densely arranged LIBs in storage scenarios are highly susceptible to fire propagation, posing challenges to fire safety. In this paper, full-scale LIB box storage shelf models were established using an FDS (Fire Dynamics Simulator) based on the actual shelf configurations. The fire propagation characteristics following thermal runaway were discussed considering common shelf types, the horizontal spacing of adjacent LIB boxes and the longitudinal shelf spacing. Furthermore, the suppression performance of a water mist system was analyzed under varying droplet sizes and spray cone angles. The simulation results indicated that, under the investigated conditions and periods, selecting the shelf with side panels and perforated bottom layers, increasing the horizontal spacing of LIB boxes to 0.8 m and the longitudinal shelf spacing to 1.5 m could effectively reduce the range and combustion intensity of fire propagation. In addition, the water mist system exhibited the most favorable cooling and thermal mitigation performance at a droplet size of 50 μm and a spray cone angle of 75°.