Multidimensional fire propagation of lithium-ion phosphate batteries for energy storage

In electrochemical energy storage stations, battery modules are stacked layer by layer on the racks. During the thermal runaway process of the battery, combustible mixture gases are vented. Once ignited by high-temperature surfaces or arcing, the resulting intense jet fire can cause the spread of both the same-layer and upper-layer battery modules. The direction of thermal runaway propagation of the battery involves both horizontal and vertical dimensions. Currently, there is a lack of quantitative research on the multidimensional fire propagation mechanism and heat flow patterns of the “thermal runaway-spontaneous heating-flaming” process in lithium-ion phosphate batteries. This paper conducts multidimensional fire propagation experiments on lithium-ion phosphate batteries in a realistic electrochemical energy storage station scenario. It investigates the propagation characteristics of lithium-ion phosphate batteries in both horizontal and vertical directions, the heat flow patterns during multidimensional propagation, and elucidates the influence mechanism of flame radiation heat transfer on thermal runaway propagation. Research indicates that when the heat transfer reaches 56.6 kJ, it triggers the fire propagation of cell. The heat required to trigger the fire propagation of a battery module is 35.99 kJ. In vertical fire propagation, the thermal runaway propagation time of the upper module is shorter (reduced from 122.3 s to 62.3 s), the temperature is higher (increased from 610.6 °C to 645 °C), the heat release is greater (increased from 205.69 kJ to 221.05 kJ), and the combustion is more intense. The research results of this paper can provide a theoretical basis and technical guidance for the fire safety design of energy storage stations.