Abstract:  In this paper, the common 18650 lithium- ion battery is taken as the experimental object, the fire behavior, heat transfer, temperature change and the concentration change of smoke components in the process of thermal runaway of single lithium- ion battery and lithium- ion battery pack under the linear horizontal arrangement mode were studied. Combined with the experimental phenomena and temperature changes, the thermal runaway process of single lithium- ion battery was divided into initial stage, deflagration stage and late combustion stage. The thermal runaway propagation process of lithium- ion battery with linear horizontal arrangement is studied. The change of thermal conductivity k is quantitatively analyzed. It is proposed that the closer the battery is to the heat source, the earlier thermal runaway occurs. For the battery far away from the heat source, due to the decrease of the thermal conductivity k, the less heat is obtained, the longer the thermal runaway occurs, and the maximum temperature at the deflagration stage is also reduced. When the distance is long enough, the thermal conductivity decreases to the minimum, and the battery behind can not receive enough heat, and the propagation process of thermal runaway will be blocked. It was concluded that the smoke released from thermal runaway of lithium- ion battery pack mainly contained SO2, NO2, CO, HCl and NH3, and the concentrations of NO2 and SO2 accounted for 47% and 27% respectively.

Key words:  , fire protection, lithium- ion battery, thermal runaway, thermal runaway propagation, thermal conductivity, smoke composition