Abstract: Taking the 21700- type ternary lithium- ion battery as research project,under the environment of air,nitrogen and water mist,the surface temperature of lithium- ion battery and the concentration of escaping gas were monitored onine under the condition of thermal runaway to explore heat transfer and thermal runaway fire expansion between lithium- ion batteries.The results showed that different environment systems have significant influence on thermal runaway fire behavior of lithium-ion battery. Thermal runaway of lithium- ion battery can't be controlled effectively when experimental space is filled with the high concentration nitrogen. However,due to the decrease of oxygen concentration, the thermal runaway second burning stage doesn't occur,which can reduce the risk of fire spread and prolong the response time of thermal runaway effectively. The peak volume fraction of CO in the nitrogen environment is 2 049×10- 6,which are 154.6% and 180.0% of that in air and water mist environments. Under the misty environment,the mist converges at the positive electrode,which will easily reduce the working efficiency of safety valve. Once the internal pressure of the lithium-ion battery is too high,the more serious explosion will occur. In the transportation,storage and application of lithium- ion batteries,excessive humidity should be avoided. The occurrence of thermal runaway can be prevented by replacing the environmental atmosphere and improving the heat dissipation capacity contrapuntally,to strengthen the safety protection of lithiumion battery.

Key words: environmental systems;lithium-ion battery;thermal runaway, inert gas, heat spread