Abstract: This paper is the first to carry out the test of penetrating and releasing fire extinguishing agent in order to explore a more efficient ways of extinguishing fire. Experimental conditions were designed according to three main factors affecting fire suppression efficiency (release path, filling pressure, type of fire extinguishing agent) to highlight the fire suppression efficiency of penetrating and releasing fire extinguishing agent. When the battery is thermal runaway, the results show that the temperature of the cathode and inside of the battery can be reduced to a lower temperature than the external application of fire extinguishing agent, which the difference is 168.2 ℃ and 61.4 ℃ respectively, and the temperature does not rise again. When the fire extinguishing agent with the filling pressure of 0.6 MPa is penetrating and releasing, the cooling rate of liquid water at the cathode is as high as 30.1 ℃/s, while 0.9 MPa is only 7.2 ℃/s. Under the same conditions, the cooling rate of 2-BTP fire extinguishing agent with high viscosity is as high as 41.9 ℃/s at 0.6 MPa and still 35.2 ℃/s at 0.9 MPa. This indicates that the inhibition effect of liquid water is more obviously affected by filling pressure than that of 2-BTP extinguishing agent. To sum up, penetrating and releasing of fire extinguishing agent can reduce the temperature of cathode from 643.6 ℃ to 55.5 ℃, and make the maximum cooling rate of cathode reach 252.4 ℃/s. Compared with releasing fire extinguishing agent outside, it shows better inhibitory effect on lithium-ion battery fire.

Key words: lithium-ion battery thermal runaway, penetrating fire extinguishing, liquid water, 2-BTP extinguishing agent, cooling rate