Abstract: As the core component of strategic industries like new energy vehicle, lithium-ion battery has received widespread attention for its safety. Battery safety incidents often begin with thermal runaway, which means chain reactions occurred with production of heat and flammable gas. A test for internal pressure of lithium-ion battery during thermal runaway is proposed, based on which experiments are conducted. On the basis of accurate data from the test, process of thermal runaway is depicted in detail, finding that gas production can quickly change internal pressure, and the gas of 1 000 ℃ and 0.25~0.50 MPa show distinctive impact on heat transfer and dissipation. Meanwhile, the change of internal pressure is earlier than that of the voltage and the temperature. This test plays an important part in researches on thermal runaway mechanism and improving battery safety technologies like thermal runaway early warning and venting valve.

Key words: lithium-ion battery, battery safety, thermal runaway, thermal runaway propagation, internal pressure test