Abstract: As a passive safety measure to alleviate the thermal runaway of the battery system, the vent plays a very important role in the cell design. The opening pressure, area and position of the vent have an important impact on the pressure relief process after the thermal runaway of the cell. This paper mainly introduces the pressure relief process of the vent opening caused by heat and gas production after the cell thermal runaway. Through theoretical calculation, experimental test and simulation analysis, the pressure relief characteristics of the vent are systematically described and analyzed. Firstly, the pressure relief process of the vent is analyzed theoretically based on the basic principles and equations of fluid mechanics, and the basic state of the pressure relief choke flow after the vent is opened in the process of thermal runaway is expounded; Secondly, by carrying out two kinds of experiments of heating thermal runaway and overcharging thermal runaway of the cell, the temperature of the jerry roll(JR) and the internal pressure of the cell were monitored in real time, so as to obtain the heat and gas production rate before the vent was opened; Finally, the process of heat production, gas production and pressure relief of the cell is simulated. Based on COMSOL, system model of the pressure relief of the vent is established, and the influencing factors such as the opening pressure, the area and the position of the vent are classified and simulated. Also,the simulation results are compared with the experimental test data. A more optimized structure design of the vent is obtained, which provides a certain reference for the optimal design of the power battery.

Key words: The power battery,  , vent,  , choking flow,  , dynamic simulation,  , pressure relief characteristics