A series of thermal failure researches were conducted to explore the effects of parameters on the failure propagation behavior within battery modules, including the gap between batteries, the state of charge (SOC) and traditional phase change material (PCM). Based on the results, obvious domino phenomena were revealed during the process of thermal failure propagation, where the thermal failure of module (3 × 3) could be divided into six phases. It was illustrated that increasing battery gap could effectively prevent thermal failure propagation by postponing each phase of failure and decreasing the propagation speed. The propagation speed agreed well with the square of battery gap, and it grew linearly with the increasing module SOC. Due to the low conductivity and diffusivity of traditional PCM, it was found that the failure propagation behavior of the module wrapped with PCM would be severer.