Lithium-Ion battery cells and automotive battery systems are constantly improving as a result of the rising popularity of electric vehicles. With higher energy densities of the cells, the risks in case of failure rise as well. In the worst case, a fast exothermic reaction known as thermal runaway can occur. During thermal runaway, the cell can emit around 66% of its mass as gas and particles. An experimental setup was designed and showed that the gas-particle-vent of a cell going through thermal runaway can cause electric breakthroughs. These breakthroughs could start electric arcing in the battery system, which could lead to additional damages such as burning through the casing or igniting the vent gas, making the damage more severe and difficult to control. Uncontrollable battery fires must be prevented. The emitted gas was analyzed and the ejected particles were examined to discuss the potential causes of the breakthroughs.