PolyTAP and its composites are flame-retardant materials. In addition, the PolyTAP has electrically insulative properties and stability at elevated temperatures (4). All these properties make PolyTAP well suited to enhance the safety of SEB cells under abuse conditions. This is confirmed by nail penetration tests shown in Fig. 2C, where the temperature rise is only 100°C (without cell deformation, smoking, or fire) versus almost 1000°C (catching fire) in the baseline case (Fig. 2D). The superior safety performance of the SEB cell is further illustrated by the electrical performance of the cell during nail penetration. For the baseline cell, the cell voltage decreases to 0.1 V within 5 s after the nail penetration. The sharp voltage drop indicates that the shorting current is extremely high due to low internal resistance of the baseline cell. In contrast, the voltage of the SEB cell drops from 4.171 to 3.085 V within 5 s after penetration, showing a slow and controlled discharge due to the high internal resistance of the SEB cell. The substantially higher resistance in the SEB cell than the baseline is caused by the electrically nonconductive layers formed on the surface of the graphite and NCM particles, as schematically shown in Fig. 2B.