Figure 3D presents the relative interfacial reactivity as derived from the charge-transfer resistance of EIS results. This further confirms that increased operational temperature effectively decreases the charge-transfer resistance of SEB cells and consequently increases the cell reactivity and power. The reactivity boost over the baseline LIB cell is 2.06 for SEB-2. Overall, both relative power and relative reactivity illustrate the ability of SEB cells to achieve high power on demand. On the other hand, the values of relative reactivity of these two cells shown in Fig. 3D indicate that the SEB cell will be 5× safer and undergo 5× less aging at room temperature, which is supported by self-discharge and capacity retention tests displayed in fig. S2. Furthermore, the comparison of relative reactivity for the two cell types at 60°C indicates that the SEB cell is more than 2× less prone to thermal runaway.