The addition of the nickel foil increases cell mass by 1.3%, while the ratio of DCRs in Eq. 1 is the relative power presented in Fig. 3C at 60°C. On the basis of these values, the power density is not reduced but rather increased by a factor of 2.02, 1.79, and 1.37 in the case of SEB-1, SEB-2, and SEB-3, respectively. Thus, in the case of SEB-3 with the highest internal resistance, the power density is still 37% higher than the baseline cell operated at room temperature.