To probe the electrode properties of the hybrid battery, we first evaluated the performance of each electrode in 0.5 M H 2 SO 4 at 25 C using a standard three-electrode system. In the cyclic voltammograms (CVs) shown in Fig. 2 (a), the redox potentials of Pb/PbSO 4 and PbO 2 /PbSO 4 conversions reached the fastest point at −0.3 and 1.75 V vs. reversible …