“…17,20 The two reduction peaks at 1.55 and 1.24 V represent the reduction process from NiS to Ni. 38,39 In the second cycle, the two peaks at 1.55 and 1.24 V shift to 1.63 and 1.27 V, which is due to the activation of the materials. In the anodic scan, four oxidation peaks can be observed near 1.23, 2.0, 2.29, and 2.53 V (delithiation).…”