Fig. 4.

Morphology change of Zn negative electrode and NVO positive electrode after cycling and kinetics of electrochemical process. SEM images and corresponding EDS analysis of Zn negative electrodes (1 A g^–1, 100th cycle) from Zn/NVO batteries based on a ZnSO₄ and b ZnSO₄/Na₂SO₄ electrolytes. Scale bars, 2 μm. SEM images of NVO electrodes at different states: c origin, d first discharged to 0.3 V, e first charged to 1.25 V, and f after 100 cycles at 0.1 A g^–1 in ZnSO₄/Na₂SO₄ electrolyte. Scale bars, 1 μm. g CV curves of NVO electrode at different scan rates in ZnSO₄/Na₂SO₄ electrolyte and h the corresponding plots of log (peak current) vs. log (scan rate) at each peak. i The capacitive contributions at different scan rates in ZnSO₄/Na₂SO₄ electrolyte