Figure 3.

a) Typical profile during the first discharge–charge process at 30 mA g⁻¹. b) Evolution of ex situ XRD patterns of MnO₂ electrodes recorded at different states denoted in a). c–h) Corresponding SEM images of MnO₂ electrodes collected at states denoted by 1, 4, 7, 9, 11 and 13.