Fig. 7. (a) CV curves measured at different potential windows at a scan rate of 50 mV s⁻¹, (b) GCD curves in different potential windows at the current density of 5 A g⁻¹, (c) CV curves at different scan rates ranging from 10 to 500 mV s⁻¹ within the potential window of 0–1.6 V, (d) galvanostatic charge/discharge curves at different current densities, and (e) cycling stability and coulombic efficiency at a constant current density of 5 A g⁻¹ of the 1.5 at% Cu-doped Mn₃O₄//G ASC. (f) Ragone plots of the 1.5 at% Cu-doped Mn₃O₄//G ASC compared with other Mn₃O₄ based ASC.