Fig. 5. (a) CV curves of the MgCo2O4 NCA electrode and Ni foam electrode at a scan rate of 5 mV s1 in 6 M KOH solutions; (b)e(f): only the MgCo2O4 NCA electrode; (b) CV curves at
different scan rates; (c) GCD curves at different current densities; (d) specific capacitance as a function of current density; (e) cycle performance at a current density of 1 A g1 (inset
shows GCD curves of the first 10 and last 10 cycles from 1000 cycles); (f) EIS and equivalent circuit.