Figure 3

(a) First discharge-charge curves of the CNTs and the CNTs@MnO_x and CNTs@MnO composites at 0.1 mA cm⁻² current density; (b) discharge-charge curves of the CNTs@MnO composite at different current densities; (c) discharge-charge curves for selected cycles of the CNTs@MnO composite at the current density of 0.4 mA cm⁻² with a fixed capacity of 1000 mAh g⁻¹_(composite); (d) variation with cycle number of the discharge terminal voltage at the current density of 0.4 mA cm⁻² with a fixed capacity of 1000 mAh g⁻¹_(composite).