Nyquist plot of Li/MnO
cells after five charging and discharging cycles at open circuit voltage. The frequency ranged from 0.1 Hz to 100 kHz with an applied AC signal amplitude of 5 mV. (a) Caddice-clew-like and (b) urchin-like MnO2 samples. Symbols represent experimental data and lines represent fitted spectra using equivalent circuit. The inset is the equivalent circuit.