Amorphous MnO2 as Cathode Material for Sodium-ion Batteries

Amorphous MnO2 has been prepared from the reduction of KMnO4 in ethanol media by a facile one-step wet chemical route at room temperature. The electrochemical properties of amorphous MnO2 as cathode material in sodium-ion batteries (SIBs) are studied by galvanostatic charge/discharge testing. And the structure and morphologies of amorphous MnO2 are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectra. The results reveal that as-synthesized amorphous MnO2 electrode material exhibits a spherical morphology with a diameter between 20 and 60 nm. The first specific discharge capacity of the amorphous MnO2 electrode is 123.2 mAh center dot g(-1) and remains 136.8 mAh center dot g(-1) after 100 cycles at the current rate of 0.1 C. The specific discharge capacity of amorphous MnO2 is maintained at 139.2, 120.4, 89, 68 and 47 mAh center dot g(-1) at the current rate of 0.1 C, 0.2 C, 0.5 C, 1 C and 2 C, respectively. The results indicate that amorphous MnO2 has great potential as a promising cathode material for SIBs.