Amorphous MnO 2 as Cathode Material for Sodium‐ion Batteries

Amorphous MnO 2 has been prepared from the reduction of KMnO 4 in ethanol media by a facile one‐step wet chemical route at room temperature. The electrochemical properties of amorphous MnO 2 as cathode material in sodium‐ion batteries ( SIBs ) are studied by galvanostatic charge/discharge testing. And the structure and morphologies of amorphous MnO 2 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 MnO 2 electrode material exhibits a spherical morphology with a diameter between 20 and 60 nm. The first specific discharge capacity of the amorphous MnO 2 electrode is 123.2 mAh •g −1 and remains 136.8 mAh •g −1 after 100 cycles at the current rate of 0.1 C. The specific discharge capacity of amorphous MnO 2 is maintained at 139.2, 120.4, 89, 68 and 47 mAh •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 MnO 2 has great potential as a promising cathode material for SIBs .