A novel method of electrolytically coating alpha/y-manganese oxide on Pt was investigated in Mn(NO3)(2) . 6H(2)O aqueous solution. Through cathodic polarization tests, three major reactions were verified: (i) O-2 + 4H(+) + 4e(-)-> 2H(2)O (similar to 0.5 to 0.07 V), (ii) O-2 + 2H(2)O + 4e(-) -> 4 OH- (0.07 to -0.6 V), and (iii) 2H(2)O + 2e(-) -> H-2 + 2 OH- (-0.6 to -2.5 V). The coated specimens obtained at the third stage were further annealed and characterized by thermogravirmetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electron microscopy, and cyclic voltammetry. XRD and TG-DTA diagrams indicated that the coating film was Mn(OH)(2), it condensed into MnO at 450 degrees C, oxidized into alpha/-y-MnO2 at 600 degrees C, and finally transformed into Mn2O3 at 900 degrees C. The alpha/y-MnO2 coated specimen (0.2 mu m) revealing crumpled, nanosized flakes was used as the cathode of a lithium battery. Its specific capacity increased from 182 mAh/g for the first cycle to 209 mAh/g for the 10th cycle between 4.0 and 2.0 V; the crystalline stability also increased. The mixed phases and the nanocrumpled structures of the alpha/gamma-MnO2 coated film were considered as the main factors resulting in the improved capacity and stability during cyclic lithium insertion and extraction. (c) 2005 The Electrochemical Society. [DOI: 10. 1149/1.1854618] All rights reserved.