Nanosized cryptomelane manganese dioxide (MDO) and its SnO2-coated product were prepared through a redox reaction between KMnO4 and Mn(II) acetate. XRD analysis showed the cryptomelane-type structure for both materials. Chemical analysis detected the presence of K in parent and K and Sn in coated oxide. The coating was evidenced by TEM images, which display a thin layer of SnO2 at the surface of nanosized MnO2 particles. Vibrational spectroscopic measurements confirmed the integrity of the MnO2 lattice. The net effect of the SnO2 coating results in better electrochemical performance of the Li//MnO2 cells.