MnO2 thin films have been deposited electrochemically from a MnSO4 solution. The deposition conditions have been optimized. The open circuit voltage versus lithium content of the LixMnO2 cathode shows a linear relation with a break in the slope at x = 0.5. The specific energy density is 580 Wh/kg and the volume energy density 2916 Wh/l. The chemical diffusion coefficient of lithium in the MnO2 film is 4.27 to 4.85 x 10(-13) cm2/s for 0 less-than-or-equal-to x less-than-or-equal-to 0.2 and 1.1 X 10(-11) cm2/S for x = 0.9. The good reversibility of lithium insertion and extraction has been shown by voltammetry and shallow charge-discharge cycling.