Orthorhombic LiMnO2 was synthesized via a solid-state reaction. Its electrochemical properties as cathode in lithium batteries were examined. It was found that initially, a few cycles are necessary to activate the electrochemical reactivity of o-LiMnO2, which is related to the transformation from the orthorhombic phase to a spinel-like phase. A maximum discharge capacity of 180-190 mA h g(-1) for o-LiMnO2 electrodes was achieved. An electrochemical impedance spectroscopy (EIS) study showed that the charge-transfer resistance (R-CT) for the initial o-LiMnO2 electrode is much larger than that for the o-LiMnO2 electrode in the charged state. The o-LiMnO2 electrode demonstrated a better cyclability than that of the spinel LiMn2O4 directly synthesized by solid-state reaction.