Mesoporous birnessite-manganese oxide (b-MnO 2 ) was studied for air electrode for Li-air rechargeable battery. In this study, mesoporous b-MnO 2 with an average pore size of 3.52nm and BET surface area of 237m 2 g −1 was successfully prepared using inorganic/organic phase. Prepared mesoporous b-MnO 2 was applied for air electrode for Li-air battery and discharge capacity of 345mAh g −1 was observed at a current of 0.13mAcm −2 . With the dispersion of small amount of Pd to mesoporous b-MnO 2 , it was found that the Li-air cell showed a reasonably large discharge capacity of 487mAh g −1 at 0.13mAcm −2 at the initial cycle. The first discharge plateau around 2.71V vs. Li/Li + and charge plateau at 3.58V vs. Li/Li + with highly reversible capacity were observed. The energy efficiency for the charge and discharge was estimated to be ca. 76.4%. The ex-situ XRD result of the mesoporous b-MnO 2 /Pd/TAB-2 (85/5/10) air electrode suggested that the observed capacity mainly came from Li + and O 2 to form Li 2 O 2 after discharge to 2.0V. Formation of Li 2 CO 3 was hardly observed.