Polythiophene Mesoporous Birnessite-MnO2/Pd Cathode Air Electrode for Rechargeable Li-Air Battery

• Mesoporous b-MnO2 was successfully synthesized by using a modified interfacial method.
• Mesoporous b-MnO2 has a BET specific surface area of 237 m2 g−1 with pore diameter of 3.52 nm.
• Mesoporous b-MnO2/Pd/TAB-2 catalyst electrode shows the initial discharge capacity of ca. 487 mAhg-catalyst−1 at a current density of 0.13 mA cm−2.
• A stable cycle performance of Li-Air battery is due to the electrocatalytic effect of Pd on mesoporous b-MnO2.

Mesoporous birnessite-manganese oxide (b-MnO2) was studied for air electrode for Li-air rechargeable battery. In this study, mesoporous b-MnO2 with an average pore size of 3.52 nm and BET surface area of 237 m2 g−1 was successfully prepared using inorganic/organic phase. Prepared mesoporous b-MnO2 was applied for air electrode for Li-air battery and discharge capacity of 345 mAh g−1 was observed at a current of 0.13 mA cm−2. With the dispersion of small amount of Pd to mesoporous b-MnO2, it was found that the Li-air cell showed a reasonably large discharge capacity of 487 mAh g−1 at 0.13 mA cm−2 at the initial cycle. The first discharge plateau around 2.71 V vs. Li/Li+ and charge plateau at 3.58 V 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-MnO2/Pd/TAB-2 (85/5/10) air electrode suggested that the observed capacity mainly came from Li+ and O2 to form Li2O2 after discharge to 2.0 V. Formation of Li2CO3 was hardly observed.